Radiographic image conversion screens

Claim 1

A radiographic image conversion screen, having a speed and/or an image quality at least equal to that of a conventional radiographic image conversion screen which has only a green emitting rare earth phosphor layer, consisting essentially of: (a) a support; (b) a first fluorescent layer formed on said support and consisting essentially of a blue emitting phosphor which is selected from the group consisting of: (I) a yttrium or yttrium-gadolinium oxysulfide phosphor represented by the formula: (Y.sub.1-c-d-e, Gd.sub.c, Tb.sub.d, Tm.sub.e).sub.2 O.sub.2 S where c, d and e are numbers within the ranges of 0≦c≦0.60, 0.0005≦d≦0.02 and 0≦e≦0.01, respectively; and (II) a rare earth oxyhalide phosphor represented by the formula: (Ln'.sub.1-x-y-z, Tb.sub.x, Tm.sub.y, Yb.sub.z)OX where Ln' is at least one element selected from the group consisting of lanthanum and gadolinium, X is at least one element selected from the group consisting of chlorine and bromine, and x, y and z are numbers within the ranges of 0≦x≦0.01, 0≦y≦0.01, 0≦z≦0.005 and 0≦x+y; and (c) a second fluorescent layer formed on said first fluorescent layer and consisting essentially of a green emitting rare earth oxysulfide phosphor represented by the formula: (Ln.sub.1-a-b, Tb.sub.a, Tm.sub.b).sub.2 O.sub.2 S where Ln is at least one element selected from the group consisting of lanthanum, gadolinium and lutetium, and a and b are numbers within the ranges of 0.0005≦a≦0.09 and 0≦b≦0.01, respectively, or the formula: (Y.sub.1-i-a-b, Ln.sub.i, Tb.sub.a, Tm.sub.b).sub.2 O.sub.2 S where Ln is at least one element selected from the group consisting of lanthanum, gadolinium and lutetium, and i, a and b are numbers within the ranges of 0.65≦i≦0.95, 0.0005≦a≦0.09 and 0≦b≦0.01, respectively.

Claim 9

A method of obtaining a radiographic image of a subject with a radiographic apparatus, comprising: obtaining a radiographic image of said subject with said radiographic device in which an image conversion screen, having a speed and/or an image quality at least equal to that of a conventional radiographic image conversion screen which has only a green emitting rare earth phosphor layer, consists essentially of: (a) a support; (b) a first fluorescent layer formed on said support and consisting essentially of a blue emitting phosphor which is selected from the group consisting of: (I) a yttrium or yttrium-gadolinium oxysulfide phosphor represented by the formula: (Y.sub.1-c-d-e, Gd.sub.c, Tb.sub.d, Tm.sub.e).sub.2 O.sub.2 S where c, d and e are numbers within the ranges of 0≦c≦0.60, 0.0005≦d≦0.02 and 0≦e≦0.01, respectively; and (II) a rare earth oxyhalide phosphor represented by the formula: (Ln'.sub.1-x-y-z, Tb.sub.x, Tm.sub.y, Yb.sub.z)OX where Ln' is at least one element selected from the group consisting of lanthanum and gadolinium, X is at least one element selected from the group consisting of chlorine and bromine, and x, y and z are numbers within the ranges of 0≦x≦0.01, 0≦y≦0.01, 0≦z≦0.005 and 0≦x+y; and (c) a second fluorescent layer formed on said first fluorescent layer and consisting essentially of a green emitting rare earth oxysulfide phosphor represented by the formula: (Ln.sub.1-a-b, Tb.sub.a, Tm.sub.b).sub.2 O.sub.2 S where Ln is at least one element selected from the group consisting of lanthanum, gadolinium and lutetium, and a and b are numbers within the ranges of 0.0005≦a≦0.09 and 0≦b≦0.01, respectively, or the formula: (Y.sub.1-i-a-b, Ln.sub.i, Tb.sub.a, Tm.sub.b).sub.2 O.sub.2 S where Ln is at least one element selected from the group consisting of lanthanum, gadolinium and lutetium, and i, a and b are numbers within the ranges of 0.65≦i≦0.95, 0.0005≦a≦0.09 and 0≦b≦0.01, respectively.

Claim 10

A method of obtaining a radiographic image of a subject with a radiographic apparatus, comprising: obtaining a radiographic image of said subject with said radiographic device in which an image conversion screen, having a speed and/or an image quality at least equal to that of a conventional radiographic image conversion screen which has only a green emitting rare earth phosphor layer, consists essentially of: (a) a support; (b) a first fluorescent layer formed on said support and consisting essentially of a blue emitting phosphor which is selected from the group consisting of: (I) a yttrium or yttrium-gadolinium oxysulfide phosphor represented by the formula: (Y.sub.1-c-d-e, Gd.sub.c, Tb.sub.d, Tm.sub.e).sub.2 O.sub.2 S where c, d and e are numbers within the ranges of 0≦c≦0.60, 0.0005≦d≦0.02 and 0≦e≦0.01, respectively; and (II) a rare earth oxyhalide phosphor represented by the formula: (Ln'.sub.1-x-y-z, Tb.sub.x, Tm.sub.y, Yb.sub.z)OX where Ln' is at least one element selected from the group consisting of lanthanum and gadolinium, X is at least one element selected from the group consisting of chlorine and bromine, and x, y and z are numbers within the ranges of 0≦x≦0.01, 0≦y≦0.01, 0≦z≦0.005 and 0≦x+y; and (c) a second fluorescent layer formed on said first fluorescent layer and consisting essentially of a green emitting rare earth oxysulfide phosphor represented by the formula: (Ln.sub.1-a-b, Tb.sub.a, Tm.sub.b).sub.2 O.sub.2 S where Ln is at least one element selected from the group consisting of lanthanum, gadolinium and lutetium, and a and b are numbers within the ranges of 0.0005≦a≦0.09 and 0≦b≦0.01, respectively, or the formula: (Y.sub.1-i-a-b, Ln.sub.i, Tb.sub.a, Tm.sub.b).sub.2 O.sub.2 S where Ln is at least one element selected from the group consisting of lanthanum, gadolinium and lutetium, and i, a and b are numbers within the ranges of 0.65≦i≦0.95, 0.0005≦a≦0.09 and 0≦b≦0.01, respectively.