Phosphor and light-emitting device

Abstract

This phosphor is represented by the general formula Mx (Si, Al) 2 (N, O) 3 + / -y (where M is Li and one or more alkaline earth metal elements, 0.52 < = x < = 0.90, 0 < = y < = 0.36, and 2-5 mol% of M is Ce, and the rate of change in fluorescence intensity before and after heating and cooling measured in accordance with prescribed steps satisfies 3.9% or less.

Description

Technical Field

[0001] The present invention relates to a phosphor and a light-emitting device. Background Art

[0002] In order to manufacture a white LED (Light Emitting Diode), a phosphor is usually used. That is, a phosphor is used as a wavelength conversion material for obtaining white light from blue light emitted from a blue LED.

[0003] With the spread of white LEDs in lighting applications and the research on the application of white LEDs to image display devices, etc., the development of phosphors that can convert blue light into longer-wavelength light has continued.

[0004] As one such phosphor, for example, Patent Document 1 describes the following: A phosphor represented by the general formula M x (Si, Al)2(N, O) 3±y (where M is Li and one or more alkaline earth metal elements, 0.52 ≤ x ≤ 0.9, 0.06 ≤ y ≤ 0.23), and a phosphor in which a part of M is replaced by a Ce element, wherein the Si / Al atomic ratio is 1.5 or more and 6 or less, and the O / N atomic ratio is 0 or more and 0.1 or less, 5 to 50 mol% of M is Li, and 0.5 to 10 mol% of M is Ce.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent No. 5969391 Gazette Summary of the Invention

[0008] However, as a result of the research by the present inventors, it has been found that there is room for improvement in the reduction of the fluorescence characteristics when the phosphor described in Patent Document 1 is used in a high-temperature environment.

[0009] One of the purposes of the present inventors in this research is to provide a phosphor that can suppress the reduction of fluorescence characteristics when used in a high-temperature environment.

[0010] As a result of the research by the present inventors, the following invention has been completed.

[0011] According to one aspect of the present invention, the following phosphor and light-emitting device are provided.

[0012] 1. A phosphor represented by the general formula M x (Si, Al)2(N, O) 3±yA phosphor in which part of M is replaced by a Ce element, where M is Li and one or more alkaline earth metal elements, 0.52 ≤ x ≤ 0.90, 0 ≤ y ≤ 0.36, where

[0013] 2 mol% or more and 5 mol% or less of M is Ce, and the change rate of fluorescence intensity before and after heating and cooling measured according to the following steps is 3.9% or less.

[0014] (Steps)

[0015] Fill the phosphor into a quartz petri dish and place it on a heating and cooling stage for a microscope capable of measuring the excitation light irradiation and the luminescence intensity of the phosphor.

[0016] First, in the atmosphere, after holding at 30 °C for 5 minutes, irradiate with excitation light having a wavelength of 455 nm, and measure the integrated luminescence intensity of the phosphor; then, heat at 100 °C / minute, hold at 300 °C for 10 minutes, measure the luminescence intensity, turn off the heating, cool to 30 °C, hold for 15 minutes, and then measure the luminescence intensity again.

[0017] When the initial integrated luminescence intensity measured at 30 °C before heating and cooling is set to 100%, and the luminescence intensity (%) measured at 30 °C after heating and cooling is set to EI 30 When, the change rate of fluorescence intensity before and after heating and cooling is calculated by the formula (100% - EI 30 ).

[0018] 2. The phosphor according to 1., wherein

[0019] When the luminescence intensity (%) of the phosphor measured at 300 °C after heating and before cooling measured according to the above steps is set as the fluorescence intensity maintenance rate, the fluorescence intensity maintenance rate at 300 °C is 69.0% or more.

[0020] 3. The phosphor according to 1. or 2., wherein

[0021] When measuring the diffuse reflectance spectrum of the phosphor in the wavelength range of 500 - 850 nm, the difference X1 - X2 between the diffuse reflectance X1 of light with respect to a wavelength of 700 nm and the diffuse reflectance X2 of light with respect to the fluorescence peak wavelength when irradiating with excitation light having a wavelength of 455 nm is 3.0% or less.

[0022] 4. The phosphor according to any one of 1. to 3., wherein

[0023] The diffuse reflectance X2 of light with respect to the fluorescence peak wavelength when irradiating with excitation light having a wavelength of 455 nm is 88% or more and 97% or less.

[0024] 5. The phosphor according to any one of 1. to 4., wherein,

[0025] When irradiated with excitation light of 455 nm, the wavelength of the fluorescence peak is 580 nm or more and 610 nm or less.

[0026] 6. The phosphor according to any one of 1. to 5., wherein,

[0027] When irradiated with excitation light of 455 nm, the full width at half maximum of the fluorescence peak is 130 nm or more and 142 nm or less.

[0028] 7. The phosphor according to any one of 1. to 6., wherein,

[0029] The external quantum efficiency with respect to the excitation light of 455 nm is 70% or more.

[0030] 8. The phosphor according to any one of 1. to 7., wherein,

[0031] The internal quantum efficiency with respect to the excitation light of 455 nm is 80% or more.

[0032] 9. A light-emitting device including the phosphor according to any one of 1. to 8. and a light-emitting light source.

[0033] According to the present invention, there is provided a phosphor capable of suppressing a decrease in fluorescence characteristics when used in a high-temperature environment, and a light-emitting device using the same. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 FIG. is a schematic cross-sectional view showing an example of the structure of the light-emitting device. DETAILED DESCRIPTION

[0035] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, in all the drawings, the same reference numerals are assigned to the same components, and the description is appropriately omitted. Also, the drawings are schematic views and do not match the actual dimensional ratios.

[0036] In this specification, the expression "X to Y" in the description of the numerical range means X or more and Y or less, unless otherwise specified. For example, "1 to 5 mass%" means "1 mass% or more and 5 mass% or less".

[0037] <Phosphor>

[0038] Regarding the phosphor of the present embodiment represented by the general formula M x (Si, Al)2(N, O) 3±yThe phosphor represented by the general formula, where M is Li and one or more alkaline earth metal elements, 0.52 ≤ x ≤ 0.90, 0 ≤ y ≤ 0.36, a part of M is replaced by Ce element, and 2 mol% or more and 5 mol% or less of M is Ce.

[0039] Moreover, the phosphor of the present embodiment is configured such that the change rate of fluorescence intensity before and after heating and cooling measured according to the following steps satisfies 3.9% or less.

[0040] (Steps)

[0041] The phosphor is filled into a quartz petri dish and placed on a heating and cooling stage for a microscope capable of measuring the irradiation of excitation light and the luminescence intensity of the phosphor.

[0042] First, in the atmosphere, after maintaining at 30 °C for 5 minutes, excitation light with a wavelength of 455 nm is irradiated, and the integrated luminescence intensity of the phosphor is measured. Then, the temperature is raised at 100 °C / minute, maintained at 300 °C for 10 minutes, the luminescence intensity is measured, the heating is turned off, cooled to 30 °C, maintained for 15 minutes, and then the luminescence intensity is measured again.

[0043] When the initial integrated luminescence intensity measured at 30 °C before heating and cooling is set to 100%, and the luminescence intensity (%) measured at 30 °C after heating and cooling is set to EI 30 the change rate of fluorescence intensity before and after heating and cooling is calculated by the formula (100% - EI 30 ).

[0044] The phosphor of the present embodiment is different from the phosphor described in Patent Document 1 at least in that the change rate of fluorescence intensity before and after heating and cooling is 3.9% or less. The phosphor of the present embodiment is excellent in terms of internal quantum efficiency when used in a high-temperature environment, for example, compared with the phosphor described in Patent Document 1, and thus can efficiently convert blue light into long-wavelength light.

[0045] In recent years, the high-output and thin-type of light-emitting devices have been promoted, and the working environment in light-emitting devices equipped with phosphors has a tendency to become hotter and hotter.

[0046] According to the insight of the present inventor, it has been found that: by annealing the phosphor represented by the general formula M x (Si, Al)2(N, O) 3±y at a temperature lower than the firing temperature in an atmospheric environment containing a reducing gas, the high-temperature fluorescence characteristics of the phosphor (the fluorescence characteristics of the phosphor during heating or after heating and cooling) can be improved, and the reduction of fluorescence characteristics when used in a high-temperature environment simulating the actual process can be suppressed.

[0047] As a result of further in-depth research, it was found that as a high-temperature fluorescence property, by using the change rate of fluorescence intensity before and after the above heating and cooling as an index, the thermal degradation inhibition ability of the fluorescence property can be stably evaluated.

[0048] Based on this finding, it was found that by setting the change rate of fluorescence intensity before and after heating and cooling below the above upper limit value, it is possible to suppress the decrease in fluorescence property when used in a high-temperature environment, thus completing the present invention.

[0049] The phosphor of the present embodiment can be manufactured by selecting an appropriate manufacturing method / manufacturing conditions in addition to using an appropriate material. As the "appropriate manufacturing method / manufacturing conditions", for example, annealing treatment is performed on the phosphor. Details of the manufacturing method / manufacturing conditions will be described in detail later.

[0050] The phosphor of the present embodiment will be further described.

[0051] (Crystal structure, chemical composition, etc.)

[0052] The framework structure of the phosphor crystal of the present embodiment is composed of (Si, Al)-(N, O)4 tetrahedral bonds, and the M element is located in the interstitial space. The composition of the above general formula holds within a wide range in which the overall parameters of the valence number and amount of the M element, the Si / Al ratio, and the N / O ratio maintain electrical neutrality. As a typical phosphor represented by the above general formula, when the M element is Ca and x = 1, and further Si / Al = 1 and O / N = 0, it is CaAlSiN3. When a part of Ca in CaAlSiN3 is replaced by Eu, it becomes a red phosphor, and when it is replaced by Ce, it becomes a yellow-orange phosphor.

[0053] The crystal structure of the phosphor of the present embodiment is usually a structure based on the CaAlSiN3 crystal. One of the characteristics of this phosphor is that the constituent elements and composition are greatly changed so as to obtain very high luminous efficiency even under Ce activation.

[0054] In the above general formula, the M element is a combination of a Li element and an alkaline earth metal element, and a part of it is replaced by a Ce element that becomes a luminescence center. By using the Li element and through the combination with a divalent alkaline earth element and a trivalent Ce element, the average valence number of the M element can be widely controlled. And Li + has a very small ionic radius, and can greatly change the crystal size according to its amount, thereby obtaining various fluorescence emissions.

[0055] The coefficient x of the M element in the above general formula is 0.52 or more and 0.90 or less, preferably 0.60 or more and 0.90 or less, more preferably 0.70 or more and 0.90 or less. If the coefficient x exceeds 0.90, that is, approaches the CaAlSiN3 crystal, the fluorescence intensity tends to decrease. If the coefficient x is less than 0.52, the fluorescence intensity tends to decrease significantly because a large amount of heterogeneous phases other than the target crystal phase are generated.

[0056] The coefficient y of (N, O) in the above general formula is preferably 0 or more and 0.36 or less, more preferably 0 or more and 0.30 or less, and further preferably 0 or more and 0.23 or less. Thereby, the fluorescence intensity can be improved.

[0057] In the present embodiment, the O / N atomic ratio (molar ratio) is 0 or more and 0.1 or less, preferably 0.01 or more and 0.08 or less, and further preferably 0.02 or more and 0.07 or less. If the O / N atomic ratio is too large, the amount of heterogeneous phase generated increases, the luminous efficiency decreases, and the covalent bond property of the crystal decreases, tending to cause deterioration of the temperature characteristics (decrease in brightness at high temperature).

[0058] Regarding the Si / Al atomic ratio (molar ratio), generally, if the average valence number, amount of the M element, and O / N atomic ratio are set within a specified range, it can be determined inevitably. The Si / Al atomic ratio is 1.5 or more and 6 or less, preferably 2 or more and 4 or less, and more preferably 2.5 or more and 4 or less.

[0059] The Li content in the phosphor is 5 to 50 mol% of the M element, preferably 15 to 49 mol%, and further preferably 25 to 48 mol%. The effect of Li is easily exerted at 5 mol% or more, but if it exceeds 50 mol%, the crystal structure of the target phosphor cannot be maintained and heterogeneous phases are generated, and the luminous efficiency tends to decrease.

[0060] For the sake of caution, it is stated in advance that the "Li content" refers to the Li content in the finally obtained phosphor, rather than the amount based on the raw material formulation. The Li compound used in the raw materials has a high vapor pressure and is easily volatile, and a considerable amount volatilizes when synthesizing nitrides / nitroxides at high temperature. That is, the amount of Li based on the raw material formulation deviates significantly from the content in the final product, so it does not represent the Li content in the phosphor.

[0061] If the content of Ce as the luminescence center of the phosphor is too small, the contribution to luminescence tends to become small. If it is too large, there is a tendency for concentration quenching of the phosphor caused by energy transfer between Ce 3+ Therefore, the content of Ce is 2 to 5 mol% of the M element, preferably 2.5 to 5 mol%.

[0062] The alkaline earth metal element used as the M element in the above general formula can be any element. However, when Ca is used, high fluorescence intensity can be obtained, and the crystal structure is stabilized within a wide range of compositions. Therefore, the M element is preferably Ca. It can be a combination of multiple alkaline earth metal elements. For example, a part of the Ca element can be replaced by the Sr element.

[0063] The crystal structure of the phosphor is orthorhombic and can be the same as the aforementioned CaAlSiN3 crystal. As an example, the lattice constants of the CaAlSiN3 crystal are a = 0.98007 nm, b = 0.56497 nm, and c = 0.50627 nm. In the present embodiment, the lattice constants are generally a = 0.93500 - 0.96500 nm, b = 0.55000 - 0.57000 nm, and c = 0.48000 - 0.50000 nm, which are all smaller values compared to the CaAlSiN3 crystal. This range of lattice constants reflects the aforementioned constituent elements and composition.

[0064] The crystal phase present in the phosphor is preferably the above single crystal phase. However, as long as there is no significant impact on the fluorescence characteristics, the phosphor may contain a heterogeneous phase. Examples of heterogeneous phases with low impact on fluorescence characteristics under blue light excitation include α-sialon, AlN, LiSi2N3, LiAlSi2N4, etc. The amount of the heterogeneous phase is preferably such that the diffraction line intensity of other crystal phases evaluated by powder X-ray diffraction is 40% or less relative to the strongest diffraction line intensity of the above crystal phase.

[0065] The phosphor of the present embodiment is excited by light in a wide wavelength region from ultraviolet to visible light. For example, when irradiated with blue light having a wavelength of 455 nm, it sometimes exhibits broad fluorescence emission with an orange peak wavelength of 580 - 610 nm and a half-width at half-maximum of the fluorescence spectrum of 130 - 142 nm.

[0066] Such a phosphor is suitable as a phosphor for a wide range of light-emitting devices. Moreover, similar to conventional nitride / nitroxide-based phosphors represented by CaAlSiN3, the phosphor of the present embodiment has excellent heat resistance, chemical stability, and small brightness reduction due to temperature rise. Such characteristics are particularly suitable for applications requiring durability.

[0067] (High-temperature fluorescence characteristics)

[0068] As described above, the rate of change in fluorescence intensity before and after heating and cooling of the phosphor powder of this embodiment is 3.9% or less, preferably 0.1% or more and 3.5% or less, and more preferably 0.1% or more and 3.0% or less. | Thereby, a decrease in fluorescence characteristics (for example, internal quantum efficiency) when used in a high-temperature environment can be suppressed. Moreover, while increasing the Ce concentration in the phosphor, the external quantum efficiency can be improved.

[0069] From another perspective, the fluorescence intensity retention rate of the phosphor of this embodiment at 300 °C relative to the value at 30 °C is preferably 69.0% or more, more preferably 69.5% or more and 95% or less, and particularly preferably 70.0% or more and 85% or less. Thereby, a decrease in fluorescence characteristics when used in a high-temperature environment can be suppressed.

[0070] The fluorescence intensity retention rate at 300 °C is defined as the luminescence intensity (%) of the phosphor measured at 300 °C after heating and before cooling as measured by the above-described procedure. The fluorescence intensity retention rate at 300 °C can also be used as an index of high-temperature fluorescence characteristics.

[0071] (Diffuse reflectance)

[0072] From another perspective, the diffuse reflectance X1 of the phosphor of this embodiment with respect to light of wavelength 700 nm is preferably 89% or more and 98% or less, more preferably 91% or more and 98% or less, and particularly preferably 92% or more and 98% or less. By making X1 within this numerical range, there is a tendency for the luminescence intensity to further increase.

[0073] Moreover, from another perspective, the diffuse reflectance X2 of the phosphor of this embodiment with respect to light at the fluorescence peak wavelength is preferably 88% or more and 97% or less, more preferably 90% or more and 97% or less, and particularly preferably 91% or more and 97% or less. By making X2 within this numerical range, there is a tendency for the luminescence intensity to further increase.

[0074] Moreover, from another perspective, the difference between X2 and X1 (X2 - X1) is preferably 3.0% or less, further preferably 2.0% or less, and particularly preferably 0.1% or more and 1.8% or less. Thereby, the characteristics of the phosphor are further improved.

[0075] Moreover, from another perspective, when the diffuse reflectance with respect to light of wavelength 800 nm is X3, the difference between X3 and X1 (X3 - X1) is preferably 0.1% or more and 1.4%, further preferably 0.1% or more and 1.0% or less, and particularly preferably 0.1% or more and 0.8% or less. Thereby, the characteristics of the phosphor are further improved.

[0076] (Particle size distribution)

[0077] By appropriately designing the particle size distribution of the particles (phosphor particles) contained in the phosphor of the present embodiment, it is sometimes possible to further improve the quantum efficiency or improve the balance of various properties.

[0078] Specifically, the volume-based cumulative 50% diameter D50 (so-called median particle size) of the phosphor of the present embodiment measured by the laser diffraction scattering method is preferably 8 μm or more and 25 μm or less, more preferably 10 μm or more and 20 μm or less, and still more preferably 12 μm or more and 20 μm or less.

[0079] From another point of view, the volume-based cumulative 10% diameter D of the phosphor of the present embodiment measured by the laser diffraction scattering method 10 is preferably 2 μm or more and 15 μm or less, more preferably 5 μm or more and 12 μm or less. D 10 The case where D is a relatively large value corresponds to the case where the amount of fine powder (fine phosphor particles that tend to reduce the conversion efficiency of blue light) in the phosphor is relatively small. Therefore, since D 10 is a relatively large value to a certain extent, there is a tendency for the conversion efficiency of blue light to be further improved.

[0080] Moreover, from another point of view, the volume-based cumulative 90% diameter D of the phosphor of the present embodiment measured by the laser diffraction scattering method 90 is preferably 15 μm or more and 50 μm or less, more preferably 18 μm or more and 40 μm or less. D 90 The case where D is not too large corresponds to the case where the amount of coarse particles in the phosphor is small. D 90 A phosphor with D not being too large is effective in reducing the chromaticity deviation of the light-emitting device.

[0081] (Absorbance)

[0082] From another point of view, the absorbance A of the phosphor of the present embodiment at a wavelength of 700 nm 700 is preferably 1% or more and 10% or less, more preferably 2% or more and 9% or less, and particularly preferably 3% or more and 9% or less. Thereby, the internal quantum efficiency is improved.

[0083] Moreover, from another point of view, the absorbance A of the phosphor of the present embodiment at a wavelength of 600 nm 600 is preferably 1% or more and 13% or less, more preferably 2% or more and 12% or less, and still more preferably 3% or more and 11% or less. It is considered that by making A 600 not too large, the fluorescence characteristics are further improved.

[0084] As another aspect, the value of the internal quantum efficiency of the phosphor of the present embodiment with respect to the excitation light of 455 nm is preferably 80% or more.

[0085] Moreover, as another aspect, the value of the external quantum efficiency of the phosphor of the present embodiment with respect to the excitation light of 455 nm is preferably 70% or more.

[0086] (Manufacturing method)

[0087] The phosphor of the present embodiment can be manufactured, for example, by a series of steps including the following (1) to (4). From the viewpoint of appropriately adjusting the high-temperature fluorescence characteristics of the phosphor, the manufacturing process of the phosphor preferably includes a (4) annealing treatment step.

[0088] (1) Preparation step of raw material mixed powder

[0089] (2) Firing step

[0090] (3) Crushing step of fired product

[0091] (4) Annealing treatment step

[0092] Hereinafter, (1) to (4) will be specifically described.

[0093] (1) Preparation step of raw material mixed powder

[0094] In the preparation step of the raw material mixed powder, appropriate raw material powders are usually mixed to obtain the raw material mixed powder.

[0095] As the raw material powder, nitrides of constituent elements, namely, silicon nitride, aluminum nitride, lithium nitride, cerium nitride, nitrides of alkaline earth elements (such as calcium nitride), etc. are preferably used. Generally, nitride powders are unstable in air and the particle surfaces are covered with an oxide layer. Even when nitride raw materials are used, as a result, the raw materials will still contain a certain amount of oxides to some extent. In the case of controlling the O / N ratio of the phosphor, considering these, and in the case of oxygen deficiency, a part of the nitride can be made into an oxide (including a compound that becomes an oxide by heat treatment). Examples of the oxide include cerium oxide.

[0096] In the raw material powder, the volatilization of the lithium compound based on heating is significant, and sometimes almost all of it volatilizes depending on the firing conditions. Therefore, the compounding amount of the lithium compound is preferably determined according to the firing conditions and considering the volatilization amount during the firing process.

[0097] Among the nitride raw material powders, lithium nitride, cerium nitride, and nitrides of alkaline earth elements react violently with moisture in the air. Therefore, these treatments are preferably carried out in a glove box replaced with an inert environment.

[0098] From the perspective of operational efficiency, it is preferred that (i) a specified amount of raw material powders of silicon nitride, aluminum nitride and various oxides that can be handled in air are first weighed and fully mixed in air to prepare a preliminary mixed powder, and (ii) the preliminary mixed powder is then mixed with a substance that is easily reactive with water, such as lithium nitride, in a glove box to prepare a raw material mixed powder.

[0099] (2) Firing process

[0100] In the firing step, the raw material mixed powder prepared in the step (1) of preparing the raw material mixed powder is filled in an appropriate container and heated using a firing furnace or the like.

[0101] The calcination temperature is preferably 1600 to 2000°C, more preferably 1700 to 1900°C, from the viewpoint of sufficient reaction and suppression of volatilization of lithium.

[0102] From the viewpoint of sufficient reaction and suppression of lithium volatilization, the calcination time is preferably 2 to 24 hours, more preferably 4 to 16 hours.

[0103] The firing process is preferably carried out in a nitrogen environment. Furthermore, it is preferred to appropriately adjust the pressure of the firing environment. Specifically, the pressure of the firing environment is preferably above 0.5 MPa·G. When the firing temperature is particularly above 1800°C, the phosphor tends to decompose easily, but the high pressure of the firing environment can suppress the decomposition of the phosphor.

[0104] Incidentally, in consideration of industrial productivity, the pressure of the firing environment is preferably less than 1 MPa·G.

[0105] The container filled with the raw material mixed powder is preferably stable in a high temperature nitrogen environment and is made of a material that does not react with the raw material mixed powder or its reaction product. The material of the container is preferably boron nitride.

[0106] (3) Pulverization process of the burned product

[0107] The burned product obtained in (2) is usually in a block form, and therefore it is preferably pulverized into a certain small size by mechanically applying force.

[0108] In the pulverization, various devices such as a crusher, a mortar, a ball mill, a vibration mill, a jet mill, and an impact mill can be used. It is also possible to combine two or more of these devices for pulverization. In the embodiments described below, a coarse pulverization of the calcined product is first obtained using an impact mill, and then further pulverized using a jet mill. Although the details are not yet clear, by performing such pulverization, it is easy to obtain a phosphor with a diffuse reflectance X1 of 88% or more and 99.9% or less.

[0109] (4) Annealing

[0110] In the annealing treatment, a predetermined amount of phosphor is filled in a crucible, and the phosphor is heated at a predetermined temperature for a predetermined time in a firing furnace in a reducing gas atmosphere containing hydrogen gas.

[0111] Specifically, the annealing temperature is lower than the above-mentioned firing temperature, preferably about 700 to 1200 °C. The annealing time is appropriately set according to the annealing temperature.

[0112] The environment during annealing is reducing. For example, it is preferably to contain about 4% by volume of hydrogen gas (reducing gas) in nitrogen gas (inert gas).

[0113] It is preferable to use an open crucible and the filling amount of the phosphor in the crucible is small. In the annealing treatment, the reducing gas atmosphere can be brought into sufficient contact with the surface of the phosphor.

[0114] It is preferable to use a dense ceramic crucible. It is possible to suppress the reaction between the components contained in the furnace and the crucible and prevent an unexpected change in the atmosphere environment.

[0115] Although the detailed mechanism is not clear, it is considered that in a reducing gas atmosphere, at a relatively low temperature, by annealing treatment such as heating the phosphor in an open system, the surface of the phosphor can be appropriately modified.

[0116] <Light-emitting device, image display device, and lighting device>

[0117] By combining the phosphor of the present embodiment and a light-emitting light source, a light-emitting device can be obtained.

[0118] The light-emitting light source typically emits ultraviolet light or visible light. For example, when the light-emitting light source is a blue LED, the blue light emitted from the light-emitting light source irradiates the phosphor, and then the blue light is converted into longer-wavelength light. That is, the phosphor of the present embodiment can be used as a wavelength-converting material for converting blue light into longer-wavelength light.

[0119] Reference Figure 1 , an example of the specific structure of the light-emitting device will be described.

[0120] Figure 1 is a schematic cross-sectional view showing an example of the structure of the light-emitting device. As Figure 1 shown, the light-emitting device 100 includes a light-emitting element 120 (light-emitting light source), a heat sink 130, a housing 140, a first lead frame 150, a second lead frame 160, bonding wires 170, bonding wires 172, and a composite body 40.

[0121] The light-emitting element 120 is a semiconductor element that emits excitation light. Either a light-emitting diode (LED) or a light-emitting element (LD) having a resonator can be used as the semiconductor element. As the light-emitting element 120, for example, an LED chip that generates light having a wavelength of 300 nm or more and 500 nm or less, which corresponds to near-ultraviolet to blue light, can be used.

[0122] The light-emitting element 120 is mounted on a predetermined area on the upper surface of the heat sink 130. By mounting the light-emitting element 120 on the heat sink 130, the heat dissipation performance of the light-emitting element 120 can be improved. Alternatively, a packaging substrate can be used instead of the heat sink 130.

[0123] One electrode (not shown) disposed on the upper surface side of the light-emitting element 120 is connected to the surface of the first lead frame 150 via a bonding wire 170 such as a gold wire. And another electrode (not shown) formed on the upper surface of the light-emitting element 120 is connected to the surface of the second lead frame 160 via a bonding wire 172 such as a gold wire.

[0124] In the housing 140, a recess having a substantially funnel shape whose aperture gradually expands from the bottom surface upward is formed. The light-emitting element 120 is disposed on the bottom surface of the recess. The wall surface of the recess surrounding the light-emitting element 120 functions as a reflector.

[0125] The composite body 40 is filled in the recess formed by the housing 140 with the wall surface. The composite body 40 is a wavelength conversion member that converts the excitation light emitted from the light-emitting element 120 into light having a longer wavelength.

[0126] The composite body 40 has at least the phosphor of the present embodiment dispersed in a sealing material 30 such as resin. In order to obtain white light of higher quality, the sealing material 30 may contain not only the phosphor of the present embodiment but also other phosphors.

[0127] The light-emitting device 100 emits a mixed color of the light of the light-emitting element 120 and the light emitted from the phosphor particles 1 excited by absorbing the light emitted from the light-emitting element 120. The light-emitting device 100 preferably emits white light by mixing the light of the light-emitting element 120 and the light generated from the phosphor particles 1.

[0128] Incidentally, in Figure 1 , a surface-mount type light-emitting device is illustrated, but the light-emitting device is not limited to the surface-mount type, and may also be a cartridge type, a COB (chip on board) type, or a CSP (chip scale package) type.

[0129] As the use of the light emitting device, an image display device such as a display or a lighting device can be cited. For example, the light emitting device 100 can be used as a backlight to manufacture a liquid crystal display. In addition, by using one or more light emitting devices 100 and implementing appropriate wiring, etc., a lighting device can also be manufactured.

[0130] The embodiments of the present invention are described above, but these are examples of the present invention, and various structures other than the above can also be adopted. In addition, the present invention is not limited to the above embodiments, and modifications and improvements within the scope of achieving the purpose of the present invention are included in the present invention.

[0131] Example

[0132] Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited at all to the descriptions of these Examples.

[0133] <Manufacturing of phosphor powder>

[0134] (Comparative Example 1 and Comparative Example 4)

[0135] (1) Preparation of raw material mixed powder

[0136] First, pre-mixing was performed. Specifically, Si3N4 (manufactured by Ube Industries, Ltd., E10 grade), AlN (manufactured by Tokuyama Corporation, E grade) and CeO2 (manufactured by Shin-Etsu Chemical Co., Ltd., C grade) in the raw materials listed in Table 1 were mixed for 30 minutes (dry mixing) using a small V-type mixer, and then sieved with a nylon sieve with a mesh size of 150 μm. Thus, a pre-mixed powder was obtained.

[0137] Next, in a glove box in a nitrogen atmosphere, the remaining portion of the raw materials listed in Table 1 (Ca3N2 (Ca3N2 manufactured by Taiheiyo Cement Corporation) and Li3N (Li3N manufactured by Materion)) was added to the pre-mixed powder, fully dry-mixed, and then sieved with a sieve with a mesh of 500 μm. Thus, a raw material mixed powder was obtained.

[0138] (2) Firing

[0139] The raw material mixed powder was filled into a container made of boron nitride, and the container was placed in a furnace, and the raw material mixed powder was sintered at 1800° C. for 8 hours in a 0.72 MPa·G N 2 environment.

[0140] (3) Crushing of burned material

[0141] The fired product obtained in (2) was pulverized using an impact mill. The pulverization using the impact mill was repeated until the passing rate through a vibrating sieve with a mesh size of 250 μm exceeded 90%.

[0142] The fired product pulverized using the impact mill was further pulverized using a jet mill (manufactured by Nippon Pneumatic Mfg. Co., Ltd., model: PJM-80SP). The pulverization conditions were set as follows: sample supply rate: 50 g / minute, pulverization air pressure: 0.3 MPa.

[0143] Through the above steps, a phosphor powder was obtained.

[0144] (Examples 1, 2 and Comparative Example 2)

[0145] The phosphor powder obtained in Comparative Example 1 was subjected to an annealing treatment under the conditions described in Table 1 to obtain a phosphor powder.

[0146] Regarding this annealing treatment, according to the conditions described in Table 1, a specified amount of the phosphor powder was filled into an alumina crucible (without a lid), and in the specified environment described in Table 1, at a specified maximum temperature (where the temperature was raised from room temperature to the maximum temperature at a heating rate of 3 °C / minute), the phosphor powder filled in the crucible was heated for a specified time. After heating, it was cooled from the maximum temperature to 500 °C at a rate of about 1.3 °C / minute, and then cooled from 500 °C to 300 °C at a rate of about 1.1 °C / minute. After 300 °C, it was cooled in the furnace.

[0147] In addition, compared with Example 1, in the annealing treatment of Example 2, the sample amount was increased and the heating temperature was set higher. In the annealing treatment of Comparative Example 2, an environment filled with N2 gas without containing H2 gas was used. In Examples 1 to 3, a mixed gas in which a specified amount of H2 gas was mixed with N2 gas was introduced through atmospheric pressure flow and filled into the environment.

[0148] (Example 3)

[0149] The phosphor powder obtained in Comparative Example 4 was subjected to an annealing treatment under the conditions described in Table 1 to obtain a phosphor powder.

[0150] (Comparative Example 3)

[0151] The β-sialon phosphor powder (manufactured by DENKA COMPANY LIMITED, grade name: GR-MW540K8SD) was subjected to an annealing treatment under the conditions described in Table 1 to obtain a β-sialon phosphor powder (after annealing treatment).

[0152] <Confirmation of Chemical Composition / Crystal Structure>

[0153] Regarding some phosphor powders, the composition was analyzed as follows.

[0154] Amounts of Ca, Li, Ce, Si, and Al: The phosphor powder was dissolved by the alkali fusion method and then measured by an ICP emission spectroscopic analyzer (5110 VDV manufactured by Agilent).

[0155] Amounts of O and N: Measured using an oxygen and nitrogen analyzer (EMGA-920 manufactured by HORIBA).

[0156] Based on the measurement results, the general formula M x (Si, Al)2(N, O) 3±y was used to calculate x, y, the Si / Al atomic ratio, the O / N atomic ratio, the Li ratio of M, and the Ce ratio of M.

[0157] For the phosphors of Examples 1 to 3, powder X-ray diffraction (XRD) measurements based on Cu-Kα rays were performed using an X-ray diffractometer (UltimaIV-N manufactured by Rigaku Corporation). From the analysis of the obtained XRD patterns, it was confirmed that the main phase of the crystal with lattice constants a = 0.9486 nm, b = 0.5586 nm, and c = 0.4933 nm exists in the orthorhombic system.

[0158] <Measurement of Diffuse Reflectance>

[0159] Regarding the diffuse reflectance, measurement was performed using a device equipped with an integrating sphere unit (ISV-469) on an ultraviolet-visible spectrophotometer (V-550 manufactured by JASCO Corporation). During the measurement, baseline correction was performed using a standard reflector (Spectralon).

[0160] A solid sample holder filled with the phosphor powder was installed at a specified position inside the device, and the diffuse reflectance spectrum was measured in the wavelength range of 500 to 850 nm. The diffuse reflectance with respect to the light at wavelengths of 600 nm, 700 nm, 800 nm, and the light at the fluorescence peak wavelength of the phosphor powder (described later) was calculated.

[0161] <Measurement of Particle Size Distribution>

[0162] Regarding the particle size distribution, measurement was performed using LS13 320 (manufactured by Beckman Coulter, Inc.) by the laser diffraction scattering method in accordance with JIS R 1629:1997. Water was used as the measurement solvent.

[0163] As a specific step, first, a small amount of phosphor powder was put into an aqueous solution containing 0.05% by mass of sodium hexametaphosphate as a dispersant. Then, a dispersion was prepared by performing a dispersion treatment using a horn-type ultrasonic homogenizer (output 300 W, horn diameter 26 mm). An appropriate amount of this dispersion was added to a measurement solvent to measure the particle size distribution. From the obtained cumulative volume frequency distribution curve, the 10% volume diameter (D 10 ), 50% volume diameter (D 50 ), and 90% volume diameter (D 90 ) were determined.

[0164] <Measurement of Fluorescence Spectrum>

[0165] Using a spectrofluorometer (F-7000, manufactured by Hitachi High-Tech Science Corporation) calibrated with rhodamine B and a secondary standard light source, the fluorescence spectrum of the phosphor powder was measured. Specifically, the spectrum of the fluorescence emitted by exciting the phosphor powder with monochromatic light of wavelength 455 nm was measured, and the fluorescence peak wavelength (nm) and the full width at half maximum of the fluorescence peak (nm) were determined.

[0166] <Measurement of Internal Quantum Efficiency and External Quantum Efficiency>

[0167] Using a spectrophotometer (MCPD-7000, manufactured by Otsuka Electronics Co., Ltd.), the internal quantum efficiency and external quantum efficiency of each phosphor powder were obtained according to the following steps.

[0168] (1) The phosphor powder was filled into the recessed part of the concave groove in a manner such that the surface was smooth. This concave groove was installed at a specified position (sample part) inside the integrating sphere. Monochromatic light with a wavelength of 455 nm, which was spectrally separated from a light-emitting source (Xe lamp), was introduced into this integrating sphere using an optical fiber. This monochromatic light (excitation light) was irradiated onto the phosphor powder filled in the recessed part of the concave groove, and the fluorescence spectrum was measured. From the obtained spectral data, the number of excitation reflected light photons (Qref) and the number of fluorescence photons (Qem) were calculated. The number of excitation reflected light photons was calculated in the wavelength range of 450 nm or more and 465 nm or less, and the number of fluorescence photons was calculated in the range of 465 nm or more and 800 nm or less.

[0169] (2) Further, a standard reflector with a reflectivity of 99% (Spectralon manufactured by Labsphere Inc.) was installed in the sample section instead of the concave groove, and the spectrum of the excitation light with a wavelength of 455 nm was measured. Then, the number of excitation light photons (Qex) was calculated based on the spectrum in the wavelength range of 450 nm or more and 465 nm or less.

[0170] (3) Based on Qref, Qem, and Qex obtained from the above (1) and (2), the internal quantum efficiency and external quantum efficiency were calculated based on the following formula.

[0171] Internal quantum efficiency = (Qem / (Qex - Qref)) × 100

[0172] External quantum efficiency = (Qem / Qex) × 100

[0173] <Measurement of high-temperature fluorescence characteristics>

[0174] The obtained phosphor powder was filled in a quartz petri dish and placed on a cooling and heating stage for microscopy installed in a dark box capable of measuring the irradiation of excitation light and the luminescence intensity of the phosphor powder. The excitation light was irradiated from above using an optical fiber, and the luminescence spectrum at a position 45° with respect to the excitation light was measured using a spectrophotometer (MCPD-7000) through the optical fiber.

[0175] In the atmosphere, after maintaining at 30 °C for 5 minutes, excitation light with a wavelength of 455 nm was irradiated, and the integrated luminescence intensity (wavelength range 465 - 800 nm) of the phosphor powder was measured. Then, the temperature was increased at a rate of 100 °C / minute, maintained at 300 °C for 10 minutes, the luminescence intensity was measured, the heating was turned off, cooled to 30 °C, and after maintaining for 15 minutes, the luminescence intensity was measured again.

[0176] When the initial integrated luminescence intensity measured at 30 °C before heating and cooling was set to 100%, and the luminescence intensity (%) measured at 30 °C after heating and cooling was set to EI 30 at that time, the change rate of fluorescence intensity before and after heating and cooling was calculated by the formula (100% - EI 30 ).

[0177] And, the luminescence intensity (%) of the phosphor powder measured at 300 °C after heating and before cooling was set as the fluorescence intensity maintenance rate at 300 °C.

[0178] <Measurement of absorbance at a wavelength of 600 nm>

[0179] Using a spectrophotometer equipped with an integrating sphere (MCPD-7000 manufactured by Otsuka Electronics Co., Ltd.), the absorbance of each phosphor powder at a wavelength of 600 nm was determined according to the following steps.

[0180] (1) A standard reflector with a reflectance of 99% (Spectralon manufactured by Labsphere) was installed at a specified position (sample section) inside the integrating sphere, and monochromatic light with a wavelength of 600 nm spectrally separated from the light-emitting source (Xe lamp) was irradiated onto the standard reflector. Then, the number of photons of the excitation light (Qex) was calculated in the wavelength range of 595 - 610 nm.

[0181] (2) The standard reflector was replaced with the test sample, and otherwise, the number of photons of the excitation-reflected light of the sample (Qref) was calculated in the same manner as in (1). As the test sample, a sample in which the phosphor powder was filled into the recessed portion of the concave groove so that the surface became smooth was used.

[0182] (3) The absorbance A at a wavelength of 600 nm was calculated by the formula (Qex - Qref) / Qex 600 .

[0183] <Measurement of Absorbance at Wavelength 700 nm>

[0184] Using a spectrophotometer equipped with an integrating sphere (MCPD-7000 manufactured by Otsuka Electronics Co., Ltd.), the absorbance of each phosphor powder at a wavelength of 700 nm was determined according to the following steps.

[0185] (1) A standard reflector with a reflectance of 99% (Spectralon manufactured by Labsphere) was installed at a specified position (sample section) inside the integrating sphere, and monochromatic light with a wavelength of 700 nm spectrally separated from the light-emitting source (Xe lamp) was irradiated onto the standard reflector. Then, the number of photons of the excitation light (Qex) was calculated in the wavelength range of 695 - 710 nm.

[0186] (2) The standard reflector was replaced with the test sample, and otherwise, the number of photons of the excitation-reflected light of the sample (Qref) was calculated in the same manner as in (1). As the test sample, a sample in which the phosphor powder was filled into the recessed portion of the concave groove so that the surface became smooth was used.

[0187] (3) The absorbance A at a wavelength of 700 nm was calculated by the formula (Qex - Qref) / Qex 700 .

[0188] <Heating Test>

[0189] Regarding the obtained phosphor powder, after heating at 200 °C for 300 h (accelerated test), the internal quantum efficiency and the diffuse reflectance at a wavelength of 600 nm were measured according to the above <Measurement of internal quantum efficiency and external quantum efficiency> and the above <Measurement of diffuse reflectance>, respectively.

[0190] Various information was summarized in Table 1.

[0191] [Table 1]

[0192]

[0193] As shown in Table 1, the phosphors represented by the general formula M x (Si, Al)2(N, O) 3±y in Examples 1 to 3 showed excellent results in the luminescence characteristics (internal quantum efficiency) after the heating test (accelerated test) compared to Comparative Examples 1, 2, and 4.

[0194] In addition, when the phosphor of β-sialon in Comparative Example 3 was subjected to the same annealing treatment as in Example 1, the internal quantum efficiency or the diffuse reflectance at 600 nm showed a significant decrease compared to before the annealing treatment.

[0195] This application claims the priority based on Japanese Patent Application No. 2022-181259 filed on November 11, 2022, the entire disclosure of which is incorporated herein by reference.

[0196] Symbol Explanation

[0197] 1 Phosphor particle

[0198] 30 Sealing material

[0199] 40 Composite

[0200] 100 Light-emitting device

[0201] 120 Light-emitting element

[0202] 130 Heat sink

[0203] 140 Housing

[0204] 150 First lead frame

[0205] 160 Second lead frame

[0206] 170 Bonding wire

[0207] 172 Bonding wire

Claims

1. A phosphor represented by the general formula M x (Si, Al)2(N, O) 3±y and having a part of M substituted with Ce element, wherein, M is Li and one or more alkaline earth metal elements, 0.52 ≤ x ≤ 0.90, 0 ≤ y ≤ 0.36, wherein, more than 2 mol% and less than 5 mol% of M is Ce, and the change rate of fluorescence intensity before and after heating and cooling measured according to the following steps is 3.9% or less. Steps: Fill the phosphor into a quartz petri dish and place it on a heating and cooling stage for a microscope capable of measuring the excitation light irradiation and the luminescence intensity of the phosphor. First, in the atmosphere, after maintaining at 30 °C for 5 minutes, irradiate the excitation light with a wavelength of 455 nm and measure the integrated luminescence intensity of the phosphor; then, heat up at 100 °C / minute, maintain at 300 °C for 10 minutes, measure the luminescence intensity, turn off the heating, cool to 30 °C, maintain for 15 minutes, and then measure the luminescence intensity again. When the initial integrated luminescence intensity measured at 30°C before heating and cooling is set to 100%, and the luminescence intensity (%) measured at 30°C after heating and cooling is set to EI 30 ), the change rate of fluorescence intensity before and after heating and cooling is calculated by the formula (100% - EI 30 ).

2. The phosphor according to claim 1, wherein, When the luminescence intensity (%) of the phosphor measured at 300 °C after heating and before cooling measured according to the above steps is set as the fluorescence intensity maintenance rate, the fluorescence intensity maintenance rate at 300 °C is 69.0% or more.

3. The phosphor according to claim 1 or 2, wherein, When measuring the diffuse reflectance spectrum of the phosphor in the wavelength range of 500 - 850 nm, the difference X1 - X2 between the diffuse reflectance X1 of the light with respect to the wavelength of 700 nm and the diffuse reflectance X2 of the light with respect to the fluorescence peak wavelength when irradiating the excitation light of 455 nm is 3.0% or less.

4. The phosphor according to claim 1 or 2, wherein, The diffuse reflectance X2 of the light with respect to the fluorescence peak wavelength when irradiating the excitation light of 455 nm is 88% or more and 97% or less.

5. The phosphor according to claim 1 or 2, wherein, The wavelength of the fluorescence peak when irradiating the excitation light of 455 nm is 580 nm or more and 610 nm or less.

6. The phosphor according to claim 1 or 2, wherein, The full width at half maximum of the fluorescence peak when irradiating the excitation light of 455 nm is 130 nm or more and 142 nm or less.

7. The phosphor according to claim 1 or 2, wherein, The external quantum efficiency with respect to the excitation light of 455 nm is 70% or more.

8. The phosphor according to claim 1 or 2, wherein, The internal quantum efficiency with respect to the excitation light of 455 nm is 80% or more.

9. A light-emitting device comprising the phosphor according to claim 1 or 2 and a light-emitting light source.

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