JP2863288B2 - Method for producing photochromic thin film - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a photochromic thin film used for a light control glass, an information recording medium, and the like.

2. Description of the Related Art A photochromic substance is conventionally known as a material that causes a reversible color change by light.

Above all, photochromic substances composed of organic compounds are
There are many substances by various photoreactions such as cis-trans isomerization, photo-ring opening reaction, photo-ring closing reaction and photo-dimerization.

As an application, sunglasses whose color is changed by ultraviolet rays, an optical switch element based on a change in optical refractive index, a rewritable optical memory, and the like are considered.

In application, bistability of a colorless state and a colored state of a photochromic substance is important.

The photochromic substance is often used in a thin film, and as a thin film manufacturing method, a casting method, a polymer dispersion casting method, a vacuum evaporation method, a Langmuir-Blodgett method (hereinafter abbreviated as an LB method) and the like are known.

Problems to be Solved by the Invention Even a photochromic substance that shows a good photochromic reaction in a solution may not show a stable photochromic reaction in a film when the film is thinned.

It is considered that the cause of this is that the photochromic substance crystallizes in the thin film or forms a certain association state that does not easily cause a photochromic reaction.

Also, such a state occurs partially in the thin film,
In many cases, the film is not uniformly dispersed, and cannot provide a uniform film quality.

As a solution to this problem, there is a method in which an ion complex monomolecular film is formed at the gas-liquid interface of an aqueous solution in which a water-soluble photochromic substance having an anionic group is dissolved, and then the thin film is formed by the LB method.

However, it was not possible to control the photochromic reaction in the thin film thus formed.

The present invention has been made to overcome the conventional problems, and has as its object to provide a method for producing a photochromic thin film that is excellent in controllability of a photochromic reaction and that can produce a thin film having good film quality.

Means for Solving the Problems In order to achieve the above object, a method for producing a photochromic thin film of the present invention comprises, as an aqueous phase, an aqueous solution of a photochromic substance of a spiropyran compound having an anionic group, A step of developing a cationic surfactant in which at least one kind of anionic surfactant is mixed to form a monomolecular film; a step of forming an ion complex monomolecular film at the gas-liquid interface; Thinning the molecular film using the Langmuir-Blodgett method.

Action Self-organizing 2 possessed by cationic surfactant
By forming an aggregate state such as a molecular film structure, a monomolecular film having a uniform film quality can be produced.

When the photochromic substance having an anionic group forms an ion complex with the monomolecular film, a thin film exhibiting a favorable photochromic reaction can be obtained.

By mixing at least one kind of nonionic surfactant in this monomolecular film, the ratio of the cationic surfactant per unit area is reduced. The free volume per unit increases. Therefore, the photochromic substance can easily move, and the reaction speed of the photochromic reaction can be controlled. In addition, since the interaction between photochromic substances, for example, the formation of an aggregate can be controlled, the photoreaction characteristics such as the stability of the colorant can be controlled accordingly.

Also, by mixing at least one or more anionic surfactants into the monomolecular film, the anionic group and the cationic group in the monomolecular film form a complex to neutralize or Since the anionic group generates an electrostatic repulsion between the photochromic substance having the anionic group and the photochromic substance, the formation ratio of the ion complex can be controlled. This changes the free volume, the interaction between the photochromic substance, and the interaction force between the photochromic substance and the monolayer,
Photochromic reaction characteristics can be controlled.

Examples Examples of the present invention will be described below.

The used photochromic substance having an anionic group is a spiropyran molecule (spiropyran A and B) represented by the following chemical structural formula, and has a sulfo group at the N-position.

These molecules are water-soluble because they do not have long hydrocarbon chains and have sulfo groups.

The following quaternary ammonium dioctadecyl-dimethyl-ammonium and octadecylamine (surfactant C) were used as the cationic surfactant.

CH ₃ (CH ₂ ) ₁₇ NH ₂ surfactant D As the cationic surfactant, amine or ammonium having at least one long hydrocarbon chain was used. In addition, pyridinium group, imidazole group, etc. Surfactant molecules having such a cationic group can be applied.
Among these, a surface active substance capable of forming a bimolecular film in a self-organized manner, such as the surface active substance C, is preferable because a uniform thin film is formed.

In this example, methyl stearate (surfactant E) of a linear saturated fatty acid ester shown below was used as a nonionic surfactant mixed with a monomolecular film composed of a cationic surfactant.

CH ₃ (CH ₂ ) ₁₆ COOCH ₃ Surfactant E As the anionic surfactants, the following linear saturated fatty acids, stearic acid (surfactant F) and octadecanesulfonic acid (surfactant G) are used. did.

CH ₃ (CH ₂ ) ₁₆ COOH Surfactant F CH ₃ (CH ₂ ) ₁₇ SO ₃ H Surfactant G As the anionic surfactant, a linear saturated fatty acid or a linear hydrocarbon sulfonic acid can be used. It is also effective to use a fatty acid, sulfonic acid, phosphoric acid or the like having a long hydrocarbon chain of more than two. Surfactants which form salts of these acids can also be used.

Example 1 Cationic surfactant C and nonionic surfactant E were used as monomolecular film components in a ratio of 1: 2, 1: 5 and 1:10.
A developed sample prepared to have the composition described above was prepared.

Using an aqueous solution in which spiropyran B was dissolved at a concentration of 6 μM as an aqueous phase, a monolayer developed sample prepared at the gas-liquid interface was developed to form a monolayer.

After compression at 10 mm / min to a surface pressure of 35 mN / m, the solution was left under constant pressure for 30 minutes to form spiropyran B on the monomolecular film.

The monomolecular film at the gas-liquid interface is surface-pressured to 35 mN by the LB method.
When 7 layers were accumulated on a quartz plate substrate under the conditions of / m and a cumulative speed of 10 mm / min, a high-quality thin film could be formed and was homogeneous and colored blue.

FIG. 1 shows absorption spectra of spiropyran thin films of each composition.

As can be seen from FIG. 1, as the proportion of the nonionic component E increases, the amount of ion complex formed per unit area decreases, and the absorption intensity decreases.

Further, in the 1: 2 LB film, the spiropyran B colored state forms a J association pair to form a deep blue color (absorption maximum wavelength of about 616 nm).
m), whereas in 1 to 10, the space occupied by the spiropyran substance increases and the mutual interaction is relaxed,
The absorption of the monomer (the maximum absorption wavelength of about 580 nm) is shown.

Since the J-aggregate was formed in the 1: 2 LB film, the colored state was stabilized, and the absorbance hardly changed when irradiated with visible light at 25 mW / cm ² for 30 minutes.

However, in 1 to 10, a decrease in absorbance of 80% or more due to irradiation at the same energy and at the same time was observed.

From these results, it is possible to control the photochromic reaction characteristics accompanying the control of the association by controlling the composition ratio by mixing the nonionic surfactant with the cationic surfactant forming the ion complex.

Example 2 As a monomolecular film component, a cationic surfactant D and anionic surfactants F and G were used in a ratio of 1: 0.2: 0, 1: pair.
A developed sample was prepared with a composition of 0.2 to 0.5.

Using an aqueous solution in which spiropyran A was dissolved at a concentration of 5 μM as an aqueous phase, a monomolecular film developed sample prepared at the gas-liquid interface was developed to form a monomolecular film.

After compression at a pressure of 10 mm / min to a surface pressure of 35 mN / m, spiropyran A was ion-complex formed on the monomolecular film by standing at a constant pressure for 30 minutes.

The monomolecular film at the gas-liquid interface is surface-pressured to 35 mN by the LB method.
/ m and a cumulative speed of 10 mm / min, five layers were accumulated on a quartz plate substrate.

Each of the prepared thin films was colorless and transparent and had good film quality.

In the 1: 0.2: 0 LB film, the color of spiropyran A formed a J-aggregate by irradiation with ultraviolet light and showed a blue color (absorption maximum wavelength of about 578 nm). Neutralization of the anionic group and the cationic group between the surfactants in the membrane occurs, the space occupied by spiropyran A increases, and the mutual interaction between molecules is relaxed, and the absorption of the monomer ( Absorption maximum wavelength of about 550 nm).

The attenuation of the absorbance of the colored body was evaluated in the dark state of the two LB films.

The half-life of the LB film of 1 to 0.2 to 0 forming the J-aggregate was about 1 month, whereas the half-life of the LB film was 1 to 0.2 to 0 for the monomer.
The half-life was 30 minutes for the 0.5 LB film.

From these results, it was possible to control the formation of the aggregate by mixing the anionic surfactant with the cationic surfactant which forms the ion complex and control the composition ratio, thereby controlling the coloring state of the photochromic reaction.

Effect of the Invention As described above, an aqueous solution in which the photochromic substance having an anionic group of the present invention is dissolved is used as an aqueous phase, a cationic surfactant is developed to form a monomolecular film, and an ion complex is formed at the interface. A method for producing a photochromic thin film by mixing at least one kind of nonionic surfactant or at least one kind of anionic surfactant in the monomolecular film, whereby the photochromic reaction characteristics are controlled, and the film quality is improved. A good quality thin film could be provided.

[Brief description of the drawings]

FIG. 1 is an absorption spectrum diagram of a photochromic thin film produced in one example of the present invention.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C09K 9/02 G03C 1 / 74,1 / 685 G02F 1/17

Claims (7)

(57) [Claims] An aqueous solution in which a photochromic substance of a spiropyran compound having an anionic group is dissolved is used as an aqueous phase, and a cationic surfactant mixed with at least one nonionic surfactant is developed to form a monomolecular film. A photochromic thin film comprising: a step of forming an ion complex monolayer at the gas-liquid interface; and a step of thinning the ion complex monolayer using a Langmuir-Blodgett method. 2. An aqueous solution in which a photochromic substance of a spiropyran compound having an anionic group is dissolved is used as an aqueous phase, and a cationic surfactant mixed with at least one anionic surfactant is developed to form a monomolecular film. A method for producing a photochromic thin film, comprising: a step of forming an ion complex monolayer at the gas-liquid interface thereof; and a step of thinning the ion complex monolayer using a Langmuir-Blodgett method. 3. The method for producing a photochromic thin film according to claim 1, wherein the anionic group is a sulfo group, a carboxyl group or a salt thereof. 4. A spiropyran compound having a chemical structure represented by the following general formula:
3. The method for producing a photochromic thin film according to item 1. Where X is H ⁺ or HN ⁺ (C ₂ H ₅ ) ₃ , R 1 is NO ₂ ,
R2 represents either H, of OCH _3. 5. The method according to claim 1, wherein the cationic surfactant is an amine having a linear saturated hydrocarbon chain, and at least one of the linear saturated hydrocarbon chains has 8 to 30 carbon atoms. Or the method for producing a photochromic thin film according to 2. 6. The method for producing a photochromic thin film according to claim 1, wherein the nonionic surfactant is a linear saturated fatty acid ester. 7. An anionic surfactant comprising a carboxylic acid,
3. The method for producing a photochromic thin film according to claim 2, wherein the photochromic thin film is a sulfonic acid or a salt thereof, which has a monomolecular film and has at least one hydrocarbon chain having 8 to 30 carbon atoms.