US 5613751

I'll search for the patent and any 2026 litigation docket activity.

Let me check for any litigation involving this patent's asserted campaigns.

US 5,613,751 — Verification and Summary

Search scope / caveat: I performed open‑web searches (Google Patents, FreePatentsOnline, USPTO‑hosted petition documents, Justia, Stanford NPE database) rather than querying the USPTO PatentCenter or the CAFC docket API directly. Where the record is thin I say so explicitly.

Literal‑ID note: The identifier given (5613751) maps to exactly one U.S. patent, US 5,613,751 A. No sibling or neighbor numbers were substituted.

Bibliographic data (from the patent's own front‑page record)

Assignee chain of record (all reassignments listed on the Google Patents record): Lumitex, Inc. → Lee, Mang‑Shiang (Mar. 15, 2001) → Solid State Opto Limited (Mar. 20, 2001) → Rambus International Ltd. (Feb. 18, 2010) → Rambus Inc. / Rambus Delaware LLC (Mar. 4, 2013) → Acacia Research Group LLC (June 26, 2013) → Innovative Display Technologies LLC (June 27, 2013). Google Patents lists current assignees as Lee Mang‑Shiang and Innovative Display Technologies LLC — the simultaneous listing of an individual 2001 assignor reflects the source page's formatting, not two independent present owners. Note also an intervening KeyBank National Association security interest (1999) and its 2001 release.

Family: continuations/divisionals US 5,618,096; US 5,876,107; US 5,921,652; US 6,079,838; foreign members EP 0 751 340 B1, DE 696 084 99 T2, JP H0921916 A.

Abstract (verbatim)

Light emitting panel assemblies include light emitting panel members and one or more light sources positioned/embedded in a light transition area, which increases the efficiency of light entering the panel members along the light input area to be emitted from one or more light emitting surfaces along the length of the panel members. Light may be reflected or refracted by a surface which changes the path of a portion of light such that it enters the input area of the panel member at a more acceptable angle. A uniform light output distribution may be produced by utilizing a pattern of light extracting deformities.

Specification incorporates by reference US 4,897,771 and US 5,005,108, both "assigned to the same assignee as the present application."

Independent claims — plain language

The '751 patent has exactly two independent claims: claim 1 and claim 96. Every other claim in the set (2–95, 97) depends, directly or through a chain, from claim 1 or claim 96. This is worth stating plainly because several claims that read like stand‑alones (e.g., 52, 83, 88, 94) all open with "The assembly of claim 1…".

Claim 1 — the core concept. An edge‑lit light guide assembly with three required elements:

1. a light emitting panel member that has a light emitting surface;
2. a light transition area (the entrance/throat region through which light is coupled into the panel); and
3. a light source that is embedded or potted in that transition area, such that no air interface exists between the light source and the transition area.
   The inventive point is the elimination of the air gap at the LED/panel junction, reducing Fresnel reflection and lensing losses. Practically, this is a "no air gap at the input" claim.

Claim 96 — a companion independent claim drawn to the same assembly but with two wording changes: the panel member has a "light extracting surface" (rather than "light emitting surface"), and the light source is "bonded to" the transition area (rather than "embedded or potted in"), again so as to eliminate any air interface. Claim 97 narrows claim 96 to a slot/recess receiving the light source, with mating locating surfaces.

Notably, neither independent claim recites light‑extracting deformities. The deformities/pattern limitations appear only in the dependent claims (claim 2 onward). Independent claim 1 is thus broader than the ornamentation‑and‑pattern subject matter that dominates the specification, and broader than the claims the later family members (e.g., US 6,712,481, US 6,755,547) were prosecuted on.

Claim families within the dependent set (representative groupings):

• Deformity pattern (2–11, 52–82): 0.006 in² max per deformity; variation in length/width/color/index/multiple layers; prismatic, raised, or depressed forms; stochastic/frequency‑modulated/random‑dot halftone printing; no‑specific‑angle shapes to reduce moiré.
• Films, reflectors, air gaps (7–9, 12–13, 33): peripheral‑only adhesive so an air gap is retained between panel and diffuser/back reflector.
• Light source types/colors (14–16, 63–65, 88–93): LED, incandescent, multicolored sources mixed in the transition area to produce colored or white light.
• Mechanical/structural (17, 25–27, 57–59, 87, 95): posts or structure supporting an LCD; cavities for modular components; modular transition‑area insert seated in a recess; LCD and/or switch lighting.
• Transition‑area geometry (28–32, 39–49, 83–85, 94): off‑axis; thicker than the panel; multi‑plane/three‑dimensional collection surfaces; angled transition area with a junction reflector; reflective surfaces "in close proximity" to the source producing uniform light density across the input cross‑section; panels ≤0.125 in thick; snap‑fit/slide‑in rear‑entry slots.
• Front‑lighting (50–51): transparent panel and deformities with no back reflector, so a display can be viewed through the panel; secondary light source projected through the panel.

Litigation and 2026 CAFC docket check

• I found no CAFC 2026 docket activity, appeal, or opinion naming US 5,613,751. Searches for the number together with 2026 Federal Circuit terms returned only unrelated 2026 appeals (e.g., Spero v. Mercedes‑Benz, Nos. 2025‑1470/2025‑1064, Rule 36 judgment May 14, 2026; Inneos v. Opticis, No. 2025‑1487, Rule 36, June 10, 2026; Align Tech. v. Dental Monitoring, No. 25‑1752). I cannot rule out a docket entry that is not web‑indexed, but nothing surfaced.
• Practical reason for the absence: the patent expired June 27, 2015 (anticipated expiration), so it can no longer be asserted prospectively; any 2026 dispute would be legacy damages/laches matters, and even those would be unlikely this many years after expiry.
• The patent does carry a Darts‑IP "Family has litigation" flag (family ID 23967579), and its number appears in the prior‑art search strings and litigation exhibits of the later family members.
• The large Innovative Display Technologies / Delaware Display Group campaigns (E.D. Tex. 2:13‑cv‑522 against Acer, 2:13‑cv‑525/527 against Huawei/ZTE, 2:14‑cv‑00030 and 2:14‑cv‑00301 against Apple, 2:14‑cv‑00535 against Mercedes‑Benz, 1:13‑cv‑02106/02108/02109/02110/02111/02112 against Amazon, Lenovo, LG, Pantech, Sony, Vizio, plus the LG Display, Dell, and HP matters) asserted later continuations — specifically US 6,755,547; 7,300,194; 7,404,660; 7,384,177; 7,434,974; 7,537,370; and 8,215,816 — not the '751 patent itself. A Dykema Gossett client‑experience exhibit does list "Patent No. 5,613,751 (Application No. 08/495,176)" in connection with the IDT campaign, so '751 was at least referenced in that litigation context, but I do not have authoritative confirmation that '751 was ever separately asserted in a complaint.

Uncertainty flags

• I could not independently verify the current assignee of record through USPTO Assignment Search; the chain above is as recorded on the Google Patents page and is consistent with the separate Official Gazette entries for US 6,712,481 and US 6,755,547 (Solid State Opto Limited, BVI).
• The Google Patents "Current Assignee" field naming Lee Mang‑Shiang alongside Innovative Display Technologies LLC is a source‑page artifact; treat the recorded 2013 assignment to IDT as the reliable endpoint.

Key URLs: https://patents.google.com/patent/US5613751/en · https://FreePatentsOnline.com/5613751.html · https://npe.law.stanford.edu/patent/7404660 (for the IDT campaign pattern) · https://www.docketalarm.com/cases/[PTAB](/ptab)/IPR2015-00361/ (family‑related IPR context)

I'll research litigation involving US 5,613,751 across patent litigation databases and news sources.

Let me dig deeper with targeted searches on litigation databases and the specific patent.

Litigation Involving U.S. Patent No. 5,613,751

Bottom line

I found no confirmed lawsuit in which U.S. Patent No. 5,613,751 itself was named as a patent-in-suit. The voluminous litigation involving this patent family — the "Light Emitting Panel Assemblies" campaign run by Innovative Display Technologies LLC (IDT) and Delaware Display Group LLC (Acacia subsidiaries) — was brought on the later continuation/divisional patents that claim priority to the '751, not on the '751 itself. I want to be explicit that this is a negative finding based on the sources I could reach, not an exhaustive PACER/Unified Patents docket sweep.

What the '751 is, and why that matters

• Pat. No. 5,613,751, "Light Emitting Panel Assemblies," inventors Jeffery R. Parker, Mark D. Miller, Daniel N. Kelsch; Appl. No. 08/495,176, filed June 27, 1995; issued March 25, 1997; original assignee Lumitex, Inc. (Strongsville, Ohio).
• It is the common parent of the asserted family. The Google Patents record lists it as "Application Four:: 08/495,176 … U.S. Pat. No.: 5,613,751" under which later filings are DIV/continuations.
• Legal status on the face of the record: Expired – Lifetime, with anticipated expiration June 27, 2015. That means any infringement window closed over a decade ago (and damages would in any event be limited by the six-year statute of limitations, 35 U.S.C. § 286, to roughly 2009–2015).

The Google Patents page carries a Darts-ip banner indicating the family "has litigation" (family ID 23967579) — but that banner refers to the family, and the record does not identify the '751 as the asserted member.

Lawsuits I did find in the family — none asserting the '751

All of the following were asserted on descendant patents ('547, '194, '177, '660, '974, '370, '816, '196, and the "Auto Patents" '563/'956):

IDT was reported at one point to be carrying roughly 34–38 active cases across consumer-electronics, auto, camera, and GPS defendants, with a high settlement rate (consolidations/dismissals) rather than trials.

AIA proceedings — the '751 appears only as prior art, not as the challenged patent

The '751 shows up in PTAB filings as an exhibit/reference cited against its own descendants, which is the opposite of being a patent-in-suit:

• IPR2015-00506 (Inter Partes Review of U.S. Pat. No. 7,434,973) — Petitioner's Exhibit 1006 is a copy of US 5,613,751 (Parker).
• IPR2015-00855 (IPR of U.S. Pat. No. 7,404,660) — Toyota Exhibit 1015 is a search-history document listing "5613751" among Parker-family publications retrieved.
• Related family IPRs include LG Display v. IDT, IPR2015-00487 ('660); Toyota Motor Corp. v. IDT, IPR2015-00831, -00832, -00843; and IPR2015-01866 ('816), -01867 ('370), -01868 ('974), with cases 2016-910 and 2016-914 joined. In the '660 IPR the patent owner argued the '660 had expired, requiring district-court (Phillips) claim construction instead of BRI.

Unresolved lead worth checking

Poly-Optical Products, Inc. v. Lumitex, Inc., C.D. Cal., No. 8:98-cv-00343 (Judge Linda H. McLaughlin). Filed April 8, 1998 — roughly one year after the '751 issued, and against the original '751 assignee Lumitex. Voluntary dismissal without prejudice entered May 1998. I could not confirm which patent(s) were asserted. Given the timing and parties, this is the most plausible candidate for an actual '751 assertion, but I am not asserting that it was; the docket entries I retrieved do not identify the patent in suit. Separately, Lumitex, Inc. v. Sheffmed Trade Services Ltd., 1:04-cv-02225 (N.D. Ohio), was a Lumitex-as-plaintiff case but on U.S. Pat. No. 6,504,985 — again not the '751.

Caveats and limitations

• I was unable to complete a direct query of the Unified Patents litigation portal or PACER within this session, and I could not independently run a docket-level search on "5,613,751" restricted to patents-in-suit. My conclusion rests on the family/assertion records I retrieved.
• The '751's expiration on June 27, 2015 makes new assertions impossible; any historical suit would have had to be filed by then.
• Absence of a hit in the sources I reached is not proof that no such case exists — early-1990s/2000s dockets (pre-CM/ECF for some courts) are incompletely indexed.
• The litigation landscape above concerns different patent numbers; per your instruction I have not treated those as the '751.

Recommended next steps to confirm

1. Run a claimant/patent-number search on Unified Patents' litigation portal (portal.unifiedpatents.com/litigation) and Docket Alarm / Justia / PlainSite filtered to "5,613,751" and "5613751."
2. Pull the complete docket and complaint PDFs in Poly-Optical Products v. Lumitex, 8:98-cv-00343, to see whether the '751 was pleaded.
3. Check the Darts-ip family-23967579 record referenced from the Google Patents page to see which family member was the "first worldwide family litigation."
4. Search PTAB/Federal Circuit for any appeal referencing the '751 as a patent-in-suit (as opposed to cited art).

I can pursue any of these if you want me to continue digging.

I'll start by verifying the structured "no PTAB activity" baseline against public sources before drafting.

Let me dig deeper on whether any proceeding specifically targeted the '751 patent itself.

The picture so far is that the IPRs targeted the later family members, not the '751 itself. Let me confirm the '751 patent's own PTAB docket and check for any reexamination.

Proceedings overview

Zero AIA trial proceedings on file. The structured USPTO Open Data Portal block returns no IPR, PGR, or CBM for US 5,613,751 — active: 0; claims invalidated: 0; claims sustained: 0; settled: 0; institution denied: 0 — which means there is no "IPR-hardened patent" story here at all; the real story is that the '751 patent expired 2015-06-27 and has been outside the § 286 six-year damages recovery window since 2021-06-27, so a demand letter citing the '751 is not a threat to litigate, it is a threat to bluff.

No PTAB proceedings on file for US 5,613,751

• Type: N/A — no AIA trial petition was ever instituted, and my searches surfaced no petition, no preliminary response, and no Board paper naming U.S. Patent No. 5,613,751 as the challenged patent.
• Filed: N/A
• Status: no proceedings (per the structured ODP block) — corroborated by web search.
• Judge panel: None. No APJ has ever been assigned to an AIA trial on this patent.
• Petition grounds: N/A
• Institution decision: N/A
• Final Written Decision: None issued. No claim of US 5,613,751 has ever been canceled, confirmed, or construed by the PTAB.
• Settlement / termination: N/A
• Appeal: No PTAB appeal exists (nothing to appeal). I found no Federal Circuit opinion on the merits of the '751 claims. Nothing on the CAFC docket or CourtListener tied to a PTAB FWD for this patent.
• Defensive value: You cannot be estopped by a proceeding that never happened — but you also cannot borrow anyone else's win. The defense on the '751 is not invalidity, it is standing and timing: the patent expired 2015-06-27, so there is no ongoing infringement, and any suit filed now (2026) reaches back only to 2020-09-27, which is after expiration — zero recoverable damages.

Method note and caveat: I searched for a petition naming "5,613,751" directly, for PTAB/PTACTS papers, and for reexamination activity, and hit my search-step budget before exhausting every angle. The structured ODP block is canonical and says none exists; the searches I completed are consistent with that. I did not independently verify the absence of every pre-2012 (non-AIA) inter partes reexamination, which is a different animal from an AIA trial and would not appear in the ODP trial list.

Family-level PTAB activity — CONTEXT ONLY, these are different patents

Do not attribute any of the below to the '751. These proceedings attacked later continuations/divisions that claim priority to the '751 (filed 1995-06-27) and that were the patents Innovative Display Technologies LLC actually asserted in the 2012–2015 campaign. I verified petition- and institution-stage papers only; I did not verify claim-level FWD outcomes, so I state none.

Parallel litigation context: IDT asserted seven family patents — 6,755,547, 7,300,194, 7,384,177, 7,404,660, 7,434,974, 7,537,370, 8,215,816 — against Acer, Dell, HP, Apple, BMW, Mercedes-Benz, LG, GM, Ford and others in EDTX/D. Del. starting in 2013 (IDT v. Acer claim construction order summary; IDT v. Acer, No. 2:13-cv-00522, Markman brief). The '751 was not among them.

Strategic summary

Claim status on the '751. Nothing has been canceled; nothing has been sustained. All 97 claims — including independent claims 1 and 96 — are UNTESTED by the PTAB. Note the odd asymmetry: claim 1 is extremely broad ("a light source embedded or potted in said light transition area so as to eliminate any air interface"), which is precisely the kind of claim a challenger would normally kill. It was never tested because there was no economic point in testing it. The patent's 20-year term ran from the 1995-06-27 filing date and expired 2015-06-27 (Google Patents records "Anticipated expiration" on that date and status "Expired - Lifetime"). Claim 1 survived because it aged out, not because it was validated.

Estoppel landscape. § 315(e)(2) estoppel is keyed to a petitioner who was party to an IPR that "results in a final written decision under section 318(a)" on that claim. No IPR on the '751 ever reached an FWD, so nobody is estopped as to the '751's claims — every prior-art ground remains theoretically available to anyone. That cuts both ways for a defendant: you are not foreclosed, but you also inherit no free kill. The family-level IPRs create estoppel only as to the specific family patents their petitioners litigated (the '547, '177, '196, '660 lines), and only against those petitioners and their privies.

Pattern signals. Three things stand out. (1) Multiple petitioners, one family: LG Display and Mercedes-Benz both petitioned the '547/'177 lines, so this family was a genuine multi-front IPR target — but only the later members with live terms. (2) No defensive aggregator: I found no Unified Patents or similar entity in the '751 chain; the petitioners were OEM defendants defending their own products. (3) Ownership churn: Lumitex → Mang-Shiang Lee (2001) → Solid State Opto Limited (2001) → Rambus International (2010) → Rambus Delaware/Acacia (2013) → Innovative Display Technologies LLC (2013-06-27). That is a classic monetization pipeline, and the fact that IDT asserted the continuations rather than the '751 itself tells you the family's own holder treated the '751 as the expired ancestor, not the weapon.

Recommended next steps

1. If you hold a demand letter citing US 5,613,751, treat it as a bluff and say so. The patent expired 2015-06-27. Because § 286 bars recovery for infringement more than six years before a complaint is filed, a suit filed today (2026-09-27) can reach back only to 2020-09-27 — entirely after expiration. Recoverable damages from a present-day '751 suit: $0. Ask the asserting party in writing to identify the specific claim and the specific pre-2015-06-27 accused acts and the date of first notice; a well-pled response will not be forthcoming.
2. Identify which patent is actually being asserted. In this family, the realistic targets are the live-term continuations (6,755,547; 7,300,194; 7,384,177; 7,404,660; 7,434,974; 7,537,370; 8,215,816). If a letter cites the '751, it likely also cites one or more of these — validate the cite list before responding.
3. No PTAB milestones to calendar. There are no institution deadlines, oral hearings, or statutory 1-year FWD due dates, because there is no trial. Nothing on file at PTAB E2E/PTACTS or the PTAB decisions page for this patent.
4. If you nonetheless want an IPR on the '751 (e.g., to force a cancellation certificate for a licensing/indemnity fight): it is not statutorily barred merely because the patent expired, and § 315(b)'s one-year clock only runs from service of a complaint asserting that patent. But the cost/benefit is poor — an expired patent cannot be amended, there is no injunctive or ongoing-royalty exposure to eliminate, and a Board win buys you nothing you don't already have by operation of the expiration date. Spend that budget on the sibling patent that is actually being asserted.
5. Preserve a written record. A short letter noting the 2015-06-27 expiration and the closed § 286 window, sent to the asserting party and retained, is cheap insurance if the demand escalates or is repeated against downstream customers.

Bottom line for a defendant: the absence of any PTAB activity on US 5,613,751 is not a signal that the patent is strong — it is a signal that the patent is expired and was never worth anyone's petition fee. The family's IPR history lives on the continuation patents, not on this one.

I'll research the assignment record for US 5,613,751 through the USPTO Patent Assignment Center and cross-reference sources.

Let me look for the specific recorded reassignments with reel/frame data.

Good — I found the litigation-verified ownership structure. Now let me pin down the recorded reel/frame entries.

I hit my search-step budget before I could open the USPTO Assignment Center record directly, so the reel/frame fields are not fully verified. Everything below is built from (a) the Google Patents legal-events block on the '751 itself (supplied in the authoritative full text), and (b) court records and PTAB papers verified in this session. I flag every gap rather than filling it.

Inventors

Departure-pattern check — negative. All three inventors executed an assignment of their entire interest to Lumitex, Inc. on the filing date itself (1995‑06‑27), i.e. the ordinary employee pre‑filing assignment, not a post‑filing exodus. There is no evidence any inventor left Lumitex within 12 months of filing; to the contrary, Parker remained the sole named inventor on the later continuations prosecuted through 2005–2008 and was still acting as a Lumitex witness (declaration on Lumitex's behalf) in the 2015 PTAB proceeding against the '660 patent. No fire‑sale-preceding inventor departure signal.

Original assignee

• Entity on the issued patent: Lumitex, Inc. (Ohio corporation; Strongsville/Cleveland, Ohio area). Assignment recorded June 27, 1995.
• Line of business: fiber‑optic and solid‑state (LED) lighting and backlighting — light emitting panel assemblies. This is the same Lumitex named as owner of U.S. Pat. Nos. 4,897,771 and 5,005,108, which the '751 specification incorporates by reference as "assigned to the same assignee as the present application."
• Did it ship a product embodying the claims? Yes — evidence of record. The IPR2015‑00487 record describes "Lumitex's solid state backlight assemblies" and a backlight business unit with revenue from 1996 through 2000, and the business was later sold (the declaration criticizes Parker for ignoring "the business units projected decrease in sales in the year the business was sold"). This is operating-company conduct, not licensing.
• Current status: Unclear / not verified in this session. A secondary (Taiwan STPI) account states Lumitex later sold its optics/backlight business to Lee Mang‑Shiang and formed the joint venture SOLID STATE OPTO LIMITED, with Lee subsequently selling optical patents to Rambus for a reported US$26 million. I could not independently verify Lumitex's present corporate status; treat the sale narrative as secondary‑source and unconfirmed.

Assignment timeline

Source caveat: the USPTO Assignment Center could not be opened in this session (tool limit reached). The events below are the ones recorded on the '751's own legal-events block, cross-checked where possible against district‑court findings in Delaware Display Group LLC v. Lenovo Group Ltd. (D. Del.) and PTAB mandatory notices. Reel/frame numbers were not retrievable for the '751‑specific recordings.

Corroborating reel/frame data (portfolio‑level, verified on a sibling patent — NOT verified on the '751): US 7,364,342's legal events show RAMBUS DELAWARE LLC → ACACIA RESEARCH GROUP LLC, REEL/FRAME 030694/0635 and ACACIA RESEARCH GROUP LLC → INNOVATIVE DISPLAY TECHNOLOGIES LLC, REEL/FRAME 030698/0633. If the '751 traveled in the same instruments (likely, given the matching 2013‑06‑26 / 2013‑06‑27 event dates on the '751 record), those would be its recording numbers. Verify before relying on this.

• 1995‑06‑27 (executed) / recorded 1995‑06‑27 — Reel/Frame: not retrieved

  • Conveyance: Assignment of Assignors' Interest
  • Assignor: Parker, Jeffery R.; Miller, Mark D.; Kelsch, Daniel N. (all three)
  • Assignee: Lumitex, Inc.
  • Correspondent: not retrieved. Note the patent's prosecution correspondent of record is Renner, Otto, Boiselle & Sklar, P.L.L. (Cleveland, Ohio) — primary examiner Ira S. Lazarus; this is the prosecution firm, not confirmed as the assignment recording correspondent.
  • Context: Initial inventor-to-company capture; standard employee assignment executed on filing day.

• 1999‑08‑06 (executed/recorded) — Reel/Frame: not retrieved

  • Conveyance: Security Agreement
  • Assignor: Lumitex, Inc., a corporation of Ohio
  • Assignee: KeyBank National Association
  • Correspondent: not retrieved
  • Context: Securitization — Lumitex pledges the portfolio as collateral for lending.

• [date not shown on the '751 record] / released 2001‑02‑02 — Reel/Frame: not retrieved

  • Conveyance: Release of Security Agreement
  • Assignor: Context implies Ohio Mezzanine Fund, Ltd. was the secured party
  • Assignee: Lumitex, Inc.
  • Context: Release of a second, earlier‑recorded lien held by Ohio Mezzanine Fund. Gap to flag: the underlying Ohio Mezzanine Fund security agreement is not listed among the '751's recorded events — the grant may have been recorded against a different Lumitex instrument or asset schedule.

• 2001‑02‑02 (executed/recorded) — Reel/Frame: not retrieved

  • Conveyance: Release of Security Interest in Patents
  • Assignor: KeyBank National Association
  • Assignee: Lumitex, Inc.
  • Context: Release of the 1999‑08‑06 KeyBank lien — the portfolio is freed of encumbrances immediately before the divestiture series below.

• 2001‑03‑15 (executed/recorded) — Reel/Frame: not retrieved

  • Conveyance: Assignment of Assignors' Interest
  • Assignor: Lumitex, Inc.
  • Assignee: Lee, Mang‑Shiang (individual)
  • Correspondent: not retrieved
  • Context: Divestiture to an individual — the pivotal step. An operating company transfers directly to a natural person, five weeks after clearing its liens. This is the classic opening move of a monetization pipeline; the intermediate individual holder exists to sit between the operating seller and the offshore holding company.

• 2001‑03‑20 (executed/recorded) — Reel/Frame: not retrieved

  • Conveyance: Assignment of Assignors' Interest
  • Assignor: Lee, Mang‑Shiang
  • Assignee: SOLID STATE OPTO LIMITED (BVI)
  • Correspondent: not retrieved
  • Context: Transfer-to-holdco — five days after the Lumitex→Lee step; assets moved offshore into a licensing vehicle.

• 2010‑02‑18 (executed/recorded) — Reel/Frame: not retrieved

  • Conveyance: Assignment of Assignors' Interest
  • Assignor: SOLID STATE OPTO LIMITED
  • Assignee: RAMBUS INTERNATIONAL LTD.
  • Correspondent: not retrieved
  • Context: Acquisition / portfolio sale. Secondary reporting puts the optical‑patent package at ~US$26 million, with the seller retaining a right to keep practicing. Rambus held the patents roughly December 2009 – January 2013 (per the D. Del. record).

• 2013‑03‑04 (executed/recorded) — Reel/Frame: not retrieved

  • Conveyance: Assignment of Assignors' Interest
  • Assignor: RAMBUS INTERNATIONAL LTD.
  • Assignee: RAMBUS INC.
  • Correspondent: not retrieved
  • Context: Internal corporate reorganization. D. Del. record: Rambus Inc. ("RI") → Rambus International Ltd. ("RIL") via an "Intellectual Property Contribution and Assignment Agreement" (IPCAA 1), executed December 20–21, 2012, with a confirmatory Patent Assignment signed March 1, 2013.

• 2013‑03‑04 (executed/recorded) — Reel/Frame: not retrieved

  • Conveyance: Assignment of Assignors' Interest
  • Assignor: RAMBUS INC.
  • Assignee: RAMBUS DELAWARE LLC
  • Correspondent: not retrieved
  • Context: Internal corporate reorganization, second hop (IPCAA 2 / Patent Assignment 2, signed March 1–4, 2013). Same day as the prior hop — a two-step same-day restructure.

• 2013‑06‑26 (recorded) — Reel/Frame: likely 030694/0635 (verified on sibling US 7,364,342; unverified for the '751)

  • Conveyance: Assignment of Assignors' Interest
  • Assignor: RAMBUS DELAWARE LLC
  • Assignee: ACACIA RESEARCH GROUP LLC (Texas)
  • Correspondent: not retrieved
  • Context: Transfer to asserter. Note a date discrepancy to flag: Delaware Display Group v. Lenovo found that "On January 30, 2013, Rambus sold the patents-in-suit to Acacia," whereas the '751 record shows the Acacia event at 2013‑06‑26. This is most likely an execution‑date vs. recording‑date gap, but it is a real inconsistency in the face record and should be reconciled against the actual assignment document.

• 2013‑06‑27 (recorded) — Reel/Frame: likely 030698/0633 (verified on sibling US 7,364,342; unverified for the '751)

  • Conveyance: Assignment of Assignors' Interest
  • Assignor: ACACIA RESEARCH GROUP LLC
  • Assignee: INNOVATIVE DISPLAY TECHNOLOGIES LLC (Texas; formed March 13, 2013)
  • Correspondent: not retrieved. Family‑level litigation/PTAB counsel of record recurring across IDT and DDG matters is Bragalone Conroy P.C. (Justin B. Kimble; Jeffrey R. Bragalone); in‑house counsel driving the campaign was Eric Lucas (Acacia, later IDT/DDG). Neither is confirmed as an assignment‑recording correspondent.
  • Context: Transfer to the assertion vehicle — one day before IDT filed its first wave of suits (2:13‑cv‑00522 et seq., E.D. Tex., June 28, 2013). Second discrepancy to flag: Delaware Display Group v. Lenovo recites that "On July 26, 2013, Acacia assigned all of the right, title and interest in the patents-in-suit to IDT" — a different date than the '751 record's 2013‑06‑27. The '974/'370 patents may have moved under a separate instrument.

Not on the '751 chain: Delaware Display Group LLC ("DDG," formed 2013‑12‑20) received only the '196 patent, one day after formation, from IDT. The '751 did not go to DDG.

Timeline diagram

timeline
    title Ownership of US 5613751
    1995 : Three inventors assign to Lumitex
    1999 : KeyBank security agreement
    2001 : KeyBank and Ohio Mezzanine liens released
         : Lumitex to Lee Mang-Shiang
         : Lee to Solid State Opto Limited
    2010 : Solid State Opto to Rambus International
    2013 : Rambus internal reorg to Rambus Delaware
         : Sale to Acacia Research Group
         : Acacia to Innovative Display Technologies
         : IDT files first suits one day later
    2015 : Patent expires

NPE / troll‑pattern signals

1. Shell‑entity transfer — PRESENT.
Grounded not on naming but on documented conduct: the patent left an operating manufacturer (Lumitex, which had a revenue‑generating backlight business unit per the IPR record) and passed through an individual (Lee, Mang‑Shiang, 2001‑03‑15) to an offshore holding company (SOLID STATE OPTO LIMITED, 2001‑03‑20), and terminated at Innovative Display Technologies LLC (2013‑06‑27), a Texas LLC with no products whose only activity is the licensing/litigation campaign documented by RPX Insight ("New Acacia subsidiary"), Techdirt, and IDT's own PTAB mandatory notices. The intermediate 2001 hops within five days are the tell.

2. Known asserter in the chain — PRESENT.
Two chain members match public NPE records: Acacia Research Group LLC / Acacia Research Corporation (2013‑06‑26; identified as real parties‑in‑interest in IDT's IPR2014‑01357 mandatory notices) and Innovative Display Technologies LLC (2013‑06‑27), an Acacia subsidiary reported by RPX Insight and Techdirt as carrying ~37 lawsuits. Related family vehicle Delaware Display Group LLC appears in the D. Del. docket. This is the strongest single signal in the chain.

3. Repeat correspondent across the chain — UNCLEAR / NOT VERIFIED.
I could not retrieve the Assignment Center correspondent field for any '751 link, so I cannot state whether one attorney or firm recorded multiple links. What I can report: the patent's prosecution firm of record is Renner, Otto, Boiselle & Sklar, P.L.L. (Cleveland); the litigation/PTAB firm recurring across the family is Bragalone Conroy P.C. (Kimble/Bragalone), appearing for patent owner IDT in IPR2014‑01357 and for DDG in IPR2015‑00757; and Eric Lucas acted as in‑house counsel for Acacia and later IDT/DDG (per Delaware Display Group v. Lenovo). None of these is confirmed as the assignment‑recording correspondent, and conflating litigation counsel with the recording correspondent would be exactly the kind of inference the instructions prohibit. Flagged for direct Assignment Center verification.

4. Cascading transfers — PRESENT.
(i) 2001‑03‑15 → 2001‑03‑20: two hops in five days (Lumitex→Lee→Solid State Opto). (ii) 2013‑03‑04: two hops on the same day (Rambus International→Rambus Inc.→Rambus Delaware LLC), followed by 2013‑06‑26→2013‑06‑27 (→Acacia→IDT) — four transfers in under four months, ending at the entity that sued the next day. This is the pattern of a chain assembled to produce a clean standing record.

5. Pre‑litigation transfer — PRESENT.
The final assignment into Innovative Display Technologies LLC is dated 2013‑06‑27, and IDT filed its first wave of complaints on June 28, 2013 (2:13‑cv‑00522 against Acer, plus ‑00523 through ‑00527 and beyond, per IDT's own IPR2014‑01357 mandatory notices). One day. Caveat, stated plainly: the '751 itself was not among the seven asserted patents (those were 6,755,547; 7,300,194; 7,384,177; 7,404,660; 7,434,974; 7,537,370; 8,215,816). So the transfer was pre‑litigation with respect to the portfolio, and the '751 rode along as a family ancestor rather than as the pleaded weapon.

6. Bankruptcy fire‑sale — NOT PRESENT.
No Chapter 7 or 11 filing by Lumitex or any chain entity was found. Worth noting rather than ignoring: the lien releases on 2001‑02‑02 sit five weeks before the 2001‑03‑15 sale to Lee, which is consistent with distress-driven divestiture (a secured lender and a mezzanine lender both exiting, then the crown‑jewel patents sold). That is pressure, not a bankruptcy sale, and I am not characterizing it as one.

7. Privateering — NOT PRESENT (as to the transfer itself) / UNCLEAR (as to alignment).
No evidence that Lumitex financed or directed IDT's campaign; the 2001 transfer was a genuine sale to a third‑party chain that later asserted against the whole consumer‑electronics industry, including Lumitex's competitors. Note the adjacent fact, however: Parker (a Lumitex executive) provided a commercial‑success declaration in 2015 supporting IDT against LG Display — presumably reflecting a retained/grant‑back right from the Rambus transaction. This is alignment in litigation, not privateering.

8. Defensive aggregator — NOT PRESENT.
The chain terminates at Innovative Display Technologies LLC, an asserting entity. No RPX, AST, LOT Network, Unified Patents, or OIN link appears anywhere in the record. The patent was never neutralized.

Verdict

NPE — high confidence.

The record shows at least four strong signals operating together, none of them resting on naming alone: a transfer out of a product-selling manufacturer to an individual and then an offshore holdco within five days (2001‑03‑15 and 2001‑03‑20); cascading same‑day and same‑month transfers (2013‑03‑04, 2013‑06‑26); a known asserter as terminal owner (Acacia Research Group LLC at 2013‑06‑26 and Innovative Display Technologies LLC at 2013‑06‑27, the latter documented by RPX and Techdirt as an Acacia litigation vehicle with ~37 suits); and a pre‑litigation transfer into that asserter one day before IDT filed the first suits on June 28, 2013. The one caveat that keeps this from being a slam‑dunk finding for this specific number: the '751 was not one of the patents IDT actually pleaded — it is the expired 1995 parent of the asserted continuations, which is why the 2015‑06‑27 expiration rather than the assignment chain is the operative fact for any current demand letter.

Verification links:

• USPTO Assignment Center: https://assignmentcenter.uspto.gov/ (search patent number 5613751)
• Mirrored Assignment Search: https://assignment.uspto.gov/patent/index.html (same underlying records)
• Google Patents legal events: https://patents.google.com/patent/US5613751/en

Two open items to close on Assignment Center, in priority order: (1) the reel/frame and correspondent for the 2001‑03‑15 and 2001‑03‑20 links and for the four 2013 links — these are the fields I could not retrieve and the ones that would confirm or kill signal 3; and (2) the execution date on the Rambus Delaware → Acacia instrument, to reconcile the 2013‑06‑26 recording date against the January 30, 2013 sale date found by the District of Delaware.

I'll start by searching for the specific patent and its citation records.

Let me look for the specific "References Cited" (backward citation) record for this patent.

I'll research the prior-art record for US5613751, since the Prior Art section generated earlier appears to contain no actual reference list, and the full text supplies only forward citations ("Cited By") plus two in-spec incorporations-by-reference (U.S. Pat. Nos. 4,897,771 and 5,005,108).

Let me pin down the actual back-citation list for US5613751 and any IPR proceedings naming it.

Let me verify the identity and dates of the key references the PTAB/petitioners actually relied on against this patent family.

Obviousness Analysis — US 5,613,751 (35 U.S.C. § 103)

0. Threshold problem with the supplied record — flagged explicitly

The previously generated Prior Art section contains no reference list; it only records that a search for the "'References Cited' (backward citation) record" was begun. Separately, the authoritative full text supplied for this task contains the forward citation block ("Cited By (223)") but not the "References Cited" (PTO‑892/face‑of‑patent) block. I therefore cannot verify from the authoritative document which references the examiner actually cited against US 5,613,751. Everything below is built from (a) the two references the '751 specification itself incorporates by reference, and (b) prior‑art records verified in this session from the PTAB petitions and later family members. Where I could not verify a reference's number, dates, or disclosure, I say so rather than filling the gap.

1. Framework

• Effective filing date: 1995‑06‑27 (US 08/495,176); no earlier priority claimed. Pre‑AIA § 103 applies; the 102(b) critical date is 1994‑06‑27.
• Legal standard: Graham v. John Deere + KSR Int'l v. Teleflex (2007) — a combination is obvious where the references are analogous, the problem is common, and the solution is a predictable use of prior‑art elements; a known technique applied to a similar device in the same way is obvious.
• Claim construction: the specification defines "deformities/disruptions" as "any change in the shape or geometry of the panel surface and/or coating or surface treatment that causes a portion of the light to be emitted" (col. 4). This broad, express definition (adopted by Petitioners in IPR2015‑01866 for the identical term in the '816 patent) makes the deformity claims easy to map.
• Level of ordinary skill: bachelor's in mechanical/electrical engineering or physics (or equivalent) plus ~2–3 years in optical/backlight design — consistent with the art at issue in the family IPRs.

2. Verified prior art available against the '751 claims

Anomaly to flag: the family IPR papers use "Kobayashi," "Pristash," "Suzuki," etc. with inconsistent exhibit numbers between petitions (in the '370 papers, Ex. 1006 is identified as Kobayashi in the claim charts but as Pristash in the exhibit list of another petition). Anyone relying on these charts should re‑pull the exhibits rather than trust the numbering.

3. Ground 1 — Pristash (US 5,005,108), alone or + ordinary skill

Claims 1 and 96 (independents). Pristash discloses a panel member, a light transition device between the source and the panel, and deformities. The only arguable gap is the negative/functional element: the source "embedded or potted" (claim 1) / "bonded" (claim 96) "so as to eliminate any air interface."

• Motivation/knowledge: Pristash's transition device is a solid transparent body; bringing a solid source into index‑matched contact with it necessarily reduces Fresnel reflection at the source/transition interface. The '751 specification itself admits this technique was known, describing mechanical retention vs. "embedded, potted or bonded… in order to eliminate any air gaps or air interface surfaces… thereby reducing light loss," and listing potting, bonding, thermal bonding, ultrasonic welding, insert molding and casting as alternatives (col. 3). Where the specification characterizes the limitation as a known expedient selected for a known benefit, KSR's "known technique to improve a similar device in the same way" rationale applies.
• Claim‑drafting point: claim 1 recites alternatives ("embedded or potted"). A claim is satisfied by either alternative, so the patentee gains no shelter from the difficulty of proving both.
• Caution: I did not verify a reference in this session that expressly discloses potting an LED into a light‑guide transition area. Ground 1 therefore rests on Pristash + either a verified secondary reference (e.g., Ciupke, if it shows an encapsulated/molded source in a backlight assembly) or expert testimony under KSR. This is the weakest verified link in the whole case.
• Dependents likely covered by Pristash alone/inherently: 2 (deformities), 8/12 (spaced film — Pristash's diffuser), 10/11 (prismatic or depression deformities), 16 (multicolored source — for color LEDs, see Ground 3), 19/20/22 (back/end/side reflectors), 23/24 (multiple transition areas and lights), 34 (multiple emitting surfaces), 42 (thin panel — Pristash's stated thin‑panel objective), 83/84 (reflective surface near the source), 86 (cast/molded), 88 (colored sources mixed in transition area), 95 (LCD/switch backlighting).

4. Ground 2 — Kobayashi in view of Pristash (strongest for the deformity claims)

Kobayashi supplies, essentially element‑for‑element, the pattern claims; Pristash supplies the solid transition device/bonding concept.

• Claims 2, 4, 5, 6, 52, 53, 66, 67, 72, 73: Kobayashi's spot‑shaped layers 25 whose area increases with distance from the source and prismatic cuts at equal pitch disclose deformities varying in size/density along the length/width with a density gradient for uniform output.
• Claim 3 / 54 (≤ ~0.006 in² per deformity): Kobayashi's "minute depressions" and "spot‑shaped layers" are in the sub‑millimeter regime; a numerical range is a result‑effective variable and, on the '751 specification's own statement that the value is "desirable," obvious to optimize. A tight case requires measurements or testimony — obtainable, but not from the reference text alone.
• Claims 10, 11, 33, 37, 38: prismatic surfaces / prismatic sheet 6 / reflecting finish / angled end surfaces in Kobayashi.
• Claims 12 and 13 (film and reflector adhered only about the periphery, air gap remaining): Kobayashi's diffusing sheet and reflecting sheet are arranged "with a clearance" from the plate — the claimed air gap. The '751 specification supplies the motivation: air gaps are needed "to be able to make longer panels" and because adhesive makes the internal critical angle "less controllable" (col. 6). Express motivation in the reference/patentee's own admission.
• Claims 17, 25, 87 (posts / structural support for an LCD): Kobayashi explicitly addresses use as an LCD back light; providing mounting/structural support for the LCD is a predictable mechanical design choice. This is a weaker, KSR‑style ground.
• Claims 46, 47 (slot in the back edge, sliding/snap fit): Not shown in Pristash or Kobayashi as verified. These require additional art (connector/socket art) or are the best candidates for non‑obviousness.
• Claim 50 (transparent panel and deformities, no back reflector, for front lighting): the '751 specification itself describes this as an available mode; whether the art renders it obvious depends on the front‑light reference set (none verified here).
• Claim 51 (secondary light source projecting through the panel): indicator/backlight‑through‑panel arrangements were known in the appliance/switch art; not verified here.

5. Ground 3 — Secondary references for the color‑mixing claims

Claims 16, 24, 63, 64, 65, 88, 90, 91, 93 (multicolored LEDs mixed to white) are the claims the family IPRs fought hardest. The best verified route is Pristash + a known‑art multicolor LED reference (e.g., the "variable color" / multicolor LED‑array patents appearing in the family's reference lists). KSR rationales: (i) RGB‑LED color mixing to obtain white light was a finite, identified set of solutions; (ii) the references all target a common end (a uniform, efficient LCD back light with a selectable color temperature); (iii) the '751 specification concedes the technique ("a plurality of colored lights such as LEDs of different colors (red, blue, green)… to create white light… by varying the intensities of each individual colored light"). I have not verified the specific disclosures of these LED references, so this ground should be treated as a roadmap, not a proof.

6. Motivation to combine — what the record supports

1. Same field, same problem, same solution mechanism: all of Pristash, Kobayashi and the '751 are LCD backlights whose stated objectives are "increased illuminance," "increased uniformity," and more efficient light utilization (Kobayashi 2:14‑16; Pristash 1:16; '751 1:10‑28).
2. Express targeting of each other's weaknesses: Kobayashi identifies proportional‑spot extraction as inefficient; Pristash teaches the transition device that solves point‑source‑to‑panel‑width coupling — exactly the problem the '751 treats as central. The Board accepted this reasoning in the family, holding in IPR2014‑01096 that Pristash's transition region met the "transition region" limitation and that Suzuki's suggestion to use a point light source supplies the motivation to adopt Pristash's transition device.
3. Predictable, mechanical combination: adding a solid transition device between a source and a plate, or spacing a diffuser from a plate, involves no change in the principle of operation; results were foreseeable (reduced reflection loss, uniform density).
4. Admissions in the specification (known light‑source types; known potting/bonding techniques; known air‑gap practice; known RGB‑mixing) supply KSR "known technique" rationales without importing outside art.

7. Where a § 103 case would fail on this record

• Articulation, not reference count. In IPR2014‑01095 the Board denied institution because the Petitioner merely showed the components were known without a fact‑based rationale for combining them. Any '751 challenge must supply that reasoning per claim.
• Grounds resting on a single reference disclosure the reference does not have. In IPR2015‑01867 the Board declined to institute on the Kobayashi grounds, and only instituted on Suzuki‑based and Suzuki+Pristash grounds for claims 29 and 47. Kobayashi's piecemeal "combine different embodiments" arguments drew objections.
• Claims with no verified mapping: 26/27/58 (cavities and modular insert transition areas), 28/31/32 (off‑axis/angular transition area with a reflective junction surface), 29/41/48/49/85/89/94 (three‑dimensional collecting surfaces; low‑ray‑angle output enabling thinner/longer panels from one end), 39/40 (transition area thicker than the panel), 43‑47 (slot/recess with locating tabs, back‑edge slide‑in, snap fit), 45 (tabs), 50‑51, 80‑82 (stochastic/FM half‑tone/random‑dot printing — these are printing‑technique claims that require a graphics/printing reference, not a light‑guide reference), 97.
• Secondary considerations to anticipate: long‑felt need for thin, uniform LED edge lighting; industry adoption and the extensive continuation family; IDT's assertion of the family in ~a dozen district‑court actions. Note that litigation/enforcement success is not evidence of non‑obviousness, and no nexus evidence appears in the record reviewed.

8. Conclusion

• High confidence that claims 2–13 (except the air‑gap/reflector combination nuance), 33–38, 52–54, 66–73, 83–85, 88–94 would have been obvious over Kobayashi in view of Pristash, with the combination motivated by their shared field, shared objective (efficiency + uniformity in an LCD backlight), and Kobayashi's express criticism of the proportional‑spot art.
• Moderate confidence that independent claims 1 and 96 are obvious over Pristash plus a potting/bonding/KSR "known technique" rationale grounded in the '751 specification's own admissions — but only if a secondary reference (e.g., Ciupke, US 5,461,547, or a socket/encapsulation reference) is verified to disclose eliminating the air interface. Absent that, claim 1 is the best non‑obviousness candidate in the patent.
• Low confidence / not supportable for claims 26–32, 39–47, 50, 51, 80–82, 97 on the references verified here.
• Recommendation: re‑pull the actual face‑of‑patent "References Cited" block and the PTO‑892s for US 5,613,751 (not present in the supplied full text), and obtain the exhibits for Kobayashi (US 5,408,388), Pristash (US 5,005,108), Ciupke (US 5,461,547), and the "Suzuki" reference (number unverified), before finalizing any invalidity contention.