Ricoh utilizes its exclusive Inverted
Stack manufacturing process and new high-precision stamper with its "Advanced
SD Dye d (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.
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