Particle dispersion for display, display medium and display device

A display medium comprising:

• a pair of substrates, at least one of the pair of substrates being transparent;
• and
• a particle dispersion for display, the particle dispersion for display comprising:
• first particles for display comprising a colorant and a first polymer having a first charging group, the first particles for display being movable in response to an electric field;
• a first polymeric dispersant attached to the first particles for display;
• second particles for display comprising a colorant and a second polymer having a second charging group, the second particles for display being movable in response to an electric field;
• a second polymeric dispersant attached to the second particles for display;
• and
• a dispersing medium in which the first particles for display and the second particles for display are dispersed,
• the first polymeric dispersant and the second polymeric dispersant having different weight average molecular weights so that the first particles for display and the second particles for display start moving upon application of different voltages, and
• the weight average molecular weight of the first polymeric dispersant being at least from about 3 times to about 20 times greater than that of the second polymeric dispersant, or the weight average molecular weight of the second polymeric dispersant being at least from about 3 times to about 20 times greater than that of the first polymeric dispersant.

A display medium comprising:

• a pair of electrodes, at least one of the pair of electrodes being transparent;
• and
• a space formed between the pair of electrodes, the space comprising a particle dispersion for display, the particle dispersion for display comprising:
• first particles for display comprising a colorant and a first polymer having a first charging group, the first particles for display being movable in response to an electric field;
• a first polymeric dispersant attached to the first particles for display;
• second particles for display comprising a colorant and a second polymer having a second charging group, the second particles for display being movable in response to an electric field;
• a second polymeric dispersant attached to the second particles for display;
• and
• a dispersing medium in which the first particles for display and the second particles for display are dispersed,
• the first polymeric dispersant and the second polymeric dispersant having different weight average molecular weights so that the first particles for display and the second particles for display start moving upon application of different voltages, and
• the weight average molecular weight of the first polymeric dispersant or the second polymeric dispersant, whichever is greater, being at least from about 3 times to about 20 times greater than the other.