Fluorescent particles, composite material, light-emitting device and method for producing phosphor particles

Abstract

α-Sialon phosphor particles containing Eu, wherein at least one slit is formed on a surface of the α-sialon phosphor particle, wherein the distance from the surface of the α-sialon phosphor particle to the bottom of the slot is equal to or greater than 200 nm and equal to or less than 1500 nm in at least one cross-section of the slot, wherein the α-sialon phosphor particle is formed from an α-sialon phosphor containing an Eu element, represented by the general formula: (M1 x , M2y,Eu z ) (Si 12-(m+n) Al m+n )(O n N 16-n ) (assuming that M1 is a monovalent Li element and M2 is a divalent Ca element), and in the general formula x = 0, 0 < y < 2.0, 0 < z ≤ 0.5, 0 < x + y, 0.3 ≤ x + y + z ≤ 2.0, 0 < m ≤ 4.0 and 0 < n ≤ 3.0 are satisfied, and wherein the α-sialon phosphor particle is produced by a process comprising: Mixing of raw materials containing an element that forms a Eu-containing α-sialon phosphor particle; Heating a mixture of the raw materials to obtain an α-sialon phosphor; Pulverizing the α-sialon phosphor obtained by heating to obtain the α-sialon phosphor particle; and Subjecting the α-sialon phosphor particle obtained by pulverization to an acid treatment to form the slit on the surface of the α-sialon phosphor particle, wherein the acid treatment is carried out by stirring the α-sialon phosphor particle obtained by pulverization in an aqueous acid solution at a stirring speed of 400 rpm or more, wherein the aqueous acid solution is an aqueous hydrofluoric acid solution or an aqueous mixed acid solution obtained by mixing hydrofluoric acid and nitric acid, and where the stock solution concentration of the aqueous acid solution is equal to or higher than 0.7% and equal to or lower than 100%.

Description

TECHNICAL AREA

[0001] The present invention relates to a phosphor particle, a composite material, a light-emitting device and a method for producing phosphor particles. TECHNICAL BACKGROUND

[0002] As nitride and oxynitride phosphors, an α-sialon phosphor in which a specific rare-earth element is activated is known to exhibit useful fluorescence properties and has been used in white LEDs and similar applications. The α-sialon phosphor has a structure in which the Si-N bonds of the α-silicon nitride crystals are partially replaced by Al-N and Al-O bonds, and certain elements (Ca, Li, Mg, Y, or lanthanide metals, excluding La and Ce) penetrate the crystal lattice and are dissolved in solid form to maintain electrical neutrality. The fluorescence properties are expressed by the fact that some of these elements, such as rare-earth elements, penetrate the lattice, are dissolved in solid form, and act as luminescence centers.The α-sialon phosphor, in which calcium is dissolved and the elements are partially replaced by euchromium, is excited relatively efficiently over a broad wavelength range from ultraviolet to blue light and emits yellow to orange light. As an attempt to further improve the fluorescence properties of such an α-sialon phosphor, it has been proposed, for example, to select an α-sialon phosphor with a specific average particle diameter by means of a classification treatment (Patent Document 1). Furthermore, Patent Document 2 describes a fluorescent material, a method for its preparation, and a luminescent element that uses this fluorescent material. Patent Document 3 discloses a light-emitting semiconductor device. ASSOCIATED DOCUMENT PATENT DOCUMENT [Patent document 1] JP 2009 - 96 882 A [Patent document 2] US 2009 / 0 021 141 A1 [Patent document 3] EP 2 666 841 A1 BRIEF DESCRIPTION OF THE INVENTIONAL PROBLEM

[0003] The present inventors have conducted intensive studies to improve the fluorescence properties of an α-sialon phosphor and have found that the fluorescence properties of the α-sialon phosphor vary depending on the surface shape of an α-sialon phosphor particle. Furthermore, the present invention was developed as a result of progress in investigating which type of surface shape contributes to the fluorescence properties of the α-sialon phosphor. The present invention was undertaken in light of these circumstances. The present invention provides a method for further improving the fluorescence properties of α-sialon phosphor particles. SOLUTION TO THE TASK

[0004] According to the present invention, a phosphor particle is provided which is an α-sialon phosphor particle containing Eu, wherein at least one slit is formed on a surface of the α-sialon phosphor particle, wherein the distance from the surface of the α-sialon phosphor particle to the bottom of the slot is equal to or greater than 200 nm and equal to or less than 1500 nm in at least one cross-section of the slot, wherein the α-sialon phosphor particle is formed from an α-sialon phosphor containing an Eu element, represented by the general formula: (M1 x ,M2 y ,Eu z ) (Si 12-(m+n) Al m+n )(O n N 16-n) (assuming that M1 is a monovalent Li element and M2 is a divalent Ca element), and in the general formula x = 0, 0 < y < 2.0, 0 < z ≤ 0.5, 0 < x + y, 0.3 ≤ x + y + z ≤ 2.0, 0 < m ≤ 4.0 and 0 < n ≤ 3.0 are satisfied, and wherein the α-sialon phosphor particle is produced by a process comprising: Mixing of raw materials containing an element that forms a Eu-containing α-sialon phosphor particle; Heating a mixture of the raw materials to obtain an α-sialon phosphor; Pulverizing the α-sialon phosphor obtained by heating to obtain the α-sialon phosphor particle; and Subjecting the α-sialon phosphor particle obtained by pulverization to an acid treatment to form the slit on the surface of the α-sialon phosphor particle, wherein the acid treatment is carried out by stirring the α-sialon phosphor particle obtained by pulverization in an aqueous acid solution at a stirring speed of 400 rpm or more, wherein the aqueous acid solution is an aqueous hydrofluoric acid solution or an aqueous mixed acid solution obtained by mixing hydrofluoric acid and nitric acid, and where the concentration of the aqueous acid solution is equal to or higher than 0.7% and equal to or lower than 100%.

[0005] Furthermore, according to the present invention, a phosphor particle is provided which is an α-sialon phosphor particle containing Eu, wherein at least one slit is formed on a surface of the α-sialon phosphor particle, wherein a width in a direction perpendicular to an extension direction of the slit is equal to or greater than 50 nm and equal to or less than 500 nm with respect to an opening through the slit formed on the surface of the α-sialon phosphor particle in at least one cross-section of the slit, wherein the α-sialon phosphor particle is formed from an α-sialon phosphor containing an Eu element, represented by the general formula: (M1 x , M2 y ,Eu z ) (Si 12-(m+n) Al m+n )(O n N 16-n ) (assuming that M1 is a monovalent Li element and M2 is a divalent Ca element), and in the general formula x = 0, 0 < y < 2.0, 0 < z ≤ 0.5, 0 < x + y, 0.3 ≤ x + y + z ≤ 2.0, 0 < m ≤ 4.0 and 0 < n ≤ 3.0 are satisfied, and wherein the α-sialon phosphor particle is produced by a process comprising:

[0006] Mixing of raw materials containing an element that forms a Eu-containing α-sialon phosphor particle; Heating a mixture of the raw materials to obtain an α-sialon phosphor; Pulverizing the α-sialon phosphor obtained by heating to obtain the α-sialon phosphor particle; and Subjecting the α-sialon phosphor particle obtained by pulverization to an acid treatment to form the slit on the surface of the α-sialon phosphor particle, wherein the acid treatment is carried out by stirring the α-sialon phosphor particle obtained by pulverization in an aqueous acid solution at a stirring speed of 400 rpm or more, wherein the aqueous acid solution is an aqueous hydrofluoric acid solution or an aqueous mixed acid solution obtained by mixing hydrofluoric acid and nitric acid, and where the concentration of the aqueous acid solution is equal to or higher than 0.7% and equal to or lower than 100%.

[0007] Furthermore, according to the present invention, a phosphor particle is provided which is an α-sialon phosphor particle containing Eu, wherein at least one slit is formed on a surface of the α-sialon phosphor particle, where L > P is satisfied, where a maximum diameter of the α-sialon phosphor particle when viewed from above is defined as P and a total path length along the slot is defined as L, wherein the α-sialon phosphor particle is formed from an α-sialon phosphor containing an Eu element, represented by the general formula: (M1 x , M2 y ,Eu z ) (Si 12-(m+n) Al m+n )(O n N 16-n) (assuming that M1 is a monovalent Li element and M2 is a divalent Ca element), and in the general formula x = 0, 0 < y < 2.0, 0 < z ≤ 0.5, 0 < x + y, 0.3 ≤ x + y + z ≤ 2.0, 0 < m ≤ 4.0 and 0 < n ≤ 3.0 are satisfied, and wherein the α-sialon phosphor particle is produced by a process comprising: Mixing of raw materials containing an element that forms a Eu-containing α-sialon phosphor particle; Heating a mixture of the raw materials to obtain an α-sialon phosphor; Pulverizing the α-sialon phosphor obtained by heating to obtain the α-sialon phosphor particle; and Subjecting the α-sialon phosphor particle obtained by pulverization to an acid treatment to form the slit on the surface of the α-sialon phosphor particle, wherein the acid treatment is carried out by stirring the α-sialon phosphor particle obtained by pulverization in an aqueous acid solution at a stirring speed of 400 rpm or more, wherein the aqueous acid solution is an aqueous hydrofluoric acid solution or an aqueous mixed acid solution obtained by mixing hydrofluoric acid and nitric acid, and where the concentration of the aqueous acid solution is equal to or higher than 0.7% and equal to or lower than 100%.

[0008] Furthermore, according to the present invention, a composite material is provided which contains the aforementioned phosphor particles and a sealing material that seals the phosphor particles.

[0009] Furthermore, according to the present invention, a light-emitting device is provided which includes a light-emitting element that emits excitation light and the aforementioned composite material that increases the wavelength of the excitation light.

[0010] Furthermore, according to the present invention, a method for producing the aforementioned phosphor particle is provided, wherein the method comprises a mixing step of mixing raw materials containing an element forming an α-sialon phosphor particle containing α-sialon, a heating step of heating a mixture of the raw materials to obtain an α-sialon phosphor, a pulverization step of pulverizing the α-sialon phosphor particle obtained by the heating step to obtain the α-sialon phosphor particle, and a step of subjecting the α-sialon phosphor particle obtained by the pulverization step to an acid treatment to form a slit on a surface of the α-sialon phosphor particle. wherein the acid treatment is carried out by stirring the α-sialon phosphor particle obtained by pulverization in an aqueous acid solution at a stirring speed of 400 rpm or more, wherein the aqueous acid solution is an aqueous hydrofluoric acid solution or an aqueous mixed acid solution obtained by mixing hydrofluoric acid and nitric acid, and where the concentration of the aqueous acid solution is equal to or higher than 0.7% and equal to or lower than 100%. ADVANTAGEOUS EFFECTS OF THE INVENTION

[0011] According to the present invention, the fluorescence properties of an α-sialon phosphor particle can be improved. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1(a) is a schematic view of a slit on the surface of an α-sialon phosphor particle. Fig.1(b) is a schematic view of a slot having an oblique V-shaped cross-section. Fig. Figure 2 is a view showing the maximum diameter of an α-sialon phosphor particle in top view. Fig. Figure 3 is a schematic view showing one aspect of the slot. Fig. Figure 4 is a schematic view showing another aspect of the slot. Fig. Figure 5 is a schematic cross-sectional view showing the structure of a light-emitting device according to one embodiment. Fig. Figure 6 is a SEM image of an α-sialon phosphor particle from Example 1. Fig. Figure 7 is a SEM image of a cross-section of a slit formed in the α-sialon phosphor particle from Example 1. Fig.Figure 8 is a SEM image of an α-sialon phosphor particle from Example 2 and a SEM image of a cross-section of the formed slit. Fig. Figure 9 is a SEM image of an α-sialon phosphor particle from the additional comparison example. Fig. Figure 10 is a SEM image of an α-sialon phosphor particle of the additional comparison example. DESCRIPTION OF THE EXECUTION FORMS

[0012] The following section describes in detail embodiments of the present invention.

[0013] The phosphor particle according to one embodiment consists of an α-sialon phosphor particle containing Eu as an activating substance. At least one slit is formed on the surface of the α-sialon phosphor particle. Here, the slit is a groove-shaped depression formed on the surface of the α-sialon phosphor particle, meaning that in a cross-section perpendicular to the direction of extension of the depression (hereinafter, where a "cross-section" is simply mentioned, a cross-section perpendicular to the direction of extension of a slit, which is a groove-shaped depression, is meant), the width becomes narrower as the depth of the depression increases, and the deepest part of it remains within the α-sialon phosphor particle.

[0014] With the α-sialon phosphor particle of the present embodiment, it is possible to improve the fluorescence properties while maintaining the excitation wavelength range and the fluorescence wavelength range of an α-sialon phosphor particle in related prior art. Therefore, as a result, the light emission properties of a light-emitting device using the α-sialon phosphor particle can be improved. A detailed mechanism for this is not clear, but, for example, a slit formed on the surface of the α-sialon phosphor particle could be a depression structure, characteristically representing the removal of a heterogeneous phase that does not contribute to fluorescence.It is assumed that in the α-sialon phosphor particle on which such a slit is formed, a heterogeneous phase that does not contribute to fluorescence is also largely removed from the surface of the α-sialon phosphor particle outside the slit. Therefore, it is expected that the fluorescence properties of the α-sialon phosphor particle are improved by increasing the proportion of parent crystals of a phosphor that contributes to fluorescence on the surface of the α-sialon phosphor particle. Furthermore, it is assumed that the light incident on the slit enters the interior of the α-sialon phosphor particle and is efficiently discharged from there, thereby improving the fluorescence properties of the α-sialon phosphor particle. (α-Sialon phosphor particles)

[0015] The Eu-containing α-Sialon phosphor particle is formed from an α-Sialon phosphor, which is described below.

[0016] The α-Sialon phosphor is an α-Sialon phosphor containing an Eu element, represented by the general formula: (M1 x ,M2 y ,Eu z ) (Si 12-(m+n) Al m+n )(O n N 16-n ) (provided that M1 is a monovalent Li element and M2 are one or more divalent elements selected from the group consisting of Mg, Ca and lanthanide elements (except La and Ce)).

[0017] The solid-state dissolution composition of the α-Sialon phosphor is expressed in the general formula by x, y and z, where m and n are determined by a Si / Al ratio and an associated O / N ratio, and satisfies x = 0, 0 < y < 2.0, 0 < z ≤ 0.5, 0 < x + y, 0.3 ≤ x + y + z ≤ 2.0, 0 < m ≤ 4.0 and 0 < n ≤ 3.0.

[0018] Particularly when Ca is used as M2, the α-sialon phosphor is stabilized over a wide range of compositions. Specifically, by partially replacing the Ca elements with Eu, which is a luminescent center, excitation by light across a broad wavelength range from ultraviolet to blue light can be achieved, resulting in a phosphor emitting visible light in the yellow to orange range.

[0019] From the perspective of achieving incandescent-colored light in lighting applications, the α-Sialon phosphor does not contain Li as a solid-state solution composition.

[0020] In general, α-sialon phosphors have a second crystalline phase that differs from that of the α-sialon phosphor, or an amorphous phase, which is necessarily present. The solid-state-dissolution composition cannot be strictly defined by composition analysis or the like. A single α-sialon phase is preferred as the crystalline phase of the α-sialon phosphor, and the α-sialon phosphor may also contain aluminum nitride, a polytypoid, or the like as a further crystalline phase.

[0021] In α-sialon phosphor particles, a multitude of coaxial primary particles are sintered to form aggregated secondary particles. The primary particles in the present embodiment refer to the smallest particles that can be observed with an electron microscope or the like, whereby the particles may exist individually.

[0022] The lower limit of the average particle diameter of the α-sialon phosphor particles is preferably equal to or greater than 1 µm, more preferably equal to or greater than 5 µm, and even more preferably equal to or greater than 10 µm. Furthermore, the upper limit of the average particle diameter of the α-sialon phosphor particles is preferably equal to or less than 30 µm, and more preferably equal to or less than 20 µm. The average particle diameter of the α-sialon phosphor particles is a measure of the secondary particles. If the average particle diameter of the α-sialon phosphor particles is equal to or greater than 5 µm, the transparency of a composite material described later can be further improved.On the other hand, by adjusting the average particle diameter of the α-sialon phosphor particles to 30 µm or less, the occurrence of chipping can be suppressed when the composite is cut with a dicer or the like.

[0023] Below the average particle diameter of the α-sialon phosphor particles is the median diameter (D). 50 ) in a volume-based integrated fraction, which was determined by a laser diffraction scattering method according to JIS R1629: 1997.

[0024] The shape of α-sialon phosphor particles is not particularly limited. Examples of shapes include spherical, cubic, columnar, and amorphous forms. (Slit formation on the surface of an α-sialon phosphor particle)

[0025] At least one slit is formed on the surface of the α-sialon phosphor particle. The presence or absence of a slit on the surface of the α-sialon phosphor particle can be confirmed, for example, using a scanning electron microscope (SEM). Furthermore, the cross-sectional shape and dimensions of the slit can be confirmed by cutting the α-sialon phosphor particle so that the cross-section is exposed perpendicular to, or intersecting, the direction of the slit, and observing the resulting cross-section with the SEM. A method for cutting the α-sialon phosphor particle is not particularly limited. Examples of such methods include cross-sectional polishing (CP), which is based on an ion milling technique.

[0026] Fig. Figure 1(a) is a schematic view of a slit on the surface of an α-sialon phosphor particle. As in Fig.As shown in 1(a), a slit 20 is a cut formed on the surface of an α-sialon phosphor particle 10 or a groove-shaped depression on the surface of the α-sialon phosphor particle.

[0027] The width W of the slot 20 is the opening width of the slot 20 on the surface of the α-sialon phosphor particle 10 in a direction perpendicular to the extension direction or the longitudinal direction of the slot 20. The width W of the slot 20 refers to the width of the surface of the α-sialon phosphor particle 10 when viewed from the vertical direction of the surface. The width W of the slot 20 can vary from location to location within a given slot 20. According to one embodiment of the present invention, in at least one cross-section of a region containing the slot 20, the lower limit of the width W is equal to or greater than 50 nm, preferably equal to or greater than 100 nm, and more preferably equal to or greater than 150 nm. Furthermore, in this embodiment of the present invention, the upper limit of the width W is equal to or less than 500 nm, preferably equal to or less than 450 nm, and more preferably equal to or less than 400 nm.In at least one cross-section of the region containing the slot 20, it is possible to further improve the fluorescence properties of the α-sialon phosphor particle 10 by adjusting the lower limit of the width W of the slot 20 to the specified range. By adjusting the upper limit of the width W of the slot 20 to the specified range, it is possible to further improve the fluorescence properties of the α-sialon phosphor particle 10 while maintaining the intensity of the α-sialon phosphor particle 10.

[0028] The depth D of slot 20 is a length from the surface of the α-sialon phosphor particle 10 to the bottom of slot 20. That is, a length from the edge of the wall to the bottom of the slot is defined as the depth D of slot 20. Incidentally, in a case where the heights of the left and right walls in Fig.1(a) are different, i.e., in a case where there is a step on the surface section, a length from the edge of the higher wall to the bottom of the slot is defined as the depth D of the slot 20. The depth D of the slot 20 can vary from place to place within the respective slot 20.

[0029] According to one embodiment of the present invention, in at least one cross-section of a region containing the slot 20, the lower limit of the depth D of the slot 20 is equal to or greater than 200 nm, preferably equal to or greater than 250 nm, and more preferably equal to or greater than 300 nm. Conversely, in this embodiment of the present invention, the upper limit of the depth D of the slot 20 is equal to or less than 1500 nm, preferably equal to or less than 1400 nm, and more preferably equal to or less than 1300 nm. In at least one cross-section of the region containing the slot 20, the fluorescence properties of the α-sialon phosphor particle 10 can be further improved by adjusting the lower limit of the depth D to the specified range.By adjusting the upper limit of the depth D of the slot 20 to the range, it is possible to further improve the fluorescence properties of the α-sialon phosphor particle 10 while maintaining the intensity of the α-sialon phosphor particle 10.

[0030] As in Fig. As shown in 1(a), the slot 20 preferably has a V-shaped cross-sectional section formed from two surfaces of a wall 22 and a wall 24 in a cross-section perpendicular to the extension direction of the slot 20.

[0031] It is assumed that the V-shaped cross-sectional section formed by the slot 20 is generated in a case where a heterogeneous phase that does not contribute to fluorescence is removed to a greater extent from the surface of the α-sialon phosphor particle 10. Therefore, it is assumed that it is possible to further improve the fluorescence properties of the α-sialon phosphor particle 10 by enclosing the slot 20 with a V-shaped cross-sectional section.

[0032] Fig. Figure 1(b) is a schematic view of a slot 20 in a case where the slot 20 has an oblique V-shaped cross-section. As in Fig. As shown in Figure 1(b), the angle θ formed in the cross-section of the slot 20 between a wall 22 forming the slot 20 and a surface 12 of the α-sialon phosphor particle is an acute angle. The angle θ is preferably equal to or less than 80 degrees.

[0033] It is assumed that by adjusting the angle θ to an acute angle, i.e. by adjusting the shape of the cross-section of the slot 20 to an obliquely inclined V-shape, the light incident into the slot 20 is absorbed into the interior of the α-sialon phosphor particle 10 and efficiently guided out of it, making it possible to further improve the fluorescence properties of the α-sialon phosphor particle 10.

[0034] As in Fig. As shown in Figure 1(b), the depth D of the slot 20, in a case where the angle θ is an acute angle, is defined by the distance between the intersection point of the wall 22 forming the angle θ and the surface 12 of the α-sialon phosphor particle 10 in the slot 20 to the deepest part. (Note that in the case of the slot of Fig.1(a) the length from an edge of the ‘higher wall’ from the two wall surfaces to the bottom of the slot is defined as D, which for D in the slot of Fig. 1(b) does not apply).

[0035] A plurality of slits 20 can be formed on the surface of a specific α-sialon phosphor particle 10. It is assumed that the plurality of slits 20 formed on the surface of the α-sialon phosphor particle 10 is generated when a heterogeneous phase, which does not contribute to fluorescence, is removed to a greater extent from the surface of the α-sialon phosphor particle 10. Therefore, it is assumed that the fluorescence properties of the α-sialon phosphor particle 10 are further enhanced by the plurality of slits 20 on its surface.Furthermore, the presence of the multitude of slits 20 can increase the amount of light incident on the entire slit 20, thus increasing the amount of light that penetrates the interior of the α-sialon phosphor particle 10 and exits through the slit 20, and thereby further improving the fluorescence properties of the α-sialon phosphor particle 10.

[0036] In this case, the direction of extension of the plurality of slots 20 is not limited. The directions of extension can be parallel to each other or different from each other. Furthermore, the majority of the slots 20 can be separated from each other or intersect. In addition, the majority of the slots 20 can extend radially around the connection.

[0037] As in Fig.Figure 2 shows that the maximum diameter of the α-sialon phosphor particle 10 in a top view is defined as P. According to an embodiment of the present invention, in which a total path length along the slot 20 is defined as L, L > P is satisfied. Accordingly, by further increasing the amount of light incident on and exiting the slot 20, the amount of light entering and exiting the interior of the α-sialon phosphor particle 10 in the slot 20 can be further increased. As a result, the fluorescence properties of the α-sialon phosphor particle 10 can be further improved.

[0038] Fig. Figure 3 is a schematic view for the case where the α-sialon phosphor particle 10 is a columnar body. As in Fig.As shown in Figure 3, in a case where the α-sialon phosphor particle 10 is a columnar body, the slot 20 preferably extends from one end to the other end of a side surface of the columnar body along an axial direction of the columnar body. Accordingly, the amount of light entering the interior of the α-sialon phosphor particle 10 in the slot 20 can be further increased by increasing the total path length of the slot 20 and by further increasing the amount of light incident on and exiting the slot 20. As a result, the fluorescence properties of the α-sialon phosphor particle 10 can be further improved.

[0039] Fig. Figure 4 is a schematic view showing another aspect of the slot. The one in Fig.Figure 4 shows an α-sialon phosphor particle 10 with a plurality of slits extending radially around a connection. According to this embodiment, by increasing the total path length of the slit 20 and by further increasing the amount of light incident on and exiting the slit 20, the amount of light absorbed into and exiting the interior of the α-sialon phosphor particle 10 in the slit 20 can be further increased. This allows the fluorescence properties of the α-sialon phosphor particle 10 to be further improved. The α-sialon phosphor particle 10 can be formed from a plurality of crystal grains, and the slit 20 can be formed between the adjacent crystal grains.

[0040] The fluorescence properties of the phosphor particles described above can be improved by including the slit 20 on the particle surface. Furthermore, the phosphor powder containing the phosphor particles described above (with slits) has the effect mentioned above, namely the improvement of the fluorescence properties. (Method for producing phosphor particles)

[0041] A process for producing the α-sialon phosphor particle of the present embodiment is described. In the α-sialon phosphor particles, a portion of the raw material powder is primarily subjected to a reaction to form a liquid phase, and each of the elements moves through the liquid phase during the synthesis process, thereby promoting the formation of a solid solution and grain growth.

[0042] First, the raw materials containing an element that forms the Eu-containing α-sialon phosphor particles are mixed. Calcium is dissolved in high concentrations in the low-oxygen α-sialon phosphor particles synthesized using calcium nitride as the calcium raw material. In particular, in a case where the calcium solid solution concentration is high, it is possible to obtain a phosphor with a light emission peak wavelength on a higher wavelength side (equal to or greater than 590 nm, more precisely equal to or greater than 590 nm and equal to or less than 610 nm, and even more precisely equal to or greater than 592 nm and equal to or less than 608 nm) than that of a prior art composition using an oxide raw material. In particular, the general formula should preferably be 1.5 < x + y + z ≤ 2.0.Fine-tuning of the emission spectrum is also possible by partially replacing the elements Ca with Li, Mg, Sr, Ba, Y and lanthanide elements (with the exception of La and Ce).

[0043] Examples of other raw material powders include silicon nitride, aluminum nitride, and a Eu compound. Examples of the Eu compound include europium oxide, a compound that transforms into europium oxide upon heating, and europium nitride. Europium nitride, which can reduce the amount of oxygen in the system, is preferred.

[0044] If an appropriate amount of the previously synthesized α-sialon phosphor particles is added to a raw material powder, this addition can serve as a starting point for grain growth to obtain α-sialon phosphor particles with relatively short axis diameters, and the particle shapes can be controlled by changing the shapes of the α-sialon particles to be added.

[0045] Examples of methods for mixing the aforementioned raw materials include a dry mixing process and a process in which wet mixing is carried out in an inert solvent that does not react substantially with the respective components of the raw materials, and in which the solvent is subsequently removed. Examples of mixing equipment include a V-mixer, a vibrating mixer, a ball mill, and a vibratory mill. Mixing calcium nitride, which is unstable in the atmosphere, is preferably carried out in a glovebox under an inert atmosphere, since hydrolysis and oxidation of the substance affect the properties of the synthetic product.

[0046] A container made of a material exhibiting low reactivity with a raw material and a phosphor to be synthesized, e.g., a container made of boron nitride, is filled with a powder obtained by mixing (hereinafter simply referred to as raw material powder). The powder is then heated in a nitrogen atmosphere for a predetermined time. In this way, an α-sialon phosphor can be obtained. The temperature for the heat treatment is preferably equal to or higher than 1650°C and equal to or lower than 1950°C.

[0047] By setting the heat treatment temperature to 1650°C or higher, it is possible to reduce the amount of residual, unreacted products and allow the primary particles to grow sufficiently. Furthermore, by setting the temperature during heat treatment to 1950°C or lower, significant sintering between the particles can be suppressed.

[0048] From the perspective of suppressing sintering between the particles during heating, it is preferred that the container be filled with a larger volume of the raw material powder. In particular, it is preferred that the bulk density at the time of filling the container with the raw material powder be 0.6 g / cm³. 3 or is adjusted less.

[0049] The heating time for the heat treatment is preferably equal to or greater than 2 hours and equal to or less than 24 hours in relation to a time range in which no inconveniences such as the presence of a large amount of unreacted substances, insufficient growth of primary particles and sintering between the particles occur.

[0050] In the aforementioned step, an α-sialon phosphor with a bar-shaped outer form is produced. By subjecting this bar-shaped α-sialon phosphor to a pulverization step, in which the phosphor is pulverized by a pulverizer such as a crusher, mortar mill, ball mill, vibratory mill, or jet mill, and a sieve classification step after such pulverization treatment, it is possible to obtain a powder consisting of α-sialon phosphor particles with a controlled D50 particle diameter of secondary particles. Furthermore, it is possible to adjust the D50 particle diameter of the secondary particles by performing a step in which the phosphor powder is dispersed in an aqueous solution to remove the secondary particles that have small particle diameters and hardly settle.

[0051] The α-sialon phosphor particles according to the present embodiment are produced by carrying out the steps mentioned above and a subsequent acid treatment step. In the acid treatment step, the α-sialon phosphor particle is stirred in an aqueous acid solution. The aqueous acid solution is an aqueous hydrofluoric acid solution or an aqueous mixed acid solution obtained by mixing hydrofluoric and nitric acids. The stock concentration of the aqueous acid solution is equal to or greater than 0.7% and equal to or less than 100%, and preferably equal to or greater than 0.7% and equal to or less than 40%. Furthermore, the temperature at which the acid treatment is carried out is preferably equal to or greater than 60°C and equal to or less than 90°C, and the reaction time (immersion time) is preferably equal to or greater than 15 minutes and equal to or less than 80 minutes.If stirring is performed at high speed, the acid treatment of the particle surface is likely to be sufficiently carried out. The term "high speed," as used here, depends on the stirring device employed, but in a case where a laboratory-grade magnetic stirrer is used, the stirring speed is equal to or greater than 400 rpm, and preferably equal to or greater than 400 rpm and equal to or less than 500 rpm. For the usual purpose of stirring, which consists of continuously supplying fresh acid to the particle surface, a stirring speed of about 200 rpm is sufficient, but if stirring is performed at a high speed of equal to or greater than 400 rpm, it is likely that the particle surface will be sufficiently treated by a physical action in addition to a chemical one.The number, shape, and length of the slits formed on the surface of the α-sialon phosphor particles can be controlled by optimally adjusting the stock concentration of an aqueous acid solution used for acid treatment, the temperature during the acid treatment, the reaction time, and the like. For example, by adopting conditions that approximate a combination of the stock concentration of an aqueous acid solution used in the examples, the temperature during the acid treatment, and the reaction time, and referring to a wealth of examples described below, it is possible to form a slit with a desired number, shape, and length on the surface of the α-sialon phosphor particle. (composite material)

[0052] The composite material according to one embodiment comprises the aforementioned phosphor particles and a sealing material that encapsulates the phosphor particles. In the composite material according to the present embodiment, a plurality of the aforementioned phosphor particles are dispersed in the sealing material. A known material such as a resin, glass, or ceramic can be used as the sealing material. Examples of resins used for the sealing material include transparent resins such as silicone resin, epoxy resin, and urethane resin.

[0053] Examples of a method for producing the composite material include a manufacturing process in which a powder formed from α-sialon phosphor particles of the present embodiment is added to a liquid resin, a glass powder or ceramic, and the mixture is uniformly mixed and then hardened or sintered by heat treatment. (Light-emitting device)

[0054] Fig. Figure 5 is a schematic cross-sectional view showing the structure of a light-emitting device according to the present embodiment. As in Fig. Figure 5 shows a light-emitting device 100 comprising a light-emitting element 120, a heat sink 130, a housing 140, a first conductor frame 150, a second conductor frame 160, a bond wire 170, a bond wire 172 and a composite material 40.

[0055] The light-emitting element 120 is mounted in a predetermined region on the top of the heat sink 130. Mounting the light-emitting element 120 on the heat sink 130 improves its heat dissipation. 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 can be used as the light-emitting element 120, generating light with a wavelength of 300 nm or greater and 500 nm or less, which corresponds to near-ultraviolet to blue light. One electrode (not shown in the drawings) located on the upper surface of the light-emitting element 120 is connected to the surface of the first conductor frame 150 via the bond wire 170, for example, a gold wire. Furthermore, the other electrode (not shown in the drawings), also located on the upper surface of the light-emitting element 120, is connected to the surface of the second conductor frame 160 via the bond wire 172, for example, a gold wire.

[0057] The housing 140 has a substantially funnel-shaped depression, the diameter of which gradually increases from the bottom surface upwards. The light-emitting element 120 is mounted on the bottom surface of the depression. The wall surface of the depression, which surrounds the light-emitting element 120, serves as a reflective plate.

[0058] The recess, whose wall surface is formed by the housing 140, is filled with the composite material 40. The composite material 40 is a wavelength conversion element that increases the wavelength of the excitation light emitted by the light-emitting element 120. The composite material of the present embodiment is used as the composite material 40, and the phosphor particles 1 of the present embodiment are dispersed in a sealing material 30, such as a resin. The light-emitting device 100 emits a mixture of light from the light-emitting element 120 and light generated by the phosphor particles 1, which are excited by absorption of the light from the light-emitting element 120. The light-emitting device 100 preferably emits white light due to the mixture of the light from the light-emitting element 120 and the light generated by the phosphor particles 1.

[0059] In the light-emitting device 100 of the present embodiment, the fluorescence properties of the phosphor particle 1 and the composite material 40 can be improved by using an α-sialon phosphor particle with a slit formed on its surface as the phosphor particle 1, as mentioned above, and an improvement in the light emission intensity of the light-emitting device 100 can be promoted.

[0060] Fig. Figure 5 shows a light-emitting device for surface mounting. However, the light-emitting device is not limited to surface mounting. The light-emitting device can be implemented as a cannonball, a chip-on-board (COB), or a chip-scale package (CSP).

[0061] The embodiments of the present invention have been described above, but these are examples of the present invention and various configurations different from the examples can also be assumed. [Examples]

[0062] The present invention will now be described with reference to examples and comparative examples. (Example 1)

[0063] A mixture of 62.4 parts by mass of silicon nitride powder (manufactured by Ube Kosan Co., Ltd., grade E10), 22.5 parts by mass of aluminum nitride powder (manufactured by Tokuyama Corporation, grade E), 2.2 parts by mass of europium oxide powder (manufactured by Shin-Etsu Chemical Co., Ltd., grade RU), and 12.9 parts by mass of calcium nitride powder (manufactured by Kojundo Chemical Lab. Co., Ltd.) was used in a glove box to create a raw material powder. The raw material powders were dry-mixed and then passed through a 250 µm nylon sieve to obtain a blended raw material powder. A cylindrical boron nitride container (manufactured by Denka Co., Ltd., grade N-1) with a lid and an internal volume of 0.4 liters was filled with 120 g of the blended raw material powder.

[0064] This raw material mixture powder was subjected to heat treatment at 1800°C for 16 hours in a nitrogen atmosphere at atmospheric pressure in an electric furnace of a carbon heater, along with a container. Since the calcium nitride contained in the mixed raw material powder is readily hydrolyzed in air, the boron nitride container filled with the mixed raw material powder was immediately placed in the electric furnace after being removed from the glove box and immediately evacuated to a vacuum to prevent any reaction of the calcium nitride.

[0065] The synthetic product was lightly crushed in a mortar and completely sieved through a 150 µm mesh sieve to obtain a phosphor powder. The crystalline phase of this phosphor powder was then investigated by X-ray diffraction (XRD measurement) using CuKα rays; the crystalline phase found was a Ca-α-sialon (α-sialon including Ca) containing the Eu element.

[0066] Subsequently, 50 ml of 50% hydrofluoric acid and 50 ml of 70% nitric acid were mixed to obtain a mixed stock solution. 300 ml of distilled water were added to the mixed stock solution, and the concentration of the mixed stock solution was diluted to 25% to prepare 400 ml of an aqueous mixed acid solution. 30 g of a powder formed from the aforementioned α-sialon phosphor particles were added to the aqueous mixed acid solution. The temperature of the aqueous mixed acid solution was maintained at 80°C, and the mixture was subjected to acid treatment by immersion in a magnetic stirrer at a rotational speed of 450 rpm for 60 minutes.The powder after acid treatment was thoroughly washed with distilled water, filtered, dried and then sieved through a sieve with a mesh size of 45 µm to produce a powder consisting of the α-sialon phosphor particles of Example 1. (Example 2)

[0067] A powder of α-sialon phosphor particles of Example 2 was prepared by the same procedure as in Example 1, except that an aqueous mixed acid solution with a stock solution concentration of 1.0% was prepared by adding 396 ml of distilled water to a mixed stock solution obtained by mixing 3.2 ml of 50% hydrofluoric acid and 0.8 ml of 70% nitric acid, instead of the aqueous mixed acid solution used in Example 1, and the phosphor powder was immersed for 30 minutes while the temperature of the aqueous mixed acid solution was maintained at 80°C. (Example 3)

[0068] A powder of α-sialon phosphor particles from Example 3 was prepared by the same procedure as in Example 1, except that an aqueous mixed acid solution with a stock solution concentration of 1.0% was prepared by adding 396 ml of distilled water to a mixed stock solution obtained by mixing 1.2 ml of 50% hydrofluoric acid and 2.8 ml of 70% nitric acid, instead of the aqueous mixed acid solution used in Example 1, and the phosphor powder was immersed for 30 minutes while maintaining the temperature of the aqueous mixed acid solution at 80°C. (Example 4)

[0069] A powder of α-sialon phosphor particles from Example 4 was prepared by the same procedure as in Example 1, except that an aqueous mixed acid solution with a stock solution concentration of 1.0% was prepared by adding 396 ml of distilled water to a mixed stock solution obtained by mixing 2.0 ml of 50% hydrofluoric acid and 2.0 ml of 70% nitric acid, instead of the aqueous mixed acid solution used in Example 1, and the phosphor powder was immersed for 30 minutes while the temperature of the aqueous mixed acid solution was maintained at 80°C. (Example 5)

[0070] A phosphor powder formed from α-sialon phosphor particles of Example 5 was prepared by the same procedure as in Example 1, except that an aqueous hydrofluoric acid solution with a stock solution concentration of 25% was prepared by adding 300 ml of distilled water to 100 ml of 50% hydrofluoric acid (stock solution) instead of the aqueous mixed acid solution used in Example 1, and the phosphor powder was immersed for 30 minutes while the temperature of the aqueous acid solution was maintained at 80°C. (Comparative example 1)

[0071] A powder of α-sialon phosphor particles of Comparative Example 1 was prepared by the same procedure as in Example 1, except that an aqueous mixed acid solution with a stock solution concentration of 0.5% was used by adding 398 ml of distilled water to a mixed stock solution obtained by mixing 1.0 ml of 50% hydrofluoric acid and 1.0 ml of 70% nitric acid instead of the aqueous mixed acid solution used in Example 1, the temperature of the aqueous mixed acid solution was maintained at 80°C, and the mixture was subjected to an acid treatment in which the aqueous mixed acid solution was immersed for 30 minutes with a magnetic stirrer while stirring at a rotational speed of 300 rpm.

[0072] In the process for producing a powder from α-sialon phosphor particles of comparative example 1, the stock solution concentration of the aqueous mixed acid solution used for the acid treatment was adjusted to a level customary in the prior art. (Evaluation of properties)[Light emission properties]

[0073] For each of the obtained α-sialon phosphor particle powders, the absorption rate, internal quantum efficiency and external quantum efficiency were measured using a spectrophotometer (MCPD-7000 manufactured by Otsuka Electronics Co., Ltd.) and calculated according to the following procedure.

[0074] A powder formed from the α-sialon phosphor particles of the examples or the comparison example was filled into a well cell to create a smooth surface, and an integrating sphere was attached. Monochromatic light, spectrally split to a wavelength of 455 nm by a light emission source (Xe lamp), was introduced into the integrating sphere via an optical fiber. A sample of the phosphor was irradiated with the monochromatic light as the excitation source, and the fluorescence spectrum of the sample was measured. A standard reflective plate (Spectralon, manufactured by Labsphere Inc.) with a reflectance of 99% was attached to a sample unit, and the spectrum of the excitation light at a wavelength of 455 nm was measured. At this point, the number (Qex) of excitation photons was calculated from a spectrum in the wavelength range of 450 nm or greater and 465 nm or less.

[0075] A powder composed of α-sialon phosphor particles was attached to the sample unit, and the number (Qref) of reflected excitation photons and the number (Qem) of fluorescence photons were calculated from the obtained spectral data. The number of reflected excitation photons was calculated in the same wavelength range as the number of excitation photons, and the number of fluorescence photons was calculated in the range of 465 nm or greater and 800 nm or less. Absorption rate=(Qex−Qref) / Qex×100 Internal quantum efficiency = (Qem / (Qex−Qref))×100 External quantum efficiency = (Qem / Qex) × 100

[0076] In one instance where the standard sample NSG1301, sold by Sialon Co., Ltd., was measured using the measurement method, the external quantum efficiency was 55.6% and the internal quantum efficiency was 74.8%. The device was calibrated using this sample as the standard.

[0077] The peak wavelengths of the emission spectra of the powders formed from the α-sialon phosphor particles of examples 1 to 5, which were determined by measurement (wavelength of the incident light: 455 nm), are each at 600 nm (relatively high wavelength). [Measurement of particle size]

[0078] The particle size was measured using a laser diffraction method based on JIS R1629:1997 with the Microtrac MT3300EX II (MicrotracBEL Corporation). 0.5 g of α-sialon phosphor particles were distributed in 100 cm 3Ion exchange water was added, the mixture was dispersed for 3 minutes using the US-150E ultrasonic homogenizer (Nissei Corporation, chip size: φ20 mm, amplitude: 100%, oscillation frequency: 19.5 kHz, oscillation amplitude: approximately 31 µm), and then the particle size was measured with the MT3300EX II. The median diameter D50 was determined from the resulting particle size distribution. [Slot confirmation]

[0079] The surface of the α-sialon phosphor particle was examined using a scanning electron microscope (SEM). Fig. Figure 6(a) is a SEM image of the α-sialon phosphor particle from Example 1. As in Fig. As shown in Figure 6(a), it was confirmed that a plurality of slits were formed on the surface of the α-sialon phosphor particle in Example 1. The plurality of slits overlap and extend radially around the intersection point (connection).

[0080] Fig.Figure 8(a) is a SEM image of the α-sialon phosphor particle from Example 2. As in Fig. As shown in Figure 8(a), the slit 20 extends from one surface to the other surface of the particle in Example 2.

[0081] In Examples 1 and 2, it was confirmed that α-sialon phosphor particles are present where the sum L of the path lengths along the multiple slits is greater than a maximum diameter P when viewed from above. Furthermore, it was confirmed that slits have formed on the surfaces of the α-sialon phosphor particles in Examples 3 to 5. In contrast, in Comparative Example 1, it was confirmed that no slit was present on the surface of the phosphor particle. [Observation of the slot cross-section]

[0082] The α-sialon phosphor particle from Example 1 was cut using an ion milling device to create a cross-section that intersected the slot. The cutting process was carried out particularly along the [unclear] Fig. 6(b) straight line shown. The states of the cross-sections of the two resulting slots, which were viewed in the SEM, are shown in Fig. 7(a) and Fig. Figure 7(b) illustrates this. In a cross-section of the α-sialon phosphor particle from Example 1, the slit depth was 808 nm and the slit width (the width when viewed from the vertical direction of the surface of the α-sialon phosphor particle) was 433 nm. Furthermore, the cross-sectional shape of the slit was V-shaped and inclined. In another cross-section, the slit was V-shaped with a depth of 936 nm and a width of 267 nm.

[0083] Similarly, the α-sialon phosphor particle from Example 2 was cut using an ion milling device to create a cross-section that cuts the slot. Specifically, the cutting process was performed along the Fig. 8(b) is carried out along the straight line shown. With reference to the obtained cross-section, the state of the obtained cross-section in Fig. 8(c) can be seen in the SEM. In a cross-section of the α-sialon phosphor particle of Example 2, a V-shaped slit with a slit depth of 309 nm and a slit width of 85.6 nm was observed.

[0084] Furthermore, slits with a V-shaped cross-section were also observed in the α-sialon phosphor particles of examples 3 to 5. [Table 1] Example 1 Example 2 Example 3 Example 4 Example 5 Comparative example 1 Acid treatment acid solution 50% hydrofluoric acid (ml) 50 3,2 1,2 2,0 100 1,0 70% nitric acid (ml) 50 0,8 2,8 2,0 0 1,0 Liquid ratio (amount of hydrofluoric acid:amount of nitric acid) 5:5 8:2 3:7 5:5 10:0 5:5 Distilled water (ml) 300 396 396 396 300 398 Concentration of stock solution (%) 25 1,0 1,0 1,0 25 0,5 Reaction conditions Temperature (°C) 80 80 80 80 80 80 Time (min) 60 30 30 30 30 30 Particle size D 50 (µm) 16,3 15,6 14,5 16,2 14,3 15,6 Surface shape Presence or absence of a slot Available Available Available Available Available Miss Properties of light emission Absorption rate (%) 87,7 88,9 88,4 89,3 88,2 89,1 Internal quantum efficiency (%) 77,1 79,9 80,3 79,5 80,2 73,7 External quantum efficiency (%) 67,6 71,0 71,0 71,1 70,7 65,7

[0085] As shown in Table 1, it was confirmed that in each of the α-sialon phosphor particles of Examples 1 to 5, which have a slit formed on the surface, both the internal quantum efficiency and the external quantum efficiency were higher than that of the comparison example 1 and the fluorescence properties were improved. (Additional comparative example: Example where the conditions for acid treatment in Example 3 have been changed)

[0086] α-Sialon phosphor particles were produced in the same way as in Example 3, except that the stirring speed of the magnetic stirrer during the acid treatment was reduced from 450 rpm to 200 rpm, i.e., to a normal level.

[0087] The mean diameter D50 of the phosphor particles obtained in this additional comparison example was 14.5 µm. The obtained phosphor particles were then examined using SEM in various fields of view, but no phosphor particles with slits on their surface were found. For illustration, the SEM images of the obtained phosphor particles are shown in the Fig. 9 and Fig. 10 shown.

[0088] Furthermore, the internal quantum efficiency of the obtained phosphor particles was 75.4% and the external quantum efficiency was 66.6%, which deteriorated compared to Example 3 (and other examples). Reference symbol list 1 phosphor particle 10 α-Sialon phosphor particles 20 slots 30 Sealing material 40 Composite material 100 light-emitting devices 120 light-emitting elements 130 heat sinks 140 cases 150 first ladder frame 160 second ladder frame 170 bond wire 172 Bond wire

Claims

[1] α-Sialon phosphor particle containing Eu, wherein at least one slit is formed on a surface of the α-sialon phosphor particle, wherein the distance from the surface of the α-sialon phosphor particle to the bottom of the slot is equal to or greater than 200 nm and equal to or less than 1500 nm in at least one cross-section of the slot, wherein the α-sialon phosphor particle is formed from an α-sialon phosphor containing an Eu element, represented by the general formula: (M1 x , M2y,Eu z ) (Si 12-(m+n) Al m+n )(O n N 16-n ) (assuming that M1 is a monovalent Li element and M2 is a divalent Ca element), and in the general formula x = 0, 0 < y < 2.0, 0 < z ≤ 0.5, 0 < x + y, 0.3 ≤ x + y + z ≤ 2.0, 0 < m ≤ 4.0 and 0 < n ≤ 3.0 are satisfied, and wherein the α-sialon phosphor particle is produced by a process comprising: Mixing of raw materials containing an element that forms a Eu-containing α-sialon phosphor particle; Heating a mixture of the raw materials to obtain an α-sialon phosphor; Pulverizing the α-sialon phosphor obtained by heating to obtain the α-sialon phosphor particle; and Subjecting the α-sialon phosphor particle obtained by pulverization to an acid treatment to form the slit on the surface of the α-sialon phosphor particle, wherein the acid treatment is carried out by stirring the α-sialon phosphor particle obtained by pulverization in an aqueous acid solution at a stirring speed of 400 rpm or more, wherein the aqueous acid solution is an aqueous hydrofluoric acid solution or an aqueous mixed acid solution obtained by mixing hydrofluoric acid and nitric acid, and where the stock solution concentration of the aqueous acid solution is equal to or higher than 0.7% and equal to or lower than 100%. [2] α-Sialon phosphor particle containing Eu, wherein at least one slit is formed on a surface of the α-sialon phosphor particle, wherein a width in a direction perpendicular to an extension direction of the slit is equal to or greater than 50 nm and equal to or less than 500 nm with respect to an opening through the slit formed on the surface of the α-sialon phosphor particle in at least one cross-section of the slit, wherein the α-sialon phosphor particle is formed from an α-sialon phosphor containing an Eu element, represented by the general formula: (M1 x , M2y,Eu z ) (Si 12-(m+n) Al m+n )(O n N 16-n ) (assuming that M1 is a monovalent Li element and M2 is a divalent Ca element), and in the general formula x = 0, 0 < y < 2.0, 0 < z ≤ 0.5, 0 < x + y, 0.3 ≤ x + y + z ≤ 2.0, 0 < m ≤ 4.0 and 0 < n ≤ 3.0 are satisfied, and wherein the α-sialon phosphor particle is produced by a process comprising: Mixing of raw materials containing an element that forms a Eu-containing α-sialon phosphor particle; Heating a mixture of the raw materials to obtain an α-sialon phosphor; Pulverizing the α-sialon phosphor obtained by heating to obtain the α-sialon phosphor particle; and Subjecting the α-sialon phosphor particle obtained by pulverization to an acid treatment to form the slit on the surface of the α-sialon phosphor particle, wherein the acid treatment is carried out by stirring the α-sialon phosphor particle obtained by pulverization in an aqueous acid solution at a stirring speed of 400 rpm or more, wherein the aqueous acid solution is an aqueous hydrofluoric acid solution or an aqueous mixed acid solution obtained by mixing hydrofluoric acid and nitric acid, and where the stock solution concentration of the aqueous acid solution is equal to or higher than 0.7% and equal to or lower than 100%. [3] α-Sialon phosphor particle containing Eu, wherein at least one slit is formed on a surface of the α-sialon phosphor particle, where L > P is satisfied, where a maximum diameter of the α-sialon phosphor particle when viewed from above is defined as P and a total path length along the slot is defined as L, wherein the α-sialon phosphor particle is formed from an α-sialon phosphor containing an Eu element, represented by the general formula: (M1 x , M2y,Eu z ) (Si 12 - (m+n) Al m+n )(O n N 16-n) (assuming that M1 is a monovalent Li element and M2 is a divalent Ca element), and in the general formula x = 0, 0 < y < 2.0, 0 < z ≤ 0.5, 0 < x + y, 0.3 ≤ x + y + z ≤ 2.0, 0 < m ≤ 4.0 and 0 < n ≤ 3.0 are satisfied, and wherein the α-sialon phosphor particle is produced by a process comprising: Mixing of raw materials containing an element that forms a Eu-containing α-sialon phosphor particle; Heating a mixture of the raw materials to obtain an α-sialon phosphor; Pulverizing the α-sialon phosphor obtained by heating to obtain the α-sialon phosphor particle; and Subjecting the α-sialon phosphor particle obtained by pulverization to an acid treatment to form the slit on the surface of the α-sialon phosphor particle, wherein the acid treatment is carried out by stirring the α-sialon phosphor particle obtained by pulverization in an aqueous acid solution at a stirring speed of 400 rpm or more, wherein the aqueous acid solution is an aqueous hydrofluoric acid solution or an aqueous mixed acid solution obtained by mixing hydrofluoric acid and nitric acid, and where the stock solution concentration of the aqueous acid solution is equal to or higher than 0.7% and equal to or lower than 100%. [4] Phosphor particles according to claim 2 or 3, wherein the distance from the surface of the α-sialon phosphor particle to the bottom of the slot is equal to or greater than 200 nm and equal to or less than 1500 nm in at least one cross-section of the slot. [5] Phosphor particle according to claim 1 or 3, wherein a width in a direction perpendicular to an extension direction of the slit is equal to or greater than 50 nm and equal to or less than 500 nm with respect to an opening through the slit formed on the surface of the α-sialon phosphor particle in at least one cross-section of the slit. [6] Phosphor particles according to claim 1 or 2, wherein L > P is satisfied, wherein a maximum diameter of the α-sialon phosphor particle when viewed from above is defined as P and a total path length along the slot is defined as L. [7] Phosphor particles according to any one of claims 1 to 6, wherein the slot has a V-shaped cross-sectional section in a cross-section perpendicular to an extension direction of the slot. [8] Phosphor particle according to any one of claims 1 to 7, wherein the α-sialon phosphor particle has a plurality of slits formed. [9] Phosphor particle according to claim 8, wherein the particle has a plurality of slits which are separated from each other. [10] Phosphor particle according to claim 8 or 9, wherein the particle has a plurality of intersecting slits. [11] Phosphor particle according to any one of claims 8 to 10, wherein the particle has a plurality of slits extending radially around a node. [12] Phosphor particle according to any one of claims 1 to 11, wherein the α-sialon phosphor particle is a column-shaped body, wherein the slit extends from one end to the other end of a side surface of the column-shaped body along an axial direction of the column-shaped body. [13] Composite material comprising: the phosphor particles according to any one of claims 1 to 12; and a sealing material that seals the fluorescent particles. [14] Light-emitting device comprising: a light-emitting element that emits excitation light; and the composite material according to claim 13, which increases a wavelength of the excitation light. [15] Method for producing the phosphor particle according to any one of claims 1 to 12, comprising: Mixing of raw materials containing an element that forms a Eu-containing α-sialon phosphor particle; Heating a mixture of the raw materials to obtain an α-sialon phosphor; Pulverizing the α-sialon phosphor obtained by heating to obtain the α-sialon phosphor particle; and Subjecting the α-sialon phosphor particle obtained by pulverization to an acid treatment to form a slit on a surface of the α-sialon phosphor particle, wherein the acid treatment is carried out by stirring the α-sialon phosphor particle obtained by pulverization in an aqueous acid solution at a stirring speed of 400 rpm or more, wherein the aqueous acid solution is an aqueous hydrofluoric acid solution or an aqueous mixed acid solution obtained by mixing hydrofluoric acid and nitric acid, and where the stock solution concentration of the aqueous acid solution is equal to or higher than 0.7% and equal to or lower than 100%.

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