Composite optical disk with structure for preventing adhesive from leaking into the center hole

A single-side reproduction type composite optical disk structure comprising:

• a first transparent disk plate having a first center hole, a first stamper clamp groove and a first information recording area formed on its one main surface;
• a second transparent disk plate having a second center hole having a diameter equal to that of the first center hole, and a second stamper clamp groove and a second information recording area formed on its one main surface;
• a transparent adhesive sandwiched between said first and said second transparent disk plates to bond the one main surfaces of them;
• a first ring-shaped projection formed on the main surface of said first transparent disk plate so as to surround the first center hole, forming a portion thereof;
• a second ring-shaped projection formed on the main surface of said second transparent disk plate so as to surround the second center hole, forming a portion thereof;
• said first and second projections having an approximately equal height and abutting each other, thereby preventing the adhesive from flowing into the first and second center holes.