# US 9,519,087 B2 · Prismatic retroreflective sheeting with reduced retroreflectivity of infra-red light > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,519,087 B2 - Document ID: US9519087B2 - Status: Granted - Kind: B2 - Application number: 13/502,251 - Filed: 2010-10-12 - Published: 2012-08-09 - Granted: 2016-12-13 - Earliest claimed: 2009-10-16 - Assignees: 3M Innovative Properties Company - Applicants: Toshitaka Nakajima; Masami Yokoyama; Akira Muramoto - Inventors: Toshitaka Nakajima; Masami Yokoyama; Akira Muramoto - Web page: https://patentgrep.com/patent/US9519087B2 ## CPC - G02B 5/124: plural reflecting elements forming part of a unitary plate or sheet - B60R 13/10: Registration, licensing, or like devices - G02B 5/208: {for use with infrared or ultraviolet radiation, e.g. for separating visible light from infrared and/or ultraviolet radiation} - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - B60R: VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR ## Abstract The present application relates to retroreflective sheeting that is capable of use in a license plate and that can be accurately read and/or detected by an ALPR system. The retroreflective sheeting is a prismatic retroreflective sheeting that provides reduced retroreflectivity of infra-red light. The retroreflective sheeting can also be a prismatic retroreflective sheeting that exhibits reduced retroreflectivity of incident infra-red light and substantially unaffected retroreflectivity of incident visible light. ## Claims ### Claim 1 A retroreflective sheet defining a first side and a second side opposite to the first side, the retroreflective sheet comprising: cube corner elements including a substantially planar viewing surface and a structured surface, wherein the substantially planar viewing surface is nearer the first side than the structured surface is; a reflector layer adjacent to the structured surface of the cube corner elements, wherein the reflector layer is configured to reflect at least visible light incident transmitted through the cube corner elements to the reflector layer; and an infra-red non-transmissive material in the retroreflective sheet between the reflector layer and the first side of the retroreflective sheet, wherein the infra-red non-transmissive material leaves retroreflectivity of visible light incident on the substantially planar viewing surface of the cube corner elements and transmitted through the cube corner elements to the reflector layer substantially unaffected. ### Claim 2 (depends on 1) The retroreflective sheet of claim 1, wherein the cube corner elements are one of full cubes, truncated cubes, cube corner type trigonal pyramids, cube corner type cavities, and the like. ### Claim 3 (depends on 1) The retroreflective sheet of claim 1, further including a whiteness-enhancing material. ### Claim 4 (depends on 1) The retroreflective sheet of claim 1, wherein the reflector layer includes one of a mirror-surfaced reflection layer and a multi-layer optical film. ### Claim 5 (depends on 1) The retroreflective sheet of claim 1, further including at least one of a protective layer and a sealing film. ### Claim 6 (depends on 1) The retroreflective sheet of claim 1, wherein the infra-red non-transmissive material forms a separate layer from the cube corner elements and the reflector layer. ### Claim 7 (depends on 1) The retroreflective sheet of claim 1, wherein the infra-red non-transmissive material is in the cube corner elements. ### Claim 8 (depends on 3) The retroreflective sheet of claim 3, wherein the whiteness-enhancing material is in the cube corner elements. ### Claim 9 (depends on 3) The retroreflective sheet of claim 3, wherein the whiteness-enhancing material and the infra-red non-transmissive material form a separate layer from the cube corner elements and the reflector layer. ### Claim 10 A retroreflective sheet defining a first side and a second side opposite to the first side, the retroreflective sheet comprising: cube corner elements including a substantially planar viewing surface and a structured surface, wherein the substantially planar viewing surface is nearer the first side than the structured surface is; a reflector layer adjacent to the structured surface of the cube corner elements, wherein the reflector layer is configured to reflect at least visible light incident transmitted through the cube corner elements to the reflector layer; and an infra-red non-transmissive layer adjacent to the substantially planar viewing surface of the cube corner elements, wherein the infra-red non-transmissive material leaves retroreflectivity of visible light incident on the substantially planar viewing surface of the cube corner elements and transmitted through the cube corner elements to the reflector layer substantially unaffected. ### Claim 11 (depends on 10) The retroreflective sheet of claim 10, further including at least one of a protective layer and a sealing layer. ### Claim 12 (depends on 10) The retroreflective sheet of claim 10, wherein the cube corner elements are one of full cubes, truncated cubes, cube corner type trigonal pyramids, cube corner type cavities, and the like. ### Claim 13 (depends on 10) The retroreflective sheet of claim 10, further including a whiteness-enhancing material deposited on the infra-red non-transmissive layer. ### Claim 14 (depends on 10) The retroreflective sheet of claim 10, wherein the reflector layer includes one of a mirror-surfaced reflection layer and a multi-layer optical film. ### Claim 15 A retroreflective sheet defining a first side and a second side opposite to the first side, the retroreflective sheet comprising: cube corner elements including a substantially planar viewing surface and a structured surface, wherein the substantially planar viewing surface is nearer the first side than the structured surface is; and a reflector layer adjacent to the structured surface of the cube corner elements, wherein the reflector layer is configured to reflect at least visible light incident transmitted through the cube corner elements to the reflector layer; wherein the cube corner elements include an infra-red non-transmissive material, and wherein the infra-red non-transmissive material leaves retroreflectivity of visible light incident on the substantially planar viewing surface of the cube corner elements and transmitted through the cube corner elements to the reflector layer substantially unaffected. ### Claim 16 (depends on 15) The retroreflective sheet of claim 15, further including a whiteness-enhancing material. ### Claim 17 (depends on 16) The retroreflective sheeting of claim 16, wherein the whiteness-enhancing material is deposited into a front side of the cube corner elements. ### Claim 18 (depends on 15) The retroreflective sheet of claim 15, wherein the cube corner elements include a whiteness-enhancing material. ### Claim 19 (depends on 15) The retroreflective sheet of claim 15, further including at least one of a protective layer and a sealing layer. ### Claim 20 (depends on 15) The retroreflective sheet of claim 15, wherein the cube corner elements are one of full cubes, truncated cubes, cube corner type trigonal pyramids, cube corner type cavities, and the like. ### Claim 21 (depends on 15) The retroreflective sheet of claim 15, wherein the reflector layer includes one of a mirror-surfaced reflection layer and a multi-layer optical film. ### Claim 22 (depends on 1) A license plate utilizing the retroreflective sheet according to claim 1. ### Claim 23 (depends on 22) An Automated License Plate Reader (ALPR) system, comprising: a license plate according to claim 22; a light source that directs light at the license plate; and a machine capable of imaging the license plate. ### Claim 24 (depends on 10) A license plate utilizing the retroreflective sheet according to claim 10. ### Claim 25 (depends on 15) A license plate utilizing the retroreflective sheet according to claim 15. ### Claim 26 (depends on 24) An Automated License Plate Reader (ALPR) system, comprising: a license plate according to claim 24; a light source that directs light at the license plate; and a machine capable of imaging the license plate. ### Claim 27 (depends on 25) An Automated License Plate Reader (ALPR) system, comprising: a license plate according to claim 25; a light source that directs light at the license plate; and a machine capable of imaging the license plate. ### Claim 28 (depends on 1) The retroreflective sheet of claim 1 wherein the infra-red non-transmissive material is visible light transmissive. ### Claim 29 (depends on 10) The retroreflective sheet of claim 10 wherein the infra-red non-transmissive material is visible light transmissive. ### Claim 30 (depends on 15) The retroreflective sheet of claim 15 wherein the infra-red non-transmissive material is visible light transmissive. ### Claim 31 A retroreflective sheet defining a first side and a second side opposite to the first side, the retroreflective sheet comprising: cube corner elements including a substantially planar viewing surface and a structured surface, wherein the substantially planar viewing surface is nearer the first side than the structured surface is; a whiteness-enhancing material; and an infra-red non-transmissive material in the retroreflective sheet between the structured surface of the cube corner elements and the first side of the retroreflective sheet, wherein the infra-red non-transmissive material leaves retroreflectivity of visible light incident on the substantially planar viewing surface of the cube corner elements and transmitted through the cube corner elements to the structured surface substantially unaffected. ### Claim 32 (depends on 31) The retroreflective sheet of claim 31 wherein the infra-red non-transmissive material is visible light transmissive. ### Claim 33 A retroreflective sheet defining a first side and a second side opposite to the first side, the retroreflective sheet comprising: cube corner elements including a substantially planar viewing surface and a structured surface, wherein the substantially planar viewing surface is nearer the first side than the structured surface is; and an infra-red non-transmissive material in the cube corner elements, wherein the infra-red non-transmissive material leaves retroreflectivity of visible light incident on the substantially planar viewing surface of the cube corner elements and transmitted through the cube corner elements to the structured surface substantially unaffected. ### Claim 34 (depends on 33) The retroreflective sheet of claim 33 wherein the infra-red non-transmissive material is visible light transmissive. ### Claim 35 (depends on 31) A license plate utilizing the retroreflective sheet according to claim 31. ### Claim 36 (depends on 33) A license plate utilizing the retroreflective sheet according to claim 33. ### Claim 37 (depends on 35) An ALPR system, comprising: a license plate according to claim 35; a light source that directs light at the license plate; and a machine capable of imaging the license plate. ### Claim 38 (depends on 36) An ALPR system, comprising: a license plate according to claim 36; a light source that directs light at the license plate; and a machine capable of imaging the license plate.