JP2007093457A - Radiographic image conversion panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiographic image conversion panel having high dispersibility of phosphor particles. <P>SOLUTION: In the radiographic image conversion panel where at least a phosphor layer is laminated on a support body, at least one kind of binders contained in the phosphor layer contain epoxy group of three or more functions. Preferably, the epoxy equivalent of the binders, containing the epoxy group of three or more functions, is 400 or lower. Preferably, the filling factor of the phosphor particles contained in the phosphor layer is also 60 vol% or higher. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a radiation image conversion panel used in a radiation image conversion method using a stimulable phosphor.

A divalent europium-activated barium fluorohalide phosphor (BaFX: Eu ²⁺ ) that emits light (instantaneous light emission) from the near ultraviolet region to the blue region when excited by radiation such as X-rays, γ-rays, electron beams, or ultraviolet rays. However, X represents a halogen atom other than fluorine.) Is known, and is used as a phosphor for a radiation intensifying screen used for X-ray photography or the like.

  In recent years, after irradiating phosphors with radiation such as X-rays, γ-rays, electron beams, or ultraviolet rays, and then exciting them with electromagnetic waves (excitation light) in the wavelength range from visible rays to infrared rays, In the radiography, such phosphors are found to be very useful as radiographic image conversion techniques that replace conventional radiography in radiography. Has attracted attention.

  This radiation image conversion technique uses a radiation image conversion panel (accumulative phosphor sheet) in which a phosphor layer containing a stimulable phosphor is provided on a support, and the radiation or subject transmitted through the subject. After the radiation emitted from the panel is absorbed by the photostimulable phosphor on the panel, the photostimulable phosphor is excited in time series using an electromagnetic wave (excitation light) selected from a wavelength range from visible light to infrared. The radiation energy stored in the photostimulable phosphor is emitted as fluorescence (stimulated luminescence), and an electrical signal is obtained by photoelectrically reading, and the obtained electrical signal is imaged. is there.

  By using this radiation image conversion panel, it is possible to form an image with a smaller exposure amount than in the conventional radiography method, and the obtained image can be processed by a computer. Abundant radiographic images can be obtained, and a defective image can be relieved.

  Various techniques relating to the radiation image conversion panel are known (see, for example, Patent Documents 1 and 2). Patent Document 1 discloses that yellowing can be prevented by adding an epoxy resin to a stimulable phosphor containing iodine. Patent Document 2 discloses that yellowing can be prevented by a silane coupling agent containing an epoxy group. Here, “yellowing” refers to a phenomenon in which the phosphor layer gradually yellows due to the liberation of iodine and the sensitivity is significantly reduced.

However, these techniques simply contain an epoxy resin and are effective in preventing yellowing, but the dispersibility of the phosphor particles may be reduced. When the dispersibility is lowered, the detection quantum efficiency is lowered, so that the radiation image conversion panel may be defective. Therefore, in order to improve the dispersibility of the phosphor particles, it is necessary to sufficiently study the addition form of the epoxy resin (particularly, epoxy group).
Japanese Patent Publication No. 6-31912 JP 2003-270399 A

  The object of the present invention is to solve the above-described conventional problems. That is, an object of the present invention is to provide a radiation image conversion panel having high dispersibility of phosphor particles.

  As a result of intensive studies to solve the above problems, the present inventors have found that the following problems can be solved by the present invention.

  That is, the present invention is a radiation image conversion panel in which at least a phosphor layer is laminated on a support, and at least one binder contained in the phosphor layer has a trifunctional or higher functional epoxy group. It is the radiation image conversion panel characterized by these.

  The radiation image conversion panel of the present invention preferably includes at least one of the following first and second embodiments.

(1) A 1st aspect is an aspect whose epoxy equivalent of the said binder containing the said 3 or more functional epoxy group is 400 (g / eq.) Or less.
(2) A 2nd aspect is an aspect whose filling rate of the fluorescent substance particle contained in the said fluorescent substance layer is 60 vol% or more.

  ADVANTAGE OF THE INVENTION According to this invention, the radiation image conversion panel with high dispersibility of a fluorescent substance particle can be provided.

[Radiation image conversion panel]
In the radiation image conversion panel of the present invention, at least a phosphor layer is laminated on a support. And at least 1 sort (s) of binder in a fluorescent substance layer has a trifunctional or more than epoxy group. Such epoxy groups have good binding properties with the phosphor particles. Accordingly, by including a binder having an epoxy group having three or more functional groups (hereinafter, sometimes referred to as “epoxy group-containing binder”), the epoxy group-containing binder may be combined with other binders and phosphor particle surfaces. Therefore, aggregation of the phosphor particles can be prevented. As a result, the dispersibility of the phosphor particles can be improved.

  The number of epoxy groups (number per molecule) is preferably 3 to 40 functional groups, more preferably 4 to 20 functional groups. The number of epoxy groups can be easily determined if the basic structure of the epoxy resin is known. It can also be determined from the epoxy equivalent and the molecular weight of the epoxy.

  The epoxy equivalent of the epoxy group-containing binder is preferably 400 (g / eq.) Or less, and more preferably 50 to 300 (g / eq.). By being 400 (g / eq.) Or less, an effect that dispersibility is improved by adding a small amount of epoxy can be obtained. The epoxy equivalent can be determined based on, for example, “JIS K 7236”.

  The epoxy group-containing binder containing a tri- or higher functional epoxy group is preferably, for example, an olefin oxidation (alicyclic) type or a glycidyl ether type. Examples of the alicyclic type include those shown in the Examples. Typical examples of the glycidyl ether type include a cresol novolak type and a dicyclopentadiene type.

  The ratio (A / B) between the epoxy group-containing binder A contained in the phosphor layer and the other binder B described later is preferably 50/50 to 1/99, and 30/70 to 3 /. More preferably, it is 97. By being 50/50 to 1/99, it is possible to achieve both the yellowing prevention effect and the dispersibility improvement effect of the phosphor by the epoxy resin while maintaining the flexibility and mechanical strength of the film obtained by other binders. Can do.

  The above-mentioned epoxy may be used in combination with an epoxy group having two or less functional groups. Examples of other binders other than epoxy resins include proteins such as gelatin; natural polymer compounds such as gum arabic; polyvinyl butyral and polyacetic acid. And synthetic polymer materials such as vinyl, nitrocellulose, ethyl cellulose, vinylidene chloride-vinyl chloride copolymer, polymethyl methacrylate, vinyl chloride-vinyl acetate copolymer, polyurethane, cellulose acetate butyrate, polyvinyl alcohol, and linear polyester; .

  Hereinafter, the radiation image conversion panel of the present invention may have other layers as necessary as long as the phosphor layer is formed on the support. If the layer structure of the radiation image conversion panel of this invention is illustrated, the structure by which the reflection layer, the fluorescent substance layer, and the protective layer were formed in this order on the support body can be mentioned. Hereinafter, the support and the material of each layer will be described.

(Support)
As the support, those made of materials such as PET, polycycloolefin, PEN (polyethylene naphthalate), PVA (polyvinyl alcohol), nanoalloy polymer of PET and PEI (polyetherimide), and transparent aramid are preferably used. In particular, it is desirable that the substrate has a glass transition temperature (Tg) of 85 ° C. or higher, preferably 100 ° C. or higher. Polycycloolefin having a glass transition temperature of 85 ° C. or higher, PEN (polyethylene naphthalate), PVA (polyvinyl) Alcohol), PET and PEI (polyetherimide) nanoalloy polymer, and transparent aramid are preferred. Furthermore, what consists of materials, such as a polycycloolefin which has a glass transition temperature of 100 degreeC or more, PEN (polyethylene naphthalate), a nanoalloy polymer of PET and PEI (polyetherimide), a transparent aramid, is more preferable.

(Phosphor layer)
The phosphor layer contains phosphor particles made of a stimulable phosphor and a binder. As for the binder, there are an epoxy group-containing binder and other binders, and these are as described above.

Examples of stimulable phosphors used in the phosphor layer include general formulas (M _1-f · M _f ^I ) X · bM ^III X3 ″: cA (Japanese Patent Publication No. 7-84588). Stimulable phosphors represented by general formula (I)) are preferred. From the viewpoint of stimulated emission luminance, M ^I in the general formula (I) is preferably Na or K containing Rb, Cs and / or Cs, and particularly preferably at least one alkali metal selected from Rb and Cs. M ^III is preferably at least one trivalent metal selected from Y, La, Lu, Al, Ga and In. X ″ is preferably at least one halogen selected from F, Cl and Br. The b value representing the content of M ^III X3 ″ is preferably selected from the range of 0 ≦ b ≦ 10 ⁻² .

In the general formula (I), the activator A is preferably at least one metal selected from Eu, Tb, Ce, Tm, Dy, Ho, Gd, Sm, Tl and Na, particularly Eu, Ce, Sm, Tl and At least one metal selected from Na is preferred. The C value representing the amount of the activator is preferably selected from the range of 10 ⁻⁶ <C <0.1 from the viewpoint of the stimulated emission luminance.

Furthermore, the following photostimulable phosphors can also be used. SrS: Ce, Sm, SrS: Eu, Sm, ThO ₂ : Er, and La ₂ O ₂ S: Eu, Sm described in US Pat. No. 3,859,527

ZnS as described in JP 55-12142 discloses: Cu, Pb, BaO · xAl 2 O 3: Eu ( provided that, 0.8 ≦ x ≦ 10), _{^{and, M II O · xSiO 2:}} A ( However, M ^II is Mg, Ca, Sr, Zn, Cd or Ba,, a is Ce, Tb, Eu, Tm, Pb, Tl, Bi or Mn, x is 0.5 ≦ x ≦ 2. 5),

(Ba _1-xy , MgX, Cay) FX: aEu ²⁺ described in JP-A No. 55-12143 (where X is at least one of Cl and Br, and x and y are 0 <X + y ≦ 0.6 and xy ≠ 0, and a is 10 ⁻⁶ ≦ a ≦ 5 × 10 ⁻² )

  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 and Br, A is Ce and At least one of Tb, and x is 0 <x <0.1),

(Ba _1-X , M ²⁺ X) FX: yA described in JP-A-55-12145 (where M is at least one of Mg, Ca, Sr, Zn, and Cd, and 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),

M ^II FX · xA: yLn described in JP-A-55-160078 (where M ^II is at least one of Ba, Ca, Sr, Mg, Zn and Cd, and A is BeO, 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 2 O 5, Ta 2 O ₅ and at least one of ThO ₂ , Ln is at least one of Eu, Tb, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Sm and Gd, and X is Cl, Br and I And x and y are 5 × 10 ⁻⁵ ≦ x ≦ 0.5 and 0 <y ≦ 0.2, respectively,

(Ba _1-x , M ^II _x ) F ₂ · aBaX ₂ : yEu, zA described in JP-A-56-116777 (where M ^II is beryllium, magnesium, calcium, strontium, zinc and cadmium) At least one of them, X is at least one of chlorine, bromine and iodine, A is at least one of zirconium and scandium, and a, x, y and z are each 0.5 ≦ a ≦ 1.25 0 ≦ x ≦ 1, 10 ⁻⁶ ≦ y ≦ 2 × 10 ⁻¹ , and 0 <z ≦ 10 ⁻² ),

(Ba _1-x , M ^II _x ) F ₂ · aBaX ₂ : yEu, zB described in JP _-A- 57-23673 (where M ^II is beryllium, magnesium, calcium, strontium, zinc and cadmium) At least one of them, X is at least one of chlorine, bromine and iodine, and a, x, y and z are 0.5 ≦ a ≦ 1.25, 0 ≦ x ≦ 1, 10 ⁻⁶ ≦, respectively. phosphors represented by a composition formula of y ≦ 2 × 10 ⁻¹ and 0 <z ≦ 10 ⁻² ),

(Ba _1-x , M ^II _x ) F ₂ · aBaX ₂ : yEu, zA described in JP-A-57-23675 (where M ^II is beryllium, magnesium, calcium, strontium, zinc and cadmium) At least one of them, X is at least one of chlorine, bromine and iodine, A is at least one of arsenic and silicon, and a, x, y and z are each 0.5 ≦ a ≦ 1.25 0 ≦ x ≦ 1, 10 ⁻⁶ ≦ y ≦ 2 × 10 ⁻¹ , and 0 <z ≦ 5 × 10 ⁻¹ ),

M ^III OX: xCe described in JP-A-58-69281 (where M ^III is a group consisting of Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb and Bi) A phosphor represented by a composition formula of at least one trivalent metal selected from the group consisting of: X is one or both of Cl and Br, and x is 0 <x <0.1.

Ba _1-X M _{X / 2} L _{X / 2} F _X : yEu ²⁺ described in JP _-A- 58-206678 (where M is selected from the group consisting of Li, Na, K, Rb and Cs) L represents Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Al, Ga, In and X represents at least one trivalent metal selected from the group consisting of Tl; X represents at least one halogen selected from the group consisting of Cl, Br and I; and x represents 10 ⁻² ≦ x ≦ 0.5 , Y is 0 <y ≦ 0.1)

BaFX · xA: yEu ²⁺ described in JP-A-59-27980 (where X is at least one halogen selected from the group consisting of Cl, Br and I; A is a tetrafluoroborate compound) A phosphor expressed by a composition formula: x is 10 ⁻⁶ ≦ x ≦ 0.1 and y is 0 <y ≦ 0.1),

BaFX · xA: yEu ²⁺ described in JP-A-59-47289 (where X is at least one halogen selected from the group consisting of Cl, Br and I; A is hexafluorosilicate) A calcined product of at least one compound selected from the group of hexafluoro compounds consisting of salts of monovalent or divalent metals of acid, hexafluorotitanic acid and hexafluorozirconic acid; and x is 10 ⁻⁶ ≦ x ≦ 0 .1, y is 0 <y ≦ 0.1)

BaFX · xNaX ′: aEu ²⁺ described in JP-A-59-56479 (where X and X ′ are at least one of Cl, Br, and I, respectively, and x and a are each A phosphor represented by a composition formula of 0 <x ≦ 2 and 0 <a ≦ 0.2,

M ^II FX · xNaX ′: yEu ²⁺ : zA described in JP-A-59-56480 (where M ^II is at least one alkaline earth metal selected from the group consisting of Ba, Sr and Ca) X and X ′ are each at least one halogen selected from the group consisting of Cl, Br and I; A is at least one transition metal selected from V, Cr, Mn, Fe, Co and Ni And x is 0 <x ≦ 2, y is 0 <y ≦ 0.2, and z is 0 <z ≦ 10 ⁻² ),

M ^II FX, aM ^I X ′, bM ′ ^II X ″ ₂ , cM ^III X ₃ , xA: yEu ²⁺ (M ^II represents Ba, Sr and At least one alkaline earth metal selected from the group consisting of Ca; M ^I is at least one alkali metal selected from the group consisting of Li, Na, K, Rb and Cs; M ′ ^II is 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 is at least one divalent metal selected from the group consisting of At least one halogen selected from the group consisting of Cl, Br and I; X ′, X ″ and X are at least one halogen selected from the group consisting of F, Cl, Br and I; and a is ≦ a ≦ 2, b is 0 ≦ b ≦ 10 ^-2, c is an 0 ≦ c ≦ 10 ^-2 and ^{a + b + c ≧ 10 -6} ,; x is 0 <x ≦ 0.5, y is 0 <y ≦ A phosphor represented by a composition formula of 0.2),

M ^II X ₂ · aM ^II X ′ ₂ : xEu ²⁺ described in JP-A-60-84381 (where M ^II 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, and X ≠ X ′; and a is 0.1 ≦ a ≦ 10.0, x Is a stimulable phosphor represented by a composition formula of 0 <x ≦ 0.2,

M ^II FX · aM ^I X ′: xEu ²⁺ described in JP-A-60-101173 (where M ^II is at least one alkaline earth metal selected from the group consisting of Ba, Sr and Ca) Yes; 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 Cl, Br and I; X ′ is F, Cl, Br And at least one halogen selected from the group consisting of I and I; and a and x are 0 ≦ a ≦ 4.0 and 0 <x ≦ 0.2, respectively. ,

M ^I X: xBi described in JP-A-62-25189 (where M ^I is at least one alkali metal selected from the group consisting of Rb and Cs; X consists of Cl, Br and I) A stimulable phosphor represented by a composition formula: at least one halogen selected from the group; and x is a numerical value in the range of 0 <x ≦ 0.2.

LnOX: xCe described in JP-A-2-229882 (where Ln is at least one of La, Y, Gd and Lu, X is at least one of Cl, Br and I, and x is 0 < x ≦ 0.2, the ratio of Ln to X is 0.500 <X / Ln ≦ 0.998 in atomic ratio, and the maximum wavelength λ of the stimulable excitation spectrum is 550 nm <λ <700 nm) A cerium-activated rare earth oxyhalide phosphor represented,
Etc.

  The filling rate in the phosphor layer of the phosphor particles composed of the phosphor as described above is preferably 60 vol% or more, and preferably 65 to 85 vol%. By being 60 vol% or more, X-ray absorption can be increased and image quality can be improved.

  Here, the “filling rate” refers to a proportion of the volume occupied by the phosphor particles in the volume of the phosphor layer. In order to determine the filling rate, first, the phosphor layer is peeled off from the radiation image conversion panel, and the area and thickness are measured as a single unit to determine the volume of the phosphor layer. Thereafter, the phosphor layer is burned to vaporize the binder to obtain only phosphor particles. The volume of the phosphor particles is determined by dividing the mass of the phosphor particles by the intrinsic density of the phosphor. Finally, the filling rate is obtained by “(volume of phosphor particles only) ÷ (volume of phosphor layer) × 100”.

(Protective layer)
For the protective layer formed on the phosphor layer, a solution prepared by dissolving a transparent organic polymer substance such as cellulose derivative or polymethyl methacrylate in an appropriate solvent is applied on the phosphor layer. A protective film-forming sheet such as an organic polymer film such as polyethylene terephthalate or a transparent glass plate prepared separately and provided with an appropriate adhesive on the surface of the phosphor layer, or inorganic A compound formed on the phosphor layer by vapor deposition or the like is used.

  Alternatively, it may be a protective layer formed of a coating film of an organic solvent-soluble fluorine-based resin, in which perfluoroolefin resin powder or silicone resin powder is dispersed and contained.

(Reflective layer)
The reflective layer is a layer provided as appropriate for the purpose of improving the sensitivity of the radiation image conversion panel. The reflective layer preferably has a short scattering length and high reflectivity.

Examples of the light reflective material used in the reflective layer include Al ₂ O ₃ , ZrO ₂ , TiO ₂ , BaSO ₄ , SiO ₂ , ZnS, ZnO, MgO, CaCO ₃ , Sb ₂ O ₃ , and Nb ₂ O _5. 2PbCO ₃ .Pb (OH) ₂ , M ^II FX (where M ^II is at least one of Ba, Ca and Sr, and X is at least one of Cl and Br), lithopone (BaSO ₄ + ZnS), white silicates such as magnesium silicate, basic lead silicate, basic lead phosphate and aluminum silicate; and hollow polymer particles (polymer pigments).

  The hollow polymer particles are fine particles made of, for example, a styrene polymer or a styrene / acrylic copolymer and having an outer diameter in the range of 0.2 to 1 μm and a small pore diameter (inner diameter) in the range of 0.05 to 0.7 μm. is there. The use of the hollow polymer particles as the light reflecting substance is described in detail in Japanese Patent Application No. 60-278665 by the applicant.

Among these light reflecting materials, preferred are Al ₂ O ₃ , ZrO ₂ , TiO ₂ , BaSO ₄ , SiO ₂ , ZnS, and ZnO and M ^II FX (where M ^II is Ba, Ca and Sr). And X is at least one of Cl and Br). The light reflecting material may be a single species or a mixture of two or more species.

[Method of manufacturing radiation image conversion panel]
The radiation image conversion panel of the present invention can be manufactured, for example, as follows. For example, a reflective layer forming step (the step is optional) for forming a reflective layer on a support, and a phosphor material (including a binder) is applied to the temporary support and then peeled off from the temporary support. A phosphor sheet manufacturing process for preparing a phosphor sheet containing a material, a phosphor layer forming process for forming a phosphor layer by bonding the phosphor sheet on a reflective layer, and a cutting process for cutting to a desired size It is manufactured through such as. Hereinafter, each step will be described.

(Reflective layer forming process)
In the reflective layer formation step, the reflective layer is formed by first adding the compound described above for preventing yellowing, such as the light-reflective material and the epoxy group-containing compound, and a binder to an appropriate solvent, and thoroughly mixing them. Then, a coating liquid is prepared in which the particles of the light-reflecting substance and the particles of the compound for preventing yellowing are uniformly dispersed in the binder solution. Next, the coating liquid is uniformly applied to the surface of the support (or the surface of the adhesion-imparting layer provided thereon) to form a coating film, and then the coating film is heated and dried to form a coating on the support. Can be formed.

  The binder and solvent for the reflective layer can be selected from those used as the binder and solvent for forming the phosphor layer. When the light reflective material is hollow polymer particles, an aqueous polymer material such as an acrylic acid copolymer may be used as a binder. Furthermore, the coating liquid may contain various dispersants, plasticizers, colorants, and the like used in the phosphor layer forming coating liquid described below.

  The mixing ratio of the binder and the light reflecting material in the coating solution is generally selected from the range of 1: 1 to 1:50 (mass ratio), preferably in the range of 1: 2 to 1:20 (mass ratio). is there. The amount of the compound for preventing yellowing varies depending on the kind and amount of the light-reflecting substance and the kind of the binder, but the compound is a phosphite, an organic tin compound or an organic acid metal salt. In some cases, it is generally preferably in the range of 0.0001 to 3% by weight and more preferably in the range of 0.003 to 0.3% by weight with respect to the light reflecting material. In the case of an epoxy group-containing compound, generally it is preferably in the range of 0.001 to 10% by weight, more preferably in the range of 0.03 to 3% by weight with respect to the light reflecting material. The thickness of the reflective layer is preferably 5 to 100 μm. Furthermore, as described in JP-A-58-200200, for the purpose of improving the sharpness of an image, a minute unevenness may be provided on the surface of the reflective layer on the side where the phosphor layer is provided. .

(Phosphor sheet manufacturing process)
This step is a step of producing a phosphor sheet containing a phosphor material by forming a layer made of a stimulable phosphor material on a temporary support and peeling the layer from the temporary support. The phosphor layer can be formed on the temporary support by a known method such as a coating method.

  In the coating method, the phosphor is thoroughly mixed with a solvent to prepare a coating solution in which the stimulable phosphor is uniformly dispersed in the binder solution, and this coating solution is uniformly applied to the surface of the support. To form a coating film. This coating operation can be performed by using a normal coating means, for example, a doctor blade, a roll coater, a knife coater, or the like.

  When the phosphor layer is formed by a coating method, the phosphor layer contains a stimulable phosphor and a binder that contains and supports the phosphor in a dispersed state. In addition, additives such as a colorant may be contained in the phosphor layer. The phosphor layer can be formed on the temporary support by the following known method.

  First, a stimulable phosphor and a binder are added to a solvent and mixed well to prepare a coating solution in which the stimulable phosphor is uniformly dispersed in the binder solution. The mixing ratio of the binder to the stimulable phosphor in the coating solution varies depending on the characteristics of the intended radiation image conversion panel, the type of stimulable phosphor, etc., but generally the binder (containing the epoxy group described above) The mixing ratio (mass ratio) of all the binders including the binder and the stimulable phosphor is selected from the range of 1: 1 to 1: 100, and particularly selected from the range of 1: 8 to 1:40. It is preferable.

  Solvents for preparing the coating solution include lower alcohols such as methanol, ethanol, propanol and butanol; chlorine atom-containing hydrocarbons such as methylene chloride and ethylene chloride; ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; methyl acetate and ethyl acetate. And esters of lower fatty acids such as butyl acetate and lower alcohols; ethers such as dioxane and ethylene glycol monoethyl ether; mixtures of two or more thereof. In addition, you may contain a well-known dispersing agent, a plasticizer, a yellowing prevention agent, etc. as needed.

  The layer thickness of the phosphor layer varies depending on the characteristics of the intended radiation image conversion panel, the type of phosphor, the mixing ratio of the binder and the phosphor, and is generally about 20 μm to 1 mm. More preferably, the thickness is 50 μm to 500 μm. In addition, as a temporary support body, a polyethylene terephthalate sheet | seat etc. can be used.

(Phosphor layer forming process)
The said process is a process of bonding a fluorescent substance sheet | seat on a reflection layer, and forming a fluorescent substance layer. In pasting, it is preferable to apply a pressure application treatment. By bonding together while applying pressure, the surface of the radiation image conversion panel can be made harder. As a bonding method involving pressure application processing, it is preferable to apply bonding by calendar processing.

  When performing the calendar process, it is preferable that the roll diameter of the calendar roll is 100 to 400 mmφ and the load is 100 N / cm to 2000 N / cm. Moreover, it is preferable to make temperature of a roll into the temperature equivalent to or higher than the softening temperature of the main binder, and it is usually preferable to set it as 40 to 100 degreeC. Furthermore, the feed rate of the roll is preferably 0.1 to 5 m / min. By setting it as the above condition ranges, damage to the phosphor can be reduced and the packing density of the phosphor layer can be increased.

(Cutting process)
This step is a step of forming a desired shape of the radiation image conversion panel using a convex punching blade or a guillotine blade corresponding to the outer size.

  In addition to the steps as described above, various steps such as a step of forming a protective layer can be appropriately provided. Further, as a method for forming the reflective layer, the phosphor layer, and the like on the support, a method of sequentially laminating layers may be applied in addition to the embodiment described above.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

[Example 1]
(Phosphor sheet manufacturing process)
The following materials were mixed in 86 g of a solvent (methyl ethyl ketone) to prepare a phosphor sheet-forming coating solution (binder / phosphor (mass ratio) = 1/30, 3 Pa · s). Mixing was performed using a propeller mixer, and the mixture was dispersed for 30 minutes at a rotational speed of 10,000 rpm.

  This phosphor sheet-forming coating solution was applied on a temporary support (polyethylene terephthalate sheet coated with a silicone release material, thickness: 190 μm) with a doctor blade (300 mm width). After drying at room temperature for about 10 minutes with weak air, and drying at 110 ° C., the dried coating film was peeled off from the temporary support to prepare a phosphor sheet.

-Material-
(1) Phosphor: a tetrahedral phosphor (BaFBr _0.85 I _0.15 : Eu ²⁺ ), 700 g of large size particles (median diameter 7.0 μm) and 300 g of small size particles (median diameter 3.5 μm)
(2) Epoxy group-containing binder: 6.7 g of epoxy resin (Epolyde GT401 (solid), epoxy equivalent 210-235, tetrafunctional) manufactured by Daicel Chemical Industries, Ltd.)
(3) Other binder materials: Polyurethane elastomer (Dai Nippon Ink Chemical Co., Ltd. Pandex T-5265 (solid) dissolved in methyl ethyl ketone to a solid content concentration of 13% by mass) 205 g

The epolide GT401 is epoxidized butanetetracarboxylic acid tetrakis- (3-cyclohexenylmethyl) -modified ε-caprolactone and has a chemical structure represented by the following chemical formula (1). In the following formulae, R ¹ represents an alkyl group.

(Reflective layer forming process)
The following materials were mixed in 387 g of a solvent (methyl ethyl ketone) to prepare a reflection layer forming coating solution (viscosity of about 2 to 3 Pa · s). The prepared coating liquid for forming a reflective layer was applied on a support so as to have a thickness of 100 μm, and dried to form a reflective layer. In addition, the polyethylene terephthalate sheet | seat (Toray Lumirror S-10, thickness 100 micrometers, haze degree (typical) = 27 degreeC) was used for the support body.

-Material-
(1) Binder: 100 g of soft acrylic resin (Criscoat P-1018GS (20% toluene solution) manufactured by Dainippon Ink & Chemicals, Inc.)
(2) Powder material: 444 g of reflective material (high purity alumina (UA-5105 manufactured by Showa Denko KK), average particle size: 0.4 μm)
(3) Powder material: 2.2g of colorant (Gun-blue: Daiichi Kasei Kogyo SM-03S)
(4) Dispersant: 2 g of Preneact AL-M (aluminum coupling agent, manufactured by Ajinomoto Co., Inc.)

(Heat compression treatment (phosphor layer forming process))
Using a calendar machine, the support on which the reflective layer was formed and the phosphor sheet were bonded by thermal compression as described below.

  First, the surface of the phosphor sheet on which the temporary support was bonded and the reflective layer on the support were overlapped, and the upper (phosphor sheet side) roll temperature was 45 ° C., the lower side (support side) ) The laminating was performed at a roll temperature of 45 ° C. and a feed rate of 0.3 m / min. By this heat compression treatment, the phosphor layer was completely fused through the reflective layer of the support.

(Formation of protective layer)
The following materials were mixed in 38 g of a solvent (methyl ethyl ketone) to prepare a coating solution for forming a protective layer. A protective layer-forming coating solution was applied onto the phosphor layer that had been subjected to calendering (thermal compression treatment), and dried at 120 ° C. to form a protective layer having a thickness of 3 μm. Then, it cut | judged to the size of 200 mm x 250 mm (cutting process), and produced the radiation image conversion panel. In addition, the filling rate of the phosphor particles in the phosphor layer was 70 vol%.

-Material-
(1) Fluorine resin (76 g of fluoroolefin-vinyl ether copolymer, Lumiflon LF-504X (30% xylene solution) manufactured by Asahi Glass Co., Ltd.)
(2) Cross-linking agent: 7.5 g of polyisocyanate (Sumijoule N3500 (solid content: 100%) manufactured by Sumitomo Bayer Co., Ltd.)
(3) Catalyst: 0.25 mg of dibutyltin laurate (KS1260 manufactured by Kyodo Yakuhin Co., Ltd.)

[Example 2]
Example 1 except that the epoxy resin in the epoxy group-containing binder of the phosphor layer was changed to 6.7 g of Epolide EHPE3150 (solid, epoxy equivalent 170-190, average 15 functions) manufactured by Daicel Chemical Industries, Ltd. Thus, a radiation image conversion panel was produced. In addition, the filling rate of the phosphor particles in the phosphor layer was 70 vol%.

The epolide EHPE3150 is a 1,2-epoxy-4- (2-oxiranyl) cyclosoxane adduct of 2,2-bis (hydroxymethyl) -1-butanol and represented by the following chemical formula (2). It has such a chemical structure. In the following formulae, R ² represents an alkyl group, and n is 15 on average.

[Example 3]
A radiation image conversion panel was produced in the same manner as in Example 1 except that the material of the phosphor layer was changed as follows. In addition, the filling rate of the phosphor particles in the phosphor layer was 71 vol%.

-Material-
(1) Phosphor: a tetrahedral phosphor (BaFBr _0.85 I _0.15 : Eu ²⁺ ), 700 g of large size particles (median diameter 7.0 μm) and 300 g of small size particles (median diameter 3.5 μm)
(2) Epoxy group-containing binder: 3.3 g of epoxy resin (Epolyde EHPE3150 (solid), epoxy equivalent of 170 to 190, average of 15 functions) manufactured by Daicel Chemical Industries, Ltd.)
(3) Other binder materials: polyurethane elastomer (Dai Nippon Ink Chemical Co., Ltd. Pandex T-5265 (solid) dissolved in methyl ethyl ketone to a solid content concentration of 13% by mass) 230.8 g

[Comparative Example 1]
The epoxy resin in the epoxy group-containing binder of the phosphor layer was changed to 6.7 g of yellowing inhibitor (epoxy resin, Epicoat # 1001 (solid, epoxy equivalent 450-500, bifunctional) manufactured by Yuka Shell Epoxy Co., Ltd.) Except for the above, a radiation image conversion panel was produced in the same manner as in Example 1. The filling rate of the phosphor particles in the phosphor layer was 69 vol%.

[Evaluation of image quality performance]
After irradiating the surface of the radiation image conversion panel with X-rays of tungsten tube and tube voltage of 80 kVp via the MTF chart (equivalent to 10 mR), the excitation energy on the radiation image conversion panel is changed to 5 J / with semiconductor laser light having a wavelength of 660 nm. received by the m ² excitation energy by irradiating the radiation image conversion panel surface photostimulated luminescence light emitted from the surface of the radiation image convertor panel respectively photodetector (photomultiplier spectral sensitivity S-5). The received light was converted into an electric signal, and based on this, an image was obtained by an image reproducing device, and the sharpness was measured. Similarly, the surface of the radiation image conversion panel was uniformly irradiated with X-rays equivalent to 10 mR to obtain a granular value of the Wiener spectrum. From these measured values, the detected quantum efficiency (DQE 10 mR) at a spatial frequency of 1 cy / mm was measured. The results are shown in Table 1 below.

  From Table 1, it can be said that the example has significantly improved detection quantum efficiency of 10 mR compared to the comparative example, and the dispersibility of the phosphor particles is good. Also, from Table 1, the radiation image conversion panel of Comparative Example 1 had a low detection quantum efficiency, whereas the radiation image conversion panels of Examples 1 to 3 all had a good detection quantum efficiency. That is, it was confirmed that the dispersibility of the phosphor particles was good.

Claims (3)

A radiation image conversion panel in which at least a phosphor layer is laminated on a support,
The radiation image conversion panel, wherein at least one binder contained in the phosphor layer has a trifunctional or higher functional epoxy group.   The radiation image conversion panel according to claim 1, wherein an epoxy equivalent of the binder containing the trifunctional or higher functional epoxy group is 400 (g / eq.) Or less.   The radiation image conversion panel according to claim 1 or 2, wherein a filling rate of the phosphor particles contained in the phosphor layer is 60 vol% or more.