McDermott Will & Emery LLP
Reversible image display medium
This invention provides a reversible image display medium comprising two substrates opposed to each other with a predetermined gap therebetween, one or more developer-accommodating cells formed between the two substrates, and a dry developer accommodated in each cell, in which the dry developer contains at least two kinds of frictionally chargeable dry developer particles having different chargeable polarities and different optical reflection densities, the reversible image display medium having at least any of the following features:(1) at least one kind of the developer particles being magnetic particles containing a binder resin having a magnetic substance incorporated therein, the magnetic particles having a saturation magnetization degree in the range of 20 emu/g to 50 emu/g;(2) at least one kind of the dry developer particles has a volume resistivity &rgr; in the range of 1.0&times;1010 &OHgr;&middot;cm to 1.0&times;1014 &OHgr;&middot;cm;(3) the dry developer contains inorganic fine powder as a fluidization agent, the inorganic fine powder having a BET specific surface area of 80 m2/g to 300 m2/g; and(4) the dry developer is accommodated in the cell in an amount of 20 vol. % to 50 vol. % based on the volume of the cell.
Minolta Co., Ltd.
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Takaji Hiroshi Hidetoshi Masahiko Keyaki
Kurita Mizuno Miyamoto Matsuura Yogome