possible to restore spotty diffusion film? - Page 1
Forum section: electronics / projects

author: coppercone2
author_rank: Super Contributor
timestamp: December 20, 2023, 07:53:31 am
content: If a diffusion film for a LCD has splotches on it, like damage, is it possible to restore its surface via the right grit of sand paper or something?I thought maybe heating it and pressing it into sand paper with a roller or just sanding itbut I also think this might mean there was some kind of event that caused heating there and it should be totally replaced maybe.I took it apart because during cleaning a bit of cleaner (IPA) got in there but not that deep, as I further took it apart I found the damage. The LCD was having intermittant issues before that.

author: Gyro
author_rank: Super Contributor
timestamp: December 20, 2023, 09:24:32 am
content: I would think the grain texture is much finer than any sandpaper and the damage would be very visible. I tried a similar technique with the (presumably much coarser) scratched surface of a second hand Kindle and the results were not pleasing! I think the diffuser works on a more complex principle than just surface texture too - internal facets in the film structure?Have you tried detergent washing?

author: coppercone2
author_rank: Super Contributor
timestamp: December 20, 2023, 03:47:57 pm
content: yeah idk how they got in there. I don't thin its alcohol damage, and the LCD was acting up. Is it possible there was some kinda over heating event on the LCD and it damaged the film? but the polarizer and frenzel lens are OKi am probobly gonna replace the whole thing because the intermittent fault is just obnoxious. I think someone was in there before maybe because the tape was a bit fucked upand yes, I have tried soap too. If its some kind of stain I thought maybe I can try acetone with alcohol. But I just ordered a replacement. I will keep it around until I make sure the replacement works, then just forget about it in the trash can.fact is, intermittent issue, weird anomaly on screen, better replace it. I def don't want to redissaemble this if it goes intermittent again to save like a hundred bucks. perilous. and this rules out a possibility.Like, a snap hinge is gonna break when I play games with this LCD, and then I have a problem. Like if this turns into plastic chassis repairs I am gonna fucking scream. I already did the wave tek, it looks like its seeping tar (black superglue). At least it will hold. fuck the clear glue it never seems to hold

author: coppercone2
author_rank: Super Contributor
timestamp: December 20, 2023, 11:51:42 pm
content: but, is it really finer then 5000 grit?how do they make it anyway. I assumed it was a textured roller.I made my own for a PCB mask alignment light table, but I went insanely heavy, using 1 piece of wax paper and 3 pieces of acrylic that were sanded progressively less. it works OK but weighs a ton but for an alignment thing the weight is goodOnly way I can think to do it is some kinda textured roller, actual sanding (seems really hard for a film in a fast process) or something with lasersI think its textured, because making a 'foam' like material is lossy (its a RF resistor)

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: December 21, 2023, 07:36:23 pm
content: Sounds like it needs to be replaced. I don't think you can fix it but just FYI, matte surfaces are usually made with loose abrasive, not sandpaper. Ground glass can be made by hand with fine aluminum oxide or carborundum powder, water and another small flat piece of glass to rub it in a random circular motion.

author: coppercone2
author_rank: Super Contributor
timestamp: December 21, 2023, 08:05:28 pm
content: how do you do it? That makes me think of lapping. Or do you mean loose and dry? Like a bed of loose abrasive ? I mean alot like a pool of abrasive that the sheet sits on top of.If I wanted to do it for some other reason, what would be a process? I had KINDA matte looks from using a random orbital sander.. but thats with sand paper. I could put a buffing pad on it, with paste. Using it dry seems like itsmadunhealthy. I polish wood by using random orbital sander with compound on it before, but since i got a rotary polisher (m18 fuel)... it just works better. I have enough skill to polish a car or whatever using the rotary polisher with the right compounds and pads (important) that I did not feel the need to shell out for the random orbital polisher (they 2-3x more expensive). I feel like my polishing problem was solved by getting high end polishing pads and compounds and learning how to use the rotary buffer... I know how to get rid of the holograms and stuff. If you are wondering, Buffing with a random orbital wood sander does not work, the motor in those things just does not have enough power to do wet compound/polish polishing with foam pads or whatever. The milwakee fuel m18 rotary polisher has tons of torque to over come that friction with the big foam disk.but for a sheet, that all seems moot, even taking the random orbital wood sander to a sheet of plastic seems totally insane. Maybe if you fixture it on a vacuum table or something..........And my new one should be here shortly. Hope this works (first gift from santa in many years)Maybe the proxxon random orbital polisher can do it on a sheet that is some how adhered with wet medium. But I don't own one (its small). Proxxon EP/A**********************how about sticking the sheet to the bottom of a vibra tumbler with fine wet medium??

author: CatalinaWOW
author_rank: Super Contributor
timestamp: December 21, 2023, 08:58:01 pm
content: I have doubts about the possibility of repair, but if you are willing to risk destroying the remaining functionality you might try just spraying on a matte coating, or making a matte paint with glass beads in an appropriate binder.

author: coppercone2
author_rank: Super Contributor
timestamp: December 21, 2023, 10:56:34 pm
content: I mean how do you do this. Because most of it is OK just a splotch that shows through.Air brush for miniatures and some skill?

author: tooki
author_rank: Super Contributor
timestamp: December 22, 2023, 11:48:53 am
content: Some diffusion films might be simple matte surfaces, but as a general rule, the backlight films inside an LCD are a smorgasbord of high-tech products with very specific properties. I very much doubt you can mimic that by abrading the surface. Just buy replacement film on aliexpress.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: December 22, 2023, 01:31:36 pm
content: Still don't think it will work for this, but as for making ground glass, you just make a slurry of abrasive and water then rub two flat things together in a random or circular pattern. Have done it many times for old cameras. Too coarse and the image will appear rough and grainy. Too fine and it won't be diffused enough to be even off-axis.

author: coppercone2
author_rank: Super Contributor
timestamp: December 23, 2023, 04:16:28 am
content: I replaced it. I found some structural cracks near the LCD I think it took a impact, there was probobly bad connections or something somewhere. new one works OK.I will save the diffusers and other stuff from it. I can cut it with scissors to maek something maybe.