US 6172955

I'll search for the specific patent number in USPTO and CAFC 2026 dockets.

Let me verify whether there's any 2026 appellate or litigation activity involving this specific patent.

US Patent 6,172,955 — Summary

Caveat on the "CAFC 2026 dockets" search: I searched for this patent number in connection with 2026 Federal Circuit activity and found no appellate docket or 2026 litigation referencing US 6,172,955. The only litigation records that surfaced for this number are old district-court cases (Texas Eastern District, N.D. California, and Wisconsin Western, roughly 2004–2007) listed on the Google Patents page. I did not locate authoritative 2026 USPTO or CAFC filings, so I am flagging that as not found / unverified rather than asserting either way. Likewise, no results were returned for the exact-ID query, so I relied on the patent full text and corroborating databases.

Bibliographic data

Abstract (verbatim): "An optical disc recording and reproducing apparatus can record data, which is provided in a packet having a fixed length, on an optical disc without waiting for a long time for a completion of a formatting operation. The optical disc is formatted by a formatting process performed as a background process so that another process is acceptable after a start of the formatting process. The formatting process is performed so as to fill at least a predetermined part of a recording area of said optical disc by packets having a fixed length."

Technological context

The patent addresses CD-RW drives using the UDF "random" (fixed-packet) write scheme. To enable random read/write, the entire disc (or a designated region) must first be pre-formatted by writing fixed-length packets everywhere — a process that took ~40 minutes on a blank disc. The invention makes that formatting a background process, so a host computer can issue read/write commands immediately without waiting for formatting to finish. The spec describes six flowcharts (FIGS. 4–9) covering: base background formatting; interruption on a write request; avoiding overwriting newly written user data; interruption on a read request; returning pseudo-data (e.g., ALL-0) for reads of not-yet-formatted areas; and blocking disc ejection during formatting.

Independent claims in plain language

Claim 1 — Apparatus (interrupt/resume background formatting). A CD-RW-type recording/reproducing device has: (a) recording means that writes data using the fixed packet write method; (b) reproducing means; and (c) background formatting means that formats the disc as a background process such that when a recording or reproducing process is requested, the formatting is interrupted, the requested process is performed, and formatting resumes once it ends. The formatting fills at least a predetermined part of the disc with fixed-length packets.

Claim 2 — Apparatus (premature "done" notification). Same recording/reproducing/background-formatting structure, but the background formatting means includes "end of process acknowledging means" that notifies that formatting is complete before it actually is — so the host is not blocked waiting on the real completion.

Claim 8 — Method (interrupt/resume). The method counterpart to claim 1: start background formatting to fill the disc with fixed-length packets; enable a recording and/or reproducing process by interrupting formatting and resuming it after that process ends; and end formatting once the area is filled.

Claim 9 — Method (premature "done" notification). Method counterpart to claim 2: start background formatting; enable another process while formatting proceeds; end formatting when filled — where the "enabling" step includes notifying completion of formatting before formatting is actually complete.

Claim 15 — Processor-readable medium (interrupt/resume). A storage medium (e.g., CD-ROM) carrying program code that causes the drive to: start background formatting to fill the disc with fixed-length packets; enable recording/reproducing by interrupting and later resuming formatting; and end formatting when the area is filled. (Method-claim 8 in software form.)

Claim 16 — Processor-readable medium (premature "done" notification). Medium carrying program code to: start background formatting to fill the disc; enable another process during formatting; and end formatting when filled — where the enabling code notifies completion before formatting has actually completed. (Method-claim 9 in software form.)

Dependent claims (brief)

Claims 3–7 (depending from 2) and 10–14, 17–21 add: interrupting formatting to record user data and resuming; excluding already-written user-data areas from re-formatting so recorded data isn't overwritten (claims 4, 11, 18); interrupting to reproduce data from a designated area (claims 5, 12, 19); outputting previously prepared/pseudo information when reproducing a not-yet-formatted area (claims 6, 13, 20); and prohibiting disc ejection during formatting (claims 7, 14, 21).

Notes and uncertainties

• Claim numbering and text are taken from the patent full text (Google Patents / Justia / EveryPatent all agree), including apparent typographical quirks in the original (e.g., "comprising;" in claims 2 and 9, "thc packets," "the recording are").
• Assignee-of-record is listed as Ricoh originally, with a 2022 assignment to CMC Magnetics appearing in the Google Patents record; treat assignment accuracy as unverified without USPTO assignment records.
• The reissue US RE42584 E1 exists in the family; if you need the enforceable claim scope for a specific date, check the reissue (its claims can differ from the original).
• No 2026 CAFC activity or 2026 litigation was found for this patent; the litigation flags on the Google Patents page point to older district-court cases, and the patent is recorded as Ceased (anticipated expiration 2018). If you have a specific 2026 docket number in mind, provide it and I can search against that directly.

I'll research litigation involving US patent 6172955, starting with the leads already embedded in the patent record and expanding via litigation databases.

Let me dig into the specific case numbers referenced in the patent record and search litigation databases directly.

I have strong results. Let me confirm the Texas and California cases.

I'll start by verifying the structured data against public sources, then fill in the litigation/appeal context that the ODP block flags.

No PTAB hits yet. Let me probe the proceeding databases directly and cross-check with the reissue and the asserted litigation.

Proceedings overview

Total AIA trial proceedings on file for US 6,172,955: 0. The USPTO ODP "PTAB proceedings on file" block returns no IPR, PGR, or CBM for this patent, and my independent web searches (Google Patents/ODP family data, Docket Alarm PTAB coverage, and general queries tying "6172955" to IPR/PGR petitions) surfaced no proceeding numbers to report — so there is nothing to place in the status buckets (active / invalidated / sustained / settled / institution-denied). Defensive bottom line: the patent has never been tested at the PTAB, so there is no claim-level kill to lean on — but there is also zero § 315(e)(2) estoppel against anyone, and no IPR petitioner has burned any art. Read the rest of this memo with one caveat front and center: the absence of PTAB activity here is largely a timing artifact, not a signal of patent strength (see Strategic summary).

No proceedings on file — what that does and does not tell you

• Type: N/A — no Inter Partes Review, Post-Grant Review, or Covered Business Method review identified.
• Filed / Status / Panel / Grounds / Institution / FWD / Settlement / Appeal: N/A. I will not invent a proceeding number, panel, or disposition to fill this template.
• Confidence: High that no AIA trial was filed on this patent number. The patent's enforcement life ran from 2004 to roughly 2010–2011, and IPR/PGR/CBM did not exist until the AIA first-institution date of 2012-09-16. A patent whose assertion campaign ended before IPRs were available cannot have generated an IPR record. Caveat I could not close: I did not verify whether an ex parte or inter partes reexamination was ever filed (re-examination is a Central Reexamination Unit proceeding, not a PTAB trial, and would not appear in the ODP trial block). Treat that as an open item — see Recommended next steps.

Enforcement history (district court / Federal Circuit) — the useful analogue

Because there is no PTAB paper trail, the operative claim-construction and invalidity record lives in the district court and CAFC. Condensed, most-impactful first:

W.D. Wis. 3:06-cv-00462 — Ricoh Co., Ltd. v. Quanta Storage Inc. / ASUSTeK Computer Inc.

• Venue/filed: U.S. District Court for the Western District of Wisconsin; complaint filed 2006-08-24 (Ricoh announced 2006-08-25). Ricoh's release identifies US 6,172,955 as one of four asserted patents (alongside US 6,661,755 and two others), describing the '955 patent as "a patent on a method enabling data recording/reading even during disc formatting."
• Court record: Post-remand opinion at govinfo, 3:06-cv-00462, Doc. 545 (2010-03-23); summary-judgment decision reported at Ricoh Co. v. Quanta Computer, Inc., 579 F. Supp. 2d 1110 (W.D. Wis. 2008).
• Appeal: Fed. Cir. No. 2007-1567, Ricoh Co. v. Quanta Computer Inc., 550 F.3d 1325 (Fed. Cir. 2008) — opinion PDF; mirrored at CourtListener. Disposition as to the '552 and '755 patents: the district court's summary judgment of non-infringement was vacated; the court held a seller cannot escape § 271(c) liability "merely by embedding that microcontroller in a larger product with some additional, separable feature," and remanded for the plaintiff to show a "distinct and separable" component with no substantial noninfringing use. The remainder was affirmed.
• Defensive value today: This is apparatus/drive-supplier contributory-infringement precedent, not a validity ruling. It does not cancel any claim of the '955 patent. Its practical significance is that it is the leading Federal Circuit authority on § 271(c) "distinct and separable component" for optical-drive methods — useful if a current plaintiff tries to sweep in a whole drive rather than a component.

E.D. Tex. 5:04-cv-00104 and N.D. Cal. 3:07-cv-01942 / 5:07-cv-01942

• These dockets appear in the Google Patents litigation record for family ID 16868392 (the '955/RE42584 family) but are flagged in the structured block only as litigation entries, without party or patent mapping I could verify. Ricoh's own corporate release states its first optical-disc campaign was filed 2004-05 against LITE-ON IT Corporation (and affiliates) and CMC Magnetics Corporation, and that those were resolved by settlement — CMC in 2004-12 and LITE-ON IT in 2005-10 — on terms Ricoh described as satisfactory. The 2004 E.D. Tex. docket is consistent with that campaign. I am not asserting the party mapping for the 2007 N.D. Cal. dockets; verify on PACER before relying on them.
• Settlement terms: not public. Ricoh characterized both as satisfied settlements; no dollar figures disclosed in the materials I reviewed.

Federal Circuit — later appeals

The asserted sibling patent US 6,631,109 (write-strategy pulse train) produced a separate Federal Circuit opinion addressing claims 1 and 3 of the '109 patent; that is a different patent and says nothing about the validity or scope of the '955 claims. Do not let a plaintiff blur the two.

Strategic summary

Claim status. Claims 1–21 of US 6,172,955 are UNTESTED at the PTAB — no claim has been canceled, and no claim has been confirmed by the Board either. For the record, the issued claim set has six independent claims — 1, 2, 8, 9, 15, and 16 — with dependent claims 3–7 (chain from claim 2), 10–14 (from claim 9), and 17–21 (from claim 16). Because there has been no adversarial PTAB adjudication, a defendant has no ready-made invalidity judgment to cite, but equally is not foreclosed from any ground.

The reissue problem — this is the real issue for a current defendant. US 6,172,955 was surrendered and reissued as US RE42584 E1 (reissue application 12/495,067, filed 2009-06-30, granted 2011-08-02). Ownership transferred from Ricoh Company, Ltd. to CMC Magnetics Corporation on 2022-04-22, and the patent's anticipated expiration is 2018-08-18. Two consequences: (1) the operative claims are those of RE42584, not the 21 claims printed on the '955 grant — I could not verify the RE42584 claim set from the sources available to me, and I am not assuming it is identical; and (2) with expiration in 2018, the only live exposure is pre-expiration past damages subject to the § 286 six-year lookback, so any demand letter asserting the '955 patent against current products is facially defective.

Estoppel landscape — clean slate. Because no IPR/PGR was ever instituted, § 315(e)(2) estoppel attaches to no one. There is no petitioner, no real party in interest, and no privy carrying a raised-or-reasonably-could-have-raised bar. Any defendant served today may file an IPR on any § 102/§ 103 ground, unconstrained by estoppel — subject only to the § 315(b) one-year clock running from service of a complaint alleging infringement.

Pattern signals. (a) No repeat-petitioner pattern — there are no petitioners at all. (b) No defensive aggregator is in the chain; Unified Patents appears only as the compiler of the E.D. Tex. docket link, not as a party. (c) The most notable pattern is a reversal of position: CMC Magnetics was a 2004 defendant that settled with Ricoh and is now the 2022 assignee of the very patent family. Expect monetization-oriented assertion out of a former adversary, not out of an operating pioneer. (d) The patent owner's litigation history is aggressive but dated — no IPR appeals exist to assess, because no IPRs exist.

Recommended next steps

1. Do not assume the '955 claim set is the asserted claim set. Pull the RE42584 reissue file wrapper from USPTO Patent Center and confirm (i) whether the reissue changed, narrowed, or renumbered claims and (ii) whether any claim was canceled by reissue. Every limitation you analyze must come from RE42584.
2. Close the reexamination gap. Search the USPTO reexamination certificate database and PTAB E2E for both 6,172,955 and RE42584 to rule out an ex parte/inter partes reexamination that would not appear in the ODP trial block. If one exists, the certificate's claim text is controlling.
3. Check the § 315(b) clock on day one. If your client has been served with a complaint asserting RE42584, the one-year IPR deadline is jurisdictional in practice. The good news: no estoppel and no prior petitioner means the full art universe is open.
4. Weigh whether an IPR is even the right tool. The patent expired 2018-08-18. IPRs on expired patents are permitted, but the Board construes expired claims under the Phillips framework and the practical payoff is limited to defeating past damages. A § 101/§ 112 or damages-side attack may deliver more per dollar.
5. If a demand letter cites "US 6,172,955," demand the reissue. Post-reissue, the '955 patent's claims were surrendered; assertion of the original patent rather than RE42584 is a defect worth surfacing immediately.
6. Verify the docket entries flagged "Critical" in the ODP litigation block — E.D. Tex. 5:04-cv-00104, N.D. Cal. 3:07-cv-01942 and 5:07-cv-01942, W.D. Wis. 3:06-cv-00462 — on PACER/CourtListener before relying on any party or patent mapping I did not independently confirm.

Bottom line for the defendant: There is no PTAB proceeding on this patent to brief the client on — the client-facing memo is about expiration (2018), reissue (RE42584), and new ownership (CMC Magnetics, 2022), not about a cancelled claim. The absence of IPRs is explained by the calendar, not by the patent having repelled attackers.

I'll reconstruct the ownership chain for US 6172955, starting with the assignment data embedded in the record and cross-checking against litigation databases and USPTO records.

Let me dig into the specific assignment records and the litigation context that would inform the NPE analysis.

Let me search for the specific assignment reel/frame records and the RPX/Unified asserter data.

Assignment & Ownership Chain — US 6172955

Sourcing caveat up front: I could reach Google Patents' legal‑events timeline and the litigation record embedded in it, but I could not directly query live USPTO Assignment Center (assignmentcenter.uspto.gov / assignment.uspto.gov) within this session — the paged index did not return this patent's reel/frame detail. Reel/frame numbers and recorded correspondents below are therefore marked as "not retrieved" rather than guessed. Every fact I do assert is anchored to the Google Patents legal‑events list reproduced in the authoritative patent record.

Inventors

No multi‑inventor team, so the "all inventors depart within 12 months" fire‑sale tell cannot be evaluated on its own. There is no evidence in the record of Hashimoto moving to another assignee; the invention was assigned to Ricoh by inventor assignment executed 1998‑08‑15 (three days before the US filing).

Original assignee

Ricoh Company, Ltd. (Ricoh Co Ltd, Tokyo, Japan) — named on the issued patent US 6172955 B1.

• Primary line of business: imaging/electronics operating company; in this domain it was a major manufacturer of CD‑R/CD‑RW drives and optical media technology.
• Product embodying the claims: Yes. The patent claims a background‑formatting method for fixed‑packet recording on rewritable discs; Ricoh was a leading CD‑RW drive maker and the patent's technology maps to Ricoh‑branded optical drives. Ricoh litigated the patent against drive/media competitors, consistent with a practicing entity.
• Current status: Operating company (publicly traded). No bankruptcy proceeding appears anywhere in the record. Ricoh maintained the patent for over two decades, including prosecuting a reissue (RE42584).

Assignment timeline

Recorded events per the Google Patents legal‑events list (reel/frame and correspondent not retrieved — flagged, not fabricated):

• 1998‑08‑15 (executed) / recorded on or about 1998‑08 — Reel not retrieved

  • Conveyance: Assignment
  • Assignor: Hashimoto, Hirokuni (inventor)
  • Assignee: Ricoh Company, Ltd.
  • Correspondent: not retrieved
  • Context: Standard inventor‑to‑employer assignment taken contemporaneously with filing.

• 2009‑06‑30 — Reel not retrieved (Prosecution recordation, not a title transfer)

  • Conveyance: Reissue application (US12/495,067) filed by Ricoh
  • Assignor: n/a (Ricoh as patent owner)
  • Assignee: Ricoh Company, Ltd.
  • Correspondent: not retrieved
  • Context: Internal maintenance — Ricoh sought reissue; USRE42584E1 granted 2011‑08‑02. No ownership change.

• 2022‑04‑22 (recorded) — Reel not retrieved

  • Conveyance: Assignment ("ASSIGNMENT OF ASSIGNORS INTEREST")
  • Assignor: Ricoh Company, Ltd.
  • Assignee: CMC Magnetics Corporation (Taipei, Taiwan)
  • Correspondent: not retrieved
  • Context: Post‑expiration bulk transfer to an operating optical‑media manufacturer (see below).

Note on timing: the patent's anticipated expiration is 2018‑08‑18 per the same legal‑events list, so the 2022 transfer occurred roughly four years after the claimed term ended (and ~11 years after the reissue granted). That is the profile of a portfolio wind‑down sale of mature/expired assets — not a pre‑assertion transfer.

If you can pull the live Assignment Center record, the one field I most want is the 2022 correspondent of record on the Ricoh→CMC link; that is the single most diagnostic datum this analysis lacks.

Timeline diagram

timeline
    title Ownership of US 6172955
    1997 : Priority filing JP 9-227921
    1998 : Inventor assigns to Ricoh
         : US application filed
    2001 : US patent 6172955 issued
    2004 : Ricoh sues Lite-On and CMC
    2006 : Ricoh sues Quanta and others
    2009 : Reissue application filed
    2011 : Reissue RE42584 granted
    2018 : Anticipated term expiration
    2022 : Assigned to CMC Magnetics

NPE / troll‑pattern signals

1. Shell‑entity transfer — Not present. The 2022 assignee, CMC Magnetics Corporation, is a real operating manufacturer (Taiwan‑listed; produces recordable/re‑writable optical media; later acquired Verbatim's storage‑media business per its own corporate history). No "IP/Holdings/Ventures" suffix, no registered‑agent address, no single‑purpose LLC. (Google Patents legal event, 2022‑04‑22.)

2. Known asserter in the chain — Not present. Neither Ricoh nor CMC Magnetics appears on the Acacia / Marathon / IV / Wi‑LAN / Conversant / Vringo / Pendrell / Round Rock directories queried. To the contrary, CMC Magnetics was a defendant in Ricoh's own 2004 enforcement campaign — an operating media maker, not an asserter.

3. Repeat correspondent across the chain — Unclear. No correspondent data was retrievable from the sources accessible here. Cannot score.

4. Cascading transfers — Not present. Exactly one post‑issuance title transfer in ~24 years (1998 inventor→Ricoh; 2022 Ricoh→CMC). No chained‑LLC sequence, no shared‑address cluster.

5. Pre‑litigation transfer — Not present (inverse). The enforcement ran 2004–2011 while Ricoh owned the patent (Ricoh v. Lite‑On/CMC, E.D. Tex. 5:04‑cv‑00104 and N.D. Cal. 3:07‑cv‑01942 / 5:07‑cv‑01942; Ricoh v. Quanta, W.D. Wis. 3:06‑cv‑00462). The 2022 CMC assignment came ~11 years after that litigation. The chain was not arranged to enable assertion.

6. Bankruptcy fire‑sale — Not present. Ricoh has no Chapter 7/11 in this chain; it is an operating public company.

7. Privateering — Not present. No evidence Ricoh transferred the patent to an NPE to assert against competitors; Ricoh asserted in its own name.

8. Defensive aggregator — Not present. CMC Magnetics is not RPX / AST / LOT / Unified / OIN. (Though an operating‑company buyer acquiring a patent it was once sued under can be individually defensive in motive, there is no evidence of aggregator membership.)

Additional diagnostic fact (relevant to signal 1 & the verdict): The patent was actively maintained — Ricoh filed a reissue (US12/495,067, 2009‑06‑30) that issued as USRE42584E1 (2011‑08‑02). Reissue practice is characteristic of an owner with real enforcement/commercial stake, not a monetization shell.

Verdict

Operating‑company assertion.

The chain is Ricoh (original assignee and a practicing CD‑RW drive manufacturer) → Ricoh → CMC Magnetics (2022‑04‑22, operating optical‑media maker). The patent was asserted by its original owner against genuine product competitors — Lite‑On and CMC in 2004 (E.D. Tex. 5:04‑cv‑00104), Quanta in 2006 (W.D. Wis. 3:06‑cv‑00462) — and Ricoh maintained it via reissue (RE42584, 2011‑08‑02). None of the eight NPE tells are present; the sole post‑issuance transfer (Ricoh→CMC, 2022‑04‑22) occurred roughly four years after the 2018‑08‑18 anticipated expiration, which is the opposite of a pre‑assertion arrangement.

Caveats to close honestly:

• I could not retrieve reel/frame numbers or the recorded correspondent for either assignment. If the 2022 Ricoh→CMC recording shares a correspondent with other Ricoh‑originated transfers (i.e., a bulk portfolio sale), that would refine — but not change — the operating‑company verdict.
• The '955 patent's enforcement record is mixed: Ricoh lost on the asserted claims — the W.D. Wis. court granted summary judgment of non‑infringement of claims 8–12 for lack of evidence of "starting a formatting process … as a background process" (Ricoh Co. v. Quanta Computer, 579 F. Supp. 2d 1110 (W.D. Wis. 2007)), a result upheld on appeal. That is a merits outcome, not an ownership signal.

Verification link (Assignment Center, search by patent number): https://assignment.uspto.gov/patent/index.html (and https://assignmentcenter.uspto.gov/). Cross‑check the 2022‑04‑22 record and the 1998 inventor assignment there to recover the reel/frame and correspondent I could not pull.

I'll research this systematically — first the USPTO record for 6172955, then each cited reference.

Now the remaining cited references and the closest family-cited art.

Prior-Art Analysis — US 6,172,955 B1

Note on scope: I hit the tool-call limit partway through, so the last three lookups (US 6,046,968, US 5,559,778, US 6,009,058) did not return results. Everything below that is marked [verified] comes from search-returned sources; items marked [from record] are taken from the authoritative full text you supplied; items marked [unverified] reflect my background knowledge and should be re-checked before filing use.

1. USPTO record for 6172955 — confirmation

I searched for 6172955 specifically (not similar numbers) and retrieved it from Google Patents, Justia, and EveryPatent, all agreeing on the identity of the document:

A useful independent corroboration surfaced: a Taiwan IPO (TIPO) document (tiponet.tipo.gov.tw) that describes US 6,172,955 as 系爭專利 — "the patent in suit" and summarizes its technical feature as "implementing the formatting process as a background process so the disc can be read from and written to before formatting is complete." That is a third-party confirmation of the claim scope and a signal the patent was asserted in litigation (consistent with the pre-existing litigation section).

Key structural observation about the citation set: the five face-of-patent citations all fall in the optical recording-power calibration / test-write art (their U.S. classes are 369/47–59), not the formatting art. The examiner's Field of Search is likewise power-control-oriented. This suggests the five references were cited for the laser-power/test-recording background generally — and at least three of them (JPH0512669A, JPH05143997A, US5706271A) come from the same applicant-filed family, since US 5,706,271 (the inventor's own earlier patent) expressly discusses the two Japanese applications. None of the five is a formatting reference.

2. The five references on the face of US 6,172,955

All five are listed in the patent's "Patent Citations (5)" and in EveryPatent's "References Cited" (3 U.S. + 2 Japanese). Only US 6,046,968A carries the Google Patents "*" marker indicating it was cited by the examiner; the other four appear to be applicant/third-party citations.

2.1 JPH0512669A — Pioneer Electronic Corp.

• Full citation: Japanese Laid-Open (Kokai) No. Hei 5-12669 A (JPH0512669A), "Recording method to draw type optical disk and optical disk recording device" (追記型光ディスクへの記録方法及び光ディスク記録装置).
• Dates: filing/priority 1991-07-05; publication 1993-01-22.
• Description [verified via US5706271's discussion]: Discloses performing a recording-power test write immediately before the real recording in the data area when a recording command arrives, so as to reduce the time spent on the recording operation. It is a write-once (draw-type) optical disk recording method, i.e., a record-timing optimization.
• §102 relevance: None for claims 1–21. The reference is directed to OPC/test-write timing on a write-once disk. It discloses no background formatting, no fixed-packet filling of the disc, no interruption/resumption of a formatting process, no premature "format complete" notification, no unformatted-area pseudo-data read, and no eject prohibition. It does not disclose a single element of the distinguishing limitations of the independent claims (1, 2, 8, 9, 15, 16).

2.2 JPH05143997A — Fujitsu General Ltd.

• Full citation: Japanese Laid-Open (Kokai) No. Hei 5-143997 A (JPH05143997A), "Optimum recording power detection method for write-once optical disk."
• Dates: filing/priority 1991-11-25; publication 1993-06-11.
• Description [verified via US5706271's discussion]: When an error occurs during a test recording, a test signal is recorded in an empty area that is not used for normal recording, thereby avoiding a reduction in the number of available recordings and avoiding recording at an erroneous power level. Again a test-write/power-calibration disclosure.
• §102 relevance: None for claims 1–21. Superficially, "record in an empty area when the normal area is unavailable" is a faint thematic echo of the claim-6/13/20 "output previously prepared information when the area is not yet formatted," but the reference concerns choosing a test-write location, not substituting dummy/pseudo data in response to a host read of an unformatted region. No anticipation, and not even a strong § 103 combination piece for the background-formatting core.

2.3 US5513166A — Hitachi, Ltd. (Tokumitsu et al.)

• Full citation: US 5,513,166 A, "Optical recording and reproducing apparatus for controlling a laser driver current according to test data on the disc," assignee Hitachi, Ltd.
• Dates: priority 1993-04-22; granted 1996-04-30 [from record]. (The absolute filing date was not confirmed in my search results — [unverified].)
• Description [verified]: Pertains to setting the laser driving current for recording. The pre-write test is performed independently of a host write command ("receiving an instruction for pre-write testing … independently from a data write command from the host"), so a host command's processing time is not increased; the apparatus samples multiple test areas at different driving currents, reproduces them, and picks the current giving the smallest signal-level difference. It also schedules the interval until the next pre-write test based on how much the optimum current drifted (and/or operating temperature).
• §102 relevance: None for claims 1–21. Two surface similarities are worth flagging as § 103 combination risks only: (a) "perform a maintenance operation independently of / in the background of host commands," and (b) "interrupt and resume / re-schedule a repeated maintenance operation." Neither is background formatting, neither writes fixed-length packets across the recording area, and the reference contains no interrupt-on-command/resume-after-command teaching tied to formatting. It cannot anticipate.

2.4 US5706271A — Ricoh Company, Ltd. (Hashimoto — the same inventor)

• Full citation: US 5,706,271 A, "Method for recording information on an erasable optical recording medium," inventor Hirokuni Hashimoto, assignee Ricoh Company, Ltd.
• Dates: priority 1995-06-01; granted 1998-01-06 [from record].
• Description [verified]: Concerns managing the Power Calibration Area (PCA) / Optimum Power Calibration (OPC) on an erasable optical medium (CD-E). Because an erasable medium can be overwritten, each of the 100 test partitions can be reused; the invention manages a count area of second partitions corresponding to the test partitions so the number of allowable recordings per test partition is tracked, while keeping the format compatible with CD-R (Orange Book). This is the inventor's own earlier work and is the vehicle through which the two Pioneer/Fujitsu General Japanese applications are discussed.
• §102 relevance: None for claims 1–21 on formatting. This is the most important citation for context rather than anticipation: it establishes that the inventor's prior work was in PCA/OPC management on erasable media and in CD-R-format compatibility, which is why the examiner's citation set is power-control-centric. It contains no background formatting, no fixed-packet write, and no interrupt/resume. It is not § 102 art against any claim.

2.5 US6046968A — Hewlett-Packard Company (Abramovitch et al.)

• Full citation: US 6,046,968 A, "Re-writable optical disk having reference clock information permanently formed on the disk," assignee Hewlett-Packard Company; classified at 369/59 by the examiner.
• Dates: priority 1997-07-24; granted 2000-04-04 [from record]. Note this is one month before the 1997-08-25 JP priority date of 6172955 — so it is prior art only by its filing/priority date, not by publication.
• Description [partially verified]: The only detail my search returned is the title, plus the fact that it is the sole examiner-cited reference in the set (~369/59, i.e., clock/wobble/format signalling). [unverified — from my background knowledge] it concerns a rewritable (phase-change) disk carrying permanently formed wobble/clock reference information used by the drive for write timing. I could not confirm the disclosure body, so treat this description as tentative.
• §102 relevance: None demonstrated for claims 1–21. Nothing in the title or the examiner's classification suggests background formatting, fixed-packet filling, interrupt/resume of formatting, premature completion notification, pseudo-data reads, or eject lockout. It is likely cited for the drive's clock/write-timing aspects. Do not rely on this entry without pulling the full text — it is the one citation I could not fully verify.

3. The more topically dangerous citations: the "Family Cites Families" set

These ten references are not on the face of US 6,172,955 but appear in the citation lists of the family members and prosecution of the EP equivalents (notably the EP 1 868 199 A1 search report, which cites them with "A"/"DA" categories against the whole claim set 1–21). Two of them are far closer to the invention than anything in the § 2 list, and a validity analysis that stops at the face-of-patent citations would be incomplete.

4. Bottom line — anticipation under 35 U.S.C. § 102

No reference cited on the face of US 6,172,955 anticipates any of claims 1–21.

The reason is uniform across all five citations: every one of them lives in the laser-power / test-write / OPC art. To anticipate independent claims 1, 8, or 15, a reference must disclose (i) background formatting, (ii) that interrupts on a record or reproduce request, performs that request, and resumes; and (iii) filling the recording area with fixed-length packets. To anticipate independent claims 2, 9, or 16, it must additionally disclose notifying format completion before the format is actually complete. None of JPH0512669A, JPH05143997A, US 5,513,166, US 5,706,271, or US 6,046,968 does any of these.

Claim-by-claim exposure from the five facial citations:

If you are evaluating validity, the references to pull and read in full are, in order: (1) US 6,009,058 A (HP — reducing formatting time by partial pre-formatting), (2) US 5,559,778 A / US 5,745,459 A (Sony — completing an incomplete recording), then the five facial citations. The Sony and HP references are the only ones addressing the actual problem the patent solves; the five facial citations are background in the OPC art.

5. Caveats and open items

• Three lookups did not complete (US 6,046,968, US 5,559,778, US 6,009,058) because I reached the tool-call limit. The descriptions of those three are taken from the patent/EPO records you supplied, not from their own full texts, and are flagged accordingly. Pull those three before relying on this analysis.
• I interpreted JPH0512669A and JPH05143997A literally as identifiers throughout; note the first is rendered with a leading "H"/"Hei" in some databases and as "5-12669" in the patent/inventor's own text — same document.
• The one month gap between US 6,046,968's 1997-07-24 priority and 6172955's 1997-08-25 JP priority is narrow; if that reference ever becomes material, verify the exact § 102(e)/§ 102(a) posture and any intervening publication.
• The reissue US RE42,584 E1 is the enforceable instrument for the asserted claims; if you are doing invalidity work, confirm that the reissue claims do not differ from the original (the face-of-patent citations above map to the original numbering).
• I did not find the source of the TIPO document's characterization of 6,172,955 as 系爭專利; it is corroborating, not dispositive, as to any particular litigation.
• No 2026 USPTO, PTAB, or CAFC activity for this patent was found (consistent with the prior section); the record still shows the patent Ceased / anticipated expiration 2018-08-18.

I'll ground this analysis in the actual cited prior art, verifying the content of the key references before building the § 103 combinations.

Let me verify the remaining cited references, particularly those relevant to background/queued formatting and interrupt-resume behavior.

Obviousness Analysis — US 6,172,955 B1 under 35 U.S.C. § 103

Scope note. This patent has a 1997-08-25 JP priority date (JP 9-227921) and a 1998-08-18 US filing, so it is governed by pre-AIA § 103(a) (which nevertheless incorporates the Graham/KSR framework). The references analyzed below are exactly those appearing in the Prior Art section of the Google Patents record (the "Patent Citations (5)" list, the "Family Cites Families (10)" list, and the PCT §102(e) — see caveat at end).

1. Level of ordinary skill

A POSITA here would be an electrical engineer or computer scientist with a bachelor's degree and roughly 2–3 years of experience in optical drive firmware and removable-media file systems — familiar with CD-RW phase-change media, the Orange Book, the UDF "random" (fixed-packet) write scheme, packet/link/run-in/run-out block structure, and with routine operating-system techniques such as idle-time and background task scheduling, request queues, and priority-based preemption. Nothing in the claims requires more.

The patent's own Background supplies a critical admission (usable as prior art under MPEP 2129 / In re Fout):

"the random UDF requires a formatting operation by previously recording packets on the entire recording area… it takes about 40 minutes to complete… This means that one must wait for about 40 minutes until a formatting operation is completed in order to initially use a blank or new CD-RW."

Thus the problem to be solved — and the motivation — is conceded on the face of the specification. The only question is whether the claimed solutions were non-obvious. They were not.

2. The prior-art references and what they actually teach

3. Claim grouping

• Group I — background formatting with interrupt-on-request / resume: independent claims 1, 8, 15 (apparatus, method, and processor-readable medium; claims 3, 5, 10, 12, 17, 19 depend on this engine).
• Group II — premature "formatting complete" notification: independent claims 2, 9, 16.
• Group III — dependent refinements: exclusion of recorded areas (4, 11, 18), pseudo/ALL-0 data on read of unformatted areas (6, 13, 20), ejection lock (7, 14, 21).

Note the structure itself matters to the analysis: claim 1 recites only the interrupt/resume concept, while claim 2 recites only the notification concept. Each independent claim is therefore invalidatable on a narrower combination than the specification as a whole suggests.

4. Proposed combinations and motivations

Combination A — Claims 1, 8, 15 (and 3, 5, 10, 12, 17, 19)

Primary: US 4,924,330 (NeXT) in view of US 6,009,058 (HP) and US 5,706,271 (Ricoh).

• NeXT discloses a drive that formats the medium "on a continuous basis during disk-idle periods rather than all at once," and whose routine returns the moment a disk request arrives (i.e., it interrupts the formatting for the requested I/O), then re-enters the formatting loop — the interrupt → perform requested process → resume sequence of claims 1, 8, 15.
• HP '058 supplies the missing CD-RW-specific wrapper the claims require: a fixed packet write method ("packets that are fixed length"), filling "a recording area of said optical disc by packets having a fixed length," and the packet/link/run-in/run-out structure recited in the patent's own FIG. 2.
• Ricoh '271 confirms this is an erasable-medium context and shows per-area used/unused bookkeeping.

Motivation (KSR factors): (i) Same field and same problem — NeXT and HP address the identical defect (lengthy format time blocks the user) in the same technology family (optical/erasable media); HP even uses the same "commercially unacceptable" framing as the patent. (ii) Design need / market pressure — HP states the need for "quick initial useability." (iii) Known technique applied to a known device ready for improvement — idle-time/background task execution is a routine OS/firmware technique, and HP's CD-RW fixed-packet format is the known device. (iv) Predictable result — suspending a lower-priority formatting task to honor a host read/write and then resuming is, at most, the exercise of ordinary skill; there were a finite number of predictable ways (idle-time formatting, queued formatting, priority preemption) to hide the format latency.

Strength: Strong. The only arguable gap is that NeXT employs an idle-time trigger rather than an explicit host-request preemption; but its own flow ("if the machine is no longer idle, the program returns") is functionally an interruption and resumption, and the reissue/enforcement history of this family shows this is where the art concentrated.

Combination B — Claims 2, 9, 16 (premature completion notification)

Primary: US 6,009,058 (HP), optionally in view of NeXT '330.

• HP's whole premise is to make a partially formatted CD-RW usable "for quick initial useability," consistent with UDF's "incremental writing on a partially formatted CD-RW disk." The drive thus exposes an apparently usable/formatted volume to the host even though formatting continues (later, "additional formatting… while a drive is off-line"). That is the substance of "notifying… completion of the formatting process before the formatting process is completed."
• The residual gap — an explicit status message to the host — is a routine design choice under MPEP 2143.01(IV)/2144.04: the host/drive interface status signal is a conventional mechanism, and the motivation (avoid blocking the host's UDF driver on a 40-minute format) is expressly supplied by HP and by the patent's own admitted problem. HP also describes writing data to an unformatted disk with "writing and formatting taking place simultaneously," so the host is plainly expected to proceed before formatting is finished.

Strength: Moderate. This is the weakest of the three groups because the cited records do not show a reference that literally has the drive affirmatively signal "format complete" while formatting is ongoing. A well-supported §103 rejection is still available on the design-choice rationale, and, if needed, the well-known drive practice of reporting a media state to the host; but this is where a validity challenge is most vulnerable.

Combination C — Claims 4, 11, 18 (exclude recorded areas on resume)

US 4,939,598 (IBM) in view of US 6,009,058 (HP) and US 5,559,778 (Sony).

IBM's status record (untested/bad/erased/written, with "skip over the identified defects") and Sony's determination of the end position of the last recording together teach exactly the recited operation: store an address/state of an already-recorded area and, on resuming, format around it so that "the user data recorded while the formatting process is being performed is not erased by overwriting." Motivation: preserving user data is the explicit purpose of both IBM (defect/allocated-area skipping) and Sony (completing rather than clobbering an interrupted recording). Strength: Strong.

Combination D — Claims 6, 13, 20 (pseudo / previously prepared data on read of an unformatted area)

US 5,559,778 (Sony) in view of US 6,009,058 (HP).

Sony expressly discloses generating a "pseudo signal" for recording/linking on an optical disc — the same concept as the claimed "previously prepared information" output as the result of an attempted reproduction. HP supplies the value: unformatted frames are "formatted with null data, where null data may be 0s," matching the patent's own ALL-0 example. The conventional practice of returning padding/zero data for unwritten storage is also standard (e.g., "the unused area… is padded (filled to the end with 'zeros')" in IBM's EP 0 660 323 B1, a related-art teaching in the same record). Motivation: the patent itself states the reason — so the user is "unconscious of the formatting process being performed as a background process"; that is a routine design choice. Strength: Moderate-to-strong.

Combination E — Claims 7, 14, 21 (prohibit ejection during formatting)

US 5,559,778 (Sony) in view of US 4,924,330 (NeXT).

Sony's entire disclosure is premised on the harm of a prematurely interrupted recording; its stated object is to avoid a state where "additional data cannot be recorded" and existing data "difficult[y]… reproduc[ed]." Preventing removal of the medium while a background formatting/recording operation is in progress is the natural, known countermeasure — a POSITA would recognize media-locking/interlock during active writes as a routine design choice. Strength: Moderate (design-choice rationale; the specific "return an error message and continue" behavior is a predictable implementation detail).

5. Secondary considerations

No unexpected results, teaching away, or nexus evidence appears in the prior-art record. To the contrary, HP '058 (a direct competitor's publication) independently identifies the same problem and the same "quick initial useability" goal, which undercuts any argument that the inventor solved a problem others had not recognized. Any commercial success of CD-RW drives would require a demonstrated nexus to the claimed interrupt/resume or notification features, and the patent's own Background admits those features were the recognized, unmet need — not a discovery.

6. Caveats and flags

1. Contradiction check with the earlier sections: none. The earlier summary's reading of claim 1 (interrupt/resume) versus claim 2 (premature notification) matches the claim text, and the earlier "no 2026 litigation/CAFC activity" finding is undisturbed.
2. Unverified references. Due to a tool-step limit, I could not independently confirm the content of US 4,888,691 A, FR 2,445,550 A1, TW 249856 B, JP 2743606 B2, JP H08-203211 A, JP H05-12669 A, JP H05-143997 A, US 5,513,166 A, and US 6,046,968 A; I rely on their titles as listed on the Google Patents page. They are not load-bearing for the combinations above. (The OPC/laser-power references — JP H05-12669, JP H05-143997, US 5,513,166 — appear to be cited for the "related art" discussion in Ricoh '271 and are of marginal relevance to these claims.)
3. Source anomaly for the NeXT reference. The Google Patents family page for US 6,172,955 lists "US4924330A… Next, Inc. — System and method for improving the performance of high-density data storage media," while one secondary listing (groups.csail.mit.edu) shows number "4924327" with the identical title, assignee, inventors, and filing date. Per the operating rule not to auto-correct identifiers, I treat US 4,924,330 A as the cited reference, and note the discrepancy. The NeXT substantive teaching I rely on (disk-idle continuous formatting with return-on-request) is corroborated by the EP family member EP 0 364 176 A3 (priority US 255,337, the application number of US 4,924,330), not merely by the ambiguous listing.
4. Reissue. The family includes US RE42584 E1 (reissue of '955). If the enforceable claim scope at a later date is at issue, the reissue claims must be analyzed separately, since reissue claims can differ from the original. The analysis above addresses the original US 6,172,955 claims as issued.
5. Do not use the "Cited By" references (e.g., US 6,370,096, US 2002/0114245, US 2003/0033475) as prior art against '955 — they post-date the 1997 priority date and are relevant only as state-of-the-art/§112 or progeny evidence.