A while back i bought a brand new Philips made in poland 33/640 tube. It appears to have a 04-12-24 date print. I put it in storage for a bit.
I went looking for fluorescing color 27 lamps and what caught my eye - this tube!

I expected this to be a 'hidden' modern 930 tube. 930 tubes fluoresce a similar sort of green under 365nm UVA light. After all, i've found 840 tubes stamped as 640 before, so this one might very well be one of such.
But no! The spectrum looks very similar to any old halophosphate tube. The peaky green phosphor as used in a 930 tube is not there. With one difference: the 'emergency use only' tube has a bump at 517nm while other color 33/640 tubes have a bump at 490nm. It must be a different phosphor added to the mix. No other 33/640 tube that i own, fluoresces like this!

Does anyone have an explanation for this? How/why would they change a long running, fine working type of phosphor composition?
The light does not have a immediately visible green hue to it, at least no more ghostly than a color 33 already is usually.

I could imagine that they want to make this lamp especially effective in dimly lit, scotopic vision environments where the standard lighting is gone. Focusing the light energy in the green area would make sense. But this is very much speculation.

Small batch of "non critical performance" lamps, have not flushed the machine from some other phosphor ?

I have some Chinese 36W/765 branded "Electra" (made possibly by one of the Philips factories ? - similar end caps), in the same batch are some tubes with slightly different phosphors (they appear the same lit, but out of 4 tubes 3 have visible phosphorescence when switched off and 1 does not)

And some Chinese 36W/765 Hyundai (made possibly by FSL ?). First those tubes are noticably brighter than some other 765's (though not as bright as 865), their light appears (subjectively) to have somewhat better CRI, and they also have the afterglow. This have been consistent through all Hyundai lamps i seen over the years of different batches

I don't think this is a contamination issue. None of the triphosphor-phosphors show up. I am not aware of any colored tubes being made in 2024. Could be that they are, but i am not aware of it. Did Philips Poland make anything other than emergency lighting stuff in 2024?
I have taken one spectrum from a NEC 3 color r/g/b lamp, and that color green is clearly centered at 530nm, not at 517.

It appears to correspond with the kind of phosphor used in some green 'neon' indicator lights, but because of the low brightness of those and the not so big size of the green peak in the 13w's spectrum, i can't tell for sure.

'Normal' halo mixes do not react to UVA at all, but remember Philips did not promise a halo here, just 640 color. So they may have added some blue-green BAM or whatever rare earth phosphor. May be this lamp has a pronounced afterglow, useful for an emergency light, and actually associated with blue-green strontium aluminate phosphors?

The UVA radiation of emergency tubes is intentional, as many emergency signage paints use "brighteners", compounds that when excited by the UVA radiate in visible and so make them to stand out better. And the UVA emission is intended to excite these pigments.
Plus many signage uses "glow in the dark" pigments, which also get very effectively excited by that UVA.

They did not promise a halophosphate, but i am not aware of pure bi/triphosphor mixtures that dip below a CRI of 80.
The spectrum also 100% looks like conventional halophosphate - with the exception of that green hump. Halophosphates indeed don't react to UVA at all.

With regards to afterglow - i will verify that tonight. Would be an interesting 'last ditch' effort to allow someone to orient themselves in a fully dark room. If that's the case, it warrants a trip back to Aurora-Kontakt to see if their other modern production "emergency lighting" lamps also have that same effect.

Strontium aluminate - that one seems to have a medium-narrow curve, just dumping this link here to try and download it tonight after work: https://doi.org/10.1007/s10854-022-08902-6

The afterglow is not about the lamp itself, but about the various yellow/green/orange stripes and markings in areas like emergency corridors or so (the markings on various obstacles, edges of stairway steps, various safety stickers,...).
The point is, the emergency fixture should not illuminate only in visible, but also in some UVA, so that the safety markings would work as designed when illuminated only by those emergency lights.

The Japanese produced fluorescent lamps with a green glow in the dark coating.

It does not show luminescence, it goes dark instantly when you turn it off.

The spectrum does not show any more UVA than other fluorescent lamps, so it is not specially designed to make dayglo pigments light up. The only reason why 'emergency use only' is printed on it, is because fluorescents here are still allowed to be made for use in emergency lighting fixtures.

If only we had a Philips engineer here who could chime in why that specific phosphor was added to a very cheap lamp, close to the end of that technology being produced at all.

There was also one detail: Pholops had in their offerings "emergency light" F6T5 (dunno the exact marking), especially designed to run on the battery inverters which tend to underdrive the lamps and so makes them suffer for cathode sputtering. It had thinner, lower current filaments, plus maybe few other modifications to run better at the reduced power ballasts.