JPS6286086A - Phosphor and preparation thereof - Google Patents

Abstract

PURPOSE:To obtain a phosphor suitable for use in radiation sensitized screens, by rotary drying of an aq. solution contg. a fluoride and halide of an alkaline earth metal and an Eu compd. under reduced pressure and calcining the dried mixture. CONSTITUTION:0.5mol of at least one alkaline earth metal fluoride (A) such as BaF2, SrF2 or CaF2, 0.5ml of at least one alkaline earth metal halide (B) such as BaCl2, SrB2 or CaI2, at least one Eu compd. (C) such as Eu halide, Eu oxide or Eu nitrate, and, if necessary, an ammonium halide (D) as a flux are weighed in such amounts as will provide an intended fluorescent compsn. They are mixed and are dissolved in 200-500ml of an aq. medium to prepare a soln. The soln. is dried in a rotary dryer under a reduced pressure of about 60-360mmHg, and is calcined to obtain a particulate divalent Eu-activated alkaline earth metal fluorohalide phosphor represented by the formula (wherein M is Ba, Sr or Ca; X is Cl, Br or I; and 0<x<=0.2) and having an average particle diameter of 2.0-50mum and a length/width/height ratio of 1/1-2/0.5-2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a divalent europium activated alkaline earth metal fluorohalide phosphor and a method for producing the same.

[Technical Background of the Invention] A divalent europium-activated alkaline earth metal fluoride halide phosphor (MI[FX:
Eu'', where Ml is at least one alkaline earth metal selected from the group consisting of Ba, Sr and Ca, and X is a halogen other than fluorine). This phosphor is For example, hour/minute IM+ 51-2859
As disclosed in Publication No. 1, when excited with radiation such as X-rays, electron beams, and ultraviolet rays, it exhibits near-ultraviolet light emission (sparkling light emission) with an emission maximum near 390 nm+.
Line lJ! It is useful as a phosphor for radiation-sensitizing screens used in shadows, etc.

Furthermore, in recent years, 5L divalent europium-activated alkaline earth metal fluoride halide phosphors have been
- When excited with electromagnetic waves in the visible to infrared region after irradiation with radiation such as ultraviolet light and ultraviolet light, near-ultraviolet light emission (i.e.,
It has been found that phosphorescence (photostimulated luminescence) is exhibited. For this reason, as disclosed in, for example, Japanese Unexamined Patent Publication No. 55-12145, this phosphor is used for radiation therapy that utilizes the photostimulability of the phosphor. It has attracted much attention as a phosphor for radiation image conversion panels used in the Q-image conversion method.

L phosphors are generally produced by a method that consists of mixing phosphor raw materials to prepare a mixture of raw materials (preparation step), and then firing this raw material mixture in a weakly reducing atmosphere (baking step 1). be able to.

Traditionally, raw material mixtures have been prepared by simply mixing the phosphor raw materials, such as alkaline earth metal fluorides, alkaline earth metal halides, and europium compounds, or by mixing the phosphor raw materials and then using i o o 'c. This is carried out by a method of heat treatment at a temperature of about 100 ml, or by a method of mixing and dissolving the phosphor raw material in a solvent such as water and then drying it.

The obtained IF phosphor raw material mixture is then fired at a temperature in the range of 400 to 1300'O in a weakly reducing atmosphere to produce the desired phosphor.

[Summary of the Invention] The present invention provides a bivalent europium-activated alkaline earth metal fluorohalide-based i6 light material having a specific particle shape and its! The purpose is to provide the A construction method.

The present invention also provides a divalent europium-activated alkaline earth metal fluoride halide phosphor for radiation intensifying screens and radiation image conversion panels that can improve image quality, and a method for producing the same. This is also the purpose.

The purpose of section L is to obtain the basic composition formula (I): MIIFX:xEu2° (I) (where Ml is at least an alkaline earth metal selected from the group consisting of Ba, Sr, and Ca; X is Cl
divalent europium-activated alkaline earth metal fluoride; at least one species of halogen selected from the group consisting of A halide-based phosphor whose particle shape is 1 to 2 in width and height with respect to length l.
After preparing a raw material mixture of a phosphor having the basic compositional formula CI) and a phosphor having a ratio in the range of 0.5 to 2, the raw material mixture is In a method for producing a ′-゛ photoreceptor, which comprises firing.

After dissolving the alkaline earth metal fluoride, alkaline earth metal halide and europium compound in an aqueous solvent,
By preparing a raw material mixture by rotary drying this solution under reduced pressure, the ratio of width and height to length 1 is in the range of 1 to 2 and 0.5 to 2, respectively. A method for producing a phosphor characterized by producing a phosphor having a substantially cubic particle shape;

In addition, in the present invention, the expression "cuboid" means that the vertices of the three sides do not necessarily form corners.

That is, the present invention provides a method for producing a divalent europium-activated alkaline earth metal fluorohalide phosphor by preparing a raw material mixture by rotating and drying an aqueous solution of the phosphor raw material under reduced pressure. This provides shaped phosphor particles.

According to the present invention, in the step of preparing a raw material mixture, a phosphor raw material consisting of an alkaline earth metal fluoride, an alkaline earth metal halide, and a europium compound (activator) is mixed and dissolved in an aqueous solvent such as water. The resulting solution is rotated using a rotary evaporator or the like, dried under reduced pressure, and then fired to prevent the original mixture from sintering during the firing process, to produce phosphor particles in the shape of a female parallelepiped. can do.

Furthermore, the present inventor has found that the particle size of the phosphor can be adjusted to a desired size by adjusting the amount of aqueous solvent used to dissolve the phosphor raw material and the degree of reduced pressure during drying. I found it.

L: Phosphor particles produced by conventional methods are irregular in shape and have uneven surfaces, so when used in radiation intensifying screens or radiation image conversion panels, fluorescence or excitation light is scattered on the surface. The phosphor particles of the present invention are approximately cubic and have a good shape, and are free from surface irregularities. Since this is significantly reduced by WJ, it is possible to prevent diffuse reflection on the particle surface and improve image quality.

[Structure of the Invention] The divalent europium-activated alkaline earth metal fluoride/halogenide phosphor of the present invention having a specific particle shape can be produced, for example, by the method described below.

First, as a phosphor raw material, L) BaF2. At least one alkaline earth metal fluoride selected from the group consisting of SrF2 and CaF2, 2) BaCl2, Srcl2, CaC2, BaBr2.5rBr2, CaBr2, BaI2,
At least one kind of alkaline earth total halogenide selected from the group consisting of SrI2 and CaI2, and 3) at least one kind selected from the group consisting of europium compounds such as halides, oxides, nitrates, and sulfates. compound.

Prepare. In some cases, in the production of a phosphor using ammonium halogenide (NHaX': Using the alkaline earth metal/\loginide of 2) and the europium compound of 3), the composition formula (II): MIIFX:xEu (II) (where Mll consists of Ba, Sr and Ca) at least one alkaline earth metal selected from the group consisting of; X is at least one halogen selected from the group consisting of Cl, Br, and Cl; ) and mix them in relative proportions.

Prepare a mixture of phosphor raw materials.

To prepare the phosphor raw material mixture, first, the phosphor raw materials listed in L) to 3) are added and mixed into an aqueous solvent containing water or a small amount of an acid, alkali, or an alcohol-based water-miscible organic solvent. shall be. The aqueous solvent comprises 1) an alkaline earth metal fluoride and 2) an alkaline earth diagonal halogenated article of 0.
It is generally used in a range of 200 to 500 mM for 5 moles (ie, a state that can produce 1 mole of phosphor). Further, for mixing, common mixers such as various mixers, V-type blenders, ball mills, loft mills, etc. are used.

Next, this solution is rotary dried under reduced pressure using a rotary dryer such as a rotary evaporator.

Vacuum drying is 400 to 700 mmHg higher than atmospheric pressure at the crotch.
It is carried out at low pressure, and if desired the solution is heated to 100'C! You can also do this while heating at a temperature below F (ha).

In this way: The prepared phosphor raw material mixture is filled into a heat-resistant container such as a quartz port, an alumina crucible, or a quartz crucible, and fired in an electric furnace.

The firing temperature is suitably in the range of 400-1300°C, preferably in the range of 500-1000°C. The firing time varies depending on the filling amount of the phosphor raw material mixture, the firing temperature, the temperature at which it is taken out from the furnace, etc., but is generally 0.5 to 6
The time is appropriate.

The firing atmosphere is a nitrogen gas atmosphere containing a small amount of hydrogen gas, or - = carbon monoxide containing carbon oxide,
Use a weakly reducing atmosphere, such as an atmosphere. Generally, a valence of europium or a trivalent europium compound is used as a raw material for the phosphor (listed in L), but in that case, the trivalent europium is converted into divalent europium by a weakly reducing atmosphere during the firing process. be done.

In order to prevent sintering of the phosphor during the firing process, it is desirable to set suitable firing conditions or to add gold 1-oxide such as silicon dioxide to the raw material mixture.

In addition, after firing the phosphor raw material mixture once under the firing conditions listed in L, the fired product is taken out of the electric furnace and allowed to cool, and if necessary, a conventional pulverizer such as a mortar, ball mill, tube mill, or centrifugal mill is used. The fired product may be ground into a fine powder, and then the fired product may be placed in an electric furnace for re-firing (secondary firing). The firing temperature during re-firing is suitably 400 to 800°C, and the firing time is suitably 0.5 to 12 hours. As the firing atmosphere for re-firing, in addition to a slightly reducing atmosphere, a neutral atmosphere such as a nitrogen gas atmosphere or an argon gas atmosphere can also be used.

The phosphor of the present invention in powder form is obtained by the firing described in .

Note that the obtained phosphor may be further subjected to various general operations in the production of phosphors, such as washing, drying, and sieving, if necessary.

According to the manufacturing method explained for 1 unit of salt, the basic composition formula (): % formula % () (where Mff is at least an alkaline earth metal selected from the group consisting of Ba, Sr, and Ca; is at least one halogen selected from the group consisting of C1, Br and I; and X is O<x≦0.
A divalent europium-activated alkaline earth metal fluorohalide phosphor of the present invention having a numerical value in the range of 2) is obtained.

The particle -f of this IIF light body has the shape of a Nu cube, and the ratio of its length (X), width (y) and height 2) is 1:
1-2: in the range of 0.5-2 (x:y:z).

Further, the particle size of the phosphor changes depending on the amount of water in the aqueous solvent and the degree of pressure reduction in the process of preparing the phosphor raw material mixture. In general, it has been found that the smaller the amount of aqueous solvent used to dissolve the phosphor raw material, and the greater the degree of depressurization (lower pressure), the more the distribution of phosphor particles shifts toward smaller particle diameters. ing. That is, by adjusting the concentration of the solution and the drying rate, the particle size of the phosphor can be suitably changed.

Therefore, the f average particle size of the phosphor obtained by the production method of the present invention with L distribution is 1. Although the conditions at AE level vary depending on the shade, it is usually in the range of 2.0 to 50 meters.

In addition, in producing the phosphor of the present invention, various additional components may be added in addition to the basic components listed in L for the purpose of improving the luminance of the phosphor and improving the afterglow characteristics.

Examples of such additive components include the following substances.

Metal oxides as described in JP-A No. 55-160078; Tetrafluoroboric acid compounds as described in JP-A No. 59-27980; JP-A-Sho 5
Hexafluoro compounds as described in Japanese Patent Application No. 9-47289; alkali metal halides, -valent metal halides and trivalent total dioptric halides as described in Japanese Patent Application No. 57-184455; In addition, as a coactivator, it is described in JP-A-56-116777.
zirconium and scandium; boron as described in JP-A-57-23673; arsenic and silicon as described in JP-A-57-23675; and JP-A-59-56480 Transition metals as listed in .

If the phosphor produced by the production method of the present invention contains additional components in addition to the basic components listed above, the additional components may be added at the time of mixing the phosphor raw materials or before firing. added.

Next, examples of the present invention will be described. However, these do not limit the present invention.

[Example 1] 87.7 g of barium fluoride (BaF2), barium bromide (
BaBr2) 148.6 g and europium bromide (E
uBr, ) 0.196g in distilled water (H2O) 400ml
and mixed to form an aqueous solution. This aqueous solution was heated to 500 mm below atmospheric pressure using a rotary evaporator.
Rotation was carried out at low Hg pressure and temperature of 90°C.

Next, the obtained phosphor raw material mixture was filled into an alumina crucible, which was then placed in a high-temperature double-air furnace and fired.

Calcination is carried out by - 9 days in an atmosphere of carbon dioxide containing carbon oxide.
The test was carried out at a temperature of 00°C for 1.5 hours. After the firing was completed, the fired product was taken out of the furnace and cooled. The obtained fired product is pulverized to form a powdered divalent europium activated fluorobromide/helium phosphor (B a FB r : 0.
001 E u"") was obtained.

[Example 2] Powdered divalent europium-activated barium fluoride bromide phosphor was prepared by performing the same procedure as in Example 1 except that the amount of distilled water was changed to 300 mM. Obtained.

[Example 3] By performing the same operation as in Example 1, except that the amount of distilled water in Example 1 was changed to 300 ml, and the pressure was set to 600 mm Hg lower than atmospheric pressure. A powdered divalent europium-activated barium fluoride bromide phosphor was obtained.

The grains of each phosphor obtained have a cubic shape, with vertical (
The ratios of X), width (y) and height Z) are all l:
It was in the range of 1=~2:0.5~2(x:y:Z).

Further, the particle distribution of each phosphor is shown in FIG.

FIG. 1 is a graph showing the particle-size distribution of divalent europium-activated barium fluoride bromide phosphor.

In FIG. 1, polygonal lines 1 to 3 correspond to phosphors manufactured under the following conditions, respectively.

Line 1: Water 400ml Pressure Atmospheric pressure -500mmHg (Example 1) Line 2: Water 300ml Pressure Atmospheric pressure -500mmHg (Example 2) Line 3: Water 300ml Pressure Atmospheric pressure -600mmHg (Example 3) Figure 1 As is clear from the graph shown in , the smaller the amount of water used to dissolve the phosphor raw material and the greater the degree of depressurization (lower pressure), the smaller the particle size distribution of the phosphor shifts. In other words, the average particle size became smaller.

[Brief explanation of drawings]

FIG. 1 is a graph showing the particle-size distribution of a divalent europium-activated barium fluoride bromide phosphor, which is an example of the phosphor of the present invention.

Claims (5)

[Claims] 1. Basic compositional formula (I): M^IIFX:xEu^2^+(I) (where M^II is at least one alkaline earth metal selected from the group consisting of Ba, Sr, and Ca:
X is at least one kind of halogen selected from the group consisting of Cl, Br and I; and x is 0<x≦0.
A divalent europium-activated alkaline earth metal fluorohalide-based phosphor having a numerical value in the range of 2),
A phosphor characterized in that its particle shape is approximately cubic, with width and height ratios ranging from 1 to 2 and from 0.5 to 2 to 1, respectively. 2. The phosphor according to claim 1, wherein the average particle diameter of the phosphor is in the range of 2.0 to 50 μm. 3. Basic compositional formula (I): M^IIFX:xEu^2^+ (I) (where M^II is at least one alkaline earth metal selected from the group consisting of Ba, Sr, and Ca;
X is at least one halogen selected from the group consisting of Cl, Br and I; and x is 0<x≦0.2
A method for producing a phosphor comprising preparing a raw material mixture of a divalent europium-activated alkaline earth metal fluorohalide phosphor having a value in the range of , and then firing this raw material mixture. After dissolving similar metal fluorides, alkaline earth metal halides and europium compounds in an aqueous solvent,
By preparing a raw material mixture by rotary drying this solution under reduced pressure, a substantially cubic shape having width and height ratios of 1 to 2 and 0.5 to 2, respectively, is formed by rotating and drying this solution under reduced pressure. A method for producing a phosphor, comprising producing a phosphor having a particle shape. 4. Water 200-500% for each 0.5 mol of the above alkaline earth metal fluoride and alkaline earth metal halide
3. The method for producing a phosphor according to claim 3, characterized in that the pressure during reduced pressure rotary drying is 400 to 700 mmHg lower than atmospheric pressure. 5. 4. The method for producing a phosphor according to claim 3, wherein the average particle diameter of the phosphor is in the range of 2.0 to 50 μm.