JP2010132839A - Water-repellent configuration and water-repellent structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide water-repellent configuration exhibiting an excellent water-repellent function over a long period of time and a water-repellent structure that includes such configuration, for example, an automotive component, such as a window panel or a display. <P>SOLUTION: In the water-repellent configuration including fine convexoconcaves, the fine convexoconcaves comprises a resin 3 and inorganic particles 2 combined with the resin, and water-repellent functional groups are linked to surfaces of the inorganic particles 2 exposed from the resin 3. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is a water-repellent structure having a fine concavo-convex structure that exhibits a water-repellent function that prevents the adhesion of water droplets, and has excellent wear resistance and can exhibit water repellency over a long period of time. And a water-repellent structure having such a structure.

  In various window panels for automobiles, railway vehicles, ships, airplanes, etc., wiper systems have been introduced to remove rain, but by making the window panels water repellent, window panels that do not require wipers are realized. There are attempts to reduce costs and production man-hours.

As a water repellency technique for such a panel, super water repellency can be imparted by attaching nanoparticles to the surface of a fine concavo-convex structure made up of countless fine protrusions using coating or plasma CVD. (See Patent Document 1).
JP 2008-122435 A

  However, in the water-repellent antireflection structure described in Patent Document 1 described above, since the particles on the surface are only adhered by coating or plasma particle formation, the particles are likely to fall off the surface. There was a problem of poor long-term durability against splashing.

  The present invention has been made to solve the above-mentioned problems, and the object of the present invention is to provide a water-repellent structure capable of exhibiting an excellent water-repellent function over a long period of time, and such a structure. The object is to provide a water-repellent structure provided, for example, an automobile part such as a window panel or a display.

  As a result of intensive studies to achieve the above object, the inventors of the present invention assumed that the fine concavo-convex structure exhibiting a water repellency function is made of a resin material containing highly active inorganic particles, and through these inorganic particles. The inventors have found that the above object can be achieved by bonding a water repellent functional group, and have completed the present invention.

The present invention is based on the above knowledge, and the water-repellent structure of the present invention has a fine concavo-convex structure, and the fine concavo-convex structure is composed of a resin and inorganic particles bonded to the resin. It is characterized in that a water repellent functional group is bonded to the surface.
The water-repellent structure of the present invention is characterized in that the water-repellent structure is provided on at least one surface of the substrate.

  According to the present invention, since the concavo-convex structure portion in the water-repellent structure is made of inorganic particles and a resin material, the strength of the concavo-convex structure is increased, and damage, scratches, and wear can be prevented. In addition, the surface of the inorganic particles is highly active and binds firmly to resin materials and water-repellent functional groups, preventing the inorganic particles themselves from dropping and the water-repellent components from falling off the particles, and maintaining high water repellency over a long period of time. can do.

  Hereinafter, the water-repellent structure of the present invention and the structure provided with such a structure will be described in more detail together with the manufacturing method and embodiments thereof. In the present specification, “%” means mass percentage unless otherwise specified.

FIG. 1 shows an example of the shape of fine irregularities in the water-repellent structure of the present invention, and an infinite number of cone-shaped projections 1 such as the cone shown in FIG. 1 (a) and the pyramid shown in FIG. 2 (b). It can consist of:
FIG. 1 shows an example in which innumerable protrusions 1 are arranged on a plane at predetermined intervals. For example, the projections 1 have a wave shape such as a sine wave curve or a saw-shaped cross section, and the convex and concave portions are three-dimensional. It is also possible to adopt a concavo-convex structure that continues to

Here, the interval (pitch) P between the cone-shaped projections 1 is preferably about 0.1 mm or less, which is smaller than the diameter of the water droplets, from the viewpoint of ensuring good water repellency.
In order to secure transparency for use as a display cover or a window panel, the interval P is preferably 400 μm or less. Furthermore, in order to prevent reflection of outside scenery and illumination and to obtain an antireflection function to ensure visibility, the thickness is desirably 400 nm or less. When the pitch P exceeds 400 nm, diffracted light is generated and the reflectance tends to increase. More desirably, it is 380 nm or less, and further desirably 250 nm or less. If it is 250 nm or less, almost no diffracted light is observed.

In FIG. 1, cones and quadrangular pyramids are shown as examples of the shape of the cone-shaped protrusions 1 constituting the fine concavo-convex structure, but the bottom shape of the cone-shaped projection 1 may be other various shapes such as a triangle or a hexagon. It may be square.
In addition, the shape of the cone-shaped projection 1 in the present invention is not only an accurate cone (the bus is a straight line) and a pyramid (a ridge is a straight line, a side is a flat surface), but the cross-sectional area is gradually reduced from the bottom to the tip side. As long as it has such a shape, it may be a cone having a curved bus line or a pyramid having a curved side surface.

Furthermore, although the water repellency is somewhat sacrificed, it is possible to make the tip flat (ie, the cone shape into a frustum shape) or round in consideration of moldability and damage resistance. is there.
In addition, the straight line connecting the center and the apex of the bottom surface of the conical protrusion 1 does not necessarily need to be perpendicular to the bottom surface.

  Thus, in the present invention, “conical shape” means not only an accurate cone or pyramid, but also a bell-shaped or vertebral deformed cone shape, a deformed pyramid shape having a curved side surface, a tip Means shapes that include flat, rounded, and slanted shapes.

  FIG. 2 shows a cross-sectional structure of each cone-shaped protrusion 1 in the water-repellent structure of the present invention. FIG. 2 (a) shows a state immediately after molding of fine irregularities by a resin material containing inorganic particles 2. The cone-shaped protrusion 1 is composed of inorganic particles 2 and a resin 3, and the inorganic particles 2 are dispersed in the resin.

In the present invention, the inorganic particles 2 include inorganic oxide particles such as silicon dioxide, titanium dioxide, zirconium dioxide and aluminum oxide, metal colloid particles such as gold, silver, platinum and iron, and ceramic particles such as barium titanate. Can be used. In particular, in order to improve durability, an inorganic oxide system having high compressive strength and improved adhesion with a resin by surface modification or the like is preferable.
The shape of these particles is not particularly limited, and examples thereof include a true spherical shape, a rugby ball shape, a confetti shape, an indeterminate shape, and a porous shape.

  Moreover, as a magnitude | size of the inorganic particle 2, it is preferable that it is 50 nm or less in a spherical equivalent diameter, More preferably, it is the range of 10-20 nm. This is because when the particle diameter exceeds 50 nm, transparency may be lost, and it is difficult for particles to enter the fine protrusions during molding, and it becomes difficult to improve the durability of the fine structure.

  On the other hand, the material of the resin 3 may be any material that can form a fine concavo-convex structure together with the inorganic particles 2 by the method described later. For example, polyethylene, polypropylene, polyvinyl alcohol, polyvinylidene chloride, polyethylene terephthalate, polyvinyl chloride , Polystyrene, ABS resin, AS resin, acrylic resin, polyamide, polyacetal, polybutylene terephthalate, polycarbonate, modified polyphenylene ether, polyphenylene sulfide, polyether ether ketone, fluororesin, polyarate, polysulfone, polyethersulfone, polyamideimide, polyether Thermoplastic resins such as imide and thermoplastic polyimide, phenolic resin, melamine resin, urea resin, epoxy resin, unsaturated polyester resin, alkyl Thermosetting resins such as resins, silicone resins, diallyl phthalate resins, polyamide bismaleimides, polybisamide triazoles, and blended materials of two or more of these can be used. For example, it can be suitably used for windows (windshields) and instrument covers.

  As will be described later, when an active energy ray is used for molding, a resin capable of initiating polymerization by the active energy ray is used. Examples of such resins include UV curable acrylic urethane resins, UV curable polyester acrylate resins, UV curable epoxy acrylate resins, UV curable polyol acrylate resins, and UV curable epoxy resins. If necessary, a polymerization initiator that generates radicals by irradiating active energy rays can be used, and a curing agent such as isocyanate can be added in order to solidify more firmly.

  The amount of the inorganic particles 2 added to the resin material is desirably in the range of 20 to 60%. That is, if it is less than 20%, the strength of the fine concavo-convex structure is not sufficiently improved, and if it exceeds 60%, the dispersion state of the particles tends to deteriorate, and the molded product tends to become brittle, or the transparency tends to deteriorate.

In the water-repellent structure of the present invention, it is necessary that the inorganic particles 2 are chemically bonded to the resin 3, thereby preventing the inorganic particles 2 from falling off the fine uneven structure.
For example, the strength of the bond between the resin 3 and the inorganic particles 2 can be improved by using a silane coupling agent, a titanate coupling agent, or an aluminate coupling agent according to the type of the inorganic particles 2.

  In the present invention, the term “bond” means that the surface of the inorganic particles and the main chain or side chain of the resin are chemically bonded, and specific examples include bonds such as covalent bonds and ionic bonds. .

FIG. 2B shows a state in which the surface of fine irregularities made of the inorganic particles 2 and the resin 3 is etched to remove the resin on the surface and expose the inorganic particles 2 in the resin to the surface.
The etching method at this time is not particularly limited as long as it is a method capable of etching a resin, and examples thereof include electron beam lithography, plasma discharge, corona discharge, vacuum ultraviolet irradiation, chemical etching using acid, alkali, and solvent. be able to.

Then, surface treatment is performed on the fine irregularities in which the inorganic particles 2 are exposed by etching, whereby water-repellent functional groups are bonded to the particle surfaces to make the inorganic particles 2 water repellent.
The water-repellent functional groups at this time include fluorine functional groups such as perfluoroalkyl groups, perfluoroether groups, hydrofluoroalkyl groups and hydrofluoroether groups, hydrocarbon groups such as dodecane, pentadecane and hexadecane, alkylpolysilanes, and Specific examples of the treatment method include dry treatment such as vapor deposition and sputtering, and wet treatment such as dip, gravure coating, and die coating.

In the water-repellent structure of the present invention, the method for forming such fine irregularities is not particularly limited, and examples thereof include a hot press method (hot embossing method) and an injection molding method.
In particular, nanoimprint is preferably used as a method for easily forming fine irregularities having a wavelength of light or less. As a forming method by this nanoimprint, any method using heat or active energy rays may be used.

  The method using heat is a method in which the thermoplastic resin is heated and a mold is pressed to transfer the fine irregularities as described above to the resin. In addition, the method using active energy rays is solidified by putting a polymer or oligomer that is polymerized and cured by active energy rays into a mold, monomers, and irradiating active energy rays such as ultraviolet rays, X-rays, other electron beams, and electromagnetic waves. It is a method to make it.

The stamper used for the above molding is not particularly limited as long as it can form the fine irregularities as described above, and an appropriate one can be used in consideration of productivity, cost, and the like. it can.
In the present invention, nanoimprint means transfer in the range of several nanometers to several tens of micrometers.

  As the press apparatus used in the present invention, a press machine having a heating / pressurizing mechanism and a press machine having a mechanism capable of irradiating an active energy ray from above the light transmissive stamper are preferable for efficient pattern transfer.

The stamper has a fine pattern to be transferred, and the method for forming the pattern on the stamper is not particularly limited. For example, photolithography, electron beam drawing method, or the like is selected according to the desired processing accuracy. can do.
The stamper material may be a silicon wafer, various metal materials, glass, ceramics, plastics, carbon materials, etc., as long as it has strength and workability with the required accuracy. Specifically, Si, SiC , SiN, polycrystalline Si, glass, Ni, Cr, Cu, C, and those containing one or more of these.

The water-repellent structure of the present invention comprises the above-described water-repellent structure on at least one surface of the substrate.
At this time, the water-repellent structure portion having the fine uneven structure and the substrate may be the same type of material or different materials as long as there is no problem in bonding. Also, it can be integrally molded simultaneously or bonded with an adhesive or the like.

  In the above water-repellent structure, it is desirable to use a transparent material such as acrylic resin or polycarbonate, and to make the entire structure transparent, so that the structure can be applied to a window material or the like. It is also possible to use glass for the substrate portion.

  Since the automobile part of the present invention is provided with the above water-repellent structure of the present invention, it has excellent durability and exhibits excellent water-repellent performance over a long period of time. By applying, a windshield that does not require a wiper can be realized.

  Hereinafter, the present invention will be described more specifically based on examples. However, it is needless to say that the present invention is not limited to these examples.

Example 1
Using a commercially available electron beam drawing apparatus, a mold was prepared in which conical recesses having an opening diameter of 100 nm and a depth of 200 nm were arranged in a hexagonal close-packed manner at an interval of 100 nm. Into this mold, silica particles having a spherical equivalent diameter of 10 nm and an ultraviolet curable polymethyl methacrylate resin having γ-methacryloxypropyltrimethoxysilane containing silanol groups are poured, and the polymethyl methacrylate resin as a base material is pressed. By irradiating with ultraviolet rays in the applied state and solidifying, silanol groups in silica particles and γ-methacryloxypropyltrimethoxysilane are subjected to a dehydration condensation reaction, and a Si—O—Si covalent bond is formed. A methyl methacrylate resin was obtained. The addition amount of silica particles in the particle-containing resin material was 35% by mass, and the substitution amount of γ-methacryloxypropyltrimethoxysilane group in the ultraviolet curable polymethyl methacrylate resin was 5% by mass.
In this way, a molded product was prepared having a fine concavo-convex structure in which conical fine protrusions 1 having a bottom diameter D = 100 nm and a height H = 200 nm were arranged in a hexagonal close-packed manner at a distance P between apexes of 100 nm on both sides.

  Next, the surface of the molded product is etched by plasma discharge treatment to expose silica particles on the surface, and surface treatment is performed using trimethoxysilane having a perfluoroether group as a water repellent functional group. The water-repellent structure of this example in which trianolsilane having a fluoroether group and silanol groups in silica particles were subjected to a dehydration condensation reaction and Si—O—Si covalently bonded was obtained.

  The water-repellent structure thus obtained was evaluated for water adhesion and wear resistance according to the following procedure, and the results are shown in Table 1.

(Example 2)
Using a commercially available electron beam drawing apparatus, a mold was prepared in which conical recesses having an opening diameter of 300 nm and a depth of 500 nm were arranged in a hexagonal close-packed manner at an interval of 300 nm. An ultraviolet curable polymethyl methacrylate resin in which silica particles were covalently bonded to Si—O—Si was obtained in the same manner as in the above example except that the amount of silica particles added to this mold was 30% by mass. .
As a result, a molded article was prepared that had a fine concavo-convex structure in which conical fine protrusions 1 having a bottom surface diameter D = 300 nm and a height H = 500 nm were closely arranged in a hexagonal distance P = 300 nm on both sides.

Next, the surface of this molded product was similarly etched to expose the silica particles on the surface, and then subjected to the same water-repellent surface treatment to obtain the water-repellent structure of this example.
And the performance evaluation similar to the said Example was performed about the water-repellent structure obtained in this way, and the result is combined with Table 1, and is shown.

(Example 3)
Ultraviolet curing in which silica particles are covalently bonded to Si-O-Si in the same manner as in the above example except that the amount of silica particles added is 60% by mass using the same mold as in Example 2. Polymethylmethacrylate resin was obtained. In this way, a molded product was prepared having a fine concavo-convex structure in which conical fine protrusions 1 having a bottom surface diameter D = 300 nm and a height H = 500 nm were arranged in a hexagonal close-packed manner at a distance P between apexes of 300 nm.

Next, the surface of this molded product was similarly etched to expose the silica particles on the surface, and then subjected to the same water-repellent surface treatment to obtain the water-repellent structure of this example.
And the performance evaluation similar to the said Example was performed about the water-repellent structure obtained in this way, and the result is combined with Table 1, and is shown.

Example 4
Using a commercially available electron beam drawing apparatus, a mold was prepared in which conical recesses having an opening diameter of 200 nm and a depth of 500 nm were arranged in a hexagonal close-packed manner at intervals of 200 nm. An ultraviolet curable polymethyl methacrylate resin in which silica particles were covalently bonded to Si—O—Si was obtained in the same manner as in the above example except that the addition amount of silica particles was 20% by mass in this mold. . As a result, a molded article was prepared which had a fine concavo-convex structure in which conical fine protrusions 1 having a bottom diameter D = 200 nm and a height H = 500 nm were arranged in a hexagonal close-packed manner at a distance P between apexes of 200 nm on both sides.

Next, this molded article was subjected to the same etching treatment and water-repellent surface treatment to obtain a water-repellent structure of this example.
And the performance evaluation similar to the said Example was performed about the water-repellent structure obtained in this way, and the result is combined with Table 1, and is shown.

(Comparative Example 1)
By using the same mold as in Example 1 above, an ultraviolet curable acrylic resin containing no silica particles is poured, and ultraviolet rays are irradiated in a state where the base material acrylic is pressed, whereby the bottom diameter D = 100 nm, high A molded article having a fine concavo-convex structure in which conical fine protrusions 1 having a height H of 200 nm are arranged in a hexagonal close-packed manner at a distance P between apexes of 100 nm was obtained.

Next, after etching the surface of this molded product by plasma discharge treatment, surface treatment is performed using trimethoxysilane having a perfluoroether group as a water-repellent functional group, whereby the water-repellent structure of this comparative example is obtained. Obtained.
And about the structure obtained in this way, the same performance evaluation is performed and the result is combined with Table 1, and is shown.

[Performance evaluation method]
(1) Water adhesion About each structure obtained by each of the above Examples and Comparative Examples, first, using a traverse type abrasion tester, a load of 9.8 kPa, using a friction cloth made of canvas cloth (JIS L 3102), The reciprocating wiping operation was performed 200 times under the conditions of a stroke length of 100 mm and a friction speed of 30 reciprocations / minute.
And after such a dry wiping test, based on the method prescribed | regulated to JISL1092, the water repellency was evaluated in five steps according to the following criteria using a spray tester (manufactured by Toyo Seiki).
1: Those that spread wet on the entire surface 2: Water droplets that spread on the surface without retaining a spherical shape 3: Those that adhere to the surface of spherical water droplets 4: Those that adhere to the surface slightly spherical water droplets on the surface 5: Water droplets do not adhere to the surface

(2) Abrasion resistance For each structure after the dry wiping test and water repellency evaluation test described above, the wiping surface of each structure is visually observed. The thing where was recognized as "x".

  As shown in Table 1, in the water-repellent structures according to Examples 1 to 4 of the present invention, both the water repellency and the wear resistance are extremely good, whereas in the comparative examples not containing inorganic particles, It was confirmed that the abrasion was inferior, and therefore the water repellency after the dry wiping test was also inferior.

(A) It is a perspective view which shows the shape of what consists of conical protrusion as a typical example of the microstructure used for this invention. (B) It is a perspective view which shows the shape of what consists of a pyramidal projection as a typical example of the microstructure used for this invention. It is sectional drawing of the cone-shaped processus | protrusion in the water-repellent structure of this invention, Comprising: It is sectional drawing which each shows the state immediately after shaping | molding (a), after an etching (b), and after a water-repellent process (c).

Explanation of symbols

1 Cone-shaped projection 2 Inorganic particle 3 Resin

Claims (7)

  A water-repellent structure comprising a fine concavo-convex structure, wherein the fine concavo-convex structure comprises a resin and inorganic particles bonded to the resin, and water-repellent functional groups are bonded to the surface of the inorganic particles exposed from the resin. .   2. The water repellent structure according to claim 1, wherein the fine irregularities are innumerable conical protrusions arranged at a pitch of 400 nm or less.   3. The water-repellent structure according to claim 1, wherein the inorganic particles have a spherical equivalent diameter of 50 nm or less.   The water-repellent structure according to any one of claims 1 to 3, wherein the added amount of the inorganic particles is 20 to 60% by mass ratio.   A water repellent structure comprising the water repellent structure according to any one of claims 1 to 4 on at least one surface of a substrate.   The water repellent structure according to claim 5, which is made of a transparent material.   An automobile part comprising the water-repellent structure according to any one of claims 1 to 4.

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