| 摘要 |
PURPOSE:To increase holding force for abrasive grains so as to improve tensile strength, heat-resistance and moisture resistance by dispersing abrasive grains having a specific grain size uniformly into aromatic polyimide having heat- resistance. CONSTITUTION:Abrasive grains of such as cubic boron nitride having an average grains size of 0.1-60mum, preferably 0.5-40mum, are dispersed uniformly and enclosed into heat-resistant aromatic polyimide with mixing ratio of 0.5-50vol.% to form a polishing sheet in the form of thin flexible film having the thickness of 5-200mum, preferably 20-150mum. Here, the aromatic polyimide is obtained by polymerizing and imidizing the equal moles of aromatic tetracarboxylic acid component containing principally pyromerit acid or anhydride thereof and aromatic diamine component. A flexible sheet formed in such a manner has excellent tensile strength, heat-resistance, moisture-resistance and medicine- resistance.
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