JP2007322767A - Anti-reflection structure, anti-reflection structural body and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anti-reflection structure having flaw resistance, provided with a structure that dirt such as sebum hardly enters into a space part of a fine structure and capable of exhibiting excellent anti-reflection performance over a long term, and to provide an anti-reflection structural body provided with the structure and its manufacturing method. <P>SOLUTION: Fine particles 13 smaller than the wave length of visual light are filled to form gaps among the particles into space parts of projecting or recessed fine structure provided with many pyramid like fine projecting parts 12 or many pyramid like recessed parts 22 each having a circular or polygonal bottom smaller than the wave length of the visual light, that is, into the surroundings of the pyramid like fine projecting parts 12 or openings of the fine recessed parts 22, wherein the effective refractive index of the filled part is controlled to 1.10 to 1.35. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention includes an antireflection structure capable of exhibiting an antireflection function of light, and such an antireflection structure, and as an antireflective panel, for example, various vehicles including automobiles, ships, airplanes, and the like The present invention relates to an antireflection structure that can be suitably used for various meters, display devices, and the like, and a method for manufacturing such an antireflection structure.

  In various display devices such as a liquid crystal display and a CRT display, and familiar examples, if a shadow such as external light or indoor lighting is reflected on the screen of a home television, the visibility of the original image may be significantly reduced.

  For example, a driver's seat of an automobile has a display unit that stores various instruments such as a speedometer and a fuel meter. A meter front cover is fitted in front of the display unit. In addition, since the scenery outside the vehicle is reflected through the front window and the side window, it may be difficult to see various displays on the display unit.Therefore, a meter hood is placed above the display to allow external light to enter the meter front cover. I try to prevent it.

As a structure for preventing such reflection of light, a multilayer antireflection film composed of a plurality of thin films having different refractive indexes is known. However, the reflectance can be further reduced as compared with such a multilayer antireflection film. As an example, an antireflection structure using an uneven microstructure has been proposed (see, for example, Patent Document 1).
In the antireflection structure described in Patent Document 1, the refractive index of light is increased in the thickness direction by forming innumerable fine irregularities made of a transparent material on the surface of a transparent molded product at a pitch equal to or less than the wavelength of light. For example, an infinite number of fine irregularities in the shape of corrugations or serrations are formed on the surface, so that the ratio of the transparent material existing on the outermost surface of the irregularities is as close to 0% as possible. Thus, the refractive index of air is substantially equal to the refractive index of the air, while the ratio of the air is almost infinitely close to 0% at the bottom of the irregularities, and is equal to the refractive index of the molded product. As a result of the refractive index corresponding to the cross-sectional area occupied by the transparent material in the cross section, the refractive index of light continuously changes between the refractive index of air and the refractive index of the transparent material in the thickness direction of the antireflection structure. Because it comes to refraction Based on the same principle as a multilayer antireflection film consisting of a plurality of thin films having different refractive indices (in this case, the refractive index changes stepwise), the antireflection performance superior to that of the antireflection film is exhibited. Become.

Further, an antireflection structure using a concave (hole) microstructure has been proposed as a shape having antireflection performance based on the same principle (see, for example, Patent Document 2).
JP 2002-267815 A Japanese Patent Application Laid-Open No. 2004-177806

However, in the antireflection structure described in Patent Document 1, although the light reflectance can be significantly reduced as described above, it is only necessary to touch the surface of the human hand or wipe the surface. The tip of the fine unevenness constituting the antireflection structure is broken, and the antireflection performance is easily impaired, and there is a problem that the scratch resistance is inferior.
On the other hand, in the concave microstructure described in the above-mentioned Patent Document 2, there is no problem with the scratch resistance, but when dirt such as sebum is clogged in the concave portion forming the hole shape, it is difficult to wipe off and the concave shape is sebum. When the structure is buried, there is a problem that the antireflection performance is remarkably lowered.

  The present invention has been made to solve the above-described problems in the conventional antireflection structure having a convex or concave microstructure formed at a pitch equal to or less than the wavelength of light. It has a structure that is excellent in adhesion and has a structure in which dirt such as sebum is difficult to enter into the space portion of the fine structure, and has such a structure with an antireflection structure that can exhibit excellent antireflection performance over a long period of time. It is another object of the present invention to provide an antireflection structure and a method for manufacturing the same, and further provide an automobile part having the antireflection structure, such as a meter front cover and a window glass.

  As a result of intensive studies to achieve the above object, the inventors of the present invention have formed a space portion of the fine structure, that is, a space portion around the fine protrusion in the convex fine structure, and a hole shape in the concave fine structure. The inventors have found that the above object can be achieved by filling nanoparticles, such as silica, into the openings of the fine recesses formed, and have completed the present invention.

  The present invention is based on the above findings, and the antireflection structure of the present invention includes innumerable conical fine protrusions having a substantially circular or polygonal bottom surface, and the bottom surface of the protrusion or a circle circumscribing the bottom surface. A space having a convex microstructure having a diameter D of 380 nm or less, which is shorter than the wavelength of visible light, is filled with nanoparticles smaller than the wavelength of visible light so that voids are formed between the particles, and the nanoparticles are filled. The effective refractive index of the portion is 1.10 to 1.35. Similarly, the antireflection structure of the present invention includes innumerable cone-shaped fine concave portions having substantially circular or polygonal openings, and Fill the space portion of the concave microstructure in which the opening D of the concave portion or the circle circumscribing the opening is similarly 380 nm or less with the same nano particles so that there are voids between the particles, and the nanoparticles Effective bending of the part filled with It is characterized in that the rate is 1.10 to 1.35.

  The antireflection structure of the present invention is characterized in that the antireflection structure of the present invention is provided on at least one surface of a transparent substrate. In the method of manufacturing the antireflection structure, the fine structure described above is used. Prepare a mold with a structure, and press this mold against the substrate in a state where it is heated more than the point for glass transfer of the transparent substrate, or active energy ray curing between the mold and the transparent substrate By irradiating active energy rays in the state of interposing a functional resin, the fine structure described above is formed on the surface of the transparent base material, and the particles are filled in the space portion of the fine structure. Yes.

  Furthermore, the automotive component of the present invention is characterized by including the antireflection structure.

  According to the present invention, the space portion of the fine structure smaller than the wavelength of visible light, that is, the space portion around the fine protrusion in the convex fine structure, and the inside of the opening of the fine concave portion forming a hole in the concave fine structure. Since the nanoparticle smaller than the wavelength of visible light is filled in a state having voids, the effective refractive index of the filled portion is in the range of 1.10 to 1.35. While ensuring the light reflection prevention function based on the nano-structure, the nano-particles are embedded in the space part of the microstructure and the surface can be flattened, preventing the deformation of the protrusions and the penetration of sebum into the recess openings As a result, the scratch resistance and stain resistance are improved, and the antireflection function can be maintained over a long period of time.

  In addition, since the antireflection structure of the present invention is provided with the antireflection structure on at least one surface thereof, the reflectance of light is greatly reduced to prevent reflection of outdoor scenery and the like. When applied to various parts including automobiles, for example, a meter front cover, a hoodless meter in which a hood for blocking external light is eliminated can be realized.

  Hereinafter, the antireflection structure of the present invention and the antireflection structure to which the antireflection structure is applied will be described in detail together with the manufacturing method thereof.

  As described above, the antireflection structure of the present invention includes innumerable cone-shaped microprojections having a substantially circular or polygonal bottom surface, or innumerable cone-shaped microrecesses having an approximately circular or polygonal opening. In a structure in which a space having a convex or concave microstructure is filled with particles smaller than the wavelength of visible light so that voids are formed between the particles and the effective refractive index is 1.10 to 1.35. In addition, the nanoparticles existing around the fine protrusions prevent deformation and breakage of the tip of the fine protrusions, and the presence of the nanoparticles inside the openings of the fine recesses leaves room for dirt such as sebum to enter. Accordingly, the antireflection performance is maintained for a long time.

  FIG. 1 is a schematic cross-sectional view showing an embodiment of the antireflection structure of the present invention having the above antireflection structure, and FIG. 1 (a) shows a convex fine structure having cone-shaped fine protrusions. FIG. 1 (b) shows a concave microstructure having a cone-shaped fine recess.

  In FIG. 1A, an antireflection structure 10 having a convex fine structure is formed on a transparent substrate 11 in a conical shape in this example, and has an infinite number of cones having a bottom diameter D and a height H. The fine protrusions 12 are arranged densely (for example, in a hexagonal close-packed state) at a pitch A (distance between the centers of the bottom surfaces), and the space portion of such a convex fine structure, that is, each cone-shaped fine protrusion 12 is filled with nanoparticles 13 smaller than the wavelength of visible light so as to form voids, and each of the cone-shaped fine protrusions 12 is filled with the nanoparticles 13 and the voids up to the tip. The surface of the antireflection structure 10 is a flat surface.

At this time, the bottom surface diameter D of the cone-shaped fine protrusions 12 needs to be 380 nm or less, thereby ensuring an antireflection function.
In addition, the pitch A expressed by the distance between the centers of the bottom surfaces is preferably 380 nm or less, thereby ensuring the antireflection function.

Further, it is desirable that the distance of the perpendicular line extending from the apex of the fine protrusion 12 to the bottom surface, that is, the height H of the fine protrusion 12 is in the range of 150 to 1500 nm.
That is, when the height of the fine protrusions 12 is less than 150 nm, there is a problem that sufficient antireflection properties cannot be exhibited. On the other hand, when it exceeds 1500 nm, moldability becomes difficult, but no further antireflection effect can be expected. This is due to the inconvenience that may occur.

  On the other hand, the antireflection structure 20 having a concave microstructure shown in FIG. 1B has a conical shape in this example on the surface of the transparent substrate 11, and has an infinite number of dimensions having an opening diameter D and a depth H. Are arranged densely (for example, in a hexagonal close-packed state) at a pitch A (distance between the centers of the openings), and the space portion of such a concave microstructure, that is, the fine recess The openings of 22 are filled with the nanoparticles 13 in the same manner, and each of the cone-shaped fine recesses 22 is filled with the nanoparticles 13 and the gaps up to the opening surface thereof. The surface is flat like the antireflection structural body 10 having the convex fine structure described above.

At this time, the opening diameter D of the cone-shaped fine concave portion 22 needs to be 380 nm or less, and this can ensure an antireflection function.
Further, the pitch A expressed by the distance between the centers of the openings is preferably 380 nm or less, thereby ensuring an antireflection function.

  Further, the distance from the lowest point of the bottom of the fine recess 22 to the opening surface, that is, the depth H of the fine recess 22 is 150 to 1500 nm as in the case of the antireflection structure 10 having the convex microstructure. It is desirable to be in the range.

  In addition, about the shape of the cone-shaped microprotrusion 12 and the recessed part 22 in the said reflection preventing structures 10 and 20, although all demonstrated cone shape, ie, the shape of a bottom part and an opening part is circular, these bottom part and opening were demonstrated. When the shape of the part is a polygon (projection and recess shape is a pyramid), the diameter D of the circle circumscribing the polygon needs to be set to the above-described value of 380 nm or less.

In addition, regarding the pitch in this case, it is desirable that the distance between the centroid points of adjacent polygons is the pitch A, and this is the above value.
Note that the positions of the center of gravity of the bottom surface and the opening that are polygons can be obtained by general linear algebra calculation, and the sum of the position vectors of each vertex of the polygon is divided by the number of vertices. That is, the position g of the center of gravity in the n-gon can be obtained by g = (Σa) / n.

Examples of the nanoparticles 13 filled in the space around the cone-shaped fine protrusion 12 and the inside of the opening of the cone-shaped fine recess 22 include silica, alumina, magnesium fluoride, calcium fluoride, resin particles, and the like. Transparent particles can be used, and a slurry in which these particles are dispersed in a suitable solvent together with a binder is applied onto a convex or concave microstructure to fill the space or inside of the openings, and between the particles. It can be fixed in a state where voids are formed.
And by making the effective refractive index of the filling part which consists of such a nanoparticle 13 and a space | gap into the range of 1.10-1.35, more desirably 1.10-1.25, the said filling is carried out. The light reflection preventing function based on the continuous change of the refractive index from the surface of the structure toward the thickness direction is exhibited between the portion and the portion other than the portion.

In addition, as said nanoparticle 13, it is desirable to use the thing provided with the magnitude | size of 1-50 nm, and the refractive index of the said particle itself in the range of 1.35-1.55.
That is, when the diameter of the nanoparticle 13 is less than 1 nm, the voids included are reduced, so that the light transmittance is lowered. When the diameter exceeds 50 nm, the fine recesses tend not to be filled. On the other hand, when the refractive index exceeds 1.55, it is difficult to make the effective refractive index of the filled portion composed of the nanoparticles 13 and the voids within the above range.

  Here, the above-mentioned effective refractive index is a unit volume in which the length of one side in the horizontal direction of the structure is larger than 780 nm, which is the upper limit wavelength of visible light, and the length in the vertical direction of the structure is 1 to 10 nm. Means the average value of the refractive index in the unit volume, and can be obtained by calculating the average of the refractive index distributed in the unit volume.

  In FIGS. 1 (a) and 1 (b), the antireflection structure having the conical fine protrusions 12 or the fine concave portions 22, that is, the side longitudinal sectional shape of the conical fine protrusions 12 or the concave portions 22 is linear. However, in the present invention, not only a straight line but also a curved line, that is, a side surface of the fine protrusion 12 or the fine concave portion 22 is a quadratic curved surface (a bottom surface or an opening is a polygon) or a cubic curved surface. In the present invention, a shape including a pyramid having a curved surface and a conical shape is referred to as a “conical shape”. I have decided.

That is, in the antireflection structure of the present invention, the convex fine structure will be described as an example. When the height of each cone-shaped fine protrusion 12 is H, the diameter of the bottom surface of the fine protrusion 12 (when the bottom surface is a polygon) Is the diameter of the circle circumscribing the polygon) as D, and as shown in FIG. 2, the base in the vertical cross section passing through the apex of the cone-shaped fine protrusion 12 is taken on the X axis, and the apex is taken on the Z axis, When the X coordinate value on the ridge line is represented by the following n-th order linear format (1) or (2), the order n in the linear format is preferably in the range of 1.1 to 5. A more desirable range is 1.5 to 4, and a further desirable range is 2 to 4.
X = (D / 2) × {1- (Z / H) ⁿ } (1)

  FIG. 3A shows a cone approximate shape represented by the above linear form (1) having a height H = 750 nm and a bottom diameter D = pitch A = 250 nm on both sides of a polymethyl methacrylate base material, and the order n is FIG. 6 shows the relationship between the order n and the average reflectance (wavelength: 380 to 780 nm) when protrusions having various different shapes are formed. As is apparent from this figure, the order n is 1.1. It can be seen that the reflectance can be lowered as compared with the conventional one in the range of ˜5.

In the above linear form (1), when the order n exceeds 1, the cross-sectional shape of the cone-shaped fine protrusion 12 becomes a bell shape with the side surface bulging outward as shown in FIG. When 1 is 1, the ridge shape of the protrusion is a straight line as shown in FIG. 4B, and a complete cone or pyramid shape is obtained. Further, when the order n is smaller than 1, as shown in FIG.
That is, the order n is 1.1 to 5, and the reflectance when the cone-shaped fine protrusion 12 forms a bell shape is smaller than that of a cone shape or a pyramid shape.

  Further, the base of the vertical cross section passing through the apex of the cone-shaped fine protrusion 12 is taken on the X axis, the apex is taken on the Z axis, and the Z coordinate value on the ridge line is expressed in the following n-order line format (2). You can also.

As shown in FIG. 5, FIG. 3 (b) is represented by the above linear form (2) with a distance H (depth) = 750 nm and an aperture diameter D = pitch A = 250 nm on both sides of the polymethyl methacrylate base material. This figure shows the relationship between the order n and the average reflectance (wavelength: 380 to 780 nm) in the case where the fine concave portions 22 having various shapes different in order n are formed. As is clear from the above, it is desirable that the order n in the line format be in the range of 1.1 to 5. A more desirable range is 1.5 to 4, and a further desirable range is 2 to 4.
Z = {H / (D / 2) ⁿ } × X ⁿ (2)

By providing the antireflection structure of the present invention on one side, preferably both sides, of a transparent substrate, an antireflection structure can be obtained, and such a structure can be used as a panel of various display devices, a show window, or an exhibition case. By applying to a transparent panel, etc., it is possible to reduce the reflection of external light and room lighting, effectively prevent reflection of reflected images, and improve the visibility of images, displays, and internal exhibits .
In addition, by applying various parts such as automobiles, such as glass for windows and roofs, meter front covers, headlamps, rear finishers, and films used for the forefront of display devices such as liquid crystals, the same anti-reflection is applied. An effect can be obtained.

  When the antireflection structure of the present invention is manufactured, a mold having a convex or concave microstructure composed of the cone-shaped fine protrusions 12 or the fine concave portions 22 as described above is prepared, and the mold is molded. After heating above the glass transition point of the transparent base material to be processed, the active energy ray-curable resin is applied by pressing against the base material (thermal nanoimprint method) or between the mold and the transparent base material. By irradiating active energy rays such as ultraviolet rays in the intervening state and curing the resin (UV nanoimprint method), the convex or concave microstructure as described above is formed on the surface of the transparent substrate. By applying a slurry in which particles such as silica and alumina are dispersed in a solvent together with a binder on these fine structures, the space portion Filling inside the opening, it can be fixed in a state having voids between the particles by drying.

Examples of the material for the transparent substrate include polyethylene, polypropylene, polyvinyl alcohol, polyvinylidene chloride, polyethylene terephthalate, polyvinyl chloride, polystyrene, ABS resin, AS resin, acrylic resin, polyamide, polyacetal, polybutylene terephthalate, and glass reinforced. Thermoplastic resins such as polyethylene terephthalate, polycarbonate, modified polyphenylene ether, polyphenylene sulfide, polyether ether ketone, liquid crystalline polymer, fluororesin, polyarate, polysulfone, polyethersulfone, polyamideimide, polyetherimide, thermoplastic polyimide, and phenol Resin, melamine resin, urea resin, epoxy resin, unsaturated polyester resin, alkyd resin, silicone resin, dia Rufutareto resin, polyamide bismaleimide, poly bisamide thermosetting resin triazole and the like, and can be used two or more kinds of these blended material.
In addition, as a transparent base material, it does not necessarily need to be colorless and transparent, and it can also color.

Examples of the active energy ray curable resin that starts and cures upon irradiation with ultraviolet rays, for example, include ultraviolet curable acrylic urethane resins, ultraviolet curable polyester acrylate resins, ultraviolet curable epoxy acrylate resins, and ultraviolet rays. A curable polyol acrylate resin, an ultraviolet curable epoxy resin, and the like can be used, and a polymerization initiator that generates radicals by irradiating active energy rays can be used as necessary. Such a curing agent can also be added.
The active energy rays used here typically include ultraviolet rays, X-rays, other electron beams, electromagnetic waves, and the like, and are not particularly limited, but from the viewpoint of safety and ease of work, Visible light and ultraviolet light are often used.

It is also possible to use an inorganic transparent material such as glass. In this case, the antireflection structure as described above is formed on the surface of the inorganic material by a sol-gel method using organosilane. A convex or concave microstructure can be formed on the surface of the substrate by the method or a method of pouring a molten inorganic transparent material into a mold having the antireflection structure of the present invention.
If necessary, after pouring a molten inorganic transparent material, a second mold having the same antireflection structure is pressed before cooling, or an inorganic transparent material with a mold pressed on both sides is used. By heating up to the softening point and applying pressure to transfer the shape, a convex or concave microstructure can be formed on both sides of the substrate.

  EXAMPLES Hereinafter, the present invention will be described more specifically based on examples. However, the present invention is not limited only to these examples.

Example 1
By a thermal nanoimprint method using a concave mold created with a commercially available electron beam drawing apparatus, the diameter D of the bottom surface forming a circle is 250 nm, the pitch A between the center points of the bottom surface is 250 nm on both sides of the polymethyl methacrylate, Convex shape having innumerable cone-shaped fine protrusions having a ridge line shape represented by a linear form (1) in which the distance (height) H of the perpendicular line dropped to the bottom surface is 750 nm and the order n is represented by the linear form (1) of the 1.1 order. The microstructure was transferred.

  Next, 54 parts by weight of silica particles having an average particle diameter of 13 nm and a refractive index of 1.46 on one surface of the polymethylmethacrylate base material having the convex microstructure and polymethylphenyl A slurry in which 6 parts by weight of silane is dispersed in 50 parts by weight of methanol is applied, irradiated with ultraviolet light, dried by heating to 100 ° C., and an effective refractive index consisting of the silica particles and voids is formed in the space portion of the microstructure. The portion of 1.20 was formed to produce an antireflection structure.

Note that the other surface of the obtained antireflection structure was left with a convex microstructure without applying silica particle slurry.
And as a result of measuring the reflectance when light injects from the surface of the side filled with silica particles, it was 0.53%.

  Moreover, when the pencil scratch test and dirt wiping test of the antireflection structure surface filled with silica particles were carried out according to the following procedure, good results were obtained in both cases. These results are shown in Table 1.

[Pencil scratch test]
Using the same equipment and conditions as in the pencil hardness test based on JIS K 5600-5-4, scratch the test surface with a 1 kg load using an HB pencil, ○ What was confirmed was evaluated as x.
[Dirt wiping test]
0.1 mL of squalane (refractive index of 1.45) is dropped onto the test surface, spread with Kimwipe, and then reciprocated 10 times using Microstar (manufactured by Teijin) to wipe off the oil stains. The reflectance was measured.

(Example 2)
Except that the convex mold obtained by inverting the concave mold used in Example 1 was used, the same operation as in Example 1 was repeated, and a circular opening was formed on the surface of polymethyl methacrylate. A concave microstructure having an infinite number of cone-shaped fine recesses of the same size and shape as the cone-shaped fine protrusions of Example 1 above, and similarly filling silica particles in the openings of the fine recesses As a result, a portion having an effective refractive index of 1.20 was formed, and a convex fine structure similar to that of Example 1 was transferred to the back surface side to produce an antireflection structure of this example.

And as a result of measuring the reflectance when light injects from the surface of the side filled with silica particles, it was 0.56%.
Further, when the pencil scratch test and the dirt wiping test on the antireflection structure surface filled with silica particles were conducted in the same manner, good results were obtained. These results are also shown in Table 1.

(Example 3)
The same operation as in Example 2 was repeated except that a convex mold having an order n of 3 in the linear form (1) and H of 250 nm was used, and the surface of the polymethyl methacrylate was innumerable. A concave microstructure having a cone-shaped concave portion is transferred, and a portion having an effective refractive index of 1.20 is formed by filling silica particles in the opening of the fine concave portion in the same manner, and the back side A convex fine structure similar to that in Example 1 was transferred to the antireflection structure of this example.

And when the reflectance when light was incident from the surface on the side filled with silica particles was measured, it was 0.46%.
Similarly, as a result of conducting a pencil scratch test and a dirt wiping test on the surface of the antireflection structure filled with silica particles, good results were obtained. These results are also shown in Table 1.

Example 4
By a thermal nanoimprint method using a convex mold created by a commercially available electron beam drawing apparatus, the diameter D of the circular opening is 250 nm and the pitch A between the center points of the opening is 250 nm on both sides of the polymethyl methacrylate. A concave-shaped micro-recess having an infinite number of cone-shaped fine concave portions having a ridge line shape in which the distance (depth) H from the opening surface to the bottom portion is 750 nm and the order n is represented by a quadratic linear form (2) The structure was transcribed.

Next, by applying the same silica particle slurry to one surface of the polymethylmethacrylate base material having the concave microstructure, the effective refraction composed of the silica particles and voids in the opening of the fine recess. A portion having a rate of 1.20 was formed to produce an antireflection structure.
And as a result of measuring the reflectance when light injects from the surface of the side filled with silica particles, it was 0.31%. The other surface of the obtained antireflection structure was left as a concave microstructure without applying silica particle slurry.

  Moreover, when the pencil scratch test and the dirt wiping test were carried out by the same method, good results were obtained in both cases. These results are also shown in Table 1.

(Comparative Example 1)
Using the same concave mold as in Example 1 except that the diameter D of the circular bottom surface is 500 nm and the pitch A between the center of the bottom surface is 500 nm, innumerable cone-shaped fine protrusions are formed on the surface of the polymethyl methacrylate substrate. A portion having an effective refractive index of 1.20 consisting of the silica particles and voids is formed in a space portion of the microstructure by transferring the convex microstructure provided and applying the silica particle slurry thereon. Then, the same convex fine structure as in Example 1 was transferred to the back surface side to obtain the antireflection structure of this example.

And when the reflectance when light was incident from the surface on the side filled with silica particles was measured, the reflectance was as high as 1.78%.
Similarly, when a pencil scratch test and a dirt wiping test were performed on the antireflection structure surface filled with silica particles, no increase in reflectivity was observed even after wiping oil and fat dirt, and good results were obtained in all cases. . These results are also shown in Table 1.

(Comparative Example 2)
Using a convex mold similar to that used in Example 2 above, the same method is repeated, and conical fine recesses having the same shape and dimensions as the surface side of Example 2 are formed on both sides of the polymethyl methacrylate base. An infinite number of concave microstructures were transferred, and the antireflection structure of this example was obtained without applying silica particle slurry.

And as a result of measuring the reflectance of the said antireflection structure, it was 0.10%.
In addition, as a result of performing the same pencil scratch test and dirt wiping test, in the pencil scratch test, the occurrence of scratches was confirmed, an increase in the reflectivity after wiping off the oil and grease dirt was observed, and the stain removability was inferior. confirmed. These results are also shown in Table 1.

(Comparative Example 3)
Using a convex mold similar to that used in Example 2 above, the same operation is repeated, and a number of cone-shaped fine recesses having the same shape and dimensions as the surface side of Example 2 are formed on the surface of polymethyl methacrylate. The concave microstructure prepared in the above was transferred, and 49.5 parts by weight of silica particles having an average particle diameter of 10 nm and a refractive index of 1.46 and 0.5 parts by weight of polymethylphenylsilane were mixed with 50 parts by weight of methanol. The slurry dispersed in the part is applied, irradiated with ultraviolet rays, heated to 100 ° C. and dried to form a portion having an effective refractive index of 1.45 consisting of silica particles and voids in the opening of the fine recess. Then, the same convex fine structure as in Example 1 was transferred to the back surface side to obtain the antireflection structure of this example.

And as a result of measuring the reflectance when light was incident from the surface on the side filled with silica particles of the obtained antireflection structure, it was as high as 3.87%.
On the other hand, when the pencil scratch test and the dirt wiping test on the antireflection structure surface filled with silica particles were conducted in the same manner, no increase in reflectivity was observed even after wiping oil and fat dirt, and good results were obtained. These results are also shown in Table 1.

  As apparent from Table 1, silica particles are filled with voids in a space of a convex or concave microstructure having a cone-shaped fine protrusion or recess having a predetermined size and shape, and the refractive index of the filling portion is set to a predetermined value. In Examples 1 to 4 which are set to be values, while having an excellent antireflection function and excellent in scratch resistance and dirt removal, in Comparative Example 1 in which the pitch of the cone-shaped fine recesses is large Although the anti-scratch property and dirt removal property are excellent, the anti-reflection performance is inferior, and in Comparative Example 2 in which silica particles are not filled, the anti-reflection performance is excellent, but the scratch resistance and stain removal property are poor. In Comparative Example 3 in which the effective refractive index of the silica-filled portion was high, it was found that the antireflection performance was inferior although it was excellent in scratch resistance and dirt removal.

FIG. 4 is a cross-sectional view showing a convex microstructure (a) having cone-shaped fine protrusions and a concave microstructure (b) having cone-shaped fine recesses as examples of the antireflection structure of the present invention. (A) It is explanatory drawing which represented the ridgeline shape of the cone-shaped fine processus | protrusion in the antireflection fine structure of this invention by the n-th line format (1). (B) It is explanatory drawing which represented the ridgeline shape of the cone-shaped fine processus | protrusion in the antireflection fine structure of this invention by the n-th line form (2). (A) It is a graph which shows the relationship between order n and an average reflectance, when the ridgeline shape of the cone-shaped microprotrusion which is not filled with microparticles | fine-particles is represented by nth-order line format (1). (B) It is a graph which shows the relationship between order n and an average reflectance, when the ridgeline shape of the cone-shaped fine recessed part which is not filled with microparticles | fine-particles is represented by nth-order line format (2). (A) (b) And (c) is the schematic which showed the relationship with the order n about the ridgeline shape change in the cone-shaped microprotrusion represented by the n-th line form (1). It is a perspective view which shows the example of a shape of the cone-shaped fine recessed part formed in the base-material surface.

Explanation of symbols

10 Antireflection structure (convex microstructure)
11 Transparent substrate 12 Cone-shaped fine protrusion 13 Particle (+ void)
20 Antireflection structure (concave microstructure)
22 Cone-shaped fine recess

Claims (15)

  An infinite number of cone-shaped microprojections having a substantially circular or polygonal bottom surface, and a space portion of a convex microstructure having a diameter D of 380 nm or less circumscribing the bottom surface or the bottom surface is smaller than the wavelength of visible light An antireflection structure, wherein nanoparticles are filled so as to form voids, and an effective refractive index of a portion filled with the nanoparticles is 1.10 to 1.35.   2. The antireflection structure according to claim 1, wherein a pitch A between centroids of the bottom surface is 380 nm or less.   The antireflection structure according to claim 1 or 2, wherein a distance H of a perpendicular line extending from the apex of the cone-shaped fine protrusion to the bottom surface is 150 nm to 1500 nm. The line form of the line that includes the apex of the cone-shaped fine protrusion and connects the apex and the base in the cross section perpendicular to the bottom is expressed by the following equation (1), and the order n is 1.1 to 5: The antireflection structure according to any one of claims 1 to 3.
X = (D / 2) × {1- (Z / H) ⁿ } (1) The line form of the line that includes the apex of the cone-shaped fine protrusion and connects the apex and the base in the cross section perpendicular to the bottom is expressed by the following equation (2), and the order n is 1.1 to 5: The antireflection structure according to any one of claims 1 to 3.
Z = {H / (D / 2) ⁿ } × X ⁿ (2)   A wavelength of visible light is provided in a space portion of a concave microstructure having an infinite number of cone-shaped fine concave portions having a substantially circular or polygonal opening, and a diameter D of a circle circumscribing the opening or the opening is 380 nm or less. An antireflection structure, wherein smaller nanoparticles are filled so as to form voids, and an effective refractive index of a portion filled with the nanoparticles is 1.10 to 1.35.   The antireflection structure according to claim 6, wherein the pitch A between the center of gravity of the openings is 380 nm or less.   The antireflection structure according to claim 6 or 7, wherein a distance H from the bottom of the cone-shaped fine concave portion to the opening surface is 150 nm to 1500 nm. The line form of the line connecting the bottom vertex and the opening end in the cross section perpendicular to the opening surface including the bottom of the cone-shaped fine recess is expressed by the following formula (1), and the order n is 1.1 to 5: The antireflection structure according to claim 6, wherein the antireflection structure is provided.
X = (D / 2) × {1- (Z / H) ⁿ } (1) The line form of the line connecting the bottom vertex and the opening end in the cross section perpendicular to the opening surface including the bottom of the cone-shaped fine recess is expressed by the following equation (2), and the order n is 1.1-5: The antireflection structure according to claim 6, wherein the antireflection structure is provided.
Z = {H / (D / 2) ⁿ } × X ⁿ (2)   11. The reflection according to claim 1, wherein the nanoparticles filled in the space portion have a primary particle diameter of 1 to 50 nm and a refractive index of 1.35 to 1.55. Prevention structure.   An antireflection structure comprising the antireflection structure according to any one of claims 1 to 11 on at least one surface of a transparent substrate.   A mold having the microstructure according to any one of claims 1 to 11 is pressed against the substrate in a state of being heated to a glass transfer point or more of the transparent substrate, and formed on the surface of the substrate. A method for producing an antireflection structure, wherein the space portion of the fine structure is filled with particles.   An active energy ray is irradiated in a state where an active energy ray-curable resin is interposed between a mold having the microstructure according to any one of claims 1 to 11 and a transparent base material, and the base material A method for producing an antireflection structure, wherein particles are filled in the space portion of the fine structure formed on the surface of the substrate.   An automotive part comprising the antireflection structure according to any one of claims 1 to 11.

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