JPS61228400A - Radiation image conversion method and radiation image conversion panel image conversion used therein - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a radiation image conversion method and a radiation image conversion panel used in the method. More specifically, the present invention relates to a radiation image conversion method using a photostimulable bismuth-activated alkali metal halide phosphor, and a radiation image conversion panel used in the method.

[Technical Background of the Invention and Prior Art] Conventionally, as a method of obtaining a radiation image as an image, a combination of a radiographic film having an emulsion layer made of a silver salt photosensitive material and an intensifying screen is used. , a so-called radiographic method is used. As one of the methods to replace the above-mentioned conventional radiography method, for example,
A radiation image conversion method using a stimulable phosphor as described in Japanese Patent No. 12145 is known. In this method, radiation transmitted through the subject or radiation emitted from the subject is absorbed into a stimulable phosphor, and then the phosphor is exposed to electromagnetic waves (excitation light) such as visible light or infrared rays in a time-series manner. By exciting the phosphor, the radiation energy stored in the phosphor is emitted as fluorescence (stimulated luminescence), this fluorescence is read photoelectrically to obtain an electrical signal, and this electrical zero signal is converted into an image. be.

The radiation image conversion method has the advantage that it is possible to obtain an X-ray image with a rich amount of information with a much lower exposure dose than when conventional radiography is used. Therefore, this radiation image conversion method has a very high utility value especially in direct medical radiography such as X-ray photography for the purpose of medical diagnosis.

As a stimulable phosphor used in the above radiation image conversion method, JP-A-55-12145 discloses a rare earth element-activated alkaline earth metal fluoride halide phosphor represented by the following composition formula: .

CBat-x, M”,) FX: yA (However, M2
+ is at least one of Mg, Ca, S r, Zn, and Cd;
At least one of r, Ho, Nd, Yb, and Er, where X is 0≦X≦0.6, and y is O≦y≦0
．． 2) After absorbing radiation such as X-rays, this phosphor emits light in the near-ultraviolet region (stimulated luminescence) when irradiated with electromagnetic waves in the visible light to infrared region.

As mentioned above, the above rare earth element-activated alkaline earth metal halide phosphors have been known as phosphors used in radiation image conversion methods that utilize stimulable phosphors, but they exhibit photostimulability. Not much is known about the phosphor itself other than this rare earth element-activated alkaline earth metal/X-halogenide phosphor.

[Summary of the Invention] The present invention is based on the invention of a novel stimulable phosphor, and provides a radiation image conversion method and a radiation image conversion panel using the stimulable phosphor.

That is, one object of the present invention is to provide a radiation image conversion method using a novel stimulable phosphor, and a radiation image conversion panel used in the method.

The present inventors have conducted various studies with the aim of searching for stimulable phosphors. As a result, the novel bismuth-activated alkali metal halide phosphor represented by the following compositional formula (I) exhibits stimulated luminescence, that is, the phosphor can be used for X-rays, ultraviolet rays, electron beams, γ-rays, α-rays, β-rays, It was discovered that stimulated luminescence occurs in the near-ultraviolet to blue region when irradiated with radiation such as radiation and then excited with electromagnetic waves in the visible to infrared region of 450 to 900 nm, and based on this knowledge, the present invention was completed. It has come to this.

Composition formula (I): % formula % () (where Ml is at least one alkali metal selected from the group consisting of Rh and C8; X is C1, B
(at least one kind of halogen selected from the group consisting of r and I; and X is a numerical value in the range of 0<x≦0.2). After the radiation emitted from the subject is absorbed by the bismuth-activated alkali metal halide phosphor represented by the above composition formula (I), this phosphor is irradiated with electromagnetic waves in the wavelength range of 450 to 900 nm. In particular, in the radiation-image conversion method of the present invention, which is characterized in that the radiation energy stored in the phosphor is emitted as fluorescence and this fluorescence is detected, Ml in the compositional formula (I) is Cs. Particularly high sensitivity can be obtained when certain phosphors are used.

Further, the radiation image storage panel of the present invention substantially comprises a support and at least one phosphor layer formed on the support and comprising a binder containing and supporting the stimulable phosphor in a dispersed state. It is characterized in that at least one of the phosphor layers contains a bismuth-activated alkali metal halide phosphor represented by the above compositional formula (I).

[Structure of the Invention] FIG. 1 illustrates the stimulated excitation spectrum of the bismuth-activated alkali metal halide phosphor used in the radiation image conversion method of the present invention.
, 2 and 3 are CsC1:Bi phosphor and CsB, respectively.
These are photostimulation excitation spectra of r:Bi phosphor and CsI:Bi phosphor.

It can be seen from the IT diagram that the phosphor used in the present invention exhibits stimulated luminescence when excited with electromagnetic waves in the wavelength range of 450 to 900 nm after irradiation with radiation. Furthermore, from FIG. 1, the position of the maximum peak of the photostimulation excitation spectrum of the phosphor used in the present invention is determined by the X of CsX constituting the matrix of the phosphor being CM (curve 1), Br (curve 2) and engineered, respectively. (Curve 3), it can be seen that the latter is on the longer wavelength side, and in particular, phosphors in which X is I are efficiently excited by infrared rays such as semiconductor laser light. In the radiation image conversion method of the present invention, the wavelength of the electromagnetic wave used as excitation light is 450~
It is based on this fact that the wavelength is defined as 900 nm.

FIG. 2 illustrates the stimulated emission spectrum of the bismuth-activated alkali metal halide phosphor used in the radiation image conversion method of the present invention.
．． 2 and 3 are the stimulated emission spectra of the above c7) CsCJl:Bi phosphor, CsBr:Bi phosphor and CsI:Bi phosphor, respectively.

As is clear from the fJS2 diagram, the phosphor used in the present invention exhibits stimulated luminescence in the near ultraviolet to blue region, and the peak of its stimulated luminescence spectrum is in the wavelength region of about 350 to 450 nm. Therefore, in the radiation image conversion method of the present invention, when the phosphor is excited with electromagnetic waves in the wavelength range of 500 to 850 nm after radiation irradiation, it is easy to separate the stimulated luminescence and the excitation light, and the phosphor is Stimulated luminescence results in high brightness. Moreover, from FIG. 2, the position of the maximum peak of the stimulated emission spectrum of the phosphor used in the present invention is similar to the maximum peak position of the stimulated excitation spectrum described above, and the position of the maximum peak of the stimulated emission spectrum of the phosphor used in the present invention is CfL (curve 1), Br, respectively
(Curve 2) and I (Curve 3), it can be seen that the latter is on the longer wavelength side.

The stimulated luminescence properties of the bismuth-activated alkali metal halide phosphor used in the present invention have been explained above using a specific phosphor as an example. However, the stimulated luminescence properties of other phosphors used in the present invention are also Almost the same as the stimulated luminescence properties of the above-mentioned phosphors, and after irradiation with radiation 450 ~
When excited with electromagnetic waves in the wavelength region of 900 nm, it exhibits stimulated luminescence in the near ultraviolet to blue region, and its emission peak is at 350 nm.
It has been confirmed that it is around ~45 Onm.

The bismuth-activated alkali metal halide phosphor used in the radiation image conversion method of the present invention has a photostimulated excitation spectrum in a wide wavelength range of 450 to 900 nm, and therefore the radiation image conversion method of the present invention using this phosphor In this method, the wavelength of the excitation light can be changed appropriately, that is, the excitation light source can be appropriately selected depending on the purpose. For example, since the photostimulation excitation spectrum of the above-mentioned phosphor extends to about 900 nm, it is possible to use a small semiconductor laser (having an emission wavelength in the infrared region) with a small size and low driving power as an excitation light source. , it becomes possible to downsize the apparatus for carrying out the radiation image conversion method. Particularly when using a phosphor whose matrix is composed of halogen, efficient excitation can be achieved by using a semiconductor laser as the excitation light source.

In addition, in terms of the brightness of stimulated luminescence and the wavelength separation from the emitted light, the excitation light in the radiation image conversion method of the present invention is 50%
Preferably, it is an electromagnetic wave in the wavelength range of 0 to 850 nm.

In the radiation image conversion method of the present invention, the above composition formula (I)
The bismuth-activated alkali metal halide phosphor represented by is preferably used in the form of a radiation image storage panel (also referred to as a stimulable phosphor sheet) containing the bismuth-activated alkali metal halide phosphor.

The basic structure of a radiation image storage panel is a support and at least one phosphor layer provided on one side of the support. The phosphor layer consists of a stimulable phosphor and a binder that contains and supports the stimulable phosphor in a dispersed state. Note that a transparent protective film is generally provided on the surface of the phosphor layer opposite to the support (the surface not facing the support) to protect the phosphor layer from chemical deterioration or Protects from physical impact.

That is, the radiation image conversion method of the present invention is preferably carried out using a radiation image conversion panel having a phosphor layer made of a bismuth-activated alkali metal halide phosphor represented by the above composition formula (I).

In the radiation image conversion method of the present invention using the stimulable phosphor represented by the composition formula (I) in the form of a radiation image conversion panel, the radiation transmitted through the subject or emitted from the subject is The radiation is absorbed by the phosphor layer of the radiation image conversion panel in proportion to the amount of radiation, and a radiation image of the subject or subject is formed on the radiation image conversion panel as an image of accumulated radiation energy. This Met image is 450-90
By exciting it with electromagnetic waves (excitation light) in the 0 nm wavelength range, it can be emitted as stimulated luminescence (fluorescence),
By photoelectrically reading this stimulated luminescence and converting it into an electrical signal, it becomes possible to image the accumulation of radiation energy.

The radiation image conversion method of the present invention will be specifically explained using the schematic diagram shown in FIG. 3, taking as an example an embodiment in which a stimulable phosphor represented by composition formula (I) is used in the form of a radiation image conversion panel do.

In FIG. 3, 11 is a radiation generating device such as an X-ray;
2 is a subject, 13 is a radiation image conversion panel containing a stimulable phosphor represented by the above compositional formula (I), and 14 is a radiation image conversion panel for emitting an M product image of radiation energy on the radiation image conversion panel 13 as fluorescence. A light source as an excitation source, 15 a photoelectric conversion device that detects fluorescence emitted from the radiation image conversion panel 13, 16 a device that reproduces the photoelectric conversion signal detected by the photoelectric conversion device 15 as an image, and 17 a reproduced image. A device for displaying an image, and a filter 18 for transmitting only the fluorescence emitted from the radiation image conversion panel 13 without transmitting the reflected light from the light source 14.

Although FIG. 3 shows an example of obtaining a radiographic image of a subject, the subject 12 itself emits radiation (
In this specification, this is referred to as a subject), there is no particular need to install the radiation generating device 11 described above. Further, the photoelectric conversion device 15 to the image display device 17 can be replaced with other suitable devices that can reproduce information emitted as fluorescence from the radiation image conversion panel 13 as an image in some form.

As shown in FIG. 3, when the subject 12 is irradiated with radiation such as X-rays from the radiation generating device 11, the radiation passes through the subject 12 in proportion to the radiation transmittance of each part of the subject 12. The radiation that has passed through the subject 12 then enters the radiation image conversion panel 13 and is absorbed by the phosphor layer of the radiation image conversion panel 13 in proportion to the intensity of the radiation. That is, a radiation energy accumulation image (a kind of latent image) corresponding to a radiation transmission image is formed on the radiation image conversion panel 13.

Next, using the light source 14 on the radiation image conversion panel 13,
When irradiated with electromagnetic waves in a wavelength range of 0 to 900 nm, the accumulated radiation energy image formed on the radiation image conversion panel 13 is emitted as fluorescence. The emitted fluorescence is proportional to the intensity of the radiation energy absorbed by the phosphor layer of the radiation image conversion panel 13. This optical signal composed of the intensity of fluorescence is converted into an electrical signal by a photoelectric conversion device 15 such as a photomultiplier tube, and an image reproduction device 16 converts the optical signal into an electrical signal.
is reproduced as an image, and this image is displayed by the single-image display device 17.

The operation of reading out the image information accumulated in a radiation image conversion panel as fluorescence is generally performed by scanning the panel in time series with a laser beam, and by photoelectron amplification of the fluorescence emitted from the panel through an appropriate light condenser. This is done by detecting with a photodetector such as a multiplier tube and obtaining time-series electrical signals.

In order to obtain an image with better observation and interpretation performance, this readout may consist of a pre-reading operation by irradiating low-energy excitation light and a main-reading operation by irradiating high-energy excitation light (JP-A-58 (Refer to Japanese Patent Publication No. 67240), this pre-reading operation has the advantage that the readout conditions for the main reading operation can be suitably set.

Furthermore, solid photoelectric conversion elements such as photoconductors and photodiodes can also be used as photoelectric conversion devices (Japanese Patent Application No. 58-86226, Japanese Patent Application No. 58-862).
No. 27, Japanese Patent Application No. 1983-219313 and Japanese Patent Application No. 1983
Specifications of No.-219314 and JP-A-58-12
(Refer to Publication No. 1874), in this case, a large number of solid-state photoelectric conversion elements are configured to cover the entire surface of the panel, and may be integrated with the panel or placed close to the panel. Alternatively, the photoelectric conversion device may be a line sensor in which a plurality of photoelectric conversion elements are connected in a line, or may be composed of one solid-state photoelectric conversion element corresponding to one pixel.

In the above case, the light source may be a point light source such as a laser, or a line light source such as an array of light emitting diodes (LEDs), semiconductor lasers, etc. arranged in a row. By performing readout using the fluorescent light, it is possible to prevent loss of fluorescence emitted from the panel, and at the same time, increase the solid angle of light reception and increase the S/N ratio. Further, since the obtained electrical signal is converted into a time series by electrical processing of a photodetector rather than by time-series irradiation of excitation light, it is possible to increase the readout speed.

The radiation image conversion panel from which the image information has been read is erased by irradiating it with light in the wavelength range of the excitation light of the phosphor or by heating it. It is preferable to do so (Japanese Patent Application Laid-open No. 11392/1983 and
(Refer to Publication No.-12599). By performing this erasing operation, it is possible to prevent noise from occurring due to afterimages when the panel is used next time. Furthermore, by performing the erasing operation twice, once after reading and immediately before the next use, it is possible to prevent the generation of noise due to natural radioactivity and perform the erasing more efficiently (Japanese Patent Laid-Open No. 57-116
(Refer to 300% publication).

In the radiation image conversion method of the present invention, the radiation used to obtain a radiation transmission image of the subject can exhibit stimulated luminescence when the phosphor is further excited by the electromagnetic waves after being irradiated with the radiation. Any type of radiation may be used, and for example, commonly known radiation such as X-rays, electron beams, and ultraviolet rays can be used. Furthermore, the radiation directly emitted from the subject when obtaining a radiation image of the subject may be any radiation that is similarly absorbed by the phosphor and serves as an energy source for stimulated luminescence. Examples include radiation such as gamma rays, alpha rays, and beta rays.

As a light source of electromagnetic waves that excites the phosphor that has absorbed radiation from the subject or subject as described above, 45
In addition to light sources that emit light with a band spectral distribution in the wavelength range of 0 to 900 nm, Ar ion laser-1H
Lasers such as e-Ne lasers, Ruby lasers, semiconductor lasers, glass lasers, YAG lasers, Kr ion lasers, 1 dye lasers, and light sources such as light emitting diodes can be used. Among these, laser light is preferable as the excitation light source used in the present invention because it can irradiate the radiation image conversion panel with a laser beam with high energy density per unit area. From these points, a preferable laser beam is a He-Ne laser. In addition, a semiconductor laser is preferable as an excitation light source because it is compact, requires low driving power, and can be directly modulated so that the laser output can be easily stabilized.

As mentioned above, a semiconductor laser is particularly preferable as a light source for excitation of a phosphor whose matrix halogen is I, since efficient excitation is possible.

Next, a radiation image conversion panel used in the radiation image conversion method of the present invention will be explained.

As described above, this radiation image storage panel consists of a support substantially including a support and a support provided on the support containing a bismuth-activated alkali metal halide phosphor represented by the composition formula (I) in a dispersed state. and at least one phosphor layer made of a binder.

The radiation image conversion panel having the above configuration is, for example,
It can be manufactured by the method described below.

First, the above composition formula (I
) The bismuth-activated alkali metal halide phosphor represented by:

This bismuth-activated alkali metal halide phosphor is
For example, it can be manufactured by the manufacturing method described below.

First, as a phosphor raw material, 1) RbCJl, CsC1, RbBr, CsBr.

At least one alkali metal halide selected from the group consisting of RbI and CsI; 2) At least one compound selected from the group consisting of bismuth compounds such as halides, oxides, nitrates, and sulfates. In some cases, ammonium halide (NHaX'; where X' is CfL, Br, or E) may also be used as a flux.

When producing a phosphor, the above alkali metal halide of 1) and the bismuth compound of 2) are used to stoichiometrically form the composition formula (I) 2M'X: x B i
(I) (where Ml is Rb and Cs
at least one alkali metal selected from the group consisting of; X is at least one halogen selected from the group consisting of C1, Br and I; and X is O<X
A mixture of phosphor raw materials is prepared by weighing and mixing them so that the relative ratio corresponds to (a numerical value in the range of ≦0.2).

In the method for producing the phosphor used in the present invention, Ml representing the alkali metal in composition formula (I) is preferably Cs, mainly from the viewpoint of stimulated luminance, and the X value representing the activation amount of bismuth is preferred. is 5 X 10-'≦X≦
It is preferably in the range of 10-2.

The phosphor raw material mixture may be prepared by: i) simply mixing the phosphor raw materials in 1) and 2) above, or ii) by combining the phosphor raw materials in 1) above.
After mixing the phosphor raw materials of and 2) in a solution state,
This solution may be dried by drying under reduced pressure, vacuum drying, spray drying, etc. under heating (preferably 50 to 200°C), and the phosphor raw materials may be mixed.

In either method i) or ii) above, a conventional mixer such as various mixers, a V-type blender, a ball mill, or a rod mill is used for mixing.

Next, the phosphor raw material mixture obtained as described above is filled into a heat-resistant container such as a quartz port, an alumina crucible, or a quartz crucible, and fired in an electric furnace at a firing temperature of 50°C.
A range of 0 to 1000°C is appropriate, preferably 600°C.
It is in the range of ~800°C. Although the firing time varies depending on the filling amount of the phosphor raw material mixture and the firing temperature, 0.5 to 6 hours is generally appropriate. The firing atmosphere may be a nitrogen gas atmosphere containing a small amount of hydrogen gas or a weakly reducing atmosphere such as a carbon dioxide atmosphere containing -carbon oxide; an inert gas atmosphere such as nitrogen gas or argon gas; and air. Utilizes the acidic atmosphere of

The phosphor of the present invention in powder form is obtained by the above baking.

Note that the obtained powdered phosphor may be further subjected to various general operations in the production of phosphors, such as washing, drying, and sieving, as necessary.

Examples of binders for the phosphor layer formed by dispersing the bismuth-activated alkali metal halide phosphor include proteins such as gelatin, polysaccharides such as dextran, or gum arabic. Natural polymeric substances; and polyvinyl butyral, polyvinyl acetate, nitrocellulose, ethylcellulose, vinylidene chloride/vinyl chloride copolymer, polyalkyl (meth)
Examples include binders typified by synthetic polymeric materials such as acrylates, vinyl chloride/vinyl acetate copolymers, polyurethanes, cellulose acetate butyrate, polyvinyl alcohol, linear polyesters, and the like. Particularly preferred among such binders are nitrocellulose, linear polyesters, polyalkyl (meth)acrylates, mixtures of nitrocellulose and linear polyesters, and mixtures of nitrocellulose and polyalkyl (meth)acrylates. The phosphor layer is
For example, it can be formed on the support by the following method.

First, a particulate stimulable phosphor and a binder are added to a suitable solvent and thoroughly mixed to prepare a coating solution in which the stimulable phosphor is uniformly dispersed in the binder solution.

Examples of solvents for preparing coating solutions include lower alcohols such as methanol, ethanol, n-propanol, and n-butanol; chlorine-containing hydrocarbons such as methylene chloride and ethylene chloride; acetone, methyl ethyl ketone, and methyl isobutyl ketone. Examples include ketones; esters of lower fatty acids and lower alcohols such as methyl acetate, ethyl acetate, and butyl acetate; ethers such as dioxane, ethylene glycol monoethyl ether, and ethylene glycol monomethyl ether; and mixtures thereof.

The mixing ratio of the binder and the stimulable phosphor in the coating solution varies depending on the characteristics of the intended radiation image conversion panel, the type of phosphor, etc., but in general, the mixing ratio of the binder and the stimulable phosphor is :1 to 1:100 (weight ratio), and particularly preferably 1:8 to 1:40 (weight ratio).

The coating liquid also contains a dispersant to improve the dispersibility of the phosphor in the coating liquid, and a dispersant to improve the bonding force between the binder and the phosphor in the phosphor layer after formation. Examples of dispersants used for such purposes include phthalic acid, stearic acid, caproic acid, lipophilic surfactants, etc., which may be mixed with various additives such as plasticizers. can. Examples of plasticizers include phosphate esters such as triphenyl phosphate, tricresyl phosphate, and diphenyl phosphate; phthalate esters such as diethyl phthalate and dimethoxyethyl phthalate; ethyl phthalyl ethyl glycolate, and butyl phthalyl glycolate. and polyesters of polyethylene glycol and aliphatic dibasic acids, such as polyesters of triethylene glycol and adipic acid and polyesters of diethylene glycol and succinic acid.

The coating solution containing the phosphor and binder prepared as described above is then uniformly applied to the surface of the support to form a coating film of the coating solution.

This coating operation can be carried out using conventional coating means such as a doctor blade, roll coater, knife coater, etc.

As a support, an intensifying screen (
The material can be arbitrarily selected from various materials used as supports for (or sensitizing screens) or materials known as supports for radiation image storage panels. Examples of such materials include films of plastic substances such as cellulose acetate, polyester, polyethylene terephthalate, polyamide, polyimide, triacetate, polycarbonate, metal sheets such as aluminum foil, aluminum alloy foil, regular paper, baryta paper, resin. Examples include coated paper, pigment paper containing pigments such as titanium dioxide, and paper sized with polyvinyl alcohol.

However, in consideration of the characteristics and handling of the radiation image storage panel as an information recording material, a particularly preferred material for the support in the present invention is a plastic film. This plastic film may be kneaded with a light-absorbing substance such as carbon black, or may be kneaded with a light-reflecting substance such as titanium dioxide.The former is a high-sharp type of radiation image converter. The latter is a suitable support for radiation image storage panels of high sensitivity type.

In known radiation image conversion panels, a phosphor layer is provided in order to strengthen the bond between the support and the phosphor layer, or to improve the sensitivity or image quality (sharpness, granularity) of the radiation image conversion panel. A polymeric substance such as gelatin is coated on the surface of the side support to form an adhesion-imparting layer, or a light-reflecting layer made of a light-reflecting substance such as titanium dioxide, or a light-reflecting layer made of a light-absorbing substance such as carbon black. The support used in the present invention, which is known to be provided with an absorbing layer, etc., can also be provided with these various layers, and the structure thereof may vary depending on the purpose, use, etc. of the desired radiation image storage panel. can be selected arbitrarily.

Furthermore, as described in Japanese Unexamined Patent Publication No. 58-200200 by the present applicant, in order to improve the sharpness of the obtained image, the surface of the support on the phosphor layer side (the phosphor layer of the support) When an adhesion-imparting layer, a light-reflecting layer, a light-absorbing layer, or the like is provided on the side surface, minute irregularities may be formed on the surface (meaning the surface).

After forming a coating film on the support as described above, the coating film is dried to complete the formation of the stimulable phosphor layer on the support. The thickness of the phosphor layer varies depending on the characteristics of the intended radiation image conversion panel, the type of phosphor, the mixing ratio of the binder and the phosphor, etc., but is usually 204 m to in.

However, the thickness of this layer is preferably between 50 and 500 gm.

In addition, the stimulable phosphor layer does not necessarily need to be formed by directly applying a coating solution onto the support as described above, but can be formed by separately applying it onto a sheet such as a glass plate, metal plate, or plastic sheet. After a phosphor layer is formed by applying a liquid and drying, the phosphor layer may be pressed onto a support, or the support and the phosphor layer may be bonded together using an adhesive.

Although only one stimulable phosphor layer may be used, two or more layers may be stacked. In the case of multiple layers, it is sufficient that at least one of the layers contains a bismuth-activated alkali metal halide phosphor of composition formula (I), and the luminous efficiency against radiation increases sequentially toward the surface of the panel. A structure in which a plurality of phosphor layers are stacked may be used. In both cases of single layer and multilayer, a known stimulable phosphor can be used in combination with the above phosphor.

Examples of such known stimulable phosphors include, in addition to the above-mentioned phosphors, ZnS:Cu, Pb, Ba0exA120. :
Eu (however, 0.8≦X≦10), and M”O
*XSiO2:A (However, M” is Mg, Ca, S r
, Zn.

Cd or Ba, A is Ce, Tb, Eu, Tm,
Pb, T1. B i or M n te, X is
0.5≦X≦2.5), as described in JP-A-55-12143 (
al+ x −y, M g x, Ca y
) F
at least one of r, and X and y are O<
X+y≦0.6, and xy≠o, and a is 10-”
≦a≦5×10−2), and.

LnO described in JP-A-55-12144
X: xA (However, Ln is La, Y.

At least one of Gd and Lu, X is at least one of C1 and Br, A is Ce and Tb
and X is 0<x<0.
1), M”X2 described in Japanese Patent Application No. 58-193162
@ aM"X' 2 : xEu2° (However, M'
[ is at least one kind of alkaline earth metal selected from the group consisting of Ba, Sr and Ca; X and X' are at least one kind of halogen selected from the group consisting of C1, Br and I, and X≠ and a is a numerical value in the range of 0.1≦a≦1090, and X is 0
<A numerical value in the range of X≦0.2).

In a normal radiation image storage panel, as mentioned above, a transparent protective film is provided on the surface of the phosphor layer on the side opposite to the side that contacts the support to physically and chemically protect the phosphor layer. It is being It is preferable to provide such a transparent protective film also in the radiation image conversion panel of the present invention.

The transparent protective film may be made of, for example, a cellulose conductor such as cellulose acetate or nitrocellulose; or a synthetic polymer material such as polymethyl methacrylate, polyvinyl butyral, polyvinyl formal, polycarbonate, polyvinyl acetate, or vinyl chloride/vinyl acetate copolymer. It can be formed by applying a solution prepared by dissolving a transparent polymer substance in a suitable solvent onto the surface of the phosphor layer. Alternatively, it can also be formed by a method such as adhering a transparent thin film separately formed from polyethylene terephthalate, polyethylene, polyvinylidene chloride, polyamide, etc. to the surface of the phosphor layer using a suitable adhesive. Transparency formed in this way; I! The film thickness of I is preferably about 0.1 to 204 m.

Next, examples of the present invention will be described. However, these Examples do not limit the present invention.

[Example 1] 186.4 g of cesium chloride (CsC) and 0.266 g of bismuth fluoride (BiFs) were thoroughly mixed using a ball mill.

Next, the obtained phosphor raw material mixture was filled into an alumina crucible, which was then placed in a high-temperature electric furnace and fired. Firing was performed in air at a temperature of 600° C. for 2 hours. After the firing was completed, the fired product was taken out of the furnace and cooled.

In this way, a powdered bismuth-activated cesium chloride phosphor (CsC content: 0.001 B i ) was obtained.

[Example 2] Powdered bismuth was produced by performing the same operation as in Example 1 except that 8 g of cesium bromide (CsBr) 212 was used instead of cesium chloride. Activated cesium bromide phosphor (CsBr
: 0.001 Bi) was obtained.

[Example 3] Powdered bismuth-activated iodide was prepared by performing the same procedure as in Example 1 except that 259.8 g of cesium iodide (CsI) was used instead of cesium chloride. Cesium phosphor (Cs I: 0.001
B i) was obtained.

Next, the tube voltage of 8 was applied to each of the phosphors obtained in Examples 1 to 3.
After irradiating with 0 KVp X-rays, the stimulated emission spectrum was measured when excited with He-Ne1z-Qi light (wavelength: 632.8 nm). The results obtained are shown in FIG.

In FIG. 2, Curve 1: CsC1:0.001 Stimulated emission spectrum curve 2 of CsC1:0.001 B i phosphor (Example 1): CsBr: 0. Stimulated emission spectrum curve 3 of OQI B i phosphor (Example 2): Cs I : 0.001 This is the stimulated emission spectrum of the B i phosphor (Example 3).

In addition, a tube voltage of 80K was applied to each of the phosphors obtained in Examples 1 to 3.
After irradiation with X-rays of Vp, the photostimulation excitation spectrum at the peak emission wavelength of each phosphor when excited with light in the wavelength range of 450 to 11,000 nm was measured. The results obtained are shown in FIG.

In FIG. 1, Curve 1: Cs Cl: 0.001 Photostimulation excitation spectrum of B i phosphor (Example 1) Curve 2: Cs B r : 0.001 Photostimulation of B i phosphor (Example 2) Excitation spectrum curve 3: This is a photostimulated excitation spectrum of Cs I : 0.001 B i phosphor (Example 3).

[Example 4] A radiation image storage panel was manufactured using each of the three types of bismuth-activated alkali metal halide phosphors obtained in Examples 1 to 3 by the method described below.

First, methyl ethyl ketone is added to a mixture of phosphor particles and linear polyester resin, and the nitrification degree is ii, s%.
Next, tricresyl phosphate, n-butanol, and methyl ethyl ketone were added to this dispersion, followed by thorough stirring using a propeller mixer. Mix it.

A coating liquid was prepared in which the phosphor was uniformly dispersed, the mixing ratio of the binder and the phosphor was 1 = 10, and the viscosity was 25 to 35 PS (25°C).

Next, a titanium dioxide kneaded polyethylene terephthalate sheet (support, thickness: 2
The coating liquid was applied uniformly onto the sample (50 gm) using a doctor blade. After coating, the support on which the coating film has been formed is placed in a dryer, and the temperature inside the dryer is adjusted to 25°C.
The temperature was gradually increased from 100°C to 100°C to dry the coating film.

In this way, a phosphor layer having a layer thickness of 2'50 pm was formed on the support.

Then, by placing and adhering a transparent film of polyethylene terephthalate (thickness: 12 JLm, coated with a polyester adhesive) on top of this phosphor layer with the adhesive layer side facing down, a transparent protective film is formed. A radiation image storage panel comprising a support, a phosphor layer, and a transparent protective film was obtained.

Next, each radiation image conversion panel obtained in Example 4 was irradiated with X-rays at a tube voltage of 80 KVP, and then excited with He-Ne laser light to measure the sensitivity (stimulated luminance) of the panel. This sensitivity measurement was performed using a bandpass filter (B-390) with a peak wavelength of 390 nm, a half width of 60 nm, and a peak wavelength transmittance of 78% as a light receiving filter. The results are shown in Table 1.

In addition, in Table 1, the sensitivity is CsI of Example 3:
0.001 B The sensitivity of a panel using phosphor is 1
It is shown as a relative value of 00.

Table 1 Relative sensitivity C5C! ; L: 0.001 B i phosphor (Example 1)
Panel used: 500CsBr: 0.001
Panel using B i phosphor (Example 2) 700C
s I: 0.001 Panel using B i phosphor (Example 3) 100

[Brief explanation of the drawing]

FIG. 1 shows CsC1:0.001B, which is a specific example of the bismuth-activated alkali metal halide phosphor of the present invention.
Figure 3 shows the photostimulated excitation spectra of the i phosphor, the CsBr: 0.001 Bi phosphor and the CsI: 0.001 Bi phosphor (curves 1, 2 and 3, respectively). FIG. 2 shows CsCf1HO,001B, which is a specific example of the bismuth-activated alkali metal halide phosphor of the present invention.
Figure 3 is the stimulated emission vector (curves 1.2 and 3, respectively) of the i phosphor, the Cs B r : 0.001 B i phosphor and the Cs I : 0.001 B i phosphor. FIG. 3 is a schematic diagram illustrating the radiation image conversion method used in the present invention.

Claims (1)

[Claims] 1. After the radiation transmitted through the subject or emitted from the subject is absorbed by a bismuth-activated alkali metal halide phosphor represented by the following compositional formula (I),
A radiation image conversion method comprising: irradiating this phosphor with electromagnetic waves in a wavelength range of 450 to 900 nm to cause the radiation energy stored in the phosphor to be emitted as fluorescence, and detecting this fluorescence. Composition formula (I): M^1X:xBi(I) (where M^1 is at least one alkali metal selected from the group consisting of Rb and Cs; X is Cl,
At least one type of halogen selected from the group consisting of Br and I; and x is a numerical value in the range of 0<x≦0.2) 2. M^1 in the composition formula (I) is Cs. A radiation image conversion method according to claim 1, characterized in that: 3. x in compositional formula (I) is 5×10^-^4≦X
The radiation image conversion method according to claim 1, wherein the value is in the range of ≦10^-^2. 4. The radiation image conversion method according to claim 1, wherein the electromagnetic wave is an electromagnetic wave in a wavelength range of 500 to 850 nm. 5. The radiation image conversion method according to claim 1, wherein the electromagnetic wave is a laser beam. 6. Substantially composed of a support and at least one phosphor layer made of a binder containing and supporting the stimulable phosphor in a dispersed state provided on the support, the phosphor layer A radiation image conversion panel characterized in that at least one layer thereof contains a bismuth-activated alkali metal halide phosphor represented by the following compositional formula (I). Composition formula (I): M^1X:xBi(I) (where M^1 is at least one alkali metal selected from the group consisting of Rb and Cs; X is Cl,
At least one type of halogen selected from the group consisting of Br and I; and x is a numerical value in the range of 0<x≦0.2) 7. M^1 in the composition formula (I) is Cs. A radiation image conversion panel according to claim 6 characterized by: 8. x in compositional formula (I) is 5×10^-^4≦x
The radiation image conversion panel according to claim 6, characterized in that the value is in the range of ≦10^-^2.