Fluorescent member, its manufacturing method, and light-emitting device

Abstract

To provide a fluorescent member that has both heat conductivity and fluorescence and furthermore has improved machinability and can increase the degree of freedom in designing the shape and dimension of the fluorescent member without requiring a high-temperature calcination process (high-temperature process exceeding 250°C) and a method for producing the same, and a light-emitting device.SOLUTION: Provided is a fluorescent member that is a sintered body for wavelength conversion and has magnesium oxide and magnesium hydroxide as main component, contains a chelating agent in gaps between magnesium oxide particles, and contains a matrix filled with magnesium hydroxide and phosphor particles dispersed in the matrix.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a fluorescent member and a manufacturing method thereof, and also to a semiconductor light-emitting element and a light-emitting device comprising the fluorescent member. [Background technology]

[0002] Light-emitting devices equipped with semiconductor light-emitting elements such as light-emitting diodes (LEDs: Light Emission Diodes) and laser diodes (LDs: Laser Diodes) are excellent in terms of low power consumption and long life, and are used in lighting devices, backlights for liquid crystal display devices, light sources for laser devices, etc. Among them, white LEDs are becoming widely used as an alternative to fluorescent lamps.

[0003] A known method of white LED is to emit white light by combining a light-emitting diode (primary light source) with a fluorescent material. Molded products made of phosphor particles dispersed in resin have been developed as the fluorescent material. However, resin has low thermal conductivity and is prone to becoming hot due to heat generated by the light-emitting diode (primary light source) and heat generated by energy conversion loss during the excitation-light emission process in the fluorescent material, so there is a problem that resin cannot be used for high-output LEDs or lasers.

[0004] To solve this problem, phosphor-dispersed YAG ceramics, in which phosphor particles are dispersed in transparent YAG ceramics, have been developed. Furthermore, phosphor-dispersed Sialon ceramics (Patent Document 1) and wavelength conversion materials in which inorganic phosphor particles are dispersed in magnesium oxide (Patent Document 2) have been proposed. However, although these methods have excellent heat resistance, they require high-temperature firing at 1000°C or higher in the manufacturing process, which causes the problem that the phosphor particles are easily deteriorated.

[0005] The present inventors have recently proposed a fluorescent material that has excellent thermal conductivity and can suppress deterioration of phosphor particles, and contains a matrix whose main components are magnesium oxide and magnesium hydroxide, and phosphor particles dispersed in this matrix (Patent Document 3).

[0006] Although not an example of a fluorescent material, a method for processing ceramics has been proposed in which the surface of ceramic powder is activated by grinding, fibers are mixed therewith, and then a ceramic solidified body is obtained by alkali treatment (Patent Document 4). In addition, a method has been disclosed in which at least one inorganic compound less than 50 μm is combined with a solvent capable of partially dissolving the inorganic compound to form a mixture, and the mixture is pressurized at a temperature below 200° C. and above the boiling point of the solvent while evaporating the solvent to form a densified sintered material (Patent Document 5). In addition, a porous solidified body has been proposed in which a water-containing amorphous substance is used as a starting material, and the water content of the water-containing amorphous substance is removed and hardened by applying pressure and heating by hydrothermal hot pressing (Patent Document 6). In addition, an example of combined use of magnesium oxide and a chelating agent, which will be specified in the "Means for solving the problems" described later, has been reported (Non-Patent Document 1). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2018 / 38259 [Patent Document 2] JP 2018-180271 A [Patent Document 3] International Publication No. 2021 / 015261 [Patent Document 4] JP 2009-203102 A [Patent Document 5] US Publication No. 2017 / 0088471 [Patent Document 6] International Publication No. 2021 / 015261 [Non-patent literature]

[0008] [Non-Patent Document 1] LF Amaral et al., Ceramics International, 37, (2011) 1537-1542 Summary of the Invention [Problem to be solved by the invention]

[0009] In the fluorescent material of Patent Document 3 mentioned above, that is, a fluorescent material using a matrix whose main components are magnesium oxide and magnesium hydroxide, if the machinability can be improved and the design freedom in the shape and dimensions of the fluorescent material can be increased, it will be possible, for example, to make the material thinner, which is expected to accelerate practical application and lead to the development of a variety of applications. Although the above describes problems associated with white LEDs and the like, similar problems can occur with fluorescent materials in general.

[0010] The present invention has been made in view of the above-mentioned background, and aims to provide a fluorescent material that combines thermal conductivity and fluorescence without the need for a high-temperature firing process (a high-temperature process exceeding 250°C), and that further improves machinability and allows for greater freedom in designing the shape and dimensions of the fluorescent material, as well as a manufacturing method thereof and a light-emitting device. [Means for solving the problem]

[0011] As a result of extensive investigations, the present inventors have found that the problems of the present invention can be solved in the following aspect, and have thus completed the present invention. [1]: A matrix mainly composed of magnesium oxide and magnesium hydroxide, in which a chelating agent is present in the gaps between the magnesium oxide particles and magnesium hydroxide is filled; and a fluorescent member which is a sintered body for wavelength conversion containing phosphor particles dispersed in the matrix. [2]: obtaining a preform of at least a mixture of magnesium oxide, which is a raw material powder of the matrix, and the phosphor particles; The fluorescent member described in [1] is a sintered body obtained by impregnating the preform with water and a chelating agent, and then sintering under pressure, and is characterized in that the fluorescent member is obtained without performing a high-temperature process exceeding 250°C on the preform after the water impregnation. [3]: The fluorescent material according to [2], further comprising a step of removing particles having a particle diameter of 50 μm or more from the raw material powder. [4]: A semiconductor light emitting element that emits a first light; a fluorescent member according to any one of [1] to [3], which is disposed on the light emission side of the semiconductor light emitting element and emits a second light when the first light becomes excitation light; [5]: Obtaining a mixture of at least a matrix raw material powder and phosphor particles; preforming the mixture to obtain a preform; The method includes a step of impregnating the preformed body with water and a chelating agent, and then obtaining a sintered body by sintering under pressure, and does not include a process of treating the preformed body after the water impregnation at a high temperature exceeding 250°C; A method for manufacturing a fluorescent member, wherein the matrix is ​​mainly composed of magnesium oxide and magnesium hydroxide. [6]: A method for producing a fluorescent member according to [5], characterized in that it includes a step of removing particles having a particle diameter of 50 μm or more from the raw material powder. Effect of the Invention

[0012] The present invention has the excellent effect of providing a fluorescent material that combines thermal conductivity and fluorescence without the need for a high-temperature firing process (a high-temperature process exceeding 250°C), and that further improves machinability and allows for greater freedom in designing the shape and dimensions of the fluorescent material, as well as a manufacturing method thereof and a light-emitting device. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of a light emitting device according to an embodiment of the present invention. [Diagram 2]FIG. 11 is a schematic cross-sectional view showing an example of a light emitting device according to a modified example. [Diagram 3] Fluorescence spectrum of the fluorescent member according to the present embodiment. [Figure 4] 1 is a scanning transmission electron microscope (STEM) image of Reference Example 1. [Diagram 5] FIG. 1 is an oxygen mapping diagram of Reference Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] An example of an embodiment to which the present invention is applied will be described below. Other embodiments are also included in the scope of the present invention as long as they are consistent with the gist of the present invention. The numerical values ​​specified in this specification are values ​​obtained by the method disclosed in the embodiment or example. In order to clarify the explanation, the following description and drawings have been appropriately simplified. Furthermore, matters necessary for the implementation of the present invention that are not specifically mentioned in this specification can be understood as design matters of a person skilled in the art based on the prior art in the field.

[0015] 1. Fluorescent materials The fluorescent member according to the present embodiment is composed of a sintered body for wavelength conversion, containing magnesium oxide and magnesium hydroxide as main components, a matrix in which a chelating agent is dispersed in the gaps between magnesium oxide particles and magnesium hydroxide is filled, and phosphor particles dispersed in the matrix. The shape of the fluorescent member may be, for example, a disk, a plate, a convex lens, a concave lens, a sphere, a hemisphere, a cube, a rectangular parallelepiped, a columnar shape such as a square column or a cylinder, or a cylindrical shape such as a square tube or a cylinder. When applied to a white LED, the fluorescent member according to the present embodiment may be disposed on the light emission side of, for example, a blue LED serving as an excitation light source.

[0016] In the fluorescent member, at least a part of the first light emitted from a semiconductor light-emitting element or the like is absorbed by the phosphor particles as excitation light, and the second light is emitted. In addition, the phosphor particles in this specification include particles that emit so-called fluorescence as well as particles that emit phosphorescence. The first light refers to light of a specific wavelength or light of a specific band, and the first light may be one type or multiple types. An example of a case where there are multiple types is a case where there is a semiconductor light-emitting element that emits a first light of blue light and a semiconductor light-emitting element that emits a first light of ultraviolet light. The second light refers to light emitted from the phosphor particles when at least a part of the first light becomes excitation light for the phosphor particles. The second light may also be one type or multiple types. As an example of a case where there are multiple types, there is a case where multiple types of phosphor particles with different emission bands are dispersed in the same fluorescent member. In addition, an embodiment in which phosphor particles with different emission bands are dispersed in different fluorescent members can also be exemplified.

[0017] When a fluorescent member is used to obtain white light, for example, phosphor particles that emit red light when stimulated by blue light as excitation light and phosphor particles that emit green light when stimulated by blue light as excitation light are contained in the fluorescent member. Furthermore, the fluorescent member is made transparent to transmit the blue light that does not contribute to excitation. As a result, the blue light that has passed through the fluorescent member and the red and green lights emitted from the fluorescent member are mixed together to obtain white light. In another example, ultraviolet or violet light is used as excitation light, and the fluorescent member contains phosphor particles that emit blue light, phosphor particles that emit red light when excited by ultraviolet or violet light, and phosphor particles that emit green light when excited by ultraviolet or violet light. This causes the blue, red, and green lights emitted from the fluorescent member to mix together. As a result, white light can be obtained by the fluorescent member of this embodiment. In this case, in addition to a design in which a part of the excitation light is transmitted through the fluorescent member, a design in which all of the excitation light is absorbed by the fluorescent member may also be used.

[0018] In the fluorescent member of this embodiment, from the viewpoint of making the emission of fluorescence uniform and the total transmittance of the excitation light uniform, it is preferable that the fluorescent particles are uniformly present throughout. In this way, the excitation light transmitted through the fluorescent member and the fluorescence emitted from the fluorescent member are mixed, making it easy to adjust the color of the light emitted from the fluorescent member. Instead of the above embodiment, a concentration gradient may be provided in the distribution of the phosphor particles, or a fluorescent member containing different phosphor particles in different regions may be used. Such a fluorescent member can be easily obtained by changing the process during the manufacturing process. It is also possible to join different types of fluorescent members.

[0019] A suitable example of the thickness of the fluorescent member may vary depending on the application, but is, for example, 100 μm or more. An optical film may be provided on at least one of the entrance surface side and the exit surface side of the fluorescent member. For example, an anti-reflection film may be provided as the optical film.

[0020] According to the fluorescent material of this embodiment, it is possible to obtain a fluorescent material without necessarily requiring a high-temperature firing process (a high-temperature process exceeding 250° C.), as described below. This fundamentally solves the problem of degradation and alteration of phosphor particles, and significantly increases the types of applicable phosphor particles. In addition, it is possible to prevent degradation of phosphor particles. As a result, it is possible to provide a fluorescent material for wavelength conversion with excellent fluorescence properties.

[0021] 1-1. Matrix This fluorescent member has a matrix in which phosphor particles are dispersed. This matrix is ​​mainly composed of magnesium oxide and magnesium hydroxide, and a chelating agent is present in the gaps between the magnesium oxide particles, and magnesium hydroxide is filled in the gaps. In this specification, the matrix may include the above-mentioned main component and chelating agent, as well as additives that are added arbitrarily. The matrix does not include trace components of less than 1 mass % other than the phosphor particles and chelating agent in the fluorescent member. In addition, the main component refers to a component that is contained in the matrix at 90 mass % or more. In this embodiment, magnesium oxide and magnesium hydroxide are the main components of the matrix. The ratio of magnesium oxide to magnesium hydroxide is not important. Examples of matrix components other than the main component include sodium chloride (NaCl), zinc oxide (ZnO), barium titanate (BaTiO 3 ), calcium carbonate (CaCO 3 A dispersant may also be added.

[0022] The mass ratio of magnesium hydroxide to magnesium oxide in the matrix of the fluorescent member according to this embodiment ([magnesium hydroxide] / [magnesium oxide]) can be appropriately designed depending on the application, but from the viewpoint of effectively increasing thermal conductivity, it is preferably 0.4 or less, more preferably 0.3 or less, and even more preferably 0.25 or less. There is no particular lower limit to the mass ratio of magnesium hydroxide to magnesium oxide as long as densification can be achieved, but from the viewpoint of easily carrying out the densification process at a low temperature, it is preferably 0.1 or more.

[0023] The average particle size of magnesium oxide in the matrix is ​​not particularly limited, but is preferably 0.1 μm to 10 μm from the viewpoint of thermal conductivity. The average particle size of magnesium oxide in the matrix is ​​obtained by measuring as follows using a linear intercept method or the like in accordance with ISO13383-1:2012. That is, the observation surface is mirror-polished, and the crystal grains are made clear by plasma etching, and then a structural photograph of the crystal grains is obtained with a scanning electron microscope. A straight line is drawn on the obtained structural photograph, and the intersection distance between the line and the particle interface is measured to obtain the particle size. This measurement of particle size is repeated, and the obtained values ​​are averaged to obtain the average particle size of magnesium oxide.

[0024] The chelating agent in this matrix is ​​Mg 2+ There are no particular limitations on the compound, so long as it can form a multidentate coordinate bond with the chelating agent. By using a chelating agent, it is possible to make the magnesium hydroxide that fills the gaps between the magnesium oxide particles finer and more uniformly distributed, thereby reducing residual stress. As a result, it is possible to improve machinability and increase the design freedom of the shape and dimensions of the fluorescent component.

[0025] The content of the chelating agent may be appropriately designed depending on the volume of the gaps between the magnesium oxide particles. For example, a solution in which the chelating agent is dissolved may be introduced in the entire volume of the gaps between the magnesium oxide particles, with respect to the total volume of the gaps being 100%. The amount of the chelating agent added in this case may be, for example, 0.01 to 3.0 parts by mass with respect to 100 parts by mass of the magnesium oxide in the preform. From the viewpoint of increasing density, the amount is more preferably 0.01 to 1.0 part by mass, and even more preferably 0.05 to 0.2 parts by mass. The coordination number of the chelating agent is not particularly limited, but Mg 2+ From the viewpoint of the stability of the complex formed by the chelating agent, the coordination number is preferably 2 to 6, and more preferably 3 to 6.

[0026] Suitable examples of the chelating agent include aminopolyacetic acids such as nitrilotriacetic acid, iminodiacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, glycoletherdiaminetetraacetic acid, hydroxyethyliminodiacetic acid, triethylenetetraaminehexaacetic acid, dienecolic acid, and methylglycinediacetic acid, or salts thereof; organic acids such as diglycolic acid, oxydisuccinic acid, carboxymethyloxysuccinic acid, citric acid, lactic acid, tartaric acid, oxalic acid, malic acid, oxydisuccinic acid, gluconic acid, carboxymethylsuccinic acid, and carboxymethyltartaric acid, or salts thereof; aminotri(methylenephosphonic acid), 1-hydroxyethylidene-1,1-diphosphonic acid, ethylenediaminetetra(methylenephosphonic acid), and diethylenetriaminepenta(methylenephosphonic acid). The chelating agent can be used alone or in combination of two or more.

[0027] Incidentally, when resin is used as the matrix of the fluorescent material, the thermal conductivity is about 0.1 W / (m·K), and when glass is used, the thermal conductivity is about 1 W / (m·K). In contrast, the fluorescent material of this embodiment, which uses a matrix containing magnesium oxide and magnesium hydroxide as its main components, can significantly improve the thermal conductivity. By optimizing the manufacturing process of the fluorescent material, it is easy to achieve a thermal conductivity of 5 W / (m·K) or more.

[0028] From the viewpoint of achieving better thermal conductivity, the thermal conductivity of the fluorescent member of this embodiment is preferably 5 W / (m·K) or more, more preferably 6 W / (m·K) or more, and even more preferably 8 W / (m·K) or more. There is no upper limit to the thermal conductivity, but in the case of a matrix mainly composed of magnesium oxide and magnesium hydroxide, the thermal conductivity is theoretically 50 W / (m·K), and therefore, by changing the process and controlling the path of heat conduction, a higher thermal conductivity can be achieved. Note that the thermal conductivity in this specification refers to the thermal conductivity of the fluorescent member measured in accordance with JIS R1611, and specifically refers to the value measured by the method described in the examples.

[0029] 1-2. Phosphor particles According to this embodiment, since sintering can be performed at room temperature without heating as described later, any phosphor particles can be used. The phosphors constituting the phosphor particles include α-sialon phosphor, β-sialon phosphor, KSF (K 2 SiF 6 :Mn) phosphors, CASN phosphors, SCASN phosphors, cerium-activated yttrium aluminum garnet (YAG) phosphors, cerium-activated lutetium aluminum garnet (LAG) phosphors, europium- and / or chromium-activated nitrogen-containing calcium aluminosilicate (CaO-Al 2 O 3 -SiO 2 ) phosphor, europium-activated silicate ((Sr,Ba) 2 SiO 4 )-based phosphors and the like. Nitride phosphor particles are preferred from the viewpoint of suppressing a decrease in luminous intensity accompanying a rise in temperature due to laser excitation, etc. Examples of phosphors constituting the nitride phosphor particles include α-sialon phosphors, β-sialon phosphors, CASN phosphors, and SCASN phosphors.

[0030] The phosphor particles are preferably nitride phosphor particles containing nitrogen in the phosphor composition. Specific examples include nitride phosphors containing strontium and silicon in the crystal phase (e.g., SCASN, Sr 2 S 5 N 8 ), nitride phosphors containing calcium and silicon in their crystal phases (e.g., SCASN, CASN, CASON), nitride phosphors containing strontium and silicon in their crystal phases (e.g., SCASN), nitride phosphors containing barium and silicon in their crystal phases (e.g., BSON), and nitride phosphors containing calcium, silicon and aluminum in their crystal phases (e.g., SCASN, CASN, CASON). Another classification of nitride phosphors is lanthanum nitride silicates (e.g., LSN), alkaline earth metal nitride silicates (e.g., Sr 2 S 5 N 8), alkaline earth metal nitridosilicates (CASN, SCASN, (Ca,Sr)AlSi 4 N 7 ) etc. More specifically, for example, β-sialon, which can be represented by the following general formula: S 6-z Al z O z N 8-z :Eu(0 in the formula <z<4.2)、 α-SiAlON, which can be represented by the following general formula: (M1 x ,M2 y ,EU z )(Si 12-(m+n) Al m+n )(O n N 16-n ) (wherein M1 is a monovalent element, M2 is one or more divalent elements selected from the group consisting of Mg, Ca, Y, and lanthanide elements (excluding La and Ce), 0≦x<2.0, 0≦y<2.0, 0 <z≦0.5、0<x+y、0.3≦x+y+z≦2.0、0<m≦4.0、0<n≦3.0)、 LSN;Ln x S 6 N y M z (In the formula, Ln represents one or more elements selected from rare earth elements excluding elements used as activating elements, M represents one or more elements selected from activating elements, and x, y, and z each independently represent a value that satisfies the following formula: 2.7≦x≦3.3, 10≦y≦12, 0 <z≦1.0) CASN, represented by the following general formula: CaAlSiN 3 :EU, SCASN, which can be represented by the following general formula: (Ca,Sr,Ba,Mg)AlSiN 3 : Eu and / or (Ca,Sr,Ba)AlSi(N,O) 3 :EU, CASON, which can be represented by the following general formula; (CaAlSiN 3 ) 1-x (Si 2 N 2 O) x:Eu(0 in the formula <x<0.5)、 It can be represented by the following general formula: CaAlSi 4 N 7 ;Euy(Sr,Ca,Ba)1-y:Al 1+x S 4-x O x N 7-x (In the formula, 0≦x<4, 0≦y<0.2), Sr can be expressed by the following general formula 2 S 5 N 8 ;(Sr,Ca,Ba) 2 Al x S 5-x O x N 8-x :Eu (0≦x≦2 in the formula), BSON;M can be expressed by the following general formula: x Ba y (Sr, Ca, Mg, Zn) z L 6 O 12 N 2 (In the formula, M represents an activating element selected from Cr, Mn, Fe, and lanthanides (excluding La, Pm, Gd, and Lu), L represents a metal element belonging to Group 4 or 14 of the periodic table that contains Si, and x, y, and z each independently represent a value that satisfies the following formula: 0.03≦x≦0.9, 0.9≦y≦2.95, x+y+z=3) and the like. Among these phosphors, from the viewpoint of not losing brightness when sintered, nitride phosphors that do not contain oxygen as a constituent element (including oxygen that is inevitably mixed in), namely LSN, CASN, SCASN, and Sr 2 S 5 N 8 It is preferable to use nitride phosphors such as β-sialon and BSON.

[0031] The type of phosphor particles to be added is not particularly limited, and multiple types may be added depending on the purpose. The content of phosphor particles in the fluorescent member can be appropriately adjusted depending on the shape (thickness, etc.) of the fluorescent member, the desired transparency (total transmittance of excitation light), and the fluorescence (fluorescence intensity, emission wavelength).

[0032] The average particle size of the phosphor particles in the matrix is ​​not particularly limited, but from the viewpoint of obtaining a good balance between the transmittance of the excitation light, good fluorescent properties, and dispersibility, it is preferably 500 nm to 30 μm, and more preferably 1 to 10 μm. The average particle size of the phosphor particles in the matrix is ​​determined using the linear intercept method in accordance with ISO13383-1:2012. The specific measurement method is the same as that for magnesium oxide.

[0033] 2. Manufacturing method of fluorescent materials Next, an example of a method for producing a fluorescent member according to the present embodiment will be described, but the method for producing a fluorescent member of the present invention is not limited to the following. In the method for producing a fluorescent member according to the present embodiment, at least phosphor particles and raw powder of a matrix are mixed to obtain a mixture, the mixture is preformed, and the preform is impregnated with water and a chelating agent. The chelating agent can be dissolved in water and impregnated. Alternatively, the preform can be impregnated with a chelating agent dissolved in another solvent instead of water. Since the amount of the chelating agent to be added is extremely small compared to the volume of the preform, it is preferable to impregnate the preform with a chelating agent dissolved in water in order to uniformly disperse the chelating agent in the gaps between the MgO particles. Note that this does not exclude the addition of a chelating agent when forming a mixture of raw powder and phosphor particles instead of or in combination with the process of impregnating with water.

[0034] Then, a sintering process is performed under pressure to obtain a sintered body. According to the manufacturing method of this embodiment, a fluorescent member having both excellent thermal conductivity and fluorescence can be manufactured without necessarily requiring a high-temperature process exceeding 250° C.

[0035] In this specification, sintering refers to the phenomenon in which the surface area of ​​a powder decreases, and refers to a method in which a fluorescent material is fixed under pressure at a temperature of 250°C or less in a sintering process after obtaining a preform and impregnating it with water (hereinafter also referred to as "low-temperature sintering"). It is synonymous with so-called cold sintering. By performing low-temperature sintering, as described below, the water (liquid phase) and chelating agent impregnated in the preform are introduced to the particle-particle interface, and the particles are uniformly swollen with an appropriate amount of water. Then, under pressure conditions, material diffusion through the liquid phase is promoted, and a dense bulk ceramic is obtained accompanied by the generation of magnesium hydroxide by the reaction of part of the magnesium oxide with water.

[0036] By using a chelating agent, Mg 2+ It is possible to promote the miniaturization of the nuclei by the formation of ion complexes. In addition, by using a chelating agent, the chelating agent is adsorbed onto the surface of the magnesium oxide particles, and the dissolution rate of magnesium oxide is controlled, thereby improving the dispersibility of magnesium hydroxide in the gaps between the magnesium oxide particles. As a result, the quality of the fluorescent member is improved, and a dramatic improvement in machinability is achieved, for example, making it possible to make the fluorescent member thinner, and increasing the degree of freedom in designing the shape and dimensions of the fluorescent member.

[0037] The lower limit of the sintering temperature is not particularly limited, but is preferably room temperature. In this specification, the term "preformed" refers to forming an amorphous state such as granules into a solid shape of a certain shape, for example, by pressure, and refers to a molded body before impregnating with water. The process of forming the preformed body can also be performed at a temperature exceeding 250°C. In addition, in the process of obtaining the preformed body, the particles are in point contact with each other and the surface area does not change significantly, so in this specification, "sintering" refers to the process after impregnation with water, and does not include the process of forming the preformed body. A detailed explanation will be given below.

[0038] First, the raw powder and phosphor particles are weighed and mixed. The average particle diameter calculated from the specific surface area S and density ρ of magnesium oxide in the raw powder as 6 / (S·ρ) is preferably 20 to 1000 nm, more preferably 30 to 800 nm, and even more preferably 40 to 700 nm. The specific surface area was measured according to ISO9277. By having the average particle diameter of magnesium oxide in the raw powder in the range of 20 to 1000 nm, it is possible to achieve both good thermal conductivity and mechanical properties. In order to more effectively promote denseness, the raw powder of the matrix may use a plurality of magnesium oxides with different average particle diameters. For example, denseness may be increased by using relatively small second particles that fill the gaps formed between the first particles.

[0039] The average particle size of the phosphor particles used as a raw material is not particularly limited within the scope of the present invention, but from the viewpoint of achieving a good balance between light transmittance, dispersibility, and fluorescence, it is preferably 500 nm to 30 μm, and more preferably 1 to 10 μm. The average particle size of the raw material powder of the phosphor particles of this embodiment is calculated from the specific surface area and density.

[0040] The compounding ratio of the raw powder forming the matrix and the phosphor particles is not particularly limited, and is appropriately adjusted according to the transparency and fluorescence of the target fluorescent member. The content of the phosphor particles when the raw powder forming the matrix is ​​100 vol%, is, for example, 0.1 to 30 vol%, and from the viewpoint of compactness, is preferably 0.5 to 20 vol%, and more preferably 1 to 15 vol%. The total transmittance of the fluorescent member for the excitation light in the optical path direction is preferably, for example, 10% or more.

[0041] The matrix raw material powder and phosphor particles may be separately pulverized and / or crushed before mixing. As a result of intensive research by the present inventors, it has become clear that the densification of the fluorescent material can be promoted by removing particles of 50 μm or more (e.g., coarse particles and aggregated particles) from the raw material powder.

[0042] At least one of the matrix raw powder and phosphor particles is weighed out to a predetermined molar ratio. Additives may be added as long as they do not interfere with the formation of the matrix of the fluorescent member. Examples of additives include magnesium chloride, hydrochloric acid, acetic acid, and ammonia. At least magnesium oxide is used as the raw powder, and a preform containing magnesium oxide and phosphor particles is impregnated with water and then sintered at a low temperature, whereby magnesium hydroxide is obtained by the reaction between magnesium oxide and water.

[0043] The method for obtaining the mixture is not particularly limited, and may be, for example, obtained through a dry or / and wet process. In the case of the dry process, for example, the raw materials are mixed in a mortar. A dispersant may be added at this time. From the viewpoint of homogenizing the size of the powder in the mixture, two or more sieves with different mesh sizes may be used in stages to obtain a mixture having a predetermined particle size.

[0044] The preform can be formed after the mixture is obtained or at the same time as the process of obtaining the mixture. In the case of wet mixing, a solvent (ethanol, etc.) is used in a ball mill or the like to mix the materials to prepare a slurry, and then the solvent is removed to obtain the mixture and the preform at the same time. In this case, preform can be further performed by pressure or the like. The preform can be performed by any existing method without any restrictions. For example, the mixture is filled into a mold and a preform is obtained by pressing. Pressurization may be isotropic or anisotropic (for example, uniaxial). Heating may also be performed. From the viewpoint of preventing deterioration of the phosphor particles, it is preferable to heat the material at 250° C. or less, and from the viewpoint of the simplicity of the device, it is more preferable to perform cold isostatic pressing at room temperature. From the viewpoint of obtaining a high-quality fluorescent member, it is preferable to pressurize the material at the preform stage so as to achieve homogenization of the internal structure. In order to homogenize the internal structure, the crushing of aggregates of the raw material powder and the process conditions (pressurization conditions, etc.) of the preform are important.

[0045] An example of preforming is a method in which a preform is obtained by uniaxial press forming at a pressure of 50 MPa for 30 seconds, the preform is chamfered, and then vacuum-packed, and cold isostatic pressing (CIP) is performed once or multiple times at a pressure of 200 MPa for 1 minute to obtain a preform. The maximum pressure of preforming is preferably 5 to 1000 MPa, more preferably 200 to 1000 MPa, and even more preferably 500 to 1000 MPa, from the viewpoint of achieving homogenization of the internal structure of the preform.

[0046] Next, the preform is impregnated with water and a chelating agent. The chelating agent is dissolved in water or a solvent other than water and then impregnated. The water may contain additives other than the chelating agent within a range that does not impair the object of the present invention, and may be neutral, acidic or alkaline. The addition of water can be carried out under atmospheric pressure, but may also be carried out under vacuum or reduced pressure. By carrying out the addition under vacuum or reduced pressure, the water can be distributed uniformly in a short time. This is particularly effective when the preform is thick.

[0047] The amount of water to be added should be enough to fill the gaps in the preform, and the optimum amount may vary depending on the relative density of the preform. The promotion of mass transfer can also be promoted by the process temperature of the low-temperature sintering in the next step, so the optimum amount of water to be added may also vary depending on the process temperature. The amount of water to be added should be limited to the amount necessary to achieve densification of the fluorescent member. For example, when the magnesium oxide in the preform is 100 parts by mass, the amount of water to be added can be, for example, 1 to 20 parts by mass.

[0048] The optimum amount of the chelating agent to be added may vary depending on the particle size of the magnesium oxide and the relative density of the preform. The promotion of mass transfer may vary depending on the type of chelating agent, and the optimum value may vary. The promotion may also be achieved by the process temperature of the low-temperature sintering in the next step, so the optimum amount of the chelating agent to be added may also vary depending on the process temperature. The amount required to achieve densification of the fluorescent member may be set as the upper limit. When the magnesium oxide in the preform is taken as 100 parts by mass, the amount of the chelating agent to be added may be, for example, 0.01 to 3.0 parts by mass. From the viewpoint of densification, 0.01 to 1.0 parts by mass is more preferable, and 0.05 to 0.2 parts by mass is even more preferable.

[0049] The preform is impregnated with water and a chelating agent, and then sintered at low temperature under pressure to obtain a sintered body. The magnesium ions of the magnesium oxide in the preform are dissolved by the impregnation with water. The dissolved magnesium ions form a complex with the chelating agent. As a result, the concentration distribution of magnesium ions in the water becomes homogenous without being locally high, and the nuclei for magnesium hydroxide formation become smaller. In addition, the chelating agent is adsorbed on the surface of the magnesium oxide particles, and the rate at which magnesium ions dissolve from the magnesium oxide can be controlled by the chelating agent.

[0050] The mass transfer of the complexed magnesium ions is promoted through the liquid phase under pressure associated with low-temperature sintering, and the complex is precipitated as magnesium hydroxide or magnesium oxide. As a result, the fluorescent member can be densified. For this reason, a pressure sufficient to promote mass transfer through the liquid phase is required. From the viewpoint of sufficient densification, the maximum pressure is preferably 200 to 1500 MPa, more preferably 300 to 1200 MPa, and even more preferably 500 to 1000 MPa. By setting the pressure to 200 to 1500 MPa, it is possible to promote dissolution and deposition of the particles constituting the matrix part into the liquid phase without high-temperature sintering, and to promote densification due to plastic deformation. As a means for applying pressure, a known method can be applied. Pressurization by hydrostatic pressure is particularly suitable because it can apply pressure isotropically. The pressurization time varies depending on the mechanism of the chemical reaction contributing to densification and the pressure, but is preferably 1 to 60 min.

[0051] When the process is carried out at room temperature, the preform is impregnated with water, then vacuum-packed, and subjected to CIP molding once or multiple times for 60 minutes at a pressure of 1000 MPa using a cold isostatic pressing device to obtain a sintered body. When the process is heated, a WIP (Warm Isostatic Pressing) device can be used to perform molding.

[0052] From the viewpoint of thermal conductivity, it is preferable that the ratio of magnesium oxide to magnesium hydroxide is higher, and from the viewpoint of densification of the fluorescent material, it is preferable to add a large amount of water and generate magnesium hydroxide by the reaction of magnesium oxide and water. Densification of the fluorescent material can be promoted by heating, so a high-temperature process may be carried out at a temperature of 250°C or less to promote densification. From the viewpoint of energy saving and simplicity of the device, it is preferable to carry out low-temperature sintering at room temperature.

[0053] The above manufacturing method is merely an example, and the fluorescent member of the present embodiment can be manufactured by various manufacturing methods. For example, a mixture of phosphor particles, raw powder containing at least magnesium oxide, and ice particles may be obtained, and the mixture may be preformed below freezing point and then sintered at low temperature, or the mixture may be sintered at low temperature without preforming to obtain a fluorescent member. A fluorescent member may also be obtained by combining a freeze-drying method with a low-temperature sintering method. Specifically, a mixture of phosphor particles, raw powder containing at least magnesium oxide, water, and a solvent (e.g., methanol) having a lower sublimation point than water is obtained, and the mixture is sprayed by a freeze-drying method to form droplets, and a granule from which the solvent has been removed while leaving water is obtained, and the granule is sintered at low temperature to obtain a fluorescent member.

[0054] From the viewpoint of effectively increasing the luminous efficiency, the relative density of the fluorescent member is preferably 85% or more. Here, the relative density refers to the value (mass ratio) obtained by dividing the density of the fluorescent member measured according to the Archimedes method in accordance with JIS Z 2501:2000 by the true density of the raw material powder of the matrix component (not including phosphor particles). The relative density of the fluorescent member is more preferably in the range of 88% or more, and even more preferably 90% or more.

[0055] According to this embodiment, a fluorescent material containing phosphor particles can be provided that is highly densified without high-temperature firing by promoting solid-liquid reactions that promote material transfer in a solid through a liquid phase. Densification reduces pores, providing a fluorescent material with excellent light transmission. Moreover, high thermal conductivity can be achieved by using magnesium oxide as a matrix component. Furthermore, since high-temperature firing at over 250°C is not essential, it is possible to use a variety of phosphor particles. As a result, conventional problems such as deterioration and alteration of phosphor particles due to high-temperature firing and unintended reactions with the matrix part are fundamentally solved, and material design with a higher degree of freedom is possible. As a result, a high-quality fluorescent material can be provided. And a fluorescent material that combines high thermal conductivity and fluorescence can be provided. The fluorescent material of this embodiment is expected to be applied to various components, not just high-power LEDs.

[0056] 3. Light emitting device The light emitting device of the present embodiment includes a semiconductor light emitting element that emits a first light, and a fluorescent member of the present embodiment that is disposed on the light output side of the semiconductor light emitting element and that emits a second light using the first light as excitation light. The light emitting device includes at least one semiconductor light emitting element and at least one fluorescent member, each of which is independent of the other.

[0057] FIG. 1 shows a schematic diagram of a white LED as an example of the light emitting device according to the present embodiment. In the white LED 10, a blue LED 2 is provided on a substrate 1 as a primary light source, and a fluorescent member 5 is provided in at least a part of the emission light path of the blue LED 2. The fluorescent member 5 may be formed in any shape according to the shape of the blue LED 2. A part of the emitted light of the blue LED 2 excites phosphor particles 4, for example, yellow phosphor particles, dispersed in a matrix 3 of the fluorescent member 5, and emits yellow light. In addition, the light of the blue LED 2 that does not contribute to the excitation of the phosphor particles in the fluorescent member passes through the fluorescent member 5 and is emitted from the white LED 10 as blue light. A plurality of emitted lights are mixed together to produce white light from the white LED 10.

[0058] The example in FIG. 1 is just one example, and red and / or green LEDs may be used instead of or in combination with blue LEDs, and fluorescent materials may be used to improve the color quality of the white light. The yellow phosphor particles are just one example, and red and / or green phosphor particles may be used instead of or in combination with yellow phosphor particles. Of course, phosphor particles of other colors may be used. Furthermore, it goes without saying that semiconductor light-emitting elements such as laser diodes may be used instead of LEDs.

[0059] In the case of white LED 10, the thickness of fluorescent member 5 and the concentration of phosphor particles in fluorescent member 5 are appropriately designed to optimize the amount of blue light from blue LED 2 that transmits through fluorescent member 5 and the amount of light that the phosphor particles in fluorescent member 5 absorb and emit light of another wavelength (green light, red light, etc.). The excitation light from the blue LED is, for example, light with a wavelength of 300 nm to 500 nm (light in the ultraviolet region to light in the blue region).

[0060] Instead of the fluorescent member 5 of the white LED 10 of FIG. 1, a white LED 10a using a fluorescent member 20 consisting of a first fluorescent member 21 and a second fluorescent member 22 may be used as shown in FIG. 2. The first fluorescent member 21 contains first phosphor particles 12 in a first matrix 11 that absorb the first light from the blue LED 2 and emits light. On the other hand, the second fluorescent member 22 contains second phosphor particles 14 in a second matrix 13 that absorb the light emitted from the first fluorescent member 21 and emits light with a longer wavelength. By using the fluorescent member 20 in which the first fluorescent member 21 and the second fluorescent member 22 are joined together, it is possible to emit light with a longer wavelength by using a part of the emitted light of the fluorescent member 20 as second excitation light. With this configuration, it is also possible to adjust the color tone of white.

[0061] Example The present invention will be described in more detail below with reference to examples, although the present invention is not limited to the following examples.

[0062] (a) Relative density The relative density was obtained by dividing the density of the fluorescent member measured according to the Archimedes method in accordance with JIS Z 2501:2000 by the true density of the raw material powder of the matrix component (not including phosphor particles). (b) Internal quantum efficiency The quantum efficiency was measured using a quantum efficiency measurement system QE-2000 (manufactured by Otsuka Electronics Co., Ltd.) in a reflection mode at an excitation wavelength of 455 nm. (c) Thermal conductivity The thermal conductivity of each sample was determined in accordance with JIS R 1611 using a laser flash method thermal constant measuring device TC-9000 (manufactured by Advance Riko Co., Ltd.). (d) Emission spectrum The measurement was performed using a quantum efficiency measurement system QE-2000 (manufactured by Otsuka Electronics Co., Ltd.) in reflection mode with 455 nm excitation light, and the emission spectrum was measured from 500 nm to 800 nm. (e) Scanning transmission electron microscope-energy dispersive X-ray analysis (STEM-EDX) To observe the cross-sectional structure of the fluorescent material, the bulk sample after low-temperature sintering was cut into small pieces and thinned using an ion milling device (Gatan Model 691 PIPS) to prepare the measurement sample. The cross-section was then observed using an EDX-equipped scanning transmission electron microscope (JEOL JEM-F200 multi-function analytical transmission electron microscope) and oxygen mapping was performed.

[0063] Examples of fluorescent members and comparative examples are shown below. Example 1 Commercially available magnesium oxide powder (2000A, manufactured by Ube Materials) was prepared as the raw material powder. In order to remove aggregated particles and coarse particles contained in the raw material powder, it was sieved through nylon sieves with openings of 250 μm, 100 μm, 75 μm, and 50 μm in that order. Next, red phosphor CASN (manufactured by Sialon) was added so that the MgO powder was 90 vol% and phosphor particles were 10 vol%, and mixed in a rotation-revolution mixer (product name: Awatori Rentaro, manufactured by Thinky Corporation). Then, 1 g of the mixed powder was filled into a cylindrical stainless steel mold with a diameter of 15 mm, and a temporary compact was produced at room temperature using a uniaxial press (trade name: Hydraulic Shop Press, manufactured by Woodward Fab) at 50 MPa for 30 seconds. Then, the mixture was sealed in a vacuum pack and subjected to a preliminary CIP treatment at 1000 MPa, room temperature, and a holding time of 1 minute using a cold isostatic press (trade name: Dr.CHEF, manufactured by Kobe Steel, Ltd.) to obtain a pre-molded body. Then, 1 part by mass of 0.5 M EDTA aqueous solution (manufactured by Nacalai Tesque, Inc., 0.5 mol / L, pH 8.0) and 5 parts by mass of water (total of 6 parts by mass) were added to the obtained pre-molded body relative to 100 parts by mass of MgO powder, and the pre-molded body was impregnated with an aqueous solution containing a chelating agent by reducing the pressure with an aspirator.

[0064] Thereafter, the mixture was sealed in a vacuum pack and subjected to low-temperature sintering at room temperature using the above-mentioned cold isostatic pressure device at 1000 MPa for a holding time of 60 minutes to obtain a cylindrical sintered body.

[0065] Example 2 A sintered body according to Example 2 was obtained in the same manner as in Example 1, except that a red phosphor CASN (RE-650YMDB, manufactured by Denka Co., Ltd.) was used as the phosphor particles.

[0066] Example 3 A sintered body according to Example 3 was obtained in the same manner as in Example 1, except that NTA (sodium nitrilotriacetate monohydrate, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used as the chelating agent.

[0067] Example 4 A sintered body according to Example 4 was obtained in the same manner as in Example 1, except that IDA (disodium iminodiacetate monohydrate, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used as the chelating agent.

[0068] Comparative Example 1 A sintered body according to Comparative Example 1 was obtained in the same manner as in Example 1, except that no chelating agent was used.

[0069] Comparative Example 2 A sintered body according to Comparative Example 2 was obtained using the same raw materials and process as in Comparative Example 1, except that no process for removing aggregates and coarse particles contained in the raw material powder was carried out.

[0070] (Reference example 1) As the raw MgO powder, DISPERMAG (registered trademark) TN-1 (average particle size 0.57 μm, manufactured by Tateho Chemical Industries Co., Ltd.) and PUREMAG (registered trademark) FNM-G (average particle size 0.54 μm, manufactured by Tateho Chemical Industries Co., Ltd.) were weighed to a mass ratio of 7:3, and mixed with a mixer to obtain a matrix powder mixture. Then, a red phosphor (SiAlON Corporation, CASN) was further added to this mixture as phosphor particles. The raw powder and phosphor particles were thoroughly mixed in a mortar to obtain a phosphor particle-containing mixture so that the volume ratio of the raw powder and the phosphor particles was 9:1, and a pre-molded body was obtained by filling 1 g of this phosphor particle-containing mixture into a cylindrical stainless steel mold with a diameter of 15 mm and performing primary molding with a uniaxial pressure molding machine (product name: Hydraulic Shop Press, manufactured by Woodward Fab) under the conditions of 50 MPa for 30 sec.

[0071] Next, hydrostatic pressure was applied at room temperature at 1000 MPa for 1 min to obtain a preform. The relative density of the preform was 65%. The preform was impregnated with 10% by mass of water under reduced pressure (-0.05 MPa). After that, hydrostatic pressure was applied at room temperature at 1000 MPa for 60 min using a cold isostatic pressurizing device (product name: Dr.CHEF, manufactured by Kobe Steel, Ltd.) to perform low-temperature sintering to obtain a cylindrical sintered body. The relative density of the fluorescent member was 88%.

[0072] Fig. 3 shows the fluorescence spectrum of the fluorescent member of Example 1. The figure also shows the spectrum of the CASN phosphor particles. From the figure, it was confirmed that the fluorescent properties did not change even in the fluorescent member that was sintered after adding a chelating agent.

[0073] Figure 4 shows a TEM image of Reference Example 1, and Figure 5 shows the results of oxygen mapping of Reference Example 1. In Figure 4, there are gaps at the grain boundaries between the MgO particles, and many needle-like and plate-like particles are seen in the gaps. Furthermore, the EDX surface analysis in Figure 5 shows that these grain boundary phases have a higher oxygen ratio than the MgO particles. These figures show that Mg(OH) 2It was confirmed that the matrix was filled with magnesium hydroxide. From the results of Figures 3 to 5 and the results of Table 1, it is understood that the matrix of the fluorescent member has a chelating agent dispersed in the gaps between the magnesium oxide particles, and is filled with magnesium hydroxide.

[0074] <Workability 1> The internal structure of the sintered bodies of the Examples and Comparative Examples was observed using an optical microscope. The evaluation criteria were as follows. The limit resolution of the optical microscope was 0.2 μm (same below). ○: No cracks were found inside when observing the internal structure. ×: Cracks were found inside the specimen when the internal structure was observed.

[0075] <Workability 2> The sintered bodies of the Examples and Comparative Examples were subjected to dry polishing by machining to evaluate the processability. The evaluation criteria were as follows: ○: Processing to a thickness of 0.1 mm is possible by dry polishing, and no cracks or chips are found in the external appearance or internal structure of the processed sample. ×: When the sample is processed to a thickness of 0.1 mm by dry polishing, the sample is destroyed during processing. Alternatively, cracks or chips are confirmed in the appearance or internal structure of the sample after processing.

[0076] The results of the relative density (after sintering), density, quantum efficiency, thermal conductivity, and processability of each example are shown in Table 1. The amount of chelating agent added per 100 parts by mass of magnesium oxide in the preform is also shown in Table 1. Also, blank in Table 1 indicates that no experiment was performed. [Table 1] [Industrial Applicability]

[0077] The fluorescent member according to the present invention can be used as a component of light-emitting devices such as white LEDs and high-power LEDs, and can be used in a variety of applications in combination with components such as displays, such as vacuum fluorescent display tubes (VFDs) and PDPs, because it has high thermal conductivity, fluorescence, and machinability. It can also be used for applications other than fluorescent members for wavelength conversion, such as stress-induced light-emitting devices, electron beam irradiation light-emitting devices, and thermoluminescence light-emitting devices. [Explanation of symbols]

[0078] 1 Board 2 Blue LEDs 3. Matrix 4. Phosphor particles 5 Fluorescent materials 10 white LED 11 First Matrix 12 First phosphor particles 13 The Second Matrix 14 Second phosphor particles 21 First fluorescent member 22 Second fluorescent member

Claims

1. a matrix containing magnesium oxide and magnesium hydroxide as main components, a chelating agent being present in gaps between magnesium oxide particles, and magnesium hydroxide being filled therein; and a fluorescent member which is a sintered body for wavelength conversion containing phosphor particles dispersed in the matrix.

2. a semiconductor light emitting element that emits a first light; A light emitting device comprising: the fluorescent member according to claim 1 , which is disposed on a light emission side of the semiconductor light emitting element, and which emits a second light in response to the first light as excitation light.

3. Obtaining a mixture of at least a matrix raw material powder and phosphor particles; preforming the mixture to obtain a preform; The method includes a step of impregnating the preformed body with water and a chelating agent, and then obtaining a sintered body by sintering under pressure, and does not include a process of treating the preformed body after the water impregnation at a high temperature exceeding 250°C; A method for manufacturing a fluorescent member, wherein the matrix is ​​mainly composed of magnesium oxide and magnesium hydroxide.

4. 4. The method for producing a fluorescent member according to claim 3, further comprising the step of removing particles having a particle diameter of 50 μm or more from the raw material powder.

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