JPH0662948B2 - Radiation image conversion method and radiation image conversion panel used in the method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a radiation image conversion method and a radiation image conversion panel used in the method. More specifically, the present invention relates to a radiation image conversion method using a stimulable divalent europium-activated alkaline earth metal halide phosphor, and a radiation image conversion panel used in the method.

BACKGROUND OF THE INVENTION Conventionally, as a method for obtaining a radiographic image as an image, a so-called radiography has been used which uses a combination of a radiographic film having an emulsion layer made of a silver salt photosensitive material and an intensifying screen (intensifying screen). The law is being used. As one of the methods replacing the above-mentioned conventional radiographic method, for example, a radiation image conversion method utilizing a stimulable phosphor as described in JP-A-55-12145 is known.
This method allows the stimulable phosphor to absorb the radiation transmitted through the subject or the radiation emitted from the subject, and then the phosphor is time-series by electromagnetic waves (excitation light) such as visible light and infrared light. When excited by, the radiation energy accumulated in the phosphor is emitted as fluorescence (stimulated luminescence), the fluorescence is photoelectrically read to obtain an electric signal, and the electric signal is imaged. .

The radiation image conversion method described above has an advantage that an X-ray image having a large amount of information can be obtained with a much smaller exposure dose than in the case of using a conventional radiographic method. Therefore, this radiographic image conversion method is very useful in direct medical radiography such as X-ray photography for the purpose of medical diagnosis.

As a stimulable phosphor used in the above-mentioned radiation image conversion method, a divalent europium-activated alkaline earth metal fluorohalide phosphor (M ^II FX: Eu ²⁺ , where M
^II is at least one alkaline earth metal selected from the group consisting of Ba, Sr and Ca, and X is a halogen other than fluorine). This phosphor is X
After absorbing radiation such as rays, it emits light in the near-ultraviolet region (stimulated emission) when irradiated with electromagnetic waves in the visible or infrared region.

As described above, the radiation image conversion method utilizes the photostimulability of the phosphor, but the phosphor itself exhibiting photostimulability, except for this divalent europium-activated alkaline earth metal fluoride halide phosphor, is not much. unknown.

The present applicant has already applied for a patent for a radiation image conversion method and a radiation image conversion panel using a novel divalent europium-activated alkaline earth metal halide phosphor represented by the following composition formula (Japanese Patent Application No. 58- 193162
issue).

Compositional formula: M ^II X ₂ · a M ^II X ′ ₂ : xEu ²⁺ (where M ^II is at least one alkaline earth metal selected from the group consisting of Ba, Sr and Ca; X
And X ′ is at least one halogen selected from the group consisting of Cl, Br and I, and X ≠ X ′; and a is a numerical value in the range of 0.1 ≦ a ≦ 10.0, x is a numerical value in the range of 0 <x ≦ 0.2.) This divalent europium-activated alkaline earth metal halide phosphor is obtained from its X-ray diffraction pattern as described in the above-mentioned application. It has been found that the M ^II FX: Eu ²⁺ phosphor is a different kind of phosphor having a different crystal structure, and it is irradiated with radiation such as X-rays, ultraviolet rays, and electron beams, and then has a wavelength of 450 to 1000 nm. When excited by an electromagnetic wave in the region, it exhibits near-ultraviolet or blue emission (stimulated emission) having an emission maximum near 405 nm.

The radiation image conversion method using the radiation image conversion panel made of the above stimulable phosphor is a very advantageous image forming method as described above, but the sensitivity is also as high as possible in this method. desirable. The sensitivity of a radiation image conversion panel to radiation is generally higher as the stimulated emission brightness of the phosphor used therein is higher. Therefore, it is desired that the stimulable phosphor used for the panel has as high a stimulable emission luminance as possible.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a radiation image conversion method with improved sensitivity and a radiation image conversion panel used in the method.

In order to achieve the above object, the present inventor has conducted various studies on the novel divalent europium-activated alkaline earth metal halide phosphor described above. As a result, they have found that a phosphor obtained by adding a specific amount of silicon monoxide to the phosphor exhibits high-intensity stimulated luminescence, and arrived at the present invention.

That is, the radiation image conversion method of the present invention absorbs the radiation transmitted through the subject or emitted from the subject in the divalent europium-activated alkaline earth metal halide-based phosphor represented by the following composition formula (I). After this, the phosphor is irradiated with an electromagnetic wave in the wavelength region of 450 to 1000 nm to release the radiation energy accumulated in the phosphor as fluorescence, and the fluorescence is detected.

Compositional formula (I): M ^II X ₂ · aM ^II X ′ ₂ · bSiO: xEu ²⁺ (I) (where M ^II is Ba; X and X ′ are both Cl, Br and I) At least one halogen selected from the group and X ≠ X ′; and a is a numerical value in the range of 0.1 ≦ a ≦ 10.0 and b
Is a numerical value in the range of 0 <b ≦ 3 × 10 ⁻² , and x is 0 <x
Also, the radiation image conversion panel of the present invention is a radiation image conversion substantially composed of a support and a stimulable phosphor layer provided on the support. The panel is characterized in that the stimulable phosphor layer contains a divalent europium-activated alkaline earth metal halide-based phosphor represented by the composition formula (I).

The present invention is to add a specific amount of silicon monoxide to the above-mentioned novel divalent europium-activated alkaline earth metal halide phosphor to irradiate the phosphor with radiation such as X-ray and then a wavelength of 450 to 1000 nm. It was completed based on the new finding that the stimulated emission luminance when excited by electromagnetic waves in the region is significantly improved.

Therefore, the sensitivity of the radiation image conversion method can be improved by using the divalent europium-activated alkaline earth metal halide-based phosphor represented by the above composition formula (I). Further, the radiation image conversion panel of the present invention comprising the above-mentioned phosphor shows a markedly improved sensitivity.

[Structure of the Invention] The divalent europium-activated alkaline earth metal halide-based phosphor used in the present invention has a composition formula (I): M ^II X ₂ · aM ^II X ′ ₂ · bSiO: xEu ²⁺ (I (Wherein M ^II is Ba; X and X ′ are both at least one halogen selected from the group consisting of Cl, Br and I, and X ≠ X ′; and a is 0 A numerical value in the range of 1 ≦ a ≦ 10.0, b
Is a numerical value in the range of 0 <b ≦ 3 × 10 ⁻² , and x is 0 <x
It is a numerical value in the range of ≦ 0.2).

In the phosphor represented by the above composition formula (I), the amount b of silicon monoxide (SiO) is represented from the viewpoint of stimulated emission luminance.
The value is preferably in the range of 10 ⁻⁴ ≦ b ≦ 10 ⁻² . The value a representing the ratio of M ^II X ₂ to M ^II X ′ ₂ in the composition formula (I) is preferably in the range of 0.25 ≦ a ≦ 6.0, more preferably 0.5 ≦. The range of a ≦ 2.0, and the x value representing the activation amount of europium is 10 ^−5.
It is preferably in the range of ≤x≤10 ^-1 .

Ba which is an example of the phosphor represented by the above composition formula (I)
In the Cl ₂ .BaBr ₂ .bSiO: 0.001Eu ²⁺ phosphor, the b value, which represents the amount of silicon monoxide in the phosphor, and the stimulated emission luminance have a relationship as shown in FIG.

Figure 1 shows BaCl ₂ · BaBr ₂ · bSiO: 0.001
B value and stimulated emission luminance of Eu ²⁺ phosphor [80 KVp
Laser beam (780 nm) after irradiating X-ray of
Is a graph showing a relationship with stimulated emission luminance when excited by. As is clear from FIG. 1, the b value is 0 <b ≦ 3 ×.
BaCl ₂ · BaBr ₂ · bSi in the range of 10 ⁻²
The O: 0.001Eu ²⁺ phosphor exhibits stimulated emission with higher brightness than the phosphor (b = 0) to which silicon monoxide is not added. Based on such a fact, the b value of the divalent europium-activated alkaline earth metal halide phosphor used in the radiation image conversion method of the present invention is defined in the range of 0 <b ≦ 3 × 10 ^−2. Is. Also, from FIG. 1, especially when the b value is 1
It is clear that the phosphor in the range of 0 ⁻⁴ ≦ b ≦ 10 ⁻² exhibits a significantly high intensity of stimulated emission.

Regarding the divalent europium-activated alkaline earth metal halide phosphors used in the present invention other than those in which X, X'and a are as described above, the relationship between the b value and the stimulated emission luminance is the same as in FIG. It has been confirmed that there is a tendency.

The stimulated emission spectrum and stimulated excitation spectrum of the divalent europium-activated alkaline earth metal halide phosphor represented by the above composition formula (I) are described in Japanese Patent Application No. 58-193162, respectively. This is almost the same as the stimulated emission spectrum and stimulated excitation spectrum of the existing divalent europium-activated alkaline earth metal halide-based phosphor. The wavelength region of the stimulated excitation spectrum is as wide as 450 to 1000 nm, and therefore the wavelength of the excitation light can be appropriately changed in the radiation image conversion method of the present invention using this phosphor, that is,
The excitation light source can be appropriately selected according to the purpose. For example, since the stimulated excitation spectrum of the above phosphor extends to about 1000 nm, a semiconductor laser (having an emission wavelength in the infrared region) that is small and has low driving power can be used as the stimulated light source. Therefore, it is possible to downsize the device for implementing the radiation image conversion method. Further, from the viewpoint of luminance of stimulated emission and wavelength separation from the emitted light, the excitation light in the radiation image conversion method of the present invention is preferably an electromagnetic wave in the wavelength region of 500 to 850 nm.

The divalent europium-activated alkaline earth metal halide phosphor represented by the above composition formula (I) can be produced, for example, by the production method described below.

First, as the phosphor raw material, at least one selected from the group consisting of 1) at least two different barium halides, 2) silicon monoxide, and 3) europium compounds such as halides, oxides, nitrates, and sulfates. Prepare a kind of compound. In some cases, ammonium halide or the like may be used as a flux.

In the production of the phosphor, first, using the barium halide of 1), the silicon monoxide of 2) and the europium compound of 3), the composition formula (II): M ^II X ₂ · aM ^II X ′ ₂ · bSiO: xEu ... (II) (where M ^II , X, X ′, a, b and x are defined as above) are weighed and mixed to obtain a relative ratio.

The above mixture operation is carried out, for example, in the form of a suspension. Then, by removing water from the suspension of the phosphor raw material mixture, a solid dry mixture is obtained. This water removal operation is preferably performed at room temperature or at a temperature not too high (for example, 200 ° C. or lower) by vacuum drying, vacuum drying, or both.
Of course, the mixing operation is not limited to the above method.

The silicon monoxide in 2) above may be added to this dry mixture without being added at the time of weighing and mixing the phosphor raw materials.

Next, the obtained dry mixture is finely pulverized, and the pulverized product is filled in a heat-resistant container such as a quartz boat or an alumina crucible and fired in an electric furnace. Firing temperature is 4
The range of 00 to 1300 ° C. is suitable, and the firing time is generally 0.5 to 6 hours, although it varies depending on the filling amount of the phosphor raw material mixture and the firing temperature. 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. If the europium compound used contains trivalent europium, the trivalent europium is reduced to divalent europium during the firing process.

It is also possible to use a method in which the phosphor raw material mixture is once fired under the above firing conditions, the fired product is allowed to cool, then pulverized, and then refired (secondary firing). The re-baking is performed under the neutral atmosphere or weak reducing atmosphere described above at 400 to 80.
It is carried out at a firing temperature of 0 ° C. for 0.5 to 12 hours.

The powdery phosphor used in the present invention is obtained by the above-mentioned firing. Regarding the obtained powdery phosphor,
If necessary, various general operations in the production of the phosphor such as washing, drying and sieving may be further performed.

By utilizing the manufacturing method described above, the divalent europium-activated alkaline earth metal halide-based phosphor represented by the above composition formula (I) 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 halide-based phosphor represented by is preferably used in the form of a radiation image conversion panel (also referred to as a stimulable phosphor sheet) containing the phosphor.

The radiation image conversion panel has, as a basic structure, a support and at least one stimulable phosphor layer provided on one surface thereof. The stimulable phosphor layer is composed of a stimulable phosphor and a binder containing and supporting the stimulable phosphor in a dispersed state. In addition, a transparent protective film is generally provided on the surface of the phosphor layer opposite to the support (the surface not facing the support), and the phosphor layer is chemically altered or Protects against physical shock.

That is, the radiation image conversion method of the present invention is carried out using a radiation image conversion panel having a phosphor layer composed of the divalent europium-activated alkaline earth metal halide phosphor represented by the composition formula (I). Is desirable.

In the radiation image conversion method of the present invention in which the stimulable phosphor represented by the composition formula (I) is used in the form of a radiation image conversion panel, the radiation transmitted through the subject or emitted from the subject has a radiation dose. Is absorbed by the phosphor layer of the radiation image conversion panel in proportion to, and a radiation image of the subject or the subject is formed on the radiation image conversion panel as an accumulated image of radiation energy. This accumulated image is 450-100
By exciting with an electromagnetic wave (excitation light) in the wavelength region of 0 nm, it can be emitted as stimulated emission (fluorescence),
By photoelectrically reading this stimulated emission and converting it into an electric signal, it becomes possible to form an accumulated image of radiation energy.

The radiation image conversion method of the present invention will be specifically described with reference to the schematic diagram shown in FIG. 2 by taking as an example the mode in which the stimulable phosphor represented by the composition formula (I) is used in the form of a radiation image conversion panel. To do.

In FIG. 2, 11 is a radiation generator for X-rays and the like, 1
Reference numeral 2 is a subject, 13 is a radiation image conversion panel containing a stimulable phosphor represented by the composition formula (I), and 14 is excitation for emitting an accumulated image of radiation energy on the radiation image conversion panel 13 as fluorescence. A light source as a source, 15 is a photoelectric conversion device that detects fluorescence emitted from the radiation image conversion panel 13, 16 is a device that reproduces the photoelectric conversion signal detected by the photoelectric conversion device 15 as an image, and 17 is a reproduced image. And a filter 18 for transmitting only fluorescence emitted from the radiation image conversion panel 13 without transmitting reflected light from the light source 14.

Although FIG. 2 shows an example of obtaining a radiation transmission image of a subject, in the case where the subject 12 itself emits radiation (this is referred to as a subject in the present specification), The radiation generator 11 need not be installed in particular. Further, the photoelectric conversion device 15 to the image display device 17 can be changed to another suitable device capable of reproducing the information emitted as fluorescence from the radiation image conversion panel 13 as an image in some form.

As shown in FIG. 2, when the subject 12 is irradiated with radiation such as X-rays from the radiation generator 11, the radiation passes through the subject 12 in proportion to the radiation transmittance of each part thereof. The radiation transmitted through the subject 12 then enters the radiation image conversion panel 13 and is absorbed by the phosphor layer of the radiation image conversion panel 13. That is, an accumulated image of radiation energy (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, 45
When an electromagnetic wave in the wavelength region of 0 to 1000 nm is irradiated, the accumulated image of radiation energy 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 in the phosphor layer of the radiation image conversion panel 13. The optical signal composed of the intensity of this fluorescence is converted into an electrical signal by the photoelectric conversion device 15 such as a photomultiplier tube, and the image reproduction device 1
The image is reproduced by 6 and the image is displayed by the image display device 17.

The operation of reading out the image information accumulated in the radiation image conversion panel as fluorescence is generally performed by scanning the panel with laser light in time series, and the fluorescence emitted from the panel by this scanning is photoelectron-enhanced through an appropriate light collector. This is performed by detecting with a photodetector such as a double tube and obtaining a time-series electric signal.
This read-out may be composed of a pre-reading operation by irradiating low-energy excitation light and a main reading operation by irradiating high-energy excitation light in order to obtain an image with more excellent observation / interpretation performance (JP-A-58). -67240). By performing this pre-read operation, there is an advantage that the read condition in the main read operation can be set appropriately.

Further, for example, a solid-state photoelectric conversion element such as a photoconductor and a photodiode can be used as a photoelectric conversion device (Japanese Patent Application No. 58-86226 and Japanese Patent Application No. 58-862).
No. 27, Japanese Patent Application No. 58-213313 and Japanese Patent Application No. 58
-219314, and JP-A-58-12
1874). In this case, a large number of solid-state photoelectric conversion elements are configured so as to cover the entire surface of the panel and may be integrated with the panel, or may be arranged in the state of being close to the panel. Further, the photoelectric conversion device may be a line sensor in which a plurality of photoelectric conversion elements are linearly connected, or may be composed of one solid-state photoelectric conversion element corresponding to one pixel.

The light source in the above case may be a point light source such as a laser, or a line light source such as an array in which light emitting diodes (LEDs) and semiconductor lasers are connected in a row. By performing the reading using such a device, it is possible to prevent the loss of the fluorescence emitted from the panel and increase the light receiving solid angle to increase the S / N ratio.
Further, the obtained electric signal is not time-sequentially irradiated with the excitation light but is time-sequentially processed by the electric processing of the photodetector, so that the reading speed can be increased.

The radiation image conversion panel from which the image information has been read out is irradiated with light in the wavelength region of the excitation light of the phosphor or heated to erase the remaining radiation energy. However, it is preferable to do so (JP-A-56-11392 and JP-A-56).
-12599 gazette). By performing this erasing operation, it is possible to prevent generation of noise due to an afterimage when the panel is used next time. Furthermore, by performing the erasing operation twice after the reading and immediately before the next use, it is possible to prevent the generation of noise due to natural radioactivity and perform the erasing more efficiently (Japanese Patent Laid-Open No. 57-116).
(See Japanese Patent Publication No. 300).

In the radiation image conversion method of the present invention, the radiation used to obtain a radiation transmission image of a subject may exhibit stimulated emission when the phosphor is excited by the electromagnetic wave after being irradiated with this radiation. Any radiation may be used as long as it is common, and for example, commonly known radiation such as X-rays, electron beams, and ultraviolet rays can be used.
Further, the radiation emitted directly from the subject in the case of obtaining a radiation image of the subject may be any radiation as long as it becomes an energy source of stimulated luminescence by being absorbed by the phosphor in the same manner, Examples are γ rays, α rays, β
Radiation such as rays and neutron rays can be mentioned.

As a light source of excitation light for exciting the phosphor that has absorbed the radiation from the subject or the subject, 450 to 100
Besides a light source that emits light having a band spectral distribution in the wavelength region of 0 nm, for example, an Ar ion laser, K
Lasers such as r-ion lasers, He-Ne lasers, ruby lasers, semiconductor lasers, glass lasers, YAG lasers, dye lasers and light sources such as light emitting diodes can also be used. Among them, the laser can irradiate the radiation image conversion panel with a laser beam having a high energy density per unit area,
It is preferable as the excitation light source used in the present invention. Among them, preferred lasers are He—Ne lasers, Ar ion lasers, and Kr ion lasers in terms of stability and output. Further, the semiconductor laser is preferable as a light source for excitation because of its small size, low driving power, and the ability to directly stabilize the laser output because it can be directly modulated.

The light source used for erasing may be one that emits light in the excitation wavelength region of the stimulable phosphor, and examples thereof include a tungsten lamp, a fluorescent lamp, a halogen lamp, and a high-pressure sodium lamp. it can.

The radiation image conversion method of the present invention is a storage unit that absorbs and stores the energy of radiation in a stimulable phosphor, a photodetection (readout) unit that irradiates this phosphor with excitation light and emits the energy of radiation as fluorescence, Also, it can be applied to a built-in type radiation image conversion device in which an erasing unit for releasing the energy remaining in the phosphor is built in one device (Japanese Patent Application No. 57-84436 and Japanese Patent Application No. 58-6).
6730). By using such a built-in type device, the radiation image conversion panel (or the recording material containing the stimulable phosphor) can be circulated and reused, and a stable and homogeneous image can be obtained. it can.
In addition, the built-in type device can reduce the size and weight of the device, and can be easily installed and moved. Furthermore, by mounting this device on a moving vehicle, it is possible to perform cyclic radiography.

Next, the radiation image conversion panel used in the radiation image conversion method of the present invention will be described.

As described above, this radiation image conversion panel substantially comprises a support and a divalent europium-activated alkaline earth metal halide-based phosphor represented by the composition formula (I) provided on the support. It is composed of a stimulable phosphor layer composed of a binder contained and supported in a dispersed state. The stimulable phosphor layer can be formed on the support by the following method, for example.

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

First, the particulate stimulable phosphor and the binder are added to an appropriate solvent and mixed sufficiently to prepare a coating solution in which the stimulable phosphor is uniformly dispersed in the binder solution.

Examples of the solvent for preparing the coating solution include lower alcohols such as methanol, ethanol, n-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. Ester of lower fatty acid and lower alcohol such as methyl acetate, ethyl acetate, butyl acetate; ether such as dioxane, ethylene glycol monoethyl ether, 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 kind of the phosphor, etc., but generally the mixing ratio of the binder and the phosphor is 1 It is preferably selected in the range of 1 to 1: 100 (weight ratio), and particularly preferably in the range of 1: 8 to 1:40 (weight ratio).

The coating liquid contains a dispersant for improving the dispersibility of the phosphor in the coating liquid, and also for improving the binding force between the binder and the phosphor in the formed phosphor layer. Various additives such as plasticizers may be mixed. Examples of dispersants used for such purpose include:
Examples thereof include phthalic acid, stearic acid, caproic acid and lipophilic surfactants. 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 glycolate, butyl phthalyl butyl glycolate, etc. And a polyester of polyethylene glycol and an aliphatic dibasic acid, such as a polyester of triethylene glycol and adipic acid, a polyester of diethylene glycol and succinic acid, and the like.

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

The support may be arbitrarily selected from various materials used as a support for intensifying screens (or intensifying screens) in conventional radiography or materials known as a support for radiation image conversion panels. it can. Examples of such materials include films of plastic substances such as cellulose acetate, polyester, polyethylene terephthalate, polyamide, polyimide, triacetate, polycarbonate, metal sheets such as aluminum foil, aluminum alloy foil, ordinary paper, baryta paper, resin. Examples thereof include coated paper, pigment paper containing a pigment 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 preferable material for the support in the present invention is a plastic film. This plastic film may be kneaded with a light absorbing substance such as carbon black, or may be kneaded with a light reflecting substance such as titanium dioxide. The former is a support suitable for a radiation image conversion panel of high sharpness type, and the latter is a support suitable for a radiation image conversion panel of high sensitivity type.

In a known radiation image conversion panel, 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, graininess) of the radiation image conversion panel. The surface of the side support is coated with a polymer substance such as gelatin to form an adhesion-imparting layer, or a light-reflecting layer made of a light-reflecting substance such as titanium dioxide, or a light-absorbing substance made of a light absorbing substance such as carbon black It is known to provide an absorbing layer and the like.
The support used in the present invention can also be provided with these various layers, and their configuration can be arbitrarily selected according to the desired purpose and application of the radiation image conversion panel.

Further, as disclosed in JP-A-58-200200, for the purpose of improving the sharpness of the image obtained, the surface of the support on the phosphor layer side (the surface of the support on the phosphor layer side is When an adhesion-providing layer, a light-reflecting layer, a light-absorbing layer, or the like is provided, it means the surface thereof), and minute irregularities may be formed.

After forming the coating film on the support as described above, the coating film is dried to complete the formation of the stimulable phosphor layer on the support. The layer thickness of the phosphor layer varies depending on the characteristics of the intended radiation image conversion panel, the type of phosphor, the mixing ratio of the binder and the phosphor, etc., but is usually 20 μm to 1 mm. However, this layer thickness is preferably 50 to 500 μm.

Further, the stimulable phosphor layer does not necessarily have to be formed by directly applying the coating solution on the support as described above, and for example, the coating solution may be separately formed on a sheet such as a glass plate, a metal plate or a plastic sheet. After forming the phosphor layer by applying and drying, the support may be bonded to the phosphor layer by pressing it onto the support or using an adhesive.

The stimulable phosphor layer may have only one layer, but may have two or more layers. In the case of multiple layers, at least one layer may be a layer containing the divalent europium-activated alkaline earth metal halide phosphor of the composition formula (I),
You may make it the structure which laminated | stacked several fluorescent substance layer so that the light emission efficiency with respect to a radiation may become high one by one toward the direction near the surface of a panel. In addition, in the case of both single layer and multiple layers,
A known stimulable phosphor can be used in combination with the above phosphor.

Examples of such known stimulable phosphor, in addition to the phosphor described above, ZnS is described in _{JP-A-55-12142: Cu, Pb, BaO ·} xAl 2 O 3:
Eu (however, 0.8 ≦ x ≦ 10), and M ^II O · x
SiO ₂ : A (however, M ^II is Mg, Ca, Sr, Z
n, Cd, or Ba, and A is Ce, Tb, Eu,
Tm, Pb, Tl, Bi, or Mn, and x is
0.5 ≦ x ≦ 2.5), and described in JP-A-55-12143 (Ba).
_{1-xy, Mg x, Ca} y) FX: aEu 2+ ( However, X
Is at least one of Cl and Br, x and y are 0 <x + y ≦ 0.6, and xy ≠ 0,
a is 10 ⁻⁶ ≦ a ≦ 5 × 10 ⁻² ), and LnO described in JP-A-55-12144.
X: xA (where Ln is La, Y, Gd, and Lu
At least one of X, at least one of Cl and Br, A at least one of Ce and Tb, and x is 0 <x <0.1), and the like. You can

In a normal radiation image conversion panel, a transparent protective film for physically and chemically protecting the phosphor layer is provided on the surface of the phosphor layer on the side opposite to the side in contact with the support as described above. Has been. It is preferable to install such a transparent protective film also in the radiation image storage panel of the present invention.

The transparent protective film may be, for example, a cellulose derivative such as cellulose acetate or nitrocellulose; or a transparent polymer material such as polymethylmethacrylate, polyvinyl butyral, polyvinyl formal, polycarbonate, polyvinyl acetate, or vinyl chloride / vinyl acetate copolymer. It can be formed by a method in which a solution prepared by dissolving a high-molecular substance in a suitable solvent is applied to the surface of the phosphor layer. Alternatively, a transparent thin film separately formed from polyethylene terephthalate, polyethylene, polyvinylidene chloride, polyamide or the like may be adhered to the surface of the phosphor layer using an appropriate adhesive, or the like. The thickness of the transparent protective film thus formed is preferably about 0.1 to 20 μm.

Incidentally, JP-A-55-163500, JP-A-57-
As described in Japanese Patent Publication No. 96300, the radiation image conversion panel of the present invention may be colored with a coloring agent, and the sharpness of an image obtained by coloring can be improved. Further, as described in JP-A-55-146447, in the radiation image storage panel of the present invention, white powder may be dispersed in the phosphor layer for the same purpose.

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

Example 1 An aqueous solution of barium bromide (BaBr ₂ ) (1.55 × 10 ⁻³ mol
/ G) 192.7 g, an aqueous solution of barium chloride (BaCl ₂ ) (1.18 × 10 ⁻³ mol / g) 253.5 g, and an aqueous solution of europium bromide (EuBr ₃ ) (2.841 × 10 ⁻⁴ mol
/ Ml) 1.06 m. This aqueous solution was dried under reduced pressure at 60 ° C. for 3 hours and then vacuum dried at 150 ° C. for 3 hours.

Next, 10 g of the obtained phosphor raw material mixture and 0.88 mg of silicon monoxide (SiO) were sufficiently mixed and then filled in an alumina crucible, which was placed in a high temperature electric furnace and fired. The calcination was performed in a carbon dioxide atmosphere containing carbon monoxide at a temperature of 850 ° C. for 1.5 hours. After the firing was completed, the fired product was taken out of the furnace and cooled. Thus, the divalent europium-activated barium chlorobromide phosphor (BaCl ₂ · BaBr ₂₎ containing silicon monoxide is obtained.
・ 0.001SiO: 0.001Eu ²⁺ ) was obtained.

[Example 2] The same procedure as in Example 1 was carried out except that the amount of silicon monoxide added was changed to 0.1 mg, to activate divalent europium containing silicon monoxide. Barium chloride bromide phosphor (BaCl ₂ · BaBr
₂ · 0.0001SiO: 0.001Eu ²⁺ ) was obtained.

Example 3 In Example 1, the amount of silicon monoxide added was 8.75 mg.
A divalent europium-activated barium chlorobromide phosphor (BaCl ₂ .BaB) containing silicon monoxide was obtained by performing the same operation as in Example 1 except that
r ₂ .0.01SiO: 0.001Eu ²⁺ ) was obtained.

Comparative Example 1 A divalent europium-activated barium chlorobromide phosphor (BaCl) was prepared in the same manner as in Example 1 except that silicon monoxide was not added to the phosphor raw material mixture. ₂ · BaBr ₂ · 0.001Eu ²⁺ ) was obtained.

Next, each of the phosphors obtained in Examples 1 to 3 and Comparative Example 1 was irradiated with X-rays having a tube voltage of 80 KVp, and the stimulated emission luminance when excited with a semiconductor laser beam (780 nm) was measured. The results are summarized in FIG.

Figure 1 shows BaCl ₂ · BaBr ₂ · bSiO: 0.001
3 is a graph showing the relationship between the content (b value) of silicon monoxide in the Eu ²⁺ phosphor and stimulated emission luminance.

As apparent from FIG. 1, BaCl used in the present invention
₂ · BaBr ₂ · bSiO: 0.001Eu ²⁺ phosphor is b
When the value is in the range of 0 <b ≦ 3 × 10 ^-2 , the stimulated emission luminance is improved. In particular, a phosphor having ab value in the range of 10 ⁻⁴ ≦ b ≦ 10 ⁻² exhibits stimulated emission with high brightness.

[Example 4] A radiation image conversion panel was manufactured as follows using the phosphors obtained in Examples 1 to 3 and Comparative Example 1.

Methyl ethyl ketone is added to a mixture of a powdery divalent europium-activated barium chlorobromide-based phosphor and a linear polyester resin, and nitrocellulose having a nitrification degree of 11.5% is further added to contain the phosphor in a dispersed state. A dispersion was prepared. Next, tricresyl phosphate, n-butanol, and methyl ethyl ketone were added to this dispersion, and the mixture was sufficiently stirred and mixed using a propeller mixer to uniformly disperse the phosphor, and the mixing ratio of the binder and the phosphor was adjusted. 1: 1
A coating liquid having a viscosity of 25 to 35 PS (25 ° C.) was prepared. Next, the coating solution was uniformly applied using a doctor blade onto a titanium dioxide kneaded polyethylene terephthalate sheet (support, thickness: 250 μm) placed horizontally on a glass plate. After the application, the support on which the coating film was formed was placed in a dryer, and the temperature inside the dryer was gradually raised from 25 ° C to 100 ° C to dry the coating film. In this way, the layer thickness is 250μ on the support.
m phosphor layer was formed.

Then, a transparent film of polyethylene terephthalate (thickness: 12 μm, having a polyester adhesive applied) is placed on the phosphor layer with the adhesive layer side facing down to adhere the transparent protective film. Was formed.

In this way, various radiation image conversion panels composed of the support, the phosphor layer and the transparent protective film were manufactured.

A tube voltage of 8 was applied to each radiation image conversion panel obtained in Example 4.
After irradiating 0 KVp X-ray, a semiconductor laser light (780
The sensitivity (stimulated emission luminance) of the panel when excited at (nm) was measured. The results are shown in Table 1.

[Brief description of drawings]

FIG. 1 is a specific example of the phosphor used in the present invention B
It is a graph which shows the relationship between b value and stimulated emission luminance in aCl ₂ · BaBr ₂ · bSiO: 0.001Eu ²⁺ phosphor. FIG. 2 is a schematic diagram for explaining the radiation image conversion method of the present invention. 11: Radiation generation device, 12: Subject, 13: Radiation image conversion panel, 14: Light source, 15: Photoelectric conversion device, 16: Image reproduction device, 17: Image display device, 18: Filter

Claims (12)

[Claims] 1. A divalent europium-activated alkaline earth metal halide-based phosphor represented by the following composition formula (I) absorbs radiation emitted from a subject or a subject, and then the fluorescence is obtained. 450-1000nm on the body
The radiation image conversion method is characterized in that the radiation energy accumulated in the phosphor is emitted as fluorescence by irradiating electromagnetic waves in the wavelength region of, and the fluorescence is detected. Compositional formula (I): M ^II X ₂ · aM ^II X ′ ₂ · bSiO: xEu ²⁺ (I) (where M ^II is Ba; X and X ′ are both C, Br and I) At least one halogen selected from the group and X ≠ X ′; and a is a numerical value in the range of 0.1 ≦ a ≦ 10.0 and b
Is a numerical value in the range of 0 <b ≦ 3 × 10 ⁻² , and x is 0 <x
It is a numerical value in the range of ≦ 0.2) 2. b in the composition formula (I) is 10 ⁻⁴ ≦ b ≦ 1.
The radiation image conversion method according to claim 1, which is a numerical value in the range of 0 ^-2 . 3. A in the composition formula (I) is 0.25 ≦ a ≦
The radiation image conversion method according to claim 1, wherein the numerical value is in the range of 6.0. 4. The radiation image conversion method according to claim 1, wherein X and X'in the composition formula (I) are either C or Br, respectively. 5. In the composition formula (I), x is 10 ⁻⁵ ≦ x ≦ 1.
The radiation image conversion method according to claim ¹ , which is a numerical value in the range of 0 ^-1 . 6. The radiation image conversion method according to claim 1, wherein the electromagnetic wave is an electromagnetic wave in a wavelength region of 500 to 850 nm. 7. The radiation image conversion method according to claim 1, wherein the electromagnetic wave is a laser beam. 8. A radiation image conversion panel substantially composed of a support and a stimulable phosphor layer provided on the support, wherein the stimulable phosphor layer has the following composition formula (I And a divalent europium-activated alkaline earth metal halide phosphor represented by the formula (1). Compositional formula (I): M ^II X ₂ · aM ^II X ′ ₂ · bSiO: xEu ²⁺ (I) (where M ^II is Ba; X and X ′ are both C, Br and I) At least one halogen selected from the group and X ≠ X ′; and a is a numerical value in the range of 0.1 ≦ a ≦ 10.0 and b
Is a numerical value in the range of 0 <b ≦ 3 × 10 ⁻² , and x is 0 <x
It is a numerical value in the range of ≦ 0.2) 9. b in the composition formula (I) is 10 ⁻⁴ ≦ b ≦ 1
The radiation image conversion panel according to claim 8, which is a numerical value in the range of 0 ^-2 . 10. A in the composition formula (I) is 0.25 ≦ a.
The radiation image conversion panel according to claim 8, wherein the radiation image conversion panel has a numerical value in the range of ≦ 6.0. 11. The radiation image conversion panel according to claim 8, wherein X and X'in the composition formula (I) are each C or Br. 12. X in the composition formula (I) is 10 ⁻⁵ ≦ x ≦
The radiation image storage panel according to claim 8, which has a numerical value in the range of 10 ^-1 .