JP2003135972A - Porous thin film containing photocatalyst and coating agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a porous thin film containing a photocatalyst which has a large surface area where a photocatalytic reaction occurs and which can develop an excellent photocatalytic function, and to provide a coating agent to form the porous thin film containing the photocatalyst. SOLUTION: The porous thin film containing the photocatalyst consists of a thin film containing the photocatalyst formed by applying a coating liquid containing a photocatalyst active material and/or its precursor and a subliming agent on a base body and then subliming the subliming agent to form pores, and the thin film has 10 to 450 nm film thickness after the formation of the pores and has 30 to 3000 nm diameter of the pores. The coating agent for the formation of the porous thin film containing the photocatalyst contains the photocatalytic active material and/or its precursor and the subliming agent.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a photocatalyst-containing porous thin film, a coating agent for forming the thin film, and an article having the photocatalyst-containing porous thin film. More specifically, the present invention provides a photocatalyst-containing porous thin film which has a large surface area in which a photocatalytic reaction occurs and can exhibit an excellent photocatalytic function, a coating agent for forming the photocatalyst-containing porous thin film, and the photocatalyst-containing porous film. The present invention relates to an article having a thin film on its surface.

[0002]

2. Description of the Related Art A photocatalytically active material (hereinafter sometimes simply referred to as a photocatalyst) is irradiated with light having an energy larger than its band gap to be excited to generate electrons in the conduction band and positive in the valence band. A hole is created. Then, generated electrons are superoxide anion by reducing surface oxygen (· O ₂ ^-) with to produce, holes oxidize surface hydroxyl groups to produce the hydroxyl radical (· OH), these reactive It is known that active oxygen species exert a strong oxidative decomposition function to decompose organic substances attached to the surface of the photocatalyst with high efficiency. Applying such photocatalyst functions, for example, deodorization, antifouling, antibacterial, sterilization, and decomposition / removal of various substances that pose a problem on environmental pollution in wastewater and waste gas are being studied. There is.

As another function of the photocatalyst, when the photocatalyst is photoexcited, for example, International Patent Publication 96/2
As disclosed in Japanese Patent No. 9375, it is also known that the photocatalyst surface exhibits superhydrophilicity in which the contact angle with water is 10 degrees or less. By applying the superhydrophilic function of such a photocatalyst, for example, to prevent pollution by soot contained in the exhaust gas of automobiles such as soundproof walls and street lights of highways, or film for automobile body coats and side mirrors, The use of photocatalysts for antifogging and self-cleaning window glass has been studied.

As such a photocatalyst, a compound having various semiconductor characteristics, such as titanium dioxide, has hitherto been used.
Metal oxides such as iron oxide, tungsten oxide and zinc oxide, and metal sulfides such as cadmium sulfide and zinc sulfide are known. Among them, titanium dioxide, especially anatase titanium dioxide, is a practical photocatalyst. Is useful as This titanium dioxide exhibits excellent photocatalytic activity by absorbing light having a specific wavelength in the ultraviolet region included in daily light such as sunlight.

By the way, in such a thin film containing a photocatalyst, the total surface area of the photocatalytic thin film is extremely important in order to effectively exhibit the decomposition reaction of organic substances due to its photocatalytic activity. The main reason for this is that the photocatalytic reaction is a heterogeneous reaction that occurs only on the surface. Further, when positively utilizing the superhydrophilicity of the photocatalytic function in order to provide easy washability and antifogging property, it is possible to impart an uneven structure to the surface of the photocatalytic thin film to improve the wettability of the surface with water. preferable.

On the other hand, application to a solar cell using a photocatalyst such as titanium oxide has been actively promoted. Also in this case,
One of the important issues is to increase the surface area of the photocatalyst layer, and it is expected that the power generation efficiency can be greatly improved by increasing the surface area of the photocatalyst layer and improving the contact area with the sensitizing dye. Has been done.

However, in general, the remarkable uneven structure scatters light, which causes the transparency of the photocatalytic thin film to be significantly reduced. Therefore, in order to maintain high transparency, the concavo-convex structure should have a wavelength of visible light (400 nm or less).
In many cases, it is necessary to control the size to (nm or less).

As described above, in many applications of photocatalysts, there is a strong demand for photocatalyst thin films that maintain transparency and have a multi-surface area (uneven structure). As such a photocatalyst thin film, for example, a photocatalyst thin film which is made porous by adding polyethylene glycol to a coating liquid and burning off the polyethylene glycol during baking is known. However, in this case, heat treatment at 200 ° C. or higher is required to completely burn off the organic matter,
For example, there is a problem in that a photocatalytic thin film made porous by this method cannot be formed on an organic substrate having poor heat resistance. It has also been attempted to form a porous photocatalyst thin film by adding a water-soluble polymer compound such as polyvinyl alcohol to a coating liquid, removing the additive by washing with water after film formation. However, in this case, there is a problem that a step of removing the additive is required, the operation becomes complicated, and the cost is inevitably high.

[0009]

Under the circumstances described above, the present invention can be formed on an organic substrate having poor heat resistance by a simple operation, and a surface area where a photocatalytic reaction occurs can be obtained. And a photocatalyst-containing porous thin film capable of exhibiting an excellent photocatalytic function, a coating agent for forming the photocatalyst-containing porous thin film, and an article having the photocatalyst-containing porous thin film on the surface thereof. To do.

[0010]

Means for Solving the Problems As a result of intensive studies on the photocatalyst-containing porous thin film, the present inventors have found that after applying a coating liquid containing a photocatalytically active material or its precursor and a sublimation agent to a substrate, It was found that the above object can be achieved by a photocatalyst-containing porous thin film having a specific film thickness obtained by sublimating the sublimation agent to form pores having a diameter within a certain range. The invention was completed.

That is, according to the present invention, (1) a photocatalyst in which a coating liquid containing a photocatalytically active material and / or its precursor and a sublimation agent is applied to a substrate and then the sublimation agent is sublimated to form pores. Containing thin film, the thickness of the thin film after forming the pores is 10 to 450 nm, and the diameter of the pores is 30 to 30
A photocatalyst-containing porous thin film having a thickness of 00 nm, (2) applying a coating liquid to a substrate, sublimating a sublimation agent to form pores, and then performing crystallization treatment to obtain a photocatalyst active material precursor as a photocatalyst. The photocatalyst-containing porous thin film as described in the above item (1), which is converted into an active material, (3) the pores have a diameter larger than the thickness of the thin film, and have pores on the surface of the thin film. The photocatalyst-containing porous thin film according to the above (1) or (2), which has a structure penetrating to the material surface.

(4) The above (1), wherein the sublimation agent is a compound that sublimes at 120 ° C. or lower under normal pressure or reduced pressure.
The photocatalyst-containing porous thin film according to item (2) or (3),
(5) Any one of the above (1) to (4), wherein the sublimation agent is naphthalene and / or its analogue, and the content of the sublimation agent in the solid content of the coating liquid is 35 to 60% by weight. Item 6. The photocatalyst-containing porous thin film, (6) The photocatalyst-containing porous thin film according to any one of (1) to (5) above, wherein the photocatalytically active material is titanium dioxide, and (7) the photocatalytically active material. And / or a precursor thereof and a sublimation agent, and a coating agent for forming a photocatalyst-containing porous thin film, and (8) the photocatalyst-containing material according to any one of the above items (1) to (6) The present invention provides an article having a porous thin film.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The photocatalyst-containing porous thin film of the present invention is prepared by applying a coating liquid containing a photocatalytically active material as a photocatalytically active component and / or its precursor and a sublimation agent to It is formed by sublimation to form pores.

The photocatalytically active material is not particularly limited, and conventionally known materials such as titanium dioxide, strontium titanate (SrTiO ₃ ) and barium titanate (B) are used.
aTi ₄ O ₉ ), sodium titanate (Na ₂ Ti
₆ O ₁₃ ), zirconium dioxide, α-Fe ₂ O ₃ , tungsten oxide, K ₄ Nb ₆ O ₁₇ , Rb ₄ Nb ₆ O ₁₇ , K ₂ Rb ₂
Examples thereof include Nb ₆ O ₁₇ , cadmium sulfide, zinc sulfide and the like. These may be used alone or 2
You may use it in combination of two or more kinds, but among these,
Titanium dioxide, especially anatase type titanium dioxide, is useful as a practical photocatalytically active material. This titanium dioxide exhibits excellent photocatalytic activity by absorbing light having a specific wavelength in the ultraviolet region included in daily light such as sunlight.

The precursor of these photocatalytically active materials is not particularly limited as long as it can be converted into the photocatalytically active material by some treatment including crystallization.
Conventionally known compounds can be used. For example, as the titanium dioxide precursor, one containing a partial hydrolyzate of titanium alkoxide is used. In the present invention, as the photocatalytically active component, only the photocatalytically active material may be used, only its precursor may be used, or they may be used in combination.

On the other hand, the sublimation agent is preferably one which is completely dissolved in the coating liquid and can be sublimated at a temperature of 120 ° C. or lower under normal pressure or a reduced pressure of up to about 1 hPa. For example, naphthalene or an analog thereof, p-dichlorobenzene, camphor, camphene, ε-caprolactam, salicylic acid, oxalic acid,
Examples thereof include nitroaniline, nitrophenol, and p-benzoquinone. Among these, those sublimated at a temperature of 120 ° C. or lower under normal pressure are particularly preferable.
These may be used alone or in combination of two or more.

In the present invention, as a method for applying a coating liquid onto a substrate to form a photocatalyst-containing porous thin film, for example, (1) a coating liquid containing a photocatalytically active material precursor and a sublimation agent is applied to a substrate. After coating, the sublimation agent is sublimated to form pores, and then subjected to some treatment including heat treatment to convert the precursor into a photocatalytically active material and promote adhesion to a substrate, thereby containing a photocatalyst. A method for forming a porous thin film, and (2) after applying a coating liquid containing photocatalytically active material particles and a sublimation agent in an inorganic binder capable of solidifying at a temperature of about room temperature to 120 ° C. to a substrate, A method of heat-treating at a temperature of about 120 ° C. or lower to sublimate the sublimation agent and solidify the binder to form a photocatalyst-containing porous thin film can be preferably used.

First, the method (1) will be described. In this method, as the photocatalytically active material precursor contained in the coating liquid, any of the above-mentioned photocatalytically active material precursors can be used, but especially a titanium dioxide precursor, for example, a partial hydrolyzate of titanium alkoxide is used. Those including are preferable. Further, when the photocatalytically active material precursor is in the form of particles, a material containing an inorganic binder together with the precursor particles can be used.

The inorganic binder is not particularly limited, and conventionally known ones, for example, those containing Si-based, Ti-based, Zr-based metal alkoxides, metal chlorides, metal isocyanates and the like can be mentioned.

The coating solution is prepared by
It can be prepared by adding the above-mentioned photocatalytically active material precursor, or the precursor particles and an inorganic binder, and a sublimation agent. In the present invention, the sublimation agent is preferably completely dissolved in the coating liquid. Further, the solid content concentration in the coating liquid is not particularly limited as long as it has a viscosity capable of forming a thin film having a desired film thickness on a substrate. The solvent may be any one capable of dissolving the photocatalyst precursor (not in the form of particles) or the inorganic binder and the sublimation agent,
It is not particularly limited, for example, using a photocatalyst precursor or a material containing a partial hydrolyzate of titanium alkoxide as an inorganic binder, when using naphthalene as a sublimation agent, alcohol solvents such as ethanol, isopropanol, ethyl cellosolve are preferred. To be

The content of the sublimation agent in the solid content of the coating liquid depends on the types of the sublimation agent, the photocatalytically active material precursor and the inorganic binder, and cannot be determined unconditionally, but the sublimation agent is naphthalene or its When it is an analog, it is usually 35 to 60% by weight, preferably 4
It is selected in the range of 5 to 55% by weight. When this content deviates from the above range, it is difficult to form a thin film having a desired porous structure.

For the purpose of accelerating the photocatalytic activity, the coating liquid may optionally contain a conventionally known photocatalytic accelerator. As this photocatalyst accelerator,
Preferable examples include platinum group metals such as platinum, palladium, rhodium and ruthenium. These may be used alone or in combination of two or more. From the viewpoint of photocatalytic activity, the addition amount of the photocatalyst promoter is usually selected in the range of 1 to 20% by weight based on the total weight of the photocatalyst active material and the photocatalyst promoter formed by the crystallization treatment described below. .

In the present invention, the coating solution thus obtained is coated on a substrate by a known method such as a dip coating method, a spin coating method, a spray coating method, a bar coating method, a knife coating method, a roll coating method. Method, blade coating method, die coating method, gravure coating method, etc., the film thickness of the finally formed thin film is 10 to 450 n.
m, preferably 30 to 200 nm,
By heating and drying at a temperature of 120 ° C. or lower under normal pressure or a reduced pressure of up to about 1 hPa, the sublimation agent is sublimated at the same time as solidification of the thin film to form a porous thin film.
Then, the photocatalytically active material precursor in the thin film is crystallized,
Convert to photocatalytically active material. As this crystallization method,
There is no particular limitation, and conventionally known methods such as heating, ultraviolet irradiation, microwave irradiation, and electron beam irradiation can be used.

In this way, the diameter of the holes is 30 to 30.
In the range of 00 nm and the film thickness is 10 to 450 nm,
It is possible to form the porous photocatalyst-containing thin film of the present invention preferably in the range of 30 to 200 nm. Film thickness is 1
If it is less than 0 nm, it is difficult to form it, and even if it is formed, it is difficult to exhibit a sufficient photocatalytic function. On the other hand, if the film thickness exceeds 450 nm, it becomes difficult to make it porous, and the object of the present invention cannot be achieved.

Next, the method (2) will be described. In this method, as the photocatalytically active material particles contained in the coating liquid, any of the particles of the photocatalytically active material described above can be used, but titanium dioxide particles are particularly preferable. The particle size of the photocatalytically active material particles is not particularly limited, but from the viewpoint of increasing the surface area, particles having a primary particle size of about 1 to 10 nm are aggregated to form 50 to 40 particles.
The thickness of about 0 nm is preferable. The inorganic binder is not particularly limited, and conventionally known ones, for example, those containing a metal alkoxide such as Si-based, Ti-based, Zr-based, metal chloride, metal isocyanate, etc. can be mentioned. On the other hand, as the sublimation agent, the same ones as in the case of (1) above can be mentioned.

The coating solution is prepared in a suitable solvent.
It can be prepared by adding the above-mentioned photocatalytically active material particles, an inorganic binder, and a sublimation agent. In the present invention, the sublimation agent is preferably completely dissolved in the coating liquid. Further, as the solid content concentration in the coating liquid, as long as it has a viscosity capable of forming a thin film having a desired film thickness on a substrate,
There is no particular limitation. The solvent is not particularly limited as long as it can dissolve the inorganic binder and the sublimation agent, and for example, a solvent containing a partial hydrolyzate of silicon alkoxide is used as the inorganic binder and when naphthalene is used as the sublimation agent. Preferred are alcohol solvents such as methanol, ethanol, and isopropanol.

The content of the sublimation agent in the solid content of the coating liquid depends on the types of the sublimation agent and the inorganic binder and cannot be determined unconditionally, but when the sublimation agent is naphthalene or its analogue. Is usually 3
It is selected in the range of 5 to 60% by weight, preferably 45 to 55% by weight. When this content deviates from the above range, it is difficult to form a thin film having a desired porous structure.

For the purpose of promoting the photocatalytic activity, the coating liquid may optionally contain a conventionally known photocatalytic accelerator. As this photocatalyst accelerator,
The same as those exemplified in the above (1) can be mentioned, and the addition amount thereof is usually 1 based on the total weight of the photocatalytically active material particles and the photocatalytic promoter from the viewpoint of photocatalytic activity.
-20% by weight is selected.

In the present invention, the coating liquid thus obtained is applied to the substrate in the same manner as in the above (1) to form a thin film having a thickness of 10 to 450 n.
m, preferably 30 to 200 nm,
By heating and drying at a temperature of 120 ° C. or lower under atmospheric pressure or a reduced pressure of up to about 1 hPa, the sublimation agent sublimes at the same time as the solidification of the thin film, and the pore diameter is 30 to 3000 nm as in (1) above. And the film thickness is 10 to 4
The photocatalyst-containing porous thin film of the present invention having a thickness of 50 nm, preferably in the range of 30 to 200 nm, is formed.

In the photocatalyst-containing porous thin film of the present invention, the pores usually have a diameter larger than that of the thin film,
In addition, the thin film surface has an opening portion and penetrates to the surface of the base material. That is, the base material at the bottom of the holes is normally exposed, and the characteristics of the base material can be preferably utilized.

For example, when an article provided with a photocatalyst layer is used for air cleaning or water purification treatment, its effect is often determined by the adsorption ability of the substance to be removed to the article. The object to be removed which shows good adsorption ability to the photocatalyst layer provided on the article is effectively removed by the photocatalytic action, but the object to be removed having poor adsorption ability to the photocatalyst layer cannot be expected to be removed by the photocatalytic action in many cases. . However, in the present invention, since the surface of the base material at the bottom of the pores is exposed, it is preferable to use a substance capable of effectively adsorbing an object to be removed which is inferior in adsorption ability to such a photocatalyst layer as the base material. Or by pre-supporting this substance on the surface of the substrate,
The above problem can be easily solved.

The base material on which the photocatalyst-containing porous thin film of the present invention is formed is not particularly limited, and various base materials, for example, inorganic base materials such as metal, glass and ceramics, plastics, organic fibers, wood materials, etc. The organic base material can be mentioned. In the case of an organic base material, if a photocatalyst-containing porous thin film is directly provided on the surface of the base material, the base material is inevitably deteriorated by a photocatalytic action.
It is preferable to provide it through the organic-inorganic composite gradient film (Japanese Patent Application No. 11-264592) found by the present inventors.

The organic-inorganic composite gradient film is preferably applied to an organic base material such as a plastic base material. By providing the composite gradient film on the base material, the surface layer is
The content rate of the metal component in the composite gradient film is almost 100%, which gradually decreases in the direction of the base material, and is almost zero in the vicinity of the base material.
%. That is, in the organic-inorganic composite gradient film, the surface in contact with the organic base material is substantially composed of the organic polymer compound component, and the other open system surface is composed only of the metal oxide compound component. ing. Therefore, by providing the photocatalyst-containing porous thin film of the present invention on this composite gradient film, deterioration of the organic base material can be suppressed.

The inorganic base material can be used in any of the above-mentioned methods (1) and (2). In the method (1), a photocatalytically active material precursor is added.
When crystallized by heat treatment and converted into a photocatalytically active material, the heat treatment is usually performed at a temperature of 400 ° C. or higher, so that the inorganic base material or the organic base material having excellent heat resistance can be used as the base material. A polyimide base material and the like having excellent properties are preferably used. In addition, in the method of (1),
When crystallizing by a means that does not require high temperature heating,
The following organic base materials made of general-purpose plastics can also be used.

On the other hand, in the method (2), an organic base material made of general-purpose plastic such as polypropylene, polyethylene terephthalate, polymethylmethacrylate having a heat resistant temperature of 120 ° C. or higher can also be used.

The present invention also provides a coating agent for forming a photocatalyst-containing porous thin film, and an article having the above-mentioned photocatalyst-containing porous thin film of the present invention. The coating agent of the present invention contains a photocatalytically active material and / or its precursor and a sublimation agent, and this coating agent will be described in the description of the coating liquid for the photocatalyst-containing porous thin film of the present invention. That's right.

Further, the use of the article having the photocatalyst-containing porous thin film of the present invention is not particularly limited, and any use can be used for the application to which the photocatalytic reaction can be applied. For example, it is useful for deodorizing, antifouling, antibacterial, sterilizing, decomposing / removing various substances which are a problem in environmental pollution in wastewater or waste gas, and solar cell parts. Furthermore, by applying the superhydrophilic function of the photocatalyst, for example, to prevent contamination by soot contained in the exhaust gas of automobiles such as sound barriers on highways and street lights, or film for automobile body coats and side mirrors. It can also be used for antifogging and self-cleaning window glass.

[0038]

EXAMPLES The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples. The film thickness and pore diameter of the thin film obtained in each example were measured according to the methods described below. (1) A thin film such as a pair of tweezers having a sharp tip is used to partially peel off the thin film at 10 places, and the step is measured with a surface profile measuring microscope (VF-7500, manufactured by Keyence Corporation).
This average value was used as the film thickness of the thin film. (2) Pore diameter A scanning electron microscope (SEM) image was obtained on the surface of the thin film, 20 pores were randomly selected from the image and the diameters were measured, and the average value was taken as the pore diameter of the thin film. did.

Example 1 A 65 × 15 × 1 mm slide glass substrate was used as a base material. Photocatalyst coating agent containing photocatalyst particles and silica-based binder [Ishihara Sangyo Co., Ltd., trade name "ST-
K03 ", solid concentration 90g / liter] 2ml and 50
2 ml of naphthalene ethanol solution with g / l concentration
Was mixed with 6 ml of ethanol and stirred to prepare a coating liquid.

Using this coating solution, a slide glass substrate was spin-coated (1500 rpm, 12 rpm).
Second), and after sufficiently drying, at 120 ° C. for 10
The target photocatalyst-containing porous thin film was formed by heat treatment for minutes. The properties of this thin film are shown in Table 1. In addition, FIG. 1 shows an SEM photograph of the obtained thin film as viewed from above.

Example 2 The same operation as in Example 1 was carried out except that the amount of the naphthalene ethanol solution having a concentration of 50 g / l was 1.6 ml and the amount of ethanol was 6.4 ml. The target photocatalyst-containing porous thin film was formed. The properties of this thin film are shown in Table 1.

Example 3 The same operation as in Example 1 was carried out except that the amount of the naphthalene ethanol solution having a concentration of 50 g / liter was changed to 2.4 ml and the amount of ethanol was changed to 5.6 ml. The target photocatalyst-containing porous thin film was formed. The properties of this thin film are shown in Table 1.

Example 4 Titanium tetraisopropoxide [Wako Pure Chemical Industries, Ltd.]
Made by] 6.4 g and 2-propanol [Wako Pure Chemical Industries, Ltd.]
A mixture of 1.8 g of concentrated hydrochloric acid [manufactured by Wako Pure Chemical Industries, Ltd.] and 6 ml of 2-propanol was slowly added dropwise to a mixture of 60 ml of the above product and stirred for 1 hour. This is referred to as Binder A. Suspension of titanium oxide in 11 ml of 2-propanol [Sumitomo Osaka Cement Co., Ltd.
Made, product name "PCT-15T", solid concentration 135g /
1 ml of binder A and 6 ml of a 50 g / l concentration naphthalene ethanol solution were added, and mixed and stirred to prepare a coating liquid. Using this coating liquid, Example 1
A target photocatalyst-containing porous thin film was formed in the same manner as in. The properties of this thin film are shown in Table 1.

Example 5 As a base material, a slide glass substrate of 65 × 15 × 1 mm was used. Binder A prepared in the same manner as in Example 4
11 ml and 13 ml of 2-propanol were mixed and stirred, and 6 ml of a naphthalene ethanol solution having a concentration of 50 g / liter was further added thereto, and mixed and stirred to prepare a coating liquid. Using this coating solution, a spin glass method (1500 rpm,
The film was formed for 12 seconds), dried sufficiently, heat-treated at 120 ° C. for 10 minutes to form a thin film, and then baked at 500 ° C. to form an intended photocatalyst-containing porous thin film. . The properties of this thin film are shown in Table 1.

Example 6 A 65 × 15 × 1 mm slide glass substrate was used as a base material. Photocatalyst coating agent containing photocatalyst particles and silica-based binder [Ishihara Sangyo Co., Ltd., trade name "ST-
K03 ", solid concentration 90 g / liter] 8 ml and 50
8 ml of naphthalene ethanol solution with g / l concentration
Was mixed and stirred with 184 ml of ethanol to prepare a coating liquid. Using this coating liquid, a dip coating method (pulling speed = 10
(0 m / min), and after thoroughly drying, 120 ℃
The target photocatalyst-containing porous thin film was formed by heat-treating for 10 minutes. The properties of this thin film are shown in Table 1.

Example 7 The procedure of Example 6 was repeated except that the bar coating method (coating liquid film 6.9 μm) was used instead of the dip coating method in Example 6 to carry out the same procedure as in Example 6. A photocatalyst-containing porous thin film was formed. The properties of this thin film are shown in Table 1.

Example 8 The procedure of Example 6 was repeated, except that the pulling rate in the dip coating method was changed to 10 m / min, to form the desired photocatalyst-containing porous thin film.
The properties of this thin film are shown in Table 1.

Example 9 A slide glass substrate having a size of 65 × 15 × 1 mm was used as a base material. Photocatalyst coating agent containing photocatalyst particles and silica-based binder [Ishihara Sangyo Co., Ltd., trade name "ST-
K03 ", solid concentration 90g / liter] 40ml and 5
Naphthalene ethanol solution with a concentration of 0 g / liter 40 m
l was mixed with 120 ml of ethanol and stirred to prepare a coating liquid. Using this coating liquid, a dip coating method (pulling speed = 2
(0 m / min), and after thoroughly drying, 120 ℃
The target photocatalyst-containing porous thin film was formed by heat-treating for 10 minutes. The properties of this thin film are shown in Table 1.

Example 10 A target photocatalyst-containing porous thin film was formed in the same manner as in Example 9 except that the pulling rate in the dip coating method was 150 m / min. The properties of this thin film are shown in Table 1. A micrograph of the obtained thin film when viewed from above is shown in FIG.

Comparative Example 1 A thin film was formed in the same manner as in Example 9 except that the pulling rate in the dip coating method was 300 m / min. Table 1 shows the properties of this thin film.
Shown in.

[0051]

[Table 1]

(Note) 1) Film forming method: SC = spin coating method, DC = dip coating method, BC
= Bar coat method 2) Presence / absence of porous structure ◯: Has a porous structure. X: Does not have a porous structure.

From Table 1, the photocatalyst-containing porous thin films obtained in Examples 1 to 10 had a film thickness of 17 to 390 nm, which was in the range of 10 to 450 nm specified in the present invention. The diameter of the pores was 50 to 2000 nm, which was in the range of 30 to 3000 nm specified in the present invention.
Further, in all cases, the diameter of the holes was larger than the film thickness. On the other hand, the photocatalyst-containing thin film obtained in Comparative Example 1 had a film thickness of 490 nm, which was 10 in accordance with the present invention.
The upper limit of ˜450 nm was exceeded, and a porous structure was not obtained.

[0054]

EFFECTS OF THE INVENTION According to the present invention, it can be formed on an organic substrate having a low heat resistance by a simple operation, and the surface area where a photocatalytic reaction occurs is large, and an excellent photocatalytic function can be exhibited. A photocatalyst-containing porous thin film can be provided.

[Brief description of drawings]

1 is an SEM photograph of the thin film obtained in Example 1. FIG.

2 is a micrograph of the thin film obtained in Example 10. FIG.

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Claims (8)

[Claims] 1. A photocatalyst-containing thin film in which a coating liquid containing a photocatalytically active material and / or its precursor and a sublimation agent is applied to a substrate, and then the sublimation agent is sublimated to form pores. The thickness of the thin film after formation is 10 to 450 nm
And a photocatalyst-containing porous thin film having pores with a diameter of 30 to 3000 nm. 2. The photocatalyst according to claim 1, wherein the coating liquid is applied to a substrate, the sublimation agent is sublimated to form pores, and then crystallization treatment is performed to convert the photocatalytically active material precursor into a photocatalytically active material. Containing porous thin film. 3. The photocatalyst according to claim 1 or 2, wherein the pores have a diameter larger than the thickness of the thin film, have pores on the surface of the thin film, and have a structure penetrating to the surface of the base material. Containing porous thin film. 4. The sublimation agent is 12 under normal pressure or reduced pressure.
A compound that sublimes at 0 ° C. or lower.
The porous thin film containing a photocatalyst according to item 1. 5. The sublimation agent is naphthalene and / or an analogue thereof, and the content of the sublimation agent in the solid content of the coating liquid is 35 to 60% by weight. The photocatalyst-containing porous thin film described. 6. The photocatalyst-containing porous thin film according to claim 1, wherein the photocatalytically active material is titanium dioxide. 7. A coating agent for forming a photocatalyst-containing porous thin film, comprising a photocatalytically active material and / or a precursor thereof and a sublimation agent. 8. An article comprising the photocatalyst-containing porous thin film according to any one of claims 1 to 6.