U.S. Philips Corporation

Jan L Van Koesveld

Roelof Egbert Schuil

A cathode-ray tube provided with a luminescent screen comprising a luminescent indium orthoborate activated by trivalent chromium. The tube yields an efficient emission in the near infrared part of the spectrum. If the borate further comprises Eu as an activator, an efficient Eu.sup.3+ emission is obtained in addition to the Cr emission.

Cathode-ray tube provided with a luminescent indium orthoborate

A display tube comprising in an evacuated envelope means to generate at least one electron beam which is focused on a display screen and describes a field thereon, which display screen comprises a terbium-activated blue-luminescing phosphor on a carrier, and in which the light emitted by the phosphor falls through a filter. If the energy of the emissions of the phosphor which find their origin in the .sup.5 D.sub.3 -level of terbium is at least 40% of the energy of the emissions of all terbium levels and the filter has a transmission of more than 75% at those wavelengths where the .sup.5 D.sub.3 .fwdarw..sup.7 F.sub.5 and the .sup.5 D.sub.3 .fwdarw..sup.7 F.sub.4 emissions of terbium are located and the filter has a transmission of less than 10% at those wavelengths where the .sup.5 D.sub.4 .fwdarw..sup.7 F.sub.5 and the .sup.5 D.sub.4 .fwdarw..sup.7 F.sub.4 and the .sup.5 D.sub.4 .fwdarw..sup.7 F.sub.3 emissions of terbium are located so that the color point of the filtered light is located in the range x.ltoreq. 0.200 and y.ltoreq.0.100 in the CIE color triangle, a well saturated blue picture is displayed having a satisfactorily high energy efficiency.

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Eindhoven, Netherlands

Jan L Van Koesveld