JPS6123680A - Radiation image converting method and radiation image converting panel used therefor - Google Patents

Abstract

PURPOSE:To obtain an X-ray image having plenty of information with less irradiation dose, by allowing a radiation from an irradiated material to be absorbed by a specified phosphor, irradiating the phosphor with electromagnetic waves and detecting the emitted fluorescence. CONSTITUTION:A radiation passed through a material to be irradiated or radiated from a material to be detected is allowed to be absorbed by a bivalent europium-activated alkaline earth metal composite halide phosphor having a composition of the formula. The phosphor is irradiated with electromagnetic waves in a wavelength region of 450-1,000nm to allow radiation energy stored in the phosphor to be released as fluorescence and the fluorescence is then detected. In the formula, MII, MII' are each Ba, Sr, Ca; X, X', X'' are each Cl, Br, I; X'not equal to X''; 0.1<=a<=10.0; 0.1<=b<=10.0; 0<x<=0.2. Pref. said radiation image converting method is carried out by using a radiation panel contg. a phosphor layer composed of the bivalent europium-activated alkaline earth metal composite halide phosphor.

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 divalent europium-activated alkaline earth metal composite halogenide phosphor, and a radiation image conversion panel used in the method.

[Technical Background of the Invention] Conventionally, a method for obtaining a radiation image as an image uses a combination of a radiographic film having an emulsion layer made of a silver salt photosensitive material and an intensifying screen. Photography 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. 5-12145 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 released as fluorescence (stimulated luminescence), and this fluorescence is read photoelectrically to obtain an electrical signal.
The challenge is to convert this electronic pot signal into an image.

According to the above radiographic image conversion method, conventional radiographic method 0
This 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 using the method. Therefore, the radiographic 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.

Conventionally, as a stimulable phosphor used in the above-mentioned radiation image conversion method, a divalent europium-activated alkaline earth metal fluorohalide phosphor (MIIFX: Eu2+, where MII is a group consisting of Ba, Sr, and Ca) has been used. At least one kind of alkaline earth metal selected from the above, or a halogen other than fluorine has been proposed. This phosphor absorbs radiation such as X-rays and then 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 radiation image conversion method utilizes the photostimulability of the phosphor, but the stimulable phosphor itself is composed of this divalent europium-activated alkaline earth metal.

The present applicant has already filed an application for a radiation image conversion method and a radiation image conversion panel using a new divalent europium-activated alkaline earth metal halide phosphor represented by the following compositional formula (Japanese Patent Application No. 193162/1982). ).

Compositional formula: MIIX2#aMIIX'2:XEu-(
However, PdN is Ba. at least one alkaline earth metal selected from the group consisting of Sr and Ca;
and X′ is C9. , Br and I, and XsX
'; 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 0<X≦062) Conodivalent europium activated alkaline earth metal halide phosphor The MIIFX:E. u2+
It has been found that phosphor is a different type of phosphor with a different crystal structure, and after being irradiated with radiation such as X-rays, ultraviolet rays, and electron beams, it is excited by electromagnetic waves in the wavelength range of 450 to 10 QOn, m. Then, it exhibits near-ultraviolet to blue light emission (stimulated light emission) having an emission maximum around 405 nm.

[Summary of the Invention] The present invention provides a radiation image conversion method using a phosphor in which an alkaline earth metal fluorohalide is further added to the novel divalent europium-activated alkaline earth metal halide phosphor; The present invention provides a radiation image conversion panel used in the method.

That is, the radiation image conversion method of the present invention absorbs radiation transmitted through a subject or emitted from a subject into a divalent europium-activated alkaline earth metal composite halide phosphor represented by the following composition formula (I). After that, the phosphor is irradiated with electromagnetic waves in the wavelength range of 450 to 10 QOnm, thereby emitting the radiation energy stored in the phosphor as fluorescence, and this fluorescence is detected.

Compositional formula (I): MIIFX* a (MII 'X' 2 mbMII
'X' 2): xEu2+ (I) (However, MI
I and MW' are each at least one kind of alkaline earth metal selected from the group consisting of Ba, Sr and Ca; X' and x' are each at least one type of halogen selected from the group consisting of Cl, Br, and halogen. and X ′field
A numerical value in the range of 1≦a≦10.0, and b is 0.1≦0
．． Furthermore, the radiation image conversion panel of the present invention includes a phosphor layer comprising a support and a binder containing and supporting the stimulable phosphor in a dispersed state provided on the support. The phosphor layer is characterized in that it contains a divalent europium-activated alkaline earth metal fluorohalide phosphor represented by the above compositional formula (I).

The present invention provides a phosphor obtained by further adding an alkaline earth metal fluorohalide to the novel divalent europium-activated alkaline earth metal halide phosphor, which has a wide excitation wavelength range, This was completed based on the knowledge that the stimulated luminescence intensity increases significantly when the amount is within a specific range.

[Structure of the Invention] FIG. 1 illustrates the stimulated excitation spectra of the divalent europium-activated alkaline earth metal composite halide phosphor used in the radiation image conversion method of the present invention, respectively: (I):BaFBr*0. 5(Ba(,Q2eBaBr
2'): 0.001Eu'' Stimulated excitation spectrum of phosphor (2): BaFBr・0.5(BaBr2・Ba
l2): 0.001E This is the photostimulation excitation spectrum of u2+ phosphor. As is clear from FIG. 1, the divalent europium-activated alkaline earth metal composite halide phosphor used in the present invention has a temperature of 450 to 1000 after irradiation with radiation.
．． When excited with electromagnetic waves in the wavelength range of 500 to 850 nm, stimulated luminescence is exhibited.In particular, when excited with electromagnetic waves in the wavelength range of 500 to 850 nm, it is easy to separate stimulated luminescence and excitation light, and Stimulated luminescence results in 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 11,000 nm.

Further, FIG. 2 illustrates the stimulated emission spectrum of the divalent europium-activated alkaline earth metal composite halide phosphor used in the radiation image conversion method of the present invention.
In Fig. 2, curves 1.2 and 3 are respectively 1:BaFBrao, 5(BaCjL2sBaBr2
): 0.001E u 2+ Stimulated emission spectrum of phosphor 2: BaFBr*0.5 (BaBr2*Bal2)
:0.001E u” Stimulated emission spectrum of phosphor 3
:EaFCu-0,5(BaBr2*Bal2):0.
001E is a stimulated emission spectrum of u 2+ phosphor. As is clear from FIG. 2, the divalent europium-activated alkaline earth metal composite halide 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 approximately 390. ~400 nm.

The stimulated luminescence properties of the divalent europium-activated alkaline earth metal composite halide phosphor used in the present invention have been explained using a specific phosphor as an example. The stimulated luminescence properties are almost the same as those of the above-mentioned phosphors, and when excited with electromagnetic waves in the wavelength range of 450 to 11,000 nm after irradiation with radiation, it exhibits stimulated luminescence in the near ultraviolet to blue region.
It has been confirmed that the peak of the luminescence is approximately 390 to 400 nm.

Figure 3 shows BaFBraa (BaCJ12-BaB
r 2 ): 0.0OIE u 2 + phosphor a value and stimulated luminescence intensity [after irradiation with X-rays of 80 KVp,
FIG. 2 is a graph showing the relationship between "stimulated luminescence intensity when excited with excitation light]. In Figure 3, the curve l is H as the excitation light.
This is a graph when e-Ne laser light (632,8 nm) is used, and curve 2 is a graph when a light emitting diode (632,8 nm) is used as excitation light.
780 nm) is used. In addition, the third
In the figure, the point on the left vertical axis is B a F E r :0
．． 001E u 2+ phosphor Nol1 MR light intensity is shown,
Also, the point on the right vertical axis is BaCJL2・B a B r 2
:O,0OIE u 2+41 light body (7Ul exhaustion Q light intensity').

As is clear from FIG. 3, BaF used in the present invention
Braa (BaCJL2eBaBr2): 0.001
The E u ” phosphor is at least the conventionally known B a F phosphor.
B r : 0.001 E u 2+ If it exhibits stimulated luminescence with higher brightness than the phosphor, and if the a value is within a specific range, it will be the novel a Cl 2 ・B a Br
2: Exhibits stimulated luminescence with higher brightness than 0.001Eu' phosphor.

In addition, the relationship between the a value and the stimulated emission intensity of the phosphor differs depending on the wavelength of excitation light, and in short wavelength excitation, BaFB
When the content of r is relatively high (a value is small), the emission intensity becomes large; on the other hand, when the long wavelength excitation is performed (BaCJ12
*BaBr2) (7) When the content is relatively large (a value is large), the emission intensity becomes large. Therefore, among phosphors with a value in the range of 0.01≦a≦10.0, phosphors with afn in the range of 0.2'≦a≦10.0 have a short wavelength of 7° Onm or less. A phosphor that exhibits high-intensity stimulated luminescence upon excitation and has an a value in the range of 0.04≦a≦1.0 exhibits high-intensity stimulated luminescence upon long-wavelength excitation of 700 nm or more.

Although Fig. 3 shows the case where the ratio of BaC intersection 2 to BaBr2 is l: 1 (b=1), the b value can be varied within the range of 0.1≦b≦10.0. A similar relationship can be obtained even if Also, pdN, MII”, x, x
It has been confirmed that for the phosphors used in the present invention where ' and

The divalent europium-activated alkaline earth metal composite/\rogenide firefly 1 used in the radiation image conversion method of the present invention is:
The wavelength range of the stimulated excitation spectrum is 450-1100.
The wavelength of the excitation light that matches well with the phosphor can be changed by changing the content (a value) of the alkaline earth metal halide. In the radiation image conversion method, it is possible to appropriately change the wavelength of excitation light. That is, it becomes possible to appropriately select the excitation light source depending on the purpose. For example, since the stimulated excitation spectrum of the above-mentioned phosphor extends to about 11,000 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. Furthermore, from the viewpoint of the intensity 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 850 nm.

In the radiation image conversion method of the present invention, the above composition formula (I)
The divalent europium-activated alkaline earth metal composite 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 alkaline earth metal composite halide phosphor represented by the above composition formula (I). is 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-Zo.

By exciting it with electromagnetic waves (excitation light) in the Onm 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. 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 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 image of accumulated radiation energy on the radiation image conversion panel 13 as fluorescence. Light source as excitation source, 15
16 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 device that displays the reproduced image, and , 18 are filters that do not allow the reflected light from the light source 14 to pass through, but only allow the fluorescence emitted from the radiation image conversion panel 13 to pass through.

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), 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. 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 electromagnetic waves in a wavelength range of 0 to looOnm are irradiated, 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 the image reproducing device 1
6, 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 (as disclosed in Japanese Patent Application Laid-Open No. (See Publication No. 58-67240). By performing this pre-read operation, there is an advantage that the read conditions for the main read 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).
27 No. 5, Japanese Patent Application No. 58-219313 and Japanese Patent Application No. 1983
Specifications of No. 8-219314 and JP-A-58-1
21874), 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. You can leave it there. Further, 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. By performing readout using a suitable 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 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 (#Open/Close 57-11
(See Publication No. 6300).

In the radiation image conversion method of the present invention, the radiation used to obtain a radiation transmitted image of the subject is such that the phosphor exhibits stimulated luminescence when excited by the electromagnetic waves after receiving the radiation. Any radiation can be used as long as it can be used. For example, commonly known radiation such as X-rays, electron beams, and ultraviolet rays can be used.

Also.

When obtaining a radiation image of a subject, the radiation directly emitted from the subject may be any radiation that is similarly absorbed by the phosphor and serves as an energy source for stimulated luminescence. can include radiation such as gamma rays, alpha rays, and beta rays.

As a light source of excitation light for exciting the phosphor that has absorbed radiation from the subject or the subject, 450 to 110
In addition to light sources that emit light with a uniform spectral distribution in the wavelength range of 00 nm, for example, Ar ion laser-1
Lasers such as Kr ion lasers, He-Ne lasers, ruby lasers, semiconductor lasers, glass lasers, YAG lasers, dye lasers, and light sources such as light emitting diodes can also be used. Among them, a laser is preferable as an excitation light source used in the present invention because it has a high energy density per unit area and can irradiate a radiation image conversion panel with a laser beam.
Among them, preferred are the 1% laser, the t1He-Ne laser, the Ar ion laser, and the Kr ion laser in terms of stability and output, and semiconductor lasers are compact as described above. It is preferable as an excitation light source for reasons such as low driving power, direct modulation, and easy stabilization of laser output.

Further, the light source used for erasing may be any one that emits light in the excitation wavelength range of the stimulable phosphor, and examples thereof include a tungsten lamp, a fluorescent lamp, and a halogen lamp.

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 releases the radiation energy as fluorescence; and a built-in eraser to release the energy remaining in the phosphor,
It can also be applied to a built-in type radiation image conversion device (Japanese Patent Application No. 57-84436 and Japanese Patent Application No. 58-84).
6fli 730), by using such a built-in device, a radiation image conversion panel (
or a recording medium containing a stimulable phosphor) can be reused, and stable and homogeneous images 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 essentially of a support and a divalent europium-activated alkaline earth metal composite halide phosphor provided on the support and represented by the composition formula (I). and at least one phosphor layer comprising a supporting binder contained in a dispersed state.

The radiation image conversion panel having the above configuration is, for example,
It can be manufactured by the method described below.6 First, the above composition formula (I
) The divalent europium-activated alkaline earth metal composite halide phosphor is explained below.

This divalent europium-activated alkaline earth metal composite halide phosphor can be manufactured, for example, by the manufacturing method described in the first section.

First, as phosphor raw materials, 1) BaFCJl, BaFBr, BaFI, 5rFC,
l, 5rFBr, 5rF1. CaFC1. At least one alkaline earth metal fluorohalide selected from the group consisting of CatBr and CaFI, 2) BaCJ12, BaBr2, Ba12, Sr0 2)
．． 3) at least two alkaline earth metal halides selected from the group consisting of 5rBr2, SrI2, CaCuz, CaBrz and Ca12; 3) at least two selected from the group consisting of compounds of europium such as halides, oxides, nitrates and sulfates; Prepare a kind of compound.

Here, the phosphor raw material (MIIFX) in l) above is prepared from an alkaline earth metal fluoride (MIIFz) and other alkaline earth metal halides (MlX 2 ) by a known wet method or dry method. A manufactured one can be used. Alternatively, MIIF2 and M
"X2 may be used directly as a phosphor raw material.

As the phosphor raw material in 2) above, two or more alkaline earth metal halides containing at least different halogens are used. In some cases, further ammonium halide (NH4X";
, B r *RI is I), etc. may be used as the flux.

When manufacturing a phosphor, the above alkaline earth metal fluorohalide, 2) alkaline earth metal halide, and 3) europium compound are used to stoichiometrically form the composition formula (■). : MIIFX*a (MIIX'2* bMI'X'' 2): xEu (II) (However, M depth and M strength are Ha, Sr, and C, respectively.
at least one alkaline earth metal selected from the group consisting of &; X, X' and X'' are Cl, B, respectively;
is at least one kind of halogen selected from the group consisting of It is a numerical value in the range of 0.1゛≦b≦10.0, 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 (a numerical value in the range of 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. After heating this mixture at a temperature of 100° C. or higher for several hours, the phosphor raw material of 1.3) may be mixed into the obtained heat-treated product, or 1ii) First, The above phosphor raw materials 1) and 2) are mixed in a suspension state, and this suspension is heated (preferably 5
It may be carried out by drying under reduced pressure, vacuum drying, spray drying, etc. at a temperature of 0 to 200° C., and then mixing the phosphor raw material of 3) above with the obtained dried product.

As a modification of the method ii) above, the phosphor raw materials of 1), 2) and 3) above are mixed and the resulting mixture is subjected to the heat treatment as described above, or the phosphor raw materials of 1) and 3) above are mixed. A method may also be used in which the above-mentioned phosphor raw materials are mixed, the mixture is subjected to the above heat treatment, and the phosphor raw material of 2) above is mixed into the obtained heat-treated product. Further, as a modification of the method 1ii) above, a method of mixing the phosphor raw materials of 1), 2) and 3) above in a suspension state and drying this suspension, or a method of drying the suspension, or ) are mixed in the form of a suspension, this suspension is dried, and the resulting dry product is mixed with the above 2).
A method of mixing phosphor raw materials may also be used.

In any of the above methods i), ii), and 1ii), mixing is carried out using various mixers, a type blender,
Conventional mixers such as ball mills and rod mills are used.

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 0-1300°C is suitable, preferably 700°C.
-1000°C range. 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 europium compound with a trivalent valence of ni-ropium is used as the phosphor raw material in 3) above, but in this case, in the firing process, the trivalent europium is converted into divalent europyram due to the weakly reducing atmosphere mentioned above. will be reduced to

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.

In addition, in the divalent europium-activated alkaline earth metal composite halide phosphor represented by the composition formula (I), i
Ml and Mxia' in Weiwu (Z) may be the same or different, X and X'' and x'' may be the same or different, but X' and X11 must be different.

From the viewpoint of stimulated luminescence brightness, MII and MII'' in composition formula (I) are preferably Ha, and X is Cl and B.
Preferably, either r and X' and X
''' is preferably either Cl or Br, respectively. Also, from the viewpoint of stimulated luminescence brightness, MloX
'2 ToM! The b value representing the ratio with 'x'2 is 0.3
It is preferably in the range of ≦b≦3.3, more preferably in the range of 0.5≦b≦2.0, and the X value representing the activation amount of europium is lO′≦X≦lO″4. Preferably within the range.

Examples of binders for the phosphor layer formed by dispersing the divalent europium-activated alkaline earth metal composite halide phosphor include proteins such as gelatin,
Polysaccharides such as dextran, or natural polymeric substances such as gum arabic; and polyvinyl butyral, polyvinyl acetate, nitrocellulose, ethyl cellulose, vinylidene chloride φ vinyl chloride copolymer, poly(meth)acrylate, vinyl chloride, Examples include binders typified by synthetic polymeric substances such as vinyl acetate copolymer, polyurethane, cellulose acetate butyrate, polyvinyl alcohol, linear polyester, and the like. Particularly preferred among such binders are nitrocellulose, linear polyesters, polyalkyl (meth)acrylates 1, mixtures of nitrocellulose and linear polyesters, and nitrocellulose and polyalkyl (meth)acrylates. It is a mixture.

The phosphor layer can be formed on the support, for example, by the following method.

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

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. 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 generally the mixing ratio of the binder and the stimulable phosphor is 1. :1 to 1: Zo.

(weight ratio), and especially 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 phthalic acid, stearic acid, caproic acid, and lipophilic surfactants. Examples of plasticizers include phosphoric acid esters such as triphenyl phosphate, tricresyl phosphate, and diphenyl phosphate; phthalic esters such as diethyl phthalate and dimethoxyethyl phthalate; ethyl phthalyl ethyl glycolate, and butyl phthalyl butyl 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, 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 large 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, etc.

Usually it is 20pm to 1mm. However, the thickness of this layer is preferably 50 to 500 μm.

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 phosphor layer may be pressed onto a support, or the support and the phosphor layer may be bonded together 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 alkaline earth metal composite halide of composition formula (I). Any layer may be used as long as it contains a phosphor, and a plurality of phosphor layers may be stacked so that the luminous efficiency with respect to radiation increases sequentially toward the surface of the panel. Furthermore, in both the single-layer and multilayer cases, a known stimulable phosphor can be used in combination with the above-mentioned phosphor.

Examples of such known stimulable phosphors include, in addition to the above-mentioned phosphors, ZnS:Cu,Pb,BaO*xAl2O3, which is described in JP-A-55-12142:
Eu (however, 0.8≦X≦10), and MII
O@XSiO2:A (however, M-tolu
, Zn, Cd, or Ba, and A is Ce, Tb, E
u, Tm, Pb, 7 sentences, Bi, or M n Te,
X is 0.5≦X≦2.5), as described in JP-A-55-1.2143 (R
aw-x-y, Mgx, Cay) FX: aEu2+ (However, X is at least one of Cl and Br, and X and y are O<x+y≦0.6, and x y
x O, and a is lO″≦a≦5X lO′), and LnOX:xA (Ln is La, Y, G
d, and at least one of Lu, X is at least one of Cl and Br, A is at least one of Ce and Tb, and X is O<x<O,,
1), etc.

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 in contact with the support to physically and chemically protect the phosphor layer.
A membrane is provided. Such a transparent protective film is preferably provided also in the radiation image conversion panel of the present invention.

Transparent protective films, such as cellulose derivatives such as cellulose acetate and nitrocellulose; or synthetic polymeric substances such as polymethyl methacrylate, polyvinyl butyral, polyvinyl formal, polycarbonate, polyvinyl acetate, and vinyl chloride/vinyl acetate copolymers. It can be formed by coating the surface of the phosphor layer with a suspension prepared by dissolving a transparent polymeric substance in an appropriate solvent. Alternatively, polyethylene terephthalate, polyethylene, polychloride, vinylidene, 74
１″′″１゛″nu°jゝFormationゝ１Transparent thin film with fluorescence
It can also be formed by bonding the surface of a single layer using a suitable adhesive. The thickness of the transparent protective film formed in this way is approximately 0.1 to 20
It is desirable to set it to 8Lm.

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

[Example 1] Barium fluoride bromide (BaFBr) 236.3 g, barium chloride (B acjLz @ 2H20) 104.1
g, barium bromide (BaBr2a2H,20) 14
8,6. g and europium bromide (EuBr3)0
．． Add 783-g to 800 ml of distilled water (H2O),
The mixture was mixed to form a suspension. This suspension was dried under reduced pressure at 60°C for 3 hours, and then further vacuum dried 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 divalent europium-activated barium composite halide phosphor [B a FB r @0.5 (B aC pattern 2
*BaB'r2): 0.001 E u 2+] was obtained.

[Example 2] Powdered divalent powder was obtained by performing the same procedure as in Example 1 except that 195.6 g of barium iodide (BaI2.2H20) was used instead of barium chloride. Europium-activated barium composite halide phosphor [BaFBr*0.5 (BaBr 2 e
BaI2): 0.001 Eu'] was obtained.

[Example 3 In Example 1, barium fluoride chloride (BaFCfi) was used instead of barium fluoride bromide and barium bromide.
8g and barium iodide (BaI 2 .2H20)
195, 6 g'. By performing the same operation as in Example 1, except for the following steps, a powdered divalent europium-activated barium composite halide phosphor [BaF
Cl・0.5 (BaC5L2・Bal2): 0.00
1 Eu”] was obtained.

Next, each phosphor obtained in Examples 1 and 2 was applied with a tube voltage of 8
After irradiation with 0 KVP X-rays, the stimulated excitation spectrum at the peak wavelength of stimulated luminescence (approximately 392 nm and 402 nm) was measured when excited with light in the wavelength range of 450 to 11000 nm.

The results are shown in Figure 2-(I) and (2).

(I):BaFBreO,5(BaCl2*BaBr
2) :0.001Eu'' phosphor (Example 1)
Photostimulation excitation spectrum (2): BaF, B r eO,5 (BaBr
2 * BaI z ): 0.001 E u ” Stimulated excitation spectrum of phosphor (Example 2) In addition, each phosphor obtained in Examples 1 to 3 was applied with a tube voltage of 80 K.
After irradiating with X-rays of Vp, the stimulated emission spectrum was measured when excited with a light emitting diode (wavelength near 80 nm). The results are shown in FIG.

In FIG. 2, curves 1 to 3 are respectively.

1: BaFBreo, 5 (BaCl2*BaBr2)
:0.001E Stimulated emission spectrum of u2+ phosphor (Example 1), 2:BaFBreO,5(BaBr2'Bal2):O
, Stimulated emission spectrum of GOIE u 2+ phosphor (Example 2), 3: BaFCJ1*0.5 (BaBr2'Bal2):
Stimulated emission spectrum of 0.001E u 'phosphor (Example 3).

shows.

[Example 4] The divalent europium-activated alkaline earth metal composite halide phosphor obtained in Example 1 [BaF B r #0.
5 (B a Cl 2 e B a Br 2 ):
Methyl ethyl ketone is added to a mixture of particles of [O,QOIEu'] and linear polyester resin, and the degree of nitrification is increased to 1.
A dispersion containing phosphor in a dispersed state was prepared by adding 1.5% nitrocellulose.Next, tricresyl phosphate, n-butanol, and methyl ethyl ketone were added to this dispersion, and then a propeller mixer was added. The phosphor is uniformly dispersed, the mixing ratio of the binder and the phosphor is 1;10, and the viscosity is 25 to 35P.
A coating solution of S (25°C) was prepared.

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 with a layer thickness of 250 pm was formed on the support.

Then, a transparent protective film of polyethylene terephthalate (thickness: 12 gm, coated with a polyester adhesive) is placed and adhered 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 produced.

[Example 5] In Example 4, the valent europium-activated barium composite halide phosphor rBaFBr obtained in Example 2 was used as a stimulable phosphor.
):0.001 Eu2+] By performing the same treatment as in Example 4, the support,
A radiation image storage panel composed of a phosphor layer and a transparent protective film was manufactured.

[Example 6] In Example 4, the divalent europium-activated barium composite halide phosphor obtained in Example 3 was used as a stimulable phosphor [BaFC-0,5 (BaCCl0'' Ba
I2): 0.001 Eu′ was used, except for Ilcot. By performing the same treatment as in Example 4,
A radiation image storage panel consisting of a support, a phosphor layer and a transparent protective film was manufactured.

Next, each of the radiation image conversion panels obtained in Examples 4 to 6 was irradiated with X-rays at a tube voltage of 80 KVp, and then excited with 780 nm light to measure the sensitivity (stimulated luminance) of the panel. The results are shown in Table 1. In Table 1, the sensitivity of each panel is BaC3L2' BaBr2:0 described in the specification of Japanese Patent Application No. 193162/1982.
．． The relative sensitivity is expressed as 100, which is the sensitivity measured under the same conditions of a radiation image conversion panel obtained by performing the same treatment as in Example 4 except for using the 001Eu2+ phosphor.

Table 1 relative sensitivity Example 4 140 Example 5 100 Example 6 30

[Brief explanation of the drawing]

FIGS. 1-(I) and (2) are diagrams illustrating the photostimulated excitation spectrum of the divalent europium-activated alkaline earth metal composite halide phosphor used in the present invention. FIG. 2 is a diagram illustrating the stimulated emission spectrum of the divalent europium-activated alkaline earth metal composite halide phosphor used in the present invention. Figure 3 shows BaFBr* a (BaC 2), which is a specific example of the divalent europium-activated alkaline earth metal composite halide phosphor used in the present invention.
:0.001E It is a graph showing the relationship between the a value and the stimulated luminescence intensity in u2+ 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 (14)

[Claims] 1. After the radiation transmitted through the subject or emitted from the subject is absorbed by the divalent europium-activated alkaline earth metal composite halide phosphor represented by the following composition formula (I), this phosphor has a wavelength of 450 to 1000 nm. A method for converting a radiation image, comprising: emitting radiation energy stored in the phosphor as fluorescence by irradiating the phosphor with electromagnetic waves in a wavelength range of , and detecting the fluorescence. Composition formula (I): M^IIFX・a (M^II'X'_2・ bM^II'X"_2): xEu^2^+ (I) (However, M^II and M^II' are each at least one alkaline earth metal selected from the group consisting of Ba, Sr and Ca; X, X' and X'' are Cl,
At least one kind of halogen selected from the group consisting of Br and I, and X'≠X''; and a is a numerical value in the range of 0.01≦a≦10.0, and b is 0.
It is a numerical value in the range of 1≦b≦10.0, and x is 0<x≦0
．． 2) 2. 2. The radiation image conversion method according to claim 1, wherein b in compositional formula (I) is a numerical value in the range of 0.3≦b≦3.3. 3. 2. The radiation image conversion method according to claim 1, wherein M^II and M^II' in compositional formula (I) are both Ba. 4. 2. The radiation image conversion method according to claim 1, wherein X in compositional formula (I) is either Cl or Br. 5. In compositional formula (I), X' and X'' are each C
2. The radiation image conversion method according to claim 1, wherein the radiation image conversion method is either 1 or Br. 6. x in compositional formula (I) is 10^-^5≦x≦10
2. The radiation image conversion method according to claim 1, wherein the value is in the range of ^-^2. 7. 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. 8. 2. The radiation image conversion method according to claim 1, wherein the electromagnetic wave is a laser beam. 9. It is substantially composed of a support and a phosphor layer provided on the support and made of a binder containing and supporting a stimulable phosphor in a dispersed state, and the phosphor layer has the following composition formula: A radiation image storage panel comprising a divalent europium-activated alkaline earth metal composite halide phosphor represented by (I). Composition formula (I): M^IIIFX・a(M^III^'X'2・bMI'X"_
2): xEu^2^+(I) (However, M^III and M^III^' are each at least one kind of alkaline earth metal selected from the group consisting of Ba, Sr, and Ca; X, X' and x” are Cl, Br and I, respectively
at least one kind of halogen selected from the group consisting of, and X'≠X''; and a is 0.01≦a
A numerical value in the range of ≦10.0, and b is 0.1≦b≦10
．． is a numerical value in the range of 0, and x is a numerical value in the range of 0<x≦0.2) 10. Claim 9, characterized in that b in compositional formula (I) is a numerical value in the range of 0.3≦b≦3.3.
The radiation image conversion panel described in Section 1. 11. M^III and M^III^' in composition formula (I)
10. The radiation image conversion panel according to claim 9, wherein both are Ba. 12. 10. The radiation image storage panel according to claim 9, wherein x in compositional formula (I) is either Cl or Br. 13. 10. The radiation image storage panel according to claim 9, wherein X' and X'' in compositional formula (I) are each Cl or Br. 14. x in compositional formula (I) is 10^-^5≦x≦1
The radiation image conversion panel according to claim 9, characterized in that the value is in the range of 0^-^2.