Invalidity dossier
US 5408388
Planar illuminating device
Current assignee: Stanley Electric Co Ltd
Added 9/23/2026, 4:47:11 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 5408388 A
Title: Planar illuminating device
Assignee/Original Assignee: Stanley Electric Co., Ltd.
Inventors: Uruo Kobayashi, Yoji Oki, Nobuo Matsui, Yoshinori Go
Key dates (as listed): Priority date 1992-01-24; filing date 1993-01-22; publication/grant date 1995-04-18; anticipated expiration 2013-01-22. Legal status: Expired – Lifetime.
Application number: US 08/009,208
Purpose: The device is a planar (flat) illuminating device intended for use as a back light for liquid crystal displays of portable office automation apparatuses, such as a word processor or a personal computer.
Plain-language scope: The device includes a flat light-transmitting plate (e.g., high-transparency acrylic resin) with two light sources placed adjacent to opposite side edges, a reflector behind the plate, and a light diffuser in front of it. What the claims/description present as the improvement is a reflecting finish applied directly to the rear face of the plate, with its reflecting surface facing generally toward the front face, and whose reflectance varies with distance from either light source. The front face additionally carries parallel prismatic cuts whose longitudinal axes run substantially parallel to rays passing through the plate from the sources. The combination of reflecting finish and reflector is described as increasing surface illuminance and uniformity. The description further notes a drawback of conventional arrangements—equalizing illuminance across the diffusing sheet to the level of its darkest part reduces overall device efficiency. According to the "Definitions" excerpt, a second aspect adds spot-shaped reflecting layers on the rear surface with higher reflectance than the reflector, larger where farther from the light sources, and a rear tapering portion.
Source: https://patents.google.com/patent/US5408388/en
Not established by the excerpt: The full claim set and claim language; the complete detailed description and omitted figures; the specific prior-art references relied upon; and the accuracy of the listed legal status, assignee, or dates (these are expressly described in the source as assumptions, not legal conclusions). No litigation, ownership-transfer, validity, or prior-art research was performed.
Generated 10/1/2026, 9:44:10 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.