PTAB

IPR2018-01751

Sony Corporation v. FUJIFILM Corporation

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1. Case Identification

2. Patent Overview

  • Title: Magnetic Recording Medium
  • Brief Description: The ’451 patent discloses a magnetic recording medium, such as magnetic tape for long-term data storage. The invention claims to reduce media noise and improve performance for high-sensitivity magnetoresistive (MR) read-heads by defining specific structural parameters for the magnetic layer, including a residual magnetization (Φr) and a specific ratio of magnetic cluster sizes under DC magnetized (Sdc) versus AC erased (Sac) conditions.

3. Grounds for Unpatentability

Ground 1: Claims 1-14 are obvious over Ejiri in view of Hokkyo and Chen

  • Prior Art Relied Upon: Ejiri (Application # 2002/0015861), Hokkyo (a 1997 journal article), and Chen (a 1999 journal article).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner asserted that Ejiri, whose lead inventor is the same as the ’451 patent’s, discloses a particulate magnetic recording medium for high-density recording that meets nearly every limitation of the challenged claims. This includes the use of an MR head, a similar layered structure, specified particle sizes, and magnetic layer thickness. However, Ejiri did not explicitly disclose the claimed ratio of magnetic cluster sizes (Sdc/Sac). Petitioner argued that Hokkyo and Chen supply the teachings necessary to render this ratio obvious. Hokkyo taught that medium noise is caused by magnetic clusters and can be analyzed by comparing the DC magnetized state (where cluster effects are prominent) with the AC erased state (which reflects fundamental particle noise). Chen taught that magnetic clusters are a primary cause of medium noise and that reducing their size improves the signal-to-noise ratio (SNR), demonstrating this relationship using Magnetic Force Microscopy (MFM) measurements.
    • Motivation to Combine (for §103 grounds): A Person of Ordinary Skill in the Art (POSITA) would combine the teachings of these references to optimize the performance of the recording medium disclosed in Ejiri. The primary motivation was the well-established industry goal of reducing medium noise to improve data storage density. A POSITA would have looked to Hokkyo’s analytical framework and Chen’s experimental validation to understand and minimize the magnetic clustering that Ejiri itself identified as a problem, thereby arriving at a medium with the claimed Sdc/Sac ratio. The combination was presented as a predictable application of known principles to achieve an expected improvement.
    • Expectation of Success (for §103 grounds): Petitioner argued that a POSITA would have had a high expectation of success because minimizing magnetic cluster size was a known result-effective variable, and the methods to achieve it (e.g., improving particle dispersion, applying shear forces) were conventional and part of routine optimization in the field.
    • Key Aspects: A central contention was that the claimed Sdc/Sac ratio is not a new invention but merely a "non-standard characterization" of the well-understood goal of achieving optimal particle dispersion. Petitioner asserted that an ideal dispersion yields a ratio of 1, and the patent’s claimed range of 0.8 to 2.0 simply captures the result of routine optimization. Furthermore, Petitioner argued that the ’451 patent fails to demonstrate the criticality of the claimed range, as its own data does not show unexpected results and lacks controlled experiments to isolate the effect of the Sdc/Sac ratio.

4. Key Claim Construction Positions

  • "residual magnetization Φr": Petitioner proposed this term be interpreted as the product of the magnetic material’s remanence (Mr) and the magnetic layer’s thickness (t), or Mr*t. This construction was argued to be consistent with how a POSA would understand the term to arrive at the claimed units of mA from standard magnetic property units (A/m) and thickness (m). This interpretation was critical for Petitioner to map the values disclosed in Ejiri (e.g., 5-50 mT·µm) directly onto the claimed range (5-50 mA).
  • "ratio (Sdc/Sac) of average area of magnetic clusters...": Petitioner argued this phrase should be given its plain and ordinary meaning as understood from the specification. While acknowledging the ratio itself was not a standard term of art, its components (magnetic clusters under DC and AC conditions) were well-known. Petitioner contended that Fujifilm’s potential construction requiring the use of MFM for measurement would be unduly narrow, but argued the combination of Ejiri, Hokkyo, and Chen renders the claims obvious even under that narrower construction.

5. Relief Requested

  • Petitioner requests institution of an inter partes review and cancellation of claims 1-14 of the ’451 patent as unpatentable under 35 U.S.C. §103.