An improved moving particle display device having a plurality of pixels (12, 14; 21, 22, 23, 24) is disclosed. The pixels are formed between first (1) and second (2) substrates that are spaced apart by a plurality of partition walls (10; 20). Each pixel comprises charged particles (115) that are movable under the influence of primary electric field lines of force (16) to set the optical appearance of the pixel. The pixels further comprise blocking material (210) for physically blocking the charged particles from entering predetermined regions (200) of the pixels that are likely to have secondary electric field lines of force (18) that extend through the partition walls. Hence, the charged particles are blocked from entering regions of the pixels having secondary electric field lines of force that could attract the particles to move into any gaps (9) that exist between the partition walls and the substrates.