Fluorescent compositions and low-velocity electron excited fluorescent display devices utilizing the same

A low-velocity electron excited fluorescent display device comprising a sealed evacuated tube, an anodic plate enclosed in said tube having a fluorescent screen on one side thereof, and a cathode enclosed in said tube standing face to face with said fluorescent screen and emitting electrons which impinge upon said fluorescent screen and excite said fluorescent screen, wherein said fluorescent screen is composed of

• a fluorescent composition consisting essentially of a mechanical mixture of a conductive material selected from the group consisting of indium oxide (In.sub.2 O.sub.3), zinc oxide (ZnO), stannic oxide (SnO.sub.2), titanium dioxide (TiO.sub.2), tungsten oxide (WO.sub.3), niobium pentoxide (Nb.sub.2 O.sub.5), cadmium sulfide (CdS), copper sulfide (Cu.sub.2 S) and mixtures thereof, said conductive material having a particle diameter distribution wherein the median value is within the range of 2.5 to 14.mu. and standard deviation (log .sigma.) is not more than 0.7, and a phosphor selected from the group consisting of a blue emitting phosphor, a green emitting phosphor, a red emitting phosphor and a yellow emitting phosphor in a mixing weight ratio ranging from 1:99 to 1:4,
• said blue emitting phosphor being selected from the group consisting of a silver activated zinc sulfide phosphor (ZnS:Ag), a silver and aluminium activated zinc sulfide phosphor (ZnS:Ag,Al), a silver activated zinc sulfoselenide phosphor [Zn(S,Se):Ag], a silver and aluminium activated zinc sulfoselenide phosphor [Zn(S,Se):Ag,Al], a cerium activated yttrium silicate phosphor (Y.sub.2 SiO.sub.5 :Ce), a cerium activated strontium gallium sulfide phosphor (SrGa.sub.2 S.sub.4 :Ce), a cerium activated calcium magnesium silicate phosphor (Ca.sub.2 MgSiO.sub.5 :Ce), a titanium activated calcium magnesium phosphor [(Ca,Mg).sub.2 SiO.sub.4 :Ti], an europium activated barium magnesium aluminate phosphor [(Ba,Mg)O.sub.2.6Al.sub.2 O.sub.3 :Eu.sup.2+ ], an europium activated strontium barium phosphate phosphor, [(Sr,Ba).sub.3 (PO.sub.4).sub.2 :Eu.sup.2+ ], an europium activated calcium chloroborate phosphor (Ca.sub.2 B.sub.5 O.sub.9 Cl:Eu.sup.2+) and mixtures thereof,
• said green emitting phosphor being selected from the group consisting of a manganese activated zinc silicate phosphor (Zn.sub.2 SiO.sub.4 :Mn), a manganese and arsenic activated zinc silicate phosphor (Zn.sub.2 SiO.sub.4 :Mn,As), a terbium activated rare earth oxysulfide phosphor (Ln.sub.2 O.sub.2 S:Tb, wherein Ln is at least one element selected from the group consisting of Y, Gd, Lu and La), a cerium activated yttrium aluminium gallium oxide phosphor [Y.sub.3 (Al.sub.1-a,Ga.sub.a).sub.5 O.sub.12 :Ce, wherein a is 0.ltoreq.a.ltoreq.0.5], an europium activated strontium gallium sulfide phosphor (SrGa.sub.2 S.sub.4 :Eu.sup.2+), a copper and aluminium activated zinc cadmium sulfide phosphor [(Zn.sub.1-b,Cd.sub.b)S:Cu,Al, wherein b is 0.ltoreq.b.ltoreq.0.1], a copper activated zinc cadmium sulfide phosphor [(Zn.sub.1-c,Cd.sub.c)S:Cu, wherein c is 0.ltoreq.c.ltoreq.0.1], a silver activated zinc cadmium sulfide phosphor [(Zn.sub.1-d,Cd.sub.d)S:Ag, wherein d is 0.3.ltoreq.d.ltoreq.0.5], a silver and aluminium activated zinc cadmium sulfide phosphor [(Zn.sub.1-e,Cd.sub.e)S:Ag,Al, wherein e is 0.2.ltoreq.e.ltoreq.0.5] and mixtures thereof,
• said red emitting phosphor being selected from the group consisting of an europium activated rare earth oxysulfide phosphor (Ln.sub.2 O.sub.2 S:Eu, wherein Ln has the same definition as described above), an europium activated rare earth oxide phosphor (Ln.sub.2 O.sub.3 :Eu, wherein Ln has the same definition as described above), an europium activated rare earth vanadate phosphor (LnVO.sub.4 :Eu, wherein Ln has the same definition as described above), an europium activated rare earth borate phosphor (LnBO.sub.3 :Eu, wherein Ln has the same definition as described above), an europium activated rare earth phosphate phosphor (LnPO.sub.4 :Eu, wherein Ln has the same definition as described above), a silver activated zinc cadmium sulfide phosphor [(Zn.sub.1-f, Cd.sub.f)S:Ag, wherein f is 0.65.ltoreq.f.ltoreq.0.9], a manganese activated zinc phosphate phosphor [Zn.sub.3 (PO.sub.4).sub.2 :Mn], a manganese activated cadmium borate phosphor (Cd.sub.2 B.sub.2 O.sub.5 :Mn) and mixtures thereof, and
• said yellow emitting phosphor being selected from the group consisting of a copper activated zinc sulfoselenide phosphor [Zn(S.sub.1-g,Se.sub.g):Cu, wherein g is 0.05.ltoreq.g.ltoreq.0.6], a copper and aluminium activated zinc sulfoselenide phosphor [Zn(S.sub.1-h,Se.sub.h):Cu,Al, wherein h is 0.05.ltoreq.h.ltoreq.0.6], a silver activated zinc cadmium sulfide phosphor [(Zn.sub.1-i,Cd.sub.i)S:Ag, wherein i is 0.5<i.ltoreq.0.7], a silver and aluminium activated zinc cadmium sulfide phosphor [(Zn.sub.1-j,Cd.sub.j)S:Ag,Al, wherein j is 0.5<j.ltoreq.0.7], a gold and aluminium activated zinc cadmium sulfide phosphor [(Zn.sub.1-k,Cd.sub.k)S:Au,Al, wherein k is 0.ltoreq.k.ltoreq.0.2], a copper activated zinc cadmium sulfide phosphor [(Zn.sub.1-l,Cd.sub.l)S:Cu, wherein l is 0.1<l.ltoreq.0.2], a copper and aluminium activated zinc cadmium sulfide phosphor [(Zn.sub.1-m, Cd.sub.m)S:Cu,Al, wherein m is 0.1<m.ltoreq.0.2], lead and manganese activated calcium silicate phosphor (CaSiO.sub.3 :Pb,Mn) and mixtures thereof.