Discoloration on color cathode ray tube and its correction system using L‐shaped magnetic material

Abstract Color cathode ray tubes (CRTs) have been used as display devices for television sets and computers. Color CRTs contain a shadow mask to select electron beams for a particular color. The shadow mask is made of very thin (0.1 to 0.25 mm) iron and is easily magnetized. When the shadow mask is magnetized, the magnetic field profile in the CRT is modified, causing discoloration due to the deviation of electron beam trajectory. To investigate the influence of the magnetization of the shadow mask on the electron trajectory, the magnetic characteristics of the shadow mask and its holder and magnetic field profile in the color CRT were analyzed using three‐dimensional magnetic field analysis. In addition, the influence of the magnetized shadow mask on the electron beam trajectory was calculated to find the quantity of mislanding. In this paper, the magnetic field control method by placing L‐shaped magnetic materials is proposed and it was proved experimentally that the correction of color discoloration can be achieved by this method.