JP6660484B2 - Phosphor element and lighting device - Google Patents

Description

  The present invention relates to a phosphor element and a lighting device that emits white light.

  Recently, automotive headlights using laser light sources have been actively studied, and one of them is a white light source combining a blue laser or an ultraviolet laser with a phosphor. By condensing the laser light, the light density of the excitation light can be increased, and by concentrating a plurality of laser lights on the phosphor, the light intensity of the excitation light can be increased. As a result, the luminous flux and the luminance can be simultaneously increased without changing the light emitting area. For this reason, a white light source combining a semiconductor laser and a phosphor has been receiving attention as a light source replacing the LED. For example, the fluorescent glass used in automotive headlights is Nippon Electric Glass Co., Ltd.'s "Lumiface" fluorescent glass, the National Research and Development Agency of Materials and Materials, Tamura Seisakusho Co., Ltd. The body is considered.

  For a white laser, the structure shown in Non-Patent Document 1 is disclosed by SORAA, USA. In this laser, the light of the excitation laser is directly incident on the phosphor from obliquely above and a reflection film is formed on the opposite surface of the phosphor, so that the excitation light and the fluorescence are reflected and extracted upward as white light. ing. This white laser is expected to be applied as a special light source or a light source for optical communication, because it can integrate an excitation laser and a phosphor, reduce the size, and obtain illumination light with high directivity.

  On the other hand, Patent Literature 1 discloses a white light emitting device using a fluorescent fiber. In this device, excitation light is made incident on an optical fiber made of a phosphor, and white light is emitted from a side peripheral surface of the optical fiber.

  Further, in Patent Document 2, an outer peripheral surface of an optical fiber made of a fluorescent material is covered with a metal film, excitation light is made incident on the optical fiber, and white light is emitted from an emission-side end surface of the optical fiber.

J. W. Raring et al., "Laser diode phosphor modules for unprecedented SSL optical control," 2016 Illuminating Engineering Society (IES) Annual Conference, Orlando, FL (Oct. 24, 2016).

Patent No. 4299826 Patent No. 5214193

  However, the structure described in Non-Patent Document 1 has a poor fluorescence extraction efficiency, requires an absorber for Beam Dump because the excitation light leaks from the side surface of the phosphor, and the excitation laser light is also lost. I understand.

  In the structure described in Patent Literature 1, it is difficult to obtain white light having high intensity and directivity, and since fluorescent light and excitation light are emitted from various places on the outer peripheral surface, color unevenness of white light is observed.

  In the structure described in Patent Document 2, white light with high directivity can be obtained, but it has been found that there is a limit to the efficiency (extraction efficiency) of extracting the fluorescence converted from the excitation light to the emission side.

  An object of the present invention is to make excitation light incident on an optical waveguide, and to improve the efficiency of extracting white light from the optical waveguide in a phosphor element that generates fluorescence, and to prevent color unevenness of the obtained white light. It is to be.

The present invention, an excitation light to the optical waveguide propagating, glass, an optical waveguide with a rare earth element ion-into the single crystal or polycrystal of doped phosphor, irradiating the excitation light to the rare earth element ions It is the oscillation fluorescence by, the optical waveguide has the excitation light and the fluorescent Tona Ru emergence end face for emitting white light, opposing end surface opposite to the emitting side end face and the outer peripheral surface Optical waveguide,
A clad layer covering the outer peripheral surface of the optical waveguide, and a reflective film covering the clad layer, comprising a reflective film made of a metal film or a dielectric multilayer film ;
An area of the emission-side end face is larger than an area of the opposed end face, and the outer peripheral surface of the optical waveguide includes an inclined portion inclined by 2 ° or more and 13 ° or less with respect to a center axis of the optical waveguide. It is characterized by.

Further, the present invention is a lighting device including a light source that oscillates excitation light and a phosphor element,
The phosphor element is the phosphor element, and white light is radiated from an end surface on an emission side of the optical waveguide.

  According to the present invention, among the fluorescent light generated in the optical waveguide, not only the fluorescent light reflected at the boundary with the cladding layer can propagate to the end face on the emission side, but also the cladding layer cannot satisfy the total reflection condition of the optical waveguide. The fluorescent light that enters the optical waveguide is also reflected by each reflective film provided on the outer peripheral surface of the optical waveguide and reenters the optical waveguide. Then, by increasing the area of the output side end face of the optical waveguide relatively and inclining the outer peripheral surface (boundary surface with the cladding layer) of the optical waveguide by 2 to 13 ° with respect to the central axis, the amount of emitted light is increased. Was found to be able to suppress color unevenness of the emitted white light at the same time, and reached the present invention.

(A) is a perspective view schematically showing a phosphor element 1 according to an embodiment of the present invention, (b) is a front view showing an emission side end face 2f, and (c) is a facing end face 2e. FIG. FIG. 3 is a schematic diagram showing a planar dimension of the phosphor element 1. It is a schematic diagram which shows the planar dimension of the phosphor element 11 which concerns on other embodiment. FIG. 2 is a schematic cross-sectional view illustrating a dimension in a thickness direction of the phosphor element 1 according to the embodiment of the present invention. FIG. 9 is a schematic diagram illustrating a light propagation state in a phosphor element 21 according to a comparative example. FIG. 3 is a schematic diagram illustrating a light propagation state in a phosphor element 1. (A) is a perspective view schematically showing a phosphor element 31 according to an embodiment of the present invention, (b) is a front view showing an emission-side end face 32f, and (c) is a facing end face 32e. FIG. FIG. 3 is a schematic view showing a cross section of a phosphor element 41. FIG. 4 is a schematic diagram showing light propagation in a cross section of a phosphor element 41.

1 and 2 show a phosphor element 1 according to an embodiment of the present invention.
In this example, the optical waveguide 2 has a quadrangular cross section and is elongated. An outer peripheral surface extends between the output side end surface 2f and the opposite end surface 2e of the optical waveguide 2, and the outer peripheral surface has an elongated bottom surface 2a, an upper surface 2b opposed to the bottom surface 2a, and a pair of side surfaces 2c, 2d. . The outer peripheral surface of the optical waveguide 2 is covered with a cladding layer 3, and the cladding layer 3 is covered with a reflection film 4.

  The clad layer 3 includes a bottom clad layer 3a that covers the bottom surface 2a of the optical waveguide 2, an upper clad layer 3b that covers the upper surface 2b, and side clad layers 3c and 3d that cover the side surfaces 2c and 2d. . The reflecting film 4 includes a bottom reflecting film 4a on the bottom cladding layer 3a, an upper reflecting film 4b on the upper cladding layer 3b, and side reflecting films 4c and 4d on the upper cladding layers 3c and 3d. It has. A passivation film may be formed on the reflection film in order to prevent the deterioration of the reflection film. An oxide film can be exemplified as the passivation film.

  According to the present invention, the area AO of the output side end face 2f is made larger than the area AI of the opposing end face 2e. The excitation light may be incident from the opposite end face 2e, or may be incident from the emission end face 2f and be totally reflected by the reflection film on the opposite end face 2e.

  According to the present embodiment, among the fluorescence converted in the optical waveguide 6, not only the fluorescence reflected at the boundary between the optical waveguide 2 and the cladding layer can propagate to the end face on the emission side, but also the total reflection condition of the optical waveguide. The fluorescence that enters the cladding layer without satisfying the above conditions is also reflected by the reflection films provided on the bottom surface, the top surface, and each side surface and re-enters the optical waveguide. Can be increased.

In addition, it is important that an inclined portion inclined with respect to the central axis of the optical waveguide is provided on the outer peripheral surface of the optical waveguide. The advantages of this will be further described.
First, a case will be described in which an inclined portion inclined with respect to the central axis is not provided on the outer peripheral surface of the optical waveguide. FIG. 5 relates to this embodiment.

  In the phosphor element 21 of the comparative example shown in FIG. 5, the width W of the optical waveguide 12 is constant and the thickness is also constant. The area of the output side end face 12f of the optical waveguide 12 and the area of the opposing end face 12e are the same. In this case, when the excitation light A propagates through the optical waveguide 12 and hits the phosphor particles 16, the phosphor particles 16 emit fluorescent light. At this time, the fluorescent light is emitted uniformly from the phosphor 16 in all directions.

  Here, the fluorescence F emitted from the phosphor 16 toward the emission side end face 12f reaches the interface with the cladding layer at the incident angle θp. Here, when the refractive index np of the optical waveguide, the refractive index nc of the cladding layer, and the incident angle θp satisfy the condition of total reflection, the fluorescent light is reflected at the interface, propagates in the optical waveguide, and propagates from the exit side end face 12f. Emit. On the other hand, when the incident angle θp of the fluorescence does not satisfy the condition of total reflection, the light is refracted as shown by an arrow G, reflected by the reflection films 4c and 4d, and reflected as shown by an arrow H. The light propagating while repeating such reflections is not propagated in the optical waveguide, but is partially attenuated in the phosphor by absorption of the reflection film or absorption of the phosphor, and partially reaches the emission side end face 12f. However, since this light has no directivity and is emitted from the emission end, there is a fluorescent component of a component that cannot be mixed with the excitation light propagating in the optical waveguide, so that the extraction efficiency of white light cannot be significantly improved.

  If the cladding layer is not provided and each reflective film is in direct contact with the phosphor, both the excitation light and the fluorescent light propagate without repeating the reflection on the reflective film without propagating through the optical waveguide. Part of the light and the fluorescent light is attenuated in the phosphor, and both lights reaching the output side end face 12f have no directivity and are emitted from the end face. Therefore, it is difficult to extract white light in the front direction, and the extraction efficiency is improved. Is difficult.

  The fluorescent light C generated from the phosphor 16 in a direction perpendicular to the longitudinal direction of the optical waveguide is reflected by the reflection film as shown by the arrow D, and is repeatedly reflected in the optical waveguide, and finally attenuated. Become. The fluorescence E generated from the phosphor 16 toward the facing end face 12e repeats the same reflection as described above, and finally reaches the facing end face.

  On the other hand, in the phosphor element 1 of FIG. 2, the width W of the upper surface of the optical waveguide 2 gradually increases from the facing end face 2e (WI) to the emission end face 2f (WO). Θ is the angle between the central axis K of the optical waveguide 2 and the side surfaces 6c and 6d. In the present example, the angle θ is constant and is in the range of 2 to 13 °. Is preferably constant, but does not need to be constant, and may vary between the output end face and the opposing end face. Preferably, the width W smoothly increases continuously from the facing end face to the emission end face.

  Here, as shown in FIG. 6, when the excitation light A propagates in the optical waveguide and hits the phosphor particles 16, the phosphor particles 16 emit fluorescent light. At this time, the fluorescent light is uniformly emitted from the phosphor in all directions. Here, the fluorescence F emitted from the phosphor 16 to the end face on the emission side reaches the interface with the cladding layer at the incident angle θp. When the refractive index np of the optical waveguide, the refractive index nc of the cladding layer, and the incident angle θp satisfy the total reflection condition, the fluorescence is reflected at the interface and propagates in the optical waveguide.

  For example, when the side surface 6d of the optical waveguide is inclined by θ with respect to the longitudinal direction K, the incident angle θp of the fluorescent light F becomes larger by θ as compared with the example of FIG. 5, and total reflection occurs at the interface with the cladding layer. Easier to do. For this reason, the fluorescence F, which did not satisfy the total reflection condition in the example of FIG. 5, is totally reflected at the interface with the cladding layer, propagates through the optical waveguide, and is not absorbed by the reflection film. I do.

  On the other hand, when the incident angle θp of the fluorescent light does not satisfy the total reflection condition, for example, the fluorescent light C generated from the fluorescent body 16 in a direction perpendicular to the central axis K of the optical waveguide similarly enters the cladding layer. Although the angle is θ, it is assumed that the total reflection angle cannot be satisfied at this time. In this case, the fluorescence C is reflected by the reflection film 4d, but the angle of incidence on the interface between the opposite side surface 2c and the cladding layer 3c is further increased by θ. Then, the condition of total reflection can be satisfied at the interface between the phosphor and the cladding layer, and finally the light propagates in the optical waveguide. When the light enters the side surface 2d of the optical waveguide at a right angle, the light is reflected by the reflection film 4d. However, the angle of incidence at the interface of the side surface 6c increases by θ, so that the light travels toward the emission end face side and is reflected. As the reflection is repeated by the film 4c and the reflection film 4d, the incident angle θp increases, so that the total reflection condition can be satisfied at the interface between the phosphor and the cladding layer, and the light propagates in the optical waveguide.

  From the above, when the outer peripheral surface of the optical waveguide 2 is inclined with respect to the central axis K, the fluorescence proceeds to either the emission end surface side or the opposite end surface side and repeats reflection, and is attenuated in the phosphor. This makes it possible to eliminate the fluorescent light.

  The direction of the fluorescence E traveling from the phosphor 16 toward the facing end face 2e changes to the emission side end face by the angle θ each time it is reflected by the reflection film. The propagation direction changes, and finally the light propagates through the optical waveguide and exits from the exit side end face. Nevertheless, the fluorescent light that has reached the opposite end face is reflected by the fluorescent reflection film provided on the opposite end face, and this light finally propagates through the optical waveguide and can be emitted from the emission side end face.

  In the embodiment shown in FIG. 3, the width W of the optical waveguide 2 is WI at the facing end face 2e and WO at the emission end face 2f. The width W increases from WI toward WO. In this example, the angle θ between the central axis of the optical waveguide and the side surface 2d is 2 to 13 °. In this example, the side surface 2c is parallel to the optical axis of the excitation light, and the side surface 2d is inclined by 2θ with respect to the optical axis of the excitation light.

  In a preferred embodiment, the thickness of the optical waveguide increases from the opposite end face toward the emission end face. For example, in the phosphor element 51 of FIG. 4, the thickness T of the optical waveguide 2 is TI at the facing end face 2e and TO at the emission end face 2f. Then, the thickness T increases from TI to TO.

  Here, α is the inclination angle between the central axis K of the optical waveguide 2 and the bottom surface 2a and the top surface 2b. In the present example, the inclination angle α is constant and is 2 to 13 °. α is preferably constant, but need not be constant, and may vary between the output end face and the opposite end face. Preferably, the thickness T smoothly increases continuously from the facing end face to the emission end face.

  The effect of changing the width of the optical waveguide is described above, but the same applies to the case of changing the thickness. The fluorescence reflected by the top and bottom surfaces is propagated from the exit side end surface by the same mechanism. It can be emitted as light.

  In addition, both the width W and the thickness T are configured to be continuously increased from the facing end face toward the emission end face, so that the omnidirectional fluorescence generated in the phosphor is reduced to the optical waveguide propagation light. The light can be converted and can be emitted to the emission-side end face with high efficiency. Similarly, white light can be extracted with high efficiency by mixing with the excitation light propagating in the optical waveguide.

  In the above embodiment, the cross-sectional shape of the optical waveguide is a quadrilateral. However, the cross-sectional shape of the optical waveguide is not limited to a quadrilateral, and may be a polygon such as a circle, an ellipse, and a hexagon.

  For example, in the phosphor element 31 of FIG. 7, an optical waveguide 32 having a circular cross section is provided. The optical waveguide 32 has an emission-side end face 32f shown in FIG. 7B, an opposed end face 32e shown in FIG. 7C, and an outer peripheral face 32a between the emission-side end face and the opposed end face. A cladding layer 33 is provided on the outer peripheral surface 32 a of the optical waveguide 32, and a reflection film 34 is provided on the cladding layer 33. The diameter DO of the emission-side end face 32f is larger than the diameter DI of the opposed end face 32e, and the outer peripheral face 32a forms an inclined surface inclined at an angle of 2 to 13 ° with respect to the central axis.

  In a preferred embodiment, the width of the optical waveguide varies from the top to the bottom. For example, in the phosphor element 41 shown in FIG. 8, the optical waveguide 42 has a trapezoidal cross section and is elongated. An outer peripheral surface extends between the output side end surface 42f and the opposite end surface 42e of the optical waveguide 42, and the outer peripheral surface has an elongated bottom surface 42a, an upper surface 42b facing the bottom surface 42a, and a pair of side surfaces 42c and 42d. The outer peripheral surface of the optical waveguide 42 is covered with the cladding layer 3, and the cladding layer 3 is covered with the reflection film 4.

Then, the width of the optical waveguide 42 gradually increases from the width on the top surface to the width on the bottom surface. Β is the inclination angle of the side surface 42c (42d) with respect to the bottom surface 42a of the optical waveguide 42.
This structure alone cannot be expected to increase the amount of emitted fluorescent light, but it can further increase the amount of emitted fluorescent light by combining it with a structure that is inclined by the inclination angle α in the thickness direction of the optical waveguide. it can. In other words, the fluorescent light propagating in the width direction of the optical waveguide propagates in the thickness direction of the optical waveguide when reflected on the side surface or a reflection surface parallel to the side surface when the side surface is inclined at an inclination angle β. Therefore, even when the inclination of the angle θ is not provided in the width direction of the optical waveguide, it is possible to propagate the optical waveguide only by the inclination in the thickness direction, and it is possible to increase the amount of emitted light.

The operation and effect of the present embodiment will be described with reference to FIG.
In this example, the fluorescent light is emitted from the phosphor 16 in all directions. Among them, the light G emitted right beside is reflected by the side surface 42c (42d) as shown by the arrow H. At this time, since the side surface 42c (42d) is inclined with respect to the normal M of the bottom surface, the fluorescence is reflected toward the bottom surface and further reflected as indicated by the arrow I on the bottom surface. As described above, during the multiple reflection, the fluorescent light is reflected on the top surface, the bottom surface, and the side surface, and does not repeat between the side surfaces. Here, when at least one of the width and the thickness of the optical waveguide is changed between the emission end face and the opposite end face as described above, the emission of the fluorescence to the emission end face is promoted. In the case of such an inclination, the fluorescence reflected on the side surface can change the direction of the reflected light to the light reflected on the top and bottom sides. For this reason, by combining with a structure having a changed thickness, all of the fluorescence generated in the phosphor can be efficiently emitted as an optical waveguide propagating light to the exit side end face, and excitation light propagating with the optical waveguide can also be emitted. Mixing makes it possible to extract white light with high efficiency.

  In the above example, the optical waveguide width at the bottom surface is larger than the optical waveguide width at the upper surface. However, the optical waveguide width at the bottom surface may be smaller than the optical waveguide width at the upper surface. From this viewpoint, a triangular shape may be adopted in which either optical waveguide width is zero. The width of the optical waveguide is preferably changed smoothly, but may be changed stepwise.

  In a preferred embodiment, a reflecting portion for reflecting the fluorescent light is provided on the opposite end face. The reflecting portion that reflects the fluorescence may reflect the excitation light or may transmit the excitation light.

  The opposing end surface may be an incident surface for receiving the excitation light. In this case, it is preferable that a film that totally reflects the fluorescence and does not reflect the excitation light be formed on the opposite end face side. Alternatively, the emission-side end surface may be an incident surface for allowing the excitation light to enter. In this case, a reflection film that totally reflects the excitation light is provided on the facing end face side.

  The waveguide-type phosphor element of the present invention may be a grating-free phosphor element that does not include a grating (diffraction grating) in the optical waveguide, or may be a grating element.

  In the present invention, the outer peripheral surface of the optical waveguide includes an inclined portion inclined at 2 ° or more and 13 ° or less with respect to the central axis of the optical waveguide. By setting the inclination angle to 2 ° or more, the intensity of light oscillated from the emission-side end face can be increased. From this viewpoint, the inclination angle is more preferably set to 4 ° or more. Further, when the inclination angle exceeds 13 °, the color unevenness of the white light emitted from the emission-side end face becomes large. Therefore, the inclination angle is set to 13 ° or less, but is more preferably 10 ° or less.

  Further, the area of the inclined portion preferably occupies 30% or more of the area of the outer peripheral surface of the optical waveguide, more preferably occupies 50% or more, and may occupy 100%.

  The width W and the diameter of the optical waveguide are preferably 20 μm or more, and more preferably 50 μm or more, from the viewpoint of efficiently coupling the excitation light and increasing the amount of emitted light. On the other hand, from the viewpoint of optical waveguide propagation, W is preferably 900 μm or less, more preferably 500 μm or less, and even more preferably 300 μm or less.

  From the viewpoint of the present invention, the ratio (AO / AI) of the area AO of the emission-side end face to the area AI of the opposite end face is preferably 1.2 or more, and more preferably 1.4 or more. On the other hand, AO / AI is preferably 20 or less, more preferably 5.5 or less.

  The thickness T of the optical waveguide is preferably 20 μm or more, and more preferably 50 μm or more, from the viewpoint of efficiently coupling the excitation light and increasing the amount of emitted light. On the other hand, from the viewpoint of the present invention, T is preferably set to 900 μm or less, and from the viewpoint of reducing the influence of scattering due to surface roughness on the side surface when forming the optical waveguide, T is preferably 200 μm or less, and 150 μm or less. More preferred.

  The inclination angle β of each side surface with respect to the normal M of the bottom surface of the optical waveguide (see FIGS. 8 and 9) is preferably 10 ° or more, and more preferably 15 ° or more, from the viewpoint of increasing the amount of emitted light. Β is preferably 50 ° or less, more preferably 35 ° or less.

  The length of the optical waveguide (the distance between the output side end face and the opposing end face) L (see FIG. 2) is not particularly limited, but generally, it is necessary to repeat reflection until fluorescent light propagates through the optical waveguide. Preferably, it can be set to 2 mm or less in order to reduce a loss caused by propagation.

  The material of the reflective film may be a metal film of gold, aluminum, copper, silver, or the like, a mixed crystal film containing these metal components, or a dielectric multilayer film. When a metal film is used as the reflection film, a metal layer of Cr, Ni, Ti, or the like can be formed as a buffer layer of the metal film in order to prevent the cladding layer from peeling off.

The material of the cladding layer may be any material having a lower refractive index than the phosphor. It is preferable that the refractive index difference between the cladding layer and the phosphor is 0.05 or more. The material of such a cladding layer is preferably SiO ₂ , Al ₂ O ₃ , MgF ₂ , CaF ₂ , MgO, or the like.

  A buffer layer can be provided between the cladding layer and the reflection film. Although the material of such a bonding layer is not particularly limited, aluminum oxide, tantalum oxide, and titanium oxide are preferable. However, it is preferable that the thermal conductivity is higher than that of the phosphor, and from such a viewpoint, aluminum oxide is most preferable.

  The phosphor may be phosphor glass, single crystal, polycrystal. In the case of a phosphor glass, a rare earth element ion is dispersed in a glass serving as a base.

  The base glass includes silica, boron oxide, calcium oxide, lanthanum oxide, barium oxide, zinc oxide, phosphorus oxide, aluminum fluoride, magnesium fluoride, calcium fluoride, strontium fluoride, and oxide glass containing barium chloride. For example, YAG (yttrium aluminum garnet) may be used.

  The rare earth element ions dispersed in the glass are preferably Tb, Eu, Ce, and Nd, but may be La, Pr, Sc, Sm, Er, Tm, Dy, Gd, and Lu.

_Y 3 _Al 5 _O 12 as the phosphor _{monocrystal, Ba 5 Si 11 A l 7} N 25, Tb 3 Al 5 O 12 is preferred. The doping component to be doped into the phosphor is rare earth element ions such as Tb, Eu, Ce, and Nd. From the viewpoint of suppressing thermal degradation, the phosphor is preferably a single crystal, but even if it is a polycrystal, if it is a dense body, it can reduce the thermal resistance at the grain boundary portion and increase the light transmission. It can function as an optical waveguide.

  As the light source, a semiconductor laser made of a GaN material having high reliability for exciting the phosphor for illumination is suitable. Further, a light source such as a laser array arranged one-dimensionally can also be realized. It may be a super luminescence diode or a semiconductor optical amplifier (SOA).

The method for generating white light from the semiconductor laser and the phosphor is not particularly limited, but the following methods are conceivable.
A method of generating white fluorescence by generating yellow fluorescence with a blue laser and a phosphor A method of generating white light by generating red and green fluorescence with a blue laser and a phosphor A method of generating white light by generating green fluorescence A method of generating white light by generating blue and yellow fluorescent light by a phosphor from a blue laser or an ultraviolet laser

(Examples A1 to A3 and Comparative Examples A1 to A3)
A phosphor element 1 having a configuration as shown in FIGS. 1 and 2 was manufactured.
A cladding layer made of Al ₂ O ₃ having a thickness of 0.3 μm is formed on a substrate made of a phosphor of 300 μm in thickness, 15 mm in length and 15 mm in width made of Ce doped YAG (yttrium aluminum garnet) single crystal as a reflection film. An aluminum alloy was formed to a thickness of 1 μm. Thereafter, the above-mentioned phosphor substrate was bonded to a 2-inch sapphire substrate with a thermoplastic resin (wax) using the aluminum alloy film as a bonding surface. The bonded body after the lamination was cut so that the phosphor portion had a width of 15 mm and a length of 2 mm.

  Next, groove processing was performed by a dicing apparatus using a # 6000 blade having a width of 200 μm to form inclined portions 2c and 2d in the horizontal direction. The inclination angles θ of the inclined portions 2c and 2d were changed to 0 °, 2 °, 5 °, 10 °, 13 °, 15 °, and 20 °, respectively. The thickness of the optical waveguide made of the phosphor was made constant between the emission end face and the opposite end face.

Next, Al ₂ O ₃ was formed as an upper cladding layer at 2 μm, and an aluminum alloy was formed as a reflection film at 1 μm. It was confirmed that a 0.3 μm clad layer and a 0.5 μm metal film were formed on the side surface of the optical waveguide formed of the phosphor.

  Thereafter, the input side and the output side of the optical waveguide were polished at about 50 μm. On the opposite end face on the incident side, a dichroic film was formed by an IBS (Ion-beam Sputter Coater) film-forming apparatus so as to be non-reflective in the 450 nm band of excitation light and totally reflected in the 560 nm band of fluorescent light. Finally, dicing cutting is performed so that the element width becomes 1 mm, the element size width is 1 mm × length 1.99 mm, and the phosphor element is separated from the sapphire substrate by heating on a hot plate. The phosphor element 1 shown in FIG.

  The fabricated device was irradiated with laser light having a wavelength of 450 nm, and the brightness and color unevenness of output light emitted from the output side were measured. However, these were measured as follows.

(Brightness)
The average output represents the time average of the total luminous flux. The total luminous flux measurement is performed by using an integrating sphere (spherical luminometer), lighting the light source to be measured and the standard light source to which the total luminous flux is valued at the same position, and comparing the light sources. Specifically, the measurement was performed using the method specified in JISC7801.

(Color unevenness)
The output light was evaluated by a chromaticity diagram using a luminance distribution measuring device. Then, in the chromaticity diagram, when the median value is within the range of x: 447 ± 0.005 and y: 0.3553 ± 0.005, “no color unevenness” is set. There is unevenness. "

  As a result, as shown in Table 1, the brightness of the output light was significantly improved by setting the inclination angle to 2 ° or more. Further, it was found that when the inclination angle exceeded 13 °, color unevenness occurred in the output light. Observation of this output light revealed that the central portion was white light without color unevenness, but the outer peripheral portion was a pattern in which only fluorescent light was present. This phenomenon became more pronounced when the angle was increased. Was.

  In each of the phosphor elements of Examples A1 to A3, the incident-side end face has a shape including a spot shape of a laser beam and a sufficient positioning tolerance for mounting, so that a low-cost and high-efficiency white light is obtained. A laser can be realized. For example, when a 4 W class laser is used, white laser light having high directivity of 450 lm or more can be obtained.

(Examples B1 to B3)
A phosphor element was manufactured in the same manner as in Example 1. However, different from Example 1, as shown in FIG. 4, the side surface 2a of the optical waveguide 2 was inclined by the angle α in the thickness direction. Then, fluorescence was generated in the same manner as in Example 1, and the brightness and uneven color of the emitted light were measured. Table 2 shows the results.

(Examples C1 to C7)
A phosphor element was manufactured in the same manner as in Examples A1 to A3. However, unlike Examples A1 to A3, each side surface of the optical waveguide 42 was inclined by an angle β with respect to a normal M of the bottom surface as shown in FIGS. Then, fluorescence was generated in the same manner as in Example 1, and the brightness and uneven color of the emitted light were measured. Table 3 shows the results.

(Comparative Examples D1 to D3)
A fiber doped phosphor of 150 μm, 498 μm, 1000 μm, and 2 mm in length made of Ce-doped YAG (yttrium aluminum garnet) single crystal grown by the pull-down method, and a cladding layer made of Al ₂ O ₃ having a thickness of 0 mm An aluminum alloy was formed on the outer periphery of the phosphor so as to have a thickness of 0.3 μm and an aluminum alloy of 1 μm as a reflection film.

  Thereafter, the input side and the output side of the substrate are polished with an end face of about 50 μm, and the end face on the incident side is non-reflective and fluorescent in the 450 nm band which is excitation light by an IBS (Ion-beam Sputter Coater) film forming apparatus. In a certain 560 nm band, a dichroic film for total reflection was formed to produce a phosphor element having a length of 1.99 mm.

  About the produced element, the brightness of output light and the color nonuniformity were measured like Example A1-3. Table 4 shows the results.

  As a result, as shown in Table 4, the brightness was about 800 to 900 lm, and the illumination light that could be extracted to the emission side was smaller than in the example. This is because the component that cannot be totally reflected is repeatedly reflected by the reflection film, but the reflectance of the total reflection film is 90% or less, so that the fluorescence is attenuated for each reflection and the illumination light that can reach the emission side is reduced. Can be Regarding the color unevenness, white light having no color unevenness was found at the center at a diameter of 498 μm, but the outer peripheral portion was a pattern in which only fluorescent light was present. When the diameter was increased, this phenomenon became remarkable. I was

Claims (12)

Propagating the excitation light into the optical waveguide, glass, an optical waveguide comprising a phosphor doped with rare earth element ions in single crystal or polycrystal,
The excitation light irradiates the rare earth element ions to emit fluorescence, and the optical waveguide emits white light composed of the excitation light and the fluorescence, an emission end face, and an opposite end face opposite to the emission end face. An optical waveguide having an end surface and an outer peripheral surface,
A clad layer covering the outer peripheral surface of the optical waveguide, and a reflective film covering the clad layer, comprising a reflective film made of a metal film or a dielectric multilayer film;
An area of the emission-side end face is larger than an area of the opposed end face, and the outer peripheral surface of the optical waveguide includes an inclined portion inclined by 2 ° or more and 13 ° or less with respect to a center axis of the optical waveguide. A phosphor element characterized by the above-mentioned. The single _{crystal, Y 3 Al 5 O 12,} Ba 5 Si 11 A l 7 N characterized by comprising the ₂₅ or _Tb 3 _Al 5 _{O 12,} a phosphor element according to claim 1, wherein. The _{polycrystalline, Y 3 Al 5 O 12,} Ba 5 Si 11 A l 7 N 25 or Tb ₃ Al ₅ O characterized by comprising the _12, the phosphor element according to claim 1,.   The phosphor element according to any one of claims 1 to 3, wherein the inclined portion occupies 30% or more of the outer peripheral surface of the optical waveguide.   5. The optical waveguide according to claim 1, wherein the outer peripheral surface includes a bottom surface, a top surface facing the bottom surface, and a pair of side surfaces between the bottom surface and the top surface. 6. A phosphor element according to claim 1.   6. The phosphor element according to claim 5, wherein the width of the upper surface of the optical waveguide increases from the opposite end surface toward the emission end surface.   7. The phosphor element according to claim 5, wherein the thickness of the optical waveguide increases from the opposite end face toward the emission end face.   The phosphor element according to claim 5, wherein a width of the optical waveguide changes from the top surface to the bottom surface.   The phosphor element according to claim 8, wherein an inclination angle of each of the side surfaces with respect to a normal line of the bottom surface is equal to or less than 50 ° and equal to or more than 10 °.   The phosphor element according to any one of claims 1 to 9, wherein a reflection part for reflecting the fluorescence is provided on the opposed end face.   The phosphor element according to any one of claims 1 to 9, wherein the opposite end surface is an incident surface for receiving the excitation light. An illumination device including a light source that emits excitation light and a phosphor element,
The lighting device, wherein the phosphor element is the phosphor element according to any one of claims 1 to 11, wherein the white light is emitted from the emission-side end face of the optical waveguide. .

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