Ce-ACTIVATED α-SIALON PHOSPHOR AND METHOD FOR PRODUCING SAME

Abstract

A Ce-activated α-sialon phosphor which has an emission peak within the wavelength range of 470-525 nm in an emission spectrum at the time when excited with light having a wavelength of 405 nm, wherein the diffuse reflectance with respect to light having the wavelength at which the emission peak is positioned is 86.5% or more.

Description

Ce-activated α-sialon phosphor and its manufacturing method

[0001] The present disclosure relates to a Ce-activated α-sialon phosphor and a method for producing the same.

[0002] α-SiAlON (Si-Al-O-N) is a solid solution in which specific elements penetrate into the crystal lattice of α-SiN, forming a solid solution, and some of the Si-N bonds are replaced with Al-N bonds or Al-O bonds to maintain electrical neutrality. Fluorescence is generated by replacing some of the elements that have penetrated into the solid solution with a luminescent center element.

[0003] Patent Document 1 describes a compound having the general formula: (M1) Ｘ (M2) Ｙ (Si, Al) １２ (O, N) １６ (wherein M1 is one or more elements selected from the group consisting of Li, Mg, Ca, Y and lanthanide metals (excluding La and Ce), and M2 is one or more elements selected from Ce, Pr, Eu, Tb, Yb and Er, and 0.3<X+Y<1.5, 0<Y<0.7), and characterized in that it contains 30 ppm or more and 1% or less of fluorine as an impurity.

[0004] WO 2005 / 123876

[0005] Phosphors containing α-sialon with Ce as the luminescent center element have attracted attention as phosphors that exhibit fluorescence in the blue to green range. An object of the present disclosure is to provide a Ce-activated α-sialon phosphor with excellent internal quantum efficiency, and a method for manufacturing a Ce-activated α-sialon phosphor with excellent internal quantum efficiency.

[0006] The present inventors have found that a Ce-activated α-sialon with improved internal quantum efficiency can be obtained by setting the diffuse reflectance for light of a wavelength at which the emission peak is located at a predetermined value or higher. Furthermore, the present inventors have found that one effective means of increasing the diffuse reflectance described above is to blend an Eu source with the Ce-activated α-sialon and then subject the resulting material to an annealing treatment. In other words, the present inventors have found that a Ce-activated α-sialon phosphor with excellent internal quantum efficiency can be produced by subjecting the Ce-activated α-sialon to a heat treatment together with an Eu source. The present disclosure is based on the above findings.

[0007] The present disclosure provides the following items [1] to

[12] . [1] A Ce-activated α-sialon phosphor having an emission peak in the wavelength range of 470 to 525 nm in its emission spectrum when excited with light having a wavelength of 405 nm, and having a diffuse reflectance of 86.5% or more for light having the wavelength at which the emission peak is located. [2] The Ce-activated α-sialon phosphor according to item [1], which contains Eu. [3] The Ce-activated α-sialon phosphor according to item [1] or [2], in which the Eu content is 0.0001 to 1.5 mass% based on the total mass of the Ce-activated α-sialon phosphor. [4] The Ce-activated α-sialon phosphor according to any one of items [1] to [3], in which the half-width of the emission peak is 100 nm or more. [5] The Ce-activated α-sialon phosphor according to any one of [1] to [4], wherein in the emission spectrum, the ratio of the emission intensity observed at a wavelength of 580 nm to the emission peak intensity is less than 45%. [6] The Ce-activated α-sialon phosphor according to any one of [1] to [5], wherein the Ce-activated α-sialon phosphor contains, as constituent elements, M, Ce, Si, Al, O, and N, where M is at least one element selected from the group consisting of Li, Ca, Mg, Y, and lanthanide elements (excluding La, Ce, and Eu), and the M content is 1 to 4 mol %, the Ce content is 0.05 to 2 mol %, the Si content is 25 to 45 mol %, the Al content is 4 to 12 mol %, the O content is 0.5 to 5 mol %, and the N content is 40 to 60 mol %, based on the total content of M, Ce, Si, Al, O, and N in the Ce-activated α-sialon phosphor. [7] The Ce-activated α-sialon phosphor according to any one of [1] to [6], wherein the Ce-activated α-sialon phosphor contains an α-sialon represented by the following general formula (1): (M ａ＋ ｘ , Ce ３＋ ｙ ) Si １２－（ｍ＋ｎ） Al （ｍ＋ｎ） O ｎ N １６－ｎ(1) [In the general formula (1), M is at least one element selected from the group consisting of Li, Ca, Mg, Y, and lanthanide elements (excluding La, Ce, and Eu), and when the valence of M is a, m = ax + 3y, and Ce ３＋ is substituted at the M site, and 0.3≦x+y≦2, 0.03≦y≦0.5, and 0≦n≦m.] [8] A method for producing a Ce-activated α-sialon phosphor, comprising a step of heat-treating a mixture containing Ce-activated α-sialon and an Eu source at 1200 to 1500°C to obtain a heat-treated product. [9] The production method according to [8], wherein the content of the Eu source in the mixture is 0.1 to 3.0 parts by mass per 100 parts by mass of the Ce-activated α-sialon.

[10] The production method according to [8] or [9], wherein the heat treatment is carried out in an atmosphere containing at least one gas selected from the group consisting of a rare gas and a reducing gas.

[11] The production method according to any one of [8] to

[10] , further comprising a step of acid-treating the heat-treated product.

[12] The manufacturing method according to any one of [8] to

[11] , further comprising a step of obtaining a Ce-activated α-sialon by firing a raw material composition containing a Si source, an Al source, and a Ce source.

[0008] According to the present disclosure, it is possible to provide a Ce-activated α-sialon phosphor having excellent internal quantum efficiency, and a method for producing a Ce-activated α-sialon phosphor having excellent internal quantum efficiency.

[0009] FIG. 1 shows the emission spectra of the α-sialon phosphors of Examples 1 and 2 and Comparative Examples 7 and 12.

[0010] Hereinafter, embodiments of the present disclosure will be described. However, the following embodiments are merely examples for explaining the present disclosure, and are not intended to limit the present disclosure to the following contents.

[0011] Unless otherwise specified, the materials exemplified in this specification can be used singly or in combination of two or more. When multiple substances corresponding to each component are present in the composition, the content of each component in the composition means the total amount of the multiple substances present in the composition, unless otherwise specified. In this specification, the "steps" may be steps independent of each other or steps performed simultaneously.

[0012] [Ce-activated α-sialon phosphor] One embodiment of the present disclosure is an α-sialon phosphor activated with Ce. Hereinafter, this Ce-activated α-sialon phosphor may also be simply referred to as a "Ce-activated α-sialon phosphor."

[0013] The Ce-activated α-sialon phosphor may have a diffuse reflectance of 86.5% or more for light of a wavelength at which an emission peak is located in an emission spectrum when excited with light of a wavelength of 405 nm. When multiple peaks are observed in the emission spectrum when the Ce-activated α-sialon phosphor is excited with light of a wavelength of 405 nm, the peak with the greatest intensity is regarded as the "emission peak" in this specification.

[0014] A high predetermined diffuse reflectance is considered to mean that the crystals contained in the Ce-activated α-sialon phosphor contain few defects that absorb the light emitted by the phosphor. Therefore, a Ce-activated α-sialon phosphor having a diffuse reflectance equal to or greater than the predetermined value is considered to have excellent internal quantum efficiency. It has been difficult to achieve a predetermined diffuse reflectance of 86.5% or more in a Ce-activated α-sialon phosphor. However, the inventors, through extensive research, have found that a Ce-activated α-sialon phosphor having such a high diffuse reflectance can be obtained by subjecting the Ce-activated α-sialon to a specific treatment.

[0015] The Ce-activated α-sialon phosphor contains Ce as the luminescent center element. The Ce-activated α-sialon phosphor may be substantially free of Eu as the luminescent center element, and may contain substantially only Ce as the luminescent center element. The Ce-activated α-sialon phosphor being substantially free of Eu as the luminescent center element means that no luminescent peak derived from Eu is observed in the emission spectrum of the Ce-activated α-sialon phosphor when excited with light having a wavelength of 405 nm. Furthermore, the Ce-activated α-sialon phosphor containing substantially only Ce as the luminescent center element means that only peaks derived from Ce are observed in the emission spectrum of the Ce-activated α-sialon phosphor when excited with light having a wavelength of 405 nm. For example, even if the Ce-activated α-sialon phosphor contains Eu, if no luminescent peak derived from Eu is observed, Eu is deemed not to be included as the luminescent center element in this specification.

[0016] The Ce-activated α-sialon phosphor may contain M, Ce, Si, Al, O, and N as constituent elements. Here, M is at least one element selected from the group consisting of Li, Ca, Mg, Y, and lanthanide elements (excluding La, Ce, and Eu). The content of M may be 1 mol% or more, or 2 mol% or more, based on the total content of M, Ce, Si, Al, O, and N in the Ce-activated α-sialon phosphor (hereinafter also referred to as "the total content of the above constituent elements"). Furthermore, the content of M may be 4 mol% or less, or 3 mol% or less, based on the total content of the above constituent elements in the Ce-activated α-sialon phosphor. The content of Ce may be 0.05 mol% or more, or 0.1 mol% or more, based on the total content of the above constituent elements in the Ce-activated α-sialon phosphor. The Ce content may be 2 mol % or less, or 1 mol % or less, based on the total content of the above-mentioned constituent elements in the Ce-activated α-sialon phosphor.

[0017] The Si content may be 25 mol% or more, or 30 mol% or more, based on the total content of the above constituent elements in the Ce-activated α-sialon phosphor. The Si content may be 45 mol% or less, or 40 mol% or less, based on the total content of the above constituent elements in the Ce-activated α-sialon phosphor. The Al content may be 4 mol% or more, 5 mol% or more, or 6 mol% or more, based on the total content of the above constituent elements in the Ce-activated α-sialon phosphor. The Al content may be 12 mol% or less, 10 mol% or less, 9 mol% or less, or 8 mol% or less, based on the total content of the above constituent elements in the Ce-activated α-sialon phosphor. The contents of M, Ce, Si, and Al are determined by ICP optical emission spectroscopy using a multi-type ICP optical emission spectrometer.

[0018] The O content may be 0.5 mol% or more, or 1 mol% or more, based on the total content of the above constituent elements in the Ce-activated α-sialon phosphor. The O content may be 5 mol% or less, or 4 mol% or less, based on the total content of the above constituent elements in the Ce-activated α-sialon phosphor. The N content may be 40 mol% or more, or 45 mol% or more, based on the total content of the above constituent elements in the Ce-activated α-sialon phosphor. The N content may be 60 mol% or less, or 55 mol% or less, based on the total content of the above constituent elements in the Ce-activated α-sialon phosphor. The O and N contents are determined by analyzing the amounts of oxygen and nitrogen using an oxygen / nitrogen analyzer.

[0019] For example, in an α-sialon phosphor activated with Ce, based on the total content of M, Ce, Si, Al, O, and N in the Ce-activated α-sialon phosphor, the M content may be 1 to 4 mol%, the Ce content may be 0.05 to 2 mol%, the Si content may be 25 to 45 mol%, the Al content may be 4 to 12 mol%, the O content may be 0.5 to 5 mol%, and the N content may be 40 to 60 mol%.

[0020] The Ce-activated α-sialon phosphor may contain, as its main crystal, a crystal having the same crystal structure as α-sialon. The Ce-activated α-sialon phosphor may contain a heterophase as long as the spirit of the present disclosure is not impaired. In the powder X-ray diffraction pattern of the Ce-activated α-sialon phosphor, the ratio of the maximum diffraction line intensity of the heterophase to the diffraction line intensity of the (101) plane may be 10% or less, 5% or less, 3% or less, or 2% or less. In this specification, the powder X-ray diffraction pattern refers to a pattern obtained by powder X-ray diffraction using CuKα radiation at 25°C. The maximum diffraction line of the heterophase refers to the diffraction line with the greatest diffraction intensity among the diffraction lines in the powder X-ray diffraction pattern that cannot be assigned to α-sialon.

[0021] The Ce-activated α-sialon phosphor may contain, for example, an α-sialon represented by the following general formula (1): (M ａ＋ ｘ , Ce ３＋ ｙ ) Si １２－（ｍ＋ｎ） Al （ｍ＋ｎ） O ｎ N １６－ｎ (1) [In the general formula (1), M is at least one element selected from the group consisting of Li, Ca, Mg, Y, and lanthanide elements (excluding La, Ce, and Eu), and when the valence of M is a, m = ax + 3y, and Ce ３＋ is substituted at the M site, and 0.3≦x+y≦2, 0.03≦y≦0.5, and 0≦n≦m.

[0022] The Ce-activated α-sialon phosphor may contain Ca, or may contain α-sialon in which Ca is dissolved. In the above general formula (1), M may be Ca, or may be two or more elements selected from the group consisting of Ca and at least one element selected from the group consisting of Li, Mg, Y, and lanthanide elements (excluding La, Ce, and Eu). When M is Ca, a = 2 in general formula (1). The presence of Ca in the Ce-activated α-sialon phosphor can be confirmed by quantitative elemental analysis using an ICP optical emission spectrometer.

[0023] In general formula (1), x + y may be 0.4 or more, 0.5 or more, 0.6 or more, or 0.7 or more, and may be 1.8 or less, 1.5 or less, 1.3 or less, 1.1 or less, 1.0 or less, or 0.9 or less. In general formula (1), y may be 0.05 or more, or 0.06 or more, and may be 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less. In general formula (1), n ​​may be 0.01 or more, 0.05 or more, or 0.10 or more, and may be less than m.

[0024] The Ce-activated α-sialon phosphor contains the α-sialon represented by the general formula (1) above, which means that in the powder X-ray diffraction pattern of the Ce-activated α-sialon phosphor, the ratio of the maximum diffraction line intensity of a different phase to the diffraction line intensity of the (101) plane is 10% or less, and the content ratio of each constituent element (M, Ce, Si, Al, O, and N) calculated by analysis by ICP optical emission spectroscopy using a multi-type ICP optical emission spectroscopy analyzer and analysis of the oxygen and nitrogen amounts using an oxygen-nitrogen analyzer is equal to the ratio represented by the general formula (1).

[0025] The Ce-activated α-sialon phosphor may be represented by, for example, the general formula (1). In this case, M, x + y, y, and n may each be as described above. The constituent elements and proportions of the Ce-activated α-sialon phosphor can be determined by analyzing the oxygen and nitrogen amounts using an oxygen / nitrogen analyzer and by ICP optical emission spectroscopy using a multi-type ICP optical emission spectroscopy analyzer. The fact that the Ce-activated α-sialon phosphor is represented by the general formula (1) means that when the constituent elements and proportions of the Ce-activated α-sialon phosphor are determined by the above analysis, the content ratios of Ce, Si, Al, O, N, and M in the general formula (1) are equal to the ratios shown in the general formula (1), and the content of elements other than the above elements is 1.5 mass% or less.

[0026] The Ce-activated α-sialon phosphor may contain Eu. The Eu content may be 0.0001 mass% (1 mass ppm) or more, or 0.0002 mass% (2 mass ppm) or more, based on the total mass of the Ce-activated α-sialon phosphor. The Eu content may be 5.0 mass% or less, 3.0 mass% or less, or 1.5 mass% or less, based on the total mass of the Ce-activated α-sialon phosphor. The Eu content may be, for example, 0.0001 to 5.0 mass%, 0.0001 to 3.0 mass%, or 0.0001 to 1.5 mass%, based on the total mass of the Ce-activated α-sialon phosphor. In this specification, the Eu content refers to the content determined by quantitative elemental analysis using an ICP optical emission spectrometer. The Eu content is specifically determined by the method described in the Examples. When the Ce-activated α-sialon phosphor contains Eu as a luminescent center element, the above-mentioned Eu content means the total amount of Eu content as the luminescent center element and Eu content that does not function as a luminescent center element.

[0027] The Ce-activated α-sialon phosphor may have an emission spectrum in which the emission peak is located at a wavelength of 470 to 525 nm when excited with light having a wavelength of 405 nm. The lower limit of the wavelength range may be, for example, 480 nm or 490 nm. The upper limit of the wavelength range may be, for example, 520 nm or 510 nm. The wavelength range corresponds to the range in which an emission peak is observed when the α-sialon phosphor is activated with Ce and at least substantially not activated with Eu. The emission peak wavelength is specifically determined by the method described in the Examples of this specification.

[0028] In the emission spectrum when the Ce-activated α-sialon phosphor is excited with light having a wavelength of 405 nm, the half width of the emission peak may be 100 nm or more, 101 nm or more, or 102 nm or more. The half width of the emission peak may be, for example, 150 nm or less, 130 nm or less, 120 nm or less, 115 nm or less, or 110 nm or less. In this specification, the half width means the full width at half maximum. The half width is specifically determined by the method described in the examples of this specification.

[0029] In the emission spectrum of a Ce-activated α-sialon phosphor excited with light having a wavelength of 405 nm, the ratio of the emission intensity observed at a wavelength of 580 nm to the emission peak intensity (emission intensity observed at a wavelength of 580 nm / emission peak intensity; hereinafter, simply referred to as "emission intensity ratio") may be less than 90%, less than 70%, less than 60%, less than 50%, less than 45%, less than 40%, less than 35%, or less than 30%. The emission intensity ratio may be, for example, 0% or more, or 10% or more. It is believed that in the emission spectrum, emission originating from Ce is observed near 470 to 525 nm, and emission originating from Eu is observed near 580 nm. Therefore, particularly when the wavelength at which the emission peak is located is 470 to 525 nm, a small emission intensity ratio is believed to mean that the amount of Eu contained as the emission center element is small relative to the amount of Ce contained as the emission center element. The emission intensity ratio can be determined specifically by the method described in the Examples of this specification.

[0030] The chromaticity x calculated from the emission spectrum of the Ce-activated α-sialon phosphor when excited with light having a wavelength of 405 nm may be 0.170 or more, or 0.180 or more. The chromaticity x calculated from the emission spectrum of the Ce-activated α-sialon phosphor when excited with light having a wavelength of 405 nm may be 0.340 or less, or 0.325 or less. The chromaticity y calculated from the emission spectrum of the Ce-activated α-sialon phosphor when excited with light having a wavelength of 405 nm may be 0.270 or more, or 0.275 or more. The chromaticity y calculated from the emission spectrum of the Ce-activated α-sialon phosphor when excited with light having a wavelength of 405 nm may be 0.550 or less, or 0.545 or less. The chromaticity x and chromaticity y calculated from the emission spectrum of the Ce-activated α-sialon phosphor when excited with light having a wavelength of 405 nm refer to values ​​determined by the methods described in the examples.

[0031] The Ce-activated α-sialon phosphor may have a diffuse reflectance of 86.5% or more, 87.0% or more, or 87.5% or more for light having an emission peak wavelength in its emission spectrum when excited with light having a wavelength of 405 nm. The Ce-activated α-sialon phosphor may have a diffuse reflectance of 100.0% or less, 95.0% or less, or 90.0% or less for light having an emission peak wavelength in its emission spectrum when excited with light having a wavelength of 405 nm.

[0032] The diffuse reflectance of the Ce-activated α-sialon phosphor for light with a wavelength of 600 nm may be 85.0% or more, 88.5% or more, 89.0% or more, 90.0% or more, 91.0% or more, or 91.5% or more. A diffuse reflectance for light with a wavelength of 600 nm within the above range means that defects in the crystal structure constituting the phosphor and the occurrence of heterogeneous phases, which are non-luminescent components, are further reduced, contributing to further improvements in the internal quantum efficiency and external quantum efficiency of the α-sialon phosphor. The diffuse reflectance of the Ce-activated α-sialon phosphor for light with a wavelength of 600 nm may be, for example, 100.0% or less, 95.0% or less, or 93.0% or less.

[0033] The diffuse reflectance of the Ce-activated α-sialon phosphor for light with a wavelength of 700 nm may be 85.0% or more, 88.0% or more, 89.5% or more, 90.0% or more, 91.0% or more, or 91.5% or more. A diffuse reflectance for light with a wavelength of 700 nm within the above range means that defects in the crystal structure constituting the phosphor and the occurrence of heterogeneous phases, which are non-luminescent components, are further reduced, contributing to further improvements in the internal quantum efficiency and external quantum efficiency of the α-sialon phosphor. The diffuse reflectance of the Ce-activated α-sialon phosphor for light with a wavelength of 700 nm may be, for example, 100.0% or less, 95.0% or less, or 94.0% or less.

[0034] The diffuse reflectance of the Ce-activated α-sialon phosphor for light with a wavelength of 800 nm may be 85.0% or more, 89.0% or more, 90.0% or more, 90.5% or more, 91.0% or more, or 92.5% or more. A diffuse reflectance for light with a wavelength of 800 nm within the above range means that defects in the crystal structure constituting the phosphor and the occurrence of heterogeneous phases, which are non-luminescent components, are further reduced, contributing to further improvements in the internal quantum efficiency and external quantum efficiency of the α-sialon phosphor. The diffuse reflectance of the Ce-activated α-sialon phosphor for light with a wavelength of 800 nm may be, for example, 100.0% or less, 98.0% or less, or 95.0% or less.

[0035] In this specification, the term "diffuse reflectance" refers to a value determined from the diffuse reflectance spectrum of a Ce-activated α-sialon phosphor measured using a spectrophotometer. Specifically, the diffuse reflectance is determined by the method described in the Examples section of this specification. The spectrophotometer that can be used is, for example, the "V-550" (product name) manufactured by JASCO Corporation.

[0036] The Ce-activated α-sialon phosphor may have an absorptance of 65.0% or more, 70.0% or more, 72.0% or more, or 75.0% or more at a wavelength of 405 nm, and may have an absorptance of 100.0% or less, 90.0% or less, or 80.0% or less at a wavelength of 405 nm.

[0037] From the viewpoint of further improving the internal quantum efficiency, the absorptance of the Ce-activated α-sialon phosphor at light having a wavelength of 600 nm may be 0.0% or more, 2.0% or more, 5.0% or more, 7.0% or more, 9.0% or more, or 9.5% or more. The absorptance of the Ce-activated α-sialon phosphor at light having a wavelength of 600 nm may be 20.0% or less, 18.0% or less, 15.0% or less, or 12.0% or less.

[0038] From the viewpoint of improving external quantum efficiency, the Ce-activated α-sialon phosphor may have an absorptance of 3.0% or more, 5.0% or more, 7.0% or more, or 8.0% or more for light with a wavelength of 700 nm, and may have an absorptance of 15.0% or less, 13.0% or less, 10.0% or less, or 9.0% or less for light with a wavelength of 700 nm.

[0039] The absorptance of light of a specific wavelength is calculated as follows. First, a phosphor is attached to the opening of an integrating sphere, and light of a specific wavelength is introduced into the integrating sphere as excitation light, and the emission spectrum is measured using a spectrophotometer. From the obtained emission spectrum data, the number of excitation reflected light photons (Qref) and the number of fluorescence photons (Qem) are calculated. Then, the spectrum of the excitation light is measured in the same manner as above, except that a standard reflector is attached to the opening of the integrating sphere instead of the phosphor. From the obtained spectrum data, the number of excitation light photons (Qex) is calculated. Then, the absorptance of light of a specific wavelength is calculated using the following formula: absorptance of light of a specific wavelength = ((Qex - Qref) / Qex) x 100 The absorptance of light of a specific wavelength can be specifically calculated by the method described in the Examples of this specification. As the spectrophotometer, an "MCPD-7000" (product name) manufactured by Otsuka Electronics Co., Ltd., or the like can be used.

[0040] The internal quantum efficiency of the Ce-activated α-sialon phosphor according to the present disclosure when excited with light having a wavelength of 405 nm can be, for example, 75.0% or more, 76.0% or more, 77.0% or more, 78.0% or more, or 79.0% or more. In this specification, the internal quantum efficiency refers to the internal quantum efficiency calculated based on data on the emission spectrum obtained when the phosphor is excited with light having a wavelength of 405 nm. Specifically, the internal quantum efficiency is determined by the method described in the examples of this specification.

[0041] The Ce-activated α-sialon phosphor according to the present disclosure may have an absorptance of 65.0% or more at a wavelength of 405 nm and an internal quantum efficiency of 76.0% or more, and from the viewpoint of practical use, may have an absorptance of 72.0% or more at a wavelength of 405 nm and an internal quantum efficiency of 78.0% or more.

[0042] [Method for manufacturing Ce-activated α-sialon phosphor] The Ce-activated α-sialon phosphor described above can be manufactured, for example, by the following method. One example of a method for manufacturing a Ce-activated α-sialon phosphor includes a step of heat-treating a mixture containing Ce-activated α-sialon and an Eu source at 1200 to 1500°C to obtain a heat-treated product. Another embodiment of the present disclosure is a method for manufacturing a Ce-activated α-sialon phosphor, including the step.

[0043] <Ce-activated α-sialon (raw material sialon)> Ce-activated α-sialon (hereinafter also referred to as "raw material sialon") contains Ce as the luminescence center element and can emit fluorescence itself. The raw material sialon need not substantially contain Eu as the luminescence center element, and may contain substantially only Ce as the luminescence center element. "The raw material sialon substantially does not contain Eu as the luminescence center element" means that no luminescence peak derived from Eu is observed in the emission spectrum of the raw material sialon when excited with light having a wavelength of 405 nm. "The raw material sialon substantially contains only Ce as the luminescence center element" means that only peaks derived from Ce are observed in the emission spectrum of the raw material sialon when excited with light having a wavelength of 405 nm. For example, even if the raw material sialon contains Eu, if no independent luminescence peak derived from Eu is observed, Eu is considered not to be an element contained as a luminescence center element in this specification.

[0044] The raw material SiAlON may contain M, Ce, Si, Al, O, and N as constituent elements. Here, M is at least one element selected from the group consisting of Li, Ca, Mg, Y, and lanthanide elements (excluding La, Ce, and Eu). The contents of M, Ce, Si, Al, O, and N may be within the numerical ranges described above as the contents of each element in the Ce-activated α-sialon phosphor, based on the total contents of M, Ce, Si, Al, O, and N in the Ce-activated α-sialon phosphor. Here, the phrase "in the Ce-activated α-sialon phosphor" should be read as "in the raw material SiAlON."

[0045] For example, in the raw material sialon, based on the total content of M, Ce, Si, Al, O, and N in the raw material sialon, the M content may be 1 to 4 mol%, the Ce content may be 0.05 to 2 mol%, the Si content may be 25 to 45 mol%, the Al content may be 4 to 12 mol%, the O content may be 0.5 to 5 mol%, and the N content may be 40 to 60 mol%, or the M content may be 1 to 4 mol%, the Ce content may be 0.05 to 2 mol%, the Si content may be 25 to 45 mol%, the Al content may be 5 to 9 mol%, the O content may be 0.5 to 5 mol%, and the N content may be 40 to 60 mol%.

[0046] The raw material SiAlON may contain, as a main crystal, a crystal having the same crystal structure as that of α-SiAlON, or may be composed of crystals having the same crystal structure as that of α-SiAlON. In the powder X-ray diffraction pattern of the raw material SiAlON, the ratio of the maximum diffraction line intensity of the heterophase to the diffraction line intensity of the (101) plane may be 10% or less, 5% or less, 3% or less, or 2% or less.

[0047] The raw material sialon may include, for example, an α-sialon represented by the following general formula (1): (M ａ＋ ｘ , Ce ３＋ ｙ ) Si １２－（ｍ＋ｎ） Al （ｍ＋ｎ） O ｎ N １６－ｎ (1) [In the general formula (1), M is at least one element selected from the group consisting of Li, Ca, Mg, Y, and lanthanide elements (excluding La, Ce, and Eu), and when the valence of M is a, m = ax + 3y, and Ce ３＋ is substituted at the M site, and 0.3≦x+y≦2, 0.03≦y≦0.5, and 0≦n≦m.

[0048] The raw material sialon may contain Ca, or may contain α-sialon in which Ca is dissolved. In the above general formula (1), M may be Ca, or may be two or more elements selected from the group consisting of Ca and at least one element selected from the group consisting of Li, Mg, Y, and lanthanide elements (excluding La, Ce, and Eu). When M is Ca, a = 2 in general formula (1). The inclusion of Ca in the raw material sialon can be confirmed by quantitative analysis of the elements using an ICP optical emission spectrometer.

[0049] In general formula (1), x + y may be 0.4 or more, 0.5 or more, 0.6 or more, or 0.7 or more, and may be 1.8 or less, 1.5 or less, 1.3 or less, 1.1 or less, 1.0 or less, or 0.9 or less. In general formula (1), y may be 0.05 or more, or 0.06 or more, and may be 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less. In general formula (1), n ​​may be 0.01 or more, 0.05 or more, or 0.10 or more, and may be less than m.

[0050] The fact that the raw material sialon contains α-sialon represented by the above general formula (1) means that in the powder X-ray diffraction pattern of the raw material sialon, the ratio of the maximum diffraction line intensity of a different phase to the diffraction line intensity of the (101) plane is 10% or less, and the content ratio of each constituent element (M, Ce, Si, Al, O, and N) calculated by analysis by ICP optical emission spectroscopy using a multi-type ICP optical emission spectroscopy analyzer and analysis of the oxygen and nitrogen amounts using an oxygen / nitrogen analyzer is equal to the ratio represented by general formula (1).

[0051] The raw material sialon may be represented by, for example, the general formula (1). In this case, M, x + y, y, and n may each be as described above. The constituent elements and proportions of the raw material sialon can be determined by analyzing the oxygen and nitrogen amounts using an oxygen / nitrogen analyzer and by ICP optical emission spectroscopy using a multi-type ICP optical emission spectroscopy analyzer. The fact that the raw material sialon is represented by the general formula (1) means that when the constituent elements and proportions of the raw material sialon are determined by the above analysis, the content ratios of Ce, Si, Al, O, N, and M in general formula (1) are within the ranges shown in general formula (1), and the content of elements other than the above elements is 1.5 mass% or less.

[0052] The manufacturing method according to one embodiment may include a step of obtaining a raw material SiAlON (hereinafter also simply referred to as a "step of obtaining α-sialon"). In the step of obtaining α-sialon, for example, a raw material composition containing a Si source, an Al source, and a Ce source is fired to obtain the raw material SiAlON.

[0053] The Si source refers to a compound or element containing silicon as a constituent element, the Al source refers to a compound or element containing aluminum as a constituent element, and the Ce source refers to a compound or element containing cerium as a constituent element. In this specification, a compound containing silicon as a constituent element is also referred to as a silicon compound, a compound containing aluminum as a constituent element is also referred to as an aluminum compound, and a compound containing cerium as a constituent element is also referred to as a cerium compound. The silicon compound, aluminum compound, and cerium compound may each be any of a nitride, oxide, oxynitride, and hydroxide. At least one of the Si source, Al source, and Ce source may be a nitride. The nitride can also be called a nitrogen source because it contains nitrogen, which is a constituent element of the raw material sialon.

[0054] Examples of silicon compounds include silicon nitride (Si ３ N ４ ), and silicon dioxide (SiO ２ ) etc.

[0055] Examples of aluminum compounds include aluminum nitride (AlN), aluminum oxide (Al ２ O３ ), and aluminum hydroxide (Al(OH) ３ ) etc.

[0056] Examples of cerium compounds include cerium oxide (CeO ２ ), cerium nitride (CeN), cerium hydroxide (Ce(OH) ４ ), and cerium fluoride (CeF ３ ) are listed.

[0057] The raw material composition may contain other raw materials containing elements capable of forming α-sialon, in addition to the Si source, Al source, and Ce source. Examples of other raw materials include a Li source and a Ca source. The Li source refers to a compound or element containing lithium as a constituent element, and the Ca source refers to a compound or element containing calcium as a constituent element. In this specification, a compound containing lithium as a constituent element is also referred to as a lithium compound, and a compound containing calcium as a constituent element is also referred to as a calcium compound. The lithium compound and the calcium compound may each be any of halides, nitrides, oxides, oxynitrides, carbonates, and hydroxides. Examples of lithium compounds include lithium halides such as lithium fluoride, lithium nitride, lithium oxide, lithium carbonate, and lithium hydroxide. Examples of calcium compounds include calcium halides such as calcium fluoride, calcium oxide, calcium carbonate, calcium nitride, and calcium hydroxide.

[0058] The raw material composition may further contain α-sialon or Ce-activated α-sialon, which can serve as aggregate or cores for obtaining raw sialon.

[0059] The raw material composition can be prepared, for example, by weighing and mixing each compound. The compounding ratio of each compound is designed according to the composition of the raw material sialon, the Ce-activated α-sialon phosphor, and the α-sialon contained therein. Mixing may be performed using a dry mixing method or a wet mixing method. The dry mixing method, also known as a dry blend method, may be a method of mixing each component using a V-type mixer, for example. The wet mixing method may be a method of adding a solvent or dispersant such as water to prepare a solution or slurry, mixing each component, and then removing the solvent or dispersant. Alternatively, each compound may be weighed, mixed, and then the particle size adjusted to be used as the raw material composition. The particle size can be adjusted, for example, by sieving.

[0060] The firing temperature of the raw material composition may be 1600°C or higher, 1650°C or higher, or 1700°C or higher, from the viewpoints of promoting grain growth of the main crystalline phase of α-sialon and achieving a sufficient amount of Ce in solid solution. Furthermore, the firing temperature of the raw material composition may be 2000°C or lower, 1900°C or lower, or 1800°C or lower, from the viewpoints of sufficiently suppressing decomposition of the main crystalline phase of α-sialon. The firing temperature of the raw material composition may be, for example, 1600 to 2000°C, 1650 to 1900°C, or 1700 to 1800°C.

[0061] The firing time of the raw material composition may be 1 hour or more, 3 hours or more, or 5 hours or more from the viewpoint of promoting the growth of primary particles of α-sialon, and may be 30 hours or less, 28 hours or less, or 25 hours or less from the viewpoint of economy.

[0062] The firing may be carried out, for example, in a nitrogen gas atmosphere. The nitrogen gas atmosphere may be atmospheric pressure, but heating under conditions of high nitrogen pressure can suppress decomposition of the produced α-sialon at high temperatures. The firing may also be carried out, for example, in a pressurized atmosphere. When the firing is carried out under a pressurized atmosphere, the pressure may be 0.001 MPaG or more, 0.005 MPaG or more, 0.01 MPaG or more, or 0.02 MPaG or more. The pressure may be 100 MPaG or less, 50 MPaG or less, 10 MPaG or less, 5 MPaG or less, or 1 MPaG or less.

[0063] In the step of obtaining α-sialon, the firing may be performed once or twice or more. The firing may be performed, for example, five times or less, or four times or less. When the firing is performed twice or more, the firing conditions may be the same or different from each other.

[0064] The raw material SiAlON to be used for the heat treatment may be the fired product obtained by the above method as is, or may be used after adjusting the particle size. The particle size adjustment can be carried out, for example, by crushing (coarse crushing) using a stamp mill or the like, pulverizing using a jet mill or the like, or sieving using a vibrating sieve or the like.

[0065] <Heat Treatment Step> A manufacturing method according to one embodiment includes a step of heating (annealing) a mixture containing raw SiAlON and an Eu source at 1200 to 1500°C to obtain a heat-treated product (hereinafter also referred to as the "heat treatment step"). The inventors have discovered that such a heat treatment step can produce a Ce-activated α-SiAlON phosphor with excellent internal quantum efficiency. A heating temperature of 1200 to 1500°C is lower than the typical firing temperature for obtaining raw SiAlON from the above-described raw material composition. Heating at such a temperature suppresses further grain growth of the raw SiAlON while reducing the density of crystal defects contained in the heat-treated product. This is thought to improve the diffuse reflectance of the raw SiAlON phosphor for light with an emission peak wavelength in its emission spectrum when excited with light having a wavelength of 405 nm, thereby further improving its internal quantum efficiency.

[0066] In particular, in the heat treatment step, the raw SiAlON is heated together with the Eu source, thereby improving the internal quantum efficiency. It is generally known that α-SiAlON phosphors using Ce as the luminescent center element emit fluorescence in different wavelength ranges than those using Eu. Furthermore, in Ce-activated α-SiAlON phosphors, using an element that emits other fluorescence, such as Eu, in combination with Ce is considered undesirable for obtaining excellent luminescence characteristics. Therefore, in the production process of α-SiAlON phosphors using Ce as the luminescent center, the addition of elements that can serve as other luminescent center elements, such as Eu, is avoided. However, in the heat treatment step, the raw SiAlON is intentionally heated together with the Eu source, which is thought to improve the internal quantum efficiency by more efficiently reducing the density of crystal defects, although the reason is unclear.

[0067] The mixture containing the raw material sialon and the Eu source can be obtained, for example, by adding the Eu source to the raw material sialon and mixing them.

[0068] The Eu source refers to a compound or simple substance containing europium as a constituent element. In this specification, a compound containing europium as a constituent element is also referred to as a europium compound. Examples of europium compounds include europium oxide (europium oxide), europium hydroxide (europium hydroxide), europium nitride (europium nitride), europium sulfide (europium sulfide), and europium halides (europium halides). Examples of europium halides include europium fluoride, europium chloride, europium bromide, and europium iodide. In these compounds, the valence of europium may be trivalent or divalent. The europium compound may be, for example, one or more selected from the group consisting of europium oxide, nitride, and halide. The compound of europium preferably comprises europium oxide.

[0069] The content of the Eu source in the mixture may be 0.01 parts by mass or more, 0.05 parts by mass or more, 0.1 parts by mass or more, or 0.3 parts by mass or more, relative to 100 parts by mass of the raw material SiAlON in the mixture. By setting the content of the Eu source within the above numerical range, the internal quantum efficiency of the Ce-activated α-SiAlON phosphor can be further improved. Furthermore, the content of the Eu source in the mixture may be 10.0 parts by mass or less, 8.0 parts by mass or less, 5.0 parts by mass or less, 3.0 parts by mass or less, or 2.0 parts by mass or less, relative to 100 parts by mass of the raw material SiAlON in the mixture. By setting the content of the Eu source within the above numerical range, the amount of heterophases that adversely affect the luminescence characteristics of the Ce-activated α-SiAlON phosphor can be reduced. The content of the Eu source in the mixture may be, for example, 0.01 to 10 parts by mass, 0.05 to 5.0 parts by mass, or 0.1 to 3.0 parts by mass relative to 100 parts by mass of the raw material sialon in the mixture.

[0070] The heating temperature in the heat treatment step is 1200 to 1500°C, but may be 1250°C or higher, or 1280°C or higher. By setting the heating temperature within the above numerical range, the internal quantum efficiency of the Ce-activated α-sialon phosphor can be further improved. Furthermore, the heating temperature may be 1450°C or lower, 1400°C or lower, or 1360°C or lower. By setting the heating temperature within the above numerical range, the internal quantum efficiency of the Ce-activated α-sialon phosphor can be further improved. The heating temperature in the heat treatment step may be, for example, 1250 to 1450°C, or 1250 to 1400°C.

[0071] In the heat treatment step, the heat treatment may be performed in an atmosphere containing at least one gas selected from the group consisting of a rare gas and a reducing gas. Examples of rare gases include argon gas and helium gas. The rare gas may be argon gas. Examples of reducing gases include hydrogen gas, ammonia gas, hydrocarbon gas, and carbon monoxide gas. The reducing gas may be hydrogen gas. In the atmosphere in which the heat treatment is performed, the content of at least one gas selected from the group consisting of a rare gas and a reducing gas may be 80 mass% or more, 90 mass% or more, 95 mass% or more, or 99 mass% or more, based on the total volume of the atmosphere. Furthermore, the content of argon gas may be 70 mass% or more, 80 mass% or more, 90 mass% or more, 95 mass% or more, or 99 mass% or more, based on the total volume of the atmosphere.

[0072] The heat treatment may be performed under atmospheric pressure or under a pressurized atmosphere. When the heat treatment is performed under a pressurized atmosphere, the pressure may be, for example, 0.05 MPaG or less, or 0.01 MPaG or less. The pressure may be the same as or lower than the pressure during firing in the step of obtaining the α-sialon.

[0073] The heating time in the heat treatment may be 2 hours or more, 4 hours or more, or 6 hours or more from the viewpoint of further enhancing the internal quantum efficiency improvement effect. Moreover, the heating time may be 24 hours or less, 20 hours or less, or 12 hours or less from the viewpoint of economic efficiency. The heating time may be, for example, 6 hours to 12 hours.

[0074] In the heat treatment step, the number of heat treatments may be one, two or more. The number of heat treatments may be, for example, five or less, or four or less. When the number of heat treatments is two or more, the type and content of the Eu source, the heating temperature, the heating atmosphere, and the heating time in each heat treatment may be the same or different and can be set appropriately within the above-mentioned ranges. However, the heating temperature is at least in the range of 1200 to 1500°C.

[0075] The manufacturing method according to one embodiment may further include other steps in addition to the step of obtaining α-sialon and the heat treatment step described above. Examples of the other steps include a step of treating the heat-treated product obtained by the heat treatment with an acid (acid treatment step), and a step of classifying the heat-treated product or the acid-treated product (classification step).

[0076] <Acid Treatment Step> The acid treatment is carried out by bringing the heat-treated product into contact with acid. Specifically, for example, the heat-treated product is put into acid and stirred. By carrying out the acid treatment, the amount of altered phases formed by the heat treatment and the amount of remaining compounds and heterogeneous phases derived from the Eu source can be reduced, thereby further improving the internal quantum efficiency of the Ce-activated α-sialon phosphor. The acid treatment step yields an acid-treated product.

[0077] Examples of acids used in the acid treatment include hydrofluoric acid (hydrofluoric acid), nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, and mixtures thereof (mixed acids). For example, a mixed acid of hydrofluoric acid and nitric acid may be used. In the mixed acid of hydrofluoric acid and nitric acid, HNO ３ The mass ratio of the content of HF to the content of may be, for example, 0.5 / 1 to 1 / 1.

[0078] The time for which the acid treatment is performed may be, for example, 10 minutes or more and may be 1 hour or less. The time for which the acid treatment is performed refers to the time during which the heat-treated product is in contact with the acid. The acid treatment may be performed at room temperature or while heating. The temperature for which the acid treatment is performed may be, for example, 30°C or more, 50°C or more, or 70°C or more. The temperature for which the acid treatment is performed may be 100°C or less, or 90°C or less. The temperature for which the acid treatment is performed refers to the temperature of the acid used in the acid treatment.

[0079] The number of times of acid treatment may be one, or two or more. The number of times of acid treatment may be, for example, five times or less, or four times or less. When the number of times of acid treatment is two or more, the treatment time, temperature, and type of acid in each treatment may be the same or different, and can be appropriately set within the above-mentioned ranges. When acid treatment is performed twice, for example, acid treatment using a mixed acid of hydrofluoric acid and nitric acid may be performed first, followed by acid treatment using hydrochloric acid. According to such treatment, for example, Eu not dissolved in the heat-treated product is converted into EuF by the mixed acid. ３ After changing the EuF ３ can be removed by dissolving in hydrochloric acid.

[0080] <Classification step> The classification may be, for example, wet classification or dry classification. An example of wet classification is elutriation classification. In elutriation classification, for example, the heat-treated product or the acid-treated product is added to a mixed solvent containing ion-exchanged water and a dispersant (e.g., sodium hexametaphosphate) or a mixed solvent containing ion-exchanged water and aqueous ammonia, and the mixture is stirred and then allowed to stand, thereby removing particles with a small particle size.

[0081] The α-sialon phosphor obtained by the above-described manufacturing method has excellent internal quantum efficiency. The above-described manufacturing method can also be regarded as a method for improving the internal quantum efficiency of the α-sialon phosphor. For example, a method for improving the internal quantum efficiency of the phosphor includes heat-treating a mixture containing Ce-activated α-sialon and an Eu source at 1200 to 1500°C to obtain a heat-treated product. As specific aspects of this method, each aspect of the above-described manufacturing method can be applied without particular limitation.

[0082] The Ce-activated α-sialon phosphor described above may be used alone or in combination with other phosphors. Because the Ce-activated α-sialon phosphor has excellent internal quantum efficiency, it can be suitably used in light-emitting devices such as LEDs. The Ce-activated α-sialon phosphor can also be used by dispersing it in, for example, a curable resin. Examples of the curable resin include resins used as sealing resins for light-emitting devices.

[0083] Although several embodiments have been described above, the present disclosure is not limited to the above embodiments. Furthermore, the descriptions of the above embodiments can be applied to each other.

[0084] The present disclosure will be described in more detail below with reference to examples and comparative examples, although the present disclosure is not limited to the following examples.

[0085] [Preparation of Raw Material Sialon] <Preparation of Raw Material Sialon A> The designed composition was ０．６４５ Ce ０．０７ Si ９．７５ Al ２．２５ O ０．７５ N １５．２５ and prepared a raw material powder a having a blending composition of 52.3 mol% silicon nitride powder (manufactured by UBE Corporation, E10 grade), 36.2 mol% aluminum nitride powder (manufactured by Tokuyama Corporation, E grade), 1.1 mol% cerium oxide powder (manufactured by Shin-Etsu Chemical Co., Ltd., C type), 2.6 mol% calcium fluoride powder (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent), and 7.8 mol% calcium carbonate powder (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent). In the raw material powder a, the content of calcium fluoride powder (CaF ２ / (CaF ２ + CaCO ３ )) was 25 mol%. The blending composition of calcium fluoride and calcium carbonate was calculated so as to satisfy the above-mentioned design composition in terms of calcium oxide with the same number of moles of calcium. Raw material powder a was mixed in a bag for several minutes, and the resulting mixture was passed through a nylon sieve (mesh opening: 150 μm) to obtain a raw material composition.

[0086] 35 g of the raw material composition was filled into a boron nitride crucible with an inner diameter of 60 mm and a height of 30 mm, and fired in an electric furnace equipped with a carbon heater under a nitrogen gas atmosphere of 0.03 MPaG. The firing temperature was 1750°C, and the firing time was 8 hours. The obtained fired product was crushed using a stamp mill (manufactured by Nitto Kagaku Co., Ltd., high-speed stamp mill ANS-143PL) so that the entire fired product passed through a sieve (mesh opening: 250 μm), thereby obtaining raw material Sialon A (phosphor of Comparative Example 1).

[0087] <Preparation of Raw Material Sialon B> The amount of calcium fluoride powder mixed was 5.2 mol %, and the amount of calcium carbonate powder mixed was 5.2 mol % (CaF ２ / (CaF ２ + CaCO ３ A raw material composition was obtained in the same manner as in <Preparation of Raw Material Sialon A> above, except that the sintering ratio (%) was 50 mol%. 300 g of this raw material composition was loaded into a boron nitride crucible with an inner diameter of 150 mm and a height of 55 mm, and fired in an electric furnace equipped with a carbon heater at 1750°C for 16 hours under a nitrogen gas atmosphere of 0.03 MPaG to obtain a fired product. The fired product was coarsely crushed using a stamp mill, then pulverized using a jet mill (Nippon Pneumatic Mfg. Co., Ltd., PJM-80, sample feed rate: 50 g / min, crushing pressure: 0.2 MPa), and then passed through a vibrating sieve (mesh opening: 45 μm). The powder that passed through the vibrating sieve was collected as raw material Sialon B (phosphor of Comparative Example 3).

[0088] <Preparation of Raw Material Sialon C> A raw material composition was obtained in the same manner as in <Preparation of Raw Material Sialon B> above, except that calcium carbonate powder was changed to calcium oxide (calcium carbonate powder decarbonated by treating it in the air at 1000°C for 8 hours). 200 g of this raw material composition was filled into a boron nitride crucible with an inner diameter of 100 mm and a height of 85 mm, and fired in an electric furnace equipped with a carbon heater at 1750°C for 24 hours under a nitrogen gas atmosphere of 0.03 MPaG to obtain a fired product. The obtained fired product was subjected to coarse crushing, pulverization, and sieving in the same manner as in <Preparation of Raw Material Sialon B> above, to obtain raw material Sialon C (phosphor of Comparative Example 7).

[0089] <Preparation of Raw Material Sialon D> A raw material product was obtained in the same manner as in <Preparation of Raw Material Sialon B> above, except that calcium carbonate powder was changed to calcium oxide. 300 g of this raw material composition was filled into a boron nitride crucible with an inner diameter of 150 mm and a height of 55 mm, and fired in an electric furnace equipped with a carbon heater at 1750°C for 16 hours under a nitrogen atmosphere of 0.03 MPaG to obtain a fired product. The obtained fired product was subjected to coarse crushing, pulverization, and sieving in the same manner as in <Preparation of Raw Material Sialon B> above, to obtain raw material Sialon D (phosphor of Comparative Example 8).

[0090] <Preparation of Raw Material SiAlON E> Raw material SiAlON E (phosphor of Comparative Example 12) was obtained in the same manner as in <Preparation of Raw Material SiAlON D> above, except that a raw material powder was used that was obtained by adding 0.5 mass% europium oxide powder (RU grade, manufactured by Shin-Etsu Chemical Co., Ltd.) to the raw material powder used in <Preparation of Raw Material SiAlON D> above.

[0091] [Treatment of Raw Sialon] Raw Sialon A to E were subjected to one or more of the following heat treatment, acid treatment, and elutriation treatment as shown in Tables 1 and 2 to obtain the phosphors of Comparative Examples 2, 4 to 6, 9 to 11, and Examples 1 to 8. The phosphors of Examples 1 to 8 contained α-sialon represented by the following general formula (1-1). (Ca ２＋ ｘ , Ce ３＋ ｙ ) Si １２－（ｍ＋ｎ） Al （ｍ＋ｎ） O ｎ N １６－ｎ (1-1) [In the general formula (1-1), m = 2x + 3y, and Ce ３＋ is substituted at the Ca site, 0.7≦x+y≦0.9, 0.03≦y≦0.08, and 0≦n≦m / 2.

[0092] <Heat Treatment> For Comparative Examples 4 to 6 and 9 to 10, the α-sialon (raw material sialon) shown in Tables 1 and 2 was heat-treated in an electric furnace equipped with a carbon heater under an argon gas atmosphere at 0.03 MPaG at the temperatures shown in Tables 1 and 2. The heating time was 8 hours. For Examples 1 to 8, the α-sialon shown in Tables 1 and 2 was mixed with europium oxide powder (RU grade, manufactured by Shin-Etsu Chemical Co., Ltd.) in the amounts shown in Tables 1 and 2 as the Eu source, and the resulting mixture was heat-treated in the same manner as above. The amount of Eu source shown in Tables 1 and 2 refers to the amount based on the total mass of each α-sialon. For Comparative Example 11, cerium oxide powder (C type, manufactured by Shin-Etsu Chemical Co., Ltd.) instead of europium oxide powder was added to raw material sialon D in an amount of 1 mass% based on the total mass of raw material sialon D, and the resulting mixture was heat-treated in the same manner as above.

[0093] <Acid Treatment> The heat-treated product obtained by the heat treatment in the case of "with heat treatment" and the α-sialon shown in Tables 1 and 2 in the case of "without heat treatment" were introduced into a mixed acid of hydrofluoric acid and nitric acid (48% by mass hydrofluoric acid: 60% by mass nitric acid: water = 1:1:6 (volume ratio)) heated to 80°C, and stirred for 30 minutes. Thereafter, the acid-treated product was recovered by filtration, washing with water, and drying.

[0094] <Classification (elutriation) Treatment> In Examples 2 and 6, fine powder contained in the acid-treated product obtained after the acid treatment was removed by sedimentation classification. More specifically, water containing a small amount of dispersant was first prepared in a beaker. The acid-treated product was dispersed in the water and allowed to stand for a predetermined time, and then the supernatant liquid up to a predetermined height from the water surface was removed using a liquid pump. A predetermined amount of water containing a small amount of the dispersant was then added to the beaker, and the fine powder was removed by repeating the dispersion, standing, and supernatant removal processes. The predetermined time and predetermined height were adjusted according to Stokes' equation so that fine powder with a particle size of less than 7.5 μm was removed in Example 2, and so that fine powder with a particle size of less than 5 μm was removed in Example 6.

[0095] [Evaluation] <Diffuse Reflectance> The diffuse reflectance of the phosphors of each Comparative Example and Example was measured using an integrating sphere device (product name: ISV-469) attached to an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, product name: V-550). After baseline correction using a standard reflector attached to the device, a solid sample holder filled with the phosphor to be measured was attached to the spectrophotometer, and the diffuse reflectance was measured in the wavelength range of 220 to 850 nm. Of the measurement results, the diffuse reflectance values ​​at the peak wavelengths of the emission spectrum of each phosphor, 600 nm, 700 nm, and 800 nm, were recorded. The results are shown in Tables 1 and 2.

[0096] <Excitation Light Absorbance, Fluorescence Characteristics, and Chromaticity x and Chromaticity y> For each of the phosphors of the Comparative Examples and Examples, the excitation light absorbance, emission peak wavelength, emission peak half-width, emission intensity ratio, internal quantum efficiency, and external quantum efficiency when the excitation wavelength was 405 nm were calculated using the following procedure. The results are shown in Tables 1 and 2.

[0097] First, the phosphor to be measured was filled into a concave cell so that the surface was smooth, and the cell was attached to the opening of an integrating sphere. Monochromatic light, which was separated into wavelengths of 405 nm from a Xe lamp serving as a light source, was introduced into the integrating sphere using an optical fiber as excitation light for the phosphor. This monochromatic excitation light was irradiated onto the phosphor to be measured, and the emission spectrum was measured. A spectrophotometer (manufactured by Otsuka Electronics Co., Ltd., product name: MCPD-7000) was used for the measurement. Of the emission spectra obtained above, the spectra of the phosphors of Comparative Examples 7 and 12 and Examples 1 and 2 are shown in Figure 1.

[0098] The emission peak wavelength and half width (full width at half maximum) were determined from the obtained emission spectrum data. Furthermore, the fluorescence intensity at the emission peak wavelength (emission peak intensity) and the fluorescence intensity at 580 nm were determined from the obtained emission spectrum data, and the emission intensity ratio was calculated using the following formula. The emission intensity observed at 580 nm was used as an index of emission derived from Eu. Emission intensity ratio = {(emission intensity at 580 nm) / (emission peak intensity)} × 100

[0099] Furthermore, the number of reflected excitation light photons (Qref) and the number of fluorescent photons (Qem) were calculated from the obtained emission spectrum data. The number of reflected excitation light photons was calculated in the same wavelength range as the number of excitation light photons, and the number of fluorescent photons was calculated in the range of 415 to 800 nm. Furthermore, using the same device, a standard reflector with a reflectance of 99% (Spectralon (registered trademark) manufactured by Labsphere) was attached to the opening of the integrating sphere to measure the spectrum of excitation light with a wavelength of 405 nm. At that time, the number of excitation light photons (Qex) was calculated from the spectrum in the wavelength range of 400 to 415 nm.

[0100] From the above calculation results, the 405 nm excitation light absorptance, internal quantum efficiency, and external quantum efficiency of the phosphor to be measured were calculated based on the following formulas: 405 nm excitation light absorptance = ((Qex - Qref) / Qex) x 100 Internal quantum efficiency = (Qem / (Qex - Qref)) x 100 External quantum efficiency = (Qem / Qex) x 100 From the above formulas, the relationship between the external quantum efficiency, 405 nm excitation light absorptance, and internal quantum efficiency can be expressed as follows: External quantum efficiency = 405 nm excitation light absorptance x internal quantum efficiency

[0101] Furthermore, from the spectral data in the wavelength region of 415 to 800 nm of the obtained emission spectrum, the x value (chromaticity x) of the CIE chromaticity coordinates and the y value (chromaticity y) of the CIE chromaticity coordinates in the XYZ color system defined in JIS Z 8781-3:2016 "Colorimetry - Part 3: CIE tristimulus values" were calculated in accordance with JIS Z 8724:2015 "Methods for measuring color - Light source color," thereby determining the chromaticity x and chromaticity y.

[0102] A standard sample of Eu-activated β-sialon phosphor (manufactured by Sialon Corporation, Standard Phosphor Green, Lot No. NSG1301; the absorptance, internal quantum efficiency, and external quantum efficiency of 405 nm excitation light measured in accordance with ISO 24936 were 81%, 81%, and 65%, respectively) was measured for absorptance, internal quantum efficiency, external quantum efficiency, chromaticity x, and chromaticity y of 405 nm excitation light in accordance with the above-mentioned measurement method. The absorptance, internal quantum efficiency, and external quantum efficiency of 405 nm excitation light were 83.5%, 83.0%, and 69.3%, respectively, and the chromaticity x and chromaticity y were 0.347 and 0.628, respectively.

[0103] The measured values ​​of excitation light absorbance, fluorescence characteristics, and chromaticity x and chromaticity y may vary if the manufacturer, production lot number, etc. of the measurement device changes. Therefore, the values ​​measured using the measurement method described in this specification are used as various measured values. However, if the manufacturer, production lot number, etc. of the measurement device changes, each measured value can be corrected using the measured value using the standard sample described above as the reference value.

[0104] <Absorptance of Light at 600 nm and 700 nm> When measuring the emission spectrum, monochromatic light dispersed to wavelengths of 600 nm or 700 nm from a Xe lamp was used instead of monochromatic light dispersed to a wavelength of 405 nm from a Xe lamp, and the spectrum of excitation light having a wavelength of 600 nm or 700 nm was measured instead of the spectrum of excitation light having a wavelength of 405 nm. The absorptance of light at 600 nm and 700 nm was measured in the same manner as the excitation light absorptance described above. The results are shown in Tables 1 and 2.

[0105]

[0106]

[0107] <Eu Content> The Eu content was determined for the phosphors of Examples 3 to 6, 8, and Comparative Example 12. The Eu content was determined using an ICP optical emission spectrometer. The phosphor was dissolved to prepare a sample solution by alkali fusion for concentrations of 0.1% or more, or by pressurized acid decomposition for concentrations less than 0.1%. Quantitative analysis of europium was performed on the resulting sample solution using an ICP optical emission spectrometer (Agilent, product name: 5110VDV). The Eu content was calculated from the obtained results. Furthermore, for Examples 3 to 8 and Comparative Example 12, the phosphors were treated for 30 minutes with 18% by mass hydrochloric acid heated to 80°C (hydrochloric acid wash). For Examples 3 to 6, 8, and Comparative Example 12, the Eu content was further measured after the hydrochloric acid wash. The results are shown in Table 3. The Eu content listed in Table 3 refers to the mass ratio based on the total mass of each phosphor. Furthermore, for Examples 3, 4, 6 to 8 and Comparative Example 12, Table 4 shows the excitation light absorptance, fluorescence characteristics, chromaticity, absorptance at 600 nm and absorptance at 700 nm after washing with hydrochloric acid, as well as the change in these values ​​from the values ​​before washing with hydrochloric acid (value after washing with hydrochloric acid - value before washing with hydrochloric acid).

[0108]

[0109]

[0110] The Eu content of the phosphors of Examples 3 to 5, 6, and 8 changed significantly before and after washing with hydrochloric acid. On the other hand, no significant change in the Eu content was observed before and after washing with hydrochloric acid for the phosphor of Comparative Example 12. For Comparative Example 12, the Eu source was added during the production of the Ce-activated α-sialon, which is thought to have caused Eu to penetrate into the α-sialon crystals in the Ce-activated α-sialon phosphor, whereas for the phosphors of Examples 3 to 5, 6, and 8, Eu did not penetrate into the α-sialon crystals.

Claims

1. A Ce-activated α-sialon phosphor having an emission peak in the wavelength range of 470 to 525 nm in its emission spectrum when excited with light having a wavelength of 405 nm, and having a diffuse reflectance of 86.5% or more for light having the wavelength at which the emission peak is located.

2. The Ce-activated α-sialon phosphor according to claim 1, which contains Eu.

3. The Ce-activated α-sialon phosphor according to claim 2, wherein the Eu content is 0.0001 to 1.5 mass % based on the total mass of the Ce-activated α-sialon phosphor.

4. A Ce-activated α-sialon phosphor according to any one of claims 1 to 3, wherein the half-width of the emission peak is 100 nm or more.

5. A Ce-activated α-sialon phosphor according to any one of claims 1 to 3, wherein in the emission spectrum, the ratio of the emission intensity observed at a wavelength of 580 nm to the emission peak intensity is less than 45%.

6. The Ce-activated α-sialon phosphor according to any one of claims 1 to 3, wherein the Ce-activated α-sialon phosphor contains, as constituent elements, M, Ce, Si, Al, O, and N, and the M is at least one element selected from the group consisting of Li, Ca, Mg, Y, and lanthanide elements (excluding La, Ce, and Eu), and the following are based on the total content of the M, the Ce, the Si, the Al, the O, and the N in the Ce-activated α-sialon phosphor: the M content is 1 to 4 mol %, the Ce content is 0.05 to 2 mol %, the Si content is 25 to 45 mol %, the Al content is 4 to 12 mol %, the O content is 0.5 to 5 mol %, and the N content is 40 to 60 mol %.

7. The Ce-activated α-sialon phosphor according to any one of claims 1 to 3, which contains an α-sialon represented by the following general formula (1): (M ａ＋ ｘ , Ce ３＋ ｙ )Si １２－（ｍ＋ｎ） A （ｍ＋ｎ） O ｎ N １６－ｎ (1) In the general formula (1), M is at least one element selected from the group consisting of Li, Ca, Mg, Y, and lanthanide elements (excluding La, Ce, and Eu), and when the valence of M is a, m=ax+3y, and Ce ３＋ is substituted at the M site, 0.3≦x+y≦2, 0.03≦y≦0.5, and 0≦n≦m.

8. A method for producing a Ce-activated α-sialon phosphor, comprising the step of heat-treating a mixture containing a Ce-activated α-sialon and an Eu source at 1200 to 1500°C to obtain a heat-treated product.

9. The method according to claim 8, wherein the content of the Eu source in the mixture is 0.1 to 3.0 parts by mass per 100 parts by mass of the Ce-activated α-sialon.

10. The method according to claim 8 or 9, wherein the heat treatment is carried out in an atmosphere containing at least one gas selected from the group consisting of a rare gas and a reducing gas.

11. The method according to claim 8 or 9, further comprising a step of treating the heat-treated product with an acid.

12. The method according to claim 8 or 9, further comprising the step of obtaining the Ce-activated α-sialon by firing a raw material composition containing a Si source, an Al source, and a Ce source.

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