Transparent and Flexible SiOC Films on Colorless Polyimide Substrate for Flexible Cover Window

Abstract

We fabricated transparent and flexible silicon oxycarbide (SiOC) hard coating (HC) films on a colorless polyimide substrate to use as cover window films for flexible and foldable displays using a reactive roll-to-roll (R2R) sputtering system at room temperature. At a SiOC thickness of 100 nm, the R2R-sputtered SiOC film showed a high optical transmittance of 87.43% at a visible range of 400 to 800 nm. The R2R-sputtered SiOC films also demonstrated outstanding flexibility, which is a key requirement of foldable and flexible displays. There were no cracks or surface defects on the SiOC films, even after bending (static folding), folding (dynamic folding), twisting, and rolling tests. Furthermore, the R2R-sputtered SiOC film showed good scratch resistance in a pencil hardness test (550 g) and steel wool test under a load of 250 g. To test the impact protection ability, we compared the performance of thin-film heaters (TFHs) and oxide-semiconductor-based thin-film transistors (TFTs) with and without SiOC cover films. The similar performance of the TFHs and TFTs with the SiOC cover window films demonstrate that the R2R-sputtered SiOC films offer promising cover window films for the next generation of flexible or foldable displays.

Invisible and Flexible Printed Sensors Based on ITO Nanoparticle Ink for Security Applications

“…That is why the ultimate goal was to find a suitable flexible colorless substrate that can withstand such temperatures. We have investigated several temperature-stable flexible polymers listed in Table 1 (Ni et al, 2015;Park et al, 2021) and selected CPI material due to the tolerable performance after low vacuum furnace annealing and after the FLA steps.…”

Using an Interlayer to Toughen Flexible Colorless Polyimide-Based Cover Windows

“…It has been reported that [10] while standalone colorless PI films exhibited ~20% strain at break, ε b , the same films coated with a flexible HC underwent a dramatic decrease in ε b to as low as ~2% with increasing HC thickness up to 35 µm. As the fracture strain of brittle coatings on polymer substrates typically decreases with increasing coating thickness [8,9], this embrittlement is likely attributed to the fracture behavior of the bilayer cover window instead of a chemical interaction [11,12]. Understanding mechanisms for the embrittlement is crucial to achieving reliable colorless PI-based cover windows.…”

“…For flexible cover windows, striking a balance between flexibility and mechanical robustness has been enabled by recent technological advancement in thin glasses and colorless polyimide (PI) films [5][6][7][8]. While both materials have been used in flexible devices, thin glasses are too fragile for use as the outermost layer of the devices without additional protective layers [9]. On the other hand, colorless polyimide (PI) films offer more flexibility and toughness than thin glasses, but they are much softer and therefore require a polymeric flexible hard coat (HC) layer to improve their mechanical robustness.…”

18‐1: Composite UTG Cover Window Selectively Reinforced with Glass‐Cloth for Improvement of Both Pen‐Drop Resistance and Foldability

“…Another recently adopted idea is to form a folding and non-folding area division in the UTG cover window. The foldable area is formed around the hinge through slimming [4] or laser patterning UTG into a mesh shape [5]. The remaining non-folding area still can utilize high thickness and high strength properties of UTG.…”