US 5917664

I'll search for US patent 5917664 specifically, including USPTO sources and any 2026 CAFC activity.

Let me check for any litigation or CAFC docket activity involving this patent.

Search scope and results

I searched for US Patent 5,917,664 specifically and confirmed the following authoritative sources (no results for similar numbers were used):

• USPTO/Google Patents full text and claims: https://patents.google.com/patent/[US5917664A](/patent/US5917664A)/en
• USPTO patent image (front page facsimile): https://patentimages.storage.googleapis.com/b0/15/a3/58959973f440fa/[US5917664](/patent/US5917664).pdf
• Justia patent page (Patent # 5,917,664): https://patents.justia.com/patent/5917664

On CAFC 2026 dockets: I did not find any Federal Circuit 2026 docket, appeal, IPR, or district-court action involving US 5,917,664. This is consistent with the fact that the patent's legal status reads "Expired – Lifetime," with an anticipated expiration of 2016-02-05 (twenty years from the 1996-02-05 filing). I cannot assert with certainty that no litigation ever touched this patent; I am only reporting that my searches returned nothing for 2026 CAFC activity, and I found no authoritative docket record. Treat any absence of litigation as "not found," not "confirmed none."

Bibliographic summary (per the front page and Google Patents record)

Front-page notice worth flagging: the patent carries an asterisk at the issue date ("*Jun. 29, 1999") with the notice: "This patent issued on a continued prosecution application filed under 37 CFR 1.53(d), and is subject to the twenty year patent term provisions of 35 U.S.C. 154(a)(2)." So the term runs from the 1996-02-05 filing, which is why the listed expiration is 2016.

Abstract (verbatim)

"A brightness enhancement film has a plurality of linear prisms. The prisms are disposed in pairs, each pair having first and second prisms and each prism has a prism angle and a valley angle. Either the prism angles or the valley angles, but not both, are equal."

Plain-language overview of the independent claims

The patent has three independent claims — claims 1, 4, and 8 — plus eight dependent claims (2, 3, 5, 6, 7, 9, 10, 11).

Claim 1 — the film itself. A film that boosts the apparent on-axis brightness of a light source. It has two surfaces. The first surface is a structured (prism-bearing) surface carrying many linear prisms. The defining feature: the prisms are arranged in side-by-side pairs, with each pair having a first and a second prism. Every prism can be described by two angles — a prism angle (the included angle at the peak) and a valley angle (the angle at the groove between prisms). The claim requires that either the prism angles or the valley angles of each pair are equal, but not both. In other words, if the peaks match, the valleys must differ; if the valleys match, the peaks must differ. This asymmetry is what produces the "soft cutoff."

Claim 4 — a backlight incorporating that film. A backlight for use with a display, comprising: (a) a light source; (b) a light pipe positioned to receive light from the light source; and (c) the brightness-enhancement film of claim 1 (same structured-surface/paired-prism/"either-but-not-both angles equal" requirement).

Claim 8 — an electronic display incorporating that film. An electronic display comprising: (a) a light source; (b) a light pipe positioned to receive light from the light source; (c) the brightness-enhancement film of claim 1; and (d) a liquid crystal display (LCD) module.

Dependents, briefly:

• Claim 2 / claim 5 / claim 9 — the prism angles are equal.
• Claim 3 / claim 6 / claim 10 — the valley angles are equal.
• Claim 7 / claim 11 — adds a diffuser between the light pipe and the film.

Drafting note: claims 10 and 11 are written as "A backlight according to claim 8…" even though claim 8 is directed to an electronic display (not a backlight). This is an internal inconsistency in the claim set as printed, and I am reporting it literally rather than correcting it.

How the claims map to the disclosed embodiments

• FIG. 7 embodiment (claims 1/2/3 axis): prism angles all 90° (equal), while valley angles alternate 70° and 110° (not equal). The specification describes this as "prisms canted in alternating directions," which widens the output light cone and produces the soft cutoff (expected on-axis gain slightly lower than prior art, but a more gradual falloff).
• FIG. 19 embodiment: the mirror-image approach — symmetric prisms with alternating peak/prism angles of 110° and 70° (not equal), with valley angles both 90° (equal).
• FIGS. 8 and 20 show backlight/display systems corresponding to claims 4/7 and 8/11, including light source, light pipe, reflector, optional diffuser, one or two crossed prism sheets, and an LCD module.

Confidence and caveats

• High confidence on all bibliographic fields, the abstract, and the claim text — these come from the front-page facsimile and the full-text record.
• Not verified: I could not retrieve an authoritative USPTO Patent Center/PTAB docket or a CAFC 2026 docket entry for this patent. My statement that no 2026 CAFC activity was found reflects search results only, not a certified docket check.
• Per your instruction, I have preserved the identifiers exactly as they appear (patent 5,917,664; application 08/596,792; PCT/US1997/001627) and have not normalized or auto-corrected any of them.