JP4942057B2 - Method for producing hydrophilic silica film and acrylic resin substrate with hydrophilic silica film - Google Patents

Description

  The present invention relates to a method for producing a hydrophilic silica film, a hydrophilic silica film, and an acrylic resin substrate with a hydrophilic silica film.

  Conventionally, super-hydrophilic coating materials have been used for the purpose of imparting antifogging 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, in this production method, there are restrictions on the solvent in the production process of the hydrophilic material, and a solvent exchange process is required. Moreover, the process of heating to the high temperature of 300 degreeC or more is required in the manufacturing process. It is desired to eliminate such a restriction as much as possible, to eliminate the solvent exchange process, and to impart hydrophilicity to a material with low cost and low heat resistance.

  The present invention has been made to meet such demands, and an object of the present invention is to produce a silica film excellent in hydrophilicity and an acrylic resin substrate with a hydrophilic silica film at low cost and low temperature.

  In order to achieve the above object, the method for producing a hydrophilic silica film of the present invention comprises at least a reaction step in which a tetraalkyl orthosilicate, an organic solvent and water are mixed and reacted, and a solution obtained by the reaction step on a substrate. A film forming step of supplying and forming a film; and a post-hydrolysis step of performing hydrolysis by bringing the film obtained by the film forming step into contact with water.

  Moreover, the manufacturing method of another hydrophilic silica film | membrane of this invention further performs the heating process heated within the range of 100-250 degreeC after a post-hydrolysis process.

  Further, in another method for producing a hydrophilic silica film of the present invention, the reaction step is particularly a step in which a hydroxyketone derivative is further added and reacted.

  In another method for producing a hydrophilic silica film of the present invention, the organic solvent is ethanol in particular.

  The hydrophilic silica film of the present invention has a contact angle of water droplets on the film of 20 degrees or less and an average pore diameter of 1 to 10 nm.

  Moreover, the acrylic resin substrate with a hydrophilic silica film of the present invention has a contact angle of water droplets of 20 degrees or less on the film, and the visible light transmittance of the acrylic resin substrate with the film attached is 92% or more. It is.

  According to the present invention, a silica film excellent in hydrophilicity and an acrylic resin substrate with a hydrophilic silica film can be produced at low cost and at a low temperature.

FIG. 1 is a flowchart showing a rough flow of an example (first production method) of a method for producing a hydrophilic 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. FIG. 3 is a flowchart showing a rough flow of an example (second manufacturing method) of the method for manufacturing the hydrophilic silica film according to the present embodiment. FIG. 4 is a graph of nitrogen adsorption / desorption isotherms of each silica powder produced in Experimental Example 1. FIG. 5 is a graph showing the pore size distribution of each silica powder of FIG. FIG. 6 is a graph of nitrogen adsorption / desorption isotherms of each silica powder produced in Example 2 without post-hydrolysis treatment. FIG. 7 is a graph showing the pore size distribution of each silica powder shown in FIG. FIG. 8 is a graph showing an infrared absorption peak in the vicinity of 1000 cm ^{−1 of} each silica powder produced by performing a post-hydrolysis treatment in Experimental Example 2. FIG. 9 is a graph showing an infrared absorption peak near 1000 cm ^{−1 of} each silica powder produced in Experimental Example 2 without performing post-hydrolysis treatment. FIG. 10 shows the infrared absorption peak in the vicinity of 2900 cm ^{−1 for} each of the silica powder produced using EtOH as a solvent and the one that was not subjected to the post-hydrolysis treatment in Experimental Example 2. It is a graph shown in comparison. FIG. 11 is a graph of the nitrogen adsorption / desorption isotherm of each silica powder prepared in Experimental Example 3 without using hydroxyacetone. FIG. 12 is a graph showing the pore size distribution of each silica powder shown in FIG. FIG. 13 is a graph showing the transmittances of the thin film-attached PMMA substrate and the non-film-formed PMMA substrate analyzed in Example 4 using an ultraviolet-visible spectrophotometer. FIG. 14 shows the infrared absorption peak in the vicinity of 2900 cm ^{−1 of} each of the silica powder produced using EtOH as a solvent and the one not subjected to the post-hydrolysis treatment in Experimental Example 5. It is a graph shown in comparison.

  Next, each embodiment of the manufacturing method of the hydrophilic silica film of this invention, the acrylic resin substrate with a hydrophilic silica film, and a hydrophilic silica film is demonstrated.

<1. Hydrophilic silica membrane>
The hydrophilic silica film according to the present embodiment preferably has a water droplet contact angle of 20 degrees or less and an average pore diameter of 1 to 10 nm. In this embodiment, the average pore diameter is calculated by the BET method. 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 hydrophilic silica membrane according to the present embodiment, the larger the pore volume measured by the nitrogen adsorption / desorption method, the better. Moreover, the higher the pencil hardness based on JIS K5600-5-4, the better.

<2. Acrylic resin substrate with hydrophilic silica film>
In the acrylic resin substrate with a hydrophilic silica film according to the present embodiment, the contact angle of water droplets on the film is 20 degrees or less, and the visible light transmittance of the acrylic resin substrate with the film attached is 92%. That's it. The visible light transmittance is a value measured with an ultraviolet-visible spectrophotometer with a hydrophilic silica film attached to one surface of an acrylic resin substrate.

<3. Method for producing hydrophilic silica film>

3.1 First Manufacturing Method FIG. 1 is a flowchart showing a rough flow of an example (first manufacturing method) of a method for manufacturing a hydrophilic silica film according to the present embodiment.

  As shown in FIG. 1, the first method for producing a hydrophilic silica film is a reaction in which at least tetraalkyl orthosilicate, alcohol or ketone (hereinafter referred to as “organic solvent” or simply “solvent”) and water are mixed. A reaction step (step S100), a film formation step (step S200) for forming a film by supplying a solution (coating solution) obtained by the reaction step (step S100) to the substrate, and the film formation step (step A drying step (step S300) for drying the membrane obtained by S200) at a temperature of 40 ° C. or less, a post-hydrolysis treatment step (step S400) for hydrolyzing the membrane obtained by the drying step (step S300), A heating step (step S) for heating the film obtained by the post-hydrolysis treatment step (step S400). It includes a 00), a. However, the drying process (step S300) is not an essential process and can be excluded.

  FIG. 2 is a flowchart illustrating an example of a manufacturing process that further embodies the flowchart illustrated in FIG. 1.

  A first method for producing a hydrophilic silica film includes a first mixing step (step S110) of mixing a tetraalkylorthosilicate and a solvent, and a second mixing step of mixing at least water and a solvent (step S120). And a reaction step (step S130) in which the tetraalkyl orthosilicate solution prepared by the first mixing step (step S110) and the solution prepared by the second mixing step (step S120) are mixed to react both solutions. After the reaction step (step S130), a standing step (step S140) for allowing the solution after the reaction to stand, and forming a film by supplying the solution after the standing step (step S140) to the substrate A process (step S200), the drying process (step S300), the post-hydrolysis process (step S400), It includes a serial heating step (step S500), the. The first mixing step (step S110), the second mixing step (step S120), the reaction step (step S130), and the stationary step (step S140) are specific to the reaction step (step S100) shown in FIG. This is a subdivided process.

  Next, based on the flowchart shown in FIG. 2, the detail of each process is demonstrated.

(1) Reaction process (step S100)
(1.a) First mixing step (step S110)
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.

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

  The amount of the solvent is preferably an amount such that the total number of moles of each solvent used in steps S110 and S120 / the number of moles of tetraalkyl orthosilicate is in the range of 0.5 to 1.5. The amount is preferably in the range of 0.8 to 1.2.

  The mixing method of the solvent and the tetraalkyl orthosilicate is a method of stirring the mixed solution of the solvent and the tetraalkyl orthosilicate in the container using a stirrer equipped with a stirring blade, and the above-mentioned mixed solution in the container. A method of rotating the stirrer by placing the container on a magnetic stirrer with a stir bar, a method of stirring the container with the above mixed solution immersed in an ultrasonic vibrator containing water, etc. Can be adopted. However, the mixing method of the solvent and the tetraalkylorthosilicate is not limited to the above-described examples, and includes any known mixing method.

  The temperature at the time of mixing is preferably selected at a temperature at which the solvent is less likely to volatilize. For example, when methanol, ethanol, 1-propanol, 2-propanol or acetone is selected as the solvent, the temperature is preferably in the range of 5 to 60 ° C., particularly 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 S120)
A solvent similar to the solvent used in step S110 can be used. The solvent used in step S120 may be a different type of solvent from the solvent used in step S110, but is preferably the same type of solvent as used in step S110.

  The water is preferably ion-exchanged water with little 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, more preferably 4 to 6 mol, with respect to 1 mol of the tetraalkylorthosilicate or hydroxyketone derivative.

  It is preferable to add and mix a hydroxyketone derivative in addition to the water and the solvent. As the hydroxyketone derivative, 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, with respect to 1 mol of the tetraalkyl orthosilicate. preferable.

  The mixing method of the solvent and water or the solvent, water and the hydroxyketone derivative includes any known mixing method in addition to the same method as the mixing method in step S110. As described in step S110, it is preferable to select a temperature at which the solvent hardly volatilizes as the temperature at the time of mixing.

(1.c) Reaction process (step S130)
The reaction process is a process of obtaining a sol solution by mixing the solution mixed in step S110 and the solution mixed in step S120. The mixing method in the reaction step includes any known mixing method in addition to the same method as the mixing method in steps S110 and S120. The temperature at the time of mixing is preferably selected at a temperature at which the solvent is less likely to volatilize, as in steps S110 and S120. The mixing time is preferably 8 to 72 hours, particularly 12 to 48 hours, and more preferably 18 to 36 hours.

(1.d) Standing step (Step S140)
The standing step is an aging step for allowing the hydrolysis and condensation polymerization of the tetraalkylorthosilicate to proceed slowly. The temperature at the time of standing is preferably selected so that the hydrolysis and condensation polymerization described above gradually proceed. For example, when tetramethoxysilane is used as the tetraalkylorthosilicate, the standing temperature is preferably 20 to 55 ° C, and more preferably 35 to 45 ° C. Further, the standing time is preferably 24 to 168 hours, particularly 48 to 144 hours.

  Through the above steps S110 to S140, the reaction process (step S100) is completed, and a sol solution for film formation is completed.

(2) Film formation process (step S200)
The substrate on which the silica solution, which is a sol solution for film formation, is applied is not particularly limited, but in consideration of heating at a maximum temperature of 200 ° C. in the subsequent steps, a material that does not soften or melt at 200 ° C. Is preferred. 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 film thickness of 60 to 150 nm, when rotating for 60 seconds, it is preferable to rotate the substrate at 1000 to 5000 rpm. The film thickness is likely to change depending on the type of 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 a solvent, the substrate is rotated at 1000 to 3000 rpm. Is preferably rotated. 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.

(3) Drying process (step S300)
The drying step is a step of reducing the solvent and water in the film, and a fixing step of the formed film, and it is preferable to determine the drying temperature and drying time according to the state of the film obtained by spin coating. . If possible, it tends to be preferable to dry at a low temperature for a long time. If a standard drying temperature and drying time are illustrated, it will dry at 15-35 degreeC, Preferably it is 20-28 degreeC for 12 to 48 hours, Preferably it is 18 to 36 hours. In addition, this process can also be excluded.

(4) Post-hydrolysis process (step S400)
The post-hydrolysis treatment step is a step in which the film formed on the substrate is immersed in water (whether the whole substrate is immersed or only the film is brought into contact with water) to cause further hydrolysis of the film. Although the water temperature should just be 0 degreeC or more, the range of 40-95 degreeC, especially 70-90 degreeC, Furthermore, 75-85 degreeC is preferable. It is because the effect of hydrolysis can be enhanced and peeling or destruction of the membrane can be effectively prevented. Any method such as dipping, showering or flowing water can be employed for the post-hydrolysis treatment. In this embodiment, it is preferable to employ dipping that is simple and has a high hydrolysis effect. The time for the post-hydrolysis treatment is preferably 30 to 240 minutes, particularly 60 to 180 minutes, and more preferably 90 to 150 minutes.

(5) Heating process (step S500)
The heating process is a process of removing water and the like contained in the film formed on the substrate and a process of improving the hardness of the film. A dryer, an electric furnace, or the like can be selected as appropriate depending on the temperature to be heated. The heating temperature is preferably in the range of 100 to 250 ° C. and lower. The heating time is not particularly limited as long as it is sufficient to remove the adsorbed water and the remaining organic substances as much as possible. However, for example, the heating time is 15 to 240 minutes, particularly 30 to 180 minutes, and even 60. ~ 150 minutes is preferred.

3.2 Second Manufacturing Method FIG. 3 is a flowchart showing a rough flow of an example (second manufacturing method) of a method for manufacturing a hydrophilic silica film according to the present embodiment.

  As shown in FIG. 3, the second method for producing a hydrophilic silica film is different from the first production process described above only in that the heating process (step S500) is not performed. Therefore, since each process other than the heating process (step S500) is the same as the content described in the first manufacturing method, a duplicate description is omitted.

"Experiment 1"
1. Preparation of coating solution In a beaker (beaker A), 0.926 g of hydroxyacetone (HA), 1.125 g of water, and various solvents (10 ml) were added and stirred at 25 ° C. for about 1 hour. . Stirring was carried out using a stirrer (model: VARIOMAG POLY15) manufactured by KOMET. The stirring speed was 550 rpm. The solvent was four types shown in Table 1, methanol (MeOH), ethanol (EtOH), 1-propanol (1-PrOH) and 2-propanol (2-PrOH). Since the specific gravity of each solvent was different, the mass (Xg) of 10 ml of each solvent was different as shown in Table 1. On the other hand, 1.903 g of tetramethoxysilane (TMOS) and 10 ml of various solvents were put into another beaker (beaker B), and stirred under the same conditions as beaker A. The solvent used for beaker A and beaker B was the same type of solvent.

  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 24 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 allowed to stand at 40 ° C. The standing time was 48 hours when MeOH or 1-PrOH was used as the solvent, and 72 hours when EtOH or 2-PrOH was used as the solvent. Through this series of processes, the preparation of the coating solution was completed. Even if the kind of the solvent was changed, the molar ratio of TMOS: solvent: water was 1: 1: 5, and the Si equivalent molar concentration was 0.52M.

2. Preparation of Thin Film Next, a silicon substrate (SUMCO, 25 mm × 25 mm × 1 mm) was prepared, and the substrate was fixed to a rotating plate of a spin coater (MIKASA, model: SPINCATOR 1H-D7). Next, the rotational speed of the spin coater is set so that the rotational speeds of the various substrates are 1000, 2000, and 3000 rpm, and the rotation of the rotating plate is started. The coating solution prepared earlier is applied to the rotating substrate. For 60 seconds to form a film 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 heated at 200 ° C. for 2 hours. The heated substrate was stored at 25 ° C.

3. Evaluation For the evaluation of the specific surface area and pore volume of silica, a nitrogen adsorption / desorption measuring device (manufactured by Micromeritics Instruments Corporation, model: ASAP2010) was used. The BET method was used for calculating the average pore diameter. The BJH method was used to derive the pore size distribution.

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. A point with relative pressure (P / P ₀ ) as x-coordinate and (P / P ₀ ) / V (1- (P / P ₀ )) as y-coordinate is plotted on the xy plane 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. Also, assuming that the BJH method is a cylindrical pore, variables are introduced and simulated to calculate the pore size distribution so that the integrated value of the pore surface area is close to the obtained BET specific surface area. It is a technique to do.

  FT-IR (manufactured by Shimadzu Corporation, model: IR-Prestige 21) was used for analysis of the binding species in the silica. The sample used for the measurement was a silica powder produced by drying a coating solution (silica solution) under reduced pressure, post-hydrolysis treatment at 80 ° C. for 2 hours, and heating at 200 ° C. for 2 hours. Thereafter, in each experimental example, the silica powder produced in each step that shared the step except the film formation step by spin coating was subjected to each analysis of specific surface area, pore volume, and bond type.

  A contact angle meter (manufactured by Kyowa Interface Science Co., Ltd., Model: Drop Master 300) was used to measure the contact angle of water droplets on the silica film. The measurement environment was room temperature (25 ° C.), humidity 40% R.D. H. It was. The contact angle was measured 5 seconds after dropping 2 μL of water droplets. The number of measurement points was five, and the average of three middle points of the contact angle values at the five points was determined. For comparison, an unformed Si substrate was also used for evaluation.

  The surface roughness on the film of the substrate surface was examined using a scanning probe microscope (manufactured by Seiko Instruments Inc., model: SPA400).

  The hardness of the film on the surface of the substrate was measured using a pencil hardness measurement meter (manufactured by Yasuda Seiki Seisakusho, model: No. 553-S) based on a pencil hardness measurement method (JIS K5600-5-4).

  The thickness of the film on the substrate surface was measured using a spectroscopic ellipsometer (manufactured by Horiba Joban Yvon, model: UVISEL).

4). Experimental Results Table 2 shows the evaluation results of the silica powder produced in Experimental Example 1. In Table 3, the evaluation result of the thin film produced in Experimental Example 1 and the hydrophilicity evaluation result of the Si substrate as a comparison are shown. FIG. 4 is a graph of the nitrogen adsorption / desorption isotherm of each silica powder. In FIG. 4, a white mark means an adsorption plot, and a black mark means a desorption plot. The same applies to subsequent graphs of nitrogen adsorption / desorption isotherms. FIG. 5 is a graph showing the pore size distribution of each silica powder of FIG.

  As shown in Table 3, regardless of which solvent was used, a hydrophilic silica film having a contact angle of 10 degrees or less was obtained. In each solvent, the larger the number of rotations of the substrate, the smaller the film thickness, the smaller the contact angle, and the lower the pencil hardness. As shown in FIG. 4, when MeOH or EtOH was used as the solvent, the adsorption / desorption isotherm became I type, and when 1-PrOH or 2-PrOH was used as the solvent, the adsorption / desorption isotherm became IV type. In the case of type I, it can be determined that nitrogen molecules are adsorbed by Langmuir (adsorption in a single layer). On the other hand, in the case of type IV, it can be determined that nitrogen molecules are adsorbed in multiple layers. Further, as shown in Table 2 and FIG. 5, it was found that when MtOH or EtOH was used as the solvent, silica having smaller pores was obtained than when other solvents were used. These powder samples were white.

"Experimental example 2"
1. Preparation of coating solution, preparation of thin film, and evaluation Two types of methods, the method of excluding post-hydrolysis treatment steps from the preparation of the thin film of Experimental Example 1 and the same method as Experimental Example 1, in order to investigate the effect of post-hydrolysis treatment A thin film was prepared by the method described above. The rotation speed of the spin coater was fixed at one kind of 2000 rpm. The preparation and evaluation of the coating solution were the same as in Experimental Example 1.

2. Experimental Results Table 4 shows the evaluation results of the silica powder prepared in Experimental Example 2. Table 5 shows the evaluation results of the thin film produced in Experimental Example 2. FIG. 6 is a graph of the nitrogen adsorption / desorption isotherm of each silica powder produced without post-hydrolysis treatment. FIG. 7 is a graph showing the pore size distribution of each silica powder shown in FIG.

  As shown in Table 5, it was found that, regardless of which solvent is used, a silica film having a higher hydrophilicity, a smaller film thickness, and a lower hardness can be obtained by post-hydrolysis. If the post-hydrolysis treatment was not performed, the contact angle exceeded 30 degrees, and the result was greatly inferior in hydrophilicity compared to the case where the post-hydrolysis treatment was performed. Further, as shown in FIG. 6, when MeOH or EtOH is used as a solvent, its adsorption / desorption isotherm becomes I type, and when 1-PrOH or 2-PrOH is used as a solvent, its adsorption / desorption isotherm becomes IV type. It was. However, the amount of nitrogen adsorbed was small compared to the case where post-hydrolysis treatment was performed. The powder sample is discolored from yellow to brown, and the inclusion of organic matter is expected in the sample. As shown in Table 4 and FIG. 7, it was found that when MtOH or EtOH was used as the solvent, silica having smaller pores was obtained than when other solvents were used. However, the difference due to the solvent was small compared to Experimental Example 1.

FIG. 8 is a graph showing an infrared absorption peak in the vicinity of 1000 cm ^{−1 of} each silica powder produced by post-hydrolysis treatment. FIG. 9 is a graph showing an infrared absorption peak in the vicinity of 1000 cm ^{−1 of} each silica powder produced without post-hydrolysis treatment. In addition, FIG. 10 compares the infrared absorption peaks in the vicinity of 2900 cm ^{−1 of} the silica powder produced using EtOH as a solvent and the one subjected to the post-hydrolysis treatment and the one not subjected to the post-hydrolysis treatment. It is a graph to show.

As is clear when FIG. 8 and FIG. 9 are compared, the silica powder produced by the post-hydrolysis treatment has a peak showing a Si—OH bond in the vicinity of 980 cm ⁻¹ . The peak showing the bond was not observed in the silica powder produced without post-hydrolysis treatment. Further, as apparent from FIG. 10, the silica powder produced by the post-hydrolysis treatment did not have a peak in the vicinity of 2800 to 3000 cm ⁻¹ , but the silica produced without the post-hydrolysis treatment. In the powder, peaks due to —CH ₂ and —CH ₃ were observed. From this result, post-hydrolysis contributes to the removal of hydrophobic functional groups such as —CH ₂ and —CH ₃ and the accompanying generation of Si—OH bonds. It is thought that there is an effect to improve the sex.

"Experiment 3"
1. Preparation of Coating Solution In a beaker A1, 7.93 g of EtOH, 1.125 g of water, and 0.926 g of HA were added and stirred at 25 ° C. for about 1 hour. In addition, 0.576 g of EtOH was put into beaker A2 instead of 0.926 g of HA, and 1.125 g of water and 8.031 g of EtOH were put therein and stirred at 25 ° C. for about 1 hour. The stirring conditions of beaker A1 and beaker A2 are the same as the stirring conditions of beaker A of Experimental Example 1. On the other hand, 1.903 g of TMOS and 7.93 g of EtOH were put into beaker B1 and beaker B2, respectively, and stirred under the same conditions as beaker B of Experimental Example 1.

  Next, beaker C1 and beaker C2 were prepared, and both contents of beaker A1 and beaker B1 were put into beaker C1 and stirred at 25 ° C. for about 24 hours. Similarly, the contents of both beaker A2 and beaker B2 were put into beaker C2, and stirred at 25 ° C. for about 24 hours. The stirring speed was 550 rpm. Thereafter, stirring of the contents of the beakers C1 and C2 was stopped, and the beakers C1 and C2 were allowed to stand at 40 ° C. for 96 hours. Through this series of treatments, the preparation of two types of coating solutions was completed.

2. Preparation and Evaluation of Thin Films Next, two types of thin films were prepared under the same conditions as in Experimental Example 1 except that the rotation speed of the spin coater was fixed at one type of 2000 rpm. The evaluation method was the same as in Experimental Example 1.

3. Experimental Results Table 6 shows the evaluation results of the silica powder prepared in Experimental Example 3. Table 7 shows the evaluation results of the thin film produced in Experimental Example 3. FIG. 11 is a graph of the nitrogen adsorption / desorption isotherm of each silica powder produced without using hydroxyacetone. FIG. 12 is a graph showing the pore size distribution of each silica powder shown in FIG.

  As shown in Table 6, Table 7 and FIG. 12, when the heating step at 200 ° C. is performed, the difference in the average pore diameter is different depending on the presence or absence of hydroxyacetone. I was not able to admit.

"Experimental example 4"
1. Preparation of coating solution, preparation and evaluation of thin film In order to examine the effect of the heat treatment, a thin film was produced by a method in which the heat treatment step was excluded from the production of the thin film in Experimental Example 1. The rotation speed of the spin coater was fixed at one kind of 2000 rpm. In addition to the silicon substrate, an acrylic resin (referred to as PMMA resin) substrate (manufactured by Sampratec, 25 mm × 50 mm × 1 mm) was also used as the substrate. The substrate made of PMMA resin was subjected to corona treatment using a corona discharge device (manufactured by Shinko Electric Instrumentation Co., Ltd., model: Coronafit CFG-500) before film formation. For the evaluation, light transmittance using an ultraviolet-visible spectrophotometer (manufactured by Hitachi, Ltd., model: U-4100) was also added. The production and evaluation of coating solutions other than those described above were the same as in Experimental Example 1. As a comparison, the Si substrate in an unformed state and the substrate made of PMMA were also used for the evaluation of the contact angle.

2. Experimental Results Table 8 shows the evaluation results of the thin film on each Si substrate prepared in Experimental Example 4. Table 9 shows the evaluation results of the thin film on each PMMA substrate produced in Experimental Example 4. FIG. 13 is a graph showing transmittances of a thin film-attached PMMA substrate and an unformed PMMA substrate analyzed using an ultraviolet-visible spectrophotometer.

  As is clear from comparison with Experimental Example 1, when the heating step was excluded, a tendency for the contact angle to increase was recognized. However, the silica film produced using EtOH as the solvent maintained a small contact angle regardless of the heating step. When MtOH or EtOH was used as the solvent, a silica film having a relatively high hardness was obtained even without a heating step. Moreover, as shown in Table 9, the contact angle was 15.1 degrees or less when any solvent was used. Further, as shown in FIG. 13, it was found that when the visible light transmittance was compared between the PMMA substrate on which the silica film was formed using EtOH as the solvent and the non-film-formed PMMA substrate, the transmittance was almost equal.

“Experimental Example 5”
1. Preparation of coating solution, preparation and evaluation of thin film In order to investigate the effect of the post-hydrolysis treatment under conditions in which heat treatment is not performed, a method and an experiment in which the post-hydrolysis treatment step is excluded from the preparation of the thin film of Experimental Example 4 A thin film was prepared by two methods, the same method as in Example 4. Preparation and evaluation of coating solutions other than those described above were the same as in Experimental Example 4.

2. Experimental Results Tables 10 and 11 show the evaluation results of the thin film produced in Experimental Example 5.

  It was found that, regardless of which solvent was used, a silica film having higher hydrophilicity, smaller film thickness, and lower hardness can be obtained by post-hydrolysis treatment. If the post-hydrolysis treatment is not performed, the hydrophilicity is inferior. Therefore, the post-hydrolysis treatment is considered to be a necessary step regardless of the type of the substrate.

FIG. 14 is a graph showing a comparison of infrared absorption peaks in the vicinity of 2900 cm ^{−1 of} silica powders prepared using EtOH as a solvent and those subjected to post-hydrolysis treatment and those not subjected to post-hydrolysis treatment. It is.

As is clear from FIG. 14, no peak was observed in the vicinity of 2800 to 3000 cm ⁻¹ in the silica powder produced by the post-hydrolysis treatment, but the silica powder produced without the post-hydrolysis treatment was used. , Peaks due to —CH ₂ and —CH ₃ were observed. This result is the same as the result shown in FIG. 10 in Experimental Example 2, and the post-hydrolysis is performed by removing a functional group having hydrophobicity such as —CH ₂ and —CH ₃ and accompanying Si—OH. It is thought that it contributes to the generation of bonds and has an effect of increasing the hydrophilicity of the film when the film is formed.

"Experimental example 6"
1. Preparation of coating solution, preparation of thin film and evaluation A coating solution identical to that of Experimental Example 3 was prepared, and a thin film was prepared and evaluated in the same process as in Experimental Example 4 excluding the heat treatment process. In addition, the standing time in the preparation process of the coating solution was 96 hours.

2. Experimental Results Table 12 shows the evaluation results of the thin film produced in Experimental Example 6.

  As shown in Table 12, as is clear from the comparison with Experimental Example 3, when the heating step at 200 ° C. is not performed, the silica film produced using hydroxyacetone has a smaller contact angle and is hydrophilic. It was found to be excellent. Therefore, it is considered preferable to use hydroxyacetone when the heating step is not performed.

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

Claims (2)

A reaction step in which at least tetraalkyl orthosilicate, ethanol, hydroxyacetone and water are mixed and reacted;
A film forming step of forming a film by supplying a solution obtained by the reaction step to a substrate;
A hydrolysis step in which the membrane obtained by the membrane formation step is brought into contact with water for hydrolysis , and
A method for producing a hydrophilic silica film, comprising: Visible light transmission produced by the method for producing a hydrophilic silica film according to claim 1, wherein the contact angle of water droplets on the film is 20 degrees or less, and the film is attached to an acrylic resin substrate having a thickness of 1 mm. hydrophilic silica film with an acrylic resin substrate rate is characterized Rukoto which have a hydrophilic silica film composed of 92% or more.

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