Impact of production transfer on Philips HPL4 characteristics

In 2003 Philips introduced the HPL4 Pro, a series of high-end mercury fluorescent lamps in the 50-125 W range, aimed specifically at the European market. Those lamps benefited from improvements in processing, material quality, manufacturing methods and better phosphor blends which resulted in unparalleled (in their lamp class) reliability, efficiency and light color quality. Those lamps were available in two colors: neutral-white /642 and warm white /634. The latter replaced the company's HPL Comfort. Those lamps were initially assembled at Philips's Weert factory in the Netherlands, with the burner production in Turnhout, Belgium, and when the Weert plant closed at the end of 2006, the whole production was transferred to Malu, Shanghai, in China.

Some corners were cut in this process in order to further reduce costs, which resulted in properties changes of the mercury lamps. The impact is most visible in the light color, shown for a 50 W /634 type in the picture above, with the Dutch variant on the left. This color change is the result of an altered phosphor, which consists of blend of red-emitting yttrium vanadate phosphate borate material and orange-emitting and blue-absorbing yttrium aluminum garnet (YAG). What we see on the right is clearly the result of a reduced YAG content, which translates into a cooler light color with a slight pinkish hue (Philips still specified this as color /634). The production of those lamps eventually ceased in April 2015 when the import and manufacturing of high-pressure mercury lamps was banned in Europe.