On a semi serious note, this is precisely how most 3D printers work.
Many use wax as a production material.
I once saw one loaded with a starch based substance, and it could print a reasonable looking (and just about edible) pizza base. :D
Wouldn't it be simpler to use a device more like a scanner, (upside down and sans glass) with a row of closely spaced jets across the head?
You could heat the whole head arrangement up, and apply pressure to a reservoir of melted emulsion to spray it out.
Then, if you varied the speed of the head, you could adjust the coating thickness.
What temperature do you need to keep the goop at? That was an Epson inkjet that uses piezo electric heads (Epson 7600 or 9600 to be exact)... I have a lot of experience with the previous 9500 printer. I would not recommend using the 7600 as the heads have a smaller nozzle and it generally uses finer drops. I would recommend getting a old (but functional) Epson 3000 printer (4 color) and drive it with something like Quad Tone RIP to put down a little extra goop. Viscosity will be the biggest problem unless the emulsion flows like water, anything thicker will not work. Also heat is the enemy of the piezo heads, too warm and the heads will stop working.
Note also that there are many industrial piezo inkjet printers that could do this job, mosy of the UV cure should be able to do it, but they cost more than $10,000USD to start.
And goop = whatever you are spraying.
Tell me more about the exact needs for the coating/curing process, and the exact specification of the goop you want to spray and maybe I can help. As you can tell, coating my own papers is something I have never thought of doing, but (gasp) I'm very familiar with the digital end of things and very up on my printer repair skills.
The 'goop' has to be between 90 and 110 deg F, and can be just about any viscosity you want from thick to thin, as long as you coat the required amount of silver per unit area.
It can be made to be as thick as the current inks, but would have to be hot as above.
The paper would have to absorb the liquid, or it would have to be somehow kept flat to dry.
Keeping flat would be easy for the Epson 3000, but I don't know if you could keep the temp up to 110 while it flies through the air before it hits the paper. You might have to build a heat box so that the air temperature is up at 90-110 or hotter, and there could be some problems with the heads at this temp, but it's kind of unlikely to be a problem. You may want to pre-heat the paper too, but that might be easy with some of the electric heaters on the market. Just run it over a heater bar as it unspools from the roll before it goes into the heater box.
What solvents are used in this process? Is it just water or something more volitile?
I wonder what it would take to get a chilled bar on the output of the printer to rapidcure the paper?
The required silver per unit area may be much harder to obtain with the very thin viscosity needed to spray this. The viscosity of modern pigment inkjet inks for Epson printers is only slightly thicker than water, and I do mean slightly. Wish I remembered the actual value but probably only .05 thicker, safe to say the same as water.
Would it be easier to make an automated blade coating machine that would take roll paper or large sheets? Seems like it should work similar to the way ink is transferred from the well to the press rollers on a printing press. Maybe a hybrid where the thicker goop is pumped through spray nozzels in a constant stream, then a blade to smooth the goop into a uniform layer. Then a rapid dry section near the output of the machine. You could precisely regulate the amount of sprayed goop so that there was minimal waste coming off the sides of the blade. If you heated the spray nozzels, and the rollers, and maybe the paper, this seems like it would be a better design. And yes I know I am probably reinventing the paper coating machines that (may) still be used today. I think this is a more viable machine for this task.
Is this an all dark process, or can it be in light until the goop cures/dries? What about IR and near IR light? A radiant heater might speed up the process so that it is a dry to dry process, else you might need to use the contact heaters to rapid dry the paper.
And Greg, it would have to be dark throughout the process. The light that you could use would depend on the color sensitivity and speed of the emulsion. Long wave IR light (heat) would probably be ok, unless of course its an IR emulsion.
Interestingly enough, when Tony Perez (CEO at Kodak and former HP person) first saw a Kodak coating machine, he likened it to a huge inkjet printer. "Except for running in the dark".
You can do the same task with jet technology, you just need the special industrial jets. There're out there, just very expensive.
There might be a spray coating head that would make this easier, then all you need is a pump. If you really want to pursue this, I would suggest looking for spray coating technology. I don't think the common inkjet printer will be the answer, at least not with a single pass. A spray with a trailing blade seems like the best option, especially if you use a goop that can be exposed to a safelight so that you can monitor the process until it is perfected.