JP2003201118A - Method for manufacturing inorganic metal compound powder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for efficiently manufacturing functional inorganic metal compound powder such as a phosphor which has little impurity compound and is composed of fine powder of excellent crystallinity. <P>SOLUTION: In the method for manufacturing the inorganic metal compound powder by a spraying pyrolysis/synthesis method, a process for removing water contained in a raw material fluidized body outside the system by a diffusion drying method or the like before pyrolysis in a heating furnace is added. Otherwise the raw material fluidized body is subjected to two steps of heat treatment in the heating furnace and a process for removing water outside the system is provided at least between a first step heating process and a second step heating process. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an improvement in a method for producing an inorganic metal compound powder by a spray pyrolysis / synthesis method. More specifically, the present invention relates to a method for producing an inorganic metal compound powder having a narrow powder diameter distribution, a dense interior, less aggregation, and a substantially spherical shape, particularly a functional inorganic metal compound powder, for example, a phosphor.

[0002]

2. Description of the Related Art Conventionally, one of the methods for producing functional inorganic metal compound powders such as phosphors is a spray pyrolysis method or a spray thermal reaction synthesis method (hereinafter, "spray pyrolysis / synthesis method"). A manufacturing method called ") is known. The spray pyrolysis / synthesis method refers to the inorganic metal compound powder to be produced (in the specification, "desired inorganic metal compound powder"
(Also referred to as)), a solution (hereinafter referred to as “raw material solution”) obtained by dissolving or suspending a compound containing a metal element is sprayed into an entrained gas to form droplets, and the droplets are dried, and the entrained gas is then dried. It is a method for producing a desired inorganic metal compound powder by introducing it into a heating furnace and subjecting it to heat treatment for thermal decomposition and thermal reaction {eg, Chemical Engineering Papers, Vol. 18, No. 3 (1992). , Special Table 2001-513
828 patent publication gazette etc.}.

The inorganic metal compound powder produced by the spray pyrolysis / synthesis method is a solid-phase reaction in which a mixture of raw material powders is put in a firing container such as a crucible and heated and fired at high temperature for a long time. 1) compared to the powder obtained
A powder having a regular shape close to a sphere can be obtained, 2) a powder having almost no agglomeration can be obtained without finely pulverizing a fired product with a ball mill, etc. 3) a fine powder having a small particle size can be easily obtained. It has the advantage that the particle size of the obtained powder is relatively easy to control.

However, according to the conventional spray pyrolysis / synthesis method, a droplet containing a raw material solution, which is introduced together with an entrained gas into a heating furnace, and a solid substance which is a dried product of the droplet dried during flowing. Of the raw material powder and the entrained gas (hereinafter referred to as “raw material fluid” including the raw material solution droplets, the solid powder dried while the droplets are flowing, and the entrained gas carrying these) , Because it cannot be completely removed from the reaction system, the desired inorganic metal compound powder synthesized is likely to become a hollow powder due to the influence of moisture remaining in the raw material fluid, and a dense inorganic metal compound powder having a large bulk density. Therefore, there is a drawback that a film having a high film density cannot be obtained when the inorganic metal compound powder produced by this method is formed into a film.

Further, since water is present in the reaction system,
The reaction may be hindered, or the synthesis reaction of the desired inorganic metal compound powder may be hindered by the influence of impurities generated by the reaction between the heat-resistant material of the heating furnace or the reaction path and water, Since a product may be produced, it is difficult to obtain a phosphor having good emission brightness and emission color purity when a phosphor or the like is produced as a desired inorganic metal compound powder. There was a bad effect to make it worse. Further, if the raw material fluid contains water, water having a large heat capacity must be heated, which is inefficient in terms of energy. When synthesizing the inorganic metal compound powder by the spray pyrolysis / synthesis method, as a method for removing water in the raw material fluid, for example, a classifier such as a weight classifier or a circle center classifier is used for the raw material fluid. Although a method of reducing the water vapor concentration has been proposed (see Japanese Patent Application Laid-Open No. 2001-152144), the operation is complicated, and the water removal is not always sufficient, so that the water in the raw material fluid can be efficiently removed. A simple method of removing the pigment has been desired.

[0006]

DISCLOSURE OF THE INVENTION The present invention, when synthesizing an inorganic metal compound powder by a spray pyrolysis / synthesis method, simply and efficiently removes water in a raw material fluid to be subjected to pyrolysis or reaction synthesis, To provide a method for producing an inorganic metal compound powder capable of efficiently producing a functional inorganic metal compound powder such as a phosphor made of a dense powder having excellent crystallinity by suppressing by-product of impurity compound powder. With the goal.

The inventors of the present invention, in order to efficiently remove the water in the raw material fluid before pyrolysis or reaction synthesis from the system when producing the inorganic metal compound powder by the spray pyrolysis / synthesis method. As a result of a detailed examination of the means, the water content (liquid droplets containing a metal compound in the raw material fluid before being introduced into a heating furnace for causing thermal decomposition or reaction synthesis and subjected to heat treatment or heat reaction treatment at high temperature Moisture, gaseous moisture in accompanying gas, moisture contained in metal compound powder, etc.)
, That the above object can be achieved by removing by applying a so-called diffusion drying method, further, it is not possible to form a hollow powder having cavities in the powder of the desired inorganic metal compound which is the final product, and to obtain a dense powder. It was found that it was possible to obtain, and the purpose at a higher level could be achieved. Furthermore, the heating treatment step is performed by adding the step of removing the water in the heat treatment product fluid, which has been subjected to the first heating of the first stage, to the outside of the system by heating the raw material fluid in two stages. In the synthesis of inorganic metal compound powders in which the presence of water adversely affects the properties of the resulting material, it has been found to be particularly advantageous for improving the properties. The "system" here means a flow path for forming a raw material fluid, heat treatment, or heat reaction treatment.

[0008]

The present invention has been completed based on the above findings. 1. The method for producing an inorganic metal compound powder according to the present invention is a method of spraying a solution containing a constituent metal element of a desired inorganic metal compound powder into an entrained gas to form droplets, and then drying the droplets to form a solid. In the method of producing a desired inorganic metal compound powder by forming a powdery inorganic metal compound raw material powder and subsequently subjecting it to a heat treatment or a heat reaction treatment, the droplets and / or the It is characterized in that at least a part of water contained in the accompanying gas is removed out of the system. (Claim 1)

2. The method for producing an inorganic metal compound powder according to the present invention is a method of spraying a solution containing a constituent metal element of a desired inorganic metal compound powder into an entrained gas to form droplets, and then drying the droplets to form a solid. In the method for producing a desired inorganic metal compound powder by forming a powdery inorganic metal compound raw material powder and subsequently subjecting it to a heat treatment or a heat reaction treatment, the heat treatment or the heat reaction treatment is performed by a first heating furnace. Heat treatment or heat reaction treatment and the second heat treatment or heat reaction treatment by the second heating furnace are divided into two stages, and at least heat treatment is generated before being introduced into the second heating furnace. It is characterized in that at least a part of the water contained in the substance and / or the accompanying gas is removed out of the system. (Claim 2)

3. The method for producing an inorganic metal compound powder according to the present invention is characterized in that, in the production method described in 2 above, the first heat treatment or heat reaction treatment is performed in a temperature range of 250 ° C to 1500 ° C. (Claim 3) 4. The method for producing an inorganic metal compound powder according to the present invention is characterized in that, in the production method according to 2 or 3, the second heat treatment or heat reaction treatment is performed in a temperature range of 500 ° C to 1800 ° C. To do. (Claim 4) 5. The method for producing an inorganic metal compound powder according to the present invention is the method for producing an inorganic metal compound powder according to any one of 2 to 5 above, wherein the droplets and / or the entrained gas are also introduced before being introduced into the first heating furnace. It is characterized in that at least a part of water contained therein is removed to the outside of the system. (Claim 5)

6. The method for producing an inorganic metal compound powder according to the present invention is the method for producing an inorganic metal compound powder according to any one of 1 to 5 above, wherein a drying medium capable of taking in water in the droplets and / or the accompanying gas, and the droplets and / or Alternatively, the entrained gas and the entrained gas are brought into contact with each other through a porous membrane, and the water content in the droplet and / or the entrained gas is diffused and moved into the drying medium, thereby entraining the droplet and / or the entrained gas. It is characterized in that at least a part of water contained in the gas is removed out of the system. (Claim 6) 7. The method for producing an inorganic metal compound powder according to the present invention is the method according to any one of 1 to 6 above, wherein the water content in the drying medium is water content in the droplets and / or the entrained gas. It is characterized by being smaller than the rate. (Claim 7)

8. The method for producing an inorganic metal compound powder according to the present invention is characterized in that, in the production method according to any of 6 or 7, the drying medium is a gas. (Claim 8) 9. The method for producing an inorganic metal compound powder according to the present invention is the method for producing an inorganic metal compound powder as described in 8 above, wherein the water vapor concentration of the gas is one of the water vapor concentration of the accompanying gas.
It is characterized by being / 2 or less. (Claim 9) 10. The method for producing an inorganic metal compound powder according to the present invention,
In the manufacturing method described in 8 or 9, at least a part of the gas is cooled to 100 ° C. or lower before being brought into contact with the droplet and / or the entrained gas. (Claim 10)

11. The method for producing an inorganic metal compound powder according to the present invention is characterized in that, in the method for producing a powder according to 6 above, the drying medium is a solid desiccant. (Claim 11) 12. The method for producing an inorganic metal compound powder according to the present invention,
11. In the production method described in 11, the solid desiccant is at least one selected from the group consisting of silica gel, calcium chloride and zeolite. (Claim 12) 13. The method for producing an inorganic metal compound powder according to the present invention,
13. The manufacturing method according to any one of 1 to 12 above, wherein the desired inorganic metal compound is a phosphor. (Claim 13)

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The method for producing an inorganic metal compound powder of the present invention will be described in more detail below. The method for producing an inorganic metal compound powder according to the present invention is a method for producing an inorganic metal compound powder by a spray pyrolysis / synthesis method, wherein water in a raw material fluid before being pyrolyzed by being introduced into a heating furnace is contained in an entrained gas. Instead of leaving it in the state of water vapor,
Adding a step of completely removing it outside the reaction system by the diffusion drying method (the invention of claim 1), or adding the raw material fluid to 2
Heat treatment in a heating furnace divided into stages, at least the first
The invention is characterized in that a moisture removing step is provided between the heating step of the second step and the heating step of the second step (the invention of claim 2).

FIG. 1 shows an inorganic metal compound powder according to the invention of claim 1 (hereinafter, also simply referred to as "inorganic metal compound").
FIG. 6 is a schematic view illustrating a manufacturing process of the manufacturing method of FIG. First,
A raw material solution of a desired inorganic metal compound, that is, a solution containing a constituent metal element of a desired inorganic metal compound is sprayed in an entrained gas into droplets by an atomizing apparatus A to which various atomizing means are applied. As a raw material, an inorganic salt or an organometallic compound (raw material compound) that is soluble in water and decomposes into oxides, sulfides, etc. when heated to a high temperature and can react to generate a desired inorganic metal compound (raw material compound) is used. It is dissolved in a solvent such as to prepare a raw material solution. However, the raw material compound does not necessarily have to be water-soluble, and may be a compound that has a small particle size and is hardly soluble in the solvent used if it is uniformly suspended in a solvent such as water. When the raw material compound is insoluble in water, it can be used after being dissolved in an acid or the like in advance.

It goes without saying that the raw material compound is mixed in the raw material solution in an amount including the constituent metal elements of the desired inorganic metal compound in the constituent ratio. The solute concentration C is preferably in the range of 0.01 ≦ C ≦ 5. Here, C is the total number of moles of all metal elements contained in 1 liter of the aqueous solution. If the solute concentration is lower than 0.01, the productivity becomes low because the desired amount of inorganic metal compound that can be synthesized is small relative to the amount of water removed by drying. On the other hand, if the solute concentration is higher than 5,
Droplets are less likely to be generated. The content of the constituent metal elements in the raw material solution is determined by the balance between the size of droplets generated from the raw material solution and the particle size of the desired inorganic metal compound finally obtained. The larger the content of the constituent metal elements, the larger the particle size of the desired inorganic metal compound obtained, if the size of the generated droplets is the same.

In order to facilitate the thermal decomposition and synthesis of the desired inorganic metal compound, it is preferable to use a nitrate of a constituent metal element of the desired inorganic metal compound as a raw material compound. The reason is that the nitrate powder is easily decomposed by heating to form an inorganic metal compound. Therefore, it is preferred that at least 10% by weight of the metal salt dissolved in the solution is nitrate, and more preferred that at least 50% by weight is nitrate.

Further, in the method for producing an inorganic metal compound of the present invention, metal elements other than the constituent metal elements of the desired inorganic metal compound and additives may be contained in the raw material solution for various purposes. For example, it is preferable to include a sulfur-containing compound such as thiourea or thioacetamide when synthesizing a sulfide. Furthermore, if alkali metal or alkaline earth metal halides, ammonium halides, boric acid, etc. are added to the raw material solution as crystallinity improvers, the heating temperature in the thermal decomposition / synthesis furnace can be lowered or the retention The time can be shortened.

The pH of the raw material solution is preferably adjusted to 7 or less, and more preferably adjusted to 5 or less. This is because when the pH of the raw material solution is appropriately adjusted to 7 or less, a homogeneous aqueous solution is formed, and homogeneous droplets can be formed by spraying, so that a homogeneous desired inorganic metal compound can be synthesized. . PH of raw material solution
When the value exceeds 7, a large amount of hydroxide precipitates, and as a result,
Since the content of the precipitate component in the sprayed droplets increases and the composition of the raw material compound in the droplets fluctuates, the crystal nuclei of the desired inorganic metal compound do not uniformly occur, and the desired inorganic metal compound As a result, the composition changes or the particle size changes, and it is not possible to obtain a desired inorganic metal compound that is homogeneous and has good characteristics. Even when solid components such as raw material compounds are mixed in the raw material solution, the mixing ratio is preferably 10% by weight or less, and more preferably 1% by weight or less.

Depending on the desired inorganic metal compound,
It is important to use a raw material that does not contain impurities that reduce its properties. For example, when the desired inorganic metal compound is a phosphor that emits visible light by irradiating with ultraviolet rays or electron beams, when impurities of transition metals such as iron and nickel significantly reduce the characteristics of the phosphor. Therefore, in order to obtain good emission characteristics, it is preferable to use a raw material compound having a small content of an impurity element such as iron or nickel, which serves as a killer center, as a raw material solution component.

As the atomizing means for forming fine droplets from the raw material solution, any generally known means can be used. For example, a method of forming a liquid droplet of 1 to 50 μm by sucking the liquid with pressurized air to form a liquid droplet of 4 to 10 using ultrasonic waves of about 2 MHz from a piezoelectric crystal.
A method of forming a droplet of μm, an orifice having a hole diameter of 10 to 20 μm is vibrated by a vibrator, and a liquid supplied to the orifice at a constant speed is discharged from the hole in a constant amount according to the frequency of vibration of 5 to 50 μm The raw material compound solution is sprayed into the entrained gas by a method such as the method of forming liquid droplets, and the raw material fluid is formed by droplets.

The accompanying gas is selected according to the kind of the desired inorganic metal compound, and air, oxygen, nitrogen, hydrogen, a small amount of carbon monoxide, nitrogen containing hydrogen or hydrogen sulfide, or argon can be used. For example, if the desired inorganic metal compound is a phosphor, it is important to select a gas according to the chemical composition of the phosphor and the type of activator ions involved in light emission in order to obtain good emission characteristics. . That is, when synthesizing a phosphor whose main phase is an oxide having Eu ³⁺ or the like as a activating ion, which is easy to maintain valence in an oxidizing atmosphere, an oxidizing gas such as air or oxygen is preferable, In the case of synthesizing a phosphor having an oxide having Eu ²⁺ or the like as an active ion as the main phase, which easily maintains the valence, a reducing gas such as hydrogen, nitrogen containing a small amount of hydrogen, or argon is preferable. Also,
When synthesizing the sulfide phosphor and the oxysulfide phosphor, it is preferable to use an entrained gas containing hydrogen sulfide.

The fine droplets thus obtained flow as a raw material fluid along with the flow of gas, and if necessary, various classification means are applied before starting the next drying step. The droplets may be classified by B. By classifying the droplets, it is possible to narrow the particle size distribution of the desired inorganic metal compound powder produced. As a classification method, an inertial classification method using a cyclone or the like is adopted. The liquid removed from the raw material fluid by classification may be recovered and reused for droplet formation.

The raw material fluid containing fine liquid droplets atomized by the atomizing device A and classified by the classifying device B as required is heat-treated in the heating furnace D to be thermally decomposed and decomposed.
Before the synthesis, the moisture is removed by the diffusion dryer C by the diffusion drying method. In the method for producing an inorganic metal compound of the present invention, the feature of the invention of claim 1 is that the raw material fluid is heated by a diffusion dryer C to which a diffusion drying method is applied in advance to remove water and then introduced into a heating furnace D. It is to disassemble. The diffusion drying method here means that the raw material fluid is brought into contact with or in close proximity to a drying medium capable of taking in moisture such as a desiccant or dry air, and the action of the drying medium is performed without heating. This is a method of removing and reducing the water in the raw material fluid from the system by diffusing and incorporating the water in the raw material fluid into a drying medium. The drying medium in which the water content of the raw material fluid is taken in is
By exchanging appropriately, the flow path of the raw material fluid (reaction system)
Is never refluxed.

FIG. 2 is a schematic sectional view showing an example of a diffusion dryer for removing water by the diffusion drying method in the present invention. The diffusion dryer C of the present example has a large number of small holes penetrating its wall surface in the center of a column g made of, for example, cylindrical glass, stainless steel, plastic, porcelain, etc. A cylindrical partition wall m having an outer diameter smaller than the inner diameter of the column g and both ends opened is inserted in the axial direction of the column g. The partition wall m is a sheet made of stainless steel, nylon, Teflon (registered trademark) or the like having a large number of small holes penetrating from one surface to the other surface, or a mesh or porous film processed into a cylindrical shape. , Is wound several times to a predetermined thickness, fixed with a string or the like, and arranged in the column g. The inner hollow portion formed by the partition wall m serves as a raw material fluid transport path o through which the raw material fluid flows. The openings at both ends of the column g are sealed by a sealing plug s made of silicon or the like in which a raw material fluid inlet / outlet hole t communicating with the raw material fluid transport passage o formed by the tubular diaphragm m is provided in the central portion. The space between the inner wall of the column g and the outer side of the diaphragm m is filled with the drying medium d.

As the drying medium d to be filled in the diffusion dryer C used in the present invention, a solid desiccant such as silica gel, calcium chloride or zeolite is preferable from the viewpoint of easy handling. While the raw material fluid is flowing through the internal raw material fluid conveying path o surrounded by the diaphragm m, the moisture in the raw material fluid flows through the diaphragm m into the drying medium d filled outside. It is supposed to be diffused, absorbed and removed. When a mesh is used as the diaphragm m, the mesh should be of a size such that the filled solid desiccant does not enter the raw material fluid transfer path o inside the mesh and air can flow. Must be used. The smaller the mesh size, the easier the holding of the drying medium d becomes, but it becomes difficult to diffuse the water. Therefore, it is necessary to select the mesh size as large as possible in consideration of the size of the drying medium d. For example, when silica gel having a particle diameter of 2 mm is used as the drying medium d, it is suitable that a mesh having an opening of about 1 mm is wound a plurality of times to form a tubular shape. When a solid desiccant is used as the drying medium d, it is necessary to lower the temperature of the solid desiccant because the solid desiccant does not adsorb moisture when the temperature of the circulating gas is high. The temperature must be adjusted so that it is at least 100 ° C. or lower.

As another mode of the diffusion dryer C, instead of filling the above-mentioned solid desiccant, a drying gas is aerated as a drying medium d in the space between the inside of the column g and the diaphragm m, It is also possible to remove the water in the raw material fluid that passes through the raw material fluid conveyance path o inside the membrane m through the diaphragm m by diffusing it into the drying gas. The advantage of this method is that it is particularly advantageous for continuous operation. When the diffusion dryer C using a drying gas as the drying medium d is used, the moisture content of the drying gas is reduced by bringing the drying gas to be aerated into contact with a cooling unit at 100 ° C. or lower. Is more preferable because it can be obtained. At this time, the gas from which the water has been removed can be used again as a drying gas for the drying medium d for drying the raw material fluid.

In this way, if the water content is removed before the raw material fluid is introduced into the heating furnace by the diffusion drying method,
Since water can be removed without heating, a hollow powder is less likely to be formed, and a more dense desired inorganic metal compound powder can be obtained. Further, since the raw material fluid and water can be easily separated, the amount of water carried to the heating step can be efficiently reduced.

Next, the raw material fluid from which the moisture has been removed by the diffusion dryer C is heated in a heating furnace D kept at a predetermined temperature.
The raw material compound is thermally decomposed by being heated to a predetermined residence time, and a desired inorganic metal compound is generated by a chemical reaction between the thermal decomposition products, and further, crystal growth thereof occurs, and finally A powder of the desired inorganic metal compound is formed. The fluid containing the desired inorganic metal compound that has undergone the heating step in the heating furnace D is collected by the powder collector E such as a bag filter. Then, if necessary,
After-treatment such as washing and dispersion is performed to obtain a desired inorganic metal compound powder having good dispersibility.

The drying treatment fluid (entrained gas containing the drying treatment product) that has passed through the diffusion dryer C and before being introduced into the thermal decomposition / synthesis furnace D does not contain or contains water. Since it is extremely small, it is possible to suppress a side reaction that occurs when a large amount of water is contained, and it is not necessary to heat water having a large specific heat, which is convenient because the energy consumption is small. The heating temperature of the drying treatment fluid in the heating furnace D and the residence time (heating time) vary depending on the composition of the desired inorganic metal compound, but the temperature is approximately 500-18.
At a temperature of 00 ° C., the residence time is generally selected from the range of approximately 0.5 seconds to 10 minutes. If the heating time is too short, the desired reaction such as thermal decomposition and crystal growth of a desired inorganic metal compound cannot be completed. On the other hand, heating beyond the required reaction time is a waste of energy and is not preferable.

FIG. 3 is a schematic view illustrating the manufacturing process of the method for manufacturing an inorganic metal compound according to the second aspect of the invention. The manufacturing method according to the invention of claim 2 is, as in the manufacturing method according to the invention of claim 1 described above, a raw material fluid which is made into droplets by the atomizing device A and sprayed in the accompanying gas to classify the raw material fluid. After the droplets have been classified by B, the droplets are conveyed to the first heating furnace D1 which is maintained at a predetermined temperature, retained for a certain period of time and pyrolyzed (the first heating step), and then If the heat treatment fluid (entrained gas containing a thermal decomposition product) obtained in the first heating furnace D1 is introduced into the diffusion dryer C and water is generated in the first heating step, the generated water is generated. Remove all water components including. Then, the dry treatment fluid (the entrained gas containing the heat treatment product obtained in the first heating step) from which the water has been removed is introduced into the second heating furnace D2 which is maintained at a predetermined temperature. Then, heat treatment is performed for a certain time (second heating step), and a desired inorganic metal compound flowing out of the furnace along with the accompanying gas is collected by a powder collector E such as a bag filter. .

The moisture removing means in the moisture removing step performed between the first heating step and the second heating step may not necessarily be the diffusion drying method, and the dehydrating means is not limited. However, it is preferable to apply the diffusion drying method by using the diffusion dryer C illustrated in FIG. 2, for example. When the moisture is removed from the system by the diffusion drying method, the heat treatment fluid and the moisture can be easily separated, so that the amount of moisture carried to the next heating step can be efficiently reduced.

As described above, the feature of the method for producing an inorganic metal compound according to the invention of claim 2 is that at least two raw material fluids are used.
The heat-treated product is heat-treated in stages, and the heat-treated product produced in the first-stage heating step is temporarily moisturized with some entrained gas by some moisture removing means, for example, a diffusion dryer C as illustrated in FIG. The second step is to carry out the second heat treatment by removing the water and further performing the second heat treatment so that the product obtained by the first heat treatment does not contain water. Therefore, it is preferable that various side reactions that occur when water is contained do not occur and that water with a large heat capacity is not heated, so that energy is wasted less. The removal of water in the raw material fluid can be considerably performed by performing the heating step only once and providing a step of removing the water out of the system before the heating step as in the case of the invention of claim 1 above. However, in that case, the water of crystallization in the raw material compound desorbed in the heating step and the water generated by the thermal decomposition of the raw material compound cannot be removed out of the system. Therefore,
According to the invention of claim 2, the heating step is performed in two stages, and the first step
Providing a step of removing water outside the system between the heating step of the second step and the heating step of the second step is a more effective method for complete removal of water.

In the manufacturing method according to the second aspect of the invention, the means for removing water from the raw material fluid is as described above.
It is essential to provide between the first heating step and the second heating step, but in addition to that, moisture removal is also performed on the raw material fluid before the first heating treatment. It is more preferable to provide means. That is, after performing the water removing means on the raw material fluid, the first stage heat treatment is performed,
The heat treatment fluid (the entrained gas containing the product of the first heat treatment) may be subjected to the moisture removal treatment again, and then the second heat treatment. Moisture removal performed before the first heating step is particularly effective for reducing hollow powder, but when droplets containing a large amount of water are rapidly heated, the concentration of solute in the center of the droplets and on the surface of the droplets is increased. Since the hollow powder is likely to be generated due to the non-uniformity, the heating condition of the first stage is set to a heating condition that reduces the amount of heat required for the heating step and suppresses the generation of the hollow powder. When the amount of heat required in the first heating step is reduced in this way, the droplets and solid particles still contain water, so that water remains in the drying treatment fluid even after the second step of removing water. Therefore, a side reaction is likely to occur due to the influence of this residual water content. So the first
After preliminarily removing the water in the raw material fluid before the heat treatment of the first stage, heat treatment is performed under heating conditions that suppress the formation of hollow powder, and the water content is again added to the product. When the second stage heat treatment is performed after the removal operation, a pure desired inorganic metal compound free from hollow powder and free from by-products can be obtained.

In the first heating step, depending on the heating temperature, water is evaporated from the droplets, the contained compound is crystallized,
Desorption of water of crystallization, thermal decomposition, reaction between contained components, etc. occur. The heating temperature in the first heating step is preferably in the temperature range of 250 ° C to 1500 ° C depending on the kind of the desired inorganic metal compound. At 250 ° C. or lower, there is no point in using the heating step in two stages, because desorption of crystal water of the raw material compound and decomposition of the nitrate salt do not occur when a nitrate compound is used as the raw material compound. The heat treatment fluid (entrained gas containing the heat treatment product) after the first heating step is a desired inorganic metal compound or its precursor, the introduced gas, a by-product generated by the decomposition of the raw material compound,
Including water, etc. By-products include, for example, various nitric oxides, oxygen, when the raw material solution contains a metal nitrate.
Nitrogen and the like are produced as by-products.

On the other hand, the heating temperature in the second heating step is 500 ° C. or higher depending on the kind of the desired inorganic metal compound.
It is selected from the temperature range of 1800 ° C. Residence time (heating time) in the second heating furnace D2, which is the second heating step
Also depends on the type of desired inorganic metal compound, but 0.5 seconds to 1
Select in the range of 0 minutes. If the heating time is too short, the desired reaction, that is, thermal decomposition, crystal growth, etc., cannot be completed.
On the other hand, it is not preferable to heat-treat for more than the required heating time because it wastes energy. The product that has undergone the second heating step in the heating furnace D2 is collected by the powder collector E such as a bag filter. Wash, if necessary,
Processing such as dispersion may be performed.

According to the method for producing an inorganic metal compound of the present invention, a fine powder of an inorganic metal compound having a small amount of agglomeration, a spherical shape and a small powder diameter is obtained, and further obtained by a conventional spray pyrolysis / synthesis method. Compared with the above, there is almost no hollow powder, and a dense powder can be obtained. As the desired inorganic metal compound to which the production method of the present invention can be applied, particularly, a phosphor that emits light in a wavelength range from ultraviolet to visible spectrum by irradiation with ultraviolet rays or electron beams, especially a phosphor containing an oxide as a main component. Is mentioned. The phosphor containing an oxide as a main component has a high heating temperature in the heating step, and a side reaction due to the presence of water is likely to occur. When the heating temperature is high, the energy cost for heating particularly accounts for a large proportion of the manufacturing cost. Therefore, when the oxide-based phosphor is manufactured by the manufacturing method of the present invention, compared with the case of the conventional manufacturing method. , The energy saving effect due to the removal of water becomes remarkable, and side reactions due to the presence of water, such as corrosion of the furnace core tube and mixing of its components with the desired inorganic metal compound, and surface deterioration of the desired inorganic metal compound are major problems. Therefore, the production method of the present invention is particularly effective when applied to the production of oxide-based phosphors.

[0038]

EXAMPLES Next, examples of the present invention and comparative examples will be specifically described by taking the case where the desired inorganic metal compound is a phosphor as an example, but the present invention is limited by the following examples. Not something.

Example 1 Yttrium nitrate and Eu nitrate
Ropium was mixed at a molar ratio of 94: 6 and dissolved in water.
The raw material solution with a total metal content of 0.3 mol / l
Prepared. This raw material solution is equipped with a 1.7MHz oscillator
Ultrasonic atomizer to make fine droplets and
About 1 L / min. 2 on the flow of air
Passing through the raw material fluid conveyance path o of the diffusion dryer C having the structure shown
To remove water from the droplets, and the droplets of the raw material solution are dried.
1600 of the raw material fluid, which is a mixture of powder and air
Pass through an electric furnace set at ℃ for 10 seconds
By heating it, only the powder from this raw material fluid is bugged.
Collected with a filter, composition formula (Y_0.94, Eu _0.6)₂O₃
A phosphor powder represented by

The particle diameter of this phosphor powder is the median diameter d.
X-ray diffraction spectrum by Cu-Kα characteristic X-ray of this spherical powder having a particle size distribution of 50 = 1.2 μm and standard deviation 0.42 μm was measured and found to be (Y _0.94 , Eu
The presence of components having a crystal structure other than _0.6 ) ₂ O ₃ was not recognized. In addition, from the observation of the phosphor particles by an electron micrograph, the presence of particles having a shape thought to be ruptured fragments of hollow particles was not recognized. 254 this phosphor
When excited with ultraviolet rays of nm, a good red emission was shown. The diffusion drier C used was a glass tube having a length of 75 cm and a diameter of 6 cmφ as a column g, and a nylon mesh having a mesh of 19 mesh and an opening of 1.04 mm processed into a cylindrical shape having an inner diameter of 2 cmφ. It was provided in column g. Further, the space between the column g and the partition wall m was filled with silica gel dried at 120 ° C. as the drying medium d.

[Comparative Example 1] A raw material fluid having droplets placed on a stream of air was immediately introduced into the diffusion dryer C without introducing the raw material fluid into the diffusion dryer C.
The composition formula (Y _0.94 , E) was obtained in the same manner as in Example 1 except that the composition was heated in an electric furnace set at 00 ° C.
A phosphor powder represented by u _0.6 ) ₂ O ₃ was manufactured. The particle diameter of this phosphor powder is a spherical powder having a median diameter d50 of 1.6 μm and a standard deviation of 0.60 μm, and the X-ray diffraction spectrum of the Cu-Kα characteristic X-ray was measured. , (Y _0.94 , Eu _0.6 ) ₂ O ₃ was observed. Also, from the observation of the phosphor particles by an electron micrograph, the existence of particles such as fragments due to the rupture of hollow particles was also recognized. When this phosphor was excited by ultraviolet rays of 254 nm, it emitted red light, whose emission intensity was 94% of that of the phosphor of Example 1. Since the phosphor of Example 1 and the phosphor of Comparative Example 1 have the same operating conditions of the atomizer, the size of the supplied droplet and the dissolved mass contained in the droplet are the same, and the median diameter is the same. Comparative Example 1 rather than Example 1
It is shown that the phosphor of Example 1 is a denser phosphor because the phosphor of Example 1 is larger.

Example 2 Barium nitrate, europium nitrate, magnesium nitrate and aluminum nitrate were each dissolved in water and the ratio of Ba: Eu: Mg: Al was 0.
They were mixed so as to be 9: 0.1: 1.0: 10.0 to prepare a raw material solution having a total metal molar concentration of 0.3 mol / l. This raw material solution was made into fine droplets by an ultrasonic atomizer equipped with a 1.7 MHz oscillator. This liquid droplet is approximately 1 L / min. The same flow rate of nitrogen gas containing 2% of hydrogen (hydrogen-nitrogen mixed gas) was passed through the raw material fluid conveyance path o of the diffusion dryer C as described in Example 1 to remove the droplets. The water was removed. The obtained dried treatment fluid, that is, the mixture of the powder in which the droplets of the raw material solution are dried and the hydrogen / nitrogen mixed gas is passed through an electric furnace set at 1600 ° C. for 10 seconds to heat the mixture. Then, only the powder was collected from this fluid with a bag filter to obtain a phosphor powder represented by the composition formula (Ba _0.9 , Eu _0.1 ) MgAl _{10 17} .

The particle diameter of this phosphor powder is the median diameter d.
X-ray diffraction spectrum by Cu-Kα characteristic X-ray of this spherical powder having a particle size distribution of 50 = 1.0 μm and standard deviation 0.36 μm was measured to find that (Ba _0.9 , E
The presence of any composition other than the composition of u _0.1 ) MgAl _{10 17} was not observed. In addition, from the observation of the phosphor particles by an electron micrograph, the presence of particles having a shape thought to be ruptured fragments of hollow particles was not recognized. This phosphor is 2
When excited with 54 nm ultraviolet light, it showed good blue emission.

[Comparative Example 2] A droplet was placed on a flow of nitrogen gas (hydrogen / nitrogen mixed gas) containing 2% of hydrogen, and a diffusion dryer C was used.
The phosphor represented by the composition formula (Ba _0.9 , Eu _0.1 ) MgAl ₁₀ 0 ₁₇ was prepared in the same manner as in Example 2 except that the phosphor was immediately introduced into an electric furnace set at 1600 ° C. without being introduced into the furnace and heat-treated. A powder was produced. The particle size of this phosphor powder is
A spherical powder having a median diameter d50 of 1.1 μm and a standard deviation of 0.46 μm and having a particle size distribution was measured by an X-ray diffraction spectrum using Cu-Kα characteristic X-rays.
Some diffraction peaks of compositions other than the composition of (Ba _0.9 , Eu _0.1 ) MgAl _{10 17} were detected. In addition, from the observation of the phosphor particles by an electron micrograph, the presence of particles having a shape thought to be ruptured fragments of hollow particles was also recognized. When this phosphor was excited by ultraviolet rays of 254 nm, it exhibited excellent blue light emission, but its emission intensity was 95% of that of the phosphor of Example 1.

Example 3 The same as Example 1 except that dry air was aerated as the drying medium d instead of packing the silica gel in the space between the column g and the partition wall m of the diffusion dryer C. Thus, a phosphor powder represented by the composition formula (Y _0.94 , Eu _0.6 ) ₂ O ₃ was obtained. At this time, the air that has been ventilated as the drying medium d of the diffusion dryer C and that has exited from the outlet of the diffusion dryer C cools part of its path to the liquid nitrogen temperature to reduce the water concentration in the air, and again It was circulated and used as the drying medium d of the diffusion dryer C. The particle size of this phosphor powder has a median diameter d50 of 1.4 μm and a standard deviation of 0.52 μm.
Spherical powder having a particle size distribution of m. Cu-K of this powder
When the X-ray diffraction spectrum by α-characteristic X-ray was measured, the existence of components having a crystal structure other than (Y _0.94 , Eu _0.6 ) ₂ O ₃ was not recognized. In addition, from the observation of the phosphor particles by an electron micrograph, the presence of particles having a shape thought to be ruptured fragments of hollow particles was not recognized.
When this phosphor was excited by ultraviolet rays of 254 nm, it exhibited favorable red light emission having almost the same emission intensity as that of the phosphor of Example 1.

Example 4 A raw material solution for producing the phosphor of Example 1 was used, and the raw material solution was made into fine droplets by an ultrasonic atomizer equipped with a 1.7 MHz oscillator,
This liquid droplet is approximately 1 L / min. On the air flow having the flow velocity of 10 μm, the first stage water is removed from the liquid droplets by passing through the raw material fluid conveying path o of the diffusion dryer C having the structure shown in FIG. A dry process fluid of a mixture of dry powder and air was placed in an electric furnace set at 1000 ° C for 1 hour.
The first stage heat treatment is performed by passing it through 0 seconds, and the heat treatment fluid is passed through another diffusion dryer C having the same structure as the diffusion dryer C to remove the second stage moisture. After that, it was subsequently passed through an electric furnace set at 1600 ° C. for 10 seconds this time, and the second stage heat treatment was performed. Only powder was collected with a bag filter from the fluid that had been subjected to the second-stage heat treatment, and (Y _0.94 , Eu
A phosphor powder represented by _0.6 ) ₂ O ₃ was obtained. The particle diameter of this phosphor powder is a spherical powder having a median diameter d50 of 1.0 μm and a standard deviation of 0.34 μm, and the X-ray diffraction spectrum of the Cu-Kα characteristic X-ray was measured. , (Y _0.94 , Eu _0.6 ) ₂ O ₃ was not found. In addition, from the observation of the phosphor particles by an electron micrograph, the presence of particles having a shape thought to be ruptured fragments of hollow particles was not recognized. When this phosphor was excited with 254 nm ultraviolet light, excellent red light emission was exhibited.

[Embodiment 5] Similar to Embodiment 1, FIG.
The raw material fluid from which water has been removed using the diffusion dryer C having the structure shown in FIG. 1 is passed through an electric furnace set at 1000 ° C. for 10 seconds to perform the first heating step of the raw material fluid. After the completion, without performing the second stage water removal, the heat treatment fluid was immediately passed through the electric furnace set at 1600 ° C. for 10 seconds to perform the second stage heat treatment. The composition formula (Y _0.94 , Eu
A phosphor represented by _0.6 ) ₂ O ₃ was synthesized. The particle diameter of this phosphor powder is a spherical powder having a median diameter d50 of 1.2 μm and a standard deviation of 0.42 μm, and the X-ray diffraction spectrum of the Cu-Kα characteristic X-ray was measured. , (Y _0.94 , Eu _0.6 ) ₂ O ₃ was found to have a composition having a crystal structure. In addition, from the observation of the phosphor particles by an electron micrograph, the presence of particles having a shape such as broken pieces of hollow particles was not recognized. When this phosphor was excited with 254 nm ultraviolet light, excellent red light emission was exhibited, but the emission intensity thereof was 90% of that of the phosphor of Example 4.

Comparative Example 4 A raw material fluid containing droplets of a raw material solution was passed through an electric furnace set at 1000 ° C. for 10 seconds without removing water by the diffusion dryer C, and the raw material was passed through the raw material fluid. After completing the first-stage heating process of the fluid, the second-stage moisture removal by the diffusion dryer C is not performed,
The heat treatment fluid was immediately passed through an electric furnace set at 1600 ° C. for 10 seconds to perform the second heat treatment, and the composition formula (Y _0.94 , A phosphor represented by Eu _0.6 ) ₂ O ₃ was manufactured. The particle diameter of this phosphor powder is such that the median diameter d50 is 1.
A spherical powder having a particle size distribution of 6 μm and a standard deviation of 0.60 μm was used to measure the X-ray diffraction spectrum of the powder using Cu-Kα characteristic X-rays, which showed that (Y _0.94 , Eu _0.6 ) ₂ O
The presence of a composition having a crystal structure other than ₃ was slightly recognized. Further, from the observation of the phosphor particles by an electron micrograph, the existence of particles having a shape like a fragment of hollow particles was recognized. When this phosphor was excited by ultraviolet rays of 254 nm, it emitted red light, whose emission intensity was 85% of that of the phosphor of Example 4.

[0049]

EFFECTS OF THE INVENTION Since the present invention is configured as described above, it is possible to suppress the generation of hollow particles and the by-product of an impurity compound having an unnecessary composition by a spray pyrolysis / synthesis method, and to provide a dense crystal having excellent crystallinity. It is possible to efficiently produce a powder of such an inorganic metal compound, and the present invention is particularly useful for producing a functional inorganic metal compound such as a high-luminance phosphor.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a process of a method for producing an inorganic metal compound powder according to the present invention.

FIG. 2 is a schematic cross-sectional view of a diffusion dryer applied in a method for producing an inorganic metal compound powder.

FIG. 3 is a schematic view showing another example of the process of the method for producing an inorganic metal compound powder according to the present invention.

[Explanation of symbols]

A atomizer B classifier C diffusion dryer D1, D2 heating furnace E powder collector d Dry medium g column m bulkhead o Raw material fluid transport path s Sealing plug t Raw material fluid inlet / outlet hole

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C09K 11/80 C09K 11/80 (72) Inventor Naoto Kijima 1000 Kamoshida-cho, Aoba-ku, Yokohama-shi, Kanagawa Mitsubishi Chemical Yokohama Institute of Technology F-term (reference) 4G042 DA02 DB12 DB22 DB29 DC03 DD01 DE06 DE14 4G076 AA02 AA18 AB07 AC02 AC07 BA31 BD03 CA02 CA03 CA26 CA33 DA11 4H001 CF02 XA08 XA12 XA13 XA39 XA56 XA63

Claims (13)

[Claims] 1. A solid inorganic metal compound raw material powder is obtained by spraying a solution containing a constituent metal element of a desired inorganic metal compound powder into an entrained gas to form liquid droplets, and then drying the liquid droplets. In the method for producing a desired inorganic metal compound powder by subsequently subjecting it to heat treatment or heat reaction treatment, the amount of water contained in the droplets and / or the entrained gas before the heat treatment or heat reaction treatment is A method for producing an inorganic metal compound powder, which comprises removing at least one part out of the system. 2. A solid inorganic metal compound raw material powder is obtained by spraying a solution containing a constituent metal element of a desired inorganic metal compound powder into an entrained gas to form droplets, and then drying the droplets. In the method for producing a desired inorganic metal compound powder by subsequently subjecting it to a heat treatment or a heat reaction treatment, the heat treatment or the heat reaction treatment is referred to as a first heat treatment or a heat reaction treatment by a first heating furnace. , A second heat treatment by a second heating furnace or a heat reaction treatment in two stages, and at least a heat treatment product before being introduced into the second heating furnace and / or the entrained gas. A method for producing an inorganic metal compound powder, which comprises removing at least a part of water contained in the outside of the system. 3. The method for producing an inorganic metal compound powder according to claim 2, wherein the first heat treatment or heat reaction treatment is performed in a temperature range of 250 ° C. to 1500 ° C. 4. The method for producing an inorganic metal compound powder according to claim 2, wherein the second heat treatment or heat reaction treatment is performed in a temperature range of 500 ° C. to 1800 ° C. 5. Even before being introduced into the first heating furnace, at least a part of water contained in the droplets and / or the accompanying gas is removed out of the system. Item 7. A method for producing an inorganic metal compound powder according to any one of Items 2 to 5. 6. The droplet and / or the entraining medium capable of taking in the water in the entrained gas and the drying medium and / or the entrained gas are brought into contact with each other through a porous membrane, and the droplet and / or Alternatively, at least a part of the water contained in the droplets and / or the accompanying gas is removed to the outside of the system by diffusing the water in the accompanying gas and moving it into the drying medium. The method for producing an inorganic metal compound powder according to any one of claims 1 to 5. 7. The water content in the drying medium is smaller than the water content in the droplets and / or the entrained gas, according to any one of claims 1 to 6. A method for producing the inorganic metal compound powder described. 8. The method for producing an inorganic metal compound powder according to claim 6, wherein the drying medium is a gas. 9. The method for producing an inorganic metal compound powder according to claim 8, wherein the vapor concentration of the gas is ½ or less of the vapor concentration of the accompanying gas. 10. The inorganic metal compound powder according to claim 8, wherein at least a part of the gas is cooled to 100 ° C. or lower before being brought into contact with the droplet and / or the entrained gas. Production method. 11. The method for producing an inorganic metal compound powder according to claim 6, wherein the drying medium is a solid desiccant. 12. The solid desiccant is silica gel,
The method for producing an inorganic metal compound powder according to claim 11, which is at least one selected from the group consisting of calcium chloride and zeolite. 13. The method for producing an inorganic metal compound powder according to claim 1, wherein the desired inorganic metal compound is a phosphor.