Invalidity dossier
US 5056892
Totally internally reflecting thin, flexible film
Current assignee: 3M Innovative Properties Co
Added 9/23/2026, 6:05:11 PM
Active provider: DeepSeek · deepseek-flash
Patent summary
Title, assignee, inventors, filing/issue dates, abstract, and a plain-language overview of the claims.
Patent Overview — US 5056892 A
Title: Totally internally reflecting thin, flexible film
Assignee/Applicant of record: Original assignee Minnesota Mining and Manufacturing Co.; current assignee listed as 3M Innovative Properties Co (per the source's own note that Google has not analyzed or warranted the accuracy of assignee listings).
Key dates (as listed in the source):
- Prior art date / priority date: 1985-11-21
- Priority claimed from US 07/218,087 (filed 1988-07-12)
- Application US 07/472,621 filed: 1990-01-30
- Granted / published: 1991-10-15
- Anticipated expiration: 2008-10-15; legal status: Ceased
Purpose and plain-language scope (from the supplied text):
The patent describes a thin, flexible film of transparent material with a structured surface on one side and a smooth surface on the other. The structured surface is a linear array of miniature, substantially right-angled isosceles prisms arranged side-by-side, forming peaks and grooves, with the prisms' perpendicular sides at roughly 45° to the opposite smooth surface. The combination of surfaces can totally internally reflect light incident within certain angular ranges, so the film needs no coating and can retain efficiency over long periods. Because the smooth surface may lie in a continuous arcuate curve while still reflecting, and because the film is flexible, it can be shaped for varied uses—for example, solar-energy concentration on a trough, or forming a conduit/optical tunnel with prisms disposed parallel, orthogonal, or at any angle to the tunnel axis. The excerpt indicates light is only totally internally reflected under conditions it does not fully specify.
Classifications noted: e.g., G02B5/045 (prism arrays), G02B5/124 (cube-corner reflex reflectors), G02B6/0038 (light-guide grooves), F21V5/002, F24S23/10.
What the excerpt does not establish: It does not give the full claims, the complete description, the named inventor beyond "Sanford Cobb, Jr.," embodiments, materials, or quantitative angular ranges, and it omits text after the phrase "light will only be totally internally reflected and…" No litigation, ownership-transfer, validity, or prior-art conclusions are drawn here.
Generated 10/1/2026, 9:43:01 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.