JPS59149978A - Preparation of fluorescent substance - Google Patents

Abstract

PURPOSE:To obtain an inexpensive fluorescent crystal particle in high yields without necessitating a grinding process, by a method wherein a stock mixture of a fluorescent substance is melted and the molten mixture is cooled through contact with an aqueous medium to be pulverized. CONSTITUTION:Stock materials for a fluorescent substance such as barium fluoride, barium chloride, magnesium fluoride and europium oxide are respectively weighed in predetermined amounts to be mixed and the obtained mixture is melted under heating. The melt is brought into contact with an aqueous medium by a method for dripping the same in said aqueous medium and cooled to obtain a fluorescent crystal particle dispersed in the aqueous medium. In the next step, the fluorescent crystal particle is taken out by filtration and washed, dried and, if necessary, baked to obtain an objective fluorescent substance. Especially pref. fluorescent substances to which this inventive production method can be applied include a fluoride fluorescent substance (e.g., a divalent europium activated divalent metal fluoride fluorescent substance) and an oxyhalide fluorescent substance.

Description

[Detailed description of the invention] The present invention relates to a novel method for producing phosphors.

Conventionally, phosphors are produced by first processing phosphor raw materials by a dry method or a wet method, that is, in a dry state or in a slurry state.
The phosphor material is manufactured by a method comprising preparing a mixture of homogeneous phosphor materials with a uniform thickness by thoroughly mixing the phosphor material mixture, and then firing the phosphor raw material mixture at a temperature lower than its melting point.

2. In the conventional phosphor manufacturing method, the firing process is carried out to grow the host crystal and at the same time diffuse the activator element into the host crystal, which affects the resulting phosphor's luminance and luminance. This is an important process related to the characteristics of the steel. Generally, this firing step is carried out at a temperature close to the melting point of the host crystal so that the growth of the host crystal and the introduction of the activator element into the host crystal can be carried out efficiently. It tends to cause coalescence, and therefore it is usually necessary to subject the phosphor obtained after firing to a crushing process and an accompanying classification process. For this reason, the manufacturing process of the phosphor becomes complicated2, and the yield of the obtained phosphor tends to decrease. Further, generally, the sintering phenomenon in this firing process has only a negative effect on the luminescent properties of the phosphor, especially its luminance.

In other words, conventional methods for producing phosphors have problems such as complicated manufacturing processes and insufficient yields of the phosphors obtained. has become a major obstacle.

The purpose of the present invention is to provide a new method for producing a phosphor that makes it possible to simplify the production process and omit the pulverization process. It is characterized in that phosphor crystal particles are obtained by cooling by contacting with a medium.

That is, in the present invention, the phosphor raw materials are heated to a temperature higher than their melting point, melted, and mixed, and then the molten material is cooled by contacting with an aqueous medium, and then the solidified material is dried, thereby forming the phosphor. This is a manufacturing method for manufacturing crystal particles. Therefore, compared to the above-mentioned conventional phosphor manufacturing methods, it is possible to prepare a homogeneous phosphor raw material mixture by a dry method or a wet method before the phosphor thickness *'1 is subjected to the firing process, or alternatively after the calcination process. It is possible to omit the manufacturing process of the phosphor, such as the crushing of the sintered phosphor and the accompanying classification.
Further, since a decrease in the yield of the phosphor that occurs in these steps can be avoided, a significant reduction in the manufacturing cost of the phosphor can be realized.

In addition, according to the present invention, it is possible to obtain a fine particulate phosphor with a particle size ranging from 1 pm to several tens of pm, and it is possible to obtain a phosphor "crystalline particle" having excellent powder fluidity.
Becomes Noh.

In the production of glass, a method is known in which a melt of a glass raw material mixture is brought into contact with an aqueous medium and cooled to obtain glass in the form of particles. However, the glass particles obtained in this case are amorphous particles and not crystalline particles as obtained by the method of the present invention.

Next, the present invention will be explained in detail.

The novel phosphor manufacturing method of the present invention can be applied to any type of phosphor that generates crystal particles when a melt of a raw material mixture is brought into contact with an aqueous medium and cooled. However, it is particularly preferable to use it for producing a phosphor containing a halogen as a matrix component. Examples of such phosphors containing halogen as a host component include fluorohalide phosphors such as divalent Ni\ropium-activated divalent metal fluorohalide phosphors; rare earth element-activated rare earth oxyhalide phosphors. Examples include oxyhalide-based phosphors such as phosphors, halophosphate-based phosphors, and haloborate-based phosphors.

Among them, fluorohalide-based phosphors and oxyhalide-based phosphors can be mentioned as particularly preferable phosphors to be produced by the production method of the present invention. Especially 1, BaFBr:Eu2 contained in the former
+, BaFcJ2: E u2+, BaFI
:Eu”, (Ba, 5r)FBr:Eu 24 and other divalent europium-activated divalent metal fluorohalide phosphors, and La0Br contained in the latter: Ce, La0
Br:Tb, La0Br:Tm, La0C1:Ce,
Rare element-activated island earth oxyhalide phosphors such as La0Cjl:Tb and La0C:Tm have high absorption efficiency for radiation such as X-rays, and when excited by radiation such as X-rays, Mg Visual area light emission (instantaneous light emission)
This indicates that it can be used as a phosphor for radiation-sensitizing screens used in medical radiography such as X-ray photography for the purpose of medical diagnosis, and industrial radiography for the purpose of non-destructive testing of materials. In addition, divalent europium-activated divalent metal fluorohalide phosphors and rare earth element-activated rare earth oxyhalide phosphors are stimulable phosphors, and are stimulable when exposed to radiation such as xi. When it is irradiated, it absorbs - part of the energy, and then when it is irradiated with electromagnetic waves in the wavelength range of 450 to 800 nm, it emits light in the near ultraviolet to IjI viewing range (I original emission).

In recent years, these phosphors have attracted much attention as phosphors that can be used in radiation image conversion methods that utilize the photostimulability of phosphors. That is, the divalent europium-activated divalent metal fluorohalide phosphor and the rare earth element-activated rare earth oxyhalide phosphor are suitable for use in radiation-image conversion panels ( It can be used for stimulable phosphor sheets).

The method for producing the phosphor of the present invention includes, for example, P2O5, B2O
3. To produce a composite oxide phosphor containing a large amount of glass former such as SiO Not applicable, because such amorphous particles generally have very low luminance. However, even if the phosphor contains a glass former as a component, the present invention does not apply to phosphors that produce crystal particles that emit high-intensity light when the melt is brought into contact with an aqueous medium and cooled. The manufacturing method is subject to application.

The method for producing the phosphor of the present invention can be carried out by the operations described below, taking as an example the production of the divalent europium-activated divalent metal fluorohalide phosphor.

First, as a phosphor raw material, 1) BaF2 (barium fluoride), 2) at least one barium halide selected from the group consisting of BaCJ12, BaBr2, and BaI2, 3) MgF2, MgCl21. MgB r2, Mg engineering 2
, CaF2. CaCl2, CaB r2, Ca12, S
rF2, Sr(, Q2.5rBr2SrI2, ZnF
2, Znl: JJ2, ZnBr2Z n I 2 ,'
Cd F 2, Cd Cnz, Cd Br
At least one divalent metal halide selected from the group consisting of CdI2 and CdI2, and 4) a trivalent europium compound (such as europium halogenide, europium fermentation, europium nitrate, europium sulfate, etc.) are used. In some cases, further /X ammonium chloride (NH4X'; where X' is F, C1,
Br or I) may be added as a franks.

Using the above raw materials, the compositional formula (1) = (B a
1-z, M''X) FX:yE
u (I) (where M2- is Mg, Ca, S
is at least one monovalent metal selected from the group consisting of r, Zn, and Cd, and X is CfL, Br, and I
and X is a number in the range of 0≦X≦0.6;
y is a numerical value in the range of 0<y≦0.2).

This mixture also contains a ``luminescent material'' as an additive.

For the purpose of enhancing luminescent properties such as instantaneous luminance and stimulated luminescence luminance, a small amount of an alkali metal halide such as sodium bromide, a metal oxide such as silicon dioxide, etc. may be added.

Next, this phosphor raw material mixture is melt-mixed.

The melting step is carried out, for example, by filling a heat-resistant container such as a platinum crucible with this phosphor raw material mixture and heating and melting the container while stirring in an electric furnace. The melting temperature is generally above the melting point of the phosphor raw material and 200°C below the melting point.
A range that does not exceed is appropriate. Therefore, the melting temperature varies depending on the type of target phosphor, the composition of the phosphor raw material mixture, etc.; If it is a raw material mixture, it is preferable to melt it at a temperature of 1100 to 14500C. Although the melting time varies depending on the filling amount of the phosphor raw material mixture and the melting temperature, 0.5 to 5 hours is generally appropriate. As the melting atmosphere, it is preferable to use a weakly reducing atmosphere such as a nitrogen gas atmosphere containing a small amount of hydrogen gas or a carbon dioxide atmosphere containing -carbon oxide. In the melting process, trivalent europium is reduced to divalent europium.

After melting, the melt is brought into contact with an aqueous medium, such as by dropping it into an aqueous medium, to cool the melt. The aqueous medium used in this case means water alone or a medium in which a suitable acid, alkali, water-soluble salt, or water-miscible organic solvent is added to water. The melt dropped into the aqueous medium instantly solidifies, and the phosphor crystals are dispersed in the form of fine particles.

By melting and cooling the phosphor raw material mixture as described above, phosphor crystal particles dispersed in an aqueous medium are obtained.Next, the phosphor crystal particles are collected by means of a cancer sieving or the like, and after washing, Dry to obtain powder-like phosphor.

The powdered phosphor thus obtained usually has a particle size in the range of lILm - several 1101L.

It should be noted that it is also possible to further sinter the obtained phosphor for the purpose of enhancing luminous properties such as luminance.The sintering process in this case is as follows: This is done by filling a heat-resistant container such as a crucible or quartz crucible and heating and firing it in an electric furnace.The firing temperature is suitably 600 to 1000°C.The firing time depends on the amount of phosphor packed and the firing temperature. Generally, 0.5 to 12 hours is appropriate, although it varies depending on the situation.

In addition to the weakly reducing atmosphere mentioned above, the firing atmosphere is
A neutral atmosphere such as a nitrogen gas atmosphere or an argon gas atmosphere can also be used.

The phosphor produced by melting, cooling, or further baking as described above is finely particulate, has good fluidity, and has excellent homogeneity.
There is no need to grind the fired product or, in some cases, further classify it to reduce the average particle size, as in the past.
However, in practicing the present invention, various common operations in the production of phosphors such as pulverization, washing, drying and sieving may be carried out as desired, and the present invention excludes the addition of these steps. It's not something you do.

The phosphor manufactured by basically has the composition formula (): % formula % () (where M2+ is at least one divalent metal selected from the group consisting of Mg, Ca, Sr, Zn, and Cd. , X is at least one kind of /\logen selected from the group consisting of C1, Br, and I; and
The present invention is a divalent europium-activated divalent metal fluorohalide phosphor represented by O≦X≦0.6 (where y is a numerical value in the range o<y≦0.2).

In the above, the method for producing a divalent europium-activated divalent metal fluorohalide phosphor was described as an example of the method for producing the phosphor of the present invention, but the material to be produced by the method for producing the phosphor of the present invention is not limited to the above-mentioned phosphors, but can also be used for the production of other types of phosphors, and even when used for the production of these other types of phosphors, powder Fine particle phosphor crystals with excellent fluidity can be easily produced.

By manufacturing the phosphor as described above, the present invention can simplify the manufacturing process and significantly reduce the manufacturing cost of the phosphor compared to the conventional method of manufacturing the phosphor. This is to realize the following.

Also, according to the invention, by cooling the reaction melt of the phosphor raw material by contacting it with an aqueous medium.

It can be cooled efficiently. Further, the obtained phosphor crystals are usually in the form of fine particles with a particle size in the range of Igm to several 10 μm, and have excellent powder fluidity.

. Next, examples of the present invention will be described, but these examples are not intended to limit the present invention.

Group Example 1] A phosphor raw material mixture was prepared by mixing 175.34 g of barium fluoride (BaF2), 297.1 g of barium bromide (BaBrz), and 0.783 g of europium bromide (EuBr3). This phosphor raw material mixture was filled into a platinum crucible, which was then placed in a high-temperature electric furnace and melted while stirring. Melting was carried out in a carbon dioxide atmosphere containing -carbon oxide at a temperature of 1300'O for 1 hour.

This melt was then dropped into water. The fine particle dispersion produced in water was collected by filtration, washed with methanol, and vacuum dried at a temperature of 150°C.

When a part of the obtained particles was analyzed by X-ray diffraction, a BaFBr crystal pattern was confirmed, and it was also confirmed that the particles exhibited high-intensity instantaneous and stimulated luminescence. That is, the obtained particles are BaFBr:0
．． 001 Eu” phosphor crystal particles.

Next, the dried phosphor particles were filled into an alumina crucible, which was then placed in a high-temperature electric furnace and fired. Firing was performed at a temperature of 800° C. for 1 hour in a nitrogen gas atmosphere. After the firing was completed, the fired product was taken out of the furnace and cooled. The fired phosphor exhibited instantaneous and stimulated luminescence with higher brightness than the unfired phosphor. In addition, when the particle size of the obtained phosphor was measured, it was found to be 2 to 50 g.
It was distributed within the range of In addition, this powdered phosphor is
It showed very good fluidity.

Patent applicant Fuji Photo Film Co., Ltd. Agent j
r Physician Yasuo Yanagawa procedural amendment January 1980! 3rd 1, Indication of the case 1982 Patent Application No. 23549 2 Title of the invention Method for manufacturing phosphor 3 Person making the amendment Relationship to the case Patent applicant 4, detailed description of 1 invention in the attorney's specification We will correct the "Description" column as follows.

Ki 12 Jigetsu 1 - - Old Yufuku 1 - (1) Page 8, line 2 Melt → Melt (2) Page 6, line 9 Melt →
Melting (3) Page 8, line 17 Melting →
Melting (4) Page 8, line 3 Melting →
Melting (5) Page 11, line 10 Melting
→ Melting (B) Page 12, line 6 Melting
→ Melting tool top

Claims (1)

[Claims] 1. Production of a phosphor characterized by melting a phosphor material mixture and then cooling the melt by bringing it into contact with an aqueous medium to obtain phosphor crystals and particles. Law. 2. The method for producing a phosphor according to claim 1, wherein the phosphor is a phosphor containing halogen as a host component. 3. The method for producing a phosphor according to claim 2, wherein the phosphor is a fluorohalide phosphor. 4. The above-mentioned fluorohalide-based phosphor is a divalent europium-activated divalent metal fluorohalide phosphor. A method for producing a phosphor according to claim 3, wherein 5. The method for producing a phosphor according to claim 2, wherein the phosphor is an oxyhalide phosphor. 6. The method for producing a phosphor according to claim 5, wherein the oxyhalide-based phosphor is a rare earth element-activated rodent oxyhalide phosphor. 7. After melting a phosphor raw material mixture, the melt is brought into contact with an aqueous medium and cooled to obtain phosphor crystal particles. 1. The phosphor crystal particles are then fired. Law. 8. The method for producing a phosphor according to claim 7, wherein the phosphor containing halogen as a matrix component. 9. The method for producing a phosphor according to claim Bq4, wherein the phosphor is a fluorohalide phosphor. 10. The method for producing a phosphor according to claim 9, wherein the fluorohalide-based phosphor is a divalent europium-activated divalent metal fluorohalide phosphor. 11. A method for producing an It light material according to claim 1, wherein the phosphor is an oxyhalide phosphor. It is a rare earth element activated rare earth oxyhalide phosphor!
11. The method for producing a phosphor according to claim 11, wherein the phosphor has a 11r characteristic.