PTAB

IPR2020-00938

Seoul Semiconductor Co Ltd v. Document Security Systems Inc

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1. Case Identification

2. Patent Overview

  • Title: Light-Emitting Device Having a Phosphor Particle Layer With Specific Thickness
  • Brief Description: The ’119 patent describes a light-emitting device, typically a white LED, designed to overcome non-uniform color output caused by inconsistent phosphor distribution. The invention confines phosphor particles to a thin, conformal layer directly over the LED die and within a reflective cup to achieve more uniform light conversion and color.

3. Grounds for Unpatentability

Ground 1: Claims 1-4 and 7 are anticipated by Nichia-614.

  • Prior Art Relied Upon: Nichia-614 (Japanese Patent Publication No. 2003-115614).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Nichia-614, which was not considered during prosecution, discloses every limitation of the challenged claims. Independent claim 1 is met because Nichia-614 teaches an LED die within a reflective cup, covered by a conformal layer of phosphor particles in direct contact with the die. This layer has a "substantially equal" thickness of approximately 20 µm (less than the claimed 100 µm) and covers a portion of the reflective sidewalls. Independent claim 2 is met because Nichia-614's method of forming the phosphor layer involves a slurry containing a volatile solvent (ethylene glycol) that is evaporated during a drying step, leaving a residue of phosphor particles, which meets the product-by-process recitation. The dependent claims are met by Nichia-614's disclosure of the light source as an LED (claim 3) and the presence of a clear "mold member" over the phosphor layer (claim 4).

Ground 2: Claims 1-7 are obvious over Nichia-341.

  • Prior Art Relied Upon: Nichia-341 (Application # 2003/0080341).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner asserted Nichia-341 teaches all elements of claims 1-7. It discloses forming a wavelength-converting layer by precipitating particles onto an LED die within a reflective cup, resulting in a conformal, single-particle layer of substantially uniform thickness (e.g., 15-30 µm). Petitioner argued that Nichia-341’s use of "fluorescent material" (e.g., YAG) would be understood by a POSITA as interchangeable with the claimed "phosphor," as evidenced by contemporaneous patent literature. For claim 2’s process limitation, Petitioner contended that Nichia-341’s disclosure of using volatile acid anhydrides and solvents like ethylene glycol in its slurry, which evaporate during the heat-curing process, meets the "residue of a slurry" requirement.
    • Motivation to Combine (N/A - Single Reference): Not applicable.
    • Expectation of Success: The teachings in Nichia-341 regarding the creation of a uniform particle layer to control light conversion made the claimed structure obvious.
    • Key Aspects: This ground covers all challenged claims and hinges on the argument that a POSITA would have considered "fluorescent material" and "phosphor" to be synonymous or at least obvious substitutes for achieving the same light-conversion function.

Ground 3: Claim 1 is obvious over Matsushita alone or in view of Nichia-614.

  • Prior Art Relied Upon: Matsushita (Japanese Publication No. 2000-150966) and Nichia-614.

  • Core Argument for this Ground:

    • Prior Art Mapping: Petitioner argued Matsushita alone renders claim 1 obvious, as it discloses an LED in a reflective cup with a conformal phosphor layer in direct contact, with a thickness of 7-30 µm. The figures in Matsushita depict a layer that appears substantially uniform.
    • Motivation to Combine (for §103 grounds): If the Board were to find that Matsushita does not explicitly teach a "substantially uniform" phosphor layer, a POSITA would have been motivated to combine its teachings with Nichia-614. Nichia-614 explicitly addresses the problem of "color tone unevenness" resulting from non-uniform phosphor layers and teaches forming a "substantially equal" thickness layer as the solution. A POSITA would combine Nichia-614's technique for achieving uniformity with Matsushita's device structure to achieve the predictable result of improved color consistency.
    • Expectation of Success (for §103 grounds): A POSITA would have reasonably expected success in applying the known uniformity-enhancing methods of Nichia-614 to the general LED structure of Matsushita, as both references operate on the same principle of phosphor-based wavelength conversion.

  • Additional Grounds: Petitioner asserted additional obviousness challenges, including that claim 5 is obvious over Nichia-614 and Nichia-341, and claim 6 is obvious over that same combination further in view of Koike (Patent 6,345,903), based on motivations to add known diffusing agents and encapsulants to improve light scattering and device durability.

4. Key Claim Construction Positions

  • "conformal": Petitioner argued this term, added during prosecution, should be construed to mean the layer of phosphor particles "conforms to the shape of the underlying die."
  • "said layer comprising a residue of a slurry...": Petitioner argued this phrase in claim 2 is a non-limiting product-by-process limitation. For validity purposes, the analysis should focus only on whether the prior art discloses the final structure (a layer of phosphor particles), not the method by which it was made. Petitioner asserted that the Examiner initially treated the phrase this way before tacitly withdrawing the position.

5. Relief Requested

  • Petitioner requests institution of an inter partes review and cancellation of claims 1-7 of the ’119 patent as unpatentable.