I thought it might be fun to salvage the polarizer from a broken laptop LCD screen, but it has put up quite a fight. I first tried direct mechanical brute force and managed to shatter the glass. Thankfully, not injuring myself doing it. When physical power doesn’t cut it, we turn to chemistry.
The risk of this approach comes from the fact the polarizer is made of plastic of unknown composition. Ideally I could find a solvent that will dissolve the adhesive and leave the plastic intact. If I was better at chemistry I might have some methodical way to find that solvent, but all I’ve got is trial-and-error. To aid in the trial-ing (and the error-ing) I have a portion of the polarizer I’ve already freed from brute force, carrying with it a layer of tacky glue. It’s enough for me to get started.
I had a rough progression of least- to most-aggressive solvents. First up to bat was 70% isopropyl alcohol, and the glue just laughed at its feeble efforts. After I let the alcohol dry, I tried WD-40, which also did nothing. I wiped up as much of it as I could before moving on to the next contestant: Goo-Gone.
Goo-Gone had some effect. It did not magically dissolve the glue as it tends to do with most other glues I come across, but it did soften this stuff somewhat, and it didn’t seem to damage the plastic. Using Goo-Gone to soften the glue, I was able to peel the sheet of polarizer free of the remaining glass and finally freed myself of the risk of puncturing some body part from thin pieces of broken glass.
However, that’s only half a victory as the glue remained stubbornly attached to the plastic making it unusable for light polarization fun. More Goo-Gone only seemed to spread it around and didn’t dissolve it. So I moved on to the next item: mineral spirits. It further softened the glue enough for me to start rubbing them off the plastic. It was a very labor intensive process, but I could start to see the shiny surface of my polarizer sheet. But I soon reached the limits of this approach as well. I started sensing uneven bumps in the surface and I couldn’t figure out what’s going on until I dried off all the mineral spirits for a look.
It appears there are multiple parts to this glue, and there is a much tougher component that clung on to the film. They were applied in lines and that explained the ridges I could feel in my fingertips while this film was damp with mineral spirit.
Finding the limits of mineral spirits for this task, I moved on to acetone a.k.a. nail polish remover. This is something I knew could melt certain plastics, as it’s used to smooth and weld plastic parts 3D-printed in ABS. However, I also knew it is not equally destructive to all plastic, as it seems to do very little (or absolutely nothing) to 3D-printed PLA parts and acetone itself sometimes comes in plastic bottles. Lacking experience in identifying plastics, I proceeded on my trial-and-error process.
The good news: using a small amount of acetone in a test corner, I found that it quickly dissolved the adhesive, turning them into soft goop that are trivial to remove. Wiping it off, I see the clear surface of polarization film with no evidence of chemical etching or erosion. I think this is the ticket!
But then I went too far by soaking the entire sheet in acetone, expecting to pull out a completely clean polarizer. When immersed in acetone, the polarizer film became brittle and cracked into little pieces. It marked the end of this experiment, but next time (I’m confident there’ll be a next time) I’ll try a few intermediate steps to see if I can find a good point on the spectrum between “few drops in a corner” and “soaking the entire sheet.”
Trying to salvage something from this screen’s LCD module was a bust, but I still have a very fascinating backlight module to play with.