[xrox]

Just read a paper on LCD mura problems. I now see why it is so difficult to solve this issue.


Mura = Luminence non-uniformity (flashlighting, clouding...etc)


Translation Mura = Blemish

Mura Causes in LCD displays:


1 - non uniform tft thickness

2 - non uniform density of Liquid crystal material

3 - non uniform gap between substrates

4 - non uniform color of color filters

5 - non uniform lamp array

6 - non uniform optical filter

7 - warped light guide/diffuser



Note that OLEDs also suffer from this for different reasons.

 

[Gary McCoy]

But mura is virtually non-existent on today's LCD displays, aside from the very low cost suppliers. I haven't even seen any mura for over two years.

 

[borf]

I also always wondered why mura is still a problem.. Thanks. I don't notice it except on a completely black screen. Viewing angles I notice all the time. Some days I think I have an RPTV.

 

[xrox]



Quote:
Originally Posted by Gary McCoy /forum/post/14599183


But mura is virtually non-existent on today's LCD displays, aside from the very low cost suppliers. I haven't even seen any mura for over two years.

Firstly, the paper I'm quoting is from 2008. Secondly, mura is the industry term used to describe what AVSer's like to call flashlighting and clouding. So you say this issue is completely resolved in top of the line LCDs? Why do I still see it on XBR's and Samsung's then? I guess it is one of those personal perception things then.

 

[Fanaticalism]



Quote:
Originally Posted by Gary McCoy /forum/post/14599183


But mura is virtually non-existent on today's LCD displays, aside from the very low cost suppliers. I haven't even seen any mura for over two years.

This is false. I saw this on the Samsung LCD which I sold to my brother. I see it it on my buddies A750 (his is really bad), I see it on all the lcds that are in the studio room of my local Magnolia.

 

[borf]

Do you see it watching content?

 

[gus738]

yes its a common issue, among other lcd flaws, which is why plasma should be perferd over it, or HD CRT TUBE, any future technology display should be forgotten as its not here yet....


get plasma


it has less if any issues compared to lcd

 

[Fanaticalism]



Quote:
Originally Posted by borf /forum/post/14612993


Do you see it watching content?

Yes, it is visible during content. For example, you will notice in say a persons face, that one portion is a bit less "saturated". I would have to say that it is most annoying during dark scenes with the lights dimmed at night.

 

[TNG]



Quote:
Originally Posted by gus738 /forum/post/14613218


yes its a common issue, among other lcd flaws, which is why plasma should be perferd over it, or HD CRT TUBE, any future technology display should be forgotten as its not here yet....


get plasma


it has less if any issues compared to lcd

Technically plasma undergoes allot of the same processes that LCD does. There is still the standard litho, CVD, metal dep and all of the other processes that LCD goes through, so Mura can still be a problem. Coating thickness variations do not dissappear just because it is a plasma.

 

[Patrick.]

Plasmas as a general rule do not suffer from these types of defects, at least not in any 2008 plasma I've seen. Screen uniformity is much better, especially compared to an S-PVA LCD.

 

[xrox]



Quote:
Originally Posted by TNG /forum/post/14615932


Technically plasma undergoes allot of the same processes that LCD does. There is still the standard litho, CVD, metal dep and all of the other processes that LCD goes through, so Mura can still be a problem. Coating thickness variations do not dissappear just because it is a plasma.

For plasma the front filter and the cell dielectric/MgO thickness variations can cause Mura. But the effect will be very subtle and actually in the case of MgO thickness it will resolve itself over time. On an LCD there are 7 seperate possible causes of light leakage variations and those variatons can be severe and permanent. In fact, they can get worse over time.

 

[gus738]

in response to the plasma effect do you guys see this on any plasma COMPARED to lcd? i think not, the only if any issue is


temporarly IR because during sunlight/ambient light lcd have gone to glossy screen that makes it the same or worse so its no longer a factor, the again i never bother to consider lcd technology even for my pc as its a crt tube.

 

[spincut]

Mura is hardly gone. Granted, it was last generation or so, i had to return my sony XBR2 lcd due to mura and Sonys inability to address the issue (and i wasted a whole winter on the phone with their incompetent techs).

 

[TNG]



Quote:
Originally Posted by xrox /forum/post/14616000


For plasma the front filter and the cell dielectric/MgO thickness variations can cause Mura. But the effect will be very subtle and actually in the case of MgO thickness it will resolve itself over time. On an LCD there are 7 seperate possible causes of light leakage variations and those variatons can be severe and permanent. In fact, they can get worse over time.

True.


I have had some experience in the past couple of years with the manufacture of TFT panels (not for display purposes). Most of the equipment our company makes is for the application of CFR and BM resist for panel manufacturers in Asia, so I think of "Mura" probably in a whole different way than most people here. I look at it as a effect of poor resist thickness uniformity in litho, and on smaller panels as spin effect of having a rectangular panel in a spincoater. Semiconductor coating is easy with spin processes because it is round, rectangular panels have high and low area of thickness when spun because of resist migration (corners are difficult to deal with) on the panels.