JP2005127850A - Radiological image conversion panel and manufacturing method of radiological image conversion panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive radiological image conversion panel having an improved specific performance coincident with a photographing purpose without damaging productivity. <P>SOLUTION: In this manufacturing method of the radiological image conversion panel, a stimulable phosphor layer 12 is provided on a substrate 11 and sealed by a moisture-proof protection film 20. The stimulable phosphor layer 12 is covered with the moisture-proof protection film 20 without allowing to adhere to the stimulable phosphor layer 12, and then one kind or two or more kinds of gases selected from among rare gases, nitrogen gas and carbon dioxide gas are filled between the stimulable phosphor layer 12 and the moisture-proof protection film 20, to thereby manufacture this radiological image conversion panel having the improved specific performance for contrast, humidity resistance and brightness deterioration prevention. Many kinds of radiological image conversion panels can be manufactured by an approximately same process, and the inexpensive radiological image conversion panel having the improved specific performance coincident with the photographing purpose in a facility can be provided without damaging productivity. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a radiation image conversion panel using a stimulable phosphor and a method for manufacturing a radiation image conversion panel.

  Conventionally, as a method of imaging a radiation image without using a silver salt in order to obtain a radiation image, there is a method of recording a radiation image using a radiation image conversion panel in which a stimulable phosphor layer is provided on a substrate. Has been developed.

  In order to record a radiation image using the radiation image conversion panel, radiation transmitted through the subject is absorbed by the stimulable phosphor layer, and radiation energy corresponding to the radiation transmission density of each part of the subject is accumulated. Radiation energy accumulated in the photostimulable phosphor is emitted as photostimulated luminescence by irradiating the photostimulable phosphor layer with electromagnetic waves (excitation light) such as visible light and infrared rays in time series. Can be made. A signal based on the intensity of the light is converted into an electric signal by photoelectric conversion, for example, and can be reproduced as a visible image on a recording material such as a silver halide photographic light-sensitive material or a display device such as a CRT.

  Such radiation image conversion panels are often used in medical X-ray diagnostic imaging equipment and the like. In general, the radiation image conversion panel is often handled by storing a photostimulable phosphor on a substrate on a sheet and storing it in a radiation imaging cassette.

  A radiographic cassette (hereinafter referred to as “cassette”) is a flat housing that can accommodate a radiographic image conversion panel, and prevents physical damage to the photostimulable phosphor during transportation or imaging. It is intended to prevent the extinction of image information accumulated by irradiating the stimulable phosphor after imaging with excitation light. As shown in FIG. 3, the radiation image conversion panel 30 is disposed in the cassette 40 so that the photostimulable phosphor layer 31 faces the front plate 41 of the cassette 40.

  In the radiography, the subject 50 is disposed so as to face the outer surface of the front plate 41 of the cassette 40 in which the radiographic image conversion panel 30 is housed, and the X-rays transmitted through the subject 50 are transmitted through the cassette 40 and the radiographic image conversion panel 30. Irradiate to. In radiography by this method, a radiographic image with abundant information can be obtained with an extremely small exposure dose as compared with a method using silver salt.

  In imaging using the radiation image conversion panel, the specific performance of the radiation image conversion panel may be insufficient depending on the imaging region and the imaging environment. Specifically, in lumbar imaging, the contrast of the image tends to be insufficient due to the influence of low-energy radiation (scattered rays) scattered when passing through the subject or the front plate of the cassette. Moreover, in chest lung field radiography with a high tube voltage and a low dose, the luminance is insufficient and the graininess may deteriorate. Furthermore, the use under high temperature and high humidity has a problem that deterioration due to moisture absorption is accelerated. In order to improve these characteristics, the photostimulable phosphor layer itself and the protective layer for sealing the photostimulable phosphor layer have been improved.

  As the photostimulable phosphor, a photostimulable phosphor represented by the following general formula (1), particularly a photostimulable phosphor showing e in the range of 0.003 ≦ e ≦ 0.005 is used. Thus, it has been shown that a highly sensitive radiation image conversion panel can be obtained (see, for example, Patent Document 1).

^{M 1 X · aM 2 X '} 2 · bM 3 X''3: eA ··· (1)
[Wherein M ¹ is at least one alkali metal selected from the group consisting of Li, Na, K, Rb and Cs, and M ² is Be, Mg, Ca, Sr, Ba, Zn, Cd, Cu and Ni. M ³ is Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, at least one divalent metal selected from the group consisting of Is at least one trivalent metal selected from the group consisting of Lu, Al, Ga and In, and X, X ′ and X ″ are at least one halogen selected from the group consisting of F, Cl, Br and I. , A is from the group consisting of Eu, Tb, In, Ga, Cs, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Gd, Lu, Sm, Y, Tl, Na, Ag, Cu and Mg It is at least one metal selected, and a, b, and e represent numerical values in the range of 0 ≦ a <0.5, 0 ≦ b <0.5, and 0.0001 <e ≦ 1.0, respectively. ]

  Recently, a radiation panel using a photostimulable phosphor activated with Eu based on an alkali halide such as CsBr has been proposed. In particular, by using Eu as an activator, X-ray conversion efficiency which has been impossible in the past has been proposed. It is expected that improvement will be possible.

  It is also known to use polyethylene terephthalate film or polyethylene terephthalate film deposited with a thin film such as metal oxide or silicon nitride as a moisture-proof protective film to prevent deterioration of the stimulable phosphor layer due to moisture absorption. (For example, refer to Patent Document 2).

As a method for removing scattered radiation, there is a method of providing a radiation absorbing layer made of metal or the like on the inner surface of a cassette front plate to absorb low-energy radiation (see, for example, Patent Document 3).
JP 2003-028995 A JP 2002-107495 A JP 2003-114299 A

  Since it is difficult to improve all the performance of the radiation image conversion panel, such as brightness, contrast, graininess, and moisture resistance at the same time, a radiation image conversion panel with improved specific performance will be used depending on the application. . However, increasing the variety of radiation image conversion panels with improved specific performance in a small number of types impairs productivity.

  An object of the present invention is to provide an inexpensive radiation image conversion panel that has improved specific performance in conformity with an imaging purpose without impairing productivity.

  In order to solve the above problems, the invention described in claim 1 is directed to a radiation image conversion panel in which the stimulable phosphor layer 12 provided on the substrate 11 is sealed with a moisture-proof protective film 20. A rare gas is filled between the fluorescent layer 12 and the moisture-proof protective film 20.

  The invention according to claim 2 is the radiation image conversion panel according to claim 1, wherein the rare gas is at least one or more of He, Ne, Ar, Kr, and Xe. To do.

According to the first or second aspect of the invention, the weak X-rays scattered between the photostimulable phosphor layer 12 and the moisture-proof protective film 20 are scattered by a subject or a peripheral material. In order to repeat absorption of weak X-rays after absorption and excitation, light emission in about 10 ⁻² seconds, noise near the surface of the photostimulable phosphor layer 12 due to scattered X-rays is removed, and the reproduced image Contrast can be improved.

  According to a third aspect of the present invention, in the radiation image conversion panel formed by sealing the stimulable phosphor layer 12 provided on the substrate 11 with the moisture-proof protective film 20, the stimulable phosphor layer 12 and the moisture-proof layer are provided. Nitrogen gas is filled between the protective film 20 and the protective film 20.

  According to the invention described in claim 3, since the stimulable phosphor layer 12 and the moisture-proof protective film 20 are filled with nitrogen gas, the radiation image conversion panel is in the air. Water vapor can be prevented from entering, and the moisture resistance of the photostimulable phosphor layer 12 can be improved.

  The invention according to claim 4 is a radiation image conversion panel in which the photostimulable phosphor layer 12 provided on the substrate 11 is sealed with a moisture-proof protective film 20, and the photostimulable phosphor layer 12 and the moisture-proof layer. Carbon dioxide gas is filled between the protective film 20 and the protective film 20.

  According to the invention described in claim 4, carbon dioxide gas is filled between the photostimulable phosphor layer 12 and the moisture-proof protective film 20. The stimulated emission luminance can be improved by 5 to 10%, and luminance deterioration of the radiation image conversion panel due to intermittently irradiated X-rays can be prevented.

  Invention of Claim 5 is a manufacturing method of the radiation image conversion panel which provides the photostimulable phosphor layer 12 in the board | substrate 11, and seals this photostimulable phosphor layer 12 with the moisture-proof protective film 20. The photostimulable phosphor layer 12 is covered with the moisture-proof protective film 20 without being in close contact with the photostimulable phosphor layer 12, and then the rare gas is interposed between the photostimulable phosphor layer 12 and the moisture-proof protective film 20. In addition, any one or more of nitrogen gas and carbon dioxide gas is filled.

  According to the invention described in claim 5, the stimulable phosphor layer 12 is covered with the moisture-proof protective film 20 without being in close contact with the stimulable phosphor layer 12, and then the stimulable phosphor layer 12 and the moisture-proof layer are covered. Any one of contrast, moisture resistance, and luminance deterioration prevention can be improved by filling one or more gases of rare gas, nitrogen gas and carbon dioxide gas with the protective film 20. A radiation image conversion panel can be manufactured.

  According to the present invention, the stimulable phosphor layer is filled with one or more gases of noble gas, nitrogen gas and carbon dioxide gas between the moisture-proof protective film and the photostimulable fluorescence. By sealing the body layer, it is possible to manufacture a radiation image conversion panel in which specific performances of contrast, moisture resistance, and luminance deterioration prevention are improved. Therefore, it is possible to manufacture various types of radiation image conversion panels in almost the same process, and to provide an inexpensive radiation image conversion panel with improved specific performance that matches the purpose of imaging in a facility without impairing productivity. be able to.

  Hereinafter, the present invention will be described in detail. As shown in FIG. 1, the radiation image conversion panel of the present invention includes a phosphor plate 10 having a stimulable phosphor layer 12 formed on one surface of a substrate 11, and at least the photostimulability of the phosphor plate 10. It comprises a moisture-proof protective film 20 that covers and seals the phosphor layer 12. Further, between the photostimulable phosphor layer 12 and the moisture-proof protective film 20, at least one kind of gas such as rare gas, nitrogen gas and carbon dioxide gas is enclosed.

  The substrate 11 preferably has a low moisture permeability, and various types of glass, polymer materials, metals, and the like are used. In particular, cellulose acetate film, polyethylene terephthalate film, polyethylene naphthalate film, polyamide film, polyimide film, triacetate film, plastic film such as polycarbonate film, flat glass such as quartz, borosilicate glass, chemically tempered glass, aluminum sheet, iron sheet A metal sheet such as a copper sheet and a metal sheet having a coating layer of the metal oxide are preferable. The surface of the substrate 11 may be a smooth surface, or may be a mat surface for the purpose of improving the adhesion with the stimulable phosphor.

  Moreover, although the layer thickness of these board | substrates 11 changes with thickness of the board | substrate 11 to be used, it is generally 80 micrometers-5000 micrometers, and from the point on handling, More preferably, they are 80 micrometers-3000 micrometers. Furthermore, you may provide the undercoat layer which improves the adhesiveness with a stimulable fluorescent substance in the surface in which the stimulable fluorescent substance layer 12 of the board | substrate 11 is provided.

  The photostimulable phosphor layer 12 is formed with a layer thickness of 50 μm or more, preferably 300 to 500 μm. As the photostimulable phosphor used for the photostimulable phosphor layer 12, those represented by the general formula (1) can be used.

^{M 1 X · aM 2 X '} 2 · bM 3 X''3: eA ··· (1)

Here, M ¹ is at least one alkali metal selected from the group consisting of Li, Na, K, Rb and Cs, and in particular, is at least one alkali metal selected from the group consisting of K, Rb and Cs. preferable.

M ² is at least one divalent metal selected from the group consisting of Be, Mg, Ca, Sr, Ba, Zn, Cd, Cu and Ni, in particular, at least selected from Be, Mg, Ca, Sr and Ba A kind of divalent metal is preferable.

At least one M ³ represents that Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Al, selected from the group consisting of Ga and In In particular, at least one trivalent metal selected from the group consisting of Y, La, Ce, Sm, Eu, Gd, Lu, Al, Ga and In is preferable.

  X, X ′ and X ″ are at least one halogen selected from the group consisting of F, Cl, Br and I, and in particular, X is preferably at least one halogen selected from the group consisting of Br and I. .

  A is selected from the group consisting of Eu, Tb, In, Ga, Cs, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Gd, Lu, Sm, Y, Tl, Na, Ag, Cu, and Mg. And at least one metal selected from the group consisting of Eu, Cs, Sm, Tl and Na.

a, b, and e each represent a numerical value in the range of 0 ≦ a <0.5, 0 ≦ b <0.5, and 0 <e ≦ 0.2. Particularly, b preferably represents a numerical value in the range of 0 ≦ b ≦ 10 ^−2. .

  The columnar crystal 13 preferably has a stimulable phosphor represented by the following general formula (2).

  CsX: A (2)

  Here, X represents Br or I, and A represents Eu, In, Ga, or Ce.

  The photostimulable phosphor is manufactured by the following manufacturing method using, for example, the following phosphor materials (a) to (d).

  (A) At least one selected from the group consisting of LiF, LiCl, LiBr, LiI, NaF, NaCl, NaBr, NaI, KF, KCl, KBr, KI, RbF, RbCl, RbBr, RbI, CsF, CsCl, CsBr and CsI Species or two or more compounds.

_{(B) BeF 2, BeCl 2} , BeBr 2, BeI 2, MgF 2, MgCl 2, MgBr 2, MgI 2, CaF 2, CaCl 2, CaBr 2, CaI 2, SrF 2, SrCl 2, SrBr 2, SrI 2 _{, BaF 2, BaCl 2, BaBr} 2, BaI 2, ZnF 2, ZnCl 2, ZnBr 2, ZnI 2, CdF 2, CdCl 2, CdBr 2, CdI 2, CuF 2, CuCl 2, CuBr 2, CuI 2, NiF ₂ , at least one compound selected from the group consisting of NiCl ₂ , NiBr ₂ and NiI ₂ .

_{(C) ScF 3, ScCl 3} , ScBr 3, ScI 3, YF 3, YCl 3, YBr 3, YI 3, LaF 3, LaCl 3, LaBr 3, LaI 3, CeF 3, CeCl 3, CeBr 3, CeI 3 , PrF ₃ , PrCl ₃ , PrBr ₃ , PrI ₃ , NdF ₃ , NdCl ₃ , NdBr ₃ , NdI ₃ , PmF ₃ , PmCl ₃ , PmBr ₃ , PmI ₃ , SmF ₃ , SmCl ₃ , SmBr ₃ , SmF ₃ , SmI _{3 3, EuCl 3, EuBr 3,} EuI 3, GdF 3, GdCl 3, GdBr 3, GdI 3, TbF 3, TbCl 3, TbBr 3, TbI 3, DyF 3, DyCl 3, DyBr 3, DyI 3, HoF 3, _{HoCl 3, HoBr 3, HoI 3} , ErF 3, ErCl 3, ErBr 3, ErI 3, TmF 3, TmCl 3, TmBr 3, TmI 3, YbF 3, YbCl 3, YbBr 3, YbI 3, LuF 3, LuCl 3 , LuBr ₃ , LuI ₃ , AlF ₃ , AlCl ₃ , AlBr ₃ , AlI ₃ , GaF ₃ , GaCl ₃ , GaBr ₃ , GaI ₃ , InF ₃ , InCl ₃ , InBr ₃ and InI ₃ and at least one selected from the group consisting of Species or two or more compounds.

  (D) From the group consisting of Eu, Tb, In, Ga, Cs, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Gd, Lu, Sm, Y, Tl, Na, Ag, Cu and Mg At least one or two or more metals selected.

  The phosphor materials of the above (a) to (d) are weighed so as to satisfy the ranges of a, b and e in the general formula (1) and mixed with pure water. At this time, the mixture may be sufficiently mixed using a mortar, ball mill, mixer mill or the like.

  Next, a predetermined acid is added so that the pH value C of the obtained mixed solution is adjusted to 0 <C <7, and then water is evaporated.

  Next, the obtained raw material mixture is filled in a heat-resistant container such as a quartz crucible or an alumina crucible and fired in an electric furnace. The firing temperature is preferably 500 to 1000 ° C. The firing time varies depending on the filling amount of the raw material mixture, the firing temperature and the like, but is preferably 0.5 to 6 hours.

  The firing atmosphere includes a nitrogen gas atmosphere containing a small amount of hydrogen gas, a weak reducing atmosphere such as a carbon dioxide gas atmosphere containing a small amount of carbon monoxide, a neutral atmosphere such as a nitrogen gas atmosphere and a rare gas atmosphere, or a small amount of oxygen gas. A weak oxidizing atmosphere is preferred.

  After firing once under the aforementioned firing conditions, the fired product is taken out from the electric furnace and pulverized, and then the fired product powder is again filled in a heat-resistant container and placed in the electric furnace, and again under the same firing conditions as described above. If the firing is performed, the luminous brightness of the photostimulable phosphor can be further increased, and when the fired product is cooled to the room temperature from the firing temperature, the fired product is taken out of the electric furnace and allowed to cool in the air. Although a desired photostimulable phosphor can be obtained, it may be cooled in the same weakly reducing atmosphere, neutral atmosphere or weakly oxidizing atmosphere as at the time of firing.

  In addition, by moving the fired product from the heating part to the cooling part in an electric furnace and quenching in a weakly reducing atmosphere, neutral atmosphere or weakly oxidizing atmosphere, the resulting stimulable phosphor is excited. The light emission luminance can be further increased.

  The photostimulable phosphor layer 12 is formed on one surface of the substrate 11 by vapor deposition or coating method using the photostimulable phosphor. As the vapor deposition method, an evaporation method, a sputtering method, a CVD method, an ion plating method, or the like can be used.

In the vapor deposition method, first, after the substrate 11 is installed in a vapor deposition apparatus, the inside of the apparatus is evacuated to a vacuum degree of about 1.333 × 10 ⁻⁴ Pa. Next, the stimulable phosphor is set as an evaporation source in an evaporation apparatus in the vapor deposition apparatus, and is heated and evaporated by a method such as a resistance heating method or an electron beam method, so that the stimulable phosphor is formed on the surface of the substrate 11 with a desired thickness. Let it grow.

  As a result, the photostimulable phosphor layer 12 containing no binder is formed. In the above vapor deposition step, the photostimulable phosphor layer 12 can be formed in a plurality of times.

  In the vapor deposition step, a plurality of photostimulable phosphor materials are co-deposited using a plurality of resistance heaters or electron beams as an evaporation source, and at the same time, the target photostimulable phosphor is synthesized on the substrate 11. It is also possible to form the photostimulable phosphor layer 12.

  In the production of the photostimulable phosphor layer 12 by the above vapor deposition method, the temperature of the substrate 11 on which the photostimulable phosphor layer 12 is formed is preferably set to 50 ° C. to 400 ° C. From the viewpoint of characteristics, 100 ° C. to 250 ° C. is preferable. When a resin is used for the substrate 11, the heat resistance of the resin is taken into consideration, and 50 ° C. to 150 ° C., more preferably 50 ° C. to 100 ° C.

FIG. 2 is a diagram illustrating a state in which the photostimulable phosphor layer 12 is formed on the substrate 11 by vapor deposition. The incident angle of the stimulable phosphor vapor flow 16 with respect to the normal direction (R) of the surface of the substrate 11 fixed to the substrate holder 15 is θ ₂ (60 ° in the figure), and the substrate 11 of the columnar crystal 13 formed is formed. Assuming that the angle with respect to the normal direction (R) of the surface is θ ₁ (30 ° in the figure), empirically θ ₁ is about half of θ ₂ , and the columnar crystal 13 is formed at this angle.

  The growth angle of the columnar crystal 13 of the stimulable phosphor is preferably 10 to 70 °, preferably 20 to 55 °. To make the growth angle 10-70 °, the incident angle should be 20-80 °, and to make it 20-55 °, the incident angle should be 40-70 °. When the growth angle is large, the columnar crystal 13 falls too much with respect to the substrate 11, and the film becomes brittle.

  In order to supply the vapor flow of the stimulable phosphor or the stimulable phosphor material at an incident angle with respect to the surface of the substrate 11, there is a method in which the substrate 11 is arranged to be inclined with respect to the evaporation source. Alternatively, a method may be employed in which the substrate 11 and the evaporation source are installed in parallel to each other and only an oblique component is deposited on the substrate 11 through a slit or the like from the evaporation surface.

  In these cases, it is preferable that the distance between the shortest portion of the substrate 11 and the evaporation source is approximately 10 cm to 60 cm in accordance with the average range of the stimulable phosphor.

  In order to improve the modulation transfer function (MTF) in the stimulable phosphor layer 12 composed of the columnar crystals 13, the size of the columnar crystals 13 is preferably about 1 μm to 50 μm, and more preferably 1 μm to 30 μm. That is, when the columnar crystal 13 is thinner than 1 μm, the MTF decreases because the stimulated excitation light is scattered by the columnar crystal 13, and the directivity of the stimulated excitation light also decreases when the columnar crystal 13 is 50 μm or more. However, the MTF decreases.

  Note that the size of the columnar crystal 13 is an average value of the diameters in terms of a circle of the cross-sectional area of each columnar crystal 13 when the columnar crystal 13 is observed from a plane parallel to the substrate 11, and is at least 100 columnar crystals or more. Calculated from a micrograph containing 13 in the field of view.

  Further, the size of the gap between the columnar crystals 13 is preferably 30 μm or less, and more preferably 5 μm or less. When the gap exceeds 30 μm, the filling rate of the phosphor in the phosphor layer is lowered and the sensitivity is lowered.

  The thickness of the columnar crystal 13 is affected by the temperature of the substrate 11, the degree of vacuum, the vapor flow incident angle, and the like, and the columnar crystal 13 having a desired thickness can be produced by controlling these.

  In addition, the gap formed between the columnar crystals 13 may be filled with a filler such as a binder, and in addition to reinforcing the stimulable phosphor layer 12, a highly light-absorbing substance and a highly light-reflecting substance may be used. It may be filled. In addition to providing a reinforcing effect by the filler, it is effective for reducing the light diffusion in the lateral direction of the stimulated excitation light incident on the stimulable phosphor layer 12.

In the sputtering method, as in the vapor deposition method, after the substrate 11 is placed in the sputtering apparatus, the inside of the apparatus is once evacuated to a vacuum of about 1.333 × 10 ⁻⁴ Pa, and then Ar, Ne as sputtering gases. An inert gas such as is introduced into the sputtering apparatus to obtain a gas pressure of about 1.333 × 10 ⁻¹ Pa. Next, the photostimulable phosphor layer 12 is grown on the substrate 11 to a desired thickness by sputtering using the photostimulable phosphor as a target.

  Various applied treatments can be used in the sputtering process as in the vapor deposition method. The same applies to the CVD method, the ion plating method, and others.

  The growth rate of the photostimulable phosphor layer 12 in the vapor deposition method is preferably 0.05 μm / min to 300 μm / min. When the growth rate is less than 0.05 μm / min, the productivity of the radiation image conversion panel is poor and is not preferable. Further, when the growth rate exceeds 300 μm / min, it is difficult to control the growth rate, which is not preferable.

  In the coating method, first, the stimulable phosphor and the binder are added to an appropriate solvent, and these are mixed well to prepare a coating solution in which the particles of the stimulable phosphor and the binder are uniformly dispersed, It is formed by coating on a substrate material to be the substrate 11. Under the present circumstances, a binder is used in 0.01-1 mass part with respect to 1 mass part of stimulable fluorescent substance. However, in terms of sensitivity and sharpness of the 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.

  Examples of the solvent used for preparing the coating solution include lower alcohols such as methanol, ethanol, isopropanol and n-butanol, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, methyl acetate, ethyl acetate and n-butyl acetate. Esters of lower fatty acids and lower alcohols such as dioxane, ethers such as ethylene glycol monomethyl ether and ethylene glycol monoethyl ether, aromatic compounds such as triol and xylose, halogenated hydrocarbons such as methylene chloride and ethylene chloride, and these A mixture etc. are mentioned.

  In the coating solution, a dispersing agent for improving the dispersibility of the stimulable phosphor in the coating solution, or a combination of the stimulable phosphor and the binder in the stimulable phosphor layer 12 after coating is used. Various additives such as a plasticizer for improving the strength may be mixed.

  Examples of the dispersant include phthalic acid, stearic acid, caproic acid, lipophilic surfactant and the like. Examples of plasticizers include phosphate esters such as triphenyl phosphate, tricresyl phosphate and diphenyl phosphate, phthalate esters such as diethyl phthalate and dimethoxyethyl phthalate, ethyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate And the like, polyesters of triethylene glycol and adipic acid, polyesters of polyethylene glycol and aliphatic dibasic acid such as polyesters of diethylene glycol and succinic acid, and the like.

  The coating liquid is adjusted 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 adjusted coating solution is applied onto the substrate material using a doctor blade, roll coater, knife coater or the like. Next, the stimulable phosphor layer 12 is formed by drying the formed coating film by gradually heating it.

  When the photostimulable phosphor layer 12 is provided by the coating method, the substrate material is cut into a predetermined size together with the photostimulable phosphor layer 12. Cutting can be performed by any general method, but it is preferable to use a decorative cutting machine, a punching machine, or the like in terms of workability and accuracy. When the substrate material is sufficiently small, the substrate material may be used as the substrate 11 without performing cutting.

  The film thickness of the photostimulable phosphor layer 12 formed by the vapor deposition method or the coating method depends on the characteristics of the intended radiation image conversion panel, the type of stimulable phosphor, and the mixing ratio of the binder and the phosphor. Although it varies depending on the above, it is preferably selected from the range of 10 to 1000 μm, more preferably selected from the range of 10 to 500 μm.

  When the phosphor plate is formed as described above, a moisture-proof protective film 20 that covers and seals the photostimulable phosphor layer 12 is provided. As the moisture-proof protective film 20, cellulose acetate, nitrocellulose, polymethyl methacrylate, polyvinyl butyral, polyvinyl formal, polycarbonate, polyester, polyethylene terephthalate, polyethylene naphthalate, polyethylene, polyvinylidene chloride, nylon, polytetrafluoroethylene, poly Resin films such as trifluoride-ethylene chloride, ethylene tetrafluoride-hexafluoropropylene copolymer, vinylidene chloride-vinyl chloride copolymer, vinylidene chloride-acrylonitrile copolymer can be used. The resin film is easy to process, and even if the thickness is reduced to 100 μm or less, there is no problem in strength during the manufacturing process, and since it is a thin layer, it is preferable in terms of initial image quality.

Moreover, these moisture-proof protective films 20 may have laminated | stacked the layer of the inorganic substance with low moisture permeability and oxygen permeability. Examples of such inorganic substances include SiO _x (SiO, SiO ₂ ), Al ₂ O ₃ , ZrO ₂ , SnO ₂ , SiC, and SiN. Of these, Al ₂ O ₃ and SiO _x are particularly light transmissive. It is particularly preferable because it has a high moisture permeability and oxygen permeability, that is, it can form a dense film with few cracks and micropores. SiO _x and Al ₂ O ₃ may be laminated alone, but if both are laminated together, moisture permeability and oxygen permeability can be increased, so both SiO _x and Al ₂ O ₃ are laminated. Also good.

  The lamination of the inorganic substance on the moisture-proof protective film 20 can be performed by a method such as PVD method, sputtering method, CVD method, PE-CVD (Plasma enhanced CVD). Lamination may be performed after the phosphor layer is coated with the resin film, or may be performed before the phosphor layer is coated. The laminated thickness is preferably about 0.01 μm to 1 μm.

  Moreover, you may use the laminated film formed by laminating | stacking metal films, such as an aluminum film. Or you may use the commercially available moisture-proof resin film in which the vapor deposition layer was formed previously. Examples of such a moisture-proof resin film include Toppan Printing Co., Ltd. GL-AE. A plurality of the above films may be laminated to form the moisture-proof protective film 20.

  As a method for sealing the photostimulable phosphor layer 12 with the moisture-proof protective film 20, any known method may be used. For example, a moisture-proof protective film 20 having an outermost layer as a heat-fusible resin film is disposed above and below the phosphor plate 10 and the outer side of the moisture-proof moisture-proof resin film is heated by an impulse heater. Then, the photostimulable phosphor layer 12 can be sealed by pressure bonding.

  Sealing of the photostimulable phosphor layer 12 with the moisture-proof protective film 20 is performed using at least one kind of gas such as He, Ne, Ar, Kr, Xe, or the like, nitrogen gas, carbon dioxide gas, or two or more kinds. It is carried out in a mixed gas atmosphere. The pressure of the gas is preferably 500 to 8000 Pa, more preferably 4500 to 7500 Pa.

  By sealing the photostimulable phosphor layer 12 with the moisture-proof protective film 20 in the gas atmosphere, a rare gas, nitrogen gas, or carbon dioxide is interposed between the photostimulable phosphor layer 12 and the moisture-proof protective film 20. Any one or two or more gases of carbon gas can be filled. Thereby, the specific performance of the radiation image conversion panel can be improved.

In the radiation image conversion panel filled with a rare gas such as He, Ne, Ar, Kr, or Xe, the rare gas filled between the stimulable phosphor layer 12 and the moisture-proof protective film 20 is used as a subject or a peripheral material. The X-rays scattered by are absorbed and excited, and after emitting light in about 10 ⁻² seconds, the weak X-rays are absorbed again. For this reason, noise near the surface of the photostimulable phosphor layer 12 due to scattered X-rays can be removed, and the contrast of the reproduced image can be improved.

  In the radiation image conversion panel filled with nitrogen gas, the nitrogen gas is filled between the photostimulable phosphor layer 12 and the moisture-proof protective film 20, so that the water vapor in the air into the radiation image conversion panel is reduced. Infiltration can be prevented and the moisture resistance of the photostimulable phosphor layer 12 can be improved. This effect is particularly significant when the moisture-proof protective film 20 is a film obtained by depositing a thin film such as a metal oxide or silicon nitride on a polyethylene terephthalate film or a polyethylene naphthalate film.

  In the radiation image conversion panel filled with carbon dioxide gas, as shown in an experiment to be described later, the stimulable emission brightness of the stimulable phosphor layer 12 can be improved by 5 to 10%, and the radiation image by X-rays The luminance deterioration of the conversion panel can be prevented.

  The gas filled between the photostimulable phosphor layer 12 and the moisture-proof protective film 20 of the radiation image conversion panel changes the atmosphere when the photostimulable phosphor layer 12 is sealed with the moisture-proof protective film 20. It is possible to change arbitrarily. Therefore, a variety of radiation image conversion panels can be manufactured through substantially the same process, and a radiation image conversion panel with improved specific performance that meets the purpose of imaging in a facility can be provided at low cost.

  Hereinafter, the present invention will be described with reference to examples. In addition, this invention is not limited by these Examples.

  Various radiation image conversion panels were produced according to the method described below.

  <Production of Substrate> A light reflecting layer was provided on one surface of a 500 μm-thick transparent crystallized glass to obtain a substrate. The light reflecting layer was formed into a film by depositing titanium oxide (manufactured by Furuuchi Chemical Co., Ltd.) and zirconium oxide (manufactured by Furuuchi Chemical Co., Ltd.) on a substrate using a vapor deposition apparatus. The thickness of the light reflecting layer was adjusted so that the reflectance of light having a wavelength of 400 nm was 85% and the reflectance of light having a wavelength of 660 nm was 20%.

  <Preparation of phosphor plate> A photostimulable phosphor made of CsBr: Eu was deposited on the substrate to form a photostimulable phosphor layer. First, it was fixed in a vacuum chamber in a vapor deposition apparatus and heated to 240 ° C. Next, nitrogen gas was introduced into the vacuum chamber, and the degree of vacuum was set to 0.1 Pa. The surface of the substrate provided with the light reflecting layer was directed to the vapor deposition source. The distance between the deposition source and the substrate was 60 cm. In addition, an aluminum slit was disposed between the deposition source and the substrate so that the stimulable phosphor vapor was incident at an angle of 30 ° with respect to the normal direction of the substrate surface. Vapor deposition was carried out while conveying the substrate in the surface direction, and a stimulable phosphor layer having a columnar structure with a thickness of 300 μm was formed on the substrate to obtain a phosphor plate.

  <Preparation of moisture-proof protective film> The moisture-proof protective film provided on the stimulable phosphor layer side of the phosphor plate is a film obtained by depositing polyethylene terephthalate (PET12) having a thickness of 12 μm on which various mats have been processed, and alumina. A 12 μm-thick PET (VMPET12, manufactured by Toyo Metallizing Co., Ltd.) was attached by dry lamination. For dry lamination, a two-component reaction type urethane adhesive was used.

  Moreover, the moisture-proof protective film provided on the substrate side of the phosphor plate was formed by laminating 9 μm thick aluminum foil and 100 μm thick PET by dry lamination and applying a heat-fusible lacquer on the aluminum foil side. .

  <Sealing of phosphor panel> The moisture-proof protective film was disposed on both sides of the phosphor panel. This was installed in a vacuum chamber, and after reducing the pressure to 200 Pa, helium gas was introduced to replace the gas in the chamber. After that, the atmospheric pressure in the chamber is readjusted to 7000 Pa, and under this reduced pressure, the moisture-proof protective film is fused together at the periphery of the phosphor panel using an impulse sealer, the phosphor panel is sealed, and radiation image conversion is performed. I got a panel. The impulse sealer heater was 8 mm wide.

  A radiation image conversion panel was obtained by replacing the helium gas of Example 1 with neon gas.

  A radiation image conversion panel was obtained by replacing the helium gas of Example 1 with argon gas.

  A radiation image conversion panel was obtained by replacing the helium gas of Example 1 with krypton gas.

  A radiation image conversion panel was obtained by replacing the helium gas of Example 1 with xenon gas.

  A radiation image conversion panel was obtained by replacing the helium gas of Example 1 with carbon dioxide gas.

  A radiation image conversion panel was obtained by replacing the helium gas of Example 1 with nitrogen gas.

[Comparative Example 1]
A radiation image conversion panel was obtained by replacing the helium gas of Example 1 with the atmosphere.
[Comparative Example 2]
A radiation image conversion panel was obtained by replacing the helium gas of Example 1 with oxygen gas.

  The following evaluation was performed on the radiation image conversion panels of Examples 1 to 7 and Comparative Examples 1 and 2.

<Contrast Evaluation> A 40 mm-thick lead disk was copied onto the radiation image conversion panel, and X-rays with a tube voltage of 80 kVp were uniformly irradiated. Thereafter, the radiation image conversion panel is scanned from the photostimulable phosphor layer side with a semiconductor laser (660 nm) to excite the photostimulable phosphor layer, and stimulated emission is received by a photoreceiver (photoelectron multiplication of spectral sensitivity S-5). Tube) to receive the light and read the image. The obtained image was output by a laser writing type film printer. The output image was visually observed, and the contrast between the lead disk portion (white) and its peripheral portion (black) was evaluated in five stages according to the following criteria. In addition, it was judged that evaluation 2 or less is unsuitable for diagnosis practically.
5: The brightness difference between the periphery of the lead disk and black and white is clearly confirmed.
4: Although the peripheral edge of the lead disk is slightly blurred, the brightness difference between black and white is almost clearly confirmed.
3: The peripheral edge of the lead disk looks blurry, and the brightness difference between black and white is not clear.
2: The brightness difference between the lead disk periphery and black and white is not clear, and the lead disk size is not reproduced.
1: The lead disk shape and the brightness difference between black and white are unclear, and the whiteness of the center is low.

  <Initial luminance> X-rays having a tube voltage of 80 kVp were irradiated from the substrate side to the radiation image conversion panel. Thereafter, the radiation image conversion panel is scanned from the photostimulable phosphor layer side with a semiconductor laser (660 nm) to excite the photostimulable phosphor layer, and stimulated emission is received by a photoreceiver (photoelectron multiplication of spectral sensitivity S-5). The intensity was measured and displayed as a relative value with the initial luminance of the radiation image conversion panel of Comparative Example 1 being 1.0.

  <Luminance reduction due to X-rays> Radiation image conversion panel is irradiated with X-rays (80 kV) of 2000 X-rays intermittently, and then left under a 6000 Lux fluorescent lamp with UV light cut for 2 days to completely erase the X-ray information. did. Thereafter, the stimulated emission intensity was measured by the same method as the measurement of the initial luminance, and the relative luminance after 2000 X-ray irradiation was displayed as a relative value with the initial luminance set to 100.

  <Luminance reduction due to humidity> After the radiation image conversion panel was subjected to humidity degradation treatment for 50 days in an environment of 40 ° C. and 90% humidity, the stimulated emission intensity was measured by the same method as the measurement of initial luminance. The relative luminance after the humidity deterioration treatment was displayed as a relative value with the initial luminance set to 100.

The above evaluation is shown in Table 1.

  The radiographic image conversion panels (Examples 1 to 5) filled with a rare gas had higher contrast than the case where the atmosphere was filled (Comparative Example 1). Moreover, in the radiation image conversion panel (Example 6) filled with carbon dioxide gas, the initial luminance was higher than that of Comparative Example 1, and the luminance decrease due to X-ray irradiation was also small. In addition, in the radiation image conversion panel (Example 7) filled with nitrogen gas, the luminance decrease after the humidity deterioration process was small as compared with Comparative Example 1. In addition, when oxygen was filled (Comparative Example 2), the contrast was low, the initial luminance was lowered, the luminance was lowered due to X-ray irradiation, and the luminance was lowered after the humidity deterioration treatment, which was not suitable for diagnosis in practice. .

  As described above, by filling the radiographic image conversion panel with any of rare gas, carbon dioxide gas, and nitrogen gas, specific performance such as contrast, brightness, and durability can be improved. In addition, these gases may be used independently and may mix and use 2 or more types of gases.

It is sectional drawing which shows the example of a form of the radiographic image conversion panel of this invention. It is sectional drawing which shows the formation method of the photostimulable phosphor layer of the radiographic image conversion panel of this invention. It is a schematic diagram which shows the imaging method using a radiographic image conversion panel.

Explanation of symbols

10 phosphor panel 11 substrate 12 stimulable phosphor layer 13 columnar crystal 15 substrate holder 16 vapor flow 20 moisture-proof protective film

Claims (5)

  In a radiation image conversion panel formed by sealing a photostimulable phosphor layer provided on a substrate with a moisture-proof protective film, a rare gas is filled between the photostimulable phosphor layer and the moisture-proof protective film. A radiation image conversion panel characterized by comprising:   The radiation image conversion panel according to claim 1, wherein the rare gas is at least one or more of He, Ne, Ar, Kr, and Xe.   In a radiation image conversion panel formed by sealing a photostimulable phosphor layer provided on a substrate with a moisture-proof protective film, nitrogen gas is filled between the photostimulable phosphor layer and the moisture-proof protective film. A radiation image conversion panel characterized by comprising:   In a radiation image conversion panel formed by sealing a photostimulable phosphor layer provided on a substrate with a moisture-proof protective film, carbon dioxide gas is filled between the photostimulable phosphor layer and the moisture-proof protective film. Radiation image conversion panel characterized by being made.   A method for producing a radiation image conversion panel in which a photostimulable phosphor layer is provided on a substrate, and the photostimulable phosphor layer is sealed with a moisture-proof protective film, and is moisture-proof without being in close contact with the photostimulable phosphor layer. The stimulable phosphor layer is covered with a stimulable protective film, and then one or more gases of noble gas, nitrogen gas, and carbon dioxide gas are provided between the stimulable phosphor layer and the moisture-proof protective film. The manufacturing method of the radiographic image conversion panel characterized by the above-mentioned.

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