Townsend & Townsend
Polishing sheet material and method for its production
 A process and product by process of making a polishing sheet material especially useful in the polishing of silicon wafer is disclosed. There is known a process of producing a poromeric suede-like polyurethane layer which comprises applying a solution of polyurethane on an impermeable synthetic resin film, subjecting the polyurethane layer to wet coagulation to form a honeycomb-like cellular structure of polyurethane on the synthetic resin film, removing the synthetic resin film from the cellular polyurethane layer, and abrading a thin surface skin of the cellular layer to form the poromeric suede-like polyurethane layer. In the present invention, a supporting layer made of a non-poromeric, soft synthetic resin sheet having good flatness is joined to a reverse side of the suede-like polyurethane layer to form a polishing sheet material. 
B B H Y Y H Y B Y B A B Y B
B29L B24D H01L Y10T Y10T H01L Y10T B29K Y10S B29C A47L B24D Y10T B24B
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Shinichi Tsuguji
Watanabe Kimura