Change colors of liquid crystal display

[RevDNS]

Hello,

​

I am trying to modify the LCD of CB Radio: Albrecht AE 6890.
Originally it working in inversion, a blue background with white marks.
LED's backlight has white color, but I has changed it to red.
Results:



Everything would be fine in dark places, but in a bright environment LCD is blue.
I have pulled off both polarizing films and tried rotate in all possible ways.
I can't obtain black background with white marks as on picture:



Can anyone help me with this LCD?
Thanks a lot!

 

[barry]

WHAT??? You had a white LED which gave a blue background and white numerals. Then you changed the LED to red, which gave you a red background with red numerals. But you want it to be black with white numerals?? Why would you expect a red LED to give you white numerals? And your pictures are showing two TOTALLY DIFFERENT displays.

It’s not clear, but I think your top display is transmissive, and the bottom one is reflective. Not the same.

 

[RevDNS]

But you want it to be black with white numerals?? Why would you expect a red LED to give you white numerals?

I would like to get a black background with transparent letters.
When the sun falls on them, they are white, but when the backlight turn on change color to the same as backlight.

 

[betwixt]

It isn't impossible to what you want but it isn't as easy as you imagine.
Light falling on the face of the LCD (such as Sunlight) passes through TWO polarizing layers but light from the back only passes through one. To understand fully, you should research how LCDs work, there is lots of information on the net. The important thing to remember is that reflective LCDs have a mirror surface at the back to reflect light arriving at the front back out again when the polarizing layers let that happen, backlit LCDs have a light source where the mirror would be so the light path only passes one way through the polarizing liquid.

Brian.

 

[RevDNS]

Ok, so I get polarizer's from monochromatic LCD of multimeter.
Unfortunately, by rotating polarizer at the top and reflecting foil at the bottom the darkest color I can get is blue.

 

[betwixt]

I'm getting confused.
Are you trying to produce different hues by rotating the polarizer? You may be able to adjust the shading a little - with the risk of 'over shoot' or 'over lap' of fully on and fully off states but you will not change the actual color. All LCD are monochromatic at pixel level, if you want a different but still monochromatic color you should change the backlight LED, if you want adjustable colors the LCD technology is somewhat different.

Brian.

 

[RevDNS]

All I want is change white signs on blue background into white signs (or red - depending on backlight color) on black background.
As I understand, I've a STN LCD type and all I need is transform it to FSTN (the difference between this two types is the retardation film).

Am I wrong?
If not, where can you buy retardation film or maybe I can find it in the old LCD from the computer display?

 

[betwixt]

You can't change the fluid in an LCD I'm afraid.

The best you will manage is to change the backlight to a red one.

Depending on the construction of the LCD, if the backlight LED is accessible (some are mounted beside the glass aiming inwards) you could experiment with a further filter between the LED and the LCD edge. No promises but you might be able to reduce light scatter and thereby improve contrast if the LED light is polarized.

Brian.