JPH05202190A - Production of hybrid silica gel - Google Patents

Abstract

PURPOSE:To obtain hybrid silica gel having excellent light durability, chemically fixed in silica gel by treating a silicon alkoxide with a photochromic compound containing an alkoxysilyl group in the molecule in the presence of an alkali metal compound. CONSTITUTION:(A) A silicone alkoxide such as tetraethoxysilane or phenyltriethoxysilane is treated with (B) a photochromic compound containing an alkoxysilyl group in the molecule in the presence of (C) an alkali metal compound such as sodium methoxide or lithium hydroxide, co-hydrolyzed and condensed to give hybrid silica gel having photochromic properties.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing hybrid silica gel having photochromic properties, and more particularly to a method for producing photochromic hybrid silica gel having improved durability as a photochromic material.

[0002]

2. Description of the Related Art Conventionally, the sol-gel method has been known as a low temperature synthesis method for silica glass, and a siloxane bond is formed from a raw material in a solution state by hydrolysis and polycondensation reaction to form a silicon oxide. Is. In the case of producing a binary or higher oxide, the raw materials can be mixed on a molecular order, so that a uniform copolymerized oxide can be produced. Further, in the synthesis of silica glass by the melting method, a substance that decomposes at a high temperature such as an organic substance cannot be doped into the silica glass, but the sol-gel method of solution mixing synthesizes glass at a relatively low temperature. As a result, it is possible to dope organic substances into the silica glass. Studies on doping various dyes into silica gel using this method have been conducted, for example, Makishima et al. (J. Am. Ceram. Soc, 69 (4) 198).
6), Tani et al. (J. Appl. Phys, 58 (9) 1.Nov.1985), David AVN.
IL et al. (J. Non. Cry. Solids, 74, 1985, 395) have been introduced.

We have long been conducting research on doping functional organic substances into silica gel particles. So far, we have succeeded in doping the functional dyes such as photochromic compounds into silica gel and expressing the function in silica gel. Furthermore, they have found that the photochromic compound having an alkoxysilyl group can be chemically immobilized in silica gel to prevent the photochromic compound from being eluted from the silica gel.

[0004]

However, it has been newly found that the photochromic compound immobilized in silica gel by the above method may have low durability. The cause was presumed as follows as a result of examination. When an organic substance is contained, it cannot be heat-treated at a high temperature, so many hydroxyl groups remain in the silica gel, and the amount of acid sites in the silica gel is quite large.
Corresponds to pH 3-4. Therefore, the doped photochromic compound is prone to deterioration, and particularly in the case of the photochromic compound, deterioration reaction is promoted by light irradiation and oxidative deterioration is remarkable. Therefore, conventional silica gels exhibiting photochromic properties have not been practically sufficient in terms of durability, and it has been important to solve these problems.

The object of the present invention is to reduce the acid sites or the acid strength of silica gel as a method for suppressing the deterioration of the photochromic compound immobilized in hybrid silica gel.

[0006]

Means for Solving the Problems As a result of intensive research conducted by the present inventor to solve the above-mentioned problems of the prior art,
We have succeeded in improving the durability of photochromic properties of silica gel doped by chemically immobilizing a compound exhibiting photochromic properties by controlling the acid strength of silica gel.

That is, the present invention provides the general formula (1) or (2) Si (OR ¹ ) ₄ (1) (wherein R ¹ represents a hydrogen atom or an alkyl group) R ² _n Si (OR ³ ) _4-n (2) (in the formula, R ² represents an alkyl group, an alkenyl group, or a phenyl group, R ³ represents a hydrogen atom or an alkyl group, and n represents an integer of 1 or 2) The silicon alkoxide to be reacted with a photochromic compound having an alkoxysilyl group to synthesize silica gel,
Then, the silica gel is subjected to the general formula (3) M (OR) n (3) (wherein M is an alkali metal atom or an alkaline earth metal atom, n is a valence of the metal M, and R is a hydrogen atom or an alkyl group). Each of the above) is treated with an alkali metal compound represented by the formula (1).

In another invention, M (OR) n (3) (wherein M is an alkali metal atom or an alkaline earth metal atom) in the presence of an alkali metal compound represented by the general formula (3), n represents the valence of the metal M, and R represents a hydrogen atom or an alkyl group, respectively.) General formula (1) or (2) Si (OR ¹ ) ₄ (1) (In the formula, R ¹ is a hydrogen atom or an alkyl group. R ² _n Si (OR ³ ) _4-n (2) (In the formula, R ² represents an alkyl group, an alkenyl group, or a phenyl group, R ³ represents a hydrogen atom or an alkyl group, and n Is an integer of 1 or 2.) and a photochromic compound having an alkoxysilyl group are reacted with a silicon alkoxide, and a method for producing a photochromic hybrid silica gel.

The present invention will be described in detail below.

The photochromic hybrid silica gel (hereinafter referred to as "photochromic gel") of the present invention means that a so-called sol-gel method is used to chemically give silica gel a photochromic property by using an organic compound exhibiting the photochromic property. The photochromic compound is dispersed and contained in molecular units or clusters after being fixed. The shape of the photochromic gel is not limited at all, and may take any form such as a thin film, a bulk gel, a fiber and particles.

As the silicon alkoxide represented by the general formula (1) used in the production method of the present invention, tetramethoxysilane, tetraethoxysilane, tetramethylsilane, tetraethoxysilane, tetra, etc. wherein R ¹ is a methyl group, an ethyl group, a propyl group, a butyl group or the like. Examples include propoxysilane and tetrabutoxysilane.

In the silicon alkoxide represented by the general formula (2) which is also used for production, R ² is an alkyl group, an alkenyl group or a phenyl group. Examples of the alkyl group include linear or branched alkyl groups such as methyl group, ethyl group, propyl group, butyl group, octyl group, decyl group and octadecyl group. Examples of the alkenyl group include linear or branched alkenyl groups such as an ethenyl group, a propenyl group, a butenyl group and a hexenyl group. R ³ represents an alkyl group, and preferably the same substituents as those exemplified for R ¹ can be mentioned.

Specific examples of the silicon alkoxide of the general formula (2) include phenyltrimethoxysilane, phenyltriethoxysilane, methyltrimethoxysilane,
Ethyltrimethoxysilane, propyltrimethoxysilane, n-butyltrimethoxysilane, isobutyltrimethoxysilane, n-hexyltrimethoxysilane, n-
Octadecyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, amyltriethoxysilane, n-octyltriethoxysilane, n-octadecyltriethoxysilane, n-dodecyltriethoxysilane, methyltributoxysilane, ethyltributoxy Examples thereof include silane, ethyltripropoxysilane, vinyltriethoxysilane, allyltriethoxysilane, diphenyldimethoxysilane, dimethyldiethoxysilane, and vinylmethyldiethoxysilane.

Although the silicon alkoxide of the general formula (1) and the silicon alkoxide of the general formula (2) may be used alone, those of the general formula (1) improve the strength of the photochromic gel and have a physical durability. Of the general formula (2) has the effect of decreasing the acid sites of the photochromic gel and improving the chemical durability.
They can be used in combination at any ratio depending on the desired physical properties of silica gel.

The photochromic compound having an alkoxysilyl group used in the present invention (hereinafter referred to as a silyl group-containing photochromic compound) is not particularly limited as long as it has an alkoxysilyl group cohydrolyzable with the above-mentioned silicon alkoxy in the molecule. Instead, various organic photochromic compounds can be used. For example, a compound obtained by introducing an alkoxy group into a photochromic compound such as azobenzenes, spiropyrans, and spiroxazines is preferably used. Specific examples of the compound group are shown below, but the compound group is not limited thereto.

[0016]

[Chemical 1]

[0017]

[Chemical 2]

Since the photochromic compound has an alkoxysilyl group in the molecule, it can be condensed with the silicon alkoxide by hydrolysis to form a Si--O--Si bond and chemically bond with silica gel. it can.

In M (OR) n represented by the general formula (3) used in the production method of the present invention, M is an alkali metal atom or an alkaline earth metal, n is a valence of the metal M, and R is R.
Represents a hydrogen atom or an alkyl group, respectively. Specifically, when R is an alkyl group, lithium methylate, lithium ethylate, lithium propionate, sodium methylate, sodium ethylate, sodium propionate, potassium methylate, potassium ethylate, potassium propionate, magnesium dimethoxide. , Calcium dimethoxide, barium dimethoxide, strontium dimethoxide, calcium dimethoxide and the like. Of these, solid ones are preferably used after being dissolved in a solvent such as alcohol in order to uniformly proceed the reaction treatment.

When R is hydrogen, examples thereof include lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide, strontium hydroxide, calcium hydroxide and barium hydroxide. Also in this case, it is preferable to use an aqueous solution or an alcohol solution.

The photochromic gel of the present invention is manufactured by the following two methods.

The first method is to coexist an alkali metal compound represented by the general formula (3) with the general formula (1) or (2).
Is a method of reacting a silicon alkoxide represented by and a silyl group-containing photochromic compound, and producing by co-hydrolysis and condensation reaction. This method is a so-called sol-gel method, and known methods can be adopted without any limitation.

For example, co-hydrolysis and condensation are performed by reacting the above-mentioned three kinds of compounds in an aqueous acidic alcohol solution having a pH of 2-3 and a molar ratio of 10-40. Specifically, a silicon alkoxide and a silyl group-containing photochromic compound are partially reacted in an acidic alcohol aqueous solution to form an oligomer, and then 1 to 0.01 mol of an alkali metal compound is added to 1 mol of the silicon alkoxide. After mixing with the alcoholic solution containing it, the reaction is further advanced to produce a photochromic gel. If the amount of the alkali metal compound used exceeds the above range, the silica gel tends to be dissolved and the matrix itself tends to be affected, which is not preferable. If it is less than the above range, the effect of addition is small.
Of course, co-hydrolysis and condensation of the silicon alkoxide and the silyl group-containing photochromic compound may be performed in an acidic alcohol aqueous solution containing an alkali metal compound in advance.

The former method of once producing an oligomer is preferably employed because it can produce various forms of photochromic gel as described in detail below.

For example, in the case of producing a particle-shaped photochromic gel, a mixed solution containing the above-mentioned alkali metal compound and oligomer is added dropwise to a 10 to 20 times volume of aqueous ammonia-alcohol solution at pH 10 to 13 to make an emulsion. A method is adopted in which a liquid is obtained and the obtained solid is recovered by centrifugation or the like. Further, in the case of producing a bulk photochromic gel, for example, a method in which the mixed solution is placed in a container having small holes and allowed to stand to allow the reaction to proceed and the solvent to gradually volatilize is suitable. Further, a thin film photochromic gel can be produced by dip-coating or spin-coating the above mixed solution on a substrate.

The amount of the silyl group-containing photochromic compound used is not particularly limited and can be used in an arbitrary ratio, but it is usually used in an amount of 0.2 to 1 times the mol of the total amount of silicon alkoxide.

A reaction solvent is usually used for the purpose of allowing the hydrolysis and condensation reaction to proceed uniformly, but alcohol is preferably used. As this alcohol, methanol,
Examples include ethanol, propanol, and butanol.

As mentioned above, in order to accelerate the hydrolysis and condensation reactions, it is a preferred embodiment to use an acidic catalyst such as hydrochloric acid, sulfuric acid, acetic acid or citric acid, or a basic catalyst such as sodium hydroxide or ammonia. .. Water is a component necessary for the hydrolysis reaction, and the amount used is appropriately selected depending on the amount of the substance to be hydrolyzed, the form of the obtained photochromic gel and the like.

The hydrolysis temperature is not particularly limited as long as it does not decompose the added silyl group-containing photochromic compound. The higher the temperature is, the faster the hydrolysis proceeds, but when an acidic catalyst is added during the hydrolysis, high temperature promotes oxidative deterioration, so about 10 to 60 ° C. is preferable.

After hydrolysis, heat treatment is usually carried out to remove water and alcohol remaining in the gel. The heat treatment temperature varies depending on the intended product, but is not particularly limited as long as the photochromic function of the photochromic compound portion is not lost. Usually 100 ~
Processed at 200 ° C.

Another method for producing the photochromic gel of the present invention is to react a silicon alkoxide represented by the general formula (1) or (2) with a silyl group-containing photochromic compound, and once carry out a hybridization by a cohydrolysis or condensation reaction. In this method, silica gel is produced and then treated with an alkali metal compound represented by the general formula (3).

For example, a silicon alkoxide represented by the general formula (1) or (2), an organoalkoxysilane, and a silyl group-containing photochromic compound are added to pH 2 to 3
The resulting oligomer is hydrolyzed with the aqueous acidic alcohol solution to further advance the reaction to form a hybrid silica gel, which is then reacted with the alkali metal compound represented by the general formula (3).

Usually, both are reacted in an organic solvent such as alcohol, and then the solvent is removed. The shape of the hybrid silica gel is not particularly limited, such as thin film and particles. In the case of particles, it is preferable to disperse the particles to be treated in advance in a solvent and then mix them with an alcohol solution of an alkali metal compound. A method of performing ultrasonic treatment for a certain period of time is also suitable for sufficiently dispersing.

Also in this second production method, the production conditions such as the solvent, catalyst, hydrolysis temperature and heat treatment temperature in the previous production method are also adopted. However, when the silicon alkoxide of the general formula (1) and the silicon alkoxide of the general formula (2) are used in combination, when the amount of the latter is large, the particles of the latter alone tend to be generated, and therefore, it is usually 5 ˜40 mol%.

The second production method is a preferable method because the treatment agent does not affect the synthesis of silica gel itself because it is treated with an alkali metal compound after the production of hybrid silica gel, but a large-sized bulk photochromic gel is produced. In this case, it is difficult to treat the inside even with a porous body, so the first manufacturing method is preferably adopted. In the case of a thin film-shaped or particle-shaped photochromic gel, the same thing can be obtained even if either method is adopted.

When an alkali metal compound in which R is an alkyl group is used, the compound immediately reacts with M to react with M.
The second production method is preferably adopted when it is necessary to produce silica gel in an aqueous solution system because it tends to be (OH) n.

[0037]

[Operation and effect] The photochromic gel produced by the present invention reduces the acid sites in the silica gel and reduces the acid strength by subjecting it to a reaction treatment in the presence or absence of an alkali metal compound during or after the production of silica gel. It is a thing. As a result, it is possible to prevent deterioration of the compound portion exhibiting photochromic characteristics that easily cause deterioration, and improve the durability of the photochromic characteristics.

Of course, since the photochromic compound portion is chemically bonded and fixed to silica gel, the photochromic compound does not elute with an organic solvent or the like. Furthermore, when the silicon alkoxide of the general formula (1) and the silicon alkoxide of the general formula (2) are used together as a silica gel raw material, the gel itself has sufficient strength and is excellent in solvent resistance and heat resistance. For example, photochromic hybrid silica gel particles produced using only the silicon alkoxide of the general formula (2) swell in ethanol, dissolve in tetrahydrofuran, and have a melting point near 160 ° C. On the other hand, the hybrid silica gel particles produced by using the silicon alkoxide of the general formula (1) in combination with 10 mol% do not dissolve in ethanol and do not have a melting point until the organic group burns. Further, when it is used together in an amount of 30 mol%, it will not dissolve in tetrahydrofuran.

[0039]

The present invention will be described in more detail with reference to the following examples and comparative examples, but the present invention is not limited to these examples.

Example 1 2 g of tetraethoxysilane and spirooxazine (a)
PH of 3 in a solution of 0.24 g in 20 ml of ethanol
4.5 ml of hydrochloric acid aqueous solution of was added, and the mixture was stirred at 25 ° C. for 5 hours. 1.1 g of a 28 wt% sodium methoxide-containing methanol solution was added to the reaction solution, and the mixture was further stirred for 30 minutes.
This reaction liquid was added dropwise to an aqueous ammonia alcohol solution (25% aqueous ammonia 11.2 ml, ethanol 56 ml) with stirring. The produced solid was separated by centrifugation, washed with water and ethanol, and dried at 120 ° C. for 4 hours to obtain photochromic gel particles having a particle size of 0.2 to 0.4 μm.

When the surface acid strength of the silica gel particles was measured by an indicator method, the pKa was 5 to 6, and the acid strength was low.

Polymethylmethacrylate (PMMA) 2
g was dissolved in 40 ml of dioxane, and a dispersion of 0.02 g of the photochromic gel particles prepared by the above method in 2 ml of dioxane was mixed, followed by ultrasonic treatment, and then 1 ml of this preparation was placed in a petri dish. A cast film was prepared by evaporating the cast dioxane. This PMMA film is continuously irradiated with a Xe lamp,
The PMMA film was taken out every 30 minutes and the absorbance based on the photochromic reaction was measured. The results are shown in FIG. In this figure, the absorbance is the ratio with the initial absorbance based on the absorbance immediately after the start of irradiation. In the figure, by comparison with Comparative Example 1 which will be described later, it can be seen that the photochromic gel of the present invention has a doubled time in which the absorbance reaches 60% of the initial absorbance, and the light durability is improved.

When the above obtained photochromic gel was subjected to Soxhlet extraction with ethanol, the same photochromic properties as those before the extraction were shown after the extraction.

Comparative Example 1 2 g of tetraethoxysilane and spirooxazine (a)
To a solution prepared by dissolving 0.24 g in 20 ml of ethanol,
3, hydrochloric acid-ethanol aqueous solution 3.6 ml (water 0.2 m
1) was added, and the mixture was stirred at 25 ° C. for 5 hours. The reaction solution was treated with an ammonia-ethanol aqueous solution (25% ammonia water 1
1.2 ml, ethanol 56 ml) was added dropwise with stirring. The produced solid was separated from the reaction solution by centrifugation, washed with water and ethanol, and then dried at 120 ° C. for 4 hours to obtain silica gel particles having photochromic properties.

When the surface acid strength of the silica gel particles was measured in the same manner as in Example 1, the pKa was 3-4. or,
A cast film was prepared in the same manner as in Example 1, and the change in absorbance with time was measured. Figure 1 together with the results
It was shown to.

Example 2 2 g of tetraethoxysilane and spirooxazine (a)
PH of 3 in a solution of 0.24 g in 20 ml of ethanol
4.5 ml of hydrochloric acid aqueous solution of was added, and the mixture was stirred at 25 ° C. for 5 hours. 1.1 g of a 28 wt% sodium methoxide-containing methanol solution was added to the reaction solution, and the mixture was further stirred for 30 minutes. This reaction solution was covered with a lid having small holes to gradually expose the solvent. It was sufficiently dried to form a xerogel and then dried at 120 ° C. for 4 hours to prepare a photochromic gel.

The pKa of this photochromic gel was 6. After crushing this photochromic gel once,
When pelletized and continuously irradiated in the same manner as in Example 1, the absorbance half-life was 1.8 times that of the silica gel of Comparative Example 2 produced using only tetraethoxysilane described below. Extended to.

Comparative Example 2 20 g of tetraethoxysilane and spirooxazine (a)
To a solution of 2.4 g dissolved in 20 ml of ethanol, pH 3
45 ml of aqueous hydrochloric acid solution (2.5 ml of water) was added to
The mixture was stirred at ° C for 15 hours. The reaction solution was allowed to stand, a lid with small holes was placed, and the solvent was gradually evaporated. It was sufficiently dried to form a xerogel and then dried at 120 ° C. for 4 hours to produce silica gel.

Pellets were prepared from this silica gel in the same manner as in Example 2, and the change in absorbance with time was examined.

Example 3 A reaction solution containing sodium methoxide prepared in the same manner as in Example 2 was dip-coated on a clean glass substrate. After the solvent was volatilized, heat treatment was performed at 120 ° C. for 10 minutes, cooling was performed, and then dip coating was performed again.
After repeating this operation 10 times, it heat-processed at 120 degreeC for 4 hours, and obtained the gel film.

The pKa of this gel film was 5-6. Further, when continuous irradiation with a Xe lamp was performed in the same manner as in Example 1, the absorbance half-life was 2.1 times that of the film of Comparative Example 3 produced using only tetraethoxysilane described below. there were.

Comparative Example 3 A gel film was obtained from the reaction solution containing no sodium methoxide prepared in the same manner as in Comparative Example 2 by the same dip coating method as in Example 3. The change with time in the absorbance of the film based on the photochromic reaction was examined in the same manner as in Example 3.

Example 4 2 g of tetraethoxysilane and spirooxazine (a)
To a solution prepared by dissolving 0.24 g in 20 ml of ethanol,
Hydrochloric acid ethanol-3 aqueous solution 3.6 ml (water 0.2 m
1) was added, and the mixture was stirred at 25 ° C. for 5 hours. The reaction solution was treated with an ammonia-ethanol aqueous solution (25% ammonia water 1
1.2 ml, ethanol 56 ml), the mixture was added dropwise with stirring, separated, washed and dried to prepare hybrid silica gel particles. 0.6 g of the silica gel particles were dispersed in 20 ml of a methanol solution containing 3.24 × 10 ^-2 g of sodium methoxide, and ultrasonicated for 1 hour. The particles were collected by centrifugation, washed with water and ethanol, and then heat-treated at 120 ° C. for 4 hours to obtain photochromic gel particles.

The pKa of the photochromic gel particles is 5
Met. Further, when a PMMA film was prepared in the same manner as in Example 1 and the light durability was examined, silica gel particles (pKa = 3 to 4) produced in the same manner as in this example except that the treatment with sodium methoxide was not carried out. Prepared from P
It was found that the half-life of absorbance was 1.7 times that of the MMA film, and the light durability was improved.

Example 5 2 g of tetramethoxysilane, 2 g of allyltrimethoxysilane and 0.45 g of spiropyran (e) were added to 2 parts of methanol.
To a solution dissolved in 0 ml, 3.6 ml of a pH 2 hydrochloric acid-methanol aqueous solution (0.2 ml of water) was added, and the mixture was stirred at 25 ° C. for 5 hours. The reaction solution was dip-coated on a clean glass substrate. After the solvent was volatilized, heat treatment was performed at 120 ° C. for 10 minutes, cooling was performed, dip coating was performed again, and this operation was repeated 10 times to obtain a film. The film is immersed in 20 ml of an aqueous solution containing 1.4 × 10 ^-2 g of lithium hydroxide for 1 hour, and then 120
It heat-processed at 4 degreeC for 4 hours, and obtained the photochromic gel film. The film exhibited photochromic activity which was colored by irradiation with ultraviolet rays and was erased by irradiation with visible light. It was also found that the half-life of the absorbance was 1.5 times that of the one not immersed in the aqueous lithium hydroxide solution, and the light durability was improved.

Example 6 2 g of tetraethoxysilane and 0.2 of azobenzene (g)
To a solution of 4 g dissolved in 20 ml of ethanol, 3.6 ml of hydrochloric acid-ethanol solution having a pH of 3 (0.2 ml of water) was added, and the mixture was stirred at 25 ° C for 5 hours. Aqueous ammonia-alcohol solution (25% aqueous ammonia 11.2 ml,
The mixture was dropped into ethanol (56 ml) with stirring, separated, washed and dried to prepare hybrid silica gel particles. 0.6 g of the silica gel particles were dispersed in 20 ml of an aqueous solution containing 3.0 × 10 ^-2 g of potassium hydroxide, and ultrasonicated for 1 hour. The particles were collected by centrifugation, washed with water and ethanol, and dried at 120 ° C. for 4 hours to obtain photochromic gel particles.

When the photochromic gel particles were alternately irradiated with ultraviolet rays and visible light, it was observed that the photochromic characteristics due to cis-trans photoisomerization were rapidly obtained.

Further, a PMMA film was prepared from the silica gel particles in the same manner as in Example 1 and the change in absorbance with time was examined. As a result, the half-life was 1.7 as compared with that not treated with potassium hydroxide. Doubled.

Example 7 To a solution of 2.1 g of phenyltriethoxysilane and 0.45 g of spiropyran (e) dissolved in 20 ml of ethanol was added 4.5 ml of a hydrochloric acid aqueous solution having a pH of 3, and the mixture was stirred at 25 ° C. for 1 hour.
Stir for 5 hours. Tetraethoxysilane 0.
8 g was added, and the mixture was further stirred for 5 hours. Aqueous ammonia-alcohol solution (25% ammonia water 11.2
ml, ethanol 56 ml) with stirring, and then separated, washed and dried to prepare hybrid silica gel particles. 0.6 g of the silica gel particles were dispersed in 20 ml of an aqueous solution containing 1.4 × 10 ⁻² g of lithium hydroxide, and ultrasonicated for 1 hour. Collect the particles by centrifugation, wash with water and ethanol, 120 ° C
Photochromic gel particles were obtained by drying for 4 hours.

A PMMA film was prepared using the photochromic gel particles in the same manner as in Example 1 and examined for light durability. As a result, the half-life of absorbance was 1. 0 as compared with that not treated with lithium hydroxide. It stretched four times.

[Brief description of drawings]

FIG. 1 is a PMMA containing photochromic (hybrid silica) gel particles prepared in Example 1 and Comparative Example 1.
It is a figure which shows the time-dependent change of the light absorbency based on the photochromic reaction of a film.

Claims (2)

[Claims] 1. General formula (1) or (2) Si (OR ¹ ) ₄ (1) (In the formula, R ¹ represents a hydrogen atom or an alkyl group.) R ² _n Si (OR ³ ) _4-n (2) (wherein R ² represents an alkyl group, an alkenyl group, or a phenyl group, R ³ represents a hydrogen atom or an alkyl group, and n represents an integer of 1 or 2). And a photochromic compound having an alkoxysilyl group are reacted to synthesize silica gel,
Then, the silica gel is subjected to the general formula (3) M (OR) n (3) (wherein M is an alkali metal atom or an alkaline earth metal atom, n is a valence of the metal M, and R is a hydrogen atom or an alkyl group). Each of the above) is treated with an alkali metal compound represented by the formula (1). 2. In the presence of an alkali metal compound represented by the general formula (3), M (OR) n (3) (wherein, M is an alkali metal atom or an alkaline earth metal atom, and n is a metal). R represents a hydrogen atom or an alkyl group, respectively.) General formula (1) or (2) Si (OR ¹ ) ₄ (1) (In the formula, R ¹ represents a hydrogen atom or an alkyl group. R ² _n Si (OR ³ ) _4-n (2) (In the formula, R ² represents an alkyl group, an alkenyl group, or a phenyl group, R ³ represents a hydrogen atom or an alkyl group, and n is 1 or The method for producing a photochromic hybrid silica gel is characterized by reacting a silicon alkoxide represented by the formula 2) with a photochromic compound having an alkoxysilyl group.