Obviousness

Based on the provided patent text for US11574991, titled "Organic light emitting diode display with semiconductor layer having bent portion," there are no specific prior art documents (e.g., patent numbers, publication IDs) listed or referenced within the "Prior art keywords" section or the "Background" section that can be used to perform an obviousness analysis under 35 U.S.C. § 103 by combining specific references. The "Prior art keywords" section provides general terms like "thin film," "film transistor," and "organic light," while the "Background" section describes the general state of the art and the problem the invention aims to solve.

Therefore, I cannot identify combinations of specific prior art references and explain a motivation to combine them, as no such references are provided in the authoritative text for this analysis.

However, the patent text does describe the problem addressed by the invention in the background:
"In the switching thin film transistor, a thin gate insulating layer is formed between a gate electrode and a semiconductor layer to enable rapid switching operation. Because the thickness of the gate insulating layer of the driving thin film transistor, which is formed on the same layer as the switching thin film transistor, is reduced, a driving range of a gate voltage applied to the gate electrode of the driving thin film transistor becomes narrow. Therefore, it may be difficult to control the magnitude of the gate voltage Vgs of the driving thin film transistor to ensure a large number of gray levels."

The claimed invention, particularly in independent claim 1, addresses this by providing an OLED display where "a driving semiconductor layer of the driving thin film transistor is bent and in a plane substantially parallel to the substrate." This bent shape allows for a longitudinally formed driving channel region in a narrow space, broadening the driving range of the gate voltage and enabling more precise control of gray levels, thus increasing resolution and improving display quality.

A person having ordinary skill in the art (PHOSITA) in the field of OLED display technology would be aware of the common components (TFTs, capacitors, OLEDs) and the challenges associated with achieving high resolution and precise gray scale control in active matrix displays. While the motivation to solve the problem of a narrow driving range for TFTs in OLED displays is clearly articulated in the patent's background, without specific prior art disclosures detailing bent semiconductor layers or similar channel length extension techniques in the context of driving TFTs for OLEDs, it is not possible to construct an obviousness argument based on combinations of unnamed references.