PTAB

IPR2025-01137

Caihong Display Devices Co Ltd v. Corning Inc

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Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Method for Manufacturing a Glass Sheet
  • Brief Description: The ’684 patent discloses a method and apparatus for manufacturing glass sheets, particularly for flat panel displays, using a fusion downdraw process. The invention focuses on a pull roll apparatus with multiple pairs of rollers to create cross-tension and vertical draw tension to improve glass sheet flatness and reduce residual stress.

3. Grounds for Unpatentability

Ground 1: Claims 1-14 are obvious over JP ’826 in view of one or more of Butts, JP ’027, KR ’349, Ferngren, and Smids.

  • Prior Art Relied Upon: JP ’826 (JP Publication # 1998-201826), Butts (Application # 2005/0268655), Smids (Patent 4,612,030), JP ’027 (JP Publication # 2007-0151027), KR ’349 (KR Publication # 2004-07349), and Ferngren (Patent 1,586,618).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner asserted that JP ’826 is the primary reference, disclosing a downdraw method for manufacturing glass sheets with key elements of the claimed invention. This includes using cantilevered, downtilted "stub roll pairs" to draw the edges of a glass sheet outward and a main "pull roll pair" below to create vertical tension. Petitioner argued that while JP ’826 teaches controlling the speed of these rollers, it fails to explicitly teach monitoring and controlling their torque. To supply this limitation, Petitioner relied on Butts, which teaches that controlling torque instead of speed prevents slippage between the rollers and the glass surface, a known defect of speed-only control systems. For claim 7, which adds third and fourth stub roll pairs, Petitioner introduced Smids. Smids allegedly taught using a series of multiple (five) stub roll pairs to stretch glass, providing the rationale for adding more pairs to the JP ’826 system for enhanced tension control.
    • Motivation to Combine: A POSITA would combine JP ’826 and Butts because Butts addresses the known problem of slippage inherent in the speed-control method of JP ’826. Implementing Butts’s superior torque-control system was presented as a straightforward modification to improve a known process. Similarly, a POSITA would incorporate the teaching of Smids to add more roller pairs to the JP ’826 apparatus to achieve the predictable benefit of improved tension consistency and reduced warping, a primary goal in glass sheet manufacturing. All references were asserted to be from the same technical field.
    • Expectation of Success: Petitioner contended that combining these known elements from analogous art would have yielded predictable results. A POSITA would expect that applying torque control (Butts) and additional rollers (Smids) to the downdraw process (JP ’826) would successfully reduce slippage and warping without undue experimentation.

Ground 2: Claims 1-14 are obvious over KR ’349 in view of one or more of Bogdahn, Ferngren, and Fredholm.

  • Prior Art Relied Upon: KR ’349 (KR Publication # 2004-07349), Bogdahn (Application # 2005/0076675), Fredholm (Application # 2009/0019892), and Ferngren (Patent 1,586,618).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner presented KR ’349 as an alternative primary reference that teaches a downdraw glass manufacturing apparatus with diffusion and tension rollers. To meet the claim limitations for monitoring and controlling torque, Petitioner relied on Bogdahn. Bogdahn taught coordinating torques between different rollers in a vertical drawing process for cylindrical glass to prevent gearing differences and surface damage. Petitioner argued this teaching is directly applicable to the flat glass process of KR ’349. For claim 7’s requirement of additional roller pairs, Petitioner introduced Fredholm, which disclosed using multiple cantilevered auxiliary rollers to strategically control tension, viscosity, and shear stress in a fusion draw process.
    • Motivation to Combine: A POSITA would be motivated to apply the torque coordination taught in Bogdahn to the KR ’349 process to achieve the same benefits of preventing gearing differences and reducing surface damage. Petitioner argued that manufacturing flat glass and cylindrical glass are closely related arts involving vertical stretching, making the combination logical. A POSITA would also incorporate Fredholm’s auxiliary rollers into the KR ’349 system to predictably improve tension control and reduce warping, a well-known objective in the field.
    • Expectation of Success: Petitioner argued that a POSITA would have a reasonable expectation of success in applying Bogdahn’s established torque control principles and Fredholm’s use of additional rollers to the KR ’349 system. The combination was framed as the application of known solutions to solve known problems, leading to predictable improvements in the final glass product.

4. Relief Requested

  • Petitioner requests the institution of an inter partes review and the cancellation of claims 1-14 of Patent 8,627,684 as unpatentable.