CN1963604B

CN1963604B - Liquid crystal display having sub-pixel regions defined by sub-electrode regions

Info

Publication number: CN1963604B
Application number: CN200610101677XA
Authority: CN
Inventors: 宫地弘一; 盐见诚; 长江伸和; 中岛睦
Original assignee: Sharp Corp
Current assignee: Sharp Corp
Priority date: 1998-07-24
Filing date: 1999-07-24
Publication date: 2010-05-26
Anticipated expiration: 2019-07-24
Also published as: CN1716016A; CN100460937C; CN1963604A; JP3386374B2; JP2000047251A

Abstract

The liquid crystal display device comprises a first substrate and a second substrate; and a liquid crystal layer interposed between the first and second substrates, the liquid crystal layer having liquid crystal molecules therein. The first substrate includes a first electrode facing the liquid crystal layer. The second substrate includes a second electrode facing the liquid crystal layer. The first and second electrodes and the area of the liquid crystal layer to which the voltages are applied by the first and second electrodes define a pixel region of the display unit. The pixel region includes a plurality of sub-pixel regions, and liquid crystal molecules in each sub-pixel region are arranged in an axisymmetric manner. At least one of the first and second electrodes includes a plurality of openings regularly arranged in the pixel region. At least one of the first and second electrodes has a plurality of openings including a plurality of polygonal sub-electrode regions.

Description

Liquid crystal display having sub-pixel regions defined by sub-electrode regions

This application is a divisional application of chinese patent application No.200510081855.2 entitled "liquid crystal display having sub-pixel regions defined by sub-electrode regions" filed on 1999, 7/24.7 by sharp corporation.

Technical Field

The present invention relates to a liquid crystal display device used for a monitor such as a computer, a word processor, a car navigation system, a television receiver, and the like, and a method of manufacturing the same.

Background

Nowadays, TN (twisted nematic) liquid crystal display devices (hereinafter, referred to as "LCD devices") have been widely used. In the TN-LCD device, liquid crystal molecules are in a twisted arrangement form in a non-voltage applied state by rubbing the upper and lower alignment layers in different directions from each other. TN-LCD devices have problems with gray scale inversion and display quality that is significantly dependent on viewing angle.

In order to solve these problems, a liquid crystal material having negative dielectric anisotropy and a vertical alignment is proposed. The vertical arrangement provides a dark display in the absence of applied voltage. Using a phase plate with negative refractive index anisotropy, a satisfactory dark display can be obtained over a very large viewing angle range. The use of such a phase plate substantially compensates for birefringence induced by the liquid crystal layer in which liquid crystal molecules are vertically aligned in the absence of an applied voltage. In this way, high-contrast display is achieved over a wide range of viewing angles. However, the vertical alignment has a problem of a gray scale inversion phenomenon, which is observed in the same direction as a direction in which liquid crystal molecules are tilted under the application of a voltage.

Japanese unexamined patent publication No. Hei 6-301036 discloses an LCD device having an opening at the center of a counter electrode region corresponding to a pixel electrode. Such a structure will cause an electric field between the pixel electrode and the counter electrode inclined with respect to the surface of the structure, which is perpendicular with respect to the surface without such a structure. Therefore, when a voltage is applied to the vertical alignment, the liquid crystal molecules are tilted in an axisymmetric manner. The dependency of display quality on the viewing angle of such an LCD device is uniform in all directions, compared to an LCD device in which liquid crystal molecules are tilted in one direction. Thus, the LCD device disclosed in the above publication gives a very satisfactory viewing angle characteristic.

Japanese unexamined patent publication Hei 8-341590 discloses an LCD device having protrusions around a pixel region or spaced apart pixel regions, and an alignment fixing layer. This structure defines the position and size of a liquid crystal region in which liquid crystal molecules are arranged in an axisymmetric manner, and stabilizes the axisymmetric arrangement of the liquid crystal molecules.

However, the structure disclosed in japanese unexamined patent publication No. hei 6-301036 makes it difficult to generate an electric field uniformly inclined with respect to the electrode surface in the entire pixel region. Therefore, the liquid crystal molecules in a part of the pixel region respond to the applied voltage in a delayed manner, which causes a phenomenon that the image is not separated.

The structure disclosed in japanese unexamined patent publication hei 8-341590 requires protrusions in order to form a protective or similar structure on the substrate. This would increase the manufacturing steps and increase the cost.

Disclosure of Invention

One aspect of the present invention provides a liquid crystal display device, including: a first substrate; a second substrate; and a liquid crystal layer interposed between the first and second substrates, the liquid crystal layer having liquid crystal molecules therein. The first substrate includes a first electrode facing the liquid crystal layer. The second substrate includes a second electrode facing the liquid crystal layer. The first electrode, the second electrode, and the liquid crystal layer define a pixel region, which is a display cell, by regions to which voltages are applied by the first electrode and the second electrode. The pixel region includes a plurality of sub-pixel regions, and liquid crystal molecules in each sub-pixel region are arranged in an axisymmetric manner. At least one of the first electrode and the second electrode includes a plurality of openings regularly arranged in the pixel region. At least one of the first and second electrodes has a plurality of openings comprising a plurality of polygonal sub-electrode regions, each sub-electrode region having at least a portion of the plurality of openings at least at a corner thereof or along and overlapping a side thereof. A plurality of sub-pixel electrodes are defined by the plurality of sub-electrode regions.

According to a specific embodiment of the present invention, the first electrode includes a plurality of pixel electrodes arranged in a matrix form, and each of the plurality of pixel electrodes is connected to the scan line and the signal line through the switching device. The second electrode is a counter electrode facing the plurality of pixel electrodes. Each of the plurality of pixel electrodes has at least one of the plurality of sub-electrode regions.

According to a specific embodiment of the present invention, at least two of the plurality of sub electrode regions are polygonal identical to each other and share a common side.

According to a specific embodiment of the present invention, each polygon is rotationally symmetric, and the liquid crystal molecules are arranged in an axisymmetric manner with respect to an axis of rotational symmetry of the polygon.

According to a specific embodiment of the invention, at least two of the plurality of sub-electrode regions are polygons sharing a common side and the opening is at least 2 μm away from the pixel electrode.

According to a particular embodiment of the invention, said polygons are identical to each other.

According to a specific embodiment of the invention, the liquid crystal layer is formed of a liquid crystal material having a negative dielectric anisotropy, and liquid crystal molecules of the liquid crystal material are substantially vertically aligned with respect to the first substrate and the second substrate surfaces in the absence of an applied voltage.

According to an embodiment of the present invention, at least one of the first substrate and the second substrate includes a columnar protrusion outside the pixel region to control a thickness of the liquid crystal layer.

According to a specific embodiment of the invention, the liquid crystal layer comprises a chiral dopant and the liquid crystal molecules have a helical pitch of about 4 times the thickness of the liquid crystal layer.

According to a specific embodiment of the present invention, the liquid crystal display device further includes a pair of polarizers interposed between the first substrate and the second substrate, and at least one uniaxial phase plate having negative refractive index anisotropy.

According to a specific embodiment of the present invention, the liquid crystal display device further includes a pair of polarizers interposed between the first substrate and the second substrate, and at least one uniaxial phase plate having positive refractive index anisotropy.

According to an embodiment of the present invention, the liquid crystal display device further includes a pair of polarizers interposed between the first substrate and the second substrate, and at least one biaxial phase plate at least one of between the first substrate and the polarizer closer to the first substrate than the second substrate and between the second substrate and the polarizer closer to the second substrate than the first substrate.

According to a specific embodiment of the present invention, at least two of the plurality of sub electrode regions are polygons sharing a common side, and at least one side at least one sub electrode region coincides with at least one edge of the pixel electrode.

According to a specific embodiment of the present invention, the liquid crystal display device further includes a pair of polarizers interposed between the first substrate and the second substrate, and at least one uniaxial phase plate having negative refractive index anisotropy at least one of between the first substrate and the polarizer closer to the first substrate than the second substrate and between the second substrate and the polarizer closer to the second substrate than the first substrate.

According to a specific embodiment of the present invention, the liquid crystal display device further includes a pair of polarizers interposed between the first substrate and the second substrate, and at least one uniaxial phase plate having positive refractive index anisotropy at least one of between the first substrate and a polarizer closer to the first substrate than the second substrate and between the second substrate and a polarizer closer to the second substrate than the first substrate.

According to an embodiment of the invention, an alignment-fixing layer is provided between the liquid crystal layer and at least one of the first electrode and the second electrode at least at one of the first substrate and the second substrate for controlling the axisymmetric alignment of the liquid crystal molecules.

According to a specific embodiment of the invention, the liquid crystal layer comprises chiral dopants and the liquid crystal molecules have a helical pitch of about 4 times the thickness of the liquid crystal layer.

According to a specific embodiment of the invention, at least one of the first electrode and the second electrode has a plurality of regularly arranged concave portions.

According to an embodiment of the present invention, at least one of the first substrate and the second substrate includes a columnar protrusion for controlling a thickness of the liquid crystal layer.

According to a specific embodiment of the present invention, the liquid crystal display device further includes a pair of polarizers interposed between the first substrate and the second substrate, and at least one uniaxial phase plate having negative refractive index anisotropy at least one of between the first substrate and a polarizer closer to the first substrate than the second substrate and between the second substrate and a polarizer closer to the second substrate than the first substrate.

Another aspect of the present invention provides a method of manufacturing a liquid crystal display device including a first substrate, a second substrate, and a liquid crystal layer interposed between the first substrate and the second substrate and made of a liquid crystal material having liquid crystal molecules, wherein the first substrate includes a first electrode facing the liquid crystal layer; the second substrate includes a second electrode facing the liquid crystal layer; the first electrode, the second electrode and the liquid crystal layer are defined by the area to which the first electrode and the second electrode are applied with voltage, and the pixel area is a display unit; the pixel region includes a plurality of sub-pixel regions, and liquid crystal molecules in each sub-pixel region are arranged in an axisymmetric manner; the manufacturing method comprises the following steps: forming a plurality of openings at least one of the first and second electrodes, the plurality of openings being regularly arranged in the pixel region such that at least one of the first and second electrodes has a plurality of openings, the openings including a plurality of polygonal sub-electrode regions, each sub-electrode region having a portion of the plurality of openings at least one corner thereof and along and overlapping a side thereof; injecting a mixture of a light-curable resin and a liquid crystal material into a gap between the first substrate and the second substrate; irradiating the mixture with light while applying a voltage to the mixture, so that the photocurable resin is cured to form a collimation fixing layer.

In the LCD display device of the present invention, the electrode for applying a voltage to the liquid crystal layer has an opening (this area does not function as an electrode) in the pixel region, which is a display unit. Since no electric field is generated at the opening, the electric field around the opening is inclined with respect to the direction orthogonal to the electrode surface. For example, liquid crystal molecules having negative dielectric anisotropy are aligned such that their longitudinal axes are perpendicular to the electric field. Therefore, due to the oblique electric field, the liquid crystal molecules are aligned in a radial (i.e., axisymmetric) manner around the opening. Thus, the display quality of the present LCD device with respect to viewing angle due to the refractive index anisotropy of the liquid crystal molecules is uniform in all directions.

In an embodiment of the polygonal sub-electrode region having openings at least at the corners or along and overlapping the sides thereof, the liquid crystal molecules in the plurality of sub-pixel regions of each pixel region are arranged in an axisymmetric manner. In the embodiment where the polygonal sub-electrode regions are identical to each other, the sub-pixel regions defined by the polygonal sub-electrode regions are arranged in a highly symmetrical manner. Therefore, the uniformity of the viewing angle characteristics is improved. In embodiments where each polygon has rotational symmetry (n-fold symmetry), the viewing angle characteristics are further improved.

In the embodiment in which the electrode in the pixel region has a concave portion, the liquid crystal molecules of the above concave portion are vertically aligned with respect to the region of the vertical alignment layer, which is depressed in correspondence with the concave portion. In other words, the liquid crystal molecules of the concave portion described above are tilted in an axisymmetric manner with respect to the central axis of the concave portion. In the embodiment in which the concave portion is located at an intermediate position between two adjacent openings, the axis for the axisymmetric arrangement coincides with the central axis of the concave portion. Therefore, the position of the central axis for the axisymmetric arrangement is fixed and stable.

In the embodiment where the opening is at least 2 μm away from the edge of the pixel electrode, the arrangement of the liquid crystal molecules is prevented from becoming unstable due to the lateral electric field generated by the scanning lines and the signal lines (bus lines) provided for connection with the active devices near the edge of the pixel electrode.

In embodiments where at least one side of at least one sub-electrode region coincides with at least one edge of the pixel electrode, disclination is suppressed at the edge of the pixel electrode.

In embodiments where the alignment fixing layer is disposed between the liquid crystal layer and at least the first substrate or the second substrate, the arrangement of the liquid crystal molecules is stable, which gives a bright display.

Thus, the present invention described herein can provide an LCD device with the advantage of having good viewing angle characteristics without causing the phenomenon of inseparability of images, and a method of manufacturing such a display.

Drawings

These and other advantages of the present invention will become more apparent to those skilled in the art from a reading and understanding of the following detailed description when taken with reference to the accompanying drawings.

FIG. 1A is a cross-sectional view of an LCD device according to a first embodiment of the present invention, showing a state where no voltage is applied;

FIG. 1B is a cross-sectional view of the LCD device shown in FIG. 1A, showing a state when a voltage is applied;

fig. 2 is a top view of an active matrix substrate of the LCD device shown in fig. 1A;

FIG. 3 is a schematic view of the LCD device of FIG. 1A viewed with a polarized light microscope in an orthogonal polarization state, the LCD device being applied with a voltage for gray scale display;

fig. 4A, 4B and 4C are top views of an active matrix substrate showing several alternative pixel electrode opening arrangements in the first embodiment;

FIGS. 5A, 5B and 5C are top views of an active matrix substrate showing several alternative pixel electrode opening arrangements in a first embodiment;

fig. 6 is a top view of an active matrix substrate of an LCD device in a second embodiment of the present invention;

fig. 7 is a cross-sectional view of the active matrix substrate taken along line VII-VII' in fig. 6;

FIG. 8 is a schematic view of a second embodiment of an LCD device for gray scale display, viewed with a polarized light microscope in an orthogonal polarization state, to which a voltage is applied;

fig. 9A, 9B and 9C are top views of an active matrix substrate showing several alternative pixel electrode opening arrangements in a second embodiment;

10A, 10B and 10C are top views of an active matrix substrate showing several alternative pixel electrode opening arrangements in a second embodiment;

fig. 11 is a top view of an active matrix substrate of an LCD device in a third embodiment of the present invention;

fig. 12A, 12B and 12C are top views of an active matrix substrate showing several alternative pixel electrode opening arrangements in a third embodiment;

fig. 13A, 13B and 13C are top views of an active matrix substrate showing several alternative pixel electrode opening arrangements in a third embodiment;

FIG. 14A is a cross-sectional view of an active matrix substrate of an LCD device in a fourth embodiment of the present invention, showing a state where no voltage is applied;

FIG. 14B is a cross-sectional view of the LCD device shown in FIG. 14A, showing a state when a voltage is applied;

fig. 15 is a top view of an active matrix substrate of the LCD device shown in fig. 14A;

FIG. 16 is a schematic view of the LCD device of FIG. 14A viewed with a polarized light microscope in an orthogonal polarization state, the LCD device being applied with a voltage for gray scale display;

fig. 17A, 17B and 17C are top views of an active matrix substrate showing several alternative pixel electrode opening arrangements in a fourth embodiment;

fig. 18A, 18B and 18C are top views of an active matrix substrate showing several alternative pixel electrode opening arrangements in a fourth embodiment;

FIG. 19A is a cross-sectional view of an active matrix substrate of an LCD device in a fifth embodiment of the present invention, showing a state where no voltage is applied;

FIG. 19B is a sectional view of the LCD device shown in FIG. 19A, showing a state when a voltage is applied;

FIGS. 20A and 20B are each a schematic view of an LCD device viewed by polarized light microscopy in orthogonal polarization states, showing an axisymmetric arrangement of liquid crystal molecules disturbed by plastic beads;

fig. 21A, 21B, 21C and 21D are each a top view of an active matrix substrate in a sixth embodiment of the present invention, each substrate including one columnar projection;

FIGS. 22A and 22B are each a schematic view showing a sixth embodiment of an LCD device for gray scale display, viewed with a polarized light microscope in an orthogonal polarization state, to which a voltage is applied;

FIGS. 23A and 23B are each a schematic view showing a seventh embodiment of an LCD device for gray scale display, viewed with a polarized light microscope in an orthogonal polarization state, to which a voltage is applied;

FIGS. 24A and 24B are each a sectional view of an LCD device including one or more phase plates according to an eighth embodiment of the present invention;

FIG. 25A is a graph showing the dependence of light transmittance on viewing angle including the LCD device shown in FIG. 24B in a dark display state;

FIG. 25B is a graph showing the relationship between light transmittance and retardation of a phase plate at a viewing angle of 60 °;

fig. 26A and 26B are each a sectional view of an eighth embodiment LCD device including one or more phase plates;

FIG. 27A is a graph showing the dependence of light transmittance on viewing angle including the LCD device shown in FIG. 26B in a dark display state;

FIG. 27B is a graph showing the relationship between the transmittance of light and the retardation of a phase plate at a viewing angle of 60 °;

fig. 28A, 28B and 28C are each a sectional view of an eighth embodiment LCD device including one or more phase plates.

Detailed Description

The invention is described below by way of example with reference to the accompanying drawings. In the following examples, a transmissive LCD device will be described, but the present invention is not limited to such an LCD device.

(example 1)

The LCD device 100 according to the first embodiment of the present invention is described below. Fig. 1A and 1B are schematic sectional views of an LCD device 100. Fig. 1A shows the case where no voltage is applied, and fig. 1B shows the case where a voltage is applied. Fig. 1A and 1B show a pixel region of the LCD device 100. The following description will be given in consideration of this one pixel region unless otherwise noted.

The LCD device 100 includes an active matrix substrate 20, a counter substrate (color filter substrate) 30, and a liquid crystal layer 40 interposed between the active matrix substrate 20 and the counter substrate 30. The active matrix substrate 20 includes a transparent substrate 21, an insulating layer 22, pixel electrodes 24, and a collimating layer 26. The insulating layer 22, the pixel electrodes 24 and the alignment layer 26 are provided on the surface 21a of the substrate 21 in this order, the surface 21a facing the liquid crystal layer 40. The active matrix substrate 20 includes active devices (typically TFTs) and wires for supplying voltages to the pixel electrodes 24, which are not shown in fig. 1A and 1B for simplicity. The counter substrate 30 comprises a transparent substrate 31, a color filter layer 32, a counter electrode 34 and a collimating layer 36. A color filter layer 32, a counter electrode 34 and a collimating layer 36 are provided in this order on a surface 31a of the substrate 31, the surface 31a facing the liquid crystal layer 40. The alignment layers 26 and 36 in this example are vertical alignment layers and the liquid crystal layer is made of a liquid crystal material which is a negative dielectric material.

The pixel electrode 24 has a plurality of openings 24a, which are circular in this example. Needless to say, none of the plurality of openings 24a functions as an electrode. As will be described in greater detail below, the plurality of openings 24a define a polygonal sub-electrode region 50 having openings 24a at its corners or along and overlapping its sides. The liquid crystal molecules 40a in the sub-pixel region 60 defined by the sub-electrode regions 50 are arranged in an axisymmetric manner due to the respective openings 24 a.

In the case where no voltage is applied to the liquid crystal layer 40 as shown in fig. 1A, the liquid crystal molecules 40a are aligned perpendicular to the

surfaces

26a and 36a of the vertical alignment layers 26 and 36 by the alignment force of the alignment layers. References in this specification to "first substrate surface" and "second substrate surface" refer to directions parallel to surface 26 a. In the case where a voltage is applied to the liquid crystal layer 40 as shown in fig. 1B, the liquid crystal molecules 40a having negative dielectric anisotropy are aligned such that the longitudinal axes thereof are perpendicular with respect to the electric line of force E. In the vicinity of the opening 24a, the electric line of force E is inclined with respect to the

surfaces

21a and 31a of the substrates 21 and 31 (substantially parallel to the

surfaces

26a and 36a of the vertical alignment layers 26 and 36). Therefore, the liquid crystal molecules 40a near the openings 24a are arranged radially around each opening 24 a. The liquid crystal molecules 40a farther from the opening 24a are inclined at a larger angle with respect to a straight line perpendicular to the

surfaces

21a and 31a than the liquid crystal molecules 40a closer to the opening 24 a. Accordingly, the liquid crystal molecules 40a in the sub-pixel region 60 are arranged in an axisymmetric manner.

Fig. 2 is a top view of the active matrix substrate 20 of the pixel region of the LCD device 100 shown in fig. 1A and 1B. Fig. 1A and 1B show a cross section taken along the line I-I' in fig. 2.

As shown in fig. 2, the active matrix substrate 20 includes a TFT70 for controlling a voltage applied to the pixel electrode 24, a gate line (scanning line) 72 for supplying a scanning signal to the gate of the TFT70, a source line (signal line) 74 for supplying a data signal to the source of the TFT70, and a storage capacitor common line 76 having the same potential as the pixel electrode 24. In this example, a so-called Cs common structure is employed, which forms a storage capacitance using the storage capacitance common line 76. In addition, a so-called Cs gate structure may be employed, in which the storage capacitance is formed by the gate line 72, or a form of the storage capacitance may be omitted.

As described above, the pixel electrode 24 has a plurality of openings 24 a. The opening 24a will be described in detail with reference to fig. 2. As shown in fig. 2, the opening 24a defines

sub electrode regions

50a, 50B, and 50c (each corresponding to the sub electrode region 50 in fig. 1A and 1B). The

sub electrode regions

50a, 50b, and 50c have openings 24a at respective corners thereof. In more detail, the

sub electrode regions

50a, 50b, and 50c are each a polygon defined by a central line connecting the centers of each two openings 24a that are closest to each other. The

sub electrode regions

50a, 50b and 50c in this example are quadrilateral. A cutout portion (lower left portion in fig. 2) of the pixel electrode 24a near the sub-electrode region 50c forms an opening. The

sub-electrode regions

50a and 50c are square, have quadruple symmetry axes at the centers thereof, and are merged with each other. The sub-electrode region 50b is rectangular and has a two-fold axis of symmetry at its center. The sub electrode regions 50b each share one side with the

sub electrode regions

50a and 50 c.

The LCD device 100 in the first embodiment may be manufactured in such a manner as described below (referring to reference numerals associated with fig. 1A and 1B). The active matrix substrate 20 can be manufactured by a known method for manufacturing an active matrix substrate, except that the pixel electrodes 24 are formed by the resulting pattern of the openings 24a shown in fig. 2. Thus, the active matrix substrate 20 can be manufactured without increasing the number of manufacturing steps. The counter electrode 30 can also be made by known methods. The pixel electrode 24 and the counter electrode 34 are made of, for example, ITO (indium tin oxide) having a thickness of about 50 nm.

A vertical alignment layer 26 is applied by printing to the stack comprising the substrate 21, the insulating layer 22 and the pixel electrode 24. A vertical alignment layer 36 is applied by printing to the stack comprising the substrate 31, the color filter layer 32 and the counter electrode 34. The vertical alignment layers 26 and 36 are made of a polyimide-based material (such as JALS-204 of japan synthetic rubber limited). In addition, the vertical alignment layers 26 and 36 may be made of various other materials that cause the liquid crystal molecules to be vertically aligned with respect to the

surfaces

26a and 36a of the vertical alignment layers 26 and 36. Such materials include, for example, octadecylethoxysilane and lecithin. Thus, the active matrix 20 and the counter substrate 30 are fabricated.

Then, plastic beads having a diameter of about 4.5 μm were distributed on the vertical alignment layer 26. On the counter substrate 30, a seal portion is formed along the periphery of the display area by screen printing, which is formed of an epoxy resin containing glass fiber. The active matrix substrate 20 and the counter substrate 30 are bonded together by heating and cured. Then, a liquid crystal material having negative dielectric anisotropy (Δ ∈ -4.0, Δ n ═ 0.08) was injected into the gap between the active matrix substrate 20 and the counter substrate 30 by a vacuum injection method. The LCD device 100 is completed in this manner.

The pixel electrode 24 in this example has an opening 24 a. In addition, the counter electrode 34 may have an opening. The effect of the present invention is achieved by forming a plurality of openings on the electrode provided in the pixel region, which is a display unit. The advantage of forming the opening 24a on the display electrode 24 is that the opening 24a is formed by the step of patterning the conductive film to form the display electrode, and the number of manufacturing steps is not increased.

Fig. 3 shows a top view of a pixel area (indicated as 100a in fig. 3) of the LCD device 100 shown in fig. 2 viewed with a polarized light microscope in an orthogonal polarization state. In fig. 3, the LCD device 100 is applied with a voltage for gray scale display. The pixel region 100a includes

sub-pixel regions

60a, 60b, and 60c, which are defined by

sub-electrode regions

50a, 50b, and 50c, respectively, in fig. 2. The partial pixel area 100a corresponding to the TFT70, the gate line 72, the source line 74 (fig. 2), and the like light blocking portion (or the portion corresponding to the black matrix) is observed to be dark (hatched in fig. 3). The opening 24a is also observed to be dark. The storage capacitor common line 76 is made of a transparent material. The long side of the pixel area pitch in this example is about 300 μm, the short side of the pixel area pitch is about 100 μm, and the diameter of each aperture 24a is about 10 μm.

As is apparent from fig. 3, the

sub-pixel regions

60a, 60b and 60c are observed to have orthogonal extinction patterns, showing that the liquid crystal molecules are arranged in an axisymmetric manner. In the

sub-pixel regions

60a and 60c having a square shape, a light extinction pattern having a quadruple symmetry axis is observed. In the sub-pixel region 60b having a rectangular shape, an extinction pattern having a two-fold symmetry axis is observed. In the peripheral area 60d surrounding the

sub-pixel regions

60a, 60b, and 60c, a similar extinction pattern to that of each sub-pixel region is observed. This phenomenon shows that the liquid crystal molecules are arranged in an axisymmetric manner in the peripheral region 60 d. In other words, in the peripheral edge region 60d, the liquid crystal molecules are arranged substantially radially around each opening 24 a. This is caused by the transmission of the arrangement of the liquid crystal molecules 40a tilted by the oblique electric field generated by the opening 24a to the liquid crystal molecules in the peripheral region 60 d.

In such an LCD device 100, each of the plurality of pixel regions as a whole has a plurality of sub-regions in which the liquid crystal molecules 40a (fig. 1A and 1B) are arranged in an axisymmetric manner. Therefore, the viewing angle characteristic of the LCD device 100 does not change depending on the azimuth angle of the viewing direction, and thus the present LCD device 100 has a high viewing angle characteristic. In the case where no voltage is applied to the liquid crystal layer 40 (fig. 1A and 1B), substantially all the liquid crystal molecules are perpendicular with respect to the surfaces 21A and 31A of the

glass substrates

21 and 31, thus giving satisfactory dark display. When a voltage is applied, a satisfactory bright display is given, and the response time is about 20 ms. When a gray scale display voltage is applied, the axisymmetric alignment of the liquid crystal molecules is not disturbed. The response time is sufficiently short and no inseparable phenomenon of the image is revealed. The axisymmetric alignment is very stable and no poor alignment occurs in the repeated operation test.

The

sub electrode regions

50a, 50b and 50c in this example are quadrilateral. Each sub-electrode region need not be quadrilateral but may be a polygon with openings at its corners or along and overlapping its sides. The sub-electrode regions may be triangular, but are preferably polygonal with four or more corners in order to provide uniform azimuthal dependence on viewing angle characteristics. A square shape has an advantage over a rectangular shape in that it has a higher rotational symmetry and thus provides a more uniform viewing angle characteristic than a rectangular shape.

Fig. 4A, 4B and 4C show alternative arrangements of sub-electrode regions 50 of the pixel electrode 24 in the first embodiment. The sub-electrode regions 50 in fig. 4A, 4B, and 4C are each a quadrangle. Fig. 5A, 5B and 5C also show alternative arrangements of sub-electrode regions of the pixel electrode 24 in the first embodiment. The sub electrode regions 50 in fig. 5A, 5B and 5C are polygonal having 5 or more corners.

Each of the hexagonal sub-electrode regions 51 in fig. 5A has an opening 24a at a corner thereof. Each of the hexagonal sub-electrode regions in fig. 5B has openings 24a at its corners and at its center so that liquid crystal molecules are arranged in a axisymmetric manner in the triangular sub-electrode regions 52. Each octagonal sub-electrode region 53 in fig. 5C has a rectangular opening 24C along its side. The opening 24a need not be circular or rectangular, but may be any shape. The sub-electrode regions (and also the sub-pixel regions) preferably have a high rotational symmetry (i.e. as close to a circle as possible), and they are preferably equilateral polygons. It is preferable that the plurality of sub-electrode regions (and also the sub-pixel regions) be arranged to have rotational symmetry. It is then preferable to arrange them in a regular manner in the same equilateral polygon.

The side of each sub-electrode region (and also the sub-pixel region) may be about 20 μm to about 50 μm in order to stably align the liquid crystal molecules in an axisymmetric manner. When the opening 24a is circular, the diameter is preferably about 5 μm to about 20 μm. When the number of openings is too large, the numerical aperture of the LCD device 100 is reduced. The number and configuration of the openings 24a (the shape of the sub-electrodes and the pixel regions) need to be appropriately determined in consideration of both the viewing angle required for using the LCD device 100 and the luminance required.

(example 2)

An LCD device according to a second embodiment of the present invention will be described with reference to fig. 6 and 7. The pixel electrode in this embodiment has an opening and also a recessed portion as will be described later in detail. Fig. 6 is a top view of an active matrix substrate 80 of the LCD device of the second embodiment. Fig. 6 shows a pixel region of the LCD device. Unless otherwise stated, the following description will be given while considering one pixel region.

As shown in fig. 6, the active matrix substrate 80 includes the pixel electrode 24. The pixel electrode 24 has an opening 24a and a concave portion 24 b. The LCD device of the second embodiment has substantially the same structure as the LCD device 100 of the first embodiment except for the concave portion 24 b. The same elements as previously discussed with respect to fig. 1A, 1B, 2 and 3 are given the same reference numerals and their description will be omitted. The concave portion 24b may be formed in the form of a counter electrode instead of the pixel electrode 24.

Fig. 7 is a cross-sectional view of the active matrix substrate 80 taken along line VII-VII' in fig. 6. The insulating layer 22 provided on the substrate 21 has a concave portion. The pixel electrode 24 disposed on the insulating layer 22 thus also has a concave portion 24 b. The depth of the concave portion 24b is, for example, about 5 μm, and the diameter is, for example, about 10 μm. The diameter of the opening 24a formed in the pixel electrode 24 is, for example, about 10 μm. A vertical alignment layer 26 is disposed on the pixel electrode 24.

When no voltage is applied, the liquid crystal molecules 40a above the concave portions 24b are aligned perpendicular to the surface 26a of the vertical alignment layer 26. When a voltage is applied, the liquid crystal molecules 40a above the concave portion 24b are obliquely arranged in an axisymmetric manner with respect to the central axis 40b of the concave portion 24b indicated by a dotted line in fig. 7. As shown in fig. 7, the direction of the tilt about the central axis 40b is opposite to the direction of the tilt of the liquid crystal molecules 40a due to the oblique electric field around the opening 24 a. Specifically, in the vicinity of the concave portion 24b, each liquid crystal molecule 40a is inclined such that one end closer to the central axis 40b of the concave portion 24b is higher (i.e., farther from the pixel electrode 24) than the other end farther from the central axis 40b of the concave portion 24 b. In contrast, in the vicinity of the opening 24a, each of the liquid crystal molecules 40a is inclined such that one end closer to the central axis 40c of the opening 24a is lower (i.e., closer to the pixel electrode 24) than the other end farther from the central axis 40c of the opening 24 a. Therefore, the concave portion 24b formed in the middle portion between two adjacent openings 24a stabilizes the axisymmetric arrangement of the liquid crystal molecules around the openings 24 a. In other words, the liquid crystal molecules 40a in the sub-pixel region 60 are stably arranged in an axisymmetric manner around the central axis 40b of the concave portion 24 b.

Returning to fig. 6, the concave portion 24b is also formed at a symmetrical position of the peripheral edge region 50d around the

sub electrode regions

50a, 50b, and 50 c. Thus, the axisymmetric alignment of the liquid crystal molecules 40a in the peripheral region around the sub-electrode region is stabilized at the position of the symmetry axis.

As is apparent from the above description, the concave portion 24b and the opening 24a together define each sub-pixel region. Therefore, it is preferable to arrange the concave portion 24b so that the polygon to be formed is the same as the polygon formed by the opening 24 a. The concave portion 24b may have any shape instead of a circular shape.

The LCD device of the second embodiment can be fabricated in a manner similar to that described in the first embodiment. The insulating layer 22 having the recessed portion can be formed by forming a silicon oxide film having a thickness of about 10 μm by sputtering or the like, and then etching with a mask having an opening corresponding to the recessed portion. Thus, the pixel electrode 24 formed on the insulating layer 22 has a concave portion 24 b. The shape, size, and depth of the concave portion 24b can be adjusted by the shape and size of the mask opening, the thickness of the insulating layer 22, and the amount of etching. The diameter of the concave portion 24b is preferably about 5 μm to about 20 μm similar to the diameter of the opening 24 a.

Fig. 8 is a top view showing a pixel region (shown as 100b in fig. 8) of the LCD device according to the second embodiment viewed by a polarized light microscope in an orthogonal polarization state. The LCD device in fig. 8 is applied with a voltage for gray scale display. The pixel region 100b includes

sub-pixel regions

60a, 60b, and 60c defined by the

sub-electrode regions

50a, 50b, and 50c, respectively, of fig. 6. A part of the pixel area 100b (or a part corresponding to the black matrix) corresponding to the light blocking member such as the TFT70, the gate line 72, the source line 74 (fig. 2) is observed to be dark (hatched in fig. 8). The opening 24a is also observed to be dark. The storage capacitor common line 76 is made of a metal material. The longer side of the pixel area pitch is about 300 μm in this example, the shorter side of the pixel area pitch is about 100 μm, and the diameter of each opening 24a is about 10 μm.

In such an LCD device, each of the plurality of pixel regions as a whole has a plurality of sub-regions in which liquid crystal molecules 40a (fig. 7) are arranged in an axisymmetric manner. The axis of symmetry is controlled and fixed by the recessed portion 24b (fig. 6). The axis of symmetry also cooperates with the recessed portion 24 b. Therefore, the LCD device has high viewing angle characteristics. The response time is sufficiently short and no inseparable phenomenon of the image is revealed. The axisymmetric alignment is very stable and does not produce poor alignment in repeated operation tests.

The

sub electrode regions

50a, 50b, and 50c in the present embodiment are quadrangular, and each sub electrode region does not have to be quadrangular. In combination with the opening 24A shown in fig. 4A, 4B, 4C, the concave portion 24B shown in fig. 9A, 9B, 9C may be formed, respectively. In combination with the opening 24a shown in fig. 5A, 5B, 5C, the concave portion 24B shown in fig. 10A, 10B, 10C may be formed, respectively. The concave portion 24b functions to fix and stabilize the center of axial symmetry. Therefore, it is preferable to form each concave portion 24b in the middle portion between two adjacent openings 24 a. Further, it is preferable that the concave portion 24b is formed in the same polygonal shape as that of the opening 24 a. It is preferable that the concave portions 24b in the peripheral region 50d (fig. 6) be arranged to form the same polygon as that formed by the concave portions 24b in the sub-electrode regions 50.

When the concave portion 24b is formed, in order to stabilize the axisymmetric arrangement of the liquid crystal molecules, the side of the sub-pixel region 60 may be about 50 μm to 100 μm. The shape and number of the concave portions 24b can be appropriately determined in consideration of both the viewing angle and the luminance required when the LCD device is used.

(third embodiment)

An LCD device according to a third embodiment of the present invention will be described below. Fig. 11 is a top view of an active matrix substrate 320 of an LCD device in a third embodiment. Fig. 11 shows a pixel region of the LCD device. The following description will be related to one pixel region unless otherwise noted. In the active matrix substrate 320, the distance d from the edge 24c of the pixel electrode 24 to the opening 324a closest to the edge 24c, and the distance d' from the edge 24d (also closest to the edge 24 d) to the opening 324a are each about 5 μm. Except for this point, the LCD device of the third embodiment is basically the same as the LCD device 100 of the first embodiment. The same elements as previously described with respect to fig. 1A, 1B, 2 and 3 have the same reference numerals, and a description thereof will be omitted.

The distances d and d' are not limited to about 5 μm, but are preferably about 2 μm or more. The distances d and d' are preferably from about 2 μm to 10 μm. When the distances d and d' are less than about 2 μm, the axisymmetric arrangement of the liquid crystal molecules is disturbed by a lateral (horizontal) electric field due to the scanning lines or signal lines (bus lines) located near the plurality of pixel electrodes 24 arranged in a matrix shape. When the distances d and d' are greater than about 10 μm, the area of the pixel electrode 24 contributing to the display is excessively reduced, and thus the light transmittance of the LCD device is rapidly excessively reduced.

The LCD device of the third embodiment can be made in an axisymmetric manner as described in the first embodiment.

When one pixel region of the LCD device of the third embodiment to which a voltage for gray scale display is applied is observed by the polarized light microscope in the orthogonal polarization state, the liquid crystal molecules are observed in a state similar to that described in the first embodiment.

In such an LCD device, each pixel region as a whole has a plurality of sub-regions in which liquid crystal molecules are arranged in an axisymmetric manner. Therefore, the LCD device has high viewing angle characteristics. The response time is sufficiently short and no phenomenon of inseparability of the image appears. The axisymmetric alignment is very stable and no poor alignment occurs in the repeated operation test.

The

sub electrode regions

50a, 50b, and 50c in the present embodiment are quadrangular. Each sub-electrode region need not be quadrilateral but may be a polygon with openings at its corners or along and overlapping its sides.

Fig. 12A, 12B and 12C show several alternative arrangements of sub-electrode regions 50 of the pixel electrode 24 in the third embodiment. The sub-electrode regions 50 in fig. 12A, 12B, and 12C are polygonal. Fig. 13A, 13B and 13C show alternative arrangements of sub-electrode regions 50 of the pixel electrode 24 in the third embodiment. The sub-electrode regions in fig. 13A, 13B, and 13C are polygonal having 5 or more corners.

In fig. 13A, each of the hexagonal sub-electrode regions 51 has an opening 324a at a corner thereof. In fig. 13B, each of the hexagonal sub-electrode regions has openings 324a at corners and at the center thereof so that liquid crystal molecules in the triangular sub-electrode regions 52 are arranged in an axisymmetric manner. In fig. 13C, each octagonal sub-electrode region 53 has a rectangular opening 324a along its side. The openings 324a need not be circular or rectangular, but may be any shape. The sub-electrode regions (and also the sub-pixel regions) preferably all have a high rotational symmetry (i.e. are as close to circular as possible), and they are preferably equilateral polygons. It is preferable that the plurality of sub-electrode regions (and also the sub-pixel regions) be arranged to have rotational symmetry. It is then preferable to arrange them in a regular manner in the same equilateral polygon.

The side of each sub-electrode region (and sub-pixel region) may be about 20 μm to about 50 μm in order to stably align the liquid crystal molecules in an axisymmetric manner. As described above, the distance d between the edge 24c and the opening 324a closest to the edge 24c and the distance d' between the edge 24c and the opening 324a (also closest to the edge 24 c) are each preferably about 2 μm or more; more preferably from about 2 μm to about 10 μm. When the opening 324a is circular, it is preferably about 5 μm to about 20 μm in diameter. When the number of the openings is excessive, the numerical aperture of the LCD device is reduced. The number and structure of the openings 324a (the shape of the sub-electrode regions and the sub-pixel regions) need to be appropriately determined in consideration of both the viewing angle required for using the LCD device and the luminance required.

In the LCD device of the third embodiment, the regularly arranged concave portions in each pixel region may be formed at least at one of the pixel electrode or the counter electrode, as in the LCD device of the second embodiment.

(example 4)

An LCD device 400 according to a fourth embodiment of the present invention is described below. Fig. 14A and 14B are schematic sectional views of the LCD device 400. Fig. 14A shows a state where no voltage is applied, and fig. 14B shows a state where a voltage is applied. Fig. 14A and 14B show a pixel electrode of the LCD device 400. The following description will be related to one pixel region unless otherwise noted. As shown in fig. 14A and 14B, the LCD device 400 includes an active matrix substrate 420, a counter substrate 30, and a liquid crystal layer 40 interposed therebetween.

In the LCD device 400, an opening 424a, which is circular in this example, is formed in the pixel electrode 24 (i.e., the lower right corner of the sub-electrode region 50a in fig. 15), and also along and overlapping the side edge of the pixel electrode 24 or at the corners thereof (i.e., the lower left corner, the upper left corner, and the upper right corner of the sub-electrode region 50 a). Except for this point, the LCD device 400 has substantially the same structure as the LCD device 100. The same elements as previously described with respect to fig. 1A, 1B, 2 and 3 have the same reference numerals, and a description thereof will be omitted.

When no voltage is applied to the liquid crystal layer 40 as shown in fig. 14A, the liquid crystal molecules 40a are aligned perpendicular to the

surfaces

26a and 36a of the vertical alignment layers 26 and 36 due to the alignment force. When a voltage is applied to the liquid crystal layer 40 as shown in fig. 14B, the liquid crystal molecules 40a having negative dielectric anisotropy are aligned such that their longitudinal axes are perpendicular with respect to the electric line of force E. In the vicinity of the opening 424a, the electric field lines E are inclined with respect to the

surfaces

21a and 31a of the substrates 21 and 31 (substantially parallel to the

surfaces

26a and 36a of the vertical alignment layers 26 and 36). Therefore, the liquid crystal molecules 40a near the opening 424a are arranged radially around each opening 24 a. The liquid crystal molecules 40a farther from the opening 424a are inclined at a larger angle with respect to a line perpendicular to the

surfaces

21a and 31a than the liquid crystal molecules 40a closer to the opening 424 a. Thus, the liquid crystal molecules 40a in the sub-pixel region 60 are arranged in an axisymmetric manner.

Fig. 15 is a top view of the active matrix substrate 420 of the pixel region of the LCD device 400 shown in fig. 14A and 14B. Fig. 14A and 14B show a cross section taken along the line X IV-X IV' of fig. 15.

As described above, the pixel electrode 24 has the plurality of openings 424 a. The opening 424a will now be described in detail with reference to fig. 15. As shown in fig. 15, an opening 424a is formed in the pixel electrode 24 (i.e., the lower left corner of the sub-electrode region 50a in fig. 15) and along and overlapping the edge of the pixel electrode 24 or at the corners thereof (i.e., the lower left corner, the upper left corner, and the upper right corner of the sub-electrode region 50 a). The opening 424a defines sub-electrode regions 50a to 50i (9 regions in this example). The sub-electrode regions 50a to 50i have openings 424a at their corners. The

sub electrode regions

50a, 50b, 50c, and 50d are square, have quadruple symmetry axes at their corners, and are identical to each other. The

sub-electrode regions

50e and 50f are rectangular in shape, and have a two-fold axis of symmetry at the center thereof. The sub electrode region 50e shares one side with each of the

sub electrode regions

50c, 50f, and 50 g. The sub electrode region 50f shares one side with each of the

sub electrode regions

50d, 50e, and 50 h.

In fig. 15, 4 edges of the pixel electrode 24 coincide with one side of each of the sub electrode regions 50a to 50 i. This arrangement substantially avoids disclination caused by the distance between the sides of the sub-electrode regions and the edges of the pixel electrode being near the edges of the pixel electrode. The reason is that the tilt direction of the liquid crystal molecules 40a changes continuously in the direction of arrow a (i.e., from the center to the edge of the pixel electrode 24) as shown in fig. 14B.

The JCD device 400 in the fourth embodiment can be fabricated in a manner similar to that in the first embodiment.

Fig. 16 shows a top view of a pixel area (indicated as 400a in fig. 16) of the LCD device 400 shown in fig. 15 viewed by polarized light microscopy in an orthogonal polarization state. The LCD device 400 in fig. 16 is applied with a voltage for gray scale display. The pixel region 400a includes sub-display regions 60a to 60i defined by the sub-electrode regions 50a to 50i in fig. 15, respectively. A part of the pixel area 400a (or a part corresponding to the black matrix) corresponding to the light blocking member such as the TFT70, the gate line 72, the source line 74 (fig. 15) is observed to be dark (hatched in fig. 16). The opening 424a is also observed to be dark. The storage capacitor common line 76 is made of a transparent material. The longer side of the pixel region pitch is about 300 μm in this example, the shorter side of the pixel region pitch is about 100 μm, and each opening 424a has a diameter of about 10 μm.

As is clear from fig. 16, the sub-pixel regions 60a to 60i are observed to have orthogonal extinction patterns, which indicates that the liquid crystal molecules are arranged in an axisymmetric manner. In the sub-pixel regions 60a to 60d defined by the square sub-electrode regions 50a to 50d (fig. 15), an extinction pattern having a quadruple symmetry axis is observed. In the sub-pixel regions 60e to 60f defined by the rectangular sub-electrode regions 50e to 50f (fig. 15), an extinction pattern having a two-fold symmetry axis is observed.

In such an LCD device 400, each of the plurality of pixel regions as a whole has a plurality of sub-regions in which the liquid crystal molecules 40a (fig. 14A and 14B) are arranged in an axisymmetric manner. Therefore, the present LCD device 400 has a high viewing angle characteristic. The response time is sufficiently short and no inseparable phenomenon of the image is revealed. The axisymmetric alignment is very stable and does not produce poor alignment in repeated operation tests.

The sub electrode regions 50a to 50i in the present embodiment are quadrangular. Each sub-electrode region need not be quadrilateral but may be a polygon with openings at its corners or along and overlapping its sides. The sub-electrode regions may be triangular, but are preferably polygonal with four or more corners in order to prevent the viewing angle characteristics from being dependent on the azimuth angle. A square shape is advantageous over a rectangle because it has a higher rotational symmetry than a rectangle and thus provides a more uniform viewing angle characteristic.

Fig. 17A, 17B and 17C show alternative arrangements of sub-electrode regions 50 of the pixel electrode 24 in the fourth embodiment. The sub electrode regions 50 in fig. 17A, 17B, and 17C are quadrangular. Fig. 18A, 18B and 18C show alternative arrangements of sub-electrode regions of the pixel electrode 24 in the fourth embodiment. The sub-electrode regions in fig. 18A, 18B, and 18C are polygonal shapes having five or more corners.

In fig. 18A, each hexagonal sub-electrode region 51 has an opening 424a at a corner thereof. In fig. 18B, each hexagonal region has openings 424a at corners and a center thereof so that liquid crystal molecules are arranged in an axisymmetric manner in the triangular sub-electrode regions 52. In fig. 18C, each octagonal sub-electrode region 53 has a rectangular opening 424a along its side. The openings 424a need not be circular or rectangular, but may be any shape. The sub-electrode regions (and also the sub-pixel regions) preferably all have a high rotational symmetry (i.e. are as close to circular as possible), and they are preferably equilateral polygons. It is preferable that the plurality of sub-electrode regions (and also the sub-pixel regions) be arranged to have rotational symmetry. It is then preferable to arrange them in a regular manner in the same equilateral polygon. In other cases, the effect of this example can be obtained in which at least one side of at least one sub-electrode region coincides with at least one edge of the pixel electrode 24.

In the LCD device 400 of the fourth embodiment, concave portions may be formed in at least one of the pixel electrode 24 or the counter electrode 34, which are regularly arranged in each pixel region, as in the LCD device 400 of the second embodiment.

The openings in the pixel electrodes in the LCD device in the third embodiment are all remote from the edges of the pixel electrodes. In the LCD device of the fourth embodiment, the side edges of the sub-electrode regions coincide with the edges of the pixel electrodes. The arrangement of the respective openings with respect to the edges of the pixel electrodes may be appropriately selected according to the use of the LCD device.

(example 5)

As described in detail below, the LCD device 500 according to the fifth embodiment of the present invention includes an alignment fixing layer in at least one of the first and second substrates in contact with the liquid crystal layer 40.

Fig. 19A and 19B are schematic sectional views of the LCD device 500. Fig. 19A shows a state when no voltage is applied, and fig. 19B shows a state when a voltage is applied. Fig. 19A and 19B show a pixel region of the LCD device 500. The following description will be given in consideration of one pixel region unless otherwise noted.

The LCD device 500 includes an active matrix substrate 520, a counter substrate (color filter substrate) 530, and a liquid crystal layer 40 interposed between the active matrix substrate 520 and the counter substrate 530. The active matrix substrate 520 includes a transparent substrate 21, an insulating layer 22, pixel electrodes 24, an alignment layer 26, and an alignment fixing layer 41 a. The insulating layer 22, the pixel electrode 24, the alignment layer 26, and the alignment fixing layer 41a are provided on the surface 21a of the substrate 21 in this order, the surface 21a facing the liquid crystal layer 40. The counter substrate 530 includes a transparent substrate 31, a color filter layer 32, a counter electrode 34, a collimating layer 36, and a collimation fixing layer 41 b. A color filter layer 32, a counter electrode 34, a collimating layer 36 and a collimation fixing layer 41b are provided on the surface 31a of the substrate 31 in this order, the surface 31a facing the liquid crystal layer 40. The LCD device 500 has substantially the same structure as the LCD device 100 except for the alignment-fixing layers 41a and 41 b. The same elements as previously discussed with respect to fig. 1A, 1B, 2 and 3 are given the same reference numerals and their description will be omitted.

The pixel electrode 24 has a plurality of openings 24a as shown in fig. 2. The plurality of openings 24a define a polygonal sub-electrode region 50 having openings 24a at the corners of the region or along and overlapping the sides thereof. The liquid crystal molecules 40a in the sub-pixel region 60 defined by the sub-electrode regions 50 are arranged in an axisymmetric manner due to the opening 24 a. The openings 24A may be arranged as shown in fig. 4A to 4C, 5A to 5C, 11, 12A to 12C, 13A to 13C, 15, 17A to 17C, and 18A to 18C.

When no voltage is applied to the liquid crystal layer 40 as shown in fig. 19A, the liquid crystal molecules 40a are aligned perpendicular to the

surfaces

26a and 36a of the vertical alignment layers 26 and 36 due to the aligning force of the alignment layers. When a voltage is applied to the liquid crystal layer 40 as shown in fig. 19B, the liquid crystal molecules 40a having negative dielectric anisotropy are aligned such that their longitudinal axes are perpendicular to the electric line of force E. In the vicinity of the opening 24a, the electric line of force E is inclined with respect to the

surfaces

21a and 31a of the substrates 21 and 31 (substantially parallel to the

surfaces

21a and 31a than the liquid crystal molecules 40a closer to the opening 24 a. Accordingly, the liquid crystal molecules 40a in the sub-pixel region 60 are arranged in an axisymmetric manner. The alignment fixing layers 41a and 41b uniformly and stably maintain the pre-tilt of the axisymmetric arrangement of the liquid crystal molecules in the sub-pixel region 60 caused when a voltage is applied to the LCD device 500. The alignment-fixing layers 41a and 41b also maintain the pretilt in the absence of an applied voltage. The alignment fixing layers 41a and 41b maintain the axisymmetric arrangement even after the power is turned off.

The LCD device 500 of the fifth embodiment can be manufactured as follows. The active matrix substrate 520 can be manufactured by a known method for manufacturing an active matrix substrate, except for forming the pixel electrode 24 by using a pattern caused by the opening 24a shown in fig. 2 to be formed. Thus, the active matrix substrate 520 can be manufactured without increasing the number of manufacturing steps. The counter substrate 30 may also be manufactured by known methods. The pixel electrode 24 and the counter electrode 34 are made of, for example, ITO (indium tin oxide) having a thickness of about 5 nm.

surfaces

26a and 36a of the vertical alignment layers 26 and 36. Such materials include, for example, octadecylethoxysilane and lecithin.

Then, plastic beads having a diameter of about 4.5 μm were distributed on the vertical alignment layer 26. On the vertical alignment layer 36, a seal portion is formed along the periphery of the display area by scanning printing, which is formed of an epoxy resin containing glass fibers. The laminate is bonded together by heating and allowed to cure. Then, a mixture of a liquid crystal material, a photocurable resin (0.3% by weight), and a photoinitiator (0.1% by weight) is injected into a gap between the active matrix substrate 520 and the counter substrate 530 using a vacuum injection method, thereby forming the liquid crystal layer 40. The liquid crystal material has a negative dielectric anisotropy (Δ ∈ -4.0, Δ n ═ 0.08). The photocurable resin may be represented by the following chemical formula. The photoinitiator may be, for example, Irgacure651 (manufactured by Ciba-Geigy Co., Ltd.).

When a voltage of, for example, 5v is applied between the pixel electrode 24 and the counter electrode 34, the liquid crystal molecules 40a which have been aligned perpendicular to the

surfaces

26a and 36a of the vertical alignment layers 26 and 36 are tilted towards a direction parallel to the

surfaces

26a and 36a (i.e. perpendicular to the electric field). Thus, the liquid crystal molecules 40a are arranged in an axisymmetric manner with respect to the central axis of each opening 24 a.

When the mixture is subjected to ultraviolet light (6 mw/cm) at room temperature (25 ℃ C.)²365nm) is irradiated to the liquid crystal layer 40 for about 10 minutes while applying a voltage of about 2.2v, which is about 0.3v higher than the threshold voltage, between the pixel electrode 24 and the counter electrode 34, the photocurable resin in the mixture is cured. Thus, the alignment fixing layers 41a and 41b are formed. Thereby completing the LCD device 500. The threshold voltage is a voltage at which light transmittance is 10% in a voltage-light transmittance curve of the LCD device.

The alignment fixture layers 41a and 41b define the pre-tilt and alignment directions of the axisymmetric alignment. The voltage applied during UV irradiation is preferably about 0.2v to about 0.5v, more preferably about 0.3v to about 0.4v, higher than the threshold voltage. When the voltage is too low with respect to the threshold voltage, the alignment force generated by the alignment fixing layers 41a and 41b is not sufficiently large. When the voltage is too high, the arrangement is extremely fixed, thereby causing a phenomenon that the image is not separated, or the like. By forming the alignment fixing layers 41a and 41b while applying an appropriate voltage, the axisymmetric alignment of the liquid crystal molecules 40a can be rapidly reproduced.

This structure eliminates the need to provide a protruding portion in the liquid crystal layer 40 in order to stabilize the liquid crystal molecules 40 a. Therefore, the number of manufacturing steps or manufacturing cost is not increased, or the numerical aperture is not reduced.

In such an LCD device 500, each of the plurality of pixel regions as a whole has a plurality of sub-regions in which the liquid crystal molecules 40a are arranged in an axisymmetric manner. Therefore, the present LCD device 100 has a high viewing angle characteristic. The response time is sufficiently short and no inseparable phenomenon of the image appears. The axisymmetric alignment is very stable and no poor alignment occurs in the repeated operation test. In this embodiment, the alignment fixing layers 41a and 41b are provided on the active matrix substrate 520 and the counter substrate 530. The alignment fixture layer may be provided in either of the two substrates.

(example 6)

In the first to fifth embodiments, the intervals for controlling the thickness of the liquid crystal layer 40 are formed by plastic beads, which are distributed on the active matrix substrate. Fig. 20A shows the arrangement of liquid crystal molecules in the pixel region 100c when the opening 24a is away from the edge of the pixel electrode. Fig. 20B shows the arrangement of liquid crystal molecules in the pixel region 400c when the opening 424a is along and overlaps the edge of the pixel electrode. When the plastic beads 92 are present in the pixel region 100c or 400c, the axisymmetric arrangement of the liquid crystal molecules in at least one sub-pixel region (60A to 60c in fig. 20A, 60A to 60i in fig. 20B) may be undesirably disturbed. In order to avoid the disturbance in the alignment due to the plastic beads 92, the LCD device according to the sixth embodiment of the present invention includes a columnar protrusion formed of a polymer provided at a position in the pixel region, wherein the columnar protrusion does not affect the display.

Fig. 21A to 21D show, by way of example, an active matrix substrate of an LCD device in a sixth embodiment. The opening 24a in fig. 21A and 21B is away from the edge of the pixel electrode 24. The opening 424a in fig. 21C and 21D follows and overlaps the edge of the pixel electrode 24. As shown in fig. 21A to 21D, columnar projections 94 are provided.

The columnar projections 94 shown in fig. 21A and 21C are formed in the following manner, for example.

An active matrix substrate is formed in the same manner as the first embodiment. On the active matrix substrate, a photocurable resin (e.g., OMR83 from Ohka Kogyo Co., Ltd. of Tokyo) was applied to a thickness of about 4 μm. The photo-curable resin is disposed by exposure and development to partially form the shape of the columnar projections 94 on the straight lines provided in the peripheral regions of the pixel regions.

In the case where the storage capacitor common line 76 is formed of a light-shielding material such as a metal material, the columnar projection 94 may be provided above the storage capacitor common line 76 as shown in fig. 21B and 21D.

Fig. 22A is a top view of the pixel region 100d of the LCD device including an active matrix substrate shown in fig. 21A or 21B, in which the opening 24a is away from the edge of the pixel electrode. Fig. 22B is a top view of the pixel region 400D of the LCD device including an active matrix substrate shown in fig. 21C or 21D, in which the opening 424a is along and overlaps the edge of the pixel electrode. The patterns shown in fig. 22A and 22B are obtained by a polarization microscope with a gray scale display voltage applied to the LCD device.

As shown in fig. 22A and 22B, the liquid crystal molecules in the vicinity of the

openings

24a and 424a are arranged radially around each

opening

24a or 424 a. The liquid crystal molecules farther from the

opening

24a or 424a are inclined at a larger angle with respect to a line perpendicular to the surface of the vertical alignment layer than the liquid crystal molecules closer to the

opening

24a or 424 a. Accordingly, the liquid crystal molecules in each of the plurality of sub-pixel regions in the pixel region 100d or 400d are arranged in an axisymmetric manner.

Therefore, the LCD device of the sixth embodiment has a high viewing angle characteristic. The response time is sufficiently short and no inseparable phenomenon of the image appears. Interference in the axisymmetric arrangement of liquid crystal molecules caused in the case where the pixel region includes plastic beads does not appear. The uniformity of the thickness of the liquid crystal layer is improved, thereby improving the display quality.

(example 7)

In the first to sixth embodiments, the liquid crystal layer 40 is formed of a nematic liquid crystal material having negative dielectric anisotropy. In a seventh embodiment of the invention, a chiral dopant (e.g., S811, manufactured by Merck & co., inc.) is added to the liquid crystal material such that the chiral pitch in the liquid crystal layer 40 is about 18 μm. In other words, the chiral dopant is added so that the liquid crystal molecules have a twist angle of about 90 °, that is, a helical pitch of about 4 times the cell thickness, for the following reason. In the case where the twist angle of the liquid crystal molecules is about 90 °, the utilization rate of light for white display and the color balance are optimal when an electric field is applied, as in the conventional twisted nematic LCD device. When the amount of the chiral dopant is too small, the twisted alignment of the liquid crystal molecules may be undesirably unstable when an electric field is applied. In the case where the amount of chiral dopant is too large, the vertical alignment of the liquid crystal molecules may be undesirably unstable when no voltage is applied.

The LCD device of the seventh embodiment has substantially the same structure as the LCD device 100 of the first embodiment except for the addition of the chiral dopant, and can be fabricated in a similar manner.

Fig. 23A is a top view of a pixel region 100e of an LCD device of the seventh embodiment, in which an opening 24a is distant from an edge of a pixel electrode. Fig. 23B is a top view of a pixel region 400e of another LCD device according to the seventh embodiment, in which an opening 424a is along and overlaps the edge of a pixel electrode. The patterns of fig. 23A and 23B are obtained by a polarization microscope when the LCD device is applied with a voltage for gray scale display.

As shown in fig. 23A and 23B, the liquid crystal molecules in the vicinity of the

openings

24a and 424a are arranged radially around each

opening

24a or 424 a. The liquid crystal molecules farther from the

opening

24a or 424 a. Thus, the liquid crystal molecules in each of the plurality of sub-pixel regions in the pixel region 100e or 400e are arranged in an axisymmetric manner.

Therefore, the LCD device of the seventh embodiment has a high viewing angle characteristic. The response time is sufficiently short and no inseparable phenomenon of the image appears. Compared with the LCD device 100, where the liquid crystal layer 40 does not contain chiral dopants, the seventh embodiment gives a brighter image with a smaller dark field. Even if the pixel electrode 24 has a large number of openings or has a large-sized opening, the transmittance of light is not lowered.

(example 8)

In the eighth embodiment of the present invention, an LCD device further including a suitable phase plate for further widening the viewing angle range will be described.

As shown in fig. 24A, the LCD device 600 includes a pair of polarizers 602a and 602b, a first substrate 620, a second substrate 630, and a liquid crystal layer 640 interposed between the

substrates

620 and 630. The first substrate 620, the second substrate 630, and the liquid crystal layer 640 may have any of the structures described in the first to seventh embodiments. Polarizer 602a is closer to the display plane and polarizer 602b is closer to the backlight. The direction in which the polarizer 602b absorbs light is the x direction. The direction perpendicular to the x direction in the display plane is the y direction. The direction perpendicular to the display plane is the z-direction.

In the LCD device 600 shown in fig. 24A, a phase plate 604A is provided between the second substrate 630 and the polarizer 602 a. In which the refractive index of the phase plate 604a is (nx, ny, nz), the phase plate 604a has a relationship of nx ═ ny > nz.

By setting the retardation of the phase plate 604a to about 1/2 to 3/2 which is the retardation of the liquid crystal layer 640, the viewing angle characteristics of the LCD device 600 are improved. The retardation of the phase plate 604a is equal to the film thickness (dp) of the phase plate 604a, x { (nx + ny))/2-nz }. The retardation of the liquid crystal layer 640 is equal to the thickness x (ne-no) of the liquid crystal layer 640. A similar effect can be obtained by disposing the phase plate 604b between the first substrate 620 and the polarizer 602 b. "ne" represents the refractive index of extraordinary rays, and "no" represents the refractive index of ordinary rays.

In the LCD device 650 shown in fig. 24B, the phase plate 604a is disposed between the second substrate 630 and the polarizer 602a, and the phase plate 604B is disposed between the first substrate 620 and the polarizer 602B. Here, the refractive index of each of the

phase plates

604a and 604b is (nx, ny, nz), and each of the

phase plates

604a and 604b has a relationship of nx ═ ny > nz.

By setting the total retardation of the

phase plates

604a and 604b to about 1/2 to 3/2 which is the retardation of the liquid crystal layer 640, the viewing angle characteristics of the LCD device 650 are improved.

Fig. 25A is a graph showing the dependence of light transmittance on viewing angle in the dark display state of the LCD device 650 (fig. 24B) including the phase plates 604a and 604B. The retardation of the liquid crystal layer was 360nm (liquid crystal layer thickness: 4.5nm, ne ═ 1.55, and no ═ 1.47). The total hysteresis of the

phase plates

604a and 604b is varied. The horizontal axis (viewing angle θ) of fig. 25A represents a viewing angle in a direction at an angle of 45 ° with respect to the polarization axis, i.e., with respect to the direction perpendicular to the display plane. The vertical axis (transmittance) in fig. 25A represents a normalized value with the light transmittance of air being 1. Fig. 25B shows transmittance values plotted with respect to hysteresis. The transmittance values were obtained at a viewing angle of 60 °.

As is clear from FIG. 25A, when no phase plate is provided (retardation: 0nm), the light transmittance increases (i.e., light leakage) with an increase in the viewing angle θ in a direction away from the polarization axis by 45 °. Thus, a satisfactory dark display state is not obtained. When the phase plate 604a (and/or 604B) is set and the retardation { dp x (nx + ny)/2-nz } thereof is set at an appropriate value, the light transmittance decreases as shown in fig. 25B. Particularly, in the case where θ is 60 °, when the total retardation of the

phase plates

604a and 604b is about 180nm (1/2 for retardation of the liquid crystal layer) to about 540nm (3/2 for retardation of the liquid crystal layer), the increase in light transmittance is reduced to half or less of the increase in light transmittance obtained when the phase plates are not provided.

As described above, when the phase plate is not provided, the dark display state with no voltage applied is satisfactory when viewed in the direction perpendicular to the display plane as described above. However, along a direction inclined with respect to the vertical direction, a phase difference generated by the liquid crystal layer causes light leakage, and thus causes deterioration of dark display. The phase plate or plates shown in fig. 24A and 24B compensate for this phase difference, and thus, will be able to give a satisfactory dark display state over a wide viewing angle range. In other words, a high contrast image can be obtained over a wide range of viewing angles.

Fig. 26A shows an LCD device 700 including a phase plate 606A disposed between a second substrate 630 and a polarizer 602 a. Fig. 26B shows an LCD device 750 including a phase plate 606a provided between the second substrate 630 and the polarizer 602a, and a phase plate 606B provided between the first substrate 620 and the polarizer 602B. Each of the phase plates 606a and 606b has a relationship of nx > ny ═ nz. By setting the total retardation of the phase plates 606a and 606b to about 1/10 to 7/10 of the retardation of the liquid crystal layer 640, the viewing angle characteristics of the LCD device 750 are improved. The hysteresis of each phase plate 606a and 606b is dp × { nx- (ny + nz)/2 }. The provision of the or each phase plate improves the dark display state when viewed in the azimuthal direction, which is 45 ° away from the optical absorption axis of the polarisers 602a and 602 b.

Fig. 27A is a graph showing the dependence of light transmittance on viewing angle in the dark display state of the LCD device 750 (fig. 26B) including the phase plates 606a and 606B. The retardation of the liquid crystal layer was 360nm (liquid crystal layer thickness: 4.5nm, ne ═ 1.55, and no ═ 1.47). The total lag of the phase plates 606a and 606b is varied. The hysteresis along the nz-axis direction, { dp × (nx + ny)/2-nz } of the phase plates 606a and 606b is fixed at 250 nm. The horizontal axis (viewing angle θ) of fig. 27A represents a viewing angle in a direction at an angle of 45 ° with respect to the polarization axis, i.e., with respect to the direction perpendicular to the display plane. The vertical axis (transmittance) in fig. 25A represents a normalized value with the light transmittance of air being 1. Fig. 27B shows transmittance values plotted with respect to hysteresis. The transmittance values were obtained at a viewing angle of 60 °.

As is clear from fig. 27A, when no phase plate is provided (retardation: 0nm), the light transmittance increases (i.e., light leakage) with an increase in the viewing angle θ in a direction deviating from the polarization axis by 45 °. Thus, a satisfactory dark display state is not obtained. When the phase plate 606a (and/or 606B) is set and the retardation dp × { nx- (ny + nz)/2} thereof is set at an appropriate value, as shown in fig. 27B, the light transmittance decreases. The transmittance is below 0.03, particularly when the total retardation of the phase plates 606a and 606b is about 36nm (1/10 for liquid crystal layer retardation) to about 252nm (7/10 for liquid crystal layer retardation). Therefore, when θ is 60 °, the increase in light transmittance is smaller than that obtained when the phase plate is not provided.

Two kinds of phase plates, i.e., 604A and 604B in fig. 24A and 24B and 606A and 606B in fig. 26A and 26B, may be combined as shown in fig. 28A. The two phase plates may be combined in any other combination. Similar viewing angle characteristics are obtained by providing the biaxial phase plate 610a (fig. 28B) or the biaxial phase plates 610a and 610B (fig. 28C). The biaxial phase plates 610a and 610b provide refractive index anisotropy substantially equal to that obtained by the two uniaxial phase plates. Replacing two uniaxial phase plates with one biaxial phase plate reduces the number of manufacturing steps.

In the first to eighth embodiments, the vertical alignment type liquid crystal layer is employed. The present invention is not limited to this structure. When a liquid crystal layer of a horizontal alignment type (e.g., twisted nematic or super twisted nematic) is used, a similar effect can be obtained.

In the first to eighth embodiments, the LCD device of the transmissive active matrix substrate is described. The present invention is not limited to this type of LCD device, but is widely used for reflective LCD devices and simple matrix LCD devices.

As described above, the present invention provides an LCD device having a high viewing angle characteristic and preventing an image non-separation phenomenon. The liquid crystal molecules are uniformly and stably arranged in an axisymmetric manner in a plurality of sub-pixel regions included in each pixel region. This arrangement of the liquid crystal molecules gives a viewing angle range that improves display quality, and responds at high speed. The LCD device of the present invention can be manufactured without any additional steps to the conventional manufacturing method, and thus, the manufacturing cost is not increased.

According to the present invention, it is possible to prevent the arrangement of the liquid crystal molecules from becoming unstable due to the lateral electric field generated by the scanning lines and the signal lines (bus lines) provided to connect the active devices.

According to the present invention, disclination generated near the edge of the pixel electrode can be eliminated.

According to the present invention, the arrangement of the liquid crystal molecules is stable, which gives a bright display.

The LCD device of the present invention can be used in monitors such as computers, word processors, car navigation systems, and television receivers.

Various other modifications will be apparent to and can be readily made by those skilled in the art without departing from the scope and spirit of the invention. It is therefore intended that the scope of the claims appended hereto be limited not by the language in which this specification is expressed, but rather that the claims be construed broadly.

Claims

1. A liquid crystal display device, comprising:

a first substrate;

a second substrate; and

a liquid crystal layer interposed between the first substrate and the second substrate,

wherein,

the first substrate has a plurality of scanning lines, a plurality of signal lines intersecting the plurality of scanning lines, and a plurality of pixel electrodes connected to each of the plurality of scanning lines and the plurality of signal lines through respective switching devices,

the second substrate includes a counter electrode facing the plurality of pixel electrodes,

a region of each of the plurality of pixel electrodes, the counter electrode and the liquid crystal layer to which a voltage is applied by the pixel electrode and the counter electrode defines a pixel region as a display unit,

the pixel region includes a plurality of sub-pixel regions in which liquid crystal molecules of the liquid crystal layer are oriented in an axisymmetric manner,

the plurality of pixel electrodes have a plurality of openings defined in each pixel region, the plurality of openings including a cross-section that has been cut from the outer shape of the pixel electrode, and

the sub-pixel regions are defined by sub-electrode regions, at least in part of which the openings defined in the pixel electrodes have their respective centres located at the corners and/or edges of the polygon, and at least part of which have their respective centres located along and overlapping the edges of the pixel electrodes or at the corners of the pixel electrodes.

2. The liquid crystal display device of claim 1, wherein the polygons defining the plurality of sub-pixel regions are identical to each other.

3. The liquid crystal display device according to claim 2, wherein the polygons are rotationally symmetric with each other, and liquid crystal molecules of the liquid crystal layer are oriented in an axisymmetric manner with respect to a rotational symmetry axis of the polygons.

4. The liquid crystal display device according to claim 1, wherein the liquid crystal layer is formed of a liquid crystal material having negative dielectric anisotropy, and liquid crystal molecules of the liquid crystal material are vertically aligned with respect to the first substrate and the second substrate in a state where no voltage is applied.

5. The liquid crystal display device of claim 1, wherein at least one of the first substrate and the second substrate includes columnar projections for controlling a thickness of the liquid crystal layer outside the pixel region.

6. The liquid crystal display device of claim 1, wherein the liquid crystal layer includes a chiral dopant and liquid crystal molecules of the liquid crystal layer have a helical pitch of about 4 times the thickness of the liquid crystal layer.

7. The liquid crystal display device according to claim 1, further comprising a pair of polarizers, and further comprising at least one uniaxial phase plate having negative refractive index anisotropy disposed between the polarizer and one of the substrates adjacent to the polarizer or between the other polarizer and the other substrate adjacent to the other polarizer,

wherein

The first substrate and the second substrate are interposed between the pair of polarizers.

8. The liquid crystal display device according to claim 1, further comprising a pair of polarizers, and further comprising at least one uniaxial phase plate having positive refractive index anisotropy disposed between the polarizer and one of the substrates adjacent to the polarizer or between the other polarizer and the other substrate adjacent to the other polarizer,

wherein

9. The liquid crystal display device according to claim 1, further comprising: a pair of polarizers, and further comprising at least one biaxial phase plate disposed between the polarizer and one substrate adjacent to the polarizer or between the other polarizer and the other substrate adjacent to the other polarizer,

wherein

10. A liquid crystal display device, comprising:

a first substrate;

a second substrate; and

wherein,

the first substrate and the second substrate respectively include a first electrode and a second electrode on one side of the liquid crystal layer,

a region of the liquid crystal layer to which a voltage is applied by the first electrode and the second electrode defines a plurality of pixel regions, each of the plurality of pixel regions being a display cell,

each of the plurality of pixel regions includes a plurality of sub-pixel regions in which liquid crystal molecules of the liquid crystal layer are oriented in an axisymmetric manner,

at least one of the first electrode and the second electrode has a plurality of openings regularly arranged in the pixel region, and

the sub-pixel regions are defined by sub-electrode regions, wherein a plurality of the openings have their respective centers located at corners and/or edges of the polygon, and at least some of the openings of the plurality of openings have their respective centers located along and overlapping edges of at least one of the first and second electrodes or at corners of at least one of the first and second electrodes.

11. The liquid crystal display device according to claim 10, wherein:

the first electrode includes a plurality of pixel electrodes arranged in a matrix form, and each of the plurality of pixel electrodes is connected to the scan line and the signal line through a switching device;

the second electrode is a counter electrode facing the plurality of pixel electrodes; and is

Each of the plurality of pixel electrodes has at least one sub-electrode region.

12. The liquid crystal display device according to claim 11, wherein: the sub electrode regions defining the plurality of sub pixel regions include a plurality of sub electrode regions, wherein the polygons are identical to each other, and each polygon shares one edge with other polygons.

13. The liquid crystal display device according to claim 12, wherein the polygons are rotationally symmetric with each other, and liquid crystal molecules of the liquid crystal layer are oriented in an axisymmetric manner with respect to a rotational symmetry axis of the polygons.

14. The liquid crystal display device of claim 10, wherein at least one of the first electrode and the second electrode includes concave portions, and the concave portions are regularly arranged in the pixel region.

15. The liquid crystal display device of claim 10, wherein at least one of the first substrate and the second substrate includes a columnar protrusion for controlling a thickness of the liquid crystal layer.

16. The liquid crystal display device according to claim 10, wherein the liquid crystal layer is formed of a liquid crystal material having negative dielectric anisotropy, and liquid crystal molecules of the liquid crystal material are aligned approximately perpendicularly with respect to the first substrate and the second substrate in a state where no voltage is applied.

17. The liquid crystal display device according to claim 10, further comprising a pair of polarizers, and further comprising at least one uniaxial phase plate having negative refractive index anisotropy disposed between the polarizer and one of the substrates adjacent to the polarizer or between the other polarizer and the other substrate adjacent to the other polarizer,

wherein

18. The liquid crystal display device according to claim 10, further comprising a pair of polarizers, and further comprising at least one uniaxial phase plate having positive refractive index anisotropy disposed between the polarizer and one of the substrates adjacent to the polarizer or between the other polarizer and the other substrate adjacent to the other polarizer,

wherein

19. The liquid crystal display device according to claim 10, further comprising: a pair of polarizers, and further comprising at least one biaxial phase plate disposed between the polarizer and one substrate adjacent to the polarizer or between the other polarizer and the other substrate adjacent to the other polarizer,

wherein

20. The liquid crystal display device of claim 10, wherein the liquid crystal layer includes a chiral dopant and liquid crystal molecules of the liquid crystal layer have a helical pitch of about 4 times the thickness of the liquid crystal layer.