Electric lamp and discharge devices – With luminescent solid or liquid material – With gaseous discharge medium
Reexamination Certificate
2001-10-05
2003-08-26
Patel, Vip (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
With gaseous discharge medium
C313S043000, C313S044000, C313S045000, C349S070000, C349S071000
Reexamination Certificate
active
06611092
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a flat fluorescent lamp having improvements in mating the same with a lamp holder. Further, the present invention relates to a liquid crystal display (LCD) device into which such a flat fluorescent lamp is incorporated.
2. Description of Related Art
Liquid crystal materials emit no light of their own, so that LCDs require a separate source of luminance. Fluorescent tubes are commonly used as the illumination sources in LCD backlights because they have the requisite properties of high efficiency, long life, etc. Small diameter straight fluorescent tubes are usually used as edge-light illuminators. On the other hand, single or multiple or serpentine fluorescent tubes are used as the direct backlight illuminators. However, in order to evenly illuminate the entire surface thereof, the direct backlight illuminators should sufficiently be held away from the LCDs, and accordingly, they become undesirably bulky. Further, such direct backlight illuminators itself is also bulky due to the usage of fluorescent tubes. In an effort to preclude this problem, flat or planar fluorescent lamps have proposed and they are gaining in popularity because of their high luminance and small depth sizes.
Prior to turning to the present invention, it is deemed preferable to briefly describe a conventional flat fluorescent lamp with reference to
FIGS. 1-3
,
FIG. 1
is a partially taken away perspective view of a conventional fluorescent lamp (denoted by
10
). As shown, two glass plates
12
and
14
are hermetically bonded to opposite sides of a rectangular frame
16
so as to form a discharge chamber
18
. The glass plates
12
and
14
are aligned with respect to the edges or peripheries thereof when bonded to the frame
16
. The peripheries of the glass plates
12
and
14
extend beyond the frame
16
. By way of example, each of the glass plates
12
and
14
has a thickness of about 2 mm, and the rail of the frame
16
is about 4 mm both in thickness (height) and in width.
FIG. 2
is a cross-section of part of the flat fluorescent lamp of FIG.
1
. As shown in
FIG. 2
, the glass plate
12
carries, on the inner surface thereof, a phosphor coating
20
that extends to in the vicinity of the upper inner corner of the chamber
18
. On the other hand, the glass plate
14
is provided with, on the inner surface thereof, a plurality of pairs of plus (+) and minus (−) electrodes (only one pair
22
a
-
22
b
is shown), which are covered by dielectric film (layer)
24
which is in turn covered by a light reflective film or coating (not shown). The glass plates
12
and
14
are hermitically bonded to the frame
16
using substrate frits
26
(for example). In order to secure a predetermined gap or distance, which equal to the height of the frame
10
, between the glass plates
12
and
14
, a plurality of spherical spacers
28
(only one is shown) are provided within the chamber
18
.
It is necessary to select the materials of the glasses
12
,
14
, frame
16
, and frits
26
so that the coefficients of linear expansion thereof are substantially identical. This is important to prevent the parts from being undesirably deformed or damaged due to thermal stress. Each of the glass plates
12
and
14
is typically made of soda-lime glass, and the frame may be made of the same material, borosilicate glass, or ceramics such as aluminium oxide or calcium oxide. As is well known, the chamber
18
is filled with an inert gas (rare gas) or an inert gas plus mercury vapor. When electric energy is applied to the lamp
10
, an electric plasma arc is formed between the electrodes
22
a
and
22
b
through the mercury vapor to produce ultraviolet light rays which bombers the phosphor coating
20
, causing the coating
20
to emit light in visible spectrum.
FIG. 3
is a schematic sectional view of part of a LCD device
40
wherein the flat fluorescent lamp
10
of
FIG. 1
is incorporated. A parts holder or supporter
42
is provided at the corner of a rear frame
44
, which holder
42
holds the parts including the flat fluorescent lamp
10
thereby determining the positions thereof. This rear frame
44
is typically made of appropriate metal and is shaped as shown, which Is applicable to other frames: intermediate frame
46
and front frame
48
.
The flat fluorescent lamp
10
is placed on the bottom of the rear frame
44
such that the glass plates
12
and
14
abut onto the sidewall of the parts holder
42
at the ends thereof, and accordingly the lamp
10
is set in the prescribed position. Deposited on the flat fluorescent lamp
10
is a light diffusion plate
50
that is also set to the preset position by the holder
42
. The light diffusion plate
50
is to diffuse the light emitted from the lamp
10
, via which a LCD panel
52
can evenly be illuminated.
As shown in
FIG. 3
, the holder
42
also sets the light diffusion plate
50
in the preset position. As is well known, the LCD panel
52
comprises two transparent substrates spaced apart by a seal having a thickness of about 10 &mgr;m (for example). In the case illustrated, only the lower substrate (denoted by
53
) extends such as to abut onto the projection
64
extending integrally from the holder
42
. The extended portion of the substrate
53
carries thereon a plurality of bonding pads, electrical lines, etc.
As mentioned above, the lamp
10
is set in the predetermined position by abutting the edges of the two glass plates
12
and
14
onto the parts holder
42
. In order to precisely position the lamp
10
within the LCD device
40
, it is necessary to exactly align the edges of the two glass plates
12
and
14
in a direction normal to the main surfaces of the glass plates
12
and
14
. In the case where a misalignment occurs with the edges of the glass plates
12
and
14
, it is no longer expected to precisely abut both the edges of the two glass plates
12
and
14
onto the sidewall of the holder
42
. The causes of potential misalignment reside in both manufacturing the glass plates and bonding them to the frame
16
. Further, since the tolerances are admitted at both manufacturing and bonding of the glass plates, it is in fact extremely difficult to precisely align the glass plates. Accordingly, the conventional flat fluorescent lamp
10
suffers from the problems that the lamp
10
is typically unable to be held firmly by the holder
16
and incur play at the abutting area, which leads to the lowering of the shook resistance of the lamp
10
and reliability of the LCD device as the whole.
SUMMARY OF THE INVENTION
It is therefore an object of the present Invention to provide a flat fluorescent lamp which features improvements in coupling the same to a lamp holder, thereby to overcome the aforesaid problems inherent in the conventional flat fluorescent lamp.
Another object of the present invention is to provide a LCD device which incorporates therein a flat fluorescent lamp featuring improvements in coupling the same to a lamp holder, thereby increasing the reliability of the device in terms of shook or impact resistance and so on.
In brief, these objects are achieved by the techniques wherein a flat fluorescent lamp is provided with one or more protrusions at the periphery thereof, which protrusion(s) extends outwardly beyond the edges of the two glass plates. A lamp holder receives the protrusion of the flat fluorescent lamp so as to hold the same in a manner that no edges of the two parallel glass plates touch or come into contact with the lamp holder.
One aspect of the present invention resides in a flat fluorescent lamp comprising: a sealed chamber formed by a chamber frame and first and second glass plates, which glass plates are bonded to opposite sides of the chamber frame in alignment with the edges thereof; a phosphor coating provided on an inner surface of the first glass plate; and a plurality of electrodes provided on an inner surface of the second glass plate for inducing electric discharge within the chamber; wherein the chamber
Hayes & Soloway P.C.
Leurig Sharlene
NEC LCD Technologies Ltd.
Patel Vip
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