| 摘要 |
A first polymerizable composition is poured into a pipe (30), then is polymerized to be a first layer (13). Next, a second polymerizable composition is poured into the pipe (30) and polymerized to be a second layer (14). These pouring and polymerizing processes are repeated to form an optical medium (10) including n-layers of polymer. Each layer is formed by polymerizing the polymerizable composition comprising same kinds of plural polymerizable contents as those in other polymerizable compositions for other layers. The layer at the inner side is formed from the polymerizable composition including larger ratio of a polymerizable content which has higher refractive index than that of at least another polymerizable content in the same polymerizable composition, compared with the polymerizable composition for forming the adjacent layer at the outer side. A difference of refractive indices between adjacent two polymer layers is at least 5×10−5 but less than 5×10−3.
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