JPS61236889A - Radiation image conversion and radiation image conversion panel therefor - Google Patents

Abstract

PURPOSE:After radiation is absorbed in a fluorescent material of Cs, Rb halides activated with brightening divalent Eu, it is irradiated with specific electromagnetic waves to allow the radiation energy to emit in the form of fluorescence and the fluorescence is detected to effect image conversion. CONSTITUTION:The radiation which has transmitted through the substrate or has been emitted from the substrate is allowed to absorb in a fluorescent material of Cs.Rb halide activated with divalent Eu of the formula (X, X' are Cl, Br, I; 0<a<=10.0; 0<x<=0.2). Then, the fluorescent material is irradiated with electromagnetic waves of 450-900nm, preferably 600-750nm wavelength to permit the radiation energy to emit as fluorescence and the fluorescence is read photoelectrically and converted into electric signals for image formation. EFFECT:X-ray images rich in information is obtained with reduced exposure to X-ray. USE:Direct radiography for medical purposes, etc.

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 halide phosphor activated by divalent europium, and a radiation image conversion panel used in the method.

[Background of the invention] Conventionally, as a method of obtaining radiation images as images.

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 an alternative to the conventional radiographic method, a radiation image conversion method using a stimulable phosphor is known, for example, as described in Japanese Unexamined Patent Publication No. 55-12145. This method involves absorbing radiation transmitted through the subject or radiation emitted from the subject into a stimulable phosphor.
Then, by exciting this phosphor in a time-series manner with electromagnetic waves (excitation light) such as visible light and infrared rays, the radiation energy accumulated in the phosphor is released into fluorescence (stimulated luminescence).
The fluorescent light is emitted as a fluorescent light, and this fluorescence is read photoelectrically to obtain an electrical signal, which is then converted into an image.

The radiation image conversion method has the advantage that it is possible to obtain an xii 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: .

(B a l+ x , M ” x ) F X :
'y A (However, M2+ is Mg, Ca, Sr, Zn
, and at least one of Cd, X is Cl, Br
, and at least one of I, A is Eu, Tb
, Ce, Tm, Dy, Pr, Ho, Nd, Yb, and Er, and x is O≦X≦0
．． 6, y is 0≦y≦0.2) After absorbing radiation such as X-rays, this phosphor emits light in the near-ultraviolet region ( (stimulated luminescence).

As mentioned above, the 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 halide phosphor.

[Summary of the Invention] The present invention is based on the discovery of a novel stimulable phosphor, and provides a radiation image conversion method using the stimulable phosphor, and a radiation image conversion panel used in the method. It is something to do.

The present inventors have conducted various studies with the aim of searching for stimulable phosphors. As a result, the novel divalent europium-activated cesium rubidium halide phosphor represented by the following compositional formula (I) exhibits stimulated luminescence, that is, the phosphor exhibits stimulated luminescence. discovered that stimulated luminescence occurs in the near-ultraviolet to blue region when irradiated with radiation such as beta rays 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. This led to the decision to do so.

Compositional formula (I): CsX@aRbX' : xEu" (I) (
However, X and X' are each at least one kind of halogen selected from the group consisting of Cl, Br, and
(is a numerical value in the range of O<x≦0.2) In other words, the radiation image conversion method of the present invention converts the radiation transmitted through the object or emitted from the object into the radiation represented by the above composition formula (I). After absorbing divalent europium into the activated cesium/rubidium halide phosphor, the phosphor is irradiated with electromagnetic waves in the wavelength range of 450 to 900 nm to cause the radiation energy stored in the phosphor to be released as fluorescence. , and detecting this fluorescence.

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 divalent europium-activated cesium rubidium halide phosphor represented by the above compositional formula (I).

[Structure of the Invention] Figure 1 shows C3C! which is an example of a divalent europium activated cesium rubidium halide phosphor used in the radiation image conversion method of the present invention. LL1RbB r :0.0
This is the photostimulation excitation spectrum of 01E u ”+ phosphor.

As is clear from FIG. 1, C5 used in the present invention
cfL*RbBr:0. oolE u” phosphor exhibits stimulated luminescence when excited by electromagnetic waves in the wavelength range of 450 to 900 nm after irradiation with radiation, especially in the wavelength range of 600 to 750 nm.
When excited with electromagnetic waves in the wavelength range of m, it is easy to separate stimulated emission and excitation light, and the stimulated emission has high brightness. The wavelength of magnetic waves is 450 to 9, which is used as light.
It is based on this fact that QQnm was defined.

Further, FIG. 2 shows CsClmRb B r :0.
This is the stimulated emission spectrum of the QOIE u 2° phosphor. As is clear from FIG. 2, C used in the present invention
s Cl ・Rb Br :O,0OIE u'+
The phosphor exhibits stimulated luminescence in the near ultraviolet to blue region, and the peak of its stimulated luminescence spectrum is around 370 nm.

The stimulated luminescence properties of the divalent europium-activated cesium-rubidium halide phosphor used in the present invention have been explained using a specific phosphor as an example, but the stimulated luminescence properties of other phosphors used in the present invention are also The characteristics are almost the same as the stimulated luminescence properties of the above-mentioned phosphors, and when excited with electromagnetic waves in the wavelength range of 450 to 900 nm after irradiation with radiation, it exhibits stimulated luminescence in the near ultraviolet to blue region, and the peak of the luminescence is 37 Onm. Confirmed to be nearby.

Figure 3 shows CsC sentence @ aRbB r: 0.001Eu
”.

a゛ value and stimulated luminescence intensity in phosphor [80 KV After irradiation with p X-rays, He-Ne laser light (632,8
FIG. As is clear from Figure 3, the a value is 0.1.
e sc! in the range of <a≦10.0. L* aRbE
r: o, 001E u” phosphor exhibits stimulated luminescence
It is based on this fact that the value is defined in the range of 0<a≦10.0. Furthermore, from FIG. 3, it is clear that C sc used in the present invention has a value in the range of a≦10.0.
It is clear that among the l*aRbBr r:0.001E u'' phosphors, those whose a value is in the range of 0.15≦a≦2.0 exhibit higher-intensity stimulated luminescence.

In addition, Cs C1・aRbB r:o, o01E u
It has been confirmed that for the divalent europium-activated cesium rubidium halide phosphors used in the present invention other than the "" phosphors, the relationship between the a value and the stimulated luminescence intensity has the same tendency as shown in Figure 3. ing.

The divalent europium-activated cesium rubidium 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 using this phosphor can be used in the radiation image conversion method of the present invention. The image conversion panel can appropriately change the wavelength of the excitation light, 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. Further, from the viewpoint of brightness of stimulated luminescence and wavelength separation from emitted light, the excitation light in the radiation image conversion method of the present invention is preferably electromagnetic waves in the wavelength range of 600 to 750 nm.

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

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 carried out using a radiation image conversion panel having a phosphor layer made of a divalent europium-activated cesium rubidium halide phosphor represented by the above composition formula (I). desirable.

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 accumulated image is 450 to 900
By excitation with electromagnetic waves (excitation light) in the nanometer wavelength range, it can be emitted as stimulated luminescence (fluorescence), and by photoelectrically reading this stimulated luminescence and converting it into an electrical signal, radiation energy can be extracted. It becomes possible to visualize the accumulated image.

The radiation image conversion method of the present invention will be specifically explained using the schematic diagram shown in FIG. 4, 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. 4, 11 is xm = which radiation generating device, 1
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 an excitation for emitting the accumulated radiation energy image on the radiation image conversion panel 13 as fluorescence. 15 is a photoelectric conversion device that detects fluorescence emitted from the radiation image conversion panel 13; 16 is a device that reproduces the photoelectric conversion signal detected by the photoelectric conversion device 15 as an image; 17 is a reproduced image 18 is a filter 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. 4 shows an example of obtaining a radiographic image of a subject, the subject 12 itself emits radiation (
(hereinafter referred to as a subject), the radiation generating device 11 described above does not need to be installed in stages, and the photoelectric conversion device 15 to the image display device 17 are arranged on a radiation image conversion panel. It is also possible to convert the information emitted as fluorescence from 13 into any other suitable amount that can be reproduced in some way as an image.

As shown in FIG. 4, when a 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.
The image is reproduced as an image by the image display device 17, and this image is displayed by the image display device 17.

The operation of reading out the image information accumulated in a radiation image conversion panel as fluorescence is generally carried out by scanning the panel with data light in time series, and transmitting the fluorescence emitted from the panel by this scanning through a suitable light condenser. This is done by detecting the signal using a photodetector such as a photomultiplier tube and obtaining a time-series electrical signal. In order to obtain an image with better observation and interpretation performance, this readout may consist of a pre-reading/reading operation by irradiating low-energy excitation light and a main-reading operation by irradiating high-energy excitation light (especially (Refer to Japanese Patent Publication No. 58-67240), by performing this pre-reading operation, there is an advantage that the readout conditions for the main reading operation can be suitably set.

Furthermore, for example, solid photoelectric conversion elements such as photoconductors and photodiodes can 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
In this case, a large number of solid-state photoelectric conversion elements may be configured to cover the entire surface of the panel and may be integrated with the panel, or may be arranged in close proximity 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 linear manner, or may be composed of one solid-state photoelectric conversion element corresponding to one pixel.

In addition to a point light source such as a laser, the light source in the above case may be a line light source such as an array of light emitting diodes (LEDs), semiconductor lasers, etc. arranged in a row. By performing readout using such a device, 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 also preferable to do so (Japanese Patent Application Laid-Open Nos. 11392-1982 and 1983)
By performing this erasing operation, it is possible to prevent the generation of noise 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, etc., and to perform the erasing more efficiently (Japanese Patent Application Laid-Open No. 57-1996-1). 11
(See Publication No. 6300).

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 as long as it is suitable, 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 as long as it is absorbed by the phosphor and becomes an energy source for the phosphor. , Examples include γ rays, α rays, β rays
The radiation layer can include any radiation.

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
Light sources such as lasers and light emitting diodes such as e-Ne lasers, ruby e lasers, semiconductor lasers, glass lasers, YAG lasers, Kr ion lasers, dye lasers, etc. 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.

In addition, the light source used for erasing may be one that emits light in the excitation wavelength range of the stimulable phosphor; examples thereof include tungsten lamps, fluorescent lamps, halogen lamps, and high-pressure sodium lamps. I can do it.

The radiation image conversion method of the present invention includes: a storage section that absorbs and stores radiation energy in a stimulable phosphor; a photodetection (readout) section that irradiates the phosphor with excitation light and emits the radiation energy as fluorescence; It can also be applied to a built-in type radiation image conversion device in which an erasing section for emitting energy remaining in the phosphor is built into one device (Japanese Patent Application No. 57-84436 and Japanese Patent Application No. 58-6
6730), by using such a built-in device, a radiation image conversion panel (or a recording material containing a stimulable phosphor) can be reused, and a stable A homogeneous image can be obtained.

Further, by using a built-in type, the device can be made smaller and lighter, and its installation and movement become easier. Furthermore, by mounting this device on a mobile vehicle, it becomes possible to carry out circular radiography.

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 conversion panel consists of a support and a divalent europium-activated cesium halide rubidium phosphor provided on the support and represented by the composition formula (1) in a dispersed state. and at least one phosphor layer comprising a supporting 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 divalent europium activated cesium rubidium halide phosphor will be explained.

This divalent europium-activated cesium rubidium halide phosphor can be produced, for example, by the production method described below.

First, as phosphor raw materials, 1) at least one type of cesium halide selected from the group consisting of CsCjl, CsBr, and C5I, 2) at least one type of rubidium halide selected from the group consisting of Rbll, RbBr, and RbI, and 3) halogen At least one compound selected from the group consisting of compounds of europium such as compounds, oxides, nitrates, and sulfates is prepared.

In some cases, ammonium halide (NH
.

When producing a phosphor, the above 1) cesium halide, 2) rubidium halide, and 3) europium compound are used to stoichiometrically form the composition formula (■): CsX* aRbX' : xEu ( rl)
(However, X and Xo are each at least one kind of halogen selected from the group consisting of CJL, Br, and Engineering: and a is a numerical value in the range of O<a≦1O00, and X is O<x≦0.2 A mixture of phosphor raw materials is prepared by weighing and mixing them in a relative ratio corresponding to (a numerical value in the range of ).

Preparation of phosphor raw material mixture.

i) It may be carried out by simply mixing the phosphor raw materials of 1), 2) and 3) above, or ii) First, the phosphor raw materials of 1) and 2) above are mixed in a solution state, This solution is heated (preferably 50 to 2
00℃), vacuum drying, vacuum drying.

It may be carried out by drying by spray drying or the like, and then mixing the phosphor raw material of 3) above into the obtained dried product.

In addition, as a modification of the method ii) above, the above 1) and 2)
And 3) the method of mixing the phosphor raw materials in a solution state and drying this solution may be used.

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 boat, an alumina crucible, or a quartz crucible, and fired in an electric furnace at a firing temperature of 40°C.
A range of 0 to 1300°C is appropriate, preferably 700°C.
It is in the range of ~1000°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. As the firing atmosphere, a weakly reducing atmosphere such as a nitrogen gas atmosphere containing a small amount of hydrogen gas or a carbon dioxide atmosphere containing -carbon oxide is used. Generally, a trivalent europium compound is used as the phosphor raw material in 3) above, but in this case, during the firing process, the trivalent europium is reduced to divalent europium by the weakly reducing atmosphere mentioned above. be done.

A powdered phosphor 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.

In the method for producing a phosphor of the present invention, X and Xo in cesium halide (CsX) and rubidium halide (RbX') may be the same or different.

In addition, from the viewpoint of stimulated luminescence brightness, C in the composition formula (n)
The a value representing the ratio of sX and RbX' is 0.15≦a≦
From the viewpoint of stimulated luminescence brightness, the X value representing the activation amount of europium in the composition formula (n) is preferably in the range of 10-5≦x≦1O-2. preferable.

Next, examples of binders for the phosphor layer formed by dispersing the divalent europium-activated cesium-rubidium halide phosphor include proteins such as gelatin, polysaccharides such as dextran, or gum arabic. Natural polymeric substances such as: and polyvinyl butyral, polyvinyl acetate, nitrocellulose, ethylcellulose.

Examples of binders include synthetic polymeric substances such as vinylidene chloride/vinyl chloride copolymer, polyalkyl (meth)acrylate, vinyl chloride/vinyl acetate copolymer, polyurethane, cellulose acetate butyrate, polyvinyl alcohol, linear polyester, etc. be able to. 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. It is.

The phosphor layer can be formed on the support by, for example, the following method: First, add particulate stimulable phosphor and a binder to a suitable solvent, and mix them thoroughly. , a coating solution in which the stimulable phosphor is uniformly dispersed in a binder solution is prepared.

Examples of solvents for preparing coating solutions include lower alcohols such as methanol, ethanol, n-propanol, and n-2 tanol; chlorine-containing hydrocarbons such as methylene chloride and ethylene chloride; acetone, methyl ethyl ketone, methyl isobutyl ketone, etc. 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 varies depending on the manufacturing process. :1 to 1:100 (weight ratio), and particularly preferably from 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, which may be mixed with various additives such as plasticizers, include
Examples include tarric acid, stearic acid, caproic acid, and lipophilic surfactants. Examples of plasticizers include phosphate esters such as triphenyl phosphate, tricresyl phosphate, and diphenyl phosphate; heptathalic acid esters such as diethyl phthalate and dimethoxyethyl phthalate; ethyl phthalyl ethyl glycolate, 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 first 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 a 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 plastic film is sometimes a preferable material for the support in the present invention. 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 reflective layer made of a light reflective substance such as titanium dioxide, or a light absorbing substance such as carbon black. It is known to provide a light absorption layer consisting of 0
The support used in the present invention can also be provided with these various layers, and their configurations can be arbitrarily selected depending on the purpose, use, etc. of the desired radiation image storage panel.

Furthermore, as described in JP-A-58-200200, in order to improve the sharpness of the obtained image, the surface of the support on the phosphor layer side (the surface of the support on the phosphor layer side) When an adhesion-imparting layer, a light-reflecting layer, a light-absorbing layer, etc. are provided, minute irregularities may be formed on the surface (meaning the surface thereof).

After forming the 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, and is usually 20 ILm to inm. However, the thickness of this layer is preferably 50 to 500 μm.

In addition, the stimulable phosphor layer does not necessarily have to be formed by directly applying a coating liquid onto the support as described above, but may be formed separately on a sheet such as a glass plate, metal plate, or plastic sheet. After forming a phosphor layer by applying a coating liquid and drying it.

The support and the phosphor layer may be bonded together by pressing this onto the support or using an adhesive.

The stimulable phosphor layer may be only one layer, but it may be two or more layers.In the case of multiple layers, at least one of the layers is a divalent europium-activated cesium rubidium halide phosphor of composition formula (I). It suffices if the calendar contains
It is also possible to have a structure in which a plurality of phosphor layers are stacked so that the luminous efficiency against radiation increases sequentially toward the surface of the panel, and in both single-layer and multi-layer cases,
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 and Pb described in Japanese Patent Application Laid-Open No. 55-12142.

BaO*xA120. :Eu (However, 0.8≦X≦
10) , OJ: Bi, M 0sXSi02:A (However, MI[ is Mg, Ca, Sr, Zn, Cd, or
a, where A is Ce%Tb, Eu.

(Tm, Pb, Tl, Bi, or Mnte, X is 0.5≦X≦2.5), as described in JP-A-55-12143 (B
a1-X-F, Mgx, Cay
) F X :aEu” (However, or 0 sentences and B
at least one of r, and X and y are O<
x+y≦0.6. and xy≠0, and a is 1O-6
≦a≦5×10-2), LnO described in JP-A-55-12144
X:xA (Ln is La%Y, Gd, and Lu
X is at least one of CQ and Br, A is at least one of Ce and Tb, and X is ', O<x<0.1), and M"X2 dispute aMIIX' 2:
Eu” (where 1M is at least one kind of alkaline earth metal selected from the group consisting of Ba, Sr and Ca; X and Xo are at least one kind of halogen selected from the group consisting of Cl, Br and I; , and XI
&X'; and a is a numerical value in the range of 0.1≦a≦10.0, and X is a numerical value in the range of O<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 derivative 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 coating the surface of the phosphor layer with a solution prepared by dissolving a transparent polymeric material in an appropriate solvent, or by applying a solution prepared by dissolving a transparent polymer material such as polyethylene terephthalate, polyethylene terephthalate,
It can also be formed by a method such as adhering a transparent thin film separately formed from polyethylene, polyvinylidene chloride, polyamide, etc. to the surface of the phosphor layer using a suitable adhesive. The thickness of the transparent protective film thus formed is preferably about 0.1 to 20 ILm.

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

[Example 1] 168.36 g of cesium chloride (Cs0), 185.47 g of rubidium bromide (RbBr), and 392 g of europium bromide (E u B r 3 ) 0 were added to 800 mal of distilled water (H20). and mixed to form an aqueous solution. After drying this aqueous solution under reduced pressure at 60°C for 3 hours, it was further subjected to vacuum dry explosion at 150°C for 3 hours.

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 is carried out at 900°C in a carbon dioxide atmosphere containing carbon oxide.
The test was carried out at a temperature of 2 hours. After firing is completed,
The fired product was taken out of the furnace and cooled. In this way,
Powdered CsC1LLIRbBr: 0.001 Eu
A 2+ phosphor was obtained.

[Example 2] Powdered CsBr*RbBr: A 0.001 E u ”° phosphor was obtained.

[Example 3] In Example 1, a powdered C3C6LIIRb process was prepared by performing the same operation as in Example 1 except that 2.37 g of rubidium iodide (RbI) was used instead of rubidium bromide. :0.001 E u 2° phosphor was obtained.

Furthermore, a tube voltage of 80 K' was applied to the phosphor obtained in Example 1.
V, p (7) After irradiating with X-rays, the stimulated emission spectrum when He-Ne is excited with laser light (wavelength 632.8 nm) and the peak wavelength of the stimulated emission (approximately 37 nm)
The photostimulated excitation spectrum at 0 nm) was measured. The results obtained are shown in FIGS. 1 and 2.

FIG. 1 shows the stimulated excitation spectrum of CsC1*RbBr:0.001 Eu'' phosphor.

Figure 2 shows CsC・l*RbBr:0.001 Eu”
The stimulated emission spectrum of the phosphor is shown.

[Example 4] Powdered C3CjL"RbBr obtained in Example 1: 0
．． Methyl ethyl ketone was added to the mixture of 001Eu2° phosphor and linear polyester resin, and the nitrification degree was 11.
．． A dispersion containing the phosphor in a dispersed state was prepared by adding 5% nitrocellulose.Next, tricresyl phosphate, n-butanol, and methyl ethyl ketone were added to this dispersion, and then thoroughly mixed using a propeller mixer. Stir and mix to ensure that the phosphor is uniformly dispersed, the mixing ratio of binder and phosphor is 1:10, and the viscosity is 25 to 35 PS (
Next, apply the coating solution uniformly using a doctor blade onto a titanium dioxide-mixed polyethylene terephthalate sheet (support, thickness = 2501 Lm) placed horizontally on a glass plate. did. After coating, the support on which the coating film has been formed is placed in a dryer,
The temperature inside this dryer was gradually raised from 25°C to 100°C to dry the coating film. In this way,
A phosphor layer having a layer thickness of 2501 Lm was formed on the support.

Then, a transparent film of polyethylene terephthalate (thickness: 12#Lm, coated with polyester adhesive) is placed on top of this phosphor layer with the adhesive layer side facing down and adhered. A protective film was formed to produce a radiation image storage panel composed of a support, a phosphor layer, and a transparent protective film.

[Example 5] In Example 4, CsB r * obtained in Example 2
R, bBr: 0.001 By performing the same operation as in Example 4 except for using Eu2+ phosphor, a radiation image conversion panel composed of a support, a phosphor layer, and a transparent protective film was prepared. Manufactured.

[Example 6] In Example 4, C5CfL − obtained in Example 3
Rb I: 0.001 E u ''+ A radiation image conversion panel composed of a support, a phosphor layer, and a transparent protective film was prepared by performing the same operation as in Example 4 except for using the phosphor. was manufactured.

Next, each radiation image conversion panel obtained in Examples 4 to 6 was irradiated with X-rays with a tube voltage of 80 KVp, and then
The sensitivity (stimulated luminance) of each panel was measured by excitation with light of m. The results are shown in Table 1.

Margin below Table 1 Relative sensitivity Example 4 100 Example 5
70 Example 6 30

[Brief explanation of the drawing]

Figure 1 shows Cs which is an example of a divalent europium activated cesium rubidium halide phosphor used in the present invention.
C1*RbBr:0.001Eu'' phosphor. Figure 2 shows the photostimulation spectrum of C1*RbBr:0.001Eu'' phosphor.
CfL@RbBr: Stimulated emission spectrum of 0.001Eu2° phosphor. Figure 3 shows CsC1* aRbBr: 0.001Eu”
2 is a graph showing the relationship between the a value and stimulated luminescence intensity in a phosphor. FIG. 4 is a schematic diagram illustrating the radiation image conversion method of the present invention. 11: Radiation generator 12: Subject 13: Radiation image conversion panel 14: Light source 15: Photoelectric conversion device 16: Image reproduction device 17: Image display device 18: Filter

Claims (8)

[Claims] 1. After the radiation transmitted through the subject or emitted from the subject is absorbed by the divalent europium-activated cesium/rubidium halide phosphor represented by the composition formula (I) below, this phosphor has a wavelength of 450 to 900 nm. A radiation image conversion method comprising: emitting radiation energy stored in the phosphor as fluorescence by irradiating a region with electromagnetic waves; and detecting the fluorescence. Composition formula (I): CsX・a_RbX':x_Eu^2^+ (I)
(However, X and X' are Cl, Br and I, respectively.
at least one kind of halogen selected from the group consisting of; and a is a numerical value in the range of 0<a≦10.0;
x is a numerical value in the range of 0<x≦0.2) 2. a in the composition formula (I) is 0.15≦a≦2
．． 2. The radiation image conversion method according to claim 1, wherein the value is in the range of 0. 3. x in compositional formula (I) is 10^-^5≦x
The radiation image conversion method according to claim 1, wherein the value is in the range of ≦10^-^2. 4. 2. The radiation image conversion method according to claim 1, wherein the electromagnetic wave is an electromagnetic wave in a wavelength range of 600 to 750 nm. 5. 2. The radiation image conversion method according to claim 1, wherein the electromagnetic wave is a laser beam. 6. It is substantially composed of a support and at least one phosphor layer made of a binder containing and supporting a stimulable phosphor in a dispersed state provided on the support, and of the phosphor layer, At least one layer of the divalent europium-activated cesium halide represented by the following compositional formula (I).
A radiation image conversion panel characterized by containing rubidium phosphor. Compositional formula (I): CsX・aRbX': xEu^2^+ (I) (wherein, X and X' are each at least one kind of halogen selected from the group consisting of Cl, Br and I; and a is It is a numerical value in the range of 0<a≦10.0, and x is 0<a≦10.0.
It is a numerical value in the range of x≦0.2) 7. a in compositional formula (I) is 0.15≦a≦2.0
7. The radiation image conversion panel according to claim 6, wherein the value is in the range of . 8. x in compositional formula (I) is 10^-^6≦x≦1
7. The radiation image conversion panel according to claim 6, wherein the value is in the range of 0^-^2.