How LCDs Work

And the listeners to this podcast probably know what that means, but it might be looking at one right now in fact exactly UM, but a lot of people don't know exactly how they're made. I was one of those, UM, and I went back into uh the l c D article that we have on the site, and basically, it's, uh, the screen that you see on your laptop computer or your desktop display is a is a sandwich, as we

say in the South. It's UM. It's got a mirror, it's got a couple of pieces of glass and in between it it had as uh something to collect that conducts electricity. UM. And the missing piece in this sandwich UM is not Bologney. It is a fan of liquid crystals. UM. The crystals themselves are sort of in between you might say, what is a liquid crystal. It's sort of in between a solid and a liquid UM. And the key is

that uh conductor, the electricity that's behind it UM. These crystals are twisted UM and basically, depending on how much of an electrical charge they receive, the untwist to let more light through. And what you see when you look at the display is the light reflecting off that mirror behind the crystals, and they change to display a different picture, you know, depending on how much electricity red uses or white uses UM. And it's a you know, pretty simple thing,

you know. They they're they're one of the big things right now is l c D s and televisions, l c d s and laptops and computers, right and that light is always on, which is why you hear people talk about l c d s and contrast with with with the blacks, because even when your screen is black, it's still back lit. So if you have an older l c D screen, it may not show blacks as

well as some of the newer ones. Uh. If you were to to have your your computer on, but have a black screen, uh, and then turn off the lights. You would still be able to kind of see where the screen was, right. Yeah, it's sort of a dark gray, you know, the right gray, rather than a complete black like you might see with a plasma television. That's one of the deals that a lot of people who are

plasma afficionados prefer. Yeah, right, right, and and but people also point out that l c D displays tend to be better as far as an energy consumption goes then plasma. That plasma actually takes up more energy to to warm up and keep running. Um, so you would think that l c D s are really the more green, anscious way to go if you're gonna buy electronics. But we just found out something that that kind of puts this

into a different light. Yeah, I was, I was reading a story I think it was initially I've seen it in It's actually been in several places that Grist magazine, which is an environmental website. Um, you know, it's been in uh New Scientists, I believe, and it was an article that was based in the Geophysical Research Letters. It is, you know, it's on my coffee table unfortunately has filled coffee on it and wasn't able to read this article.

But it's all about this chemical called nitrogen trifluoride, which is apparently not something you put on your teeth. No. No, Nitrogen trifluoride is a gas that's used in the production of l c d s. It's one of several gases that are used. Um. It's used in a thin film deposition. Now that's that's kind of not to get too technical, but you use a vapor to create a very thin film home which l c ds need in order to work. Um. And it's not just l c d s, they're they're

used for things like semiconductors and other things as well. Uh. The problem is that nitrogen trifluorides a pretty nasty gas. Uh, not just hazardous to humans if you inhale it, although I don't recommend doing that. First of all, it's got a moldy odor, so it doesn't smell very good, and it can also poison your liver and kidneys, So if you if you're used to have in those, I would recommend not taking a big whiff of nitrogen trifluoride. But

it also is environmentally hazardous. Turns out it's extremely environmentally hazardous. Yeah. Try seventeen thousand times more serious than carbon dioxide. That's a that's a big number. Yeah, it's a very big number. Um. The funny thing is this, uh, this was actually intended. This gas is actually replacing uh, chemicals called perfluora carbons, which are greenhouse gases. Um. And they removed those because

of environmental concerns that they were contributing to global warming. Right, and and nitrogen trifluoride wasn't even on the Kyoto Protocols, you know, international Climate Change Agreement, that that wasn't listed, so it completely skipped under the radar. It wasn't until this, uh, this information in the geophysical research letters that people really started to pay attention and say, hey, this stuff is

is serious business. That's true. Um. As it turns out, there was so little of it being made around the time of the the Kyoto Treaty writing you know, being written in the nineties that they just they really had no idea of the environmental impact of it. But apparently if you produced if you took all the uh n F three produced in two thousand and eight, according to the article, and released it in the atmosphere, it would have the same impact as the annual carbon dioxide emissions

of Austria. Yep. That's UM family global warming, if you will. And just to give you a little more perspective, UM, there's initial projections for for nitrogen trifluoride production next year UM suggest that there will be around eight thousand metric tons of the stuff made in order to to make these various devices. UM. And then so this is eight

thousand metric tons that eventually will enter the environment. And maybe years and years from now when people start throwing their their lc D displays away and they you know, rupture or whatever, it might be a while before this stuff actually makes it into the environment. But you multiply eight thousand metric tons by seventeen thousand times the strength of a carbon dioxide as far as a greenhouse gas goes, you end up with a hundred and thirty six million

tons equivalent of carbon dioxide. It sounds like a lot, all right, I'm not gonna lie the hundred three or six million that's metric tons. That's that's a lot of tons. But in two thousand five, the United States produced nearly six billion metric tons of carbon dioxide from energy consumption. That's everything from coal firing to you know, everything as far as the energy production and consumption goes, including the energy that you would need to you know, say run

your l c D devices exactly. So the six billion versus thirty six million, I mean, that's still you're talking about so many you know, orders of magnitude. But that doesn't mean that we should ignore this nitrogen tri fluoride problem. You know, that's just on my on my gut feeling here.

I think it's sort of like the trans fat thing when it when it popped up, people all of a sudden went oh, well, uh, you know, I had no idea that was going on, and they you know, now that it's starting to you know, show up in the public consciousness, then now we're going to have to find some other solution that isn't you know, per flora carbons or something else to to make l c D s because you know, in the long run, the l c D is a is more is more energy efficient than

a cathode ray tube or you know, some of the other devices that it is replacing, So you know, it's uh, it's a balancing. You're going to have to find some other solution to the other thing is that when you're looking at something like lc D displays that that seems like it's a much more manageable problem than reducing huge amounts of carbon dioxide emissions. It's at least something that

we can take steps to to fix. You know, it's not a problem that's so huge that you just look at it and goggle and wonder what do I do? Although I good I should also point out this gas it's kind of ironic. Um it's also used in the production of photovoltaic cells also known as solar panels. So even when we're trying to be environmentally conscious and use renewable energy sources, we may be in the in the production of those sources, we might be doing some pretty

severe damage to our environment. Yeah, well, I think that's probably enough depression for one podcast, don't you. Yeah, I'm I'm thoroughly worn out. Okay, Well, I'm sure guys are two. So if you would like to learn more about l c D s, read our article on how l c D S work at how stuff works dot com, and we'll talk to you again soon for more on this and thousands of other topics. Does it how stuff works dot com. Let us know what you think. Send an

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