Illumination – Light source and modifier – Fluorescent type
Reexamination Certificate
2000-08-14
2002-04-16
O'Shea, Sandra (Department: 2875)
Illumination
Light source and modifier
Fluorescent type
C362S255000, C313S493000, C313S635000, C313S488000
Reexamination Certificate
active
06371627
ABSTRACT:
BACKGROUND OF THE INVENTION
a) Technical Field of the Invention
The present invention relates to a cold cathode tube for use in Liquid Crystal Display (LCD), and in particular, to a cold cathode tube in which the inner wall is coated with an ultra-violet (UV) light reflective film capable of reflecting ultraviolet light.
b) Description of the Prior Art
FIG. 1
shows a sectional view of a conventional cathode tube
1
, which is a circular shape. The inner wall of the tube
11
is coated with InO
2
, which is an UV absorbing film
12
. The inner side of the film
12
is then coated with a thin layer of fluorescent material
13
. The tube
11
is filled with a small amount of a gas. The principle of a cathode tube is that voltage from an electric power source is applied across the tube and the electrical energy, via electron and photon to initiate the gas to release UV light. The light impinges against the fluorescent material
13
and is then converted to visible light and is emitted for application. This conventional cathode tube
1
is provided as a light source. However, due to its circular shape, the visible rays are emitted out in all direction. Such inherited exhaustion is due to the shape restriction of the cathode tube. As shown in
FIG. 2
, when it is used in LCD, the external side of the tube
1
must be mounted with a lampshade
14
with an open end corresponding to the light source panel
2
.
The reflective function of the lampshade
14
allows the visible light to reflect to the light source panel
2
so as to increase the light output efficiency of the tube
1
. However, the mounting of the lampshade
14
will increase the cost of production, and the entire cathode tube cannot be miniaturized. In addition, the emitted light energy will be lowered during the process of light reflection from the lamnpshade
14
to the light source panel
2
. Due to the fact that the visible light will lose some of the energy as a result of the fluorescent agent layer
13
. At the same time, the UV absorbing thin film
12
will absorb the unconverted UV such that the output energy within the tube
1
cannot effectively utilizes the energy within the tube. This will lower the light effectiveness of tube.
Further, the external diameter of the tube
1
is smaller than the height of the incident face
21
of the light source panel
2
so as to connect the lampshade
14
to the incident face
21
to lead light energy to the light source panel
2
. This will restrict the tube and in turn, restrict the output light energy.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a cold cathode tube having a fluorescent material coated along the inner wall thereof and the tube being filled with a small amount of gas, characterized in that the inner wall of the tube is coated with a ultra-violet ray reflective film capable of reflecting ultra-violet light, and the light emission surface at the inner side of the ultra-violet light reflective film does not coat with a fluorescent material, and the remaining region of the light emission surface at the outer wall is coated with a visible light-reflective layer. In addition, the length of the parallel section of the tube can be extended to increase the light emission area, and thus the efficiency of light energy output is increased.
Yet another object of the present invention is to provide a cold cathode tube, wherein the flat board shaped light output face of the tube is extended with a parallel section connected with a circular arch-shaped section.
A further object of the present invention is to provide a cold cathode tube, wherein the length of the parallel section can be extended to increase the light emission area so as to increase the light energy output of the tube.
Other features and benefits of the present invention will become apparent from the detailed description with the accompanying drawings contained thereinafter.
REFERENCES:
patent: 5008789 (1991-04-01), Arai et al.
patent: 5808409 (1998-09-01), Matsuda et al.
Chen Hsiu-Wen
Miyashita Kazuhiro
DelGizzi Ronald E.
O'Shea Sandra
Radiant Opto-Electronics Corporation
Rosenberg , Klein & Lee
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