THE LIQUID CRYSTALS – The thing that makes moving images possible.

Whenever I want to relax myself or even when I travel and I want to use my free time in the most enjoyable way I either read a book, listen to music or watch a movie. Reading a book and listening music was always the most available way to entertain yourself, but recently watching a moving image, namely a video of something is equally easier. In the past not very long time ago, when you wanted to see a movie you had only 2 options either at home on your TV or downtown at the cinema. Today you can do it everywhere you want. You can use your smartphone, you can use a tablet, the TV sets exsiting today are ultra perfomant so if you have a big one at home you don’t even need to go to the cinema, when you fly on long distances you can enjoy watching a video on the screen encased in the backside of the seat in front of you, screens are very performant today, they are everywhere. But what is this stuff? What makes them so special that we are so addicted to them?

Well… the screens are the essential elements that make the digital world possible. We now depend on them. They are the things that make the moving images possible. But this started from something that is equally old as the first human civilissations: THE PAINTINGS.

Long before the television and photography was available people did paint all sort of images which represented portraits or landscaped or a story that could generate some sort of emotions, this is called Painting Art. There were a lot of famous painting artists in world who created remarcable masterpieces of art with their painting and this happend for millenia, until not later than 100 years ago when photography started to become available. Still today there are many talented artists able to paint amaizing and very detailed views of everything. But let’s see below how the high-tech of today happenend.

When you dab paint on a canvas, the liquid sticks to it, and to any other layers of paint you´ve already put down – just as our early ancestors learnt with their cave paintings, paint is effectivelly a coloured glue. Thus a paint´s job is to turn from a liquid into a solid and then stay in place permanently. Different paints achieve this in different ways.

Watercolor paint does it by drying, releasing water into the air through evaporation and leaving only the pigments on the page. Oil paint is made of oils – usually poppy, nut or linseed oils. It doesn´t  dry. Instead, it  has another trick up its sleeve: it reacts with oxygen in the air. Normally, this type of reaction is to be avoided, because oxidation turns butter and cooking oils, for example, rancid and bitter-tasting. But in case of oil paint it is an advantage. Oils are comprised of long hydrocarbon chain molecules. The oxygen grabs a carbon atom from one chain and joins it to another through a reaction, in process opening up that molecule to further reactions. In other words, oxygen acts as a hardener (just as water acts as a hardener in superglue) – and yes, this is yet another polymerization reaction.

This reaction is extremely useful because it produces a hard, waterproof finish of plastic on the canvas (oil painting could more accurately be referred to as plastic painting); it´s incredibly resilient and holds up very well with age. The  polymerization takes time though, since oxygen has to diffuse through the top, hard layers of paint before it can get to the unreacted oil underneath. This is the downside of oil paint – you have to wait a long time for it to harden. But the great masters of oil painting, like Van Eyck, Vermeer and Titian, used this to their advantage. They overlaid many thin layers of oil paint, which one by one chemically reacted with oxygen and hardened, building up a number of layers of semi-transparent plastic, one on top of another, a complex encasting of many  differently coloured pigments. Layering paintings gradually like this allows the painter to create wonderfully nuanced work because when the light hits the canvas, it doesn´t just bounce off the top layer – some of it penetrates deep in the painting and rebounding as coloured light. Or alternatively, it is fully absorbed by the different layers and thus produces deep blacks. It´s a sophisticated  way of controlling colour, luminosity and texture, which is  exactly why oil paint was adopted by the Renaissance artists.

Analysis of Titian´s painting Ressurection reveals 9 layers of oil paint, all working to create complex visual effects. It´s exactly the intricate expressiveness of oil paint that made Renaissance art so sensual and passionate. The effect of layering is so powerful  that it has transcended its roots in painting with oils and is now incorporated into all professional digital illustration tools. If you use Photoshop, or Illustrator, or any other computer graphics tools, you´ll be making images in layers. As with layering, so linseed oil is also used for many applications beyond oil paint, such as for treating wood, whereby it creates a transparent, protective, plastic barrier – just as oil paint does, but this time, without colour. Cricket bats are just one of many wooden objects traditionally given an outer coating using linseed oil. You can also go the whole hog and use linseed oil to make a solid material called linoleum, again through a polymerization reaction.

A lino print, Secret Lemonade Drinker, by Ruby Wright

Linoleum, a plastic, has been used by designers and interior decorators as a waterproof floor covering. Artists use linoleum, too. They carve images into it just as they do with woodcuts, to create prints. Here again, layers are the primary way of building up complexity in the final work. As visually absorbing as they are, neither printmaking nor oil painting will give you a moving image. But if you take a carbon-based molecule, one not so different from those found in linseed oil, such as 4-cyano-4´-pentylbiphenyl, suddenly a moving image becomes possible.

the molecular structure of 4-cyano-4´- pentylbiphenyl, commonly used in liquid cristals

The main body of a 4-cyano-4´pentylbiphenyl molecule is made up of two hexagonal rings. This gives it its rigid structure, but the electrons binding it together are not evenly distributed: it is a polar molecule. There are areas concentrated in negative electrical charge and some concentrated in positive electrical charge. The positive charges on one molecule attract the negative charges on another, increasing the tendency of molecules to align with each other in an organized structure – a crystal. But the tail of 4-cyano-4´-pentylbiphenyl has a CH3 group on it, one that´s flexible and wriggles acting in opposition to the formation of a crystal. Hence 4-cyano-4´-pentylbiphenyl structures are partly organized and partly fluid – a so-called liquid crystal.

Above a temperature of 35°C, the influence of the CH3 tail wins and 4-cyano-4´- pentylbiphenyl behaves like a normal transparent oil. But cool it down to room temperature, and the liquid becomes milky in appearance. It´s not solid at this temperature, but something odd has happened to it. The molecules have begun to align with one other in much the same way that fish align when they´re part of a shoal. It´s very unusual for liquids to have a structure like this. One of the definitive qualities of a liquid is that its atoms and molecules have too much energy to stay in one place for any length of time, and so they are constantly rotating, vibrating and migrating. But liquid crystals are different – the molecules are still dynamic, and can flow, but they keep an alignment of their orientation, which has been compared to the regular alignment of atoms in a crystal – hence the name.

An illustration of the difference in structure between a crystal, a liquid crystal and a liquid

The alignment ist´t perfect, though; because the molecules are in a liquid state, they keep moving around, swapping places with each other and joining other shoals. But the polar molecules give the liquid crystal another useful property – they respond to applied electric fields. They do so by changing their direction of alignment. Thus you can get a whole shoal to point in a particular direction by applying a voltage. This turns out to be key to the technological success of liquid crystals; it´s what allows them to be integrated into electronic devices.

When light travels through a liquid crystal, subtle changes occur: the polarization changes. To make sense of this, think about light as a wave: a wave of oscillating electric and magnetic fields. But which direction do they oscillate in? Up and down, side to side or left and right? Standard light from the sun oscillates in all of these directions. But if it bounces off a smooth surface, the surface will encourage the oscillations to move in certain directions, and suppress others, depending on which ones it´s aligned with. Thus the rebounding light will contain some oscillations and not others. This is called polarized light. It´s not just surfaces that do this to light. Some transparent materials will change the polarization of light, too; polarized sunglasses, for instance. The lenses of polarized sunglasses only let one direction of oscillation through. This obviously reduces the intensity of the light reaching your eyes, which is why you see the world as darker. They´re especially usefull at the beach, not just because they shade your eyes, but because the glare coming off the surface of a smooth sea is also polarized, and the lenses are designed to block it out. Fishermen use polarized sunglasses to help them see underwater more easily, and photographers use polarized lenses for the same reason – to cut the glare.

The screenplays for Sci-Fi and Fantasy movies are not only based on our immagination, the stories behind have seeds of truth. Let’s take for example the SpiderMan movies: in reality some spiders can detect polarized light, and when I watched this movie I wondered if this could be part of Spider-Man´s ability to react quickly to danger, his so-called ´spider-sense´. In the film he´d just narrowly escaped being captured by Doctor Octopus with an uncanny, split-second decision that allowed him to evade the villain´s tentacles. The special effects were indeed amazing, but these are actually based on real facts, there are spider species that can indeed detect polarized light.

Liquid crystals change the polarization of light – that´s how the image of Spider-Man was being conjured up in the screen in front of me when I watched the movie. If you put a lens from your polarized sunglasses on the surface of a crystal, the light coming out of the liquid crystal will appear bright if its polarization is aligned with the lens, but otherwise it will appear dark. But here is the neat trick: if you switch the structure of the liquid crystal also changes. So at the flick of a switch, you can turn the light on and off. Suddenly, you have a device that is capable of giving out white light, and then none, and then going back to white again, as fast as you can electronically switch the liquid-crystal structure – the makings of a black-and-white screen.

This, it may sound simple, but it took decades to achieve. It was an Austrian botanist by the name of Friedrich Reinitzer who first categorized the weird behavior of liquids crystals in 1888, just two years before Oscar Wilde wrote The Picture of Dorian Gray. While many scientists studied them over the course of the next 18 years, no one could really find a use for them. It wasn´t until 1972, when the Hamilton Watch Company launched the first digital watch, called the Pulsar Time Computer, that liquid crystals found their moment. The watch looked great, unlike any other watch that had come before it, and it cost more than the average car. People who bought it thought they were buying the future – and they were right: digital technology was coming, and this was the first mass-market item in what would become a trillion-dollar industry.

The Pulsar Time Computer was made with LEDsLight Emitting Diodes – which were themselves made from semiconductor crystals that emit red light in response to an electric current. They looked great especially on a black background, and the rich and famous went craze for them – even James Bond wore one in the 1973 film Live and Let Die. The drawback of LEDs at that time, though, was their high energy consumption, those first digital watchers had very short battery lives. In order to satisfy the new-found sensational demand for digital watches, there would need to be a more energy-efficient screen technology. Suddenly, after decades of being a lab curiosity, liquid crystals had their use. They quickly dominated the digital-watch market because the electric power required to switch a liquid-crystal pixel from white to black is absolutely minuscule. They  were cheap too – so cheap that manufacturers started making the whole display screen out of liquid crystals – this is the grey screen you see on a digital watch. The watch electronically switches certain areas of the grey liquid crystal to block polarized light which creates black. This allows the watch to show changing numbers, so you can view the time, or date, or anything else that can be conveyed in this small, digital format.

A casio calculator watch

One of my stongest memories from childhood in the 1980s is the insane jealousy I felt when my best friend came back to school after the holidays with the new Casio digital watch and calculator. I was ridiculously impressed as he nonchalantly pressed the tiny little buttons which beeped happily at him. Of course, I see now it´s kind of dumb – who really wants a tiny calculator? But still, at the time, I was completely captivated. It was the beginning of my addiction to gadgets. Even though digital watches have lost their cool, they´ve been replaced by a seemingly never-ending parade of other gadgets, not least of which have been mobile phones, which are still using liquid-crystal displays. It may seem surprising but it is the same basic technology used in a digital watch that has also yielded the modern smartphone screen, capable of displaing color video. This brings us right back to oil paintings, and the puzzle of creating the moving painting depicted in the novel The Picture of Dorian Gray. Liquid crystals could perhaps be just what´s needed – but how do they create colour?

We all know that if you take yellow paint and mix it with blue, our eyes interpret that mixture as green, similarly, if you take red paint and add blue, you get purple. Colour theory shows that you can make any particular colours by mixing together combination of primary colours. In the printing industry, cyan (C) , magenta (M) and yellow (Y) are generally used with the addition of black (K) liquid to control contrast. This is also how inkjet printers work and why you see the abbreviation CMYC on the side of printer cartridges. These colours are printed on the page by your printer, dot by dot, and it´s our eyes and visual system that integrate them into a coherent colour. We´ve known that the eye can be fooled this way for a long time. Newton took note of this manipulation in the 17th century and it was used as a painting technique by the Pointillists in the 19th century. The main advantage is that the blobs of pigments remain physically unmixed and so their brightness and luminosity can be controlled to create the effect you want. As predicted by colour theory, it´s possible to make any colour by mixing paints this way as long as the dots are small and placed close together. But changing the colour once you´ve made them is another story. You´d have to physically change the ratios of pigments on the canvas. Which means you would have to remove some dots and add others. Unless, of course, you found a way to put down dots with every possible combination of colours.

This is essentially how liquid-crystal colour displays work, whether they´re on your phone, your TV or, encased in the back of the seat in front of you on the plane. We call the dots: pixels. Each pixel has 3 coloured filters that let 3 primary colours through. For displays these are red (R) , green (G) and Blue (B)- hence the abbreviation RGB. If they are all emitted egually, then the pixel appears white, even though it´s made up of 3 separate colours. You can see this for yourself if you put a small drop of water on your phone and look through it on to the screen. The water behaves as a magnifying glass which allows you to see the sets of 3 different pixels: red, green and blue.

Just as the masters of oil painting had to work out how to bring darkness and shadow into their work by mixing colours and inventing a colour theory for perception, so are today´s liquid-crystal displays engineers and scientists pushing the boundaries of colour display with moving images. And just as in the Renaissance, when oil painting battled it out with other techniques, like fresco and egg tempera, so these days do Liquid-Crystal Displays (LCDs) compete with Organic Light-Emitting Diodes (OLEDs). This battle which is currently being played out it ever new generation of TVs, tablets and smartphones, has its own arcane language. LCDs, you might be told by an online blog, can´t show deep  blacks because the polarizers that keep light from coming through during a dark scene in a movie aren´t 100% effective; you end up with greys.

Organic Light-Emitting Diodes

Similarly, because of the way colour is created in LCDs, the absolute brightness of some hues suffers. Hence the issue with the blinds in the cabin on a plane, and not wanting to have sunlight reflecting off the screen making things worse. Nevertheless, the displays have got better and better thanks to great innovations that ultimately aren´t so different from layering oil paint. For example the addition of an active-matrix layer allows some of the pixels to be switched independently from others. Thus some parts of the image can be given higher contrast than others – instead of having to set the contrast for the whole image. This is useful for scenes of a movie that are partially lit. It is all done automatically of course, with transistor technology – that´s what the ´active´ means in ´active matrix´. Engineers have also learnt to improve the way the image changes depending on your viewing angle. It used to be that you couldn´t  see the screen very well at certain angles, but now a ´diffuser layer´ is incorporated, which spreads the light out as it leaves the screen. In comparison, the technology of OLEDs, which are the succesors of the red-light-emitting diodes of the original digital watch, the Pulsar Time Computer, are now energy-efficient. They also have a  much larger palette of colours, and near-perfect viewing angles. But, despite being much more expensive than LCDs, they´re still not yet as bright.

OLED Applications

LCDs may not be perfect, but they are essentially the dynamic canvas that Oscar Wilde dreamed of. It´s now possible to have a portrait of yourself on display in your hall (or your attic) that updates daily. When liquid-crystal displays became really cheap a few years ago, people started giving them to one another as presents in the form of dynamic photo frames. But these didn´t end up being that popular. In fact people hated them, just as Dorian Gray loathed his dynamic portrait. I´m convinced it wasn´t the quality of the image that they hated – plenty of people love looking at themselves on their liquid-crystal smartphone display – but rather, something about the very nature of these displays. They´re impostors, something fluid, magical and dreamlike pretending to be a solid, dependable and real photograph of a  moment frozen in time.

When applied to television in the form of flat-panel TVs, that same technology has been hugely popular. Switching the colour of the pixels in a coordinated manner allows TV screens to display moving pictures. They´re why we can see actors talking, gesturing and making different facial expressions, and in the case of the SpiderMan movie, leaping from building to building, saving the world from evil. When I watched this movie, even though I knew what I was watching wasn´t real, that it was just a collection of primary-colour pixels flashing along to an accompanying soundtrack, it still stimulated me, both intellectually and emotionally, completely absorbing me in the story. But here is the thing I find really difficult to understand. If I compare the experience of watching this film on a plane with standing in an art gallery viewing a masterpiece such as Titian´s Resurrection, I know which one is more likely to move me. It´s the film, I´m afraid. I´m not proud of this. I know that Titian´s paintings are great art and superhero movies played on a 10-inch display on the back side of a seat in a plane, are not. Why am I so shallow? Could it be that at 12.000 meter altitude I lose all taste in art? Or it is something to do with the heightened emotional state of flying?

Static images like paintings and photographs allow us to contemplate ourselves, and how much  we´ve changed from viewing to viewing. As we revisit great works of art, be they by Titian, Van Gogh or Frida Kahlo, over our lifetimes we can trace our reactions to them. The images may remain the same, but our sense of what they mean changes as we change. The magical liquid screens on aeroplanes act in the opposite manner; they are dymamic, and offer us a vivid window into another world. They let us escape ourselves. Flying above the clouds at 12.000 meters, in a darkened cabin, we enter into a fantasy. We can act, for a little while, like gods, looking down on the deeds of human through our liquid portals, observing them, laughing at their foolishness, shaking our heads at their crazy ways. In doing so, our emotions are heightened. Some  academic research suggest that this is due to an extreme contrast between a feeling of intimacy and warmth with those depicted in the film and the stark reality of flying while sitting next to strangers in a tube 12.000 meters in the air. This certainly rings true for me.

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