JP3081913B2 - Controlling wettability by electron irradiation - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for controlling the wettability of a material relating to surface coating, surface modification, tribology, and the like. It can be applied to fields such as chemical etching.

[0002]

2. Description of the Related Art The wettability of a material surface with water is related to the easiness of fogging of the glass in the field of glass, for example, and when the material is washed with an aqueous solution. It is also important from an industrial point of view, because it also affects the ease of cleaning.

[0003] The wetting characteristics of such a material surface are macroscopically affected by the surface tension between the material surface and water.
It is said that the larger the contact angle between the material and water, the more water repellent (water repellent). Therefore, in order to change the surface wetting characteristics, a material having hydrophobicity or hydrophilicity is generally selected.

[0004] However, researching a hydrophobic or hydrophilic material by trial and error not only requires a great deal of effort,
Even if the required wetting property is obtained by an empirical method by changing the chemical composition, it does not always satisfy all the other properties required as the surface properties of the material. For example, in many cases, the surface hardness, friction characteristics, and the like did not meet the requirements. In addition, since the physical properties of the inside of the material and the surface of the material are not always the same, various problems remain. For example, there is a problem that it is very difficult to control the surface hardness and friction characteristics of a glass material such as SiO _x and SiN _x because the surface composition is easily changed.

[0005] Therefore, from the viewpoint of changing only the surface characteristics while maintaining the mechanical properties inside the material, surface coating techniques have been actively performed. For example, glass having infrared reflection characteristics, surface conductive glass, and the like have been developed. Further, in order to change the surface wetting characteristics, for example, a fluorine-based material is applied as a hydrophobic coating. However, the mechanism of surface wetting properties is complex, and is not sufficient as a coating technology.
Further, it was not always possible to satisfy all other properties required as surface properties of the material.

[0006]

SUMMARY OF THE INVENTION The present invention proposes a method capable of controlling the wettability of a material surface by a novel technique which is completely different from the conventional technique.

[0007]

According to the present invention, the surface of a material is irradiated with electrons, and the wettability by electron irradiation is controlled while maintaining the surface crystal lattice state of the material surface. Is a control method. The present invention can be applied to, for example, an alkali halide, specifically NaF 2 as a material, and it is more preferable that the irradiation amount of electrons is 1 to 2 per 1 nm square and the irradiation energy is 30 eV or less. .

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Although the mechanism of wettability between a material and water has not always been clarified, the present inventor has conducted research on this wettability. The adsorption status of
He found that it was directly related to the macro situation.

[0009] The state of adsorption at the micro level can be changed by irradiating the material surface with a low irradiation amount and low energy electrons, and by controlling the wettability of the material by the electron irradiation. They have found that they can do it. In addition, it has also been clarified that since the electron irradiation has a low irradiation amount and low energy, the wettability can be changed without changing the surface crystal structure.

As described above, in the present invention, it is important to change the surface wettability without changing the surface crystal structure by electron irradiation. Accordingly, since the wettability can be controlled by the present invention after optimizing the surface properties other than the wettability, there is an advantage that good results can be obtained for each property.

According to the present invention, the wettability can be controlled by electron irradiation for the following reasons. According to recent studies by the inventors using a scanning force microscope, the adsorption form of water on a material surface at a micro level (approximately 10 nm level) depends on the interaction between the H ₂ O-substrate (material) surface, that it can be explained by the relationship between the strength of the interaction of H ₂ O -H ₂ O revealed.

That is, in a study using NaF as a material, the adsorption mode of water on the (001) plane is as follows.
The LiF (001) type, which shows the growth morphology of the Volmer-Weber mechanism, and the NaCl (001) type, which shows uniform adsorption of a single layer, were just in the middle. This result, H ₂ O of NaF (001) - it is possible to the strength of the interaction of the underlying surface, H ₂ O -H ₂ intensity of O interaction is described almost equal.
This result, H ₂ O - the strength of the interaction of the underlying surface H ₂ O
-H ₂ When O greater than the strength of the interaction is uniformly wetted, in the opposite case less likely to wet.

Here, the NaF (001) surface is irradiated with 4 electrons.
Irradiation with several electrons having an energy of 30 eV per nm × 4 nm revealed that the water adsorption mode of NaF (001) was H ₂ O −H ₂
When the interaction intensity of O ₂ is stronger than the interaction intensity of the H ₂ O-substrate surface, the growth morphology by the Volmer-Weber mechanism (Li
F (001) type). This is considered to be because the intensity of the interaction between the H ₂ O and the underlying surface became weaker by the electron irradiation than the intensity of the interaction between the H ₂ O and the H ₂ O. In addition,
In the above electron irradiation, the crystal lattice on the underlying surface was maintained.

[0014] Thus, by electron irradiation, while maintaining the surface crystal lattice of the underlying surface, H ₂ O material surface - the relationship between the strength of the interaction strength of the interaction of the underlying surface and H ₂ O -H ₂ O It can be considered that since it can be changed, it is possible to control the state of water adsorption at the micro level, and thus to control the wettability of the material.

Materials to which the present invention can be applied include NaF, LiF
In addition to alkali halides such as NaCl and NaCl, any material can be used as long as its surface interaction can be changed by electron irradiation, such as SiN _x and SiO _{x, which} are important as glass materials, and metal oxides.

The irradiation amount and energy of electron irradiation depend on the material, but are one to two per nm, and the irradiation energy is 30 eV.
The following is preferred. There is a problem that it is difficult to change the state of water adsorption with an irradiation amount of less than one per nm, and a problem that it becomes difficult to maintain the surface lattice with an irradiation amount of more than two. Furthermore, if the irradiation energy is greater than 30 eV, desorption of surface atoms will occur,
It is not preferable in that the surface composition changes.

According to the present invention, the surface of a material can be irradiated with electrons to control the wettability to water while maintaining the surface crystal lattice state of the material surface. It is useful for modifying the friction characteristics, which leads to the development of scratch-resistant materials. Specifically, a material effective for surface coating is selected from physical properties, the surface interaction energy of this surface coating material with water is examined, and the amount of electron irradiation on the surface is evaluated together with the material. Irradiation may be performed.

As mentioned above, "wetability to water" has been described, but it is needless to say that the present invention can be applied to control of wettability to an aqueous solution having the same mutual strength as water.
Further, since the present invention can locally change the wettability of the material surface by electron irradiation, it can be applied to local cleaning and etching of the material surface with an aqueous solution.

[0019]

[Example] A NaF single crystal was prepared, and the (001) face of this NaF was
In a vacuum of 10 ^-6 Torr, several electrons per 4 nm x 4 nm are converted to 30
Irradiated with eV energy. The surface of the obtained sample was observed using a scanning force microscope (Scanning Force Microscope: SFM) in an air atmosphere at room temperature and a humidity of 30 to 50%.

FIG. 1 shows the state of adsorption of water on the surface of a sample subjected to electron irradiation in comparison with a sample not subjected to electron irradiation. FIG. 1A shows an example of a sample without electron irradiation, and FIG. 1B shows an example of a sample with electron irradiation. In the absence of electron irradiation, a water film with a different thickness is formed on the NaF (001) surface, whereas a droplet pattern is observed on the electron-irradiated surface. FIG. 2 shows the crystal lattice structure of the sample surface. FIG. 3A shows an example of a sample without electron irradiation, and FIG. 2B shows an example of a sample with electron irradiation. FIG.
This shows that the crystal structure of the surface hardly changes even after electron irradiation. The friction characteristics of the surface are
Changed slightly.

The change in the characteristics as described above is caused by the fact that an F center is formed on the surface by electron irradiation, and an OH center is formed on the surface by a reaction between the F center and water in the atmosphere.
It is considered that the strength of the interaction between the H ₂ O and the base surface was weakened.

Although the case where the material is NaF has been described above, the present invention is not limited to the material disclosed in the embodiment, and the surface crystal lattice state is maintained by electron irradiation while the H ₂ O underlayer is maintained. Applicable to all materials that can change the strength of surface interaction. At the time of actual commercialization, a method of changing the wetting characteristics and friction characteristics by electron irradiation after coating the surface of a material effective for the bulk material may be used.

[0023]

According to the method for controlling wettability by electron irradiation of the present invention, the surface of a material is irradiated with electrons to control the wettability to water while maintaining the surface crystal lattice state of the material surface. Since the wettability can be controlled by different methods, it becomes possible to develop a surface coating capable of satisfying all other properties required as the surface properties of the material.

[Brief description of the drawings]

FIG. 1 is a diagram showing the state of adsorption of water on the surface of NaF in comparison with the case where electron irradiation is not performed and the case where electron irradiation is performed.

FIG. 2 is a diagram showing a state of a surface crystal lattice of NaF 2 in a case where electron irradiation is not performed and in a case where electron irradiation is performed.

Claims (4)

(57) [Claims] 1. A method for controlling wettability by electron irradiation, comprising irradiating electrons to the surface of a material and controlling the wettability to water while maintaining the surface crystal lattice state of the material surface. 2. The material according to claim 1, wherein the material is an alkali halide.
The method for controlling wettability by electron irradiation according to the above. 3. The method for controlling wettability by electron irradiation according to claim 1, wherein the material is NaF. 4. An electron irradiation amount of 1 to 2 per 1 nm square.
The method for controlling wettability by electron irradiation according to any one of claims 1 to 3, wherein the irradiation energy is 30 eV or less.