Light source device

Abstract

To provide a light source device that allows light with high visibility to be efficiently extracted.SOLUTION: A light source device includes: a light-emitting element that includes a semiconductor layer including a light-emitting layer that emits light, and whose upper surface is a light-emitting surface; a phosphor layer provided on the light-emitting element and including a phosphor that is excited by the light and emits fluorescence in a first wavelength range; a diffractive optical element layer provided on the upper surface of the phosphor layer, made of a material that is translucency to the light and the fluorescence, and including an antenna array in which a plurality of nano-antennas made of metal or metal oxide are arranged at a predetermined period according to a wavelength in a second wavelength range that is in a wavelength range shorter than the peak wavelength of the fluorescence in top view; and a dielectric multilayer film provided on the upper surface of the diffractive optical element layer and having a reflective property for light in the second wavelength range.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a light source device that emits light with wavelength conversion. [Background technology]

[0002] A light source device is known that uses a phosphor that emits fluorescence when excited by excitation light in a specific wavelength range, and extracts light in a desired wavelength range by mixing light emitted from a light-emitting element with light whose wavelength has been converted by the phosphor.

[0003] For example, Patent Document 1 discloses a fluorescence light source device in which a dielectric multilayer film that transmits excitation light and reflects fluorescence emitted by the fluorescence plate is formed on the excitation light receiving surface of the fluorescence plate. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 6056724 [Non-patent literature]

[0005] [Non-Patent Document 1] R. Kamakura, S. Murai, Y. Yokobayashi, K. Takashima, M. Kuramoto, K. Fujita, and K. Tanaka, J. Appl. Phys. 124, 213105(2018), "Enhanced photoluminescence and directional white-light generation by plasmonic array" [Overview of the project] [Problems that the invention aims to solve]

[0006] For example, one could consider providing a dielectric multilayer film on a phosphor layer containing the phosphor described above, and selectively reflecting light with low luminosity in a specific wavelength range from the phosphor layer back to the phosphor layer, thereby converting that specific wavelength of light to a wavelength with higher luminosity for effective utilization. In this case, since the light emitted from the phosphor layer has a Lambertsian distribution that diffuses isotropically from the emission surface, even at a specific wavelength, there is a range in the angle of incidence to the dielectric multilayer film, and some of the light is transmitted through the dielectric multilayer film. In this case, the problem has been that the light with low luminosity cannot be effectively utilized.

[0007] This invention has been made in view of the above-mentioned points, and aims to provide a light source device that can efficiently extract light with high visual sensitivity. [Means for solving the problem]

[0008] The light source device according to the present invention includes a light-emitting element having an upper surface as the emission surface and comprising a semiconductor layer including a light-emitting layer that emits light; a phosphor layer provided on the light-emitting element and comprising a phosphor that is excited by the light and emits fluorescence in a first wavelength range; a diffractive optical element layer provided on the upper surface of the phosphor layer and comprising an antenna array in which, when viewed from above, a plurality of nanoantennas made of metal or metal oxide are arranged at a predetermined period corresponding to the wavelength of a second wavelength range which is in a wavelength range shorter than the peak wavelength of the fluorescence, and made of a material that is transparent to the light and the fluorescence; and a dielectric multilayer film provided on the upper surface of the diffractive optical element layer and is reflective to light in the second wavelength range. [Brief explanation of the drawing]

[0009] [Figure 1] This is a top view of the light source device according to the embodiment. [Figure 2] This is a cross-sectional view of a light source device according to an embodiment. [Figure 3] This is a partially enlarged cross-sectional view, showing an enlarged portion of Figure 2. [Figure 4] This figure shows the planar shape and arrangement pattern of the nanoantenna in the example. [Figure 5]It is a diagram showing the relationship between the spectra of the excitation light and the white LED and the sensitivity. [Figure 6] It is a diagram showing the diffraction lines according to the embodiment. [Figure 7] It is a diagram showing the array pattern of the nanoantenna according to the modification. [Figure 8] It is a diagram showing the diffraction lines according to the modification. [Figure 9] It is a top view showing another example of the shape of the nanoantenna. [Figure 10] It is a top view showing another example of the shape and array pattern of the nanoantenna.

Best Mode for Carrying Out the Invention

[0010] Hereinafter, preferred embodiments of the present invention will be described, but these may be appropriately modified and combined. In the following description and the accompanying drawings, substantially the same or equivalent parts will be described with the same reference numerals.

Embodiment

[0011] While referring to the accompanying drawings, the configuration of the light source device 10 according to the present embodiment will be described.

[0012] First, while referring to FIGS. 1 and 2, the overall configuration of the light source device 10 will be described.

[0013] FIG. 1 is a top view of the light source device . FIG. 2 is a cross-sectional view of the light source device 10 shown in FIG. 1 cut along the line 2-2 in FIG. 1.

[0014] The light source device 10 includes a light-emitting element 13 mounted on a mounting substrate 11 and a wavelength conversion member 15 provided on the light-emitting surface of the light-emitting element 13.

[0015] The mounting substrate 11 is a substrate whose upper surface is a rectangular mounting surface 11S. In other words, the mounting substrate 11 is a flat substrate with a rectangular planar shape when viewed from above from a direction perpendicular to the upper surface which is the mounting surface 11S. The mounting substrate 11 is a substrate made of a material such as AlN or alumina.

[0016] The n-side power supply pad 17 is a rectangular metal wiring electrode pattern formed on the mounting surface 11S. One side of the n-side power supply pad 17 is provided parallel to the short side of the mounting substrate 11. The n-side power supply pad 17 is formed to be connectable to an external power source, for example, via a through-hole 17H ​​that penetrates the mounting substrate 11 and n-side back wiring 18 provided on the lower surface of the mounting substrate 11.

[0017] The p-side power supply pad 19 is a rectangular metal wiring electrode pattern formed on the mounting surface 11S, spaced apart from the n-side power supply pad 17. The p-side power supply pad 19 is located between one short side of the mounting surface 11S and the n-side power supply pad 17. The long side of the p-side power supply pad 19 is the same length as the side of the adjacent n-side power supply pad 17. The p-side power supply pad 19 is formed to be connectable to an external power supply, for example, through a through-hole 19H that penetrates the mounting substrate 11 and via p-side back wiring 20 provided on the lower surface of the mounting substrate 11.

[0018] The configuration of the light-emitting element 13 will be described below.

[0019] The support substrate 21 is a rectangular, flat substrate whose planar shape is the same as that of the n-power supply pad, and is a component of the light-emitting element 13. The support substrate 21 is a conductive substrate such as a Si substrate. The support substrate 21 is arranged on the mounting surface 11S such that its main surface is parallel to the mounting surface 11S. The support substrate 21 is arranged so as to overlap with the n-side power supply pad 17 when viewed from above.

[0020] The back electrode 23 is a metal film formed on the main surface of the support substrate 21 facing the mounting surface 11S, i.e., on the lower surface of the support substrate 21, and is a component of the light-emitting element 13. The back electrode 23 is bonded to the n-side power supply pad 17, for example, via a conductive bonding material (not shown). In other words, the support substrate 21 and the mounting substrate 11 are bonded by the back electrode 23 being bonded to the n-side power supply pad 17.

[0021] The semiconductor laminate 25 is a component of the light-emitting element 13, is provided on the upper surface of the support substrate 21, and consists of multiple semiconductor layers, including an active layer. The semiconductor laminate 25 has a rectangular planar shape, and each side is arranged to be parallel to each side of the support substrate 21.

[0022] The semiconductor laminate 25 is bonded to the upper surface of the support substrate 21 via a metal bonding layer (not shown). For example, the metal bonding layer consists of two layers that are spaced apart from each other on the upper surface of the support substrate 21 and are electrically insulated from each other. One of the two layers is electrically connected to the support substrate 21, and the other is electrically insulated from the support substrate 21 by, for example, an insulating layer formed on the upper surface of the support substrate 21.

[0023] More specifically, the semiconductor laminate 25 is constructed by stacking a p-type semiconductor layer, an active layer, and an n-type semiconductor layer in that order from the support substrate 21 side. The wavelength of the emitted light from the active layer is corresponding to the material and composition of the semiconductor laminate 25. The upper surface of the semiconductor laminate 25 is the light emission surface.

[0024] In this embodiment, for example, the p-type semiconductor layer of the semiconductor stack 25 is a Mg-doped GaN layer. The active layer (light-emitting layer) of the semiconductor stack 25 is a semiconductor layer having a multiple quantum well structure consisting of an InGaN well layer and a GaN barrier layer, for example. The n-type semiconductor layer of the semiconductor stack 25 is a Si-doped GaN layer, for example. Furthermore, blue light with a wavelength of approximately 450 nm is emitted from the active layer of the semiconductor stack 25.

[0025] The p-type semiconductor layer of the semiconductor stack 25 is electrically connected to the junction layer that is insulated from the support substrate 21 among the junction layers described above. The n-type semiconductor layer of the semiconductor stack 25 is electrically connected to the junction layer that is electrically connected to the support substrate 21.

[0026] The power supply unit 27 is a component of the light-emitting element 13 and is a metal electrode provided on the support substrate 21. The power supply unit 27 has a rectangular shape and is arranged so that its long side is parallel to one side of the semiconductor laminate 25.

[0027] For example, the power supply unit 27 is insulated from the support substrate 21 by an insulating layer (not shown) formed on the upper surface of the support substrate 21. Furthermore, the power supply unit 27 is electrically connected to the junction layer (not shown) of the support substrate 21 that is insulated from the support substrate 21. Therefore, the power supply unit 27 is electrically connected to the p-type semiconductor layer of the semiconductor laminate 25.

[0028] The power supply unit 27 is electrically connected to the p-side power supply pad 19 provided on the mounting surface 11S via a bonding wire 29.

[0029] Thus, the light-emitting element 13 is composed of a support substrate 21, a back electrode 23, a semiconductor laminate 25, and a power supply unit 27. The semiconductor laminate 25 is formed by bonding a plurality of semiconductor layers, including an active layer grown on a growth substrate (not shown), to the support substrate 21 via a bonding layer, and then removing the growth substrate by, for example, laser lift-off.

[0030] In other words, the light-emitting element 13 is a top-emitting type LED element having a so-called thin-film laminated structure. The top surface of the semiconductor laminate 25 becomes the light-emitting surface of the light-emitting element 13.

[0031] The wavelength conversion member 15 is positioned on the semiconductor laminate 25 of the light-emitting element 13 and is a member that converts the wavelength of light emitted from the active layer of the light-emitting element 13. The wavelength conversion member 15 has a rectangular parallelepiped shape. As shown in Figures 1 and 2, the lower surface of the wavelength conversion member 15 is slightly larger than the upper surface of the semiconductor laminate 25 and extends to the outside of the upper surface of the semiconductor laminate 25.

[0032] The lower surface of the wavelength conversion member 15 is bonded to the upper surface of the semiconductor laminate 25 of the light-emitting element 13 by a translucent adhesive 31. In other words, the wavelength conversion member 15 is bonded to the light-emitting element 13 via the translucent adhesive 31.

[0033] The structure of the wavelength conversion member 15 will be described in detail below.

[0034] The phosphor layer 35 is a layer containing a wavelength conversion material such as a phosphor that is excited by light emitted from the light-emitting element 13 and emits fluorescence. In this embodiment, the phosphor layer 35 is a ceramic phosphor plate consisting of a single phase of yttrium aluminum garnet (YAG:Ce) with cerium as the light-emitting center. The phosphor layer 35 may also be a plate in which a thin film containing a phosphor is formed on the surface of a glass support, for example. Alternatively, the phosphor layer 35 may be a resin layer containing phosphor particles such as a YAG:Ce phosphor.

[0035] The phosphor described above is excited by blue light with a wavelength of approximately 450 nm and emits yellow fluorescence with a wavelength of approximately 460 to 750 nm. Therefore, in this embodiment, when blue light emitted from the light-emitting surface of the light-emitting element 13 is introduced into the phosphor layer 35, a portion of the blue light is wavelength-converted to yellow fluorescence, while the remainder passes through the phosphor layer 35 without wavelength conversion. Consequently, the blue light that has passed through the phosphor layer 35 and the yellow fluorescence from the phosphor contained in the phosphor layer 35 are emitted from the upper surface of the phosphor layer 35.

[0036] White light is extracted from the light source device 10 by mixing the blue light and yellow fluorescence emitted from the upper surface of the phosphor layer 35. Considering stable whitening, it is preferable that the phosphor layer 35 has a thickness in the range of 40 to 200 μm. In this embodiment, the thickness of the phosphor layer 35 is 100 μm.

[0037] Since fluorescence is emitted in all directions from the excited phosphor, the fluorescence emitted from the upper surface of the phosphor layer 35 diffuses isotropically from the upper surface of the phosphor layer 35.

[0038] The diffractive optical element layer 37 is a diffractive functional layer having a diffractive element structure (not shown in Figures 1 and 2) consisting of metal pieces arranged within the layer, in other words, in a plane parallel to the mounting surface 11S. The diffractive optical element layer 37 diffracts light incident on the diffractive optical element layer 37 from the upper surface of the phosphor layer 35, thereby tilting the direction of propagation of the light in a direction along axis AX, which is an axis perpendicular to the mounting surface 11S. In other words, the diffractive optical element layer 37 has the function of making the angle of incidence of light incident on the dielectric multilayer film 39 smaller than the angle of incidence of the light incident on the diffractive optical element layer 37.

[0039] The dielectric multilayer film 39 is a multilayer reflector that has the function of reflecting light in a specific wavelength range from the fluorescence emitted from the phosphor layer 35. Specifically, the dielectric multilayer film 39 is configured to reflect light in the relatively short wavelength range of fluorescence, which is less visible. Light in the short wavelength range from the fluorescence emitted from the phosphor can excite the phosphor when it is again incident on the phosphor.

[0040] Since the reflection characteristics of the dielectric multilayer film 39 utilize Bragg reflection, the desired reflection characteristics cannot be obtained for light incident at large incident angles outside the range assumed during the design phase. Therefore, the light source device 10 of this embodiment is configured to increase the reflectivity of the dielectric multilayer film 39 for the above-mentioned specific wavelength of light by reducing the incident angle to the dielectric multilayer film 39 using the diffractive optical element layer 37.

[0041] As described above, the wavelength conversion member 15 is composed of a phosphor layer 35, a diffractive optical element layer 37 formed on the phosphor layer 35, and a dielectric multilayer film 39 formed on the diffractive optical element layer 37.

[0042] The excitation light incident on the wavelength conversion member 15 is directed toward the upper surface 15T of the wavelength conversion member 15. At this time, a portion of the excitation light excites the phosphor in the phosphor layer 35, emitting yellow fluorescence, and a portion of this yellow fluorescence is narrowed and reflected by the functional layer consisting of the diffractive optical element layer 37 and the dielectric multilayer film 39 and returned to the phosphor layer 35. The upper surface 15T of the wavelength conversion member 15 becomes the light extraction surface of the light source device 10.

[0043] The reflective member 41 (not shown in Figure 1) is provided so as to cover the side surface of the wavelength conversion member 15. The reflective member 41 is a member containing light-reflective particles. The reflective member 41 is, for example, made by mixing light-reflective particles with a resin. For example, particles such as titanium oxide, zinc oxide, and alumina can be used as the light-reflective material for the reflective member 41. Alternatively, thermosetting resins such as silicone resin and epoxy resin can be used for the reflective member 41.

[0044] Of the light emitted from the light-emitting surface of the light-emitting element 13 and incident on the wavelength conversion member 15, the light that propagates to the side surface of the wavelength conversion member 15 is reflected at the interface between the wavelength conversion member 15 and the reflecting member 41.

[0045] For example, the upper surface of the reflective member 41 and the upper surface 15T of the wavelength conversion member 15 are formed to be at the same height from the light-emitting surface of the light-emitting element 13.

[0046] The reflective member 41 has the function of preventing light emission from the sides of the light-emitting element 13 and the wavelength conversion member 15, thereby improving the light extraction efficiency.

[0047] Furthermore, the reflective member 41 embeds the light-emitting element 13, the p-side power supply pad 19, and the bonding wire 29 on the mounting substrate 11. The reflective member 41 can also function as a sealing material for the light source device 10.

[0048] Next, the configuration and function of the diffractive optical element layer 37 and the dielectric multilayer film 39 will be described in detail with reference to Figure 3. Figure 3 is a partially enlarged cross-sectional view showing an enlarged view of portion A enclosed by the dashed line in Figure 2.

[0049] The first light-transmitting layer 43 is formed on the phosphor layer 35. The first light-transmitting layer 43 is made of a material that is transparent to excitation light from the light-emitting element 13 and to fluorescence obtained by wavelength conversion of said excitation light by the phosphor. Furthermore, from the viewpoint of efficiently introducing fluorescence from the phosphor layer 35, the first light-transmitting layer 43 is made of a material with a refractive index higher than that of the phosphor layer 35.

[0050] In this embodiment, the refractive index of the YAG:Ce phosphor plate used in the phosphor layer 35 is 1.82, and the first translucent layer 43 uses TiO2 (refractive index 2.33), which is translucent to excitation light and fluorescence and has a higher refractive index than the phosphor layer 35. The thickness of the first translucent layer 43 is, for example, 200 nm.

[0051] The first translucent layer 43 may be made of other materials, as long as it is translucent to excitation light from the light-emitting element 13 and fluorescence from the phosphor, and has a refractive index higher than that of the phosphor layer 35. For example, the first translucent layer 43 may be made of Ta2O5 (refractive index 2.165), which is translucent to excitation light and fluorescence and has a refractive index higher than that of the phosphor layer 35.

[0052] The first translucent layer 43 is formed on the upper surface of the phosphor layer 35 by, for example, EB deposition.

[0053] The nanoantenna 45 is a structure that forms the diffraction grating structure within the diffractive optical element layer 37 described above. It is a columnar structure made of metal arranged in multiple rows on the upper surface of the first translucent layer 43, spaced apart from each other in the in-layer direction, in other words, in a plane parallel to the mounting surface 11S. In this embodiment, the nanoantenna 45 is made of Al (aluminum). The nanoantenna 45 is arranged in a plane parallel to the mounting surface 11S, in other words, in a top view, with a certain period and a certain arrangement pattern to form an antenna array.

[0054] In this embodiment, the antenna array consisting of nanoantennas 45 is formed over the entire upper surface of the first translucent layer 43.

[0055] Figure 4 is a top view showing the planar shape and top view arrangement pattern of the nanoantenna 45 in this embodiment. As shown in Figure 4, the nanoantenna 45 has a square planar shape. Furthermore, multiple nanoantennas 45 are arranged in a hexagonal lattice arrangement pattern with a predetermined period P to form an antenna array.

[0056] The antenna array can be formed in any region on the upper surface of the first translucent layer 43. For example, the antenna array can be formed in a region corresponding to the region where the semiconductor laminate 25 of the light-emitting element 13 is formed when viewed from above.

[0057] In this embodiment, the array period P of the nanoantennas 45 is 340 nm. The length W of one side of each of the multiple nanoantennas 45 in a top view is, for example, 200 nm. Also, the height H of each of the multiple nanoantennas 45 (Figure 4) is, for example, 130 nm.

[0058] The shape of the nano-antenna 45 can be columnar or conical, and in addition to a rectangular prism shape, it can also be cylindrical, conical, pyramidal, or other shapes.

[0059] Furthermore, the nanoantenna 45 may be formed from metals other than Al, such as Au, Ag, and Ni, or from metal oxides such as TiO2 and Al2O3.

[0060] Multiple nanoantennas 45 can be formed, for example, by forming a resist pattern on an Al surface deposited on a first translucent layer 43 by EB deposition or the like, using nanoimprinting, and then performing RIE etching.

[0061] The multiple nanoantennas 45 strongly diffract light in a specific wavelength range from the light incident on the diffractive optical element layer 37. In other words, the multiple nanoantennas 45 function as diffractive optical elements. Specifically, the multiple nanoantennas 45 cause the incident angle θ from the phosphor layer 35 to the diffractive optical element layer 37. in The incident angle θ from the diffractive optical element layer 37 to the dielectric multilayer film 39 is greater than 1. in The direction of light propagation in that specific wavelength range is changed so that 2 becomes smaller.

[0062] As shown in Figure 3, the second translucent layer 47 is formed on the first translucent layer 43 so as to embed a plurality of nanoantennas 45. The second translucent layer 47 is made of a material that is translucent to excitation light from the light-emitting element 13 and to fluorescence obtained by wavelength conversion of said excitation light by a phosphor.

[0063] The second translucent layer 47 is, for example, an SiO2 layer. For example, the second translucent layer 47 is formed by depositing a film using a sputtering apparatus or the like after the formation of a plurality of nanoantennas 45. The upper surface of the second translucent layer 47 is planarized by, for example, chemical mechanical polishing (CMP).

[0064] The diffractive optical element layer 37, which comprises a first translucent layer 43, a plurality of nanoantennas 45, and a second translucent layer 47, diffracts a portion of the light in a specific wavelength range that is incident on the diffractive optical element layer 37, thereby controlling the light distribution of that portion of light. narrow It keratinizes.

[0065] The dielectric multilayer film 39 is formed on the second translucent layer 47 and is constructed by alternately stacking two types of dielectric films with different refractive indices. In this embodiment, the dielectric multilayer film 39 is constructed by alternately stacking SiO2 films and Ta2O5 films by vapor deposition or the like.

[0066] The dielectric multilayer film 39 is an optical element designed to reflect light of a specific wavelength incident on its stacking surface within a predetermined incident angle range centered, for example, 0°. The dielectric multilayer film 39 is designed to transmit excitation light from the light-emitting element 13, reflect light in a specific wavelength range shorter than the peak wavelength of fluorescence from the phosphor layer 35, and transmit light near the peak wavelength of fluorescence from the phosphor layer 35 and light with wavelengths longer than that. Specifically, the dielectric multilayer film 39 is designed to reflect light with wavelengths of 475 nm to 510 nm, which is the wavelength range in which the blue excitation light spectrum and the yellow fluorescence spectrum overlap, and to transmit light with wavelengths of 425 nm to 475 nm, which is the wavelength range containing most of the blue excitation light, and light with wavelengths longer than 510 nm, which contains most of the yellow fluorescence.

[0067] Now, referring to Figure 5, the relationship between the wavelength of each light and luminous efficiency in this embodiment will be explained.

[0068] Figure 5 shows the excitation spectrum of the excitation light from the light-emitting element 13, the white LED spectrum which is an example of the emission light spectrum from an LED element that emits white light, and the spectrum showing the luminous sensitivity with light at a wavelength of approximately 555 nm, which is most strongly perceived by the human eye, set to 1. In Figure 5, the wavelength range of 475-510 nm is indicated by an arrow.

[0069] As shown in Figure 5, the wavelength at which luminous sensitivity peaks is approximately 555 nm, which is the wavelength at which the human eye experiences maximum sensitivity when acclimatizing to a bright environment. The white LED spectrum includes a peak of blue light at approximately 450 nm and a peak centered around yellow light at approximately 550 nm.

[0070] As is clear from Figure 5, light in the 475-510 nm wavelength range has lower visual sensitivity compared to light at 555 nm. Therefore, even if light in the 475-510 nm wavelength range is emitted from the light source device 10, it is difficult for the human eye to perceive it as bright light, and thus cannot be effectively utilized as emitted light from the light source device 10.

[0071] In this embodiment, in order to effectively utilize light in the 475-510nm wavelength range, it is converted into light with higher visual sensitivity. That is, the wavelength of the 475-510nm light is brought closer to a longer wavelength of approximately 550nm.

[0072] Since the wavelength range of 475-510 nm is included in the excitation light wavelength range, by re-incidentating light in the 475-510 nm wavelength range onto the phosphor layer 35, the phosphor can convert the wavelength to longer wavelength yellow light, resulting in light with high visual sensitivity.

[0073] Based on the above, the light source device 10 of this embodiment is configured to reflect light with wavelengths of 475 nm to 510 nm using the dielectric multilayer film 39 and cause it to incident on the phosphor layer 35.

[0074] On the other hand, as described above, the reflectivity of the dielectric multilayer film 39 varies depending on the angle of incidence of light. In this embodiment, the dielectric multilayer film 39 is designed to reflect light in the wavelength range of 475 nm to 510 nm when the angle of incidence of the incident light is within a predetermined range centered on 0°. For example, as the angle of incidence increases to 30° and 60°, the wavelength range in which high reflectivity is obtained shifts to the lower wavelength side. Therefore, light in the wavelength range of 475 nm to 510 nm is less likely to be reflected by the dielectric multilayer film 39 as the angle of incidence increases.

[0075] Therefore, in order to reflect light in the wavelength range of 475 nm to 510 nm as designed by the dielectric multilayer film 39, it is necessary to reduce the incident angle of light in the wavelength range as designed onto the dielectric multilayer film 39.

[0076] Referring again to Figure 3, the behavior of light in the wavelength range of 475 nm to 510 nm in the diffractive optical element layer 37 and the dielectric multilayer film 39 will be explained.

[0077] As described above, the fluorescence from the phosphor layer 35 is emitted at an incident angle θ. in It includes light with a large value of 1. In this embodiment, the incident angle θ on the diffractive optical element layer 37 in The light with wavelengths of 475 nm to 510 nm incident in 1 passes through the diffractive optical element layer 37, is diffracted by the action of the nano-antenna 45, and the incident angle θ when it enters the dielectric multilayer film 39 from the diffractive optical element layer 37 is in 2 is the angle of incidence θ in The light becomes less than 1. Consequently, the incident angle of the light with a wavelength of 475 nm to 510 nm onto the dielectric multilayer film 39 is more likely to fall within a predetermined design angle range centered at 0° of the dielectric multilayer film 39, and the light with a wavelength of 475 nm to 510 nm is more likely to be reflected by the dielectric multilayer film 39.

[0078] In this way, the action of the nanoantennas 45 contained in the diffractive optical element layer 37 results in a large amount of light with a small incident angle onto the dielectric multilayer film 39, so that more of the fluorescence from the phosphor layer 35 can be reflected by the dielectric multilayer film 39 and returned to the phosphor layer 35.

[0079] The light that returns to the phosphor layer 35 excites the phosphor, causing yellow fluorescence with wavelengths longer than 475 nm to 510 nm to be emitted from the excited phosphor. The yellow fluorescence with wavelengths longer than 475 nm to 510 nm, along with the blue light that has passed through the phosphor layer 35, is transmitted through the dielectric multilayer film 39 and emitted from the upper surface 15T of the wavelength conversion member 15.

[0080] As a result, more highly luminous light is emitted from the upper surface 15T of the wavelength conversion member 15, increasing the luminous flux. More specifically, the yellow fluorescence that has been wavelength-converted and returned to the phosphor layer 35 is mixed with blue light and contributes to an increase in the luminous flux of white light emitted from the light source device 10.

[0081] Therefore, the light source device 10 has high wavelength conversion efficiency and can efficiently emit light with high visual sensitivity.

[0082] For example, in this embodiment, if the nano-antenna 45 is not provided, even if the light has a wavelength of 475 nm to 510 nm, if the incident angle on the dielectric multilayer film 39 is large, the light will not be reflected but will pass through the dielectric multilayer film 39 and be extracted from the light emission surface 15T. As described above, light with a wavelength of 475 nm to 510 nm has low luminous sensitivity and therefore cannot be effectively utilized as the emitted light of the light source device 10.

[0083] The antenna function of the nanoantennas 45 described above is caused by optical diffraction occurring due to multiple nanoantennas 45 formed within the diffractive optical element layer 37, as explained above. The conditions under which diffraction occurs are expressed by the following Rayleigh anomaly equation (1).

[0084]

number

[0085]

number

[0086]

number

[0087] λ is the wavelength of light, a is the value obtained by multiplying the period P of the diffractive optical element (nano-antenna 45) by √3 / 2, θ in is the angle of incidence of light to the diffractive optical element layer 37, n is the refractive index of the material surrounding the nanoantenna 45, and m1 and m2 represent the order of diffraction.

[0088] Substitute the above formulas (2) and (3) into (1). First, set α, β, and γ as follows.

[0089] [Number]

[0090] [Number]

[0091] [Number]

[0092] Substitute formulas (2) and (3) into (1) using formulas (4) to (6) and solve for λ, resulting in the following formula (7).

[0093] [Number]

[0094] Using formula (7), when plotting the wavelength as a function of the incident angle θ in on the diffraction optical element layer 37, a diffraction line can be drawn. Drawing diffraction lines for each refractive index around the antenna and for each diffraction order, the LSPR (local surface plasmon resonance) band indicating the degree of attenuation of light by the action of the antenna is modulated along the diffraction line.

[0095] Instead of the incident angle θin, when drawing the diffraction line in the same way as a function of the exit angle θ em from the diffraction optical element layer 37, it is found that the region bounded by the diffraction line and the region caused by the difference in the degree of polarization and enhancement of the light actually affected by the antenna action narrow match well (Non-Patent Document 1). Therefore, using the above formula, the wavelength of the light affected by the action of the nanoantenna 45 is determined as a function of the exit angle θ emThe diffraction lines plotted as a function of θ allow us to estimate which wavelength ranges of light are strongly diffracted. Note that the emission angle θ from the diffractive optical element layer 37 is also θ. em The incident angle θ to the dielectric multilayer film 39, as explained in Figure 3, is the incident angle θ in The answer is 2.

[0096] Figure 6 shows the wavelength λ and the emission angle θ from the diffractive optical element layer 37. em This figure shows the diffraction line expressed as a function of θ. In the graph in Figure 6, the horizontal axis is the emission angle θ from the diffractive optical element layer 37. em The vertical axis represents the wavelength of light emitted from the diffractive optical element layer 37.

[0097] In the graph in Figure 6, the solid line represents the θ, using the refractive index n=2.33 of TiO2 that constitutes the first translucent layer 43. em These are diffraction lines plotted at wavelengths λ calculated using equation (7) with diffraction order (m1, m2) = (1, 0) (TiO2(1, 0)).

[0098] Similarly, the dashed-dot line in the graph of Figure 6 is the diffraction line plotted when the diffraction order (m1, m2) = (1, -1) for TiO2 (TiO2(1, -1)), and the dashed-dot line in the graph of Figure 6 is the diffraction line plotted when the diffraction order (m1, m2) = (-1, 0) for TiO2 (TiO2(-1, 0)).

[0099] In the graph in Figure 6, the dashed line represents the θ, using the refractive index n=1.457 of SiO2, which constitutes the second translucent layer 47. em These are diffraction lines plotted by setting the diffraction order (m1, m2) = (-1, 0) using equation (7) for each wavelength λ (SiO2(-1, 0)).

[0100] As shown in Figure 6, the exit angle θ em At the low-angle side, a region B is formed, enclosed by the solid line TiO2(1,0) and the dashed line (SiO2(-1,0)). Light in the wavelength range within region B is strongly diffracted by the nano-antenna 45, resulting in a small emission angle θ within region B. emAs shown in Figure 6, the light within region B includes light in the wavelength range of 475-510 nm.

[0101] As described above, the Rayleigh anomaly equations (1) to (3) include the wavelength of light λ, the refractive index n around the nanoantenna 45, and the period P of the nanoantenna 45 as parameters. Therefore, changing the refractive index n and the period P of the nanoantenna 45 changes the diffraction line, and the range of wavelengths and emission angles of light on which the nanoantenna 45 acts changes. Accordingly, in this embodiment, by adjusting the refractive index n and the period P of the nanoantenna 45 so that the desired wavelength range is included in the region where the antenna effect is strong, the emission angle θ for light in the desired wavelength range can be changed. em That is, the incident angle θ onto the dielectric multilayer film 39. in 2 can be made smaller. In other words, using the diffraction lines described above, the period P of the nanoantenna 45 and the refractive index n around the nanoantenna 45 can be determined according to the desired wavelength range.

[0102] For example, the refractive index n may be kept constant by fixing the materials of the first translucent layer 43 and the second translucent layer 47, and the wavelength range of light on which the nanoantenna 45 acts may be optimized by changing the period P of the nanoantenna 45 and drawing diffraction lines. Alternatively, for example, the period P of the nanoantenna 45 may be kept constant, and diffraction lines may be drawn using the refractive indices of multiple candidate materials for the first translucent layer 43 to select the optimal material.

[0103] As described in detail above, the light source device of this embodiment includes a semiconductor layer including a light-emitting layer that emits light, a light-emitting element with its upper surface as the emission surface, a phosphor layer provided on the light-emitting element and containing a phosphor that is excited by excitation light, which is light emitted from the light-emitting element, and emits fluorescence in a first wavelength range, a diffractive optical element layer provided on the upper surface of the phosphor layer and including an antenna array in which, when viewed from above, a plurality of nanoantennas made of metal or metal oxide are arranged at a predetermined period corresponding to the wavelength in a second wavelength range which is in a wavelength range shorter than the peak wavelength of fluorescence, and is made of a material that is transparent to excitation light and fluorescence, and a dielectric multilayer film provided on the upper surface of the diffractive optical element layer and is reflective to light in the second wavelength range.

[0104] The diffractive optical element layer 37 is composed of, for example, a first translucent layer formed on the upper surface of the phosphor layer and transparent to excitation light and fluorescence, a plurality of nanoantennas arranged in a predetermined period when viewed from above on the upper surface of the first translucent layer, and a second translucent layer formed on the upper surface of the first translucent layer so as to embed the plurality of nanoantennas and transparent to excitation light and fluorescence.

[0105] As described above, the light source device of this embodiment is provided with a dielectric multilayer film that reflects light with low luminosity towards the phosphor layer. The dielectric multilayer film has an angle dependence, and even light in the wavelength range that is reflective will be transmitted if the angle of incidence is large. Since the fluorescence from the phosphor layer diffuses isotropically, a large portion of the fluorescence is not reflected due to the large angle of incidence to the dielectric multilayer film. Therefore, in this embodiment, a diffractive optical element layer is provided between the phosphor layer and the dielectric multilayer film, and the action of nanoantennas contained in the diffractive optical element layer increases the amount of light with a small angle of incidence to the dielectric multilayer film for the fluorescence from the phosphor layer that has low luminosity. As a result, more of the light with low luminosity emitted from the phosphor layer is returned to the phosphor layer and converted into light with high luminosity. Therefore, light with high luminosity can be extracted efficiently.

[0106] The nanoantenna function described above can be achieved by optimizing the refractive indices of the first and second translucent layers and the period in which the antennas are arranged, using the Rayleigh anomaly equation described above, so that light in the desired wavelength range is diffracted.

[0107] In this embodiment, an example in which the nanoantennas 45 are arranged in a hexagonal lattice has been described, but the embodiment is not limited to this. The nanoantennas 45 only need to be arranged at a certain period, and may be arranged in a square lattice or a rectangular lattice, for example.

[0108] [Differentiation] Figure 7 shows the arrangement of the nanoantennas 51 according to a modified example of the above embodiment. As shown in Figure 7, the nanoantennas 51 are arranged in a square grid. The antennas 51 differ from the nanoantennas 45 shown in Figure 3 only in their arrangement.

[0109] Figure 8 shows a modified light source device having a nanoantenna 51 and otherwise configured similarly to the light source device 10 of the embodiment, where the wavelength λ is the emission angle θ from the diffractive optical element layer 37. em This figure shows the diffraction lines expressed as a function of .

[0110] The diffraction lines shown in Figure 8 can be created in the same way as in Figure 6, but the period parameter a is set to the period (nm) of the nano-antenna 51, without multiplying by √3 / 2 as in Figure 6.

[0111] The diffraction lines shown in Figure 8 are those obtained when the period of the nanoantenna 51 is set to 290 nm, after optimizing the region diffracted by the nanoantenna 51 to include the wavelength range of 475-510 nm.

[0112] As shown in Figure 8, the exit angle θ em At the low-angle side, a region C is formed, enclosed by the solid line TiO2(1,0) and the dashed line SiO2(-1,0). Light within this region C is diffracted by the nanoantenna 51. As shown in Figure 8, the light within region C includes light in the wavelength range of 475-510 nm.

[0113] Furthermore, as described above, the shape of the nano-antenna 45 can be columnar or conical, and in addition to a rectangular prism shape, it can also be cylindrical, conical, pyramidal, or other shapes.

[0114] Figure 9 is a top view showing an example in which nanoantennas 61, in which the shape of the nanoantenna 45 is cylindrical or conical, are arranged in a hexagonal lattice.

[0115] Figure 10 is a top view showing an example in which nanoantennas 71, in which the shape of the nanoantenna 45 is cylindrical or conical, are arranged in a square grid.

[0116] The configurations in the above-described embodiments are merely illustrative and can be modified as appropriate depending on the application and other factors.

[0117] For example, in the above embodiment, the diffractive optical element layer 37 has a first translucent layer 43, and an example in which a nanoantenna 45 is formed on the first translucent layer 43 has been described, but the invention is not limited to this. For example, the nanoantenna 45 may be formed on the phosphor layer 35, or the nanoantenna 45 formed on the phosphor layer 35 may be embedded by the second translucent layer 47. It is preferable to provide the first translucent layer 43 because the refractive index of the first translucent layer 43 is higher than that of the phosphor layer 35, allowing light from the phosphor layer 35 (excitation light passing through the phosphor layer 35 and fluorescence emitted from the phosphor) to be efficiently introduced into the diffractive optical element layer, and because the first translucent layer 43 can suppress the reflection of light from the phosphor layer 35 by the nanoantenna 45 back to the phosphor layer 35 side.

[0118] In the above embodiment, the case in which the light-emitting element 13 included in the light source device is a thin-film type LED element was described, but it is not limited to this. For example, a flip-chip type light-emitting element may be used instead of the light-emitting element 13.

[0119] In the above embodiment, an example was described in which the wavelength conversion member 15 is bonded to the light-emitting element 13, but the embodiment is not limited to this. The wavelength conversion member 15 may be placed at a position away from the light-emitting element 13, as long as excitation light from the light-emitting element 13 is incident on it. [Explanation of Symbols]

[0120] 10 Light source device 11. Implemented circuit board 13 Light-emitting element 15 Wavelength conversion component 25 Semiconductor Stacks 35 Phosphor layer 37 Diffractive optical element layer 39 Dielectric Multilayer Film 41 Reflective material 43. First translucent layer 45 nano antenna 47. Second translucent layer

Claims

1. A light-emitting element comprising a semiconductor layer including a light-emitting layer that emits light, with the upper surface being the light-emitting surface, A phosphor layer provided on the light-emitting element, which includes a phosphor that is excited by the light and emits fluorescence in a first wavelength range, A diffractive optical element layer provided on the upper surface of the phosphor layer, The dielectric multilayer film provided on the upper surface of the diffractive optical element layer comprises, The diffractive optical element layer includes a first translucent layer provided on the upper surface of the phosphor layer and transparent to light and fluorescence; a plurality of nanoantennas made of metal or metal oxide arranged on the upper surface of the first translucent layer; and a second translucent layer formed on the upper surface of the first translucent layer so as to embed the plurality of nanoantennas and transparent to light and fluorescence in a first wavelength range. The plurality of nanoantennas are arranged in a manner that, when viewed from above, narrows the angle of light in a second wavelength range, which is shorter than the peak wavelength of fluorescence in the first wavelength range and longer than the peak wavelength of the light. The dielectric multilayer film is a light source device that reflects light in the second wavelength range.

2. The light source device according to claim 1, wherein the refractive index of the first translucent layer is higher than the refractive index of the phosphor layer.

3. The light source device according to claim 1, wherein the second wavelength range includes a wavelength range of 475 nm to 510 nm.

4. The light source device according to claim 1, wherein the plurality of nanoantennas are arranged in a hexagonal or square grid arrangement pattern.

5. The light source device according to claim 1, wherein each of the plurality of nanoantennas has the shape of a cylinder, cone, prism, or pyramid.

6. The plurality of nanoantennas are made of Al, Au, Ag, Ni, or TiO ２ A light source device according to claim 1, comprising the following components.

7. The first translucent layer is TiO ２ Or Ta ２ O ５ A light source device according to claim 1 or 2, comprising the above.

8. The second translucent layer is SiO ２ A light source device according to claim 1 or 2, comprising the above.

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