JP3081468B2 - Liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device having a wide viewing angle and high display quality by controlling the orientation of a liquid crystal director.

[0002]

2. Description of the Related Art Liquid crystal display devices have advantages such as thinness, light weight, and low power consumption, and are being put to practical use as display devices in the fields of OA equipment, AV equipment, and the like. In a liquid crystal display device, two substrates provided with transparent electrodes of a predetermined pattern are bonded together with a liquid crystal layer having a thickness of several μm therebetween, and further sandwiched between two polarizing plates whose polarization axes are orthogonal to each other. It is constituted by. In particular, the matrix type in which the liquid crystal is driven by arbitrarily selecting an intersection where the scanning electrode group and the data electrode group are arranged and applying a voltage to the display pixel capacitor can drive tens of thousands to hundreds of thousands of pixels. Is possible,
Suitable for large screen, high definition display devices.

In particular, an active matrix type in which a TFT (Thin Film Transistor) is arranged for each display pixel as a switching element for selection and enables line-sequential driving is used for a display such as a TV. The active matrix type is a configuration for realizing the equivalent circuit diagram shown in FIG. 17, in which a scanning signal gate line (G) and a data signal drain line (D) are formed on the same transparent substrate, and both lines (G , D), a TFT (T) using a non-single-crystal semiconductor layer such as a-Si or p-Si as an active layer is formed. On the same substrate, display electrodes serving as one electrode of a display pixel capacitor (LC) are arranged in a matrix and connected to a TFT (T). A common electrode is entirely formed on the other transparent substrate opposed to the liquid crystal layer, and a portion facing each display electrode serves as a display pixel capacitance (LC). The display electrode and the common electrode are made of a transparent conductive film such as ITO so that a change in the optical state of the liquid crystal in the gap can be viewed directly. The gate line (G) is line-sequentially selected for scanning, all the TFTs (T) on the same scanning line are turned on, and a data signal synchronized with this is supplied to the drain line (D).
Is supplied to each display electrode via the. The common electrode also has a voltage set in synchronization with the scanning of the gate line (G), an electric field is formed in the liquid crystal layer in the gap due to a voltage difference between the display electrodes facing each other, and the orientation of the liquid crystal changes to change light. The transmittance is controlled. During non-selection, the voltage applied to the display pixel capacitance (LC) is held by the OFF resistance of the TFT (T), and the driving state of the liquid crystal is continued. The TFT (T) is connected to an auxiliary capacitance (SC) formed by superposing an auxiliary capacitance electrode (SE) on the display electrode. The auxiliary capacitance (SC) is arranged in parallel with the display pixel capacitance (LC) to improve the voltage holding ratio.

Further, a polymer film of polyimide or the like is formed on the surface of both substrates in contact with the liquid crystal layer, and a process of rubbing the surface with a cotton cloth or the like to uniformly align molecular chains in the same direction (rubbing process) is performed. This controls the initial alignment of the liquid crystal. That is, when the orientation of the liquid crystal director is specified by the interaction at the contact surface with the orientation film, the liquid crystal layer is controlled so as to conform to the entire liquid crystal layer due to its continuity.

In particular, when the rubbing directions of the two substrates are set to be orthogonal to each other, the liquid crystal director is controlled to be in a state of being successively twisted by 90 ° between the two substrates. Such a type is called a TN (Twisted Nematic) method. In the TN mode, the liquid crystal layer is a nematic phase having positive dielectric anisotropy, and has a parallel alignment structure in which the liquid crystal director has a slight tilt angle (pretilt angle) along the rubbing direction. Thereby, the liquid crystal director changes in the direction of increasing the pretilt angle toward the direction of the generated electric field. That is, by applying a desired voltage to each display pixel capacitor and forming an electric field in the liquid crystal layer in the gap, the liquid crystal director increases the dielectric constant of the liquid crystal layer from the initial alignment state due to the anisotropy of the dielectric constant. And the torsion state is eliminated. In addition, liquid crystal has anisotropy in the refractive index, and the light transmission state changes with the change in the alignment. Therefore, by controlling the electric field strength by adjusting the voltage applied to the display pixel capacitance. , A desired transmittance is obtained. In particular, in the NW (Normally White) mode, two polarizing plates are installed so that the polarization axis is the same as the rubbing direction of each substrate. When no voltage is applied, the linearly polarized light transmitted through one polarizing plate is applied. Is rotated along the twist of the liquid crystal director and passes through the other polarizer, displaying white.When voltage is applied, the linearly polarized light does not rotate in the liquid crystal layer and the transmitted light is narrowed down by the other polarizer to black. Will be displayed. On the other hand, in the NB (Normally Black) mode, by installing two polarizing plates so that the polarization axes are aligned, when no voltage is applied, the linearly polarized light that has passed through one of the polarizing plates turns in the liquid crystal layer and turns into the other. When a voltage is applied, the linearly polarized light does not rotate in the liquid crystal layer but passes through the other polarizing plate to increase the transmittance and display white.

In general, when the orientation of the liquid crystal is controlled by applying a voltage and the transmitted light is modulated by a change in birefringence,
It is called CB (Electrically Controlled Birefringence) system. In particular, the vertical alignment ECB method performs vertical alignment processing on both substrate surfaces, and a cell having a vertical alignment structure using a nematic phase having negative dielectric anisotropy as a liquid crystal layer,
This is a configuration arranged between orthogonal polarizers. When no voltage is applied, the linearly polarized light transmitted through one polarizing plate is not subjected to birefringence in the liquid crystal layer and is blocked by the other polarizing plate to display black. The polarized light undergoes birefringence, changes to elliptically polarized light, and passes through the other polarizing plate.

[0007]

On the above-mentioned principle, in the conventional liquid crystal display device, the orientation of the liquid crystal with respect to the optical path changes relatively with the change of the viewing angle, so that the display characteristics greatly depend on the viewing angle. Changed, and the viewing angle dependence was high.
In particular, in the TN method, since the initial orientation is previously aligned in the same direction by rubbing, even during driving,
In all regions of the display pixel, the display is aligned with the same orientation vector, and the average orientation vector of the entire display pixel changes with a change in the viewing angle. Conventionally, viewing angle dependency is particularly high in the vertical direction, and the viewing angle is narrow.

In the vertical alignment ECB method, when a voltage is applied, the tilt direction of the liquid crystal director varies due to a lateral electric field in the cell or irregularities on the substrate surface. For this reason, the viewing angle dependency has been increased, and the transmittance has changed in a band shape along the boundary between the regions having different inclination directions, which adversely affects the display. Such a band-shaped region having an abnormal transmittance is called disclination, and if disclination occurs frequently, the screen may be rough or the screen may be dark.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has first and second substrates disposed opposite to each other with a liquid crystal layer interposed therebetween. A plurality of display electrodes, a thin film transistor for supplying a signal voltage to the display electrodes, a common electrode formed entirely on the opposite surface side of the second substrate, and an alignment disposed around the display electrodes A control electrode; and an alignment control window that is an electrode-absent portion in the common electrode. A desired voltage is applied to a capacitor which is formed at a portion where the display electrode and the common electrode face each other with the liquid crystal layer interposed therebetween and becomes a display pixel. And a liquid crystal display device in which the orientation of the liquid crystal is controlled by an electric field tilted obliquely by the orientation control electrode and a weak electric field that is not driven by the liquid crystal formed by the orientation control window. Windows End is formed in a strip located at the corners opposite to each other of the display electrodes, the width is expanded in the end portions, a configuration in which covering comprises a corner portion of the display electrode.

Second, the alignment control window is formed in a band shape having both ends located at corners of the display electrode facing each other, and the corners of the display electrode are left obliquely cut away. The angle of the bend corner of the edge line of the electrode is set to be obtuse, and the alignment control window passes through the display electrode including the center part of a line cut out at the corner part of the display electrode and protrudes from the display electrode. Configuration.

Third, in the first or second configuration,
The alignment control electrode is formed so as to partially protrude while partially overlapping and surrounding the periphery of the display electrode, and to be absent at a connection portion with the thin film transistor. Fourth, in the first or second configuration, the alignment control window is bent at one or more positions at an obtuse angle, and the areas of the display pixel regions divided by the alignment control window are equal to each other. Configuration.

Fifth, in the first, second or fourth configuration, the alignment control window is formed in a single band shape, and both ends are formed so as to be located at the same corner for all display pixels. In addition, all the areas divided by the orientation control window have the same area. Sixth, in the first, second, or fourth configuration, the alignment control window is formed in two intersecting bands in a display pixel, and four ends of the alignment control window are connected to the four pixels of the display pixel, respectively. Each of the regions is located at one corner and divided by the orientation control window, and the area of each region is equalized.

Seventh, in the sixth configuration, at the intersection of the two strip-shaped orientation control windows, a corner of the electrode existing portion of the common electrode is cut out, and the edge of the orientation control window is cut off. The bending angle of the line is an obtuse angle.

[0014]

In the first structure, the electric field in the cell is adjusted by arranging at predetermined positions an orientation control electrode for generating an oblique electric field in the cell and an orientation control window for generating an electric field absence region in the cell. In addition, in a liquid crystal display device in which the viewing angle is widened by controlling the alignment using the elasticity based on the continuity of the liquid crystal together with the electric field effect, an alignment control window is opened in the common electrode at the portion corresponding to the corner of the display electrode. As a result, an electric field is not formed in this portion even when a voltage is applied, or the electric field is weakly lower than the driving threshold value of the liquid crystal, and the liquid crystal director is fixed in the initial state. For this reason, it is possible to prevent a region having an abnormal transmittance from being generated in the display pixel due to the disorder of the alignment. That is, since the liquid crystal director is controlled by an oblique electric field inclined in a direction perpendicular to the edge line of the display electrode and the alignment control electrode formed along the edge line, both sides of the corner near the corner of the display electrode And the alignment is unstable. If the alignment abnormality occurs in this portion, the abnormal region expands due to the continuity of the liquid crystal, which adversely affects the display. For this reason, by fixing the orientation by covering the corners of the display electrode with the orientation control window,
It is possible to eliminate the disorder of the orientation and minimize the loss of the effective display area.

In the second configuration, the edge of the display electrode and the edge of the orientation control window intersect at a right angle or an angle close to a right angle by obliquely notching the corner of the display electrode. Alignment disorder is prevented. That is, since an oblique electric field is generated also at the edge line of the alignment control window, if the angle formed outside the alignment control window and inside the display electrode becomes larger than a right angle at the intersection with the edge line of the display electrode, The inclination direction of the electric field at the edge line of the control window is different from the inclination direction of the electric field at the edge line of the display electrode, and a difference in orientation occurs on the boundary of the region where the orientation is controlled. Therefore, by cutting the corner of the display electrode at the intersection with the orientation control window and intersecting the edge line of the orientation control window and the edge line of the display electrode at a right angle or an angle having the same effect as the right angle, the display electrode The orientation control action along the edge line is invalidated, and the orientation can be stabilized only by the action of the orientation control window.

In the third configuration, the orientation control electrode is partially overlapped with the display electrode and partially arranged so as to protrude, so that the storage capacitor is formed in the overlap portion and the alignment control electrode is located outside the edge line of the display electrode. The alignment control electrodes in the region are arranged in planar contact with the display electrodes, and the alignment control effect is enhanced. Further, by eliminating the alignment control electrode at the connection portion with the thin film transistor, disconnection of the display electrode due to a step of the alignment control electrode is prevented, and poor connection or disconnection between the thin film transistor and the display electrode is prevented.

In the fourth configuration, an alignment control window which is a boundary between regions in which the directions of the liquid crystal directors are different from each other is formed in a partially bent shape, and each of the display pixels divided by the alignment control window is formed. By making the areas of the areas equal, the brightness becomes equal in a plurality of preferential viewing angle directions corresponding to each area. That is, in the region of the alignment control window, the liquid crystal director does not change and is maintained in the initial alignment state due to the absence of an electric field or an electric field equal to or less than the threshold value. The boundaries of the regions whose orientations are controlled in different directions are fixed, and the orientation is stable as a whole due to the continuity of the liquid crystal. For this reason, by equalizing the area of each area divided by the orientation control window, the brightness becomes equal in the preferential viewing angle direction unique to each area, these are combined in the entire display pixel, and the viewing angle dependency is reduced. The viewing angle widens.

In the fifth configuration, the positions of both ends of the alignment control window are made equal for all the display pixels of the TN type liquid crystal display device, and the directions of the liquid crystal directors at the time of driving differ from the initial twisted state. , The display pixels are divided in the same manner, the viewing angle characteristics become equal, and a uniform display screen is obtained. Further, by making the area of each region of the display pixel divided by the alignment control window the same, the brightness of each display pixel becomes equal, and thus the display quality is improved.

In the sixth configuration, in the vertical alignment ECB type liquid crystal display device, the display pixel is divided into four equal parts by the alignment control window, whereby the preferential viewing angle direction peculiar to each region is synthesized, and the field of view is widened. In the seventh configuration, the bend of the edge line of the alignment control window is moderated, whereby the overlap of the oblique electric field along the edge line is reduced, and the generation of the abnormal alignment region is prevented.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments. FIG. 1 is a plan view of a display pixel portion of a TN cell according to a first embodiment of the present invention. A gate line (11) and a drain line (15) intersect on a substrate, and a display electrode (14) is arranged in a region surrounded by both lines (11, 15). In addition, both lines (11,
At the intersection of 15), a gate electrode (11G), a gate insulating film, a non-single-crystal semiconductor layer (13), and source / drain electrodes (15S, 15D) are sequentially laminated to form a TFT, and a source electrode is formed. (15S) is connected to the display electrode (14). The alignment control electrode (16) disposed so as to surround the periphery of the display electrode (14) partially overlaps the display electrode (14) with the gate insulating film interposed therebetween, and partially overlaps the display electrode (14). 14) It protrudes from.

On the other hand, a common electrode is entirely formed on the side of the opposing substrate which is disposed so as to oppose the liquid crystal, and an alignment control window (22) which is a strip-shaped electrode-free portion is opened.
The alignment control window (22) is formed along the diagonal line of the display electrode (14), has a wide width at both ends, and widely covers the corner portion of the display electrode (14). FIG. 2 shows a cross-sectional view along the line AA in FIG. The gate line (11), the gate electrode (11G), and the orientation control electrode (16) are formed by depositing and etching Cr on a substrate (10) such as glass. A gate insulating film (12) such as SiNX is formed on these,
The display electrode (14) is formed by patterning ITO. In a portion corresponding to the gate electrode (11G), which is not shown, on the gate insulating film (12),
The non-single-crystal semiconductor layer (13) and the source / drain electrodes (15S, 15D) are sequentially laminated to form a TFT. Further, an alignment film (17) of polyimide or the like is formed on the entire surface, and rubbing is performed in a direction indicated by an arrow (18) in FIG. Polyimide having a small pretilt angle (1 ° or less) is used.

On the other hand, a liquid crystal layer (30) having a positive dielectric anisotropy
(20) Substrates made of glass or the like placed opposite to each other
A common electrode (21) of ITO is formed on the entire surface, and an orientation control window (22) is formed by opening an electrode absent portion by etching removal. Further, a polyimide alignment film (23) is formed on the entire surface similarly to the substrate (10) side, and rubbing is performed in a direction indicated by an arrow (24) in FIG. The liquid crystal is 90 ° between both substrates according to the control of the alignment films (17, 23).
It is arranged in a twist.

When a voltage is applied to the cell having this structure, FIG.
As shown in (1), the electric field in the liquid crystal layer (30) is adjusted to control the orientation of the liquid crystal. That is, the electric field (32x) is inclined obliquely at the edge of the display electrode (14) due to the voltage difference from the orientation control electrode (16), and the electric field (32y) is also applied to the common electrode at the edge of the orientation control window (22). (2
It is inclined obliquely so as to spread from the electrode existing region to the electrode non-existing region in 1). As a result, the liquid crystal director (31) having a positive dielectric anisotropy has the shortest oblique electric field (3).
2x, 32y). At this time, by setting the pretilt angle to be small and 1 ° or less, the influence of the pretilt on the control by the alignment control electrode (16) and the alignment control window (22) is nullified. In such an orientation control, the directions of the sides facing the display electrode (14) are opposite to each other, and the orientation control electrodes (1
The alignment state controlled by 6) spreads in the display pixel region due to the continuity of the liquid crystal. The boundaries between these different regions in the alignment state are fixed on the alignment control window (22). That is, in the region corresponding to the alignment control window (22), there is no electric field or the intensity is less than the threshold value, and the liquid crystal director (31) is maintained in the initial state. For this reason, the boundaries of the respective regions of the liquid crystal director controlled in different directions from each other on both sides of the alignment control window (22) are fixed in these regions, and the alignment state is smoothly connected and stable due to the continuity of the liquid crystal. At this time, the liquid crystal directors (31) are raised in directions opposite to each other with respect to the alignment control window (22). Since each area has a different preferential viewing angle direction, when the display screen is observed, these are combined and visually recognized. For this reason, as a result, the preferential viewing angle direction is widened, and display with a wide viewing angle with small viewing angle dependency can be performed.

The voltage of the alignment control electrode (16) is set to a voltage different from that of the display electrode (14). In the embodiment, the same voltage as that of the common electrode (21) is applied to obtain an alignment control effect. At the same time, the complexity of the drive circuit is avoided. FIG. 3 is an enlarged plan view of a corner portion of the display electrode (14). The display electrode edge (14E) is located between both edges (16Ea, 16Eb) of the alignment control electrode, and the corner (C) of the display electrode edge (14E) is in the area of the alignment control window (22). The distance (a) between the display electrode edge (14E) and the orientation control electrode edge (16Ea), and the display electrode edge (14E) and the orientation control electrode edge (16Ea).
The distance (b) to b) is designed to be 3 μm or more. The width (c) of the alignment control window (22) is about 5 μm, and the width is increased from about 30 μm before the corner (C) of the display electrode (14). The design is such that the distance (d) from the corner (C) to both edges (22E) of the orientation control window is 5 μ or more. The orientation control window (22) further includes a display electrode (1).
4), the edge of the alignment control electrode (16E
The distance (e) to (a) is designed to be 5 μ or more.

The above design takes into account a mask shift and a bonding shift. Thereby, the alignment control electrode (16) completely protrudes from the display electrode (14) to weaken the alignment control action, or conversely, the alignment control electrode (16) completely enters the inside of the display electrode (14) to control the alignment. In addition to preventing the function from working, the corner (C) of the display electrode (14) is prevented from protruding from the alignment control window (22). That is, at the time of mask alignment and bonding alignment, each is 1 to 2 μm.
And 3 to 4 .mu.m, but the above design prevents problems due to misalignment.

With this configuration, the liquid crystal director (3
With the initial alignment direction (18) of 1) as an axis, the rising control direction (X) by the alignment control electrode (16) and the rising control direction (Y) by the alignment control window (22) are both within 90 °. Since the arrangement is within the range, both controls are applied as the same action, and the rising side of the liquid crystal director (31) is specified to one side by voltage application, and effective alignment control is performed. That is, for a certain cross section, as shown in FIG. 2, for each region of the display pixel divided by the alignment control window (22), the alignment control electrode (16)
The oblique electric field (32x) generated by the oblique direction and the oblique electric field (32y) generated by the orientation control window (22) are inclined in the same direction, and the orientation is stabilized.

On the other hand, FIG. 4 shows a problem when the corner (C) of the display electrode (14) goes out of the area of the alignment control window (22). At this time, good alignment control is performed in the upper left region bordering the alignment control window (22), but in the lower right region, the display electrode (14) that is outside the alignment control window (22). The orientation is disturbed near the corner. That is, in this portion, the alignment control electrode (1) is disposed at a right angle around the initial alignment direction (18) of the liquid crystal director (31).
One of the rising control directions (X1) and (X2) according to 6) exceeds 90 °. For this reason, both controls act in different directions on the liquid crystal director (31),
A region where the rising side is opposite occurs, and such a region is widened due to the continuity of the liquid crystal, so that the region becomes a so-called reverse tilt domain (R), which adversely affects the display.

In FIG. 4, the display electrode edge (1
4E) at the intersection of the orientation control window edge (22E) and the region of the display electrode (14) and the orientation control window (22).
The angle (α) formed outside the region is 90 ° or more. In such a portion, the alignment control electrode (1) is set around the initial alignment direction (18) of the liquid crystal director (31).
6) and the orientation control window (2)
Either of the rising control directions (Y) according to 2) exceeds 90 °, and both controls are performed by the liquid crystal director (3).
Acts in the opposite direction to 1). Therefore, the region where the operation of the orientation control electrode (16) is effective is located in the orientation control window (22).
Becomes a reverse tilt domain (R) for an area where the action is effective, which adversely affects the display.

Therefore, in the present invention, as shown in FIG. 3, by covering the corner (C) of the display electrode (14) with the alignment control window (22), the liquid crystal director in this portion is fixed in the initial state. Thus, the disorder of the orientation is suppressed and the reverse tilt domain is prevented. FIG. 5 is an enlarged plan view of a connection portion between the display electrode (14) and the source electrode (15S). The display electrode edge (14E), the orientation control electrode edges (16Ea, 16Eb), and the source electrode edge (15S).
E) and the orientation control window edge (22E). Near the entrance of the display electrode (14), the orientation control electrode (1)
In order to prevent disconnection of the display electrode (14) due to the step of 6), the alignment control electrode (16) is absent at this portion. The alignment control window (22) is provided with an alignment control electrode (16).
And the vicinity of the entrance of the display electrode (14). Thereby, it is possible to prevent the orientation from being disturbed due to the uneven electric field due to the presence or absence of the orientation control electrode (16).

In design, the display electrode (14) at the connection with the source electrode (15S) has a width (f) of 10 μm.
And the vertical length (g) is set to 10 μm. As a result, the main area of the display pixel is separated from the TFT,
The portion where the orientation is disturbed by the step is drawn outside the effective display area. The minimum width (h) of the entrance portion where the alignment control electrode (16) is absent is about 8 μm, so that the display electrode (1
4) The connection resistance to 4) is reduced. Orientation control window (22)
The width (5 μm) in the pixel region is widened from about 30 μm before the intersection of the extension line and the display electrode edge (14E) such that the angle of the orientation control window edge (22E) becomes obtuse. ing. Orientation control window edge (22E)
Are the display electrode edge (14E) and the display electrode edge (1
4E) and a margin (i) for bonding so as to include the intersection between the orientation control electrode edge (22E) and the inside.
Is designed to be 5 μm.

Next, a second embodiment of the present invention will be described.
FIG. 6 is a plan view of the display pixel portion. A description overlapping with the first embodiment is omitted. The same reference numerals in FIG. 6 denote the same parts as in FIG. A-A
The cross-sectional structure along the line is the same as FIG. In the present embodiment, the corner of the display electrode (14) is cut out at the portion where the alignment control window (22) faces, and the alignment control window (22) is formed at the cut-off portion of the display electrode (14). It protrudes outside through the edge line.

FIG. 7 is an enlarged plan view of a corner portion of the display electrode (14). The display electrode edge (14E) is located between both edges (16Ea, 16Eb) of the alignment control electrode, and these edges (14E, 16Ea, 16Eb) are both bent in parallel at an obtuse angle, respectively.
It intersects the orientation control window edge (22E) at an angle close to a right angle. The corners (C1, C1) on both sides of the edge line (14Ea) of the display electrode thus formed.
C2) has an obtuse angle, so that the density of the electric field is relaxed and the disorder of the orientation is suppressed. Each of these corners (C1,
The farther distance (j) between C2) and the orientation control window edge (22E) is 5 μm or more. As a result, even if there is a misalignment, the corners (C1, C1
2) does not shift to the outside on the opposite side of the alignment control window (22), and the alignment disorder as described with reference to FIG. 4 is prevented. That is, at the intersection of the display electrode edge (14E) and the orientation control window edge (22E), the angle (α) formed within the region of the display electrode (14) and outside the region of the orientation control window (22) is 90 °. It can be avoided that the structure greatly exceeds. The edge line (14Ea) in which the corner portion of the display electrode (14) is cut is aligned in the same direction as the initial alignment direction (18) of the liquid crystal director (31). The window edge (22E) need not be exactly right-angled. That is, thereby, the alignment control (X3) from the edge line (14Ea) to the liquid crystal director (31) becomes invalid, the alignment control (X2) by the alignment control electrode (16) and the alignment from the alignment control window edge (22E). One of the rising sides is specified by the component of the control (Y) along the axial direction of the liquid crystal director (31). Orientation control window (22)
Is the distance (k) further outward from the edge line (14Ea)
Is set to about 10 μm to prevent the alignment control window (22) from reaching the edge line (14Ea) due to misalignment.

Next, a third embodiment of the present invention will be described. FIG. 8 is a plan view of the display pixel portion. First and second
The description which overlaps with the embodiment is omitted. 8 that are the same as those in FIGS. 1 and 6 are denoted by the same reference numerals. The present embodiment is a display pixel structure located in a row adjacent to the display pixel shown in FIG. 1 or FIG. 6 when the position of the TFT in the display pixel is left and right reversed in each row in the triangle structure.

The alignment control window (22) is formed substantially along the diagonal line from the upper right to the lower left of the display pixel, similarly to the first and second embodiments, and the TFT is connected to the lower right of the display electrode (14). ing. The shape of the display electrode (14) shown here is an example for expanding the effective display area and improving the aperture ratio corresponding to the gate line (11) and the drain line (15) having a triangle structure. In FIG. 6, a symmetrical structure can be adopted. Display electrode (1
In the part where the edge line is complicated in the side of 4),
By forming the bent angle of the edge line to be an obtuse angle, the density of the electric field is alleviated, and the disorder of the orientation due to the congestion of the electric field is prevented. The rubbing direction (1
The edge line extending in the same direction as in 8) has no effect on the liquid crystal director (31) in controlling the alignment, so that there is no effect of disturbing the controlled alignment in other portions. In addition, in order to divide the distorted display pixel into two regions having the same area, the alignment control window (22) is bent at a small angle (β) at an appropriate position, and is bent at an obtuse angle close to 180 °. It is formed in a shape bent into a mold. In FIG. 8, the structure shown in FIG. 3 is used as the shape of the portion where the end of the alignment control window (22) covers the corner of the display electrode (14). However, the present invention is not limited to this. Instead, the structure shown in FIG. 7 may be used.

FIG. 9 is an enlarged plan view of the connection between the display electrode (14) and the source electrode (15S). As in FIG.
In order to prevent disconnection of the display electrode (14) due to a step of the alignment control electrode (16), the alignment control electrode (16) is absent at the entrance of the display electrode (14). Next, a fourth embodiment of the present invention will be described. FIG. 10 shows a vertical alignment ECB according to the present invention.
It is a top view of a display pixel part at the time of applying to a cell of a system. FIG. 11 shows a cross-sectional structure along the line BB of FIG. In the following description, the same parts as those described above will not be described. The same reference numerals in the drawing denote the same objects as those in the above-described embodiment.

The alignment control window (25), which is an electrode-free portion in the common electrode (21), is formed in an X shape along the diagonal line of the display pixel, and divides the display pixel into four. That is, the four ends cover the three corners of the display electrode (14) and the connection with the source electrode (15S). Liquid crystal layer (4
0) has negative dielectric anisotropy, and the liquid crystal director (41) is vertically aligned between the alignment films (19) and (26).

When a voltage is applied to the cell having this structure, FIG.
As shown in FIG. 1, the electric field in the liquid crystal layer (40) is adjusted to control the orientation of the liquid crystal. That is, the electric field (42x) is inclined obliquely at the edge of the display electrode (14) due to the voltage difference from the orientation control electrode (16), and the electric field (42y) is also applied to the common electrode at the edge of the orientation control window (25). (2
It is inclined obliquely so as to spread from the electrode existing region to the electrode non-existing region in 1). As a result, the liquid crystal director (41) having a negative dielectric anisotropy allows the oblique electric field (42x,
42y). The alignment state controlled by the alignment control electrode (16) on the four sides of the display electrode (14) spreads in the display pixel region due to the continuity of the liquid crystal. Fixed on the control window (26). That is, the liquid crystal director maintained in the initial vertical alignment state by the alignment control window (26) by the alignment control window (26) in the same principle as described with reference to FIG. Are connected smoothly and the whole display pixel is stabilized. At this time, the liquid crystal director (41) sets the alignment control window (2).
In each of the regions divided by 4), the regions are uniformly aligned and inclined, and the regions are different from each other.
Leaning in one direction. Since each area has a different preferential viewing angle direction, when the display screen is observed, these are combined and visually recognized. For this reason, as a result, the preferential viewing angle direction is widened, and display with a wide viewing angle with small viewing angle dependency can be performed.

Further, as shown in FIG. 10, the central portion of the orientation control window (24) has a structure in which a corner of the electrode existing region is cut out and a large angle (γ) of the edge line is interposed to form an edge. It avoids making the angle of the line smaller. In other words, in a portion where the edge line is bent at a small angle, the density of the oblique electric field is generated, so that the orientation is easily disturbed. For this reason, such a problem is prevented by increasing the bending angle of the edge line.

FIG. 12 is an enlarged plan view of a corner portion of the display electrode (14). The design is the same as in FIG. The three corner portions of the display electrode (14) are also symmetrical in the left-right and up-down directions with respect to this structure. Due to the structure in which the corner (C) of the display electrode (14) is located within the region of the orientation control window (24), in each region divided by the orientation control window (24), the orientation control by the orientation control electrode (16) ( X) and orientation control (Y) by orientation control window (24)
Are slowly synthesized, and the liquid crystal directors (41) are evenly aligned.

FIG. 13 shows a problem when the corner (C) of the display electrode (14) extends outside the region of the alignment control window (24). At this time, the region (R) in which the alignment control (X1) by the alignment control electrode (16) is effective is the alignment control electrode (1).
The liquid crystal director (41) is significantly different from the region controlled by the combination of the alignment control (X2) according to 6) and the alignment control (Y) with the alignment control window (24).
When such a region (R) is widened due to the continuity of the liquid crystal, display is adversely affected.

Therefore, in the present invention, the orientation control window (24) is designed to be wide at the corner of the display electrode (14), so that even if a displacement occurs during bonding, the corner (C) is moved from the orientation control window (24). The liquid crystal director (41) in the corner part is fixed in the initial state by not making it stick,
The problem as shown in FIG. 13 is prevented. The connection between the display electrode (14) and the source electrode (15S) has the same structure as that of FIG. 5, and is covered by an orientation control window (24).

Next, a fifth embodiment of the present invention will be described.
FIG. 14 is a plan view of the display pixel portion. A description overlapping with the fourth embodiment is omitted. FIG. 11 shows a cross-sectional structure along the line BB. In this embodiment, three corners of the display electrode (14) are notched, and the orientation control window (2) is cut out.
4) is protruded outside through the edge line of the cutout portion of the display electrode (14).

FIG. 15 is an enlarged plan view of a corner portion of the display electrode (14). The design is the same as in FIG. An edge line (14) in which a corner of the display electrode (14) is cut out.
Ea) alignment control (X3) and alignment control window (24)
The alignment control (Y) by the alignment control (X2) by the alignment control electrode (16) is smoothly synthesized. For this reason,
The liquid crystal directors (41) are uniformly aligned in each area divided by the alignment control window (24), and the problem shown in FIG. 13 is prevented.

Further, the display electrode (14) and the source electrode (1)
5S) has the same structure as that of FIG. 5 and is covered with an orientation control window (24). FIG. 16 is a plan view of a display pixel portion according to a sixth embodiment of the present invention, which is a structure of a display pixel located in a row adjacent to the display pixel shown in FIG. 10 or FIG. 14 in a triangle structure. Display electrode (1
In 4), the area is extended along lines (11, 15) corresponding to the triangle arrangement in order to improve the aperture ratio, and the alignment control electrode (16) is used as the display electrode (14).
Are arranged along the edge line. The alignment control window (24) is bent at a small angle (β) in order to equalize the area of each of the divided display pixels.

[0045]

As is apparent from the above description, in a liquid crystal display device in which an alignment control electrode and an alignment control window are arranged in a cell and an electric field in a liquid crystal layer is adjusted to control the alignment of liquid crystal. By designing the shape of the edge line of the electrode and the edge line of the orientation control window, the density and congestion of the electric field generated obliquely along the edge line are reduced, the orientation disorder is eradicated, and the display quality and aperture ratio are reduced. Improved.

[Brief description of the drawings]

FIG. 1 is a plan view of a liquid crystal display according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is an enlarged plan view of a main part of the liquid crystal display device according to the first embodiment of the present invention.

FIG. 4 is a diagram illustrating the operation and effect of the present invention.

FIG. 5 is an enlarged plan view of a main part of the liquid crystal display device according to the embodiment of the present invention.

FIG. 6 is a plan view of a liquid crystal display according to a second embodiment of the present invention.

FIG. 7 is an enlarged plan view of a main part of a liquid crystal display device according to a second embodiment of the present invention.

FIG. 8 is a plan view of a liquid crystal display according to a third embodiment of the present invention.

FIG. 9 is an enlarged plan view of a liquid crystal display device according to a third embodiment of the present invention.

FIG. 10 is a plan view of a liquid crystal display according to a fourth embodiment of the present invention.

FIG. 11 is a sectional view taken along line BB of FIG. 10;

FIG. 12 is an enlarged plan view of a main part of a liquid crystal display device according to a fourth embodiment of the present invention.

FIG. 13 is a diagram illustrating the operation and effect of the present invention.

FIG. 14 is a plan view of a liquid crystal display according to a fifth embodiment of the present invention.

FIG. 15 is an enlarged plan view of a main part of a liquid crystal display device according to a fifth embodiment of the present invention.

FIG. 16 is a plan view of a liquid crystal display device according to a sixth embodiment of the present invention.

FIG. 17 is an equivalent circuit diagram of a liquid crystal display device.

[Explanation of symbols]

 10, 20 Substrate 11 Gate line 12 Gate insulating film 13 a-Si 14 Display electrode 15 Drain line 16 Alignment control electrode 17, 19, 23, 26 Alignment film 18, 24 Rubbing direction 21 Common electrode 22, 25 Alignment control window 30 Liquid crystal Layers 31, 41 Liquid crystal directors 32, 42 Electric field

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-7-199190 (JP, A) JP-A-6-301036 (JP, A) JP-A-6-164656 (JP, A) JP-A-6-164656 194657 (JP, A) JP-A-3-137619 (JP, A) JP-A-6-130394 (JP, A) JP-A-6-43461 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/1368 G02F 1/1343

Claims (7)

(57) [Claims] 1. A liquid crystal display comprising: a first substrate and a second substrate disposed to face each other with a liquid crystal interposed therebetween; a plurality of display electrodes disposed on a side facing the first substrate; and a signal voltage supplied to the display electrodes A thin film transistor, a common electrode formed entirely on the opposite surface side of the second substrate, and an alignment control window that is an electrode absent portion in the common electrode, wherein the display electrode and the common electrode together to hold a desired voltage to the capacitor as a display pixel is formed in the opposing portions sandwiching the liquid crystal layer, wherein the table
In a liquid crystal display device in which the orientation of the liquid crystal is controlled by an electric field obliquely inclined at the edge of the indicator electrode and a weak electric field in which the liquid crystal formed by the orientation control window is not driven, both ends of the orientation control window are the display electrode. The liquid crystal display device is formed in a band shape positioned at a corner portion facing each other, and is widened at the both end portions to cover the corner portion. 2. A method according to claim 1, wherein the first and second substrates are opposed to each other with a liquid crystal interposed therebetween, a plurality of display electrodes are disposed on a side opposite to the first substrate, and a signal voltage is supplied to the display electrodes. A thin film transistor, a common electrode formed entirely on the opposite surface side of the second substrate, and an alignment control window that is an electrode absent portion in the common electrode, wherein the display electrode and the common electrode together to hold a desired voltage to the capacitor as a display pixel is formed in the opposing portions sandwiching the liquid crystal layer, wherein the table
In a liquid crystal display device in which the orientation of the liquid crystal is controlled by an electric field obliquely inclined at the edge of the indicator electrode and a weak electric field in which the liquid crystal formed by the orientation control window is not driven, both ends of the orientation control window are the display electrode. Is formed in a band shape located at the corner part facing each other, and,
The corners of the display electrodes are obliquely cut away and the angle of the bent corners of the remaining portions of the electrodes is made obtuse, and the alignment control window cuts out the corners of the display electrodes. A liquid crystal display device, wherein the liquid crystal display device passes through the display electrode including a central portion of the line. 3. The display device according to claim 1, wherein an alignment control electrode is provided around the display electrode to obliquely incline an electric field at an edge of the display electrode.
The liquid crystal display device according to the above. 4. The display device according to claim 1, wherein the alignment control window is bent at an obtuse angle at one or a plurality of positions, and the areas of the display pixels divided by the alignment control window are equal to each other. The liquid crystal display device according to claim 1. 5. The alignment control window is formed in a single band shape, and both end portions are formed so as to be located at the same corner for all display pixels, and each region divided by the alignment control window is provided. 5. The liquid crystal display device according to claim 1, wherein the areas are all equal. 6. The alignment control window is formed in two intersecting strips in a display pixel, and four ends of the alignment control window are located at four corners of each display pixel. 5. The liquid crystal display device according to claim 1, wherein the areas divided by the alignment control window are all equal in area. 7. A corner of an electrode existing portion of the common electrode is cut off at an intersection of the two strip-shaped alignment control windows, and a bend of an edge line of the alignment control window is formed as an obtuse angle. 7. The liquid crystal display device according to claim 6, wherein: