Invalidity dossier
US 5980025
Thermal inkjet printhead with increased resistance control and method for making the printhead
Current assignee: Xerox Corp
Added 9/23/2026, 9:02:21 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 5,980,025
Title: Thermal inkjet printhead with increased resistance control and method for making the printhead
Patent Number: US5980025A
Application Number: US08/976,419
Inventors: Cathie J. Burke; Alan D. Raisanen
Assignee: Xerox Corp (original and current assignee listed)
Priority/Filing Date: 1997-11-21
Publication (Grant) Date: 1999-11-09
Purpose
The invention relates generally to thermal ink jet printing and, more particularly, to printheads with polysilicon resistive heaters provided with improved resistance control.
Plain-Language Scope
The patent addresses a problem in prior-art thermal inkjet printheads: a silicon nitride layer (17), typically deposited by LPCVD, can have high compressive stress (up to 6×10⁸ dynes/cm²). This stressed layer applies mechanical strain to the underlying polysilicon heater (34), causing resistivity changes via piezoresistive effects and dopant redistribution.
The disclosed solution: a thin buffer oxide film is deposited over the polysilicon heater elements, followed by a thinner-than-normal silicon nitride layer, then a glass oxide composite layer. Because the nitride is a continuous blanket layer beneath the glass, the quality of the nitride-to-glass seal becomes less critical—any ink infiltrating past that seal is stopped at the continuous nitride film.
The printhead includes a plurality of ink-filled channels in thermal connection with a resistor heater section. The resistor array comprises a first moderately-doped n+ polysilicon layer with a buffer oxide layer overlying it, passivation means for thermal isolation and ink erosion protection, and electrical circuits providing input drive signals. A method for fabricating the printhead is also claimed.
What the Excerpt Does Not Establish
The supplied text is an excerpt. It does not reproduce the full claims, the complete fabrication method steps, detailed process parameters, or the full specification. It also does not establish the actual legal scope, prosecution history, or any findings regarding the incorporated references (U.S. Pat. Re. Nos. 32,572; 4,774,530; 4,951,063).
Generated 10/1/2026, 9:41:00 PM
Cases on file (0)
Specific litigation cases in our database that name US patent 5980025. The free-form analysis below may also discuss cases beyond this list.
No cases on file mention this patent. Upload a CSV or add a case manually in Admin → Manage litigation cases.
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.