JP2009042714A - Water-repellent antireflection structure and manufacturing method thereof - Google Patents

Abstract

[PROBLEMS] To provide a water-repellent antireflection structure having an excellent water-repellent function and an anti-reflection function of light, a water-repellent anti-reflective structure having such a structure, a manufacturing method thereof, and the above-mentioned water-repellent reflective structure. Providing automotive parts, such as displays and window panels, with a prevention structure.
An infinite number of cone-shaped protrusions 2 having a circular or polygonal bottom surface and a diameter of the circular bottom surface or a circle circumscribing the polygon forming the bottom surface are 50 to 380 nm, and a pitch of 50 to 380 nm. The aspect ratio of these conical projections is 1.5 or more, and the surface is formed of a material having a contact angle with water of 90 ° or more.
[Selection] Figure 1

Description

  The present invention relates to a water repellent antireflective structure comprising a fine structure having a water repellent function for preventing the attachment of water droplets, and such a fine structure. The present invention relates to a water-repellent antireflection structure that can be suitably used for various window panels such as aircraft, display devices, and the like, and further to a method for manufacturing the structure.

  Various types of window panels for vehicles, ships, airplanes, etc. have been equipped with wiper systems to remove rain. By making the window panels water repellent, window panels that do not require wipers have been realized, reducing costs and man-hours. It is hoped to do.

In recent years, as a method for solving the above problems, a method has been developed in which the surface of a sub-wavelength grating that is two-dimensionally arranged with a grating period shorter than the wavelength of light to be used is made to have a low surface energy (for example, patents). Reference 1).
According to such a subwavelength grating, a refractive index distribution can be provided on the surface, an antireflection characteristic can be obtained, and a water repellency characteristic can be provided by increasing the surface area.
JP 2006-178147 A

  However, in the sub-wavelength grating structure described in Patent Document 1 described above, it is difficult to achieve both antireflection characteristics and water repellency characteristics.

  The present invention has been made to solve the above-mentioned problems, and its object is to provide a water-repellent reflection structure having such a structure as well as a water-repellent reflection-preventing structure having a further excellent water-repellent function. An object of the present invention is to provide a prevention structure and a method for manufacturing the same, and further to provide an automotive part having the above water-repellent antireflection structure, for example, a display or a window panel.

    As a material constituting the surface of the cone-shaped projection that exhibits the antireflection function, the present inventors have made extensive studies to achieve the above object, and a material having a contact angle with water of 90 ° or more. In addition, the inventors have found that the above object can be achieved by specifying the aspect ratio of the cone-shaped projections, and have completed the present invention.

  That is, the present invention is based on the above knowledge, and the water-repellent antireflection structure of the present invention has a circular or polygonal bottom surface, and the diameter of the circle that circumscribes the diameter of the circular bottom surface or the polygon that forms the bottom surface. Innumerable cone-shaped projections having a diameter of 50 to 380 nm are arranged at a pitch of 50 to 380 nm, the aspect ratio of these cone-shaped projections is 1.5 or more, and at least the surface of the cone-shaped projections The contact angle with respect to water of the material which comprises is characterized by being 90 degrees or more.

The water-repellent antireflection structure of the present invention is characterized in that the above-described water-repellent antireflection structure is provided on at least one surface of a substrate.
Further, in the method for producing the water-repellent antireflection structure, a mold (stamper) having a structure in which the cone-shaped projections in the water-repellent antireflection structure are inverted is prepared, and such a cone-shaped structure is formed by hot embossing. Forming protrusions on the surface of the substrate or irradiating active energy rays with the active energy ray-curable resin interposed between the mold and the substrate to prevent the water-repellent antireflection on the surface of the substrate It is characterized by forming a cone-shaped projection having a structure. Furthermore, the automotive component of the present invention is characterized by including the water-repellent antireflection structure of the present invention.

  According to the present invention, the antireflection function of light is exhibited by the innumerable cone-shaped protrusions arranged at a pitch smaller than the wavelength of visible light and shorter than the wavelength of visible light, and the aspect of the cone-shaped protrusion The contact angle with water of the material constituting at least the surface of the cone-shaped projection is 90 ° or more, that is, the material constituting the cone-shaped projection, or these cone-shaped projections As a material for covering the surface of the protrusion, a material having a contact angle with water of 90 ° or more is used, so that both antireflection properties and water repellency can be achieved. Can be obtained.

  Hereinafter, the water-repellent antireflection structure of the present invention and the structure to which the water-repellent antireflection structure is applied will be described in more detail along with the manufacturing method and embodiments thereof.

  1A and 1B are a front view and a plan view showing a typical example of the water-repellent antireflection structure of the present invention. As described above, the water-repellent antireflection structure 1 shown in the figure has an infinite number of circular or polygonal bottom surfaces (showing the circular bottom surface in FIG. 1) of 50 to 380 nm smaller than the wavelength of visible light. It consists of cone-shaped projections 2. Since these pyramidal projections are arranged at a pitch P of 50 to 380 nm smaller than the wavelength of visible light, the refractive index in the thickness direction determined by the area occupied by the material in each cross section in the thickness direction changes abruptly. There is no. And since the refractive index of air changes from 1.0 to the refractive index of the material, the light incident on the water-repellent antireflection structure 1 is almost diffracted and reflected. Therefore, the light reflectance at the incident surface can be effectively reduced.

On the other hand, by forming a fine structure composed of innumerable pyramidal projections in a certain area on the plane, the surface area is increased, and the surface tension of the plane with respect to water in the area is apparently increased. The microstructure surface becomes water repellent.
In addition, depending on the shape of the cone-shaped protrusion, not only the apparent surface tension of the plane with respect to water increases, but also the water repellent function is significantly improved by forming an air layer between the water and the fine structure when adhering to the water droplets. Can be made.

First, the relationship between the water contact angle of the material and the water repellency is as shown in FIG. That is, when the contact angle of the material with respect to water is 90 ° or more, the material has water repellency, and the water repellency is improved as the contact angle of the material with respect to water increases. On the other hand, when the contact angle of water with respect to the material is smaller than 90 °, the material does not have water repellency and has hydrophilic properties.
Therefore, since the present invention aims to improve the water repellency, a material having a water contact angle of 90 ° or more is selected.

In the present invention, attention was paid to the relationship between the contact angle and the aspect ratio of the material forming the surface of the cone-shaped protrusion 2 as a condition for achieving both the antireflection structure and the water-repellent structure.
The contact angle with respect to water of the material forming the surface of the cone-shaped projection 2 is 90 ° or more for the above-mentioned reason, and the aspect ratio is 1.5 or more, whereby an air layer is formed between the water droplet and the fine structure. The antireflection function can be effectively exhibited while reliably forming the water and ensuring water repellency. As a result, both antireflection and water repellent functions can be achieved.

The size of the bottom surface of the cone-shaped projection 2 is expressed by the diameter D when the shape is circular, and when the shape is a polygon, the size is expressed by the diameter D of the circle circumscribing the polygon forming the bottom surface. To do. The diameter D is not more than the wavelength of visible light, specifically 50 to 380 nm, preferably 50 to 250 nm.
Here, when the diameter D is larger than 380 nm, diffusion or diffraction occurs and the reflectance of light increases. On the other hand, if it is smaller than 50 nm, it is very difficult to obtain such a fine structure uniformly and industrially.

Specifically, the pitch P of the cone-shaped protrusions 2 is defined as a distance between the vertices or a distance between the centers of gravity of the bottom surfaces (in the case of a circle, which coincides with the center). The pitch P also needs to be equal to or less than the wavelength of visible light, specifically 50 to 380 nm, preferably 50 to 250 nm.
When the pitch P exceeds 380 nm, diffusion and diffracted light are generated as described above, and the antireflection property is lowered. Moreover, it is because it is industrially difficult to set it as less than 50 nm. In addition, since the cone-shaped protrusion 2 is in the most densely arranged state when D = P, it is preferable to do so.

On the other hand, the aspect ratio of the cone-shaped projection 2 is the ratio of the height H of the cone-shaped projection 2 to the bottom surface diameter D of the cone-shaped projection 2 or the diameter D of the circle circumscribing the polygon forming the bottom surface ( H / D). In the present invention, the aspect ratio (H / D) needs to be in the range of 1.5 or more.
That is, when the aspect ratio (H / D) of the cone-shaped protrusion 2 is less than 1.5, it is difficult to form an air layer between the droplets and to ensure an antireflection effect. .

Furthermore, when the aspect ratio exceeds 3, the cone-shaped protrusion 2 is likely to be damaged when receiving an external force, and it is difficult to maintain these functions for a long period of time. Therefore, an aspect ratio of 3 or less is preferable from the viewpoint of durability.
In particular, when importance is placed on the antireflection effect, the aspect ratio (H / D) is preferably 2 or more.

Moreover, in FIG. 1, the cone-shaped thing was shown as a shape of the cone-shaped processus | protrusion 2 which comprises the water-repellent antireflection structure 1 of this invention. However, as the shape of the cone-shaped projection 2 in the present invention, not only an accurate cone (a generatrix is a straight line) and a pyramid (a ridge is a straight line, a side is a plane), 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. In consideration of formability and breakage resistance, it is also possible to make the tip part flat or rounded with a truncated cone shape or a truncated pyramid shape.
Furthermore, the straight line connecting the center and vertex of the bottom surface of the cone-shaped protrusion 2 (the center point of the upper surface in the truncated cone-shaped protrusion) does not necessarily need to be perpendicular to the bottom surface, and even satisfies the above numerical value. If it is, it may be tilted.
Thus, in the present invention, “conical shape” means not only an accurate cone or pyramid, but also a deformed cone shape of a bell shape or a real shape of a vertebra, a deformed pyramid shape having a curved side surface, Means a shape including a truncated cone, a truncated pyramid, and an inclined one without a tip protrusion.

  As described above, the bottom shape of the cone-shaped protrusion 2 may be circular or polygonal as long as the above numerical value is satisfied. A circular shape is preferable for improving and further reducing the average reflectance.

The ridgeline of the cone-shaped protrusion 2, that is, a generatrix line in the cone-shaped protrusion, and a line connecting the apex of the bottom polygon in the pyramid-shaped protrusion is a linear form represented by the formula (1) (however, N = 1.1-3) is desirable. By doing so, the rate of change in refractive index from the top to the bottom of the fine structure becomes uniform, and the antireflection function can be further improved.
That is, when the base in the vertical cross section passing through the apex of the cone-shaped projection 2 is taken on the X axis and the apex is taken on the Z axis, the Z coordinate value on the ridge line is as shown in FIG. Can be expressed as At this time, correction can also be made by adding a constant term depending on the position of the vertex.
Z = H− {H / (D / 2) ⁿ } × X ⁿ (1)

  Further, the conical protrusions 2 may be in a regular arrangement or an irregular random arrangement as long as the above numerical values are satisfied. Furthermore, two or more types of fine structures having different shapes may be included, but in order to improve the uniformity of the antireflection function, a periodic structure in which the same cone-shaped projections are arranged at uniform intervals. It is preferable to have a square arrangement or a hexagonal close arrangement.

When the contact angle between the material constituting the cone-shaped protrusion 2 itself or the water droplet of the material coated on the surface of the cone-shaped protrusion 2 is 110 ° or more, the water-repellent property is further improved. .
In the water-repellent antireflection structure of the present invention, in consideration of water repellency against raindrops, the wettability of the material constituting the surface of the cone-shaped projection 2 is defined by the contact angle with water. However, the water-repellent antireflection structure of the present invention is applied to applications that come into contact with liquids other than water, for example, viewing window panels such as reactors and distillation towers in various plant devices, and lens surfaces of endoscopes. In some cases, it is necessary to set the contact angle with respect to the contacting liquid to be greater than or equal to the specified value according to each application.

  In the production of the water-repellent antireflection structure of the present invention, the method for forming the above-mentioned cone-shaped protrusion is not particularly limited, and examples thereof include a hot press method (hot embossing method) and an injection molding method. In particular, nanoimprinting is suitably used as a method for easily forming a microstructure having a wavelength equal to or smaller than the wavelength of light. The nanoimprinting method may be a method using either heat or active energy rays.

    The method using heat is a method of transferring the cone-shaped projections as described above to the resin by heating the thermoplastic resin and pressing a mold. The method using active energy rays is a method in which a polymer, oligomer, monomer or the like that is polymerized and cured by active energy rays is put in a mold and solidified by irradiation with active energy rays such as ultraviolet rays or X-rays.

The stamper used for the above molding is not particularly limited as long as it is a method capable of forming the above-mentioned fine cone-shaped projections, and an appropriate one is considered in consideration of productivity and cost. Can be used.
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, or the like can be used depending on the desired processing accuracy. You can choose.
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.

  As a material (base material) for forming the structure, any material may be used as long as it can provide a fine structure composed of the cone-shaped projections by any of the methods described above. For example, polyethylene, polypropylene, polyvinyl alcohol, polyvinylidene chloride, polyethylene terephthalate, polyvinyl chloride, polystyrene, ABS resin, AS resin, acrylic resin, polyamide, polyacetal, polybutylene terephthalate, glass reinforced polyethylene terephthalate, polycarbonate, modified polyphenylene ether, Thermoplastic resins such as polyphenylene sulfide, polyether ether ketone, liquid crystalline polymer, fluororesin, polyarate, polysulfone, polyethersulfone, polyamideimide, polyetherimide, thermoplastic polyimide, phenol resin, melamine resin, urea resin, epoxy Resin, unsaturated polyester resin, alkyd resin, silicone resin, diallyl phthalate resin, polyamid It is possible to use thermosetting resins such as bismaleimide and polybisamidotriazole, and further blended materials of two or more of them, and those that are particularly transparent include, for example, windows (windshields) and instruments. It can be suitably used for a cover or the like.

When using an active energy ray, 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.
In addition, examples of the active energy ray used here generally include ultraviolet rays, X-rays, other electron beams, electromagnetic waves, and the like, but are not particularly limited.

  In the present invention, when it is intended to further improve the water repellency by further increasing the contact angle with water, the water defined in the present invention is applied to the surface of the cone-shaped protrusion obtained as described above. A material having a contact angle with respect to is coated.

Such a coating treatment method is not particularly limited as long as the fine uneven structure formed by the cone-shaped protrusions is not filled with the coating material. For example, the LB method, the PVD method, and the CVD method are used. , Self-organization method, sputtering method, and a method of applying a single molecule diluted with a solvent.
For example, examples of the water-repellent material having a contact angle with water of 110 ° or more used for the coating treatment as described above include long-chain alkoxysilanes, fluoroalkoxysilanes, and polydimethylsiloxane.

  It is also possible to form a cone-shaped projection by the above-mentioned method after subjecting the flat plate before forming the cone-shaped projection to a water repellent treatment with an arbitrary thickness using the above materials. It is.

The water-repellent antireflective structure of the present invention is formed by forming the water-repellent antireflective structure on at least one surface of the substrate, and may be formed on both the light incident surface and the transmitted light exit surface. preferable.
There is no particular limitation on the formation of the water-repellent antireflection structure composed of the cone-shaped projections. There is a method of making and transferring the above-mentioned cone-shaped projections there.

When such a structure is applied to a molded product and incorporated in a display device, it is most effective to apply it to the front surface. If this structure is applied to at least one surface, the back surface is in contact with the material. It is also possible to apply a conventional antireflection method with no corner limitation.
As such an antireflection method, for example, a method of using an antireflection structure provided with only a fine structure having a wavelength equal to or less than the wavelength of light, or a reflection between a thin film surface and a substrate adhesion surface by controlling the film thickness of the antireflection layer Examples include a method of canceling reflected light by causing interference of light.

The molded article (water-repellent anti-reflection structure) having the water-repellent anti-reflection structure of the present invention is, for example, a mobile device such as an automobile or motorcycle meter panel, a mobile phone, an electronic notebook, a signboard, a clock, or the like. It is used for display devices that require an antireflection function at the forefront and that may be exposed to water such as rain or oil stains.
The type of display device is not particularly limited. For example, a combination of mechanical display and illumination, such as an analog meter, and a backlight or light emitting surface such as a liquid crystal, LED, or EL, such as a digital meter or monitor are used. In some cases, a reflective liquid crystal is used as in conventional mobile devices.

Since such molded products are used in places exposed to light, in order to prevent deterioration due to light, it is possible to add UV absorbers, antioxidants, radical scavengers, etc. to the material. desirable.
Further, a bluing agent or a fluorescent coloring pigment for compensating for yellowing due to deterioration of the resin can be used.

  Since the water-repellent antireflection structure of the present invention has the above-mentioned water-repellent antireflection structure formed on at least one surface of a substrate, the reflection of light can be suppressed to an extremely low level, as described above. In addition, by applying it to various parts including automobiles, such as meter covers and windshields, it is possible to prevent reflection of outdoor scenery and interiors, etc. The removability is improved, and it is possible to realize a windshield that does not require a wiper.

  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. In the present specification, “%” for concentration, content, and the like represents a mass percentage unless otherwise specified.

Example 1
A stamper in which conical concave portions having an opening diameter of 250 nm and a depth of 375 nm were squarely arranged at a pitch of 250 nm was produced using a commercially available electron beam drawing apparatus. Using this stamper, conical protrusions (aspect ratio: 1.5) having a bottom diameter D = 250 nm and a height H = 375 nm are squarely arranged at a pitch P = 250 nm on both sides of an acrylic plate having a thickness of 2 mm. The water-repellent antireflection structure was transferred. By subjecting this surface to a CVD treatment with fluoroalkylsilane (Fluorotechnology: Fluorosor FG-5010, contact angle 118 °), the water-repellent antireflection structure of this example was obtained.

  The water repellent antireflection structure thus obtained was evaluated for the antireflection function, the contact angle with water, the water repellency and the durability in the following manner.

(Reflectance measurement)
As an evaluation method of the anti-reflection function, for each wavelength of 380 to 780 nm, incidence is performed using a specular aluminum as a reference sample by a variable angle spectrophotometer (manufactured by Otsuka Electronics: visible / near infrared automatic variable angle measuring device). The reflectance at an angle of 0 ° was measured, the value was multiplied by a reference correction coefficient, and the average reflectance was calculated from the obtained spectrum.

[Contact angle of water]
As a method for evaluating the contact angle of water, using a contact angle meter (Kyowa Interface Chemical Co., Ltd .: CA-X), 10 μL of water was allowed to stand on the sample surface with a syringe, and the contact angle was measured five times. The average value was used as the contact angle.

[Water repellency]
As a method for evaluating the water repellent function, evaluation was performed based on the following criteria using a spray tester (manufactured by Toyo Seiki Co., Ltd.) based on the method defined in JIS L1092.
◎: Droplet does not adhere to the surface ○: Adhesive surface of the droplet is hemispherical ×: Droplet adheres to the surface

〔durability〕
As a durability evaluation method, tribogear (HEIDON) was used, and abrasion cloth: broad cloth, load: 1N, sliding was performed 100 times at a sliding speed of 30 reciprocations / minute, and evaluation was performed in the same manner as the above water repellency evaluation.
◎: Droplet does not adhere to the surface ○: Adhesive surface of the droplet is hemispherical ×: Droplet adheres to the surface

  The average reflectance in the visible light range (380 to 780 nm) of the water-repellent antireflection structure obtained in Example 1 was 0.65%. Further, the contact angle of water droplets on the surface of the water repellent antireflection structure was 145 °, the water repellency evaluation was “」 ”, and the durability was“ 「”. These results are shown in Table 1.

(Example 2)
A stamper in which conical recesses having an opening diameter of 250 nm and a depth of 375 nm were arranged in a hexagonal close-packed manner at a pitch of 250 nm was produced using a commercially available electron beam drawing apparatus. By applying UV curable acrylic monomer to this stamper and irradiating with UV light, both sides of the acrylic plate having a thickness of 2 mm have conical projections (aspect ratio: D = 250 nm, height H = 375 nm). 1.5) was transferred to the antireflection structure in which hexagonal arrangement with a pitch P = 250 nm. And the water-repellent antireflection structure of this example was obtained by giving this surface a water-repellent treatment (T & K Corporation: Nanos B, contact angle 116 °) by a vacuum deposition method.
And as a result of performing the same performance evaluation about the water-repellent antireflection structure thus obtained, the average reflectance is 0.68%, the contact angle of water droplets on the surface of the structure is 144 °, The water repellency and durability were both “◎”. These results are also shown in Table 1.

(Example 3)
Using a commercially available electron beam drawing apparatus, an approximately conical concave portion having an opening diameter of 250 nm, a depth of 500 nm, and a ridge line shape represented by the equation (1) of n = 1.5 is hexagonal at a pitch of 250 nm. Close-packed stampers were produced. By applying ultraviolet curable acrylic monomer to this stamper and irradiating with ultraviolet rays, a substantially conical protrusion (aspect ratio) having a bottom diameter D = 250 nm and a height H = 500 nm is formed on both sides of the acrylic plate having a thickness of 2 mm. : 2) was transferred an antireflection structure in which hexagonal arrangement was performed at a pitch P = 250 nm. Next, the water-repellent antireflection structure of this example was obtained by performing the same water-repellent treatment as in Example 3 by vacuum deposition.
And as a result of performing the performance evaluation similar to the said Example 1, an average reflectance is 0.09%, the contact angle of the water droplet in the said water-repellent antireflection structure surface is 162 degrees, and about water repellency and durability, either Was also “◎”. These results are also shown in Table 1.

(Examples 4 to 6)
By changing the stamper depth in the same manner as in Example 2, the aspect ratio: 2.5 (Example 4), the aspect ratio: 3.0 (Example 5), and the aspect ratio: 4.0 (Implementation) Each water-repellent antireflection structure as in Example 6) was obtained.
And the result of having performed the same performance evaluation is combined with Table 1, and is shown.

(Example 7)
A stamper in which conical recesses having an opening diameter of 250 nm and a depth of 375 nm were arranged in a hexagonal close-packed manner at a pitch of 250 nm was produced using a commercially available electron beam drawing apparatus. Using this stamper, conical protrusions (aspect ratio) having a bottom surface diameter D = 250 nm and a height H = 375 nm on the front and back surfaces of a perfluoroalkyl methacrylate plate having a contact angle with water of 110 ° and a thickness of 2 mm. : 1.5) was transferred in a hexagonal arrangement with a pitch P = 250 nm to transfer the water-repellent antireflection structure, and the water-repellent antireflection structure of this example was obtained.
And about the water-repellent antireflection structure obtained in this way, when the same performance evaluation as the said Example 1 was performed, the average reflectance was 0.71%. The contact angle of water droplets on the surface of the water-repellent antireflection structure was 142 °, and the water repellency and durability were both “「 ”. These results are also shown in Table 1.

(Example 8)
By changing the depth of the stamper in the same manner as in Example 7, a water repellent antireflection structure of this example having an aspect ratio of 2.0 was obtained.
And the result of having performed the same performance evaluation is combined with Table 1, and is shown.

Example 9
A stamper in which conical recesses having an opening diameter of 250 nm and a depth of 500 nm were arranged in a hexagonal close-packed manner at a pitch of 250 nm was produced using a commercially available electron beam drawing apparatus. Using this stamper, the flat surface has a reflectivity of 7%, a contact angle with water of 30 °, and has a bottom surface diameter D = 250 nm and a height H = 500 nm on both front and back surfaces of a glass plate having a thickness of 2 mm. The antireflection structure in which the conical protrusions (aspect ratio: 2) were arranged in a hexagonal close-packed manner at a pitch P = 250 nm was transferred. Next, CF ₃ (CF ₂ ) ₇ (CH ₂ ) ₂ Si (OCH ₃ ) ₃ (contact angle: 110 °) as a fluoroalkoxysilane was surface-treated by a spin coating method, and the water-repellent antireflection structure of this example was obtained. Obtained.
And as a result of performing performance evaluation similar to the said Example 1, an average reflectance is 0.41%, the contact angle of the water droplet on the said water-repellent antireflection structure surface is 161 degrees, and a water-repellent evaluation result is "(double-circle)". However, the durability was “◯”. These results are also shown in Table 1.

(Examples 10 and 11)
By changing the stamper depth in the same manner as in Example 7, the respective water-repellent antireflection structures having an aspect ratio of 2.5 (Example 10) and an aspect ratio of 3.0 (Example 11) are obtained. Got the body.
And the result of having performed the same performance evaluation is combined with Table 1, and is shown.

Example 12
A stamper in which conical concave portions having an opening diameter of 250 nm and a depth of 375 nm were squarely arranged at a pitch of 250 nm was produced using a commercially available electron beam drawing apparatus. Using this stamper, conical projections with a bottom diameter D = 250 nm and a height H = 375 nm (aspect ratio: 100 nm) are formed on both front and back surfaces of an acrylic plate grafted with fluorine having a contact angle with water of 100 ° and a thickness of 2 mm. 1.5) was transferred to form a water-repellent antireflection structure having a square arrangement with a pitch P = 250 nm, thereby obtaining the water-repellent antireflection structure of this example.
As a result of performing the same performance evaluation on the water-repellent antireflection structure thus obtained, the average reflectance was 0.80%, the contact angle of water droplets on the surface of the structure was 128 °, and the water repellency and durability. The sexes were all “◯”. These results are shown in Table 2.

(Examples 13 to 15)
By using a stamper having a different opening diameter and depth in the same manner as in Example 12, the bottom diameter D: 250 nm, the height H: 500 nm, the aspect ratio: 2.0 (Example 13), and the bottom diameter D: 200 nm, height H: 500 nm, aspect ratio: 2.5 (Example 14), bottom diameter D: 250 nm, height H: 750 nm, aspect ratio: 3.0 (Example 15) An aqueous antireflection structure was obtained.
And the result of having performed the same performance evaluation is combined with Table 2, and is shown.

(Example 16)
A stamper in which conical concave portions having an opening diameter of 250 nm and a depth of 375 nm were squarely arranged at a pitch of 250 nm was produced using a commercially available electron beam drawing apparatus. Using this stamper, conical protrusions (aspect ratio: 1.5) having a bottom diameter D = 250 nm and a height H = 375 nm are formed on both front and back surfaces of an acrylic plate having a contact angle with water of 92 ° and a thickness of 2 mm. A fine structure formed by square arrangement at a pitch P = 250 nm was transferred to obtain a water-repellent antireflection structure of this example.
And as a result of performing the performance evaluation similar to the said Example 1, an average reflectance is 1.0%, the water-drop contact angle in the said water-repellent anti-reflective structure surface is 120 degrees, and both about water repellency and durability It was “○”. These results are also shown in Table 2.

(Examples 17 to 19)
By changing the depth of the stamper in the same manner as in Example 16, the aspect ratio: 2.0 (Example 17), the aspect ratio: 2.5 (Example 18), and the aspect ratio: 3.0 Each water-repellent antireflection structure which is (Example 19) was obtained.
And performance evaluation similar to the said Example 1 was performed. The results are also shown in Table 2.

(Comparative Example 1)
A stamper in which conical concave portions having an opening diameter of 250 nm and a depth of 250 nm were arranged in a hexagonal close-packed manner at a pitch of 250 nm was produced using a commercially available electron beam drawing apparatus. By applying an ultraviolet curable acrylic monomer to the stamper and irradiating with ultraviolet rays, conical protrusions (aspect ratio: aspect ratio: D = 250 nm on the bottom surface) and H = 250 nm on the front and back surfaces of the acrylic plate having a thickness of 2 mm. 1.0) is transferred to form an antireflection structure in which hexagonal arrangement is performed at a pitch P = 250 nm. And the water-repellent antireflection structure of this example was obtained by giving this surface a water-repellent treatment (T & K Corporation: Nanos B, contact angle 116 °) by a vacuum deposition method.
And as a result of performing performance evaluation similar to the said Example 1 about the water-repellent antireflection structure obtained in this way, an average reflectance is 0.92% and the contact of the water droplet on the surface of the said structure The angle was 134 °, and the water repellency and durability were all “◯”. These results are also shown in Table 1.

(Comparative Example 2)
Using a commercially available electron beam drawing apparatus, an approximately conical concave portion having an opening diameter of 300 nm, a depth of 330 nm, and an ridge line shape represented by the equation (1) of n = 1.5 is hexagonal at a pitch of 300 nm. An arrayed stamper was made. By applying ultraviolet curable acrylic monomer to this stamper and irradiating with ultraviolet rays, a substantially conical protrusion (aspect ratio) having a bottom surface diameter D = 300 nm and a height H = 330 nm is formed on both front and back surfaces of an acrylic plate having a thickness of 2 mm. : 1.1) was transferred to form a fine structure in which hexagonal arrangement was performed at a pitch P = 300 nm. Next, this surface was subjected to the same water-repellent treatment (T & K Corporation: Nanos B, contact angle 116 °) by a vacuum vapor deposition method to obtain the water-repellent antireflection structure of this example.
The water repellent antireflection structure thus obtained was subjected to the same performance evaluation. As a result, the average reflectance was 0.90%. Further, the contact angle of water droplets on the surface of the structure was 136 °, and the water repellency and durability were both “◯”. These results are also shown in Table 1.

(Comparative Example 3)
By changing the stamper depth in the same manner as in Comparative Example 2, a water-repellent antireflection structure of this example having an aspect ratio of 1.4 was obtained.
And the same performance evaluation was performed and the result is combined with Table 1 and shown.

(Comparative Example 4)
A stamper in which conical recesses having an opening diameter of 250 nm and a depth of 250 nm were arranged in a hexagonal close-packed manner at a pitch of 250 nm was produced using a commercially available electron beam drawing apparatus. Using this stamper, a conical protrusion (aspect ratio) having a bottom surface diameter D = 250 nm and a height H = 250 nm on the front and back surfaces of a perfluoroalkyl methacrylate plate having a contact angle with water of 110 ° and a thickness of 2 mm. : 1.0) was transferred to form a water-repellent antireflection structure having a hexagonal close-packed arrangement with a pitch P = 250 nm to obtain the water-repellent antireflection structure of this example.
The water repellent antireflection structure thus obtained was evaluated for performance in the same manner as in Example 1. As a result, the average reflectance was 0.95%. Further, the contact angle of water droplets on the surface of the water-repellent antireflection structure was 120 °, and the water repellency and durability were both “◯”. These results are also shown in Table 1.

(Comparative Examples 5 and 6)
By changing the stamper depth in the same manner as in Comparative Example 4, each water-repellent antireflection structure having an aspect ratio of 1.1 (Comparative Example 5) and an aspect ratio of 1.4 (Comparative Example 6) is obtained. Got the body.
And the result of having performed the same performance evaluation is combined with Table 1, and is shown.

(Comparative Example 7)
A stamper in which conical concave portions having an opening diameter of 500 nm and a depth of 500 nm were squarely arranged at a pitch of 500 nm was produced using a commercially available electron beam drawing apparatus. Using this stamper, conical protrusions with a bottom diameter D = 500 nm and a height H = 500 nm (aspect ratio: aspect ratio: on both the front and back surfaces of an acrylic plate graft-polymerized with fluorine having a contact angle with water of 100 ° and a thickness of 2 mm. 1.0) was transferred to form a water-repellent antireflection structure of the present example.
As a result of performance evaluation similar to Example 1, the average reflectance was 0.98%, the water droplet contact angle on the surface of the water-repellent antireflection structure was 120 °, the water repellency was “◯”, and the durability Was "○". These results are also shown in Table 2.

(Comparative Examples 8 and 9)
By changing the depth of the stamper in the same manner as in Comparative Example 7, the respective water-repellent antireflection structures having an aspect ratio of 1.1 (Comparative Example 8) and an aspect ratio of 1.4 (Comparative Example 9) Got the body.
And the result of having performed the same performance evaluation is combined with Table 1, and is shown.

(Comparative Example 10)
A stamper in which conical concave portions having an opening diameter of 250 nm and a depth of 250 nm were squarely arranged at a pitch of 250 nm was produced using a commercially available electron beam drawing apparatus. Using this stamper, conical protrusions (aspect ratio: 1.0) having a bottom surface diameter D = 250 nm and a height H = 250 nm are formed on the front and back surfaces of an acrylic plate having a contact angle with water of 92 ° and a thickness of 2 mm. A fine structure formed by square arrangement at a pitch P = 250 nm was transferred to obtain a water-repellent antireflection structure of this example.
As a result of performance evaluation similar to the above example, the average reflectance was 1.19%, the water droplet contact angle on the surface of the water-repellent antireflection structure was 112 °, the water repellency evaluation result was “x”, and durability The sex was also “x”. These results are also shown in Table 2.

(Comparative Examples 11 and 12)
By changing the stamper depth in the same manner as in Comparative Example 10, the water-repellent antireflection structure having an aspect ratio of 1.1 (Comparative Example 11) and an aspect ratio of 1.4 (Comparative Example 12) is obtained. Got the body.
And the result of having performed the same performance evaluation is combined with Table 2, and is shown.

(Comparative Example 13)
As a result of performing the same performance evaluation on an acrylic flat plate having a reflectivity of 7% when flat and a contact angle with water of 102 ° and a thickness of 2 mm, the water repellency was “x”.

  Further, in order to confirm the effect of the aspect ratio of the cone-shaped protrusions on the water-repellent property in the water-repellent anti-reflective structure according to the present invention, the structure is obtained from the contact angle with water of the obtained water-repellent anti-reflective structure. Value obtained by subtracting the contact angle of the surface material with respect to water (the increase in the contact angle of the water-repellent antireflection structure by the aspect ratio): Δ was determined for Examples 1 to 19 and Comparative Examples 1 to 12. The result is shown in FIG. Although not described in Table 1, a structure using a material having a contact angle of 118 ° with respect to water on the surface of the structure and having an aspect ratio of 1.5 (Example 1) These data are also added to FIG.

From Tables 1 and 2 and FIG. 4, when the aspect ratio of the cone-shaped protrusions in the water-repellent antireflection structure is 1.5 or more, the contact angle increase Δ of the water-repellent antireflection structure due to the aspect ratio increases rapidly. In addition, the contact angle of the water-repellent antireflection structure with water is 120 ° or more. Moreover, since the average reflectance of the water-repellent antireflection structure also shows 1% or less, it can be seen that the water-repellent antireflection structure of the present invention can achieve both antireflection and water repellency.
Furthermore, it can be seen that when the contact angle of the material on the surface of the structure with respect to water is 110 ° or more, the effect of the aspect ratio of the cone-shaped protrusions on the water-repellent property in the water-repellent antireflection structure is particularly large. Accordingly, when the contact angle of the material on the structure surface with respect to water is 110 ° or more, the contact angle with water of the water repellent antireflection structure is 142 ° or more, and the water repellent antireflection structure of the present invention has antireflection properties. It can be seen that both excellent water repellency (super water repellency) can be achieved.

  Tables 1 and 2 show that when the aspect ratio of the cone-shaped protrusions in the water-repellent antireflection structure is 2 or more, the average reflectance of the water-repellent antireflection structure is 0.5% or less. Therefore, it can be seen that the water-repellent antireflection structure of the present invention achieves both excellent antireflection properties and water repellency.

  From Tables 1 and 2, it can be seen that when the aspect ratio of the cone-shaped protrusions in the water-repellent antireflection structure is 4 or more, the durability is poor. Therefore, it is preferable that the aspect ratio of the cone-shaped protrusion is 3 or less from the viewpoint of durability.

(A) And (b) is the front view and top view which show an example of the water-repellent antireflection structure of this invention. It is explanatory drawing showing the relationship between the contact angle with respect to the water of material, and a water-repellent property. It is explanatory drawing which represented the ridgeline shape of the cone-shaped processus | protrusion in the water-repellent antireflection fine structure of this invention by n-order Formula (1). It is a graph showing the contribution with respect to the water-repellent property of the aspect ratio of the cone-shaped protrusion in the water-repellent antireflection microstructure in the present invention.

Explanation of symbols

1 water-repellent antireflection structure 2 cone-shaped projection

Claims (11)

  Innumerable cone-shaped projections having a circular or polygonal bottom surface and a diameter of the circular bottom surface or a circle circumscribing the polygonal bottom surface being 50 to 380 nm are arranged at a pitch of 50 to 380 nm, and the cone A water-repellent antireflection structure, wherein an aspect ratio of a body-like protrusion is 1.5 or more, and a contact angle with respect to water of a material constituting at least a surface of the cone-like protrusion is 90 ° or more.   The water repellent antireflection structure according to claim 1, wherein a contact angle with respect to water of a material constituting at least a surface of the conical protrusion is 110 ° or more.   The water-repellent antireflection structure according to claim 1, wherein an aspect ratio of the cone-shaped protrusion is 2 or more.   The water-repellent antireflection structure according to any one of claims 1 to 3, wherein an aspect ratio of the conical protrusion is 3 or less.   The water-repellent antireflection structure according to any one of claims 1 to 4, wherein the cone-shaped projections are arranged in a square or hexagonal arrangement. The water-repellent reflection according to any one of claims 1 to 5, wherein the ridge line shape of the cone-shaped protrusion is represented by the following formula (1), and the order n is 1.1 to 5. Prevention structure.
Z = H− {H / (D / 2) ⁿ } × X ⁿ (1)   A water repellent antireflective structure comprising the water repellent antireflective structure according to any one of claims 1 to 6 on at least one surface of a substrate.   8. The water repellent antireflection structure according to claim 7, wherein the substrate is made of a transparent material.   9. The method for producing a water-repellent antireflection structure according to claim 7, wherein the cone-shaped projections are formed on a substrate by hot embossing when the water-repellent antireflection structure according to claim 7 is produced.   When manufacturing the water-repellent antireflection structure according to claim 7 or 8, an active energy ray-curable resin is interposed between a mold having a microstructure in which the cone-shaped projections are inverted and a substrate. A method for producing a water-repellent antireflective structure, comprising irradiating active energy rays in a wet state to form the cone-shaped projections on the surface of the substrate.   An automotive part comprising the water-repellent antireflection structure according to any one of claims 1 to 6.

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