Liquid crystal cells – elements and systems – Particular structure – Particular illumination
Reexamination Certificate
2001-03-22
2003-07-29
Niebling, John F. (Department: 2812)
Liquid crystal cells, elements and systems
Particular structure
Particular illumination
C362S027000
Reexamination Certificate
active
06600526
ABSTRACT:
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a liquid crystal display (LCD) device having an improved backlight unit and, more particularly, to the improvement of the structure of the reflecting member in the backlight unit of the LCD device.
(b) Description of the Related Art
The LCD device has the advantages of smaller thickness and lightweight, and thus is used as a flat display panel in a variety of applications. The LCD device generally includes a display panel, a backlight unit for irradiating the display panel from the rear surface thereof and a housing for receiving therein the display panel and the backlight unit in one body so that the front screen of the display panel is exposed from a front opening of the housing.
FIG. 1
shows the peripheral part of a conventional LCD device, generally designated by numeral
10
, which includes a display panel
12
for displaying images on the front screen thereof, a backlight unit
14
disposed at the rear of the display panel for irradiating the display panel
12
from the rear surface thereof, and a housing
16
for receiving therein the display panel
12
and the backlight unit
14
as a single unit.
Referring additionally to
FIG. 2
showing the developed configuration of the LCD device of
FIG. 1
, the housing
16
includes a flat case
18
, with a central opening, for receiving therein the backlight unit
14
, and a cover
20
for covering the display panel
12
disposed in front of the backlight unit
14
. The cover
20
is engaged with the flat case
18
by using an engagement structure so that the cover
20
thrust the display panel
12
toward the backlight unit
14
within the housing
16
.
The cover
20
is formed as a metallic frame having an opening
21
for exposing the front screen of the display panel
12
and a side wall
20
a
having a front rim defining the opening
21
. The cover
20
functions also as an electrostatic shield. The display panel
12
includes a polarizing plate
25
as a part thereof, and mounts thereon LCD drivers
22
and
24
at the peripheral area thereof.
The backlight unit
14
includes, as shown in
FIG. 1
, a light source or elongate lamp
34
, an optical-conductive plate
26
having a light-emission front surface
26
a
and a light-reception side surface
26
b
adjacent to the elongate lamp
34
, a reflection sheet
28
disposed at the rear of the light-conductive plate
26
for reflecting the light within the light-conductive plate
26
toward the light-emission front surface
26
b
thereof, and a laminated optical layer structure
33
on the front surface
26
a
of the light-conductive plate
26
. The laminated optical layer structure
33
includes, consecutively as viewed from the light-conductive plate
26
, a first optical diffusion sheet
30
, a first lens sheet
32
, a second lens sheet
32
, and a second optical diffusion sheet
30
.
The optical diffusion sheets
30
have a function for diffusing the light to uniformalize the brightness of the front screen of the display panel
26
, whereas the lens sheets
32
have a function for focusing the light toward the front screen of the display panel
26
.
The elongate lamp
34
of the backlight unit
14
has a cylindrical shape extending along the light-reception side surface
26
b
of the light-conductive plate
26
with a gap therebetween. The backlight unit
14
has a U-shaped reflecting member
36
made of a metal for encircling the lamp
34
together with the light-conductive plate
26
. The front leg
36
a
of the reflecting member
36
abuts the first optical diffusion sheet
30
and the first lens sheet
32
on the light-emission surface
26
a
of the light-conductive plate
26
. The rear leg
36
b
of the reflecting member
36
extends between the reflection sheet
28
and the inner bottom surface of the flat case
18
.
As shown in
FIG. 3
depicting a portion of
FIG. 1
, the engagement structure
39
for the flat case
18
and the display panel
12
includes an engagement hole
39
a
formed in the flat case
18
and a protrusion
39
b
formed on a molded chassis
40
, which is sandwiched between the display panel
12
and the cover
20
. The flat case
18
and the molded chassis
40
are coupled by the engagement structure
39
and bolts
38
.
The molded chassis
40
is made of plastics and, as shown in
FIG. 1
, has a side wall
40
a
including a first portion
40
c
sandwiched between the display panel
12
and the cover
20
and a second portion
40
d
disposed in contact with the side wall
18
a
of the flat case
18
for encircling the backlight unit
14
. The molded chassis
40
also has an extension
40
b
extending from the first portion
40
c
between the display panel
12
and the backlight unit
14
for buffering the thrust force acting therebetween.
The reflecting member
36
is thrust by the second portion
40
d
toward the light-conductive plate
26
so that the reflecting member
36
and the second portion
40
c
sandwich therebetween a low-voltage cable
42
for the lamp
34
. The second optical diffusion sheet
30
and the second lens sheet
32
extend between the extension
40
b
of the molded chassis
40
and the reflecting member
36
.
FIG. 4
shows a modified configuration of the elongate reflecting member
46
in the art, wherein the front leg
36
a
of the reflecting member
36
abuts the light-reception side surface
26
b
of the light-conductive plate
26
.
For assembly of the LCD device of
FIG. 1
, the lamp
34
is first received in the reflecting member
36
, which is then attached to the laminated body
44
including the reflection sheet
28
and the light-conductive plate
26
, and the resultant components are held by the molded chassis
40
within the flat case
18
.
Subsequently, the flat case
18
and the molded chassis
40
are fixed together by the bolts
38
and the engagement structure
39
, followed by stacking thereon the optical layer structure
33
including the optical diffusion sheets
30
and the lens sheets
32
. Thus, the backlight unit
14
is fabricated.
Thereafter, the display panel
12
mounting thereon the LCD drivers
22
and
24
is stacked onto the emission surface of the backlight unit
14
, followed by disposing the cover
20
onto the display panel
12
and fixed to the flat case
18
by using the engagement and fixing mechanisms.
In the conventional LCD device as described above, there are some drawbacks to be removed.
First, the light-conductive plate
26
is liable to damages at the light-emission surface
26
a
or the light-receptions surface
26
b
when the reflecting member
36
receiving therein the lamp
34
is attached to the laminated body
44
. This degrades the product throughput of the LCD device.
Second, the fabrication steps for the LCD device including the step of attaching the reflecting member
36
to the light-conductive plate
26
are complicated, and thus automated fabrication is difficult to achieve.
Third, the overall thickness of the LCD device is not satisfactorily small enough.
Fourth, the gap or space between the lamp
34
and the reflecting member
36
is not satisfactorily large enough. This limits the amount of emitted light from the lamp
34
to be reflected by the reflecting member
36
toward the light-reception surface
26
b.
In the conventional techniques, such as described in JP-A-10-162617, -7-49497, -6-347784 and UM-A-6-87937, the above drawbacks in the LCD device are not removed.
SUMMARY OF THE INVENTION
It is an object of the present invention to solve at least one of the drawbacks as recited above and thereby provide an LCD device having an improved structure in relation to the backlight unit.
The present invention provides, in one aspect thereof, a liquid crystal display (LCD) device including a display panel having a display screen at a font side thereof, a backlight unit disposed at a rear side of the display panel for irradiating the display panel at the rear side thereof, and a housing for holding the display panel and the backlight unit in one body, the backlight unit includi
NEC LCD Technologies Ltd.
Niebling John F.
Stevenson Andre' C
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