Ricoh utilizes its exclusive Inverted Stack manufacturing process and
new high-precision stamper with its "Advanced SD Dye δ (Delta)
type" recording elements to produce these two-layer discs with the 8.5-GB
capacity, high-reliability recording quality, superior compatibility,
and durability.
Single-layer DVD+R discs have a structure consisting of a substrate + recording layer + reflective layer + substrate. Double-layer discs, on the other hand, require two recording layers and two reflective layers and have a structure consisting of substrate + recording layer 1 + semi-transparent reflective layer + intermediate plastic layer + recording layer 2 + reflective layer + substrate.
In contrast to the “layered system” in which discs are manufactured by stacking all the layers on top of a substrate, the new “inverted stack system” manufactures a disc A consisting of the substrate ~ the semi-transparent reflective layer and a disc B consists of recording layer 2 ~ the substrate, and then adhere these two discs together to make a single disc.
Some advantages of this system are ;
(1) Manufacturing of discs A and B proceeds in parallel up to the adhesion process, so it enables a high volume production.
(2) In the “layered system”, a stamper needs to be peeled off between the formation processes of the two recording layers. This process requires a plastic stamper. The Inverted Stack Manufacturing System, however, can use a regular metal stamper with high durability at lower costs.
(3) Since discs A and B are manufactured independently and adhered at the end of the process, the testing precision can be dramatically improved.
On the other hand, the wobble (spiral grooves), which is required for each recording layer, is created in disc A between the substrate and recording layer in the same way as a single-layer disc. In disc B, on the other hand, the wobble must be created between the reflective layer and substrate. This results in different structures for discs A and B and requires advanced design technology. In addition, the wobble in disc B is located in the farthest point from the pickup, so the disc requires a sharper and more precise groove formation and a high-precision stamper.
Ricoh's exclusive Inverted Stack System overcomes these technical obstacles and provides high-reliability DVD+R DL discs at a reasonable price.
