| 摘要 |
PURPOSE:To mold a substrate for optical disc, the groove surface of which is concave and, at the same time, the warpage of which lies within the specified range and consequently produce a photomagnetic disc, in which the warpage of the substrate does not exceed the set value, by a method wherein some difference is set between the set temperatures on the fixed side and on the movable side of the mold. CONSTITUTION:When a substrate for optical disc is molded by an injection molder with a stamper, some difference is set between the set temperatures on the fixed side and on the movable side of the mold. Thus, the substrate for optical disc, the groove surface of which is concave and, at the same time, the warpage of which lies within the range of +1.0 to +6.0 mrad, is molded. In this case, the preferable set temperature range of mold under the condition that polycarbonate, which is the molding material for normal injection molding, is used, is 80-130 deg.CC. At the same time, the set temperature on the fixed side is set to be higher than that on the movable side of mold and the preferable range of the difference between the set temperatures is 5-15 deg.CC. Thus, a photomagnetic disc can be produced without developing the warpage of the substrate exceeding the set value. Accordingly, the photomagnetic disc having excellent record reproduction characteristics and favorable productivity can be produced. |
