LCDs with persistent images (page 1: The overdrive donwside: LCDs burn in)

One day you discover on your monitor an image that can´t be erased…

We regularly play the roll of the bearer of bad news concerning LCDs. Lately you have already seen:
-14% tax on DVI (only Europe)
- absence of HDCP certification for almost all displays on the market;
- Mura effect on panels and backlight spots
- problems of color quality with time
- flagrant lack of brightness homogeneity in big monitors
All this is without recalling the recurrent problem of dead pixels.
If this wasn´t enough, here is something as interesting: the persistence of images on LCDs, which isn´t often covered by warranties.

We are not trying to shoot down LCD monitors to praise other alternatives, existing or future technologies. It’s more that with monitor tests, we progressively increase our knowledge in this domain and we sometime discover hidden defects.

It all started with the LG L2300C

The bad news of the day is that some LCDs tend to keep a ghost image of fixed images that have been displayed a little too long. In fact this problem isn´t completely new, but up to today, it was so minimal that we couldn´t consider it as problematic. No one mentioned it because no one noticed it. Unfortunately, the situation is getting worst.

We really became aware of the problem while testing the LG L2300C (in French). This 23" monitor is sold at very low prices, less than 800€. Its panel is a TV panel and its resolution, 1366 x 768 pixels, isn´t really appropriate for office use.

One Friday night, we forgot to switch off the test monitor. In the background there was our electronic mail service software tool. Monday morning when we came back, we had the unpleasant surprise of seeing that it was superimposed over all our images and several hours later, it was still there. We called LG, who was very honest, something that we are not used to with manufacturers.

Our electronic messaging software is in superimposition on the grey of Photoshop.
In the middle of the image we can see Canon´s logo that was present in a mail that we received last Friday.
LG didn´t really test the monitor before sending it to us and they were unaware of this problem. They weren´t surprised, however, to hear of this defect and they admitted that their big monitors intended for public display were also subject to this type of phenomenon for a year now. According to them, it happened with the change of the panel generation in 2005. Feedback from Korea didn’t give them an explanation and most of all didn’t correct it. There is only one way to counter this problem; display a white image for hours and this is what they told us to do with the L2300C. We did this alternately between work periods and after the third day, the persisting image really started not to become unnoticeable.

The good news is that it isn´t an irremediable burn in which happens in some plasmas. According to LG, the problem only happens with fixed images. Liquid crystals locked in the cells have red, green and blue filters that would progressively get stuck. There will be within the same cell, a part of the liquid crystals that would correctly react to the desired image and others that would get stuck in the position of the image that was displayed for the longest time.

Displaying a white image would enable a passing of a maximum of light, hot (place your hand on the surface of your LCD) and melt the part that is solid.

If they already were aware of this problem, the fact that we encountered it on the L2300C bothered LG who thought that only public displays were affected by this problem. Seeing that it appeared on a monitor available in stores for the general public is all the more problematic that they don´t have a miracle solution to counter it. The proof of how much this concerned them is that the L2300C is almost impossible to find on the market today. Its lifetime would have been very short.