JP2003119462A - Oxygen-introduced rare earth-activated alkaline earth metal fluoride halide-based photostimulable phosphor and radiographic image transformation panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a photostimulable phosphor having high emission intensity and excellent in erasing characteristics and to provide a radiographic image transformation panel using the photostimulable phosphor. SOLUTION: The oxygen-introduced rare earth-activated alkaline earth metal fluoride halide-based photostimulable phosphor is expressed by the formula (1): Ba(1-x) M<2> x FBry I(1-y) : aM<1> , bLn, cO and the content of phosphorus in the photostimulable phosphor is <=50 ppm.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a stimulable phosphor, and more particularly to an oxygen-introduced rare earth activated alkaline earth metal fluorohalide stimulable phosphor and a radiation image conversion using the stimulable phosphor. It's about panels.

[0002]

2. Description of the Related Art Radiation images such as X-ray images are widely used in the fields of disease diagnosis and the like. This X-ray image can be obtained by irradiating the phosphor layer (fluorescent screen) with X-rays that have passed through the subject to generate visible light, which is the same as when taking a normal photo. Then, a so-called radiographic method is widely used in which a silver halide photographic light-sensitive material (hereinafter, also simply referred to as a light-sensitive material) is irradiated and then developed to obtain a visible silver image.

However, in recent years, a new method of directly taking out an image from a phosphor layer has been proposed instead of an image forming method using a light-sensitive material having a silver halide salt.

As this method, the radiation that has passed through the subject is absorbed by the phosphor, and then the phosphor is excited by, for example, light or thermal energy, so that the radiation energy accumulated by the phosphor is absorbed. Then, there is a method of detecting this fluorescence and imaging it.

Specifically, for example, US Pat. No. 3,85
A radiation image conversion method using a stimulable phosphor as described in JP-A No. 9,527 and JP-A No. 55-12144 is known.

This method uses a radiation image conversion panel containing a stimulable phosphor, and the radiation transmitted through the object is applied to the stimulable phosphor layer of the radiation image conversion panel to apply the radiation to each part of the object. Accumulates radiation energy corresponding to the radiation transmission density, and then accumulates in the stimulable phosphor by time-sequentially exciting the stimulable phosphor with electromagnetic waves (excitation light) such as visible light and infrared rays. The emitted radiation energy is emitted as stimulated emission, and the signal due to the intensity of this light is photoelectrically converted to obtain an electric signal, and this signal is recorded, such as a recording material such as a silver halide photographic light-sensitive material, a CRT, etc. Is reproduced as a visible image on the display device.

According to the above radiographic image recording / reproducing method, the radiation dose is much smaller than that of the conventional radiographic method using a combination of a radiographic film and an intensifying screen, and the radiation amount is rich in information. It has the advantage that an image can be obtained.

As described above, the stimulable phosphor is a phosphor that exhibits stimulated emission when irradiated with excitation light after being irradiated with radiation, but in practice, excitation with a wavelength in the range of 400 to 900 nm is used. A phosphor that emits stimulated emission in the wavelength range of 300 to 500 nm by light is generally used.

A radiation image conversion panel using these stimulable phosphors releases radiation energy by scanning excitation light after storing radiation image information. Therefore, radiation images can be stored again after scanning. It can be used repeatedly. In other words, in the conventional radiographic method, the radiographic film is consumed for each photographing, whereas in the radiographic image conversion method, the radiographic image conversion panel is repeatedly used. It is advantageous.

The radiation conversion panel comprises a support and a stimulable phosphor layer provided on the surface thereof, or a self-supporting stimulable phosphor layer, and the stimulable phosphor layer is usually stimulable. Some include a phosphor and a binder that dispersively supports the phosphor, and some include only an aggregate of the stimulable phosphor formed by a vapor deposition method or a sintering method. Also known is one in which the gap between the aggregates is impregnated with a polymer substance. Further, a protective film made of a polymer film or a vapor deposition film of an inorganic material is usually provided on the surface of the stimulable phosphor layer opposite to the support side.

Examples of stimulable phosphors used in the radiation conversion panel include JP-A Nos. 55-12145 and 55-16.
No. 0078, No. 56-74175, No. 56-1167.
No. 77, No. 57-23673, No. 57-23675
No. 58-206678, No. 59-27289,
59-27980, 59-56479, 59
Rare earth element-activated alkaline earth metal fluorohalide-based phosphors described in JP-A-56480;
No. 0, No. 60-84381, No. 60-106752
No. 60-166379, No. 60-221483
No. 60-228592, No. 60-228593
No. 61-23679, No. 61-120882,
JP-A-61-2120883, JP-A-61-120885, JP-A-61-235486, JP-A-61-235487, and the like, a divalent europium-activated alkaline earth metal fluorohalide-based phosphor; Oxyhalide phosphor activated with a rare earth element described in 12144; JP-A-58-6
Cerium-activated trivalent metal oxyhalide phosphor described in JP-A-9281; Bismuth-activated alkali metal halide phosphor described in JP-A-60-70484; JP-A-60-1
No. 41783 and No. 60-157100, the divalent europium-activated alkaline earth metal halophosphate phosphors;
A divalent europium-activated alkaline earth metal haloborate phosphor described in JP-A-60-157099;
Divalent europium-activated alkaline earth metal hydrohalide phosphors described in 0-217354;
Nos. 21173 and 21182, cerium-activated rare earth compound halide phosphors; JP-A-614039.
Cerium-activated rare earth halophosphate phosphor described in No. 0; Divalent europium-activated cerium rubidium halide phosphor described in JP-A-60-78151;
-78151, a divalent europium-activated composite halide phosphor, and the like. Among them, a divalent europium-activated alkaline earth metal fluoride halide-based phosphor containing iodine, and iodine are included. Known stimulable phosphors such as rare earth element-activated oxyhalide phosphors and iodine-containing bismuth-activated alkali metal halide phosphor-based phosphors are still known, but still high-luminance stimulable phosphors. Is required. Further, as the use of radiation image conversion methods utilizing stimulable phosphors has progressed, there has been a demand for further improvement in image quality of radiation images obtained, for example, improvement in sharpness and graininess. The above-mentioned method for producing the stimulable phosphor is a solid-phase method or a method called a sintering method, in which pulverization after firing is essential, sensitivity,
There is a problem that it is difficult to control the particle shape that affects the image performance. Among the means for improving the image quality of a radiation image, it is effective to make the stimulable phosphor fine particles and the finely divided stimulable phosphor particles have the same particle size, that is, to narrow the particle size distribution. .

JP-A-9-291278 and JP-A-7-2
The method of producing a stimulable phosphor from a liquid phase disclosed in, for example, No. 33369 is a method of obtaining a fine-particle stimulable phosphor precursor by adjusting the concentration of a phosphor raw material solution. It is effective as a method for producing a stimulable phosphor powder having a uniform distribution. However, there is an increasing demand for a radiation conversion panel capable of obtaining a higher quality image for accurate diagnosis, and further for a stimulable phosphor for realizing the radiation conversion panel. In particular, in order to obtain an effective image while reducing the exposure dose, there is a strong demand for a high-luminance photostimulable phosphor.

Further, in the implementation of the above-described radiation image recording / reproducing method, the radiation image conversion panel itself is hardly deteriorated by the irradiation of the radiation and the irradiation of the excitation light, so that it can be repeatedly used for a long period of time. Usually, the radiation energy stored in the panel is read out by using laser light as excitation light, and first scanning the panel with this laser light to excite the stimulable phosphor in the panel in time series. The emitted radiation energy is emitted as fluorescence, and this fluorescence is detected by a photodetector. In actual use, the radiation energy accumulated in the panel is not sufficiently exhausted only by scanning with laser light. Therefore, in order to prepare for the next recording, it is necessary to release the radiation energy remaining in the panel to erase the image recorded by the previous recording (erasing process). Efficiently performing this erasing process leads to speeding up imaging and eventually diagnosis, so various attempts have been made to improve it. For example, JP-A-5
As disclosed in Japanese Unexamined Patent Publication No. 6-11192, there is proposed a method of erasing residual radiation energy by irradiating the panel with light in the excitation wavelength region of stimulated emission of the phosphor after reading the panel. However, even if the same amount of light is irradiated, the easiness of erasing the residual radiation energy (erasing property) differs depending on the stimulable phosphor, so that it is possible to release more residual radiation energy with a certain amount of light. That is, it is desired to obtain a phosphor that is easily erased.

[0014]

SUMMARY OF THE INVENTION An object of the present invention is to obtain a stimulable phosphor having high emission brightness and excellent erasing characteristics, and further, radiation using the stimulable phosphor. To get an image conversion panel.

[0015]

The above-mentioned object of the present invention can be solved by the following constitution.

1. In the oxygen-introduced rare earth-activated alkaline earth metal fluorohalide-based stimulable phosphor represented by the general formula (1), the phosphorus content in the stimulable phosphor is 50 ppm or less. An oxygen-introduced rare earth activated alkaline earth metal fluorohalide stimulable phosphor.

2. 2. The oxygen-introduced rare earth-activated alkaline earth metal according to 1, wherein the precursor of the oxygen-introduced rare earth-activated alkaline earth metal fluoride halide stimulable phosphor has a phosphorus content of 50 ppm or less. Metal fluorinated halide stimulable phosphor.

3. The phosphorus content in the stimulable phosphor is 30 ppm or less, and the oxygen-introduced rare earth-activated alkaline earth metal fluorohalide-based stimulable phosphor according to 1 or 2.

4. Phosphorus content in the precursor of the stimulable phosphor is 30 ppm or less, oxygen-introduced rare earth activated alkaline earth metal fluorohalide stimulable fluorescence described in 1, 2 or 3. body.

5. 5. The oxygen-introduced rare earth-activated alkaline earth metal fluorohalide-based stimulant according to any one of 1 to 4, wherein the precursor of the stimulable phosphor is produced in a liquid phase. Fluorescent substance.

6. 6. A radiation image conversion panel comprising the oxygen-introduced rare earth-activated alkaline earth metal fluorohalide-based stimulable phosphor according to any one of 1 to 5 above.

That is, as a result of intensive studies made by the present inventors in view of the above-mentioned problems, the phosphorus concentration in the stimulable phosphor was determined in order to obtain a stimulable phosphor having high brightness and good erasing characteristics. The inventors have found that it is necessary to control, and have reached the present invention.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION A typical embodiment of the method for producing an oxygen-introduced rare earth-activated alkaline earth metal fluorohalide stimulable phosphor of the present invention will be described in detail below.

In the present invention, the stimulable phosphor has the composition represented by the above general formula (1), but in addition to this, it is possible to contain a trace amount of aluminum or silicon.

In the present invention, the concentration of phosphorus in the stimulable phosphor must be 50 ppm or less, preferably 30 ppm or less. In order to obtain the above composition, the phosphorus content in the phosphor precursor is preferably 50 ppm or less, and more preferably the phosphorus content in the phosphor precursor is 30 ppm. It has been found that it is difficult to reduce the phosphorus content to zero, but it is preferable to set the phosphorus content to the lowest possible range. By setting the phosphorus content within the range of the present invention, it is possible to provide better image and erasing characteristics. In order to control the amount of phosphorus in the stimulable phosphor and the phosphor precursor, a method of controlling the phosphorus concentration in the raw material barium halide can be mentioned.

The phosphorus content in the stimulable phosphor and the phosphor precursor is determined by inductively coupled plasma emission spectroscopy (hereinafter referred to as ICP-A).
(Called ES) can be used. The sample is preferably made into a solution by the following method. A certain amount of a stimulable phosphor or a stimulable phosphor precursor whose phosphorus content is to be measured is weighed out, heated with hydrochloric acid and dried repeatedly, and then the residue is dissolved with hydrochloric acid and water to determine the content. Accept. By measuring the concentration of phosphorus in this liquid, stimulable phosphor,
The content of phosphorus in the stimulable phosphor precursor can be known. For ICP-AES measurement, the analysis wavelength is 213.
618 nm and an output of 1.3 kW are preferably used, and it is preferable to quantify by a calibration curve method.

As the method for producing the stimulable phosphor in the present invention, it is possible to use a so-called solid phase method in which powder raw materials described in JP-A-9-291277 are mixed and heated, but the liquid phase method is used. It is preferable to use it from the viewpoint of controlling the particle size of the phosphor. For the production of the stimulable phosphor precursor by the liquid phase method, the precursor production method described in JP-A-10-140148 and the precursor production apparatus described in JP-A-10-14777 can be preferably used. Here, the stimulable phosphor precursor refers to a state in which the substance of the general formula (1) has not been subjected to a high temperature of 600 ° C. or higher, and the stimulable phosphor precursor has a stimulable luminescent property and an instantaneous luminescent property. Hardly shows.

(Manufacturing Method 1) First, raw material compounds other than the fluorine compound are dissolved in an aqueous medium. That is,
BaI ₂ and Ln halides, and optionally M ² halides, and further M ¹ halides are put into an aqueous medium and thoroughly mixed and dissolved to prepare an aqueous solution in which they are dissolved. However, the BaI ₂ concentration is 2 m
The amount ratio of the BaI ₂ concentration and the aqueous solvent is adjusted so that it becomes ol / L or more. At this time, if desired, a small amount of acid, ammonia, alcohol, water-soluble polymer,
Water-insoluble metal oxide fine particle powder and the like may be added.
This aqueous solution (reaction mother liquor) is maintained at 50 ° C.

Next, an aqueous solution of inorganic fluoride (ammonium fluoride, alkali metal fluoride, etc.) is injected into the stirred and maintained aqueous solution at 50 ° C. using a pipe with a pump or the like. This injection is preferably carried out in the areas where the stirring is particularly vigorous. By injecting this inorganic fluoride aqueous solution into the reaction mother liquor, the rare earth activated alkaline earth metal fluoride halide type phosphor precursor crystals corresponding to the above general formula (1) are precipitated.

The oxygen-introduced rare earth-activated alkaline earth metal fluorohalide-based stimulable phosphor represented by the general formula (1) of the present invention is, as described above, an ammonium halide (N
H ₄ Br or NH ₄ Cl or NH ₄ I) and a halide of Ln, and when x in the general formula (1) is not 0, a halide of M ² is further added, and y is 0.
If not, it further contains M ¹ halide, and the ammonium halide concentration after dissolution is 3 mol.
/ L or more of the step of preparing an aqueous solution;
While maintaining the temperature of B, add an aqueous solution of inorganic fluoride and B
Precipitation of rare earth activated alkaline earth metal fluoride halide phosphor precursor crystals by continuously or intermittently adding an aqueous solution of aI ₂ while maintaining the ratio of the former fluorine and the latter Ba constant. Also, a production method (production method 2) comprising the steps of obtaining a product; a step of separating this precursor crystal precipitate from an aqueous solution; and a step of firing the separated precursor crystal precipitate while avoiding sintering (production method 2) can do.

Next, this manufacturing method will be described in detail. (Production Method 2) First, a raw material compound except BaI ₂ and a fluorine compound and ammonium halide (NH ₄ Br or NH ₄ Cl or NH ₄ I) are dissolved in an aqueous medium. That is, ammonium halide, Ln halide, and optionally M ² halide, and further M ¹ halide are put into an aqueous medium and mixed sufficiently to dissolve them to prepare an aqueous solution in which they are dissolved. To do. However, the concentration of ammonium halide is 3
The amount ratio of ammonium halide and water is adjusted so as to be in the range of mol / L or more. At this time, if desired, a small amount of acid, ammonium, alcohol, water-soluble polymer, water-insoluble metal oxide fine particle powder or the like may be added. This aqueous solution (reaction mother liquor) is maintained at 50 ° C. Next, to this stirred and maintained aqueous solution, an aqueous solution of an inorganic fluoride (ammonium fluoride, alkali metal fluoride, etc.) and an aqueous solution of BaI ₂ are simultaneously added to the fluorine of the inorganic fluoride and the latter. Is continuously or intermittently injected using a pipe with a pump or the like while adjusting the ratio of BaI ₂ to BaI ₂ to be constant. This injection is preferably carried out in the areas where the stirring is particularly vigorous. Thus, during the phosphor crystal formation, Ba
The rare earth activated alkaline earth metal fluorohalide-based phosphor precursor crystals corresponding to the general formula (1) are precipitated by allowing the reaction to proceed so that the ions do not become excessive.

A stimulable precursor crystal can be obtained by the above two production methods. Next, the phosphor precursor crystal is separated from the solution by filtration, centrifugation, etc., sufficiently washed with methanol etc., and dried. A sintering inhibitor such as alumina fine powder or silica fine powder is added to and mixed with the dried phosphor precursor crystal, and the sintering inhibitor fine powder is uniformly attached to the crystal surface. It is also possible to omit the addition of the sintering inhibitor by selecting the firing conditions. Next, the phosphor precursor crystals are filled in a heat-resistant container such as a quartz port, an alumina crucible, or a quartz crucible, and placed in the core of an electric furnace to perform firing while avoiding sintering. The firing temperature is suitably in the range of 400 to 1300 ° C, and 500 to 1
The range of 000 ° C is preferred. The firing time varies depending on the filling amount of the phosphor raw material mixture, the firing temperature, the temperature at which the material is taken out of the furnace, and the like, but 0.5 to 12 hours is generally suitable.

As the firing atmosphere, a neutral atmosphere such as a nitrogen gas atmosphere or an argon gas atmosphere, or a weakly reducing atmosphere such as a nitrogen gas atmosphere containing a small amount of hydrogen gas or a carbon dioxide atmosphere containing carbon monoxide is used. To be done.
In the present invention, firing in a weak reducing atmosphere is preferred.

In addition, the amount of oxygen in the stimulable phosphor can be controlled by setting the atmosphere in which a small amount of oxygen is introduced during firing. It is also possible to perform firing by the method described in JP-A-2000-8034.

The particles (crystals) according to the present invention preferably have an average particle size of 1 to 10 μm and are monodisperse. The average particle size is 1 to 5 μm and the average particle size distribution (%) is 20. % Or less, more preferably an average particle size of 1 to 3 μm,
The average particle size distribution is preferably 15% or less. The average particle size in the present invention is obtained by randomly selecting 200 particles from an electron micrograph of particles (crystals) and calculating the average by the volume particle size in terms of sphere.

As the support used in the radiation image conversion panel of the present invention, various polymer materials, glass, metals and the like are used. In particular, those which can be processed into a flexible sheet or web for handling as an information recording material are preferable, and in this respect, cellulose acetate film, polyester film, polyethylene terephthalate film, polyamide film, polyimide film, triacetate film, Plastic film such as polycarbonate film, aluminum, iron,
A metal sheet of copper, chromium or the like or a metal sheet having a coating layer of the metal oxide is preferable.

The layer thickness of these supports varies depending on the material of the support used and the like, but is generally 80 μm to 10 μm.
It is 00 μm, and more preferably 80 μm to 500 μm from the viewpoint of handling.

The surface of these supports may be a smooth surface, or may be a matte surface for the purpose of improving the adhesiveness with the stimulable phosphor layer. Furthermore, these supports are provided with an undercoat layer on the surface on which the stimulable phosphor layer is provided for the purpose of improving the adhesiveness with the stimulable phosphor layer.
It preferably contains a polymer resin that can be crosslinked with a crosslinking agent and a crosslinking agent.

The polymer resin that can be used in the undercoat layer is not particularly limited, but examples thereof include polyurethane, polyester, vinyl chloride copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer. Polymer,
Vinyl chloride-acrylonitrile copolymer, butadiene-
Acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivative (nitrocellulose etc.), styrene-butadiene copolymer, various synthetic rubber resins, phenol resin, epoxy resin, urea resin, melamine resin, phenoxy resin, silicone resin , Acrylic resin, urea formamide resin and the like. Among them, polyurethane, polyester, vinyl chloride copolymer, polyvinyl butyral, nitrocellulose and the like can be mentioned. In the invention according to claim 2, the average glass transition temperature (Tg) of the polymer resin used in the undercoat layer is ) Is 25
One of the characteristics is that the temperature is ℃ or more, preferably 25
Is to use a polymer resin having a Tg of ˜200 ° C.

The cross-linking agent that can be used in the undercoat layer according to the present invention is not particularly limited, and examples thereof include polyfunctional isocyanates and their derivatives, melamine and its derivatives,
Amino resins and their derivatives can be mentioned,
It is preferable to use a polyfunctional isocyanate compound as the crosslinking agent, and examples thereof include Coronate HX and Coronate 3041 manufactured by Nippon Polyurethane Company.

The undercoat layer according to the present invention can be formed on a support by the following method, for example.

First, the polymer resin and the cross-linking agent described above are added to a suitable solvent, for example, the solvent used in the preparation of the coating solution for the stimulable fluorescent layer described below, and the resulting mixture is mixed sufficiently to obtain the coating solution for the undercoat layer. To prepare.

The amount of the cross-linking agent used varies depending on the characteristics of the intended radiation image conversion panel, the type of material used for the stimulable phosphor layer and the support, the type of polymer resin used for the undercoat layer, etc. Considering the maintenance of the adhesive strength of the stimulable phosphor layer to the support, it is preferably added in a ratio of 50% by mass or less with respect to the polymer resin, and particularly 15 to 5%.
It is preferably 0% by mass.

The film thickness of the undercoat layer is the desired characteristics of the radiation image conversion panel, the type of material used for the stimulable phosphor layer and the support, the type of polymer resin and crosslinker used for the undercoat layer, etc. It is preferably 3 to 50 μm, and particularly preferably 5 to 40 μm, although it depends on the above. You can turn it off.

The undercoat layer according to the present invention preferably contains a polymer resin which can be crosslinked with a crosslinking agent and a crosslinking agent.

The polymer resin that can be used in the undercoat layer is not particularly limited, but examples thereof include polyurethane, polyester, vinyl chloride copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer. Polymer,
Vinyl chloride-acrylonitrile copolymer, butadiene-
Acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivative (nitrocellulose etc.), styrene-butadiene copolymer, various synthetic rubber resins, phenol resin, epoxy resin, urea resin, melamine resin, phenoxy resin, silicone resin , Acrylic resin, urea formamide resin and the like. Among them, polyurethane, polyester, vinyl chloride copolymer, polyvinyl butyral, nitrocellulose and the like can be mentioned. In the invention according to claim 2, the average glass transition temperature (Tg) of the polymer resin used in the undercoat layer is ) Is 25
One of the characteristics is that the temperature is ℃ or more, preferably 25
Is to use a polymer resin having a Tg of ˜200 ° C.

The cross-linking agent which can be used in the undercoat layer according to the present invention is not particularly limited, and examples thereof include polyfunctional isocyanates and their derivatives, melamine and its derivatives,
Amino resins and their derivatives can be mentioned,
It is preferable to use a polyfunctional isocyanate compound as the crosslinking agent, and examples thereof include Coronate HX and Coronate 3041 manufactured by Nippon Polyurethane Company.

The undercoat layer according to the present invention can be formed on a support by the following method, for example.

First, the above-mentioned polymer resin and the cross-linking agent are added to a suitable solvent, for example, the solvent used in the preparation of the coating solution for the stimulable fluorescent layer described below, and the resulting mixture is mixed thoroughly to obtain a coating solution for the undercoat layer. To prepare.

The amount of the cross-linking agent used varies depending on the characteristics of the intended radiation image conversion panel, the type of material used for the stimulable phosphor layer and the support, the type of polymer resin used for the undercoat layer, etc. Considering the maintenance of the adhesive strength of the stimulable phosphor layer to the support, it is preferably added in a ratio of 50% by mass or less with respect to the polymer resin, and particularly 15 to 5%.
It is preferably 0% by mass.

The film thickness of the undercoat layer is the desired characteristics of the radiation image conversion panel, the type of material used for the stimulable phosphor layer and the support, the type of polymer resin and crosslinking agent used for the undercoat layer, etc. It is preferably 3 to 50 μm, and particularly preferably 5 to 40 μm, although it depends on the above.

Examples of the binder used in the stimulable phosphor layer in the present invention include proteins such as gelatin, polysaccharides such as dextran, or natural polymer substances such as gum arabic; and polyvinyl butyral and poly. Vinyl acetate, nitrocellulose, ethyl cellulose,
Binders represented by synthetic polymeric substances such as vinylidene chloride / vinyl chloride copolymer, polyalkyl (meth) acrylate, vinyl chloride / vinyl acetate copolymer, polyurethane, cellulose acetate butyrate, polyvinyl alcohol, linear polyester, etc. Can be mentioned. Particularly preferred among such binders are nitrocellulose, linear polyesters, polyalkyl (meth) acrylates, mixtures of nitrocellulose and linear polyesters, mixtures of nitrocellulose and polyalkyl (meth) acrylates and It is a mixture of polyurethane and polyvinyl butyral. Note that these binders may be crosslinked with a crosslinking agent.

The stimulable phosphor layer can be formed on the undercoat layer by the following method, for example. First, an iodine-containing stimulable phosphor, a compound such as a phosphite ester for preventing yellowing and a binder are added to a suitable solvent, and these are sufficiently mixed to obtain a phosphor particle and a binder solution in a binder solution. A coating solution in which particles of the compound are uniformly dispersed is prepared.

Examples of the binder used in the present invention include proteins such as gelatin, polysaccharides such as dextran or gum arabic, polyvinyl butyral,
Polyvinyl acetate, nitrocellulose, ethyl cellulose, vinyl chloride / vinyl chloride copolymer, polymethylmethacrylate, vinyl chloride / vinyl acetate copolymer, polyurethane, cellulose acetate butyrate,
A film-forming binder which is usually used in a layer structure such as polyvinyl alcohol is used. Generally, the binder is used in the range of 0.01 to 1 part by mass with respect to 1 part by mass of the stimulable phosphor. However, from the viewpoint of sensitivity and sharpness of the obtained radiation image conversion panel, it is preferable that the amount of the binder is small, and the range of 0.03 to 0.2 parts by mass is more preferable from the viewpoint of easy coating.

The mixing ratio of the binder and the stimulable phosphor in the coating liquid (however, when all the binder is an epoxy group-containing compound, it is equal to the ratio of the compound and the phosphor),
Although it varies depending on the characteristics of the intended radiation image conversion panel, the type of phosphor, the addition amount of the epoxy group-containing compound, etc., generally, examples of the solvent for preparing the binding coating solution include methanol, enothal, 1-propanol, and 2 -Lower alcohols such as propanol and n-butanol; chlorine atom-containing hydrocarbons such as methylene chloride and ethylene chloride; ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; methyl acetate, ethyl acetate,
Mention may be made of esters of lower fatty acids such as butyl acetate with lower alcohols; ethers such as dioxane, ethylene glycol ethyl ether, ethylene glycol monomethyl ether; toluene; and mixtures thereof.

The coating liquid contains a dispersant for improving the dispersibility of the phosphor in the coating liquid, and a binder between the binder and the phosphor in the stimulable phosphor layer after formation. Various additives such as a plasticizer for improving the binding strength may be mixed. Examples of dispersants used for such purpose include phthalic acid, stearic acid, caproic acid, lipophilic surfactants and the like. Examples of plasticizers include phosphoric acid esters such as triphenyl phosphate, tricresyl phosphate, diphenyl phosphate; phthalic acid esters such as diethyl phthalate and dimethoxyethyl phthalate; ethyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate, etc. Glycolic acid ester of
Examples thereof include polyesters of triethylene glycol and adipic acid, polyesters of polyethylene glycol such as polyesters of diethylene glycol and succinic acid, and aliphatic dibasic acids.

The coating solution prepared as described above is then uniformly applied to the surface of the undercoat layer to form a coating film of the coating solution. This coating operation can be performed by using an ordinary coating means such as a doctor blade, a roll coater or a knife coater.

Next, the formed coating film is gradually heated and dried to complete the formation of the stimulable phosphor layer on the undercoat layer. The layer thickness of the stimulable phosphor layer varies depending on the characteristics of the intended radiation image conversion panel, the type of stimulable phosphor, the mixing ratio of the binder and the phosphor, etc., but is usually 2
The thickness is 0 μm to 1 mm. However, this layer thickness is preferably 50 to 500 μm.

The coating liquid for the stimulable phosphor layer is prepared by using a dispersing device such as a ball mill, a sand mill, an attritor, a triple roll mill, a high speed impeller disperser, a Kady mill, and an ultrasonic disperser. The prepared coating solution is applied onto a support using a coating solution such as a doctor blade, a roll coater or a knife coater and dried to form a stimulable phosphor layer. The coating liquid may be applied onto the protective layer and dried, and then the stimulable phosphor layer and the support may be bonded to each other.

The film thickness of the stimulable phosphor layer of the radiation image conversion panel of the present invention depends on the desired characteristics of the radiation image conversion panel, the type of stimulable phosphor, the binder and the stimulable phosphor. Although it depends on the mixing ratio and the like, it is preferably selected from the range of 10 μm to 1000 μm, more preferably 10 μm to 500 μm.

The examples of the stimulable phosphor such as europium-activated barium fluoroiodide have been mainly described above. The europium-activated barium fluorobromide and other photostimulants represented by the general formula (1) are also described. For the production of the fluorescent substance, the above may be referred to.

[0062]

EXAMPLES The present invention will be illustrated below with reference to examples.

Example 1 (Preparation of Phosphor Precursor and Phosphor) In order to synthesize a europium-activated barium fluoroiodide stimulable phosphor precursor, 2500 ml of BaI ₂ aqueous solution (4 mol / L) and E were prepared.
uI ₃ aqueous solution (0.2mol / L) 26.5ml was charged to the reactor. The content of phosphorus in BaI ₂ used here was 50 ppm. Furthermore, 6 mol /
72.9 ml of L HNO ₃ was added. The reaction mother liquor in this reactor was kept warm at 83 ° C. with stirring. 322 ml of an aqueous solution of ammonium fluoride (8 mol / L) was injected into the reaction mother liquor using a roller pump to form a precipitate. In order to prevent changes in particle shape due to heat retention and sintering even after the end of injection, and to prevent changes in particle size distribution due to interparticle fusion,
1% by mass of ultrafine alumina powder was added and sufficiently stirred with a mixer to uniformly attach the ultrafine alumina powder to the crystal surface. This was filled in a quartz boat and baked at 850 ° C. for 2 hours in a hydrogen gas atmosphere using a tube furnace to obtain europium-activated barium fluoroiodide phosphor particles. Next, the phosphor particles were classified to obtain particles having an average particle diameter of 5 μm. The average particle size of the stimulable phosphor was measured from a scanning electron micrograph.

<< Preparation of Radiation Image Conversion Panel >> [Formation of Undercoat Layer] An undercoat layer coating solution described below was used to form a foamed polyethylene terephthalate film (188E60 manufactured by Toray Industries, Inc.) having a thickness of 188 μm using a doctor blade.
L) and dried at 100 ° C. for 5 minutes to form an undercoat layer having a dry film thickness of 30 μm.

(Coating liquid for undercoat layer) Polyester resin dissolved product (Vylon 55SS manufactured by Toyobo Co., Ltd., solid content 35%) 28
To 8.2 g, 0.34 g of β-copper phthalocyanine dispersion product
(Solid content 35%, pigment content 30%) and 11.22 g of a polyisocyanate compound (Coronate HX manufactured by Nippon Polyurethane Industry Co., Ltd.) as a curing agent were mixed and dispersed with a propeller mixer to prepare an undercoat layer coating solution.

[Formation of Phosphor Layer] (Preparation of Phosphor Layer Coating Solution) 300 g of the above-prepared europium-activated barium fluoroiodide phosphor particles and polyester resin (Vylon 530 manufactured by Toyobo Co., Ltd., solid content 30)
%, Solvent: methyl ethyl ketone / toluene = 5/5) 5
2.63 g was added to a mixed solvent of 0.13 g of methyl ethyl ketone, 0.13 g of toluene and 41.84 g of cyclohexanone and dispersed by a propeller mixer to prepare a phosphor layer coating solution. The solvent ratio of cyclohexane in the phosphor layer coating liquid is 53% by mass.

(Formation of Phosphor Layer 1, Production of Phosphor Sheet 1) The prepared phosphor layer coating solution was applied onto the above-mentioned undercoat layer with a doctor blade to give a film thickness of 180 μm.
After that, the phosphor layer 1 was formed by drying at 100 ° C. for 15 minutes to prepare a phosphor sheet 1.

[Production of Moisture-Proof Protective Film] As the protective film on the phosphor layer coated surface side of the above-prepared phosphor sheet 1, one having the following constitution (A) was used.

Structure (A) NY15 /// VMPET12 /// VMPET12 /
// PET12 /// CPP20 NY: Nylon PET: Polyethylene terephthalate CPP: Casting polypropylene VMPET: Alumina-deposited PET (commercially available product: manufactured by Toyo Metallizing Co., Ltd.) μm).

The above "///" means a dry lamination adhesive layer, and the thickness of the adhesive layer is 3.0 μm. The used adhesive for dry lamination is
A two-component reactive urethane adhesive was used.

The protective film on the back surface side of the support of the phosphor sheet 1 is CPP 30 μm / aluminum film 9 μm.
/ Polyethylene terephthalate was used as a dry laminated film having a structure of 188 μm. In this case, the thickness of the adhesive layer was 1.5 μm, and a two-component reactive urethane adhesive was used.

[Preparation of Radiation Image Conversion Panel] The phosphor sheet 1 prepared above was cut into squares each having a side of 20 cm, and the peripheral portion was impulse-sealed under reduced pressure using the moisture-proof protective film prepared above. A radiation image conversion panel was produced by fusing and sealing using. still,
The fusion was performed so that the distance from the fusion portion to the peripheral edge of the phosphor sheet was 1 mm. The heater of the impulse sealer used for fusing has a width of 3 mm.

Example 2 Photostimulable phosphor particles and radiation image conversion were performed in the same manner as in Example 1 except that BaI ₂ having a phosphorus content of 35 ppm was used instead of BaI ₂ having a phosphorus content of 50 ppm. Got the panel.

Example 3 Photostimulable phosphor particles and a radiation image conversion panel were prepared in the same manner as in Example 1, except that BaI ₂ containing 21 ppm of phosphorus was used instead of BaI ₂ containing 50 ppm of phosphorus. Got

Example 4 Photostimulable phosphor particles and radiation image conversion were carried out in the same manner as in Example 1 except that BaI ₂ having a phosphorus content of 10 ppm was used in place of BaI ₂ having a phosphorus content of 50 ppm. Got the panel.

Example 5 175.3 g of BaF ₂ powder, BaI ₂ used in Example 1
Powder 391.1 g, EuF ₃ powder 0.418 g, B
Weigh 9.97 g of a (NO ₃ ) ₂ powder and place it in an automatic mortar.
Grind and mix for 0 minutes. This was filled in a quartz boat and baked at 850 ° C. for 2 hours in a hydrogen gas atmosphere using a tube furnace to obtain europium-activated barium fluoroiodide phosphor particles. Next, the phosphor particles were pulverized and classified to obtain particles having an average particle size of 5 μm. A radiation image conversion panel was obtained by the method described in Example 1.

Comparative Example 1 Photostimulable phosphor particles and radiation image conversion were carried out in the same manner as in Example 1 except that BaI ₂ having a phosphorus content of 72 ppm was used instead of BaI ₂ having a phosphorus content of 50 ppm. Got the panel.

Comparative Example 2 Photostimulable phosphor particles and radiation image conversion were carried out in the same manner as in Example 1 except that BaI ₂ having a phosphorus content of 85 ppm was used instead of BaI ₂ having a phosphorus content of 50 ppm. Got the panel.

Comparative Example 3 A stimulable phosphor particle and a radiation image conversion panel were obtained in the same manner as in Example 5 except that BaI ₂ of Comparative Example 1 was used.

(Evaluation of Concentration of Phosphorus in Photostimulable Phosphor) The concentration of phosphorus in the photostimulable phosphor was evaluated by the following method.

2 g of the sample was placed in a 100 ml Teflon (R) heatable beaker and hydrochloric acid (EL manufactured by Kanto Chemical Co., Inc.
20 ml of grade) was added, heated and dried until the water content disappeared. Add hydrochloric acid and heat-dry 2
Repeated times.

Next, the sample was dissolved using 5 ml of the above hydrochloric acid and ultrapure water to make the total volume 50 ml. The obtained solution was used as an ICP emission spectrometer (SPS400 manufactured by Seiko Instruments Inc.)
0) was used to perform the analysis. The analysis wavelength and the output were 213.618 nm, and the output was 1.3 kW.

The phosphorus content was determined by a calibration curve method using a standard solution as a reagent for atomic absorption spectrometry (manufactured by Kanto Chemical Co., Inc.).

(Evaluation of Radiation Image Conversion Panel) The brightness of each radiation image conversion panel was measured according to the following method.

For each radiation image conversion panel, X-rays with a tube voltage of 80 kVp were irradiated from the back surface side of the phosphor sheet support, and then the panel was irradiated with He-Ne laser light (633n).
m) to be excited and stimulated emission emitted from the phosphor layer is received by a photodetector (photoelectron image multiplier with spectral sensitivity S-5), its intensity is measured, and this is taken as the luminance. It was defined and displayed as a relative value with the brightness of the radiation conversion panel 1 as 100.

Erase characteristics The erasing property was evaluated by the following method.

A tube voltage of 80 kV is applied to each radiation image conversion panel.
Irradiation energy after irradiation with p X-rays of 100 mR for 4.
Initially by irradiating and exciting a semiconductor laser beam of ³ J / m ² (wavelength: 660 nm), and stimulating the stimulated emission light emitted from the phosphor particles through the optical filter (B-410) to the photoelectron multiplier. The stimulated luminescence amount was measured. Subsequently, a white fluorescent lamp equipped with a UV cut filter was used to perform an erasing operation by irradiating at 5000 lux for 70 seconds. For each phosphor particle after the erasing operation, the amount of stimulated luminescence after erasing was measured in the same manner as the measurement of the initial amount of stimulated luminescence. The erasing property was evaluated by the erasing value obtained by the following formula. The smaller the erase value, the better the erase characteristic.

[0088] Erasure value = (amount of stimulated luminescence after erasing / initial amount of stimulated luminescence) The results are summarized in Table 1 below.

[0089]

[Table 1]

By setting the phosphorus content within the range of the present invention, it was possible to obtain a radiation image conversion panel using a stimulable phosphor having high emission brightness and good erasing characteristics.

[0091]

By setting the phosphorus content in the stimulable phosphor within a specific low range, a radiation image conversion panel having high emission brightness and excellent erasing characteristics can be obtained.

Continued front page    F term (reference) 2G083 AA03 BB01 CC02 DD02 DD12                       EE03 EE04                 4H001 CA04 CA08 CF01 XA04 XA09                       XA12 XA20 XA35 XA38 XA53                       XA56 YA03 YA08 YA11 YA15                       YA19 YA37 YA55 YA58 YA59                       YA60 YA62 YA63 YA64 YA65                       YA66 YA67 YA68 YA69 YA70

Claims (6)

[Claims] 1. An oxygen-introduced rare earth activated alkaline earth metal fluorohalide-based stimulable phosphor represented by the following general formula (1), wherein the phosphorous content in the stimulable phosphor is 5:
An oxygen-introduced rare earth-activated alkaline earth metal fluorohalide-based stimulable phosphor characterized by being 0 ppm or less. General formula (1) Ba _(1-x) M ² _x FBr _y I _(1-y) : aM ¹ ,
bLn, cO [wherein, M ¹ is at least one alkali metal selected from the group consisting of Li, Na, K, Rb, and Cs, and M ² is at least one selected from the group consisting of Be, Mg, Sr, and Ca. Alkaline earth metal, Ln: Ce, Pr, Sm, Eu, Gd, Tb, Tm, D
at least one rare earth element selected from the group consisting of y, Ho, Nd, Er and Yb, x, y, a, b and c are each 0 ≦ x ≦ 0.3,0
<Y ≦ 0.3, 0 ≦ a ≦ 0.05, 0 <b ≦ 0.2,0
<C ≦ 0.1 is represented. ] 2. The phosphorus content in the precursor of the oxygen-introduced rare earth activated alkaline earth metal fluorohalide stimulable phosphor is 50 ppm or less.
2. An oxygen-introduced rare earth-activated alkaline earth metal fluorohalide-based stimulable phosphor. 3. The phosphor content in the stimulable phosphor is 3
The oxygen-introduced rare earth-activated alkaline earth metal fluorohalide-based stimulable phosphor according to claim 1 or 2, which is 0 ppm or less. 4. The phosphorus content in the precursor of the stimulable phosphor is 30 ppm or less, 1.
The oxygen-introduced rare earth-activated alkaline earth metal fluorohalide-based stimulable phosphor described in 2 or 3 above. 5. The method according to claim 1, wherein the precursor of the stimulable phosphor is produced in a liquid phase.
2. An oxygen-introduced rare earth-activated alkaline earth metal fluorohalide-based stimulable phosphor according to the item 1. 6. A radiation image conversion panel comprising the oxygen-introduced rare earth-activated alkaline earth metal fluorohalide-based stimulable phosphor according to any one of claims 1 to 5.