1986 Philips MHW-TD 70W

Although research efforts on tin halide lamps were quite significant at Philips during the 1970s, it was Osram that developed a tin-based salt fill formulation that would have a tremendous impact on the lighting market. This innovation, patented in 1978, is the combination of the NTI salt mix (i.e., Na, Tl, In) with tin halides, complemented with a lithium additive. This fill chemistry enabled compact low-wattage discharge lamps emitting a pleasant warm-white light with a good color rendering. At that time, engineers at Philips focused more on applications such as light/image projection and medium/high bay lighting, and as a result they missed entirely on lamp design opportunities investigated at Osram. While the Dutch eventually released their own tin halide lamps in the form of compact short-arc sources in 1981 (i.e., the SN) in order to cater for the small image/video projection market, Osram introduced its tin-filled warm-white HQI-TS 70W/WDL the following year.

Osram’s HQI-TS lighting system was an instant success in the large retail lighting market because the technology provided an energy-efficient solution to the ubiquitous tungsten-halogen lamp. The demand was so significant that it took Osram four years to develop a manufacturing capacity suitable to the needs of the new market they opened to itself. As a result of this success, Philips began developing its own variant of the HQI-TS in the early 1980s. At that time the two companies exchanged lamp technologies via a patent license agreement, and the Dutch simply applied Osram’s design principles for their own lamps, which shortened the development time considerably. The consequence is that the same Na-Tl-In-Li-Sn halide mix was used, and the burner design was similar, logically leading to similar lamp characteristics. The result is the present MHW-TD, which was the first compact low-wattage metal halide lamp mass produced by Philips.

Philips effectively entered the compact low-wattage HID lamp market (essentially for retail lighting) with this MHW-TD 70W in 1986. The Dutch had an earlier unsuccessful attempt in 1984 with the MHN 150W designed with a standard elliptical jacket and with a Na-Tl-Tm fill chemistry, but the lamp did not prove successful. In 1986 Philips essentially offered the same range of compact double-ended metal halide lamps as Osram, with one warm-white 70 W MHW, which was produced in Turnhout, Belgium, and two neutral-white MHN lamps in 150 and 250 W which were initially outsourced from Osram, until 1989 when the Dutch company began manufacturing these lamps at its HID mother factory in Turnhout, Belgium. This marked the beginning of a true success story for Philips as this company would eventually grow to become the leader in the commercial and retail lighting market following their development and release of the first successful ceramic metal halide lamp in the Autum of 1994.

Philips continues to produce the MHW-TD to this day as a low-cost compact metal halide light source, and while the same fill chemistry is still being used, the lamp design has changed slightly in order to reduce production costs. The present model, being or a very early kind, is made with an undoped quartz glass material which is transparent to shortwave radiations. As a result, the lamp emits a significant amount of UV light and generates ozone during its run up phase. For this reason, such early lamps were required to be used behind a protective glass, mainly to limit the color fading of illuminated merchandises. This issue was eventually solved around the mid-1990s with the release of doped quartz in those general lighting lamps (technology used since the 1980s in specialty HID lamps).