Wavelength conversion member and illumination device employing same

Abstract

The present invention has: a flat plate-shaped phosphor part including a phosphor that is excited by excitation light and emits fluorescence; and a plurality of nanoantennas that are provided so as to form a grid-shaped array pattern in each of a plurality of regions on one surface in a plan view seen from a direction perpendicular to the surface of the phosphor part, and that are constituted from a metal material or a dielectric material, the array pattern of the plurality of nanoantennas in one region among the plurality of regions being a pattern obtained by rotating the array pattern of the plurality of nanoantennas in another region about an axis perpendicular to a single plane.

Description

Wavelength conversion member and lighting device using same

[0001] The present invention relates to a wavelength conversion member and an illumination device using the same.

[0002] A device that collimates emitted light using a nano-sized antenna (hereinafter referred to as a nanoantenna) has been disclosed. For example, Patent Document 1 discloses a lighting device that includes a light source that emits blue light, a phosphor layer that emits fluorescence when excited by the light emitted from the light source, and a plurality of nanoantennas arranged in a lattice pattern on the upper surface of the phosphor layer.

[0003] JP 2018-13688 A

[0004] For example, when light emitted from a lighting device such as that described in Patent Document 1 is irradiated onto a screen located at a distance from the lighting device, fluorescent components in some wavelength ranges of the fluorescent light emitted from the phosphor layer are strongly enhanced by the action of the nanoantenna, resulting in a problem of color unevenness in the light irradiated onto the screen.

[0005] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a wavelength conversion device and a lighting device that can suppress color unevenness in light emitted through a nanoantenna.

[0006] The wavelength conversion device according to the present invention comprises a flat phosphor section including a phosphor that emits fluorescence when excited by excitation light, and a plurality of nanoantennas made of a metal material or a dielectric material, which are arranged to form a lattice-like arrangement pattern in each of a plurality of regions on one surface of the phosphor section when viewed in a plan view perpendicular to the one surface, and which are characterized in that the arrangement pattern of the plurality of nanoantennas in one of the plurality of regions is a pattern obtained by rotating the arrangement pattern of the plurality of nanoantennas in the other regions around an axis perpendicular to the one surface.

[0007] FIG. 1 is a top view of an illumination device according to Example 1. FIG. 2 is a cross-sectional view of an illumination device according to Example 1. FIG. 3 is a diagram schematically showing a state when light emitted from an illumination device according to Example 1 is irradiated onto a screen. FIG. 4 is a graph showing various diffraction lines when the emission angle of fluorescence emitted from a phosphor section in an illumination device according to Example 1 is changed. FIG. 5 is a graph showing luminosity sensitivity to light in the wavelength range of visible light. FIG. 6 is a top view of an illumination device according to a modified example of Example 1. FIG. 7 is a cross-sectional view of an illumination device according to Example 2. FIG. 8 is a graph showing the reflectance of a dielectric multilayer film for visible light in an illumination device according to Example 2. FIG. 9 is a graph showing the spectrum of excitation light of a phosphor in a phosphor section.

[0008] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same components are designated by the same reference numerals, and the description of the same components will be omitted.

[0009] [Lighting Device of Example 1] The configuration of a lighting device 100 according to Example 1 will be described with reference to Figures 1 and 2. Figure 1 is a top view of the lighting device 100 according to Example 1. Figure 2 is a cross-sectional view of the lighting device 100 taken along line 2-2 in Figure 1. Note that the left-right direction in Figure 1 is the width direction of the lighting device 100, and the up-down direction in Figure 2 is the height direction of the lighting device 100.

[0010] The lighting device 100 is configured to include a mounting substrate 11, a light-emitting element 12 including a light-emitting layer provided on the mounting substrate 11, and a wavelength conversion device 13 provided on the light-emitting element 12 and including a phosphor portion that receives light emitted from the light-emitting layer and emits fluorescence.

[0011] [Mounting Substrate] First, the mounting substrate 11 will be described. The mounting substrate 11 is a flat substrate having a rectangular upper surface. The mounting substrate 11 is made of, for example, aluminum nitride (AlN) or aluminum oxide (Al ２ O ３ The light emitting element 12 is made of a material having high thermal conductivity and electrical insulation properties, such as SiO 2 , which can efficiently release heat generated when the light emitting element 12 is driven.

[0012] [Light Emitting Element] Next, a description will be given of the configuration of the light emitting element 12 serving as a light source. The light emitting element 12 is provided on the upper surface of the mounting substrate 11, and is a light emitting diode (LED) having a rectangular upper surface.

[0013] The light emitting element 12 includes a semiconductor structure layer 15 having a light emitting layer, a support substrate 16 disposed on the upper surface of the semiconductor structure layer 15, and a p-electrode 17 and an n-electrode 18 disposed on the lower surface of the semiconductor structure layer 15 and bonded to the mounting substrate 11. In other words, the light emitting element 12 is flip-chip mounted on the mounting substrate 11.

[0014] The semiconductor structure layer 15 is a semiconductor laminate including an n-type semiconductor layer, a light-emitting layer, and a p-type semiconductor layer (none of which are shown), each of which is made primarily of gallium nitride (GaN). When the light-emitting element 12 is driven, the light-emitting layer of the semiconductor structure layer 15 emits blue light having a peak wavelength of 450 nm.

[0015] The support substrate 16 is a flat substrate having a rectangular upper surface. The support substrate 16 is made of, for example, sapphire (Al ２ O ３ The support substrate 16 is made of a material that is translucent to the blue light emitted from the light-emitting layer of the semiconductor structure layer 15, such as GaN or the like. The upper surface of the support substrate 16 is the light-emitting surface through which the blue light emitted from the light-emitting layer of the semiconductor structure layer 15 is emitted from the light-emitting element 12.

[0016] The p-electrode 17 is an electrode electrically connected to the p-type semiconductor layer of the semiconductor structure layer 15. The p-electrode 17 is joined to a p-side wiring (not shown) formed on the upper surface of the mounting substrate 11 via a conductive joining member (not shown).

[0017] The n-electrode 18 is an electrode electrically connected to the n-type semiconductor layer via a through electrode (not shown) that vertically penetrates the light-emitting layer and p-type semiconductor layer of the semiconductor structure layer 15 and has its side surfaces covered with an insulator. In other words, the n-electrode 18 is electrically connected only to the n-type semiconductor layer and is insulated from the light-emitting layer and p-type semiconductor layer. The n-electrode 18 is bonded to an n-side wiring (not shown) formed on the upper surface of the mounting substrate 11 via a conductive bonding member (not shown).

[0018] [Wavelength conversion device] Next, a description will be given of the configuration of the wavelength conversion device 13. The wavelength conversion device 13 is a device having a wavelength conversion function that receives light emitted from the light emitting element 12 and emits fluorescence of a different wavelength. The wavelength conversion device 13 is configured to include a phosphor section 21 and a plurality of nanoantennas 22 formed on the phosphor section 21.

[0019] The phosphor section 21 is a plate-like body having a rectangular upper surface shape, and is provided on the upper surface of the support substrate 16 so as to overlap with the outer edge of the support substrate 16 of the light-emitting element 12 in a plan view of the lighting device 100 seen from above.

[0020] The phosphor section 21 is made of a phosphor that emits fluorescence when excited by blue light as excitation light emitted from the light emitting element 12. The fluorescence emitted from the phosphor when excited by blue light has a broad green to orange wavelength range spanning 480 to 700 nm, and has a yellow peak wavelength at 520 to 570 nm.

[0021] The phosphor section 21 is, for example, a single-crystal transparent ceramic phosphor plate made of yttrium aluminum garnet (YAG:Ce) phosphor using cerium (Ce) as an activator.

[0022] The phosphor section 21 is not limited to a phosphor plate made of a single-crystal YAG:Ce phosphor, but is preferably configured to be less prone to scattering inside. Therefore, it is preferably a single-phase phosphor plate made of a single material, and in this case, it may be polycrystalline.

[0023] When the blue light emitted from the light emitting element 12 is incident on the phosphor section 21, part of the light passes through the phosphor section 21 as is, and part of the light excites the phosphor, causing the excited phosphor to emit fluorescence.

[0024] Therefore, excitation light that has passed through phosphor section 21 without contributing to the generation of fluorescence and fluorescence emitted from the phosphor are emitted from the upper surface of phosphor section 21. As a result, white light that is a mixture of blue light and yellow fluorescence emitted from the upper surface of phosphor section 21 is extracted from lighting device 100.

[0025] The nanoantennas 22 are minute columnar or pyramidal protrusions of nanometer size. In this embodiment, the nanoantennas 22 are cylindrical structures formed on the upper surface of the phosphor section 21. A plurality of nanoantennas 22 are formed on the upper surface of the phosphor section 21, and are arranged at a predetermined period. The nanoantennas 22 are arranged at a period smaller than the peak wavelength of the fluorescence emitted from the phosphor of the phosphor section 21.

[0026] As shown in FIG. 1, the nanoantenna 22 is formed on the upper surface of the phosphor section 21 and is divided into three regions: a first region A1, a second region A2, and a third region A3, and each of the three regions has a triangular lattice-like arrangement pattern.

[0027] The first region A1, the second region A2, and the third region A3 each have a strip shape with the longitudinal direction extending in the left-right direction in Figure 1 when viewed in a plan view from a direction perpendicular to the top surface of the phosphor section 21, and are arranged in this order along the vertical direction in Figure 1.

[0028] The nanoantennas 22 in the first region A1 are arranged along an arrangement line AL1 to form a triangular lattice pattern. The arrangement line AL1 is a reference line for the arrangement patterns of the nanoantennas 22 in the second region A2 and the third region A3, which will be described later.

[0029] The nanoantennas 22 in the second region A2 are arranged along an arrangement line AL2 to form a triangular lattice pattern. The arrangement line AL2 forms an angle θ with a reference line RL that is parallel to the arrangement line AL1. Ａ２ It has the following characteristics.

[0030] In other words, the arrangement pattern of the nanoantennas 22 in the second region A2 is determined by rotating the arrangement pattern of the nanoantennas 22 in the first region A1 around an axis perpendicular to the top surface of the phosphor portion 21 at an angle θ Ａ２ In the lighting device 100, the pattern is rotated by an angle θ Ａ２ is an angle other than an integer multiple of 60°, for example, 19°.

[0031] The nanoantennas 22 in the third region A3 are arranged along an arrangement line AL3 to form a triangular lattice pattern. The arrangement line AL3 is at an angle θ Ａ３ It has the following characteristics.

[0032] In other words, the arrangement pattern of the nanoantennas 22 in the third region A3 is determined by rotating the arrangement pattern of the nanoantennas 22 in the first region A1 at an angle θ Ａ３ In the lighting device 100, the pattern is rotated by an angle θ Ａ３ is an angle other than an integer multiple of 60° and the angle θ Ａ２ The angle is different from the angle θ, for example, 41°.

[0033] 2, the nanoantennas 22 are formed at the same period P. The period P of the nanoantennas 22 is preferably smaller than the peak wavelength of the fluorescence emitted from the phosphor of the phosphor portion 21, and is preferably, for example, 420 nm to 520 nm.

[0034] Furthermore, each of the nanoantennas 22 has the same diameter W. The diameter W of the nanoantennas 22 is preferably, for example, 75% to 85% of the above-mentioned period P. Specifically, for example, when the period P is 500 nm, the diameter W of the nanoantennas 22 is 375 nm to 425 nm.

[0035] Furthermore, each of the nanoantennas 22 has the same height H from the upper surface of the phosphor portion 21. The height H of the nanoantenna 22 is preferably, for example, 225 nm to 325 nm.

[0036] Each of the nanoantennas 22 is made of a dielectric material or a metal material. More specifically, the nanoantennas 22 are made of a material that does not easily absorb light with wavelengths in the visible light region and has a high refractive index. For example, the nanoantennas 22 are made of titanium oxide (TiO ２ ), zirconium oxide (ZrO ２ ), niobium pentoxide (Nb ２ O ５ ), lanthanum oxide (La ２ O３ ), tantalum pentoxide (Ta ２ O ５ ), hafnium oxide (HfO ２ ) or other transparent dielectric material.

[0037] The nanoantenna 22 preferably has a high refractive index, particularly a refractive index of 1.9 or higher, because the greater the difference in refractive index between the nanoantenna 22 and air, the higher the scattering efficiency. More specifically, the nanoantenna 22 is made of a material having a plasma frequency of surface plasmon resonance, as well as an alloy or laminate containing such a material. For example, the nanoantenna 22 is made of a metal material having a plasma frequency of surface plasmon resonance, such as Au (gold), Ag (silver), Cu (copper), Pt (platinum), Pd (palladium), Al (aluminum), or Ni (nickel).

[0038] The above-described period P, diameter W, height H, and constituent material of the nanoantenna 22 are all common to the nanoantennas 22 in the first region A1, the second region A2, and the third region A3.

[0039] Here, the angle-narrowing effect of the nanoantenna 22 will be explained. When the fluorescence reaches the upper surface of the phosphor section 21 at an angle equal to or greater than the critical angle, the fluorescence is totally reflected by the upper surface of the phosphor section 21. When total reflection occurs, an evanescent wave is generated that seeps from the upper surface of the phosphor section 21 toward the low-refractive-index medium. This evanescent wave propagates along the upper surface of the phosphor section 21, in other words, along the interface between the phosphor section 21 and air.

[0040] When the evanescent wave propagating along the upper surface of the phosphor section 21 reaches the nanoantenna 22, it is emitted in the form of visible light with the same wavelength as the fluorescence in a direction that conforms to the diffraction conditions determined by the above-described period P. This phenomenon causes the fluorescence to be emitted in an angular range that conforms to the diffraction conditions, thereby promoting a narrowing of the angle of the fluorescence emitted from the upper surface of the phosphor section 21. The narrowing of the angle of the fluorescence by the nanoantenna 22 means, for example, that the action of the nanoantenna 22 increases the fluorescence emitted at a light distribution angle within ±30°.

[0041] 1 and 2 are merely schematic illustrations for explaining the nanoantennas 22. The phosphor portion 21 is, for example, 1 mm square, and in this case, more nanoantennas 22 are provided than those shown in FIGS.

[0042] [Suppression of Color Unevenness in Light Emitted from Illumination Device] Here, suppression of color unevenness in light emitted from the illumination device 100 in this embodiment will be described with reference to FIGS.

[0043] Fig. 3 is a diagram schematically illustrating a state in which light emitted from the illumination device 100 of this embodiment is irradiated onto a screen S located at a location distant from the illumination device 100. In Fig. 3, a circular irradiation pattern IP is formed on the screen S by irradiation with the light emitted from the illumination device 100. The irradiation pattern IP is a pattern of white light in which blue light and yellow fluorescent light are mixed.

[0044] Also, on the screen S, bright line patterns BP1 (dashed line in the figure), BP2 (dotted line in the figure), and BP3 (dash line in the figure) appear, with bright lines radiating out from the center of the irradiation pattern IP at 60° intervals so as to overlap with the irradiation pattern IP.

[0045] Here, the bright line patterns shown in Fig. 3 will be described with reference to Fig. 4. Bright line patterns BP1, BP2, and BP3 are each fluorescent components in a specific wavelength range that are enhanced by the nanoantenna 22 and appear due to the arrangement of the nanoantenna 22 in the first region A1, the second region A2, and the third region A3, respectively.

[0046] FIG. 4 shows the diffraction order (m １ ,m ２ (m １ ,m ２ Under the diffraction condition expressed as (x, y)), the emission angle θ of the fluorescence emitted from the upper surface of the phosphor section 21 is ｅｍ 4 is a graph showing the results of plotting wavelengths calculated for each wavelength. In FIG. 4, a TiO ２The model is a nanoantenna 22 made of a fluorescein (refractive index 2.4) formed at a period P of 420 nm. The emission angle θ of the fluorescence emitted in a direction perpendicular to the upper surface of the phosphor section 21 is ｅｍ is set to 0°.

[0047] 4 is a region where the fluorescence generated within the phosphor section 21 and reaching the upper surface of the phosphor section 21 is enhanced by the nanoantenna 22. In particular, the region HA indicated by the two-dot chain line in the figure is a region where the fluorescence is strongly enhanced by the nanoantenna 22.

[0048] Specifically, the fluorescent components of the fluorescent light having a wavelength of 480 to 550 nm that reach the upper surface of the fluorescent body part 21 are emitted at an emission angle θ of 20° to 40°. ｅｍ This wavelength of 480 to 550 nm corresponds to the green wavelength region of visible light. That is, in the lighting device 100, the green fluorescent component is strongly enhanced by the nanoantenna 22 when it is emitted from the upper surface of the phosphor section 21 at the angle described above.

[0049] Figure 5 is a graph showing luminosity, which indicates the degree of intensity at which the human eye perceives light in the wavelength range of visible light. As shown in Figure 5, luminosity in the wavelength range of visible light peaks at yellow light around 550 nm, and tends to increase in the green to orange wavelength range.

[0050] 3 again, as described above, the fluorescence generated in the phosphor section 21 is emitted from the upper surface of the phosphor section 21 at an emission angle θ of 20° to 40°. ｅｍ The green fluorescent component emitted at is strongly enhanced by the nanoantenna 22.

[0051] Therefore, the green fluorescent components enhanced by the nanoantennas 22 in each of the first region A1, the second region A2 and the third region A3 appear on the screen S as bright line patterns BP1, BP2 and BP3, respectively, along the arrangement direction of the nanoantennas 22 arranged in a triangular lattice pattern in each region, i.e., bright lines spreading radially every 60°.

[0052] As described above, the arrangement patterns of the nanoantennas 22 in the second region A2 and the third region A3 are patterns obtained by rotating the arrangement pattern of the nanoantennas 22 in the first region A1 at different angles around an axis perpendicular to the top surface of the phosphor section 21. According to the lighting device 100 of this embodiment, the nanoantennas 22 have such an arrangement configuration, which makes it possible to suppress color unevenness in the light emitted from the lighting device 100.

[0053] Here, for example, in the lighting device 100, if the nanoantennas 22 have a uniform arrangement pattern in the first region A1, in other words, if the arrangement patterns in the second region A2 and the third region A3 are not rotated, only one bright line pattern will appear on the screen S. In other words, the bright line pattern BP1, the bright line pattern BP2, and the bright line pattern BP3 will appear on the screen S in a state where they are overlapped with each other without any misalignment.

[0054] When bright line patterns overlap on the screen S in this way, coupled with the high visibility in the visible light range shown in Figure 5, the difference in color between the areas where the bright line patterns appear and the areas where they do not appears to the human eye becomes significant. Specifically, while the irradiation pattern IP is white, the overlapping bright line patterns appear in a strong green. Therefore, the light irradiated onto the screen S from the lighting device 100 may exhibit strong color unevenness.

[0055] According to the lighting device 100 of this embodiment, the arrangement patterns in the second area A2 and the third area A3 are offset from the arrangement pattern in the first area A1 by an angle θ Ａ２ and angle θ Ａ３ Since the illumination device 100 is rotated by only one angle, the arrangement directions of the nanoantennas 22 in the first region A1, the second region A2, and the third region are different from each other in a plan view of the illumination device 100 seen from above.

[0056] Therefore, the bright line pattern BP2 that appears on the screen S is rotated by an angle θ Ａ２Similarly, the bright line pattern BP3 that appears on the screen S is shifted from the bright line pattern BP1 by an angle θ Ａ３ That is, the bright line pattern BP1, the bright line pattern BP2, and the bright line pattern BP3 do not overlap with each other on the screen S as shown in FIG.

[0057] Therefore, according to the lighting device 100 of this embodiment, by changing the arrangement of the nanoantennas 22 for each region, the bright line patterns do not overlap with each other, making color unevenness less noticeable than when the nanoantennas 22 have a uniform arrangement.

[0058] In other words, since the arrangement direction of the nanoantennas 22 differs from region to region, the bright lines are finely dispersed on the screen S, making it difficult for color unevenness to occur in the light irradiated onto the screen S. Therefore, according to the lighting device 100 of this embodiment, it is possible to suppress color unevenness from occurring in the light emitted from the lighting device 100 via the nanoantennas 22.

[0059] The light emitted from the lighting device 100 of this example has a luminous flux similar to that of the light emitted from a lighting device in which all of the nanoantennas 22 are uniformly arranged as described above. For example, the luminous flux of the light emitted from the lighting device in which all of the nanoantennas 22 are uniformly arranged is 231 lm / W, whereas the luminous flux of the light emitted from the lighting device 100 of this example is 232 lm / W.

[0060] Therefore, according to the lighting device 100 of this embodiment, it is possible to maintain the luminous flux of the light emitted from the lighting device 100 while suppressing color unevenness from occurring in the light.

[0061] 1 are merely examples, and the number of regions and the number of nanoantennas 22 formed in each region are not limited as long as it is possible to suppress color unevenness in the emitted light. For example, there may be only two regions, the first region A1 and the second region A2.

[0062] Furthermore, for example, an arrangement of the first region A1, the second region A2, and the third region A3 may be regarded as one set, and multiple sets of these may be formed on the upper surface of the phosphor section 21. In this case, it is preferable that the number of each region occupying the entire region is divided as evenly as possible.

[0063] The size of each unit area is preferably such that at least 10 periods of nanoantennas 22 can be formed, and for example, it is preferable that one side of the unit area is 5 μm or more in each lattice axis direction.

[0064] In the lighting device 100 of this embodiment, the angle θ is the rotation angle of the array pattern in the second area A2. Ａ２ is 19°, and the angle θ Ａ３ However, if the nanoantenna 22 has a triangular lattice arrangement pattern, the angle may be any angle other than a multiple of 60 degrees, and is not limited to this. For example, the angle θ Ａ２ is set to 5°, and the angle θ Ａ３ may be set to 50°.

[0065] The difference in rotation angle between adjacent regions is preferably 20°, more preferably 10°, and even more preferably 5° or less. By arranging the adjacent regions so as to minimize the angle difference, it is possible to form as many nanoantennas 22 as possible in each of the adjacent regions.

[0066] In the lighting device 100 of this embodiment, the nanoantenna 22 has a triangular lattice arrangement pattern in each of the first region A1, the second region A2, and the third region A3, but is not limited to this and may have, for example, a square lattice arrangement pattern.

[0067] When the nanoantennas 22 have a square lattice arrangement pattern in each region, the illumination pattern IP of the light emitted from the illumination device 100 and projected onto the screen may have color unevenness due to a bright line pattern in which bright lines appear radially every 90°. Ａ２ and angle θ Ａ３By setting the angles to be different from each other and to be angles other than multiples of 90°, it is possible to suppress color unevenness from occurring in the emitted light.

[0068] In the lighting device 100 of this embodiment, the nanoantenna 22 has a cylindrical shape, but is not limited to this and may have other shapes. For example, the nanoantenna 22 may have a conical or truncated conical shape. In this case, the diameter of the base of the nanoantenna having a conical or truncated conical shape corresponds to the diameter W of the nanoantenna 22 described above.

[0069] In the illumination device 100 of this embodiment, the wavelength conversion device 13 emits fluorescence upon receiving excitation light from the light emitting element 12 serving as the light source, but the light source is not limited to this and may be, for example, a laser light source that emits laser light. In this case, the illumination device 100 may be configured such that the wavelength conversion device 13 and the light source are separate.

[0070] [Method of Manufacturing Wavelength Converter] Hereinafter, a method of manufacturing the wavelength converter 13 of the lighting device 100 in this embodiment will be described with reference to FIGS. 1 and 2. FIG.

[0071] First, TiO is deposited on the entire upper surface of the flat phosphor portion 21 by electron beam evaporation or sputtering. ２ A dielectric layer made of a transparent dielectric material is formed. At this time, the thickness of the dielectric layer becomes the height H of the nanoantenna 22.

[0072] Next, a metal film made of aluminum (Al) is formed on the dielectric layer formed on the upper surface of the phosphor section 21, and a resist film made of resin is applied to the metal film. After that, a nanoimprint mold having a plurality of holes is used to press the mold onto the resist film and then peeled off, thereby performing a desired patterning on the resist film.

[0073] In this patterning, by matching the period and diameter of each of the multiple holes in the nanoimprint mold to the period P and diameter W of the nanoantenna 22 described above, a resist film having a shape corresponding to the arrangement of the nanoantenna 22 in this embodiment can be formed.

[0074] At this time, by performing patterning while rotating the nanoimprint mold at a predetermined angle for each of the first region A1, second region A2, and third region A3 described above, it is possible to form a resist film having a shape corresponding to the arrangement of the nanoantenna 22 in each of the first region A1, second region A2, and third region A3.

[0075] Next, using the patterned resist film as a mask, the metal film in the area where the nanoantenna 22 is not to be formed is dry-etched to form a metal mask for etching the dielectric layer.

[0076] Next, the dielectric layer on which the metal mask is formed is etched by dry etching. For example, if the metal film is made of Al and the transparent dielectric is made of TiO ２ In this case, etching gases of chlorine (Cl) and argon (Ar) are used for the metal film, and carbon tetrafluoride (CF ４ ), Ar and oxygen (O ２ ) or other etching gases are used.

[0077] Finally, the metal mask remaining in the above process is removed by dry etching or wet etching, thereby completing the wavelength conversion device 13 including the nanoantenna 22 arranged as described above.

[0078] The metal film is made of Al, and the transparent dielectric is made of TiO ２ When it consists of ４ , Ar and O ２ When dry etching of a dielectric layer is performed using this etching gas, the metal film is also partially etched. Therefore, if the thickness of the metal film on the dielectric layer is previously thinned, the metal film and the dielectric layer are removed from the edge of the dielectric layer during etching, and this method can form nanoantennas with a conical or truncated conical shape.

[0079] [Modification of Illumination Device] A modification of the illumination device 100 according to Example 1 will be described below with reference to Fig. 6. Fig. 6 is a top view of an illumination device 110 according to a modification of Example 1. The illumination device 110 differs from Example 1 in the arrangement of the nanoantennas 22, but is similar to Example 1 in other respects, such as the period P, diameter W, and height H of the nanoantennas 22.

[0080] In the lighting device 110 of this modification, the nanoantennas 22 are arranged in a triangular lattice pattern in each of nine regions, the fourth region A4 to the twelfth region A12, which are arranged in a matrix. The arrangement patterns of the nanoantennas 22 in the fifth region A5 to the twelfth region A12 are rotated at different rotation angles around an axis perpendicular to the top surface of the phosphor section 21 with respect to the arrangement pattern in the fourth region A4.

[0081] The nanoantennas 22 in the fourth region A4 have an arrangement similar to that of the nanoantennas 22 in the first region A1 described above, and are arranged along the arrangement line AL4 to form a triangular lattice arrangement pattern.

[0082] The nanoantennas 22 in each of the fifth to twelfth regions A5 to A12 are arranged along the array lines AL5 to AL12, respectively, to form a triangular lattice pattern. Each of the array lines AL5 to AL12 forms an angle that is a multiple of 7° with respect to a reference line (not shown in FIG. 6) that is parallel to the array line AL4. Note that the angle differs for each region and is an angle other than a multiple of 60°.

[0083] In other words, the arrangement pattern of the nanoantennas 22 in each of the fifth region A5 to the twelfth region A12 is a pattern obtained by rotating the arrangement pattern of the nanoantennas 22 in the fourth region A4 by an angle that is a multiple of 7° around an axis perpendicular to the top surface of the phosphor section 21.

[0084] Specifically, for example, the arrangement pattern of the nanoantennas 22 in the fifth region A5 is a pattern obtained by rotating the arrangement pattern of the nanoantennas 22 in the fourth region A4 by 7 degrees around an axis perpendicular to the top surface of the phosphor section 21, and the arrangement pattern of the nanoantennas 22 in the sixth region A6 is a pattern obtained by rotating the arrangement pattern of the nanoantennas 22 in the fourth region A4 by 14 degrees around an axis perpendicular to the top surface of the phosphor section 21.

[0085] That is, in a plan view of the lighting device 110 seen from above, the arrangement patterns of the nanoantennas 22 in adjacent regions among the fifth region A5 to the twelfth region A12 have a rotation angle of 7° with respect to each other.

[0086] Even when the arrangement pattern of the nanoantennas 22 is rotated in each of the matrix-arranged regions, as in the lighting device 110 of this modified example, it is possible to suppress color unevenness in the light emitted from the lighting device 110 via the nanoantennas 22.

[0087] In the lighting device 110 of this modification, the arrangement patterns of the nanoantennas 22 in the fifth region A5 to the twelfth region A12 are rotated at different angles, but this does not need to be different in all regions, and a plurality of regions may have the same angle. For example, there may be three regions each having an arrangement pattern rotated at angles of 7°, 28°, and 49°, respectively.

[0088] [Lighting Device of Example 2] Next, the configuration of a lighting device 200 according to Example 2 will be described with reference to Figures 7 to 9. Figure 7 is a cross-sectional view of the lighting device 200 taken along the same position as line 2-2 in Figure 1. The lighting device 200 differs from Example 1 in that the wavelength conversion device 13 has a multilayer film reflector 23, but is otherwise similar to Example 1, for example, in the arrangement of the nanoantennas 22 in the first to third areas A1 to A3.

[0089] The multilayer reflector 23 is formed over the upper surface of the phosphor section 21 and is a reflector configured by laminating multiple layers of dielectric materials having relatively low refractive indexes and dielectric materials having high refractive indexes. On the upper surface of the multilayer reflector 23, each of the nanoantennas 22 is formed in the manner shown in Example 1.

[0090] The multilayer film reflector 23 is made of, for example, silicon oxide (SiO ２ ) and Al ２ O ３ is used as a high refractive index dielectric material, and TiO ２ , ZrO ２ , Nb ２ O ５ , La ２ O ３ , Ta ２ O ５ , HfO ２ is used.

[0091] In the lighting device 200, the multilayer film reflecting mirror 23 reflects light in the green wavelength range of light in the visible light region at a predetermined reflectance and transmits light of other wavelengths. That is, the multilayer film reflecting mirror 23 reflects only the fluorescent component in the green wavelength range of the fluorescence generated in the phosphor section 21 and transmits fluorescent components other than the green wavelength range and blue light as excitation light that has transmitted through the phosphor section 21.

[0092] Fig. 8 is a graph showing an example of the reflectance of light in the visible wavelength range of the multilayer film reflector 23. As shown in Fig. 8, the multilayer film reflector 23 has a reflectance of 60% or less for light in the green wavelength range of approximately 480 to 530 nm.

[0093] Therefore, in the lighting device 200 of this embodiment, the multilayer film reflector 23 is formed over the upper surface of the phosphor section 21, so that when fluorescence in the green wavelength range, which can be a cause of the color unevenness described above, reaches the multilayer film reflector 23, part of the fluorescence can be reflected into the phosphor section 21.

[0094] Fig. 9 is a graph showing the excitation spectrum of the phosphor in the phosphor section 21 with respect to excitation light. In Fig. 9, the horizontal axis represents wavelength, and the vertical axis represents intensity. In Fig. 9, the region indicated by the dashed dotted line represents light in the green wavelength range. As shown in Fig. 9, light in the green wavelength range has a lower intensity than blue light, but can excite the phosphor in the phosphor section 21.

[0095] Therefore, in the lighting device 200 of this embodiment, by forming a multilayer film reflector 23 on the upper surface of the phosphor section 21 to reflect fluorescent components in the green wavelength range, the fluorescent components reflected by the multilayer film reflector 23 can be used again as excitation light to excite the phosphor in the phosphor section 21.

[0096] Therefore, according to the lighting device 200 of this embodiment, in addition to the effect of suppressing color unevenness in the emitted light by rotating the arrangement pattern of the nanoantennas 22 for each region, color unevenness in the emitted light can also be suppressed by using the multilayer film reflector 23 to prevent a portion of the fluorescent component in the green wavelength range from being emitted from the phosphor section 21. Therefore, according to the lighting device 200 of this embodiment, color unevenness in the light emitted from the lighting device 200 via the nanoantennas 22 can be suppressed.

[0097] The reflectance of the multilayer film reflector 23 for light in the green wavelength range is not limited to the reflectance described above and may be set appropriately. The reflectance may be set, for example, according to the number of regions for each array pattern of the nanoantenna 22, and may be adjusted appropriately to the extent that the luminous flux of the light emitted from the lighting device 200 is not reduced.

[0098] REFERENCE SIGNS LIST 100, 110, 200 Lighting device 11 Mounting substrate 12 Light-emitting element 13 Wavelength conversion device 15 Semiconductor structure layer 16 Support substrate 17 P-electrode 18 N-electrode 21 Phosphor portion 22 Nanoantenna 23 Dielectric multilayer film

Claims

1. A wavelength conversion device comprising: a flat phosphor section including a phosphor that emits fluorescence when excited by excitation light; and a plurality of nanoantennas made of a metallic or dielectric material that are arranged to form a lattice-like arrangement pattern in each of a plurality of regions on one surface of the phosphor section when viewed in a plan view from a direction perpendicular to the one surface, wherein the arrangement pattern of the plurality of nanoantennas in one of the plurality of regions is a pattern obtained by rotating the arrangement pattern of the plurality of nanoantennas in the other regions around an axis perpendicular to the one surface.

2. The wavelength conversion device described in claim 1, characterized in that the multiple nanoantennas are arranged to form a triangular lattice arrangement pattern in each of the multiple regions, and the arrangement pattern of the multiple nanoantennas in one region is a pattern rotated at an angle other than a multiple of 60° with respect to the arrangement pattern of the multiple nanoantennas in the other regions.

3. The wavelength conversion device described in claim 1, characterized in that the multiple nanoantennas are arranged to form a square lattice arrangement pattern in each of the multiple regions, and the arrangement pattern of the multiple nanoantennas in one region is a pattern rotated at an angle other than a multiple of 90° with respect to the arrangement pattern of the multiple nanoantennas in the other regions.

4. A wavelength conversion device according to claim 1, wherein the plurality of regions are strip-shaped regions each arranged along a single direction in the plan view.

5. A wavelength conversion device according to claim 1, wherein the plurality of regions are arranged in a matrix in the plan view.

6. A wavelength conversion device as described in claim 1, characterized in that it has a dielectric multilayer film formed on said one surface of said phosphor portion and configured to reflect fluorescent components in a partial wavelength range within the wavelength range of said fluorescence.

7. A wavelength conversion device according to claim 6, characterized in that the fluorescence has a wavelength range of 480 to 700 nm, and the dielectric multilayer film is configured to reflect fluorescent components in the wavelength range of 480 to 530 nm.

8. A wavelength conversion device according to claim 7, wherein said dielectric multilayer film has a reflectance of 60% or less with respect to said fluorescent component.

9. A wavelength conversion device as described in claim 1, characterized in that the multiple nanoantennas are arranged at a period of 420 nm or more and 520 nm or less in each of the multiple regions.

10. A wavelength conversion device as described in claim 9, characterized in that the multiple nanoantennas have a cylindrical, conical, or truncated conical shape in each of the multiple regions, and the diameter of the bottom surface is 75% or more and 85% or less of the period.

11. A wavelength conversion device as described in claim 9 or 10, characterized in that the multiple nanoantennas have a height of 225 nm or more and 325 nm or less in each of the multiple regions.

12. An illumination device comprising: the wavelength conversion device according to claim 1; and a light source which emits the excitation light toward another surface of the phosphor section opposite to the one surface.

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