Invalidity dossier
US 5931555
Background lighting apparatus for liquid crystal display
Current assignee: Seiko Epson Corp
Added 9/23/2026, 8:10:15 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 5,931,555
Title: Background lighting apparatus for liquid crystal display
Patent number: US 5,931,555 (US5931555A)
Application number: US08/794,652
Inventor(s): Fumiaki Akahane, Tooru Yagasaki, Tatsuaki Funamoto
Assignee: Seiko Epson Corp (original and current assignee as listed)
Key dates:
- Prior art date: 1989-05-18
- Filing date: 1997-02-03
- Publication/grant date: 1999-08-03
- Anticipated expiration: 2010-05-18
- Status: Expired – Fee Related
- Priority claims noted to US07/525,408 (US5130898A) and JP02046356A, among others
Purpose: The invention relates to background lighting apparatus, and more particularly to thin background light sources for liquid crystal panel displays, such as those used in computers, word processors, and LCD television sets.
Plain-language scope (from supplied text): The excerpt describes a plate-type lighting apparatus in which light enters from an edge or end face of a transparent plate and is guided internally. A pattern combining an irregular reflecting surface/portion and a totally reflecting portion is arranged to achieve uniform light output at a high brightness level. The disclosure contrasts this with prior approaches using multiple superimposed transparent plates with light diffusion dot patterns (e.g., as described in Japanese Laid Open No. 63-62105), which the text says increase display thickness and can produce nonuniform brightness. It also notes that increasing irregular reflection can brighten output but causes brightness to fall off with distance from the light source, and that raising source luminance increases heat generation, affecting color image quality; maintaining uniform temperature distribution is described as important because liquid crystal transmissivity is temperature-dependent.
Source: https://patents.google.com/patent/US5931555/en
What the excerpt does not establish: The supplied text is explicitly an excerpt ("consult the source for omitted text"). It does not provide the full claims, the complete written description, all drawings/figure descriptions, a full prior-art analysis, or the detailed structural embodiments. It also does not establish litigation, ownership transfers, validity, or the actual legal scope of the claims; those were not researched and are not addressed here.
Generated 10/1/2026, 9:41:32 PM
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Litigation summary
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PTAB challenges
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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.