| 主权项 |
1. A display layer comprising an electrophoretic medium and having first and second surfaces on opposed sides thereof; the electrophoretic medium comprising a first type of particles, a second type of particles, a third type of particles and a fourth type of particles which is additive particles, all dispersed in a solvent or solvent mixture;
the first, second and third types of particles having respectively first, second and third optical characteristics differing from one another; the first type of particles having a charge of one polarity and the second, third and fourth types of particles having charges of the opposite polarity, and the second type of particles having an electric field threshold; such that: (a) application of an electric field which is greater than the electric field threshold and having the same polarity as the second type of particles will cause the second optical characteristic to be displayed at the first surface; (b) application of an electric field which is greater than the electric field threshold and having the same polarity as the first type of particles will cause the first optical characteristic to be displayed at the first surface; and (c) once the first optical characteristic is displayed at the first surface, application of an electric field which is lower than the electric field threshold and having the same polarity as the third type of particles will cause the third optical characteristic to be displayed at the first surface. |
