D E S C R I P T I O N
Title of Invention
LIQUID CRYSTAL DISPLAY DEVICE
Technical Field
The present invention relates to a liquid crystal
display device.
Background Art
A liquid crystal cell of a general liquid crystal
display device has a structure in which a liquid crystal
layer is held by transparent substrates such as glass
substrates. The liquid crystal display device includes a
15 liquid crystal panel configured such that a polarizer, or a
polarizer and a retardation plate, are disposed on the
front and back of the liquid crystal cell.
In a first example, a liquid crystal display device
includes a backlight unit as a light source on a back
20 surface of a liquid crystal panel, which is on a side
opposite to an observer. In a second example, a liquid
crystal display device makes use of an external light
source such as room light, in addition to a backlight unit.
In a liquid crystal display device which is capable of
25 performing three-dimensional image display, and a liquid
crystal display device which is capable of controlling a
viewing angle, a liquid crystal panel which makes use of a
backlight unit or an external light source is configured to
control, according to purposes of display, an emission
angle of light which is emitted to the outside from a front
surface of the liquid crystal panel, which is on an
5 observer side.
Various display methods are known for liquid crystal
display devices, or display devices, which are capable of
performing three-dimensional image display. These display
methods include methods using glasses, and methods not
10 using glasses. The methods using glasses include an
anaglyph method which makes use of a difference in color,
or a polarization-glasses method which makes use of
polarization. In the method of using glasses, it is
necessary for an observer to wear purpose-specific glasses
15 at a time of three-dimensional image display, and this is
troublesome. In recent years, there has been an increasing
demand for methods which require no glasses.
In order to adjust the angle of light which is emitted
from the liquid crystal panel to a single observer or
20 plural observers (hereinafter, in some cases, "single
observer" and "plural observers" are referred to as "twoview
type" and "multi-view type", respectively), a study
has been made of a technique of providing an optical
control element on the front surface or back surface of the
25 liquid crystal panel.
There is a case in which the optical control element
is used in a liquid crystal display device which is capable
of performing three-dimensional image display and requires
no glasses.
An example of the optical control element is a
lenticular lens which is configured such that optical
5 lenses are arranged two-dimensionally, and realizes regular
refraction. The lenticular lens is used such that a
transparent resin or the like is processed in a sheet shape
and attached to the front surface or back surface of a
liquid crystal display device. Patent document 1 (Japanese
10 Patent No. 4010564) and patent document 2 (Japanese Patent
No. 4213226) disclose three-dimensional image display
techniques using lenticular lenses (lenticular screens).
Prism sheets including convex lenses are disclosed in
patent documents 3 to 8 (Jpn. Pat. Appln. KOKAI Publication
15 No. 2010-506214, Jpn. Pat. Appln. KOKAI Publication
No. 2010-524047, Jpn. Pat. Appln. KOKAI Publication
No. 2010-541019, Jpn. Pat. Appln. KOKAI Publication
No. 2010-541020, Japanese Patent No. 4655465, and Japanese
Patent No. 3930021) .
The relationship between various arrangements of
pixels (color pixels) of color filters and light-ray
control elements (lenticular sheets) including aperture
portions in a direction of the arrangement is disclosed in
patent document 9 (Jpn. Pat. Appln. KOKAI Publication
25 NO. 2008-249887).
In addition, a technique of successively disposing
color filters of the same color in a lateral direction is
disclosed, for example, in Claim 1 of patent document 10
(Jpn. Pat. Appln. KOKAI Publication No. 2009-3002).
Summary of Invention
Technical Problem
In the above-described patent documents 1-8,
lenticular lenses are used. Patent document 1 discloses a
technique in which a display element (a pixel or a subpixel)
is formed in a parallelogrammatic shape or a
triangular shape, or a display element is disposed with an
10 offset, thereby substantially providing an angle between a
pixel (or a sub-pixel) array and a lenticular screen.
Patent document 1, like patent document 2, discloses a
technique of giving a successive (smooth) horizontal
parallax to an observer. In patent document 1, there is a
15 case in which aliasing occurs in display due to a
substantially obliquely disposed pixel array and an edge of
the lenticular screen crossing this pixel array. Patent
document 1 discloses, for example, neither a technique of
optimizing an alignment direction, in which liquid crystal
20 molecules become line-symmetric, by using a threedimensional
optical control element, nor a technique of
associating a triangular prism and a laterally elongated
pixel, and effecting switching between a three-dimensional
image and a two-dimensional image. Nor does patent
25 document 1 disclose a technique of using liquid crystal
molecules with a negative dielectric constant anisotropy in
a liquid crystal display device for three-dimensional image
display.
Patent document 2 discloses a technique in which an
offset angle is provided between a major axis of a
lenticular screen and a pixel array. In patent document 2,
5 a loss in resolution of three-dimensional image display is
reduced by a lenticule to which an offset angle is given,
and smooth display is provided even when the head of the
observer moves (the screen is smoothly switched). However,
in patent document 2, since the edge of the obliquely
10 disposed lenticular screen crosses the pixel array, there
is a case in which aliasing occurs in display. Patent
document 2 discloses, for example, neither a technique of
optimizing a relationship between an alignment direction,
in which liquid crystal molecules become line-symmetric,
15 and a three-dimensional optical control element, nor a
technique of associating a triangular prism and a laterally
elongated pixel, and effecting switching between a threedimensional
image and a two-dimensional image. Nor does
patent document 2 disclose a technique of using liquid
20 crystal molecules with a negative dielectric constant
anisotropy in a liquid crystal display device for threedimensional
image display.
In patent documents 3 to 6, a liquid crystal of an
optically compensated bend (OCB) mode is applied to three-
25 dimensional image display. In patent documents 3 to 6, OCB
is explained merely from the standpoint of a response time
of a liquid crystal, which is necessary for threedimensional
image display. However, none of patent
documents 3 to 6 discloses a liquid crystal display device
which optimizes light distribution by liquid crystal
molecules per se, which are used in a liquid crystal panel,
5 and enables bright three-dimensional image display and twodimensional
image display. For example, none of patent
documents 3 to 6 discloses in which direction OCB liquid
crystal molecules are to be arranged with respect to a
light distribution angle of a light source for a right-eye
10 image and a light distribution angle of a light source for
a left-eye image, thereby to optimize three-dimensional
image display for the right eye and left eye. In addition,
there is a case in which the OCB liquid crystal has a lower
viewing-angle characteristic than IPS (a liquid crystal
15 panel of a lateral electric field using horizontally
aligned liquid crystal molecules) or VA (a liquid crystal
panel of a vertical electric field using vertically aligned
liquid crystal molecules). The OCB liquid crystal
requires, each time the panel is activated, a transition
20 operation from a splay alignment, which is an initial
alignment, to a bend alignment at a time of driving. Thus,
there is a case in which the OCB liquid crystal is not
preferable for a liquid crystal display device for smallsized
mobile equipment.
Each of patent documents 3 to 7 discloses a doublesurface
prism sheet having a cross-sectional shape as
disclosed in patent document 8. A liquid crystal display
device of each of patent documents 3 to 7 performs threedimensional
image display by using light sources provided
on both sides of the backlight unit. However, like patent
document 8, none of patent documents 3 to 7 discloses a
5 measure for eliminating moire due to interference between
the prism sheet and the liquid crystal panel, which tends
to occur in three-dimensional image display. Furthermore,
none of patent documents 3 to 7 discloses a liquid crystal
display device which optimizes light distribution by liquid
10 crystal molecules per se, which are provided in a liquid
crystal panel, and enables bright three-dimensional image
display and two-dimensional image display.
Patent document 8 discloses a double-surface prism
sheet which includes a cylindrical lens row that is
15 parallel to a triangular prism row, with a focus position
of the cylindrical lens agreeing with an apex of the prism.
FIG. 1 or FIG. 2 of patent document 8 illustrates a
technique of effecting three-dimensional image display by
using this double-surface prism sheet and both-side light
20 sources provided on the backlight unit. However, in the
technique of patent document 8, it is difficult to
eliminate moir6 due to interference between the cylindrical
lens row and the liquid crystal panel, which tends to occur
in three-dimensional image display. In addition, patent
25 document 8 does not disclose a liquid crystal display
device which optimizes light distribution by liquid crystal
molecules per se, which are used in the liquid crystal
panel, and enables bright three-dimensional image display
and two-dimensional image display. Patent document 8
neither takes into account the matching between a color
filter, which is generally used in a color liquid crystal
5 display device, and the double-surface prism sheet, nor
discloses the relationship in correspondency between the
double-surface prism sheet and laterally elongated pixel.
Furthermore, patent document 8 does not disclose
optimization from the standpoint of the alignment of liquid
10 crystal molecules used in the liquid crystal panel or the
liquid crystal operation.
Patent document 9 discloses a combination between a
light-ray control element, which is a lenticular sheet, and
various arrangements of color pixels. However, patent
15 document 9 does not disclose a liquid crystal display
device in which elongated color pixels are formed in a
direction in which the two eyes of the observer are
disposed, one active element is provided in one color
pixel, and, when a liquid crystal layer is driven by active
20 elements of neighboring color pixels, tilt directions of
liquid crystal molecules become line-symmetric between
laterally neighboring pixels, with respect to the center
axis in the vertical direction of the two neighboring
pixels. In addition, patent document 9 does not disclose a
25 technique in which a picture element at a time of threedimensional
image display is composed of two red pixels,
two green pixels and two blue pixels. Besides, patent
document 9 does not disclose a liquid crystal display
device including, on that surface of an array substrate
which is opposite to a liquid crystal layer, an edge-littype
light guide including a solid-state light-emission
5 element array, and a unit for causing the solid-state
light-emission element to emit light by applying a voltage
to the solid-state light-emission element in synchronism
with a video signal and an operation of liquid crystal
molecules.
Patent document 10 discloses a technique in which
color elements (color pixels) of the same color are
arranged in a long-side direction of a display area and the
color elements are arranged in stripes. However, patent
document 10 does not disclose a technique of displaying a
15 three-dimensional image by using a lenticular lens, for
example, by using a liquid crystal alignment which is linesymmetric
with respect to the long-side direction. Patent
document 10 neither takes into account the synchronism with
the solid-state light-emission element and the video
20 signal, nor relates to a three-dimensional image display
technique.
As regards the display of a three-dimensional image,
an improvement in display quality is desired. However,
none of patent documents 1 to 10 discloses a technique of
25 line-symmetry driving the liquid crystal layer by active
elements, the laterally elongated pixels agreeing with the
direction in which the two eyes of the observer are
disposed and the driving of the liquid crystal, or the
optimal configuration of the lenticular lens and the solidstate
light-emission element.
The present invention has been made in consideration
5 of the above circumstances, and the object of the invention
is to provide a liquid crystal display device for
eliminating moire which is incidental to three-dimensional
image display, and for more brightly and effectively
realizing three-dimensional display and two-dimensional
10 display.
Solution to Problem
In the embodiment, a liquid crystal display device
includes an array substrate, a color filter substrate, a
liquid crystal layer, a backlight, and a controller. The
15 array substrate includes a plurality of pixel electrodes
corresponding to a plurality of pixels arranged in a
matrix. The color filter substrate is opposed to the array
substrate and includes color filters corresponding to the
plurality of pixels. The liquid crystal layer is provided
20 between the array substrate and the color filter substrate.
The backlight unit is provided on a back surface side of
the array substrate, the back surface side being opposite
to a liquid crystal layer side of the array substrate. The
controller is configured to control an application timing
25 of a liquid crystal driving voltage to the pixel
electrodes, and a light emission timing of the backlight
unit. The plurality of pixels are configured to each have
a plan-view shape of a parallelogram which is elongated in
a lateral direction, and configured such that identical
colors are arranged in the lateral direction, and different
colors are arranged in a vertical direction. Pixels
5 neighboring in the lateral direction of the plurality of
pixels have shapes of line-symmetry with respect to a
center line of the neighboring pixels. Liquid crystal
molecules of the neighboring pixels have a negative
dielectric constant anisotropy, and, when the liquid
10 crystal driving voltage is applied to the pixel electrodes
corresponding to the neighboring pixels, the liquid crystal
molecules rotate horizontally relative to a substrate plane
in a direction of the line-symmetry with respect to the
center line.
Advantageous Effects of Invention
In the embodiment of the invention, display nonuniformity
such as moir6 can be eliminated, a threedimensional
image with a high display quality can be
displayed, three-dimensional display and two-dimensional
20 display can be switched, and three-dimensional display and
two-dimensional display can be more brightly and
effectively realized.
Brief Description of Drawings
FIG. 1 is a cross-sectional view illustrating an
25 example of a liquid crystal display device according to a
first embodiment.
FIG. 2 is a plan view illustrating an example of a
cylindrical lens and a triangular prism of an optical
control element according to the first embodiment.
FIG. 3 is a plan view illustrating an example of a
color filter substrate of the liquid crystal display device
5 according to the first embodiment.
FIG. 4 is a cross-sectional view illustrating an
example of the liquid crystal display device according to
the first embodiment.
FIG. 5 is a cross-sectional view illustrating an
10 example of a liquid crystal operation and emission light at
a time when a liquid crystal driving voltage is applied to
a pixel electrode of one of two neighboring pixels.
FIG. 6 is a cross-sectional view illustrating an
example of the liquid crystal operation and emission light
15 at a time when a liquid crystal driving voltage is applied
to a pixel electrode of the other of the two neighboring
pixels.
FIG. 7 is a cross-sectional view illustrating an
example of the liquid crystal operation and emission light
20 at a time when a liquid crystal driving voltage is applied
to the the pixel electrodes of the two neighboring pixels.
FIG. 8 is a plan view illustrating an example of a
shape of pixel electrodes of two neighboring pixels and a
rubbing direction of an alignment film of the liquid
25 crystal display device according to the first embodiment.
FIG. 9 is a plan view illustrating an example of a
liquid crystal operation at a time when a liquid crystal
driving voltage is applied to a pixel electrode of'one of
two neighboring pixels.
F I G . 10 is a cross-sectional view illustrating an
example of a state of electric force lines at a time when a
5 liquid crystal driving voltage is applied.
F I G . 11 is a plan view illustrating an example of the
liquid crystal operation at a time when a liquid crystal
driving voltage is applied to a pixel electrode of the
other of the two neighboring pixels.
F I G . 12 is a plan view illustrating an example of the
liquid crystal operation at a time when a liquid crystal
driving voltage is applied to the pixel electrodes of the
two neighboring pixels.
F I G . 13 is a cross-sectional view illustrating an
15 example of a liquid crystal display device according to a
second embodiment.
F I G . 14 is a cross-sectional view illustrating an
example of the liquid crystal display device according to
the second embodiment.
F I G . 15 is a cross-sectional view illustrating an
example of synchronization between a pixel electrode of one
of two neighboring pixels and a solid-state light emission
element.
F I G . 16 is a cross-sectional view illustrating an
25 example of synchronization between a pixel electrode of the
other of two neighboring pixels and a solid-state light
emission element.
FIG. 17 is a cross-sectional view illustrating an
example of a state of rising of liquid crystal molecules in
a case where a charged body, such as a finger, has
approached a liquid crystal panel.
5 Description of Embodiments
Embodiments of the invention will be described
hereinafter with reference to the accompanying drawings.
In the description below, identical or substantially
identical functions and structural elements are denoted by
10 like reference numerals, and a description thereof is
omitted, or a description is given only where necessary.
In the embodiments below, only characteristic parts
will be described, and a description is omitted of parts
which are not different from structural elements of
15 ordinary liquid crystal display devices.
In the embodiments below, a pixel may be a sub-pixel.
By way of example, a display unit of a liquid crystal
display device is assumed to be a picture element which is
composed of six pixels including two red pixels, two green
20 pixels and two blue pixels. However, the number of pixels
included in the picture element may be freely changed.
In the embodiments below, a direction of arrangement
of pixels, which is parallel to a direction of disposition
of the right and left eyes of an observer is defined as a
25 lateral direction, and a direction of arrangement of
pixels, which is perpendicular to this lateral direction,
is defined as a vertical direction.
A color pixel has a shape which is long in the lateral
direction. In the description below, there is a case in
which the lateral direction is described as a pixel
longitudinal direction. The color pixel has a shape which
5 is short in the vertical direction. In the description
below, there is a case in which the vertical direction is
described as a pixel transverse direction.
In the description below, there is a case in which two
pixels of the same color are described as a pair. In
10 addition, in the picture element including six pixels, it
is assumed that two pixels of the same color are arranged
in the lateral direction, and pixels of three different
colors are arranged in the vertical direction.
[First Embodiment]
FIG. 1 is a cross-sectional view illustrating an
example of a liquid crystal display device according to the
embodiment. FIG. 1 shows a cross section in the lateral
direction.
A liquid crystal display device 1 includes, as basic
20 structural elements, a liquid crystal panel 2, polarizers
3, a backlight unit 4, and a controller 12. The polarizer
3 may be formed by attaching a retardation plate.
In each of the embodiments below, a pair of polarizers
3 may be configured as crossed Nicols. In addition, the
25 absorption axes of the paired polarizers 3 may be made
parallel, and the liquid crystal display device 1 may
include a spiral element between one of the polarizers 3
- 16 -
and the liquid crystal panel 2, the spiral element being
configured to convert first linearly polarized light of
this one of the polarizers 3 to second linearly polarized
light which is perpendicular to the first linearly
5 polarized light.
The liquid crystal panel 2 includes a color filter
substrate 5, an array substrate 6 and a liquid crystal
layer 7. The color filter substrate 5 and the array
substrate 6 are opposed to each other. The liquid crystal
10 layer 7 is interposed between the color filter substrate 5
and the array substrate 6.
In the present embodiment, a plurality of pixels are
disposed in a matrix.
The liquid crystal panel 2 includes red pixels, green
15 pixels and blue pixels. In the embodiment, each pixel has
a parallelogrammatic shape which is longer in the lateral
direction than in the vertical direction, when viewed in
plan.
The lateral direction, as described above, is the
20 direction in which the right eye 81 and left eye 82 of the
observer are disposed. In the embodiment, it is assumed
that neighboring pixels of the same color are arranged in
the lateral direction (a horizontal direction in a lateraldirectional
cross section of FIG. 1). The polarizers 3,
25 retardation plates (not shown), etc. are provided on a
front surface (a plane on the observer side) side and a
back surface (a plane on a side opposite to the observer)
side of the liquid crystal panel 2.
The backlight unit 4 is provided on the back surface
of the liquid crystal panel 2 (the back surface side of the
array substrate 6, which is opposite to the liquid crystal
5 layer 7 side) via the polarizer 3. The backlight unit 4
includes, as basic structural elements, solid-state light
emission elements 91, 92, such as LEDs (light-emitting
diodes), an optical control element 101 which is an array
of triangular prisms, an optical control element 102 which
10 is an array of cylindrical lenses, and a reflection plate
11.
The array of cylindrical lenses shown in F I G . 1 has a
longitudinal (longer-side) direction in a direction
perpendicular to the lateral-directional cross section of
15 F I G . 1. The optical control element 101, which is the
array of triangular prisms, and the optical control element
102, which is the array of cylindrical lenses, may be
formed of an acrylic resin or the like, and may be formed
as an integral molded article of back-to-back attachment.
The pitch of the array of triangular prisms and the
pitch of the array of cylindrical lenses may be in a
relationship of 1:1, or, as illustrated in F I G . 1, the
pitch of the array of triangular prisms may be set to be
finer than the pitch of the array of cylindrical lenses.
As illustrated in F I G . 2, an angle 8 is provided
between a longitudinal axis of the cylindrical lens and a
longitudinal axis of the triangular prism.
The plural triangular prisms have an angle 8 to the
vertical direction. The plural triangular prisms are
arranged with a fine pitch. The angle 8 may be set in a
range of, e.g. 3O to 42O. The angle 8 may be greater than
5 this range. The angle 8 is set at such an angle as not to
interfere with the optical axis of the polarizer or liquid
crystal alignment.
The backlight unit 4 may include, for example, a
diffusion plate, a light guide plate, a polarization split
10 film, and a retroreflection polarization element, but these
components are omitted in FIG. 1.
The solid-state light emission element 91, 92 may be,
for instance, a white LED which emits white light including
three wavelengths of red, green and blue in the light
15 emission wavelength range. The solid-state light emission
element 91, 92 may be, for instance, a pseudo-white LED in
which a GaN-based blue LED and a YAG-based phosphor
material are combined. In order to enhance color rendering
properties, an LED with a major peak of one color or more,
20 such as a red LED, may be used together with a pseudo-white
LED. For example, use may be made of a light source in
which red and green phosphors are stacked on a blue LED.
The backlight unit 4 may include a plurality of solidstate
light emission elements 91 and a plurality of solid-
25 state light emission elements 92. In this case, the
plurality of solid-state light emission elements 91 and the
plurality of solid-state light emission elements 92 may
include LEDs which individually emit any one of red, green
and blue. The plurality of solid-state light emission
elements 91 and the plurality of solid-state light emission
elements 92 may include LEDs which emit light of an
5 ultraviolet range, or may include LEDs of an infrared
range.
The controller 12 executes various control processes
in the liquid crystal display device 1. For example, the
controller 12 controls the timing of application of a
10 liquid crystal driving voltage to pixel electrodes 221,
222, and the timing of light emission of the backlight unit
4. For example, the controller 12 realizes threedimensional
image display by synchronizing and controlling
the timing of light emission of the solid-state light
15 emission elements 91, 92, and the timing of application of
a driving voltage of the liquid crystal layer 7, based on a
right-eye video signal and a left-eye video signal.
In the meantime, the liquid crystal display device 1
may include a light reception element 13. In this case,
20 the light reception element 13 is used for data input by an
optical sensor. For example, the light reception element
13 detects specific-wavelength light which is emitted from
a light emission element such as an ultraviolet-range or
infrared-range LED. The controller 12 detects a position
25 of the light-reception element 13, where specificwavelength
light has been detected. In addition, for
example, based on the light detected by the light reception
element 13, the controller 12 detects the position of the
observer or the position of a pointer such as a finger.
The light reception element 13 may be an oxide
semiconductor active element with a transparent channel
5 layer formed of a composite metal oxide, or may be capable
of detecting light of the ultraviolet range. The light
reception element 13 may be an image-pickup element
(camera) such as a CMOS or CCD, which is mounted on the
housing of the liquid crystal display device. This light
10 reception element 13 may be used for biometrics
authentication or personal authentication, in addition to
touch sensing and image pickup. In addition, the light
reception element 13 may be, for example, a plurality of
optical sensors which are provided in a matrix on the array
15 substrate 6.
The controller 12 detects, for example, the position
of the observer, based on an output value of the light
reception element 13, and adjusts an emission angle P of
emission light from the solid-state light emission element
20 91, 92, based on the position of the observer. Thereby, an
emission angle a to the two eyes (right eye 81 and left eye
82) of the observer can be adjusted, and the visibility of
a three-dimensional image can be improved.
FIG. 3 is a plan view illustrating an example of the
25 color filter substrate 5 of the liquid crystal display
device 1 according to the embodiment. FIG. 3 is a front
view of the color filter substrate 5, and illustrates a
state in which the color filter substrate 5 is viewed from
the observer.
Each pixel has a laterally elongated shape. In
FIG. 3, each pixel has a parallelogrammatic shape which is
5 long in the lateral direction and short in the vertical
direction. This parallelogrammatic shape has a long side
with an angle y to the lateral direction, and has a short
side parallel to the vertical direction.
Two pixels of the same color are arranged in
10 juxtaposition. A plurality of pixels of the same color are
arranged in the lateral direction, and a plurality of
pixels of different colors are arranged in the vertical
direction. Those pixels of the plural pixels, which
neighbor in the lateral direction, have a shape of line-
15 symmetry with respect to a center line of the neighboring
pixels. The arrangement of pixels in the lateral direction
has a repetitive pattern of two pixels of the same color in
a V shape or an inverted-V shape.
The plural pixels include a first picture element
20 which is composed of laterally arranged green pixels G1 and
G2, red pixels R1 and R2 and blue pixels B1 and B2, and a
second picture element which is composed of laterally
arranged green pixels G3 and G4, red pixels R3 and R4 and
blue pixels B3 and B4.
The angle y between the long side of the
parallelogrammatic shape and the lateral direction is set
in a range of, e.g. about 5 O to 30°, and is set at, for
instance, about 15O. With the pixel having the angle y to
the lateral direction, moir6 can be reduced, and moreover
the liquid crystal molecules can be made easily rotatable
in an FFS (IPS) liquid crystal display device. In the
5 present embodiment, by arranging the pixels of the same
color in the lateral direction, three-dimensional image
display with less color non-uniformity can be realized.
A black matrix BM partitions the pixels. In FIG. 3,
the black matrix BM is formed between vertically
10 neighboring pixels, and is not formed between the laterally
neighboring pixels. Specifically, the black matrix BM is
formed at an upper side and a lower side of each pixel. By
not forming the black matrix BM between the laterally
neighboring pixels, bright three-dimensional image display
15 with less color moire can be realized.
Under the color filter substrate 5, the array
substrate 6 is provided via the liquid crystal layer 7. In
other words, the color filter substrate 5 and array
substrate 6 are opposed. The liquid crystal layer 7 is
20 provided between the color filter substrate 5 and array
substrate 6. The array substrate 6 includes active
elements 14a, 14b. As the active element 14a, 14b, for
example, a thin-film transistor (TFT) is used.
Incidentally, the array substrate 6 may be configured to
25 include some other active element as a light reception
element.
In the description below, pixels G1 and G2 will be
described as typical examples, but other pixels have the
same features.
A width Lp of two pixels GI and G2 in the lateral
direction is made to agree with the width of a
5 semicylindrical lens. The pixel GI, G2 may be configured
to include a light reception element 13 used as an optical
sensor, in addition to the active element 14a, 14b which
drives the liquid crystal layer 7.
FIG. 4 is a cross-sectional view illustrating an
10 example of the liquid crystal display device 1 according to
the embodiment. FIG. 4 corresponds to an A-A' cross
section in FIG. 3. Plural green pixels G1 and G2 are
formed in juxtaposition in the lateral direction
(horizontal direction) .
The color filter substrate 5 is configured such that a
black matrix BM, a color filter (color layer) 16, a
transparent resin layer 17 and an alignment film 181 are
formed on a transparent substrate 15. In the cross section
of FIG. 4, the black matrix BM is not depicted, but the
20 black matrix BM is formed, for example, between the
transparent substrate 15 and color filter 16. The color
filter substrate 5 includes color filters 16 corresponding
to the plural pixels. Of the color filters 16, a green
filter is associated with the green pixel, a red filter is
25 associated with the red pixel, and a blue filter is
associated with the blue pixel.
In the liquid crystal display device 1, the
transparent substrate 15 side of the color filter substrate
5 faces the observer, and the alignment film 181 side of
the color filter substrate 5 faces the liquid crystal layer
7. In FIG. 4, polarizers are omitted.
Since the cross section of FIG. 4 is a cross section
of a part where the black matrix BM is not formed, the
black matrix BM is not shown in FIG. 4. However, for
example, in a case where priority is placed on the contrast
in two-dimensional image display rather than in three-
10 dimensional image display, a black matrix BM in the
vertical direction may be formed, for example, at positions
PI of end portions of a pixel set GS composed of two pixels
G1 and G2, and at a position P2 at a central part of the
two pixels G1 and G2. The positions PI, P2 are between the
15 transparent substrate 15 and color filter 16 in the
vertical direction (the direction of stacking of layers of
the liquid crystal panel 2) of the cross section of FIG. 4.
The array substrate 6 is configured such that
insulation layers 20a and 20b, a common electrode 21, an
20 insulation layer 20c, pixel electrodes 221 and 222, and an
alignment film 182 are formed on the transparent substrate
19. For example, SiN is used for the insulation films 20a
to 20c. The array substrate 6 includes a plurality of
pixel electrodes 221, 222, which correspond to the plural
25 pixels GI, G2.
In the liquid crystal display device 1, the
transparent substrate 19 side of the array substrate 6 is
the back side of the liquid crystal panel 2, and the
alignment film 182 side of the array substrate 6 faces the
liquid crystal layer 7.
The pixel electrode 221 of the pixel G1 and the pixel
5 electrode 222 of the pixel G2 are formed in line-symmetry
with respect to the center axis of the pixel set GS. The
pixel electrode 221 of the pixel G1 and the pixel electrode
222 of the pixel G2 are spaced apart, with the center line
of the neighboring pixels G1 and G2 being interposed.
The common electrode 21 of the pixels G1 and G2 is
formed in symmetry with respect to the center line of the
pixel set GS.
The common electrode 21, which is provided in the
laterally neighboring pixels G1 and G2, has a shape of
15 line-symmetry with respect to the center line of the
laterally neighboring pixels G1 and G2.
The pixel electrode 221, 222 may be configured to
have, for example, a comb shape pattern or a stripe
pattern.
The common electrode 21 and pixel electrode 221, 222
are formed of, for example, transparent, electrically
conductive films.
In the present embodiment, the electrode configuration
of the pixel set GS is line-symmetric. Specifically, the
25 positions of the electrodes of the two neighboring pixels
G1 and G2 are line-symmetric.
Accordingly, the bearing of the longitudinal direction
of the liquid crystal molecules of the liquid crystal layer
7 of the pixel G1 in a case where a voltage is applied
between the pixel electrode 221 and the common electrode
21, and the bearing of the longitudinal direction of the
5 liquid crystal of the liquid crystal layer 7 of the pixel
G2 in a case where a voltage is applied between the pixel
electrode 222 and the common electrode 21, are linesymmetric.
The pixel electrodes 221, 222 and the common electrode
10 21 overlap, as viewed in plan from the observer side, and
the overlapping part can be used as a storage capacitance
for liquid crystal display.
The liquid crystal layer 7 includes liquid crystal
molecules L1 to L8 with initial vertical alignment. Each
15 of the liquid crystal molecules L1 to L8 has a shape with a
longitudinal direction, and has a negative dielectric
constant anisotropy.
Referring to FIG. 5 to FIG. 7, a description is given
of the relationship between a liquid crystal operation and
20 emission light.
FIG. 5 is a cross-sectional view showing an example of
the liquid crystal display device 1, FIG. 5 illustrating
the liquid crystal operation and emission light 231 at a
time when a liquid crystal driving voltage is applied to
25 the pixel electrode 221 of the pixel G1 that is one of the
two neighboring pixels G1 and G2.
In FIG. 5, the active element 14a applies a voltage to
the pixel electrode 221 of the pixel GI. Then, an electric
field from the pixel electrode 221 to the common electrode
21 occurs. The liquid crystal molecules L1 to L4 with
initial horizontal alignment rotate horizontally relative
5 to the substrate plane, in a manner to become perpendicular
to electric force lines generated by applying the voltage
to the pixel electrode 221. In FIG. 5, the longitudinal
direction of the liquid crystal molecules L1 to L4 is
directed in the vertical direction in the cross section of
10 FIG. 5 in a state in which no voltage is applied to the
pixel electrode 221, and the longitudinal direction of the
liquid crystal molecules L1 to L4 is rotated and directed
in the horizontal direction (lateral direction) after a
voltage is applied to the pixel electrode 221.
By this liquid crystal operation, leftward emission
light 231 is emitted. As described above, the angle a of
the emission light 231 is adjusted by the optical control
element 101, 102.
FIG. 6 is a cross-sectional view showing an example of
20 the liquid crystal display device 1, FIG. 6 illustrating
the liquid crystal operation and emission light 232 at a
time when a liquid crystal driving voltage is applied to
the pixel electrode 222 of the pixel G2 that is the other
of the two neighboring pixels G1 and G2.
In FIG. 6, the active element 14b applies a voltage to
the pixel electrode 222. Then, an electric field from the
pixel electrode 222 to the common electrode 21 occurs. The
liquid crystal molecules L5 to L8 with initial horizontal
alignment rotate horizontally relative to the substrate
plane, in a manner to become perpendicular to electric
force lines generated by applying the voltage to the pixel
5 electrode 222. In FIG. 6, the longitudinal direction of
the liquid crystal molecules L5 to L8 is directed in the
vertical direction in the cross section of FIG. 6 in a
state in which no voltage is applied to the pixel electrode
222, and the longitudinal direction of the liquid crystal
10 molecules L5 to L8 is rotated and directed in the
horizontal direction (lateral direction) after a voltage is
applied to the pixel electrode 221.
The direction of rotation of liquid crystal molecules
L1 to L4 in the pixel G1 is opposite to the direction of
15 rotation of liquid crystal molecules L5 to L8 in the pixel
G2.
By this liquid crystal operation, rightward emission
light 232 is emitted. As described above, the angle a of
the emission light 232 is adjusted by the optical control
20 element 101, 102.
By executing, in synchronism, the liquid crystal
operation illustrated in FIG. 5 and FIG. 6 and the light
emission of the solid-state light emission elements 91 and
92, it is possible to perform three-dimensional image
25 display or to display different images in the direction of
the right eye 81 and in the direction of the left eye 82.
FIG. 7 is a cross-sectional view showing an example of
the liquid crystal display device 1, FIG. 7 illustrating
the liquid crystal operation and emission light 231, 232 at
a time when a liquid crystal driving voltage is applied to
the pixel electrodes 221, 222 of the two neighboring pixel
5 G1 and G2.
In this embodiment, if a liquid crystal driving
voltage is applied to the pixel electrodes 221 and 222
corresponding to the neighboring pixel G1 and G2, the
liquid crystal molecules of the neighboring pixels G1 and
10 G2 tilt in line-symmetric directions with respect to the
center axis.
By applying a voltage to the pixel electrodes 221 and
222 of the two neighboring pixel G1 and G2, bright twodimensional
image display with a large viewing angle can be
15 realized.
In this manner, the liquid crystal display device 1
according to the embodiment can very easily effect
switching between a three-dimensional image and a twodimensional
image.
In the present embodiment, the description has been
given by using liquid crystal molecules L1 to L8 with
negative dielectric constant anisotropy. However, this
embodiment is similarly applicable to liquid crystal
molecules with positive dielectric constant anisotropy.
A description will be given below of the shape of the
pixel electrode 221, 222, and the rotation of liquid
crystal molecules L1 to L8, as viewed in plan. The
rotation as viewed in plan is horizontal rotation.
FIG. 8 is a plan view illustrating an example of the
shape of pixel electrodes 221, 222 of two neighboring
pixels G1, G2 and a rubbing direction of the alignment film
5 181, 182 of the liquid crystal display device 1 according
to the present embodiment.
In this embodiment, the pixel electrode 221, 222 of
the pixel G1, G2 has a comb shape. The pixel electrodes
221 and 222 are line-symmetric with respect to the center
10 line of the neighboring pixels G1 and G2. A plurality of
comb-tooth portions of the pixel electrode 221, 222 extend
from the end portion side of the pixel set GS toward the
center side. A connecting portion of the plural comb-tooth
portions of the pixel electrode 221, 222 is disposed on the
15 end portion side of the pixel set GS. The longitudinal
direction of the plural comb-tooth portions of the pixel
electrode 221, 222 is parallel to the long side of the
pixel G1, G2. The width of the comb-tooth portion is F1,
and the space width (gap) of comb-tooth portions is Fs.
A rubbing direction 24 of the alignment film 181, 182
is parallel to the vertical direction (the short side of
the pixel). The initial alignment direction of the liquid
crystal molecules L1 to L8 becomes identical to this
rubbing direction. Accordingly, in the initial alignment
25 state, the longitudinal direction of the liquid crystal
molecules L1 to L8 becomes parallel to the vertical
direction, as viewed in plan. The rubbing may be
mechanical rubbing, or may be realized by alignment
treatment by optical alignment.
As the material of the alignment film 181, 182, for
example, polyimide or polyorganosiloxane is used. The
5 alignment film 182 is formed on the pixel electrodes 221,
222.
The alignment film 181, 182 may have photosensitivity.
In addition, instead of the photosensitive alignment film
181, 182, photosensitive monomers may be dispersed in the
10 liquid crystal layer 7. In this manner, in the case of
using the photosensitive alignment film 181, 182, or in the
case of dispersing the photosensitive monomers in the
liquid crystal layer 7, alignment treatment is realized by
radiating light while applying a voltage between the pixel
15 electrode 221, 222 and the common electrode 21.
FIG. 9 is a plan view illustrating an example of the
liquid crystal operation at a time when a liquid crystal
driving voltage is applied to the pixel electrode 221 of
the pixel G1 that is one of the two neighboring pixels G1
20 and G2.
In addition, FIG. 10 is a cross-sectional view
illustrating an example of the state of electric force
lines at a time when a liquid crystal driving voltage is
applied. FIG. 10 corresponds to a C-C' cross section in
25 FIG. 9.
In FIG. 9 and FIG. 10, a voltage is applied to the
pixel electrode 221, and thereby electric force lines occur
in a direction which is perpendicular to the longitudinal
direction of the comb-tooth portions of the pixel electrode
221 and is directed from the pixel electrode 221 toward the
common electrode 21. The liquid crystal molecules L1 to L4
5 on the pixel electrode 221 of the pixel G1 horizontally
rotate so as to become perpendicular to the electric force
lines. As a result, the longitudinal direction of the
liquid crystal molecules L1 to L4 becomes substantially
parallel to the longitudinal direction of the comb-tooth
10 portions of the pixel electrode 221.
FIG. 11 is a plan view illustrating an example of the
liquid crystal operation at a time when a liquid crystal
driving voltage is applied to the pixel electrode 222 of
the pixel G2 that is the other of the two neighboring
15 pixels G1 and G2.
In FIG. 11, a voltage is applied to the pixel
electrode 222, and thereby electric force lines occur in a
direction which is perpendicular to the longitudinal
direction of the comb-tooth portions of the pixel electrode
20 222 and is directed from the pixel electrode 222 toward the
common electrode 21. The liquid crystal molecules L5 to L8
on the pixel electrode 222 of the pixel G2 horizontally
rotate so as to become perpendicular to the electric force
lines. As a result, the longitudinal direction of the
25 liquid crystal molecules L5 to L8 becomes substantially
parallel to the longitudinal direction of the comb-tooth
portions of the pixel electrode 222.
FIG. 12 is a plan view illustrating an example of the
liquid crystal operation at a time when a liquid crystal
driving voltage is applied to the pixel electrodes 221 and
222 of the two neighboring pixels G1 and G2.
5 If a voltage is applied to the pixel electrodes 1221
and 222, the liquid crystal molecules L1 to L4 on the pixel
electrode 221 horizontally rotate in the pixel GI, and the
liquid crystal molecules L5 to L8 on the pixel electrode
222 horizontally rotate in the pixel G2. The direction of
10 rotation in the pixel G1 and the direction of rotation in
the pixel G2 are line-symmetric with respect to the center
line of the pixels G1 and G2. Thereby, the symmetric
property of the liquid crystal operation in the pixels G1
and G2 is improved, and the viewing angle is increased.
As the liquid crystal material, for example, a liquid
crystal material including fluorine atoms in a molecular
structure (hereinafter referred to as "fluorine-based
liquid crystal") is preferable. The fluorine-based liquid
crystal is low in viscosity and dielectric constant, and is
20 small in amount of taken-in ionic impurities. In the case
where the fluorine-based liquid crystal is used as the
liquid crystal material, the degradation in capability,
such as a decrease in voltage retention ratio due to
impurities, is small, and display non-uniformity and
25 display image persistence can be suppressed. As the liquid
crystal with negative dielectric constant anisotropy, for
example, a nematic liquid crystal having a birefringence
index of about 0.1 in the neighborhood of room temperature
can be used. As the liquid crystal with positive
dielectric constant anisotropy, various liquid crystal
materials are applicable. In a liquid crystal display
5 device for which a high responsivity, rather than
suppression in power consumption, is required, a liquid
crystal having a large dielectric constant anisotropy may
be used. The thickness of the liquid crystal layer 7 is
not particularly limited. In the embodiment, And of the
10 liquid crystal layer 7, which is effectively applicable,
is, for example, in a range of about 300 nm to 500 nm.
In the liquid crystal display device 1 of the abovedescribed
embodiment, display non-uniformity such as moir6
can be eliminated, the display quality of a three-
15 dimensional image can be enhanced, bright display can be
performed, and easy switching can be made between threedimensional
display and two-dimensional display. These
advantageous effects will be concretely described below.
In the present embodiment, laterally elongated pixels
20 are formed. In this structure, a row of green pixels, a
row of red pixels and a row of blue pixels are arranged in
the lateral direction.
In ordinary vertically elongated pixels, three kinds
of pixels, namely a red pixel, a green pixel and a blue
25 pixel, are arranged in the lateral direction. In order to
drive active elements located below the pixels, drivers for
sending video signals in the vertical direction are
necessary for the three colors.
By contrast, in the embodiment, since the laterally
elongated pixels of the same color are arranged in the
lateral direction and the three different colors are
5 arranged in stripes in the vertical direction, the number
of drivers of pixels can be reduced to 1/3 for the ordinary
pixels, and the liquid crystal panel 2 can be manufactured
at low cost. Since the power consumption of the drivers
which handle video signals is high, the present embodiment
10 can provide the liquid crystal display device 1 with low
power consumption.
In addition, since the pixel width in the lateral
direction of the pixels of each color in the liquid crystal
display device 1 according to the embodiment is laterally
15 large and is fixed, high-quality display with no color nonuniformity
in units of a picture element can be realized,
compared to the case of vertically elongated, inclined
pixels. Furthermore, since thin-film transistors of an
oxide semiconductor, which has low sensitivity in the
20 visible light range, can be used as the active elements
14a, 14b for driving the liquid crystal, the liquid crystal
display device 1 with a fine black matrix BM and a large
aperture ratio can be provided.
In this embodiment, display non-uniformity such as
25 moire, which is a problem in conventional three-dimensional
display, can be eliminated, and, with bright display,
switching between three-dimensional display and twodimensional
display can be realized by a simple
configuration.
The liquid crystal display device 1 according to the
embodiment is applicable to display devices which are
5 disposed on a mobile phone, a game console, a tablet
terminal, a notebook PC (personal computer), a television,
a car dashboard, etc.
Incidentally, as a modification of the embodiment, the
liquid crystal display device 1 may further include, in
10 order to eliminate moir6, a plurality of triangular prisms
having a longitudinal direction which is substantially
perpendicular to the longitudinal direction of the plural
triangular prisms.
In addition, for more effective three-dimensional
15 image display, the longitudinal direction of the plural
triangular prisms and the longitudinal direction of the
plural semicylindrical lenses may be made substantially
parallel, and the width of the triangular prism may be set
at double the length of the pixel in the lateral direction.
The width of the semicylindrical lens may be set at an
integer number of times of the width of two pixels in the
lateral direction.
Another optical control element including an array of
a plurality of semicylindrical lenses may be disposed
25 between the array substrate 6 and the backlight unit 4, or
on that surface side (observer side) of the color filter
substrate 5, which is opposite to the liquid crystal layer
7 side. Furthermore, the longitudinal direction of the
semicylindrical lenses included in this other optical
control element may be set to be perpendicular to the
lateral direction.
5 [Second Embodiment]
The present embodiment is a modification of the first
embodiment, and a description is given of a liquid crystal
display device further including a transparent electrode
film between the transparent substrate 15 of the color
10 filter substrate and the color filter 16.
FIG. 13 is a cross-sectional view illustrating an
example of a liquid crystal display device according to the
present embodiment. FIG. 13 is a cross-sectional view in
the lateral direction.
FIG. 14 is a cross-sectional view illustrating an
example of a liquid crystal display device 30 according to
the second embodiment.
The liquid crystal display device 30 includes, as
basic structural elements, a liquid crystal panel 26,
20 polarizers 3, and a backlight unit 27. Incidentally, like
the liquid crystal display device 1 according to the abovedescribed
first embodiment, the liquid crystal display
device 30 may include a controller 12 and a light reception
element 13.
Solid-state light emission elements 91, 92 are
disposed at both ends of the backlight unit 27. The
polarizer 3 may be formed by attaching a retardation plate.
The liquid crystal panel 26 is configured such that a
color filter substrate 28 and an array substrate 6 are
opposed to each other, and a liquid crystal layer 7 is
provided between the color filter substrate 28 and the
5 array substrate 6. In the liquid crystal panel 26, a
plurality of laterally elongated parallelogrammatic pixels,
which include red pixels, green pixels and blue pixels, are
arranged in the lateral direction. In this embodiment, the
pixels are arranged in the lateral direction such that the
10 pixels of the same color neighbor. The polarizer 3 and a
retardation plate (not shown) are provided on a front
surface and/or a back surface of the liquid crystal panel
2. The main structure of the liquid crystal display device
30 according to this embodiment is substantially the same
15 as that of the above-described first embodiment.
The liquid crystal display device 30 according to the
embodiment includes the color filter substrate 28 which
further includes a transparent electrode film 31 between
the transparent substrate 15 and color filter 16.
In the present embodiment, for example, a black matrix
BM is formed along each side of the parallelogrammatic
pixel. Specifically, in this embodiment, the black matrix
BM is disposed between laterally neighboring pixels and
between vertically neighboring pixels. The long sides of
25 the parallelogram have an angle y to the lateral direction,
for the purpose of a measure against moir6 at a time of
three-dimensional image display.
In the embodiment, both the longitudinal direction of
the triangular prism in the optical control element 101 and
the longitudinal direction of the cylindrical prism in the
optical control element 102 are perpendicular to the
5 lateral direction and the normal direction of the liquid
crystal panel 26 (i.e. perpendicular to the cross section
of FIG. 13). In addition, both the triangular prism and
the cylindrical lens have the same width as the width Lp of
two pixels. An end portion in the lateral direction of the
10 pixel, an end portion in the lateral direction of the
triangular prism and an end portion in the lateral
direction of the cylindrical lens are aligned.
FIG. 15 is a cross-sectional view illustrating an
example of synchronization between the pixel electrode 221
15 of the pixel GI, which is one of the two neighboring pixels
G1 and G2, and the solid-state light emission element 91.
FIG. 16 is a cross-sectional view illustrating an
example of synchronization between the pixel electrode 222
of the pixel G2, which is the other of the two neighboring
20 pixels GI and G2, and the solid-state light emission
element 92.
FIG. 15 and FIG. 16 illustrate cross sections of the
two pixels G1 and G2, and represent the operations for
three-dimensional image display of the optical control
25 elements 101, 102.
FIG. 15 illustrates an optical path in a case where a
liquid crystal driving voltage has been applied to the
pixel electrode 221, and the solid-state light emission
element 91 has been caused to emit light in synchronism
with the application of this voltage. By applying the
liquid crystal driving voltage to the pixel electrode 221
5 in FIG. 15, liquid crystal molecules L1 to L4 of the leftside
pixel G1 in FIG. 15 horizontally rotate. In
synchronism with the application of the voltage to the
pixel electrode 221, the solid-state light emission element
91 is caused to emit light. As illustrated in FIG. 15, the
10 light emitted from the solid-state light emission element
91 passes through the triangular prism of the optical
control element 101 and the cylindrical lens of the optical
control element 102, and is emitted toward the right eye 81
of the observer as emission light 321. An emission angle a
15 can be set, mainly based on a distal-end angle E of the
triangular prism and a curvature r of the cylindrical
prism. For example, by adjusting the magnitude of the
distal-end angle of the triangular prism, the emission
light of the left-side solid-state light emission element
20 91 can be emitted to the opposite left eye 81.
FIG. 16 illustrates an optical path in a case where a
liquid crystal driving voltage has been applied to the
pixel electrode 222, and the solid-state light emission
element 91 has been caused to emit light in synchronism
25 with the application of this voltage. By applying the
liquid crystal driving voltage to the pixel electrode 222
in FIG. 16, liquid crystal molecules L5 to L8 of the rightside
pixel G2 in FIG. 16 horizontally rotate. In
synchronism with the application of the voltage to the
pixel electrode 222, the solid-state light emission element
92 is caused to emit light. As illustrated in FIG. 16, the
5 light emitted from the solid-state light emission element
92 passes through the triangular prism of the optical
control element 101 and the cylindrical lens of the optical
control element 102, and is emitted toward the left eye 82
of the observer as emission light 322.
Based on video signals of a three-dimensional image,
the light emission timing of the solid-state light emission
element 91, 92 and the timing of voltage application to the
pixel electrode 221, 222 are synchronized and controlled,
and thereby three-dimensional image display can be
15 realized.
As has been described above, by providing the angle y
to the lateral direction with respect to the plan-view
shape of the pixel GI, G2, the moire in three-dimensional
image display can greatly be reduced. Furthermore, by not
20 providing the black matrix BM in the vertical direction,
the moire due to an alignment error between the pixel and
the optical control element 101, 102 can be reduced. In
the case where priority is to be placed on the contrast at
a time of liquid crystal display, the black matrix BM for
25 partitioning the pixels in the vertical direction is
provided.
In the present embodiment, the transparent electrode
film 31 reduces the effect of an external electric field.
In addition, by setting the transparent electrode film 31
and the common electrode 21 at the same potential, it
becomes possible to prevent the liquid crystal molecules L1
5 to L8 from rising toward the color filter substrate 28 due
to an electric field occurring between the transparent
electrode film 31 and the pixel electrode 221, 222.
F I G . 17 is a cross-sectional view illustrating an
example of a state of rising of liquid crystal molecules in
10 a case where a charged body, such as a finger, has
approached the liquid crystal panel.
In the present embodiment, by providing the
transparent electrode film 31 in the color filter substrate
28, the rising of liquid crystal molecules L1 to L5, as
15 illustrated in F I G . 16, can be suppressed.
The liquid crystal molecules L1 to L8, which are
prevented from rising toward the color filter substrate 28,
horizontally rotate when a liquid crystal driving voltage
is applied to the pixel electrode 221, 222.
In the color filter substrate 28, the color filter 16
and transparent resin layer 9 are formed on the transparent
electrode film 31. The color filter 16 and transparent
resin layer 17 function as dielectrics (insulators),
An equipotential line occurring from the pixel
25 electrode 221, 222 and common electrode 21 of the array
substrate 6 spreads toward the color filter 16 and
transparent resin layer 17 which are dielectrics. As the
effect of this, the transmittance of the liquid crystal
display device 30 can be improved. Specifically, when the
transparent electrode film 3 1 is provided between the
transparent substrate 15 and color filter 16; even the
5 liquid crystal molecules of the liquid crystal layer 7 in
the vicinity of the color filter substrate 28 can be more
easily driven by the application of the liquid crystal
driving voltage to the pixel electrode 221, 222, and the
transmittance can be enhanced. Incidentally, if the
10 transparent electrode film 31 is formed between the
transparent resin layer 17 and the alignment film 181, the
transparent conductive film 31 comes in contact with the
liquid crystal layer 7 via the alignment film 181, the
spread of the equipotential line is substantially limited
15 to the thickness range of the liquid crystal layer 7, the
liquid crystal molecules near the pixel electrodes 221, 222
are mainly driven, and the liquid crystal molecules of the
liquid crystal layer 7 in the vicinity of the color filter
substrate 28 are hardly driven. In this configuration in
20 which the transparent electrode film 31 is formed between
the transparent resin layer 17 and the alignment film 181,
the spread of the equipotential line decreases, and the
transmittance becomes lower than in the configuration of
the liquid crystal display device 30 of this embodiment.
It is desirable that the specific dielectric constant
between the color filter 16 and transparent resin layer 17
be small in a range of 3.0 to 4.5 and be a uniform value.
When a color material with a high specific dielectric
constant, such as carbon, is used as a light-shield color
material of the black matrix BM, the black matrix BM
including carbon may be formed between the transparent
5 electrode film 31 and the color filter 16. In this case,
it is possible to reduce the effect on the equipotential
line by the black matrix BM with the high specific
dielectric constant. By performing the formation of the
black matrix BM and the formation of an alignment mark by
10 the black matrix BM on the transparent substrate 15 in
advance, the formed alignment mark can be utilized at a
time of forming the transparent electrode 17.
In the present embodiment, the transparent electrode
film 31 is a transparent electrode, and may be formed in a
15 stripe pattern. For example, in order to detect touching
. of a finger or the like, an electrostatic capacitance,
which is formed between the transparent electrode film 31
with the stripe pattern and the common electrode 211, 212,
may be detected. Thereby, the liquid crystal display
20 device 30 can be provided with a touch sensing function.
For example, an electrically conductive metal oxide
thin film of, e.g. IT0 or IZO can be used as the material
of the pixel electrode 221, 222 and the common electrode
211, 212 of the array substrate 6 of the liquid crystal
25 display device 30 according to the embodiment.
The pixel electrode 221, 222 and the common electrode
211, 212 are electrically insulated by an insulation film
20c in the thickness direction thereof. The thicknesses of
the color filter 16, transparent resin layer 17 and
insulation layers 20a to 20c can be adjusted based on the
thickness of the liquid crystal layer 7, dielectric
5 constant, application voltage and driving condition.
In the case where the insulation layers 20a to 20c are
formed of SiNx (silicon nitride), the practical range of
film thickness of the insulation layers 20a to 20c is, for
example, 0.1 pm to 1.0 pm. In the liquid crystal display
10 device 30 according to the present embodiment, since an
oblique electric field can more effectively be utilized,
the range, in which electric force lines act at a time of
driving voltage application, may be increased in the
direction of film thickness including the liquid crystal
15 layer 7, transparent resin layer 17 and color filter 16.
Thereby, the transmittance of light can be increased. For
example, Jpn. Pat. Appln. KOKAI Publication No. 2009-105424
discloses a technique of forming signal lines, such as gate
lines and source lines, by a single layer of an aluminum
20 alloy having a low contact property with IT0 that is an
electrically conductive metal oxide. To further stack an
insulation layer on the pixel electrode 221, 222 is
preferable since this has an effect of reducing an image
persistence of the liquid crystal (the effect of non-
25 uniformity or accumulation of electric charge) at the time
of driving the liquid crystal.
The signal lines may be, for example, aluminum lines
or copper lines. In a case where the signal line includes
copper, for example, the signal line may be formed by a
multilayer structure in which copper and titanium are
stacked, or a multilayer structure in which copper,
5 titanium and silicon are stacked. The titanium included in
the signal line may be replaced with, for example,
molybdenum, tungsten, or other high-melting-point metal.
In the case where the active element 91, 92 is a thinfilm
transistor of an oxide semiconductor with a channel
10 layer which is transparent in a visible range, the line
width of the pattern of the light-shield layer, such as the
black matrix BM, can be reduced, and the brightness of the
liquid crystal display device 30 can be enhanced. In the
case where the thin-film transistor of the oxide
15 semiconductor is used in the liquid crystal display device
30, optical alignment can efficiently be performed and the
reliability of the liquid crystal display device 30 can be
enhanced. In a conventional PSA technique using a liquid
crystal to which a photopolymerizable monomer is added,
20 there is a case in which the reliability of the liquid
crystal display device is degraded by a residual nonpolymerized
monomer or an insufficiently cured optical
alignment film due to ultraviolet shielding by the lightshield
portion of the thin-film transistor that occupies a
25 large area relating to the silicon semiconductor or the
black matrix BM which partitions colored pixels, or the
color filter with poor ultraviolet transmittance. However,
as in the embodiment, by using the thin-film transistor of
the oxide semiconductor, it is possible to decrease the
area of the light-shield portion, to perform exposure on a
wide area, and to greatly enhance the reliability.
5 Compared to this thin-film transistor of the oxide
semiconductor, a thin-film transistor of a silicon
semiconductor has sensitivity to light in a visible range,
and it is thus necessary to light-shield the thin-film
transistor with a larger area by a light-shield layer such
10 as a black matrix BM.
As the oxide semiconductor, composite metal oxides
which are transparent in the visible range are applicable.
A semiconductor material including these metal oxides as
components is an oxide including two or more elements of
15 zinc, indium, tin, tungsten, magnesium, and gallium. As
materials, for instance, use may be made of zinc oxide,
indium oxide, indium-zinc-oxide, tin oxide, tungsten oxide
(WO), indium-gallium-zinc-oxide (In-Ga-Zn-0),i ndiumgallium-
oxide (In-Ga-O), zinc-tin-oxide (Zn-Sn-0), or zinc-
20 tin-silicon-oxide (Zn-Sn-Si-O),o r other materials. These
materials are substantially transparent, and the band gap
should preferably be 2.8 eV or more, and should more
preferably be 3.2 eV or more. The structure of these
materials may be any one of a single crystal, a
25 polycrystal, a microcrystal, a mixed crystal of a
crystalline/amorphous structure, a nanocrystal-dispersed
amorphous structure, and an amorphous structure. It is
desirable that the film thickness of an oxide semiconductor
layer be 10 nm or more. The oxide semiconductor layer is
formed by using a method such as a sputtering method, a
pulse laser deposition method, a vacuum evaporation method,
5 a CVD (Chemical Vapor Deposition) method, an MBE (Molecular
Beam Epitaxy) method, an ink jet method, or a print method.
Preferably, the oxide semiconductor layer is formed by the
sputtering method, pulse laser deposition method, vacuum
evaporation method, ink jet method, or print method. As
10 regards the sputtering method, an RF magnetron sputtering
method or a DC sputtering method is usable, but, more
preferably, the DC sputtering method is used. As a
starting material (target material) for sputtering, an
oxide ceramic material or a metallic target material can be
15 used. As regards the vacuum evaporation, heating
evaporation, electron beam evaporation, and an ion plating
method can be used. As the print method, transfer
printing, flexography, gravure printing, and gravure offset
printing are usable, but other methods may be used. As the
20 CVD method, a hotwire CVD method and plasma CVD are usable.
Furthermore, other methods may be used, such as a method in
which a hydrate of an inorganic salt (e.g. chloride) is
dissolved in alcohol, etc., and baked and sintered, thereby
forming an oxide semiconductor.
Next, a description is given of the structures of the
thin-film transistor of the oxide semiconductor and the
array substrate 6. As illustrated in FIG. 16, in the array
substrate 6, insulation layers 20a, 20b, common electrodes
211, 212, an insulation layer 20c, pixel electrodes 221,
222, and an alignment sustaining layer 252 are formed in
the named order on a transparent substrate (e.g. glass
5 substrate) 19. The array substrate 6 includes active
elements 14a, 14b for applying a liquid crystal driving
voltage to the pixel electrodes 221, 222, and gate lines
and source lines which are electrically connected to the
active elements 14a 14b.
The active element 14a, 14b has, for example, a
bottom-gate-type top contact etch stopper structure.
Alternatively, the active element 14a, 14b may have, for
example, a bottom-gate-type top contact structure excluding
an etch stopper, or a back channel structure. The
15 transistor structure is not limited to the bottom gate
structure, and may be a top gate structure, a double gate
structure, or a dual gate structure.
In the manufacture of the active element 14a, 14b, to
begin with, an IT0 thin film of 140 nm is formed by a DC
20 magnetron sputtering method. Then, the IT0 thin film is
patterned in a desired shape, and a gate electrode and an
auxiliary capacitor electrode are formed. Further, a SiH,
thin film of 350 nm is formed thereon by using a plasma CVD
method, with use of SiH,, NH3 and Ha as a material gas, and
25 thus a gate insulation film that is a transparent
insulation film is formed. In addition, as a channel
layer, an amorphous In-Ga-Zn-0 thin film of 40 nm is formed
by a DC sputtering method by using an InGaZn04 target, and
the amorphous In-Ga-Zn-0 thin film is pattered in a desired
shape, and thus a transparent channel layer is formed.
Further, an SiON thin film is formed by an RF sputtering
5 method by using a Si3H4 target while introducing Ar and 02,
and the SiON thin film is patterned in a desired shape, and
thus a channel protection layer is formed. Furthermore, an
IT0 thin film of 140 nm is formed by a DC magnetron
sputtering method and is patterned in a desired shape, and
10 a source/drain electrode is formed.
In the liquid crystal display device 30 according to
the above-described embodiment, rising of liquid crystal
molecules L1 to L8 can be suppressed, and the same
advantageous effects as with the liquid crystal display
15 device 1 according to the above-described first embodiment
can be obtained.
[Third Embodiment]
In the present embodiment, transparent resins and
organic pigments, which are used for the color filter
20 substrates 5, 28 according to the above-described first and
second embodiments, will be exemplarily described.
(Transparent resins)
A photosensitive color composition, which is used for
forming the black matrix BM and color filter 16, includes,
25 in addition to a pigment-dispersed body, a multifunctional
monomer, a photosensitive resin or a nonphotosensitive
resin, a polymerization initiator, and a solvent. Organic
resins with high transparency which can be used in the
present embodiment, for instance, a photosensitive resin or
a nonphotosensitive resin, are generally referred to as
transparent resins.
5 As the transparent resins, use can be made of
thermoplastic resins, thermosetting resins, or
photosensitive resins. As the thermoplastic resins, for
example, use can be made of a butyral resin, styrene-maleic
acid copolymer, chlorinated polyethylene, chlorinated
10 polypropylene, polyvinyl chloride, vinyl chloride-vinyl
acetate copolymer, polyvinyl acetate, polyurethane resin,
polyester resin, acrylic resin, alkyd resin, polystyrene
resin, polyamide resin, rubber resin, cyclized rubber
resin, celluloses, polybutadiene, polyethylene,
15 polypropylene, and polyimide. In addition, as the
thermosetting resins, for example, use can be made of an
epoxy resin, benzoguanamine resin, rosin-modified maleic
acid resin, rosin-modified fumaric acid resin, melamine
resin, urea resin, and phenol resin. The thermosetting
20 resin may be produced by a reaction between a melamine
resin and a compound including an isocyanate group.
(Alkali-soluble resins)
For the formation of the light-shield pattern such as
the black matrix BM, the transparent pattern and the color
25 filter, which are used in the present embodiment, it is
preferable to use photosensitive resin compositions which
are capable of patterning by photolithography. It is
desirable that these transparent resins be resins to which
alkali-solubility is imparted. As the alkali-soluble
resins, resins including a carboxyl group or a hydroxyl
group may be used, or other resins may be used. As the
5 alkali-soluble resins, for example, use can be made of an
epoxy acrylate resin, novolak resin, polyvinylphenol resin,
acrylic resin, carboxyl group-containing epoxy resin, and
carboxyl group-containing urethane resin. Of these, the
epoxy acrylate resin, novolak resin and acrylic resin
10 should preferably be used as the alkali-soluble resins,
and, in particular, the epoxy acrylate resin and novolak
resin are preferable.
(Acrylic resins)
As typical transparent resins which are applicable in
15 the embodiment, the following acrylic resins are
exemplarily described.
As the acrylic resins, use can be made of polymers
which are obtained by using, as monomers, for instance,
(meth)acrylic acid; alkyl (meth)acrylate such as methyl
20 (meth) acrylate, ethyl (meth) acrylate, propyl
(meth) acrylate, butyl (meth) acrylate, t -buthyl
(meth) acrylate, benzyl (meth)a crylate, or lauryl
(meth)acrylate; hydroxyl group-containing (meth)acrylate
such as hydroxyethyl (meth)acrylate or hydroxypropyl
25 (meth)acrylate; ether group-containing (meth)acrylate such
as ethoxyethyl (meth)a crylate or glycidyl (meth)a crylate;
and alicyclic (meth)acrylate such as cyclohexyl
(meth) acrylate, isobornyl (meth) acrylate, or
dicyclopentenyl (meth)acrylate.
Incidentally, the monomers described above by way of
example can be used singly or in combination of two or more
5 kinds. Further, the acrylic resin may be produced by using
a copolymer by a compound, such as styrene, cyclohexyl
maleimide, or phenyl maleimide, which is copolymerizable
with these monomers.
In addition, for example, a resin with
10 photosensitivity may be produced by a reaction between a
copolymer obtained by copolymerizing carboxylic acid having
an ethylenic unsaturated group such as (meth)acrylic acid,
and a compound including an epoxy group and an unsaturated
double bond, such as glycidyl methacrylate. For example, a
15 resin with photosensitivity may be produced by adding a
carboxylic acid-containing compound, such as (meth)acrylic
acid, to a polymer of epoxy group-containing
(meth)acrylate, such as glycidyl methacrylate, or a
copolymer between this polymer and other (meth)acrylate.
(Organic pigments)
As red pigments, for example, use can be made of C. I.
Pigment Red 7, 9, 14, 41, 48:1, 48:2, 48:3, 48:4, 81:1,
81:2, 81:3, 97, 122, 123, 146, 149, 168, 177, 178, 179,
180, 184, 185, 187, 192, 200, 202, 208, 210, 215, 216, 217,
25 220, 223, 224, 226, 227, 228, 240, 242, 246, 254, 255, 264,
272, and 279.
As yellow pigments, for example, use can be made of C.
I. Pigment Yellow 1, 2, 3, 4, 5, 6, 10, 12, 13, 14, 15, 16,
17, 18, 20, 24, 31, 32, 34, 35, 35:1, 36, 36:1, 37, 37:1,
40, 42, 43, 53, 55, 60, 61, 62, 63, 65, 73, 74, 77, 81, 83,
86, 93, 94, 95, 97, 98, 100, 101, 104, 106, 108, 109, 110,
5 113, 114, 115, 116, 117, 118, 119, 120, 123, 125, 126, 127,
128, 129, 137, 138, 139, 144, 146, 147, 148, 150, 151, 152,
153, 154, 155, 156, 161, 162, 164, 166, 167, 168, 169, 170,
171, 172, 173, 174, 175, 176, 177, 179, 180, 181, 182, 185,
187, 188, 193, 194, 199, 213, and 214.
As blue pigments, for example, use can be made of C.
I. Pigment Blue 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 22,
60, 64, and 80. Of these, C. I. Pigment Blue 15:6 is
preferable.
As violet pigments, for example, use can be made of C.
15 I. Pigment Violet 1, 19, 23, 27, 29, 30, 32, 37, 40, 42,
and 50. Of these, C. I. Pigment Violet 23 is is
preferable.
As green pigments, for example, use can be made of C.
I. Pigment Green 1, 2, 4, 7, 8, 10, 13, 14, 15, 17, 18, 19,
20 26, 36, 45, 48, 50, 51, 54, 55, and 58. Of these, C. I.
Pigment Green 58, which is a halogenated zinc
phthalocyanine green pigment, is preferable.
(Color materials of black matrix BM)
A light-shielding color material included in the layer
25 of the black matrix BM is a color material which exhibits a
light-shield function by having absorption in a visible
light wavelength range. In the embodiment, as the lightshielding
color materials, for example, organic pigments,
inorganic pigments, and dyes are usable. As the inorganic
pigments, for example, carbon black and titanium oxide can
be used. As the dyes, for example, an azoic dye,
5 anthraquinone dye, phthalocyanine dye, quinonimine dye,
qyinoline dye, nitro dye, carbonyl dye, and methine dye are
usable. As regards the organic pigments, the abovedescribed
organic pigments can be adopted. Incidentally, a
light-shielding component may be one kind, or a combination
10 of two or more kinds with a proper ratio. In addition, a
volume resistance may be increased by resin coating on the
surface of these color materials, or, conversely, the
volume resistance may be decreased by imparting a slight
electrical conductivity by increasing the content ratio of
15 the color material to the base material of the resin.
However, since the volume resistance value of such lightshield
material is in a range of about 1 x lo8 - 1 x 1015
Q0cm, this is not such a level as to affect the resistance
value of the transparent conductive film. Similarly, the
20 specific dielectric constant of the light-shield layer can
be adjusted in a range of about 3 to 30 by the selection or
content ratio of the color material. The specific
dielectric constants of the coating film of the black
matrix BM, the coating film of the color pixel and the
25 transparent resin layer can be adjusted within the abovedescribed
range of the specific dielectric constant, in
accordance with the design conditions and liquid crystal
driving conditions of the liquid crystal display device 1,
30.
In the present embodiment, there is no need to form a
large light-shield part in a case of using a silicon-based
5 thin-film transistor, such as an amorphous silicon-based
thin-film transistor. It is possible to eliminate moire
due to non-uniformity of a black matrix pattern within a
pixel at a time of using a silicon-based thin-film
transistor, and due to an alignment defect relative to the
10 optical control element 101, 102.
The above-described embodiments may be variously
altered and applied without departing from the spirit of
the invention. The above embodiments may be freely
combined and used.
We claim:
1. A liquid crystal display device comprising:
an array substrate including a plurality of pixel
electrodes corresponding to a plurality of pixels arranged
5 in a matrix;
a color filter substrate opposed to the array
substrate and including color filters corresponding to the
plurality of pixels;
a liquid crystal layer provided between the array
10 substrate and the color filter substrate;
a backlight unit provided on a back surface side of
the array substrate, the back surface side being opposite
to a liquid crystal layer side of the array substrate; and
a controller configured to control an application
15 timing of a liquid crystal driving voltage to the pixel
electrodes, and a light emission timing of the backlight
unit ,
wherein the plurality of pixels are configured to each
have a plan-view shape of a parallelogram which is
20 elongated in a lateral direction, and configured such that
identical colors are arranged in the lateral direction, and
different colors are arranged in a vertical direction,
pixels neighboring in the lateral direction of the
plurality of pixels have shapes of line-symmetry with
25 respect to a center line of the neighboring pixels, and
liquid crystal molecules of the neighboring pixels
have a negative dielectric constant anisotropy, and, when
the liquid crystal driving voltage is applied to the pixel
electrodes corresponding to the neighboring pixels, the
liquid crystal molecules rotate horizontally relative to a
substrate plane in a direction of the line-symmetry with
5 respect to the center line.
2. The liquid crystal display device of Claim 1,
wherein the plurality of pixels include a picture element
composed of two red pixels, two green pixels and two blue
pixels,
10 the plurality of pixels are parallelogrammatic with a
long side having an angle y to the lateral direction, and a
short side parallel to the vertical direction,
two pixels neighboring in the lateral direction are of
the same color and have a V shape or an inverted-V shape,
15 and a pattern of the V shape or the inverted-V shape is
repeated in the lateral direction,
the color filter substrate includes a black matrix
which partitions the pixels,
the backlight unit is an edge-lit-type unit including
20 a solid-state light-emission element array,
the controller is configured to execute, based on a
video signal, synchronization control between the
application timing of the liquid crystal driving voltage to
the pixel electrodes, and the light emission timing of the
25 backlight unit, and
the black matrix is formed between pixels neighboring
in the vertical direction and is not formed between pixels
neighboring in the lateral direction.
3. The liquid crystal display device of Claim 1,
further comprising a plurality of active elements which are
electrically connected to the plurality of pixel electrodes
5 and are formed of an oxide semiconductor using a composite
metal oxide as a transparent channel material.
4. The liquid crystal display device of Claim 1,
wherein the pixel electrode includes a plurality of combtooth
portions each having a longitudinal direction
10 parallel to a long side of the pixel, and has a comb shape
of line-symmetry with respect to the center line of the
neighboring pixels.
5. The liquid crystal display device of Claim 1,
wherein the color filter substrate includes a transparent
15 electrode film and the color filters on a transparent
substrate.
6. The liquid crystal display device of Claim 2,
wherein the color filter substrate includes the black
matrix, a transparent electrode film and the color filters
20 on a transparent substrate.
7. The liquid crystal display device of Claim 1,
further comprising an optical control element disposed
between the array substrate and the backlight unit and
including an array of a plurality of triangular prisms and
25 an array of a plurality of semicylindrical lenses,
wherein a predetermined angle is provided between a
longitudinal direction of the plurality of triangular
prisms and a longitudinal direction of the plurality of
semicylindrical lenses.
8. The liquid crystal display device of Claim 1,
further comprising an optical control element disposed
5 between the array substrate and the backlight unit and
including an array of a plurality of triangular prisms and
an array of a plurality of semicylindrical lenses,
wherein a longitudinal direction of the plurality of
triangular prisms is substantially parallel to a
10 longitudinal direction of the plurality of semicylindrical
lenses, and
a width of the triangular prism is double a length of
the pixel in the lateral direction.
9. The liquid crystal display device of Claim 8,
15 wherein a width of the semicylindrical lens is an integer
number of times of a width of two pixels in the lateral
direction.
10. The liquid crystal display device of Claim 1,
further comprising a light reception element configured to
2 0 detect light which is incident from an observer side,
wherein the controller is configured to adjust an
emission angle of light by the backlight unit, based on
data measured by the liqht reception element.