WEBVTT - How LCDs Work

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<v Speaker 1>Brought to you by the reinvented two thousand twelve camera.

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<v Speaker 1>It's ready. Are you get in touch with technology? With

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<v Speaker 1>tech stuff from how stuff works dot com. Hey there,

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<v Speaker 1>welcome to the podcast. My name is Chris Polette. I'm

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<v Speaker 1>an editor here and How Stuff Works with me as

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<v Speaker 1>writer Jonathan Strickland. Howdy and uh. We've been looking at

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<v Speaker 1>some of the most popular articles on the site to

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<v Speaker 1>get some ideas for podcasts, and today we decided on

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<v Speaker 1>how l c D s work. That's liquid crystal displays.

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<v Speaker 1>And the listeners to this podcast probably know what that means,

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<v Speaker 1>but it might be looking at one right now in

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<v Speaker 1>fact exactly UM, but a lot of people don't know

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<v Speaker 1>exactly how they're made. I was one of those, UM,

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<v Speaker 1>and I went back into uh the l c D

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<v Speaker 1>article that we have on the site, and basically, it's, uh,

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<v Speaker 1>the screen that you see on your laptop computer or

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<v Speaker 1>your desktop display is a is a sandwich, as we

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<v Speaker 1>say in the South. It's UM. It's got a mirror,

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<v Speaker 1>it's got a couple of pieces of glass and in

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<v Speaker 1>between it it had as uh something to collect that

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<v Speaker 1>conducts electricity. UM. And the missing piece in this sandwich

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<v Speaker 1>UM is not Bologney. It is a fan of liquid crystals. UM.

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<v Speaker 1>The crystals themselves are sort of in between you might say,

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<v Speaker 1>what is a liquid crystal. It's sort of in between

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<v Speaker 1>a solid and a liquid UM. And the key is

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<v Speaker 1>that uh conductor, the electricity that's behind it UM. These

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<v Speaker 1>crystals are twisted UM and basically, depending on how much

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<v Speaker 1>of an electrical charge they receive, the untwist to let

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<v Speaker 1>more light through. And what you see when you look

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<v Speaker 1>at the display is the light reflecting off that mirror

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<v Speaker 1>behind the crystals, and they change to display a different picture,

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<v Speaker 1>you know, depending on how much electricity red uses or

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<v Speaker 1>white uses UM. And it's a you know, pretty simple thing,

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<v Speaker 1>you know. They they're they're one of the big things

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<v Speaker 1>right now is l c D s and televisions, l

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<v Speaker 1>c d s and laptops and computers, right and that

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<v Speaker 1>light is always on, which is why you hear people

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<v Speaker 1>talk about l c d s and contrast with with

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<v Speaker 1>with the blacks, because even when your screen is black,

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<v Speaker 1>it's still back lit. So if you have an older

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<v Speaker 1>l c D screen, it may not show blacks as

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<v Speaker 1>well as some of the newer ones. Uh. If you

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<v Speaker 1>were to to have your your computer on, but have

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<v Speaker 1>a black screen, uh, and then turn off the lights.

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<v Speaker 1>You would still be able to kind of see where

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<v Speaker 1>the screen was, right. Yeah, it's sort of a dark gray,

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<v Speaker 1>you know, the right gray, rather than a complete black

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<v Speaker 1>like you might see with a plasma television. That's one

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<v Speaker 1>of the deals that a lot of people who are

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<v Speaker 1>plasma afficionados prefer. Yeah, right, right, and and but people

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<v Speaker 1>also point out that l c D displays tend to

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<v Speaker 1>be better as far as an energy consumption goes then plasma.

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<v Speaker 1>That plasma actually takes up more energy to to warm

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<v Speaker 1>up and keep running. Um, so you would think that

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<v Speaker 1>l c D s are really the more green, anscious

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<v Speaker 1>way to go if you're gonna buy electronics. But we

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<v Speaker 1>just found out something that that kind of puts this

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<v Speaker 1>into a different light. Yeah, I was, I was reading

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<v Speaker 1>a story I think it was initially I've seen it

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<v Speaker 1>in It's actually been in several places that Grist magazine,

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<v Speaker 1>which is an environmental website. Um, you know, it's been

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<v Speaker 1>in uh New Scientists, I believe, and it was an

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<v Speaker 1>article that was based in the Geophysical Research Letters. It is,

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<v Speaker 1>you know, it's on my coffee table unfortunately has filled

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<v Speaker 1>coffee on it and wasn't able to read this article.

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<v Speaker 1>But it's all about this chemical called nitrogen trifluoride, which

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<v Speaker 1>is apparently not something you put on your teeth. No. No,

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<v Speaker 1>Nitrogen trifluoride is a gas that's used in the production

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<v Speaker 1>of l c d s. It's one of several gases

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<v Speaker 1>that are used. Um. It's used in a thin film deposition.

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<v Speaker 1>Now that's that's kind of not to get too technical,

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<v Speaker 1>but you use a vapor to create a very thin

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<v Speaker 1>film home which l c ds need in order to work. Um.

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<v Speaker 1>And it's not just l c d s, they're they're

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<v Speaker 1>used for things like semiconductors and other things as well. Uh.

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<v Speaker 1>The problem is that nitrogen trifluorides a pretty nasty gas. Uh,

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<v Speaker 1>not just hazardous to humans if you inhale it, although

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<v Speaker 1>I don't recommend doing that. First of all, it's got

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<v Speaker 1>a moldy odor, so it doesn't smell very good, and

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<v Speaker 1>it can also poison your liver and kidneys, So if

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<v Speaker 1>you if you're used to have in those, I would

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<v Speaker 1>recommend not taking a big whiff of nitrogen trifluoride. But

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<v Speaker 1>it also is environmentally hazardous. Turns out it's extremely environmentally hazardous. Yeah.

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<v Speaker 1>Try seventeen thousand times more serious than carbon dioxide. That's

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<v Speaker 1>a that's a big number. Yeah, it's a very big number. Um.

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<v Speaker 1>The funny thing is this, uh, this was actually intended.

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<v Speaker 1>This gas is actually replacing uh, chemicals called perfluora carbons,

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<v Speaker 1>which are greenhouse gases. Um. And they removed those because

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<v Speaker 1>of environmental concerns that they were contributing to global warming. Right,

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<v Speaker 1>and and nitrogen trifluoride wasn't even on the Kyoto Protocols,

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<v Speaker 1>you know, international Climate Change Agreement, that that wasn't listed,

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<v Speaker 1>so it completely skipped under the radar. It wasn't until this, uh,

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<v Speaker 1>this information in the geophysical research letters that people really

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<v Speaker 1>started to pay attention and say, hey, this stuff is

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<v Speaker 1>is serious business. That's true. Um. As it turns out,

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<v Speaker 1>there was so little of it being made around the

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<v Speaker 1>time of the the Kyoto Treaty writing you know, being

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<v Speaker 1>written in the nineties that they just they really had

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<v Speaker 1>no idea of the environmental impact of it. But apparently

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<v Speaker 1>if you produced if you took all the uh n

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<v Speaker 1>F three produced in two thousand and eight, according to

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<v Speaker 1>the article, and released it in the atmosphere, it would

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<v Speaker 1>have the same impact as the annual carbon dioxide emissions

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<v Speaker 1>of Austria. Yep. That's UM family global warming, if you will.

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<v Speaker 1>And just to give you a little more perspective, UM,

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<v Speaker 1>there's initial projections for for nitrogen trifluoride production next year

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<v Speaker 1>UM suggest that there will be around eight thousand metric

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<v Speaker 1>tons of the stuff made in order to to make

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<v Speaker 1>these various devices. UM. And then so this is eight

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<v Speaker 1>thousand metric tons that eventually will enter the environment. And

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<v Speaker 1>maybe years and years from now when people start throwing

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<v Speaker 1>their their lc D displays away and they you know,

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<v Speaker 1>rupture or whatever, it might be a while before this

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<v Speaker 1>stuff actually makes it into the environment. But you multiply

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<v Speaker 1>eight thousand metric tons by seventeen thousand times the strength

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<v Speaker 1>of a carbon dioxide as far as a greenhouse gas goes,

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<v Speaker 1>you end up with a hundred and thirty six million

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<v Speaker 1>tons equivalent of carbon dioxide. It sounds like a lot,

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<v Speaker 1>all right, I'm not gonna lie the hundred three or

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<v Speaker 1>six million that's metric tons. That's that's a lot of tons.

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<v Speaker 1>But in two thousand five, the United States produced nearly

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<v Speaker 1>six billion metric tons of carbon dioxide from energy consumption.

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<v Speaker 1>That's everything from coal firing to you know, everything as

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<v Speaker 1>far as the energy production and consumption goes, including the

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<v Speaker 1>energy that you would need to you know, say run

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<v Speaker 1>your l c D devices exactly. So the six billion

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<v Speaker 1>versus thirty six million, I mean, that's still you're talking

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<v Speaker 1>about so many you know, orders of magnitude. But that

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<v Speaker 1>doesn't mean that we should ignore this nitrogen tri fluoride problem.

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<v Speaker 1>You know, that's just on my on my gut feeling here.

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<v Speaker 1>I think it's sort of like the trans fat thing

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<v Speaker 1>when it when it popped up, people all of a

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<v Speaker 1>sudden went oh, well, uh, you know, I had no

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<v Speaker 1>idea that was going on, and they you know, now

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<v Speaker 1>that it's starting to you know, show up in the

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<v Speaker 1>public consciousness, then now we're going to have to find

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<v Speaker 1>some other solution that isn't you know, per flora carbons

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<v Speaker 1>or something else to to make l c D s

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<v Speaker 1>because you know, in the long run, the l c

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<v Speaker 1>D is a is more is more energy efficient than

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<v Speaker 1>a cathode ray tube or you know, some of the

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<v Speaker 1>other devices that it is replacing, So you know, it's uh,

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<v Speaker 1>it's a balancing. You're going to have to find some

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<v Speaker 1>other solution to the other thing is that when you're

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<v Speaker 1>looking at something like lc D displays that that seems

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<v Speaker 1>like it's a much more manageable problem than reducing huge

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<v Speaker 1>amounts of carbon dioxide emissions. It's at least something that

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<v Speaker 1>we can take steps to to fix. You know, it's

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<v Speaker 1>not a problem that's so huge that you just look

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<v Speaker 1>at it and goggle and wonder what do I do?

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<v Speaker 1>Although I good I should also point out this gas

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<v Speaker 1>it's kind of ironic. Um it's also used in the

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<v Speaker 1>production of photovoltaic cells also known as solar panels. So

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<v Speaker 1>even when we're trying to be environmentally conscious and use

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<v Speaker 1>renewable energy sources, we may be in the in the

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<v Speaker 1>production of those sources, we might be doing some pretty

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<v Speaker 1>severe damage to our environment. Yeah, well, I think that's

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<v Speaker 1>probably enough depression for one podcast, don't you. Yeah, I'm

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<v Speaker 1>I'm thoroughly worn out. Okay, Well, I'm sure guys are two.

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<v Speaker 1>So if you would like to learn more about l

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<v Speaker 1>c D s, read our article on how l c

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<v Speaker 1>D S work at how stuff works dot com, and

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<v Speaker 1>we'll talk to you again soon for more on this

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<v Speaker 1>and thousands of other topics. Does it how stuff works

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<v Speaker 1>dot com. Let us know what you think. Send an

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