Invalidity dossier
US 5438484
Added 9/23/2026, 1:42:24 PM
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Patent summary
Title, assignee, inventors, filing/issue dates, abstract, and a plain-language overview of the claims.
Patent Overview — US 5,438,484
Title: Surface lighting device and a display having such a lighting device
Patent number: US 5,438,484 A (application US 07/984,836)
Assignee: Canon KABUSHIKI KAISHA (Canon Inc.), per the assignment recorded 1992-12-03.
Inventors: Toshiyuki Kanda, Hisao Tajima, Hiroshi Takabayashi, Takashi Yamamoto, Hideo Mori.
Key dates (as listed, with Google's own caveats):
- Priority date: 1991-12-06 (claimed from JP 3348565A; a second priority claimed 1992-05-20 from JP 4151225A)
- Filing date: 1992-12-03
- Publication/grant date: 1995-08-01
- Anticipated expiration: 2012-12-03; status listed as "Expired – Lifetime."
- A later application (US 08/373,096) claims priority to this case and issued as US 5,664,873.
Purpose and plain-language scope: The document describes a surface lighting device—an edge-lit, plate-like light guide that spreads light from a source across a surface—and a display incorporating such a lighting device. Per the indexed subject matter, the disclosure involves a light guide, a divided light guide/light source arrangement, diffusion processes, a reflecting element or layer, and a display (e.g., liquid-crystal) application. The indexed classification places it in edge-lit planar light guides (G02B6/00 series), illuminated signs, and display applications, including "diffusing sheet or layer" and "reflecting element, sheet or layer" subclasses.
What the supplied excerpt does not establish: the excerpt is a Google Patents bibliographic/classification capture only—it does not include the claims, the written description, the drawings, or any prior-art references, so the exact claimed scope, the specific embodiments, and any cited or distinguished prior art cannot be verified from it. It also provides no litigation, ownership-transfer, validity, or patentability information, and no findings on those topics are made here.
Generated 10/1/2026, 9:52:54 PM
Cases on file (0)
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Litigation summary
Past and pending lawsuits — plaintiffs, defendants, jurisdictions, outcomes, and notable rulings.
Proceedings on file (0)
All PTAB activity →AIA trial proceedings (IPR / PGR / CBM) filed at the USPTO Patent Trial and Appeal Board against this patent. Sourced from the USPTO Open Data Portal and refreshed every six hours; each proceeding number deep-links to the PTAB E2E docket.
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.