JPH0649265A - Transparent water-repelling film - Google Patents

Abstract

PURPOSE:To provide a transparent water-repelling film capable of keeping excellent water-repellency over a long period. CONSTITUTION:The transparent water-repelling film 2 contains transparent ceramic material 22 held in the cavities 21 of a porous film 20 made of a fluorine-containing polymer. The porous film 20 gives water-repellency and the transparent ceramic material 22 gives mechanical strength and the adhesiveness to a glass substrate 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent water repellent film which is formed on the surface of windshields of automobiles to impart water repellency.

[0002]

2. Description of the Related Art Water-repellent glass has been studied for the purpose of repelling water droplets adhering to windshields and side mirrors and improving the visibility in rainy weather. For example, it is conceivable to make the glass itself water-repellent, but at the present time there are many technical problems to be solved and it has not been put to practical use. Therefore, it was conceived to form a transparent coating having water repellency on the surface of the glass substrate, and various proposals have been made.

For example, Japanese Patent Application No. 1-217812 proposes to form a silicone-based water-repellent film such as polydimethylsiloxane on the surface of a glass substrate. Since the silicone resin has extremely good water repellency, this water repellent film has excellent water repellency.

[0004]

By the way, in a silicone-based water-repellent coating, the contained water-repellent groups are oriented on the surface side of the coating, and the SiO groups are oriented on the glass substrate side. Therefore, when the outermost surface is worn when it is polished with a glass cleaner or the like, the orientation is disturbed, the water-repellent group is also dropped off, the water repellency is lowered, and finally the water repellency disappears at an early stage.

The present invention has been made in view of such circumstances, and an object thereof is to provide a transparent water-repellent film capable of maintaining excellent water repellency for a long period of time.

[0006]

The transparent water-repellent coating of the present invention for solving the above-mentioned problems is characterized in that the transparent ceramics are contained and held in the pores of the porous film made of the fluorine-containing polymer. As the fluorine-containing polymer, one showing water repellency is used, and polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PC
TFE), tetrafluoroethylene-6 fluoropropylene copolymer, polyvinyl fluoride (PVF), polyvinylidene fluoride (PFVD) and the like.

If the transparent ceramic is transparent,
SiO is not limited₂, TiO ₂, ZrO₂, Al
₂O₃Variously selected from the above. Fluorine-containing polymer
Holding transparent ceramics in the pores of a porous membrane
In order to do so, as described in the examples, fluorine group-containing
A porous film made of a polymer does not contain organic silane compounds.
Voids due to which sol is impregnated and gelled by hydrolysis
It can be contained and retained.

In order to improve transparency, it is preferable that the transparent ceramics and the porous film have similar refractive indices.

[0009]

In the transparent water-repellent coating of the present invention, a porous membrane made of a fluorine-containing polymer showing water repellency serves as a substrate.
Therefore, even if the water-repellent material (porous film) on the surface is removed by abrasion, a new water-repellent material (porous film) will appear one after another, so that water repellency can be maintained for a long time. it can.

Further, since the water-repellent material is a polymer, it is inferior in mechanical properties such as abrasion resistance by itself, but it is sufficient as a water-repellent film because it is protected by the transparent ceramics retained in the pores. It has mechanical properties. Furthermore, the porous film itself made of the fluorine-containing polymer is opaque due to light scattering in many pores contained therein and is inferior in transparency. However, in the transparent water-repellent coating of the present invention, since the transparent ceramics fills the pores, light scattering is prevented and high transparency is secured.

[0011]

EXAMPLES The present invention will be specifically described below with reference to examples. (Embodiment 1) FIG. 1 shows a schematic cross-sectional view of a water-repellent coating according to an embodiment of the present invention. The water-repellent coating 2 is formed on the glass substrate 1 to have a thickness of about 10 μm, and has a porous film 20 made of PTFE and transparent ceramics made of SiO ₂ filled in the pores 21 of the porous film 20. 22 and 22.

Hereinafter, a method for producing the water-repellent coating 2 will be described to replace the detailed description of the structure. First, the PTFE porous membrane 20 produced by stretching is prepared. The porous membrane 20 has a thickness of 10 μm and the pores 21 have an average pore diameter of 0.1.
μm, porosity 50%. On the other hand, a SiO ₂ sol is prepared. This SiO ₂ sol is obtained by stirring 208 g of tetraethoxysilane and 427 g of ethanol in a 1 liter beaker for 20 minutes. Furthermore, 83 g of water and 0.1
It was formed by adding 104 g of N hydrochloric acid aqueous solution, stirring and mixing for 2 hours, and aging at 25 ° C. for 24 hours in a sealed container.

Then, the porous film 20 is dipped in the SiO ₂ sol and reduced in pressure to impregnate the pores 21 of the porous film 20. Then, the porous film 20 impregnated with SiO ₂ sol
Is placed on the surface of the soda lime glass substrate 1, pressed by a roller, and then naturally dried. It is placed in a dipping device placed in a closed system, and the porous film 20 on the glass substrate 1 is again impregnated with SiO ₂ sol under a reduced pressure of 0.5 atm. Then, after returning to atmospheric pressure, the glass substrate 1 is pulled up together with the porous film 20 at a pulling rate of 30 mm / min.
₂ Film the sol on the whole surface and let it dry naturally.

After that, it is placed in a baking oven and heated at 300 ° C. for 1 hour.
After baking for a period of time, S impregnated into the pores 21 of the porous film 20
The iO ₂ sol and the film-like SiO ₂ sol formed on the surface thereof are gelled. The water-repellent glass thus produced is impregnated into the pores 21 of the porous film 20 to form gelled S.
The transparent ceramics 22 made of iO ₂ firmly adheres to the glass substrate 1, and the porous film 20 is thereby also adhered to the glass substrate 1.
Is in close contact with. However, as it is, it does not show water repellency because the surface of the porous film 20 is covered with the SiO ₂ gel film. Therefore, the surface is polished with a slurry in which the ceria abrasive is suspended to expose the surface of the porous film 20. As a result, a water-repellent glass having the water-repellent coating 2 of this embodiment is manufactured.

The water-repellent coating 2 thus obtained was transparent, had a contact angle of 100 degrees with water, and had high water repellency. In addition, in order to investigate the durability, a flannel cloth containing a glass cleaner containing compound was used, and 300 g / c
Although it was reciprocated 10,000 times under a load of m ² , polishing was performed, and no deterioration in water repellency was observed and it had high fastness. The pore diameter of the pores 21 of the porous film 20 is preferably 0.2 μm or less. When the pore diameter becomes larger than 0.2 μm, the transparent ceramics 22 impregnated in the pores and the porous film 2 around the transparent ceramics 22 are impregnated.
There is a case where optical scattering occurs between 0 and opaque and the transparency is lowered.

The porosity of the porous film 20 is 20 to 90.
The range of% is desirable. When the porosity is smaller than this range, the integrity with the transparent ceramics 22 is reduced and the robustness is reduced. If the porosity is higher than this range, the area occupied by the porous film 20 may be reduced, and the water repellency may be reduced or the water repellency may be varied. (Example 2) A water-repellent film was formed in the same manner as in Example 1 except that a porous film having a film thickness of 1 µm and a thickness of 1/10 of Example 1 was used. As a result, a water repellent film having the same water repellency and fastness as in Example 1 could be formed.

However, in the glass substrate having the water-repellent coating of the present embodiment, as shown in FIG. 2, the reflection spectrum (5 degree reflection) of the surface of the water-repellent coating showed slight coloring due to optical interference. . The average refractive index of the water-repellent coating is 1.4.
Is different from the refractive index of soda lime glass of 1.53, and is due to the thin film of the water repellent film. (Example 3) Therefore, in place of the SiO ₂ sol of Example 1, a SiO ₂ —TiO ₂ mixed sol was used, and a porous film having a film thickness of 1 μm and 1/10 of that of Example 1 was used. A water repellent film was formed in the same manner as in Example 1 except for the above. Incidentally, SiO ₂ -TiO ₂ mixed sol by mixing the tetra-n-butoxy titanium 60g ethanol 60g, SiO ₂ This was prepared and aged for 24 hours in Example 1
What was mixed with the total amount of the sol and stirred for 1 hour was used.

The reflection spectrum of the surface of the water-repellent film of the water-repellent glass obtained is shown in FIG. As shown in FIG. 3, coloring was not recognized in the reflected light. This is because TiO ₂ was mixed in the water-repellent film, so that the refractive index increased and became close to that of the glass substrate. The water-repellent film obtained in this example showed excellent water repellency and fastness as in Example 1.

[0019]

That is, according to the water-repellent coating of the present invention, the water repellency does not decrease or disappear even if it is polished with a glass cleaner containing a compound, etc., so that the water repellency is maintained for a long time Is excellent.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a water-repellent film according to an embodiment of the present invention and a glass substrate having the water-repellent film.

FIG. 2 is a reflection spectrum of the surface of the water-repellent coating of Example 2.

FIG. 3 is a reflection spectrum of the surface of the water-repellent coating of Example 3.

[Explanation of symbols]

1: Glass substrate 2: Water repellent film 20: Porous film 21: Porosity 22: Transparent ceramics

Claims (1)

[Claims] 1. A transparent water-repellent film, wherein transparent ceramics are contained and held in the pores of a porous film made of a fluorine-containing polymer.