JPS6230237B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a radiation image conversion method, and more particularly to a radiation image conversion method using a photostimulable phosphor. Conventionally, to obtain a radiation image as an image, a photographic film having an emulsion layer made of a silver salt photosensitive material and an X
The so-called radiographic method that uses a line-intensifying screen is used, and it is one of the radiographic image conversion methods that can obtain a radiographic image with superior image sharpness and resolution than the radiographic method obtained with this method. as U.S. Patent No. 3859527, U.S. Patent No. 4236264, and JP
The methods described in Publications No. 55-163472 and No. 55-116340 are attracting attention. This radiation image conversion method uses a storage phosphor (a phosphor that emits light when excited with electromagnetic waves selected from visible light and infrared rays after being irradiated with radiation. Here, radiation refers to X-rays, α
Electrode waves or particle beams such as rays, β rays, γ rays, high-energy neutron beams, electron beams, vacuum ultraviolet rays, and ultraviolet rays. ), the radiation transmitted through the subject is absorbed by a stimulable phosphor, and then the stimulable phosphor is excited with electromagnetic waves selected from visible light and infrared rays, and the stimulable phosphor is accumulated. This radiation energy is emitted as fluorescence (stimulated luminescence), and this fluorescence is detected and imaged. Conventionally, one type of fluorohalide fluorophore has the following formula: BaFX: aEu ²⁺ (where X is at least one of Cl, Br, and I).
is a seed, and a is a number that satisfies the condition 0<a≦0.2. ) A divalent europium-activated barium fluoride halide phosphor is known. This phosphor emits high-intensity near-ultraviolet light (instantaneous light emission) when excited by X-rays, ultraviolet rays, electron beams, etc., and has been put to practical use, especially as a phosphor for X-ray intensifying screens. This phosphor also exhibits high brightness exhaustible luminescence. After being irradiated with radiation, this phosphor has a temperature of 450 to
When excited by electromagnetic waves in the 1100 nm wavelength range, it emits high-intensity near-ultraviolet light. This phosphor can therefore be used in the radiation image conversion method described above (see US Pat. No. 4,239,968). By the way, when the above-mentioned radiation image conversion method is used for X-ray image conversion for the purpose of medical diagnosis, it is desirable that the method be as sensitive as possible in order to reduce the radiation dose to the patient. It is desirable that the stimulable phosphor used has as high a luminance as possible due to stimulation. From this point of view, it is desired to improve the sensitivity of the radiation image conversion method using the BaFX:Eu ²⁺ phosphor described above, and therefore, it is desirable to improve the luminance due to the stimulation of the BaFX:Eu ²⁺ phosphor. Improvements are desired. The present invention was made under the above-mentioned circumstances, and by using a phosphor that has higher emission brightness due to stimulation than the BaFX:Eu ²⁺ phosphor described above as a stimulable phosphor. , BaFX: The purpose of the present invention is to provide a radiation image conversion method that is more sensitive than a radiation image conversion method that uses Eu ²⁺ phosphor. In order to achieve the above purpose, the inventors
BaFX: We have conducted various studies on improving the luminance of Eu ²⁺ fluorophores through photostimulation. the result,
BaFX: Consists of barium fluoride halide (BaFX), which is the base material of Eu ²⁺ fluorophore, and sodium halide (NaX', where X' is at least one of Cl, Br, and I). A new phosphor that has a complex halide as a matrix and activates this matrix with divalent europium can be used after being irradiated with radiation.
They discovered that when excited by electromagnetic waves in the wavelength range of 450 to 1100 nm, they emit near-ultraviolet light with higher brightness than conventional BaFX:Eu ²⁺ phosphors, leading to the completion of the present invention. The radiation image conversion method of the present invention is performed using the following formula, BaFX・xNaX′:aEu ²⁺ (where X and X′ are both at least one of Cl, Br, and I, and x and a are each 0< x≦2 and 0<a≦0.2) A stimulable phosphor containing a divalent europium-activated composite halide phosphor represented by x≦2 and 0<a≦0.2 absorbs the radiation transmitted through the subject, After that, this phosphor
It is characterized in that it is excited by electromagnetic waves in the wavelength range of 450 to 1100 nm to cause the phosphor to emit the accumulated radiation energy as a phosphor, and then detect this phosphor. The above 2 used in the radiation image conversion method of the present invention
Similar to the conventional BaFX:Eu ²⁺ phosphor, the europium-activated composite halide phosphor emits near-ultraviolet light when excited with electromagnetic waves in the wavelength range of 450 to 1100 nm after being irradiated with radiation such as X-rays. Although it exhibits luminescence, the luminance of this stimulated luminescence is higher than that of BaFX:Eu ²⁺ fluorophore. Therefore, the radiation image conversion method of the present invention uses BaFX:
It is more sensitive than radiation image conversion methods using Eu ²⁺ fluorophores. Among the divalent europium-activated composite halide phosphors mentioned above, those whose x value in the above formula is in the range of 10 ^-5 ≦x≦5×10 ^-1 have particularly high emission brightness due to stimulation. , therefore the radiation image conversion method of the invention using a phosphor with an x value in this range is particularly sensitive. In addition, among NaX', NaI and NaBr have particularly high emission brightness due to photostimization.
Furthermore, it is particularly preferable to use NaI because the degree to which the accumulated radiation energy decreases over time before excitation (hereinafter referred to as fading) can be reduced. Also, the preferable range of a value in the above formula is 10 ^-5 ≦a≦
10 ^-1 . The present invention will be explained in detail below. The divalent europium-activated composite halide phosphor used in the radiation image conversion method of the present invention is manufactured, for example, by the manufacturing method described below. First, the phosphor raw material includes at least one of (i) barium fluoride (BaF ₂ ), (ii) barium chloride (BaCl ₂ ), barium bromide (BaBr ₂ ), and barium iodide (BaI ₂ ); (iii) at least one of sodium chloride (NaCl), sodium bromide (NaBr) and sodium iodide (NaI), and (iv) compounds of trivalent europium such as halides, oxides, nitrates, sulfates, etc. is used. Using these four phosphor raw materials, the phosphor raw material is stoichiometrically expressed by the formula BaFX・xNaX′:aEu ³⁺ (where X, X′, x and a have the same meanings as above) Prepare the mixture. The phosphor raw material mixture may be prepared by simply mixing the above four phosphor raw materials, or it may be prepared in advance by preparing BaFX using BaF ₂ from (i) above and barium halide from (ii) above. It may be prepared by producing BaFX, and then mixing the above-mentioned (iii) sodium halide and the above-mentioned (iv) activator raw material with this BaFX. In the latter method for preparing a phosphor raw material mixture, various known methods are employed to generate BaFX from BaF ₂ and barium halide. For example, BaFX can be easily produced by mixing BaF ₂ and barium halide and heating the resulting mixture at a temperature of 100°C or higher for several hours (dry method, Japanese Patent Publication No. 1973-
(See No. 28591). BaFX can also be easily produced by adding a barium halide solution to a BaF ₂ suspension, stirring the mixture while heating, preferably under reduced pressure, and gradually evaporating the water to dryness. (Wet method, see JP-A-51-61499). In addition, in both the dry method and wet method above,
By intervening an activator raw material in the reaction system
Uniform mixing of BaFX and the activator raw material can also be achieved simultaneously with the production of BaFX. In any method for preparing a phosphor raw material mixture, BaF ₂ , barium halide, sodium halide, and activator raw material, or BaFX, sodium halide, and activator raw material are thoroughly mixed. Mixing is carried out using a conventional mixer such as a mortar, ball mill, or rod mill. Next, the obtained phosphor raw material mixture was placed in a quartz boat.
It is filled into a heat-resistant container such as an aluminum crucible or quartz crucible and fired in an electric furnace. Firing temperature is 600
A temperature of 1000°C to 1000°C is suitable. The firing time varies depending on the filling amount of the phosphor raw material mixture, firing temperature, etc.
Generally, 1 to 6 hours is appropriate. A weakly reducing atmosphere such as a nitrogen gas atmosphere containing a small amount of hydrogen gas or a carbon dioxide atmosphere containing a small amount of carbon monoxide is used as the firing atmosphere, thereby reducing trivalent europium to divalent europium during the firing process. do. After firing once under the above firing conditions, the fired product is taken out of the electric furnace, left to cool, and pulverized.The fired product powder is then filled into a heat-resistant container again, placed in the electric furnace, and fired under the same firing conditions as above. Re-firing may be performed. In this case, a neutral atmosphere such as a nitrogen gas atmosphere or an argon gas atmosphere may be used instead of the weakly reducing atmosphere as the firing atmosphere. After firing, the resulting fired product is loosened and treated by various operations commonly employed in the production of phosphors, such as sieving, to obtain the phosphor of the present invention. The following formula obtained by the manufacturing method described above, BaFX・xNaX′:aEu ²⁺ (where X and X′ are both at least one of Cl, Br and I, and x and a are each The divalent europium-activated composite halide phosphor expressed ^by After being irradiated with radiation such as X-rays
When excited by electromagnetic waves in the 1100 nm wavelength range, it emits near-ultraviolet light. The brightness of the luminescence due to the photoexcitation is higher than that of BaFX:Eu ²⁺ fluorophore. Therefore, the radiation image conversion method of the present invention using this phosphor is
BaFX: More sensitive than radiographic image conversion methods using Eu ²⁺ fluorophores. Figure 1 illustrates the excitation spectrum of the divalent europium-activated composite halide phosphor used in the radiation image conversion method of the present invention, using a sample irradiated with X-rays at a tube voltage of 80 KVp. BaFBr・10 ^-3 NaBr measured by:
This is the excitation spectrum of 10 ^-3 Eu ²⁺ fluorophore. 1st
As is clear from the figure, BaFBr・^10-3 NaBr:
The excitation wavelength range of 10 ^-3 Eu ²⁺ fluorophore is from 450 to
The optimum excitation wavelength range is 1100 nm, particularly 450 to 750 nm. The excitable wavelength range of the divalent europium-activated composite halide phosphor used in the radiation image conversion method of the present invention varies slightly depending on the composition of the phosphor, but is generally shown in FIG. The optimum excitation wavelength range is 450 to 1100 nm, which is almost the same as the results obtained in the previous study. In this range, the phosphor can be excited without substantially increasing its temperature. This excitable wavelength range and optimal excitation wavelength range almost match the excitable wavelength range and optimal excitation wavelength range of BaFX:Eu ²⁺ fluorophore. ^Figure 2 illustrates the emission spectrum due to stimulation of the divalent europium-activated composite halide phosphor used ⁱⁿ the radiation image conversion method of the present invention. After irradiating the Eu ²⁺ phosphor with X-rays at a tube voltage of 80 KVp, the phosphor was exposed to He
This is an emission spectrum measured by excitation with -Ne laser light (633 nm). The composition of the divalent europium-activated composite halide phosphor used in the radiation image conversion method of the present invention differs slightly depending on the composition of the phosphor, but the composition of the divalent europium-activated composite halide phosphor used in the radiation image conversion method of the present invention is as shown in FIG. Shows near-ultraviolet light emission. And the emission spectrum due to stimulation of the composite halide phosphor is
BaFX: Almost the same as the emission spectrum due to stimulation of Eu ²⁺ fluorophore. Figures 3 and 4 show BaFBr・
xNaBr: 10 ^-3 Eu ²⁺ fluorophore and BaFCl xNaBr:
10 ^-3 After irradiating Eu ²⁺ phosphors with X-rays with a tube voltage of 80 KVp, they were exposed to a He−Ne laser (633n
m) is the host component of the fluorophore when excited by
This is a graph showing the relationship between the amount x value of NaBr (horizontal axis ⁾ and the luminescence brightness due to photostimulation ( ^vertical axis). It is expressed as a relative value when the emission brightness is set ^to 100, and the vertical axis in ^FIG .
As is clear from FIGS. 3 and 4, the BaFBr/xNaBr:10 ^-3 Eu ²⁺ phosphor and BaFCl・xNaBr: 10 ^-3 Eu ²⁺ fluorophore has an x ^value of 0 ^.
BaFCl: Shows stimulated luminescence with higher brightness than 10 ^-3 Eu ²⁺ phosphor. Furthermore, the x value is in the range of 10 ^{-5 ≦} x≦5×10 ^-1 for both BaFBr・xNaBr: 10 ⁻³ Eu ²⁺ fluorophore and BaFCl・xNaBr: 10 −3 Eu ²⁺ fluorophore. Fluorescent materials have particularly high luminance. Furthermore, Figures 3 and 4 show the relationship between the x value and the emission brightness due to stimulation for BaFBr/xNaBr: 10 ^-3 Eu ²⁺ phosphor and BaFCl/xNaBr: 10 ^-3 Eu ²⁺ phosphor, respectively. Although the relationship is shown, x also applies to BaFBr・xNaI: 10 ^-3 Eu ²⁺ fluorophore BaFCl・xNaI: 10 ^-3 Eu ²⁺ fluorophore with different sodium halide base components.
The relationship between the value and the emission brightness due to photosensitivity is the third
It was almost the same as Fig. 4. Also
BBaFBr・xNaCl: 10 ^-3 Eu ²⁺ , BaFCl・xNaCl:
The relationship between the x value of the 10 ^-3 Eu ²⁺ phosphor and the luminance due to photostimulation is not as convex upward as the curves in Figures 3 or 4, but the luminance due to stimulation is 10 ^-5 ~2. showed a relationship that improves Furthermore, Figures 3 and 4 both show the relationship between the x value and the luminescence brightness due to photostimulation for a phosphor with an Eu ²⁺ content a value of 10 ^-3 , but when the a value changes It was confirmed that the relationship between the x value and the emission brightness due to photostimulation for the phosphors obtained was similar to that shown in FIGS. 3 and 4. The radiation image conversion method of the present invention will be specifically explained using schematic diagrams. In FIG. 5, 11 is a radiation generating device, 12 is a subject, 13 is a radiation image conversion panel having a stimulable phosphor layer containing the divalent europium-activated composite halide phosphor, and 14
15 is a light source as an excitation source for emitting the radiation latent image accumulated in the radiation image conversion panel as fluorescence; 15 is a photoelectric conversion device for detecting the fluorescence emitted from the radiation image conversion panel; 16 is a photoelectric conversion device for detecting the fluorescence emitted from the radiation image conversion panel; 15 is a device for reproducing the detected photoelectric conversion signal as an image; 17 is a device for displaying the reproduced image; 18
is a filter for cutting off the reflected light from the light source 14 and allowing only the light emitted from the radiation image conversion panel 13 to pass through. From 15 onwards, it is sufficient that the optical information from 13 can be reproduced as a drawing line in some form, and is not limited to the above. As shown in FIG. 5, when the subject 12 is placed between the radiation generating device 11 and the radiation image conversion panel 13 and radiation is irradiated, the radiation is transmitted to the subject 12.
The radiation is transmitted as the radiation transmittance of each part changes, and the transmitted image (that is, the image of the intensity of the radiation) is incident on the radiation image conversion panel 13. This incident transmitted image is absorbed by the stimulable phosphor layer of the radiation image conversion panel 13, thereby generating a number of electrons or holes in proportion to the amount of radiation absorbed in the phosphor layer, This accumulates at the trap level of the stimulable fluorophore. That is, an accumulated radiographic image (a kind of latent image) is formed. This latent image is then excited with light energy to become visible. That is, the excitation light emitted from the light source 14 scans the stimulable phosphor of the radiation image conversion panel 13 to expel the electrons or holes accumulated at the trap level, causing the accumulated image to be emitted as fluorescent light. As mentioned above, the excitable wavelength range of the divalent europium-activated composite halide phosphor used in the stimulable phosphor layer of the radiation image conversion panel 3 is 450 to 1100 nm, and the optimum excitation wavelength is Range is 150 to
Since it is 750nm, the excitation light is 450nm to 450nm.
Electromagnetic waves with a wavelength of 1100 nm, preferably between 450 and 750 nm are used. This range (450~750n
In case of m), since the stimulable phosphor layer can be excited without substantially increasing its temperature, deterioration of the phosphor and the phosphor layer due to temperature changes can be prevented. The intensity of the fluorescence emitted from the stimulable phosphor layer upon excitation by the excitation light is determined by the number of accumulated electrons or holes, that is, the number of radiation absorbed by the stimulable phosphor layer of the radiation image conversion panel 13. It is proportional to the strength of energy, and this optical signal is converted into an electrical signal by a photoelectric conversion device 15 such as a photomultiplier tube,
The image reproduction device 16 reproduces the image as an image, and the image display device 17 displays this image. The radiation image conversion panel used in the radiation image conversion method of the present invention has a stimulable phosphor layer containing the divalent europium-activated composite halide phosphor dispersed in a suitable binder. If the stimulable phosphor layer is self-supporting, the stimulable phosphor layer itself can serve as a radiation image storage panel, but generally the stimulable phosphor layer is provided on a suitable support. A radiation image conversion panel is constructed. Furthermore, a protective film is usually provided on one side of the stimulable phosphor layer (the side opposite to the side on which the support is provided) for physically or chemically protecting the phosphor layer. Further, an undercoat layer may be provided between the phosphor layer and the support for the purpose of more closely adhering the stimulable phosphor layer and the support. Note that the radiation image conversion method panel having the above structure may be colored with a coloring agent as disclosed in JP-A-55-163500 (if the stimulable phosphor layer is not colored). (In cases where the excitation light is incident on the excitation light incident side, it is preferable that the degree of coloring is gradually increased from the excitation light incident side to the opposite side. xNaX': in addition to the aEu ²⁺ fluorescein, optionally 450 of the known storage fluorescers.
A stimulable phosphor that emits light by stimulation with electromagnetic waves in the wavelength range of ~1100 nm may be used in combination. Preferred known storage phosphors for use in combination include rare earth-activated lanthanum oxyhalide phosphors described in JP-A No. 55-12144 and U.S. Pat. No. 4,236,078.
No., JP-A No. 55-12143, No. 55-12145, No. 55-
No. 84389, No. 56-2385, No. 56-2386, No. 56-
Examples include rare earth-activated alkaline earth metal fluorohalide phosphors described in No. 74175 and the like. Further, white powder may be dispersed in the stimulable phosphor layer of the radiation image storage panel as disclosed in Japanese Patent Application Laid-Open No. 146447/1983. Furthermore, the radiation image conversion panel was published in Japanese Patent Application Laid-Open No. 56-11393 or
56-12600, a metal reflective layer or a white pigment reflective layer may be provided on the side of the stimulable phosphor layer opposite to the excitation light incident side.
By using a colorant or white powder in this manner and by providing a light reflecting layer, a radiation image conversion panel that provides images with high sharpness can be obtained. In the radiation image conversion method of the present invention, the light source for the light energy that excites the stimulable phosphor layer of the radiation image conversion panel may be other than a light source that emits light with a banded spectral distribution in the wavelength range of 450 to 1100 nm. He-Ne laser light (633nm),
A light source that emits light of a single wavelength, such as YAG laser light (1064 nm), ruby laser light (694 nm), or argon laser light (488 nm), is used. Particularly when using laser light, high excitation energy can be obtained. Among laser beams, especially He
It is more preferable to use −Ne laser light. As explained above, the divalent europium-activated composite halide phosphor used in the radiation image conversion method of the present invention has higher emission brightness due to stimulation than the conventional BaFX:Eu ²⁺ phosphor. . Therefore, the radiation image conversion method of the present invention is more sensitive than the radiation image conversion method using only BaFX:Eu ²⁺ fluorophore. Next, the present invention will be explained with reference to Examples. Example 1 BaF ₂ 175.5 g (1 mol), BaBr ₂ 297.1 g (1 mol), NaBr 0.206 g (2 × 10 ^-3 mol) and
0.783 g (2×10 ⁻³ mol) of EuBr ₃ was weighed out and thoroughly mixed using a ball mill. The obtained phosphor raw material mixture was filled into a quartz boat, placed in a tube furnace, and fired. Firing was performed at 900℃ while flowing nitrogen gas containing 1% by volume of hydrogen gas at a flow rate of 280c.c./min.
It lasted two hours. After firing, the quartz boat was taken out of the tube furnace and allowed to cool to room temperature. After the obtained fired product was pulverized using a ball mill, the fired product powder was again filled into a quartz boat and placed in a tube furnace for secondary firing. The secondary firing was carried out at 700° C. for 1 hour while flowing nitrogen gas at a flow rate of 280 c.c./min. After the secondary firing, the quartz boat was taken out from the tube furnace and allowed to cool to room temperature, and the resulting fired product was loosened and passed through a sieve. In this way, BaFBr・
10 ^-3 NaBr:10 ^-3 Eu ²⁺ fluorophore was obtained. Also, instead of NaBr, 0.117 g of NaCl (2×10 ^-3
mol) and 0.30 g (2 x 10 ^-3 mol) of NaI, respectively.
BaFBr・10 ^-3 NaCl: 10 ^-3 Eu ²⁺ fluorophore and
A BaFBr.10 ^-3 NaI:10 ^-3 Eu ²⁺ phosphor was produced.
Furthermore, a BaFBr·10 ⁻³ Eu ²⁺ phosphor was produced in the same manner as described above except that NaBr was not used. Next, a radiation image storage panel was manufactured using the four types of phosphors described above. Both radiation image storage panels were manufactured as follows. First, 8 parts by weight of the phosphor and 1 part by weight of nitrified cotton (binder) were mixed using a solvent (mixture of acetone, ethyl acetate, and butyl acetate) to prepare a coating solution having a viscosity of approximately 50 centistokes. Next, this coating solution was uniformly coated on a horizontally placed polyethylene terephthalate film (support), and left to dry naturally overnight to form a phosphor layer with a layer thickness of about 300 μm, and a radiographic image was formed. It was made into a conversion panel. Next, the luminescence brightness due to stimulation of the four types of radiation image conversion panels obtained was measured. Measurement of luminescence brightness due to this photostimulation involves applying a tube voltage to the radiation image conversion panel.
After irradiating with 80KVp X-rays, this is excited with He-Ne laser light (633nm), and the fluorescence emitted from the phosphor layer is detected by a photoreceiver (photomultiplier tube with spectral sensitivity S-5). This was done by receiving light. BaFBr・10 ^-3 NaBr: 10 ^-3 EU ²⁺ fluorophore,
BaFBr・10 ^-3 NaCl: 10 ^-3 Eu ²⁺ fluorophore and
All radiation image conversion panels using BaFBr・10 ^-3 NaI phosphor have luminance due to stimulation of BaFBr:
10 ^-3 This was approximately twice as high as that of a radiation conversion panel using Eu ²⁺ phosphor. The detailed numerical values are shown in Table 1 below. Therefore, the radiation image conversion method of the present invention using these radiation image conversion panels is based on BaFBr: 10 ^-3 Eu ²⁺
The sensitivity is approximately twice as high as that of a radiation image conversion method using a radiation conversion panel using only phosphors. Example ₂ 175.3 g (1 mol) of BaF 2 as a phosphor raw material,
BaCl ₂ 208.2g (1 mol), NaCl 0.117g (2×10 ^-3
_BaFCl ^.
10 ^-3 NaCl: 10 ^-3 Eu ²⁺ fluorophore was produced. Also
^{BaFCl .}
10 ^-3 NaBr: 10 ^-3 Eu ²⁺ fluorophore and BaFCl.
A 10 ^-3 NaI:10 ^-3 Eu ²⁺ fluorophore was produced. moreover
Same as above except without using NaCl.
A BaFCl:10 ^-3 Eu ²⁵ fluorophore was prepared. Next, Example 1 was carried out using the four types of phosphors obtained.
A radiation image conversion panel was manufactured in the same manner as described above. Thereafter, the luminescence brightness due to stimulation of the four types of radiation image conversion panels obtained was measured in the same manner as in Example 1. BaFCl・10 ^-3 NaCl: 10 ^-3 Eu ²⁺ fluorophore, BaFCl・
10 ^-3 NaBr: 10 ^-3 Eu ²⁺ fluorophore and BaFCl.
10 ^-3 NaI: 10 ^-3 The radiation image conversion panel using Eu ²⁺ phosphor has an emission brightness due to stimulation of 10 -3 NaI: 10 -3 BaFCl:
It was more than twice as strong as a radiation image conversion panel using a 10 ^-3 Eu ²⁺ phosphor. The detailed numerical values are shown in Table 1 below. Therefore, the radiation image conversion method of the present invention using these radiation image conversion panels uses BaFCl:
It is more than twice as sensitive as a radiation image conversion method that uses a radiation image conversion panel that uses only 10 ^-3 Eu ²⁺ phosphors. Example 3 61.7g (0.6 mol) and 247.0g of NaBr, respectively
BaFBr/0.3NaBr:
A 10 ^-3 Eu ²⁺ phosphor, a BaFBr.1.2NaBr:10 ^-3 Eu ²⁺ phosphor, and a BaFBr.2.4NaBr:10 ^-3 Eu ²⁺ phosphor were produced. Next, Example 1 was carried out using the three types of phosphors obtained.
A radiation image conversion panel was manufactured in the same manner as described above. Thereafter, the luminescence brightness due to stimulation of the three types of radiation image conversion panels obtained was measured in the same manner as in Example 1. As shown in Table 1 below, BaFBr・
0.3NaBr: 10 ^-3 Eu ²⁺ fluorophore and BaFBr・
The radiation image conversion panel using the 1.2NaBr: 10 ^-3 Eu ²⁺ phosphor has an emission brightness due to stimulation that is as high as that of Example 1.
BaFBr: About 1.7 times and about 1.2 times, respectively, of the radiation image conversion panel using 10 ^-3 Eu ²⁺ phosphor, but BaFBr and 2.4NaBr: which have a higher amount of NaBr:
The radiation image conversion panel using the 10 ^-3 Eu ²⁺ phosphor has an emission brightness due to stimulation of BaFBr of Example 1:
It was about 0.7 times that of a radiation image conversion panel using 10 ^-3 Eu ²⁺ phosphor. Therefore, BaFBr・0.3NaBr:
10 ^-3 Eu ²⁺ fluorophore and BaFBr/1.2NaBr:
The radiation image conversion method of the present invention using a radiation image conversion panel using a 10 ^-3 Eu ²⁺ phosphor is BaFBr:
10 ^-3 compared to a radiation image conversion method using a radiation image conversion panel using only Eu ²⁺ fluorophores.
It is 1.7 times and approximately 1.2 times more sensitive, but BaFBr・
2.4NaBr: A radiation image conversion method using a radiation image conversion panel using a 10 ^-3 Eu ²⁺ phosphor is BaFBr:
The sensitivity is approximately 30% lower than the radiation image conversion method that uses a radiation image conversion panel that uses only 10 ^-3 Eu ²⁺ phosphors.

【table】

【table】 [Brief explanation of the drawing]

Figures 1 and 2 respectively show BaFBr and 10 ^-3 NaBr used in the radiation image conversion method of the present invention.
These are the excitation spectrum and the emission spectrum due to exhaustion of the 10 ^-3 Eu ²⁺ fluorophore. Figures 3 and 4
The figure shows BaFBr・xNaBr: 10 ^-3 Eu ²⁺ and BaFCl・
xNaBr: 10 ^-3 It is a graph showing the relationship between the x value of NaBr amount and the emission brightness due to photostimulation in a Eu ²⁺ phosphor. FIG. 5 is a schematic explanatory diagram of the radiation image conversion method of the present invention. 11...Radiation generating device, 12...Subject, 1
3... Radiation image conversion panel, 14... Light source, 15
...Photoelectric conversion device, 16...Image reproduction device, 17
...Image display device, 18...Filter.

Claims (1)

[Claims] Linear formula BaFX・xNaX′:aEu ²⁺ (where X and X′ are each at least one of Cl, Br, and I, and x and a are each 0<x≦2 The radiation transmitted through the object is absorbed by a stimulable phosphor containing a divalent europium-activated composite halide phosphor expressed as 0<a≦0.2; fluorescent material
1. A radiation image conversion method characterized by exciting with electromagnetic waves in a wavelength range of 450 to 1100 nm to cause a phosphor to emit accumulated radiation energy as fluorescence, and detecting this fluorescence.