| 摘要 |
This invention relates to an incandescent lamp bulb comprising a visible light transmitting and infrared ray reflecting film formed on at least either one of the inside and outside of a tubular, transparent bulb, said film being composed of a lamination of alternate high and low refractive index layers, wherein the optical film thickness of any one of the high reflective index layers ranges from 0.21 to 0.31 mu , that of the topmost low refractive index layer ranges from 1/2x0.21 to 1/2x0.31 mu , that of at least one low refractive index layer ranges from 2x0.21 to 2x0.31 mu , and that of any remainder low refractive index layer ranges from 0.21 to 0.31 mu .
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