Electrophoretic device having a transparent light state
A light attenuator comprises a cell comprising a first substrate and a second substrate spaced apart from the first substrate. A layer between the substrates contains an electrophoretic ink, a surface of the layer adjacent the second substrate comprising a monolayer of closely packed protrusions projecting into the layer. The protrusions have surfaces defining a plurality of depressions in the volumes there between. The ink includes charged particles of at least one type, the particles being responsive to an electric field applied to the cell to move between a first extreme light state, in which particles are maximally spread within the cell to lie in the path of light through the cell and to strongly attenuate light transmitted through the cell; over the surface of the protrusions, which deflect the particles from their path from the first substrate to the second substrate; to a second extreme light state in which the particles are maximally concentrated within the depressions to remove them from the path of light through the cell and to substantially transmit light through the cell.
1. A light-attenuating electrophoretic device comprising:
a cell comprising a first substrate and a second substrate spaced apart from said first substrate;
a layer comprising an electrophoretic ink disposed between said first substrate and said second substrate, the layer including charged particles of at least one type, the particles being responsive to an electric field applied thereto;
a first transparent planar electrode adjacent the first substrate;
a second transparent planar electrode adjacent the second substrate, wherein the first and second transparent planar electrodes are substantially co-extensive with the layer comprising the electrophoretic ink;
a non-planar polymer structure adjacent the second substrate including light-masking walls, said light-masking walls contacting said first substrate through a light-masking adhesive layer,
the second transparent planar electrode being disposed between the second substrate and the non-planar polymer structure,
the non-planar polymer structure additionally including transparent protrusions, said transparent protrusions having surfaces defining a plurality of depressions in a volume of the layer comprising an electrophoretic ink disposed between said first substrate and said second substrate, said transparent protrusions projecting into said layer, and wherein said transparent protrusions are each circumscribed by said depressions and said light-masking walls,
wherein the light-attenuating electrophoretic device includes a first extreme light state, in which particles are maximally spread within the cell to lie in the path of light travelling into the cell and to strongly attenuate light entering or transmitted through the cell; and
a second extreme light state in which said particles are maximally concentrated within said depressions to remove the particles from the path of light into the cell and to reflect or substantially transmit light through the cell.
2. The light-attenuating electrophoretic device of claim 1 , wherein said light-masking adhesive is printed on a contact area of said light-masking walls, and where contact area is less than 25% of said electrophoretic device's face-area.
3. The light-attenuating electrophoretic device of claim 1 , wherein said light-masking adhesive comprises black colorant.
4. The light-attenuating electrophoretic device of claim 3 , wherein said light-masking adhesive layer comprises a black polymer layer and an adhesive.
5. The light-attenuating electrophoretic device of claim 1 , wherein said light-masking walls define a space between said protrusions and said first substrate.
6. The light-attenuating electrophoretic device of claim 1 , wherein the first transparent electrode is disposed between the first substrate and an insulating layer.