JP2014009253A - Method for producing sulfide phosphor, and the sulfide phosphor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for stably producing a sulfide phosphor exhibiting red luminescence having high phase purity, high chromatic purity and high luminance.SOLUTION: A strontium carbonate and a calcium carbonate represented by composition formula (SrCa)EuS are weighed to satisfy that x satisfies 0≤x≤1, y satisfied 0.2≤y≤0.6 and dissolved with a hydroxy-carboxylic acid, an europium compound weighed so as to be the above composition and a gallium compound weighed so as to have a molar ratio of an alkaline-earth metal to a gallium is in a range of 2:1 to 20:1 are mixed. An alcohol is added to the resultant mixture to obtain a gel body. Then the gel body is subjected to oxidation firing to prepare a mixture precursor including a carbonate and an oxide. The mixture precursor is subject to a reduction sulfuration and firing in a carbon disulfide or hydrogen sulfide gas under a condition of 850 to 1,000°C.

Description

  The present invention relates to a method for producing a sulfide phosphor and the sulfide phosphor. More specifically, the present invention relates to a phosphor that emits high-brightness orange to red fluorescence with near-ultraviolet to blue light used in lighting, displays, and the like. The present invention relates to a suitable method for producing a sulfide phosphor and the sulfide phosphor.

  In recent years, with the development of blue LEDs and near-ultraviolet LEDs, development of white light-emitting elements that obtain white by combining LEDs and phosphors is progressing.

  When producing a white light emitting element using this blue LED, as described in Patent Documents 1, 2, and 3, for example, a white light emitting element combining a blue LED and a yellow phosphor has been developed. These white light-emitting elements are increasingly used for illumination and as backlight light sources for liquid crystal displays.

  However, white light composed of such blue and its complementary color has poor color reproducibility and low color rendering, so a white light-emitting element called a three-wavelength type has been developed.

  As a three-wavelength type white light emitting element, for example, a white light emitting element using a blue light emitting element, a phosphor that emits green light by receiving blue light emitted from the light emitting element, and a phosphor that emits red light. An element is known (for example, refer to Patent Document 4).

Examples of red phosphors that can be excited by blue light include nitride phosphors such as CaAlSiN: Eu, (Sr, Ca) AlSiN, Ca ₂ Si ₅ N ₈ , Sr ₂ Si ₅ N ₈ (for example, Patent Document 5, 6, and Non-Patent Document 1), and sulfide phosphors such as CaS: Eu, SrS: Eu, and (Ca, Sr) S: Eu (see, for example, Patent Document 7) are known.

  Among them, sulfide phosphors have been known for a long time, and calcium and strontium carbonates and sulfates are mixed with europium oxide as a precursor, and the phosphor is then fired in hydrogen sulfide. I am making it.

  For this sulfide phosphor, many attempts have been made to improve the characteristics of the red phosphor. For example, Patent Document 8 and Patent Document 9 describe red phosphors having calcium sulfide as a base, Eu as a luminescent center, and Mn, Li, Ce, Gd and the like as sensitizers.

  In addition, it is well known to use a flux in the production of a phosphor. For example, Patent Document 10 discloses that sulfur is sulfided in hydrogen sulfide at a temperature of about 1000 ° C., and then heat treatment is performed by adding the flux. ing. Further, for example, Patent Document 11 discloses a method of mixing and baking sulfide and flux.

  Further, as a sulfidation method, a reduction sulfidation method of an oxide or carbonate using carbon disulfide has been developed (for example, Patent Document 12 and Non-Patent Document 2). In addition, in the case of adding a flux, it is also known that the sulfidation and the flux firing are divided and fired twice.

Generally, as the flux, carbonates such as Pb oxide, Mo oxide, Na ₂ CO ₃ , chlorides of alkali metals and alkaline earth metals, and the like are often used. It is also known that sulfide is used as a flux when producing a phosphor. For example, Non-Patent Document 3 describes using CaS: Eu as Na ₂ S or K ₂ S as a flux. Has been.

Further, for example, in Non-Patent Documents 4 and 5 and Patent Document 13, SrS—Ga ₂ S ₃ phase diagrams and CaS—Ga ₂ S ₃ phase diagrams and SrGa ₂ S ₄ and CaGa ₂ S ₄ single crystal growth based thereon are shown. The self-flux effect of Ga ₂ S ₃ is described. However, the phase diagram between SrGa ₂ S ₄ and Ga ₂ S ₃ , CaGa ₂ S ₄ and Ga ₂ S ₃ has been investigated, but the liquidus at the composition close to SrS and CaS is described. Not. In these equilibrium diagrams, the eutectic temperature of SrS or CaS and SrGa ₂ S ₄ or CaGa ₂ S ₄ is about 1100 ° C., and it is necessary to fire at a temperature of 1100 ° C. or higher in order to obtain the self-flux effect. It is thought that there is. However, when firing at a temperature of 1100 ° C. or higher, the problem is that the quartz tube used in the furnace is softened, and the precursor is melted, so that the crystal grains become large, which is about 1 μm to 20 μm suitable for LED phosphors. There arises a problem that particles cannot be obtained.

  As described above, phosphor preparation using various fluxes has been studied so far. However, since these fluxes are harmful and have hygroscopic properties, the flux is removed after firing. It was necessary.

  For example, since chloride flux is easily dissolved in water, it can be removed by washing with water. However, there is a problem that sulfides, particularly alkaline earth metal sulfides, are vulnerable to water. Further, the SrS sulfide phosphor has a problem that afterglow for several seconds to several tens of seconds occurs due to defects generated by chloride flux.

  As described above, the use of flux in the production of sulfide phosphors can be expected to produce crystals with high purity, but there are various problems described above, and it is not easy to solve these problems. There wasn't.

Japanese Patent Laid-Open No. 10-093146 Japanese Patent Application Laid-Open No. 10-065221 Japanese Patent Laid-Open No. 10-242513 JP 2000-244021 A JP 2006-008721 A JP 2006-152296 A JP 56-82876 A JP 2002-80845 A JP 2003-41250 A JP 2005-509081 A JP 2005-146190 A JP 2009-212264 A JP 2006-282409 A

Hiromu Watanabe and Naoto Kijima Journal of Alloys and Compounds 475 (2009) 434-439 Valery Petrykin and Masato Kakihana J. Am. Ceram. Soc., 92 [S1] S27-S31 (2009) M. Pham-Thi, N. Ruelle and C. Fouassier Jpn. J. Appl. Phys. 31 (1992) 2786 C. Komatsu, T. Takizawa Journal of Crystal Growth 210 (2000) 677 C. Komatsu-Hidaka, T. Takizawa Journal of Crystal Growth 222 (2001) 574

  The present invention has been proposed in view of such circumstances, and a sulfide capable of stably producing a sulfide phosphor having high phase purity, high color purity, and high luminance red light emission. It aims at providing the manufacturing method of fluorescent substance.

  The inventors of the present invention have made extensive studies to solve the above-described problems. As a result, a mixture precursor containing alkaline earth metal carbonate, which is a constituent of the phosphor, and a predetermined amount of gallium oxide is produced, and the precursor is subjected to a reduction sulfidation treatment, thereby providing a sulfide. The inventors have found that the surface of the particles is covered with a eutectic of gallium oxide and alkaline earth metal sulfide to act as a flux, and the present invention has been completed.

That is, the method for producing a sulfide phosphor according to the present invention is represented by a composition formula: (Sr _1-x Ca _x ) _1-y Eu _y S, where x is 0 ≦ x ≦ 1 and y is A method for producing a sulfide phosphor satisfying 0.2 ≦ y ≦ 0.6, wherein a predetermined amount of strontium carbonate and calcium carbonate weighed so as to have the above composition are dissolved in oxycarboxylic acid, It was obtained by mixing a predetermined amount of europium compound weighed to have a composition and a gallium compound weighed so that the molar ratio of alkaline earth metal to gallium was in the range of 2: 1 to 20: 1. A gel body preparation step for obtaining a gel body by adding alcohol to the mixed solution, and a precursor preparation step for preparing a mixture precursor containing carbonate and oxide by oxidizing and baking the gel body; The mixture precursor is 850 ° C to 1000 ° C. Wherein the at temperature conditions and a reduction firing step of firing by reducing sulfidation with carbon disulfide or hydrogen sulfide gas.

  Here, in the gel body preparation step, the strontium carbonate and calcium carbonate are added in an amount corresponding to 3 to 7 times the total number of moles of all metals and gallium constituting the sulfide phosphor. It is preferable to dissolve using an acid.

  Moreover, in the said gel body preparation process, the amount of alcohol equivalent to 3 times-14 times mole of the total mole number of all the metals and gallium which comprise the said sulfide fluorescent substance is added to the said liquid mixture, and it gelatinizes. It is preferable.

The sulfide phosphor according to the present invention is obtained by the above-described method for producing a sulfide phosphor, and is represented by a composition formula: (Sr _1-x Ca _x ) _1-y Eu _y S, where x is A sulfide phosphor in which 0 ≦ x ≦ 1 and y is 0.2 ≦ y ≦ 0.6, and a eutectic layer of gallium sulfide and alkaline earth metal sulfide is formed on the surface thereof. It is characterized by becoming.

  According to the method for producing a sulfide phosphor according to the present invention, for example, it is possible to produce a red light-emitting phosphor having high phase purity, high luminance, and high color purity by preventing generation of a green or yellow crystal phase. Can do. Further, according to this manufacturing method, it is not necessary to remove the formed flux by washing with water or the like, and no afterglow is generated, so that a sulfide phosphor can be stably and efficiently produced. And its industrial value is extremely great.

It is a figure for demonstrating an example of the method of including carbon disulfide in an inert gas. And X-ray diffraction pattern of the sulfide phosphor prepared in Example 1 and Example 4, SrS: is a diagram showing an X-ray diffraction pattern of Eu0.2% and _Ga 2 _{S 3 β.} It is a figure which shows the emission spectrum of the sulfide fluorescent substance produced in Example 1, 2, 3, 5. It is a figure which shows the result of having measured the excitation characteristic by the maximum light emission wavelength regarding the sulfide fluorescent substance produced in Example 2, 3, 5 and the comparative example 5. FIG.

Hereinafter, a specific embodiment to which the present invention is applied (hereinafter referred to as “the present embodiment”) will be described in detail in the following order with reference to the drawings. In addition, this invention is not limited to the following embodiment, A various change is possible in the range which does not deviate from the summary.
1. 1. Manufacturing method of sulfide phosphor 1-1. Outline of manufacturing method 1-2. Each step of the manufacturing method 2. Sulfide phosphor 2-1. Structure and effect of sulfide phosphor 2-2. 2. Structural analysis of sulfide phosphors Example 3-1. Production of sulfide phosphor 3-2. Evaluation of sulfide phosphors

<< 1. Method for producing sulfide phosphor >>
<1-1. Overview of manufacturing method>
The method for producing a sulfide phosphor according to the present embodiment is represented by a composition formula (Sr _1-x Ca _x ) _1-y Eu _y S that emits orange to red fluorescence, where x is 0 ≦ x This is a method for producing a sulfide phosphor in which ≦ 1 and y is 0.2 ≦ y ≦ 0.6.

  Specifically, in this production method, a predetermined amount of a gallium (Ga) compound is added together with an alkaline earth metal carbonate and a europium (Eu) compound that are constituents of the above-described sulfide phosphor, A gel body containing all metal elements uniformly is manufactured by a legal method, and the gel body is oxidized and baked to obtain a mixture precursor containing carbonate and Ga oxide containing the components uniformly, and this mixture precursor Is reduced and sulfided under a predetermined temperature condition.

In this manufacturing method, Ga oxide contained in the mixture precursor containing carbonate and oxide is sulfided by reduction sulfidation treatment to become gallium sulfide (Ga ₂ S ₃ ), and SrS, which is a constituent component of the phosphor, Ga ₂ S ₃ is generated at the same time as CaS is generated. The produced Ga ₂ S ₃ is produced at a temperature lower than the temperature generated in the conventionally known liquid phase, covers the surface of the alkaline earth metal sulfide particles, and acts as a flux. Thereby, the crystal growth of sulfide can be promoted, and a phosphor having high purity and high brightness can be effectively generated.

  In addition, in the sulfide phosphor obtained by this manufacturing method, the eutectic layer of gallium sulfide and alkaline earth metal sulfide covering the surface does not affect the light emission characteristics and has water resistance and moisture resistance effects. . Therefore, there is no need to perform water washing, no afterglow is generated, and the problems in producing a sulfide phosphor that has conventionally occurred using a flux can be solved at once.

<2-2. Each process of manufacturing method>
Hereinafter, the method for manufacturing a sulfide phosphor according to the present embodiment will be described more specifically for each step.

As described above, the method for producing a sulfide phosphor according to the present embodiment is a sulfide phosphor that emits fluorescence from orange to red, and has the composition formula (1): (Sr _1-x Ca _x ). _This is a method for producing a sulfide phosphor represented by _1-y Eu _y S, where x is 0 ≦ x ≦ 1 and y is 0.2 ≦ y ≦ 0.6.

  In this manufacturing method, an aqueous solution obtained by mixing raw materials is used to prepare a gel body by a complex polymerization method, and the gel body is oxidized and fired to prepare a mixture precursor containing carbonate and oxide. A precursor preparation step, and a reduction sulfide step in which the precursor is reduced and sulfided to obtain a sulfide phosphor having a surface coated with a eutectic layer of gallium sulfide and an alkaline earth metal sulfide.

(1) Gel body preparation step In the gel body preparation step, the raw material strontium (Sr) carbonate and calcium (Ca) carbonate are dissolved with an organic acid so as to have a predetermined composition represented by the above composition formula, A europium (Eu) compound is added and a gallium (Ga) compound is added and mixed. And an alcohol is added to the obtained liquid mixture, and it gels by heating at predetermined temperature and making it gelatinize.

  Specifically, first, in the gel body preparation step, strontium carbonate and calcium carbonate are dissolved in oxycarboxylic acid, and a europium compound and a gallium compound are mixed into the solution to obtain a mixed solution.

  Strontium carbonate as a strontium source and calcium carbonate as a calcium source are relatively inexpensive materials. By using these as raw materials, a phosphor with reduced cost can be produced.

  In the gel body preparation step, these raw material compounds are dispersed in water, stirred at room temperature, and oxycarboxylic acid is added to the dispersion to complex and completely dissolve the metal element.

  Here, as the oxycarboxylic acid, for example, citric acid, malic acid, tartaric acid, tartronic acid, glyceric acid, oxybutyric acid, hydroacrylic acid, lactic acid, glycolic acid and the like can be used, and among them, citric acid is used. More preferred.

  The amount of oxycarboxylic acid added is the total number of moles (Sr, Ca, Eu) of all metals (Sr, Ca, Eu) constituting the sulfide phosphor to be produced and gallium (Ga) added later. , The total of Ga) is preferably about 3 to 7 times mol. If the amount of oxycarboxylic acid added is less than 3 times the total number of moles of all metals, strontium carbonate and calcium carbonate as raw materials cannot be completely dissolved, and white precipitation of calcium citrate Etc. are formed. Moreover, there is a possibility that the complexation of the metal element does not proceed sufficiently. On the other hand, when the addition amount exceeds 7 times mole, the cost increases and the economic efficiency deteriorates, which is not preferable.

  The complexing treatment of the metal element by adding oxycarboxylic acid is not particularly limited. For example, the aqueous solution is heated to about 50 ° C. to 80 ° C. and stirred for about 30 minutes to 1 hour. Do.

  As the compound of the activation element Eu to be added, a water-soluble europium compound such as europium nitrate or oxide can be used. For example, as europium nitrate, the raw europium oxide is dissolved with a nitric acid solution of 3 times mole or more, and the europium oxide is completely dissolved by stirring for about 1 hour, and then the europium solution is dried. Can be obtained by: At the time of drying, it is heated to a temperature of about 80 ° C. to 120 ° C. to evaporate and remove excess nitric acid, and then quantified to a predetermined concentration. If excessive free nitric acid remains in the aqueous solution, a reaction occurs rapidly during the preparation of the gel body, and therefore it is preferable to remove it in advance.

  As the gallium compound, a water-soluble gallium compound such as gallium nitrate or oxide can be used. For example, gallium nitrate can be obtained by dissolving metal gallium as a raw material in a nitric acid solution having a molar ratio of 5 times or more of the metal gallium, stirring it completely, and then drying the gallium solution. . At the time of drying, it is heated to a temperature of about 80 ° C. to 120 ° C. to remove excess nitric acid by evaporation. Note that it is preferable that gallium nitrate is not in contact with the atmosphere because a gallium oxide film is formed when heated in the atmosphere.

The addition amount of strontium carbonate, calcium carbonate, and europium compound is weighed and mixed so that the metal ratio of the desired phosphor composition is obtained. In the present embodiment, the composition is represented by (Sr _1-x Ca _x ) _1-y Eu _y S, where x is 0 ≦ x ≦ 1 and y is 0.2 ≦ y ≦ 0. The raw material strontium carbonate, calcium carbonate, and europium compound are weighed and mixed. Since the atomic ratio in the raw material to be supplied and the atomic composition ratio of the obtained phosphor are substantially the same, each raw material is weighed and mixed so that the desired composition ratio is obtained. It can be a range.

  What is important in this manufacturing method is the amount of gallium compound added. In this embodiment, a gallium compound weighed so as to have a molar ratio of alkaline earth metal (total of Sr and Ca) to gallium (Ga) in the range of 2: 1 to 20: 1 is added.

Regarding the addition amount of the gallium compound, when the Ga amount is larger than the molar ratio (Sr + Ca): Ga of 2: 1, green or yellow light is emitted during the reduction sulfidation process in the reduction firing process described later (Sr, Ca, Eu). It is not preferable because Ga ₂ S ₄ is easily formed. Further, when the amount of Ga is more than 2: 1, since it is close to the eutectic composition of (Sr, Ca) S— (Sr, Ca) Ga ₂ S ₄ , the amount of liquid phase can be increased due to a decrease in melting point. Since it becomes easy to melt, a powdery phosphor cannot be obtained.

  On the other hand, if the amount of Ga is less than the (Sr + Ca): Ga molar ratio of 20: 1, the amount of liquid phase produced by reacting with gallium sulfide on the surface of the obtained alkaline earth metal sulfide powder is reduced. The liquid phase is difficult to cover the entire surface, and the flux effect cannot be obtained sufficiently.

  Therefore, by adding a gallium compound so that the molar ratio of (Sr + Ca): Ga is in the range of 2: 1 to 20: 1 and mixing with the raw material compound, generation of a phosphor emitting green or yellow light is suppressed. Thus, the phase purity can be increased, and the surface of the sulfide crystal can be effectively coated with gallium sulfide to promote crystal growth by the flux effect. Thereby, it is possible to stably obtain red-emitting phosphor particles having high luminance and high color purity.

  Next, in the gel body preparation step, the aqueous solution is gelled by adding alcohol to the mixed solution in which the gallium compound is added and mixed. Thus, by gelling the aqueous solution in which the raw materials are mixed into a gel body, the raw materials can be uniformly dispersed, and in particular, the rare earth elements europium and gallium that are the emission centers can be uniformly dispersed. Thus, the crystal growth can be promoted more effectively, and a phosphor exhibiting high luminance emission can be obtained.

  As the alcohol added to the mixed solution, it is preferable to use glycol. Specifically, it is preferable to use ethylene glycol or propylene glycol as the glycol.

  The amount of alcohol added is three times the total number of moles (total of Sr, Ca, Eu, Ga) of all metals (Sr, Ca, Eu) and gallium (Ga) constituting the sulfide phosphor to be produced. The amount is preferably about an amount corresponding to -14 times mole, and more preferably about 5 times to 12 times mole. If the amount of alcohol added is less than 3 times the moles of all the metal elements, the esterification reaction described later hardly occurs and gelation may not proceed efficiently. On the other hand, when the addition amount exceeds 14 times mole, the effect of alcohol addition does not increase any more, which is not preferable because the cost increases and the economic efficiency deteriorates.

  This alcohol gels with oxycarboxylic acid such as citric acid by polymerization with ethylene, but when the amount of alcohol is large, water evaporates and becomes an alcohol solvent. Then, since white precipitation is likely to occur at this time, it is suitable that the amount of alcohol is the same as that of oxycarboxylic acid to about twice the amount of oxycarboxylic acid.

  In the gelation reaction by addition of alcohol, for example, the temperature of the aqueous solution is heated to about 80 ° C. to 150 ° C. and stirred. By heating and stirring the aqueous solution in this manner, an esterification reaction is effectively generated in the aqueous solution and polymerization is performed to produce polyester, whereby the aqueous solution is gelled.

  Regarding the above-described gelation temperature, if it is less than 80 ° C., the gelation time becomes long, and if it exceeds 150 ° C., uniform gelation becomes difficult. Further, the gelation time varies depending on the water content of the aqueous solution, but it is preferable to perform the gelation by stirring for 5 hours to 12 hours at the gelation temperature described above.

  In the gelation of the aqueous solution, when the esterification reaction proceeds, nitric acid in the aqueous solution is rapidly decomposed to generate a reddish gas, and bubbles may be formed in the polyester to expand rapidly. Since the bubbles are easily dissolved in water, it may be polyesterified by stirring and polymerizing by adding water as appropriate and preparing an aqueous solution again. In addition, if nitric acid remains in the aqueous solution, it should be noted that a rapid reaction may occur during the thermal decomposition of the organic matter.

(2) Precursor preparation process In a precursor preparation process, the mixture precursor containing carbonate and an oxide is produced by performing an oxidation baking process with respect to the gel body obtained at the gel body preparation process.

  Here, the gel body obtained in the gel body preparation step contains organic substances derived from the added raw materials (carbonate, oxycarboxylic acid, alcohol, etc.). Therefore, in the precursor preparation step, it is preferable to subject the gel body to a decomposition treatment of the organic matter contained in the gel body by subjecting the gel body to a heat treatment prior to the oxidation firing treatment for the gel body. Thereby, the fall of the brightness | luminance by the undecomposed thing of the organic substance which remains can be suppressed, the emitted light intensity of the fluorescent substance obtained can be raised, and the fluorescent substance which shows high-intensity light emission can be produced.

  As heat processing temperature with respect to a gel body, it is preferable to set it as 400 to 500 degreeC, and it is more preferable to set it as 450 to 460 degreeC. Moreover, as heat processing time, it is preferable to set it as 1 hour-20 hours, and it is more preferable to set it as 4 hours-12 hours. In addition, by first performing heat treatment at 100 ° C. to 200 ° C. and then increasing the temperature to 400 ° C. to 500 ° C., the influence of rapid decomposition of organic substances contained in the gel can be avoided.

  The atmosphere for the heat treatment is not particularly limited, but it is preferably performed in an air atmosphere. Thereby, the organic substance in a gel body can be decomposed | disassembled more effectively and the brightness | luminance fall of fluorescent substance can be prevented.

  Subsequently, in the precursor preparation step, the gel body or the heat-treated product of the gel body is contained in the gel body by subjecting the gel body or the heat-treated product of the gel body to an oxidation firing process in an air atmosphere at a temperature condition of 700 ° C. to 900 ° C. A mixture precursor composed of a carbonate and an oxide containing uniform components is prepared.

Specifically, this oxidation baking treatment decomposes a mixture of (Ca, Sr, Eu) CO ₃ carbonate and Ga ₂ O ₃ oxide in which europium is uniformly dispersed, or partially carbonate. A mixture containing (Ca, Sr, Eu) O, Ga ₂ O ₃ oxide and (Ca, Sr, Eu) CO ₃ carbonate obtained in this manner is formed. This difference in the resulting mixture is due to the temperature conditions in the firing process.

  In the oxidation firing treatment, if the firing temperature is less than 700 ° C., the remaining organic matter and nitric acid are not easily decomposed by combustion, which is not preferable. On the other hand, when the temperature exceeds 900 ° C., the precursor is partially crystallized and the constituent components are hardly uniform, which is not preferable. The firing time is preferably 1 hour to 4 hours.

  Further, this oxidation firing treatment is preferably performed in an air atmosphere or an oxygen atmosphere as described above. By performing the heat treatment in an atmosphere containing oxygen, the organic matter remaining in the gel body can be effectively decomposed, and it is possible to suppress the carbon from remaining on the surface and reducing the luminance of the phosphor.

  Further, in this oxidation baking treatment, the thermal decomposition is often insufficient due to oxygen deficiency or agglomeration only by heat treatment on the gel body, so that the organic matter can be sufficiently burned and removed, and the oxidation reaction can be performed. It is preferable to promote. Therefore, when heat-treating the gel body, it is desirable to lightly grind the heat-treated product with a mortar or the like. Further, when oxygen or air is flowing, the precursor preparation step and the subsequent reduction firing step can be performed continuously.

(3) Reduction firing step In the reduction firing step, the mixture precursor obtained in the precursor preparation step is subjected to reduction sulfidation treatment and firing under a predetermined temperature condition. By this reductive sulfidation treatment, the precursor is reductively sulfidized to form a host crystal, and Sr or Ca site of the host crystal is doped with Eu, thereby obtaining a sulfide phosphor in which Eu is uniformly dispersed. .

  The manufacturing method according to the present embodiment is characterized in that in this reduction firing step, the gallium oxide in the mixture precursor is sulfided and acts as a flux. Specifically, the gallium oxide contained in the mixture precursor is sulfided by the reduction sulfurization treatment to generate gallium sulfide, and the gallium sulfide acts as a flux.

  More specifically, when Ga oxide is sulfided by reduction baking treatment to produce gallium sulfide, alkaline earth metal carbonate in which Eu is uniformly dispersed is sulfided in parallel therewith. Then, the generated gallium sulfide and the alkaline earth metal sulfide cause a eutectic reaction on the surface of the sulfide particle, and become a liquid phase at the eutectic temperature or higher, covering the particle surface. Through the cooling process, a coating layer composed of a eutectic reaction layer is formed. The coating layer made of a eutectic of gallium sulfide and alkaline earth metal sulfide exhibits a self-flux effect on the surface of the generated sulfide crystal, and works to promote crystal growth of the particles. This makes it possible to form phosphor particles with high phase purity, high luminance, and high color purity.

  What is important at this time is the sulfiding temperature in the reduction sulfiding treatment. The optimum sulfidation temperature varies depending on the ratio of (Sr, Ca) to Ga. When Ga is large, a sufficient liquid phase is generated to cover the surface of (Sr, Ca) S at a low temperature, so that the temperature is low or short. On the other hand, when the amount of Ga is small, the liquid phase is small, so that sulfidation at a high temperature for a long time is required. Therefore, judging from the viewpoint of performing an efficient treatment at any Ga amount, the sulfidation temperature needs to be 850 ° C. or higher at which the sulfidation reaction proceeds, and is set to 875 ° C. or higher that allows more efficient sulfidation. It is more preferable.

Here, regarding the upper limit of the sulfiding temperature, when the sulfiding temperature is a high sulfiding temperature exceeding 1000 ° C., (Sr, Ca) S and Ga ₂ S ₃ react to partially (Sr, Ca) Ga ₂ S. ₄ may be formed. Since this (Sr, Ca) Ga ₂ S ₄ : Eu has a property of emitting light from green to yellow, the color purity of the red phosphor is lowered. Therefore, it is necessary to set the temperature to 1000 ° C. or less at which (Sr, Ca) Ga ₂ S ₄ is not generated. In addition, when crystals are melted during the reductive sulfidation treatment, the fired product must be pulverized later. In this case, there is a risk that the luminance is lowered due to generation of defects accompanying the pulverization. For this reason, the upper limit of the sulfiding temperature is more preferably 950 ° C. or lower.

Although it does not specifically limit as processing time of a reductive sulfidation process, It is preferable to hold | maintain about 1 to 12 hours on the temperature conditions mentioned above. If the sulfidation time is shorter than 1 hour, the sulfidation is insufficient, and if it is longer than 12 hours, (Sr, Ca) Ga ₂ S ₄ is partially formed and the phase purity and color purity may be lowered.

The eutectic reaction between the alkaline earth metal sulfide and gallium sulfide is, for example, 1105 ° C. (SrS side), 995 which is the reaction temperature of SrS—Ga ₂ S ₃ described in Non-Patent Documents 4 and 5 described above. It was found that the process proceeds at a temperature much lower than ° C. (Ga ₂ S ₃ side). This is presumably because when reducing and sulfiding Ga, not only Ga ₂ S ₃ but also GaS and the like are produced, so that the reaction temperature is lowered.

As the gas used for the reduction sulfurization treatment, a mixed gas of hydrogen sulfide (H ₂ S) gas and an inert gas, an inert gas containing carbon disulfide (CS ₂ ), or the like can be used.

When a mixed gas of hydrogen sulfide (H ₂ S) gas and inert gas is used, the concentration of H ₂ S can be in the range of 1 volume% to 50 volume%. If the concentration of H ₂ S is less than 1% by volume, the gas flow rate used for sulfidation increases, or a long-time treatment is required, so that efficient treatment cannot be performed. On the other hand, if the concentration exceeds 50% by volume, it may cause deterioration of piping and gas packing, which makes it difficult to handle. Therefore, from the viewpoint of the efficiency of the sulfidation treatment, the hydrogen sulfide gas varies depending on the reaction conditions as appropriate, but is generally 1.5 to 6 times mol, more preferably 3 to 5 times mol of the required amount of sulfur. It is preferable for practical use to flow.

When an inert gas containing carbon disulfide (CS ₂ ) is used, carbon disulfide can be included in the inert gas in a range of 10% by volume to 50% by volume. Since carbon disulfide has a strong reducing power, it can be processed at a lower sulfurization temperature than when hydrogen sulfide gas is used, and the sulfurization time can be shortened at the same temperature. Thus, by being able to carry out the reductive sulfidation treatment under a lower temperature condition, it becomes possible to efficiently produce a phosphor having a desired composition while suppressing sulfur from volatilizing and escape. However, since the flux is generated by a eutectic reaction, in consideration of the time during which Ga ₂ S ₃ and (Sr, Ca) S react to form a liquid phase, the sulfurization time is at least 30 minutes or more, preferably 45 minutes or more. Is needed.

  The temperature of the carbon disulfide or inert gas used is preferably 15 ° C. or higher and lower than 46 ° C., and particularly preferably 20 ° C. to 25 ° C. If the temperature is less than 15 ° C., the concentration of carbon disulfide contained in the argon gas is low, and the reduction sulfidation may not proceed effectively. On the other hand, if the temperature is 46 ° C. or higher, it becomes higher than the boiling point of carbon disulfide, and it becomes difficult to control the evaporation amount, and it is difficult to perform uniform reduction sulfurization.

  In addition, as a method of including carbon disulfide in the inert gas, for example, as shown in FIG. 1, an inert gas such as argon gas is circulated in the liquid carbon disulfide and vaporized in the inert gas. For example, a method of adding carbon disulfide can be used.

As the inert gas, an inert gas such as argon (Ar) gas is preferably used. Nitrogen (N ₂ ) gas can be used as the inert gas in addition to argon gas, but it is not preferable because nitride may be formed by using nitrogen at a high temperature.

  In the reduction and sulfidation treatment, the container used for the synthesis of the phosphor is not particularly limited, and an oxide such as graphite, zirconia, and alumina, and a heat-resistant container such as boron nitride (BN) can be used. Among them, it is preferable to use graphite because alumina is reduced and impurities increase at high temperatures.

  Further, the firing furnace for performing the reduction sulfidation treatment is not particularly limited, and for example, a tubular furnace in which the furnace core tube is quartz can be used. Moreover, as temperature rising conditions, a temperature rising rate can be performed, for example as 10-30 degree-C / min.

  In addition, when firing in a tubular furnace, immediately after the start of heating so that the gas in the quartz tube can be expelled, a mixed gas of hydrogen sulfide gas and inert gas, an inert gas containing carbon disulfide, etc. It is preferable to flow gas. In particular, in a period of about 10 to 20 minutes from the start of heating, it is preferable to flow a gas that is twice to three times the volume of the entire quartz tube. Further, it is preferable to adjust the flow rate of the supply gas so that the amount of gas serving as the reduction medium becomes a sufficient amount at the temperature at which the reduction sulfurization starts. Even during firing, a sufficient amount of gas is required as described above. Therefore, it is preferable to keep the gas flowing until cooling is completed and the temperature reaches room temperature.

  By performing the reductive sulfidation treatment in this way, a baked powder of the sulfide phosphor represented by the composition formula (1) can be obtained. In addition, carbon may adhere to the surface of the obtained baked powder. In such a phosphor with carbon attached to the surface, the light emission luminance may decrease. Therefore, it is preferable to form a new surface on the surface by pulverizing the obtained fired powder after the above-described reduction sulfurization treatment. Thereby, the fall of the brightness | luminance of fluorescent substance can be prevented and a high-intensity fluorescent substance can be obtained.

According to the production method comprising the steps described in detail above, the composition formula (1) is represented by (Sr _1-x Ca _x ) _1-y Eu _y S, where x is 0 ≦ x ≦ 1 and y is A sulfide phosphor satisfying 0.2 ≦ y ≦ 0.6 can be manufactured.

According to such a manufacturing method, the Ga oxide contained in the mixture precursor containing carbonate and oxide is sulfided by reduction sulfidation to become gallium sulfide (Ga ₂ S ₃ ), and the generated Ga ₂ A eutectic with the alkaline earth metal sulfide formed at the same time as S ₃ is formed to coat the particle surface of the sulfide and act as a flux. Thereby, the crystal growth of sulfide can be promoted, and a sulfide phosphor having high phase purity, high luminance and high color purity can be effectively generated.

≪2. Sulfide phosphor >>
<2-1. Structure and effect of sulfide phosphor>
The sulfide phosphor produced by the production method described above is represented by the composition formula (1): (Sr _1-x Ca _x ) _1-y Eu _y S, where x is 0 ≦ x ≦ 1, y is It satisfies 0.2 ≦ y ≦ 0.6.

  The sulfide phosphor represented by the above composition formula has strontium sulfide (SrS) and / or calcium sulfide (CaS) as a base crystal and europium (Eu) as an emission center. In this sulfide phosphor, the emission wavelength can be arbitrarily controlled by adjusting x (0 ≦ x ≦ 1) in the formula, which is the content ratio of strontium sulfide and / or calcium sulfide. That is, the emission wavelength of CaS: Eu is 655 nm, the emission wavelength of SrS: Eu is 615 nm, and the emission wavelength can be arbitrarily controlled between the wavelengths by adjusting the content ratio of strontium and calcium. .

In this sulfide phosphor, in the manufacturing process described above, the gallium oxide contained in the mixture precursor is reduced to gallium sulfide (Ga ₂ S ₃ ) by the reduction sulfidation treatment, and the gallium sulfide is converted into an alkaline earth metal. A eutectic reaction is caused with the particle surface of the sulfide to form a eutectic of gallium sulfide and an alkaline earth metal so as to cover the particle surface. That is, in this sulfide phosphor, the eutectic layer of gallium sulfide and alkaline earth metal sulfide is coated on the particle surface.

  In such a sulfide phosphor, the self-flux effect is exerted on the surface of the sulfide crystal formed by the eutectic layer, and the crystal growth of the particles is promoted, whereby the phase purity is high and the brightness is high. Phosphor particles.

  Further, the gallium sulfide constituting the eutectic layer does not affect the light emission characteristics, does not generate afterglow, and can impart water resistance and moisture resistance to the phosphor particles. Therefore, unlike the conventional method using a flux such as chloride, an operation for removing the flux by washing with water or the like is not required.

<2-2. Structural analysis of sulfide phosphors>
Here, FIG. 2 shows an X-ray diffraction pattern for sulfide phosphors produced in Example 1 and Example 4 described later, and an X-ray diffraction pattern for SrS: Eu0.2% and Ga ₂ S ₃ β. Is shown.

As shown in the X-ray diffraction pattern of FIG. 2, a peak derived from Ga ₂ S ₃ is detected although the intensity is weak, and becomes a eutectic with the sulfide phosphor represented by the composition formula (1). Can be confirmed. In addition, except for the peak derived from Ga ₂ S ₃ , no foreign phase is observed at all, and it can be seen that the crystal has extremely high phase purity.

≪3. Examples >>
Hereinafter, the present invention will be described in more detail with reference to examples. In addition, this invention is not limited to the following Example.

<3-1. Production of sulfide phosphors>
Example 1 (Sr _0.995 Eu _0.005 S + 0.166 × Ga ₂ S ₃ (when Sr: Ga = 3: 1))
(Preparation of gallium nitrate solution and europium nitrate solution)
Metal gallium (Ga) was placed in a nitric acid solution 7 times the number of moles of Ga, and the vessel was capped so that the nitric acid would not volatilize, and was stirred and dissolved on a hot plate at 80 ° C. for 1 day. In the reaction, since NOx is generated, an opening is provided in the lid. After dissolving Ga, excess nitric acid was evaporated and removed on a hot plate at 130 ° C., and distilled water was added to prepare a gallium nitrate solution having a Ga concentration of 0.5 mol / liter.

On the other hand, after europium oxide (Eu) (3N: Eu ₂ O ₃ manufactured by Furuuchi Chemical Co., Ltd.) 0.005 mol (1.9126 g) was completely dissolved in a nitric acid solution (60% manufactured by Kanto Chemical Co., Ltd.). The solution was evaporated to dryness to obtain europium nitrate. Distilled water was added to this europium nitrate and dissolved in 100 ml to prepare an aqueous solution with an Eu concentration of 0.1 mol / liter.

(Gel body production process)
To a beaker containing distilled water, 1.853 g of strontium carbonate (manufactured by Kanto Chemical Co., Ltd., 3N) was added, and the temperature of the hot stirrer was set to 80 ° C., followed by stirring at 150 rpm. An amount of citric acid corresponding to 6 moles of all metal elements (Sr + Eu + Ga) was added thereto and stirred for 1 hour to prepare a solution in which strontium carbonate was completely dissolved.

  Subsequently, a europium nitrate solution (0.1 mol / liter) was added to the solution so that Sr: Eu = 99.5: 0.5, and the mixture was stirred at 80 ° C. for 30 minutes. Then, a gallium nitrate solution (1 mol / liter) was added to the obtained aqueous solution in a beaker so that the metal molar ratio was (Sr + Eu): Ga = 6: 1, and the mixture was prepared. Thereafter, the mixture was stirred for 1 hour on a hot plate at 80 ° C., propylene glycol in an amount corresponding to 12 moles of the total number of metal elements (Sr + Eu + Ga) was added to the mixture and stirred for another 2 hours, A gel body was prepared by stirring at 140 ° C. for 1 hour to evaporate nitric acid at 120 ° C. for 1 hour.

(Precursor production process)
Next, the obtained gel was heated with a mantle heater set at 180 ° C. for 1 hour, and the set temperature was raised to 450 ° C. and baked for 2 hours to decompose the organic matter. Further, the mixture was baked in a box furnace at 550 ° C. for 2 hours in the air and at 750 ° C. for 2 hours to prepare a mixture precursor powder containing carbonate and oxide.

(Reduction firing process)
Next, the obtained precursor powder is put in a graphite vessel and subjected to reduction sulfidation treatment at 900 ° C. for 1 hour in an argon (Ar) gas containing carbon disulfide (CS ₂ ) in a tubular furnace, thereby sulfiding the surface. A sulfide phosphor represented by Sr _0.995 Eu _0.005 S coated with a gallium eutectic was produced.

[Example 2] (Ca _0.995 Eu _0.005 S + 0.166 × Ga ₂ S ₃ (when Ca: Ga = 3: 1))
Ca _0.995 whose surface was coated with a gallium sulfide eutectic in the same manner as in Example 1 except that 1.792 g of calcium carbonate (3N manufactured by Kanto Chemical Co., Ltd.) was used instead of strontium carbonate. A sulfide phosphor represented by Eu _0.005 S was produced.

Example 3 ((Sr _0.5 Ca _0.5 ) _0.995 Eu _0.005 S + 0.166 × Ga ₂ S ₃ ((Sr + Ca): Ga = 3: 1 and Sr: Ca = 0.5: 0.5)
In order to compose strontium and calcium at a ratio of 0.5: 0.5, gallium sulfide was formed on the surface in the same manner as in Example 1 except that 1.089 g of strontium carbonate and 0.739 g of calcium carbonate were mixed. A sulfide phosphor represented by (Sr _0.5 Ca _0.5 ) _0.995 Eu _0.005 S coated with a eutectic was prepared.

Example 4 (Sr _0.995 Eu _0.005 S + 0.083 × Ga ₂ S ₃ (when (Sr + Eu): Ga = 6: 1))
In the same manner as in Example 1, except that the addition amount of gallium nitrate (1 mol / L) was added so that the molar ratio of metal was (Sr + Eu): Ga = 12: 1. A sulfide phosphor represented by Sr _0.995 Eu _0.005 S coated with crystal was produced.

[Example 5]
In the reductive sulfidation treatment, Sr whose surface was coated with a gallium sulfide eutectic in the same manner as in Example 4 was used except that Ar gas containing 10% hydrogen sulfide gas was used and the sulfidation time was 5 hours. A sulfide phosphor represented by _0.995 Eu _0.005 S was produced.

[Example 6]
It is represented by Sr _0.995 Eu _0.005 S coated with a gallium sulfide eutectic on the surface in the same manner as in Example 1 except that the sulfurization temperature was set to 925 ° C. during the reduction sulfurization treatment. A sulfide phosphor was prepared.

[Example 7]
In the reductive sulfidation treatment, the surface is represented by Sr _0.995 Eu _0.005 S coated with a gallium sulfide eutectic on the surface in the same manner as in Example 1 except that the sulfidation temperature was 850 ° C. A sulfide phosphor was prepared.

[Comparative Example 1]
It is represented by Sr _0.995 Eu _0.005 S in the same manner as in Example 1 except that the gallium nitrate solution was added so that the ratio of Sr to Ga (Sr: Ga) was 6: 5. A sulfide phosphor was prepared.

  In Comparative Example 1, the sample after sulfidation melted and expanded, and the inside was a cavity. Therefore, the obtained sulfide phosphor was pulverized and the fluorescence characteristics were measured.

[Comparative Example 2]
Implementation was performed except that 0.866 g of strontium carbonate and 0.587 g of calcium carbonate were mixed and the gallium nitrate solution was added so that the ratio of Sr, Ca and Ga (Sr: Ca: Ga) was 3: 3: 5. A sulfide phosphor represented by (Sr _0.5 Ca _0.5 ) _0.995 Eu _0.005 was produced in the same manner as in Example 3.

  In Comparative Example 2, the sample after sulfidation melted and expanded, and the inside was a cavity. Therefore, the obtained sulfide phosphor was pulverized and the fluorescence characteristics were measured.

[Comparative Example 3]
A sulfide phosphor represented by Sr _0.995 Eu _0.005 S was produced in the same manner as in Example 1 except that the sulfurization temperature was set to 800 ° C. during the reduction sulfurization treatment.

[Comparative Example 4]
A sulfide phosphor represented by Sr _0.995 Eu _0.005 S was produced in the same manner as in Example 4 except that the sulfurization temperature was changed to 1020 ° C. during the reduction sulfurization treatment.

  In Comparative Example 4, the sample after sulfidation melted and expanded, and the inside was a cavity. Therefore, the obtained sulfide phosphor was pulverized and the fluorescence characteristics were measured.

[Comparative Example 5]
It is represented by Sr _0.995 Eu _0.005 S in the same manner as in Example 1 except that the gallium nitrate solution is added so that the ratio of Sr to Ga (Sr: Ga) is 24: 1. A sulfide phosphor was prepared.

[Comparative Example 6]
In order to compose strontium and calcium at a ratio of 85:15, 2.227 g of strontium carbonate and 0.266 g of calcium carbonate were mixed, and the ratio of (Sr + Ca) to Eu ((Sr + Ca): Eu) was 99.8: 0. A precursor was prepared in the same manner as in Example 1 except that the europium nitrate solution was added so as to be .2 and no gallium nitrate was added.

To the obtained precursor, 25% by weight of strontium chloride (SrCl ₂ ) as a flux was added, and this was pulverized in a mortar and placed in a graphite container.

Next, the graphite vessel is put into a tubular furnace using a double vessel containing a graphite tube in a quartz tube, and reduced by heat treatment at 925 ° C. for 1 hour under Ar flow through liquid carbon disulfide. Sulfidation was performed to produce a sulfide phosphor represented by (Sr _0.85 Ca _0.15 ) _0.995 Eu _0.005 S.

  The Ar flow rate is 50 ml / min for 10 minutes from the start of the heat treatment, then 10 ml / min until the temperature reaches 460 ° C., 20 ml / min until the temperature reaches from 460 ° C. to 925 ° C., and during the heat treatment for 1 hour at 925 ° C. The total time of 4 hours and 20 minutes from the end of the heat treatment until the furnace temperature reached 40 ° C. was set to 10 ml / min.

[Comparative Example 7]
A sulfide phosphor represented by (Sr _0.85 Ca _0.15 ) _0.995 Eu _0.005 S was prepared in the same manner as in Comparative Example 6 except that strontium chloride used as a flux was not added. Produced. The obtained powder was black.

<3-2. Evaluation of sulfide phosphors>
(Measurement of fluorescence characteristics (luminance) and measurement results)
Luminance is evaluated as a fluorescent property by using YAG: Ce (P61: P46 manufactured by Kasei Optonics Co., Ltd.), which is well known as a yellow phosphor for LEDs, as a reference material. 1 to Comparative Example 5 The Eu-added sulfide phosphors prepared were compared.

  Table 1 below summarizes the fluorescence characteristics of the sulfide phosphors produced in the examples and comparative examples. The afterglow is evaluated by irradiating each sulfide phosphor with the Xe lamp emitted through a filter that transmits only light from 455 nm to 465 nm in a dark room, and photographing the fluorescence 10 seconds after the irradiation is stopped with a digital camera. did. Then, the presence or absence of afterglow was determined based on whether or not the photograph had fluorescence.

  FIG. 3 shows the emission spectrum (excitation wavelength: 460 nm) of the sulfide phosphor prepared in Examples 1, 2, 3, and 5. FIG. 4 shows the results of measuring the excitation characteristics at the maximum emission wavelength of the sulfide phosphors produced in Examples 2, 3, 5 and Comparative Example 5.

  As shown in Table 1 and FIG. 3, Ga is added so that the molar ratio of the alkaline earth metal and Ga is in the range of 2: 1 to 20: 1, and the sulfidation temperature in the reduction sulfidation treatment is 850 ° C. to In the case of Example 1 to Example 7 in the range of 1000 ° C., the emission luminance of the obtained sulfide phosphor is greatly improved, and the luminance is 1.5 to 1.8 times higher than YAG: Ce. was gotten.

On the other hand, as shown in the results of Comparative Examples 1 to 5, when the Ga addition amount and the sulfiding temperature are not in the above-described ranges, the emission luminance of the obtained sulfide phosphor is significantly higher than that of YAG: Ce. Even if it did not decrease, it was almost the same as YAG: Ce, and there was no improvement in luminance. Further, in Comparative Example 6, since SrCl ₂ was used as a flux, an effect of improving luminance was obtained, but afterglow occurred. Furthermore, in Comparative Example 7, the luminance was remarkably lowered because the obtained sulfide phosphor became black.

Moreover, as can be seen from the graph showing the excitation characteristics in FIG. 4, the sulfide phosphors obtained in Examples 2, 3, and 5 and the sulfide phosphor obtained in Comparative Example 5 are excited. It can be seen that the characteristics are different. This is because the surface of the phosphor of (Sr _1-x Ca _x ) _1-y Eu _y S prepared in Examples 2, 3, and 5 was melted, and a thin alkaline earth metal sulfide and Ga were formed on the particle surface. eutectic material layer between the ₂ S ₃ is considered to be due to coated form. Since this eutectic layer absorbs light of 400 nm or less, emission of excitation of 400 nm or less is reduced in Examples 2, 3, and 5, as shown in FIG.

(X-ray diffraction measurement and measurement results)
X-ray diffraction measurement was performed on the sulfide phosphors produced in Example 1 and Example 4. FIG. 2 shows the respective X-ray diffraction patterns. FIG. 2 also shows the X-ray diffraction patterns of the phosphor of SrS: Eu 0.2% and the phosphor of Ga ₂ S ₃ β.

As shown in FIG. 2, the diffraction pattern was almost the same as that of SrS, and a weak peak associated with Ga ₂ S ₃ was also detected. From this, it was found that the eutectic of gallium sulfide was coated. In addition, no other phases were observed, and it was found that the crystals had high phase purity.

Claims (4)

Composition formula: (Sr _1-x Ca _x ) _1-y Eu _y S, where x is 0 ≦ x ≦ 1 and y is 0.2 ≦ y ≦ 0.6 A manufacturing method of
A predetermined amount of strontium carbonate and calcium carbonate weighed to have the above composition are dissolved in oxycarboxylic acid, and a predetermined amount of europium compound weighed to have the above composition, an alkaline earth metal and gallium A gel body preparation step of obtaining a gel body by adding an alcohol to a mixed liquid obtained by mixing a gallium compound weighed so that the molar ratio is in the range of 2: 1 to 20: 1;
A precursor producing step of producing a mixture precursor containing a carbonate and an oxide by oxidizing and firing the gel body;
And a reduction firing step of firing the mixture precursor by reducing and sulfiding in carbon disulfide or hydrogen sulfide gas under a temperature condition of 850 ° C. to 1000 ° C.   In the gel body preparation step, the strontium carbonate and calcium carbonate are used in an amount corresponding to 3 to 7 times the total number of moles of all metals and gallium constituting the sulfide phosphor. The method for producing a sulfide phosphor according to claim 1, wherein the sulfide phosphor is dissolved.   In the gel body preparation step, the mixture solution is gelled by adding an amount of alcohol corresponding to 3 to 14 times the total number of moles of all metals and gallium constituting the sulfide phosphor. The method for producing a sulfide phosphor according to claim 1 or 2, characterized in that It is obtained by the method for producing a sulfide phosphor according to claim 1 and is represented by a composition formula: (Sr _1-x Ca _x ) _1-y Eu _y S, where x is 0 ≦ x ≦ 1. , Y is a sulfide phosphor in which 0.2 ≦ y ≦ 0.6,
A sulfide phosphor comprising a eutectic layer of gallium sulfide and alkaline earth metal sulfide formed on the surface thereof.

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