Audio Video News

Blu-ray has reached another milestone. The infant format has attracted its first patent lawsuit, reports GameSpot.

Irvine, California-based Target Technology filed suit a few weeks ago alleging that Sony, uh, borrowed the reflective coating used in Blu-ray discs. Does that make Target just another opportunistic patent troll? Not necessarily--the company actually specializes in developing reflective coatings for optical discs.

A little background: All optical discs have pits representing zeroes and ones that are pressed into a plastic substrate. To make the pits visible to the laser, a reflective metallic coating is sprayed on. The aluminum coating used in CD and DVD manufacture is not reflective enough for Blu-ray, whose smaller pits are harder to read. Gold would do it, but that's too expensive. So Blu-ray uses a silver alloy. And that's where Target comes in.

The patent in question was filed in April 2004 and granted in March 2006. It is for a "silver-based alloy thin film [that] is provided for the highly reflective or semi-reflective coating layer of optical discs."

If Sony tries to wiggle out by combining silver with different materials, it may have a hard time finding alternatives. Says the patent: "Elements that can be added to silver to produce useful silver alloys include zinc, aluminum, copper, manganese, germanium, yttrium, bismuth, scandium, and cobalt. These alloys have moderate to high reflectivity and reasonable corrosion resistance in the ambient environment."