Do ePaper displays wear out? - Page 1
Forum section: electronics / projects

author: papo
author_rank: Regular Contributor
timestamp: December 13, 2014, 10:48:34 pm
content: HelloThis isn't really about a particular project, but since I've seen a bunch of projects involving ePaper displays, I'd like to share and ask a question. The back-story is that we got somebody an eBook reader for Christmas last year, the device broke down and the replacement just arrived. Both devices are on the picture in the attachment, the new one on the left; the device on the right is one year old as explained and has been used regularly, but not super-extensively.Apparently the display has aged somehow, it is much greyer than on the new unit. It's actually even a bit worse in real life than it is in the picture. In any case, I'd like to know whether this is normal. I'm not entirely sure any-longer, but if memory serves the aged unit's display was as white as the new one when we bought it.Thank you and best regardsMatt

author: Artlav
author_rank: Frequent Contributor
timestamp: December 14, 2014, 12:51:36 am
content: You said it broke? Does it still turn on, or is that a residual image?If the latter, then an unpowered display do fade over time.Also, an improperly shut down one can change as well - they need a careful power down sequence.

author: papo
author_rank: Regular Contributor
timestamp: December 14, 2014, 01:05:31 am
content: Thanks for your reply!Quote from: Artlav on December 14, 2014, 12:51:36 amThe failure is about it not able to log into the online account and I don't think it is in anyway related to the display. So it's not like the display isn't working; in fact you can still read all the books that are downloaded and I set both units to the home screen just to have comparable displays for the picture. So both units went through display changes and display refresh cycles right before the picture was taken.Quote from: Artlav on December 14, 2014, 12:51:36 amThis is very interesting. None of the two units shut down per se. If left untouched for a couple of minutes, they both go into some sort of sleep mode where a static picture is shown. Than one is greyish on the old unit, but basically everything is greyish there. Even right after the screen has been rendered. I don't know a lot about these displays, so I guess I am wondering whether them turning grey is normal behaviour, a result of not using them (hardly the case here, this was used on a regular basis), a result of over-using them, a result of improper shutdown, handling etc.

author: Maxlor
author_rank: Frequent Contributor
timestamp: December 14, 2014, 02:09:32 am
content: It also seems to me that the display on the right is less sharp, there's some bluriness to the text. Might be just an image artifact of course.Try looking at the displays under a microscope or a good loupe. I would guess you see more grainyness on the older display. If so, there would seem to be some aging, may some of the particles got demagnetized (ever drop the reader?)

author: SL4P
author_rank: Super Contributor
timestamp: December 14, 2014, 02:26:52 am
content: Without any knowledge whatsoever, I'd first be asking that the 'old' display was kept in 'typical' ambient conditions.. temperature, humidity etc.Left in sunlight while left unused?Those types of questions.An interesting study to keep track of.Thanks

author: ajb
author_rank: Super Contributor
timestamp: December 14, 2014, 02:44:07 am
content: Are you sure the new device is exactly the same as the old?Perhaps the replacement is a newer hardware revision with an improved display?

author: amyk
author_rank: Super Contributor
timestamp: December 14, 2014, 07:00:31 am
content: Yes, they do age:http://e-ink-reader.ru/eink_degradation_en.htmlThere's quite a bit of per-display calibration that goes on (see this thread for more detailshttps://www.eevblog.com/forum/microcontrollers/interfacing-epd-(e-ink)-display-from-kindle-anyone-tried/) but the typical variance of these displays is much greater than with LCDs.I wonder if it's possible to "revive" these screens by driving them between black and white repeatedly to "shake up" the pixels and unstick them... or by adjusting the drive voltage upwards.

author: TerraHertz
author_rank: Super Contributor
timestamp: December 14, 2014, 07:20:25 am
content: I've never used an e-ink device, so I'm asking this from complete ignorance. But is there no screen brightness & contrast configuration in a menu somewhere? You're sure the old unit is set to the same values as the new one?Point being, if there is such an adjustment but you don't know about it, maybe it got accidentally changed?This question asked from the viewpoint of someone who has to keep fixing and explaining the exact same PC 'user-errors' to their 86 year old mother, regularly.

author: RobertoLG
author_rank: Frequent Contributor
timestamp: December 14, 2014, 07:39:49 am
content: I have a kindle 4( the most basic one), it had some ghosting/shadowing when I got it new and there was a software update that got rid of it, works fine till now, but I don't let the screen exposed to sun or heat for long periods

author: tggzzz
author_rank: Super Contributor
timestamp: December 14, 2014, 10:12:33 am
content: Quote from: TerraHertz on December 14, 2014, 07:20:25 amNo, and that's a major advantage of the display technology. Perfectly visible in sunlight and torchlight without, zero power dissipation. Try that with LCD/LED!

author: papo
author_rank: Regular Contributor
timestamp: December 14, 2014, 10:57:52 am
content: Wow lots of good stuff, thanks to all!Quote from: Maxlor on December 14, 2014, 02:09:32 amI attached pictures showing a magnified section on each unit. It is indeed more grainy, less crisp. Note that my USB microscope does some auto exposure that I can't turn off, but that's as good as it gets on a Sunday with the stuff I have at home. This is not my unit so I can't tell for sure, but it belongs to a responsible person so I would not expect heavy abuse. We even got her a leather case to protect it from sunlight. I'm still wondering whether the display is supposed to age like that within a year.Quote from: SL4P on December 14, 2014, 02:26:52 amApparently the device was kept in a drawer or protected by the cover when not in use. I can't vouch for that but I trust the owner to handle her gear carefully.Quote from: ajb on December 14, 2014, 02:44:07 amAs I wrote originally, I am not 100% sure, I wasn't expecting to have to do a side by side comparison one year later. But when I look at the new unit, I go "wow that's a nice and crisp display". Nothing like the old unit, and I remember having exactly the same reaction when we bought it last winter. So I'd say the display has indeed aged, unless my mind is playing tricks. By the way the unit I am calling 'new' here, i.e. the replacement unit, appears to be older than the one we bought last year. This just occurred to me... I have to dig more into this, but it would mean that this is not an ageing effect per se, but more of a wear-out (or wrong handling) thing.Quote from: amyk on December 14, 2014, 07:00:31 amThanks for that link. I can't do the voltage thing, but I was thinking about doing the "shake up" before returning the old unit. Then again such black/white flickering happens every now and then when the screen is being redrawn, so it appears as if that would be happening already without success.Quote from: TerraHertz on December 14, 2014, 07:20:25 amYeah I know and I was a bit scared that there was such an option somewhere when I posted. Although I checked and I really can't find any contrast adjustment in the menu, and it's not like there is many settings. After having read the link provided by amyk, I'm confident that this is a 'normal' process. Which is a bit of a shame, because the crisp ePaper display would be the only reason to ever buy a dedicated eBook reader and if this is how they look after one year of use -- thanks but no thanks.

author: 0xdeadbeef
author_rank: Super Contributor
timestamp: December 14, 2014, 11:30:28 am
content: I would assume it's not only the use, but also exposing to sunlight that bleaches out the dark pigments.Anyway, as ghosting was mentioned above: at least older generations of ePaper were very prone to ghosting when switching between two images. Over a longer period this can also lead to a grayish picture. That's why eBook readers tend to invert the screen now and then. Changing the algorithm (when/how often to invert etc.) is about the only thing I can imagine to be possible with an firmware update to improve ghosting.

author: Artlav
author_rank: Frequent Contributor
timestamp: December 14, 2014, 01:40:19 pm
content: Quote from: papo on December 14, 2014, 01:05:31 amWhat i was talking about happens between the driver and the screen, not on the device level.The typical cycle for that kind of screen is charge, update image, discharge.If that discharge wasn't done properly, then the charge will dissipate randomly, producing weird effects on the screen.So, if the driver was suddenly broken or went completely unpowered right before or after a screen update, the image might get distorted.But since yours still work, then that's just a bit of irrelevant trivia here.

author: Bud
author_rank: Super Contributor
timestamp: December 14, 2014, 07:26:17 pm
content: I have a Sony reader which is about 4-5 years old, i have not noticed screen quality degrading.

author: RobertoLG
author_rank: Frequent Contributor
timestamp: December 14, 2014, 09:50:28 pm
content: like I said before, in my case it was a screem update problem that was solved with a software update, maybe this one just came with a bad screen