JP2002308623A - Thin film having fine pore structure and method for manufacturing fine pore structural body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a thin film of a tin oxide meso structural body provided with a fine pore structure having high structural regularity and a crystalline fine pore wall, and to provide a manufacturing method thereof. SOLUTION: The thin film has the fine pore structure formed by containing an oxide, holds a surfactant in the fine pore and contains tin oxide crystal in the fine pore wall. The manufacturing method for the fine pore structural body has a process for preparing a reaction solution containing a metallic compound and the surfactant, a process for applying the reaction solution on a substrate and a process for holding the substrate in an atmosphere containing steam.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a thin film having a pore structure and a pore structure. The present invention also relates to a porous inorganic oxide used for a catalyst, an adsorbent, and the like, and more specifically, to a tin oxide mesostructure and a method for producing the same.

[0002]

2. Description of the Related Art Porous materials are used in various fields such as adsorption and separation. As the functional material, it is desirable that the pore diameter is uniform. In recent years, porous silica having a structure in which pores having a uniform diameter are arranged in a honeycomb shape has been developed by two different methods almost simultaneously.

[0003] On the other hand, "Nature" Vol.
It is described on page 10, specifically, a substance called MCM-41 synthesized by hydrolyzing an alkoxide of silicon in the presence of a surfactant.

[0004] The other is "Journal of Che."
MICRO SOCIETY CHEMICAL CO
1993, p. 680, specifically, a substance called FSM-16 synthesized by intercalating alkylammonium between layers of kanemite which is a kind of layered silicic acid.

In both cases, it is considered that the structure of the porous silica is controlled by using an aggregate of surfactants as a template. It is known that porous silica having such a regular pore structure exhibits various macroscopic morphologies. Examples include thin films, fibers, microspheres, monoliths, and the like.

[0006] Porous silica is expected to be applied to functional materials such as optical materials and electronic materials in addition to catalysts and adsorption materials. In recent years, formation of a porous structure made of various materials such as transition metal oxides, metals, and sulfides as well as porous silica has been reported.

[0007]

In order to exhibit high functionality as a functional material, it is desirable that the pore wall of the pore structure be crystallized. Therefore,
An object of the present invention is to provide a method for producing a pore structure having a crystal structure on a pore wall. Another object of the present invention is to provide a thin film having a pore structure having a crystal structure on a pore wall.

[0008]

The method for producing a pore structure according to the present invention comprises a step of preparing a reaction solution containing a metal compound and a surfactant, a step of applying the reaction solution on a substrate, and a step of: A step of holding the substrate in an atmosphere containing water vapor.

Further, the thin film having a pore structure according to the present invention is a thin film having a pore structure containing an oxide, wherein a surfactant is retained in the pores, and It is characterized in that the pore walls contain tin oxide crystals.

[0010] The pore structure of the present invention is a tin oxide mesostructure having a honeycomb pore structure formed by using a surfactant as a template, and holds the surfactant in the pores. In addition, the structure has pores characterized by containing tin oxide crystals in the pore walls. Note that the honeycomb structure includes a hexagonal structure and a structure including the hexagonal structure which is slightly distorted.

Further, the tin oxide mesostructure is in the form of a film having a mesostructured selective orientation. Further, the average crystallite diameter L (nm) and the pore spacing M (nm) of the microcrystals calculated from the diffraction peaks observed by the X-ray diffraction analysis using the Scherrer equation and the Bragg equation are represented by the following equations ( 1)

[0012]

(Equation 2)

It is characterized by satisfying.

The average crystallite diameter calculated from the diffraction peak observed by X-ray diffraction analysis of the microcrystal using the Scherrer equation and the Bragg equation is 1 to 5 nm. Further, the tin oxide mesostructure is formed on a substrate.

In the present invention, humidity means relative humidity (%) unless otherwise specified. Relative humidity R
(%) Is defined as e (g / m ² ) representing the amount of water vapor (indicating absolute humidity) actually contained in an atmosphere containing water vapor, and E (g / m ² ) representing the amount of saturated water vapor at the temperature of the atmosphere. , Relative humidity R (%) = (e / E) × 100.

[0016]

(Embodiment 1) A method for manufacturing a pore structure according to the present invention will be described with reference to FIG. FIG. 1 is a process chart showing a method for forming a pore structure according to the present invention. In FIG. 1, step S1 is a step of preparing a reaction solution containing a compound containing a metal (indicating a metal compound) and a surfactant, step S2 is a step of applying the reaction solution on a substrate, and step S3 is a step of The step of holding the substrate in an atmosphere containing water vapor is shown.

First, as shown in step S1 of FIG. 1, a reaction solution is prepared. The reaction solution contains a compound containing a metal (metal compound) and a surfactant. Then, the reaction solution is applied on the substrate (Step S2). next,
The substrate is held in an atmosphere containing water vapor (Step S3).

By going through the steps S1 to S3,
The solvent of the reaction solution applied on the substrate is evaporated (dried)
At the same time, a membrane-like pore structure is formed. Here, the term “dry” includes the case where the surface of the film is dried while the surfactant is retained inside the pores.

Such a structure is formed because, as the solvent evaporates, the concentration of the surfactant exceeds the critical micelle concentration, self-assembly of the surfactant starts, and the compound containing the metal or the compound This is because the self-assembly of the intermediate formed from and the surfactant is promoted. In particular, S3
Through the process, a pore structure including a metal oxide crystal on the pore wall is obtained.

The crystals in the present invention include not only microcrystals, but also polycrystals and single crystals, and refer to crystals whose structure regularity is higher than that of amorphous. In the present invention, the pore structure also includes a structure in which a surfactant is held in pores.

The above reaction solution contains a compound containing a metal, a surfactant and a solvent. The metal in the compound containing a metal (metal compound) is specifically Ti, Zr, N
b, Ta, Al _, Si, Sn, W, Hf, and the like. In particular, tin oxide is said to exhibit properties as a semiconductor, and is expected to be applied to optical elements, gas sensors, and the like.

In the case of forming a pore structure containing tin oxide crystals in the pore walls, tin compounds such as stannous chloride and stannic chloride, tin isopropoxide and tin ethoxide may be used. And the like can be used. The pore structure including a crystal in the pore wall is, for example, a case where a porous pore wall is substantially microcrystallized.

The content of the metal compound contained in the reaction solution is in the range of 10 to 50% by weight, preferably 20 to 40% by weight.

A surfactant has a pore structure depending on its shape.
The pore size and its shape can be determined. Surface activity
Agents include, for example, non-ionic polyoxyethylene
Len (10) dodecyl ether <C₁₂H_{twenty five}(CH_TwoCH_Two
O)_TenOH>, polyoxyethylene (10) tetradeci
Ruether <C₁₄H₂₉(CH_TwoCH_TwoO) _TenOH>, poly
Oxyethylene (10) hexadecyl ether <C₁₆H
₃₃(CH_TwoCH_TwoO) _TenOH>, polyoxyethylene (1
0) Stearyl ether <C₁₈H₃₇(CH_TwoCH_TwoO)_Ten
OH>, polyoxyethylene (20) hexadecyl ether
Tell <C₁₆H₃₃(CH_TwoCH_TwoO) ₂₀OH>
Can be.

The pore diameter can be reduced as the alkyl chain length contained in the surfactant is reduced. Conversely,
HO (CH ₂ CH ₂ O) ₂₀ (CH ₂ CH (CH ₃ ) O)
Large pores can be formed by using a triblock copolymer such as ₇₀ (CH ₂ CH ₂ O) ₂₀ H.

The content of the surfactant contained in the reaction solution is in the range of 5 to 50% by weight, preferably 10 to 30% by weight.

As the solvent in the reaction solution, an alcohol such as methanol, ethanol, or isopropyl alcohol (IPA) can be used. A mixed solvent of these alcohols and water can also be used. Even if it is not an alcohol, any solvent can be used as long as it is liquid at normal temperature and can dissolve the compound containing the metal (for example, tin chloride).

The substrate is preferably a substrate that is stable to the reaction solution, that is, a substrate that does not or hardly causes a chemical reaction between the reaction solution and the substrate. To illustrate,
Glass, ceramics, resin (for example, polyimide), metal and the like can be used. Of course, a flexible film such as plastic can be used as the substrate.

The application of the reaction solution to the substrate in the step S2 may be performed in air, but may also be performed in an atmosphere gas containing nitrogen or argon (first atmosphere). Further, the S2 step can be performed in an oxidizing atmosphere or a reducing atmosphere containing hydrogen.

The temperature (first temperature) of the atmosphere in which the substrate is placed during coating is preferably in the range of 0 ° C. to 50 ° C. Of course, the first temperature is room temperature (for example, 15 ° C. to 35 ° C.).
° C range).

The humidity at the time of coating is 0 to 80%
, Preferably in the range of 10% to 40%. However, it is preferable that after the step S2, the reaction solution (particularly the solvent) on the substrate is once dried, and then the step S3 is performed. For example, after the step S2, it is preferable to perform a drying step of drying the solvent at a temperature of 25 ° C. to 50 ° C. and a humidity of 10% to 30%, and then perform the step S3.

Next, a coating method will be described. A casting method is effective as a simple and short coating method.

Further, when it is desired to apply the coating uniformly on the substrate,
When strict control of the film thickness is desired, the dip coating method is effective. In this method, a substrate is immersed in a reaction solution, and the substrate is pulled up at a constant speed to uniformly apply the reaction solution on the substrate. The amount of application, that is, the thickness of the thin film to be formed, can be controlled by, for example, the pulling speed. The film is thicker if the pulling speed is high, and thin if the pulling speed is low.

Further, when it is desired to form a uniform and thin film, a spin coating method is effective. This is a method in which a reaction solution is dropped on a substrate and the substrate is rotated to uniformly apply the solution on the substrate. The amount of application, that is, the thickness of the formed thin film can be controlled by the rotation speed of the substrate. A faster rotation speed results in a thinner film, and a slower rotation speed results in a thicker film.
In addition, any method that can apply a reaction solution onto a substrate, such as a spray coating method that is excellent in mass productivity, can be applied to the present invention.

The atmosphere (second atmosphere) containing water vapor in the step S3 may be a water vapor atmosphere in a saturated state or a humidity of 40% to 100%, preferably 60% to 100%, more preferably 70% or more. The atmosphere has a humidity of 90% or less.

Note that the first atmosphere in the step S2 may be an atmosphere containing water vapor. In particular, it is also possible to change the humidity in the first atmosphere and the second atmosphere.

In the step S2, the temperature (° C.), relative humidity (%), and absolute humidity (g / m ² ) of the first atmosphere are T _S2 , R _S2 , and e _S2 , respectively. The temperature, relative humidity and absolute humidity of the second atmosphere in the step _S3 are represented by T _S3 and R, respectively.
_S3 and _eS3 . The saturated steam amount (g / m ² ) at the temperature of the step _S2 is E (T _S2 ), and the saturated steam amount at the temperature of the S3 step is E (T _S3 ).

In the present invention, it is desirable that e _S2 <e _S3 . If e _S2 <e _S3 , R _S2 · E (T _S2 ) <R
_S3 · E (T _S3 ). If T _S2 <T _S3 , E
(T _S2 ) <E (T _S3 ). The applicable range of R _S2 and R _S3 is as follows. R _S2 = 0% to 80% (T _S2 = 0 ° C. to 50 ° C.) R _S3 = 40% to 100% (T _S3 = 15 ° C. to 100 ° C.)

The temperature of the processing atmosphere in the step S3 (second
Is in the range of 15 ° C. to 100 ° C., preferably 25 ° C. to 60 ° C. It is preferable that the second temperature is higher than the first temperature. For example, 25 ° C. of room temperature can be selected as the first temperature, and 40 ° C. can be selected as the second temperature.

By performing the step S3 at a low temperature of 15 ° C. or more and 100 ° C. or less, a structure containing a metal oxide crystal on the pore wall while the surfactant is contained in the pore structure is obtained. Obtainable. In particular, it is preferable that the surfactant is held inside the pores in terms of the strength of the pore structure.
In addition, a surfactant having a function in advance may be used, or the surfactant and the functional material may coexist in the reaction solution. Here, the function is a function in which conductivity is exhibited by irradiation of light, for example.

The processing time of the substrate in the step S3 can be performed for several hours to several hundred hours. Note that S3
Even when the process is performed in an atmosphere having a humidity of 100%, the process is preferably performed in a gas atmosphere instead of a liquid. Through the steps S1 to S3 as described above, a metal oxide pore structure is formed on the substrate. A thin film-shaped pore structure is formed on the substrate.

The IUPAC (International)
nal Union of Pure and App
According to Led Chemistry), the porous body is
Microporous having a pore diameter of 2 nm or less, 2 to 50 nm
And macroporous of 50 nm or more.

In the present invention, since the pore size can be appropriately changed depending on the type of the surfactant as described above, any of these classified porous structures is included. The present invention can be expected to have a great effect particularly on the formation of a mesoporous structure having a larger pore diameter than a microporous one.

Known microporous materials include zeolites such as natural aluminosilicates and synthetic aluminosilicates, and metal phosphates. These are used as selective adsorption using pore size, shape-selective catalytic reaction, and reaction vessels of molecular size.

As the mesoporous structure, in particular, a tin oxide mesostructure is considered promising, and the formation of the structure will be specifically described below. The coating method (S2
In the reaction solution applied on the substrate by the step (b), as the solvent evaporates, the concentration of the surfactant exceeds the critical micelle concentration, and self-assembly of the surfactant starts,
Further, self-organization of the tin compound or an intermediate formed from the tin compound and the surfactant is promoted.

That is, the aggregate of the surfactants forms micelles and serves as a template for pores, thereby forming a honeycomb structure.
When this forming process is performed in an atmosphere containing water vapor (S3
Step), the improvement of the regularity of the mesostructure is greatly promoted. This is thought to be because the hydrolysis and condensation of the tin compound or an intermediate formed from the tin compound proceed as the water is gradually supplied to the structure, and the crystallization of the pore walls proceeds.

When the holding temperature in the step S3 is low, crystallization of the pore walls becomes possible while maintaining the high structural regularity of the mesoporous structure. It is preferable that the crystal is completely crystallized, but it may be in a polycrystalline or microcrystalline state as long as a desired function can be exhibited.

As a method of crystallization, 400 ° C.
Firing at a high temperature, such as “NATURE” No. 3
96, p. 152 (1998), firing at such a high temperature has a high possibility of disturbing the mesostructure.
Not preferred. Therefore, in the method of the present invention, the holding temperature is 1
The temperature is preferably not higher than 00 ° C., specifically, a low temperature of 40 ° C. is possible.

The term “in water vapor” means that the water vapor content of the atmosphere in the reaction vessel is preferably in a saturated state at the above-mentioned temperature, but the holding time is increased even in an atmosphere where the relative humidity is 40% or more and less than 100%. It is possible to improve the regularity of the mesostructure and to crystallize the pore walls.

If all treatments are performed at a temperature lower than the temperature at which the surfactant is removed, the mesostructure holding the surfactant serving as a template for the pores has a structure having crystallized pore walls. Can provide body.

Of course, once the pore walls are crystallized, the surfactant can be removed or its amount can be reduced. For example, firing, ultraviolet light irradiation, oxidative decomposition with ozone, extraction with a supercritical fluid, extraction with a solvent, etc. may be mentioned.

The processing temperature in the step S3 is 400
By increasing the temperature to about ° C or performing a heat treatment at a high temperature after the step S3, it is possible to remove or reduce the surfactant held in the pores. Also, by extending the processing time in the S3 step, it is possible to remove or reduce the surfactant to some extent.

In the present invention, a thin film having a thickness of 0.1 μm to several μm or tens of μm can be formed as the mesostructured thin film after the step S3. For example, in the case of the dip method, 0.2 μm to 3 μm, and in the case of the cast method,
A thin film of 2 μm to 10 μm can be formed. Of course, the thickness is not limited to these.

(Embodiment 2) Next, the pore structure of the present invention is a thin film having a pore structure of a honeycomb structure, in which a surfactant is retained in the pores. In addition, the pore walls contain oxide crystals.

The pore structure is formed of a metal oxide, for example, tin oxide. The crystal here includes not only a single crystal and a polycrystal but also a microcrystal. By holding the surfactant in the pores, it is possible to maintain the mechanical strength as compared with the case where the surfactant is removed.

The structure according to the present invention is characterized in that the tin oxide mesostructure particularly has both structural regularity and crystalline pore walls. In order to achieve both high structural regularity and crystallinity of the pore walls, the average crystallite diameter of the tin oxide microcrystals is preferably within the pore wall thickness.

FIG. 8 is a schematic view showing the structure of a tin oxide mesostructure according to the present invention. In the figure, 71 is a pore wall, 72
Is a pore, 73 is an interplanar spacing d ₁₀₀ , 74 is a pore spacing M, 75
Indicates the pore wall thickness La. Generally, the pore wall thickness La is as shown in FIG.
, The pore spacing M measured by X-ray diffraction analysis
(Nm) or less.

The pore spacing M (nm) can be determined by the following formula (2) from the mesostructure plane spacing d ₁₀₀ (nm) determined by X-ray diffraction analysis.

[0059]

(Equation 3)

The interplanar spacing d ₁₀₀ (nm) of the mesostructure is obtained from the diffraction angle 2θ of the peak observed by X-ray diffraction analysis according to the following equation (3) based on Bragg's law.

[0061]

(Equation 4)

Here, λ (nm) is the wavelength of the X-ray,
In the present invention, CuKα is used for the radiation source.

Accordingly, the average crystallite diameter L (nm) of the crystal calculated from the diffraction peak observed in the X-ray diffraction analysis using the Scherrer equation and the Bragg equation satisfies the following equation (1). Is desirable.

[0064]

(Equation 5)

Specifically, the average crystallite diameter L (nm) is
It is preferably in the range of 1 to 10 nm, preferably 1 to 5 nm.

The Scherrer equation is shown below. From the following formula, the average crystallite diameter L can be determined from the half width B (rad) of the peak observed by X-ray diffraction analysis and the diffraction angle 2θ of the peak.

[0067]

(Equation 6)

The pore diameter refers to the size of the pore, that is, the diameter of the pore when it is a circle. In the case of a polygon, the distance is twice the distance from the center of the hole to the vertex of the hole. However, the polygon may be considered as a circle and its diameter may be considered.

(Embodiment 3) Various devices to which the pore structure shown in the above embodiment is applied will be described. Examples of applications of the pore structure include a filter used for selecting or adsorbing various materials, a gas sensor, and the like.

[0070]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples. However, the present invention is not limited to these Examples. It can be changed freely within a range where a structure can be obtained.

Example 1 First, the surface of a glass substrate was washed with isopropyl alcohol and pure water, and irradiated with UV in an ozone generator to clean the surface.

Next, polyoxyethylene (10) stearyl ether <C ₁₈ H ₃₇ (CH ₂
CH ₂ O) was dissolved ₁₀ OH> 2.0 g, after stirring for 30 minutes, was added anhydrous stannic chloride 5.2 g, was reacted solution was stirred for further 30 minutes. The operations up to this point were performed in a nitrogen atmosphere.

Thereafter, the reaction solution was taken out into the atmosphere, and the reaction solution was applied to a glass substrate by a casting method. The temperature was about 25 ° C. and the humidity was about 30%.

The substrate coated with the reaction solution is placed in air at 40
The film was kept in an atmosphere at a temperature of 7 ° C. for 7 days to form a thin film on the substrate.
In an atmosphere of 40 ° C., as shown in FIG. 2, the substrate 12 is accommodated in the reaction vessel 15 of the dryer 11, and water 13 is allowed to coexist at the same time to generate almost saturated water vapor 14 (humidity 100%) I let it.

The thin film formed on the substrate by the above method was uniform without cracks and the like, and was transparent. The thickness of the thin film was 2 μm. The surfactant was retained within the pores. When the X-ray diffraction analysis was performed on the thin film,
As shown in FIG. 3, a strong diffraction peak was observed at a plane spacing of 4.8 nm, and it was confirmed that the crystal had a mesostructure.

Next, when observed by a transmission electron microscope (TEM), tube-like pores 32 were confirmed on the plane of the film as shown in FIG. 4, and pores 42 having a honeycomb structure as shown in FIG. Was formed over the entire film. That is, it was confirmed that all of the tubular pores were formed in parallel with the substrate over the entire film, and had a mesostructured selective orientation. However, this structure is slightly laterally distorted and does not exactly match the hexagonal structure reported hitherto.

Next, electron diffraction analysis was performed on the thin film, particularly in a region where a highly ordered mesostructure was confirmed by observation with a transmission electron microscope. As a result, SnO ₂ , cassite (Cassite)
a pattern almost identical to the diffraction pattern of “write” was obtained. Further, the mesostructure was not destroyed by the electron beam during the observation.

Further, in the grazing incidence X-ray diffraction analysis, as shown in FIG. 6, _two atoms belonging to SnO ₂ and Cassiterite
θ = 26.6 °, 33.9 °, 51.7 °, 65.8 °
A clear peak was confirmed. In other words, it can be said that microcrystals grew in the pore walls while maintaining the mesostructure.

In the range of 2θ = 21 ° to 31 °, the peak half width B (rad) and the peak diffraction angle 2
When θ was determined and the average crystallite diameter L was determined by the Scherrer method, it was 2.2 nm. The following is Scherrer's formula.

[0080]

(Equation 7)

From these results, according to the present invention, a porous structure having both a highly regular pore structure and a crystalline pore wall was obtained.
It was confirmed that a tin oxide mesostructured thin film having high continuity and uniformity was obtained.

In preparing the reaction solution, polyoxyethylene (20) hexadecyl ether <C ₁₆ H ₃₃ (CH ₂ CH ₂ O) ₂₀ OH> was used as a surfactant, and water ( Even when alcohol was used (other conditions were the same as above), a mesoporous structure similar to that of the above example was obtained.

Example 2 As in Example 1, the surface of the glass substrate was washed with isopropyl alcohol and pure water, and irradiated with UV light in an ozone generator to clean the surface.

Next, triblock coco was added to 20 g of ethanol.
Polymer <HO (CH_Two CH_Two O) ₂₀(CH_Two CH (C
H_Three ) O)₇₀(CH_Two CH_Two O)₂₀Dissolve H> 2.0g
After stirring for 30 minutes, 5.2 g of anhydrous stannic chloride was added.
The mixture was further stirred for 30 minutes to obtain a reaction solution. In addition, this
The above operation was performed under a nitrogen atmosphere.

Thereafter, the reaction solution was taken out into the atmosphere and applied to a glass substrate by dip coating. The lifting speed during dip coating was 3.5 mm / s. The temperature was about 25 ° C. and the humidity was about 30%.

The substrate coated with the reaction solution is placed in air at 40
The film was kept in an atmosphere at a temperature of 7 ° C. for 7 days to form a thin film on the substrate.
In addition, in a 40 ° C. atmosphere, water was simultaneously present as shown in FIG. 2 to generate almost saturated water vapor (100% humidity).

The thin film formed on the substrate by the above method was uniform without cracks and the like, and was transparent. The thickness of the thin film was 0.7 μm. The thin film was subjected to X-ray diffraction analysis. As a result, a strong diffraction peak was observed at an interplanar spacing of 11.6 nm, and it was confirmed that the thin film had a mesostructure.

Next, when observed with a transmission electron microscope,
Tubular pores were confirmed on the plane of the membrane as shown in FIG. 4, and pores having a honeycomb structure were formed over the entire membrane as shown in FIG. 5 in the cross section of the membrane. That is,
All of the tubular pores were formed parallel to the substrate over the entire film, and it was confirmed that the film had a mesostructured selective orientation. However, this structure is slightly laterally distorted and does not exactly match the hexagonal structure reported hitherto.

Next, when electron beam diffraction analysis was performed on the thin film, particularly in a region where a highly ordered mesostructure was confirmed by observation with a transmission electron microscope, SnO ₂ , Cassiterite
A pattern almost matching the diffraction pattern was obtained. Further, the mesostructure was not destroyed by the electron beam during the observation.

In the grazing incidence X-ray diffraction analysis, SnO
_2. 2θ attributed to Cassiterite = 26.
Clear peaks were observed at 6 °, 33.9 °, 51.8 °, and 65.9 °. In other words, it can be said that microcrystals grew in the pore walls while maintaining the mesostructure.

The half width of the peak was determined in the range of 2θ = 21 ° to 31 °, and the average crystallite diameter was determined by the Scherrer method to be 3.4 nm. From these results, it was confirmed that according to the present invention, a tin oxide mesostructured thin film having high continuity and uniformity, having both a pore structure having high structural regularity and a crystalline pore wall was obtained.

Example 3 First, the surface of a glass substrate was washed with isopropyl alcohol and pure water in the same manner as in Example 1,
V irradiation was performed to clean the surface.

Next, polyoxyethylene was added to 20 g of ethanol.
(10) Stearyl ether <C ₁₈H₃₇(CH_Two CH
_Two O)_TenOH> 2.0g is dissolved and stirred for 30 minutes, then anhydrous
5.2 g of stannic chloride are added and stirred for a further 30 minutes.
To obtain a reaction solution. The operation up to this point is in a nitrogen atmosphere
Went under.

Thereafter, the reaction solution was taken out into the atmosphere, and the reaction solution was applied to a glass substrate by spin coating. The spin coating was performed at a rotation speed of 1000 rpm for 20 seconds. The temperature was about 25 ° C. and the humidity was about 30%.

The substrate coated with the reaction solution is placed in air for 40 minutes.
The film was kept in an atmosphere at a temperature of 7 ° C. for 7 days to form a thin film on the substrate.
In the atmosphere of 40 ° C., water was allowed to coexist as shown in FIG. 2 to generate almost saturated water vapor (100% humidity).

The thin film formed on the substrate by the above method was uniform without cracks and the like, and was transparent. The thickness of the thin film was 2 μm. The thin film was subjected to X-ray diffraction analysis. As a result, a strong diffraction peak was observed at an interplanar distance of 4.9 nm, and it was confirmed that the thin film had a mesostructure.

Next, when observed by a transmission electron microscope,
Tubular pores were confirmed on the plane of the membrane as shown in FIG. 4, and pores having a honeycomb structure were formed over the entire membrane as shown in FIG. 5 in the cross section of the membrane. That is,
All of the tubular pores were formed parallel to the substrate over the entire film, and it was confirmed that the film had a mesostructured selective orientation. However, this structure is slightly laterally distorted and does not exactly match the hexagonal structure reported hitherto.

Next, electron diffraction analysis was performed on the thin film, particularly in a region where a highly ordered mesostructure was confirmed by observation with a transmission electron microscope, which revealed that SnO ₂ , Cassiterite
A pattern almost matching the diffraction pattern was obtained. Further, the mesostructure was not destroyed by the electron beam during the observation.

In the grazing incidence X-ray diffraction analysis, SnO
_2. 2θ attributed to Cassiterite = 26.
Clear peaks were observed at 5 °, 33.8 °, 51.7 °, and 65.9 °. In other words, it can be said that microcrystals grew in the pore walls while maintaining the mesostructure.

The half width of the peak was determined in the range of 2θ = 21 ° to 31 °, and the average crystallite diameter was determined by the Scherrer method. As a result, it was 2.1 nm. From these results, it was confirmed that according to the present invention, a tin oxide mesostructured thin film having high continuity and uniformity, having both a pore structure having high structural regularity and a crystalline pore wall was obtained.

Comparative Example 1 Next, as a comparative example, a case where a thin film is formed by applying a reaction solution to a substrate and holding the substrate in an atmosphere of 40 ° C. in air without water at the same time will be described. As in Example 1, the surface of the glass substrate was washed with isopropyl alcohol and pure water, and irradiated with UV in an ozone generator to clean the surface.

Next, polyoxyethylene (10) stearyl ether <C ₁₈ H ₃₇ (CH ₂ C) was added to 20 g of ethanol.
H ₂ O) was dissolved ₁₀ OH> 2.0 g, after stirring for 30 minutes, was added anhydrous stannic chloride 5.2 g, was reacted solution was stirred for further 30 minutes. The operations up to this point were performed in a nitrogen atmosphere.

Thereafter, the reaction solution was taken out into the atmosphere, and the reaction solution was applied to a glass substrate by a casting method. The temperature was about 25 ° C. and the humidity was about 30%. The substrate coated with the reaction solution is placed in an atmosphere of 40 ° C. in air (25% humidity).
%) For 7 days to form a thin film on the substrate. The thin film formed on the substrate by the above method was white and opaque. The thickness of the thin film was 2 μm.

When the thin film was subjected to X-ray diffraction analysis, no clear diffraction peak was observed as shown in FIG.
A mesostructure with structural regularity could not be formed.

Example 4 A reaction solution was applied on a glass substrate in the same manner as in Example 1, using the same reaction solution as in Example 1. Application is performed at room temperature (2
5 ° C.) and 40% relative humidity. Thereafter, the temperature was maintained at 40 ° C. and the relative humidity at 80% in an environmental tester, and the temperature was maintained for 230 hours. As a result, a mesoporous pore structure was formed on the substrate. The thickness of the thin film was 2 μm.

Incidentally, according to the X-ray diffraction analysis, the plane spacing was 4.
A strong peak was observed at 6 nm, indicating a mesostructure. The average crystallite size determined by the Scherrer method was 2.2 nm.

[0107]

As described above, according to the present invention,
A method for producing a pore structure having a crystal structure on a pore wall can be provided. Further, a thin film having a pore structure having a crystal structure of tin oxide on the pore wall can be provided. In particular, by applying a reaction solution containing a tin compound and a surfactant to a substrate, and holding the substrate in steam for a certain time,
The pore walls can be crystallized even at a low temperature during the holding, and a tin oxide mesostructured thin film having both a pore structure with high structural regularity and a crystalline pore wall can be obtained.

[Brief description of the drawings]

FIG. 1 is a process chart showing a method for forming a pore structure according to the present invention.

FIG. 2 is a schematic view showing a state of holding a substrate when forming a thin film according to the present invention.

FIG. 3 shows X of the tin oxide mesostructured thin film in Example 1.
It is a line diffraction pattern.

FIG. 4 shows a plane T of a tin oxide mesostructured thin film according to the present invention.
It is a schematic diagram of an EM image.

FIG. 5 is a cross section T of a tin oxide mesostructured thin film according to the present invention.
It is a schematic diagram of an EM image.

FIG. 6 is an oblique incidence X-ray diffraction pattern of a tin oxide mesostructured thin film in Example 1.

FIG. 7 is an X-ray diffraction pattern of a thin film in Comparative Example 1.

FIG. 8 is a schematic view showing the structure of a tin oxide mesostructure according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 Dryer 12 Substrate 13 Water 14 Steam 15 Reaction vessel 31, 41 Tin oxide mesostructure 32, 42, 72 Pores 71 Pores wall 73 Surface distance d ₁₀₀ 74 Pore distance M 75 Pore wall thickness La

Claims (17)

[Claims] 1. A method for preparing a reaction solution containing a metal compound and a surfactant, a step of applying the reaction solution on a substrate, and a step of holding the substrate in an atmosphere containing water vapor. Of producing a porous structure. 2. The method for producing a pore structure according to claim 1, wherein a tin compound is used as a metal compound in the reaction solution, and the pore structure is formed of tin oxide. 3. The method according to claim 2, wherein the tin compound is a tin chloride. 4. The method according to claim 1, wherein the reaction solution contains an alcohol. 5. The method according to claim 1, wherein the application of the reaction solution is performed by a casting method, a dip coating method, or a spin coating method. 6. The method according to claim 1, wherein the step of holding the substrate in an atmosphere containing water vapor is performed at 100 ° C. or lower. 7. The method for producing a pore structure according to claim 1, wherein the atmosphere containing water vapor has a relative humidity of 40% or more and 100% or less. . 8. The method according to claim 1, wherein the absolute humidity in the step of holding the substrate in an atmosphere containing water vapor is higher than the absolute humidity in the step of applying the reaction solution on the substrate. The method for producing a pore structure according to any one of the above items. 9. The temperature of the gas atmosphere in the step of holding the substrate is higher than the temperature of the gas atmosphere in the step of applying the reaction solution on the substrate, and the relative humidity in the step of holding the substrate is: The method for producing a pore structure according to any one of claims 1 to 6, wherein the relative humidity is higher than a relative humidity in a step of applying the reaction solution on a substrate. 10. The pore structure, wherein the pore diameter is 2-5.
2. A mesoporous material having a thickness of 0 nm.
7. The method for producing a pore structure according to any one of Items 6 to 6. 11. The method according to claim 1, wherein the reaction solution contains water and does not contain alcohol. 12. The method according to claim 1, wherein the surfactant is a nonionic surfactant. 13. A thin film having a pore structure comprising an oxide, wherein a surfactant is retained in the pores,
A thin film having a pore structure, characterized in that the pore walls contain tin oxide crystals. 14. The thin film having a pore structure according to claim 13, wherein said pore structure is a film having a selective orientation of a meso structure. 15. An average crystallite diameter L (nm) and a pore interval M (nm) of the crystal calculated from the diffraction peak observed by X-ray diffraction analysis using the Scherrer equation and the Bragg equation.
Is given by the following equation (1). 14. The thin film having a pore structure according to claim 13, wherein: 16. An average crystallite diameter calculated from a diffraction peak observed by X-ray diffraction analysis of the crystal using a Scherrer equation and a Bragg equation is 1 to 5 nm. 16. A thin film having the pore structure according to 15. 17. The thin film having a pore structure according to claim 13, wherein the pore structure is formed on a substrate.