JP2005091188A - Radiological image conversion panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiological image conversion panel more excellent in contrast by avoiding back scattering of an X ray detrimental to imaging. <P>SOLUTION: The radiological image conversion panel has a stimulable phosphor layer 12 on a substrate 11. An X-ray absorbent layer 13 is formed by including an X-ray absorbent body in the opposite face of the phosphor layer 12 to the substrate 11. Because the X-ray absorbent layer is formed on the opposite face of the phosphor layer to the substrate, the X ray radiated against the conversion panel from the substrate side and passing through the phosphor layer can be absorbed by the X-ray absorbent layer. The X ray passing through the X-ray absorbent layer, scattered at a rear matter and incident again to the conversion panel can be absorbed by the X-ray absorbent layer. Therefore, back scattering of the X ray detrimental to imaging can be avoided so that the radiological image conversion panel more excellent in contrast can be obtained. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a radiation image conversion panel using a photostimulable phosphor.

  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.

  A method for recording a radiation image using the radiation image conversion panel is, for example, as follows. First, the radiation image conversion panel is fixed to the reading device, and the subject is placed in front of the radiation image conversion panel. Next, the subject is irradiated with X-rays from the front, and the X-rays transmitted through the subject are incident on the stimulable phosphor layer to accumulate radiation energy corresponding to the radiation transmission density of each part of the subject. By irradiating the stimulable phosphor layer that stores energy with electromagnetic waves (excitation light) such as visible light and infrared rays in time series excitation, the radiation energy accumulated in the stimulable phosphor is stimulated. Release as luminescence. A signal based on the intensity of the stimulated light emission 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.

  The superiority or inferiority of the radiation image conversion method using the radiation image conversion panel greatly depends on the stimulable light emission luminance of the panel and the light emission uniformity of the panel, and in particular, these characteristics greatly depend on the characteristics of the stimulable phosphor used. It is known to be ruled.

  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.

  Such radiation image conversion panels are often used in medical X-ray diagnostic imaging equipment and the like. In medical diagnostic imaging equipment, a radiation image conversion panel with higher sensitivity and sharpness is particularly required in order to reduce the exposure dose of radiation irradiated to a patient.

  In order to improve the sensitivity and sharpness of the radiation image conversion panel, for example, in Patent Document 1, the thickness of the phosphor layer is set in the range of 300 to 700 μm and the stimulable phosphor layer is totally stimulated. Sensitivity and sharpness are improved by setting the ratio of the volume occupied by the fluorescent material to 85 to 97%.

  Patent Document 2 uses a photostimulable phosphor represented by the following general formula (1), particularly a photostimulable phosphor having an e value in the range of 0.003 ≦ e ≦ 0.005. This indicates that a highly sensitive radiation image conversion panel can be obtained.

^{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. represents at least one trivalent metal selected from the group consisting of, M ³ is Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, 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. ]
JP 2002-214397 A (second page) JP 2003-028995 A

  However, when imaging is performed by irradiating X-rays from the front while the radiation image conversion panel is fixed to the reader, the X-rays pass through the radiation image conversion panel and then the radiation image conversion panel of the apparatus. There is a problem that the contrast is lowered because the photostimulable phosphor is exposed after being scattered at the rear portion and incident on the radiation image conversion panel again.

  An object of the present invention is to provide a radiographic image conversion panel that prevents backscattering of X-rays that are harmful to imaging and has a higher contrast.

  In order to solve the above-mentioned problems, the invention described in claim 1 of the present invention is the radiation image conversion panel having the stimulable phosphor layer 12 on the substrate 11 as shown in FIG. The phosphor layer 12 is formed by containing a stimulable phosphor represented by the following general formula (1), and the following general formula (2) is formed on the surface of the stimulable phosphor layer 12 opposite to the substrate 11. An X-ray absorber layer 13 formed by containing an X-ray absorber represented by the formula is provided.

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

M ¹ X ・ aM ² X ' ₂・ bM ³ X'' ₃・ ・ ・ （２）

Here, M ¹ is at least one alkali metal selected from the group consisting of Li, Na, K, Rb and Cs, and M ² is selected from Be, Mg, Ca, Sr, Ba, Zn, Cd, Cu and Ni. At least one divalent metal selected from the group consisting of M ³ is Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu , At least one trivalent metal selected from the group consisting of 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 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. A, b, and e are numerical values in the range of 0 ≦ a <0.5, 0 ≦ b <0.5, and 0 <e ≦ 0.2, respectively.

The invention according to claim 2 is the radiation image conversion panel according to claim 1, wherein M ¹ in the general formula (1) and the general formula (2) is selected from the group consisting of K, Rb and Cs. And at least one alkali metal.

  Invention of Claim 3 is a radiation image conversion panel of Claim 1 or 2, Comprising: X in the said General formula (1) and the said General formula (2) is selected from the group which consists of Br and I It is at least one kind of halogen.

The invention described in claim 4 is the radiation image conversion panel according to any one of claims 1 to 3, M ² in the formula (1) and the general formula (2) is Be, Mg And at least one divalent metal selected from Ca, Sr and Ba.

The invention described in claim 5 is the radiation image conversion panel according to any one of claims 1 to 4, M ³ in the general formula (1) and the general formula (2) is Y, La And at least one trivalent metal selected from the group consisting of Ce, Sm, Eu, Gd, Lu, Al, Ga and In.

Invention of Claim 6 is a radiographic image conversion panel as described in any one of Claims 1-5, Comprising: b in the said General formula (1) and the said General formula (2) is 0 <= b <=. It is characterized by a numerical value in the range of 10 ^-2 .

  Invention of Claim 7 is a radiographic image conversion panel as described in any one of Claims 1-6, Comprising: A in the said General formula (1) and the said General formula (2) is Eu, Cs, It is at least one metal selected from the group consisting of Sm, Tl and Na.

  Invention of Claim 8 is a radiation image conversion panel as described in any one of Claims 1-7, Comprising: The said stimulable fluorescent substance layer 12 is the columnar crystal of the said stimulable fluorescent substance. It is characterized by having.

The invention according to claim 9 is the radiation image conversion panel according to claim 8, wherein the columnar crystal has a stimulable phosphor represented by the following general formula (3).
CsX: A (3)

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

  Invention of Claim 10 is a radiation image conversion panel as described in any one of Claims 1-9, Comprising: The said X-ray absorber layer 13 is 0.005-20 micrometers in thickness, It is characterized by the above-mentioned. And

  Invention of Claim 11 is a radiographic image conversion panel as described in any one of Claims 1-10, Comprising: The said X-ray absorber layer 13 is 0.02-5 micrometers in thickness, It is characterized by the above-mentioned. And

  According to the present invention, by providing an X-ray absorber layer on the surface of the photostimulable phosphor layer opposite to the substrate, X is irradiated from the substrate side to the radiation image conversion panel and transmitted through the photostimulable phosphor layer. Lines can be absorbed by the X-ray absorber layer. Further, X-rays that are transmitted through the X-ray absorber layer, scattered by an object behind, and incident on the radiation image conversion panel again can be absorbed by the X-ray absorber layer. Therefore, the backscattering of X-rays harmful to imaging can be prevented, and a radiographic image conversion panel with better contrast can be obtained.

  Hereinafter, embodiments of the present invention will be described in detail. In the radiation image conversion panel according to the embodiment of the present invention, as shown in FIG. 1, the stimulable phosphor layer 12 is deposited on one surface of the substrate 11 by a vapor deposition method to a thickness of 50 μm or more, preferably 300 to 700 μm. Is formed. Further, an X-ray absorber layer 13 is formed on the photostimulable phosphor layer 12 by a vapor deposition method so as to have a layer thickness of 0.005 to 20 μm or more, preferably 0.02 to 5 μm. The photostimulable phosphor layer 12 and the X-ray absorber layer 13 are integrally formed as columnar crystals 14 by a vapor deposition method. The photostimulable phosphor layer 12 and the X-ray absorber layer 13 are sealed with a protective layer or a sealing material (not shown) so as not to come into contact with air.

  As the substrate 11, resin-impregnated carbon fiber (carbon fiber reinforced resin) can be used, and specifically, commercially available carbon fiber (# 132 manufactured by Toho Rayon Co., Ltd., impregnated with epoxy resin) can be used. In addition, a heat-resistant material can be arbitrarily selected from known materials as the substrate 11 of the conventional radiation image conversion panel, and is made of a quartz glass sheet, a metal sheet made of aluminum, iron, tin, chrome, etc., and aramid. A resin sheet or a laminate of these can be used.

  As the stimulable phosphor preferably used in the present invention, 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. 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. .

  Further, the columnar crystal 14 preferably has a stimulable phosphor represented by the following general formula (3).

  CsX: A (3)

  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, NiCl ₂ , at least one compound selected from the group consisting of NiBr ₂ and NiI _2, or two or more compounds.

_{(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. 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 an argon 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 by vapor deposition on the one surface of the substrate 11 using the photostimulable phosphor as an evaporation source. 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 degree of vacuum of about 1.333 × 10 ⁻² 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.

  The film thickness of the photostimulable phosphor layer 12 is 50 μm or more, preferably 300 to 700 μm, although it varies depending on the intended use of the radiation image conversion panel and the type of stimulable phosphor.

  In preparation 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, 50 ° C. to 150 ° C., more preferably 50 ° C. to 100 ° C. is preferable in consideration of heat resistance of the resin.

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 crystals 14 to be formed is formed. Assuming that the angle with respect to the normal direction (R) of the surface is θ ₁ (30 ° in the figure), θ ₁ is empirically about half of θ ₂ , and the columnar crystal 14 is formed at this angle.

  The growth angle of the columnar crystal of the stimulable phosphor is preferably 10 to 70 °, and 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 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 made of columnar crystals, the size of the columnar crystals is preferably about 1 μm to 50 μm, and more preferably 1 μm to 30 μm. That is, when the columnar crystal is thinner than 1 μm, the excitation excitation light is scattered by the columnar crystal, so that the MTF decreases. When the columnar crystal is 50 μm or more, the directivity of the excitation excitation light decreases, and the MTF Will decline.

  The size of the columnar crystal is an average value of the diameters in terms of a circle of the cross-sectional area of each columnar crystal when the columnar crystal is observed from a plane parallel to the substrate 11, and at least 100 columnar crystals are being viewed. Calculate from the photomicrographs included.

  Further, the size of the gap between the columnar crystals 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 is influenced by the temperature, the degree of vacuum, the vapor flow incident angle, and the like, and it is possible to produce a columnar crystal having a desired thickness by controlling these.

  In addition, the gap formed between the columnar crystals 14 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.

  An X-ray absorber layer 13 is formed on the photostimulable phosphor layer 12 formed as described above. In addition, it is preferable that the X-ray absorber layer 13 has a high transmittance of light having an excitation wavelength (640 to 700 nm) and a stimulated emission wavelength (400 to 500 nm) of the stimulable phosphor. As the X-ray absorber preferably used for the X-ray absorber layer 13, those represented by the general formula (2) can be used.

M ¹ X ・ aM ² X ' ₂・ bM ³ X'' ₃・ ・ ・ （２）

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

  The X-ray absorber can be produced in the same manner as the photostimulable phosphor except that the phosphor material (d) is not used. Further, the X-ray absorber layer 13 can be formed using the manufactured X-ray absorber by using a vapor deposition method in the same manner as the stimulable phosphor layer 12.

  The film thickness of the X-ray absorber layer 13 is preferably 0.005 to 20 μm, and more preferably 0.02 to 5 μm.

  After the X-ray absorber layer 13 is formed, a protective layer is provided on the surface of the X-ray absorber layer 13 opposite to the substrate 11 as necessary. The protective layer may be formed by directly applying a coating solution for the protective layer to the surface of the X-ray absorber layer 13, or a protective layer separately formed in advance may be adhered to the X-ray absorber layer 13. The thickness of these protective layers is preferably 0.1 to 2000 μm.

  As a material for the protective layer, a moisture-proof resin film can be suitably used. As moisture-proof resin film, cellulose acetate, nitrocellulose, polymethyl methacrylate, polyvinyl butyral, polyvinyl formal, polycarbonate, polyester, polyethylene terephthalate, polyethylene, polyvinylidene chloride, nylon, polytetrafluoroethylene, polytrifluoride-chloride Ethylene, tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene chloride-vinyl chloride copolymer, vinylidene chloride-acrylonitrile copolymer, and the like 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 resin films 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 should be laminated. Is more preferable.

  Lamination of the inorganic substance to the resin film can be performed by methods 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. 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.

  While a carbon fiber having a thickness of 1 mm (# 132 manufactured by Toho Rayon Co., Ltd.) was conveyed at a conveyance speed of 1.0 m / min, a pressure of 4.9 × 10 N / cm was applied to the conveyance heat roll to obtain a substrate. A stimulable phosphor layer (CsBr: Eu) and an X-ray absorber material (CsBr) are vapor-deposited on one side of the substrate to form a stimulable phosphor layer 12 and an X-ray absorber layer, thereby obtaining a radiation image conversion panel. It was.

  Vapor deposition is performed using an aluminum slit, the distance between the substrate and the slit being 60 cm, and transporting the substrate in a direction parallel to the substrate, and adjusting the thickness of the stimulable phosphor layer to 400 μm. did. In the vapor deposition, the substrate 11 was placed in a vapor deposition device, and then, the phosphor raw material (CsBr: Eu) and the X-ray absorber raw material (CsBr) were used as a vapor deposition source and placed in a crucible that was press-molded and water-cooled. .

Thereafter, the inside of the vapor deposition device was once evacuated, N ₂ gas was introduced, the degree of vacuum was adjusted to 1.33 × 10 ⁻² Pa, and the photostability was maintained while maintaining the substrate temperature at 50 ° C. to 100 ° C. A phosphor layer was deposited. When the thickness of the photostimulable phosphor layer reached 400 μm, the evaporation source was changed to an X-ray absorber, and the X-ray absorber layer was evaporated until the film thickness reached 50 μm.

  In the same manner as in Example 1, the stimulable phosphor layer was vapor-deposited until the film thickness became 400 μm, and the X-ray absorber layer was deposited until the film thickness became 20 μm.

  In the same manner as in Examples 1 and 2, the stimulable phosphor layer was vapor-deposited until the film thickness became 400 μm, and the X-ray absorber layer was deposited until the film thickness became 5 μm.

  In the same manner as in Examples 1 to 3, the stimulable phosphor layer was vapor-deposited until the film thickness became 400 μm, and the X-ray absorber layer was deposited until the film thickness became 1 μm.

  In the same manner as in Examples 1 to 4, the stimulable phosphor layer was vapor-deposited until the film thickness became 400 μm, and the X-ray absorber layer was deposited until the film thickness became 0.1 μm.

  In the same manner as in Examples 1 to 5, the photostimulable phosphor layer was vapor-deposited until the film thickness became 400 μm, and the X-ray absorber layer was deposited until the film thickness became 0.02 μm.

  In the same manner as in Examples 1 to 6, the stimulable phosphor layer was vapor-deposited until the film thickness became 400 μm, and the X-ray absorber layer was deposited until the film thickness became 0.005 μm.

[Comparative Example 1]
The photostimulable phosphor layer was deposited in the same manner as in Examples 1 to 7 until the film thickness was 400 μm. The X-ray absorber layer was not deposited.

  <Contrast Evaluation> A lead disk having a diameter of 40 mm was attached to the radiation image conversion panel, and X-rays having a tube voltage of 80 kVp were irradiated with 10 mAs. Next, the radiation image conversion panel is excited by scanning with a 100 mW semiconductor laser (680 nm), and the stimulated emission emitted from the phosphor layer is received by a photomultiplier tube (R1305, manufactured by Hamamatsu Photonics) and an electrical signal is received. And A / D converted and recorded on a magnetic tape to obtain image data. From the recorded image data, the signal value difference (contrast) between the center and the periphery of the disc was analyzed by a computer to obtain the contrast ratio. It shows that it is so favorable that the value of contrast ratio is low.

  <Evaluation of sharpness> The radiation image conversion panel was irradiated with X-rays having a tube voltage of 80 kVp by 10 mAs through a rectangular wave chart for MTF measurement of 1.0 lp / mm. Next, the radiation image conversion panel is excited by scanning with a 100 mW semiconductor laser (680 nm), and the stimulated emission emitted from the phosphor layer is received by a photomultiplier tube (R1305, manufactured by Hamamatsu Photonics) and an electrical signal is received. To obtain image data. The obtained image data was analyzed with a computer to determine the modulation transfer function (MTF) value (%) of the X-ray image. The higher the MTF value, the better.

Table 1 shows the results of measuring the contrast ratio and sharpness.

  In Example 1, the contrast ratio was 0.0085, and the sharpness was 50%. In Example 2, the contrast ratio was 0.009 and the sharpness was 60%. In Example 3, the contrast ratio was 0.01 and the sharpness was 65%. In Example 4, the contrast ratio was 0.015, and the sharpness was 70%. In Example 5, the contrast ratio was 0.02, and the sharpness was 73%. In Example 6, the contrast ratio was 0.025, and the sharpness was 75%. In Example 7, the contrast ratio was 0.0085, and the sharpness was 50%. In Comparative Example 1, the contrast ratio was 0.03, and the sharpness was 75.5%.

  As the layer thickness of the X-ray absorber layer increased, the contrast became better. It is considered that backscattering can be prevented by the X-ray absorber layer. On the other hand, the sharpness decreased as the thickness of the X-ray absorber layer increased. From the above results, the thickness of the X-ray absorber layer 13 should not be too thick, preferably 0.005 to 20 μm, and more preferably 0.02 to 5 μm.

It is sectional drawing which shows the radiographic image conversion panel of the embodiment of this invention. It is sectional drawing which shows a mode that a photostimulable fluorescent substance layer is formed in a support body by vapor deposition.

Explanation of symbols

11 Substrate 12 Stimulable phosphor layer 13 X-ray absorber layer

Claims (11)

In a radiation image conversion panel having a photostimulable phosphor layer on a substrate, the photostimulable phosphor layer is formed by containing a photostimulable phosphor represented by the following general formula (1), and the photostimulability A radiation image conversion panel comprising an X-ray absorber layer formed by containing an X-ray absorber represented by the following general formula (2) on the surface of the phosphor layer opposite to the substrate.
^{M 1 X · aM 2 X '} 2 · bM 3 X''3: eA ··· (1)
M ¹ X ・ aM ² X ' ₂・ bM ³ X'' ₃・ ・ ・ （２）
Here, M ¹ is at least one alkali metal selected from the group consisting of Li, Na, K, Rb and Cs, and M ² is selected from Be, Mg, Ca, Sr, Ba, Zn, Cd, Cu and Ni. At least one divalent metal selected from the group consisting of M ³ is Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu , At least one trivalent metal selected from the group consisting of 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 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. A, b, and e are numerical values in the range of 0 ≦ a <0.5, 0 ≦ b <0.5, and 0 <e ≦ 0.2, respectively. The radiation image conversion panel according to claim 1, wherein M ¹ in the general formula (1) and the general formula (2) is at least one alkali metal selected from the group consisting of K, Rb, and Cs. .   3. The radiation image conversion panel according to claim 1, wherein X in the general formula (1) and the general formula (2) is at least one halogen selected from the group consisting of Br and I. 4. The M ² in the general formula (1) and the general formula (2) is at least one divalent metal selected from Be, Mg, Ca, Sr, and Ba. The radiation image conversion panel according to one item. M ³ in the general formula (1) and the general formula (2) is at least one trivalent metal selected from the group consisting of Y, La, Ce, Sm, Eu, Gd, Lu, Al, Ga, and In. The radiation image conversion panel according to any one of claims 1 to 4, wherein The radiographic image conversion according to claim 1, wherein b in the general formula (1) and the general formula (2) represents a numerical value in a range of 0 ≦ b ≦ 10 ^−2. panel.   The A in the general formula (1) and the general formula (2) is at least one metal selected from the group consisting of Eu, Cs, Sm, Tl, and Na. The radiation image conversion panel according to one item.   The radiation image conversion panel according to claim 1, wherein the photostimulable phosphor layer has a columnar crystal of the photostimulable phosphor. The radiation image conversion panel according to claim 8, wherein the columnar crystal has a stimulable phosphor represented by the following general formula (3).
CsX: A (3)
Here, X represents Br or I, and A represents Eu, In, Ga, or Ce.   The radiation image conversion panel according to claim 1, wherein the X-ray absorber layer has a thickness of 0.005 to 20 μm.   The radiation image conversion panel according to claim 1, wherein the X-ray absorber layer has a thickness of 0.02 to 5 μm.

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