JP2007187773A - Reflection prevention structure, reflection prevention molding and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflection prevention structure which can prevent reflection of a reflected image even when absolute quantity of incident light is large and which can assure excellent visibility and further to provide a reflection prevention molding provided with such structure and its manufacturing method. <P>SOLUTION: In minute periodic structure 2 provided with countless minute protrusions 2p (minute structure) arranged at a pitch shorter than a wavelength of a visible ray, coarse structure 3 having size longer than the wavelength of the visible ray is dispersed preferably at an area ratio of 1 to 10%. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention can exhibit an antireflection function of light (antireflection) and a function of scattering reflected light (antiglare), and can prevent reflection of an image even when the amount of incident light is large. Structure and such an antireflection structure, and as an antireflective panel, for example, antireflection which can be suitably used for vehicles such as automobiles, various meters such as ships and aircraft, display devices, etc. The present invention relates to a molded body, and further to a method for producing the antireflection molded body.

  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 meter front cover is fitted in the front of a display unit that houses various instruments such as a speedometer and a fuel gauge in a driver's seat of an automobile. The front window and side windows are passed through this cover. When the scenery outside the vehicle is reflected, various displays on the display unit may be difficult to see. Therefore, a meter hood is arranged above the display to block outside light.

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 a fine structure has been proposed (for example, see Patent Document 1).
JP 2002-267815 A

In Patent Document 1, the refractive index of light is changed in the thickness direction by forming innumerable fine irregularities made of a transparent material on the surface of the transparent molded article at a pitch equal to or less than the wavelength of light. An antireflection structure is described.
That is, for example, by forming innumerable fine irregularities having a waveform or a triangle on the surface, the proportion of the transparent material existing on the outermost surface of the irregularities is almost as close to 0%, and substantially air While the refractive index becomes equal to the refractive index, the ratio of air to the bottom of the unevenness is almost as close to 0% as the refractive index of the molded product. As a result of the refractive index corresponding to the area, 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. Based on the same principle as that of a multilayer antireflection film composed of a plurality of thin films having different rates (the refractive index changes stepwise), it has antireflection performance superior to that of the antireflection film.

  However, in the antireflection structure described in Patent Document 1, although the reflectance is significantly reduced, the reflection of light cannot be completely eliminated. For example, when the absolute amount of incident light is large such as sunlight. Since the amount of reflection increases accordingly, the reflection of the image cannot be completely prevented, and the reflected image such as the contour is partially seen, and the visibility of the display and video is impaired. was there.

  The present invention has been made to solve the above-mentioned problems in the conventional antireflection structure comprising fine irregularities formed at a pitch equal to or less than the wavelength of light, and the object is to have a large absolute amount of incident light. Even in this case, reflection of the reflected image can be prevented, and together with the antireflection structure capable of ensuring excellent visibility, the antireflection molded body having such a structure and its manufacturing method, An object of the present invention is to provide an automotive part having the antireflection structure, such as a meter front cover and a window glass.

  As a result of intensive studies in order to achieve the above object, the present inventors have obtained an antireflection structure (anti-reflection) composed of a fine structure smaller than the wavelength of light as described above, and a coarseness larger than the wavelength of light. It has been found that the above-mentioned object can be achieved by mixing the reflection light scattering structure (anti-glare) with the structure, and the present invention has been completed.

  The present invention is based on the above knowledge, and the antireflection structure of the present invention has a wavelength of visible light in a fine periodic structure having an infinite number of fine structures arranged at a pitch shorter than the wavelength of visible light. The coarse structure with longer dimensions is preferably interspersed with an area ratio of 1 to 10%.

  The antireflection molded body of the present invention is characterized in that the antireflection structure of the present invention is provided on at least one surface of the molded body, and in the method of manufacturing the antireflection molded body, Prepare a mold with one of them, and press either of the mold and the base material in a heated state, or place an active energy ray-curable resin between the mold and the base material. The antireflection structure of the present invention described above is formed on the surface of the base material by irradiating active energy rays in the state of being made.

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

  According to the present invention, a fine structure composed of innumerable convex portions or concave portions is arranged at a pitch shorter than the wavelength of visible light, and a dimension longer than the wavelength of visible light is provided in a fine periodic structure having an anti-reflection function. In addition, since the coarse structure having the anti-glare function is scattered, an excellent antireflection function is exhibited by the fine periodic structure, while there is scattered light from the coarse structure scattered in places. Since the formation of the reflected image is hindered, the reflection of the reflected image can be greatly reduced even when the amount of incident light is large.

  In addition, since the antireflection molded body of the present invention is provided with the antireflection structure on the surface thereof, it is possible to almost prevent the reflection image from being reflected even when the amount of incident light is extremely large. Thus, it can be applied to various parts including automobiles. For example, when applied to a meter front cover, it is possible to realize a hoodless meter in which a hood for blocking outside light is eliminated.

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

  1 and 2 show an example of an embodiment of the antireflection structure of the present invention, and the antireflection structure 1 of the present invention is shown in FIG. 1 (a) and FIG. In this embodiment, as shown in FIG. 3, in this example, a fine period is formed by arranging innumerable fine protrusions 2p having a pyramid shape (regular quadrangular pyramid) at a pitch A shorter than the wavelength of visible light. A pyramidal coarse structure 3 (antiglare structure) having a square bottom surface having a diagonal line having a length B longer than the wavelength of visible light is included in the fine periodic structure 2. It has an irregularly scattered structure.

Here, the coarse structure 3 may be a convex shape protruding on the surface as shown in FIG. 2 (a) or a concave shape recessed as shown in FIG. 2 (b).
In consideration of the ease of manufacturing a mold for forming such an antireflection structure and the cost, the coarse structure 3 has a convex shape as shown in FIG. It is desirable that the height be substantially the same as the height of the fine protrusions 2p constituting the periodic structure 2.

  The pitch A between the adjacent fine protrusions 2p is preferably greater than 50 nm and less than 380 nm. That is, it is extremely difficult to industrially produce a fine structure in which the pitch A is 50 nm or less. On the other hand, when the pitch A is 380 nm or more, which is the shortest wavelength of visible light, the desired antireflection effect is obtained. By not being able to.

In FIGS. 1A and 1B, the shape of the bottom surface of the fine convex portion 2p is illustrated as a square, but in the present invention, the shape of the fine convex portion 2p is limited to a regular square pyramid. However, various shapes such as a cone and a polygonal pyramid can be adopted, but from the viewpoint of reducing the reflectance by reducing the plane portion as much as possible, the bottom surfaces of the adjacent fine convex portions 2p are not separated from each other. It is desirable that they are placed in contact.
From such a viewpoint, the bottom surface shape of the fine convex portion 2p is typically a circular shape having no anisotropy in shape, or a regular triangle, square, or regular hexagon that can be laid without a gap on a plane. desirable.

  On the other hand, regarding the size of the coarse structure 3 scattered in the fine periodic structure 2, if the bottom shape is a square as shown in FIGS. The diameter B (in this case, corresponding to the length of the diagonal line) is preferably more than 780 nm and less than 10 μm. That is, when the circumscribed circle diameter (diagonal length) B is 780 nm or less, which is the longest wavelength of visible light, it may not be possible to diffract all visible light by diffracting only visible light at a specific wavelength. If the thickness is 10 μm or more, the presence of such a coarse structure 3 may be visible to the human eye.

Further, the shape of the bottom surface of the coarse structure 3 is not limited to the square as described above, and various shapes such as a circle and a polygon can be adopted.
The size of the coarse structure 3 at this time is such that the diameter B in the case of a circle and the diameter B of the circumscribed circle in the case of a polygon are within the above range. When the bottom shape is a rectangle, a regular hexagon, a regular octagon, or the like, the diameter of the circumscribed circle matches the length of the diagonal line.

FIGS. 3A to 3D are plan views showing examples of arrangement patterns of the coarse structures 3 in the fine periodic structure 2 of the antireflection structure 1 of the present invention. Coarse structures 3 (anti-glare structures) having bottom shapes such as squares, rectangles, and circles are randomly arranged in a fine periodic structure 2 (anti-reflection structure) composed of fine convex portions 2p.
Here, the total area ratio of the coarse structure 3 occupying the entire surface of the antireflection structure is desirably in the range of 1 to 10%. That is, when the occupied area ratio of the coarse structure 3 is less than 1%, the scattered light from the coarse structure 3 cannot be sufficiently obtained, and the reflected image cannot be prevented from being formed. When there is a large amount of reflection, it may not be possible to sufficiently reduce the reflection of the reflected image. Conversely, if it exceeds 10%, the scattered light from the coarse structure 3 increases and the surface of the antireflection structure 1 becomes cloudy. This is due to the tendency to become visible.

In FIG. 3, the shape of the fine protrusions 2p constituting the fine periodic structure 2 is all a regular square pyramid. However, as described above, the shape of the fine protrusions 2p is not limited. Needless to say, the bottom shape of the structure 3 is not limited to a rectangle or a circle.
Further, in the above description, the fine periodic structure 2 composed of the fine convex portions 2p is exemplified, but it goes without saying that the fine periodic structure 2 may be composed of fine concave portions.

By molding the antireflection structure of the present invention on a substrate, typically a transparent substrate on one side, preferably on both sides, an antireflection molded body can be obtained. Such a molded body can be used for various display devices. By applying to transparent panels such as panels, show windows, and display cases, reflection of external light and room lighting is reduced, and reflection of reflected images is effectively prevented. Visibility can be improved.
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.

  In the antireflection molded body of the present invention, the above-mentioned antireflection structure of the present invention can be formed on one side thereof, while a multilayer antireflection film can be formed on the other side, thereby forming the antireflection structure on both sides. Compared to the above, although the antireflection function is slightly inferior, the weak point of the antireflection structure, which is easily damaged, can be covered by directing the multilayer antireflection film to the outer surface side.

  When manufacturing the antireflection molded body of the present invention, a mold having a fine periodic structure 2 composed of innumerable fine protrusions 2p as described above and a coarse structure 3 scattered therein is prepared. The active energy can be obtained by relatively pressing both of the mold and the base material in a heated state or by interposing an active energy ray-curable resin between the mold and the base material. The antireflection structure 1 as described above can be formed on the surface of the substrate by irradiating a line and curing the resin.

  As the material for the substrate, typically, a transparent material is desirable. 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, polyphenylene sulfide, polyether ether ketone, liquid crystalline polymer, fluororesin, polyarate, polysulfone, polyethersulfone, polyamideimide, polyetherimide, Thermoplastic resins such as thermoplastic polyimide, phenolic resin, melamine resin, urea resin, epoxy resin, unsaturated polyester resin, Rukido resins, silicone resins, can be used a diallyl phthalate resin, polyamide bismaleimide, poly bisamide thermosetting resin triazole and the like, and two or more of these blended material.

Examples of the active energy ray curable resin that starts and cures upon irradiation with ultraviolet rays, for example, include ultraviolet curable acrylic urethane meter resins, ultraviolet curable polyester acrylate resins, ultraviolet curable epoxy acrylate resins, and ultraviolet curable resins. Type polyol acrylate resin, UV curable epoxy resin, etc., and if necessary, a polymerization initiator that generates radicals by irradiating active energy rays can be used. Various curing agents 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, a method of forming the antireflection structure as described above by cutting the glass surface with an electron beam or the like, or the reflection of the present invention. The antireflection structure can be formed on the surface of the substrate by a method in which a molten inorganic transparent material is poured into a mold having the prevention structure.
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 to the softening point and applying a pressure to transfer the shape, a fine structure can be formed on both sides of the substrate.

  Below, based on an Example, this invention is demonstrated further more concretely. In addition, this invention is not limited only to these Examples.

Example 1
Using a mold created with a commercially available electron beam drawing apparatus, this mold was heated to 150 ° C., and then pressed against both sides of the polymethylmethacrylate substrate at a pressure of 10 MPa for 1 hour, and then up to 70 ° C. or less. By cooling, the diameter of the circumscribed circle is included in the fine periodic structure 2 in which the fine convex portions 2p having a bottom surface diameter of 350 nm and a height of 900 nm are arranged in a hexagonal close-packed state (pitch A = 350 nm). Anti-reflection with both sides of anti-reflection structure 1 in which B (diagonal length) is 1000 nm and coarse structure 3 having a square pyramid shape with a height of 900 nm is arranged randomly with an occupied area ratio of 2% A shaped body was formed.

(Example 2)
Using a mold created with the same electron beam drawing apparatus, the same operation as in Example 1 was repeated, and a conical shape having a bottom diameter of 250 nm and a height of 750 nm was formed on both sides of the polymethyl methacrylate base. In the fine periodic structure 2 in which the fine protrusions 2p formed are arranged in a hexagonal close-packed state (pitch A = 250 nm), a coarse structure 3 having a conical shape having a diameter B of 1000 nm and a height of 750 nm is also provided. The antireflection structure 1 randomly arranged with an occupied area ratio of% was molded.

(Example 3)
By using a mold created by the same electron beam drawing apparatus and repeating the same operation as in Example 1, a conical shape having a bottom diameter of 250 nm and a height of 500 nm is formed on both sides of the polymethyl methacrylate base. In the fine periodic structure 2 in which the fine convex portions 2p forming the hexagonal fine structure are arranged in a hexagonal close-packed state, the coarse structure 3 that forms a concave dome shape with a diameter B of 1000 nm and a depth of 500 nm is random with an occupation area ratio of 5% The antireflection structure 1 arranged in the above was molded.

Example 4
A mold made with the same electron beam drawing apparatus is brought into close contact with a polycarbonate substrate coated with an ultraviolet curable acrylic resin by spin coating on the surface, and irradiated with ultraviolet rays in this state. A fine periodic structure 2 in which fine convex portions 2p having a diameter of 250 nm and a height of 500 nm in a conical shape are arranged in a hexagonal close-packed state was molded.
Next, by irradiating the laser beam from above, the coarse structure 3 having an indented concave shape with a bottom diameter of 200 nm and a depth of 500 nm is randomly included in the fine periodic structure 2 with an occupied area ratio of 10%. The arranged antireflection structure 1 was molded.

(Example 5)
Using a mold created with the same electron beam drawing apparatus, the same operation as in Example 1 was repeated, and a conical shape with a bottom diameter of 250 nm and a height of 500 nm was formed on the back side of the polymethylmethacrylate substrate. In the fine periodic structure 2 in which the fine convex portions 2p forming a hexagonal close-packed state are arranged, a coarse structure 3 having a concave conical shape with a diameter B of 1000 nm and a depth of 750 nm is randomly distributed with an occupation ratio of 3%. The antireflection structure 1 arranged in the above was molded.
Next, on the surface side of the base material, from the side close to the base material, a first layer having a film thickness of 181.9 nm and a refractive index of 1.38, a film thickness of 12.8 nm and a refractive index of 2 A second layer having a thickness of 34.9 nm and a refractive index of 1.45; a fourth layer having a thickness of 37.4 nm and a refractive index of 2.5; A fifth layer having a refractive index of 22.3 nm and a refractive index of 1.45, a sixth layer having a thickness of 28.6 nm and a refractive index of 2.5, and a refractive index of 97.1 nm and a refractive index of A multilayer antireflection film consisting of 7 layers was formed by sequentially depositing 1.38 seventh layers.

(Example 6)
By using a mold created by the same electron beam drawing apparatus and repeating the same operation as in Example 1, the bottom diameter is 350 nm and the top diameter is 50 nm on both sides of the polymethyl methacrylate substrate. In the fine periodic structure 2 in which the fine convex portions 2p having a truncated cone shape of 900 nm are arranged in a hexagonal close-packed state (pitch A = 350 nm), the circumscribed circle diameter B (diagonal length) is 1000 nm and high An antireflection structure 1 in which a coarse structure 3 having a square pyramid shape of 500 nm is randomly arranged with an occupation area ratio of 2% was molded.

(Comparative Example 1)
Using a mold created with the same electron beam drawing apparatus, the same operation as in Example 1 was repeated, and a conical shape having a bottom diameter of 250 nm and a height of 750 nm was formed on both sides of the polymethyl methacrylate base. The fine periodic structure 2 in which the fine convex portions 2p formed are arranged in a hexagonal close-packed state was molded.
And the same evaluation test was implemented about the reflection preventing molded object which consists only of the said fine periodic structure.

(Comparative Example 2)
Using a mold created by the same electron beam drawing apparatus, the same operation as in Example 1 was repeated, and a conical shape having a bottom diameter of 250 nm and a height of 500 nm was formed on both sides of the polymethyl methacrylate base. In the fine periodic structure 2 in which the fine protrusions 2p formed are arranged in a hexagonal close-packed state, a coarse structure 3 having a conical shape with a diameter B of 600 nm and a height of 500 nm is randomly arranged with an occupation area ratio of 30%. An antireflection structure was formed.
And the same evaluation test was done about the obtained antireflection molded object.

[Evaluation test method]
About each anti-reflective molded object obtained by the said Example and comparative example, it evaluated about the average reflectance, white turbidity, and reflection by the following points.
The results are shown in Table 1 together with the specifications of each antireflection molded body.

(1) Average reflectivity Using a variable angle spectrophotometer (manufactured by Otsuka Electronics Co., Ltd.), the reflectivity of each antireflection molded body at a light incident angle of 0 degrees and a measurement angle of 0 degrees is set every 10 nm within a wavelength range of 380 to 780 nm. The average value was taken as the average reflectance.

(2) Measurement of white turbidity Using a haze meter (Nippon Denshoku Co., Ltd. haze meter "NDH2000"), the white turbidity of each antireflection molded product was measured according to JIS K7361.

(3) Reflection test An angle of 60 degrees is formed with respect to the normal line standing at the center of each antireflection molded body, and the center of a 20 W fluorescent lamp is placed at a distance of 100 cm from the center of the molded body. When the surface of the anti-reflective molded body is specularly reflected from the fluorescent lamp and observed at a position where the distance from the center of the molded body is 100 cm, an image of the fluorescent lamp is reflected. “X” was evaluated as “◯” when the fluorescent lamp outline could not be confirmed at all.

  As a result, in the molded article of Comparative Example 1 having an antireflection structure without a coarse structure, reflection of a reflected image by a fluorescent lamp is observed, and the bottom diameter of the coarse structure is smaller than the maximum wavelength of visible light. Reflection of Examples 1 to 6 having a coarse structure of a predetermined size in the fine periodic structure 2 having a predetermined shape and dimensions, while reflection of a fluorescent lamp was also observed in the molded body by In the prevention molded body, it was confirmed that the average reflectance and haze value (white turbidity) were low, and no reflection image was observed.

(A) It is a top view which shows an example of embodiment in the reflection preventing structure of this invention. (B) It is an enlarged view of the antireflection structure shown in FIG. (A) And (b) is each longitudinal cross-sectional view of the antireflection structure shown to Fig.1 (a). (A)-(d) is each a top view which shows the example of the arrangement pattern of the coarse structure in the reflection preventing structure of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antireflection structure 2 Fine periodic structure 2p Fine convex part (fine structure)
3 Coarse structure

Claims (14)

  Antireflection structure characterized in that coarse structures having dimensions longer than the wavelength of visible light are scattered in a fine periodic structure in which innumerable fine structures are arranged at a pitch shorter than the wavelength of visible light. . The shape of the bottom surface of the coarse structure is circular or polygonal, and the pitch between the fine protrusions in the fine periodic structure is A, the diameter of the circle that forms the bottom surface of the coarse structure or the polygonal circumscribed circle that forms the bottom surface Is B,
50 nm <A <380 nm
780 nm <B <10 μm
The antireflection structure according to claim 1, wherein   The antireflection structure according to claim 1 or 2, wherein an area ratio of the coarse structure is 1 to 10%.   The antireflection structure according to any one of claims 1 to 3, wherein the coarse structure has a convex shape or a concave shape.   The antireflection structure according to any one of claims 1 to 4, wherein the fine convex portion of the fine periodic structure is a cone or a polygonal pyramid.   The antireflection structure according to any one of claims 1 to 5, wherein bottom surfaces of adjacent fine convex portions in the fine periodic structure are arranged in contact with each other.   The antireflection structure according to any one of claims 1 to 6, wherein the coarse structure has a convex shape and has substantially the same height as the fine convex portion in the fine periodic structure.   The antireflection structure according to claim 1, wherein coarse structures are randomly scattered in the fine periodic structure.   An antireflection molded article comprising the antireflection structure according to any one of claims 1 to 8 on at least one surface.   The antireflection molded body according to claim 9, which is transparent.   11. The antireflection molded body according to claim 10, further comprising a multilayer antireflection film on the other surface.   A molding die provided with the antireflection structure according to any one of claims 1 to 8 and at least one of the base material is relatively pressed against each other, and the antireflection structure is applied to the surface of the base material. A process for producing an antireflection molded body, characterized in that   The substrate surface is irradiated with active energy rays in a state where an active energy ray-curable resin is interposed between the mold having the antireflection structure according to any one of claims 1 to 8 and the substrate. A method for producing an antireflection molded body, wherein the antireflection structure is formed on a substrate.   An automobile part comprising the antireflection structure according to any one of claims 1 to 8.

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