TWI448535B - Eu method for the production of metalloid phosphite phosphors - Google Patents

Description

Method for producing Eu-activated alkaline earth metal silicate phosphor

The present invention relates to a citrate-based phosphor which exhibits high-luminance yellow luminescence by ultraviolet light to a visible region and which emits Eu ²⁺ (Sr _1-y , Eu _y ) ₃ SiO ₅ (where 0 < y <0.1); and the composition of the composition (Ba _x , Sr _1-xy , Eu _y ) ₃ SiO ₅ showing high-brightness green to yellow luminescence by excitation of ultraviolet light to the visible region (where 0<x<1, 0<y<0.1), Eu of the composition formula (Ba _x , Sr _1-xy , Eu _y ) ₂ SiO ₄ (where 0<x<1, 0<y<0.1) A method for producing a ²⁺ -activated alkaline earth metal silicate-based phosphor.

A white LED (Light Emitting Diode) is a liquid crystal display (LCD) that combines the emission of a near-ultraviolet to blue-emitting LED with a phosphor to produce white light. The backlight source is actively developed, and the development applied to lighting applications continues to advance as an application for the next generation.

As a white LED phosphor used in the white LED, YAG:Ce ³⁺ which exhibits yellow fluorescence by blue excitation or green to yellow fluorescence (Ba, Sr) has been known. , Ca) ₂ SiO ₄ :Eu ²⁺ , Sr ₃ SiO ₅ :Eu ^{2+ ,} etc., but a phosphor of higher brightness is desired.

In general, the method of synthesizing a phosphor is, for example, as described in Non-Patent Document 1, and the raw material powders are mixed in a wet or dry manner, placed in a calcination vessel, and calcined and heated at a high temperature, by the raw materials. It is synthesized by solid phase reaction.

As the activator, in the production of a phosphor using Ce ³⁺ , Eu ²⁺ or Tb ³⁺ , heat treatment is generally carried out in a reducing gas atmosphere using an inert gas containing a few % of H ₂ gas. In the high-temperature heat treatment, for example, in the case of Sr ₃ SiO ₅ :Eu ²⁺ , SrO reacts with SiO ₂ to form a parent oxide crystal, and is calcined in a reducing gas atmosphere to reduce the Eu of the activator from trivalent to 2 valence, and replace Sr ²⁺ in the parent crystal. Thereby, a Sr ₃ SiO ₅ :Eu ²⁺ phosphor can be synthesized.

In general, in order to obtain a high-intensity Sr ₃ SiO ₅ :Eu ²⁺ phosphor, it is necessary to increase the purity of the crystal phase, and to uniformly disperse Eu ²⁺ as an activator in the matrix crystal. As described in Patent Document 2, when a metal oxide is produced by a solid phase method, it is necessary to perform calcination for a long period of time at a high temperature. However, if the calcination temperature is increased or the calcination time is prolonged, the sintering is enhanced and the particle diameter is increased. Therefore, in the phosphor in which the sintered body is pulverized in order to reduce the particle size, there is a problem that the luminescence intensity is lowered due to damage due to pulverization.

As a countermeasure for lowering the calcination temperature or reducing the particle size of the particle diameter, a liquid phase method for synthesizing a metal oxide by using a liquid phase to prepare a body before a metal oxide and calcining the precursor is studied. . In the liquid phase method, the metal element is dissolved and mixed in the solvent, so that uniform mixing at the atomic level can be performed, and it is not necessary to cause solid phase diffusion of the oxide raw material powder as in the solid phase method, so that synthesis at a low temperature can be expected . Moreover, the increase in crystal grain size can also be suppressed by low-temperature synthesis.

As an example of such a liquid phase method, there is a precipitation method disclosed in Patent Document 1. In Patent Document 1, a precipitate is formed from a metal salt and tetraethoxysilane (TEOS) or tannin, and a phosphor is synthesized by drying and heat treatment. The metal salt and the TEOS do not form a precipitate at the same time, but merely bring the powder raw material closer to a finer state, and there is a problem that it is not uniformly mixed at the elemental level.

Further, in Patent Document 2, as a liquid phase method, a citric acid method, a coprecipitation method, a metal alkoxide method (sol-gel method), a thermal decomposition method, a complex polymerization method, and a PVA method are described. A method of producing a precursor by wet synthesis such as a hydrothermal gelation method, and comparing these, and using a hydrothermal gelation method, can efficiently synthesize a metal oxide phosphor.

According to Patent Document 2, when a mixed solution of one or more kinds of metal elements and TEOS and a solvent is hydrothermally treated, a gel body in which metal elements are uniformly dispersed can be produced, and the gel can be dried and heat-treated. A composite metal oxide precursor can be obtained. Since the gel utilizes the gelling ability of TEOS, it has characteristics of less organic matter. By hydrothermal gelation of a liquid phase mixed at an atomic level, a uniform body can be produced. Since the diffusion distance of the elements of the precursor system is short, a composite metal oxide having a uniform chemical composition can be formed by heat treatment at a relatively low temperature. However, since the gelation ability of TEOS is utilized, when the composition ratio of the ruthenium in the metal component is small, there is a problem that all the metal element components cannot be contained in the gel.

On the other hand, in the case of producing a body before the alkaline earth metal silicate-based phosphor by a liquid phase method other than the hydrothermal gelation method, a decane oxide such as TEOS is generally used. A uniform gel can be produced by using a metal salt and TEOS as a raw material, and dissolving and mixing these in a suitable solvent. When a non-aqueous solvent is used as the solvent, a homogeneous mixture can be obtained. However, if water is used as the solvent, since tetraethoxy decane is hydrophobic, hydrolysis reaction occurs at the interface between TEOS and water, which is locally caused. The possibility of reaction, and there is a problem that it is difficult to obtain a homogeneous mixture. On the other hand, there are also problems such as non-aqueous solvents, especially organic solvents, which are harmful to the human body or fire.

However, in recent years, Non-Patent Document 2 and Patent Document 3 disclose a water-soluble cerium compound (WSS, Water Soluble Silicon) which is a raw material of neodymium. The water-soluble cerium compound is a propylene glycoloxy group substituted with four ethoxy groups of TEOS, and since it contains a hydroxyl group, it can be stably present in an acidic aqueous solution at room temperature. The aqueous solution of the water-soluble cerium compound is hydrolyzed and polycondensed by heating or the like to obtain a SiO ₂ gel. This water-soluble cerium compound is known to have a greater gelation ability than TEOS.

Non-Patent Document 2 discloses that a water-soluble cerium compound and a metal zinc raw material aqueous solution are mixed and hydrothermally treated to prepare a precursor, which is calcined in a reducing gas atmosphere to obtain Mn-added Zn ₂ SiO _{4 .} Fluorescent body. The ratio of the metal element (sum of Zn to Si) to Si in the fluorescent system is 3:1. In the case of TEOS, gelation of the whole metal component is difficult, but it can be made by using a water-soluble cerium compound. A gel containing all metal components. However, since the hydrothermal synthesis method must be used for the production of the precursor, there is a problem that heat treatment in a pressure vessel such as an autoclave is necessary.

In this case, the inventors of the present invention have tried to produce a ratio of 4:1 (Sr _{1-y )} to a metal component by a hydrothermal gelation method using a water-soluble cerium compound. Eu _y ) ₃ SiO ₅ phosphor, (Ba _x , Sr _1-xy , Eu _y ) ₃ SiO ₅ , and the ratio of metal component elements to Si is 3:1 (Ba _x , Sr _1-xy , Eu _{y 2} Eu-activated silicate phosphor precursors of the SiO ₄ phosphor. As a result, it was found that it is difficult to make the entire metal component uniform and all contained in the gel, and it is easy to cause composition variation or uneven element distribution.

[Previous Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open Publication No. 2007-131843

Patent Document 2: Japanese Patent Laid-Open Publication No. 2008-007390

Patent Document 3: Japanese Patent Laid-Open Publication No. 2010-7032

[Non-patent literature]

Non-Patent Document 1: "Fluorescent Handbook", Ohmsha Corporation, P. 166

Non-Patent Document 2: N. Takahashi, Y. Suzuki, M. Kakihana, "Synthesis of Zn2SiO4: Mn2+green emission phosphor by hydrothermal gelation method using a novel water soluble silicon compound", Jounal of the Ceramic Society of Japan, 2009, Vol. 117, No. 3, p. 313-315

SUMMARY OF THE INVENTION An object of the present invention is to provide a production method which is capable of eliminating various technical problems as described above when manufacturing an Eu-activated alkaline earth metal silicate phosphor as follows, and is capable of synthesizing chemical composition uniformity at a lower temperature than the prior art. The body is high before, and the precursor is heat-treated, thereby efficiently and inexpensively producing a high-brightness alkaline earth metal silicate phosphor having a uniform chemical composition and a single phase, the Eu-activated alkaline earth metal silicate phosphor System composition formula (Sr _1-y ,Eu _y ) ₃ SiO ₅ (where 0 < y < 0.1), composition formula (Ba _x , Sr _1-xy , Eu _y ) ₃ SiO ₅ (where 0 < x < 1 , 0 < y < 0.1), and the ratio of all metal component elements (Sr, Ba, Eu, Si) to Si is 4:1; composition formula (Ba _x , Sr _1-xy , Eu _y ) ₂ SiO ₄ ( Wherein, 0<x<1, 0<y<0.1), and the ratio of all metal component elements (Ba, Sr, Eu, Si) to Si is 3:1.

The inventors of the present invention have made an effort to solve the above problems, and as a result, have obtained the following findings, and have completed the present invention: a composition of the self-composition formula (Sr _1-y , Eu _y ) ₃ SiO ₅ (where 0 < y < 0.1) Formula (Ba _x , Sr _1-xy , Eu _y ) ₃ SiO ₅ (where 0<x<1, 0<y<0.1), composition formula (Ba _x , Sr _1-xy , Eu _y ) ₂ SiO ₄ ( Wherein, the total metal component of lanthanum, cerium, lanthanum, cerium which is a constituent of the alkaline earth metal silicate phosphor selected from the group of 0<x<1, 0<y<0.1) is made into an aqueous solution, and After mixing, the liquid temperature is maintained at 30 to 100 ° C, thereby forming a gel in which the total metal component is uniformly distributed, and then, by drying the gel, heat treatment in the atmosphere, and heat treatment in a reducing gas atmosphere, An alkaline earth metal silicate phosphor having a uniform chemical composition and consisting of a single phase crystalline phase is obtained.

That is, the first invention of the present invention is a method for producing an Eu-activated alkaline earth metal silicate phosphor, which is a compositional formula (Sr _1-y , Eu _y ) ₃ SiO ₅ (where 0 < y < 0.1) ), composition formula (Ba _x , Sr _1-xy , Eu _y ) ₃ SiO ₅ (where 0<x<1, 0<y<0.1), composition formula (Ba _x , Sr _1-xy , Eu _y ) ₂ a method for producing an Eu-alkaline earth metal silicate phosphor selected from the group consisting of SiO ₄ (where 0<x<1, 0<y<0.1),

It is characterized by the following steps 1:

[step 1]

An aqueous solution of each of the raw materials of each of the ruthenium, osmium, iridium, and osmium constituting the metal component is prepared, and the mixed aqueous solution of the aqueous solution prepared by mixing is maintained at a liquid temperature of 30 to 100 ° C to form a total amount of the total metal component. The step of uniformly dispersing the gel in a state.

A second invention of the present invention is a method for producing an Eu-activated alkaline earth metal silicate phosphor, which is a compositional formula (Sr _1-y , Eu _y ) ₃ SiO ₅ (where 0 < y < 0.1), Composition formula (Ba _x , Sr _1-xy , Eu _y ) ₃ SiO ₅ (where 0<x<1, 0<y<0.1), composition formula (Ba _x , Sr _1-xy , Eu _y ) ₂ SiO ₄ (Manufacturing method of Eu-activated alkaline earth metal silicate phosphor selected from the group of 0<x<1, 0<y<0.1),

It is characterized by including the following steps 1 to 4:

[step 1]

An aqueous solution of each of the raw materials of the respective constituents of cerium, lanthanum, cerium, and lanthanum constituting the metal component is prepared, and the mixed aqueous solution of the aqueous solution prepared by mixing is maintained at a liquid temperature of 30 to 100 ° C to form a total amount of the total metal component. a step of uniformly dispersing the gel in a state;

[Step 2]

a step of drying the gel formed by the step 1 to form a dried product, and removing the solvent contained therein;

[Step 3]

a step of heat-treating the dried product in the second step in an atmospheric environment to remove the organic matter to obtain a calcined powder;

[Step 4]

The step of obtaining a phosphor powder by heat-treating the calcined powder formed in the step 3 in a reducing gas atmosphere.

According to a third aspect of the invention, there is provided a method for producing an Eu-activated alkaline earth metal silicate phosphor according to the first aspect or the second aspect of the invention, wherein the mixed aqueous solution in the step 1 is used as a metal component. The concentration of hydrazine is set to 1 to 5.5 mol/L.

According to a fourth aspect of the present invention, there is provided a method for producing an Eu-activated alkaline earth metal silicate phosphor according to the first aspect or the second aspect, wherein the aqueous solution of the ruthenium raw material in the step 1 is added to tetramethoxy decane. After the 1,2-propanediol is heated, stirred, and mixed, hydrochloric acid is added to form a water-soluble hydrazine aqueous solution.

According to a fifth aspect of the present invention, there is provided a method for producing an Eu-activated alkaline earth metal silicate phosphor according to the second aspect of the present invention, which comprises, after the step 3, the calcined powder formed in the above step 3 by classification The step of removing coarse particles of 100 μm or more.

According to the present invention, when the Eu-activated alkaline earth metal silicate phosphor is produced as follows, the body having a higher uniformity of the chemical composition can be synthesized at a lower temperature than the prior method, and the precursor is heat-treated, thereby being efficient. Producing a uniform and single-phase high-brightness Eu-activated alkaline earth metal silicate phosphor, which is an alkaline-based alkaline earth metal silicate phosphorescent system with all metal components (Ba, Sr, Eu, Si) and Si The ratio is 3:1 composition formula (Ba _x , Sr _1-xy , Eu _y ) ₂ SiO ₄ (where 0<x<1, 0<y<0.1); all metal component elements (Sr, Ba, The ratio of Eu, Si) to Si is a composition formula of 4:1 (Sr _1-y , Eu _y ) ₃ SiO ₅ (where 0 < y < 0.1), composition formula (Ba _x , Sr _1-xy , Eu _{y 3} SiO ₅ (where 0 < x < 1, 0 < y < 0.1).

Further, according to the production method of the present invention, since it is not necessary to synthesize a gel containing an all-metal component uniformly, such as a pressure vessel of an autoclave, the manufacturing cost is remarkably lowered, which is industrially significant.

Hereinafter, the embodiments of the present invention will be described in detail, but the embodiments described below are representative of the present invention, and are not limited to the embodiments as long as they do not deviate from the gist of the present invention.

First, the manufacturing procedure of the Eu-activated alkaline earth metal silicate phosphor will be described.

The manufacturing process of the Eu-activated alkaline earth metal silicate phosphor of the present invention includes: forming an aqueous solution (hereinafter, also referred to as a raw material aqueous solution) as a raw material of each element of ruthenium, osmium, iridium, and osmium which constitutes a metal component. After mixing these, the liquid temperature is maintained at 30 to 100 ° C, thereby heating the raw material at a temperature of 30 to 100 ° C to form a state in which other metal components containing cerium, lanthanum, cerium are uniformly dispersed. Step 1 of the transparent gel; step 2 of obtaining a dried solvent to remove the solvent by drying the transparent gel formed in the step 1; thereafter, the dried product is heat-treated in the atmosphere to prepare a calcined powder Step 3 of obtaining Eu-activated alkaline earth metal silicate phosphor precursor; stepwise removing stepwise removal of coarse particles of 100 μm or more, if necessary; forming Eu-activated alkaline earth by heat treatment in a reducing gas atmosphere Step 4 of the metal silicate phosphor.

Hereinafter, the above steps 1 to 4 will be described in detail.

[step 1]

In this step, an aqueous solution of a raw material of ruthenium, osmium, iridium, and osmium which constitutes a metal component is prepared, and after mixing these, it is maintained at a temperature of 30 to 100 ° C, thereby obtaining an all-metal of ruthenium, osmium, iridium, and osmium. The step of uniformly dispersing the gel of the total amount of ingredients.

In this step 1, first, an aqueous solution of a raw material of all metal components of cerium, lanthanum, cerium, and lanthanum is prepared. The niobium raw material is not particularly limited as long as it is dissolved in water and the pH of the aqueous solution is 7 or less, and a chloride, an oxide, an acetate, a nitrate, a carbonate, a sulfate, an oxalate or the like of rhodium may be used. In particular, in the case where the anion component can be easily removed by heating, it is preferred to use a nitrate, an acetate, a carbonate, an oxalate or the like. When the metal salt is dissolved, a hydroxycarboxylic acid such as citric acid, lactic acid or malic acid may be added. In this case, since the composition variation from the addition can be suppressed, it is preferable to form an aqueous solution of a carbonate having a small solubility as compared with a nitrate or the like. About bismuth raw materials and bismuth raw materials are also the same as bismuth raw materials. Furthermore, the aqueous solution of the raw materials of cerium, lanthanum and cerium can be separately mixed, or a mixed aqueous solution can be prepared in one container from the beginning.

Then, in the present invention, the above-mentioned known water-soluble cerium compound is used as the cerium raw material. If the pH of the aqueous solution is more than 7, the water-soluble cerium compound immediately starts to gel, and there is a flaw in the formation of a non-uniform gel. Further, when the pH is less than 1, gelation is difficult, and therefore the pH is in the range of 1 to 7.

Further, when the amount of water relative to the constituent metal element is too large, the gel and the liquid are separated into two layers, and metal ions are eluted in the liquid phase, so that the gel becomes a non-uniform composition. If the amount of water is too small relative to the metal element, there is a case where it is still impossible to form a uniform aqueous solution, and the metal precipitates before the gel formation to form a non-uniform gel. In the present invention, since the all-metal component element is uniformly dispersed, It is important, so it is important that the concentration of the metal element in the preparation of the aqueous solution is set to 1 to 5.5 mol/L. Ideally, it can be set to 2 to 5.5 mol/L.

Here, the specific production conditions of the water-soluble cerium compound can be produced by the method described in the production example of Patent Document 3. Specifically, 1,2-propanediol (0.4 mol) was added to tetramethoxysilane (0.1 mol), and the mixture was mixed for 24 hours while stirring using a heating stirrer to adjust the liquid temperature to 54 ° C, and then added. Hydrochloric acid (0.0001 mol), the liquid temperature was 54 ° C, and mixed for another hour to obtain a water-soluble hydrazine aqueous solution. Further, in Production Examples 1 to 9 of Patent Document 3, various water-soluble cerium compounds are described, and any of them can be used in the present invention.

Then, each aqueous solution prepared under the above conditions is mixed, stirred at room temperature for 30 minutes to 1 hour, and the obtained solution is added to a container and maintained at a temperature of 30 to 100 ° C to obtain a uniform gel. When the temperature is lower than 30 ° C, gelation takes time. If the temperature exceeds 100 ° C and the water boils, both drying and gelation are caused. Therefore, it is important to set the temperature to 30 ° C to 100 ° C. Further, it is more preferably 50 to 100 °C. The gelation time is not particularly limited as long as it is a uniform gelation time as a whole, and a uniform gel is usually obtained in about 24 hours.

The container is not particularly limited, and those having heat resistance up to a heating temperature, such as glass, polypropylene, or polytetrafluoroethylene, can be used.

[Step 2]

Step 2 is a step of removing the solvent from the gel obtained in the step 1, and obtaining a dried product.

The removal of the solvent is relatively simple by heating. Since the solvent component contained in the gel is water, ethanol or propylene glycol, it is preferably 100 to 120 °C. The heating time also depends on the amount of the sample, and is preferably about 1 to 6 hours.

[Step 3]

Step 3 is a step of heat-treating the dried solid obtained in the step 2 in the atmosphere to thermally decompose the organic matter, thereby obtaining a calcined powder as a body before the Eu-alkali-based metal citrate phosphor.

The purpose of the heat treatment in the atmosphere is to perform decomposition of the organic matter contained in the raw material, removal of carbon by decomposition, and crystal growth of the oxide mother crystal of the Eu-alkaline earth metal silicate phosphor.

The conditions of the heat treatment in the atmosphere are carried out at a temperature of from 400 to 1600 °C. Further, the heat treatment may be carried out once by heat treatment, or may be carried out in a plurality of times. When the heat treatment is carried out in multiple portions, it is preferred to carry out crushing with a mortar or the like at each heat treatment.

The details of the heat treatment are as follows: first, decomposition of the organic substance causes evaporation or thermal decomposition and combustion of propylene glycol and hydroxycarboxylic acid contained in the raw material, and in order to burn the organic substance, a temperature of 400 or more in the atmosphere is required, and only decomposition of the organic substance is required. In the case of the case, it is preferably carried out in an environment of 400 to 600 °C.

The second carbon removal completely removes the carbon formed during the decomposition of the organic substance, and decomposes the metal element when it is carbonated. At a temperature lower than 700 ° C, carbon cannot be removed. If it exceeds 1300 ° C, melting or sintering may occur. Therefore, heat treatment at a temperature exceeding 1300 ° C is carried out in consideration of the heat treatment time. In the case of performing carbon removal alone, it is preferred to carry out heat treatment in a temperature range of from 700 ° C to 1300 ° C.

Further, in the case where an oxide precursor crystal is formed, it is calcined in the atmosphere.

The calcination temperature is such that when the oxide mother crystal is Sr ₃ SiO ₅ , it is difficult to obtain a crystal phase at a temperature lower than 1300 ° C; and it is preferably reacted with alumina crucible at a temperature exceeding 1600 ° C. It is in the temperature range of 1300 ° C to 1600 ° C. Especially preferred is 1450 ° C to 1550 ° C. If the heat treatment temperature is too low, the Sr ₂ SiO ₄ phase which is out of phase is formed as an impurity, and the luminous intensity of the finally obtained phosphor is lowered, which is not preferable. When the heat treatment temperature is too high, Sr ₃ SiO ₅ crystal is sintered or melted, and it is difficult to obtain a powdery phosphor without pulverization. The pulverization of the phosphor causes damage to the crystal, and thus is not preferable for obtaining a high-luminance phosphor.

In the case where the oxide mother crystal is (Ba _x , Sr _1-x ) ₃ SiO ₅ or (Ba _x , Sr _1-x ) ₂ SiO ₄ , it is difficult to obtain a crystal phase at a temperature lower than 1000 ° C. The temperature exceeding 1600 ° C is a reaction with alumina crucible, and therefore it is preferably in the range of from 1000 ° C to 1400 ° C. Especially preferred is 1200 ° C to 1350 ° C.

If the heat treatment temperature is too low, the BaCO ₃ phase or the SrCO ₃ phase which is also in a heterogeneous phase remains as unreacted impurities, and the luminous intensity of the finally obtained phosphor is lowered, which is not preferable. On the contrary, if the heat treatment temperature is too high, the calcined product is sintered or melted, and it is necessary to obtain a powdery phosphor by pulverization. Further, since pulverizing the phosphor causes damage to the crystal, it is not preferable for obtaining a high-luminance phosphor.

The heat treatment time is 1 to 24 hours, preferably 2 to 4 hours. When the heat treatment time is short, the reaction for forming the mother crystal is insufficient, the purity of the crystal phase is lowered, and the luminescence intensity is low. If the heat treatment time is long, the sintering is promoted, and coarse particles which are hard to be sintered are formed, or are fixed to the container, which is not preferable.

Further, the above heat treatment may be performed by heat treatment a plurality of times, or may be subjected to heat treatment once under optimum conditions, or may be subjected to one heat treatment cycle while continuously changing to heat treatment conditions suitable for each heat treatment.

Further, when the oxide mother crystal is Sr ₃ SiO ₅ , if a Sr ₂ SiO ₄ phase which is out of phase is formed, compared with Sr ₃ SiO ₅ , it is easy to be sintered at a low temperature, so that it is reduced in the subsequent step 4. In the calcination of the gas atmosphere, coarse particles are further formed to lower the fluorescence characteristics. Therefore, it is preferred to remove coarse particles of 100 μm or more by classification in advance.

[Step 4]

Step 4 is a step of heat-treating the calcined powder obtained in the step 3 in a reducing gas atmosphere, and replacing the Eu ²⁺ with the divalent europium ion or the divalent europium ^ion in the parent crystal to obtain a phosphor. The calcined powder used herein may be an oxide which completely decomposes the carbonate in the step 3, or may be a calcined powder in a state containing a part of the carbonate.

The temperature (calcination temperature) of the heat treatment differs depending on the composition, the calcination conditions, the sintering flux, etc., and when the oxide mother crystal is Sr ₃ SiO ₅ , it is preferably 1300 to 1600 ° C as in the step 3, preferably. It is 1450 ~ 1550 °C.

Further, when the oxide mother crystal is (Ba _x , Sr _1-x ) ₃ SiO ₅ or (Ba _x , Sr _1-x ) ₂ SiO ₄ , it is preferably 1000 to 1400 ° C as in the case of step 3. It is 1000 to 1350 °C.

As the reducing gas atmosphere, a gas of 1 to 10 vol% of H ₂ may be mixed in an inert gas such as N ₂ or Ar.

As described above, by the above-mentioned "Step 1" to "Step 4", it is possible to produce a high-brightness Eu-activated alkaline earth metal silicate phosphor having a high purity of the target crystal phase and uniform and good dispersion of constituent elements.

Furthermore, it is considered that and expects that the Eu-activated alkaline earth metal silicate phosphor of the present invention can be applied to the production of an oxide mother crystal into a composition formula of Sr ₂ SiO ₄ or a composition containing other alkaline earth metal elements. The case of an alkaline earth silicate phosphor.

(Example)

Hereinafter, the present invention will be specifically described by way of examples.

As the Eu-activated alkaline earth metal silicate phosphor, a yellow phosphor having a composition formula (Sr _1-y , Eu _y ) ₃ SiO ₅ (where 0 < y < 0.1) was used, and a method for producing the same was shown.

The water-soluble cerium compound is referred to Production Example 1 (water-soluble cerium compound A) described in paragraph [0046] of Patent Document 3.

The identification and semi-quantification of the crystal phase of the produced phosphor are carried out by X-ray diffraction and Rietveld analysis.

The evaluation of the compositional deviation is performed by quantitative analysis of each element by ICP (Inductively Coupled Plasma) luminescence analysis.

The evaluation of the luminescence characteristics was carried out by using a fluorescence spectrophotometer FP-6500 (manufactured by JASCO Corporation) to measure excitation and luminescence spectra. Further, the luminescence spectrum was measured by setting the excitation light wavelength to 455 nm, and the excitation spectrum was measured at the peak wavelength of the luminescence spectrum.

(Example 1)

The Eu-activated citrate phosphor of the composition formula (Sr _1-y ,Eu _y ) ₃ SiO ₅ (where 0 < y < 0.1) was produced by the following procedure.

[step 1]

As a metal element compound, weighed SrCO ₃ (3N, manufactured by Kanto Chemical Co., Ltd.) and Eu (NO ₃ ) ₃ ‧6H ₂ O (3N, manufactured by Sanjin and Chemical Co., Ltd.) to make the formula (Sr _{1- y} , Eu _y ) ₃ SiO ₅ becomes y = 0.01. In the aqueous solution of citric acid (98.0%, manufactured by Wako Pure Chemical Industries, Ltd.), the total concentration of lanthanum and cerium (hereinafter referred to as the concentration of the aqueous solution of the metal salt (Sr+Eu)) was adjusted to 4.0 mol/L. SrCO ₃ was stirred at 40 ° C for 1 hour, whereby a clear solution was obtained. Further, the weighed Eu(NO ₃ ) ₃ ‧6H ₂ O was dissolved in water to obtain an aqueous solution.

Then, the water-soluble cerium compound was added with 1,2-propanediol (0.4 mol) to tetramethoxy decane (0.1 mol), and the mixture was mixed for 24 hours while stirring using a heating stirrer to bring the liquid temperature to 54 ° C. . Thereafter, hydrochloric acid (0.0001 mol) was added to make a liquid temperature of 54 ° C, mixed with a water-soluble hydrazine compound, and combined with a SrCO ₃ solution, and stirred at room temperature for 30 minutes to obtain a transparent mixed solution.

The mixed solution prepared as described above was placed in a polypropylene container, sealed with a lid, and kept at 50 ° C for 24 hours to obtain a transparent gel. The gel has elasticity and is not separated into two layers, and is in a state of uniformity according to the appearance.

[Step 2]

The clear gel obtained in the step 1 was kept in a dryer at 120 ° C for 6 hours, and the solvent in the gel was removed to obtain a dried gel. The dried gel is a clear solid.

[Step 3]

The dried gel obtained in the step 2 was crushed in an agate mortar, heat-treated in an electric furnace at 550 ° C for 3 hours in an electric furnace, taken out and crushed, and again at 800 ° C for 3 hours. Heat treatment. After taking out and crushing, it was kept at 1200 ° C for 3 hours, and the temperature was further raised to 1500 ° C for 3 hours. The heat treatment was carried out in an atmosphere, taken out and crushed, and coarse particles of 100 μm or more were removed by classification to obtain a pre-preparation. Burning powder.

[Step 4]

The calcined powder obtained in the step 3 is placed in a molybdenum container, and heat-treated in a tungsten heating electric furnace at 1500 ° C for 3 hours while introducing a 4% H ₂ + 96% Ar mixed gas to obtain a powder. Fluorescent powder.

The results of X-ray diffraction measurement of the obtained phosphor powder are shown in Fig. 1. Further, the results of measuring the fluorescence characteristics are shown in Fig. 2 .

In the X-ray diffraction results of Fig. 1, it was found that the obtained phosphor powder was a substantially single phase of Sr ₃ SiO ₅ . Further, in the fluorescence characteristics of Fig. 2, broad excitation absorption was observed across 300 to 500 nm, and a peak was observed at around 585 nm, and yellow light emission was confirmed. Compared with the YAG:Ce shown for comparison, the luminescence spectrum is more distinct, and the luminescence peak intensity and luminescence peak area are larger, and the high-luminance composition formula (Sr _1-y , Eu _y ) ₃ SiO ₅ ( Among them, Eu < 0 < y < 0.1) activates the citrate phosphor.

(Example 2)

A phosphor powder was produced in the same manner as in Example 1 except that in Example 1, the aqueous solution concentration of yttrium and lanthanum was 2.0 mol/L. The results are shown in Table 1.

(Example 3)

A phosphor powder was produced in the same manner as in Example 1 except that in Example 1, the aqueous solution concentration of yttrium and lanthanum was changed to 5.5 mol/L. The results are shown in Table 1.

(Comparative Example 1)

A phosphor powder was produced in the same manner as in Example 1 except that in Example 1, the aqueous solution concentration of yttrium and lanthanum was changed to 0.1 mol/L. The results are shown in Table 1.

(Comparative Example 2)

A phosphor powder was produced in the same manner as in Example 1 except that in Example 1, the aqueous solution concentration of yttrium and lanthanum was 0.15 mol/L. The results are shown in Table 1.

(Comparative Example 3)

A phosphor powder was produced in the same manner as in Example 1 except that in Example 1, the aqueous solution concentration of yttrium and lanthanum was changed to 0.2 mol/L. The results are shown in Table 1.

(Comparative Example 4)

A phosphor powder was produced in the same manner as in Example 1 except that in Example 1, the aqueous solution concentration of yttrium and lanthanum was 6.0 mol/L. The results are shown in Table 1.

As is clear from Table 1, when the concentration of the aqueous solution of the metal salt (Sr+Eu) is low, the separation into two layers, and the moisture content from the gel separation increases, and if the concentration of the aqueous solution of the metal salt (Sr+Eu) is increased, it is not separated into Two layers, a transparent gel in a uniform state can be obtained. Further, when the concentration of the aqueous solution of the metal salt (Sr+Eu) was 6 mol/L (Comparative Example 4), the metal salt could not be completely dissolved. Therefore, in order to uniformly disperse the metal component element (Sr+Eu) in the gel, the concentration of the metal salt (Sr+Eu) aqueous solution can be set to 1 to 5.5 mol/L, and preferably 2 to 5.5 mol. /L.

(Example 4)

A phosphor powder was produced in the same manner as in Example 1 except that the holding temperature at the time of gelation in the first step of Example 1 was changed to 80 °C. The results of visual observation of the gelation state of the sample are shown in Table 2.

In addition, the criterion for the gelation described in Table 2 is that when the container is shaken or reversed, the case where there is no fluidity is "○", and the case where fluidity is still "x".

(Example 5)

A phosphor powder was produced in the same manner as in Example 1 except that the holding temperature at the time of gelation in the first step of Example 1 was changed to 100 °C. The results of visual observation of the gelation state of the sample are shown in Table 2.

(Comparative Example 5)

A phosphor powder was produced in the same manner as in Example 1 except that the holding temperature at the time of gelation in the first step of Example 1 was changed to 25 °C. The results of visual observation of the gelation state of the sample are shown in Table 2.

(Comparative Example 6)

A phosphor powder was produced in the same manner as in Example 1 except that the holding temperature at the time of gelation in the first step of Example 1 was 25 ° C and the holding time was 96 hours. The results of visual observation of the gelation state of the sample are shown in Table 2.

According to Table 2, when the temperature was maintained at 25 ° C during the gelation, the gel remained fluid even after being kept for 24 hours, and the fluidity remained after being extended to 96 hours, and it was impossible to obtain a uniform state. On the other hand, in the range of 50 ° C to 100 ° C, either of them may be separated into two layers to obtain a transparent gel in a uniform state.

(Comparative Example 7)

In the second step of the first embodiment, the transparent mixed solution was placed in a container made of polytetrafluoroethylene, placed in a pressure-resistant container made of stainless steel, sealed, and kept at 200 ° C for 24 hours to be gelated. The obtained sample contained a gel and a liquid and was separated into two layers.

The weight of the liquid separated from the gel was 20% by mass of the whole. The gel dry powder obtained in Example 1 and Comparative Example 7 was analyzed for the components (Sr, Eu, Si), and the results of the deviation from the additive composition are shown in Table 3.

As is clear from Table 3, the ratio of the amount of Sr contained in the total amount of Sr, Si, and Eu contained in the gel of Comparative Example 7 was small, and the composition was largely deviated from the additive composition, and the ratio of the amount of Si was large.

As shown above, the retention temperature at the time of gelation is important in the present invention, and is an important factor for the formation of a uniform composition.

[Comparison of quantum efficiency]

The results of quantum efficiency in the measurement of the fluorescence characteristics (measured by the excitation light wavelength: Ex = 455 nm) of the phosphor particles obtained in Example 1 using an integrating sphere are shown in Table 4. For comparison, as a conventional example, a general YAG:Ce was measured as a general yellow phosphor.

As can be seen from Table 4, in Example 1, the internal quantum efficiency showed a very high value of 71.1%, which was superior to the prior YAG:Ce phosphor.

(Example 6)

Then, Eu is used to make an alkaline earth metal citrate fluorite with a composition formula (Ba _x , Sr _1-xy , Eu _y ) ₃ SiO ₅ (where 0<x<1, 0<y<0.1). Light body.

In the same manner as in Example 1, except that in the first embodiment, the cerium carbonate was weighed, the phosphor powder was prepared in the same manner as in Example 1 except that the molar ratio of Sr:Ba was 0.86:0.13. That is, the alkaline earth metal silicate phosphor is activated by Eu represented by the composition formula (Ba _0.86 , Sr _0.13 , Eu _0.01 ) ₃ SiO ₅ .

When the obtained phosphor powder was subjected to X-ray diffraction measurement, it was found that no carbonate or other impurity phase was observed, and the phosphor powder was substantially single phase. Further, the fluorescence characteristics were measured. As a result, as shown in Fig. 2, it was found that the excitation was peaked at around 350 nm, and the luminescence peak was observed at around 600 nm, and it was confirmed that the light was orange.

Therefore, an Eu-activated alkaline earth metal silicate phosphor having a high luminance composition formula (Ba _x , Sr _1-xy , Eu _y ) ₃ SiO ₅ can be obtained.

(Example 7)

The Eu-activated alkaline earth metal silicate phosphor of the composition formula (Ba _x , Sr _1-xy , Eu _y ) ₂ SiO _{4 was} produced by the following procedure.

[step 1]

As a metal element compound, BaCO ₃ (3N, manufactured by Kanto Chemical Co., Ltd.), SrCO ₃ (3N, manufactured by Kanto Chemical Co., Ltd.), and Eu ₂ O ₃ (3N, manufactured by Furuchi Chemical Co., Ltd.) were weighed. The formula (Ba _x , Sr _1-xy , Eu _y ) ₂ SiO ₄ becomes x=0.69, y=0.08. It is added to an aqueous solution of citric acid (98.0%, manufactured by Wako Pure Chemical Industries, Ltd.) so that the total concentration of lanthanum, cerium, and lanthanum (hereinafter referred to as the concentration of the metal salt (Sr+Eu) aqueous solution) becomes 4 mol/L. The BaCO ₃ and SrCO _{3 were} weighed and stirred at 40 ° C for 1 hour, whereby a clear solution was obtained. Further, the weighed Eu(NO ₃ ) ₃ ‧6H ₂ O was dissolved in water to obtain an aqueous solution.

Then, the water-soluble hydrazine compound was added with 1,2-propanediol (0.4 mol) to tetramethoxy decane (0.1 mol), and the mixture was mixed for 24 hours while stirring with a heating stirrer to bring the liquid temperature to 54 °C. Thereafter, hydrochloric acid (0.0001 mol) was added to make the liquid temperature 54 ° C, mixed with the water-soluble cerium compound, and combined with the BaCO ₃ solution and the SrCO ₃ solution, and stirred and mixed at room temperature for 30 minutes to obtain a transparent mixed solution. .

The mixed solution prepared as described above was placed in a polypropylene container, sealed with a lid, and kept at 50 ° C for 24 hours to obtain a transparent gel. The gel has elasticity and is not separated into two layers, and is in a state of being uniform according to the appearance.

[Step 2]

The transparent gel obtained in the step 1 was kept in a dryer at 120 ° C for 6 hours, and the solvent in the gel was removed to obtain a dried gel. The dried gel is a clear solid.

[Step 3]

The dried gel obtained in the step 2 was crushed in an agate mortar, heat-treated at 550 ° C for 3 hours in an air atmosphere using an electric furnace, taken out and crushed, and further heat-treated at 800 ° C for 3 hours. After taking out and crushing, heat treatment was carried out in an atmosphere maintained at 1200 ° C for 6 hours, taken out and crushed to obtain a calcined powder.

[Step 4]

The calcined powder obtained in the step 3 was placed in a molybdenum container, and heat-treated at 1200 ° C for 3 hours while introducing a 4% H ₂ + 96% Ar mixed gas to obtain a powder. Fluorescent powder.

When the obtained phosphor powder was subjected to X-ray diffraction measurement, it was found that no carbonate or other impurity phase was observed, and the phosphor powder was substantially single phase. Further, the results of measuring the fluorescence characteristics are shown in Fig. 3 .

In the fluorescence characteristics of Fig. 3, it was found that there was a peak excitation excitation near 370 nm, and the luminescence showed a peak near 529 nm, which was confirmed to be green luminescence. A high-brightness composition (Ba _x , Sr _1-xy , Eu _y ) ₂ SiO ₄ Eu-activated alkaline earth metal silicate phosphor is obtained.

(Comparative Example 8)

The composition formula (Ba _x , Sr _{1 ) was} synthesized in the same manner as in Example 7 except that the heat treatment temperature in the atmospheric environment of the step 3 was set to 1300 ° C, and the heat treatment temperature in the reducing gas atmosphere of the step 4 was set to 1300 ° C. _-xy ,Eu _y ) ₂ Eu-activated alkaline earth metal citrate phosphor of SiO ₄ . After the step 4, the sample was sintered and hardened, and it was necessary to pulverize in order to obtain a powdery sample. The fluorescence characteristics of the sample after the pulverization were evaluated. As a result, as shown in Fig. 3, it was found that the excitation absorption at the peak of 370 nm was observed in the same manner as in Example 7, and the luminescence showed a peak near 529 nm, but compared with In the sample of Example 7, the luminescence intensity was poor.

(Comparative Example 9)

The composition formula (Ba _x , Sr _{1 ) was} synthesized in the same manner as in Example 7 except that the heat treatment temperature in the atmospheric environment of the step 3 was set to 1000 ° C and the heat treatment temperature in the reducing gas atmosphere of the step 4 was set to 1000 ° C. _-xy ,Eu _y ) ₂ Eu-activated alkaline earth metal citrate phosphor of SiO ₄ .

As a result of evaluating the fluorescence characteristics of the sample, as shown in FIG. 3, it was found that, similarly to Example 7, excitation absorption having a peak at around 370 nm was observed, and the emission was peaked at around 529 nm, but compared with the example. The sample of 7 has a much lower luminous intensity.

As described above with reference to the examples and comparative examples, the Eu-activated citrate phosphor of the composition formula (Sr _1-y ,Eu _y ) ₃ SiO ₅ (where 0 < y < 0.1) according to the present invention is produced. In this way, a high-brightness yellow phosphor having a broad range of excitation absorption from ultraviolet to blue and having a light-emitting band around 585 nm can be obtained.

Further, according to the composition formula of the present invention (Ba _x , Sr _1-xy , Eu _y ) ₃ SiO ₅ (where 0 < x < 1, 0 < y < 0.1) Eu-activated alkaline earth metal silicate phosphoric acid In the method for producing a body, a high-intensity orange phosphor having a wide range of excitation absorption from ultraviolet light to blue and having a light-emitting band around 600 nm can be obtained.

Further, Eu-activated alkaline earth metal silicate phosphors of the composition formula (Ba _x , Sr _1-xy , Eu _y ) ₂ SiO ₄ (where 0 < x < 1, 0 < y < 0.1) according to the present invention According to the production method, a high-luminance green phosphor having a broad range of excitation absorption from ultraviolet light to blue and having a light-emitting band at around 529 nm can be obtained.

1 is a view showing an X-ray diffraction pattern of a sample of Example 1.

2 is a view showing the fluorescence spectra of Example 1 and Example 6, and for comparison, a commercially available YAG:Ce (spectrum of the prior example) is also displayed.

3 is a graph showing the fluorescence spectra of Example 7 and Comparative Examples 8 and 9, and for comparison, commercially available YAG:Ce (spectrum of the prior example) is also displayed.

Claims (4)

A method for producing Eu-activated alkaline earth metal silicate phosphors, which is a composition of the formula (Sr _1-y , Eu _y ) ₃ SiO ₅ (where 0 < y < 0.1) Eu-activated alkaline earth metal citrate fluorite A method for producing a light body, comprising the following steps 1 to 4: [Step 1] comprising samarium (Er), yttrium (Si) as a constituent metal component at a predetermined molar ratio. a step of forming a gel in a state in which the total amount of all metal components contained in the mixed aqueous solution is uniformly dispersed, and a molar ratio of Sr to Eu as the constituent metal component is (1-y):y (0) <y<0.1), the Sr aqueous solution and the Eu aqueous solution are made to have a total concentration of Sr and Eu of 1.0 to 5.5 (mol/l) to prepare an Sr aqueous solution and an Eu aqueous solution; secondly, tetramethoxy decane Or adding 1,2-propanediol to tetraethoxy decane, heating, stirring, and mixing, adding hydrochloric acid to prepare a water-soluble hydrazine aqueous solution, as an aqueous solution of hydrazine raw material; preparing the above-mentioned Sr aqueous solution, Eu aqueous solution and water-soluble In the aqueous solution of hydrazine, the molar ratio of the total metal element concentration of Sr, Eu, and Si contained in the aqueous solution to the Si concentration is 4:1. Mixing, mixing the obtained aqueous solution, maintaining the mixed aqueous solution at a liquid temperature of 30 to 100 ° C to form a gel in a state in which the total amount of the entire metal component is uniformly dispersed; [Step 2] a step of drying the formed gel to form a dried product and removing the solvent contained therein; [Step 3] heat-treating the dried product in the step 2 in an atmosphere to remove the organic matter, thereby obtaining a calcined powder [Step 4] A step of obtaining a phosphor powder by subjecting the calcined powder formed in the step 3 to heat treatment in a reducing gas atmosphere. A method for producing Eu-activated alkaline earth metal silicate phosphors, which is a composition formula (Ba _x , Sr _1-xy , Eu _y ) ₃ SiO ₅ (where 0<x<1, 0<y<0.1) A method for producing a Eu-activated alkaline earth metal silicate phosphor comprising the following steps 1 to 4: [Step 1] containing Ba (Ba) and lanthanum as constituent metal components at a predetermined molar ratio a step of forming a gel in a state in which the total amount of all metal components contained in the mixed aqueous solution is uniformly dispersed in a mixed aqueous solution of (Sr), lanthanum (Eu), and lanthanum (Si); The molar ratio of Sr to Eu is x: (1-xy): y (0 < x < 1, 0 < y < 0.1), and the Ba aqueous solution, the Sr aqueous solution and the Eu aqueous solution contain Ba and Sr. A total of Eu is 1.0 to 5.5 (mol/l) to prepare a Ba aqueous solution, an Sr aqueous solution and an Eu aqueous solution. Secondly, 1,2-propanediol is added to tetramethoxynonane or tetraethoxysilane and heated and stirred. After mixing, hydrochloric acid is added to prepare a water-soluble hydrazine aqueous solution as an aqueous solution of hydrazine raw material; and the above-mentioned Ba aqueous solution, Sr aqueous solution, Eu aqueous solution, and water-soluble hydrazine aqueous solution are prepared. The total metal element concentration of Ba, Sr, Eu, and Si contained in each aqueous solution is mixed with a molar ratio of Si concentration of 4:1, and the obtained mixed aqueous solution is maintained at a liquid temperature of 30 to 100 ° C. a step of mixing a water solution to form a gel in a state in which the total amount of all metal components is uniformly dispersed; [Step 2] a step of drying the gel formed by the step 1 to form a dried product, and removing the solvent contained therein [Step 3] a step of heat-treating the dried product in the step 2 in an atmosphere to remove the organic matter to obtain a calcined powder; [Step 4] reducing the above-mentioned calcined powder formed through the step 3. The step of obtaining a phosphor powder by performing heat treatment in a gas atmosphere. A method for producing Eu-activated alkaline earth metal silicate phosphors, which is a composition formula (Ba _x , Sr _1-xy , Eu _y ) ₂ SiO ₄ (where 0<x<1, 0<y<0.1) A method for producing a Eu-activated alkaline earth metal silicate phosphor comprising the following steps 1 to 4: [Step 1] 钡 (Ba) and 锶 as a constituent metal component in a predetermined molar ratio a step of forming a gel in a state in which the total amount of all metal components contained in the mixed aqueous solution is uniformly dispersed in a mixed aqueous solution of (Sr), lanthanum (Eu), and cerium (Si); and Ba and Sr as the constituent metal components The molar ratio to Eu is x: (1-xy): y (0 < x < 1, 0 < y < 0.1), and the Ba aqueous solution, the Sr aqueous solution and the Eu aqueous solution contain Ba, Sr and Eu. Ba aqueous solution, Sr aqueous solution and Eu aqueous solution are prepared in a total concentration of 1.0 to 5.5 (mol/l); secondly, 1,2-propanediol is added to tetramethoxynonane or tetraethoxysilane and heated, stirred and mixed. Thereafter, hydrochloric acid is added to prepare a water-soluble hydrazine aqueous solution, which is used as an aqueous solution of hydrazine raw material; and the above-mentioned Ba aqueous solution, Sr aqueous solution, Eu aqueous solution, and water-soluble hydrazine aqueous solution are prepared. The molar ratio of the total metal element concentration of Ba, Sr, Eu, and Si contained in the aqueous solution to the Si concentration is 3:1, and the obtained mixed aqueous solution is maintained at a liquid temperature of 30 to 100 ° C. a step of mixing a water solution to form a gel in a state in which the total amount of all metal components is uniformly dispersed; [Step 2] a step of drying the gel formed by the step 1 to form a dried product, and removing the solvent contained therein [Step 3] a step of heat-treating the dried product in the step 2 in an atmosphere to remove the organic matter to obtain a calcined powder; [Step 4] reducing the above-mentioned calcined powder formed through the step 3. The step of obtaining a phosphor powder by performing heat treatment in a gas atmosphere. The method for producing an Eu-activated alkaline earth metal silicate phosphor according to any one of claims 1 to 3, wherein the method comprising the step (3) is formed by the step 3 after the step 3 The step of removing coarse particles of 100 μm or more from the calcined powder.