JPH06148791A - Photochromic thin film and production thereof - Google Patents

Abstract

PURPOSE:To improve the heat stability of an anionic photochromic molecule and to improve the characteristic as a optical recording material. CONSTITUTION:In the photochromic thin film, the anionic photochromic molecule such as anionic spiropylanes compd. and the nonpolar molecule such as arom. hydrocarbon is adsorped on the heat decomposition product thin film of unorg. lamellar crystal having anion adsorptivity such as hydrotalcite type compd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photochromic thin film, which is attracting attention as one of photon mode recording materials, and a manufacturing method thereof.

[0002]

2. Description of the Related Art Photon mode recording materials have received attention as next-generation optical recording materials capable of ultra-high density recording, and many studies have been made on photochromic materials. However, there are many problems regarding the stability, non-destructive read-out, repeated durability, etc. of the colored body, and it has not yet been put to practical use.

Spirobenzopyrans, which are a type of photochromic material, have a large difference in absorption spectrum before and after light irradiation, and are characterized in that various colors can be obtained by selecting a substituent, but they are thermally stable. It is not very popular. Therefore, a method of dispersing spirobenzopyrans in a binder resin has been attempted. However, in this case, there is a problem that the recording, reading, and erasing speeds decrease, and the performance as an optical recording material decreases.

Under these circumstances, Japanese Patent Publication No. 4-1677
No. 6, in a film having a composite layered structure of clay and a bilayer membrane obtained from an ion complex of a cationic surfactant having a linear higher alkyl group and an anionic layered clay compound, spirobenzo is disclosed. An optical recording material in which pyrans are dispersed is proposed. In this proposal, as the anionic layered clay compound, an ion-exchangeable silicate capable of inserting a cationic organic compound between layers, for example, montmorillonite is used. In addition, spirobenzopyrans are not listed as anionic ones. According to the publication, the bilayer film exhibits a phase transition behavior between clay layers, and at a temperature lower than the phase transition temperature, the film is in a lamellar crystalline state with low molecular mobility, and at a temperature higher than the phase transition temperature, the mobility is low. Since it has a high smectic liquid crystal state, it is said that recording can be performed rapidly at a temperature above the phase transition temperature, and stable recording can be stored at low temperatures below the phase transition temperature.

Further, in Japanese Patent Laid-Open No. 2-264246, as a proposal for easily and highly stably supporting a spiropyran on a solid phase matrix, a cationic spiropyran is used, and a silicic acid having a three-layer structure such as montmorillonite is used. The use of salt minerals (smectite group minerals) as a matrix is disclosed.

However, in these proposals, the stability of the anionic spiropyran compound cannot be improved, so that the selection of the substituent is limited, and the color development is limited.

In JP-A-4-151142, a photochromic substance having an anionic group and a cationic surface-active substance are used to form an ion complex, and a Langmuir-Blodgett method is used to form a thin film of the ion complex. However, it is difficult for the Langmuir-Blodgett method to uniformly form a large-area film, and it is difficult to industrially mass-produce the film.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the thermal stability of anionic photochromic molecules and the characteristics of optical recording materials.

[0009]

These objects are achieved by the present invention described in (1) to (8) below. (1) A photochromic thin film having a structure in which an anionic photochromic molecule and a nonpolar molecule are adsorbed on a thermally decomposed substance thin film of an inorganic layered crystal having anion adsorption capability. (2) The photochromic thin film according to (1) above, wherein the anionic photochromic molecule is a spiropyran compound. (3) The photochromic thin film according to (1) or (2), wherein the inorganic layered crystal is a hydrotalcite type compound. (4) The photochromic thin film according to any one of (1) to (3) above, wherein the non-polar molecule is an aromatic hydrocarbon. (5) A method for producing the photochromic thin film according to any one of (1) to (4) above, wherein the reaction liquid in which anionic photochromic molecules are dissolved in a nonpolar solvent is used to heat an inorganic layered crystal having anion adsorption ability. A method for producing a photochromic thin film, comprising a step of immersing a thin film of a decomposed substance so that an anionic photochromic molecule and a nonpolar molecule are adsorbed to the thin film of the thermally decomposed substance. (6) The method for producing a photochromic thin film according to the above (5), wherein an aqueous dispersion of fine particles of inorganic layered crystals having anion adsorption ability is formed into a film, dried, and then heat-treated to form the thermally decomposed product thin film. (7) The method for producing a photochromic thin film according to (6) above, wherein the concentration of the aqueous dispersion is 0.1 to 5% by weight. (8) As the heat treatment, a pyrolysate thin film of 400 to 60 is used.
The above (6) or (7), which is maintained at 0 ° C. for 0.1 to 5 hours.
Method for manufacturing photochromic thin film of.

[0010]

In the present invention, the thermal decomposition product thin film of an inorganic layered crystal having an anion adsorption ability such as a hydrotalcite type compound is provided with an anionic photochromic molecule such as an anionic spiropyran compound and an aromatic hydrocarbon or the like. Non-polar molecules are adsorbed. An anionic spiropyran-based compound can be adsorbed on the hydrotalcite-type compound, but photochromism is not exhibited by single adsorption. However, by co-adsorbing the anionic spiropyran-based compound and the nonpolar molecule, photochromism is exhibited, and the thermal stability of the colored body is remarkably improved.
In this case, the non-polar molecule is used as a solvent for the anionic photochromic molecule.

The reason why photochromism is exhibited by coadsorption with a non-polar molecule is considered to be that the mobility of the anionic spiropyran-based compound is increased by coadsorption and reversibility of the characteristic change due to light occurs.

The thermal decomposition product of the inorganic layered crystal on which the photochromic molecule is adsorbed is in the form of a thin film, and if a hydrotalcite type compound is used, it becomes a highly transparent thin film, so that the action of the photochromic molecule is not hindered and it is extremely excellent. S
/ N and contrast are obtained.

[0013]

Specific Structure The specific structure of the present invention will be described in detail below. The photochromic thin film of the present invention has a structure in which an anionic photochromic molecule and a non-polar molecule are adsorbed on a thermal decomposition product thin film of an inorganic layered crystal having anion adsorption ability.

As the inorganic layered crystal having an anion adsorption ability used in the present invention, a hydrotalcite type compound is particularly preferable.

The hydrotalcite type compound is MgO ₆
It is a clay mineral composed of an octahedral sheet consisting of AlO ₆ and ZnO _{6 and the} like, and the layered skeleton is cationic by substituting Al ³⁺ for Mg ²⁺ , Zn ^{2+ and the} like. . Therefore, an inorganic anion or anionic organic molecule can be incorporated between the layers. Hydrotalcite type compounds include, for example, “Surface vol.30, No.7, 598-607, (1992)
, Etc.

The hydrotalcite type compound used in the present invention is not particularly limited, but a magnesium-aluminum hydrotalcite type compound is usually preferable. The magnesium-aluminum hydrotalcite type compound is
When carbonate ions are inserted between layers, {Mg _1-x A
l _x (OH) ₂ } (CO ₃ ) _{x / 2} (usually x is 0.2 to
0.33)}. The structure of the unit layer of the magnesium-aluminum hydrotalcite-type compound when ions are inserted between the layers is represented by the following chemical formula 1.

[0017]

[Chemical 1]

The anionic photochromic molecule can be selected from cis-trans isomers such as azo dyes and indigo dyes, ring-closing reaction types such as fulgide, ring-opening reaction types such as spiropyran compounds, and the like. It is preferable to use a spiropyran-based compound because of its excellent photochromic properties.

As the spiropyran compound,
The spirobenzopyran compound represented by the general formula shown in is preferable.

[0020]

[Chemical 2]

In the above chemical formula 2, X, R ¹ , R ² and R ³ are, for example, hydrogen atom, halogen atom, sulfone group, carboxyl group, phosphoric acid group, nitro group, hydroxyl group, alkyl group, alkylcarbonyl group, It can be appropriately selected from an alkylsulfonyl group, an alkyloxy group, an alkylcarbonyloxy group and the like, and X, R ¹ , R ² and R
^At least one of the ^three may be an anionic group. The alkyl group preferably has about 1 to 5 carbon atoms. The alkyl group may have a substituent such as a sulfone group, a carboxyl group, a phosphoric acid group, a nitro group, a hydroxyl group, an amino group, etc., and a part or all of hydrogen atoms may be substituted with a halogen atom. Good. Further, the sulfone group may form a salt with an amine such as triethylamine.

Specifically, a compound having an anionic property-imparting group, for example, a sulfone group, a carboxyl group or a phosphoric acid group, or a group having these groups at at least one position of X, R ¹ , R ² and R ³ is used. You can use it. Specific compound examples are shown in Table 1 below.

[0023]

[Table 1]

The non-polar molecule is a solvent when adsorbing the anionic photochromic molecule, and is adsorbed together when adsorbing the anionic photochromic molecule. The non-polar molecule to be used is not particularly limited, but aromatic hydrocarbons and other cyclic compounds such as benzene, toluene, xylene, cyclohexane, etc., or aliphatic hydrocarbons that are liquid at room temperature, their halides, ketones such as acetone, etc. It is preferable to select from the group, tetrahydrofuran and the like.

A preferred method for producing the photochromic thin film of the present invention will be described using a hydrotalcite type compound as the inorganic layered crystal. in this way,
First, an anionic photochromic molecule is dissolved in a nonpolar solvent to prepare a reaction solution. Next, the thermally decomposed substance thin film of the hydrotalcite type compound is immersed in the reaction solution.

The thermal decomposition product thin film is produced by forming an aqueous dispersion of fine particles of a hydrotalcite type compound into a thin film, drying it, and then subjecting it to heat treatment.

The concentration of the aqueous dispersion is 0.1 to 5% by weight.
It is preferable that By setting the concentration within the above range, a large-area film can be formed without cracking. When the concentration is less than the above range, it is difficult to form a uniform film, and when the concentration is more than the above range, cracking frequently occurs in the thin film during drying.

In order to form the aqueous dispersion into a film, it is possible to use a method capable of forming a uniform film, for example, a method of coating on a substrate using a dip coating method, a spin coating method, a casting method or the like. The material of the substrate in this case may be appropriately selected from glass, ceramics, resin and the like, but it is preferable to use a heat resistant material because heat treatment is performed after the film formation.

The thickness of the thin film is preferably 0.1 μm or more. It is difficult to form a homogeneous film having a thickness of less than 0.1 μm. There is no particular upper limit on the thickness of the thin film, but it is usually 100 μm or less. The thicker the film, the more the amount of the anionic photochromic molecules adsorbed, but when the film is thicker and has a larger area, the film is likely to crack. Therefore, when it is necessary to increase the thickness of the film, it is preferable to divide the film into units of small area to prevent cracking.
Specifically, for example, when applied to an optical disc, the substrate is provided with concentric or spiral grooves,
It is preferable to form a thin film in this groove. Further, when applied to a display panel for images and the like, it is preferable to provide a rectangular or circular concave portion for each pixel on the substrate and form a thin film in each concave portion.

The thin film formed as described above varies depending on the method for producing the hydrotalcite-type compound, but the hydrotalcite-type compound is used as the host species, and guest species such as carbonate ions are adsorbed between the layers. It consists of intercalation compounds.

The thin film thus formed is heat-treated to discharge at least a part of guest species such as carbonate ions. In this case, the heat treatment condition is preferably 400 to 600 ° C. and about 0.1 to 5 hours. If the treatment temperature is too low or the treatment time is too short, the guest species may not be sufficiently discharged, and it may be difficult to adsorb the photochromic molecule. If the treatment temperature is too high or the treatment time is too long, stress may occur in the thin film or the substrate, and the thin film may be cracked or peeled off. In addition, the material of the substrate is limited.

In the thin film subjected to such heat treatment, the hydrotalcite type compound loses at least a part of the guest species and becomes a pyrolyzed product in which a part of the structure is changed by thermal decomposition. The fact that the hydrotalcite-type compound is thermally decomposed and the structure is changed can be confirmed by an X-ray diffraction method. Specifically, it is recognized that the layer spacing of the layered crystal is narrowed, and the peak of the hydrotalcite type compound disappears, and a peak suggesting that it has changed to a rock salt type compound appears.

The thermally decomposed product thin film obtained by the heat treatment is immersed and held in a reaction solution in which an anionic photochromic molecule is dissolved in a nonpolar solvent, and the anionic photochromic molecule and the solvent constituent molecule are formed into a thermally decomposed product thin film. Adsorb. The temperature of the reaction liquid at this time is preferably about 0 to 80 ° C., and the holding time is preferably about 0.1 to 10 hours. Further, the reaction is preferably performed in an inert gas atmosphere. The concentration of the reaction solution is not particularly limited,
It may be appropriately set within the range of stable dissolution.

The photochromic thin film of the present invention has high transparency because it contains a thermal decomposition product of a hydrotalcite type compound as a main component. Specifically, it is in the visible range (wavelength 4
Optical density in the range of 0 to 800 nm) is 1000 cm ^-1
It can be:

The inorganic layered crystal having anion adsorption ability, the anionic photochromic molecule, and the nonpolar molecule may be produced according to a conventional method, or commercially available ones may be used.

[0036]

EXAMPLES The present invention will be described in more detail below by showing specific examples of the present invention.

The following solutions A and B were prepared. Solution A: a solution prepared by dissolving 8.0 g of NaOH and 0.53 g of Na ₂ CO ₃ in 1 liter of distilled water Solution B: 2.60 g of Mg (NO ₃ ) ₂ and Al (NO ₃ ) ₃
A solution of 1.60 g dissolved in 50 ml distilled water

Solution B was added to solution A at room temperature and stirred for 2 hours,
A white precipitate was obtained. The precipitate and the solvent were separated by a centrifuge, and the precipitate was washed 3 times with a solution having the same composition as solution A. Further, after washing three times with distilled water, the water was separated to obtain a jelly-like solid containing magnesium-aluminum hydrotalcite-type compound particles in which carbonate ions were incorporated between the layers. The content of the hydrotalcite-type compound in this solid was measured by a drying method (weighing after drying at 80 ° C. for 6 hours), and it was 9% by weight.

Next, a 1% by weight aqueous dispersion of a hydrotalcite type compound was prepared using the above solid, and was applied onto a clean glass substrate by the dip coating method, and then the solution was applied at 60 ° C. for 5 hours.
When dried for a time, a transparent continuous thin film having a thickness of about 2 μm was obtained. The optical density of this thin film at a wavelength of 400 nm was 100 cm ^-1 . As a result of X-ray diffraction, the layer spacing at this time was 8A. The absorption of visible light is 400 nm
Was the largest. The film thickness was determined by a step meter (DekTak), and the optical density was determined by a VIS-UV spectrophotometer.

When this thin film was heat-treated at 450 ° C. for 3 hours, transparency was almost maintained, no change in thickness was observed, and no peeling from the substrate was observed. The optical density of the thin film after heat treatment at 400 nm was 200 cm ^-1 . As a result of performing X-ray diffraction after the heat treatment, carbonate ions were desorbed and thermally decomposed, and changed to rock salt type magnesium-aluminum oxide (Mg _0.7 Al _0.3 O _1.15 ).
The layer spacing was found to be 4A.

The thin film after the heat treatment was formed into a spirobenzopyran compound (in the above Chemical Formula 2, X is H and R ¹ is-(CH ₂ ).
₃ SO ₃ H.N (C ₂ H ₅ ) ₃ , R ² is NO ₂ , and R ³ is a compound (SP-150 manufactured by Nippon Senshoku Co., Ltd.) in which the compound is immersed in a toluene solution (0.2 mM), and then nitrogen is added. Under the atmosphere 20
After being kept at ℃ for 1 hour, it was dried. This toluene solution was transparent. The thin film after drying has a pale pink color. When the absorption spectrum of the thin film was measured, it was 350 nm.
Large absorption was observed in the vicinity, and it was estimated that SP-150 was mainly adsorbed on the thin film as a decolorizer. Also,
As a result of X-ray diffraction, the layer spacing at this time was 4A.

When this thin film was irradiated with UV light of 254 nm for 5 minutes, it changed into a deep pink color, and it was 540 in spectroscopic measurement.
An increase in absorption around nm was observed, confirming clear photochromism. And visible light of 545 nm (10 mmW /
When it was irradiated with cm ² for 5 minutes, it became almost transparent.
And it was confirmed that these states were reversible. The dark pink state and the almost transparent state were stable for 3 hours or more.

For comparison, SP-150 was dissolved in ethanol, which is a polar solvent, to prepare a reaction solution, which was otherwise immersed and dried in the same manner as described above. Either after drying or after irradiation with UV light. The thin film was almost transparent, and neither absorption around 350 nm after drying nor absorption around 540 nm after UV irradiation was observed. Further, when the solvent of the reaction liquid is water, the reaction liquid is red, and the thin film dried after being immersed in the reaction liquid is also red, and SP-150 is mainly adsorbed in the thin film as a coloring material. It was considered. However, the color of the thin film did not change when exposed to visible light, and no photochromism was observed.

From the results of the above examples, the effect of the present invention is clear.

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[Procedure amendment]

[Submission date] August 25, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction content]

[0010]

In the present invention, the thermal decomposition product thin film of an inorganic layered crystal having an anion adsorption ability such as a hydrotalcite type compound is provided with an anionic photochromic molecule such as an anionic spiropyran compound and an aromatic hydrocarbon or the like. Non-polar molecules are adsorbed. An anionic spiropyran-based compound can be adsorbed on the hydrotalcite-type compound, but the photochromism is not clear when adsorbed alone. However, by co-adsorbing the anionic spiropyran-based compound and the nonpolar molecule, photochromism is clearly expressed, and moreover, the thermal stability of the colored body is remarkably improved. In this case, the non-polar molecule is used as a solvent for the anionic photochromic molecule.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0042

[Correction method] Change

[Correction content]

When this thin film was irradiated with UV light of 254 nm for 5 minutes, it changed into a deep pink color, which was 54 in spectroscopic measurement.
An increase in absorption near 0 nm was observed, and clear photochromism was confirmed. Then, visible light of 545 nm (10
When it was irradiated with mW / cm ² for 5 minutes, it became almost transparent. And it was confirmed that these states were reversible. The dark pink state and the almost transparent state were stable for 3 hours or more.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0043

[Correction method] Change

[Correction content]

For comparison, SP-150 was dissolved in ethanol, which is a polar solvent, to prepare a reaction solution, which was otherwise immersed and dried in the same manner as described above. Either after drying or after irradiation with UV light. In the above, the thin film was almost transparent, and neither absorption around 350 nm after drying nor absorption around 540 nm after UV light irradiation was observed. Also, when the solvent of the reaction solution is water, the reaction solution is red,
After soaking in the reaction solution, the dried thin film is yellow and has SP-150
It is thought that is mainly adsorbed in the thin film as a decolorized substance. However, the color of the thin film did not change much when irradiated with UV light, and no clear photochromism was observed.

Claims (8)

[Claims] 1. A photochromic thin film having a structure in which an anionic photochromic molecule and a non-polar molecule are adsorbed on a thermally decomposed substance thin film of an inorganic layered crystal having an anion adsorption ability. 2. The photochromic thin film according to claim 1, wherein the anionic photochromic molecule is a spiropyran compound. 3. The photochromic thin film according to claim 1, wherein the inorganic layered crystal is a hydrotalcite type compound. 4. The photochromic thin film according to claim 1, wherein the non-polar molecule is an aromatic hydrocarbon. 5. The method for producing the photochromic thin film according to claim 1, wherein the reaction liquid in which anionic photochromic molecules are dissolved in a nonpolar solvent is thermally decomposed to form an inorganic layered crystal having anion adsorption ability. 1. A method for producing a photochromic thin film, which comprises a step of immersing a thin film of a chemical substance so that an anionic photochromic molecule and a nonpolar molecule are adsorbed to the thermal decomposition substance thin film. 6. The method for producing a photochromic thin film according to claim 5, wherein the thermal decomposition product thin film is formed by forming an aqueous dispersion of fine particles of inorganic layered crystals having anion adsorption ability into a film, drying the film, and then heat treating the film. . 7. The concentration of the aqueous dispersion is 0.1 to 5% by weight.
7. The method for producing a photochromic thin film according to claim 6. 8. A thermally decomposed material thin film is used as the heat treatment.
The method for producing a photochromic thin film according to claim 6, which is held at 0 to 600 ° C. for 0.1 to 5 hours.