Particles for electrophoretic displays

Particles comprising an organic or inorganic pigment core particle encapsulated by a polymer having monomer units of

• a) at least one monomer,
• b) at least one polymerisable ionic liquid of Formula (I) or at least one polymerisable ionic liquid of Formula (II)
• X1—R1-A1−C1+ Formula (I)
• X2—R2—C2+A2− Formula (II)
• wherein X1 and X2 are a polymerisable group, R1 and R2 are a spacer group, A1− is an anion selected from borate, imide,phosphate, sulfonate, sulfate, succinate, naphthenate, or carboxylate, and C1+ a cation selected from phosponium, sulfonuim, oxonium, ammonium, uranium, thioronium, guanidinium or heterocyclic cations, wherein if C1+ is an ammonium cation [NR4]+, R is a straight-chain or branched alkyl having 4-20 C atoms, and wherein A2− and C2+ are as follows:
• C2+
• A2−
• c) optionally at least one polymerisable dye, and
• d) optionally at least one polymerisable steric stabiliser
• and the particles comprise at least one surfactant, wherein if C1+ is a heterocyclic cation it is of the following formula:
• wherein
• R1′to R4′each, independently of one another, denote
• a straight-chain or branched alkyl having 1- 20 C atoms, which optionally can be partially fluorinated, but not in α-position to hetero-atom, and which can also include oxygen or/and sulfur atoms in any positions in between carbon atoms;
• saturated, partially or fully unsaturated cycloalkyl having 5- 7 C atoms, which may be substituted by alkyl groups having 1-6 C atoms,
• where the substituents R1′, R2′, R3′and /or R4′ together may also form a ring system.