PowerBook 100 series screen vignetting

[all2coolnick]

I have a number of early PowerBooks like the 180 which have the same issue and I’m wondering if anyone knows what causes this or how to fix it. The display works fine and when first booted is fine. But then over the period of a few minutes, the corners get darker and this spreads in causing a vignette effect as shown in the photo. It seems very organic so I assume it’s not a problem with the image data. It does not look like a backlight problem. 

 

[Papichulo]

this is common on active matrix screens and nothing you can do about it except get a new screen. there's posts on here about putting it in the oven but i never did it.