JPH0343316B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a photochromic material and an optical recording medium using the same.

Conventional technology Conventionally, materials that produce reversible color changes have been used.
Photochromic materials are known. Fulgide is one of the photochromic materials.

Formula (1) is the general formula for fulgide. As can be seen from this formula, fulgide is a compound in which alkylidene groups are attached to each of the two methylene carbons of succinic anhydride or its derivative.

(However, at least one of R2 and R3 is an aromatic ring, X=O, N-R) Many fulgides have been announced so far. One example of this is fulgide represented by formula (2), and its photochromism will be briefly explained.

Fulgide of formula (2) uses a furan ring as an aromatic ring and is colorless. To this fulgide (2)
When exposed to 337 nm ultraviolet light, it changes to the benzofuran form (3) and exhibits a red color. When exposed to visible light of 473 nm, it returns to (2) again.

Incidentally, such photochromism is almost common to other fulgides as well, with the only difference being the absorption wavelength.

Fulgide is reported to have a long cyclic life compared to other photochromic compounds. However, to date, examples intended for use as optical recording media have been in polymer matrices (U.S. Pat. No. 4,220,708) or in clay (U.S. Pat.
There is only one reported example of photochromism (No. 4503177).

By the way, as electronic parts become smaller and more sophisticated, fulgide must be made into a uniform ultra-thin film in order to apply this photochromic characteristic to optical recording media, photon detection elements, etc.

LB (Langmiur Blossom) film is a uniform ultra-thin film made of a typical organic compound. In order to form an LB film, the molecule must contain a hydrophobic group (e.g., a hydrocarbon chain) and a hydrophilic group (e.g., a carbonyl group), and both of them must be
It is necessary to have an appropriate balance.

Problems to be Solved by the Invention There are two problems when using conventional fulgide as an optical recording medium.

One is that an isomerization reaction occurs. Fulgide has positional isomers that do not exhibit photochromism. Until now, fulgide had a side reaction to form this positional isomer, which lowered the conversion rate of this reaction.

Another problem is that it is difficult to make the film thin. The LB method is the best method for creating uniform thin films, but to date there has been no example of forming an LB film using fulgide. this is,
This is because fulgide does not have a long hydrophobic chain, or even if it does have a hydrophobic long chain, the balance with the hydrophilic group is poor, and therefore it is difficult to develop it on the air-water interface to create an LB film.

The purpose of the present invention is to impart steric hindrance to fulgide by introducing a long chain to suppress the isomerization reaction. Moreover, at the same time, the purpose is to form a thin film using the LB method and to be able to impart fulgide photochromism onto the thin film.

Means for Solving the Problems A photochromic material represented by the following general formula is constructed (where R is an alkyl chain of C=5 to 31).
This is also used to construct an optical recording medium.

Effect The long hydrocarbon chain introduced into the above compound provides steric hindrance, which can prevent a reduction in conversion rate due to isomerization.

Moreover, by using the present photochromic material having both hydrophilic and hydrophobic groups, it is possible to obtain a uniform ultra-thin film (LB film) that does not impair the photochromic properties of fulgide at all.

Examples Fulgide in the present invention will be explained in detail.

Example 1 The chemical structural formula shown below shows an example of fulgide according to the present invention (hereinafter referred to as FT-10).

The synthesis method of FT-10 is shown below.

(Step 1) To a benzene solution of 1 mole of 2,5-dimethylthiophene and 1 mole of stearoyl chloride was added a benzene solution of 1 mole of anhydrous tin chloride () over 1 hour at 0°C. After stirring for several hours, add ice (1.5
Kg) and poured into 5M hydrochloric acid (500ml). The aqueous layer was extracted with ethyl acetate, and the combined organic layers were washed with water and concentrated. 0.7 mol of ketothiophene was obtained by recrystallization from petroleum ether.

(Step 2) Petroleum ether was added to 1 mol of sodium hydride and stirred for 5 minutes. After standing still and removing the supernatant, a mixture of 1.5 mol of acetone and 1 mol of diethyl succinate anhydride was added. Add 1 ethanol to it
When added dropwise, the reaction started and hydrogen was violently evolved. After hydrogen generation had subsided, diethyl ether was added and further stirred. After 1 hour, the reaction mixture was diluted with ethyl acetate and carefully acidified by extraction with 1M aqueous sodium carbonate solution to liberate the organic layer. It was extracted with ethyl acetate, dried over anhydrous magnesium sulfate, concentrated, and the half ester was extracted with ethyl acetate.
0.8 mol was obtained.

(Step 3) 0.8 mol of the half ester obtained in Step 2 was dissolved in 500 ml of ethanol, 50 ml of concentrated sulfuric acid was added, and the mixture was heated to reflux. After 3 hours, it was concentrated, and the residue was diluted with ether, washed with an aqueous sodium bicarbonate solution, dried and concentrated again. The resulting residue was fractionated by column chromatography to obtain 0.8 mol of diester.

(Step 4) Petroleum ether was added to 1.2 mol of sodium hydroxide and stirred for 5 minutes. After standing still and removing the supernatant, add 0.7 mol of ketothiophene obtained in step 1,
The mixture of 0.8 mol of diester obtained in step 3 is
It was dissolved in as little petroleum ether as possible and added. When one drop of ethanol was added thereto, the reaction started and hydrogen was violently generated. After hydrogen generation had subsided, diethyl ether was added and stirring was continued. After 4 hours, the reaction mixture was diluted with ethyl acetate and carefully acidified by extraction with 1M aqueous sodium carbonate to liberate the organic layer. It was extracted with ethyl acetate, dried over anhydrous magnesium sulfate, and concentrated. The obtained residue was fractionated by column chromatography to obtain 0.5 mol of half ester.

(Step 5) 0.5 mol of the obtained half ester was dissolved in 10% alcoholic potassium hydroxide, heated under reflux for 5 hours, poured into 6N hydrochloric acid, extracted with ethyl acetate, dried over anhydrous sodium sulfate, and concentrated. 0.3 mol of dicarboxylic acid was obtained. Furthermore, 100 ml of acetyl chloride was added to 0.3 mol of this dicarboxylic acid,
Stir for 60 minutes at room temperature. Thereafter, the reaction mixture was concentrated, and the residue was separated and purified using silica gel column chromatography. In this way, 0.02 mol of the target fulgide FT-10 was obtained.

By spreading Fulgide FT-10 synthesized using the above method on the air-water interface and accumulating it on a quartz substrate, we were able to obtain a uniform ultra-thin film (LB film) with a film thickness of approximately 100A.

Note that this embodiment, which uses stearoyl chloride as a raw material, is also desirable for forming the LB film. Furthermore, in R of the claims, when the number of carbon atoms was 14 to 22, a good LB film was formed.

Note that a photochromic compound (R is a carbon chain in which C=31) using dotriacontanoyl chloride instead of stearoyl chloride as a raw material formed an LB film. However, for compounds with longer chains than this, it is difficult to obtain the raw acid chloride.

Fulgide using hexanoyl chloride instead of the raw material stearoyl chloride (R is a carbon chain with C=5)
formed an LB film. However, with fulgide using pentanoyl chloride, it was not possible to obtain an LB film due to the poor balance between hydrophilicity and hydrophobicity.

Next, an example of an optical recording medium using fulgide as described above will be described.

Example 2 An optical recording medium was constructed using the above-mentioned fulgide (abbreviated as FT-10).

Using 0.3mol/1 toluene solution of FT-10, place it on silica glass washed with trichloroethane.
A recording layer was formed by spin coating at 600 rpm for 60 seconds. This recording layer was initially transparent, but upon irradiation with ultraviolet light (λmax = 340 nm), the recording layer quickly developed a red color (λmax = 510 nm). Furthermore, when this was irradiated with visible light (λmax=510 nm), the color rapidly faded within the recording layer.

Example 3 Using FT-10 as a benzene solution, a recording layer was created on a substrate using the LB method under the following conditions.

Substrate: Silica glass immersed in a 10% toluene solution of chlorotrimethylsilane for 10 minutes and then washed with trichloroethane Trough: 140mm x 600mm Subphase: PH7.0 Phosphate buffer Temperature 18℃ Compression speed: 10mm/min Cumulative pressure : 13 mN/m Cumulative number: 16 layers Similarly to the recording layer in Example 2, the reaction proceeded reversibly in this recording layer using two types of light sources with different wavelengths.

Example 4 A benzene solution having a mixing ratio of FT-10/octadecane=1/2 was prepared, and a recording layer was formed in the same manner as in Example (1). Similar to the recording layer in Example 2, this recording layer also underwent a reversible reaction using two types of light sources with different wavelengths. Furthermore, in this case,
At room temperature in the dark, the half-life of FT-10 is 1 week.
In the case of FT-10 alone as shown in Example 3, the half-life is 8 hours or more in the colored form (the half-life is about 1 hour)
The stability was significantly improved.

The absorption spectra of colorless bodies and colored bodies are shown in the figure as curves A and B.

In addition, the conditions for forming the LB film in the above example are only representative examples, and it is noted that good LB film formation can be achieved under other conditions.
A membrane is obtained.

Effects of the Invention According to the present invention, it is possible to provide a uniform ultra-thin film by the LB method without losing the photochromic properties of fulgide, and it is also possible to realize an optical recording medium with a long recording life.

[Brief explanation of drawings]

FIG. 1 is an absorption spectrum diagram of a recording layer of an optical recording medium in an example of the present invention.

Claims (1)

[Scope of Claims] 1. A photochromic material represented by the following general formula (where R is a hydrocarbon chain with C=5 to 31). 2 Optical recording medium using a photochromic compound represented by the following general formula (where R is C=5-31
alkyl chain). 3. The optical recording medium according to claim 2, which has a recording layer made of an LB film of a photochromic compound. 4. The optical recording medium according to claim 2, which has a recording layer made of an LB film of a mixture of a photochromic compound and a hydrocarbon or a fatty acid.