Electronics > Repair
Transflective LCD polarizer orientation
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pete1zed:
Hi,

The original post said that when the new polarizer film was applied, the background was LCD appeared green/yellow, compared to a neutral light grey with the original polarizer.

Did anyone find a source for the polarizer film to eliminate the green/yellow background?

I have exactly the same problem (please see the images attached).

I tried linear and circular polarising film (left and right, and including a left and right with a retardation layer) -- all with the same green/yellow background issue.

Any ideas anyone?

There is a comment above saying a retardation layer is required on both the front and back, so maybe I'll try that next...

pete1zed:
Hi again: here is an update on my attempts to find a front FSTN polarizing film

I have ordered this FSTN polarizer film. 

The issue is....

From polarization.com:
Yes, an FSTN display needs a clear retarder between the top polarizer
and the LCD to covert the elliptical polarization coming out of the
display back to linear polarization.
Unfortunately, there is not just one kind of FSTN: there are many
variations needing different retardation and orientations. That is one
reason we do not offer them, because the market for a specific one would
be too small.
There are some that use circular polarizers, what means that they have a
quarter-waver retarder at 45 degrees to the polarizer (for example we
have seen BMW navigation systems with a right-circular polarizer). But
the most common types need some type of elliptical polarizer.

To solve that, I also found this site that sells different retardation films,
http://www.polarizerfilm.com/fstn-polarizer.html

...but I'll wait for the above polarizer to turn up before making further orders.

pete1zed:
Problem solved:  No more yellow background from my FSTN display using this polarizer

Note: this is the transparent polarizer for the front of the LCD, but they also have films for the rear

There is  a  join in the layers which runs diagonally. So max size of a screen you could fit in without having the line is 150x180 mm.  You could cut enough for two screens from the 350x300 mm sheet

Attached is a picture showing what happens if you fail to avoid the join

wraper:

--- Quote from: pete1zed on May 21, 2021, 11:57:26 am ---There is  a  join in the layers which runs diagonally. So max size of a screen you could fit in without having the line is 150x180 mm.  You could cut enough for two screens from the 350x300 mm sheet

Attached is a picture showing what happens if you fail to avoid the join

--- End quote ---
I guess you received an unlucky one. Most likely it was cut from a large roll, where sometimes joint may happen. The same thing happens with cables, sometimes copper strands from two pieces are twisted together and later covered with insulation. Normally place this defect should be marked but sometimes it's not.
pete1zed:
Or maybe these pieces with the stripe are correctly binned at the factory. 

A factory worker then gets these out of the bin and sells them. 

The piece I received has the diagonal stripe directly from corner to corner, which is how you would cut it to remove the un-usable section in the most efficient way from the legitimate product.

I do not know...
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