Printed membrane keyboards

Thanks to everyone who was interested in my searches!

The study shows that the dimensions, thickness and rigidity of the plastic are in a rigid relationship and allow only small variations from the optimal values.
I have placed one of the variants of the membrane cell. Unfortunately, I have not yet found 0.3mm plastic in the local availability and I do not have a 3D printer that is supposed to print transparent light-scattering elements.
I am considering the issue of printing in a printing house with a solvent or sublimation printer.

The membrane shown contains three layers of polyester with a total thickness of 350 µm. The layer in the middle is a printed drawing 100 microns thick, laminated in an envelope with a film 125 microns thick. A tact button 2.5 mm high is placed in a hole in a washer of the same height, 10 mm in diameter. Pressing is clear. Unfortunately, the polyester "sandwich" has some permanent deformation, visible in oblique light.

Rigid backing like card plastic is needed, and we can't increase the thickness of the membrane more than 0.4-0.5mm