Invalidity dossier
US 5390436
Display system
Current assignee: ILLUMINATION RESEARCH GROUP Inc
Added 9/23/2026, 6:46:50 PM
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Patent summary
Title, assignee, inventors, filing/issue dates, abstract, and a plain-language overview of the claims.
Patent Overview: US5390436A — "Display System"
Title: Display system
Patent number: US5390436A
Application number: US08/030,416
Inventor: John Ashall
Original/current assignee: Illumination Research Group Inc (also listed as Illumination Res Group Inc); assignments recorded from Illumination Research Group (Properties) Pty. Ltd. and Ashlar Screenprints Pty. Ltd.
Priority date: 1990-09-20
Filing date: 1991-09-20
Publication/grant date: 1995-02-21
Status: Expired – Lifetime (anticipated expiration 2012-02-21)
Purpose: The patent addresses drawbacks of back-illuminated signs, which required large banks of lights, raising running and maintenance costs, and required dismantling the entire sign to replace lights. The stated aim is to reduce the number of lights needed to illuminate a display of the same size and to alleviate other prior-art problems.
Plain-language scope: The invention is an illuminated display system comprising a transparent medium with two opposing surfaces to be illuminated, where both surfaces carry a matrix of dots substantially covering them. The patent states that applying the dot matrix to both sides provides greater and more even illumination, even for large signs—a result the text says prior art does not discuss and theory does not predict.
Further disclosed features: a light source generally fixed to only one edge of the sheet (additional edge sources only for very large signs); dot density preferably increasing along the sheet away from the light-source edge, achieved by increasing dot numbers with smaller gaps, or by enlarging dots at constant gaps; dots of any shape (square, round, rectangular, triangular, irregular) and translucent, opaque, or preferably white; application by etching, painting, screen printing, or other means; alternatively a dot-matrix film adhered to the sheet; glass, plastic, or preferably acrylic medium; and an opaque, light-coloured (preferably white) backing plate. The invention also covers articles: the transparent medium itself, and a transparent film with a dot matrix for fixing onto a transparent sheet.
What the excerpt does not establish: It does not provide claim language, the full description, the abstract, or prior-art references. It does not establish litigation, ownership transfers, validity, or the accuracy of the listed legal status.
Source: https://patents.google.com/patent/[US5390436](/patent/US5390436)/en
Generated 10/1/2026, 9:42:36 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
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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.