JPH0318817A - Active matrix array - Google Patents

Abstract

PURPOSE:To obtain a high picture quality display being free from a luminance difference by setting the parasitic capacity generated between each picture element electrode and two pieces of signal lines being adjacent thereto to almost the same, and also, reversing the polarity of the potential of each adjacent signal line and driving it. CONSTITUTION:The subject array is provided with a thin film transistor Tnm, a scanning line Yn, and a signal line Ym, one thin film transistor Tnm is formed against each picture element, and simultaneously, a capacitor C being almost the same as a source - drain parasitic capacity of the transistor Tnm is formed between second signal lines Ym being adjacent to each picture element. In this state, the potential polarity of the signal line Ym is inverted against the opposed common potential at every one screen scan, and also, the potential of each adjacent signal line Ym is set to the opposite polarity. Accordingly, the influence of the source - drain parasitic capacity of the transistor Tnm can be offset by inversion driving of the signal line. In such a way, a high picture quality display being free from a luminance difference can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an active matrix array that can be used in liquid crystal display panels, liquid crystal light valves, and the like.

2. Description of the Related Art As shown in FIG. 3, the basic configuration of a conventional active matrix array is as shown in FIG. , the switching element Tnm (
In the figure, it consists of a thin film transistor). A liquid crystal is inserted between the picture element electrode and the opposing common electrode, and the electro-optical characteristics of the liquid crystal are controlled by the potential applied to the picture element electrode. Also,
Each picture element electrode Pnm has a capacitance lcn between it and the opposing common electrode.
One of the requirements of the active matrix method is that the potential of the picture element electrode is maintained for a certain period of time by this capacitance. In other words, after switching element Tnm is selected by scanning line The potential of the picture element changes with a time constant τ determined by the capacitance Cnm. Therefore, as long as the time constant is sufficiently large for the non-selection time of the scanning line, the potential of the picture element is maintained.

However, in an actual active matrix array, various parasitic capacitances occur due to the structure of the switching elements, manufacturing process, etc., which causes the above-mentioned pixel voltage to fluctuate. In particular, the parasitic capacitor Csp that occurs between the signal line Ym and the picture element electrode Pnm causes the picture element potential to fluctuate by ΔVX (Csp/Cnm) with respect to the potential change Δ■ of the signal line Ym. It has a big impact on the quality of the image. FIG. 4 is a timing chart of picture element potentials for explaining the influence of Csp on the upper and lower luminance difference of a displayed image. This figure is a general timing chart and driving method when driving a liquid crystal element having a thin film transistor array. In other words, since the liquid crystal needs to be driven with alternating current, the polarity of the signal line potential is reversed for each screen with respect to the common electrode. This figure shows the potential change of each pixel due to the difference in scanning line selection time when a constant voltage is applied as a signal. When considering Csp, as can be seen from the figure, when the polarity of the signal line potential is reversed for each screen, the picture element potential is changed by the amount calculated by the above-mentioned calculation formula in accordance with the change.

This change always acts in the direction of lowering the voltage applied to the liquid crystal, and as is clear from the figure, the picture element that is selected immediately after the signal line potential is reversed (corresponding to the top on the display screen), and the selected pixel A picture element where the signal line potential is reversed immediately after (
(at the bottom of the display screen), there is a difference in the effective voltage applied to the liquid crystal ('/& the time average value of the square of the voltage applied to the crystal). This causes a difference in brightness between the top and bottom of the screen. Furthermore, since the pixel potential is affected by changes in the signal line potential, this causes a large reduction in gradation.

Incidentally, this capacitance between the signal line and the picture element is generated due to the shape of the channel portion of the transistor, especially the light shielding layer of the transistor with a-3i as the active layer, and it is difficult to completely eliminate this capacitance.

Furthermore, - When the size of picture elements is made finer to achieve high density and high definition, the capacitance Cnm of the liquid crystal decreases and equivalently Csp
There is a problem in that the value of /Cnm becomes large, and as a result, image quality is greatly affected.

Problems to be Solved by the Invention An object of the present invention is to significantly reduce the image quality deterioration caused by the capacitance between the signal line and the pixel electrode, which is a problem in active matrix type liquid crystal display elements, and to enable high-quality display. The purpose is to provide an active matrix array.

Means for Solving the Problems In order to solve the above problems, the active matrix array of the present invention includes a plurality of scanning lines (gate lines) and signal lines (source lines), pixel electrodes provided corresponding to each intersection, and at least one switching element connected to each picture element electrode, configured to equalize the capacitance generated between each picture element electrode and two signal lines adjacent thereto. This is a method in which the polarities of the voltages of adjacent signal lines are reversed and driven.

Function: As in the above-mentioned configuration, the parasitic capacitance generated between the picture element electrode and the two adjacent signal lines are made almost the same, and the polarities of the adjacent signal line potentials are reversed for driving. By doing this, the inversion direction of the signal line potential during screen scanning is reversed between adjacent signal lines to cancel out fluctuations in pixel potential, and high-quality display without brightness difference is possible.

Embodiment FIG. 1 shows an equivalent circuit of an active matrix array according to an embodiment of the present invention.

In FIG. 1, Tnm indicates a thin film transistor. Xn and Ym indicate a scanning line and a signal line, respectively. In the 0-line configuration, one thin film transistor is formed for each picture element, and at the same time, the transistor's source and This is a capacitor that is approximately the same as the parasitic capacitance between the drains. Specifically, a configuration in which the gate electrode and semiconductor layer of the same transistor corresponding to Tnm are removed is created between the adjacent signal line and the picture element. FIG. 2 shows a thin film transistor array having the configuration shown in FIG.
A liquid crystal display panel with 0X80Q picture elements is driven by the driving method described in the present invention, that is, the potential polarity of the signal line is inverted with respect to the opposing common potential for each screen scan, and the potentials of adjacent signal lines are of opposite polarity. As is clear from Figure 0, which shows the voltage-luminance characteristics at the top and bottom of the screen when driven using the method of driving the screen using the method of driving the screen (hereinafter referred to as signal line inversion), there is no difference in characteristics between the top and bottom of the screen. I understand that.

This is because, as described above, the influence of the parasitic capacitance between the source and drain of the transistor is offset by the signal line inversion drive.

Effects of the Invention As described above, the present invention makes the parasitic capacitances generated between each picture element electrode and two adjacent signal lines almost the same, and also changes the polarity of the signal line potentials adjacent to each other. By reversing the drive direction, it is possible to display high-quality images with no difference in brightness.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the circuit configuration of an active matrix array according to a first embodiment of the present invention, and FIG. 2 shows the circuit configuration of FIG. It shows the voltage-luminance characteristics of the display panel. Third
The figure is an explanatory diagram showing a typical example of a conventional active matrix array, and FIG. 4 is an explanatory diagram of a typical driving method of the active matrix array. Xn...Scanning line, Ym...Signal line, P
nm...Picture element electrode.

Claims (2)

[Claims] (1) Multiple scanning lines (gate lines) and signal lines (source lines)
, consists of a picture element electrode provided corresponding to each intersection, and a switching element connected to each picture element electrode, and equalizes the capacitance generated between each picture element electrode and two adjacent signal lines. An active matrix array characterized by driving adjacent signal lines with opposite polarities of voltage. (2) With respect to the picture element electrode, a switching element is formed between the adjacent first signal line and the picture element electrode, and a switching element is formed between the corresponding second signal line and the picture element electrode. 2. The active matrix array according to claim 1, wherein a capacitor is formed which is the same as a parasitic capacitance generated between the picture element and the signal line by forming the switching element.