JP2001279471A - Method for producing thin film onto porous body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a thin film onto a porous body in which a uniform thin film is formed on the surface of a porous body. SOLUTION: The first thin film 2 with a thickness of <=0.1 μm is transfer printed the surface of a porous body 1. Next, the second thin film 3 is formed on the surface of the first thin film 2. The surface of the porous body 1 can be smoothened by the first thin film 2, and the second thin film 3 can uniformly be formed on the smoothened surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a thin film on the surface of a thin film of silica aerogel having properties such as heat insulation, electric insulation, low refractive index and low dielectric constant.

2. Description of the Related Art Silica airgel is disclosed in U.S. Pat.
As disclosed in US Pat. No. 2,927, US Pat. No. 4,432,956, US Pat. No. 4,610,863, alkoxysilane (also referred to as silicon alkoxide or alkyl silicate) is hydrolyzed and condensed by condensation. The obtained gel compound can be obtained by drying in the presence of a dispersion medium under supercritical conditions at or above the critical point of the dispersion medium. Also, JP-A-5-2790
As disclosed in Japanese Patent Application Laid-Open No. 11-138375 and Japanese Patent Application Laid-Open No. 7-138375, by subjecting silica airgel to a hydrophobizing treatment, the moisture resistance of the silica airgel can be increased, and a decrease in the characteristics of the silica airgel can be prevented. Silica airgel has properties such as high heat insulation, high electrical insulation, low refractive index, and low dielectric constant, and is expected to be applied to various fields by utilizing these properties.
For example, a highly functional substrate can be manufactured by forming a thin film of silica airgel on the surface of the substrate and further forming a thin functional film on the surface of the silica airgel. For example, a conductive metal thin film such as copper is provided as a functional thin film on the surface of a silica airgel thin film, and a circuit is formed using the conductive metal thin film, thereby producing a circuit board utilizing the low permittivity of silica airgel. Is what you can do.

However, silica airgel is a porous material and has irregularities, and it is difficult to uniformly form a functional thin film on the surface of the silica airgel, and it has not been put to practical use. is the current situation. In addition, since the surface of the porous body has irregularities, it is difficult to uniformly form a functional thin film on the surface is a problem that the porous body generally has. The present invention has been made in view of the above points, and has as its object to provide a method of forming a thin film on a porous body that can uniformly form a thin film on the surface of a porous body such as silica airgel. Things.

According to a first aspect of the present invention, there is provided a method for forming a thin film on a porous body, comprising transferring a first thin film having a thickness of 0.1 μm or less to the surface of the porous body. The second thin film is formed on the surface of the first thin film. The invention according to claim 2 is characterized in that the first thin film forming method is a Langmuir-Blodgett method. The invention according to claim 3 is characterized in that, when forming the first thin film by the Langmuir-Blodgett method, the first thin film is formed of a polymer having a group having a photocrosslinkable group in a side chain. Things. The invention according to claim 4 is characterized in that, when forming the first thin film by the Langmuir-Blodgett method, the surface of the hydrophobic porous body is hydrophilized by a polymer constituting the first thin film. Things. The invention according to claim 5 is characterized in that the second thin film is a conductive material thin film. The invention according to claim 6 is characterized in that the second thin film is an infrared reflective thin film. The invention according to claim 7 is characterized in that the second thin film is a transparent inorganic oxide thin film. The invention of claim 8 is
The second thin film is a transparent conductive thin film. In a ninth aspect of the present invention, the second thin film is a phosphor thin film. Claim 1
Invention 0 is characterized in that the porous body is silica airgel.

Embodiments of the present invention will be described below. Silica airgel is disclosed in US Pat. No. 4,402,927.
No. 4,432,956 and No. 4,610,862
As disclosed in Japanese Patent Publication No. 3 (1993), a wet gel compound comprising a silica skeleton obtained by hydrolysis and polymerization of alkoxysilane (also referred to as silicon alkoxide or alkyl silicate) is converted into alcohol or carbon dioxide. In the presence of such a solvent (dispersion medium), the solvent can be produced by drying in a supercritical state at or above the critical point of the solvent. Supercritical drying is, for example, immersing the gel-like compound in liquefied carbon dioxide, replacing all or part of the solvent contained in the gel-like compound with liquefied carbon dioxide having a lower critical point than this solvent, and thereafter, carbon dioxide Or a mixture of carbon dioxide and a solvent under supercritical conditions. Silica airgel is disclosed in U.S. Pat.
As provided in JP-A-124364, it can be produced in the same manner as described above using sodium silicate as a raw material. Here, as disclosed in Japanese Patent Application Laid-Open Nos. Hei 5-279011 and Hei 7-138375,
It is preferable to impart hydrophobicity to the silica airgel by subjecting the gel compound obtained by the hydrolysis and polymerization reaction of the alkoxysilane to a hydrophobic treatment as described above. The hydrophobic silica airgel imparted with such hydrophobicity makes it difficult for moisture, water and the like to infiltrate, and can prevent the performance of the silica airgel such as the refractive index and the light transmittance from deteriorating. The step of this hydrophobic treatment is
It can be performed before or during supercritical drying of the gel compound. The hydrophobizing treatment is performed in order to make the hydroxyl group of the silanol group present on the surface of the gel compound react with the functional group of the hydrophobizing agent, and to replace the hydrophobic group with the hydrophobic group of the hydrophobizing agent to make the surface hydrophobic. . As a method of performing the hydrophobizing treatment, for example, after immersing the gel in a hydrophobizing treatment solution in which the hydrophobizing agent is dissolved in a solvent, mixing and so on, the permeation of the hydrophobizing agent into the gel,
There is a method of performing a hydrophobic reaction by heating as necessary. Here, examples of the solvent used for the hydrophobizing treatment include methanol, ethanol, isopropanol, xylene, toluene, benzene, N, N-dimethylformamide, and hexamethyldisiloxane. The material is not limited to these as long as it can be easily dissolved and can be replaced by the solvent contained in the gel before the hydrophobic treatment. In the case where supercritical drying is performed in a subsequent step, a medium which can be easily subjected to supercritical drying, for example, the same type as that of methanol, ethanol, isopropanol, liquid carbon dioxide, or the like, or a medium which can be replaced with the same is preferable. As the hydrophobizing agent, for example, hexamethyldisilazane, hexamethyldisiloxane, trimethylmethoxysilane, trimethyldimethoxysilane, dimethyldimethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, trimethylethoxysilane, dimethyldiethoxysilane, Methyltriethoxysilane and the like can be mentioned. The silica airgel produced as described above is porous, and when a liquid substance is applied, the liquid substance easily penetrates by capillary action, and the microporous structure of the silica airgel is destroyed, and the properties of the silica airgel are impaired. There is a risk. In particular, in the case of silica airgel that has not been subjected to a hydrophobic treatment, the microporous structure of the silica airgel is destroyed regardless of whether the liquid substance is aqueous or oily. On the other hand, the hydrophobic silica airgel that has been subjected to the hydrophobizing treatment does not suffer from the destruction of the microporous structure for an aqueous liquid substance, but suffers the destruction of the microporous structure for an oily liquid substance. Therefore, the invention of claim 1 does not apply a liquid substance to the surface of the silica airgel 1 to form a thin film, but instead transfers a thin film prepared in advance to the surface of the silica airgel 1, as shown in FIG. As shown, a first thin film 2 is formed on the surface of a silica airgel 1, and the surface of the silica airgel 1 is smoothed by the first thin film 2.
The first thin film 2 formed on the surface of the silica airgel 1 is thin so that the silica airgel 1 can effectively exhibit properties such as high heat insulation, high electrical insulation, a low refractive index, and a low dielectric constant without deteriorating. It is desirable to form the first thin film 2
Is set to 0.1 μm or less. The lower limit of the film thickness is not particularly set, but in order to obtain the effect of smoothing the surface of the silica airgel 1, it is desirable to have a film thickness of 0.001 μm or more. As a method of forming the first thin film 2 by transfer, in addition to the Langmuir-Blodgett method described later, a method of transferring a cast film obtained from a high-concentration polymer solution to the surface of the silica airgel 1 can be considered. However, it is difficult to control the film thickness of the polymer cast film to 0.1 μm or less, and the film thickness often becomes 0.1 μm or more. When the thickness of the first thin film 2 formed of a polymer is increased, the stress generated in the polymer film during curing after the formation of the first thin film 2 of the polymer causes an interface surface with the silica airgel 1 to be generated. As a result, the first thin film 2 may be peeled off, and the surface of the silica airgel 1 may not be smoothed. According to a second aspect of the present invention, the first thin film 2 is formed on the surface of the silica airgel 1 by a Langmuir-Blodgett method. In the Langmuir-Blodgett method (hereinafter abbreviated as LB method), a polymer thin film is formed on a water surface by spreading a water-insoluble solution of the polymer on the water surface, and the silica aerogel is formed on the polymer thin film at an appropriate surface pressure. 1 is a method in which the first thin film 2 is formed by bringing the surface of the first thin film 2 into contact and transferring the polymer thin film onto the surface of the silica airgel 1 from the water surface. Although the silica airgel 1 can form the first thin film 2 by the LB method regardless of whether the surface is hydrophilic or hydrophobic, it is preferable that the silica airgel 1 has been subjected to a hydrophobic treatment in advance. The surface of the silica airgel 1 can be smoothed by forming the first thin film 2 on the surface of the silica airgel 1 with the polymer thin film by the LB method. The polymer thin film formed by the LB method has a feature that the film thickness is a single molecule level and can be produced as a very thin film of the order of several nanometers. There is a feature that the film thickness can be controlled on a nano scale by changing the thickness. Further, as described later, it is said that the cumulative film structure can be changed and the properties of the film surface can be changed by a method of accumulating a polymer thin film on the surface of the silica airgel 1, such as a vertical immersion method or a horizontal adhesion method. There are also features.
In forming a polymer thin film by the LB method, examples of the polymer include amphiphilic polymers such as polyimide, polyalkyl acrylate, polyester, polyvinyl acetal, and polyglutamate. According to the invention of claim 3, as the polymer formed as the first thin film 2 on the surface of the silica airgel 1 by the LB method as described above, a polymer having a photocrosslinkable group in a side chain is used. Things. Examples of the photocrosslinkable group include a cinnamate group. After the first thin film 2 is formed on the surface of the silica airgel 1 with a polymer having a photocrosslinkable group in the side chain, the polymer constituting the first thin film 2 is irradiated with ultraviolet light. The first thin film 2 having high properties such as heat resistance can be fixed by three-dimensionally fixing the structure of the polymer constituting the first thin film 2 by photocrosslinking between the chains. You can do it. Therefore,
For example, the first thin film 2 can be thermally stabilized against a temperature rise when, for example, aluminum is deposited on the first thin film 2 to form the second thin film 3 as described later. Things. In forming the first thin film 2 on the surface of the silica airgel 1 by the LB method as described above, the surface of the hydrophobic silica airgel 1 is changed to a polymer constituting the first thin film 2. Is made hydrophilic. As described above, as a method of forming a polymer thin film by the LB method, there are a vertical dipping method and a horizontal deposition method. FIG. 2 shows a method of forming a polymer thin film by a horizontal deposition method. When a water-insoluble solution of an amphiphilic polymer is spread on the surface of water 10, as shown in FIG. Each polymer 11 has a hydrophilic portion 11a at the lower end where it contacts water 10;
The polymer thin film 12 is arranged in parallel on the water surface with the hydrophobic portion (lipophilic group) 11b positioned at the upper end not in contact with water.
Is formed. Then, when the surface of the silica airgel 1 is horizontal and pressed against the polymer thin film 12, the hydrophobic portions 11 b of the respective polymers 11 adhere to the hydrophobic surface of the silica airgel 1. Next, when the silica aerogel 1 is pulled up, as shown in FIG. 2 (b), the polymer thin film 12 is removed from the water surface while the hydrophobic portion 11b of each polymer 11 adheres to the surface of the silica aerogel 1. The first thin film 2 is transferred to the surface and can be formed on the surface of the silica airgel 1. Thus, the first thin film 2 formed by only one layer by one adhesion operation
In each of the polymers 11 constituting the first thin film 2, the hydrophobic portion 11b is arranged on the side of the silica airgel 1 and the hydrophilic portion 11a is arranged on the opposite side. Is formed of the hydrophilic portion 11a of each polymer 11, and the surface of the silica airgel 1 can be made hydrophilic by the first thin film 2. As described above, when the surface of the silica airgel 1 is made hydrophilic by forming the first thin film 2 on the surface of the hydrophobic silica airgel 1, as described later, a transparent conductive thin film such as indium tin oxide is used. In forming the second thin film 3 on the first thin film 2, the second thin film 3 can be formed stably. On the other hand, FIG. 3 shows a method of forming a polymer thin film by a vertical immersion method. When a water-insoluble solution of an amphiphilic polymer is spread on the surface of water 10, FIG. ), Each polymer 11 has a hydrophilic portion 11a at the lower end and a hydrophobic portion 1a.
1b is arranged in the direction located at the upper end, and the polymer thin film 12
Are formed on the water surface. When the surface of the silica airgel 1 is perpendicular to the water surface and the silica airgel 1 is immersed in water, the hydrophobic surface of each polymer 11 is placed on the hydrophobic surface of the silica airgel 1 as shown in FIG. Sex part 1
1b is attached, and the hydrophobic portion 11b is a silica airgel 1
Is formed on the surface of the silica airgel 1 with the hydrophilic portions 11a arranged on the surface side. As described above, the surface side of the first polymer thin film 12 formed on the surface of the silica airgel 1 is hydrophilic because the hydrophilic portions 11a are arranged. Next, when the silica airgel 1 is pulled out of the water, the surface side of the polymer thin film 12 adhered to the surface of the silica airgel 1 is hydrophilic.
Adheres to the surface of the polymer thin film 12 on the surface of the silica airgel 1, and the two-layer polymer thin film 12 adheres to the surface of the silica airgel 1 as shown in FIG. The first thin film 2 formed by accumulating the two polymer thin films 12 in this manner can be provided on the surface of the silica airgel 1, and the surface of the first thin film 2 has hydrophobic properties. Part 1
Since 1b is arranged, the surface of the silica airgel 1 can be made hydrophobic. After forming the first thin film 2 on the surface of the silica airgel 1 as described above and smoothing the surface of the silica airgel 1, FIG. 1 (b)
By forming the second thin film 3 on the first thin film 2 as described above, a functional thin film is provided on the surface of the silica airgel 1. Since the surface of the silica airgel 11 is smoothed by the first thin film 2, a functional thin film can be uniformly formed on the surface of the silica airgel 1 as the second thin film 3. Here, in forming the second thin film 3 as a functional thin film, in the invention of claim 5, the second thin film 3 is formed of a conductive material thin film. As the conductive substance, a conductive metal such as copper, aluminum, magnesium, and silver can be used, but copper is generally preferred in terms of conductivity and cost. By forming the second thin film 3 with a conductive material thin film in this way, the silica airgel 1 can be used as a metal-clad substrate. The conductive material thin film 3 is formed with a photoresist, masked, exposed,
The circuit board can be used as a circuit board by forming a circuit pattern by performing development and etching processes. Silica airgel 1 has a dielectric constant of 1.05
Since it shows a very small value of about 2.0, it can be used as an excellent low dielectric constant circuit board for use in highly integrated circuits. In the invention of claim 6, the second thin film 3 is formed of an infrared reflective thin film. This infrared reflective thin film can be formed of a thin film of aluminum or titania. By forming the second thin film 3 as an infrared-reflective thin film in this way, infrared light can be reflected, and the silica airgel 1 can be used as a heat insulating substrate. Moreover, the silica airgel 1 has a thermal conductivity of 0.01 to 0.025 m.
Since it has a very low density of about W / mK and a very low density, the coefficient of thermal conductivity at the interface with the infrared reflective thin film becomes large, so that it exhibits more excellent heat insulating properties.
In the invention of claim 7, the second thin film 3 is formed of a transparent inorganic oxide thin film. Silica or the like can be used as the transparent inorganic oxide. The light transmission performance is such that light is totally reflected at the interface between the silica airgel 1 and the thin film 3 made of a transparent inorganic oxide thin film, and the thin film 3 made of the transparent inorganic oxide thin film is used as a light conducting path having high light transmission performance. It can be used as an optical waveguide substrate having excellent characteristics. Since the silica airgel 1 has a very low refractive index of 1.008 to 1.1, the first half light blocking ratio at the interface between the light conducting path and the outside is high, and even if the light conducting path is formed in a curved pattern, the light of the light is low. Transmission loss can be minimized. Here, the first thin film 2 is interposed between the silica airgel 1 and the second thin film 3, but the first thin film 2 has a thickness of 0.1 μm or less and is smaller than the wavelength of light. It does not affect the total reflection of light between the silica airgel 1 and the second thin film 3 at all. Therefore, it is not preferable that the thickness of the first thin film 2 is equal to or greater than the wavelength of the conducting light, because the light to be transmitted cannot be transmitted. In the invention of claim 8, the second thin film 3 is formed of a transparent conductive thin film. This transparent conductive thin film can be formed of a transparent conductive material such as indium tin oxide (ITO), indium zinc oxide (IXO), silver, and chromium. By forming the second thin film 3 with a transparent conductive thin film in this way, the silica airgel 1 can be used as a light emitting element substrate. For example, the surface of the transparent conductive second thin film 3 has E
Providing an L (electroluminescence) layer, further providing a back metal electrode on the surface of the EL layer, and applying an electric field between the transparent conductive second thin film 3 and the back metal electrode to cause the EL layer to emit light. And can be used for a display as an EL light emitting element.
Here, silica airgel 1 has a light refractive index of 1.008.
The light passing through this silica airgel 1 having a low refractive index has a high extraction rate to the atmosphere,
EL with high extraction rate for extracting light emitted from the layer to the outside
It can be used as a light emitting element. Here, the first thin film 2 is interposed between the silica airgel 1 and the second thin film 3, and the first thin film 2 has a thickness of 0.1 μm.
m, which is smaller than the wavelength of light, so that it has no effect on the extraction rate of light to the atmosphere. As the EL layer, those conventionally used as organic EL and inorganic EL can be used. Further, since the silica airgel 1 has a light refractive index as small as 1.008 to 1.1, it has an optical function equivalent to the presence of air. Can form a display. In the ninth aspect of the present invention, the second thin film 3 is formed of a phosphor thin film made of a phosphor material. In this device, the fluorescent substance constituting the second thin film 3 emits light by ultraviolet irradiation, and can be used as a fluorescent thin film substrate having a high light extraction efficiency by the same principle as the above EL light emitting element. In the above-described embodiment, an example in which a thin film is formed on the surface of silica airgel has been described. However, the method for forming a thin film according to the present invention can be applied to all porous materials other than silica airgel. It is. As a porous body other than silica airgel, as a hydrophilic porous body, for example, a wet gel obtained by a hydrolysis polymerization reaction of an alkoxysilane or a gelation reaction of a sodium silicate solution is dried by ordinary heating or reduced pressure. Porous silica (xerogel) obtained by the above method. Examples of the hydrophobic porous body include a hydrophobicized product of the above xerogel, a porous polymer obtained by drying a low-concentration gelled melamine resin, polystyrene and polymethyl methacrylic resin. There is a porous polymer or the like obtained by selectively dissolving and removing the polystyrene resin with a solvent after drying the melt of the polystyrene resin and the polystyrene resin, and the material is not particularly limited.

The present invention will be described below in detail with reference to examples. (Example 1) Using a soda glass substrate having a hydrophobic silica airgel film formed on the surface thereof, polyvinyl octanal acetal was immersed at a surface pressure of 25 mN / m by the LB method to obtain a hydrophobic silica airgel film. A first thin film having a thickness of 10 nm was formed on the surface of. This first thin film is formed by one layer of a polymer thin film, and the surface is hydrophilic. Next, at room temperature, 0.003 Pa, 10
A transparent conductive thin film made of an IXO thin film having a thickness of 200 nm was formed as a second thin film on the first thin film by sputtering under the condition of 0 W. (Example 2) Using a soda glass substrate having a hydrophobic silica airgel film formed on the surface thereof, polyvinyl octanal acetal was immersed at a surface pressure of 25 mN / m by the LB method to obtain a hydrophobic silica airgel film. A first thin film having a thickness of 10 nm was formed on the surface of. This first thin film is formed by one layer of a polymer thin film, and the surface is hydrophilic. Next, at 200 ° C., 0.003 Pa,
By sputtering under the condition of 300 W, a 200 nm thick IT is formed as a second thin film on the first thin film.
A transparent conductive thin film made of an O thin film was formed. (Example 3) Using a soda glass substrate having a hydrophobic silica airgel film formed on its surface, polyvinyl octanal acetal was immersed at a surface pressure of 25 mN / m by the LB method to obtain a hydrophobic silica airgel film. After forming a first polymer thin film having a thickness of 10 nm on the surface of
Polyvinyl octanal acetal with a surface pressure of 25 mN /
m, the thickness is 10 nm
Was formed, and a first thin film was formed. This first thin film is formed by two polymer thin films, and the surface is hydrophobic. Next, a transparent conductive thin film made of an ITO thin film having a thickness of 200 nm was formed as a second thin film on the first thin film by sputtering at 200 ° C. under the conditions of 0.003 Pa and 300 W. (Example 4) A soda glass substrate having a hydrophobic silica airgel film formed on its surface was used to immerse a polyvinyl octanal acetal-sinmate-copolymer under a condition of a surface pressure of 25 mN / m by the LB method to obtain a hydrophobic material. A first thin film having a thickness of 10 nm was formed on the surface of the porous silica airgel film. Thereafter, photocrosslinking was performed by irradiating ultraviolet rays having a wavelength of 298 nm for 5 minutes to fix the first thin film. Next, a conductive material thin film made of an Al thin film having a thickness of 50 nm was formed as a second thin film on the first thin film by an evaporation method. (Comparative Example 1) Using a soda glass substrate having a hydrophobic silica airgel film formed on its surface, only a transparent conductive thin film made of an IXO thin film was formed on the surface of the hydrophobic silica airgel in the same manner as in Example 1. Comparative Example 2 Using a soda glass substrate having a hydrophobic silica airgel film formed on its surface, only a transparent conductive thin film made of an ITO thin film was formed on the surface of the hydrophobic silica airgel in the same manner as in Example 2. (Comparative Example 3) A soda glass substrate having a hydrophobic silica airgel film formed on the surface was used, and only the Al thin film conductive material thin film was formed on the surface of the hydrophobic silica airgel in the same manner as in Example 4. Using the thin film-formed substrates obtained in Examples 1 to 4 and Comparative Examples 1 to 3 as described above, the conduction performance of the uppermost conductive thin film at a distance of 1 cm was measured by a tester. Table 1 shows the results.

[Table 1] As can be seen from Table 1, in each of the examples, since the surface of the silica airgel was smoothed by the first thin film, the conductive thin film was formed uniformly, and the conductivity increased. Is confirmed. (Example 5) Using a soda glass substrate having a hydrophobic silica airgel film formed on the surface thereof, polyvinyl octanal acetal was immersed at a surface pressure of 25 mN / m by the LB method to obtain a hydrophobic silica airgel film. A first thin film having a thickness of 10 nm was formed on the surface of. This first thin film is formed by one layer of a polymer thin film, and the surface is hydrophilic. Next, a 100 nm-thick aluminum quinolinol complex (tris (8-hydroquinoline) aluminum: "ALq3" manufactured by Dojindo Laboratories, Inc.) as a second thin film on the first thin film by an evaporation method at room temperature. Was formed. (Comparative Example 4) On the surface of a soda glass substrate on which a silica airgel film was not formed, “AL
Only a phosphor thin film made of "q3" was formed. The thin film-formed substrates obtained in Example 5 and Comparative Example 4 were irradiated with 20 W black light, and the emission luminance was measured. Table 2 shows the results.

[Table 2] As can be seen from Table 2, in the case of Example 5, the surface of the silica airgel was smoothed by the first thin film, so that the phosphor thin film was formed uniformly and the luminous property was high. It is confirmed that. (Example 6) A first thin film was formed on the surface of silica airgel by the LB method in the same manner as in Example 1 using a soda glass substrate on which silica airgel was formed with a thickness of 5 mm.
In the same manner as in Example 4, an infrared reflective thin film made of an Al thin film was formed as a second thin film on the first thin film. Comparative Example 5 An infrared reflective thin film made of an Al thin film was formed on the surface of a soda glass substrate on which no silica airgel was formed, in the same manner as in Example 4. Example 6 above
The thermal conductivity of the thin film-formed substrate obtained in Comparative Example 5 was measured in accordance with the ASTM method, and the transmittance of light having a wavelength of 1000 nm was measured with a spectrophotometer. Table 3 shows the results.

[Table 3] As can be seen from Table 3, in Example 6, since the surface of the silica airgel was smoothed by the first thin film, the infrared reflective thin film was formed uniformly, and the infrared transmittance was low. It is confirmed that.

As described above, the method for forming a thin film on a porous body according to the first aspect of the present invention comprises transferring a first thin film having a thickness of 0.1 μm or less to the surface of the porous body. Since the second thin film is formed on the surface of the first thin film, the surface of the porous body can be smoothed with the first thin film, and the second thin film can be uniformly formed on the smoothed surface. Can be formed, and the function of the second thin film can be effectively exerted. In addition, the first thin film is formed on the surface of the porous material by transfer, and does not break the microporous structure of the porous material such as silica airgel, and the first thin film is 0.1 μm The thickness is as thin as below, and the function of the second thin film is not impaired. Further, in the invention of claim 2, the first thin film forming method is a Langmuir-Blodgett method. Therefore, in the Langmuir-Blodgett method, the film thickness is at a single molecule level, and is very small on the order of several nanometers. The first thin film can be prepared as a thin film, the thickness can be controlled on the nano scale by changing the side chain length of the polymer, and the method of accumulating the polymer thin film on the surface of the porous body Thus, the properties of the film surface can be changed. According to the invention of claim 3, the first thin film is formed of a polymer having a group having a photocrosslinkable side chain in forming the first thin film by the Langmuir-Blodgett method. By irradiating ultraviolet rays after forming the first thin film, the polymer constituting the first thin film can be photocrosslinked between side chains, and can be a first thin film having high properties such as heat resistance. It is. Further, according to the invention of claim 4, in forming the first thin film by the Langmuir-Blodgett method, the surface of the hydrophobic porous body is made hydrophilic by a polymer constituting the first thin film. Even if the porous body is hydrophobic, a hydrophilic second thin film can be easily formed. According to the invention of claim 5, since the second thin film is a conductive material thin film, when the porous body is silica airgel, it is possible to produce a circuit board that effectively utilizes the low dielectric constant characteristics. It is. According to the invention of claim 6, since the second thin film is an infrared-reflective thin film, when the porous body is silica airgel, a heat insulating substrate can be produced by effectively utilizing its low thermal conductivity. is there. According to the invention of claim 7, since the second thin film is a transparent inorganic oxide thin film, when the porous body is silica airgel, it is possible to produce a light guide substrate that effectively utilizes the low refractive index. You can do it. According to the invention of claim 8, since the second thin film is a transparent conductive thin film, when the porous body is silica airgel, it is possible to produce a transparent conductive thin film substrate that effectively utilizes the low refractive index. You can do it. According to the ninth aspect of the present invention, since the second thin film is a phosphor thin film, when the porous material is silica airgel, it is possible to produce a fluorescent thin film substrate utilizing its low refractive index effectively. It is.

[Brief description of the drawings]

FIG. 1 shows an example of an embodiment of the present invention,
(A), (b) is a sectional view, respectively.

FIG. 2 shows an example of the BL method, in which (a),
(B) is a schematic sectional view, respectively.

FIG. 3 shows another example of the BL method, in which (a),
(B), (c) is a schematic sectional view, respectively.

[Explanation of Signs] 1 silica airgel 2 first thin film 3 second thin film

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masaru Yokoyama 1048 Kazuma Kadoma, Kadoma City, Osaka Prefecture F-term in Matsushita Electric Works, Ltd. 4G072 AA28 BB09 BB15 CC08 FF01 GG03 NN11 UU03 4K029 AA08 BA45 BA50 BA62 BC07 BD09 CA05 FA07 4K044 AA11 AA12 BA10 BA12 BA21 BB03 CA13

Claims (10)

[Claims] 1. A porous material, wherein a first thin film having a thickness of 0.1 μm or less is transferred to a surface of a porous body and formed, and a second thin film is formed on the surface of the first thin film. A method of forming a thin film on a body. 2. The method for forming a thin film on a porous body according to claim 1, wherein the first method for forming a thin film is a Langmuir-Blodgett method. 3. The method for forming a thin film on a porous body according to claim 2, wherein the first thin film is formed of a polymer having a group having a photocrosslinkable group in a side chain. 4. The method for forming a thin film on a porous body according to claim 2, wherein the surface of the hydrophobic porous body is hydrophilized by a polymer constituting the first thin film. . 5. The method for forming a thin film on a porous body according to claim 1, wherein the second thin film is a conductive material thin film. 6. The method for forming a thin film on a porous body according to claim 1, wherein the second thin film is an infrared reflective thin film. 7. The method of forming a thin film on a porous body according to claim 1, wherein the second thin film is a transparent inorganic oxide thin film. 8. The method for forming a thin film on a porous body according to claim 1, wherein the second thin film is a transparent conductive thin film. 9. The method for forming a thin film on a porous body according to claim 1, wherein the second thin film is a phosphor thin film. 10. The method for forming a thin film on a porous body according to claim 1, wherein the porous body is silica airgel.