Electro-optic media and writable display incorporating the same

An electro-optic device in combination with a first stylus and a second stylus, the first stylus comprising a magnetic material proximate to a first tip of the first stylus, the second stylus having a non-magnetic tip, the electro-optic device comprising:

• a first surface on a viewing side;
• a second surface on the opposite side of the first surface;
• an electrophoretic medium disposed between a light-transmissive electrically conductive layer and an array of pixel electrodes and comprising a plurality of particles in a fluid, the plurality of particles comprising:
• a first type of particles having a first color, a first charge of a first charge polarity;
• a second type of particles having a second color, a second charge of a second charge polarity;
• and
• a third type of particles having a third color, a third charge of the second charge polarity;
• wherein,
• the first, second and third colors are different from one another;
• the first charge polarity is opposite to the second charge polarity;
• the plurality of particles are configured to migrate within the fluid in a direction responsive to an applied electric field;
• the third type of particles are configured to migrate within the fluid in a direction responsive to an applied magnetic field gradient;
• the second type of particles have an electric field threshold;
• the second type of particles are not responsive to a magnetic field gradient;
• such that:
• (a) application of a voltage potential difference between the light-transmissive electrically conductive layer and a pixel electrode to generate an electric field stronger than the electric field threshold and having a polarity driving the second type of particles adjacent to the light-transmissive electrically conductive layer, will cause a pixel corresponding to the pixel electrode to display the second color at the first surface, wherein the application of the voltage potential may be achieved by contacting the non-magnetic tip of the second stylus on the first surface of the electro-optic device;
• (b) application of a voltage potential difference between the light-transmissive electrically conductive layer and a pixel electrode to generate an electric field stronger than the electric field threshold and having a polarity driving the first type of particles adjacent to the light-transmissive electrically conductive layer, will cause a pixel corresponding to the pixel electrode to display the first color at the first surface;
• (c) once the first color is displayed at the first surface, application of a voltage potential difference between the light-transmissive electrically conductive layer and a pixel electrode to generate an electric field weaker than the electric field threshold and having a polarity driving the third type of particles adjacent to the light-transmissive electrically conductive layer, will cause a pixel corresponding to the pixel electrode to display the third color;
• (d) once the first color is displayed at a first location of the first surface, contacting a first location with the magnetic tip of the first stylus once, causes the third type of particles to migrate towards the first location;
• and
• (e) once the third type of particles migrate towards the first location caused by the contacting of the magnetic tip of the first stylus, contacting again the first location with the magnetic tip of the first stylus using a back-and-forth movement of the stylus, causes the second type of particles to migrate towards the first location.