JP2001295026A - Water-repellent article, and method of water-repellent thin film coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the conventional problem that no thin film of single-layer structure combining a function of providing water repellency to the surface of an article with a function of reducing reflectivity has been obtained so far and the appearance of a water-repellent thin film excellent in wear resistance has been expected. SOLUTION: The article is constituted by coating a glass plate with a fluorine-containing water-repellent thin film. The thin film has a composition gradient, with respect to titanium oxide and silicon dioxide, so that refractive index becomes decreased with distance from the substrate in the thickness direction of the thin film. Thin film deposition is performed by a sputtering method, and fluorine in the film is doped by introducing fluorine compound gas such as ethylene fluoride into a vacuum film deposition system while thin film deposition is carried out by sputtering.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an article having a substrate coated with a water-repellent transparent oxide thin film and a method for coating the water-repellent thin film. In particular, the present invention relates to an article coated with a water-repellent thin film having a reduced surface reflectance and a method for coating the thin film.

[0002]

2. Description of the Related Art Conventionally, as a method of imparting water repellency to a substrate surface, a method of obtaining a water repellency by applying and drying an alcohol solution containing a fluorine compound, or a sol-gel using a fluorine-containing solution as a starting material. A method is known in which a liquid containing a water-repellent component prepared by a method is applied to a substrate and then heated and baked to form a water-repellent thin film. A fluorine compound adheres to a substrate such as a glass plate obtained by such a method, and water repellency is imparted by the water repellency function of the fluorine compound. An article having water repellency on the surface has antifouling performance.

Further, in order to provide an antireflection function to the substrate surface, an antireflection film is formed on the substrate surface by a vacuum film forming method (evaporation method or sputtering method). In order to provide a higher antireflection function, a multilayer film in which a high refractive index film and a low refractive index film are laminated is formed on a substrate. In that case, it is required to precisely control the thickness of each film, and therefore, an expensive vacuum film forming apparatus having a function excellent in film thickness controllability is required. That is, the conventional method has disadvantages in productivity such that the coating cost of the antireflection film is increased and it takes time to laminate and coat a large number of films.

[0004]

The water-repellent thin film obtained by the above-described method is not necessarily required to have the mechanical (physical) strength of the thin film when applied to, for example, an automobile window glass or a show window window glass. This is not sufficient, that is, it is not sufficiently strong against external physical forces (such as friction), and there is a problem that the thin film is damaged or peeled off in some cases. For this reason, in order to use a glass plate coated with a water-repellent thin film in a relatively severe use environment such as a window glass of an automobile, the durability of the water-repellent thin film must be improved. was there. That is, an object of the present invention is to have a low reflection characteristic equivalent to that of a multilayered antireflection film of the prior art, and to have practical water repellency even when used in a part directly in contact with the outside, and to reduce the coating cost. It is an object of the present invention to provide an article coated with a single-layer thin film which can be reduced and a method for manufacturing the same.

[0005]

SUMMARY OF THE INVENTION The present invention provides an article comprising a substrate coated with a fluorine-containing water-repellent thin film,
The thin film contains at least one kind of high-refractive-index metal oxide and silicon dioxide, which is a low-refractive-index oxide, with a composition gradient such that the refractive index decreases as the distance from the substrate increases in the thickness direction of the thin film. It is a water-repellent article characterized by doing.

The high refractive index metal oxide of the present invention is preferably selected from the group consisting of titanium oxide, zirconium oxide, tantalum oxide and praseodymium titanate. Each of these metal oxides has a refractive index of 2.1 or more at a wavelength of 550 nm when formed into a thin film,
When mixed with a low-refractive-index silicon dioxide film to form a refractive index gradient in the film thickness direction to reduce the reflectance,
This is because they are well mixed with silicon dioxide. Among them, titanium oxide has the largest refractive index, which is advantageous in greatly reducing the reflectance on the substrate surface.

The water-repellent thin film contains fluorine, and the fluorine imparts water repellency to the surface. Fluorine may be contained only in the vicinity of the surface of the water-repellent thin film, may be contained inside the thin film together with the surface, or may be contained in the entire thickness direction of the thin film. By containing it only on the surface of the thin film, an expensive fluorine material can be used economically and efficiently. On the other hand, by including fluorine throughout the thin film, even if the surface of the thin film is worn by cleaning or the like, the fluorine is still present on the surface of the water-repellent thin film, so that there is an advantage that the water repellency is maintained.

As a method for coating the water-repellent thin film of the article of the present invention, two sets of cathodes are arranged in close proximity to a film-forming apparatus capable of adjusting a reduced-pressure atmosphere containing fluorine and attached to one of the cathodes. When the metal target of the metal oxide is used as a cathode, the silicon target attached to the other cathode is used as the anode, and when the metal target is used as the anode, the silicon target is used as a cathode. It is preferable to apply a voltage in which the metal and silicon targets are alternately inverted to simultaneously sputter the metal and silicon targets with reactive oxygen, and pass the substrate through the space in front of the metal target and the silicon target in this order.

According to the above method, the effect of making the substrate surface of the water-repellent thin film reflectivity and the effect of making the substrate water-repellent can be simultaneously provided.

[0010]

The target used in the present invention is preferably at least one metal selected from the group consisting of titanium, zirconium, tantalum and titanium praseodymium. A metal material such as titanium as a high-refractive-index film and a silicon material as a silicon dioxide film are attached to the cathode by metal bonding or the like, and a high refractive index is passed while passing the substrate in one direction through the space in front of these two targets. The film of the refractive index material and the film of the low refractive index material are coated, and a composition gradient is continuously provided in the thickness direction of the film. Thereby, a refractive index gradient is provided in the thickness direction of the film. On the other hand, a fluorine compound gas is introduced as a sputtering gas to be introduced into the film forming chamber of the film forming apparatus,
A fluorine compound is contained in the thin film by gas doping to impart water repellency to the formed thin film. That is, in the present invention, the function of reducing the reflectance and the function of water repellency can be imparted simultaneously with the coating of the water-repellent thin film. It is preferable to add a trace amount of boron or the like to the silicon material in order to maintain the stability of the glow discharge to prevent the target from being charged.

In the present invention, the refractive index gradient is provided in the thickness direction of the thin film by continuously changing the composition of the water-repellent thin film in the thickness direction of the film. By changing the refractive index gradient profile in various ways, it is possible to obtain a desired low reflectivity.

The gas introduced into the film formation chamber during sputtering (depressurized atmosphere gas) is a mixed gas of argon and oxygen (in some cases, oxygen gas) for coating a water-repellent thin film by reactive sputtering. Only) and a fluorine compound gas for containing fluorine in the thin film. The introduction amount of the fluorine compound is preferably 1% or more and 10% or less with respect to the total flow rate of the introduced gas. If it is less than 1%, the effect of imparting water repellency to the thin film is reduced,
On the other hand, if it exceeds 10%, the denseness of the thin film decreases, and the wear resistance of the thin film decreases.

The fluorine compound used in the present invention is preferably in a gaseous state at room temperature, is efficiently incorporated into the film, and has low toxicity. From such a viewpoint, methane tetrafluoride, ethylene tetrafluoride, propylene hexafluoride and butylene octafluoride are preferred. These fluorine compound gases can impart water repellency without reducing the denseness of the thin film to be coated.

As the substrate used in the present invention, various glass plates and resin plates can be used. Various known silicate glasses have a refractive index of 1.50 to 1.53, and known polyolefin resins and polycarbonate resins have a refractive index of 1.5 to 1.75. It is possible to reduce the reflectance of the substrate surface by coating a thin film of a high-refractive-index material in the vicinity of the substrate and increasing the composition of silicon dioxide so that the refractive index decreases as the distance from the substrate increases. it can.

[0016]

FIG. 1 is a sectional view of a water-repellent article 1 according to one embodiment of the present invention. The water-repellent article 1 has a glass plate 2 coated with a water-repellent thin film 3. The water-repellent thin film 3 has a refractive index gradient in the thickness direction, the refractive index near the glass plate is 2.40, and the refractive index near the surface in contact with air is 1.40.
50. Due to the refractive index gradient of the thin film, the surface reflectance of about 4% of the glass plate is reduced to 1% or less. The water-repellent thin film has a fluorine compound-containing layer 4 in a certain thickness range near its surface. This layer makes the surface of the water-repellent thin film 3 water-repellent. The fluorine-containing layer may be present entirely in the thickness direction. By forming a fluorine-containing layer near the surface, it is possible to suppress the amount of use of a relatively expensive fluorine compound and obtain water repellency, which is preferable from the viewpoint of economy.

FIG. 2 is a schematic sectional view of a vacuum film forming apparatus 10 used to carry out the present invention.

The vacuum film forming apparatus 10 has a vacuum exhaust port 16 connected to a vacuum exhaust means (not shown) and a gas introducing pipe 14 connected to a gas introducing means (not shown), so that a reduced pressure atmosphere can be adjusted. 15. Two sputtering cathodes 11A and 11B to which a negative voltage can be applied by a DC power supply (not shown) are provided at the bottom of the film forming chamber 15. Sputtering cathode 11A has titanium metal 12A, and sputtering cathode 11B has silicon target 12B.
Are attached by metal bonding. The two planar-type cathodes constitute a set with respect to the plasma discharge to be generated, and are arranged in close proximity to each other. The glass plate 13 is moved in the direction of the arrow in the figure to coat (deposit) a water-repellent thin film having a composition gradient in the thickness direction.

When the metal target 12A is used as a cathode, the silicon target 12B is used as an anode, while when the silicon target 12B is used as a cathode, the metal target 12A is used as an anode. The cycle of alternately inverting the polarities of these targets is usually preferably 1 kHz to 100 kHz. This alternating inversion of the polarity is usually performed using an oscillator.

The voltage waveform applied to the cathode is a sine wave,
It is sufficient that the applied voltage waveform is a positive / negative balanced voltage that neutralizes the electric charges charged on the surfaces of the two target materials with respect to the time axis, such as a square pulse wave and a time asymmetric wave. Glow discharge is stably maintained by sputtering both titanium metal and silicon metal targets simultaneously. Two targets are sputtered simultaneously. Argon, oxygen, and a fluorine compound gas are introduced from the gas introduction pipe 14 into the film forming chamber 15 during sputtering. Thus, a reduced-pressure atmosphere gas composed of argon, oxygen, and a fluorine compound gas is produced. The glow discharge is maintained mainly by the argon gas, and reactive sputtering is performed by oxygen, whereby the glass plate is coated with a mixed thin film of titanium oxide and silicon dioxide. The fluorine compound gas is taken into the thin film.

Hereinafter, the present invention will be described with reference to Examples and Comparative Examples. The substrate used was a float glass plate having a soda-lime silicate composition in each of Examples and Comparative Examples. This transparent glass plate alone had a visible light transmittance of about 92% and a surface reflectance of about 4%.

Example 1 In the vacuum film forming apparatus shown in FIG.
As 2B, silicon is bonded by a metal bond method, and a mixed gas of argon and oxygen is introduced, and the component of the coating is SiOx.
(X is 2 or slightly less than 2) and TiOy (y is slightly less than 1.33 or 1.33). At the same time, ethylene tetrafluoride as a fluorine compound gas was introduced from the gas introduction pipe 14 so as to be 5% of the total introduced gas. The atmospheric pressure during sputtering was set to 0.4 Pa. High-frequency power was applied to the sputtering cathode, and a glass plate passing in front of the two targets was coated with a water-repellent thin film in which titanium oxide and silicon dioxide were mixed by about 100 nm by a high-frequency magnetron sputtering method. As a result, the wavelength 550
The reflectance in nm was 0.2%, and the reflectance on the surface of the glass plate could be reduced to about one-twentieth. Also 450
The reflectance was almost the same even at wavelengths of 650 nm and 650 nm, and it was confirmed that an antireflection function was provided in a wide wavelength range. The contact angle of the surface of the water-repellent thin film of this sample measured by a droplet method using pure water was 95 °, and it was confirmed that the sample had large water-repellency. Further, for this sample, a Taber abrasion test equivalent to the abrasion resistance test defined by JIS-R3221 (load: 250 g
f, the number of rotations was 100), and the contact angle on the abraded surface was measured. As a result, the contact angle was about 91 °, and no remarkable decrease in the contact angle was observed.

Examples 2 to 5 A water-repellent thin film was made of glass in the same manner as in Example 1 except that the kind of the fluorine compound gas and the amount introduced into the film forming chamber were changed as shown in Table 1. Coated on board. Table 1 shows the reflectance at a wavelength of 550 nm and the contact angles before and after the Taber abrasion test as in Example 1. As is clear from Table 1, the contact angle hardly changed before and after the Taber abrasion test, and a sample having high abrasion resistance was obtained.

Comparative Example A sample was prepared in the same manner as in Example 1 except that no fluorine compound gas was introduced. A commercially available fluorine-based water-repellent agent (trade name: Garako) was carefully applied to the surface of the antireflection film of this sample to impart water repellency. The reflectance of the obtained sample at a wavelength of 550 nm is:
The contact angle before and after the Taber abrasion test was about 0.3%, which was equivalent to that of Example 1.
Although it was 01 °, it decreased to 22 ° after the test, and this water-repellent thin film was poor in water-repellency durability.

[0025]

Table 1 ================================== Example Introduced gas composition (atmospheric gas composition) Water repellency Thin film (volume%) Film surface anti-water contact angle (°) Emissivity (%) Before test After test −−−−−−−−−−−−−−−−−−−−−−−−−− −−−−−−−−−−− (Example) 1 alcohol 47.5 oxygen 47.5 ethylene tetrafluoride 5 0.3 95 91 2 alcohol 45.0 oxygen 45.0 methane tetrafluoride 10 0.2 88 92 3 alcohol 49.5 oxygen 49.5 ethylene tetrafluoride 1 0.3 92 91 4 Alcohol 47.5 Oxygen 47.5 Hexafluorofluoride 5 0.4 95 93 5 Alcohol 47.5 Oxygen 47.5 Phthylene octafluoride 5 0.4 98 92 ----------------------------- −−−−−−−−−−−−−−− (Comparative example) 1 Alcohol 50.0 Oxygen 50.0 No introduction 0.3 101 22 =================== ================

From the above Examples and Comparative Examples, the water-repellent thin film of the present invention contains not only the initial state but also the surface of the film, because the fluorine compound imparting water repellency is contained in and on the film surface. Even if worn, the water repellency does not decrease. At the same time, the surface reflectance of the glass plate can be reduced to 1/20.

[0027]

As described above, the water-repellent thin film coated on the article of the present invention has a high refractive index metal oxide and a low refractive index oxide, silicon dioxide, whose refractive index decreases with increasing distance from the substrate in the thickness direction of the thin film. Since it is contained so as to have a composition gradient as well as a fluorine compound in the thin film, it has both a large water repellency and a reflectance reducing function.

Further, according to the method for coating a water-repellent thin film of an article of the present invention, the water repellency and low reflectivity of the thin film can be simultaneously provided in a single coating step, so that the article can be economically manufactured. Can be manufactured.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of one embodiment of the article of the present invention.

FIG. 2 is a schematic sectional view of a vacuum film forming apparatus used for carrying out the present invention.

[Explanation of symbols]

 1: Article of the present invention 2: Glass plate 3: Water-repellent thin film 4: Fluorine compound-containing layer 10: Vacuum film forming apparatus 11A, 11B: Sputtering cathode 12A, 12B: Target 13: Substrate 14: Gas introduction pipe 15: Composition Membrane room 16: Vacuum exhaust port

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Shinki Nakamura 3-5-1, Doshomachi, Chuo-ku, Osaka-shi, Osaka F-term in Nippon Sheet Glass Co., Ltd. 4G059 AA01 AA11 AC04 AC22 EA01 EA04 EA05 EA07 EA18 EB04 4K029 AA09 AA11 BA43 BA46 BA48 BB02 BC00 BC08 BD00 CA06 DC03 DC05 DC16 EA05 KA01

Claims (5)

[Claims] An article comprising a substrate coated with a fluorine-containing water-repellent transparent oxide thin film, wherein the thin film is at least one kind of a high-refractive-index metal oxide and a low-refractive-index oxide. A water-repellent article comprising silicon dioxide with a composition gradient such that the refractive index decreases as the distance from the substrate in the thickness direction of the thin film increases. 2. The water-repellent material according to claim 1, wherein the high refractive index metal oxide is selected from the group consisting of titanium oxide, zirconium oxide, tantalum oxide and praseodymium titanate. Goods. 3. A method for coating a water-repellent transparent oxide thin film on an article according to claim 1 or 2, wherein two cathodes are paired in a film forming apparatus capable of adjusting a reduced pressure atmosphere containing fluorine. When the metal target of the metal oxide attached to one cathode is used as a cathode, the silicon target attached to the other cathode is used as an anode, and when the metal target is used as an anode, the silicon is used. A voltage whose polarity is alternately inverted is applied to the two cathodes so that the target serves as a cathode, and the metal and silicon targets are simultaneously subjected to reactive sputtering with oxygen, and the substrate is treated with the metal target. And passing through the space in front of the silicon target in this order. 4. The method according to claim 3, wherein the metal target is at least one selected from the group consisting of titanium, zirconium, tantalum, and praseodymium. 5. The method of claim 1, wherein the reduced-pressure atmosphere containing fluorine is methane tetrafluoride, ethylene tetrafluoride, propylene hexafluoride,
5. The method for coating a water-repellent thin film according to claim 3, wherein at least one selected from the group consisting of fluorine gas of butylene octafluoride is introduced into the film forming apparatus.