HPL-Comfort High Colour Rendering Lamp
Philips developments in mercury fluorescent lamps began in 1937 with the HPL300, employing sulphide phosphors to increase red ratio from 1 to 4%. In 1950 these were replaced by a new HPL lamp using arsenate phosphors to achieve 7.5-9% red. This was superseded in 1968 (HPL-N) using Sylvania's 1964 development of vanadate phosphors, featuring 11% red, 10% higher efficacy and a whiter colour.

Efforts then focussed on reducing the colour temperature to achieve a warmer light for indoor lighting. The first step was Philips' HPL-Deluxe lamp of 1972, delivering 3300-3700K with 14-16% red. This was achieved by enlarging the phosphor particles from 1.8 to 6.8 microns, permitting a thicker coating to achieve a greater red conversion while reducing light absorption. The result is a more efficient lamp with better colour rendering. However its popularity was limited due to the fact that it had a distinctly pinkish hue.

In 1983 this problem was solved in the HPL-Comfort lamps, which in effect combine the efficient HPL-Deluxe phosphors with YAG:Ce from the Sylvania Warmtone lamp, which was inefficient but did have a good warm white colour. The yellowish body colour of the latter phosphor is responsible for weakening the mercury blue lines to push the colour point back to the blacbody locus. Ordinarily this phosphor has a blue-green radiation which would be undesirable, but at the high bulb temperatures its output is shifted to orange. HPL-Comfort thus offers a higher efficacy than standard vanadate-coated lamps, with a lower colour temperature, higher CRI and a white light on the blackbody locus. This development swiftly rendered the earlier 'deluxe' lamps obsolete, but has not displaced the ubiquitous vanadate lamps on account of the higher cost of the YAG material.
Manufacturer: N.V. Philips Gloeilampenfabrieken
Lamp Power: 80 Watts
Lamp Voltage: 115 Volts
Lamp Current: 0.80 Amps 1.20A staring current
Cap Type: E27/27 Nickel Plated Brass
Bulb Type: E-70 E-22 in eighths/inch
Bulb Finish: YVO4:Eu,Tb + YAG:Ce Soda-lime
Electrodes: Backwound Tungsten BaCO3-CaCO3-Y2O3 emitter
Arc Length: 21 mm 13/16 inches
Atmosphere: Hg 15mg + Ar 35 torr Outer: Nitrogen
Luminous Flux: 4,000 lm @ 100h
Luminous Efficacy: 50 lm/W @ 100h
Colour Temperature & CRI: CCT: 3500K CRI: Ra 57
Chromaticity Co-ordinates: CCx: 0.400 CCy: 0.380
Rated Lifetime: 28,000 hrs to 50% survival
Warm-up & Re-strike Time: 5' to 80% flux
Burning Position: Universal  
Overall Length: 155mm 61/8 inches
Light Centre Length: 99mm 37/8 inches
Factory: Turnhout Belgium
Date of Manufacture: October 1993 3K
Original / Present Value: £16.06 (1995) £18.99 (2002)
References: 1) Philips Training Manual MTO Turnhoutlampen, Hogedruk-Kwiklampen, Van der Stap & Goethals, 1986, pp. 11-12 en 48.
2) Philips Booklet "High Pressure Mercury Vapour Lamps", April 1986.
3) Philips UK Lighting Catalogue, 1993/94.
4) Philips UK Price List, December 1995.