JPWO2019043772A1 - Phosphor element and lighting device - Google Patents

Abstract

In a phosphor element that emits fluorescence by making excitation light incident on an optical waveguide, the oscillation efficiency of white light from the optical waveguide is improved and color unevenness of the obtained white light is prevented. A phosphor element (1) is an optical waveguide (2) made of a phosphor that propagates excitation light in an optical waveguide and generates fluorescence, and the optical waveguide (2) emits excitation light and fluorescence. Covering the outer peripheral surface of the optical waveguide (2), the optical waveguide having the outgoing end surface (2f), the opposing end surface (2e) opposite to the outgoing side end surface (2f), and the outer peripheral surface (2c, 2d) A clad layer (3) and a reflective film (4) covering the clad layer (3) are provided. The area of the emission side end face (2f) is larger than the area of the opposing end face (2e). The outer peripheral surface of the optical waveguide (2) includes inclined portions (2c, 2d) inclined by 2 ° or more and 13 ° or less with respect to the central axis (K) of the optical waveguide.

Description

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

  Recently, research on automobile headlights using a laser light source has been actively conducted, and one of them is a white light source combining a blue laser or an ultraviolet laser and a phosphor. The light density of the excitation light can be increased by condensing the laser light, and the light intensity of the excitation light can also be increased by condensing a plurality of laser lights on the phosphor. As a result, the luminous flux and the luminance can be increased simultaneously without changing the light emitting area. For this reason, a white light source combining a semiconductor laser and a phosphor has been attracting attention as a light source that replaces the LED. For example, the phosphor glass used in automotive headlights is the phosphor glass “Lumifas” manufactured by Nippon Electric Glass Co., Ltd., National Research and Development Corporation, National Institute for Materials Science, Tamra Manufacturing Co., Ltd. The body is considered.

  Regarding the white laser, the structure shown in Non-Patent Document 1 is disclosed by US SORAA. In this laser, the excitation laser light is directly incident from above the phosphor, and a reflection film is formed on the opposite surface of the phosphor, so that the excitation light and fluorescence are reflected and extracted as white light upward. 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 and downsize an excitation laser and a phosphor and obtain highly directional illumination light.

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

  Further, in Patent Document 2, the outer peripheral surface of an optical fiber made of a phosphor is covered with a metal film, excitation light is incident on the optical fiber, and white light is emitted from the end surface on the emission side 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, in the structure described in Non-Patent Document 1, the extraction efficiency of the fluorescence is poor, and the excitation light leaks from the side surface direction of the phosphor, so that an absorber for Beam Dump is required, and the excitation laser light is also lost. I understand.

  With the structure described in Patent Document 1, it is difficult to obtain white light with high intensity and directivity, and color unevenness of white light is observed because fluorescence and excitation light are emitted from various locations on the outer peripheral surface.

  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) with which fluorescence converted from excitation light is extracted to the emission side.

  An object of the present invention is to improve the extraction efficiency of white light from an optical waveguide and prevent color unevenness of the obtained white light in a phosphor element that emits fluorescence by causing excitation light to enter the optical waveguide. It is to be.

The phosphor element according to the present invention is
An optical waveguide made of a phosphor that propagates excitation light in an optical waveguide and generates fluorescence, wherein the optical waveguide emits the excitation light and the fluorescence, and an end surface opposite to the exit side end surface And an optical waveguide having an outer peripheral surface,
A clad layer covering the outer peripheral surface of the optical waveguide, and a reflective film covering the clad layer,
An area of the output side end face is larger than an area of the facing end face, and the outer peripheral face of the optical waveguide includes an inclined portion that is inclined by 2 ° or more and 13 ° or less with respect to a central axis of the optical waveguide. It is characterized by.

Further, the present invention is an illumination 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 fluorescence generated in the optical waveguide, the fluorescence reflected at the boundary with the cladding layer can be propagated to the emission side end surface, and the total reflection condition of the optical waveguide cannot be satisfied. Fluorescence incident on the inside is also reflected by each reflecting film provided on the outer peripheral surface of the optical waveguide and reenters the optical waveguide. On this basis, the area of the output-side end face of the optical waveguide is relatively increased, and the outer peripheral surface of the optical waveguide (interface with the cladding layer) is inclined by 2 to 13 ° with respect to the central axis. At the same time, it has been found that color unevenness of the emitted white light can be suppressed, and the present invention has been achieved.

(A) is a perspective view which shows typically the phosphor element 1 which concerns on embodiment of this invention, (b) is a front view which shows 2 f of radiation | emission side end surfaces, (c) is the opposing end surface 2e. FIG. 2 is a schematic diagram showing a planar dimension of the phosphor element 1. FIG. It is a schematic diagram which shows the planar dimension of the phosphor element 11 which concerns on other embodiment. It is typical sectional drawing which shows the dimension of the thickness direction of the phosphor element 1 which concerns on embodiment of this invention. It is a schematic diagram which shows the propagation state of the light in the phosphor element 21 which concerns on a comparative example. 3 is a schematic diagram showing a light propagation state in phosphor element 1. FIG. (A) is a perspective view which shows typically the phosphor element 31 which concerns on embodiment of this invention, (b) is a front view which shows the output side end surface 32f, (c) is the opposing end surface 32e. FIG. 3 is a schematic diagram showing a cross section of phosphor element 41. FIG. 3 is a schematic diagram showing light propagation in a cross section of phosphor element 41. FIG.

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 quadrilateral cross section and is elongated. The outer peripheral surface extends between the emission-side end surface 2f and the opposing end surface 2e of the optical waveguide 2, and the outer peripheral surface has an elongated bottom surface 2a, an upper surface 2b facing the bottom surface 2a, and a pair of side surfaces 2c and 2d. . The outer peripheral surface of the optical waveguide 2 is covered with a clad layer 3, and the clad layer 3 is covered with a reflective film 4.

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

  In accordance with the present invention, the area AO of the exit 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 opposing end surface 2e, or may be incident from the emission side end surface 2f and totally reflected by the reflection film on the opposing end surface 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 be propagated to the emission side end face, but also the total reflection condition of the optical waveguide. Fluorescence incident on the cladding layer without being satisfied is reflected by the reflecting films provided on the bottom surface, top surface, and each side surface and reenters the optical waveguide. Can be increased.

In addition, it is important that an inclined portion that is 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 where an inclined portion inclined with respect to the central axis is not provided on the outer peripheral surface of the optical waveguide will be described. 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. Further, 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, fluorescence is emitted from the phosphor particles 16. At this time, the fluorescence is uniformly emitted 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 total reflection condition, the fluorescence is reflected at the interface, propagates in the optical waveguide, and is transmitted from the output side end face 12f. Exit. On the other hand, when the incident angle θp of the fluorescence does not satisfy the total reflection condition, the light is refracted as indicated by an arrow G, reflected by the reflective films 4c and 4d, and reflected as indicated by an arrow H. The light propagating while repeating such reflection is not propagated through the optical waveguide, but part of the light is attenuated in the phosphor by absorption of the reflective film or absorption of the phosphor, and part of the light reaches the emission-side end face 12f. However, since this light has no directivity and is radiated from the output end, there is a fluorescent component that cannot be mixed with the excitation light propagating in the optical waveguide. Therefore, the extraction efficiency of white light cannot be greatly improved.

  When no reflection layer is provided and each reflection film is in direct contact with the phosphor, both the excitation light and the fluorescence propagate without being propagated through the optical waveguide. Part of the light and fluorescence is attenuated in the phosphor, and both lights that have reached the emission side end face 12f are emitted from the end face without directionality, so it is difficult to extract white light in the front direction, and the extraction efficiency is improved. Is difficult.

  The fluorescence C generated from the phosphor 16 in the direction perpendicular to the longitudinal direction of the optical waveguide is reflected by the reflecting film as indicated by an arrow D, repeatedly reflected in the optical waveguide, and finally attenuated. Become. Further, the fluorescence E generated from the phosphor 16 toward the opposing end face 12e repeats the same reflection as described above, and finally reaches the opposing 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 is gradually increased from the opposing end surface 2e (WI) toward the emission side end surface 2f (WO). Θ is an angle between the central axis K of the optical waveguide 2 and the side surface 6c and side surface 6d. In this example, the angle θ is constant and within a range of 2 to 13 °. In addition, although it is preferable that θ is constant, it is not necessary to be constant, and it may be changed between the emission side end surface and the opposed end surface. Preferably, the width W continuously and smoothly increases from the opposing end surface toward the emission side end surface.

  Here, as shown in FIG. 6, when the excitation light A propagates in the optical waveguide and hits the phosphor particles 16, fluorescence is emitted from the phosphor particles 16. At this time, the fluorescence is uniformly emitted from the phosphor in all directions. Here, the fluorescence F emitted from the phosphor 16 toward the emission side end face 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 through 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 fluorescence F becomes larger by θ than in the example of FIG. 5, and is totally reflected at the interface with the cladding layer. It becomes easy to do. For this reason, the fluorescent light F that could not satisfy the total reflection condition in the example of FIG. 5 is totally reflected at the interface with the cladding layer, and propagates in the optical waveguide and is not absorbed by the reflective film. To do.

  On the other hand, when the incident angle θp of the fluorescence does not satisfy the total reflection condition, for example, the fluorescence C generated from the phosphor 16 in the direction perpendicular to the central axis K of the optical waveguide is similarly incident on 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, so that these reflections are repeated. In addition, the total reflection condition can be satisfied at the interface between the phosphor and the cladding layer, and finally the light propagates through the optical waveguide. When the light is incident on the side surface 2d of the optical waveguide at a right angle, the light is reflected by the reflection film 4d. However, since the angle incident on the interface of the side surface 6c is increased by θ, the light travels toward the output end surface and is reflected. The incident angle θp increases as reflection is repeated at the film 4c and the reflection film 4d, and the total reflection condition can be satisfied at the interface between the phosphor and the cladding layer, and the light propagates through 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 travels to either the emission side end face side or the opposite end face side and repeats reflection, and attenuates in the phosphor. This makes it possible to eliminate the fluorescence that occurs.

  The fluorescence E directed from the phosphor 16 toward the opposite end face 2e is changed in direction toward the exit end face by the angle θ every time it is reflected by the reflection film. The propagation direction changes, and finally propagates through the optical waveguide and exits from the exit end face. Nevertheless, the fluorescence that has reached the opposing end face is reflected by the fluorescent reflecting film provided on the opposing end face, and this light can finally propagate through the optical waveguide and be emitted from the exit end face.

  In the embodiment of FIG. 3, the width W of the optical waveguide 2 is WI at the opposed end face 2e and WO at the exit end face 2f. The width W increases from WI to 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 2θ with respect to the optical axis of the excitation light.

  In a preferred embodiment, the thickness of the optical waveguide increases from the opposing end surface toward the emission side end surface. For example, in the phosphor element 51 of FIG. 4, the thickness T of the optical waveguide 2 is TI at the opposed end face 2e and TO at the exit end face 2f. The thickness T increases from TI toward TO.

  Α is an inclination angle between the central axis K of the optical waveguide 2 and the bottom surface 2a and the top surface 2b. In this example, the inclination angle α is constant and is 2 to 13 °. α is preferably constant, but is not necessarily constant, and may be changed between the emission-side end surface and the opposed end surface. Preferably, the thickness T continuously and smoothly increases from the opposing end surface toward the emission side end surface.

  The effect of changing the width of the optical waveguide has been described above, but the same is true when the thickness is changed. Fluorescence reflected by the top and bottom surfaces is propagated from the output side end face by the same mechanism. It can be emitted as light.

  Further, both the width W and the thickness T are continuously increased from the opposite end surface toward the emission side end surface, so that the light propagates in the optical waveguide against the omnidirectional fluorescence generated in the phosphor. It can be converted and can be emitted to the emission side end face with high efficiency, and white light can be extracted with high efficiency by mixing with the excitation light similarly propagating through the optical waveguide.

  In the above-described 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, or 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 surface 32a between the emission side end face and the opposed end face. A clad layer 33 is provided on the outer peripheral surface 32 a of the optical waveguide 32, and a reflective film 34 is provided on the clad layer 33. The diameter DO of the emission side end face 32f is larger than the diameter DI of the opposing end face 32e, and the outer peripheral face 32a forms an inclined face that is 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 surface to the bottom surface. For example, in the phosphor element 41 shown in FIG. 8, the optical waveguide 42 has a trapezoidal cross section and is elongated. The outer peripheral surface extends between the emission-side end surface 42f and the opposing end surface 42e of the optical waveguide 42. 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 clad layer 3, and the clad layer 3 is covered with the reflective film 4.

The width of the optical waveguide 42 gradually increases from the width at the top surface toward the width at the bottom surface. Β is an inclination angle of the side surface 42c (42d) with respect to the bottom surface 42a of the optical waveguide 42.
Although this structure alone cannot be expected to increase the amount of emitted fluorescence light, it can further increase the amount of emitted fluorescence light when combined with a structure that is inclined by an inclination angle α in the thickness direction of the optical waveguide. it can. In other words, when the side surface is inclined at an inclination angle β, the fluorescence propagating in the width direction of the optical waveguide is propagated in the thickness direction of the optical waveguide when reflected by this side surface or a reflecting surface parallel to the side surface. Therefore, even when the inclination of the angle θ is not provided in the width direction of the optical waveguide, the optical waveguide can be propagated only by the inclination in the thickness direction, and the amount of emitted light can be increased.

The effect of this embodiment is described with reference to FIG.
In this example, fluorescence is radiated from the phosphor 16 in all directions, but the light G emitted right beside of this is reflected as indicated by an arrow H by the side surface 42c (42d). At this time, since the side surface 42c (42d) is inclined with respect to the normal line 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. Thus, while repeating multiple reflection, the fluorescence 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 thickness of the optical waveguide is changed between the emission side end face and the opposite end face as described above, emission of fluorescence to the emission side end face is promoted. When tilted in this way, the fluorescence reflected from the side surface can be redirected to light that reflects the reflected light upward and bottom. From this, by combining with a structure with a changed thickness, all the fluorescence generated in the phosphor can be emitted efficiently as optical waveguide propagating light to the emission side end face, It is possible to extract white light with high efficiency by mixing.

  In the above example, the optical waveguide width on the bottom surface is made larger than the optical waveguide width on the top surface, but the optical waveguide width on the bottom surface can be made smaller than the optical waveguide width on the top surface. From this point of view, a triangular shape in which one of the optical waveguide widths is zero may be used. The optical waveguide width is preferably changed smoothly, but may be changed stepwise.

  In a preferred embodiment, a reflecting portion that reflects fluorescence is provided on the opposing end surface. The reflection part that reflects the fluorescence may reflect the excitation light or transmit the excitation light.

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

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

  In this invention, the outer peripheral surface of an optical waveguide includes the inclination part which inclines 2 degrees or more and 13 degrees or less with respect to the central axis of an 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, it is more preferable that the inclination angle is 4 ° or more. Further, when the inclination angle exceeds 13 °, the color unevenness of white light emitted from the emission side end face becomes large. Therefore, it is set to 13 ° or less, but 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 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 excitation light and increasing the amount of emitted light. On the other hand, from the viewpoint of propagation through the optical waveguide, 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 opposing 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, and 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 excitation light and increasing the amount of emitted light. On the other hand, from the viewpoint of the present invention, T is preferably 900 μm or less, and from the viewpoint of reducing the influence of scattering due to the surface roughness on the side surface when forming the optical waveguide, 200 μm or less is preferable, and 150 μm or less is preferable. Further preferred.

  The inclination angle β (see FIGS. 8 and 9) of each side surface with respect to the normal M of the bottom surface of the optical waveguide 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, and more preferably 35 ° or less.

  The length of the optical waveguide (distance between the end surface on the emission side and the opposite end surface) L (see FIG. 2) is not particularly limited, but generally it is necessary to repeat reflection until the fluorescence propagates through the optical waveguide. Preferably, it can be 2 mm or less in order to reduce the loss accompanying propagation.

  The material of the reflective film may be a metal film such as 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 reflective film, a metal layer such as Cr, Ni, Ti or the like can be formed as a buffer layer of the metal film so that the clad layer is not peeled off.

The clad layer may be made of a material having a refractive index smaller than that of the phosphor. The difference in refractive index between the cladding layer and the phosphor is preferably 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 reflective film. The material of such a bonding layer is not particularly limited, but aluminum oxide, tantalum oxide, and titanium oxide are preferable. However, the thermal conductivity is preferably larger than that of the phosphor, and aluminum oxide is most preferable from such a viewpoint.

  The phosphor may be phosphor glass, single crystal, or polycrystalline. In the case of a phosphor glass, rare earth element ions are dispersed in a base glass.

  Examples of the base glass include 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.

As the phosphor single crystal, Y ₃ Al ₅ O ₁₂ , Ba ₅ Si ₁₁ A ₁₇ N ₂₅ , and Tb ₃ Al ₅ O ₁₂ are preferable. Further, as a doping component to be doped in the phosphor, rare earth element ions such as Tb, Eu, Ce, and Nd are used. From the viewpoint of suppressing thermal deterioration, the phosphor is preferably a single crystal, but even if it is a polycrystal, if it is a dense body, the thermal resistance at the grain boundary can be lowered and the translucency can be increased. And can function as an optical waveguide.

  As the light source, a semiconductor laser made of a GaN material having high reliability is preferable for exciting an illumination phosphor. A light source such as a laser array arranged in a one-dimensional manner 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.
Method of obtaining white light by generating yellow fluorescence with blue laser and phosphor Method of obtaining white light by generating red and green fluorescence with blue laser and phosphor Also, red and blue with phosphor from blue laser or ultraviolet laser Method of generating white fluorescence by generating green fluorescence Method of obtaining white light by generating blue and yellow fluorescence with a phosphor from a blue laser or 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 produced.
A clad layer made of Al ₂ O _{3 is} 0.3 μm thick as a reflective film on a substrate made of a phosphor made of 300 μm thick, 15 mm long and 15 mm wide made of Ce-doped YAG (yttrium, aluminum, garnet) single crystal. An aluminum alloy film having a thickness of 1 μm was formed. Thereafter, the 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 pasting was cut so that the phosphor portion had a width of 15 mm and a length of 2 mm.

  Next, grooves were formed by a dicing apparatus with a blade having a width of 200 μm and # 6000 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 constant between the emission side end face and the opposite end face.

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

  Thereafter, the input side and the output side of the optical waveguide were subjected to end face polishing of about 50 μm. A dichroic film that is non-reflective in the 450 nm band, which is excitation light, and totally reflected in the 560 nm band, which is fluorescent light, is formed on the incident end face by an IBS (Ion-beam Sputter Coater) film forming apparatus. Finally, dicing cutting is performed so that the element width becomes 1 mm, the element size width is 1 mm × length is 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 2 was produced.

  The produced device was irradiated with laser light having a wavelength of 450 nm, and the brightness and color unevenness of the 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. To measure the total luminous flux, an integrating sphere (spherical photometer) is used to turn on the light source to be measured and the standard light source to which the total luminous flux is priced, and compare them. In detail, it measured using the method prescribed | regulated by JISC7801.

(Color unevenness)
The output light was evaluated with a chromaticity diagram using a luminance distribution measuring device. In the chromaticity diagram, when there is a median value in the range of x: 0.3447 ± 0.005 and y: 0.3553 ± 0.005, “no color unevenness” is indicated. "There is unevenness".

  As a result, as shown in Table 1, the brightness of the output light was remarkably improved by setting the inclination angle to 2 ° or more. Further, it was found that when the tilt angle exceeds 13 °, color unevenness occurs in the output light. When this output light was observed, it was white light with no color unevenness at the center, but the outer periphery had a pattern with only fluorescence, and this phenomenon was not noticeable when the angle was increased. It was.

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

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

(Examples C1 to C7)
A phosphor element was produced in the same manner as in Examples A1 to A3. However, unlike Examples A1 to A3, as shown in FIGS. 8 and 9, each side surface of the optical waveguide 42 is inclined by an angle β with respect to the normal line M of the bottom surface. Then, fluorescence was generated in the same manner as in Example 1, and the brightness and color unevenness of the emitted light were measured. The results are shown in Table 3.

(Comparative Examples D1 to D3)
A Ce-doped YAG (Yttrium / Aluminum / Garnet) single crystal grown by the pull-down method and having a diameter of 150 μm, 498 μm, 1000 μm, and a length of 2 mm, and a clad layer made of Al ₂ O ₃ with a thickness of 0 An aluminum alloy film was formed on the outer peripheral portion of the phosphor to have a thickness of 3 μm and a reflective film of 1 μm.

  Thereafter, the input side and the output side of the substrate are polished to about 50 μm, and the incident side end face is not reflected in the 450 nm band, which is excitation light by an IBS (Ion-beam Sputter Coater) film forming apparatus, and is fluorescent. 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, it carried out similarly to Example A1-3, and measured the brightness and color nonuniformity of output light. The results are shown in Table 4.

  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 that of 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 attenuates at each reflection and the illumination light that can reach the emission side is reduced. It is done. As for color unevenness, white light with no color unevenness was obtained at the center at a diameter of 498 μm. However, the outer peripheral part has a pattern containing only fluorescence, and this phenomenon becomes significant when the diameter is increased. It was.

The phosphor element according to the present invention is
An optical waveguide made of a phosphor that propagates excitation light in an optical waveguide and generates fluorescence, and phosphor particles are dispersed in the phosphor, and the optical waveguide emits the excitation light and the fluorescence. An optical waveguide having a side end face, an opposite end face opposite to the emission side end face, and an outer peripheral face;
A clad layer covering the outer peripheral surface of the optical waveguide, and a reflective film covering the clad layer,
An area of the output side end face is larger than an area of the facing end face, and the outer peripheral face of the optical waveguide includes an inclined portion that is inclined by 2 ° or more and 13 ° or less with respect to a central axis of the optical waveguide. It is characterized by.

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 output side end face is larger than an area of the facing end face, and the outer peripheral face of the optical waveguide includes an inclined portion that is inclined by 2 ° or more and 13 ° or less with respect to a central axis of the optical waveguide. It is characterized by.

Claims (10)

An optical waveguide made of a phosphor that propagates excitation light in an optical waveguide and generates fluorescence, wherein the optical waveguide emits the excitation light and the fluorescence, and an end surface opposite to the exit side end surface And an optical waveguide having an outer peripheral surface,
A clad layer covering the outer peripheral surface of the optical waveguide, and a reflective film covering the clad layer,
An area of the output side end face is larger than an area of the facing end face, and the outer peripheral face of the optical waveguide includes an inclined portion that is inclined by 2 ° or more and 13 ° or less with respect to a central axis of the optical waveguide. A phosphor element characterized by the above.   The phosphor element according to claim 1, wherein the inclined portion occupies 30% or more of the outer peripheral surface of the optical waveguide.   The phosphor according to claim 1, wherein the outer peripheral surface of the optical waveguide 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. element.   The element according to claim 3, wherein a width of the upper surface of the optical waveguide increases from the facing end surface toward the emitting side end surface.   5. The element according to claim 3, wherein a thickness of the optical waveguide increases from the facing end surface toward the emitting side end surface. 6.   The element according to claim 3, wherein the width of the optical waveguide changes from the upper surface toward the bottom surface.   The element according to claim 6, wherein an inclination angle of each side surface with respect to a normal line of the bottom surface is 50 ° or less and 10 ° or more.   The element according to claim 1, wherein a reflection portion that reflects the fluorescence is provided on the facing end surface.   The element according to claim 1, wherein the facing end surface is an incident surface on which the excitation light is incident. An illumination device including a light source that oscillates excitation light and a phosphor element,
The said phosphor element is a phosphor element as described in any one of Claims 1-9, and white light radiates | emits from the said output side end surface of the said optical waveguide, The illuminating device characterized by the above-mentioned.

Images