JPH04182309A - Production of porous silica thin film - Google Patents

Abstract

PURPOSE:To obtain a porous silica thin film having such a pore structure as to be controlled to a nanometer level by preparing a multilayered two-molecule thin film comprising an amphiphilic material on a substrate, using this thin film as a die to impregnate with a silica compd. and then extracting and removing the amphiphilic material. CONSTITUTION:An extending liquid is prepared by dispersing a cation-type amphiphilic material which can form a two-molecule thin film in water, and for example, the amphiphilic material is dodecyloxyazobenzene oxypentyldimethylammonium bromide expressed by the formula. This extending liquid is spread on a substrate, from which water is removed by vaporization to prepare a multilayered two-molecule thin film comprising the amphiphilic material. Then, this thin film is brought into contact with a silica compd., and the multilayered two-molecule thin film is extracted and removed to obtain a porous silica thin film having a multilayered structure.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a porous silica thin film having a multilayer structure consisting of an ultra-thin film on the nanometer level.

[Prior Art] Porous silica gel made from sodium silicate, porous glass made by a method utilizing the phase separation property of borosilicate glass, a sol-gel method, etc.

Silica-related compounds such as layered polysilicates are used in fields such as material separation and catalyst supports, taking advantage of their porous structure.

In applications such as substance separation and catalyst supports, it is necessary to increase the amount of permeation of substances to be separated and reactants. Therefore, it is required to form a film-like thin film that maintains the film strength and reduces the film thickness by reducing the film strength. Furthermore, in order to effectively exert the effects caused by the pore structure of the thin film, it is required to control the pore structure at the nanometer level.

However, most of the conventional silica-related compound raw materials are in the form of powder, which makes it difficult to form them into thin films, and they are used in the form of granules, plates, blocks, etc. after being granulated.

For example, in the typical sol-gel method for forming silica into a thin film, a silica thin film is created by applying a hydrolyzed solution of an alkoxysilane substance onto a substrate and forming a gel coating film by heat treatment or the like. There is. However, when producing silica thin films using the sol-gel method, solvent evaporation and siloxane bonds (Si-〇-3i) occur during thin film formation.
) volume contraction occurs due to the crosslinking reaction. Therefore, cracks are likely to occur, and the obtained thin film has a brittle structure. From this point of view, it is actually very difficult to produce a film-like thin film.

In addition, when using a substrate, supporting film, etc., the substrate, supporting film, etc. are required to have good adhesion between the coating film and the substrate, etc., and mechanical strength to withstand volume shrinkage during film formation. Restrictions are added to the materials of membranes, etc. Furthermore, in the case of a silica-coated thin film, a porous body is used as a substrate, a support film, etc., depending on the intended use of the obtained thin film. However, due to the pore structure of this porous body, it is difficult to obtain a thin film with a uniform thickness, especially an ultra-thin film at the submicron level.

Furthermore, since the silica thin film produced by the sol-gel method is a three-dimensional crosslinked product, the obtained thin film has an amorphous pore structure.

[Problems to be Solved by the Invention] As described above, when using conventional powder molding methods, sol-gel methods, etc., it is possible to determine the amount of permeation of substances to be separated or reactants that is suitable for the intended use, such as material separation or catalyst support. It has been difficult to produce a film-like porous silica thin film that can increase the size of the film. In particular, it has been impossible to precisely control the film thickness on a nanometer level.

Therefore, the inventors of the present invention have conducted intensive research on a method for manufacturing a film-like silica thin film to reduce the film thickness in order to maintain the film strength and reduce the film resistance, and have finally completed the present invention. Ta.

That is, the present invention utilizes the property of certain amphiphilic substances to form a multilayer bilayer thin film with high regularity at the molecular level, in other words, at the nanometer level.
The aim is to manufacture silica thin films with controlled pore structures at the nanometer level.

[Means for Solving the Problems] In the present invention, after a developing solution of an amphiphilic substance capable of forming a bilayer film is developed on a substrate, the amphiphilic substance is developed by removing the solvent from the liquid film on the substrate. Prepare a multilayer bilayer thin film of a chemical substance. Then, this multilayer bilayer thin film is brought into contact with a solution containing a silica compound, and the silica compound is infiltrated into the pore spaces using the multilayer bilayer thin film as a template. Then, if necessary, the amphipathic substance is extracted and removed using an organic solvent to produce a film-like silica thin film.

Alternatively, a predetermined amount of the silica compound can be penetrated by repeating the process of bringing the multilayer bilayer thin film into contact with a silica compound-containing solution, then contacting an acid, and then contacting the silica compound-containing solution again once or multiple times. You can also do it.

The amphiphilic substance used in the present invention is a compound that simultaneously has both a polar group and a hydrophobic group in the same molecule.

Polar groups include sulfonates, sulfates, ammonium salts, polyamine salts, carboxylates, sulfonyl salts, phosphates, phosphonates, phosphonium salts, polyethers,
Alcohols, polyols containing sugar residues, and combinations of these groups can be used. However, when considering reactivity with silica compounds, ion pair type compounds such as ammonium salts, particularly those having cationic residues, are preferred.

On the other hand, as the hydrophobic group, an alkyl group, an alkylaryl group, an alicyclic group, a fused polycyclic group, and a combination of these groups can be used. However, in order to form a stable bilayer membrane similar to biological membranes, a certain specific partial chemical structure is required. For example, the alkyl long chain has two or more alkyl chains, or an alkyl long chain containing a rigid segment such as azobenzene or biphenyl. In this regard, regarding the chemical structural characteristics of amphiphilic substances that have a bilayer membrane structure, the reason for their high ability to form thin films, and typical examples of compounds, patent application No. 1-5
Since it is explained in detail in No. 8889, it will be omitted here.

A developing solution of an amphipathic substance is prepared by dissolving or dispersing a predetermined amount of an amphiphilic substance in a solvent. Water is often used as the solvent, but it is also possible to use organic solvents.

The substrate on which the developing solution is developed includes a glass substrate 9, a quartz plate, a fluorobore, a graphite plate, a silicon substrate, a dense polymer film, a porous polymer film, and the like. The surface of the substrate may be subjected to a hydrophilic/hydrophobic treatment or a hydrophobic treatment depending on the type of developing solution. For example, it is also effective to make a part of the substrate surface hydrophilic and to make the remaining surface hydrophobic so that the developing solution is spread over a predetermined area on the substrate surface.

When the solvent is removed from the developing solution spread on the substrate, an amphiphilic bilayer thin film is formed. In the process of removing the solvent, it is preferable to remove the solvent gradually in order to ensure the regularity of the molecular assembly of the amphiphilic substance. The conditions for solvent removal depend on the solvent system of the developing solution, but an example for an aqueous solution system is 25°C near room temperature, relative humidity 6
The test is carried out over three days in a constant temperature and humidity layer set at 0%. At this time, the thickness of the multilayer bilayer thin film of the amphiphilic substance to be adjusted is determined by the surface area of the substrate to be developed, the concentration of the amphiphilic substance in the developing solution, the volume of the developing solution, etc. The thickness of the silica thin film produced is also determined.

The multilayer bilayer thin film of amphiphile obtained after removing the solvent retains sufficient self-supporting properties even when peeled from the substrate. However, when considering operability, it is preferable to perform a contact treatment such as immersion in a silica compound-containing solution to the multilayer bilayer thin film still attached to the substrate.

The silica compound in the present invention mainly refers to a compound having a 5i-0 bond. The solution containing the silica compound is preferably an aqueous solution when considering the solubility of the multilayer bilayer thin film of the amphiphilic substance in an organic solvent. In addition, to increase the solubility of silica compounds,
A silica compound-containing solution adjusted to be acidic or basic can also be used. Silica compounds that can be used in the present invention include potassium silicate, sodium silicate,
Examples include colloidal silica, but are not particularly limited thereto.

The viscosity of the silica compound-containing solution increases as the concentration of the silica compound increases. Therefore, while the multilayer bilayer thin film is left immersed, a gelled film of the silica compound is formed on the surface of the solution due to evaporation of the solvent, which may make handling difficult.

Therefore, it is appropriate that the concentration of the silica compound be in the range of 1 to 15% by weight.

The immersion time of the multilayer bilayer thin film in the silica compound-containing solution is determined by the ion exchange reactivity between the amphiphilic substance and the silica compound in the multilayer bilayer thin film, which will be described later. The reaction between an amphiphilic substance and a silica compound has some advantages and disadvantages depending on the type of amphiphilic substance in the multilayer bilayer thin film, but in the case of poly( weight%
In a range of silica concentrations, the process is completed within about 12 hours. Therefore, it is sufficient to perform the immersion treatment for a longer time than this.

After washing the multilayer bilayer thin film of an amphipathic substance immersed in a silica compound-containing solution with water and drying it, an organic solvent selected according to the type of amphiphilic substance is used as an extractant.
Extract and remove amphiphiles. This treatment removes the amphiphilic substance and yields a multilayered silica thin film consisting of an ultra-thin film on the nanometer level.

The obtained silica thin film has a large surface area and a porous structure, as shown in Examples below.

However, since the thickness of the film is extremely small, it may lack self-supporting properties or break into small pieces. Therefore, the present inventors investigated a method of producing a self-supporting film-like silica thin film by promoting the growth of the silica thin film within the layer plane. As a result, a multilayer bilayer thin film of an amphiphilic substance immersed in a silica compound-containing solution was washed with water and dried, and then brought into contact with an acid.
A method of repeating the treatment of immersion in a solution of a silica-containing compound once or multiple times, or a method of adding a radical polymerization monomer to a developing solution for preparing an amphiphilic multilayer bilayer thin film,
We have found that a method using a multilayer bilayer thin film containing an ultrathin polymer prepared by polymerizing this monomer in a multilayer bilayer thin film is effective.

For example, when acid treatment is employed, a multilayer bilayer thin film immersed in a silica compound-containing solution is washed with water and dried, and then subjected to a treatment of being brought into contact with an acid gas, an aqueous solution, or its vapor. After washing and drying, the multilayer bilayer thin film is again immersed in a silica compound-containing solution. This series of treatments is applied once to a multilayer bilayer thin film of an amphiphilic substance.
When the amphipathic substance is extracted and removed using an organic solvent selected according to the type of amphiphilic substance as an extractant after repeated application several times or more times, the amphiphilic substance is removed to the extent that it can be sufficiently handled with tweezers. A thin film of silica with supporting properties is produced.

In most cases, the counter-anion species of the cationic amphiphilic substance is a halogen anion such as chlorine, bromine, or iodine, and therefore a hydrohalic acid containing a halogen anion is recommended as the acid used. However, sulfuric acid, nitric acid, phosphoric acid,
Other acids such as carboxylic acids can also be used.

The method of contacting a multilayer bilayer thin film of an amphiphilic substance treated with a silica compound-containing solution is, for example, when the vapor pressure of the acid is high, such as hydrochloric acid, in the form of a gas, or with the vapor of an aqueous solution such as hydrochloric acid. Exposure is also effective. However, a method of immersing a multilayer bilayer thin film in an aqueous acid solution is simple and effective.

The acid concentration of the aqueous solution is not particularly limited, but is 0.
．． A value of about 1 to IM is suitable from the viewpoint of ease of handling. This immersion treatment is similar to the treatment using a silica compound-containing solution, in which the reaction is completed in the 0.1 to LM(7) concentration range.
Two hours or more is sufficient.

The treatment with a silica compound-containing solution performed subsequent to the acid treatment can be performed under the same conditions as the treatment with a silica compound-containing solution in the previous step.

A series of operations including acid treatment can be repeatedly performed on a multilayer bilayer thin film of an amphiphilic substance. Although the number of repetitions at this time varies somewhat depending on the type of amphiphilic substance constituting the multilayer bilayer thin film, the effect of the repetition treatment may be saturated after 2 to 5 times or more. In this way, by contacting a multilayer bilayer thin film of an amphiphilic substance alternately with a silica compound-containing solution and an acid, the self-supporting properties of the obtained silica thin film are improved.

Furthermore, amphiphilic substances capable of forming bilayer membranes can incorporate radically polymerizable monomers into multilayer bilayer thin films, as shown in Japanese Patent Application No. 1-58885. The incorporated radically polymerizable monomer forms a two-dimensionally crosslinked ultra-thin film laminate. Therefore, by using this ultra-thin film laminate, it is also possible to produce a film-like silica thin film with self-supporting properties.

That is, a developing solution in which a radically polymerizable monomer is added to a cationic amphiphilic substance capable of forming a bilayer membrane,
After spreading on a substrate using the same method, the solvent is evaporated to prepare an amphiphilic multilayer bilayer thin film containing the monomer. Then, the radically polymerizable monomer contained in the multilayer bilayer thin film is polymerized by thermal polymerization, photopolymerization, radiation polymerization, etc., and a multilayer bilayer film composite thin film containing a two-dimensionally crosslinked ultra-thin polymer is produced. get. This composite thin film is similarly immersed in a silica compound-containing solution, or immersed in a silica compound-containing solution combined with acid treatment to produce a silica thin film. At this time, the immersion treatment in a silica compound-containing solution and the acid treatment can be performed under the same conditions as for a multilayer bilayer thin film prepared from a developing solution that does not contain a radically polymerizable monomer.

The radically polymerizable monomer used and the method of polymerizing this monomer to prepare a multilayer bilayer composite thin film containing an ultra-thin polymer are disclosed in Japanese Patent Application No. 1-58885, but the invention is not limited thereto. Other monomers and preparation methods can also be employed. As an example of the radically polymerizable monomer, polyfunctional monomers of the following formula may be used alone or in combination. Note that R in the following formula represents CH3 or H.

(Example of polyfunctional monomer) (n-2 to 20) CH20COC=CHa ■ CH20(CH-CHzO)2COC=CH*CH,○
C0C=CH.

Furthermore, monofunctional monomers and diluents such as ethylene glycol and glycerin can be mixed with these polyfunctional monomers. Examples of usable monofunctional monomers include the following.

(Example of monofunctional monomer) CL = CC00 (CH*CH*0) IICH-' (
n=2-141■ CH2=CC00(CH,CH20)IIH(n=2~
14) CH2=CC00CH, CH20H The multilayer bilayer composite thin film that has been treated with a silica compound-containing solution etc. is finally subjected to heat treatment in an oxidizing atmosphere to become a silica thin film. Specifically, a multilayer bilayer composite thin film is heated at 300° in an electric furnace under air or under a flow of oxygen gas.
By heating above C, the amphiphile and the ultra-thin polymer are incinerated and removed.

[Function] Among amphiphilic substances having a polar group and a hydrophobic group at both ends of the molecule, certain types form molecular aggregates having a bilayer membrane structure similar to biological membranes. The amphiphilic substance that forms this bilayer membrane can not only be obtained as an aqueous dispersion, but also
After spreading an aqueous dispersion of amphiphile on a solid substrate,
By gradually removing water, it can be formed into a transparent, self-supporting multilayer bilayer thin film. and,
Even within the obtained film-like multilayer bilayer thin film,
It is known that the regular bilayer membrane structure of amphiphilic substances is maintained and that it takes a lamellar structure with high two-dimensional planarity [for example, Th1n Solid Films,
121. See L89 (1984)]. On the contrary,
It is difficult to form a thin film that is self-supporting and has a regular molecular organization structure using an amphiphilic substance that does not have the ability to form a bilayer film, that is, a general surfactant.

Therefore, the present inventors focused on the highly regular organizational structure at the molecular level of multilayer bilayer thin films prepared from amphiphilic substances that have the ability to form bilayer membranes, and When forming a silica layer using a lamellar structure with high two-dimensional planarity as a template, we thought that a silica thin film consisting of an ultra-thin film on the molecular level, that is, on the order of nanometers, could be obtained in the form of a film. Here, the amphiphilic substance whose parent xylem is an ion-pair type has ion-exchange properties in the counter ion, and easily exchanges ions while maintaining its tissue structure. Taking advantage of this property, we attempted to interlayer a silica compound in the parent wood of a multilayer bilayer thin film. Since silica compounds consisting of SL-〇 bonds are generally anionic, a cationic type was selected as the amphipathic substance.

The ion exchange reaction between the amphiphile and the silica compound proceeds in a nearly stoichiometric manner, and the interlayers of the parent xylem of the amphiphile are filled with the silica compound. Finally, when the amphiphilic substance is extracted and removed using a suitable organic solvent, a silica thin film consisting of an ultra-thin film on the order of nanometers is obtained in the form of a film.

At this time, the interlayers of the multilayer bilayer thin film may not be sufficiently filled with the silica compound due to the difference in molecular cross-sectional area, etc. between the silica compound and the amphiphilic substance that are interlayered by the ion exchange reaction. In such cases, the silica thin film obtained after extracting the amphiphile is so thin that it may not be self-supporting or may break into small pieces. Therefore, it is necessary to introduce a large amount of silica compound between the layers of the multilayer bilayer thin film.

In order to introduce this silica compound, in the present invention,
Treatment with acid creates ion exchange within the multilayer bilayer thin film!・It is activated. The anionic silica compound introduced between the layers by ion exchange is protonated and neutralized by acid treatment, and in order to maintain electrical neutrality, the counter anion of the acid to be treated is reintroduced into the multilayer bilayer thin film. , ion exchange sites are activated. By repeating this process, a stoichiometric amount or more of the silica compound can be interlayered into the multilayer bilayer thin film. However, there is a limit to the amount of silica compound introduced, and it may become saturated with respect to the number of repetitions. Although the cause of this is not clear at this stage, it is presumed that it is due to the spatial constraints of the parent tree of the multilayer bilayer thin film.

In a multilayer bilayer composite thin film of an amphiphilic substance containing an ultrathin polymer prepared by polymerizing a radically polymerizable monomer, compared to a multilayer bilayer thin film prepared only from an amphiphilic substance, A tissue structure of amphiphiles with similar high regularity is formed. This means that Che
m, Lett,, p2059-2062 (198
As shown in 9), this is clear from experimental results such as X-ray diffraction. In addition, when using a multilayer bilayer composite thin film containing an ultra-thin layer polymer, the ultra-thin layer polymer acts as a binder for the silica compound introduced by ion exchange, and the layer plane growth of the silica compound during oxidation treatment. It is assumed that it promotes sex.

[Example] Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 - The following formula (1
) was used.

a+zm*ho<ΣN=NeOaiN' (CIl,,
)3Br-...-<1) This amphipathic substance (1)
was dispersed in pure water to prepare a 20mM developing solution. The obtained developing solution was developed on a Fluoropore (hereinafter simply referred to as Fluoropore) surrounded by a cellulose acetate film frame, and the developing solution was left as it was in an atmosphere of 25°C and 60% relative humidity for 3 days. By holding, water in the developing solution was evaporated, and a self-supporting, translucent, yellow multilayer bilayer thin film was obtained.

The produced multilayer bilayer thin film was immersed in a potassium silicate aqueous solution diluted to 10% by weight, left for 12 hours, and then taken out from the aqueous solution. After the treatment, the multilayer bilayer thin film exhibited a slightly swollen state.

This multilayer bilayer thin film was then thoroughly washed with pure water, dried, and then immersed in a methanol solvent to extract and remove the amphipathic substance (1).

The obtained silica thin film was a white transparent film with a thickness of 10 μm and was slightly brittle. When this silica thin film was observed using a scanning electron microscope (SEM), its microstructure was found to be a multilayer film structure consisting of ultra-thin films on the order of nanometers. Further, the surface area of the silica thin film determined from the amount of nitrogen adsorption was 260 m2/g.

Example 2 - As an amphipathic substance with bilayer membrane forming ability, the following formula (2) is used.
A compound with the structure was used.

A 20mM aqueous dispersion solution prepared from this amphiphilic substance (2) was spread on Fluorobor, and water was evaporated under the same conditions as in Example 1 to produce a translucent multilayer bilayer thin film.

The obtained multilayer bilayer thin film was immersed in a potassium silicate aqueous solution diluted to 10% by weight, and treated in the same manner as in Example 1. The obtained silica thin film was white pieces.

Therefore, a multilayer bilayer thin film of amphiphilic substance (2) was immersed in a potassium silicate aqueous solution, then immersed in a 0.2M hydrobromic acid aqueous solution for 12 hours, and then immersed again in a potassium silicate aqueous solution for 12 hours. This operation was repeated three times, and finally the amphipathic substance (2) was extracted and removed with a methanol solution. As a result, a silica thin film having a film thickness of about 30 μm and having sufficient self-supporting properties was obtained.

When we investigated the cross section of this silica thin film using SEM, we found that the first
As shown in the figure, a multilayer film structure was observed in which ultra-thin films of several nanometers were aligned parallel to the film surface of the silica thin film.

In addition, the surface area calculated from the amount of nitrogen adsorption is 210 m2/g
Met.

Example 3 - As an amphiphilic substance with bilayer membrane forming ability, the following formula (3) is used.
The compound shown in was used.

A 50mM aqueous dispersion solution prepared from this amphiphilic substance (3) was spread on Fluorobor, and water was evaporated in the same manner as in Example 1 to obtain a translucent white multilayer bilayer thin film. Ta.

For the prepared multilayer bilayer thin film, a 10% by weight aqueous solution of sodium silicate was used in place of the potassium silicate in Example 2, and 10% by weight of an aqueous solution of sodium silicate was added alternately with a 0.2M aqueous solution of hydrobromic acid.
The immersion process was repeated 4 times every 2 hours, and finally the amphipathic substance (3) was extracted and removed using a methanol solvent. The obtained silica thin film was in the form of a white film with self-supporting properties. Further, the surface area of the silica thin film determined from the amount of nitrogen adsorption was 200 m2/g.

Example 4 - A 20 mM aqueous dispersion of amphiphilic substance (2) in pure water was added with an equimolar amount of bifunctional monomer (4) as amphiphilic substance (2) and bifunctional monomer (4) as a polymerization initiator. A developing solution was prepared by mixing 2 mol% of 4(2-hydroxyethoxy)phenyl-(2-hydroxyethoxy-2-propyl)ketone with respect to monomer (4). This developing solution was developed on Fluoropore, the water was evaporated in the same manner as in Example 1, and then the bifunctional mercury (4)
was crosslinked and polymerized.

The prepared multilayer bilayer composite thin film in the form of a transparent film was immersed in an aqueous potassium silicate solution in the same manner as in Example 1.

After washing with pure water and drying, it was placed in a box-type electric furnace, heated at a rate of 10° C./min, and left at 500° C. for 10 hours.

The obtained silica thin film had sufficient self-supporting properties and was in the form of a translucent film. Although the surface area of this silica thin film was 170 m2/g, which tended to be slightly low, observation of the cross section of the film by SEM revealed a multilayer film structure consisting of an ultra-thin film on the order of nanometers.

Comparative Example 1 A silica thin film was prepared by a sol-gel method using an alkoxysilane as a starting material. That is, ethanol 50
20 parts by weight of alkoxysilane Si(O
CH3)4 and 10 parts by weight of 0.05 for hydrolysis
After adding N dilute aqueous hydrochloric acid solution and stirring for 1 minute, the mixture was spread on a glass petri dish and left to stand. Most of the solvent in the developing solution evaporated after one day and night, and it became a colorless and transparent very brittle silica flake. When the cross section was observed using a SEM, it was found to have a featureless microstructure as shown in FIG.

Furthermore, the surface area determined from the amount of nitrogen adsorption also showed a low value of 1 m2/g or less.

[Effects of the Invention] As explained above, in the present invention, a silica compound is contained between the layers of a multilayer bilayer thin film by utilizing the unique structure of a bilayer membrane assembly formed by amphiphilic substances. After
The amphipathic substance is extracted and removed using an appropriate solvent. The silica thin film produced in this way was formed using the multilayer bilayer structure of an amphiphilic substance as a template.
The structure is controlled on the order of nanometers, and the surface area is extremely large. Moreover, since it has self-supporting properties, handling of the silica thin film is easy. Therefore, when using this silica thin film as a substance separation membrane, catalyst carrier, etc.
It is used as a highly functional material due to its large surface area.

[Brief explanation of the drawing]

Fig. 1 is an SEM photograph showing the multilayer structure of the silica thin film produced in Example 2, and Fig. 2 is an SEM photograph showing the featureless and dense structure of the silica thin film produced by the sol-gel method as a comparative example. It's a photo.

Claims (4)

[Claims] (1) After developing a developing solution of a cationic amphiphilic substance capable of forming a bilayer film on a substrate, a multilayer bilayer of the amphiphilic substance is formed by removing the solvent from the liquid film on the substrate. A method for producing a porous silica thin film, which comprises preparing a membrane thin film, bringing the multilayer bilayer thin film into contact with a solution containing a silica compound, and then extracting and removing the multilayer bilayer thin film. (2) After contacting with the solution of the silica compound according to claim 1, the multilayer bilayer thin film of the amphiphilic substance is further brought into contact with an acid, and then brought into contact with the solution of the silica compound again one or more times. A method for producing a porous silica thin film characterized by repeated steps. (3) After preparing a multilayer bilayer thin film of an amphiphilic substance containing a radically polymerizable monomer by using a solution to which a radically polymerizable monomer is added as a developing solution according to claim 1, the radically polymerizable monomer is added to the solution. A multilayer bilayer composite thin film containing an ultrathin polymer that is polymerized and two-dimensionally crosslinked is formed, a solution containing a silica compound is brought into contact with the multilayer bilayer composite thin film, and then the multilayer bilayer composite thin film is A method for producing a porous silica thin film, which comprises removing the thin film by incineration. (4) After being brought into contact with the solution containing the silica compound according to claim 3, the multilayer bilayer thin film of the amphiphilic substance containing the polymerized radically polymerizable monomer is further brought into contact with an acid, and the silica compound is again brought into contact with the solution containing the silica compound. A method for producing a porous silica thin film, the method comprising repeating the process of bringing it into contact with a solution once or multiple times.