Phosphor powder, light-emitting device, display device and lighting device

Abstract

x(Si,Al);2(N,O);3±y所示，惟，M係Li及一種以上之鹼土金屬元素，0.52≦x≦0.9、0.06≦y≦0.36，M之一部分被Ce元素取代的螢光體，Si / Al原子比係1.5以上6以下，且O / N原子比係0以上0.1以下，M之5~50mol%為Li，M之0.5~10mol%為Ce。將該螢光體粉末之以雷射繞射散射測定之體積基準累積10%徑、體積基準累積50%徑及體積基準累積90%徑各別設為D;10、D;50及D;90時，(D;90-D;10) / D;50為0.7以上1.1以下。;

Description

Technical Field

[0001] This invention relates to phosphor powder, light-emitting device, image display device, and lighting device. Prior Technology

[0002] Phosphors are typically used to manufacture white LEDs (Light Emitting Diodes). That is, phosphors are used as wavelength conversion materials to obtain white light from the blue light emitted by blue LEDs. With the increasing popularity of white LEDs in lighting applications and the exploration of their use in image display devices, the development of phosphors that can convert blue light into longer wavelengths continues.

[0003] One approach to improving phosphors is to alter their chemical composition. For example, Patent Document 1 describes a phosphor with the general formula Mx(Si,Al)2(N,O)3±y (where M is Li and one or more alkaline earth metal elements, 0.52≦x≦0.9, 0.06≦y≦0.23), wherein a portion of M is replaced by Ce, the Si / Al atomic ratio is 1.5 to 6, the 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. [Previous Technical Documents] [Patent Literature]

[0004] [Patent Document 1] Japanese Patent No. 5969391 Summary of the Invention

[0005] [The problem that the invention aims to solve]

[0006] In view of this specification, the phosphor described in Patent Document 1, specifically regarding the conversion efficiency of blue light, still has room for improvement in terms of the fluorescence peak intensity, internal quantum efficiency, and external quantum efficiency when the phosphor is irradiated with blue light.

[0007] The inventors of this case conducted this exploration with the aim of providing phosphor powder that exhibits high fluorescence peak intensity and good internal and external quantum efficiency when irradiated with blue light. [Methods for solving problems]

[0008] The inventors of this case explored and completed the following invention.

[0009] According to the present invention, A fluorescent powder is provided, containing fluorescent particles of the general formula Mx(Si,Al)2(N,O)3±y, wherein M is Li or one or more alkaline earth metal elements, with a molecular weight of 0.52≦x≦0.9 and 0.06≦y≦0.36, and a portion of M is replaced by Ce. The Si / Al atomic ratio is 1.5 to 6, and the O / N atomic ratio is 0 to 0.1. 5-50 mol% of M is Li, and 0.5-10 mol% of M is Ce. When the cumulative 10% diameter, cumulative 50% diameter, and cumulative 90% diameter of the phosphor powder measured by laser diffraction are set to D10, D50, and D90 respectively, (D90-D10) / D50 is between 0.7 and 1.1.

[0010] Furthermore, according to the present invention, a light-emitting device is provided, comprising the above-mentioned phosphor powder and a light-emitting light source.

[0011] Furthermore, according to the present invention, an image display device is provided, which includes the above-described light-emitting device.

[0012] Furthermore, according to the present invention, a lighting device is provided, comprising the above-described light-emitting device. [Effects of the Invention]

[0013] The phosphor powder system of this invention has high internal quantum efficiency and good blue light conversion efficiency. Simple Explanation of the Diagram

[0014] [Figure 1] A schematic cross-sectional view showing an example of the structure of a light-emitting device. [Figure 2] The XRD pattern of the phosphor of Example 1 obtained by powder X-ray diffraction (XRD). Implementation

[0015] Hereinafter, embodiments of the present invention will be described in detail with reference to drawings. In the diagram, the same components use the same symbols, and descriptions are omitted appropriately. The diagrams are for illustrative purposes only. The shapes or dimensions of the components in the diagrams do not necessarily correspond to real-world objects.

[0016] In this specification, the use of "X~Y" in the description of numerical ranges, unless otherwise specified, indicates that X is greater than or less than Y. For example, "1~5% by mass" means "more than 1% by mass and less than 5% by mass".

[0017] <Fluorescent Powder> The phosphor powder of this embodiment comprises phosphor particles represented by the general formula Mx(Si,Al)2(N,O)3±y. In this formula, M consists of Li and one or more alkaline earth metal elements, with a ratio of 0.52≦x≦0.9 and 0.06≦y≦0.36. Furthermore, a portion of M is replaced by Ce, the Si / Al atomic ratio is 1.5 to 6, the 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. Furthermore, when the cumulative diameter of the phosphor powder of this embodiment measured by laser diffraction is set to D10, D50 and D90 respectively, the cumulative diameter of the 10% volume reference, the cumulative diameter of the 50% volume reference, and the cumulative diameter of the 90% volume reference are respectively set to D90, (D90-D10) / D50 is 0.7 or more and 1.1 or less.

[0018] The phosphor powder of this embodiment differs from the phosphor described in Patent Document 1 at least in that the ratio of (D 90-D 10) / D 50 is 0.7 to 1.1. The phosphor powder of this embodiment has a better blue light conversion efficiency compared to the phosphor described in Patent Document 1.

[0019] The index (D 90-D 10) / D 50 can be interpreted as the "sharpness" of the particle size distribution of fluorescent powder standardized by D 50. The ratio (D 90-D 10) / D 50 is less than 1.1, meaning the particle size distribution of the phosphor powder is sufficiently sharp, which corresponds to a situation where there are fewer excessively fine particles (microparticles) with poor luminescence efficiency in the phosphor powder. Therefore, it is believed that the phosphor powder of this embodiment has good blue light conversion efficiency. That is, there is a tendency for a smaller (D 90-D 10) / D 50 to result in less micronized powder. However, considering the time or cost of manufacturing, the lower limit in this embodiment is 0.7.

[0020] The phosphor powder of this embodiment can be manufactured by using appropriate materials and selecting appropriate manufacturing methods and conditions. "Appropriate manufacturing methods and conditions" include, for example, one or more of the following: (i) performing appropriate classification treatment on the phosphor powder (preferably sedimentation classification), and (ii) adjusting the pulverization method of the phosphor powder. Details regarding the manufacturing methods and conditions will be explained later.

[0021] Continuing with the description of the phosphor powder of this embodiment.

[0022] (Crystal structure, chemical composition, etc.) The crystalline framework of fluorescein is formed by bonds of (Si,Al)-(N,O)₄ tetrahedrons, with the metal element (M) located in the interstices. The above general formula is established by ensuring that the valence and amount of M, the Si / Al ratio, and the N / O ratio all remain within a wide range to maintain electroneutrality. A representative fluorescein represented by this formula is CaAlSiN₃, where M is Ca with x=1, Si / Al=1, and O / N=0. When one portion of Ca in CaAlSiN₃ is replaced by Eu, a red fluorescein will become a yellow to orange fluorescein when Ce is substituted.

[0023] The crystalline structure of the phosphor particles contained in the phosphor powder of this embodiment is generally based on CaAlSiN3 crystals. One characteristic of these phosphor particles is that they significantly alter the composition and elements, achieving very high luminous efficiency even with Ce activation. In the above general formula, element M is a combination of Li and alkaline earth metal elements, a portion of which is replaced by Ce, which serves as the luminescence center. By using Li and combining it with divalent alkaline earth elements and trivalent Ce, the average valence of element M can be widely controlled. Furthermore, the ionic radius of Li+ is very small, allowing for significant variations in crystal size through its quantity, resulting in various forms of fluorescence. In the above general formula, the coefficient x of element M should be between 0.52 and 0.9, preferably between 0.6 and 0.9, and more preferably between 0.7 and 0.9. If the coefficient x exceeds 0.9, that is, close to CaAlSiN3 crystallization, there is a tendency for the fluorescence intensity to decrease. If the coefficient x is less than 0.52, there is a tendency for the fluorescence intensity to decrease significantly due to the large-scale formation of heterogeneous phases other than the intended crystalline phase.

[0024] In this embodiment, the average valence or amount of element M is maintained electrically neutral by the Si / Al ratio and O / N ratio, and y = 0 in the case of a single crystal without defects. However, when considering the overall composition of the phosphor, there may be a second crystalline phase or an amorphous phase, or crystal defects may occur when considering the crystal itself, leading to a loss of charge balance. In this embodiment, from the viewpoint of improving fluorescence intensity, y is preferably 0.06 to 0.36, more preferably 0.1 to 0.35, and even more preferably 0.06 to 0.23.

[0025] In this embodiment, the O / N atomic ratio (molar ratio) is between 0 and 0.1, preferably between 0.01 and 0.08, and more preferably between 0.02 and 0.07. If the O / N atomic ratio is too large, there is a tendency for the amount of heterogeneous phase formation to increase, the luminous efficiency to decrease, the covalent nature of crystals to decrease, and the temperature characteristics to deteriorate (brightness decreases at high temperatures).

[0026] Generally, if the average valence, amount, and O / N atomic ratio of element M are within a predetermined range, the Si / Al atomic ratio (molar ratio) will necessarily be determined. The Si / Al atomic ratio is between 1.5 and 6, preferably between 2 and 4, and even more preferably between 2.5 and 4.

[0027] The Li content in fluorescein particles should be 5-50 mol% of the M element, preferably 15-45 mol%, and even more preferably 25-45 mol%. A content above 5 mol% facilitates the effective utilization of Li, but if it exceeds 50 mol%, the desired crystalline structure of the fluorescein cannot be maintained, resulting in anisotropic phases and a decrease in luminous efficiency. To be on the safe side, it should be clarified that "Li content" refers to the Li content in the final phosphor powder, not the amount in the raw material doping substrate. The Li compounds used in the raw materials have high vapor pressure and are easily volatile. A considerable amount will volatilize during the high-temperature synthesis of nitrides and oxynitrides. In other words, the amount of Li in the raw material doping substrate will differ significantly from the content in the final product, and therefore does not represent the Li content in the phosphor.

[0028] The Ce content at the luminescence centers of fluorescein particles is crucial. Too little Ce tends to reduce its contribution to luminescence, while too much Ce tends to cause concentration extinction of the fluorescein due to energy transfer between Ce³⁺ ions. Therefore, the Ce content should be 0.5–10 mol% of M, preferably 0.5–5 mol%.

[0029] The alkaline earth metal element used as element M in the above general formula can be any element, but when Ca is used, high fluorescence intensity can be obtained, and the crystal structure can be stabilized over a wide compositional range. Therefore, element M should preferably include Ca. Element M can also be a combination of multiple alkaline earth metal elements; for example, a portion of element Ca can be replaced by element Sr.

[0030] The fluorescent particles have an orthorhombic crystal structure, which is the same as that of the aforementioned CaAlSiN3 crystal. For example, the lattice constants of CaAlSiN3 crystal are a = 0.98007 nm, b = 0.56497 nm, and c = 0.50627 nm. In this embodiment, the lattice constants are typically a = 0.935~0.965 nm, b = 0.550~0.570 nm, and c = 0.480~0.500 nm, all of which are relatively small compared to CaAlSiN3 crystal. This range of lattice constants reflects the aforementioned constituent elements and composition.

[0031] The crystalline phase present in fluorescent particles should preferably be the aforementioned single crystalline phase. However, fluorescent particles may also contain heterogeneous phases if they do not significantly affect fluorescence properties. Examples of heterogeneous phases that have a low impact on fluorescence properties under blue light excitation include α-aluminum silicon nitride, AlN, LiSi₂N₃, and LiAlSi₂N₄. The amount of heterogeneous phase should preferably be such that the diffraction intensity of other crystalline phases, when evaluated by powder X-ray diffraction, is less than 40% of the strongest diffraction intensity of the aforementioned crystalline phase.

[0032] The phosphor powder of this embodiment is excited by light in a broad wavelength range from ultraviolet to visible light. For example, when irradiated with blue light at a wavelength of 455 nm, it exhibits orange fluorescence with a peak wavelength of 570-610 nm and a fluorescence spectrum with a half-width of 125 nm or more. Such a phosphor powder is suitable for use as a phosphor in various light-emitting devices. Furthermore, the phosphor powder of this embodiment, like conventional nitride and oxide phosphors such as CaAlSiN3, possesses excellent heat resistance and chemical stability, and exhibits minimal brightness reduction with increasing temperature. These characteristics make it particularly suitable for applications requiring durability.

[0033] (Particle size distribution) As mentioned above, in the phosphor powder of this embodiment, the ratio of (D90-D10) / D50 is 0.7 to 1.1 or less. This value is preferably 0.75 to 1.05 or less, more preferably 0.75 to 1 or less, and even more preferably 0.75 to 0.95 or less.

[0034] In this embodiment, appropriately designing parameters regarding particle size distribution beyond (D 90-D 10) / D 50 can sometimes further improve the conversion efficiency of blue light or enhance the balance of various performance characteristics. Specifically, as follows.

[0035] The cumulative 10% diameter (D10) of the fluorescent powder in this embodiment, measured by laser diffraction, should preferably be 5 μm to 12 μm, and more preferably 7 μm to 11 μm. A larger D10 value indicates a lower amount of microparticles (excessively fine fluorescent particles that tend to decrease blue light conversion efficiency) in the fluorescent powder, expressed as a different index than (D90-D10) / D50. A relatively large D10 value tends to indicate higher blue light conversion efficiency.

[0036] The median diameter (D50) of the fluorescent powder in this embodiment, measured by laser diffraction, is preferably between 8 μm and 25 μm, and more preferably between 12 μm and 22 μm. A fluorescent powder with a D50 that is neither too large nor too small is ideal for its applicability to various applications and for its operability in industrial applications.

[0037] The cumulative 90% diameter (D90) of the fluorescent powder in this embodiment, measured by laser diffraction, should preferably be between 18 μm and 38 μm, and more preferably between 18 μm and 30 μm. An excessively large D90 corresponds to a low amount of coarse particles in the fluorescent powder. Fluorescent powder with a low D90 effectively reduces chromatic aberration in the light-emitting device.

[0038] (Manufacturing method) The phosphor powder of this embodiment is preferably manufactured by a series of steps including (1) to (4), a series of steps including (1) to (3) and (5), or a series of steps including (1) to (5). From the viewpoint of appropriately adjusting (D 90-D 10) / D 50, the manufacturing steps of the phosphor powder should preferably include (5) a classification process (preferably sedimentation classification). (1) Preparation steps of raw material mixed powder (2) Calcination steps (3) Pulverization steps of calcined materials (4) Acid treatment steps (5) Grading steps (settlement grading is preferred)

[0039] The following will provide a detailed explanation of (1) to (5).

[0040] (1) Preparation steps of raw material mixed powder In the preparation step of raw material mixed powder, appropriate raw material powders are usually mixed to obtain raw material mixed powder. As raw material powders, nitrides of constituent elements are suitable, such as silicon nitride, aluminum nitride, lithium nitride, cerium nitride, and nitrides of alkaline earth elements (e.g., calcium nitride). Generally, nitride powders are unstable in air, and the particle surface is covered with an oxide layer. Even when using nitride raw materials, the raw material will still contain a certain degree of oxides. While controlling the O / N ratio of the phosphor, this should be considered, and under oxygen deficiency, a portion of the nitride can also become an oxide (including compounds that become oxides through heat treatment). Examples of oxides include cerium oxide.

[0041] In raw material powders, lithium compounds exhibit significant volatilization due to heating, and depending on the calcination conditions, sometimes the vast majority will volatilize. Therefore, the optimal amount of lithium compound to incorporate should be determined by considering the amount of volatilization during the calcination process, taking into account the calcination conditions.

[0042] In nitride raw material powders, lithium nitride, cerium nitride, and alkaline earth element nitrides react violently with moisture in the air. Therefore, their operation should preferably be carried out in a glove box with an inert environment. From the perspective of operational efficiency, (i) firstly, a predetermined amount of silicon nitride, aluminum nitride and various oxide raw material powders that can be operated in air are weighed and thoroughly mixed in air to prepare a premixed powder; (ii) then, in a glove box, the premixed powder is mixed with substances that are easily reacted with moisture, such as lithium nitride, to prepare a raw material mixed powder.

[0043] (2) Calcination steps The calcination step involves filling the raw material mixture powder prepared in the preparation step of (1) into a suitable container and heating it using a calcination furnace or the like.

[0044] Considering the need for a complete reaction and to suppress lithium volatilization, the calcination temperature should be 1600~2000℃, and more preferably 1700~1900℃. Considering both the need for a complete reaction and the need to suppress lithium volatilization, the calcination time should be 2 to 24 hours, and more preferably 4 to 16 hours.

[0045] The calcination process should preferably be carried out under a nitrogen atmosphere. Furthermore, the pressure of the calcination environment should be appropriately adjusted. Specifically, the pressure of the calcination environment should be 0.5 MPa·G or higher. When the calcination temperature is especially above 1800℃, the fluorite tends to decompose easily; by using a high pressure in the calcination environment, the decomposition of the fluorite can be suppressed. Furthermore, considering industrial productivity, the pressure of the calcination environment should be less than 1 MPa·G.

[0046] The container for filling the raw material mixture should preferably be made of a material that is stable in a high-temperature nitrogen environment and does not react with the raw material mixture or its reaction products. The container material should preferably be boron nitride.

[0047] (3) Pulverization steps of calcined materials (2) The obtained calcined material is usually in block form. It is more ideal to crush it into a certain size by applying mechanical force. Pulverization can be performed using various devices such as pulverizers, mortars, ball mills, vibratory mills, jet mills, and crushers. Two or more of these devices can also be combined for pulverization. In the embodiments described later, a coarse pulverized material of the calcined material is first obtained using a crusher, and then the coarse pulverized material is further finely pulverized using a jet mill. By appropriately controlling the pulverization conditions, one or more of D10, D50, D90, and (D90-D10) / D50 can be adjusted.

[0048] (4) Acid treatment steps The acid treatment step involves, for example, immersing the pulverized material obtained in (3) above in an acidic aqueous solution. Although the details are unclear, it is believed that acid treatment removes or reduces the "heterogeneous phases" of the phosphor that do not contribute to luminescence or reduce luminescence efficiency.

[0049] Regarding acidic aqueous solutions, examples include acidic aqueous solutions containing one acid selected from hydrofluoric acid, nitric acid, hydrochloric acid, etc., or mixed acid aqueous solutions obtained by mixing two or more of the above acids. Nitric acid or hydrochloric acid is preferred, with hydrochloric acid being more suitable. The concentration of the acidic aqueous solution should be appropriately set according to the strength of the acid used, for example, 0.5-50% by mass, preferably 1-30% by mass, and even more preferably 1-10% by mass. The temperature for acid treatment should be between 25°C and 90°C, and more preferably between 60°C and 90°C. Treatment at higher temperatures makes it easier to remove heterogeneous phases. The acid treatment time (immersion time) should be between 15 minutes and 80 minutes, or between 15 minutes and 60 minutes. After acid treatment, it is ideal to thoroughly wash and dry the phosphor powder with water.

[0050] (5) Grading steps To reduce the amount of microparticles (excessively fine fluorescent particles that tend to decrease the conversion efficiency of blue light) in the powder, appropriate classification is recommended. For effective removal of microparticles, sedimentation classification as described below is preferable.

[0051] First, the powder obtained in the pulverization step of (3) calcination or the powder obtained in the acid treatment step of (4) is dispersed in a container in a suitable liquid, such as an aqueous solution of sodium hexametaphosphate, to prepare a dispersion. Then, the dispersion is allowed to stand for a certain period of time to allow the larger particles of powder in the dispersion to precipitate. Then, the supernatant is drained. In addition to the above operations, repeat the process of adding fresh sodium hexametaphosphate aqueous solution to the container of residual precipitate several times to disperse the powder, allow it to stand, and drain the supernatant. "Several times" should preferably be 5 times or more. There is no specific upper limit to the number of times, but considering factors such as cost, it can be 15 times or less, specifically 10 times or less.

[0052] The specific conditions for classification are not particularly limited as long as the final result is fluorescent powder with a (D 90 - D 10) / D 50 ratio of 0.7 to 1.1. For reference only, it is advisable to set classification conditions by removing microparticles smaller than 10 μm, and even more preferably by removing microparticles smaller than 7.5 μm. Regarding sedimentation classification, the conditions can be referenced to Stokes' Law concerning particle settling velocity. An example of the specific conditions for settlement classification can be found in the embodiments described later.

[0053] <Light-emitting devices, image display devices and lighting devices> By combining the phosphor powder of this embodiment with a light source, a light-emitting device can be obtained. The light source typically emits ultraviolet or visible light. For example, when the light source is a blue LED, the blue light emitted by the self-emissive light source hits the phosphor powder, and the blue light is converted into longer wavelength light. That is, the phosphor powder of this embodiment can be used as a wavelength conversion material to convert blue light into longer wavelength light.

[0054] An example of the specific structure of the light-emitting device will be described with reference to Figure 1. Figure 1 is a schematic cross-sectional view showing an example of the structure of a light-emitting device. As shown in Figure 1, the light-emitting device 100 includes a light-emitting element 120, 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 material 40.

[0055] The light-emitting element 120 is mounted on a predetermined area on the top surface of the heat sink 130. By mounting the light-emitting element 120 on the heat sink 130, the heat dissipation performance of the light-emitting element 120 can be improved. Alternatively, a packaging substrate can be used instead of the heat sink 130.

[0056] The light-emitting element 120 is a semiconductor element that emits excitation light. For example, an LED chip that emits light with wavelengths between 300 nm and 500 nm, corresponding to near-ultraviolet to blue light, can be used as the light-emitting element 120. One electrode (not shown) disposed on the top surface of the light-emitting element 120 is connected to the surface of the first lead frame 150 via bonding wires such as gold wires 170. Furthermore, 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 bonding wires such as gold wires 172.

[0057] The outer casing 140 has a roughly funnel-shaped recess with an aperture that gradually widens from bottom to top. The light-emitting element 120 is disposed on the bottom surface of this recess. The walls of the recess surrounding the light-emitting element 120 function as a reflector.

[0058] The composite 40 is filled into the aforementioned recess in which the outer shell 140 forms the wall. The composite 40 is a wavelength conversion component that converts the excitation light emitted by the self-emitting element 120 into light with a longer wavelength. The composite 40 contains at least the phosphor powder of the present embodiment dispersed in the sealant 30 such as resin. In order to obtain a higher quality white light, the sealant 30 may contain other phosphor powders in addition to the phosphor powder of the present embodiment. The light-emitting device 100 emits a mixed color of light from the light-emitting element 120 and light emitted by the phosphor particles 1 that absorb the light emitted from the light-emitting element 120 and are excited. The light-emitting device 100 preferably emits white light by mixing the light from the light-emitting element 120 and the light emitted from the phosphor particles 1.

[0059] In addition, Figure 1 illustrates a surface-mount type light-emitting device, but the light-emitting device is not limited to the surface-mount type, and can also be a projectile type, COB (chip on board) type, or CSP (chip-scale package) type.

[0060] In terms of applications, light-emitting devices can be listed as image display devices such as monitors and lighting devices. For example, light-emitting device 100 can be used as a backlight to manufacture a liquid crystal display. In addition, lighting devices can also be manufactured by using one or more light-emitting devices 100 and applying appropriate wiring.

[0061] The above description describes embodiments of the present invention, but these are merely examples, and various configurations other than those described may also be used. Furthermore, the present invention is not limited to the above embodiments; modifications and improvements within the scope of achieving the objectives of the present invention are included in the present invention. [Example]

[0062] The embodiments of the present invention are described in detail based on examples and comparative examples. For the sake of caution, it should be noted that the present invention is not limited to the embodiments.

[0063] <Manufacturing of Fluorescent Powder> (Example 1) (1) Preparation of raw material mixed powder First, a preliminary mixing process is performed. Specifically, the Si3N4, AlN, and CeO2 materials listed in Table 1 are mixed (dry mixing) for 30 minutes using a small V-type mixer, and then sieved through a nylon sieve with a mesh size of 150 μm. This yields a pre-mixed powder. Then, in a glove box under nitrogen atmosphere, the remaining raw materials (Ca3N2 and Li3N) listed in Table 1 were added to the prepared mixed powder, and the mixture was thoroughly dry-mixed. After that, it was sieved through a sieve with a mesh size of 500 μm. This yielded the raw material mixed powder.

[0064] (2) Calcination The raw material mixture was filled into a container made of boron nitride. The container was placed in a furnace, and the raw material mixture was calcined at 1800°C for 8 hours under a N2 environment of 0.72 MPa·G.

[0065] (3) Crushing of calcined materials The calcined material obtained in (2) was crushed using a crusher. The crushing was repeated until the passing rate of the vibrating screen with a mesh size of 250 μm exceeded 90%. The calcined material obtained by crushing with a pulverizer was further pulverized using a jet mill (manufactured by Nippon Pneumatic Mfg. Co., Ltd., PJM-80SP). The pulverization conditions were set as follows: sample feed rate: 50 g / min, pulverizing air pressure: 0.3 MPa.

[0066] (4) Acid treatment The pulverized calcined material is then placed in hydrochloric acid for acid treatment. Specifically, first, prepare a hydrochloric acid aqueous solution by mixing 35-37% hydrochloric acid and distilled water at a volume ratio of 50mL:300mL and heating it to 80℃. Add this hydrochloric acid aqueous solution to the pulverized calcined material in (3) and stir for 0.5 hours for acid treatment. The acid-treated calcined material was thoroughly washed with distilled water and then dried at 110°C for 3 hours. It was then passed through a sieve with a mesh size of 45 μm to remove coarse / agglomerated particles.

[0067] (5) Removal of fine powder resulting from sedimentation and classification First, prepare a 0.05% (w / w) sodium hexametaphosphate aqueous solution. Then, add this aqueous solution to a container with an inner diameter of 70 mm and a height of 120 mm until the height reaches 110 mm. Then, the calcined product obtained after acid treatment was added to the container containing the aqueous solution, stirred thoroughly to disperse it, and then allowed to stand for 22 minutes. After standing, the supernatant was drained in portions 90 mm from the top. Next, sodium hexametaphosphate aqueous solution was added until the height reached 110 mm, and the powder was stirred again to disperse it, repeating the same treatment. This operation was repeated 7 times to remove the micropowder contained in the acid-treated powder (furthermore, according to Stokes' law, the fractionation point is 7.5 μm). Afterwards, the slurry at the bottom of the container was washed with water and filtered to recover the solid components. It was then dried at 110°C for 3 hours to allow it to pass through a sieve with a mesh size of 45μm, thus breaking down the aggregated particles. Phosphor powder is obtained through the above methods.

[0068] (Comparative Example 1) Without sedimentation and classification, the phosphor powder was obtained in the same manner as in Example 1.

[0069] (Example 2) (a) The raw materials listed in Table 1 were used, (b) no acid treatment was performed (the calcined material obtained by pulverizing by jet mill was fed to sedimentation and classification without acid treatment), and (c) the pulverizing air pressure in the jet mill was set to 0.6 MPa. Otherwise, the phosphor powder was obtained in the same manner as in Example 1.

[0070] (Example 3) (a) The raw materials listed in Table 1 are used as raw materials, and (b) no acid treatment is performed (the calcined material pulverized by jet mill is fed to sedimentation and classification without acid treatment). Otherwise, the phosphor powder is obtained in the same manner as in Example 1.

[0071] (Comparative Example 2) Without sedimentation and classification, the phosphor powder was obtained in the same manner as in Example 3.

[0072] (Example 4) (a) The raw materials listed in Table 1 are used as raw materials; (b) no acid treatment is performed (the calcined material crushed by jet mill is fed to sedimentation classification without acid treatment); (c) the grinding air pressure in the jet mill is set to 0.4 MPa; and (d) the calcined material crushed by jet mill is passed through a sieve with a mesh size of 45 μm to remove coarse / agglomerated particles and then fed to sedimentation classification. Otherwise, fluorescent powder is obtained in the same manner as in Example 1.

[0073] (Comparative Example 3) Without sedimentation and classification, the phosphor powder was obtained in the same manner as in Example 4.

[0074] <Confirmation of Chemical Composition / Crystal Structure> The composition of a portion of the fluorescent powder was analyzed as follows. The amounts of Ca, Li, Ce, Si, and Al were determined by dissolving the phosphor powder using an alkaline dissolution method and then measuring it using an ICP emission spectrometer (CIROS-120 manufactured by Rigaku Corporation). The amounts of O and N were determined using an oxygen and nitrogen analyzer (HORIBA, EMGA-920). Based on the measurement results, the x, y, Si / Al atomic ratio, O / N atomic ratio, Li ratio of M, and Ce ratio of M in the general formula Mx(Si,Al)2(N,O)3±y were obtained. In addition, for the impurities Cr and Fe, the phosphor powder was dissolved by a mixed acid of hydrofluoric acid and nitric acid through a pressurized acid decomposition method, and then measured by an ICP emission spectrometer.

[0075] For the phosphor of Example 1, powder X-ray diffraction (XRD) measurements were also performed using an X-ray diffraction apparatus (Ultima IV-N manufactured by Rigaku Corporation) with Cu-Kα lines. The obtained XRD pattern is shown in Figure 2. Analysis of the obtained XRD pattern confirmed that the main phase is an orthorhombic crystal with lattice constants a = 0.9486 nm, b = 0.5586 nm, and c = 0.4933 nm, and a small amount of LiAlSi₂N₄ exists as a heterogeneous phase.

[0076] Furthermore, the chemical composition of the phosphor powders in Example 4 and Comparative Example 3 was not determined. However, the composition of the raw material mixture powder did not differ significantly from that in the various examples and comparative examples. Moreover, the differences in the manufacturing steps of the various examples and comparative examples were considered unlikely to have a significant impact on the chemical composition of the final obtained phosphor powder. Therefore, the composition of the phosphor powders in Example 4 and Comparative Example 3 is considered to correspond to the general formula Mx(Si,Al)2(N,O)3±y in the same way as in other examples and comparative examples.

[0077] <Determination of Particle Size Distribution> Particle size distribution was determined using an LS13 320 (Beckman Coulter, Inc.) according to JIS R 1629:1997 by laser diffraction scattering. Water was used as the solvent for the determination. In terms of the specific process, firstly, a small amount of fluorescent powder is added to an aqueous solution containing 0.05% by mass of sodium hexametaphosphate as a dispersant. Then, a dispersion is prepared using a horn-type ultrasonic homogenizer (300W output, 26mm horn diameter). The particle size distribution is then measured using this dispersion. From the obtained cumulative volumetric frequency distribution curve, the 10% volume diameter (D10), 50% volume diameter (D50), and 90% volume diameter (D90) are determined. Then, (D90-D10) / D50 is calculated.

[0078] <Evaluation> (Fluorescence peak intensity) The fluorescence spectrum of the fluorescein powder was measured using a spectrophotometer (Hitachi High-Tech Science Corporation, F-7000) calibrated with rose red B and a secondary standard light source. Specifically, the spectrum of fluorescence emitted by the fluorescein powder excited by monochromatic light at a wavelength of 455 nm was measured to determine the fluorescence peak intensity and fluorescence peak wavelength. The fluorescence peak intensity varies depending on the measuring apparatus and conditions. The fluorescence peak intensities listed in the table below are values ​​with the fluorescence peak intensity of the standard (YAG, more specifically, Mitsubishi Chemical P46Y3) set to 100.

[0079] (Internal quantum efficiency and external quantum efficiency) Using a spectrophotometer (MCPD-7000 manufactured by Otsuka Electronics Co., Ltd.), the internal and external quantum efficiencies of each phosphor powder were determined according to the following procedure. (1) Fluorescent powder is filled into the recessed portion of a concave groove to make the surface smooth. The concave groove is installed in a predetermined position (sample section) inside an integrating sphere. Monochromatic light with a wavelength of 455 nm from a light source (Xe lamp) is guided into the integrating sphere using an optical fiber. The monochromatic light (excitation light) is irradiated onto the fluorescent powder filled in the recessed portion of the concave groove, and the fluorescence spectrum is measured. From the obtained spectral data, the peak wavelength is obtained, and the excitation-reflected photon number (Qref) and the fluorescence photon number (Qem) are calculated. The excitation-reflected photon number is calculated in the wavelength range of 450 nm to 465 nm, and the fluorescence photon number is calculated in the wavelength range of 465 nm to 800 nm. (2) In addition, a standard reflective plate (Spectralon manufactured by Labsphere) with a reflectivity of 99% was installed in the sample section to replace the concave groove, and the spectrum of the excitation light at a wavelength of 455 nm was measured. The number of excitation photons (Qex) was calculated from the spectrum in the wavelength range of 450 nm to 465 nm. (3) The internal quantum efficiency and external quantum efficiency are calculated from the Qref, Qem and Qex obtained from (1) and (2) above. Internal quantum efficiency = (Qem / (Qex-Qref)) × 100 External quantum efficiency = (Qem / Qex) × 100

[0080] All information is presented in Table 1. In Table 1, "ND" is short for Not Detected.

[0081] In addition, the raw materials listed in the "Raw Materials Used" column of Table 1 are as follows.

[0082] Ca 3N 2-1:Ca 3N 2 made by TAIHEIYO CEMENT CORPORATION Ca3N2-2: Ca3N2 produced by CERAC (now Materion).

[0083] Li 3N-1: Li 3N manufactured by Materion Li 3N-2: Li 3N manufactured by CERAC (now Materion). Li 3N-3: Li 3N prepared by a high-purity chemical research institute

[0084] CeO 2-1: CeO 2, grade C manufactured by Shin-Etsu Chemical Co., Ltd.

[0085] Si 3N 4-1: Si 3N 4, E10 grade, manufactured by Ube Industries.

[0086] AlN-1: Produced by Tokuyama Corporation, AlN, E grade.

[0087] [Table 1] Examples / Comparative Examples Example 1 Comparative Example 1 Example 2 Example 3 Comparative Example 2 Example 4 Comparative Example 3 Raw materials (mass %) Ca 3N 2 19.528 19.528 19.528 19.528 19.528 16.55 16.55 Li 3N 3.900 3.900 3.900 3.900 3.900 4.96 4.96 CeO₂ 3.345 3.345 3.345 3.345 3.345 1.46 1.46 Si₃N₄ 55.437 55.437 55.437 55.437 55.437 62.63 62.63 AlN 17.791 17.791 17.791 17.791 17.791 14.42 14.42 Raw materials used Ca₃N₂ Ca₃N₂-1 Ca₃N₂-1 Ca₃N₂-2 Ca₃N₂-2 Ca₃N₂-2 Ca₃N₂-2 Ca₃N₂-2 Li₃N Li₃N-1 Li₃N-1 Li₃N-2 Li₃N-2 Li₃N-2 Li₃N-3 Li₃N-3 CeO₂ CeO 2-1 CeO 2-1 CeO 2-1 CeO 2-1 CeO 2-1 CeO 2-1 CeO 2-1 Si 3N 4 Si 3N 4-1 Si 3N 4-1 Si 3N 4-1 Si 3N 4-1 Si 3N 4-1 Si 3N 4-1 Si 3N 4-1 AlN AlN-1 AlN-1 AlN-1 AlN-1 AlN-1 AlN-1 AlN-1 Chemical composition x 0.78 0.76 0.84 0.83 0.84 Undetermined Undetermined y 0.33 0.34 0.14 0.20 0.34 Undetermined Undetermined Si / Al 2.49 2.46 2.72 2.70 2.72 Undetermined Undetermined O / N 0.04 0.05 0.05 0.05 0.05 Undetermined Undetermined Li / M (mol%) 32.39 30.43 39.40 40.31 40.45 Undetermined Undetermined Ce / M (mol%) 2.87 3.02 2.73 2.72 2.73 Undetermined Undetermined Impurities (ppm) Cr ND ND Undetermined ND 3.1 Undetermined Undetermined Fe 6.6 7.3 Undetermined 6.5 17.4 Undetermined Undetermined Particle size distribution D 10(µm) 9.9 6.0 9.3 9.7 6.4 8.8 5.7 D 50(µm) 16.2 14.7 13.8 15.2 13.9 13.5 11.5 D 90(µm) 25.0 24.5 20.2 24.0 23.0 21.5 19.9 (D 90-D 10) / D 50 0.94 1.26 0.79 0.94 1.19 0.93 1.24 Fluorescence peak wavelength (nm) 595.8 600.3 596.3 598.5 595.3 579.5 587.8 Regarding the method of preparation It includes hydrochloric acid treatment and sedimentation classification. Hydrochloric acid treatment, no sedimentation grading Acid-free treatment, with sedimentation classification Acid-free treatment, with sedimentation classification Acid-free treatment, sedimentation-free grading Acid-free treatment, with sedimentation classification Acid-free treatment, sedimentation-free grading Relative fluorescence peak intensity (455nm, P46Y3 ratio) 126.3 118.6 111.5 108.8 100.9 99.6 90.3 Internal quantum efficiency 80.9% 80.0% 77.1% 75.3% 71.9% 81.0% 76.9% External quantum efficiency 70.9% 65.8% 67.7% 67.1% 62.6% 63.8% 56.6%

[0088] Based on the comparison between Example 1 and Comparative Example 1, Examples 2 and 3 and Comparative Example 2, and Example 4 and Comparative Example 3, it can be seen that even if the chemical composition of the phosphor is almost the same, phosphor powders with (D 90-D 10) / D 50 of 0.7 to 1.1 exhibit better fluorescence peak intensity, internal quantum efficiency, and external quantum efficiency compared to phosphor powders with (D 90-D 10) / D 50 exceeding 1.1.

[0089] This application asserts priority based on Japanese Patent Application No. 2020-189204, filed on November 13, 2020, and incorporates all of its disclosures in this application.

[0090] 1: Fluorescent particles 30: Sealing material 40: Complex 100: Light-emitting device 120: Light-emitting element 130: Heatsink 140: Outer shell 150: First lead frame 160: Second lead frame 170: Joint line 172: Joint line

Claims

1. A fluorescent powder containing fluorescent particles of the general formula Mx(Si,Al)2(N,O)3±y, wherein M is Li and one or more alkaline earth metal elements, with a 0.52≦x≦0.9 and a 0.06≦y≦0.36, wherein a portion of M is replaced by Ce, the Si / Al atomic ratio is 1.5 to 6 and the 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, and when the cumulative 10%, 50%, and 90% diameters of the fluorescent powder measured by laser diffraction are respectively set as D10, D50, and D90, the ratio (D90-D10) / D50 is 0.7 to 0.

95.

2. The fluorescent powder as claimed in claim 1, wherein, D10 is between 5μm and 12μm.

3. The fluorescent powder as claimed in claim 1 or 2, wherein, D90 is between 18μm and 38μm.

4. The fluorescent powder as claimed in claim 1 or 2, wherein, D50 is between 8μm and 25μm.

5. A light-emitting device comprising a phosphor powder as described in any one of claims 1 to 4 and a light-emitting source.

6. The light-emitting device as claimed in claim 5, wherein, The light source emits ultraviolet or visible light.

7. An image display device comprising a light-emitting device as claimed in claim 5 or 6.

8. A lighting device having a light-emitting device as claimed in claim 5 or 6.

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