JPH0476090A - Stimulable phosphor - Google Patents

Abstract

PURPOSE:To obtain the title phosphor which is improved in the luminous intensi ty of stimulation and in resolution and can reduce radiation dose by calcining a specified raw material mixture in a neutral or reducing atmosphere. CONSTITUTION:A raw material mixture prepared so as to provide a relative ratio corresponding to formula I or II (wherein L is at least one trivalent metal selected from Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Al, Ga, In, and Tl; X is a halogen selected from F, Cl, and I; 10<-4x<0.5; 0<y<0.1; 0< z<0.1) is calcined in a neutral or reducing atmosphere at 500-1100 deg.C to give the title phosphor of formula III or IV. A paint containing this phosphor is applied to a polyethylene terephthalate film and dried, and a protective film is formed thereon to give an X-ray image transformation sheet.

Description

[Detailed Description of the Invention] [Summary] Regarding a photostimulable phosphor, the composition formula (
1) or (2), BaI-x Lx Br2: Eu” (
1) BaI-8LXBr2-2X2:Eu”
(2) (L is Sc, Y, La, Ce,
Pr, Nd, Pm, Sm.

GdXTb, Dy, tlo, ErXTm, Yb
, Lu, AI, Ga, In and Tl, and X represents F.
, CI and I, X represents 10-'< x < o, s, y represents O < y < 0.
1, z is a numerical value that does not satisfy the condition 0 < z < 0.1. ) It is composed of a phosphor represented by

[Industrial application field]

FIELD OF THE INVENTION This invention relates to photostimulable phosphors, their manufacture and uses.

In place of conventional medical X-ray photography (fluorescent screen film), a new digital radiographic system 1 is being developed and is beginning to be used. The sensor part of the system uses an imaging plate coated with a stimulable phosphor. Regarding such methods,
The basic method is detailed in US Pat. No. 3,859,527.

The stimulable phosphor BaBrz:Eu" is a phosphor that has two functions: X-ray detection and memory. When irradiated with X-rays or ultraviolet rays, the luminescent center Eu is excited, It emits blue light. This is so-called photoluminescence. At the same time, some electrons in lEu are excited. The electrons are captured by the color center. The color center is Br
- is a lattice defect, and the defect becomes positively charged. Since the electrons are negatively charged, they are captured at the center of the color.

This is memory. Next, when the stimulable phosphor is irradiated with red to infrared light, the electrons captured in the color center are excited, and when they return to their original Eu state, they emit blue light. This is stimulated luminescence. This stimulated luminescence intensity is proportional to the X-ray intensity.

The imaging beam 1, which has been irradiated with X-rays, is scanned with a red or infrared laser. The stimulated luminescence obtained at that time is converted into an electrical signal using a photomultiplier tube. This electrical signal is subjected to image processing to obtain an X-ray photograph.

If the stimulated luminescence efficiency of the phosphor is increased, higher resolution can be obtained, and the exposure dose can also be reduced.

[Conventional technology]

BaClBr:Eu" and the like are known as stimulable phosphors. In order to increase the luminous efficiency of BaClBr:Eu2+, for example, Japanese Patent Application Laid-Open No. 120882/1982 proposes the use of additives such as NaCl. .This increases the efficiency of photoluminescence.However,
Regarding BaBrz:Eu'', there has been little research regarding additives that increase the stimulated luminescence efficiency.

[Problem to be solved by the invention]

nu is said to be a luminescent center, and when added to BaBr2, light emission of 400 nm can be obtained. This luminescence is converted into an electrical signal by a photomultiplier tube and used to detect an X-ray image.

- As mentioned above, the stimulable phosphor also has a memory function.

Therefore, when such a phosphor is used for X-ray photography for the purpose of medical diagnosis, it is desired that the luminance of the phosphor be as high as possible in order to reduce the radiation dose to the human body.

Therefore, it is an object of the present invention to provide a stimulable phosphor that has high luminous efficiency and can reduce the exposure dose to the human body when used in X-ray photography for the purpose of medical diagnosis.

[Means to solve the problem]

According to the present invention, in order to solve the problem described in J-, the composition formula (
1) or (2), Ba1. , Xl-x Br2: Eu”
(1) Bal-Xt, XBrz-2X, :Eu2°
(2) (L is Sc, Y, La= Ce
, Pr, Nd, Pm, Sm, Gd, , TbXDy
, Ho, Er, Tm, Yb, Lu, AI,
represents at least one trivalent metal selected from the group consisting of Ga, In and Tl; X represents a halogen selected from the group consisting of F, CI and I;
<o, s, y are 0<y<0.1, z is Q<z<
This is a numerical value that satisfies the condition of 0.1. ) is provided.

In the phosphor of the present invention, if X is too large, the sensitivity will be low, and if it is too small, the luminous efficiency will not be sufficiently improved. If y is too large, the sensitivity will be low (j), which is not practical.

[Effect]

In the present invention, a part of NoriJ, which is one of the constituent components of the photostimulable phosphor having the composition BaBr2:Eu2+, is replaced with a trivalent metal, which results in photostimulated luminescence. Strength is directed.

The stimulable phosphor of the present invention has a composition formula (3) or (4),
Bat-x t, X Brz: Euy (
3) Bat-811, Brzz-z X 2: 1iuy
(4) (However, L, Medium 500-1100
"It can be manufactured by firing at a temperature of C.

Components of such a raw material mixture include BaBr2, other barium halides, EuBr3. EuF...
For 1Euc13 or Eu13 and L, bromides of the metals mentioned above, or those metals or their oxides dissolved in hydrobromic acid (IIBr) and dried can be used.

The stimulable phosphor of the present invention can be advantageously used as a phosphor for producing an X-ray image conversion sheet. Such a sheet is constructed, for example, by applying a paint containing a stimulable phosphor onto a film of polyethylene terephthalate 1-, drying it, and then forming a protective film on its surface.

Therefore, such a sheet can be applied to a conversion panel of a radiation image recording/reading device used for medical X-ray diagnosis. In this device, when a conversion panel including a layer of photostimulable phosphor is irradiated with X-rays and then scanned with excitation light such as a laser beam, stimulated luminescence is generated from the conversion panel. This stimulated luminescence can be detected, converted into a time-series signal, and displayed on a (j?T), or made into a visible image by intensity modulating the laser beam and printing it on a silver halide film. It can be done.

〔Example] The present invention will be further explained below with reference to Examples.

Example - Soil I7 in the above-mentioned compositional formula (3) was replaced with Gd, raw materials were mixed to give the composition ratio shown in Table 1, this raw material mixture was filled into a quartz boat, and reduced and fired at 840°C for 2 hours. I did it. As raw material components, BaBrz+EuBrx and Gd2O3 were dissolved in hydrochloric acid and dried.

Furthermore, helium gas containing hydrogen gas was used as the reducing atmosphere. For comparison, we also made a prototype without additives. The stimulated emission intensity of the phosphor thus obtained was measured (excitation light 780 nm).

The results are also shown in Table 1.

In the above-mentioned compositional formula (4), M is Gd, X is CI, raw materials are mixed to give the composition ratio shown in Table 2, and this raw material mixture is charged into a quartz boat and heated at 2.840°C. Reduction firing was performed for 2 hours. As raw material components, for sample number 1, BaBrz, EuBr, and Gd2O* were dissolved in hydrochloric acid and dried, and for sample number 2, BaBrz, EuCl3, and Gd2O were dissolved in hydrochloric acid. , dried ones were used. Furthermore, helium gas containing hydrogen gas was used as the reducing atmosphere.

For comparison, we also made a prototype without additives. The stimulated emission intensity of the obtained phosphor was measured (excitation light 780 r+m). The results are also shown in Table 2.

Note that in Tables 1 and 2, the stimulated luminescence intensity is 10 mR.
After irradiation with an X-ray dose of
0 mW) is shown.

In Examples 1 and 2 described above, similar results were obtained even when Y or Ga was used instead of Gd.

〔Effect of the invention〕

Since the stimulable phosphor of the present invention has high stimulable luminescence intensity, it is possible to reduce the exposure dose to the human body in X-ray photography using a digital radiography system.

Claims (4)

[Claims] 1. Composition formula (1) or (2), Ba_1_-_xL_xBr_2:Eu^2^+_y(
1) Ba_1_-_xL_xBr_2_-_zX_z:
Eu^2^+_y(2) (L is Sc, Y, La
, Ce, Pr, Nd, Pm, Sm, Gd, Tb, Dy,
represents at least one trivalent metal selected from the group consisting of Ho, Er, Tm, Yb, Lu, Al, Ga, In and Tl; X represents a halogen selected from the group consisting of F, Cl and I; x is 10^-^4<x<0.5, y
is a numerical value that satisfies the following conditions: 0<y<0.1, and z satisfies the following conditions: 0<z<0.1. ) is a photostimulable phosphor. 2. When manufacturing the phosphor according to claim 1, compositional formula (3) or (4), Ba_1_-_xL_xBr_z:Eu_y(3)Ba
_1_-_xL_xBr_2_-_zX_z:Eu_y
(4) (However, L, 500-1100 in reducing atmosphere
A method for producing a stimulable phosphor comprising firing at a temperature of °C. 3. X containing the phosphor according to claim 1 as a stimulable phosphor
Line image conversion sheet. 4. A radiation image recording and reading device characterized in that a conversion panel is constructed using the X-ray image conversion sheet according to claim 3.