Display device based on electrowetting effect
In a reflective a display device based on layer break up or layer displacement having at least two different states, in which one of the fluids ( 5 ) e.g. oil in a first state adjoins at least a first support plate ( 3 ) and in the second state the other fluid ( 6 ) at least partly adjoins the first support plate, in which picture elements are separated by areas ( 13 ) having a hydrophilic surface dyes (or sometimes pigments) are added to the oil (usually hydrocarbon but also possibly silicone or fluorocarbon), to provide sufficient optical intensity.
1. An optical switch comprising a first transparent support plate and a second support plate and at least a first fluid and a second fluid immiscible with each other within a cavity between the first support plate and the second support plate, a dye being dissolved in the first fluid and the second fluid being electroconductive or polar, the first fluid being switchable between a first state in which the first fluid forms a layer in a path of light in the cavity and a second state in which the first fluid is moved aside or is broken up in small droplets, and the first fluid having a Figure of Merit (FoM=ε·C) of at least 1000 cm −1 , ε being an extinction coefficient and C a concentration of the dye.
2. An optical switch according to claim 1 , wherein the dissolved dye is replaced by a pigment.
3. An optical switch according to claim 2 , wherein the concentration of the dye is at most 1 M (mol/L).
4. An optical switch according to claim 1 or 2 , wherein the concentration of the dye is at most 0.1 M.
5. An optical switch according to claim 1 or 2 , wherein the concentration of the dye is at least 0.01 M.
6. An optical switch according to any one of claims 1 to 3 , wherein the first fluid comprises an oil and wherein the oil comprises at least one of silicone oil, hydrocarbon oil or fluorocarbon oil.
7. A display device comprising picture elements, each picture element comprising an optical switch according to any one of claims 1 to 3 .
8. An optical switch according to claim 1 , wherein the concentration of the dye is at most 1 M (mol/L).