To enable a high density recording of information and reproducing of the information recorded as such by enhancing the rightangularity between an information recording medium surface and a rotating shaft so that a deflection of the medium surface upon rotating it can be reduced. 情報記録媒体面と回転軸との直角度を高めて、回転時における媒体面の振れを小さくして、情報の高密度記録とその再生を可能にする。 - 特許庁