# US 11,994,285 B2 · Controlling off-state appearance of a light emitting device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,994,285 B2 - Document ID: US11994285B2 - Status: Granted - Kind: B2 - Application number: 17/964,194 - Filed: 2022-10-12 - Published: 2023-02-09 - Granted: 2024-05-28 - Earliest claimed: 2015-07-23 - Assignees: Lumileds LLC - Applicants: Lumileds LLC - Inventors: Hisashi Masui; Oleg Shchekin; Ken Shimizu; Marcel Bohmer; Frank Jin; Jyoti Bhardwaj - Web page: https://patentgrep.com/patent/US11994285B2 ## CPC - F21V 9/40: with provision for controlling spectral properties, e.g. colour, or intensity - C09B 67/0097: {Dye preparations of special physical nature; Tablets, films, extrusion, microcapsules, sheets, pads, bags with dyes} - F21K 9/00: Light sources using semiconductor devices as light-generating elements, e.g. using light-emitting diodes [LED] or lasers - F21K 9/20: Light sources comprising attachment means - F21V 14/003: {by interposition of elements with electrically controlled variable light transmissivity, e.g. liquid crystal elements or electrochromic devices} - G02B 27/0955: {Lenses (lenses per se G02B3/00)} - H05B 45/28: using temperature feedback - H10H 20/84: Coatings, e.g. passivation layers or antireflective coatings - H10H 20/8512: {Wavelength conversion materials} - H10H 20/8581: {characterised by their material} - H10H 20/851: Wavelength conversion means - F21V: FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR - C09B: ORGANIC DYES OR CLOSELY-RELATED COMPOUNDS FOR PRODUCING DYES {, e.g. PIGMENTS}; MORDANTS; LAKES (fermentation or enzyme using processes to synthesise a desired chemical compound C12P) - F21K: NON-ELECTRIC LIGHT SOURCES USING LUMINESCENCE; LIGHT SOURCES USING ELECTROCHEMILUMINESCENCE; LIGHT SOURCES USING CHARGES OF COMBUSTIBLE MATERIAL; LIGHT SOURCES USING SEMICONDUCTOR DEVICES AS LIGHT-GENERATING ELEMENTS; LIGHT SOURCES NOT OTHERWISE PROVIDED FOR - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL - H10H: INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS ## Abstract Systems for apparatuses formed of light emitting devices. Solutions for controlling the off-state appearance of lighting system designs is disclosed. Thermochromic materials are selected in accordance with a desired off-state of an LED device. The thermochromic materials are applied to a structure that is in a light path of light emitted by the LED device. In the off-state the LED device produces a desired off-state colored appearance. When the LED device is in the on-state, the thermochromic materials heat up and become more and more transparent. The light emitted from the device in its on-state does not suffer from color shifting due to the presence of the thermochromic materials. Furthermore, light emitted from the LED device in its on-state does not suffer from attenuation due to the presence of the thermochromic materials. Techniques to select and position thermochromic materials in or around LED apparatuses are presented. ## Claims ### Claim 1 A structure comprising: a semiconductor light emitting device having an on-state and an off-state; a phosphor layer disposed on the semiconductor light emitting device; and a thermochromic layer disposed on the phosphor layer, the thermochromic layer comprising a pigment having a transparent liquid state at a first temperature and a colored solid state at a second temperature lower than the first temperature, the pigment configured to transition from the colored solid state to the transparent liquid state within 250 milliseconds of the semiconductor light emitting device being switched from the off-state to the on-state, wherein the pigment is a leuco dye. ### Claim 2 (depends on 1) The structure of claim 1, wherein the color of the colored solid state is blue, black, or red. ### Claim 3 (depends on 1) The structure of claim 1, wherein the leuco dye is a spirolacetone, a spiropyran, or a fluorane. ### Claim 4 (depends on 1) The structure of claim 1, wherein the thermochromic layer comprises a carrier slurry, the carrier slurry comprising the pigment. ### Claim 5 (depends on 4) The structure of claim 4, wherein the carrier slurry comprises silicone. ### Claim 6 (depends on 1) The structure of claim 1, wherein the thermochromic layer comprises an antioxidant. ### Claim 7 (depends on 1) The structure of claim 1, wherein the thermochromic layer is hermetically sealed. ### Claim 8 (depends on 1) The structure of claim 1, wherein when the semiconductor light emitting device switches from off state to on state, the pigment switches from colored solid state to transparent liquid state within 200 milliseconds. ### Claim 9 (depends on 1) The structure of claim 1, wherein the pigment has a switching temperature of 62° C. or lower. ### Claim 10 An apparatus comprising: a camera; and a camera flash unit comprising: a semiconductor light emitting device having an on-state and an off-state; a phosphor layer disposed on the semiconductor light emitting device; and a thermochromic layer disposed on the phosphor layer, the thermochromic layer comprising a pigment having a transparent liquid state at a first temperature and a colored solid state at a second temperature lower than the first temperature, the pigment configured to transition from the colored solid state to the transparent liquid state within 250 milliseconds of the semiconductor light emitting device being switched from the off-state to the on-state, wherein the pigment is a leuco dye. ### Claim 11 (depends on 10) The apparatus of claim 10, comprising a phone. ### Claim 12 (depends on 10) The structure of claim 10, wherein the color of the colored solid state is blue, black, or red. ### Claim 13 (depends on 10) The structure of claim 10, wherein the thermochromic layer comprises a carrier slurry, the carrier slurry comprising the pigment. ### Claim 14 (depends on 13) The structure of claim 13, wherein the carrier slurry comprises silicone. ### Claim 15 (depends on 10) The structure of claim 10, wherein the thermochromic layer comprises an antioxidant. ### Claim 16 (depends on 10) The structure of claim 10, wherein the thermochromic layer is hermetically sealed. ### Claim 17 (depends on 10) The structure of claim 10, wherein when the semiconductor light emitting device switches from off state to on state, the pigment switches from colored solid state to transparent liquid state within 200 milliseconds. ### Claim 18 (depends on 10) The structure of claim 10, wherein the pigment has a switching temperature of 62° C. or lower.