JPS61236891A - Radiation image conversion and panel therefor - Google Patents

Abstract

PURPOSE:After radiation is allowed to absorb in a complex halide fluorescent material activated with a brightening divalent Eu, the fluorescent material is irradiated with specific electromagnetic wave to allow the radiation energy to emit as fluorescence and radiation image conversion is effected by detecting the fluorescence. CONSTITUTION:Radiation beams after transmission through the substrate or emitting from the substrate is absorbed in a divalent Eu-activated complex halide fluorescent material of the formula (MII is Ba, Sr, Ca; MI is Li, Rb, Cs; X, X' are Cl, Br, I; 0.1<=a<=20.0; 0<x<=0.2). Then, the fluorescent material is irradiated with electromagnetic waves of 450-900nm, preferably 500-800nm wavelength to allow the radiation energy to emit as fluorescent light. The fluorescence is read optoelectrically and converted into electric signals to form an image. EFFECT:An X-ray image rich in information is obtained from reduced exposure to X-rays. 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 composite halide phosphor activated with divalent europium, and a radiation image conversion panel used in the method.

[Background of the Invention] Conventionally, as a method of obtaining a radiation image as an image, a so-called radiographic method is used, which uses a combination of a radiographic film having an emulsion layer made of a silver salt photosensitive material and an intensifying screen. is being 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 signal is converted into an image. .

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: .

(B a , -x + M'' x ) F X :
y A (However, M2+ is at least one of Mg, Ca, Sr, Zn, and Cd, X is at least one of C1, Br, and I, A is Eu, Tb%Ce
, Tm, Dy, Pr, Ho, Nd, Yb, and Er, and x is 0≦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 (photostimulation) when irradiated with electromagnetic waves in the visible light to infrared region. luminescence).

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 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 composite halide phosphor represented by the following compositional formula (I) exhibits stimulated luminescence, that is, the phosphor exhibits stimulated luminescence. They discovered that stimulated luminescence occurs in the near-ultraviolet to blue region when irradiated with radiation such as β-rays and then excited with electromagnetic waves in the visible to infrared region of 450 to 900 nm, and based on this knowledge, they completed the present invention. It has come to this.

Compositional formula (I): MIIX2 e aMIIX': xEu2°
(I) (However, Ml is at least one kind of alkaline earth metal selected from the group consisting of Ba, Sr, and Ca; MI is at least one kind of alkali metal selected from the group consisting of Li, Rh, and Cs; X and X
' are each at least one kind of halogen selected from the group consisting of C1, Br, and A: and a is 0.1
It is a numerical value in the range of ≦a≦20.0, and X is O<x≦0.
2) In other words, the radiation image conversion method of the present invention transmits through the object. Alternatively, after the radiation emitted from the subject is absorbed into the divalent europium-activated composite halide phosphor represented by the above compositional formula (I), this phosphor has a
It is characterized in that by irradiating electromagnetic waves in a wavelength range of 900 nm, the radiation energy stored in the phosphor is emitted as fluorescence, and this fluorescence is detected.

Furthermore, 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 a stimulable phosphor in a dispersed state. It is characterized in that at least one of the phosphor layers contains a divalent europium-activated composite halide phosphor represented by the above compositional formula (I).

[Structure of the Invention] FIG. 1 illustrates the stimulated excitation spectrum of a divalent europium-activated composite halide phosphor used in the radiation image conversion method of the present invention.

In Fig. 1, curve 1 and curve 2 are respectively BaB
r, eLiBr: 0.001Eu” phosphor and B a
B r , @CsB r:o,001E It is a photostimulation excitation spectrum of u2° phosphor.

As is clear from FIG. 1, BaB used in the present invention
r2 *LiBr:0-001Eu” phosphor and B
aB r 2 * CsB r: 0.001E u""
Phosphors exhibit stimulated luminescence when excited with electromagnetic waves in the wavelength range of 450 to 900 nm after irradiation with radiation. In particular, when excited with electromagnetic waves in the wavelength range of 500 to 800 nm, they exhibit stimulated luminescence and excitation light. is easy to separate, and its stimulated luminescence has high brightness. It is based on this fact that in the radiation image conversion method of the present invention, the wavelength of the electromagnetic wave used as excitation light is defined as 450 to 900 nm.

Further, FIG. 2 illustrates the stimulated excitation spectrum of the divalent europium-activated complex monohalide phosphor used in the radiation image conversion method of the present invention. are respectively BaBr2 eLi
Br: 0.001Eu""phosphor and B aB r
2*CsB r:0.001E This is the stimulated emission spectrum of the u2° phosphor.

As is clear from FIG. 2, B a used in the present invention
B r 2 * L i B r:0.001E u2
° phosphor and B aB r 2@CsB r:o,
The oolE u'' phosphor exhibits stimulated luminescence in the near-ultraviolet to blue region, and its stimulated luminescence spectrum has peaks at about 405 nm and about 410 nm, respectively.

The stimulated luminescence properties of the divalent europium-activated composite halide phosphor used in the present invention have been explained using a specific phosphor as an example. However, other phosphors used in the present invention can also be It has been confirmed that when irradiated with radiation such as a line and then excited with electromagnetic waves in the wavelength range of 450 to 900 nm, stimulated luminescence (peak wavelength of light emission = around 390 to 42 Onm) is exhibited in the near ultraviolet to blue region.

Figure 3 shows B aB r 2m aL i B r:o
, 001E u "Graph showing the relationship between the a value and the stimulated emission intensity [stimulated emission intensity when irradiated with 80 KVp X-rays and then excited with He-Ne laser light (832,8 mm)] As is clear from Fig. 3, BaBr2 whose a value is in the range of 0.1≦a≦20.0
* aLiBr: 0.0 OIEu2+ phosphor exhibits stimulated luminescence 0 The a value of the divalent europium-activated composite halide phosphor used in the radiation image conversion method of the present invention is in the range of 0.1≦a≦20゜0. The provisions were made based on these facts. Moreover, from FIG. 3, BaB r 2 @aL i B r:o, 001E used in the present invention whose a value is in the range of 0.1≦a≦20.0
Among the u2+ phosphors, the a value is 1.5≦a≦10.
It is clear that phosphors in the range of 0 exhibit stimulated luminescence with higher brightness. In addition, B aB r , *aL
i B r: o, 001E u "For the divalent europium-activated composite halide phosphor used in the present invention other than the phosphor, the relationship between the a value and the stimulated luminescence intensity is 88
It has been confirmed that the trend is similar to that shown in Figure 3.

The divalent europium-activated composite halide phosphor used in the radiation image conversion panel of the present invention has a stimulated excitation spectrum in a wide wavelength range of 450 to 900 nm, and therefore the radiation image conversion method of the present invention uses this phosphor. In this case, 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. Further, from the viewpoint 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 preferably electromagnetic waves in the wavelength range of 500 to 800 nm.

In the radiation image conversion method of the present invention, the above composition formula (I)
The divalent europium-activated composite 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 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 preferably carried out using a radiation image conversion panel having a phosphor layer made of a divalent europium-activated composite halide phosphor represented by the above-mentioned compositional 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 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. The radiation image conversion method of the present invention can be converted into an image by using the composition formula (
Taking as an example an embodiment in which the stimulable phosphor represented by I) is used in the form of a radiation image conversion panel, it will be specifically explained using the schematic diagram shown in FIG.

In FIG. 4, 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 an excitation for emitting the accumulated radiation energy image on the radiation image conversion panel 13 as fluorescence. 15 is a photoelectric conversion device for detecting the fluorescence emitted from the radiation image conversion channel 13; 16 is a device for reproducing the photoelectric conversion signal detected by the photoelectric conversion device 15 as an image; 17 is a device for reproducing the photoelectric conversion signal detected by the photoelectric conversion device 15; 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 12 eyes of the subject emit radiation (
(hereinafter referred to as a subject), it is not necessary to particularly install the radiation generating device 11, and the radiation image conversion panel 13 from the photoelectric conversion device 15 to the image display device 17 is It is also possible to convert it into any other suitable device that can somehow reproduce the information emitted in the form of fluorescence 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 lo00 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. An optical signal composed of the strength and weakness of this fluorescence is converted into an electrical signal by a photoelectric conversion device 15 such as a photomultiplier tube, and an image reproduction device fi.
16, the image is reproduced as an image, and the image display device 17 displays this image.

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
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 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
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 and perform the erasing more efficiently (Japanese Patent Laid-Open No. 57-116
(See Publication No. 300).

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 a radiation, and even commonly known radiation such as Jf, 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 gamma rays, alpha rays, and beta rays.
Examples include radiation such as 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 a light source that emits light with a band spectral distribution in the wavelength range of 0 to 900 nm, Ar ionizer,
Light sources such as lasers and light emitting diodes, such as a He-NeLy laser, a Luhey laser f-1 semiconductor laser, a glass ψ laser, a YAG laser, a Kr ion laser, and a dye laser, 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, the preferred laser beam is Ar ion laser-1K.
r-ion laser-1He-Ne laser and semiconductor laser. Furthermore, semiconductor lasers are preferable as excitation light sources because they are compact, require low driving power, and can be directly modulated, making it easy to stabilize laser output.

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

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 storage panel substantially contains a support and a divalent europium-activated composite halide phosphor provided on the support and represented by the composition formula (I) in a dispersed state. at least one phosphor layer comprising a supporting binder.

The radiation image conversion panel having the above configuration is, for example, 1
It can be manufactured by the method described below.

First, the above composition formula (I
) The divalent europium-activated composite halide phosphor represented by:

This divalent europium-activated composite halide phosphor is
For example, it can be manufactured by the manufacturing method described below.

First, as a raw material for phosphor.

1) B a CfL 2, S rcjL 2, Ca
CjL2. BaBr2.5rBr2, CaBr2, Ba
At least one alkaline earth metal halide selected from the group consisting of I, SrI2 and CaI, 2) LiCA, RbCJI CsC1, LiBr, Rb
3) at least one alkali metal halide selected from the group consisting of Br, CsBr, LiI, RbI, and CsI; and 3) at least one selected from the group consisting of europium compounds such as halides, oxides, nitrates, and sulfates. Compound.

Prepare.

In some cases, ammonium halide (NH
4X'''; tatashi, xn (IL, Br or I), etc. may be used as the flux.

When producing a phosphor, the above alkaline earth metal halide of 1), the alkali metal halide of 2) and the europium compound of 3) are used to stoichiometrically form the composition formula (U): M厘X2 *aMIIX': xEu
(II) (However, MII is at least one kind of alkaline earth metal selected from the group consisting of Ba, Sr, and Ca; Ml is at least one kind of alkali metal selected from the group consisting of Li, Rh, and Cs; X and X' are each at least one kind of halogen selected from the group consisting of CJlg, Br and I; and a is a numerical value in the range of 0°1≦a≦20.0, and X is 0<
A mixture of phosphor raw materials is prepared by weighing and mixing them so as to have a relative ratio corresponding to x≦0.2.

The phosphor raw material mixture may be prepared by: i) simply mixing the phosphor raw materials in 1), 2) and 3) above, or ii) first adding the phosphor raw materials in 1) and 2) above. The mixture may be heated at a temperature of 100° C. or higher for several hours, and then the phosphor raw material of 3) above may be mixed with the obtained heat-treated product, or alternatively, item i) First, The above phosphor raw materials 1) and 2) are mixed in a solution state, and this solution is heated (preferably 50 to 50%
200° C.) by vacuum drying, vacuum drying, spray drying, etc., 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) a method of mixing the phosphor raw materials and subjecting the resulting mixture to the above heat treatment; and as a modified method of the above method 1ii), the phosphor raw materials of 1), 2) and 3) are mixed in a solution state. Alternatively, a method may be used in which the solution is mixed with water and then dried.

In any of the above methods i), ii), and i), conventional mixers such as various mixers, V-type blenders, ball mills, and rod mills are 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 0-1300°C is appropriate, preferably 700°C.
N is in the range of 1000°C. The firing time varies depending on the filling amount of the phosphor raw material mixture and the firing temperature, etc.
Generally, 0.5 to 6 hours is 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. In general, above 3
) is used as a phosphor raw material in which a europium compound having a trivalent europium valence is used; in this case, during the firing process, the trivalent europium is reduced to divalent europium by the weakly reducing atmosphere.

A powdered phosphor is obtained by the above firing.

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 X' in the alkaline earth metal halide (M''X2) and the alkali metal halide CMIX') are as follows.

From the point of view of stimulated luminance, which may be the same or different from each other, X representing halogen is B.
r or C1, and one compositional formula (I
In I), the a value representing the ratio of M' .

Roughly speaking, from the point of view of stimulated luminescence luminance, the X value representing the activation amount of europium in composition formula (n) is 10-8≦X≦1O.
-2 is preferred.

Examples of binders for the phosphor layer formed by dispersing the divalent europium-activated composite 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 substances such as acrylates, vinyl chloride/vinyl acetate copolymers, polyurethanes, cellulose acetate butyrate, polyvinyl alcohol, linear polyesters, and the like. Among these binders, particularly preferred are:
Nitrocellulose, linear polyester, polyalkyl (
meth)acrylates, mixtures of nitrocellulose and linear polyesters, and mixtures of nitrocellulose and polyalkyl (meth)acrylates.

The phosphor layer can be formed on the support by, for example, a primary 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 and methyl ethyl 1
Ketones such as ketones and methyl isobutyl ketone; 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 monoethyl ether; and mixtures thereof. can be mentioned.

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 generally the mixing ratio of the binder and the stimulable phosphor is 1. :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, butyl phthalyl glycolate, etc. 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, the phosphor layer is used 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 support surface on the side where it is applied to form an adhesion-imparting layer, or a light-reflecting layer made of a light-reflecting substance such as titanium dioxide, or a light-absorbing substance such as carbon black. It is known to provide a light absorption layer etc.
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 201 Lm to 1 mm. However, the thickness of this layer is preferably 50 to 5001 Lm.

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 forming a phosphor layer by applying a 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 contains the divalent europium-activated composite halide phosphor of composition formula (I). The phosphor layer may have a structure in which multiple phosphor layers are layered so that the luminous efficiency against radiation increases sequentially toward the surface of the panel, and either a single layer or a multilayer structure may be used. Also, 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, which are described in JP-A-55-12142.

BaC1xA120. :Eu (However, 0.8≦X≦
10), and MIIO*xSi02:A (however,
MII is Mg, Ca, Sr, Zn, Cd, or Ba and A is Ce, Tb, Eu, Tm, Pb, Ti, Bi
, or Mn, and X is 0.5≦X≦2.5), as described in JP-A-55-12143 (B
a r-x-y, Mgx, Cay
) F X :aEu” (X is 0 sentence and Br
at least one of the following, and X and y are O<
x +y≦0.6, there is x y s Ote, a is,
10-"≦a≦5X10-2), LnO described in JP-A-55-12144
X: xA (Ln is La, Y, Gd, and Lu
X is at least one of C1 and Br, A is at least one of Ce and Tb, and X is 0<x<O, l), and the present application MIIX2eaMIIX"2:x E described in Japanese Patent Application No. 193162/1983 filed by a person
u '''' (where Ml 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 CM, Br, and Yes, and X
≠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 Such a transparent protective film is preferably provided 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 transparent synthetic polymer material such as polymethyl methacrylate, polyvinyl butyral, polyvinyl formal, polycarbonate, polyvinyl acetate, vinyl chloride/vinyl acetate copolymer, etc. It can be formed by coating the surface of the phosphor layer with a solution prepared by dissolving a polymeric substance in an appropriate solvent. 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. The thickness of the transparent protective film thus formed is preferably about 0.1 to 20 gm.

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

[Example 1] Barium bromide (Rant 2) 297.15g.

After weighing 86.84 g of lithium bromide (LiBr) and 0.392 g of europium bromide (EuBri), they were thoroughly mixed and ground in a ball mill to prepare a phosphor raw material mixture.

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 carried out at 850°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 divalent europium activated barium lithium bromide phosphor (B aB r 2a L i B r: 0.00
1E u2°) was obtained.

[Example 21 In Example 1, powdered divalent europium was produced by performing the same operation as in Example 1 except that 212.90 g of cesium bromide (CsEr) was used instead of lithium bromide. Activated barium cesium bromide phosphor (B
aBr2.CsBr: 0.001 E u ”) was obtained.

[Example 3] In Example 1, 208.25 g of barium chloride (BaC!Lz) was used instead of barium bromide, and 165.37 g of rubidium bromide (RbBr) was used instead of lithium bromide.
A powdered divalent europium-activated composite halide phosphor (B ac!; L2 @ RbBr
: 0.001 E u”) was obtained.

[Example 4] Example 1 except that 99 g of calcium chloride (CaCJLz) was used instead of barium bromide, and 259.81 g of cesium iodide (C5I) was used instead of lithium bromide. By performing operations similar to the method described above, a powdered divalent europium-activated composite halide phosphor (CaCA, ecsI: 0.001
u2+) was obtained.

[Example 5] Example 1 except that 208.25 g of barium chloride (BaCJLz) was used instead of barium bromide, and 259.81 g of cesium iodide (CsI) was used instead of lithium bromide. By performing operations similar to the method described above, a powdered divalent europium-activated composite halide phosphor (BaCl 2 a Cs I: 0.0G
1 E u 2°) was obtained.

[Example 6] In Example 1, barium chloride A was used instead of barium bromide.
(BaCJLz) 208.25g, and 120°92g of rubidium chloride (Rb C1) instead of lithium bromide
A powdered divalent europium-activated composite halide phosphor (BaCjLz/RbCfL: 0.0
01 Eu2°) was obtained.

Next, each of the phosphors obtained in Example 1 and Example 2 was irradiated with X-rays at a tube voltage of 80 KVp, and then excited with He-Ne laser light (wavelength 632.8 nm). And the stimulated excitation spectrum at the peak wavelength of stimulated luminescence was measured. The obtained results are shown in the second
As shown in Fig. 1 and Fig. 1.

In FIG. 2, curve 1 and curve 2 are respectively curve 1 :BaBr2 *LiBr:Q, 001 Eu
Stimulated emission spectrum of 2゜phosphor.

Curve 2: Stimulated emission spectrum of BaBr2*CsBr:0.001Eu'' phosphor.

In addition, in Fig. 1, curve 1 and curve 2 are respectively curve 1: photostimulation excitation spectrum of BaBr2@LiBr:O,QOIEu2◆ phosphor, and curve 2: photostimulation excitation spectrum of BaBr2 CsBr:0.001 Eu'' phosphor. The excitation spectrum is shown.

[Example 7] Powdered divalent europium-activated barium lithium bromide phosphor (BaBr2.L i Br
Methyl ethyl ketone was added to a mixture of a linear polyester resin and a linear polyester resin, and further nitrocellulose with a degree of nitrification of 11.5% was added to prepare a dispersion containing a phosphor in a dispersed state.

Next, tricresyl phosphate, n-butanol, and methyl ethyl ketone were added to this dispersion, and the mixture was thoroughly stirred and mixed using a propeller mixer to ensure that the phosphor was uniformly dispersed and that the binder and phosphor were mixed at the same ratio. is 1:lO1
A coating solution with a viscosity of 25 to 35 PS (25°C) was prepared.
Next, a titanium dioxide kneaded polyethylene terephthalate sheet (support, thickness: 2
The coating liquid was applied uniformly onto the sample (501Lm) 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 set to 25°C.
The coating film was dried by gradually raising the temperature from °C to 100 °C. In this way, a layer thickness of 250 gm was obtained on the support.
A phosphor layer was formed.

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

[Example 8] In Example 7, BaBr2 obtained in Example 2
* Cs B r : 0.001 By performing the same operation as in Example 7 except for using the E u 2+ phosphor, a radiation image conversion device composed of a support, a phosphor layer, and a transparent protective film was prepared. Manufactured the panel.

[Example 9] In Example 7, BaCJL2- obtained in Example 3
RbBr: 0.001 By performing the same operation as in Example 7 except for using Eu2° phosphor,
A radiation image storage panel consisting of a support, a phosphor layer, and a transparent protective film was manufactured.

[Example 10] In Example 7, Ba(,12・
Csl : O, OOI Eu" By performing the same operation as in Example 7 except for using the phosphor, a radiation image conversion panel composed of a support, a phosphor layer, and a transparent protective film was prepared. Manufactured.

[Example iB In Example 7, BaCJ12 obtained in Example 5
・RbC1: 0.001 By performing the same operation as the method of Example 7 except for using Eu'+ phosphor, a radiation image conversion device consisting of a support, a phosphor layer, and a transparent protective film was obtained. Manufactured the panel.

[Example 12] In Example 7, BaC12・R obtained in Example 6
bcJL: 0.001 E u'° By performing the same operation as in Example 7 except for using the phosphor, a radiation image conversion panel composed of the support, the phosphor layer, and the transparent protective film was prepared. Manufactured.

Next, each radiation image conversion panel obtained in Examples 7 to 12 was irradiated with X-rays at a tube voltage of 80 KVp, and then 632.8 n
The sensitivity of each panel was measured by excitation with light of m. The results are shown in Table 1.

Below margin Table 1 relative sensitivity Example 7 100 Example 8 80 Example 9 35 Example IQ 15 Example 11 50 Example 12 30

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 shows a specific example of the divalent europium-activated composite halide phosphor of the present invention, BaBr2.L i B r
: 0.001 E u 2+ phosphor and BaBr
2m Cs B r : 0.001 E u Stimulated excitation spectrum of 2° phosphor (curves 1 and 2, respectively)
It is. FIG. 2 shows a specific example of the divalent europium-activated composite halide phosphor of the present invention, BaBr2.L i Br
: 0.001 E u 2° phosphor and BaBr
2m CsB r : 0. ．． 001E u2° phosphor stimulated emission spectra (curves 1 and 2, respectively). FIG. 3 shows a specific example of the divalent europium-activated composite halide phosphor of the present invention, BaBr2.aL i B
r: 0.001 E u"" It is a graph showing the relationship between the a value and the stimulated luminescence intensity in a phosphor. FIG. 4 is a schematic diagram illustrating the radiation image conversion method of the present invention.

Claims (12)

[Claims] 1. After the radiation transmitted through the object or emitted from the object is absorbed by the divalent europium-activated composite halide phosphor represented by the following composition formula (I), this phosphor is exposed to radiation in the wavelength range of 450 to 900 nm. A radiation image conversion method comprising: emitting radiation energy stored in the phosphor as fluorescence by irradiating it with electromagnetic waves; and detecting this fluorescence. Composition formula (I): M^IIX_2・aM^ I X':xEu^2^+ (
I) (However, M^II is at least one kind of alkaline earth metal selected from the group consisting of Ba, Sr and Ca; M^I is at least one kind of alkali metal selected from the group consisting of Li, Rb and Cs. and X and X' are each at least one kind of halogen selected from the group consisting of Cl, Br and I; and a is 0
．． It is a numerical value in the range of 1≦a≦20.0, and x is 0<x≦
(The value is in the range of 0.2) 2. a in the composition formula (I) is 1.5≦a≦10
．． 2. The radiation image conversion method according to claim 1, wherein the value is in the range of 0. 3. 2. The radiation image conversion method according to claim 1, wherein X in compositional formula (I) is either Br or Cl. 4. 2. The radiation image conversion method according to claim 1, wherein M^II in the compositional formula (I) is Ba. 5. 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. 6. 2. The radiation image conversion method according to claim 1, wherein the electromagnetic wave is an electromagnetic wave in a wavelength range of 500 to 800 nm. 7. 2. The radiation image conversion method according to claim 1, wherein the electromagnetic wave is a laser beam. 8. 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, A radiation image storage panel characterized in that at least one layer thereof contains a divalent europium-activated composite halide phosphor represented by the following compositional formula (I). Composition formula (I): M^IIX_2・aM^IX': xEu^2^+(I)
(However, M^II is at least one kind of alkaline earth metal selected from the group consisting of Ba, Sr, and Cl; M^I is at least one kind of alkali metal selected from the group consisting of Li, Rb, and Cs. :X and X'
are each at least one kind of halogen selected from the group consisting of Cl, Br, and I; and a is 0.1≦
It is a numerical value in the range of a≦20.0, and x is 0<x≦0.2
) 9. a in compositional formula (I) is 1.5≦a≦10.0
9. The radiation image conversion panel according to claim 8, wherein the radiation image conversion panel has a numerical value in the range of . 10. 9. The radiation image storage panel according to claim 8, wherein X in compositional formula (I) is either Br or Cl. 11. 9. The radiation image storage panel according to claim 8, wherein M^II in compositional formula (I) is Ba. 12. x in compositional formula (I) is 10^-^5≦x≦
9. The radiation image conversion panel according to claim 8, wherein the value is in the range of 10^-^2.