During a 3D print, when a layer is exposed, it polymerizes the entire region between the previous layers and the resin tray bottom. The layer is stuck to both the bottom of the resin tray, and to the previous layer of the print. If the adhesion to the bottom of the resin tray is greater than the adhesion to the previous layer when the build platform moves to the next layer, the layer will rip off the 3D Print and stick to the bottom of the resin tray.
The film is designed to decrease this adhesion to the resin tray (decreasing the pull-off force)
If you have pre-cut/pre-fit film you may skip this step. Otherwise, if you have a film sheet, cut the film sheet to the size of the glass slide you are using with a little bit of buffer, (~ 1/4″ on each side)
Step 2 - Clean the Glass
Clean your glass slide with cleaning solvents and a non-abrasive lint-free wipe to get rid of grime and smudges. (Make sure there are no finger prints)
Step 3 - Attach the Film
Peel the protective backing off the sticky-back film. Do not bend the film. Align one edge of the sticky-back film to the glass, and lay the film onto the glass.
Step 4 - Squeegee the Film
Put a non-abrasive lint-free wipe on the squeegee. Press it against the film gently, and push it across to push out any bubbles.
Step 5 - Cut Off Excess
With the razor blade or scissors, cut off the extra film.