Obviousness

To analyze the obviousness of US patent 11574990 under 35 U.S.C. § 103, we must consider whether the claimed invention as a whole would have been obvious to a person having ordinary skill in the art (PHOSITA) at the time of the invention, given the scope and content of the prior art, and any motivation to combine or modify those references. The key is to provide an articulated reasoning with a rational underpinning, rather than mere conclusory statements.

The core innovation of US11574990, as described in independent claims 1 and 18, is the bent driving semiconductor layer of the driving thin film transistor (TFT) in an OLED display, which lies substantially parallel to the substrate. The patent states that this bent structure, such as a zigzag, '□', or 'S' form, allows the driving channel region to be longitudinally formed in a narrow space, broadening the driving range of the gate voltage and enabling more precise gray level control and improved display quality.

Prior Art References:

Based on the provided patent text, the "Prior art keywords" are listed as "thin film," "film transistor," "light emitting," "organic light," and "emitting diode." While the patent itself discusses general background on OLED displays and TFTs, it does not explicitly cite external prior art documents in the "Description of Related Art" section. However, the Google Patents information does include "Prior art keywords" and "Prior art date".

To assess obviousness, we will consider the general knowledge in the field prior to the priority date of August 2, 2012, as disclosed within the patent itself and generally recognized in the art of OLED displays and TFT technology.

Analysis of Obviousness under 35 U.S.C. § 103:

Claim 1:
An organic light emitting diode display comprising:

• a substrate;
• a scan line on the substrate for transferring a scan signal;
• a data line crossing the scan line and for transferring a data signal;
• a driving voltage line crossing the scan line and for transferring a driving voltage;
• a switching thin film transistor coupled to the scan line and the data line;
• a driving thin film transistor coupled to a switching drain electrode of the switching thin film transistor; and
• an organic light emitting diode (OLED) coupled to a driving drain electrode of the driving thin film transistor,
  wherein a driving semiconductor layer of the driving thin film transistor is bent and in a plane substantially parallel to the substrate.

Known Elements in Prior Art:

• OLED displays with substrates, scan lines, data lines, and driving voltage lines: These are fundamental components of active matrix OLED (AMOLED) displays and are well-established in the prior art. The patent itself describes this as a conventional setup.
• Switching thin film transistors and driving thin film transistors in OLED pixels: The patent clearly states that "The organic light emitting diode display includes a plurality of pixels, each including an organic light emitting diode that is a self-light emitting element, and a plurality of thin film transistors and capacitors for driving the organic light emitting diode. The plurality of thin film transistors includes a switching thin film transistor and a driving thin film transistor." This indicates these elements are known.
• OLEDs coupled to driving TFTs: This is the basic functional connection for pixel illumination in AMOLED displays.

Distinguishing Feature of Claim 1:

The distinguishing feature of Claim 1 is the "driving semiconductor layer of the driving thin film transistor is bent and in a plane substantially parallel to the substrate." The patent describes this bending as allowing the driving channel region to be "longitudinally formed in a narrow space," which "broadens the driving range of the gate voltage applied to the driving gate electrode" and improves gray level control and display quality. Examples of bent shapes include zigzag, '□', or 'S' forms.

Motivation to Combine/Modify Prior Art:

The central question for obviousness is whether a PHOSITA would have been motivated to bend the driving semiconductor layer of a driving TFT in an OLED display to achieve the stated advantages.

• General Motivation for Space Optimization and Performance Enhancement in Displays: The display industry constantly seeks to increase resolution, improve display quality, and optimize space utilization. A PHOSITA would be motivated to find ways to increase transistor channel length within a limited pixel area to improve transistor performance, such as broadening the gate voltage driving range.
• Known Techniques for Lengthening Semiconductor Channels: Bending or folding semiconductor layers to increase channel length within a confined area is a known design principle in semiconductor device fabrication, not exclusive to OLEDs. For instance, in general transistor design, a longer channel can offer better control over current and voltage characteristics. While not specifically mentioned in the provided patent text as explicit prior art for bent semiconductor layers in driving TFTs for OLEDs, the concept of modifying channel geometry to achieve desired electrical characteristics and optimize space is a common engineering practice.
  • US Patent 10,245,776 B2, filed in 2016, discusses methods for forming electronic devices with bent display edges and refers to flexible display layers such as organic light-emitting-diode layers, including thin-film-transistor structures. While this patent is after the priority date of US11574990, it indicates the general trend and knowledge around flexible displays and bending structures in the display field.
  • US Patent 7,166,006 B2, filed in 2004, describes methods of manufacturing OLED devices by deposition on curved substrates and mentions the use of flexible substrates, typically plastic, for displays. This also shows a general awareness of non-planar structures in OLED manufacturing.
• Problem-Solution Motivation: The patent explicitly states the problem: "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 solution offered is broadening this driving range by longitudinally forming the driving channel region through bending. A PHOSITA facing the known challenge of narrow driving ranges in driving TFTs for OLEDs would actively seek solutions to increase the effective channel length to improve gate voltage control and gray scale resolution.
• Predictable Result: Given the general knowledge that increasing channel length in a transistor can provide better control over its electrical characteristics, and the known need to broaden the driving range for gray level control in OLEDs, a PHOSITA would have a predictable expectation that bending the semiconductor layer to effectively lengthen the channel would help address this problem. The specific "zigzag," '□', or "S" forms are variations of a common design approach to maximize length within a constrained area, and their selection would be within the purview of routine optimization for a PHOSITA.

Conclusion for Claim 1:
A PHOSITA, motivated by the known need to broaden the driving range of driving TFTs for improved gray scale control in OLED displays and aware of general semiconductor design principles for increasing effective channel length within a confined space (e.g., by bending or folding), would have found it obvious to implement a bent driving semiconductor layer in a driving TFT of an OLED display. The specific geometries (zigzag, 'S', 'W') would be considered predictable variations or routine optimization.

Claim 18:
An organic light emitting diode display comprising:

• a substrate;
• a scan line on the substrate for transferring a scan signal;
• an initialization voltage line on the substrate for transferring an initialization voltage;
• a data line crossing the scan line for transferring a data signal;
• a driving voltage line crossing the scan line for transferring a driving voltage;
• a switching thin film transistor coupled to the scan line and the data line;
• a driving thin film transistor coupled to a switching drain electrode of the switching thin film transistor;
• an organic light emitting diode (OLED) coupled to a driving drain electrode of the driving thin film transistor;
• a light emission control thin film transistor between the driving drain electrode and the OLED; and
• a bypass thin film transistor between the initialization voltage line and a light emission control drain electrode of the light emission control thin film transistor, wherein the bypass thin film transistor transfers a portion of a driving current transferred by the driving thin film transistor according to a bypass control signal transferred by a bypass control line.
  wherein a driving semiconductor layer of the driving thin film transistor is bent and in a plane substantially parallel to the substrate.

Known Elements in Prior Art:

• All elements of Claim 1 (substrate, scan line, data line, driving voltage line, switching TFT, driving TFT, OLED, bent driving semiconductor layer) as discussed above.
• Initialization voltage line and initialization thin film transistor: The patent explicitly describes an "initialization voltage line 124 for transferring an initialization voltage Vint for initializing the driving thin film transistor T1". It also details an initialization thin film transistor T4 configured to be turned on by a prior scan signal to transfer this initialization voltage to the driving gate electrode.
• Light emission control thin film transistor: The patent describes a "light emission control line 123 for transferring a light emission control signal En to the operation control thin film transistor T5 and the light emission control thin film transistor T6". It further states that this transistor is "configured to be turned on by the light emission control signal to transfer the driving voltage from the driving thin film transistor to the OLED" and is "between the driving drain electrode and the OLED".
• Bypass thin film transistor and bypass control line: The sixth exemplary embodiment (FIGS. 10 and 11) introduces the bypass thin film transistor T7 and bypass control line 128. The purpose of the bypass thin film transistor is to "disperse, or divert, a portion of the minimum current of the driving thin film transistor T1 as a bypass current Ibp to a current path other than the current path of the organic light emitting diode," particularly to improve contrast ratio by achieving a more precise black luminance.

Distinguishing Features of Claim 18 (beyond Claim 1):

The primary distinguishing feature of Claim 18 over Claim 1 is the inclusion of the "bypass thin film transistor between the initialization voltage line and a light emission control drain electrode of the light emission control thin film transistor," which transfers a portion of the driving current based on a bypass control signal.

Motivation to Combine/Modify Prior Art for Bypass TFT:

• Problem-Solution for Black Luminance and Contrast Ratio: The patent explicitly identifies the problem of displaying a precise black image, where even a minimum current (e.g., 10 pA or less) can cause unintended luminance. The solution presented is to use a bypass thin film transistor to divert this minimum current away from the OLED, thereby "implementing a precise black luminance image" and improving the contrast ratio.
• General Practice of Current Control and Diversion: In electrical circuits, techniques for current diversion or shunting to achieve precise control, particularly at low current levels, are common. A PHOSITA would be aware of various methods to control and reroute current paths.
• Motivation for Improved Display Quality (Contrast Ratio): The desire for higher contrast ratios and more accurate black levels is a constant driving force in display technology. If a PHOSITA recognized that stray or minimum currents were hindering true black representation, they would be motivated to introduce a mechanism to manage or divert these currents.
• Combining Known Elements to Achieve a Known Result: The bypass thin film transistor is used to divert current, a known function of a transistor. Placing it between the initialization voltage line (which can provide a reference or sink for the diverted current) and the light emission control drain electrode (where the driving current to the OLED is controlled) is a logical design choice for a PHOSITA seeking to precisely control the current reaching the OLED at very low levels. The "bypass control signal" would be a standard way to activate or deactivate such a bypass path.

Conclusion for Claim 18:
A PHOSITA, motivated by the well-known need to improve contrast ratio and black luminance in OLED displays by precisely controlling or diverting minimal driving currents, would have found it obvious to incorporate a bypass thin film transistor into the pixel circuit. Such a transistor, connected to an initialization voltage line and the light emission control drain electrode, and actuated by a bypass control signal, would be a predictable application of known electrical engineering principles to achieve a desired and well-understood result (current diversion for improved black level). The addition of the bypass TFT to a pixel structure already employing a bent driving semiconductor layer (as discussed for Claim 1) would be a straightforward combination of known solutions to address distinct but related display performance issues.

Overall Obviousness under 35 U.S.C. § 103:

The independent claims of US11574990 appear to combine known elements (various TFTs, lines, OLEDs) with a specific structural modification (bent driving semiconductor layer) and a functional addition (bypass TFT). While the specific combination might be novel, the question under § 103 is whether this combination would have been obvious to a PHOSITA.

Given the existing challenges in OLED display technology regarding gate voltage driving range and precise gray level control (especially for black luminance), and the general engineering principles for optimizing semiconductor device characteristics and controlling current paths, a PHOSITA would have been motivated to:

1. Introduce a bent semiconductor layer: To increase the effective channel length of the driving TFT within a compact pixel layout, thereby broadening the gate voltage driving range and improving gray scale control. This is a predictable approach to address a known problem in compact semiconductor devices.
2. Incorporate a bypass thin film transistor: To specifically manage and divert residual or minimum currents that negatively impact black luminance and contrast ratio in OLED displays. This addresses a known display quality issue with a standard current control mechanism.

The combination of these elements would likely be viewed by a PHOSITA as a logical evolution in OLED display design to address identified performance limitations. The specific implementation details (e.g., zigzag shape, placement of bypass transistor) would be within the realm of routine design choices and optimization. The references in the patent itself to the problems being solved (narrow driving range, difficulty controlling gray levels, low gray level stains, black luminance issues) indicate that these were known problems in the art, which further motivates a PHOSITA to seek solutions.