ELECTROPHORETIC FLUID
The present invention is directed to an electrophoretic fluid comprising transparent particles, as an additive. The presence of the transparent particles in the fluid provides improved display performance.
1 . An electrophoretic fluid comprising charged non-transparent particles and transparent particles all of which are dispersed in a solvent, wherein the refractive index of the transparent particles is substantially the same as that of the solvent.
2 . The fluid of claim 1 , wherein the refractive index is lower than 1.5.
3 . The fluid of claim 1 , wherein the transparent particles take up less than 20% by volume of the fluid.
4 . The fluid of claim 1 , wherein the transparent particles take up less than 10% by volume of the fluid.
5 . The fluid of claim 1 , wherein the transparent particles are formed from an organic material.
6 . The fluid of claim 1 , wherein the transparent particles are formed from an inorganic material.
7 . The fluid of claim 5 , wherein the transparent particles are formed from a monomer or oligomer selected from the group consisting of acrylate or methacrylate, siloxane modified acrylate or methacrylate, and halogenated acrylate or methacrylate.
8 . The fluid of claim 1 , wherein the transparent particles have an average size of less than 0.5 μm.
9 . The fluid of claim 1 , wherein the transparent particles have an average size of less than 0.3 μm.
10 . The fluid of claim 1 , wherein the transparent particles have an average size of less than 0.1 μm.
11 . The fluid of claim 1 , wherein the non-transparent charged pigment particles are white particles which carry a positive or negative charge polarity.
12 . The fluid of claim 1 , wherein the non-transparent charged pigment particles are black and white particles carrying opposite charge polarities.
13 . The fluid of claim 1 , wherein the solvent is a hydrocarbon solvent.
14 . The fluid of claim 1 , wherein the solvent is halogenated or fluorinated.
15 . The fluid of claim 1 , wherein the transparent particles are non-charged.
16 . The fluid of claim 1 , wherein the transparent particles are charged.
17 . The fluid of claim 16 , wherein the transparent particles carry a charge the polarity of which is the same as that carried by one type of the non-transparent charged pigment particles, but have a different level of mobility than that of the non-transparent charged pigment particles.
18 . The fluid of claim 1 , further comprising a charge control agent.