Invalidity dossier
US 5598280
Added 9/23/2026, 6:34:13 PM
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Patent summary
Title, assignee, inventors, filing/issue dates, abstract, and a plain-language overview of the claims.
Patent Overview — US5598280A
Title: Film lens and a surface light source using the same
Assignee: Dai Nippon Printing Co., Ltd. (original and current assignee listed). Inventors: Toshikazu Nishio, Michiko Takeuchi, Nobu Masubuchi.
Key dates: Priority 1993-03-23 (JP 08695493A; a second priority 1993-11-29 from JP 5323214A); filed 1994-03-22; granted/published 1997-01-28. Legal status shown as "Expired – Lifetime," with anticipated expiration 2014-03-22.
Purpose: The patent addresses edge-light surface light sources used as back-lighting for displays such as liquid crystal display units, illuminated advertising displays, and traffic-control signs. The stated objects are to emit uniform, high-luminance light within a desired angular range without increasing power consumption or heat release, to avoid luminance variation depending on in-plane position, and to eliminate interference fringes of equal thickness ("Newton's rings").
Plain-language scope: A film lens has a light-transmitting base with concave or convex unit lenses on one side and projections on the opposite side whose profile height is at least the wavelength of the source light and no greater than 100 μm. These projections hold a gap between the film lens and the light guide plate, so light can propagate through the guide plate by total reflection rather than escaping where the two smooth surfaces would otherwise be in optical contact. This is described as yielding uniform luminance across the whole surface instead of concentration near the light source. The projections are arranged noncyclically, with each projection width Δx ≤ 100 μm, and projection size distribution is said to restrain interference fringes. A lens-scale dimension is also given in relation to maximum source wavelength and the angular radius of the source.
The excerpt describes edge-lit prior art (light guide plate with scattering reflector; triangular-prism lenticular film; stacked crossed film lenses causing interference fringes) and figures showing embodiments with projections as a separate layer or formed directly on the film lens.
Source: https://patents.google.com/patent/[US5598280](/patent/US5598280)/en
Not established by this excerpt: the full text of the claims, the complete detailed description, exact claim language or scope, prosecution history, and any figures' content beyond their captions.
Generated 10/1/2026, 9:42:42 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.