Enhanced thin-film transistor driven high-aperture in-plane switching liquid crystal displays without common line and black matrix

Masahiko Ando,Makoto Yoneya

doi:10.1038/s41598-021-90924-x

Abstract

We developed active-matrix in-plane switching liquid crystal displays (IPS-LCDs) with a new vertical structure composed of thin-film transistors (TFTs) that have an aperture ratio of 60% to reduce energy consumption. The novel TFT has a channel and a back channel made of a hydrogenated amorphous-silicon semiconductor layer sandwiched by thin silicon oxide insulating layers. The transfer characteristics are enhanced by uniformly shifting the threshold voltage to be higher than the maximum LC driving voltage (typically > 5 V). The enhanced TFT characteristics provided with a new driving scheme and shielding electrodes enables both the common line and black matrix to be eliminated. We fabricated an IPS TFT-LCD panel with aperture and contrast ratios that are 160% those of the conventional pixel structure.

Highlights

We developed active-matrix in-plane switching liquid crystal displays (IPS-LCDs) with a new vertical structure composed of thin-film transistors (TFTs) that have an aperture ratio of 60% to reduce energy consumption
We developed active-matrix in-plane switching liquid crystal displays (IPS-LCDs) with a new stacking structure of thin-film transistors (TFTs) with an aperture ratio of 60%
Because of the electrical dipoles of the channel and back-channel interfaces of the gate metal/SiN/SiOx/amorphous silicon (a-Si):H/SiOx TFT structure, the TFT transfer curve is uniformly enhanced such that Vth is higher than the maximum LC driving voltage

Summary

Introduction

We developed active-matrix in-plane switching liquid crystal displays (IPS-LCDs) with a new vertical structure composed of thin-film transistors (TFTs) that have an aperture ratio of 60% to reduce energy consumption. The advent of the in-plane switching (IPS) LCD mode was ground-breaking as it afforded a very wide viewing angle for TV applications[6,7], while the introduction of the fringe field switching (FFS) mode using LC materials with negative dielectric anisotropy dramatically improved the transmittance[8,9] These LCD modes have been combined with a novel pixel structure with a noise-shielding electrode to increase the aperture ratio[10]. By introducing an enhanced switching mode of a-Si:H TFT wherein the threshold voltage is shifted higher than the maximum pixel voltage (typically > 5 V), we were able to eliminate the common line from the IPS TFT LCD panel by using the gate line as the common line and thereby increase the pixel aperture ratio. To enhance the transfer characteristics, we tried several methods and their combinations, such as using an MNOS

Methods

Results

Discussion

Conclusion