JPS63183981A - Fluorescent material and radiation image conversion panel produced by using said fluorescent material - Google Patents

Abstract

PURPOSE:To provide the titled fluorescent material consisting of a specific bivalent metal fluorohalide fluorescent material containing Eu and Si as activators, emitting accelerated phosphorescence of high luminance and providing a radiation conversion panel having high sensitivity compared with the luminance and sensitivity of a conventional fluorescent material containing only Eu as the activator. CONSTITUTION:A bivalent metal fluorohalide fluorescent material expressed by formula (MII is Be, Mg, Ca, Sr, Zn or Cd; X is Cl, Br or I; 0.5<=a<=1.25; 0<=x<=1; 10<-6=y<=2X10<-1>; 0<z<=5X10<-3>). The fluorescent material can be produced by mixing fluorescent material raw materials composed of barium fluoride, beryllium fluoride, barium chloride, europium chloride and silicon dioxide, etc., putting the mixture into a refractory crucible, calcining at 600-1,000 deg.C (preferably 700-950 deg.C) for 1-6hr preferably in a neutral or weakly reducing atmosphere, crushing the product, calcining again preferably under the same conditions and subjecting the calcined material to crushing, washing, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a divalent metal fluorohalide phosphor and a radiation image storage panel having a phosphor layer comprising the phosphor.

Conventionally, a so-called photographic method has been used to obtain radiation images as images, using a photographic film having an emulsion layer made of a silver salt photosensitive material, but in recent years, due to problems such as the depletion of silver resources, silver salts have been used. It has become desirable to have a method for imaging emitted If-ray patterns without the use of radioactivity.

By the way, some types of phosphors are exposed to ionizing radiation,
After absorbing radiation such as electron beams, vacuum ultraviolet rays, and ultraviolet rays, it emits light when excited by visible light or infrared electromagnetic waves. This phenomenon is called ``stimulable phosphor'', and a phosphor that exhibits ``stimulable phosphor'' is called a ``stimulable phosphor''. Radioactive conversion methods using photobodies are known (US Pat. No. 3,859,527). This method uses a radiation image conversion panel (so-called storage type radiation S image conversion panel) having a phosphor layer made of a photostimulable phosphor. After that, the phosphor layer is excited with visible light or infrared rays to emit the radiation energy accumulated in the photostimulable phosphor as fluorescence, and by detecting this, a radiation image of the subject is obtained. It is. In putting this radiation image conversion method into practice, the radiation is often ionizing radiation such as xm and the subject is a person, and therefore it is necessary to reduce the exposure dose of the subject as much as possible. From this point of view, it is desired that the stimulable phosphor used in the radiation B image conversion panel has higher stimulable luminance.

The composition formula is (Ba 1-x, MICX) F2 ・a
[3a and y are respectively 0.5≦a≦1.25
, O≦×≦1 and 10″6≦y×10−1) The europium-activated divalent metal fluorohalide phosphor is a practical photostimulable phosphor. This europium-activated 2
Some valent metal fluorohalide phosphors are known. For example, JP-A-55-12143 and JP-A-55-12
No. 145 has the compositional formula (E3a 1-X, M
X) FX: V Eu (however, M is magnesium,
at least one of calcium, strontium, zinc, and cadmium, X is at least one of chlorine, bromine, and iodine, and X and y are each O
A divalent metal fluorohalide stimulable phosphor represented by the following formula is described. As mentioned above, when using a photostimulable phosphor in a radiation image conversion panel, a photostimulable phosphor exhibiting higher luminance stimulated luminescence is desired, so the europium-activated divalent metal fluorocarbon A stimulable phosphor that exhibits higher luminance stimulated luminescence than a halide phosphor is desired.

Therefore, the present invention provides the above-mentioned conventional europium activation 2 (1i
The object of the present invention is to provide a phosphor that exhibits stimulated luminescence with higher brightness than a metal 70 halogenide phosphor.

Another object of the present invention is to provide a radiation image conversion panel having higher sensitivity than the conventional radiation image conversion panel having a phosphor layer made of a europium-activated divalent metal fluorohalide phosphor. It is.

In order to achieve the above object, the present inventors have conducted various experiments on a europium co-activator, which is an activator for the phosphor. As a result, the inventors found that if silicon is appropriately incorporated into the phosphor as a co-activator for europium, the luminance of the phosphor due to stimulation can be significantly improved, and the present invention has been completed. .

The 2@[i metal fluorohalide phosphor of the present invention has the compositional formula (Bat-x, Mx) Fz・a 3a Xz:
V Eu, Z Si (however, M is beryllium, magnesium, calcium,
at least one of strontium, zinc and cadmium; X is at least one of chlorine, bromine and iodine; a, X;

■ and 2 are respectively 0.5≦a≦1.25, O≦
x≦1, 104≦Y×10−1 and 0<z≦5X1
It is a number that satisfies the condition 0-3).

Further, the radiation image conversion panel of the present invention is a radiation image conversion panel having a phosphor layer made of a stimulable phosphor, wherein the stimulable phosphor is the divalent metal fluorohalide fluorophore of the present invention. It is characterized by consisting of a body.

When the phosphor of the present invention is irradiated with and absorbed radiation such as ionizing radiation such as xsi+ and γ rays, electron beam, vacuum ultraviolet rays, and ultraviolet rays, and then excited with light having a wavelength of 450 to 800 nm,
It exhibits stimulated luminescence with significantly higher brightness than conventional europium-activated divalent metal fluorohalide phosphors. Therefore, the radiation phosphor conversion panel of the present invention having a phosphor layer comprising the phosphor of the present invention is different from the radiation phosphor conversion panel having a phosphor layer comprising a conventional europium-activated divalent metal fluorohalide phosphor. Significantly more sensitive than panels. Shining light i! i
I! In terms of degree, the more preferable y and binary range of the compositional formula of the phosphor of the present invention are 10°5≦y≦10−, respectively.
2 and 10°7≦Z×10−3. The phosphor of the present invention also emits near-ultraviolet to blue light (instantaneous luminescence) when excited by radiation such as ionizing radiation I4 rays, electron beams, vacuum ultraviolet rays, and ultraviolet rays. Further, the phosphor of the present invention exhibits thermal fluorescence when heated after irradiating and absorbing radiation such as ionizing radiation, electron beam, vacuum ultraviolet rays, and ultraviolet rays.

The phosphor of the present invention is manufactured by the manufacturing method described below.

First, the raw materials for the phosphor include 1) barium fluoride (88Fz), 11) beryllium fluoride (Be Fz), magnesium fluoride (M (I Fz), calcium fluoride (Ca
Fz ), strontium fluoride (Sr F2 >, zinc fluoride (Zn Fz ) and cadmium fluoride (Cd F
one or more divalent metal fluorides consisting of 1ii) barium chloride (88C1z), barium bromide <Ba8rz>, barium iodide (Ba12)
, ammonium chloride (NHa CL), ammonium bromide (NHa 8r > and ammonium iodide <NHa
One or more halides consisting of I>, ψ europium chloride (ELJ CR13), europium oxide (EtlzO3), europium fluoride (El
j F3 ), sulfur W11-Robium [Euz(SOa'
) one or more europium compounds such as si, and V) silicon dioxide (SiO2), orthosilicic acid (HASiO
One or more compounds selected from the group of compounds consisting of silicon compounds such as a) are used. The above phosphor raw materials are stoichiometrically <Bat-x, Mx)Fz・a
BaXz: yEu, zsi (where M is at least is of beryllium, magnesium, calcium, strontium, zinc and cadmium, x is at least one of chlorine, bromine and iodine, a, X,
y and 2 are respectively 0,5≦a≦1.25, O≦
x≦1.104≦y×10−1 and O<z≦5X10
The mixture is weighed and thoroughly mixed using a ball mill, mixer mill, etc., so that the mixture composition formula becomes (a number that satisfies the condition -3). Note that when the X value of the above mixed composition formula is O, the above phosphor raw material ii) is unnecessary, and when the x value is 1, the above phosphor raw material i) is unnecessary, and the above phosphor raw material ii) is unnecessary. It is essential to use at least barium halide as the body raw material 11:). In addition, when ammonium halide (NHa The halogen (X>) dissipates out of the reaction system as NH4X during the firing process described below.

Next, the raw material mixture is filled into a heat-resistant container such as an alumina crucible or a quartz crucible, and fired in an electric furnace. The appropriate firing temperature is 600 to 1000°C, preferably 700°C.
00 to 950°C. Baking TI! The period f varies depending on the filling amount of the raw material mixture, the firing temperature employed, etc., but in general, 1 to 6 hours is appropriate. Firing may be performed in the air, but it is preferable to perform the firing in a neutral atmosphere such as an argon gas atmosphere or a nitrogen gas atmosphere, or in a weakly reducing atmosphere such as a carbon oxide gas atmosphere or a nitrogen gas atmosphere containing a small amount of hydrogen gas. is preferable. Incidentally, the luminance of the resulting phosphor can be further increased by firing once under the above firing conditions, taking out the fired product outside the electric furnace, pulverizing it, and then firing again under the above conditions. The phosphor of the present invention is obtained by pulverizing the fired product obtained after firing, and then performing various operations generally employed in the production of phosphors, such as washing, drying, and sieving.

The divalent metal fluorohalide phosphor of the present invention produced as described above exhibits higher luminance stimulated luminescence than conventional europium-activated divalent metal fluorohalide phosphors, and Shows instantaneous luminescence and thermal fluorescence.

FIG. 1 shows one of the phosphors of the present invention.
qr.

MQo, os) F2-3a Brz: 0.00
02 Eu.

This figure illustrates the emission spectrum of photostimulation when a 0.000025 i phosphor is irradiated with 80 KVp X-rays and then excited with 630 nm light. As is clear from FIG. 1, the divalent metal fluorohalide phosphor of the present invention has an emission spectrum with a peak at approximately 390 nn, similar to the conventional divalent metal fluorohalide phosphor using only europium as an activator. It exhibits near-ultraviolet to blue stimulated luminescence.

The instantaneous emission spectrum of the phosphor of the present invention when excited with radiation such as X-rays, electron beams, and ultraviolet rays was almost the same as the stimulated emission spectrum illustrated in FIG.

Even if the composition of the phosphor of the present invention changes within the range of the above compositional formula, the emission spectrum hardly changes, and all phosphors emit near-ultraviolet to blue light with an emission spectrum peak at approximately 390 nn. Shows exhaustion and instantaneous luminescence.

Figure 2 shows one of the phosphors of the present invention (Bao,
qr:.

Zn0.05) F2-13a Brz: 0
．． 0002 Eu.

This is a graph showing the relationship between the amount of silicon (binary) for a zSi phosphor and the luminance when this phosphor is irradiated with 80KVD XS and then excited with 630n+g light to cause exhaustion. be. In FIG. 2, the vertical axis showing the photostimulated emission brightness is the conventional one in which silicon is not co-activated (Ba o, Q!;
, Zn o, o parable) Fz ・(3a 3r 2
:0.0002 The luminance of the Eu phosphor is 100
It is expressed as a relative value. As is clear from Fig. 2, when the europium activation amount (y value) is constant and the z value is in the range of Q<Z≦5X10-3 (Bao,
qr, ZnO, OS) F2-8a 3r z:
The 0.0002 Eu, Z Si phosphor is conventional <Bao, B.

Zno,og) Fz-3a Br2:
It exhibits stimulated luminescence with higher brightness than the 0.0002 Ell phosphor, and exhibits stimulated luminescence with even higher brightness within this range, particularly when 10°T≦2×10 −3 . In addition, the second
The figure is (3aa, Ii).

Zno, 5s) Fz -Ba Brz: 0.
0002 Eu.

This is a graph showing the relationship between binary values and photostimulated luminance for a ZSi phosphor. Even when the y value changes, the relationship between binary values and stimulated luminance has almost the same tendency as in Figure 2. It was confirmed that there is. Furthermore, it was confirmed that even if the matrix composition varied within the range of the above compositional formula, the relationship between the binary values and the stimulable luminance was almost the same as that shown in FIG. 2.

The europium activation 1 (y value) range in the divalent metal fluorohalide phosphor of the present invention is the same (10 ``6≦y×10-1. From the point of view of photostimulated emission brightness, a more preferable V value range is 10°5≦
y≦10−2. Furthermore, the Mffi (x value) range and B
The aXzl (a value) gap is set to O≦x≦1 and 0.5≦a≦1.25, respectively, from the viewpoint of photostimulated emission brightness, as in the case of conventional divalent metal fluorohalide phosphors. Limited.

The excitation spectrum of the divalent metal fluorohalide phosphor of the present invention is almost the same as that of the conventional divalent metal 70-ring halide phosphor using only europium as an activator. The photomaterial exhibits stimulated luminescence when excited with light having a wavelength of 450 to 800 nm, and particularly exhibits high-intensity stimulated luminescence when excited with light having a wavelength of 450 to 700 ni within this wavelength range.

Next, the radiation image conversion panel of the present invention will be explained.

The radiation image storage panel of the present invention has a phosphor layer comprising the divalent metal fluorohalide phosphor of the present invention. Generally, the phosphor layer is formed by dispersing the phosphor in a suitable binder. If the phosphor layer is self-supporting, the phosphor layer itself can serve as a radiation image conversion panel, but generally the phosphor layer is formed on one or both sides of a sheet-like support and the phosphor layer is formed on one or both sides of a sheet-like support. It is considered as an a-image conversion panel. Furthermore, a protective film for physically or chemically protecting the phosphor layer is usually provided on the surface of the phosphor layer (on the opposite side of the phosphor layer from the support). Furthermore, an undercoat layer may be provided between the phosphor layer and the support for the purpose of increasing the degree of adhesion between the phosphor layer and the support.

The radiation image storage panel of the present invention is generally manufactured as follows. First, a phosphor coating solution is prepared by mixing 0.01 to 1 part by weight of a binder to the single most layer of the divalent metal fluorohalide phosphor of the present invention, and this is coated by an appropriate coating method. A phosphor layer is formed by coating on a horizontally placed support and drying to form a radiation image storage panel. In this case, the binder used is a binder commonly used for layer formation, such as nitrified cotton, vinyl chloride-vinyl acetate copolymer, polyvinyl butyral, polyvinyl acetate, or polyurethane. Various sheet-like materials such as PlusDeck sheets, glass plates, paper, and metal plates can be used as the support, but materials that are flexible and easy to process are preferred for handling purposes, so polyester films, polyethylene terephthalate, etc. It is particularly preferable to use a film, a plastic sheet such as a cellulose acetate film, or paper.

The thickness of the phosphor layer is appropriately set in the range of 10 to 1000 μm. Furthermore, when providing a protective film on the phosphor layer of the radiation image storage panel, polyvinyl chloride, polyethylene terephthalate, polymethacrylate, cellulose acetate, etc. may be added on the phosphor layer obtained as described above. A protective film can be formed by directly applying a coating solution prepared by dissolving these resins in a suitable solvent and drying them, or by adhering a transparent thin film made of these resins formed separately in advance to the surface of the phosphor layer. Form. In addition, when providing a phosphor layer on a support,
As mentioned above, a phosphor layer may be formed by directly applying a coating liquid containing a stimulable phosphor dispersed in a binder onto a support, or a phosphor layer may be formed by separately forming a phosphor layer in advance. The optical layer may be adhered onto the support.

As explained above, when the phosphor of the present invention is irradiated with and absorbed radiation such as ionizing radiation, electron beam, vacuum ultraviolet ray, ultraviolet ray, etc., and then excited with light of 450 to 800 nm, the phosphor of the present invention can be activated by using only europium as an activator. It exhibits stimulated luminescence with higher brightness than divalent metal fluorohalide phosphors. Therefore, the radiation image conversion panel of the present invention having a phosphor film made of the phosphor of the present invention is different from that of the conventional 2, which uses only europium as an activator.
It has higher sensitivity than a radiation image conversion panel having a phosphor film made of a valent metal fluorohalide phosphor. In this way, the phosphor of the present invention emits radiation! Although the phosphor of the present invention is particularly useful as a phosphor for IA image conversion panels, the use of the phosphor of the present invention is not limited thereto. In other words, the phosphor of the present invention has a high ionization number! ) 11. When excited with electron beams, vacuum ultraviolet rays, ultraviolet rays, etc., it shows instantaneous near-ultraviolet to blue light emission, so it can also be used in intensifying screens, cathode a-tubes, fluorescent lamps, etc.

Further, the phosphor of the present invention exhibits thermal fluorescence when heated after irradiating and absorbing ionizing radiation, electron beam, vacuum ultraviolet rays, ultraviolet rays, etc., and therefore can be used in thermal fluorescent dosimeters and the like.

As described above, the industrial utility value of the present invention is extremely large.

Next, the present invention will be explained by examples.

EXAMPLE As shown in (1) to (7) below, each phosphor raw material was weighed and thoroughly mixed using a ball mill to prepare seven types of phosphor raw material mixtures.

(11Ba Fz 175.3g (1 mol), BaB
rz”2Hz O333,29 (1 mol), Eu C
30.052 g (0,0002 mol) and HaS
i On 0.002g (0,00002 mol) (2) 3a F2 166.51? (0.95 mol), 5rFz6.3g (0.05 mol/L/), BaB
rz ・2Hz0336.4g (1,01 mol), E
u CLs 0.077 g (0,0003 mol) and Ha S! Oa 0.002g (0,00002
(mol) (3) Ba F2 166.5g (0.95mol)
, zn Fz5.2g (0.05 mol), BaBrz
・2HzO333.2g (1 mol), Eu C2
30,052 g (0,0002 mol) and HaS
i Oa 0.002 g (0,00002 mol) (4) Ba Fz 166.5 g (0.95 mol), CdFz 7.59 (0.05 mol), BaBrz
-21-12゜333゜1g (1 mol), Eu
CL3' 0.052SF (0,0002 mol) and HaSiOs 0.002g < 0.0000
2 mol) (5) Ba F2 168.3g (0.96 mol)
, 3e Fzl, 12 g (0.04 mol), Ba
CfLz ・2Hz0244.2g<1 mol)
, Eu F3 0.042 g (0,0002 mol) and S! 02 0.002g < 0.00003 mol) f61 8a F2 164.8g (0.94 mol),
M(llFz3.7g (0.06 mol), BaC9,z
2HzO251.6g (1.03mol), Ell
F3 0.042g (0,0002 mol) and Ha
S! Oa 0.001g (0,00001 mol) +7+ Ba F2 168.31J (0.96 mol), 3e F2 1.12 g < 0.04 mol)
, BaBrz”2Hz0303.19 (0.91 mo/
Lz), 3a C9Jz ・2 H2024, 4g
(0.1 mol), Ell F3 0.104g<o
, ooos mol) and H4S iOa O,002
g (0,00002 mol) Next, each of the above seven types of phosphor raw material mixtures was packed into an alumina crucible, placed in an electric furnace, and fired at a temperature of 850° C. for 3 hours in a carbon oxide gas atmosphere. After firing, the crucible was taken out of the electric furnace and rapidly cooled in air. After crushing the obtained baked product, it is sieved to make the particle size uniform,
I got a phosphor.

For each of the seven types of phosphors produced in this way, 80
After irradiating with KVD XS, use a spectrometer (Hitachi Spectrophotometer M
These phosphors were excited with 630 ni light obtained by spectroscopy of light emitted from a xenon lamp set in a PF-2A model, and the stimulated luminescence brightness was measured. As a result, the stimulated luminescence brightness of these phosphors is higher than that of conventional europium-activated divalent metal fluorohalide fluorescers prepared using the same method except that no co-activator is used, as shown in the table below. This was significantly higher than the stimulated luminance measured under the same conditions.

Next, for each of the above seven types of phosphors of the present invention,
A phosphor coating solution having a viscosity of approximately 50 centistokes was prepared by mixing 8 parts by weight of the phosphor and 1 part of nitrified cotton using a solvent (a mixture of acetone, ethyl acetate, and butyl acetate). Next, this coating solution was placed horizontally and applied uniformly onto a polyethylene terephthalate film (support) using a knife coater, and dried at 50°C to form a phosphor layer with a layer thickness of approximately 300μ. An acetone solution of cellulose acetate was uniformly applied onto the phosphor layer and dried to form a transparent protective film with a layer thickness of about 8 μm, thereby producing seven types of radiation image storage panels. Separately, for comparison, a radiation image conversion panel was prepared in the same manner as above using the conventional NiObium-activated divalent metal fluorohalide phosphor.

The sensitivity of the radiation am conversion panel of the present invention obtained in this way (tube voltage aoKv for each radiation image conversion panel)
After irradiating with p X-rays, @e-Ne laser beam (633
As in the case of the comparison of the stimulated luminescence luminance of the phosphors in the table above, the luminescence luminance due to stimulation when excited with
The emission was higher than that of the 111 radiation image conversion panel having a phosphor layer consisting of an i181I fluorohalide phosphor.

[Brief explanation of the drawing]

FIG. 1 is a graph illustrating the stimulated emission spectrum of the phosphor of the present invention. FIG. 2 is a graph illustrating the relationship between the amount of coactivator (Z value) and the stimulated luminance in the phosphor of the present invention.

Claims (6)

[Claims] (1) The composition formula is (Ba_1_-_x, M^II_x)F_2・aBaX_
2: yEu, zSi (where M^II is at least one of beryllium, magnesium, calcium, strontium, zinc and cadmium, X is at least one of chlorine, bromine and iodine, a, x, y and z are 0.5≦a≦1.25, 0≦x≦1, 10, respectively
^-^6≦y≦2×10^-^1 and 0<z≦5×1
2, which is a number that satisfies the condition 0^-^3)
Valuable metal fluorohalide phosphor. (2) The divalent metal fluorohalide phosphor according to claim 1, wherein y is a number satisfying the following condition: 10^-^5≦y≦10^-^2. (3) The divalent metal fluorocarbon according to claim 1 or 2, wherein z is a number satisfying the following condition: 10^-^7≦z≦2×10^-^3 Halide phosphor. (4) In a radiation image conversion panel having a phosphor layer made of a photostimulable phosphor, the above-mentioned photostimulable phosphor has a composition formula (Ba_1_-_x, M^II_x)F_2・aBaX_
2: yEu, zSi (where M^II is at least one of beryllium, magnesium, calcium, strontium, zinc and cadmium, X is at least one of chlorine, bromine and iodine, a, x, y and z are 0.5≦a≦1.25, 0≦x≦1, 10, respectively
^-^6≦y≦2×10^-^1 and 0<z≦5×1
2, which is a number that satisfies the condition 0^-^3)
A radiation image conversion panel comprising a valent metal fluorohalide phosphor. (5) The radiation image conversion panel according to claim 4, wherein y is a number satisfying the following condition: 10^-^5≦y≦10^-^2. (6) The radiation image conversion panel according to claim 4 or 5, wherein z is a number satisfying the following condition: 10^-^7≦z≦2×10^-^3 .