TW202436591A - Phosphor and light emitting device - Google Patents

Abstract

The phosphor powder of the present invention is represented by the general formula M _x(Si,Al) ₂(N,O) _3+y(where M is Li and one or more alkaline earth metal element, 0.52≦x≦0.90, O≦y≦0.36), wherein the phosphor powder contains phosphor particles in which a part of M is replaced with element Ce, and a portion of the surface of the phosphor particle includes an altered surface portion that is raised.

Description

Fluorescent body and light emitting device

The present invention relates to a fluorescent body and a light emitting device.

In order to manufacture white LEDs (Light Emitting Diodes), a phosphor is usually used. That is, a phosphor is used as a wavelength conversion material for obtaining white light from blue light emitted by a blue LED. With the popularization of white LEDs for lighting purposes and the discussion of using white LEDs for image display devices, the development of phosphors that can convert light into longer wavelengths than blue light continues.

As one of such phosphors, for example, Patent Document 1 describes a phosphor represented by the general formula M _x (Si, Al) ₂ (N, O) _3±y (however, M is Li and one or more alkaline earth metal elements, 0.52≦x≦0.9, 0.06≦y≦0.23), a part of M is substituted by Ce element, Si/Al atomic ratio is 1.5 to 6, O/N atomic ratio is 0 to 0.1, 5 to 50 mol% of M is Li, and 0.5 to 10 mol% of M is Ce. [Prior Art Document] [Patent Document]

[Patent Document 1] Japanese Patent No. 5969391

[The problem that the invention wants to solve]

However, the inventors of this case have found through research that the fluorescent properties of the fluorescent body described in the above-mentioned patent document 1 still have room for improvement. [Means for solving the problem]

The inventors of this case conducted this research with the aim of providing a fluorescent powder having excellent fluorescent properties.

The inventors of this case, as a result of their discussions, even completed the invention provided below.

According to one aspect of the present invention, the following phosphors and light-emitting devices are provided. 1. A phosphor powder, comprising phosphor particles represented by the general formula M _x (Si,Al) ₂ (N,O) _3±y , wherein a portion of M is substituted by a Ce element, but M is Li and one or more alkali earth metal elements, 0.52≦x≦0.90, 0≦y≦0.36, and a portion of the surface of the phosphor particles contains a raised surface modification portion. 2. The phosphor powder as described in 1., wherein the surface modification portion comprises a flat structure. 3. The phosphor powder as described in 1. or 2., wherein the surface modification portion comprises an oxide or a hydroxide. 4. The fluorescent powder as described in any one of 1. to 3., wherein, in the volume frequency particle size distribution of the fluorescent powder measured by laser diffraction scattering method, when the particle size at the point where the cumulative volume from the small particle side becomes 50% is D ₅₀ , D ₅₀ is 8 μm or more and 25 μm or less. 5. The fluorescent powder as described in any one of 1. to 4., wherein the composition of the fluorescent material is such that 2 mol% or more and 5 mol% or less of M is Ce. 6. A fluorescent body, which is a fluorescent body powder as described in any one of 1. to 5., wherein, when the diffuse reflectance spectrum of the fluorescent body is measured in the wavelength range of 500-850nm, the difference X1-X2 between the diffuse reflectance X1 for light of wavelength 700nm and the diffuse reflectance X2 for light of peak fluorescence wavelength when irradiated with excitation light of 455nm is 3.0% or less. 7. A fluorescent body, which is a fluorescent body powder as described in any one of 1. to 6., wherein the diffuse reflectance X2 for light of peak fluorescence wavelength when irradiated with excitation light of 455nm is 88% or more and 97% or less. 8. A fluorescent body, which is a fluorescent body powder as described in any one of 1. to 7., wherein the wavelength of the fluorescent peak when irradiated with 455nm excitation light is 580nm to 610nm. 9. A fluorescent body, which is a fluorescent body powder as described in any one of 1. to 8., wherein the half-width of the fluorescent peak when irradiated with 455nm excitation light is 130nm to 142nm. 10. A light-emitting device, which comprises the fluorescent body powder as described in any one of 1. to 9. and a light-emitting light source. [Effect of the invention]

According to the present invention, a fluorescent powder having excellent fluorescent properties and a light-emitting device using the same can be provided.

The following is a description of the embodiments of the present invention using drawings. In all drawings, the same components are given the same symbols and the description is omitted as appropriate. In addition, the drawings are schematic diagrams and do not correspond to the actual size ratios.

In this manual, the description of "X~Y" in the description of the numerical range means greater than X and less than Y unless otherwise specified. For example, "1~5 mass%" means "greater than 1 mass% and less than 5 mass%".

<Phosphor> The phosphor powder of this embodiment comprises phosphor particles represented by the general formula _Mx (Si,Al) ₂ (N,O) _3±y , wherein M is Li and one or more alkali earth metal elements, 0.52≦x≦0.90, 0≦y≦0.36, and a part of M is substituted by Ce element.

In the fluorescent powder of this embodiment, at least a part of the surface of the fluorescent particles includes a raised surface modified portion.

According to the inventors of the present invention, by annealing the fluorescent particles in an open system at a temperature lower than the firing temperature in a reducing gas environment, it is known that the surface of the fluorescent particles represented by the general formula M _x (Si,Al) ₂ (N,O) _3±y can be appropriately modified, although the detailed mechanism is unclear. That is, by the annealing treatment, fluorescent particles having a plurality of surface modified portions formed on the surface of the fluorescent particles can be obtained. It is understood that the fluorescent powder containing the fluorescent particles having such surface modified portions on the surface can improve the internal quantum efficiency, the diffuse reflectivity at 600nm and other luminescence characteristics, and thus the present invention is completed.

Generally, it is known that the pulverization process in the production step of fluorescent powder forms pulverized flakes of the fluorescent body, and the pulverized flakes are attached to the fluorescent particles. However, the inventors of the present case have confirmed that when the annealing process is not performed, although the pulverized flakes of the fluorescent body are attached to the surface of the fluorescent particles, the surface modified portion is not formed.

The surface modified portion on the surface of the fluorescent particles of this embodiment is different from the above-mentioned fluorescent powder pieces in at least one of the shapes, attachment patterns and compositions.

From the SEM photograph of the fluorescent particle, it can be seen that the surface modified portion may have a flat structure instead of having a crushed surface on the particle surface like a crushed piece. In addition, the surface modified portion may have a structure without a concave portion between the surface of the fluorescent particle and the surface.

Most of the surface modified part will not fall off from the surface by washing the fluorescent particles with water, but will remain attached to the surface. However, most of the crushed pieces will fall off from the surface by washing the fluorescent particles with water. The surface modified part will be more strongly attached to the surface of the fluorescent particles chemically and/or physically than the crushed pieces.

Furthermore, the results of the chemical composition analysis of the fluorescent powder show that the oxygen content after the annealing treatment is higher than that before the annealing treatment. From such results, although the detailed mechanism is not clear, it is believed that the surface modified part, as a substance whose surface of the fluorescent particles is modified, contains an oxide or hydroxide of the fluorescent.

Furthermore, the surface modified portion is formed on the surface of the phosphor particles by annealing the phosphor represented by the general formula M _x (Si,Al) ₂ (N,O) _3±y . On the other hand, it was confirmed that even if the silicon aluminum oxynitride phosphor whose crystal phase is the β phase (so-called β-type silicon aluminum oxynitride phosphor) is annealed, the surface modified portion is not formed on its surface. Furthermore, even if there are objects attached to the particle surface of the β-type silicon aluminum oxynitride phosphor, they are only the crushed pieces of the phosphor.

As can be seen from the SEM photo of the fluorescent particle, the plurality of surface modification parts may include a group of particles in which a portion of the surface of a fluorescent particle is adsorbed at intervals, or a portion of the surface is not exposed and connected to form a coating layer. In any case, it is preferred that at least a portion of the surface of the fluorescent particle has a portion exposed. In addition, the plurality of surface modification parts may form a plurality of strip-shaped coating layers, and the fluorescent particle may not have a strip-shaped coating layer.

In recent years, light-emitting devices have become increasingly high-output and thinner, and the operating environment of light-emitting devices in which fluorescent bodies are installed has tended to become increasingly hot. The fluorescent powder of this embodiment can also be used in such a high-temperature environment.

The fluorescent powder of this embodiment is different from the fluorescent material described in Patent Document 1 at least in that it includes a surface modification part attached to the surface of the fluorescent material particles. The fluorescent material of this embodiment has better fluorescent properties than the fluorescent material described in Patent Document 1. For example, in terms of internal quantum efficiency, blue light can be converted into long-wavelength light with good efficiency.

The fluorescent body of this embodiment is further described.

(Crystal structure, chemical composition, etc.) The skeleton structure of the phosphor crystal is formed by bonding (Si, Al)-(N, O) ₄ regular tetrahedrons, and the M element is located in the gap. The composition of the above general formula is established by the parameters such as the valence and amount of the M element, the Si/Al ratio, and the N/O ratio, which are all within the range of maintaining electrical neutrality. For the representative phosphor represented by the above general formula, there is CaAlSiN ₃ in which the M element is Ca and x=1, and Si/Al=1, O/N=0. When a part of Ca in CaAlSiN ₃ is replaced by Eu, it becomes a red phosphor, and when it is replaced by Ce, it becomes a yellow to orange phosphor.

The crystal structure of the phosphor of this embodiment is usually based on CaAlSiN ₃ crystals. One of the characteristics of the phosphor is that the constituent elements and composition vary significantly, resulting in a very high luminescence efficiency even when Ce is activated. In the above general formula, the M element is a combination of the Li element and an alkali earth metal element, and a part of it is replaced by the Ce element that becomes the luminescence center. By using the Li element, and a combination of a divalent alkali earth element and a trivalent Ce element, the average valence of the M element can be controlled within a wide range. In addition, the ion radius of Li ⁺ is very small, and the crystal size can be greatly changed according to its amount, thereby obtaining a variety of fluorescent luminescence. The coefficient x of the M element in the above general formula is 0.52 or more and 0.90 or less, preferably 0.60 or more and 0.90 or less, and more preferably 0.70 or more and 0.90 or less. If the coefficient x exceeds 0.9, that is, it is close to _CaAlSiN3 crystals, and the fluorescence intensity tends to decrease. If the coefficient x is less than 0.52, a large amount of heterophases other than the target crystal phase will be generated, so the fluorescence intensity tends to decrease significantly.

The coefficient y of (N, O) in the above general formula is preferably 0 to 0.36, more preferably 0 to 0.30, and even more preferably 0 to 0.23. Thereby, the fluorescence intensity is improved.

In this embodiment, the O/N atomic ratio (molar ratio) is greater than 0 and less than 0.1, preferably greater than 0.01 and less than 0.08, and more preferably greater than 0.02 and less than 0.07. If the O/N atomic ratio is too large, the amount of heterogeneous phase generation will increase, the luminescence efficiency will decrease, and the covalent bonding of the crystal will decrease, which will tend to cause deterioration of temperature characteristics (reduction of brightness at high temperatures).

The Si/Al atomic ratio (molar ratio) can be determined if the average valence and amount of the M element and the O/N atomic ratio are set to a specific range. The Si/Al atomic ratio is 1.5 to 6, preferably 2 to 4, and more preferably 2.5 to 4.

The Li content in the phosphor is 5-50 mol% of the M element, preferably 15-49 mol%, and more preferably 25-48 mol%. The effect of Li is easy to be exerted when it is above 5 mol%. If it exceeds 50 mol%, the crystal structure of the target phosphor cannot be maintained and heterogeneous phases will be generated, and the luminescence efficiency is easy to decrease. For the sake of caution, it is explained in advance that "Li content" refers to the Li content in the final phosphor, not the amount based on the raw material doping. The vapor pressure of the Li compound used in the raw material is high and it is easy to evaporate. When synthesizing nitrides/oxynitrides at high temperatures, a considerable amount will evaporate. In other words, the amount of Li based on the raw material is greatly deviated from the content in the final product, so it does not represent the Li content in the phosphor.

The Ce content of the luminescent center of the phosphor. If it is too little, the contribution to luminescence tends to decrease. If it is too much, the energy transfer between Ce ³⁺ tends to cause concentration extinction of the phosphor. Therefore, the Ce content is 2~5mol% of the M element, preferably 2.5~5mol%.

The alkaline earth metal element used as the M element in the above general formula may be any element. When Ca is used, high fluorescence intensity is obtained and the crystal structure is stabilized in a wide composition range. Therefore, it is preferable that the M element is Ca. It may also be a combination of multiple alkaline earth metal elements, for example, a part of the Ca element may be replaced by the Sr element.

The crystal structure of the phosphor is an orthorhombic system, and may be the same structure as the aforementioned CaAlSiN ₃ crystal. An example of the lattice constants of the CaAlSiN ₃ crystal is a=0.98007nm, b=0.56497nm, c=0.50627nm. In this embodiment, the lattice constants are usually a=0.93500~0.96500nm, b=0.55000~0.57000nm, c=0.48000~0.50000nm, which are all smaller values compared to the CaAlSiN ₃ crystal. The range of the lattice constants reflects the range of the aforementioned constituent elements and composition.

The crystalline phase present in the phosphor is preferably the above-mentioned single crystalline phase. However, the phosphor may contain a heterophase as long as it does not significantly affect the fluorescent properties. Examples of heterophases that have a low effect on the fluorescent properties when excited by blue light include α-silicon aluminum oxynitride, AlN, LiSi ₂ N ₃ , and LiAlSi ₂ N ₄ . The amount of the heterophase is preferably such that the intensity of the diffraction rays of other crystalline phases is 40% or less relative to the intensity of the strongest diffraction rays of the above-mentioned crystalline phase when evaluated by powder X-ray diffraction method.

The phosphor of this embodiment can be excited by light in a wide wavelength range from ultraviolet light to visible light. For example, when irradiated with blue light of a wavelength of 455nm, sometimes an orange color with a peak wavelength of 580~610nm and a half-width of the fluorescence spectrum of 130~142nm will be exhibited. Such a phosphor is suitable for use in a wide range of light-emitting devices. In addition, the phosphor of this embodiment, like the known nitride and oxynitride-based phosphors represented by _CaAlSiN3 , has excellent heat resistance and chemical stability, and has the characteristic of little reduction in brightness due to temperature increase. Such characteristics are particularly suitable for applications requiring durability.

(Diffuse reflectivity) From another perspective, the diffuse reflectivity X1 of the fluorescent body of this embodiment for light with a wavelength of 700nm is preferably 89% to 98%, more preferably 91% to 98%, and even more preferably 92% to 98%. By controlling X1 within such a numerical range, the luminous intensity tends to be further improved.

From another perspective, the diffuse reflectivity X2 of the fluorescent body of this embodiment for light of the peak wavelength of fluorescence is preferably 88% to 97%, more preferably 90% to 97%, and even more preferably 91% to 97%. By controlling X2 within such a numerical range, the luminous intensity tends to be further improved.

From another perspective, the difference between X2 and X1 (X2-X1) is preferably 3.0% or less, more preferably 2.0% or less, and even more preferably 0.1% or more and 1.8% or less. This further improves the properties of the fluorescent body.

From another perspective, when the diffuse reflectivity for light with a wavelength of 800 nm is X3, the difference between X3 and X1 (X3-X1) is preferably 0.1% to 1.4%, more preferably 0.1% to 1.0%, and even more preferably 0.1% to 0.8%. In this way, the characteristics of the fluorescent body are further improved.

(Particle size distribution) By appropriately designing the particle size distribution of the particles (fluorescent particles) contained in the fluorescent body of this embodiment, it is sometimes possible to further improve the quantum efficiency or to further improve the balance of various performances. Specifically, the volume-based cumulative 50% diameter D50 (so-called median diameter) of the fluorescent body of this embodiment measured by the laser diffraction scattering method is preferably 8 μm or more and 25 μm or less, more preferably 10 μm or more and 20 μm or less, and even more preferably 12 μm or more and 20 μm or less.

From another point of view, the volume basis cumulative 10% diameter _D10 of the phosphor of the present embodiment measured by the laser diffraction scattering method is preferably 2 μm or more and 15 μm or less, and more preferably 5 μm or more and 12 μm or less. A larger value of _D10 corresponds to a smaller amount of fine powder (excessively fine phosphor particles that tend to reduce the conversion efficiency of blue light) in the phosphor. Therefore, by making _D10 a larger value, there is a tendency for the conversion efficiency of blue light to be higher.

From another perspective, the volume basis cumulative 90% diameter D ₉₀ of the phosphor of the present embodiment measured by the laser diffraction scattering method is preferably 15 μm to 50 μm, more preferably 18 μm to 40 μm. If D ₉₀ is not too large, it corresponds to a situation where the amount of coarse particles in the phosphor is small. A phosphor with D ₉₀ not too large is effective in reducing the chromaticity deviation of the light-emitting device. (Absorbance) From another perspective, the absorbance A ₇₀₀ of the phosphor of the present embodiment at a wavelength of 700 nm is preferably 1% to 10%, more preferably 2% to 9%, and even more preferably 3% to 9%. Thereby, the internal quantum efficiency is improved.

From another perspective, the absorbance A600 of the fluorescent body of this embodiment at a wavelength of 600nm is preferably 1% to 13%, more preferably 2% to 12%, and even more preferably 3% to 11%. It is believed that by making _A600 not too large, the fluorescent properties will be further improved.

From another perspective, the internal quantum efficiency of the fluorescent body of this embodiment for 455nm excitation light should be 80% or more. From another perspective, the external quantum efficiency of the fluorescent body of this embodiment for 455nm excitation light should be 70% or more.

(Manufacturing method) The phosphor of this embodiment can be manufactured, for example, by a series of steps including the following (1) to (4). From the viewpoint of appropriately adjusting the formation of the surface modification portion in the phosphor surface, the phosphor manufacturing steps preferably include (4) an annealing step. (1) Preparation step of raw material mixed powder (2) Firing step (3) Pulverization step of the sintered product (4) Annealing step

Below, (1) to (4) are explained in detail.

(1) Preparation step of raw material mixed powder In the preparation step of raw material mixed powder, suitable raw material powders are usually mixed to obtain raw material mixed powder. As for raw material powder, nitrides of constituent elements, i.e. silicon nitride, aluminum nitride, lithium nitride, barium nitride, nitrides of alkaline earth elements (e.g. calcium nitride), etc. are suitable. Generally speaking, nitride powders are unstable in the air, and the surface of particles is covered with an oxide layer. Even when nitride raw materials are used, as a result, a certain amount of oxides will still be contained in the raw materials. In the case of controlling the O/N ratio of the phosphor, while taking these into consideration, when oxygen is insufficient, part of the nitride can also be converted into oxides (including compounds that become oxides by heat treatment). Examples of oxides include barium oxide, etc.

Among the raw material powders, the volatility of lithium compounds due to heating is significant, and sometimes most of them are volatilized depending on the firing conditions. Therefore, the amount of lithium compounds to be added is preferably determined by considering the volatility during the firing process, which depends on the firing conditions.

Among the nitride raw material powders, lithium nitride, barium nitride, and nitrides of alkaline earth elements react violently with moisture in the air. Therefore, it is better to perform such operations in a glove box replaced with an inactive ambient gas. Considering the efficiency of the operation, (i) first, weigh a predetermined amount of silicon nitride, aluminum nitride, and various oxide raw material powders that can be operated in air, and mix them thoroughly in air in advance to prepare a pre-mixed powder, (ii) then, in the glove box, mix the pre-mixed powder with materials that easily react with moisture, such as lithium nitride, to prepare a raw material mixed powder.

(2) Firing step The firing step is to fill the raw material mixed powder prepared in (1) the raw material mixed powder preparation step into an appropriate container and heat it using a kiln or the like.

The firing temperature is preferably 1600~2000℃, and more preferably 1700~1900℃, from the perspective of allowing the reaction to proceed fully and from the perspective of suppressing the volatility of lithium. The firing time is preferably 2~24 hours, and more preferably 4~16 hours, from the perspective of allowing the reaction to proceed fully and from the perspective of suppressing the volatility of lithium.

The firing step is preferably carried out in a nitrogen environment. In addition, it is better to adjust the pressure of the firing environment gas appropriately. Specifically, the pressure of the firing environment gas is preferably 0.5MPa･G or more. Especially when the firing temperature is above 1800℃, there is a tendency for the fluorescent body to decompose easily, but the high pressure of the firing environment gas can suppress the decomposition of the fluorescent body. By the way, considering the industrial productivity, it is better that the pressure of the firing environment gas is less than 1MPa･G.

The container filled with the raw material mixed powder is preferably made of a material that is stable in a high temperature nitrogen environment and does not react with the raw material mixed powder and its reaction products. The material of the container is preferably boron nitride.

(3) Crushing step of the calcined product (2) Since the obtained calcined product is usually in block form, it is better to mechanically apply force and crush it into a certain degree of small size. For crushing, various devices such as crusher, mortar, ball mill, vibration mill, jet mill, comminuter, etc. can be used. It is also possible to combine two or more of these devices for crushing. In the embodiment described below, a coarse crushed product of the calcined product is first obtained using a comminuter, and then the coarse crushed product is crushed into a finer size using a jet mill. The details are unclear, but by performing such crushing, it is easy to obtain a fluorescent body with a diffuse reflectance X1 of 88% or more and 99.9% or less.

(4) Annealing treatment Annealing treatment is to fill a predetermined amount of phosphor into a crucible, and heat the phosphor at a predetermined temperature and for a predetermined time in a furnace in a reducing gas environment containing hydrogen. Specifically, the annealing temperature is lower than the above-mentioned firing temperature, preferably about 700~1200℃. The annealing time is appropriately set depending on the annealing temperature. The ambient gas during annealing is reducing, for example, preferably nitrogen (inactive gas) containing about 4 volume % of hydrogen (reducing gas). It is better to use an uncovered crucible and fill the crucible with a small amount of phosphor. During the annealing process, the mixed gas environment and the surface of the phosphor can be fully contacted. It is better to use a dense crucible made of alumina. It can suppress the reaction between the components contained in the furnace and the crucible and the gas environment from changing unexpectedly. The detailed mechanism is uncertain, but it is believed that the surface of the phosphor can be appropriately modified by annealing treatment in which the phosphor is heated at a relatively low temperature in an open system in a reducing mixed gas environment.

<Light-emitting device, image display device, and lighting device> By combining the fluorescent body of this embodiment with a light-emitting light source, a light-emitting device can be obtained. The light-emitting light source typically emits ultraviolet light or visible light. For example, when the light-emitting light source is a blue LED, the blue light emitted from the light-emitting light source hits the fluorescent body, and then the blue light is converted into light of a longer wavelength. That is, the fluorescent body of this embodiment can be used as a wavelength conversion material that converts light into light of a longer wavelength than the blue light.

An example of a specific structure of a light-emitting device is described with reference to FIG1 . FIG1 is a schematic cross-sectional view showing an example of a structure of a light-emitting device. As shown in FIG1 , a light-emitting device 100, a light-emitting element 120 (light-emitting light source), a heat sink 130, a housing 140, a first lead frame 150, a second lead frame 160, a bonding wire 170, a bonding wire 172, and a composite 40 are provided.

The light emitting element 120 is a semiconductor element that emits excitation light. The semiconductor element may be a light emitting diode (LED) or a light emitting element (LD) with a resonator. As the light emitting element 120, for example, an LED chip that emits light with a wavelength of 300 nm to 500 nm, which is equivalent to near-ultraviolet light to blue light, may be used.

The light-emitting element 120 is mounted on a specific area on the heat sink 130. By mounting the light-emitting element 120 on the heat sink 130, the heat dissipation of the light-emitting element 120 can be improved. In addition, a packaging substrate can be used instead of the heat sink 130. One of the electrodes (not shown) disposed on the top surface side of the light-emitting element 120 is connected to the surface of the first lead frame 150 via a bonding wire 170 such as a gold wire. In addition, another electrode (not shown) formed on the top surface of the light-emitting element 120 is connected to the surface of the second lead frame 160 via a bonding wire 172 such as a gold wire.

The housing 140 is provided with a funnel-shaped recessed portion whose aperture gradually expands from the bottom to the top. The light-emitting element 120 is disposed on the bottom of the recessed portion. The wall surface of the recessed portion surrounding the light-emitting element 120 functions as a reflector.

The composite 40 is filled in the above-mentioned recessed portion whose wall is formed by the outer shell 140. The composite 40 is a wavelength conversion component that converts the excitation light emitted by the light-emitting element 120 into light of a longer wavelength. The composite 40 is a material in which at least the phosphor of the present embodiment is dispersed in the sealing material 30 such as resin. In order to obtain higher quality white light, the sealing material 30 includes not only the phosphor of the present embodiment but also other phosphors. The light-emitting device 100 emits a mixed color of the light of the light-emitting element 120 and the light emitted from the fluorescent particles 1 that are excited by absorbing the light emitted by the light-emitting element 120. The light-emitting device 100 preferably emits white light by mixing the light of the light-emitting element 120 and the light generated from the fluorescent particles 1.

In addition, FIG. 1 illustrates a surface-mounted light-emitting device, but the light-emitting device is not limited to the surface-mounted type, and may also be a cannonball type, a COB (chip on board) type, or a CSP (chip size package) type.

As for the use of the light emitting device, there can be listed image display devices such as displays and lighting devices. For example, the light emitting device 100 can be used as a backlight to manufacture a liquid crystal display. In addition, by using one or more light emitting devices 100 and applying appropriate wiring, a lighting device can also be manufactured.

The above is an explanation of the embodiments of the present invention, but these are examples of the present invention, and various structures other than the above can also be adopted. In addition, the present invention is not limited to the above embodiments, and modifications and improvements within the scope of achieving the purpose of the present invention are included in the present invention. [Example]

The present invention is described in detail below with reference to the embodiments, but the present invention is not limited to the description of the embodiments. <Production of phosphor powder> (Comparative Example 1) (1) Preparation of raw material mixed powder First, preliminary mixing is performed. Specifically, Si ₃ N ₄ (manufactured by Ube Industries, Ltd., E10 grade), AlN (manufactured by Tokuyama Co., Ltd., E grade) and CeO ₂ (manufactured by Shin-Etsu Chemical Co., Ltd., C grade) among the raw materials listed in Table 1 are mixed (dry blended) for 30 minutes using a small V-type mixer, and then sieved with a nylon sieve with a mesh size of 150 μm. A preliminary mixed powder is obtained. Then, in a glove box with a nitrogen atmosphere, the remaining raw materials listed in Table 1 (Ca ₃ N ₂ (Ca ₃ N ₂ manufactured by Pacific Cement) and Li ₃ N (Li ₃ N manufactured by Materion)) were added to the prepared mixed powder, and the mixture was thoroughly dry-blended. The mixture was then sieved with a sieve having a mesh size of 500 μm to obtain a raw material mixed powder.

(2) Firing The raw material mixture powder is filled into a boron nitride container. The container is placed in a furnace and the raw material mixture powder is fired at 1800°C for 8 hours in a 0.72MPa･G _N2 environment.

(3) Crushing of the calcined product The calcined product obtained in (2) was crushed using a pulverizer. The crushing by the pulverizer was repeated until the pass rate of the vibration screen with a mesh size of 250 μm exceeded 90%. The calcined product crushed by the pulverizer was further crushed using a jet mill (manufactured by Nippon Pneumatic Mfg. Co., Ltd., PJM-80SP). The crushing conditions were set as sample feed rate: 50 g/min, crushing air pressure: 0.3 MPa. In the above manner, a fluorescent powder was obtained.

(Examples 1, 2 and Comparative Example 2) The fluorescent powder obtained in Comparative Example 1 was subjected to an annealing treatment under the conditions described in Table 1 to obtain a fluorescent powder. The annealing treatment was performed by filling a predetermined sample amount of fluorescent powder into an alumina crucible (without a lid) under the conditions described in Table 1, and heating the fluorescent powder filled into the crucible in a predetermined sintering furnace under a predetermined ambient gas described in Table 1 at a predetermined maximum temperature (however, the temperature was raised from room temperature to the maximum temperature at a rate of 3°C/min) for a predetermined time. After heating, the sample is cooled from the maximum temperature to 500°C at about 1.3°C/min, and from 500°C to 300°C at about 1.1/°C/min, and then cooled in the furnace to below 300°C. In addition, the annealing treatment of Example 2 increases the sample amount and sets a higher heating temperature compared to Example 1. In the annealing treatment of Example 2, an ambient gas filled with _N2 gas instead of _H2 gas is used. In Examples 1 to 3, a mixed gas mixed with a specific amount of _H2 gas relative to _N2 gas is introduced by blowing at atmospheric pressure so that it is filled in the ambient gas.

(Example 3) The fluorescent powder obtained in Comparative Example 3 was subjected to annealing treatment under the conditions described in Table 1 to obtain a fluorescent powder.

(Comparative Example 2) The β-type silicon aluminum oxynitride fluorescent powder (manufactured by Denka Co., Ltd., grade name: GR-MW540K8SD) was subjected to annealing treatment under the conditions described in Table 1 to obtain β-type silicon aluminum oxynitride fluorescent powder (after annealing treatment).

<Confirmation of chemical composition/crystalline structure> The composition of a portion of the fluorescent powder was analyzed as follows. The amount of Ca, Li, Ce, Si and Al: The fluorescent powder was dissolved by alkali dissolution method, and then measured using an ICP emission spectrometer (5110VDV manufactured by Agilent). The amount of O and N: Measured using an oxygen and nitrogen analyzer (EMGA-920 manufactured by HORIBA). Based on the measurement results, x, y, Si/Al atomic ratio, O/N atomic ratio, Li ratio in M, and Ce ratio in M in the general formula M _x (Si,Al) ₂ (N,O) _3±y were determined.

For the phosphors of Examples 1 to 3, powder X-ray diffraction (XRD) was measured using Cu-Kα radiation using an X-ray diffraction device (Ultima IV-N manufactured by Riko Co., Ltd.). From the analysis of the obtained XRD pattern, it was confirmed that the main phase was an orthorhombic system with lattice constants of a = 0.9486nm, b = 0.5586nm, and c = 0.4933nm.

<SEM photos> For the surfaces of the obtained fluorescent powders of Examples 1 to 3 and Comparative Examples 1 to 3, SEM photos were taken using a scanning electron microscope (accelerating voltage of electron beam: 3 kV, magnification: 2000 and 5000 times). Figure 2 shows the fluorescent powder of Example 1, Figure 3 shows the fluorescent powder of Example 2, and Figure 4 shows the fluorescent powder of Example 3. Figure 5 shows the fluorescent powder of Comparative Example 1, Figure 6 shows the fluorescent powder of Comparative Example 2, and Figure 7 shows the fluorescent powder of Comparative Example 3.

For Comparative Examples 1 to 3, the SEM photographs confirmed that the smooth surface was exposed on most of the surface of the fluorescent particles, and the crushed pieces formed by the crushed fluorescent particles were attached to the smooth surface. In addition, by washing the fluorescent powders of Comparative Examples 1 to 3 with water, it was confirmed that the crushed pieces could be removed from the surface of the fluorescent particles to a certain extent.

On the other hand, for Examples 1 to 3, the SEM photographs above confirmed that there were multiple raised portions on the surface of the fluorescent particles. It was confirmed that the raised portions, unlike the crushed pieces, had no crushed surface and had some flat structures. In addition, the results of the chemical composition analysis of the fluorescent powders above showed that the amount of oxygen element (weight %) was higher in Examples 1 to 2 than in Example 1, and higher in Example 3 than in Example 3. It was confirmed that even if the fluorescent powders of Examples 1 to 3 were washed with water, the raised portions were almost not removed from the surface of the fluorescent particles after washing. From such results, it was determined that the raised portions formed as part of the surface of the fluorescent particles were surface modified portions formed by the surface modification of the fluorescent particles by the annealing treatment.

<Measurement of diffuse reflectance> The diffuse reflectance is measured using a UV-visible spectrophotometer (V-550) manufactured by JASCO Corporation equipped with an integrating sphere device (ISV-469). During the measurement, a standard reflector (Spectralon) is used for baseline correction. The solid sample holder filled with fluorescent powder is installed at a specific position in the device, and the diffuse reflectance spectrum in the wavelength range of 500~850nm is measured to obtain the diffuse reflectance for light with a wavelength of 600nm, light with a wavelength of 700nm, light with a wavelength of 800nm, and light with the peak wavelength of the fluorescent powder (described later).

<Measurement of particle size distribution> The particle size distribution was measured by the laser diffraction scattering method according to JIS R 1629:1997 using LS13 320 (manufactured by Beckman Coulter Co., Ltd.). Water was used as the measuring solvent. As for the specific procedure, first, a small amount of fluorescent powder was added to an aqueous solution to which 0.05 mass % of sodium hexametaphosphate was added as a dispersant. Then, a dispersion was prepared by dispersion treatment using a horn-type ultrasonic homogenizer (output 300 W, horn diameter 26 mm). The dispersion was appropriately added to the measuring solvent and the particle size distribution was measured. From the obtained cumulative volume frequency distribution curve, the 10% volume diameter (D ₁₀ ), 50% volume diameter (D ₅₀ ) and 90% volume diameter (D ₉₀ ) were obtained.

<Measurement of fluorescence spectrum> The fluorescence spectrum of the fluorescent powder was measured using a spectrofluorescence photometer (F-7000, manufactured by Hitachi Advanced Technologies, Inc.) calibrated with Rose Bengal B and a sub-standard light source. Specifically, the spectrum of fluorescence emitted by the fluorescent powder when excited by monochromatic light of a wavelength of 455 nm was measured to obtain the fluorescence peak wavelength (nm) and the half-width (nm) of the fluorescence peak.

<Measurement of internal quantum efficiency and external quantum efficiency> Using a spectrophotometer (MCPD-7000 manufactured by Otsuka Electronics Co., Ltd.), the internal quantum efficiency and external quantum efficiency of each fluorescent powder were determined according to the following procedure. (1) The fluorescent powder is filled into the concave portion of the concave groove in a manner that makes the surface smooth. The concave groove is installed at a specific position (sample portion) in the integrating sphere. Monochromatic light with a wavelength of 455nm from a light emitting light source (Xe lamp) is introduced into the integrating sphere using an optical fiber. The monochromatic light (excitation light) is irradiated onto the fluorescent powder filled in the concave portion of the concave groove to measure the fluorescence spectrum. The number of excitation reflected light photons (Qref) and the number of fluorescent photons (Qem) are calculated from the obtained spectrum data. The number of photons of the excitation reflected light is calculated in the wavelength range of 450nm to 465nm, and the number of photons of the fluorescent light is calculated in the range of 465nm to 800nm. (2) In addition, a standard reflector with a reflectivity of 99% (Spectralon manufactured by Labsphere) is installed on the sample part instead of the concave groove, and the spectrum of the excitation light with a wavelength of 455nm is measured. Then, the number of excitation light photons (Qex) is calculated from the spectrum in the wavelength range of 450nm to 465nm. (3) From the Qref, Qem and Qex obtained in (1) and (2) above, the internal quantum efficiency and external quantum efficiency are calculated according to the following formula. Internal quantum efficiency = (Qem/(Qex-Qref)) × 100 External quantum efficiency = (Qem/Qex) × 100

<Measurement of absorbance at a wavelength of 600 nm> Using a spectrophotometer equipped with an integrating sphere (MCPD-7000 manufactured by Otsuka Electronics Co., Ltd.), the absorbance of each fluorescent powder at a wavelength of 600 nm was determined according to the following procedure. (1) A standard reflector plate with a reflectivity of 99% (Spectralon manufactured by Labsphere) was installed at a specific position (sample portion) in the integrating sphere, and monochromatic light with a wavelength of 600 nm from a light source (Xe lamp) was irradiated onto the standard reflector plate. Then, the number of photons of the excitation light (Qex) was calculated in the wavelength range of 595 to 610 nm. (2) The number of excitation reflected photons (Qref) of the sample was calculated in the same manner as in (1), except that the standard reflector plate was replaced with the measurement sample. As the measurement sample, a sample in which the fluorescent powder is filled in the concave portion of the concave groove so that the surface becomes smooth is used. (3) The absorbance A ₆₀₀ at a wavelength of 600 nm is calculated using the formula (Qex-Qref)/Qex.

<Measurement of absorbance at a wavelength of 700 nm> Using a spectrophotometer equipped with an integrating sphere (MCPD-7000 manufactured by Otsuka Electronics Co., Ltd.), the absorbance of each fluorescent powder at a wavelength of 700 nm was determined according to the following procedure. (1) A standard reflector plate with a reflectivity of 99% (Spectralon manufactured by Labsphere) was installed at a specific position (sample portion) in the integrating sphere, and monochromatic light with a wavelength of 700 nm from a light source (Xe lamp) was irradiated onto the standard reflector plate. Then, the number of photons of the excitation light (Qex) was calculated in the wavelength range of 695 to 710 nm. (2) The number of photons of the sample reflected by the excitation (Qref) was calculated in the same manner as in (1), except that the standard reflector plate was replaced with the sample to be measured. As the measurement sample, a sample in which the fluorescent powder is filled in the concave portion of the concave groove so that the surface becomes smooth is used. (3) The absorbance A ₇₀₀ at a wavelength of 700 nm is calculated using the formula (Qex-Qref)/Qex.

The various information is summarized in Table 1.

[Table 1]

As shown in Table 1, the phosphor powders represented by the general formula M _x (Si,Al) ₂ (N,O) _3±y of Examples 1 to 3 show better luminescence properties such as internal quantum efficiency and diffuse reflectivity at 600nm than those of Comparative Examples 1 to 3. Moreover, the β-silicon aluminum oxynitride phosphor of Comparative Example 3, when subjected to the same annealing treatment as that of Example 1, shows a result that the internal quantum efficiency and diffuse reflectivity at 600nm are greatly reduced compared to before the annealing treatment.

This application claims priority based on Japanese application No. 2022-181260 filed on November 11, 2022, the disclosure of which is incorporated herein in its entirety.

1: Fluorescent particles 30: Sealing material 40: Composite 100: Light-emitting device 120: Light-emitting element 130: Heat sink 140: Housing 150: First lead frame 160: Second lead frame 170: Bonding wire 172: Bonding wire

[Figure 1] is a schematic cross-sectional view showing an example of the structure of a light-emitting device. [Figure 2] (a) and (b) show SEM photographs of the fluorescent powder of Example 1. [Figure 3] (a) and (b) show SEM photographs of the fluorescent powder of Example 2. [Figure 4] (a) and (b) show SEM photographs of the fluorescent powder of Example 3. [Figure 5] (a) and (b) show SEM photographs of the fluorescent powder of Comparative Example 1. [Figure 6] (a) and (b) show SEM photographs of the fluorescent powder of Comparative Example 2. [Figure 7] (a) and (b) show SEM photographs of the fluorescent powder of Comparative Example 3.

1: Fluorescent particles

30: Sealing material

40: Complex

100: Light-emitting device

120: Light-emitting element

130: Heat sink

140: Shell

150: 1st lead frame

160: 2nd lead frame

170:Joining line

172:Joint line

Claims (10)

A fluorescent powder comprises fluorescent particles represented by the general formula M _x (Si,Al) ₂ (N,O) _3±y , wherein a part of M is substituted by Ce element, wherein M is Li and one or more alkali earth metal elements, 0.52≦x≦0.90, 0≦y≦0.36, and a part of the surface of the fluorescent particles comprises a raised surface modified portion. As in claim 1, the fluorescent powder, wherein the surface modified portion comprises a flat structure. The fluorescent powder of claim 1 or 2, wherein the surface modification portion comprises an oxide or a hydroxide. The fluorescent powder of claim 1 or 2, wherein, in the volume frequency particle size distribution of the fluorescent powder measured by laser diffraction scattering method, when the particle size at the point where the cumulative volume from the small particle side becomes 50% is taken as _D50 , _D50 is not less than 8 μm and not more than 25 μm. The fluorescent powder of claim 1 or 2, wherein the composition of the fluorescent material is such that 2 mol % or more and 5 mol % or less of M is Ce. A fluorescent body, which is a fluorescent body powder as claimed in claim 1 or 2, wherein when the diffuse reflectance spectrum of the fluorescent body is measured in the wavelength range of 500-850nm, the difference X1-X2 between the diffuse reflectance X1 for light of a wavelength of 700nm and the diffuse reflectance X2 for light of a peak wavelength of fluorescence when irradiated with excitation light of 455nm is 3.0% or less. A fluorescent body is a fluorescent body powder as claimed in claim 1 or 2, wherein the diffuse reflectivity X2 of light with a peak fluorescence wavelength when irradiated with excitation light of 455 nm is 88% or more and 97% or less. A fluorescent body is the fluorescent body powder as claimed in claim 1 or 2, wherein the wavelength of the fluorescent peak when irradiated with 455nm excitation light is 580nm or more and 610nm or less. A fluorescent body is a fluorescent body powder as claimed in claim 1 or 2, wherein the half width of the fluorescence peak when irradiated with 455 nm excitation light is not less than 130 nm and not more than 142 nm. A light-emitting device comprises the fluorescent powder and a light source as claimed in claim 1 or 2.