Invalidity dossier
US 5641219
Uniform illumination light emitting device
Current assignee: Individual
Added 9/23/2026, 9:18:23 PM
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Patent summary
Title, assignee, inventors, filing/issue dates, abstract, and a plain-language overview of the claims.
Patent Overview — US5641219A
Title: Uniform illumination light emitting device
Patent number: US5641219A (application US08/480,929)
Inventor: Tatsuji Mizobe
Assignee: Individual (original assignee: Individual)
Key dates: Priority date 1990-06-22 (claimed from US07/541,944, which issued as US5057974A); filing date 1995-06-07; publication/grant date 1997-06-24; anticipated expiration 2014-06-24. Legal status: Expired – Fee Related.
Purpose: The patent addresses planar light emitting or illuminating devices used to illuminate advertisements, signboards, billboards, guideboards, and similar items—particularly the difficulty of illuminating a light emitting surface uniformly when light is introduced from a peripheral portion of a thin light emitting board. The stated object is uniform illumination over the entire light emitting surface.
Plain-language scope: A planar light emitting device includes a light transmissive substrate made of transparent material (e.g., acrylic resin) with a predetermined exterior shape; light sources (e.g., fluorescent lamps, light emitting diodes, or incandescent lamps) that introduce light into the substrate; a light reflective layer around the substrate periphery to prevent light leakage; light reflective objects on the surface opposite the light emitting surface, distributed at a density inversely proportional to illuminance at each position of the rear surface; and a light reflecting plate or sheet covering the rear surfaces of those objects. The reflective objects may take the form of lines or dots, applied via opaque liquids (special inks or coating paints), rough surfaces or narrow shallow grooves, or small metal pieces/metallic film. Embodiments show a rectangular desk-top device and a curved substrate (FIG. 7).
Source: https://patents.google.com/patent/[US5641219](/patent/US5641219)/en
What the excerpt does not establish: The classification listing shows several CPC groups, but the excerpt does not identify specific claims or their exact wording, dependent-claim structure, or total claim count (item counts appear in the source index but claim text is not included here). It does not establish figures' full content, the omitted description portions, prosecution history, or the accuracy of the stated legal status and dates, which the source itself notes are assumptions rather than legal conclusions.
Generated 10/1/2026, 9:34:23 PM
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Litigation summary
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Proceedings on file (0)
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No PTAB proceedings on file. This patent has not been challenged via IPR, PGR, or CBM. The absence is itself a signal — well-asserted patents eventually attract IPRs. The LLM analysis below may surface filings the ODP feed hasn’t indexed yet.
PTAB challenges
AIA trial proceedings at the USPTO Patent Trial and Appeal Board — IPR, PGR, and CBM. Petitioners, judge panels, claim-level invalidation outcomes from Final Written Decisions, and Federal Circuit appeals. The single most important defensive datapoint after litigation history.
Assignment history
Inventors, original assignee, and the chain of ownership recorded with the USPTO — including the correspondent attorney who recorded each assignment, since shell-LLC chains often share one repeat-player attorney even when the entity names look unrelated. Surfaces NPE / patent-troll patterns: shell-entity transfers, known asserters in the chain, repeat correspondent fingerprints, pre-litigation assignments, and bankruptcy fire-sales.
Prior art
Earlier patents, publications, and products that may anticipate or render the claims unpatentable.
Obviousness
Combinations of prior art that suggest the claimed invention would have been obvious under 35 U.S.C. § 103.
Extensions
Patent term adjustments, term extensions, continuations, divisionals, family members, and expiration dates.
Derivative works
Defensive disclosure: derivative variations of each claim designed to render future incremental improvements obvious or non-novel.