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lydmann
Joined: 12 Aug 2006 Posts: 56 Location: Norway
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Link Posted: Sun Jan 29, 2017 7:06 pm Post subject: |
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I want to salute cmjohnson. Because you try, and you push for improvement. And KAL should support you for holding this forum alive! Be positive to people KAL. We need cmjohnson
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xmob135lc
Joined: 15 Sep 2012 Posts: 80
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Link Posted: Sun Jan 29, 2017 10:29 pm Post subject: |
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The only way I can see this work if all three tubes are made with the same dark UV emitter ,
and the RGB QD are 1-1-1 outer layer (film) with absorption tuned to dark UV (~ 430 nm).
Then if the dark UV layer is stable , you don't have to worry about R-G-B misbehaving is seperate ways, even better the outer layer can be replaced with new crops .
Such high tech dark UV material is Srl2:Eu (Strontium Iodide), and it's sort of developed for heavy bombardment, and high resultant light output .
http://rmdinc.com/wp-content/uploads/2012/10/SrI2-Properties-Performace-Sheet.pdf
Quite possibly it still has enough light output so if you use band pass filter centered at 460nm there is enough output to get away without blue QD layer, (while it can lit up red/ green QD-s forcefully with the 430nm peak).
I don't think RGB QD when subjected to electron bombardment are anywhere near as stable, plus they used to tune commercial QD for UV absorption.
You can test this with an ordinary blue tube BTW. Then extrapolate how powdered Srl2 has exponentially better output.
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cmjohnson
Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s
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Link Posted: Mon Jan 30, 2017 1:32 am Post subject: |
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So what you're proposing is basically a two layer phosphor, the inner layer being a UV emitter, and the outer layer being a phosphoro that fluoresces red, green, or blue when bombarded with UV.
Interesting. I have no doubt that this COULD work. But performance would be unknown until proven, and I suspect that you
have just doubled the cost of the tubes.
Note how QD displays work. It's an LCD display with the LCD backlight being pure blue. It shines on a QD sheet which generates RGB in the form of very unform white light. This creates a pure white backlight for the LCD panel to work with. You do not directly see the colored outputs of the quantum dots, you see the white light of them being filtered thru the built-in RGB sub-pixel filters in the LCD panel. Note, the blue light is directly from the LED driver panel, while only the red and green are actually derived from quantum dots.
I'm simply not at all sure about the stability of quantum dots if used in place of conventional phosphors in a CRT. It may be that
they do degrade when you hit them with 34.9 KV. But as I've read, quantum dots are reportedly very stable and don't easily break down. So I don't really know there.
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xmob135lc
Joined: 15 Sep 2012 Posts: 80
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Link Posted: Mon Jan 30, 2017 2:23 am Post subject: |
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Technically QD-s have not much to do with pure white (usually) ,or phosphors, rather with crystals, because the color these emit actually depends on the size of the particle ,and the reason these are so expensive is because both the particle size and wavelength they emit is uniform , and manufacturers have to go lengths to keep tolerance, so actually it's peaky spectra (so maybe you should ask for some "bad" batch, for a song, and suspend it in some gel, & in theory you could "cook" such "bad batch" QD-s too, in this application tolerance is not important ) . In papers I saw (about microLEDs coated with QD) , they expect around 10.000hours and efficiency dropped 50% in 24 hours. Standard LED stuff used to be 20-40% over >10.000.
(Current blue /450 nm) : The photon yield for ZnS(Ag) is ≈ 26,000 photons/ MeV
(Proposal / 430 nm ) : Srl2:Eu Light Yield 80,000 ph/MeV
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cmjohnson
Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s
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Link Posted: Mon Jan 30, 2017 3:59 am Post subject: |
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What I was saying is that QD flat panels use what is effectively a pure white backlight that consists of blue LEDs driving red and green QDs, and some of the blue light is also mixed into the backlight, which is what creates the pure white backlight that the LCD panel is illuminated with.
QD phosphors by themselves are intrinsicially very monochromatic with the size of the QD particles being the primary determinant of their emission color. And they're TINY, smaller than a virus.
It's also surprisingly easy to make some forms of quantum dots. There are youtube tutorials on how to make them which do not
require a large investment in supplies or equipment. However, none of them define how to turn QDs in liquid solution into a QD phosphor powder suitable for mixing with a binder and painting onto the inside of a CRT's faceplate.
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xmob135lc
Joined: 15 Sep 2012 Posts: 80
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Link Posted: Mon Jan 30, 2017 12:37 pm Post subject: |
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Most of white light in LCD-s comes from GaN blue led and YAG:Ce phosphor cap. Then they use QD-s to make it peaky cause the former combination gives broad spectra.
In LCD-s if they don't have W subpixel they have no reason to to make pure white, they can just offset subpixel values.
Well youtube stuff doesn't sound like "current crop" with stable and long lifetimes .
BTW just checked , the strontium iodide crystal has apparently 30% more light output than P43 green, quite a thing given P43 has scattering .
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xmob135lc
Joined: 15 Sep 2012 Posts: 80
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Link Posted: Wed Feb 08, 2017 2:02 am Post subject: |
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http://www.hellma-materials.com/html/seiten/output_adb_file.php?id=63
here they denote significantly higher value to strontium crystal, 100% more than P43.
Apparently if you turn such a single crystal into a powder it has the same properties, as in single crystal form .
Another benefit is the same RGB decay. I think quantum dots have decay on order of tens of nanoseconds on the other hand this one is multiple microseconds, so ,
If this makes 48p / 60p better I would buy such a set (twice).
Last edited by xmob135lc on Wed Feb 08, 2017 9:07 am; edited 1 time in total
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gjaky
Joined: 05 Jun 2010 Posts: 2789 Location: Budapest, Hungary
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Link Posted: Wed Feb 08, 2017 8:34 am Post subject: |
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xmob135lc wrote: |
here they denote significantly higher value to strontium crystal, 100% more than P43.
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But P43 is not the standard phosphor and is known for less output than standard.
_________________ projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
current: VDC Marquee 9500LC
The MOD: VNB-DB, VIM-DB
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xmob135lc
Joined: 15 Sep 2012 Posts: 80
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Link Posted: Wed Feb 08, 2017 8:59 am Post subject: |
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gjaky wrote: | xmob135lc wrote: |
here they denote significantly higher value to strontium crystal, 100% more than P43.
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But P43 is not the standard phosphor and is known for less output than standard. |
P22 also has the inexcusable flaw: afterglow .
Probably the difference between rare earth p43 and standard green is less than what 34kv vs. 40kv anode voltage would make & in case of new tubes, and this late in the CRT game ,I think latter would be preferable in a stationary projector, because electrons would go significantly deeper into the powder (also the binder counts here), that could give even >15-20% more afterall (especially if the binder is a good choice).
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cmjohnson
Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s
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Link Posted: Wed Feb 08, 2017 11:40 am Post subject: |
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If I win a lottery and end up with more than a million dollars in disposable income after setting up a suitable retirement/sustainment fund, then I'll invest in a CRT phosphor research project including small scale production capacity.
I doubt it'd fly as a crowdfunded project but maybe I should try?
Really I may try that just for the fun of it.
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xmob135lc
Joined: 15 Sep 2012 Posts: 80
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Link Posted: Wed Feb 08, 2017 12:31 pm Post subject: |
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The reason there shouldn't be fun, but some kind of convoluted means of getting people to participate even if they don't necessarily need the physical goods at all or on the near term.
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lydmann
Joined: 12 Aug 2006 Posts: 56 Location: Norway
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