Stamper plate mounting device of an injection mold for making an optical disc substrate

A stamper plate mounting device of an injection mold for making an optical disc substrate, the mounting device including a first cavity plate having a central hole in a surface thereof symmetrically located with respect to a longitudinal axis, at least a portion of the first cavity plate adjacent the central hole being ferromagnetic;

• a second cavity plate facing the first cavity plate to form a cavity therebetween, one of the first and second cavity plates being movable with respect to the other cavity plate;
• and a stamper plate having an aperture therein, an inner circumference of said stamper plate defining the aperture;
• comprising
• holding means having a first end fitting within the central hole and a second end, said second end having a flange for holding the inner circumference of the stamper plate against the first cavity plate, the aperture in the stamper plate being substantially coaxial with the central hole of the first cavity plate;
• and
• a magnet embedded in one of (a) the first cavity plate adjacent the first end of said holding means, and (b) the first end of said holding means, said magnet having magnetic poles extending in a direction parallel to the longitudinal axis, the stamper plate being drawn by said holding means toward the first cavity plate due to a magnetic force generated by the magnet acting on said holding means when the first end of said holding means is within the central hole of the first cavity plate.