JP2006232935A - Method for producing silicate phosphor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a silicate phosphore, capable of sieving the desired silicate phosphor having a small particle diameter from a crude product in a high recovering rate and showing a high productivity. <P>SOLUTION: This method for producing the silicate phosphor comprises a process of preparing slurry by performing a wet type crushing/mixing of a multiple kinds of metal compounds including silicon oxide, a process of drying the slurry, a process of calcinating the dried product, and a process of crushing/sieving the crude product obtained by calcinating to obtain the silicate phosphor having the small diameter, wherein the sieving process is performed by feeding the crude product to the inside of a cylindrical screen 5, while rotating a blade 4 in a high speed within the cylindrical screen 5 having a prescribed mesh openings for passing the silicate phosphore having ≤20 μm maximum particle diameter and blocking the passage of the particle-formed materials having larger diameter than that. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a silicate phosphor, and more particularly to a method for manufacturing a fine silicate phosphor suitable for a vacuum ultraviolet light-emitting device such as a plasma display panel (PDP) or a rare gas lamp.

  Conventionally, silicate phosphors have been used in fluorescent lamps, cathode ray tubes, phosphorescent materials, vacuum ultraviolet light-excited light emitting elements, and the like. Usually, this silicate phosphor is obtained by wet-grinding and mixing a plurality of types of metal compounds containing silicon oxide to produce a slurry, drying the slurry, and then firing it.

  For example, Patent Document 1 discloses a method for producing a silicate phosphor using a predetermined metal compound. According to this manufacturing method, since a silicate phosphor having a small primary particle diameter is obtained, it becomes possible to efficiently apply the phosphor in a minute discharge space such as a display cell of a PDP, and the emission luminance is high. It is described that a display such as a PDP can be manufactured. In general, a silicate phosphor having a maximum particle size of 20 μm or less is desired.

  In the actual production process, it is necessary to mix a plurality of types of metal compounds and fire them, then finely pulverize the product, and then remove coarse particles (foreign matter) using a sieving machine. However, the finely pulverized crude product has the disadvantages that it easily aggregates and easily forms lumps, and easily adheres to the wall surface of equipment. For this reason, there is a problem that sieving of the product is difficult, the recovery rate of the silicate phosphor having a small primary particle diameter is low, and the productivity is poor.

  For example, in the vibrating screen shown in FIG. 4, as shown in Comparative Example 1 described later, the crude product aggregates on the mesh to be a screen to form lumps. For this reason, sieving could not be performed smoothly and the recovery rate was low.

Further, in the wind screen shown in FIG. 5, as shown in Comparative Example 2 described later, the crude product adhered to the casing, the cyclone, and the pipe, and the operation was impossible.
JP2003-183644A ([0016] etc.)

  An object of the present invention is to provide a method for producing a highly productive silicate phosphor capable of efficiently sieving a desired small particle size silicate phosphor from a crude product with a high recovery rate. It is.

  As a result of intensive research to solve the above problems, the present inventors supply a crude product to the inside of the cylindrical screen as a sieving machine while rotating the blade at a high speed inside the cylindrical screen. In this case, the screen does not agglomerate to form lumps and clogging of the screen hardly occurs, so that a desired small particle size silicate phosphor can be efficiently screened with a high recovery rate. As a result, the present invention has been completed.

  That is, the method for producing a silicate phosphor of the present invention includes a step of preparing a slurry by wet-grinding and mixing a plurality of types of metal compounds containing silicon oxide, a step of drying the slurry, and firing the dried product. And a step of pulverizing and sieving the crude product obtained by baking to obtain a silicate phosphor having a small particle size, wherein the sieving step has a maximum particle size of 20 μm or less. A crude product is formed inside the cylindrical screen while rotating the blade at a high speed inside the cylindrical screen having a predetermined opening that allows passage of the salt phosphor and prevents passage of particles having a larger particle size. It is characterized by being performed.

  In the present invention, it is preferable that the cylindrical screen is made of synthetic fiber and the screen has an opening of 45 to 75 μm.

  According to the manufacturing method of the present invention, the coarse product is supplied to the inside of the cylindrical screen while sieving while rotating the blade at a high speed inside the cylindrical screen having a predetermined opening. It is possible to efficiently screen silicate phosphors having a maximum particle size of 20 μm or less without causing aggregation of the product to cause lumps and almost no clogging of the screen. effective.

  Hereinafter, the present invention will be described in detail. FIG. 1 is a process diagram showing a method for producing a silicate phosphor according to an embodiment of the present invention. As shown in FIG. 1, the manufacturing method according to the present embodiment includes steps ((a) to (c)) of preparing a slurry by wet-grinding and mixing a plurality of types of metal compounds including silicon oxide, and drying the slurry. A step ((d)) and a step ((e) to (g)) of firing the dried product, and further, a step of pulverizing the fired product obtained in the firing step ((h), ( i)), a step of removing impurities from the pulverized product, washing and drying ((j) to (l)), and a step of adjusting the particle size ((m)).

<Slurry adjustment process>
As a metal compound that is a raw material of the slurry, at least silicon oxide is used. To obtain a silicate phosphor having high brightness, BET specific surface area of 10 m ² / g or more, preferably 100 m ² / g or more, more preferably to use a silicon oxide 200 to 400 m ² / g .

The silicate phosphor in the production method of the present invention has a general formula mM ¹ O · nM ² O · 2SiO ₂ (wherein M ¹ is one or more selected from the group consisting of Ca, Sr and Ba, M ² Is one or more selected from the group consisting of Mg and Zn, m is 0.5 or more and 3.5 or less, and n is 0.5 or more and 2.5 or less.) Eu as an activator A silicate phosphor containing at least one selected from the group consisting of Mn and Mn is preferable. A silicate having high brightness when m is less than 0.5, m is greater than 3.5, n is less than 0.5, and n is greater than 2.5 There is a possibility that a phosphor cannot be obtained.

For example, when producing CaMgSi ₂ O ₆ : Eu, which is a blue phosphor, the raw material is a compound of Ca, Ba, Mg, Eu and silicon oxide that can form CaMgSi ₂ O ₆ : Eu by firing. Further, Si compounds other than silicon oxide may be added.

  Among the metal compounds that are the raw materials of the slurry, as compounds other than silicon oxide, in addition to oxides of metal elements constituting the silicate phosphor, hydroxides, carbonates, nitrates, halides of these metal elements A conventionally known metal compound that becomes an oxide at a high temperature, such as oxalate, can be used.

  In the slurry adjustment step, first, the above-described slurry raw material and a predetermined amount of water or organic solvent are charged into a mixer such as a ball mill, a V-type mixer, or a stirring device ((a)), and premixed using the mixer. ((B)). Moreover, it is preferable to add a dispersing agent in order to promote mixing during the preliminary mixing. Any dispersant may be used, but for example, a dispersant containing no metal ions such as ammonium polycarboxylate, such as SN Dispersant 5468 manufactured by San Nopco Corporation, is preferable. Next, the premixed mixture is wet-pulverized and mixed with a pulverizer to prepare a slurry ((c)). This wet pulverization and mixing is repeated as necessary until the slurry raw material is uniformly dispersed in water. The concentration of the plurality of types of metal compounds containing silicon oxide is preferably about 5 to 20% by mass. The viscosity of the slurry is preferably adjusted to about 100 to 5000 cP at room temperature.

<Drying process>
Next, the slurry obtained above is dried with a dryer. For example, a medium fluidized bed dryer is preferably used as the dryer. That is, the slurry is supplied into a fluid chamber in which hot air is blown to flow a large number of medium particles, and dry particles having a predetermined particle diameter are continuously recovered as a solid content in the slurry.

<Baking process>
Next, the dried particles obtained in the drying step are fired. In the drying step, dry particles having a small particle diameter of 3 mm or less can be obtained, and the dry particles can be fired as they are without being crushed. In this firing step, only reduction firing may be performed, but in the following, the case of performing calcination and reduction firing will be described. First, the dried particles are calcined in an air atmosphere ((e)). The calcination temperature is preferably about 600 to 1000 ° C., and the firing time is preferably about 0.5 to 40 hours. Next, the fired product obtained by calcination may be finely pulverized with a pulverizer ((f)).

  Next, the obtained pulverized product is reduced and fired in a reducing atmosphere ((g)). The temperature for reduction firing is preferably about 1000 to 1400 ° C., and the firing time is preferably about 0.5 to 40 hours. As a method for obtaining a reducing atmosphere, there is a method of firing in a mixed atmosphere of nitrogen and hydrogen or a rare gas and hydrogen. Further, water vapor may be contained in these atmospheres.

  In firing, for example, an alumina boat can be filled with dry particles and fired at a predetermined temperature in a predetermined gas atmosphere. In addition, if necessary, a reaction accelerator (flux) such as boron oxide, aluminum fluoride, or ammonium chloride can be mixed with the slurry raw material, thereby further improving the crystallinity and the brightness of the silicate. A phosphor may be obtained.

<Crushing process>
Next, the fired product obtained in the firing step is crushed ((h)) and further pulverized ((i)). In order to improve the crystallinity of the obtained phosphor, each step of (g) reduction firing, (h) pulverization, and (i) pulverization may be repeated as necessary.

<Washing and drying process>
Next, the pulverized product obtained in the pulverization step is immersed in an acid such as dilute hydrochloric acid to remove impurities contained in the pulverized product ((j)), and then water is added and filtered using a centrifugal filter or the like. After washing with water ((k)), the product is dried with a drier to obtain a crude product ((l)).

<Particle size adjustment process>
Finally, the crude product is sieved to obtain a silicate phosphor adjusted to a predetermined particle size ((m)). FIG. 2 shows an example of a high-speed rotary sieve used in this process. In this high-speed rotary sieve, a screw 3 is provided on the proximal end side of a rotary shaft 2 inserted into the casing 1, and a blade 4 (rotor blade) is attached on the distal end side of the screw 3. The blade 4 is inserted in a cylindrical screen 5 attached in the casing 1 and having a predetermined opening. The blades 4 are installed with an interval such that the outer peripheral surface does not contact the inner surface of the cylindrical screen 5, for example, an interval of about 0.5 to 10 mm. The proximal end of the rotating shaft 2 is connected to the motor 6.

  A hopper 12 is provided above the screw 3. The hopper 12 has a raw material supply port 7 in the upper part, and a crushing blade 8 is built therein. The blade 8 is rotated by a motor 9. On the other hand, the casing 1 below the cylindrical screen 5 is provided with a fine powder discharge port 10 for discharging fine powder that has passed through the cylindrical screen 5. The tip of the casing 1 is provided with a coarse powder outlet 11 for discharging coarse powder.

  In the high-speed rotary sieve configured as described above, the crude product supplied from the raw material supply port 7 to the hopper 12 is crushed by the crushing blade 8 in the hopper 12 and then falls into the casing 1. The screw 3 feeds the inside of the cylindrical screen 5. Within the cylindrical screen 5, the crude product is dispersed on the inner surface of the screen 5 by the blade 4 rotating at high speed. At this time, if necessary, the blade 4 may be formed with a predetermined twist angle, whereby the crude product can easily move on the inner surface of the screen 5 in the tip direction. The crushing blade 8 in the hopper 12 can be omitted if necessary. The rotation speed of the blade 4 is preferably about 1000 to 2000 rpm.

  The crude product accelerated by the blade 4 rotating at high speed is pressed against the inner surface of the screen 5, and fine powder smaller than the opening of the cylindrical screen 5 is passed out of the cylindrical screen 5 and discharged from the fine powder discharge port 10. On the other hand, the particulate matter larger than the opening of the screen 5 is sent to the tip without passing through the screen 5 and is discharged from the coarse powder outlet 11. When the crude product is pressed against the inner surface of the screen 5, minute vibrations are generated before and after the blade 4, so that the screen 5 can be prevented from being clogged.

  It is preferable that the cylindrical screen 5 is made of synthetic fiber and has an opening of 45 to 75 μm. Thereby, the silicate phosphor, which is a fine powder having a maximum particle size of 20 μm or less, can be separated from the granular material having a larger particle size, and clogging of the screen can be suppressed. Examples of the synthetic fiber include polyester fiber.

  Silicate phosphors with a maximum particle size of 20 μm or less can be applied efficiently in a micro discharge space such as a PDP display cell, for example, and various light emission type displays such as PDP with high emission luminance Can be produced.

  The silicate phosphor having a maximum particle size of 20 μm or less preferably contains 80% by mass or more of particles having a primary particle size of 5 μm or less in the particle size distribution and has an average particle size (D50) of 1 to 4 μm. .

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further in detail, this invention is not limited to a following example.

<Preparation of slurry>
In the stirring tank, first of all, the following raw materials are charged with pure water, followed by a dispersant, and the remaining raw materials are charged at the following ratios, stirred and premixed, and then wet pulverized and mixed to prepare a slurry. It was adjusted.
Pure water 73.3kg
Silicon oxide 3.7kg
2.7 kg of calcium carbonate
Strontium carbonate 0.45kg
Europium oxide 0.043kg
Basic magnesium carbonate 2.94 kg
Dispersant (Ammonium polycarboxylate aqueous solution) 0.34 kg

<Drying, firing, grinding, washing and drying of slurry>
The slurry was dried and calcined in an air atmosphere. Next, the fired product obtained by calcination was finely pulverized with a pulverizer, and the obtained pulverized product was reduced and fired in a reducing atmosphere. Next, the fired product obtained in the firing step was crushed and further pulverized. Next, the pulverized product obtained in the pulverization step is immersed in an acid such as dilute hydrochloric acid to remove impurities contained in the pulverized product, washed with water by adding water and filtering using a centrifugal filter or the like, and a dryer. To obtain a crude product.

<Granularity adjustment>
Finally, the crude product was sieved using a high-speed rotary sieve (TURBO-SCREENER manufactured by Turbo Kogyo Co., Ltd.) shown in FIG. The sieving conditions are as follows.
Hopper 12: Cylindrical screen without crushing blade 8 5: Made of polyester fiber, opening 45 μm, tension strength 10N
Rotating shaft 2: 1800 rpm
Blade 4: Supply amount of straight crude product: 1.0 kg
Crude product feed time: 5 minutes The results of sieving are shown in FIG. In FIG. 3, the graph (A) shows the particle size distribution of the crude product, and the graph (B) shows the particle size distribution of the silicate phosphor discharged from the fine powder discharge port 10. In addition, the particle size distribution was measured using a laser diffraction type particle size distribution measuring device (Mastersizer 2000 manufactured by Malvern).
In each graph, “D50” indicates the particle size value when the cumulative value of frequency% reaches 50% when the frequency% is sequentially added from the small particle size value in the particle size distribution shown in the graph. Say. Similarly, “D90” refers to a particle size value when the cumulative value of frequency% reaches 90%, and “D100” refers to a particle size value when the cumulative value of frequency% reaches 100%. Say.
As is clear from the value of “D100”, by sieving the crude product using a high-speed rotary sieving machine, the coarse particles are largely eliminated, and the silicate phosphor having a maximum particle size of 20 μm or less is obtained. You can see that The recovery rate was 98.5%. Moreover, clogging did not occur in the cylindrical screen 5 during the sieving operation.

[Comparative Example 1]
Instead of the high-speed rotary sieve used in Example 1, the crude product was sieved using a vibrating sieve shown in FIG. The vibrating screen shown in FIG. 4 has a nylon mesh 22 (screen) having a mesh opening of 300 μm stretched inside a casing 21 provided with a crushing chamber 20 at the upper part, and a synthetic resin ball for tapping is provided below the mesh 22. 23 (polyurethane ball having a diameter of 20 mm), and a coarse particle discharge port 24 is provided at the upper part of the mesh 22 and a fine powder discharge port 25 is provided at the lower part. A punching plate 26 having a diameter of 10 mm is provided in the crushing chamber 20, and a zirconia ball 27 having a diameter of 15 mm is placed on the upper portion thereof. The lower portion of the crushing chamber 20 communicates with the casing 21. .
In this vibrating screen, the crushing chamber 20 and the casing 21 are vibrated by a vibration device (not shown), and after the crude product is crushed in the crushing chamber 20 and tapped by the casing 21, fine powder passes through the mesh 22. And it is comprised so that it may discharge | emit from the fine powder discharge port 25. FIG.
However, 5.33 kg of the crude product was added over about 5 hours and sieved, but because of the strong cohesive force of the powder, it became lumpy on the mesh 22 and actually discharged from the fine powder outlet 25. The silicate phosphor with a small particle size was 1.965 kg, and the recovery rate was as low as 37%.

[Comparative Example 2]
Instead of the high-speed rotary sieve used in Example 1, the crude product was sieved using a wind sieve shown in FIG. The wind screen shown in FIG. 5 includes a front chamber 31 having a raw material inlet 30 and an air inlet 38, a rear chamber 33 that is in contact via a screen 32, a cyclone 34 (body diameter 200 mm), and a bag filter 35 (filtering). An area of 32 m ² ). The screen 32 has an opening of 300 μm. The front chamber 31 is provided with a coarse powder recovery pot 37.
The air fed into the front chamber 31 enters the rear chamber 33 from the front chamber 31 through the screen 32, and then is discharged through the cyclone 34 and the bag filter 35. Of the crude product introduced into the front chamber 31 from the raw material introduction port 30, fine powder that has passed through the screen 32 together with air is collected by the cyclone 34, collected in the collection pot 36 at the bottom, and the rest in the bag filter 35. Be captured.
Since this wind screen is equipped with a rotary cleaner that blows backwash air toward the screen 32, the screen 32 was less clogged, but in the rear chamber 33 and in the subsequent pipes and the cyclone 34. The operation was not able to be continued due to the strong adhesion of fine powder.

It is process drawing which shows the manufacturing method of the silicate fluorescent substance concerning one Embodiment of this invention. It is the schematic which shows an example of the high-speed rotary sieve in this invention. (A) is a graph which shows the particle size distribution of the crude product obtained in the Example, (B) is a graph which shows the particle size distribution of the fine powder silicate phosphor which sieved the said crude product. It is the schematic which shows a vibration sieve. It is the schematic which shows a wind screen machine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Casing 2 Rotating shaft 3 Screw 4 Blade 5 Cylindrical screen 7 Raw material supply port 8 Slurry tank 10 Fine powder discharge port 11 Coarse powder discharge port 12 Hopper

Claims (2)

A step of preparing a slurry by wet-grinding and mixing a plurality of types of metal compounds containing silicon oxide, a step of drying the slurry, a step of firing the dried product, and grinding and grinding the crude product obtained by firing Sieving to obtain a silicate phosphor having a small particle size,
In the sieving step, a blade is passed inside a cylindrical screen having a predetermined opening that allows passage of a silicate phosphor having a maximum particle size of 20 μm or less and prevents passage of particles having a larger particle size. A method for producing a silicate phosphor, which is performed by supplying a crude product into the cylindrical screen while rotating at a high speed. The method for producing a silicate phosphor according to claim 1, wherein the cylindrical screen is made of synthetic fiber, and the screen has an opening of 45 to 75 μm.

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