PTAB

IPR2025-00698

Savant Technologies LLC v. Feit Electric Co Inc

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Key Events
Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Wavelength Conversion Component with a Diffusing Layer
  • Brief Description: The ’539 patent describes a wavelength conversion component for a light emitting device (LED). The technology aims to improve the "off-state" appearance of white-light LEDs by incorporating a light-diffusing layer containing scattering particles, such as titanium dioxide (TiO2), to mask the natural yellow color of the phosphor material, making the unlit device appear white.

3. Grounds for Unpatentability

Ground 1: Obviousness over Krummacher, Stokes, and Shimizu - Claims 1-11, 18-20, and 23-25 are obvious over Krummacher in view of Stokes and Shimizu.

  • Prior Art Relied Upon: Krummacher (Application # 2008/0079015), Stokes (Patent 6,791,259), and Shimizu (Patent 6,069,440 and Patent 5,998,925).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Krummacher taught the core structure of the invention: a white-light LED source comprising a blue LED, a phosphor-containing wavelength conversion layer, and a separate, overlying light-diffusing layer containing TiO2 particles. The stated purpose of Krummacher’s diffusing layer was to solve the known problem of an unattractive yellow off-state appearance by making the device appear white. However, Krummacher did not specify the precise particle size for preferential light scattering or the exact wavelength of the blue light. Petitioner asserted that Stokes remedied this by explicitly teaching the selection of TiO2 particle sizes (e.g., 100-200 nm) to "preferentially scatter blue or UV LED light as compared to yellow...light from the luminescent material." Stokes further taught that this preferential scattering improves light uniformity and conversion efficiency. Finally, Shimizu, a reference for conventional white-light LEDs, disclosed the use of blue LEDs that emit light at wavelengths greater than 440 nm, fulfilling another key claim limitation. The specific requirement that scattering of blue light be "at least twice as much" as yellow light was argued to be an inherent and obvious result of selecting particle sizes from the overlapping ranges disclosed in Stokes.
    • Motivation to Combine: A Person of Ordinary Skill in the Art (POSITA), starting with Krummacher’s device, would combine its teachings with Stokes and Shimizu to optimize performance and implement known standards. Krummacher itself directed a POSITA to use a conventional white-light LED structure, for which Shimizu was a well-known example. The motivation to incorporate Stokes’ teachings was to improve the light source’s uniformity and efficiency by maximizing the scattering of blue excitation light toward the phosphor, a declared advantage in Stokes.
    • Expectation of Success: A POSITA would have had a high expectation of success because the combination involved applying known principles (preferential scattering) to a known structure (a diffusing layer on an LED) to achieve predictable results (improved off-state appearance and light uniformity).

Ground 2: Obviousness over Hussell, Krummacher, Stokes, and Van Woudenberg - Claims 18 and 28 are obvious over Hussell in view of Krummacher, Stokes, and Van Woudenberg.

  • Prior Art Relied Upon: Hussell (Application # 2010/0124243), Krummacher (Application # 2008/0079015), Stokes (Patent 6,791,259), and Van Woudenberg (WO 2008/044171).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner contended that Hussell disclosed the foundational light bulb structure of claims 18 and 28, including an LED "filament" comprising a hollow wavelength conversion tube with phosphor material. However, Hussell's YAG phosphors would appear undesirably yellow in the off-state. Petitioner argued that Krummacher and Van Woudenberg both identified this exact problem and taught the solution: adding an external light-diffusing layer to create a neutral white off-state appearance. Stokes provided the necessary teaching for selecting the particle size within that diffusing layer to preferentially scatter blue light. Van Woudenberg further supplied the conventional blue LED emission spectrum (e.g., 430-480 nm), satisfying the claim limitation of blue light >= 440 nm.
    • Motivation to Combine: A POSITA would be motivated to modify Hussell’s light bulb to solve the well-documented problem of its yellow off-state appearance. Both Krummacher and Van Woudenberg provided the explicit reason and solution for doing so. A POSITA would therefore apply Krummacher’s diffusing layer to Hussell’s filament structure. The motivation to further incorporate Stokes and Van Woudenberg was to implement the diffusing layer with an optimized, well-understood particle size and a standard blue LED to achieve predictable optical performance.
    • Expectation of Success: A POSITA would have had a reasonable expectation of success in applying a known solution (a light-diffusing layer) from Krummacher to solve a known problem (yellow off-state appearance) in Hussell's device, using standard components and principles taught by Stokes and Van Woudenberg.

4. Arguments Regarding Discretionary Denial

  • Petitioner argued that discretionary denial under 35 U.S.C. § 325(d) would be inappropriate. The petition asserted that the primary references relied upon—Krummacher, Stokes, and Hussell—were never considered by the Examiner during the original prosecution. Petitioner further argued that the applicants failed to inform the Examiner that Figure 10 of the ’539 patent, which illustrates the key light-scattering principle, was based on well-known prior art data from DuPont, which Stokes had properly credited as "prior art." These material differences were alleged to refute the Examiner’s stated reason for allowance.

5. Relief Requested

  • Petitioner requested institution of an inter partes review (IPR) and cancellation of claims 1-11, 18-20, 23-25, and 28 of the ’539 patent as unpatentable.