Phosphor element and light source device

Abstract

To provide a phosphor element capable of reducing color unevenness on a light irradiation surface by reducing color unevenness on a light emission surface, and a light source device including such phosphor element.SOLUTION: A phosphor element according to one embodiment of the present invention comprises a yellow phosphor layer formed from eutectic of Ce:YAG and Al2O3, and a volume scattering layer provided on at least one of a light irradiation surface and a back surface of the yellow phosphor layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a phosphor element and a light source device. [Background technology]

[0002] In recent years, LED lighting has rapidly replaced incandescent and fluorescent lamps as a highly energy-efficient lighting source. One of the challenges of LED light sources is the phenomenon commonly known as the yellow ring. In this phenomenon, for example, in a white LED that combines a blue LED chip and a yellow phosphor, the center glows bright white and the periphery glows in a yellow ring shape. Because the blue excitation light emitted from the blue LED chip is highly directional, the blue excitation light and yellow fluorescence mix in an appropriate ratio in the center of the yellow phosphor located directly above the blue LED chip, resulting in the white light emitted to the outside. However, the ratio of blue excitation light reaching the periphery of the yellow phosphor is lower than in the center, and most of the blue excitation light is converted into yellow fluorescence, resulting in the light emitted to the outside being a high proportion of yellow fluorescence. This results in the yellow ring phenomenon.

[0003] In lighting fixtures that use LEDs as light sources, the yellow ring can cause color unevenness on the illuminated surface (the illuminated object). Conventionally, a diffuser plate has been used to address this issue (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-164216 Summary of the Invention [Problem to be solved by the invention]

[0005] When a diffuser plate is used, color unevenness on the irradiated surface is reduced by combining the transmitted excitation light and the fluorescent light using an optical system installed between the diffuser plate and the irradiated surface. However, the combined light of the transmitted excitation light and the fluorescent light obtained from this optical system has a certain spread angle. Therefore, when the diffuser plate is applied to lighting devices intended to illuminate a limited area at a distance with high illuminance, such as automotive headlights or outdoor spotlights, the illumination spot on the irradiated surface may be larger than the desired area. Therefore, it is desirable to provide a phosphor element that can reduce color unevenness on the irradiated surface by reducing color unevenness on the light exit surface, and a light source device equipped with such a phosphor element. [Means for solving the problem]

[0006] A phosphor element according to one embodiment of the present invention includes a yellow phosphor layer formed from a eutectic of Ce:YAG and Al2O3, and a volume scattering layer provided on at least one of the light irradiation surface and the back surface of the yellow phosphor layer.

[0007] A light source device according to one embodiment of the present invention includes a phosphor element and a light source unit capable of irradiating the phosphor element with blue excitation light. The phosphor element provided in this light source device includes a yellow phosphor layer made of a eutectic of Ce:YAG and Al2O3, and a volume scattering layer provided on at least one of the light irradiation surface irradiated with the blue excitation light and the back surface of the yellow phosphor layer. [Effects of the Invention]

[0008] According to a phosphor element and a light source device according to an embodiment of the present invention, a volume scattering layer is provided on at least one of the light irradiation surface and the back surface of a yellow phosphor layer made of a eutectic of Ce:YAG and Al2O3, which makes it possible to reduce color unevenness in the light emission spot that appears on the light exit surface of the phosphor element compared to a case in which a yellow phosphor layer and a diffusion plate are laminated together, thereby reducing color unevenness on the irradiation surface. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating an example of a cross-sectional configuration of a phosphor element according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing an example of an optical path within the phosphor layer of FIG. [Figure 3] FIG. 3 is a diagram illustrating an example of a light path in the volume scattering layer of FIG. [Figure 4] FIG. 4 is a diagram showing an example of a light emitting spot on the light exit surface of a phosphor element according to a comparative example and an example of a light emitting spot on the light exit surface of a phosphor element according to this embodiment. [Figure 5] FIG. 5 is a diagram showing an example of the luminance distribution of transmitted excitation light and fluorescent light when no volume scattering layer is provided. [Figure 6] FIG. 6 is a diagram showing an example of the luminance distribution of transmitted excitation light and fluorescent light when a volume scattering layer is provided. [Figure 7] FIG. 7 is a diagram showing an example of the ratio of transmitted excitation light to transmitted fluorescent light with and without a volume scattering layer. [Figure 8] FIG. 8 is a diagram showing an example of the ratio of transmitted excitation light to transmitted fluorescent light with and without a volume scattering layer. [Figure 9] FIG. 9 is a diagram showing a modified example of the size of the phosphor element of FIG. [Figure 10] FIG. 10 is a diagram showing a modified example of the shape and size of the phosphor element of FIG. [Figure 11] FIG. 11 is a diagram showing a modification of the cross-sectional structure of the phosphor element of FIGS. [Figure 12] FIG. 12 is a diagram showing a modification of the cross-sectional structure of the phosphor element shown in FIGS. [Figure 13] FIG. 13 is a diagram showing an example of the ratio between the spot diameter of transmitted excitation light appearing on the light exit surface when there is no volume scattering layer and the spot diameter of transmitted excitation light appearing on the light exit surface when there is a volume scattering layer. [Figure 14] FIG. 14 is a diagram illustrating an example of a schematic configuration of an illumination device according to the second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following description is one specific example of the present invention, and the present invention is not limited to the following embodiment. Furthermore, the present invention is not limited to the arrangement, dimensions, dimensional ratios, etc. of each component shown in each drawing.

[0011] <1. Background> Yellow rings can occur not only in LED-excited phosphor light sources, but also in lighting devices that use laser-excited phosphor light sources (laser lighting devices), which have become increasingly popular in recent years. Laser light, like LED light, is highly directional, so in the center of the yellow phosphor where the blue laser excitation light is irradiated, the blue laser excitation light and yellow fluorescence mix in an appropriate ratio, resulting in white light being emitted to the outside. However, in the yellow phosphor, the proportion of blue laser excitation light that reaches the periphery of the center is lower than in the center, so most of the blue laser excitation light that reaches the periphery is converted into yellow fluorescence light, resulting in light with a high proportion of yellow fluorescence being emitted to the outside. This results in the phenomenon known as a yellow ring.

[0012] In the field of laser lighting, the purpose is not to illuminate an entire room over a wide area like ordinary household lighting fixtures, but to illuminate a limited area at a distance with high illuminance, such as in vehicle headlights and outdoor spotlights.Lamps known as long-distance lighting, such as vehicle headlights and outdoor spotlights, often use optical systems that shape the light emitted from the light source (emitted light) into a beam shape that is as close to parallel as possible, and minimize the beam diameter of the emitted light, allowing the emitted light to reach a long distance.

[0013] In lighting fixtures with such optical systems, the light-emitting surface profile of the light source tends to be reflected in the illumination surface profile. Therefore, if the aforementioned yellow ring is present on the light-emitting surface of the light source, the yellow ring will also be projected onto the illumination surface. As described in Patent Document 1, a method of using a diffuser to diffuse light (transmitted excitation light and fluorescent light) downstream in the optical path at a certain diffusion angle and reducing color unevenness by combining the transmitted excitation light and fluorescent light using an optical system installed between the diffuser and the illumination surface makes it difficult to maintain parallel light emitted from the lighting fixture, resulting in an inability to illuminate a limited area at a distance. Therefore, after extensive research, the inventors of the present application came up with an invention that can reduce color unevenness on the illumination surface by reducing color unevenness on the light-emitting surface.

[0014] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following description is one specific example of the present invention, and the present invention is not limited to the following embodiment. Furthermore, the present invention is not limited to the arrangement, dimensions, dimensional ratios, etc. of each component shown in each drawing.

[0015] 2. First Embodiment [composition] The configuration of a phosphor element 1 according to a first embodiment of the present invention will be described. FIG. 1 illustrates an example of a cross-sectional configuration of the phosphor element 1. For example, as shown in FIG. 1, the phosphor element 1 includes a phosphor layer 10 and a volume scattering layer 20. The phosphor element 1 corresponds to a specific example of a "phosphor element" according to an embodiment of the present disclosure. The phosphor layer 10 corresponds to a specific example of a "yellow phosphor layer" according to an embodiment of the present disclosure. The volume scattering layer 20 corresponds to a specific example of a "volume scattering layer" according to an embodiment of the present disclosure. FIG. 2 illustrates an example of the optical path of light propagating within the phosphor layer 10. FIG. 3 illustrates an example of the optical path of light propagating within the volume scattering layer 20.

[0016] The phosphor layer 10 and the volume scattering layer 20 are bonded to each other to form a laminate. The phosphor layer 10 and the volume scattering layer 20 are bonded to each other by, for example, an adhesive, diffusion bonding, fusion bonding, or room-temperature bonding. The upper surface 10A of the phosphor layer 10 serves as the light irradiation surface S1 of the phosphor element 1, and the surface of the phosphor layer 10 facing the upper surface 10A serves as the back surface 10B. The upper surface 20A of the volume scattering layer 20 is in contact with the back surface 10B of the phosphor layer 10. The back surface 20B of the volume scattering layer 20 serves as the light exit surface S2 of the phosphor element 1.

[0017] The phosphor layer 10 is made of an inorganic material. For example, as shown in FIG. 2, the phosphor layer 10 is a yellow phosphor layer made of a eutectic of a Ce-doped YAG single crystal (Ce:YAG single crystal) and an Al2O3 single crystal. The Ce:YAG single crystal is capable of absorbing blue excitation light to generate yellow fluorescent light. The phosphor layer 10 has a three-dimensional structure in which the Ce:YAG single crystal and the Al2O3 single crystal are intertwined, such as a lamellar structure. Within the phosphor layer 10, there is a boundary between the Ce:YAG single crystal and the Al2O3 single crystal. This boundary also has a complex three-dimensional structure. The phosphor layer 10 functions as a volume scattering layer.

[0018] The phosphor layer 10 is formed, for example, by a plate-shaped element cut from a crystal growth rod made of a eutectic of Ce:YAG single crystal and Al2O3 single crystal. When the phosphor layer 10 is formed by the above-described plate-shaped element, the phosphor layer has superior heat resistance and thermal conductivity compared to a phosphor layer made of a layer in which phosphor powder is dispersed in a resin binder. When the phosphor layer 10 is formed by the above-described eutectic, particularly when the phosphor layer 10 has a lamellar structure, light incident on the upper surface 10A of the phosphor layer 10 is diffused in a direction parallel to the upper surface 10A of the phosphor layer 10 by the eutectic boundary and further by the lamellar structure, and is then emitted from the back surface of the phosphor layer 10. Specifically, the light incident on the upper surface 10A of the phosphor layer 10 is excitation light (incident excitation light La) that excites the Ce:YAG single crystal. The incident excitation light La is light in the blue wavelength band. The incident excitation light La is obtained, for example, from a blue laser element. The incident excitation light La obtained from a blue laser element is light with higher directivity than LED light. The incident excitation light La may also be obtained, for example, from a blue LED element. The incident excitation light La obtained from a blue LED element is light with relatively high directivity, although not as high as laser light.

[0019] Assume that incident excitation light La is incident on the entire upper surface 10A, and light including transmitted excitation light Lb, which is part of the incident excitation light La, that has passed through the phosphor layer 10, and fluorescent light Lc, which is generated when the phosphor layer 10 is excited by the incident excitation light La, is emitted from the rear surface 10B of the phosphor layer 10. At this time, the excitation light La that has entered the phosphor layer 10 is diffused in a direction parallel to the upper surface 10A of the phosphor layer 10 by the eutectic boundaries and further by the lamellar structure, and is emitted as transmitted excitation light Lb from the entire rear surface 10B of the phosphor layer 10. Furthermore, within the phosphor layer 10, the Ce:YAG single crystals are excited by the excitation light that has diffused in a direction parallel to the upper surface 10A of the phosphor layer 10, and the fluorescent light Lc generated thereby is emitted from the entire rear surface 10B of the phosphor layer 10. This results in small unevenness and variation in the ratio of the luminance of the transmitted excitation light Lb to the luminance of the fluorescent light Lc (luminance of fluorescent light Lc / luminance of transmitted excitation light Lb) across the entire rear surface 10B of the phosphor layer 10. Hereinafter, this ratio will be referred to as the luminance ratio Lc / Lb.

[0020] The volume scattering layer 20 is a non-luminescent layer that does not emit fluorescent light. The volume scattering layer 20 is made of a transparent ceramic material that can scatter and transmit the transmitted excitation light Lb, which is part of the incident excitation light La and has passed through the phosphor layer 10, and the fluorescent light Lc, which is generated when the phosphor layer 10 (Ce:YAG single crystal) is excited by the incident excitation light La. Examples of transparent ceramic materials include Al2O3, BaSO4, Si3N4, ZrO2, YO3, AlN, and glass. The volume scattering layer 20 is a ceramic plate made of a transparent ceramic material. The incident light Lin (transmitted excitation light Lb and fluorescent light Lc) on the upper surface 20A of the volume scattering layer 20 is volume-scattered at the grain boundaries of the fired grains present in the transparent ceramic material, diffuses in a direction parallel to the upper surface 20A of the volume scattering layer 20, and is emitted from the rear surface 20B of the volume scattering layer 20. The light emitted from the rear surface 20B of the volume scattering layer 20 is the light (transmitted light Lout) that is scattered and transmitted through the volume scattering layer 20 out of the incident light Lin.

[0021] FIG. 4 shows an example of an emission spot Pout′ appearing on the light exit surface of phosphor element 100, which includes a laminate including a yellow phosphor layer having the same structure as phosphor layer 10 but approximately 10 times the chip size of phosphor element 1, and a volume scattering layer having the same structure as volume scattering layer 20 but approximately 10 times the chip size of phosphor element 1. Suppose that blue excitation light (incident blue excitation light), which is more directional than LED light, is incident on only a portion of the upper surface of the yellow phosphor layer of phosphor element 100. At this time, an incident excitation light spot Pin, such as that shown in FIG. 4, is generated on the upper surface of the yellow phosphor layer of phosphor element 100. Light is emitted from the back surface of the volume scattering layer of phosphor element 100, including transmitted excitation light that is part of the incident blue excitation light and has passed through the back surface of phosphor element 100, and transmitted fluorescent light that is part of the yellow fluorescent light generated in the yellow phosphor layer of phosphor element 100 and has passed through the back surface of phosphor element 100. As a result, a light emitting spot Pout' such as that shown in FIG.

[0022] Here, the incident blue excitation light has higher directionality than the fluorescent light. Therefore, the incident blue excitation light is sufficiently diffused in the portion of the volume scattering layer facing the incident excitation light spot Pin. Therefore, in the central region of the light emission spot Pout', including the position facing the incident excitation light spot Pin, a white spot WS is generated by the combination of the transmitted excitation light and the transmitted fluorescent light. On the other hand, in the portion of the volume scattering layer facing the peripheral region of the incident excitation light spot Pin, the incident blue excitation light is not sufficiently diffused. Therefore, in the peripheral region of the light emission spot Pout', including the position facing the incident excitation light spot Pin, a yellow ring YR, mainly composed of transmitted fluorescent light, is generated.

[0023] In this embodiment, the phosphor element 1 (a laminate of the phosphor layer 10 and the volume scattering layer 20) is sized so that a yellow ring YS does not appear in the combined light of the transmitted excitation light Lb and the fluorescent light Lc that is emitted from the back surface 10B (light exit surface S2) when the incident excitation light La is irradiated onto the top surface 10A (light irradiation surface S1). In other words, a light-emitting spot Pout with small unevenness and variation in the luminance ratio Lc / Lb is obtained over the entire back surface 10B (light exit surface S2) of the phosphor element 1.

[0024] FIG. 5 is a diagram illustrating an example of the luminance distribution of the transmitted excitation light Lb and the fluorescent light Lc at the light exit surface S2 when the volume scattering layer 20 is omitted in the phosphor element 1 and the rear surface 10B of the phosphor layer 10 serves as the light exit surface S2. FIG. 5 shows the results when the diameter Ds of the incident excitation light spot Pin is 1000 μm and the thickness Tp of the phosphor layer 10 is 200 μm. FIG. 6 is a diagram illustrating an example of the luminance distribution of the transmitted excitation light Lb and the fluorescent light Lc at the light exit surface S2 when the rear surface 20B of the volume scattering layer 20 serves as the light exit surface S2. FIG. 6 shows the results when the diameter Ds of the incident excitation light spot Pin is 1000 μm, the thickness Tp of the phosphor layer 10 is 200 μm, and the thickness Ts of the volume scattering layer 20 is 150 μm.

[0025] 7 and 8 show an example of the ratio between the transmitted excitation light Lb and the fluorescent light Lc (luminance of the fluorescent light Lc / luminance of the transmitted excitation light Lb) with and without the volume scattering layer 20. Figures 7 and 8 show the results when the diameter Ds of the incident excitation light spot Pin is 1000 μm and the thickness Tp of the phosphor layer 10 is 200 μm. Figure 7 shows the results when the thickness Ts of the volume scattering layer 20 is 150 μm, and Figure 8 shows the results when the thickness Ts of the volume scattering layer 20 is 100 μm.

[0026] 5 to 7, it can be seen that the provision of the volume scattering layer 20 reduces the difference in luminance between the fluorescent light Lc and the transmitted excitation light Lb, or the luminance ratio Lc / Lb, in the area surrounding the area facing the incident excitation light spot Pin on the light exit surface S2, compared to when the volume scattering layer 20 is omitted. In other words, compared to when the volume scattering layer 20 is omitted, the yellow ring YS is closer to white and more blurred. This can be said to be the effect of the volume scattering layer 20 scattering both the transmitted excitation light Lb and the fluorescent light Lc. Furthermore, it can be seen from FIGS. 7 and 8 that the provision of the volume scattering layer 20 reduces unevenness and variation in the luminance ratio Lc / Lb in the area facing the incident excitation light spot Pin on the light exit surface S2, compared to when the volume scattering layer 20 is omitted. Furthermore, from Figures 7 and 8, it can be seen that as the volume scattering layer 20 becomes thicker, the area on the light emission surface S2 where the luminance ratio Lc / Lb becomes larger (i.e., the area where the yellow ring YS is generated) shifts further outward in the surrounding area facing the incident excitation light spot Pin.

[0027] [effect] Next, the effects of the phosphor element 1 according to this embodiment will be described.

[0028] In this embodiment, there is provided a phosphor layer 10 made of a eutectic of Ce:YAG and Al2O3, and a volume scattering layer 20 provided on the rear surface 10B side of the phosphor layer 10. This makes it possible to reduce color unevenness of the light-emitting spot Pout that appears on the light-emitting surface S2 (rear surface 20B) of the phosphor element 1, compared to, for example, a case in which the phosphor layer 10 and a diffuser plate are laminated. As a result, it is possible to reduce color unevenness on the surface (irradiation surface) irradiated with the light emitted from the phosphor element 1.

[0029] In this embodiment, the volume scattering layer 20 is made of an inorganic material, specifically Al2O3, BaSO4, Si3N4, ZrO2, Y2O3, AlN, or glass. This makes the phosphor layer 10 superior in heat resistance and thermal conductivity compared to phosphor layer 10 made of a layer in which phosphor powder is dispersed in a resin binder. As a result, it is possible to suppress deterioration of optical characteristics due to heat generated in the phosphor layer 10.

[0030] In this embodiment, the volume scattering layer 20 is in contact with the rear surface 10B of the phosphor layer 10. This allows the light (transmitted excitation light Lb and fluorescent light Lc) emitted from the rear surface 10B of the phosphor layer 10 to be efficiently incident on the volume scattering layer 20. As a result, the light utilization efficiency of the phosphor element 1 can be improved.

[0031] <3. Modification of the First Embodiment> [Variation 3-1] In the above-described embodiment, the phosphor element 1 (the laminate of the phosphor layer 10 and the volume scattering layer 20) may be sized so that a portion of the yellow ring YS that does not form a ring is generated on the back surface 10B (light-emitting surface S2) of the phosphor element 1, as shown in FIG. 9 . Even in this case, the phosphor element 1 (the laminate of the phosphor layer 10 and the volume scattering layer 20) is sized so that a yellow ring YS is not generated in the combined light of the transmitted excitation light Lb and the fluorescent light Lc that is output from the back surface 10B (light-emitting surface S2) when the incident excitation light La is irradiated onto the top surface 10A (light-irradiated surface S1). In other words, a light-emitting spot Pout with small unevenness and variation in the luminance ratio Lc / Lb is obtained across the entire back surface 10B (light-emitting surface S2) of the phosphor element 1. As a result, color unevenness on the surface (irradiated surface) irradiated with the light emitted from the phosphor element 1 can be reduced.

[0032] [Variation 3-2] In the above-described embodiment, the phosphor element 1 (a laminate of the phosphor layer 10 and the volume scattering layer 20) may be circular, as shown in FIG. 10 . In this case, the phosphor element 1 (a laminate of the phosphor layer 10 and the volume scattering layer 20) is sized so that a yellow ring YS does not appear in the combined light of the transmitted excitation light Lb and the fluorescent light Lc that is emitted from the back surface 10B (light emitting surface S2) when the incident excitation light La is irradiated onto the top surface 10A (light emitting surface S1). This reduces color unevenness of the light-emitting spot Pout that appears on the light emitting surface S2 (back surface 20B) of the phosphor element 1, compared to, for example, a case in which the phosphor layer 10 and a diffuser plate are laminated. As a result, color unevenness in the surface (irradiation surface) irradiated with the light emitted from the phosphor element 1 can be reduced.

[0033] [Variation 3-3] In the above-described embodiment and modifications 3-1 and 3-2, the volume scattering layer 20 may be in contact with the upper surface 10A of the phosphor layer 10, as shown in FIG. 11, for example. In this case, the incident excitation light La can be diffused by the volume scattering layer 20 before the incident excitation light La enters the phosphor layer 10. This makes it possible to reduce color unevenness of the light-emitting spot Pout that appears on the light-emitting surface S2 (rear surface 10B) of the phosphor element 1, compared to, for example, a case in which the phosphor layer 10 and a diffusion plate are stacked. As a result, it is possible to reduce color unevenness on the surface (irradiation surface) irradiated with the light emitted from the phosphor element 1.

[0034] Furthermore, in this modification, the incident excitation light La is diffused by the volume scattering layer 20, thereby reducing the irradiation power density of the incident excitation light La on the phosphor layer 10. This reduces the local load on the phosphor layer 10, making it possible to reduce local heat generation due to non-radiative transition. As a result, it is possible to reduce temperature quenching of the phosphor layer 10.

[0035] [Variation 3-4] In the above-described embodiment and modifications 3-1 and 3-2, for example, as shown in FIG. 12 , a volume scattering layer 20 may be provided in contact with the back surface 10B of the phosphor layer 10 and a volume scattering layer 20 in contact with the top surface 10A of the phosphor layer 10. By providing the volume scattering layer 20 in contact with the top surface 10A of the phosphor layer 10, the incident excitation light La can be diffused by the volume scattering layer 20 before the incident excitation light La enters the phosphor layer 10. This reduces the irradiation power density of the incident excitation light La on the phosphor layer 10, thereby reducing the local load on the phosphor layer 10 and reducing local heat generation due to non-radiative transition. As a result, temperature quenching of the phosphor layer 10 can be reduced.

[0036] Furthermore, by providing the volume scattering layer 20 in contact with the upper surface 10A of the phosphor layer 10 and the volume scattering layer 20 in contact with the back surface 10B of the phosphor layer 10, it is possible to reduce color unevenness of the light emitting spot Pout that appears on the light exit surface S2 (back surface 20B) of the phosphor element 1, compared to, for example, a case in which the phosphor layer 10 and a diffuser plate are laminated. As a result, it is possible to reduce color unevenness on the surface (irradiation surface) that is irradiated with the light emitted from the phosphor element 1.

[0037] [Variation 3-5] In the above-described embodiment and modified examples 3-1, 3-2, 3-3, and 3-4, the volume scattering layer 20 may be formed, for example, by a sprayed film formed on the surface of the phosphor layer 10 by a thermal spraying method. When the volume scattering layer 20 is provided in contact with the upper surface 10A of the phosphor layer 10, the volume scattering layer 20 is formed by a sprayed film in contact with the upper surface 10A of the phosphor layer 10. When the volume scattering layer 20 is provided in contact with the rear surface 10B of the phosphor layer 10, the volume scattering layer 20 is formed by a sprayed film in contact with the rear surface 10B of the phosphor layer 10. The sprayed film has a thickness of, for example, about 10 μm.

[0038] The sprayed film is a deposited film obtained by spraying a solution of the above-mentioned transparent ceramic material or a material in a nearly molten state of the above-mentioned transparent ceramic material onto the surface of the phosphor layer 10. In the sprayed film, molten particles flying during spraying collide with the surface of the phosphor layer 10 and are crushed, depositing them in a flattened state. Therefore, the flattened molten particles have the property of reflecting and propagating incident light (transmitted excitation light Lb and fluorescent light Lc) in a direction parallel to the surface of the phosphor layer 10. Therefore, even a thin sprayed film can more effectively propagate the incident light (transmitted excitation light Lb and fluorescent light Lc) in a direction parallel to the surface of the phosphor layer 10.

[0039] In this modification, the volume scattering layer 20 is formed by a sprayed film. This allows for a thinner phosphor element 1 compared to the phosphor elements 1 according to the above-described embodiment and modifications 3-1, 3-2, 3-3, and 3-4, since the volume scattering layer 20 is formed by a sprayed film. Furthermore, since the volume scattering layer 20 is formed by a sprayed film, the adhesion between the phosphor layer 10 and the volume scattering layer 20 is high, and the heat resistance of the volume scattering layer 20 is extremely high. Therefore, when a phosphor element 1 including a volume scattering layer 20 formed by a sprayed film is used as part of a light source of an illumination device, the durability and reliability of the light source can be improved. Furthermore, the spraying method does not require a step of bonding the volume scattering layer 20 to the phosphor layer 10, thereby simplifying the manufacturing process of the phosphor element 1. As a result, the cost of the phosphor element 1 can be reduced.

[0040] 13 shows an example of the ratio ((D2 / D1)×100) between the spot diameter D1 of the transmitted excitation light Lb appearing on the light exit surface S2 when there is no volume scattering layer 20 and the spot diameter D2 of the transmitted excitation light Lb appearing on the light exit surface S2 when there is the volume scattering layer 20. D1 and D2 are the half-widths of the luminance distribution corresponding to the transmitted excitation light Lb, which are included in the two-dimensional luminance data obtained by imaging the light exit surface S2. Figure 13 shows the ratio ((D2 / D1) x 100) when the volume scattering layer 20 is composed of a ceramic plate with a thickness of 100 μm, the ratio ((D2 / D1) x 100) when the volume scattering layer 20 is composed of a ceramic plate with a thickness of 150 μm, the ratio ((D2 / D1) x 100) when the volume scattering layer 20 composed of a sprayed film is provided in contact with the upper surface 10A of the phosphor layer 10, and the ratio ((D2 / D1) x 100) when the volume scattering layer 20 composed of a sprayed film is provided in contact with the back surface 10B of the phosphor layer 10.

[0041] 13, even when the volume scattering layer 20 is formed of a sprayed film with a thickness of 10 μm, it is possible to obtain a light emitting spot Pout with a diameter equivalent to that when the volume scattering layer 20 is formed of a ceramic plate with a thickness of 100 μm. Therefore, it is possible to achieve a chip size equivalent to that of the phosphor element 1 according to the above-described embodiment and modified examples 3-1, 3-2, 3-3, and 3-4, but thinner than the phosphor element 1 according to the above-described embodiment and modified examples 3-1, 3-2, 3-3, and 3-4.

[0042] [Variation 3-6] In the above-described embodiment and modifications 3-1, 3-2, 3-3, 3-4, and 3-5, the phosphor element 1 may be a reflective type. In this case, the phosphor element 1 may further include, for example, a light-reflecting layer in contact with the light-emitting surface S2 in the above-described embodiment and modifications 3-1, 3-2, 3-3, 3-4, and 3-5. In this case, the light incident surface S1 also serves as the light-emitting surface S2, and light including the reflected excitation light reflected by the light-reflecting layer and the fluorescent light Lc, out of the incident excitation light La, is emitted from the light incident surface S1 that also serves as the light-emitting surface S2. This reduces color unevenness of the light-emitting spot Pout appearing on the light-emitting surface S2 of the phosphor element 1 compared to, for example, a case in which a phosphor layer 10 and a diffuser plate are stacked. As a result, color unevenness in the surface (irradiation surface) irradiated with the light emitted from the phosphor element 1 can be reduced.

[0043] 4. Second Embodiment Next, the configuration of an illumination device 200 according to a second embodiment of the present invention will be described. Fig. 14 shows a schematic configuration example of the illumination device 200. For example, as shown in Fig. 14, the illumination device 200 includes a phosphor element 1 according to the above-described embodiment and modifications 3-1 to 3-5, an excitation light source unit 210, a condenser lens 220, and an irradiation lens 230. Hereinafter, the phosphor element 1 according to the above-described embodiment and modifications 3-1 to 3-5 will be simply referred to as phosphor element 1.

[0044] The excitation light source unit 210 may be configured to include, for example, a blue laser, and generate incident excitation light La from the blue laser, and irradiate the light irradiation surface S1 of the phosphor element 1 with the incident excitation light La via the condenser lens 220. The excitation light source unit 210 may be configured to include, for example, a blue LED element, and generate incident excitation light La from the blue LED element, and irradiate the light irradiation surface S1 of the phosphor element 1 with the incident excitation light La via the condenser lens 220. The condenser lens 220 is configured to condense the incident excitation light La emitted from the excitation light source unit 210, and irradiate the light irradiation surface S1 of the phosphor element 1 with the incident excitation light La. The condenser lens 220 is configured so that the incident excitation light La irradiates only a portion of the light irradiation surface S1.

[0045] 4, 9, and 10, the phosphor element 1 (laminate of the phosphor layer 10 and the volume scattering layer 20) is sized so that a yellow ring YS does not appear in the combined light of the transmitted excitation light Lb and the fluorescent light Lc that is emitted from the back surface 10B (light exit surface S2) when incident excitation light La is irradiated onto the top surface 10A (light irradiation surface S1). In other words, a light-emitting spot Pout with small unevenness and variation in the luminance ratio Lc / Lb is obtained over the entire back surface 10B (light exit surface S2) of the phosphor element 1.

[0046] The illumination lens 230 is an optical system that can shape the light emitted from the phosphor element 1 (combined light Lm of transmitted excitation light Lb and fluorescent light Lc) into a beam shape that is as close to parallel as possible, and can allow the combined light Lm to reach the illumination surface 240 by minimizing the beam diameter of the combined light Lm.

[0047] In this embodiment, the phosphor element 1 is used as a part of the light source, which allows a beam with little color unevenness to reach a long distance.

[0048] In this embodiment, the phosphor element 1 may be a reflective type. In this case, the phosphor element 1 further includes a light-reflecting layer in contact with the light-emitting surface S2 in, for example, the first embodiment and modifications 3-1, 3-2, 3-3, 3-4, and 3-5. In this case, the light incident surface S1 also serves as the light-emitting surface S2, and light including the reflected excitation light reflected by the light-reflecting layer and the fluorescent light Lc, out of the incident excitation light La, is emitted from the light incident surface S1 also serving as the light-emitting surface S2. The illumination lens 230 is an optical system that adjusts the light (combined light of the reflected excitation light and the fluorescent light Lc) emitted from the light incident surface S1 also serving as the light-emitting surface S2 of the phosphor element 1 into a beam shape as close to parallel light as possible, thereby minimizing the beam diameter of the combined light and allowing the combined light to reach the illumination surface 240. This reduces color unevenness of the light emitting spot Pout appearing on the light exit surface S2 of the phosphor element 1 compared to when, for example, the phosphor layer 10 and a diffusion plate are laminated together. As a result, color unevenness on the surface (irradiation surface) irradiated with the light emitted from the phosphor element 1 can be reduced.

[0049] The phosphor element 1 can also be applied to various fields such as laser displays, laser lighting, projector mapping, and medical care. Examples of the laser displays include laser projectors, laser TVs, and head-mounted displays. Examples of the laser lighting include light sources for microscopes, vehicle headlamps, indirect indoor lighting, and light sources for plant factories. Examples of the medical applications include light sources for endoscopes and laser scalpels. [Explanation of symbols]

[0050] 1...phosphor element, 10...phosphor layer, 20...volume scattering layer, 20A...first main surface, 20B...second main surface, 200...illumination device, 210...excitation light source unit, 220...condenser lens, 230...illumination lens, 300...illumination surface, Ds...illumination spot diameter, La...incident excitation light, Lb...transmitted excitation light, Lc...fluorescent light, Lin...incident light, Lout, Lout'...transmitted light, Lm...combined light, Ps...incident excitation light spot, S1...light irradiation surface, S2...rear surface, Tp, Ts...thickness, WS...white spot, YR...yellow ring.

Claims

1. Ce:YAG and Al ２ O ３ a yellow phosphor layer formed by a eutectic of a volume scattering layer provided on at least one of the light irradiation surface and the back surface opposite to the light irradiation surface of the yellow phosphor layer; Equipped with Phosphor element.

2. The volume scattering layer is made of an inorganic material. The phosphor element according to claim 1 .

3. The volume scattering layer is made of Al ２ O ３ , BaSO ４ , Si ３ N ４ , ZrO ２ , Y ２ O ３ , composed of AlN or glass The phosphor element according to claim 2 .

4. The volume scattering layer is in contact with at least one of the light irradiation surface and the back surface. The phosphor element according to claim 1 .

5. The volume scattering layer is formed by a sprayed film in contact with at least one of the light irradiation surface and the back surface of the yellow phosphor layer. The phosphor element according to claim 1 .

6. A phosphor element; a light source unit capable of irradiating the phosphor element with blue excitation light; Equipped with The phosphor element is Ce:YAG and Al ２ O ３ a yellow phosphor layer formed by a eutectic of a volume scattering layer provided on at least one of a light irradiation surface on which the blue excitation light is irradiated and a back surface opposite to the light irradiation surface of the yellow phosphor layer; have Light source device.

7. The yellow phosphor layer and the volume scattering layer are sized so that a yellow ring does not appear in the light-emitting spot that appears on the surface of the back side of the phosphor element when the blue excitation light is irradiated onto the surface of the light-irradiation side of the phosphor element. The light source device according to claim 6 .

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