Ce-ACTIVATED α-SIALON PHOSPHOR

Abstract

To provide a Ce-activated α-sialon phosphor having superior internal quantum efficiency.SOLUTION: One aspect of the present disclosure provides a Ce-activated α-sialon phosphor. The phosphor has an emission peak within a wavelength range of 470 to 525 nm in the emission spectrum when excited with light at a wavelength of 405 nm, and the diffuse reflectance for the light at the wavelength where the emission peak appears is 86.5% or more.SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to a Ce-activated α-sialon phosphor.

Background Art

[0002] α-type sialon (Si-Al-O-N) is a solid solution having a structure in which specific elements penetrate and dissolve into the crystal lattice of α-type silicon nitride, and in order to maintain electrical neutrality, a part of the Si-N bond is replaced by an Al-N bond or an Al-O bond. Fluorescence is exhibited by replacing a part of the elements that have penetrated and dissolved with a luminescent center element.

[0003] Patent Document 1 discloses an α-type sialon represented by 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), 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 the α-type sialon is characterized by containing 30 ppm or more and 1% or less of fluorine as an impurity.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

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

Means for Solving the Problems

[0006] The inventors have found that by setting the diffuse reflectance of light having a wavelength at which the emission peak is located to a predetermined value or more, a Ce-activated α-sialon with improved internal quantum efficiency can be obtained. As one means for increasing the diffuse reflectance as described above, it is effective to blend a Eu source with the Ce-activated α-sialon and perform an annealing treatment. The present disclosure is based on the above findings.

[0007] The present disclosure provides the following [1] to [7]. [1] A Ce-activated α-sialon phosphor having an emission peak in the wavelength range of 470 to 525 nm in the emission spectrum when excited by light with a wavelength of 405 nm, and having a diffuse reflectance of 86.5% or more with respect to the light having the wavelength at which the emission peak is located. [2] The Ce-activated α-sialon phosphor according to [1], which contains Eu. [3] The Ce-activated α-sialon phosphor according to [1] or [2], wherein the content of Eu is 0.0001 to 1.5% by 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 [1] to [3], wherein the full width at half maximum 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 the ratio of the emission intensity observed at a wavelength of 580 nm to the intensity of the emission peak in the emission spectrum is less than 45%. [6] The α-sialon phosphor activated by Ce 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 based on the total content of M, Ce, Si, Al, O, and N in the α-sialon phosphor activated by Ce, the content of M is 1 to 4 mol%, the content of Ce is 0.05 to 2 mol%, the content of Si is 25 to 45 mol%, the content of Al is 4 to 12 mol%, the content of O is 0.5 to 5 mol%, and the content of N is 40 to 60 mol%. The α-sialon phosphor activated by Ce according to any one of [1] to [5]. [7] The α-sialon phosphor activated by Ce contains an α-type sialon represented by the following general formula (1). The α-sialon phosphor activated by Ce according to any one of [1] to [6]. (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). When the valence of M is a, m = ax + 3y, Ce 3+ replaces the M site, 0.3 ≤ x + y ≤ 2, 0.03 ≤ y ≤ 0.5, and 0 ≤ n ≤ m.]

Advantages of the Invention

[0008] According to the present disclosure, an α-sialon phosphor activated by Ce with excellent internal quantum efficiency can be provided.

Brief Description of the Drawings

[0009]

Figure 1

Modes for Carrying Out the Invention

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

[0011] Unless otherwise specified, the materials exemplified in this specification can be used alone or in combination of two or more. The content of each component in the composition means the total amount of the plurality of substances present in the composition when there are a plurality of substances corresponding to each component in the composition, unless otherwise specified. The "steps" in this specification may be independent steps or steps performed simultaneously.

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

[0013] The above Ce-activated α-sialon phosphor may have a diffuse reflectance of 86.5% or more with respect to the light having the wavelength at which the emission peak is located in the emission spectrum when excited with light of wavelength 405 nm. When a plurality of peaks are observed in the emission spectrum when the Ce-activated α-sialon phosphor is excited with light of wavelength 405 nm, the peak with the highest intensity is treated as the "emission peak" in this specification.

[0014] It is considered that the high above-mentioned predetermined diffuse reflectance means that there are few defects in the crystal contained in the Ce-activated α-sialon phosphor that absorb the light emitted by the phosphor. Therefore, the Ce-activated α-sialon phosphor having the above diffuse reflectance of a predetermined value or more is considered to have excellent internal quantum efficiency. Here, in the Ce-activated α-sialon phosphor, it has been difficult to set the above-mentioned predetermined diffuse reflectance to 86.5% or more. However, as a result of intensive research, the present inventors 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 a luminescence center element. The Ce-activated α-sialon phosphor may not substantially contain Eu as a luminescence center element, and may substantially contain only Ce as a luminescence center element. The fact that the Ce-activated α-sialon phosphor does not substantially contain Eu as a luminescence center element means that no emission peak derived from Eu is observed in the emission spectrum of the Ce-activated α-sialon phosphor when excited with light of a wavelength of 405 nm. Also, the fact that the Ce-activated α-sialon phosphor substantially contains only Ce as a luminescence center element means that only the peak derived from Ce is observed as a peak in the emission spectrum of the Ce-activated α-sialon phosphor when excited with light of a wavelength of 405 nm. For example, even if the Ce-activated α-sialon phosphor contains Eu, if the above-mentioned emission peak derived from Eu is not observed, in this specification, it shall be determined that Eu is not an element contained as a luminescence center element.

[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"). Also, 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. Also, the content of Ce may be 2 mol% or less, or 1 mol% or less, based on the total content of the above constituent elements in the Ce-activated α-sialon phosphor.

[0017] The content of Si may be 25 mol% or more, or 30 mol% or more, based on the total content of the above-mentioned constituent elements in the Ce-activated α-sialon phosphor. Also, the content of Si may be 45 mol% or less, or 40 mol% or less, based on the total content of the above-mentioned constituent elements in the Ce-activated α-sialon phosphor. The content of Al may be 4 mol% or more, 5 mol% or more, or 6 mol% or more, based on the total content of the above-mentioned constituent elements in the Ce-activated α-sialon phosphor. Also, the content of Al 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-mentioned constituent elements in the Ce-activated α-sialon phosphor. The contents of M, Ce, Si, and Al are determined by analysis using an ICP emission spectroscopic analysis method with a multi-type ICP emission spectrometer.

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

[0019] For example, in the case of a Ce-activated α-sialon phosphor, based on the total content of M, Ce, Si, Al, O, and N in the Ce-activated α-sialon phosphor, the content of M is 1 to 4 mol%, the content of Ce is 0.05 to 2 mol%, the content of Si is 25 to 45 mol%, the content of Al is 4 to 12 mol%, the content of O is 0.5 to 5 mol%, and the content of N is 40 to 60 mol%, and the content of M is 1 to 4 mol%, the content of Ce is 0.05 to 2 mol%, the content of Si is 25 to 45 mol%, the content of Al is 5 to 9 mol%, the content of O is 0.5 to 5 mol%, and the content of N is 40 to 60 mol% may be sufficient.

[0020] The Ce-activated α-sialon phosphor may contain, as a main crystal, a crystal having the same crystal structure as α-sialon. The Ce-activated α-sialon phosphor may contain heterogeneous phases as long as the gist 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 heterogeneous phase 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 the present specification, the powder X-ray diffraction pattern means one obtained by the powder X-ray diffraction method using CuKα rays under the condition of 25°C. Further, the maximum diffraction line of the heterogeneous phase means the one having the maximum diffraction intensity among the diffraction lines that cannot be attributed to α-sialon in the powder X-ray diffraction pattern.

[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). When the valence of M is a, m = ax + 3y, and Ce 3+It replaces the M site, where 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 solid-dissolved. In the general formula (1) above, M may be Ca, or may be two or more elements including 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, in the general formula (1), a = 2. That the Ce-activated α-sialon phosphor contains Ca can be confirmed by performing quantitative analysis of elements using an ICP emission spectroscopic analyzer.

[0023] In the 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 also 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 the general formula (1), y may be 0.05 or more, or 0.06 or more, and may also be 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less. In the general formula (1), n may be 0.01 or more, 0.05 or more, or 0.10 or more, and may also be less than m.

[0024] That the Ce-activated α-sialon phosphor contains α-sialon represented by the general formula (1) above 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 the heterogeneous phase to the diffraction line intensity of the (101) plane is 10% or less, and the content ratios of the respective constituent elements (M, Ce, Si, Al, O, and N) calculated by analysis by an ICP emission spectroscopic analysis method using a multi-type ICP emission spectroscopic analyzer and analysis of the amounts of oxygen and nitrogen by an oxygen-nitrogen analyzer are equal to the ratios shown in the general formula (1).

[0025] The Ce-activated α-sialon phosphor may be represented by, for example, the above general formula (1). In this case, M, x + y, y, and n may be as described above. The constituent elements and ratios of the Ce-activated α-sialon phosphor can be determined by analyzing the amounts of oxygen and nitrogen using an oxygen-nitrogen analyzer and by ICP emission spectroscopic analysis using a multi-type ICP emission spectrometer. That the Ce-activated α-sialon phosphor is represented by the above general formula (1) means that when the constituent elements and ratios 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 rate of elements other than the above elements is 1.5 mass% or less.

[0026] The Ce-activated α-sialon phosphor may contain Eu. The content of Eu 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 content of Eu may be 5.0 mass% or less, 3.0 mass% or less, 1.5 mass% or less, or 1.5 mass% or less based on the total mass of the Ce-activated α-sialon phosphor. The content of Eu 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 content of Eu means that which is obtained by performing quantitative analysis of elements using an ICP emission spectrometer. Specifically, the content of Eu is obtained by the method described in the examples. When the Ce-activated α-sialon phosphor contains Eu as a luminescence center element, the above content of Eu means the total amount of the content of Eu as a luminescence center element and the content of Eu that does not function as a luminescence center element.

[0027] When the Ce-activated α-sialon phosphor is excited with light having a wavelength of 405 nm, in the emission spectrum, the wavelength at which the emission peak is located is 470 to 525 nm. The lower limit value of the above wavelength range may be, for example, 480 nm, or 490 nm. The upper limit value of the above wavelength range may be, for example, 520 nm, or 510 nm. The above wavelength range corresponds to the range in which an emission peak is observed when the α-sialon phosphor is activated with Ce and is 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] When the Ce-activated α-sialon phosphor is excited with light having a wavelength of 405 nm, in the emission spectrum, the full width at half maximum of the emission peak may be 100 nm or more, 101 nm or more, or 102 nm or more. The full width at half maximum 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 full width at half maximum means the full width at half height. The full width at half maximum is specifically determined by the method described in the examples of this specification.

[0029] When the Ce-activated α-sialon phosphor is excited with light having a wavelength of 405 nm, in the emission spectrum, the ratio of the emission intensity observed at a wavelength of 580 nm to the intensity of the emission peak (emission intensity observed at a wavelength of 580 nm / intensity of the emission peak. Hereinafter, also simply referred to as "ratio of emission intensity") 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 ratio of emission intensity may be, for example, 0% or more, or 10% or more. In the above emission spectrum, it is considered that emission derived from Ce is observed around 470 to 525 nm, and emission derived from Eu is observed around 580 nm. Therefore, particularly when the wavelength at which the emission peak is located is 470 to 525 nm, the small ratio of the emission intensity means that the amount of Eu contained as the emission center element is small compared to the amount of Ce contained as the emission center element. The ratio of emission intensity is specifically determined by the method described in the examples of this specification.

[0030] The chromaticity x of the Ce-activated α-sialon phosphor may be 0.170 or more, or 0.180 or more. Further, the chromaticity x of the Ce-activated α-sialon phosphor may be 0.340 or less, or 0.325 or less. The chromaticity y of the Ce-activated α-sialon phosphor may be 0.270 or more, or 0.275 or more. Further, the chromaticity y of the Ce-activated α-sialon phosphor may be 0.550 or less, or 0.545 or less. The chromaticity x and chromaticity y of the Ce-activated α-sialon phosphor mean the values obtained by the method described in the examples.

[0031] In the emission spectrum when the Ce-activated α-sialon phosphor is excited with light having a wavelength of 405 nm, the diffuse reflectance of the Ce-activated α-sialon phosphor with respect to the light having the wavelength at which the emission peak is located may be 86.5% or more, 87.0% or more, or 87.5% or more. In the emission spectrum when the Ce-activated α-sialon phosphor is excited with light having a wavelength of 405 nm, the diffuse reflectance of the Ce-activated α-sialon phosphor with respect to the light having the wavelength at which the emission peak is located may be, for example, 100.0% or less, 95.0% or less, or 90.0% or less.

[0032] The diffuse reflectance of the Ce-activated α-sialon phosphor with respect to light having 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. The fact that the diffuse reflectance with respect to light having a wavelength of 600 nm is within the above range means that defects in the crystal structure constituting the phosphor and the generation of heterogeneous phases that are non-emitting components are more reduced, contributing to further improvement in the internal quantum efficiency and external quantum efficiency of the α-sialon phosphor. The diffuse reflectance of the Ce-activated α-sialon phosphor with respect to light having 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 with respect to light having 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. The fact that the diffuse reflectance with respect to light having a wavelength of 700 nm is within the above range means that the defects in the crystal structure constituting the phosphor and the generation of heterogeneous phases that are non-luminescent components are further reduced, contributing to further improvement in the internal quantum efficiency and external quantum efficiency of the α-sialon phosphor. The diffuse reflectance of the Ce-activated α-sialon phosphor with respect to light having 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 with respect to light having 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. The fact that the diffuse reflectance with respect to light having a wavelength of 800 nm is within the above range means that the defects in the crystal structure constituting the phosphor and the generation of heterogeneous phases that are non-luminescent components are further reduced, contributing to further improvement in the internal quantum efficiency and external quantum efficiency of the α-sialon phosphor. The diffuse reflectance of the Ce-activated α-sialon phosphor with respect to light having 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 diffuse reflectance means a value determined from the diffuse reflection spectrum of the Ce-activated α-sialon phosphor measured using a spectrophotometer. Specifically, the diffuse reflectance is obtained by the method described in the examples of this specification. As the spectrophotometer, “V-550” (product name) manufactured by JASCO Corporation can be used.

[0036] The absorption rate of the Ce-activated α-sialon phosphor for light having a wavelength of 405 nm may be 65.0% or more, 70.0% or more, 72.0% or more, or 75.0% or more. The absorption rate of the Ce-activated α-sialon phosphor for light having a wavelength of 405 nm may be 100.0% or less, 90.0% or less, or 80.0% or less.

[0037] The light absorption rate of the Ce-activated α-sialon phosphor at 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 from the viewpoint of improving the internal quantum efficiency. The light absorption rate of the Ce-activated α-sialon phosphor at 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] The light absorption rate of the Ce-activated α-sialon phosphor at a wavelength of 700 nm may be 3.0% or more, 5.0% or more, 7.0% or more, or 8.0% or more from the viewpoint of improving the external quantum efficiency. The light absorption rate of the Ce-activated α-sialon phosphor at a wavelength of 700 nm may be 15.0% or less, 13.0% or less, 10.0% or less, or 9.0% or less.

[0039] The light absorption rate of light at a specific wavelength means the following. First, attach the phosphor to the opening of the integrating sphere, introduce light at a specific wavelength into the integrating sphere as excitation light, and measure the emission spectrum using a spectrophotometer. From the obtained emission spectrum data, calculate the number of excitation reflected photons (Qref) and the number of fluorescence photons (Qem). Also, measure the spectrum of the excitation light in the same manner as above except that a standard reflector is attached to the opening of the integrating sphere instead of the phosphor. Calculate the number of excitation light photons (Qex) from the obtained spectrum data. Then, calculate the light absorption rate at a specific wavelength using the following formula. Light absorption rate of light at a specific wavelength = ((Qex - Qref) / Qex) × 100 Specifically, the light absorption rate of light at a specific wavelength is determined by the method described in the examples of this specification. As the spectrophotometer, "MCPD-7000" (trade name) manufactured by Otsuka Electronics Co., Ltd. etc. can be used.

[0040] When excited by light with a wavelength of 405 nm, the internal quantum efficiency of the Ce-activated α-sialon phosphor according to the present disclosure 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 means the internal quantum efficiency calculated based on the data of 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 absorption rate of light with a wavelength of 405 nm of 65.0% or more and an internal quantum efficiency of 76.0% or more. From the viewpoint of practical use, the absorption rate of light with a wavelength of 405 nm may be 72.0% or more and the internal quantum efficiency may be 78.0% or more.

[0042] The α-sialon phosphor activated with Ce described above can be produced, for example, by the following method. An example of the method for producing an α-sialon phosphor activated with Ce includes a step of heat-treating a mixture containing an α-sialon activated with Ce and a Eu source at 1200 to 1500 °C to obtain a heat-treated product.

[0043] The α-sialon activated with Ce (hereinafter also referred to as "raw material sialon") contains Ce as a luminescence center element and can emit fluorescence by itself. The raw material sialon may not substantially contain Eu as a luminescence center element, and may contain substantially only Ce as a luminescence center element. That the raw material sialon does not substantially contain Eu as a luminescence center element means that no emission 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. Also, that the raw material sialon substantially contains only Ce as a luminescence center element means that only the peak derived from Ce is observed as a peak in the emission spectrum of the raw material sialon when excited with light having a wavelength of 405 nm.

[0044] The raw material sialon may contain, as constituent elements, M, Ce, Si, Al, O, and N. 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 as the contents of each element based on the total content of M, Ce, Si, Al, O, and N in the Ce-activated α-sialon phosphor described above. Here, the phrase "in the Ce-activated α-sialon phosphor" shall 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 content of M may be 1 to 4 mol%, the content of Ce may be 0.05 to 2 mol%, the content of Si may be 25 to 45 mol%, the content of Al may be 4 to 12 mol%, the content of O may be 0.5 to 5 mol%, and the content of N may be 40 to 60 mol%. The content of M may be 1 to 4 mol%, the content of Ce may be 0.05 to 2 mol%, the content of Si may be 25 to 45 mol%, the content of Al may be 5 to 9 mol%, the content of O may be 0.5 to 5 mol%, and the content of N may be 40 to 60 mol%.

[0046] The raw material sialon may contain, as the main crystal, a crystal having the same crystal structure as α-sialon, or may consist of a crystal having the same crystal structure as α-sialon. In the powder X-ray diffraction pattern of the raw material sialon, the ratio of the maximum diffraction line intensity of the heterogeneous phase 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 contain, for example, α-sialon represented by the following general formula (1). (M a+ x ,Ce 3+ y )Si 12-(m+n) Al (m+n) O n N16-n (1) [In 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). When the valence of M is a, m = ax + 3y, and Ce 3+ substitutes the M site, 0.3 ≦ x + y ≦ 2, 0.03 ≦ y ≦ 0.5, and 0 ≦ n ≦ m.]

[0048] The starting material sialon may contain Ca and may contain α-sialon in which Ca is solid-dissolved. In the above general formula (1), M may be Ca, or may be two or more elements including 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, in general formula (1), a = 2. Whether the starting material sialon contains Ca can be confirmed by performing quantitative analysis of elements using an ICP emission spectroscopic analyzer.

[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 also 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 also 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 also be less than m.

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

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

[0052] The manufacturing method according to an example may have 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 a raw material sialon.

[0053] The Si source means a compound or a simple substance having silicon as a constituent element, the Al source means a compound or a simple substance having aluminum as a constituent element, and the Ce source means a compound or a simple substance having cerium as a constituent element. In this specification, a compound having silicon as a constituent element is also referred to as a silicon compound, a compound having aluminum as a constituent element is also referred to as an aluminum compound, and a compound having cerium as a constituent element is also referred to as a cerium compound. The silicon compound, the aluminum compound, and the cerium compound may each be any of a nitride, an oxide, an oxynitride, and a hydroxide. At least one of the Si source, the Al source, and the Ce source may be a nitride. Since the nitride has nitrogen that becomes a constituent element of the raw material sialon, it can also be called a nitrogen source.

[0054] Examples of the silicon compound include silicon nitride (Si3N4), silicon dioxide (SiO2), and the like.

[0055] Examples of aluminum compounds include aluminum nitride (AlN), aluminum oxide (Al2O3), and aluminum hydroxide (Al(OH)3).

[0056] Examples of cerium compounds include cerium oxide (CeO2), cerium nitride (CeN), cerium hydroxide (Ce(OH)4), and cerium fluoride (CeF3).

[0057] The raw material composition may include other raw materials containing elements that can form α-sialon other than the Si source, Al source, and Ce source. Examples of other raw materials include a Li source, a Ca source, etc. The Li source means a compound or a simple substance containing lithium as a constituent element, and the Ca source means a compound or a simple substance 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 a halide, a nitride, an oxide, an oxynitride, a carbonate, and a hydroxide. Examples of the lithium compound include lithium halides such as lithium fluoride, lithium nitride, lithium oxide, lithium carbonate, and lithium hydroxide. Examples of the calcium compound include calcium halides such as calcium fluoride, calcium oxide, calcium carbonate, calcium nitride, and calcium hydroxide.

[0058] The raw material composition may further include α-sialon or α-sialon activated with Ce. The α-sialon or α-sialon activated with Ce can serve as an aggregate or a nucleus for obtaining the raw material 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 and the Ce-activated α-sialon phosphor, as well as the α-sialon contained therein. For mixing, a dry mixing method or a wet mixing method may be used. The dry mixing method, also called the dry blending method, may be, for example, a method of mixing each component using a V-type mixer or the like. The wet mixing method may be, for example, a method of adding a solvent or dispersion medium such as water to prepare a solution or slurry, mixing each component, and then removing the solvent or dispersion medium. Further, after weighing and mixing each compound, the one with adjusted particle size may be used as the raw material composition. The adjustment of the particle size can be carried out, for example, by sieving.

[0060] From the viewpoint of promoting the grain growth of the main crystal phase of α-sialon and making the solid solution amount of Ce more sufficient, the firing temperature of the raw material composition may be 1600 °C or higher, 1650 °C or higher, or 1700 °C or higher. Also, from the viewpoint of sufficiently suppressing the decomposition of the main crystal phase of α-sialon, the firing temperature of the raw material composition may be 2000 °C or lower, 1900 °C or lower, or 1800 °C or lower. The firing temperature of the raw material composition may be, for example, 1600 - 2000 °C, 1650 - 1900 °C, or 1700 - 1800 °C.

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

[0062] The firing may be carried out, for example, in a nitrogen gas atmosphere. The nitrogen gas atmosphere may be at atmospheric pressure, but the decomposition of α-sialon at high temperatures generated by heating under conditions of high nitrogen pressure can be suppressed. Further, the firing may be carried out, for example, in a pressurized atmosphere. When the atmosphere is pressurized, 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. Further, 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 number of firing times may be 1 time, or may be 2 times or more. The number of firing times may be, for example, 5 times or less, or 4 times or less. When the number of firing times is 2 times or more, the respective firing conditions may be the same as each other or may be different.

[0064] As the raw material sialon used for the heat treatment, the fired product obtained by the above method may be used as it is, or may be used after adjusting the particle size. The adjustment of the particle size 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, sieving using a vibrating sieve or the like.

[0065] A manufacturing method according to an example has a step of heating (annealing) a mixture containing a raw material sialon and a Eu source at 1200 to 1500 °C to obtain a heat-treated product (hereinafter, also referred to as the "heat treatment step"). The heating temperature of 1200 to 1500 °C corresponds to a temperature lower than the general temperature as the firing temperature for obtaining the raw material sialon from the above-mentioned raw material composition. By heating at such a temperature, while suppressing the further progress of grain growth of the raw material sialon, by reducing the density of crystal defects contained in the heat-treated product, the diffuse reflectance of the raw material sialon phosphor with respect to the light of the emission peak wavelength in the emission spectrum when excited by light with a wavelength of 405 nm is improved, and it is considered that the internal quantum efficiency can be further improved.

[0066] In particular, in the above heat treatment step, by heating the raw material sialon together with a Eu source, the internal quantum efficiency can be improved. Generally, in α-sialon phosphors, it is known that fluorescence appears in different wavelength ranges depending on whether Ce or Eu is used as the luminescent center element. In Ce-activated α-sialon phosphors, it is considered undesirable to use another element that emits fluorescence, such as Eu, in combination with Ce in order to obtain excellent luminescence characteristics. In the manufacturing method of α-sialon phosphors with Ce as the luminescent center, it is avoided to add an element that can be another luminescent center element such as Eu. However, in the above heat treatment step, by deliberately heating the raw material sialon together with a Eu source, for reasons not yet clear, it is considered that the internal quantum efficiency is improved because the reduction in the density of crystal defects proceeds more efficiently.

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

[0068] The Eu source means a compound or a 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 oxides (europium oxide), europium hydroxides (europium hydroxide), europium nitrides (europium nitride), europium sulfides (europium sulfide), and europium halides (europium halide). 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 oxides, nitrides, and halides. The europium compound preferably contains europium oxide.

[0069] The content of the Eu source in the above mixture may be 0.01 part by mass or more, 0.05 part by mass or more, 0.1 part by mass or more, or 0.3 part by mass or more with respect 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. Also, the content of the Eu source in the above 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 with respect 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 heterogeneous phase that adversely affects 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 with respect 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. Also, 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 selected from the group consisting of a noble gas and a reducing gas. Examples of the noble gas include argon gas and helium gas. The noble gas may be argon gas. Examples of the reducing gas 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 selected from the group consisting of a noble gas and a reducing gas may be 80% by mass or more, 90% by mass or more, 95% by mass or more, or 99% by mass or more based on the total volume of the atmosphere. Further, the content of argon gas may be 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or 99% by mass or more based on the total volume of the atmosphere.

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

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

[0074] In the heat treatment step, the number of times of heat treatment may be 1 time, or may be 2 times or more. The number of times of heat treatment may be, for example, 5 times or less, or 4 times or less. When the number of times of heat treatment is 2 times or more, the type and content of the Eu source, the heating temperature, the heating atmosphere, and the heating time in each time may be the same as or different from each other, and can be appropriately set within the above ranges. However, the heating temperature is at least in the range of 1200 to 1500 °C.

[0075] The manufacturing method according to one example may further include steps other than the step of obtaining the above-described α-sialon and the heat treatment step. Examples of other steps include a step of treating the heat-treated product obtained by the above 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] The acid treatment is performed by bringing the above heat-treated product into contact with an acid. Specifically, for example, it is performed by putting the heat-treated product into an acid and stirring it. By performing the acid treatment, the amount of the altered phase formed by the heat treatment, the compound derived from the remaining Eu source, and the heterogeneous phase can be reduced, so that the internal quantum efficiency of the Ce-activated α-sialon phosphor can be further improved. The acid treatment step yields an acid-treated product.

[0077] Examples of the acid used for the acid treatment include hydrofluoric acid (HF), nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, and mixtures thereof (mixed acids). As the acid, for example, a mixed acid of HF and nitric acid may be used. In the mixed acid of HF and nitric acid, the mass ratio of the content of HF to the content of HNO3 may be, for example, 0.5 / 1 to 1 / 1.

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

[0079] The number of acid treatments may be once or may be two or more times. The number of acid treatments may be, for example, five or less, or four or less. When the number of acid treatments is two or more, the treatment time, temperature, and type of acid in each treatment may be the same as or different from each other in each treatment and can be appropriately set within the above ranges. When performing the acid treatment twice, for example, after the acid treatment using a mixed acid of hydrofluoric acid and nitric acid, the acid treatment using hydrochloric acid may be performed. According to such a treatment, for example, non-solid-solved Eu in the heat-treated product can be changed to EuF3 by the mixed acid, and then the EuF3 can be removed by dissolving it in hydrochloric acid.

[0080] 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, etc.) or a mixed solvent containing ion-exchanged water and aqueous ammonia, stirred, and then allowed to stand to remove particles with a small particle size.

[0081] The Ce-activated α-sialon phosphor described above may be used alone or in combination with other phosphors. Since the Ce-activated α-sialon phosphor has excellent internal quantum efficiency, it can be suitably used, for example, in a light-emitting device such as an LED. The Ce-activated α-sialon phosphor can also be used, for example, by being dispersed in a cured resin. As the cured resin, for example, a resin used as a sealing resin for a light-emitting device or the like can be used.

[0082] Although several embodiments have been described above, the present disclosure is not limited to the above embodiments at all. Also, the description contents of the above-described embodiments can be applied to each other.

Examples

[0083] Hereinafter, the content of the present disclosure will be described in more detail with reference to Examples and Comparative Examples. However, the present disclosure is not limited to the following Examples.

[0084] [Production of Raw Material Sialon] [Production of Raw Material Sialon A] Set the design composition to Ca 0.645 Ce 0.07 Si 9.75 Al 2.25 O 0.75 N 15.25 and prepare a raw material powder a having a blending composition of 52.3 mol% of silicon nitride powder (manufactured by UBE Industries, Ltd., E10 grade), 36.2 mol% of aluminum nitride powder (manufactured by Tokuyama Corporation, E grade), 1.1 mol% of cerium oxide powder (manufactured by Shin-Etsu Chemical Co., Ltd., C type), 2.6 mol% of calcium fluoride powder (manufactured by Fujifilm Wako Pure Chemical Corporation, special grade reagent), and 7.8 mol% of calcium carbonate powder (manufactured by Fujifilm Wako Pure Chemical Corporation, special grade reagent). In the raw material powder a, the content of calcium fluoride powder (CaF2 / (CaF2 + CaCO3)) based on the total amount of calcium compounds was 25 mol%. The blending composition was calculated so that calcium fluoride and calcium carbonate satisfied the above design composition in terms of the same number of moles of calcium converted to calcium oxide. The raw material powder a was bag-mixed for several minutes, and the obtained mixture was passed through a nylon sieve (mesh size: 150 μm) to obtain a raw material composition.

[0085] 35 g of the above 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 a nitrogen gas atmosphere of 0.03 MPaG using an electric furnace equipped with a carbon heater. The firing temperature was 1750 °C, and the firing time was 8 hours. The obtained fired product was crushed by a stamp mill (manufactured by Nippon Tokushu Toryo Co., Ltd., high-speed stamp mill ANS-143PL) so that all of the fired product passed through a sieve (mesh size: 250 μm) to obtain raw material sialon A (the phosphor of Comparative Example 1).

[0086] [Production of Raw Material Sialon B] A raw material composition was obtained in the same manner as in the above <Production of raw material sialon A>, except that the blending amount of calcium fluoride powder was 5.2 mol% and the blending amount of calcium carbonate powder was 5.2 mol% (CaF2 / (CaF2 + CaCO3) = 50 mol%). 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 at 1750 °C for 16 hours in a nitrogen gas atmosphere of 0.03 MPaG using an electric furnace equipped with a carbon heater to obtain a fired product. The obtained fired product was coarsely crushed by a stamp mill and then crushed by a jet mill (manufactured by 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 passing through the vibrating sieve was recovered as raw material sialon B (the phosphor of Comparative Example 3).

[0087] <Production of raw material sialon C> A raw material composition was obtained in the same manner as in the above <Production of raw material sialon B>, except that calcium carbonate powder was changed to calcium oxide (obtained by decarbonating calcium carbonate powder by treating it in the atmosphere 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 at 1750 °C for 24 hours in a nitrogen gas atmosphere of 0.03 MPaG using an electric furnace equipped with a carbon heater to obtain a fired product. For the obtained fired product, coarsening, crushing, and sieving were performed in the same procedure as in the above <Production of raw material sialon B> to obtain raw material sialon C (the phosphor of Comparative Example 7).

[0088] <Production of raw material sialon D> Firing, coarsening, crushing, and sieving were performed in the same manner as in the above <Production of raw material sialon B>, except that calcium carbonate powder was changed to calcium oxide, to obtain raw material sialon D (the phosphor of Comparative Example 8).

[0089] <Production of raw material sialon E> The phosphor of Comparative Example 12 was obtained in the same manner as in <Production of Raw Material Sialon D> except that 0.5% by mass of europium oxide powder (manufactured by Shin-Etsu Chemical Co., Ltd., RU grade) was added to the raw material powder used in <Production of Raw Material Sialon D> by external division.

[0090] [Treatment of Raw Material Sialon] For raw material sialons A to E, as shown in Tables 1 to 2, phosphors of Comparative Examples 2, 4 to 6, 9 to 11 and Examples 1 to 8 were obtained by subjecting them to one or more of the following heat treatment, acid treatment, and elutriation treatment. 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, Ce 3+ replaces the Ca site, 0.7 ≦ x + y ≦ 0.9, 0.03 ≦ y ≦ 0.08, and 0 ≦ n ≦ m / 2.]

[0091] [Heat Treatment] For Comparative Examples 4 to 6 and 9 to 10, the α-sialons shown in Tables 1 to 2 were heat-treated at the temperatures described in Tables 1 to 2 in an argon gas atmosphere of 0.03 MPaG using an electric furnace equipped with a carbon heater. The heating time was 8 hours. For Examples 1 to 8, europium oxide powder (manufactured by Shin-Etsu Chemical Co., Ltd., RU grade) in the amounts shown in Tables 1 to 2 was added as a Eu source to the α-sialons shown in Tables 1 to 2, and the resulting mixtures were heat-treated in the same manner as above. The amounts of the Eu source described in Tables 1 to 2 mean the amounts based on the total mass of each α-sialon. For Comparative Example 11, cerium oxide powder (manufactured by Shin-Etsu Chemical Co., Ltd., C type) instead of europium oxide powder was added in an amount of 1% by mass based on the total mass of the raw material sialon D to the raw material sialon D, and the resulting mixture was heat-treated in the same manner as above.

[0092] <Acid treatment> In the case where the heat treatment was “performed”, the heat-treated product obtained by the heat treatment was put into a mixed acid of hydrofluoric acid and nitric acid (48% by mass concentration hydrofluoric acid: 60% by mass concentration nitric acid: water = 1: 1: 6 (volume ratio)) heated to 80 ° C, and stirred for 30 minutes. Thereafter, filtration, washing with water, and drying were performed to recover the acid-treated product.

[0093] <Classification (elutriation)> 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, first, water containing a small amount of a dispersant was prepared in a beaker. The acid-treated product was dispersed in the water, allowed to stand for a predetermined time, and then the supernatant liquid from the water surface to a predetermined height was removed with a liquid feed pump. Thereafter, a predetermined amount of water containing a small amount of the above dispersant was added to the beaker, and dispersion, standing, and supernatant removal were repeated to remove the fine powder. The predetermined time and the predetermined height were adjusted so that fine powder having a particle size of less than 7.5 μm was removed in Example 2 and fine powder having a particle size of less than 5 μm was removed in Example 6 according to Stokes' formula.

[0094] [Evaluation] <Diffuse reflectance> The diffuse reflectance of the phosphors of each comparative example and example was measured using an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, trade name: V-550) equipped with an integrating sphere device (trade name: ISV-469). After baseline correction was performed 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. Among the measurement results, the peak wavelength of the emission spectrum of each phosphor and the values of the diffuse reflectance at 600 nm, 700 nm, and 800 nm were recorded. The results are shown in Tables 1 to 2.

[0095] <Excitation light absorption rate, fluorescence characteristics, and chromaticity x and chromaticity y> For the phosphors of each comparative example and example, the excitation light absorption rate, emission peak wavelength, full width at half maximum of the emission peak, ratio of emission intensity, internal quantum efficiency, and external quantum efficiency when the excitation wavelength was 405 nm were calculated by the following procedure. The results are shown in Tables 1 to 2.

[0096] First, the phosphor to be measured was filled into a concave cell so that the surface was smooth and attached to the opening of the integrating sphere. Monochromatic light spectrally separated from a Xe lamp, which is an emission light source, to a wavelength of 405 nm was introduced into the integrating sphere as excitation light for the phosphor using an optical fiber. The phosphor to be measured was irradiated with this monochromatic light as excitation light, and the emission spectrum was measured. A spectrophotometer (manufactured by Otsuka Electronics Co., Ltd., trade name: MCPD-7000) was used for the measurement. Among the emission spectra obtained above, the spectra of the phosphors of Comparative Examples 7 and 12 and Examples 1 and 2 are shown in FIG. 1.

[0097] From the obtained emission spectrum data, the emission peak wavelength and the full width at half maximum (FWHM) were determined. Also, from the obtained emission spectrum data, the fluorescence intensity (intensity of the emission peak) at the emission peak wavelength and the fluorescence intensity at 580 nm were determined, and the ratio of the emission intensity was determined by the following formula. The intensity of the emission observed at 580 nm is adopted as an index of the emission derived from Eu. Ratio of emission intensity = {(fluorescence intensity at 580 nm) / (intensity of the emission peak)} × 100

[0098] Furthermore, from the data of the obtained emission spectrum, the number of excitation reflection photons (Qref) and the number of fluorescence photons (Qem) were calculated. The number of excitation reflection 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 415 to 800 nm. Also, using the same apparatus, a standard reflector with a reflectance of 99% (Spectralon (registered trademark), manufactured by Labsphere) was attached to the opening of the integrating sphere, and the spectrum of the excitation light with a wavelength of 405 nm was measured. At that time, the number of excitation photons (Qex) was calculated from the spectrum in the wavelength range of 400 to 415 nm.

[0099] From the above calculation results, based on the following calculation formulas, the absorption rate of the 405-nm excitation light, the internal quantum efficiency, and the external quantum efficiency of the phosphor to be measured were determined. Absorption rate of 405-nm excitation light = ((Qex - Qref) / Qex) × 100 Internal quantum efficiency = (Qem / (Qex - Qref)) × 100 External quantum efficiency = (Qem / Qex) × 100 Note that the relational expressions between the external quantum efficiency, the absorption rate of the 405-nm excitation light, and the internal quantum efficiency can be expressed as follows. External quantum efficiency = Absorption rate of 405-nm excitation light × Internal quantum efficiency

[0100] Also, from the spectral data in the wavelength range 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 "Method for measuring color - Color of light source" to obtain the chromaticity x and the chromaticity y.

[0101] Regarding the standard sample of Eu-activated β-sialon phosphor (manufactured by Cyalon Co., Ltd., Standard Phosphor Gree, Lot No. NSG1301. The absorption rate, internal quantum efficiency, and external quantum efficiency of the excitation light at 405 nm measured by the method compliant with ISO24936 were 81%, 81%, and 65% respectively), in accordance with the above-mentioned measurement method, the absorption rate of the excitation light at 405 nm, internal quantum efficiency, external quantum efficiency, and chromaticity x and chromaticity y were measured. As a result, the absorption rate of the excitation light at 405 nm was 83.5%, the internal quantum efficiency was 83.0%, the external quantum efficiency was 69.3%, the chromaticity x was 0.347, and the chromaticity y was 0.628.

[0102] Each measured value regarding the excitation light absorption rate, fluorescence characteristics, and chromaticity x and chromaticity y may vary when the manufacturer of the measuring device, manufacturing lot number, etc. change. Therefore, as various measured values, the values measured by the measurement method described in this specification are adopted. However, when changing the manufacturer of the measuring device, manufacturing lot number, etc., it is also possible to correct each measured value using the measured values of the above-mentioned standard sample as reference values.

[0103] <Absorption Rates of Light at 600 nm and 700 nm> When measuring the emission spectrum, except that monochromatic light spectrally separated from the Xe lamp at a wavelength of 600 nm or 700 nm was used instead of the monochromatic light spectrally separated from the Xe lamp at a wavelength of 405 nm, and the spectrum of the excitation light with a wavelength of 600 nm or 700 nm was measured instead of the spectrum of the excitation light with a wavelength of 405 nm, the absorption rates of light at 600 nm and 700 nm were measured in the same manner as the above-mentioned excitation light absorption rate. The results are shown in Tables 1 - 2.

[0104]

Table 1

[0105]

Table 2

[0106] <Content of Eu> For the phosphors of Examples 3 to 6, 8 and Comparative Example 12, the Eu content was determined. The Eu content was determined using an ICP emission spectroscopic analyzer. For quantification of 0.1% or more, the phosphor was dissolved by an alkali fusion method to prepare a sample solution, and for quantification of less than 0.1%, a pressurized acid decomposition method was used. Using an ICP emission spectroscopic analyzer (manufactured by Agilent Technologies, trade name: 5110 VDV), quantitative analysis of europium was performed on the obtained sample solution. From the obtained results, the Eu content was calculated. Also, for Examples 3 to 8 and Comparative Example 12, the phosphor was treated for 30 minutes with 18 mass% hydrochloric acid heated to 80°C (hydrochloric acid washing). For Examples 3 to 6, 8 and Comparative Example 12, after hydrochloric acid washing, the Eu content was further measured. The results are shown in Table 3. Note that the Eu content described in Table 3 means the mass ratio based on the total mass of each phosphor. Also, for Examples 3, 4, 6 to 8 and Comparative Example 12, the excitation light absorption rate, fluorescence characteristics, chromaticity, and the absorption rates of light at 600 nm and 700 nm after hydrochloric acid washing, as well as the change amount of these values from the values before hydrochloric acid washing (value after hydrochloric acid washing - value before hydrochloric acid washing) are shown in Table 4.

[0107]

Table 3

[0108]

Table 4

[0109] For the phosphors of Examples 3 to 5, 6, 8, the Eu content changed significantly before and after hydrochloric acid washing. On the other hand, for the phosphor of Comparative Example 12, no significant change in the Eu content was observed before and after hydrochloric acid washing. For Comparative Example 12, since a Eu source was added during the production of α-sialon activated with Ce, Eu has entered into the crystal of α-type sialon in the Ce-activated α-sialon phosphor. On the other hand, in the phosphors of Examples 3 to 5, 6, 8, it is considered that Eu has not entered into the crystal of α-type sialon.

Claims

1. In the emission spectrum when excited by light with a wavelength of 405 nm, having an emission peak within a wavelength range of 470 to 525 nm, An α-sialon phosphor activated with Ce, wherein the diffuse reflectance with respect to light having a wavelength at which the emission peak is located is 86.5% or more.

2. The α-sialon phosphor activated with Ce according to Claim 1, containing Eu.

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

4. The α-sialon phosphor activated with Ce according to any one of Claims 1 to 3, wherein the full width at half maximum of the emission peak is 100 nm or more.

5. The α-sialon phosphor activated with Ce 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 intensity of the emission peak is less than 45%.

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

7. The α-sialon phosphor activated with Ce according to any one of Claims 1 to 3, wherein the α-sialon phosphor activated with Ce contains an α-type 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 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). When the valence of M is a, m = ax + 3y, and Ce ３＋ substitutes the M site, 0.3 ≤ x + y ≤ 2, 0.03 ≤ y ≤ 0.5, and 0 ≤ n ≤ m.]

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