Phosphor coating method and arc tube

Abstract

A method of uniformly applying a phosphor onto the internal surface of a glass tube of spiral configuration having opening at its both ends. While holding glass tube (11) of double spiral configuration so as to cause openings (24,25) thereof to position in the superior region, phosphor suspension (26) is poured through one of the openings. The glass tube is shaken so that the phosphor suspension covers the entirety of the internal surface thereof. The glass tube is turned upside down and held so as to cause the openings to position in the inferior region. While rotating the glass tube around pivot axis (A), the phosphor suspension is caused to flow out. The glass tube is turned upside down once more and held so as to cause the openings to position in the superior region for a given period of time with the result that the phosphor suspension is caused to flow to uniformize the thickness thereof. Further once more the glass tube is turned upside down and held so as to cause the openings to position in the inferior region. In that state, while applying hot air outside, ordinary-temperature dry air is blown into the interior of the glass tube to thereby carry out preliminary drying. Thereafter, the glass tube is placed in a drying oven, and drying is performed while blowing hot air into the interior of the glass tube.

Description

technical field [0001] The invention relates to a luminescent tube and a phosphor coating method. Background technique [0002] A fluorescent lamp has a phosphor film formed on the inner surface of its glass tube. This phosphor film is formed by sintering after preparing a phosphor suspension and applying it. [0003] However, in order to meet the era of energy saving, the development of various fluorescent lamps that can replace ordinary light bulbs is being advanced. Recently, in particular, the application of a helical light emitting tube having a helical glass tube, which is advantageous for miniaturization, has been studied. [0004] A double-helical glass tube (see Patent Document 1) has a turn-back portion at the center of the glass tube, and has a shape that rotates around a rotation axis toward both ends from the turn-back portion. Therefore, the compactness can be maintained, and the discharge distance and the light emission amount can be increased. [0005] Th...

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Problems solved by technology

[0013] However, according to the studies of the inventors of the present application, it has been found that the coating amount of the phosphor suspension on the inner surface of the double-helical glass tube manufactured through the above-mentioned (i) (□) (□) steps is in the following two points uneven

[0014] (1) The overall inhomogeneity of the glass tube, that is, the closer to the turn-back part, the less the coating amount, and the farther away from the turn-back part (the closer it is to the mouth), the more the coating amount

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