Phosphor, method for producing phosphor, and light-emitting device

Abstract

To provide a phosphor that exhibits favorable luminescent characteristics upon excitation with ultraviolet light.SOLUTION: A phosphor having a composition represented by KAlmOn:xEu,yMn. In this formula, m is 8 to 25, n is 16 to 40, x>0, y>0, and x / y is 0.5 to 1.5. When this phosphor is irradiated with light having a wavelength of 340 nm, its emission spectrum includes a peak having a maximum between wavelengths 500 to 520 nm, and a full width at half maximum of that peak is 22 to 29 nm.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a phosphor, a method for manufacturing the phosphor, and a light-emitting device. [Background technology]

[0002] Phosphors that absorb ultraviolet light and emit visible light are known. For example, Non-Patent Document 1 discloses a phosphor having a composition of KAl 11 O 17 :0.1Eu 2+ ,0.15Mn 2+ is excited by ultraviolet light with a wavelength of 340 nm and emits visible light with a wavelength of 510 nm. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Lu G, Wang Y, Piao S, Zhang J, Zhang X, Zhou X, et al. Design of a superb Eu2+-Mn2+ co-doped narrow-band green phosphor via nearly 100% energy transfer efficiency. J Am Ceram Soc. 2023;106:1216-1229. Summary of the Invention [Problem to be solved by the invention]

[0004] According to the inventor's past findings and preliminary studies, the phosphor described in Non-Patent Document 1 has room for improvement in, for example, the light-emitting characteristics. Furthermore, there is a need for green phosphors that emit light with a wavelength of around 510 nm, but most conventional green phosphors only emit light with wavelengths longer than that. Furthermore, when using green light as a light-emitting material, there has been a demand for a phosphor with a narrower half-width, because by using a phosphor with a narrower half-width and a sharper spectrum, it is possible to extract a high percentage of the target wavelength.

[0005] The present invention has been made in view of the above circumstances, and one of the objects of the present invention is to provide a phosphor that is excited by ultraviolet light and has good light-emitting properties. [Means for solving the problem]

[0006] The present inventors have completed the invention provided below and solved the above problems.

[0007] 1. The composition is KAl m O n A phosphor represented by: xEu, yMn, m is 8~25, n is 16~40, x>0, y>0, x / y is 0.5~1.5, A phosphor in which, when irradiated with light having a wavelength of 340 nm, the emission spectrum has a peak with a maximum between wavelengths of 500 and 520 nm, and the full width at half maximum of the peak is 22 to 29 nm. 2. 1. The phosphor according to claim 1, In the emission spectrum, the peak intensity of the peak is I max The emission intensity at a wavelength of 450 nm is I 450 When I 450 / I max The value of is 0.1 or less for phosphors. 3. 1. or 2. The phosphor according to The phosphor has x between 0.05 and 0.40. 4. The phosphor according to any one of 1. to 3., The phosphor has y between 0.10 and 0.35. 5. The formula is KAl 11 O 17a mixing step of mixing a compound represented by the formula: a firing step of firing the mixture; A method for producing a phosphor comprising the steps of: 6. 5. A method for producing the phosphor according to claim 5, The method for producing a phosphor, wherein the europium source comprises an oxide, nitride, halide or hydroxide of europium. 7. 5. or 6. A method for producing a phosphor according to the above, The method for producing a phosphor, wherein the manganese source comprises an oxide, nitride, halide or carbonate of manganese. 8. A method for producing the phosphor according to any one of items 5 to 7, The method for producing a phosphor, wherein the firing temperature in the firing step is 1350 to 1750°C. 9. a light-emitting element capable of emitting ultraviolet light; a wavelength conversion member containing the phosphor according to any one of 1. to 4.; A light emitting device comprising: [Effects of the Invention]

[0008] According to the present invention, there is provided a phosphor that is excited by ultraviolet light and has good light-emitting properties. [Brief explanation of the drawings]

[0009] [Figure 1] 1 shows an emission spectrum when the phosphor of Example 4 is irradiated with light having a wavelength of 340 nm. [Figure 2] 1 shows an emission spectrum when the phosphor of Comparative Example 1 is irradiated with light having a wavelength of 340 nm. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The drawings are for illustrative purposes only and do not necessarily correspond to actual items.

[0011] In this specification, unless otherwise specified, the expression "X to Y" in the description of a numerical range means at least X and at most Y. For example, "1 to 5% by mass" means "at least 1% by mass and at most 5% by mass."

[0012] <Phosphor> The composition of the phosphor of this embodiment is KAl m O n In this composition formula, m is 8 to 25, n is 16 to 40, x>0, y>0, and x / y is 0.5 to 1.5. In the emission spectrum when the phosphor of this embodiment is irradiated with light having a wavelength of 340 nm, there is a peak with a maximum between wavelengths of 500 and 520 nm, and the full width at half maximum of this peak is 22 to 29 nm.

[0013] According to the description in Non-Patent Document 1 and the findings of the present inventors, the phosphor having the above composition is (i) Excitation of Eu by near-ultraviolet light (ii) The excitation energy is transferred to Mn (Energy transfer) (iii) Mn emits light (green light) with a peak having a maximum wavelength between 500 and 520 nm. It is thought that the light is emitted by the following mechanism.

[0014] According to the findings and preliminary studies of the present inventors, one possible reason for the inefficient energy transfer in the phosphor specifically produced in Non-Patent Document 1 is that the ratio of Eu to Mn was not appropriate. Therefore, the present inventors optimized the ratio of Eu to Mn so that x / y was 0.5 to 1.5.

[0015] Furthermore, the phosphor specifically produced in Non-Patent Document 1 was thought to contain many impurities and heterogeneous phases that do not contribute to or interfere with light emission, probably due to the production method. Based on past findings and preliminary studies, the inventors considered that the "full width at half maximum" in the emission spectrum is related to the amount of impurities or heterogeneous phases, and attempted to optimize it as an index that can be correlated with the emission characteristics. As a result, the inventors optimized the emission spectrum when the phosphor was irradiated with light of a wavelength of 340 nm, so that the full width at half maximum of the peak with a maximum wavelength between 500 and 520 nm was 22 to 29 nm.

[0016] As described above, the phosphor of this embodiment has good light emission characteristics due to the optimization of the ratio of Eu and Mn and the optimization of the full width at half maximum, which is thought to be related to the amount of impurities or heterogeneous phases.

[0017] The phosphor of this embodiment can be manufactured by using appropriate materials in appropriate amounts and by adopting appropriate manufacturing processes and manufacturing conditions. Details will be described later, but to briefly explain the appropriate manufacturing processes and manufacturing conditions, the phosphor of this embodiment can be manufactured by first using a phosphor having the composition formula KAl 11 O 17 The compound represented by the formula (I) is prepared, mixed with a europium source and a manganese source to form a mixture, and then calcined the mixture. If an appropriate manufacturing process and manufacturing conditions are not adopted, it may not be possible to manufacture the phosphor of this embodiment.

[0018] The phosphor of this embodiment will be further described.

[0019] (Crystal structure and composition) The phosphor of this embodiment is generally a KAl having a β-Al2O3 crystal structure. 11 O 17 However, in consideration of the presence of heterogeneous phases that inevitably occur during manufacturing and the volatilization of some elements (especially K) during manufacturing, the values ​​of m and n are set to a wide range in the composition formula described above. Incidentally, regarding the volatilization of K, please refer to the examples below, which show that the higher the firing temperature, the greater the proportion of elements other than K (i.e., the relatively smaller the proportion of K). The value of m may be 8 to 25, preferably 10 to 25, more preferably 11.5 to 24, and even more preferably 13 to 23. The value of n may be 16 to 40, preferably 18 to 39, more preferably 20 to 38, and even more preferably 23 to 27.

[0020] As described above, the amount of Eu, the amount of Mn, and the ratio thereof can affect the luminescence characteristics. x has only to be greater than 0, and is preferably 0.05 to 0.40, more preferably 0.75 to 0.35, and even more preferably 0.10 to 0.30. y should be greater than 0, and is preferably 0.10 to 0.50, more preferably 0.10 to 0.40, and even more preferably 0.15 to 0.30. The ratio x / y may be 0.5 to 1.5, but is preferably 0.6 to 1.3, and more preferably 0.7 to 1.1.

[0021] The values ​​of x, y, and x / y are thought to be related not only to the peak intensity of light emission in the wavelength range of 500 to 520 nm, but also to the suppression of unintended light emission, i.e., the suppression of light emission in wavelengths other than 500 to 520 nm. By appropriately adjusting x, y, and x / y, it is possible to further suppress light emission in wavelengths other than 500 to 520 nm.

[0022] (Emission spectrum) As described above, the emission spectrum when the phosphor of this embodiment is irradiated with light having a wavelength of 340 nm has a peak with a maximum between wavelengths of 500 and 520 nm. The full width at half maximum of this peak is 22 to 29 nm. This value is preferably 22 to 27 nm, more preferably 23 to 27 nm, and even more preferably 24 to 26 nm.

[0023] From another perspective, the peak intensity of the peak having a maximum between wavelengths of 500 and 520 nm in the emission spectrum when the phosphor of this embodiment is irradiated with light of a wavelength of 340 nm is defined as I max The emission intensity at a wavelength of 450 nm is I 450 When I450 / I max The value of is preferably 0.1 or less, more preferably 0.05 or less. According to the inventor's findings, the light emission with a wavelength of around 450 nm is thought to be excited light emission from Eu. In other words, the wavelength of light emitted when Eu, once excited, returns to the ground state without energy transfer from Eu to Mn, is thought to be around 450 nm. 450 / I max It is believed that the luminous efficiency can be further improved by designing the phosphor so that the value of is small.

[0024] (others) The phosphor of this embodiment is usually in powder form, that is, an aggregate of a plurality of phosphor particles. When the phosphor of this embodiment is in powder form, its particle size distribution is not particularly limited. Considering application to wavelength conversion members, for example, the particle size distribution may be such that 90 mass % or more of the phosphor powder passes through a sieve with a mesh size of 45 μm. Of course, the particle size distribution is not limited to this.

[0025] <Method of manufacturing phosphor> The phosphor of this embodiment is The formula is KAl 11 O 17 a mixing step of mixing a compound represented by the formula: a firing step of firing the mixture; It can be produced by

[0026] The above manufacturing method uses the compound with the composition formula KAl 11 O 17 This can be said to be a manufacturing method in which Eu and Mn are dissolved in a crystal (host crystal) of a compound represented by the formula: Although the details are unknown, it is speculated that by adopting this manufacturing method, Eu and Mn can be more easily incorporated into the crystal structure as intended, and the formation of heterophases can be suppressed. Incidentally, in Non-Patent Document 1, a phosphor is produced by mixing a europium source, a manganese source, Al2O3, and K2CO3 and firing them once. According to the findings of the present inventors, when such a production method is adopted, a large amount of heterogeneous phases may occur, resulting in the above-mentioned half-value width not reaching the desired value, or it may be difficult to dissolve Eu and Mn in the desired amounts.

[0027] For the compound represented by the composition formula KAl 11 O 17 if it is available on the market, it may be used. If it is not available on the market, for example, after calculating the molar ratio of Al2O3 and K2CO3, it can be prepared by procedures such as pulverizing in a mortar, dry blending, and firing at a temperature of 1400 to 1800 °C in an inert atmosphere such as nitrogen gas. The molar ratio of Al2O3 and K2CO3 may be determined according to the reaction formula K2CO3 + 11Al2O3 → 2KAl 11 O 17 + CO2. For details, refer to the examples described later. [[ID=...]]

[0028] KAl obtained on the market 11 O 17 Or KAl obtained as described above 11 O 17 and a europium source and a manganese source are mixed in an appropriate ratio to obtain a mixture, and the mixture is fired to produce a phosphor having a composition represented by KAl m O n :xEu,yMn. Specifically, KAl... 11 O 17 a europium source, and a manganese source are dry blended in an appropriate ratio to form a mixture. The mixture is placed in, for example, a crucible made of boron nitride and fired in an inert atmosphere such as nitrogen gas, preferably at 1350 to 1750 °C. The firing time can be, for example, about 1 to 8 hours. In this way, a phosphor having a composition of KAl m ...<ID=38 O nIt is possible to produce a phosphor represented by the formula: xEu, yMn, which has an emission spectrum when irradiated with light of a wavelength of 340 nm, a maximum between wavelengths of 500 and 520 nm, and a full width at half maximum of 22 to 29 nm.

[0029] The europium source may be an oxide, nitride, halide or hydroxide of europium, with Eu2O3 being preferred. The manganese source may be an oxide, nitride, halide, or carbonate of manganese. The valence of manganese in the manganese oxide may vary, but considering the valence of manganese in the final product, MnO is preferred as the manganese source.

[0030] <Light-emitting device> A light emitting device can be configured by a light emitting element capable of emitting ultraviolet light and a wavelength conversion member containing the above-mentioned phosphor. In the light emitting device, ultraviolet light emitted from the light emitting element strikes the wavelength conversion member, causing the phosphor in the wavelength conversion member to emit light. As described above, the phosphor of this embodiment has an emission spectrum in which a peak with a maximum wavelength is present between 500 and 520 nm when irradiated with light having a wavelength of 340 nm. In other words, a wavelength conversion member containing the phosphor of this embodiment typically emits green light.

[0031] A preferred example of a light-emitting element capable of emitting ultraviolet light is an ultraviolet LED.

[0032] The wavelength conversion member can be composed of the above-mentioned phosphor (usually in powder form) and a sealing material that seals the phosphor. As the encapsulant, for example, various curable resin materials (materials that are cured by heat and / or light) can be used. Any curable resin material can be used as long as it is sufficiently transparent and can provide the optical properties required for displays and lighting devices. Examples of the sealing material include silicone resin materials. Regarding silicone resin materials, curable materials are supplied by companies such as Dow Corning Toray Co., Ltd. and Shin-Etsu Chemical Co., Ltd. Silicone resin materials are preferred from the viewpoints of high transparency and excellent heat resistance. Other examples of the sealing material include epoxy resin materials and urethane resin materials.

[0033] One possible application of the light-emitting device is to a display. Recently, studies have been conducted on self-luminous light emitting devices (displays) that emit the three primary colors of red, green, and blue by irradiating a phosphor with ultraviolet light as excitation light. The phosphor of this embodiment can emit green light when irradiated with ultraviolet light, and is therefore considered to be suitable for use in green pixels in such self-luminous light emitting devices. By using the phosphor of this embodiment, i.e., a phosphor whose emission spectrum when irradiated with light of a wavelength of 340 nm has a peak with a maximum between wavelengths of 500 and 520 nm, and whose full width at half maximum of the peak is 22 to 29 nm, it is believed that it will be possible to manufacture a self-luminous light-emitting device with a wider color gamut than conventional ones.

[0034] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations may be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications and improvements within the scope of achieving the object of the present invention are included in the present invention. [Example]

[0035] The embodiments of the present invention will be described in detail based on Examples and Comparative Examples. However, it should be noted that the present invention is not limited to the Examples.

[0036] <Examples 1 to 4: Production of phosphor> (1st stage: KAl 11 O 17 (Production) Al2O3 (Taimei Chemical Co., Ltd.) and K2CO3 (Kojundo Chemical Co., Ltd.) were prepared. The Al2O3 and K2CO3 were weighed out in a ratio of 89.86 mass % and 10.14 mass % respectively, ground in a mortar, and dry-blended to such an extent that the mixture could pass substantially completely through a nylon sieve with 250 μm openings. Thus, a blend of Al2O3 and K2CO3 was obtained. The blend was placed in a boron nitride crucible and fired under a nitrogen gas atmosphere (N2: 0.85 MPa) at 1800°C for 4 hours. The fired product was then pulverized in a mortar to a size that allowed the powder to pass completely through a nylon sieve with 250 μm openings.

[0037] (Second stage: solid solution of Mn and Eu) KAl produced above 11 O 17 A mixture was prepared by dry-blending 94.49% by mass of ammonium nitrate, 3.56% by mass of Eu2O3 (purchased from Nippon Yttrium Co., Ltd.), and 1.95% by mass of MnO (purchased from Kojundo Chemical Co., Ltd.). This mixture was placed in a boron nitride crucible and fired for 4 hours under a nitrogen gas atmosphere (N2: 0.85 MPa) at the temperature listed in Table 1. The fired product thus obtained was pulverized in a mortar to a size sufficient to pass through a nylon sieve with 250 μm openings. In this way, a phosphor was produced.

[0038] <Comparative Example 1: Production of phosphor> Instead of going through a two-stage process as in Examples 1 to 4, a phosphor was produced in a one-stage process with reference to the description in the aforementioned Non-Patent Document 1. Specifically, a mixture of K2CO3 = 11.9 mass %, Al2O3 = 79.8 mass %, Eu2O3 = 7.5 mass %, and MnCO3 = 0.82 mass % was fired once at 1400°C under the conditions described in Non-Patent Document 1 to produce the phosphor. The raw material MnCO3 was purchased from Kojundo Chemical Co., Ltd. The other raw materials were obtained from the same sources as in Examples 1 to 4.

[0039] <Determining composition (element ratio)> The content of elements in the phosphor was measured by the following procedure. First, the phosphor was dissolved by pressure acid decomposition to prepare a sample solution. Next, the obtained sample solution was quantitatively analyzed for elements using an ICP optical emission spectrometer (Shimadzu Corporation, ICPE-9820). In this analysis, the detection limits for each element were K: 1 ppb or less, Al: 1 to 10 ppb, Mn: 1 ppb or less, and Eu: 1 ppb or less. For O (oxygen), the mass of O was calculated by subtracting the mass of all elements other than O from the total mass of the phosphor (100 parts by mass), and this mass was converted into the amount of substance to determine the value of the subscript n.

[0040] <Measurement and evaluation: Emission spectrum, chromaticity X, chromaticity Y, internal quantum efficiency, and external quantum efficiency> BaSO4 was placed as a reference in the side opening (φ10 mm) of an integrating sphere (φ60 mm). Specifically, BaSO4 (product code 022-00425) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. was filled into the recess of a concave cell, and the cell was placed in the opening of the integrating sphere. Monochromatic light with a wavelength of 340 nm was introduced into the integrating sphere via an optical fiber, and the spectrum of the reflected light was measured using a spectrophotometer (manufactured by Otsuka Electronics Co., Ltd., product name QE-2100). The number of excitation light photons (Qex) was calculated from the spectrum in the wavelength range of 300 to 650 nm.

[0041] Next, a concave cell was filled with the phosphor powder obtained in each example so that the surface was smooth, and the cell was set in the opening of the integrating sphere. Monochromatic light with a wavelength of 340 nm was irradiated, and the reflected and fluorescent excitation spectra were measured using a spectrophotometer.

[0042] Based on the obtained emission spectrum, the full width at half maximum of the peak with a maximum wavelength between 500 and 550 nm was calculated. 450 / I max The value of (I max and I 450 is defined above).

[0043] Based on the obtained emission spectrum, the chromaticity X and chromaticity Y were also calculated. Specifically, the CIE chromaticity coordinate x value (chromaticity X) in the XYZ color system defined in JIS Z8781-3:2016 was calculated in accordance with JIS Z8724:2015 from the spectral data in the wavelength range of 300 to 650 nm of the fluorescence spectrum.

[0044] The number of reflected excitation light photons (Qref) and the number of fluorescent photons (Qem) were calculated from the obtained spectral 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 wavelength range of 300 to 650 nm. From the obtained numbers of the three types of photons, the absorptivity (=(Qex-Qref) / Qex×100), internal quantum efficiency (=Qem / (Qex-Qref)×100), and external quantum efficiency (=Qem / Qex×100) were calculated.

[0045] For reference, the emission spectrum when the phosphor of Example 4 is irradiated with light having a wavelength of 340 nm is shown in FIG. 1, and the emission spectrum when the phosphor of Comparative Example 1 is irradiated with light having a wavelength of 340 nm is shown in FIG.

[0046] The various information is summarized in the table below.

[0047] [Table 1]

[0048] As shown in the table above, the composition is KAl m O n The phosphors of Examples 1 to 4, which are expressed by the formula xEu,yMn, where x / y is 0.5 to 1.5, and in which the full width at half maximum of the peak having a maximum between 500 and 520 nm is 22 to 29 nm in the emission spectrum when irradiated with light of a wavelength of 340 nm, exhibited good internal quantum efficiency and external quantum efficiency. In contrast, the internal quantum efficiency and external quantum efficiency of the phosphor of Comparative Example 1, where x / y is 0.17, which is smaller than 0.5, were poor compared to Examples 1 to 4. The internal quantum efficiency and external quantum efficiency vary considerably depending on the measurement light source and calibration method, making it difficult to make a simple comparison with the internal quantum efficiency and external quantum efficiency values ​​of conventional phosphors. However, at least to the best of the inventor's knowledge, it can be said that the phosphors of Examples 1 to 4 exhibit good internal quantum efficiency and external quantum efficiency.

Claims

1. The composition is KAl ｍ O ｎ : xEu, yMn, m is 8 to 25, n is 16 to 40, x>0, y>0, and x / y is 0.5 to 1.5; A phosphor in which, when irradiated with light having a wavelength of 340 nm, the emission spectrum has a peak having a maximum between wavelengths of 500 and 520 nm, and the full width at half maximum of the peak is 22 to 29 nm.

2. The phosphor according to claim 1 , In the emission spectrum, the peak intensity of the peak is I ｍａｘ and the emission intensity at a wavelength of 450 nm is I ４５０ When I ４５０ / I ｍａｘ A phosphor having a value of 0.1 or less.

3. 3. The phosphor according to claim 1 or 2, A phosphor in which x is 0.05 to 0.

40.

4. 3. The phosphor according to claim 1 or 2, A phosphor in which y is 0.10 to 0.

35.

5. The composition formula is KAl １１ O １７ a mixing step of mixing a compound represented by the formula: a firing step of firing the mixture; A method for producing a phosphor comprising the steps of:

6. 6. A method for producing a phosphor according to claim 5, The method for producing a phosphor, wherein the europium source comprises an oxide, nitride, halide or hydroxide of europium.

7. 7. A method for producing the phosphor according to claim 5 or 6, comprising: The method for producing a phosphor, wherein the manganese source comprises an oxide, nitride, halide or carbonate of manganese.

8. 7. A method for producing the phosphor according to claim 5 or 6, comprising: The method for producing a phosphor, wherein the firing temperature in the firing step is 1350 to 1750°C.

9. a light-emitting element capable of emitting ultraviolet light; A wavelength conversion member containing the phosphor according to claim 1 or 2; A light emitting device comprising:

Images