PTAB

IPR2020-00320

Samsung Display Co Ltd v. Solas OLED Ltd

Log In
Key Events
Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Display Panel and Method of Fabricating the Same
  • Brief Description: The ’338 patent relates to active-matrix organic light-emitting diode (AMOLED) display panels. The technology is directed at two main features: (1) low-resistance conductive "interconnections" that project from the surface of the transistor array substrate to reduce signal delay and voltage drop, and (2) a specific three-transistor pixel circuit (driving, switching, and holding) to drive each pixel.

3. Grounds for Unpatentability

Ground 1: Obviousness over Kobayashi and Shirasaki - Claims 1-2, 5-6, and 9-11 are obvious over Kobayashi in view of Shirasaki.

  • Prior Art Relied Upon: Kobayashi (Application # 2002/0158835) and Shirasaki (Application # 2004/0113873).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Kobayashi, which concerns AMOLED displays, discloses all elements of the challenged claims except for the specific three-transistor pixel circuit. Kobayashi taught using projecting "auxiliary wiring elements" (analogous to the claimed "common interconnections") electrically connected to the cathode to lower its overall resistance and improve display uniformity. However, Kobayashi disclosed a conventional two-transistor pixel circuit. Shirasaki, whose lead inventor is the same as the ’338 patent's, explicitly taught the claimed three-transistor pixel circuit (including a driving, switch, and holding transistor) and described it as a solution to the performance problems of conventional two-transistor circuits.
    • Motivation to Combine: Petitioner asserted that a person of ordinary skill in the art (POSITA) would combine these references because both are directed to improving AMOLED display panels. Shirasaki provided an express motivation by describing the deficiencies of two-transistor circuits, such as inaccurate tone control and display variations due to temperature changes, and teaching its three-transistor circuit as the solution to "stably display images with desired luminance." The combination would be a simple substitution of a known, improved element (Shirasaki's circuit) for an older one (Kobayashi's circuit).
    • Expectation of Success: A POSITA would have had a reasonable expectation of success because both references operate in the same technical field. Shirasaki's express disclosure that its circuit was meant to replace two-transistor circuits in conventional displays (like Kobayashi's) would confirm the predictability of the modification, which involved routine and well-understood fabrication steps.

Ground 2: Obviousness over Childs and Shirasaki - Claims 1-3 and 5-13 are obvious over Childs in view of Shirasaki.

  • Prior Art Relied Upon: Childs (WO 03/079441) and Shirasaki (Application # 2004/0113873).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that this combination renders the claims obvious for reasons similar to Ground 1, but with Childs supplying the teachings for the projecting interconnections. Childs disclosed an AMOLED display with projecting "conductive barrier material" used as interconnections connected to supply lines and addressing lines (analogous to the claimed "feed" and "select" interconnections). These interconnections were taught to reduce line resistance and voltage drops. Like Kobayashi, Childs disclosed a two-transistor pixel circuit. Petitioner contended it would have been obvious to replace Childs' two-transistor circuit with the superior three-transistor circuit taught by Shirasaki.
    • Motivation to Combine: The motivation was identical to that in Ground 1. Shirasaki expressly taught the benefits of its three-transistor circuit over the two-transistor designs used in the prior art, such as the one in Childs. A POSITA seeking to improve the performance and display quality of the Childs device would have been motivated by Shirasaki to incorporate its advanced pixel circuit.
    • Expectation of Success: A POSITA would have expected success for the same reasons as in Ground 1. Both references are in the field of AMOLED displays, and Shirasaki's disclosure provided a clear roadmap and predictable outcome for improving the functionality of the device disclosed in Childs. Childs itself noted that its design could be used with various pixel circuit configurations.

4. Key Claim Construction Positions

  • "transistor array substrate" (claim 1): Petitioner proposed this term should be construed as the entire layered structure beneath the pixel electrodes, from the bottommost insulating substrate up to the topmost insulating layer (e.g., a planarization film) on whose surface the pixel electrodes are formed. This construction was based on the specification's explicit definition ("i.e., on the surface of the transistor array substrate 50").
  • "interconnections which are formed to project from a surface of the transistor array substrate" (claim 1): Based on the construction above, Petitioner argued this term means interconnections formed to extend above the upper surface of the topmost layer of the transistor array substrate. This was supported by figures and descriptions in the ’338 patent showing the interconnections formed on top of the final planarization film.

5. Arguments Regarding Discretionary Denial

  • Petitioner argued that institution was proper because neither the prior art references nor the specific invalidity arguments were considered by the USPTO during the original prosecution. Specifically, Petitioner highlighted that Shirasaki, which disclosed the three-transistor circuit limitation that was key to allowance, was never before the Examiner.

6. Relief Requested

  • Petitioner requested institution of an inter partes review and cancellation of claims 1-3 and 5-13 of the ’338 patent as unpatentable under 35 U.S.C. §103.