U.S. Philips Corporation

Johannes T Van Roosmalen

Johannes T Klomp

Jacob Koorneef

Marcel Brouha

Robert H Fastenau

Matthijs J Baan Hofman

A method of manufacturing a color display tube having a magnetic quadrupole post-focusing mask, in which the mask is magnetized by magnetic field shaping means of soft iron, or the magnetic equivalent, having raised portions, for example strips placed against opposite sides of the mask sheet and subjected to an external strong magnetic field by an electromagnet to induce magnetic poles through the thickness of the mask sheet. The geometric arrangement of the raised portions of the field shaping means is such that cyclically a north pole, a south pole, a north pole and a south pole are induced into the sheet material surrounding each aperture. Using this technique, the entire area of a mask sheet can be magnetized in one operation. Also masks for small tubes and high definition tubes can be made.

Method of manufacturing a color display tube having a magnetic

A cathode-ray tube of the post-focusing type comprising color selection means in the form of a ferromagnetic plate having a large number of apertures. The plate is magnetized so that a magnetic quadrupole lens is formed in each aperture. The ferromagnetic plate consists of an Fe-Co-Cr alloy having 25-27% by weight of Co and the remainder essentially Fe.

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Eindhoven, Netherlands

Johannes T Van Roosmalen