 EL matrix display
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Conundrum
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Fri Dec 17 2010, 10:00AM
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Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062
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Hi all.
I was looking at Jeri's article on using pcb traces as EL electrodes.
This got me thinking about where to find traces which were close enough together to make a proper matrix display.
Found this in the form of a broken LCD panel's back PCB with long traces running between via's.
Removed all the chips and suchlike from the back PCB, cut down to size and then sanded the edges to remove any shorts.
First attempt didn't work very well as the dielectric was too thick.
Tried again with just phosphor and pre-cleaned the pcb with diluted acetone very briefly so as not to dissolve away the resist.
Once painted using the Sellotape trick, I dried the phosphor using a 350W hobby heat gun and 10/30 second on/off cycle for four minutes and installed an ITO sheet with tape mask over the unused sections.
Had to use a tiny bit of moisture to make a reliable contact but it works fine when this is done.
(i believe that the microencapsulation means the phosphors are not affected in the short term)
Works well as you can see, apologies for the appalling focus but i do not have the special super-macro lens i used last time.
A little tip, this would work a lot better with ATO (antimony tin oxide) or a vapour deposited SnO2 coating.
As for colour, if a white phosphor was used and two sheets of salvaged-from-dead-LCD colour filter and front ITO UV glued together back to back then this would work well.
I also found that graphite lubricating powder if applied carefully between the glass and phosphor can improve the brightness somewhat, reduced needed applied pressure and avoids the need for a moisture layer.
This might be a worthwhile experiment to use tyre repair cement and graphite with, in principle the contact needed might only be a micrometre thick and still work.
-A
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