JP7078899B2 - Water- and oil-repellent structure - Google Patents

Description

The present invention relates to a water-repellent oil-repellent structure, and more particularly to a highly durable water-repellent oil-repellent structure provided with a water-repellent metal compound.

Conventionally, a water-repellent structure in which a porous membrane is impregnated with a water-repellent material such as a fluorine-based oil or a silicon-based oil is known. In the water-repellent structure, the water-repellent material exudes from the inside of the porous membrane to maintain water repellency.

However, the water-repellent structure impregnated with the water-repellent material has low durability because the water-repellent material is depleted due to wear and the like received when wiping off dirt and the like.

In Patent Document 1, by coating the surface of fine protrusions formed of a thermoplastic resin or the like with a ceramic material, the fine protrusions and the ceramic material covering the surface of the fine protrusions exhibit water repellency in combination. , A water-repellent film having improved wear resistance by preventing wear and damage of the fine protrusions is described.

International publication 2011/151885 Pamphlet

However, in the water-repellent film in which the surface of the fine protrusions is coated with a ceramic material, liquids such as oil other than water cannot be repelled, and the oil or the like infiltrates between the fine protrusions to make the fine protrusions. Since the air in between is expelled, not only the oil repellency is not exhibited, but also the water repellency is lowered.

The present invention has been made in view of the problems of the prior art, and an object of the present invention is to prevent a liquid such as oil from infiltrating between fine protrusions and to repel water for a long period of time. It is an object of the present invention to provide a water-repellent oil-repellent structure having excellent wear resistance capable of exhibiting oiliness.

As a result of diligent studies to achieve the above object, the present inventor has formed an oil-repellent surface-modified film on the side surface of the fine protrusions having a fine protrusion structure formed of a water-repellent metal compound. We have found that it is possible to prevent oil from entering between the protrusions, and have completed the present invention.

That is, the water-repellent oil-repellent structure of the present invention comprises a water-repellent metal compound having a fine protrusion structure.
The water-repellent metal compound is a metal oxide and / or a metal nitride.
The metal element constituting the metal oxide and the metal nitride is at least one kind of metal element selected from the group consisting of zirconium, hafnium and rare earth elements.
The fine protrusion structure is a cone trapezoid or a columnar shape, has an oil-repellent surface-modified film on the side surface of the fine protrusion, and the water-repellent metal compound protrudes from the surface-modified film at the apex portion of the fine protrusion. It is characterized by being exposed.

According to the present invention, since an oil-repellent surface-modified film is formed on the side surface of the fine protrusions of the fine protrusion structure formed of the water-repellent metal compound, the wear resistance that exhibits the water-repellent and oil-repellent properties for a long period of time can be obtained. It is possible to provide an excellent water-repellent and oil-repellent structure.

It is a schematic sectional drawing which shows an example of the water-repellent oil-repellent structure of this invention. It is a schematic sectional drawing which shows another example of the water-repellent oil-repellent structure of this invention.

<Water- and oil-repellent structure>
The water-repellent and oil-repellent structure of the present invention will be described in detail.
The water-repellent and oil-repellent structure has a fine protrusion structure made of a water-repellent metal compound, and the fine protrusion structure has an oil-repellent surface-modified film on at least a side surface of the fine protrusion, and the fine protrusion The water-repellent metal compound is exposed at the apex portion of the above.

The water-repellent metal compound is a water-repellent material made of an inorganic substance, and is harder and has higher wear resistance than an organic material such as a resin.

The fine protrusion structure formed of the water-repellent metal compound is hard to wear and maintains its shape, and the water repellency of the water-repellent metal compound itself and the air held between the fine protrusions combine to repel the water for a long period of time. Expresses aqueous.

However, the water repellency of the water-repellent metal compound is considered to be due to the fact that the electron arrangement of the water-repellent metal compound is such that the 4f orbital interacting with water is shielded by the electrons of the outer 5s2p6 orbital. The water-repellent metal compound gets wet with an organic liquid such as oil.

Then, the oil enters between the fine protrusions and expels air, smoothes the surface of the fine protrusion structure, and also reduces the water repellency.

Since the water-repellent oil-repellent structure of the present invention has an oil-repellent surface modification film on the side surface of the fine protrusions of the fine protrusion structure, it exhibits oil repellency and prevents oil from entering between the fine protrusions. Since it retains air between them, it exhibits water and oil repellency for a long period of time.

Further, in the water-repellent and oil-repellent structure of the present invention, the water-repellent metal compound is exposed at the apex portion of the fine protrusion.

The fluorocarbon-based material that forms the surface modification film, which will be described later, generates fluorine radicals when exposed to ultraviolet rays, and when metal oxides contained in the soil such as aluminum oxide and iron oxide adhere to the fluorine radicals, the above-mentioned fluorine radicals are formed. And oxygen of the metal oxide are replaced to form a metal halide such as aluminum fluoride.

The metal halide is a strong Lewis acid that attacks the ether bonds contained in the molecular structure of the fluorocarbon-based material and acts as a catalyst for breaking the molecular chain of the fluorocarbon-based material.

When the molecular chain of the fluorocarbon-based material is cleaved, a hydroxyl group is generated at the end of the cleaved molecular chain, the water repellency of the surface modification film itself decreases, and water easily enters between the fine protrusions. The water repellency of the water repellent and oil repellent structure is sharply reduced.

The apex portion of the fine protrusion of the fine protrusion structure is the part most likely to come into contact with dirt, and this part is not covered with the surface modification film and the water-repellent metal compound is exposed, so that the surface modification film is exposed. Long-term contact between the metal and dirt is prevented, and water repellency and oil repellency are maintained for a long period of time without forming hydroxyl groups due to deterioration of the surface modification film at the apex portion.

The film thickness of the surface modification film is preferably 2 nm or more and 50 nm or less, and more preferably 5 nm or more and 20 nm or less.

If the film thickness of the surface-modified film is less than 2 nm, oil may easily infiltrate between the fine protrusions, and if it exceeds 50 nm, the surface-modified film may easily come into contact with dirt, and the fine protrusions may be present. It may be difficult to hold air between the protrusions due to the narrowing of the space between them.
The film thickness of the surface modification film can be measured by a cross-sectional SEM image.

The height (h) of the water-repellent metal compound exposed at the apex portion of the fine protrusion is preferably 15 nm or more and 25 nm or less. Since the water-repellent metal compound protrudes from the surface-modified film in the above range, the surface-modified film is less likely to come into contact with dirt, and oil can be prevented from entering between the fine protrusions.

Examples of the shape of the fine protrusions include a cone such as a cone and a pyramid, a frustum such as a frustum and a pyramid, and a column such as a cylinder and a prism.

The pitch (P) of the fine protrusion structure is preferably 5 nm or more and 380 nm or less, and more preferably 50 nm or more and 200 nm or less.

If the pitch of the fine protrusion structure is less than 5 nm, it is difficult to form a surface-modified film, and if it exceeds 380 nm, the haze value may increase due to Rayleigh scattering or the like, or the total light transmittance may decrease. ..

Further, the gap between the adjacent fine protrusions is preferably 1/10 or more and 1/2 of the pitch. Water repellency and oil repellency are improved by holding air in the gaps in the above range between the fine protrusions.

The height (H) of the fine protrusions is preferably 50 to 400 nm.
If the height of the fine protrusions is less than 50 nm, it may be difficult to sufficiently develop water repellency and oil repellency, and if it exceeds 400 nm, the strength of the fine protrusions may be likely to decrease, and a water-repellent metal compound such as a sol-gel method may be used. Depending on the method for producing the film, cracks may easily occur due to volume shrinkage during production.

When the shape of the fine protrusion is columnar, the diameter (D) is preferably 50 nm or more and 100 nm or less.

As the water-repellent metal compound, a metal oxide or a metal nitride having a water contact angle of 95 ° or more can be used, and as the metal element of the metal oxide or the metal nitride, zirconium, hafnium, and a rare earth element can be used. Can be mentioned.

As the oil-repellent surface modification film, a fluorocarbon-based material having a small surface energy can be used, and examples thereof include perfluoropolyether and perfluorododecylsilane.

The water- and oil-repellent structure of the present invention can be suitably used for automobile parts and optical parts.
Examples of the automobile parts include a large-area glass window such as a front window, a rear window, and a side window, as well as a light cover, an instrument panel, a mirror, and a camera lens.

<Making a water- and oil-repellent structure>
In the water-repellent and oil-repellent structure, a film of a water-repellent metal compound formed on a substrate is formed into a fine protrusion structure, and then a surface-modified film of a fluorocarbon-based material is formed, and the surface of the apex portion of the fine protrusion is formed. It can be produced by removing the modified film.

The film of the water-repellent metal compound can be formed by a sol-gel method in which a metal alkoxide is hydrolyzed and dehydrated and condensed, a sputtering method, a vapor deposition or the like. The fine protrusion structure can be obtained by photolithography, wet etching, a method of adding an organic phase separator to a solgel reaction solution of metal alkoxide, phase separation and firing, and adding an additive such as boron to the silica glass material at 800 ° C or higher. It can be formed by a method such as heating the glass to phase separation and eluting boron with an acid.

As the base material, transparent flat glass or the like can be used.
The haze value of the base material is preferably 0.1% or less, and the total light transmittance is preferably 93% or more. When the total light transmittance and the haze value of the base material are within the above ranges, the transparency required for automobile parts, optical parts and the like can be obtained.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the following Examples.

[Example 1]
(Formation of fine protrusion structure)
A 5% polyvinyl alcohol aqueous solution was cast into a silicon mold in which a conical shape having a pitch of 200 nm and a height of 220 nm was arranged in a hexagonal fine structure, dried with water, and then peeled off to prepare an inverted mold.

Gadolinium alkoxide was applied to this inverted mold in a glove box filled with argon, the coated surface was sandwiched between glasses, taken out of the glove box, and left in the open air for 24 hours to temporarily cure the gadolinium alkoxide film.

Next, the temporarily cured gadolinium alkoxide film is fired in an electric furnace at 500 ° C. to promote the dehydration reaction of the gadolinium alkoxide and to burn out the inverted form of polyvinyl alcohol to form the gadolinium oxide (Gd ₂ O ₃ ) film. Made.

This gadolinium oxide (Gd ₂ O ₃ ) film shrank due to the dehydration reaction of gadolinium alkoxide and had a fine protrusion structure having a pitch of 200 nm and a height of 200 nm.
The water contact angle of the smooth gadolinium oxide (Gd ₂ O ₃ ) film was 101 °.

(Formation of surface modification film)
The above-mentioned gadolinium oxide (Gd ₂ O ₃ ) film was immersed in perfluoroether (Fluorosurf FG5020) for 48 hours, and the gadolinium oxide (Gd ₂ O ₃ ) film was pulled up at a rate of 1 mm / s. The reaction was carried out for 1 hr in a constant temperature bath having a humidity of 60% and ultrasonically washed to form a surface-modified film having a film thickness of 10 nm.

Next, the excess surface-modified film at the tip of the fine protrusion was removed by atmospheric pressure plasma, and gadolinium oxide (Gd ₂ O ₃ ) was projected from the surface-modified film by 20 nm to obtain a water-repellent and oil-repellent structure.

[Example 2]
A surface-modified film is formed on the zirconium oxide _{( Zr2O3} ) film in the same manner as in Example 1 except that the metal alkoxide is replaced with zirconium alkoxide, and the surface-modified film is projected by 20 nm to repel water and oil. Obtained a structure.
The water contact angle of the smooth zirconium oxide (Zr ₂ O ₃ ) film was 103 °.

[Example 3]
(Formation of fine protrusion structure)
A holmium oxide (Ho ₂ O ₃ ) film having a film thickness of 500 nm is formed on a glass substrate by sputtering, a photoresist is applied, and a photoresist film having a diameter of 70 nm and a pitch of 200 nm between dots is formed by an electron beam. did.

The holmium oxide (Ho ₂ O ₃ ) film on which the photoresist film was formed was subjected to plasma gas etching at a pressure of 20 mTorr using _C4F8 gas in an inductively coupled high frequency plasma ₍ ICP) device, and the diameter was 70 nm. A holmium oxide (Ho ₂ O ₃ ) film having pillar-like fine protrusions having a height of 200 nm and a pitch of 200 nm was obtained.
The water contact angle of the smooth holmium oxide (Ho ₂ O ₃ ) film was 105 °.

(Formation of surface modification film)
A holmium oxide (Ho ₂ O ₃ ) membrane was immersed in a 5% solution of tetraethoxyperfluorododecylsilane that had been heated to reflux in advance for 2 hours, the sample was pulled up at a speed of 1 mm / s, and then the temperature was 100 ° C. and the humidity was 60%. After 1 hr reaction in a constant temperature bath, ultrasonic cleaning was performed to form a surface-modified film having a film thickness of 2 nm.

Next, the excess surface-modified film at the tip of the fine protrusion was removed by atmospheric pressure plasma, and holmium oxide (Ho ₂ O ₃ ) was projected from the surface-modified film by 20 nm to obtain a water-repellent and oil-repellent structure.

[Example 4]
_A surface _- modified film was formed on the yttrium oxide ₍ Y2O3) film in the same manner as in Example ₃ except that the yttrium oxide (Y2O3) film having a film thickness of 500 nm was formed by sputtering. A water- and oil-repellent structure was obtained by projecting 20 nm from the surface modification film.
The water contact angle of the smooth yttrium _acid ( _Y2O3 ) film was 100 °.

[Example 5]
(Formation of fine protrusion structure)
A hafnium oxide (Hf ₂ O ₃ ) film was formed in the same manner as in Example 1 except that the metal alkoxide was replaced with hafnium alkoxide.
The water contact angle of smooth hafnium oxide (Hf ₂ O ₃ ) was 97 °.

(Formation of surface modification film)
Perfluoropolyether (Optur DAX: manufactured by Daikin) was vapor-deposited on the hafnium oxide (Hf ₂ O ₃ ) film at 100 ° C. and 50 Torr for 1 hour in a vacuum chamber to form a surface modification film having a film thickness of 45 nm.

Next, the excess surface-modified film at the tip of the fine protrusion was removed by atmospheric pressure plasma, and hafnium oxide (Hf ₂ O ₃ ) was projected from the surface-modified film by 20 nm to obtain a water-repellent and oil-repellent structure.

[Comparative Example 1]
(Formation of fine protrusion structure)
After applying an ultraviolet curable monomer (crosslinked acrylic) to one side of a polyethylene terephthalate (PET) substrate, a mold for forming fine protrusions is pressed against the ultraviolet curable monomer, and ultraviolet rays are irradiated from the substrate side. The ultraviolet curable monomer was cured to form a conical fine protrusion structure having a pitch of 200 nm and a height of 200 nm.

The base material was peeled off from the mold, and a hafnium oxide (Hf ₂ O ₃ ) film having a thickness of 10 nm was formed on the surface of the fine protrusion structure by a sputtering method to obtain a water-repellent and oil-repellent structure.

[Comparative Example 2]
(Formation of fine protrusion structure)
In the same manner as in Comparative Example 1, a fine protrusion structure of methyl methacrylate was formed on a polyethylene terephthalate (PET) substrate.

(Formation of surface modification film)
Formation of surface-modified film A surface-modified film was formed in the same manner as in Example 1 except that the surface-modified film at the apex of the fine protrusion was not removed, and a water-repellent and oil-repellent structure was obtained.

<Evaluation>
The water- and oil-repellent structures of Examples 1 to 5 and Comparative Examples 1 and 2 were evaluated by the following methods.
The evaluation results are shown in Table 1.

(durability)
After sliding back and forth a predetermined number of times on a canvas cloth, the contact angle of water and the contact angle of oleic acid were measured using a fully automatic contact angle meter (Drop Master: manufactured by Kyowa Interface Science Co., Ltd.).

(transparency)
The haze value and total light transmittance were measured using a haze meter (manufactured by Murakami Color Technology Laboratory Co., Ltd.) in accordance with JIS K 7136 using a haze / transmittance meter.

(Weatherability)
An outdoor exposure test was carried out by fixing the water- and oil-repellent structure to a height of 1 m from the ground at an inclination angle of 45 ° toward the south for 6 months.
The water- and oil-repellent structure after outdoor exposure was fixed, and 10 μL of water droplets were attached to the sample surface.

◯: Water droplets have fallen.
X: Water droplets adhered.

From the above results, it can be seen that the water- and oil-repellent structures of Examples 1 to 5 can exhibit water- and oil-repellent properties for a long period of time.
In particular, Comparative Example 2 in which the apex portion of the fine protrusions is covered with the surface-modified film has low weather resistance, and the water-repellent metal compound is exposed at the apex portion of the fine protrusions, resulting in deterioration of the surface-modified film. It was confirmed that the decrease in water repellency could be prevented.

Further, in Comparative Example 2 in which the fine protrusion structure is a resin, the contact angle between water and oleic acid after wear is lowered, so that the wear resistance is improved by forming the fine protrusion structure with a water-repellent metal compound. It can be seen that air can be retained in the gaps between the fine protrusions.
Further, it can be seen that in Examples 1 and 2 in which the film thickness of the surface modification film is 10 nm, the contact angle of water after wear is large and the durability is high as compared with Examples 3 to 5.

1 Fine protrusions (water-repellent metal compound)
2 Surface modification film

Claims (5)

Equipped with a water-repellent metal compound having a fine protrusion structure,
The water-repellent metal compound is a metal oxide and / or a metal nitride.
The metal element constituting the metal oxide and the metal nitride is at least one kind of metal element selected from the group consisting of zirconium, hafnium and rare earth elements.
The fine protrusion structure is a cone trapezoid or a columnar shape, has an oil-repellent surface-modified film on the side surface of the fine protrusion, and the water-repellent metal compound protrudes from the surface-modified film at the apex portion of the fine protrusion. A water- and oil-repellent structure characterized by being exposed. The water- and oil-repellent structure according to claim 1, wherein only the apex portion of the water-repellent metal compound is exposed from the surface modification film on the side surface of the fine protrusion. The water-repellent oil-repellent structure according to claim 1 or 2, wherein the height (h) of the exposed water-repellent metal compound at the apex portion of the fine protrusion is 15 nm or more and 25 nm or less. The water- and oil-repellent structure according to any one of claims 1 to 3 , wherein the surface modification film has a film thickness of 2 nm or more and 50 nm or less. The water- and oil-repellent structure according to any one of claims 1 to 4 , wherein the surface-modified film is made of a fluorocarbon-based material.

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