# US 12,113,278 B2 · Radar retroreflective article

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- Number: US 12,113,278 B2
- Document ID: US12113278B2
- Status: Granted
- Kind: B2
- Application number: 17/608,046
- Filed: 2020-05-21
- Published: 2022-07-07
- Granted: 2024-10-08
- Earliest claimed: 2019-05-24
- Assignees: 3M Innovative Properties Company
- Applicants: 3M Innovative Properties Company
- Inventors: Jaewon Kim; Mohsen Salehi; Michael A. McCoy; Susannah C. Clear
- Web page: https://patentgrep.com/patent/US12113278B2

## CPC

- H01Q 15/23: Combinations of reflecting surfaces with refracting or diffracting devices
- H01Q 15/08: formed of solid dielectric material
- H01Q 15/18: comprising plurality of mutually inclined plane surfaces, e.g. corner reflector {(H01Q15/16 takes precedence)}
- G01S 13/931: of land vehicles
- H01Q: ANTENNAS, i.e. RADIO AERIALS (radiators or antennas for microwave heating H05B6/72)
- G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES

## Abstract

This disclosure relates generally to radar retroreflective articles comprising one or more dielectric layers adjacent to a reflective layer, wherein the dielectric layer or layers aids in increasing the radar cross section of the radar retroreflective articles.

## Claims

### Claim 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.

### Claim 2 (depends on 1)

The retroreflective item according to claim 1, wherein the thickness of the dielectric layer is from 0.2 mm to 10 mm.

### Claim 3 (depends on 1)

The retroreflective item according to claim 1, wherein the dielectric layer refracts a radar signal having an incident angle of 5 degrees with respect to the plane of the retroreflective item at least 60 degrees (30 degrees with respect to a normal to the surface).

### Claim 4 (depends on 1)

The retroreflective item according to claim 1, wherein the radar signal is from 76 GHz to 81 GHz.

### Claim 5 (depends on 1)

The retroreflective item according to claim 1, wherein the radar signal is from 21 GHz to 27 GHz.

### Claim 6 (depends on 1)

The retroreflective item according to claim 1, wherein the radar signal is from 105 GHz to 115 GHz.

### Claim 7 (depends on 1)

The retroreflective item according to claim 1, wherein the reflective layer is immediately adjacent to the dielectric layer.

### Claim 8 (depends on 1)

The retroreflective item according to claim 1, wherein the retroreflective layer comprises a metallic material.

### Claim 9 (depends on 1)

The retroreflective item according to claim 1, wherein the dielectric layer comprises poly(methyl methacrylate), polyethylene terephthalate, polycarbonate, polyurethane, pvc, polyethylene, polypropylene, silicones, acrylates including trimethylolpropane and poly(ethyleneglycol) acrylates, and combinations thereof.

### Claim 10 (depends on 1)

The retroreflective item according to claim 1, wherein the side dimension of the cube corner elements is from 2 mm to 20 mm.

### Claim 11 (depends on 1)

The retroreflective item according to claim 1, wherein the dielectric layer has a permittivity from 4 to 20.

### Claim 12 (depends on 1)

The retroreflective item according to claim 1, wherein the retroreflective item is a pavement marking.

### Claim 13 (depends on 1)

The retroreflective item according to claim 1, further comprising an adhesive layer adjacent or immediately adjacent the retroreflective layer.

### Claim 14 (depends on 1)

The retroreflective item according to claim 1, further comprising an adhesive layer adjacent or immediately adjacent the retroreflective layer and a liner adjacent or immediately adjacent the adhesive layer.