On this site, we’ll show you how to harvest an LCD from your computer monitor. The LCD is mostly transparent but you can connect it to a computer and program the transmissivity (or polarization state rotation) of each pixel.
No user serviceable parts inside.
Before we begin, a word of caution! LCD panels are not intended for dissection, and mishandling the parts inside can result in SERIOUS INJURY. You should only attempt this if you have a basic understanding of electronics and can be deliberate and use common sense. Among other things, there is a high voltage power supply inside the display, which could potentially hold electric charge even after the display is disconnected from wall power. The LCD panel is composed of thin glass which can be razor sharp. If you break the panel, toxic liquid crystal will leak out. You can find the MSDS for various types of liquid crystal online. However, there will be no way to know exactly what type is in the particular display you are disassembling.
Now that we got that out of the way, let’s liberate the LCD panel from its prison without breaking it!
We should understand a bit about what’s inside your typical LCD monitor. For the purposes of this simple tutorial, there are three discrete parts to consider, each of which are composed of many sub-parts:
- LCD Panel: This is composed of two sheets of thin glass, patterned with transparent electrodes, and containing between them liquid crystal fluid. You can see in the photo above, that this panel will also have drive electronics bonded to the top. The glass also has two polarizing films affixed to it with glue, one to the front and one to the back. We’ll get to this in a moment.
- Backlight: The backlight will appear as a big silver box behind the LCD panel. The LCD panel can be electrically programmed to be either transparent or opaque. When you see light coming out of an LCD display, you’re seeing light generated by the backlight. When you see a white area of the screen, you’re looking through a fully transparent LCD into the backlight. In older LCD panels the backlight is composed of a Cold Cathode Compact Florescent Lamp (CCFL) and a light guide. The CCFL lights the edge of the light guide, which provides a nearly uniform area light source behind the display. In newer panels, the CCFL has been replaced with a strip of white LEDs, but the principle is the same.
- Power Supply: You should use extreme care when removing the power supply. It converts wall power (e.g. AC 120V, for North America) to the various voltage levels required by the panel. DC 12V, 5V, 3.3V, etc… If your display also has a CCFL backlight, the power supply can generate a very high voltage rail (e.g. 1kV) to run the CCFL. Be very careful with a voltage source this high! It won’t necessarily behave like low voltage DC sources you are used to, and you should not operate it without proper insulation.
Let’s get started.
Choose a display
How do you choose a display to disassemble? Well, it depends on what you want to do. In our prototypes we were often interested in high speed displays, and chose 120Hz Nvidia 3D Vision compatible screens from Viewsonic. We’ve also used cheaper displays for other projects. Typically, you want a newer display that has flat flex cable bonded only to the top. Older displays have the row and column drivers on two edges, which can make it harder to get the electronics out of the way. Sometimes that’s unavoidable when you need something special, such as a custom grayscale medical display. If that’s the case, you can often order a longer flat flex cable from digikey.com to replace the one that came installed in the panel.
Remove the exterior covering
Make very certain you’ve unplugged the display from wall power, and that all electronic components are fully discharged. Each display is a little different. If you’re lucky you can find a teardown online, however, we’re assuming here you’re not worried about putting the display back together later, so it’s acceptable if parts of this process are a little destructive. Here I show disassembling a Sceptre X20WG-NagaII (no longer available) which we used in the BiDi Screen project. But current displays are nearly identical in construction.
Start the disassembly by removing any foot or stand.
After you’ve removed any visible screws (check all the recessed holes), you’ll often have to pry the front and back covers apart. If you want to preserve them, use a soft plastic tool designed for this purpose. Otherwise, just go at it with a screw driver.
Once you have the covers apart, there will be some additional components to unscrew, such as the front control panel in the case of this display. Now you can see the LCD and backlight stack.
Unplug the front panel control.
Flip the screen back onto its face, making sure that it is resting on a soft surface. You should be able to pull off the plastic from the back as well. If it resists, there’s probably another screw you’ve missed! The board on the left in this photo is the power supply. Use extreme caution when dealing with it.
Disconnect the power supply from the metal backing. Here, this involved removing three screws that affix the power supply, one screw affixing the ground strap, and two screws affixing the black A/C plug.
Disconnect the cables that supply power to the screen and backlight. The power cables to the screen (and audio signals in this case) are the bundle of wires on the left in the image above. The high voltage CCFL cables are the pink and blue pairs of cables in the image below.
Remove the display connectors. You may need needle nose pliers to remove the bolts.
Getting at the good stuff.
At this point there is typically a metal ground plane between the power supply and the LCD drive electronics. You should find some screws around the edge of the display panel which will release this back plane. If you’ve disconnected everything it should usually lift away without much trouble. Be sure you feed all the wires through the holes and don’t tear anything.
There will often be some clips holding the backlight supply cables in place.
Remove the cover from the screen drive electronics.
Remove the DVI/VGA connector from the board. Carefully pry up the edges. The plastic housing for this plug is delicate.
Remove the video driver board from the metal backing by shifting it and bending up the metal clips holding it down. Take care not to break the delicate connections in the four ribbon cables connecting it to the LCD panel.
Now you can separate the LCD from the backlight. You’ll have a few screws to remove, and some retaining clips to pry back.
Often there is a metal frame or some clips to remove from the front of the assembly. Once you’ve taken these parts off, you should be able to fold the LCD glass away from the backlight.
At this point, if you carefully reconnected the power and data cables, and took care to keep a safe distance from everything high voltage, you would be able to power the LCD and see the difference between an LCD with and without a backlight. In the image below I’m tipping the LCD glass away from the backlight panel, while displaying an image of a jellyfish on my desktop. I don’t recommend running things without constructing a secure case for the high voltage parts though.
More advanced stuff.
Removing polarizing films.
In a lot of cases, if you want to image through an LCD panel, you must remove the front polarizing film, which is usually diffuse (blurry) and replace it with your own polarizing film. There’s a myth going around out there that this is difficult. Really, it just needs some patience and a bottle of acetone.
The polarizer is like a giant decal adhered to the front of the glass. If you peel up a corner with a pen knife, you should be able to pull off the whole polarizer without too much effort. The LCD glass can bend a little bit, but be careful not to break it, or to tear the sensitive FFC connectors bonded to the glass.
Now comes the boring part. Unless you’re very lucky, you’ll notice an ugly residue left on the glass. This is the remainder of the glue used to adhere the polarizer to the screen. Take some acetone, in a well ventilated space (outside if possible), and carefully clean off the glue residue. Use a soft cloth. Below you can see there is still lots of glue remaining in the top right corner.
I mentioned that there are two polarizers attached to the LCD panel. The polarizer on the back of the panel is glued on just like the one on the front. The rear polarizer is not diffuse, though. Typically you can leave it attached, even if you’re imaging through your LCD panel. If you do leave it attached, be very careful when cleaning the front of the panel with acetone. The acetone will dissolve the polarizer material and leave it foggy, so don’t let it run off the edge of the panel.
Take care to use the correct alignment of the replacement front polarizer with the rear polarizer. Usually LCDs operate between crossed polarizers, which will make each liquid crystal cell transparent when not energized. However, the polarization axis will often be at 45 degrees to the edge of the monitor. This is unfortunate, because it means that when replacing the front polarizer you will have to cut a rectangle oriented at 45 degrees out of the rectangular replacement polarizing film you’ve bought. It’s a little wasteful! But there’s lots of fun stuff you can do with a polarizer, like learning to see the Hadinger’s Brush. If you leave the front polarizer off of your LCD you can make a custom linear polarization state generator at each display pixel!
If you’re interested, there are lots of cool films in the backlight. (Check out the BEF). You can pull it apart without too much trouble. You can see all the films splayed apart here, on top of the light guide, and the CCFL on the edge of the light guide.
Here’s what the CCFL looks like. Just a mini florescent tube!