Colored transparent diffractive optical element decorative molding

Abstract

To provide a diffraction optical element decorative molding capable of reverse side lighting, with which an appearance is obtained such that a mark such as a design is visible on the surface side when lighted from a visible reverse side and an optical diffraction grating pattern is invisible and not noticeable when not lighted.SOLUTION: This chromatic transparent molding includes: a flat face side having a light permeable tabular shape part, for emitting light and visual recognition; and an optical diffracting grating face, on the reverse side of which formed are a plurality of minute protrusions and recesses. A region of these minute protrusions and recesses is formed by a design, etc., and a portion of light that enters when lighted from the reverse side is guided and irregularly reflected, the minute protrusions and recesses region enabling the design to be visually recognized from the flat surface side that constitutes the outer face part of the molding body. When not lighted, it has an appearance such that the coloration of the diffraction grating part is not noticeable.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a molded product that can be illuminated from the back side, which is a diffractive optical element but does not appear rainbow-colored from the outside and does not appear to be a diffractive optical element at first glance. [Background technology]

[0002] A diffractive optical element (DOE) is an optical element that utilizes the diffraction phenomenon of light, and by irradiating a laser light source or the like onto a DOE on which an arbitrary optically designed fine pattern is formed, it is possible to shape the light beam into the designed pattern shape and project the shape onto a screen. As a conventional pattern irradiator that uses a DOE, for example, there is a projector that can irradiate a fixed pattern over a long distance, as described in Patent Document 1.

[0003] Other application examples include gesture sensors for 3D mapping and face recognition sensors, as disclosed in Patent Document 2.

[0004] The fine unevenness as a DOE is formed by a periodic, step-shaped fine structure as shown in, for example, Patent Document 3.

[0005] Diffractive optical elements (DOEs) have the same iridescent appearance as optical diffraction gratings. The iridescent appearance of optical diffraction gratings is known as structural color in the biomimetics field and is used in decorative and other aesthetic applications. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2015-96918 A [Patent Document 2] Patent No. 6048895 [Patent Document 3] JPWO2019 / 093146 publication Summary of the Invention [Problem to be solved by the invention]

[0007] However, when rainbow colors are to be avoided as an exterior decorative part, diffractive optical elements (DOEs) have a rainbow appearance due to the characteristics of optical diffraction gratings. Also, when a molded product has a single color, there is a problem that the rainbow colors shine and the appearance loses uniformity.

[0008] In view of the above problems, an object of the present invention is to provide a molded product that can be illuminated from the back side, which is a diffractive optical element molded product but does not appear rainbow-colored from the outside and does not look like a diffractive optical element at first glance. [Means for solving the problem]

[0009] A molded product according to one aspect of the present invention that solves the above-mentioned problems is made of a single material, has a light-transmitting plate-like portion, and has a first surface having a flat surface that is the visible side, and a second surface that is the back side that is illuminated by the light source and has a plurality of fine concave-convex portions formed thereon, and has a flat transparent portion arranged outside the partition of a shaped area having the fine concave-convex portions that become a diffractive optical element, and the transparent portion has a shape of a letter, figure, or symbol, and the letter, figure, or symbol may be displayed by the transparent portion when the back side is illuminated, or the boundary region of the diffractive optical element combining the fine concave-convex portions may be a curve, etc., and may display a letter, figure, symbol, mark, character, or design that changes appearance due to light scattering of the fine concave-convex portions when illuminated from the back side.

[0010] The diffractive optical element (DOE) molded product of the invention of claim 1 is a molded product having a plate-like portion with optical transparency, the molded product comprising a first surface having a flat surface, and a second surface on which the flat surface portion and a plurality of fine concave-convex portions are formed, the plurality of fine concave-convex portions of the second surface being configured with an optical diffraction grating structure, and the optical diffraction grating having the fine concave-convex portions has an area shape that is a character, a figure, a symbol, a picture, or a design, and the molded product has the characteristic that the optical diffraction grating can shape a light beam and can project characters, figures, symbols, pictures, or designs.

[0011] The diffractive optical element (DOE) molded product of the invention of claim 2 is the molded product according to claim 1, which is a colored transparent molded product, and when the molded product is viewed from the outside toward the first surface, the area shape of the optical diffraction grating is not visible, and when illuminated from the back surface, which is the second surface, the area shape of the optical diffraction grating is visible, making it an optical diffraction grating molded product that can be illuminated from the back surface.

[0012] The diffractive optical element (DOE) molded product of the invention of claim 3 is a molded product according to any one of claims 1 or 2, characterized in that there is a height difference between the flat surface portion of the second surface and the multiple fine concave and convex portions.

[0013] The diffractive optical element (DOE) molded product of the invention of claim 4 is a molded product characterized by being made of a resin having a colored transparency such that the interference color of the diffractive optical element (DOE) on the second surface side is not visible.

[0014] A diffractive optical element (DOE) molded article according to the invention of claim 5 is the molded article according to any one of claims 1 to 4, in which the transmitting portion has a transmitting property only for infrared light.

[0015] A diffractive optical element (DOE) molded article according to a sixth aspect of the present invention is the molded article according to any one of the first to fifth aspects, in which the light-transmitting plate-like portion is wedge-shaped.

[0016] The diffractive optical element (DOE) molded product of the invention of claim 7 is a molded product according to any one of claims 1 to 6, in which the pattern of the area shape of the optical diffraction grating and the shape of the pattern projected by light beam shaping are similar in shape.

[0017] The diffractive optical element (DOE) molded product of the invention of claim 8 is a molded product according to any one of claims 1 to 7, in which the shape of the pattern projected by the light beam shaping is used as an anti-counterfeiting determination. Effect of the Invention

[0018] As described above, according to the present invention, a colored transparent molded product has a light-transmitting plate-like portion, and is equipped with a flat surface side from which light is emitted and visible, and an optical diffraction grating surface on the back side of which a plurality of fine concave-convex portions are formed, and the area of ​​the fine concave-convex portions is formed with a pattern or the like, and when light is illuminated from the back side, a portion of the light that enters is guided and diffusely reflected, and the pattern area of ​​the fine concave-convex portions makes the pattern visible from the flat surface side which is the outer surface of the molded product body, and a molded product can be provided which is characterized by an appearance in which the color of the diffraction grating portion is not noticeable when not illuminated. [Brief description of the drawings]

[0019] [Figure 1] FIG. 2 is a perspective view showing an outline of a molded product according to an embodiment. [Diagram 2] FIG. 2 is a perspective view showing an outline of the function of the molded product according to the embodiment. [Diagram 3] FIG. 2 is a schematic diagram showing a projection function of a molded product according to an embodiment. [Figure 4] FIG. 2 is a schematic cross-sectional view of a molded article according to an embodiment. [Diagram 5] 4A to 4C are diagrams showing examples of the shape of a surface of a molded product according to an embodiment. [Figure 6] 6A to 6C are diagrams showing examples of height differences in fine concave-convex portions according to an embodiment; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention can be implemented in many different forms, and is not limited narrowly to the following embodiments and examples. Below, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values ​​shown in the embodiments are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In this specification and drawings, elements having substantially the same functions and configurations are denoted by the same reference numerals to avoid repeated explanations, and elements not directly related to the present invention are not illustrated.

[0021] FIG. 1 is a diagram showing an outline of a diffractive optical element (DOE) molded product (hereinafter referred to as "this molded product") 1 according to this embodiment.

[0022] More specifically, the molded product 1 is a molded product having a light-transmitting plate-like portion, and is provided with a first surface 11 having a flat surface 110, and a second surface 12 having a plurality of fine concave-convex portions 21 having a microstructure that will become the designed diffractive optical element (DOE) 2.

[0023] The molded product may be made of glass or resin as long as it is optically transparent. If there are no particular problems with the required heat resistance and durability, resin is selected as the material because it is more suitable for mass production.

[0024] In the present molded product 1, the resin, which is the main component, is preferably a polymeric material that has transparency and can be processed and molded into a desired shape. As described later, the resin that can be used in the present molded product 1 is not limited as long as it can obtain the desired refractive index, but examples thereof include thermoplastic resins such as polycarbonate, polyethylene, polypropylene, polyvinyl chloride, polyester, acrylic, cycloolefin polymer (COP), and cyclic olefin copolymer (COC), thermosetting resins such as phenolic resin, polyurethane, and thermosetting polyimide, and photocurable resins. In addition, the resin may be any of colorless transparent, colorless translucent, colored transparent, and colored translucent. The resin may be appropriately adjusted depending on the intended use of the radio wave reflecting resin composition and its molded article. The resin may be any of a thermoplastic resin and a thermosetting resin. Olefin resins, styrene resins, vinyl chloride resins, polyesters, polycarbonates, acrylonitrile-styrene copolymer resins (AS resins), polyacrylonitrile, butadiene resins, acrylonitrile-butadiene-styrene copolymer resins (ABS resins), acrylic resins, polyacetal, polyphenylene ether, phenolic resins, epoxy resins, melamine resins, urea resins, polyimides, polysulfides, polyurethanes, vinyl acetate resins, fluorine resins, aliphatic polyamides, synthetic rubbers, aromatic polyamides, polyvinyl alcohols, etc. can be used. Examples of olefin resins include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE), polypropylene, etc. Examples of polyesters include polyethylene terephthalate (PET), polytrimethylene terephthalate, polybutylene terephthalate, etc. Examples of aliphatic polyamides include nylon 6, nylon 66, etc. Examples of synthetic rubbers include ethylene-propylene-(non-conjugated diene) rubber, polybutadiene rubber, polyisoprene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, etc. Examples of aromatic polyamides include polymetaphenylene isophthalamide, polyparaphenylene terephthalamide, etc.

[0025] The molded part may be covered with dyes, pigments, coatings, vapor deposition, sputtering, etc., and may be colored as long as the transparency is adequately maintained.

[0026] The degree of coloring of the molded product is preferably deep enough that the color of the diffraction grating on the back side cannot be visually recognized, and may be an achromatic color such as black or dark gray, or a dark chromatic color such as dark blue, dark green, dark red, etc. The colored part may be either the inside or the outer surface of the molded product, as long as the effect of the present invention is exerted.

[0027] As shown in Fig. 2, in this molded product 1, the resin has optical transparency. Here, "optical transparency" refers to the property of transmitting at least a part of incident light. Although not limited thereto, specifically, in the plate-like portion of the resin, the transmittance of light (633 nm) in the flat portion and the fine concave-convex portion is preferably more than 10% and not more than 60%, and more preferably 20% or more and not more than 50%. 60% By making it lower, as shown in Fig. 2(a), it is possible to attenuate the interference light that returns to the first surface due to the diffraction interference caused by the minute unevenness of the DOE on the back side of the second surface when the light incident from the first surface is diffracted, making it possible to obtain the effect of preventing the observer from recognizing the rainbow-colored light diffraction grating of the DOE on the back side. Setting it to 0% is not preferable because the light scattered by the projection light source and the projection light are not transmitted.

[0028] Furthermore, the present molded product 1 has a first surface 11 on which a flat surface is formed as described above. As shown in Fig. 2(b), in the present molded product 1, light is incident from the second surface 12, propagates through the resin, at least a part of the light is scattered, and the light is emitted from the first surface 1, entering the observer's eye, making it possible to recognize the shape. Here, the "flat surface" refers to a surface that does not have any irregularities that would scatter light, unlike the convex parts of the second surface, and has a smoothness comparable to that of a mirror surface.

[0029] In this molded product 1, a flat transparent section separate from the fine unevenness 21 may be arranged, and the transparent section may have a shape of a character, figure, or symbol, and the character, figure, or symbol may be displayed by the transparent section when illuminated from the backside. Also, the shape of the section of the fine unevenness may be a character, figure, or symbol, and the character, figure, or symbol may be displayed by scattering light in the fine unevenness when illuminated from the backside.

[0030] As shown in FIG. 3, when a light source beam 5 is irradiated onto the DOE region, the light beam is shaped into a designed shape, and a pattern or the like can be projected onto the projection surface.

[0031] The diffractive optical element 22 can be designed, for example, by using the iterative Fourier transform method (IFTA). When the iterative Fourier transform method is used, the processing is performed on the premise that the projection plane 5 is far from the diffractive optical element 22, and the diffraction image on the projection plane can be treated as a Fraunhofer diffraction image. The multiple fine concave-convex portions in this molded product can adopt various shapes as long as they can have the above-mentioned functions, but it is preferable that they have a structure that is periodically arranged. However, it goes without saying that the geometric structure can be appropriately adjusted as long as the molded product can exhibit its functions.

[0032] Furthermore, in design theory, the shape of the DOE area and the projected image do not need to be the same shape; however, if the device to which it will be applied is assumed to be a switch, making the shape of the light-emitting part and the shape to be projected similar can be intended to enhance usability as an icon.

[0033] As shown in Figure 4, the fine unevenness of the DOE can be a binary type with two simple uneven levels, or a structure with an increased number of levels. Increasing the number of levels reduces the zero-order light and improves the light utilization efficiency. The structure of the fine unevenness is appropriately selected based on the desired specifications and the production process.

[0034] In this molded product 1, the size of the fine irregularities 21, or the pitch P, is preferably in the range of 0.1 μm or more and 10 μm or less, and more preferably 0.4 μm or more and 2 μm or less, so as to be able to sufficiently diffract and interfere with light.

[0035] Generally, methods that combine electron beam lithography and plasma etching, or manufacturing methods using X-ray or optical lithography are known for producing fine projections and recesses as DOEs. The formed fine projections and recesses can be used as a mold for transfer and mass production.

[0036] The area in the diffractive optical element area 2 may be designed as a CGH (Computer-Generated Hologram) or GCA (Grating Cell Array) in addition to a DOE with coherent light as the design light source. As the light source of the DOE, a laser, which is a coherent light, is easy to design. In the case of GCA, it is preferable that the light source is an LED. In the case of an LED, in addition to the effect of making the optical diffraction grating area stand out when back-illuminated, the light source for projection can be the same LED, so the number of parts of the product using the product of the present invention can be reduced. On the other hand, by separating the back-illumination light source and the light source for projection, it becomes possible to project a shaped beam of light onto the projection surface by the DOE when the back-illumination light source is OFF, i.e., when the DOE area such as a pattern is not emitting light.

[0037] In the present invention, an optical element that diffracts light, shapes a light source beam, and projects it, including CGH and GCA, is called a DOE.

[0038] The DOE has a smaller area than the projection, pattern, etc. In this case, the smallest cells can be periodically and repeatedly arranged on a plane like tiles.

[0039] In the DOE region 2, the area in the pattern that does not contribute to the DOE projection may be a diffraction grating or a fine uneven structure that scatters light. In this way, the number of patterns in the pattern shape of the light-emitting region on the second surface side is increased.

[0040] The projected pattern may be a dot, grid, matrix, or target mark in addition to a design. In this case, if the projection light source 42 is an infrared laser or LED, it is invisible to the human eye but can be recognized by a detector, so it can be used as an infrared sensor in addition to the effect of making the diffractive optical element shape appear on the molded product surface. For example, it can be used as a sensor for face recognition in combination with a button switch that can be illuminated from the back. The projection surface can also be a plate-shaped diffusion plate, and the shaped beam light projected through the diffusion plate can be viewed from the opposite side to the light source side.

[0041] The first surface 11 may have a curved surface or a textured surface as appropriate, so long as the shape of the pattern or the like can be recognized when illuminated from the back side or when projected.

[0042] As shown in Fig. 5, the plate-like portion of the molded product 1 does not necessarily have to be a parallel plate, and at least one of the first surface 11 and the second surface 12 may be a curved surface (Fig. 5(a)). Also, the cross section may be wedge-shaped in order to optically deflect the emitted light (Fig. 5(b)). The light beam can be deflected appropriately so that the light from the light source is not viewed directly.

[0043] Due to the degree of freedom in the shape of the first surface, it can be added to various parts, such as interior parts attached to mechanical devices such as cars, static parts such as switch panels, light guide plates, displays, emblems, etc. The present invention can also be achieved by disposing a liquid crystal light-emitting body on the back surface of this molded product, and there is an effect of not impairing the aesthetic appearance of the front surface side.

[0044] In addition, as shown in the schematic cross-sectional view of Figure 6, the height difference between the ridges of the convex parts of each section makes it possible to optically guide and scatter the light when illuminating the back side, making the outline of the shape more prominent, which is an advantageous shape for the effects of the invention. Also, by making the structure so that the fine shapes are not touched during production, it has the effect of protecting the fine shapes.

[0045] The side surface 23 with the height difference may be provided with an appropriate gradient angle. In the production process, when the molded product is made of resin, not only does this make it easier to release from the mold, but also has the effect of making the outline of the pattern stand out when illuminated from the back because the light scattering angle of the side surface is different from that of the DOE region.

[0046] When the molded product is colored, there is a drawback in that the light transmittance decreases, but by adjusting the height difference appropriately and making only the optical diffraction grating part thinner on the first surface side than the other surfaces to the extent that the optical diffraction grating does not appear rainbow-colored, it is possible to increase the light transmittance and increase the transmittance of the light source for backside illumination and the projection light source. When the molded product is colored, the theoretical formula for absorbance that depends on thickness (optical path length) makes it possible to theoretically predict the amount of light attenuation due to the difference in thickness inside and outside the fine concave-convex region, and the thickness of the molded product part in the DOE region and other regions can be appropriately designed.

[0047] Furthermore, the performance of the molded article 1 can be improved by providing a protective film, an anti-reflection film, or the like on the first surface and the second surface, as required.

[0048] The material of the plate-shaped portion of the molded product 1 may be glass or resin that transmits only specific wavelength ranges such as ultraviolet light and infrared light. A cover plate or cover glass for protecting the first surface from the outside world can be eliminated.

[0049] By imparting a unique design to the DOE projection pattern, the present invention can be used as a light guide plate that can be illuminated from the back side, and can also be used as an anti-counterfeiting element by irradiating it with a projection light source and determining the pattern.

[0050] As is clear from the above description, in this molded product, the fine unevenness serving as the optical diffraction grating of the diffractive optical element (DOE) can be made into the shape of letters, figures and symbols (hereinafter referred to as "letters, etc.") in this area, so that they can be displayed as letters, etc. when illuminated from the back side. On the other hand, it goes without saying that by providing this fine unevenness in a specified area, while leaving some flat areas without this fine unevenness in the shape of letters, etc., it becomes possible to express so-called blank letters, etc. EXAMPLES

[0051] The optical diffraction molded article according to the above embodiment was actually produced and its effects were confirmed.

[0052] First, a DOE for optical beam shaping optics was designed using software capable of pattern design using the iterative Fourier transform method. Based on the designed data, a resist pattern with fine projections and recesses was formed using optical lithography. A nickel mold was produced by transferring the fine projection and recess pattern from the resist pattern using electroforming to attach it to a mold for production using the injection molding method. The nickel mold was attached to the mold and transferred to resin by injection molding.

[0053] The specifications of the molded product were as follows: one side of a 0.8 mm thick black transparent plate with a pair of flat surfaces had multiple irregularities with a depth of 1 μm and a pitch of 1 μm. The area with the fine irregularities was repeatedly laid out with a minimum cell size of 0.6 mm square to create a pattern area of ​​25 mm square.

[0054] When the molded product was visually observed under normal fluorescent lighting, it appeared as a single black molded product surface, and the rainbow color caused by the optical diffraction grating of the diffractive optical element on the back side was not visible. It was also confirmed that when the back side was illuminated, the 25mm square area shape pattern of the diffractive optical element emitted light due to light scattering, and when the back side was not illuminated, the area disappeared. It was also confirmed that the flat area without fine irregularities did not scatter light, and that the outline pattern could be expressed by the optical diffraction grating area.

[0055] In addition, when a green laser pointer (semiconductor laser) was irradiated onto the optical diffraction grating region as a light source, the designed projection pattern was projected onto the screen.

[0056] As described above, it has been confirmed that the effects of the present invention can be fully achieved in actual resin molded products. [Industrial Applicability]

[0057] INDUSTRIAL APPLICABILITY The present invention has industrial applicability as a decorative molded product such as a panel, a switch, a light guide plate, etc., which serves as an optical diffraction optical element, and a manufacturing method thereof. [Explanation of symbols]

[0058] 1: Molded product 2: Diffractive optical element (DOE) area 3: Projected image 4:Light source 5: Ray of light 6: Projection surface (screen) 11: First Side 12: The second side 12a: Fine unevenness top surface 12b: Finely uneven bottom surface 21: Multiple fine uneven parts 23a:DOE area side part 23b:DOE area side part 41:Light source 1 42:Light source 2 51: External incident light 51a: External incident light (attenuated light) 51b: External incident light (attenuated diffracted light) 52a: Incident light for scattering 52b:Scattered display light 52c: Scattered attenuated light 55a: Projection light 55a: Projection shaped beam light 110: Back side flat surface

Claims

1. A molded article comprising a colored transparent plate-like member having a first surface having a flat surface, and a second surface on which a flat surface portion and a plurality of fine concave-convex portions are formed, the flat surface portion and the fine concave-convex portions having a transmittance of 633 nm light of more than 10% and not more than 60%, The plurality of minute projections and recesses on the second surface are configured to have an optical diffraction grating structure, In the molded product, the area shape of the diffractive optical element (DOE) having the fine concave-convex portion is a character, a figure, a symbol, a picture, or a pattern, There is a height difference between the flat surface portion of the second surface and the lower surfaces of the plurality of fine concave-convex portions, and A side portion of the second surface of the diffractive optical element (DOE) region is inclined with respect to a flat surface portion thereof, The molded product is characterized in that the diffractive optical element (DOE) enables light beam shaping and enables characters, figures, symbols, pictures, and patterns to be projected.

2. The molded article according to claim 1, When the molded article is viewed from the outside toward the first surface, A molded product in which the area shape of the diffractive optical element (DOE) is not visible, When illuminated from the second surface side, which is the back surface side, The area shape of the diffractive optical element (DOE) can be visually recognized; A diffractive optical element (DOE) molded product that can be illuminated from the back side.

3. The molded article according to any one of claims 1 to 2, A molded article made of a resin having a colored transparency such that the interference color of the diffractive optical element (DOE) on the second surface side is not visible.

4. The molded article according to any one of claims 1 to 3, A molded product in which the transparent portion transmits only infrared light.

5. The molded article according to any one of claims 1 to 4, The light-transmitting plate-like member is wedge-shaped.

6. The molded article according to any one of claims 1 to 5, A molded product in which the shape of the character, figure, symbol, picture or pattern in the area shape of the diffractive optical element (DOE) is similar to the shape of the character, figure, symbol, picture or pattern projected by the light beam shaping.

7. The molded article according to any one of claims 1 to 6, A molded product in which the shape of the projected characters, figures, symbols, designs, or patterns by the light beam shaping is used as an anti-counterfeiting determination.

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