JP7170235B2 - Wavelength conversion member - Google Patents

Description

The present invention relates to wavelength conversion members.

2. Description of the Related Art Conventionally, a light-emitting device is known in which a wavelength conversion member containing a phosphor and a laser beam that excites the phosphor are combined. The light-emitting device is expected as a device that enables downsizing and high output of solid-state lighting. As such a wavelength conversion member, there is known one that includes a wavelength conversion body composed of phosphor particles that emit light when irradiated with excitation light and a binder that holds the phosphor particles. Specifically, a wavelength converter is known in which a silicone resin is filled with a phosphor.

2. Description of the Related Art In recent years, due to the demand for higher output of light emitting devices, wavelength conversion members are being irradiated with high-power excitation light such as laser light. However, organic binders such as silicone resins are poor in heat resistance and heat dissipation. Therefore, when a wavelength conversion member containing an organic binder is irradiated with high-power excitation light, discoloration or scorching occurs in the organic matter that constitutes the binder, resulting in a decrease in light transmittance and light output efficiency of the wavelength conversion member. gets worse. Further, when a wavelength conversion member containing an organic binder is irradiated with high-power excitation light, the wavelength conversion member generates heat because the thermal conductivity of the organic matter is generally less than 1 W/m·K. As a result, the wavelength conversion member containing an organic binder has a problem that temperature quenching of the phosphor tends to occur.

Therefore, in Patent Document 1, inorganic phosphor particles and easily sinterable ceramic particles are contained, the easily sinterable ceramic particles are interposed between the inorganic phosphor particles, and the inorganic phosphor particles are easily sinterable. A wavelength converting member is disclosed that is bound by conductive ceramic particles. It is also disclosed that the sinterable ceramic particles are sinterable alumina particles. In addition, in Patent Document 1, the easily sinterable ceramic particles have excellent thermal conductivity compared to glass or the like, so that the heat generated by the inorganic phosphor particles is efficiently released to the outside, and the temperature of the phosphor is quenched. It is described that it can be made difficult to occur.

JP 2017-107071 A

However, in the wavelength conversion member of Patent Document 1, since the inorganic phosphor particles are bound by the sinterable ceramic particles, the inorganic phosphor particles and the sinterable ceramic particles are in point contact with each other. ing. Therefore, even if easily sinterable ceramic particles are used, the contact area between the inorganic phosphor particles and the easily sinterable ceramic particles is small, and a heat conduction path is not sufficiently formed. In some cases, heat dissipation was insufficient. Then, when such a wavelength conversion member is irradiated with high-power excitation light, there is a problem that the temperature quenching of the phosphor cannot be sufficiently suppressed.

The present invention has been made in view of such problems of the prior art. It is another object of the present invention to provide a wavelength conversion member that is excellent in heat dissipation even when irradiated with high-power excitation light and capable of suppressing temperature quenching of phosphors.

In order to solve the above problems, a wavelength conversion member according to an aspect of the present invention includes a plurality of phosphor particles and a plurality of inorganic particles, and an amorphous inorganic compound is coated on the surface of the phosphor particles. It has an amorphous part containing The inorganic particles and the amorphous portion contain the same metal element, and the metal element is at least one selected from the group consisting of alkali metals, alkaline earth metals, transition metals, base metals and semimetals.

FIG. 1 is a cross-sectional view schematically showing an example of the wavelength conversion member according to this embodiment. FIG. 2 is a schematic diagram showing an enlarged view of the inside of the wavelength conversion member according to this embodiment. FIG. 3 is a cross-sectional view schematically showing another example of the wavelength conversion member according to this embodiment. FIG. 4 is a photograph showing the result of observing a part of the test sample of the example with a transmission electron microscope. FIG. 4(a) is a photograph showing the result of observing the surface state of the phosphor in the test sample. FIG. 4(b) is a photograph showing an enlarged portion of "○" in FIG. 4(a). FIG. 4(c) is a photograph showing a further enlargement of the photograph of FIG. 4(b). FIG. 5 is a photograph showing the result of observing a portion of the test sample of the example with a transmission electron microscope. FIG. 5(a) is a photograph showing a further enlargement of the photograph of FIG. 4(c). FIG. 5(b) is a diagram showing an electron beam diffraction pattern of an inorganic compound existing between the phosphor particles and the zinc oxide particles in FIG. 5(a). FIG. 6 is a photograph showing the result of observing another portion of the test sample of Example with a transmission electron microscope. FIG. 6(a) is a photograph showing the result of observing the surface state of the phosphor in the test sample. FIG. 6(b) is a photograph showing an enlarged portion of "○" in FIG. 6(a). FIG. 6(c) is a photograph showing a further enlargement of the photograph of FIG. 6(b). FIG. 7 is a photograph showing the result of observing another portion of the test sample of Example with a transmission electron microscope. FIG. 7(a) is a photograph showing a further enlargement of the photograph of FIG. 6(c). FIG. 7(b) is a diagram showing an electron beam diffraction pattern of an inorganic compound present between the phosphor particles and the zinc oxide particles in FIG. 7(a). FIG. 8 is a scanning transmission electron micrograph (STEM) and oxygen (O), zinc (Zn), silicon (Si), yttrium when energy dispersive X-ray analysis was performed on the test sample of the example. FIG. 4 shows mapping data for (Y) and aluminum (Al); FIG. 9 is a diagram showing the results of energy dispersive X-ray analysis performed on a portion of the test sample of Example. FIG. 9(a) shows a bright field image (BF) of the test sample and mapping data of oxygen (O), silicon (Si) and zinc (Zn). FIG. 9(b) is a graph showing the results of simple quantification after extracting the spectrum from the mapping data for the amorphous portion indicated by “◯” in FIG. 9(a). FIG. 10 is a diagram showing the result of performing energy dispersive X-ray analysis on another portion of the test sample of Example. FIG. 10(a) shows a bright field image (BF) of the test sample and mapping data for oxygen (O), silicon (Si) and zinc (Zn). FIG. 10(b) is a graph showing the result of simple quantification after extracting the spectrum from the mapping data for the amorphous portion indicated by “◯” in FIG. 10(a).

Hereinafter, the wavelength conversion member according to this embodiment will be described in detail. Note that the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may differ from the actual ratios.

[Wavelength conversion member]
As shown in FIG. 1, the wavelength conversion member 1 of this embodiment includes a wavelength conversion body 10 that is a member that converts the wavelength of incident light. The wavelength converter 10 has a plurality of phosphor particles 20 that convert the wavelength of incident light, and a binder layer 30 that connects the phosphor particles 20 together. The phosphor particles 20 dispersed inside the wavelength converter 10 are excited by incident light (excitation light) and emit light having a longer wavelength than the incident light. Therefore, the wavelength converter 10 exhibits the action of wavelength-converting the incident light by the action of the phosphor particles 20 .

In the wavelength converter 10 shown in FIG. 1, the entire surfaces of the individual phosphor particles 20 are covered with the binder layer 30 . However, the present embodiment is not limited to such an aspect, and the binder layer 30 may be formed so as to connect at least adjacent phosphor particles 20 . Therefore, as an embodiment other than the wavelength converter 10 shown in FIG. 1 , a part of the surface of each phosphor particle 20 may be exposed without being covered with the binder layer 30 .

(Phosphor particles)
The phosphor particles 20 contained in the wavelength conversion member 1 absorb light (excitation light) in the excitation wavelength range of the phosphor particles 20 and emit light (converted light) having a longer wavelength than the excitation light. The phosphor particles 20 may be particles formed from an appropriate phosphor.

Based on the light emitted by the phosphors, examples of phosphors include CaAlSiN ₃ :Eu ²⁺ , (Ca,Sr)AlSiN ₃ :Eu ²⁺ , CaS:Eu ²⁺ , (Ca,Sr) ₂ Si ₅ N ₈ :Eu red phosphors such as ²⁺ . Also green phosphors such as _CaSc2O4 : _Ce3 ⁺ , _Ca3Sc2Si3O12 : _Ce3 ⁺ , ₍ ^Ca , Sr, Ba) _Al2O4 : _Eu2 ⁺ , _SrGa2S4 : _{Eu2 +} mentioned. Y ₃ Al ₅ O ₁₂ :Ce ³⁺ , (Ca, Sr, Ba, Zn) ₂ SiO ₄ :Eu ²⁺ and other yellow phosphors, and (Ba, Sr) ₂ SiO ₄ :Eu ²⁺ and other yellow-green phosphors. be done. Further _examples include orange phosphors such as _Sr3SiO5 : _{Eu2 +} and _{Ca0.7Sr0.3AlSiN3} : ^{Eu2 +} .

Further, based on the compound system of phosphors, examples of phosphors include (Y, Gd) ₃ (Al, Ga) ₅ O ₁₂ : Ce, (Ca, Sr, Ba) ₂ SiO ₄ : Eu, Li ₂ SrSiO ₄ :Eu, (Ba, Sr) ₃ SiO ₅ :Eu and other oxide phosphors. Also _{, Ca3Sc2Si3O12} :Ce, _SrAl2O4 :Eu _{, Tb3Al5O12} :Ce, _BAM :Eu, BAM:Mn, Eu, ₍ Mg, Ca, _Sr , Ba) _{10 (} Oxide phosphors such as PO ₄ ) ₆ Cl ₂ :Eu and Sr ₅ (PO ₄ ) ₃ Cl:Eu are also included. Furthermore, ZnS:Cu,Al, _CaGa2S4 :Eu, _SrGa2S4 :Eu, _BaGa2S4 :Eu, Ca ₍ Ga,Al, _In ) _2S4 :Eu, Sr ₍ Ga,Al, _In ) ₂ S ₄ :Eu, Ba(Ga, Al, In) ₂ S ₄ :Eu and other sulfide phosphors. Oxysulfide phosphors such as Y ₂ O ₂ S:Eu and La ₂ O ₂ S:Eu are also included. _CaSi2O2N2 :Eu, _SrSi2O2N2 : _Eu , _BaSi2O2N2 : _Eu , _{( Ca} , _Ba ) _Si2O2N2 : _Eu , _{( Sr} , _Ba ) _Si2O2 Nitride-based or oxynitride-based phosphors such as N ₂ :Eu and (Ca, Sr)Si ₂ O ₂ N ₂ :Eu can also be used.

The phosphor particles 20 are preferably made of an oxide phosphor having a garnet crystal structure. Garnet compounds are chemically stable and easy to handle in atmospheric pressure. Furthermore, the phosphor particles of the garnet compound can easily be monodisperse particles having a polyhedral shape or monodisperse particles having a shape close to a polyhedron. Therefore, it is possible to obtain the wavelength conversion body 10 having a high phosphor filling rate and excellent translucency.

The particle diameter of the phosphor particles 20 is not particularly limited, but the larger the average particle diameter of the phosphor particles 20, the smaller the defect density in the phosphor particles 20, the less the energy loss during light emission, and the higher the luminous efficiency. get higher Therefore, from the viewpoint of improving luminous efficiency, the average particle diameter of the phosphor particles 20 is preferably 1 μm or more and 100 μm or less, more preferably 1 μm or more and 30 μm or less. In this specification, unless otherwise specified, the value of "average particle size" is measured using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM), and several to several tens of fields of view. A value calculated as an average value of the particle diameters of the particles observed inside is adopted.

(binder layer)
As shown in FIG. 2, the binder layer 30 included in the wavelength conversion member 1 connects adjacent phosphor particles 20 together. Preferably, the binder layer 30 contains a plurality of inorganic particles 31, and the inorganic particles 31 are in contact with each other. This makes it possible to connect the phosphor particles 20 by intermolecular force or the like between the inorganic particles 31 and to fix the phosphor particles 20 .

The inorganic particles 31 contain at least one metal element selected from the group consisting of alkali metals, alkaline earth metals, transition metals, base metals and semi-metals. As used herein, alkaline earth metals include beryllium and magnesium, in addition to calcium, strontium, barium and radium. Base metals include aluminum, zinc, gallium, cadmium, indium, tin, mercury, thallium, lead, bismuth and polonium. Metalloids include boron, silicon, germanium, arsenic, antimony and tellurium. Among these, the inorganic particles 31 preferably contain at least one metal element of zinc and magnesium. The inorganic particles 31 containing these metal elements can easily form the amorphous portion 32 derived from the inorganic particles 31 by a pressure heating method, as will be described later.

The inorganic particles 31 preferably contain at least one of the oxide and nitride of the metal element, and more preferably contain at least one of the oxide and nitride of the metal element as a main component. In other words, the inorganic particles 31 preferably contain 50 mol % or more, more preferably 80 mol % or more, of at least one of the oxide and nitride of the metal element. Since the oxides and nitrides of the above metal elements have high thermal conductivity, the inorganic particles 31 containing them are used to increase the thermal conductivity of the binder layer 30 and improve the heat dissipation of the wavelength conversion member 1. becomes possible.

The inorganic particles 31 are preferably crystalline particles containing at least one metal element selected from the group consisting of alkali metals, alkaline earth metals, transition metals, base metals and semi-metals. In addition, the inorganic particles 31 are preferably crystalline particles containing at least one of the oxide and nitride of the above metal element, and crystals containing at least one of the oxide and nitride of the above metal element as a main component. More preferably, the particles are of high quality.

Although the average particle size of the inorganic particles 31 is not particularly limited, it is preferably smaller than the average particle size of the phosphor particles 20 . The average particle diameter of the inorganic particles 31 is more preferably 300 nm or more and 30 μm or less, even more preferably 300 nm or more and 10 μm or less, and particularly preferably 300 nm or more and 5 μm or less. When the average particle diameter of the inorganic particles 31 is 300 nm or more, the inorganic particles 31 are brought into contact with each other and a heat conduction path is easily formed, so that the heat dissipation of the wavelength conversion member 1 can be enhanced. Further, when the average particle diameter of the inorganic particles 31 is within this range, the phosphor particles 20 can be firmly connected to each other, and the strength of the wavelength conversion member 1 can be increased.

The shape of the inorganic particles 31 is not particularly limited, but may be spherical, for example. Further, the inorganic particles 31 may be whisker-like (needle-like) particles or scale-like particles. Whisker-like particles or scale-like particles have a higher contact with other particles than spherical particles, and tend to improve thermal conductivity. Therefore, by using particles having such a shape as the inorganic particles 31, it is possible to enhance the heat dissipation of the binder layer 30. FIG. As the whisker-like inorganic particles 31, for example, particles containing at least one selected from the group consisting of aluminum nitride (AlN), zinc oxide (ZnO) _, and aluminum oxide ( _Al2O3 ) can be used. can. As the scale-like inorganic particles 31, for example, particles containing boron nitride (BN) can be used.

Here, in the wavelength conversion member, when the binder layer is composed of only a plurality of inorganic particles as in Patent Document 1, the inorganic particles and the phosphor particles, and the inorganic particles are in a state of point contact with each other. Conductive paths are not sufficiently formed. As a result, the heat dissipation of the wavelength conversion member becomes insufficient, and the temperature quenching of the phosphor cannot be sufficiently suppressed in some cases. Therefore, in the wavelength conversion member 1 of this embodiment, the surfaces of the phosphor particles 20 are provided with the amorphous portions 32 containing an amorphous inorganic compound. The amorphous portion 32 is made of an inorganic material and has excellent thermal conductivity. Therefore, by providing the amorphous portion 32 on the surface of the phosphor particles 20, the thermal conduction path from the phosphor particles 20 to the inorganic particles 31 is increased. It is possible to suppress temperature quenching.

More specifically, in the wavelength conversion member 1, the binder layer 30 includes a plurality of inorganic particles 31 and an amorphous portion 32 containing an amorphous inorganic compound. Then, as shown in FIG. 2 , the inorganic particles 31 are interposed between adjacent phosphor particles 20 to connect the phosphor particles 20 . Although it is preferable that the inorganic particles 31 are in contact with each other, adjacent inorganic particles 31 may not be in contact with each other and the amorphous portion 32 may be interposed therebetween. The amorphous portion 32 preferably exists so as to be in contact with at least the surface of the phosphor particles 20, and may also exist between the phosphor particles 20 and the inorganic particles 31 and between the adjacent inorganic particles 31. more preferred. As a result, in the binder layer 30, both the inorganic particles 31 and the amorphous portion 32 serve as heat conduction paths. Therefore, the heat from the phosphor particles 20 generated by excitation with high-density light is efficiently dissipated to the outside of the wavelength converter 10 through both the inorganic particles 31 and the amorphous portion 32 . As a result, temperature rise of the entire wavelength converter 10 is less likely to occur, so temperature quenching of the phosphor particles 20 is suppressed, and high-output light emission can be obtained.

The amorphous portion 32 preferably contains an amorphous inorganic compound. Specifically, the amorphous portion 32 may be a portion composed only of an amorphous inorganic compound, or may be a portion composed of a mixture of an amorphous inorganic compound and a crystalline inorganic compound. . Also, the amorphous portion 32 may be a portion in which a crystalline inorganic compound is dispersed inside an amorphous inorganic compound. When an amorphous inorganic compound and a crystalline inorganic compound are mixed, the amorphous inorganic compound and the crystalline inorganic compound may have the same chemical composition, or may have different chemical compositions. may have

The inorganic particles 31 and the amorphous portion 32 contain the same metal element, and the metal element is preferably at least one selected from the group consisting of alkali metals, alkaline earth metals, transition metals, base metals and semi-metals. That is, the inorganic compound forming the inorganic particles 31 and the amorphous inorganic compound forming the amorphous portion 32 contain at least the same metal element. However, the inorganic compound forming the inorganic particles 31 and the amorphous inorganic compound forming the amorphous portion 32 may have the same chemical composition, or may have different chemical compositions. Specifically, when the metal element is zinc, both the inorganic compound forming the inorganic particles 31 and the amorphous inorganic compound forming the amorphous portion 32 may be zinc oxide (ZnO). Alternatively, although the inorganic compound forming the inorganic particles 31 is ZnO, the amorphous inorganic compound forming the amorphous portion 32 may be a zinc-containing oxide other than ZnO.

When the amorphous portion 32 is a portion in which an amorphous inorganic compound and a crystalline inorganic compound are mixed, the amorphous inorganic compound and the crystalline inorganic compound may have the same chemical composition. , and may differ from each other in chemical composition.

In the wavelength conversion member 1, the inorganic particles 31 and the amorphous portion 32 preferably contain an oxide of at least one metal element selected from the group consisting of alkali metals, alkaline earth metals, transition metals, base metals and semi-metals. . Since such an oxide of a metal element has high thermal conductivity, it is possible to improve the heat dissipation of the binder layer 30 and suppress temperature quenching of the phosphor particles 20 .

The metal element oxide contained in both the inorganic particles 31 and the amorphous portion 32 is preferably at least one selected from the group consisting of zinc oxide, magnesium oxide, and a composite of zinc oxide and magnesium oxide. Since the oxides of these metal elements have higher thermal conductivity, it is possible to improve the heat dissipation of the binder layer 30 . Further, as will be described later, by using oxides of these metal elements, it is possible to form the amorphous portion 32 by a simple method.

In the wavelength conversion member 1, the inorganic particles 31 and the amorphous portion 32 may contain a nitride of at least one metal element selected from the group consisting of alkali metals, alkaline earth metals, transition metals, base metals and semimetals. good. Since nitrides of these metal elements also have high thermal conductivity, it is possible to improve the heat dissipation of the binder layer 30 . Boron nitride (BN) can be given as a nitride of a metal element contained in both the inorganic particles 31 and the amorphous portion 32 .

As described above, in this embodiment, the inorganic particles 31 and the amorphous portion 32 contain the same metal element. However, the amorphous portion 32 may contain metal elements that are not contained in the inorganic particles 31 . Specifically, when the inorganic particles 31 are made of zinc oxide (ZnO), the amorphous portion 32 contains at least zinc oxide. However, the amorphous portion 32 may contain silicon other than zinc oxide. Although the route of silicon incorporation is not particularly limited, for example, silicon may be incorporated as an impurity during manufacturing and segregated in the amorphous portion 32 . Even when the amorphous portion 32 contains a metal element that is not contained in the inorganic particles 31, the amorphous portion 32 is made of an inorganic compound and has high thermal conductivity. can be increased.

When the inorganic particles 31 are made of zinc oxide and the amorphous portion 32 contains zinc oxide and silicon, the silicon is preferably contained as an oxide. Moreover, the oxide of silicon may be crystalline or amorphous.

As described above, organic substances have low thermal conductivity, so if the binder layer 30 contains an organic substance, there is a possibility that temperature quenching of the phosphor will occur. Further, when the organic matter is irradiated with high-power excitation light, the organic matter may be discolored or scorched, and the light output efficiency of the wavelength conversion member may be lowered. Therefore, the amorphous portion 32 is preferably made of an inorganic compound, and preferably contains as little organic matter as possible. However, the amorphous portion 32 may contain an organic substance of an impurity level that does not affect the thermal conductivity.

Since the wavelength conversion member 1 shown in FIG. 1 can convert the wavelength of incident light only by the wavelength conversion body 10, the wavelength conversion body 10 alone can be used in a light emitting device. However, as shown in FIG. 3, the wavelength conversion member 1A of this embodiment preferably includes a wavelength conversion body 10 and a substrate 40 that supports the wavelength conversion body 10 . By using the substrate 40, the mechanical durability of the wavelength converter 10 can be enhanced. In addition, by using the substrate 40, the heat of the wavelength converter 10 caused by excitation with high-density light can be efficiently dissipated to the outside through the substrate 40. FIG. Therefore, temperature quenching of the phosphor particles 20 can be suppressed, and high-power light emission can be obtained.

The substrate 40 can be brought into close contact with the wavelength converter 10 by adhering it to the binder layer 30 forming the wavelength converter 10 . Therefore, the wavelength converter 10 may be directly provided on the surface of the substrate 40 as shown in FIG. Also, the wavelength converter 10 may be indirectly provided on the surface of the substrate 40 . For example, between the substrate 40 and the wavelength conversion body 10, there may be provided a member that has excellent adhesion to the substrate 40 and is fixed to the wavelength conversion body 10. FIG. As such a member, for example, a member made of a metal thin film, an oxide thin film, or a combination thereof can be used.

The substrate 40 is not particularly limited as long as it can support the wavelength converter 10. For example, at least one substrate selected from the group consisting of a transparent substrate, a metal substrate and a ceramic substrate can be used. A glass substrate can be mentioned as a transparent substrate. Metal substrates may include copper substrates or stainless steel substrates. Ceramic substrates include sapphire substrates and aluminum nitride substrates. When the substrate 40 is made of a metal substrate, the heat generated in the wavelength converter 10 can be efficiently dissipated because the metal substrate generally has high thermal conductivity. Further, when the substrate 40 is made of a ceramic substrate, the difference in thermal expansion coefficient between the substrate 40 and the wavelength converter 10 is small, so the wavelength converter 10 is difficult to separate from the substrate 40 . Among ceramic substrates, a sapphire substrate and an aluminum nitride substrate are more preferable because of their high heat resistance.

In the wavelength conversion members 1 and 1A, the thickness of the wavelength conversion body 10 is not particularly limited, but is preferably 40 μm to 400 μm, more preferably 80 μm to 200 μm. When the thickness of the wavelength conversion body 10 is within the above range, relatively high heat dissipation can be maintained.

Thus, the wavelength conversion members 1 and 1A according to the present embodiment include multiple phosphor particles 20 and multiple inorganic particles 31 . The surface of the phosphor particle 20 has an amorphous portion 32 containing an amorphous inorganic compound. The inorganic particles 31 and the amorphous portion 32 contain the same metal element, and the metal element is at least one selected from the group consisting of alkali metals, alkaline earth metals, transition metals, base metals and semimetals. Since both the inorganic particles 31 and the amorphous portion 32 contain an inorganic compound, they have high thermal conductivity. Therefore, in the binder layer 30, since both the inorganic particles 31 and the amorphous portion 32 serve as heat conduction paths, the heat of the wavelength converter 10 can be efficiently dissipated to the outside even when high-power excitation light is irradiated. can be done. As a result, temperature quenching of the phosphor particles 20 is suppressed, and high-power light emission can be obtained.

Further, as shown in FIG. 2, the amorphous portion 32 fills not only the surfaces of the phosphor particles 20 but also the voids between the phosphor particles 20 and the inorganic particles 31 and the voids between the adjacent inorganic particles 31. can be provided to Therefore, it is possible to reduce voids that remain inside the binder layer 30 and reduce the thermal conductivity, thereby improving the thermal conductivity of the binder layer 30 as a whole.

In wavelength conversion members 1 and 1A, the total volume of phosphor particles 20 is preferably larger than the total volume of inorganic particles 31 . By increasing the total volume of the phosphor particles 20, the packing density of the phosphor is increased. Therefore, it is possible to further increase the density of the output light from the phosphor particles 20 in the wavelength conversion members 1 and 1A.

It is also preferable that the total volume of the inorganic particles 31 is larger than the total volume of the phosphor particles 20 in the wavelength conversion members 1 and 1A. By increasing the total volume of the inorganic particles 31, the adjacent phosphor particles 20 are easily separated from each other. By separating the phosphor particles 20, even if the phosphor particles 20 are irradiated with high-power excitation light and generate heat, the inorganic particles 31 and the amorphous portion 32 serve as a heat conduction path, and the wavelength converter 10 is efficiently discharged to the outside. It dissipates heat well. Therefore, the heat dissipation of the binder layer 30 is enhanced, and the temperature quenching of the phosphor particles 20 can be suppressed.

In wavelength conversion members 1 and 1A, the average particle size of phosphor particles 20 is preferably larger than the average particle size of inorganic particles 31 . Since the average particle diameter of the inorganic particles 31 is smaller than that of the phosphor particles 20 , the phosphor particles 20 can be connected by an intermolecular force or the like between the inorganic particles 31 to fix the phosphor particles 20 . In addition, by increasing the average particle diameter of the phosphor particles 20, the excitation light emitted from the excitation source can be efficiently absorbed, and the absorbed excitation light can be easily converted into color-tone-controlled fluorescence.

[Method for producing wavelength conversion member]
Next, a method for manufacturing the wavelength conversion members 1 and 1A according to this embodiment will be described. Note that the phosphor particles and the inorganic particles are the same as those described in the above-described wavelength conversion member, so description thereof will be omitted.

The wavelength converter 10 in the wavelength conversion members 1 and 1A can be manufactured by pressurizing and heating phosphor particles and inorganic particles in a state containing moisture. By using such a pressurized heating method, it becomes possible to partially dissolve the inorganic particles 31 and form the amorphous portion 32 on the surface of the phosphor particles 20 .

Specifically, first, the powder of the phosphor particles 20 and the powder of the inorganic particles 31 are mixed to prepare a composite powder. The method of mixing the powder of the phosphor particles 20 and the powder of the inorganic particles 31 is not particularly limited, and may be dry or wet. Further, the powder of the phosphor particles 20 and the powder of the inorganic particles 31 may be mixed in air or in an inert atmosphere.

Next, an acidic aqueous solution or an alkaline aqueous solution is added to the composite powder. By adding an acidic aqueous solution or an alkaline aqueous solution, it becomes possible to accelerate the elution of the inorganic particles 31 . As the acidic aqueous solution, an aqueous solution with a pH of 1 to 3 can be used. As the alkaline aqueous solution, an aqueous solution with a pH of 10 to 14 can be used.

The inorganic particles 31 preferably have solubility in at least one of an acidic aqueous solution and an alkaline aqueous solution. Specifically, the inorganic particles 31 more preferably have solubility in at least one of an acidic aqueous solution of pH 1-3 and an alkaline aqueous solution of pH 10-14. By having solubility in at least one of the acidic aqueous solution and the alkaline aqueous solution, a part of the inorganic compound constituting the inorganic particles 31 dissolves in the pressure heating step. The dissolved inorganic compound enters the surfaces of the phosphor particles 20 , the gaps between the phosphor particles 20 and the inorganic particles 31 , and the gaps between the inorganic particles 31 in the composite powder. Then, by removing moisture in the composite powder in this state, inorganic particles constituting the inorganic particles 31 are formed on the surfaces of the phosphor particles 20, between the phosphor particles 20 and the inorganic particles 31, and between the inorganic particles 31. It becomes possible to form an amorphous portion 32 containing a compound.

The phosphor particles 20 preferably have at least one of acid resistance and alkali resistance. Specifically, it is more preferable that the phosphor particles 20 have no solubility in at least one of an acidic aqueous solution of pH 1-3 and an alkaline aqueous solution of pH 10-14. By having at least one of acid resistance and alkali resistance, the particle shape of the phosphor particles 20 can be maintained even in the pressure heating process, so it is possible to suppress the decrease in the luminous efficiency of the phosphor particles 20. .

When the above acidic aqueous solution is added to the composite powder, the inorganic particles 31 preferably have solubility in the acidic aqueous solution, and the phosphor particles 20 preferably have acid resistance. Moreover, when the above-described alkaline aqueous solution is added to the composite powder, the inorganic particles 31 preferably have solubility in the alkaline aqueous solution, and the phosphor particles 20 preferably have alkali resistance.

Next, the inside of the mold is filled with a composite powder containing an acidic aqueous solution or an alkaline aqueous solution. After filling the composite powder into the mold, the mold may be heated as necessary. By applying pressure to the composite powder inside the mold, a high temperature and high pressure state is created inside the mold. At this time, the phosphor particles 20 and the inorganic particles 31 are densified, and at the same time, the inorganic particles 31 are connected to each other and the phosphor particles 20 and the inorganic particles 31 are connected to each other. In addition, in a high-temperature and high-pressure state, the inorganic compound constituting the inorganic particles 31 dissolves in the aqueous solution, and the dissolved inorganic compound spreads over the surfaces of the phosphor particles 20, the gaps between the phosphor particles 20 and the inorganic particles 31, and the inorganic particles. It penetrates into the voids between the particles 31 . By removing moisture in this state, the amorphous portion 32 containing the inorganic compound that constitutes the inorganic particles 31 is formed.

The heating and pressing conditions for the composite powder containing the acidic aqueous solution or the alkaline aqueous solution are not particularly limited as long as the dissolution of the inorganic particles 31 proceeds. For example, it is preferable to heat a composite powder containing an acidic aqueous solution or an alkaline aqueous solution to 50 to 300° C., preferably 80 to 250° C., and then pressurize it at a pressure of 10 to 600 MPa, preferably 50 to 400 MPa.

Then, the wavelength conversion body 10 can be obtained by removing the molded body from the inside of the mold. The method for fixing the wavelength converter 10 to the substrate 40 is not particularly limited, and for example, it may be fixed using an adhesive. Further, the obtained wavelength conversion body 10 and the substrate 40 may be fixed together by applying pressure.

As described above, in the wavelength conversion members 1 and 1A of the present embodiment, the binder layer 30 including the inorganic particles 31 and the amorphous portion 32 is formed by using the pressure heating method, and the surface of the phosphor particles 20 is can be provided with an amorphous portion 32 . In addition, the manufacturing method of the wavelength conversion members 1 and 1A is not limited to the above-described pressure heating method, and for example, a warm isostatic pressing method (WIP) can also be applied.

In the manufacturing method described above, the inside of the mold is filled with the composite powder containing the acidic aqueous solution or the alkaline aqueous solution, but the present embodiment is not limited to such an aspect. That is, after filling the inside of the mold with the composite powder, the aqueous solution may be added to the composite powder by dripping an acidic aqueous solution or an alkaline aqueous solution onto the composite powder. In addition, in the above-described manufacturing method, pressurization and heating are performed using a mold, but the present embodiment is not limited to such an aspect. That is, in the production method of the present embodiment, an autoclave may be used instead of the mold to pressurize and heat the raw material. Alternatively, the raw material may be pressurized and heated using a vacuum press molding machine.

A sol-gel method is conventionally known as a method for forming an amorphous inorganic compound. However, since the sol-gel method uses an organic substance as a raw material, a large amount of the organic substance remains in the resulting inorganic compound. In a wavelength conversion member using such an inorganic compound, the residual organic matter reduces the thermal conductivity and tends to raise the temperature, so temperature quenching of the phosphor tends to occur, and the light output efficiency deteriorates. end up In addition, the temperature rise of the phosphor during light emission causes the organic matter to burn and become colored, resulting in deterioration of the light output efficiency. However, in the method of manufacturing the wavelength conversion members 1 and 1A of the present embodiment, the amorphous portion 32 is formed by heating and pressing the inorganic particles 31, so the binder layer 30 contains almost no organic matter. Therefore, the obtained wavelength conversion members 1 and 1A can suppress the temperature quenching of the phosphor and exhibit high light output efficiency.

EXAMPLES Hereinafter, the present embodiment will be described in more detail with reference to examples, but the present embodiment is not limited to the examples.

[Preparation of test sample]
First, YAG particles (Y ₃ Al ₅ O ₁₂ :Ce ³⁺ ) having an average particle diameter _D50 of about 19 μm were prepared as phosphor particles. Zinc oxide particles (ZnO) having an average particle diameter _D50 of about 1 μm were prepared as inorganic particles. Then, YAG particles and zinc oxide particles were dry-mixed at a rate of 50% by volume to obtain 0.52 g of composite powder.

Next, the obtained composite powder was put into a cylindrical molding die (Φ10) having an internal space. Further, 100 μL of 1 M acetic acid was added to the composite powder filled inside the molding die. Then, the composite powder containing acetic acid was pressurized at 400 MPa and 80° C. for 1 hour to obtain a test sample of this example.

[Evaluation of test sample]
(Transmission electron microscope observation)
The resulting test samples were observed with a transmission electron microscope. FIG. 4 shows the result of observing the test sample with a transmission electron microscope. As shown in FIG. 4, it can be seen that a plurality of zinc oxide particles (ZnO particles) having a particle diameter smaller than that of the phosphor are in contact with the surface of the phosphor. Furthermore, it can be seen that an inorganic compound exists on the surface of the phosphor, between the phosphor and zinc oxide particles, and between adjacent zinc oxide particles.

Further, FIG. 5(a) shows the result of further enlarging the photograph of FIG. 4(c), and FIG. 5(b) shows the electron beam diffraction pattern of the inorganic compound portion in FIG. 5(a). As shown in FIG. 5(b), the electron diffraction pattern of the inorganic compound showed no pattern indicating crystallinity, indicating that the inorganic compound present on the surface of the phosphor is amorphous.

FIG. 6 shows the result of observing the test sample with a transmission electron microscope and enlarging a portion different from FIG. As in FIG. 4, it can be seen that a plurality of zinc oxide particles having a particle diameter smaller than that of the phosphor are in contact with the surface of the phosphor. Furthermore, it can be seen that an inorganic compound exists on the surface of the phosphor, between the phosphor and zinc oxide particles, and between adjacent zinc oxide particles.

Further, FIG. 7(a) shows the result of further enlarging the photograph of FIG. 6(c), and FIG. 7(b) shows the electron beam diffraction pattern of the inorganic compound portion in FIG. 7(a). As shown in FIG. 7B, a pattern indicating crystallinity was observed in the electron beam diffraction pattern of the inorganic compound. That is, a slight lattice indicating crystallinity was observed in the portion of the inorganic compound in FIG. 7(a).

From these facts, it can be seen that the test sample has both a portion consisting only of an amorphous inorganic compound and a portion containing a mixture of an amorphous inorganic compound and a crystalline inorganic compound as an amorphous portion. .

(Energy dispersive X-ray analysis (EDX))
Energy dispersive X-ray analysis (EDX) was performed on the obtained test samples. FIG. 8 shows scanning transmission electron micrographs (STEM) as well as mapping data for oxygen (O), zinc (Zn), silicon (Si), yttrium (Y) and aluminum (Al).

From FIG. 8, yttrium and aluminum are observed only in the phosphor particles, and are not observed in the zinc oxide particles and the amorphous portion, so it is presumed that yttrium and aluminum are not eluted from the phosphor particles. Moreover, since both zinc and oxygen are observed in the zinc oxide particles and the amorphous portion, it is found that the zinc oxide particles and the amorphous portion contain zinc, which is the same metal element.

As a result of the EDX analysis shown in FIG. 8, it was confirmed that the test sample contained silicon as an impurity, and that silicon was segregated in the amorphous portion. Therefore, it can be seen that the amorphous portion may contain a silicon compound in addition to zinc oxide generated by elution from the zinc oxide particles.

FIG. 9 shows the results of energy dispersive X-ray analysis of the test sample. FIG. 9A shows mapping data of oxygen (O), silicon (Si), and zinc (Zn) in addition to the bright field image (BF). FIG. 9(b) shows the result of simple quantification after extracting the spectrum from the mapping data for the amorphous portion indicated by “◯” in FIG. 9(a). FIG. 10 shows the result of performing energy dispersive X-ray analysis on the test sample, and shows the result of observing a portion different from that in FIG. FIG. 10(a) shows mapping data of oxygen (O), silicon (Si), and zinc (Zn) in addition to a bright field image (BF). FIG. 10(b) shows the result of simple quantification after extracting the spectrum from the mapping data for the amorphous portion indicated by “◯” in FIG. 10(a).

From FIG. 9(b), it can be seen that the number of silicon atoms in the amorphous portion shown in FIG. 9(a) is larger than that of zinc atoms. On the other hand, it can be seen from FIG. 10(b) that the number of silicon atoms in the amorphous portion shown in FIG. 10(a) is smaller than that of zinc atoms. Therefore, it can be seen that an amorphous inorganic compound can be formed regardless of whether zinc atoms or silicon atoms are abundant in the amorphous portion.

Although the present embodiment has been described above, the present embodiment is not limited to these, and various modifications are possible within the scope of the gist of the present embodiment.

The entire contents of Japanese Patent Application No. 2018-135828 (filing date: July 19, 2018) are incorporated herein.

According to the present disclosure, it is possible to provide a wavelength conversion member that is excellent in heat dissipation even when irradiated with high-power excitation light and capable of suppressing temperature quenching of phosphors.

Reference Signs List 1, 1A wavelength conversion member 20 phosphor particles 31 inorganic particles 32 amorphous portion

Claims (8)

including a plurality of phosphor particles and a plurality of inorganic particles,
The surface of the phosphor particles has an amorphous portion containing an amorphous inorganic compound,
The inorganic particles and the amorphous portion contain the same metal element, and the metal element is at least one selected from the group consisting of alkali metals, alkaline earth metals, transition metals, base metals and semimetals ,
In the wavelength conversion member , the amorphous portion is present on the surface of the phosphor particles and between adjacent inorganic particles . The wavelength conversion member according to claim 1 , wherein the inorganic particles connect adjacent phosphor particles. The wavelength conversion member according to claim 1 or 2 , wherein the inorganic particles have an average particle size of 300 nm or more and 30 µm or less. The wavelength conversion member according to any one of claims 1 to 3 , wherein the inorganic particles are soluble in at least one of an acidic aqueous solution and an alkaline aqueous solution. The wavelength conversion member according to any one of claims 1 to 4 , wherein the inorganic particles and the amorphous portion contain an oxide of the metal element. 6. The wavelength conversion member according to claim 5 , wherein the oxide of the metal element is at least one selected from the group consisting of zinc oxide, magnesium oxide, and a composite of zinc oxide and magnesium oxide. The wavelength conversion member according to any one of claims 1 to 6 , wherein the phosphor particles have at least one of acid resistance and alkali resistance. The wavelength conversion member according to any one of claims 1 to 7 , wherein the average particle size of the phosphor particles is larger than the average particle size of the inorganic particles.

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