Invalidity dossier
US 5771328
Added 9/23/2026, 9:59:41 PM
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Patent summary
Title, assignee, inventors, filing/issue dates, abstract, and a plain-language overview of the claims.
US 5,771,328 — Patent Overview
Title: Light directing film having variable height structured surface and light directing article constructed therefrom
Patent number: US 5,771,328 A
Application number: US 08/832,132
Inventors: David L. Wortman; Sanford Cobb, Jr.; Mark E. Gardiner
Original assignee: Minnesota Mining and Manufacturing Co.
Current assignee (as listed): 3M Co
Priority date: 1995-03-03
Filing date: 1997-04-03
Publication/grant date: 1998-06-23
Legal status (as listed): Expired – Lifetime; anticipated expiration 2015-03-03
Purpose (plain language): The film is used in optical displays to increase the amount of light exiting in a direction approximately normal ("on axis") to the display surface. Because a display's light source often dominates power consumption (e.g., battery-powered laptops, calculators, watches, phones), boosting on-axis light reduces the energy needed for a given luminance. The excerpt also notes that uneven light transmission becomes more visible when a display is viewed within a cut-off region of the film.
Scope (plain language): The patent provides a light directing film with a first surface and an opposing structured surface containing an array of prism elements. That array includes a repeating pattern of prism zones: at least a first zone where prism element peaks sit at a first distance above a reference plane, and a second zone where peaks sit at a lesser distance from that plane. Per the excerpt, "the height of the prism elements in each zone may be tailored to achieve a desire[d]" result — the sentence is truncated in the supplied text.
Classifications (as listed): e.g., G02B6/0053 (prismatic brightness-enhancement sheet); G02B5/045 (prism arrays); G02B5/0231 (microprismatic surface); B29D11/00788 (producing optical films); F21V5/02.
Source: https://patents.google.com/patent/US5771328/en
What the excerpt does not establish: It omits the claims, full description, drawings, and any figures; the "desire[d]" sentence is cut off. It gives no verified claim scope, no litigation or ownership-transfer details, and no prior-art analysis (the listed "prior art keywords" are indexing terms only). Classifications and assignee entries are stated as listed, not independently verified; the excerpt notes such data may be inaccurate or assumed.
Generated 10/1/2026, 9:33:53 PM
Cases on file (0)
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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.