JP2018163828A - Phosphor element and illumination device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress color unevenness of emitted white light in continuous use, when fluorescent light is generated by making excitation light be incident on a phosphor plate.SOLUTION: A phosphor element 1A includes: a first heat dissipation substrate 6A; a second heat dissipation substrate 6B; a phosphor plate 2 including an incident face 2a of excitation light A, an opposite face 2b opposed to the incident face, a first joint face 2c opposed to the first heat dissipation substrate 6A, a second joint face 2d opposed to the second heat dissipation substrate 6B, and a pair of side faces 2e, 2f, and configured to convert the excitation light A incident on the phosphor plate into fluorescent light, and emit the fluorescent light and the excitation light from the opposite face or the incident face; a first joint layer 3A kept into contact with the first joint face 2c and composed of metal oxide; a second joint layer 3B kept into contact with the second joint face 2d and composed of metal oxide; a first reflection film 4A disposed between the first joint layer and the first heat dissipation substrate; and a second reflection film 4B disposed between the second joint layer and the second heat dissipation substrate.SELECTED DRAWING: Figure 1

Description

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

  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 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 in which a semiconductor laser and a phosphor are combined attracts attention as a light source that replaces an 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.

  According to Patent Document 1, by converting YAG into a single crystal, even if the temperature rises, the conversion efficiency does not deteriorate, and high-efficiency fluorescence characteristics are exhibited, enabling application in the high power field. This material can obtain white light by emitting yellow light which is a complementary color with 450 nm blue excitation light, and development for application to projectors and headlights is underway.

Regarding illumination phosphors, Ce: YAG single crystal phosphors in which Ce is doped in yttrium aluminum garnet (Y ₃ Al ₅ O ₁₂ : YAG) have also been developed. Conventionally, Ce: YAG phosphors have been realized by sintering synthesis or being dispersed in glass. However, when the power density of excitation light is increased, heat radiation becomes difficult and efficiency is lowered. It was.

  Ce-doped single crystal YAG has a characteristic that the conversion efficiency does not deteriorate even if the crystal itself generates heat, and is expected to be used for light sources such as headlights and projectors.

  Patent Documents 2, 3, and 4 disclose an illumination device using a reflective phosphor element. This is a structure in which a metal film is formed on the surface of the phosphor layer opposite to the incident surface on which excitation light is incident, and the metal film and the heat dissipation substrate (support substrate) are joined. Examples of the material of the phosphor layer include those in which phosphor is dispersed in glass, phosphor polycrystal, and single crystal.

  Patent Document 5 discloses an illumination device using a reflective phosphor element. This is a structure in which a dielectric multilayer film is formed on the surface of the phosphor layer opposite to the incident surface on which excitation light is incident, and the dielectric multilayer film and the heat dissipation substrate (support substrate) are joined. The dielectric multilayer film transmits excitation light and reflects fluorescence emitted from the phosphor layer. This dielectric multilayer film is configured by alternately laminating low refractive index layers and high refractive index layers.

  Patent Documents 6 and 7 describe a phosphor plate in which a phosphor is bonded to a heat dissipation substrate.

  Furthermore, according to Patent Document 8, a buffer layer is provided on the outer periphery of the columnar phosphor, and a metal reflective film is provided on the outer periphery of the buffer layer. And the flat heat dissipation board | substrate is joined with respect to the end of fluorescent substance.

Patent 5620562 Patent 5530165 JP2012-129135 JP2013-120713 WO 2015-45976 WO 2013/175706 A1 JP2014-060164 Patent 59955541

  In a conventional phosphor element for illumination, a heat dissipation substrate made of a material having a high heat dissipation property is joined and integrated with a phosphor plate, so that heat generated in the phosphor plate is radiated as much as possible. It is.

  However, as the inventors proceeded with the study, the following problems became apparent. That is, in order to increase the fluorescence intensity, it is necessary to increase the light intensity of the excitation light. However, when the excitation light intensity is increased, color unevenness may occur with the passage of time during use, and the quality of the emitted light may deteriorate. For this reason, it is necessary to suppress the color unevenness of the emitted light during continuous use and maintain the quality of the emitted light.

  An object of the present invention is to suppress color unevenness of emitted white light during continuous use when excitation light is incident on a phosphor plate to generate fluorescence.

The phosphor element of the present invention is
First heat dissipation board,
Second heat dissipation board,
An excitation light incident surface, a facing surface facing the incident surface, a first bonding surface facing the first heat dissipation substrate, a second bonding surface facing the second heat dissipation substrate, and a pair of side surfaces A phosphor plate that converts excitation light incident on the phosphor plate into fluorescence, and emits the fluorescence and excitation light from the opposing surface or incident surface;
A first bonding layer made of a metal oxide in contact with the first bonding surface;
A second bonding layer made of a metal oxide in contact with the second bonding surface;
A first reflective film provided between the first bonding layer and the first heat dissipation substrate; and a second reflective film provided between the second bonding layer and the second heat dissipation substrate. It is characterized by having.

  The present invention also relates to an illumination device including a light source that oscillates laser light and the phosphor element.

  The present inventor tried to emit white light by joining a heat dissipation substrate to the phosphor plate and causing excitation light to enter the phosphor plate, but suppresses color unevenness of the emitted light. It was difficult. Therefore, when the cause of color unevenness was examined, a tendency that the temperature distribution in the phosphor plate was large was observed. Therefore, it was considered that the variation in the fluorescence conversion efficiency in each part was caused by the uneven temperature in the phosphor plate, and this appeared as a deviation in the wavelength distribution of the output light.

  For this reason, the present inventor bonded the first bonding surface and the second bonding surface, which are different from the incident surface and the emission surface of the phosphor plate, to the separate heat dissipation substrate, respectively. I thought of escaping heat to both sides. However, in this case, even if there is no color unevenness in the initial stage, color unevenness may occur over time.

  As a result of further examination of the cause by the present inventor, it has been found that when the reflective film is directly formed on the bonding surface of the phosphor plate, color unevenness occurs over time. Further, when further observing the element in which the color unevenness occurs, peeling may be observed microscopically at the interface between the reflective film and the phosphor layer bonding layer. It has been found that such fine peeling locally suppresses heat conduction, changes the wavelength and intensity of the fluorescence obtained, and causes color unevenness.

  Therefore, the inventor bonded the heat dissipation substrate to both sides of the phosphor plate, and first provided a metal oxide bonding layer on the bonding surface of the phosphor plate, and between each bonding layer and the heat dissipation substrate. A structure for forming a reflective film was conceived. As a result, it has been found that not only the color unevenness of the emitted light can be suppressed in the initial stage, but also the color unevenness can be suppressed over time, and the present invention has been achieved.

1 is a perspective view schematically showing a phosphor element 1A according to an embodiment of the present invention. It is a perspective view which shows typically the phosphor element 1B which concerns on other embodiment of this invention. It is a perspective view which shows typically the phosphor element 1C which concerns on other embodiment of this invention. It is a perspective view which shows typically phosphor element 1D which concerns on other embodiment of this invention. It is a perspective view which shows typically the phosphor element 1E which concerns on other embodiment of this invention. It is a perspective view which shows typically the phosphor element 1F which concerns on other embodiment of this invention. It is a perspective view which shows typically the phosphor element 20 of a comparative example. It is a perspective view which shows typically the phosphor element 21 of a comparative example. The calculated value of the temperature distribution in Example 1 is shown. The calculated value of the temperature distribution in the comparative example 1 is shown. The simulation result of the temperature distribution in Example 1 is shown.

FIG. 1 is a perspective view schematically showing a phosphor element 1A according to an embodiment of the present invention.
The phosphor element 1A is obtained by joining and integrating the phosphor plate 2, the first heat dissipation substrate 6A, and the second heat dissipation substrate 6B.

  The phosphor plate 2 includes an excitation light incident surface 2a, a facing surface 2b facing the incident surface 2a, a pair of opposite side surfaces 2e and 2f, a first bonding surface 2c, and a second bonding surface facing this. 2d. The first heat dissipation substrate 6A is bonded to the first bonding surface 2c via the first bonding layer 3A, the first reflective film 4A, and the first buffer layer 5A. The second heat dissipation substrate 6B is bonded to the bonding surface 2d via the second bonding layer 3B, the second reflective film 4B, and the second buffer layer 5B.

  Each of the heat dissipation boards 6A and 6B includes six surfaces 6a, 6b, 6c, 6d, 6e, and 6f, respectively. When excitation light is incident from the incident surface 2a as indicated by the arrow A, a part of the excitation light is converted into fluorescence, and the fluorescence and the remaining excitation light are emitted from the facing surface 2b as indicated by the arrow B.

  In this example, the buffer layer 8 and the reflective film 7 are formed on the side surfaces 2e and 2f of the phosphor plate 2 and on the side surfaces 6e and 6f of the heat dissipation substrates, respectively.

  The phosphor element 1B in FIG. 2 is the same as the phosphor element 1A in FIG. However, in the phosphor element 1B, the bonding surface 6e of the first heat dissipation substrate 6A and the first reflective film 4A are in direct contact, and no buffer layer is provided between them. Further, the joint surface 6e of the second heat dissipation substrate 6B and the second reflective film 4B are in direct contact, and no buffer layer is provided between them.

  The phosphor element 1C in FIG. 3 is the same as the phosphor element 1A in FIG. However, in the phosphor element 1C, a reflective film 9 is further provided on the opposing surface 2b of the phosphor plate 2 and on the surface 6b of each heat dissipation substrate 6A, 6B. When excitation light is incident on the incident surface 2a of the phosphor plate 2 as indicated by an arrow A, a part of the phosphor plate 2 changes to fluorescence. Then, the excitation light and the fluorescence are reflected by the reflection film 9 and are emitted as emitted light as indicated by an arrow B from the incident surface 2a.

  The phosphor element 1D in FIG. 4 is the same as the phosphor element 1C in FIG. However, in the phosphor element 1D, the buffer layer 10 made of a metal oxide and the reflective film 11 are laminated in this order on the opposing surface 2b of the phosphor plate 2 and the surfaces 6b of the heat dissipation substrates 6A and 6B.

  The phosphor element 1E in FIG. 5 is the same as the phosphor element 1A in FIG. However, in the phosphor element 1E, a plurality of buffer layers 5A and 5C are provided between the heat dissipation substrate 6A and the reflective film 4A, and a plurality of layers are provided between the heat dissipation substrate 6B and the reflective film 4B. Buffer layers 5B and 5D are provided.

  The phosphor element 1F in FIG. 6 is the same as the phosphor element 1C in FIG. However, in the phosphor element 1E, a plurality of buffer layers 5A and 5C are provided between the heat dissipation substrate 6A and the reflective film 4A, and a plurality of layers are provided between the heat dissipation substrate 6B and the reflective film 4B. Buffer layers 5B and 5D are provided.

  In the present invention, the reflection films 4A and 4B are interposed between the phosphor plate and each heat dissipation substrate, respectively, so that excitation light and fluorescence scattered from the phosphor plate toward the heat dissipation substrate are entered into the phosphor plate. The fluorescence intensity can be further improved. Furthermore, by providing the bonding layers 3A and 3B made of metal oxides between the reflecting films 4A and 4B and the phosphor plate 2, the occurrence of color unevenness over time can be suppressed.

  The phosphor constituting the phosphor plate is not limited as long as excitation light can be converted into fluorescence, but may be phosphor glass, phosphor single crystal, or phosphor polycrystal.

The phosphor glass is obtained by dispersing rare earth element ions 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. It can be illustrated.

  The rare earth element ions dispersed in the phosphor 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 Al ₇ N ₂₅ , and Tb ₃ Al ₅ O ₁₂ are preferable. A part of Y (yttrium) of Y ₃ Al ₅ O ₁₂ may be substituted with Lu. Further, as a doping component to be doped in the phosphor single crystal, rare earth ions are preferable, and Tb, Eu, Ce, and Nd are particularly preferable, but La, Pr, Sc, Sm, Er, Tm, Dy, Gd, and Lu are used. There may be.

Examples of the phosphor polycrystal include TAG (terbium, aluminum, garnet), sialon, BOS (barium, orthosilicate), and YAG (yttrium, aluminum, garnet). A part of Y (yttrium) of YAG may be substituted with Lu.
As a doping component to be doped in the phosphor polycrystal, rare earth ions are preferable, and Tb, Eu, Ce, and Nd are particularly preferable. La, Pr, Sc, Sm, Er, Tm, Dy, Gd, and Lu Also good.

  The phosphor element of the present invention is a non-grating phosphor element that does not include a grating (diffraction grating) in the phosphor plate.

  The material of the bonding layer is a metal oxide. Examples thereof include aluminum oxide, magnesium oxide, aluminum nitride, tantalum oxide, silicon oxide, silicon nitride, aluminum nitride, and silicon carbide.

When the bonding layer is between the phosphor and the reflective film, the bonding layer is preferably made of a material having a lower refractive index than the phosphor. In this way, total reflection due to the difference in refractive index between the phosphor and the bonding layer can be used, light components reflected by the reflection film can be reduced, and light is absorbed by reflection by the reflection film. Can be suppressed. Furthermore, aluminum oxide and magnesium oxide are the best from the viewpoint of heat dissipation.

  The thickness of the bonding layer is preferably 1 μm or less, which can reduce the influence on heat dissipation. From the viewpoint of bonding strength, the thickness of the bonding layer is preferably 0.05 μm or more.

  The reflective film between the phosphor plate and the heat dissipation substrate, the reflective film on the side surface of the phosphor plate, and the reflective film on the opposite surface of the phosphor plate reflect the fluorescence that has passed through the phosphor layer. If there is no particular limitation. The reflection film does not need to totally reflect the excitation light, and may transmit a part of the excitation light or may transmit the entire excitation light.

In a preferred embodiment, each reflective film is a metal film or a dielectric multilayer film.
When the reflective film is a metal film, it can be reflected in a wide wavelength range, the incident angle dependency can be reduced, and durability against temperature and weather resistance are excellent. On the other hand, when the reflective film is a dielectric multilayer film, since there is no absorption, the incident light can be made 100% reflected light without loss and can be composed of an oxide film. Adhesion can be increased and peeling can be prevented.

  The reflectance of the excitation light by the reflection film is 80% or more, but is preferably 95% or more, and may be totally reflected.

The dielectric multilayer film is a film in which high refractive materials and low refractive materials are alternately stacked. As the high refractive material _{index, TiO 2, Ta 2 O 3} , Ta 2 O 3, ZnO, and _{Si 3 N 4, Nb 2 O} 5 can be exemplified. As the low refractive index material _can be exemplified by _{SiO 2, MgF 2, CaF 2} .
The number of laminated dielectric multilayer films and the total thickness are appropriately selected depending on the wavelength of fluorescence to be reflected.

Moreover, as a material of a metal film, the following is preferable.
(1) Single layer film of Al, Ag, Au, etc. (2) Multilayer film of Al, Ag, Au, etc.

  The thickness of the metal film is not particularly limited as long as it can reflect fluorescence, but is preferably 0.05 μm or more, more preferably 0.1 μm or more. Moreover, in order to improve the adhesiveness of a metal film and a base material, it can also form via metal films, such as Ti, Cr, Ni.

  The method for forming the dielectric multilayer film and the metal film is not particularly limited, but vapor deposition, sputtering, and CVD are preferable. In the case of the vapor deposition method, the film can be formed by adding ion assist.

  The material of the buffer layer is a metal oxide. Examples of this include aluminum oxide, magnesium oxide, aluminum nitride, tantalum oxide, and silicon oxide, but aluminum oxide and magnesium oxide are the best from the viewpoint of heat dissipation, and silicon nitride, aluminum nitride, and silicon carbide may be used. A plurality of buffer layers can be provided between the reflective film and the heat dissipation substrate. Also in this case, the above-mentioned metal oxide can be illustrated as a material of each buffer layer. Particularly preferably, the material of the buffer layer in contact with the reflective film is aluminum oxide, and the material of the buffer layer in contact with the heat dissipation substrate is tantalum oxide.

  The thermal conductivity (25 ° C.) of the heat dissipation substrate is preferably 20 W / m · K or more, more preferably 30 W / m · K or more, and most preferably 100 W / m · K or more. Moreover, although there is no upper limit in particular in the heat conductivity of a thermal radiation board | substrate, it can be 350 W / m * K or less from a viewpoint of practical acquisition.

  Examples of the material of the heat dissipation substrate include aluminum oxide, sapphire, magnesium oxide, aluminum nitride, gallium nitride, boron nitride, silicon, silicon carbide, and graphite.

  Further, a partial transmission film can be further provided on the incident surface of the phosphor plate. The partially transmissive film is a film that reflects a part of the excitation light and transmits the rest. Specifically, the reflectance with respect to the excitation light of the partial transmission film is 9% or more, and preferably 50% or less. Examples of the material of the partial transmission film include the metal film for the reflection film and the dielectric multilayer film.

  When joining the phosphor plate and the heat dissipation substrate, the joining layer and the reflective film can be joined directly. Direct bonding is generally divided into a metal / covalent bond and a diffusion bond, but is directed to a metal / covalent bond that undergoes surface activation treatment in a high vacuum.

  The surface activated bonding will be described. By irradiating a highly flat substrate with argon ions, impurity atoms on the surface are removed, leaving dangling bonds. This state is a very activated surface state, and can be bonded to a bonding partner at room temperature to bond dissimilar materials.

  On the other hand, in the interatomic diffusion bonding method, a metal layer such as Ti is formed on a support substrate, for example, and then bonded. As with surface activated bonding, bonding can be performed at a low temperature of room temperature to 400 ° C. or lower.

  In a preferred embodiment, the distance Lph between the entrance surface and the exit surface of the phosphor plate is set to 0.1 mm or more and 1.0 mm or less. If Lph is less than 0.1 mm, the distance that the fluorescence propagates through the phosphor is short and cannot be mixed well with the excitation light. For this reason, Lph is set to 0.1 mm or more, more preferably 0.15 mm or more. Further, if Lph is larger than 1.0 mm, the loss of fluorescence increases, and color unevenness is likely to occur in the emitted light. Therefore, it is set to 1.0 mm or less, but more preferably 0.9 mm or less.

  In a preferred embodiment, the distance Tph between the first bonding surface and the second bonding surface of the phosphor plate and the distance Wph between the pair of side surfaces are 2.5 mm or more and 5.0 mm or less. If these are less than 2.5 mm or more than 5.0 mm, the heat dissipation characteristics to the heat dissipation substrate deteriorate, the temperature of the phosphor rises, and the temperature distribution is likely to cause color unevenness in the emitted light. Although it is set to 0.5 to 5.0 mm, it is more preferably set to 3.0 to 4.5 mm.

  Further, the dimensions Ws and Ls of the heat dissipation substrate can be set to the same values as Wph and Lph of the phosphor substrate from the manufacturing process. However, Ts can be uniquely designed from the viewpoint of heat dissipation, and is preferably 500 μm or more, more preferably 1.0 mm or more. However, it is preferably 3.0 mm or less from the viewpoint of miniaturization.

  As the light source, a semiconductor laser made of a GaN material having high reliability is suitable for exciting the phosphor for illumination. 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). Further, an LED can be used, or excitation light from a light source can be incident on a phosphor element through an optical fiber.

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 Red, blue with phosphor from blue laser or ultraviolet laser Method of generating green fluorescence and obtaining white light Method of obtaining blue and yellow fluorescence with a phosphor from a blue laser or ultraviolet laser to obtain white light

(Examples 1 and 2)
A phosphor element 1A as shown in FIG. 1 was produced.
Specifically, a buffer layer 5A made of Al2O3 was formed by sputtering on an aluminum nitride substrate having a thickness of 3 mm, an aluminum film 4A was formed by 0.4 μm, and a bonding layer made of Al2O3 was formed by 0.2 μm. Next, a bonding layer made of Al 2 O 3 was formed to a thickness of 0.5 μm on Ce-doped YAG (yttrium / aluminum / garnet) polycrystalline phosphor plate 2. Furthermore, both were bonded together by Al2O3 layers by direct bonding at room temperature with an ion gun to obtain a composite substrate.

  Thereafter, a buffer layer 5B made of Al 2 O 3 was formed to 0.2 μm on another aluminum nitride substrate, an aluminum film 4B as a reflective film was formed to 0.4 μm, and a bonding layer made of Al 2 O 3 was further formed to 0.2 μm. Further, a bonding layer made of Al2O3 was formed to a thickness of 0.5 μm on the surface of the polycrystalline phosphor of the composite substrate, and the two layers were bonded together by direct bonding at room temperature with an ion gun between the Al2O3 layers.

  The obtained composite substrate was cut into a desired size with a slicer. The sample of Example 1 was a sample in which both the incident surface and the cut surface serving as the exit surface were mirror-polished after cutting. A sample in which only the exit surface was mirror-finished and the incident surface was cut and roughened was used as the sample of Example 2. In both the samples of Examples 1 and 2, a buffer layer 8 made of Al 2 O 3 was formed to 0.2 μm and an aluminum film as a reflective film 7 was formed to 0.4 μm on both the cut side surfaces by sputtering.

(Comparative Example 1)
A phosphor element 20 as shown in FIG. 7 was produced.
The phosphor element 20 is the same as the phosphor element 1A of FIG. 1, but the reflection films 4A and 4B are in contact with the joint surfaces 2c and 2d of the phosphor plate 2, respectively, and the reflection films 4A and 4B. And buffer layers 5A and 5B are provided between the heat dissipation substrates 6A and 6B, respectively.

  Specifically, a buffer layer 5A made of Al 2 O 3 was formed to a thickness of 0.2 μm on a 3 mm thick aluminum nitride substrate by sputtering. Next, 0.4 μm of an aluminum film as a reflective film 4A and 0.2 μm of a bonding layer made of Al 2 O 3 were formed on a polycrystalline phosphor plate of YAG (yttrium, aluminum, garnet) doped with Ce. Furthermore, both were bonded together by Al2O3 layers by direct bonding at room temperature with an ion gun to obtain a composite substrate.

  Thereafter, 0.4 μm of an aluminum film and 0.2 μm of a bonding layer made of Al 2 O 3 were formed as a reflection film 4B on the bonding surface 2d of the phosphor plate 2 of the bonded composite substrate by sputtering. Next, a buffer layer 5B made of Al 2 O 3 was similarly formed on another aluminum nitride substrate to a thickness of 0.2 μm, and both substrates were bonded together by direct bonding at room temperature using an ion gun.

  Next, the bonded composite substrate was cut into desired dimensions with a slicer. After cutting, both the incident surface and the cut surface serving as the exit surface were polished to give mirror surfaces. Further, a buffer layer 8 made of Al 2 O 3 was formed to 0.2 μm on both sides of the cut surface by sputtering, and an aluminum film was formed to be 0.4 μm as the reflective film 7.

(Comparative Example 2)
A phosphor element 21 as shown in FIG. 8 was produced.
Specifically, a polycrystalline phosphor plate 12 of YAG (yttrium, aluminum, garnet) doped with Ce having a width of 3 mm, a height of 3 mm, and a thickness of 0.3 mm was prepared. Moreover, the alumina substrate 13 processed into a cylindrical shape having a width of 3.2 mm, a height of 3.2 mm, a thickness of 0.3 mm, and an inner shape of a width of 3 mm, a height of 3 mm, and a thickness of 0.3 mm; An aluminum substrate 14 processed into a cylindrical shape having a width of 3.4 mm, a height of 3.4 mm, a thickness of 0.3 mm, and an inner shape having a width of 3.2 mm, a height of 3.2 mm, and a thickness of 0.3 mm was prepared. These substrates were placed so that they were in contact with each other.

  In this state, the side surfaces 12c, 12d, 12e, and 12f between the entrance surface 12a and the exit surface 12b of the phosphor plate 12 are in contact with the inner peripheral surface of the outer alumina substrate 13, respectively. Is in contact with the inner peripheral surface of the outer aluminum substrate 14. The aluminum substrate 14 functions as a reflective film, and the alumina substrate 13 functions as a buffer layer.

  Next, aluminum nitride having a width of 3 mm, a height of 3 mm, and a thickness of 0.3 mm was mounted as the heat dissipation substrate 15 so as to be in contact with the surface of the reflective film 14 to obtain a module.

(Measurement)
A GaN-based blue laser light source with an output of 3 W was optically coupled to each phosphor element to produce a module. The spot size with which the phosphor element was irradiated had a radius of 1 mm, and the power density was 0.95 W / mm ² at this time. Table 1 shows the initial characteristic results. Table 2 shows the results of evaluating the characteristics again after performing 500 cycles at −10 ° C. and 85 ° C. as a temperature cycle test. However, each item was measured as follows.

(Luminance)
The luminance was measured using a total luminous flux measurement method using a 10 inch integrating sphere (DAS-2100) manufactured by labshere.

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

In Example 1 and Example 2, no color unevenness was observed both in the initial stage and after the temperature cycle test.
That is, the calculated value of the temperature distribution of the phosphor after the 500 cycle test in Example 1 is shown in the graph of FIG. 9 and the simulation diagram of FIG. In this case, the temperature is below the thermal degradation threshold of the phosphor at any location before and after the temperature cycle test, the internal quantum efficiency of the fluorescence is not reduced, and there is no color unevenness.

  Also in the case of Example 2, the temperature distribution of the phosphor after the 500 cycle test is below the thermal degradation threshold of the phosphor at any location, the internal quantum efficiency of the fluorescence is not reduced, and color unevenness is observed. There wasn't.

  The calculated values of the temperature distribution of the phosphor after the 500 cycle test in Comparative Example 1 are shown in FIG. In this case, before the temperature cycle test, the temperature was 300 ° C. or lower in any place, and no color unevenness was generated as in Example 1. However, after the temperature cycle test, color unevenness occurred even though the temperature was 300 ° C. or less as a whole. When the sample was examined in a destructive test, the reflective film was peeled off from the phosphor plate, the reflectance of the excitation light and the fluorescence decreased, the luminance decreased, and at the same time, the color distribution was created and color unevenness occurred. I found out that

  In the case of Comparative Example 2, color unevenness occurred. The reason for this is that the heat dissipation effect is not sufficient, the temperature does not depend on the temperature cycle, the maximum temperature exceeds the threshold for thermal degradation, and the temperature distribution in the phosphor becomes asymmetric, resulting in thermal degradation of the phosphor. As a result, the internal quantum efficiency of the fluorescence is reduced, and the temperature distribution is different from the irradiation distribution of the excitation light.

Claims (5)

First heat dissipation board,
Second heat dissipation board,
An excitation light incident surface, a facing surface facing the incident surface, a first bonding surface facing the first heat dissipation substrate, a second bonding surface facing the second heat dissipation substrate, and a pair of side surfaces A phosphor plate that converts the excitation light incident on the phosphor plate into fluorescence and emits the fluorescence and the excitation light from the opposing surface or the incident surface,
A first bonding layer made of a metal oxide in contact with the first bonding surface;
A second bonding layer made of a metal oxide in contact with the second bonding surface;
A first reflective film provided between the first bonding layer and the first heat dissipation substrate; and a second reflection film provided between the second bonding layer and the second heat dissipation substrate. A phosphor element comprising a reflective film.   The element according to claim 1, wherein a side surface reflection film is provided on each side surface of the phosphor plate.   A first buffer layer made of a metal oxide is provided between the first reflective film and the first heat dissipation substrate, and between the second reflective film and the second heat dissipation substrate. 3. The device according to claim 1, further comprising a second buffer layer made of a metal oxide.   The element according to claim 1, wherein the fluorescence and the excitation light are emitted from the facing surface.   An illumination device comprising: a light source that oscillates laser light; and the phosphor element according to claim 1.

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