Does LCD Polarizer Film Darken With Age?

[Jim Olson]

In recent years I have re-lamped several IPS Flexview LCD panels in Thinkpad T-series machines. Some I did myself in our office lab. Others were done commercially by Moniserv in San Francisco.

I recommend paying others to replace a CCFL lamp. It requires special tools and parts that are hard to come by.

I've been surprised that re-lamping rarely brings an aging LCD panel back to its factory brightness. Never does the resulting display have the crisp blue hue of a new LCD panel. At first I thought the inverter module's high voltage output might have diminished with thousands of hours of use, but AC voltmeters (and simply swapping inverter modules between new and old machines) say otherwise. The problem is not lowered CCFL drive voltage.

In some instances I found that warping of the LCD panel was the cause of some brightness loss. Carrying a closed Thinkpad causes the sheet metal around the LCD panel to flex. This is how the matte film on the LCD develops faint images of the keyboard. In some instances the bottom edge of the LCD panel (the shiny metallic trough that encloses the CCFL) gets permanently bent and does not correctly reflect light upward into the panel, causing non-uniform brightness across it. My suspicion is that the spacing of the lamp from its reflector is distorted when the LCD panel is bent.

But these explanations do not account for all the brightness loss in a re-lamped LCD.

Does anyone know whether the UV light emitted by the CCFL lamp causes the polarizer films or the acrylic light pipe to darken with time? I can imagine that the first inch of the light pipe north of the CCFL absorbs a lot of UV. I know that acrylic diffusers on office light fixtures decidedly darken with age due to UV absorption.

It might be the case that the polarizer film simply darkens with age, regardless of UV absorption.

I'd appreciate feedback from others on this. Helps me pass the time until the industry migrates back to 4:3 IPS panels for laptops. The 16:9 format panels now in vogue in the computer industry serve no useful purpose except to encourage sidebar ads on webpages.

[Norway Pad]

I have no direct answer to your question. But I participated in a LCD discussion in the T6x forum not too long ago, where we had the following post from another member:

I think, I have had quite a lot experience with these screens so far to give some comments.
I used several ID-Tech SXGA/UXGA screens on the R50p, T42p and they were really good, although an older technology generation. IDTech IPS was one of the finest displays I have ever seen.
Then I had a few T60 SXGA+ with the infamous IPS from LG-Philips. They had a very poor supplier with CCFL lamps which lasted only about 6 months and then started fading drastically. After about 2 years all LG-Philips SXGA screens were yellow and dim. I replaced the CCFL lamps myself (as usual) and used lamps from a broken Samsung LCD which are known to be bright and have a blueish tint.
Result: excellent SXGA displays. So the problem was the subpar CCFL supplier for LG-Philips.

This sort of contradicts your experience. Have you worked with the LG Phillips LCDs, or have you worked with the other panels, like the ID-Tech? And what is your definition of insufficient quality of the brightness/color after the CCFL swap? Is the difference visible only when they are compared side by side to a new panel?

I am a bit curious about this, as I am planning to replace the CCFL in a LG Philips SXGA+ IPS "test" panel that I will hopefully receive soon. No big deal if it breaks, but if it works, I am considering doing this to another panel as well, and swap these into any future dim T60s I will buy. (Hopefully also into my T42, if that's possible. I need to check that out) In my case, the SXGA+ IPS panel in my T60 was so dim that I had problems seeing it in certain light conditions. So hopefully a CCFL swap will bring back at least 80-90% of the brightness.

[RealBlackStuff]

There is very little info available about the "brightness" of a CCFL.
AFAIK this should be given in degrees Kelvin, but I don't see it anywhere.
LCDparts.net / moniserv.com claim to have the brightest, but do they really?
I've also noticed that the original CCFL from e.g. a 15" ID-Tech is thicker (ca. 2.2 mm) than the replacement CCFL (ca. 2.0 mm) from LCDparts.
Don't know if a thicker CCFL is brighter?

see also this: http://www.byfort.com/ccfllamps.htm

[Raceboy]

It is the colour temperature that is given in Kelvin degrees, the higher the number, the more blueish the colour is. 4500K is approximately what FlexVies are and this is pretty much like normal daylight.

[Jim Olson]

Norway Pad, thanks for the response. My Flexviews have been ID Tech's.

You raise an interesting point (lamp color temperature) that I did not consider before writing my previous post.

It is entirely possible that replacement CCFL lamps are offered by their manufacturers in various color temperatures as are F32T8 lamps used in office light fixtures.

After I taught myself that it was folly to attempt my own CCFL replacement in Flexviews, I've used Moniserv in San Francisco. I never thought to ask Moniserv if they use replacement lamps with the same >4000K temperature that ID Tech used in its panels.

Judging from the appearance of the finished panel, the two recent CCFL retrofits Moniserv did for me looked more like 3500K office fixture lamps: less blue and more red. However, that could be simply an artifact of polarizer discoloration.

As an electrical engineer nearing 60 years old, I have extensive lab skill and tools for SMT construction, but I found CCFL replacement to be a challenge. The lamps are so thin that they nearly break under their own weight. I concluded that the silicone donuts around the lamp and the silicone wire grommets at the ends are extremely important to proper operation of the panel. I found both of these parts to be degraded in the panels I worked on, probably due to ozone generation in the light cavity. As a home builder, I had no source for replacements and thus re-used the old silicone parts.

I bet the silicone donuts serve as spacers to the sidewalls of the light cavity. After some tinkering I concluded that non-uniform spacing of the lamp to the sidewalls causes brightness variation over the panel.

[Norway Pad]

I went ahead and ordered two CCFL lamps tonight, so I will see how a LG Philips SXGA can benefit from it (Or if it ever will work again after I work on it ) I will try to find a way to actually test the panel without having to dismantle my T60 so I can post a comparison picture here on the forum.

I concluded that the silicone donuts around the lamp and the silicone wire grommets at the ends are extremely important to proper operation of the panel. I found both of these parts to be degraded in the panels I worked on, probably due to ozone generation in the light cavity. As a home builder, I had no source for replacements and thus re-used the old silicone parts.

These parts can actually be bought as well, I found out: http://www.lcdparts.net/CCFLADetail3D.a ... uctID=1731

[RealBlackStuff]

Those silicone caps from LCDparts are useless, they would not fit on any of the CCFL-ends that I have replaced.
If you are careful, you just re-use the 'old' silicone caps.
You can reuse the grommets as well, but that requires an awful lot of patience and VERY steady hands, so as not to break the CCFL tube.

[Norway Pad]

Thanks for the advice, RBS. Much appreciated and will be kept in the back of my mind.

...so as not to break the CCFL tube.

There is a reason I bought 2 of them.