| 摘要 |
PURPOSE:To enhance cleanability by using magnetic power having such a grain size distribution where peaks of the distribution curve exist at at least two points. CONSTITUTION:The grain size distribution of the magnetic powder has the two peaks of the distribution curve. The grains sizes of the respective peaks exist on both sides of the average grain size of the magnetic powder. More specifically, this magnetic powder is a mixture composed of the magnetic powders of two kinds of the grain size groups; large grain sizes (for example, 200-400mum) and small grain sizes (for example, 40-100mum). The powder which contacts a residual toner 11 of a copying machine on a photosensitive drum 2 is the magnetic powder 12 of the small grain sizes and the contact probability of the toner 11 and the powder increases. Since the part of the ears except at the top end of a magnetic brush is formed of the powder 13 of the large grain sizes, the rigidity of the ears increases. The cleaning performance is thereby improved.
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