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

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.