Caihong Display Devices Co Ltd v. Corning Inc

1. Case Identification

• Case #: IPR2025-01040
• Patent #: 9,512,025
• Filed: May 22, 2025
• Petitioner(s): Caihong Display Devices Co., Ltd.
• Patent Owner(s): Corning Incorporated
• Challenged Claims: 1-20

2. Patent Overview

• Title: Apparatus and Method for Manufacturing Glass Ribbon
• Brief Description: The ’025 patent discloses an apparatus and method for manufacturing glass ribbons for displays using a fusion down draw process. The invention focuses on using a replaceable heating cartridge with an inclined heat-directing surface to reduce devitrification of the glass at its edges during manufacturing.

3. Grounds for Unpatentability

Ground 1: Claims 1-20 are obvious over El Kahlout in view of CN ’869 and Tsuda.

• Prior Art Relied Upon: El Kahlout (Application # 2011/0209502), CN ’869 (CN102765869), and Tsuda (Application # 2012/0111060).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that the combination of the three references renders all challenged claims obvious under 35 U.S.C. §103. The invalidity argument was structured by using El Kahlout as the primary reference and supplementing its teachings with Tsuda and CN ’869.
  • Petitioner asserted El Kahlout discloses the foundational apparatus and method for making glass ribbons via a fusion process. This base system included the core components recited in independent claims 1 (apparatus), 8 (cartridge), and 15 (method), such as a forming wedge with downwardly inclined surfaces, an edge director intersecting those surfaces, and a plurality of edge rollers positioned downstream to engage the glass ribbon, all enclosed within a housing.
  • To address the limitations of a "replaceable heating cartridge," Petitioner turned to Tsuda. Petitioner argued Tsuda teaches a replaceable external heater for a "guide member" (which Petitioner contended is analogous to El Kahlout's edge director). Tsuda allegedly discloses that using an external heater facilitates replacement and repair, thereby teaching the "removably positioned" and "replaceable" limitations of the challenged claims.
  • For the key limitations concerning the heater’s geometry, Petitioner relied on CN ’869. Petitioner argued CN ’869 discloses a platinum heating apparatus with inclined heating surfaces (surfaces 4 and 5) relative to a horizontal plane. This recessed-shape heater was designed to compensate for temperature variations at the ends of an isopipe. Petitioner contended this directly teaches the ’025 patent’s "heat directing surface that is inclined at an angle of less than about 90°" and the orientation of the heater to face the glass forming body, thereby satisfying the view factor limitations.
  • For the dependent claims, Petitioner argued that the claimed features were obvious modifications. The specific angle ranges for the heat directing surface (e.g., 45° to 75° in claims 2 and 9) were presented as the result of routine optimization of the inclined surfaces already taught by CN ’869. Likewise, configuring the surface with a plurality of facets or as a curved surface (claims 3, 5, 10, 13, 17, 19) was argued to be an obvious design choice to effectively surround the edge director and concentrate heat.
  • Motivation to Combine: Petitioner argued a person of ordinary skill in the art (POSITA) would combine these references because they all address known problems in the same technical field of fusion down draw glass manufacturing. A POSITA would combine Tsuda's teaching of a replaceable heater with El Kahlout's system to improve serviceability and reduce manufacturing downtime, a well-understood industry objective. Similarly, a POSITA would incorporate the inclined heater geometry from CN ’869 into the combined El Kahlout/Tsuda system to solve the persistent problem of heat loss at the glass edges, thereby reducing devitrification and improving final product quality.
  • Expectation of Success: Petitioner asserted a POSITA would have a reasonable expectation of success in making the proposed combination. The integration of a known replaceable heater (Tsuda) and a known angled heating surface (CN ’869) into a standard fusion draw apparatus (El Kahlout) involved applying established engineering principles to achieve the predictable results of improved maintainability and temperature control.

4. Arguments Regarding Discretionary Denial

• Petitioner argued that discretionary denial under §325(d) would be inappropriate because the petition presents a combination of art and arguments not substantively considered during prosecution. Petitioner specifically noted that the CN ’869 reference was never before the Examiner and that the three-way combination of El Kahlout, Tsuda, and CN ’869 represents a substantially new argument.

5. Relief Requested

• Petitioner requests institution of an inter partes review and cancellation of claims 1-20 of the ’025 patent as unpatentable.