JPH0631915B2 - Radiation image conversion panel - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a radiation image conversion panel used in a radiation image conversion method using a stimulable phosphor, and more specifically, to a radiation image conversion panel containing iodine. The present invention relates to a radiation image conversion panel using a fluorescent substance.

[Technical Background of the Invention and Prior Art] Recently, as a method for obtaining a radiation image as an image, Japanese Patent Laid-Open No.
A radiation image conversion method using a stimulable phosphor as described in JP-A-12145 is proposed and put to practical use. The radiation image conversion method uses a radiation image conversion panel containing a stimulable phosphor (also referred to as a stimulable phosphor sheet), and the radiation transmitted through a subject or the radiation emitted from a subject is stored in the panel. Accumulated in the stimulable phosphor by absorbing it in the stimulable phosphor, and then exciting the stimulable phosphor in time series with electromagnetic waves (excitation light) such as visible light and infrared rays. The emitted radiation energy is emitted as fluorescence (stimulated luminescence), the fluorescence is photoelectrically read to obtain an electric signal, and the obtained electric signal is imaged.

According to this method, compared with the conventional radiographic method using a combination of a radiographic film and an intensifying screen, it is possible to obtain a radiographic image having a large amount of information with a much smaller radiation dose. There is. Therefore, this method has a very high utility value particularly in direct medical radiography such as X-ray photography for the purpose of medical diagnosis.

The radiation image conversion panel used in the radiation image conversion method has, as a basic structure, a support and a stimulable phosphor layer provided on one surface thereof. The surface of the stimulable phosphor layer opposite to the support (the surface not facing the support) is generally provided with a transparent protective film. Protects against chemical alteration or physical shock.

The stimulable phosphor layer is composed of a stimulable phosphor and a binder that contains and supports the stimulable phosphor in a dispersed state. The stimulable phosphor layer absorbs radiation such as X-ray and then emits excitation light. It has the property of exhibiting stimulated emission upon irradiation. Therefore, the radiation transmitted through the subject or emitted from the subject is absorbed by the stimulable phosphor layer of the radiation image conversion panel in proportion to the radiation dose, and the radiation image of the subject or the subject is displayed on the panel. It is formed as an accumulated image of radiation energy. This accumulated image can be emitted as stimulated emission light by irradiating the excitation light, and the accumulated image of radiation energy is imaged by photoelectrically reading this stimulated emission light and converting it into an electric signal. It becomes possible to do.

Although the radiation image conversion method is a very advantageous image forming method as described above, the radiation image conversion panel used in this method is also similar to the intensifying screen used in the conventional radiographic method,
It is desired to provide an image having high sensitivity and good image quality (sharpness, graininess, etc.). In particular, when the human body is used as a subject, it is desired that the sensitivity of the panel be as high as possible in order to reduce the exposure dose as much as possible.

Hitherto, as a stimulable phosphor used in a radiation image conversion panel, a divalent europium-activated barium fluorohalide phosphor (BaFX: Eu ²⁺ ; where X is I, or I and Cl and / or Br , A divalent europium-activated barium halide phosphor (BaXX ′: E)
u ²⁺ ; provided that X and X ′ are at least one halogen selected from Cl, Br and I, and X ≠
X ′, and at least one of X and X ′ contains I), a cerium-activated rare earth oxyhalide phosphor (LnOX: Ce; where Ln is at least one rare earth element selected from Y, La and lanthanide) And
X is I, or I and Cl and / or Br),
And bismuth activated alkali metal halide phosphor ^(M I X: Bi; however, ^{M I} is Rb and / or C
s and X is I, or I and Cl and / or Br
, Etc.) containing iodine as a phosphor component has been proposed.

However, when these iodine-containing stimulable phosphors are used, iodine is liberated from the phosphors to form iodine molecules (I ₂ ), so that the stimulable phosphor layer is gradually colored yellow. Tend to be. The radiation image conversion panel in which the stimulable phosphor layer is yellowed as described above has a problem that the sensitivity is significantly lowered.

In order to prevent yellowing of the panel as described above, the applicant has a group consisting of a compound having an epoxy group in the stimulable phosphor layer and / or a phosphorous acid ester, an organic tin compound and an organic acid metal salt. A patent application has already been filed for a radiation image conversion panel containing at least one compound selected from the above (Japanese Patent Application Nos. 61-25571 and 61-90618).

SUMMARY OF THE INVENTION It is an object of the present invention to provide a radiation image conversion panel in which yellowing is prevented.

Another object of the present invention is to provide a radiation image conversion panel with improved sensitivity.

Another object of the present invention is to provide a radiation image conversion panel having improved aging resistance and light resistance.

The above-mentioned object is a radiation image conversion panel having a support, a stimulable phosphor layer and a protective film in this order, and the stimulable phosphor layer contains iodine-containing stimulable phosphor in a dispersed state. And a compound having an epoxy group in each of the stimulable phosphor layer and the protective film selected from the group consisting of phosphite ester, organic tin compound and organic acid metal salt. It can be achieved by the radiation image conversion panel of the present invention, which is characterized in that

In the present specification, organic acid metal salt does not include organic tin.

That is, the present invention provides a phosphorous ester, an organotin compound and an organic acid not only for the protective film but also for the stimulable phosphor layer of a radiation image conversion panel using a stimulable phosphor containing iodine as a phosphor component. By containing at least one compound selected from the group consisting of metal salts and / or a compound having an epoxy group, yellowing of the panel is prevented and the sensitivity is remarkably improved.

The present inventors have found that when a stimulable phosphor containing iodine is used in a radiation image conversion panel, the stimulable phosphor layer is likely to turn yellow, and as a result, the stimulable luminescent light emitted from the phosphor is emitted. It was found that the sensitivity of the panel is remarkably lowered because the light in the blue region is absorbed in the stimulable phosphor layer. This yellowing of the stimulable phosphor layer means that iodine is liberated as I ₂ molecules from the phosphor in the coating liquid for forming the phosphor layer in the panel manufacturing process, or the phosphor formed by coating is formed. The iodine liberated from the phosphor in the layer is I ₂
It was found to be due to the formation of molecules.

Further, a protective film is usually provided on the side of the stimulable phosphor layer opposite to the side in contact with the support for the purpose of physically and chemically protecting the phosphor layer. It has been found that not only the body layer, but also this adjacent protective film tends to turn yellow due to liberated I ₂ molecules. In particular, when the protective film is formed on the phosphor layer by a coating method, the coating liquid contacts the iodine-containing phosphor to generate free I ₂ ,
This tends to cause the protective film to turn yellow. This also reduces the sensitivity of the panel, since the stimulated emission light is also absorbed by the yellowed protective film.

Further, the yellowing of the stimulable phosphor layer and the protective film impairs the appearance of the panel, which causes a problem of reducing the commercial value.

According to the radiation image storage panel of the present invention, the coating solution for forming the stimulable phosphor layer in the panel manufacturing process and the coating solution for forming the protective film in the case of the coating method respectively include phosphite ester, By adding at least one compound selected from the group consisting of organic tin compounds and organic acid metal salts and / or a compound having an epoxy group, iodine released from the stimulable phosphor is trapped by these compounds. In addition, formation of I ₂ molecules does not occur in the coating liquid, and I ₂ molecules are not generated by the coating liquid when forming the protective film. Alternatively, by using a thin film in which these compounds are dispersed and contained in advance as a protective film, the stimulable phosphor layer and the protective film formed in any case contain the compound, Iodine liberated from the fluorophore is not trapped by these compounds to form I ₂ molecules.

This is presumably because in the former phosphite ester, organic tin compound and organic acid metal salt, these compounds function as a kind of chelating agent for iodine and effectively capture iodine to be in a stable state. . For example, it is considered that tin in the organotin compound is bound to an iodine atom as a ligand to be in an extremely stable state. As a result, yellowing of the stimulable phosphor layer and the protective film is prevented, and a highly sensitive panel can be obtained. In addition, the appearance shape of the panel does not change color over time, and its commercial value can be maintained.

When an epoxy resin is used as the compound having an epoxy group, this epoxy resin simultaneously has a function as a polymer substance forming a binder and a protective film,
It is possible to further strengthen the bond between the stimulable phosphor layer and the support and to further enhance the original function of the protective film for protecting the phosphor layer. It is to be noted that the present invention includes the case where the binder and / or the polymer substance forming the protective film of the stimulable phosphor layer are all made of epoxy resin.

In particular, in the case where both the compound having an epoxy group in the stimulable phosphor layer and the protective film and at least one compound selected from the group consisting of phosphite, organic tin compounds and organic acid metal salts are contained. A panel with higher sensitivity can be obtained.

[Structure of the Invention] The radiation image storage panel of the present invention having the above-described preferable characteristics can be manufactured, for example, by the following method.

The support used in the present invention can be arbitrarily selected from various materials used as a support for intensifying screens in conventional radiography or various materials known as a support for radiographic 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.

On the surface of the support, a polymer substance such as gelatin is coated to provide adhesion (undercoat layer) for the purpose of strengthening the bond between the support and the stimulable phosphor layer, and sensitivity or image quality is provided. For the purpose of improving the antistatic property of the panel, or for providing a light reflecting layer made of a light reflecting substance such as titanium dioxide or zirconium oxide or a light absorbing layer made of a light absorbing substance such as carbon black. An antistatic layer made of a conductive material such as carbon black, In ₂ O ₃ and SnO ₂ may be provided.

Further, as described in JP-A-58-200200, the surface of the support on the side where the phosphor layer is provided (adhesion-imparting layer, light When a reflection layer, a light absorption layer, an antistatic layer, or the like is provided, it means the surface thereof), and minute irregularities may be provided.

A stimulable phosphor layer is formed on this support.

The stimulable phosphor layer, which is a characteristic requirement of the present invention, is a stimulable phosphor containing iodine, and at least one compound selected from the group consisting of phosphite ester, organic tin compound and organic acid metal salt. And / or a compound having an epoxy group in a dispersed state.

The stimulable phosphor containing iodine used in the present invention,
The composition of the phosphor contains iodine. That is, it contains iodine as at least one of the matrix component, additive component and activator component of the phosphor.

This stimulable phosphor containing iodine is a phosphor that exhibits stimulated emission when irradiated with excitation light after being irradiated with radiation as described above, but from a practical viewpoint, the wavelength is 400 to
300 with excitation light (for example, laser such as He-Ne laser and semiconductor laser) in the range of 900 nm
A phosphor that exhibits stimulated emission in the wavelength range of up to 500 nm is desirable.

Examples of the iodine-containing stimulable phosphor used in the radiation image storage panel of the present invention include (1) (Ba _{1- x} , M ²⁺ _x ) FX described in JP-A-55-12145. : YA (However, M ²⁺ is M
At least one of g, Ca, Sr, Zn, and Cd, X is at least one of Cl, Br, and I, A is Eu, Tb, Ce, Tm, Dy, Pr, Ho,
At least one of Nd, Yb, and Er, and x is 0 ≦ x ≦ 0.6, y is 0 ≦ y ≦ 0.2), and the rare earth element-activated alkaline earth represented by the composition formula Metal Fluorohalide Phosphor; Further, this phosphor may contain the following additives: Li described in JP-A-56-74175.
X ′, BeX ″ ₂ , M ^III X ₃ (provided that X ′, X ″
And X are respectively at least one of Cl, Br and I; M ^III is a trivalent metal); Be described in JP-A-55-160078.
O, MgO, CaO, SrO, BaO, ZnO, Al ₂
O ₃ , Y ₂ O ₃ , La ₂ O ₃ , In ₂ O ₃ , SiO ₂ ,
TiO ₂ , ZrO ₂ , GeO ₂ , SnO ₂ , Nb
Metal oxides such as ₂ O ₅ , Ta ₂ O ₅ and ThO ₂ ; Z described in JP-A-56-116777.
r, Sc; B described in JP-A-57-23673, As described in JP-A-57-23675,
Si; M described in JP-A-58-206678
L (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, L
u, Al, Ga, In, and at least one trivalent metal selected from the group consisting of Tl); A baked product of a tetrafluoroboric acid compound described in JP-A-59-27980. Hexafluorosilicic acid, hexafluorotitanic acid, and hexafluorozirconic acid monovalent or divalent metal salts described in JP-A-59-47289; Na
X '(wherein X'is at least one of Cl, Br and I); V and C described in JP-A-59-56480.
Transition metals such as r, Mn, Fe, Co and Ni; M described in JP-A-59-75200
^I X ′, M ′ ^II X ″ ₂ , M ^III X ₃ , A (however, M
^I is at least one alkali metal selected from the group consisting of Li, Na, K, Rb, and Cs, and M ′ ^II
Is at least one divalent metal selected from the group consisting of Be and Mg; M ^III is at least one trivalent metal selected from the group consisting of Al, Ga, In, and Tl; A is a metal oxide X ', X "and X
F respectively, Cl, at least one halogen selected from the group consisting of Br and I); disclosed in JP 60-101173 Laid ^{M I}
X '(provided that M ^I is at least one alkali metal selected from the group consisting of Rb and Cs; X'is at least one halogen selected from the group consisting of F, Cl, Br and I); M ^II 'described in Japanese Patent Laid-Open No. 61-23679
X ′ ₂ · M ^II ′ X ″ ₂ [wherein M ^II ′ is at least one alkaline earth metal selected from the group consisting of Ba, Sr and Ca; X ′ and X ″ are respectively Cl,
At least one halogen selected from the group consisting of Br and I, and X '≠ X "); and L described in Japanese Patent Application No. 60-106752.
nX ″ ₃ [where Ln is Sc, Y, La, Ce, P
r, Nd, Pm, Sm, Gd, Tb, Dy, Ho, E
at least one rare earth element selected from the group consisting of r, Tm, Yb and Lu; X ″ is F, Cl, Br
And at least one halogen selected from the group consisting of I); (2) M ^II X ₂ · aM ^II X ′ ₂ : xEu ²⁺ (provided that M ^II is B
at least one alkaline earth metal selected from the group consisting of a, Sr and Ca; X and X ′ are Cl,
At least one halogen selected from the group consisting of Br and I, and X ≠ X '; and a is 0.1 ≦ a ≦ 10.0 and x is 0 <x ≦ 0.2) A divalent europium-activated alkaline earth metal halide phosphor represented by the following composition formula; Further, the phosphor may contain the following additives: JP-A-60-166379 M ^I
X ″ (provided that M ^I is at least one alkali metal selected from the group consisting of Rb and Cs; X ″ is at least one halogen selected from the group consisting of F, Cl, Br and I); K described in JP-A-60-221483
X ″, MgX ₂ , M _III X ′ ₃ (where M ^III is S
at least one trivalent metal selected from the group consisting of c, 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; B: described in JP-A-60-228593. Is Si
_{O 2, P 2} O ₅ oxide such; are described in JP 61-120882 Laid Li
X ″, NaX ″ (where X ″ is at least one halogen selected from the group consisting of F, Cl, Br and I); Si described in JP-A-61-120883.
O: Sn described in JP-A-61-120885
X ″ ₂ (where X ″ is at least one halogen selected from the group consisting of F, Cl, Br and I); Cs described in JP-A-61-235486.
X ″, SnX ₂ (wherein X ″ and X are at least one halogen selected from the group consisting of F, Cl, Br and I, respectively); and Cs described in JP-A-61-235487.
X ″, Ln ³⁺ (where X ″ is F, Cl, Br and I
Is at least one halogen selected from the group consisting of; Ln is Sc, Y, Ce, Pr, Nd, Sm, Gd,
It is at least one rare earth element selected from the group consisting of Tb, Dy, Ho, Er, Tm, Yb and Lu); (3) LnOX: xA described in JP-A-55-12144 (however, 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) A rare earth element activated rare earth oxyhalide phosphor represented by the composition formula; (4) M ^III OX: xCe described in JP-A-58-69281 (where M ^III is Pr, Nd, P
m, Sm, Eu, Tb, Dy, Ho, Er, Tm, Y
b, and at least one trivalent metal selected from the group consisting of Bi; X is at least one of Cl, Br, and I; x is 0 <x <0.1) in represented by cerium activated trivalent metal oxyhalide phosphors; (5) ^M I X are described in Japanese Patent Application No. Sho 60-70484 Pat: xBi (However, ^{M I} is selected from the group consisting of Rb and Cs At least one alkali metal; X is at least one halogen selected from the group consisting of Cl, Br and I; and x is 0 <x ≦
Bismuth-activated alkali metal halide phosphor represented by the composition formula of (0.2); (6) M ^II ₅ (PO ₄ ) ₃ X described in JP-A-60-141783. : XEu ²⁺ (However, M ^II is C
is at least one alkaline earth metal selected from the group consisting of a, Sr and Ba; X is at least one halogen selected from the group consisting of F, Cl, Br and I, and x is 0 <x ≦ 0 ., Which is a numerical value in the range of 0.2), and the divalent europium-activated alkaline earth metal halophosphate phosphor represented by the composition formula; (7) M ^II ₂ BO ₃ described in JP-A-60-157099. X: xEu ²⁺ (However, M ^II is Ca, S
at least one alkaline earth metal selected from the group consisting of r 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 is a divalent europium-activated alkaline earth metal haloborate phosphor; (8) described in JP-A-60-157100. M ^II ₂ PO ₄ X: xEu ²⁺ (where M ^II is Ca, S
at least one alkaline earth metal selected from the group consisting of r 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 the divalent europium-activated alkaline earth metal halophosphate phosphor represented by the composition formula; (9) Described in JP-A-60-217354. M ^II HX: xEu ²⁺ (wherein M ^II is at least one alkaline earth metal selected from the group consisting of Ca, Sr and Ba; X is at least selected from the group consisting of Cl, Br and I) Is a kind of halogen; x is 0
<Divalent europium-activated alkaline earth metal hydrohalide phosphor represented by a composition formula of <x ≦ 0.2); (10) JP-A-61-21183. LnX ₃ · aLn′X ′ ₃ : xCe ³⁺ (where LnX
And Ln ′ are at least one rare earth element selected from the group consisting of Y, La, Gd and Lu; 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 ≦ 1
A numerical value in the range of 0.0, and x is a numerical value in the range of 0 <x ≦ 0.2). A cerium-activated rare earth composite halide phosphor represented by the composition formula; (11) JP-A-61-21182. JP _LnX 3 ^· aM I X that are described in ': xCe ³⁺ (although, Ln is Y, La, is at least one rare earth element selected from the group consisting of Gd and Lu; ^{M I} is Li, Na ,
At least one alkali metal selected from the group consisting of K, Cs and Rb; X and X ′ are each C
at least one halogen selected from the group consisting of 1, Br and I; 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. ) cerium activated rare earth halide phosphor represented by the composition formula; (12) LnPO disclosed in JP 61-40390 discloses ₄ · _{aLnX 3:} xCe ³⁺ (although, Ln is Y, La, At least one rare earth element selected from the group consisting of Gd and Lu; X is at least one halogen selected from the group consisting of F, Cl, Br and I; and a is 0 ≦ a ≦ 10.0 Cerium-activated rare earth halophosphate phosphor represented by the composition formula: (x) is a numerical value in the range, and x is a numerical value in the range of 0 <x ≦ 0.2; (13) Japanese Patent Application No. 60-78151 Listed Are CsX · aRbX ': xEu ²⁺ (However, X and X' is at least one halogen, respectively Cl, selected from the group consisting of Br and I; and a is 0 ≦
a is a numerical value in the range of 10.0, and x is 0 <x ≦ 0.2
Divalent europium activated cesium halide, rubidium phosphor represented by a composition formula in the range which is of numbers); and (14) M is described in Japanese Patent Application No. Sho 60-78153 Pat ^II X ₂ · aM ^I X ′: xEu ²⁺ (wherein M ^II is at least one alkaline earth metal selected from the group consisting of Ba, Sr and Ca; M ^I is at least one selected from the group consisting of Li, Rb and Cs Alkali metal; X and X ′ are each at least one halogen selected from the group consisting of Cl, Br and I; and a is a numerical value in the range of 0.1 ≦ a ≦ 20.0, and x is A divalent europium-activated composite halide phosphor represented by a composition formula of 0 <x ≦ 0.2).

Among the above stimulable phosphors, divalent europium-activated alkaline earth metal fluoride halide-based phosphors containing iodine, divalent europium-activated alkaline earth metal halide-based phosphors containing iodine, iodine Rare earth element-activated rare earth oxyhalide-based phosphors containing bismuth and bismuth activated alkali metal halide-based phosphors containing iodine are particularly preferable because they exhibit high-intensity stimulated emission. However, the stimulable phosphor containing iodine used in the present invention is not limited to the above-mentioned phosphor, and contains iodine as a phosphor composition, and when irradiated with excitation light after irradiation with radiation. Any phosphor may be used as long as it exhibits stimulated emission.

A typical phosphite ester (phosphorus chelate) used in the present invention is a compound represented by the following general formula [I] or [II].

(However, A is an oxygen atom or a sulfur atom; R ¹ ,
R ² , R ³ and R ⁴ are each a hydrogen atom, an alkyl group or an aryl group, and may be the same or different from each other; X ¹ is a group consisting of a carbon atom, an oxygen atom and / or a hydrogen atom. Examples of preferable phosphite include (1) triphenylphosphite (2) Diphenyldecyl phosphite (3) Didecyl phenyl phosphite (4) Tridecyl phosphite (C ₁₀ H ₂₁ O) ₃ P (5) Trioctyl phosphite (C ₈ H ₁₇ O) ₃ P (6) Tridodecyl phosphite (C ₁₂ H ₂₅ O) ₃ P (7 ) Trioctadecyl phosphite (C ₁₈ H ₃₇ O) ₃ P (8) Trinonylphenyl phosphite (9) tridodecyl trithiophosphite (C ₁₂ H _{25 S)} can be exemplified 3 P.

The compounds represented by the above general formula [I] or [II] may be used alone or in combination.

The organotin compound used in the present invention is, for example, a compound represented by the following general formula [III].

(However, R ⁵ and R ⁶ are each a hydrogen atom, an alkyl group or an aryl group, and may be the same or different from each other; Y ¹ , Y ² , Y ³ and Y
⁴ are each an alkyl group, an aryl group, a fatty acid, a fatty acid derivative, a mercaptan or a mercapto acid, and they may be the same or different from each other; X ² is an oxygen atom, a sulfur atom or maleic acid; (Or an integer of 1 or more) Generally, an organic tin compound tends to exist relatively stably in a state where a part of the organic ligand bonded to tin is replaced with halogen or the like. In the above general formula [III], Y ¹ to Y
^It is believed that at least one of the ^four ligands is replaced with iodine to stabilize it.

Examples of preferred organotin compounds include dioctyl tin mercapto, monobutyl tin trimethyl maleate,
Monobutyltin trioctyl maleate, dibutyltin dilaurate, dibutyltin laurate methyl maleate, dibutyltin dioleyl maleate, dibutyltin dimethyl maleate, dimethyltin maleate, dibutyltin methoxymethyl maleate, dibutyltin dimaleate and dibutyltin. Mention may be made of mixtures with dimethyl maleate, dibutyltin dioctyl maleate, dibutyltin dioctyl thioglycate, dibutyltin dilauryl mercaptide, tribenzyltin octyl maleate, tribenzyltin trimethylmaleate.

The organic acid metal salt used in the present invention is, for example, a compound represented by the following general formula [IV].

(R ⁷ COO) _m M [IV] (wherein R ⁷ is an alkyl group or an aryl group which may have a substituent having 1 to 20 carbon atoms; M is calcium, zinc, cadmium or barium; m Is 1
In the organic acid metal salt having the above general formula [IV], a part of the organic acid is replaced by iodine to form (R ⁷ COO) _m-1 M
It is believed to form I. However, in this specification, the metal of the organic acid metal salt does not include tin.

Examples of the organic acid in the organic acid metal salt include octylic acid, lauric acid, stearic acid, oleic acid, ricinoleic acid, naphthenic acid, 2-ethylhexylic acid, resin acid, synthetic carboxylic acid, benzoic acid, salicylic acid, and organic phosphorous acid. Can be mentioned. The organic acid may also be phenol and alkylphenol.

Examples of preferable organic acid metal salts include barium stearate, barium laurate, barium ricinoleate, barium naphthenate, barium 2-ethylhexoate,
So-called metal soaps such as calcium stearate, calcium laurate, calcium ricinoleate, zinc stearate, zinc laurate, zinc ricinoleate, and zinc 2-ethylhexoate can be mentioned.

The phosphite ester, the organotin compound and the organic acid metal salt may be used alone or in combination of two or more compounds.

Further, the compound having an epoxy group used in the present invention has at least one epoxy group in one molecule. Is to have.

The epoxy group-containing compound may be a monomer or a polymer. Examples of monomers include 1,2-epoxypropane and 1,2-epoxybutane. Examples of the polymer include bisphenol A type epoxy resin represented by the following general formula.

When the epoxy group-containing compound is a polymer, it is preferable since it can function as a binder as well as an additive for preventing yellowing. All the binders in the phosphor layer may be epoxy group-containing compounds.

At least one compound selected from the phosphite ester, the organic tin compound and the organic acid metal salt and the epoxy group-containing compound may be used alone, or may be used in combination.

Iodine liberated from the stimulable phosphor does not form I ₂ molecules because it is efficiently captured by these compounds, and therefore the stimulable phosphor layer does not turn yellow. In particular, it is preferable to use a compound such as a phosphite ester in combination with an epoxy group-containing compound because deterioration over time (decrease in sensitivity) can be prevented more effectively than when they are used alone.

Examples of the binder used in the stimulable phosphor layer in the present invention include proteins such as gelatin, polysaccharides such as dextran, or natural polymer substances such as gum arabic; and polyvinyl butyral and polyvinyl acetate. Represented by synthetic polymer substances 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. There may be mentioned a binder. Particularly preferred among such binders are nitrocellulose, linear polyesters, polyalkyl (meth) acrylates, mixtures of nitrocellulose and linear polyesters, mixtures of nitrocellulose and polyalkyl (meth) acrylates and It is a mixture of polyurethane and polyvinyl butyral. Note that these binders may be crosslinked with a crosslinking agent.

The stimulable phosphor layer can be formed on the support by the following method, for example.

First, an iodine-containing stimulable phosphor, a compound such as a phosphite ester for preventing yellowing and a binder are added to a suitable solvent, and these are sufficiently mixed to obtain a phosphor particle and a binder solution in a binder solution. A coating solution in which particles of the compound are uniformly dispersed is prepared.

Examples of the solvent for preparing the coating liquid include lower alcohols such as methanol, ethanol, 1-propanol, 2-propanol and n-butanol; chlorine atom-containing hydrocarbons such as methylene chloride and ethylene chloride; acetone, methyl ethyl ketone and methyl isobutyl. Ketones such as ketones; esters of lower fatty acids with lower alcohols such as methyl acetate, ethyl acetate, butyl acetate; ethers such as dioxane, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether; toluene; and mixtures thereof. You can

The mixing ratio of the binder and the stimulable phosphor in the coating liquid (however, when all the binder is an epoxy group-containing compound, it is equal to the ratio of the compound and the phosphor) is the desired radiation image conversion. Generally, the mixing ratio of the binder and the phosphor is selected from the range of 1: 1 to 1: 100 (weight ratio), though it depends on the characteristics of the panel, the type of the phosphor, the amount of the epoxy group-containing compound added, and the like. And it is preferable to select from the range of 1: 8 to 1:40 (weight ratio).

The addition amount of the phosphite ester, the organic tin compound and the organic acid metal salt varies depending on the kind and amount of the stimulable phosphor, the kind of the binder, etc., but generally 0.0001 to It is in the range of 3% by weight, and preferably in the range of 0.003 to 0.3% by weight. The addition amount of the epoxy group-containing compound is generally in the range of 0.001 to 10% by weight with respect to the phosphor, preferably 0.1.
It is in the range of 03 to 3% by weight. When the amount of the epoxy group-containing compound added is less than 0.001% by weight, almost no yellowing-preventing effect is obtained, while when it is more than 10% by weight, even if all the binder is the compound, the yellowing effect is low. Although it has the effect of preventing the deterioration, it will adversely affect various characteristics such as the light emitting characteristics of the phosphor, the flexibility of the panel, and the durability.

The coating liquid contains a dispersant for improving the dispersibility of the phosphor in the coating liquid, 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 dispersants used for such purpose include phthalic acid, stearic acid, caproic acid, lipophilic surfactants and the like. Examples of plasticizers include phosphoric acid esters such as triphenyl phosphate, tricresyl phosphate, diphenyl phosphate; phthalic acid esters such as diethyl phthalate and dimethoxyethyl phthalate; ethyl phthalyl 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 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.

Then, the formed coating film is gradually heated and dried to complete the formation of the stimulable phosphor layer on the support. The layer thickness of the stimulable phosphor layer varies depending on the characteristics of the intended radiation image conversion panel, the type of the stimulable 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.

Next, a protective film is provided on the surface of the stimulable phosphor layer opposite to the side in contact with the support for the purpose of physically and chemically protecting the phosphor layer.

The protective film, which is the second characteristic requirement of the present invention, comprises at least one compound selected from the group consisting of the above phosphite ester, an organic tin compound and an organic acid metal salt and / or a compound having an epoxy group, It is a layer made of a polymer substance that is contained and supported in a dispersed state.

Phosphite used for preventing yellowing of the protective film,
The organic tin compound, the organic acid metal salt, and the compound containing an epoxy group can be selected from the compounds used in the stimulable phosphor layer. These compounds contained in the stimulable phosphor layer and the protective film may be the same as or different from each other.

Since iodine released from the stimulable phosphor in the stimulable phosphor layer is efficiently captured by the above compound, formation of I ₂ molecule in the protective film is blocked, and therefore yellowing of the protective film is prevented. You can In particular, by using a compound such as a phosphite ester in combination with an epoxy group-containing compound, it is possible to more effectively prevent deterioration over time (decrease in sensitivity) as compared with the case of using the former alone or the latter alone. You can

Examples of transparent polymer substances include cellulose acetate,
Cellulose derivatives such as nitrocellulose; or polymethyl methacrylate, polyvinyl butyral, polyvinyl formal, polycarbonate, polyvinyl acetate, vinyl chloride / vinyl acetate copolymer, polyethylene terephthalate, polyethylene, polyvinylidene chloride,
Mention may be made of synthetic polymeric substances such as polyamide.

The protective film is prepared by adding a compound such as a phosphite ester for preventing yellowing and a transparent polymer substance to a suitable solvent and mixing them sufficiently to prepare a coating solution, which is prepared as a stimulable phosphor. The coating liquid can be formed on the phosphor layer by forming a coating film of the coating solution by uniformly coating the surface of the layer and then heating and drying the coating film. Alternatively, a thin film containing the compound dispersed therein is formed by separately applying the coating liquid on a sheet such as a glass plate, a metal plate, or a plastic sheet, and drying it, and then bonding this to the surface of the phosphor layer with an adhesive. By doing so, a protective film may be provided.

The amount of the compound for preventing yellowing varies depending on the type and amount of the stimulable phosphor in the phosphor layer, the type of polymer substance, etc., but the compound is a phosphite ester, an organotin compound or When it is an organic acid metal salt, it is generally in the range of 0.003 to 30% by weight with respect to the polymer substance,
It is preferably in the range of -0.01 to 1% by weight. When the compound is an epoxy group-containing compound, it is generally in the range of 0.03 to 100% by weight, preferably 1
-30% by weight.

As the solvent for preparing the coating liquid, the solvent used when forming the stimulable phosphor layer described above can be used.

The thickness of the transparent protective film thus formed is preferably about 0.1 to 20 μm.

The stimulable phosphor layer and the protective film may be simultaneously coated on the support by multilayer coating. That is, the coating solution for forming the phosphor layer and the coating solution for forming the protective film, the coating solution for the phosphor layer is arranged on the side of the support using a dual hopper type coating device, etc. It can be formed by uniformly and simultaneously applying multiple layers to form a coating film of the coating solution, and then heating and drying the coating film. Alternatively, the phosphor layer coating liquid may be first coated on the support, and immediately thereafter, the protective film coating liquid may be coated thereon, and then both coating films may be heated and dried to simultaneously form.

In this case, the binder used in the phosphor layer coating liquid and the polymer substance used in the protective film coating liquid may or may not be compatible with each other. An interface is not formed between the stimulable phosphor layer and the protective film formed, and a portion containing the stimulable phosphor and a portion not containing the stimulable phosphor are apparently present in the single-layer phosphor layer. become. Further, the solvents used for both coating liquids may be the same or different, but it is preferable to use mutually compatible solvents in order to make the drying rates of both coating films the same.

The coating amount of both coating solutions varies depending on the viscosity of the coating solutions, the mixing ratio of the binder and the stimulable phosphor, and the like, but is usually 10
It is selected from the range of 0: 1 to 1: 1 (volume ratio), and preferably in the range of 10: 1 to 1: 1. Further, as the polymer substance used for forming the protective film, melamine, phenol resin, etc. can be used in addition to the above substances.

When the protective film is provided on the stimulable phosphor layer via the adhesive layer, this adhesive layer may also contain the above-mentioned compound for preventing yellowing. The compound is contained in the adhesive in the same proportion as described above.

Further, the radiation image conversion panel of the present invention may have its end portions coated with a polymer substance, and the edge sticking may also contain the above-mentioned compound for preventing yellowing. In that case, the content of the phosphite ester, the organotin compound and the organic acid metal salt, and the content of the epoxy group-containing compound are each generally 0.003 to 30% by weight with respect to the polymer substance constituting the border. And 0.03 to 1
It is in the range of 00% by weight.

JP-A-55-163500, JP-A-57-963
As described in Japanese Patent Publication No. 00, etc., the radiation image storage panel of the present invention may be colored with a coloring agent,
The sharpness of the 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 stimulable phosphor layer for the same purpose.

Next, examples and comparative examples of the present invention will be described. However,
Each of these examples does not limit the invention.

Example 1 Particles of stimulable divalent europium-activated barium fluorobromide-based phosphor (BaFBr _0.85 I _0.15 : 0.001 Eu ²⁺ ),
Polyurethane resin (Pandix T-5265M, Dainippon Ink and Chemicals, Inc.), nitrocellulose (RS-120, Daicel Chemical Industries, Ltd.), bisphenol A type epoxy resin (average molecular weight: 800) and alkyldiallyl phosphite Was added to a mixed solvent of methyl ethyl ketone and toluene (1: 1 by volume) with the following composition, and then sufficiently stirred and mixed by using a propeller mixer to uniformly disperse the phosphor particles, thereby forming a binder and a phosphor. A coating solution (I) for forming a phosphor layer having a mixing ratio of 1:30 (weight ratio) and a viscosity of 25 to 35 PS (25 ° C.) was prepared.

Composition of coating liquid (I) Photostimulable phosphor 600 g Polyurethane resin 15.8 g Nitrocellulose 2.0 g Epoxy resin 2.0 g Alkyl diallyl phosphite 0.2 g Separately, polyurethane resin (Desmolak 4200, Sumitomo Bayer Urethane Co., Ltd. )), Nitrocellulose, aliphatic isocyanate (crosslinking agent; Desmodur Z4370, manufactured by Sumitomo Bayer Urethane Co., Ltd.) and alkyl diallyl phosphite with the following composition in a mixed solvent of toluene and isopropyl alcohol (1: 1, volume). Ratio), a coating solution (II) for forming a protective film having a viscosity of 2 to 3 PS (25 ° C.)
Was prepared.

Composition of coating liquid (II) Polyurethane resin 6.9 g Nitrocellulose 2.0 g Aliphatic isocyanate 1.0 g Alkyl diallyl phosphite 0.1 g Next, carbon kneaded polyethylene terephthalate film (support, thickness: 250 μm) was made into glass. Place it horizontally on a plate, and apply the coating liquid (I) and the coating liquid (II) on it.
Was simultaneously coated in multiple layers by using a double hopper type coating apparatus. After coating, the support on which the coating film is formed is placed in a dryer to dry the coating film, and the layer thickness on the support is about 25.
A stimulable phosphor layer having a thickness of 0 μm and a protective film having a thickness of about 10 μm were formed.

Thus, a radiation image conversion panel composed of the support, the stimulable phosphor layer and the protective film was produced.

[Example 2] In Example 1, 0.5 wt.
g was newly added and the same procedure as in Example 1 was carried out except that 6.4 g of the polyurethane resin was used, whereby a radiation image composed of the support, the stimulable phosphor layer and the protective film was formed. A conversion panel was manufactured.

[Comparative Example 1] A support, a stimulable phosphor layer, and a stimulable phosphor layer were prepared in the same manner as in Example 1 except that alkyldiallyl phosphite was not added to the coating liquid (II). A radiation image conversion panel composed of a protective film was manufactured.

Each of the obtained radiation image conversion panels was evaluated by the following sensitivity test and forced deterioration test.

(1) Sensitivity test After irradiating the radiation image conversion panel with X-rays having a tube voltage of 80 KVp, He-Ne laser light (wavelength: 632.8 nm)
It was excited with and the sensitivity was measured.

(2) Forced deterioration test Radiation image conversion panel temperature 60 ℃, relative humidity 80% RH
After leaving it for 1 week under the condition of 1, the sensitivity was measured in the same manner as above.

Further, the radiation image conversion panel was irradiated with a light amount of 100,000 lux for 3 hours using a high-pressure sodium lamp, and then the sensitivity was measured in the same manner as above.

The above results are summarized in Table 1.

As is clear from Table 1, the radiation image conversion panel of the present invention (Example 1) in which the stimulable phosphor layer and the protective film contain a phosphite ester is the same as the stimulable phosphor layer and the protective film during production. There was no yellowing, and the sensitivity was remarkably higher than that of the radiation image conversion panel (Comparative Example 1) in which the protective film did not contain phosphite.

Further, the radiation image conversion panel of the present invention containing a phosphorous acid ester and an epoxy group-containing compound in the protective film (Example 2).
It was clear that the aging resistance and the light resistance were further improved.

Claims (10)

[Claims] 1. A radiation image conversion panel having a support, a stimulable phosphor layer and a protective film in this order, wherein the stimulable phosphor layer contains iodine-containing stimulable phosphor in a dispersed state. And a compound having an epoxy group in each of the stimulable phosphor layer and the protective film selected from the group consisting of phosphite ester, organic tin compound and organic acid metal salt. A radiation image conversion panel comprising: 2. The protective film contains at least one compound selected from the group consisting of phosphite ester, organic tin compound and organic acid metal salt in an amount of 0.003 to 30% by weight based on the polymer substance constituting the protective film. The radiation image conversion panel according to claim 1, wherein the radiation image conversion panel is contained in the range of%. 3. The stimulable phosphor layer comprises a phosphite ester,
At least one compound selected from the group consisting of an organic tin compound and an organic acid metal salt is contained in the range of 0.0001 to 3% by weight with respect to the stimulable phosphor. The radiation image conversion panel according to item 1. 4. The phosphite is represented by the following general formula [I]:
A compound represented by the following formula and a compound represented by the following general formula [II]: Claim 1
The radiation image conversion panel according to the item. (However, A is an oxygen atom or a sulfur atom; R ¹ ,
R ² , R ³ and R ⁴ are each a hydrogen atom, an alkyl group or an aryl group, and may be the same or different from each other; X ¹ is a group consisting of a carbon atom, an oxygen atom and / or a hydrogen atom. is there) 5. The organotin compound is represented by the following general formula [II
The radiation image conversion panel according to claim 1, which is a compound represented by the formula [I]. (However, R ⁵ and R ⁶ are each a hydrogen atom, an alkyl group or an aryl group, and may be the same or different from each other; Y ¹ , Y ² , Y ³ and Y
⁴ are each an alkyl group, an aryl group, a fatty acid, a fatty acid derivative, a mercaptan or a mercapto acid, and they may be the same or different from each other; X ² is an oxygen atom, a sulfur atom or maleic acid; Or an integer greater than or equal to 1) 6. The radiation image conversion panel according to claim 1, wherein the organic acid metal salt is a compound represented by the following general formula [IV]. (R ⁷ COO) _m M [IV] (wherein R ⁷ is an alkyl group or an aryl group which may have a substituent having 1 to 20 carbon atoms; M is calcium, zinc, cadmium or barium; m Is 1
Is an integer greater than or equal to) 7. A compound having an epoxy group is used in the protective film in an amount of 0.03 to 10 relative to the polymer substance constituting the protective film.
The radiation image storage panel according to claim 1, wherein the radiation image storage panel is contained in an amount of 0% by weight. 8. The stimulable phosphor layer contains a compound having an epoxy group in an amount of 0.001 to 10% by weight based on the stimulable phosphor. A radiation image conversion panel according to claim 1. 9. The compound having an epoxy group is 1, 2
The radiation image storage panel according to claim 1, wherein the radiation image storage panel is at least one compound selected from the group consisting of epoxypropane, 1,2-epoxybutane, and epoxy resin. 10. A divalent europium-activated alkaline earth metal fluoride halide phosphor containing iodine as the stimulable phosphor layer, and a divalent europium-activated alkaline earth metal halide fluorescent as containing iodine. Body, containing a rare earth element-activated rare earth oxyhalide-based phosphor containing iodine, and at least one stimulable phosphor selected from the group consisting of bismuth-activated alkali metal halide-based phosphor containing iodine. The radiation image conversion panel according to claim 1, which is characterized in that.