Screen half bright half dim

[Henry1]

They my screen looks inconsistent on the screen , it happened last night when i left it on for charging.

And today I found the screen looks different .

[javelinface]

Hullo! Welcome to the forums!

I found that this happened with my unit that I leave on for days, compiling code with the screen on. I’d get patches that are dull and washed out.
It would be to do with heat, and general use. Eg, if I accidentally leave it on while in a storage use, and it heats up, its generally quite affected.
I found that leaving it off for a day or so usually solves it.
That said, an LCD is essentially a consumable item, even for a computer or laptop.
If it can be helped, I guess try not to a) leave it ok unnecessarily and b) avoid extended periods of heat.

Here’s some more info:

Quoting from Vartech Systems, a supplier of rugged displays:

LC displays (LCD) have a well-defined isotropic or operating temperature limit, above which the actual liquid crystal molecules will lose their orientation and will assume a random orientation instead of ‘twisting’ through the light valve.

Basically, the crystal orientation in the liquid crystal gets randomized, and the effect is that light can’t pass through, so the image is darkened. I suspect that as the temperature straddles that operating temperature limit you may get a dim image where some crystals are still more or less in alignment while others are randomized.

Reading a bit further on,

Isotropic conditions will cause positive image displays to become dark (see image below), while negative image LCD’s become transparent. This is the Nematic-to-Isotropic Transition Temperature or NI Transition.

Most computer LCDs are positive image displays, and thus you wind up with your dark display.

The site goes on to note that temperatures above 100°C (212°F) can permanently damage the coating on LCD displays, though Samsung claims that storing your display at temperatures above 45°C (113°F) can damage it, so it’s possible that Vartech’s 100°C threshold is specifically a property of their ruggedized displays.

Vartech also mentions that as temperatures drop the viscosity of the LC increases, resulting in slower response times (which will first manifest as “ghosting”, and further as very slow image updates/transitions, like a bad PowerPoint slideshow in slow-mo). The site doesn’t make mention of whether excessively low temperatures can permanently damage a display, but the line

Low temp effects are usually reversible

suggests that it is at least theoretically possible for extremely low temperatures to cause irreversible damage.

source

[Henry1]

Thank you so much. It’s such a beautiful explanation. I learnt a lot about LCD.

Does it mean the screen will be damaged irreversibly if you keep it very long? I am basically planning a screen replacement.

Also, would a heat sink work if the heat is playing. major role here?

Sorry for my english.

[LovelyA72]

It’s nearly impossible to install a heat sink without shell modification. The best solution right now is to open your gameshell outer shell and make sure it’s well ventilated.

[Henry1]

does the screen issue also happen to you? I am wondering if it is a common issue because of heat.

[javelinface]

It’s an extreme case of being left on for longer than the battery can last. It happens on phones that have been left on for too long, doing power intensive activities. My PS vita has it so bad, it accidentally burnt in the image of whatever I had running. This is known as image persistence. See here.

Image persistence

Back in the old days, screen savers existed to avoid this phenomenon on CRT displays, although that’s a slightly different case. Another thing you can do is change the power profile to one that isn’t performance. This will allow the screen to dim and turn off when idle; then eventually turn off.

Just basically don’t leave it on unnecessarily long and you’ll be fine. And like I said, just leave it off for a day or so to allow your LCD to return to normal.

[Petrakis]

Usually for PC monitors you could unstuck them with this https://www.jscreenfix.com/

I wonder if something similar for cpi would do the job.