Patent Number: 
Section: description

Embodiments of a scattered ray absorption grid of the present invention will be described hereunder with reference to the accompanying drawings. FIG. 1 is a drawing showing a schematic constitution of the scattered ray absorption grid common to first to tenth embodiments of the present invention.  less than First Embodiment greater than  FIG. 2 is a section view showing a schematic constitution of one of plate members for constituting the scattered ray absorption grid of the first embodiment. The scattered ray absorption grid 10 of the first embodiment is composed of a grid portion 14 (see FIG. 1) constituted by a plurality of plate members 13, which are formed by hardening powder 11 containing tungsten 50% by weight with binder 12 so as to have a spatial filling rate of40%. Each of the plate members for constituting a grid is manufactured by the following manufacturing steps in which tungsten and a polymer resin that is an organic binder (binder) are thermally kneaded, injected into a mold, and then cooled. First, 250 grams of thermoplastic polyurethane resin, which is an organic binder of pellet shape that has a melting point of 120xc2x0 C., was mixed into 5 kg of tungsten powder which have an average particle diameter of 7xcexc and contains tungsten 50% by weight. The mixture was dried at 110xc2x0 C. for three hours and dehydrated. Next, as shown in FIG. 3, the mixture 29 made of the pellet-shaped polyurethane resin and the tungsten powder was placed in a hopper 21 of a molding machine 20 and heated to 180xc2x0 C. in a barrel 22 of the molding machine 20 to be fluidized. Then, the mixture was kneaded by a rotation of a screw 23. Thereafter, the mixture made of the polyurethane resin and the tungsten powder that was fluidized in the barrel 22 was injected into a mold 24 for a grid. Then, the mixture made of the polyurethane resin and the tungsten powder injected into the mold 24 for a grid was cooled, and a mold product 25 as shown in FIG. 4 was taken out of the mold 24 for a grid. A spool 26 and a runner 27 were removed from the mold product 25, and one of slender and thin plate-shaped plate members 13 for constituting a grid having a thickness of 0.1 mm, a width of 10 mm, and a length of 440 mm was obtained, in which the tungsten powders were hardened with the polyurethane resin so as to have a spatial filling rate of 40%. Thereafter, the scattered ray absorption grid 10 was assembled using these plate members 13, and a good scattered ray absorption property was obtained.  less than Second Embodiment greater than  FIG. 5 is a sectional view showing a schematic constitution of one of the plate members of which the scattered ray absorption grid of a second embodiment of the present invention is constituted. FIG. 1 shows a schematic constitution of the scattered ray absorption grid 30 of the second embodiment which is constituted by use of a plurality of plate members. The scattered ray absorption grid 30 according to the second embodiment comprises a grid portion 36 (see FIG. 1) which is constituted by use of a plurality of plate members 35. Each of the plate members 35 for constituting a grid is constituted by arranging, on a substrate 34, a tungsten layer 33 formed by hardening a powder containing tungsten 50% by weight with a binder 32 so that the powder acquires a spatial filling rate of 40%. The plate member 35 is manufactured by the following manufacturing steps in which tungsten powder is dispersed in a solution obtained by allowing a polymer resin, which is an organic binder (binder), to dissolve into an organic solvent, and then this tungsten powder solution is coated on a polymer film to be a substrate and dried. First, 150 grams of an unsaturated polyester resin (Byron 300 made by Toyobo Co. Ltd.), which is an organic binder, was added to 5 kg of tungsten powder, which have an average particle diameter of 7xcexc and contain tungsten 50% by weight. Next, methyl ethyl ketone was added to the tungsten powder solution while agitating the tungsten powder solution by a propeller mixer, and an adjustment was made so that the solution had a viscosity of 20 poise. Thereafter, the tungsten powder solution was coated on polyethylene A terephthalate (PET) resin of a film state having a thickness of 20xcexc, which is a substrate, and the tungsten powder solution coated on the PET resin substrate 34 was dried. Then, each of the plate members 35 for constituting a grid was obtained in such a manner that on the first layer made of the film-shaped PET resin substrate 34, the tungsten layer 33 that is a second layer material obtained by hardening tungsten powder with an unsaturated polyester resin so that the tungsten powder shows a spatial filling rate of 40% was laminated, thus obtaining a thin plane having a thickness of 0.1 mm. And, a slender plate member having a width of 10 mm and a length of 440 mm was cut out from said plane. Thereafter, when the scattered ray absorption grid 30 was assembled by use of the plurality of plate members 35 for constituting a grid, a good scattered ray absorption property was obtained.  less than Third Embodiment greater than  FIG. 6 is a sectional view showing a schematic constitution of one of the plate members for constituting a grid by which the scattered ray absorption grid of a third embodiment of the present invention is constituted. FIG. 1 shows a schematic constitution of the scattered ray absorption grid 40 of the third embodiment which is constituted by use of a plurality of plate members. The scattered ray absorption grid 40 according the third embodiment is composed of a grid portion 44 (see FIG. 1) constituted by use of a plurality of plate members 43, which are formed by hardening tungsten powder 41 containing tungsten 60% by weight with a binder 42 so as to show a spatial filling rate of 50%. Each of the plate members 43 for constituting a grid is manufactured by the following manufacturing steps in which tungsten powder 41 and lead solder (an alloy with lead and tin as main constituents) which acts as a binder are thermally kneaded, and extruded through a thin rectangular slit, thus obtaining each of the plate members for constituting a grid. First, 1700 grams of lead solder was mixed into 5 kg of tungsten powder. The tungsten powder have an average particle diameter of 7xcexc and contain tungsten 60% by weight; and the lead solder is particle-shaped binder having a melting point of 22020  C. which is less than that of tungsten. Next, as shown in FIG. 7, the mixture 59 described above was placed in a hopper 51 of an extrusion machine 50 and heated to 250xc2x0 C. in a barrel 52 to be fluidized. Then, the mixture was kneaded by a screw 53. Thereafter, the mixture of the lead solder and the tungsten powders in the barrel 52, which was fluidized, was continuously extruded onto a stainless steel plate 55 from a thin rectangular slit 54 having a width of about 0.1 mm. The mixture 59xe2x80x2 of the lead solder and the tungsten powder which had been extruded onto the stainless steel plate 55 was then cooled, and a slender plate material having a width of 10 mm and a length of 440 mm was cut out from a thin plane having a thickness of 0.1 mm. Thus, each of the plate members 43 for constituting a grid was obtained. Thereafter, when the scattered ray absorption grid 40 was assembled by use of the plurality of plate members 43 for constituting a grid, a good scattered ray absorption property was obtained.  less than Fourth Embodiment greater than  FIG. 8 is a section view showing a schematic constitution of a first original sheet for a plate member, which constitutes a scattered ray absorption grid of a fourth embodiment of the present invention. A schematic constitution of the scattered ray absorption grid of the fourth embodiment of the present invention is shown in FIG. 1, which is constituted by use of the plate members for constituting a grid, which are cut out from the first original sheet for the plate member. Note that, the original sheet for the plate member means a material before being cut out from the original sheet to a predetermined shape as the plate member for constituting a grid. While agitating solution with a propeller mixer, in which polyurethane resin of 130 g that is an organic polymer binder was added to powder of 5 kg formed of tungsten showing a purity of 99%, which has an average particle size of 5 xcexcm, an adjustment was made so that tungsten powder solution shows a viscosity of 20 P by adding methyl ethyl ketone to this substance. Thereafter, this tungsten powder solution was coated on a film-shaped PET resin substrate 51 having a thickness of 180 xcexcm, which is made of polyethylene terephthalate (PET) resin and serves as a substrate. The tungsten powder solution coated on the PET resin substrate 51 was dried, thus forming a tungsten layer 52 of a thickness of 100 xcexcm, which shows a spatial filling rate of 62%. Thus, the first original sheet 53 for the plate member was obtained (see FIG. 8). Thereafter, by cutting out a slender plate member from this first original sheet 53 for the plate member, which has a width of 10 mm and a length of 440 mm, a plate member 54 for constituting a grid was obtained (see FIG. 1), and a scattered ray absorption grid 50 was assembled by use of many of the plate members 54 for constituting a grid. Thus, a good scattered ray absorption property was obtained.  less than Fifth Embodiment greater than  FIG. 9 is a perspective view showing a schematic constitution of a calendar roll used for manufacturing a second original sheet for a plate member, which constitutes a scattered ray absorption grid of a fifth embodiment of the present invention. FIG. 10 is a section view showing a schematic constitution of the second original sheet for the plate member. A schematic constitution of the scattered ray absorption grid of the fifth embodiment of the present invention is shown in FIG. 1, which is constituted by use of the plate members for constituting a grid, which are cut out from the second original sheet for the plate member. As shown in FIG. 9, the first original sheet 53 for the plate member manufactured by the same steps as those in the fourth embodiment was allowed to pass through a calendar roll 65 comprising a thermal compression rolls 65A and 65B, whereby the first original sheet 53 for the plate member was thermally compressed at temperature of 70xc2x0 C. and at pressure of 50 MPa. Thus, the second original sheet 63 for the plate member (see FIG. 10) was obtained, in which a tungsten layer 62 of a thickness of 90 xcexcm showing a spatial filling rate of 70% was laminated on a PET resin substrate 61. Thereafter, a plate member 64 for constituting a grid was obtained by cutting out a slender plate member from the second original sheet 63 for the plate member, which has a width of 10 mm and a length of 440 mm. A scattered ray absorption grid 60 was assembled by use of many of the plate members 64 for constituting a grid. A good scattered ray absorption property was obtained.  less than Sixth Embodiment greater than  FIG. 11 is a section view showing a schematic constitution of a third original sheet for a plate member, which constitutes a scattered ray absorption grid of a sixth embodiment of the present invention. FIG. 12 is a perspective view showing a lamination block body formed by laminating the plurality of third original sheets for the plate member so as to be superposed upon another. FIG. 13 is a perspective view showing a state where the lamination block body is sliced thus acquiring a lamination cut body. FIG. 14 is a drawing showing a state where the lamination cut body is sandwiched between a convex block and a concave block, thus holding the lamination cut body therebetween. FIG. 15 is a drawing showing the scattered ray absorption grid of the sixth embodiment of the present invention. First, as shown in FIG. 11, a line-shaped adhering layer 64 made of polyester resin was coated by a thickness of 10 xcexcm on the PET resin substrate 61 opposite to the tungsten layer 62 of the original sheet 63 for the plate member, which was obtained in the fifth embodiment. Thus, an original sheet 65 for a plate member was formed. Next, as shown in FIG. 12, the foregoing original sheet 65 for the plate member and a resin spacer 65xe2x80x2 having the same shape as that of the original sheet 65 and a different thickness from that of the original sheet 65 were alternately superposed upon another in plural number. A lamination body formed in such a manner was kept in atmosphere at temperature of 90xc2x0 C. and at pressure of 20 MPa for 50 minutes, and then cooled, thus forming a lamination block body 66. Next, as shown in FIG. 13, this lamination block body 66 is sliced by use of a band saw to a width of 5 mm, and a cross section of the lamination block body 66 cut by the band saw was polished. Thus, a lamination cut body 67 was obtained. Next, as shown in FIG. 14, this lamination cut body 67 was sandwiched between a semicylindrical convex block 68 made of aluminum and a concave block 68xe2x80x2 having a shape obtained by transferring the semicylindrical shape thereto, and kept in atmosphere of temperature of 90xc2x0 C. for 50 minutes, followed by cooling. Then, the lamination cut body 67 was taken out therefrom. Thus, a scattered ray absorption grid 69 having a radius of curvature of 1.8 m in which a center of curvature of an arc-shaped curved surface converges on the straight line L1 as shown in FIG. 15 was obtained, and this scattered ray absorption grid 69 showed a good scattered ray absorption property.  less than Seventh Embodiment greater than  FIG. 16 is a section view showing a schematic constitution of a fourth plate member for constituting a grid, which constitutes a scattered ray absorption grid of a seventh embodiment of the present invention. FIG. 17 is a perspective view of a rectangular material for constituting a grid obtained by cutting the fourth plate member for constituting a grid. FIG. 18 is a perspective view of a rectangular block body for constituting a grid, which is formed by arranging the rectangular materials for constituting a grid and adhering them to each other. FIG. 19 is a perspective view of the scattered ray absorption grid of the seventh embodiment of the present invention, which is formed by adhering a top plate and a lower plate to the rectangular block body for constituting a grid. First, as shown in FIG. 16, line-shaped polyester resin was coated on the PET resin substrate 51 opposite to the tungsten layer 52 of the first original sheet 53 for the plate member manufactured by the same steps as those in the fourth embodiment, thus laminating a line-shaped polyester resin adhering layer 71 of a thickness of 40 xcexcm thereon. Thus, a fourth original sheet 72 for a plate member was prepared. This fourth original sheet 72 for the plate member was cut to be a rectangular shape having a width of 5 mm, thus obtaining a rectangular material 73 for constituting a grid as shown in FIG. 17. The rectangular material 73 for constituting a grid and a resin spacer 73xe2x80x2 having the same shape as that of the material 73 and a different thickness from that of the material 73 were alternately arranged and sequentially adhered to each other so that directions of rectangular surfaces of the materials 73 having a width of 5 mm converge on the straight line L2 apart from the materials 73 by 1.8 m as shown in FIG. 18. Thus, a rectangular block body 74 for constituting a grid was formed. Note that, when the rectangular material 73 and the resin spacer 73xe2x80x2 were adhered, each rectangular material 73 and each resin spacer 73xe2x80x2 were made to be inclined so as to converge on the line L2 by allowing an adhering layer of a thickness of 40 xcexcm to flow, and fixedly adhere to each other. Next, a top plate 75 and a lower plate 76 which have a thickness of 0.3 mm were adhered respectively to a converging side and a diverging side of the rectangular material 73 for constituting a grid which constitutes the foregoing rectangular block body 74 for constituting a grid. Thus, a scattered ray absorption grid 70 as shown in FIG. 19 was obtained, in which each of the rectangular materials 73 is arranged so as to converge toward the line L2 apart therefrom by 1.8 m. This scattered ray absorption grid 70 showed a good scattered ray absorption property.  less than Eighth Embodiment greater than  FIG. 20 is a section view showing a schematic constitution of a fifth original sheet for a plate member, which constitutes a scattered ray absorption grid of an eighth embodiment of the present invention. In FIG. 1, shown is a schematic constitution of the scattered ray absorption grid of the eighth embodiment of the present invention, which is constituted by use of plate members for constituting a grid, which are cut out from the fifth original sheet for the plate member. While agitating solution obtained by adding polyurethane resin of 130 g to powder of 5 kg formed of tungsten carbide WC having an average particle size of 4 xcexcm with a propeller mixer, methyl ethyl ketone was added to this substance, and a viscosity of the tungsten carbide powder solution was adjusted so as to be 20 P. The tungsten carbide is tungsten compound having a purity of 99%, and the polyurethane resin is an organic high polymer binder. Thereafter, this tungsten carbide powder solution was coated on a film-shaped PET resin substrate 81 made of polyethylene terephthalate (PET) resin. The PET resin substrate 81 is a substrate having a thickness of 180 xcexcm. The tungsten carbide powder solution coated on this PET resin substrate 81 was dried, thus forming a tungsten carbide layer 82 which has a spatial filling rate of 60% and a thickness of 150 xcexcm. Thus, the fifth original sheet 83 for the plate member as shown in FIG. 20 was obtained. Thereafter, a slender plate material having a width of 10 mm and a thickness of 440 mm was cut out from the fifth original sheet 83 for the plate member, whereby a plate member 84 for constituting a grid was obtained. A scattered ray absorption grid 80 was assembled by use of many of the plate members 84, and a good scattered ray absorption property was obtained.  less than Ninth Embodiment greater than  FIG. 21 is a section view showing a schematic constitution of a sixth original sheet for a plate member which constitutes a scattered ray absorption grid of a ninth embodiment of the present invention. Furthermore, in FIG. 1, shown is the scattered ray absorption grid of the ninth embodiment of the present invention, which is constituted by use of plate members for constituting a grid cut out from the sixth original sheet for the plate member. While agitating tungsten powder solution obtained by adding polyurethane resin of 80 g to powder with a propeller mixer, methyl ethyl ketone was added to this solution. The tungsten powder solution was prepared in such a manner that polyurethane resin, as an organic high polymer binder, of 80 g was added to powder obtained by mixing powder of 3.5 kg formed of tungsten having an average particle size of 5 xcexcm and a purity of 99% with powder of 1.5 kg formed of tungsten having an average particle size of 1.5 xcexcm and a purity of 99%. By the addition of the methyl ethyl ketone to the above tungsten powder solution, its viscosity was adjusted so as to be 20 P. Thereafter, this tungsten powder solution was coated on a film-shaped PET resin substrate 91 having a thickness of 180 xcexcm, which is made of polyethylene terephthalate (PET) resin and serves as a substrate. The tungsten powder solution coated on the PET resin substrate 51 was dried, thus forming a tungsten layer 92 of a thickness of 100 xcexcm, which shows a spatial filling rate of 66%. Thus, the sixth original sheet 93 for the plate member was obtained (see FIG. 21). Then, a slender plate material having a width of 10 mm and a thickness of 440 mm was cut out from the sixth original sheet 93 for the plate member, whereby a plate member 94 for constituting a grid was obtained. A scattered ray absorption grid 90 (see FIG. 1) was assembled by use of many of the plate members 94, and a good scattered ray absorption property was obtained.  less than Tenth Embodiment greater than  FIG. 22 is a perspective view showing a schematic constitution of a calendar roll used for manufacturing a seventh original sheet for a plate member, which constitutes a scattered ray absorption grid of a tenth embodiment of the present invention. FIG. 23 is a conceptional view showing a state where a filling density of tungsten in the seventh original sheet for the plate member is increased. A schematic constitution of the scattered ray absorption grid of the tenth embodiment of the present invention is shown in FIG. 1, which is constituted by use of the plate members for constituting a grid, which are cut out from the seventh original sheet for the plate member. As shown in FIG. 22, the sixth original sheet 93 for the plate member manufactured by the same steps as those in the ninth embodiment was allowed to pass through a calendar roll 65 comprising a thermal compression rolls 65A and 65B, whereby the original sheet 93 was thermally compressed at temperature of 70xc2x0 C. and at pressure of 50 MPa. Thus, the seventh original sheet 96 for the plate member, which has a tungsten layer 95 of a thickness of 92 xcexcm showing a spatial filling rate of 72%, was obtained. As shown in FIG. 23, in the seventh original sheet 96 for the plate member, small particles S that are powders formed of tungsten having an average particle size of 1.5 xcexcm enter between large particles B that are powders formed of tungsten having an average particle size of 5 xcexcm, and the small particles S fill spatially between the large particles B effectively. Accordingly, it is possible to further increase the filling density of the tungsten in the tungsten layer 95 of the seventh original sheet 96 for the plate member compared to the tungsten layer 92 of the sixth original sheet 93 for the plate member. Thereafter, a plate member 97 for constituting a grid was obtained by cutting out a slender plate member from the seventh original sheet 96 for the plate member, which has a width of 10 mm and a length of 440 mm. A scattered ray absorption grid 98 was assembled by use of many of the plate members 97. A good scattered ray absorption property was obtained. In each of the foregoing embodiments, though the content of the tungsten in the powder and the spatial filling rate of the powder in the plate member formed by said powder are shown by numerical values, the content and the spatial filling rate are not limited to this range. When the scattered ray absorption grid is constituted either by use of the plate members for constituting a grid obtained by hardening the powder containing tungsten 50% by weight or more with the binder so that the powders show the spatial filling rate of 40% or more, or by use of the plate members obtained in such a manner that the powder containing tungsten 50% by weight or more are hardened with the binder so that the powders show the spatial filling rate of 40% or more, a good scattered ray absorption property is obtained similarly to the foregoing embodiments. Furthermore, the spacer filled between the plate members for constituting a grid (13, 35, 43, 54, 64, 84, 94 and 97 in FIG. 1), which constitute the scattered ray absorption grid in the foregoing embodiments, should be the one which shows lessened X-ray absorption. For example, aluminum, wood, paper, cloth, resin, unwoven fabric and foaming resin can be used as the foregoing spacer. According to the present invention as described above, the processing of the plate members for constituting a grid is very easy by using tungsten powder which has an excellent radiation absorption property, and productivity of the grid portion made of tungsten is enhanced. Accordingly, a scattered ray absorption grid which is relatively low in cost and shows an excellent scattered ray absorption property can be obtained.