JP2006008838A - Stimulable phosphor, method for producing the same, radiation image conversion panel and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stimulable phosphor causing little lowering of luminance by X-ray damage and having excellent moisture resistance, a method for producing the phosphor, a radiation image conversion panel produced by using the phosphor and a method for producing the panel. <P>SOLUTION: The stimulable phosphor is produced by (A) a step to form a stimulable phosphor and (B) a step to cover the stimulable phosphor with a metal oxide and a silane coupling agent in the presence of a catalyst. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a photostimulable phosphor that is less affected by X-ray damage and has excellent moisture resistance, a manufacturing method thereof, a radiation image conversion panel, and a manufacturing method thereof.

  Radiation images such as X-ray images are often used for disease diagnosis and the like. In order to obtain this X-ray image, the X-ray that has passed through the subject is irradiated onto the phosphor layer (phosphor screen), thereby generating visible light, which is the same as when taking a normal picture with a silver salt. So-called radiographs, which are developed by irradiating a film using a film, are used. However, in recent years, a method has been devised in which an image is directly extracted from a phosphor layer without using a film coated with silver salt.

  In this method, radiation that has passed through the subject is absorbed by the phosphor, and then the phosphor is excited by light or thermal energy, for example, so that the radiation energy accumulated by the phosphor is emitted as fluorescence. There is a method of detecting and imaging this fluorescence. Specifically, for example, a radiation image conversion method using a stimulable phosphor as described in US Pat. No. 3,859,527 and Japanese Patent Application Laid-Open No. 55-12144 is known.

  This method uses a radiation image conversion panel containing a stimulable phosphor, and applies radiation transmitted through the subject to the stimulable phosphor layer of this radiation image conversion panel to support the radiation transmission density of each part of the subject. The radiation energy accumulated in the stimulable phosphor is then accumulated by exciting the stimulable phosphor in time series with electromagnetic waves (excitation light) such as visible light and infrared rays. The energy is released as stimulated light emission, a signal based on the intensity of this light is photoelectrically converted to obtain an electrical signal, and this signal is reproduced as a visible image on a recording material such as a photosensitive film or a display device such as a CRT. Is.

  According to the above-described radiographic image recording / reproducing method, a radiographic image with abundant information can be obtained with a much smaller exposure dose than in the case of radiographic method using a combination of conventional radiographic film and intensifying screen. There is an advantage that you can.

  As described above, the stimulable phosphor is a phosphor that exhibits stimulating light emission when irradiated with radiation and then irradiated with excitation light. In practice, the stimulable phosphor has a wavelength of 300 to 300 by excitation light having a wavelength in the range of 400 to 900 nm. A phosphor that exhibits stimulated emission in the wavelength range of 500 nm is generally used.

Examples of stimulable phosphors that have been used in radiation image conversion panels in the past include:
(1) (Ba _1-X , M ²⁺ X) FX: yA described in JP-A-55-12145 (where M ²⁺ is at least one of Mg, Ca, Sr, Zn and Cd) 1, X is at least one of Cl, Br and I, A is at least one of Eu, Tb, Ce, Tm, Dy, Pr, Ho, Nd, Yb and Er, and x is 0 ≦ x ≦ 0.6, y is 0 ≦ y ≦ 0.2) The rare earth element-activated alkaline earth metal fluoride halide phosphor represented by the composition formula; May be included: X ′, BeX ″, M ³ X ″ ′ ₃ described in JP-A-56-74175, wherein X ′, X ″ and X ″ ′ are each Cl , Br and I, and M ³ is a trivalent metal);
BeO as described in JP 55-160078 discloses, BgO, CaO, SrO, BaO , ZnO, Al 2 O 3, Y2O 3, La 2 O 3, In 2 O 3, SiO 2, TiO 2, ZrO ₂ , GeO ₂ , SnO ₂ , Nb ₂ O ₅ , Ta ₂ O _5, ThO _{2 and} other metal oxides; Zr and Sc described in JP-A-56-116777; JP-A-57-23673 B described in the publication; As, Si described in JP-A-57-23675;
M · L described in JP-A-58-206678 (where M is at least one alkali metal selected from the group consisting of Li, Na, K, Rb and Cs; L is Sc, Y, (La, Ce, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Al, Ga, In, and Tl are at least one trivalent metal) A calcined product of a tetrafluoroboric acid compound described in JP-A-59-27980; hexafluorosilicic acid, hexafluorotitanic acid and hexafluorozirconium described in JP-A-59-27289; Baked product of monovalent or divalent metal salt of acid; NaX ′ described in JP-A-59-56479 (where X ′ is at least one of Cl, Br and I) In a); V which are described in JP 59-56480 Publication, Cr, Mn, Fe, transition metals such as Co and Ni;
M1X ′, M ′ ² X ″, M ³ X ″ ′, A described in JP-A-59-75200 (where M ¹ is selected from the group consisting of Li, Na, K, Rb and Cs) At least one alkali metal, M ′ ² is at least one divalent metal selected from the group consisting of Be and Mg; and M ³ is at least one selected from the group consisting of Al, Ga, In, and Tl. A is a metal oxide; X ′, X ″ and X ″ ′ are at least one halogen selected from the group consisting of F, Cl, Br and I, respectively; M ¹ X ′ described in JP-A-101173 (where M ¹ is at least one alkali metal selected from the group consisting of Rb and Cs; X ′ is from the group consisting of F, Cl, Br and I) At least chosen It is a species of halogen);
M ² ′ X ′ ₂ .M ² ′ X ″ ₂ described in JP-A 61-23679 (where M ² ′ is at least one alkaline earth selected from the group consisting of Ba, Sr and Ca) X ′ and X ″ are at least one halogen selected from the group consisting of Cl, Br and I, respectively, and X ′ ≠ X ″); and Japanese Patent Application No. 60-106752 LnX ″ ₃ (wherein Ln is selected from the group consisting of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. At least one rare earth element; X ″ is at least one halogen selected from the group consisting of F, Cl, Br and I);
(2) M ² X ₂ · aM ² ' ₂ : xEu ²⁺ described in JP-A-60-84381 (where M ² is at least one alkali selected from the group consisting of Ba, Sr and Ca) X and X ′ are at least one halogen selected from the group consisting of Cl, Br and I, and X ≠ X ′; and a is 0.1 ≦ a ≦ 0.0 , X is 0 <x ≦ 0.2); a divalent europium-activated alkaline earth metal halide phosphor represented by a composition formula:
Further, the phosphor may contain the following additives: M ¹ X ″ described in JP-A-60-166379 (where M ¹ is a group consisting of Rb and Cs) X ″ is at least one halogen selected from the group consisting of F, Cl, Br and I); KX ″ described in JP-A-60-222143 , MgX ″ ′ ₂ , M ³ X ″ ″ ₃ (where M ³ is at least one trivalent metal selected from the group consisting of Sc, Y, La, Gd and Lu; X ″, X ″ ′ and X "" Is at least one halogen selected from the group consisting of F, Cl, Br and I); B described in JP-A-60-228592; JP-A-60-228593 Si described O ₂ , P ₂ O _5, etc .; LiX ″ and NaX ″ described in JP-A-61-120882 (where X ″ is at least selected from the group consisting of F, Cl, Br and I) A kind of halogen; SiO described in JP-A-61-120883; SnX ″ ₂ described in JP-A-61-120885 (where X ″ is F, Cl, Br and At least one halogen selected from the group consisting of I);
CsX ″, SnX ″ ′ ₂ described in JP-A-61-235486 (where X ″ and X ″ ′ are at least one halogen selected from the group consisting of F, Cl, Br and I, respectively) And CsX ″, Ln ³⁺ described in JP-A No. 61-235487 (where X ″ is at least one halogen selected from the group consisting of F, Cl, Br and I; Ln is Sc, Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, and at least one rare earth element selected from the group consisting of Lu);
(3) LnOX: xA described in JP-A-55-12144 (where Ln is at least one of La, Y, Gd, and Lu; X is at least one of Cl, Br, and I) A is at least one of Ce and Tb; and x is 0 <x <0.1). The rare earth element activated rare earth oxyhalide phosphor represented by the composition formula:
(4) M ³ OX: xCe described in JP-A-58-69281 (where M ³ is Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb and Bi) At least one metal oxide selected from the group consisting of: X is at least one of Cl, Br, and I; x is 0 <x <0.1) Activated trivalent metal oxyhalide phosphor;
(5) M ¹ X: xBi described in Japanese Patent Application No. 60-70484 (where M ¹ is at least one alkali metal selected from the group consisting of Rb and Cs; X is Cl, Br And at least one halogen selected from the group consisting of I and I; and x is a numerical value in the range of 0 <x ≦ 0.2); a bismuth activated alkali metal halide phosphor;
(6) M ² 5 (PO ₄ ) ₃ X: xEu ²⁺ described in JP-A-60-141784 (where M ² is at least one alkali selected from the group consisting of Ca, Sr and Ba) X is an at least one halogen selected from the group consisting of F, Cl, Br and I; and x is a numerical value in the range of 0 <x ≦ 0.2. Divalent europium activated alkaline earth metal halophosphate phosphor;
(7) M ² ₂ BO ₃ X: xEu ²⁺ described in JP-A-60-157099 (wherein M ² is at least one alkaline earth metal selected from the group consisting of Ca, Sr and Ba) X is at least one halogen selected from the group consisting of Cl, Br and I; x is a numerical value in the range of 0 <x ≦ 0.2) Alkaline earth metal haloborate phosphors;
(8) M ² ₂ PO ₄ X: xEu 2+ described in JP-A-60-157100 (where M ² is at least one alkaline earth metal selected from the group consisting of Ca, Sr and Ba) X is at least one halogen selected from the group consisting of Cl, Br, and I; x is a numerical value in the range of 0 <x ≦ 0.2) and a divalent europium activated alkaline earth represented by a composition formula: Metal halophosphate phosphors;
(9) M ² HX: xEu ²⁺ described in JP-A-60-217354 (wherein M ² is at least one alkaline earth metal selected from the group consisting of Ca, Sr and Ba; X is at least one halogen selected from the group consisting of Cl, Br and I; x is a numerical value in the range of 0 <x ≦ 0.2) and a divalent europium activated alkaline earth Metal hydride halide phosphors;
(10) LnX ₃ · aLn′X ′ ₃ : xCe ³⁺ described in JP-A No. 61-21173 (where Ln and Ln ′ are each selected from the group consisting of Y, La, Gd and Lu) At least one rare earth element; X and X ′ are at least one halogen selected from the group consisting of F, Cl, Br and I, respectively, and X ≠ X ′; and a is 0.1 < a numerical value in the range of a ≦ 10.0, and x is a numerical value in the range of 0 <x ≦ 0.2.) The cerium-activated rare earth composite halide phosphor represented by the composition formula:
(11) LnX ₃ · aM ¹ X ′: xCe ³⁺ described in JP-A-61-21182 (where Ln and Ln ′ are at least selected from the group consisting of Y, La, Gd and Lu, respectively) M ¹ is at least one alkali metal selected from the group consisting of Li, Na, K, Cs and Rb; X and X ′ are each selected from the group consisting of Cl, Br and I And at least one halogen; and a is a numerical value in the range of 0 <a ≦ 10.0, and x is a numerical value in the range of 0 <x ≦ 0.2). Complex halide phosphors;
(12) LnPO ₄ · aLnX ₃ : xCe ³⁺ described in JP-A No. 61-40390 (where Ln is at least one rare earth element selected from the group consisting of Y, La, Gd and Lu) X is at least one halogen selected from the group consisting of F, Cl, Br and I; and a is a numerical value in the range of 0.1 ≦ a ≦ 10.0, and x is 0 <x ≦ 0. A cerium-activated rare earth halophosphate phosphor represented by a composition formula:
(13) CsX: aRbX ′: xEu ²⁺ described in Japanese Patent Application No. 60-78151 (where X and X ′ are at least one halogen selected from the group consisting of Cl, Br and I, respectively) And a is a numerical value in the range of 0 <a ≦ 10.0, and x is a numerical value in the range of 0 <x ≦ 0.2). The divalent europium activated cesium halide Rubidium phosphor; and (14) M ² X ₂ · aM ¹ X ′: xEu ²⁺ described in Japanese Patent Application No. 60-78153 (where M ² is from the group consisting of Ba, Sr and Ca) At least one alkaline earth metal selected; M ¹ is at least one alkali metal selected from the group consisting of Li, Rb and Cs; and X and X ′ are each selected from the group consisting of Cl, Br and I Be At least one kind of halogen; and a is a numerical value in a range of 0.1 ≦ a ≦ 20.0, and x is a numerical value in a range of 0 <x ≦ 0.2. And divalent europium activated composite halide phosphors.

  Among the photostimulable phosphors described above, a divalent europium activated alkaline earth metal fluoride halide phosphor containing iodine, a divalent europium activated alkaline earth metal halide phosphor containing iodine, and iodine. The rare earth element activated rare earth oxyhalide phosphors containing bismuth and the bismuth activated alkali metal halide phosphors containing iodine show high brightness stimulated luminescence.

  Radiation image conversion panels using these photostimulable phosphors, after accumulating radiation image information, release accumulated energy by scanning excitation light, so that radiation images can be accumulated again after scanning and used repeatedly. Is possible. In other words, the conventional radiographic method consumes a radiographic film for each photographing, whereas this radiographic image conversion method repeatedly uses the radiographic image conversion panel, which is advantageous from the viewpoint of resource protection and economic efficiency. It is.

  Therefore, it is desirable to provide the radiation image conversion panel with performance that can withstand long-term use without degrading the image quality of the obtained radiation image.

  However, photostimulable phosphors used in the production of radiation image conversion panels generally have a high hygroscopic property, and when they are left in a room under normal climatic conditions, they absorb moisture in the air and deteriorate significantly over time.

  Specifically, for example, when a stimulable phosphor is placed under high humidity, the radiation sensitivity of the phosphor decreases as the absorbed moisture increases. In general, the latent image of the radiation image recorded on the photostimulable phosphor regresses with the passage of time after irradiation, so the intensity of the reconstructed radiation image signal is from radiation irradiation to scanning with excitation light. However, when the stimulable phosphor absorbs moisture, the latent image retraction speed increases.

  Therefore, when a radiation image conversion panel having a photostimulable phosphor that has absorbed moisture is used, the reproducibility of a reproduction signal at the time of reading a radiation image is lowered.

  In addition, it is known that the photostimulable phosphor particles generally have a photostimulability depending on the particle size. JP-A No. 55-163500 discloses an average particle size of 1 to 30 μm. Is preferred. Japanese Patent Publication No. 3-79680 discloses the relationship between the phosphor particle size and characteristic values such as sensitivity, graininess, and sharpness.

  An attempt to control the size and shape of the photostimulable phosphor particles is disclosed in Japanese Patent Application Laid-Open No. 7-233369 as a liquid phase method. Here, as a conventional method, a rare earth activated alkaline earth metal fluoride halide-based phosphor is disclosed. The production method of the exhaust phosphor is made by dry-mixing alkaline earth metal fluorides of raw material compounds, alkaline earth metal halides other than fluoride, halides of rare earth elements, ammonium fluoride together, or aqueous A method is disclosed in which a rare earth-activated alkaline earth metal fluoride halide photostimulable phosphor is precipitated in an aqueous solution, while suspended and mixed in a medium, and then fired and pulverized.

  By the liquid phase method of precipitating rare earth activated alkaline earth metal fluoride halide photostimulable phosphors in the above aqueous solution, phosphor particles with a small particle size can be obtained without deterioration of performance due to grinding. became.

  However, since the sensitivity is high and the particle size is reduced, deterioration due to moisture and X-ray damage have become more problematic than before.

Conventionally, in order to prevent the deterioration phenomenon due to moisture absorption of photostimulable phosphor particles, a method using a titanate coupling agent (see, for example, Patent Document 1) or a method using silicone oil (see, for example, Patent Document 2). ), A method using a silane coupling agent (see, for example, Patent Document 3) has been proposed, but production of a photostimulable phosphor having excellent photostimulated luminescence, little X-ray damage, and good graininess. A method, photostimulable phosphor and radiation image conversion panel have not yet been obtained.
Japanese Patent Publication No. 2-278196 Japanese Patent Publication No. 5-52919 Japanese Examined Patent Publication No. 62-209398

  An object of the present invention is to provide a photostimulable phosphor that is less susceptible to luminance reduction due to X-ray damage and has excellent moisture resistance, a method for producing the same, a radiation image conversion panel using the phosphor, and a method for producing the same.

  The above object of the present invention is achieved by the following configurations.

(Claim 1)
A method for producing a photostimulable phosphor, comprising producing the photostimulable phosphor by the following steps.
(A) Step of producing a stimulable phosphor (B) Step of coating the stimulable phosphor with a metal oxide and a silane coupling agent in the presence of a catalyst (Claim 2)
2. The method for producing a photostimulable phosphor according to claim 1, wherein the catalyst is a compound containing tin.

(Claim 3)
The method for producing a photostimulable phosphor according to claim 1 or 2, wherein the addition amount of the catalyst is 0.01 to 2.0 mass% with respect to the photostimulable phosphor.

(Claim 4)
The method for producing a photostimulable phosphor according to any one of claims 1 to 3, wherein the silane coupling agent is a compound having a mercapto group.

(Claim 5)
The stimulable phosphor is a stimulable phosphor represented by the following general formula (1), and is obtained by the method for producing a stimulable phosphor according to any one of claims 1 to 4. A stimulable phosphor characterized by that.

General formula (1)
(Ba _1-x M ¹ ) FX: yM ² , zLn
Wherein M ¹ is at least one alkaline earth metal atom selected from the group consisting of Mg, Ca, Sr, Zn and Cd, and M ² is selected from the group consisting of Li, Na, K, Rb and Cs. At least one alkali metal atom, X is at least one halogen atom selected from the group consisting of Cl, Br and I, Ln is Ce, Pr, Sm, Eu, Gd, Tb, Tm, Dy, Ho, Nd, Er and And at least one rare earth element selected from the group consisting of Yb, where x, y, and z represent numerical values of 0 ≦ x ≦ 0.6, 0 ≦ y ≦ 0.05, and 0 ≦ z ≦ 0.2, respectively. .)
(Claim 6)
A radiation image conversion panel comprising a photostimulable phosphor layer containing the photostimulable phosphor according to claim 5 on a support.

(Claim 7)
A step of producing a stimulable phosphor represented by the general formula (1), a step of coating the stimulable phosphor with a metal oxide and a silane coupling agent in the presence of a catalyst, and a support A method for producing a radiation image conversion panel, comprising the step of producing a photostimulable phosphor layer containing the coated photostimulable phosphor.

  INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a photostimulable phosphor that is less affected by X-ray damage and has excellent moisture resistance, a manufacturing method thereof, a radiation image conversion panel using the same, and a manufacturing method thereof.

As a result of diligent research, the present inventor has found that a photostimulable phosphor excellent in moisture resistance can be obtained by producing a photostimulable phosphor in the following steps with little reduction in luminance due to X-ray damage. . The present invention is characterized in that the photostimulable phosphor is coated with a metal oxide and a silane coupling agent in the presence of a catalyst.
(A) Step of generating photostimulable phosphor (B) Step of coating the photostimulable phosphor with a metal oxide and a silane coupling agent in the presence of a catalyst The present invention will be described in detail below.

  While investigating the phenomenon of sensitivity degradation due to moisture absorption of stimulable phosphors, the present inventors have found that performance degradation is caused by phosphor deliquescence and phosphor modification due to moisture absorption. This phenomenon is particularly likely to occur with stimulable phosphors containing X atoms.

  Therefore, preventing either deliquescence or alteration is not a fundamental solution. Accordingly, it has been found that the above-described problem can be solved by the above-described configuration of the present invention by intensive studies to prevent both deliquescence and alteration.

  The above-mentioned deliquescence refers to a phenomenon in which phosphor particles take water vapor in the air and make an aqueous solution by themselves. Alteration means that the fluorescence characteristics of the phosphor itself change due to water vapor in the air, although it does not deliquesce. . Although the mechanism of alteration is not clear, structural changes inside the phosphor particles are considered.

  The present invention is effective in preventing both deliquescence and alteration, but it is also effective for phosphor particles having no deliquescence properties. The effect of the present invention is to prevent phosphor alteration and deliquescence.

  The hygroscopic property of the phosphor is considered to occur due to various causes including capillary aggregation, but once water vapor is generated between the phosphor particles as water droplets, performance degradation occurs due to deliquescence.

In the present invention, for example, this deliquescence can be suppressed with any of the following configurations.
(1) The photostimulable phosphor is coated with a metal oxide and a silane coupling agent in the presence of a catalyst.
(2) After firing the stimulable phosphor precursor in the presence of the first metal oxide, the precursor is coated with a silane coupling agent in the presence of the catalyst, or in the presence of the first metal oxide. After the photostimulable phosphor precursor is calcined, it is coated with a silane coupling agent and a second metal oxide in the presence of a catalyst. Here, the precursor of the photostimulable phosphor refers to a substance that hardly exhibits photostimulable luminescence or instantaneous luminescence. For example, it refers to a state in which the compound represented by the general formula (1) has not passed through a high temperature of 600 ° C. or higher. Further, the stimulable phosphor precursor in the solid-phase method is a stimulable phosphor material itself, a mixture of stimulable phosphor materials, or a high temperature of 600 ° C. or higher for these substances. State.

  Hereinafter, these methods will be described.

About (1) It is estimated that the coating process by the metal oxide in this invention has an effect which prevents generation | occurrence | production of such a deliquescent. In particular, the effect is large in the case of a metal oxide that has been subjected to a hydrophobic treatment. However, the same effect can be given to the metal oxide by coating the phosphor with the metal oxide and then treating with a silane coupling agent in the presence of a catalyst.

  A silane coupling agent is effective in preventing the deterioration of the phosphor in the presence of a catalyst, but it has been difficult to directly form a silicon-containing film with the phosphor particles and the silane coupling agent on the phosphor particles.

  In the present invention, the second metal oxide coating treatment and the surface treatment with the silane coupling agent are performed in the presence of the catalyst, so that the silicon oxide film containing the silane coupling agent is dispersed on the phosphor particles. It is considered that the silane coupling agent functions effectively in order to form a continuous phase so as to fill in the periphery of the substrate.

  The coating with the second metal oxide and the surface treatment with the silane coupling agent are performed simultaneously in the presence of the catalyst, or the surface treatment with the silane coupling agent is performed in the presence of the catalyst after the coating of the metal oxide in the order of the surface treatment. Is effective.

  The second metal oxide used in the present invention is preferably composed of one or more of silica, alumina and titanium oxide and having a particle size of 2 to 50 nm. Those having a particle size of 2 nm or less are difficult to obtain industrially, and if it exceeds 50 nm, it is difficult to satisfactorily coat the surface of the phosphor particles.

(Metal oxide)
Examples of such metal oxides include dry method metal oxides such as silica, alumina, and titanium dioxide by flame hydrolysis method and arc method, as well as wet methods obtained by decomposition with salt acid such as sodium silicate. What is obtained by various manufacturing methods, such as a thing by hydrolysis of a metal oxide and organogel, is used.

  Examples of the method for hydrophobizing a metal oxide include a treatment with a silane coupling agent such as dimethylchlorosilane, hexamethyldisilane, octyltrimethoxysilane, and a treatment with silicone oil. Further, metal oxides already hydrophobized can be obtained industrially.

  Any ordinary method can be used to mix an appropriate amount of metal oxide with phosphor particles having an average particle diameter of several to several tens of μm, but a turbula shaker mixer (Shinmaru Enterprises Co., Ltd.) can be used. In a 0.5 to 10.0% by mass metal oxide dispersion, using a mixing device such as the above) and using a method of gradually adding phosphor particles to the total amount of metal oxide. A method in which the phosphor particles are stirred and then filtered and dried is preferable in terms of uniform coating of the particles.

(Silane coupling agent)
The silane coupling agent used in the present invention is represented by the following general formula (2).

  In the formula, R represents an aliphatic or aromatic hydrocarbon group, which may have an unsaturated group (for example, a vinyl group) interposed therebetween, or ROR'-, RCOOR'-RNHR'- (where R is an alkyl group, An aryl group, R ′ may be an alkylene group, an arylene group) or other substituents.

X ₁ , X ₂ , and X _{3 each} represents an aliphatic or aromatic hydrocarbon, an acyl group, an amide group, an alkoxy group, an alkylcarbonyloxy group, an epoxy group, a mercapto group, or a halogen atom, and X ₁ , X ₂ , X ₃ may be the same or different from each other. However, at least one is a group other than hydrocarbon. X ₁ , X ₂ and X ₃ are preferably groups that undergo hydrolysis.

  Specific examples of the silane coupling agent include methyltrimethoxysilane, methyltriethoxysilane, vinyltriacetoxysilane, vinyltrichlorosilane, vinyltriethoxysilane, γ-chloropropyltrimethoxysilane, γ-chloropropylmethyldichlorosilane, γ-chloropropylmethyldimethoxysilane, γ-chloropropylmethyldiethoxysilane, γ-aminopropyltriethoxysilane, N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, N- (β-aminoethyl) -Γ-aminopropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane , Γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ-isocyanatopropyltriethoxysilane, γ- (2-aminoethyl) Aminopropylmethyldimethoxysilane, γ-anilinopropyltrimethoxysilane, vinyltrimethoxysilane, N-β- (N-vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane / hydrochloride, aminosilane compound and the like It is done. Of these, vinyl type, mercapto type, glycidoxy type, and methacryloxy type are particularly preferable, and mercapto type is more preferable.

  Particularly preferred silane coupling agents include γ-mercaptopropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, mercaptopropyltriethoxysilane, and the like, and the same effects as these mercapto silane coupling agents are given. 1-mercaptomethyl-1,1,3,3,3-pentamethyldisiloxane, 1- (3-mercaptopropyl) -1,1,3,3,3-pentamethyldisiloxane, and the like.

  According to the study by the present inventors, when the X-ray exposure is repeated on the radiation image conversion panel having the stimulable phosphor, the brightness is lowered. One of the causes is the halogen of the stimulable phosphor, particularly iodine. It turned out to be yellowing by precipitation. The reducing silane coupling agent has the effect of preventing discoloration of the stimulable phosphor, and the above-mentioned particularly preferred silane coupling agent and siloxane have the effect of preventing sensitivity deterioration due to coloring of the phosphor in addition to the moisture-proofing effect. Is also added. In particular, the effect of preventing discoloration of a compound containing a mercapto group is remarkable when the phosphor contains iodine in the structure, and effectively prevents yellowing of the phosphor due to free iodine.

(catalyst)
The silane coupling agent is hydrolyzed with water to form silanol and partially condensed to an oligomer state. Subsequently, it adsorbs on the surface of the inorganic substance (phosphor, metal oxide) in a hydrogen bond manner. Then, it is dehydrated and condensed by a drying treatment to form a strong chemical bond with the inorganic substance. The catalyst used in the present invention promotes this reaction, and a silanol condensation catalyst is used.

  Silanol condensation catalysts include tin-based catalysts and titanium-based catalysts. Tin-based catalysts include dibutyltin diacetate, dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin dioleate, bis (acetoxydibutyltin) oxide, bis (lauroxydibutyltin) oxide, dibutyltin bisacetylacetonate, dibutyltin bismalein Acid monobutyl ester, dioctyltin bismaleic acid monobutyl ester, stannous octoate, tetrabutyltin, monobutyltin trichloride, dibutyltin dichloride, monobutyltin oxide, dibutyltin oxide, tetraoctyltin, dioctyltin dichloride, dioctyltin oxide And tetramethyltin. Examples of the titanium-based catalyst include isopropoxy titanium bis (acetylacetonate), titanium tetra (acetylacetonate), dioctanoxy titanium dioctanoate, diisopropoxy titanium bis (ethyl acetoacetate), and the like. These silanol condensation catalysts are commercially available.

  In the present invention, a tin-based catalyst is preferable.

  In attaching the silane coupling agent to the phosphor particles coated with the metal oxide, a known method can be used. For example, using a Hensyl mixer, a dry method in which the catalyst and silane coupling agent are dropped or sprayed while stirring and mixing the phosphor particles, stirring while dropping the catalyst and silane coupling agent on the slurry-like phosphor, and dropping is completed. A slurry method in which the phosphor is precipitated and filtered, and then the phosphor is dried to remove the residual solvent. The phosphor is dispersed in the solvent, and after adding the catalyst and the silane coupling agent and stirring, the solvent is evaporated. For example, a method of forming an adhesion layer, or a method of adding a catalyst and a silane coupling agent to the coating dispersion for stimulable phosphor. The silane coupling agent is preferably dried at 60 to 130 ° C. for about 10 to 200 minutes in order to ensure the reaction with the phosphor.

  Note that the effect of the present invention remarkably appears when the coating with the metal oxide and the surface treatment with the silane coupling agent are simultaneously performed in the presence of the catalyst.

  As an example of such a treatment method, phosphor particles immediately after firing in a dispersion of a metal oxide, a catalyst and a silane coupling agent are disintegrated in the liquid, and simultaneously with the disintegration of the phosphor, After surface treatment with coating, catalyst and silane coupling agent, filtration and drying method, metal oxide, method of adding catalyst and silane coupling agent to coating dispersion for stimulable phosphor layer, etc. However, it is not limited to these.

  In the present invention, when the amount of the metal oxide exceeds 10% by mass with respect to the phosphor, the sensitivity decreases, and when it is less than 0.05% by mass, the effect of the present invention is halved.

  On the other hand, when the amount of the silane coupling agent is more than 5% by mass with respect to the amount of the phosphor, the sensitivity is lowered, the coating film is hardened, and cracks are generated on the film surface. If it is 0.1% by mass or less, the effect of the present invention is halved.

(2) First, an example using a catalyst and a silane coupling agent will be described. In accordance with the present invention, the precursor particles before firing are fired after coating with the first metal oxide and then surface treated with a catalyst and a silane coupling agent to obtain phosphor particles having high moisture resistance. The effect of improving the moisture resistance of the particles is maintained even when applied as a phosphor layer on the support through an application step. It is considered that the phosphor particles and the metal oxide are bonded by an electric force. However, if a force greater than this electric force is applied during the dispersion, preparation, or coating process, the metal oxide is peeled off from the phosphor particles. In other words, if a catalyst and a silane coupling agent are used in the method (2), this peeling can be suppressed, and moisture resistance and an X-ray damage preventing effect can be obtained even after application.

  In particular, the amount of the first metal oxide is determined within a range that does not impair the firing efficiency, and the phosphor particles are coated with the insufficient amount of the second metal oxide after firing, and then the treatment with the catalyst and the silane coupling agent is performed. Thus, it is possible to obtain an effect of suppressing a decrease in light emission characteristics due to a decrease in firing efficiency.

  It is unclear why the metal oxide does not peel from the phosphor particles during the dispersion, preparation, and coating process, but it is assumed that some bonding occurs between the phosphor particles and the metal oxide during firing. .

  The amount of the first metal oxide in the present invention is preferably alumina in terms of preventing sintering of the phosphor particles, and is preferably 0.01 to 2.0% by mass with respect to the amount of phosphor precursor in terms of firing efficiency. .

  In addition, when alumina is used as the first metal oxide, the moisture resistance of the phosphor is further improved when silica is used as the second metal oxide. It is not clear why the moisture resistance is further improved by silica, but it is presumed that a strong electrical force works with alumina particles fixed on the phosphor surface because the charging characteristics are different from those of alumina.

  The particle size of the metal oxide used in the present invention is preferably 2 to 50 nm. Those having a particle size of less than 2 nm are difficult to obtain industrially, and if it exceeds 50 nm, it is difficult to satisfactorily coat the surface of the phosphor particles.

  In the present invention, when the total amount of the metal oxide is 10% by mass or less with respect to the phosphor, the decrease in sensitivity can be reduced, and when it is more than 0.01% by mass, the effect of the present invention can be further improved.

  In addition, when the amount of the silane coupling agent is 5% by mass or less with respect to the amount of the phosphor, it is possible to reduce the decrease in sensitivity, and it is difficult to harden the coating film, and it is possible to reduce the occurrence of cracks on the film surface. Moreover, when more than 0.1 mass%, the effect of this invention can be improved more.

  The metal oxide used in this embodiment (2) is the same as the metal oxide used in the above embodiment (1). Further, the first metal oxide and the second metal oxide may be the same material or different materials.

(Panel fabrication, phosphor layer, coating process, support, protective layer)
As the support used in the radiation image conversion panel of the present invention, various polymer materials, glass, metal and the like are used. In particular, a material that can be processed into a flexible sheet or web is suitable for handling as an information recording material, and in this respect, cellulose acetate film, polyester film, polyethylene terephthalate film, polyamide film, polyimide film, triacetate film Further, a plastic film such as a polycarbonate film, a metal sheet of aluminum, iron, 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, but is generally 3 to 1000 μm, and more preferably 80 to 500 μm from the viewpoint of handling.

  The surface of these supports may be a smooth surface, or may be a mat surface for the purpose of improving the adhesion to the photostimulable phosphor layer.

  Further, these supports may be provided with an undercoat layer on the surface on which the photostimulable phosphor layer is provided for the purpose of improving the adhesion to the photostimulable phosphor layer.

  Examples of binders used in the photostimulable phosphor layer in the present invention include proteins such as gelatin, polysaccharides such as dextran, or natural polymer materials such as gum arabic; and polyvinyl butyral, polyvinyl acetate, Represented by synthetic polymer materials such as nitrocellulose, ethyl cellulose, 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 by a crosslinking agent. The photostimulable phosphor layer can be formed on the undercoat layer by the following method, for example.

  First, a stimulable phosphor, a compound such as a phosphite for preventing yellowing, and a binder are added to a suitable solvent, and these are mixed well to add phosphor particles and the compound in the binder solution. A coating solution in which particles 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, vinylidene chloride / vinyl chloride copolymer, polymethyl methacrylate. Film-forming binders usually used for layer construction such as vinyl chloride / vinyl acetate copolymer, polyurethane, cellulose acetate butyrate, polyvinyl alcohol, etc. are 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, in terms 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 in view of the ease of application.

  The mixing ratio of the binder to the stimulable phosphor in the coating solution (however, if the binder is an epoxy group-containing compound, it is equal to the ratio of the compound to the phosphor) is the intended radiation image conversion. Although it varies depending on the characteristics of the panel, the type of phosphor, the addition amount of the epoxy group-containing compound, etc., in general, examples of the solvent for preparing the binder coating solution include methanol, enotal, 1-propanol, 2-propanol, n- Lower alcohols such as butanol; hydrocarbons containing chlorine atoms such as methylene chloride and ethylene chloride; ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; esters of lower fatty acids such as methyl acetate, ethyl acetate and butyl acetate; and lower alcohols; , Ethylene glycol ethyl ether, ethylene glycol monomethyl ether Ether; toluene; and it can include mixtures thereof.

  Examples of the solvent used for the preparation of the stimulable phosphor layer coating solution include lower alcohols such as methanol, ethanol, isopropanol and n-butanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, ketones such as cyclohexanone, methyl acetate, Esters of lower fatty acids and lower alcohols such as ethyl acetate and n-butyl acetate, ethers such as dioxane, ethylene glycol monoethyl ether and ethylene glycol monomethyl ether, aromatic compounds such as triol and xylol, methylene chloride, ethylene chloride and the like Examples thereof include halogenated hydrocarbons and mixtures thereof.

  The coating solution has a dispersing agent for improving the dispersibility of the phosphor in the coating solution, and a binding force between the binder and the phosphor in the stimulable phosphor layer after formation. Various additives, such as a plasticizer for improving, may be mixed. Examples of the dispersant used for such purpose include phthalic acid, stearic acid, caproic acid, lipophilic surfactant and the like. Examples of plasticizers include phosphoric esters such as triphenyl phosphate, tricresyl phosphate and diphenyl phosphate; phthalic esters such as diethyl phthalate and dimethoxyethyl phthalate; ethyl phthalyl ethyl 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.

  Dispersants such as stearic acid, phthalic acid, caproic acid, and lipophilic surfactants for the purpose of improving the dispersibility of stimulable phosphor layer phosphor particles in the stimulable phosphor layer coating solution. May be mixed. Moreover, you may add the plasticizer with respect to a binder as needed. Examples of the plasticizer include phthalate esters such as diethyl phthalate and dibutyl phthalate, aliphatic dibasic acid esters such as diisodecyl succinate and dioctyl adipate, ethyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate And the like.

  Preparation of the stimulable phosphor layer coating solution is performed using a dispersing device such as a ball mill, a sand mill, an attritor, a three-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 photostimulable phosphor layer.

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

  A phosphor sheet having a phosphor layer coated on a support is cut into a predetermined size. Any general method can be used for cutting, but a decorative cutting machine, a punching machine, or the like is preferable in terms of workability and accuracy.

  The phosphor sheet cut into a predetermined size is generally sealed with a moisture-proof protective film. Examples of the sealing method include a method in which a phosphor sheet is sandwiched between upper and lower moisture-proof protective films, and a peripheral portion is heated and fused with an impulse sealer, or a laminating method in which pressure is heated between two heated rollers. Etc.

  In the method of heat-sealing with the above impulse sealer, heat-sealing under a reduced pressure environment is more preferable in terms of preventing displacement of the phosphor sheet in the moisture-proof protective film and eliminating moisture in the atmosphere.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

Example 1
(Production of radiation image conversion panel)
In order to synthesize the stimulable phosphor precursor of europium-activated barium fluoroiodide, 2500 ml of BaI ₂ aqueous solution (1.75 mol / l) and 125 ml of EuBr ₃ aqueous solution (0.067 mol / l) were placed in the reactor. . The reaction mother liquor in the reactor was kept at 83 ° C. with stirring. 250 ml of an aqueous ammonium fluoride solution (8 mol / l) was poured into the reaction mother liquor using a roller pump to form a precipitate. After completion of the injection, the precipitate was aged by maintaining the temperature and stirring for 2 hours. Next, the precipitate was separated by filtration, washed with methanol, and then vacuum-dried to obtain europium-activated barium fluoroiodide crystals. 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 europium-activated barium fluoroiodide phosphor particles obtained were converted into metal oxides (0.5% by mass of the phosphor), catalyst (see Table 1 for the amount added to the phosphor) and silane. The slurry was immersed in an ethanol dispersion to which a coupling agent (2.0% by mass of the phosphor) was added to form a slurry, and then crushed and dried at 80 ° C. for 3 hours. After drying, classification was performed to obtain particles having an average particle diameter of 7 μm. In addition, the metal oxide, catalyst, and silane coupling agent used at this time are as follows.

<Metal oxide>
A1: Silica particles (Nippon Aerosil Co., Ltd., particle size 12 nm)
<catalyst>
B1: Dibutyltin diacetate B2: Dibutyltin dilaurate B3: Isopropoxy titanium bis (acetylacetonate)
<Silane coupling agent>
C1: γ-mercaptopropyltrimethoxysilane C2: γ-glycidoxypropyltrimethoxysilane Next, as the phosphor layer forming material, 427 g of the above-obtained europium-activated barium fluoroiodide phosphor, polyurethane resin (Sumitomo Bayer) Urethane Co., Ltd., Desmolac 4125) 15.8 g and bisphenol A type epoxy resin 2.0 g are added to a methyl ethyl ketone-toluene (1: 1) mixed solvent, dispersed by a propeller mixer, and a coating solution having a viscosity of 25 to 30 Pa · s. Was prepared. This coating solution was applied onto an undercoated polyethylene terephthalate film using a doctor blade, and then dried at 100 ° C. for 15 minutes to form a phosphor layer having a thickness of 230 μm. The coated sample is cut into a square of 10 cm × 10 cm, a film in which PET (30 μm) and CPP (40 μm) are bonded is used as a protective film, the phosphor plate is wrapped with the CPP surface inside, and the phosphor is subjected to reduced pressure. A radiation image conversion panel was prepared by thermally fusing the four sides outside the plate.

(Evaluation of radiation image conversion panel)
The radiation image conversion panel was evaluated for water repellency, moisture resistance and X-ray damage as follows. The results are shown in Table 1.

<Water repellency>
Water repellency is expressed by the degree of hydrophobicity (MW value) by the methanol wettability method. Generally, 20 or more is said to be hydrophobic, and 5 or less is said to be hydrophilic.

<Moisture resistance>
Prepare two copies of each of the above prepared radiographic image conversion panels, and use a part as it is as a reference sample, and the remaining part is treated in an atmosphere of 40 ° C. and 90% RH for 15 days, and this is subjected to forced deterioration treatment. A sample was used. The luminance of the radiation image conversion panel using the reference sample and the forced deterioration sample was evaluated, the luminance deterioration rate due to the forced deterioration was measured, and this was used as an index of moisture resistance.

The brightness was measured using Regius 170 (manufactured by Konica Corporation). Each radiation image conversion panel (sample) was irradiated with X-rays having a tube voltage of 80 kVp and 200 mR, and then each sample was subjected to He—Ne laser light (633 nm). ) Excited by scanning at 4.0 J / m ² , and the stimulated luminescence emitted from the phosphor layer is received through the optical filter (B-410) by the light receiver (photoelectron image multiplier with spectral sensitivity S-5). Measure the amount of photostimulated luminescence, define this as luminance, calculate the luminance deterioration rate of the radiation image conversion panel using the forced deterioration processing sample for the radiation image conversion panel using the reference sample, and rank it according to the following criteria I did.

5: The luminance deterioration rate is less than 2% 4: The luminance deterioration rate is less than 2-5% 3: The luminance deterioration rate is less than 5-10% 2: The luminance deterioration rate is less than 10-15% 1: The luminance deterioration rate is 15% In the above rank, if it is 4 or more, it is practically acceptable.

<X-ray damage>
The luminance measured by the same method as the measurement method of moisture resistance is set as the initial luminance, and the radiation image conversion panel (sample) is irradiated with X-rays having a tube voltage of 80 kVp and 200 mR, and a He—Ne laser beam (633 nm) of 4.0 J / Luminance was measured after irradiation and scanning were performed 500 times by scanning with m ² , exciting and reading. The luminance deterioration rate with respect to the initial luminance was calculated and ranked according to the following criteria.

5: The luminance deterioration rate is less than 2% 4: The luminance deterioration rate is less than 2-5% 3: The luminance deterioration rate is less than 5-10% 2: The luminance deterioration rate is less than 10-15% 1: The luminance deterioration rate is 15% In the above rank, if it is 3 or more, it is practically acceptable.

  As is clear from Table 1, it can be seen that the sample of the present invention is superior in water repellency, moisture resistance and X-ray damage to the comparative example.

Claims (7)

A method for producing a photostimulable phosphor, comprising producing the photostimulable phosphor by the following steps.
(A) Step of generating photostimulable phosphor (B) Step of coating the photostimulable phosphor with a metal oxide and a silane coupling agent in the presence of a catalyst 2. The method for producing a photostimulable phosphor according to claim 1, wherein the catalyst is a compound containing tin. The method for producing a photostimulable phosphor according to claim 1 or 2, wherein the addition amount of the catalyst is 0.01 to 2.0 mass% with respect to the photostimulable phosphor. The method for producing a photostimulable phosphor according to any one of claims 1 to 3, wherein the silane coupling agent is a compound having a mercapto group. The stimulable phosphor is a stimulable phosphor represented by the following general formula (1), and is obtained by the method for producing a stimulable phosphor according to any one of claims 1 to 4. A stimulable phosphor characterized by that.
General formula (1)
(Ba _1-x M ¹ ) FX: yM ² , zLn
Wherein M ¹ is at least one alkaline earth metal atom selected from the group consisting of Mg, Ca, Sr, Zn and Cd, and M ² is selected from the group consisting of Li, Na, K, Rb and Cs. At least one alkali metal atom, X is at least one halogen atom selected from the group consisting of Cl, Br and I, Ln is Ce, Pr, Sm, Eu, Gd, Tb, Tm, Dy, Ho, Nd, Er and And at least one rare earth element selected from the group consisting of Yb, where x, y, and z represent numerical values of 0 ≦ x ≦ 0.6, 0 ≦ y ≦ 0.05, and 0 ≦ z ≦ 0.2, respectively. .) A radiation image conversion panel comprising a photostimulable phosphor layer containing the photostimulable phosphor according to claim 5 on a support. A step of producing a stimulable phosphor represented by the general formula (1), a step of coating the stimulable phosphor with a metal oxide and a silane coupling agent in the presence of a catalyst, and a support A method for producing a radiation image conversion panel, comprising the step of producing a photostimulable phosphor layer containing the coated photostimulable phosphor.