Flynn, Thiel, Boutell & Tanis, P.C.
Optical disk
 An optical disc having a transparent substrate, being recordable with a signal (s) by irradiating recording light at the side of the transparent substrate thereof, comprises a cover sheet being attached on the transparent substrate at a surface side for incidence of recording light and reproducing light, in detachable manner, wherein the stretching rate of the cover sheet is selected to be equal or less than 200%. Further, the thermal contraction rate of the cover sheet is selected to be equal or less than 1.5%, and the bonding force thereof onto a surface of the transparent substrate per 25 mm width to be from 10 g/25 mm width to 300 g/25 mm width. Thereby, the curve on the optical disc can be suppressed, if it is attached with the cover sheet of the surface of the transparent substrate thereof. 
Taiyo Yuden Co., Ltd.
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Yuaki Yuji Hideaki
Shin Arai Ito