Shift register circuit and image display apparatus containing the same

Abstract

Threshold voltage shifts of transistors which are constituents of a bidirectional shift register are reduced to prevent a malfunction in the shift register. A bidirectional unit shift register includes first and second pull-down circuits (41, 42) connected to the gate of a first transistor (Q1) that supplies a first clock signal (CLK) to an output terminal (OUT). The first pull-down circuit (41) includes a first inverter that uses the gate of the first transistor (Q1) as the input node and that is activated by the first clock signal (CLK), and a second transistor (Q5A) that discharges the gate of the first transistor (Q1) according to the output of the first inverter. The second pull-down circuit (42) includes a second inverter that uses the gate of the first transistor (Q1) as the input node and that is activated by a second clock signal ( / CLK) having a different phase from the first clock signal (CLK), and a third transistor (Q5A) that discharges the gate of the first transistor according to the output of the second inverter.

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, scanning line driving circuits of image display devices, and more particularly to a bidirectional shift register capable of reversing the direction of signal shifting. Background technique [0002] In an image display device such as a liquid crystal display device (hereinafter referred to as a "display device"), a gate line (scanning line) is provided for each pixel row (pixel line) of a display panel arranged in a matrix of pixels to display a signal. A period of one horizontal period selects and drives the gate line sequentially, so as to update the display image. Thus, 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 performs a round-trip shift operation during one frame period of a display sign...

AI Technical Summary

Problems solved by technology

[0024] As described above, although Patent Document 2's Figure 7 The unit shift register has a transistor T1A to prevent the above problems, but since its gate fluctuates according to the clock signal, it is turned off at the cycle of the clock signal

Therefore, when the off-state current of the transistors T0 and T1 is large, the level of the gate may exceed the threshold voltage while the transistor T1A is off.

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