JPH09295836A - Production of water-repelling clear coat - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a water-repelling clear coat by using a coating liquid easily applicable in air, resistant to the deterioration of the water-repelling coating liquid with time and capable of easily forming a uniform coating layer on a substrate by restricting the surface tension of a water-repelling coating solution containing a specific silane compound within a specific range. SOLUTION: This process for producing a water-repelling clear coat comprises a step to immerse a substrate in a water-repelling coating solution of a compound having fluorocarbon chain and a methoxysilyl group or a fluorocarbon chain and an ethoxysilyl group, a step to take the substrate out of the water-repelling coating solution and evaporate the solvent and a step to hydrolyze and polymerize the compound to form a water-repelling coat on the substrite. In the above process, the surface tension of the water-repelling coating solution is adjusted to be lower than the surface energy of the substrate in the step to immerse the substrate into the water-repelling coating solution. The surface tension of the water-repelling coating solution is maintained to <=18dyne/cm.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a transparent water-repellent coat.

[0002]

2. Description of the Related Art As a water-repellent coat that imparts water repellency to a base material while maintaining the base texture of the base material such as the color and luster of the base material,
There are water-repellent thin films using chlorosilane, ethoxysilane, or methoxysilane compounds. Examples of the above-mentioned base material include glass and metal, but when glass is used as the base material and a transparent water-repellent coat is formed,
Water repellency can be imparted to the substrate while maintaining the transparency of the glass itself, while when a metal is used as the substrate, it is possible to impart water repellency to the substrate while maintaining the luster of the metal. It can be done.

Therefore, a conventional method for forming a water repellent coat using the above compound will be described below with reference to the drawings.

First, FIG. 2 is a flow chart showing a method for forming a water repellent coat when chlorosilane is used among the above compounds. First, a solvent (water repellent coating solution) in which CF3 (CF2) 7C2H4SiCl3 (main material of water repellent coating using a compound of chlorosilane) is dissolved as a substance containing chlorine and silicon is prepared. Next, in a dry atmosphere, the above CF3 (CF2) 7C2H4SiC
The substrate on which the water-repellent coat is to be formed is immersed in a solvent (non-aqueous solvent) in which 13 is dissolved for a certain period of time and then washed with chloroform. Then, the transparent water-repellent film having a thickness of about 1 nm is formed on the base material by washing the base material with water in the air atmosphere (for example, Japanese Patent Laid-Open No. 4-194266).

Next, FIG. 3 is a flow chart showing a method for forming a water repellent coat when methoxysilane is used among the above compounds. First, as a substance containing a methyl group and silicon, CF3 (CF2) 7C2H4Si (OCH
3) Prepare an ethanol solution (water repellent coating solution) in which hydrochloric acid and water are dissolved. Then, the substrate on which the water repellent coat is to be formed is immersed in the above ethanol solution. Then, after drying at room temperature, heat treatment at 100 ° C. is performed to form a transparent water-repellent coat on the substrate.

[0006]

However, the above-mentioned conventional method for producing a water-repellent coat has the following problems.

First, in the method for producing a water-repellent coat using a chlorosilane compound, since the water-repellent molecule is a monomolecular film covalently bonded to the base material, the color and gloss of the coated base material and the base texture of the base material. Can be maintained (in other words, a water-repellent coating can be formed uniformly on the substrate), but since the chlorosilane compound reacts rapidly with water (the chemical formula below), handle it in a dry atmosphere. It is necessary and requires a special device (in other words, the water-repellent coating solution deteriorates with time). Specifically, it is necessary to keep the relative humidity at 1% or less, and as a means for this, a method of purging nitrogen gas or the like can be mentioned.

[0008]

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[0009]

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Next, in the method for producing a water-repellent coat using an ethoxysilane or a methoxysilane compound, the reactivity with water is lower than that of a chlorosilane compound (in other words, deterioration over time does not easily occur), and the atmosphere is not changed. Although they have the advantage of being easy to handle, these silane compounds have low reactivity, so in order to react with the substrate, an acid or alkali catalyst is added to the silane compound solution that will be the coating solution, and the compound is hydrolyzed. It is necessary to do it (see the chemical formula below). Further, since the surface tension of ethanol is 22 dnye / cm, it is difficult to uniformly apply the formed solution for forming the water-repellent coat to the substrate. This is because it is difficult to apply the water-repellent coating solution uniformly to the substrate.

[0011]

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Further, the molecules after hydrolysis such as hydrochloric acid gradually undergo dehydration polymerization reaction with each other as shown in the following chemical formula, so that the coating solution gradually deteriorates (that is,
There is a problem that the silanolated compound on the right side of (Chemical formula 3) cannot exist in that state.

[0013]

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The present invention solves the above problems, and can be easily coated in the atmosphere, the water-repellent coating solution is less deteriorated over time, and a water-repellent coating can be easily and uniformly formed on a substrate. It is an object of the present invention to provide a method for producing a transparent water-repellent coat using a coating liquid that can be used.

[0015]

In order to achieve the above-mentioned object, a method for producing a transparent water-repellent coat of the present invention comprises a fluorocarbon chain and a methoxysilyl group, or a fluorocarbon chain and an ethoxysilyl group. When a substrate is treated with a water-repellent coating solution in which a molecule containing is dissolved, the surface tension of the water-repellent coating solution is set to be lower than the surface energy of the substrate surface when treating the substrate (specifically For example, 18
dyne / cm or less). With this configuration, it is possible to prevent the water-repellent coating solution from deteriorating with time, and it is possible to uniformly form a water-repellent coating having a film thickness of one molecule or more on the surface of the base material.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION A method for producing a water repellent coat according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a flow chart showing a method of manufacturing a water repellent coat according to this embodiment.

As shown in FIG. 1, first, a component containing a fluorocarbon chain and a methoxysilyl group or a fluorocarbon chain and an ethoxysilyl group is treated with a nonaqueous solvent having a surface tension of 18 dyne / cm or less (specifically, Is dissolved in a fluorocarbon solvent) to prepare a water repellent coating solution. Next, a substrate having active hydrogen on its surface (for example, glass, ceramic,
A metal or the like) is immersed in the above water-repellent coating solution.

By the above dipping step, dissolved molecules are adsorbed on the surface of the base material, but this action lowers the surface energy of the surface of the base material. Generally, when a molecule having a fluorocarbon chain is adsorbed on the surface of a substrate and the surface is covered with a perfluoromethyl group (CF3), the surface energy becomes 18 dyne / cm.

Here, when the surface tension of the solvent is larger than 18 dye / cm, when the substrate is taken out of the solution, the substrate repels the solution, and the solution does not remain on the substrate surface. Only the adsorbed molecules are attached to the base material, and only molecules having a thickness of about a monomolecular film are attached to the surface of the base material. On the other hand, when the surface tension of the solvent is set to 18 dyne / cm or less as in the present invention (see above), when the base material is taken out of the solution, the base material is completely wetted by the solvent and therefore remains on the base material. When the solution evaporates, molecules containing a fluorocarbon chain and a methoxysilyl group or a fluorocarbon chain and an ethoxysilyl group in the solution are adsorbed on the substrate, and molecules having a monomolecular film thickness or more are attached.

That is, in the present invention, the surface energy of the solution applied to the base material is equal to or lower than the surface energy of the base material, so that the wettability of the solution is extremely improved, and as a result, the monomolecular molecules are uniformly distributed on the base material. It is possible to form a film having the above film thickness.

Then, the above-mentioned molecules having a monomolecular film thickness or more can be polymerized by subsequent drying, washing with water, or treatment with an acid or an alkali. A transparent water repellent coat is formed.

Specific examples of the present invention will be shown below. (Example 1) As a substrate for forming a transparent water-repellent coat, an alkali glass coated with a silica film was selected. The reason why the above silica film is coated is to prevent the water-repellent coating formed on the substrate from being denatured due to the elution of alkali ions from the glass surface. The silica coat was formed on glass by coating with a silica coating agent and baking at 400 ° C. for 30 minutes, and the thickness of the silica coat was set to about 0.1 μm.

Next, CF3 (CF2) 7C2H4Si (OC
H3) 3 to n-perfluorooctane (surface tension is 15 dy
ne / cm) was dissolved in a volume ratio of 5% to prepare a coating solution. As described above, since the surface tension of n-perfluorooctane is 18 dyne / cm or less, this water repellent coating solution has a surface tension of the substrate or less.

After the above glass substrate was immersed in this solution for 30 minutes, it was taken out of the solution and dried at room temperature for 30 minutes. Next, the base material was washed with water for 10 minutes and then baked at 150 ° C. for 30 minutes to form a water repellent coat. The water-repellent coat formed by this method will be referred to as coat A.

The water-repellent coating solution formed as described above was stored for one week at 20 ° C. in an atmosphere of 40% humidity (normal temperature and normal humidity), and then applied to a silica-coated glass substrate by the same method as described above. Coated with an aqueous film. This coat will be referred to as coat B.

The following table shows the static contact angle of the coat formed by the above method with water and the static contact angle with water measured at room temperature after being exposed to an atmosphere of 300 ° C. for 250 hours.

[0028]

[Table 1]

As is clear from the above results, according to the present invention, the water-repellent coating solution immediately after preparation and the solution after preparation 1
It can be seen that the characteristics of the coat produced using the water-repellent coating solution left for a week did not change, and that deterioration over time did not occur. Furthermore, the static contact angle of the coat remains 100 degrees or more even after being exposed to the atmosphere of 300 ° C. for 250 hours,
It is considered that this water-repellent coat has a strong covalent bond with the base material and that a film of a single molecule or more is formed.

Example 2 A transparent water-repellent coat was formed on a silica-coated glass substrate by the same method as in Example 1 described above. However, before washing with pure water, the substrate was immersed for 10 minutes in an aqueous solution of acetic acid (used as one of the acids used for the catalyst) in which 1% by volume was dissolved.

Here, the coat formed using the water-repellent coating solution immediately after preparation is referred to as coat C, and the coat formed using the water-repellent coating solution left for one week after preparation is referred to as coat D. And

The static contact angle of the coat formed by the above method with water and the value of the static contact angle with water measured at room temperature after being exposed to an atmosphere of 300 ° C. for 250 hours are shown in the following table.

[0033]

[Table 2]

As is apparent from the above results, according to the present invention, the characteristics of the coating solution prepared using the coating solution immediately after preparation and the coating solution left for one week after preparation are not different. . Furthermore, 300 ℃
Even after being exposed to the atmosphere for 250 hours, the static contact angle of the coat was maintained at 100 degrees or more, and this water-repellent coat formed a strong covalent bond with the base material and formed a film of a single molecule or more. It is considered to be a thing.

The heat resistance of the thin film formed in this example is higher than that of the thin film formed in Example 1. This is CF3 by immersing in acetic acid aqueous solution before washing with water.
The hydrolysis of (CF2) 7C2H4Si (OCH3) 3 proceeds,
CF3 (CF2) 7C2H4S forming a coat before heat treatment
It is considered that the ratio of the hydrolyzate of i (OCH3) 3 was higher than that of the coat of Example 1, and therefore the density of molecules covalently bonded to the substrate after the heat treatment was high.

[0036]

As described above, according to the present invention, the transparent water-repellent coat can be easily coated in the atmosphere, and the reaction solution which does not deteriorate with time is used. When mass-producing, solution management is easy, which leads to reduction of mass-production cost.

Further, according to the present invention, since the water-repellent coating solution has a surface energy equal to or lower than the surface energy of the substrate, the wettability of the water-repellent coating solution is improved and, as a result, the film thickness of a monomolecular film or more can be easily obtained. A water repellent coat can be formed.

[Brief description of drawings]

FIG. 1 is a flowchart showing a method for manufacturing a water repellent coat according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a conventional method for producing a water-repellent coat.

FIG. 3 is a flowchart showing a conventional method for producing a water-repellent coat.

Claims (4)

[Claims] 1. A step of immersing a base material in a water repellent coating solution in which a molecule containing a fluorocarbon chain and a methoxysilyl group or a molecule containing a fluorocarbon chain and an ethoxysilyl group is dissolved, and the base material. A method for producing a transparent water-repellent coat, comprising: removing the solvent from the water-repellent coat solution; evaporating a solvent; and hydrolyzing / polymerizing the molecules to form a water-repellent coat on the substrate. hand,
The method for producing a transparent water-repellent coat, wherein the surface tension of the water-repellent coating solution is not more than the surface energy of the substrate in the step of immersing the substrate in the water-repellent coating solution. 2. The substrate is immersed in an acidic aqueous solution or a basic aqueous solution in the step of forming a water-repellent coating on the substrate by hydrolyzing and polymerizing molecules. A method for producing the transparent water-repellent coat described. 3. The surface tension of the water repellent coating solution is 18 dny.
e / cm or less, Claim 1 or 2 characterized by the above-mentioned.
The method for producing the transparent water-repellent coat according to [4]. 4. The method for producing a transparent water-repellent coat according to claim 1, wherein the solvent of the water-repellent coat solution is a fluorocarbon solvent.