US 5081473

US Patent 5,081,473 — Analyst Summary

Source of record: Full text fetched from Google Patents, https://patents.google.com/patent/[US5081473](/patent/US5081473)/en (fetched 2026-09-24). This message treats that text as authoritative.

1. Bibliographic data (as stated in the record)

2. Abstract (as printed)

"A transducer for a thermal ink jet printhead has a primary heating region having a tantalum layer, a silicon nitride layer and a polysilicon resistor layer. An n⁻ drift layer resistor serves as a secondary heating region and a field layer of silicon dioxide acts as an insulator. The field layer is sandwiched between the primary heating region and the secondary heating region. The secondary heating region by heating the field layer causes the heat generated in the primary heating region to be directed toward ink which lies above the primary heating region. An electrical contact connects the polysilicon resistor layer of the primary heating region to a driving transistor located on the same silicon wafer as the transducer. The driving transistor has a field oxide layer sandwiched between an n⁻ drift layer and a field plate layer, the field plate layer causing secondary pinch off of the n⁻ drift layer thus enabling higher operating voltages."

3. Independent claims — plain-language overview

The patent has 20 claims total, with two independent claims: claim 1 and claim 13. (Claims 2–12 depend from claim 1; claims 14–20 depend from claim 13.)

Claim 1 — The dual-heater transducer

A transducer that converts electrical energy into heat and directs that heat at an object (in the preferred embodiment, ink). Its structure is a sandwich:

• a transducer field oxide layer in the middle;
• a primary heating region on one side of that oxide, facing the object to be heated; and
• a secondary heating region on the opposite side of the oxide.

The stated functional result is that the secondary heater warms the field oxide, which enables close temperature control of the primary heating region and the object. In other words: a buried under-heater that pre-warms the structure so the top resistor can bring the ink to ejection temperature quickly and repeatably.

Claim 13 — The high-voltage field-plate driver

A driver for a transducer comprising:

• a field oxide layer;
• an n⁻ drift layer on one side of it; and
• means, connected to the opposite side of the field oxide layer, for causing "secondary pinch off" of the n⁻ drift layer.

The "secondary pinch off" means-plus-function element is the architectural core of the driver half of the invention: the field plate spreads the electric field across the n⁻ drift region so the drain junction does not reach avalanche breakdown, permitting higher supply voltages than a conventional MOS driver could tolerate.

4. Dependent claims in brief

Depending from claim 1:

• 2 — adds means for selectively applying current to both heating regions.
• 3 — defines the primary heating region as a three-layer stack: polysilicon resistor on the field oxide, then silicon nitride, then tantalum on top (the tantalum contacting the ink).
• 4 — the secondary heating region is an n⁻ drift layer.
• 5 — that n⁻ drift layer is phosphorous-doped silicon at about 2×10¹⁶ ions/cm³.
• 6 — the current-applying means is a common bus line feeding both heating regions.
• 7 — the n⁻ drift layer is formed in a silicon wafer.
• 8 — adds a driver transistor in the same wafer, with its drain in electrical contact with the polysilicon resistor layer.
• 9 — the object being heated is ink.
• 10 — the transducer is associated with an ink flow channel, making it a thermal ink jet transducer.
• 11 and 12 — add driver-side structure (driver field layer, n⁻ drift layer and field plate; the field plate being polysilicon).

Drafting note (analyst observation, not a legal conclusion): Claims 11 and 12 are captioned "A driver device according to claim 10…" even though claim 10 is a transducer claim depending from claim 1. Read literally and in context, these claims mix transducer chain dependency with driver subject matter. Anyone construing this patent should read claims 11–12 in light of the specification, which describes driver 60 of FIG. 2 separately.

Depending from claim 13:

• 14 — n⁻ drift layer is phosphorous-doped silicon.
• 15 — field oxide layer is silicon dioxide.
• 16 — the pinch-off causing means is a layer of phosphorous-doped polysilicon.
• 17 — adds a gate layer surrounded by the field oxide layer.
• 18 — that gate layer is phosphorous-doped silicon.
• 19 — the gate layer dopant concentration is 10²⁰ ions/cm³.
• 20 — the pinch-off means is phosphorous-doped silicon at 10²⁰ ions/cm³.

5. Technical gist (specification highlights)

• Dual-heater architecture: a polysilicon drop-ejection resistor (layer 12, ~0.5 µm CVD, ~10²⁰ ions/cm³) sits on a ~1.35 µm thermal SiO₂ field oxide (layer 4); underneath the oxide, in the substrate, is an ion-implanted n⁻ drift resistor (layer 2, ~2×10¹⁶ ions/cm³, ~0.5 µm, 145–175 µm long) that functions as a substrate heater. The field oxide is deliberately sandwiched between them.
• Thermal rationale: the buried n⁻ resistor heats the field oxide above ambient so the top resistor's heat preferentially conducts upward into the ink rather than down into the silicon. Stated benefits are reduced warm-up time, tighter droplet-volume control (target 35°–45 °C operating point), and mitigation of ink degassing/air-bubble and reliability issues from prolonged elevated temperature.
• Switching scheme: the polysilicon resistor gets short pulses (<10 µs) for ejection; the n⁻ drift substrate heater is switched separately at a longer duty cycle for temperature regulation. The n⁻ resistor is turned on by grounding n⁺ diffusion layer 6, isolated from aluminum contact 24 so it can be independently controlled — either off-chip via a bond pad or via on-chip power MOS drivers.
• Interface layers: silicon nitride 28 (~1500 Å, CVD) and sputtered tantalum 30 (~5000 Å) over the resistor; PSG (or BPSG / spin-on-glass alternatives) for planarization before aluminum metallization; aluminum 24 to the driver drain, aluminum 26 to a ~35–40 V common bus (18).
• Driver (FIG. 2): NMOS with n⁻ silicon layer 34 (~500 nm, ~2×10¹⁶ ions/cm³) over p⁻ wafer 70, ~1.35 µm thermal SiO₂ 36, and heavily doped polysilicon field plate 48 (~450 nm, ~10²⁰ ions/cm³). Field plate 48 causes the claimed "secondary pinch off" of layer 34. Optional alternative embodiment merges the field plate (48) and gate (50) into a single polysilicon deposition/etch step.
• Numbers given for a 128-jet device: n⁻ drift resistor sheet resistance ~5 kΩ/sq; resistance ≈100 Ω (200 µm × 10,800 µm); an 80 Ω n⁻ drift resistor at 100% duty cycle can match full-black heating of all drop-ejection resistors, though in practice ink carries away substantial heat so only a fraction is needed.

6. Search results / litigation check — explicit uncertainty

I ran live searches for this patent number and for related 2026 CAFC activity. Results:

• No CAFC 2026 docket entry, district-court case, or ITC proceeding involving US 5,081,473 appeared in any search result. My searches returned zero hits for the litigation query and only unrelated/noise results for the patent-number query (other Xerox thermal-ink-jet patents and EPO documents). I therefore cannot confirm or deny any litigation, and I am not asserting one exists or does not exist.
• Structural reason this matters: the Google Patents record shows the patent expired 2010-07-26 (anticipated expiration, 20 years from the 1990 filing), and the maintenance fee stream ran at 4, 8 and 12 years. An expired patent cannot support a live infringement action, so any 2026 CAFC docket presence would be unusual absent some collateral issue.
• Assignee chain of record: Xerox Corp → security interests recorded to Bank One, NA (2002-06-28) and JPMorgan Chase Bank (2003-10-31), with a release by JPMorgan Chase recorded 2022-09-07 in favor of Xerox Corporation. These are financing/security instruments, not transfers of title.
• I could not independently verify the current assignee beyond the listing "Xerox Corp" in the fetched record; I have no authoritative confirmation of a later outright assignment.

Bottom line on uncertainty: the bibliographic, abstract, claim and specification content above is taken directly from the authoritative full text and is reliable. The absence of litigation findings is a negative search result from a limited tool set, not a verified clean history.

7. One-paragraph takeaway

US 5,081,473 (Hawkins & Burke, Xerox, filed and priority 1990-07-26, issued 1992-01-14, now expired) claims two cooperating ideas on a single silicon thermal-ink-jet chip: (1) an under-the-field-oxide substrate heater (an n⁻ drift resistor) sandwiched below the drop-ejection polysilicon heater to pre-warm the printhead for fast warm-up and tight droplet-volume control, and (2) a field-plated high-voltage MOS driver, whose polysilicon field plate spreads the field across the n⁻ drift region ("secondary pinch off") so the on-chip driver can survive the elevated supply voltages the heater array requires. The independent claims are claim 1 (the sandwich transducer) and claim 13 (the field-plate driver defined partly in means-plus-function terms).

I'll search for litigation involving US Patent 5,081,473 across litigation-tracking sources.

The first searches returned mostly unrelated patents (e.g., 7,645,473, 6,721,473). Let me search litigation-specific databases for the exact patent.

The Xerox v. HP inkjet suits involved U.S. Patent 5,030,971 — a different number. Let me query litigation-specific databases directly for 5,081,473.

Litigation Search — U.S. Patent No. 5,081,473

Patent identified (as literal ID): U.S. Patent No. 5,081,473 — "Temperature control transducer and MOS driver for thermal ink jet printing chips" (Hawkins & Burke; assignee Xerox Corp; filed 1990‑07‑26; granted 1992‑01‑14; expired 2010‑07‑26).

Result: No litigation found

Based on my searches, I found no litigation — district court, ITC, CAFC, or PTAB/PGR — in which U.S. Patent No. 5,081,473 is identified as an asserted or challenged patent. I am reporting this as a negative finding, not as a confirmed "zero," because I was unable to directly query PACER, the Unified Patents litigation portal (portal.unifiedpatents.com/litigation/caselist), or RPX Insight's litigation database — the searches of those sources either returned unrelated matters or did not resolve to this patent. This should be independently verified against PACER/Unified before being relied upon.

Important caution — a near-miss that must NOT be conflated

My searches repeatedly surfaced the Xerox v. Hewlett‑Packard thermal ink‑jet patent campaign of 1998–2000, but that campaign asserted U.S. Patent No. 5,030,971 — a different patent number — not 5,081,473. Under the strict rule that IDs are interpreted literally and not auto-corrected, these are distinct patents and I have not attributed that litigation to 5,081,473. For context only (and clearly flagged as not this patent):

• Xerox Corp. v. Hewlett‑Packard Co. — filed May 14, 1998, in the U.S. District Court for the Western District of New York (Rochester), before Judge Michael Telesca; asserting U.S. 5,030,971 (multi‑color thermal ink‑jet printhead). The court granted HP summary dismissal (Sept. 1999); Xerox stated it would appeal. This was one of six cross‑suits filed May 1998–June 1999, all of which were settled/dismissed in March 2000.

This matter is offered only to explain the likely source of confusion (same assignee, same technology family, adjacent patent number). It is not litigation involving 5,081,473.

What the record actually shows for 5,081,473

• No "Cited By" or citation references to litigation. The Google Patents page lists 20 "Cited By" publications and 9 cited references — all are patent documents (e.g., US 4,429,321; US 4,472,875; US 4,532,530; US 4,539,571; US 4,623,903; US 4,719,477; US 4,769,527; US 4,947,192), not litigation records.
• No PTAB/IPR/PGR proceeding surfaced naming 5,081,473.
• Family: The only related publication is the Japanese counterpart JPH0679872A ("Transducer for ink jet printing head"). No litigation against that counterpart was found either.

Bottom line

No known litigation exists for U.S. Patent No. 5,081,473 on the basis of my searches. If you need a court‑admissible negative, I recommend a direct PACER docket search and a Unified Patents / RPX Insight lookup keyed to the exact string "5081473," plus confirmation that the earlier Xerox–HP ink‑jet litigation asserted 5,030,971 rather than 5,081,473. I could not complete those direct lookups here, so flag the finding as unverified.

Proceedings overview

Total AIA trial proceedings on file for US 5,081,473: 0. The structured "PTAB proceedings on file" block (USPTO Open Data Portal) returns no IPR, PGR, or CBM for this patent, and my independent web searches turned up none either — the only "508 patent" PTAB hits on the open web are an unrelated patent (a bio-impedance/cellular-analysis patent), and no PTAB petition, institution decision, FWD, or Federal Circuit appeal names US 5,081,473. There are therefore no claims canceled, none sustained, none settled, and no institution denials — all 20 claims are UNTESTED at the Board. The bottom-line defensive posture is unusual and worth stating precisely: there is nothing to defend against, because the patent term itself is over. The '473 patent has a statutory status of "Expired – Lifetime," with an anticipated expiration of 1990-07-26 + 20 years = 2010-07-26 (Google Patents legal-status entry, "Anticipated expiration," 2010-07-26), and maintenance fees were paid at the 4-, 8-, and 12-year windows (1995-05-10, 1999-05-10, 2003-05-20), so it did not lapse early.

Per-proceeding detail

None to report. No AIA proceeding number exists for US 5,081,473, and I will not invent one. Two structural reasons explain the empty docket:

1. AIA trials did not exist during the patent's life. IPR/PGR/CBM practice began 2012-09-16 (§ 6 of the AIA; IPR effective date). The '473 patent expired on or about 2010-07-26, roughly two years before any IPR could have been filed against it.
2. PGR and CBM are categorically unavailable. PGR applies only to patents with an effective filing date on or after 2013-03-16, and CBM applies only to covered business-method patents — the '473 patent is a pre-AIA semiconductor/thermal-inkjet chip patent (B41J 2/16, B41J 2/14024 line), not a financial-services method.

For completeness on the "absence is a signal" heuristic: this is one of the rare cases where the absence is not evidence of litigation-hardening. Well-asserted patents attract IPRs; this patent was never a plausible IPR target because it was already dead. The related-art landscape confirms the patent is cited as prior art by later TIJ chip patents (e.g., US 5,448,273 to Xerox, US 5,774,148 to Lexmark, US 6,357,863 to Lexmark), i.e., it functioned as background art, not as an assertion vehicle. See Google Patents – US5081473A.

Strategic summary

Claim status. All claims 1–20 remain uncanceled and untested: independent claims 1 (transducer with field oxide sandwiched between primary and secondary heating regions) and 13 (driver with n⁻ drift layer and means for causing secondary pinch-off), and dependents 2–12 and 14–20. No claim has been invalidated by the Board and no claim has been upheld by the Board. "Untested" here should not be read as "strong" — it means no PTAB record exists at all.

Estoppel landscape. There is no § 315(e)(2) estoppel attaching to anyone, because there was never an IPR petitioner. Conversely, there is no inter partes or ex parte reexamination-based estoppel I could locate either, so a defendant would not face a "could have raised" bar from a prior administrative challenge. Practically, estoppel analytics are moot: the patent expired before the earliest date on which most current defendants could have infringed it.

Pattern signals. No repeat-petitioner pattern (no petitioners at all); no PTAB appeals by Xerox; no defensive aggregator (Unified Patents, RPX, etc.) involvement in the record. The only post-grant administrative activity of any kind is the chain of security-interest assignments (Bank One 2002, JPMorgan Chase 2003, release 2022) — routine Xerox corporate financing, not patent-challenge activity. The JP counterpart JPH0679872A ("Transducer for ink jet printing head," published 1994-03-22) likewise shows no challenge in the record I could retrieve.

Recommended next steps

• Do not treat this patent as a live assertion risk. If you receive a demand letter citing US 5,081,473, verify the expiration in USPTO Patent Center (the Google Patents record shows anticipated expiration 2010-07-26 with all maintenance fees paid at 4/8/12 years). Infringement under 35 U.S.C. § 271 requires an unexpired patent, and § 286 damages reach back only six years — which here would run from a date well after expiry. A demand built on the '473 patent is, on its face, baseless unless it is paired with a live continuation or reissue; check for any continuation/divisional claiming priority to application 07/558,092 before responding.
• If a letter or pleading cites an "IPR number" for this patent, treat it as fabricated. There is no IPR, PGR, or CBM for US 5,081,473, so any such citation is either a different patent or invented. Ask for the proceeding number and verify it directly in PTAB E2E and the PTAB Decisions database.
• Because there are no FWDs or CAFC opinions to cite, there is nothing to link. I did not locate any Federal Circuit docket or CourtListener entry involving US 5,081,473; had one existed, the disposition would be quoted here verbatim. I want to be explicit about the limits of that finding: my check was web-search based plus the structured ODP block, not an exhaustive docket-by-docket review of the Federal Circuit's pre-2010 rolls.
• Flag for the file, not for argument: if the assertion against you is on a different patent in the same Xerox TIJ lineage (e.g., US 4,947,192, US 5,300,968, or family members like EP 0 434 946 / EP 0 598 369), that patent may well have its own PTAB history — pull it separately rather than assuming the '473 result carries over.

I'll verify the assignment record details and check for any litigation or correspondent data before writing this up.

Let me try to pin down the correspondent of record on the 2002/2003/2022 recordings.

US 5081473 — Assignment & Ownership Reconstruction

Patent: US 5,081,473 A — Temperature control transducer and MOS driver for thermal ink jet printing chips
Application: 07/558,092 · Filed: 1990-07-26 · Issued: 1992-01-14 · Assignee of record at issue: Xerox Corporation
Record set used: Google Patents legal-events / assignment data (which mirrors the USPTO Assignment Center records by reel-frame), plus Xerox SEC exhibit filings. USPTO Assignment Center: https://assignmentcenter.uspto.gov/ (indexed at https://assignment.uspto.gov/patent/index.html). Google Patents mirror: https://patents.google.com/patent/US5081473/en

Inventors

Pattern notes. Both inventors assigned to Xerox before issuance (signed 1990-07-19 and 1990-07-24; recorded 1990-07-26 on the filing date) — the ordinary, non-flagged pattern for a corporate lab. There is no evidence in the assignment record of either inventor departing within 12 months, and no re-assignment by the inventors to any third party. Hawkins in particular is a repeat Xerox thermal-ink-jet inventor (the patent itself incorporates US 4,774,530 and US 4,532,530, both Hawkins/Xerox). I could not verify post-1990 employment histories from the assignment record alone — treat "still at Xerox when the case issued" as the only defensible finding.

Original assignee

Xerox Corporation, a New York corporation (then Stamford, CT; later Norwalk, CT). Assignee named on the face of the issued patent and on the sole ownership assignment of record (reel 005429/0397).

• Line of business: xerographic copiers, printers and reprographic/document-management hardware; this patent sits in Xerox's thermal ink jet (TIJ) printhead program, which developed drop-ejection resistor architectures in the late 1980s–early 1990s.
• Product embodying the claims: Xerox was an operating manufacturer and did commercialize thermal ink jet printheads and ink jet printers in this era; the chip architecture claimed here (polysilicon TIJ resistor on field oxide over an n⁻ drift substrate heater) is a manufacturing-level feature of such a printhead. I can confirm Xerox was a shipping hardware manufacturer, but I cannot verify from the record which specific Xerox printer model(s) embodied these claims — I will not assert a model number.
• Current status: Operating. Xerox Corporation remains an active public registrant (Xerox Holdings Corporation); no Chapter 7/11 filing has occurred. Xerox's near-insolvency period (2000–2002) was resolved through out-of-court secured financing, which is precisely what produced the 2002 and 2003 recordings below. Xerox subsequently acquired Lexmark (completed 2025), consolidating its position as an operating print-hardware company.

Assignment timeline

Four items are recorded against this patent. Only the first is an ownership assignment; the remaining three are security interests granted by Xerox to its lenders, plus the release of the later one. Google Patents' "Assigned to" labels for the bank entries are misleading — a security interest is not a conveyance of title.

• 1990-07-19 / 1990-07-24 (executed) / recorded 1990-07-26 — Reel 005429/0397

  • Conveyance: Assignment of interest (Assignment)
  • Assignor: William G. Hawkins and Cathie J. Burke (joint inventors)
  • Assignee: Xerox Corporation, a corp. of NY
  • Correspondent: Not exposed in the record set I can reach. Execution window (1990-07-19 → 1990-07-24) and same-day-as-filing recording are consistent with an in-house Xerox patent-department filing, but I will not name an attorney without the reel image.
  • Context: Original corporate assignment — inventors to employer, the standard employment-obligation assignment.

• 2002-06-21 (executed) / recorded 2002-06-28 — Reel 013153/0001

  • Conveyance: Security interest / Security Agreement (Xerox's "Patent Security Agreement" under the Amended and Restated Credit Agreement dated as of 2002-06-21)
  • Assignor (lien grantor): Xerox Corporation
  • Assignee (secured party): Bank One, NA, as Administrative Agent and Collateral Agent (an Illinois banking association)
  • Correspondent: Not retrievable for this reel. Note: Xerox's parallel June-2002 real-property security filings were prepared by Susan D. Kennedy, Esq., Davis Polk & Wardwell, and Xerox's later trademark security-interest recordings (reels 7892/0506 and 8107/0307) carry Latham & Watkins LLP, c/o Angela M. Amaru as correspondent of record. Neither is confirmed as the correspondent on reel 013153/0001 — flagged as unverified.
  • Context: Securitization — Xerox pledged essentially its entire patent portfolio as collateral for the $7B Amended Credit Agreement negotiated during its 2000–2002 liquidity crisis. Title never left Xerox.

• 2003-06-25 (executed) / recorded 2003-10-31 — Reel 015134/0476

  • Conveyance: Security Agreement (collateral-agent security interest under the Credit Agreement dated as of 2003-06-19)
  • Assignor (lien grantor): Xerox Corporation
  • Assignee (secured party): JPMorgan Chase Bank, as Collateral Agent (a NY banking corporation)
  • Correspondent: Not retrievable for this reel; same Davis Polk / Latham & Watkins ambiguity as above. Unverified.
  • Context: Securitization — refinancing/replacement of the Bank One collateral package; still a lien, not a transfer. Correspondence name changed, ownership did not.

• 2022-08-22 (effective) / recorded 2022-09-07 — Reel 066728/0193

  • Conveyance: Release by Secured Party (Release)
  • Assignor (releasing party): JPMorgan Chase Bank, N.A., as successor-in-interest administrative agent and collateral agent to JPMorgan Chase Bank
  • Assignee (beneficiary of release): Xerox Corporation
  • Correspondent: Not retrievable for this reel. Unverified.
  • Context: Termination of the 2003 collateral package — a lien discharge, recorded 12 years after the patent expired (2010-07-26). Housekeeping, not a transfer.

Supplementary note (not an ownership event, and not recorded against this patent): a separate Xerox release is recorded at patent assignment 19872/0199 (JPMorgan Chase Bank, NA → Xerox Corporation, executed 2006-12-04, recorded 2007-09-25), covering a portfolio of Xerox radio-frequency-tag patents. US 5,081,473 is not listed among the properties in that instrument, so it does not appear in this patent's chain. Mentioned only so the two Xerox/JPMorgan releases are not conflated.

Maintenance-fee track (for completeness, from the legal-events record): 4-year fee paid 1995-05-10; 8-year fee paid 1999-05-10; 12-year fee paid 2003-05-20. Anticipated expiration 2010-07-26 (20 years from filing, which controls over 17-years-from-issue for this pre-URAA case). Status now: Expired – Lifetime.

Timeline diagram

timeline
    title Ownership of US 5081473
    1990 : Filed 1990-07-26 by Xerox Corp
         : Hawkins and Burke assign to Xerox
    1992 : Patent issues 1992-01-14
    1995 : 4 year maintenance fee paid
    1999 : 8 year maintenance fee paid
    2002 : Xerox pledges portfolio to Bank One
    2003 : Portfolio repledged to JPMorgan
         : 12 year maintenance fee paid
    2010 : Patent expires 2010-07-26
    2022 : JPMorgan releases the 2003 lien

NPE / troll-pattern signals

1. Shell-entity transfer — not present. Every recorded party is an operating company or a bank acting as collateral agent: Xerox Corporation, Bank One NA (Administrative/Collateral Agent), JPMorgan Chase Bank (Collateral Agent). There is no LLC, no "IP Holdings / Licensing / Ventures" suffix, no registered-agent service address, and no assignment of title at all after 1990 (reels 005429/0397, 013153/0001, 015134/0476, 066728/0193).

2. Known asserter in the chain — not present. No assignee or assignor in the chain matches Acacia, Marathon, Intellectual Ventures, IPNav, Wi-LAN, Mosaid/Conversant, Vringo, Pendrell, Innovatio, MPHJ, Lumen View, Round Rock, DGC, or any Spangenberg entity. The only counterparties are Xerox and two banks.

3. Repeat correspondent across the chain — unclear (data gap). I could not retrieve the correspondent-of-record field for reel 013153/0001, 015134/0476, or 066728/0193. What I can say is that the correspondent on Xerox's later intellectual-property security recordings is outside counsel rather than an NPE-recording shop — e.g., Latham & Watkins LLP, c/o Angela M. Amaru, 1271 Avenue of the Americas, New York, NY 10020, appears as correspondent on Xerox trademark security-interest reels 7892/0506 and 8107/0307 (2023), and Davis Polk & Wardwell (Susan D. Kennedy) prepared Xerox's June-2002 real-property security instruments. These are large general-practice firms doing secured-finance work for an operating company; a single appearance is expressly not a finding, and I have no recurrence within this patent's chain to point to. Per the reel images should be pulled to close this gap.

4. Cascading transfers — not present. Four recordings over 32 years is the opposite of cascading. And three of the four are lien grants/releases by lenders, not conveyances: 2002 (lien), 2003 (lien), 2022 (release). Title moved exactly once, in 1990, and stayed put.

5. Pre-litigation transfer — not present. I found no infringement litigation naming US 5,081,473 in any of the sources checked, and no assignment within 6 months preceding any suit. The patent also expired 2010-07-26, so it is not assertable now. Note that the 1990 assignment predates issuance and is the inventors-to-employer assignment, i.e. the opposite of a late assertion-enabling transfer.

6. Bankruptcy fire-sale — not present. Xerox never filed Chapter 7 or 11. The 2002 Bank One and 2003 JPMorgan recordings are out-of-court secured financings (Amended and Restated Credit Agreement of 2002-06-21; Credit Agreement of 2003-06-19) that granted the lenders a security interest and a power of sale upon default — a contingency that never triggered. The Xerox assets that were actually sold (e.g., the 2000 sale of interests to Fuji Xerox, the 2001 Fuji Xerox stake) are separate from this patent, and there is no record of this patent being sold in any proceeding.

7. Privateering — not present. No transfer of US 5,081,473 to any third-party assertion vehicle, and no evidence that Xerox used an NPE against competitors via this patent. Xerox's TIJ work in this period was cross-licensed against HP/Canon-type portfolios, not farmed to an asserter.

8. Defensive aggregator (anti-NPE) — not present. The chain does not terminate at RPX, AST, LOT, Unified Patents, or OIN. The chain terminates back at Xerox, by operation of expiry and a lender release.

Verdict

Insufficient data

The ownership chain is intact and unremarkable: the sole conveyance of title is the inventors→Xerox assignment executed 1990-07-19/24 and recorded 1990-07-26 at reel 005429/0397; the only subsequent recordings (reel 013153/0001, executed 2002-06-21/recorded 2002-06-28 to Bank One NA as Administrative Agent; reel 015134/0476, executed 2003-06-25/recorded 2003-10-31 to JPMorgan Chase Bank as Collateral Agent; and the release at reel 066728/0193, effective 2022-08-22) are secured-financing liens and their discharge, not transfers — so no shell entity, no known asserter, no pre-litigation transfer, and no bankruptcy sale appear anywhere in the chain. I cannot reach a stronger affirmative classification because the correspondent-of-record field for reels 013153/0001, 015134/0476 and 066728/0193 could not be retrieved, which is the one datum that would fully close the repeat-counsel signal; pulling those three reel images at https://assignmentcenter.uspto.gov/ would resolve it. Practically, this patent cannot be asserted at all — it expired 2010-07-26 — and the current owner of record remains Xerox Corporation, an operating printer manufacturer.

I'll research this systematically. Let me start by confirming the target patent and then examine each cited reference.

Let me gather details on the remaining cited references.

Prior-Art Analysis — US Patent 5,081,473

Target Patent Confirmed

US 5,081,473 A — "Temperature control transducer and MOS driver for thermal ink jet printing chips"

• Application No. US 07/558,092; filed July 26, 1990; granted January 14, 1992
• Inventors: William G. Hawkins; Cathie J. Burke; Assignee: Xerox Corp.
• Foreign counterpart: JP 3178118A / JPH0679872A (priority 1990-07-26, filed 1991-07-18)
• Status: Expired – Lifetime (anticipated expiration 2010-07-26)
• Source: https://patents.google.com/patent/US5081473/en

Core inventive concept (for mapping purposes): a thermal-ink-jet transducer in which a silicon-dioxide field oxide layer is sandwiched between a primary heating region (polysilicon resistor + silicon nitride + tantalum, above the oxide, facing the ink) and a secondary heating region (an n⁻ drift diffusion in the silicon substrate beneath the field oxide) used to pre-heat/regulate temperature; plus an on-chip MOS driver with an n⁻ drift layer under a field oxide and a polysilicon field plate that provides "secondary pinch-off" for high-voltage operation.

Summary of the Nine References Cited on the Face of the '473 Patent

Note: The specification also expressly incorporates by reference US 4,774,530 ("Ink Jet Printhead") and US 4,532,530 (Hawkins, "Bubble Jet Printing Device"); US 4,532,530 also appears on the citations list.

All references except No. 9 published more than one year before the 1990-07-26 filing, so they are available as pre-AIA § 102(b) art. US 4,947,192 (No. 9) is the exception — see the caveat below.

Reference-by-Reference Analysis

1. US 4,429,321 — Matsumoto, Canon

• Full citation: US 4,429,321, "Liquid Jet Recording Device," Shigeyuki Matsumoto, Canon Kabushiki Kaisha. App. 06/311,894; filed 1981-10-15; JP priority 1980-10-23; published 1984-01-31.
• Description: A liquid-jet recording head with a plurality of electrothermal transducers, each transferring heat to ink in an actuation chamber, and a driving circuit of function elements formed in the surface of the same substrate (or transducers laminated onto a substrate carrying the function elements). Explicitly aimed at high-density, full-line recording heads.
• Claim mapping (§ 102): Most directly reads on the "driver and transducer integrated on one wafer" limitations — claim 8 (driver transistor in the wafer with its drain in electrical contact with the resistor layer) and claim 10 (thermal ink jet transducer). Its laminated transducer structure is also relevant to claim 3.
• Assessment: Does not disclose the two-heating-region/field-oxide sandwich of claim 1, so it is not a clean § 102 anticipation; its relevance is chiefly § 103 (integration background).

2. US 4,620,212 — NEC

• Full citation: US 4,620,212, "Semiconductor Device with a Resistor of Polycrystalline Silicon," NEC Corporation. Priority 1982-05-28; published 1986-10-28.
• Description: Two groups of polysilicon resistors stacked with an insulating film between them, wired together to form a single resistor of higher resistance within roughly half the area — a solution to density, not to thermal printheads.
• Claim mapping (§ 102): The stacked "polysilicon resistor / insulating film / resistor" geometry is structurally reminiscent of the claimed sandwich. Relevant to claim 3 (polysilicon resistor layer contacting an insulating film) and, loosely, to the two-layer arrangement of claim 1.
• Assessment: Contains no heating/ink-jet teaching and no secondary heating function; it is a § 103 structural reference only, not an anticipation of any claim.

3. US 4,539,571 — Suzuki, Tokyo Shibaura Denki

• Full citation: US 4,539,571, "Thermal Printing System," Tokyo Shibaura Denki K.K. Priority 1982-09-14; published 1985-09-03. (Characterized in the '473 specification as Suzuki's auxiliary resistor that "keeps a printhead warm.")
• Description: A thermal printing system incorporating an auxiliary resistor to hold the printhead at an elevated temperature.
• Claim mapping (§ 102): This is the most on-point reference for the temperature-control function of the secondary heater. It maps to the purpose/functions of claim 1 (secondary heating region enabling "close temperature control of the primary heating region and the object") and to claim 2 (means for selectively applying current to both regions).
• Assessment: It is a thermal-printhead (not ink-jet, no field-oxide sandwich) teaching. Best characterized as § 103 art for the "auxiliary heater for thermal control" concept; it does not anticipate the specific layered structure.

4. US 4,472,875 — Christian et al., Teletype

• Full citation: US 4,472,875, "Method for Manufacturing an Integrated Circuit Device," Teletype Corporation. Priority 1983-06-27; published 1984-09-25.
• Description: A method of fabricating an IC by forming a transducer and a driver circuit for a thermal printhead on a single substrate.
• Claim mapping (§ 102): Relevant to the integrated transducer+driver subject matter of claim 8 and to the thermal-printhead context of claim 10. Because it is a method patent and the '473 claims at issue are apparatus claims, it is a § 103 reference (structure resulting from the method), not a § 102 anticipation.

5. US 4,532,530 — Hawkins, Xerox

• Full citation: US 4,532,530, "Bubble Jet Printing Device," Hawkins, Xerox Corporation. Priority 1984-03-09; published 1985-07-30. (Expressly incorporated by reference into the '473 specification.)
• Description: Foundational bubble-jet (thermal ink-jet) printhead structure and operation.
• Claim mapping (§ 102): Background/structural teaching for the ink-ejecting environment of claims 9 and 10 (object = ink; transducer operatively associated with an ink flow channel to form a TIJ transducer).
• Assessment: Enabling/background art; the '473 claims' distinguishing sandwich architecture is absent, so no anticipation.

6. US 4,623,903 — Hashimoto, Canon

• Full citation: US 4,623,903, "Thermal Head," Canon Kabushiki Kaisha. Priority 1984-03-22; published 1986-11-18. (Characterized in the specification as a thermal printhead with a main heater resistor and an auxiliary resistor for maintaining constant head temperature.)
• Description: A thermal head with a main heating resistor plus an auxiliary resistor used to keep the head at a constant temperature.
• Claim mapping (§ 102): Directly relevant to the dual-resistor temperature-regulation concept of claim 1 (primary + secondary heating regions) and claim 2 (selective current application to both).
• Assessment: Strong § 103 reference on the "main + auxiliary heater" idea, but it lacks the field-oxide-sandwiched/substrate-diffused arrangement; not a § 102 anticipation.

7. US 4,769,527 — Hart et al., British Aerospace

• Full citation: US 4,769,527, "Thermal Image Generating Device," Hart et al., British Aerospace Plc. Priority 1985-09-04; published 1988-09-06. (Specification: "a pair of resistors are used to create a more uniform image.")
• Description: A thermal image-generating device employing a pair of resistors to improve image uniformity.
• Claim mapping (§ 102): Relevant to the plural-resistor aspect of claim 1 and the selective-driving of claim 2; peripheral to the ink-jet specifics.
• Assessment: § 103 background art; no anticipation.

8. US 4,719,477 — Hess, Hewlett-Packard

• Full citation: US 4,719,477, "Integrated Thermal Ink Jet Printhead and Method of Manufacture," Hess, Hewlett-Packard Company. App. 06/820,754; filed 1986-01-17; published 1988-01-12.
• Description: An integrated thermal ink-jet printhead with an on-chip MOSFET driver, built up by successive thin-film/barrier-layer deposition (orifice plate, first barrier layer, heater resistors, second barrier layer, reservoir layer) on a substrate.
• Claim mapping (§ 102): Maps to claim 8 (MOS driver on the same chip as the transducer, drain connected to the heater resistor) and claim 10 / claim 9 (TIJ transducer). The resistor + protective/insulating layer stack is also relevant to claim 3.
• Assessment: A significant § 103 reference for the "on-chip MOSFET driver" limitation and for the resistor/passivation stack, but it does not disclose the n⁻ drift field-plate secondary pinch-off driver (claims 11, 13, 16, 20) nor the substrate-diffused secondary heater (claims 1, 4, 5, 7); no § 102 anticipation.

9. US 4,947,192 — Hawkins & Burke, Xerox

• Full citation: US 4,947,192, "Monolithic Silicon Integrated Circuit Chip for a Thermal Ink Jet Printer," Hawkins & Burke, Xerox Corporation. US priority 1988-03-07; granted 1990-08-07. (EP counterpart EP 0 401 440; see also EP 0 494 076.)
• Description: A thermal ink-jet printhead formed by monolithically integrating MOS logic elements and drivers onto the same silicon substrate as the resistive elements; in a preferred embodiment the transistor switches and resistors are formed from a single polysilicon layer, with the resistive element formed on a thermally grown field oxide layer (≈1–4 µm thick) — the same field-oxide-based heater architecture the '473 patent builds upon.
• Claim mapping (§ 102): This is the closest art. It reads on:
  • Claim 1 — resistive element on a thermally grown field oxide (though it does not clearly show a second, substrate-diffused heating region on the opposite side of that oxide);
  • Claim 3 — polysilicon resistor on the field oxide (the SiN/Ta overlayers are the '473 addition);
  • Claim 8 — MOS driver monolithically integrated on the same wafer with the resistive element;
  • Claim 10 — thermal ink-jet transducer;
  • Claim 15 — silicon-dioxide field oxide.
• ⚠ Important statutory caveat: US 4,947,192 issued 1990-08-07, after the 1990-07-26 filing date of the '473 patent, so it is not § 102(a)/(b) art. Its US filing (1988-03-07) predates the '473 filing, but because it names the same inventive entity (Hawkins & Burke) and the same assignee (Xerox), it is not "by another" and therefore is not § 102(e) prior art either. It is properly treated as a commonly owned / related application — relevant to double-patenting (obviousness-type) and § 103 considerations rather than to a § 102 anticipation.

Bottom Line

• No single cited reference cleanly anticipates claim 1. The defining element — a field-oxide layer sandwiched between a primary heating region above it and a substrate-diffused (n⁻) secondary heating region below it — appears to be the novel structural contribution, and none of the nine references discloses that exact sandwich with the temperature-control function.
• The best § 102-type (single-reference) candidate is US 4,947,192 (Hawkins/Burke), because of its field-oxide-based heater plus monolithic MOS driver — but its same-inventor/same-assignee status removes it from § 102 and relegates it to a double-patenting/§ 103 matter.
• The "secondary/auxiliary heater for temperature control" claims (1, 2, 6) are most strongly challenged as a § 103 combination of Suzuki (US 4,539,571) or Hashimoto (US 4,623,903) with the integrated-transducer art.
• The "on-chip MOS driver + transducer" claims (8, 10) are most strongly challenged as a § 103 combination of Matsumoto (US 4,429,321) / Christian (US 4,472,875) / Hess (US 4,719,477).
• The field-plate "secondary pinch-off" driver claims (11, 13, 16, 20) are not clearly met by any cited reference and appear to rest on the '473 patent's own contribution.

Confidence/limitations: The citations list, their dates, assignees, and the specification's own characterizations are taken directly from the authoritative full text of US 5,081,473. My element-by-element mapping is an analytical judgment based on that text; a definitive § 102/S 103 conclusion requires the full text/claims of each reference and confirmation of the applicable pre-AIA §§ 102(e)/103(c) and double-patenting posture (especially for the commonly owned US 4,947,192). I did not obtain the complete claim text of the six secondary references (US 4,539,571, US 4,472,875, US 4,532,530, US 4,623,903, US 4,769,527, and the balance of US 4,429,321), so those mappings should be treated as provisional.

I'll ground this analysis in the actual prior-art references listed on the patent page. Let me pull details on the cited references.

Let me pull the remaining cited references and the closely-related Xerox monolithic-chip art.

Obviousness Analysis — US 5,081,473 (35 U.S.C. § 103)

Patent: US 5,081,473 A, Temperature control transducer and MOS driver for thermal ink jet printing chips
Inventors / Assignee: William G. Hawkins; Cathie J. Burke / Xerox Corp.
Priority & filing: 1990‑07‑26 (US 07/558,092); JP 3178118 filed 1991‑07‑18
Analysis date: as of the date of this analysis
Source page: https://patents.google.com/patent/US5081473/en

1. Framework and scope

This is a pre‑AIA case (filed 1990), so § 103 is applied with the Graham v. John Deere factors — scope/content of the prior art, differences, PHOSITA level, and secondary considerations — informed by KSR Int'l v. Teleflex (a flexible "expansive and flexible" motivation test rather than a rigid teaching‑sampling‑suggesting requirement). Because the patent issued 1992‑01‑14 and would have expired 2010‑07‑26, this is a retrospective validity analysis, not an enforcement defense the page shows was ever litigated.

PHOSITA (my construction — the page contains no prosecution history or litigation record to fix it): a person with a B.S. in electrical engineering, materials science, or equivalent, plus 3–5 years' experience in silicon device fabrication for thermal ink jet (TIJ) printheads, familiar with phosphosilicate glass (PSG) planarization, polysilicon resistors, LOCOS field oxide, high‑voltage MOS design, and TIJ drop‑ejection energetics.

2. The prior‑art record on this page

The nine references cited by the examiner are all pre‑date the 1990‑07‑26 filing:

Also incorporated by reference in the specification: US 4,774,530 (Hawkins).

Two record caveats that materially affect the analysis:

1. US 4,947,192 published 1990‑08‑07 — twelve days after the 1990‑07‑26 filing date. It cannot be § 102(a)/(b) art. It is only available, if at all, as pre‑AIA § 102(e) art (U.S. patent granted on an earlier‑filed application, filed 1988‑03‑07). But § 102(e) art must be "by another"; the search record shows US 4,947,192 lists Hawkins and Burke as inventors — the same inventive entity as this patent. On that record it is arguably not § 102(e) prior art to this application at all. It is nonetheless the examiner's cited reference and is useful as evidence of the ordinary skill level / the inventors' own earlier state of the art, but a § 103 rejection built on it is vulnerable. (Its EP counterpart, EP 0 401 440, is likewise a family member, not independent art.)
2. The "Cited By" art cannot be used. EP 0 562 271 / KR 100301918 / JP 3393148 (Texas Instruments, priority 1992‑03‑26 — a high‑voltage "RESURF" structure with drift region), US 5,448,273, US 5,774,148 (Lexmark, field oxide as thermal barrier), and US 6,357,863 (Lexmark, linear substrate heater) all post‑date the 1990‑07‑26 priority date and are not statutory prior art under § 102/§ 103. They are useful only as evidence of how the field later developed.

3. The differences to be overcome

Compared with the above record, the claims add four things: (a) the field oxide sandwiched between an upper primary heating region and a lower secondary heating region (claim 1); (b) the specific heater stack — polysilicon resistor + Si₃N₄ + Ta (claim 3); (c) an on‑chip driver whose drain contacts the polysilicon resistor (claim 8); and (d) a driver having a polysilicon field plate on the opposite side of the driver field oxide from an n⁻ drift layer, the field plate causing "secondary pinchoff" for higher‑voltage operation (claims 11–20).

4. Claim‑by‑claim § 103 combinations

A. Claim 1, 2, 6, 9, 10 — the two‑region, field‑oxide‑sandwiched transducer

Primary combination: US 4,947,192 + US 4,539,571 (Suzuki), or + US 4,623,903 (Hashimoto); optionally with US 4,532,530 (Hawkins).

• US 4,947,192 supplies the whole upper half of claim 1: a TIJ resistive element formed on a thermally grown field oxide, with MOS logic and drivers integrated on the same substrate. (Subject to the § 102(e) caveat above.)
• Suzuki supplies the "secondary heating region" function clause almost verbatim in substance: an auxiliary heating element "positioned close to and along the main heating elements," current‑fed during operation, whose entire stated purpose is to hold the printhead at a uniform temperature below print temperature, with a temperature‑compensating circuit for the calorific value. Hashimoto supplies the alternative: a main heating resistor plus an auxiliary heating resistor "for maintaining constant temperature," formed simultaneously with the mains by known film techniques.
• Claim 6 (common bus line connected to both primary and secondary heating regions) is met by Hashimoto's FIG. 4 arrangement, where main element D₁₁ and auxiliary element D₁₂ are connected in parallel between the same common feeder pattern C and an individual feeder pattern.
• Claims 9 ("the object is ink") and 10 ("operatively associated with an ink flow channel … thereby producing a thermal ink jet transducer") are met by any of Hawkins '530, Hess '477, or Matsumoto '321.

Motivation to combine (KSR rationales a, b, c, d, e):

1. Known problem, known solution. The specification itself admits that droplet/pixel size is temperature‑sensitive and that an elevated operating point (~35–45 °C) is desirable, and it cites Suzuki and Hashimoto by number as the prior answer to exactly that problem. Where the prior art addresses the very problem the applicant identifies, motivation is inherent.
2. Design incentive to relocate, not redesign. The patent's own stated object is to reduce warm‑up time **"with a minimal impact on present fabricating methods or on chip area." **Both Suzuki (element placed "close to and along" the mains) and Hashimoto (who expressly criticizes the extra output lines and connector pins the auxiliary resistors require) teach auxiliary heaters that consume additional die area and wiring. The top surface of a TIJ heater chip is fully occupied by the resistor/electrode stack and the ink‑channel structures, so the only remaining area is the substrate beneath the pre‑existing field oxide. Relocating the auxiliary resistor into that substrate — i.e., to the opposite side of the field oxide — is a simple substitution of one known location for another, using a known technique (diffused/implanted silicon resistor, per NEC '212 and Hess '477) to improve a known device in the same way, with a predictable result.
3. Predictable physics. A thermally grown SiO₂ layer ~1.35 µm thick over a line‑width‑scale resistor is a thermal resistor; driving a long‑duty‑cycle heater immediately beneath it should predictably raise the steady‑state temperature of the region above. The specification's asserted benefit — heat from the secondary region "heats the transducer field oxide layer above ambient while the primary heating region increases the temperature of the ink" — is the straightforward, expected consequence of placing a continuous heater under a thin dielectric, not an unexpected result.
4. Finite, predictable design space. Put the auxiliary heater (i) alongside the main heaters, (ii) under the field oxide, or (iii) off‑chip. Each option was known; the choice among them is a design choice, and claims 1–7, 9–10 contain no criticality (no claimed thickness, spacing, duty cycle, or thermal‑resistance relationship between the two regions) that would distinguish the alleged invention from the predictable result of that choice.

Independent anticipation note on claim 1: claim 1 requires only a "secondary heating region located on an opposite side of the transducer field oxide layer … dissipating thermal energy to the transducer field oxide layer." It does not require that region to be a resistor, to be separately switched, or to be electrically isolated. Read on its face, the claim reads on a structure in which the on‑chip driver devices (or the substrate region holding them) dissipate heat on the underside of the field oxide — precisely the geometry disclosed in Matsumoto '321 (transducer layers laminated above a substrate in which the semiconductor function elements are formed) and Hess '477. That is a § 102 argument against claim 1 as much as a § 103 argument; I flag it as a claim‑scope observation and recommend the full claim charts be built against the actual disclosures.

B. Claim 3 — polysilicon resistor / Si₃N₄ / Ta stack

Combination: US 4,947,192 + US 4,719,477 (Hess). '192 supplies the polysilicon resistor on the field oxide; Hess supplies the overlying passivation/cavitation stack — an Si₃N₄ layer above a resistor film, a Ta layer as the outermost cavitation barrier, PSG planarization and Al interconnect. Both are TIJ heater chips; both use identical materials for identical functions; the specification even concedes that "the layers of the transducer and the driver which are formed of identical materials are preferably formed at the same time." A POSITA optimizing a heater stack for passivation and cavitation resistance would combine them as a matter of routine design.

C. Claims 4, 5, 7 — n⁻ drift secondary heater; 2 × 10¹⁶ P/cm³; formed in the silicon wafer

Combination: the group‑A combination (temperature‑control rationale) + US 4,719,477 / US 4,462,0212 / Matsumoto '321. Moving the auxiliary heater into the wafer necessarily means forming it as a diffused or implanted region in the silicon, and phosphorus‑doped n⁻ drift/accumulation regions in the range ~10¹⁶ /cm³ are the standard high‑resistivity, high‑voltage silicon resistor. The recited value 2 × 10¹⁶ ions/cm³ is a result‑effectively disclosed, routine optimization parameter; under In re Aller / In re Boesch, a specific numerical value selected from a disclosed broader range requires evidence of criticality, which the specification does not supply (it gives only sheet resistance ~5 kΩ/sq. and the 200 µm × 10,800 µm geometry, not a showing that 2 × 10¹⁶ is critical to any claimed result).

D. Claim 8 — driver transistor in the same wafer, drain in contact with the polysilicon resistor

Combination: US 4,719,477 (Hess) + US 4,429,321 (Matsumoto) + US 4,472,875 (Christian). Hess expressly discloses MOSFET drivers fabricated in the same silicon substrate that supports the printhead resistors and electrically interconnected to them by a second level of metallization ("on‑chip driver construction … to move these pulse driver transistors from external electronic circuitry to the printhead substrate"). Matsumoto discloses electrothermal transducers and their driving function elements structurally formed in/on one substrate. Christian discloses a method of manufacturing such an integrated device. The only refinement in claim 8 is that the contact is specifically to the drain — an inevitable consequence of using a MOSFET as the switch, and thus at most a design choice dictated by the chosen device type.

E. Claims 11–12 (field plate on the transducer‑chip driver)

Claim 11 (improperly written as "A driver device according to claim 10," i.e., appended to an ink‑jet transducer claim) and claim 12 add a driver field plate layer on the opposite side of the driver field oxide from an n⁻ drift layer. None of the nine examiner‑cited references appears to disclose a polysilicon field plate over a drain‑side field oxide for the purpose of spreading the electric field (the "secondary pinchoff" / RESURF‑like function claimed in claim 13's "means for causing secondary pinch off").

F. Claims 13–20 — the stand‑alone high‑voltage driver with pinchoff means

This is, in my assessment, the strongest nonobviousness position in the claim set and the weakest § 103 position for a challenger working only from this page's cited art. No reference in the record discloses the claimed "means for causing secondary pinch off of the n⁻ drift layer" connected on the opposite side of the field oxide. Matsumoto '321 and Hess '477 both motivate integrating drivers on the TIJ chip for the interconnect‑count and cost reasons they state, but neither addresses the breakdown‑voltage problem that follows from dissipating tens of volts in an on‑chip driver — which is precisely the problem claims 13–20 solve.

A challenger would have to bring in a separate high‑voltage‑MOS/RESURF reference (or rely on the documented general knowledge that a field plate over a drift region spreads the field and suppresses avalanche breakdown near the drain) and combine it with Hess '477 / Matsumoto '321. If such a reference exists with a pre‑1990‑07‑26 date, claims 13–20 become vulnerable on a "use of a known technique to improve a similar device in the same way" rationale: the patent itself concedes the field plate is a known device type applied to a new location — it says "Tests have verified that field plate 48 does indeed cause secondary pinchoff of n⁻ drift layer 34," i.e., it confirms the known physical mechanism rather than discovering it. But on the record provided on this page, I cannot cite a pre‑1990 reference disclosing the field‑plate/pinchoff structure, and I will not invent one. The post‑1990 Texas Instruments RESURF family (EP 0 562 271 and its JP/KR members) is not available as prior art and cannot be used.

5. Summary of the § 103 case

6. Secondary considerations

The page discloses no evidence of unexpected results, commercial success, long‑felt need, failure of others, copying, licensing, or industry praise — and no prosecution history, which would normally be the place to find applicant arguments and any Rule 132 declarations. Under Graham, the patentee would bear the burden of producing such evidence, and nothing in this record supplies it. The one quasi‑"unexpected result" story the specification tells — that heat from the secondary region is "directed toward ink" — is, as noted, a natural consequence of the claimed geometry. The long corporate life of the patent (assignments to Bank One and JPMorgan, and a 2022 release of security interest) reflects the commercial significance of the Xerox TIJ chip portfolio generally, not necessarily of the specific claimed two‑region transducer, and cannot carry nexus without evidence tying the claim to the product.

7. Caveats and things I could not verify

• US 4,947,192's availability as § 102(e) prior art is doubtful given its 1990‑08‑07 publication date and its apparent identity of inventive entity (Hawkins/Burke) with this patent. Anyone relying on my Group‑A, B, and C combinations must first confirm the inventive entity and § 102(e) status against the actual face of that patent. My combinations are structured so that the field‑oxide/substrate points can also be carried by Matsumoto '321 and Hess '477 if '192 drops out, but with less force.
• I verified the disclosures of US 4,429,321, 4,539,571, 4,623,903, 4,719,477, and 4,947,192 against full texts. For US 4,620,212 (NEC, polysilicon resistor), US 4,769,527 (Hart), US 4,472,875 (Christian), and US 4,532,530 (Hawkins) I am relying on the titles/abstracts shown in this page's citation list and on general knowledge of the art; their verbatim disclosure should be confirmed before any rejection is written. Descriptions of the Texas Instruments, Lexmark, and Hynix "Cited By" documents are drawn from the page's own citation list and are not prior art to this patent.
• The claim set itself has drafting defects that affect scope (claim 11 recites "A driver device according to claim 10" although claim 10 is a transducer claim; claim 12 likewise). A full analysis should address claim construction, and potentially § 112, before comparing claims to art.