JPS6225189A - Fluorescent substance and production thereof - Google Patents

Abstract

PURPOSE:To obtain a novel fluorescent substance showing excellent stimulation emission characteristics, by calcining a mixture of an alkaline metallic halide compound and a bismuth compound. CONSTITUTION:(A) One or more alkaline metallic halides selected from RbCl, CsCl, RbBr, CsBr, RbI and CsI is blended with one or more selected from bismuth compounds such as balide, oxide, nitrate, sulfate, etc., by a ball mill. The mixture is packed into a heat-resistant container, preferably calcined at 600-800 deg.C for 0.5-6hr, to give the aimed fluorescent substance shown by the composition formula M<1>X:xBi (M<1> is Rb or Cs; X is Cl, Br or I; x is in 0<x<=0.2).

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 bismuth-activated alkali metal halide phosphors and methods for producing the same.

[Technical Background of the Invention and Prior Art] Conventionally, as a method of obtaining a radiation image as an image, a combination of a radiographic film having an emulsion layer made of a silver salt photosensitive material and an intensifying screen is used. , a so-called radiographic method is used. As one of the methods to replace the above-mentioned conventional radiography method, for example,
A radiation image conversion method using a stimulable phosphor as described in Japanese Patent No. 12145 is known. In this method, radiation transmitted through the subject or radiation emitted from the subject is absorbed into a stimulable phosphor, and then the phosphor is exposed to electromagnetic waves (excitation light) such as visible light or infrared rays in a time-series manner. By exciting the phosphor, the radiation energy stored in the phosphor is emitted as fluorescence (stimulated luminescence), this fluorescence is read photoelectrically to obtain an electrical signal, and this electrical signal is converted into an image. .

The radiation image conversion method has the advantage that it is possible to obtain an X-ray image with a rich amount of information with a much lower exposure dose than when conventional radiography is used. Therefore, this radiation image conversion method has a very high utility value especially in direct medical radiography such as X-ray photography for the purpose of medical diagnosis.

As a stimulable phosphor used in the above radiation image conversion method, JP-A-55-12145 discloses a rare earth element-activated alkaline earth metal fluoride halide phosphor represented by the following composition formula: .

(Bat-x, M”x) FX: yA (However, M2
° is at least one of Mg, Ca, S r, Zn, and Cd, X is at least one of 0, Br, and I, A is Eu, Tb, Ce, Tm, Dy, Pr
, Ho.

(at least one of Nd, Yb, and Er, and X is 0≦X≦o, and s and y are 0≦y≦0.2) This phosphor absorbs radiation such as X-rays After that, when it is irradiated with electromagnetic waves in the visible light to infrared region, it emits light in the near-ultraviolet region (stimulated luminescence).

As mentioned above, the above rare earth element-activated alkaline earth metal halide phosphors have been known as phosphors used in radiation image conversion methods that utilize stimulable phosphors, but they exhibit photostimulability. Not much is known about the phosphor itself other than this rare earth element-activated alkaline earth metal halide phosphor.

Note that, like the phosphor of the present invention, thallium or sodium-activated cesium iodide phosphor (CsI:Tl
, CsI:Na) is known, and this phosphor emits light (instantaneous light emission) when irradiated with radiation such as X-rays, electron beams, and ultraviolet rays.

[Summary of the Invention] An object of the present invention is to provide a novel stimulable phosphor that can be used in the radiation image conversion method described above, and a method for producing the same.

As a result of various studies, the present inventors have discovered that the following novel bismuth-activated alkali metal halide phosphor exhibits remarkable stimulated luminescence properties, leading to the present invention.

That is, the phosphor of the present invention has the composition formula (1)2M1X:
xBi (I) (where Ml is at least one alkali metal selected from the group consisting of Rb and Cs; X is CM, B
and X is a numerical value in the range of 0<x≦0.2).

In addition, the method for producing the bismuth-activated alkali metal halide phosphor of the present invention has a stoichiometric ratio of M1X:xBi (I) (however,
(The definitions of M', shall be.

The bismuth-activated alkali metal halide phosphor of the present invention represented by the compositional formula (I) has x! i, When excited with electromagnetic waves in the wavelength range of 450 to 900 nm after being irradiated with radiation such as ultraviolet rays or electron beams, it exhibits stimulated luminescence in the near ultraviolet to blue band, especially when Ml is Cs in the composition formula (I). The phosphor exhibits high-brightness stimulated luminescence, and also has a composition formula (
The bismuth-activated alkali metal halide phosphor of the present invention represented by I) emits instantaneous light in the near-ultraviolet to blue region when excited by irradiation with radiation such as X-rays, ultraviolet rays, and electron beams.

[Configuration of the Invention] Bismuth-activated alkali metal halide of the present invention
The □ substance phosphor can be manufactured, for example, by the manufacturing method described below.

First, as phosphor raw materials: 1) RhCM, CsCfL, RbBr, CsBr, Rb
At least one alkali metal halide selected from the group consisting of I and CsI; 2) At least one compound selected from the group consisting of bismuth compounds such as halides, oxides, nitrates, and sulfates. In some cases, ammonium halide (NH, X', where x' is Cl, Br, or H) may be used as a flux.

When producing a phosphor, the above alkali metal halide in l) and the bismuth compound in 2) are used to stoichiometrically form the composition formula (I): M'X: x B i
(I) (However, the definitions of Ml, X, and X are the same as above.) Weigh and mix to obtain a relative ratio corresponding to

Prepare a mixture of phosphor raw materials.

In the method for producing a phosphor of the present invention, Ml representing an alkali metal in compositional formula (I) is preferably Cs, mainly from the viewpoint of stimulated luminescence brightness. Further, the X value representing the activation amount of bismuth is preferably in the range of 5×10-'≦X≦10''2.

The phosphor raw material mixture may be prepared by: i) simply mixing the phosphor raw materials of 1) and 2) above; or;

ii) After mixing the above phosphor raw materials 1) and 2) in the state of solution, this solution is heated (preferably 50 to 2
It may be carried out by drying under reduced pressure, vacuum drying, spray drying, etc. at 00° C.) and then mixing the phosphor raw materials.

In both methods i) and ii) above, a conventional mixer such as a mixer, a V-type blender, a ball mill, or a rod mill is used for mixing.

Next, the phosphor raw material mixture obtained as described above 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 at a firing temperature of 50°C.
A range of 0 to tooo°C is appropriate, preferably 600°C.
It is in the range of ~800°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 nitrogen gas atmosphere containing a small amount of hydrogen gas or a weakly reducing atmosphere such as a carbon dioxide atmosphere containing -carbon oxide; an inert gas atmosphere such as nitrogen gas or argon gas; and air. Utilizes the acidic atmosphere of

The phosphor of the present invention in powder form is obtained by the above baking.

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 bismuth-activated alkali metal halide phosphor produced by the production method described above has one set of Yiwu (I): M1X:XBi (I) (however, M
l 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 is O<x≦0.2. (a range of numerical values).

After the bismuth-activated alkali metal halide phosphor of the present invention is irradiated with radiation such as X-rays, ultraviolet rays, and electron beams,
When excited with electromagnetic waves in the visible to infrared region of 450 to 900 nm, it exhibits stimulated luminescence in the near ultraviolet to blue region.

Figure 1 illustrates the photostimulated excitation spectrum of the bismuth-activated alkali metal halide phosphor of the present invention; in Figure 1, curves 1.2 and 3 are CsC
1:Bi phosphor, CsBr:Bi phosphor and CsI
: Stimulated excitation spectrum of Bi phosphor.

From FIG. 1, it can be seen that the phosphor of the present invention has a 450 to 9
It can be seen that stimulated luminescence is exhibited when excited with electromagnetic waves in the wavelength region of 00 nm. Furthermore, from FIG. 1, the positions of the maximum peaks of the photostimulation excitation spectrum of the phosphor of the present invention are as follows:
(Curve 2) and (Curve 3), the latter is on the longer wavelength side, and in particular, it can be seen that phosphors in which X is I are efficiently excited by infrared rays such as semiconductor laser light.

FIG. 2 illustrates the stimulated emission spectra of the bismuth-activated alkali metal halide phosphor of the present invention. In FIG. 2, curves 1.2 and 3 represent the above CsC1:Bi phosphor and CsBr: Bi phosphor and C
sI: Stimulated emission spectrum of Bi phosphor.

As is clear from FIG. 2, the phosphor of the present invention exhibits stimulated luminescence in the near ultraviolet to blue region, and the peak of its stimulated luminescence spectrum is in the wavelength region of about 350 to 450 nm. Therefore, the phosphor of the present invention was irradiated with radiation for 500 to 850 nm.
In the case of excitation with electromagnetic waves in the wavelength range of m, it is easy to separate the stimulated luminescence and the excitation light, and the stimulated luminescence has high brightness. Moreover, from FIG. 2, the position of the maximum peak of the stimulated emission spectrum of the phosphor of the present invention is the same as the maximum peak position of the stimulated excitation spectrum described above.
It can be seen that the X of sX is 11 m in C (curve 1), Br (curve & 12), and I (curve 3), and the latter is on the longer wavelength side.

Above, CsG9. The stimulated excitation spectrum and stimulated emission spectrum of the bismuth-activated alkali metal halide phosphor of the present invention have been explained by taking the cases of the :Bi phosphor, the CsBr:BE phosphor, and the CsI :Bi phosphor as examples. It has been confirmed that the stimulated excitation spectrum and stimulated emission spectrum of other phosphors are similar to those described above.

Note that the bismuth-activated alkali metal halide phosphor of the present invention emits light (instantaneous light emission) in the near-ultraviolet to blue region even when excited by irradiation with radiation such as X-rays, ultraviolet rays, and electron beams. The spectrum (instantaneous emission spectrum) is almost the same as the stimulated emission spectrum.

Based on 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. As a phosphor for radiation image conversion panels used in radiation image conversion methods using exhaustible phosphors, and for intensifying screens used in radiography for medical diagnosis and non-destructive testing of materials. Particularly useful for the body.

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

[Example 1] 186.4 g of cesium chloride (CsC,Q) and 0.266 g of bismuth fluoride (BiFs) were thoroughly mixed using a ball mill.

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 in air at a temperature of 600° C. for 2 hours. After the firing was completed, the fired product was taken out of the furnace and cooled.

In this way, a powdered bismuth-activated cesium chloride phosphor (CsCu:0.OOI B i) was obtained.

[Example 2] Example 1 except that 212.8 g of cesium bromide (CsBr) was used instead of cesium chloride in Example 1.
By performing an operation similar to the method described above, a powdered bismuth-activated cesium bromide phosphor (CsB r : 0.0
01 B i) was obtained.

[Example 3] Powdered bismuth-activated iodide was prepared by performing the same procedure as in Example 1 except that 259.8 g of cesium iodide (CsI) was used instead of cesium chloride. Cesium phosphor (CsI:0.OOI B
i) was obtained.

Next, the tube voltage of 8 was applied to each of the phosphors obtained in Examples 1 to 3.
After irradiation with 0 KVp X-rays, the stimulated emission spectrum when excited with He-Ne laser light (wavelength: 632.8 nm) and the stimulated excitation spectrum at the peak wavelength of the stimulated emission were measured. The results obtained are shown in FIGS. 2 and 1.

In fig.

Curve 1: CaO content: 0.001 Stimulated emission spectrum curve 2 of B i phosphor (Example 1): Cs B r : 0.001 Stimulated emission spectrum curve 3 of B i phosphor (Example 2): This is a stimulated emission spectrum of Cs I: 0.001 B i phosphor (Example 3).

In FIG. 1, Curve 1: Cs Cl: 0.001 Photostimulation excitation spectrum of B i phosphor (Example 1) Curve 2: Cs B r : 0.001 Photostimulation of B i phosphor (Example 2) Excitation spectrum curve 3: Cs i : 0.001 This is the photostimulated excitation spectrum of the B i phosphor (Example 3).

In addition, the tube voltage of 8 was applied to each of the phosphors obtained in Examples 1 to 3.
After irradiating with 0 KVp X-rays, the stimulated luminescence brightness was measured when excited with He-Ne laser light. The measurement of this stimulated luminescence brightness is performed using a filter with a peak wavelength of 3 as the light-receiving filter.
90nm, half value fIa 60nm, peak wavelength transmittance 78
% bandpass filter (B-340). The results are shown in Table 1.

In addition, in Table 1, the stimulated luminescence luminance is Example 3t7)
Cs I: 0.001 B i The brightness of the phosphor is 10
It is shown as a relative value with zero.

Table 1 Relative stimulated luminance Example 1 500 Example 2 700 Example 3 100

[Brief explanation of drawings]

Figure 1 shows CsC1:0.001B, which is a specific example of the bismuth-activated alkali metal halide phosphor of the present invention.
Figure 3 shows the photostimulated excitation spectra (curves 1, 2 and 3, respectively) of the i phosphor, the Cs B r : 0.001 B i phosphor and the Cs I : 0.001 B i phosphor. FIG. 2 shows CsCfL: 0.001 B, which is a specific example of the bismuth-activated alkali metal halide phosphor of the present invention.
Figure 3 is the stimulated emission vector (curves l, 2 and 3, respectively) of the i phosphor, the Cs B r : 0.001 B i phosphor and the CS I : 0.001 B i phosphor.

Claims (7)

[Claims] 1. Compositional formula (I): M^1X:xBi (I) (where M^1 is at least one alkali metal selected from the group consisting of Rb and Cs; X is Cl,
A bismuth-activated alkali metal halide phosphor, which is at least one halogen selected from the group consisting of Br and I; and x is a numerical value in the range of 0<x≦0.2. 2. The phosphor according to claim 1, wherein M^1 in compositional formula (I) is Cs. 3. x in compositional formula (I) is 5×10^-^4≦x≦
The phosphor according to claim 1, wherein the phosphor has a numerical value in the range of 10^-^2. 4. Stoichiometric composition formula (I): M^1X:xBi (I) (where M^1 is at least one alkali metal selected from the group consisting of Rb and Cs: X is Cl,
At least one type of halogen selected from the group consisting of Bl and I; and x is a numerical value in the range of 0<x≦0.2. A method for producing a bismuth-activated alkali metal halide phosphor represented by the compositional formula (I), which comprises firing this mixture at a temperature in the range of 500 to 1000°C. 5. 5. The method for producing a phosphor according to claim 4, wherein M^1 in compositional formula (I) is Cs. 6. x in compositional formula (I) is 5×10^-^4≦x≦
5. The method for producing a phosphor according to claim 4, wherein the numerical value is in the range of 10^-^2. 7. Claim 4, characterized in that the phosphor raw material mixture is fired at a temperature in the range of 600 to 800°C.
Method for producing the phosphor described in Section 1.