Invalidity dossier
US 5769522
Surface light source device
Current assignee: Enplas Corp
Added 9/23/2026, 7:47:35 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 — US 5,769,522 A
Title: Surface light source device
Assignee: Enplas Corp (original and current assignee per the supplied record)
Key dates (from the source):
- Priority date: 1991-09-09 (claimed from JP1991080357U); a second priority claimed 1991-11-28 (JP1991105342U); also claims priority from US07/910,746
- Filing date: 1996-07-24 (application US08/685,841)
- Publication/grant date: 1998-06-23
- Status listed: Expired – Lifetime; anticipated expiration 2012-07-08
- Inventors: Isamu Kaneko, Hideaki Katoh, Kazuaki Yokoyama, Tsuyoshi Ishikawa
Purpose: The device is intended as a back light for liquid crystal display units. The stated problem is that conventional transparent-panel back lights emit their brightest light at a steep inclination (e.g., about 75° for acrylic of refractive index 1.49, or about 60° for a tapered panel with two sources), so images observed from the normal viewing direction appear relatively dark. The stated objects are to enhance brightness in the direction perpendicular to the diffusing panel(s).
Plain-language scope: In one aspect, the device has at least one light source; a transparent panel with at least one end surface of incidence near the light source; a plurality of diffusing panels on the top surface with spaces between them; and a reflecting surface on the rear surface. In another aspect, a single diffusing panel is used together with a transparent sheet bearing saw-tooth-shaped protrusions on one surface. The sheet may instead carry many very small conical or pyramidal protrusions, whose tips or vertices may be rounded. For liquid crystal use, rows of protrusions may lie oblique to the panel's bus lines or frame sides. Light enters the panel's end face and exits through the diffusing panel(s) or sheet.
Source: https://patents.google.com/patent/US5769522/en
What the excerpt does not establish: It gives no claim text, so claim scope, dependencies, and claim count are unknown. It provides no complete figure descriptions or reference numerals beyond the excerpted definitions, no examples, and no legal-status conclusion. Litigation, ownership transfers, validity, and prior-art analysis were not researched and are not addressed here.
Generated 10/1/2026, 9:41:48 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.