Invalidity dossier
US 4975808
Backlighting apparatus
Current assignee: Motorola Solutions Inc
Added 9/23/2026, 5:18:23 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: US4975808A — "Backlighting Apparatus"
Identification. US4975808A (application US07/415,741), filed and granted priority on 1989-10-02, published 1990-12-04. Inventors: David L. Bond and Kevin D. Kaschke. Original assignee: Motorola, Inc. (Schaumburg, Illinois, a corp. of DE); current assignee listed as [Motorola Solutions Inc.](/litigations/by-defendant/Motorola%20Solutions%20Inc.) Status: Expired – Lifetime, with anticipated expiration 2009-10-02.
Purpose. The invention relates generally to backlighting and specifically to backlighting liquid crystal displays (LCDs). The excerpt explains the underlying problem: LCDs act as light shutters rather than light emitters, so they require light behind them. Two backlighting techniques are described — a reflector behind the LCD (effective in high ambient light, such as sunlight, but ineffective in low ambient light) and an artificial light source behind the LCD (effective in low ambient light but overpowered by high ambient light, leaving segments dim or unreadable). Artificial sources listed include incandescent bulbs, LEDs, electroluminescent panels, fluorescent tubes, and halogen bulbs. The excerpt further notes that combining backlighting with the LCD and drive circuitry yields a "display module," and that some modules are so thin, or so restricted in length and width, that illumination sources must be placed on the sides of a light pipe to backlight the LCD.
Plain-language scope (from the excerpt). The disclosed subject matter concerns a backlighting apparatus, with prior-art keywords listed as light, distributing, reflecting, recess, and sides, and classifications spanning edge-lit/planar light guides (G02B6/00–6/0068) and edge-illuminated signs (G09F13/18). The text mentions features such as a diffuser sheet on top of the light pipe, recesses shaped to house part of a light source, tapered/wedge-shaped light guides, scattering dots of varying density or size for homogeneous output, reflecting elements, and multi-source arrangements.
What the excerpt does not establish. It does not reproduce the claims, abstract, or full description; the images, detailed embodiments, and figures are omitted. It therefore cannot establish the precise claimed scope, the exact structures disclosed, or the specific prior art relied upon. It also provides no information on litigation, ownership transfers, validity, or the accuracy of the listed legal status and assignees.
Source: https://patents.google.com/patent/[US4975808](/patent/US4975808)/en
Generated 10/1/2026, 9:43:41 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
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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.