JPH0141191B2 - - Google Patents

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 using a photographic film having an emulsion layer made of a silver salt photosensitive material has been used to obtain a radiation image as an image.
In recent years, due to problems such as the depletion of silver resources, a method of imaging radiographic images without using silver salts has become desirable. By the way, some types of phosphors emit light when they are made to absorb radiation such as ionizing radiation, electron beams, vacuum ultraviolet rays, and ultraviolet rays and then are excited by electromagnetic waves such as visible light or infrared rays. This phenomenon is called ``stimulable phosphor'', and a phosphor that exhibits ``stimulable phosphor'' is called a ``stimulable phosphor''. A radiation image conversion method using a light body is known (U.S. Patent No.
No. 3859527). This method uses a radiation image conversion panel (so-called storage type radiation image conversion panel) that has a phosphor layer made of a photostimulable phosphor, and the phosphor layer of the panel receives radiation that has passed through the subject. After absorbing the phosphor layer, the phosphor layer is excited with visible light or infrared rays to cause the stimulable phosphor to emit the accumulated radiation energy as fluorescence, and by detecting this, a radiation image of the subject is obtained. It is something. When this radiation image conversion method is put into practice, the radiation is often ionizing radiation such as X-rays and the subject is a person, so 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 image conversion panel has higher stimulable luminance. The composition formula is (Ba _1-x , M〓x)F ₂・aBaX ₂ :yEu (where M〓 is at least one of beryllium, magnesium, calcium, strontium, zinc, and cadmium, and X is chlorine, bromine, and iodine. and a, x, and y are numbers satisfying the following conditions, respectively: 0.5≦a≦1.25, 0≦x≦1, and 10 ^-6 ≦y≦2×10 ^-1 ) The europium-activated divalent metal fluorohalide phosphor is a practical photostimulable phosphor, and after irradiation and absorption, the
When excited with 800 nm light, it exhibits high-intensity stimulated luminescence. Some of these europium-activated divalent metal fluorohalide phosphors are known. For example, Japanese Patent Application Publication No. 55
-12143 and JP-A-55-12145, the composition formula is (Ba _1-x , M〓x)FX:yEu (where M〓 is at least one of magnesium, calcium, strontium, zinc and cadmium). The species, X, is at least one of chlorine, bromine, and iodine, and x and y are numbers satisfying the conditions 0≦x≦0.6 and 0≦y≦2×10 ^-1 , respectively. Divalent metal fluorohalide stimulable fluorophores have been 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. Accordingly, an object of the present invention is to provide a phosphor that exhibits stimulated luminescence with higher brightness than the conventional europium-activated divalent metal fluorohalide phosphor. Furthermore, the present invention also provides the above-mentioned conventional europium activated 2
The object of the present invention is to provide a radiation image conversion panel having higher sensitivity than a radiation image conversion panel having a phosphor layer made of a valent metal fluorohalide phosphor. 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 by incorporating an appropriate amount of silicon into the phosphor as a co-activator for europium, the luminance of the phosphor due to stimulation can be significantly improved, leading to the completion of the present invention. . The divalent metal fluorohalide phosphor of the present invention has a composition formula (Ba _1-x , M〓x)F ₂・aBaX ₂ :yEu, zSi (where M〓 is beryllium, magnesium, calcium, strontium, zinc, and At least one of 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, respectively
10 ^-6 ≦y≦2×10 ⁻¹ and 0<z≦5×10 ⁻³ ). Further, the radiation image conversion panel of the present invention is a radiation image conversion panel having a phosphor layer made of a photostimulable phosphor, in which the above-mentioned photostimulable phosphor is
It is characterized by being composed of a valent metal fluorohalide phosphor. The phosphor of the present invention can be used for ionizing radiation such as X-rays and γ-rays,
After irradiating and absorbing radiation such as electron beams, vacuum ultraviolet rays, and ultraviolet rays, when excited with light with a wavelength of 450 to 800 nm, it produces a much brighter luminescence than conventional europium-activated divalent metal fluorohalide phosphors. Shows exhaustion. Therefore, the radiation image conversion panel of the present invention having a phosphor layer made of the phosphor of the present invention is different from the conventional radiation image conversion panel having a phosphor layer made of a europium-activated divalent metal fluorohalide phosphor. Significantly more sensitive than panels. From the viewpoint of stimulated luminescence brightness, the more preferable y and z value ranges of the compositional formula of the phosphor of the present invention are 10 ^-5 ≦y≦10 ^-2 , respectively.
and 10 ^-7 ≦z≦2×10 ^-3 . The phosphor of the present invention also emits near-ultraviolet to blue light (instantaneous luminescence) when excited by radiation such as ionizing radiation, electron beams, vacuum ultraviolet rays, and ultraviolet rays. Further, the phosphor of the present invention exhibits thermal fluorescence when heated after being irradiated with and absorbed 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 barium fluoride (BaF ₂ ), beryum fluoride (BeF ₂ ), magnesium fluoride (MgF ₂ ), calcium fluoride (CaF ₂ ), strontium fluoride (SrF ₂ ), and zinc fluoride ( One or more divalent metal fluorides consisting of ZnF ₂ ) and cadmium fluoride (CdF ₂ ), barium chloride (BaC ₂ ), barium bromide (BaBr ₂ ), barium iodide (BaI ₂ ), chloride Ammonium ( _NH4C ), Ammonium Bromide ( _NH4Br ) and Ammonium Iodide ( _NH4I )
One or more halides consisting of europium chloride (EuC ₃ ), europium oxide (Eu ₂ O ₃ ), europium fluoride (EuF ₃ ),
One or more europium compounds such as europium sulfate [Eu ₂ (SO ₄ ) ₃ ], silicon dioxide (SiO ₂ ), ortho-silicic acid (H ₄ SiO ₄ )
One or more compounds selected from the group consisting of silicon compounds such as the following are used. The above phosphor raw materials are stoichiometrically expressed as (Ba _1-x , M〓x)F ₂・aBaX ₂ :yEu, zSi (where M〓 is beryllium, magnesium, calcium, strontium, zinc, and cadmium). at least one, X is at least one of chlorine, bromine and iodine, a, x, y
and z are 0.5≦a≦1.25, 0≦x≦1, respectively
(The number satisfies the following conditions: 10 ^-6 ≦y≦2×10 ^-1 and 0<z≦5×10 ^-3 ) Weigh it so that it has a mixing composition formula of Mix. Note that when the x value of the above mixed composition formula is 0, the above phosphor raw material is unnecessary, and when the x value is 1, the above phosphor raw material is unnecessary, and at least It is essential to use barium halide. In addition, when ammonium halide (NH ₄
may be present in the raw material mixture, but these excess halogens (X) are dissipated out of the reaction system as NH ₄ X 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℃.
Preferably it is 700 to 950°C. The firing time 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 air, but firing may be performed 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. It is preferable to do so. 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. Figure 1 shows one of the phosphors of the present invention (Ba0.95, Mg0.05) F ₂ · BaBr ₂ : 0.0002Eu,
After irradiating 0.00002Si phosphor with 80KVp X-rays
This is an example of the emission spectrum of photostimulation when excited with 630 nm light. As is clear from FIG. 1, the divalent metal fluorohalide phosphor of the present invention is similar to the conventional divalent metal fluorohalide phosphor using only europium as an activator.
It exhibits near-ultraviolet to blue stimulated luminescence with an emission spectrum peak at 390 nm. 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 also 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-mentioned compositional formula, the emission spectrum hardly changes. Shows exhaustive and instantaneous luminescence. Figure 2 shows one of the phosphors of the present invention (Ba0.95, Mg0.05) F ₂・BaBr ₂ : 0.0002Eu, ZSi
This is a graph showing the relationship between the amount of silicon (z value) in a phosphor and the luminance when the phosphor is irradiated with 80KVp X-rays and then excited with 630nm light to cause exhaustion. be. In Figure 2, the vertical axis showing the stimulated emission brightness is the stimulated emission brightness of the conventional (Ba0.95, Zn0.05)F ₂ BaBr ₂ :0.0002Eu phosphor in which silicon is not co-activated. It is expressed as a relative value with 100. As is clear from Figure 2, when the amount of europium activation (y value) is constant, the z value is 0<z≦
In the range of 5×10 ^-3 (Ba0.95, Zn0.05)
F ₂・BaBr ₂ : 0.0002Eu, zSi phosphor shows higher luminance stimulated luminescence than the conventional (Ba0.95, Zn 0.05) F ₂・BaBr ₂ : 0.0002Eu phosphor, and within this range However, particularly when 10 ^-7 ≦z≦2×10 ^-3 , even higher luminance stimulated luminescence is exhibited. In addition, Fig. 2 is a graph showing the relationship between the z value and the stimulated luminance for the (Ba0.95, Zn0.05)F ₂ · BaBr ₂ : 0.0002Eu, zSi phosphor. It was confirmed that even when the z value was changed, the relationship between the z value and the photostimulated emission brightness had almost the same tendency as shown in FIG. 2. Furthermore, it was confirmed that even if the matrix composition was changed within the range of the above compositional formula, the relationship between the z value and the stimulable luminance was almost the same as that shown in FIG. 2. The range of europium activation amount (y value) in the divalent metal fluorohalide phosphor of the present invention is 10 ^-6 as in the case of the conventional divalent metal fluorohalide phosphor using only europium as an activator. ≦y≦
It is 2×10 ^-1 . A more preferable y value range from the viewpoint of stimulable luminance is 10 ^-5 ≦y≦10 ^-2 . Furthermore, the M value (x value) range and the _Ba As in the case of fluorescent materials, the conditions are limited to 0≦x≦1 and 0.5≦a≦1.25, respectively. The excitation spectrum of the divalent metal fluorohalide phosphor of the present invention is almost the same as that of the conventional divalent metal fluorohalide phosphor using only europium as an activator. The body is
It exhibits stimulated luminescence when excited by light with a wavelength of 450 to 800 nm, and within this wavelength range, it exhibits stimulated luminescence.
It exhibits high-intensity stimulated luminescence when excited by light with a wavelength of 700 nm. Next, the radiation image conversion panel of the present invention will be explained. The radiation image conversion panel of the present invention is the above-mentioned radiation image conversion panel of the present invention.
It has a phosphor layer made of a valent metal fluorohalide phosphor. 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 to absorb radiation. It is considered to be an 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 (the surface of the phosphor layer opposite to 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 with 1 part by weight of the divalent metal fluorohalide phosphor of the present invention, and this is horizontally coated using an appropriate coating method. A phosphor layer is formed by coating it on a support placed on a substrate and drying it 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 plastic 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. It is particularly preferable to use a plastic sheet such as film, 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, the phosphor layer is formed by directly applying a coating liquid containing a photostimulable phosphor dispersed in a binder onto the support as described above. Alternatively, a separately formed phosphor 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 produced using only europium as an activator. 2
It exhibits stimulated luminescence with higher brightness than valent 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 has a phosphor film made of a conventional divalent metal fluorohalide phosphor using only europium as an activator. It is more sensitive than a radiation image conversion panel. As described above, the phosphor of the present invention is particularly useful as a phosphor for radiation image conversion panels, but the use of the phosphor of the present invention is not limited to this. That is, the phosphor of the present invention emits near-ultraviolet to blue instantaneous light when excited by ionizing radiation, electron beams, vacuum ultraviolet rays, ultraviolet rays, etc., and therefore can be used in intensifying screens, cathode ray tubes, fluorescent lamps, etc. Can be done. 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 with reference to Examples. Examples 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. (1) BaF ₂ 175.3g (1 mol), BaBr ₂・2H ₂ O333.2
g (1 mol), EuC ₃ 0.052 g (0.0002 mol) and H ₄ SiO ₄ 0.002 g (0.00002 mol) (2) BaF ₂ 166.5 g (0.95 mol), SrF ₂ 6.3 g (0.05
mol), BaBr ₂・2H ₂ O336.4g (1.01 mol),
EuC ₃ 0.077g (0.0003mol) and
H ₄ SiO ₄ 0.002g (0.00002mol) (3) BaF ₂ 166.5g (0.95mol), ZnF ₂ 5.2g (0.05
mol), BaBr ₂・2H ₂ O333.2g (1 mol), EuC
₃ 0.052g (0.0002 mol) and H ₄ SiO ₄ 0.002g
(0.00002 mol) (4) BaF ₂ 166.5 g (0.95 mol), CdF ₂ 7.5 g (0.05 mol)
mol), BaBr ₂・2H ₂ O333.1g (1 mol), EuC
₃ 0.052g (0.0002 mol) and H ₄ SiO ₄ 0.002g
(0.00002 mol) (5) BaF ₂ 168.3 g (0.96 mol), BeF ₂ 1.12 g (0.04 mol)
mol), BaC ₂・2H ₂ O244.2g (1 mol),
EuF ₃ 0.042g (0.0002 mol) and SiO ₂ 0.002g
(0.00003 mol) (6) BaF ₂ 164.8 g (0.94 mol), MgF ₂ 3.7 g (0.06 mol)
mol), BaC ₂・2H ₂ O251.6g (1.03 mol),
EuF ₃ 0.042g (0.0002 mol) and H ₄ SiO ₄ 0.001
g (0.00001 mol) (7) BaF ₂ 168.3 g (0.96 mol), BeF ₂ 1.12 g (0.04
mol), BaBr ₂・2H ₂ O303.1g (0.91 mol),
_BaC2・_2H2O24.4g (0.1mol), _EuF3 0.104g
(0.0005 mol) and H ₄ SiO ₄ 0.002 g (0.00002
Next, each of the above seven types of phosphor raw material mixtures was packed into an aluminium 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. The obtained fired product was pulverized and then passed through a sieve to make the particle size uniform, thereby obtaining a phosphor.
After irradiating each of the seven types of phosphors produced in this way with 80KVp X-rays, the light emitted from a xenon lamp set in a spectrometer (Hitachi spectrophotometer MPF-2A model) was analyzed. These phosphors were excited with 630 nm light and the stimulated luminescence brightness was measured. As a result, the stimulated luminescence brightness of these phosphors was found to be higher than that of conventional europium-activated divalent metal fluorohalide fluorescers prepared using the same method except that no co-activator was used, as shown in the table below. The luminance was significantly higher than the stimulated luminance measured under the same conditions.

[Table] Next, for each of the above seven types of phosphors of the present invention, 8 parts by weight of the phosphor and 1 part by weight of nitrified cotton were mixed using a solvent (mixture of acetone, ethyl acetate, and butyl acetate). A phosphor coating solution with a viscosity of approximately 50 centistokes was prepared. Next, place this coating solution horizontally and apply it evenly onto a polyethylene terephthalate film (support) using a knife coater, and dry at 50°C until the layer thickness is approx.
A phosphor layer with a thickness of 300 μm was formed, and then an acetone solution of cellulose acetate was uniformly applied on the phosphor layer, and dried to form a transparent protective film with a layer thickness of approximately 8 μm. A radiation image conversion panel was fabricated. Separately, for comparison, a radiation image conversion panel was prepared in the same manner as above using the conventional europium-activated divalent metal fluorohalide phosphor. Sensitivity of the radiation image conversion panels of the present invention thus obtained (photosensitivity when excited with He-Ne laser light (633 nm) after irradiating each radiation image conversion panel with X-rays with a tube voltage of 80 KVp) As with the comparison of the stimulated luminance of the phosphors in the table above, the luminance of the conventional europium-activated divalent metal fluorohalide phosphor prepared for comparison The cost was higher than that of a radiation image conversion panel having a light layer.

[Brief explanation of drawings]

FIG. 1 is a rough diagram 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 (1)

[Claims] 1. The compositional formula is (Ba _1-x , M〓x)F ₂ ·aBaX ₂ :yEu,zSi (where M〓 is at least one of beryllium, magnesium, calcium, strontium, zinc, and cadmium) The species, X is at least one of chlorine, bromine and iodine, and a, x, y
and z are 0.5≦a≦1.25, 0≦x≦1, respectively
10 ^-6 ≦y≦2×10 ⁻¹ and 0<z≦5×10 ⁻³ ) A divalent metal fluorohalide phosphor. 2. The divalent metal fluorohalide phosphor according to claim 1, wherein y is a number satisfying the condition 10 ^-5 ≦y≦10 ^-2 . 3. Claim 1, characterized in that the above z is a number that satisfies the condition: 10 ^-7 ≦z≦2×10 ^-3
The divalent metal fluorohalide phosphor according to item 1 or 2. 4 In a radiation image conversion panel having a phosphor layer made of a photostimulable phosphor, the above-mentioned photostimulable phosphor has a compositional formula (Ba _1-x , M〓x)F ₂・aBaX ₂ :yEu, zSi (However, M〓 is at least one of beryllium, magnesium, calcium, strontium, zinc, and cadmium, X is at least one of chlorine, bromine, and iodine, and a, x, y
and z are 0.5≦a≦1.25, 0≦x≦1, respectively
10 ^-6 ≦y≦2×10 ^-1 and 0<z≦5×10 ^-3 ) A radiation image characterized by being made of a divalent metal fluorohalide phosphor. Conversion panel. 5. The radiation image conversion panel according to claim 4, wherein y is a number satisfying the condition 10 ^-5 ≦y≦10 ^-2 . 6 Claim 4, characterized in that the above z is a number satisfying the condition 10 ^-7 ≦z≦2×10 ^-3
5. The radiation image conversion panel according to item 5.