Bidirectional shift register and image display device using the same

A bidirectional shift register comprising:

• a shift register part that includes N (N is an integer of 6 or more) cascade-connected unit register circuits and outputs an output pulse in a shift sequence of one of a forward direction and a backward direction to an output terminal;
• a clock signal generation part that supplies M-phase (M is an integer 3 or more) clock pulses to the respective unit register circuits of the shift register part sequentially in the forward direction at a time of a forward shift operation of the shift register part or sequentially in the backward direction at a time of a backward shift operation;
• and
• a trigger signal generation part that generates a forward direction trigger signal which changes to ON level at a time of start of the forward shift, and generates a backward direction trigger signal which changes to ON level at a time of start of the backward shift, wherein
• each of the unit register circuits includes a forward direction set terminal, a backward direction set terminal, a forward direction reset terminal, a backward direction reset terminal, a set circuit to set a potential at a reference point to a first potential when a set signal is inputted to one of the set terminals, a reset circuit, being separated from the set circuit to set the potential at the reference point to a second potential when a reset signal is inputted to one of the reset terminals, and an output circuit to output the output pulse in synchronization with the inputted clock pulse in a state where the reference point is at the first potential,
• a first, a second, an (N−1)th and an Nth unit register circuits are dummy register circuits,
• a k-th unit register circuit (k for all integers of 2<k<N−1) outputs the output pulse from the output circuit to the output terminal,
• at the start of the forward shift, the forward direction trigger signal is inputted to the forward direction set terminal of the first unit register circuit as the set signal, and to the forward direction reset terminal of the (N−1)th and Nth unit register circuits as the reset signal,
• at the start of the backward shift, the backward direction trigger signal is inputted to the backward direction set terminal of the Nth unit register circuit as the set signal, and to the backward direction reset terminal of the first and second unit register circuits as the reset signal.