Invalidity dossier
US 4906070
Totally internally reflecting thin, flexible film
Current assignee: 3M Innovative Properties Co
Added 9/23/2026, 7:41:33 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: US4906070A
Title: Totally internally reflecting thin, flexible film
Patent number: US4906070A
Application number: US07/218,087
Inventor: Sanford Cobb, Jr.
Original assignee: Minnesota Mining and Manufacturing Co
Current assignee (as listed): 3M Innovative Properties Co
Priority date: 1985-11-21
Filing date: 1988-07-12
Publication (grant) date: 1990-03-06
Legal status (as listed): Expired – Lifetime; anticipated expiration 2007-03-06
Source: https://patents.google.com/patent/[US4906070](/patent/US4906070)/en
Purpose: The film is a transparent material whose two surfaces cooperate to totally internally reflect light incident within certain angular ranges. Because it requires no coating, the film is described as capable of maintaining efficiency over long periods, and its flexibility lets it be formed into various shapes and used in several ways.
Plain-language scope (from the supplied text): A thin, flexible transparent film has 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; the prisms' perpendicular sides make an angle of approximately 45° with the smooth surface when planar. Light refracted at one surface is totally internally reflected at the other when it strikes at more than the critical angle (the arc sine of the reciprocal of the material's index of refraction). The film can be curled into a smooth continuous arcuate curve without significantly affecting performance in many applications. Suggested uses include a solar-energy concentrating trough and a light conduit/optical tunnel of various cross-sections, which can be manipulated to act as an illuminator by permitting controlled light leakage (e.g., rounded peaks).
What the supplied excerpt does not establish: It does not provide the full claim text (claims are listed only as counts), the complete description, detailed embodiments or examples, specific materials data, or the figures. It also does not establish litigation, ownership transfers beyond the listed reassignment entries, validity, or prior art beyond the "prior art keywords" field.
Generated 10/1/2026, 9:41:53 PM
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Litigation summary
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Proceedings on file (0)
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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.