Shift register circuit and image display apparatus equipped with the same

Abstract

Malfunction caused by leakage current of the transistor and shift in threshold voltage is prevented in the shift register in which the signal can be shifted bi-directionally. The bi-directional unit shift register includes a first transistor Q 1 for providing a first clock signal CLK to an output terminal OUT, a second transistor Q 2 for discharging the output terminal OUT based on a second clock signal, third and fourth transistors Q 3 , Q 4 for providing first and second voltage signals Vn, Vr complementary to each other to a first node, which is a gate node of the first transistor Q 1 , and a fifth transistor Q 5 connected between the first node and the output terminal OUT. The fifth transistor Q 5 is in an electrically conducted state based on the first clock signal CLK when the gate of the transistor Q 1 is at L (Low) level.

Description

Technical field [0001] The present invention relates to a shift register circuit composed only of field effect transistors of the same conductivity type used in, for example, a scanning line driver circuit of an image display device, and more particularly to a bidirectional shift register capable of reversing the direction of signal shift . Background technique [0002] In image display devices such as liquid crystal display devices (hereinafter referred to as "display devices"), gate lines (scanning lines) are provided in accordance with pixel rows (pixel lines) of a display panel in which a plurality of pixels are arranged in a matrix, and the display The gate lines are sequentially selected and driven within a period of one horizontal period of the signal, thereby enabling the display image to be updated. In this way, as a gate line driver circuit (scanning line driver circuit) for sequentially selecting and driving pixel lines, that is, gate lines, a shift register that perfo...

AI Technical Summary

Problems solved by technology

[0019] As a result of the increase in the potential of the first node due to the above-mentioned leakage current and the clock signal, there is a problem of malfunction as follows: If the voltage between the gate and the source of the first transistor exceeds the threshold voltage, the first transistor that should be turned off is turned on. pass, the gate line is activated unnecessarily

In recent years, a display device using an amorphous silicon TFT (a-Si TFT) as a unit shift register of a gate line driver circuit has been widely used. However, a-Si TFT has the following problem: if the gate electrode is continuously biased voltage, the threshold voltage shifts, and its drive capability (capability to flow current) decreases

If this phenomenon continues, the output terminal will be in a floating state during the non-selection period, and since the potential of each gate line is unstable, malfunctions are likely to occur and the display quality will deteriorate.

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