Patent ID: 11868020
Assignee: E INK CORPORATION
Field: Optics (Instruments)
Classification: CPC G | IPC G

Claim 14:
15. A method for driving an electrophoretic display device comprising:
(i) providing an electrophoretic display device comprising (a) a layer of the electrophoretic medium, said electrophoretic medium comprising a fluid and first, second, third and fourth types of particles dispersed in the fluid, the first, second, third and fourth types of particles having respectively first, second, third and fourth colors differing from one another, the first and third types of particles having charges of one polarity and the second and fourth types of particles having charges of the opposite polarity, the first type of particles having a greater zeta potential or electrophoretic mobility than the third type of particles, and the second type of particles having a greater zeta potential or electrophoretic mobility than the fourth type of particles, wherein one of the types of particles is white and the other three types of particles are non-white, one of the types of non-white particles is partially light-transmissive, and the remaining two types of non-white particles are light-reflective, wherein a layer of the partially light-transmissive type of particles has a contrast ratio of not more than about 0.5, (b) a front electrode and a rear electrode disposed on opposed sides of the layer of electrophoretic medium, and (c) voltage control means arranged to control the potentials of the front and rear electrodes;
(ii) applying a fifth driving voltage having a polarity driving the two types of particles of one polarity towards the viewing surface for a ninth period of time;
(iii) applying a sixth driving voltage have a polarity opposite to that of the fifth driving voltage and a magnitude less than that of the fifth driving voltage for a tenth period of time longer than the ninth period of time;
(iv) repeating steps (ii) and (iii); and
(v) after the repetition of steps (ii) and (iii), applying a sixth driving voltage having the same polarity as the fourth driving voltage, the magnitude and/or time of application of the sixth driving voltage not being sufficient to drive the display to display the color of the second type of particles at the viewing surface, thereby displaying the color of a mixture of two non-white light reflective particles at the viewing surface.