Flexible bezel‐less thin‐film transistor backplane with through‐plastic‐vias for seamless tiling

Abstract

Tiling with a variety of panel units is a promising approach to customizing displays in terms of size, shape, and aspect ratio. However, tiled displays with conventional panel units have a major drawback in that they suffer from noticeable seams due to the bezels of the panel units. Here, we demonstrate a flexible bezel‐less thin‐film transistor (TFT) backplane for seamless tiling. By using through‐plastic‐vias (TPVs) that penetrate an ultrathin polyimide (PI) film substrate, a bezel‐less backplane with an ultra‐narrow bezel width of 8 μm was realized, in which oxide TFTs in pixel circuits on the backplane are driven from the back side of the PI film substrate using three‐dimensional signal wires, which go through the TPVs. The resistance of a TPV was evaluated with a TPV chain with 1000 TPVs connected in series and was found to be as small as 1.3 Ω. Furthermore, the transfer characteristics of an oxide TFT in a test element group for a pixel circuit were evaluated from the back side of the PI film substrate. The TFT exhibited clear switching behavior with an on/off current ratio of more than 108 and a high mobility of 25 cm2/Vs, which are sufficient to drive light‐emitting devices.