PCT/JP2017/03 7650
`P04653 87WOO l/PIPM-A0482WOOI
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`SPECIFICATION
`
`WAVELENGTH CONVERTER AND WAVELENGTH CONVERSION MEMBER
`
`TECHNICAL FIELD
`
`[0001]
`
`The
`
`present
`
`invention
`
`relates
`
`to
`
`a wavelength
`
`converter
`
`using
`
`photoluminescence, and particularly, relates to a wavelength converter and a wavelength
`
`conversion member, which are excellent in heat dissipation and efficiency even when
`
`irradiated with hi gh-power excitation light.
`
`BACKGROUND ART
`
`[0002]
`
`Heretofore, as a wavelength converter using photoluminescence, there has been
`
`known a wavelength converter composed of: a plurality of phosphor particles which emit
`
`light by being irradiated with excitation light, and a binder that holds the plurality of
`
`phosphor particles.
`
`Specifically, a wavelength converter in which silicon resin is filled
`
`with a phosphor has been known. For example, the wavelength converter has a form of
`
`a layered or plate-shaped body formed on a metal substrate.
`
`[0003]
`
`In recent years, the wavelength converter has been required to increase power of
`
`excitation light in order to enhance a light output.
`
`Therefore, for the wavelength
`
`converter, high-power excitation light of a laser light source or the like has been being
`
`used as the excitation light. However, such an organic binder as the silicon resin is poor
`
`in heat dissipation. Therefore, when the wavelength converter having the organic binder
`
`is irradiated with the high—power excitation light of the laser light source or the like, the
`
`organic binder is discolored and burnt to decrease light transmittance of the wavelength
`
`converter, whereby light output efficiency of the wavelength converter is prone to
`
`decrease.
`
`[0004]
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`Note that, though there is an example of using an inorganic binder without using
`
`the organic binder, the binder involves heat generation, whereby luminance of phosphor
`
`is prone to decrease due to temperature quenching thereof, and the light output efficiency
`
`of the wavelength converter is prone to decrease.
`
`CITATION LIST
`
`PATENT LITERATURE
`
`[0005]
`
`PTL 1: Japanese Unexamined Patent Publication No. 2014—116587
`
`PTL 2: Japanese Unexamined Patent Publication No. 2016-20420
`
`SUMNIARY OF INVENTION
`
`TECHNICAL PROBLEM
`
`[0006]
`
`For this, there is conceived a method of blending a substance other than the
`
`phosphor with the wavelength converter, thereby improving thermal conductivity of the
`
`wavelength converter.
`
`For example, such a known method as described in PTL l and
`
`PTL 2 makes it possible to improve the thermal conductivity.
`
`[0007]
`
`However, in this case, the substance other than the phosphor in the wavelength
`
`converter is prone to increase a probability at which an angle of an optical path of each
`
`of excitation light and fluorescence is changed due to scattering and refraction, and is
`
`prone to decrease a probability at which each of the excitation light and the fluorescence
`
`is taken from an inside of the wavelength converter to an outside thereof.
`
`[0008]
`
`Then, a mode where each of the excitation light and the fluorescence is guided
`
`in an in-plane direction in the inside of the wavelength converter becomes more dominant,
`
`and as a result, there is a problem that light extraction efficiency decreases or that output
`
`spots increase.
`
`[0009]
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`As described above, heretofore, there has not been known a configuration of a
`
`wavelength converter excellent in heat dissipation and efficiency even when irradiated
`
`with the high-power excitation light.
`
`[0010]
`
`The present invention has been made in consideration of the above—described
`
`problems.
`
`It is an object of the present invention to provide a wavelength converter and
`
`a wavelength conversion member, which are excellent in heat dissipation and efficiency
`
`even when irradiated with the high-power excitation light.
`
`[Solution to Problem]
`
`[0011]
`
`In order to solve the above-described problems, a wavelength converter
`
`according to a first aspect of the present invention includes: inorganic phosphor particles
`
`; translucent non—fluorescent light emitting inorganic particles; and an inorganic
`
`binder, wherein the inorganic phosphor particles and the translucent non-fluorescent light
`
`emitting inorganic particles are bound to each other by the inorganic binder, an average
`
`particle size of the translucent non-fluorescent light emitting inorganic particles is equal
`
`to or more than an average particle size of the inorganic phosphor particles, thermal
`
`conductivity of the translucent non—fluorescent light emitting inorganic particles is larger
`
`than thermal conductivity of the inorganic phosphor particles, a refractive index of the
`
`translucent non-fluorescent light emitting inorganic particles stays within a range of ::6%
`
`of a refractive index of the inorganic phosphor particles, and fluorescence is emitted upon
`
`receiving excitation light.
`
`[0012]
`
`In order to solve the above-described problems, a wavelength conversion
`
`member according to a second aspect of the present invention includes: a substrate having
`
`a reflecting surface, and the above—described wavelength converter supported on the
`
`sub strate.
`
`BREWIHECRETKEJOFDRAMHNGS
`
`[0013]
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`FIG.
`
`1 is an example of a scanning electron micrograph (SEM) of nanoparticles
`
`of aluminum oxide for use in Example 1.
`
`FIG. 2 is an example of an XRD spectrum of the nanoparticles of the aluminum
`
`oxide for use in Example 1.
`
`FIG. 3 is an example of a photograph of a cross section observed by a scanning
`
`electron microscope (SEM), the cross section being obtained by cutting the wavelength
`
`conversion member obtained in Example 1 in a thickness direction.
`
`FIG. 4 is an example of a photograph of a cross section obtained by enlarging a
`
`part of FIG. 3.
`
`DESCRHHIONIMKEMBODHMENTS
`
`[0014]
`
`A description will be given of a wavelength converter and a wavelength
`
`conversion member according to this embodiment.
`
`[0015]
`
`(Wavelength conversion member)
`
`The wavelength conversion member includes: a substrate having a reflecting
`
`surface; and a wavelength converter supported on this substrate.
`
`[0016]
`
`(Substrate)
`
`The substrate has roles of reinforcing the wavelength converter formed on a
`
`surface thereof, and of dissipating heat generated in an inside of the wavelength converter.
`
`[0017]
`
`As the substrate, for example, there can be used a translucent one such as glass
`
`and sapphire and a non—translucent one such as aluminum and copper. When the
`
`substrate has translucency, it becomes possible to apply light via the substrate to phosphor
`
`particles in the wavelength converter. Herein, the fact that a material has transparency
`
`means that the material is transparent with respect to the visible light (with a wavelength
`
`of 380 nm to 800 nm). Moreover, the fact that the material is transparent means that an
`
`absorption coefficient for the visible light by the material is 0.1 or less. Moreover, it is
`
`preferable that the absorption coeffi cient for the visible light by the material for use in the
`
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`substrate be as low as possible since it is possible to sufficiently apply light via the
`
`substrate to the phosphor particles in the wavelength converter.
`
`[0018]
`
`Note that, when the substrate does not have translucency, the surface of the
`
`substrate becomes a reflecting surface for reflecting light, which is emitted from the
`
`wavelength converter, by the substrate.
`
`That is, the substrate may have a reflecting
`
`surface on the surface. Herein, the reflecting surface means a surface on which the
`
`visible light is reflected with high reflectance. Moreover, high reflectance means
`
`reflectance of 80% or more. Note that the reflecting surface may be the surface itself of
`
`the substrate or a surface of another member than the substrate, the surface being provided
`
`on the surface of the substrate. As such another member, for example, a multilayer film
`
`to be described later is used.
`
`[0019]
`
`When the substrate has a reflecting surface on the surface, light emitted from the
`
`wavelength converter formed on the surface of the substrate is reflected on the reflecting
`
`surface of such a substrate surface and is guided through the inside of the wavelength
`
`converter, and accordingly, is prone to be affected by light scattering and refraction in the
`
`wavelength converter.
`
`In a wavelength converter according to the embodiment, a
`
`difference between refractive indices of translucent non-fluorescent
`
`light emitting
`
`inorganic particles and inorganic phosphor particle stay within a range of ::6%, that is,
`
`numerical values of the refractive indices are approximate to each other. Therefore,
`
`even if the light emitted from the wavelength converter is reflected on the reflecting
`
`surface of the substrate surface, such influences from the light scattering and refraction
`
`in the wavelength converter can be reduced.
`
`[0020]
`
`The reflecting surface is, for example, made of metal or a multilayer film.
`
`Herein, the multilayer film means a film formed by laminating two or more thin films
`
`having translucency and different refractive indices on one another.
`
`[0021]
`
`For example, aluminum is used as the metal that constitutes the reflecting surface.
`
`It is preferable that the metal that constitutes the reflecting surface have high reflectance
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`to the visible light since light extraction efficiency of the wavelength converter and the
`
`wavelength conversion member is improved.
`
`[0022]
`
`As the multilayer film, specifically, used is a film formed by laminating plural
`
`types of thin films, each of which is made of a metal oxide such as aluminum oxide having
`
`translucency, or the like.
`
`It is preferable that the reflecting surface be made of the metal
`
`or the multilayer film since the light extraction efficiency of the wavelength converter
`
`and the wavelength conversion member is improved.
`
`[0023]
`
`(Wavelength converter)
`
`The wavelength converter
`
`is composed of inorganic phosphor particles,
`
`translucent non-fluorescent light emitting inorganic particles and an inorganic binder.
`
`The inorganic phosphor particles and the translucent non—fluorescent light emitting
`
`inorganic particles are bound to each other by the inorganic binder.
`
`[0024]
`
`<Inorganic Phosphor Parti cl e>
`
`The inorganic phosphor particles are particles of an inorganic compound capable
`
`of photoluminescence. A type of the inorganic phosphor particles is not particularly
`
`limited as long as the inorganic phosphor particles are capable of photoluminescence.
`
`As the inorganic phosphor particles, for example, used are crystalline particles with a
`
`garnet structure made of YAG,
`
`that is, Y3A15012, and phosphor particles made of
`
`(Sr,Ca)AlSiN3:Eu.
`
`[0025]
`
`An average particle size of the inorganic phosphor particles usually ranges from
`
`1 to 10 um, preferably ranges from 11 to 30 um.
`
`It is preferable that the average particle
`
`size of the inorganic phosphor particles stay within the above—described range since the
`
`inorganic phosphor particles are producible by an inexpensive production process such
`
`as an application method and it is relatively easy to adjust chromaticity thereof.
`
`[0026]
`
`The average particle size of the inorganic phosphor particles is obtained by
`
`observing an arbitrarily preprocessed wavelength converter by a scanning electron
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`microscope (SEM) or the like and obtaining an average value of diameters of inorganic
`
`phosphor particles of which numb er is sufficiently significant from a statistical viewpoint,
`
`for example, 100.
`
`[0027]
`
`Moreover, it is possible to determine a composition of the inorganic phosphor
`
`particles by a known analysis method such as energy dispersive X-ray analysis (EDX)
`
`and X-ray diffraction analysis (XRD).
`
`[0028]
`
`The inorganic phosphor particles may be made of a single type of phosphor
`
`having the same composition, or may be a mixture of phosphor particles having two or
`
`more types of compositions.
`
`[0029]
`
`<Inorganic binder>
`
`The inorganic binder just needs to be capable of binding at least two inorganic
`
`phosphor particles to each other, and a type thereof is not particularly limited.
`
`For
`
`example, alumina, silica or the like is used as the inorganic binder.
`
`[0030]
`
`As the inorganic binder, for example, used is an aggregate of inorganic
`
`nanoparticles (that is, a fixed body of inorganic nanoparticles).
`
`Specifically, as the
`
`inorganic binder, there can be used a fixed body of inorganic nanoparticles with an
`
`average particle size of approximately 100 nm, the inorganic nanoparticles having air
`
`gaps.
`
`The fixed body of the inorganic nanoparticles means a solid of the inorganic
`
`nanoparticles, which is directly formed by covalent bond or formed thereby via grain
`
`boundary phases. When the inorganic binder is the fixed body of the inorganic
`
`nanoparticles, this fixed body of the inorganic nanoparticles binds the inorganic phosphor
`
`particles and the above—described translucent non—fluorescent light emitting inorganic
`
`particles to each other.
`
`[0031]
`
`As the fixed body of the inorganic nanoparticles, for example, used are: an
`
`alumina fixed body formed by fixing a large number of alumina nanoparticles to one
`
`another; and a silica fixed body formed by fixing a large number of silica nanoparticles
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`to one another. The alumina fixed body is obtained, for example, such that alumina
`
`nanoparticles in alumina sol are fixed to one another. The silica fixed body is obtained,
`
`for example, such that silica nanoparticles in silica sol are fixed to one another.
`
`[0032]
`
`When the inorganic binder is the fixed body of the inorganic nanoparticles, an
`
`average particle size of the inorganic nanoparticles which constitute the fixed body ranges
`
`from 50 to 200 nm for example, preferably ranges from 80 to 150 nm.
`
`It is preferable
`
`that the average particle size of the inorganic nanoparticles stay within the above-
`
`described range since adhesion between the inorganic nanoparticles and the substrate is
`
`improved.
`
`[0033]
`
`It is desirable that thermal conductivity of the inorganic binder be, for example,
`
`1 w/mK or more. When the thermal conductivity of the inorganic binder stays within
`
`this range, heat dissipation of the wavelength converter is good.
`
`[0034]
`
`The inorganic binder can be produced by a known method, for example, such as
`
`a method using the sol-gel method and a method using the aerosol deposition.
`
`[0035]
`
`The inorganic binder may be made of a single type of inorganic binder having
`
`the same composition, or may be a mixture of inorganic binders having two or more types
`
`of compositions.
`
`[0036]
`
`<Translucent non-fluorescent light emitting inorganic particle>
`
`The translucent non-fluorescent
`
`light emitting inorganic particles mean
`
`inorganic metal oxide particles which are transparent in the visible light region (with a
`
`wavelength of 380 nm to 800 nm) and do not emit fluorescence or light by being excited
`
`by light with the wavelength in the visible light region. Here, the fact that the inorganic
`
`metal oxide particles are transparent in the visible light region means that an absorption
`
`coefficient for light in the visible light region is extremely small.
`
`Specifically, the fact
`
`that the inorganic metal oxide particles are transparent in the visible light region means
`
`that the absorption coefficient for the visible light by the material is 0.1 or less.
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`It is
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`preferable that the translucent non—fluorescent
`
`light emitting inorganic particles be
`
`transparent in the visible light region since the light extraction efficiency is improved.
`
`Moreover, the phrase “do not emit fluorescence by being excited by light with the
`
`wavelength in the visible light region” means that neither fluorescence nor light is emitted
`
`even if irradiated with the light in the above—described visible light region with the
`
`wavelength of380 nm to 800 nm.
`
`[0037]
`
`As will be described later,
`
`thermal conductivity of the translucent non-
`
`fluorescent light emitting inorganic particles is larger than the thermal conductivity of the
`
`inorganic phosphor particles. The wavelength converter according to the embodiment
`
`includes the translucent non-fluorescent light emitting inorganic particles in addition to
`
`the inorganic phosphor particles, and accordingly, has higher heat dissipation than in the
`
`case of not including the translucent non—fluorescent light emitting inorganic particles.
`
`[0038]
`
`Moreover, as will be described later, a refractive index of the translucent non-
`
`
`fluorescent light emitting inorganic particles stays within the range of ::6% of a refractive
`
`index of the inorganic phosphor particles, and is less different from the refractive index
`
`of the inorganic phosphor particles.
`
`The wavelength converter according to the
`
`embodiment includes the translucent non-fluorescent light emitting inorganic particles in
`
`addition to the inorganic phosphor particles, however, optical characteristics thereof do
`
`not change much from the case of not including the translucent non-fluorescent light
`
`emitting inorganic particles.
`
`[0039]
`
`For example, alumina is mentioned as a material for use in the translucent non-
`
`fluorescent light emitting inorganic particles.
`
`It is preferable that the material for use
`
`int he translucent non—fluorescent light emitting inorganic particles be alumina since
`
`thermal conductivity thereof is high.
`
`[0040]
`
`An average particle size of the translucent non-fluorescent
`
`light emitting
`
`inorganic particles usually ranges from 1 to 100 um, preferably ranges from 11 to 30 um.
`
`It is preferable that the average particle size of the translucent non-fluorescent light
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`emitting inorganic particles stay Within the above—described range since the translucent
`
`non-fluorescent light emitting inorganic particles are producible by an inexpensive
`
`production process such as an application method and it is relatively easy to adjust
`
`chromaticity thereof.
`
`It is possible to analyze the average particle size and composition
`
`of the translucent non—fluorescent light emitting inorganic particles by the same method
`
`as
`
`the above-described measurement method for
`
`the average particle size and
`
`composition of the inorganic phosphor particles.
`
`[0041]
`
`The translucent non—fluorescent light emitting inorganic particles may be made
`
`of a single type of translucent non-fluorescent light emitting inorganic particles having
`
`the same composition, or may be a mixture of translucent non-fluorescent light emitting
`
`inorganic particles having two or more types of compositions.
`
`[0042]
`
`<Shapes of inorganic phosphor particles and translucent non-fluorescent light emitting
`
`inorganic particles>
`
`It is desirable that, in the wavelength converter, at least a part of particles among
`
`large numbers of the inorganic phosphor particles and the translucent non-fluorescent
`
`light emitting inorganic particles, which constitute the wavelength converter, have a
`
`spherical shape or a polyhedral particle shape derived from a crystal structure of garnet.
`
`Herein, the polyhedral particle shape derived from the crystal structure of the garnet
`
`means a polyhedral shape derived from the crystal structure of the garnet and having
`
`facets. More specifically,
`
`the polyhedral particle shape derived from the crystal
`
`structure of the garnet means that the polyhedral inorganic phosphor particles have a
`
`rhombic dodecahedron shape, or a biased polyhedron shape, or a shape in which edge
`
`portions connecting the facets to one another are rounded in each of these shapes.
`
`Hereinafter, the “polyhedral particle shape derived from the crystal structure of the garnet”
`
`Will also be referred to as a “gamet-derived polyhedral shape”.
`
`[0043]
`
`Moreover, “at least a part of the particles has a spherical shape or a polyhedral
`
`particle shape derived from the crystal structure of the garnet” means that at least a part
`
`of particles are spherical particles or particles having the gamet-derived polyhedral shape.
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`Here, “at least a part of the particles” means one or more particles, and in usual, means a
`
`plurality of particles.
`
`In usual, the wavelength converter includes a large number of the
`
`inorganic phosphor particles and a large number of the translucent non-fluorescent light
`
`emitting inorganic particles. Therefore, the wavelength converter sometimes includes
`
`both of the spherical particles and the particles having the garnet—derived polyhedral
`
`shape.
`
`[0044]
`
`The reason why it is desirable that at least a part of the particles among the large
`
`numbers of inorganic phosphor particles and translucent non—fluorescent light emitting
`
`inorganic particles have the spherical shape or the polyhedral particle shape derived from
`
`the crystal structure of garnet is as follows.
`
`For example, scale-shaped particles are
`
`different in terms of optical behavior from the spherical particles and the particles with
`
`the polyhedral particle shape derived from the crystal structure of the garnet. Therefore,
`
`when the above-described at least a part of particles are the spherical particles or the
`
`particles with the polyhedral particle shape derived from the crystal structure ofthe garnet,
`
`then portions with a similar optical behavior are formed in the wavelength converter,
`
`whereby a wavelength converter excellent in light emission efficiency is obtained.
`
`Moreover, the translucent non—fluorescent light emitting inorganic particles have higher
`
`thermal conductivity than the inorganic phosphor particles. Therefore, the wavelength
`
`converter according to this embodiment, which includes the inorganic phosphor particles
`
`and the translucent non-fluorescent
`
`light emitting inorganic particles, becomes a
`
`wavelength converter superior in heat dissipation to a wavelength converter that does not
`
`include the translucent non-fluorescent light emitting inorganic particles.
`
`[0045]
`
`(Relationship in average particle size between translucent non-fluorescent light emitting
`
`inorganic particles and inorganic phosphor particles)
`
`The average particle size of the translucent non-fluorescent
`
`light emitting
`
`inorganic particles is equal to or more than the average particle size of the inorganic
`
`phosphor particles.
`
`It is preferable that the average particle size of the translucent non-
`
`fluorescent light emitting inorganic particles be equal to or more than the average particle
`
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`size of the inorganic phosphor particles since the heat dissipation of the wavelength
`
`converter and the wavelength conversion member is improved.
`
`[0046]
`
`(Relationship in thermal conductivity between translucent non-fluorescent light emitting
`
`inorganic particles and inorganic phosphor particles)
`
`The thermal conductivity of the translucent non-fluorescent
`
`light emitting
`
`inorganic particles is larger than the thermal conductivity of the inorganic phosphor
`
`particles.
`
`It is preferable that the thermal conductivity of the translucent non-fluorescent
`
`light emitting inorganic particles be larger than the thermal conductivity of the inorganic
`
`phosphor particles since the heat dissipation of the wavelength converter and the
`
`wavelength conversion member is improved.
`
`[0047]
`
`(Relationship in refractive index between translucent non—fluorescent light emitting
`
`inorganic particles and inorganic phosphor particles)
`
`The refractive index of the translucent non-fluorescent light emitting inorganic
`
`particles stays within the range of ::6% of the refractive index of the inorganic phosphor
`
`particles.
`
`It is preferable that the refractive index of the translucent non-fluorescent light
`
`emitting inorganic particles stay within the range of ::6% of the refractive index of the
`
`inorganic phosphor particles since the light extraction efficiency of the wavelength
`
`converter and the wavelength conversion member is improved.
`
`[0048]
`
`(Fluorescence of wavelength converter)
`
`The wavelength converter according to the embodiments emits fluorescence
`
`upon receiving excitation light. Known excitation light can be used as the excitation
`
`light.
`
`[0049]
`
`(Production method of wavelength converter and wavelength conversion member)
`
`The wavelength converter according to this embodiment is formed on the
`
`substrate, whereby a wavelength conversion member composed of the substrate and the
`
`wavelength converter can be produced.
`
`For example, a nanoparticle—mixed solution
`
`containing the inorganic phosphor particles, the translucent non-fluorescent light emitting
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`inorganic particles and the inorganic binder is applied on the reflecting surface of the
`
`substrate, followed by natural drying, whereby the wavelength converter according to this
`
`embodiment
`
`is formed on the reflecting surface of the substrate.
`
`In usual,
`
`the
`
`wavelength converter is supported on the reflecting surface of the substrate by being
`
`bound on the reflecting surface of the substrate by the inorganic binder. As described
`
`above, when the wavelength converter is bound to the reflecting surface of the substrate,
`
`the wavelength conversion member composed of the substrate having the reflecting
`
`surface and the wavelength converter supported on this substrate can be produced.
`
`[0050]
`
`(Function of wavelength conversion member)
`
`Functions of the wavelength conversion member will be described.
`
`The
`
`functions of the wavelength conversion member change depending on whether the
`
`substrate has optical transparency. For example, when a substrate that does not have the
`
`optical transparency is used as the substrate, then in the wavelength conversion member,
`
`secondary light of the inorganic phosphor particles, which is generated in the wavelength
`
`converter, is radiated from a front surface side of the wavelength converter. Meanwhile,
`
`when a substrate that has the optical transparency is used as the substrate, then in the
`
`wavelength conversion member, the secondary light of the inorganic phosphor particles,
`
`which is generated in the wavelength converter, is radiated from the front surface side of
`
`the wavelength converter and from a front surface side of the substrate.
`
`[0051]
`
`(Effects of wavelength converter and wavelength conversion member)
`
`The wavelength converter and the wavelength conversion member according to
`
`the above-described embodiment are excellent in heat dissipation and efficiency even
`
`when irradiated with the high-power excitation light.
`
`[0052]
`
`The effects will be specifically described.
`
`In the wavelength converter
`
`according to this embodiment, the average particle size of the translucent non-fluorescent
`
`light emitting inorganic particles is equal to or more than the average particle size of the
`
`inorganic phosphor particles, and the translucent non—fluorescent light emitting inorganic
`
`
`particles have the refractive index of ::6% of the refractive index of the inorganic
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`P04653 87WOO l/PIPM-A0482WOOI
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`phosphor particles.
`
`Therefore,
`
`in the wavelength converter according to this
`
`embodiment, the probability at which the angle of the optical path is changed due to the
`
`scattering or refraction of the excitation light and the fluorescence in the inside of the
`
`wavelength converter becomes equivalent to the conventional one.
`
`[0053]
`
`Hence, in the wavelength converter according to this embodiment, in the inside
`
`of the wavelength converter, the probability at which the angle of the optical path of each
`
`of the excitation light and the fluorescence is changed due to the scattering or the
`
`refraction can be decreased, and as a result, it is possible to improve the light extraction
`
`efficiency and to reduce the output spots.
`
`[0054]
`
`Moreover,
`
`in the wavelength converter according to this embodiment,
`
`the
`
`translucent non—fluorescent
`
`light emitting inorganic particles have larger thermal
`
`conductivity than the inorganic phosphor particles, and form an inorganic phosphor film.
`
`Therefore, the wavelength converter according to this embodiment has higher heat
`
`dissipation than the conventional wavelength converter.
`
`[0055]
`
`From the above, the wavelength converter according to this embodiment and the
`
`wavelength conversion member including this wavelength converter are excellent in heat
`
`dissipation and efficiency even when irradiated with the hi gh-power excitation light.
`
`EXAMPLES
`
`[0056]
`
`Hereinafter, this embodiment will be described more in detail by examples;
`
`however, this embodiment is not limited to these examples.
`
`[0057]
`
`[Example 1]
`
`(Preparation of nanoparticle-mixed solution)
`
`First, as inorganic phosphor particles, YAG particles (YAG374A165 produced
`
`by Nemoto Lumi Material Co, Ltd; thermal conductivity: lO W/mK; refractive index:
`
`1.80) with an average particle size D50 of approximately 20.5 um were prepared.
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`PCT/JP2017/03 7650
`P04653 87W001/PIPM-A0482W001
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`Moreover, as a raw material containing nanoparticles as an inorganic binder, prepared
`
`was an aqueous solution into which nanoparticles of aluminum oxide (A1203) with an
`
`average particle size D50 of approximately 20 nm were dispersed. Moreover, as
`
`translucent non-fluorescent light emitting inorganic particles, prepared were particles of
`
`aluminum oxide (thermal conductivity: 3O W/mK, refractive index: 1.75) with an average
`
`particle size D50 of 30 um. The above-described YAG particles and the above-described
`
`translucent non-fluorescent light emitting inorganic particles were added to and kneaded
`
`with the aqueous solution in which the nanoparticles of the aluminum oxide were
`
`dispersed, whereby a nanoparticle—mixed solution was produced.
`
`[0058]
`
`FIG.
`
`1 is an example of a scanning electron micrograph (SEM) of the above-
`
`described nanoparticles of the aluminum oxide (A1203).
`
`FIG. 2 is an example of an
`
`XRD spectrum of the ab ove—described nanoparticles of the aluminum oxide (A1203).
`
`[0059]
`
`(Application of nanoparticle-mixed solution)
`
`A tape is mounted onto a metal substrate made of aluminum to form a step
`
`difference. The nanoparticle-mixed solution was dropped to a portion surrounded by
`
`the step difference, and subsequently, the nanoparticle—mixed solution was applied using
`
`an applicator equipped with a bar coater.
`
`[0060]
`
`(Formation of wavelength converter)
`
`The metal substrate applied with the nanoparticle—mixed solution was naturally
`
`dried. Then, a dried body having a film thickness of 100 um was obtained. This dried
`
`body became a wavelength converter including: YAG particles; aluminum oxide particles
`
`as the translucent non-fluorescent light emitting inorganic particles; and a binder layer
`
`that fixes the YAG particles and the translucent non—fluorescent light emitting inorganic
`
`particles to each other.
`
`In this way, a wavelength conversion member in which the film-
`
`like wavelength converter with a thickness of 100 um was formed on the metal substrate
`
`was obtained.
`
`[0061]
`
`(Evaluation)
`
`1 5
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`PCT/JPZO 17/03 7650
`P04653 87WOO l/PIPM-A0482WOOI
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`<Microscopy>
`
`FIG. 3 is an example of a photograph of a cross section observed by a scanning
`
`electron microscope (SEM), the cross section being obtained by cutting the wavelength
`
`conversion member obtained in Example 1 in a thickness direction.
`
`In FIG. 3, a flat
`
`portion shown on an upper side thereof is a surface 15 of a wavelength converter 10 that
`
`constitutes the wavelength conversion member. Moreover, FIG. 4 is an example of a
`
`photograph of a cross section obtained by enlarging a part of FIG. 3.
`
`As shown in FIG. 3 and FIG. 4, in the wavelength converter 10, YAG particles
`
`11 on which facets can be confirmed and aluminum oxide particles 12 as spherical
`
`translucent non-fluorescent light emitting inorganic particles on which facets cannot be
`
`confirmed are bond to each other via an inorganic binder 13.
`
`Therefore, in the wavelength converter 10, at least YAG particles 11 shown in
`
`FIG. 4 among a large number of the YAG particles which constitute the wavelength
`
`converter 10 have a polyhedral particle shape (a gamet-derived polyhedral shape) derived
`
`from the crystal structure of the garnet, which has facets.
`
`Moreover, in the wavelength converter 10, at least aluminum oxide particles 12
`
`shown in FIG. 4 among a large number of the aluminum oxide particles which constitute
`
`the wavelength converter 10 become spherical.
`
`Hence, it has been seen that, in the waveleng