| 摘要 |
PURPOSE:To prevent the sharpness of display from decreasing even if air enters a display chamber by providing plural balls made of nonmagnetic bodies fixedly in respective plural display chambers and also charging magnetic particles different in color from those balls, and forming a magnetic thin film on the hemisphere side of each ball which faces its display surface side. CONSTITUTION:Four balls 5 are put in each display chamber 4 and a set of magnetic particles 6 is charged. Each ball 5 is made of a nonmagnetic body of about 2mm in diameter and provided fixedly in a display chamber 4. A magnetic thin film 7 is formed on the hemisphere of the ball 5 and arranged opposite the side of a display plate 2. Further, the magnetic particles 6 are formed by crushing a member with high magnetic permeability such as chromium oxide and ferrite to about 100-150mum and made as spherical as possible.
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