Dai Nippon Toryo Co., Ltd.

Nippon Hoso' Kyokai

Kasei Optonix, Ltd.

Kinichiro Narita

Takashi Hase

Akiyasu Kagami

Yoshiyuki Mimura

Minoru Hiraki

Ryuya Toyonaga

Junro Koike

Takehiro Kojima

Koichi Takahashi

Masatake Yoshikawa

Yoshinori Tanigami

Masaru Naitou

A process for recovering highly pure rare earth oxides from a waste rare earth phosphor containing at least Fe and/or Ca as impurities, which comprises dissolving the waste rare earth phosphor in an excess amount of a strong acid capable of dissolving the waste rare earth phosphor, adding to the solution at a temperature of at least 70.degree. C. oxalic acid in an amount of from 0.3 to 1.8 times the theoretical amount to obtain precipitates of rare earth oxalates, washing the precipitates with warm water having a temperature of at least 50.degree. C. and then baking them.

Process for recovering highly pure rare earth oxides from a waste rare

Fluorescent compositions which contain indium oxide and one phosphor selected from the group hereinafter defined in a weight ratio within the range of 1/9 to 9/1l, and fluorescent display devices having said fluorescent compositions in the form of a fluorescent screen, which can emit green, blue or red light under low-velocity electron excitation, said group consisting of a terbium activated lanthanum oxysulfide phosphor or a terbium activated lanthanum yttrium oxysulfide phosphor [(La.sub.1-x, Y.sub.x).sub.2 O.sub.2 S:Tb, wherein O.ltoreq.x &lt;1], a copper and aluminum activated zinc cadmium sulfide phosphor [(Zn.sub.1-x, Cd.sub.x)S: Cu, Al, wherein O.gtoreq.x .ltoreq.0.1], a europium activated strontium gallium sulfide phosphor (SrGa.sub.2 S.sub.4 :Eu.sup.2+), a cerium activated yttrium aluminum gallate phosphor [Y.sub.3 (Al.sub.1-y, Ga.sub.y).sub.5 O.sub.12 :Ce, wherein O.ltoreq.y.ltoreq.O.5], a manganese activated zinc silicate phosphor (Zn.sub.2 SiO.sub.4 :Mn), a terbium activated yttrium oxysulfide phosphor (Y.sub.2 O.sub.2 S:Tb), a silver activated zinc sulfide phosphor (ZnS:Ag), a europium activated yttrium oxysulfide phosphor (Y.sub.2 O.sub.2 S:Eu), a europium activated yttrium oxide phosphor (Y.sub.2 O.sub.3 :Eu), and a europium activated yttrium vanadate phosphor (YVO.sub.4 :Eu).

Low-velocity electron excited fluorescent display device

Fluorescent compositions which contain indium oxide and one phosphor selected from the group hereinafter defined in a weight ratio within the range of 1/9 to 9/1, and fluorescent display devices having said fluorescent compositions in the form of a fluorescent screen, which can emit green, blue or red light under low-velocity electron excitation, said group consisting of a terbium activated lanthanum oxysulfide phosphor or a terbium activated lanthanum yttrium oxysulfide phosphor [(La.sub.1-x,Y.sub.x).sub.2 O.sub.2 S:Tb, wherein 0.ltoreq.x&lt;1], a copper and aluminium activated zinc cadmium sulfide phosphor [(Zn.sub.1-x,Cd.sub.x)S:Cu, Al, wherein 0.ltoreq.x.ltoreq.0.1], a europium activated strontium gallium sulfide phosphor (SrGa.sub.2 S.sub.4 :Eu.sup.2+), a cerium activated yttrium aluminium gallate phosphor [Y.sub.3 (Al.sub.1-y,Ga.sub.y).sub.5 O.sub.12 :Ce, wherein 0.ltoreq.y.ltoreq.0.5], a manganese activated zinc silicate phosphor (Zn.sub.2 SiO.sub.4 :Mn), a terbium activated yttrium oxysulfide phosphor (Y.sub.2 O.sub.2 S:Tb), a silver activated zinc sulfide phosphor (ZnS:Ag), a europium activated yttrium oxysulfide phosphor (Y.sub.2 O.sub.2 S:Eu), a europium activated yttrium oxide phosphor (Y.sub.2 O.sub.3 :Eu), and a europium activated yttrium vanadate phosphor (YVO.sub.4 :Eu).

A process for preparing a divalent europium activated alkaline earth metal aluminate phosphor represented by the composition formula

Process for preparing a divalent europium activated alkaline earth metal

Fluorescent compositions which contain zinc oxide and one phosphor selected from the group hereinafter defined in a weight ratio within the range of 1/9 to 9/1, and fluorescent display devices having said fluorescent compositions in the form of a fluorescent screen, which can emit green, blue or red light under low-velocity electron excitation, said group consisting of a copper and aluminium activated zinc cadmium sulfide phosphor [(Zn.sub.1-x, Cd.sub.x)S:Cu, Al, wherein 0.ltoreq.x.ltoreq.0.1], a cerium activated yttrium aluminium gallium oxide phosphor [Y.sub.3 (Al.sub.1-y, Ga.sub.y).sub.5 O.sub.12 :Ce, wherein 0.ltoreq.y.ltoreq.0.5], a manganese activated zinc silicate phosphor (Zn.sub.2 SiO.sub.4 :Mn), a terbium activated yttrium lanthanum oxysulfide phosphor [(Y.sub.1-z, La.sub.z).sub.2 O.sub.2 S: Tb, wherein 0.ltoreq.z.ltoreq.1], a europium activated strontium gallium sulfide phosphor (SrGa.sub.2 S.sub.4 :Eu.sup.2+), a silver activated zinc sulfide phosphor (ZnS:Ag), and a europium activated yttrium oxysulfide phosphor (Y.sub.2 O.sub.2 S:Eu).

Fluorescent compositions which contain zinc oxide and one phosphor selected from the group hereinafter defined in a weight ratio within the range of 1/9 to 9/1, and fluorescent display devices having said fluorescent compositions in the form of a fluorescent screen, which can emit green, blue or red light under low-velocity electron excitation, said group consisting of a copper and aluminium activated zinc cadmium sulfide phosphor [(Zn.sub.1-x, Cd.sub.x)S:Cu, Al, wherein 0.ltoreq.x.ltoreq.0.1], a cerium activated yttrium aluminium gallium oxide phosphor [Y.sub.3 (Al.sub.1-y, Ga.sub.y).sub.5 O.sub.12 :Ce, wherein 0.ltoreq.y.ltoreq.0.5], a manganese activated zinc silicate phosphor (Zn.sub.2 SiO.sub.4 :Mn), a terbium activated yttrium lanthanum oxysulfide phosphor [(Y.sub.1-z, La.sub.z).sub.2 O.sub.2 S:Tb, wherein 0.ltoreq.z.ltoreq.1], a europium activated strontium gallium sulfide phosphor (SrGa.sub.2 S.sub.4 :Eu.sup.2+), a silver activated zinc sulfide phosphor (ZnS:Ag), and a europium activated yttrium oxysulfide phosphor (Y.sub.2 O.sub.2 S:Eu).

Fluorescent compositions

Fluorescent compositions for low-velocity electron excited fluorescent

A fluorescent display device capable of emitting blue to green light of high luminance and purity is composed of a vacuum tube having an anodic plate bearing thereon a fluorescent screen and a cathode facing the fluorescent screen. The fluorescent screen comprises a gallate-based phosphor represented by the formula

In an air-tight at least partially transparent container, a phosphor, a gas or gas mixture and a pair of discharging electrodes are contained. The discharge gap is in the range of 0.1 to 3.0mm, and the pressure of the gas or gas mixture sealed in the container is such that the product of the pressure and the discharge gap is in the range of 30 to 300 Torr.mm. The gas or gas mixture has discharge radiation spectra within the region of wavelength shorter than 200nm. The phosphor is a manganese activated aluminate phosphor represented by the formula

Gaseous discharge light emitting element

Fluorescent compositions which contain indium oxide and one phosphor selected from the group hereinafter defined in a weight ratio within the range of 1/9 to 9/1, and fluorescent display devices having said fluorescent compositions in the form of a fluorescent screen, which can emit green, blue or red light under low-velocity electron excitation, said group consisting of a terbium activated lanthanum oxysulfide phosphor or a terbium activated lanthanum yttrium oxysulfide phosphor [(La.sub.1-x, Y.sub.x).sub.2 O.sub.2 S:Tb, wherein 0.ltoreq.x&lt;1], a copper and aluminium activated zinc cadmium sulfide phosphor [(Zn.sub.1-x, Cd.sub.x)S: Cu, Al, wherein 0.ltoreq.x.ltoreq.0.1], a europium activated strontium gallium sulfide phosphor (SrGa.sub.2 S.sub.4 :Eu.sup.2+), a cerium activated yttrium aluminium gallate phosphor [Y.sub.3 (Al.sub.1-y, Ga.sub.y).sub.5 O.sub.12 :Ce, wherein 0.ltoreq.y.ltoreq.0.5], a manganese activated zinc silicate phosphor (Zn.sub.2 SiO.sub.4 :Mn), a terbium activated yttrium oxysulfide phosphor (Y.sub.2 O.sub.2 S:Tb), a silver activated zinc sulfide phosphor (ZnS:Ag), a europium activated yttrium oxysulfide phosphor (Y.sub.2 O.sub.2 S:Eu), a europium activated yttrium oxide phosphor (Y.sub.2 O.sub.3 :Eu), and a europium activated yttrium vanadate phosphor (YVO.sub.4 :Eu).

Growing community of inventors

Chigasaki, Japan

Kinichiro Narita