Wavelength conversion member and lighting device using the same

Abstract

To provide a wavelength conversion device and a lighting device which can suppress the generation of color unevenness in light emitted through nano antennas.SOLUTION: A lighting device includes: a tabular phosphor part having a phosphor; a dielectric multilayer film which is formed on one surface of the phosphor part and which is configurated in a manner to reflect a fluorescent component in a part of a wavelength region of fluorescence emitted by the phosphor; and a plurality of nano antennas periodically provided on the dielectric multilayer film.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] There is disclosed a device that collimates emitted light using a nano-sized antenna (hereinafter referred to as a nanoantenna). For example, Patent Document 1 discloses a lighting device having a light source that emits blue light, a phosphor layer that is excited by the light emitted from the light source to emit fluorescence, and a plurality of nanoantennas provided in a lattice pattern on the upper surface of the phosphor layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-13688 A Summary of the Invention [Problem to be solved by the invention]

[0004] For example, when light emitted from a lighting device such as that described in Patent Document 1 is irradiated onto a screen located away from the lighting device, fluorescent components in some wavelength ranges of the fluorescence emitted from the phosphor layer are strongly enhanced by the action of the nanoantennas, 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. [Means for solving the problem]

[0006] The wavelength conversion device according to the present invention is characterized by having a flat phosphor section containing a phosphor, a dielectric multilayer film formed on one surface of the phosphor section and configured to reflect fluorescent components in a partial wavelength range within the wavelength range of the fluorescence emitted by the phosphor, and a plurality of nanoantennas periodically arranged on the dielectric multilayer film. [Brief description of the drawings]

[0007] [Figure 1] 1 is a top view of an illumination device according to a first embodiment. [Diagram 2] 1 is a cross-sectional view of a lighting device according to a first embodiment. [Diagram 3] 4 is a graph showing the reflectance of the dielectric multilayer film for visible light in the lighting device according to Example 1. [Figure 4] 3 is a diagram illustrating a state in which light emitted from the illumination device according to the first embodiment is irradiated onto a screen. FIG. [Diagram 5] 4 is a graph showing various diffraction lines when the emission angle of the fluorescence emitted from a phosphor section in the lighting device according to Example 1 is changed. [Figure 6] 1 is a graph showing luminosity for light in the visible light wavelength range. [Figure 7] 4 is a graph showing a spectrum of a phosphor in a phosphor portion with respect to excitation light. [Figure 8] FIG. 11 is a cross-sectional view showing the configuration of an illumination device according to a second embodiment. [Figure 9] FIG. 11 is a cross-sectional view of a wavelength converter according to a second embodiment. [Figure 10] FIG. 11 is a top view of a wavelength converter according to a third embodiment. [Figure 11] 11 is a diagram illustrating a state in which light emitted from an illumination device according to a third embodiment is irradiated onto a screen. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an embodiment 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. EXAMPLES

[0009] [Lighting device of embodiment 1] The configuration of a lighting device 100 according to Example 1 will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is a top view of the lighting device 100 according to Example 1. Fig. 2 is a cross-sectional view of the lighting device 100 taken along line 2-2 in Fig. 1. Note that the left-right direction in Fig. 1 is the width direction of the lighting device 100, and the up-down direction in Fig. 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 board] 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 a material having high thermal conductivity and electrical insulation properties that can efficiently dissipate heat generated when the light emitting element 12 is driven, such as aluminum nitride (AlN) or aluminum oxide (Al2O3).

[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 shape when viewed from above.

[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 joined 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 consisting of an n-type semiconductor layer, a light emitting layer, and a p-type semiconductor layer (none of which are shown), each of which is mainly made of gallium nitride (GaN). When the light emitting element 12 is driven, the light emitting layer of the semiconductor structure layer 15 emits light having a peak wavelength of about It emits blue light at 450nm.

[0015] The support substrate 16 is a flat substrate with a rectangular upper surface shape. The support substrate 16 is made of a material, such as sapphire (Al2O3) or GaN, that is transparent to the blue light emitted from the light emitting layer of the semiconductor structure layer 15. The upper surface of the support substrate 16 is a light emission 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 the p-type semiconductor layer of the semiconductor structure layer 15 and has a side surface 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 the p-type semiconductor layer. The n-electrode 18 is joined to an n-side wiring (not shown) formed on the upper surface of the mounting substrate 11 via a conductive joining 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 of receiving light emitted from the light emitting element 12 and emitting fluorescence of a different wavelength. The wavelength conversion device 13 is configured to include a phosphor section 21, a multilayer film reflector 22 formed on the phosphor section 21, and a plurality of nanoantennas 23 formed on the multilayer film reflector 22.

[0019] The phosphor section 21 is a plate-like body having a rectangular upper surface shape. The phosphor section 21 is provided on the upper surface of the supporting substrate 16 so as to overlap with the outer edge of the supporting 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 generated 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 unit 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 it is, and the other part excites the phosphor, causing the excited phosphor to emit fluorescence.

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

[0025] The multilayer film reflector 22 is formed across the upper surface of the phosphor section 21 and is a dielectric multilayer film composed of multiple layers of dielectric materials having relatively low refractive indices and dielectric materials having high refractive indices stacked on top of each other.

[0026] The multilayer film reflector 22 uses, for example, silicon oxide (SiO2) or aluminum oxide (Al2O3) as a low refractive index dielectric material, and titanium oxide (TiO2), zirconium oxide (ZrO2), niobium pentoxide (Nb2O5), lanthanum oxide (La2O3), tantalum pentoxide (Ta2O5), and hafnium oxide (HfO2) as a high refractive index dielectric material.

[0027] In the lighting device 100, the multilayer film reflector 22 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 reflector 22 reflects only the fluorescent components in the green wavelength range of the fluorescent light generated in the phosphor section 21 and transmits fluorescent components other than the green wavelength range and the blue light that has transmitted through the phosphor section 21.

[0028] Fig. 3 is a graph showing an example of the reflectance of light in the visible wavelength range in the multilayer film reflector 22 of the wavelength converter 13. Fig. 3 shows the reflection spectrum of the multilayer film reflector 22 formed by stacking about 80 layers of silicon oxide (SiO2) as a low refractive index dielectric material and niobium pentoxide (Nb2O5) as a high refractive index dielectric material.

[0029] 3, the reflectance spectrum of the multilayer film reflector 22 is 48 to 53% at wavelengths of 490 nm or more and 520 nm or less, 3% or less at wavelengths of 400 nm or more and 475 nm or less, and 6% or less at wavelengths of 540 nm or more and 700 nm or less. In particular, the reflectance at approximately 450 nm, which is the emission peak wavelength of the excitation light, is 5% or less.

[0030] 3, the multilayer film reflector 22 has a reflectance of 10% or more and 60% or less for light in the green wavelength range of approximately 480 to 530 nm. The reflectance in the shorter wavelength range and the longer wavelength range is less than 10%. When the fluorescence in the green wavelength range generated in the phosphor section 21 reaches the multilayer film reflector, a part of the fluorescence is reflected back into the phosphor section 21.

[0031] It is preferable that the reflectance of the multilayer film reflector 22 for light in wavelength ranges other than the green wavelength range is as low as possible, and is preferably kept at least below 10%, and more preferably to 1% or less.

[0032] The nanoantennas 23 are minute columnar or pyramidal protrusions of nano size. In this embodiment, the nanoantennas 23 are cylindrical structures formed on the upper surface of the multilayer film reflector 22. A plurality of nanoantennas 23 are formed on the upper surface of the phosphor section 21 and are arranged at a predetermined period. The nanoantennas 23 are arranged at a period smaller than the peak wavelength of the fluorescence emitted from the phosphor of the phosphor section 21. The nanoantennas 23 have a triangular lattice arrangement pattern on the upper surface of the multilayer film reflector 22.

[0033] Each of the nanoantennas 23 is formed at the same period P as one another, as shown in Fig. 2. The period P of the nanoantennas 23 is preferably smaller than the peak wavelength of the fluorescence emitted from the phosphor of the phosphor section 21 described above, and is preferably, for example, 420 nm to 520 nm.

[0034] Moreover, each of the nanoantennas 23 has the same diameter W. The diameter W of the nanoantennas 23 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 23 is 375 nm to 425 nm.

[0035] Moreover, each of the nanoantennas 23 has the same height H from the upper surface of the multilayer film reflector 22. The height H of the nanoantennas 23 is preferably, for example, 225 nm to 325 nm.

[0036] Each of the nanoantennas 23 is 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 23 are made of transparent dielectric materials such as TiO, ZrO2, Nb2O5, La2O3, Ta2O5, and HfO2. The greater the difference in refractive index between the nanoantennas 23 and air, the higher the scattering efficiency, so the higher the refractive index, and in particular, a refractive index of 1.9 or more is preferable.

[0037] Here, the angle-narrowing effect of the nanoantenna 23 will be described. When the fluorescence reaches the top surface of the multilayer reflector 22 at an angle equal to or greater than the critical angle, the fluorescence is totally reflected by the top surface of the multilayer reflector 22. When total reflection occurs, an evanescent wave is generated that seeps out from the top surface of the multilayer reflector 22 toward the low refractive index medium. This evanescent wave propagates along the top surface of the multilayer reflector 22, in other words, along the interface between the phosphor section 21 and the air.

[0038] When the evanescent wave propagating along the upper surface of the multilayer film reflecting mirror 22 reaches the nanoantenna 23, 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-mentioned period P. This phenomenon causes the fluorescence to be emitted in an angular range that conforms to the diffraction conditions, promoting a narrowing of the angle of the fluorescence emitted from the upper surface of the multilayer film reflecting mirror 22. The narrowing of the angle of the fluorescence by the nanoantenna 23 refers to, for example, an increase in the fluorescence emitted with a light distribution angle within ±30° due to the action of the nanoantenna 23.

[0039] 1 and 2 are merely schematic views for explaining the nanoantennas 23. The phosphor section 21 and the multilayer film reflector 22 are, for example, 1 mm square, and in this case, more nanoantennas 23 are provided than those shown in FIGS.

[0040] [Suppression of color unevenness in light emitted from lighting equipment] Here, the suppression of color unevenness in the light emitted from the lighting device 100 in this embodiment will be described with reference to FIGS.

[0041] FIG. 4 is a diagram showing a schematic state in which light emitted from the illumination device 100 of this embodiment is irradiated onto a screen S located at a distance from the illumination device 100. As shown in FIG.

[0042] In Fig. 4, a circular irradiation pattern IP is formed on the screen S by irradiating the light emitted from the lighting device 100. The irradiation pattern IP is a white light pattern in which blue light and yellow fluorescence are mixed. In addition, a bright line pattern BP appears on the screen S, in which bright lines radiate out every 60° from the center of the irradiation pattern IP so as to overlap with the irradiation pattern IP.

[0043] Here, the bright line pattern shown in Fig. 4 will be described with reference to Fig. 5. Bright line pattern BP appears as a result of the arrangement of nanoantennas 23 formed on the multilayer film reflector 22, where the fluorescent components in a specific wavelength range are enhanced by the nanoantennas 23.

[0044] FIG. 5 shows the emission angle θ of the fluorescence emitted from the upper surface of the multilayer film reflecting mirror 22 under the diffraction condition where the diffraction orders are expressed as (m1, m2 (m1 and m2 are integers)). em 5 is a graph showing the plot of wavelengths calculated for each wavelength. In Fig. 5, a model is used in which nanoantennas 23 made of TiO2 (refractive index 2.4) are formed at a period P of 420 nm on the upper surface of a multilayer reflector 22 made of a YAG:Ce phosphor. Note that the emission angle θ of the fluorescence emitted in a direction perpendicular to the upper surface of the multilayer reflector 22 is em is set to 0°.

[0045] In FIG. 5, the solid line is the diffraction line (YAG(1,0)) when the diffraction order is (m1,m2)=(1,0). The dashed line is the diffraction line (YAG(1,-1)) when the diffraction order is (m1,m2)=(1,-1). The dashed line is the diffraction line (YAG(-1,0)) when the diffraction order is (m1,m2)=(-1,0). The dotted line is the diffraction line (Air(-1,0)) when the diffraction order is (m1,m2)=(-1,0).

[0046] 5 is a region (wavelength and angle) where the fluorescence generated in the phosphor section 21 and reaching the upper surface of the multilayer film reflector 22 is enhanced by the nanoantenna 23. In particular, the region (wavelength and angle) surrounded by the diffraction line (Air(-1,0)) and the diffraction line (YAG(1,0)) and in the vicinity of the diffraction line (Air(-1,0)), i.e., the region HA shown by the two-dot chain line in the figure, is a region where the fluorescence is strongly enhanced by the nanoantenna 23.

[0047] Specifically, the fluorescent light components having wavelengths of 480 to 550 nm among the fluorescent light reaching the upper surface of the multilayer film reflecting mirror 22 are emitted at an emission angle θ of 20° to 40°. em This wavelength of 480 to 550 nm mainly includes the green wavelength range. That is, in the lighting device 100, the green fluorescent component is strongly enhanced by the nanoantenna 23 when it is emitted from the upper surface of the multilayer film reflecting mirror 22 at the above-mentioned angle.

[0048] Fig. 6 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 Fig. 6, luminosity in the wavelength range of visible light shows a tendency to peak at yellow light near 550 nm and to increase in the green to orange wavelength range.

[0049] 4 again. As described above, the fluorescence generated in the phosphor section 21 is emitted from the upper surface of the multilayer film reflecting mirror 22 at an emission angle θ of 20° to 40°. em The green fluorescent component emitted at is strongly enhanced by the nanoantenna 23.

[0050] Therefore, the green fluorescent component enhanced by the nanoantenna 23 on the upper surface of the multilayer reflector 22 appears on the screen S in a pattern that follows the arrangement direction of the nanoantennas 23 arranged in a triangular lattice shape, that is, as a bright line pattern BP in which bright lines radiate out every 60°.

[0051] In the lighting device 100, as described above, the multilayer film reflector 22 having reflectivity to fluorescence in the green wavelength range is formed over the upper surface of the phosphor section 21, so that when the fluorescence in the green wavelength range reaches the multilayer film reflector 22, a part of the fluorescence is reflected into the phosphor section 21. This makes it possible to suppress the intensity of the bright line pattern BP that appears on the irradiation pattern IP irradiated from the lighting device 100 onto the screen S.

[0052] Here, for example, when the lighting device 100 does not have a multilayer film reflector 22 provided on the upper surface of the phosphor section 21, in other words, when the nanoantenna 23 is formed on the upper surface of the phosphor section 21, the difference in color between the area where the bright line pattern BP appears and the area where it does not appear becomes large when viewed by the human eye, coupled with the high visibility in the visible light range shown in Figure 6.

[0053] Specifically, the irradiation pattern IP is white, whereas the bright line pattern BP appearing on the irradiation pattern IP is a strong green color. Therefore, the light irradiated onto the screen S from the lighting device 100 not provided with the multilayer film reflector 22 may have strong color unevenness.

[0054] According to the lighting device 100 of this embodiment, the green fluorescent component emitted from the lighting device 100 can be reduced compared to when the lighting device 100 does not have the multilayer film reflector 22. In other words, the bright line pattern BP overlapping the irradiation pattern IP irradiated onto the screen S can be made less noticeable, and color unevenness can be suppressed. Therefore, according to the lighting device 100 of this embodiment, color unevenness in the light emitted from the lighting device 100 via the nano antenna 23 can be suppressed.

[0055] Fig. 7 is a graph showing the excitation spectrum of the phosphor in phosphor section 21. In Fig. 7, the horizontal axis shows wavelength, and the vertical axis shows intensity. In Fig. 7, the region shown by the dashed dotted line shows light in the green wavelength range. As shown in Fig. 7, light in the green wavelength range has a lower intensity than blue light, but can excite the phosphor in phosphor section 21.

[0056] Therefore, in the lighting device 100 of this embodiment, by forming a multilayer film reflector 22 that reflects fluorescent components in the green wavelength range on the upper surface of the phosphor section 21, the fluorescent components reflected by the multilayer film reflector 22 can be used again as excitation light that excites the phosphor of the phosphor section 21.

[0057] Therefore, according to the lighting device 100 of this embodiment, by providing the multilayer film reflector 22 on the upper surface of the phosphor section 21, it is possible to suppress color unevenness in the emitted light and reuse the green fluorescent component reflected by the multilayer film reflector 22 as excitation light. In other words, it is possible to improve the efficiency of generating fluorescence in the phosphor section 21 due to the green fluorescent component.

[0058] The reflectance of the multilayer film reflector 22 for light in the green wavelength range may be set as appropriate without being limited to the embodiment shown in Fig. 3. The reflectance may be adjusted as appropriate, for example, to an extent that color unevenness is not observed when the light is irradiated from the illumination device 100 to the screen S, as viewed by the human eye, and to an extent that the luminous flux of the emitted light is not reduced.

[0059] The wavelengths reflected by the multilayer film reflector 22 are not limited to those shown in Fig. 3 and can be set as appropriate. Since the wavelength of the light amplified by the nanoantenna 23 and emitted varies based on the size and period of the nanoantenna 23, it is preferable to set the multilayer film reflector 22 so as to mainly reflect a wavelength band including the wavelength to be amplified. Specifically, the wavelengths reflected by the multilayer film reflector 22 can be set to include the wavelengths amplified by each nanoantenna 23, as explained above with reference to Fig. 5.

[0060] Furthermore, the wavelength and reflectance reflected by the multilayer film reflector 22 can be appropriately adjusted from the viewpoint of obtaining a desired emission color. The adjustment can be made in consideration of the balance between the excitation light and the wavelength-converted light so that the mixed light of the excitation light and the wavelength-converted light by the phosphor portion has the desired emission color.

[0061] In the illumination device 100 of this embodiment, the nanoantenna 23 has a cylindrical shape, but is not limited thereto and may have other shapes. For example, the nanoantenna 23 may have a cone or a truncated cone shape. In this case, the diameter of the base of the nanoantenna having a cone or truncated cone shape corresponds to the diameter W of the nanoantenna 23 described above.

[0062] [Method of manufacturing wavelength conversion device] A method for producing the wavelength converter 13 of the illumination device 100 in this embodiment will be described below with reference to FIGS.

[0063] First, a multilayer film reflector 22 having a predetermined reflectance for light in the green wavelength range is formed by alternately stacking a plurality of low refractive index dielectric films and high refractive index dielectric films over the upper surface of the phosphor section 21. For example, the multilayer film reflector 22 is formed by stacking about 40 sets of a combination of SiO2 as a low refractive index material and Nb2O5 as a high refractive index material.

[0064] Next, a dielectric layer made of a transparent dielectric material such as TiO2 is formed by electron beam evaporation or sputtering over the upper surface of the multilayer reflector 22. At this time, the thickness of the dielectric layer becomes the height H of the nanoantenna 23.

[0065] Next, a metal film made of aluminum (Al) is formed on the dielectric layer formed on the upper surface of the multilayer film reflector 22, and a resist film made of resin is applied onto 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 the mold is peeled off, thereby performing a desired patterning on the resist film.

[0066] 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 above-mentioned nanoantenna 23, a resist film can be formed in a shape that corresponds to the arrangement of the nanoantenna 23 in this embodiment.

[0067] Next, using the patterned resist film as a mask, the metal film in the area where the nanoantenna 23 is not to be formed is dry-etched to form a metal mask for etching the dielectric layer.

[0068] Next, the dielectric layer on which the metal mask is formed is etched by dry etching. For example, when the metal film is made of Al and the transparent dielectric is made of TiO2, etching gases of chlorine (Cl) and argon (Ar) are used for the metal film, and etching gases of carbon tetrafluoride (CF4), Ar, and oxygen (O2) are used for the transparent dielectric.

[0069] Finally, the metal mask remaining in the above process is removed by dry etching or wet etching, thereby completing the wavelength converter 13 including the nanoantenna 23 arranged as described above.

[0070] In addition, when the metal film is made of Al and the transparent dielectric is made of TiO2, the metal film is also partially etched when the dielectric layer is dry etched using an etching gas of CF4, Ar and O2. Therefore, if the thickness of the metal film on the dielectric layer is previously thin, the metal film and the dielectric layer are removed from the end of the dielectric layer during etching, and this method can form a nanoantenna having a conical or truncated conical shape. EXAMPLES

[0071] [Lighting device of Example 2] Next, the configuration of a lighting device 200 according to Example 2 will be described with reference to Fig. 8. Fig. 8 is a cross-sectional view of the lighting device 200. The lighting device 200 differs from Example 1 in the configuration of the lighting device 200 and a part of the configuration of the wavelength conversion device 27, but other points, such as the formation mode of the nanoantenna 23, are similar to Example 1.

[0072] The housing 25 is a box-shaped housing, and has an opening OP1 on one of two opposing faces. The housing 25 also has an opening OP2 on one of two opposing faces in a direction perpendicular to the direction in which the two faces face each other.

[0073] The laser light source 26 is a light source having a light emitting layer made of an indium gallium nitride (InGaN)-based semiconductor fixed within the opening OP1. The laser light source 26 emits light L1 with a blue wavelength (hereinafter also referred to as blue light L1) toward the downward direction in the figure.

[0074] The wavelength converter 27 is fixed on the optical axis OA in the housing 25 and has a wavelength conversion function of receiving blue light L1 emitted from the laser light source 26 and emitting fluorescence having a wavelength different from that of the blue light L1. In this embodiment, the wavelength converter 27 receives the light L1 emitted from the laser light source 26 and emits light L2 upward in the figure.

[0075] 8, the dichroic mirror DM is a mirror fixed at an angle of 45 degrees with respect to the optical axis OA of the blue light L1 from the laser light source 26 inside the housing 25. The dichroic mirror DM is a mirror that reflects light of a specific wavelength and transmits light of other wavelength ranges.

[0076] In this embodiment, the dichroic mirror DM transmits light of a blue wavelength and reflects light of a fluorescent wavelength. Therefore, the blue light L1 incident on the dichroic mirror DM is transmitted and proceeds to the wavelength converter 27.

[0077] The dichroic mirror DM transmits blue wavelength light out of the light L2 emitted from the wavelength converter 27, and reflects the fluorescent component of the light L2 in a direction perpendicular to the optical axis OA, i.e., toward the opening OP2. In Fig. 8, the fluorescent component light reflected by the dichroic mirror DM is shown as light L2'.

[0078] The lens 28 is fixed within the opening OP2. The lens 28 receives the light L2' reflected by the dichroic mirror DM, shapes the light L2' into a desired light distribution, and generates light L3 as illumination light.

[0079] [Wavelength conversion device of embodiment 2] Next, the configuration of a wavelength converter 27 of an illumination device 200 according to Example 2 will be described with reference to Fig. 9. Fig. 9 is a cross-sectional view of the wavelength converter 27 taken along the same position as line 2-2 in Fig. 1. Only differences from the wavelength converter 13 in Example 1 will be described below.

[0080] The multilayer film reflector 31 is a dielectric multilayer film formed on the lower surface of the phosphor section 21. Similar to the multilayer film reflector 22, the multilayer film reflector 31 is formed by alternately laminating a dielectric material having a relatively low refractive index and a dielectric material having a high refractive index.

[0081] The multilayer film reflector 31 has reflectivity for light in the visible light region, and therefore reflects blue light as excitation light that is incident on the wavelength converter 27 and transmitted through the phosphor section 21, and fluorescence generated by excitation by the blue light.

[0082] Furthermore, the multilayer reflector 31 also reflects the green fluorescent component reflected by the multilayer reflector 22 back to the upper surface side of the wavelength conversion device 27. Therefore, for example, the green fluorescent component that has transmitted through the phosphor section 21 without contributing to the excitation of the phosphor in the phosphor section 21 can contribute to the excitation of the phosphor in the phosphor section 21 again by being reflected by the multilayer reflector 31.

[0083] That is, according to the lighting device 200 of the present embodiment, since the wavelength conversion device 27 is provided with a multilayer film reflector 31, when the green fluorescent component is reflected by the multilayer film reflector 22 and passes through the phosphor section 21, it excites the phosphor again within the phosphor section 21, thereby improving the intensity of the fluorescence emitted from the lighting device 200.

[0084] Therefore, according to the illumination device 200 of the present embodiment, it is possible to improve the intensity of the fluorescence emitted from the illumination device 200 while suppressing the occurrence of color unevenness in the light emitted from the illumination device 200.

[0085] In the wavelength converter 27 of this embodiment, the multilayer film reflector 22 is provided on the lower surface of the phosphor section 21, but other configurations may be used as long as they are capable of reflecting light in the visible light range. For example, a metal reflecting film made of silver (Ag) or aluminum (Al) may be provided on the lower surface of the phosphor section 21. EXAMPLES

[0086] [Lighting device of Example 3] Next, the configuration of a lighting device 300 according to Example 3 will be described with reference to Fig. 10. Fig. 10 is a top view of the lighting device 300. The lighting device 300 differs from Example 1 in the arrangement of the nanoantenna 23, but other points, such as the configuration of the multilayer film reflector 22, are similar to those of Example 1.

[0087] In the lighting device 300, the nanoantenna 23 is formed on the upper surface of the multilayer film reflector 22 and is divided into three regions, a first region A1, a second region A2 and a third region A3, as shown in FIG. 10, and each of the three regions has a triangular lattice arrangement pattern.

[0088] The first region A1, the second region A2, and the third region A3 each have a rectangular shape with the longitudinal direction extending in the left-right direction in FIG. 10 when viewed in a plan view from a direction perpendicular to the top surface of the multilayer film reflector 22, and are arranged in this order along the top-bottom direction in FIG. 10.

[0089] The nanoantennas 23 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 23 in the second region A2 and the third region A3 described later.

[0090] The nanoantennas 23 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 A2 It has.

[0091] In other words, the arrangement pattern of the nanoantennas 23 in the second region A2 is rotated by an angle θ A2 In the illumination device 300, the pattern is rotated by an angle θ A2 is an angle other than an integer multiple of 60°, for example 19°.

[0092] The nanoantennas 23 in the third region A3 are arranged along an arrangement line AL3 to form a triangular lattice arrangement pattern. The arrangement line AL3 forms an angle θ A3 It has.

[0093] In other words, the arrangement pattern of the nanoantennas 23 in the third region A3 is rotated by an angle θ A3 In the illumination device 300, 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°.

[0094] 11 is a diagram illustrating a state in which light emitted from the illumination device 300 of this embodiment is irradiated onto a screen S located at a distance from the illumination device 300, similar to Fig. 4. A circular irradiation pattern IP is formed on the screen S, similar to the first embodiment.

[0095] In addition, 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 every 60°, overlapping with the irradiation pattern IP.

[0096] According to the illumination device 300 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 300 is rotated by only one angle, the arrangement directions of the nanoantennas 23 in the first region A1, the second region A2, and the third region A3 are different from one another in a plan view of the illumination device 300 seen from above.

[0097] Therefore, the bright line pattern BP2 that appears on the screen S is rotated by an angle θ A2 Similarly, the bright line pattern BP3 that appears on the screen S is shifted from the bright line pattern BP1 by an angle θ A3 11. That is, the bright line pattern BP1, the bright line pattern BP2, and the bright line pattern BP3 are arranged so as not to overlap with each other on the screen S, as shown in FIG.

[0098] Therefore, according to the lighting device 300 of this embodiment, by changing the arrangement of the nanoantennas 23 for each region, the bright line patterns do not overlap with each other, in other words, the bright line patterns are distributed as many times as the number of regions, making color unevenness less noticeable than when the nanoantennas 23 have a uniform arrangement.

[0099] Therefore, according to the illumination device 300 of this embodiment, in addition to suppressing color unevenness in the emitted light by providing the multilayer reflector 22, color unevenness in the emitted light can also be suppressed by dispersing the bright line pattern.

[0100] In the illumination device 300 of this embodiment, the three regions, the first region A1, the second region A2, and the third region A3 shown in Fig. 1 are merely examples, and the number of regions and the number of nanoantennas 23 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.

[0101] Also, 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.

[0102] The size of each unit area is preferably such that at least 10 periods of nanoantennas 23 can be formed, and for example, each side of the unit area is preferably 5 μm or more.

[0103] In the illumination device 300 of this embodiment, the angle θ A2 is 19°, and the angle θ A3 However, if the nanoantenna 23 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°.

[0104] The difference in rotation angle between adjacent regions is desirably 20°, preferably 10°, and more preferably 5° or less. By arranging adjacent regions so as to minimize the angle difference, it is possible to form as many nanoantennas 23 as possible in each of the adjacent regions.

[0105] In the lighting device 300 of this embodiment, the nanoantenna 23 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.

[0106] When the nanoantennas 23 have a square lattice arrangement pattern in each region, the illumination pattern IP of the light emitted from the illumination device 300 irradiated 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 A3 By making the angles different from each other and other than a multiple of 90°, it is possible to suppress color unevenness in the emitted light. [Explanation of symbols]

[0107] 100, 200, 300 Lighting Equipment 11 Mounting board 12 Light emitting element 13, 27 Wavelength conversion device 15 Semiconductor structure layer 16 Support substrate 17p electrode 18n electrode 21 Phosphor Section 22, 31 Dielectric multilayer film 23 Nano Antennas 25 Case 26 Laser light source 28 Lenses

Claims

1. A flat phosphor portion including a phosphor; a dielectric multilayer film formed on one surface of the phosphor section and configured to reflect fluorescent components in a partial wavelength range of the wavelength range of the fluorescence emitted by the phosphor; and a plurality of nanoantennas periodically provided on the dielectric multilayer film.

2. The fluorescence has a wavelength range of 480 to 700 nm, 2. The wavelength conversion device according to claim 1, wherein the dielectric multilayer film is configured to reflect fluorescent components in a wavelength range of 480 to 530 nm.

3. 3. The wavelength conversion device according to claim 2, wherein the dielectric multilayer film has a reflectance of 60% or less with respect to the fluorescent component.

4. The phosphor is made of yttrium aluminum garnet activated by cerium, The wavelength conversion device according to claim 2 or 3, wherein the plurality of nanoantennas are made of titanium oxide.

5. 3. The wavelength conversion device according to claim 1, further comprising a reflective film provided on another surface of the phosphor portion opposite to the one surface thereof, the reflective film reflecting light in the visible light region.

6. The wavelength conversion device according to claim 1 , wherein the plurality of nanoantennas are arranged at a period of 420 nm or more and 520 nm or less.

7. The wavelength conversion device according to claim 6 , wherein the nanoantennas have a cylindrical, conical or truncated conical shape and a diameter of a bottom surface of the nanoantennas is 75% or more and 85% or less of the period.

8. The wavelength conversion device according to claim 6 or 7, wherein the plurality of nanoantennas have a height of 225 nm or more and 325 nm or less.

9. A phosphor portion including a phosphor; a dielectric multilayer film formed on one surface of the phosphor section and configured to reflect a fluorescent component having a wavelength equal to or shorter than a peak wavelength of the fluorescence in a wavelength range of the fluorescence emitted by the phosphor; and a plurality of nanoantennas periodically provided on the dielectric multilayer film.

10. A wavelength conversion device according to claim 1 or 2, a light source that emits excitation light for exciting the phosphor toward another surface opposite to the one surface of the phosphor section; A lighting device comprising:

11. A wavelength conversion device according to claim 5 , a light source that emits excitation light toward the one surface of the phosphor portion to excite the phosphor; A lighting device comprising:

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