JPS6345433B2 - - 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 compositional formula is (Ba _{1 -x , M〓} at least one of the following, a, x and y are respectively 0.5≦a≦1.25, 0≦x≦1 and
The europium-activated divalent metal fluorohalide phosphor represented by 10 ^-6 ≦y≦2×10 ^-1 is a practical photostimulable phosphor and can be irradiated with radiation. 450~ after absorption
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, JP-A-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). species, X is at least one of chlorine, bromine, and iodine, and x and y are each 0
A divalent metal fluorohalide stimulable phosphor is described, which is a number satisfying the following conditions: ≦x≦0.6 and 0≦y≦2×10 ^-1 . 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, they discovered that if appropriate amounts of arsenic or arsenic and silicon are contained in a phosphor as a co-activator for europium, the luminance of the phosphor due to stimulation can be significantly improved, and the present invention was completed. I came to the conclusion. The divalent _metal fluorohalide phosphor of the present invention has a compositional formula (Ba _{1 -x} , _M〓 At least one of cadmium, X is at least one of chlorine, bromine and iodine, A is arsenic or arsenic and silicon, and a, x, y and z are each 0.5
It is a number that satisfies the following conditions: ≦a≦1.25, 0≦x≦1, 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 phosphor raw materials include (i) barium fluoride (BaF ₂ ), (ii) beryllium fluoride (BeF ₂ ), magnesium fluoride (MgF ₂ ), calcium fluoride (CaF ₂ ), and strontium fluoride (SrF _{2 )} . ), one or more divalent metal fluorides consisting of zinc fluoride (ZnF ₂ ) and cadmium fluoride (CdF ₂ ), (iii) barium chloride (BaCl ₂ ), barium bromine (BaBr ₂ ), iodine Barium chloride (BaI ₂ ), ammonium chloride (NH ₄ Cl), ammonium bromide (NH ₄ Br) and ammonium iodide (NH ₄ I)
(iv) europium chloride (EuCl 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 ], and (v) diarsenic trioxide (As ₂ O ₃ ), diarsenic pentoxide (As ₂ O ₅ ), One or more compounds selected from the group consisting of arsenic compounds such as arsenic chloride (AsCl ₃ ) and arsenic pentachloride (AsCl ₅ ), and silicon compounds such as silicon dioxide (SiO ₂ ) and orthosilicic acid (H ₄ SiO ₄ ); Two or more types are used. The above raw materials for each phosphor are stoichiometrically expressed as (Ba _{1 -x , M〓} at least one, X is at least one of chlorine, bromine and iodine, A is arsenic or arsenic and silicon, a, x, y and z are each 0.5
≦a≦1.25, 0≦x≦1, 10 ^-6 ≦y≦2×10 ^-1 and 0<z≦5×10 ^-3 ) Mix thoroughly using a ball mill, mixer mill, etc. Note that when the x value of the above mixed composition formula is 0, 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 It is essential to use at least barium halide as the phosphor raw material (iii). 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 the fired product out of the electric furnace, pulverizing it, and then firing it again under the same 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 _BaF2, one of the phosphors of the present invention.
This is an example of the emission spectrum of photostimulation when a BaBr ₂ :0.0002Eu, 0.00002As phosphor is irradiated with 80KVp X-rays and then excited with 630nm light. 1st
As is clear from the figure, the divalent metal fluorohalide phosphor of the present invention has an emission spectrum peak at approximately 390 nm, similar to the conventional divalent metal fluorohalide phosphor using only europium as an activator. Shows near-ultraviolet to blue stimulated luminescence. In addition,
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 each phosphor has a wavelength of approximately 390 nm.
It exhibits near-ultraviolet to blue stimulated luminescence and instantaneous luminescence with an emission spectrum peak at . Figure 2 shows _BaF2, one of the phosphors of the present invention.
BaBr ₂ :0.0002Eu, the amount of arsenic (z value) for the zAs phosphor and the emission brightness when this phosphor is irradiated with 80KVp X-rays and then excited with 630nm light to cause photostimulation. It is a graph showing the relationship between In Figure 2, the vertical axis showing the luminescence luminance due to stimulation is expressed as a relative value with the luminance luminance of the conventional BaF ₂ / BaBr ₂ :0.0002Eu phosphor in which arsenic is not coactivated as 100. ing. As is clear from Figure 2, when the amount of europium activation (y value) is constant, the z value is 0<
BaF ₂・ in the range of z≦5×10 ^-3
BaBr ₂ : 0.0002Eu, zAs fluorophore is conventional BaF ₂ .
BaBr ₂ : Shows stimulated luminescence with higher brightness than 0.0002Eu phosphor, and within this range, especially 10 ^-7 ≦z≦2×10 ^-3
In this case, even higher luminance stimulated luminescence is exhibited.
In addition, Figure 2 shows BaF ₂・BaBr ₂ : 0.0002Eu, zAs
This is a graph showing the relationship between the z value and the stimulated luminance for a phosphor, and it shows that when the y value changes and when the co-activator (A) consists of both arsenic and silicon, arsenic and silicon It was confirmed that the relationship between the Z value, which is the total amount of light, and the luminance of photostimulated light has almost the same tendency as shown in FIG. Furthermore, even if the matrix composition changes within the range of the above compositional formula, the relationship between the z value and the stimulable luminance is the second one.
It was confirmed that the trend was almost the same as shown in the figure. 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 . In addition, the range of the amount of M (x value) and the range of _the amount of 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). Further, 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 conversion panel, polyvinyl chloride, polyethylene terephthalate, polymethacrylate, polyvinyl chloride, polyethylene terephthalate, polymethacrylate,
Either a coating solution containing a resin such as cellulose acetate dissolved in an appropriate solvent is applied directly and dried, or a transparent thin film made of these resins is separately formed in advance and adhered to the surface of the phosphor layer. Forms a protective film. 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. I can do it. 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 (8) below, each phosphor raw material was weighed and thoroughly mixed using a ball mill to prepare eight types of phosphor raw material mixtures. (1) BaF ₂ 175.3g (1 mol), BaBr ₂・2H ₂ O
333.2g (1 mol), EuCl ₃ 0.052g (0.0002 mol)
and As ₂ O ₃ 0.002 g (0.00001 mol) (2) BaF ₂ 166.5 (0.95 mol), BeF ₂ 1.4 g (0.05 mol), BaBr ₂ 2H ₂ O 333.2 g (1 mol), EuCl ₃
0.052g (0.0002 mol) and _{0.002g As2O3}
(0.00001 mol) (3) BaF ₂ 166.5g (0.95 mol), MgF ₂ 3.1g (0.05 mol), BaBr ₂・2H ₂ O 333.2g (1 mol), EuCl ₃
0.052g (0.0002 mol) and _{0.002g As2O3}
(0.00001 mol) (4) BaF ₂ 166.5g (0.95 mol), CaF ₂ 3.9g (0.05 mol), BaBr ₂・2H ₂ O 336.4g (1.01 mol), EuCl ₃
0.052g (0.0002 mol) and _{0.002g As2O3}
(0.00001 mol) (5) BaF ₂ 175.3g (1 mol), BaCl ₂・2H ₂ O
244.2g (1 mol), EuF ₃ 0.042g (0.0002 mol) and AsCl ₃ 0.004g (0.00002 mol) (6) BaF ₂ 166.5g (0.95 mol), SrF ₂ 6.3g (0.05 mol), BaCl _{2.2H 2} O 249.1g (1.02mol), _EuCl3
0.077g (0.0003 mol) and 0.002g _AsCl3
(0.00001 mol) (7) BaF ₂ 175.3g (1 mol), BaBr ₂・2H ₂ O
319.6g (0.96 mol), _{BaI2.2H2O 21.6g} (0.05 mol), _EuCl3 0.129g (0.0005 mol) and _AsCl3
0.004g (0.00002mol) (8) BaF ₂ 164.8g (0.94mol), MgF ₂ 3.7g (0.06mol), BaBr ₂・2H ₂ O 322.8g (0.969mol),
_BaI2・_2H2O 21.8g (0.051mol), _EuF3 0.104g
(0.0005 mol) and As ₂ O ₃ 0.002 g (0.00001 mol) Next, each of the above eight types of phosphor raw material mixtures was packed into an alumina crucible and placed in an electric furnace, and 2% The other phosphor raw material mixtures were fired at a temperature of 850°C in a carbon oxide gas atmosphere for 3 hours. 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 eight types of phosphors manufactured 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 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. The stimulated luminance was significantly higher than that measured under the same conditions.

[Table] Relative values are shown.
Next, for each of the above eight 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) until the viscosity was approximately A 50 centistoke phosphor coating solution was prepared. Next, this coating solution was applied uniformly onto a horizontally placed polyethylene terephthalate film (support) using a knife coater, and dried at 50°C until the layer thickness was 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 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 (1)

[Claims] 1. _The compositional formula is (Ba _{1 -x} , _M〓
is at least one of beryllium, magnesium, calcium, strontium, zinc and cadmium, X is at least one of chlorine, bromine and iodine, A is arsenic or arsenic and silicon, and a, x, y and z are 0.5≦a≦, respectively.
1.25, 0≦x≦1, ^{10 -6} ≦y≦2×10 ^-1 and 0
A divalent metal fluorohalide phosphor represented by <z≦5×10 ^-3 . 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 photostimulable phosphor has a composition formula (Ba _1-x , M〓 _x ) F ₂ ·aBaX ₂ :yEu, zA (However, M〓
is at least one of beryllium, magnesium, calcium, strontium, zinc and cadmium, X is at least one of chlorine, bromine and iodine, A is arsenic or arsenic and silicon, and a, x, y and z are 0.5≦a≦, respectively.
1.25, 0≦x≦1, ^{10 -6} ≦y≦2×10 ^-1 and 0
A radiation image conversion panel comprising a divalent metal fluorohalide phosphor represented by <z≦5×10 ^-3 . 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.