# US 7,745,360 B2 · Pavement marking, reflective elements, and methods of making microspheres > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,745,360 B2 - Document ID: US7745360B2 - Status: Granted - Kind: B2 - Application number: 12/337,506 - Filed: 2008-12-17 - Published: 2009-04-16 - Granted: 2010-06-29 - Earliest claimed: 2005-11-14 - Assignees: 3M Innovative Properties Company - Inventors: Matthew H. Frey; Anatoly Z. Rosenflanz; Kenton D. Budd - Web page: https://patentgrep.com/patent/US7745360B2 ## CPC - C03C 12/02: Reflective beads - C03C 3/127: {containing TiO2 as glass former} - C03C 10/00: Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition - E01F 9/524: Reflecting elements specially adapted for incorporation in or application to road surface markings - Y10T 428/24372: Particulate matter - Y10T 428/2438: Coated - C03C: CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS - E01F: ADDITIONAL WORK, SUCH AS EQUIPPING ROADS OR THE CONSTRUCTION OF PLATFORMS, HELICOPTER LANDING STAGES, SIGNS, SNOW FENCES, OR THE LIKE - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract Presently described are retroreflective articles, such as pavement markings, that comprise transparent microspheres partially embedded in a (e.g., polymeric) binder. Also described are (e.g., glass-ceramic) microspheres, methods of making microspheres, as well as compositions of glass materials and compositions of glass-ceramic materials. The microspheres generally comprise lanthanide series oxide(s), titanium oxide (TiO2), and optionally zirconium oxide (ZrO2). ## Claims ### Claim 1 A retroreflective article, comprising: first transparent microspheres having an index of refraction of at least 2.10 and comprising: at least 56 wt % TiO2; and at least 10 wt-% of one or more metal oxides selected from oxides of lanthanide series elements; and second transparent microspheres having an index of refraction within a range from 1.5 to 2.0; wherein the first and second transparent microspheres are at least partially embedded in a binder. ### Claim 2 (depends on 1) The retroreflective article of claim 1, wherein the first microspheres have an index of refraction of at least 2.30. ### Claim 3 (depends on 1) The retroreflective article of claim 1, wherein the first microspheres include a glass-ceramic structure. ### Claim 4 (depends on 1) The retroreflective article of claim 1, wherein the first microspheres comprise at least 25 wt-% of one or more metal oxides selected from oxides of the lanthanide series elements. ### Claim 5 (depends on 1) The retroreflective article of claim 1, wherein the first microspheres comprise between about 5 wt-% and about 15 wt-% of at least one metal oxide selected from ZrO2, HfO2, ThO2, and mixtures thereof. ### Claim 6 (depends on 1) The retroreflective article of claim 1, wherein the first micropheres comprise: 56 wt % to 70 wt-% TiO2; 20 wt % to 55 wt-% of one or more metal oxides selected from oxides of the lanthanide series elements; 5 to 25 wt-% of at least one metal oxide selected from ZrO2, HfO2, ThO2, and mixtures thereof. ### Claim 7 (depends on 1) The retroreflective article of claim 1, wherein the first microspheres include at least 90 wt-% of at least one metal oxide selected from TiO2, La2O3, ZrO2, HfO2, ThO2 and mixtures thereof. ### Claim 8 (depends on 1) The retroreflective article of claim 1, wherein the first microspheres comprise: 60 wt-% to 65 wt-% TiO2; 25 wt-% to 35 wt-% of one or more metal oxides selected from oxides of the lanthanide series elements; and 5 wt-% to 15 wt-% of at least one metal oxide selected from ZrO2, HfO2, ThO2, and mixtures thereof. ### Claim 9 (depends on 1) The retroreflective article of claim 1, wherein the binder includes a pigment selected from at least one diffusely reflecting pigment, at least one specularly reflecting pigment, and combinations thereof. ### Claim 10 (depends on 1) The retroreflective article of claim 1, wherein the microspheres are fused. ### Claim 11 (depends on 1) The retroreflective article of claim 1, wherein the microspheres include a reflective coating. ### Claim 12 (depends on 1) The retroreflective article of claim 1, wherein a transparent binder is between the microspheres and a reflective layer. ### Claim 13 (depends on 1) The retroreflective article of claim 1, wherein the microspheres comprise at least 10 wt-% of at least one metal oxide selected from La2O3, Gd2O3, and mixtures thereof. ### Claim 14 A retroreflective element, comprising: a core; and transparent microspheres at least partially embedded in the core and having an index of refraction of at least 2.10; wherein at least a portion of the transparent microspheres include at least 56 wt-% TiO2 and at least 10 wt-% of one or more lanthanide series oxides. ### Claim 15 (depends on 14) The retroreflective element of claim 14, wherein the core includes at least one of an organic material, an inorganic material, or a mixture thereof. ### Claim 16 (depends on 1) The retroreflective article of claim 1 wherein the first transparent microspheres further comprise yttrium oxide. ### Claim 17 A retroreflective article, comprising: first transparent microspheres having an index of refraction of at least 2.10 and comprising: at least 50 mol-% TiO2; and at least 5 mol-% of yttrium oxide; and second transparent microspheres having an index of refraction within a range from 1.5 to 2.0; wherein the first and second transparent microspheres are at least partially embedded in a binder. ### Claim 18 (depends on 17) The retroreflective article of claim 17 wherein the first transparent microspheres further comprise one or more metal oxides selected from oxides of lanthanide series elements. ### Claim 19 (depends on 17) The retroreflective article of claim 17, wherein the first microspheres have an index of refraction of at least 2.30. ### Claim 20 (depends on 17) The retroreflective article of claim 17, wherein the first microspheres include a glass-ceramic structure. ### Claim 21 (depends on 17) The retroreflective article of claim 17, wherein the binder includes a pigment selected from at least one diffusely reflecting pigment, at least one specularly reflecting pigment, and combinations thereof. ### Claim 22 (depends on 17) The retroreflective article of claim 17, wherein the microspheres are fused. ### Claim 23 (depends on 17) The retroreflective article of claim 17, wherein the microspheres include a reflective coating. ### Claim 24 (depends on 17) The retroreflective article of claim 17, wherein a transparent binder is between the microspheres and a reflective layer.