Phosphor powder and light-emitting device

Abstract

This phosphor powder contains particles of a phosphor represented by 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, and 0 < = y < = 0.36), in which a part of the surfaces of the particles of the phosphor are raised.

Description

Technical Field

[0001] The present invention relates to a phosphor powder 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, as a wavelength conversion material for obtaining white light from the blue light emitted from a blue LED, a phosphor is used.

[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 continues.

[0004] As one of such phosphors, 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 substituted with 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 fluorescence characteristics of the phosphor described in Patent Document 1 above.

[0009] The present inventors conducted the present research for the purpose of providing a phosphor powder having excellent fluorescence characteristics.

[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 powder and light-emitting device are provided.

[0012] 1. A phosphor powder comprising a compound represented by the general formula M x (Si, Al)2(N, O) 3±yA phosphor powder comprising particles of a 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] The phosphor powder includes a surface deteriorated portion where part of the surface of the particles of the phosphor bulges.

[0014] 2. The phosphor powder according to 1., where

[0015] The surface deteriorated portion includes a flattened structure.

[0016] 3. The phosphor powder according to 1. or 2., where

[0017] The surface deteriorated portion includes an oxide or a hydroxide.

[0018] 4. The phosphor powder according to any one of 1. to 3., where

[0019] In the volume frequency particle size distribution of the phosphor powder measured by the laser diffraction scattering method, the particle size at the point where the cumulative volume from the small particle side becomes 50% is defined as D 50 When 50 it is 8 μm or more and 25 μm or less.

[0020] 5. The phosphor powder according to any one of 1. to 4., where

[0021] The phosphor is configured such that 2 mol% or more and 5 mol% or less of M becomes Ce.

[0022] 6. The phosphor powder according to any one of 1. to 5., where

[0023] When measuring the diffuse reflectance spectrum of the phosphor in the wavelength range of 500 to 850 nm, the difference X1 - X2 between the diffuse reflectance X1 of the light at wavelength 700 nm and the diffuse reflectance X2 of the light at the fluorescence peak wavelength when irradiating with 455 nm excitation light is 3.0% or less.

[0024] 7. The phosphor powder according to any one of 1. to 6., where

[0025] The diffuse reflectance X2 of the light at the fluorescence peak wavelength when irradiating with 455 nm excitation light is 88% or more and 97% or less.

[0026] 8. The phosphor powder according to any one of 1. to 7., where

[0027] The wavelength of the fluorescence peak when irradiating with 455 nm excitation light is 580 nm or more and 610 nm or less.

[0028] 9. The phosphor powder according to any one of 1. to 8., wherein,

[0029] the full width at half maximum of the fluorescence peak when irradiated with excitation light of 455 nm is 130 nm or more and 142 nm or less.

[0030] 10. A light-emitting device comprising the phosphor powder according to any one of 1. to 9. and a light-emitting light source.

[0031] According to the present invention, there is provided a phosphor powder having excellent fluorescence characteristics and a light-emitting device using the phosphor powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic cross-sectional view showing an example of the structure of the light-emitting device.

[0033] Figure 2 It shows an SEM photograph of the phosphor powder of Example 1.

[0034] Figure 3 It shows an SEM photograph of the phosphor powder of Example 2.

[0035] Figure 4 It shows an SEM photograph of the phosphor powder of Example 3.

[0036] Figure 5 It shows an SEM photograph of the phosphor powder of Comparative Example 1.

[0037] Figure 6 It shows an SEM photograph of the phosphor powder of Comparative Example 2.

[0038] Figure 7 It shows an SEM photograph of the phosphor powder of Comparative Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0039] 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. And the drawings are schematic diagrams and do not match the actual dimensional ratios.

[0040] 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".

[0041] <Phosphor>

[0042] The phosphor powder of this embodiment contains a general formula M x (Si, Al)2(N, O)3±y The particles of the phosphor represented, in the general formula, M is Li and one or more alkaline earth metal elements, 0.52 ≤ x ≤ 0.90, 0 ≤ y ≤ 0.36, and a part of M is replaced by Ce element.

[0043] Moreover, the phosphor powder of the present embodiment includes a surface modified portion where at least a part of the surface of the phosphor particles bulges.

[0044] According to the insight of the present inventors, it has been found that although the detailed mechanism is not clear, by annealing treatment such as heating the phosphor particles in an open system at a temperature relatively lower than the firing temperature in a reducing gas environment, the surface of the phosphor particles represented by the general formula M x (Si, Al)2(N, O) 3±y can be appropriately modified. That is, by this annealing treatment, phosphor particles having a plurality of surface modified portions formed on the particle surface of the phosphor can be obtained.

[0045] It has been found that a phosphor powder containing phosphor particles having such surface modified portions on the surface can improve luminescence characteristics such as internal quantum efficiency or diffuse reflectance at 600 nm, and thus the present invention has been completed.

[0046] Generally, it is known that broken pieces of a phosphor are formed by a crushing process in the manufacturing process of the phosphor powder, and the broken pieces adhere to the phosphor particles. However, the present inventors have confirmed that, without performing the annealing treatment, the broken pieces of the phosphor adhere to the surface of the phosphor particles, but no surface modified portions are formed.

[0047] The surface modified portion on the surface of the phosphor particles of the present embodiment is different from the broken pieces of the above phosphor in at least one aspect among shape, attachment mode, and composition.

[0048] According to the SEM photograph of the phosphor particles, the surface modified portion may include a flat structure without a broken surface on the particle surface unlike the broken pieces. Moreover, the surface modified portion may have a structure without a shrinkage portion between the surface of the phosphor particles.

[0049] Most of the surface modified portion does not fall off from the surface due to washing of the phosphor particles with water, and maintains the state of adhering to the surface. However, most of the broken pieces fall off from the surface by washing the phosphor particles with water. The surface modified portion is more firmly adhered to the surface of the phosphor particles chemically and / or physically as compared with the broken pieces.

[0050] Moreover, as a result of the chemical composition analysis of the phosphor powder, it was found that the oxygen content after the annealing treatment was higher than that before the annealing treatment. Based on this result, although the detailed mechanism is not clear, it is considered that the surface modified portion contains oxides or hydroxides of the phosphor as substances obtained by surface modification of the phosphor particles.

[0051] In addition, the surface modified portion is formed on the surface of the phosphor particles by annealing the phosphor represented by the general formula M x (Si, Al)2(N, O) 3±y On the other hand, it was confirmed that even when annealing the β-type sialon phosphor (so-called β-type sialon phosphor) with a β-type crystal phase, no surface modified portion is formed on its surface. In addition, even if there are attachments on the surface of the β-type sialon phosphor particles, fragments of the phosphor can be cited.

[0052] According to the SEM photograph of the phosphor particles, a plurality of surface modified portions may include a particle group in a state of being attached to a part of the surface separately from each other on one surface of the phosphor particles, but may also be connected to each other in such a way that a part of the surface is not exposed to form a coating layer. In either case, it is preferable that at least a part of the surface of the phosphor particles has a surface-exposed portion. And a plurality of surface modified portions can form a plurality of strip-shaped coating layers, but the phosphor particles may not have strip-shaped coating layers.

[0053] In recent years, high output and thinning have been promoted in light-emitting devices, and the working environment in light-emitting devices equipped with phosphors has a tendency to become hotter and hotter.

[0054] The phosphor powder of this embodiment can also be used for use in such a high-temperature environment.

[0055] The phosphor powder of this embodiment is different from the phosphor described in Patent Document 1 at least in that it includes a surface modified portion attached to the surface of the phosphor particles. The phosphor of this embodiment has excellent fluorescence characteristics compared to the phosphor described in Patent Document 1. For example, from the viewpoint of internal quantum efficiency, blue light is efficiently converted into long-wavelength light.

[0056] Continue to describe the phosphor of this embodiment.

[0057] (Crystal structure, chemical composition, etc.)

[0058] The framework structure of the phosphor crystal is formed by the bonding of (Si, Al)-(N, O)4 tetrahedrons, and the M element is located in the interstitial sites thereof. The composition of the above general formula holds within a wide range in which the overall electrical neutrality is maintained by the valence and amount of the M element, the Si / Al ratio, and the N / O ratio. As a typical phosphor represented by the above general formula, there is CaAlSiN3 in which the M element is Ca, x = 1, further Si / Al = 1, and O / N = 0. 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 to orange phosphor.

[0059] The crystal structure of the phosphor of this embodiment is generally 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 that very high luminous efficiency can be obtained even under Ce activation.

[0060] 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 of the M element can be widely controlled. And Li + has a very small ionic radius, and can cause a large change in crystal size according to its amount, thereby obtaining various fluorescence emissions.

[0061] 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 0.9, that is, it 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.

[0062] 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.

[0063] In this 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 generation 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 temperatures).

[0064] Regarding the Si / Al atomic ratio (molar ratio), it can generally be determined necessarily if the average valence number, amount, and O / N atomic ratio of the M element are set within a specified range. 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.

[0065] The Li content in the phosphor is 5 to 50 mol% of the M element, preferably 15 to 49 mol%, and more 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 a heterogeneous phase is formed, and the luminous efficiency is likely to decrease.

[0066] 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 volatilized, and a considerable amount will be volatilized when synthesizing nitrides / nitroxides at high temperatures. That is, the Li amount 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.

[0067] If the content of Ce, which is the luminescence center of the phosphor, is too small, the contribution to luminescence tends to become smaller, and if it is too large, there is a tendency for concentration quenching of the phosphor to occur due to 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%.

[0068] The alkaline earth metal element used as the M element in the above general formula can be any element, but 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.

[0069] The crystal structure of the phosphor is orthorhombic and can be the same structure 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 to 0.96500 nm, b = 0.55000 to 0.57000 nm, and c = 0.48000 to 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.

[0070] The crystal phase present in the phosphor is preferably the above-mentioned single crystal phase. However, as long as there is no significant impact on the fluorescence characteristics, the phosphor may contain heterogeneous phases. 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-mentioned crystal phase.

[0071] The phosphor of this 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 to 610 nm and a half-width at half-maximum of the fluorescence spectrum of 130 to 142 nm.

[0072] 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 this embodiment has excellent heat resistance, chemical stability, and small brightness reduction due to temperature rise. Such characteristics are particularly suitable for applications requiring durability.

[0073] (Diffuse reflectance)

[0074] From another perspective, the diffuse reflectance X1 of the phosphor of this embodiment with respect to light having a wavelength of 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 setting X1 within this numerical range, the luminous intensity tends to be further improved.

[0075] Moreover, from another perspective, the diffuse reflectance X2 of the phosphor of this embodiment with respect to light having 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 setting X2 within this numerical range, the luminous intensity tends to be further improved.

[0076] 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.

[0077] Moreover, from another perspective, when the diffuse reflectance with respect to light having a wavelength of 800 nm is set as 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.

[0078] (Particle size distribution)

[0079] 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.

[0080] Specifically, the volume-based cumulative 50% diameter D of the phosphor of the present embodiment measured by the laser diffraction scattering method 50 (the so-called median particle size) 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.

[0081] From another perspective, 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.

[0082] Moreover, from another perspective, 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.

[0083] (Absorbance)

[0084] From another perspective, 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.

[0085] Moreover, from another perspective, 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.

[0086] As another aspect, the value of the internal quantum efficiency of the phosphor of the present embodiment with respect to excitation light of 455 nm is preferably 80% or more.

[0087] Moreover, as another aspect, the value of the external quantum efficiency of the phosphor of the present embodiment with respect to excitation light of 455 nm is preferably 70% or more.

[0088] (Manufacturing method)

[0089] 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 formation of the surface modification portion on the phosphor surface, the manufacturing process of the phosphor preferably includes a (4) annealing treatment step.

[0090] (1) Preparation step of raw material mixed powder

[0091] (2) Firing step

[0092] (3) Crushing step of fired product

[0093] (4) Annealing treatment step

[0094] Hereinafter, (1) to (4) will be specifically described.

[0095] (1) Preparation step of raw material mixed powder

[0096] In the preparation step of the raw material mixed powder, appropriate raw material powders are usually mixed to obtain the raw material mixed powder.

[0097] As the raw material powder, nitrides of constituent elements, that is, 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 and the like.

[0098] 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 blending amount of the lithium compound is preferably determined according to the firing conditions and considering the volatilization amount during the firing process.

[0099] 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.

[0100] 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 easily reacts with water such as lithium nitride in a glove box to prepare a raw material mixed powder.

[0101] (2) Firing process

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] Incidentally, in consideration of industrial productivity, the pressure of the firing environment is preferably less than 1 MPa·G.

[0107] 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.

[0108] (3) Process of pulverizing the burned product

[0109] 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.

[0110] 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.

[0111] (4) Annealing process

[0112] 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.

[0113] 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.

[0114] The atmosphere during annealing is reducing. For example, it is preferably in nitrogen (inert gas) containing about 4% by volume of hydrogen gas (reducing gas).

[0115] It is preferable to use a crucible without a lid and to fill a small amount of phosphor in the crucible. In the annealing treatment, the mixed gas atmosphere can be brought into sufficient contact with the surface of the phosphor.

[0116] 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.

[0117] Although the detailed mechanism is not yet clear, it is considered that in a reducing mixed gas atmosphere, by annealing the phosphor in an open system at a relatively low temperature, such as by heating, the surface of the phosphor can be appropriately modified.

[0118] <Light-emitting device, image display device, and lighting device>

[0119] By combining the phosphor of the present embodiment and a light-emitting light source, a light-emitting device can be obtained.

[0120] 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 light with a longer wavelength. That is, the phosphor of the present embodiment can be used as a wavelength conversion material for converting blue light into light with a longer wavelength.

[0121] Reference Figure 1 , an example of the specific structure of the light-emitting device will be described.

[0122] 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, a bonding wire 172, and a composite body 40.

[0123] The light-emitting element 120 is a semiconductor element that emits excitation light. Any one of a light-emitting diode (LED) and 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 corresponding to near ultraviolet to blue light can be used.

[0124] 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. In addition, a packaging substrate can be used instead of the heat sink 130.

[0125] 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.

[0126] In the housing 140, a recess having a substantially funnel shape with a hole diameter gradually expanding 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.

[0127] 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.

[0128] The composite body 40 is at least dispersed with the phosphor of the present embodiment in a sealing material 30 such as resin. In order to obtain white light with higher quality, the sealing material 30 may contain not only the phosphor of the present embodiment but also other phosphors.

[0129] 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.

[0130] 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 bullet type, a COB (chip on board) type, or a CSP (chip scale package) type.

[0131] 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.

[0132] 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.

[0133] Example

[0134] 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.

[0135] <Manufacturing of phosphor powder>

[0136] (Comparative Example 1)

[0137] (1) Preparation of raw material mixed powder

[0138] 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.

[0139] 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.

[0140] (2) Firing

[0141] 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.

[0142] (3) Crushing of burned material

[0143] 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%.

[0144] 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 / min, pulverization air pressure: 0.3 MPa.

[0145] Through the above steps, a phosphor powder was obtained.

[0146] (Examples 1, 2 and Comparative Example 2)

[0147] 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.

[0148] 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 / min), 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 / min, and then cooled from 500 °C to 300 °C at a rate of about 1.1 °C / min. After 300 °C, it was cooled in the furnace.

[0149] 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.

[0150] (Example 3)

[0151] The phosphor powder obtained in Comparative Example 3 was subjected to an annealing treatment under the conditions described in Table 1 to obtain a phosphor powder.

[0152] (Comparative Example 2)

[0153] 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).

[0154] <Confirmation of Chemical Composition / Crystal Structure>

[0155] Regarding some phosphor powders, the composition was analyzed as follows.

[0156] 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).

[0157] Amounts of O and N: Measured using an oxygen and nitrogen analyzer (EMGA-920 manufactured by HORIBA).

[0158] 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.

[0159] 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 existed in the orthorhombic system.

[0160] <SEM Photographs>

[0161] SEM photographs were taken of the surfaces of the obtained phosphor powders of Examples 1 to 3 and Comparative Examples 1 to 3 using a scanning electron microscope (acceleration voltage of electron beam: 3 kV, magnifications: 2000 and 5000 times).

[0162] Figure 2 Shows the phosphor powder of Example 1, Figure 3 Shows the phosphor powder of Example 2, Figure 4 Shows the phosphor powder of Example 3.

[0163] Figure 5 Shows the phosphor powder of Comparative Example 1, Figure 6 Shows the phosphor powder of Comparative Example 2, Figure 7 Shows the phosphor powder of Comparative Example 3.

[0164] In Comparative Examples 1 to 3, from the above SEM photographs, it was confirmed that most of the surfaces of the phosphor particles were exposed as smooth surfaces, and fragments formed by the fragmentation of the phosphor were attached to the smooth surfaces. Also, it was confirmed that by washing the phosphor powders of Comparative Examples 1 to 3, the above-mentioned fragments were removed from the surfaces of the phosphor particles to a certain extent.

[0165] On the other hand, in Examples 1 to 3, through the above SEM photographs, it was confirmed that there were a plurality of raised portions on the surface of the phosphor particles. It was confirmed that, among the raised portions, unlike the above-mentioned fragments, there was no fractured surface, but rather some flat structures.

[0166] Moreover, as a result of the chemical composition analysis of the above phosphor powder, it was shown that in terms of the amount of oxygen element (wt%), Examples 1 to 2 were higher than Comparative Example 1, and Example 3 was higher than Comparative Example 3. It was confirmed that even when the phosphor powders of Examples 1 to 3 were washed with water, the above-mentioned raised portions were hardly removed from the surface of the phosphor particles after washing. Based on such results, it was judged that the raised portions formed on a part of the surface of the phosphor particles were surface modification portions formed by the surface modification of the phosphor through the above annealing treatment.

[0167] <Measurement of Diffuse Reflectance>

[0168] Regarding the diffuse reflectance, measurement was carried out using a device in which an integrating sphere device (ISV-469) was installed on an ultraviolet-visible spectrophotometer (V-550) manufactured by JASCO Corporation. At the time of measurement, baseline correction was performed using a standard reflectance plate (Spectralon).

[0169] 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, and the diffuse reflectances with respect to the light of wavelength 600 nm, the light of wavelength 700 nm, the light of wavelength 800 nm, and the light of the fluorescence peak wavelength of the phosphor powder (described later) were obtained.

[0170] <Measurement of Particle Size Distribution>

[0171] Regarding the particle size distribution, measurement was carried out 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.

[0172] As a specific procedure, first, a small amount of the phosphor powder was put into an aqueous solution containing 0.05 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 the measurement solvent to measure the particle size distribution. Based on the obtained cumulative volume frequency distribution curve, the 10% volume diameter (D 10 )、50% volume diameter (D 50 ) and 90% volume diameter (D90 )。

[0173] <Determination of Fluorescence Spectrum>

[0174] Using a spectrofluorometer (manufactured by Hitachi High-Tech Science Corporation, model F-7000) 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 455 nm wavelength was measured, and the fluorescence peak wavelength (nm) and the full width at half maximum of the fluorescence peak (nm) were determined.

[0175] <Determination of Internal Quantum Efficiency and External Quantum Efficiency>

[0176] 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.

[0177] (1) The phosphor powder was filled into the recessed part of the concave groove in a smooth-surface manner. The concave groove was installed at a specified position (sample part) inside the integrating sphere. Using an optical fiber, monochromatic light with a wavelength of 455 nm spectrally separated from a light-emitting source (Xe lamp) was introduced into the integrating sphere. The 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. Based on the obtained spectral data, the number of photons of the excitation reflected light (Qref) and the number of photons of the fluorescence (Qem) were calculated. The number of photons of the excitation reflected light was calculated in the wavelength range of 450 nm or more and 465 nm or less, and the number of photons of the fluorescence was calculated in the range of 465 nm or more and 800 nm or less.

[0178] (2) Also, a standard reflector with a reflectivity of 99% (Spectralon manufactured by Labsphere) was installed at the sample part instead of the concave groove, and the spectrum of the excitation light with a wavelength of 455 nm was measured. Then, the number of photons of the excitation light (Qex) was calculated based on the spectrum in the wavelength range of 450 nm or more and 465 nm or less.

[0179] (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 equations.

[0180] Internal quantum efficiency = (Qem / (Qex - Qref)) × 100

[0181] External quantum efficiency = (Qem / Qex) × 100

[0182] <Measurement of Absorbance at a Wavelength of 600 nm>

[0183] 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 procedure.

[0184] (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 a 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.

[0185] (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 part of the concave groove in a manner that made the surface smooth was used.

[0186] (3) The absorbance A at a wavelength of 600 nm was calculated by the formula (Qex - Qref) / Qex 600 .

[0187] <Measurement of Absorbance at a Wavelength of 700 nm>

[0188] 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 procedure.

[0189] (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 a 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.

[0190] (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 part of the concave groove in a manner that made the surface smooth was used.

[0191] (3) The absorbance A at a wavelength of 700 nm was calculated by the formula (Qex - Qref) / Qex 700.

[0192] Various information is summarized in Table 1.

[0193] [Table 1]

[0194]

[0195] As shown in Table 1, the general formula M of Examples 1 to 3 x (Si, Al)2(N, O) 3±y The phosphor powders shown showed results that were superior to those of Comparative Examples 1 to 3 in light emission characteristics such as internal quantum efficiency and diffuse reflectance at 600 nm.

[0196] In addition, when the β-SiAlON phosphor of Comparative Example 3 was subjected to the same annealing treatment as in Example 1, the internal quantum efficiency and the diffuse reflectance at 600 nm were significantly reduced compared to those before the annealing treatment.

[0197] This application claims priority based on Japanese Patent Application No. 2022-181260 filed on November 11, 2022, the disclosure of which is incorporated herein in its entirety.

[0198] Explanation of symbols

[0199] 1Phosphor particles

[0200] 30 Sealing material

[0201] 40 complex

[0202] 100 Lighting Devices

[0203] 120 light emitting elements

[0204] 130 heat sink

[0205] 140 Shell

[0206] 150 1st lead frame

[0207] 160 2nd lead frame

[0208] 170 bonding wire

[0209] 172 bonding wire

Claims

1. A phosphor powder, which comprises particles of a phosphor represented by the general formula M x (Si, Al)2(N, O) 3±y and in which a part of M is substituted with a Ce element, wherein, M is Li and one or more alkaline earth metal elements, 0.52 ≤ x ≤ 0.90, 0 ≤ y ≤ 0.36, wherein, The phosphor powder includes a surface deteriorated portion where a part of the surface of the phosphor particles bulges.

2. The phosphor powder according to claim 1, wherein, The surface deteriorated portion includes a flattened structure.

3. The phosphor powder according to claim 1 or 2, wherein, The surface deteriorated portion includes an oxide or a hydroxide.

4. The phosphor powder according to claim 1 or 2, wherein, In the volume frequency particle size distribution of the phosphor powder measured by the laser diffraction scattering method, the particle size at the point where the cumulative volume from the small particle side becomes 50% is defined as D 50 When 50 it is 8 μm or more and 25 μm or less.

5. The phosphor powder according to claim 1 or 2, wherein, The phosphor is configured such that 2 mol% or more and 5 mol% or less of M becomes Ce.

6. The phosphor according to claim 1 or 2, wherein, When measuring the diffuse reflectance spectrum of the phosphor in the wavelength range of 500 to 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 with the excitation light of 455 nm is 3.0% or less.

7. 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 with the excitation light of 455 nm is 88% or more and 97% or less.

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

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

10. A light-emitting device, which includes the phosphor powder according to claim 1 or 2 and a light-emitting light source.

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