U.S. patent application number 09/815043 was filed with the patent office on 2001-09-27 for liquid crystal display device.
This patent application is currently assigned to Hitachi,Ltd.. Invention is credited to Kitada, Takaaki.
Application Number | 20010024260 09/815043 |
Document ID | / |
Family ID | 18600440 |
Filed Date | 2001-09-27 |
United States Patent
Application |
20010024260 |
Kind Code |
A1 |
Kitada, Takaaki |
September 27, 2001 |
Liquid crystal display device
Abstract
For reducing thickness of a liquid crystal display device in a
depth direction thereof, the present invention provides a liquid
crystal display device comprising a liquid crystal display device
and a backlight unit disposed behind a liquid crystal display
panel, wherein a reflector of the backlight unit has a wavy surface
at rear side thereof, and a circuit board on which electronic
components are disposed is fixed at the wavy rear surface of the
reflector, so that the electronic components are located between
the circuit board and a concave portion of the wavy rear surface of
the reflecting plate.
Inventors: |
Kitada, Takaaki; (Mobara,
JP) |
Correspondence
Address: |
Stanley P. Fisher
Reed Smith Hazel & Thomas LLP
Suite 1400
3110 Fairview Park Drive
Falls Church
VA
22042-4503
US
|
Assignee: |
Hitachi,Ltd.
|
Family ID: |
18600440 |
Appl. No.: |
09/815043 |
Filed: |
March 23, 2001 |
Current U.S.
Class: |
349/149 |
Current CPC
Class: |
G02F 1/133608 20130101;
G02F 1/13452 20130101; G02F 1/133612 20210101; G02F 1/133604
20130101; G02F 1/133605 20130101 |
Class at
Publication: |
349/149 |
International
Class: |
G02F 001/1345 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 24, 2000 |
JP |
2000-083881 |
Claims
What is claimed is:
1. A liquid crystal display device comprising: a liquid crystal
display panel; a backlight unit being arranged at a back side of
the liquid crystal pane; and a circuit board being arranged at a
back side of the backlight unit, wherein the backlight unit is
constructed by a light source being arranged opposite to the liquid
crystal display panel and a reflector reflecting light from the
light source toward the liquid crystal display panel, the reflector
has a concave surface at a part of a surface thereof opposite to
the circuit board, and an electronic component is mounted opposite
to the concave surface on the circuit board.
2. A liquid crystal display device comprising: a liquid crystal
display panel, a backlight unit, and a circuit board being arranged
in order from an observation side of the liquid crystal display
device, wherein the backlight unit has a reflector having an uneven
portion opposite to the liquid crystal display panel which waves in
a certain direction, and an electronic component of the circuit
board is located in a space between the circuit board and the
reflector.
3. A liquid crystal display device comprising: a liquid crystal
display panel; and a circuit board is arranged behind a liquid
crystal display panel being spaced therefrom by a backlight unit,
wherein the backlight unit comprises a reflector being opposite to
the liquid crystal display panel, and the circuit board is fixed to
the reflector so that an electronic component being mounted thereon
is housed in a concave portion provided at the reflector.
4. A liquid crystal display device wherein a liquid crystal display
panel, a light source, a reflector, and a printed circuit board are
arranged in a thickness direction of the liquid crystal display
device, the printed circuit board has an electronic component
mounted at a counter side thereof to the thickness direction, the
reflector having a concave surface which guides light in a
predetermined direction and is arranged to utilize a space between
the concave surface and the printed circuit board.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention is related to a liquid crystal display
device, particularly to a liquid crystal display device comprising
a backlight unit called as i.e. direct type.
[0003] 2. Description of the Related Art
[0004] As a size of a liquid crystal display panel becomes larger,
a liquid crystal display device comprising a backlight unit having
so-called direct-type structure becomes well-known.
[0005] This sort of the backlight unit is composed by housing a
plurality of light source (e.g. cold cathode ray tubes) arranged to
confront the liquid crystal display panel in a casing which also
serves as a reflecting plate (a reflector).
[0006] On the other hand, the circuit board for driving the liquid
crystal display panel is installed on a rear surface of the
backlight unit.
SUMMARY OF THE INVENTION
[0007] However, in the liquid crystal display device composed in
the aforementioned manner, the electronic components mounted on the
circuit board is disposed on an opposite plane to the backlight
unit, so that thickness of the liquid crystal display device is
large in a depth direction thereof.
[0008] Moreover, since a cover for protecting the electronic
components from external interference or obstacles needs to be
furnished on the backlight unit, the structure of the backlight
unit cannot but be complicated, and the thickness in the depth
direction of the liquid crystal display device cannot but be
larger.
[0009] The present invention is invented under these circumstances,
and an object thereof is to provide a liquid crystal display device
suitable to reduce the thickness in the depth direction
thereof.
[0010] A summary of the representative one of the present invention
disclosed in the specification for the present patent application
will be concisely described as follows.
[0011] A liquid crystal display device according to the present
invention comprises a liquid crystal display panel; a backlight
unit being arranged at a back side of the liquid crystal panel (a
rear side from a viewpoint of an observation side of the liquid
crystal display panel);and a circuit board (e.g. a printed circuit
board) being arranged at a back side of the backlight unit, and
[0012] is characterized in that the backlight unit is constructed
by a light source being arranged opposite to the liquid crystal
display panel and a reflector reflecting light from the light
source toward the liquid crystal display panel, the reflector has a
concave surface at a part of a surface thereof opposite to the
circuit board, and an electronic component is mounted opposite to
the concave surface on the circuit board.
[0013] In the thus constructed liquid crystal display device, the
circuit board provided so as not to increase thickness of the
liquid crystal display device in a depth direction thereby.
[0014] Since the reflector of the backlight unit has a wavy
structure (like a corrugated sheet, for instance) for guiding light
from the light source to the predetermined direction, the above
described structure utilizes a space between the concave surface
appearing at a rear side (from the aforementioned viewpoint of the
observation side of the liquid crystal display device) of the wavy
structure and the circuit board (e.g. a printed circuit board) for
housing the electronic components (e.g. for controlling operation
of the liquid crystal display panel).
[0015] These and other objects, features and advantages of the
present invention will become more apparent from the following
description when taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a cross sectional view showing one of embodiments
of the liquid crystal display devices according to the present
invention;
[0017] FIG. 2 is an equivalent circuit diagram showing one of
embodiments of the liquid crystal display devices according to the
present invention;
[0018] FIG. 3 is an exploded squint view showing one of embodiments
of the liquid crystal display devices according to the present
invention;
[0019] FIG. 4 is a plan view showing one of embodiments of pixels
in the liquid crystal display devices according to the present
invention;
[0020] FIG. 5 is an exploded squint view showing one of embodiments
of backlights in the liquid crystal display devices according to
the present invention; and
[0021] FIG. 6 is a plan view showing another of embodiments of the
liquid crystal display devices according to the present
invention;
DETAILED DESCRIPTION
[0022] An embodiment according to the present invention will be
explained below with reference to drawings.
[0023] <<An Equivalent Circuit of the Liquid Crystal Display
Device>>
[0024] FIG. 2 is an equivalent circuit diagram showing one of
embodiments of the liquid crystal display device according to the
present invention. While FIG. 2 is a circuit diagram, however FIG.
2 is drawn in accordance with a practical geometrical arrangement
of the liquid crystal display device.
[0025] In this embodiment, the present invention is applied to the
liquid crystal display device employing a lateral electric
field-scheme which is known as a liquid crystal display device
having a wide viewing angle.
[0026] First of all, there is a liquid crystal display panel 1
having transparent substrates 1A, 1B which are arranged opposite to
and spaced from one another by liquid crystals as a vessel thereof.
In this case of the liquid crystal display device, one of the
transparent substrate (the substrate at a lower side in FIG. 2:
also called as a matrix substrate 1A) is formed to be slightly
larger than another of the transparent substrate (the substrate at
an upper side in FIG. 2: also called as a color filter substrate
1B), and these substrates are arranged so as to adjust peripheral
edges of both of the substrates substantially to one another at
lower and right sides in FIG. 2.
[0027] Thus, peripheries of the one of the transparent substrates
1A are extended outward from those of the another of the
transparent substrates 1B at left and upper sides in FIG. 2. As
further detail will be mentioned later, the portion of the one of
the transparent substrates 1A jutting out from the another thereof
1B is utilized as an area on which gate driver circuits 5 and drain
driver circuits 6 are mounted.
[0028] In a region where each of the transparent substrates 1A, 1B
overlap one another, plurality of pixels 2 are formed to be
arranged in a matrix manner. Each of the pixels 2 comprises a
switching element TFF being formed in a area surrounding a pair of
scanning signal lines 3 (being extended in a x-direction and
juxtaposed in a y-direction in FIG. 2) and a pair of video signal
lines 4 (being extended in the y-direction and juxtaposed in the
x-direction in FIG. 2) and being operated by supplying a scanning
signal through one of the pair of scanning signal lines 3, and a
pixel electrode to which a video signal is applied from one of the
pair of video signal lines 4 through the switching element TFT.
[0029] Since the liquid crystal display device of this embodiment
employs the so-called lateral electric field-scheme as mentioned
previously, each of the pixels 2 also comprises a counter electrode
and an additional capacitance element other than the switching
element TFT and the pixel electrode as further details thereof will
be mentioned later.
[0030] One end of each of the scanning signal lines 3 (a left side
end in FIG. 2) is extended to an outside of the transparent
substrate 1B so that the one end is connected to an output terminal
of a gate driver circuit (IC: Integrated Circuit) 5 being mounted
on the transparent substrate 1A.
[0031] In this case, a plurality of the gate driver circuits 5 are
provided on the substrate 1A, a plurality of the scanning signal
lines 3 are grouped together by the gate driver circuit 5 arranged
in the vicinity thereof, and the scanning signal lines 3 of each of
the groups arranged adjacent to each other are connected to the
gate driver circuit 5 corresponding to the group, respectively.
[0032] Moreover, one end of each of the video signal lines 4 (an
upper side end in FIG. 2) is also extended to an outside of the
transparent substrate 1B so that the one end is connected to an
output terminal of a drain driver circuit (IC: Integrated Circuit)
6 being mounted on the transparent substrate 1A.
[0033] Also in this case, a plurality of the drain driver circuits
6 are provided on the substrate 1A, a plurality of the video signal
lines 4 are grouped together by the drain driver circuit 6 arranged
in the vicinity thereof, and the video signal lines 6 of each of
the groups arranged adjacent to each other are connected to the
drain driver circuit 6 corresponding to the group,
respectively.
[0034] On the other hand, a printed circuit board 10 is disposed in
the vicinity of the liquid crystal display panel 1 on which the
gate driving circuits 5 and the drain driving circuits 6 are
mounted as mentioned above, and has a electric power source
(supply) circuit 11 and control circuit (Integrated Circuit) 12
supplying input signals to the gate driving circuits 5 and the
drain driving circuits 6 being mounted thereon.
[0035] The signals from the control circuit 12 are supplied to the
gate driving circuits 5 and the drain driving circuits 6 via
flexible printed circuit boards (a gate circuit board 15, a drain
circuit board 16A, and another drain circuit board 16B).
[0036] Namely, the flexible printed circuit board (the gate circuit
board 15) having terminals which confront and are connected to
input side terminals of each of the gate driving circuits 5 is
disposed at the gate driving circuits side of the liquid crystal
display panel 1.
[0037] The gate circuit board 15 is formed so that a portion
thereof is extended to the aforementioned control circuit board 10,
and is connected to the control circuit board 10 at the extended
portion thereof via a connection portion 18.
[0038] Output signals of the control circuit 12 mounted on the
control circuit board 10 are inputted to the gate driving circuits
5 via wiring layers on the control circuit board 10, the connection
portion 18, and wiring layers on the gate circuit board 15,
respectively.
[0039] On the other hand, the drain circuit boards 16A, 16B each of
which has terminals confronting and being connected to input side
terminals of each of the drain driving circuits 6 are disposed at
the drain driving circuits side of the liquid crystal display panel
1.
[0040] The drain circuit boards 16A,16B are formed so that each of
the drain circuit boards has a portion being extended to the
aforementioned control circuit board 10 side and is connected to
the control circuit board 10 at the extended portion thereof via a
connection portion 19A,19B.
[0041] Output signals of the control circuit 12 mounted on the
control circuit board 10 are inputted to the gate driving circuits
6 mounted on the drain circuit boards 16A, 16B via wiring layers on
the control circuit board 10, the connection portions 19A, 19B, and
wiring layers on the drain circuit boards 16A, 16B,
respectively.
[0042] Moreover, the flexible printed circuit board at the drain
driving circuits side of the liquid crystal display device is
divided into two, as denoted the drain circuit boards 16A, 16B, and
disposed thereat. The flexible printed circuit board (the drain
circuit board) is divided into two or more for e.g. preventing a
thermal expansion thereof in a x-direction in FIG. 2 from affecting
thereto (e.g. a deformation of the flexible printed circuit boards
in the x-direction), as apparently as a length thereof in the
x-direction increases in accordance with enlargement of the liquid
crystal display panel size.
[0043] Each of outputs from the control circuit 12 on the control
circuit board 10 is inputted to the gate driving circuit 6
corresponding thereto via a wiring layer on the control circuit
board 10, the connection portion 19A of the drain circuit board 16A
or the connection portion 19B of the drain circuit board 16B.
[0044] Furthermore, image signals are supplied from an image signal
source 22 to the control substrate 10 via a cable 23 and an
interface substrate 24, and inputted to the control circuit 12
mounted on the control substrate 10.
[0045] Incidentally, while the liquid crystal display panel 1, the
gate circuit board 15, the drain circuit boards 16A, 16B, and the
control substrate 10 are drawn to be located substantially on a
same plane in FIG. 2, the control substrate 10 is arranged so that
main surface thereof is almost perpendicular to that of the liquid
crystal display panel 1 by bending the gate circuit board 15 and
the drain circuit boards 16A, 16B.
[0046] By arranging the control circuit board 10 as mentioned
above, an area of an i.e. picture frame of the liquid crystal
display device is reduced. The picture frame in this explanation,
is defined as a region between an outline of the liquid crystal
display device and a contour of a display area thereof, and
reducing this region provides an advantage that the display area
thereof can be relatively larger in a plane surrounding the outline
thereof.
[0047] <<Module of the Liquid Crystal Display
Device>>
[0048] FIG. 3 is an exploded squint view of one of embodiments of
modules of the liquid crystal display devices according to the
present invention.
[0049] The liquid crystal display device in FIG. 3 comprises
members which are classified roughly into a liquid crystal display
panel module 400, a backlight unit 300, a resin frame member 500, a
middle frame 700, and an upper frame 800 and assembled as modules,
respectively.
[0050] Each of these members will be explained sequentially,
hereinafter.
[0051] [Liquid Crystal Display Panel Module]
[0052] The liquid crystal display panel module comprises the liquid
crystal display panel 1, the gate driving ICs (Integrated Circuits)
5 and the drain driving ICs 6 comprising a plurality of
semiconductor ICs mounted on a periphery of the liquid crystal
display panel 1, the flexible gate circuit board 15 and the
flexible drain circuit boards 16 (16A, 16B, in FIG. 2) connected to
each input terminal of these driving ICs.
[0053] Namely, outputs of the control substrate 10 going to be
mentioned later are inputted to the gate driving ICs 5 and the
drain driving ICs 6 on the liquid crystal display panel 100 through
the gate circuit board 15 and the drain circuit boards 16A, 16B,
and each output of these driving IC is inputted to the scanning
signal line 3 or the video signal line 4 of the liquid crystal
display panel 1.
[0054] Here, a display area of the liquid crystal display panel 1
comprises a plurality of pixels arranged in a matrix manner as
mentioned above, and one of the pixels has a structure shown in
FIG. 4.
[0055] In FIG. 4, the scanning signal line 3 and a counter voltage
signal line 50 both extending in a x-direction are formed on a main
surface of the matrix substrate 1A. A pixel region is formed as a
region surrounded by these signal lines 3, 50 and the video signal
lines 4 mentioned later.
[0056] Namely, the counter voltage signal line 50 is formed between
a pair of the scanning signal lines 3 adjacent to one another (so
as to be extended along the scanning signal lines 3), and the pixel
regions are formed in respective regions spaced from one another by
the counter voltage signal line 50 in +y and -y directions
therefrom.
[0057] According to this arrangement, a number of the counter
voltage signal lines 50 juxtaposed in the y-direction can be
reduced almost to a half of that of conventional arrangement, an
area occupied by the rest half of the counter voltage signal lines
50 according to the conventional arrangement can be utilized as the
pixel regions, and areas of the pixel regions can be enlarged
thereby.
[0058] In each of the pixel regions, counter electrodes 50A
integrated with the counter voltage signal line 50 is formed for
example so that three of the counter electrodes 50A are arranged in
a same interval and extended in the y-direction. Each of these
counter electrodes 50A is extended close to but not to be connected
to the scanning signal line 3, two thereof arranged at both sides
of the pixel region are arranged to be adjacent to the video signal
line 4, and the rest one thereof is located at a center of the
pixel region.
[0059] Furthermore, on the main surface of the transparent
substrate 1A having the scanning signal lines 3, the counter
voltage signal lines 50, and the counter electrodes 50A formed
thereon as mentioned above, an insulating film formed of e.g.
silicon nitride film covering even these scanning signal lines 3
etc. is formed. The insulating film functions as an interlayer
insulating film for insulating the video signal lines 4 mentioned
later from the scanning signal lines 3 and the counter voltage
signal lines 50, as a gate insulating films for the thin film
transistor TFF, and a dielectric film for storage capacitance Cstg,
respectively.
[0060] First of all, semiconductor layers 51 are formed in a region
provided for forming the thin film transistor on a surface of the
insulating film. The semiconductor layer 51 is formed of e.g.
amorphous silicon (Si) so that a portion thereof in the vicinity of
a video signal line 2 mentioned later is overlapped with the video
signal line 2 on the scanning signal line 3. Thereby, the scanning
signal line 3 is constructed so that a part thereof serves as a
gate electrode of the thin film transistor TFT, also.
[0061] Then, the video signal lines 2 being extended in the
y-direction and juxtaposed in the x-direction are formed on the
surface of the insulating film. The video signal line 2 is extended
to a part of a surface of the semiconductor layer 51 as one of
elements of the thin film transistor TFT, and united to a drain
electrode 2A being formed on the semiconductor layer 51.
[0062] Moreover, a pixel electrode 53 being connected to a source
electrode 53A of the thin film transistor TFT is formed on the
surface of the insulating film in a pixel region. The pixel
electrode 53 is formed to be extended in the y-direction at each
center of respective pair of the counter electrode 50A. Namely, the
pixel electrode 53 is extended in the y-direction from one of ends
thereof serving as a source electrode of the thin film transistor
TFT, then extended in the x-direction on the counter voltage signal
line 50, and finally extended in the y-direction, so as to form
U-shape thereby.
[0063] Here, a part of the pixel electrode 53 overlapping the
counter voltage signal line 50 forms a storage capacitance Cstg
together with the counter voltage signal line 50 and the insulating
film as a dielectric film interposed therebetween. The storage
capacitance takes effects, for instance, on storing video
information in the pixel electrode 53 while the thin film
transistor is turned off.
[0064] Furthermore, the surface of the semiconductor layer 51
corresponding to interfaces thereof contacting with the drain
electrode 2A and the source electrode 53A is formed to be high
impurity concentration layers by doping phosphorus (P), so as to
provide ohmic contacts for each of the drain electrode 2A and the
source electrode. In this case, the aforementioned structure is
obtained by forming the aforementioned high impurity concentration
layer at a whole region of the surface of the semiconductor layer
51 at first, then forming each of the electrodes on the high
impurity concentration layer, and removing the high impurity
concentration layer other than portions thereof formed at regions
where the electrodes are formed by applying etching thereto using
the electrodes as a mask.
[0065] Then, a protective film formed of e.g. silicon nitride
(SiN.sub.x) is privided on a upper surface of the insulating film
where the thin film transistors TFT, the video signal lines 2, the
pixel electrodes 53, and the storage capacitance Cstg are formed as
mentioned previously, and an alignment film is provided on an upper
surface of the protective film so as to construct a so-called lower
substrate of the liquid crystal display panel 1.
[0066] Although FIG. 3 does not show a transparent substrate (a
color filter substrate) 1B utilized as a so-called upper substrate
of the liquid crystal display panel 1, a black matrix having
openings each of which corresponds to the pixel region are provided
at the liquid crystal side (the side facing the lower substrate) of
the transparent substrate (a color filter substrate) 1B. A contour
of each of the openings of the black matrix is denoted by a
reference numeral 54 in FIG. 3.
[0067] Moreover, color filters are provided to cover the openings
which are formed at respective portions of the black matrix 54
corresponding to the pixel regions. The color filter of one of the
pixel regions has a different color from that of another of the
pixel regions adjacent to the one of the pixel regions in the
x-direction, and these two adjoining color filters form a boundary
CF therebetween on the black matrix 54 (e.g. at a portion thereof
opposite to the video signal line 2).
[0068] A leveling film of resin or the like is formed on a surface
where the black matrix and the color filters are provided in the
aforementioned manner, and an alignment film is formed on a surface
of the leveling film.
[0069] [Backlight]
[0070] A backlight unit 300 is arranged at a rear surface of the
liquid crystal display module 400.
[0071] This kind of the backlight unit 300 is so-called direct
backlight, and as shown in FIG. 5, comprises a plurality of linear
light sources (e.g. cold cathode ray tubes) 35 extending in a
x-direction in FIG. 5 and being juxtaposed in a y-direction therein
at even intervals, and a reflecting plate (a reflector) 36 for
irradiating the liquid crystal display panel module 400 with light
from the cold cathode ray tubes 35.
[0072] The reflecting plate 36 is, for instance, wavy-shaped in a
juxtaposing direction of the cold cathode ray tubes 35 (the
y-direction). At a side of the exemplified reflecting plate 36
facing the cold cathode ray tubes, a concave portion shaped in an
arc is formed at every part thereof where each of the cold cathode
ray tubes 35 is disposed, and a convex portion shaped in an arc is
formed at every other part thereof between the cold cathode ray
tubes 35, respectively so as to irradiate the liquid crystal
display panel module with light from each of the cold cathode ray
tubes efficiently.
[0073] The reflecting plate 36 has "sides" (side walls) 37 provided
at both sides thereof crossing each longitudinal direction of the
cold cathode ray tubes 35 at right angles, and both ends of the
respective cold cathode ray tubes 35 are inserted in slits 38
formed at the sides 37 respectively, so that movements of the cold
cathode ray tubes 35 in a juxtaposed direction of the cold cathode
ray tubes (the y-direction of FIG. 5) are controlled.
[0074] [Resin Frame Member]
[0075] A resin frame member 500 composes a part of an outer frame
of the liquid crystal display device being assembled into a module,
and houses the backlight unit 300.
[0076] The resin frame member 500 disclosed here has a box-shape
having at least side wall, so that a diffusion plate (an optical
diffusion plate, not shown) being arranged to cover the backlight
unit 300 can be disposed on an upper end (an upper end surface) of
the side wall.
[0077] The diffusion plate has a function to diffuse light from the
each cold cathode ray tube 35 in the backlight unit, so that
uniform light without any brightness unbalance can be radiated
toward the liquid crystal display panel module 400.
[0078] While the resin frame member 500 is formed relatively small
in thickness thereof, however mechanical strength reduction thereof
is reinforced by the middle frame 700 (see in FIG. 3).
[0079] <<Control Substrate>>
[0080] As FIG. 1 shows, a control substrate (a control board) 10 or
a circuit board other than the control substrate is arranged at
rear side (on a rear surface) of the reflection plate 36 composing
the backlight unit 300. FIG. 1 is a cross sectional view taking
along a I-I line in FIG. 1.
[0081] The control substrate 10 is connected to both the gate
driving ICs 5 and the drain driving ICs 6 respectively mounted on
the liquid crystal display panel via the gate circuit board 15 and
the drain circuit board 16, as mentioned previously.
[0082] The control substrate 10 is constructed, for instance, by
mounting electronic components 52 on a printed circuit board 51,
the printed circuit board is fixed e.g. to the reflecting plate 36,
and the electronic components 52 are mounted on a surface of the
printed circuit board 52 at the reflecting plate 36 side.
[0083] Namely, the electronic components 52 are distributed to and
disposed at belt-like regions extending in a x-direction in FIG. 1
and lining up in a y-direction therein on the printed circuit board
51, and the respective electronic components 52 are connected to
wiring layers on the rear surface of the printed circuit board 51
(at an opposite side of the printed circuit board 51 to that for
mounting the electronic components 52) via through holes for
inputting a signal or electricity thereto or for outputting a
signal or electricity therefrom. The through hole (not shown) is a
conducting portion piercing through an insulating main body of the
printed circuit board 51, and is utilized for connecting conductive
layers provided at different layers from each other in (e.g. a
front surface side and a rear surface side of) the printed circuit
board 51.
[0084] The reflecting plate 36 has the wavy surface including both
the concave portions and the convex portions being formed at a side
thereof confronting the linear light sources 35. The wavy surface
of the reflecting plate 36 should be provided as a corrugated sheet
or the like manufactured by resin molding technique or press work
technique applied to metal or alloy plate as shown in FIG. 1 in the
view of weight reduction of or mechanical reinforcement of the
backlight unit 300. When one of main surfaces of the reflecting
plate 36 having the corrugated sheet structure at the linear light
source 35 side is defined as "a front surface" and another of the
main surfaces at opposite side to the front surface is defined as
"a rear surface", the concave portion and the convex portion
mentioned above being provided on the front surface of the
reflecting plate 36 provide a convex portion and a concave portion
on the rear surface of the reflecting plate, respectively. The
aforementioned belt-like regions of the printed circuit board 51
having the respective electronic components mounted thereon
confront the concave portions of the wavy rear surface of the
reflecting plate 36, when the reflecting plate 36 is fixed to the
rear surface of the reflecting plate 36. In other words, the
belt-like regions are located so as to avoid the convex portions of
the rear surface of the reflecting plate 36 (below the linear light
sources 35, in FIG. 1).
[0085] Therefore, the printed circuit board 51 can be disposed at a
rear side of the reflecting plate 36 to be contacted thereto (e.g.
to convex portions on the rear surface thereof), while the
respective electronic components 52 is housed in the concave
portions of the rear surface of the reflecting plate 36 (in a space
surrounded by the rear surface of the reflecting plate 36 and a
front surface of printed circuit board 51).
[0086] As a size of the liquid crystal display device becomes
larger, an area of the reflecting plate 36 becomes so large that
more electronic components can be assembled on respective regions
(respective ones of the aforementioned belt-like regions) which is
provided by dividing a main surface (the aforementioned front
surface) of the printed circuit board in accordance with the
concave portion of the rear surface thereof.
[0087] Additionally, if the reflecting plate 36 is made of a
conductive materials (e.g. metal), an insulation treatment may be
applied to a surface (esp. the aforementioned rear surface) thereof
for avoiding to be contacted directly with the electronic
components 52.
[0088] Moreover, since no electronic component is disposed on
another surface (the aforementioned rear surface) of the printed
circuit board 51, a thickness h of the liquid crystal display
device in a depth direction thereof can be reduced.
[0089] Furthermore, since any cover for keeping the electronic
components from external interference or obstacles need not to be
furnished at the side of the printed circuit board 51 where no
electronic component is disposed, the thickness h of the liquid
crystal display device in the depth direction thereof can be
smaller.
[0090] In the aforementioned embodiment, a structure for installing
the printed circuit board 51 directly to the reflecting plate 36 is
applied to the backlight unit 300.
[0091] However, it goes without saying that another board 55 for
installing the printed circuit board 51 thereto may be installed to
the reflecting plate 36 previously as FIG. 6 shows.
[0092] Of course, the board 55 used in this case, may be selected
from a metal plate as well as an insulating plate.
[0093] In the aforementioned embodiment, the backlight unit 300 is
assembled by installing the printed circuit board 51 to the
reflecting plate 36. This sort of the backlight unit 300 structure
takes an effect on locating the electronic components 52 on the
printed circuit board 51 easily in accordance with the concave
portions of the reflection plate 36. However, it goes without
saying that the backlight unit may employ the other structure, for
instance, having printed circuit board 51 installed to the resin
frame member 500.
[0094] Furthermore, the aforementioned embodiment is explained on
condition that no electronic components is mounted on a surface of
the printed circuit board 51 opposite to the reflecting plate.
However, the same effect as that of the backlight unit 300 of the
aforementioned embodiment can be taken on the liquid crystal
display device by classifying electronic components in accordance
with sizes thereof (e.g. heights of the electronic components from
a surface of the printed circuit board on which the electronic
components are mounted), and by disposing some of the electronic
components being large in height thereof, e.g. from the printed
circuit board surface (or, in thickness thereof, also) at the
reflection plate 36 side and by disposing the rest of the
electronic components (being e.g. smaller in height from the
printed circuit board surface or thinner than the formers) at
another side to the reflection plate 36.
[0095] It is apparent by the previous explanation that the liquid
crystal display device according to the present invention can
reduce thickness thereof in a depth direction thereof.
[0096] While we have shown and described several embodiments in
accordance with the present invention, it is understood that the
same is not limited thereto but is susceptible of numerous changes
and modifications as known to those skilled in the art, and we
therefore do not wish to be limited to the details shown and
described herein but intend to cover all such changes and
modifications as are encompassed by the scope of the appended
claims.
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