JP2000206560A - Active matrix type liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a display defect such as cross talk and to obtain high display quality by constituting so that a length of a first part superimposing only on an edge side of a first pixel electrode side of a shield electrode is different from that of a second part superimposing only on the edge side of a second pixel electrode side. SOLUTION: The shield electrode 17 is formed by a shifted area 17B to one pixel electrode 162 side and the shifted area 17A to the adjacent pixel electrode 161 side for a central axis 13a of a signal line 13 so that the effects of one pixel electrode 162 and two adjacent signal lines 13, 13 become equal. Then, the lengths L1, L2 of two areas of the shield electrode 17 are made so as to become L1<L2 as an example. By such a constitution, the high display quality reducing a difference between capacity between the signal line and the pixel electrode and the capacity between the adjacent signal line and the pixel electrode, and eliminating a picture quality defect such as the cross talk and luminance unevenness is obtained while suppressing the increase of the load capacity of the signal line by light shielding a liquid crystal alignment defect area with wiring.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an active matrix type liquid crystal display device.

[0002]

2. Description of the Related Art In recent years, while having a high density and a large capacity,
Practical use of liquid crystal display devices capable of obtaining high-performance and high-definition display has been promoted. There are various types of this liquid crystal display device. Among them, the liquid crystal display devices intersect with each other because of small crosstalk between adjacent pixels, high-contrast display, transmission-type display, and easy area enlargement. The thin film transistor (T) is provided in a plurality of regions which are partitioned by a plurality of scanning lines and a plurality of signal lines provided in
An active matrix type liquid crystal display device including an array substrate in which pixel electrodes each having FT) as a switching element are provided in a matrix is widely used.

[0003] A pixel desirably has a structure with a high aperture ratio. As a structure with which a high aperture ratio can be obtained, there is a wiring BM (black matrix) structure in which a signal line and a pixel electrode are overlapped. This structure has a configuration in which a pixel electrode is overlapped on a signal line via an insulating layer so that the wiring also functions as a light shield, and a parasitic capacitance between the signal line and the pixel electrode is large.

[0004] The display quality of a TFT liquid crystal display depends on the parasitic capacitance between a signal line and a pixel electrode. The influence of the parasitic capacitance is caused by forming an auxiliary capacitance or shielding a shield electrode fixed at a constant potential with an interlayer insulating film. This can be suppressed by arranging the pixel electrode and the signal line so as to overlap with each other via the film.

[0005]

Further, it is known that, in the wiring BM structure, a liquid crystal misalignment region is generated near the end of the signal line on the downstream side in the rubbing direction. Is occurring and causing a defect. Therefore, it is necessary to increase the overlap width of the signal line and the pixel electrode in order to shield the liquid crystal misalignment region with the wiring, which causes a problem that the parasitic capacitance between the signal line and the pixel electrode increases.

In order to suppress the increase in the parasitic capacitance between the signal line and the pixel electrode as much as possible, there is a method in which the overlap width of the signal line and the pixel electrode is increased only in the portion where the liquid crystal alignment failure occurs. However, according to this method, the balance between the capacitance between the signal line and the pixel electrode and the capacitance between the adjacent signal line and the pixel electrode is lost, so that display defects such as crosstalk are likely to occur.

An object of the present invention is to improve such a problem and to provide an active matrix type liquid crystal display device having high display quality.

[0008]

According to the present invention, there is provided an opposing substrate having a common electrode, an array substrate sandwiching a liquid crystal layer together with the opposing substrate, a plurality of scanning lines formed on the array substrate, and the scanning line. A plurality of signal lines formed to intersect with each other, a thin film transistor formed near an intersection of the scanning line and the signal line, and a thin film transistor formed in each region surrounded by the scanning line and the signal line. A plurality of pixel electrodes including a first pixel electrode and a second pixel electrode adjacent to each other; an auxiliary capacitance line formed to intersect the signal line; And the signal line and the shield electrode also function as a light shield, and the width of the light shield and the first pixel electrode overlap, and the width of the light shield and the second pixel electrode. Liquid crystal display devices with different overlapping widths Oite, the shield electrode has a first portion overlapping only the edge of the first pixel electrode side of the edge of the signal line, the second of edge of the signal line
A second portion overlapping only the edge on the pixel electrode side,
A liquid crystal display device characterized in that the first portion and the second portion have different lengths.

According to the present invention, the capacitance between the signal line and the pixel electrode and the capacitance between the adjacent signal line and the pixel electrode are reduced while suppressing an increase in the load capacitance of the signal line caused by shielding the defective liquid crystal alignment region with wiring. An active matrix liquid crystal display device with a small difference in capacitance and high display quality can be realized.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view of an array substrate of an active matrix type liquid crystal display device according to a first embodiment of the present invention, FIG. 2 is a partially enlarged view thereof, and FIG. 3 is a sectional view taken along line AB in FIG. FIG. 4 is a sectional view, and FIG.
FIG. 2 shows a partial cross-sectional view of the liquid crystal display device along the EFGH line.

In FIG. 1, a plurality of scanning lines 12 arranged in parallel in a row direction on an insulating substrate 11 made of transparent glass.
And a plurality of signal lines 13 arranged in parallel in the column direction so as to be orthogonal to the above. A storage capacitor line 14 is provided between these scanning lines 12 so as to be orthogonal to the signal line 13.
Is provided. A TFT 15 having an active layer of polysilicon or amorphous silicon is arranged at the lower end in the drawing near the intersection of the scanning line and the signal line.
Are arranged in the region surrounded by.

The edge of the signal line 13 and one pixel electrode 162
At least a part of the peripheral edge of the notch 16
a, the auxiliary capacitance line 14 disposed so as to overlap the 16b
Of the pixel electrode 161 intersects the signal line within one pixel pitch, and the edge of the peripheral portion of the adjacent pixel electrode 161 has a width b in FIG. They are arranged to overlap. In FIG. 2, an arrow 38a indicates an alignment vector of the alignment film 38 formed to cover the pixel electrode 162. In the following figures, the orientation vector is omitted. Further, the signal line 13 and the shield electrode 17 also serve as a light shield, and the liquid crystal misalignment region N which is on the upper side of the alignment vector.
Only at the location where A occurs (the portion along the signal line on the left side of the pixel in FIG. 2), the width a where the light shields (13, 17) and the pixel electrode 162 overlap is increased. The shield electrode 17 is shifted from the central axis 13a of the signal line 13 by one pixel 162 so that the influence of the two signal lines 13 adjacent to one pixel electrode 162 becomes equal.
The shield electrode 14 is formed by adjusting the lengths L1 and L2 of the region of the shield electrode 14 with B and the shift region 17A toward the adjacent pixel 161 side. For example, L1 <L2. Notch 1 at the edge of the pixel electrode corresponding to each shift area
6a and 16a are provided, in which the signal 13 is not superimposed. Therefore, an increase in the signal line capacitance due to hiding the liquid crystal misalignment region and an increase in the capacitance between the signal lines 13 and 13 and the pixel electrode 162 are minimized, and the TFT 15 is connected to the pixel electrode 162. Signal line 13
And the effect of the unconnected signal line 13 is substantially the same, so that the effect of the parasitic capacitance between the signal line and the pixel electrode can be minimized.

A method of manufacturing the above active matrix type liquid crystal display device will be described below with reference to FIG. First, an a-Si film of about 50 nm is deposited on a transparent insulating substrate 11 such as a high melting point glass substrate or a quartz substrate by a CVD method or the like. After furnace annealing at 450 ° C. for 1 hour, X
Irradiation with an eCl excimer laser is performed to polycrystallize a-Si. After that, the polycrystalline Si was patterned by a photoetching method to form a semiconductor layer 20 to be a channel layer of the TFT 15 in the display region. Next, a SiO film to be a gate insulating film 21 is formed on the entire surface of the insulating substrate 11 by CVD.
An x film is deposited on the order of 100 nm to 150 nm. Subsequently, on the gate insulating film 21, Ta, Cr, Al, Mo,
Simple substance such as W or Cu, or a laminated film or alloy film thereof
Then, the gate electrode 22, the gate line 12, and the auxiliary capacitance electrode 14 were formed by photoetching.

Thereafter, using the gate electrode 22 as a mask, impurities are implanted by ion implantation or ion doping to form a drain electrode 23 and a source electrode 24 of the TFT 15 in the pixel portion. For the impurity implantation, for example, phosphorus was implanted at a high concentration of PH ₃ / H ₂ at an acceleration voltage of 80 keV and at a dose of 5 × 10 15 atoms / cm ² . Then, impurities are activated by annealing the substrate. Thereafter, an Nch-type LDD (Lightly D
The impurities are implanted to form the O.Drains 25 and 26, and the substrate is annealed to activate the impurities.

Further, an interlayer insulating film SiO ₂ 27 is formed on the entire surface of the insulating substrate from 500 nm to 7
Deposit about 00 nm. Subsequently, a contact hole 28 (FIG. 2) reaching the drain electrode 23 and the source electrode 24 of the TFT 15 in the pixel portion was formed by photoetching. Next, a simple substance such as Ta, Cr, A1, Mo, W, Cu, or a laminated film or an alloy film thereof is formed to a thickness of 500 nm to 700 nm.
and then patterned into a predetermined shape by a photo-etching method to form a signal line 13, an auxiliary capacitance electrode 14,
Various wirings for connection between the drain electrode 23 of the TFT 15 and the signal line 13 were performed. Next, a transparent protective insulating film 29 made of SiNx is formed on the entire surface of the insulating substrate by PECVD, and the first through hole 30 is formed by photoetching.
To form Next, an organic insulating layer 31 is coated on the entire surface from 2 μm to 4 μm.
A second through hole 32 is formed to reach the upper electrode 14 of the auxiliary capacitance element by applying a thickness of about μm. Next, ITO is deposited to a thickness of about 100 nm by a sputtering method, and is patterned into a predetermined shape by a photo etching method.
6 was formed. Through the above steps, the array substrate 33 of the active matrix type liquid crystal display element is obtained.

On the other hand, a counter electrode 36 which is a transparent electrode made of, for example, ITO is formed on a glass substrate, for example, as a transparent insulating substrate 35 by a sputtering method.
The counter substrate 37 is obtained. Subsequently, alignment films 38 and 39 made of low-temperature curing type polyimide are applied by printing on the entire surface of the array substrate 33 and the counter substrate 37 on the pixel electrode 16 side and the counter electrode 36 side, and the alignment is performed when the substrates 33 and 37 face each other. Axis 9
After performing a rubbing process so as to be 0 °, both substrates 33,
37 are assembled facing each other to form a cell, and a nematic liquid crystal layer 40 is injected into the gap and sealed. And both substrates 3
By attaching the polarizing plates 41 and 42 to the insulating substrates 3 and 37 on the side of the insulating substrates 11 and 35, a liquid crystal display device is obtained.

The array substrate 3 thus completed
In No. 3, since the overlap width of the light shields (13, 17) and the pixel electrode 16 is increased only in the region where the liquid crystal alignment failure occurs, the capacity of the signal line 13 is increased, and the capacity between the signal line 13 and the pixel electrode 16 is increased. Can be minimized. In addition, since the capacitance between the signal line 13 and the pixel electrode 16 and the capacitance between the adjacent signal line 13 and the pixel electrode 16 are substantially equal, a good display without image quality defects such as crosstalk and uneven brightness was obtained. Further, the present invention can be variously modified. Hereinafter, the same reference numerals as those in FIG. 1 indicate the same parts.

The second embodiment shown in FIG. 5 is different from the embodiment shown in FIG. 1 in that notches 51 and 52 are provided on both pixel electrode sides of the signal line 130 instead of the shield electrode 17.
This is a case where the shield electrode 17 is formed in a non-linear key shape with respect to the center 17a. Even with such a configuration, the same effect as in the above embodiment can be obtained.

The third embodiment shown in FIG. 6 is a case where the shield electrode 170 is formed so as to extend from the previous gate line 120 in the embodiment shown in FIG. In such a configuration, a storage capacitor line is not required, and a high aperture ratio can be obtained.

In the fourth embodiment shown in FIG. 7, the end portion of the signal line 131 where a liquid crystal misalignment region occurs, that is,
This is a case where the shield electrode 170 is formed to extend from the auxiliary capacitance line 14 only on the wide side where the signal line 131 and the pixel electrode 16 overlap with each other. The length L1 of the shield electrode 170 is determined by two signal lines 131 adjacent to the pixel electrode 16,
The length of the shield electrode is adjusted so that the effects of 132 are equal. Even with such a configuration,
The same effects as in the above embodiment can be obtained. In the fifth embodiment shown in FIG. 8, the first shield electrode 171 and the second shield electrode 172 are provided on both sides of the signal line 13 in the auxiliary capacitance line 1.
4, the length L1 of the first shield electrode 171 and the length L2 of the second shield electrode 172 are different.

FIG. 9 is a cross-sectional view of FIG. 8 taken along the line AB, showing the first shield electrode 171 and the pixel electrode 16.
2 and the overlapping width c of the second shield electrode 172 and the adjacent pixel electrode 161 are different. Even with such a configuration, the same effect as in the above embodiment can be obtained.

Although this embodiment has been described with reference to an active matrix type liquid crystal display device using a polysilicon layer as a semiconductor layer, the present invention relates to an active matrix liquid crystal display device using another semiconductor layer such as an amorphous silicon layer as a semiconductor layer. Similar effects can be obtained for a matrix type liquid crystal display device.

[0023]

As described above in detail, according to the present invention, the overlap width between the light shield and the pixel electrode is increased only in the region where the liquid crystal alignment defect occurs, so that the signal line capacitance is increased and the signal line and the pixel electrode are not increased. The increase in the inter-volume can be minimized. In addition, since the capacitance between the signal line and the pixel electrode can be substantially equal to the capacitance between the adjacent signal line and the pixel electrode, an active matrix liquid crystal display device free from poor image quality such as crosstalk and uneven brightness can be realized. be able to.

[Brief description of the drawings]

FIG. 1 is a plan view of one pixel of an active matrix liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a partially enlarged plan view of FIG.

FIG. 3 is a cross-sectional view of the array substrate taken along a line AB in FIG. 2;

FIG. 4 is a partial cross-sectional view of a liquid crystal display device including an array substrate and a counter substrate corresponding thereto taken along the line DEFGH in FIG. 2;

FIG. 5 is a plan view of one pixel according to a second embodiment of the present invention.

FIG. 6 is a plan view of one pixel according to a third embodiment of the present invention.

FIG. 7 is a plan view of one pixel according to a fourth embodiment of the present invention.

FIG. 8 is a plan view of one pixel according to a fifth embodiment of the present invention.

FIG. 9 is a sectional view of the array substrate taken along line AB in FIG. 8;

[Explanation of symbols]

 12: scanning line 13: signal line 14: storage capacitance line 15: TFT 16, 161 162,...: Pixel electrode 17: shield electrode 33: array substrate 37: counter substrate 40: liquid crystal layer

Continued on the front page F-term (reference) 2H092 JA25 JA29 JA35 JA38 JA39 JA42 JA44 JB13 JB23 JB32 JB33 JB42 JB52 JB57 JB63 JB69 KA04 KA07 KA12 KA16 KA18 KB14 KB23 MA05 MA08 MA14 MA15 MA16 MA18 MA19 MA20 MA27 NA25 QA07

Claims (9)

[Claims] 1. A counter substrate having a common electrode, an array substrate sandwiching a liquid crystal layer together with the counter substrate, a plurality of scanning lines formed on the array substrate, and a plurality of lines formed intersecting the scanning lines. And a thin film transistor formed near the intersection of the scanning line and the signal line, and a first pixel electrode formed in each region surrounded by the scanning line and the signal line and adjacent to each other And a plurality of pixel electrodes including a second pixel electrode, an auxiliary capacitance line formed crossing the signal line, a shield electrode extending from the auxiliary capacitance line and formed along the signal line. A liquid crystal display device, wherein the signal line and the shield electrode also serve as a light shield, and a width at which the light shield and the first pixel electrode overlap is different from a width at which the light shield and the second pixel electrode overlap. In the above, the shield electrode A first portion overlapping only the first pixel electrode side edge of the signal line edge, and a second portion overlapping only the second pixel electrode side edge of the signal line edge. Wherein the first portion and the second portion have different lengths. 2. The signal line has a substantially linear center axis,
The shield electrode formed along the signal line has a portion formed to be shifted toward the first pixel electrode with respect to the central axis and a portion formed to be shifted toward the second pixel electrode. 2. The liquid crystal display device according to claim 1, wherein the liquid crystal display device has a non-linear shape. 3. The signal line has a non-linear shape having a portion shifted toward the first pixel electrode and a portion shifted toward the second pixel electrode with respect to a center axis thereof. 2. The liquid crystal display device according to claim 1, wherein: 4. The signal line according to claim 1, wherein at least a part of said signal line does not overlap with said first pixel electrode in said first part and with said second pixel electrode in said second part. 2. The liquid crystal display device according to 1. 5. The liquid crystal display device according to claim 1, wherein the light shield formed by the signal line and the shield electrode is linear. 6. A plurality of scanning lines formed on a substrate, a plurality of signal lines formed to intersect with the scanning lines, and a thin film transistor formed near an intersection of the scanning lines and the signal lines. A plurality of pixel electrodes formed in respective regions surrounded by the scanning lines and the signal lines; an auxiliary capacitance line formed to intersect with the signal line; And a shield electrode formed along the signal line, the signal line and the shield electrode also function as a light shield, and a width overlapping the light shield and a first pixel electrode of the pixel electrodes. A liquid crystal display device having a light-shielding body and a width overlapping the second pixel electrode adjacent to the first pixel electrode of the sparse electrode, wherein the shield electrode is the first of the edges of the signal line. The second superimposed only on the edge on the two pixel electrode side A liquid crystal display device having a portion. 7. A plurality of scanning lines formed on a substrate, a plurality of signal lines formed crossing the scanning lines, and a thin film transistor formed near an intersection of the scanning lines and the signal lines. A plurality of pixel electrodes formed in respective regions surrounded by the scanning lines and the signal lines; an auxiliary capacitance line formed orthogonal to the signal lines; And a shield electrode formed along the signal line, wherein the signal line and the shield electrode also serve as a light shield, and the width of the light shield and the first pixel electrode overlapping each other; In a liquid crystal display device in which two pixel electrodes have different overlapping widths, a first shield electrode and a second shield electrode extending from the auxiliary capacitance line and formed along the signal line are provided on both sides of the signal line. The first shield electrode having an overlapping portion; And a length of the second shield electrode is different. 8. The liquid crystal display device according to claim 1, wherein the scanning line also serves as the auxiliary capacitance line, and the shield electrode extends from the scanning line. . 9. A plurality of scanning lines formed on a substrate, a plurality of signal lines formed to intersect with the scanning lines, and a thin film transistor formed near an intersection of the scanning lines and the signal lines. A plurality of pixel electrodes formed in respective regions surrounded by the scanning lines and the signal lines; an auxiliary capacitance line formed orthogonal to the signal lines; And a shield electrode formed along the signal line, wherein the signal line and the shield electrode also serve as a light shield, and the width of the light shield and the first pixel electrode overlapping each other; In a liquid crystal display device in which two pixel electrodes overlap with each other in different widths, a notch that does not overlap with the signal line is formed at an edge of a pixel electrode adjacent to a previous signal line, and the notch is covered with the signal line around the notch. A shield electrode is superimposed on the pixel electrode. Liquid crystal display device arranged.