Dual persistence screen for a cathode ray tube

Claim 2

A cathode ray tube according to claim 1 wherein said first layer is of a phosphor material having a persistence resulting from optical excitation that is longer than the persistences exhibited by the electron excited phosphor in said second and third screen layers.

Claim 3

A cathode ray tube according to claim 1 wherein said second layer has a peak wavelength of spectral energy emission that is less than that exhibited by either of said first and third layers, and wherein said third layer has a peak wavelength of spectral energy emission that is greater than that exhibited by said second layer and at least equal to that exhibited by said first layer.

Claim 4

A cathode ray tube according to claim 1 wherein the spectral energy emission of said first phosphor material is substantially in the yellow-green wavelength region, and wherein that of said second phosphor material is substantially in the blue wavelength region, and wherein that of said third phosphor material is substantially in the red wavelength region.

Claim 5

A cathode ray tube according to claim 1 wherein said optically excited first layer phosphor exhibits a substantially yellow-green phosphorescence of long persistence being at least one material selected from the group consisting of (Zn,Cd)S:Cu P-7 yellow, and ZnS:Cu P-2; and wherein said electron excited second layer of substantially blue-emitting phosphor is of substantially short persistence being at least one material selected from the group consisting of ZnS:Ag P-22 blue, and ZnS: Ag P-7 blue, said integral energy absorbing barrier on each second layer particle being formed of at least one metallic material selected from the group consisting of cobalt, iron, and nickel; and wherein said electron excited third layer substantially red-emitting high efficiency phosphor is of substantially short persistence being at least one P-22 RE material selected from the group consisting of YVO4:Eu, Y2O3:Eu, Gd2O3:Eu, and Y2O2S:Eu.

Claim 6

A dual persistence image display screen for use in an electron discharge device having electron beams of high and low velocities, said screen comprising: a first screen layer disposed on a screen supporting surface, said first layer being formed of a first phosphor material responsive to optical excitation and exhibiting a phosphorescence of substantially long persistence; a second screen layer disposed over said first layer and formed of a second phosphor material to provide optical excitation for said first phosphor material, said second layer phosphor being an electron responsive material whereof each phosphor particle has a modified peripheral non-excitable portion in the form of an integral electron energy absorbing barrier of predetermined depth to effect an energy threshold surrounding the unmodified core of the particle and limiting the excitation thereof to said high velocity electron beam, said second screen layer being of a thickness to substantially totally absorb the energy of said high velocity electron beam; and a third screen layer uniformly disposed over said second screen layer and being of a thickness less than that of said second screen layer, said third screen layer being formed of a third phosphor material responsive to both high and low velocity electron beam excitation and exhibiting a phosphorescence of substantially short persistence, said third phosphor material having a peAk wavelength of spectral energy emission of a value at least equalling that of the phosphor of said first screen layer.

Claim 7

An image display screen according to claim 7 wherein said first layer is of a phosphor material having a persistence resulting from optical excitation that is longer than the persistences exhibited by the electron excited phosphors in said second and third screen layers.

Claim 8

An image display screen according to claim 7 wherein said optically excited first layer phosphor exhibits a substantially yellow-green phosphorescence of long persistence being at least one material selected from the group consisting of (Zn,Cd)S:Cu P-7 yellow and ZnS:Cu P-2; and wherein said electron excited second layer of substantially blue-emitting phosphor is of substantially short persistence being at least one material selected from the group consisting of ZnS:Ag P-22 blue, and ZnS:Ag P-7 blue, said integral energy absorbing barrier on each second layer particle being formed of at least one metallic material selected from the group consisting of cobalt, iron, and nickel; and wherein said electron excited third layer substantially red-emitting high efficiency phosphor is of substantially short persistence being at least one P-22 RE material selected from the group consisting of YVO4:Eu, Y2O3:Eu, Gd2O3:Eu and Y2O2S:Eu.

Claim 9

A long persistence image display screen for use in an electron discharge device, said screen comprising: a first screen layer of an optically excited phosphor material exhibiting a phosphorescence of substantially long persistence; and a second screen layer of an electron excitable phosphor disposed directly on said first screen layer to furnish said optical excitation for said first layer, each particle of said second layer phosphor material being modified peripherally to effect a non-excitable encasement therearound in the form of an integral electron energy absorbing barrier of predetermined depth and energy threshold, said second layer having a thickness to substantially totally absorb the electron energy impinging thereon.