| 摘要 |
PROBLEM TO BE SOLVED: To provide a cold cathode fluorescent lamp free from drastic brightness decrease by an ambient temperature as a back light for an LCD for a portable electronic device by setting the relative positional relation between the electrodes and an insulating space in such a relative position substantially as giving no ill effect on heat radiation of the electrodes in the heat insulating space. SOLUTION: A double-tube cold cathode fluorescent lamp 10 is constituted by forming a heat insulating space 8 between an outer tube 1 and inner tube 2, provided with electrodes 6, 6 in the tip parts of a lead wire extended inward penetrating sealing parts 4 formed in both sides of the inner tube 1, and lit by impressing the electrodes 6, 6. The interval between the inner tube 1 and the outer tube 2 is substantially uniform along the tube axis of the inner tube 1, and the interval is formed into a vacuum space by outer tube sealing parts 9, 9 or so-called diameter-contracted parts formed by contracting the outside diameter toward the inner tube 1 in parts a little inside from the ends in the left/right both ends of the outer tube, so as to be the heat insulating space 8. The electrodes 6, 6 are opposed with each other inside the outer tube sealing part 9, 9.
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