JPH08217898A - Production of water-repellent coating film - Google Patents

Abstract

PURPOSE: To provide a method for producing a water-repellent coating film, capable of supplying a transparent coating film having excellent water repellency and adhesivity which can be formed into a film at a low temperature. CONSTITUTION: A perfluoroalkylsilane is decomposed and the decomposition product is deposited and stuck to the surface of a transparent resin substrate by using a high-frequency plasma CVD method to form a water-repellent fluorine-containing film. A polycarbonate resin and an acrylic resin are used as the resin substrate 7. The high-frequency plasma CVD method is carried out by using a high-frequency plasma CVD device 9 having a reaction tube 1 to generate a high-frequency plasma. The vaporized perfluoroalkylsilane is introduced through an induction pipe 6 into the reaction tube 1. The peralkoxysilane is decomposed and is reacted with oxygen by using the high-frequency plasma CVD method and the reaction product can be deposited and stuck to the surface of the resin substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a water-repellent film by forming an organic film containing fluorine having excellent water repellency by using a plasma CVD method.

[0002]

2. Description of the Related Art There is a method of improving water repellency of a resin substrate by forming a water repellent film on the surface of the resin substrate. Conventionally, such techniques are classified into the following three types.

That is, the first is a method of immersing a resin substrate in a fluorine-based silane coupling agent [J. of Non-C
Rystalline Solids 121, (19
90), pp. 344-347, J. Am. of the Su
rface ScienceSociety of J
apan vol. 14, No. 9, (1993)]. This method uses a solution of a fluorine-based silane coupling agent as a raw material.

Secondly, a plasma treatment method using a gas such as SF ₆ or CF ₄ [Mokuzai Gakkaishi vol. 38, No. 1, pp. 73-80, (1992). Japan Rubber Association magazine vol.
66, No. 2, (1993), industrial heating vol. Two
7, No. 1, (1990)]. This method is a water repellent treatment method for a substrate, which utilizes a chemical reaction between radicals and ions generated in plasma and the substrate surface.

Third, a method of chemically bonding a fluorinated silane coupling agent and a glass substrate to form a monomolecular film [Surface Science vol. 14, No. 10, 630-6
35, (1993). Polymer Prepri
nts Japan vol. 42, No. 4, (19
93)]. This method is the current mainstream method, and is a method capable of forming a film having good water repellency. The first and third methods are methods using a fluorine-based silane coupling agent. On the other hand, the second method uses a fluorine-containing gas.

[0006]

However, the above conventional method has the following problems. In the first method, the contact angle between the surface of the formed water-repellent film and water is around 108 °, which is excellent in water repellency. However, there are some problems in adhesion to the resin substrate.

In the second method, when plasma treatment is performed using a fluorine-based gas, the surface of the substrate is generally etched by the excited fluorine ions and radicals. Therefore, this method is effective for substrates such as graphite and rubber, but is not suitable for resin substrates because the transparency of the substrate may be impaired.

In the third method, for a glass substrate,
Since the hydroxyl groups on the glass substrate are rich, the adhesion of the water-repellent film is good, but the adhesion is weak and inappropriate for a hydrophobic substrate such as a resin substrate.

In view of the above conventional problems, the present invention provides a method for producing a water-repellent coating, which has excellent water repellency and adhesion and is capable of obtaining a transparent coating capable of forming a film at a low temperature. It is what

[0010]

The present invention provides a method for producing a water-repellent coating, characterized by decomposing perfluoroalkylsilane using a high frequency plasma CVD method and depositing and adhering the decomposed product on the surface of a substrate. .

As the above-mentioned perfluoroalkylsilane, CF _3- (CF ₂ ) _n --CH ₂ --CH ₂ --Si (O
_{CH 3) 3, CF 3 -} (CF 2) n -CH 2 -CH 2 -
SiCl _{3 and the} like. In the above-mentioned perfluoroalkylsilane, n is in the range of 0 to 9, for example. Above n
Is particularly preferably 7-9. As a result, the water repellency comparable to that of polytetrafluoroethylene (PTFE) can be expected.

High frequency plasma CVD method (chemical vapor deposition method)
Is a method of discharging a gas containing a raw material gas under reduced pressure with high frequency electric energy in a high electric field, decomposing, and depositing the generated substance through a chemical reaction in a gas phase or on a resin substrate. is there. This high frequency plasma CV
Method D has the advantage that uniform and high-speed film formation is possible. Depending on the plasma conditions and film formation conditions, it is possible to form films at low temperatures near room temperature.

The high frequency plasma CVD method includes, for example, the inductive coupling type CVD method shown in the embodiment. The high frequency output of the high frequency plasma CVD method (hereinafter, also simply referred to as the CVD method) is preferably 25 to 300 W at 13.56 MHz. If it is less than 25 W, plasma may be generated only in the center of the work coil and may not spread over the entire reaction tube. On the other hand, when it exceeds 300 W, matching of plasma characteristics becomes difficult, and stable maintenance of plasma may be difficult.

The film forming temperature of the above CVD method is 20 to 120.
C. is preferred. If the temperature is lower than 20 ° C, the fluorine-containing film may not be formed. On the other hand, 120 ° C
If it exceeds the above range, when a resin substrate is used as the substrate, the resin substrate may be affected by the heat of the plasma and melted.

The partial pressure of the film-forming raw material in the above CVD method is
It is preferably 5 to 30 Pa. If it is less than 5 Pa, a high film formation rate may not be obtained, and a film may not be formed. On the other hand, if it exceeds 30 Pa, the plasma may contract and the discharge state may become unstable.

The above-mentioned substrate is preferably arranged at a position 40 to 50 cm away from the center of plasma in the reaction tube. As a result, the influence of heat due to plasma can be avoided, the surface of the substrate can be prevented from being etched by fluorine atoms, and high transparency can be maintained.

As the substrate, for example, a synthetic resin molding having a desired shape, a glass substrate, or a silicon substrate can be used. As the synthetic resin molded body, for example, either a polycarbonate resin or an acrylic resin can be used.

A fluorine-containing film is formed on the surface of the substrate by the CVD method. This fluorine-containing film is
It is a "fluorine-containing silicon oxide-based film" in which fluorine is contained in the silicon oxide film.

Further, by using the high frequency plasma CVD method,
The perfluoroalkylsilane can be decomposed and reacted with oxygen, and the reaction product can be deposited and adhered to the surface of the substrate. Also in this case, the inductively coupled CVD method can be used as the high frequency plasma CVD method. Then, the oxygen that reacts with the decomposition product of perfluoroalkylsilane is introduced into the reaction tube in a state where the flow rate is controlled by a mass flow controller or the like.

[0020]

FUNCTION AND EFFECT In the method for producing a water-repellent coating of the present invention, perfluoroalkylsilane is used as a film forming raw material. Since perfluoroalkylsilane has a high vapor pressure, it vaporizes at a low temperature of room temperature to 70 ° C. Therefore, the film can be formed at a low temperature.

Further, in this product, radicals and atoms dissociated by the high frequency plasma discharge have very high energy and react with oxygen, and the reaction product is deposited and adheres to the surface of the substrate. Therefore, the adhesion of the fluorine-containing film is high. Since the fluorine-containing film contains many fluorine atoms, it can exhibit excellent water repellency.

Further, the high frequency plasma CVD method uses DC
It is said that the progress of etching by fluorine atoms is faster than that of the (DC) plasma CVD method, but the progress of etching of the substrate can be suppressed by moving the substrate away from the center of plasma. Therefore, a highly transparent film can be formed. Further, the fluorine-containing film can be formed at a low temperature of about 120 ° C. from room temperature by moving the substrate away from the center of the plasma or adjusting the plasma output.

According to the present invention, it is possible to provide a method for producing a water-repellent coating, which has excellent water repellency and adhesion and is capable of obtaining a transparent coating capable of forming a film at a low temperature.

[0024]

EXAMPLES A method for producing a water-repellent coating according to examples of the present invention will be described with reference to FIGS. In this example, a high-frequency plasma CVD method is used to decompose perfluoroalkylsilane, which is a raw material for film formation, and to react with oxygen, and the reaction product is deposited and adhered to the surface of a transparent resin substrate to contain water-repellent fluorine. It is a method of forming a film.

This will be described in detail below. First, the high frequency plasma CVD apparatus 9 shown in FIG. 1 is prepared. The high-frequency plasma CVD apparatus 9 is vaporized by a reaction tube 1, a work coil 11 that generates high-frequency plasma in the reaction tube 1, a rotary pump 2 that suctions the inside of the reaction tube 1 under reduced pressure, and a vaporizer 3 made of SUS. Introducing tube 6 for introducing perfluoroalkylsilane, which is a film forming raw material, into the reaction tube 1
Have and. Examples of the perfluoroalkylsilane include perfluoroalkoxysilane (FAS) (CF <sub>3
- (CF 2) n -CH 2</sub> -CH 2 -Si (OC
H ₃ ) ₃ ) was used.

The reaction tube 1 is a transparent quartz glass tube having an inner diameter of 35 mm and a length of 1 m. Both ends of the reaction tube 1 are fixed by fixing holders (made of SUS) 15 and 16. The work coil 11 is wound around the outer center of the reaction tube 1 and is connected to a 13.56 MHz high frequency power supply 12.

The outlet end of the reaction tube 1 is connected to the rotary pump 2
Is connected to a suction pipe 20 which is connected to, and the inlet end of the reaction pipe 1 is connected to the introduction pipe 6. A ribbon heater 60 is wound around the introduction tube 6 to prevent the vaporized film forming raw material from aggregating. The vaporizer 3 is heated by the heater 30.

Next, a transparent acrylic resin substrate 7 is placed in the reaction tube 1. The size of the resin substrate 7 is 2.
It is 0 × 2.0 × 0.4 (cm). The placement location is set to a position A which is 40 to 50 cm away from the center of the work coil 11 in the direction of the introduction tube 6. This is because if the resin substrate is placed at the center of the work coil (position B in FIG. 1), the high temperature work coil 11 may melt the resin substrate. Further, if it is arranged in the direction of the suction tube 20 (position C in FIG. 1) with respect to the center of the work coil 11, vapor deposition of the fluorine-containing film becomes difficult. Therefore, the resin substrate 7 is arranged at the position A far from the work coil 11 and where the high-concentration perfluoroalkylsilane is present. Further, by disposing it at the position A, it is possible to prevent the surface of the resin substrate 7 from being etched by fluorine atoms.

Then, the inside of the reaction tube 1 is evacuated by the rotary pump 2 to 5 to 30 Pa. Then,
Perfluoroalkylsilane, a film-forming raw material (K
BM7803) is vaporized in the vaporizer 3, and this is introduced into the reaction tube 1 through the introduction tube 6 to have a partial pressure of 5 to 30 Pa. At this time, oxygen as a reaction gas is introduced into the reaction tube 1. The oxygen flow rate is such that the oxygen partial pressure in the reaction tube 1 is 0 to
The mass flow controller controls the pressure to be 15 Pa. At this time, the perfluoroalkylsilane may be introduced by bubbling the film forming raw material in the vaporizer 3 using an inert gas such as argon gas.

Further, a high frequency output 1 is generated by the high frequency power source 12.
Add 0-300W, 13,56MHz for 1-60 minutes,
High-frequency power is applied to the coil via the matching circuit. At this time, the temperature of the resin substrate 7 in the reaction tube 1 becomes 20 to 120 ° C. under the above film forming conditions. Thereby, high frequency plasma is generated in the reaction tube 1. Then, in the reaction tube 1, the gasified perfluoroalkylsilane is decomposed and reacts with oxygen to generate a reaction product, which is deposited and adheres to the surface of the resin substrate 5. As a result, a transparent film is formed on the surface of the resin substrate 5.

Next, when the film thickness of the obtained film was measured by the stylus method, it was 0.6 to 1.0 μm. The film forming rate is 1 to 2 μm / Hr. Met. In addition, the chemical bond state of the film was measured by FT-IR composition analysis using X-ray photoelectron spectroscopy, and the results are shown in FIG.

From the figure, a peak due to the Si--O bond was observed at 1100 cm ^-1 . From this, it was confirmed that a silicon oxide based film was formed. Also, 115
A peak due to the C—Fn bond was observed at ⁰ to 1250 cm ⁻¹ . From this, it became clear that this film contained fluorine. That is, it is understood that the above film is a fluorine-containing silicon oxide based film.

XPS (Shimadzu: ES
When the composition of the film was analyzed by CA3200),
As shown in FIG. 3, an F ₁₈ peak due to the CF ₂ —CF ₂ bond was observed near 690 eV. From this,
It can be seen that an organic film similar to PTFE is formed.

Next, the water-repellent synthetic resin molding having the film formed thereon had a high contact angle with water of 107 °, which was as high as that of Teflon. On the other hand, the contact angle of the resin substrate with water before forming the film was as low as 60 °.

Next, a peeling test of the above film was conducted. That is, the surface of the film is cut into 11 vertical and horizontal cuts at 1 mm intervals to make 100 cross-cuts. Then, a tape was adhered onto it, the tape was pulled, and the adhesion was measured. As a result, no peeling was observed on all 100 grids. From this, the fluorine-containing film of this example is
It can be seen that the adhesion is extremely high.

This is because the radicals and atoms having high energy are deposited on the resin substrate due to the perfluoroalkylsilane being turned into plasma, so that the adhesion of the coating is improved by the anchor effect or the like. In the above example, acrylic resin was used as the resin substrate, but similar results were obtained when polycarbonate resin was used. Similar results were obtained when a glass substrate or a silicon substrate was used instead of the resin substrate.

Next, the visible light transmittance of the above film was measured. The coating used for this measurement was a partial pressure of perfluoroalkylsilane of 11 Pa and a high frequency output of 300.
The film was formed with W, 13.56 MHz and a reaction time of 30 minutes. FIG. 4 shows the results. From the figure, it can be seen that the transmittance of the coating is about 90%, which means that it maintains a fairly high degree of transparency.

In the above embodiment, the oxygen partial pressure is 0P.
It was confirmed that a film having water repellency was formed even when a, that is, oxygen was not introduced. In this case, it was observed that the film thickness was thicker than when oxygen was introduced.
This is presumably because when oxygen is introduced, the cross-linking proceeds and the film becomes dense.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a high frequency plasma CVD apparatus according to an embodiment.

FIG. 2 is a diagram showing the results of FT-IR composition analysis of Examples.

FIG. 3 is a diagram showing an F ₁₈ spectrum of a film of an example.

FIG. 4 is a diagram showing a visible light transmittance of a film of an example.

[Explanation of symbols]

 1. ． ． Reaction tube, 11. ． Work coil, 12. ． High frequency power supply, 2. ． ． Rotary pump, 20. ． ． Suction tube, 3. ． ． Vaporizer, 6. ． ． Introductory tube, 7. ． ． Resin substrate, 9. ． ． High frequency plasma CVD equipment,

Claims (4)

[Claims] 1. A method for producing a water-repellent coating, which comprises decomposing perfluoroalkylsilane using a high-frequency plasma CVD method and depositing and adhering the decomposed product on the surface of a substrate. 2. A method for producing a water-repellent coating, which comprises decomposing perfluoroalkylsilane and reacting it with oxygen using a high-frequency plasma CVD method, and depositing and adhering the reaction product on the surface of a substrate. 3. The method for producing a water-repellent film according to claim 1, wherein the substrate is a synthetic resin molded body. 4. The method for producing a water-repellent coating according to claim 3, wherein the synthetic resin molded body is either a polycarbonate resin or an acrylic resin.