PTAB

IPR2026-00014

Resonac Hard Disk Corp v. Mr Technologies GmbH

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Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Magnetic Recording Medium
  • Brief Description: The ’864 patent describes a perpendicular magnetic recording (PMR) medium designed to overcome the trade-off between thermal stability and writeability. The invention purports to achieve this by adding a "nucleation host"—comprising multiple ferromagnetic layers with increasing anisotropy—on top of a hard magnetic storage layer, which is intended to reduce the required write field without sacrificing data stability.

3. Grounds for Unpatentability

Ground 1: Claims 1, 3-5, 9, 13-14, and 23 are obvious over Takenoiri alone.

  • Prior Art Relied Upon: Takenoiri (Patent 8,329,321).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Takenoiri, which was not considered during prosecution, discloses all elements of the challenged claims. Takenoiri teaches a bi-layer magnetic recording medium but explicitly discloses extending this to a "three or more layer" structure to improve recordability. This multi-layer structure inherently creates the claimed "nucleation host" (the additional, softer magnetic layers) on top of the "hard magnetic storage layer" (the original, hardest layer). Petitioner asserted that Takenoiri’s examples demonstrate a hard layer with a coercive field greater than 0.5 T and that extending its structure as taught would obviously result in a nucleation host with ferromagnetic layers of increasing anisotropy constant (K) toward the hard layer, meeting the key limitations of independent claim 1.
    • Motivation to Combine (for §103 grounds): As a single-reference ground, the motivation was presented as inherent to Takenoiri itself. A person of ordinary skill in the art (POSITA) would have been motivated by Takenoiri's own teachings to extend its bi-layer structure to a tri-layer (or more) configuration to achieve the stated goals of improving thermal stability while reducing the switching field.
    • Expectation of Success (for §103 grounds): Petitioner contended a POSITA would have a reasonable expectation of success because Takenoiri teaches how to tune coercivity and anisotropy via layer thickness and composition, providing a clear and predictable path for implementing the claimed structure.

Ground 2: Claims 2 and 6 are obvious over Takenoiri in view of Shen.

  • Prior Art Relied Upon: Takenoiri (Patent 8,329,321) and Shen (a 2005 journal article on composite perpendicular magnetic recording media).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground addressed claims reciting specific magnetic behaviors. Petitioner argued Takenoiri taught the base multi-layer structure, while Shen provided teachings on achieving the claimed magnetic properties. For claim 2, Shen's experimental data showed a measured hysteresis loop with a long, nearly linear region, allegedly meeting the claim’s mathematical condition that the slope of the magnetization curve remains substantially constant. For claim 6, Shen allegedly taught the claimed relative coercivity relationship, demonstrating that the coercive field of a soft layer (the nucleation host) is less than half that of the hard layer.
    • Motivation to Combine (for §103 grounds): A POSITA would combine Takenoiri's structure with Shen's teachings to achieve the desirable uniform switching behavior and smooth hysteresis loop that Shen demonstrates is possible with proper coupling between hard and soft layers.
    • Expectation of Success (for §103 grounds): Success was expected because both references concern analogous PMR media, and adjusting coupling layer thickness in Takenoiri’s structure to achieve Shen’s demonstrated magnetic properties was presented as a routine optimization.

Ground 3: Claims 10-12 are obvious over Takenoiri in view of Li.

  • Prior Art Relied Upon: Takenoiri (Patent 8,329,321) and Li (Patent 7,846,564).

  • Core Argument for this Ground:

    • Prior Art Mapping: This ground targeted claims reciting specific physical dimensions. Petitioner asserted that Li provided specific numerical parameters that would have been obvious to apply to Takenoiri's general structure. For claim 10, the combined teachings allegedly rendered obvious a nucleation host thickness of less than 30 nm. For claim 11, Li taught a grain size of about 4 to 10 nm, which met the claimed range. For claim 12, the layer thicknesses taught by the references allegedly resulted in a grain height greater than the grain diameter.
    • Motivation to Combine (for §103 grounds): A POSITA implementing Takenoiri's design to achieve high-density recording would look to analogous art like Li for guidance on optimizing microstructural parameters, such as grain size and layer thickness, which are known to be critical for performance.
    • Expectation of Success (for §103 grounds): A POSITA would have a reasonable expectation of success because both references teach controlling grain size and layer thickness using conventional fabrication techniques, making the incorporation of Li's specific dimensions into Takenoiri's structure a predictable refinement.

  • Additional Grounds: Petitioner asserted additional obviousness challenges for claim 15 over Takenoiri in view of Asti (a 2006 article on exchange-spring multilayers) and for claim 22 over Takenoiri in view of Chang (Patent 6,777,066), relying on similar theories of combining Takenoiri's foundational structure with specific teachings from the secondary references.

4. Relief Requested

  • Petitioner requests institution of an inter partes review and cancellation of claims 1-6, 9-15, and 22-23 of the ’864 patent as unpatentable.