US 6,982,110 B2
Information recording medium and manufacturing method thereof
Hisamitsu Kamezaki, Kanagawa (Japan); Yasuo Sawada, Tokyo (Japan); and Yasuhide Fujiwara, Kanagawa (Japan)
Assigned to Ricoh Company, Ltd., Tokyo (Japan)
Filed on May 23, 2002, as Appl. No. 10/155,491.
Claims priority of application No. 2001-157431 (JP), filed on May 25, 2001; and application No. 2001-195243 (JP), filed on Jun. 27, 2001.
Prior Publication US 2003/0007448 A1, Jan. 09, 2003
Int. Cl. B32B 3/02 (2006.01)
U.S. Cl. 428—64.1 13 Claims
OG exemplary drawing
 
1. An information recording medium comprising:
a transparent substrate; and
a recording layer or a metal layer provided on said transparent substrate directly or via a ground layer,
wherein:
said information recording medium has a RAM area on which information is recorded, reproduced or erased, and a ROM area from which only reproduction is made; and
an average thickness of the recording layer of said RAM area is larger than that of the recording layer or metal layer of the ROM area.