JP2020158624A - Phosphorescent fine particle powder and its manufacturing method - Google Patents

Abstract

To provide spherical small sized uniform phosphorescent fine particle powder, and, a manufacturing method of the spherical phosphorescent fine particle powder that is readily mass-produced (scale-up) by expanding an industrial application range and is improved in the characteristics, and a manufacturing method of a glass-coated phosphorescent material.SOLUTION: Strontium aluminate based spherical phosphorescent fine particle powder having europium and dysprosium as an activator, in which the powder contains 65% or larger by number of particle having an aspect ratio of 1.05 or smaller, and has an average particle size D50 of 20 μm or larger and 500 μm or smaller. Furthermore, a manufacturing method of the spherical phosphorescent fine particle powder that uses a flame fusion method includes the steps of: preparing powder of strontium aluminate-based phosphorescent material of which particle size is controlled in the range of 20 μm or larger and 500 μm or smaller and that has europium and dysprosium as the activator; fusing the powder together with a carrier gas by passing in the flame; and solidifying by cooling the fused powder.SELECTED DRAWING: Figure 1A

Description

The present invention relates to a phosphorescent fine particle powder and a method for producing the same, and more particularly to a method for producing a spherical phosphorescent fine particle powder using a flame method.

Currently, typical phosphorescent materials used industrially include zinc sulfide (ZnS) -based materials that use copper (II) as an activator, and europium (II) and dysprosium (III) as activators. There is a strontium aluminate type. All of them are manufactured by putting a mixture of raw material powders in a baking vessel, heating them at a high temperature for a long time while controlling the atmosphere to cause a solid phase reaction, and then pulverizing the mixture with a ball mill or the like. .. However, since the solid phase method is subjected to a pulverization process, the produced fine particles have an irregular shape, and it is difficult to produce uniform and spherical fine particles. Further, the use of zinc sulfide (ZnS) -based phosphorescent material is limited to toys and indoor safety signs because it is deteriorated by ultraviolet rays. Strontium aluminate, which uses europium (II) and dysprosium (III) as activators, hydrolyzes when in contact with water. In order to overcome this problem, means such as coating with another material having excellent ultraviolet ray transmission are adopted.

Patent Document 1 describes an inorganic fluorescent material for a glass-like or frit-like ceramic base material having a melting point of 1000 ° C. or less, which is composed of a fire-resistant raw material that imparts fire resistance and a low-fired raw material that lowers the melting point. And / or the particles of the phosphorescent inorganic fluorescent material are mixed so as to have a content of 3 to 50% by weight, and melted or calcined at a temperature in the range of 750 to 900 ° C. to form a continuous phase. It is characterized in that the inorganic fluorescent substance and / or the phosphorescent inorganic fluorescent substance particles are dispersed and contained in the ceramic base material having high translucency to form a granular material having a water absorption rate of 4.0% or less. Fluorescent inorganic artificial aggregates for roads, building materials or ships, and methods for producing the same are disclosed. However, since the melting or firing temperature is as low as 750 to 900 ° C., there is a problem that pores remain in the obtained fluorescent inorganic artificial aggregate and the light transmittance is poor.

Patent Document 2 describes a phosphorescent glass having a diameter of 20 to 3000 μm by blending and dissolving a phosphorescent pigment composed of the amino acid strontium activated by dysprosium and europium at a ratio of 5 to 60% by weight with respect to the glass material. A method for producing cullet or phosphorescent glass beads is disclosed. A method of melting in a discontinuous melting furnace is adopted for producing the phosphorescent glass ingot, and a method of crushing the phosphorescent glass ingot and heating it again by a fluidized bed firing method is adopted for producing the phosphorescent glass beads. The fabrication of phosphorescent glass beads requires two heating operations, which has the disadvantage of high energy consumption.

In Patent Document 3, a raw material solution containing a phosphor raw material is dropletized, and the dropletized raw material solution is introduced into a flame together with a carrier gas to generate fine particles, and the generated fine particles are reducible. A technique for reheating in an atmosphere in a temperature range of 1200 ° C to 1400 ° C is disclosed. Similar to Patent Document 2, there are disadvantages that two heating operations are required, energy consumption is large, and a reducing atmosphere is desirable at the time of reheating, which complicates the heating device.

In Patent Document 4, phosphor fine particles are generated by spraying a liquid raw material in a first flame or a first combustion atmosphere formed in a reaction vessel under reduced pressure, and then the phosphor fine particles are produced. Is flowed into the second flame or the second combustion atmosphere formed in the reaction vessel after the first flame or the first combustion atmosphere, thereby causing the phosphor fine particles. This is a method for producing phosphor fine particles by reheating and firing the above, wherein the first flame is an oxidizing flame, the first combustion atmosphere is an oxidizing atmosphere, the second flame is a reducing flame, and the second combustion. A method for producing phosphor fine particles is disclosed, wherein the atmosphere is a reducing atmosphere. The problems are that the first burner and the second burner must be installed in one furnace, the structure of the device is complicated, and the control to prevent the phosphor particles from being oxidized is complicated. is there.

Japanese Unexamined Patent Publication No. 10-102409 Japanese Unexamined Patent Publication No. 11-043349 Japanese Unexamined Patent Publication No. 2005-239960 Japanese Unexamined Patent Publication No. 2009-084312

As described above, the method disclosed in Patent Document 1 allows firing in a normal atmosphere in which oxygen is present, but the temperature is as low as 750 to 900 ° C., so that the obtained fluorescent inorganic artificial aggregate is obtained. Since pores remain inside and the light transmission is poor, and it is taken out as a lump from the heating furnace, it is limited to use in a relatively large size of 0.5 mm by crushing and sieving when actually using it. Will be done. In Patent Documents 2, 3 and 4, the heating operation is performed in two stages, and the process or heating device is complicated, which hinders mass production.

The present invention has been made in view of such circumstances, and is a spherical, small-particle size, homogeneous phosphorescent fine particle powder, and the production cost thereof is suppressed to expand the industrial application range and mass-produce (scale up). ) Is easy, and an object of the present invention is to provide a method for producing a spherical phosphorescent fine particle powder and a method for producing a glass-coated phosphorescent material.

(1) In order to achieve the above object, the spherical phosphorescent fine particle powder of the present invention is a strontium aluminate-based spherical phosphorescent fine particle powder using europium and dysprosium as activators, and the powder has an aspect ratio of 1. It is characterized in that it contains 65% or more of particles of 0.05 or less and has an average particle size D50 of 20 μm or more and 500 μm or less.

As a result, a homogeneous spherical phosphorescent fine particle powder having a spherical shape and a small particle size can be obtained. Such powder can be suitably used as, for example, a material for a phosphorescent paint. Since the particles are spherical with a small particle size, the paint can be applied smoothly and evenly even when added to the paint.

(2) Further, the spherical phosphorescent fine particle powder of the present invention is characterized in that D90 / D10 is 20 or less. Since the spherical phosphorescent fine particle powder having such a narrow particle size distribution has homogeneous characteristics with respect to the particle size, the variation in performance when used for various purposes is small.

(3) Further, the spherical phosphorescent fine particle powder of the present invention is characterized by containing spherical glass fine particles. Thereby, the fluorescence brightness can be changed arbitrarily.

(4) Further, the method for producing spherical phosphorescent fine particle powder of the present invention is a method for producing spherical phosphorescent fine particle powder using a flame melting method, wherein the particle size is adjusted in the range of 20 μm to 500 μm, and europium and dysprosium. It has a step of preparing a powder of a strontium aluminate phosphorescent material using the above as an activating material, a step of passing the powder into a flame together with a carrier gas and melting the powder, and a step of cooling and solidifying the melted powder. It is characterized by. Thereby, a homogeneous spherical phosphorescent fine particle powder having a spherical shape and a small particle size can be easily produced.

(5) Further, the method for producing a spherical phosphorescent fine particle powder of the present invention is a method for producing a spherical phosphorescent fine particle powder using a flame melting method, wherein the particle size is adjusted in the range of 20 μm to 500 μm, and europium and dysprosium. A step of preparing a powder of a strontium aluminate-based phosphorescent material using the above as an activating material, a step of preparing a powder of soda lime glass having a particle size adjusted to a range of 0.5 μm to 250 μm, and a powder of the phosphorescent material. It is characterized by having a step of mixing the powder of the soda lime glass and the step of passing the mixed powder into a flame together with a carrier gas to melt the powder, and a step of cooling and solidifying the melted powder. Thereby, a homogeneous spherical phosphorescent fine particle powder having a spherical shape and a small particle size can be easily produced.

(6) Further, in the method for producing spherical phosphorescent fine particle powder of the present invention, the adiabatic combustion temperature of the flame is controlled in the range of 1700 ° C. or higher and 3200 ° C. or lower. As a result, spherical phosphorescent fine particle powder can be easily produced while suppressing oxidation of the phosphorescent material.

(7) Further, the method for producing a glass-coated phosphorescent material of the present invention is a method for producing a phosphorescent material using a flame melting method, and is a strontium aluminate-based phosphorescent material powder containing europium and dysprosium as activators. The step of passing the mixed raw material powder composed of the soda lime glass powder into the flame together with the carrier gas and melting it, the step of colliding with and depositing the fireproof wall installed in the discharge direction of the mixed raw material powder, and the deposited melting. It is characterized by having a process of taking out an object outside the furnace by free dropping. As a result, a glass-coated phosphorescent material can be easily produced while suppressing oxidation of the phosphorescent material.

The spherical phosphorescent fine particle powder of the present invention is a homogeneous spherical phosphorescent fine particle powder that is spherical and has a small particle size. Further, according to the production method of the present invention, it is possible to easily produce spherical phosphorescent material fine particle powder having improved characteristics while suppressing oxidation of the phosphorescent material. In addition, a glass-coated phosphorescent material can be easily produced while suppressing oxidation of the phosphorescent material.

It is a schematic diagram of the spherical phosphorescent fine particles produced by using the flame melting method of this invention. It is a schematic diagram of the spherical phosphorescent fine particles produced by using the flame melting method of this invention. It is a schematic diagram of the glass-coated phosphorescent material produced by using the flame melting method of this invention. It is the schematic which shows the processing apparatus in a flame. (A) to (c) are schematic views which show the cross section of the burner of the in-flame processing apparatus, respectively. It is a graph which shows the fluorescence spectrum of the spherical phosphorescent fine particle of Example 1. FIG. (A) to (f) are optical micrographs of the phosphorescent material raw material, furnace bottom falling powder, and cyclone recovered powder of Example 2 by transmitted light and reflected light, respectively. It is a graph which shows the fluorescence spectrum of the spherical phosphorescent fine particle of Example 2. It is a graph which shows the fluorescence spectrum of the glass-coated phosphorescent material of Example 3.

As a result of diligent studies, the present inventors have found that the oxidation of a strontium aluminate-based phosphorescent material is unexpectedly slow, and that the phosphorescent properties are not impaired even when reheated under oxidizing atmosphere conditions, and completed the present invention. I let you. Hereinafter, embodiments of the present invention will be described.

Fluorescence and phosphorescence are phenomena in which an element in the ground state is excited by irradiation with electromagnetic waves (ultraviolet rays, X-rays, electron beams) having a specific wavelength, and emits light when returning to the original ground state. In addition, there is a phenomenon (phosphorescence) in which light emission continues even after the incident energy (excitation light) observed in an oxide illuminant or the like is interrupted. The phosphorescent material according to the present invention includes both those having a fluorescent property and those having a phosphorescent property.

[Composition of spherical phosphorescent fine particle powder]
The spherical phosphorescent fine particle powder of the present invention is a spherical phosphorescent fine particle powder substantially formed of a strontium aluminate-based phosphorescent material containing europium and dysprosium as activators. By "substantially" is meant that impurities may be contained in addition to these. The spherical phosphorescent fine particle powder contains 65% or more of particles having an aspect ratio of 1.05 or less, and has an average particle size D50 of 20 μm or more and 500 μm or less. As described above, since the particles are spherical with a small particle size, they can be suitably used as, for example, a material for a phosphorescent paint. The spherical phosphorescent fine particle powder preferably contains 80% or more of particles having an aspect ratio of 1.05 or less in order to obtain more homogeneous characteristics.

The aspect ratio is measured and calculated as follows. First, an optical micrograph of a sample is taken a plurality of times at a magnification of 100 times, and particles in which the entire image is captured in the measurement area of the photographed image are determined. Next, the maximum and minimum diameters of all the determined particles are measured. Next, the aspect ratio for each particle is calculated by dividing the maximum diameter for each particle by the minimum diameter. The measurement is performed on 20 or more particles, preferably 50 or more, and more preferably 100 or more. The measurement can be performed by printing out the image on paper and measuring it directly using a ruler, or by using image processing software.

Further, the spherical phosphorescent fine particle powder preferably has a D90 / D10 of 20 or less, more preferably 10 or less, and further preferably 5 or less. D90 / D10 represents the breadth of the particle size distribution of the powder, and the closer it is to 1, the narrower the particle size distribution is. The spherical phosphorescent fine particle powder exhibits homogeneous characteristics when D90 / D10 is 20 or less because the distribution is narrower than when it is larger than 20.

The spherical phosphorescent fine particle powder may further contain spherical glass fine particles. Further, some spherical phosphorescent fine particles may be coated on the glass. Further, some spherical phosphorescent fine particles may form composite particles with glass. As described above, the spherical phosphorescent fine particle powder containing the spherical glass fine particles can arbitrarily change the fluorescence brightness according to the amount of glass. The same applies when the spherical phosphorescent fine particles are coated on the glass, or when the spherical phosphorescent fine particles form composite particles with the glass. Further, since the spherical phosphorescent fine particles coated on the glass do not come into contact with water, deterioration due to hydrolysis is suppressed.

Even when the spherical phosphorescent fine particles including the spherical glass fine particles are coated on the glass or the spherical phosphorescent fine particles form composite particles with the glass, the number of particles having an aspect ratio of 1.05 or less is 65% or more. The average particle size D50 is 20 μm or more and 500 μm or less. Further, D90 / D10 is preferably 20 or less. The measurement method is the same.

The average particle size D50, D90, and D10 are measured by JIS R 1629 "Method for measuring particle size distribution by laser diffraction / scattering method of fine ceramics raw material". The average particle size D50 is a particle size of 50% in the volume-based integrated fraction, and D90 and D10 are particle sizes of 90% and 10% in the volume-based integrated fraction.

[Manufacturing method of spherical phosphorescent fine particle powder]
The method for producing the spherical phosphorescent fine particle powder of the present invention will be described.

(Principle of manufacturing method)
Usually, a strontium aluminate-based phosphorescent material using europium and dysprosium as activators is a high temperature of 1300 ° C. or higher in a reducing atmosphere having a hydrogen concentration of less than 5% by volume after placing a mixture of raw material powders in a firing container. It is produced by causing a solid phase reaction by heating and firing for 2 to 5 hours, and then finely pulverizing it with a ball mill or the like. However, since the solid phase method is subjected to a pulverization process, the produced fine particles have an irregular morphology.

Since the strontium aluminate-based phosphorescent material is imparted with phosphorescent properties by firing in a reducing atmosphere, it has been conventionally considered inappropriate to reheat at a high temperature under the oxidizing atmosphere condition. However, as a result of diligent studies, the present inventors have found that the oxidation of the strontium aluminate-based phosphorescent material is unexpectedly slow, and that the phosphorescent characteristics are not impaired even when reheated under oxidizing atmosphere conditions. Therefore, when spheroidization was attempted by the flame melting method, it was found that spherical phosphorescent fine particles having excellent phosphorescent characteristics could be obtained by specifying the particle size range. Even with the general-purpose flame melting method, (1) even if the atmosphere inside the furnace is a normal atmosphere, the inside of the flame through which the phosphorescent material passes is maintained in a weakly reducing atmosphere, and (2) the phosphorescent material is a flame. The time to pass through is extremely short, less than 0.1 seconds, and it is not oxidized to the extent that the phosphorescent characteristics are impaired. (3) Before it is oxidized and loses its phosphorescent properties, it is melted by a high-temperature flame to block the diffusion of oxygen. It is considered that this is to satisfy the conditions such as being done.

(Preparation of raw materials)
The raw material according to the present invention is an inorganic oxide powder that expresses phosphorescence. As the inorganic oxide powder that expresses phosphorescence, a strontium aluminate-based phosphorescent material containing europium and dysprosium as activators is suitable. The activator may be only one of europium or dysprosium, and may contain other activators and impurities. Not limited to SrAl ₂ O ₄ : Eu and Dy fine particles used in the present invention, other fine particles can also be produced. Other fine particles that can be produced include, for example, Y ₂ O ₃ : Eu fine particles, Y ₃ Al ₅ O ₁₂ called YAG doped with Tb, Y ₃ Al ₅ O ₁₂ : Tb, and Gd ₂ O ₃ : Eu. And so on.

As described in the principle of the above production method, it was found that the strontium aluminate phosphorescent material suppresses deterioration due to oxidation even if it is melted by the flame melting method, but other inorganic oxide powders expressing phosphorescence are suppressed. Even so, it is considered that deterioration due to oxidation is suppressed if it is instantly melted in the flame.

FIG. 1A is a schematic view showing a fine particle powder before treatment and a spherical fine particle powder after treatment when the fine particle powder of the phosphorescent material is flame-melted. When the phosphorescent inorganic oxide powder is passed through the fuel flame at the same time as the carrier gas, if the temperature of the flame is controlled to a temperature close to or higher than the melting point of the phosphorescent material, the particles of the phosphorescent material are melted and spherical. It becomes fine particles of. By cooling and solidifying this, spherical phosphorescent fine particles containing 65% or more of particles having an aspect ratio of 1.05 or less can be obtained. Further, by controlling the temperature and length of the flame, that is, the passage time of the fine particles, according to the particle size of the raw material powder of the fine particles of the phosphorescent material, the proportion of particles having an aspect ratio of 1.05 or less is increased. Can be done.

The raw material according to the present invention is a glass powder that melts at a lower temperature than the inorganic oxide powder that expresses phosphorescence. As the glass powder that melts at a lower temperature than the inorganic oxide powder that exhibits phosphorescence, ordinary plate glass, bottle glass for drinking water, and the like are preferable. Borosilicate glass, silica glass and the like can also be used as long as the object of the present invention is not impaired.

When a mixed powder raw material composed of fine particle powder of a phosphorescent material and glass powder is passed through a fuel flame at the same time together with a carrier gas, the temperature of the flame is sufficiently lower than the melting point of the phosphorescent material and lower than the melting point of glass. When controlled to a high temperature, the melting point of the glass is lower than the melting point of the phosphorescent material, so that a part of the glass melt adheres to the surface of the phosphorescent material particles and functions as an impermeable inorganic coating material. In addition, spherical glass fine particles are also generated at the same time.

When the temperature of the flame is controlled to a temperature close to or higher than the melting point of the phosphorescent material, both the particles of the phosphorescent material and the particles of the glass are melted and become spherical independently, and some of the phosphorescent materials The melt and the melt of the glass coalesce to form composite particles, or the softened glass melt spreads around the melt of the phosphorescent material and becomes an impermeable inorganic coating material. FIG. 1B is a schematic view showing a fine particle powder before treatment and a spherical fine particle powder after treatment when a mixed powder raw material in which a powder of fine particles of a phosphorescent material and a powder of fine particles of glass are mixed is subjected to flame melting treatment.

In the spheroidization of the inorganic powder used by the flame melting method, the particle size of the raw material powder before it is exposed to the flame is an important control factor. In the method for producing spherical phosphorescent fine particle powder according to the present invention, a strontium aluminate-based phosphorescent material having a particle size adjusted in the range of 20 μm to 500 μm and using europium and dysprosium as activators is used alone or with soda-lime glass powder. As a mixture of the above, it is obtained by passing it through a fuel flame together with a carrier gas, melting it, and cooling and solidifying it. As a result, spherical phosphorescent fine particles containing 65% or more of particles having an aspect ratio of 1.05 or less can be obtained.

The particle size range of the strontium aluminate phosphorescent material containing europium and dysprosium as activators is preferably in the range of 20 μm to 500 μm, more preferably in the range of 50 μm to 400 μm, and further preferably in the range of 70 μm to 300 μm. If the particle size is less than 20 μm, the activator in the phosphorescent material, that is, europium and dysprosium, may be oxidized and the phosphorescent property may be lost. If the particle size exceeds 500 μm, the proportion of those that do not spheroidize sufficiently and become amorphous increases. If the particle size distribution is narrowly controlled with the particle size range within the above range, the particle size distribution of the generated spherical phosphorescent fine particles is also narrowed. For example, by controlling the particle size distribution of the phosphorescent material so that D90 / D10 is 20 or less, the particle size distribution of the generated spherical phosphorescent fine particles can be sufficiently narrowed.

The range of the particle size from A to B means that the minimum opening size is A and the maximum opening size is B in the sieving classification, and the range between the minimum opening size A and the maximum opening size B is set. It is assumed that the proportion of the powder having a particle size is 90% by volume or more. The ratio of the powder having a particle size between the minimum opening size A and the maximum opening size B is preferably 95% by volume or more.

Since the melting point of glass is much lower than the melting point of the phosphorescent material, its particle size does not need to be controlled as tightly as the particle size of the phosphorescent material, but it is preferably smaller than the particle size of the phosphorescent material. For example, if the thickness is 0.5 μm to 250 μm, the object of the present invention can be achieved.

(Flame melting process)
FIG. 2 is a schematic schematic view of an apparatus for melt spheroidization (flame treatment apparatus 30) according to an embodiment of the present invention. The in-flame treatment device 30 according to the present embodiment includes a powder supply device (not shown), a burner 32 that generates a flame, a melting zone 34, a cooling zone 36, and a dust collection / recovery device (cyclone) for collecting generated fine particles. 38, a bag filter 40), and a suction fan (not shown).

Various quantitative supply means such as a screw feeder, a circle feeder, and a rotary feeder can be used to supply the powder raw material to be discharged into the flame. Generally, the ejector method is adopted when a fine solid substance is blown into a fuel flame. The principle is that when the raw material powder is dropped into the pore tube connected to the carrier gas pipeline at a constant speed, the raw material powder is sucked into the carrier gas pipeline due to the negative pressure generated on the inner wall of the carrier gas pipeline. ..

The discharge port of the fixed quantity supply means is connected to the burner 32 via an ejector, and a flame is generated at the tip of the burner 32. The burner 32 is composed of a plurality of cylinders having a coaxial center. The raw material powder discharged from the metering machine is introduced directly into the flame of the burner 32 together with the carrier gas through the innermost cylinder of the burner 32.

FIG. 3 shows an enlarged schematic view of the burner 32. The burner 32 is composed of a plurality of cylinders having a coaxial center as described above. FIG. 3A is a front view of the burner 32 in a direction perpendicular to the coaxial direction, and FIG. 3B is a side sectional view of the burner 32 in a direction parallel to the coaxial direction. The innermost cylinder is located at the center of the burner 32, and is surrounded by the middle cylinder and the outermost cylinder in this order. The length of the innermost cylinder is the longest and protrudes in the direction opposite to the discharge direction of the burner 32, and the intermediate cylinder and the outermost cylinder that sequentially surround the outside of the innermost cylinder are configured so that their lengths are gradually shortened. Has been done.

A fuel pipe for feeding fuel and a fuel-supporting gas pipe for feeding fuel-supporting gas are connected to the burner 32, and the fuel gas and fuel-supporting gas are fed to the burner through these pipes. In the burner 32, for example, city gas is sent into the intermediate cylinder surrounding the outer circumference of the innermost cylinder by a fuel pipe. Air or oxygen is sent into the outermost cylinder that surrounds the outer circumference of the intermediate cylinder by a combustion-supporting gas pipe. Further, in the innermost cylinder located at the center of the burner 32, the raw material powder discharged from the fixed quantity feeder is directly introduced into the center of the flame together with nitrogen which is a carrier gas.

As the fuel gas for the flame, for example, gaseous fuel such as methane, propane, and city gas, liquid fuel such as kerosene and heavy oil, and the like are used, but the present invention is not limited to these substances, and as long as the characteristics of the phosphorescent material are not impaired. It is also possible to use other fuels.

As the carrier gas, air, nitrogen, argon, hydrogen or the like can be used, but a neutral or reducing gas such as nitrogen, argon or hydrogen is preferable, and in particular, neutral nitrogen or argon is used. Is preferable. The discharge rate of the carrier gas is preferably 5 m / sec to 100 m / sec, more preferably 10 m / sec to 80 m / sec, and even more preferably 20 m / sec to 50 m / sec.

Note that FIGS. 3A and 3B are examples of burners, and of course, burners having other structures may be used. For example, as shown in FIG. 3C, there may be a plurality of fuel discharge ports, or there may be a plurality of raw material discharge ports and fuel support gas discharge ports.

Flow meters such as differential pressure flow meters are attached to the fuel pipes and fuel-supporting gas pipes, and the flow rates of these fuels and / or gases can be changed, and the amount of heat input and the length of the flame are controlled. To. By these controls, the adiabatic combustion temperature of the flame generated in the burner 32 is controlled in the range of, for example, 1700 ° C. to 3200 ° C. The adiabatic combustion temperature is a temperature theoretically calculated on the assumption that all the heat generated by combustion is used for heating the combustion gas without being lost to the outside. A check valve is provided in the fuel pipe and the fuel supporting gas pipe for safety.

When the powder raw material of strontium aluminate phosphorescent material or the mixed powder raw material consisting of powder of strontium aluminate phosphorescent material and soda-lime glass powder is charged into the burner 32 in association with the carrier gas, it melts in the high temperature flame of the melting zone. When the above is reached, the fine particles themselves are spheroidized by the surface tension in the process of melting and liquefying. The adiabatic combustion temperature is preferably 1700 ° C. to 3200 ° C. If the adiabatic combustion temperature is lower than 1700 ° C., the raw material particles are not sufficiently spheroidized and become amorphous. If the adiabatic combustion temperature exceeds 3200 ° C., the activator in the phosphorescent material, that is, europium and dysprosium, is oxidized and the phosphorescent property is lost.

Generally, the average particle size of the inorganic raw material powder particles spheroidized by the melt spheroidizing treatment is larger than the average particle size of the inorganic raw material powder before being charged into the burner 32. It is explained that one reason for the increase in the average particle size is that a plurality of inorganic raw material powder fine particles are spheroidized in a state of being aggregated by static electricity or intermolecular attractive force.

In the above method, the raw material powder is discharged from the center of the burner 32 and is passed through the flame. However, the raw material powder is discharged from the outside of the burner 32 toward the flame of the burner 32 to expose the raw material powder to the flame. However, the same effect can be obtained.

(Recovery of spherical phosphorescent particles)
The particles of the spherical phosphorescent material formed in the melting zone 34 are cooled in the cooling zone 36 together with the combustion exhaust gas by indirect water cooling means or air cooling means. A dust collection device and a suction fan are installed in the rear stage of the cool body, and the combustion exhaust gas, carrier gas, and cooling air generated by the combustion of fuel in the reactor are collected by the suction fan in the final stage of the spherical phosphorescent material. Aspirated with the particles. At this time, the particles of the cooled spherical phosphorescent material are collected by the dust collector. In FIG. 2, the dust collector collects the cyclone 38 and the bag filter 40 in combination, but the dust collector can be arbitrarily selected from general-purpose devices such as a cyclone, an electric dust collector, and a bag filter. it can.

[Manufacturing method of glass-coated phosphorescent material]
Although the embodiment for obtaining spherical phosphorescent fine particles has been described above, other embodiments will be described here.

FIG. 1C shows the fine particle powder before the treatment and the glass after the treatment when the mixed powder raw material obtained by mixing the fine particle powder of the phosphorescent material and the fine particle powder of the glass was flame-melted and the melt was deposited on the refractory wall. It is a schematic diagram which shows the coated phosphorescent material. A mixed raw material consisting of a strontium aluminate phosphorescent material and a soda-lime glass powder is melted by passing it through a fuel flame together with a carrier gas or by exposing it to a flame, and is placed on a refractory wall installed in the discharge direction with the mixed raw material. A glass-coated phosphorescent material can be produced by colliding, depositing, and taking out the melt outside the furnace by free fall.

When a mixed raw material composed of a strontium aluminate phosphorescent material and a soda lime glass powder is passed through a fuel flame together with a carrier gas, both of them melt. When these molten particles collide with a refractory wall installed in the discharge direction, the strontium aluminate phosphorescent material becomes a viscous starch syrup-like mass while being completely covered with soda-lime glass. When this lump becomes larger, it falls to the bottom due to its own weight. By providing an opening at the bottom, it can be taken out of the furnace. The lumps taken out of the furnace are cooled by indirect water cooling means or air cooling means to obtain a phosphorescent material coated with soda lime glass. The temperature of the collision wall is preferably 1100 ° C. or higher, more preferably 1200 ° C. or higher, because the mass must be viscous enough to fall under its own weight.

Since it is preferable that the time from melting to cooling is short, it is preferable to adjust the angle of the wall surface of the refractory wall, the smoothness of the surface, and the wettability of the surface of the refractory wall with the glass melt. In the present embodiment, since the phosphorescent material does not need to be spheroidized, the particle size range of the phosphorescent material powder may be in the range of 20 μm to 500 μm. The particle size range of the glass powder is preferably 0.5 μm to 250 μm. According to this embodiment, a phosphorescent material having high light transmission can be obtained. It can also be pulverized and used if necessary.

As described above, according to the present invention, it is possible to efficiently produce spherical phosphorescent fine particles having high fluorescence brightness and afterglow brightness, or a phosphorescent material coated with glass having high fluorescence brightness and afterglow brightness.

Next, examples will be described in detail.

[Example 1]
G-300L160 manufactured by Nemoto & Co., Ltd. was used as the strontium aluminate-based phosphorescent material using europium and dysprosium as activators. The average particle size was 65 μm for D10, 140 μm for D50, and 230 μm for D90. D90 / D10 was about 3.5. The powder raw material of this strontium aluminate phosphorescent material was passed through the center of the flame from a fixed quantity feeder and melted and spheroidized. City gas 13A was used as the fuel, oxygen was used as the supporting gas, and air was used as the carrier gas.

The amount of heat input by burning the city gas 13A was 500 MJ / hour, the oxygen ratio to the theoretical amount of combustion oxygen was 1.07, and the adiabatic combustion temperature was 2800 ° C.

The spheroidized phosphorescent material was recovered from the cyclone after cooling, and the degree of spheroidization of the phosphorescent material was evaluated by the aspect ratio (= major axis length / minor axis length) from the image of the field of view of the optical microscope. The closer the calculated value is to 1, the closer it is to a true sphere. In addition, the particle size distribution and the fluorescence spectrum were measured.

The average aspect ratio of the phosphorescent material before the flame melting treatment is 1.36, whereas the average aspect ratio of the phosphorescent material (spherical phosphorescent fine particle powder) after the flame melting treatment is 1.05. The ratio of particles having a ratio of 1.05 or less was 68% in number, and an almost true spherical phosphorescent material was obtained. The average particle size of the spheroidized phosphorescent material was 54 μm at D10, 97 μm at D50, and 190 μm at D90. D90 / D10 was about 3.5. FIG. 4 shows a fluorescence spectrum when the excitation wavelength is 393 nm. A fluorescence peak was observed in the range of 490 nm to 530 nm, and spherical phosphorescent fine particle powder having high fluorescence brightness and afterglow brightness was obtained.

[Example 2]
The same phosphorescent material as in Example 1 and soda lime glass powder (Fukuike Kogyo Co., Ltd., transparent bottle glass) were mixed at a mass ratio of 3: 7. The average particle size of the soda lime glass powder was 3.5 μm at D10, 20 μm at D50, and 60 μm at D90. D90 / D10 was about 17. This mixed raw material powder was passed through the center of the flame from the fixed quantity feeder and melted and spheroidized. Similar to Example 1, city gas 13A was used as the fuel, air was used as the fuel supporting gas, and air was used as the carrier gas.

The amount of heat input by burning the city gas 13A was 500 MJ / hour, the oxygen ratio to the theoretical amount of combustion oxygen was 1.07, and the adiabatic combustion temperature was 2000 ° C.

The spheroidized phosphorescent material (spherical phosphorescent fine particle powder) was recovered from the cyclone after cooling, and the degree of spheroidization was confirmed with an optical microscope, and the particle size distribution and fluorescence spectrum were measured. Most of the soda-lime glass and phosphorescent material after flame melting exist as independent particles, and the aspect ratios are 1.02 and 1.05 on average, respectively, and the aspect ratio is relative to the total particles. The ratio of particles of 1.05 or less was 84% in number, and a substantially true spherical phosphorescent material was obtained. The average particle size was 2.4 μm for D10, 12.3 μm for D50, and 47.9 μm for D90. D90 / D10 was about 20.

5 (a) to 5 (f) are optical micrographs of the phosphorescent material raw material, the falling powder at the bottom of the furnace, and the recovered cyclone powder of Example 2 by transmitted light and reflected light, respectively. As shown in FIGS. 5 (a) to 5 (f), even if the mixed powder (FIGS. 5 (a) and 5 (b)) is flame-melted as in Example 2, a substantially spherical soda lime glass and a phosphorescent material are used. It was found that a mixture consisting of (FIGS. 5 (c) to (f)) was obtained. Some of the particles were composite particles of a phosphorescent material and glass.

The same product can be produced by separately flame-melting the soda lime glass and the phosphorescent material, spheroidizing them, and mixing them after cooling. However, according to the present invention, this can be achieved by a single heat treatment. The fluorescence spectrum of the mixture composed of spherical soda-lime glass and spherical phosphorescent material is shown in FIG. 6. Similar to Example 1, a fluorescence peak is observed in the range of 490 nm to 530 nm, and spherical phosphorescence with high fluorescence brightness and afterglow brightness. The material was obtained. The fluorescence brightness can be arbitrarily changed by changing the ratio of the phosphorescent material to the powder of soda lime glass before the flame melts.

When the same mixed raw material as in Example 2 was used and the input heat amount was changed to 340 MJ / hour to perform the flame melting treatment, the yields in the cyclone and the bag filter were improved as compared with Example 2. However, the content of phosphorescent particles also increased. In addition, the amount of the composite particles of the phosphorescent material and the glass and the phosphorescent particles coated on the glass also increased. In Example 2, since the amount of heat input was large, a part of the mixed raw material became a glass molten mass on the melting zone, the wall of the water-cooled body, and the bottom of the furnace. However, when the input heat amount was controlled to a more appropriate range, the glass molten mass was formed. This is thought to be due to the reduction in the proportion of raw materials. Since the molten glass mass also contains phosphorescent particles, it can be used as a glass-coated phosphorescent material.

[Example 3]
A mixed raw material composed of the same phosphorescent material as in Example 2 and powder of soda-lime glass is passed through the center of the flame from a fixed quantity feeder, melted and spheroidized, and collides with a refractory wall intentionally installed in the particle ejection direction. It was discharged to the outside of the furnace through an opening provided in the bottom of the furnace. As in Example 1, city gas 13A was used as the fuel, oxygen was used as the fuel supporting gas, and air was used as the carrier gas.

The amount of heat input by burning the city gas 13A was 500 MJ / hour, the oxygen ratio to the theoretical amount of combustion oxygen was 1.07, and the adiabatic combustion temperature was 2800 ° C.

A molten mass composed of a translucent starch syrup-like phosphorescent material and soda-lime glass discharged to the bottom of the furnace was pulverized after cooling, and the fluorescence spectrum was measured. As shown in FIG. 7, as in Example 1 and Example 2, a fluorescence peak was observed in the range of 490 nm to 530 nm, and a phosphorescent material coated with glass having high fluorescence brightness and afterglow brightness was obtained. A peak of luminescence was also observed at 615 nm, which is attributed to europium (III). Unlike Examples 1 and 2, where the flame was passed in a short time, a mixture of glass and phosphorescent material was in contact with oxygen for a longer period of time in a hot furnace, causing some of the europium (II) to oxidize. This is because it was changed to Europium (III). The fluorescence brightness can be arbitrarily changed by changing the ratio of the phosphorescent material to the powder of soda lime glass before the flame melts. Further, in the same manner as the method for producing slag, if it is put into water when it is discharged to the bottom of the furnace, it can be taken out in a state of being finely crushed into particles. Further, a transparent phosphorescent model having an arbitrary shape can be produced by pouring it into a mold having an arbitrary shape in a viscous state.

Although the method for producing fine particles according to the present invention has been described above based on the embodiment, the present invention is not limited to such an embodiment, and appropriate modifications are made within the range not departing from the gist of the present invention. Needless to say, improvements may be made.

10 Luminescent material fine particles 12 Raw material powder 14 Spherical phosphorescent fine particles 16 Spherical phosphorescent fine particles powder 18 Glass fine particles 20 Mixed raw material powder 22 Spherical glass fine particles 24 Glass-coated phosphorescent material 30 In-flame treatment device 32 Burner 34 Melting zone 36 Cooling zone 38 Cyclone 40 Bug filter

Claims (7)

A strontium aluminate-based spherical phosphorescent fine particle powder using europium and dysprosium as activators.
The powder is a spherical phosphorescent fine particle powder containing 65% or more of particles having an aspect ratio of 1.05 or less and having an average particle size D50 of 20 μm or more and 500 μm or less. The spherical phosphorescent fine particle powder according to claim 1, wherein D90 / D10 is 20 or less. The spherical phosphorescent fine particle powder according to claim 1 or 2, which comprises spherical glass fine particles. A method for producing spherical phosphorescent fine particle powder using a flame melting method.
A step of preparing a powder of a strontium aluminate phosphorescent material containing europium and dysprosium as an activator, the particle size of which is adjusted in the range of 20 μm to 500 μm, and
The process of passing the powder together with the carrier gas into the flame and melting it,
A method for producing a spherical phosphorescent fine particle powder, which comprises a step of cooling and solidifying the molten powder. A method for producing spherical phosphorescent fine particle powder using a flame melting method.
A step of preparing a powder of a strontium aluminate phosphorescent material using europium and dysprosium as an activator, the particle size of which is adjusted in the range of 20 μm to 500 μm, and
The process of preparing soda lime glass powder whose particle size has been adjusted to the range of 0.5 μm to 250 μm, and
The step of mixing the phosphorescent material powder and the soda lime glass powder, and
The process of passing the mixed powder together with the carrier gas into the flame and melting it,
A method for producing a spherical phosphorescent fine particle powder, which comprises a step of cooling and solidifying the molten powder. The method for producing spherical phosphorescent fine particle powder according to claim 4 or 5, wherein the adiabatic combustion temperature of the flame is controlled in the range of 1700 ° C. or higher and 3200 ° C. or lower. It is a manufacturing method of phosphorescent material using the flame melting method.
A process of passing a mixed raw material powder consisting of strontium aluminate phosphorescent material powder containing europium and dysprosium as an activator and soda-lime glass powder into a flame together with a carrier gas to melt them.
The process of colliding with and depositing the refractory wall installed in the discharge direction of the mixed raw material powder,
A method for producing a glass-coated phosphorescent material, which comprises a step of taking out the deposited melt outside the furnace by free fall.