| 摘要 |
PROBLEM TO BE SOLVED: To reduce the weight of an envelope without extremely increasing stress or flexure by essentially composing a nearly rectangular image display area with at least an inner glass layer abutting on the inside of a vacuum envelope and the outer layer of a composite material comprising a light- transmissive resin and setting the Young's modulus of the light-transmissive resin at a specific percentage of that of glass. SOLUTION: Young's modulus EP of the light-transmissive resin is 1/10-1/5 of the Young's modulus EG of glass. Since the Young's modulus EG of glass for the vacuum envelope is 7,000-8,000 kgf/mm2, the light-transmissive resin having the Young's modulus EP of 800-1,100 kgf/mm2 at room temperature is desirable, and a poly-p-phenylene-based resin can be cited. By assuming the density of the light-transmissive resinρP and the density of glassρG,ρP3/EP is preferably smaller thanρG3/EG. In the case of multilayer board, generated stress is generally proportional to the flexure amount and the total thickness thereof, so that the weight thereof can be reduced as compared with a single- layer board, even if its bending stress is equivalent to that of the single-layer board.
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