Analysis of shadow mask thermal deformation and prediction of beam landing shifts for color CRT

In the cathode ray tube (CRT), beam landing shifts on the phosphor screen mainly result from the thermal deformation of the mask frame assembly and deteriorate the color purity. The thermal deformation of the mask frame assembly is analyzed by using the finite element method (FEM) and the beam landing shifts are predicted. For a realistic analysis, the apparent thermal conductivity and the apparent elastic modulus are calculated and the shadow mask is modeled as a shell without apertures. All the parts inside the CRT are modeled and the each radiative effect is considered. Then finite element analysis is performed for transient thermo-elastic deformation of the mask frame assembly and the beam landing shifts are calculated. Experiments are performed for a 17" CRT to validate the FEM analysis. The temperatures of all parts inside the CRT and the beam landing shift on the panel are measured and the results are discussed in comparison with the results of the FEM analysis. From the study, we show that this analysis method can be applicable for designing a mask frame assembly of a CRT that results in a landing shift of the order of a few micro-meters.