PTAB

IPR2026-00016

Resonac Hard Disk Corp v. Mr Technologies GmbH

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Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Multilayer Exchange Spring Recording Media
  • Brief Description: The ’734 patent relates to multilayer perpendicular magnetic recording (PMR) media for hard disk drives. The technology aims to overcome the "writeability problem" of thermally stable hard magnetic layers by incorporating a softer, exchange-coupled multilayer structure, termed a "nucleation host," on top of the hard layer to reduce the required switching field.

3. Grounds for Unpatentability

Ground 1: Obviousness over Takenoiri - Claims 1-2, 4, and 7-8 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 limitations of the challenged claims. Although Takenoiri primarily illustrates a bi-layer magnetic structure, it expressly teaches that the structure can have "three or more layers." Petitioner asserted that this obvious tri-layer structure maps directly onto the claims of the ’734 patent. In this configuration, Takenoiri’s first magnetic recording layer is the claimed "hard magnetic storage layer," and the second and third magnetic recording layers together form the claimed "nucleation host." Petitioner further contended that Takenoiri discloses a hard layer with a coercive field greater than 0.5 T and teaches a graded anisotropy profile (K2 > K1) for its layers, meeting the key limitations added during prosecution to overcome prior art.
    • Motivation to Modify: Petitioner argued that a person of ordinary skill in the art (POSITA), motivated by Takenoiri’s stated goal of reducing the switching field while maintaining thermal stability, would find it obvious to extend its disclosed bi-layer structure to the explicitly suggested tri-layer structure. This modification was presented as a predictable design choice to further improve recordability.
    • Expectation of Success: A POSITA would have a reasonable expectation of success in creating the tri-layer structure, as Takenoiri provides detailed examples and teaches how to tune material properties, compositions, and layer thicknesses to achieve the desired graded anisotropy and coercivity.

Ground 2: Obviousness over Takenoiri and Fullerton - Claims 5-6 and 9-11 are obvious over Takenoiri in view of Fullerton.

  • Prior Art Relied Upon: Takenoiri (Patent 8,329,321) and Fullerton (Patent 6,834,026).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground built upon the tri-layer structure established from Takenoiri in Ground 1. Petitioner argued that the dependent claims (5-6, 9-11), which recite specific materials for the perpendicular anisotropy layer (e.g., FePt based alloy, L10-ordered phase material, FePt-X, CoPt-X), are disclosed by Fullerton. Fullerton taught the use of these specific high-anisotropy materials for the hard magnetic layer in a similar PMR media context.
    • Motivation to Combine: Petitioner asserted that a POSITA would combine the teachings of Takenoiri and Fullerton to improve the thermal stability of Takenoiri's media. A POSITA implementing Takenoiri's structure would be motivated to seek materials with higher anisotropy for the hard layer, a well-known strategy for enhancing stability. Fullerton was identified as an analogous and pertinent reference disclosing exactly such materials (e.g., FePt, CoPt alloys) for the same purpose in the same field of endeavor.
    • Expectation of Success: A POSITA would have a reasonable expectation of success because Fullerton’s high-anisotropy materials were not novel and could be fabricated with known processes. Substituting these known, improved materials into Takenoiri's base structure would have been a routine and predictable optimization.

Ground 3: Obviousness over Takenoiri and Shen - Claim 12 is obvious over Takenoiri in view of Shen.

  • Prior Art Relied Upon: Takenoiri (Patent 8,329,321) and Shen (a 2005 journal article titled "Composite perpendicular magnetic recording media using [Co/PdSi]n as a hard layer and FeSiO as a soft layer").
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground also used Takenoiri's tri-layer structure as the foundation. Petitioner argued that Shen provides the final element required by claim 12: a specific mathematical property of the hysteresis loop. Claim 12 requires that a normalized derivative of magnetization ('k') remains substantially constant (not changing by more than a factor of three) within a specific range. Petitioner contended that while Takenoiri provides a conceptual illustration of a hysteresis loop, Shen provides measured, experimental data for a similar composite magnetic medium that explicitly shows this claimed property.
    • Motivation to Combine: A POSITA seeking to implement Takenoiri’s multilayer structure would be motivated to use Shen’s teachings to achieve a desirable uniform switching behavior and a smooth hysteresis loop. Shen demonstrated that proper coupling between soft and hard layers—the central principle of Takenoiri—produces the exact switching characteristics claimed in claim 12. Therefore, a POSITA would look to Shen’s experimental results to optimize the coupling in Takenoiri’s design.
    • Expectation of Success: A POSITA would have an expectation of success because Takenoiri teaches how to control coupling strength through layer thickness. By applying Shen’s guidance on achieving a smooth loop, a POSITA could predictably adjust Takenoiri’s coupling layers to produce a structure with the hysteresis loop characteristics required by claim 12.

4. Relief Requested

  • Petitioner requested that the Board institute an inter partes review and cancel claims 1-2 and 4-12 of the ’734 patent as unpatentable.