Electric lamp and discharge devices – With gas or vapor – Having electrode exterior to envelope
Patent
1997-12-24
1999-03-30
Patel, Vip
Electric lamp and discharge devices
With gas or vapor
Having electrode exterior to envelope
313631, 313114, H01J 1100
Patent
active
058893660
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a fluorescent lamp of the external electrode type which is used for document scanning illumination which is used for an information processing device such as a fax machine, character/image reader and the like, and for a back light device of a liquid crystal display cell and for similar purposes.
DESCRIPTION OF RELATED ART
As a fluorescent lamp which is used for a scanning light source of an office automation device and for back light of a liquid crystal display device and the like, a fluorescent lamp of the external electrode type is known in which on the outside surface of a glass tube there is a pair of strip-like external electrodes to which a high frequency voltage is applied for operating.
FIG. 7 is a schematic of one example of the fluorescent lamp of the external electrode type which is shown in a cross section perpendicular to the tube axis of the fluorescent lamp of the external electrode type. As is shown in the drawing, in fluorescent lamp 10 of the external electrode type the outside of glass tube 1 is provided with a pair of strip-like external electrodes 2, 2'. Glass tube 1 is filled with a rare gas or the like. Fluorescent material 3 is applied to the inside of glass tube 1. An uninterrupted high frequency voltage or pulse-like high frequency voltage is applied to external electrodes 2, 2' to operate the lamp.
In fluorescent lamp 10 of the external electrode type a discharge is produced between external electrodes 2 and 2' by the high frequency voltage applied to the pair of external electrodes 2, 2' in the discharge space within glass tube 1. Fluorescent material 3 applied to the inside of glass tube 1 is caused to emit by the UV radiation which is formed by this discharge. The light formed by the discharge is radiated to the outside from aperture 4 and the side opposite it. The light emitted from aperture 4 is radiated onto the article to be irradiated.
In the fluorescent lamp the light radiated to the outside from the side opposite aperture 4 is not effectively used. The intensity of the light with which the article to be irradiated is irradiated drops accordingly.
The applicant has therefore proposed a technique for increasing the light intensity, in which reflector material is applied to the side opposite aperture 4 of fluorescent lamp 10 of the external electrode type (Japanese Patent Application HEI 7-313704).
FIG. 8 is a cross sectional view perpendicular to the tube axis of the fluorescent lamp of the external electrode type, in which the aforementioned reflector material is applied. In the Figure the electrode width is labeled W.
In this technique reflector material 6 is applied to the side opposite aperture 4, as is shown in FIG. 8. During an emission by the discharge the light emerging from aperture 4 of fluorescent lamp 10 of the external electrode type is increased by the light reflected by reflector material 6. Thus emission by discharge can be effectively used without placing a reflector or the like outside of fluorescent lamp 10 of the external electrode type.
In an information processing device such as a fax machine, copier, image reader and the like, however, recently there has been a demand to increase the document scanning speed. There is accordingly a demand to increase the light intensity of a fluorescent lamp of the external electrode type. Furthermore, for a back light device of a liquid crystal display cell a back light device is desirable in which high light intensity can be obtained with low input power.
If the fluorescent lamp of the external electrode type described above using FIG. 8 is used, emission by discharge can be effectively used and thus the light intensity of a fluorescent lamp of the external electrode type can be increased. To adequately meet this demand, it is however desirable to increase the light intensity even more.
SUMMARY OF THE INVENTION
The invention was devised to eliminate this disadvantage. The object of the invention was to devise a fluorescent lamp of the external electrode type in
Inoue Masaki
Tada Motomori
Yokokawa Yoshihisa
Yoshioka Masaki
Patel Vip
Safran David S.
Ushiodenki Kabushiki Kaisha
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