ITO glass is the best solution for top plate. I use glass 50x50mm or 100x100mm with conductive layer 10-20 Om resistance

Кinse the glass thoroughly

PCB with proper etched image - is the best solution for back plate.  Double-side is better, but single-side is also ok - but you need to apply  mask when fill emitting layer.

Use immersion gold instead of lead or HASL - to avoid any interactions between EL powder and pcb coating

Mix the electroluminescence phosphor in epoxy resin in a ratio of 1.5: 1

You can use ZnS phosphor or Zn₂[SiO₄] 

Epoxy resin must be two-component and has the dielectric constant from 7 to 10. Higher is better. two-component Polyurethane also show good results.

Apply thin layer of the mix to conductive glass. Good thickness is 50-70um

applied emitting layer under UV light

Mix the BaTiO in two-componentepoxy resin in a ratio of 1: 1 and glue the packet with this composition and apply some pressure

New EL panel require 100-300V 400-1200Hz