CurtPalme.com Home Theater Forum

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

You know I love to ask questions and see how far things can be taken.

So I'm doing that.

I have been wondering about the potential for using quantum dot phosphors in CRTs.

So I contacted a QD phosphor manufacturer and spoke to an engineer about QD phosphors and the potential they may
have for being used in a projection CRT.

Basically to make a long story short, the answer is YES, this should be possible as long as the QD phosphor is used with a compatible binder so it sticks to the inside CRT face.

Historically speaking, lacquer is the binder used on conventional CRTs. Whether or not lacquer is compatible with quantum dot phosphors in the usual powder form remains to be seen.

The advantages that quantum dot phosphors promise to us, the CRT community:

1: Greater quantum efficiency. More light output for a given drive current level than conventional phosphors.
This means brighter images. OR, equal light output at a lower drive level. Which by itself would ensure longer tube
life before the lacquer binder begins to turn brown from heat over time. (That is what is actually happening when we see the phosphor start to develop a wear pattern.)

2: Precision selectable color gamut primary points. QD phosphors are available in the precise rec. 2020 RGB primary
wavelengths of 467, 532, and 630 nm. NO FILTER (C ELEMENTS) NEEDED. Or rec. 709 values can be selected.
Or...others.

3: Potential for smaller phosphor grain size, giving the potential for a modest sharpness improvement.

APPARENTLY, but this isn't verified, QD phosphors also don't exhibit the "excite the neighbors" phenomenon like conventional phosphors do. This phenomenon may still exist but it's apparently much reduced in magnitude. This means that the effective beam spot size is smaller, especially at higher drive levels. The picture may stay sharper at higher contrast levels due to this.

I have contacts at one of the remaining CRT manufacturers that still makes projection CRTs of types of interest to us.

Having done the preliminary research, my next step is to contact the engineering staff of that company and submit my
findings to them along with a request for them to perform QD phosphor experiments. If they will agree to this, then
it may open the door to getting something we've never had in our CRT projectors before: True HD or UHD color spaces, (and apparently with far more linear gamma even on blue) higher output, longer tube life, greater sharpness and resolving ability.

Hopefully my conversation with the manufacturer will intrigue them to the point that they agree to take on the experiments
and cover the costs out of their OWN pockets. I am actually willing in principle to contribute some money to cover some
of the costs of this experiment, in exchange for credit toward the purchase of the new QD-equipped CRTs if it gets to that point.

From a manufacturing perspective, in theory all they have to do differently is substitute the QD phosphors for the conventional phosphors. If the QD phosphors are compatible with the existing binder lacquer, then the building of the prototype tubes would be almost routine production. Needless to say, I would be intensely interested in providing
beta (or alpha) testing services regarding the new tubes, and of course, at no cost to the manufacturer. Provided I get to keep the tubes.

IF this idea works out, then it has potential to slightly revitalize the CRT side of the projection market. Although I do not pretend to believe that this would cause anybody including VDC to restart Marquee production, it would give many CRT enthusiasts quite a good reason to hang onto their existing projectors and get the upgraded CRTs.

So that's my latest hare-brained scheme. Feel free to comment.

Rec. 2020 RGB primaries:
•
Based on NHK’s Super Hi
-Vision
–
Preserves hue of primaries with smaller
gamuts

•
The widest TV color gamut standard
with physical primaries
–
RGB
primaries equivalent to
monochromatic light (467nm blue, 532nm green,
630nm red

**AnalogRocks** · Posted: Thu Jan 26, 2017 4:42 am Post subject:

Is there a binder that is non-yellowing? This would be a big step in the right direction too.

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

JVC uses a phosphor wheel in its latest D-ILA projectors (laser phosphor illuminator) that uses a non-organic binder.

This may be patented, and I don't have any further information on it. But it has potential.

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

GOT IT!!!

https://www.google.com/patents/WO2013144777A1?cl=en

gjaky · Joined: 05 Jun 2010 Posts: 2790 Location: Budapest, Hungary

Do we know how this stuff reacts for X-rays?

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

That would be something that would be learned about in the process of development.

Something tells me that x-rays will not alter quantum dot phosphors.

jbltecnicspro · Joined: 23 Apr 2016 Posts: 512

Wow, if this even goes anywhere then it will be such an awesome thing for sure. I would LOVE to see direct-view CRT monitors come back in full swing too, but then I'm getting carried away.

jbmeyer13 · Joined: 03 Dec 2010 Posts: 1135

The real question is the cost and difficulty of building these. How much would a tube manufacturer have to adjust their manufacturing processes to accomodate these unique tubes? I don't mean the materials but the actual production line. Regular VDC tubes with magnetics are something like $1,500/each and I would guess that like most anything else with manufacturing, larger production runs reduce costs. Then again there probably not producing many tubes nowadays so that could potentially work in favor of something like this.

If we are going to talk fantasy want list then what I'd like are laser based 16:9 phosphor tubes. Super small beam spot size; precise beam control and when coupled with modern electronics could create a 4K image.

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

Actually, CRT manufacture for projection tubes is pretty much all hand work. There are videos on youtube showing how CRTs are made and a projection CRT is built just like a monochrome (black and white) tube in every way that matters.

The phosphor is in a solution that is poured by hand into the tube, permitted to settle for a defined time, and then the excess is poured off. It's then heated to drive off the volatiles and after that, aluminization is performed then the tube is put together.

Switching over to QD phosphors could literally be as simple as reaching for a bottle of a different phosphor solution, with no other process changes.

If that is the case, the only the higher cost of QD phosphors would drive a cost increase. I do expect that QD phosphors are more expensive, but by how much I can't say.

It would be FAR more expensive to retool for making 16x9 aspect ratio tube glass.

A QD phosphor upgrade is most likely to be the only projection CRT upgrade that has any realistic chance of even being considered at this stage. But I think that the benefits provided by it, if PROVEN to be real, would be well enough received to be worth doing
and extend the life of many remaining CRT projectors. I am sure that there are CRT enthusiasts who would buy a set of QD phosphor equipped tubes if the promised benefits turn out to be real. Higher output, longer tube life, expanded color gamut, maybe better definition, I think that's enough to push some tube sales.

**kal** · Posted: Thu Jan 26, 2017 10:34 pm Post subject:

Who still makes 9" CRT tubes today for the projectors that people care about like Barco Cine 9 / 909, Sony G90, and the Marquee 9500 series?

Kal

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

Two companies, Lexel Imaging in Kentucky, a VDC company, and Mikado Seisakusho of Japan.

Both are making CRTs today and if you order new tubes from VDC they'll be made by Lexel.

So, while I won't bet my life savings on this, there IS a chance that QD phosphor CRTs for our projectors could actually be made.

All it requires is a commitment on the part of either company to simply make a few prototypes for a relative handful of dollars, and see if the results are marketable.

**kal** · Posted: Thu Jan 26, 2017 10:53 pm Post subject:

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

I'm going to just tell you that I've spoken to engineers at Lexel fairly recently and the process of evaluating a change as simple as a phosphor change is much closer to what I have suggested than what you have suggested. Of course they would have to make some tubes to be tested in various ways for various aspects of performance but it's hardly anything like designing and testing a new stereo or even a completely new CRT or electron gun assembly.

It comes as no surprise that I am quite willing to volunteer to test prototype tubes in a real world viewing environment, should
they decide to build some samples for testing.

If you don't think this will come to anything, that's fine, you may be right, but taking the role of naysayer in this discussion is frankly pointless and serves no useful purpose. Your input really is not going to change the outcome as you are not part of the evaluation process in any way until and unless you are given the opportunity to be an alpha or beta tester for a hypothetical QD phosphor equipped tube and you accept.

Lexel may ignore my suggestion. They may say "We could do it but we're not interested, go talk to Mikado if you want to.". Or they may say "We'll try it but we need you to pay the up-front costs for purchasing the QD phosphors". (Doubt that.) Or they may say "We'll try it. Want to be our field tester when we make a set?". Or something else.

But you attacking the idea isn't going to change any of this. What will happen, will happen.

**kal** · Posted: Thu Jan 26, 2017 11:35 pm Post subject:

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

Raw tubes from VDC have been quoted to me for $1068 each for P19LUG types. I can get Mikados for $1250 from a company
that I've gotten tubes from recently. They do simulation support and order direct from Mikado.

Red and green tubes from both vendors seem to be equal. I have seen some blue Lexels with white spots in the illuminated phosphor, but have never seen that issue with a Mikado CRT yet.

However, I've seen some variety of phosphor defects from both companies. Neither is perfect.

**kal** · Posted: Fri Jan 27, 2017 1:57 am Post subject:

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

They did not indicate to me that this is special pricing. I asked and that's the answer I got.

However, these prices are for bare tubes. All LC hardware, ground straps, anode leads, etc. would have to be added as appropriate.

**kal** · Posted: Fri Jan 27, 2017 5:14 am Post subject:

Thanks!

Sure, I assumed bare tubes. Someone would snag the rest off their existing setup. They do not need to be replaced.

Kal

garyfritz · Joined: 08 Apr 2006 Posts: 12026 Location: Fort Collins, CO

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