JP2001295039A - 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 and having water repellency has been expected. SOLUTION: The article is constituted by coating a glass plate with a fluorine-containing water-repellent thin film. The water-repellent thin film is constituted by incorporating fluorine, by means of doping from fluorine compound gas, into a silicon dioxide film deposited by sputtering. The fluorine compound gas such as ethylene fluoride is introduced into a film deposition chamber during silicon dioxide film deposition. By this method, the deposition of the thin film having refractive index lower than that of a single-component film composed of silicon dioxide and also having water repellency can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an article having a substrate surface coated with a water-repellent thin film and a method for coating the water-repellent thin film. In particular, it relates to an article coated with a water-repellent thin film, thereby reducing the surface reflectance of the substrate, and a method for coating such a 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 water-repellent liquid is applied to a substrate by using a method and then heated and baked to form a water-repellent thin film. The fluorine compound is firmly attached to the surface of the substrate, such as a glass plate, obtained by such a method, and the water repellency of the fluorine compound imparts water repellency to the substrate. It is known that an article having water repellency on its 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). To provide a higher antireflection function, a multilayer film having a structure in which a high-refractive-index film and a low-refractive-index film are laminated is formed on a substrate. In this case, the thickness of each thin film is precisely adjusted. Therefore, an expensive vacuum film forming apparatus having a function of excellent film thickness controllability is required, and the coating cost of the antireflection film becomes high, and it takes time to cover many layers. There was such an inconvenient problem from the viewpoint of productivity.

[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. It 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 an environment where the use environment is relatively severe, such as a window glass of an automobile, it is necessary to improve the water-repellent durability of the thin film. I was It is an object of the present invention to provide an article having practical water repellency and durability even when used in a part directly contacting the outside.

[0005]

The water-repellent article of the present invention is an article having a transparent substrate coated with a fluorine-containing water-repellent thin film, wherein the water-repellent thin film is formed of a transparent glass plate. It is a transparent oxide film having a refractive index smaller than the refractive index.

The refractive index of the water-repellent thin film coated on the transparent substrate of the present invention is smaller than that of the transparent substrate.
This imparts water repellency to the substrate and reduces the reflectance of the substrate.

As the transparent substrate of the present invention, a known glass plate or resin plate can be used. As a glass plate,
This is a silicate glass plate containing silicon dioxide as a main component, and for example, a glass having a known soda-lime silica composition, a glass having an aluminosilicate composition, or the like is used. The composition of the glass, the glass component is appropriately determined depending on the application, the silicate glass has a refractive index of 1.50 to 1.5
It is often 3. Known resin substrates such as polycarbonate resin and polyolefin resin often have a refractive index of 1.50 to 1.75. Since the refractive index of the water-repellent thin film of the present invention can be reduced to 1.44 or less, the refractive indices of the water-repellent thin film and the substrate are increased, which is preferable for effectively reducing the surface reflectance of the substrate.

The oxide component of the water-repellent thin film of the present invention is preferably a transparent oxide containing silicon dioxide as a main component. The silicon dioxide film usually has a refractive index of 1.48, but if it contains fluorine, the refractive index can be reduced to 1.44 or less. Fluorine (fluorine component) contained in the silicon dioxide film of the present invention imparts water repellency to the thin film,
It has the effect of making the refractive index smaller than the refractive index of the film of silicon dioxide alone. Thereby, the reflectance of the substrate surface can be further reduced.

The water-repellent thin film contains fluorine, which 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 containing fluorine throughout the inside of the thin film, even if the surface of the thin film is worn down due to abrasion or repeated cleaning, fluorine is still present on the surface of the water-repellent thin film, so that the water repellency is maintained. Having.

As a method for coating a water-repellent thin film on the article of the present invention, a set of two cathodes each having silicon as a target is disposed in close proximity to a film forming apparatus capable of adjusting a reduced pressure atmosphere containing fluorine. When the silicon target 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 other silicon target is used as a cathode, the one silicon target is used as an anode. A method of applying a voltage whose polarity is alternately reversed to the two targets, simultaneously sputtering the targets with oxygen, and passing the transparent substrate through the space in front of the targets, It is good for coating at low cost.

The target used in the present invention is preferably one in which a trace amount of boron, phosphorus or the like is added to prevent the target from being charged in order to maintain the stability of glow discharge.

The gas (depressurized atmospheric gas) introduced into the film forming chamber of the film forming apparatus during sputtering is a mixed gas of argon and oxygen for forming a water-repellent thin film by reactive sputtering. (In some cases, only oxygen gas) and a fluorine compound gas for containing fluorine in the film. The amount of the fluorine compound to be introduced is preferably 1% or more and 10% or less based on the amount of oxygen to be introduced. 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. Further, a small amount of nitrogen may be introduced so as not to depart from the gist of the present invention.

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, butylene octafluoride, and pentene decafluoride are preferred. These fluorine compound gases can impart water repellency without reducing the denseness of the thin film to be coated.

[0014]

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 is a silicon dioxide film. The silicon dioxide film may contain another metal oxide, for example, aluminum oxide, zirconium oxide, or the like, as long as the refractive index does not significantly increase. The water-repellent thin film 3 contains a fluorine compound 4. Thereby, the surface of the water-repellent thin film 3 becomes water-repellent. It is preferable that the fluorine compound 4 be contained over the entire thickness direction, because the fluorine compound 4 has a smaller refractive index than the water-repellent thin film 3 and has a larger refractive index difference from the substrate. In order to effectively reduce the reflectance, the difference between the refractive indices of the substrate and the water-repellent thin film is set to 0.1.
It is good to be 08 or more.

FIG. 2 is a schematic sectional view of a vacuum film forming apparatus 10 used for carrying out the present invention. The apparatus has a film forming chamber 15 in which a reduced-pressure atmosphere can be adjusted by having a vacuum exhaust port 16 connected to a vacuum exhaust unit (not shown) and a gas introducing pipe 14 connected to a gas introducing unit (not shown). At the bottom of the film forming chamber 15, there are provided sputtering cathodes 11A and 11B to which a negative voltage is applied by a DC power supply (not shown). Sputtering cathodes 11A and 11B have a silicon target 12A,
12B are respectively attached by metal bonding. The two planar cathodes operate as a set with respect to the plasma discharge to occur. The glass plate 13 moves in the direction of the arrow, and a water-repellent thin film is formed.

The cycle for alternately inverting the polarities of the two cathodes is usually preferably 1 kHz to 100 kHz.
The alternating reversal of the polarity is usually performed using an oscillator. In addition, the voltage waveform applied to the cathode has a sine wave, a square pulse wave, a time asymmetric wave,
It is sufficient that the applied voltage waveform is balanced between the positive and negative directions, in which the electric charge charged on the surface of one target material is neutralized. Glow discharge is stably maintained by simultaneously sputtering the silicon target. The atmosphere gas in the film forming chamber 15 at the time of sputtering is formed by introducing argon, oxygen, and a fluorine compound gas from the gas introduction pipe 14. The glow discharge is maintained mainly by the argon gas, and reactive sputtering by oxygen is performed, whereby the glass plate is coated with a thin film of silicon dioxide. The introduced fluorine compound gas is taken into the silicon dioxide thin film.

Hereinafter, the present invention will be described with reference to Examples and Comparative Examples. The substrate used was a float glass plate (55%) of soda lime silicate composition in each of Examples and Comparative Examples.
The refractive index at a wavelength of 0 nm is 1.52). 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. 2, silicon containing 0.01% by weight of boron was bonded as a sputtering target 12A, 12B by a metal bond method, and argon and oxygen were mixed at 40% by volume of argon. And a mixed gas of 60 volumes of oxygen was introduced to cover the thin film mainly composed of silicon dioxide (SiO ₂ ). At the same time, ethylene tetrafluoride was introduced as a fluorine compound gas from the gas introduction pipe 14 so that the total amount of argon, oxygen, and the fluorine compound gas was 5%. Then, the atmospheric pressure during sputtering is set to 0.4
Pa. A DC power is applied to the sputtering cathode, and is passed in front of two targets by a DC magnetron sputtering method so that the glass plate contains fluorine.
nm of silicon dioxide water repellent film. The refractive index of this thin film at a wavelength of 550 nm was 1.42 as measured by an ellipsometer, and the difference in refractive index from the glass plate was 0.10.

From the value of the refractive index, it was found that the thickness corresponding to the size of the (１ ／) wavelength of the wavelength of 550 nm was 97 nm. (Thickness that is 550 nm, four times the optical thickness). The film surface reflectance at a wavelength of 550 nm of the obtained sample was 2.0%. The reflectance of the glass plate surface could be reduced to about half. Also, when the contact angle of the surface of the water-repellent thin film of this sample was measured by a droplet method using pure water,
It was 92 °, and it was confirmed that the film had great water repellency. Further, regarding this sample, JIS-R3221
After performing a Taber abrasion test (load: 250 gf, rotation number: 100 times) equivalent to the abrasion resistance test defined in, the contact angle on the abraded surface was measured to be about 89 °. No decrease was seen.

Examples 2 to 6 In the same manner as in Example 1 except that the type of the fluorine compound gas and the amount introduced into the film forming chamber were changed as shown in Table 1, the design wavelength λ was set to 550 nm. Optical film thickness is (1/4) λn
m was coated with a water-repellent thin film. Wavelength 550
Table 1 shows the reflectance in 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.
A sample with high abrasion resistance was obtained.

Comparative Example A sample of a substrate with an antireflection film 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 silicon dioxide film (refractive index was 1.46; refractive index difference was 0.06) of this sample, and water repellency was obtained. Was given. Wavelength 550 of the obtained sample
The reflectivity in nm was 4.1%, which was higher than that of Example 1, and this film did not have an antireflection function. The contact angle before and after the Taber abrasion test equivalent to that in Example 1 was 100 ° before the test, but decreased to 23 ° after the test, and this water-repellent thin film had poor water-repellency durability. Was.

[0022]

Table 1 ================================ Example Fluorine compound with water-repellent thin film accounts for the total amount of introduced gas Gas Film side reflectance Water contact angle (°) (Volume%) (550 nm,%) Before test After test −−−−−−−−−−−−−−−−−−−−−−−−− −−−−−−−−−− (Example) 1 Tetrafluoroethylene 5 2.0 92 89 2 Methane tetrafluoride 10 1.8 88 85 3 Ethylene tetrafluoride 1 2.4 94 91 4 Phenol hexafluoride 5 1.9 96 925 Phthylene octafluoride 5 1.9 96 91 6 Pententen defluoride 5 1.7 99 86 --------------- (Comparative example) 1 No introduction 0 4.1 100 23 =================================

From the above Examples and Comparative Examples, the water-repellent thin film of the present invention contains fluorine in the silicon dioxide film, so that the water-repellency is reduced not only in the initial state but also when the film surface is worn. do not do. At the same time, since the refractive index of the silicon dioxide film is reduced, the surface reflectance of the glass plate can be reduced to half.

[0024]

The water-repellent thin film coated on the article of the present invention has a refractive index lower than the refractive index of the substrate, and has a fluorine compound contained in the thin film. It has both high water-repellent durability and 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 imparted by a single film-forming step, so that the article is economically economical. Can be manufactured well.

[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.

[Description of Signs] 1: Article of the present invention 2: Glass plate 3: Water-repellent thin film 4: Fluorine compound 10: Vacuum film forming apparatus 11A, 11B: Sputtering cathode 12A, 12B: Silicon target 13: Substrate 14: Gas introduction Pipe 15: Deposition chamber 16: Vacuum exhaust port

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) C23C 14/10 C23C 14/10 F term (Reference) 4F100 AA20B AG00A AR00A AR00B BA02 EH662 EJ582 JB06B JK09 JN01A JN18B YY00B 4G059 AA01 AA11 AC04 AC09 AC22 EA05 EA09 EA18 EB04 4K029 AA09 AA11 BA32 BA46 BC00 BC08 BD00 CA06 DC05 DC16 DC29 EA05 KA01

Claims (6)

[Claims] An article in which a water-repellent thin film is coated on a transparent substrate, wherein the thin film has a refractive index smaller than that of the transparent substrate, and is a transparent oxide containing fluorine. A water-repellent article that is a film. 2. The water-repellent article according to claim 1, wherein said transparent oxide contains silicon dioxide as a main component. 3. The transparent oxide film has a refractive index of 550 nm.
The water-repellent article according to claim 2, which has a wavelength of 1.44 or less. 4. The water-repellent article according to claim 1, wherein said fluorine is contained throughout the thickness of said water-repellent thin film. 5. A method for coating a water-repellent thin film on an article according to claim 1, wherein silicon is attached as a target to a film forming apparatus capable of adjusting a reduced pressure atmosphere containing fluorine. When two cathodes are arranged as a set in close proximity and a silicon target attached to one cathode is used as a cathode, a silicon target attached to the other cathode is used as an anode, and when the other silicon target is used as a cathode, A voltage whose polarity is alternately inverted is applied to the two targets so that the one silicon target serves as an anode, and the targets are simultaneously reactively sputtered with oxygen. A method for coating a water-repellent thin film through a space in front of a target. 6. A reduced-pressure atmosphere containing fluorine, comprising: methane tetrafluoride, ethylene tetrafluoride, propylene hexafluoride,
6. The water-repellent thin film according to claim 5, wherein at least one selected from the group consisting of a fluorine compound gas of butylene octafluoride and pentane pentafluoride is introduced into the film forming apparatus. Coating method.