A High-Reliability Carry-Free Gate Driver for Flexible Displays Using a-IGZO TFTs

Most thin-film transistor (TFT) gate drivers integrated on the display panel use the carry signals between the stages. In our previous works, we found that these carry-type gate drivers are subject to the reliability problem in a flexible display, since the errors of the stressed stages are accumulated through the carry signals. This problem possibly leads to the failure of image refresh of the display device. Therefore, the carry-free gate driver can resolve the error accumulation problem since it does not use the carry signals and instead, each unit stage operates independently. In this paper, we propose an advanced carry-free gate driver circuit to remove the drawbacks of the previous version, while keeping the advantages. More importantly, this paper is the first report to experimentally show that the error accumulation phenomenon of the carry-type gate driver and the problem is removed in the carry-free gate driver. The proposed carry-free gate driver and the carry-type gate driver are fabricated with amorphous indium-gallium-zinc-oxide TFTs on a flexible substrate for comparison purpose. The proposed gate driver shows a very high reliability since no voltage fluctuation occurs at the outputs after 10 000 cycles bending test with 2-mm bending radius.