Method for producing metal sulfide precursor and method for producing metal sulfide

Abstract

Provided are a method for producing a metal sulfide precursor and a method for producing a metal sulfide, by which a metal sulfide that is fine and has a low carbon content can be easily obtained. The method for producing a metal sulfide precursor comprises: a step in which a first raw-material liquid including a first organic solvent, which has a boiling point of 110°C or lower, and a metal salt, is prepared; a step in which a second raw-material liquid including a second organic solvent, which has a boiling point of 110°C or lower, sulfur, and an alkali metal sulfide, is prepared; a step in which the first raw-material liquid and the second raw-material liquid are mixed to obtain a reaction liquid including a metal sulfide precursor and an alkali metal salt; and a step in which the metal sulfide precursor is recovered from the reaction liquid.

Description

METHOD FOR PRODUCING METAL SULFIDE PRECURSORS AND METHOD FOR PRODUCING METAL SULFIDES

[0001] The present invention relates to a method for producing a metal sulfide precursor and a method for producing a metal sulfide.

[0002] Metal sulfides are compounds composed of divalent sulfur anions (sulfide ions) and metal cations, and are used in a variety of applications, including fluorescent materials, batteries, catalysts, semiconductors, pigments, and pharmaceuticals.

[0003] A known method for producing metal sulfides involves calcining a solid metal source, such as a carbonate or oxide, in an atmosphere of a sulfur-containing gas, such as hydrogen sulfide. Patent Document 1, for example, discloses a method for producing metal sulfides by reacting a metal carbonate with hydrogen sulfide in the presence of hydrogen and / or water vapor (claim 1 of Patent Document 1). The resulting metal sulfides are also described as being suitable for use as raw materials for engineering plastics, ion-conductive solid electrolytes for batteries, lubricants, and intermediate raw materials for chemicals (paragraph

[0017] of Patent Document 1).

[0004] Patent Document 2 describes (Sr １－ｘ－ｙ M １ ｙ EU ｘ ) Ga ２ S ４ (M １ is at least one element selected from the group consisting of Be, Mg, Ca, Ba, and Zn), ３ , Eu ２ O ３ and Ga ２ O ３ and the resulting raw material mixture was mixed with hydrogen sulfide (H ２ It is disclosed that phosphor particles are produced by heating the material in an atmosphere containing fluorine-containing compounds (Claim 1 and

[0043] of Patent Document 2).

[0005] Also known is a method of producing metal sulfides by reacting a metal source with sulfur in a solvent. For example, Non-Patent Document 1 discloses a method of synthesizing Mg polysulfides by reacting magnesium (Mg) powder with sulfur (S) in an N-methylimidazole solution (see page 1063, Figure 1a) of Non-Patent Document 1).

[0006] JP 2014-055097 A JP 2016-180023 A

[0007] Sara Drvaric Talian et al., ChemElectroChem 2021, 8, 1062-1069

[0008] Although methods for producing metal sulfides have been known for some time, there is room for improvement in these conventional methods. In other words, metal sulfides are sometimes required to have fine particles. For example, the smaller the particle size of a catalytic metal sulfide, the larger the contact area with the outside, resulting in higher catalytic performance. Therefore, a certain degree of particle size is required. Furthermore, with the demand for higher resolution in metal sulfides for display phosphors, package sizes are becoming smaller, and there is a demand for finer phosphor powders to be filled into these packages.

[0009] However, conventional methods of calcining raw materials (metal sources) in a sulfur-containing atmosphere require calcining the raw materials at high temperatures for long periods of time, which often results in particle growth during calcination, resulting in hard, coarse particles. While pulverization is an option, strong pulverization is required to break down the hard, coarse particles (intragranular fracture). However, even with strong pulverization, there is a limit to how fine the resulting powder can be. Therefore, it is difficult to obtain fine metal sulfides. Furthermore, sulfur-containing gases such as hydrogen sulfide used during calcination are highly corrosive, toxic, and flammable, making their use dangerous and requiring additional equipment such as exhaust gas treatment equipment and explosion-proof equipment. This results in problems of a complex manufacturing process and increased manufacturing costs.

[0010] Furthermore, in the method of obtaining polysulfides by reacting a metal source with sulfur in a high-boiling point imidazole solvent, as described in Non-Patent Document 1, it is difficult to completely remove the solvent from the obtained polysulfides because of the high boiling point of the solvent used. When sulfides are obtained by thermal decomposition of such polysulfides, the obtained sulfides are fine, but contain a large amount of carbon, making it difficult to obtain high-purity sulfides.

[0011] As described above, it has been difficult to obtain fine metal sulfides with a low carbon content by a simple method using conventional methods.

[0012] The present inventors have conducted extensive research in light of these problems, and as a result have discovered that a metal sulfide that is fine and has a low carbon content can be obtained by a simple method by reacting a metal salt with an alkali metal sulfide or ammonium sulfide with a metal salt in a low-boiling solvent.

[0013] The present invention was completed based on such findings, and an object of the present invention is to provide a method for producing a metal sulfide precursor and a method for producing a metal sulfide, which are capable of obtaining fine metal sulfides having a low carbon content by a simple method.

[0014] The present invention encompasses the following aspects (1) to (19). In this specification, the expression "to" includes both the numerical values ​​at both ends. That is, "X to Y" is synonymous with "X or more and Y or less." In addition, in this specification, any combination of suitable aspects can be adopted as long as technical consistency can be achieved. For example, one of the suitable numerical ranges can be combined with the other.

[0015] (1) A method for producing a metal sulfide precursor, the method comprising: preparing a first source liquid containing a first organic solvent having a boiling point of 110°C or less and a metal salt; preparing a second source liquid containing a second organic solvent having a boiling point of 110°C or less, sulfur, and an alkali metal sulfide; mixing the first source liquid and the second source liquid to obtain a reaction liquid containing the metal sulfide precursor and the alkali metal salt; and recovering the metal sulfide precursor from the reaction liquid.

[0016] (2) A method for producing a metal sulfide precursor, the method comprising: preparing a third source liquid containing a third organic solvent having a boiling point of 110°C or less and a metal salt; preparing a fourth source liquid containing a fourth organic solvent having a boiling point of 110°C or less and ammonium sulfide; mixing the third source liquid and the fourth source liquid to obtain a reaction liquid containing a metal sulfide precursor and an ammonium salt; and recovering the metal sulfide precursor from the reaction liquid.

[0017] (3) The method according to (2) above, wherein in the step of preparing the fourth raw material liquid, the ammonium sulfide contains a polysulfide of ammonium sulfide.

[0018] (4) Any of the above methods (1) to (3), further comprising a step of drying the recovered metal sulfide precursor.

[0019] (5) A method for producing a metal sulfide, comprising the step of calcining a metal sulfide precursor obtained by any one of the methods (1) to (3) above.

[0020] (6) The method according to (5) above, wherein the carbon content of the metal sulfide is 9000 ppm or less and the average primary particle diameter (D50) as determined by SEM observation is 30.0 μm or less.

[0021] (7) A method for producing a metal sulfide, comprising: a step of mixing a first metal sulfide precursor and a second metal sulfide precursor to obtain a mixed metal sulfide precursor; and a step of calcining the mixed metal sulfide precursor, wherein the first metal sulfide precursor is the metal sulfide precursor obtained by the method (1) above, and the second metal sulfide precursor is the metal sulfide precursor obtained by the method (2) or (3) above.

[0022] (8) The method according to (7), wherein the carbon content of the metal sulfide is 9000 ppm or less and the average primary particle diameter (D50) as determined by SEM observation is 30.0 μm or less.

[0023] (9) A phosphor powder containing at least a Group 2 element (A), sulfur (S), and a luminescent center element (M), having a volume-based cumulative 90% diameter (D90) of 10.0 μm or less, and having a lattice distortion (σ) of 0.300% or less as determined by analyzing an X-ray diffraction profile using the WPPF method.

[0024] (10) The phosphor powder of (9) above, having a cumulative 50% diameter (D50) on a volume basis of 0.050 μm or more and 10.0 μm or less.

[0025] (11) The phosphor powder of (9) or (10) above, wherein the product (D50×σ) of the cumulative 50% diameter (D50) on a volume basis and the lattice distortion (σ) is 0.40 μm·% or less.

[0026] (12) The phosphor powder has the formula: Ca １－ｘ Sr ｘ A phosphor powder according to any one of (9) to (11) above, having a composition represented by S:M (where M is a luminescent center element, and x is 0≦x≦1).

[0027] (13) The phosphor powder according to (12) above, wherein the luminescent center atom M contains europium (Eu).

[0028] (14) The phosphor powder according to any one of (9) to (13) above, which has an internal quantum efficiency of 40% or more.

[0029] (15) An inkjet ink containing the phosphor powder according to any one of (9) to (14) above and a solvent.

[0030] (16) A light-emitting device comprising an excitation source and the phosphor powder of any one of (9) to (14) above, wherein the phosphor powder is excited by irradiation with light from the excitation source to emit visible light.

[0031] (17) A light-emitting device comprising the light-emitting element of (16) above.

[0032] (18) The light-emitting device according to (17) above, which is a display.

[0033] (19) A method for producing a phosphor powder, comprising the following steps: preparing a first raw material liquid (first solution) containing a first organic solvent (first solvent) and a salt of a Group 2 element (A) and a salt of a luminescent center element (M) dissolved or dispersed in the first organic solvent; preparing a second raw material liquid (second solution) containing a second organic solvent (second solvent), sulfur (S), and an alkali metal sulfide dissolved in the second organic solvent; mixing and stirring the first raw material liquid and the second raw material liquid to obtain a reaction liquid (third solution) in which a sulfide containing a Group 2 element and a luminescent center element is dissolved and a precipitate containing an alkali metal salt is deposited; subjecting the reaction liquid to solid-liquid separation treatment to remove the precipitate; drying the reaction liquid from which the precipitate has been removed to obtain a phosphor precursor composed of a polysulfide containing a Group 2 element and a luminescent center element; firing the phosphor precursor to obtain a fired phosphor; The method includes a step of crushing the fired phosphor material by a pressurized jet type wet media-less crushing method or a shaking type wet media-less crushing method to obtain a crushed phosphor material.

[0034] According to the present invention, there are provided a method for producing a metal sulfide precursor and a method for producing a metal sulfide, which are capable of obtaining fine metal sulfides having a low carbon content by a simple method.

[0035] 1 shows an SEM image of a metal sulfide (Example A7). 2 shows an SEM image of a metal sulfide (Example A8). 3 shows an SEM image of a phosphor synthesized by a wet method (liquid phase method). 4 shows an SEM image of a phosphor synthesized by a dry method (solid phase method).

[0036] Specific embodiments of the present invention (hereinafter referred to as "present embodiments") are described below. However, the present invention is not limited to the following embodiments, and various modifications are possible within the scope of the present invention. Furthermore, in this specification, any combination of preferred aspects can be adopted as long as technical consistency can be achieved. For example, one preferred numerical range and another preferred numerical range can be combined arbitrarily.

[0037] <<1. Method for Producing Metal Sulfide Precursor>> This embodiment relates to a method for producing a metal sulfide precursor. The metal sulfide precursor is composed of a plurality of inorganic compound particles containing metal and sulfur. The metal sulfide precursor may be crystalline or amorphous. Furthermore, the metal sulfide precursor may be a polysulfide containing a chain of sulfur atoms (polysulfide), or may not be a polysulfide.

[0038] The metal sulfide precursor can be a precursor of a metal sulfide. That is, a metal sulfide can be obtained by calcining the metal sulfide precursor. However, the metal sulfide precursor of this embodiment is not limited to those used for producing metal sulfides. The metal sulfide precursor itself can be used for the desired application.

[0039] The type of metal contained in the metal sulfide precursor is not particularly limited. Examples of metals include at least one selected from the group consisting of lithium (Li), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), scandium (Sc), yttrium (Y), titanium (Ti), molybdenum (Mo), manganese (Mn), iron (Fe), ruthenium (Ru), cobalt (Co), nickel (Ni), copper (Cu), silver (Ag), zinc (Zn), aluminum (Al), gallium (Ga), Se (selenium), indium (In), tin (Sn), lead (Pb), arsenic (As), antimony (Sb), bismuth (Bi), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), ytterbium (Yb), and lutetium (Lu). The metal sulfide precursor may contain one metal alone or two or more metals in combination, and as used herein, the term "metal" includes metalloids.

[0040] The method for producing a metal sulfide precursor in this embodiment includes a first aspect and a second aspect, each of which will be described below.

[0041] [First Aspect] A method for producing a metal sulfide precursor in a first aspect includes the following steps: a step of preparing a first feedstock solution containing a first organic solvent having a boiling point of 110°C or less and a metal salt (first feedstock solution preparation step), a step of preparing a second feedstock solution containing a second organic solvent having a boiling point of 110°C or less, sulfur, and an alkali metal sulfide (second feedstock solution preparation step), a step of mixing the prepared first feedstock solution and second feedstock solution to obtain a reaction solution containing a metal sulfide precursor and an alkali metal salt (reaction step), and a step of recovering the metal sulfide precursor from the obtained reaction solution (recovery step). Each step will be described in detail below.

[0042] <First Raw Material Liquid Preparation Step> In the first raw material liquid preparation step, a first raw material liquid containing a first organic solvent having a boiling point of 110° C. or less and a metal salt is prepared.

[0043] The first organic solvent contains a metal salt dissolved or dispersed therein and functions to form a reaction field in the subsequent reaction step. From the viewpoint of efficiently obtaining fine and highly pure sulfides, the boiling point of the first organic solvent is preferably 110°C or less, more preferably 100°C or less, and even more preferably 80°C or less. In this specification, the boiling point refers to the value under 1 atmosphere. Specifically, the first organic solvent is preferably at least one alcohol selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, 2-butanol, isobutyl alcohol, and tert-butyl alcohol. It is desirable that the amount of water contained in the first organic solvent be as small as possible. Specifically, the amount of water is preferably 5.0% by mass or less, more preferably 0.5% by mass or less. Furthermore, it is preferable that the amount of the first organic solvent is an amount that can sufficiently dissolve or disperse the metal salt.

[0044] The metal salt is a raw material for a metal (hereinafter, sometimes referred to as a "first metal") that is the main component of the target metal sulfide or its precursor (metal sulfide precursor). Therefore, the type of metal salt can be determined depending on the composition of the target metal sulfide. Although not limited thereto, the first metal can be lithium (Li), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), scandium (Sc), yttrium (Y), titanium (Ti), molybdenum (Mo), manganese (Mn), iron (Fe), ruthenium (Ru), cobalt (Co), nickel (Ni), copper (Cu), silver (Ag), zinc (Zn), aluminum (Al), gallium (Ga), Se (Se), or the like. Examples of suitable metal salts include at least one selected from the group consisting of arsenic (As), indium (In), tin (Sn), lead (Pb), arsenic (As), antimony (Sb), bismuth (Bi), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), ytterbium (Yb), and lutetium (Lu). Among these, at least one selected from the group consisting of lithium (Li), calcium (Ca), strontium (Sr), and barium (Ba) is particularly preferred. The metal salt may contain one metal alone or two or more metals in combination. The salt may be not only an inorganic salt such as a nitrate, chloride, sulfate, or carbonate, but also an organic salt such as an acetate or formate. Among these, at least one salt selected from the group consisting of chlorides, nitrates and formates is particularly preferred.

[0045] The amount of the metal salt is preferably 0.5 to 5.0 times, in terms of molar ratio, the amount of the alkali metal sulfide added when preparing the second liquid feedstock.

[0046] The method for preparing the first raw material liquid is not limited as long as the first raw material liquid contains a first organic solvent and a metal salt dissolved or dispersed in the first organic solvent. For example, the first raw material liquid can be prepared by adding a metal salt to the first organic solvent and stirring the mixture. ２The first raw material liquid can be stirred under an inert gas atmosphere such as argon (Ar) or the like, or at room temperature and normal pressure. For example, the first raw material liquid may be stirred while being maintained at a temperature of 0°C or higher and 60°C or lower under atmospheric pressure. More preferably, the first raw material liquid is handled in an inert gas atmosphere to suppress the generation of sulfates, oxides, and hydroxides. Furthermore, when the target metal sulfide contains elements other than metal and sulfur, salts of the other elements may be added to the first raw material liquid.

[0047] <Second Feedstock Liquid Preparing Step> In the second feedstock liquid preparing step, a second feedstock liquid containing a second organic solvent having a boiling point of 110° C. or less, sulfur (S), and an alkali metal sulfide is prepared.

[0048] The second organic solvent is an alkali metal sulfide (AM ２ The second organic solvent contains dissolved or dispersed sulfur (AM, S; where AM is an alkali metal element, and S is sulfur) and functions to form a reaction field in the subsequent reaction step. From the viewpoint of efficiently obtaining fine and highly pure sulfides, the boiling point of the second organic solvent is preferably 110°C or less, more preferably 100°C or less, and even more preferably 80°C or less. Specifically, the second organic solvent is preferably at least one alcohol selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, 2-butanol, isobutyl alcohol, and tert-butyl alcohol. It is desirable that the amount of water contained in the second organic solvent be as small as possible. Specifically, the amount of water is preferably 5.0% by mass or less, more preferably 0.5% by mass or less. The type of the second organic solvent may be the same as or different from that of the first organic solvent. The amount of the second organic solvent is preferably an amount that can sufficiently dissolve or disperse the alkali metal sulfide.

[0049] Sulfur (S) is a raw material for sulfur, which is the main component of the target metal sulfide or its precursor. That is, metal sulfides can be obtained by using sulfur as a raw material. In particular, by using a large amount of sulfur, polysulfides that can be easily crushed can be obtained, and fine metal sulfides can be efficiently produced.

[0050] The amount of sulfur blended is preferably 1.0 to 10.0 times the amount of alkali metal sulfide in terms of molar ratio, from the viewpoint of allowing the sulfur to react in an appropriate amount. In addition, from the viewpoint of enhancing reactivity, the sulfur is preferably in powder form.

[0051] Alkali metal sulfides (AM ２ S) has the function of reacting with the anion component of the metal salt contained in the first raw material liquid to form a by-product that is easily removed. By using an alkali metal sulfide, the anion component can be removed in the form of an alkali metal salt. In addition, the alkali metal sulfide is also a raw material for sulfur, which is the main component of metal sulfides and their precursors. The alkali metal sulfide is preferably a sulfide of at least one alkali metal selected from the group consisting of lithium (Li), sodium (Na), potassium (K), and hydrates thereof, and sodium sulfide (Na ２ S) is particularly preferred.

[0052] The method for preparing the second raw material liquid is not limited as long as the second raw material liquid contains a second organic solvent and sulfur and an alkali metal sulfide dissolved or dispersed in the second organic solvent. For example, the second raw material liquid can be prepared by adding sulfur and an alkali metal sulfide to the second organic solvent and stirring them. ２ The second raw material liquid may be stirred in an inert gas atmosphere such as nitrogen (N) or argon (Ar), or at room temperature and normal pressure. For example, the second raw material liquid may be stirred while being maintained at a temperature of 0° C. or higher and 60° C. or lower under atmospheric pressure. It is more preferable to handle the second raw material liquid in an inert gas atmosphere in order to suppress the generation of sulfates, oxides, and hydroxides.

[0053] When preparing the first raw material liquid, a metal salt is dissolved or dispersed in a first organic solvent. Preferably, the metal salt is dissolved in the first organic solvent. From this viewpoint, it is desirable that the first organic solvent is a solvent that has high solubility for the metal salt. Similarly, it is desirable that the second organic solvent is a solvent that has high solubility for the alkali metal sulfide.

[0054] Meanwhile, in the subsequent reaction step, an ion exchange reaction occurs between the metal salt, the alkali metal sulfide, and sulfur, producing a metal sulfide precursor, which is a polysulfide containing a metal element, and an alkali metal salt as a by-product. While the polysulfide (metal sulfide precursor) dissolves in the solvent (a mixed solvent of the first organic solvent and the second organic solvent), the alkali metal salt (by-product) is barely soluble and forms a precipitate. The by-product can be removed by subjecting the solution after the reaction step to solid-liquid separation. From the perspective of removing as many by-products as possible to obtain a high-purity metal sulfide precursor, it is desirable that the first organic solvent and the second organic solvent have low solubility for the alkali metal salt (by-product).

[0055] From the above viewpoints, it is preferable to select a combination of the first organic solvent, the second organic solvent, sulfur, the metal salt, and the alkali metal sulfide. Although not limited thereto, the first organic solvent and the second organic solvent are preferably at least one alcohol selected from the group consisting of methanol, ethanol, and 1-propanol, the metal salt is preferably a chloride, and the alkali metal sulfide is preferably sodium sulfide (Na ２ S) is preferred.

[0056] Furthermore, the order of the first raw material liquid preparation step and the second raw material liquid preparation step is not limited as long as the first raw material liquid and the second raw material liquid are prepared.

[0057] <Reaction Step> In the reaction step, the first and second raw material liquids are mixed to obtain a reaction solution containing a metal sulfide precursor and an alkali metal salt. When the first and second raw material liquids are mixed, an ion exchange reaction occurs between the metal salt, alkali metal sulfide, and sulfur contained therein, producing a metal sulfide precursor, which is a polysulfide containing a metal, and an alkali metal salt as a by-product. The polysulfide (metal sulfide precursor) dissolves in the reaction solution, while the alkali metal salt (by-product) is barely soluble and forms a precipitate.

[0058] For example, calcium chloride (CaCl ２ ) was selected as the alkali metal sulfide, and sodium sulfide (Na ２When ethanol is used as both the first and second organic solvents, the reaction shown in the following formula (1) proceeds to the right, and calcium-containing polysulfides (CaS ｘ (where 2≦x)) and sodium chloride (NaCl) are produced in ethanol.

[0059] CaCl ２ +Na ２ S+S → CaS ｘ +NaCl↓ (1)

[0060] CaS ｘ While CaS has a high solubility in ethanol, NaCl has a low solubility. Therefore, NaCl hardly dissolves and forms a precipitate. Therefore, if the precipitate (NaCl) is removed from the reaction solution (ethanol) in the subsequent recovery step, the metal sulfide precursor (CaS ｘ ) can be recovered.

[0061] The method of mixing the first and second raw material liquids is not particularly limited. The second raw material liquid may be added to the first raw material liquid, the first raw material liquid may be added to the second raw material liquid, or the first and second raw material liquids may be added and mixed simultaneously. In addition, the mixing and the resulting reaction may be carried out by using nitrogen (N ２ The mixing can be carried out in an inert gas atmosphere such as argon (Ar) or the like, or at room temperature and normal pressure. Specifically, the mixing may be carried out at a temperature of 0° C. or higher and 60° C. or lower under atmospheric pressure. It is more preferable to handle the mixture in an inert gas atmosphere in order to suppress the generation of sulfates, oxides, and hydroxides.

[0062] The addition rate of the first and second raw material liquids is preferably 50 ml / min to 200 ml / min. A rate of 50 ml / min or more facilitates the recovery of by-products. A rate of 200 ml / min or less allows the metal sulfide precursor to be obtained with good productivity.

[0063] <Recovery Step> In the recovery step, the metal sulfide precursor is recovered from the reaction solution. As described above, the polysulfide (metal sulfide precursor) dissolves in the reaction solution, whereas the alkali metal salt (by-product) is barely soluble and forms a precipitate. Therefore, if the reaction solution is subjected to solid-liquid separation, the by-product as a precipitate can be separated and removed, and the metal sulfide precursor can be recovered. The solid-liquid separation can be performed by a known method, such as filtration, centrifugation, or decantation. The method is not limited as long as it can remove the precipitate.

[0064] In this way, the metal sulfide precursor can be recovered. The recovered metal sulfide precursor is in a solution state dissolved in the reaction liquid.

[0065] <Drying step> If necessary, a step of drying the recovered metal sulfide precursor (drying step) may be provided. As described above, the metal sulfide precursor recovered through the recovery step is in a solution state. By drying the metal sulfide precursor in solution, a solid metal sulfide precursor can be obtained.

[0066] Drying may be performed by a known method, such as heat drying or vacuum drying. Drying conditions vary depending on the type of solvent (first organic solvent, second organic solvent) used, and therefore cannot be determined in general. When ethanol is used, for example, conditions include maintaining the mixture at 40°C or higher and 70°C or lower for 1 hour to 72 hours.

[0067] <Washing Step> If necessary, a step of washing the metal sulfide precursor (washing step) may be provided. The metal sulfide precursor recovered in the recovery step may contain impurities derived from by-products such as alkali metals. Furthermore, excess metal elements and sulfur components may remain. By performing the washing treatment, these by-products and excess components can be reduced, and a highly pure metal sulfide can be obtained.

[0068] The washing method is not limited as long as it can reduce by-products and excess components. For example, a method of washing the metal sulfide precursor with a washing liquid such as water can be used. Specifically, a method of putting the metal sulfide precursor into a washing liquid and performing a series of operations of stirring, leaving the mixture to stand, and removing the supernatant liquid once or multiple times can be used. When washing with a washing liquid, a step of drying the washed metal sulfide precursor under heating and / or reduced pressure can be provided.

[0069] In this way, a metal sulfide precursor can be obtained. The obtained metal sulfide precursor can be used to produce metal sulfides. In addition, the metal sulfide precursor itself can be used for desired applications.

[0070] [Second Aspect] A method for producing a metal sulfide precursor in a second aspect includes the following steps: a step of preparing a third feedstock liquid containing a third organic solvent having a boiling point of 110°C or less and a metal salt (third feedstock liquid preparation step), a step of preparing a fourth feedstock liquid containing a fourth organic solvent having a boiling point of 110°C or less and ammonium sulfide (fourth feedstock liquid preparation step), a step of mixing the prepared third feedstock liquid and fourth feedstock liquid to obtain a reaction liquid containing a metal sulfide precursor and an ammonium salt (reaction step), and a step of recovering the metal sulfide precursor from the obtained reaction liquid (recovery step).

[0071] <Third Raw Material Liquid Preparing Step> In the third raw material liquid preparing step, a third raw material liquid containing a third organic solvent having a boiling point of 110° C. or less and a metal salt is prepared.

[0072] The third organic solvent contains a metal salt dissolved or dispersed therein and functions to form a reaction field in the subsequent reaction step. From the viewpoint of efficiently obtaining fine and highly pure sulfides, the boiling point of the third organic solvent is preferably 110°C or less, more preferably 100°C or less, and even more preferably 80°C or less. Specifically, the third organic solvent is preferably at least one selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, 2-butanol, isobutyl alcohol, and tert-butyl alcohol. It is desirable that the amount of water contained in the third organic solvent be as small as possible. Specifically, the amount of water is preferably 5.0% by mass or less, more preferably 0.5% by mass or less. Furthermore, it is preferable that the amount of the third organic solvent is an amount that can sufficiently dissolve or disperse the metal salt.

[0073] The metal salt is a raw material for a metal (hereinafter, sometimes referred to as a "second metal") that is the main component of the target metal sulfide or its precursor (metal sulfide precursor). Therefore, the type of second metal can be determined depending on the composition of the target metal sulfide. Although not limited thereto, the second metal can be lithium (Li), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), scandium (Sc), yttrium (Y), titanium (Ti), molybdenum (Mo), manganese (Mn), iron (Fe), ruthenium (Ru), cobalt (Co), nickel (Ni), copper (Cu), silver (Ag), zinc (Zn), aluminum (Al), gallium (Ga), Se (Se), and the like. Examples of the element include at least one selected from the group consisting of zinc (Zn), zinc oxide (Zn), zinc tin (Zn), zinc oxide (Zn), zinc fluoride ... Among these, at least one selected from the group consisting of scandium (Sc), yttrium (Y), titanium (Ti), molybdenum (Mo), manganese (Mn), iron (Fe), ruthenium (Ru), cobalt (Co), nickel (Ni), copper (Cu), silver (Ag), zinc (Zn), aluminum (Al), gallium (Ga), selenium (Se), indium (In), tin (Sn), lead (Pb), arsenic (As), antimony (Sb), bismuth (Bi), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), ytterbium (Yb), and lutetium (Lu) is particularly preferred. The metal salt may contain one type of metal alone or two or more types of metals in combination. The salt may be an inorganic acid salt such as a nitrate, chloride, sulfate, or carbonate, or an organic acid salt such as an acetate or formate.

[0074] The method for preparing the third raw material liquid is not limited as long as the third raw material liquid contains a third organic solvent and a metal salt dissolved or dispersed in the third organic solvent. For example, the third raw material liquid can be prepared by adding a metal salt to the third organic solvent and stirring the mixture. ２ The third raw material liquid can be stirred under an inert gas atmosphere such as argon (Ar) or the like, or at room temperature and normal pressure. For example, the third raw material liquid may be stirred while being maintained at a temperature of 0°C or higher and 60°C or lower under atmospheric pressure. More preferably, the third raw material liquid is handled in an inert gas atmosphere to suppress the generation of sulfates, oxides, and hydroxides. Furthermore, when the target metal sulfide contains elements other than metal and sulfur, salts of the other elements may be added to the third raw material liquid.

[0075] <Fourth Raw Material Solution Preparation Step> In the fourth raw material solution preparation step, a fourth raw material solution containing a fourth organic solvent having a boiling point of 110° C. or less and ammonium sulfide is prepared.

[0076] The fourth organic solvent contains ammonium sulfide dissolved or dispersed therein and functions to form a reaction field in the subsequent reaction step. From the viewpoint of efficiently obtaining fine and highly pure sulfides, the boiling point of the fourth organic solvent is preferably 110°C or less, more preferably 100°C or less, and even more preferably 80°C or less. Specifically, the fourth organic solvent is preferably at least one alcohol selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, 2-butanol, isobutyl alcohol, and tert-butyl alcohol. It is desirable that the amount of water contained in the fourth organic solvent be as small as possible. Specifically, the amount of water is preferably 5.0% by mass or less, more preferably 0.5% by mass or less. The type of the fourth organic solvent may be the same as or different from that of the third organic solvent. Furthermore, it is preferable that the amount of the fourth organic solvent is an amount that can sufficiently dissolve or disperse ammonium sulfide.

[0077] Ammonium sulfide has the function of reacting with the anion component of the metal salt contained in the third raw material liquid to form a by-product that is easy to remove. By using ammonium sulfide, the anion component can be removed in the form of ammonium salt. Furthermore, ammonium sulfide is also a raw material for sulfur, which is the main component of metal sulfides and their precursors. Note that ammonium sulfide may or may not be a polysulfide (ammonium polysulfide). Ammonium polysulfide can be obtained by reacting (NH ４ ) ２ It can be produced by the reaction of S with sulfur (S).

[0078] The amount of ammonium sulfide is preferably 1.0 to 10.0 times, in terms of molar ratio, the amount of the metal salt added when preparing the third liquid feedstock.

[0079] The method for preparing the fourth raw material solution is not limited as long as the fourth raw material solution contains a fourth organic solvent and ammonium sulfide dissolved or dispersed in the fourth organic solvent. For example, the fourth raw material solution can be prepared by the following procedure. First, an alkali metal sulfide (AM) is added to a solvent (fourth organic solvent). ２ S) and ammonium chloride (NH ４ The alkali metal sulfide may be at least one alkali metal sulfide selected from the group consisting of lithium (Li), sodium (Na), potassium (K), and hydrates thereof. The blending ratio of the alkali metal sulfide and ammonium chloride is 1:1, where 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, 20:1, 21:1, 22:1, 23:1, 24:1, 25:1, 26:1, 27:1, 28:1, 29:1, 30:1, 31:1, 32:1, 33:1, 34:1, 35:1, 36:1, 37:1, 38:1, 39:1, 40:1, 41:1, 42:1, 43:1, 44:1, 45:1, 46:1, 47:1, 48:1, 49:1, 50:1, 51:1, 52:1, 53:1, 54:1, 55:1, 56:1, 57:1, 58:1, 59:1, 60:1, 61:1, 62:1, 63:1, 64:1, 65:1, 66:1, 67:1, 68:1, 69:1, 70:1, 71:1, 72:1, 73:1, 74:1, 75:1, 76:1, 77:1 ２ S:NH ４ The ratio of Cl to ammonium sulfide is preferably 1:2 to 1:3. Mixing can be performed using a known mixing device such as a wet ball mill. The solvent temperature during mixing can be set to, for example, 0°C or higher and 40°C or lower. By mixing, the reaction shown in the following formula (2) proceeds to the right, and ammonium sulfide ((NH ４ ) ２ S) and alkali metal chloride (AMCl) are produced.

[0080] AM ２ S+2NH ４ Cl → (NH ４ ) ２ S+2AMCl↓...(2)

[0081] When alcohol is used as a solvent, ammonium sulfide ((NH ４ ) ２ While ammonium sulfide (S) dissolves in the solvent, the alkali metal sulfide (AMCl) does not dissolve in the solvent and forms a precipitate. Therefore, by subjecting the liquid after the reaction to solid-liquid separation treatment, the alkali metal sulfide by-product can be removed, and a solution in which ammonium sulfide is dissolved can be obtained as the fourth raw material liquid.

[0082] In the fourth raw material solution, ammonium sulfide may contain a polysulfide of ammonium sulfide (ammonium polysulfide). That is, a part or all of the ammonium sulfide contained in the fourth raw material solution may be a polysulfide (ammonium polysulfide). Ammonium polysulfide can be formed, for example, by adding sulfur to the fourth raw material solution. That is, when sulfur is added, the sulfur is converted into ammonium sulfide ((NH ４ ) ２ S) to form ammonium polysulfide ((NH ４ ) ２ S ｘ (where x is 2 or less). Ammonium polysulfide also reacts with the anion component of the metal salt contained in the third raw material liquid to form a by-product that is easy to remove. While the polysulfide (metal sulfide precursor) dissolves in the solvent (a mixed solvent of the third organic solvent and the fourth organic solvent), the ammonium salt (by-product) hardly dissolves and forms a precipitate. The by-product can be removed by subjecting the solution after the reaction step to solid-liquid separation treatment. From the viewpoint of removing as many by-products as possible to obtain a high-purity metal sulfide precursor, it is desirable that the third organic solvent and the fourth organic solvent have low solubility for the ammonium salt (by-product). The amount of sulfur added is (NH ４ ) ２ The molar ratio of the amount of S is preferably 1.0 to 5.0 times.

[0083] <Reaction Step> In the reaction step, the third and fourth raw material liquids are mixed to obtain a reaction solution containing a metal sulfide precursor and an ammonium salt. When the third and fourth raw material liquids are mixed, an ion exchange reaction occurs between the metal salt contained therein and ammonium sulfide, producing a metal sulfide precursor and an ammonium salt as a by-product. The metal sulfide precursor dissolves or disperses in the reaction solution. The ammonium salt (by-product) is barely dissolved and forms a precipitate.

[0084] For example, gallium formate (Ga(HCOO) ３ ) and ethanol (third organic solvent), and ammonium sulfide ((NH ４ ) ２ S) and ethanol (fourth organic solvent) are mixed and reacted with a fourth raw material solution containing gallium sulfide (Ga ２ S ３ ) and ammonium formate (HCOONH ４ ) is produced in ethanol.

[0085] 2Ga(HCOO) ３ +3 (NH ４ ) ２ S → Ga ２ S ３ ↓+6HCOONH ４ ↓・・・(3)

[0086] Gallium sulfide has low solubility in ethanol. Therefore, it hardly dissolves in ethanol and forms a precipitate. Ammonium formate has relatively low solubility in ethanol, although not as low as gallium sulfide. Therefore, some of it dissolves in ethanol, but the rest forms a precipitate.

[0087] The method of mixing the third and fourth raw material liquids is not particularly limited. The fourth raw material liquid may be added to the third raw material liquid, the third raw material liquid may be added to the fourth raw material liquid, or the third and fourth raw material liquids may be added and mixed simultaneously. In addition, the mixing and the resulting reaction may be carried out by using nitrogen (N ２The reaction can be carried out under an inert gas atmosphere such as argon (Ar) or the like, or at room temperature and normal pressure. Specifically, mixing may be carried out at a temperature of 0°C or higher and 100°C or lower under atmospheric pressure. More preferably, handling in an inert gas is desirable in order to suppress the generation of sulfates, oxides, and hydroxides. However, the higher the reaction temperature, the faster the ion exchange rate, and thus a finer metal sulfide precursor can be obtained. From the viewpoint of miniaturizing the metal sulfide precursor, the mixing temperature is preferably 40°C or higher and 100°C or lower.

[0088] The addition rate of the third and fourth raw material liquids is preferably 50 ml / min to 200 ml / min. A rate of 50 ml / min or more facilitates the recovery of by-products. A rate of 200 ml / min or less allows the metal sulfide precursor to be obtained with good productivity.

[0089] <Recovery Step> In the recovery step, the metal sulfide precursor is recovered from the reaction solution. As described above, the metal sulfide precursor (sulfide containing a metal) dissolves or disperses in the reaction solution. The ammonium salt (by-product) is barely soluble and forms a precipitate. When the metal sulfide precursor dissolves in the reaction solution, the reaction solution can be subjected to solid-liquid separation treatment as is to separate and remove the by-product as a precipitate, and the metal sulfide precursor can be recovered. The solid-liquid separation can be performed by a known method, such as filtration, centrifugation, or decantation. The method is not limited as long as it can remove the precipitate.

[0090] On the other hand, if the metal sulfide precursor is dispersed in the reaction solution without dissolving, both the metal sulfide precursor and the ammonium salt will precipitate and cannot be separated as is. In this case, it is preferable to add an additional solvent to dissolve either the metal sulfide precursor or the ammonium salt. This enables solid-liquid separation of the metal sulfide precursor and the ammonium salt. In this case, if a solvent with a boiling point exceeding 110°C is used as the fourth organic solvent, ammonium sulfide is likely to remain in the reaction solution. If the reaction solution is subjected to a calcination step such as that described in the third embodiment under such conditions, the remaining ammonium sulfide acts as a fluxing agent and promotes sintering of the metal sulfide precursor. This leads to coarsening of the metal sulfide. From this perspective, a solvent with a boiling point of 110°C or less is used in the present invention.

[0091] The type of additional solvent varies depending on the type of metal sulfide precursor and reaction solution, so it is difficult to uniquely determine it. However, examples include ethanol, methanol, water, etc. For example, when gallium sulfide (metal sulfide precursor) and ammonium formate (ammonium salt) are produced in ethanol (reaction) by the reaction of the above formula (3), both gallium sulfide and ammonium formate form precipitates. In this case, if ethanol as an additional solvent is further added to the reaction solution, the ammonium formate dissolves preferentially in ethanol because the solubility of ammonium formate is higher than that of gallium sulfide. Therefore, if a solid-liquid separation process is performed on the reaction solution to which the additional solvent has been added, the precipitated gallium sulfide (metal sulfide precursor) can be separated and recovered.

[0092] <Drying step> If necessary, a step of drying the recovered metal sulfide precursor (drying step) may be provided. Although the metal sulfide precursor recovered through the recovery step is in a solid state, the reaction liquid may adhere to its surface. By drying the metal sulfide precursor, the adhered reaction liquid can be removed.

[0093] <Washing Step> If necessary, a step of washing the metal sulfide precursor (washing step) may be provided. Specific means for the washing step are as described in the first embodiment.

[0094] In this way, a metal sulfide precursor can be obtained. The obtained metal sulfide precursor can be used to produce metal sulfides. In addition, the metal sulfide precursor itself can be used for desired purposes.

[0095] <<2. Method for Producing Metal Sulfide>> This embodiment is directed to a method for producing a metal sulfide. The metal sulfide is composed of a plurality of inorganic compound particles containing metal and sulfur. The metal sulfide can be obtained by calcining a metal sulfide precursor.

[0096] The type of metal sulfide is not particularly limited. For example, sulfides containing metals such as gallium (Ga), calcium (Ca), strontium (Sr), zinc (Zn), indium (In), magnesium (Mg), and / or lithium (Li) can be used. More specifically, sulfides containing metals such as CaS, SrS, Ca ｘ Sr １－ｘ S (0<x<1), MgS, Mg ｘ Ca １－ｘ S(0<x<1), Mg ｘ Ca ｙ Zn １－ｘ－ｙ S (0<x<1, 0<y<1, 0<x+y<1), ZnS, Ga ２ S ３ , SrGa ２ S ４ , CaGa ２ S ４ , BaS, Sr ｘ Ca １－ｘ Ga ２ S ４ (0<x<1), Sr ｘ Ba １－ｘ Ga ２ S ４ (0<x<1), FeS, Ag ２ S, InS, ZnInS, Li ２ S, Sc ２ S ３ , Al ２ S ３ , SnS, CuS, NiS, MoS ２ , CoS, MnS, Bi ２ S ３ , TiS ２ , SeS, As ２ S ３ , As４ S ４ , As ２ S ５ , Sb ２ S ３ , PbS, Pb ｘ Sr １－ｘ S(0<x<1), Sm ２ S ３ , LaS, CeS, PrS, NdS, PmS, GdS, TbS, RuS, LuS, EuS, YbS, and Y ２ S ３ Among these, CaS, SrS, BaS, Ca ｘ Sr １－ｘ S, SrGa ２ S ４ , CaGa ２ S ４ , Sr ｘ Ca １－ｘ Ga ２ S ４ , Sr ｘ Ba １－ｘ Ga ２ S ４ is particularly useful as a phosphor material. ２ S is particularly useful as a solid electrolyte material or a positive electrode material for lithium ion batteries and all-solid-state batteries. The metal sulfide may contain one type of metal alone or two or more types of metals in combination.

[0097] The method for producing a metal sulfide according to the present embodiment includes a third aspect and a fourth aspect. Each of the aspects will be described below.

[0098] [Third Aspect] In the third aspect, a metal sulfide is produced using the metal sulfide precursor obtained in either the first or second aspect as a raw material. The method for producing a metal sulfide in the third aspect includes the following steps: a step of calcining the metal sulfide precursor obtained in either the first or second aspect (calcination step). This production method may optionally include a step of crushing the calcined product obtained in the calcination step (crushing step), or a step of washing the calcined product obtained in the calcination step and / or the crushed product obtained in the crushing step (washing step).

[0099] <Caking step> In the calcination step, the obtained metal sulfide precursor is calcined. Calcination causes atomic rearrangement, resulting in a metal sulfide (calcined product) with higher crystallinity. Furthermore, when the metal sulfide precursor contains excess elements such as oxygen or sulfur, sulfide nuclei are generated simultaneously with the removal of these excess elements, and these nuclei undergo particle growth, resulting in the production of fine metal sulfides. For example, when a metal sulfide precursor is produced according to the first embodiment, the obtained metal sulfide precursor contains polysulfides. When this metal sulfide precursor is calcined, the polysulfides undergo a thermal decomposition reaction, and the excess sulfur is volatilized and removed, converting it into a metal sulfide. For example, CaS ｘ When a polysulfide having the composition (where 2≦x) is fired in an inert gas atmosphere, it is thermally decomposed and changes into a metal sulfide having a CaS composition as shown in the following formula (4).

[0100] CaS ｘ → CaS+(x-1) / 2S ２ ...(4)

[0101] The firing is carried out under conditions that allow a metal sulfide of the desired composition to be obtained. In order to allow the reaction to proceed sufficiently, it is preferable to carry out firing at a relatively high temperature for a long period of time. On the other hand, if the firing time is too high or too long, the sintering of the obtained metal sulfide proceeds, and the particles contained therein may grow excessively. Therefore, it is preferable to carry out firing under conditions that allow the reaction to proceed sufficiently while preventing the metal sulfide from becoming coarse-grained. The optimum firing temperature and holding time vary depending on the composition of the metal sulfide, and it is difficult to determine them in general. For example, firing is carried out under conditions that allow the temperature to be kept at 500°C or higher and 1200°C or lower for 0.50 hours or higher and 12 hours or lower. The firing is carried out under conditions that allow the temperature to be kept at 500°C or higher and 1200°C or lower for 0.50 hours or higher and 12 hours or lower. ２ ) or argon (Ar), or hydrogen (H ２ It is preferable to carry out the reaction in a reducing gas atmosphere such as HCl.

[0102] The metal sulfide precursor may be dried prior to the calcination step. In particular, when the metal sulfide precursor is in a solution state, it is preferable to dry it to a solid state. The drying may be performed by the method described in the first or second embodiment. The calcination may be performed continuously with the preceding drying treatment or as an independent treatment.

[0103] <Crushing step> If necessary, a step of crushing the fired product obtained in the firing step (crushing step) may be provided. In the crushing step, the fired product is crushed using a crushing device to obtain a crushed product. In the fired product after the firing step, fine metal sulfide particles are loosely bonded to each other. By performing the crushing treatment, the bonds between the particles are loosened, and a powder is obtained.

[0104] The crushing may be carried out using a known crushing device, such as an attritor, paint shaker, ball mill, bead mill, ultrasonic homogenizer, and / or high-pressure homogenizer. Alternatively, crushing may be carried out by a pressurized spray-type wet media-less crushing method. When crushing by the pressurized spray-type media-less crushing method, the fired material is added to a crushing solvent to form a slurry, and the resulting slurry is introduced into a pressurized spray-type wet media-less crushing device. Examples of the crushing solvent include alcohols such as methanol, ethanol, and propanol, and water. During the crushing treatment, the pressurized slurry is sprayed from a micro-nozzle. The pressure applied to the slurry is preferably 1 MPa or more, more preferably 10 MPa or more, and even more preferably 100 MPa or more.

[0105] <Washing Step> If necessary, a step (washing step) of washing the fired product obtained in the firing step and / or the crushed product obtained in the crushing step may be provided. Although small amounts, impurities derived from by-products such as alkali metals may remain in the fired product or crushed product. Furthermore, excess metal elements and sulfur components may remain. By carrying out the washing treatment, these by-products and excess components can be reduced, and a highly pure metal sulfide can be obtained.

[0106] The washing method is not limited as long as it reduces by-products and excess components. For example, a method of washing the fired or crushed material with a washing liquid such as water can be used. Specifically, a method of putting the fired or crushed material into a washing liquid and performing a series of operations of stirring, leaving it to stand, and removing the supernatant liquid once or multiple times can be used. When washing is performed with a washing liquid, a step of drying the washed crushed material under heat and / or reduced pressure can be added.

[0107] In this way, the metal sulfide of the third embodiment can be obtained. The obtained metal sulfide is a sulfide containing either one of the metals (first metal and second metal) used in the first embodiment or the second embodiment. That is, when the metal sulfide precursor obtained in the first embodiment is used as a raw material, it contains the first metal derived from the metal salt used in preparing the first raw material solution. When the metal sulfide precursor obtained in the second embodiment is used as a raw material, it contains the second metal derived from the metal salt used in preparing the third raw material solution.

[0108] The metal sulfide of this embodiment is characterized by being fine and having a low carbon content. Preferably, the carbon content of the metal sulfide is 9000 ppm or less, and the average primary particle diameter (D50) measured by SEM observation is 30.0 μm or less. The carbon content is more preferably 5000 ppm or less, and even more preferably 2000 ppm or less. The lower limit of the carbon content is not limited, but may be 1000 ppm or more. D50 is more preferably 10.0 μm or less, even more preferably 6.0 μm or less, and particularly preferably 3.0 μm or less. The lower limit of D50 is not limited, but may be 0.1 μm or more. Thus, fine metal sulfides with a low carbon content are suitable for various applications such as phosphor materials, batteries, catalysts, semiconductors, pigments, and pharmaceuticals.

[0109] [Fourth Aspect] In the fourth aspect, the metal sulfide precursor obtained in the first aspect and the metal sulfide precursor obtained in the second aspect are combined and used as a raw material to produce a metal sulfide. The method for producing a metal sulfide in the fourth aspect includes the following steps: a step of mixing a first metal sulfide precursor and a second metal sulfide precursor to obtain a mixed metal sulfide precursor (mixing step), and a step of calcining the obtained mixed metal sulfide precursor (calcining step). The first metal sulfide precursor is the metal sulfide precursor obtained by the method of the first aspect, and the second metal sulfide precursor is the metal sulfide precursor obtained by the method of the second aspect. This production method may, as necessary, include a step of crushing the calcined product obtained in the calcination step (crushing step), or a step of washing the calcined product obtained in the calcination step and / or the crushed product obtained in the crushing step (washing step).

[0110] <Mixing Step> In the mixing step, a first metal sulfide precursor and a second metal sulfide precursor are mixed to obtain a mixed metal sulfide precursor. Here, the first metal sulfide precursor is the metal sulfide precursor obtained by the method of the first aspect described above, and the second metal sulfide precursor is the metal sulfide precursor obtained by the method of the second aspect described above. Note that the first metal contained in the first metal sulfide precursor and the second metal contained in the second metal sulfide precursor may be the same type of metal or different types of metals.

[0111] The mixing ratio of the first metal sulfide precursor and the second metal sulfide precursor may be determined depending on the composition of the target metal sulfide. For example, when the first metal sulfide precursor is a calcium-containing polysulfide (CaS ｘ (where 2≦x)), and the second metal sulfide precursor is gallium sulfide (Ga ２ S ３ ) and CaGa ２ S ４ When the purpose is to produce a metal sulfide having a composition, the first metal sulfide precursor and the second metal sulfide precursor may be mixed so that the composition of the mixed metal sulfide precursor has a molar ratio of Ca:Ga=1:2.

[0112] The mixing method is not limited as long as a mixture of the first metal sulfide precursor and the second metal sulfide precursor can be obtained. For example, when the first metal sulfide precursor is in a solution state and the second metal sulfide precursor is in a solid state, the second metal sulfide precursor in a solid state can be added to the first metal sulfide precursor in a solution state, and the whole can be stirred and mixed. The mixing can also be carried out by using nitrogen (N ２ The mixing can be carried out in an inert gas atmosphere such as argon (Ar) or the like, or at room temperature and normal pressure. Specifically, the mixing may be carried out at a temperature of 0°C or higher and 100°C or lower under atmospheric pressure. It is more preferable to handle the mixture in an inert gas atmosphere in order to suppress the generation of sulfates, oxides, and hydroxides.

[0113] <Caloring Step> In the calcination step, the obtained mixed metal sulfide precursor is calcined. The calcination promotes a reaction between the first metal sulfide precursor and the second metal sulfide precursor contained in the mixed metal sulfide precursor. During this process, atomic rearrangement occurs, resulting in the production of a composite metal sulfide and improving its crystallinity. Furthermore, if the metal sulfide precursor contains excess elements such as oxygen or sulfur, these excess elements can be removed.

[0114] The firing is carried out under conditions that allow a metal sulfide of the desired composition to be obtained. In order to allow the reaction to proceed sufficiently, it is preferable to carry out firing at a relatively high temperature for a long period of time. On the other hand, if the firing time is too high or too long, the sintering of the obtained metal sulfide proceeds, and the particles contained therein may grow excessively. Therefore, it is preferable to carry out firing under conditions that allow the reaction to proceed sufficiently while preventing the metal sulfide from becoming coarse-grained. The optimum firing temperature and holding time vary depending on the composition of the metal sulfide, and it is difficult to determine them in general. For example, firing is carried out under conditions that allow the temperature to be kept at 500°C or higher and 1200°C or lower for 0.50 hours or higher and 12 hours or lower. The firing is carried out under conditions that allow the temperature to be kept at 500°C or higher and 1200°C or lower for 0.50 hours or higher and 12 hours or lower. ２ ) or argon (Ar), or hydrogen (H ２ It is preferable to carry out the reaction in a reducing gas atmosphere such as HCl.

[0115] The metal sulfide precursor may be dried prior to the calcination step. In particular, when the metal sulfide precursor is in a solution state, it is preferable to dry it to a solid state. The drying may be performed by the method described in the first or second embodiment. The calcination may be performed continuously with the preceding drying treatment or as an independent treatment.

[0116] <Crushing Step> If necessary, a step of crushing the fired product obtained in the firing step (crushing step) may be provided. The crushing step may be carried out in the same manner as described in the third embodiment.

[0117] <Washing Step> If necessary, a step of washing the fired product obtained in the firing step and / or the crushed product obtained in the crushing step (washing step) may be provided. The washing step may be carried out in the same manner as described in the third embodiment.

[0118] In this way, the metal sulfide of the fourth embodiment can be obtained. The obtained metal sulfide is a composite metal sulfide containing both the metals (first metal and second metal) used in the first and second embodiments.

[0119] The metal sulfide of this embodiment is characterized by being fine and having a low carbon content. Preferably, the carbon content of the metal sulfide is 9000 ppm or less, and the average primary particle diameter (D50) measured by SEM observation is 30.0 μm or less. The carbon content is more preferably 5000 ppm or less, and even more preferably 2000 ppm or less. The lower limit of the carbon content is not limited, but may be 1000 ppm or more. D50 is more preferably 10.0 μm or less, even more preferably 6.0 μm or less, and particularly preferably 3.0 μm or less. The lower limit of D50 is not limited, but may be 0.1 μm or more. Thus, fine metal sulfides with a low carbon content are suitable for various applications such as phosphor materials, batteries, catalysts, semiconductors, pigments, and pharmaceuticals.

[0120] Furthermore, according to the method for producing a metal sulfide of this embodiment, hydrogen sulfide (H ) which is corrosive, toxic, and flammable can be produced. ２There is no need to introduce a sulfur-containing gas such as sulfur dioxide (S) into the firing atmosphere. Therefore, the production of metal sulfides can be carried out safely and easily. Another advantage is that the firing can be carried out at room temperature and atmospheric pressure. However, the production method of this embodiment is not limited to a method that does not introduce a sulfur-containing gas. It goes without saying that a sulfur-containing gas may be introduced when the amount of sulfur component contained in the precursor is insufficient.

[0121] <<3. Phosphor Powder>> As described above, the metal sulfide of this embodiment is suitable for various applications such as phosphor materials, batteries, catalysts, semiconductors, pigments, pharmaceuticals, etc. Below, a detailed description will be given of the case where the metal sulfide is applied to phosphor powder (phosphor material).

[0122] The phosphor powder of this embodiment contains at least a Group 2 element (A), sulfur (S), and a luminescent center element (M). The phosphor powder is composed of a host crystal and the luminescent center element that is ionized and doped into the host crystal. In this embodiment, the Group 2 element and sulfur form a sulfide host crystal, which is doped with the ionized luminescent center element. The phosphor powder may be composed only of a Group 2 element, sulfur, and the luminescent center element, or may contain other elements.

[0123] The Group 2 elements (A) are elements belonging to Group 2 of the periodic table, and are a collective term for beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). The Group 2 elements, together with sulfur, constitute a sulfide, which is the host crystal. The phosphor powder may contain one type of Group 2 element, or may contain a combination of multiple types of Group 2 elements. As the Group 2 element, at least one selected from the group consisting of Ca, Sr, and Ba is preferred, at least one selected from the group consisting of Ca and Sr is more preferred, and Ca is particularly preferred.

[0124] The luminescent center element (M) is an element that becomes a luminescent ion in a phosphor. When excitation light is irradiated onto a phosphor, the luminescent ion absorbs the excitation light, and electrons in the ground level are excited to an excited level. When these excited electrons return to the ground level, the difference energy is emitted as fluorescence. Examples of luminescent center elements include rare earth elements and transition elements. Among these, it is preferable to include at least one selected from the group consisting of europium (Eu), cerium (Ce), samarium (Sm), magnesium (Mg), lanthanum (La), pselaodium (Pr), neodymium (Nd), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), copper (Cu), silver (Ag), gold (Au), nickel (Ni), zirconium (Zr), manganese (Mn), gallium (Ga), tin (Sn), lead (Pb), arsenic (As), antimony (Sb), and bismuth (Bi), and it is particularly preferable to include europium (Eu).

[0125] According to a preferred embodiment, the phosphor powder includes a host crystal containing at least one Group 2 element (A) selected from the group consisting of strontium (Sr) and calcium (Ca) and sulfur (S), and a luminescent center element (M). More preferably, the phosphor powder is represented by the general formula: Ca １－ｘ Sr ｘ The phosphor powder has a composition represented by S:M (where M is a luminescent center element, and x is 0≦x≦1). The phosphor powder may contain only one of Sr and Ca. However, it is preferable to contain both Sr and Ca. Specifically, the phosphor powder has a composition represented by the above-mentioned general formula (Ca １－ｘ Sr ｘ In the ratio of XA to XM, it is preferable that the molar amount XA of the Group 2 element A (Ca, Sr, etc.) and the molar amount XM of the luminescent center element M satisfy the condition 0.050≦x≦0.98. Furthermore, the ratio of XM to the sum of XA, XM / (XA+XM) of the Group 2 element A (Ca, Sr, etc.) and XM, XM, is preferably 0.0010 or more and 0.10 or less. A phosphor powder having such a composition and containing Eu as the luminescent center element emits red light when irradiated with excitation light having a wavelength of 450 nm.

[0126] According to another preferred embodiment, the phosphor powder includes a host crystal containing at least one Group 2 element (A) selected from the group consisting of barium (Ba), strontium (Sr), and calcium (Ca), gallium (Ga), and sulfur (S), and a luminescent center element (M). More preferably, the phosphor powder is represented by the general formula: AGa ２ S ４ The phosphor powder contains a crystal represented by the formula: XA:M (where A is at least one Group 2 element selected from the group consisting of Ba, Sr, and Ca, and M is a luminescent center element). In this case, the ratio of XA to the sum of the molar amount XA of the Group 2 element A (Ba, Sr, Ca, etc.) and the molar amount XM of the luminescent center element M (XM / (XA+XM)) is preferably 0.0010 or more and 0.30 or less. A phosphor powder having such a composition and containing Eu as the luminescent center element emits green light when irradiated with excitation light having a wavelength of 450 nm.

[0127] The phosphor powder of this embodiment is not limited to those having the above-mentioned composition, and is applicable to this embodiment as long as it contains a Group 2 element, a luminescent center element, and sulfur and exhibits fluorescent properties.

[0128] The phosphor powder of this embodiment has a cumulative 90% diameter (D90) on a volume basis of 10.0 μm or less. D90 is an index of the size and amount of coarse particles contained in the powder. Powders with a large D90 contain many large coarse particles. In this embodiment, by keeping D90 within the above-mentioned range, the phosphor powder can be refined. In contrast, phosphor powders with a D90 greater than 10.0 μm contain many coarse particles, making uniform filling into micro-packages, particularly uniform filling using an inkjet process, difficult. From this perspective, D90 is preferably 5.0 μm or less, more preferably 2.0 μm or less. On the other hand, from the perspective of easily maintaining even higher luminous efficiency, D90 is preferably 0.10 μm or more, more preferably 0.30 μm or more, and even more preferably 0.50 μm or more. Furthermore, from the viewpoint of promoting miniaturization while maintaining high luminous efficiency, D90 is preferably 0.10 μm or more and 10.0 μm or less, more preferably 0.30 μm or more and 5.0 μm or less, and even more preferably 0.50 μm or more and 2.0 μm or less. D90 is measured using a laser diffraction particle size distribution analyzer. Specifically, it is determined by the method described in the examples below or a method similar thereto.

[0129] The phosphor powder of this embodiment has a lattice distortion (σ) of 0.300% or less, as determined by analyzing the X-ray diffraction profile using the Whole Powder Pattern Fitting (WPPF) method. The WPPF (Whole Powder Pattern Fitting) method is a technique for fitting a relatively wide angular range of the XRD profile based on lattice constant information. The WPPF method has advantages such as a high ability to resolve overlapping diffraction lines.

[0130] The higher the crystallinity of the powder, the smaller the lattice strain. By keeping the lattice strain within the above-mentioned range, it is possible to increase the luminous efficiency of the phosphor powder. In contrast, phosphor powder with a lattice strain of more than 0.300% has low crystallinity and it is difficult to obtain high luminous efficiency. From the viewpoint of improving luminous efficiency, the lattice strain is preferably 0.150% or less, more preferably 0.100% or less, even more preferably 0.050% or less, even more preferably 0.010% or less, particularly preferably 0.005% or less, and most preferably 0.001% or less. The lower limit of the lattice strain is not specified. It is sufficient that it is 0% or more, and it may be 0.0001% or more. The lattice strain is determined by the method performed in the examples described below or a method equivalent thereto.

[0131] The crystallite size of the phosphor powder is preferably 50 nm (500 Å) or more, and more preferably 100 nm (1000 Å) or more. The higher the crystallinity of the powder, the larger the crystallite size. Therefore, by increasing the crystallite size, it is possible to further increase the luminous efficiency of the phosphor powder. There is no upper limit to the crystallite size, provided that it is equal to or less than the particle diameter. However, it is typically 500 nm (5000 Å) or less. The crystallite size can be determined by the method described in the Examples below or a method similar thereto.

[0132] The cumulative 50% diameter (D50) of the phosphor powder on a volume basis is preferably 0.050 μm or more and 10.0 μm or less, more preferably 0.10 μm or more and 5.0 μm or less, and even more preferably 0.20 μm or more and 2.0 μm or less, provided that it is smaller than D90. The phosphor powder of this embodiment not only has fewer coarse particles, but also allows the average particle diameter itself to be reduced. By reducing D50, it becomes possible to more effectively promote uniform filling into micro-packages. Note that D50 is measured using a laser diffraction particle size distribution analyzer. Specifically, it is determined by the method described in the examples below or a method similar thereto.

[0133] The cumulative 10% diameter (D10) of the phosphor powder on a volume basis is preferably 0.30 μm or more, more preferably 0.50 μm or more, and even more preferably 1.00 μm or more, provided that it is smaller than D90 and D50. D10 is an indicator of the size and amount of ultrafine particles contained in the powder. By appropriately increasing D10, the proportion of ultrafine particles is reduced, thereby further improving the luminescence characteristics of the phosphor powder. The following mechanism is believed to be the reason for this. Specifically, the fired product is crushed during phosphor powder production to obtain the phosphor powder. The finer the particles, the more difficult they are to crush, so stronger crushing energy is required for crushing. When strong crushing energy is applied so that a large amount of ultrafine particles are produced, the strain in the ultrafine particles increases, which is thought to degrade the luminescence characteristics of the resulting phosphor powder. In other words, phosphor powder with a low proportion of ultrafine particles is thought to have high luminescence characteristics due to the small strain in the ultrafine particles.

[0134] The product (D50 x σ) of the cumulative 50% diameter (D50) and lattice strain (σ) on a volume basis of the phosphor powder is preferably 0.40 μm·% or less, more preferably 0.20 μm·% or less, even more preferably 0.030 μm·% or less, particularly preferably 0.010 μm·% or less, and most preferably 0.007 μm·% or less. By using D50 x σ as an index and reducing this index, it is possible to achieve both finer grains and high luminous efficiency at a higher level. The lower limit of D50 x σ is not specified. It may be 0 μm·% or more, and may be 0.001 μm·% or more.

[0135] The internal quantum efficiency (IQE) of the phosphor powder is preferably 40% or more, more preferably 50% or more, and most preferably 60% or more. The internal quantum efficiency is the efficiency with which the light absorbed by the phosphor is converted into another light, and is a measure of the luminous efficiency. By using a phosphor powder with a high internal quantum efficiency, it becomes possible to increase the brightness when applied to applications such as displays. There is no specified upper limit for the internal quantum efficiency. However, it is usually 100% or less.

[0136] The external quantum efficiency (EQE) of the phosphor powder is preferably 20% or more, and more preferably 30% or more. The external quantum efficiency is the efficiency with which the incident light irradiated on the phosphor is converted into another light. There is no specified upper limit for the external quantum efficiency. However, it is usually 100% or less.

[0137] The absorptivity (Abs) of the phosphor powder is preferably 40% or more, more preferably 50% or more, and even more preferably 60% or more. The absorptivity is the proportion of incident light irradiated onto the phosphor that is absorbed by the phosphor. There is no specified upper limit for the absorptivity. However, it is usually 100% or less. The internal quantum efficiency, external quantum efficiency, and absorptivity can be determined by the method described in the Examples below or a method similar thereto.

[0138] <<4. Inkjet Ink>> The inkjet ink of this embodiment contains the above-described phosphor powder and solvent. The phosphor powder of this embodiment is fine, and the content of coarse particles is reduced. Therefore, it is suitable for phosphor powder filling using an inkjet process. The inkjet ink of this embodiment has little risk of clogging even if the nozzle diameter of the inkjet head is small. Therefore, it is suitable for filling into micro-packages for displays.

[0139] The ink contains a solvent in addition to the phosphor powder. The solvent may be water, alcohol, ketone, ester, ether, aromatic hydrocarbon solvent, aliphatic hydrocarbon solvent, or the like, either alone or in combination. The ink may also contain additives such as a binder resin, such as polyvinyl alcohol or acrylic resin, a dispersant, or a surfactant.

[0140] <<5. Light-Emitting Element>> The light-emitting element of this embodiment includes an excitation source (light source) and the above-described phosphor powder. In this light-emitting element, the phosphor powder is excited by light irradiation from the excitation source and emits visible light. A blue-emitting LED with a wavelength of 420 nm or more and 500 nm or less is suitable as the excitation source (light source). As long as light from the excitation source is incident on the phosphor powder, the arrangement of the phosphor powder and the excitation source is not limited. For example, when the light-emitting element is applied to a μLED display, an LED serving as an excitation source is arranged below each package, and a phosphor is filled and arranged above it. However, the light-emitting element of this embodiment is not limited to an element for a μLED display.

[0141] The light-emitting element may contain the phosphor powder in a powder state alone, or may contain the phosphor powder in a mixture with a resin, such as one or more resins selected from the group consisting of thermoplastic resins, thermosetting resins, ionizing radiation curable resins, and two-part curable resins.

[0142] <<6. Light-Emitting Device>> The light-emitting device of this embodiment includes the above-described light-emitting element. Examples of light-emitting devices include, but are not limited to, well-known applications such as illumination, backlights for mobile terminals, and displays (display devices). Among these, displays are preferred, μLED displays or mini-LED displays are more preferred, and μLED displays are particularly preferred.

[0143] <<7. Method for Producing Phosphor Powder>> The method for producing phosphor powder of this embodiment includes the following steps: a step of preparing a first raw material liquid (first solution) containing a first organic solvent (first solvent) and a salt of a Group 2 element (A) and a salt of a luminescent center element (M) dissolved or dispersed in the first organic solvent (first raw material liquid preparation step); a step of preparing a second raw material liquid (second solution) containing a second organic solvent (second solvent), sulfur (S), and an alkali metal sulfide dissolved in the second organic solvent (second raw material liquid preparation step); and a step of mixing and stirring the first raw material liquid and the second raw material liquid, thereby dissolving the sulfide containing the Group 2 element and the luminescent center element and The method includes the steps of obtaining a reaction solution (third solution) containing a precipitate containing an alkali metal salt (reaction step), subjecting the obtained reaction solution to solid-liquid separation to remove the precipitate (solid-liquid separation step), drying the reaction solution from which the precipitate has been removed to obtain a phosphor precursor composed of a polysulfide containing a Group 2 element and a luminescent center element (drying step), firing the obtained phosphor precursor to obtain a fired phosphor product (firing step), and crushing the obtained fired phosphor product using a pressurized jet-type wet media-less crushing method or a shaking wet media-less crushing method to obtain a crushed phosphor product (crushing step). If necessary, a step of washing the crushed phosphor product (washing step) may be provided. Details of each step are described below.

[0144] <First raw material solution preparation step> In the first raw material solution preparation step, a first raw material solution is prepared, which includes a first organic solvent and a salt of a Group 2 element (A) and a salt of a luminescent center element (M) dissolved or dispersed in the first organic solvent.

[0145] The first organic solvent contains a salt of a Group 2 element and a salt of a luminescent center element dissolved or dispersed therein, and functions to form a reaction field in the subsequent reaction step. From the viewpoint of efficiently obtaining a sulfide with high purity, the first organic solvent preferably has a boiling point of 110°C or lower. Specifically, alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and t-butyl alcohol are preferred, with ethanol being particularly preferred. One or a mixture of two or more of the above-mentioned solvents may also be used. Furthermore, the amount of the first organic solvent is preferably an amount that can sufficiently dissolve or disperse the salt of a Group 2 element and the salt of a luminescent center element.

[0146] The salt of the Group 2 element (A) is a raw material of the Group 2 element, which is the main component of the phosphor powder. Therefore, the type can be determined depending on the composition of the target phosphor powder. Although not limited, the salt of the Group 2 element is preferably a salt containing at least one element selected from calcium (Ca), strontium (Sr), and barium (Ba), more preferably a salt containing at least one element selected from Ca and Sr, and particularly preferably a salt of Ca. Furthermore, the salt is preferably at least one selected from nitrates, chlorides, sulfates, and carbonates, and particularly preferably chlorides.

[0147] The amount of the salt of the Group 2 element is preferably 1.0 to 10.0 times the amount of the alkali metal sulfide added to the second liquid feedstock in terms of molar ratio.

[0148] The salt of the luminescent center element (M) is a raw material of the luminescent center element, which is the main component of the phosphor powder. Therefore, the type can be determined depending on the composition of the target phosphor powder. Although not limited thereto, the salt of the luminescent center element is preferably a salt containing at least one element selected from the group consisting of europium (Eu), cerium (Ce), magnesium (Mg), lanthanum (La), pselaodium (Pr), neodymium (Nd), samarium (Sm), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), copper (Cu), silver (Ag), gold (Au), nickel (Ni), zirconium (Zr), manganese (Mn), gallium (Ga), tin (Sn), lead (Pb), arsenic (As), antimony (Sb), and bismuth (Bi), and a salt of Eu is particularly preferred. The salt is preferably at least one selected from nitrates, chlorides, sulfates, and carbonates, with chlorides being particularly preferred.

[0149] The amount of the salt of the luminescent center element may be determined depending on the composition of the desired phosphor powder.

[0150] The first raw material liquid may be prepared by any method as long as it contains a salt of a Group 2 element and a salt of a luminescent center element dissolved or dispersed in a first organic solvent. For example, the first raw material liquid may be prepared by adding a salt of a Group 2 element and a salt of a luminescent center element to a first organic solvent and stirring the mixture. The first organic solvent may or may not be heated during stirring. Furthermore, if the target phosphor powder contains elements other than a Group 2 element, a luminescent center element, and sulfur, a salt of the other element may be added to the first raw material liquid.

[0151] <Second Source Liquid Preparing Step> In the second source liquid preparing step, a second source liquid containing a second organic solvent, sulfur (S), and an alkali metal sulfide dissolved in the second organic solvent is prepared.

[0152] The second organic solvent contains an alkali metal sulfide and functions to form a reaction field in the subsequent reaction step. From the viewpoint of efficiently obtaining a sulfide with high purity, the second organic solvent preferably has a boiling point of 110°C or less. Specifically, alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and t-butyl alcohol are preferred, with ethanol being particularly preferred. One or a mixture of two or more of the above-mentioned solvents may also be used. The type of the second organic solvent may be the same as or different from the first organic solvent. Furthermore, the amount of the second organic solvent is preferably an amount that can sufficiently dissolve the alkali metal sulfide.

[0153] Sulfur (S) is a raw material for sulfur, which is the main component of phosphor powder. In other words, sulfide phosphor powder can be obtained by using sulfur as a raw material. In particular, by using a large amount of sulfur, polysulfides that can be easily crushed can be obtained, making it possible to efficiently produce fine phosphor powder with high luminous efficiency. From the viewpoint of suppressing the residue of raw materials that inhibit luminescence, the amount of sulfur blended is preferably 1.0 to 10.0 times the amount of alkali metal sulfide in molar ratio. Note that, from the viewpoint of increasing reactivity, it is preferable that the sulfur be in powder form.

[0154] The alkali metal sulfide reacts with the anion component of the salt contained in the first raw material liquid to form a by-product that is easy to remove. In other words, by using the alkali metal sulfide, the anion component can be removed in the form of an alkali metal salt. The alkali metal sulfide is also a raw material for sulfur, which is the main component of the phosphor powder. As the alkali metal sulfide, a sulfide of at least one alkali metal selected from the group consisting of lithium (Li), sodium (Na), potassium (K), and hydrates thereof is preferred, and Na sulfide (Na ２ S) is particularly preferred.

[0155] The second liquid feedstock may be prepared by any method as long as it contains sulfur and an alkali metal sulfide dissolved in a second organic solvent. For example, the second liquid feedstock may be prepared by adding sulfur and an alkali metal sulfide to a second organic solvent and stirring the mixture. The second organic solvent may or may not be heated during stirring. The second liquid feedstock is a suspension (slurry).

[0156] Incidentally, when preparing the first raw material liquid, a salt of a Group 2 element and a salt of a luminescent center element are dissolved or dispersed in a first organic solvent. Preferably, the salt of a Group 2 element and the salt of a luminescent center element are dissolved in the first organic solvent. From this perspective, it is desirable that the first organic solvent be a solvent that has high solubility for the salt of a Group 2 element and the salt of a luminescent center element. Similarly, it is desirable that the second organic solvent be a solvent that has high solubility for an alkali metal sulfide.

[0157] Meanwhile, in the subsequent reaction step, an ion exchange reaction occurs between the salt of the Group 2 element, the salt of the luminescent center element, the alkali metal sulfide, and sulfur, producing a phosphor precursor, which is a polysulfide containing the Group 2 element and the luminescent center element, and also producing an alkali metal salt as a by-product. While the polysulfide (phosphor precursor) dissolves in the solvent (a mixed solvent of the first organic solvent and the second organic solvent), the alkali metal salt (by-product) is barely soluble and forms a precipitate. The by-product can be removed by subjecting the solution after the reaction step to solid-liquid separation. Therefore, from the perspective of removing as many by-products as possible to obtain a high-purity phosphor powder, it is desirable that the first organic solvent and the second organic solvent have low solubility for the alkali metal salt (by-product).

[0158] From the above viewpoints, it is preferable to select a combination of the first organic solvent, the second organic solvent, the salt of the Group 2 element, the salt of the luminescent center element, and the alkali metal sulfide. Although not limited thereto, the first organic solvent and the second organic solvent are preferably ethanol, the salt of the Group 2 element and the salt of the luminescent center element are preferably chlorides, and the alkali metal sulfide is preferably sodium sulfide (Na ２ S) is preferred.

[0159] Furthermore, the order of the first raw material liquid step and the second raw material liquid step is not limited as long as the first raw material liquid and the second raw material liquid are prepared.

[0160] <Reaction Step> In the reaction step, the first raw material liquid and the second raw material liquid are mixed and stirred to obtain a reaction solution in which a sulfide containing a Group 2 element and a luminescent center element is dissolved and a precipitate containing an alkali metal salt is deposited. When the first raw material liquid and the second raw material liquid are mixed and stirred, an ion exchange reaction occurs between the salt of the Group 2 element, the salt of the luminescent center element, the alkali metal sulfide, and sulfur contained therein, producing a phosphor precursor that is a polysulfide containing a Group 2 element and a luminescent center element, and producing an alkali metal salt as a by-product. While the polysulfide (phosphor precursor) dissolves in the reaction solution, the alkali metal salt (by-product) is barely dissolved and forms a precipitate.

[0161] For example, calcium chloride (CaCl) is a salt of a Group 2 element. ２ ) as a salt of the luminescent center element, europium chloride (EuCl ３ ) as an alkali metal sulfide, sodium sulfide (Na ２ When ethanol is used as both the first and second organic solvents, the reaction shown in the following formula (1) proceeds to the right, producing polysulfides containing calcium and europium ((Ca,Eu)S ｘ ) and sodium chloride (NaCl) are produced in ethanol.

[0162] CaCl ２ +EuCl ３ +Na ２ S+S → (Ca, Eu)S ｘ +NaCl↓ (1)

[0163] (Ca,Eu)S ｘ has a high solubility in ethanol, whereas NaCl has a low solubility. Therefore, NaCl hardly dissolves and forms a precipitate.

[0164] The method of mixing the first and second raw material liquids is not particularly limited. The second raw material liquid may be added to the first raw material liquid, the first raw material liquid may be added to the second raw material liquid, or the first and second raw material liquids may be added and mixed simultaneously. In addition, the mixing and the resulting reaction may be carried out by using nitrogen (N ２ The mixing can be carried out in an inert gas atmosphere such as argon (Ar) or the like, or at room temperature and normal pressure. Specifically, the mixing can be carried out at a temperature of 0° C. or higher and 40° C. or lower under atmospheric pressure. It is more preferable to handle the mixture in an inert gas atmosphere in order to suppress the generation of sulfates, oxides, and hydroxides.

[0165] <Solid-Liquid Separation Step> In the solid-liquid separation step, the obtained reaction liquid is subjected to a solid-liquid separation treatment to remove precipitates. As described above, the polysulfide (phosphor precursor) containing a Group 2 element and a luminescent center element dissolves in the reaction liquid, whereas the alkali metal salt (by-product) is barely soluble and forms a precipitate. Therefore, the by-product can be separated and removed by the solid-liquid separation treatment. The solid-liquid separation can be performed by a known method, such as filtration, centrifugation, or decantation. The method is not limited as long as it can remove the precipitate.

[0166] <Drying Step> In the drying step, the reaction solution from which the precipitate has been removed is dried to obtain a phosphor precursor composed of a polysulfide containing a Group 2 element and a luminescent center element. Drying can be performed by a known method, such as heat drying or vacuum drying. Drying conditions vary depending on the type of solvent used (first organic solvent, second organic solvent), and therefore cannot be determined in general. When ethanol is used, for example, the drying conditions include maintaining the solution at 40°C or higher and 70°C or lower for 1 hour to 72 hours.

[0167] <Firing step> In the firing step, the obtained phosphor precursor is fired to obtain a fired phosphor. The phosphor precursor contains polysulfides. When this phosphor precursor is fired, the polysulfides undergo a thermal decomposition reaction and are converted into a fired phosphor. For example, when the group 2 element is calcium (Ca) and the luminescent center element is europium (Eu), the fired phosphor is obtained as (Ca, Eu)S. ｘ The polysulfide having the composition is thermally decomposed to produce a fired phosphor having the composition CaS:Eu.

[0168] Firing is carried out under conditions that allow a fired phosphor of the desired composition to be obtained. In order to fully promote the thermal decomposition reaction, it is preferable to carry out firing for a long period of time at a relatively high temperature. On the other hand, if the firing time is excessively high or excessively long, the resulting fired phosphor may be sintered and become coarse. Therefore, it is preferable to carry out firing under conditions that allow the thermal decomposition reaction to fully proceed while preventing the phosphor from becoming coarse. The optimal firing temperature and holding time vary depending on the phosphor composition, and it is difficult to determine them in general. For example, firing is carried out under conditions that allow the temperature to be between 500°C and 1200°C and to be held for between 0.50 hours and 12 hours. In addition, firing is carried out under conditions that allow the temperature to be between 500°C and 1200°C and to be held for between 0.50 hours and 12 hours. ２ It is preferable to carry out the baking in an inert gas atmosphere such as argon (Ar) or argon (Ar). The baking may be carried out continuously with the preceding drying treatment or as an independent treatment.

[0169] In the manufacturing method of this embodiment, the precursor used for firing is a polysulfide, which allows for the production of a fired product that can be easily crushed in subsequent processes. That is, when the polysulfide is thermally decomposed, fine phosphor particles are formed in the fired product. These phosphor particles are loosely bonded to each other. Therefore, the fired product can be easily crushed into fine particles.

[0170] In addition, since the precursor is a polysulfide, hydrogen sulfide (H ) is corrosive, toxic, and flammable. ２There is no need to introduce a sulfur-containing gas such as sulfur dioxide (S) into the firing atmosphere. This allows the phosphor powder to be produced safely. Another advantage is that firing can be carried out at room temperature and atmospheric pressure. However, the production method of this embodiment is not limited to methods that do not involve the introduction of a sulfur-containing gas. It goes without saying that a sulfur-containing gas may be introduced when the amount of sulfur contained in the precursor is insufficient.

[0171] <Crushing step> In the crushing step, the obtained phosphor fired product is crushed by a pressurized jet type wet media-less crushing method or a rocking type wet media-less crushing method to obtain a crushed phosphor product. In the fired product after the firing step, fine phosphor particles are loosely bonded to each other. By performing the crushing treatment, the bonds between the phosphor particles are loosened, and a powder is obtained.

[0172] The manufacturing method of this embodiment is characterized by the use of a pressurized injection wet media-less crushing method or a vibration wet media-less crushing method. The pressurized injection wet media-less crushing method is a technique in which high pressure is applied to a suspension (slurry) containing the material to be treated and sprayed from a micro-nozzle. The material to be treated is sprayed at high speed and crushed by shear force upon impact with the solid object, or by the effects of cavitation, turbulence, etc. Pressurized injection wet media-less crushing is distinguished from media-agitation-type pulverization such as attritors, paint shakers, ball mills, and bead mills in that it does not use media such as balls or beads. It also differs from ultrasonic homogenizers and high-pressure homogenizers in that it crushes the pressurized injected material to be treated by the effects of shear force, cavitation, and / or turbulence, etc.

[0173] Pressurized injection wet media-less crushing does not use crushing media, so damage during crushing is minimal, and crushed material with little distortion can be obtained. Another advantage is that there is little risk of impurities being mixed in. In contrast, methods that use media cause significant damage to the processed material, making it difficult to suppress the reduction in distortion. Furthermore, there is a risk of impurities being mixed in from the media. Therefore, phosphor powder with little lattice distortion can be obtained, despite the fact that there are few coarse particles.

[0174] In the crushing process, the phosphor burned material is added to a crushing solvent to form a slurry, and the resulting slurry is introduced into a pressurized injection-type wet media-less crushing device. Examples of crushing solvents include alcohols such as methanol, ethanol, and propanol, as well as water. During the crushing process, the pressurized slurry is sprayed from a micro-nozzle. The crushing process is preferably performed under conditions that sufficiently crush the coarse particles while minimizing lattice strain within the particles. It is also desirable to perform the process under conditions that suppress the generation of ultrafine particles. For example, from the viewpoint of promoting the crushing of coarse particles, the pressure (discharge pressure) applied to the slurry is preferably 1 MPa or more, more preferably 10 MPa or more. On the other hand, excessively high pressure can increase lattice strain and result in excessively large amounts of ultrafine particles. From the viewpoint of suppressing the increase in lattice strain and the generation of ultrafine particles, the pressure (discharge pressure) may be 300 MPa or less, 200 MPa or less, or even 100 MPa or less. The number of passes during crushing can be set to obtain the desired phosphor powder. The number of passes may be one, two, three, or more.

[0175] The crushing may be performed by a rocking wet media-less crushing method. The rocking wet media-less crushing method is a technique in which a container (crushing container) filled with a suspension (slurry) containing the material to be processed is rocked to apply a collision pressure to the material to be processed, thereby crushing it. Specifically, it can be performed using a high-speed rocking crushing device such as a rocking mill. Rocking wet media-less crushing has the advantage that it does not use crushing media and can produce crushed material with little lattice distortion and ultrafine particles without the risk of impurity contamination.

[0176] <Washing Step> If necessary, a step of washing the obtained crushed phosphor material (washing step) may be provided. Although the amount may be small, the crushed phosphor may contain residual alkali metal sources as by-products. Furthermore, excess Group 2 elements, luminescent center elements, and / or sulfur components may remain. By carrying out the washing process, these by-products and excess components can be reduced, and a highly pure phosphor powder can be obtained.

[0177] The washing method is not limited as long as it reduces by-products and excess components. For example, the crushed phosphor material may be washed with a washing liquid such as water. For example, the crushed material may be placed in a washing liquid, and a series of operations of stirring, leaving the material to stand, and removing the supernatant liquid may be repeated once or multiple times. When washing with a washing liquid, a step of drying the washed crushed material under heat and / or reduced pressure may be added.

[0178] The phosphor powder of this embodiment can be obtained in this manner. The phosphor powder obtained by this method is characterized by its high luminous efficiency despite its fine size. Specifically, unlike the dry (solid-phase) method, this method uses a wet (liquid-phase) synthesis method in which crystals are grown in liquid, enabling the synthesis of phosphor particles with small primary particle diameters and high crystallinity. Furthermore, in the manufacturing method of this embodiment, by-products are generated in the solution in the form of solid precipitates, and the solid by-products (precipitates) are removed by solid-liquid separation. This effectively minimizes by-product contamination. Furthermore, the specified wet media-less crushing method minimizes damage during crushing and minimizes impurity contamination. Therefore, the resulting phosphor powder has minimal distortion and high purity. Furthermore, this method is characterized by its high luminous efficiency despite its fine size.

[0179] In contrast, it is difficult to obtain fine phosphor powder using the dry method. Although a method of pulverizing the powder by strong crushing is known, it causes significant damage to the phosphor powder and introduces impurities, making it difficult to obtain phosphor powder with low distortion and high luminous efficiency.

[0180] The present invention will be described in more detail with reference to the following examples and comparative examples, but the present invention is not limited to these examples.

[0181] [Experimental Example A] (1) Method for producing metal sulfide precursor and metal sulfide [Example A1] According to the first and third embodiments, Ca ０．５ Sr ０．５ S ｘ a metal sulfide precursor comprising a polysulfide of the composition ０．５ Sr ０．５ A metal sulfide having a composition of S was prepared. Specifically, the preparation was carried out according to the following procedure.

[0182] Calcium chloride (CaCl) as a metal salt ２ ) and strontium chloride (SrCl ２ ) was prepared. In addition to sulfur (S), sodium sulfide (Na ２ S) was prepared. Furthermore, methanol (boiling point: 64.51°C) was prepared as the first organic solvent and the second organic solvent. The metal salt, sulfur, alkali metal sulfide, first organic solvent, and second organic solvent were each prepared in a nitrogen atmosphere.

[0183] Prepared CaCl ２ : 0.04000 mol and SrCl ２ 0.04000 mol of CaCl was added to 100 ml of methanol (first organic solvent) and stirred at room temperature for 10 minutes to prepare a first raw material solution (first raw material solution preparation step). ２ and SrCl ２ was dissolved in methanol. ２ 0.07272 mol of S and 0.18180 mol of S were added to 215 ml of methanol (second organic solvent), and the mixture was heated to 50° C. and stirred for 1 hour to prepare a second raw material solution (second raw material solution preparation step). ２ S and S react to form sodium polysulfide (Na ２ S ｘ ) was produced. ２ S ｘ was dissolved in methanol. The first raw material solution preparation step and the second raw material solution preparation step were carried out in a nitrogen atmosphere.

[0184] The molar ratio of metal salt to alkali metal sulfide [CaCl ２ + SrCl ２ (mol) / Na ２ S (mol)] is 1.1, and the molar ratio of sulfur to alkali metal sulfide [S (mol) / Na ２ S (mol)] was 2.5.

[0185] Next, the prepared first raw material liquid and second raw material liquid were mixed in a nitrogen atmosphere, and the resulting mixture was stirred at 50° C. for 1 hour to prepare a reaction liquid (reaction step). A reaction occurred in the reaction liquid to produce calcium and strontium polysulfides (Ca ０．５ Sr ０．５ S ｘ ) and sodium chloride (NaCl) are produced, and Ca ０．５ Sr ０．５ S ｘ NaCl precipitated in the solution containing

[0186] The precipitate was removed from the reaction solution in a nitrogen atmosphere, and the supernatant was recovered. The recovered supernatant was subjected to solid-liquid separation treatment using a centrifuge (recovery step). Thereafter, the solution obtained by the solid-liquid separation treatment was heated to 60° C. and vacuum-dried for 20 hours to obtain Ca. ０．５ Sr ０．５ S ｘ A metal sulfide precursor consisting of polysulfides of the following composition was obtained (drying step). The obtained metal sulfide precursor was dried by adding nitrogen (N ２ ) gas at a flow rate of 0.2 L / min and heated to 900 ° C for 2 hours to obtain Ca ０．５ Sr ０．５ A metal sulfide having an S composition was obtained (calcination step).

[0187] [Example A2 (Comparative Example)] When preparing the second raw material solution, the same amount (215 ml) of 1-butanol (boiling point: 117.7°C) was used as the second organic solvent instead of methanol. A metal sulfide precursor and a metal sulfide were prepared in the same manner as in Example A1. The obtained metal sulfide was identified as Ca, which corresponds to ICDD card number 01-075-0265. ０．５ Sr ０．５ It had the S composition.

[0188] [Example A3] According to the first and third embodiments, CaS ｘ A metal sulfide precursor consisting of a polysulfide of the composition and a metal sulfide of the composition CaS were prepared.

[0189] Calcium chloride (CaCl) as a metal salt ２) was prepared. In addition to sulfur (S), sodium sulfide (Na ２ S) was prepared. Furthermore, ethanol (boiling point: 78.32°C) was prepared as the first organic solvent and the second organic solvent. The metal salt, sulfur, alkali metal sulfide, the first organic solvent, and the second organic solvent were each prepared in a nitrogen atmosphere.

[0190] Prepared CaCl ２ 0.09454 mol of CaCl was added to 100 ml of ethanol (first organic solvent), and the mixture was heated to 50° C. and stirred for 10 minutes to prepare a first raw material solution (first raw material solution preparation step). ２ was dissolved in ethanol. ２ 0.07272 mol of S and 0.36360 mol of S were added to 215 ml of ethanol (second organic solvent) and stirred at 50° C. for 1 hour to prepare a second raw material solution (second raw material solution preparation step). ２ S and S react to form sodium polysulfide (Na ２ S ｘ ) was produced. ２ S ｘ was dissolved in ethanol. The first raw material solution preparation step and the second raw material solution preparation step were carried out in a nitrogen atmosphere.

[0191] The molar ratio of metal salt to alkali metal sulfide [CaCl ２ (mol) / Na ２ S (mol)] is 1.3, and the molar ratio of sulfur to alkali metal sulfide [S (mol) / Na ２ S (mol)] was 5.

[0192] Next, the prepared first raw material liquid and second raw material liquid were mixed in a nitrogen atmosphere, and the resulting mixture was stirred at 50° C. for 1 hour to prepare a reaction liquid (reaction step). ｘ ) and sodium chloride (NaCl) are produced, resulting in CaS ｘ NaCl precipitated in the solution containing

[0193] The precipitate was removed from the reaction solution in a nitrogen atmosphere, and the supernatant was recovered. The recovered supernatant was subjected to solid-liquid separation using a centrifuge (recovery step). Thereafter, the solution obtained by the solid-liquid separation treatment was heated to 60° C. and vacuum-dried for 20 hours to obtain CaS. ｘ A metal sulfide precursor consisting of polysulfides of the following composition was obtained (drying step). The obtained metal sulfide precursor was dried by adding nitrogen (N ２ The mixture was fired at 900° C. for 2 hours while flowing a 0.2 L / min flow rate gas, thereby obtaining a metal sulfide having a CaS composition consistent with ICDD card number 03-065-2926 (firing step).

[0194] Example A4 (Comparative Example) When preparing the first feedstock solution, the same amount (100 ml) of 1-butanol was used as the first organic solvent instead of ethanol. Furthermore, when preparing the second feedstock solution, the same amount (215 ml) of 1-butanol was used as the second organic solvent instead of ethanol. A metal sulfide precursor and a metal sulfide were prepared using the same procedures as in Example A3. The obtained metal sulfide had a CaS composition consistent with ICDD card number 03-065-2926.

[0195] [Example A5] According to the first and third embodiments, SrS ｘ A metal sulfide precursor consisting of a polysulfide of the composition and a metal sulfide of the composition SrS were prepared.

[0196] Strontium chloride (SrCl) as a metal salt ２ ) was prepared. In addition to sulfur (S), sodium sulfide (Na ２ S) was prepared. Furthermore, ethanol and 1-propanol (boiling point: 97.2°C) were prepared as the first organic solvent and the second organic solvent, respectively. The metal salt, sulfur, alkali metal sulfide, the first organic solvent, and the second organic solvent were each prepared in a nitrogen atmosphere.

[0197] Prepared SrCl ２ 0.08000 mol of SrCl was added to 100 ml of ethanol (first organic solvent) and stirred at room temperature for 10 minutes to prepare a first raw material solution (first raw material solution preparation step). ２was dispersed in ethanol. ２ 0.07272 mol of S and 0.36360 mol of S were added to 215 ml of 1-propanol (second organic solvent) and stirred at 50° C. for 1 hour to prepare a second raw material solution (second raw material solution preparation step). ２ S and S react to form sodium polysulfide (Na ２ S ｘ ) was produced. ２ S ｘ was dissolved in 1-propanol. The first raw material liquid preparation step and the second raw material liquid preparation step were carried out in a nitrogen atmosphere.

[0198] The molar ratio of metal salt to alkali metal sulfide [SrCl ２ (mol) / Na ２ S (mol)] is 1.1, and the molar ratio of sulfur to alkali metal sulfide [S (mol) / Na ２ S (mol)] was 5.0.

[0199] Next, the prepared first raw material liquid and second raw material liquid were mixed in a nitrogen atmosphere, and the resulting mixture was stirred at 50° C. for 1 hour to prepare a reaction liquid (reaction step). A reaction occurred in the reaction liquid to produce strontium polysulfide (SrS ｘ ) and sodium chloride (NaCl) are produced, and SrS ｘ NaCl precipitated in the solution containing

[0200] The precipitate was removed from the reaction solution in a nitrogen atmosphere, and the supernatant was recovered. The recovered supernatant was subjected to solid-liquid separation using a centrifuge (recovery step). Thereafter, the solution obtained by the solid-liquid separation treatment was heated to 60° C. and vacuum-dried for 20 hours to obtain SrS. ｘ A metal sulfide precursor consisting of polysulfides of the following composition was obtained (drying step). The obtained metal sulfide precursor was dried by adding nitrogen (N ２ The mixture was fired at 900° C. for 2 hours while flowing a 1 L / min flow rate gas, to obtain a metal sulfide having a SrS composition consistent with ICDD card number 01-076-4208 (firing step).

[0201] Example A6 (Comparative Example) When preparing the second raw material liquid, the same amount (215 ml) of 1-butanol was used as the second organic solvent instead of 1-propanol. A metal sulfide precursor and a metal sulfide were prepared using the same procedures as in Example A5. The obtained metal sulfide had a SrS composition consistent with ICDD card number 01-076-4208.

[0202] [Example A7] According to the second and third aspects, Ga ２ S ３ A metal sulfide precursor and a metal sulfide having the following composition were prepared.

[0203] Gallium formate (Ga(HCOO)) as a metal salt ３ (CO ２ ) ０．７５ (H ２ O) ０．２５ ) was prepared. Sodium sulfide (Na ２ S) and ammonium chloride (NH ４ The metal salt, sodium sulfide, ammonium chloride, the third organic solvent, and the fourth organic solvent were prepared in a nitrogen atmosphere.

[0204] The prepared gallium formate (0.008 mol) was added to 50 ml of ethanol (third organic solvent) and stirred at 50 ° C. to prepare a third raw material solution (third raw material solution preparation step). In the third raw material solution, gallium formate was dispersed in ethanol. The third raw material solution preparation step was carried out in a nitrogen atmosphere.

[0205] Separately, a fourth raw material solution was prepared according to the following procedure. ２ S: 0.035 mol and NH ４ 0.071 mol of Cl was added to 45 ml of ethanol (fourth organic solvent) and mixed for 1 hour using a ball mill to obtain a mixed solution. A reaction occurred in the mixed solution to produce ammonium sulfide ((NH ４ ) ２ S) and sodium chloride (NaCl) are produced, and (NH ４ ) ２NaCl precipitated in the solution containing S. After the reaction, the mixed solution was subjected to solid-liquid separation using a centrifuge to remove the precipitate (NaCl), and the resulting solution was purified by (NH ４ ) ２ The ethanol solution of S was collected as a fourth raw material liquid. The fourth raw material liquid was collected in a nitrogen atmosphere.

[0206] Molar ratio of alkali metal sulfide to ammonium chloride [Na ２ S (mol) / NH ４ Cl (mol)] was 2.0, and the molar ratio of ammonium sulfide to metal salt [(NH ４ ) ２ S (mol) / gallium formate (mol)] was 3.0.

[0207] Next, the prepared third raw material liquid and fourth raw material liquid were mixed in a nitrogen atmosphere, and the resulting mixture was stirred at 50° C. to prepare a reaction liquid (reaction step). ２ S ３ ) and ammonium formate (HCOONH ４ A precipitate consisting of 1,2-dimethyl-2,4-trimethylsilyl methylcellulose was formed.

[0208] Next, ethanol was added to the reaction solution as an additional solvent in a nitrogen atmosphere to dissolve ammonium formate. Then, the reaction solution to which the additional solvent had been added was subjected to solid-liquid separation treatment to separate the precipitate (Ga ２ S ３ The recovered precipitate was heated to 60° C. and vacuum-dried for 20 hours (drying step), and then further dried under nitrogen (N ２ ) gas at a flow rate of 0.2 L / min and heated to 500°C for 2 hours to obtain Ga ２ S ３ A metal sulfide having the following composition was obtained (calcination step).

[0209] [Example A8 (Comparative Example)] When preparing the third raw material solution, the same amount (50 ml) of 1-butanol was used as the third organic solvent instead of ethanol. Furthermore, when preparing the fourth raw material solution, the same amount (45 ml) of 1-butanol was used as the fourth organic solvent instead of ethanol. A metal sulfide precursor and a metal sulfide were prepared in the same manner as in Example A7. The obtained metal sulfide was a Ga ２ S ３ It had the composition:

[0210] [Example A9] According to the fourth embodiment, SrGa ２ S ｘ a metal sulfide precursor consisting of a polysulfide of the composition SrGa ２ S ４ A metal sulfide having the following composition was prepared: SrS ｘ A metal sulfide precursor consisting of polysulfides of the composition is prepared, and Ga is added according to the second embodiment. ２ S ３ These were mixed and dried to prepare a mixed metal sulfide precursor, and the mixed metal sulfide precursor was then calcined to prepare a metal sulfide.

[0211] <SrS ｘ Synthesis of Metal Sulfide Precursor> Strontium chloride (SrCl ２ ) was prepared. In addition to sulfur (S), sodium sulfide (Na ２ S) was prepared. Furthermore, ethanol was prepared as the first organic solvent and the second organic solvent. The metal salt, sulfur, alkali metal sulfide, the first organic solvent, and the second organic solvent were each prepared in a nitrogen atmosphere.

[0212] Prepared SrCl ２ 0.09454 mol of SrCl was added to 100 ml of ethanol (first organic solvent) and stirred at room temperature for 10 minutes to prepare a first raw material solution (first raw material solution preparation step). ２ was dispersed in ethanol. ２0.07272 mol of S and 0.36360 mol of S were added to 215 ml of ethanol (second organic solvent) and stirred at 50° C. for 1 hour to prepare a second raw material solution (second raw material solution preparation step). ２ S and S react to form sodium polysulfide (Na ２ S ｘ ) was produced. ２ S ｘ was dissolved in ethanol. The first raw material solution preparation step and the second raw material solution preparation step were carried out in a nitrogen atmosphere.

[0213] The molar ratio of metal salt to alkali metal sulfide [SrCl ２ (mol) / Na ２ S (mol)] is 1.3, and the molar ratio of sulfur to alkali metal sulfide [S (mol) / Na ２ S (mol)] was 5.

[0214] Next, the prepared first raw material liquid and second raw material liquid were mixed in a nitrogen atmosphere, and the resulting mixture was stirred at 50° C. for 1 hour to prepare a reaction liquid (reaction step). A reaction occurred in the reaction liquid to produce strontium polysulfide (SrS ｘ ) and sodium chloride (NaCl) are produced, and SrS ｘ NaCl precipitated in the solution containing

[0215] The precipitate was removed from the reaction solution in a nitrogen atmosphere, and the supernatant was recovered. The recovered supernatant was subjected to solid-liquid separation using a centrifuge to obtain strontium polysulfide (SrS ｘ An ethanol solution in which the above-mentioned methylcellulose was dissolved was obtained (recovery step).

[0216] <Ga ２ S ３ Synthesis of Metal Sulfide Precursor> Gallium formate (Ga(HCOO)) was used as a metal salt. ３ (CO ２ ) ０．７５ (H ２ O) ０．２５ ) was prepared. Sodium sulfide (Na ２ S) and ammonium chloride (NH ４The metal salt, sodium sulfide, ammonium chloride, the first organic solvent, and the second organic solvent were prepared in a nitrogen atmosphere.

[0217] The prepared gallium formate (0.008 mol) was added to 50 ml of ethanol (third organic solvent) and stirred at 50 ° C. to prepare a third raw material solution (third raw material solution preparation step). In the third raw material solution, gallium formate was dispersed in ethanol. The third raw material solution preparation step was carried out in a nitrogen atmosphere.

[0218] Separately, a fourth raw material solution was prepared according to the following procedure. ２ S: 0.035 mol and NH ４ 0.071 mol of Cl was added to 45 ml of ethanol (fourth organic solvent) and mixed for 1 hour using a ball mill to obtain a mixed solution. A reaction occurred in the mixed solution to produce ammonium sulfide ((NH ４ ) ２ S) and sodium chloride (NaCl) are produced, and (NH ４ ) ２ NaCl precipitated in the solution containing S. After the reaction, the mixed solution was subjected to solid-liquid separation using a centrifuge to remove the precipitate (NaCl), and the resulting solution was purified by (NH ４ ) ２ The ethanol solution containing dissolved S was collected as a fourth raw material liquid. The fourth raw material liquid was collected in a nitrogen atmosphere.

[0219] Molar ratio of alkali metal sulfide to ammonium chloride [Na ２ S (mol) / NH ４ Cl (mol)] was 2.0, and the molar ratio of ammonium sulfide to metal salt [(NH ４ ) ２ S (mol) / gallium formate (mol)] was 3.0.

[0220] Next, the prepared third raw material liquid and fourth raw material liquid were mixed in a nitrogen atmosphere, and the resulting mixture was stirred at 50° C. to prepare a reaction liquid (reaction step). ２ S ３ ) and ammonium formate (HCOONH４ A precipitate consisting of 1,2-dimethyl-2,4-trimethylsilyl methylcellulose was formed.

[0221] Next, ethanol was added to the reaction solution as an additional solvent in a nitrogen atmosphere to dissolve ammonium formate. Then, the reaction solution to which the additional solvent had been added was subjected to solid-liquid separation treatment to separate the precipitate (Ga ２ S ３ ) was recovered as a metal sulfide precursor (recovery step).

[0222] <SrGa ２ S ４ Synthesis of Metal Sulfide> SrS prepared from the first and second raw material liquids in a nitrogen atmosphere ｘ The Ga prepared from the third and fourth raw material solutions was added to an ethanol solution of the first metal sulfide precursor. ２ S ３ The first metal sulfide precursor solution and the second metal sulfide were added and stirred to obtain a mixed solution, in which the molar ratio of Sr:Ga was 1:2.

[0223] Next, the resulting mixed solution was heated to 60° C. and vacuum dried for 20 hours to obtain SrGa ２ S ｘ A mixed metal sulfide precursor consisting of polysulfides of the following composition was obtained (drying step). The obtained mixed metal sulfide precursor was dried by adding nitrogen (N ２ ) gas at a flow rate of 1 L / min and heated to 800°C for 2 hours to obtain SrGa ２ S ４ A metal sulfide having the following composition was obtained (calcination step).

[0224] [Example A10] According to the fourth embodiment, CaGa ２ S ｘ A metal sulfide precursor consisting of a polysulfide of the composition CaGa ２ S ４ A metal sulfide having the following composition was prepared: CaS ｘ A metal sulfide precursor consisting of polysulfides of the composition is prepared, and Ga is added according to the second embodiment. ２ S ３These were mixed and dried to prepare a mixed metal sulfide precursor, and the mixed metal sulfide precursor was then calcined to prepare a metal sulfide.

[0225] <CaS ｘ Synthesis of Metal Sulfide Precursor> Calcium chloride (CaCl) was used as a metal salt. ２ ) was prepared. In addition to sulfur (S), sodium sulfide (Na ２ S) was prepared. Furthermore, ethanol was prepared as the first organic solvent and the second organic solvent. The metal salt, sulfur, alkali metal sulfide, the first organic solvent, and the second organic solvent were each prepared in a nitrogen atmosphere.

[0226] Prepared CaCl ２ 0.09454 mol of CaCl was added to 100 ml of ethanol (first organic solvent), and the mixture was heated to 50° C. and stirred for 10 minutes to prepare a first raw material solution (first raw material solution preparation step). ２ was dissolved in ethanol. ２ 0.07272 mol of S and 0.18180 mol of S were added to 215 ml of ethanol (second organic solvent) and stirred at 50° C. for 1 hour to prepare a second raw material solution (second raw material solution preparation step). ２ S and S react to form sodium polysulfide (Na ２ S ｘ ) was produced. ２ S ｘ was dissolved in ethanol. The first raw material solution preparation step and the second raw material solution preparation step were carried out in a nitrogen atmosphere.

[0227] The molar ratio of metal salt to alkali metal sulfide [CaCl ２ (mol) / Na ２ S (mol)] is 1.3, and the molar ratio of sulfur to alkali metal sulfide [S (mol) / Na ２ S (mol)] was 2.5.

[0228] Next, the prepared first raw material liquid and second raw material liquid were mixed in a nitrogen atmosphere, and the resulting mixture was stirred at 50° C. for 1 hour to prepare a reaction liquid (reaction step). ｘ ) and sodium chloride (NaCl) are produced, resulting in CaS ｘ NaCl precipitated in the solution containing

[0229] The precipitate was removed from the reaction solution in a nitrogen atmosphere, and the supernatant was recovered. The recovered supernatant was subjected to solid-liquid separation using a centrifuge to obtain calcium polysulfide (CaS ｘ An ethanol solution in which the above-mentioned methylcellulose was dissolved was obtained (recovery step).

[0230] <Ga ２ S ３ Synthesis of Metal Sulfide Precursor> Gallium formate (Ga(HCOO)) was used as a metal salt. ３ (CO ２ ) ０．７５ (H ２ O) ０．２５ ) was prepared. Sodium sulfide (Na ２ S) and ammonium chloride (NH ４ The metal salt, sodium sulfide, ammonium chloride, the third organic solvent, and the fourth organic solvent were prepared in a nitrogen atmosphere.

[0231] The prepared gallium formate (0.008 mol) was added to 50 ml of ethanol (third organic solvent) and stirred at 50 ° C. to prepare a third raw material solution (third raw material solution preparation step). In the third raw material solution, gallium formate was dispersed in ethanol. The third raw material solution preparation step was carried out in a nitrogen atmosphere.

[0232] Separately, a fourth raw material solution was prepared according to the following procedure. ２ S: 0.035 mol and NH ４ 0.071 mol of Cl was added to 45 ml of ethanol (fourth organic solvent) and mixed for 1 hour using a ball mill to obtain a mixed solution. A reaction occurred in the mixed solution to produce an ammonium sulfide solution ((NH ４ ) ２S solution) and sodium chloride (NaCl) are produced, and (NH ４ ) ２ NaCl precipitated in the solution containing S. After the reaction, the mixed solution was subjected to solid-liquid separation using a centrifuge to remove the precipitate (NaCl), and the resulting solution was purified by centrifugation using (NH ４ ) ２ The ethanol solution containing dissolved S was collected as a fourth raw material liquid. The fourth raw material liquid was collected in a nitrogen atmosphere.

[0233] Molar ratio of alkali metal sulfide to ammonium chloride [Na ２ S (mol) / NH ４ Cl (mol)] was 2.0, and the molar ratio of ammonium sulfide to metal salt [(NH ４ ) ２ S (mol) / gallium formate (mol)] was 3.0.

[0234] Next, the prepared third raw material liquid and fourth raw material liquid were mixed in a nitrogen atmosphere, and the resulting mixture was stirred at 50° C. to prepare a reaction liquid (reaction step). ２ S ３ ) and ammonium formate (HCOONH ４ A precipitate consisting of 1,2-dimethyl-2,4-trimethylsilyl methylcellulose was formed.

[0235] Next, ethanol was added to the reaction solution as an additional solvent in a nitrogen atmosphere to dissolve ammonium formate. Then, the reaction solution to which the additional solvent had been added was subjected to solid-liquid separation treatment to separate the precipitate (Ga ２ S ３ ) was recovered as a metal sulfide precursor (recovery step).

[0236] <CaGa ２ S ４ Synthesis of metal sulfide> CaS prepared from the first raw material liquid and the second raw material liquid in a nitrogen atmosphere ｘ The Ga prepared from the third and fourth raw material solutions was added to an ethanol solution of the first metal sulfide precursor. ２ S ３ The first metal sulfide precursor solution and the second metal sulfide were added and stirred to obtain a mixed solution. At this time, the first metal sulfide precursor solution and the second metal sulfide were mixed so that the resulting mixed solution had a molar ratio of Ca:Ga=1:2.

[0237] Next, the resulting mixed solution was heated to 60° C. and vacuum dried for 20 hours to obtain CaGa ２ S ｘ A mixed metal sulfide precursor consisting of polysulfides of the following composition was obtained (drying step). The obtained mixed metal sulfide precursor was dried by adding nitrogen (N ２ ) gas at a flow rate of 1 L / min and heated to 800°C for 2 hours to obtain CaGa ２ S ４ A metal sulfide having the following composition was obtained (calcination step).

[0238] [Example A11] According to the first and third embodiments, Li ２ S ｘ a metal sulfide precursor consisting of a polysulfide of the composition Li ２ A metal sulfide having a composition of S was prepared.

[0239] Lithium chloride (LiCl) was prepared as a metal salt. Sulfur (S) and sodium sulfide (Na) were also prepared as an alkali metal sulfide. ２ S) was prepared. Furthermore, ethanol (boiling point: 78.32°C) was prepared as the first organic solvent and the second organic solvent. The metal salt, sulfur, alkali metal sulfide, the first organic solvent, and the second organic solvent were each prepared in a nitrogen atmosphere.

[0240] The prepared LiCl: 0.050 mol was added to ethanol (first organic solvent): 100 ml, and the mixture was heated to 50 ° C and stirred for 10 minutes to prepare a first raw material solution (first raw material solution preparation step). In the first raw material solution, LiCl was dissolved in ethanol. Separately, Na ２ 0.023 mol of S and 0.114 mol of S were added to 215 ml of ethanol (second organic solvent) and stirred at 50° C. for 1 hour to prepare a second raw material solution (second raw material solution preparation step). ２ S and S react to form sodium polysulfide (Na ２ S ｘ ) was produced. ２ S ｘwas dissolved in ethanol. The first raw material solution preparation step and the second raw material solution preparation step were carried out in a nitrogen atmosphere.

[0241] The molar ratio of metal salt to alkali metal sulfide [LiCl (mol) / Na ２ S (mol)] is 2.2, and the molar ratio of sulfur to alkali metal sulfide [S (mol) / Na ２ S (mol)] was 5.

[0242] Next, the prepared first raw material liquid and second raw material liquid were mixed in a nitrogen atmosphere, and the resulting mixture was stirred at 50° C. for 1 hour to prepare a reaction liquid (reaction step). ２ S ｘ ) and sodium chloride (NaCl) are produced, and Li ２ S ｘ NaCl precipitated in the solution containing

[0243] The precipitate was removed from the reaction solution in a nitrogen atmosphere, and the supernatant was recovered. The recovered supernatant was subjected to solid-liquid separation treatment using a centrifuge (recovery step). Thereafter, the solution obtained by the solid-liquid separation treatment was heated to 80° C. and vacuum-dried for 20 hours to obtain Li. ２ S ｘ A metal sulfide precursor consisting of polysulfides of the following composition was obtained (drying step). The obtained metal sulfide precursor was dried by adding nitrogen (N ２ ) gas at a flow rate of 0.2 L / min and heated to 500 ° C. for 2 hours to obtain Li ２ A metal sulfide having a composition of S was obtained (calcination step). The obtained product (metal sulfide) contained a trace amount of LiCl, which corresponds to ICDD card number 01-071-4664.

[0244] Example A12 (Comparative Example) When preparing the first raw material liquid, the same amount (100 ml) of 1-butanol was used as the first organic solvent instead of ethanol. When preparing the second raw material liquid, the same amount (215 ml) of 1-butanol was used as the second organic solvent instead of ethanol. A metal sulfide precursor was prepared in the same manner as in Example A11 except for the above. The obtained metal sulfide precursor was treated with nitrogen (N ２) gas at a flow rate of 0.4 L / min and heated to 500 ° C. for 3 hours to obtain Li ２ A metal sulfide having a composition of S was obtained (calcination step). The obtained product (metal sulfide) contained a trace amount of LiCl, which corresponds to ICDD card number 01-071-4664.

[0245] [Example A13] When preparing the first raw material liquid, the same amount (100 ml) of 1-propanol was used as the first organic solvent instead of ethanol. Furthermore, when preparing the second raw material liquid, the same amount (215 ml) of 1-propanol was used as the second organic solvent instead of ethanol. A metal sulfide precursor was prepared in the same manner as in Example A11. The obtained metal sulfide precursor was dissolved in nitrogen (N ２ ) gas at a flow rate of 0.6 L / min and heated to 500 ° C. for 4 hours to obtain Li ２ A metal sulfide having a composition of S was obtained (calcination step). The obtained product (metal sulfide) contained a trace amount of LiCl, which corresponds to ICDD card number 01-071-4664.

[0246] The production conditions (solvent type and metal salt type) of the metal sulfide precursors and metal sulfides of Examples A1 to A13 are summarized in Table 1 below.

[0247]

[0248] (2) Evaluation The metal sulfides prepared in Examples A1 to A13 were evaluated for various properties as follows.

[0249] <SEM Observation (Average Primary Particle Diameter)> The average primary particle diameter (SEM diameter) of the metal sulfide (sample) was measured. First, the sample was observed using a scanning electron microscope (SEM) to obtain an SEM image. The observation was performed at a magnification of 200 to 10,000 times. Next, the SEM image was analyzed using image analysis particle size distribution measurement software (Mountec, Mac-View, Version 4, File Version: v1.0.0.14) to measure the particle diameters (Heywood diameter) of the particles constituting the powder. At this time, 300 or more particles were selected and analyzed in areas where the particles did not overlap. Next, a particle size distribution based on a volume standard was obtained from the particle diameters obtained. The particle diameter at the cumulative 50% diameter of the particle size distribution was defined as the average primary particle diameter (D50).

[0250] <Carbon Content (C Amount)> The carbon content of the sample was measured under the following conditions.

[0251] -Analytical equipment: Carbon and sulfur analyzer (Horiba, Ltd., EMIA-110) -Pretreatment: None in particular -Measurement method: Combustion in oxygen stream (tubular electric furnace) - Infrared absorption method -Extraction time: 120 seconds -Temperature: 1150°C -Combustion improver: Sn powder (0.3 g) -Sample amount: 0.03 g (The sample was wrapped in a 0.15 g Sn capsule.)

[0252] <XRD Analysis> The sample powder was analyzed by X-ray diffraction (XRD) to obtain an XRD profile. In Examples A1 to 10, the sample powder was loaded onto a sample stage in the atmosphere, and measurements were performed in the atmosphere. In addition, in Examples A11 to A13, a slurry of the sample powder and liquid paraffin mixed together was loaded onto a sample stage in a nitrogen-filled glove box, and measurements were performed in the atmosphere. The XRD analysis was performed under the following conditions.

[0253] - X-ray diffraction equipment: fully automatic multipurpose X-ray diffraction equipment (Rigaku Corporation, SmartLab) - Radiation source: CuKα - Detector: D / teX Ultra 250HE (Rigaku Corporation) - Tube current: 200mA - Tube voltage: 45kV - Scanning conditions: focusing method - Scanning axis: 2θ / θ - Scanning range: 5 to 80° - Step width: 0.01° - Scanning speed: 20.0° / min

[0254] Next, the obtained XRD profile was identified using integrated powder X-ray analysis software (PDXL2, Rigaku Corporation).

[0255] (3) Evaluation Results The carbon contents (C amounts) and average primary particle diameters D50 of the metal sulfides obtained in Examples A1 to A13 are summarized in Table 2 below.

[0256] The metal sulfides of Examples A2, A4, A6, A8, and A12, which were synthesized using a solvent with a boiling point of over 110° C., had a relatively high C content of 10,000 ppm or more. The metal sulfide of Example A8 also had a relatively large average primary particle diameter D50 of 34.6 μm.

[0257] In contrast, the metal sulfides of Examples A1, A3, A5, A7, A9, A10, A11, and A13, which were synthesized using a solvent with a boiling point of 110°C or less, had a low C amount of 9000 ppm or less. Furthermore, the metal sulfides of Examples A1, A3, A5, A7, A9, A10, A11, and A13 had a D50 of 27.9 μm or less, and of these, Examples A1, A3, A5, A7, and A9 had a small D50 of 5.1 μm or less.

[0258]

[0259] SEM images of the metal sulfide of Example A7 and the metal sulfide of Example A8 are shown in Figures 1 and 2. The metal sulfide in Figure 1 is composed of relatively fine particles, whereas the metal sulfide in Figure 2 is composed of relatively coarse particles.

[0260] From the above results, it can be understood that the present embodiment provides a method for producing a metal sulfide precursor and a method for producing a metal sulfide, which can obtain fine metal sulfides having a low carbon content by a simple method.

[0261] [Experimental Example B] (1) Preparation of phosphor powder [Example B1] In Example B1, a phosphor fired product was synthesized by a wet method, and the resulting phosphor fired product was subjected to pressurized injection wet media-less crushing. Specifically, a phosphor powder was prepared according to the following procedure.

[0262] <Synthesis of fired phosphor> Calcium chloride (CaCl) was used as a starting material.２ ) powder, sulfur (S) powder, europium chloride (EuCl ３ ) powder, sodium sulfide (Na ２ S) powder was prepared. Ethanol was also prepared as a solvent. Next, CaCl ２ The powder is Na ２ 1.3 times the molar amount of S powder, EuCl ３ The powder is Na ２ The amount of S powder was 0.01 times (1 at%), and the amount of S powder was Na ２ The starting materials were weighed out so that the molar ratio was 2.5 times that of the powder S. The weighing of each starting material was carried out in a nitrogen atmosphere.

[0263] Weighed CaCl ２ Powder and EuCl ３ The powder was stirred in ethanol to dissolve completely, and a first raw material solution was prepared. ２ S powder and S powder were stirred in ethanol to obtain Na ２ The S powder was dissolved to prepare a second raw material liquid. Next, the first raw material liquid and the second raw material liquid were mixed and stirred at room temperature and normal pressure to prepare a reaction liquid. During this process, a reaction occurred in the reaction liquid, and a precipitate consisting of sodium chloride (NaCl) was formed. After removing the precipitate from the reaction liquid, the supernatant was recovered, and the recovered supernatant was subjected to solid-liquid separation using a centrifuge. The preparation of the first raw material liquid and the second raw material liquid, the preparation of the reaction liquid, and the recovery of the supernatant were carried out in a nitrogen atmosphere.

[0264] The solution obtained after the solid-liquid separation treatment was then vacuum dried at 60°C for 12 hours to obtain a phosphor precursor. The obtained phosphor precursor was placed in a firing furnace and fired at 800°C for 2 hours in a nitrogen atmosphere to obtain a fired phosphor. During firing, nitrogen was flowed into the firing furnace at a flow rate of 1 L / min.

[0265] A scanning electron microscope (SEM) image of the obtained fired phosphor is shown in Figure 3. The particle size was as fine as about 1 µm.

[0266] <Crushing of the fired phosphor product> Next, the obtained fired phosphor product was placed in ethanol to prepare a slurry with a concentration of 5% by mass. The obtained slurry was then subjected to pre-crushing using an ultrasonic cleaner (US-10PS, SND Corporation) at an output of 100 W for 3 minutes. The pre-crushed slurry was then introduced into a liquid-injection wet media-less crusher (Starburst Mini, Sugino Machine Corporation) and subjected to crushing treatment. The discharge pressure was 200 MPa, and the number of passes was one. In this manner, a phosphor powder was prepared.

[0267] [Example B2] In the crushing treatment using the pressure injection type wet media-less crusher, the number of passes was changed to 2. Otherwise, phosphor powder was produced in the same procedure as in Example B1.

[0268] [Example B3] In the crushing treatment using the pressure injection type wet media-less crusher, the number of passes was changed to 3. Otherwise, phosphor powder was produced in the same manner as in Example B1.

[0269] Example B4 (Comparative Example) A fired phosphor material was synthesized in the same manner as in Example B1. Thereafter, the fired phosphor material was crushed in the following manner to prepare a phosphor powder.

[0270] <Crushing of the fired phosphor material> The fired phosphor material was placed in ethanol to prepare a slurry with a concentration of 5% by mass. The resulting slurry was then subjected to a crushing treatment using an ultrasonic homogenizer (Mitsui Electric Seiki Co., Ltd., UX-300) for 30 minutes. The output of the ultrasonic homogenizer was set to 50% (150 W).

[0271] Example B5 (Comparative Example) A phosphor powder was prepared in the same manner as in Example B4, except that the powder was subjected to a crushing treatment using an ultrasonic homogenizer for 60 minutes.

[0272] Example B6 (Comparative Example) A fired phosphor material was synthesized in the same manner as in Example B1. Thereafter, the fired phosphor material was crushed in the following manner to prepare a phosphor powder.

[0273] <Crushing of the fired phosphor product> 5 g of the fired phosphor product was placed in ethanol and crushed in a ball mill for 30 minutes. 45 g of zirconia balls were used as media during the ball mill treatment. The ball mill pot was rotated at 300 rpm.

[0274] [Example B7 (Comparative Example)] In Example B7, a fired phosphor material was synthesized by a dry method (solid-phase method), and the resulting fired phosphor material was crushed by a ball mill. Specifically, a phosphor powder was produced according to the following procedure.

[0275] <Synthesis of fired phosphor> Calcium carbonate (CaCO ３ ) to hydrogen sulfide (H ２ The mixture was fired at 850°C for 4 hours in a europium oxide (Eu) atmosphere to obtain calcium sulfide (CaS). ２ O ３ ) was mixed in an amount of 0.3 atomic %, and the resulting mixture was fired in an argon (Ar) atmosphere at 1000°C for 4 hours to obtain a fired product. The argon (Ar) flow rate during firing was 1.0 L / min. The fired product was pulverized and classified using a jet mill (manufactured by Dec Corporation) under a fluid pressure of 12 MPa to obtain a phosphor with a CaS:Eu composition.

[0276] An SEM image of the obtained phosphor is shown in Figure 4. The obtained phosphor had a coarse particle size of about 5 µm.

[0277] <Crushing of the fired phosphor> 50 g of the obtained phosphor was placed in ethanol and crushed in a ball mill for 20 hours. 450 g of zirconia balls were used as media during the ball milling process. The ball mill pot was rotated at 300 rpm.

[0278] [Example B8] In Example B8, a fired phosphor material was synthesized by a wet method, and the resulting fired phosphor material was crushed using a rocking mill. Specifically, a phosphor powder was produced according to the following procedure.

[0279] <Synthesis of fired phosphor> Calcium chloride (CaCl) was used as a starting material. ２ ) powder, strontium chloride (SrCl ２) powder, sulfur (S) powder, europium chloride (EuCl ３ ) powder, and sodium sulfide (Na ２ S) powder was prepared. Methanol and ethanol were also prepared as solvents. Next, CaCl ２ The powder was dissolved in SrCl ２ 0.6 times the amount of powder in molar ratio (Ca / Ca+Sr) = 0.06), Na ２ S powder, CaCl ２ powder and SrCl ２ 0.9 times the molar ratio of the total powder (Na ２ S / (CaCl ２ + SrCl ２ )=0.9), EuCl ３ The powder was ２ S powder was added in an amount of 0.003 times (0.3 at%) of S powder. ２ The starting materials were weighed out so that the molar ratio was 3.0 times that of the powder S. The weighing of each starting material was carried out in a nitrogen atmosphere.

[0280] Weighed CaCl ２ powder, SrCl ２ Powder and EuCl ３ The powder was stirred in a mixed solvent of methanol and ethanol to completely dissolve the powder, thereby preparing a first raw material solution. At this time, the mixing ratio of methanol and ethanol in the first organic solvent was adjusted so that the volume ratio of ethanol to methanol was 4.3 times. ２ S powder and S powder were stirred in ethanol to obtain Na ２ The S powder was dissolved to prepare a second raw material liquid. Next, the first raw material liquid and the second raw material liquid were mixed and stirred at room temperature and normal pressure to prepare a reaction liquid. During this process, a reaction occurred in the reaction liquid, and a precipitate consisting of sodium chloride (NaCl) was formed. After removing the precipitate from the reaction liquid, the supernatant was recovered, and the recovered supernatant was subjected to solid-liquid separation using a centrifuge. The preparation of the first raw material liquid and the second raw material liquid, the preparation of the reaction liquid, and the recovery of the supernatant were carried out in a nitrogen atmosphere.

[0281] The solution obtained after the solid-liquid separation treatment was then vacuum dried at 60°C for 12 hours to obtain a phosphor precursor. The obtained phosphor precursor was placed in a firing furnace and fired at 700°C for 2 hours in a nitrogen atmosphere to obtain a fired phosphor. During firing, nitrogen was flowed into the firing furnace at a flow rate of 4 L / min. In this way, the charged composition was Sr ０．９４ Ca ０．０６ S: EU ０．００３ A fired phosphor was obtained.

[0282] <Crushing of the fired phosphor product> The obtained fired phosphor product was placed in methanol to prepare a slurry with a concentration of 17% by mass. Next, the obtained slurry was crushed using a rocking mill (Seiwa Giken Co., Ltd., RM-05). The crushing treatment was performed under the conditions of 60 Hz and 30 minutes. In this way, a phosphor powder was prepared.

[0283] [Example B9] A fired phosphor material was synthesized in the same manner as in Example B8. Thereafter, the fired phosphor material was crushed in the following manner to prepare a phosphor powder.

[0284] <Crushing of the fired phosphor product> The obtained fired phosphor product was placed in ethanol to prepare a slurry with a concentration of 1.3% by mass. The obtained slurry was then introduced into a wet media-less apparatus (Yoshida Kikai Kogyo Co., Ltd., NVL-AS200) and subjected to a crushing treatment. The discharge pressure was 75 MPa and the number of passes was 5. In this manner, a phosphor powder was prepared.

[0285]

[0286] (2) Evaluation of Phosphor Powder Using the phosphor powders obtained in the examples and comparative examples as samples, various properties were evaluated as follows.

[0287] <Luminescence efficiency (absorbance, external quantum efficiency, internal quantum efficiency)> Using a fluorescence spectrophotometer (JASCO, FP-8500DS), the absorbance (Abs), external quantum efficiency (EQE), and internal quantum efficiency (IQE) of the sample were determined according to a quantum efficiency calculation program. The respective calculation formulas are shown below.

[0288] P1(λ) was the LED light spectrum at 450 nm, and P2(λ) was the sample spectrum. The area L1 enclosed by the spectrum P1(λ) in the excitation wavelength range of 430 nm to 500 nm was calculated according to the following formula (i), and the obtained value was used as the excitation intensity. The area L2 enclosed by the spectrum P2(λ) in the excitation wavelength range of 430 nm to 500 nm was calculated according to the following formula (ii), and the obtained value was used as the sample scattering intensity. The area E2 enclosed by the spectrum P2(λ) in the excitation wavelength range of 500 nm to 850 nm was calculated according to the following formula (iii), and the obtained value was used as the sample fluorescence intensity.

[0289]

[0290] The absorptance (Abs) is the ratio of the excitation light attenuated by the sample to the incident light, and was calculated according to the following formula (iv): ｅｍ is the number of photons of the excitation light irradiated on the sample, N ｅｘ The internal quantum efficiency (IQE) is the value obtained by dividing the number of photons of fluorescence emitted from the sample, N ｅｍ is the number of photons of the excitation light absorbed by the sample, N ａｂｓ The value was calculated according to the following formula (vi):

[0291]

[0292] <Particle Size Distribution> The particle size distribution of the sample was measured using a laser diffraction particle size distribution analyzer (Microtrac Bell, MT3300EXII). First, the circulation system of the device was filled with a 99.5% ethanol solution, and the sample (phosphor powder) was added so that the transmittance was 95-60%. Upon addition, the sample was subjected to a dispersion treatment such as ultrasonic dispersion (40 W, 180 seconds). Next, the particle size was measured while circulating the particles in the solvent in the measurement cell. From the measurements, a frequency particle size distribution curve and a cumulative particle size distribution curve on a volume basis were obtained, and the cumulative 50% diameter (D50) and cumulative 90% diameter (D90) were calculated from these. The particle size measurement was performed under the following conditions.

[0293] - Flow rate: 80% - Ultrasonic: 40W, 180 seconds - Set Zero time: 10 seconds - Measurement time: 30 seconds - Number of measurements: 1 - Transmittance: Transmitted - Particle refractive index: 2.46 - Particle shape: Aspherical - Solvent refractive index: 1.36

[0294] <XRD Analysis (Lattice Distortion, Crystallite Size)> The sample (phosphor powder) was analyzed by X-ray diffraction (XRD) to obtain an XRD profile. The XRD analysis was performed under the following conditions.

[0295] - X-ray diffraction equipment: fully automatic multipurpose X-ray diffraction equipment (Rigaku Corporation, SmartLab) - Radiation source: CuKα - Detector: D / teX Ultra 250HE (Rigaku Corporation) - Tube current: 200mA - Tube voltage: 45kV - Scanning conditions: focusing method - Scanning axis: 2θ / θ - Scanning range: 10 to 140° - Step width: 0.005° - Scanning speed: 1° / min

[0296] The obtained XRD profile was then analyzed by the WPPF method to determine the lattice strain (σ) and crystallite size. Specifically, the procedure was carried out using integrated powder X-ray analysis software (PDXL2, Rigaku Corporation) as follows.

[0297] First, identification (CaS) was performed using the software's automatic search function. Next, analysis was performed using the WPPF method. At this time, a line standard data file (SRM660a), which is a file of XRD data obtained by measuring LaB6, was selected for line correction. In addition, the peak width was corrected using an external standard sample (SRM66:LaB6). The "split-type Pearson VII function" was used as the peak shape model function.

[0298] Next, on the software operation screen, from the "Basic" tab, select "Refinement parameters" - "Method" and select "Intensity decomposition." Next, refinement was performed. During refinement, various parameters were adjusted until sufficient convergence was achieved.

[0299] <SEM Observation> The sample was observed with a scanning electron microscope (SEM).

[0300] (3) Evaluation Results The evaluation results obtained for the samples of the Examples and Comparative Examples are summarized in Table 4 below.

[0301] The example samples (Examples B1 to B3) synthesized from a phosphor burned material by a wet method and crushed by a pressurized injection type wet media-less crushing method all had a D90 of 10.0 μm or less, a lattice distortion σ of 0.010% or less (0.300% or less), and a relatively high internal quantum efficiency IQE of 54% or more.

[0302] In addition, even in the example samples (Examples B8 and B9) in which the feed composition was changed and the crushing was performed using a rocking wet media-less crushing method (rocking mill) or a pressurized injection wet media-less crushing method, the D90 was 10.0 μm or less, the lattice distortion σ was 0.300% or less, and the internal quantum efficiency IQE was relatively high at 40% or more.

[0303] In contrast, in Examples B4 and B5 where the crushing treatment was performed using an ultrasonic homogenizer, the D90 exceeded 10.0 μm. Also, in Example B6 where the crushing treatment was performed using a ball mill for 30 minutes, the D90 also exceeded 10.0 μm.

[0304] In Example B7, in which the phosphor fired product was synthesized by a dry method (solid-phase method) and crushed for a long time (20 hours) using a ball mill, the D90 was 10.0 μm or less, but the lattice distortion σ was large at 0.303%, and therefore the internal quantum efficiency IQE was very low at 7.7%.

[0305] In addition, the amount of sodium (Na) in each of the examples and comparative samples was 0.04 mass %.

[0306]

[0307] From the above results, it can be seen that the present embodiment provides a fine phosphor powder with high luminous efficiency and a method for producing the same.

Claims

1. A method for producing a metal sulfide precursor, comprising: preparing a first raw material liquid containing a first organic solvent having a boiling point of 110°C or less and a metal salt; preparing a second raw material liquid containing a second organic solvent having a boiling point of 110°C or less, sulfur, and an alkali metal sulfide; mixing the first raw material liquid with the second raw material liquid to obtain a reaction liquid containing a metal sulfide precursor and an alkali metal salt; and recovering a metal sulfide precursor from the reaction solution.

1. A method for producing a metal sulfide precursor, comprising: preparing a third raw material liquid containing a third organic solvent having a boiling point of 110°C or less and a metal salt; preparing a fourth raw material liquid containing a fourth organic solvent having a boiling point of 110°C or less and ammonium sulfide; mixing the third raw material liquid with the fourth raw material liquid to obtain a reaction liquid containing a metal sulfide precursor and an ammonium salt; and recovering a metal sulfide precursor from the reaction solution. 　 The method according to claim 2 , wherein in the step of preparing the fourth raw material liquid, the ammonium sulfide includes a polysulfide of ammonium sulfide. 　 The method of any one of claims 1 to 3, further comprising the step of drying the recovered metal sulfide precursor. 　 A method for producing a metal sulfide, comprising: A method comprising the step of calcining the metal sulfide precursor obtained by the method according to any one of claims 1 to 3. 　 The method according to claim 5, wherein the metal sulfide has a carbon content of 9000 ppm or less and an average primary particle diameter (D50) measured by SEM observation of 30.0 μm or less. 　 A method for producing a metal sulfide, comprising: mixing the first metal sulfide precursor and the second metal sulfide precursor to obtain a mixed metal sulfide precursor; and calcining the mixed metal sulfide precursor; 10. A method according to claim 9, wherein the first metal sulfide precursor is a metal sulfide precursor obtained by the method of claim 1, and the second metal sulfide precursor is a metal sulfide precursor obtained by the method of claim 2. 　 The method according to claim 7, wherein the carbon content of the metal sulfide is 9000 ppm or less, and the average primary particle diameter (D50) measured by SEM observation is 30.0 μm or less.

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