Invalidity dossier
US 5550676
Surface light source element
Current assignee: Mitsubishi Chemical Corp
Added 9/23/2026, 7:16:20 PM
Active provider: DeepSeek · deepseek-flash
Patent summary
Title, assignee, inventors, filing/issue dates, abstract, and a plain-language overview of the claims.
US5550676A — Surface Light Source Element: Overview
Title: Surface light source element
Patent number: US5550676A
Application number: US08/300,518
Inventors: Makoto Ohe; Issei Chiba
Original assignee: Mitsubishi Rayon Co Ltd (listed current assignee: Mitsubishi Chemical Corp)
Priority date (as listed): 1990-09-12
Filing date: 1994-09-06
Grant/publication date: 1996-08-27
Legal status (as listed): Expired – Lifetime; anticipated expiration 2013-08-27
Purpose (plain language): The patent concerns a surface light source element — a light-guide plate of the kind used to produce even, planar illumination. The source text lists "surface light source element" as the title and associates the disclosure with light guides, luminance, liquid crystal substances, and diffusion processes (abstract/description keyword counts). Classification data place it in G02B6/00 and subclasses covering planar/plate-like light guides, coupling-out of light, coupling-in of light, reflecting elements, and 2-D arrangements of prisms, protrusions, indentations or roughened surfaces.
Plain-language scope, as far as the excerpt shows: The element distributes light from a source across a flat plate so light exits over an area, with structures on or in the light guide used for coupling light out, and arrangements varied in density, size, shape or depth to provide homogeneous output intensity (per the G02B6/0036, 6/0058 and 6/0061 classification entries). The excerpt's own prior-art keyword list is "light," "light source," "flat areas," "incident," and "source element." Materials named among the description keywords include acrylic resin, polycarbonate resin, barium sulfate, titanium oxide, and white pigment, with methods such as injection moulding, screen printing, etching, sandblasting and photolithography.
What this excerpt does not establish: It supplies no claim text, no claim count beyond a keyword tally, no figures, no detailed description, no named prior-art references, no examiner citations, and no claim of measurable advantage. It therefore cannot support any statement about the precise claimed scope, novelty, or validity. Nor does it establish litigation, ownership transfers, or current enforceability; status and assignee entries are expressly assumptions.
Source: https://patents.google.com/patent/[US5550676](/patent/US5550676)/en
Generated 10/1/2026, 9:42:14 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.