JPH0527674B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of the Invention] The present invention relates to a phosphor and a method for manufacturing the same. More specifically, the present invention relates to a composite halide phosphor activated by divalent europium and a method for producing the same. [Background of the Invention] Conventionally, divalent europium-activated alkaline earth metal fluoride halide phosphors (M〓FX: Eu ²⁺ , However, 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. This phosphor emits near-ultraviolet light (instantaneous light emission) when excited by radiation such as X-rays, and emits near-ultraviolet light (photostimulated light) when excited by electromagnetic waves in the visible to infrared region after being irradiated with radiation such as X-rays. luminescence). In addition, as a phosphor different from the above-mentioned divalent europium-activated alkaline earth metal fluoride halide phosphor, the present applicant has developed a novel divalent europium-activated alkaline earth metal halide phosphor represented by the following compositional formula. A patent application has already been filed for the body (Japanese Patent Application No. 193161-1981). 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 Cl , Br, and I, 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 applicant has proposed that the novel divalent europium-activated alkaline earth metal halide phosphor contain certain alkali metals. A patent application has already been filed for a divalent europium-activated composite halide phosphor represented by the following compositional formula containing a halide (Japanese Patent Application No. 22169/1982). Compositional ^formula _: M _〓 〓 is at least one kind of alkali metal selected from the group consisting of Rb and Cs;
X′ is at least one kind of halogen selected from the group consisting of Cl, Br, and I, and X≠X′; X″ is at least one kind selected from the group consisting of F, Cl, Br, and I. and a is a numerical value in the range of 0.1≦a≦10.0, b is a numerical value in the range of 0<b≦2.0, and x is a numerical value in the range of 0<x≦0.2). As stated in the above application specification, the new phosphor is a different type of phosphor having a different crystal structure from the M〓FX:Eu ²⁺ phosphor, based on its X-ray diffraction pattern. It has been found that
When exposed to radiation such as X-rays, ultraviolet rays, and electron beams,
It emits near-ultraviolet to blue light (instantaneous light emission) with an emission maximum around 405 nm. Furthermore, when these phosphors are irradiated with radiation such as X-rays, ultraviolet rays, or electron beams and then excited with electromagnetic waves in the wavelength range of 450 to 1000 nm, they emit light (stimulated luminescence) in the near-ultraviolet to blue region. Therefore, these phosphors are useful as phosphors for radiation intensifying screens used in X-ray photography, etc., and radiation image conversion panels used in radiation image conversion methods that utilize the photostimulability of phosphors. . [Summary of the Invention] The divalent europium-activated composite halide phosphor of the above Japanese Patent Application No. 59-22169 is the same as that of the above-mentioned Japanese Patent Application No. 58-22169.
No. 193161, the stimulated luminance of the divalent europium-activated alkaline earth metal halide phosphor is improved by containing a specific amount of rubidium halide and/or cesium halide. This patent application 1986-22169
The purpose is to improve the stimulated luminance of the divalent europium-activated composite halide phosphor of No. That is, the present invention is directed to the above-mentioned patent application, which has improved stimulated luminescence brightness when excited by electromagnetic waves in the wavelength range of 450 to 1000 nm after irradiation with radiation such as X-rays.
The object of the present invention is to provide a divalent europium-activated composite halide phosphor of No. 59-22169 and a method for producing the same. In order to achieve the above object, the inventors of the present invention have developed a phosphor containing cesium halide (i.e., M We conducted various studies on phosphor (=Cs). As a result, the inventors discovered that a phosphor obtained by coactivating the phosphor with a specific amount of a rare earth element exhibits high-intensity stimulated luminescence, leading to the present invention. That is, the phosphor of the present invention has a compositional formula (): BaX ₂ · aBaX' ₂ · bCsX'': xEu ²⁺ , yLn ³⁺ ... () (However, X and X' are both Cl, Br, and I. at least one kind of halogen selected from the group consisting of X≠X′; X″ is F, Cl,
At least one halogen selected from the group consisting of Br and I; Ln is Sc, Y, Ce, Pr,
At least one rare earth element selected from the group consisting of Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, and a is 0.1≦a≦10.0
b is a numerical value in the range of 0<b≦2.0, x is a numerical value in the range of 0<x≦0.2, and y is a numerical value in the range of 10 ^-6 ≦y≦1.8×10 ^-1 This is a divalent europium-activated composite halide phosphor co-activated with a rare earth element, which has a numerical value of . Note that a portion of the barium atoms in the divalent europium-activated composite halide phosphor of the present invention may be replaced with calcium or strontium, as long as there is no substantial change in the luminescent properties of the phosphor itself. In addition, the method for producing the phosphor of the present invention has a stoichiometric compositional formula (): BaX ₂・aBaX′ ₂・bCsX″: xEu, yLn ……() (However, X, X′, X″, Ln , a, b, x and y are the same as above) After adjusting the phosphor raw material mixture to have a relative ratio corresponding to It is characterized by firing at a temperature in the range of 1300℃. The present invention involves coactivating a cesium halide-doped phosphor with a specific amount of a rare earth element among the novel divalent europium-activated composite halide phosphors described in the above-mentioned Japanese Patent Application No. 59-22169. By doing so, it is possible to improve the stimulated luminescence brightness when the phosphor is irradiated with radiation such as X-rays and then excited with electromagnetic waves in the wavelength range of 450 to 1000 nm. [Structure of the Invention] The divalent europium-activated composite halide phosphor co-activated with a rare earth element of the present invention can be manufactured, for example, by the manufacturing method described below. First, as phosphor raw materials, (1) at least two barium halides selected from the group consisting of BaCl ₂ , BaBr ₂ and BaI ₂ , (2) at least one selected from the group consisting of CsF, CsCl, CsBr and CsI. cesium halide, and (3) Sc, Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, such as halides, oxides, nitrates, and sulfates.
(4) at least one compound selected from the group consisting of compounds of Ho, Er, Tm, Yb, and Lu; (4) at least one compound selected from the group consisting of europium compounds such as halides, oxides, sulfates, and sulfates; Prepare the compound. Here, as the phosphor raw material in (1) above, two or more barium halides containing at least different halogens are used. In some cases, ammonium halide (NH ₄ X; where X is Cl, Br or I) may also be used as a flux. When manufacturing a phosphor, the above (1) barium halide, (2) cesium halide, (3) rare earth compound, and (4) europium compound are used to stoichiometrically form the composition formula (). : BaX ₂・aBaX′ ₂・bCsX″: xEu, yLn …() (However, both X and X′ are at least one kind of halogen selected from the group consisting of Cl, Br, and I, and X≠ X′; X″ is F, Cl,
At least one halogen selected from the group consisting of Br and I; Ln is Sc, Y, Ce, Pr,
At least one rare earth element selected from the group consisting of Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, and a is 0.1≦a≦10.0
b is a numerical value in the range of 0<b≦2.0, x is a numerical value in the range of 0<x≦0.2, and y is a numerical value in the range of 10 ^-6 ≦y≦1.8×10 ^-1 A mixture of phosphor raw materials is prepared by weighing and mixing them so as to have a relative ratio corresponding to . In the method for producing the phosphor of the present invention, from the viewpoint of stimulated luminance, the y value representing the activation amount of the rare earth element in the composition formula () is in the range of 10 ^-5 ≦y≦1.6×10 ^-1 . preferable. Similarly, from the viewpoint of stimulated luminescence brightness, the a value representing the ratio of BaX ₂ and BaX′ ₂ in the composition formula () is preferably in the range of 0.3≦a≦3.3, and more preferably in the range of 0.5≦a≦2.0. and X and X' are preferably either Cl or Br, respectively. Further, the x value representing the activation amount of europium 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) to (4) above, or (ii) first, by mixing the phosphor raw materials in (1) to (4) above. After mixing the phosphor raw materials in (2) and heating this mixture at a temperature of 100°C or higher for several hours, the resulting heat-treated product is added to the above (3) and
It may be carried out by mixing the phosphor raw materials in (4), or (iii) first, the phosphor raw materials in (1) and (2) above are mixed in a solution state, and this solution is under heating (preferably
50 to 200°C) by vacuum drying, vacuum drying, spray drying, etc., and then the phosphor raw materials of (3) and (4) above are mixed with the obtained dried product. Good too. In addition, as a modification of method (ii) above, methods (1) to (4) above can be used.
A method of mixing the phosphor raw materials of (1) and (3) above and subjecting the resulting mixture to the above heat treatment, or a method of mixing the phosphor raw materials of (1) and (3) above, subjecting this mixture to the above heat treatment, and then applying the heat treatment to the resulting heat-treated product. The method of mixing the phosphor raw materials in (2) and (3) above may also be used. In addition, as a modification of method (iii) above, there is a method in which the phosphor raw materials in (1) to (4) above are mixed in a solution state and this solution is dried, or The method of mixing phosphor raw materials in a solution state, drying this solution, and then mixing the phosphor raw materials described in (2) and (3) above into the obtained dried product may be used. 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 400 to 1300°C, preferably in the range of 500 to 1000°C. From the viewpoint of luminance, etc., it is particularly preferable to perform the firing at a temperature lower than the melting point of the phosphor (approximately 875° 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. The firing atmosphere may be a neutral atmosphere such as a nitrogen gas atmosphere, an argon gas atmosphere, or a nitrogen gas atmosphere containing a small amount of hydrogen gas.
A weakly reducing atmosphere such as a carbon dioxide atmosphere containing carbon monoxide is used. Generally, a europium compound in which the valence of europium is trivalent is used as the phosphor raw material in (4) above, but in this case, the trivalent europium is reduced to divalent europium in the firing process. Note that a method may be used in which the phosphor raw material mixture is once fired under the above firing conditions, and then the fired product is left to cool, then pulverized, and then re-fired (secondary firing). Re-firing is carried out under the above neutral atmosphere or weakly reducing atmosphere at a firing temperature of 400-800℃ and a temperature of 0.5-12
It takes time. 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. By the manufacturing method described above, the divalent europium-activated composite halide phosphor co-activated with a rare earth element of the present invention represented by the following compositional formula () is manufactured. Compositional formula (): BaX ₂・aBaX′ ₂・bCsX″: xEu ²⁺ , yLn ³⁺ …() (However, the definitions of X, X′, X″, Ln, a, b, x and y are as described above. Note that the phosphor of the present invention manufactured according to the above manufacturing method is irradiated with radiation such as X-rays, ultraviolet rays, and electron beams, and then exposed to electromagnetic waves in the visible to infrared range of 450 to 1000 nm. When excited ^with
BaX ₂・aBaX′ ₂・bCsX″: Shows a stimulated emission spectrum and a stimulated excitation spectrum that are almost the same as Eu ²⁺ phosphor.Furthermore, the phosphor of the present invention is resistant to radiation such as X-rays, ultraviolet rays, and electron beams. When irradiated with , it exhibits fluorescence (instantaneous luminescence) in the near-ultraviolet to blue region, and the peak wavelength of its emission spectrum is also in the region approximately equivalent to the stimulated luminescence mentioned above.The phosphor of the present invention is particularly intended for medical diagnosis. Phosphors for radiation image conversion panels used in radiation image conversion methods using stimulable phosphors used in medical radiography such as X-ray photography and industrial radiography for the purpose of non-destructive testing of materials. It is also highly useful as a phosphor for radiation intensifying screens used in radiography for the purpose of medical diagnosis and non-destructive testing of materials. A comparative example will be described.
However, these examples do not limit the 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, 21.3 mg of cesium bromide (CsBr) and yttrium chloride ( _YCl3 .
After thoroughly mixing 64 mg of 7H ₂ O), it was filled into an alumina crucible, and the mixture was placed in a high-temperature electric furnace for firing. Firing was performed at a temperature of 850° 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, divalent europium-activated composite halide phosphors (BaCl ₂・BaBr ₂・0.1CsBr: 0.002Eu ²⁺ ,
0.0002Y ³⁺ ) was obtained. Example 2 A divalent europium-activated composite halide phosphor co-activated with yttrium was prepared by performing the same operation as in Example 1 except that the amount of yttrium chloride added was changed to 0.64 g. (BaCl ₂ / BaBr ₂ / 0.1CsBr: 0.002Eu ²⁺ ,
0.002Y ³⁺ ) was obtained. Example 3 A divalent europium-activated composite halide phosphor co-activated with yttrium was prepared by performing the same operation as in Example 1 except that the amount of yttrium chloride added was changed to 6.4 g. (BaCl ₂・BaBr ₂・0.1CsBr:
0.002Eu ²⁺ , 0.02Y ³⁺ ) were obtained. Example 4 A divalent europium-activated composite halide phosphor co-activated with yttrium ( BaCl ₂・BaBr ₂・0.1CsBr: 0.002Eu ²⁺ ,
0.1Y ³⁺ ) was obtained. Comparative Example 1 A divalent europium-activated composite halide phosphor (BaCl ₂ .
_BaBr2・0.1CsBr:0.002Eu2 ⁺ ) was obtained. Comparative Example 2 A divalent europium-activated composite halide phosphor co-activated with yttrium ( BaCl ₂・BaBr ₂・0.1CsBr: 0.002Eu ²⁺ ,
0.2Y ³⁺ ) was obtained. Next, each of the phosphors obtained in Examples 1 to 4 and Comparative Examples 1 and 2 was irradiated with X-rays at a tube voltage of 80 KVp, and then the stimulated luminescence brightness was measured when excited with semiconductor laser light (780 nm). did. The result is the first
They are summarized in the figure. Figure 1 shows BaCl ₂・BaBr ₂・0.1CsBr:
2 is a graph showing the relationship between yttrium content (y value) and stimulated luminance in 0.002Eu ²⁺ , yY ³⁺ phosphors. As is clear from FIG. 1, the BaCl ₂・
BaBr ₂・0.1CsBr: 0.002Eu ²⁺ , yY ³⁺ phosphor is
Stimulated luminance was improved when the y value was in the range of 10 ^-6 ≦y≦1.8×10 ^-1 . In particular, if the y value is 10 ^-5 ≦y
Phosphors in the range of ≦1.6×10 ^-1 exhibited high-intensity stimulated luminescence. Examples 5 to 14 Various rare earths were prepared in the same manner as in Example 1 except that 0.02 mol of each of the rare earth compounds shown in Table 1 below was used in place of yttrium chloride. Element (Ln)
divalent europium-activated composite halide phosphor co-activated with ( _BaCl2・_BaBr2・0.1CsBr:
Obtained 0.002Eu ²⁺ and 0.02Ln ³⁺ .

[Table] Next, each of the phosphors obtained in Examples 5 to 14 was irradiated with X-rays at a tube voltage of 80 KVp, and then the stimulated luminescence brightness when excited with semiconductor laser light (780 nm) was measured. The results are shown in Table 2. Note that Table 2 also shows the results of Comparative Example 1.

[Table] As is clear from Table 2, the divalent europium-activated composite halide phosphors of the present invention co-activated with rare earth elements (Examples 5 to 14) are It exhibited significantly higher luminance than the europium-activated composite halide phosphor (Comparative Example 1). Example 15 In Example 8, activation of divalent europium coactivated with gadolinium was carried out in the same manner as in Example 8 except that 16.8 g of cesium chloride (CsCl) was used instead of cesium bromide. Composite halide phosphor (BaCl ₂ , BaBr ₂ ,
0.1CsCl: 0.002Eu ²⁺ , 0.02Gd ³⁺ ) was obtained. Next, the tube voltage was applied to the phosphor obtained in Example 15.
After irradiating with 80 KVp X-rays, the stimulated luminescence brightness was measured when excited with semiconductor laser light (780 nm). The results are shown in Table 3. In addition, the third
The results of Comparative Example 1 are also listed in the table. Table 3 Relative luminance Example 15 130 Comparative example 1 100 As is clear from Table 3, the BaCl ₂ of the present invention
BaBr ₂・0.1CsCl: 0.002Eu ²⁺ , 0.02Gd ³⁺ phosphor is BaCl ₂・BaBr ₂・0.1CsBr for comparison:
It exhibited higher luminance than 0.002Eu ²⁺ phosphor.

[Brief explanation of the drawing]

FIG. 1 shows BaCl ₂・BaBr ₂・0.1CsBr, which is a specific example of the divalent europium-activated composite halide phosphor co-activated with a rare earth element of the present invention.
It is a graph showing the relationship between the y value and the stimulated luminance in 0.002Eu ²⁺ ,yY ³⁺ phosphors.

Claims (1)

[Claims] 1 Compositional formula (): BaX ₂・aBaX′ ₂・bCsX″: xEu ²⁺ , yLn ³⁺ ... () (However, X and X′ are both composed of Cl, Br, and I. at least one kind of halogen selected from the group, and X≠X';X'' is F,
At least one halogen selected from the group consisting of Cl, Br and I; Ln is Sc, Y, Ce,
Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm,
At least one rare earth element selected from the group consisting of Yb and Lu, and a is 0.1≦a≦
b is a numerical value in the range of 10.0, b is a numerical value in the range of 0<b≦2.0, x is a numerical value in the range of 0<x≦0.2, and y is a numerical value in the range of 10 ^-6 ≦y≦1.8×10 ^-1 A divalent europium-activated composite halide phosphor co-activated with a rare earth element expressed as (a numerical value in the range). 2 y in composition formula () is 10 ^-5 ≦y≦1.6×
The phosphor according to claim 1, which has a numerical value in the range of 10 ^-1 . 3. 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. 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 x in the compositional formula () is a numerical value in the range of 10 ^-5 ≦x≦10 ^-2 . 6 Stoichiometrically, the compositional formula (): BaX ₂・aBaX′ ₂・bCsX″: xEu, yLn … () (However, both X and X′ are at least one selected from the group consisting of Cl, Br, and I. It is a kind of halogen, and X≠X′; X″ is F, Cl,
At least one halogen selected from the group consisting of Br and I; Ln is Sc, Y, Ce, Pr,
At least one rare earth element selected from the group consisting of Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and Ln, and a is 0.1≦a≦10.0
b is a numerical value in the range of 0<b≦2.0, x is a numerical value in the range of 0<x≦0.2, and y is a numerical value in the range of 10 ^-6 ≦y≦1.8×10 ^-1 The phosphor raw material mixture is adjusted to have a relative ratio corresponding to Compositional formula (): BaX ₂・aBaX′ ₂・bCsX″: xEu ²⁺ , yLn ³⁺ …() (However, the definitions of X, X′, X″, Ln, a, b, x and y is the same as above) A method for producing a divalent europium-activated composite halide phosphor co-activated with a rare earth element. 7 y in composition formula () is 10 ^-5 ≦y≦1.6×
A method for producing a phosphor according to claim 6, wherein the phosphor has a numerical value in the range of 10 ^-1 . 8. The method for producing a phosphor according to claim 6, wherein a in the composition formula () is a numerical value in the range of 0.3≦a≦3.3. 9. The method for producing a phosphor according to claim 6, wherein X and X' in the compositional formula () are each Cl or Br. 10 x in composition formula () is 10 ^-5 ≦x≦10 ^-2
A method for producing a phosphor according to claim 6, wherein the phosphor has a numerical value in the range of . 11 Firing the phosphor raw material mixture at 500 to 1000℃
A method for producing a phosphor according to claim 6, which is carried out at a temperature in the range of .