Electric lamp and discharge devices – With luminescent solid or liquid material – Vacuum-type tube
Reexamination Certificate
2001-11-28
2003-06-24
Patel, Vip (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
Vacuum-type tube
C313S422000, C313S583000
Reexamination Certificate
active
06583556
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a flat-type fluorescent lamp with a flat emission surface. More particularly, the invention relates to a flat-type fluorescent lamp, an illumination unit using the lamp, and a Liquid-Crystal Display (LCD) device equipped with the lamp as its backlight, which make it possible to narrow the frame area of a LCD device and to widen its display area.
2. Description of the Related Art
Conventionally, illumination units are used to form the edge-type or direct-type backlights of LCD devices.
With the edge-light type backlight, a cylindrical fluorescent lamp is located apart from a LCD panel to extend along one edge of the panel. The lamp is not overlapped with the rear surface of the panel. A light guide plate, which is made of acrylic resin, is provided near the fluorescent lamp to guide the light from the lamp toward the rear of the panel. A diffuser sheet is provided near the light guide plate to diffuse the light emitted from the plate, thereby relaxing the unevenness of the light emitted from the plate. Thus, approximately even light is illuminated to the rear surface of the panel.
The edge-light type backlight has the following disadvantages:
First, the light from the fluorescent lamp is difficult to be guided to the rear surface of the panel efficiently and uniformly. This difficulty increases with the widening display area of LCD devices. Second, since the fluorescent lamp is located in the picture-frame area of LCD devices, the edge-light type backlight is unfavorable from the viewpoint of narrowing the picture-frame area.
With the direct-light type backlight, a lamp house is formed at the rear of the LCD panel, in which several cylindrical fluorescent lamps are arranged. If the lamps are located too close to the panel, the light from the lamps is locally illuminated to the rear surface of the panel, which means that the light has uneven brightness. To avoid this problem, the lamps need to be located to have a certain distance from the panel and at the same time, a diffuser plate is essentially provided between the lamps and the panel, thereby diffusing the light from the lamps. Thus, the direct-type backlight has a disadvantage that it is difficult to cope with the requirement of thinning LCD devices.
Flat-type fluorescent lamps are fluorescent lamps having a flat emission surface and have the basic structure that a pair of opposing plates is joined together with an intervening frame member, thereby forming a container. A gaseous substance, such as an inert gas and a mixture of an inert gas and gaseous mercury (Hg), is confined in the container.
Flat-type fluorescent lamps can be used as the direct-type backlight of LCD devices and therefore, they have an advantage that means for guiding the light from the lamp to the LCD panels is unnecessary. Since the emission surface can be opposed to the whole display area of the panel, there is another advantage that brightness unevenness is difficult to be observed even if the lamps are close to the panel. Accordingly, flat-type fluorescent lamps are expected as a technique that meets the requirement of widening and thinning of LCD devices.
Next, a prior-art LCD device equipped with a prior-art flat-type fluorescent lamp as its backlight is explained below with reference to
FIGS. 1 and 2A
and
2
B.
FIG. 1
is an exploded perspective view of the prior-art device, where the flat-type fluorescent lamp is partially cut away.
FIG. 2A
is a cross-sectional view of the assembled prior-art device along the line IIA—IIA in FIG.
1
.
FIG. 2B
is a partial, enlarged cross-sectional view of the assembled prior-art device of FIG.
2
.
As seen from
FIGS. 1 and 2A
and
2
B, the prior-art flat-type fluorescent lamp
120
comprises a rectangular emission-side plate
101
, a rectangular electrode-side plate
102
, and a rectangular frame member
103
that intervenes between the plates
101
and
102
and that has a rectangular window at its center. The plates
101
and
102
are entirely overlapped with each other by way of the member
103
in such a way that the contour of the plate
101
accords with that of the plate
102
. The rectangular outer edges (peripheral areas) of the plates
101
and
102
are placed outside the member
103
. Electrodes
104
are formed on the inner surface of the plate
102
by a screen printing method or the like. The ends of part of the electrodes
104
are extended to the outside of the member
103
on the inner surface of the plate
102
, forming four electrode terminals
107
(i.e., an anode terminal
107
a
, a cathode terminal
107
b
, a cathode terminal
107
c
, and an anode terminal
107
d
).
The prior-art LCD device shown in
FIGS. 1 and 2A
and
2
B comprises a LCD panel
108
, the prior-art flat-type fluorescent lamp
120
as the backlight, a rectangular front chassi
109
, a rectangular center chassi
110
, and a rectangular rear chassi
111
. The panel
108
is located on the emission side of the lamp
120
. The peripheral area of the panel
108
is sandwiched and held by the front and center chassis
109
and
110
, as shown in
FIGS. 2A and 2B
.
The front chassi
109
has a frame-like shape with a rectangular window at its center. The peripheral area of the chassi
109
is bent at a right angle to form its sidewalls. The chassi
109
forms the front picture-frame area of the LCD device and the side faces thereof.
The center chassi
110
has a frame-like shape with a rectangular window at its center. The peripheral area of the chassi
110
is bent at a right angle to form its sidewalls. The chassi
110
, which is located between the panel
108
and lamp
120
, holds the lamp
120
with its sidewalls in such a way as to surround the lamp
120
.
The rear chassi
111
has a rectangular bottom that forms the rear surface of the LCD device. The peripheral area of the chassi
111
is bent at a right angle at the whole edge of the bottom to form its sidewalls. The chassi
111
is located to cover the electrode-side plate
102
of the lamp
120
.
These three chassis
109
,
110
and
111
are combined together to enclose the panel
108
and the lamp
120
. As shown in
FIGS. 2A and 2B
, a circuit board
112
is mounted on the opposite surface of the rear chassi
111
to the lamp
120
(i.e., the rear surface of the LCD device. The board
112
includes an inverter circuit and other necessary circuits formed thereon.
As shown in
FIG. 2B
, a fluorescent material layer
105
is formed on the inner surface of the emission-side plate
101
of the lamp
120
. The plate
101
is formed by a transparent glass plate, on which the emission surface of the lamp
120
is formed. The emission-side plate
101
and the electrode-side plate
102
are coupled with each other by way of the frame member
103
with frit glass (i.e., glass with low-melting point)
114
, forming a closed container with a shape of rectangular parallelepiped. A gaseous substance
106
(e.g., an inert gas) is confined into the container at a pressure of approximately 10 kPa to 100 kPa. A specific voltage is applied to the substance
106
by way of the electrodes
104
.
As clearly shown in
FIG. 1
, an opening
115
is formed at the sidewall of the rear chassi
111
. The opening
115
extends to the bottom of the chassi
111
. Another opening
116
is formed at the sidewall of the center chassi
110
. These openings
115
and
116
are overlapped with each other to form a cable window
117
for allowing cables to reach the inside of the assembly of the chassis
109
,
110
, and
111
.
As clearly shown in
FIGS. 1
,
2
A and
2
B, each of the anode terminals
107
a
and
107
d
and the cathode terminals
107
b
and
107
c
is connected to one end of each cable
113
with a solder
118
. The other end of each cable
113
is connected to the circuit board
112
by way of a connector. The circuits (e.g., the inverter circuit) formed on the board
112
control the electric power applied to the gaseous substance
106
by way of the cables
113
.
The cables
113
are plac
Fujishiro Fumihiko
Kanatsu Tsutomu
Oishi Toshiya
Foley & Lardner
NEC LCD Technologies Ltd.
Patel Vip
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