PURPOSE: To restrain the thermal expansion of a shadow mask and prevent the chromatic aberration thereof due to doming by forming a shadow mask sheet metal via the use of a low thermal expansion alloy for an inner layer and non-aging steel for outer layers clamping the inner layer.
CONSTITUTION: A shadow mask sheet metal is formed as a three-layer structure body comprising an inner layer and two outer layers clamping the inner layer. A low thermal expansion alloy is used for the inner layer, while non-aging steel such as aluminum killed steel having excellent characteristics for blackening and press forming is used for the outer layers. One of the outer layers has a volumetric ratio between 0.01 and 0.5 for the inner layer, while the volumetric ratio of the other outer layer is taken between 0.01 and 0.5. As a result, a blackened film having uniform and high heat dissipation quality can be formed at a blackening process. Also, when the sheet metal is used for the shadow mask, the temperature rise and thermal expansion of the shadow mask can be restrained, thereby preventing chromatic aberration due to doming.
MATSUMOTO KAZUAKI
TSURU KIYOSHI
HAISHI HIROHISA
KASHIWAZAKI KICHIYA
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