JPS6328952B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a phosphor and a method for manufacturing the same. More specifically, the present invention relates to an alkaline earth metal halide phosphor activated with divalent europium and a method for producing the same. As a type of alkaline earth metal halide phosphor activated with divalent europium, a divalent europium activated alkaline earth metal fluoride halide phosphor (M〓FX: Eu ²⁺ , where M〓
At least one alkaline earth metal selected from the group consisting of Ba, Sr and Ca, where X is a halogen other than fluorine, is well known. For example, as disclosed in Japanese Patent Publication No. 51-28591, this phosphor exhibits near-ultraviolet light emission (instantaneous light emission) with an emission maximum around 390 nm when excited by radiation such as X-rays, electron beams, and ultraviolet rays. , especially X
It is known to be useful as a phosphor for radiation intensifying screens used in radiography and the like. Furthermore, in recent years, the above-mentioned divalent europium-activated alkaline earth metal fluoride halide phosphor has been developed.
It has been found that after irradiation with radiation such as X-rays, electron beams, and ultraviolet rays, when excited with electromagnetic waves in the visible to infrared region, the phosphor exhibits near-ultraviolet light emission, that is, the phosphor exhibits stimulated luminescence. . For these reasons, this phosphor is used for radiation image conversion panels used in radiation image conversion methods that utilize the photostimulability of phosphors, as disclosed in, for example, Japanese Patent Application Laid-open No. 12143/1983. It is attracting a lot of attention as a phosphor. As mentioned above, the divalent europium-activated alkaline earth metal fluoride halide phosphor has been known as a type of divalent europium-activated alkaline earth metal halide phosphor, but the present invention The present invention provides a divalent europium-activated alkaline earth metal halide phosphor different from this divalent europium-activated alkaline earth metal fluorohalide phosphor and a method for producing the same. That is, an object of the present invention is to provide a novel divalent europium-activated alkaline earth metal halide phosphor and a method for producing the same. The present inventors have conducted various studies to achieve the above object. As a result, two or more compounds selected from the alkaline earth metal halide group consisting of chlorides, bromides, and iodides of Ba, Sr, and Ca (base raw material) and a europium compound (activator raw material) were mixed in appropriate proportions. Mix with
500-1300 in a mildly reducing atmosphere.
It was discovered that a phosphor exhibiting instantaneous luminescence and stimulated luminescence can be obtained when fired at a temperature in the range of °C, leading to the present invention. That is, the phosphor of the present invention has a compositional formula (): M〓X ₂・aM〓X′ ₂ :xEu ²⁺ () (where M〓 is at least one kind selected from the group consisting of Ba, Sr, and Ca). is an alkaline earth metal; X and X' are at least one halogen selected from the group consisting of Cl, Br, and X≠X'; and a is 0.1≦a≦
10.0, and x is a numerical value in the range 0<x≦0.2). Furthermore, the method for producing the divalent europium-activated alkaline earth metal halide phosphor of the present invention is based on the stoichiometric composition formula (): M〓X ₂・aM〓X′ ₂ :xEu () (where M 〓 is at least one kind of alkaline earth metal selected from the group consisting of Ba, Sr, and Ca; X and X′ are at least one kind of halogen selected from the group consisting of Cl, Br, and X≠X '; and a is 0.1≦a≦
10.0 and x is a value in the range 0<x≦0.2) After preparing the phosphor raw material mixture to have a relative ratio corresponding to It is characterized by being fired at a temperature in the range of 1300°C to 1300°C. The divalent europium-activated alkaline earth metal halide phosphor of the present invention represented by the compositional formula () is irradiated with radiation such as X-rays, ultraviolet rays, and electron beams, and then excited with electromagnetic waves in the wavelength range of 450 to 1000 nm. It exhibits stimulated luminescence in the near-ultraviolet to blue region. Furthermore, when the divalent europium-activated alkaline earth metal halide phosphor of the present invention represented by the composition formula () is irradiated with radiation such as ) is shown. Next, the present invention will be explained in detail. The divalent europium-activated alkaline earth metal halide phosphor of the present invention can be produced, for example, by the production method described below. First, as phosphor raw materials, (1) BaCl ₂ , SrCl ₂ , CaCl ₂ , BaBr ₂ , SrBr ₂ ,
At least two alkaline earth metal halides selected from the group consisting of CaBr ₂ , BaI ₂ , SrI ₂ and CaI ₂ ; (2) from the group consisting of compounds of europium such as halides, oxides, nitrates and sulfates; At least one selected europium compound is prepared. Here, as the phosphor raw material in (1) above, two or more alkaline earth metal halides containing at least different halogens are used. Optionally, further ammonium halide (NH ₄ X″; where X″ is Cl, Br or)
etc. may be used as a flux. When manufacturing a phosphor, the above alkaline earth metal halide (1) and the europium compound (2) are used to form the stoichiometric composition formula (): M〓X ₂・aM〓X′ ₂ :xEu () (where M〓 is at least one kind of alkaline earth metal selected from the group consisting of Ba, Sr, and Ca; X and X' are at least one kind of halogen selected from the group consisting of Cl, Br, and and X≠X′; and a is 0.1≦a≦
10.0, and x is a numerical value in the range 0<x≦0.2. In the method for producing the phosphor of the present invention, from the viewpoint of stimulated luminance and instantaneous luminance, the a value representing the ratio of M〓X ₂ and M〓X' ₂ in the composition formula () is 0.3.
It is preferable that the a value is in the range of ≦a≦3.3, and the more preferable range of a value is 0.5≦a≦2.0. Similarly, from the viewpoint of stimulated luminescence luminance and instantaneous luminescence luminance, the x value representing the activation amount of europium in compositional formula () is preferably in the range of 10 ^-5 ≦x≦10 ^-2 . The phosphor raw material mixture may be prepared by (i) simply mixing the phosphor raw materials in (1) and (2) above, or (ii) first, the phosphor raw materials in (1) above may be prepared. After mixing the raw materials and heating this mixture at a temperature of 100℃ or more for several hours,
This may be carried out by mixing the phosphor raw material in (2) above with the obtained heat-treated product, or (iii) first, the phosphor raw material in (1) above is mixed in a solution state. , this solution is heated (preferably 50 to 200
°C) by reduced pressure drying, vacuum drying, spray drying, etc., and then the above-mentioned
This may be carried out by mixing the phosphor raw materials in (2). As a modification of the method (ii) above, there is a method in which the phosphor raw materials of (1) and (2) above are mixed and the resulting mixture is subjected to the heat treatment as described above, and a modification of the method (iii) above is available. Alternatively, a method may be used in which the phosphor raw materials in (1) and (2) above are mixed in a solution state and this solution is dried. In any of the above methods (i), (ii), and (iii), mixing can be done using various mixers, V-type blenders,
Conventional mixers such as ball mills and rod mills are used. Next, the phosphor raw material mixture obtained as described above is filled into a heat-resistant container such as a quartz boat, an alumina crucible, or a quartz crucible, and fired in an electric furnace. The firing temperature is suitably in the range of 500 to 1300°C, preferably in the range of 700 to 1000°C. Although the firing time varies depending on the filling amount of the phosphor raw material mixture and the firing temperature, 0.5 to 6 hours is generally appropriate. As the firing atmosphere, a weakly reducing atmosphere such as a nitrogen gas atmosphere containing a small amount of hydrogen gas or a carbon dioxide atmosphere containing carbon monoxide is used. Generally, a trivalent europium compound is used as the raw material for the phosphor in (2) above, but in this case, during the firing process, the trivalent europium becomes divalent due to the weakly reducing atmosphere mentioned above. Returned to europium. By the above baking, the powdered phosphor of the present invention is obtained. Note that the obtained powdered phosphor may be further subjected to various general operations in the production of phosphors, such as washing, drying, and sieving, as necessary. The divalent europium-activated alkaline earth metal halide phosphor manufactured by the manufacturing method described above has a composition formula (): M〓X ₂・aM〓X′ ₂ :xEu ²⁺ () (However, M〓 is at least one kind of alkaline earth metal selected from the group consisting of Ba, Sr, and Ca; X and X' are at least one kind of halogen selected from the group consisting of Cl, Br, and X≠ X′; and a is 0.1≦a≦
It is a numerical value in the range of 10.0, and x is a numerical value in the range of 0<x≦0.2). FIG. 1 shows a divalent europium-activated barium chloride bromide phosphor (BaCl ₂ .BaBr ₂ :
Eu ²⁺ ) X-ray diffraction pattern [a] of barium chloride (BaCl ₂ ), barium bromide (BaBr ₂ ), and known divalent europium-activated barium fluoride bromide phosphor (BaFBr: Eu ²⁺ ). It is shown in comparison with the line diffraction patterns [b, c and d, respectively]. From FIG. 1, BaCl ₂・BaBr ₂ :Eu ²⁺ of the present invention
It is clear that the crystal structure of the phosphor is completely different from that of BaCl ₂ and BaBr ₂ , which are the raw materials for the phosphor. It is also clear that the crystal structure of the phosphor of the present invention is different from that of the known BaFBr:Eu ²⁺ phosphor. Note that these X-ray diffraction patterns were all measured using Cu and _Kα1 . It has been found that such a difference in crystal structure also applies to other divalent europium-activated alkaline earth metal halide phosphors of the present invention. When the divalent europium-activated alkaline earth metal halide phosphor of the present invention is irradiated with radiation such as X-rays, ultraviolet rays, and electron beams, and then excited with electromagnetic waves in the visible to infrared region of 450 to 1000 nm, it produces a near-ultraviolet to blue region. shows stimulated luminescence (peak wavelength of emission: around 405 nm). FIGS. 2 and ₃ illustrate the stimulated excitation spectrum and stimulated emission spectrum of the divalent europium-activated alkaline earth metal halide compound phosphor of the present invention, respectively.
These are the stimulated excitation spectrum and stimulated emission spectrum of BaBr ₂ :Eu ²⁺ phosphor. From Figure 2, BaCl ₂・BaBr ₂ :Eu ²⁺ phosphor is
It is clear that when excited with electromagnetic waves in the wavelength range of 450 to 1000 nm after radiation irradiation, it exhibits stimulated luminescence, and particularly when excited with electromagnetic waves in the wavelength range of 500 to 850 nm, it exhibits high-intensity stimulated luminescence. Also, from Figure 3,
It can be seen that the BaCl ₂ .BaBr ₂ :Eu ²⁺ phosphor exhibits stimulated luminescence in the near ultraviolet to blue region, and the peak of its stimulated luminescence spectrum is approximately 405 nm. Therefore,
When this phosphor is excited with electromagnetic waves in the wavelength range of 500 to 850 nm, it is easy to separate the stimulated emission and excitation light, and the stimulated emission has high brightness. The stimulated excitation spectrum and stimulated emission spectrum of the divalent europium-activated alkaline earth metal halide phosphor of the present invention have been explained above using the case of the BaCl ₂・BaBr ₂ :Eu ²⁺ phosphor as an example. , The stimulated excitation spectrum and stimulated emission spectrum of other phosphors of the present invention are as described above.
It has been confirmed that the stimulated excitation spectrum and stimulated emission spectrum of BaCl ₂ ·BaBr ₂ :Eu ²⁺ phosphor are almost the same. Further, the divalent europium-activated alkaline earth metal halide phosphor of the present invention can be used for X-rays, ultraviolet rays,
When irradiated with radiation such as an electron beam, it emits light (instantaneous light emission) in the near-ultraviolet to blue region. FIG. 4 illustrates the instantaneous emission spectrum and its excitation spectrum in the case of ultraviolet excitation of the divalent europium-activated alkaline earth metal halide phosphor of the present invention. , 4, 5 and 6 respectively. 1: Emission spectrum of BaCl ₂ · BaBr ₂ : Eu ²⁺ phosphor 2: Emission spectrum of BaCl ₂ · BaI ₂ : Eu ²⁺ phosphor 3: BaBr ₂ · BaI ₂ : Eu Emission spectrum of ²⁺ phosphor 4: BaCl ₂・BaBr ₂ :Eu ²⁺ Excitation spectrum of phosphor 5: BaCl ₂・BaI ₂ :Eu ²⁺ Excitation spectrum of phosphor 6: BaBr ₂・BaI ₂ :Eu ²⁺ This is the excitation spectrum of the phosphor. From FIG. 4, it can be seen that the divalent europium-activated alkaline earth metal halide phosphor of the present invention emits instantaneous light in the near-ultraviolet to blue region under ultraviolet excitation, and the peak wavelength of its emission spectrum is slightly affected by the phosphor. Although it is said that it is different,
It can be seen that it is around 405 nm. In addition, FIG. 5 shows the instantaneous emission spectrum (curve 1) and its excitation spectrum (curve 2) in the case of ultraviolet excitation of BaFBr:Eu ²⁺ phosphor, which is an example of the conventional MFX:Eu ²⁺ phosphor. It is. As is clear from the comparison between FIG. 4 and FIG. 5, the emission spectrum and excitation spectrum of the phosphor of the present invention are entirely the same as the emission spectrum and excitation spectrum of the M〓FX:Eu ²⁺ phosphor. shifted to longer wavelengths. Above, the instantaneous emission spectrum and its excitation spectrum in the case of ultraviolet excitation of the divalent europium-activated alkaline earth metal halide phosphor of the present invention have been explained using three types of phosphors as examples. It has been confirmed that the emission spectra and excitation spectra of other phosphors are almost the same as those of the above three types of phosphors. Also,
It has also been confirmed that the instantaneous emission spectrum of the phosphor of the present invention when excited by X-rays and electron beams is almost the same as the instantaneous emission spectrum when excited by ultraviolet rays shown in FIG. Furthermore, Figures 3 and 4
As is clear from the comparison with curve 1 in the figure, the stimulated emission spectrum and the instantaneous emission spectrum of the divalent europium-activated alkaline earth metal halide of the present invention are almost the same. Figure 6 shows the a value and stimulated emission intensity of BaCl ₂ /aBaBr ₂ :Eu ²⁺ phosphor [stimulated emission intensity when irradiated with 80KVp X-rays and then excited with He-Ne laser light (632.8nm). FIG. As is clear from Figure 6, the a value is 0.1
BaCl ₂ of the present invention in the range of ≦a≦10.0
aBaBr ₂ : Among Eu ²⁺ phosphors, the a value is 0.3≦a
A phosphor having an a value in the range of ≦3.3 exhibits stimulated luminescence with higher brightness, and a phosphor having an a value in the range of 0.5≦a≦2.0 exhibits stimulated luminescence with even higher brightness. Incidentally, the relationship between the a value and the instantaneous luminescence intensity for the BaCl ₂ ·aBaBr ₂ :Eu ²⁺ phosphor also has the same tendency as in FIG. 6. Also, BaCl ₂・aBaBr ₂ :Eu ²⁺
It has been confirmed that for the phosphors of the present invention other than the phosphors, the relationships between the a value and the stimulated luminescence intensity and instantaneous luminescence intensity tend to be similar to that shown in FIG. 6. Due to the luminescent properties explained above, the phosphor of the present invention is suitable for use 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. It is also very useful as a phosphor for image conversion panels or as a phosphor for radiation intensifying screens. Next, examples of the present invention will be described. However, these examples do not limit the present invention. Example 1 333.2 g of barium bromide (BaBr ₂ 2H ₂ O), 244.3 g of barium chloride (BaCl ₂ 2H ₂ O), and 0.783 g of europium bromide (EuBr ₃ ) were added to distilled water (H ₂ O).
The mixture was added to 800 ml and mixed to form an aqueous solution. After drying this aqueous solution under reduced pressure at 60℃ for 3 hours,
Vacuum drying was performed at ℃ for 3 hours. Next, the obtained phosphor raw material mixture was filled into an alumina crucible, which was then placed in a high-temperature electric furnace and fired. Firing was performed at a temperature of 900° C. for 1.5 hours in a carbon dioxide atmosphere containing carbon monoxide. After the firing was completed, the fired product was taken out of the furnace and cooled. In this way, a powdered divalent europium-activated barium chloride bromide phosphor (BaCl ₂ ·BaBr ₂ :0.001Eu ²⁺ ) was obtained. Example ₂ In Example ₁ , powdered Divalent europium activated barium chloride iodide phosphor (BaCl ₂ / BaI ₂ : 0.001Eu ²⁺ )
I got it. Example 3 In Example 1, powdered diamide was prepared by performing the same procedure as in Example 1 except that 427.2 g of barium iodide (BaI ₂ 2H ₂ O) was used instead of barium chloride. Europium-activated barium bromide iodide phosphor (BaBr ₂ / BaI ₂ : 0.001Eu ²⁺ )
I got it. Next, the emission spectrum and the excitation spectrum when each of the phosphors obtained in Examples 1 to 3 was excited with ultraviolet rays were measured. The obtained results are shown in the fourth
As shown in the figure. As mentioned above, in FIG. 4, curves _{1 to} ⁶ respectively represent
Emission spectrum 2: BaCl ₂ / BaI ₂ : 0.001Eu ²⁺ phosphor (Example (2)
Emission spectrum 3: BaBr ₂ / BaI ₂ : 0.001Eu ²⁺ phosphor (Example 3)
Emission spectrum 4: BaCl ₂ / BaBr ₂ : 0.001Eu ²⁺ phosphor (Example (1)
Excitation spectrum 5: BaCl ₂・BaI ₂ : 0.001Eu ²⁺ phosphor (Example (2)
Excitation spectrum 6: BaBr ₂ · BaI ₂ : 0.001Eu ²⁺ phosphor (Example 3)
The excitation spectrum of Furthermore, the luminance of instantaneous light emission when each of the phosphors obtained in Examples 1 to 3 was excited with X-rays was measured.
The results were compared with the instantaneous luminance of conventional BaFBr:0.001Eu ²⁺ phosphor under the same excitation.
Shown in the table.

[Table] Furthermore, the tube voltage was applied to the phosphor obtained in Example 1.
The stimulated emission spectrum when irradiated with 80KVp X-rays and then excited with He-Ne laser light (wavelength 632.8nm), and the peak wavelength of the stimulated emission (approx.
The photostimulation excitation spectrum at 405 nm) was measured. The results obtained are shown in FIGS. 3 and 2. Further, after each of the phosphors obtained in Examples 1 to 3 was irradiated with X-rays at a tube voltage of 80 KVp, the brightness of stimulated luminescence when excited with 780 nm light was measured. The results are shown in Table 2 in comparison with the luminance of stimulated luminescence measured under the same conditions for a conventional BaFBr:0.001Eu ²⁺ phosphor.

【table】 [Brief explanation of the drawing]

FIG. 1 is an example of the divalent europium-activated alkaline earth metal halide phosphor of the present invention.
BaCl ₂・BaBr ₂ :0.001Eu ²⁺ X-ray diffraction pattern [a] of phosphor, and BaCl ₂ , BaBr ₂ and known
FIG. 3 shows the X-ray diffraction patterns of BaFBr:0.001Eu ²⁺ phosphor [b, c and d, respectively]. Figures 2 and 3 respectively show the stimulated excitation spectrum and stimulated emission of a BaCl ₂ /BaBr ₂ :0.001Eu ²⁺ phosphor, which is an example of the divalent europium-activated alkaline earth metal halide phosphor of the present invention. It is a spectrum. FIG. 4 shows a BaCl ₂ .BaBr ₂ :0.001Eu ²⁺ phosphor, which is a specific example of the divalent europium-activated alkaline earth metal halide phosphor of the present invention.
BaCl ₂・BaI ₂ :0.001Eu ²⁺ phosphor and BaBr ₂・
The instantaneous emission spectra of the BaI ₂ :0.001Eu ²⁺ phosphor under ultraviolet excitation (curves 1, 2 and 3, respectively) and their excitation spectra (curves 4, 5 and 6, respectively). Figure 5 shows the known
These are the instantaneous emission spectrum (curve 1) and its excitation spectrum (curve 2) of BaFBr:0.001Eu ²⁺ phosphor under ultraviolet excitation. Figure 6 shows
It is a graph showing the relationship between the a value and the stimulated emission intensity in BaCl ₂ ·aBaBr ₂ :0.001Eu ²⁺ phosphor.

Claims (1)

[Claims] 1 Composition formula (): M〓X ₂・aM〓X′ ₂ :xEu ²⁺ () (where M〓 is at least one kind of alkaline earth selected from the group consisting of Ba, Sr, and Ca) X and X' are at least one kind of halogen selected from the group consisting of Cl, Br, and X≠X'; and a is 0.1≦a≦
10.0, x is a numerical value in the range 0<x≦0.2) A divalent europium activated alkaline earth metal halide phosphor. 2. The phosphor according to claim 1, wherein a in the compositional formula () is a numerical value in the range of 0.3≦a≦3.3. 3. The phosphor according to claim 2, wherein a in the compositional formula () is a numerical value in the range of 0.5≦a≦2.0. 4. The phosphor according to claim 1, wherein X and X' in the compositional formula () are each Cl or Br. 5. The phosphor according to claim 1, wherein M in the compositional formula () is Ba. 6 x in the composition formula () is 10 ^-5 ≦x≦10 ^-2
The phosphor according to claim 1, wherein the phosphor has a numerical value in the range of . 7 Stoichiometric compositional formula (): M〓X ₂・aM〓X′ ₂ :xEu () (where M〓 is at least one alkaline earth metal selected from the group consisting of Ba, Sr, and Ca. Yes; X and X' are at least one kind of halogen selected from the group consisting of Cl, Br, and X≠X'; and a is 0.1≦a≦
10.0 and x is a value in the range 0<x≦0.2) After preparing the phosphor raw material mixture to have a relative ratio corresponding to Composition formula () characterized by firing at a temperature in the range of 1300℃ to 1300℃: M〓X ₂・aM〓X′ ₂ :xEu ²⁺ () (However, M〓, (the definition is the same as above) A method for producing a divalent europium-activated alkaline earth metal halide phosphor. 8. The method for producing a phosphor according to claim 7, wherein a in the compositional formula () is a numerical value in the range of 0.3≦a≦3.3. 9. The method for producing a phosphor according to claim 8, wherein a in the compositional formula () is a numerical value in the range of 0.5≦a≦2.0. 10. The method for producing a phosphor according to claim 7, wherein X and X' in the compositional formula () are each Cl or Br. 11. The method for producing a phosphor according to claim 7, wherein M in the compositional formula () is Ba. 12 x in the composition formula () is 10 ^-5 ≦x≦
8. The method for producing a phosphor according to claim 7, wherein the phosphor has a numerical value in the range of 10 ^-2 . 13 Firing the phosphor raw material mixture at 700 to 1000℃
8. A method for producing a phosphor according to claim 7, characterized in that the method is carried out at a temperature in the range of .