JP4391634B2 - Liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the response characteristics of a liquid crystal display device and to increase the production yield. SOLUTION: The device is a vertical alignment type one in winch the alignment of the liquid crystal while voltage is applied is controlled by forming a linear structure consisting of a plurality of structural units or linear slits in at least one of a pair of substrates 1, 12 having electrodes. In this method, an alignment controlling means (connecting part 30e) to form the characteristic point of alignment satisfying s=-1 of the liquid crystal molecules is disposed in the part where the structure on the pixel electrode 30 or the slit 30a in the aforementioned electrode crosses with the edge of the pixel electrode 30 on one substrate 1.

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a liquid crystal display device (LCD).)More specifically, VA type liquid crystal display deviceIn placeRelated.
[0002]
[Prior art]
In recent years, TN type TFT-LCD manufacturing technology has progressed in various stages, and the contrast and color reproducibility in the front have surpassed those of CRT. However, a TN (twisted nematic) -LCD has a major disadvantage that the viewing angle is narrow, and there is a problem in that the application is limited.
[0003]
FIG. 1A to FIG. 1C are diagrams for explaining this problem. FIG. 1A shows a state in which white is displayed with no voltage applied between the two electrodes 101 and 102, and FIG.₁Is a state in which halftone is applied between the two electrodes 101 and 102, and FIG. 1 (c) shows a predetermined voltage V₂Is applied between the two electrodes 101 and 102 to display black.
[0004]
In FIG. 1A to FIG. 1C, alignment films 103 and 104 are formed on opposite surfaces of the two electrodes 101 and 102 with the alignment directions different from each other by 90 degrees. Further, although not particularly illustrated, a polarizing plate is disposed outside each of the two electrodes 101 and 102 in a state where the linearly polarized light directions are twisted by 90 degrees. The liquid crystal molecules L shown in FIGS. 1A to 1C are twisted in accordance with the alignment direction of the alignment films 103 and 104, but are not shown here for convenience.
[0005]
By the way, in the state where no voltage is applied as shown in FIG. 1A, the liquid crystal molecules L are aligned in the same direction with a very slight inclination angle (about 1 ° to 5 °). In this state, it looks almost white in any direction.
In addition, the voltage V as shown in FIG.₂In the state where is applied, the intermediate liquid crystal molecules L excluding the vicinity of the surfaces of the alignment films 103 and 104 are aligned in the vertical direction, and the incident linearly polarized light is blocked by the polarizing plate, so that it appears black from the outside. At this time, light incident obliquely on one electrode 101 passes obliquely with respect to the direction of the liquid crystal molecules aligned in the vertical direction, and the deflection direction is twisted to some extent, so that it is not completely black from the outside. , Looks halftone (gray).
[0006]
Further, as shown in FIG. 1 (b), an intermediate voltage V lower than the state of FIG. 1 (c).₁In the state in which the liquid crystal molecules are applied, the liquid crystal molecules in the vicinity of the alignment films 103 and 104 are still aligned in the horizontal direction, but the liquid crystal molecules L rise obliquely in the middle portion of the cell. Therefore, the birefringence of the liquid crystal is somewhat lost, the transmittance is lowered, and a halftone (gray) display is obtained. However, this can be said only for the light that enters the liquid crystal panel perpendicularly, and the state differs depending on the light that is obliquely incident on the surface of one electrode 101, that is, when viewed from the left and right directions in the figure.
[0007]
That is, in FIG. 1B, the direction of the liquid crystal molecules L is parallel to the light traveling from the lower right to the upper left. Accordingly, since the liquid crystal hardly exhibits a birefringence effect, it looks black when viewed from the left side. On the other hand, since the direction of the liquid crystal molecules L is perpendicular to the light from the lower left to the upper right, the liquid crystal molecules L exert a large birefringence effect on the incident light, and the incident light is twisted. So you will see a color close to white. That is, in FIG. 1 (b), the display intensity varies depending on the viewing angle, and this is the biggest drawback of the TN-LCD.
[0008]
Therefore, a VA (Vertically aligned) method using a vertical alignment film has been proposed as a method for improving the viewing angle characteristics without reducing the response speed.
FIG. 2A to FIG. 2C are diagrams for explaining the VA method. The VA method is a method in which a negative liquid crystal material and a vertical alignment film are combined.
First, as shown in FIG. 2A, when no voltage is applied, the liquid crystal molecules are aligned in the vertical direction to display black. In the VA method, the alignment films 103 and 104 are subjected to a vertical alignment process.
[0009]
When a predetermined voltage is applied between the two electrodes 101 and 102 as shown in FIG. 2 (c), the liquid crystal molecules L are aligned in the horizontal direction and white display is obtained. The VA method has higher display contrast, faster response speed, and better visual characteristics in white display and black display than the TN method.
Further, as shown in FIG. 2B, when a voltage smaller than that for white display is applied between the two electrodes 101 and 102, the liquid crystal molecules L are aligned in an oblique direction. In this case, light perpendicular to the surface of the electrode 101 is displayed as a halftone on the display panel. However, in FIG. 2B, the liquid crystal molecules L are parallel to the light traveling from the lower right to the upper left. Accordingly, since the liquid crystal molecules L hardly exhibit the birefringence effect, they appear black when viewed from the left side. On the other hand, since the liquid crystal molecules L are perpendicular to the light traveling from the lower left to the upper right, the liquid crystal molecules L exert a large birefringence effect on the incident light, and the incident light is twisted and thus white. The display is close to.
[0010]
Thus, in the VA method, since the liquid crystal molecules in the vicinity of the alignment film are almost vertical even when no voltage is applied, the contrast is higher in each stage than the TN method, and the viewing angle characteristics are also excellent. However, when halftone display is performed by the VA method, there is a problem similar to the TN method in which the display intensity changes when the viewing angle is changed, and the viewing angle characteristics are still insufficient.
[0011]
The present applicant uses conventional vertical alignment, encloses a so-called negative liquid crystal having negative dielectric anisotropy as a liquid crystal material between electrodes, and the inclination direction of liquid crystal molecules when a voltage is applied is within one pixel. Japanese Patent Application No. 10-185836 discloses a configuration in which domain regulation means for regulating different areas is provided.
3 (a) to 3 (c) show that a slit S is provided in the electrode 111 of one pixel on the first substrate side as the domain regulating means, and one pixel is formed on the electrode 112 on the second substrate side. It is a figure explaining the principle of the improvement of the visual characteristic by orientation division | segmentation at the time of employ | adopting the structure which provided the processus | protrusion P in FIG.
[0012]
As shown in FIG. 3A, the liquid crystal molecules L are aligned perpendicular to the substrate surface when no voltage is applied. Further, as shown in FIG. 3C, when a predetermined voltage is applied between the electrodes 111 and 112 facing each other, the liquid crystal molecules L are substantially horizontal with respect to the substrate surface and white display is obtained.
Further, as shown in FIG. 3B, when an intermediate voltage is applied between the electrodes 111 and 112, an oblique electric field is generated in the slit S (electrode edge portion) S with respect to the substrate surface. Further, the liquid crystal molecules L in the vicinity of the surface of the protrusion P are slightly inclined from the state where no voltage is applied. The inclination direction of the liquid crystal molecules L is determined by the influence of the inclined surface of the protrusion P and the oblique electric field, and the alignment direction of the liquid crystal molecules 113 is divided in the middle of the protrusion P and the slit portion 111s.
[0013]
At this time, for example, since the liquid crystal molecules L are slightly tilted, the light transmitted from directly below the substrate is suppressed by the influence of a slight birefringence, and a gray halftone display is obtained. The light transmitted from the lower right to the upper left is difficult to transmit in the region where the liquid crystal molecules L are inclined in the left direction, but is very easily transmitted in the region where the liquid crystal molecules L are inclined in the right direction. Key display is obtained. Further, the light transmitted from the lower left to the upper right is also displayed in gray on the same principle. Thereby, uniform halftone display is obtained in all directions of one pixel.
[0014]
Therefore, in FIG. 3B, a good display with less viewing angle dependency can be obtained in all of the black, halftone and white display states.
In FIG. 3A to FIG. 3C, as a domain regulating means, a slit is provided in one pixel of the electrode 111 on the first substrate side, and within one pixel on the electrode 112 on the second substrate side. Although the projection 20 is provided, other means can be used. The new VA method is hereinafter referred to as MVA (multi-domain vertical alignment) method.
[0015]
FIG. 4A to FIG. 4C are diagrams illustrating an example of realizing the domain restriction unit.
Fig. 4 (a) shows an example that can be realized only with the electrode shape, Fig. 4 (b) shows an example of devising the shape of the substrate surface, and Fig. 4 (c) devises the electrode shape and the shape of the substrate surface. An example is shown. In any of these examples, the orientations shown in FIGS. 3 (a) to 3 (c) are obtained, but their structures are slightly different.
[0016]
Next, the case where protrusions are provided on the opposing surfaces of the two substrates shown in FIG. 4B will be described as an example.
In FIG. 4B, projections P for alternately dividing the orientation direction are formed on the electrodes 111 and 112 on the opposite surface sides of the two substrates.₁, P₂Are formed, and vertical alignment films 113 and 114 are provided on the inner surfaces thereof. The vertical alignment film is subjected to a vertical alignment process. The liquid crystal injected between the two substrates is a negative type. When no voltage is applied, the liquid crystal molecules L are aligned perpendicular to the substrate surface on the vertical alignment film. Protrusion P₁, P₂Since the liquid crystal molecules L in FIG.₁, P₂The upper liquid crystal molecules L are tilted. However, when no voltage is applied, the protrusion P₁, P₂In most of the region except for the liquid crystal molecules L, the liquid crystal molecules L are aligned almost perpendicularly to the substrate surface, so that a good black display can be obtained as shown in FIG.
[0017]
When a voltage is applied, the liquid crystal molecules L are projected P₁, P₂In the part where there is no projection, it is parallel to the substrate (the electric field is perpendicular to the substrate) but the projection P₁, P₂In the vicinity of That is, when a voltage is applied, the liquid crystal molecules L are tilted according to the strength of the electric field, but when the electric field is in a direction perpendicular to the substrate and the tilt direction is not defined by rubbing, the orientation tilted with respect to the electric field. Can have all directions of 360 °. Protrusion P₁, P₂Then, the electric field is the projection P₁, P₂The liquid crystal molecules L are inclined in a direction perpendicular to the electric field when a voltage is applied.₁, P₂This is consistent with the originally inclined direction, and is more stably oriented. Thus, the protrusion P₁, P₂Has a stable orientation due to the effects of both its slope and the electric field on the slope. Further, when a strong voltage is applied, the liquid crystal molecules L become substantially parallel to the substrate.
[0018]
As described above, the protrusion P₁, P₂Serves as a trigger for determining the orientation of the liquid crystal molecules L when a voltage is applied.
In FIG. 4 (a), both or one electrode 111, 112 has a slit S.₁, S₂Is provided. The alignment films 113 and 114 are subjected to a vertical alignment process, and negative liquid crystal is sealed between the substrates. In the state where no voltage is applied, the liquid crystal molecules are aligned perpendicular to the substrate surface, but when a voltage is applied, the slit (electrode edge) S₁, S₂Thus, an electric field in a direction oblique to the substrate surface is generated. The tilt direction of the liquid crystal molecules L is determined by the influence of the oblique electric field, and the alignment direction of the liquid crystal is divided into the left and right directions as shown in the figure.
[0019]
FIG. 4C shows an example in which the methods shown in FIGS. 4A and 4B are combined. A slit S is formed on one electrode 111, and a protrusion P is formed on the other electrode 112. Is provided.
As mentioned above, although the example which implement | achieves three domain control means was shown, various deformation | transformation are possible.
[0020]
FIG. 5 is a plan view showing the positional relationship among bus lines, protrusions, pixels, and electrodes in a liquid crystal display panel that is aligned and divided in four directions, and FIG. 6 is a cross-sectional view taken along the line II in FIG.
5 and 6, a plurality of gate bus lines 122 extending in the X direction (horizontal direction in the figure) are formed on the TFT substrate 121 at intervals in the Y direction (vertical direction in the figure). . In addition, a capacitor bus line 123 extending in the X direction is formed between the gate bus lines 122. A storage capacitor branch line 123a is formed from the capacitor bus line 123 in the Y direction so as to face a part of a drain bus line to be described later so as not to contact the gate bus line 122.
[0021]
The gate bus lines 122 and the capacitor bus lines 123 are covered with a first insulating film 124. Further, a plurality of drain bus lines 125 extending in the Y direction are formed on the first insulating film 124 at intervals in the X direction. A TFT (thin film transistor) 126 is formed corresponding to the intersection of the gate bus line 122 and the drain bus line 125. The TFT 126 includes a semiconductor layer 126a formed on the gate bus line 125 via the first insulating film 124, a drain electrode 126d formed on the semiconductor layer 126a, and a source electrode formed on the semiconductor layer 126a. The drain electrode 126d is connected to the nearby drain bus line 125. The drain bus line 125 and the TFT 126 are covered with a second insulating film 127.
[0022]
A pixel electrode 128 made of ITO is formed on the second insulating film 127 in a region surrounded by the two drain bus lines 125 and the two gate bus lines 122. The pixel electrode 128 is connected to the source electrode 126 s through a hole (not shown) in the second insulating film 127.
The potential of the capacitor bus line 123 is fixed to an arbitrary magnitude. When the potential of the drain bus line 125 varies, the potential of the pixel electrode 128 varies due to capacitive coupling caused by stray capacitance. In the configuration of FIG. 6, since the pixel electrode 128 is connected to the capacitor electrode 123 via the auxiliary capacitor, the potential fluctuation of the pixel electrode 128 can be reduced.
[0023]
In FIG. 6, a color filter 132, a black matrix 133, a common electrode 134, and an alignment film 135 are sequentially formed on a counter substrate 131 that faces the TFT substrate 121.
On the opposing surfaces of the counter substrate 131 and the TFT substrate 121, protrusions 130 and 136 each having a zigzag bent pattern extending in the Y direction are formed. The bending angle of the bending pattern is approximately 90 degrees.
[0024]
The protrusions 130 on the TFT substrate 121 side are arranged at equal intervals in the X direction, and the bent point is arranged at the approximate center of the gate bus line 122. The protrusion 136 on the counter substrate 131 side has a pattern having substantially the same shape as the protrusion 130 on the TFT substrate 121 side, and is common so as to be positioned at substantially the center between the plurality of protrusions 130 on the TFT substrate 121. It is formed on the electrode 134.
[0025]
The protrusion 130 and the pixel electrode 128 on the TFT substrate 121 side are covered with an alignment film 129, and the protrusion 136 on the counter substrate 131 side is also covered with another alignment film 135. The protrusion 130 on the TFT substrate 121 side and the protrusion 136 on the counter substrate 131 side intersect with the edge of the pixel electrode 128 at an angle of 45 degrees, respectively.
In addition, polarizing plates (not shown) are respectively disposed on the surfaces of the TFT substrate 121 and the counter substrate 131 that do not sandwich the liquid crystal material 139. These polarizing plates are arranged so that their deflection axes intersect at 45 degrees at the angular linear portion of the projections 130.136 and are crossed Nicols. That is, the deflection axis of one polarizing plate is parallel to the X direction in the figure, and the other deflection axis is parallel to the Y direction in the figure.
[0026]
The TFT substrate 121 and the counter substrate 131 are arranged in parallel with a certain distance therebetween, and a liquid crystal material 139 is filled in the gap therebetween. As described above, the liquid crystal material 139 has a negative dielectric anisotropy. The protrusions 130 and 136 are made of a material having a dielectric constant equal to or lower than that of the liquid crystal material 139.
[0027]
Next, the alignment of the liquid crystal molecules L when an intermediate voltage is applied to the pixel electrode will be described by taking a case where a slit is provided in the pixel electrode as an example.
FIG. 7 is a plan view showing an arrangement relationship of a gate bus line, a drain bus line, a capacitor bus line, and a pixel electrode 128 on a TFT substrate in which a slit S is provided in the pixel electrode instead of the protrusion 130 shown in FIG. is there.
[0028]
In FIG. 7, the pixel electrode 128a is divided into a plurality of regions by a plurality of slits S passing between the upper protrusions 136a. These regions are electrically connected to each other by a connecting portion 128b crossing each slit S. The two slits S near the center of the pixel electrode 128a intersect each other at the edge portion of the pixel electrode 128a.
[0029]
When an intermediate voltage is applied to the pixel electrode 128a. The liquid crystal molecules L on the pixel electrode 128a are inclined with respect to the surface of the pixel electrode 128a. In FIG. 7, the liquid crystal molecules L are indicated by cones, the sharp edges indicate the position of one end of the liquid crystal molecules on the TFT substrate side, and the circular surface of the cone indicates the position of the other end on the counter substrate side. There are four types of inclination directions of the liquid crystal molecules L according to the principle shown in FIG.
[0030]
As described above, the MVA method is a method of aligning a liquid crystal having a negative dielectric anisotropy almost perpendicular to the substrate surface, and has high contrast and visual characteristics without reducing the switching speed. Therefore, the display quality is good. In addition, the viewing angle characteristics can be further improved by using the domain regulating means.
[0031]
[Problems to be solved by the invention]
An MVA liquid crystal display device can achieve high image quality, high reliability, and high productivity.
However, since the VA method is weaker anchoring than the horizontal alignment type like the TN method, the VA method has a property of being easily affected by an electric field, and the MVA method inherits such a property.
[0032]
Therefore, as shown in FIGS. 8A and 8B, the alignment state of the liquid crystal molecules L around the pixel electrode 128 changes due to the variation of the potential Egc of the gate bus line and the potential (data voltage) Egg of the drain bus line. There is a case. Such a phenomenon occurs similarly in the case of the TN method, but it is considered that the VA method is more likely to occur than the TN method. Further, as a phenomenon peculiar to the MVA method, the protrusion may be charged depending on various conditions such as driving. At this time, the liquid crystal alignment at the portion intersecting with the drain bus line and the gate bus line is also changed by the influence of the charging of the protrusions.
[0033]
When the orientation around the pixel changes, the values of the stray capacitance, for example, the gate-common electrode capacitance Cgc, the gate-source capacitance Cgs, the drain-common electrode capacitance Cdc, and the like change accordingly. As a result, the potential of the pixel electrode 126s also varies due to capacitive coupling. Usually, the potential fluctuation of the pixel electrode is reduced by the auxiliary capacitor, but it may not be completely compensated. In particular, it is likely to occur when the auxiliary capacity is reduced to increase the aperture ratio. When the pixel electrode potential fluctuates, flicker called flicker occurs on the screen.
[0034]
There is a means for increasing the auxiliary capacitance to such an extent that the fluctuation of the pixel electrode potential is completely eliminated, but the aperture ratio is reduced by that amount.
Next, generation of afterimages in the MVA liquid crystal display device will be described.
The occurrence of an afterimage in the liquid crystal display device is caused by an abnormal response speed, but this occurs because the domain control direction is not fixed on the protrusions and slits on the electrodes described above.
[0035]
The instability in the domain control direction is caused by variations in cell thickness and the like, and a liquid crystal display device in which an afterimage is generated as a result is not shipped as a defective product.
As a result of investigating the cause of afterimages that remain for a long time, the following became clear.
That is, in a liquid crystal display device adopting a structure in which a plurality of protrusions or slits are formed on an electrode, as shown in FIGS. 9A and 9B, the domain state when the display is changed from black to white, It was found that afterimages remained for a long time when there was a difference in the domain state when the display was changed from halftone to white.
[0036]
In FIG. 9 (a), the number of domains on the slit S after the display is changed from black to white is divided by 6 at the boundary between all the connecting portions 128b and the connecting portions 128b of the pixel electrode 128a. Exists. Thereby, the liquid crystal molecules L in the vicinity of the slit S are aligned in a direction perpendicular to the straight portion of the slit S.
On the other hand, in FIG. 9B, the number of domains on the slit S after the display is changed in the order of black, halftone, and white is two or four divided at some connecting portions 128b. is there. As a result, there is a region where the domain does not change at the boundary between the connecting portion 128b and the middle thereof, and in this region, the liquid crystal molecules L in the vicinity of the slit S are oriented obliquely with respect to the straight portion of the slit S.
[0037]
One of the causes is that the voltage is not sufficiently applied to the protrusions 130 or the liquid crystal molecules L on the slits S in the halftone display, so that the liquid crystal molecules L are in a substantially vertical state with respect to the substrate surface as shown in FIG. Thus, the influence of the electric field at the edge of the pixel electrode 128a and the orientation of the display domain affected by the electric field extends to the divided part of the orientation control means by the connecting portion, and the orientation control by dividing the orientation control means. This is probably because the effect does not function sufficiently. That is, when the liquid crystal molecules L on the slits S or the projections 130 are in a vertical state during intermediate display, the liquid crystal molecules L in the vicinity thereof are affected by the electric field at the edge of the pixel electrode 128a, and the slits S or projections. Inclined orientation with respect to 130 straight portions.
[0038]
As a result, when the halftone display is changed to the white display, the domain (3) shown in FIG. 9 (a) disappears, the domains (2) and (4) are connected, and then the domain (5) is changed. The domain of (4) and (6) disappears, and as a result, as shown in FIG. 9 (b), domains facing the upper right direction are connected to each other, and the domain facing the lower left disappears. The domain on the slit S is reduced to two (1) and (2).
[0039]
As another cause of the afterimage generation, it is conceivable that the protrusion 130 of the orientation control unit or the bent portion of the pattern of the slit S is arranged at the edge of the pixel electrode 128a. The alignment states that can be taken by the liquid crystal molecules L at the bent portion are any of the three types shown in FIGS. 11 (a) to 11 (c).
However, due to the influence of the orientation due to the edge of the pixel electrode 128a, the orientation at the bent portion becomes the state shown in FIG. 11C, and as a result, as shown in FIG. The orientation control direction by the edge of 128a extends inward of the pixel. This influences the orientation of the domain on the slit S particularly in the case of halftone display, so that it is considered that the orientation control effect by dividing the orientation control means does not function sufficiently.
[0040]
In the TFT substrate, a region where a plurality of electrodes are stacked, in particular, the pixel electrode 128a and the capacitor electrode (capacitor bus line) 123 are insulated between them as shown in FIGS. 13 (a) and 13 (b). A short circuit may occur through the membrane. At this time, in a liquid crystal display device having a structure in which the pixel electrode 128a is divided into a plurality of regions using the slits S as the alignment control means, and these regions are electrically connected by the connecting portion 128b, FIG. ), (b) As indicated by X, by cutting the connection portion 128b near the TFT 126 in the region short-circuited with the capacitor bus line 218 in the pixel electrode 128a, the short-circuit region is separated from other regions. Thus, the liquid crystal molecules in the pixel can be partially driven.
[0041]
However, since an area short-circuited to the capacitor bus line 123 in the pixel electrode 128a exists at the center of the pixel, the area of the pixel electrode 128a is less than half as shown by a one-dot chain line in FIG. Only the pixel region can be driven, and the pixel area becomes defective in point, thereby reducing the yield of the device.
An object of the present invention is to provide a liquid crystal display device capable of reducing fluctuation in potential of a pixel electrode and reducing flicker without changing the size of an auxiliary capacitor.
[0043]
[Means for Solving the Problems]
  As illustrated in FIG.In the pixel electrode formed on one of the pair of substrates,In a vertical alignment type liquid crystal display device in which a linear slit is provided to control liquid crystal alignment during voltage application,The linear slit is formed by dividing into a plurality of portions, and a connection portion is formed between an end of the slit closest to the edge of the pixel electrode and the edge of the pixel electrode among the divided slits. By providing it, the liquid crystal molecules formed an alignment singularity of s = -1 at the connecting portion.This is solved by a liquid crystal display device.
[0044]
  In addition, the above-described problem is a pair of substrates having electrodesOn one side,In a vertical alignment type liquid crystal display device in which a linear structure is provided to control liquid crystal alignment during voltage application,By providing a protrusion having a height higher than that of the other portion on the structure at a portion where the edge of the pixel electrode provided on the other of the pair of substrates and the structure intersect, the protrusion The liquid crystal molecules formed an alignment singularity of s = + 1This is solved by a liquid crystal display device.
  In addition, the above-described problem is provided in the other of the pair of substrates in a vertical alignment type liquid crystal display device in which a linear slit is provided in one of the pair of substrates having electrodes to control liquid crystal alignment during voltage application. By providing a dividing portion where the slit is divided at a portion where the edge of the pixel electrode and the extension line of the slit intersect, the liquid crystal molecules form an alignment singularity of s = + 1 at the dividing portion. This is solved by the liquid crystal display device characterized by the above.
[0048]
The above problems are solved by a liquid crystal display device having the thin film transistor substrate.
The above-described problems are solved by any one of the liquid crystal display devices having the thin film transistor substrate.
Next, the operation of the present invention will be described.
[0049]
  The present invention relates to a liquid crystal display device having at least one of a structure on an electrode used as a domain regulating means and a slit in the electrode, in the vicinity of a portion where the extension line of the structure or the slit intersects the edge of the pixel electrode Thus, an alignment singularity is formed such that the liquid layer molecules are s = −1 or s = + 1. When the liquid crystal molecule is applied to the present invention, the domain on the slit is changed, for example, as shown in FIG. 31 (a), when the black display is changed to the white display, the domain on the slit divided by the connecting portion. Number of1-8It is eight. Also, according to FIG. 31 (a), compared to FIG. 9 (a) showing the prior art.7 and 8The number of domains increases. This is because a singular point of an orientation vector of s = −1 is formed at the edge of the pixel electrode. When the display changes from black display to white display through halftone display, as shown in FIG.6 and 8Domains are connected7Domain disappears. That is, the domain change on the slit is suppressed to a very slight level near the edge of the pixel electrode as compared with FIG.
[0050]
This makes it possible to reduce the difference in domain state between white when responding from black display to white display and white when responding from halftone display to white to an inconspicuous level. As a result, the level could be reduced to an unrecognizable level. The present invention can provide a high effect only when the orientation control means is applied in combination to a panel formed of a plurality of structural units. If the domain control means on the structure or the slit is simply provided only at the edge of the pixel electrode, the after-image occurs because the domain near the center of the pixel electrode cannot be controlled. Further, during white response from halftone display, the control means for the edge of the pixel electrode becomes ineffective, and the structure on the pixel electrode or the domain on the slit cannot be controlled at all, resulting in an afterimage.
[0051]
  Further, in the present invention, since the influence of the electric field due to the edge of the pixel electrode on the bent portion is eliminated, the occurrence of an alignment state different from the original alignment control of the structure or slit can be reduced in the vicinity of the pixel electrode edge. Thus, afterimages can be eliminated. Furthermore, in the present invention, as the electrical connection path of the pixel electrode, two systems are provided: a path through the storage capacitor forming electrode and the region where the capacitor is formed, and a path not through the area. As a result, when an electrical short circuit occurs between the storage capacitor forming electrode and the pixel electrode, the liquid crystal molecules can be driven in other regions by electrically disconnecting the region forming the capacitor from the other region. It can be used as a safe area. This pixel has slightly different display characteristics compared to the normal case where no short circuit has occurred, but depending on the number and location, clearing the standard for display defects is also a characteristic difference to some extent, so the yield of the TFT substrate Can be improved.
(2) The problem described above is that, as illustrated in FIGS. 14 to 22, a liquid crystal having a negative dielectric anisotropy between the first and second substrates having the substrate surface subjected to the vertical alignment treatment. In the liquid crystal display device in which the orientation of the liquid crystal is substantially vertical when no voltage is applied, substantially horizontal when a predetermined voltage is applied, and oblique when a voltage smaller than the predetermined voltage is applied. A first domain regulating means provided on the first substrate for regulating an alignment direction in which the liquid crystal is inclined when a voltage smaller than the predetermined voltage is applied; Second domain regulating means for regulating the alignment direction in which the liquid crystal is inclined when a voltage smaller than the voltage of the first voltage is appliedAnd saidA plurality of first bus lines formed at intervals on a surface of the first substrate or the second substrate that sandwiches the liquid crystal, and intersecting the first bus lines; A plurality of second bus lines formed at intervals above the first bus line, and a pixel electrode formed in a region partitioned by the first bus line and the second bus line When,The liquid crystal molecules are formed in a region between the pixel electrode and the first or second bus line, and the alignment direction of liquid crystal molecules included in the region between the pixel electrode and the first or second bus line is vertical. Keep dielectric structures andIt is solved by a liquid crystal display device characterized by comprising:
[0052]
Next, the operation of the present invention will be described.
According to the present invention, the dielectric structure is formed in a region between the gate bus line (first bus line) and the pixel electrode intersecting with each other or in a region between the drain bus line (second bus line) and the pixel electrode. Arranged.
Thereby, since the dielectric constant between the pixel electrode and the bus line is fixed by the dielectric structure, the stray capacitance variation between them is suppressed.
[0053]
In addition, since the dielectric structure is also formed on the bus line, the liquid crystal layer on the dielectric structure is thinned, and the liquid crystal molecules of the liquid crystal layer are difficult to move from the vertical alignment, and the applied voltage is reduced. Even if it changes, the liquid crystal molecules do not easily tilt, and the stray capacitance variation becomes very small. In addition, since the stray capacitance above the bus line has a larger component fixed by the dielectric structure, the fluctuation of the stray capacitance is reduced.
[0054]
As described above, when the fluctuation of the stray capacitance is suppressed, the pixel potential becomes constant and flicker is prevented. In addition, it is possible to increase the aperture ratio by narrowing the width of the capacitor bus line for suppressing the fluctuation of the capacitor.
[0055]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
(First embodiment)
FIG. 14 shows a planar state of the TFT substrate excluding the insulating film and dielectric protrusion of one pixel of the MVA liquid crystal display device according to the first embodiment of the present invention. FIG. 15 is a plan view showing a state where dielectric protrusions are formed on the TFT substrate shown in FIG. 16 is a cross-sectional view taken along line II-II in FIG. 15, FIG. 17 is a cross-sectional view taken along line III-III in FIG. 15, and FIG. 18 is a cross-sectional view taken along line IV-IV in FIG.
[0056]
In FIG. 14, on a first glass substrate (TFT substrate) 1 on which TFTs are formed, a plurality of gate bus lines 2 extending in the X direction (lateral direction in the figure) are in the Y direction (vertical direction in the figure). ) At intervals.
In addition, a capacity bus line (storage capacity forming electrode) 3 extending in the X direction is formed between the gate bus lines 2. An auxiliary capacity branch line 3 a facing a part of a drain bus line, which will be described later, extends from the capacity bus line 3 in the Y direction so as not to contact the gate bus line 2.
[0057]
The gate bus line 2, the capacity bus line 3, and the auxiliary capacity branch line 3a are formed simultaneously.
That is, after forming an aluminum film having a thickness of 100 nm and a titanium film having a thickness of 50 nm on the first glass substrate 1 by sputtering, these films are patterned by a photolithography method to form the gate bus line 2 and the capacitance. A bus line 3 and an auxiliary capacity branch line 3a are formed. For patterning, BCl_ThreeAnd Cl₂The reactive ion etching (RIE) method using the mixed gas is used.
[0058]
As shown in FIG. 16, the gate bus line 2 and the capacitor bus line 3 are covered with a gate insulating film 4 made of silicon nitride having a thickness of 400 nm formed by plasma enhanced chemical vapor deposition (PE-CVD). On the gate insulating film 4, a plurality of drain bus lines 5 extending in the Y direction are formed at intervals in the X direction.
[0059]
In the vicinity of the intersection of the gate bus line 2 and the drain bus line 5, a TFT (thin film transistor) 6 is formed as an active element.
As shown in FIG. 17, the TFT 6 includes an active layer 6 a formed through a gate insulating film 4 in a region straddling a part of the gate bus line 5, and an active layer 6 a on one side of the gate bus line 5. It has a drain electrode 6d formed above and a source electrode 6s formed on the active layer 6a on the other side of the gate bus line 5. The drain electrode 6d is connected to the nearby drain bus line 5. ing.
[0060]
The drain electrode 6d and the source electrode 6s are separated on the channel protective film 6b formed on the channel region of the active layer 6a.
The channel protective film 6b is formed by the following method.
That is, after a silicon nitride film is formed on the active layer 6a and the gate insulating film 4 to a thickness of 140 nm by PE-CVD, a photoresist (photosensitive resin) is formed on the silicon nitride film. Apply. Then, the photoresist is exposed and developed to form a resist pattern. The exposure process includes a first exposure step of irradiating the photoresist with exposure light from the lower surface of the glass substrate 1 using the gate bus line 2 as an exposure mask, and a photo from the upper surface of the glass substrate 1 using an ordinary exposure mask. A second exposure step of irradiating the resist with exposure light. Thus, the edge of the resist pattern is defined by the edge of the gate bus line 5. Then, when the silicon nitride film in a region not covered with such a resist pattern is etched by a wet method using buffered hydrofluoric acid or an RIE method using hydrofluoric acid-based gas, a channel protective film 6b made of a silicon nitride film is formed. Will be.
[0061]
The active layer 6a is formed by patterning a 30 nm thick non-doped amorphous silicon film formed on the gate insulating film 4 by PE-CVD.
The source electrode 6s, the drain electrode 6d, and the drain bus line 5 are all n-thickness of 30 nm.⁺After forming a type amorphous silicon film, a titanium film with a thickness of 20 nm, an aluminum film with a thickness of 75 nm and a titanium film with a thickness of 80 nm on the gate insulating film 4 and the channel protective film 6b in order, It is formed by patterning using a mask. The etching is BCl_ThreeAnd Cl₂RIE method using a mixed gas of During the etching, the channel protective film 6b functions as an etching stop film.
[0062]
The TFT 6 and the drain bus line 5 are covered with a protective insulating film 7 made of silicon oxide or silicon nitride.
A transparent pixel electrode 8 made of ITO having a thickness of 70 nm is formed in a region on the protective insulating film 7 and surrounded by the two drain bus lines 5 and the two gate bus lines 2. . The ITO film is patterned by a wet etching method using an oxalic acid-based etchant.
[0063]
The pixel electrode 8 is connected to the source electrode 6 s through the hole 7 a of the protective insulating film 7.
On the protective insulating film 7 and the pixel electrode 8, insulating protrusions 10 having a zigzag bent pattern extending in the Y direction are arranged at equal intervals in the X direction at the positions indicated by the two-dot chain line shown in FIG. Is formed. The bent angle of the bent pattern is approximately 90 degrees, and the bent point is arranged at the approximate center of the gate bus line 2. The side surface of the protrusion 10 is inclined with respect to the substrate surface.
[0064]
Further, as shown in FIGS. 15 to 18, a dielectric structure 11 interposed between the gate bus line 2, the drain bus line 5, and the pixel electrode 8 is formed on the protective insulating film 7. ing.
Such a dielectric structure 11 and the protrusion 10 are formed by the following method, for example.
[0065]
That is, a high-sensitivity negative resist and a low-sensitivity negative resist are sequentially applied on the protective insulating film 7 and the pixel electrode 8. Then, a latent image of a bent pattern is formed on the high sensitivity negative resist by the first exposure. In the first exposure, the exposure amount is set such that the low sensitivity negative resist is not exposed. Subsequently, exposure light is irradiated to the gate bus line 2 and the drain bus line 5 and the peripheral area of the low sensitivity negative resist to form a latent image. For example, exposure light is irradiated to at least a region from the top of the gate bus line 2 to the edge of the pixel electrode 8 and a region from the drain bus line 5 to the edge of the pixel electrode 8 in one pixel region. By exposure of the low sensitivity negative resist, the high sensitivity negative resist is also simultaneously exposed in the same pattern. Note that even resists having different sensitivities can be said to be substantially the same dielectric material.
[0066]
Thereafter, when a pattern is formed by developing the low-sensitivity negative resist and the high-sensitivity negative resist at the same time, the L-shaped dielectric structure 11 and the protrusion 10 having a bent pattern as shown in FIG. 15 are integrated. It is formed. In this case, since the protrusion 10 is composed of a high sensitivity negative resist, and the dielectric structure is composed of both a low sensitivity resist and a high sensitivity negative resist, the dielectric structure 11 is composed of the protrusion 10. It will be thicker.
[0067]
In the above-described example, the heights of the dielectric structure 11 and the protrusions 10 are different. However, if the height is the same, the photosensitive resist described above may be a single layer. The above-described structure can be realized. For example, the film thicknesses of the dielectric structure 11 and the protrusion 10 are 1 μm or more.
Such protrusions 10 and dielectric structures 11 are covered with an alignment film 9 made of resin together with the pixel electrodes 8 and the protective insulating film 7. The alignment film 9 is vertically aligned.
[0068]
Next, the counter substrate facing the first glass substrate 1 will be described.
The counter substrate is made of a second glass substrate 12 as shown in FIG. 16, and a red (R), green (G), and blue (B) color filter film 13 is formed thereon. On the color filter film 13, a black matrix 14 having a pattern facing the gate bus line 2, the drain bus line 5, and the capacitor bus line 3 is formed. Further, a transparent common electrode 15 made of ITO covering the black matrix 14 is formed on the color filter film 13.
[0069]
On the common electrode 15, a protrusion 16 having a zigzag bent pattern is formed. The protrusion 16 is arranged at a position that passes through substantially the center of the plurality of protrusions 10 on the first glass substrate 1 as indicated by a two-dot chain line in FIG.
The protrusion 10 on the first glass substrate 1 side and the protrusion 16 on the second glass substrate 12 side intersect with the edge of the pixel electrode 8 at an angle of 45 degrees, respectively.
[0070]
Furthermore, an alignment film 17 is formed on the counter electrode 15 to cover the protrusions 16. The alignment film 17 is vertically aligned.
The first glass substrate 1 and the second glass substrate 12 as described above are bonded to each other with a predetermined distance from each other with the alignment films 9 and 17 on the inside, and a negative distance is provided between the alignment films 9 and 17. A liquid crystal material 18 having a dielectric anisotropy of is filled. The liquid crystal molecules in the liquid crystal material 18 are aligned perpendicular to the substrate surface when no voltage is applied between the common electrode 15 and the pixel electrode 8. In addition, in a state where an intermediate voltage is applied between the pixel electrode 8 and the common electrode 15, the liquid crystal molecules are inclined in a direction substantially perpendicular to the linear portion of the pattern of the protrusions 10 and 16.
[0071]
The protrusions 10 and 16 are preferably formed of a material having a dielectric constant equal to or lower than that of the liquid crystal material 18.
A first polarizing plate 21 is disposed on the outer surface of the first glass substrate 1, and a second polarizing plate 22 is disposed on the outer surface of the second glass substrate 12. The arrangement of the polarizing plate 21 and the second polarizing plate 22 is crossed Nicol, and the patterns of the deflection axes and projections 10 and 16 of the first and second polarizing plates 21 and 22 are viewed in a state where the substrate is viewed from the vertical. The straight line intersects with the 45 degree angle.
[0072]
In the above-described embodiment, the pixel electrode 8 and the gate bus line 2 and the drain bus line 5 are each covered with the dielectric structure 11. Thereby, the gap between the alignment film 9 on the gate bus line 2 and the alignment film 17 on the common electrode 15 is narrowed, and the regulating force of the alignment film on the liquid crystal molecules is increased. In addition, a voltage drop is generated by the dielectric structure 11 between the gate bus line 2 and the common electrode 15, and the voltage applied to the liquid crystal layer is also reduced.
[0073]
As a result, as shown in FIGS. 19A and 19B, the vertical alignment regulation by the alignment films 9 and 17 becomes strong and the liquid crystal molecules L are difficult to tilt above the gate bus line 2. As a result, the alignment direction of the liquid crystal molecules L becomes less susceptible to fluctuations in the surrounding electric field, and fluctuations in stray capacitance are reduced.
In addition, the relative dielectric constant of the dielectric structure 11 is approximately 2 to 5 and does not vary, and is constant and is often smaller than the relative dielectric constant of the liquid crystal. For example, the one having 3.2 is used. The liquid crystal for MVA has ε = 3.6 and ε // = 8.4.
[0074]
As a result, as shown in FIGS. 19A and 19B, the capacitance Cgs between the pixel electrode 8 and the gate bus line 2 and the capacitance Cds between the pixel electrode 8 and the drain bus line 5 hardly change. Further, since a voltage drop occurs in the dielectric structure 11, the voltage applied to the liquid crystal layer on the gate bus line 2 is also reduced. As a result, the stray capacitance between the bus lines and between the bus line and the pixel electrode is reduced.
[0075]
From the above, since the stray capacitance variation becomes very small and a constant pixel potential can be obtained, the width of the capacitor bus line 3 can be narrowed to increase the aperture ratio. Moreover, flickering is prevented when the pixel potential becomes constant.
For example, the common voltage fluctuation of a panel manufactured using the above-described structure is 10 mV or less, the flicker rate is improved to 3% or less, and is less than half of the conventional flicker rate (5 to 7%). Thereby, the yield of the liquid crystal display panel can be improved.
[0076]
In the above-described embodiment, the formation of the dielectric structure 11 and the formation of the protrusions 10 are performed in the same process, so that the above-described liquid crystal display device can be formed with almost no increase in the number of processes compared to the conventional method.
Note that the above-described dielectric structure 11 may protrude so as to slightly overlap the pixel electrode 8.
(Second Embodiment)
In the first embodiment, in one pixel region, the dielectric structure 11 covers only the gate bus line 2, the drain bus line 5, and the pixel electrode 8 for driving the pixel electrode. It has become.
[0077]
The arrangement region of the dielectric structure is not limited thereto, and for example, as shown in FIG. 20, a dielectric structure 11a may be provided between adjacent pixel electrodes 8. The structure is such that the periphery of the pixel electrode 8 and the gate bus line 2 and drain bus line 5 are covered with a dielectric structure 11a.
By adopting such a structure, the flicker rate is further improved than that of the first embodiment.
[0078]
Alternatively, only the gate bus line 2 and the pixel electrode 8 may be covered with a dielectric structure, or only the drain bus line 5 and the pixel electrode 8 may be covered with a dielectric structure. According to these, there was no effect as much as the dielectric structures 11 and 11a shown in FIG. 15 or FIG. 20, but both the common voltage fluctuation and the flicker rate were good.
Further, in FIG. 14, a dielectric structure may be formed only in a region where the gate bus line 2 and the protrusion 11 intersect and a region in the vicinity thereof, or a region where the drain bus line 5 and the protrusion 11 intersect. A dielectric structure may be formed only in a region in the vicinity thereof. According to these, it is confirmed that the effect of charging of the protrusion 10 is reduced as compared with the first embodiment, and the change in orientation between the gate bus line 2 and the pixel electrode 8 in the vicinity of the protrusion 10 can be suppressed. It was done. In this case, the flicker rate was not as effective as the dielectric structure shown in FIG. 15 or 20, but the common voltage fluctuation and the flicker rate were good.
[0079]
The above is the embodiment in which the dielectric structure is formed on the first glass substrate 1 side, but it may be formed on the second glass substrate (counter substrate) 12 side. For example, as shown in FIG. 21, the dielectric structure 11b is formed on the common electrode 15 at the position where the dielectric structures 11 and 11a shown in FIG. 15 or 20 face each other, and the alignment film 17 is formed thereon. A structure to be formed may be adopted. In this case, there is no effect of completely fixing the floating capacitance Cgs between the gate and the pixel electrode and the floating capacitance Cds between the drain and the pixel electrode, but the effect of minimizing the orientation change can be expected due to the effect of narrowing the cell gap. . Such an effect of narrowing the cell gap is conspicuous as in the first embodiment by setting the thickness of the dielectric structure 11b to 1 μm or more.
[0080]
In the above-described example, the dielectric structure is formed of only a resist, for example. In addition, as shown in FIG. 22, each of the red, green, and blue color filters 13R, 13G, and 13B is connected to a boundary portion between pixels. The overlapping portion may be applied as a part of the dielectric structure on the counter substrate side. Thereby, the liquid crystal can be removed from the portion where the orientation change is suppressed in the region other than the pixel electrode 8, and the capacitance change accompanying the orientation change does not occur, so the same effect as the first embodiment can be obtained.
[0081]
Note that the portions where the color filters 13R, 13G, and 13B of different colors are overlapped may be only between the gate bus line 2 and the pixel electrode 8, or only between the drain bus line 5 and the pixel electrode 8. In this case, a dielectric structure may be formed on the first glass substrate 1 so as to face a portion where the color filters 13R, 13G, and 13B of different colors are overlapped.
[0082]
As shown in FIG. 22, a dielectric structure 11c may be formed on the overlapping portion of the red, green, and blue color filters 13R, 13G, and 13B, or may be omitted. Good. However, when the configuration as shown in FIG. 22 is adopted, if the overlapping portion of the color filters 13R, 13G, and 13B and the dielectric structure 11c thereon are used as support pillars to maintain the cell gap, between the substrates, An intervening spacer is unnecessary.
[0083]
Note that the dielectric structure as described above may be formed on both the second glass substrate 12 side and the first glass substrate 1 side, and thereby the cell gap is formed by the dielectric structures that are joined together vertically. You may make it maintain. By adopting an optimum structure, the common voltage fluctuation can be made 10 mV or less, and the flicker rate can be made 2% or less.
[0084]
A structure in which at least one of the protrusion 10 on the first glass substrate 1 side and the protrusion 16 on the first glass substrate 1 side is not provided around the area intersecting the gate bus line 2, or a drain bus line Alternatively, a structure that is not provided around the region intersecting with 5 or a structure that is not provided other than on the pixel electrode 8 may be employed.
In the first embodiment and the second embodiment described above, the protrusion is used as a means for regulating the alignment direction of the liquid crystal, but a slit may be formed in at least one of the pixel electrode and the common electrode instead of the protrusion.
[0085]
The dielectric structures shown in the first and second embodiments are not only applied to the MVA liquid crystal display device, but may be applied to other liquid crystal display devices. In that case, instead of the projections 10 and 16 on either the first glass substrate 1 side or the second glass substrate 12 side, slits extracted from the pixel electrode 8 or the common electrode 15 may be used.
[0086]
The first and second embodiments are based on the following invention.
(1) A liquid crystal having negative dielectric anisotropy is sandwiched between first and second substrates subjected to vertical alignment treatment on the substrate surface, and the alignment of the liquid crystal is substantially vertical when no voltage is applied. In addition, in a liquid crystal display device having an orientation that is substantially horizontal when a predetermined voltage is applied and is inclined when a voltage smaller than the predetermined voltage is applied, the voltage that is provided on the first substrate and is smaller than the predetermined voltage. And a first domain regulating means for regulating an orientation direction in which the liquid crystal is inclined when a liquid crystal is applied, and an orientation in which the liquid crystal is inclined when a voltage smaller than the predetermined voltage is applied. The second domain restricting means for restricting the direction and the first domain restricting means are provided at least on the electrode of the first substrate, and a part of the contact surface of the first substrate with the liquid crystal The liquid crystal on the slope And a plurality of first bus lines formed at intervals on a surface of the first substrate or the second substrate on the side of sandwiching the liquid crystal. A plurality of second bus lines crossing the first bus line and spaced above the first bus line, the first bus line and the second bus line And a portion corresponding to at least a part of a region between the pixel electrode and the first bus line, wherein the first substrate and the second substrate A liquid crystal display device comprising: the protrusions formed on at least one of the protrusions and a different dielectric structure.
[0087]
(2) The liquid crystal display device according to (1), wherein the protrusion and the dielectric structure are formed of the same material and in the same process.
(3) The liquid crystal display device according to (1), wherein the dielectric structure is also formed on at least one of the first bus line and the second bus line.
(4) The second domain regulating means is a protrusion protruding from the liquid crystal layer or a slit partially extracted from the electrode on the second substrate side. The liquid crystal display device described.
[0088]
(5) A red, green, or blue color filter is formed facing the pixel electrode, and the dielectric structure is configured by the color filter overlapped in a region not facing the pixel electrode. The liquid crystal display device according to (1).
(6) The region that does not face the pixel electrode is at least one of the first bus line and the pixel electrode, or the second bus line and the pixel electrode. ) Liquid crystal display device described in the above.
[0089]
(7) The liquid crystal display device according to (5), wherein another dielectric structure is overlaid on the region where the color filter is overlaid.
(8) The liquid crystal display device according to (5), wherein another dielectric structure is formed facing the region where the color filters are overlaid.
(9) The liquid crystal display device according to (1), wherein the dielectric structure is formed up to a region protruding from a part of the pixel electrode.
(10) At least one of the first domain regulating unit and the second domain regulating unit is not provided outside the pixel electrode, or at least one of the first bus line and the second bus line (1) The liquid crystal display device according to (1), wherein the liquid crystal display device is not provided around a region intersecting
(11) The liquid crystal display device according to (1), wherein the dielectric structure has a thickness of 1 μm or more.
(Third embodiment)
FIG. 23 is a cross-sectional view showing a third embodiment of the present invention, which has the same structure as that of the first embodiment except for pixel electrodes, protrusions and dielectric structures. 23, the same reference numerals as those in FIG. 10 denote the same elements.
[0090]
In FIG. 23, a gate bus line 2 and a capacitor bus line 3 are formed on a first glass substrate (TFT substrate) 1. Further, a drain bus line 5 and a thin film transistor (TFT) 6 are formed on the gate insulating film 4 covering the bus lines 2 and 3 as in the first embodiment.
The drain bus line 5 and the thin film transistor (TFT) 6 are covered with a protective insulating film 7, and a pixel electrode 30 is formed on the protective insulating film 7. As shown in FIG. 24, the pixel electrode 30 is disposed in a region surrounded by the gate bus electrode 2 and the drain bus line 5.
[0091]
In the pixel electrode 30, slits 30 a and 30 b are extracted from the edge region of the pixel electrode 30 existing on the capacitor bus line 3 in a V shape, and the pixel electrode 30 is parallel to the slits 30 a and 30 b. Other slits 30c and 30d are formed. The slit width is, for example, 10 μm.
These slits (domain regulating means) 30a to 30d divide the pixel electrode 30 into five regions. These regions are electrically connected to each other through a connecting portion 30n that divides the slits 30a to 30d into a plurality of portions.
[0092]
Further, a predetermined width w from the edge of the pixel electrode 30 to the inside.₁For example, in the range of 4 μm, a connecting portion 30e for electrically connecting five regions divided by the slits 30a to 30d is secured, and the end portions of the slits 30a to 30d are divided by the connecting portion 30e. Yes.
The connecting portion 30e serves as an orientation control means for forming an orientation singularity with s = -1. Incidentally, according to the alignment control means having the alignment singularity of s = −1, as shown in FIG. 25 (a), the liquid crystal molecules L in one direction in the two directions perpendicular to the point O become the point O. The liquid layer molecules L in the other direction are oriented opposite to the point O. Further, the liquid crystal molecules L in a direction inclined by 45 degrees with respect to those directions are directed in different directions.
[0093]
According to the alignment control means for forming the alignment singularity of s = + 1 as described in the following embodiment, all the liquid crystal molecules L around the point O are in the point O as shown in FIG. Oriented toward
The pixel electrode 30 as described above is connected to the TFT 26 and further covered with the alignment film 9 as shown in FIG.
[0094]
As shown in FIG. 23, on the surface of the second glass substrate (counter substrate) disposed to face the pixel electrode 30, as in the first embodiment, the color filter 13 and the black matrix are provided. 14, a common electrode 15, a dielectric protrusion (domain regulating means) 31, and an alignment film 17 are formed in this order.
As the alignment films 9 and 17 on the first and second glass substrates 1 and 12, for example, a trade name JALS-684 manufactured by JSR Corporation is used.
[0095]
As shown by the two-dot chain line in FIG. 24, the dielectric protrusions 31 are formed in a zigzag so as to face the positions passing between the slits 30a to 30d of the pixel electrode 30, as in the first embodiment. Yes. The protrusion 31 is made of, for example, a photosensitive acrylic resin PC-335 (trade name made by JSR). The pattern of the protrusion 31 is formed by spin-coating the resin on the substrate, baking it at 90 ° C. for 20 minutes, selectively irradiating with ultraviolet rays using a photomask, and developing an organic alkaline developer (TMAHO, 2 wt. %) And baked at 200 ° C. for 60 minutes. The protrusion 31 had a width of 10 μm and a height of 1.5 μm.
[0096]
The 1st glass substrate 1 and the 2nd glass substrate 12 which have the above structures were bonded together, and the liquid crystal was inject | poured between them, and the liquid crystal panel was created. Note that the product name MJ961213 manufactured by Merck & Co., Inc. was used as the liquid crystal material.
In the liquid crystal display device having the above-described configuration, the slits 30a to 30d of the pixel electrode 30 serving as the domain regulating means are not present on the edge of the pixel electrode 30 and the periphery thereof, and a singular point for alignment control is formed there. did. As a result, the difference in the domain state between white when the pixel display is made to respond from black to white and white when the pixel display is made to respond from halftone to white can be reduced to an inconspicuous level. The change could be reduced to a level where it cannot be recognized as an afterimage.
[0097]
The liquid crystal molecule domain regulating means is not limited to the linear slit in the pixel electrode. For example, a structure in which a linear dielectric protrusion is provided on the pixel electrode instead of the slit may be employed. In this case, when a divided portion that does not intersect with the edge of the pixel electrode is formed in the projection, an alignment singularity of s = −1 is formed at the edge portion of the pixel electrode on the extension line of the projection.
[0098]
Further, instead of forming the protrusion 31 on the common electrode 15 formed on the counter substrate 12 side, a slit may be formed in the common electrode 15.
(Fourth embodiment)
In the third embodiment, the alignment singularity of s = −1 is formed at a portion where the structure or slit formed on the pixel electrode and the edge of the pixel electrode intersect. In this embodiment, however, the pixel electrode A structure that is formed on a substrate opposite to the substrate having a structure or a structure in which an alignment singularity of s = + 1 is formed at a portion where the slit and the edge of the pixel electrode intersect will be described.
[0099]
FIG. 26 is a plan view showing a pixel electrode of a liquid crystal display device according to a fourth embodiment of the present invention, and FIG. 27 is a sectional view taken along line VII-VII.
In FIG. 26, slits 33a and 33b are extracted from the edge region of the pixel electrode 33 existing on the capacitor bus line 3 in a V shape, and the region near the gate bus line 2 in the pixel electrode 30 Other slits 33c and 33d parallel to the slits 33a and 33b are further formed. The slit width is, for example, 10 μm. The slits 33 a to 33 d are also formed at the edge of the pixel electrode 33. The slits 33a to 33d are divided by a connecting portion 33e.
[0100]
Further, in the dielectric protrusion (structure) 34 formed on the counter substrate 12 side, as shown in FIGS. 26 and 27, the portion 34a facing the edge of the pixel electrode 33 is made higher than the other regions. Thus, an alignment singularity near the edge of the pixel electrode 33 was formed at s = + 1. Of the protrusion 34, the height of the portion facing the edge of the pixel electrode 33 was 2.5 μm, and the height of the other portion was 1.5 μm.
[0101]
The protrusion 34 is formed using the same constituent material as that of the protrusion 31 of the third embodiment. First, a pattern of the protrusion 34 is formed on the common electrode 15 with a height of 1.5 μm, and the pixel electrode is further formed. A protrusion 34 a having a height of 1.0 μm is selectively stacked in a region facing the edge 33.
As described above, since the portion facing the edge of the pixel electrode 33 in the protrusion 34 on the counter substrate 12 side is made higher than the other portion, the edge of the pixel electrode 33 is formed as shown in FIGS. = + 1 orientation singularity is formed. As a result, the influence of the alignment of the liquid crystal molecules L at the edge of the pixel electrode 33 on the inner liquid crystal molecules of the pixel electrode 33 is blocked by the alignment singularity, and the halftone display is changed to the white display. The occurrence of afterimages during shooting is prevented.
[0102]
In the case where a slit is formed in the common electrode 15 of the counter substrate 12 instead of the protrusion 34, the same effect can be obtained even if the slit is divided at a portion facing the pixel electrode 33.
By the way, the combination of the TFT substrate of the third embodiment and the counter substrate of the fourth embodiment is the best structure. That is, the linear slits or protrusions formed on the TFT substrate side are divided so as not to intersect the edge of the pixel electrode, and further, the linear slits in the common electrode on the counter electrode side are not intersected with the pixel electrode. It is preferable that the portion facing the edge of the pixel electrode among the linear projections on the counter electrode side is made thicker than others.
(Fifth embodiment)
In the third embodiment, the bent part of the slit formed on the pixel electrode, that is, the intersection of the extension lines of the slits in two directions is aligned with the edge of the pixel electrode. It may be shifted to.
[0103]
FIG. 28 is a plan view showing a pixel electrode and its periphery of a liquid crystal display device according to a fifth embodiment of the present invention.
In FIG. 28, the bent portion 35 b of the slit 35 a extracted from the pixel electrode 35 is formed so as to recede from the edge of the pixel electrode 35 to the inside thereof. The distance from the bent portion 35b to the edge of the pixel electrode 35 is, for example, 4 μm, and the width of the slit 35a is 10 μm.
[0104]
On the counter substrate 12 side, a protrusion 36 is formed at a position passing between the slits 35 as in the first embodiment.
According to this, the influence of the electric field due to the edge of the pixel electrode 35 on the bent portion 35b of the slit 35a can be reduced, and the occurrence of an afterimage is suppressed.
In FIG. 28, the pixel electrode 35 is provided with a slit, but when a dielectric protrusion is formed on the pixel electrode 35 instead of the slit as in the first embodiment, the protrusion is bent. By retreating the portion inward from the edge of the pixel electrode, the influence of the electric field due to the edge of the pixel electrode 35 on the bent portion of the protrusion can be reduced, and the effect of suppressing the occurrence of an afterimage can be obtained.
[0105]
In addition, as a shape of the dielectric protrusion 37 formed as the orientation control means on the counter substrate 12, for example, as shown in FIG. 29, it is bent in a region facing the pixel electrode, and the bent portion of the pixel electrode 38 is Even if they are shifted from the edge to the inside, the influence of the electric field by the edge of the pixel electrode 38 on the bent portion can be reduced, and an afterimage suppressing effect can be obtained. In this case, the width of the projection 37 is, for example, 10 μm, and the distance between the bent portion and the edge of the pixel electrode 38 is, for example, 4 μm.
[0106]
Note that it is conceivable to form a slit in the common electrode 15 shown in FIG. 23 instead of the dielectric protrusion 37 as the orientation control means on the counter substrate 12. However, since the color filter 13 is usually formed under the common electrode 15, it is not preferable from the viewpoint of accuracy and reliability to form a slit in the common electrode 15.
In FIG. 29, the bent portions (intersections) of the slits 38 a and 38 b formed in the pixel electrode 38 extending in two directions exist outside the pixel electrode 38. This eliminates the influence on the bent part, reduces the occurrence of an alignment state different from the original alignment control by protrusions or slits, and eliminates the afterimage when changing from halftone display to white display. it can.
(Sixth embodiment)
FIG. 30 (a) is a plan view showing a pixel electrode and its periphery of a liquid crystal display device according to a sixth embodiment of the present invention.
[0107]
In FIG. 30A, the intersection of the first and second slits 40a and 40b formed in a V shape near the center of the pixel electrode 40 is separated from the edge by a slit 40e parallel to the edge of the pixel electrode 40. A structure that connects inside is adopted. The distance of the gap 40g between the slit 40e and the edge of the pixel electrode 40 is 4 μm, for example.
[0108]
In addition, third and fourth slits 40 c and 40 d are formed in the pixel electrode 40 near the gate bus line 2.
The first to fourth slits 40a to 40d are divided at a plurality of locations by a connecting portion 40f. Accordingly, the pixel electrode 40 is divided into five regions A to E by the first to fourth slits 40a to 40d, and these regions A to E are electrically connected by the connecting portion 40f.
The region C divided by the first and second slits 40a and 40b is electrically and structurally opposed to the storage capacitor forming electrode (capacitor bus line) 3. Further, at least two electrical connection paths are electrically opposed to the storage capacitor forming electrode 3.
[0109]
As a result, the connection between the region B and the region D of the pixel electrode 40 has two systems, a route B-C-D and a route B-D, as shown in FIG. When the region C of the pixel electrode 40 and the storage capacitor forming electrode 3 are short-circuited, the electrical connection between B-C and C-D is disconnected by laser irradiation to the connecting portion 40f, Since the four regions A, B, D, and E of the pixel electrode 40 are electrically connected through the continuous connecting portion 40f and the gap 40g, the liquid crystal molecules in most regions other than the region C can be driven. become.
[0110]
The pixels that can be driven except for the region C have slightly different display characteristics compared to a normal state in which the storage capacitor forming electrode 3 and the region C of the pixel electrode 40 are not short-circuited. Depending on the number of pixels in the state and where they occur, the level of the display defect is cleared, so that the yield of the TFT substrate can be improved. This is achieved by a structure in which a plurality of regions of the pixel electrode divided by the slits are connected by edge portions of the pixel electrode, which is different from the conventional structure.
[0111]
If the pixel electrode 40 is divided into at least three regions by, for example, the first and second slits 40a and 40b, such a yield improving effect can be obtained.
Next, the change of the domain on the slit when the present invention is applied will be described with reference to FIG.
[0112]
  First, as shown in FIG. 31 (a), when the black display is changed to the white display, the number of domains on the slit 40a divided by the connecting portion is as follows.1-8It is eight. Also, according to FIG. 31 (a), compared to FIG. 9 (a) showing the prior art.7 and 8The number of domains increases. This is because a singular point of an orientation vector of s = −1 is formed at the edge of the pixel electrode.
[0113]
  When the display changes from black display to white display through halftone display, as shown in FIG.6 and 8Domains are connected7Domain disappears. That is, the domain change on the slit is suppressed to a very slight level near the edge of the pixel electrode as compared with FIG. The third to sixth embodiments described above are based on the following invention.
(1) In a vertical alignment type liquid crystal display device in which a linear structure or a linear slit composed of a plurality of structural units is provided on at least one of a pair of substrates having electrodes to control liquid crystal alignment during voltage application Alignment control means for liquid crystal molecules to form an alignment singularity of s = -1 at a portion where the structure on the electrode or the slit in the electrode intersects with the edge of the pixel electrode on one of the substrates A liquid crystal display device comprising:
[0114]
(2) The electrode is a pixel electrode or a common electrode.
(3) The liquid crystal display device according to (1), wherein the linear structure is formed on a pixel electrode or a common electrode.
(4) The liquid crystal display device according to (1), wherein the slit is not formed at the edge of the pixel electrode on the extension of the slit.
[0115]
(5) The liquid crystal display device according to (1), wherein the structure is divided above or above the edge of the pixel electrode.
(6) In a vertical alignment type liquid crystal display device in which a linear structure or a linear slit composed of a plurality of structural units is provided on at least one of a pair of substrates having electrodes to control liquid crystal alignment during voltage application. The liquid crystal molecules form an alignment singularity of s = + 1 at a portion where the structure or the slit formed on one side of the substrate intersects with the edge of the pixel electrode formed on the other side of the substrate. A liquid crystal display device comprising: an alignment control means.
[0116]
(7) A vertical alignment type that controls the liquid crystal alignment during voltage application by providing a linear structure or a linear slit composed of a plurality of structural units with bent portions on at least one of a pair of substrates having electrodes. In this liquid crystal display device, the structure on one of the substrates having a pixel electrode or the bent portion of the slit is off the edge of the pixel electrode.
[0117]
(8) A vertical alignment type that controls the liquid crystal alignment during voltage application by providing a linear structure or a linear slit composed of a plurality of structural units with bent portions on at least one of a pair of substrates having electrodes. In this liquid crystal display device, the structure or the bent portion of the slit disposed on the other substrate facing the pixel electrode on one of the substrates is not disposed on the edge of the pixel electrode. A liquid crystal display device characterized by the above.
[0118]
(9) a storage capacitor forming electrode formed on the first substrate, an active element formed on the first substrate, and formed on the first substrate connected to the active element; And a pixel electrode divided into at least three regions by a slit, and electrical connection from one of the three regions of the pixel electrode to another region is made through a plurality of different regions through which the region passes. A thin film transistor substrate having a path.
(10) The thin film transistor substrate according to (9), wherein at least two of the paths of the electrical connection are electrically opposed to the storage capacitor forming electrode.
(11) The thin film transistor substrate according to (10), wherein an area facing the storage capacitor electrode is different for each path facing the storage capacitor forming electrode.
(12) The thin film transistor substrate according to (12), wherein the thickness of the dielectric layer in the region facing the storage capacitor forming electrode is different for each path facing the storage capacitor forming electrode.
(13) The thin film transistor substrate according to any one of (10) to (12), wherein the storage capacitor has a different size for each path facing the storage capacitor forming electrode.
(14) A liquid crystal display device comprising the thin film transistor substrate according to any one of (9) to (13).
(15) The liquid crystal display device according to any one of (1) to (8), comprising the thin film transistor substrate according to any one of (9) to (13).
[0119]
【The invention's effect】
As described above, according to the present invention, the region between the gate bus line (first bus line) and the pixel electrode intersecting each other, or the region between the drain bus line (second bus line) and the pixel electrode. Since the dielectric structure is disposed in the dielectric structure, the dielectric constant between the pixel electrode and the bus line is fixed by the dielectric structure, and the stray capacitance variation between them can be suppressed. In addition, since the dielectric structure is also formed on the bus line, the liquid crystal layer on the dielectric structure is thinned so that the liquid crystal molecules of the liquid crystal layer are difficult to move from the vertical orientation and float. Capacitance fluctuation can be made very small. In addition, since the stray capacitance above the bus line has a larger component fixed by the dielectric structure, fluctuations in the stray capacitance can be reduced.
[0120]
As described above, when the fluctuation of the stray capacitance is suppressed, the pixel potential becomes constant and flicker can be prevented. In addition, it is possible to increase the aperture ratio by narrowing the width of the capacitor bus line for suppressing the fluctuation of the capacitor.
In addition, according to the present invention, in a display method in which the liquid crystal alignment is controlled by a structure or slit provided on the substrate, liquid layer molecules are s in the portion intersecting the pixel electrode on the extension line of the structure or slit. Response characteristics can be improved by forming an orientation singularity such that −1 or s = + 1.
[0121]
Furthermore, in the present invention, as the electrical connection path of the pixel electrode, two systems of the path through the storage capacitor forming electrode and the region where the capacitor is formed and the path not through the storage capacitor forming electrode are provided. When an electrical short circuit occurs between the pixel electrode and the pixel electrode, by electrically disconnecting the region forming the capacitor from the other region, the other region can be used as a region where the liquid crystal molecules can be driven, The production yield of the TFT substrate can be improved.
[Brief description of the drawings]
FIG. 1 is a diagram showing a change in an image according to a viewing angle of a conventional TN type LCD.
FIG. 2 is a diagram illustrating a driving state of a conventional VA liquid crystal display.
FIG. 3 is a diagram showing the effect of alignment division in a conventional VA system.
FIG. 4 is a diagram showing various methods of conventional alignment division.
FIG. 5 is a plan view of a conventional MVA pixel unit.
6 is a cross-sectional view taken along the line II of FIG. 5 showing a conventional MVA pixel portion.
FIG. 7 is a plan view of a conventional MVA pixel unit.
FIG. 8 is a diagram illustrating an off state and an on state of a conventional MVA liquid crystal panel.
FIG. 9 is a diagram showing a change in the alignment direction of liquid crystal molecules of a conventional MVA liquid crystal panel.
FIG. 10 is a diagram showing a direction of alignment of liquid crystal molecules in a conventional MVA halftone display.
FIG. 11 is a diagram illustrating combinations of alignment directions of liquid crystal molecules on slits on a conventional MVA pixel electrode.
FIG. 12 is a diagram showing the alignment direction of liquid crystal molecules in the vicinity of the edge of a pixel electrode after a change from halftone display to white display in a conventional VA liquid crystal display.
FIG. 13 is a plan view showing a cut state of a pixel electrode in the conventional VA method and an equivalent circuit diagram thereof.
FIG. 14 is a plan view of a pixel region showing the arrangement of domain regulating means according to the first embodiment of the present invention.
FIG. 15 is a plan view of a pixel region in which a dielectric structure and protrusions according to the first embodiment of the present invention are formed.
16 is a cross-sectional view taken along the line II-II of FIG. 15 in the pixel region of the first embodiment of the present invention.
17 is a cross-sectional view taken along line III-III in FIG. 15 in the pixel region according to the first embodiment of the present invention.
18 is a cross-sectional view taken along the line VI-VI in FIG. 15 in the pixel region according to the first embodiment of the present invention.
FIG. 19 is a cross-sectional view showing the operation in the pixel region of the first embodiment of the present invention.
FIG. 20 is a plan view showing a pixel region of a liquid crystal display device according to a second embodiment of the present invention.
21 is a cross-sectional view taken along the line VV of FIG. 20 showing a pixel region of the liquid crystal display device of the second embodiment of the present invention.
22 is a cross-sectional view taken along the line VI-VI of FIG. 20 showing the TFT and the periphery thereof according to the second embodiment of the present invention.
FIG. 23 is a cross-sectional view showing a pixel region of a liquid crystal display device according to a third embodiment of the present invention.
FIG. 24 is a plan view showing a pixel region of a liquid crystal display device according to a third embodiment of the present invention.
FIG. 25 is a diagram showing the alignment direction of liquid crystal molecules at an alignment singularity according to an embodiment of the present invention.
FIG. 26 is a plan view showing a pixel region of a liquid crystal display device according to a fourth embodiment of the present invention.
27 is a cross-sectional view taken along line VII-VII in FIG. 26 in the pixel region in the liquid crystal display device according to the fourth embodiment of the present invention.
FIG. 28 is a plan view of a pixel region of a liquid crystal display device according to a fifth embodiment of the present invention.
FIG. 29 is a plan view showing another example of the pixel region of the liquid crystal display device according to the fifth embodiment of the present invention.
FIG. 30 is a plan view of a pixel region of a liquid crystal display device according to a sixth embodiment of the present invention.
FIG. 31 is a diagram showing an example of the effect of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... 1st glass substrate (TFT substrate), 2 ... Gate bus line, 3 ... Storage capacity formation electrode (capacitance bus line), 4 ... Gate insulating film, 5 ... Drain bus line, 6 ... TFT, 7 ... Protection insulation Membrane, 8 ... Pixel electrode, 9 ... Alignment film, 10 ... Projection, 11, 11a, 11b, 11c ... Dielectric structure, 12 ... Second glass substrate (counter substrate), 13, 13R, 13G, 13B ... Color filter, 14 ... black matrix, 15 ... counter electrode, 16 ... projection, 17 ... alignment film, 18 ... liquid crystal, 30, 33, 35, 38 ... pixel electrode, 31, 34, 36, 37 ... structure.

Claims (3)

In a vertical alignment type liquid crystal display device in which a linear slit is provided in a pixel electrode formed on one of a pair of substrates to control liquid crystal alignment during voltage application,
The linear slit is formed by dividing into a plurality of portions, and a connection portion is formed between an end of the slit closest to the edge of the pixel electrode and the edge of the pixel electrode among the divided slits. By providing the liquid crystal display device, a liquid crystal molecule forms an alignment singularity of s = −1 at the connection portion . In a vertical alignment type liquid crystal display device in which a linear structure is provided on one of a pair of substrates having electrodes to control liquid crystal alignment during voltage application,
By providing a protrusion having a height higher than that of the other portion on the structure at a portion where the edge of the pixel electrode provided on the other of the pair of substrates and the structure intersect, the protrusion A liquid crystal display device characterized in that liquid crystal molecules form an alignment singularity of s = + 1 . In a vertical alignment type liquid crystal display device in which a linear slit is provided on one of a pair of substrates having electrodes to control liquid crystal alignment during voltage application,
By providing a dividing portion where the slit is divided at a portion where the edge of the pixel electrode provided on the other of the pair of substrates intersects with the extension line of the slit, the liquid crystal molecules are s = + 1 at the dividing portion. A liquid crystal display device characterized by forming an alignment singularity of

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