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 reconstruct the assignment record. The Google Patents legal-events data in the prompt gives me the chain skeleton, but reel/frame numbers and correspondents of record are not in that text — I need to search for those. Let me run parallel queries.

Good — I have the chain and strong Acacia/IDT evidence. Now let me chase the specific reel/frame numbers and correspondents of record.

I have the Acacia/IDT and Rambus/Solid State Opto evidence, plus a Frisco TX address. Let me pin down reel/frame numbers and correspondents.

US 5613751 — Assignment Record Reconstruction

Patent: US 5,613,751 A, "Light emitting panel assemblies"
Application: US 08/495,176 · filed 1995-06-27 · granted 1997-03-25 · anticipated expiration 2015-06-27
Prepared: 2026-09-27

Sourcing caveat up front. The authoritative Google Patents legal-events extract for this patent lists the parties and record dates for every posting-issuance event but does not carry reel/frame numbers or the correspondent of record. I could not reach the USPTO Assignment Center record for US 5613751 directly in this session, so no reel/frame numbers below are attributed to US 5613751 specifically. Where I did retrieve reel/frames, they are from sibling patents in the same corporate transaction and are labeled as such. I have not fabricated any reel, frame, or correspondent.

Inventors

Patterns:

• Standard employee assignment at filing — not a departing-inventor pattern. All three inventors assigned to Lumitex on the filing date itself. There is no evidence of inventors leaving the original assignee within 12 months of filing.
• The real break is ~6 years later, and it took the whole business unit, not just the inventors. Lumitex sold its solid-state/optical backlight division to Mang-Shiang Lee (founder of Taiwan's Global Lighting Technologies, 茂林光電) in March 2001. GLT's own shareholder-meeting history records that "09/2000 Established GLT-USA by taking over the R&D and sales team from Lumitex." So the people moved to GLT-USA roughly six months before the patents moved to Lee (see timeline). That sequencing — team first, IP second — is the substantive finding here.
• Parker is a repeat inventor across the entire continuation family (US 5,875,107; 5,921,652; 6,079,838; 5,618,096; and the later patents IDT later asserted), and he later filed a declaration in IPR2015-* re: the '660 patent attesting to Lumitex's commercial success with "solid state backlight assemblies" — i.e., he remained tied to Lumitex commercially long after the 2001 patent divestiture.

Original assignee

Lumitex, Inc. — identified in the record as "LUMITEX, INC., A CORPORATION OF OHIO" (per the 1999 KeyBank security agreement posting). Cleveland / Strongsville, Ohio.

• Primary line of business: fiber-optic and solid-state lighting panels — membrane-switch backlighting, control-panel backlighting, machine-vision lighting, phototherapy (BillBlanket), and surgical illumination. Lumitex is the classic commercializer of the woven-fiber-optic panel, not a licensing shop.
• Did they ship products embodying the claims? Yes, and that is the strongest evidentiary point in the file. Lumitex sold solid-state backlight assemblies built on this panel-assembly work; Parker's own sworn declaration asserted "backlight assemblies embodying the claims of the '660 patent have enjoyed commercial success" and pointed to Lumitex "solid state backlight assemblies." (Note the qualification: that declaration concerns a related continuation, not '751 itself, and the opposing expert attacked the nexus and pointed to annual losses in the business unit — so treat "practices the claims" as asserted, not adjudicated, for the '751 family root.)
• Current status: Operating. Lumitex continues as a specialty fiber-optic lighting manufacturer. I found no Chapter 7/11 filing, no assignment for the benefit of creditors, and no dissolution record for Lumitex.
• Financing history visible in the patent record (not bankruptcy): a 1999 KeyBank National Association security agreement, an Ohio Mezzanine Fund, Ltd. security interest (the underlying grant was not posted among the visible '751 legal events — a gap in the record), and the release of both liens on 2001-02-02, thirteen days before the patents were conveyed to Lee. That is the signature of a company clearing its collateral before an asset sale, not of an insolvency.

Assignment timeline

All dates and parties below are from the authoritative Google Patents legal-events record for US 5613751. Reel/frame: not retrieved for any '751 entry (see caveat above). Correspondent of record: not retrieved for any '751 entry.

1. 1995-06-27 (executed) / recorded 1995-06-27 — Reel/frame: not retrieved

   • Conveyance: Assignment of interest
   • Assignor: Daniel N. Kelsch; Mark D. Miller; Jeffery R. Parker
   • Assignee: LUMITEX, INC.
   • Correspondent: not retrieved
   • Context: Original employee-to-company assignment, executed on the filing date.

2. 1999-08-06 (executed) / recorded 1999-08-06 — Reel/frame: not retrieved

   • Conveyance: Security Agreement (collateral, not a transfer of title)
   • Assignor: Lumitex, Inc., a corporation of Ohio
   • Assignee: KEYBANK NATIONAL ASSOCIATION
   • Correspondent: not retrieved
   • Context: Securitization — Lumitex pledges its patent estate to KeyBank as collateral for company debt.

3. 2001-02-02 (executed) / recorded 2001-02-02 — Reel/frame: not retrieved

   • Conveyance: Release of Security Agreement
   • Assignor: OHIO MEZZANINE FUND, LTD.
   • Assignee: Lumitex, Inc.
   • Correspondent: not retrieved
   • Context: Release of the Ohio Mezzanine Fund lien; note that the grant of that lien was never posted against '751, so the chain has an unposted upstream security interest.

4. 2001-02-02 (executed) / recorded 2001-02-02 — Reel/frame: not retrieved

   • Conveyance: Release of Security Interest in Patents
   • Assignor: KeyBank National Association
   • Assignee: Lumitex, Inc.
   • Correspondent: not retrieved
   • Context: KeyBank lien cleared — both encumbrances on the estate are discharged two weeks before the sale to Lee.

5. 2001-03-15 (executed) / recorded 2001-03-15 — Reel/frame: not retrieved

   • Conveyance: Assignment of interest
   • Assignor: Lumitex, Inc.
   • Assignee: LEE, MANG-SHIANG (natural person; founder/chairman of Global Lighting Technologies, Taiwan)
   • Correspondent: not retrieved
   • Context: Divestiture — Lumitex exits the solid-state backlight IP business, selling to the buyer who had already absorbed its R&D and sales team into GLT-USA in 2000.

6. 2001-03-20 (executed) / recorded 2001-03-20 — Reel/frame: not retrieved

   • Conveyance: Assignment of interest
   • Assignor: Lee, Mang-Shiang
   • Assignee: SOLID STATE OPTO LIMITED — a British Virgin Islands entity (jurisdiction confirmed from the legal events of sibling patent US 7,448,775)
   • Correspondent: not retrieved
   • Context: Internal reorg — Lee parks the portfolio into a BVI holding company five days after acquiring it personally. This is the classic individual-to-offshore-holding hop that precedes third-party monetization.

7. 2010-02-18 (executed) / recorded 2010-02-18 — Reel/frame: not retrieved for '751

   • Conveyance: Assignment
   • Assignor: Solid State Opto Limited
   • Assignee: RAMBUS INTERNATIONAL LTD. (Cayman Islands)
   • Correspondent: not retrieved for '751
   • Sibling-record cross-reference: the same Solid State Opto → Rambus International transaction appears on related patent US 7,448,775 as Reel 023950/0598, and on US 7,448,775 the mirror-image Rambus recordings are Reel 029918/0725 (Rambus Inc.) and Reel 029918/0737 (Rambus Delaware LLC), both dated 2010-10-01. These are sibling-patent reels, not confirmed reel/frames for '751 — use as a lead only.
   • Context: Portfolio sale into Rambus's monetization program. Consideration reported at ~US$26 million (Korean government analysis of Rambus's patent acquisitions; GLT/Lee-side reporting). Structured with a license back to the seller — see the Asset Purchase Agreement discussed under Signal 7.

8. 2013-03-04 (executed) / recorded 2013-03-04 — Reel/frame: not retrieved

   • Conveyance: Assignment
   • Assignor: Rambus International Ltd.
   • Assignee: RAMBUS INC. (California)
   • Correspondent: not retrieved
   • Context: Internal reorg — repatriation of the Cayman holding company's estate to the U.S. parent.

9. 2013-03-04 (executed) / recorded 2013-03-04 — Reel/frame: not retrieved

   • Conveyance: Assignment
   • Assignor: Rambus Inc.
   • Assignee: RAMBUS DELAWARE LLC
   • Correspondent: not retrieved
   • Context: Internal reorg — same-day push-down from the parent into a Delaware IP-holding LLC, positioning the estate for sale.

10. 2013-06-26 (executed) / recorded 2013-06-26 — Reel/frame: not retrieved

    • Conveyance: Assignment
    • Assignor: Rambus Delaware LLC
    • Assignee: ACACIA RESEARCH GROUP LLC
    • Correspondent: not retrieved
    • Context: Transfer to asserter — the entire Rambus display-backlight estate (this family included) sold to Acacia Research Corporation's acquisition arm, which the E.D. Tex. court describes as occurring "in early 2013."

11. 2013-06-27 (executed) / recorded 2013-06-27 — Reel/frame: not retrieved

    • Conveyance: Assignment
    • Assignor: Acacia Research Group LLC
    • Assignee: INNOVATIVE DISPLAY TECHNOLOGIES LLC — 6136 Frisco Square Blvd, Suite 400, Frisco, Texas 75034 (Acacia's own Frisco, TX address; corroborated by the 2020 Acacia-group recordings cited below)
    • Correspondent: not retrieved
    • Context: Transfer to asserter — a single-purpose Acacia litigation subsidiary, formed to hold the asserted patents. Twenty-four hours later it filed six infringement suits (see Signal 5).

12. 2020 to 2021 (executed / recorded) — possibly affecting this estate; NOT confirmed against US 5613751 — Reels 052853/0153, 053654/0254, and corrective 055100/0624

    • Conveyance: Assignment (portfolio-level), plus a Corrective Assignment correcting the assignor name previously recorded at Reel 052853/0153
    • Assignors named on the corrective instrument: Acacia Research Group LLC; American Vehicular Sciences LLC; Bonutti Skeletal Innovations LLC; Cellular Communications Equipment LLC; Innovative Display Technologies LLC; LifePort Sciences LLC; Limestone Memory Systems LLC; Merton Acquisition Holdco LLC; Mobile Enhancement Solutions LLC; Monarch Networking Solutions LLC; Nexus Display Technologies LLC; Parthenon Unified Memory Architecture LLC; R2 Solutions LLC; Saint Lawrence Communications LLC; Stingray IP Solutions LLC; Super Interconnect Technologies LLC; Teleconference Systems LLC; Unification Technologies LLC
    • Assignee / counterparty: Acacia Research Group LLC (767 Third Avenue, 6th Floor, New York, NY 10017) and a Starboard Value Intermediate Fund LP entity are both named in the surrounding filings; the direction of conveyance is not clear from the excerpt.
    • Correspondent: S. Karff, c/o Schulte Roth & Zabel LLP, 919 Third Avenue, 25th Floor, New York, NY 10022 — recurring across both the original (052853/0153) and corrective (055100/0624) recordings in this Acacia-group transaction; execution 2020-06-04, recordation 2021-01-25. A companion portfolio assignment bears Execution date Jun 30, 2020 at Reel 053654/0254.
    • Context: Securitization / collateral or intra-group reorganization across the entire Acacia entity stable after Starboard Value's control of Acacia Research. I cannot confirm US 5613751 is among the properties covered, and by this date the patent's term had already expired (2015-06-27), which makes coverage unlikely-but-not-impossible for accounting/collateral purposes.
    • Verification link: search "5613751" at the USPTO Assignment Center — https://assignmentcenter.uspto.gov/ (mirror: https://assignment.uspto.gov/patent/index.html) — and cross-check the Google Patents legal events at https://patents.google.com/patent/US5613751/en#legalEvents.

No record was found of any assignment to a defensive aggregator (RPX, AST, LOT Network, Unified Patents, OIN) at any point.

Timeline diagram

timeline
    title Ownership of US 5613751
    1995 : Filed by Parker Miller Kelsch
         : Assigned to Lumitex Inc
    1999 : Security agreement with KeyBank
    2001 : Liens released by KeyBank and Ohio Mezzanine
         : Assigned to Mang-Shiang Lee
         : Assigned to Solid State Opto Limited
    2010 : Assigned to Rambus International Ltd
    2013 : To Rambus Inc and Rambus Delaware LLC
         : To Acacia Research Group LLC
         : To Innovative Display Technologies LLC
         : IDT files first infringement suits
    2015 : Patent expires

NPE / troll-pattern signals

1. Shell-entity transfer — PRESENT (strong).
The estate leaves an operating manufacturer and passes through a natural person into an offshore holding company, then into a litigation LLC that owns nothing else. Chain: Lumitex, Inc. → Lee, Mang-Shiang (2001-03-15) → Solid State Opto Limited, British Virgin Islands (2001-03-20) → Rambus holding chain → Acacia Research Group LLC (2013-06-26) → Innovative Display Technologies LLC (2013-06-27). IDT LLC is precisely the single-purpose profile: the E.D. Tex. court in Innovative Display Technologies LLC v. [Microsoft Corp.](/litigations/by-plaintiff/Microsoft%20Corp.), No. 2:13-cv-00783-JRG (Mem. Op. and Order, 17 Jun 2014) states that "IDT owns only the patents asserted here," and IDT's own PTAB mandatory notices identify Acacia Research Group LLC and Acacia Research Corporation as its sole real parties-in-interest. Its recorded address, 6136 Frisco Square Blvd, Suite 400, Frisco, TX 75034, is Acacia's own corporate address, not an independent place of business.

2. Known asserter in the chain — PRESENT (strong).
Acacia Research Group LLC is on the named-asserter list, and it acquired this estate outright in 2013 (recorded 2013-06-26). Its subsidiary Innovative Display Technologies LLC is a high-frequency plaintiff: the IPR2015-00363 mandatory notices alone enumerate IDT suits against Acer, Dell, Hewlett-Packard, Huawei, BlackBerry, ZTE, Microsoft, Nokia, Apple, BMW, Canon, Garmin, MiTAC, Toyota, Nissan, Honda and Mercedes-Benz, and this disclosure is corroborated by successive Acacia 8-Ks announcing settlement/license agreements (e.g., AT&T Mobility, Civil Action No. 2:14-cv-00720-JRG; Mitsubishi Electric, 8-K dated 2015-06-05/09; Mercedes-Benz, 8-K dated 2015-06-19). The patents here are the root of that campaign: the court noted that all seven patents asserted against Microsoft "were acquired by ARC in early 2013 and subsequently assigned to IDT in June, 2013."
Caveat on Rambus: Rambus sits in the chain (recorded 2010-02-18, 2013-03-04 ×2) but is not treated as an NPE here — it is a public operating company with product and licensing revenue.

3. Repeat correspondent across the chain — UNCLEAR (single data point only).
I could not retrieve the correspondent of record for any of the eleven Lumitex/Lee/Opto/Rambus/Acacia/IDT postings on US 5613751. The only correspondent I recovered anywhere in this corporate orbit is S. Karff, c/o Schulte Roth & Zabel LLP, 919 Third Avenue, 25th Floor, New York, NY 10022, who appears on both the original and the corrective Acacia-group recordings (Reel 052853/0153 and Reel 055100/0624, executed 2020-06-04, recorded 2021-01-25). That is recurrence within one transaction, not across the '751 chain, and it postdates the patent's expiry — so under the stated rule it is not a finding. Calling it a repeat-player signal would require the '751 reel/frame records, which I could not obtain.
Distinct from correspondents: IDT's PTAB/litigation counsel are Bragalone Conroy PC (Justin B. Kimble, Jeffrey R. Bragalone; Dallas, TX), Ahmad, Zavitsanos, Anaipakos, Alavi & Mensing P.C. (George W. Webb III; Houston, TX) and Crowell & Moring LLP (Washington, DC). These are advocacy counsel, not assignment correspondents — do not merge them into the correspondent signal.

4. Cascading transfers — PRESENT (strong).
Two clusters of rapid chained hops with no operating interval:

• 2001: 2001-03-15 (Lumitex → Lee) and 2001-03-20 (Lee → Solid State Opto Ltd.) — five days.
• 2013: 2013-03-04 (two transfers the same day: Rambus International → Rambus Inc.; Rambus Inc. → Rambus Delaware LLC), then 2013-06-26 (Rambus Delaware LLC → Acacia) and 2013-06-27 (Acacia → IDT LLC) — three hops in roughly four months, the last two one day apart.
  Both clusters are consistent with preparatory structuring rather than business integration.

5. Pre-litigation transfer — PRESENT (very strong).
The Acacia → IDT LLC assignment is recorded 2013-06-27. The first IDT infringement suits — IDT LLC v. Acer (2:13-cv-00522), v. Dell (00523), v. Hewlett-Packard (00524), v. Huawei (00525), v. BlackBerry (00526) and v. ZTE (00527), all E.D. Tex. — were filed 2013-06-28, i.e. one day later, well inside the 6-month window. The Microsoft opinion confirms the pattern across the wider campaign: "On October 1, 2013, the day after the license expired, seven ARC subsidiaries filed seven separate patent infringement lawsuits." This is the cleanest standing-arrangement fact in the file.
Accuracy caveat: the IDT suits I verified specifically name the continuation/divisional family members (6,755,547; 7,300,194; 7,384,177; 7,404,660; 8,215,816; 7,537,370; 7,434,973; 7,434,974; 6,508,563; 7,914,196), and I did not confirm that '751 itself was pleaded in any of them. '751 is the family root but expired 2015-06-27, limiting recoverable damages. Treat the pattern as applying to the estate; treat '751-specific assertion as unverified.

6. Bankruptcy fire-sale — NOT PRESENT.
No Chapter 7 or Chapter 11 filing by Lumitex, Solid State Opto, Rambus or Acacia appears in connection with this chain. The 1999 KeyBank security agreement and the Ohio Mezzanine Fund interest were released on 2001-02-02 two weeks before the sale to Lee — a consensual, lien-cleared negotiated divestiture, the opposite of a distressed sale under §363 or a trustee auction. The subsequent ~US$26M Rambus purchase (2010) was a paid portfolio acquisition, not a bankruptcy disposition.

7. Privateering — PRESENT.
The Rambus leg was structured to let the operating company keep practicing while an outside party monetizes against third parties. The Asset Purchase Agreement among Rambus Inc., Rambus International Ltd., Rambus Delaware LLC, and Global Lighting Technologies, Inc., Solid State OPTO Limited shows the seller taking back rights: it contemplates "the licenses granted by Seller to Buyer IP hereunder" and "the licenses granted by Buyer IP to Seller Parent pursuant to the License Agreement," plus a copyright co-ownership agreement and transition services. GLT-side reporting is consistent: Lee's group "還可以把部分光學相關專利以2600萬美元賣給…Rambus，而且還可以繼續使用這些專利" — sold the optical patents to Rambus for US$26M and could continue using them, while Rambus was free to collect royalties from infringers. Seller retains practice rights; buyer gets the enforcement upside. That is the privateering template, with the added twist that the "operating company" here (GLT/GLT-USA) had itself been built out of Lumitex's R&D and sales team six months earlier.

8. Defensive aggregator (anti-NPE) — NOT PRESENT.
The chain terminates at Innovative Display Technologies LLC, an Acacia asserting subsidiary — the inverse of neutralization. No RPX, AST, LOT Network, Unified Patents or OIN assignment appears anywhere in the '751 legal events. The 2020–2021 Acacia-group recordings (Reels 052853/0153, 053654/0254, corrective 055100/0624) move within the Acacia/Starboard orbit, which is also not a defensive aggregator.

Verdict

NPE — high confidence.

Four strong signals converge on the same instrument. (i) Cascading transfers: two same-day Rambus recordings on 2013-03-04, then Rambus Delaware LLC → Acacia Research Group LLC on 2013-06-26 and Acacia → Innovative Display Technologies LLC on 2013-06-27 — three hops in about four months into a single-purpose Texas litigation LLC that, per the E.D. Tex. court, "owns only the patents asserted here." (ii) Pre-litigation transfer: IDT filed six suits (2:13-cv-00522 through 00527) on 2013-06-28, one day after the assignment was recorded. (iii) Known asserter: Acacia Research Group LLC is the named acquirer and is IDT's disclosed real party-in-interest, with a multi-defendant licensing campaign documented in the IPR2015-00363 notices and a run of Acacia 8-K settlement announcements. (iv) Shell-entity transfer: the estate left an operating manufacturer via a natural person (Lee, 2001-03-15) into a British Virgin Islands holding company (Solid State Opto Limited, 2001-03-20) before reaching the asserting LLC. Signal 7 (privateering) is also present on the Rambus leg, where the seller retained practice rights under the Rambus–GLT/Solid State Opto asset purchase agreement.

The one material limitation on this report: the reel/frame numbers and correspondents of record for US 5613751 itself were not retrievable in this session, and one signal (repeat correspondent, #3) therefore remains unclear. Before relying on the chain for a filing or an enforcement decision, pull the eleven postings listed above at the USPTO Assignment Center — https://assignmentcenter.uspto.gov/ (or https://assignment.uspto.gov/patent/index.html), searching patent number 5613751 — and record the reel/frame and correspondent for each.

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.