PTAB

IPR2025-00238

BOE Technology Group Co Ltd v. Optronic Sciences LLC

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Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Semiconductor Structure with Light-Shielding Layer for Displays
  • Brief Description: The ’471 patent describes a semiconductor structure, typically a thin-film transistor (TFT), for use in display devices. The structure includes a conductive light-shielding layer that asymmetrically overlaps the channel and source regions to reduce adverse effects from light irradiation, such as drain-induced barrier lowering (DIBL) and current leakage.

3. Grounds for Unpatentability

Ground 1: Obviousness over Hwang - Claims 1, 4, 6, 9, 12, 14, 17-18 are obvious over Hwang

  • Prior Art Relied Upon: Hwang (Application # 2008/0158108).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Hwang, which discloses an OLED device with a TFT structure, teaches all limitations of the challenged claims. Specifically, Hwang’s metal "auxiliary electrode" (162a) inherently performs the function of the claimed "conductive light-shielding pattern layer." Petitioner contended that because this electrode is made of metal (e.g., aluminum, tungsten) and is disclosed as being sufficiently thick to shield against low-frequency electric fields, a POSITA would understand it is necessarily opaque and thus shields against high-frequency light. Further, Petitioner asserted that the claimed dimensional ratio of the overlap (0.3≤d1/L≤0.85) would have been obvious from Hwang’s figures and the common design goals for TFTs, which favor specific proportions for source, drain, and channel regions to optimize performance and pixel density.
    • Motivation to Combine (for §103 grounds): Not applicable as this ground relies on a single reference. The motivation is inherent in solving the problems disclosed in Hwang using the structures it provides.
    • Expectation of Success (for §103 grounds): A POSITA would have an expectation of success in implementing the claimed structure as it involves recognizing the inherent physical properties of materials and common design parameters disclosed in Hwang.

Ground 2: Obviousness over Hwang and Godo - Claims 1, 4, 6, 9, 12, 14, 17-18 are obvious over Hwang in view of Godo

  • Prior Art Relied Upon: Hwang (Application # 2008/0158108) and Godo (Application # 2010/0148175).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground serves as an alternative to Ground 1, specifically addressing the d1/L dimensional ratio limitation. Petitioner argued that if Hwang alone is insufficient to render the claimed ratio obvious, Godo provides explicit dimensions for suitable TFTs used in LED display devices. Godo discloses specific lengths for the source, drain, and channel regions in its Figures 20A and 20B. Petitioner demonstrated through calculation that applying these explicit dimensions from Godo to the general TFT architecture of Hwang would necessarily result in a device with a d1/L ratio falling squarely within the claimed 0.3 to 0.85 range.
    • Motivation to Combine (for §103 grounds): A POSITA, seeking to implement the OLED device in Hwang, would be motivated to consult references like Godo to find predictable and optimized dimensions for the drive transistor. Godo’s disclosure of specific dimensions for similar bottom-gate TFTs provides a clear path for implementing Hwang’s broader teachings.
    • Expectation of Success (for §103 grounds): A POSITA would have a high expectation of success, as the combination involves applying known, specific dimensions from Godo to a compatible TFT structure in Hwang using standard photolithography and fabrication techniques.

Ground 3: Obviousness over Hwang and Yamashita - Claims 1, 4, 6, 9, 12, 14, 17-18 are obvious over Hwang in view of Yamashita

  • Prior Art Relied Upon: Hwang (Application # 2008/0158108) and Yamashita (Application # 2009/0184898).

  • Core Argument for this Ground:

    • Prior Art Mapping: This ground is an alternative for the "light-shielding" function, particularly if the Board adopts a narrower claim construction requiring an intended purpose of light shielding. Petitioner argued that Yamashita explicitly addresses the problem of scattered light from adjacent pixels degrading TFT performance in electroluminescent displays. Yamashita teaches using a metallic light-shielding layer to block this scattered light. This provides the express reasoning for a designer to intend for Hwang’s structurally equivalent metal electrode (162a) to serve the purpose of light shielding.
    • Motivation to Combine (for §103 grounds): A POSITA would combine Yamashita’s teachings with Hwang’s device to solve the well-known and documented problem of light-induced performance degradation in TFTs, a problem exacerbated in dense display panels like those disclosed by Hwang.
    • Expectation of Success (for §103 grounds): The combination required no physical modification to Hwang’s device, only the recognition—prompted by Yamashita—that Hwang's existing metal layer should be intended to perform a light-shielding function for which it is already suited.

  • Additional Grounds: Petitioner asserted an additional obviousness challenge based on the combination of Hwang, Godo, and Yamashita, arguing this combination addresses alternatives where both the dimensional and light-shielding limitations are not rendered obvious by Hwang alone.

4. Key Claim Construction Positions

  • "a conductive light-shielding pattern layer": Petitioner proposed two constructions.
    • Primary Construction: The term should be given its plain and ordinary meaning, which does not require any specific degree of electrical conductivity or optical opacity. As long as the layer possesses some conductive and some light-shielding properties and meets the structural limitations, it falls within the claim scope.
    • Alternative Construction: In the event the Patent Owner argues for a purpose-based limitation, Petitioner proposed an alternative construction: "a layer that the designer subjectively intends to serve the purpose of being electrically conductive and shielding the channel layer from some light."

5. Key Technical Contentions (Beyond Claim Construction)

  • Inherent Light-Shielding Property of Metal Layers: A central technical argument was that Hwang’s metal auxiliary electrode (162a) is inherently light-shielding based on the "skin depth" principle. Petitioner argued that because Hwang discloses this layer must be thick enough to shield the TFT from low-frequency electric fields from the OLED drive signal, it is necessarily many times thicker than the skin depth of visible light in metal. Therefore, it would be effectively opaque and function as a light shield, regardless of whether Hwang explicitly stated this purpose.

6. Arguments Regarding Discretionary Denial

  • Petitioner argued against discretionary denial under Fintiv, asserting that the factors weigh in favor of institution. The parallel district court litigation is in a very early stage, with Markman briefing and significant discovery yet to occur. There is also limited issue overlap, as the IPR challenges more claims (including independent claim 9) than are asserted in the litigation. Finally, Petitioner contended the petition presents compelling evidence of unpatentability.

7. Relief Requested

  • Petitioner requests institution of IPR and cancellation of claims 1, 4, 6, 9, 12, 14, 17, and 18 of the ’471 patent as unpatentable.