Invalidity dossier
US 5289351
Backlighting device
Current assignee: Tosoh Corp
Added 9/23/2026, 2:35:16 PM
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Patent summary
Title, assignee, inventors, filing/issue dates, abstract, and a plain-language overview of the claims.
Patent Overview — US 5,289,351 ("Backlighting Device")
- Patent number: US 5,289,351 A
- Title: Backlighting device
- Inventors: Keiji Kashima, Osamu Shoji, Naoki Yoshida
- Assignee: Tosoh Corporation
- Priority date: 1991-03-22; Filed: 1992-03-19; Granted/published: 1994-02-22; Anticipated expiration: 2012-03-19 (status listed as "Expired – Lifetime")
- Application number: US 07/854,076
Purpose. The device illuminates transmissive or semi-transmissive liquid-crystal panels from the rear, targeting a high efficiency of power-to-luminance conversion and hence high luminance. The patent notes that liquid-crystal displays lose contrast as viewing angle increases from the normal, making luminance near the normal direction a key practical index.
Plain-language scope. The device has (1) a light-transmissive light-conducting plate with a light-diffusing element, (2) a linear light source near the end portion of at least one side (edge lighting), and (3) at least one film on the plate's exit face made of a light-transmissive material that is coarser grained on its exit face than on its entrance face (the side nearer the plate). This graining changes the luminous intensity distribution so output light is more directional along the normal to the exit face, increasing luminance in that direction. Optional features described: multiple film sheets (two may further improve luminance), a light-diffusing material printed in dots, a light-diffusing plate between film and plate, and a specular or diffusing/reflecting plate. Graining methods mentioned include embossing, sand blasting, hot-press die molding, and chemical treatment. Preferred asperity dimensions are 10–1,000 µm; convex shapes (prisms, cones) may have vertical angles of 40–170 degrees.
What the excerpt does not establish. The supplied text omits the full claims, detailed examples, and much of the specification, so precise claim scope, measured results, and comparative data are not verifiable here. No litigation, ownership transfers, validity, or prior-art conclusions are drawn. Source: https://patents.google.com/patent/US5289351/en
Generated 10/1/2026, 9:52:10 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
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Extensions
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Derivative works
Defensive disclosure: derivative variations of each claim designed to render future incremental improvements obvious or non-novel.