Tricolor lamp

Cerium is an essential component in several of the new generation of phosphors in tricolor lamps that have made possible more efficient and more compact fluorescent lighting (31). 

Fig. 6.8. F.misson spectnim of a tricolor lamp with permission from Ref. [3]...

The individual phosphors for the tricolor lamp will now be discussed in separate sections. 

The green-emitting ion in the tricolor lamp is Tb. Its first allowed absorption band is 4/ -> 4/ 5d(Sect. 2.3.4.). It often lies at too high energy to make 254 nm excitation effective. In order to absorb the 254 nm radiation efficiently, a sensitizer has to be used. For this purpose the Ce ion is very suitable. Its 4/-> 5dtransition is situated at lower energy than the corresponding 4/ -> AfSd transition of Tb ". Table 6.1... 

IVible 6.1. Quantum efficiency q for ultraviolet (UV) and visible (VIS) emission for 254 nm excitation of green phosphors applied in the tricolor lamp [3],... 

Tricolor lamps show only emission in restricted wavelength intervals. For objects with a reflection spectrum peaking outside these regions the color appearance under illumination with a tricolor lamp will differ from the one under illumination with a black body radiator. Although a CRI of 83 quarantees a normal appearance for most objects, some typical colors will look unnatural under illumination with a tricolor lamp. For certain applications, therefore, a higher CRI is required. Examples of such applications are museum illumination and flower displays. For this purpose special deluxe lamp>s were developed with a CRI of 95. Simultaneously we have to accept an efficacy drop to 65 Im/W [3],... 

The phosphors in the tricolor lamp show another advantage over the halophosphate phosphors, viz. a much better maintenance during lamp life. In Fig. 6.IS the output decrease after 2(KX) hours of burning is plotted as a function of the wall load. The higher stability of the rare-earth activated phosphors is translated into a higher maintenance. The value of the wall load is determined by the tube diameter (see Fig. 6.18). Tricolor and Special Deluxe lamps are now available in a tube diameter of 25 mm, to be compared with the 36 mm of the halophosphate tube. It even proved to be possible to reduce the tube diameter to 10 mm. With this small diameter the discharge tube can be fold up and the compact luminescent lamp is bom. 

Fig. 6.18. Ratio of the lamp outputs after 2000 and 100 hours of burning as a function of the wall load. Crosses are for a halophosphate lamp, circles for a tricolor lamp. Commercial lamp diameters are indicated. Reproduced with permission from Ref. [3]...

Diglycol/CHDM/isophthalates/SIP copolymer sunscreen protectant, skin care Hydrolyzed lupine protein sunscreen vehicle, creams C12-15 alkyl benzoate sunscreen vehicle, oils C12-15 alkyl benzoate sunscreen, anti-UV-A Pansy (Viola tricolor) extract sunscreen, cosmetics TEA-salicylate sunscreen, topical p-Aminobenzoic acid Cinnamal sunscreening agent, cosmetics Guanine Homosalate suntan lamp monitors Thallium (I) chloride suntan lotions 3-Methylumbelliferone suntan preps. 

As discussed previously, Eu -doped Ms(P04)3X (M = Ca, Sr, Ba X = F, Cl, Br) phosphors generally show efircient blue emission, which can he used in tricolor fluorescent lamps and LEDs [53]. Except for this, it was interestingly found that Ba5(P04)3Cl Eu and Ba5(P04)3Cl Eu % Ce " can be used as long-persistent phosphors, but their afterglow intensity is very weak. The persistent luminescence of Ba5(P04)3Cl Eu, was enhanced with co-dopants La ", Ce ", Gd, Tb -", and Lu ... 

A prediction was made in early 1970s that a luminescent lamp with a high efficiency and high light quality could be obtained by combining three phosphors (luminescent materials) which emit in narrow wavelength intervals centered around 450 nm (blue), 550 nm (green), and 610 nm (red). Immediately, it was clear that phosphors doped with lanthanide ions were the most obvious choice to construct this tricolor luminescent lamp. 

---