The secret to Flexplay discs is an extra layer added to a standard DVD structure. This specialized layer includes a chemical compound that readily combines with oxygen in the atmosphere to form a new chemical compound.
While the original chemical compound is transparent, the new chemical compound is opaque. When the layer is transparent, the laser passes straight through to the reflective layers, reading the DVD as it normally would. When the layer is opaque, the laser can't make it to the inner reflective layer, so the disc is effectively blank to the DVD player.
The disc comes in an airtight package, so oxygen can't get to the additional layer. When you open the packaging, the oxygen in the atmosphere starts a chemical reaction. The particular chemicals are balanced so that the reaction proceeds very slowly at first, during the "rental period," and then speeds up. When the reaction speeds up, the specialized layer goes from clear to cloudy. By varying the exact chemical mix in the this added layer, Flexplay can adjust the length of the rental period.
The airtight package slows the reaction down to the point that the DVD will remain fully functional for at least a year.
You can actually see the process at work in the disc. When you first open the airtight package, the disc has a reddish color. When the compound changes, the red color turns to black.
To make these modified DVDs easy to mass produce, Flexplay needed a way to add the specialized layer without overhauling the standard manufacturing process. As we saw in the last section, the two data tracks start out on two separate discs, which the manufacturing machinery bonds together with resin adhesive. To make a Flexplay DVD, the disc manufacturers replace the normal adhesive with Flexplay's proprietary adhesive. This adhesive hardens to form the specialized plastic layer that clouds up over 48 hours.
It's anybody's guess how far this technology will go. The program doesn't have to edge out traditional video stores to be a success -- it simply needs to find a core audience who prefer its unique rental system. Only time will tell.
For more information about Flexplay DVDs and related technologies, check out the links in the next section.
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