JPH02251840A - Organic thin film - Google Patents

Abstract

PURPOSE:To obtain a Langmuir-Blodgett (LB) film which does not contain a packing material by forming the monomolecular film of a specific cationic spiropyrane compd. on lower layer of water contg. sodium polystyrene sulfonate and forming the film by an LB method on a substrate. CONSTITUTION:The org. thin film is obtd. by dropping a soln. prepd. by dissolving the cationic spiropyrane compd. expressed by formula I into a developing solvent on the lower layer of water contg. the sodium polystyrene sulfonate to form the monomolecular film on the water surface and accumulating the film on the substrate by the ordinary LB method. In the formula I, X<-> denotes halogen ion. The cationic spiropyrane compd. forms a polyion complex on the lower layer of water contg. the sodium polystyrene sulfonate, thereby forming the stabler monomolecular film. The occupying area of the molecules is thereby decreased and the orienting or packing state of the molecules is improved. The org. thin film (LB film) which does not contain the packing material is obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an organic thin film containing a spiropyran compound that responds reversibly to light and formed on a substrate by the Langmuir-Prodgett method.

[Conventional technology]

In recent years, efforts have been made to use organic thin films whose structure and physical properties change with light to apply them to memory devices and switching devices, or to control reactions.

In particular, the development of amorphous thin films containing photochromic compounds whose structures change reversibly when exposed to light and whose absorption spectra also change accordingly is becoming more active.

In addition, as a thin film forming method, the Langmuir-Prodgett method (L
Method B) is attracting attention. The organic thin film (LB film) formed by the LB method is an ultra-thin film in which the orientation of molecules is controlled. Research and development is underway.

On the other hand, photochromic compounds such as spiropyran compounds that are photoresponsive are also being considered for application in memory devices, light control materials, reaction control, etc. by taking advantage of absorption changes and structural changes due to photoisomerization.

These photochromic compounds are often mixed into polymer binders or made into polymers themselves to form thin films, but recently, LB films containing spiropyran compounds as constituents have also been studied. Ta.

As such LB films, LB films made of spiropyran compounds with long chain substituents are known, but these TB films are unstable. Therefore, in order to stabilize, for example, long-chain alkyl carboxylic acids such as alaxic acid and stearic acid, their esters, amides, long-chain alkyl amines such as stearylamine, or n-octadecane are mixed as a backing material to create a stable single molecule. Many LB films are known that are accumulated on a substrate after being formed into a film.

(Th1n 5olid Films, Volume 133,
21 pages (1985); Chemistry L
etters, p. 1443 (1987)] [Problem to be solved by the invention] As described above, the LB film of spiropyran compounds has the disadvantage of being unstable when used alone, so it is necessary to back them with other compounds to stabilize them. The method is to form a monomolecular film by mixing the materials, so it cannot be said to be a pure monomolecular film.

Furthermore, mixing causes a decrease in the concentration of the photoresponsive component during LB film removal, a decrease in intermolecular interactions such as association, a decrease in orientation, etc., and the original function is not fully expressed.

The present invention solves these problems by using a spiropyran compound that can form a stable monomolecular film even when used alone.
The purpose is to provide an LB film that does not contain a backing material.

[Means to solve the problem]

The present inventors have conducted extensive research to solve the above problems, and as a result, have arrived at the present invention. That is, the gist of the present invention is to form a monomolecular film of a cationic spiropyran compound represented by the following formula (1) (wherein X- represents a halogen ion) on a lower water layer containing sodium polystyrene sulfonate. The present invention relates to an organic thin film characterized in that it is formed and formed on a substrate by the LB method.

The present invention will be explained in more detail below.

The organic thin film of the present invention is prepared by dissolving a solution of a cationic spiropyran compound represented by formula CI) in a developing solvent.
It is obtained by dropping it onto water containing sodium polystyrene sulfonate to form a monomolecular film on the water surface, and accumulating it on a substrate using the usual LB method.

Sodium polystyrene sulfonate is 0.005 to 0
．． 5 mn+ol/1, preferably 0.01-0.3
It is added to the lower layer water at a concentration of mmol/l. Further, as the lower layer water, pure water that has been subjected to distillation and desalination treatment is used.

As the developing solvent, organic solvents such as chloroform, dichloroethane, benzene, toluene, and acetate are used.

As the substrate, a quartz plate, a glass plate, or a quartz plate, a glass plate, or the like having an electrode of gold, silver, aluminum, indium tin oxide, etc. on the surface is used.

The cationic spiropyran compound represented by formula (I) can form a polyion complex on the lower layer water containing sodium polystyrene sulfonate to form a stable monomolecular film.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited by the Examples unless the gist thereof is exceeded.

Example 1 A monomolecular film was formed using a Langmuir trough (Kyowa Interface Science Model). First, sodium polystyrene sulfonate (manufactured by Polyscience; molecular weight 500,000) was added to the lower water.
Add to a concentration of 0.04 mn+ol/4F.

A cationic spiropyran compound represented by the following formula (n) was dropped as a chloroform solution onto this lower water layer and developed to form a monomolecular film.

Here, the surface pressure-area curve (π-8 line) was measured by a conventional method, and the measurement results are shown in FIG. 1 (curve a). For comparison, the π-A curve when the lower layer water is pure water is also shown in FIG. 1 (curve b). It has been shown that the cationic spiropyran compound of the present invention forms a relatively stable monomolecular film on pure water even when it is alone. By forming polyion complexes, a more stable monomolecular film is formed, and as is clear from Figure 1, the area occupied by molecules is reduced due to the formation of polyion complexes, and the orientation or filling state of molecules is improved. It suggests.

The obtained monomolecular film was left at a surface pressure of 30 mNm-', but the surface pressure hardly changed.

When this monomolecular film was irradiated with ultraviolet light obtained by dividing light from a 500W xenon lamp using an ultraviolet transmission filter (UV-D35), the surface pressure decreased as shown in Figure 2 [(i) → (ii) ), the surface pressure is maintained even when the ultraviolet light irradiation is stopped [(i) - (iii)], and when the visible light obtained by dividing the xenon lamp light into the visible light transmission filter (Y-45) is irradiated, the surface pressure is maintained again. The pressure returned to almost its original value ((iii)→(iv)). In this way, the compound of the present invention isomerizes into merocyanine type and spiropyran type by photoisomerization on the lower layer water, causing a structural change and returning to the original structure even if the surface pressure changes, and the surface pressure also returns. It was shown that a stable monolayer was formed.

The obtained monomolecular film was deposited on a quartz plate by the usual LB method.
The layers were accumulated to obtain an LB film.

FIG. 3 shows the ultraviolet-visible absorption spectrum of the obtained LB film.

Curve A is the cumulatively obtained LBl! This is the ultraviolet-visible absorption spectrum before light irradiation. Absorption of merocyanine type, which is partially isomerized spiropyran, is seen in the visible region. When the LB film is irradiated with the aforementioned ultraviolet light, the lutohyrobilane site opens its ring and isomerizes to the merocyanine type, resulting in an increase in absorption in the visible region (curve B). Furthermore, when visible light was irradiated, almost no absorption in the visible region was observed (song v
AC).

This indicates that the merocyanine type was almost completely photoisomerized to the spiropyran type. Similar spectra were obtained even after irradiation with ultraviolet light and visible light.

As described above, the LB film of the present invention has excellent stability and complete photoisomerization.

Comparative Example 1 0.3 mmol/1 calcium chloride and 0.05
A monomolecular film containing a spiropyran compound represented by the following formula (I[I) and araxic acid mixed at a molar ratio of te3 was formed on the lower layer water containing mmol/β of sodium hydrogen carbonate in the same manner as in Example 1. did. This monomolecular film was irradiated alternately with ultraviolet light and visible light at a surface pressure of 30 mNm-' in the same manner as in Example 1, and the change in surface pressure was measured, and the results are shown in FIG. As is clear from FIG. 4, the obtained monomolecular film showed a photoisomerization reaction in which the surface pressure decreased when irradiated with ultraviolet light and increased when irradiated with visible light. Further, the variation in surface pressure due to repeated ultraviolet light irradiation and visible light irradiation was not constant, unlike in Example 1, indicating that the stability was inferior to that in Example.

Furthermore, it is known that a monomolecular film of the compound represented by formula 1ff) alone is unstable (Che■1-str
y Letter, pp, 1443 1446,
(1987), the membrane was stabilized by making it a mixed membrane with araxic acid, but even in this state it was inferior to the monomolecular membrane of Example 1 in stability.

〔Effect of the invention〕

The organic thin film of the present invention has excellent photoresponsiveness and film stability, and by utilizing absorption spectrum changes and structural changes due to photoisomerization, it can be used in memory devices, switching devices, control of electrode reactions, etc. Because it can be used, it is industrially useful.

[Brief explanation of drawings]

FIG. 1 shows the surface pressure-area curve of the monomolecular film of Example 1 developed on the lower water layer. Song by a is sodium polystyrene sulfonate concentration 0゜04 mmol
/ Il, the curve vAb indicates the case where the lower layer water is pure water. FIG. 2 shows the photoresponsiveness of the surface pressure of the monomolecular film of Example 1. Further, FIG. 4 shows the photoresponsiveness of the surface pressure of the monomolecular film of Comparative Example 1. In the figure, (1) is when UV light irradiation starts, (11) is when UV light irradiation is stopped, (iii) is when visible light irradiation is started, and (iv) is when visible light irradiation is started.
indicates when visible light irradiation is stopped. FIG. 3 shows the ultraviolet-visible absorption spectrum of the LB film obtained in Example I. Curve A shows the absorption spectrum before irradiation with light, curve B shows the absorption spectrum after irradiation with ultraviolet light, and curve C shows the absorption spectrum after further irradiation with visible light. Figure 1 Figure 3 Figure 2 Wavelength (nm) Figure 4 Time Time

Claims (1)

[Claims] (1) Above the lower layer water containing sodium polystyrene sulfonate is expressed by the following formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼...[I] (In the formula, X^- represents a halogen ion.) An organic thin film characterized in that it is formed by forming a monomolecular film of a cationic spiropyran-based compound and depositing the film on a substrate using the Langmuir-Prodgett method.