PTAB

IPR2025-00937

Caihong Display Devices Co Ltd v. Corning Inc

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Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Alkali-free, Boroaluminosilicate Glass
  • Brief Description: The ’498 patent discloses methods for producing alkali-free boroaluminosilicate glass sheets suitable for flat panel display substrates. The invention focuses on specific glass compositions and a fining process using tin oxide (SnO2) instead of more toxic agents like arsenic or antimony to achieve desired physical properties, such as high liquidus viscosity and dimensional stability.

3. Grounds for Unpatentability

Ground 1: Anticipation over Miwa '377 - Claims 1, 2, 7, 9, and 11 are anticipated by, and claim 10 is anticipated by or obvious over, Miwa '377.

  • Prior Art Relied Upon: Miwa '377 (JP Publication # 2003192377).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Miwa '377, which relates to alkali-free glass for LCD substrates, expressly discloses every limitation of the challenged claims. Specifically, Embodiment 8 of Miwa '377 described a glass composition produced by a downdraw method that meets the limitations of independent claim 1, including: a Σ[RO]/[Al2O3] ratio greater than 1.0; MgO content of 3.24 mol%; negligible arsenic (0 mol%); and SnO2 content of 0.07 mol%. Petitioner contended this embodiment also met the required liquidus viscosity, liquidus temperature (claim 7), strain point (claim 8), and use of a fusion process (claim 9). Dependent claim 2’s SnO2 limit (≤0.15 mol%) and claim 11’s liquidus viscosity (≥200,000 poise) were also allegedly met.
    • Key Aspects: For claim 10, Petitioner asserted that because Miwa '377 taught the same fusion downdraw process with similar parameters, it would inherently produce glass sheets meeting the claimed low level of gaseous inclusions.

Ground 2: Obviousness over Miwa '535, JP '741, and Peuchert '469 - Claims 1 and 3-11 are obvious over Miwa '535 in view of JP '741 and Peuchert '469.

  • Prior Art Relied Upon: Miwa '535 (JP Publication # 2004189535), JP '741 (JP Publication # 1998059741), and Peuchert '469 (Application # 2005/0101469).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Miwa '535 disclosed a very similar alkali-free boroaluminosilicate glass (Embodiment 15) that met most limitations of claim 1, including the Σ[RO]/[Al2O3] ratio, MgO content, and SnO2 content. While Miwa '535 disclosed small amounts of antimony oxide (Sb2O3), it did not explicitly teach the low arsenic (As2O3) and antimony limits of claim 1. Peuchert '469 was cited for its teaching that BaO can be replaced by SrO to achieve a glass that is substantially free of BaO, as required by dependent claim 4.
    • Motivation to Combine: A POSITA would combine Miwa '535 with JP '741, which explicitly taught restricting the use of highly toxic As2O3 in alkali-free glass manufacturing. This provided a clear reason to modify the composition in Miwa '535 to meet the low arsenic and antimony limits of claim 1. The motivation was to create a high-quality display glass using a safer, more environmentally friendly fining process, a well-known goal in the art. A POSITA would also have been motivated to incorporate Peuchert '469’s teachings to eliminate BaO for improved properties.
    • Expectation of Success: A POSITA would have had a high expectation of success because the references were all in the same field of alkali-free display glass and addressed predictable properties based on chemical composition.

Ground 3: Obviousness over Chacon and Takase - Claims 1 and 4-11 are obvious over Chacon in view of Takase.

  • Prior Art Relied Upon: Chacon (Patent 6,319,867) and Takase (JP Publication # 2004299947).

  • Core Argument for this Ground:

    • Prior Art Mapping: Petitioner asserted that Chacon taught an alkali-free aluminosilicate glass with desirable properties for display substrates, produced via a fusion downdraw process. Chacon disclosed nearly all limitations of claim 1, including the Σ[RO]/[Al2O3] ratio, MgO content ranges, and high liquidus viscosity. However, Chacon did not specify the use of SnO2 as the fining agent.
    • Motivation to Combine: A POSITA would have been motivated to modify Chacon's process by incorporating the teachings of Takase. Takase explicitly taught using SnO2 as a "clarifying agent" to replace toxic As2O3, disclosing a mass fraction of SnO2 that overlapped with the mole percent required by claim 1. The motivation was to achieve the desirable glass properties of Chacon while employing the known, safer fining agent taught by Takase.
    • Expectation of Success: Success was expected because replacing one fining agent with another known to be effective in similar glass compositions was a routine and predictable modification for a POSITA.

  • Additional Grounds: Petitioner asserted an additional anticipation challenge (Ground 4) against claims 1-2, 4, and 9 based on Peuchert '293 (Application # 2001/0034293).

4. Arguments Regarding Discretionary Denial

  • Petitioner argued against discretionary denial under both §325(d) and §314(a) (Fintiv).
  • §325(d): Petitioner contended that denial was unwarranted because the petition raised new invalidity grounds based on prior art (Miwa '377, JP '741, Peuchert '469, Takase, Peuchert '293) and combinations that were not considered by the USPTO during prosecution of the ’498 patent.
  • Fintiv: Petitioner argued denial would be inappropriate because the co-pending district court litigation has been stayed. The parallel ITC investigation does not involve all challenged claims (notably, independent claim 1 is not asserted), cannot result in patent invalidation, and its findings would not have preclusive effect. Petitioner further stated that investment in the parallel proceedings was minimal and committed not to pursue the same grounds in the ITC or district court if the IPR is instituted, thereby avoiding duplicative efforts.

5. Relief Requested

  • Petitioner requested institution of an inter partes review and cancellation of claims 1-11 of the ’498 patent as unpatentable.