P1 phosphor is the dielectric material commonly used as a viewable bistable storage target for storage cathode ray tubes such as taught in U.S. Pat. Nos. 3,293,433; 3,293;474; 3,531,675 and U.S. patent application Ser. No. 356,029, filed Apr. 30, 1973. This phosphor dielectric material has been found to have desirable dielectric characteristics to enable information written thereon via a deflected cathode ray beam of electrons to be stored for any length of time until it is desired to erase such stored information. This P1 phosphor material can also be used to display information via the deflected beam of electrons in a non-store mode of operation. Hence, the phosphor material provides bistable operation in store or non-store modes of operation depending upon which mode of operation is desired, and brightness of the visible image formed on the phosphor layer as well as image contrast, writing speed and erase speed are important features attributed to P1 phosphor.
While P1 phosphor has provided excellent operating characteristics as a bistable storage target for cathode ray tubes, the operating life of such target is not as great as desired. Operating life of CRT targets are dependent upon operator use and uniformity of screen usage.
U.S. Pat. No. 2,241,939 discloses manganese-activated zinc orthosilicate (P1) phosphor that is mixed with metal oxides, some of which can be rare earth oxides, which mixture is then subjected to heat thereby forming a specialized sensitized phosphor material for use in a mercury lamp to provide higher luminance efficiency.
U.S. Pat. No. 3,862,450 teaches the concept of bonding or adhering secondary electron emissive material on the surface of phosphor storage dielectric particles that are used to form the storage dielectric phosphor layer of a storage target of a direct-viewing bistable storage tube. Such storage dielectric layer increases the writing speed of the storage target and also the life thereof, but the increased target life is not acceptable.
U.S. patent application Ser. No. 658,977, filed Feb. 18, 1976 discloses the use of an admixture of P1 phosphor particles and yttrium oxide, or yttrium oxysulfide, or rare earth activated yttrium oxide or yttrium oxysulfide to provide a bistable storage target of greater life than that of the storage target of pure P1 phosphor; however the target life is not as long as directed.