JP2000345150A - Production of phosphor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a rare earth-activated alkaline earth metal fluorohalide-based phosphor having a high photostimulable light emission luminance and excellent in erasing and residual characteristics. SOLUTION: At least a part of a baking or a cooling step is carried out in a weakly oxidizing atmosphere and baking is then carried out while removing at least a part of a generated halogen gas at a temperature within the range of 500-950 deg.C to produce a rare earth-activated alkaline earth metal fluorohalide- based phosphor represented by the formula: (Ba1-a, MIIa)FX.bMI.cMIII.dA:xLn (MII denotes an alkaline earth metal; MI denotes an alkali metal; MIII denotes a compound of a trivalent metal; X denotes a halogen; Ln denotes a rare earth element; A denotes a metal oxide; 0<=a<=0.3; 0<=b<=2; 0<=c<=2; 0<=d<=0.5 and 0<x<=0.2) when mixing raw materials for the phosphor, preparing a raw material mixture for the phosphor, baking the raw material mixture for the phosphor and then cooling the resultant baked material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a phosphor, and more particularly, to a method for producing a rare earth-activated alkaline earth metal fluorohalide-based phosphor having high stimulated emission luminance.

[0002]

2. Description of the Related Art Conventionally, a divalent europium-activated barium fluoride halide (BaFX: Eu) which emits light in the near ultraviolet region or blue region (instantaneous emission) when excited by radiation such as X-rays, electron beams and ultraviolet rays. ²⁺ ; provided that X is a halogen other than fluorine), and is used as a phosphor for a radiographic intensifying screen used for X-ray photography and the like.

In recent years, X-rays,
It has been found that when irradiated with radiation such as an electron beam and ultraviolet light and then excited by electromagnetic waves (excitation light) in the visible to infrared region, it emits light (stimulated emission) in the near ultraviolet to blue region (hereinafter, this emission is referred to as “light emission”). Such characteristics are referred to as stimulable phosphors), and the phosphors are attracting much attention as phosphors for radiation image conversion panels used in radiation image recording / reproducing methods using stimulable phosphors.

In the above-described radiation image recording / reproducing method, radiation energy transmitted through a subject or emitted from a subject is absorbed by a stimulable phosphor of a radiation image conversion panel, and then the stimulable phosphor is irradiated with an electromagnetic wave. By sequentially exciting, the radiation energy stored in the stimulable phosphor is emitted as fluorescent light, the fluorescent light is read photoelectrically to obtain an electric signal, and then the electric signal is recorded on a recording material such as a photosensitive film. , As a visible image on a display device such as a CRT.

[0005] Such a phosphor is generally manufactured by the following method. First, a phosphor raw material mixture is prepared by uniformly mixing the phosphor raw materials in a dry state (dry method), or by uniformly mixing in a slurry state and then drying (wet method). Next, this phosphor raw material mixture is usually used as a host crystal (Ba, FX, etc.).
Sintering at a temperature close to the melting point of the above in an atmosphere such as a reducing property at about atmospheric pressure for several hours.

[0006] By sintering, the activator element diffuses into the host crystal at the same time as the host crystal of the phosphor grows, and an F ⁺ center serving as a source of a photostimulated center is also generated. As described above, baking is an important step that affects the light emission characteristics of the phosphor. Japanese Patent Application Laid-Open No. 55-12143 discloses a method of increasing the light emission luminance of the phosphor by further obtaining the obtained fired product. A method of refiring under similar conditions has been proposed. However,
From the viewpoint of downsizing of a laser used for reading and speeding up of reading, a phosphor having higher stimulated emission luminance has been required.

In the implementation of the radiation image conversion method,
The radiation image conversion panel itself is hardly deteriorated even by irradiation of radiation and electromagnetic waves, and thus is repeatedly used for a long period of time. Usually, the operation of reading out the radiation energy stored in the panel is performed by scanning the panel with laser light. Radiation energy is not exhausted only by scanning with the laser light. Therefore, in order to emit radiation energy remaining on the panel, for example, as disclosed in JP-A-56-11392, stimulated emission after reading is performed. It has been proposed to irradiate the panel with light in the excitation wavelength range of 1 to eliminate the remaining radiation energy.

However, there is a case where the residual energy is not sufficiently removed, or a phenomenon that a part of the residual energy is recovered with the lapse of time after erasure (lift of an afterimage). When the panel is used repeatedly, such erasing characteristics and afterimage characteristics adversely affect the image quality of an image. Further, if the erasing time is made longer, the time required from reading to erasing in the reading device becomes longer, which causes a reduction in the processing capability of the device and heat generation of the erasing device.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a rare-earth activated alkali having a high photostimulated emission luminance and excellent erasing and remaining characteristics. An object of the present invention is to provide a method for producing an earth metal fluorohalide-based phosphor.

[0010]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the above object can be achieved by controlling the firing conditions of the phosphor raw material mixture, and have completed the present invention. That is, in the method for producing a phosphor of the present invention, a phosphor raw material mixture is prepared by mixing phosphor raw materials, and then the phosphor raw material mixture is baked and cooled, whereby the phosphor is represented by the following basic composition formula (I). A method for producing a phosphor for producing a rare earth activated alkaline earth metal fluorohalide-based phosphor, wherein at least a part of the firing or cooling step is performed in a weakly oxidizing atmosphere, and the phosphor raw material The mixture or the fired product is fired at a temperature in the range of 500 to 950 ° C. while removing at least a part of the generated halogen gas. ^{_{(Ba 1-a, M II}} a) FX · bM I · cM III · dA: xLn ·· (I) wherein, M ^II is Sr, Ca, and at least one alkaline earth selected from the group consisting of Mg It represents a kind of metal, M ^I
Represents at least one alkali metal selected from the group consisting of Li, Na, K, Rb, and Cs, and M ^III represents a group consisting of Al, Ga, In, Tl, Sc, Y, La, Cd, and Lu. And at least one compound of a trivalent metal selected from the group (excluding Al ₂ O ₃ ). The compound of the alkali metal M ^I, a compound of the trivalent metal M ^III, represents a halide, oxide, sulfide, and the like carbonates. X represents at least one halogen selected from the group consisting of Cl, Br and I, and Ln represents Ce, Pr, S
m, Eu, Gd, Tb, Dy, Ho, Nd, Er, Tm
And at least one rare earth element selected from the group consisting of Yb. A represents at least one metal oxide selected from the group consisting of Al ₂ O ₃ , SiO ₂ and ZrO ₂ . A, b, c, d, and x are each 0 ≦
a ≦ 0.3, 0 ≦ b ≦ 2, 0 ≦ c ≦ 2, 0 ≦ d ≦ 0.5
And 0 <x ≦ 0.2.

According to the method for producing a phosphor of the present invention, the phosphor raw material is mixed to prepare a phosphor raw material mixture,
A primary firing step of primary firing at a temperature in the range of 50 ° C. and cooling; and a secondary firing step of secondary firing and cooling the fired product at a temperature in the range of 500 to 950 ° C. It is preferable that at least a part of the first firing step or the second firing step is performed in a weakly oxidizing atmosphere, and the second firing is performed while removing at least a part of the generated halogen gas.

Preferably, the calcination is performed by a calcination system having a removing means for removing at least a part of the halogen gas and a circulating means for circulating a weakly oxidizing atmosphere.
It is preferable that the amount of gas circulated in the atmosphere in the firing system is 50 liters / minute or less for 100 g of the phosphor raw material mixture. Further, the removing means comprises a low-temperature trap, and the temperature of the low-temperature trap is from -20 to 2
It is preferably in the range of 0 ° C. The firing temperature is
It is preferably in the range of 600 to 900C. The firing time is preferably in the range of 0.25 to 6 hours.

The production method of the present invention is particularly preferably used when the rare earth-activated alkaline earth metal fluorohalide-based phosphor is a europium-activated barium fluorohalide-based phosphor.

The weakly oxidizing atmosphere is placed, for example, in a furnace having a calcination partial volume of 2 to 500 liters per 1 kg of the phosphor raw material mixture, and a volume at room temperature per 1 liter of the calcination partial volume of the furnace. By introducing 0.1 to 200 ml of oxygen.

It is preferable that the amount of the introduced oxygen is 1 to 100 ml at room temperature with respect to 1 liter of the calcined partial volume. The firing time is preferably 0.5 to 6 hours. Here, the introduction of oxygen is air,
Alternatively, it is preferable to use nitrogen or oxygen diluted with an inert gas. The introduction of oxygen is preferably performed in an atmosphere in which the oxygen partial pressure in the furnace increases continuously or intermittently.

According to the present invention, there is provided a method for producing a stimulable phosphor, wherein at least a part of the firing and cooling step comprises weakly oxidizing,
By performing the treatment in a neutral or reducing atmosphere, the obtained phosphor can be erased and the afterimage characteristics can be improved. In the present invention, in addition to this, the halogen gas generated during firing is sequentially removed, and the amount of halogen contained in the phosphor crystal is appropriately adjusted, thereby realizing an improvement in the photostimulated luminance of the phosphor. Is what you do.

According to the production method of the present invention, when firing,
The halogen gas generated (vaporized) from the phosphor raw material mixture can be removed at an appropriate ratio, and the formation of vacancies generated in the phosphor crystal due to the deviation of halogen can be promoted. As a result, a large number of traps for improving the emission luminance can be present in the phosphor crystal,
It is possible to manufacture a phosphor with high light emission luminance.

Further, since the release of halogen from the phosphor raw material mixture can be promoted and the formation of vacancies in the phosphor crystal can be accelerated, the firing time can be shortened as compared with the prior art. In this respect, the production of the phosphor can be simplified.

Further, by incorporating the phosphor produced by the production method of the present invention into a radiation image conversion panel or the like and using the same in a radiation image recording / reproducing method, an image having excellent image quality can be constantly obtained. it can. Further, the processing capability and stability of the reading device can be improved without increasing the processing time of the panel.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for producing a phosphor of the present invention will be described.
The method will be described in detail sequentially according to the steps. Departure
The following 1) phosphor materials that can be used in the production method of Ming
To 5). 1) BaF_Two, BaCl_Two, BaBr_TwoAnd BaI_TwoFrom
At least one halogenated barium selected from the group consisting of
2) CaF_Two, CaCl_Two, CaBr_Two, CaI_Two, SrF
_Two, SrCl_Two, SrBr _Two, SrI_Two, MgF_Two, MgC
l_Two, MgBr_TwoAnd MgI_TwoSelected from the group consisting of
At least one alkaline earth metal halide; 3) CsCl, CsBr, CsI, NaCl, NaB
r, NaI, KCl, KBr, KI, RbCl, RbB
r, RbI, RbF, CsF, NaF, KF, LF, L
selected from the group consisting of iCl, LiBr and LiI
At least one alkali metal halide; 4) Al_TwoO_Three, SiO_TwoAnd ZrO_TwoSelected from the group consisting of
At least one metal oxide, and 5) rare earths such as halides, oxides, nitrates and sulfates
At least one member selected from the group consisting of
Compound. Optionally, additional ammonium halide (NH
_FourX 'wherein X' is F, Cl, Br or I
May be used as the flux.

In producing the phosphor, first, 1) barium halide, 2) alkaline earth metal halide, 3) alkali metal halide, 4) metal oxide, and 5) rare earth element compound Is used to prepare a mixture of phosphor raw materials by basis weight mixing so as to have a relative ratio corresponding to the composition formula (I).

The preparation of the phosphor raw material mixture may be carried out by: i) simply mixing the phosphor raw materials of the above 1) to 5); or ii) mixing the phosphor raw materials of the above 1) to 4). This mixture may be heated at a temperature of 100 ° C. or more for several hours and then mixed with the obtained heat-treated product by the phosphor material of the above 5), or the fluorescence of the above 1) to 5) may be used. The raw materials may be mixed, and the mixture may be heated at a temperature of 100 ° C. or higher for several hours. Iii) The above-mentioned phosphor raw materials 1) to 4) may be mixed in a suspension state, and the suspension may be mixed. Under heating (preferably 50-200)
C), drying may be performed by vacuum drying, vacuum drying, spray drying, or the like, and then the phosphor material of the above 5) may be mixed with the obtained dried product.

As a modification of the above method ii), a method may be used in which the phosphor raw materials of the above 1) to 5) are mixed and the mixture is subjected to the above heat treatment. As a modification of the above method iii), a method of mixing the phosphor raw materials of the above 1) to 5) in a suspension state and drying the suspension may be used. Alternatively, the phosphor raw materials of the above 2) to 4) may be added to and mixed with the mixture after the heat treatment or drying, or when firing is performed twice or more, the phosphor raw materials of the above 3) to 4) are You may add after primary baking.

In addition, Japanese Patent Application Laid-Open No. 7-2
No. 33369 and Japanese Patent Application Laid-Open No. Hei 10-195431 discloses a method for producing a tetrahedral rare earth activated alkaline earth metal fluorinated halide stimulable phosphor in which the particle shape and particle aspect ratio are controlled, In addition to the general manufacturing method of the present invention, the present invention also applies to a manufacturing method for controlling various conditions such as shearing force applied when mixing phosphor materials, addition of each phosphor material, and timing of mixing. Manufacturing methods can be applied.

In any of the above methods, known mixers such as various mixers, V-type blenders, ball mills and rod mills can be appropriately selected and used for mixing.

Next, the phosphor raw material mixture prepared as described above is charged into a heat-resistant container such as a quartz boat, an alumina crucible, a quartz crucible, a silicon carbide container, and the like, and placed in a furnace core for firing. For the firing, for example, a firing system shown in FIG. 1 is used. In this firing system, at least a part of the halogen gas generated from the phosphor mixture is removed.

FIG. 1 is a schematic view showing an example of a firing system including a firing furnace 10, a removing means 11, and a flow control device 12. In FIG. 1, as the firing furnace 10, for example,
A tube furnace is used, and the adjusted phosphor material mixture S is introduced into the furnace. As the removing means 11, for example, a low-temperature trap (constant temperature bath) is used. As the flow control device 12, for example, a combination of a tube pump, a diaphragm pump P and a flow meter is used. The firing atmosphere is controlled at a constant flow rate by the flow rate control device 12 and circulates between the firing furnace 10 and the removing means 11. In addition,
An exhaust valve V, a suction means Va, and the like are appropriately incorporated in the firing system.

In this firing system, the phosphor raw material mixture S
The halogen gas vaporized from the furnace is sent from the firing furnace 10 together with the firing atmosphere to the removing means (low-temperature trap) 11 to be cooled. The cooled halogen gas condenses into a liquid or a solid and is separated from the firing atmosphere. The cooling temperature of the low-temperature trap is preferably in the range of −20 to 20 ° C., and particularly preferably in the range of −10 to 10 ° C. Further, the gas circulation rate in the weakly oxidizing atmosphere in the firing system is preferably 50 liters / minute or less, particularly preferably 20 liters / minute or less, per 100 g of the phosphor raw material mixture. However, the cooling temperature and the gas circulation amount are appropriately adjusted depending on the firing amount of the phosphor raw material mixture.

The atmosphere from which the halogen gas is separated and removed is:
It is returned to the firing furnace 10 again via the flow control device 12.
By circulating the firing atmosphere at an appropriate flow rate through the removing means in this way, the halogen gas in the firing atmosphere is constantly removed at a suitable ratio, and the halogen gas partial pressure in the firing atmosphere can be adjusted to be constant. it can. As a result, the obtained phosphor has a large number of traps stably present in its crystal, and exhibits high emission luminance.

The firing furnace used here preferably has a firing partial volume of 2 to 500 liters, more preferably 5 to 50 liters, per 1 kg of the phosphor raw material mixture. If the volume of the fired portion is less than 2 liters per 1 kg of the phosphor raw material mixture, the phosphor is densely packed in a narrow space, making uniform firing difficult. Is too weak to deteriorate the characteristics, and both are not preferred.

The firing temperature is suitably in the range of 500 to 950 ° C., preferably in the range of 600 to 800 ° C.
The firing time varies depending on the filling amount of the phosphor raw material mixture, the firing temperature, the temperature of taking out from the furnace, and the like, but generally 0.25 to 6 hours is appropriate, and more preferably 0.25 to 6 hours.
Preferably, it is 3 hours. In addition, when a trivalent europium compound is contained as a rare earth element of the phosphor raw material in the above 5), most of the trivalent europium is reduced to divalent europium in the firing step.

In the firing and cooling step, at least a part thereof is
It is necessary to perform the treatment in a weakly oxidizing atmosphere into which a small amount of oxygen has been introduced. The amount of oxygen introduced is preferably 0.1 to 200 milliliters (0.76 to 152 Torr in oxygen partial pressure) at room temperature with respect to 1 liter of the firing partial volume of the furnace, and more preferably 1 to 100 milliliters. .
By defining the amount of oxygen introduced per 1 kg of the baked partial volume and 1 liter of the baked partial volume per 1 kg of the raw material mixture to be fired, it is possible to introduce an amount of oxygen necessary for improving the erasability and the afterimage characteristics in the firing of the raw material mixture. it can. The amount of oxygen introduced per unit liter of the fired partial volume of the furnace is 0.
When the amount is less than 1 ml, the effect of improving the erasing and remaining characteristics becomes insufficient, and when the amount is more than 200 ml, the stimulable light emission luminance is remarkably reduced.

The method of introducing oxygen in the calcination step is optional, but a simple amount of oxygen may be introduced into the furnace under a neutral or weakly reducing atmosphere at atmospheric pressure, or oxygen may be contained. The gas may be introduced into the furnace while increasing the amount of oxygen in the furnace. Further, by replacing the gas in the furnace with a gas containing a predetermined amount of oxygen, the amount of oxygen (oxygen partial pressure) in the furnace can be introduced so as to increase stepwise or continuously.

Instead of oxygen, a gas containing oxygen, such as air, or oxygen diluted with an inert gas may be introduced. The amount of oxygen to be introduced can be adjusted to an optimum value within the above range by adjusting the amount of the phosphor raw material mixture, the firing time, and the like. When air is used instead of oxygen, the introduced amount is generally 0.5 to 1000 ml, preferably 5 to 1 liter of the baked partial volume of the furnace.
In the range of ~ 500 ml.

As described below, oxygen may be introduced into the furnace once to a state close to a vacuum, and then a predetermined amount of oxygen may be introduced. This method is preferable because the required amount of oxygen can be supplied accurately and under conditions that can minimize the influence of other gases. In this method, first, the phosphor raw material mixture is placed in an electric furnace that has reached a firing temperature, and then immediately evacuated for several minutes to remove air from the furnace core. At this time, it is desirable that the degree of vacuum be 0.1 Torr or less. Next, a predetermined amount of oxygen is supplied to fill to a desired pressure. The amount of oxygen introduced at this time is, as described above, 0.1 to 200 ml per 1 liter of the firing partial volume of the furnace, and the volume of this oxygen is measured at room temperature. After accurately introducing a predetermined amount of oxygen into the furnace, the furnace atmosphere gas is further charged to adjust the furnace pressure to about 760 Torr (1 atm), that is, near the atmospheric pressure.

When firing is performed twice or more, for example, after the primary firing of the phosphor raw material mixture, the fired product is taken out of the electric furnace and allowed to cool, and if necessary, mortar, ball mill, tube mill, centrifugal mill, or the like. Pulverize into a fine powder using an ordinary pulverizer. It is placed in an electric furnace and refired (secondary firing). In the refiring, the firing temperature is 500 to 95.
It is preferably in the range of 0 ° C., and the firing time is 0.25
Preferably, it is in the range of ~ 3 hours. In the present invention, it is particularly preferable to remove the liberated halogen by using the above-mentioned firing system in the secondary firing. In the cooling step after firing, by using a weakly oxidizing atmosphere,
It is possible to obtain the same effect of improving the erasing and afterimage characteristics as the introduction of oxygen during firing.

A powdery stimulable phosphor is obtained by the above calcination. The obtained phosphor may be subjected to various general operations in the production of the phosphor, such as washing, drying, and sieving, if necessary.

By the production method described above, a rare earth activated alkaline earth metal fluorohalide-based phosphor represented by the following basic composition formula (I) is obtained.

[0039] ^{_{(Ba 1-a, M II}} a) FX · bM I · cM III · dA: xLn ·· (I)

In the formula, M ^II represents at least one kind of alkaline earth metal selected from the group consisting of Sr, Ca, and Mg, and M ^I represents one selected from the group consisting of Li, Na, K, Rb, and Cs. M ^III represents Al, Ga, In, Tl, Sc, Y, L
represents a compound of at least one trivalent metal selected from the group consisting of a, Cd, and Lu (excluding Al ₂ O ₃ ). X represents at least one halogen selected from the group consisting of Cl, Br and I, and Ln represents Ce, Pr, S
m, Eu, Gd, Tb, Dy, Ho, Nd, Er, Tm
And at least one rare earth element selected from the group consisting of Yb. A represents at least one metal oxide selected from the group consisting of Al ₂ O ₃ , SiO ₂ and ZrO ₂ . A, b, c, d, and x are each 0 ≦
a ≦ 0.3, 0 ≦ b ≦ 2, 0 ≦ c ≦ 2, 0 ≦ d ≦ 0.5
And 0 <x ≦ 0.2.

The europium-activated barium fluorohalide-based phosphor according to the present invention has the above-mentioned compositional formula (I) as a basic composition.
Various additional components can be further added for the purpose of improving the luminescent characteristics of the phosphor such as stimulable luminescence luminance and stimulable afterglow characteristics.
Examples of such additional components include the following substances. Metal oxides as described in JP-A-55-160078;
No. 80, a tetrafluoroborate compound; a hexafluoro compound described in JP-A-59-47289; an alkali metal halide as described in Japanese Patent Application No. 57-184455. monster,
Halides of divalent metals and halides of trivalent metals; and as co-activators, see JP-A-56-1167.
Zirconium and scandium described in JP-A-77-77; boron described in JP-A-57-23673; arsenic and silicon described in JP-A-57-23673; Transition metals such as V, Cr, Mn, Fe, Co, and Ni described in JP-A-59-75200, and BeX " ₂ (where X" is F, Cl, Br
And at least one halogen selected from the group consisting of and I).

When the phosphor produced by the production method of the present invention contains these additional components, the additional components are added when the phosphor raw materials are weighed and mixed, or before firing.

[0043]

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

Example 1 1200 mL of an aqueous solution of BaBr ₂ (2.5 mol / L), 40 mL of an aqueous solution of EuBr ₃ (0.04 mol / L), and 1760 mL of water were mixed for 4000 m.
Into an L volume reactor. The reaction mother liquor (BaBr ₂ concentration: 1.0 mol / L) in this reactor was kept at 60 ° C., and a screw stirring blade having a diameter of 60 mm was stirred at 500 rpm.
and the reaction mother liquor was stirred. 150 mL of ammonium fluoride aqueous solution (10 mol / mL) and 150 m of water
And 300 mL of this mixed solution was poured into a reaction mother liquor kept warm under the above-mentioned stirring using a roller pump.
The mixture was injected at a liquid sending rate of mL / min to produce a precipitate. After completion of the injection, the temperature and the stirring were continued for 2 hours to ripen the precipitate. Next, the precipitate was separated by filtration and washed with 2 L of methanol. Next, the washed precipitate was taken out,
And dried under vacuum for 4 hours to obtain about 330 g of europium-activated barium fluorobromide crystals. Observation of the obtained crystals with a scanning electron microscope revealed that most of the crystals were tetrahedral crystals. Next, when the crystal was measured with a light diffraction type particle size distribution analyzer (LA-500, manufactured by Horiba Ltd.), it was confirmed that the average crystal size was 5.0 μm. Further, 0.1 g of Na is added to 100 g of the crystal.
Br, 0.5 g of SiO ₂ was added to the above crystals to
In order to prevent a change in particle shape due to sintering during firing and a change in particle size distribution due to fusion between particles, 1% by weight of ultrafine alumina powder is added, and the mixture is sufficiently stirred with a mixer to obtain a crystal surface. Ultrafine particles of alumina were uniformly adhered to the mixture to prepare a phosphor raw material mixture.

After 100 g of this phosphor material mixture was filled in a quartz boat, it was placed in a tube furnace (calcination partial volume: 1.3 liter) of the baking system shown in FIG. 1 and a small amount of oxygen (oxygen partial pressure 10 Torr) was added. The firing was performed at a temperature of 800 ° C. for 1.5 hours in a nitrogen gas atmosphere. During firing, the firing atmosphere was circulated at a gas circulation rate of 0.9 liter / min, and the cooling temperature of the low-temperature trap was 0 ° C.
Set to.

After the firing was completed, the fired product was taken out of the furnace and cooled. The fired material is pulverized to give a powdery stimulable phosphor, a europium-activated barium fluorobromide-based phosphor (BaFBr: 0.0023 N) represented by the following composition formula:
aBr. 0.0195 SiO ₂ : 0.001 Eu ²⁺ )
I got

[Examples 2 to 6] In Example 1, the gas circulation rate of the atmosphere in the firing system was changed to 2 liter / min, 5 liter / min, 10 liter / min, 15 liter / min and 20 liter / min, respectively. By carrying out the same operation as in Example 1 except that the flow rate was changed to 1 liter / minute, various powdery europium-activated barium fluorobromide-based phosphors (Ba
FBr: 0.0023 NaBr · 0.0195 Si
O ₂ : 0.001Eu ²⁺ ) was obtained.

Comparative Example 1 A powdery europium-activated fluorofluorobromide was obtained by performing the same operation as in Example 1 except that the atmosphere was not circulated in the firing system. Barium phosphor (BaFB)
r: 0.0023 NaBr.0.0195SiO ₂ :
0.001 Eu ²⁺ ).

Next, each of the phosphors obtained in Examples 1 to 6 and Comparative Example 1 was irradiated with X-rays having a tube voltage of 80 KVp, and was then excited with He-Ne laser light (wavelength 632.8 nm). The stimulable emission luminance at that time was measured. The results are shown in FIG.

FIG. 2 is a graph in which the relative emission luminance of the phosphor is plotted against the gas circulation amount in the atmosphere in the firing system.

As is apparent from FIG. 2, the europium-activated barium fluorobromide-based phosphor (Examples 1 to 6) produced by the production method of the present invention, that is, the weakly oxidizing firing atmosphere was used in the firing step. The phosphor obtained by circulating through a low-temperature trap is produced by a conventional production method (gas circulation amount 0 (l / m
in)) and exhibit a higher stimulated emission luminance than the phosphor (Comparative Example 1) produced by (in)). In addition, in the europium-activated barium fluorobromide-based phosphor (Examples 1 to 6) produced by the production method of the present invention, the residual luminescence after erasing and the residual luminescence over time also decreased.

Embodiments 7 to 10 In Embodiment 1, the cooling temperature of the low-temperature trap in the firing system was set to -2
Except that the temperature was set to 0 ° C., −10 ° C., 10 ° C., and 20 ° C., various powdery europium-activated barium fluorobromide-based phosphors (BaFBr) were obtained by performing the same operation as in the method of Example 1. : 0.0023 NaBr · 0.019
5 SiO ₂ : 0.001 Eu ²⁺ ).

Next, each of the phosphors obtained in Examples 7 to 10 was irradiated with X-rays having a tube voltage of 80 KVp.
The stimulated emission luminance when excited by Ne laser light (wavelength 632.8 nm) was measured. The results are shown in FIG.

FIG. 3 is a graph in which the relative emission luminance of the phosphor is plotted against the cooling temperature of the low-temperature trap in the firing system.

As is apparent from FIG. 3, europium-activated barium fluorobromide-based phosphor (Examples 1 and 7 to 10) produced by the production method of the present invention, that is,
The phosphor obtained by circulating a weakly oxidizing firing atmosphere through a low-temperature trap in the firing step has a high brightness, particularly when the cooling temperature of the low-temperature trap is in the range of −20 ° C. to 20 ° C. It is clear that it shows exhausted light.

From the above results, it can be said that the stimulable phosphor obtained by the production method of the present invention is excellent in both the initial light emission and the erasability, and thus is suitable for applications where reproduction characteristics are important.

[0057]

According to the method for producing a phosphor of the present invention having the above-described structure, a rare earth activated alkaline earth metal fluorohalide-based phosphor having high stimulated emission luminance and excellent erasing and remaining characteristics is obtained. The effect is that the body can be manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a firing system used in a method for producing a phosphor of the present invention.

FIG. 2 is a graph showing a relationship between a gas circulation amount in a firing atmosphere and a relative emission luminance of a phosphor obtained.

FIG. 3 is a graph showing the relationship between the cooling temperature of the low-temperature trap and the relative emission luminance of the obtained phosphor.

[Explanation of symbols]

 Reference Signs List 10 Firing furnace 11 Removal means 12 Flow control device S Phosphor raw material mixture P Pump

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 4H001 XA03 XA08 XA09 XA11 XA12 XA13 XA14 XA17 XA19 XA20 XA21 XA31 XA35 XA37 XA38 XA39 XA40 XA48 XA49 XA53 XA55 XA56 XA57 XA71 XA81 YA59 YA59 YA59 YA59

Claims (13)

[Claims] 1. A phosphor material mixture is prepared by mixing phosphor materials, and then the phosphor material mixture is fired and cooled to obtain a rare earth activated alkaline earth metal represented by the following basic composition formula (I). A method for producing a phosphor for producing a fluorinated halide phosphor, wherein at least a part of the firing or cooling step is performed in a weakly oxidizing atmosphere, and the phosphor raw material mixture or the fired product is treated with 5% or less.
A method for producing a phosphor, comprising firing at a temperature in the range of 00 to 950 ° C. while removing at least a part of the generated halogen gas. ^{_{(Ba 1-a, M II}} a) FX · bM I · cM III · dA: xLn ·· (I) wherein, M ^II is Sr, Ca, and at least one alkaline earth selected from the group consisting of Mg It represents a kind of metal, M ^I
Represents at least one alkali metal selected from the group consisting of Li, Na, K, Rb, and Cs, and M ^III represents a group consisting of Al, Ga, In, Tl, Sc, Y, La, Cd, and Lu. And at least one compound of a trivalent metal selected from the group (excluding Al ₂ O ₃ ). X is C
Ln represents at least one halogen selected from the group consisting of l, Br and I, and Ln represents Ce, Pr, Sm, Eu, G
It represents at least one rare earth element selected from the group consisting of d, Tb, Dy, Ho, Nd, Er, Tm and Yb. A represents at least one metal oxide selected from the group consisting of Al ₂ O ₃ , SiO ₂ and ZrO ₂ . Also,
a, b, c, d, and x are each 0 ≦ a ≦ 0.
3, 0 ≦ b ≦ 2, 0 ≦ c ≦ 2, 0 ≦ d ≦ 0.5 and 0
Represents a numerical value in the range of <x ≦ 0.2. 2. A primary firing step of mixing a phosphor raw material to prepare a phosphor raw material mixture, and then performing primary firing and cooling at a temperature in the range of 500 to 950 ° C .; Secondary firing at a temperature in the range of 950 ° C., and cooling, wherein at least a part of the primary firing or the secondary firing is performed in a weakly oxidizing atmosphere; The method according to claim 1, wherein the step (a) is performed while removing at least a part of the generated halogen gas. 3. The fluorescence according to claim 1, wherein the firing is performed by a firing system having a removing unit for removing at least a part of the halogen gas and a circulating unit for circulating a weakly oxidizing atmosphere. How to make the body. 4. The method according to claim 3, wherein said removing means comprises a low-temperature trap, and a temperature of said low-temperature trap is in a range of −20 to 20 ° C. 5. The method for producing a phosphor according to claim 3, wherein the amount of gas circulated in the atmosphere in the firing system is not more than 50 L / min for 100 g of the phosphor raw material mixture. 6. The method according to claim 1, wherein the firing temperature is in a range of 600 to 900 ° C. 7. The method according to claim 1, wherein the calcination time is in the range of 0.25 to 6 hours. 8. The method according to claim 1, wherein the rare earth-activated alkaline earth metal fluorohalide-based phosphor is a europium-activated barium fluorohalide-based phosphor. 9. 2-5 weight parts / kg of phosphor raw material mixture
It is placed in a furnace having a calcined partial volume of 00 liters, and 0.1 to 200 milliliters of oxygen at room temperature is introduced into 1 liter of the calcined partial volume of the furnace to form a weakly oxidizing atmosphere. The method for producing a phosphor according to claim 1, wherein: 10. The calcination partial volume 1
The method for producing a phosphor according to claim 9, wherein the volume at room temperature is 1 to 100 milliliters per liter. 11. The method for manufacturing a phosphor according to claim 9, wherein the introduction of the oxygen is performed using air or oxygen diluted with nitrogen or an inert gas. 12. The method according to claim 9, wherein the firing is performed for 0.5 to 6 hours. 13. The method according to claim 10, wherein the introduction of oxygen is performed in an atmosphere in which the oxygen partial pressure in the furnace increases continuously or intermittently.