RLOD#9 (2020.05.13) Late-1970s Philips CFL#110-17 15W

The energy crises of the 1970s has stimulated the development of energy-efficient light sources. One important goal was the replacement of the inefficient standard incandescent lamp, and Philips’s SL, the first commercial compact fluorescent lamp introduced in 1976, was the first step in that direction. This breakthrough was made possible by the development of the narrow-band aluminate phosphors (Philips) and of the mercury amalgam (Philips and Osram). This, combined with a narrow-bore discharge tube filled with a neon-argon buffer, led to a light source with four times the energy efficiency of the incandescent lamp. However, the large physical size of the SL, determined primarily by its folded discharge tube, limited its adoption in the residential market. As a result, research efforts turned towards more compact lamp designs, resulting in interesting concepts such as the one featured here.

What makes the present lamp particularly unusual is the fact that its was not developed at Philips’s lighting division, but at the company’s famous Natuurkundig Laboratorium (NatLab) by W. Wesselink. The lamp has a modular design where the reactive ballast is integrated into the base, while the glow-switch starter (inserted in the E27 end cap) and the fluorescent lamp are detachable parts. The latter is formed by two glass bulbs fused at the rim and provided with two electrode chambers with mercury amalgams. The inner bulb is shaped with grooves that channel the discharge into a compact folded pattern. All parts of the glass envelope in contact with the mercury discharge are coated with a phosphor blend, plus a reflective layer for the inner surface closest to the ballast. Such ingenious design, later optimized by Burgmans and Ijzendoorn (both of NatLab), resulted in a very compact light source, barely larger than a 60 W GLS lamp, emitting 900 lm for a 15 W consumption, 3 W less than the equivalent SL. Unfortunately, this concept was never developed into a commercial product as Philips decided to focus on the newly created PL lamp platform, introduced in 1982 (a product of the lighting division).