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Thermal deformation of a tension mask and beam landing shift for a perfectly flat CRT under localized heating

Thermal deformation of a tension mask under localized heating was analyzed using the finite element method. Landing shift of the electron beam could be predicted based on these analysis results. In the CRT, the landing shift of the electron beam due to thermal deformation of the tension mask made the color purity of the screen worse. In order to get the final results of thermal deformation, the tensile force within the mask and the welding processes between the rail and the extended mask had to be analyzed sequentially. Then, thermo-elastic finite element analysis was performed on every part inside the CRT including the tension mask. The analysis showed that thermal radiation was the main heat transfer mechanism. Because the tension mask has numerous slits, it was efficient to model it as a shell without slits, and the effective thermal conductivity and effective elastic modulus were introduced and calculated. From the displacement analysis results of the tension mask, landing shift of the electron beam could be predicted. Experiments were also performed to confirm our analysis results. Temperature distributions and beam landing shift of the tension mask were measured and the results were in good agreement with those of analysis.