U.S. patent application number 11/956887 was filed with the patent office on 2008-04-24 for liquid crystal display device having a light path changing means having a porus film with a plurality of pores.
Invention is credited to Kweon-Sam Hong, Han-Ju Lee, In-Sung Lee, Yoon-Sung Um.
Application Number | 20080094548 11/956887 |
Document ID | / |
Family ID | 27667595 |
Filed Date | 2008-04-24 |
United States Patent
Application |
20080094548 |
Kind Code |
A1 |
Lee; Han-Ju ; et
al. |
April 24, 2008 |
Liquid crystal display device having a light path changing means
having a porus film with a plurality of pores
Abstract
Disclosed is a liquid crystal display device capable of
improving a viewing angle thereof while reducing a gray scale
inversion. The liquid crystal display device has a porous film
aligned on a liquid crystal display panel and having a plurality of
pores. The porous film has sidewalls defined by the pores and
reflecting a part of light exited from the liquid crystal display
panel. That is, the sidewalls reflect a first group of light, which
has relatively higher luminance by passing through a short axis of
liquid crystal, towards a second group of light having a relatively
lower luminance by passing through a long axis of liquid crystal.
Accordingly, the viewing angle of the liquid crystal display device
is expanded and the gray scale inversion is reduced.
Inventors: |
Lee; Han-Ju; (Seoul, KR)
; Hong; Kweon-Sam; (Seoul, KR) ; Um;
Yoon-Sung; (Yongin-si, KR) ; Lee; In-Sung;
(Seoul, KR) |
Correspondence
Address: |
McGuireWoods
Suite 1800
1750 Tysons Boulevard
McLean
VA
22102-4215
US
|
Family ID: |
27667595 |
Appl. No.: |
11/956887 |
Filed: |
December 14, 2007 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10502955 |
Jul 29, 2004 |
7324178 |
|
|
PCT/KR2003/000175 |
Jan 27, 2003 |
|
|
|
11956887 |
Dec 14, 2007 |
|
|
|
Current U.S.
Class: |
349/96 |
Current CPC
Class: |
G02F 1/133524
20130101 |
Class at
Publication: |
349/096 |
International
Class: |
G02F 1/1335 20060101
G02F001/1335 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 1, 2002 |
KR |
2002/5942 |
Jul 10, 2002 |
KR |
2002/40069 |
Claims
1. A liquid crystal display device comprising: a liquid crystal
display panel for receiving a first light, and for radiating a
second light having an image information, the liquid crystal
display panel including: i) a first substrate on which a plurality
of pixels having a first electrode is formed, ii) a second
substrate on which a second electrode opposite to the first
electrode is formed, and iii) a liquid crystal layer, disposed
between the first and second substrate, which is aligned by an
electric field applied between the first and second electrodes; and
a polarizing plate disposed on the liquid crystal display panel,
the polarizing plate including i) a polarizing layer for polarizing
the second light, and ii) a light patch changing layer including a
reflection surface, the reflection surface for reflecting a part of
the second light and outputting a third light having a compensated
luminance, the reflection surface extended in a first direction
perpendicular to an upper surface of the liquid crystal display
panel, wherein the light path changing layer is disposed on a lower
surface of the polarizing layer.
2. A liquid crystal display device comprising: a liquid crystal
display panel for receiving a first light, and for radiating a
second light having an image information, the liquid crystal
display panel including: i) a first substrate on which a plurality
of pixels having a first electrode is formed, ii) a second
substrate on which a second electrode opposite to the first
electrode is formed, and iii) a nematic liquid crystal, disposed
between the first and second substrate, for being aligned by an
electric field applied between the first and second electrodes; and
a polarizing plate disposed on the liquid crystal display panel,
the polarizing plate including: i) a polarizing layer for
polarizing the second light, and ii) a light path changing layer
including a reflection surface, the reflection surface having a
plurality of pores and inner sidewalls adjacent to each of the
pores, the inner sidewalls reflecting a part of a first group of
light of the second light towards a second group of light of the
second light, the first group of light of the second light passing
through the nematic liquid crystal in a parallel direction with
regard to a first axis of the nematic liquid crystal tilted at a
predetermined angle by the electric field, the second group of
light of the second light passing through the nematic liquid
crystal in a parallel direction with regard to a second axis of
nematic liquid crystal, and the second axis being perpendicular to
the first axis of nematic liquid crystal, wherein the first group
of light of the second light has luminance higher than luminance of
the first group of light, and wherein the light path changing layer
is disposed on a lower surface of the polarizing layer.
3. A liquid crystal display device comprising: a lower substrate
including: i) a plurality of switching devices arranged in a matrix
shape on a first substrate, ii) a first electrode electrically
coupled to the switching devices, and iii) a first alignment layer
deposited on the first substrate and having a first rubbing pattern
extended in a first direction; an upper substrate including: i) a
color filter formed on a second substrate, ii) a second electrode
formed on the color filter, and iii) a second alignment layer
deposited on the second electrode and having a second rubbing
pattern extended in a second direction; a liquid crystal layer
disposed between the upper and lower substrates; a first polarizing
means, disposed on a lower surface of the lower substrate, for
polarizing a first light incident into the lower substrate; and a
second polarizing means, disposed on the upper substrate, for
polarizing a second light exited from the upper substrate, and for
reflecting a part of the second light to output a third light
having a compensated luminance, wherein the first polarizing means
includes a first polarizing layer having a first transmission axis
parallel to the second direction, and the second polarizing means
includes a second polarizing layer having a second transmission
axis parallel to the first direction, and wherein the second
polarizing means includes a porous layer having a plurality of
pores and sidewalls being defined by the pores, the porous layer
reflects a part of the second light to output the third light
having a compensated luminance distribution and provides the third
light to the second polarizing layer, and the second light is
incident into the sidewalls of the light path changing means.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional of U.S. patent application
Ser. No. 10/502,955, filed on Jul. 29, 2004, which is a 35 U.S.C.
371 filing of PCT/KR03100175 filed on Jan. 27, 2003 which in turn
claims priority to Korean Patent Application No. 2002-5942 filed on
Feb. 1, 2002 and Korean Patent Application No.: 2002-40069 filed on
Jul. 10, 2002, the disclosures of which are each all incorporated
herein by reference in their entirety.
TECHNICAL FIELD
[0002] The present invention relates to a liquid crystal display
device, and more particularly to a liquid crystal display device
capable of improving a viewing angle thereof and simultaneously
capable of reducing a gray scale inversion.
BACKGROUND ART
[0003] Generally, a liquid crystal display (LCD) device includes a
first substrate having a first electrode, a second substrate having
a second electrode opposite to the first electrode, and liquid
crystal disposed between the first and second substrates. The
liquid crystal display device changes an alignment of liquid
crystal by applying electric field to both the first and second
electrodes to adjust quantity of light passing through liquid
crystal, thereby displaying various images.
[0004] Twisted nematic (hereinafter, referred to TN) liquid
crystal, in which a long axis of liquid crystal is continuously
twisted from the first electrode towards the second electrode at a
right angle, is mainly used in the liquid crystal display
device.
[0005] Although TN liquid crystal is irregularly aligned, it has a
predetermined alignment order with respect to an axis of liquid
crystal. TN liquid crystal has different physical properties in a
long axis direction and a short axis direction thereof,
respectively. That is, TN liquid crystal has optically anisotropic
characteristic.
[0006] Hereinafter, a conventional TN-type liquid crystal display
device, which displays images by using above-mentioned TN liquid
crystal, will be described.
[0007] FIG. 1 is an exploded perspective view of a conventional
TN-type liquid crystal display device 400.
[0008] Referring to FIG. 1, the TN-type liquid crystal display
device 400 includes a backlight unit 200 for generating light, a
display unit 100 for receiving light from the backlight unit 200 to
display images, a mold frame 250 for accommodating the backlight
unit 200 and the display unit 100, and a chassis 300 therein.
[0009] The display unit 100 has a liquid crystal display panel 110
for displaying images, printed circuit boards 120 and 140 for
supplying a driving signal and an image data signal to the liquid
crystal display panel 110, and tape carrier packages (hereinafter,
referred to TCP) 130 and 150 disposed between the liquid crystal
display panel 110 and the printed circuit boards 120 and 140 in
order to electrically connect the printed circuit boards 120 and
140 to the liquid crystal display panel 110.
[0010] The liquid crystal display panel 110 includes a thin film
transistor substrate (hereinafter, referred to TFT substrate) 112
having thin film transistors (TFTs, not shown) and pixel electrodes
(not shown), a color filter substrate 114 opposite to the TFT
substrate 112 and having color filters and common electrode, and
liquid crystal (not shown) disposed between the TFT substrate 112
and the color filter substrate 114.
[0011] In detail, the TFT substrate 112 includes a plurality of
data lines (not shown) extended in a row direction thereof and a
plurality of gate lines (not shown) extended in a column direction
thereof.
[0012] In addition, a plurality of TFTs are arranged on the TFT
substrate 112 in a matrix shape. That is, source electrodes of the
TFTs are connected to the data lines, and gate electrodes of the
TFTs are connected to the gate lines. Drain electrodes of the TFTs
are connected to the pixel electrodes.
[0013] One end of each data line is coupled to a data-side TCP 130
equipped with a data driver chip, and one end of each gate line is
coupled to the gate-side TCP 150 equipped with a gate driver
chip.
[0014] The data-side TCP 130 is connected to a data-side printed
circuit board 120 so as to timely apply image data signal inputted
from the data-side printed circuit board 120 to the data lines. In
addition, the gate-side TCP 150 is connected to the gate-side
printed circuit board 140 so as to apply a gate driving signal
inputted from the gate-side printed circuit board 140 to the gate
lines.
[0015] On the other hand, the backlight unit 200 includes a light
source 210 for generating first light, and a light guiding plate
220 for guiding the first light towards the liquid crystal display
panel 110. The light source 210 includes a lamp (lamps) 211
generating the first light and a lamp reflection plate 213 covering
one side of the lamp (lamps) 211 to reflect the first light towards
the light guiding plate 220.
[0016] The light guiding plate 220 is disposed at the other side of
the lamp 211 and includes an incident surface through which the
first light is incident, a reflection surface for guiding the first
light towards the liquid crystal display panel 110, and an exiting
surface for outputting the first light towards the liquid crystal
display panel 110.
[0017] In addition, the backlight unit 200 includes a reflection
plate 240 and a plurality of optical films 230. The reflection
plate 240 is disposed below the light guiding plate 220 and
reflects light leaked from the light guiding plate 220 towards the
liquid crystal display panel 110. The plurality of optical films
230 allows the light outputted from the light guiding plate 220 to
have uniformly distributed luminance.
[0018] Since the conventional TN type liquid crystal display device
400 having the above structure uses the TN crystal having
optical-anisotropic characteristic, a color and a contrast ratio
(C/R) of the images vary depending on viewing angles. Therefore,
the conventional TN type liquid crystal display device 400 may
limit a range of viewing angles for allowing a user to precisely
recognize information displayed in a screen of the conventional TN
type liquid crystal display device 400.
[0019] Although it is not shown in the figures, the conventional
liquid crystal display device includes a compensating film (wide
view film) having a discotic layer so as to solve the above
problem. However, although the compensating film can improve the
viewing angle, gray scale inversion occurs when the viewing angle
exceeds a predetermined level.
[0020] That is, a normal gray level can be found when a user look
at the liquid crystal display panel 110 at a front thereof.
However, an abnormal gray level is found when a viewing position of
the user is changed upward or downward the front of the liquid
crystal display panel 110. When the liquid crystal display panel
110 is viewed with a viewing angle exceeding a critical viewing
angle, a white gray scale is erroneously recognized as a black gray
scale, or the black gray scale is erroneously recognized as the
while gray scale, called "gray scale inversion".
DISCLOSURE OF THE INVENTION
[0021] The present invention has been made to solve the above
problems of the related art, therefore, it is an object of the
present invention is to provide a liquid crystal display device
capable of improving a viewing angle thereof while reducing a gray
scale inversion.
[0022] In order to achieve the above object of the present
invention, according to one aspect of the present invention, there
is provided a liquid crystal display device comprising: a liquid
crystal display panel for receiving a first light, and for
radiating a second light having an image information, the liquid
crystal display panel including: i) a first substrate on which a
plurality of pixels having a first electrode is formed, ii) a
second substrate on which a second electrode opposite to the first
electrode is formed, and iii) a liquid crystal layer, disposed
between the first and second substrate, which is aligned by an
electric field applied between the first and second electrodes; and
a light path changing means disposed on the liquid crystal display
panel, the light path changing means including a reflection
surface, the reflection surface reflecting a part of the second
light and outputting a third light having a compensated luminance,
and the reflection surface being extended in a first direction
perpendicular to an upper surface of the liquid crystal display
panel.
[0023] In one aspect of the invention, there is provided a liquid
crystal display device comprising: a liquid crystal display panel
for receiving a first light, and for radiating a second light
having an image information, the liquid crystal display panel
including: i) a first substrate on which a plurality of pixels
having a first electrode is formed, ii) a second substrate on which
a second electrode opposite to the first electrode is formed, and
iii) a liquid crystal layer, disposed between the first and second
substrate, which is aligned by an electric field applied between
the first and second electrodes; and a polarizing plate disposed on
the liquid crystal display panel, the polarizing plate including:
i) a polarizing layer for polarizing the second light, and ii) a
light path changing layer including a reflection surface, the
reflection surface for reflecting a part of the second light and
outputting a third light having a compensated luminance, the
reflection surface extended in a first direction perpendicular to
an upper surface of the liquid crystal display panel.
[0024] In further aspect, there is provided a liquid crystal
display device comprising: a liquid crystal display panel for
receiving a first light, and for radiating a second light having an
image information, the liquid crystal display panel including: i) a
first substrate on which a plurality of pixels having a first
electrode is formed, ii) a second substrate on which a second
electrode opposite to the first electrode is formed, and iii) a
nematic liquid crystal, disposed between the first and second
substrate, which is aligned by an electric field applied between
the first and second electrodes; and a light path changing means
disposed on the liquid crystal display panel, the light path
changing means including a reflection surface, the reflection
surface reflecting a part of a first group of the second light
towards a second group of the second light, the first group of the
second light passing through the nematic liquid crystal in a
parallel direction with regard to a first axis of the nematic
liquid crystal tilted at a predetermined angle by the electric
field, the second group of the second light passing through the
nematic liquid crystal in a parallel direction with regard to a
second axis of nematic liquid crystal, and the second axis being
perpendicular to the first axis of nematic liquid crystal.
[0025] In further aspect, there is provided a liquid crystal
display device comprising: a liquid crystal display panel for
receiving a first light, and for radiating a second light having an
image information, the liquid crystal display panel including: i) a
first substrate on which a plurality of pixels having a first
electrode is formed, ii) a second substrate on which a second
electrode opposite to the first electrode is formed, and iii) a
nematic liquid crystal, disposed between the first and second
substrate, which is aligned by an electric field applied between
the first and second electrodes; and a polarizing plate disposed on
the liquid crystal display panel, the polarizing plate including:
i) a polarizing layer for polarizing the second light, and ii) a
light path changing layer including a reflection surface, the
reflection surface having a plurality of pores and inner sidewalls
adjacent to each of the pores, the inner sidewalls reflecting a
part of a first group of the second light towards a second group of
the second light, the first group of the second light passing
through the nematic liquid crystal in a parallel direction with
regard to a first axis of the nematic liquid crystal tilted at a
predetermined angle by the electric field, the second group of the
second light passing through the nematic liquid crystal in a
parallel direction with regard to a second axis of nematic liquid
crystal, and the second axis being perpendicular to the first axis
of nematic liquid crystal.
[0026] In further aspect, there is provided a liquid crystal
display device comprising: a lower substrate including: i) a
plurality of switching devices arranged in a matrix shape on a
first substrate, ii) a first electrode electrically coupled to the
switching devices, and iii) a first alignment layer deposited on
the first substrate and having a first rubbing pattern extended in
a first direction; an upper substrate including: i) a color filter
formed on a second substrate, ii) a second electrode formed on the
color filter, and iii) a second alignment layer deposited on the
second electrode and having a second rubbing pattern extended in a
second direction; a liquid crystal layer disposed between the upper
and lower substrates; and a light path changing means including a
plurality of pores and sidewalls being defined by the pores, the
light path changing means disposed on the upper substrate and
reflecting a part of a first light to output a second light having
a compensated luminance distribution, the first light exited from
the upper substrate and being incident into sidewalls of the light
path changing means.
[0027] In further aspect, there is provided a liquid crystal
display device comprising: a lower substrate including: i) a
plurality of switching devices arranged in a matrix shape on a
first substrate, ii) a first electrode electrically coupled to the
switching devices, and iii) a first alignment layer deposited on
the first substrate and having a first rubbing pattern extended in
a first direction; an upper substrate including: i) a color filter
formed on a second substrate, ii) a second electrode formed on the
color filter, and iii) a second alignment layer deposited on the
second electrode and having a second rubbing pattern extended in a
second direction; a liquid crystal layer disposed between the upper
and lower substrates; a first polarizing means, disposed on a lower
surface of the lower substrate, for polarizing a first light
incident into the lower substrate; and a second polarizing means,
disposed on the upper substrate, for polarizing a second light
exited from the upper substrate, and for reflecting a part of
second light to output a third light having a compensated
luminance.
[0028] According to the liquid crystal display device of the
present invention, the porous film includes sidewalls defined by a
plurality of pores and reflects a first group of light, which is
exited from the liquid crystal display panel and passes through a
short axis of liquid crystal, towards a second group of light
passing through a long axis of liquid crystal. Therefore, a gray
scale inversion can be reduced and the viewing angle of the liquid
crystal display device can be expanded.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] The above object, and other features and advantages of the
present invention will become more apparent by describing preferred
embodiments thereof with reference to the attached drawings in
which:
[0030] FIG. 1 is an exploded perspective view showing a
conventional TN-type liquid crystal display device;
[0031] FIG. 2 is an exploded perspective view showing a liquid
crystal display device according to one exemplary embodiment of the
present invention;
[0032] FIG. 3 is a sectional view showing a structure of a liquid
crystal display device shown in FIG. 2;
[0033] FIGS. 4 and 5 are views showing a light path to be changed
by a first porous film;
[0034] FIGS. 6A to 6E are views showing a plurality of pores formed
in a first porous film;
[0035] FIGS. 7A and 7B are views showing a second porous film
according to another exemplary embodiment of the present
invention;
[0036] FIGS. 8A and 8B are views showing a third porous film
according to still another exemplary embodiment of the present
invention;
[0037] FIGS. 9 and 10 are views showing a structure of a polarizing
plate of a liquid crystal display device according to an exemplary
second embodiment of the present invention;
[0038] FIGS. 11A to 11C are graphs showing luminance variation
according to viewing angles obtained by using comparative sample
1;
[0039] FIGS. 12A to 12C are graphs showing luminance variation
according to viewing angles obtained by using sample 1;
[0040] FIGS. 13A to 13C are graphs showing luminance variation
according to viewing angles obtained by using sample 2;
[0041] FIG. 14 is an exploded perspective view showing a liquid
crystal display device according to an exemplary third embodiment
of the present invention;
[0042] FIG. 15 is a sectional view showing a liquid crystal display
device shown in FIG. 14;
[0043] FIG. 16 is a schematic view showing a display unit shown in
FIG. 14;
[0044] FIG. 17 is a schematic view showing a viewing angle
characteristic according to rubbing directions of first and second
alignment layers shown in FIG. 16;
[0045] FIG. 18 is a schematic view showing a light path to be
changed by a porous film shown in FIG. 14;
[0046] FIGS. 19 and 21 are sectional views showing a liquid crystal
display device according to the exemplary fourth embodiment of the
present invention;
[0047] FIG. 20 is a perspective view showing a display unit shown
in FIG. 19;
[0048] FIGS. 22A to 22C are graphs showing simulation results
obtained through experiment 1 according to the present
invention;
[0049] FIGS. 23A to 23C are graphs showing simulation results
obtained through experiment 2 according to the present
invention;
[0050] FIGS. 24A to 24C are graphs showing simulation results
obtained through comparative experiment 1; and
[0051] FIGS. 25A to 25C are graphs showing simulation results
obtained through comparative experiment 2.
BEST MODE FOR CARRYING OUT THE INVENTION
[0052] Hereinafter, preferred embodiments of the present invention
will be described with reference to the accompanying drawings. The
same reference numerals are used to refer the same elements.
[0053] FIG. 2 is an exploded perspective view showing a liquid
crystal display device 1000 according to an exemplary first
embodiment of the present invention and FIG. 3 is a sectional view
of the liquid crystal display device 1000 shown in FIG. 2.
[0054] Referring to FIGS. 2 and 3, the liquid crystal display
device 1000 includes a backlight unit 600 for generating first
light, and a display unit 500. The display unit 500 receives the
first light and radiates second light having image information, to
thereby display images.
[0055] The display unit 500 has a liquid crystal display panel 510
for displaying images, printed circuit boards 520 and 540 for
supplying driving signals and image data signals to the liquid
crystal display panel 510, and TCPs 530 and 550 disposed between
the liquid crystal display panel 510 and the printed circuit boards
520 and 540 so as to electrically connect printed circuit boards
520 and 540 to the liquid crystal display panel 510.
[0056] The liquid crystal display panel 510 includes a TFT
substrate 512 having TFTs and pixel electrodes, a color filter
substrate 514 facing the TFT substrate 512 and having color filters
and common electrode, and liquid crystal (not shown) disposed
between the TFT substrate 512 and the color filter substrate
514.
[0057] The TN liquid crystal, in which a long axis of liquid
crystal is continuously twisted at a right angle from the pixel
electrode towards the common electrode, is mainly used in the
liquid crystal display device.
[0058] The TFT substrate 512 includes a plurality of data lines
(not shown) extended in a row direction thereof and a plurality of
gate lines (not shown) extended in a column direction thereof. In
addition, a plurality of TFTs is arranged on the TFT substrate 512
in a matrix shape. Source electrodes of the TFTs are connected to
the data lines, and gate electrodes of the TFTs are connected to
the gate lines. Drain electrodes of the TFTs are connected to the
pixel electrodes.
[0059] One end of each data line is coupled to the data-side TCP
530 equipped with a data driver chip, and one end of each gate line
is coupled to the gate-side TCP 550 equipped with a gate driver
chip.
[0060] The data-side TCP 530 is connected to the data-side printed
circuit board 520 so as to timely apply image data signal inputted
from the data-side printed circuit board 520 to the data lines. In
addition, the gate-side TCP 550 is connected to the gate-side
printed circuit board 540 so as to apply gate driving signal
inputted from the gate-side printed circuit board 540 to the gate
lines.
[0061] A first porous film 560 is disposed on the liquid crystal
display panel 510. A dimension of the first porous film 560
corresponds to that of the liquid crystal lo display panel 510, and
the first porous film 560 has a plurality of pores. Inner sidewalls
of the first porous film 560 defined by the plurality of pores
change a path of the second light, which is exited from the liquid
crystal display panel 510 and includes image information, to output
a third light providing an expanded viewing angle.
[0062] The first porous film 560 includes a first incident surface
561 discontinuously extended in a first direction D1, a first
exiting surface 562 opposite to the first incident surface 561, and
sidewalls 563 connecting the first incident surface 561 to the
first exiting surface 562 and extended in a second direction D2.
Hereinafter, the sidewalls 563 are defined as "inner sidewalls"
defined by the plurality of pores 565. The first porous film 560 is
comprised of a high polymer resin, such as a transparent acryl
resin, having a predetermined refractive index.
[0063] Although it is not illustrated in the figures, the pores 565
can be formed at the first porous film 560 through various
well-known processes. For example, the pores 565 can be formed at
the first porous film 560 by using silica particles, by irradiating
laser beam into a high polymer film, or by performing, a
photolithography process. These techniques for fabricating the
first porous film 560 are well-known in the art, and will not be
further described below.
[0064] In addition, the backlight unit 600 includes a light source
610 for generating first light and a light guiding plate 620 for
guiding the first light towards the liquid crystal display panel
510.
[0065] The light source 610 includes a lamp (lamps) 611 for
generating the first light and a lamp reflection plate 613 for
covering one side of the lamp 611 to reflect the first light
towards the light guiding plate 620.
[0066] The light guiding plate 620 is disposed at the other side of
the lamp(s) 611, is a hexahedron-shaped plate, and includes an
incident surface for receiving the first light, a reflection
surface for guiding first light towards the liquid crystal display
panel 510, and an exiting surface for outputting the first light
towards the liquid crystal display panel 510. Accordingly, the
light guiding plate 620 guides the first light towards the liquid
crystal display panel 510.
[0067] In addition, the backlight unit 600 includes a reflection
plate 640 disposed below the light guiding plate 620 to reflect
light leaked from the light guiding plate 620 towards the liquid
crystal display panel 510, and a plurality of optical sheets 630
for allowing the light outputted from the light guiding plate 620
to have luminance uniformly distributed.
[0068] The backlight unit 600 and the display unit 500 having the
above structure are sequentially accommodated in a receiving space
of a mold frame 700. Then, the backlight unit 600 and the display
unit 500 are fixed to the mold frame 700 by a chassis 800 facing
the mold frame 700.
[0069] FIGS. 4 and 5 are views showing a light path to be changed
by the first porous film.
[0070] Referring to FIG. 4, the liquid crystal display panel 510
includes the first porous film 560. The first porous film 560
partially changes the path of the second light exited from the
liquid crystal panel 510, and outputs third light providing an
expanded viewing angle.
[0071] The liquid crystal display panel 510 includes the TFT
substrate 512 comprised of a plurality of pixels 513, the color
filter substrate 514 having color filters 514a and common electrode
514b, and liquid crystal 515 disposed between the TFT substrate 512
and the color filter substrate 514. Each pixel 513 has a TFT 512a
and a pixel electrode 512b.
[0072] When voltage is provided between the pixel electrode 512b
and the common electrode 514b, an electric field is formed between
the pixel electrode 512b and the common electrode 514b.
Accordingly, an alignment angle of liquid crystal 515 varies, so
that quantity of first light L1 incident into the liquid crystal
display panel 510 is adjusted depending on the alignment angle.
Therefore, a predetermined quantity of second light L2 is
outputted.
[0073] The second light L2 exits from the liquid crystal display
panel 510, and is incident into the first porous film 560. A first
part of the second light L2 is incident into the incident surface
651 of the first porous film 560, a second part of second light L2
is incident into the sidewalls 563 of the first porous film 560,
and the remaining of the second light L2 is incident into the pores
565 of the first porous film 560. The sidewalls 565 of the first
porous film 560 reflect a first and a second group of light (L21
and L22) of the second light L2, which are incident into the
sidewalls 565 of the first porous film 560 and have a first
incident angle larger than a critical angle of the first porous
film 560.
[0074] Although it is not illustrated in the figures, the first
porous film 560 refracts a third group of light of the second light
L2, which is incident into the incident surface 561 of the first
porous film 560 and has a second incident angle smaller than the
critical angle of the first porous film 560, to thereby output
fourth light having an exiting angle different from the second
incident angle. In addition, a remained fourth group of light L24,
excepting the first, the second and the third group of light, of
the second light L2 is outputted through the pores 565.
[0075] A size (w1) of the pores 565 formed in the first porous film
560 is preferably smaller than a size (w2) of the pixel 513 formed
on the TFT substrate 512. In addition, a thickness (d) of the first
porous film 560 is in a range of about 5 to about 10 .mu.m. It is
preferred that the thickness (d) of the first porous film 560 is
wide enough such that a sufficient quantity of light of the second
light L2, which is exited from the liquid crystal display panel
510, may be incident into the sidewalls 565 of the first porous
film 560. However, it is required to limit the thickness (d) of the
first porous film 510 so as to provide a liquid crystal display
device with a slim structure.
[0076] Referring to FIGS. 4 and 5, when voltage is provided between
the pixel electrode 512b of the TFT substrate 512 and the common
electrode 514b of the color filter substrate 514, an electric field
is formed between the pixel electrode 512b and the common electrode
514b, and a long axis of liquid crystal 515 is tilted at a
predetermined angle with respect to the first direction D1. When
the first light L1 is provided to the liquid crystal display panel
510, the quantity of first light L1 incident into the liquid
crystal display panel 510 is adjusted by the tilted liquid crystal,
to thereby output the second light L2 including image
information.
[0077] As shown in FIG. 5, if the liquid crystal 515 is tilted
toward the first direction D1, the first group of light L21 passed
through the long axis of liquid crystal 515 is reflected by a first
sidewall 563a and is exited from the first sidewall 563a, and the
second group of light L22 passed through a short axis of liquid
crystal 515 is reflected by a second sidewall 563b opposite to the
first sidewall 563a and is exited from the second sidewall 563.
[0078] In addition, front-side light L24-f of the fourth group of
light L24, which penetrates though the pores 565, passes through
the liquid crystal 515 in a direction parallel to the first
direction D1 to be exited from the liquid crystal 515. Right-side
light L24-r of the fourth group of light L24 passes through liquid
crystal 515 in a direction between the second direction D2 and a
long-axis direction to be exited from the liquid crystal 515, and
left-side light L24-l of the fourth group of light L24 is passes
through the liquid crystal 515 in a direction between the second
direction D2 and a short-axis direction to be exited from the
liquid crystal 515.
[0079] Since the first group of light L21 passes through the long
axis of liquid crystal 515, the first group of light L21 loses a
relatively large quantity of light while passing through liquid
crystal 515 compared with the second group of light L22. On the
contrary, since the second group of light L22 passes through the
short axis of liquid crystal 515, the second group of light L22
loses a relatively small quantity of light while passing through
liquid crystal 515 compared with the first group of light L21.
Therefore, the first group of light L21 of the second light L2 has
a quantity of light less than that of the second group of light L22
of the second light L2.
[0080] The first group of light L21 is reflected by the first
sidewall 563a so that the light path thereof is changed in parallel
to the short axis of liquid crystal 515. The second group of light
L22 is reflected by the second sidewall 563b so that the light path
thereof is changed in parallel to the long axis of liquid crystal
515. On the other hand, the front-side light L24-f, the left-side
light L24-l and the right-side light L24-r of the fourth group of
light L24 pass through the pores 565 of the first porous film 560,
without making contact with the first porous film 560.
[0081] Accordingly, the first group of light L21 compensates for
luminance of the left-side light L24-l tilted in a left direction
with respect to the second direction D2, to thereby exit light
having uniform luminance. In addition, the second group of light
L22 compensates for luminance of the right-side light L24-r tilted
in a right direction with respect to the second direction D2, to
thereby exit light having uniform luminance. That is, the first
porous film 560 allows the second light L2, which represents
different luminance characteristic depending on viewing points
thereof, to be exited as third light L3 to provide expanded viewing
angle. Therefore, the first porous film 560 expands the viewing
angle of the liquid crystal display device 1000 and prevents the
"gray scale inversion", which occurs when the viewing angle exceeds
a predetermined level.
[0082] In addition, since the porous film 560 allows the front-side
light L24-f to directly pass through the pores 565, luminance of
the liquid crystal display device 1000 will be improved when viewed
from a front of the liquid crystal display device 1000.
[0083] FIGS. 6A to 6E are views showing the plurality of pores
formed in the first porous film.
[0084] Referring to FIG. 6A, the first porous film 560 includes a
plurality of plural pores 565 having a regular square shape. Since
the pores 565 have the regular square shape, front, rear, left, and
right sidewalls (not shown) of the first porous film 560 have equal
sectional area. Thus, the first porous film 560 can compensate for
luminance in front, rear, left, and right directions of the pores
565.
[0085] On the other hand, referring to FIGS. 6B and 6C, the first
porous film 560 includes a plurality of plural pores 565 having a
horizontally elongated rectangular shape or a horizontally
elongated oval shape. Since the pores 565 have the horizontally
elongated rectangular shape or the horizontally elongated oval
shape, sectional areas of the front and rear sidewalls (not shown)
of the first porous film 560 are larger than sectional areas of the
left and right sidewalls of the first porous film 560. Thus, the
first porous film 560 can better compensate for luminance in the
front and rear directions of the pores 565 compared with in the
left and right directions of the pores 565.
[0086] In addition, referring to FIGS. 6D and 6E, the first porous
film 560 includes a plurality of plural pores 565 having a
vertically elongated rectangular shape or a vertically elongated
oval shape. Since the pores 565 has the vertically elongated
rectangular shape or the vertically elongated oval shape, sectional
areas of the left and right sidewalls (not shown) of the first
porous film 560 are larger than sectional areas of the front and
rear sidewalls of the first porous film 560. Thus, the first porous
film 560 can better compensate for luminance in left and right
directions of the pores 565 compared with in the front and left
directions of the pores 565.
[0087] The present invention has been described with reference to
the first porous film 560 having a single layer structure.
Hereinafter, the present invention will be described with reference
to second and third porous films having multi-layer structure.
[0088] FIGS. 7A and 7B are views showing the second porous film
according to another exemplary embodiment of the present
invention.
[0089] Referring to FIGS. 7A and 7B, the second porous film 570
includes a porous layer 571 having a plurality of pores 571, and a
supporting layer 572 for supporting an incident surface 571b of the
second porous layer 571. The supporting layer 572 is integrally
formed with the second porous layer 571.
[0090] The second porous layer 571 has the incident surface 571
discontinuously extended in the first direction D1 parallel to an
upper surface of the supporting layer 572, an exiting surface 571c
opposite to the incident surface 571, and a plurality of sidewalls
571d connecting the incident surface 571b to the exiting surface
571c and extended in the second direction D2 perpendicular to the
upper surface of the supporting layer 572.
[0091] FIGS. 8A and 8B are views showing the third porous film
according to another exemplary embodiment of the present
invention.
[0092] Referring to FIGS. 8A and 8B, the third porous film 580
includes a porous layer 581 having a plurality of pores 581, a
first supporting layer 582 for supporting an incident surface 581b
of the third porous layer 581, and a second supporting layer 583
for supporting an exiting surface 581c of the porous layer 581. The
first and second supporting layers 582 and 583 are integrally
formed with the porous layer 581.
[0093] The third porous layer 581 has the incident surface 581a
discontinuously extended in the first direction D1 parallel to
upper surfaces of the first and second supporting layers 582 and
583, the exiting surface 581c opposite to the incident surface 581,
and a plurality of sidewalls 581d connecting the incident surface
581b to the exiting surface 581c and extended in the second
direction D2 perpendicular to the upper surfaces of the first and
second supporting layers 582 and 583.
[0094] Hereinafter, a second embodiment of the present invention
will be described, in which the first, second and third porous
films 560, 570 and 580 are not provided in the liquid crystal
display device 1000 as separate elements, but integrally formed
with a polarizing plate, which is installed at an upper or a lower
portion of the liquid crystal display panel 510 to perform a
polarizing function.
[0095] FIGS. 9 and 10 are views showing a structure of the
polarizing plate of the liquid crystal display device according to
the exemplary second embodiment of the present invention.
[0096] Referring to FIG. 9, a first polarizing plate 590 includes a
polarizing layer 591 for outputting third light (not shown) by
polarizing second light (not shown), which is exited from the
liquid crystal panel 510 and includes image information, a
supporting layer 592 disposed between the polarizing layer 591 and
the liquid crystal display device 510 so as to support the
polarizing layer 591, and a porous layer 593 having a plurality of
pores and being disposed on the polarizing layer 591 so as to
output fourth light (not shown) providing an expanded viewing angle
by partially changing a path of the third light polarized by the
polarizing layer 591.
[0097] Generally, the polarizing layer 591 is formed by absorbing
iodine or dichromatic dyes into polyvinyl alcohol (PVA) layer,
which is extended in a third direction parallel to the upper
surface of the liquid crystal display panel 510.
[0098] Since iodine molecules and dye molecules have dichromatic
property, they absorb the light vibrating in parallel to the third
direction and transmit the light vibrating perpendicular to the
third direction. Accordingly, the polarizing layer 591 absorbs
light components vibrating in the third direction and transmits
light components vibrating in a fourth direction, which is parallel
to the upper surface of the liquid crystal display panel 510 and
perpendicular to the third direction.
[0099] The supporting layer 592 is comprised of triacetate
cellulose (hereinafter, referred to TAC) resin having a superior
endurance, and supports and protects the polarizing layer 591.
[0100] The porous layer 593 has an incident surface 593b
discontinuously extended in the first direction D1 parallel to an
upper surface of the polarizing layer 591, an exiting surface 593c
opposite to the incident surface 593b, and a plurality of sidewalls
593d connecting the incident surface 593b to the exiting surface
593c and extended in the second direction D2 perpendicular to the
upper surface of the polarizing layer 591. Accordingly, the porous
layer 593 outputs fourth light to provide expanded viewing angle by
partially changing the path of the third light exited from the
polarizing layer 591 through the sidewall 593d.
[0101] The porous layer 593, like the supporting layer 592,
includes TAC resin having a superior endurance, and supports and
protects the polarizing layer 591.
[0102] Referring to FIG. 10, a second polarizing plate 595 includes
a porous layer 596, a polarizing layer 597 and a supporting layer
598. The porous layer 596 has a plurality of pores and outputs
third light (not shown) to provide expanded viewing angle by
partially changing a path of second light (not shown) exited from
the liquid crystal display panel 510. The polarizing layer 597 is
disposed on the porous layer 596 to polarize the third light. The
supporting layer 598 is disposed on the polarizing layer 597 and
supports the polarizing layer 597.
[0103] The porous layer 596 has an incident surface 596b
discontinuously extended in the first direction D1 parallel to an
upper surface of the polarizing layer 597, an exiting surface 596c
opposite to the incident surface 596b, and a plurality of sidewalls
596d connecting the incident surface 596b to the exiting surface
596c and extended in the second direction D2 perpendicular to the
upper surface of the polarizing layer 597.
[0104] Accordingly, the porous layer 596 outputs third light to
provide expanded viewing angle by partially changing the path of a
polarized second light exited from the liquid crystal display panel
510 through the sidewall 596d.
[0105] Simulation of Gray Scale Inversion According to Variation of
Viewing Angles
[0106] Hereinafter, a first porous film having a plurality of pores
with a size about 5 .mu.m is used in sample 1 so as to measure
luminance of the liquid crystal display device, and a first porous
film having a plurality of pores with a size about 2 .mu.m is used
in sample 2 so as to measure luminance of the liquid crystal
display device. In addition, the first porous film is not used in
comparative sample 1.
[0107] FIGS. 11A to 11C are graphs showing luminance variation
according to viewing angles obtained by using comparative sample 1,
FIGS. 12A to 12C are graphs showing luminance variation according
to viewing angles obtained by using sample 1, and FIGS. 13A to 13C
are graphs showing luminance variation according to viewing angles
obtained by using sample 2. Each curve of each graph shown in FIGS.
11A to 13C represents one of 8-gray scales made by dividing 64-gray
scales into 8-gray scales.
[0108] In detail, FIGS. 11A, 12A and 13A represent luminance
variation depending on viewing angles varying along a upper and
lower direction of a screen of the liquid crystal display panel.
FIGS. 11B, 12B and 13B are enlarged views showing luminance
variation at upper portions of the curves in FIGS. 11A, 12A and
13A, respectively. FIGS. 11C, 12C and 13C are enlarged views
showing luminance variation at lower portions of the curves in
FIGS. 11A, 12A and 13A, respectively. In FIGS. 11A to 13C, an
x-axis represents a viewing angle (.degree.) and a y-axis
represents luminance (cd/m.sup.2).
[0109] Referring to FIGS. 11A to 11C, luminance does not increase
although each gray scale becomes higher, when the first porous film
is not used. In addition, a lower gray scale has luminance higher
than luminance of a higher gray scale. That is, the "gray scale
inversion" occurs at upper and lower portions when the viewing
angles are about 24.degree. and -44.degree., respectively.
[0110] On the contrary, referring to FIGS. 12A to 12C, when the
first porous having a plurality of pores with a size about 5 .mu.m
is used, a satisfactory viewing angle characteristic can be
achieved. That is, luminance increases according as each gray scale
becomes higher. In detail, the "gray scale inversion" just occurs
at the upper portion of the curve only when the viewing angle is
about 28.degree., the "gray scale inversion" does not occur at the
lower portion of the curve. In addition, the gray scale inversion
is reduced in FIGS. 12A to 12C using sample 1 compared with in
FIGS. 11A to 11C using comparative sample 1.
[0111] In addition, referring to FIGS. 13A to 13C, when the first
porous having a plurality of pores with a size about 2 .mu.m is
used, a satisfactory viewing angle characteristic can be achieved.
That is, luminance increases according as each gray scale becomes
higher. In detail, the "gray scale inversion" does not occur at the
upper portion of the curve up to the viewing angle of about
80.degree. In addition, the "gray scale inversion" does not occur
at the lower portion of the curve down to the viewing angle of
-80.degree. Thus, the gray scale inversion is reduced in FIGS. 13A
to 13C using sample 2 compared with in FIGS. 11A to 11C using
comparative sample 1.
[0112] FIG. 14 is an exploded perspective view showing a liquid
crystal display device according to an exemplary third embodiment
of the present invention and FIG. 15 is a sectional view showing a
liquid crystal display device shown in FIG. 14.
[0113] Referring to FIGS. 14 and 15, the liquid crystal display
device 1100 according to the exemplary third embodiment of the
present invention includes a backlight unit 600 for generating
first light, and a display unit 900 for displaying images.
[0114] The display unit 900 has a liquid crystal display panel 910
for displaying images, a lower polarizing plate 970 disposed below
the liquid crystal display panel 910, an upper polarizing plate 980
disposed above the liquid crystal display panel 910, and a porous
film 960 disposed on the upper polarizing panel 980.
[0115] The liquid crystal display panel 910 includes a TFT
substrate 912, a color filter substrate 914 and liquid crystal (not
shown). The TFT substrate 912 includes TFTs (not shown), pixel
electrodes (not shown) and a first alignment layer (not shown). The
color filter substrate 914 is opposite to the TFT substrate 912,
and has color filters (not shown), common electrode (not shown) and
a second alignment layer (not shown). Liquid crystal is disposed
between the TFT substrate 912 and the color filter substrate 914.
TN liquid crystal, in which a long axis of liquid crystal is
continuously twisted at a right angle from the pixel electrode
towards the common electrode, is mainly employed in the liquid
crystal display device.
[0116] The lower polarizing plate 970 polarizes first light
incident from the backlight unit 600, and provides the polarized
first light to the liquid crystal display panel 910. The polarized
first light is incident into the liquid crystal display panel 910,
and is deflected in a predetermined direction while passing through
the twisted liquid crystal, which has an varied aligning angle
depending on an electric field applied to the liquid crystal, so
that second light having image information is outputted.
[0117] The second light is incident into the upper polarizing plate
980. The upper polarizing plate 980 adjusts quantity of the second
light, and improves viewing angle of the second light.
[0118] FIG. 16 is a schematic view showing the display unit shown
in FIG. 14, in detail.
[0119] Referring to FIG. 16, the TFT substrate 912 includes a
plurality of gate lines 912a extended in a column direction thereof
(hereinafter, referred to a first direction D1), and a plurality of
data lines 912b extended in a row direction thereof (hereinafter,
referred to a second direction D2). In addition, a plurality of
TFTs 912c is arranged on the TFT substrate 912 in a matrix shape.
Source electrodes of the TFTs 912c are connected to the data lines
912b, and gate electrodes of the TFTs 912c are connected to the
gate lines 912a. Drain electrodes of the TFTs 912c are connected to
pixel electrodes 912d.
[0120] A first alignment layer 913 is deposited on an entire
surface of the TFT substrate 912 having TFTs 912c and pixel
electrode 912d. The first alignment layer 913 includes a polyimid
based organic layer and a first rubbing pattern (not shown) formed
on the polyimid based organic layer and rubbed in the first
direction D1.
[0121] For example, the first rubbing pattern is extended precisely
the same direction as the first direction D1 in FIG. 16, but the
first rubbing pattern can be extended in a tilted direction with
respect to the first direction D1 by a predetermined angle. The
predetermined angle is determined within a predetermined range,
such that the extended direction of the first rubbing pattern does
not extremely obviate from the first direction D1.
[0122] In addition, the color filter substrate 914 is disposed
opposite to the TFT substrate 912. The color filter substrate 914
has color filters (not shown), common electrode (not shown) and a
second alignment layer 915. Similar to the first alignment layer
913, the second alignment layer 915 includes a polyimid based
organic layer and a second rubbing pattern (not shown), the second
rubbing pattern is formed on the polyimid based organic layer, and
is rubbed in the second direction D2.
[0123] As shown in FIG. 16, if the first rubbing patterns extended
in the first direction D1 are formed in the first alignment layer
913, and the second rubbing patterns extended in the second
directions D2 are formed in the second alignment layer 915, a
process for rubbing the first and second rubbing patterns can be
simplified. In other words, when the first and second rubbing
patterns are extended in the first and second directions (D1, D2),
respectively, the distance of the rubbing process becomes shorter
compared when the first and second rubbing patterns are extended in
a diagonal direction of a screen of the liquid crystal display
device, so that the rubbing process with respect to the first and
second alignment layers 913 and 915 can be simplified.
[0124] A liquid crystal layer 916 is disposed between the TFT
substrate 912 and the color filter substrate 914.
[0125] In addition, the lower polarizing plate 970 is disposed
below the TFT substrate 912, and the upper polarizing plate 980 is
disposed above the color filter substrate 914.
[0126] The lower polarizing plate 970 includes a first polarizing
layer 971 and first and second supporting layers 972 and 973. The
first and second supporting layers 972 and 973 are disposed at a
upper and lower surfaces of the first polarizing layer 971 so as to
support the first polarizing layer 971. The first polarizing layer
971 polarizes incident light by absorbing light components
vibrating in the first direction D1 and by transmitting light
components vibrating in the second direction D2 perpendicular to
the first direction D1.
[0127] The upper polarizing plate 980 includes a second polarizing
layer 981 and third and fourth supporting layers 982 and 983. The
third and fourth supporting layers 982 and 983 is disposed at a
upper an lower surfaces of the second polarizing layer 981 so as to
support the second polarizing layer 981. The second polarizing
layer 981 polarizes incident light by absorbing light components
vibrating in the second direction D2 and by transmitting light
components vibrating in the first direction D1.
[0128] A first transmission axis extended in the first direction D1
is formed in the first polarizing layer 971, and a second
transmission axis extended in the second direction D2 is formed in
the second polarizing layer 981, so that cutting errors, which
occur during cutting the first and second polarizing layers 971 and
981, can be prevented. Accordingly, productivity of the lower and
upper polarizing plates 970 and 980 is improved, and reduces cost
for manufacturing of the lower and upper polarizing plates 970 and
980.
[0129] Although not shown in FIG. 16, a first and second
compensating films for compensating for the viewing angle of the
liquid crystal display device 1100 can be disposed at the lower and
upper polarizing plates 970 and 980, respectively. Preferably, a
direction of rubbing discotic liquid crystal formed in the first
compensating film is parallel to the first direction D1, and a
direction of rubbing the discotic liquid crystal formed in the
second compensating film is parallel to the second direction
D2.
[0130] As shown FIG. 16, the first rubbing pattern is extended in
the first direction D1, and the second rubbing pattern is extended
in the second direction D2, but the present invention does not
limited to these structures. Specifically, on the consumption that
the first rubbing pattern is aligned perpendicular to the second
rubbing pattern, each of the first and second rubbing patterns can
be extended in an upper, lower, left and right directions with
respect to a front of the screen of the liquid crystal display
device.
[0131] The directions of the first and second transmission axes
formed in the first and second polarizing plates 970 and 980 vary
in correspondence with the variations of the first and second
rubbing patterns.
[0132] Referring to FIGS. 14 to 16, the porous film 960 having a
size corresponding to a size of the liquid crystal display panel
910 is aligned on the liquid crystal display panel 910. The porous
film 960 includes a first incident surface 961 toward which second
light exited from the liquid crystal display device 910 is
incident, an exiting surface 962 for outputting second light, and
sidewalls 963 connecting the first incident surface 961 to the
exiting surface 962. A plurality of pores 965 extended from the
incident surface 961 to the exiting surface 962 are formed in the
porous film 960.
[0133] Accordingly, the porous film 960 includes a plurality of
sidewalls 964. The sidewalls 964 connect the incident surface 961
to the exiting surface 962, and define the pores 965. The sidewalls
change the path of the second light, thereby outputting third light
to provide expanded viewing angle.
[0134] FIG. 17 is a schematic view showing viewing angle
characteristic according to rubbing directions of first and second
alignment layers shown in FIG. 16, and FIG. 18 is a schematic view
showing the light path to be changed by the porous film. In FIG.
17, left and right sides with respect to a front of the screen are
marked as A and A', respectively, and, upper and lower sides with
respect to a front of the screen are marked as B and B',
respectively.
[0135] Referring to FIG. 17, a first rubbing pattern rubbed in the
right direction A' is formed in the first alignment layer, and a
second rubbing pattern rubbed in the downward direction B' is
formed in the second alignment layer. The liquid crystal 916
adjacent to the first second rubbing patterns is aligned along the
first rubbing pattern to be tilted in the right direction (A'), and
the liquid crystal 916 adjacent to the second rubbing patterns is
aligned along the second rubbing pattern to be tilted in the
downward direction (B'). Points shown in FIG. 17 represent a tilted
direction of the liquid crystal 916.
[0136] If the liquid crystal is tilted toward the right side A', a
user catches light passing through the long axis of liquid crystal
916 when the user watch the screen from the right side A' above the
screen, and the user catches light passing though the short axis of
liquid crystal 916 when the user watch the screen from the left
side B' above the screen. The light passed through the long axis of
liquid crystal 916 has a less quantity of light compared with the
light passed through the short axis of liquid crystal 916.
Accordingly, luminance variation is generated in the right and left
directions A' and A.
[0137] In order to compensate for the luminance variation, the
porous film 960 is provided to the liquid crystal display device
1100. Hereinafter, the luminance variation will be described in
FIG. 18. Since lower and upper polarizing plates are not
illustrated in FIG. 18, they will not be described below.
[0138] Referring to FIG. 18, the liquid crystal display panel 910
includes the TFT substrate 912, the color filter substrate 914 and
liquid crystal 916. The TFT substrate 912 has the TFTs 912c, the
pixel electrode 912d and the first alignment layer 913. The color
filter substrate 914 is opposite to the TFT substrate 912 and has
color filters 914a, common electrode 914b and the second alignment
layer 915. Liquid crystal 916 is disposed between the TFT substrate
912 and the color filter substrate 914.
[0139] When voltage is applied to both the pixel electrode 912b and
the common electrode 914b, an electric field is formed between the
pixel electrode 912b and the common electrode 914b. Accordingly, an
alignment angle of liquid crystal 915 varies, and quantity of light
incident into the liquid crystal display panel 910 is adjusted, to
thereby output second light L2 having a predetermined quantity of
light. Then, second light L2 is incident into the porous film 960.
According to FIG. 18, the second light L2 is incident into a first
sidewall 964a and reflected thereby at a predetermined angle. The
first sidewall 964a reflects a group of second light L2 having a
first incident angle larger than a critical angle of the porous
film 960.
[0140] The size of the pores 965 is preferably smaller than the
size of a unit pixel formed on the TFT substrate 912. In addition,
thickness t of the porous film 960 is preferably in a range about 5
to 100 .mu.m.
[0141] As shown in FIG. 18, when the electric field is formed
between the pixel electrode 912d and the common electrode 914b, the
long axis of liquid crystal 916 is tilted by a predetermined angle
with respect to the first direction D1. When the first light L1 is
provided to the liquid crystal display panel 910, the first light
L1 has some quantity of light adjusted by the tilted liquid crystal
916, so that the second light L2 having image information is
exited.
[0142] On the assumption that liquid crystal 916 is tilted in the
first direction D1, the first group of light L21 reflected by the
first sidewall 964a is outputted through the long axis of liquid
crystal 916, and the second group of light L22 reflected by a
second sidewall 964b opposite to the first sidewall 964a is
outputted through the short axis of liquid crystal 916.
[0143] Since the first group of light L21 passes through the long
axis of liquid crystal 916, relatively large loss of light will be
caused while the first group of light L21 passes through the liquid
crystal 916. On the contrary, since the second group of light L22
passes through the short axis of liquid crystal 916, relatively
small loss of light will be caused while the second group of light
L22 passes through liquid crystal 916. Therefore, the first group
of light L21 has a quantity of light less than that of the second
group of light L22.
[0144] The path of the first group of light L21 reflected by the
first sidewall 964a is changed to proceed in a direction parallel
to the long axis of liquid crystal 916. In addition, the path of
the second group of light L22 reflected by the second sidewall 964b
is changed to proceed in a direction parallel to the short axis of
liquid crystal 916. Accordingly, the luminance variation can be
reduced at the left and right sides A and A'.
[0145] Referring again to FIGS. 17 and 18, the viewing angle of the
liquid crystal display device 1100 is expanded since the first and
second rubbing patterns 913a and 915a formed on the first and
second alignment layers 913 and 915 are rubbed in the first and
second directions D1 and D2, respectively. In detail, left and
right viewing angles of the liquid crystal display device 1100 are
expanded according as luminance increases in a white mode of the
liquid crystal display device 1100. In addition, upper and lower
viewing angles are improved according as luminance decreases in a
black mode of the liquid crystal display device 1100.
[0146] According to the above principle, luminance can be increased
in the white mod by providing the first and second rubbing patterns
913a and 915a extended in the right and lower directions A' and B',
respectively, in the liquid crystal display device 1100. In
addition, it is possible to prevent light from being leaked in the
black mode of the liquid crystal display device 1100, so that
luminance is reduced in the black mode. Thus, the left and right
viewing angles and the upper and lower viewing angles of the liquid
crystal display device 1100 can be expanded.
[0147] FIGS. 19 and 21 are sectional views showing a liquid crystal
display device 1200 according to an exemplary fourth embodiment of
the present invention, and FIG. 20 is a perspective view showing a
display unit 900 shown in FIG. 19.
[0148] Referring to FIG. 19, the liquid crystal display device 1200
includes the display unit 900 for displaying images and a backlight
unit 600 for generating light. The display unit 900 has a liquid
crystal display panel 910, a lower polarizing plate 970 disposed
below the liquid crystal display panel 910, and an upper polarizing
plate 990 disposed above the liquid crystal display panel 910.
[0149] As shown in FIG. 20, the liquid crystal display panel 910
includes a TFT substrate 912, a color filter substrate 914 and
liquid crystal 916 disposed between the TFT substrate 912 and the
color filter substrate 914.
[0150] In detail, the TFT substrate 912 has a plurality of gate
lines 912a extended in the first direction, and a plurality of data
lines 912b extended in the second direction D2. In addition, a
plurality of TFTs 912c is arranged on the TFT substrate 912 in a
matrix shape. That is, source electrodes of the TFTs 912c are
connected to the data lines 912b, and gate electrodes of the TFTs
912c are connected to the gate lines 912a. Drain electrodes of the
TFTs 912c are connected to pixel electrodes 912d. A first alignment
layer 913 is deposited on an entire surface of the TFT substrate
912 having the TFT 912c and the pixel electrode 912d. An organic
layer comprised of polyimid series material is deposited on the
first alignment layer 913, and then a first rubbing pattern (not
shown) rubbed in the first direction D1 is formed on the organic
layer.
[0151] In addition, a color filter substrate 914 faces the TFT
substrate 912. The color filter substrate 914 includes color
filters (not shown), common electrode (not shown) and a second
alignment layer 915. Similar to the first alignment layer 913, an
organic layer comprised of polyimid series material is deposited on
the second alignment layer 915, and then a second rubbing pattern
(not shown) rubbed in the second direction D2 is formed on the
organic layer.
[0152] The lower polarizing plate 970 is disposed between the TFT
substrate 912 and an optical sheet 630, and the upper polarizing
plate 990 is disposed above the color filter substrate 914.
[0153] The lower polarizing plate 970 includes a first polarizing
layer 971 and a first and a second supporting layers 972 and 973.
The first polarizing layer 971 polarizes light. The first and
second supporting layers 972 and 973 is disposed on an upper a
lower surfaces of the first polarizing layer 971 so as to support
the first polarizing layer 971.
[0154] The first polarizing layer 971 is formed by adsorbing iodine
or dichromatic dyes onto a PVA layer, the PVA layer has a
transmission axis extended in the first direction D1.
[0155] The upper polarizing plate 990 includes a second polarizing
layer 991 for polarizing light, a third supporting layer 992
disposed on a lower surface of the second polarizing layer 991, and
a porous layer 993 disposed on an upper surface of the second
polarizing layer 991. The porous layer 993 has a plurality of pores
993a. The porous layer 993 includes sidewalls 993b, each sidewall
993b is defined by each pore 993a. The sidewalls 993b partially
change the path of the light incident into the upper polarizing
plate 990, thereby exiting light to provide expanded viewing
angle.
[0156] As mentioned above, since the upper polarizing plate 990 has
the porous layer 993 on the second polarizing layer 991, the upper
polarizing plate 990 polarizes third light and improves the viewing
angle of a polarized third light. On the other hand, the porous
layer 993 can be formed on the lower surface of the second
polarizing layer 991, which will be described later with reference
to FIG. 21.
[0157] Although it is illustrated that the first rubbing pattern is
extended in the first direction D1 and the second rubbing pattern
is extended in the second direction D2, the present invention does
not limited to these structures. In detail, on the assumption that
the first rubbing pattern is aligned perpendicular to the second
rubbing pattern, each of the first and second rubbing patterns can
be extended in upper, lower, left or right directions when viewed
from a front of the screen of the liquid crystal display device.
Directions of the first and second transmission axes formed in the
first and second polarizing layers 971 and 991 vary according as
directions of the first and second rubbing patterns vary.
[0158] Referring to FIG. 21, an upper polarizing plate 995 aligned
above the color filter substrate 914 includes a second polarizing
layer 996 for polarizing light, a porous layer 998 formed on a
lower surface of the second polarizing layer 996, and a third
supporting layer 997 formed on an upper surface of the second
polarizing layer 996.
[0159] Since the porous layer 998 is disposed on the lower surface
of the second polarizing layer 996, the third light exited from the
liquid crystal display device 910 provide expanded viewing angle,
then polarized by the second polarizing layer 996 to output fourth
light.
[0160] Hereinafter, gray scale inversion characteristic according
to variation of viewing angles of the liquid crystal display device
1100 having the porous film 960 will be described in detail with
reference to simulation results.
[0161] FIGS. 22A to 22C are graphs showing simulation results
obtained through experiment 1 according to the present invention,
and FIGS. 23A to 23C are graphs showing simulation results obtained
through experiment 2 according to the present invention. In
Experiments 1 and 2, the liquid crystal display device has a porous
layer, and a first and second alignment layers having a first and a
second rubbing patterns rubbed in a vertical or a horizontal
direction. In detail, in experiment 1, the porous film has a
thickness of about 11 .mu.m, and each pore formed in the porous
film has a diameter of about 5 .mu.m. In addition, in experiment 2,
the porous film has a thickness of about 18 .mu.m, and each pore
formed in the porous film has a diameter of about 1 .mu.m.
[0162] FIGS. 24A to 24C are graphs showing simulation results
obtained through comparative experiment 1, and FIGS. 25A to 25C are
graphs showing simulation results obtained through comparative
experiment 2. In the comparative experiment 1, rubbing patterns
rubbed in a diagonal direction are formed on the first and second
alignment layers. In comparative experiment 2, rubbing patterns
rubbed in vertical and horizontal directions are formed on the
first and second alignment layers.
[0163] In FIGS. 22A, 23A, 24A, and 25A, an X-axis represents a
viewing angle, and a Y-axis represents a contrast ratio. In
addition, when viewing the screen of the liquid crystal display
device 1100 from a front thereof, a vertical direction is defined
as a direction extended from an upper portion to a lower portion of
the screen, and a horizontal direction is defined as a direction
extended from a left side to a right side of the screen. In the
FIGS. 22A, 23A, 24A, and 25A, a bold solid line represents the
contrast ratio according to variation of viewing angles when
viewing the screen along the vertical direction. In addition, a
thin solid line represents the contrast ratio according to
variation of viewing angles when viewing the screen along the
horizontal direction.
[0164] On the other hand, in FIGS. 22B, 22C, 23B, 23C, 24B, 24C,
25B and 25C, an X-axis represents a viewing angle (.degree.), and a
Y-axis represents luminance (cd/m.sup.2). In detail, FIGS. 22B,
23B, 24B, and 25B show luminance variation according to variation
of viewing angles when viewing the screen along the horizontal
direction. FIGS. 22C, 23C, 24C, and 25C show variation of luminance
according to variation of viewing angles when viewing the screen
along the vertical direction. Each curve of each graph shown in
FIGS. 22B to 25C represents one of 8-gray scales made by dividing
64-gray scales into 8-gray scales.
[0165] Referring to FIGS. 24A and 25A, the contrast ratio varies
depending on the viewing angle. That is, the contrast ratio is the
highest at the front of the screen and greatly decreases according
as the distance between the front of the screen and an observation
point increase. Especially, the contrast ratio greatly decreases
according as the distance between the front of the screen and the
observation point increases along the vertical and horizontal
directions. A distribution of the contrast ratio is asymmetric
depending on the vertical direction or the horizontal
direction.
[0166] As a result, the contrast ratio can be varied depending on
each direction. Namely, the contrast ratio can be varied depending
on the direction from which a user watches the screen.
[0167] Referring to FIGS. 22A and 23A, the contrast ratio according
to the viewing angles is substantially constant, especially the
contrast ratio is hardly varied when viewing the screen along the
vertical and horizontal direction. Especially, since the size of
pores used in experiment 2 is smaller than the size of pores used
in experiment 1, the contrast ratio is more uniform in experiment 2
than in experiment 1.
[0168] As shown in FIG. 24B, when viewing the screen along the
horizontal direction, the gray scale inversion does not occur and
the asymmetric distribution of the contrast ratio is not created.
However, as shown in FIG. 24C, when viewing the screen along the
vertical direction, the gray scale inversion occurs. Especially, as
shown in FIG. 24C, when viewing the screen along the vertical
direction, the gray scale inversion occurs at an upper portion of
the curves where the viewing angle is about 24.degree. and at a
lower portion of the curves where the viewing angle is about
-44.degree.. Accordingly, the viewing angle of the liquid crystal
display device is limited.
[0169] In addition, referring to FIGS. 25B and 25C, when viewing
the screen along the vertical direction, the viewing angle is
expanded compared with a comparative experiment. That is, the gray
scale inversion is reduced when viewing the screen along the
vertical direction.
[0170] However, as shown in FIG. 25B, luminance variation is
generated between the left and right portions of the graph. That
is, the asymmetric distribution of the luminance is generated
between the left and right portions of the graph.
[0171] However, referring to FIGS. 22B, 22C, 23B and 23C, luminance
increases according as each gray scale becomes higher even when the
distance between the front of the screen and the observation point
increase. Thus, the viewing angle of the liquid crystal display
device can be expanded. In addition, as shown in FIGS. 22B and 23B,
luminance is symmetrically distributed between the left and right
portions of the graph.
[0172] While the present invention has been described in detail
with reference to the preferred embodiments thereof, it should be
understood to those skilled in the art that various changes,
substitutions and alterations can be made hereto without departing
from the scope of the invention as defined by the appended
claims.
INDUSTRIAL APPLICABILITY
[0173] According to the liquid crystal display device of the
present invention, a porous film has sidewalls defined by a
plurality of pores. The sidewalls of the porous film reflect a
first group of light of the second light. The second light is
exited from a liquid crystal display panel, and the first group of
light is light passes through a short axis of liquid crystal. The
first group of light is reflected towards a second group of light
of the second light, which passes through a long axis of liquid
crystal. Since the first group of light having relatively higher
luminance is reflected towards the second group of light having
relatively lower luminance, a viewing angle is expanded in such a
manner that a person can precisely recognize image information
displayed in a screen of the liquid crystal display panel from all
directions with respect to the screen.
[0174] In addition, a lower substrate includes a first alignment
layer having a first rubbing pattern extended in a column or row
direction, and an upper substrate includes a second alignment layer
having a second rubbing pattern extended in a lo row or column
direction.
[0175] Thus, the viewing angle in an upper and lower portions of
the screen can be improved due to the rubbing direction of the
first and second rubbing patterns.
[0176] Furthermore, since the rubbing pattern is formed on the
alignment layer in the column or row direction, a length of the
rubbing can be shortened when rubbing the alignment layer.
Accordingly, the manufacturing process for the liquid crystal
display device can be simplified and the manufacturing cost thereof
can be saved.
* * * * *