Electroluminescent matrix

Kragen Javier Sitaker, 2016-07-27 (2 minutes)

The first gas plasma screens for Plato used two grids of parallel wires which created plasma at their intersections; you could do the same with an electroluminescent material like ZnS:Cu or, maybe, SrAl₂O₄ (LumiNova).

For example, on a hard, flat insulating substrate such as glass, you could lay down a bunch of horizontal 100μm-diameter copper wires at a spacing of 250μm; on top of that, you deposit a 200μm-thick layer of small ZnS:Cu crystals, maybe dispersed in a binder (“electroluminescent paint”); and on top of that, you lay down another bunch of 100μm-diameter copper wires with a spacing of 250μm, this time vertical.

For example, 980 pixels horizontally (720 vertical wires) at this resolution would be 183 mm, and 6615 pixels vertically (990 horizontal wires) would be 251 mm. So you could get a very readable full-page monochrome display with 712800 pixels by controlling only 1710 wires, an average of 417 pixels per wire.

If you ground one of the horizontal wires, leave the others floating, and put an high-frequency AC voltage on some, but not all, of the vertical wires, you should get glowing spots where those vertical wires cross the wire you have grounded. The intensity of each spot should be jointly proportional to the voltage and the frequency. By switching from one horizontal wire to the next, you can draw an arbitrary pattern of pixels.

Potential advantages of this approach include very low cost, inexpensive fabrication technology, low power consumption, and very low duty cycle — ZnS:Cu, as used on analog oscilloscope screens, has a time constant of around nine minutes (???), while SrAl₂O₄ has a time constant of about 15 minutes. This would allow you to use a refresh time of several seconds or even minutes to hours rather than tens of milliseconds.

(I’ve been thinking for a while that if you have a laser you can rapidly deflect with mirrors, you could use that to paint an image on a glow-in-the-dark screen, thus avoiding the need for the vacuum and X-ray shielding of a CRT, and also the hundreds or thousands of wires used by this design.)

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