JP3221628B2 - Liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device,
In particular, the present invention relates to a liquid crystal display device having an individual pixel electrode for each pixel.

[0002]

2. Description of the Related Art There are a simple matrix system and an active matrix system for driving a matrix type liquid crystal display device used for an image information processing apparatus such as a video camera recorder and a television. In the active matrix system, a switching active element for preventing a signal input to a pixel electrode at the time of non-selection is provided for each pixel in order to prevent crosstalk between scanning lines caused by a simple matrix system.

FIG. 8 is an equivalent circuit diagram of one pixel of an active matrix type liquid crystal display device. 2 is a liquid crystal layer having a capacitance C _LC, 4 is a storage capacitor having a capacitance C _ADD provided in parallel with the capacitance C _LC, 6 is a MOS transistor as a switching active element, 8 liquid crystal layer 2 is a signal line for supplying the drive voltage V _S to
0 is a gate wiring for controlling the gate voltage V _G of the switching transistor 6.

[0004] In the liquid crystal display device of the above as an active matrix method, the gate of the switching transistor 6 - there are parasitic capacitance C _GD between the drain, when the gate voltage V _G at this influence is switched from the high level to the low level, As shown in FIG. 9, the voltage _VLC applied to the liquid crystal decreases. That is, voltage swing occurs. This voltage drop Δ
The V _LC is expressed by the following equation: [Delta] V _LC = where _{[C GD / (C GD +} C LC + C ADD)] · ΔV G, ΔV G is a variation of the gate voltage V _G.

[0005] If the shake ΔV _LC is large, the image quality deteriorates. Therefore, in order to improve the image quality, it is preferable to increase the storage capacitance _CADD as much as possible to reduce the ΔV _LC . However, if a large storage capacitor _CADD is formed using an opaque material used for the gate wiring and the active layer of the switching transistor for forming the storage capacitor 6, the opaque portion increases and the aperture ratio decreases. When a large storage capacitance C _ADD is used, the charge / discharge capability of the switching transistor 6 needs to be improved, and a large-sized transistor is required. In order to prevent a decrease in aperture ratio, ITO
Although a capacitance configuration made of -ITO is also conceivable, since ITO has high resistance, it is necessary to reduce the resistance with an opaque metal wiring such as Al after all, and this is not a fundamental solution for preventing a decrease in aperture ratio.

Furthermore, the parasitic capacitance is not _{limited to} the above _CGD, but also the capacitance ( _CGP ) between the gate wiring 10 and the pixel electrode 16 and the capacitance ( _CGP ) between the signal wiring 8 and the pixel electrode 16.
_SP ). These parasitic capacitances C _GP and C _SP change the liquid crystal applied voltage V _LC similarly to C _GD, and C _GP is the gate wiring 10
Causes a change reflecting the potential change of the signal line 8, and C _SP causes a change reflecting the potential change of the signal wiring 8.

[0007] In the order corresponding to a television or the like of the high-definition system high definition and high gradation minute of the display is required pixel progresses, is increasingly prominent problem of deterioration of display characteristics based on C _GP and C _SP It is becoming.

In order to avoid such a problem, if a space between the gate wiring and the pixel electrode and a space between the signal wiring and the pixel electrode are increased, a considerable area is required. Not suitable.

In view of the above, the present invention reduces the parasitic capacitance between the gate wiring and the pixel electrode or between the signal wiring and the pixel electrode and improves the aperture ratio in an active matrix type liquid crystal display device. Accordingly, it is an object of the present invention to enable high-definition and high-gradation excellent display.

Another object of the present invention is to provide a conductive layer which has a matrix wiring group, a plurality of active elements, and a liquid crystal layer and is maintained at a predetermined potential around pixel electrodes provided individually for each pixel. The present invention provides a liquid crystal display device characterized by selectively providing an image processing device, and an image information processing device including the device.

[0011]

According to the present invention, to achieve the above object, a matrix wiring having a gate wiring and a signal wiring, a plurality of active elements provided at intersections of the matrix wiring, A plurality of pixel electrodes individually provided for each of the plurality of active elements;
A storage capacitor line extending along the outer periphery of each of the plurality of pixel electrodes and arranged to face each other with an insulating layer interposed therebetween; and a common wiring opposed to the plurality of pixel electrodes. A liquid crystal display device having a common electrode and a liquid crystal layer disposed between the plurality of pixel electrodes and the common electrode. Between the capacitance wiring and the gate wiring,
, And the storage capacitor wiring is set to the same potential as the common electrode. Further, according to the present invention, as a means for achieving the above object, a matrix wiring having a gate wiring and a signal wiring, a plurality of active elements provided at intersections of the matrix wiring, and a plurality of active elements, respectively. A plurality of pixel electrodes individually provided with respect to each other, and a storage capacitor wiring extending along the outer periphery of each of the plurality of pixel electrodes and arranged to face each other with an insulating layer interposed therebetween. And a liquid crystal layer, wherein a capacitor is formed between the storage capacitor line and the signal line, and the storage capacitor line is connected to a pixel electrode facing the storage capacitor line. A liquid crystal display device is provided, which is connected to the gate wiring for another pixel electrode. In the present invention, the storage capacitor wiring can be arranged so as to protrude from the outer periphery of the pixel electrode facing the storage capacitor wiring, and can be maintained at a binary potential.

The conductive layer (storage capacitor distribution) used in the present invention
Line) is selectively provided around the pixel electrode, and the conductive layer (storage capacitor wiring) is maintained at a predetermined potential, thereby forming a floating capacitance between the pixel electrode and the matrix wiring group. Or, it is intended to prevent the adverse effect of the line capacitance from affecting the pixel electrode.

In the film forming process, the conductive layer (accumulation volume)
The quantity wiring) may be formed in the same step as the pixel electrode or may be formed in another step. The position can also be directly below the periphery of the pixel electrode itself and / or beside the pixel electrode. In addition, conductive layers (storage capacitors)
The amount wiring does not need to be always maintained at a constant potential, and may be maintained at a binary potential, for example, like a gate selection line in a matrix wiring group.

When the pixel electrode has a substantially rectangular shape, the conductive layer is preferably provided along at least three of the four sides. Specifically, the gate selection line for the pixel is provided. And the pixel electrode, at least between the signal line for the pixel and the pixel electrode, and between the signal line for the adjacent pixel and the pixel electrode.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to these embodiments, and This includes those in which elements have been replaced or design changes have been made.

Embodiment 1 FIG. 1 shows an active matrix liquid crystal display (AM-LC) according to Embodiment 1 of the present invention.
3D is a schematic diagram illustrating one pixel, and FIG. 3A illustrates a planar structure thereof, and FIG. 3B illustrates a XX ′ cross-sectional structure of a pixel electrode side portion thereof.

In FIG. 1, 6 is a MOS transistor as a switching active element, 8 is a signal wiring, and 10 is a gate as a gate selection line of a matrix wiring group for controlling the gate voltage of the switching transistor 6. Wiring. 12 is a transparent substrate, 16 is a transparent pixel electrode made of ITO, 20, 22, 2
4 is a transparent insulating film.

In this embodiment, the common potential side wiring (storage capacitance wiring) 26 for the storage capacitance is formed extending in a ring shape along the outer periphery of the pixel electrode 16. The wiring 26
Is connected to a reference voltage source V _Ref via a wiring 26a, and is maintained at a predetermined potential during driving of the pixel. Specifically, all the pixels provided on the substrate disposed opposite to each pixel electrode are set to the same potential as the common electrode maintained at the common potential. Therefore, in the present embodiment, the signal wirings 8, 8 '
Between the pixel electrode 16 and the storage capacitor wiring (storage capacitor wiring ).
Line) 26, and a capacitance is formed between the wiring 26 and the signal wirings 8, 8 ', so that the parasitic capacitance C _SP between the signal wirings 8, 8' and the pixel electrode 16 is significantly reduced. . Similarly, the storage capacitor line 26 is located between the gate line 10 and the pixel electrode 16, and a capacitance is formed between the line 26 and the gate line 10.
Parasitic capacitance C _GP is significantly reduced between. Thus,
The fluctuation of the voltage _VLC applied to the liquid crystal is remarkably reduced, and the image quality is improved. Further, based on this, the storage capacitance value can be reduced while maintaining the image quality. Since the storage capacitor wiring 26 can be made thinner, the aperture ratio is improved.

(Embodiment 2) FIG. 2 is a schematic diagram showing one pixel peripheral portion of an AM-LCD according to Embodiment 2 of the present invention.
(A) shows its planar structure and (b) shows its YY ′ cross-sectional structure.

The basic configuration of the second embodiment is the same as that of the first embodiment except that the wiring 26 is connected to the gate wiring 10 'of another pixel row and the wiring 26 is slightly outside the pixel electrode. It is a point that protrudes.

The gate wiring 10 ′ is
Thus, while the illustrated pixel row is being driven, it is held at a fixed potential. Therefore, also in the present embodiment, the parasitic capacitance C _SP between the signal line 8 and the pixel electrode 16 is significantly reduced, and the gate line 10 and the pixel electrode parasitic capacitance C _GP between the significantly reduced, thus the same effect as in the first embodiment can be obtained. According to this embodiment, the storage capacitor wiring and the gate wiring can be simultaneously formed of the same material, so that the layer configuration is simplified.

Embodiment 3 FIG. 3 is a schematic diagram showing one pixel of an AM-LCD according to Embodiment 3 of the present invention.
Shows the planar structure, and (b) shows the ZZ ′ cross-sectional structure.

The basic configuration of the third embodiment is the same as that of the second embodiment, and different points are as follows. That is, in the present embodiment, the drain region 28 of the switching transistor 6 extends along the outer periphery of the pixel electrode 16 corresponding to the common potential side wiring 26 for the storage capacitor. According to this, in addition to the same effects as those of the first and second embodiments,
Since a storage capacitor is also formed between the wiring 26 and the drain region 28, a sufficient capacitance value can be obtained even if the width of the wiring 26 is further reduced, and the aperture ratio can be further improved.

As described in detail above, according to the first to third embodiments, since the common potential side wiring for the storage capacitor extends along the outer periphery of the pixel electrode, the signal wiring and the gate wiring are provided. The fluctuation of the liquid crystal applied voltage _VLC due to the change in the voltage is reduced, and the image quality is improved. Further, as a result, the storage capacitance value can be reduced while maintaining the image quality, the switching transistor can be reduced in size, the width of the storage capacitance line can be reduced, and thus the storage capacitance line can be made of metal or metal. Even when formed of an opaque material such as a Si layer, a large aperture ratio can be obtained. The present invention increases its effectiveness as pixels become smaller.

(Embodiment 4) FIG. 4 is a schematic diagram showing one pixel of an AM-LCD according to Embodiment 4 of the present invention.
Shows a planar structure thereof, and (b) shows a cross-sectional structure thereof taken along the line AA ′.

In FIG. 4, reference numerals 10 and 10 'denote gate lines of a pixel switch (a part of which extends in a branch shape constitutes a gate electrode), and 8 denotes a signal wiring for writing a video signal to a pixel. Reference numeral 6 denotes a MOS transistor having a semiconductor region forming a drain region, a channel region, and a source region. Reference numeral 16 denotes a pixel electrode for driving the liquid crystal layer 57, and reference numeral 26 denotes a wiring for shielding disposed between the gate wiring 10 and the signal wiring 8 and the pixel electrode 16.

Reference numerals 31, 32, 33, 34 and 35 are transparent electrode layers. The shield wiring 26 is composed of two or three different layers in the manufacturing process. That is, the lower layer 26c
By forming the upper layer 26a after opening the contact hole 26b in the upper insulating layers 33 and 34, the upper layer 26a and the lower layer 26c are connected via the contact hole 26b. When this is constituted by three levels of layers, the layer filling the contact hole 26b is formed by the upper layer 26.
What is necessary is just to form in a process different from a.

The lower layer 26c, the contact hole 26b, and the upper layer 26a are provided so as to surround the periphery of the pixel electrode 16 (excluding the pixel switch component). Here,
The contact hole portion 26b is linearly opened so as to surround the periphery of the pixel electrode 16, and the lower layer 26c is formed using a conductive layer at the same level as a conductive layer (for example, aluminum wiring) for forming the signal line 8. It can be made by patterning.

The driving of the liquid crystal display device as shown in FIG.
A potential corresponding to the video signal is applied to the signal line 8 and the gate line 1
By giving 0 a potential at which the pixel switch conducts,
This is performed by setting the pixel electrode 16 to a predetermined potential. Normally, writing to a pixel electrode is performed simultaneously for one row, so that the gate lines of cells in the same row are commonly wired. When the writing of a certain row is completed, the writing of the next adjacent row is performed using the same data line, so that the signal lines are commonly wired in the same column.

As described above, the writing for each row is performed over all the rows, thereby completing the writing on the entire surface of the panel. After the writing of the last line is completed, the video can be constantly displayed by restarting the writing of the first line. In order to display the video information on the panel in this manner, the potential of the data line constantly fluctuates. In addition, the gate line also causes a large-amplitude potential fluctuation because the pixel switch is turned on and off.

In the conventional liquid crystal display device, since there is a parasitic capacitance between the gate line and the pixel electrode and between the signal line and the pixel electrode, the potential of the pixel electrode undergoes an unnecessary change. Such a fluctuation causes a decrease in display contrast or a deterioration in gradation.

In this embodiment, the influence of the gate lines and the signal lines can be greatly reduced by arranging the shield region, which is the wiring 26 to which a constant potential is applied, around the pixel electrode, and the image quality can be greatly improved. Can be improved.

In this embodiment, the lower layer 26c and the upper layer 26c
Not only a, but also the contact hole 26b is linearly opened so as to completely surround the periphery of the pixel electrode (excluding the pixel switch component), but the contact hole 26b does not necessarily need to be provided on the entire surface of the periphery. .

Next, the manufacturing method will be described.

First, island regions of a single crystal semiconductor are formed on the substrate 12 including the insulating surface to form the active elements 6.

Next, the gate insulating film 31 and the gate electrode 1
0 is formed. Next, after forming the insulating layer 32, a contact hole is opened. This contact hole is for connecting the signal line 8 with the source or drain, which is the main electrode region of the element 6. After forming the contact hole,
The signal line 8 and the lower layer 26c are simultaneously formed by depositing and patterning a conductor. Then, the insulating layer 3
3 are formed, contact holes for making contact between the element 6 and the pixel electrode 16 are formed in the insulating layers 31 and 3.
2, 33.

Next, a pixel electrode 16 is formed by depositing and patterning a transparent conductor. Here, the insulating layer 3
The surface 3 is previously flattened by a flattening process, for example, a method such as reflow of phosphorus glass or a combination of spin-on glass and etch back.

Subsequently, the pixel electrode 16 is covered with an insulating layer 34, contact holes 26b for making contact with the lower layer 26c are opened in the insulating layers 33 and 34, and then a conductor is deposited and patterned to form an upper layer 26a. To form Then, a protective layer 35 is formed, and one of a pair of substrates for sandwiching the liquid crystal layer 57 is manufactured.

Next, the substrate 56 having the common electrode is fixed at a predetermined interval, and the liquid crystal 57 is injected at the interval.
By sealing the periphery of the pair of substrates, the above-described AM-LCD is obtained.

(Embodiment 5) FIG. 5 is a schematic plan view showing a configuration of one pixel of an AM-LCD according to Embodiment 5 of the present invention.

The basic configuration of this embodiment is the same as that of the fourth embodiment.
And the differences are as follows. That is, as shown in FIG. 5, in the fifth embodiment, the contact hole 26b is partially provided, and the width m of the upper layer 26a and the lower layer 26c where the contact hole 26b is not formed is reduced. With this configuration, the pixel area can be made wider and the aperture ratio can be increased.

(Embodiment 6) FIG. 6 is a schematic sectional view showing a configuration of one pixel of an AM-LCD according to Embodiment 6 of the present invention.

The basic configuration of this embodiment is the same as that of the fourth embodiment.
This embodiment is the same as Embodiment 5 and different points are as follows. That is, as shown in FIG. 6, in the sixth embodiment, the upper layer 26a is formed by patterning the same conductive layer as the conductive layer for forming the pixel electrode 16, and the lower layer 26c forms the signal line 8. Since the same conductive layer as the conductive layer to be formed is patterned and manufactured, it is not necessary to form a conductive layer by adding a special film forming step particularly for forming a shield region. The process can be simplified.

Since the above-described shield region surrounds most of the pixel electrode, if this is formed of a light-shielding conductive material, light penetration between pixels (light crosstalk) can be prevented. .

FIG. 7 shows a liquid crystal display (LC) according to the present invention.
It is a schematic diagram which shows the image information processing apparatus using D). 3
Reference numeral 00 denotes an LCD, and a display unit 310 is provided at the center thereof. In FIG. 7, the active matrix portion is schematically shown as 204 as enlarged. In an area 203 around the display section 310, peripheral circuits including a shift register are arranged. Among the peripheral circuits, a horizontal drive circuit connected to a signal wiring and supplying a video signal is disposed above and below the display unit 310, and a drive circuit connected to a gate wiring and generating a line selection signal is disposed on the left and right sides of the display unit 310. Have been. These drive circuits are connected to and controlled by a drive control circuit 410 mounted on another substrate. Light source 4
The drive control circuit 410 is connected to a central control circuit 414 together with a lighting control circuit 411 including an inverter 12 for controlling lighting of the light source.

Further, this image information processing apparatus has an optical system 422 including a lens for inputting image information, an image sensor 421 including a photoelectric conversion element, and a driving circuit 420 therefor. In addition, the image information and / or the image information displayed by the image sensor 421 is transmitted to the recording head 4.
31 is recorded on a recording medium by a recording control circuit 430 including the P.31.

As described above in detail, according to the embodiment of the present invention, by providing a shield region between a pixel electrode and a matrix wiring so as to surround the pixel electrode, a gate line, a data signal line, etc. The adverse effect of the matrix wiring can be greatly reduced.

[0048]

According to the present invention, since the conductive layer is selectively provided around the pixel electrode, by maintaining the conductive layer at a predetermined potential, the distance between the pixel electrode and the matrix wiring group is increased. Of the pixel electrode can be prevented from being adversely affected by the stray capacitance or line capacitance.

According to the present invention, since the common potential side wiring for the storage capacitor extends along the outer periphery of the pixel electrode, the fluctuation of the voltage applied to the liquid crystal due to the voltage change of the signal wiring and the gate wiring is reduced. , Image quality is improved. Further, as a result, the storage capacitance value can be reduced while maintaining the image quality, the switching transistor can be reduced in size, and the width of the storage capacitance wiring can be reduced.
Thus, a large aperture ratio can be obtained even if the storage capacitor wiring is formed of an opaque material such as a metal or a Si layer. The present invention increases its effectiveness as pixels become smaller.

According to the present invention, by providing the shield region between the pixel electrode and the matrix wiring so as to surround the pixel electrode, the adverse effect of the matrix wiring such as the gate line and the data signal line can be greatly reduced. Can be.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an AM-LCD according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram of an AM-LCD according to a second embodiment of the present invention.

FIG. 3 is a schematic diagram of an AM-LCD according to Embodiment 3 of the present invention.

FIG. 4 is a schematic diagram of an AM-LCD according to Embodiment 4 of the present invention.

FIG. 5 is a schematic diagram of an AM-LCD according to Embodiment 5 of the present invention.

FIG. 6 is a schematic diagram of an AM-LCD according to Embodiment 6 of the present invention.

FIG. 7 is a schematic diagram showing an image information processing apparatus having an AM-LCD according to the present invention.

FIG. 8 is an equivalent circuit diagram of one pixel of an AM-LCD.

FIG. 9 is a timing chart showing driving waveforms of an AM-LCD having the circuit of FIG.

[Explanation of symbols]

 Reference Signs List 6 switching transistor 8 signal wiring 10, 10 'gate wiring 12 transparent substrate 14 substrate 16 transparent pixel electrode 20, 22, 24 transparent insulating film 26 shield wiring 28 drain region of switching transistor

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-2-63020 (JP, A) JP-A-3-196020 (JP, A) JP-A-2-278231 (JP, A) JP-A-3-27801 100626 (JP, A) JP-A-4-415 (JP, A) JP-A-63-70832 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/1362 G02F 1 / 1343

Claims (4)

(57) [Claims] A matrix wiring having a gate wiring and a signal wiring; a plurality of active elements provided at intersections of the matrix wiring; and a plurality of pixels individually provided for each of the plurality of active elements. An electrode, a storage capacitor wiring extending along the outer periphery of each of the plurality of pixel electrodes and arranged to face each other with an insulating layer interposed therebetween, and a common electrode for the plurality of pixel electrodes. A liquid crystal display device comprising: a common electrode disposed to face, and a liquid crystal layer disposed between the plurality of pixel electrodes and the common electrode, wherein a liquid crystal layer is provided between the storage capacitor wiring and the signal wiring. And a capacitor is formed between the storage capacitor line and the gate line, and the storage capacitor line is set to the same potential as the common electrode. 2. A matrix wiring having a gate wiring and a signal wiring, a plurality of active elements provided at intersections of the matrix wiring, and a plurality of pixels individually provided for each of the plurality of active elements. A liquid crystal display device comprising: an electrode; a storage capacitor wiring extending along an outer periphery of each of the plurality of pixel electrodes and arranged to face each other via an insulating layer; and a liquid crystal layer. A capacitance is formed between the storage capacitor line and the signal line, and the storage capacitor line is connected to the gate line for a pixel electrode different from the pixel electrode opposed to the storage capacitor line. A liquid crystal display device being connected. 3. The liquid crystal display device according to claim 2, wherein the storage capacitor wiring is disposed so as to protrude from the outer periphery of the pixel electrode facing the storage capacitor wiring. 4. The liquid crystal display device according to claim 2, wherein the storage capacitor wiring is held at a binary potential.