Patent ID: 7557984

Claim:
An electrophoretic display device, comprising: an electrophoretic capacitor provided with an electrophoretic layer containing at least one kind of electrophoretic particle; and a ferroelectric capacitor provided with a ferroelectric layer containing a ferroelectric material, wherein the electrophoretic particle is allowed to move to conduct a display and thus a polarity of the ferroelectric layer is inverted by a current supply to the electrophoretic capacitor and the ferroelectric capacitor that are electrically connected with each other, and the display can be retained due to a remanent polarization of the ferroelectric layer even after the current supply is stopped; and wherein a formula (A) and a formula (B) are satisfied when a voltage to be applied to the ferroelectric capacitor is V f , a charge stored in the ferroelectric capacitor when the voltage V f is applied to the ferroelectric capacitor is Q f , a relative dielectric constant of the ferroelectric material is ∈ f , an area of the ferroelectric layer in a planar view is S f , a thickness of the ferroelectric layer is d f , a relative dielectric constant of the electrophoretic layer is ∈ EPD , an area of the electrophoretic layer in a planar view is S EPD , and a thickness of the electrophoretic layer is d EPD : ∈ o ·∈ EPD ·S EPD ·V/d EPD >P r ·S f +∈ o ·∈ f ·S f ·E c +∈ o ·∈ EPD ·S EPD /d EPD ·E c ·d f (A), P r ·S f <∈ o ·∈ f ·S f ·E c +∈ o ·∈ EPD ·S EPD /d EPD ·E c ·d f (B).