JP2657595B2 - Phosphor and radiation image conversion panel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel stimulable phosphor,
And a radiation image conversion panel having a stimulable phosphor layer containing the stimulable phosphor.

[0002]

2. Description of the Related Art As an alternative to the conventional radiographic method, there is known a radiation image recording / reproducing method using a stimulable phosphor as described in, for example, JP-A-55-12145. This method uses a radiation image conversion panel (a stimulable phosphor sheet) containing a stimulable phosphor, and transmits radiation transmitted through a subject or emitted from a subject to the stimulable phosphor of the panel. By absorbing the stimulable phosphor with electromagnetic waves (excitation light) such as visible light and infrared light in a time series manner, the radiation energy stored in the stimulable phosphor is absorbed by the body. The fluorescent light is emitted (stimulated emission light), the fluorescent light is read photoelectrically to obtain an electric signal, and a radiation image of a subject or a subject is reproduced as a visible image based on the obtained electric signal. . After the reading of the panel is completed, after the remaining image is deleted, the panel is prepared for the next photographing. That is, the radiation image conversion panel can be used repeatedly.

According to the above-described radiographic image recording / reproducing method, a radiation having a much smaller amount of exposure and a richer amount of information than a conventional radiographic method using a combination of a radiographic film and an intensifying screen. There is an advantage that an image can be obtained. Furthermore, while the conventional radiographic method consumes radiographic film for each photographing operation, this radiographic image conversion method uses a radiographic image conversion panel repeatedly, which also contributes to resource conservation and economic efficiency. It is advantageous.

A stimulable phosphor is a phosphor that emits stimulable light when irradiated with radiation and then with excitation light. However, in practice, the stimulable phosphor has a wavelength of 400 to 900 nm due to the excitation light. Phosphors that exhibit stimulated emission in the 500 nm wavelength range are commonly used. Examples of stimulable phosphors conventionally used in radiation image conversion panels include divalent europium-activated alkaline earth metal halide-based phosphors. The radiation image conversion panel used in the radiation image recording / reproducing method has, as a basic structure, a support and a stimulable phosphor layer provided on the surface of the support. However, when the phosphor layer is self-supporting, a support is not necessarily required. The stimulable phosphor layer is
Usually, it comprises a stimulable phosphor and a binder containing and supporting the phosphor in a dispersed state. However, as the stimulable phosphor layer, a layer composed of only an aggregate of the stimulable phosphor without a binder formed by a vapor deposition method or a sintering method is known. Further, there is known a radiation image conversion panel having a stimulable phosphor layer in which a polymer substance is impregnated in a gap between stimulable phosphor aggregates. In any of these phosphor layers, the stimulable phosphor has a property of exhibiting stimulable emission when irradiated with excitation light after absorbing radiation such as X-rays. Radiation emitted from the specimen is absorbed by the stimulable phosphor layer of the radiation image conversion panel in proportion to the radiation dose, and a radiation image of the subject or the subject is formed on the panel as an accumulated image of radiation energy. . This accumulated image can be emitted as stimulated emission light by irradiating the excitation light,
By reading the stimulated emission light photoelectrically and converting it into an electric signal, it becomes possible to image a stored image of radiation energy.

The surface of the stimulable phosphor layer (the surface not facing the support) is usually provided with a protective film such as a polymer film or an inorganic vapor-deposited film. Is protected from chemical alteration or physical impact.

A large number of phosphors have been found in various applications. However, only a few types of phosphors exhibiting such stimulability have been confirmed. Therefore, it is still important to search for a phosphor exhibiting a practically usable level of stimulability.

In the course of research for a new stimulable phosphor, the present inventor has found that a fluorite-type fluoride (for example, a composition such as a fluorite-type fluoride) conventionally known as a substance exhibiting ion conductivity (ion conductor). As a formula, CaF ₂ .0.01Na,
It has been found that a novel compound obtained by activating the compound represented by the formula (1) with a rare earth element exhibits photostimulability.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a novel stimulable phosphor (stimulable phosphor).

[0009]

SUMMARY OF THE INVENTION The formula _{^{(I): M II F 2}} · xM I F: yA ... (I) [ where, M ^II is an alkaline earth metal, M ^I is an alkali metal and, A Is Ce, Pr, Sm, Eu, Gd, T
represents b, Tm, or Yb, and x and y represent numerical values of 0 <x ≦ 0.5 and 0 <y ≦ 0.1, respectively. ] A radiation image conversion panel comprising a rare earth element-activated fluorite-type fluoride-based stimulable phosphor represented by the formula: and a phosphor layer containing the stimulable phosphor.

In the composition formula (I), considering the intensity of the stimulated emission obtained, M ^II is preferably Mg, Ca, Sr or Ba, M ^I is preferably Na or Li, and A is preferably Eu or Ce. Further, x is preferably a numerical value in the range of 0.001 ≦ x ≦ 0.2, and y is preferably 0.001 ≦ x ≦ 0.05.

The rare earth element-activated fluorite type fluoride stimulable phosphor represented by the composition formula (I) of the present invention includes: 1) alkaline earth metal fluoride, alkali metal fluoride and rare earth element Preparing a mixture of a phosphor raw material comprising fluoride; and 2) subjecting the phosphor raw material mixture to 400 to 130 under a weakly reducing or neutral atmosphere or under a trace amount of oxygen-introduced atmosphere.
Baking at a temperature in the range of 0 ° C. for 0.5 to 10 hours. The method for producing the rare earth element activated fluorite type fluoride stimulable phosphor of the present invention will be described in detail below.

First, as raw materials of the phosphor, 1) fluoride of an alkaline earth metal (such as SrF ₂ ), 2) fluoride of an alkali metal (such as NaF), and 3) fluoride of a rare earth element (such as CeF ₃ ) Prepare In some cases, a known flux may be used.

In the manufacture of the phosphor, first, 1) the alkaline earth metal fluoride, 2) the alkali metal fluoride, and 3) the rare earth element fluoride are stoichiometrically mixed with the composition. The mixture of the phosphor raw materials is prepared by weighing and mixing so as to have a relative ratio corresponding to the formula (I).

The phosphor raw material mixture is prepared by: i) simply mixing the phosphor raw materials of the above 1) to 3); ii) first mixing the phosphor raw materials of the above 1) to 2), and then mixing the mixture at 100 ° C. After heating at the above temperature for several hours, the phosphor material of the above 3) is mixed with the obtained heat-treated product. Iii) The phosphor materials of the above 1) to 2) are first mixed in a suspension state, This suspension is heated (preferably 50-200).
Drying at reduced pressure, vacuum drying, spray drying and the like, and then mixing the phosphor material of the above 3) with the obtained dried product.

As a modification of the above method ii), a method in which the phosphor raw materials of the above 1) to 3) are mixed and the mixture is subjected to the above heat treatment may be used. As a modification of the method iii), a method of mixing the phosphor raw materials of the above 1) to 3) in a suspension state and drying the suspension may be used. Alternatively, the phosphor raw material of the above 2) may be added to and mixed with the mixture after the heat treatment or drying, or when firing is performed twice or more, the phosphor raw material of the above 2) may be added after the primary firing. Is also good. In any of the above methods i), ii) and iii), a conventional mixer such as various mixers, a V-type blender, a ball mill and a rod mill is used for mixing.

Next, the phosphor raw material mixture prepared as described above is filled in a heat-resistant container such as a quartz boat, an alumina crucible, a quartz crucible, etc., and placed in a furnace core of an electric furnace for firing. The firing temperature is suitably in the range of 400 to 1300C, preferably in the range of 500 to 1000C.
The baking time varies depending on the filling amount of the phosphor raw material mixture, the baking temperature, the temperature at which the mixture is taken out of the furnace, and the like. As firing atmosphere,
A neutral atmosphere such as a nitrogen gas atmosphere or an argon gas atmosphere, a weakly reducing atmosphere such as a nitrogen gas atmosphere containing a small amount of hydrogen gas, a carbon dioxide atmosphere containing carbon monoxide, or a trace oxygen introduction atmosphere is used. .

After the phosphor material mixture has been fired once as described above, the fired material is taken out of the electric furnace and allowed to cool, and if necessary, mortar, ball mill, tube mill,
The powder may be pulverized into a fine powder using a conventional pulverizer such as a centrifugal mill, and the pulverized product may be placed in an electric furnace and refired (secondary firing). The firing temperature for refiring is 400
~ 1300 ° C range is appropriate, and the firing time is 0.5 ~
It is suitable for 10 hours, and as the firing atmosphere, the above-mentioned weak reducing atmosphere and neutral atmosphere, and an atmosphere into which a small amount of oxygen is introduced can be used.

A powdery phosphor is obtained by the above calcination. The obtained phosphor may be subjected to various general operations in the production of the phosphor, such as washing, drying, and sieving, if necessary. Washing is performed with an organic solvent such as acetone, ethyl acetate, and ethanol because the phosphor is easily decomposed by warm water.

[0019] by the production method described above, the composition formula _{^{(I): M II F 2}} · xM I F: yA ... (I) [ where, the M ^II is an alkaline earth metal, M ^I is an alkali metal, And A is Ce, Pr, Sm, Eu, Gd, T
represents b, Tm, or Yb, and x and y represent numerical values of 0 <x ≦ 0.5 and 0 <y ≦ 0.1, respectively. ], A rare earth element activated fluorite type fluoride stimulable phosphor is obtained.

Next, a method of manufacturing the radiation image storage panel of the present invention will be described.

The stimulable phosphor layer of the radiation image conversion panel of the present invention is a layer containing a rare earth element-activated fluorite-type fluoride stimulable phosphor represented by the above general formula (I). , Comprising a stimulable phosphor and a binder that contains and supports the stimulable phosphor in a dispersed state, but if necessary, is composed of only an aggregate of the stimulable phosphor without a binder. Or a phosphor layer in which a polymer substance is impregnated in the gaps between the aggregates of the stimulable phosphor.

Next, the method for producing the radiation image storage panel of the present invention will be described, taking as an example the case where the phosphor layer comprises a stimulable phosphor and a binder containing and supporting the stimulable phosphor in a dispersed state.

The phosphor layer can be formed on a support by the following known method. First, a stimulable phosphor and a binder are added to a solvent and mixed well to prepare a coating solution in which the stimulable phosphor is uniformly dispersed in a binder solution. The mixing ratio between the binder and the stimulable phosphor in the coating solution varies depending on the characteristics of the intended radiation image conversion panel, the type of the phosphor, and the like. Generally, the mixing ratio between the binder and the phosphor is 1%. It is selected from the range of 1: 1 to 1: 100 (weight ratio), and particularly preferably selected from the range of 1: 8 to 1:40 (weight ratio). The coating solution 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. This coating operation can be performed by using ordinary coating means, for example, a doctor blade, a roll coater, a knife coater, or the like.

The support can be arbitrarily selected from materials known as supports for conventional radiation image conversion panels. In a known radiation image conversion panel, a phosphor layer is provided to enhance the bond between the support and the phosphor layer or to improve the sensitivity or image quality (sharpness, granularity) of the radiation image conversion panel. A polymer material such as gelatin is applied to the surface of the support on the side to form an adhesion-imparting layer, or a light-reflective layer made of a light-reflective material such as titanium dioxide, or a light-absorbent material such as carbon black It is known to provide an absorption layer or the like. The support used in the present invention can also be provided with these various layers, and the configuration thereof can be arbitrarily selected depending on the desired purpose and application of the radiation image storage panel. Further, JP-A-58-20020
As described in JP-A No. 0, the surface of the support on the side of the phosphor layer (the surface of the support on the side of the phosphor layer, the adhesion-imparting layer, In the case where a layer or a light absorbing layer is provided, the surface thereof means fine irregularities.

After forming the coating on the support as described above, the coating is dried to complete the formation of the stimulable phosphor layer on the support. The thickness of the phosphor layer varies depending on the characteristics of the intended radiation image conversion panel, the kind of the phosphor, the mixing ratio of the binder to the phosphor, and the like.
mm. However, this layer thickness is preferably 50 to 500 μm. The stimulable phosphor layer does not necessarily need to be formed by directly applying a coating solution on the support as described above. For example, a separate sheet such as a glass plate, a metal plate, or a plastic sheet may be used. After the phosphor layer is formed by applying a coating solution on the substrate and drying, the phosphor layer is pressed onto the support, or the support and the phosphor layer are joined by using an adhesive or the like. Is also good.

As described above, usually, a protective film is provided on the phosphor layer. The protective film is formed by applying a solution prepared by dissolving a transparent organic polymer substance such as a cellulose derivative or polymethyl methacrylate in an appropriate solvent onto the phosphor layer, or polyethylene. An organic polymer film such as terephthalate or a sheet for forming a protective film such as a transparent glass plate is separately formed and provided on the surface of the phosphor layer using an appropriate adhesive, or an inorganic compound is deposited on the phosphor by vapor deposition or the like. A film formed on the layer is used. Further, the protective film may be formed of a coating film of a fluorine-based resin soluble in an organic solvent, in which a perfluoroolefin resin powder or a silicone resin powder is dispersed and contained.

For the purpose of improving the sharpness of the obtained image, at least one of the layers constituting the radiation image conversion panel of the present invention absorbs excitation light,
The stimulated emission light may be colored by a coloring agent that does not absorb the light, or an independent colored intermediate layer may be provided (see Japanese Patent Publication No. 54-23400).

According to the above method, the support comprises the rare earth element-activated fluorite-type stimulable stimulable phosphor of the composition formula (I) and a binder containing and supporting the fluorite-stimulated stimulable phosphor in a dispersed state. The radiation image conversion panel of the present invention having the phosphor layer attached thereto can be manufactured.

[0029]

【Example】

[Example 1] strontium fluoride (SrF ₂₎ 50
g, sodium fluoride (NaF) 0.167 g (SrF
1 mol% based on ₂ ) and cerium fluoride (CeF
₃ ) After sufficiently mixing 0.758 g (1 mol% based on SrF ₂ ) with a ball mill, the mixture was charged into a quartz boat, placed in a tube-type electric furnace, and placed under a nitrogen atmosphere under a nitrogen atmosphere.
It was baked at a temperature of 0 ° C. for 5 hours. After firing, the quartz boat was taken out of the electric furnace and cooled to room temperature in a nitrogen atmosphere. The obtained fired product was pulverized and then sieved. In this manner, the cerium-activated strontium fluoride / sodium fluoride phosphor (SrF ₂ .0.01NaF: 0.
01 Ce) was obtained.

Examples 2 to 4 In Example 1, the amount of sodium fluoride (NaF) was 0.0835 g (SrF
₂ and 0.501 g (3 mol% based on SrF ₂ ), and 1.67 g (10 mol% based on SrF ₂ ). By performing the same operation, the following various cerium-activated strontium fluoride / sodium fluoride phosphors were obtained. Example 2: SrF ₂ .0.005NaF: 0.01C
e Example 3: SrF ₂ .0.03NaF: 0.01 Ce Example 4: SrF ₂ .0.1NaF: 0.01 Ce

Comparative Example 1 A cerium-activated strontium fluoride phosphor (SrF ₂ : 0.1) was prepared in the same manner as in Example 1 except that sodium fluoride was not used. 01 Ce) was obtained.

[Evaluation of phosphors]
After irradiating X-rays of Vp at 30 mR for 30 seconds, He-
The laser is excited by irradiating with Ne laser light (633 nm), and the photostimulated emission emitted from the phosphor is received by a photomultiplier tube through a filter (a band-pass filter transmitting blue light), so that the photostimulated emission luminance of the phosphor is obtained. Was measured. The peak of stimulated emission was 428 nm. Based on the height of the stimulated emission peak, the stimulated emission intensity of each phosphor was measured. Table 1 summarizes the obtained results as relative values.

Table 1 Example Phosphor Composition Stimulated Luminescence (Relative Value) 1 SrF ₂ .0.01NaF: 0.01 Ce 26.9 2 SrF ₂ .0.005 NaF: 0.01 Ce 17.9 3 SrF ₂ .0.03 NaF: 0.01 Ce 25.6 4 SrF ₂ .0.1NaF: 0.01 Ce 23.1 Ratio 1 SrF ₂ : 0.01 Ce 1.0

[Examples 5 to 14] In Example 1, strontium fluoride, sodium fluoride and cerium fluoride were appropriately changed, and the rare-earth-element-activated fluorite-type stimulable fluoride shown in Table 2 below was used. A phosphor was obtained.

Table 2 Example Phosphor Composition Stimulated Luminescence (Relative Value) 5 MgF ₂ 0.01 LiF: 0.01 Eu 6.9 6 MgF ₂ 0.01 NaF: 0.01 Eu 4.3 7 CaF ₂ 0.01 LiF: 0.01 Eu 2.8 8 CaF ₂ 0.01 NaF: _{0.01Eu 5.4 9 CaF 2 · 0.01NaF:} 0.01Ce 2.6 10 SrF 2 · 0.01LiF: 0.01Eu 6.7 11 SrF 2 · 0.01NaF: 0.01Eu 7.6 12 BaF _{2 · 0.01LiF: 0.01Eu 5.1 13 BaF} 2 · 0.01NaF: 0.01Eu 3.1 14 BaF 2 · 0.01NaF: 0.01Ce 2.8 Ratio 1 SrF ₂ : 0.01 Ce 1.0

The CaF ₂ .0.01Na of Example 8 above
F: a stimulated emission spectrum and a stimulated excitation spectrum of 0.01 Eu are shown in FIGS. 1 and 2, respectively.

Next, an example of manufacturing a radiation image conversion panel will be described.
Example 15 The cerium-activated strontium fluoride / sodium fluoride phosphor (SrF ₂ .0.01NaF: 0.01 Ce) obtained in Example 1 was used as a phosphor layer forming material.
356 g, 15.8 g of a polyurethane resin (Desmolac 4125 manufactured by Sumitomo Bayer Urethane Co., Ltd.) and 2.0 g of a bisphenol A type epoxy resin were added to a mixed solvent of methyl ethyl ketone-toluene (1: 1), and dispersed by a propeller mixer. A coating solution of 25 to 30 PS was prepared. After applying this coating solution on a polyethylene terephthalate film with an undercoat using a doctor blade,
After drying at 00 ° C. for 15 minutes, a phosphor layer was formed.

Next, as a protective film forming material, a fluororesin: fluoroolefin-vinyl ether copolymer (Lumiflon LF100 manufactured by Asahi Glass Co., Ltd.) 70 g, a cross-linking agent: isocyanate (Desmodur Z4370 manufactured by Sumitomo Bayer Urethane Co., Ltd.) 25 g, bisphenol A epoxy resin 5
g and 10 g of silicone resin fine powder (KMP-590, manufactured by Shin-Etsu Chemical Co., Ltd., particle size: 1-2 μm) were added to a mixed solvent of toluene-isopropyl alcohol (1: 1) to prepare a coating solution. This coating solution is applied onto the phosphor layer formed in advance as described above using a doctor blade, and then heat-treated at 120 ° C. for 30 minutes to be heat-cured and dried. A membrane was provided. The radiation image conversion panel was obtained by the above method.

Examples 16 to 28 The same operation as in Example 15 except that the rare earth element activated fluorite-type fluoride stimulable phosphor obtained in Examples 2 to 14 was used as the phosphor. Was performed to obtain a radiation image conversion panel comprising a support, a stimulable phosphor layer, and a protective layer.

[0040]

The novel rare earth element-activated fluorite-type fluorinated stimulable phosphor of the present invention exhibits high stimulable luminescence, and is advantageous, for example, in the form of a radiation image conversion panel and the radiation image recording / reproducing method. Available.

[Brief description of the drawings]

FIG. 1 is a photostimulated emission spectrum of CaF ₂ .0.01NaF: 0.01Eu.

FIG. 2 is a photostimulated excitation spectrum of CaF ₂ .0.01NaF: 0.01Eu.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-12299 (JP, A) JP-A-62-111637 (JP, A) JP-A-62-111635 (JP, A) JP-A-62-111635 209187 (JP, A) JP-A-61-236890 (JP, A) JP-A-61-72088 (JP, A) JP-A-5-247462 (JP, A)

Claims (2)

(57) [Claims] 1. A composition formula _{^{(I): M II F 2}} · xM I F: yA ... (I) [ where, M ^II is an alkaline earth metal, M ^I and the alkali metal, the A is Ce, Pr , Sm, Eu, Gd, T
represents b, Tm, or Yb, and x and y represent numerical values of 0 <x ≦ 0.5 and 0 <y ≦ 0.1, respectively. ] A stimulable phosphor represented by the formula: 2. A stimulable phosphor radiation image storage panel having a phosphor layer containing a stimulable phosphor composition formula _{^{(I): M II F 2}} · xM I F: yA ... (I) [ Where M ^II is an alkaline earth metal, M ^I is an alkali metal, and A is Ce, Pr, Sm, Eu, Gd, T
represents b, Tm, or Yb, and x and y represent numerical values of 0 <x ≦ 0.5 and 0 <y ≦ 0.1, respectively. ] A radiation image conversion panel characterized by being a stimulable phosphor represented by the following formula: