| 摘要 |
A coil filament in which the volume is reduced as much as possible at the light emitting part in order to reduce the size of a bulb while enhancing the illuminance of illumination light field efficiently. A flatly wound flat coil filament (1) is arranged spirally or annularly such that the axis FL in the long side direction is in parallel with the central axis CL of the coil filament or intersects at an appropriate angle .alpha. including right angle, or arranged while aligning with the radial axis HL of the coil filament or at an appropriate angle .alpha. including the radial axis HL. Alternatively, the flat coil filament is formed into U-shape and a pair of U-shaped flat coil filaments are inserted mutually from the open end such that the inside of each closed end is in noncontact state, or the flat coil filament (1) is formed into a circle and, within the range of circle of circular double coil filaments (5, 10, 12), an appropriate number of linear or circular flat coil filaments (6, 7, 9, 11, 13, 14) are arranged in the direction of the central axis CL of the circle.
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