JPS6178892A - Radiation image transformation and radiation image transformation panel used in its process - Google Patents

Abstract

PURPOSE:To obtain a high-quality image steadily, by using a specified phosphor in the method of detecting fluorescence emitted by irradiation with a light having specified wavelengths from a phosphor which has been allowed to absorb radiation from an object. CONSTITUTION:A phosphor comprising an alkaline earth metal chlorobromide activated with divalent europium, shown by formula I (wherein MII is Ba, Sr or Ca; 0<X<=0.2; 0.25<=a<=0.8) or formula II (wherein 1.2<=a<=6), is used. An object 12 is irradiated with X-rays derived from a radiation generator 11, and the transmitted X-rays, whose amount is proportional to the transmittance of an object, are introduced into a radiation image transformation panel 13 for which the above-mentioned phosphor is used, thus forming a stored image of radiation energy. The panel 13 is then irradiated with an electromagnetic wave of the wavelength of 450-1,000nm from a light source 14 to cause to emit fluorescence corresponding to the above-mentioned stored image, which is displayed on an image display 17 by means of a photoelectric transfer device and an image reproducing device.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a radiation & 9 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 dichlorobromide phosphor, 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 combination of a radiographic film having an emulsion layer made of a silver salt photosensitive material and an intensifying screen is used. A so-called radiographic method is used. As an alternative to the conventional radiographic method, a radiation image conversion method using a stimulable phosphor is known, for example, as described in Japanese Unexamined Patent Publication No. 55-12145.

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. In the phosphor by excitation,
The W-product radiation energy 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 xMA photography for the purpose of medical diagnosis.

As the stimulable phosphor used in the above radiation image conversion method, a divalent europium-activated alkaline earth metal fluoride halide phosphor (MIIFX, Eu meter, but M
! is at least one kind of alkaline earth metal selected from the group consisting of Ba, Sr, and Ca, and X is a halogen other than fluorine). This phosphor is
After absorbing radiation such as radiation, it 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 phosphors, but little is known about the stimulable phosphors themselves other than this divalent europium-activated alkaline earth metal halide phosphor. Tiny,
1 The applicant is
A patent application has already been filed 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, MII is at least one kind of alkaline earth metal selected from the group consisting of Ba, Sr, and Ca:
and X' is at least one kind of halogen selected from the group consisting of C, Br, and
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≦0.2). From its X-ray diffraction pattern as described in the above specification, the MIIFX: E
It has been found that ``fluorophore'' is a different type of phosphor with a different crystal structure, and after being irradiated with radiation such as X-rays, ultraviolet rays, and TL radiation, it is excited with electromagnetic waves in the wavelength range of 450 to 11,000 nm. Then, it exhibits near-ultraviolet to blue luminescence (stimulated luminescence) with an emission maximum around 405 nm.This phosphor also exhibits near-ultraviolet to blue luminescence (instantaneous luminescence) when irradiated with radiation.

In carrying out the radiation image conversion method described above, the operation of reading out the radiation energy stored in the radiation image conversion panel is as follows: 1. Normally, a laser beam is used as excitation light, and the panel is first scanned with this laser beam to detect the brightness in the panel. By exciting the exhaustive fluorophore in a time-series manner? This is done by emitting the accumulated radiation energy as fluorescence, and then detecting this fluorescence with a detector.

Therefore, when a readout operation is performed immediately after irradiating a radiation image conversion panel with radiation such as Afterglow (radiation afterglow) causes a decrease in the S/N ratio of the obtained image, causing one problem. In other words, if the phosphor emits afterglow at a considerable ratio to the amount of photostimulated light, the light emission (afterglow) from the phosphor particle group other than the irradiation target will be the phosphor particle group of the irradiation target. The image obtained by a radiation image conversion panel containing such a phosphor is an image! (Sharpness.

It tends to be a product with a low concentration (easily decomposed).

However, the degree of influence of the afterglow characteristic of such a stimulable phosphor on image quality also changes depending on the interval between the radiation energy accumulation operation and the excitation light readout operation. Furthermore, in actual use, the influence of the radiation afterglow on the image quality varies depending on the method of detecting stimulated luminescence.

However, it can be said that it is of great significance to improve even a little the afterglow characteristic that adversely affects image quality.

Furthermore, although the radiation image conversion method using a radiation image conversion panel made of stimulable phosphor is a very advantageous image forming method as described above, it is desirable that the sensitivity of this method be as high as possible.

Generally, the higher the stimulated luminance of the phosphor used for the radiation image conversion panel, the higher the IC1.
It becomes ~. Therefore, it is desired that the stimulable phosphor used in the panel has as high a stimulable luminance as possible.

[Summary of the Invention] The present invention provides a radiation image conversion method using a divalent europium-activated alkaline earth metal chlorobromide phosphor that can provide images with improved image quality, and a radiation image conversion panel used in the method. That is the purpose.

The present invention also provides a method for converting a radiation image using a bromide phosphor activated with divalent ne-alpha-activated alkaline earth metal, which can provide an image with high sensitivity and improved image quality, and a radiation image used in the method. Its purpose is to provide a conversion panel.

In order to achieve the above object, the present inventors conducted various studies on divalent europium-activated alkaline earth metal chlorobromide phosphors among the above novel phosphors. As a result, it was found that phosphors in which the ratio of chlorine to bromine is within a specific range have significantly improved afterglow characteristics, and the present invention has been achieved.

That is, the radiation image conversion method of the present invention converts radiation transmitted through a subject or emitted from a subject into divalent europium-activated alkaline earth metal chloride represented by the following compositional formula (I) or compositional formula (II). After absorption by the bromide phosphor, the phosphor is irradiated with electromagnetic waves in the wavelength range of 450 to 100 nm to release the radiation energy stored in the phosphor as fluorescence, and detect this fluorescence. It is characterized by

Composition formula (I): MIIC12*aM irises Br2:xEu'' (I) (where 1M11 is at least one alkaline earth metal selected from the group consisting of Ba, Sr and Ca; and a is 0,25≦a (It is a numerical value in the range of ≦0.8, and X is a numerical value in the range of O<x≦0.2)
(However, MII is at least one alkaline earth metal selected from the group consisting of Ba, Sr, and Ca:
And a is a numerical value in the range of 1.2≦a≦6.0, and
is a numerical value in the range of 0 < A radiation image conversion panel characterized in that the stimulable phosphor layer contains a divalent europium-activated alkaline earth metal chlorobromide phosphor represented by the above composition formula (Z) or composition formula (It). shall be.

The present invention is achieved by controlling the proportions of salt, nitrogen, and bromine in a specific range in the novel divalent europium-activated alkaline earth dichlorobromide phosphor.

This was completed based on new knowledge that the afterglow characteristics of phosphors are significantly improved after irradiation with radiation such as X-rays.

In other words, by using the divalent europium-activated alkaline earth metal-chlorobromide phosphor represented by the above compositional formula (I) or (II), the radiation image conversion method consistently provides images with excellent image quality. be able to. Further, by using the radiation image conversion panel of the present invention made of the above-mentioned phosphor, it is possible to constantly obtain images of excellent quality.

In particular, the radiation image conversion method and radiation image conversion panel using a phosphor represented by the composition formula (I[) use long-wavelength electromagnetic waves as excitation light, which dramatically improves image quality without significantly reducing sensitivity. It is possible to do so.

[Structure of the Invention] The divalent europium-activated alkaline earth metal chlorobromide phosphor used in the present invention has the following compositional formula (■): MIICfLz @aMIIBr2 :xEu” (
I) (where 1MII is at least one alkaline earth metal selected from the group consisting of Ba, Sr, and Ca; and a is an a value in the range of 0.25≦a≦0.8, and X is 0 <x≦0.2) or compositional formula (IF) MIICCu25a"Br2:xEu" (II)
(However, ylx is at least one alkaline earth metal selected from the group consisting of Ba, Sr, and Ca;
And a is a numerical value in the range of 1.2≦a≦6.0, and
is a numerical value in the range O<xSo, 2).

In the phosphor represented by the above compositional formula (I) used in the present invention, from the viewpoint of improving afterglow characteristics and stimulated luminescence intensity, the ratio of MIIC12 and MIIBr2 is a
It is particularly preferable that the value is in the range 0.35≦a≦0.7.

In addition, in the phosphor represented by the above compositional formula (If) used in unreleased January, from the viewpoint of improving afterglow characteristics and stimulated luminescence intensity, the a value representing the ratio of M'' Cn 2 and MIIlBr2 is is particularly preferably in the range of 1.4≦a≦4°0.

Furthermore, in the above compositional formula (I) or (If), from the viewpoint of stimulated luminescence intensity, the alkaline earth metal fviN is preferably Ba, and the X value expressed before activation of europium is lO-5≦x≦10. - is preferably in the range.

BaC9,2*, which is an example of a phosphor used in the present invention
In the aBaBr2:0.001Eu'' phosphor, the a value representing the ratio of chlorine to bromine in the phosphor and the afterglow intensity, and the a value and the stimulated luminescence intensity have a relationship as shown in FIG.

In Figure 1, the solid line is BaC9,z, aBaBr r
2 :O,0QIE u 2+ This is a graph showing the relationship between the a value and the X-ray afterglow intensity [afterglow intensity 10 seconds after irradiation with 80 KVp X-rays] in the phosphor.

The dotted line is a graph showing the relationship between the a value and the stimulated luminescence intensity [the stimulated luminescence intensity when excited with conductor laser light (780 nm) after irradiation with 130 KVp X-rays].

As is clear from FIG. 1, the a value is 0.25≦a≦0.
8 or BaC in the range of 1.2≦a≦6.02
* a B a B r 2 :0.0OIE u
"The phosphor has a reduced X-ray afterglow intensity." , based on these facts.Furthermore, if the a value is 0.35≦a≦0.7 or 1.4≦a≦4
．． Phosphors in the range of 0 are BaC z * BaB
r 2 :0.001E Compared to the phosphor (a-1), the X-ray afterglow intensity decreases significantly without reducing the stimulated emission intensity so much. Also, from FIG. The phosphor in the range of 1.4≦a≦4.0 is 78Qn
It exhibits high-intensity stimulated luminescence with long-wave excitation of m, and its x
! It is clear that the afterglow intensity is significantly reduced.

Note that for divalent europium-activated alkaline earth metal chlorobromide phosphors used in the present invention with MII other than the above, the relationship between the a value and the X-ray afterglow intensity and stimulated luminescence intensity is similar to that shown in Figure 1. It has been confirmed that there is a trend.

The divalent europium-activated alkaline earth gold FJ and chlorobromide phosphor represented by the above compositional formula (I) or (II) can be produced, for example, by the production method described below.

First, as a phosphor raw material: 1) at least one alkaline earth metal chloride selected from the group consisting of BtkClz, Srclz, and CaCJLz, 2) at least one alkaline earth metal chloride selected from the group consisting of BaBr2.5rBrz and CaBrz. Metal bromide.

3) At least one compound selected from the group consisting of europium compounds such as halides, oxides, nitrate #1 mounds, and sulfates.

Prepare. In some cases, ammonium halide or the like may also be used as a flux.

When producing a phosphor, first the alkaline earth metal chloride (l) above, the alkaline earth metal bromide (2), and the alkaline earth metal bromide (3) are used.
Using a europium compound of, stoichiometrically, the composition formula (厘):
They are weighed and mixed in a relative ratio corresponding to E u (wherein, the definitions of MII, a and X are the same as in the above-mentioned compositional formula (I) or (It)).

The above mixture operation is carried out, for example, in the form of a suspension. Then, by removing water from the suspension of this phosphor raw material mixture, a solid dry mixture is obtained. This moisture removal operation is preferably carried out at room temperature or at a not very high temperature (for example, 200°C or less) by drying under reduced pressure, vacuum drying, or both.Of course, the mixing operation is limited to the above methods. Not.

The resulting dry mixture is then finely ground.

The pulverized material is filled into a heat-resistant container such as a quartz boat or an aluminum crucible, and fired in an electric furnace. The firing temperature is suitably in the range of 500 to 1300°C, and the firing time varies depending on the filling amount of the phosphor raw material mixture and the firing temperature, but is generally suitable for 0.5 to 6 hours. As the baking IIt 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. When the europium compound used contains trivalent europium, the weakly reducing atmosphere reduces the trivalent europium to divalent europium during the firing process.

Note that a method may be used in which the phosphor raw material mixture is once fired under the above firing conditions, and then the fired product is left to cool, crushed, and then re-fired (secondary firing). The firing is carried out in the above-mentioned weakly reducing atmosphere or in a neutral atmosphere such as a nitrogen gas atmosphere or an argon gas atmosphere at a firing temperature of 500 to 800° C. for 0.5 to 12 hours.

The powdered phosphor used in the present invention is obtained by the above baking. Regarding the obtained powdered phosphor,
If necessary, various general operations in the production of phosphors such as washing, drying, sieving, etc. may be further performed.

By utilizing the manufacturing method described above, a divalent ni-a-pium activated alkaline earth metal chlorobromide phosphor represented by the above-mentioned compositional formula (I) or (II) can be obtained.

In the radiation image conversion method of the present invention, the above composition formula (I)
The divalent europium-activated alkaline earth metal chlorobromide phosphor represented by (II) or (II) is preferably used in the form of a radiation image conversion spring (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 stimulable phosphor layer provided on one side of the support. The stimulable 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 attached to 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 uses a radiation image conversion panel having a phosphor layer made of a divalent europium-activated alkaline earth metal chlorobromide phosphor represented by the above composition formula (I) or (II). It is desirable to carry out the

In the radiation image conversion method of the present invention using a stimulable phosphor represented by MII formula (I) or (I[) in the form of a radiation image conversion panel, The radiation is absorbed by the phosphor layer of the radiation image conversion panel in proportion to the radiation dose, 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 accumulation image is.

By exciting with electromagnetic waves (excitation light) in the wavelength range of 450 to 11,000 nm, it can be emitted as stimulated luminescence (fluorescence). By photoelectrically reading this stimulated luminescence and converting it into an electrical signal, radiation can be emitted. It becomes possible to visualize the energy accumulation image.

The radiation image conversion method of the present invention can be carried out using one compositional formula (I) or (I).
Taking as an example a mode 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. 2, 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) or (It), and 14 is # accumulation of radiation energy on the radiation image conversion panel 13 as fluorescence. A light source as an excitation source for emitting radiation; 15, a photoelectric conversion device for detecting fluorescence emitted from the radiation image conversion panel 13; 16, a device for reproducing the photoelectric conversion signal detected by the photoelectric conversion device 15 as an image; 1;
7 is a device for displaying a reproduced image, and 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. 2 shows an example of obtaining a radiographic image of a subject, the subject 12 itself emits radiation (
(hereinafter referred to as a subject), it is not necessary to particularly install the radiation generating device ll, and the radiation image conversion panel 13 from the photoelectric conversion device 15 to the image display device ai17 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. 2, when the subject 12 is irradiated with radiation such as X-rays from the radiation generator tt, the radiation passes through the subject 12 in proportion to the radiation transmittance of each part of the subject 12. The radiation transmitted through the subject 12 firstly 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 strength 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 the Q-1000 nm wavelength range, 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. For example, can a photomultiplier tube convert this optical signal made up of the intensity of fluorescence into electricity? c2t15 converts it into an electrical signal, reproduces it as an image by the image reproducing device 16, and displays it on the image display device 2117.
Display this image by.

The operation of reading out the image information accumulated on a radiation image conversion panel as fluorescence is generally performed by scanning the panel in time series with a laser beam, and converting the fluorescence emitted from the panel by this scanning into photoelectrons through an appropriate condenser. This is done by detecting with a photodetector such as a multiplier tube and obtaining one time-series electrical signal. 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 -219314 and JP-A-5Fll-
121874 fυ), in this case, a large number of solid-state photoelectric conversion elements are configured to cover the entire surface of the panel,
The photoelectric conversion device may be integrated with the panel or placed close to the panel, and the photoelectric conversion device may be a line sensor in which a plurality of photoelectric conversion elements are connected in a line. Alternatively, it 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 case of item L may be a line light source such as an array of light emitting diodes (LEDs), semiconductor lasers, etc. arranged in a row. By performing readout using such a device, it is possible to prevent loss of fluorescence emitted from the panel, and at the same time, increase the solid angle of light reception and increase the S/N ratio. Further, since the obtained electrical signal is converted into a time series by electrical processing of a photodetector rather than by time-series irradiation of excitation light, it is possible to increase the readout speed.

The radiation image conversion panel from which image information has been read is erased by irradiating it with light in the wavelength range of the excitation light of the flasher or by heating it. It is also possible to do this, and it is preferable to do so (see JP-A-56-11392 and JP-A-56-12599). By performing this erasing operation, the afterimage caused by the first use of this panel can be removed. Generation of noise can be prevented. 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. 57-1
(See Publication No. 16300).

In the radiation image conversion method of the present invention, the radiation used to obtain a radiation transmission image of the subject is capable of exhibiting stimulated luminescence when the phosphor is excited by the electromagnetic waves after being irradiated with this radiation. Any radiation may be used, and for example, commonly known radiation such as xkQ, 'i-son rays, 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. Examples 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 a light source that emits light with a band spectral distribution in the wavelength range of 00n, for example, an Ar ion laser-1K
Lasers such as r-ion lasers, He-Ne lasers, ruby lasers, semiconductor lasers, lasers in glass, YAG lasers, dye lasers, and light sources such as light-emitting lights can also be used. Among these, lasers are one of the most popular because they can irradiate radiation image conversion panels with laser beams with high energy density per unit area.
Among these, preferable lasers as excitation light sources used in the present invention are He-Ne lasers and Ar ion lasers in terms of their stability and output, and semiconductor lasers are small;
It is preferable as an excitation light source because the driving power is small and the laser output can be easily stabilized because direct modulation is possible.

Further, the light source used for erasing may be any light source 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.

Does the radiation image conversion method of the present invention cause the stimulable phosphor to absorb and store radiation energy? jia section, a photodetection (readout) section that irradiates this phosphor with excitation light and releases the energy of the radiation as fluorescence, and an eraser section that releases the energy remaining in the phosphor, all built into one device. It can also be applied to a built-in type radiation image conversion device 2 (Japanese Patent Application No. 57-84436 and Japanese Patent Application No. 58
-66730), by using such a built-in device, it is possible to reuse the radiation image conversion panel (or recording medium containing a stimulable phosphor), A stable and 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 consists essentially of a support and a divalent europium-activated alkaline earth metal chloride bromide compound represented by the compositional formula (I) or (II) provided on the support. and a stimulable phosphor layer made of a binder containing and supporting phosphor in a dispersed form. The stimulable phosphor layer can be formed on the support, for example, by the following method.

Examples of binders for the phosphor layer include proteins such as gelatin,
Polysaccharides such as dextran, or natural polymeric substances such as gum arabic; and polyvinyl butyral, polyvinyl acetate, nitrocellulose, ethylcellulose, vinylidene chloride/vinyl chloride copolymer, polyalkyl (meth)acrylate, vinyl chloride/vinyl acetate copolymer Examples of binders include synthetic polymeric substances such as polyurethane, cellulose acetate butyrate, polyvinyl alcohol, and linear polyester. Particularly preferred among such binders are nitrocellulose, linear polyester,
These are polyalkyl (meth)acrylates, mixtures of nitrocellulose and linear polyester, and mixtures of nitrocellulose and polyalkyl (meth)acrylates.

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

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

The mixing ratio of the binder and the stimulable phosphor in the coating solution varies depending on the characteristics of the intended radiation image conversion panel, the type of phosphor, etc., but in general, the mixing ratio of the binder and the stimulable phosphor is 1:10011 (ratio), and particularly preferably from 1:8 to 1:40 (weight ratio).

In addition, paint! Liquid a contains a dispersant to improve the dispersibility of the phosphor in the coating solution, and a plasticizer 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
Phthalic acid, stearic acid, caproic acid,! Examples include oily surfactants. 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 butyl glycolate, etc. and polyesters of polyethylene glycol and aliphatic dibasic acids, such as polyesters of triethylene glycol and adipine, 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 a conventional coating means such as a doctor blade, roll coater, knife coater, etc.

As a support, an intensifying screen (
The material can be arbitrarily selected from various materials used as supports for (or intensifying 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, aluminum foil, aluminum alloy foil, etc. ° metal sheets, ordinary paper, baryta paper, Examples include resin-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 latter is a support suitable for a conversion panel, and the latter is a support suitable for a highly sensitive type radiation image conversion panel.

In known radiation image conversion panels, a phosphor layer is provided in order to strengthen the bond between the support and the phosphor layer, or to improve the sensitivity or image quality (sharpness, granularity) of the radiation image conversion panel. A polymeric substance such as gelatin is coated on the surface of the side support to form an adhesion-imparting layer, or a light-reflecting layer made of a light-reflecting substance such as titanium dioxide, or a light-reflecting layer made of a light-absorbing substance such as carbon black. The support used in the single-shot 1j+, which is known to be provided with an absorbing layer, can also be provided with these various layers, and their composition can be changed depending on the purpose and use of the desired radiation image storage panel. It can be selected arbitrarily.

Furthermore, as disclosed 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 aS on the support as described above, the coating film is dried to complete the formation of the stimulable phosphor layer on the support. The thickness of the phosphor layer varies depending on the characteristics of the intended radiation image conversion panel, the type of phosphor, the mixing ratio of the binder and the phosphor, and is usually 20 gm to 1 mm.

However, the thickness of this layer is preferably 50 to 500 pm.

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

Only one stimulable phosphor layer may be used, but two or more layers may be used.
i! ) may be layered, at least one of which may contain the divalent europium-activated alkaline earth metal chlorobromide phosphor of composition formula (I) or (II), and the surface of the panel may be It is also possible to have a structure in which a plurality of phosphor layers are stacked as ffi layers so that the luminous efficiency against radiation increases sequentially toward the side closer to the phosphor. An exhaustible phosphor can be used in combination.

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, o 8≦X≦10), and M I
IO・x S i O2: A (However, 1MII is Mg
, Ca, Sr, Zn, Cd, or Ba, and A is C
e, Tb, Eu, Tm, Pb, Tj1. Bi or Mn, and X is 0.5≦X≦2.5).

It is described in Japanese Patent Application Laid-Open No. 55-12143 (Ba
t-x-y+Mgx, Cay) FX: aEu2+ (However, X is at least one of C and Br, X and y are 0<X+y≦0.6, and xy#O
and a is lO4≦a≦5XlO-2), and LnOX:xA described in JP-A-55-12144 (however, Ln is one of La, Y, Gd, and Lu); X is at least one of C2 and Br, A is at least one of Ce and Tb, and X is 0<x<O, l)
, etc. can be mentioned.

In a normal radiation image conversion panel, as mentioned above, a transparent coating 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;
1151 is provided. Such a transparent protective film is 1
Radiation of the present invention &! It is also preferable to install an image change inspection panel.

Transparency! [1151 is, for example, a cellulose derivative such as cellulose acetate or nitrocellulose; or polymethyl methacrylate, polyvinyl butyral, polyvinyl formal, polycarbonate, polyvinyl acetate,
It can be formed by coating the surface of the phosphor layer with a solution prepared by dissolving a transparent polymer material, such as a synthetic polymer material such as vinyl chloride or vinyl acetate copolymer, in an appropriate solvent. can. Alternatively, it may 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 05L to 20ILm.

In addition, JP-A-55-163500, JP-A-57-
As described in Japanese Patent No. 96300 and the like, the radiation image conversion panel of the present invention may be colored with a coloring agent, and the sharpness of the l1Ti image obtained can be improved by coloring. Furthermore, as described in Japanese Patent Application Laid-Open No. 55-146447, the radiation image conversion panel of the present invention may have white powder dispersed in its phosphor layer for the same purpose.

Examples and comparative examples of the present invention will be described below. However, each of these does not limit the present invention.

[Example 1 and Comparative Example 1] Barium bromide (BaB r2
cloudy 2HzO) and barium chloride (Ba0M2・2H20
), and europium bromide (EuBr3) 0.783
g was added to 800 m of distilled water (H2O) and mixed to form an aqueous solution. This aqueous solution was dried under reduced pressure at 60°C for 3 hours, and then further vacuum dried at 150°C for 3 hours.

Table 1 No. Barium Bromide Chloride/Helium 1
66.6g 439.7g2 1
68.6g 366.5g3 333.2
g 244.3g4 433.2g
171.0g5 499.8g 122
．． 2g6 533.1g 97.7g7
．． 599.8g 48.9gNext, the obtained phosphor raw material mixture was filled into an alumina crucible, which was then placed in a high-temperature electric furnace and fired. Firing was performed at a temperature of 900° C. for 1.5 hours in a carbon dioxide atmosphere containing -carbon oxide, and then the fired product was taken out of the furnace and cooled. After cooling, the fired product was pulverized to obtain various powdered divalent europium-activated barium chloride bromide phosphors represented by the following compositional formulas.

No. 1: B aci2 ・0. l! Ba
B r2: 0-001Eu 2+ phosphor (comparative example) No. 2: BaCuz ・0.33 BaBr2: 0
．． 001Eu' phosphor (Example) No. 3: BaC12/1.1lBaBr2: 0.0
01Eu8 phosphor (Example) No. 4:BaCJL2・1.0BaBr2:0.0
01Eu2') Phosphor (comparative example) No. 5: BaCuza 3.0 BaBr2: 0. [
101Eu meter phosphor (example) No. 6: BaC, u2 fist 4.0 BaBr2: 0.00
1Eu8 phosphor (Example) No. 7: B aci 2” 11.OB aB
r2: 0.001 gu phosphor (comparative example) Next, the afterglow intensity 10 seconds after each of the above phosphors was irradiated with X-rays at a tube voltage of 80 KVp was measured. Furthermore, after irradiating the phosphor with X-rays at a tube voltage of 80 KVp, the stimulated luminescence intensity was measured when excited with semiconductor laser light (780 nm).

The obtained results are summarized and shown in the form of a graph in the FiS1 diagram.

In Fig. 1, the solid line is BaC intersection 2・aBaBr r 2
:0.001E u "This is a graph showing the relationship between the a value and the X-ray afterglow intensity in the phosphor. The one-dot line is a graph showing the relationship between the a value and the stimulated luminescence intensity.

As is clear from FIG. 1, the a value is 0.25≦a≦0.
8 or 1.2≦a≦6.0 BaC12 fist aBaBr2 used in the present invention: 0.001E u
``The X-ray afterglow intensity of the phosphor decreased.

In particular, &(Il'j is 0.35≦a≦0.7 or 1
．． The phosphors in the @ circle with 4≦a≦4.0 are BaC statement 2@
B a B r 2 :0.001E u' phosphor (
a=1. Compared to Comparative Example), the X-ray afterglow intensity was significantly reduced without the stimulated luminescence intensity decreasing significantly.

[Execution fi12] Powdered divalent europium-activated barium chloride bromide phosphor (BaC1z・1.3B a B
Methyl ethyl ketone was added to a mixture of r 2 : 0.0 OIE u ”) and a linear polyester resin, and further nitrocellulose of &H?, 1 It 11.5% was added to prepare a dispersion containing a phosphor in a dispersed state. Next, tricresyl phosphate, n-pucnol, 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 together. A coating liquid having a mixing ratio of 1:10 and a viscosity of 25 to 35 PS (at 25°C) was prepared.

Next, a polyethylene terephthalate l/-) sheet (support material thickness:
250pm) using a doctor blade. And after application! The support on which the yi film is formed is placed in a dryer, and the temperature inside the dryer is set to 2.
The coating film was dried by gradually increasing the temperature from 5°C to 100°C. In this way, a layer thickness of 250 pm was obtained on the support.
A phosphor layer was formed.

Then, a transparent film of polyethylene terephthalate (thickness: 12 meters, coated with polyester adhesive) is placed on top of this phosphor layer with the adhesive layer side facing down and adhered. No. 11 protective film was formed to produce a radiation image storage panel composed of a support, a phosphor layer, and a transparent protective film.

[Comparative Example 2] In Example 2, the powdered divalent europium-activated barium chloride bromide phosphor (BaCJJ2) obtained in Comparative Example 1 was used.
*BaBr2:0.0G1Eu'') was used, but the same treatment as in Example 2 was carried out to produce a radiation image storage panel composed of a support, a phosphor layer, and a transparent protective film.

Next, each radiation image conversion panel obtained in Example 2 and Comparative Example 2 was irradiated with X-rays at a tube voltage of 80 KVp, and then
Measure the afterglow intensity in seconds and the sensitivity of the panel (I11 emission intensity) when excited with semiconductor laser light (780 nm) after irradiating xl with a tube voltage of 80 KVp,
The panel was evaluated based on this. The results are shown in Table 2.

Table 2 Relative Afterglow Intensity Relative Sensitivity Example 2 0,23 0.8 Comparative Example 2
1.0 1.0

[Brief explanation of the drawing]

:JS1 Figure 1B is a specific example of the divalent europium-activated alkaline earth metal chlorobromide phosphor used in the present invention.
a Cl 2 a a B a B r z :Q,
0OIE u” The relationship between the a value and the X-ray afterglow intensity (solid line) and the relationship between the a value and stimulated luminescence intensity in the phosphor (
(dotted line). FIG. 2 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 processing device, 18: Filter patent applicant Fuji Photo Film Co., Ltd. Agent Patent attorney Yasuo Yanagawa □

Claims (20)

[Claims] 1. After the radiation transmitted through the subject or emitted from the subject is absorbed by the divalent europium-activated alkaline earth metal chloride bromide phosphor represented by the following composition formula (I), this phosphor is A radiation image conversion method comprising: emitting radiation energy stored in the phosphor as fluorescence by irradiating electromagnetic waves in a wavelength range; and detecting this fluorescence. Composition formula (I): M^IIICl_2・a_M^IIIBr_2:x_Eu^2
^+ (I) (However, M^III is at least one kind of alkaline earth metal selected from the group consisting of Ba, Sr, and Ca; and a is a numerical value in the range of 0.25≦a≦0.8. (x is a numerical value in the range of 0<x≦0.2) 2. a in compositional formula (I) is 0.35≦a≦0.7
2. The radiation image conversion method according to claim 1, wherein the numerical value is in the range of . 3. 2. The radiation image conversion method according to claim 1, wherein M^III in compositional formula (I) is Ba. 4. x in compositional formula (I) is 10^-^5≦x≦1
2. The radiation image conversion method according to claim 1, wherein the value is in the range of 0^-^2. 5. 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. 6. 2. The radiation image conversion method according to claim 1, wherein the electromagnetic wave is a laser beam. 7. After the radiation transmitted through the subject or emitted from the subject is absorbed by the divalent europium-activated alkaline earth metal chloride bromide phosphor represented by the following composition formula (II), this phosphor is A radiation image conversion method comprising: emitting radiation energy stored in the phosphor as fluorescence by irradiating electromagnetic waves in a wavelength range; and detecting this fluorescence. Composition formula (II): M^IICL_2・aM^IIBr_2:xEu^2^+(
II) (However, M^II is at least one alkaline earth metal selected from the group consisting of Ba, Sr and Ca;
And a is a numerical value in the range of 1.2≦a≦6.0, and x
is a numerical value in the range of 0<x≦0.2) 8. a in compositional formula (II) is 1.4≦a≦4.0
8. The radiation image conversion method according to claim 7, wherein the numerical value is in the range of . 9. 8. The radiation image conversion method according to claim 7, wherein M^II in compositional formula (II) is Ba. 10. x in compositional formula (II) is 10^-^5≦x
8. The radiation image conversion method according to claim 7, wherein the value is in the range of ≦10^-^2. 11. 8. The radiation image conversion method according to claim 7, wherein the electromagnetic wave is an electromagnetic wave in a wavelength range of 500 to 850 nm. 12. 8. The radiation image conversion method according to claim 7, wherein the electromagnetic wave is a laser beam. 13. In a radiation image conversion panel substantially composed of a support and a stimulable phosphor layer provided on the support, the stimulable phosphor layer is composed of two compounds represented by the following compositional formula (I). A radiation image conversion panel comprising a valent europium-activated alkaline earth metal chlorobromide phosphor. Composition formula (I): M^IICl_2・aM^IIBr_2:xEu^2^+(
I) (However, M^II is at least one alkaline earth metal selected from the group consisting of Ba, Sr and ca;
and a is a number in the range of 0.25≦a≦0.8,
x is a numerical value in the range of 0<x≦0.2) 14. a in the composition formula (I) is 0.35≦a≦0.
14. The radiation image conversion panel according to claim 13, wherein the radiation image conversion panel has a numerical value in the range of 7. 15. 14. The radiation image storage panel according to claim 13, wherein M^II in compositional formula (I) is Ba. 16. x in compositional formula (I) is 10^-^6≦x≦1
14. The radiation image conversion panel according to claim 13, wherein the value is in the range of 0^-^2. 17. In a radiation image storage panel substantially composed of a support and a stimulable phosphor layer provided on the support, the stimulable phosphor layer is a double stimulable phosphor layer represented by the following compositional formula (II). A radiation image conversion panel comprising a valent europium-activated alkaline earth metal chlorobromide phosphor. Composition formula (II): M^IICl_2・aM^IIBr_2:XEu^2^+(
II) (However, M^II is at least one alkaline earth metal selected from the group consisting of Ba, Sr and Ca;
And a is a numerical value in the range of 1.2≦a≦6.0, and x
is a numerical value in the range of 0<x≦0.2) 18. a in compositional formula (II) is 1.4≦a≦4.
18. The radiation image conversion panel according to claim 17, wherein the value is in the range of 0. 19. 18. The radiation image conversion panel according to claim 17, wherein M^II in compositional formula (II) is Ba. 20. x in compositional formula (II) is 10^-^5≦x≦
18. The radiation image conversion panel according to claim 17, wherein the value is in the range of 10^-^2.