| 摘要 |
PROBLEM TO BE SOLVED: To provide a shadow mask structure of color cathode-ray tubes which is capable of preventing mislanding of electron beams on corresponding phosphors in starting-up of a color cathode-ray tube. SOLUTION: In a starting-up time of a color cathode-ray tube, a shadow mask mechanism occurs a transient state of temperature as a mask frame 31 still stays around 20 deg.C even though a shadow mask 32 already reaches the range of 60 to 80 deg.C. In this time, the shadow mask 32 is expanded in the H direction, so that an electron beam passing hole 32c is also shifted in the H direction (to the outside). Hence, an angle as seen from a deflection center (not shown) of electron beams to their passing hole 32c becomes larger than its designed angle. Therefore, landing positions of the electron beams (not shown) on phosphors shift outwardly from corresponding phosphor positions (not shown). As a result, the electron beams may not land on their phosphors accurately, so that color contamination occurs by imbalance among brightness emitted from the phosphors due to a decrease in brightness from a mislanded phosphor. Therefore as a countermeasure, opposite major side mask frames 11a are limited in outward expansion by fixing between their opposite both ends with each tension control 13 which are made by same material as used for the mask frame 11.
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