Invalidity dossier
US 5619351
Surface-type illumination device and liquid crystal display
Current assignee: Seiko Epson Corp
Added 9/23/2026, 4:10:37 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: US5619351A
Title: Surface-type illumination device and liquid crystal display
Patent number: US5619351A
Application number: US08/204,374
Inventor(s): Tatsuaki Funamoto; Toru Yagasaki; Fumiaki Akahane
Original/Current Assignee: Seiko Epson Corp (per supplied text)
Priority date: 1992-07-13
Filing date: 1993-07-13
Publication (grant) date: 1997-04-08
Legal status (as listed): Expired – Lifetime; anticipated expiration 2014-04-08
Purpose and plain-language scope (based only on supplied text):
The patent concerns a "surface-type illumination device" and a "liquid crystal display." According to the classifications and prior-art keywords included in the excerpt, the device involves a light guide in the form of a plate that couples light out toward a surface. The supplied text indicates the light guide includes a diffusion pattern (e.g., scattering dots or dot-like elements) on its surface, with the pattern varying in density, size, shape, or depth along the light guide to provide homogeneous light output intensity. The excerpt also references producing polarization effects via a polarizing surface or additional polarizing element, use with elongated light sources such as an incandescent or gas discharge tube, and packaging/positioning aspects of the light source relative to the light guide. Related family members noted in the supplied text include US5949505A, US6108060A, and US08/689,424.
What the excerpt does not establish:
The supplied excerpt omits the claims, detailed description, drawings, and any express statements of the invention's stated object or advantages. It therefore does not establish the precise claimed scope, the specific structural or numerical limitations of the diffusion pattern, the exact relationship between the illumination device and the liquid crystal display, or the material/composition details of the light guide or scatterers. It also does not establish: inventorship or assignment beyond the listed reassignment entry; validity, enforceability, or the accuracy of the "Expired – Lifetime" status; any litigation or ownership transfers; or the content of any prior art. No assertion is made here regarding novelty or patentability. The classification entries and "prior art keywords" are metadata, not substantive disclosures.
Source: https://patents.google.com/patent/[US5619351](/patent/US5619351)/en
Generated 10/1/2026, 9:51:06 PM
Cases on file (0)
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Litigation summary
Past and pending lawsuits — plaintiffs, defendants, jurisdictions, outcomes, and notable rulings.
Proceedings on file (0)
All PTAB activity →AIA trial proceedings (IPR / PGR / CBM) filed at the USPTO Patent Trial and Appeal Board against this patent. Sourced from the USPTO Open Data Portal and refreshed every six hours; each proceeding number deep-links to the PTAB E2E docket.
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
Earlier patents, publications, and products that may anticipate or render the claims unpatentable.
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.