US 12,113,278 B2
Radar retroreflective article
Jaewon Kim, Woodbury, MN (US); Mohsen Salehi, Woodbury, MN (US); Michael A. McCoy, St. Paul, MN (US); and Susannah C. Clear, Hastings, MN (US)
Assigned to 3M Innovative Properties Company, St. Paul, MN (US)
Appl. No. 17/608,046
Filed by 3M INNOVATIVE PROPERTIES COMPANY, St. Paul, MN (US)
PCT Filed May 21, 2020, PCT No. PCT/IB2020/054840
§ 371(c)(1), (2) Date Nov. 1, 2021,
PCT Pub. No. WO2020/240364, PCT Pub. Date Dec. 3, 2020.
Claims priority of provisional application 62/852,668, filed on May 24, 2019.
Prior Publication US 2022/0216616 A1, Jul. 7, 2022
Int. Cl. H01Q 15/23 (2006.01); H01Q 15/08 (2006.01); H01Q 15/18 (2006.01)
CPC H01Q 15/23 (2013.01) [H01Q 15/08 (2013.01); H01Q 15/18 (2013.01)] 14 Claims
OG exemplary drawing
 
1. A retroreflective item comprising,
a retroreflective layer capable of reflecting a radar signal comprising,
cube corner elements having a side dimension from 2 mm to 65 mm,
a metallic layer coated on the cube corner elements, and
a dielectric layer adjacent the retroreflective layer having a permittivity from 4 to 30,
wherein the dielectric layer is opaque,
wherein the thickness of the dielectric layer is from 0.2 mm to 15 mm,
wherein the retroreflective layer has a first major surface and an opposing second major surface and the first major surface defines a plane of the retroreflective item,
wherein the ratio of the radar cross section with and without the dielectric layer is greater than 3 when the radar signal has an incident angle of 5 degrees with respect to the plane of the retroreflective item.