Choosing Between Halo and Triband Phosphors: Lumens Per Watt, Maintenance, Efficiency Regulations

Each phosphor category has its own set of advantages and disadvantages that make them unique for a variety of application needs.  Here are some things to consider when choosing between halo and triband phosphors.

Tri-band phosphors:  Examples include: Yttrium-oxide: Eu (red); Lanthanum-phosphate: CeTb (green); Strontium-calcium-barium-chlorophosphate: Eu (blue) and others. The 3 types are blended to produce various shades of white (denoted by degrees Kelvin i.e., 3000K, 4100K, 6500K, etc.). 

Tri-band lumen output (lumens per watt) and lumen maintenance is the highest available for any given phosphor color temperature (°K).  Color rendering indices (CRI) are usually 80 to 90.

Advantages: high efficiency (lumens per watt), low depreciation, especially under high load conditions (high current or small diameter tubing), very good color rendering, well matched to LCD displays.

Disadvantages: high cost, non-continuous spectra, the red and green phosphors have “line” spectra, color rendering is not as good as “full spectrum” types.

Best Used For: LCD backlighting, sign lighting, detail lighting, machine vision, cinematography, display lighting, etc.  Situations required by law to meet triband phosphors efficiency regulations such as EPACT for common sizes.

Halo phosphate phosphors – The general formulation is Calcium-Halo phosphate: SbMn (commonly known as: warm white, cool white, daylight, etc.). Different formulations are used to achieve different color targets. The phosphors are used as single components or may be blended with each other or full spectrum types. The lumen output and maintenance is fairly high, although it drops off as the target color is bluer, as in Daylight (5500°K). The CRI for basic halo phosphors is between 50-75.

           

Advantages: low cost, good lumen efficiency, continuous spectrum

Disadvantages: low color rendering particularly in the red region of the spectrum, high depreciation under high loading, efficiency not as good as tri-bands, outlawed in general applications for common sizes by efficiency regulations such as EPACT.

Best Used For:  General home and office lighting (where allowed by Law) and where color rendition is not critical, some machine vision applications, some special task applications

Full Spectrum Phosphors – Examples include Strontium-magnesium-orthophosphate: Sn (orange), Barium-Pyrophosphate: Ti (blue-white) and others are blended to form various shades of white. These can also be blended with halo phosphors to improve the CRI.  The output (LPW) is relatively low, but the CRI is usually 80-99 with a continuous spectrum. The lumen maintenance is somewhat low.

Advantages: can be blended for excellent color rendering near 100 CRI, continuous spectrum, exempt from efficiency regulations such as EPACT, usually lower cost than tri-band types.

Disadvantages:  low lumen output, high depreciation, higher cost than halo phosphate phosphors.

Best Used For: Color matching – paint, textiles, cinema, photography, microscopes, product displays.

This information should be helpful when choosing between halo and triband phosphors. Note that there is many other phosphor types not discussed here ranging from the UVB (285-320nm) to the infra-red (700 – 800nm) region of the spectrum.  These phosphors are used for very special fluorescent applications where more saturated colors are required.

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