JPH08292448A - Display device - Google Patents

Abstract

PURPOSE: To provide a display device of an active matrix system capable of maintaining uniform display characteristics even against the deviation in the positions where a pixel structure is formed. CONSTITUTION: This display device of the active matrix system has scanning signal wirings 12 and image signal wirings 16 arranged in a matrix form, pixel electrodes 17 arranged in the regions enclosed by these wirings and semiconductor switching elements 21 electrically connected to the scanning signal wirings 12 and the pixel electrodes 17. The structure in which the semiconductor switching elements 21 and the pixel electrodes 17 are intersected in a cruciform form is formed in the display device described above. As a result, the variations in the parasitic capacitance Cgd arising from the deviation in the positions where the semiconductor switching elements 21 are formed are eliminated and the specified maintaining of the display voltage Vlc is made possible and, therefore, the display device having the excellent uniform display characteristics is embodied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device used in televisions, word processors and the like.

[0002]

2. Description of the Related Art In recent years, an active matrix system having a switching element for each display unit has been known as one of display devices for displaying characters and images using a display material typified by liquid crystal. A pixel configuration of a conventional display device of this system will be described with reference to FIGS.

Insulating substrates 11a and 11b corresponding to a first substrate and a second substrate are positioned in parallel and opposite to each other, and a liquid crystal 10 which is a display material is sandwiched in the gap. A scanning signal line 12 and an auxiliary capacitance line 13 are formed on one main surface of the insulating substrate 11a that is in contact with the liquid crystal 10, and a semiconductor switching element 15 formed of a semiconductor thin film with an insulating film 14 sandwiched therebetween is formed on the scanning signal line 12 and the auxiliary capacitance line 13. The image signal wiring 16 and the pixel electrode 17 are formed. In addition, on the one main surface of the insulating substrate 11b that is in contact with the liquid crystal 10,
The counter electrode 18 is formed.

In plan view, the scanning signal wirings 12 and the image signal wirings 16 are arranged in a matrix, and pixel electrodes 17 are provided in the area surrounded by these. The semiconductor switching element 15 has three electrodes, a source electrode, a drain electrode, and a gate electrode via an insulating film 14, on the upper surface thereof, and is electrically connected to the image signal wiring 16, the pixel electrode 17, and the scanning electrode wiring 12, respectively. It is connected. Therefore, the semiconductor switching element 15 is wired close to these, that is, near the intersection of the scanning signal wiring 12 and the image signal wiring 16. The source electrode and the drain electrode correspond to the contact surface between the semiconductor switching element 15 and the image signal wiring 16, and the contact surface between the semiconductor switching element 15 and the pixel electrode 17.

The operation of the display device having this configuration will be described. If the electric signal is supplied to the scanning signal wiring 12 at a constant cycle and the electric signal corresponding to the image to be displayed is supplied to the image signal wiring 16, the semiconductor switching element corresponding to the electric signal sent to the image signal wiring 16 15
Is activated, and electric charges flow from the image signal wiring 16 into the pixel electrode 17. As a result, a potential difference is generated between the pixel electrode 17 and the counter electrode 18 to drive the molecules of the liquid crystal 10, and the amount of light and the wavelength of light transmitted through the paths of the insulating substrate 11a, the liquid crystal 10, and the insulating substrate 11b are changed. Let An image or the like is displayed by utilizing this change in the light transmission state.

An electric equivalent circuit per pixel of this display device is shown in FIG. 4 and 5, Cgd is a parasitic capacitance generated between the scanning signal line 12 and the drain terminal of the semiconductor switching element 15 connected to the pixel electrode 17. Cgs is a parasitic capacitance generated between the source terminal of the semiconductor switching element 15 connected to the image signal wiring 16 and the scanning signal wiring 12. Clc is a pixel capacitance, which is a capacitance between the pixel electrode 17 and the counter electrode 18.
Cs is an auxiliary capacitance, and the pixel electrode 17 and the auxiliary capacitance line 1
3 and capacity. Further, T is a semiconductor switching element 15.

In this pixel, the scanning signal Vg is applied to the scanning signal line 12, the capacitance signal Va is applied to the auxiliary capacitance line 13, the image signal Vs is applied to the image signal line 16, and the counter signal Vc is applied to the counter electrode 18. Further, the pixel voltage applied to the liquid crystal 10 between the pixel electrode 17 and the counter electrode 18 is Vlc.

[0008]

In the conventional display device,
The semiconductor switching element 15 formed on the scanning signal wiring 12 is covered inside the image signal wiring 16 and the pixel electrode 17. With this structure, the parasitic capacitances Cgs and Cgd change when the position where the semiconductor switching element 15 is formed shifts as shown in FIG. 7A to FIG. 7B.

When Cgd changes, the display voltage Vlc applied to the liquid crystal 10 changes. For example, the liquid crystal is driven under the driving conditions shown in FIG. Vo as a scanning signal
n and Voff are used. In this case, the display voltage Vl
c is calculated by the formula shown in (Equation 1).

Vlc = Vs−Cgd / (Cgd + Cs + Clc) * (Von−Voff) −Vc (Equation 1) In other words, if there is a region where the semiconductor switching element 15 is misaligned in the screen, the scanning signal wiring 12
A region having a different parasitic capacitance Cgd between the pixel electrode 17 and the pixel electrode 17 is generated. As a result, the display voltage Vlc varies depending on the region, and when the entire screen is displayed in the same color, it is recognized as display unevenness.

An object of the present invention is to solve the above problems and to provide a display device which displays a uniform image without display unevenness.

[0012]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above-mentioned object, and crosses a semiconductor switching element and a pixel electrode in a cross shape to electrically connect the semiconductor switching element. It has the main composition.

[0013]

With the above-described structure, the present invention makes it possible to keep the Cgd constant even when the position where the semiconductor switching element is formed is deviated, and thus keep the display voltage Vlc constant, so that there is no unevenness and uniform display characteristics. This is to realize an excellent display device.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. It should be noted that those having the same configuration as the conventional example are designated by the same reference numerals, and detailed description thereof will be omitted.

This embodiment is similar to the conventional example shown in FIG.
The scanning signal wirings 12 and the image signal wirings 16 arranged in a matrix, the pixel electrodes 17 arranged in a region surrounded by these, the counter electrodes 18 arranged to face the pixel electrodes 17 with the liquid crystal 10 interposed therebetween, and the pixel electrodes. The auxiliary capacitance line 13 that forms the auxiliary capacitance Cs with the image signal line 1
6 is an active matrix type display device including a semiconductor switching element 21 that is connected to the scanning signal line 6 and the electric charge flowing into the pixel electrode 17.

The feature of this embodiment is that, as shown in FIGS. 1 and 2, the scanning signal wiring 1 is formed through the insulating film 14.
That is, the shape of the semiconductor switching element 21 formed on the wiring 2 crosses the pixel electrode 17 in a cross shape so that the semiconductor switching element 21 is projected. The positional relationship is that the upper surface of the semiconductor switching element 21 is electrically connected by the pixel electrodes 17 intersecting and contacting each other. Regarding the protruding width Wa, the protruding width Wa is completely protruded from the pixel electrode 17 in order to make the parasitic capacitance Cgd between the scanning signal wiring 12 and the pixel electrode 17 constant even if the position of the semiconductor switching element 21 is maximally deviated.
That is, the condition of Wa> 0 is required.

The semiconductor switching element 21 forming Cgs and the image signal wiring 16 may be connected by connecting the upper surface of the semiconductor switching element 21 so that the image signal wiring 16 crosses in a T shape. This is a structure in which the semiconductor switching element 21 is covered inside the image signal wiring 16 because the change in the parasitic capacitance Cgs due to the position shift from the image signal wiring 16 does not affect the display voltage Vlc shown in (Equation 1). Good. That is, the semiconductor switching element 2
The condition is that the length Wb of 1 covered by the image signal wiring 16 is smaller than the width Wc of the image signal wiring (Wb <Wc).

According to the present invention, when the auxiliary capacitance wiring 13 is the same wiring as the scanning signal wiring 12, and the scanning signal wiring 12 is wired above the image signal wiring 16 and the pixel electrode 17, the pixel of the active matrix system is provided. Is also valid. Further, the cross-shaped or T-shaped intersection includes the case where the semiconductor switching element 21 is on the upper side.

[0019]

As described above, in the display device of the present invention, by adopting the above-mentioned structure, even if there is a region where the position where the semiconductor switching element is formed is deviated, the scanning signal wiring and the pixel electrode are The parasitic capacitance Cgd and the display voltage Vlc can be kept constant, and a display device having excellent uniform display characteristics can be realized.

[Brief description of drawings]

FIG. 1 is a plan view of a display device according to an embodiment of the present invention.

2A is a cross-sectional view taken along the line AA of FIG. 1B is a cross-sectional view taken along the line BB of FIG. 1C is a plan view of a main part of a display device according to an embodiment of the present invention.

FIG. 3 is a plan view of a conventional display device.

4A is a cross-sectional view taken along the line AA of FIG. 3B is a cross-sectional view taken along the line BB of FIG.

FIG. 5 is an electrical equivalent circuit diagram of the display device of the present invention and the conventional display device.

FIG. 6 is a diagram showing changes over time of drive signal waveforms of the display device of the present invention and the conventional display device.

FIG. 7 is a plan view of an essential part showing a case where a position where a semiconductor switching element is formed is displaced.

[Explanation of symbols]

 10 Liquid Crystals 11a and 11b Insulating Substrate 12 Scanning Signal Wiring 13 Auxiliary Capacitance Wiring 14 Insulating Film 16 Image Signal Wiring 17 Pixel Electrode 18 Counter Electrode 21 Semiconductor Switching Element

Claims (4)

[Claims] 1. A first substrate and a second substrate which face each other in parallel.
And a scanning signal wiring and an image signal wiring arranged in a matrix on the main surface of the first substrate on the side in contact with the display material, and the scanning signal wiring and the image. The pixel electrode arranged in the area surrounded by the signal wiring and the scanning signal wiring and the image signal wiring are arranged in proximity to the intersection, and electrically connected to the scanning signal wiring through the image signal wiring, the pixel electrode and the insulating film. A semiconductor switching element electrically connected to each other, and a counter electrode provided on the main surface of the second substrate on the side in contact with the display material, the semiconductor switching element and the pixel electrode having a cross shape. A display device in which the semiconductor switching element and the pixel electrode are electrically connected by intersecting each other. 2. The display device according to claim 1, wherein the semiconductor switching element and the pixel electrode are electrically connected to each other by the pixel electrode crossing the upper surface of the semiconductor switching element in a cross shape. 3. The display device according to claim 1, wherein the semiconductor switching element and the image signal wiring intersect each other in a T-shape so that the semiconductor switching element and the image signal wiring are electrically connected to each other. 4. The display device according to claim 2, wherein the semiconductor switching element and the image signal wiring are electrically connected by intersecting the image signal wiring in a T shape on the upper surface of the semiconductor switching element.