Reversible image display medium and image display method

A reversible image display medium comprising:

• two sheets opposed to each other with a predetermined gap therebetween;
• one or more developer accommodating cells formed between said two sheets, and each having a periphery surrounded by a partition wall;
• dry developer contained in each of said cell(s);
• an electrode formed on an inner surface of one of said sheets;
• and
• an electrode formed on an inner surface of the other sheet, and opposed to said electrode, wherein
• said dry developer contains at least two kinds of frictionally chargeable dry developer particles having different chargeable polarities and different optical reflection densities.

A reversible image display medium comprising:

• two sheets opposed to each other with a predetermined gap therebetween;
• one or more developer accommodating cells formed between said two sheets, and each having a periphery surrounded by a partition wall;
• and
• dry developer contained in each of said cell(s), wherein
• said dry developer contains at least two kinds of frictionally chargeable dry developer particles having different chargeable polarities and different optical reflection densities,
• each of said sheets has a thickness from 5 μm to 100 μm,
• the gap between said sheets is in a range from 20 μm to 300 μm, and
• said medium has a whole thickness of 30 μm to 500 μm.

A reversible image display medium comprising:

• two sheets opposed to each other with a predetermined gap therebetween;
• one or more developer accommodating cells formed between said two sheets, and each having a periphery surrounded by a partition wall;
• and
• dry developer contained in each of said cell(s), wherein
• said dry developer contains at least two kinds of frictionally chargeable dry developer particles having different chargeable polarities and different optical reflection densities, and
• at least one of said two sheets has a surface resistance of 1010 ohm/□-1016 ohm/□ on its outer surface.

A reversible image display medium comprising:

• two sheets opposed to each other with a predetermined gap therebetween;
• one or more developer accommodating cells formed between said two sheets, and each having a periphery surrounded by a partition wall;
• and
• dry developer contained in each of said cell(s), wherein
• said dry developer contains at least two kinds of frictionally chargeable dry developer particles having different chargeable polarities and different optical reflection densities, and
• at least one of said two sheets has a surface resistance of 107 ohm/□ or less on its outer surface.

A reversible image display medium comprising:

• two sheets opposed to each other with a predetermined gap therebetween;
• one or more developer accommodating cells formed between said two sheets, and each having a periphery surrounded by a partition wall;
• and
• dry developer contained in each of said cell(s), wherein
• said dry developer contains at least two kinds of frictionally chargeable dry developer particles having different chargeable polarities and different optical reflection densities, and at least one kind of the developer particles are electrically nonconductive particles.

A reversible image display medium comprising:

• two sheets opposed to each other with a predetermined gap therebetween;
• one or more developer accommodating cells formed between said two sheets, and each having a periphery surrounded by a partition wall;
• and
• dry developer contained in each of said cell(s), wherein
• said dry developer contains at least two kinds of frictionally chargeable dry developer particles having different chargeable polarities and different optical reflection densities, and at least one kind of the developer particles are magnetic particles.

A reversible image display medium comprising:

• two sheets opposed to each other with a predetermined gap therebetween;
• one or more developer accommodating cells formed between said two sheets, and each having a periphery surrounded by a partition wall;
• and
• dry developer contained in each of said cell(s), wherein
• said dry developer contains at least two kinds of frictionally chargeable dry developer particles having different chargeable polarities and different optical reflection densities, and
• a rate Sn/So of an area Sn of a non-image portion with respect to a medium unit area So is in a range from 0.0001 to 0.5.

A reversible image display medium comprising:

• two sheets opposed to each other with a predetermined gap therebetween;
• one or more developer accommodating cells formed between said two sheets, and each having a periphery surrounded by a partition wall;
• and
• dry developer contained in each of said cell(s), wherein
• said dry developer contains at least two kinds of frictionally chargeable dry developer particles having different chargeable polarities and different optical reflection densities, and
• a value of (1−Sa/Sb) in a range from 0.0001 to 0.5 is obtained from arbitrary one of said developer accommodating cell(s) or arbitrary two or more successively arranged developer accommodating cells, assuming that Sa represents an area of an image display region provided by said one developer accommodating cell or said cell group including the plurality of successively arranged developer accommodating cells, and Sb represents an area surrounded by a center line of the partition wall defining an outer periphery of said one developer accommodating cell or an area surrounded by a center line of the partition wall defining an outer periphery of said cell group including the plurality of developer accommodating cells.

A reversible image display medium comprising:

• two sheets opposed to each other with a predetermined gap therebetween;
• one or more developer accommodating cells formed between said two sheets, and each having a periphery surrounded by a partition wall;
• and
• dry developer contained in each of said cell(s);
• and
• a developer movement suppressing member arranged between said two sheets for suppressing movement of said dry developer within said developer accommodating cell(s), wherein
• said dry developer contains at least two kinds of frictionally chargeable dry developer particles having different chargeable polarities and different optical reflection densities.