Wavelength conversion device and illumination device

Abstract

To provide a wavelength conversion device and a lighting unit that can increase the number of beams of emitted light, while achieving the narrow angle of the emitted light.SOLUTION: A wavelength conversion device has: a phosphor part that has an incident area on a surface of which excitation light is incident, and is formed of a phosphor excited by the excitation light to emit fluorescent light, and a plate-like part that is provided in contact with the phosphor part without obstructing the incident area of the phosphor part, has transparency to the excitation light and fluorescent light, and is formed of a light transparent body part forming a plate-like shape with the phosphor part; and a nano-antenna that is formed on the surface of the transparent body part. The incident area is arranged on one principal surface of the plate-like part, and in a top view seen from a direction perpendicular to the other principal surface of the plate-like part, the nano-antenna is formed on the surface of the light transparent body part in a non-overlapping area not overlapping the incident area. This configuration can increase the number of beams of emitted light from the wavelength conversion device, while achieving the narrow angle of the emitted light.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a wavelength conversion device and a lighting device.

Background Art

[0002] There is disclosed a lighting device that narrows the emission light using a metal antenna made of nano-sized metal particles (hereinafter referred to as a nano antenna). For example, Patent Document 1 discloses a lighting device having a transparent substrate, a wavelength converter disposed on the transparent substrate, and a plurality of nano antennas formed on the wavelength converter.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a lighting device such as that of Patent Document 1, when excitation light for exciting the phosphor in the wavelength converter is emitted from the light source, the nano antenna disposed on the wavelength converter absorbs or reflects the excitation light passing through the wavelength converter or the fluorescence generated from the phosphor, resulting in a problem that the luminous flux of the emission light emitted from the wavelength converter decreases.

[0005] Further, in a lighting device such as that of Patent Document 1, at the interface between the wavelength converter and the nano antenna, the nano antenna absorbs a part of the energy of the wavelength converter excited by the excitation light and converts it into thermal energy, resulting in a problem that quenching of the fluorescence that should originally occur occurs.

[0006] This invention has been made in view of the above-mentioned problems, and aims to provide a wavelength conversion device and an illumination device that can increase the luminous flux of emitted light while achieving a narrowing of the emitted light angle. [Means for solving the problem]

[0007] The wavelength conversion device according to the present invention comprises a phosphor portion having an incident region on its surface to which excitation light is incident and which emits fluorescence when excited by the excitation light, and a plate-shaped portion having a translucent material portion provided in contact with the phosphor portion without obstructing the incident region of the phosphor portion, which is translucent to the excitation light and the fluorescence and forms a flat plate shape together with the phosphor portion, and a nanoantenna formed on the surface of the translucent material portion, wherein the incident region is arranged on one main surface of the plate-shaped portion, and in a top view taken from a direction perpendicular to the other main surface of the plate-shaped portion, the nanoantenna is not formed on the surface of the translucent material portion in the overlapping region that overlaps with the incident region, and the nanoantenna is formed on the surface of the translucent material portion in the non-overlapping region that does not overlap with the incident region.

[0008] This configuration makes it possible to increase the luminous flux of the emitted light while simultaneously narrowing the angle of the light emitted by the wavelength converter. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic cross-sectional view showing the configuration of the lighting device according to Example 1. [Figure 2] This is a top view of the wavelength conversion device according to Example 1. [Figure 3] This is a cross-sectional view of the wavelength conversion device according to Example 1. [Figure 4] This is a cross-sectional view of the wavelength conversion device according to Modified Example 1. [Figure 5] This is a top view of the wavelength conversion device according to Modification 2. [Figure 6] This is a cross-sectional view of the wavelength conversion device according to modified example 2. [Figure 7]It is a diagram showing the experimental results in the wavelength conversion device according to Modification 2 and the comparative example. [Figure 8] It is a cross-sectional view of the wavelength conversion device according to Modification 3. [Figure 9] It is a top view of the wavelength conversion device according to Modification 4. [Figure 10] It is a cross-sectional view schematically showing the configuration of the lighting device according to Example 2. [Figure 11] It is a top view of the wavelength conversion device according to Example 2. [Figure 12] It is a cross-sectional view of the wavelength conversion device according to Example 2. [Figure 13] It is a cross-sectional view schematically showing the configuration of the lighting device according to Example 3. [Figure 14] It is a cross-sectional view of the wavelength conversion device according to Example 3. [Figure 15] It is a cross-sectional view of the wavelength conversion device according to Modification 5.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. In the drawings, the same reference numerals are given to the same components, and the description of the overlapping components is omitted.

Examples

[0011] [Lighting Device of Example 1] FIG. 1 is a cross-sectional view schematically showing the configuration of the lighting device 10 according to Example 1. In FIG. 1, hatching is omitted in view of visibility.

[0012] The housing 11 is a box-shaped housing and has openings OP1 and OP2 on each of two mutually facing surfaces. The housing 11 has a support structure 11A for supporting an object at a position between the opening OP1 and the opening OP2.

[0013] The light source 12 is a light source that is fixed within the opening OP1 and emits light L1 of a specific wavelength toward the opening OP2. In other words, the opening OP2 is formed on the optical axis OA of the light L1. In the present embodiment, the light source 12 is a laser light source having a light-emitting layer made of an InGaN-based semiconductor. In the present embodiment, blue light having a wavelength of approximately 450 nm is emitted from the light source 12 as the light L1.

[0014] The wavelength conversion device 13 is supported by the support structure 11A so as to be positioned on the optical axis OA. The wavelength conversion device 13 includes a phosphor and has a wavelength conversion function of receiving the light L1 emitted from the light source 12 and emitting fluorescence having a wavelength different from that of the light L1. That is, the wavelength conversion device 13 includes a phosphor that is excited by the light L1 as excitation light, and emits fluorescence emitted when the phosphor is excited. Hereinafter, the light L1 is also referred to as excitation light L1.

[0015] From the wavelength conversion device 13, light L2 including the transmitted light that passes through the wavelength conversion device 13 without contributing to the generation of fluorescence when receiving the light L1 and the above fluorescence is emitted.

[0016] The lens 14 as an optical member is fixed within the opening OP2. That is, the lens 14 is arranged on the optical axis OA. The lens 14 is an optical lens that receives the light L2 emitted from the wavelength conversion device 13, shapes the light L2 into a desired light distribution, and generates the light L3 as illumination light. For the lens 14, for example, a spherical lens, an aspherical lens, or the like can be used. The light L3 generated by the lens 14 is taken out to the outside of the housing 11.

[0017] In the present embodiment, the space between the light source 12 and the wavelength conversion device 13 and the space between the wavelength conversion device 13 and the lens 14 within the housing 11 are filled with air. That is, the light L2 emitted from the wavelength conversion device 13 is incident on the lens 14 through the air.

[0018] [Wavelength Conversion Device of Example 1] The wavelength conversion device 13 of the lighting device 10 according to Example 1 will be described below with reference to Figures 2 and 3. Figure 2 is a top view of the wavelength conversion device 13. Figure 2 shows the main surface of the wavelength conversion device 13 from which light L2 is emitted, as viewed from a direction perpendicular to the main surface. In other words, Figure 2 is a plan view of the wavelength conversion device 13 as seen from a direction along the optical axis OA. Figure 3 is a cross-sectional view of the wavelength conversion device 13 along the line 3-3 in Figure 2.

[0019] The wavelength conversion plate 15 has a rectangular flat plate shape on its upper surface. In this embodiment, the wavelength conversion plate 15 is formed by a plate-shaped wavelength conversion member 18 and a light-transmitting layer 19 provided to cover the upper surface of the wavelength conversion member 18.

[0020] The wavelength conversion member 18 is a flat plate-shaped member in the wavelength conversion device 13 that has the wavelength conversion function described above. The wavelength conversion member 18 is made of a phosphor that emits fluorescence when excited by the light L1 incident from the light source 12. That is, the excitation light L1 incident from the light source 12 to the wavelength conversion member 18 functions as excitation light that excites the phosphor of the wavelength conversion member 18.

[0021] In this embodiment, the central incident region IA on the lower surface of the wavelength conversion member 18 is a rectangular region that includes the area into which the excitation light L1 is incident when the wavelength conversion member 18 is attached to the illumination device 10.

[0022] In this embodiment, the incident region IA includes a region where the light intensity of the excitation light L1 incident on the lower surface of the wavelength conversion member 18 ranges from the maximum intensity to half of the maximum intensity. In a typical light source, the light intensity is strongest at the optical axis (0 degrees) and decreases as the angle with respect to the optical axis increases. The angle at which the intensity is half of the maximum intensity is called the angle at half maximum, and the incident region IA is the range in which the excitation light spreads within the angle at half maximum. That is, excitation light L1 with an intensity range from the maximum intensity to half of that intensity is incident on the incident region IA.

[0023] In this embodiment, the wavelength conversion member 18 is made of a single-crystal phosphor that is less prone to internal light scattering. Specifically, the wavelength conversion member 18 is a ceramic phosphor plate made of a single-crystal yttrium aluminum garnet (YAG:Ce) phosphor with cerium (Ce) as the light-emitting center. The wavelength conversion member 18 may be replaced with a polycrystalline phosphor. In this embodiment, the thickness of the wavelength conversion member 18 is approximately 200 μm.

[0024] As described above, in this embodiment, the light source 12 emits blue light with a wavelength of approximately 450 nm as excitation light L1. The wavelength conversion member 18 receives this blue light and emits yellow light with a wavelength of approximately 460 to 750 nm as fluorescence.

[0025] The light-transmitting layer 19 is a translucent film formed on the upper surface of the wavelength conversion member 18. In this embodiment, the light-transmitting layer 19 is made of a material having a higher refractive index (>1.82) than the wavelength conversion member 18.

[0026] Specifically, the translucent layer 19 is made of, for example, zirconium oxide (ZrO2) or niobium pentoxide (Nb2O2). 5) It is composed of materials such as tantalum pentoxide (Ta2O5), titanium dioxide (TiO2), lanthanum oxide (La2O3), and silicon nitride (Si3N4). The light-transmitting layer 19 is formed, for example, by depositing a film on the upper surface of the wavelength conversion member 18 by electron beam deposition or sputtering.

[0027] Multiple nanoantennas 16 are formed in an array on the upper surface of the wavelength conversion plate 15, i.e., on the upper surface of the light-transmitting layer 19, and the upper surface shape of each is a circular columnar metal protrusion. In this embodiment, the nanoantennas 16 are arranged in multiple rows in the frame-shaped non-overlapping region A2 on the upper surface of the wavelength conversion plate 15, excluding the overlapping region A1, which is the region that overlaps with the incident region IA when viewed from above. In other words, no nanoantennas 16 are arranged in the overlapping region A1.

[0028] In this embodiment, the nanoantennas 16 are arranged in a matrix in a top view, and adjacent nanoantennas 16 in the vertical and horizontal directions are arranged in the non-overlapping region A2 with the same period P. In this embodiment, the period P is 350 nm.

[0029] In this embodiment, each of the nanoantennas 16 is cylindrical and has the same diameter W. In this embodiment, the diameter W of each nanoantenna 16 is 150 ± 20 nm. The height of each nanoantenna 16 is 130 nm. The nanoantennas 16 are made of aluminum (Al).

[0030] In this embodiment, the nanoantennas 16 are arranged periodically at predetermined intervals. However, a region where nanoantennas 16 are not formed, even though they are located at positions corresponding to the arrangement period of the nanoantennas 16, can be considered a region where nanoantennas 16 are not arranged. In other words, a region on the upper surface of the light-transmitting layer 19 where nanoantennas 16 are not adjacent to each other at the above-mentioned period P, and where nanoantennas 16 are not formed, is considered a region where nanoantennas 16 are not arranged in this embodiment.

[0031] The light-reflecting member 17 is a light-reflecting member that extends continuously to cover the outer surface of the wavelength conversion plate 15. The light-reflecting member 17 is made of a translucent resin containing light-scattering particles, for example, a resin material containing TiO2 particles in a silicone resin.

[0032] As described above, the wavelength conversion device 13 consists of a wavelength conversion plate 15 comprising a flat wavelength conversion member 18 made of a phosphor that emits fluorescence when excited by excitation light and a light-transmitting layer 19 formed on the wavelength conversion member 18, and a nanoantenna 16 arranged on the light-transmitting layer 19. In other words, the wavelength conversion device 13 has a plate-like portion consisting of a phosphor portion made of a phosphor that emits fluorescence when excited by excitation light and a light-transmitting portion that forms a flat plate shape together with the phosphor portion, and a nanoantenna formed on the surface of the light-transmitting portion.

[0033] Furthermore, in this embodiment, as described above, the nano-antenna 16 is not placed in the superimposed region A1 that overlaps with the incident region IA exposed on the lower surface of the wavelength conversion plate 15, but rather in the non-superimposed region A2, which is a region other than the superimposed region A1.

[0034] In other words, in this embodiment, the incident region IA is exposed on one main surface of the wavelength conversion plate 15, and in a top view of the other main surface of the wavelength conversion plate 15 from a direction perpendicular to that main surface, the light-transmitting layer 19 is exposed in a non-overlapping region A2 that does not overlap with the incident region IA, and the nano-antenna 16 is formed on the surface of the light-transmitting layer 19 exposed in the non-overlapping region A2.

[0035] [Light emitted from superimposed region A1] The light L21 emitted from the superimposed region A1 described above will be explained below using Figure 3.

[0036] In this embodiment, the wavelength conversion member 18 is made of a single-crystal YAG:Ce phosphor that is less prone to internal light scattering, as described above. Therefore, the excitation light L1 incident perpendicularly to the incident region IA of the wavelength conversion member 18 propagates to the superposition region A1 while maintaining its directionality as laser light.

[0037] At this time, the fluorescence generated by excitation light L1 traveling through the inside of the wavelength conversion member 18 is scattered in all directions within the wavelength conversion member 18. Of the fluorescence traveling from the wavelength conversion member 18 through the light-transmitting layer 19 into the atmosphere, the component that travels to the superposition region A1, that is, the component whose angle of fluorescence traveling from inside the wavelength conversion plate 15 into the atmosphere is less than the critical angle, is emitted directly into the atmosphere from the superposition region A1.

[0038] In this embodiment, as described above, no nanoantennas 16 are formed in the superposition region A1 of the light-transmitting layer 19. Therefore, the excitation light L1 and the fluorescence components below the critical angle described above that pass through the wavelength conversion member 18 and reach the superposition region A1 of the light-transmitting layer 19 are emitted into the atmosphere without reflection or absorption by the nanoantennas 16. In other words, white light L21, which is generated by mixing the blue light that has passed through the wavelength conversion member 18 with the yellow light as fluorescence, is emitted from the superposition region A1 of the light-transmitting layer 19.

[0039] In this way, in this embodiment, by not arranging the nanoantenna 16 in the superimposed region A1 directly above the incident region IA, it is possible to prevent reflection or absorption of the excitation light L1 and fluorescence by the nanoantenna 16, and to emit light L21 with a high luminous flux.

[0040] In this embodiment, when the wavelength conversion device 13 is used in the illumination device 10, the light L21 represents light in an angular range up to half of the forward light beam irradiated from the superimposed region A1 forward (in the range of -90 degrees to +90 degrees), and is captured by the lens 14 described above. Specifically, as shown in Figure 3, when the angle perpendicular to the upper surface of the wavelength conversion plate 15 is set to 0 degrees at the outer edge of the superimposed region A1, the light L21 emitted spreading out at an angle of 45 degrees in the left-right direction in the figure is captured by the lens 14 described above.

[0041] [Light emitted from non-superposition region A2] Next, we will explain the light L22 emitted from the non-superposition region A2 described above using Figure 3.

[0042] In this embodiment, the excitation light L1 that travels outside the incident region IA, i.e., the component of the excitation light L1 whose intensity is less than half of the maximum intensity, and the component whose fluorescence angle traveling from inside the wavelength conversion plate 15 into the atmosphere is greater than or equal to the critical angle, travels to the non-superimposed region A2 and is emitted into the atmosphere through the non-superimposed region A2.

[0043] Of the light L22 emitted from the non-overlapping region A2, the fluorescent component is emitted with a narrow-angle light distribution (low etendue) due to the action of each of the multiple nanoantennas 16 formed in the non-overlapping region A2. In other words, the nanoantennas 16 narrow the angle of light distribution of the light emitted from the non-overlapping region A2.

[0044] In this embodiment, as shown in Figure 3, when the angle perpendicular to the upper surface of the wavelength conversion plate 15 is set to 0 degrees at the outer edge of the non-overlapping region A2, the light L22 emitted spreading out at an angle of 35 degrees in the left-right direction in the figure is captured by the lens 14 described above. This light L21 represents light within an angular range that includes half of the forward light beam irradiated from the non-overlapping region A2 forward (in the range of -90 degrees to +90 degrees). Thus, the light L22 emitted from the non-overlapping region A2 via the nanoantenna 16 is emitted at a narrower angle than the light L21 emitted from the superimposed region A1.

[0045] Even if the nanoantenna 16 is formed directly on the wavelength conversion member 18, the nanoantenna 16 can still function. However, in this embodiment, as described above, the nanoantenna 16 is formed on the light-transmitting layer 19 in the non-overlapping region A2. Therefore, the energy generated by excitation by the excitation light L1 near the upper surface of the wavelength conversion member 18 facing the nanoantenna 16 is not absorbed by the nanoantenna 16 because the light-transmitting layer 19 acts as a barrier, and is instead utilized for fluorescence generation.

[0046] Therefore, in the wavelength conversion device 13 of this embodiment, fluorescence quenching caused by contact between the wavelength conversion member and the nanoantenna is less likely to occur, and the fluorescence that is not quenched can be contributed to the emission from the nanoantenna 16.

[0047] In other words, in this embodiment, the luminous flux of light L22 emitted from the non-superposition region A2 can be increased while narrowing the angle of light with the nano-antenna 16, and consequently the luminous flux of light L2 emitted from the wavelength conversion device 13 can be increased.

[0048] According to this embodiment, by arranging the nano-antenna 16 in the non-superposition region A2 other than the superposition region A1 directly above the incident region IA of the wavelength conversion plate 15, the luminous flux of light L2 emitted from the wavelength conversion device 13 can be increased. Therefore, when the wavelength conversion device 13 is used in the illumination device 10, the light extraction efficiency of light L3 emitted from the lens 14 described above can be improved.

[0049] In this embodiment, the case in which the wavelength conversion member 18 is made of a single-crystal YAG:Ce phosphor has been described. However, the wavelength conversion member 18 may be configured in a way that minimizes light scattering within it. For example, it may be a plate made of a resin or glass medium containing phosphor particles that emit yellow fluorescence.

[0050] In this embodiment, the light-transmitting layer 19 is assumed to have a higher refractive index than the wavelength-converting member 18, but this is not limited to this. For example, the light-transmitting layer 19 may be composed of a material having a lower refractive index than the wavelength-converting member 18, such as silicon dioxide (SiO2) or aluminum oxide (Al2O3). Preferably, the thickness of the light-transmitting layer 19 is greater than or equal to the wavelength of fluorescence produced by the wavelength-converting member 18, i.e., the wavelength of yellow light.

[0051] In this embodiment, the light-transmitting layer 19 is formed by, for example, electron beam deposition or sputtering deposition, but is not limited to this, and a transparent substrate as a light-transmitting member may be bonded to the wavelength conversion member 18. For example, a transparent glass substrate or sapphire substrate may be bonded to the wavelength conversion member 18 by surface activation bonding or plasma hydrophilic bonding.

[0052] In this embodiment, the nanoantenna 16 is given a cylindrical shape, but it is not limited to this shape as long as it can exhibit the above-described light narrowing effect. For example, the nanoantenna 16 may have other columnar shapes or may be conical.

[0053] In this embodiment, the period P of adjacent nanoantennas 16 is set to 350 nm, but this period P is not limited to this value and should be approximately the optical wavelength of fluorescence produced by the wavelength conversion member 18. Specifically, the YAG:Ce phosphor has a refractive index of approximately 1.82 and emits light with wavelengths of 460 nm to 750 nm. As a result, the optical wavelength is calculated as (emission wavelength / refractive index), and it is preferable that the period P of the nanoantenna 16 is within the range of 250 nm to 420 nm. Furthermore, since the YAG:Ce phosphor exhibits strong emission in the wavelength region of 500 nm or higher, it is even more preferable that the period P be 300 nm to 420 nm.

[0054] In this embodiment, the case in which a light-reflecting member 17 is provided on the side surface of the wavelength conversion plate 15 has been described, but depending on the desired light distribution, it is not necessary to provide the light-reflecting member 17. Depending on the desired light distribution, an optical multilayer reflective film or a metallic reflective film may be used instead of the light-reflecting member 17, or a combination of these may be provided on the side surface of the wavelength conversion plate 15.

[0055] [Wavelength conversion device of modified example 1] Below, a modified example 1 of the wavelength conversion device 13 will be described with reference to Figure 4. Figure 4 is a cross-sectional view of the wavelength conversion device 13 according to modified example 1. The wavelength conversion device 13 differs from Example 1 in that it is provided with a light-reflecting film on the lower surface of the wavelength conversion member 18, and otherwise has the same configuration as Example 1.

[0056] As shown in Figure 4, the light-reflecting film 23 is a film formed on the lower surface of the wavelength conversion member 18 so as to expose the incident region IA described above. In other words, the incident region IA is exposed from the light-reflecting film 23 on the lower surface of the wavelength conversion member 18.

[0057] In this modified example, the light-reflecting film 23 is a dielectric multilayer film formed by laminating a low-refractive-index material and a high-refractive-index material. Examples of the low-refractive-index material include SiO2 and Al2O3, while examples of the high-refractive-index material include ZrO2, TiO2, Nb2O5, Ta2O5, La2O3, and Si3N4.

[0058] As described in Example 1, the fluorescence generated inside the wavelength conversion member 18 is scattered in all directions within the wavelength conversion member 18. In this modified example, the fluorescence component traveling toward the lower surface of the wavelength conversion member 18 is reflected at the interface between the wavelength conversion member 18 and the light-reflecting film 23, and travels toward the upper surface side of the wavelength conversion member 18, i.e., the light-emitting surface side.

[0059] Furthermore, in this modified example, some of the excitation light L1 and fluorescence that have progressed to the non-superimposed region A2 and have been reflected by the nanoantenna 16 can also be reflected at the interface between the wavelength conversion member 18 and the light reflective film 23, allowing them to proceed back to the light emission side.

[0060] Thus, according to this modified example, by forming a light-reflecting film 23 on the lower surface of the wavelength conversion member 18, excitation light L1 and fluorescence directed toward the lower surface of the wavelength conversion member 18 can be reflected toward the light-emitting surface. Therefore, the luminous flux of light L2 emitted from the wavelength conversion device 13 can be increased.

[0061] In this modified example, the light-reflecting member 17 and the light-reflecting film 23 may have the same configuration, or they may be integrally provided on the side and bottom surfaces of the wavelength conversion plate 15. Furthermore, the light-reflecting member 17 and the light-reflecting film 23 may be provided in combination according to their respective light reflectances.

[0062] [Wavelength conversion device of modified example 2] A modified example 2 of the wavelength conversion device 13 will be described below with reference to Figures 5 and 6. The wavelength conversion device 13 differs from Example 1 in the configuration of the wavelength conversion plate 15, but other configurations, such as the arrangement of the nano-antenna 16, are the same as in Example 1.

[0063] Figure 5 is a top view of the wavelength converter 13. Similar to Figure 2, Figure 5 shows the main surface of the wavelength converter 13 from which light L2 is emitted, as viewed from a direction perpendicular to the main surface. Figure 6 is a cross-sectional view of the wavelength converter 13 along the line 6-6 in Figure 5.

[0064] In this modified example, the wavelength conversion member 18 is a prismatic member with a rectangular top surface. The wavelength conversion member 18 is positioned in the center of the wavelength conversion plate 15 when viewed from above. In this modified example, the top and bottom surfaces of the wavelength conversion member 18 are exposed on the top and bottom surfaces of the wavelength conversion plate 15, respectively.

[0065] In this modified example, the lower surface of the wavelength conversion member 18 is the incident region IA to which the excitation light L1 is incident when the wavelength conversion member 18 is attached to the lighting device 10. That is, in this modified example, the size of the lower surface of the wavelength conversion member 18 is the size of the incident region IA. Excitation light L1, which has a light intensity ranging from the maximum intensity to half of the maximum intensity, is incident on the lower surface of the wavelength conversion member 18.

[0066] Furthermore, in this modified example, the upper surface of the wavelength conversion member 18 is the superposition region A1 of the wavelength conversion plate 15. That is, in this modified example, the entire lower surface of the wavelength conversion member 18 is the incident region IA, and the entire upper surface of the wavelength conversion member 18 is the superposition region A1. The material composition of the wavelength conversion member 18 is the same as in Example 1.

[0067] The light-transmitting member 24 is a flat, transparent substrate having a frame shape with an opening 24O in the center when viewed from above. The upper and lower surfaces of the light-transmitting member 24 are exposed on the upper and lower surfaces of the wavelength conversion plate 15, respectively. The light-transmitting member 24 is made of a material such as ZrO2, TiO2, Nb2O5, Ta2O5, La2O3, or Si3N4, which has a higher refractive index than the wavelength conversion member 18.

[0068] In this modified example, the upper surface of the wavelength conversion member 18 is exposed through the opening 24O on the upper surface of the translucent member 24, and the lower surface of the wavelength conversion member 18 is exposed through the opening 24O on the lower surface of the translucent member 24. That is, in this modified example, the surface on the upper surface of the wavelength conversion plate 15 where the wavelength conversion member 18 is exposed is the superposition region A1, and the surface where the translucent member 24 is exposed is the non-superposition region A2. In this modified example, the thickness of both the wavelength conversion member 18 and the translucent member 24 is approximately 200 μm.

[0069] Similar to Example 1, the nanoantennas 16 are arranged in an array on the surface of the wavelength conversion plate 15 where the translucent member 24 is exposed, i.e., in the non-overlapping region A2. In other words, the nanoantennas 16 are arranged in an array on the upper surface of the wavelength conversion plate 15, specifically on the translucent member 24, which is the region excluding the upper surface of the wavelength conversion member 18.

[0070] The configuration of the wavelength conversion device 13 described above in this modified example can be obtained, for example, by joining the side surface of a prismatic wavelength conversion member and the inner surface of a frame-shaped translucent member with an adhesive such as an optical adhesive or glass material, cutting and polishing the joined and integrated material to a desired thickness, and then forming a nanoantenna on the upper surface of the translucent member.

[0071] [Light emitted from superimposed region A1] The light L21 emitted from the superimposed region A1 described above will be explained below using Figure 6.

[0072] In this modified example, the excitation light L1 incident perpendicularly to the incident region IA of the wavelength conversion member 18 propagates to the superposition region A1 while maintaining its directionality as laser light, similar to Example 1. At this time, the fluorescence generated by excitation from the excitation light L1 propagating inside the wavelength conversion member 18 is scattered in all directions within the wavelength conversion member 18.

[0073] In this modified example, of the fluorescence described above, the component that proceeds to the superimposed region A1, that is, the component whose angle of fluorescence proceeding from the wavelength conversion member 18 into the atmosphere is less than the critical angle, is emitted directly into the atmosphere from the superimposed region A1, as in Example 1.

[0074] Furthermore, in this modified example, the nanoantenna 16 is not placed on the upper surface of the wavelength conversion member 18, which is the superimposed region A1. Therefore, the excitation light L1 and the fluorescence components below the critical angle described above that reach the superimposed region A1 are emitted into the atmosphere without reflection or absorption by the nanoantenna 16. In other words, as in Example 1, white light L21 is emitted from the superimposed region A1, which is produced by mixing the blue light that has passed through the wavelength conversion member 18 with the yellow light as fluorescence.

[0075] In this modified example, by not arranging the nanoantenna 16 in the superimposed region A1 directly above the incident region IA, it is possible to prevent reflection or absorption of the excitation light L1 and fluorescence by the nanoantenna 16, and to emit light L21 with a high luminous flux.

[0076] [Light emitted from non-superposition region A2] Next, we will explain the light L22 emitted from the non-superposition region A2 described above using Figure 6.

[0077] In this modified example, the light-transmitting member 24 is incident on the excitation light L1 that travels outside the incident region IA. Furthermore, as described above, the light-transmitting member 24 is made of a material having a higher refractive index than the wavelength conversion member 18. Therefore, of the fluorescence generated within the wavelength conversion member 18, the component that travels from the wavelength conversion member 18 to the light-transmitting member 24, for example, the component above the critical angle described above, does not undergo total internal reflection at the interface between the wavelength conversion member 18 and the light-transmitting member 24, but travels to the light-transmitting member 24.

[0078] Fluorescence traveling within the translucent member 24 either proceeds directly to the non-overlapping region A2 or is reflected by the light-reflecting member 17 and travels to the non-overlapping region A2. The fluorescence that reaches the non-overlapping region A2 is narrowed by the nanoantenna 16 and emitted as light L22, similar to Example 1.

[0079] In this modified example as well, the fluorescence component of light L22 emitted from the non-overlapping region A2 is emitted with a narrow-angle light distribution due to the action of each of the multiple nanoantennas 16 formed in the non-overlapping region A2.

[0080] Furthermore, in this modified example, as in Example 1, the nanoantenna 16 is formed on the translucent member 24. As a result, the translucent member 24 acts as a barrier, making it less likely for the fluorescence to be quenched, and the fluorescence that is produced without quenching can be contributed to the emission from the nanoantenna 16. Therefore, while narrowing the angle of light by the nanoantenna 16, the luminous flux of light L22 emitted from the non-superimposed region A2 can be increased, and consequently, the luminous flux of light L2 emitted from the wavelength conversion device 13 can be increased.

[0081] In addition, in this modified example, since the wavelength conversion member 18 is present only in a limited region in the planar direction, wavelength conversion to fluorescence occurs only in this limited region. Furthermore, the nanoantenna 16 is not formed directly above the wavelength conversion member 18. Therefore, compared to Example 1, it is possible to suppress the absorption of fluorescence light below the critical angle by the nanoantenna 16.

[0082] [verification] The following describes the verification performed on the wavelength conversion device 13 of the present invention, along with the results of a comparison with a wavelength conversion device as a comparative example. In this verification, the wavelength conversion device 13 with the configuration of the modified example 2 described above was used.

[0083] In this verification, the modified example 2 described above was used, but it differed from modified example 2 only in that the wavelength conversion member 18, which does not have a nano-antenna 16 directly above it, was made into a circular shape with a diameter of φ2.26 mm. The translucent member 24 is assumed to be a transparent YAG substrate (without Ce doping).

[0084] The wavelength conversion device of the comparative example used for verification will now be described. The wavelength conversion device of the comparative example has a configuration in which the light-transmitting layer 19 is not formed, as is the case with the wavelength conversion device 13 of the present invention shown in Example 1. In other words, the wavelength conversion device of the comparative example has a configuration in which the nano-antennas 16 are directly arranged in an array on the upper surface of the wavelength conversion member 18.

[0085] Furthermore, the comparative example wavelength conversion device has a configuration in which nano-antennas 16 are also arranged on the upper surface of the wavelength conversion member 18 corresponding to the superposition region A1 described above when viewed from above. In other words, in the comparative example wavelength conversion device, nano-antennas 16 are evenly arranged on the upper surface of the wavelength conversion member 18.

[0086] The common elements of the comparative example and modified example 2 used in the verification will be explained. The thickness of the wavelength conversion member 18 is 200 μm in both cases. In addition, the wavelength conversion member 18 is a YAG:Ce substrate in both cases.

[0087] The nanoantenna 16 has a square lattice arrangement with a periodic interval of 350 nm and is patterned in an area of ​​6 × 6 mm. Furthermore, the nanoantenna 16 has a cylindrical shape (fixed height of 130 nm). The material of the nanoantenna 16 is metallic aluminum.

[0088] The excitation light irradiated onto the wavelength conversion device is collimated blue laser light (wavelength 440 nm, intensity 350 mW), which is irradiated onto the central part of the formation pattern of the nano-antenna 16 with a diameter of φ2 mm.

[0089] The verification was performed by comparing the forward radiant flux (wavelength 460-800 nm, ±90 degrees) of fluorescence emitted from the wavelength conversion device.

[0090] Figure 7 is a graph showing the light extraction intensity increase relative to the area ratio of the nanoantenna 16 on the light emission surface (upper surface of the wavelength conversion plate 15) in the wavelength conversion device 13 of the present invention and the wavelength conversion device of the comparative example. In this graph, the light extraction intensity increase of the wavelength conversion device 13 of the present invention is shown by a solid line, and the light extraction intensity increase of the wavelength conversion device of the comparative example is shown by a dashed line.

[0091] Note that the comparative example is a cubic approximation curve obtained from actual measurement data, while the results of the present invention are calculated. Furthermore, the change in the area ratio of the nanoantenna 16 was achieved by changing the diameter of the nanoantenna 16.

[0092] In Figure 7, the light extraction amplification intensity of the wavelength conversion device 13 of the present invention and the wavelength conversion device of the comparative example is calculated based on the fluorescence emission flux of a transparent YAG fluorescent substrate (thickness: 200 μm) without a nanoantenna 16.

[0093] As shown in Figure 7, the light extraction intensity of both the wavelength conversion device 13 of the present invention and the wavelength conversion device of the comparative example is maximized when the area ratio of the nanoantenna 16 is approximately 25%.

[0094] Furthermore, as shown in Figure 7, the light extraction intensity of the wavelength conversion device 13 of the present invention is approximately 2.60 when the area ratio of the nano-antenna 16 is approximately 25%. Also, the light extraction intensity of the wavelength conversion device of the comparative example is approximately 2.25 when the area ratio of the nano-antenna 16 is approximately 25%.

[0095] From the above results, it can be seen that when the area ratio of the nano-antenna 16 is approximately 25%, the light extraction intensity of the wavelength conversion device 13 of the present invention is improved by approximately 15% compared to the wavelength conversion device of the comparative example. In other words, the wavelength conversion device 13 of the present invention can extract more emitted light than the wavelength conversion device of the comparative example.

[0096] In this modified example, the wavelength conversion plate 15 is described as having the wavelength conversion member 18 exposed from the opening 24O of the light-transmitting member 24 on its upper and lower surfaces, respectively, but the configuration is not limited to this.

[0097] [Wavelength conversion device of modified example 3] Modification 3 will be described below with reference to Figure 8. Figure 8 is a cross-sectional view of the wavelength conversion device 13 according to Modification 3. The wavelength conversion device 13 differs from Modification 2 in the configuration of the wavelength conversion plate 15, but other configurations, such as the arrangement of the nano-antenna 16, are the same as in Modification 2.

[0098] In this modified example, the wavelength conversion device 13 has a wavelength conversion plate 15 consisting of a translucent member 24 having a flat plate shape and a wavelength conversion member 18 joined to the lower surface of the translucent member 24. That is, in this modified example, the translucent member 24 does not have the above-mentioned opening 24O formed therein.

[0099] Specifically, the wavelength conversion device 13 has a configuration in which the upper surface of the wavelength conversion member 18 is joined to the center of the lower surface of the translucent member 24, and the area of ​​the lower surface of the translucent member 24 excluding the joint portion between the translucent member 24 and the wavelength conversion member 18 is covered by a light-reflecting film 23. The light-reflecting film 23 is made of, for example, a dielectric multilayer film that reflects the wavelength of fluorescence. Even with a wavelength conversion device 13 having such a configuration, the same effects as the above-described embodiment and modified example can be achieved.

[0100] In addition, other configurations are possible, for example, in which the light-transmitting member 24 is formed in a recessed shape, and the wavelength conversion member 18 is joined to the recessed area. That is, there may be a configuration in which only the upper surface of the wavelength conversion member 18 is exposed, and the lower surface of the wavelength conversion member 18 is not exposed.

[0101] Furthermore, the light-transmitting member 24 may have a shape opposite to the recess, that is, it may have an opening on its lower side, and the wavelength conversion member 18 may be joined to the opening. In other words, it may be configured such that only the lower surface of the wavelength conversion member 18 is exposed, and the upper surface of the wavelength conversion member 18 is not exposed.

[0102] In any of the above-described configurations, the effects of the present invention can be obtained by not forming the nanoantenna 16 in the superimposed region A1 when viewed from above, and instead forming the nanoantenna 16 only in the non-superimposed region A2.

[0103] [Wavelength conversion device of modified example 4] Below, a modification 4 of the wavelength conversion device 13 of Example 1 will be described with reference to Figure 9. Figure 9 is a top view of the wavelength conversion device 13 according to modification 4. The wavelength conversion device 13 differs from modification 2 in the configuration of the wavelength conversion plate 15, but otherwise has the same configuration as modification 2.

[0104] In this modified example, the wavelength conversion member 18 has a longitudinal shape that extends vertically in the figure when viewed from above. Also in this modified example, two translucent members 24 are formed so as to sandwich the wavelength conversion member 18 in the short direction of the wavelength conversion member 18. In this modified example, the two translucent members 24 are the same size as each other.

[0105] In this modified example, the superimposed region A1 corresponding to the incident region IA described above is the central portion of the upper surface of the wavelength conversion member 18, and the non-superimposed region A2 is the upper surface of the wavelength conversion member 18 excluding the superimposed region A1 and the upper surface of the translucent member 24.

[0106] The nanoantennas 16 are arranged in an array on the upper surface of the translucent member 24. In other words, in this modified example, the nanoantennas 16 are arranged only on the upper surface of the translucent member 24 in the non-overlapping region A2, and the nanoantennas 16 are not arranged on the upper surface of the wavelength conversion member 18 excluding the overlapping region A1. This prevents the quenching of the fluorescence described above and allows the fluorescence to contribute to an increase in luminous flux.

[0107] The configuration of the wavelength conversion device 13 in this modified example can be obtained, for example, by placing a plate-shaped wavelength conversion member between two translucent members and joining them together, then cutting and polishing the joined and integrated material to a desired thickness, and finally forming a nanoantenna on the upper surface of the translucent members. For this reason, this modified example is easier to manufacture compared to Modification Example 2. [Examples]

[0108] [Lighting device of Example 2] Figure 10 is a schematic cross-sectional view showing the configuration of the lighting device 20 according to Embodiment 2. Hatching has been omitted in Figure 10 for the sake of visibility. The following will mainly describe the differences from the lighting device 10 of Embodiment 1.

[0109] The housing 11 is a box-shaped housing, and has two opposing surfaces, one of which has an opening OP1 and the other of which has an opening OP2. Furthermore, the housing 11 has an opening OP3 on one of the two opposing surfaces in a direction perpendicular to the direction in which the two aforementioned surfaces face each other.

[0110] The light source 12 is a laser light source fixed within aperture OP1 and emitting blue wavelength light L1 toward aperture OP2. In other words, aperture OP1 is formed on the optical axis OA of light L1.

[0111] The wavelength conversion device 25 is fixed inside the aperture OP2 and has a wavelength conversion function that receives light L1 emitted from the light source 12 and emits fluorescence of a different wavelength from light L1. In this embodiment, the wavelength conversion device 25 receives light L1 emitted from the light source 12 and emits light L2 toward the aperture OP1.

[0112] As shown in Figure 10, the dichroic mirror DM is a mirror fixed within the housing 11 at a 45-degree angle to the optical axis OA of the light L1 from the light source 12. The dichroic mirror DM is a mirror that reflects light of a specific wavelength and transmits light in other wavelength ranges.

[0113] In this embodiment, the dichroic mirror DM transmits blue wavelength light and reflects fluorescent wavelength light. Therefore, the blue wavelength light L1 incident on the dichroic mirror DM is transmitted and proceeds to the wavelength converter 25.

[0114] Furthermore, the dichroic mirror DM transmits the blue wavelength light of the light L2 emitted from the wavelength converter 25, and reflects the fluorescent component of the light L2 perpendicular to the optical axis OA, i.e., toward the aperture OP3. In Figure 10, the fluorescent component light reflected by the dichroic mirror DM is shown as light L2'.

[0115] The lens 14 is fixed within the aperture OP3. The lens 14 receives light L2' reflected by the dichroic mirror DM, shapes the light L2' into a desired light distribution, and generates light L3 as illumination light. The light L3 is extracted to the outside of the housing 11, similar to Example 1.

[0116] [Wavelength conversion device of Example 2] The wavelength conversion device 25 of the lighting device 20 according to Example 2 will be described below with reference to Figures 11 and 12. Figure 10 is a top view of the wavelength conversion device 25. Figure 12 shows the main surface of the wavelength conversion device 25 from which light L2 is emitted, as viewed from a direction perpendicular to the main surface. Figure 12 is also a cross-sectional view of the wavelength conversion device 25 along the line 11-11 in Figure 11. The following will mainly describe the differences from the wavelength conversion device 13 in Example 1.

[0117] The submount 26 is a flat substrate with a rectangular top surface. The submount 26 is made of, for example, aluminum nitride (AlN) or Al2O3.

[0118] The metal reflective film 27 is a light-reflecting metal film formed over the lower surface of the wavelength conversion member 18. In this embodiment, the metal reflective film 27 is made of, for example, silver (Ag) or Al.

[0119] The lower surface of the metal reflective film 27 is joined to the upper surface of the submount 26 via a bonding member 28. In other words, the wavelength conversion plate 15 is joined to the submount 26 via the metal reflective film 27 and the bonding member 28. In this embodiment, the bonding member 28 is, for example, eutectic solder or nano-silver sintered material.

[0120] In this embodiment, the light-reflecting member 17 covers the sides of the wavelength conversion plate 15 and the metal reflective film 27 and reaches the upper surface of the submount 26. That is, in this embodiment, the lower surface of the wavelength conversion plate 15 is covered by the metal reflective film 27 and the submount 26, and only the upper surface of the wavelength conversion plate 15, i.e., the light-emitting surface, is exposed to the outside.

[0121] As described above, in this embodiment, when the wavelength conversion device 25 is used as the illumination device 20, excitation light L1 is emitted from the light source 12 located above the wavelength conversion device 25 toward the wavelength conversion device 25 located below the light source 12. Therefore, the incident region IA is provided in the center of the upper surface of the wavelength conversion member 18, as shown in Figure 12.

[0122] In this embodiment, the excitation light L1 incident on the incident region IA travels downward in the figure while emitting fluorescence inside the wavelength conversion member 18. In this embodiment, as described above, a metal reflective film 27 is formed over the lower surface of the wavelength conversion member 18. Therefore, the excitation light L1 and fluorescence are reflected upward at the interface between the wavelength conversion member 18 and the metal reflective film 27.

[0123] In this embodiment as well, the wavelength conversion member 18 is configured in such a way that light scattering is less likely to occur inside it. Therefore, as in Embodiment 1, the reflected light (excitation light L1 and fluorescence) described above proceeds to the light-transmitting layer 19 with almost no scattering occurring within the wavelength conversion member 18. Consequently, as in Embodiment 1, light L21 is extracted from the superimposed region A1 and light L22 is extracted from the non-superimposed region A2.

[0124] Therefore, in this embodiment as well, for the same reasons as in Embodiment 1, the luminous flux of light L22 emitted from the superimposed region A1 and the non-superimposed region A2 can be increased, and the luminous flux of light L2 emitted from the wavelength converter 25 can be increased.

[0125] In addition, in this embodiment, the incident region IA of the wavelength conversion device 25 is on the same plane as the exit region. Therefore, in the wavelength conversion device of this embodiment, heat can be dissipated from the back surface of the wavelength conversion member 18 via the submount 26, thereby suppressing the decrease in wavelength conversion efficiency due to heat.

[0126] In this embodiment, a metal reflective film 27 is formed on the lower surface of the wavelength conversion member 18, but the embodiment is not limited to this. For example, the dielectric multilayer film described above may be formed between the wavelength conversion member 18 and the metal reflective film 27. This can improve the reflectance of the fluorescence described above and increase the luminous flux of the light L2 as emitted light.

[0127] In this embodiment, the configuration of the wavelength conversion device 25 may be modified using the configurations of the modified examples 2 to 4 described above. In other words, the configuration of the wavelength conversion plate 15 can be changed as appropriate. [Examples]

[0128] [Lighting device of Example 3] Figure 13 is a schematic cross-sectional view showing the configuration of the lighting device 30 according to Embodiment 3. In Figure 13, hatching has been omitted for the sake of visibility. The following will mainly describe the differences from the lighting device 10 of Embodiment 1.

[0129] The housing 11 is a box-shaped housing, and on two opposing surfaces, one surface has an opening OP1 and the other surface has an opening OP2.

[0130] The wavelength converter 32 is fixed inside the aperture OP1 and incorporates a light source 33 inside. The wavelength converter 32 is a wavelength converter that has a wavelength conversion function and is excited when it receives excitation light emitted from the light source 33, and emits fluorescence with a different wavelength from the excitation light. In this embodiment, the wavelength converter 32 emits light L4 toward the aperture OP2.

[0131] The light source 33 is incorporated into the wavelength conversion device 32 and is a light source that emits light of a specific wavelength. In this embodiment, the light source 33 is a light-emitting diode (LED) having a light-emitting layer made of an InGaN semiconductor. In this embodiment, blue light with a wavelength of approximately 450 nm is emitted from the light source 33 as excitation light. Apertures OP1 and OP2 are formed on the optical axis OA of the excitation light from the light source 33.

[0132] The lens 14 is fixed within the aperture OP2. In this embodiment, the lens 14 is formed on the optical axis of the light L4, which is the illumination light emitted from the wavelength conversion device 32. The lens 14 receives the light L4 emitted from the wavelength conversion device 32, shapes the light L4 into a desired light distribution, and generates the light L5, which is the illumination light. The light L5 is taken out to the outside of the housing 11, as in Embodiments 1 and 2.

[0133] [Wavelength conversion device of Example 3] The wavelength conversion device 32 of the lighting device 30 according to Example 2 will be described below with reference to Figure 14. Figure 14 is a cross-sectional view of the wavelength conversion device 32. Figure 14 shows a cross-section at the same position as the line 3-3 of the wavelength conversion device 13 shown in Figure 2. The wavelength conversion device 32 has the same configuration of the wavelength conversion plate 15 and the arrangement of the nanoantenna 16 as the wavelength conversion device 13 of Example 1.

[0134] The light source 33 is a light source provided in contact with the center of the lower surface of the wavelength conversion member 18. The excitation light described above is emitted from the light source 33 to the center of the lower surface of the wavelength conversion member 18 in contact with it. In other words, in this embodiment, the light emission surface of the light source 33 is the incident region IA of the wavelength conversion plate 15.

[0135] The light-reflecting member 34 is a light-reflecting member formed on the lower surface of the wavelength conversion member 18 and arranged to cover the side surface of the light source 33. In other words, when viewed from a direction perpendicular to the lower surface of the wavelength conversion plate 15, the area of ​​the lower surface excluding the area in contact with the light source 33 is covered by the light-reflecting member 34.

[0136] The light-reflecting member 34 is a diffuse reflecting member that diffusely reflects both excitation light and fluorescence. In this embodiment, the light-reflecting member 34 is made of a resin material containing TiO2 particles in a silicone resin. Also in this embodiment, the light-reflecting member 34 has the same thickness as the light source 33.

[0137] The heat sink 35 is a metal component provided on the lower surface of the light source 33 and the light reflecting member 34. The heat sink 35 is provided in contact with the light source 33, which is an LED light source, and promotes the dissipation and exhaust of heat generated in the light source 33. The heat sink 35 is made of, for example, Al or copper (Cu).

[0138] In this embodiment, the light-reflecting member 17 is formed to cover the sides of each of the wavelength conversion plate 15, the light-reflecting member 34, and the heat sink 35. That is, the lower surface of the wavelength conversion plate 15 is covered by the light source 33, the light-reflecting member 34, and the heat sink 35, and only the upper surface of the wavelength conversion plate 15, i.e., the light-emitting surface, is exposed to the outside.

[0139] The light L4 emitted from the superimposed region A1 described above will be explained below using Figure 14.

[0140] In this embodiment, the excitation light emitted from the light source 33 is incident into the wavelength conversion plate 15 in a Lambertsian distribution exhibiting uniform diffusion or an equivalent distribution. In this embodiment, the superimposed region A1 is the region in which a component of the excitation light emitted from the light source 33 in a Lambertsian manner is emitted that is below the critical angle at the interface between the wavelength conversion plate 15 and the atmosphere.

[0141] Specifically, when the angle perpendicular to the upper surface of the wavelength conversion plate 15 is set to 0 degrees, the region on the upper surface of the light-transmitting layer 19 when excitation light is emitted from the light source 33 at an angle of 18.5 degrees to the left and right in the figure is the superposition region A1 in this embodiment. When the excitation light that spreads at an angle of 18.5 degrees propagates from the light-transmitting layer 19 into the atmosphere, the excitation light spreads at an angle of 35 degrees to the left and right in the figure, and light L4, which is a mixture of the excitation light and fluorescence generated in the wavelength conversion member 18, is emitted from the superposition region A1 described above.

[0142] In this embodiment, when the thickness of the wavelength conversion plate 15 in Figure 14 is defined as thickness H, and the width of the light emission surface of the light source 33, i.e., the incident region IA, is defined as width T, the emission width of the excitation light emitted from the upper surface of the wavelength conversion plate 15 can be expressed as T + 2H·tan18.5°, and this emission width becomes the width of the superimposed region A1. In other words, the boundary between the superimposed region A1 and the non-superimposed region A2 can be defined by the above formula.

[0143] Here, the angle of 18.5 degrees is set from the angle of 35 degrees when the light travels through the atmosphere. Furthermore, the 35-degree angle in the atmosphere is matched with a predetermined angle (lens capture angle) at which the light is captured by the lens 14, which is positioned at a distance from the wavelength converter 32. In addition, it is set to be the same as the 35-degree angle range (fluorescence emission angle) in which the forward luminous flux of the fluorescence wavelength light in this embodiment is halved. In other words, the angle range in which the excitation light is efficiently extracted while avoiding absorption by the nanoantenna 16, the angle range in which the fluorescence is efficiently extracted at a narrow angle by the nanoantenna 16, and the angle range in which the light emitted from the wavelength converter 32 is captured by the lens 14 are matched.

[0144] On the other hand, in the case of Lambertian light distribution, the half-angle of peak intensity is 60 degrees. Even when considering the angular range in which the forward luminous flux is halved, it is 45 degrees. In other words, light between 18.5 degrees and 45 degrees or between 60 degrees is not extracted from the superposition region A1, even though its intensity as illumination light is sufficiently strong. This angular range also includes light below the total internal reflection angle at the exit surface. If the only goal is to increase the amount of light extracted, it is advantageous to extend the superposition region A1 to the total internal reflection angle.

[0145] However, even if excitation light within this angular range is emitted, it will not be captured by lens 14. Alternatively, the intensity balance with fluorescence will be disrupted, making it difficult to use for color mixing.

[0146] Therefore, in this embodiment, a portion of the excitation light below the total reflection angle is reflected by the nanoantenna 16 in the non-superposition region A2 and then reflected again by the light-reflecting member 34 for use. Since the reflection by the nanoantenna 16 is specular reflection, the angle of the light does not change, but since the reflection by the light-reflecting member 34 is diffuse reflection, a portion of it is converted to an angle of 18.5 degrees or less, that is, an angle that can be captured by the lens 14, or an angle within half the forward luminous flux of the fluorescence wavelength by the nanoantenna 16.

[0147] Therefore, according to this embodiment, by arranging the nanoantenna 16 in a region outside the width expressed by the above formula, that is, in the non-overlapping region A2 outside the overlapping region A1, and by arranging the diffusely reflecting light reflective member 34, a portion of the excitation light irradiated at a wide angle can be converted into narrow-angle light.

[0148] Therefore, the luminous flux within the angular range usable as illumination light from the excitation light emitted from the light source 33 can be increased.

[0149] In addition, an LED is used as the light source 33 in this embodiment. Compared to the laser light source described in Embodiment 1, the LED is less expensive, and the lighting device itself can be manufactured at a lower cost.

[0150] In this embodiment, a light-reflecting member 34 is provided on the lower surface of the wavelength conversion member 18. However, for example, a light-reflecting film 23 made of a dielectric multilayer film as described in Modification 1 may be provided between the lower surface of the wavelength conversion member 18 and the light-reflecting member 34. By providing the light-reflecting film 23 so as to specularly reflect light of the fluorescence wavelength and allow excitation light (blue light) to pass through, the wavelength conversion device 32 can specularly reflect light of the fluorescence wavelength while causing diffuse reflection of excitation light by the light-reflecting member 34, thereby maintaining the angle of light on which the nano-antenna 16 acts.

[0151] In this embodiment, the wavelength conversion device 32 includes a light source 33, but it is not limited to this configuration, and the wavelength conversion plate 15 may be configured such that the light emitted from the light source 33 is incident on it in a Lambertsian manner.

[0152] In this embodiment, the wavelength conversion plate 15 may be configured with the configurations described in the modified examples 2 to 4 above. In other words, the configuration of the wavelength conversion plate 15 can be changed as appropriate.

[0153] [Wavelength conversion device of modified example 5] Below, a fifth modification of the wavelength conversion device 32 according to Example 3 will be described with reference to Figure 15. Figure 15 is a cross-sectional view of the wavelength conversion device 32 according to the fifth modification. The wavelength conversion device 32 differs from Example 3 in that it has multiple light sources, but otherwise has the same configuration as Example 3.

[0154] In this modified example, multiple light sources 33 are provided on the lower surface of the wavelength conversion member 18. Specifically, as shown in Figure 15, two light sources 33 are arranged on the heat sink 35 so as to be spaced apart from each other and in contact with the lower surface of the wavelength conversion member 18.

[0155] A light-reflecting member 34 is provided between each of the two light sources 33. In this modified example, the lower surface of the wavelength conversion member 18 that is in contact with each of the two light sources 33 is the incident region IA into which the excitation light described above is incident. In other words, in this modified example, two incident regions IA are formed.

[0156] In this modified example, no nanoantennas 16 are placed in each of the superimposed regions A1 corresponding to each of the incident regions IA described above, while nanoantennas 16 are placed in the non-superimposed regions A2, which are regions other than the superimposed regions A1.

[0157] Therefore, in this modified example, as in Example 3, by arranging the nanoantenna 16 in the non-overlapping region A2 outside the overlapping region A1 and arranging the diffusely reflecting light reflective member 34, a portion of the wide-angle irradiated excitation light can be converted into narrow-angle light.

[0158] Furthermore, in this modified example, a configuration is provided in which multiple light sources 33 are installed. Therefore, the uniformity of the color of the emitted light from the wavelength conversion device 32 can be improved.

[0159] In this modified example, the wavelength conversion plate 15 may be configured using the same configuration as described in Modified Examples 2 to 4 above. In other words, the configuration of the wavelength conversion plate 15 can be modified as appropriate.

[0160] In the above-described embodiments and modifications, the nanoantennas 16 are not formed in the superimposed region A1, but they may be formed partially. In that case, the density of the arrangement area of ​​the nanoantennas 16 formed in the superimposed region A1 (arrangement density) is lower than the density of the arrangement area of ​​the nanoantennas 16 formed in the non-superimposed region A2.

[0161] The shape or dimensions of each part of the lighting device and wavelength conversion device according to the present invention are not limited to the embodiments and modifications described above, and can be changed as appropriate depending on the application. Furthermore, the arrangement of each component of the lighting device in Embodiments 1 to 3 is shown as an example and can be changed as appropriate. [Industrial applicability]

[0162] This invention can be used as a light source for projectors, general lighting, vehicle lighting, and the like. [Explanation of Symbols]

[0163] 10, 20, 30 Lighting devices 11 cabinets 12. Light source (laser light source) 13, 25, 32 wavelength conversion device 14 lenses 15 wavelength conversion plate 16 Nano Antennas 17, 34 Light-reflecting members 18 Wavelength conversion component 19 Translucent layer 23 Light reflective film 24 Translucent material 26 Submount 27 Metal reflective film 28 Joining members 33 Light source (LED light source) 35 Heatsink

Claims

1. A wavelength conversion device having a phosphor portion consisting of a phosphor that has an incident region on its surface to which excitation light is incident and which emits fluorescence when excited by said excitation light, and a nanoantenna formed on the surface of the output surface, The incident region is located on one main surface of the wavelength converter, and in a top view taken from a direction perpendicular to the output surface, which is the other main surface of the wavelength converter, the arrangement density of the nanoantennas formed in the non-overlapping region that does not overlap with the incident region is greater than the arrangement density of the nanoantennas in the overlapping region that overlaps with the incident region. The plate-shaped portion is provided in contact with the phosphor portion, is transparent to the excitation light and the fluorescence, and together with the phosphor portion, forms a flat plate shape, The light-transmitting portion has a frame shape with an opening in the top view, A wavelength conversion device characterized in that the phosphor portion is arranged within the opening of the light-transmitting portion.

2. A wavelength conversion device having a phosphor portion consisting of a phosphor that has an incident region on its surface to which excitation light is incident and which emits fluorescence when excited by said excitation light, and a nanoantenna formed on the surface of the output surface, The incident region is located on one main surface of the wavelength converter, and in a top view taken from a direction perpendicular to the output surface, which is the other main surface of the wavelength converter, the arrangement density of the nanoantennas formed in the non-overlapping region that does not overlap with the incident region is greater than the arrangement density of the nanoantennas in the overlapping region that overlaps with the incident region. The plate-shaped portion is provided in contact with the phosphor portion, is transparent to the excitation light and the fluorescence, and together with the phosphor portion, forms a flat plate shape, The phosphor portion has an elongated shape when viewed from above. The wavelength conversion device is characterized in that the transparent portion is formed in multiple locations such as sandwiching the phosphor portion in the short direction of the phosphor portion.

3. A wavelength conversion device having a phosphor portion consisting of a phosphor that has an incident region on its surface to which excitation light is incident and which emits fluorescence when excited by said excitation light, and a nanoantenna formed on the surface of the output surface, The incident region is located on one main surface of the wavelength converter, and in a top view taken from a direction perpendicular to the output surface, which is the other main surface of the wavelength converter, the arrangement density of the nanoantennas formed in the non-overlapping region that does not overlap with the incident region is greater than the arrangement density of the nanoantennas in the overlapping region that overlaps with the incident region. A wavelength conversion device characterized in that a light-reflecting film that is reflective to the excitation light or the fluorescence is formed around the incident region on one of the main surfaces of the wavelength conversion device.

4. The wavelength conversion device according to claim 3, further comprising a plate-shaped portion provided in contact with the phosphor portion, having transparency to the excitation light and the fluorescence, and having a flat plate shape together with the phosphor portion.

5. The wavelength conversion device according to any one of claims 1 to 4, characterized in that the nanoantenna is not formed in the superimposed region.

6. The phosphor portion has one surface having the incident region and another surface opposite to the first surface, The wavelength conversion device according to claim 4, characterized in that the light-transmitting portion is formed to cover the other surface.

7. The wavelength conversion device according to any one of claims 1 to 6, characterized in that the nanoantenna is a columnar or cone-shaped metallic protrusion made of Al.

8. The wavelength conversion device according to any one of claims 1 to 7, characterized in that the phosphor portion is made of a single-crystal phosphor.

9. A wavelength conversion device according to any one of claims 1 to 8, A light source that emits the excitation light toward the incident region, A lighting device characterized by having the following features.

10. Having multiple light sources, The lighting device according to claim 9, characterized in that the incident region and the superimposed region are formed in multiple locations corresponding to each of the multiple light sources.

Images