Dynamic road marking unit

Abstract

A dynamic road marking unit is capable of switching between a first and a second display state. It has an electro-optical layer which is bistable. In principle the dynamic road marking unit only requires energy when switching between the states, i.e. when the visual properties of the dynamic road marking unit are changed.

1 . A dynamic road marking unit capable of switching between a first and a second display state and comprising an electro-optical layer ( 3 ;  11 ,  12 ), characterized in that the electro-optical layer ( 3 ;  11 ,  12 ) is bistable.  
     
     
         2 . A dynamic road marking unit according to  claim 1 , wherein the electro-optical layer is a layer of electrophoretic material ( 3 ) which contains a set of charged particles ( 6 ,  7 ) with predetermined visual properties, and wherein at least a first electrically conductive layer ( 1 ) is arranged adjacent to one side of the layer of electrophoretic material ( 3 ).  
     
     
         3 . A dynamic road marking unit according to  claim 2 , further comprising a second conductive layer ( 2 ) arranged adjacent to the other side of the layer of electrophoretic material ( 3 ).  
     
     
         4 . A dynamic road marking unit according to  claim 2  or  3 , wherein the charged particles ( 6 ,  7 ) are surrounded by a colored fluid ( 5 ).  
     
     
         5 . A dynamic road marking unit according to  claim 2  or  3 , wherein the set of charged particles ( 6 ,  7 ) comprises a set of positively charged particles ( 6 ) with first visual properties.  
     
     
         6 . A dynamic road marking unit according to  claim 2  or  3 , wherein the set of charged particles ( 6 ,  7 ) comprises a set of negatively charged particles ( 7 ) with second visual properties.  
     
     
         7 . A dynamic road marking unit according to  claim 2  or  3 , wherein the set of charged particles ( 6 ,  7 ) comprises a set of positively charged particles ( 6 ) with first visual properties and a set of negatively charged particles ( 7 ) with second visual properties different from the first visual properties.  
     
     
         8 . A dynamic road marking unit according to  claim 1 , wherein the electro-optical layer comprises at least two redox-active layers ( 11 ,  12 ) of which at least one layer is of electrochromic material, wherein conductive layers ( 14 ,  15 ) are provided to generate a voltage difference between the two redox-active layers ( 11 ,  12 ), and wherein means are provided to prevent direct electrical contact between the at least two redox-active layers ( 11 ,  12 ).  
     
     
         9 . A dynamic road marking unit according to  claim 8 , wherein the electro-optical layer further comprises an electrolyte layer ( 13 ).  
     
     
         10 . A dynamic road marking unit according to  claim 9 , wherein the electrolyte layer is a gel electrolyte layer ( 13 ).  
     
     
         11 . A dynamic road marking unit according to  claim 8 ,  9  or  10 , wherein the at least one layer of electrochromic material ( 11 ,  12 ) comprises at least one conductive polymer.  
     
     
         12 . A dynamic road marking unit according to  claim 11 , wherein the at least one layer of electrochromic material ( 11 ,  12 ) comprises at least one organic conductive polymer.  
     
     
         13 . A dynamic road marking unit according to any of  claims 8  to  12 , wherein the conductive layers ( 14 ,  15 ) comprise indium-tin oxide.  
     
     
         14 . A dynamic road marking unit according to any of  claims 8  to  12 , wherein the conductive layers ( 14 ,  15 ) comprise highly doped poly(ethylenedioxythiophene).  
     
     
         15 . A dynamic road marking unit according to any of  claims 8  to  14 , wherein the electro-optical layer comprises an electrochromic layer ( 11 ) of polypyrrole and an electro-chromic layer ( 12 ) of a mixture of normally doped poly(ethylenedioxythiophene) and normally doped polyethylenedioxypyrrole, with a gel electrolyte layer ( 13 ) sandwiched between these two layers, two conductive layers ( 14 ,  15 ) being arranged, one on each side of the electro-optical layer, adjacent to the side of the polypyrrole layer ( 11 ) not facing the gel electrolyte ( 13 ) and to the side of the layer ( 12 ) of the mixture of normally doped poly(ethylenedioxythiophene) and normally doped polyethylenedioxypyrrole not facing the gel electrolyte ( 13 ), respectively.  
     
     
         16 . A dynamic road marking unit according to  claims 8  to  15 , wherein a white reflecting layer ( 18 ) is provided adjacent to one of the conductive layers ( 16 ).  
     
     
         17 . A dynamic road marking unit according to  claim 1 , wherein the electro-optical layer is a bistable liquid crystal layer.  
     
     
         18 . A dynamic road marking unit according to any of the preceding claims, wherein a layer of visibility-enhancing optical structures ( 8 ) is arranged on the dynamic road marking unit.  
     
     
         19 . A dynamic road marking unit according to any of the preceding claims, further comprising a coating of polyurethane.  
     
     
         20 . Method of operating a dynamic road marking unit, comprising the step of switching an electro-optical layer in a dynamic road marking unit to a desired state, characterized in that the dynamic road marking unit is designed in accordance with any of  claims 1  to  19 .