JPH05214337A - Production of fluorescent substance and x-ray image transformation sheet - Google Patents

Abstract

PURPOSE:To obtain a highly sensitive fluorescent substance suitable for taking an X-ray photograph by preparing a fluorescent substance raw material containing europium of a specific composition, then adding an ammonium halide, heating the resultant mixture together with an inert gas in a (semi)hermetically sealed container and burning the mixture under a high pressure. CONSTITUTION:A fluorescent substance raw material is prepared so as to stoichiometerically provide a relative ratio corresponding to formula I (X is F, Cl, Br or I; c, is 0.0001-0.1) and an ammonium halide is then added to the fluorescent substance raw material. The obtained mixture, together with an inert gas, is subsequently filled in a (semi)hermetically sealed container, heated and then burned in a state of a high pressure to afford the objective europium- activated alkaline earth metallic halide fluorescent substance having a composition formula of formula II (x' is Cl, Br or I; z is >=0 and <1).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a europium-activated alkaline earth halide phosphor and an X-ray image conversion sheet formed using the phosphor.

Radiation images such as X-ray images are often used for disease diagnosis and the like. In order to obtain this X-ray image, X-rays that have passed through the subject are irradiated onto the phosphor layer (fluorescent screen) to generate visible light, and this visible light is irradiated onto a film using a silver salt for development. Radiographs are used.

On the other hand, as a high-sensitivity and high-resolution X-ray system, instead of the conventional method of recording a two-dimensional image of radiation indirectly or directly on a film coated with a silver salt photosensitizer, a stimulable phosphor is used. The methods used are beginning to be utilized. When receiving the energy of radiation such as X-rays, the phosphor used in this system accumulates energy in the phosphor crystal. This state is relatively stable and is maintained for a long time. When the phosphor in this state is irradiated with the first light that acts as the excitation light, the stored energy is emitted as the second light. At this time, the first light is not limited to visible light, and light having a wide wavelength range from the infrared region to the ultraviolet region is used, but the wavelength varies depending on the phosphor material used. The second light also has various wavelengths from the infrared region to the ultraviolet region, and varies depending on the phosphor material.

[0004]

2. Description of the Related Art As a kind of a halide phosphor activated by a rare earth element, a europium activated alkaline earth composite halide phosphor (BaXX ': Eu, provided that
X and X ′ are any of F, Cl, Br and I. )It has been known. This phosphor shows near-ultraviolet emission (stimulated emission) when excited by electromagnetic waves in the visible to infrared region after being excited by X-rays, electron beams, ultraviolet rays, etc., and is a stimulable phosphor used in a radiation image conversion method. Have been found to be useful as. Further, this phosphor exhibits near-ultraviolet emission having a peak of emission spectrum distribution near 390 nm when excited by X-rays, ultraviolet rays, electron beams and the like. In particular, this phosphor has a high absorption efficiency for X-rays, and its near-ultraviolet emission matches the spectral sensitivity of an X-ray film, and is therefore used as a phosphor for an X-ray intensifying screen. The excitation spectrum distribution for inducing near-ultraviolet emission has a peak near 580 nm and is mainly excited by a He-Ne laser.

[0005]

When used as an imaging plate for X-ray photography by molding or coating the above phosphor, the X-ray dose to which the subject is exposed depends on the stimulated emission intensity at the readout wavelength of the imaging plate. Since it is determined, the exposure dose can be reduced by increasing the sensitivity of the phosphor.

An object of the present invention is to provide a manufacturing method for improving the sensitivity of europium-activated alkaline earth metal halide phosphors and an X-ray image conversion sheet formed by using the phosphors.

[0007]

Among the above-mentioned objects, the method for producing a phosphor can be achieved by any of the following means.

The first means is a stoichiometric composition formula BaX ₂ : cEu where X is F, Cl, Br or I, and c is in the range of 0.0001 ≦ c ≦ 0.1. Is the numerical value of. Prepare a phosphor raw material so that the relative ratio corresponds to, add ammonium halide to the phosphor raw material, fill an airtight container or a semi-hermetic container with an inert gas, heat, and burn in a high-pressure state. , Composition formula Ba (X _1-z X ′ _z ) ₂ · cEu ²⁺ where X ′ is any one of Cl, Br and I, and z is a numerical value in the range of 0 ≦ z <0.1. The method for producing a phosphor for producing the europium-activated alkaline earth metal halide phosphor represented by

The second means is a stoichiometric compositional formula: BaX ₂ : cEu where X is F, Cl, Br or I, and c is in the range of 0.0001 ≦ c ≦ 0.1. Is the numerical value of. The phosphor material is prepared so that the relative ratio corresponds to, and this phosphor material is heated in a closed container or a semi-closed container together with hydrogen halide gas or a mixed gas of hydrogen halide gas and an inert gas. Then, it is fired in a high-pressure state to have a composition formula Ba (X _1-z X ′ _z ) ₂ · cEu ^2+, where X ′ is Cl, Br, or I, and z is 0 ≦ z <0. It is a numerical value in the range of 1. The method for producing a phosphor for producing the europium-activated alkaline earth metal halide phosphor represented by

Among the above objects, the X-ray image conversion sheet is achieved by the X-ray image conversion sheet formed by using the phosphor manufactured by the above-described phosphor manufacturing method.

[0011]

The inventors of the present invention have found that the composition formula BaX ₂ : Eu
(However, X is one of F, Cl, Br, and I.)
So far, we have been focusing on the phosphors represented by. This phosphor is 400 when X is Br.
It is a phosphor having a peak of emission spectrum distribution in the vicinity of nm, and its excitation spectrum is conventional BaXX ': E.
It has a feature that it has sensitivity on the long wavelength side as compared with the u phosphor.

The inventors of the present invention have found that the composition formula BaX ₂ : E
Prepare the phosphor material so that the relative ratio corresponds to u,
Ammonium halide gas or hydrogen halide gas is uniformly added to the phosphor raw material at a high concentration by adding ammonium halide to this and baking in a high pressure state or by baking in a high pressure state in a hydrogen halide gas atmosphere. It has been found that as a result, the diffusion of Eu is promoted and the crystal growth is made uniform to improve the sensitivity of the manufactured phosphor.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A phosphor manufacturing method and an X-ray image conversion sheet according to three embodiments of the present invention will be described below with reference to the drawings.

First Example BaBr _{2 (} 100 g) and EuBr _{3 (} 0.26 g) were mixed using a ball mill, and NH ₄ Br (3 wt%) was added thereto. It is also filled in a bowl, heated to a temperature of 840 ° C., and baked in a high pressure state for 3 minutes. After firing, the phosphor is taken out from a quartz closed container and fired in He gas at a temperature of 500 ° C. for 10 minutes to scatter excess NH ₄ Br to complete a phosphor.

Second Embodiment 100 g of BaBr ₂ and 0.26 g of EuBr ₃ were mixed using a ball mill, and a closed gas container made of quartz having a volume of 1 liter was filled with He gas containing 20% by volume of HBr and 〝. Then, it is heated to a temperature of 840 ° C. and baked in a high pressure state for 5 minutes. After firing, remove from the quartz closed container and
Fluorine is completed by firing in e gas at a temperature of 500 ° C. for 10 minutes to scatter excess bromine.

In each of the above examples, since the raw materials are water-soluble, it is possible to use those which have been wet-mixed in an aqueous solution and then dried. In that case, filtration during wet mixing, etc. It is desirable to remove impurities by the above means. Although the firing temperature varies depending on the type and composition of the phosphor raw material, it is generally suitable in the range of 500 to 1100 ° C, preferably 700 to 950 ° C. Also,
The firing time varies depending on the type and composition of the phosphor raw material, the filling amount of the phosphor raw material into the heat-resistant container, the firing temperature, etc., but in general, a period of 1 minute to 12 hours is required in the above firing temperature range, which is preferable. Is 1 minute to 2 hours. The baking container may be a semi-closed container, and it is preferable to carry out in a dry atmosphere or a neutral gas atmosphere in order to prevent moisture absorption when pulverizing and classifying the raw materials.

Third Embodiment The phosphors produced in the first and second embodiments are classified, and 100 g of this powder is combined with 6 g of polymethylmethacrylate, 0.6 g of butylphthalate and 30 parts of toluene.
The phosphor paste is mixed in a ratio of g to prepare a phosphor paste, and the phosphor paste is applied to a polyethylene terephthalate (PET) film support using a doctor blade method and dried to form a phosphor layer having a thickness of 300 μm. The phosphor layer is covered with a PET protective film to form an X-ray image conversion sheet.

A conventional method for manufacturing a phosphor will be shown below as a comparative example. Comparative Example 1 100 g of BaBr ₂ and 0.26 g of EuBr ₃ were mixed using a ball mill, and this was filled in a quartz boat, and H
While e gas is supplied at a flow rate of 4 liters / minute and H ₂ gas is supplied at a flow rate of 1 liter / minute, it is heated to a temperature of 840 ° C. and baked for 5 minutes.

Comparative Example 2 100 g of BaBr ₂ and 0.26 g of EuBr ₃ were mixed using a ball mill, 3% by weight of NH ₄ Br was added to the mixture, and the mixture was charged into a quartz boat, and He gas was added at 5 liter / min. While being supplied at a flow rate, it is heated to a temperature of 840 ° C. and baked for 5 minutes.

Table 1 shows the results of stimulating the stimulated emission intensity by crushing each of the phosphors produced in the above-mentioned first embodiment, second embodiment, comparative example 1 and comparative example 2 in an agate mortar.
Shown in. The phosphors of the first and second examples manufactured by using the manufacturing method according to the present invention are compared with the phosphors of Comparative Example 1 and Comparative Example 2 manufactured by the conventional manufacturing method. The stimulated emission intensity is significantly improved.

[0021]

Table 1 Table 1 Relative stimulated emission intensity (wavelength 780 nm) First Example 700 Second Example 750 Comparative Example 1 500 Comparative Example 2 600 Further, an X-ray image conversion sheet formed by using these phosphors. Also showed a sensitivity corresponding to that of the phosphor shown in Table 1.

[0022]

As described above, in the method for producing a phosphor and the X-ray image conversion sheet according to the present invention, the phosphor raw material is prepared so that the relative ratio corresponds to the composition formula BaX ₂ : cEu. By adding ammonium halide to this and baking in a high-pressure state, or baking in a high-pressure state in a hydrogen halide gas atmosphere, diffusion of europium is promoted, and crystal growth is made uniform, resulting in high sensitivity. A phosphor could be realized. The sensitivity of the X-ray image conversion sheet could be improved by using this phosphor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masami Hasegawa 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor Soichiro Hidaka, 1015, Kamikodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited

Claims (3)

[Claims] 1. A stoichiometric composition formula BaX ₂ : cEu where X is any one of F, Cl, Br and I, and c is a numerical value in the range of 0.0001 ≦ c ≦ 0.1. .. The phosphor raw material is prepared so that the relative ratio corresponds to, and ammonium halide is added to the phosphor raw material, and the mixture is heated in an airtight container or a semi-hermetic container with an inert gas, heated, and baked in a high pressure state. , Composition formula Ba (X _1-z X ′ _z ) ₂ · cEu ²⁺ where X ′ is any one of Cl, Br and I, and z is a numerical value in the range of 0 ≦ z <0.1. A method for producing a phosphor, comprising producing the europium-activated alkaline earth metal halide phosphor represented by: 2. A stoichiometric composition formula BaX ₂ : cEu where X is any one of F, Cl, Br, and I, and c is a numerical value in the range of 0.0001 ≦ c ≦ 0.1. .. The phosphor material is prepared so that the relative ratio corresponds to, and the phosphor material is heated in a closed container or a semi-closed container together with hydrogen halide gas or a mixed gas of hydrogen halide gas and an inert gas. Then, it is fired in a high-pressure state to have a composition formula Ba (X _1-z X ′ _z ) ₂ · cEu ^2+, where X ′ is Cl, Br, or I, and z is 0 ≦ z <0. It is a numerical value in the range of 1. A method for producing a phosphor, comprising producing the europium-activated alkaline earth metal halide phosphor represented by: 3. An X-ray image conversion sheet, which is formed by using a phosphor manufactured by the method for manufacturing a phosphor according to claim 1.