WO2012127551A1

WO2012127551A1 - Silica film and method for producing same

Info

Publication number: WO2012127551A1
Application number: PCT/JP2011/007112
Authority: WO
Inventors: 泰村上; 航清水; 淳介法華
Original assignee: 国立大学法人信州大学
Priority date: 2011-03-24
Filing date: 2011-12-20
Publication date: 2012-09-27
Also published as: JP2012201529A; JP4958192B1

Abstract

[Problem] To obtain a silica film with excellent defogging performance, high hardness and high adhesion. [Solution] The present invention pertains to a silica film having pencil hardness of 3H or more measured in accordance with JIS K5600-5-4, and is obtained by dispersing a hydrophobic region having Si-Ch₃ bonds in a hydrophilic region of a porous film surface comprising fine pores classified as micropores in the IUPAC classification and having an average diameter of not more than 2nm according to BET measurements.

Description

Silica membrane and method for producing the same

The present invention relates to a silica film having excellent antifogging properties and a method for producing the same.

Conventionally, super-hydrophilic coating materials have been used for the purpose of imparting anti-fogging properties and improving optical properties. In addition to anti-fogging properties, the coating materials are frequently used because they can be expected to impart anti-staining properties and increase the efficiency of heat exchange.

As a hydrophilic material, for example, a paint in which an optical semiconductor such as crystalline titanium oxide fine particles is mixed is known. When crystalline particles are used in the paint, the transparency and permeability of the coating film are likely to be impaired. For this reason, as one of the means for solving this problem, attempts have been made to reduce the content of the optical semiconductor, and there are also known materials that can exhibit a certain degree of super hydrophilicity even if the content of the particles of the optical semiconductor is low. (For example, refer to Patent Document 1). In addition, hydrophilic polymers and surfactants have been known as superhydrophilic materials that do not contain optical semiconductor fine particles such as titanium oxide (see, for example, Patent Document 2).

Japanese Patent Laid-Open No. 11-061042 JP-A-53-058292

However, the above prior art has the following problems. Since the material disclosed in Patent Document 1 requires light irradiation for the development of super hydrophilicity, it is difficult to exhibit antifogging properties in a dark place. On the other hand, the material disclosed in Patent Document 2 does not require light irradiation for the development of antifogging properties, but has a problem that the antifogging effect is impaired in a short time because of poor adhesion after film formation. Have. In order to enhance the adhesion, a method of coating colloidal silica with an organic polymer or an inorganic binder is also considered, but a decrease in transparency due to light absorption and scattering is inevitable.

Prior to the present invention, the present inventors have developed a silica thin film containing no particles and succeeded in producing a super-hydrophilic thin film that is extremely smooth and highly light transmissive. However, a silica film having excellent antifogging performance, high hardness and high adhesion is desired.

The present invention has been made to meet such a demand, and an object thereof is to obtain a silica film having excellent antifogging performance, high hardness and high adhesion.

In order to achieve the above object, the present inventors, when forming a hydrophobic region in the hydrophilic region of the silica membrane, moves water droplets that have contacted the hydrophobic region in contact with the hydrophilic region, where Research and development has been promoted based on the hypothesis that the wettability between the silica film and water droplets can be improved and the antifogging property can be improved. As a result, it succeeded in improving antifogging property by the structure and manufacturing method of the following silica film. Specific means are as follows.

That is, according to one aspect of the present invention, the pencil hardness measured in accordance with JIS K5600-5-4 has a hardness of 3H or more, and the pore is classified as a micropore in the IUPAC classification. This is a silica membrane in which hydrophobic regions having Si—CH ₃ bonds are dispersed in a hydrophilic region on the surface of a porous membrane composed of pores having an average diameter of 2 nm or less.

One aspect of the present invention is a pore having a pencil hardness measured in accordance with JIS K5600-5-4 of 3H or more and classified as a micropore in the IUPAC classification, and an average based on a BET measurement value A method for producing a silica film in which a hydrophobic region having a Si—CH ₃ bond is dispersed in a hydrophilic region on the surface of a porous membrane composed of pores having a diameter of 2 nm or less, comprising at least a tetraalkyl A first solution preparation step for preparing a first solution by mixing and reacting an orthosilicate, a hydroxyketone derivative, an organic solvent and water, and a second solution for preparing a second solution by mixing the alkylalkoxysilane with the first solution. A two-solution preparation step, a film formation step of forming a film by supplying a second solution to the substrate, and a hydrolysis step in which the film obtained by the film formation step is brought into contact with water for hydrolysis In the first solution preparation step, the first solution is prepared by performing a heating step of heating for 30 hours or more in the range of 35 to 60 ° C., and the molar ratio of the alkylalkoxysilane to the tetraalkylorthosilicate is 0.1 to This is a method for producing a silica film having a range of 0.5.

According to another aspect of the present invention, there is further provided a method for producing a silica film in which tetraalkyl orthosilicate is tetramethyl orthosilicate, hydroxyketone derivative is hydroxyacetone, organic solvent is ethanol, and alkylalkoxysilane is methyltrimethoxysilane. It is.

According to the present invention, a silica film having excellent anti-fogging performance, high hardness and high adhesion can be obtained.

FIG. 1 is a flowchart showing a rough flow of an example of a method for producing a silica film according to the present embodiment. FIG. 2 is a flowchart illustrating an example of a manufacturing process that further embodies the flowchart illustrated in FIG. 1. 2 is a graph showing a contact angle (CA) of a silica film produced on a glass substrate in Experimental Example 1. FIG. 4 is a graph showing the antifogging evaluation index of the silica film shown in FIG. FIG. 5 is a scanning probe photomicrograph of the surface of the silica film produced on the silicon substrate in Experimental Example 1. 6 is an infrared absorption spectrum of various silica powders produced in Experimental Example 1. FIG. FIG. 7 is a graph showing thermogravimetric changes of various silica powders produced in Experimental Example 1. FIG. 8 is a graph showing nitrogen adsorption / desorption isotherms of various silica powders produced in Experimental Example 1. FIG. 9 is a graph showing the light transmittance in a predetermined wavelength region of the glass substrate provided with the silica film produced in Experimental Example 1. FIG. 10 is a graph showing the light transmittance in a predetermined wavelength region of the acrylic resin substrate with the silica film produced in Experimental Example 1. FIG. 11 is a graph showing an antifogging evaluation index of a silica film produced on a glass substrate in Experimental Example 2. FIG. 12 is a scanning probe photomicrograph of the surface of the silica film produced on the silicon substrate in Experimental Example 2. FIG. 13 is a graph showing thermogravimetric changes of various silica powders produced in Experimental Example 2. FIG. 14 is a graph showing nitrogen adsorption / desorption isotherms of various silica powders produced in Experimental Example 2. FIG. 15 is a graph showing the light transmittance in a predetermined wavelength region of the glass substrate provided with the silica film produced in Experimental Example 2. FIG. 16 is a graph showing the light transmittance in a predetermined wavelength region of the acrylic resin substrate with the silica film produced in Experimental Example 2.

Next, preferred embodiments of the silica film of the present invention and the production method thereof will be described.

<1. Silica film>
The silica film according to the present embodiment is preferably a pore having a pencil hardness measured according to JIS K5600-5-4 of 3H or more and classified as a micropore in the IUPAC classification. A silica film in which a hydrophobic region having a Si—CH ₃ bond is dispersed in a hydrophilic region on the surface of a porous membrane composed of pores having an average diameter of 2 nm or less based on BET measurement values. Here, the “silica film” refers to a film or a laminate of films containing silica as a main component, regardless of the types of subcomponents other than silica, the ratio of each subcomponent, and the thickness of the film.

In the silica membrane according to the present embodiment, the larger the pore volume measured by the nitrogen adsorption / desorption method, the better. Also, the higher the pencil hardness based on JIS K5600-5-4, the better. The silica film according to the present embodiment uses an anti-fogging evaluation apparatus (for example, Kyowa Interface Science Co., Ltd., model number: AFA-1), and the room temperature and the measurement room temperature are both 20 ° C., the humidifying tank temperature is 40 ° C., and the humidifying tank. Humidity 80% R.D. H. After spraying water vapor three times on the measurement surface at intervals of 1 second, light transmittance (the amount of light received by each channel CH) was measured every other second for 10 seconds, and a stable value was obtained 5 seconds later. It has an anti-fogging performance in which the value of the X-axis intercept (anti-fogging evaluation index) obtained from a linear approximation curve of the received light amount distribution is 10 or less.

<2. Manufacturing method of silica film>
FIG. 1 is a flowchart showing a rough flow of an example of a method for producing a silica film according to the present embodiment.

As shown in FIG. 1, in the method for producing a silica film according to the present embodiment, at least a tetraalkylorthosilicate, a hydroxyketone derivative, an organic solvent, and water are mixed and reacted to produce a first solution. A solution preparation step (step S100), a second solution preparation step (step S200) in which an alkylalkoxysilane is mixed with the first solution to prepare a second solution, and the second solution is supplied to the substrate. A film forming process for forming a film (step S300), a first drying process for drying the film obtained by the film forming process (step S400), and a film obtained by the first drying process are brought into contact with water for hydrolysis. A post-hydrolysis step (step S500) for performing decomposition, and a second drying step (step S600) for drying the film obtained by the post-hydrolysis step, In the solution preparation step, the first solution is prepared by heating at 35 to 60 ° C. for at least 30 hours, and the molar ratio of the alkylalkoxysilane to the tetraalkylorthosilicate in the second solution preparation step is 0.1 to The range is 0.5. However, the first drying process (step S400) and the second drying process (step S600) are not essential processes, and may be excluded or changed to other processes.

FIG. 2 is a flowchart showing an example of a manufacturing process that further embodies the flowchart shown in FIG.

In the method for producing a silica film shown in the flowchart of FIG. 1, the first solution production step (step S100) for producing the first solution is a first mixing step (step S101) in which a tetraalkyl orthosilicate and an organic solvent are mixed. ), At least a hydroxyketone derivative, water and an organic solvent are mixed (step S102), a tetraalkyl orthosilicate solution prepared by the first mixing step and a solution prepared by the second mixing step are mixed. A third mixing step (step S103), and a first heating step (step S104) for heating the mixed solution after the third mixing step. Moreover, the 2nd solution preparation process (step S200) for producing a 2nd solution is the 4th mixing process (step S201) which mixes a 1st solution and an alkyl alkoxysilane, and the said 4th mixing process, A second heating step (step S202) for heating the mixed solution.

Next, the details of each process will be described based on the flowcharts shown in FIGS.

(1) First solution preparation process (step S100)
(1.a) First mixing step (step S101)
The tetraalkyl orthosilicate to be mixed is a silane compound having a general formula of Si (OR) ₄ (OR in the formula is an alkoxy group). The alkoxy group may be any of linear, branched and cyclic functional groups, and has 1 to 20, preferably 1 to 10, and more preferably 1 to 4 carbon atoms. Examples of the tetraalkyl orthosilicate include tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetra-iso-propoxysilane, tetra-n-butoxysilane, tetra-sec-butoxysilane, and tetra-tert-butoxy. Examples thereof include silane and tetraphenoxysilane. Of these tetraalkylorthosilicates, tetramethylorthosilicate (tetramethoxysilane) can be preferably used. Further, only one of these tetraalkyl orthosilicates or a combination of two or more thereof may be used.

Examples of the organic solvent mixed with the tetraalkyl orthosilicate include alcohols such as methanol, ethanol, 1-propanol, 2-propanol, butanol, and 3-methyl-3-methoxy-1-butanol; acetone, methyl isobutyl ketone, diisobutyl ketone Ketones such as can be used. As said organic solvent, you may use only said 1 type, or what mixed said 2 or more types. In this embodiment, methanol, ethanol, 1-propanol, 2-propanol, or acetone is preferable, and ethanol is more preferable, because a high-hardness silica film composed of micropores can be easily obtained at a relatively low temperature.

The amount of the organic solvent is preferably such that the total number of moles of each organic solvent used in Steps S101 and S102 / the number of moles of tetraalkyl orthosilicate is in the range of 2 to 30. The amount is preferably in the range, more preferably in the range of 12-15. The amount of the organic solvent to be mixed in Step 101 and the amount of the organic solvent to be mixed in Step S102 may be any distribution, but is preferably 50:50 by weight ratio.

The mixing method of the organic solvent and the tetraalkyl orthosilicate is a method of stirring the mixed solution of the organic solvent and the tetraalkyl orthosilicate in the container using a stirrer equipped with a stirring blade, the above-mentioned mixing in the container. A method in which a stirrer is placed in a solution and the container is placed on a magnetic stirrer and the stirrer is rotated. A method in which a container containing the above-mentioned mixed solution is immersed in an ultrasonic vibrator containing water and stirred. Etc. can be adopted. However, the mixing method of the organic solvent and the tetraalkyl orthosilicate is not limited to the above-described examples, and includes any known mixing method.

The temperature at the time of mixing is preferably selected so that the organic solvent is less likely to volatilize. For example, when methanol, ethanol, 1-propanol, 2-propanol or acetone is selected as the organic solvent, it is preferably in the range of 5 to 60 ° C., particularly preferably 40 ° C. or less. The mixing time is preferably 15 to 180 minutes, particularly 30 to 90 minutes, and more preferably 45 to 75 minutes.

(1.b) Second mixing step (step S102)
The organic solvent similar to the organic solvent used in step S101 can be used. The organic solvent used in step S102 may be a different type of solvent from the organic solvent used in step S101, but is preferably the same type of organic solvent as used in step S101.

The water is preferably ion-exchanged water with less impurities (hydrogen ions, ions other than hydroxide ions are also included in the impurities). The amount of water is preferably in the range of 2 to 10 mol, particularly 3 to 7 mol, and more preferably 4 to 6 mol with respect to 1 mol of the tetraalkylorthosilicate or hydroxyketone derivative.

As the hydroxyketone derivative mixed with water and an organic solvent, hydroxyacetone, acetoin, 3-hydroxy-3-methyl-2-butanone, fructose and the like can be used, and hydroxyacetone is particularly preferable. The hydroxyketone derivative should be in the range of 0.3 to 3.0 mol, particularly 0.5 to 2.0 mol, more preferably 0.8 to 1.2 mol, per mol of tetraalkylorthosilicate. preferable.

The mixing method of the organic solvent, water and the hydroxyketone derivative includes any known mixing method in addition to the same method as the mixing method in step S101. As described in step S101, the temperature at the time of mixing is preferably selected so that the organic solvent is less likely to volatilize.

(1.c) Third mixing step (step S103)
The reaction process is a process of mixing the solution mixed in step S101 and the solution mixed in step S102. The mixing method includes any known mixing method in addition to the same method as each mixing method in steps S101 and S102. The temperature at the time of mixing is preferably selected at a temperature at which the organic solvent is less likely to volatilize, as in steps S101 and S102. The mixing time is preferably 8 to 120 hours, particularly 12 to 80 hours, more preferably 24 to 60 hours.

(1.d) First heating step (step S104)
The first heating step is an aging step for allowing the hydrolysis and condensation polymerization of the tetraalkyl orthosilicate to proceed slowly. The temperature at the time of heating is preferably selected so as to gradually advance the hydrolysis and condensation polymerization described above. For example, when tetramethoxysilane (also known as tetramethylorthosilicate) is used as the tetraalkyl orthosilicate, the heating temperature is preferably 20 to 55 ° C., more preferably 35 to 45 ° C. In addition, the heating time is preferably 30 hours or more, and more preferably 36 hours or more in the case of 40 ° C.

The first solution is completed through the above steps S101 to S104. Note that one or two of steps S101, S102 and S103 need not be performed.

(2) Second solution preparation step (step S200)
(2.a) Fourth mixing step (step S201)
The alkylalkoxysilane mixed with the first solution is a silane compound represented by the general formula (R ₁ ) _x Si (OR ₂ ) _4-X (wherein R ₁ is an alkyl group, and OR ₂ is An alkoxy group, and X is 1, 2 or 3. The alkyl group and alkoxy group may be any of linear, branched and cyclic functional groups, and the carbon number is 1 to 20, preferably 1 to 10, and more preferably 1 to 4. Examples of the alkylalkoxysilane include trialkoxysilanes such as methyltrimethoxysilane, ethyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, phenyltrimethoxysilane, and phenyltriethoxysilane; dimethyldimethoxysilane and dimethyldimethoxysilane. Dialkoxysilanes such as ethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane; monoalkoxysilanes such as trimethylmonomethoxysilane, triethylmonomethoxysilane, trimethylmonoethoxysilane, triethylmonoethoxysilane, etc. Of these, methyltrimethoxysilane can be preferably used. Moreover, you may use only 1 type in these alkyl alkoxysilanes, or combining 2 or more types.

The amount of the alkylalkoxysilane is preferably in the range of 0.1 to 0.5, more preferably 0.4, per 1 mol of tetraalkylorthosilicate.

The mixing method of the first solution and the alkylalkoxysilane may be any mixing method as in the first mixing step. The temperature at the time of mixing is preferably in the range of 5 to 60 ° C., and particularly preferably within 40 ° C. or less. The mixing time is preferably 15 to 180 minutes, particularly 30 to 90 minutes, and more preferably 45 to 75 minutes.

(2.b) Second heating step (step S202)
The second heating step is a step for causing the reaction between the tetraalkylorthosilicate and the alkylalkoxysilane to proceed. The temperature at the time of heating is preferably selected at a temperature at which the reaction proceeds. For example, when tetramethoxysilane (also known as tetramethylorthosilicate) and alkylalkoxysilane are used as the tetraalkylorthosilicate, the heating temperature is preferably 20 to 55 ° C, and more preferably 35 to 45 ° C. The heating time is preferably in the range of 6 to 120 hours at 40 ° C.

Through the above steps S201 and S202, a second solution which is a coating solution is completed.

(3) Film formation process (step S300)
As a substrate for film formation, a glass substrate, a metal substrate typified by single crystal or polycrystalline silicon, a resin substrate typified by acrylic resin, polyethylene terephthalate resin, or the like can be used regardless of the material. In the film forming step, as described later, since the film can be formed at a temperature of 100 ° C. or lower, it can be easily formed even on a resin having low heat resistance. The film forming step is a step of applying a silica solution on the substrate, and any known method can be adopted. For example, various printing methods such as a transfer method, a screen printing method, and an ink jet printing method can be employed in addition to a coating method such as a spin coating method, a blade coating method, a roll coating method, a dipping method, and a spray method. In this embodiment, a spin coat method capable of forming a film having a simple and uniform film thickness can be suitably used.

When the spin coating method is used in the film forming step, it is preferable to determine the rotation speed and rotation time of the substrate according to the desired film thickness. For example, in order to form a film having a thickness of 60 to 150 nm, it is preferable to rotate the substrate at 1000 to 5000 rpm when rotating for 60 seconds. The film thickness is likely to change depending on the type of organic solvent in the silica solution, the liquid temperature, and the viscosity of the solution. For example, in order to form a film having a film thickness of 60 to 150 nm by rotating the substrate for 60 seconds, when methanol, ethanol, 1-propanol, 2-propanol or acetone is used as the organic solvent, it is 1000 to 3000 rpm. It is preferable to rotate the substrate. The temperature of the solution at that time is preferably 10 to 30 ° C., and the viscosity of the solution at that time is preferably 2.0 to 5.0 mPa · s.

(4) First drying step (step S400)
The first drying step is a step of reducing the organic solvent and water in the film and fixing the formed film. For example, the drying temperature and drying time are determined according to the state of the film obtained by spin coating. It is preferable to do this. If possible, it tends to be preferable to dry at a low temperature for a long time. For example, the drying temperature is 15 to 35 ° C., preferably 20 to 28 ° C., for 12 to 48 hours, preferably 18 to 36 hours. In addition, this process can also be excluded.

(5) Post-hydrolysis step (step S500)
The post-hydrolysis step is a step in which the film formed on the substrate is immersed in water (whether the entire substrate is immersed or only the film is brought into contact with water) to cause further hydrolysis of the film. The water temperature may be 0 ° C. or higher, but is preferably in the range of 40 to 95 ° C., particularly 70 to 90 ° C., more preferably 75 to 85 ° C. It is because the effect of hydrolysis can be enhanced and peeling or destruction of the membrane can be effectively prevented. For the post-hydrolysis treatment, any method such as dipping, showering or flowing water can be employed. In this embodiment, it is preferable to employ dipping that is simple and has a high hydrolysis effect. The post-hydrolysis treatment time is preferably 30 to 240 minutes, particularly 60 to 180 minutes, and more preferably 90 to 150 minutes.

(6) Second drying step (step S600)
The second drying step is a step of removing water and the like contained in the film formed on the substrate and a step of improving the hardness of the film. A dryer, an electric furnace, or the like can be appropriately selected depending on the drying temperature. The temperature can be selected in consideration of the heat resistance of the substrate, but is preferably 400 ° C. or lower. In particular, when a thermoplastic substrate is used, the range of 5 to 100 ° C., the range of 10 to 40 ° C., and further the range of 15 to 30 ° C. is set as an appropriate range. The drying time is not particularly limited as long as it is a time sufficient to remove adsorbed water and remaining organic matter as much as possible, but, for example, 15 to 240 minutes, particularly 30 to 180 minutes, and even 60 ~ 150 minutes is preferred.

Next, examples of the present invention will be described.

"Experiment 1"
1. Preparation of coating solution In a beaker (beaker A), 1.903 g of tetramethoxysilane (TMOS) manufactured by Tokyo Chemical Industry Co., Ltd. and 7.89 g of ethanol (EtOH) manufactured by Wako Pure Chemical Industries, Ltd. And stirred at 25 ° C. for about 1 hour. Stirring was performed using a stirrer (model: VARIOMAG POLY15) manufactured by KOMET Co., Ltd. The stirring speed was 550 rpm. Meanwhile, in another beaker (beaker B), 0.926 g of Hydroxy Acetone (HA) manufactured by Tokyo Chemical Industry Co., Ltd., 1.125 g of water, and ethanol (EtOH) manufactured by Wako Pure Chemical Industries, Ltd. ) 7.89 g was added and stirred under the same conditions as beaker A.

Next, another beaker (beaker C) was prepared, and the contents after stirring of each of the beakers A and B were added and stirred at 25 ° C. for about 48 hours. For the stirring, the same type of stirrer as described above was used, and the temperature and stirring speed during stirring were 25 ° C. and 550 rpm, respectively. Thereafter, stirring of the contents of the beaker C was stopped, and the beaker C was heated at 40 ° C. for about 48 hours. Through this series of treatments, the production of the first solution (herein referred to as “solution A”) was completed.

Next, a predetermined amount of methyltrimethoxysilane (MTMS) manufactured by Tokyo Chemical Industry Co., Ltd. in the range of 0 to 1.7 g is added to the solution A in the beaker C, and the mixture is stirred at 25 ° C. for about 1 hour. And heated at 40 ° C. for about 24 hours. The stirring conditions are the same as for beaker A. Through this process, a total of eight types of second solutions (herein referred to as “solution B”) of TMOS: MTMS = 1: 0 to 1 as shown in Table 1 are prepared, and the various solutions B are used as coating solutions. Used as.

2. Next, a silicon substrate (SUMCO CO., 25 mm × 25 mm × 1 mm), a glass substrate (Corning Corp., 50 mm × 25 mm × 1 mm, 50 mm × 50 mm × 1 mm) and an acrylic resin substrate (Nitto Resin Industry) Manufactured by Co., Ltd., product number: S0, 50 mm × 25 mm × 1 mm) was prepared, and the above-mentioned various substrates were fixed to a rotating plate of a spin coater (manufactured by MIKASA, model: SPINCATOR 1H-D7). Next, the rotation speed of the spin coater is set so that the rotation speed of each substrate becomes 2000 rpm, and the rotation of the rotating plate is started, and the previously prepared solution B is supplied onto the rotating substrate for 60 seconds. Then, a film was formed on the surface of the substrate, and then the rotation of the rotating plate was stopped. Next, the substrate on which the film was formed was dried at 25 ° C. for about 24 hours. Next, the dried substrate is immersed in a beaker (beaker D) containing about 20 ° C. ion-exchanged water, the beaker D is placed in a water bath, heated to 80 ° C., and allowed to stand for 2 hours. I put it. Next, the substrate was taken out from the beaker D and dried under reduced pressure at 25 ° C. for 24 hours to obtain test pieces for various evaluations.

3. Evaluation (1) Contact angle measurement As a measurement sample, a glass substrate of 50 mm x 25 mm x 1 mm with various silica films attached thereto was used. A contact angle meter (model number: MCA-J) manufactured by Kyowa Interface Science Co., Ltd. was used as the contact angle measuring device. Room temperature 25 ° C., humidity 60% H. , A 70 pL water droplet was dropped and the contact angle was measured at intervals of 0.005 seconds. The contact angle of 10 points when the landing radius was stabilized was averaged to obtain the contact angle of each sample.
(2) Evaluation of anti-fogging property As a measurement sample, a glass substrate of 50 mm × 50 mm × 1 mm with various silica films attached thereto was used. For the evaluation of antifogging property, an antifogging evaluation device (model number: AFA-1) manufactured by Kyowa Interface Science Co., Ltd. was used. Both room temperature and measurement room temperature are 20 ° C., humidification bath temperature is 40 ° C., and humidification bath humidity is 80%. H. After spraying water vapor three times on the measurement surface at intervals of 1 second, light transmittance (the amount of light received by each channel CH) was measured every other second for 10 seconds, and a stable value was obtained 5 seconds later. The value of the X-axis intercept obtained from the linear approximation curve of the received light amount distribution was taken as the antifogging evaluation index (three-point average). The antifogging evaluation index indicates that the smaller the value, the higher the antifogging performance.
(3) Transmittance measurement As a measurement sample, a glass substrate of 50 mm × 25 mm × 1 mm and an acrylic resin substrate with various silica films attached thereto were used. For the measurement of the transmittance, an ultraviolet-visible spectrophotometer (model number: U-4100) manufactured by Hitachi, Ltd. was used.
(4) Surface roughness measurement As a measurement sample, a silicon substrate with various silica films attached thereto was used. For the measurement of the surface roughness, a scanning probe microscope (model number: SPA400) manufactured by Seiko Instruments Inc. was used. For the measurement, a back Al-coated cantilever (SI-DF20) was used and observed in a tapping mode (DFM). The surface roughness was evaluated by root mean square (RMS) surface roughness.
(5) Pencil hardness measurement As a measurement sample, a silicon substrate with various silica films attached thereto was used. The hardness was measured using a pencil hardness meter (model number: No. 553-S) manufactured by Yasuda Seiki Co., Ltd. based on the pencil hardness measurement method (JIS K5600-5-4).
(6) Infrared absorption spectrum measurement The measurement sample of the infrared absorption spectrum was a silica powder obtained by drying Solution B under reduced pressure, hydrolyzing at 80 ° C. for 2 hours, and drying. For the measurement, FT-IR (model number: IR-Prestige 21) manufactured by Shimadzu Corporation was used. Evaluation was performed by the ATR method.
(7) Specific surface area measurement The measurement sample measured the silica powder heated at 200 degreeC by using the said sample for infrared absorption spectrum measurement as pre-processing. For the measurement, a nitrogen adsorption / desorption measuring device (model number: ASAP2010) manufactured by Micromeritics Instruments Corporation was used. The BET method was used for calculating the average pore diameter. Here, the BET method will be briefly described. The BET method is a method of calculating the pore diameter on the assumption that nitrogen molecules are multilayer adsorbed to fill the pores, and is effective in obtaining the pore diameter in silica. Plot points on the xy plane where the relative pressure (P / P ₀ ) is x-coordinate and (P / P ₀ ) / V (1- (P / P ₀ )) is y-coordinate by the BET method, In this method, the intercept and slope of the closest tangent line (straight line) passing through each plotted point are obtained, and the volume and area of the pores are obtained from the intercept and the slope.
(8) Water adsorption amount evaluation The measurement sample was 10 mg of powder which was dried after drying the solution B under reduced pressure at 80 ° C. for 2 hours and exposed to saturated water vapor at 25 ° C. for 1 day. For the measurement, a scanning thermogravimetric analyzer (model number: Thermoplus TG8120) manufactured by Rigaku Corporation was used. In the measurement, the temperature rising rate was 5 ° C./min.
(9) Evaluation of surface hydrophilicity / hydrophobicity distribution As a measurement sample, a silicon substrate with various silica films attached thereto was used. For the measurement, a scanning probe microscope (model number: SPA400) manufactured by Seiko Instruments Inc. was used. The measurement was performed using Au-coated cantilevers (SI-AF01A) subjected to single-molecule surface treatment (SAMs) with mercaptohexadecanol. The observation was performed in the transverse vibration friction force microscope mode (LM-FFM). Other evaluation conditions were: scanning frequency: 5 kHz, amplitude: 5 nm, deflection amount: 0 nm.

4). Experimental results <Contact angle and anti-fogging performance>
Table 2 and FIG. 3 show the contact angle (CA) of the silica film produced on the glass substrate. Table 3 and FIG. 4 show the antifogging evaluation index of the silica film.

As shown in Table 2 and FIG. 3, in the range of MTMS / TMOS = 0.25 to 0.6, the contact angle is lower than that of the silica film (comparative sample: aT1) prepared from the solution B not containing MTMS. Obtained. Further, as shown in Table 3 and FIG. 4, in the range of MTMS / TMOS = 0.125 to 0.5, higher antifogging performance than that of the comparative sample aT1 was recognized. The evaluation based on the antifogging evaluation index and the evaluation based on the contact angle do not necessarily coincide with each other. However, when a silica film is produced with the solution B containing MTMS, the antifogging performance is improved. A common phenomenon was observed in which the fogging performance rather decreased. Considering that the phenomenon that the transparent substrate actually fogs is not always due to uniform droplets, it is appropriate to set the evaluation based on the anti-fogging evaluation index as “main” and the evaluation based on the contact angle as “subordinate”. It is thought that. From this viewpoint, it was found that the silica film produced using the solution B in the range of MTMS / TMOS = 0.125 to 0.5 has higher antifogging performance than the comparative sample aT1.

<Surface roughness>
Table 4 shows the surface roughness of the silica film produced on the silicon substrate.

As shown in Table 4, regardless of whether or not MTMS was contained in the solution B, the surface of the obtained silica film was an extremely smooth surface having an RMS surface roughness of 2.0 nm or less.

<Distribution of hydrophilic and hydrophobic regions>
FIG. 5 is a scanning probe photomicrograph of the surface of a silica film produced on a silicon substrate. FIG. 6 shows infrared absorption spectra of various silica powders.

As shown in FIG. 5, the silica film (comparative sample: aT1) produced from the solution B not containing MTMS had a surface composed only of a portion with high luminance. On the other hand, as the content of MTMS increases, a low luminance region is mixed on the silica film surface. In consideration of the fact that the hydrophilic region is drawn with high luminance because the frictional force is increased, when the content of MTMS is increased, more hydrophilic regions (regions with low luminance) are mixed in the hydrophilic region. It is thought that it will change. Further, as shown in FIG. 6, it was found that the peak at 1278 cm ^{−1 and} the peak at 2975 cm ⁻¹ increase as the MTMS content increases. The former is a peak of symmetric deformation vibration of Si—CH ₃ , and the latter is a peak of reverse symmetric stretching vibration of CH ₃ . From this and the result shown in FIG. 5, it is considered that the hydrophobic region bonded to the methyl group on the surface of the silica film increases as the MTMS content increases.

<Hydrophilic region and pore>
FIG. 7 is a graph showing thermogravimetric changes of various silica powders. FIG. 8 is a graph showing nitrogen adsorption / desorption isotherms of various silica powders. Table 5 is a table summarized based on the results of FIGS. 7 and 8. In the table, the weight reduction rate is the weight reduction rate relative to the original weight at 100 ° C.

As shown in FIG. 7, the water content (water absorption) of various samples decreased as the MTMS content increased. From this, it is considered that when the MTMS in the solution B is increased, the water content is decreased and the hydrophobic region is increased. Further, as shown in FIG. 8, all the evaluated samples exhibit type I adsorption / desorption isotherms, and thus are considered to have only micropores (diameter <2 nm). Furthermore, as shown in Table 5, the result that the pore volume became smaller as the content of MTMS increased was obtained. From this, it is considered that an increase in the hydrophobic region leads to a reduction in pore volume.

<Transmissivity>
FIG. 9 shows the transmittance of a glass substrate with a silica film in a predetermined wavelength region. FIG. 10 shows the transmittance of an acrylic resin substrate with a silica film in a predetermined wavelength region. Table 6 shows the visible light transmittance summarized based on the results shown in FIGS. 9 and 10.

As shown in FIG. 9, FIG. 10 and Table 6, all the samples were highly light-transmitting films having a visible light transmittance of 92% or more.

<Hardness>
Table 7 shows the pencil hardness of various silica films produced on a silicon substrate.

As shown in Table 7, a silica film having a hardness higher than that of the comparative material aT1 could be obtained by adding MTMS to the solution B except for MTMS / TMOS = 1. In particular, a silica film having a high hardness of 3H or more was obtained in the range of MTMS / TMOS = 0.125 to 0.75.

In addition, any silica film produced in Experimental Example 1 was firmly peeled off from various substrates and not firmly peeled off from various substrates.

"Experimental example 2"
As shown in Table 8, the heating time was changed in the range of 0 to 60 hours (0 to 2.5 days) when preparing the solution A in Experimental Example 1, and then TMOS: MTMS = 1: 0.4. MTMS was added so as to have a molar ratio (MTMS = 0.68 g) to prepare Solution B. Conditions other than the above were the same as in Experimental Example 1.

Experimental results <Anti-fogging performance>
Table 9 and FIG. 11 show the antifogging evaluation index of the silica film produced on the glass substrate.

As shown in Table 9 and FIG. 11, the silica films (bTM4, bTM5, and bTM6) produced under the conditions where the heating time was 36 hours (1.5 days) or longer were the silica films produced under conditions where the heating time was shorter than that. It was found that the film (bTM1, bTM2, and bTM3) has higher antifogging performance than the membranes (bTM1, bTM2, and bTM3).

<Surface roughness>
Table 10 shows the surface roughness of the silica film produced on the silicon substrate.

As shown in Table 10, although the surface roughness of the silica film was different depending on the heating time of the solution A, the surface of the silica film was a smooth surface having an RMS surface roughness of 4.0 nm or less.

<Distribution of hydrophilic and hydrophobic regions>
FIG. 12 is a scanning probe photomicrograph of the surface of a silica film produced on a silicon substrate.

As shown in FIG. 12, it was found that as the heating time increased, the region with high luminance became larger and the shading between the high luminance portion and the low luminance portion became clear. Samples bTM4 and bTM5 with high antifogging performance have clearer hydrophilic regions (high luminance portions) and hydrophobic regions (low luminance portions) than sample bTM3, and this form improves antifogging performance. It is thought that it contributes to.

<Hydrophilic region and pore>
FIG. 13 is a graph showing thermogravimetric changes of various silica powders. FIG. 14 is a graph showing nitrogen adsorption / desorption isotherms of various silica powders. Table 11 is a table summarized based on the results of FIGS. 13 and 14. In the table, the weight reduction rate is the weight reduction rate relative to the original weight at 100 ° C.

As shown in FIG. 13, the water content (water absorption amount) of various samples improved as the heating time increased from 0 to 48 hours (within 2 days). From this, it is considered that when the heating time of the solution A at 40 ° C. is lengthened, the hydrophilic region is widened. Further, as shown in FIG. 14, all the evaluated samples exhibit type I adsorption / desorption isotherms, and thus are considered to have only micropores (diameter <2 nm). Further, as shown in Table 11, the pore volume was increased as the heating time was increased. From this, it is thought that the increase in the hydrophilic region leads to the enlargement of the pore volume.

<Transmissivity>
FIG. 15 shows the transmittance of a glass substrate provided with a silica film in a predetermined wavelength region. FIG. 16 shows the transmittance of an acrylic resin substrate with a silica film in a predetermined wavelength region. Table 12 shows the visible light transmittance summarized based on the results shown in FIGS. 15 and 16.

As shown in FIG. 15, FIG. 16 and Table 12, all the samples were films having a high light transmittance with a visible light transmittance of 92% or more.

<Hardness>
Table 13 shows the pencil hardness of various silica films produced on a silicon substrate.

As shown in Table 13, it was found that all of the evaluated silica films had a hardness of H or higher. In particular, the sample having a heating time of 24 hours or more had a high hardness of 3H.

Note that any silica film produced in Experimental Example 2 was not peeled off from various substrates or was not easily peeled off, but was firmly fixed to the various substrates.

The present invention can be used, for example, for film formation on a substrate that requires anti-fogging properties.

Claims

The pencil hardness measured according to JIS K5600-5-4 has a hardness of 3H or more,
Hydrophobic having Si—CH 3 bonds in the hydrophilic region on the surface of the porous membrane composed of pores classified as micropores in the IUPAC classification and having an average diameter of 2 nm or less based on BET measurement values A silica film characterized by comprising a dispersed region.
A pore whose hardness measured based on JIS K5600-5-4 is 3H or more, and is classified as a micropore in the IUPAC classification and having an average diameter of 2 nm or less based on a BET measurement value. A method for producing a silica film in which a hydrophobic region having a Si—CH 3 bond is dispersed in a hydrophilic region on the surface of a porous film to be constructed,
A first solution preparation step of preparing a first solution by mixing and reacting at least a tetraalkyl orthosilicate, a hydroxyketone derivative, an organic solvent and water;
A second solution preparation step of mixing the alkylalkoxysilane with the first solution to prepare a second solution;
A film forming step of forming the film by supplying the second solution to the substrate;
A hydrolysis step in which the membrane obtained by the membrane formation step is brought into contact with water for hydrolysis, and
Including
In the first solution preparation step, the first solution is prepared by performing a heating step of heating at 35 to 60 ° C. for 30 hours or more,
A method for producing a silica film, wherein the molar ratio of the alkylalkoxysilane to the tetraalkylorthosilicate is in the range of 0.1 to 0.5.
The tetraalkyl orthosilicate is tetramethyl orthosilicate,
The hydroxy ketone derivative is hydroxyacetone,
The organic solvent is ethanol,
3. The method for producing a silica film according to claim 2, wherein the alkylalkoxysilane is methyltrimethoxysilane.