Invalidity dossier
US 7868551
Fluorescent tube having an increasing internal diameter, a method of driving the fluorescent tube, an illuminating device for display device, and a display device having the illuminating device
Current assignee: Sharp Corp
Added 9/23/2026, 2:56:02 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 7,868,551 B2
Title: Fluorescent tube having an increasing internal diameter, a method of driving the fluorescent tube, an illuminating device for display device, and a display device having the illuminating device.
Assignee / Inventor: Sharp Corp (Sharp Kabushiki Kaisha); inventor Yoshiki Takata.
Key dates: Priority 2005-04-14; filed 2006-02-17; published as US20090072753A1 on 2009-03-19; granted 2011-01-11. Status listed as "Expired - Fee Related," adjusted expiration 2027-02-20 (Google's own note: legal status is an assumption, not a legal conclusion).
Purpose (plain language): The patent addresses a luminance problem in backlit displays. In a conventional illuminating device (e.g., liquid crystal display device 20 with bezel 2, display panel 3, and illuminating device 4), fluorescent tubes 21 are driven by a "one-side high-voltage driving method": the electrode part holder 15 side is the high-voltage driving side 8, and the holder 16 side is the low-voltage driving side 9. Because the metal backlight chassis 11 is typically at ground potential, it acts as an adjacent conductor, creating stray capacitances "Cs" between the tubes and the chassis. Part of the tube current leaks to the chassis as leakage current "is." That leakage grows with tube length, producing current differences between the high-voltage and low-voltage sides and a luminance gradient — brightness falls from the high-voltage side toward the low-voltage side.
Scope: The title indicates the claimed subject matter concerns a fluorescent tube whose internal diameter increases (a tube-geometry solution to the above problem), a method of driving that tube, an illuminating device for a display device, and a display device incorporating the illuminating device. The excerpt classifies the document under, among others, H05B41/2821, H05B41/2822, G02F1/133604, G02F1/133611, and H01J61/33.
What the excerpt does not establish: It provides no claim text or claim numbers, no detailed description, no drawings, and no prior-art references. It therefore cannot support any statement about the specific claimed diameter profile, the driving method steps, dependent-claim scope, or the figures. It also does not establish ownership transfers beyond the listed assignment, litigation, validity, or prior art. Consult the source for omitted text: https://patents.google.com/patent/US7868551/en
Generated 10/1/2026, 9:51:53 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
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.