JP7833142B2 - Wavelength conversion device and illumination device - Google Patents

Description

This invention relates to a wavelength conversion device and a lighting device.

A lighting device is disclosed that uses a metal antenna (hereinafter referred to as a nanoantenna) made of nano-sized metal particles to narrow the angle of emitted light. For example, Patent Document 1 discloses a lighting device having a transparent substrate, a wavelength converter arranged on the transparent substrate, and a plurality of nanoantennas formed on the wavelength converter.

Special table 2014-508379 publication

In lighting devices such as those described in Patent Document 1, when excitation light for exciting the phosphor in the wavelength converter is emitted from the light source, nanoantennas arranged on the wavelength converter absorb or reflect the excitation light and fluorescence generated from the phosphor passing through the wavelength converter, resulting in a decrease in the luminous flux of the emitted light from the wavelength converter.

Furthermore, in lighting devices such as those described in Patent Document 1, a problem arises because, at the interface between the wavelength converter and the nanoantenna, the nanoantenna absorbs a portion of the energy of the wavelength converter excited by the excitation light, converting it into thermal energy. This causes quenching of the fluorescence that should have occurred.

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 narrower beam angle.

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 consisting of 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.

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.

This is a schematic cross-sectional view showing the configuration of the lighting device according to Example 1. This is a top view of the wavelength conversion device according to Example 1. This is a cross-sectional view of the wavelength conversion device according to Example 1. This is a cross-sectional view of the wavelength conversion device according to modified example 1. This is a top view of the wavelength conversion device according to modified example 2. This is a cross-sectional view of the wavelength conversion device according to modified example 2. This figure shows the wavelength conversion device according to Modification 2 and the experimental results in the comparative example. This is a cross-sectional view of the wavelength conversion device according to modified example 3. This is a top view of the wavelength conversion device according to Modification 4. This is a schematic cross-sectional view showing the configuration of the lighting device according to Example 2. This is a top view of the wavelength conversion device according to Example 2. This is a cross-sectional view of the wavelength conversion device according to Example 2. This is a schematic cross-sectional view showing the configuration of the lighting device according to Example 3. This is a cross-sectional view of the wavelength conversion device according to Example 3. This is a cross-sectional view of the wavelength conversion device according to modified example 5.

The embodiments of the present invention will be described in detail below with reference to the drawings. Note that identical components are denoted by the same reference numerals in the drawings, and descriptions of redundant components are omitted.

[Lighting device of Example 1]
Figure 1 is a schematic cross-sectional view showing the configuration of the lighting device 10 according to Embodiment 1. In Figure 1, hatching has been omitted for the sake of visibility.

The housing 11 is a box-shaped housing, and each of its two opposing surfaces has an opening OP1 and an opening OP2. The housing 11 has a support structure 11A for supporting an object at a position between opening OP1 and opening OP2.

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

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

The wavelength conversion device 13 emits light L2, which includes the light that passes through the wavelength conversion device 13 without contributing to fluorescence generation upon receiving light L1, and the aforementioned fluorescence.

The lens 14, as an optical component, is fixed within the aperture OP2. That is, the lens 14 is positioned on the optical axis OA. The lens 14 receives light L2 emitted from the wavelength conversion device 13, shapes the light L2 into a desired light distribution, and generates illumination light L3. For example, a spherical lens or an aspherical lens can be used for the lens 14. The light L3 generated by the lens 14 is extracted to the outside of the housing 11.

In this embodiment, the space between the light source 12 and the wavelength converter 13 within the housing 11, and the space between the wavelength converter 13 and the lens 14, are filled with air. That is, the light L2 emitted from the wavelength converter 13 passes through the air before being incident on the lens 14.

[Wavelength conversion device of Example 1]
The wavelength conversion device 13 of the lighting device 10 according to Embodiment 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.

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.

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.

In this embodiment, the incident region IA in the center of 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.

In this embodiment, the incident region IA includes the 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 half-power angle, and the incident region IA is the range within the half-power angle at which the excitation light spreads. 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.

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.

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.

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.

Specifically, the light-transmitting layer 19 is _composed of materials such as zirconium oxide ( _ZrO₂ ), niobium pentoxide ( _{Nb₂O₅ )} , tantalum pentoxide ( _Ta₂O₅ ), titanium oxide ( _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.

The 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 each nanoantenna has a circular, columnar metal protrusion on its upper surface. In this embodiment, the nanoantennas 16 are arranged in multiple rows in the frame-shaped non-overlapping region A2 of 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, the nanoantennas 16 are not arranged in the overlapping region A1.

In this embodiment, the nanoantennas 16 are arranged in a matrix pattern 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.

Furthermore, 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).

In this embodiment, the nanoantennas 16 are arranged periodically at predetermined intervals. However, a region where nanoantennas 16 are not formed, even though their positions correspond to the arrangement period of the nanoantennas 16, can be considered a region where nanoantennas 16 are not present. Specifically, on the upper surface of the translucent layer 19, a region where nanoantennas 16 are not adjacent to each other at the aforementioned period P, and where nanoantennas 16 are not formed, is considered a region where nanoantennas 16 are not present in this embodiment.

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.

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, 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.

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. Instead, the nano-antenna 16 is placed in the non-superimposed region A2, which is a region other than the superimposed region A1.

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.

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

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 proceeds to the superposition region A1 while maintaining its laser beam directionality.

At this time, the fluorescence generated by excitation light L1 traveling through 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 traveling to the superposition region A1—that is, the component whose angle of fluorescence traveling from 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.

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

In this way, in this embodiment, by not placing the nanoantenna 16 in the superimposed region A1 directly above the incident region IA, it is possible to prevent reflection and absorption of the excitation light L1 and fluorescence by the nanoantenna 16, thereby enabling the emission of light L21 with a high luminous flux.

In this embodiment, when the wavelength conversion device 13 is used in the illumination device 10, the light L21 represents light within an angular range of 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 at the outer edge of the superimposed region A1 is set to 0 degrees, 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.

[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.

In this embodiment, the excitation light L1 that travels outside the incident region IA, i.e., the component of 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-superposition region A2 and is emitted into the atmosphere through this non-superposition region A2.

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 emitted from the non-overlapping region A2.

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 a 35-degree angle 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 nano-antenna 16 is emitted at a narrower angle than the light L21 emitted from the superimposed region A1.

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.

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.

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

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 can be improved.

In this embodiment, the case where the wavelength conversion member 18 is made of a single-crystal YAG:Ce phosphor was described. However, the wavelength conversion member 18 may be made of any material 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.

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 made 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.

In this embodiment, the translucent layer 19 is formed by, for example, electron beam deposition or sputtering, but it is not limited to this. A transparent substrate as a translucent 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.

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

In this embodiment, the period P of adjacent nanoantennas 16 was set to 350 nm, but this period P is not limited to this value and should be approximately the optical wavelength of the fluorescence emitted by the wavelength conversion member 18. Specifically, the YAG:Ce phosphor has a refractive index of approximately 1.82 and emits light with wavelengths from 460 nm to 750 nm. Therefore, the optical wavelength is calculated as (emission wavelength / refractive index), and the period P of the nanoantenna 16 is preferably 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 for the period P to be between 300 nm and 420 nm.

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. However, depending on the desired light distribution, the light-reflecting member 17 may not be provided. Furthermore, 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.

[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 has the same configuration as Example 1 in all other respects.

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.

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} .

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.

Furthermore, in this modified example, some of the excitation light L1 and fluorescence that have progressed into the non-superimposed region A2, which are reflected by the nanoantenna 16, can also be reflected back to the light-emitting surface by the interface between the wavelength conversion member 18 and the light-reflecting film 23.

Thus, according to this modified example, by forming a light-reflecting film 23 on the lower surface of the wavelength conversion member 18, the 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.

In this modified example, the light-reflecting member 17 and the light-reflecting film 23 may have identical configurations, 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.

[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-antennas 16, are the same as in Example 1.

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, viewed from a direction perpendicular to that main surface. Figure 6 is a cross-sectional view of the wavelength converter 13 along the line 6-6 in Figure 5.

In this modified example, the wavelength conversion member 18 is a rectangular prism-shaped 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.

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 illumination 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, exhibiting a light intensity range from the maximum intensity to half of that maximum intensity, is incident on the lower surface of the wavelength conversion member 18.

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.

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 , _{Si₃N₄ , etc.} , which has _a higher refractive index than _the wavelength conversion member 18.

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 of 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.

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, similar to Example 1. In other words, the nanoantennas 16 are arranged in an array on the upper surface of the translucent member 24, which is the region of the upper surface of the wavelength conversion plate 15 excluding the upper surface of the wavelength conversion member 18.

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.

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

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 the excitation light L1 propagating through the inside of the wavelength conversion member 18 is scattered in all directions within the wavelength conversion member 18.

In this modified example, the fluorescence component that propagates into the superposition region A1, i.e., the component whose fluorescence angle propagating from the wavelength conversion member 18 into the atmosphere is less than the critical angle, is emitted directly into the atmosphere from the superposition region A1, as in Example 1.

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

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, thereby enabling the emission of light L21 with a high luminous flux.

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

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 with a higher refractive index than the wavelength conversion member 18. Therefore, of the fluorescence generated within the wavelength conversion member 18, the component traveling 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 instead travels to the light-transmitting member 24.

The fluorescence traveling within the translucent member 24 either directly proceeds towards 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 nano-antenna 16 and emitted as light L22, similar to Example 1.

In this modified example, the fluorescence component of the 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.

Furthermore, in this modified example, similar to Example 1, the nanoantenna 16 is formed on the translucent member 24. Therefore, the translucent member 24 acts as a barrier, making quenching of the fluorescence less likely. The fluorescence that is not quenched can then be contributed to the emission from the nanoantenna 16. Consequently, while narrowing the light angle by the nanoantenna 16, the luminous flux of the light L22 emitted from the non-superimposed region A2 can be increased, and consequently, the luminous flux of the light L2 emitted from the wavelength conversion device 13 can be increased.

Furthermore, in this modified example, since the wavelength conversion member 18 exists only in a limited region in the planar direction, wavelength conversion to fluorescence occurs only in this limited region. Moreover, 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.

[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.

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 the 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).

The wavelength conversion device used in the comparative example for verification will now be described. The wavelength conversion device used as a comparative example has a configuration similar to the wavelength conversion device 13 of the present invention shown in Example 1, but without the light-transmitting layer 19. That is, 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.

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 distributed on the upper surface of the wavelength conversion member 18.

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. Furthermore, the wavelength conversion member 18 is a YAG:Ce substrate in both cases.

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

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 portion of the nano-antenna 16 formation pattern with a diameter of φ2 mm.

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

Figure 7 is a graph showing the ratio of the area of the nanoantenna 16 on the light-emitting surface (upper surface of the wavelength conversion plate 15) to the light extraction amplification 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 amplification in the wavelength conversion device 13 of the present invention is shown by a solid line, and the light extraction amplification in the wavelength conversion device of the comparative example is shown by a dashed line.

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 nano-antenna 16 was achieved by changing the diameter of the nano-antenna 16.

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

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 nano-antenna 16 is approximately 25%.

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

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 enhancement 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.

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

[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.

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 aforementioned opening 24O.

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, for example, made of a dielectric multilayer film that reflects the wavelength of fluorescence. Even with such a configuration, the same effects as those of the above-described embodiment and modification can be achieved.

Furthermore, other configurations are possible, for example, in which the translucent member 24 is formed in a recessed shape, and the wavelength conversion member 18 is joined within this recess. That is, a configuration is possible in which only the upper surface of the wavelength conversion member 18 is exposed, while the lower surface of the wavelength conversion member 18 is not exposed.

Furthermore, the translucent member 24 may have a shape opposite to the recess, that is, it may have an opening on its lower surface, and the wavelength conversion member 18 may be joined within this opening. In other words, only the lower surface of the wavelength conversion member 18 may be exposed, while the upper surface of the wavelength conversion member 18 is not.

Furthermore, in any of the above-described configurations, the effects of the present invention can be obtained by not forming the nano-antenna 16 in the superimposed region A1 in the top view, and instead forming the nano-antenna 16 only in the non-superimposed region A2.

[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.

In this modified example, the wavelength conversion member 18 has a longitudinal shape that extends vertically in the figure when viewed from above. Furthermore, in this modified example, two translucent members 24 are formed so as to sandwich the wavelength conversion member 18 in its short-side direction. In this modified example, the two translucent members 24 are of the same size.

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.

The nano-antennas 16 are arranged in an array on the upper surface of the translucent member 24. Specifically, in this modified example, the nano-antennas 16 are arranged only on the upper surface of the translucent member 24 within the non-overlapping region A2, and not 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.

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 the desired thickness, and finally forming a nanoantenna on the upper surface of the translucent members. Therefore, this modified example is easier to manufacture compared to Modification Example 2.

[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. In Figure 10, hatching has been omitted for the sake of visibility. The following will mainly describe the differences from the lighting device 10 of Embodiment 1.

The housing 11 is a box-shaped housing, and has two opposing surfaces, one of which has an opening OP1 and the other having 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.

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.

The wavelength conversion device 25 is fixed within 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.

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 source 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.

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 conversion device 25.

Furthermore, the dichroic mirror DM transmits the blue wavelength light from 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'.

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

[Wavelength conversion device of Example 2]
The wavelength conversion device 25 of the lighting device 20 according to Embodiment 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 Embodiment 1.

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 .

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.

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.

In this embodiment, the light-reflecting member 17 covers the sides of the wavelength conversion plate 15 and the metal reflective film 27, reaching 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.

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 positioned 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.

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 across 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.

In this embodiment as well, the wavelength conversion member 18 is configured to minimize light scattering within its interior. Therefore, similar to Embodiment 1, the reflected light (excitation light L1 and fluorescence) proceeds towards the light-transmitting layer 19 with almost no scattering within the wavelength conversion member 18. Consequently, similar to Embodiment 1, light L21 is extracted from the superimposed region A1, and light L22 is extracted from the non-superimposed region A2.

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 conversion device 25 can be increased.

Furthermore, in this embodiment, the incident region IA of the wavelength conversion device 25 is located on the same plane as the exit region. Therefore, in 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.

In this embodiment, the metal reflective film 27 is formed on the lower surface of the wavelength conversion member 18, but the configuration 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 reflectivity of the fluorescence described above and increase the luminous flux of the emitted light L2.

Furthermore, the configuration of the wavelength conversion device 25 in this embodiment may be modified using the configurations described in the modified versions 2 to 4 above. That is, the configuration of the wavelength conversion plate 15 can be changed as appropriate.

[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.

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

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

The light source 33 is incorporated into the wavelength conversion device 32 and emits light of a specific wavelength. In this embodiment, the light source 33 is a light-emitting diode (LED) having an emissive 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.

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 emitted from the wavelength conversion device 32 as illumination light. 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 illumination light L5. This light L5 is extracted to the outside of the housing 11, similar to embodiments 1 and 2.

[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 nano-antenna 16 as the wavelength conversion device 13 of Example 1.

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 towards the center of the lower surface of the wavelength conversion member 18 to which it is in contact. 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.

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. That is, when viewed from a direction perpendicular to the lower surface, the lower surface of the wavelength conversion plate 15 is covered by the light-reflecting member 34 in all areas except the region in contact with the light source 33.

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.

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 positioned 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, aluminum (Al) or copper (Cu).

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, while only the upper surface of the wavelength conversion plate 15, i.e., the light-emitting surface, is exposed to the outside.

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

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 where, of the excitation light emitted from the light source 33 in a Lambertsian manner, components that fall below the critical angle at the interface between the wavelength conversion plate 15 and the atmosphere are emitted.

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 where 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, which spreads at an angle of 18.5 degrees, propagates from the light-transmitting layer 19 into the atmosphere, it 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 within the wavelength conversion member 18, is emitted from the aforementioned superposition region A1.

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 * tan 18.5°, 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 using the above formula.

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 coincides with the predetermined angle (lens capture angle) at which the light is captured by the lens 14, which is positioned at a distance from the wavelength conversion device 32. In addition, it is set to be the same as the 35-degree angle range (fluorescence emission angle) at 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 conversion device 32 is captured by the lens 14 are all aligned.

On the other hand, in the case of Lambertian light distribution, the half-power angle of peak intensity is 60 degrees. Even considering the angular range where the forward luminous flux is halved, it is 45 degrees. That is, 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 includes light below the total internal reflection angle at the emission surface. If the goal is simply to increase the amount of light extracted, it is superior to extend the superposition region A1 to the total internal reflection angle.

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.

Therefore, in this embodiment, a portion of the excitation light below the total reflection angle is reflected by the nano-antenna 16 in the non-supervised region A2, and then reflected again by the light-reflecting member 34. Since the reflection by the nano-antenna 16 is specular reflection, the angle of the light does not change. However, since the reflection by the light-reflecting member 34 is diffuse reflection, a portion of it is converted to an angle within 18.5 degrees, i.e., an angle that can be captured by the lens 14, or an angle within half the forward luminous flux of the fluorescence wavelength reflected by the nano-antenna 16.

Therefore, according to this embodiment, by arranging the nanoantenna 16 in the region outside the width represented 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 wide-angle irradiated excitation light can be converted into narrow-angle light.

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.

In addition, in this embodiment, an LED is used as the light source 33. LEDs are less expensive than the laser light source described in Embodiment 1, allowing the lighting device itself to be manufactured at a lower cost.

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 generating diffuse reflection of the excitation light by the light-reflecting member 34, thereby maintaining the angle of light at which the nano-antenna 16 acts.

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

Furthermore, the wavelength conversion plate 15 in this embodiment may be configured using the modifications described in variations 2 to 4 above. In other words, the configuration of the wavelength conversion plate 15 can be modified as appropriate.

[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.

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, spaced apart from each other and in contact with the lower surface of the wavelength conversion member 18.

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, which is in contact with each of the two light sources 33, is the incident region IA to which the excitation light described above is incident. That is, in this modified example, two incident regions IA are formed.

In this modified example, no nanoantenna 16 is placed in each of the superimposed regions A1 corresponding to each of the incident regions IA described above, while nanoantenna 16 is placed in the non-superimposed region A2, which is a region other than the superimposed region A1.

Therefore, in this modified example, similar to Example 3, by arranging the nanoantenna 16 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 wide-angle excitation light can be converted into narrow-angle light.

Furthermore, in this modified configuration, multiple light sources 33 are provided. Therefore, the uniformity of the color of the emitted light from the wavelength conversion device 32 can be improved.

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

In the above-described embodiments and modifications, the nanoantennas 16 were not formed in the superimposed region A1. However, they may be formed partially. In that case, the density of the nanoantenna area 16 formed in the superimposed region A1 (arrangement density) should be lower than the density of the nanoantenna area 16 formed in the non-superimposed region A2.

The shape and 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 appropriately changed 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 appropriately changed.

This invention can be used as a light source for projectors, general lighting, vehicle lighting, and the like.

10, 20, 30 Lighting device 11 Housing 12 Light source (laser light source)
13, 25, 32 Wavelength conversion device 14 Lens 15 Wavelength conversion plate 16 Nano-antenna 17, 34 Light reflecting member 18 Wavelength conversion member 19 Light-transmitting layer 23 Light-reflective film 24 Light-transmitting member 26 Submount 27 Metal reflective film 28 Bonding member 33 Light source (LED light source)
35 Heatsink

Claims (10)

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. 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. 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. The wavelength conversion device according to claim 3, further comprising a plate-shaped portion provided in contact with the phosphor portion, having light-transmitting properties toward the excitation light and the fluorescence, and forming a flat plate shape together with the phosphor portion. 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. 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. 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 projection made of Al. 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. 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. 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.