tn display vs tft display free sample

When searching for a liquid crystal display (LCD), consideration of the device’s display technology is essential. Screen technology companies such as Apple and Samsung search for the best possible display panels and panel technology in order to offer their customers the best image quality. In competitive gaming, gaming monitors must be able to provide great image quality but also fast refresh rates so that gamers can play at a fast pace.

Before diving into how exactly liquid crystals affect display features, it is necessary to understand their general role in an LCD monitor. LCD technology is not capable of illuminating itself, so it requires a backlight. The liquid crystals are responsible for transmitting the light from backlight to the computer monitor surface in a manner determined by the signals received. They do so by essentially moving the light differently through the layer’s molecular matrix when the liquid crystals are oriented or aligned in a certain manner, a process which is controlled by the LCD cell’s electrodes and their electric currents.

The methods of alignment, however, can vary between panel types, offering different features and benefits. Two common and popular liquid crystal alignment techniques are twisted nematic (TN) and in-plane switching(IPS).

TN panels offer the cheapest method of crystal alignment. They also are the most common of the alignment methods and have been used for quite a long time in the display industry, including in cathode ray tubes (CRTs) that preceded the LCD.

In TN displays, the electrodes are positioned on either side of the liquid crystal layer. When a current is sent between the back and front electrode, something called an electric field is created that shifts and manipulates the orientation of the molecular matrix.

If no electric field is applied to the specific cell, the crystals experience a 90 degree twist in the alignment. As light from the backlight passes through this twist, the light waves are polarized, allowing them to pass through the polarizer that sits on the surface of the TN monitor.

If an electric field is applied, it can either untwist the TN liquid crystal layer partially or in full, depending on the strength of the field. The structure of TN crystals will typically straighten out when this happens, and some, if not all, light waves will not be polarized properly to pass through to the surface.

Each LCD cell composes a pixel of the display, and in each pixel are subpixels. These subpixels use standard red green blue (sRGB) colors to create a variety of colors to make the pixel display the necessary color to play its role in the overall display. If beneath the subpixel the liquid crystal fully polarizes the light, that subpixel’s specific color would be very bright in the pixel as a whole. But if the light is not polarized at all, then that color will not show up. If partially polarized, only a limited amount of that color is used in the mixture of RGB colors in the final pixel.

A more complex method of alignment is IPS. IPS monitors, unlike the TN, place both electrodes on the same level, behind the liquid crystal layer. When the electric field is applied, this forces the liquid crystal molecules to align themselves parallel to the IPS device layers instead of perpendicularly like the TN molecules.

Opposite of the TN, when the electric field is applied, IPS technology will polarize the light to pass, whereas when the electric field is not applied, the light will not be polarized to pass. Because of the orientation of the crystals, IPS displays require brighter, more powerful backlights in order to produce the correct amount of brightness for the display.

An important consideration is viewing angles. The TN offers only a limited viewing angle, especially limited from vertical angle shifts, and so color reproduction at these angles will likely not look the same as from a straight-on viewing; the TN’s colors may invert at extreme angles. The IPS counters that and allows for greater and better viewing angles that consequently offer better color reproduction at these angles than the TN. There is one issue with extreme viewing angles for IPS devices: IPS glow. This occurs when the backlight shines through the display at very wide angles, but typically is not an issue unless a device is looked at from the side.

In terms of color, as mentioned, TN devices do not have very strong color reproduction compared to other alignment technologies. Without strong color reproduction, color banding can become visible, contrast ratio can suffer, and accurate colors may not be produced. Color gamut, or the range of colors that the device can reproduce and display, is another feature that most TN displays do not excel in. This means that the full sRGB spectrum is not accessible. IPS devices, on the other hand, have good quality black color reproductions, allowing the device to achieve a deeper, richer display, but it is still not the best option if a customer is in search of high contrast (discussed further in a couple more paragraphs).

While TNs may not have the best color quality, they allow for high refresh rates (how often a new image is updated per second), often around 240 Hz. They also have the lowest input lag (receiving of signals from external controllers) at about one millisecond. TN panels often attract gamers because of the need for minimal lag and fast refresh rates in a competitive or time-sensitive setting. In consideration of moving displays like in video game displays, it is also important for fast response times (how fast a pixel can change from one amount of lighting to another). The lower the response time (the higher the response rate), the less motion blur will be shown as the display changes to show motion. TNs also offer these low response times, but it is important to remember that a powerful graphics processing unit, commonly called a GPU, is still needed to push these displays to meet the fastest refresh and response rates.

Oftentimes, refresh rates and frame rate of output devices (such as graphics cards) will not be synchronized, causing screen tearing when two different display images will be shown at once. This problem can be addressed through syncing technologies like Vsynch, Nvidia’s G-Sync, or FreeSync (a royalty-free adaptive synchronization technology developed by AMD).

Another common consideration of customers is the price of each display. TN, though it does not offer as high quality of a display, offers the lowest cost and best moving displays, making it useful if the intended use of the LCD monitor is simple and not too demanding. However, if you intend for something that calls for better color production or viewing angles, the IPS and other methods are viable choices, but at much higher costs. Even though IPS motion displays have reached the speed and rates of TNs, the price for such technology is much more expensive than the TN option.

There are other options besides the TN and IPS. One option is known as vertical alignment (VA) and it allows for the best color accuracy and color gamut. Compared to a typical IPS contrast ratio of 1000:1, VA panels can often have ratios of 3000:1 or even 6000:1. Besides improved contrast ratio, the VA is in between the TN and IPS. To compare the TN vs IPS vs VA, the VA does not have as great a viewing angle as IPS but not as poor as the TN. Its response times are slower than TN but faster than IPS (though at fast refresh rates, the VA displays often suffer from ghosting and motion blur). Due to the contrast ratio benefits, VA technologies are most often desirable for TVs.

And lastly, there is an option quite similar to IPS that is called plane to line switching (PLS). It is only produced by Samsung, who claims the PLS offers better brightness and contrast ratios than the IPS, uses less energy, and is cheaper to manufacture (but because it is only created by Samsung, it is hard to judge pricing). It also has potential in creating flexible displays.

– Liquid crystal material: Both use nematic LC materials but FSTN fluid has more cholesteric doping materials in it in order to help its molecular to twist higher degree.

– Viewing Angle: FSTN LCD has much better wide viewing angle than TN LCD especially at higher multiplexing application. TN LCD has a weak viewing direction, that is the reason we have to define 6 or 12 o’clock viewing angle. But FSTN LCD can be viewed clearly from all the viewing directions.

– Response time:  Between FSTN LCD has higher twist angle, it takes more time to make a change. It has longer response time or slower response speed than TN LCD.

– Operation Temperature Range:  Because of extremely slow response and background color change for FSTN LCDs at low temperature, FSTN LCDs can only be used within -20oC to +70oC, but TN LCDs can be used with -40oC to +90oC which can be easily used for outdoor applications. FSTN LCD response speed in extremely cold environment can be improved by adding a heater. FSTN LCD color change at low and high temperature can be solved by adding a reversed optical compensation cell as DSTN (Double STN), but the cost will be more than double.

– Power Consumption: Theoretically, FSTN and TN LCDs should consume the same level of power. But FSTN LCDs are normally used for high multiplex application, they use higher frequency drive and their LCD controllers and drivers normally consume more power than TN LCDs. While in general opinions, TN uses much less power than STN or FSTN LCD displays.

– Assembly (Display Module):  Because most of TN displays have fewer contacts, it can use pins, zebra, FPC (Flex Printed Circuit) to make the connections. When assembled in the LCD modules, normally COB (Chip on Board) is used. While FSTN displays have more contacts, high density and more reliable assembly ways have to be used. COG (Chip on Glass) excels because of its low cost and compatible for high volume production.

– Sunlight Readable: It is a big advantage for both TN and FSTN LCD. By applying a reflective or transflective polarizer at the back of the LCD, the high contrast display can be achieved under sunlight.

IPS (In-Plane Switching) lcd is still a type of TFT LCD, IPS TFT is also called SFT LCD (supper fine tft ),different to regular tft in TN (Twisted Nematic) mode, theIPS LCD liquid crystal elements inside the tft lcd cell, they are arrayed in plane inside the lcd cell when power off, so the light can not transmit it via theIPS lcdwhen power off, When power on, the liquid crystal elements inside the IPS tft would switch in a small angle, then the light would go through the IPS lcd display, then the display on since light go through the IPS display, the switching angle is related to the input power, the switch angle is related to the input power value of IPS LCD, the more switch angle, the more light would transmit the IPS LCD, we call it negative display mode.

The regular tft lcd, it is a-si TN (Twisted Nematic) tft lcd, its liquid crystal elements are arrayed in vertical type, the light could transmit the regularTFT LCDwhen power off. When power on, the liquid crystal twist in some angle, then it block the light transmit the tft lcd, then make the display elements display on by this way, the liquid crystal twist angle is also related to the input power, the more twist angle, the more light would be blocked by the tft lcd, it is tft lcd working mode.

A TFT lcd display is vivid and colorful than a common monochrome lcd display. TFT refreshes more quickly response than a monochrome LCD display and shows motion more smoothly. TFT displays use more electricity in driving than monochrome LCD screens, so they not only cost more in the first place, but they are also more expensive to drive tft lcd screen.The two most common types of TFT LCDs are IPS and TN displays.

When it comes to buying either a TV for home or a monitor for your office or a display for that gaming setup in your basement, things can be distilled down to usage and based on that; you can compare what different panels have to offer and how they will suit you. In this article, we will be having a quick look at the three most commonly used panels – TN, IPS and VA and helping you understand what they have to offer, and what they can be best used for. But first, a basic run on what an LCD is.

The major drawback of the CRT (cathode ray tube) technology was that it occupied quite a significant amount of space. The CRT displays worked on the principle of ‘light emission’ and they consumed a lot of power, which just added up to the size issue. The solution to these problems came in technological research on developing a screen that consumes less power (hence, increasing productivity), and which was smaller. Lit using fluorescent tubes, LCDs (liquid crystal displays) consume less power, are way thinner than the CRTs, and work on the principle of ‘blocking light’ rather than emitting it.

LCDs are made from a passive/active matrix grid made of conductors, the latter called as thin film display (or a TFT). Pixels are mounted on this grid at each intersection (and an active matrix has a transistor located at each pixel intersection). This network structure controls a pixel’s luminance and consuming a little amount of current. This ability leaves us with a choice to switch the current on and off more often on the grid, and this leads to a high ‘refresh rate.’ And a high refresh rate means a ‘smoother’ operation.

Developments in these screen types lead to LED TVs. The main difference between these and the LCDs is that they are lit using Light Emitting Diodes instead of fluorescent tubes. So technically, a LED display is a ‘LED backlit LCD screen.’

This LED backlighting helps in enhancing the color contrast and it consumes less power as compared to fluorescent tube lit panels. It significantly improves the overall picture quality by tapping into a wider RGB color range, and there is a better brightness achieved which allows you to see the images clearly, even in well-lit environments. On top of these things, LED backlit displays to consume less power and are lightweight too. So there are no drawbacks of this technology as such, resulting in backlighting being used in more and more panels every day. Today, we have three types of backlighting: White Edge, Full LED array, and Local Dimming LEDs.

This information, however not essential for everyone to know, is a good bit for panel enthusiasts and pro gamers, as having a high refresh rate depends on the panel’s build and it’s resolution. Now, let’s go ahead and have a look at the three most commonly used panels on these LCD monitors – TN, IPS, and VA.

The most common LCDs are based on TN (Twisted Nematic) panel designs. Manufactured on a vast scale and pretty cheap, TN displays can be found in most homes. Primarily made for supporting low response times, TN panels remain to this day, a cheaper option for gamers who want a massive resolution with a low response time and a high refresh rate. Not to say that the IPS panels don’t have these features, but an IPS panel with the same features as a TN (1ms response time, QHD resolution and a 144Hz refresh rate for example) will always be more expensive. However, while the price is good with the TN, the color quality and viewing angles take a toll. They are the drawbacks of a TN panel when compared to other panels out there.

TN displays, (TFT-LCDs for example), work by passing light through two polarized screens, a color filter and liquid crystals that tend to twist and block light in correspondence of the current applied to them. This type of an arrangement leaves a lot in your hands as you can change the amount of current applied to adjust the crystal twists. Hence, you can achieve virtually any color or shade reproduced on the screen. But while precise adjustments are possible with a TN display, there are some drawbacks to this structure.

Every LCD’s pixel is constructed using some red, green and blue sub-pixels. Colors and shades are produced by mixing different brightness levels for these pixels that result in the perception of a particular solid color by the user’s eyes. The problem with TN panels comes from its adoption of a 6-bit per channel model, which outputs 64 shades per color, instead of the 8-bit per channel, 256 shades implementation. Needless to say, color accuracy takes a toll here. And while the TN compensates for this issue with ‘dithering,’ (using alternating colors to produce a certain perceived shade) it is still a poor substitute for 24-bit color reproduction. On top of that, narrow viewing angles don’t help the case, as there is a ‘washout’ produced that puts TN panels at a low level concerning color accuracy.

But if your main concern is not the aesthetics of the performance, but the performance itself, TN LCD screens reign supreme over other panel types because of providing us low response times and high refresh rates on a budget.

Measured in milliseconds, pixel response time or ‘responsiveness’ is the time taken for a pixel to change from one shade (of gray) to another (denoted as grey-to-grey or GTG). The higher the response time, the more blur and smearing you will experience during rapid transitions. While no industry standard exists for measuring precise response times, there is a value specified by the manufacturers on these displays.

TN panel displays have very fast GTG pixel response times that are usually well under the typical 5ms TFT-LCD average. This makes these displays a good choice for competitive gamers who are willing to sacrifice some color accuracy and viewing angles for great performance at a good price.

In-Plane-Switching, or IPS, was designed to overcome the shortcomings of a Twisted Nematic panel and they are replacing TN panels. These panels also use polarized filters, liquid crystals, and transmitters. However, in this case, the arrangement is different. The liquid crystals in an IPS panel design are aligned in a way that allows less light to distort and achieves better color visibility. Additionally, IPS panels use 8-bits of depth per color unlike TN’s 6-bit, which results in a wider 256 shades spectrum. This takes care of the color accuracy problem.

The second thing that is improved in IPS panels is the range of viewing angles. While Twisted Nematic panel displays ‘washed out’ at shallow angles, IPS displays have rich colors that don’t shift/fade when viewed from side angles. One other significant improvement of the IPS screen was that there were no trailing distortions when you touched them. This made them ideal for Touch-screen applications.

While marketed as the best of the best, IPS screens have some drawbacks of their own. The major one happens to be the cost. The construction of IPS panels requires a greater number of transmitters and lighting for each pixel. Now, the higher the resolution of the constructed panel will be, the greater number of pixels will be mounted on the panel. This results in a complex architecture, and they cost more than their TN counterparts. However, with the rising competition in the market, the prices of IPS panels have come down from expensive to reasonable, and you can get a decent IPS display for a few hundred dollars. However, the more you want from your monitor as a consumer, the more pricey it will become. This leaves high-end IPS monitors most commonly found at the desks of editing professionals and competitive gamers – people who want a lot of color accuracy and detailing along with decent speed and longevity.

Today, many variants of the IPS also exist, like Samsung’s popular PLS (plane line switching) panels. These variants are not entirely different from IPS, though there are subtle ‘generational improvements’ like enhancements in viewing angles, brightness and whatnot. LG also has a variation to the IPS, called as the eIPS, which is basically a IPS panel you can get on a budget. However, in real world use, the usage experience varies by a little factor.

VA (Vertical Alignment) panel technology sits between the high speeds of TN and the color richness of IPS panels. Constructed implementing IPS’s 8-bit color depth per channel approach (that has a crystal design capable of reproducing rich colors), VA (and its variants) also retain some of the low latency of TN panels. This results in a display that is ‘almost’ as fast as TN and as colorful as IPS.

Often reaching 5000:1, VN panels have a superior contrast as compared to both IPS and TN screens, and this remains the highlight among other features. These panels reproduce better black levels than TN or IPS. However, there are more issues with VA panels today than there are advantages, and some of these issues can’t be ignored.

First on the list of cons is the color (and contrast) shift that happens when we view media from a wide angle. And while the viewing angles of VA panels are wider than TN, the shift is similar to a TN panel and renders most VA panels ‘not ideal’ for tasks that require a great amount of color accuracy. When it comes to gaming, there’s another issue. VA panels offer rapid light-to-dark pixel transitions. However, darker color shifts aren’t as speedy, and it can lead to blurring during high-performance tasks.

Just like there are variants of IPS, VA panels also have their own. To put it simply, they progressed from 1998 to 2005 (and beyond) from MVA, AMVA to AMVA+. MVA or Multi-domain Vertical Alignment technology first came out in 1998 and provided a 25ms response time with 160-170 degree viewing angles. This was, of course, a lot of value at the time. Today, these panels can be found as AMVA (Advanced MVA) in many displays, and they offer a contrast ratio as high as 5000:1 (which is the best contrast ratio in LCD technology), and QHD (2560 x 1440p) resolution at a wide screen size like 32 inches. So again, a lot of value here as well. After that, we have the AMVA+ which had improved viewing angles on the standard AMVA.

So in a nutshell, while VA panels are much better than average TN panels regarding color reproduction, they are still not good enough if you were to switch to premium TN panels oriented for gaming purposes. And when it comes to IPS panels, they dominate the list but with one disadvantage – price. If we were to talk about performance, high-end IPS panels reign over all else, with response times as low as 1ms, 144Hz refresh rates and supporting resolutions all the way up to 4K and 5K. If, however, you want to talk ‘value for money,’ TN panels give you decent colors and speed at decent rates. And if you have some more money in your pocket after selecting a TN panel of certain specifications, you can look for a VA panel that will offer you some added color quality and viewing angles. It’s all about comparison here, and understanding the fundamentals of these panels is a good starting point.

Let us start with the basics first; refresh the knowledge about TN and LCD displays in general, later we will talk about TFTs (Thin Film Transistors), how they differ from regular monochrome LCD displays. Then we will go on to the ghosting effect, so we will not only discuss the technology behind the construction of the TFT, but also some phenomena, like the ghosting effect, or grayscale inversion, that are important to understand when using an LCD TFT display.

Next, we will look at different technologies of the TFT LCD displays like TN, IPS, VA, and of course about transmissive and transflective LCD displays, because TFT displays also can be transmissive and transflective. In the last part we will talk about backlight.

Let us start with a short review of the most basic liquid crystal cell, which is the TN (twisted nematic) display. On the picture above, we can see that the light can be transmit through the cell or blocked by the liquid crystal cell using voltage. If you want to learn more about monochrome LCD displays and the basics of LCD displays, follow this link.

What is a TFT LCD display and how it is different from a monochrome LCD display? TFT is called an active display. Active, means we have one or more transistors in every cell, in every pixel and in every subpixel. TFT stands for Thin Film Transistor, transistors that are very small and very thin and are built into the pixel, so they are not somewhere outside in a controller, but they are in the pixel itself. For example, in a 55-inch TV set, the TFT display contains millions of transistors in the pixels. We do not see them, because they are very small and hidden, if we zoom in, however, we can see them in every corner of each pixel, like on the picture below.

On the picture above we can see subpixels, that are basic RGB (Red, Green, Blue) colors and a black part, with the transistors and electronic circuits. We just need to know that we have pixels, and subpixels, and each subpixel has transistors. This makes the display active, and thus is called  the TFT display. TFT displays are usually color displays, but there are also monochrome TFT displays, that are active, and have transistors, but have no colors. The colors in the TFT LCD display are typically added by color filters on each subpixel. Usually the filters are RGB, but we also have RGBW (Red, Green, Blue, White) LCD displays with added subpixels without the filter (White) to make the display brighter.

Going a little bit deeper, into the TFT cell, there is a part inside well known to us from the monochrome LCD display Riverdi University lecture. We have a cell, liquid crystal, polarizers, an ITO (Indium Tin Oxide) layer for the electrodes, and additionally an electronic circuit. Usually, the electronic circuit consists of one transistor and some capacitors to sustain the pixel state when we switch the pixel OFF and ON. In a TFT LCD display the pixels are much more complicated because apart from building the liquid crystal part, we also need to build an electronic part.

That is why TFT LCD display technologies are very expensive to manufacture. If you are familiar with electronics, you know that the transistor is a kind of switch, and it allows us to switch the pixel ON and OFF. Because it is built into the pixel itself, it can be done very quickly and be very well controlled. We can control the exact state of every pixel not only the ON and OFF states, but also all the states in between. We can switch the light of the cells ON and OFF in several steps. Usually for TFT LCD displays it will be 8-bit steps per color, so we have 256 steps of brightness for every color, and every subpixel. Because we have three subpixels, we have a 24-bit color range, that means over 16 million combinations, we can, at least theoretically, show on our TFT LCD display over 16 million distinct colors using RGB pixels.

Now that we know how the TFT LCD display works, we can now learn some practical things one of which is LCD TFT ghosting. We know how the image is created, but what happens when we have the image on the screen for a prolonged time, and how to prevent it. In LCD displays we have something called LCD ghosting. We do not see it very often, but in some displays this phenomenon still exists.

If some elements of the picture i.e., your company logo is in the same place of the screen for a long period of time, for couple of weeks, months or a year, the crystals will memorize the state and later, when we change the image, we may see some ghosting of those elements. It really depends on many conditions like temperature and even the screen image that we display on the screen for longer periods of time. When you build your application, you can use some techniques to avoid it, like very rapid contrast change and of course to avoid the positioning the same image in the same position for a longer time.

You may have seen this phenomenon already as it is common in every display technology, and even companies like Apple put information on their websites, that users may encounter this phenomenon and how to fix it. It is called image ghosting or image persistence, and even Retina displays are not free of it.

Another issue present in TFT displays, especially TN LCD displays, is grayscale inversion. This is a phenomenon that changes the colors of the screen according to the viewing angle, and it is only one-sided. When buying a TFT LCD display, first we need to check what kind of technology it is. If it is an IPS display, like the Riverdi IPS display line, then we do not need to worry about the grayscale inversion because all the viewing angles will be the same and all of them will be very high, like 80, 85, or 89 degrees. But if you buy a more common or older display technology type, like the TN (twisted nematic) display, you need to think where it will be used, because one viewing angle will be out. It may be sometimes confusing, and you need to be careful as most factories define viewing direction of the screen and mistake this with the greyscale inversion side.

On the picture above, you can see further explanation of the grayscale inversion from Wikipedia. It says that some early panels and also nowadays TN displays, have grayscale inversion not necessary up-down, but it can be any angle, you need to check in the datasheet. The reason technologies like IPS (In-Plane Switching), used in the latest Riverdi displays, or VA, were developed, was to avoid this phenomenon. Also, we do not want to brag, but the Wikipedia definition references our website.

We know already that TN (twisted nematic) displays, suffer from grayscale inversion, which means the display has one viewing side, where the image color suddenly changes. It is tricky, and you need to be careful. On the picture above there is a part of the LCD TFT specification of a TN (twisted nematic) display, that has grayscale inversion, and if we go to this table, we can see the viewing angles. They are defined at 70, 70, 60 and 70 degrees, that is the maximum viewing angle, at which the user can see the image. Normally we may think that 70 degrees is better, so we will choose left and right side to be 70 degrees, and then up and down, and if we do not know the grayscale inversion phenomena, we may put our user on the bottom side which is also 70 degrees. The viewing direction will be then like a 6 o’clock direction, so we call it a 6 o’clock display. But you need to be careful! Looking at the specification, we can see that this display was defined as a 12 o’clock display, so it is best for it to be seen from a 12 o’clock direction. But we can find that the 12 o’clock has a lower viewing angle – 60 degrees. What does it mean? It means that on this side there will be no grayscale inversion. If we go to 40, 50, 60 degrees and even a little bit more, probably we will still see the image properly. Maybe with lower contrast, but the colors will not change. If we go from the bottom, from a 6 o’clock direction where we have the grayscale inversion, after 70 degrees or lower we will see a sudden color change, and of course this is something we want to avoid.

To summarize, when you buy older technology like TN and displays, which are still very popular, and Riverdi is selling them as well, you need to be careful where you put your display. If it is a handheld device, you will see the display from the bottom, but if you put it on a wall, you will see the display from the top, so you need to define it during the design phase, because later it is usually impossible or expensive to change the direction.

We will talk now about the other TFT technologies, that allow us to have wider viewing angles and more vivid colors. The most basic technology for monochrome and TFT LCD displays is twisted nematic (TN). As we already know, this kind of displays have a problem with grayscale inversion. On one side we have a higher retardation and will not get a clear image. That is why we have other technologies like VA (Vertical Alignment), where the liquid crystal is differently organized, and another variation of the TFT technology – IPS which is In-Plane Switching. The VA and IPS LCD displays do not have a problem with the viewing angles, you can see a clear image from all sides.

Nowadays all TV sets, tablets and of course mobile phones are IPS or VA. You can turn them around and see the image clear from all sides. But, for monitor applications the TN technology is still widely used, because the monitor usually is in front of you and most of the time you look directly at it, from top, left or right side, but very rarely from the bottom, so the grayscale inversion viewing angle can be placed there. This technology still is very practical because it is affordable and has some advantages for gamers because it is very fast.

Apart from the different organization of the liquid crystals, we also organize subpixels a little bit differently in a VA and IPS LCD displays. When we look closer at the TN display, we will just see the subpixels with color filters. If we look at the VA or IPS display they will have subpixels of subpixels. The subpixels are divided into smaller parts. In this way we can achieve even wider viewing angles and better colors for the user, but of course, it is more complicated and more expensive to do.

The picture above presents the TN display and grayscale inversion. For IPS or VA technology there is no such effect. The picture will be the same from all the sides we look so these technologies are popular where we need wide viewing angles, and TN is popular where we don’t need that, like in monitors. Other advantages of IPS LCD displays are they give accurate colors, and wide viewing angles. What is also important in practice, in our projects, is that the IPS LCD displays are less susceptible to mechanical force. When we apply mechanical force to the screen, and have an optically bonded touch screen, we push the display as well as squeeze the cells. When we have a TN display, every push on the cell changes the image suddenly, with the IPS LCD displays with in-plane switching, different liquid crystals organization, this effect is lesser. It is not completely removed but it is much less distinct. That is another reason IPS displays are very popular for smartphones, tablets, when we have the touchscreens usually optically bonded.

If we wanted to talk about disadvantages, there is a question mark over it, as some of them may be true, some of them do not rely on real cases, what kind of display, what kind of technology is it. Sometimes the IPS displays can have higher power consumption than others, in many cases however, not. They can be more expensive, but not necessarily. The new IPS panels can cost like TN panels, but IPS panels definitely have a longer response time. Again, it is not a rule, you can make IPS panels that are very fast, faster than TN panels, but if you want the fastest possible display, probably the TN panel will be the fastest. That is why the TN technology is still popular on the gaming market. Of course, you can find a lot of discussions on the internet, which technology is better, but it really depends on what you want to achieve.

Now, let us look at the backlight types. As we see here, on the picture above, we have four distinct types of backlight possible. The most common, 95 or 99 per cent of the TFT LCD displays on the market are the transmissive LCD display type, where we need the backlight from the back. If you remember from our Monochrome LCD Displays lecture, for transmissive LCD displays you need the backlight to be always on. If you switch the backlight off, you will not see anything. The same as for monochrome LCD displays, but less popular for TFT displays, we have the transflective LCD display type. They are not popular because usually for transflective TFT displays, the colors lack in brightness, and the displays are not very practical to use. You can see the screen, but the application is limited. Some transflective LCD displays are used by military, in applications where power consumption is paramount; where you can switch the backlight off and you agree to have lower image quality but still see the image. Power consumption and saving energy is most important in some kind of applications and you can use transflective LCD displays there. The reflective type of LCD displays are almost never used in TFT. There is one technology called Low Power Reflective Displays (LPRD) that is used in TFT but it is not popular. Lastly, we have a variation of reflective displays with frontlight, where we add frontlight to the reflective display and have the image even without external light.

Just a few words about Low Power Reflective Displays (LPRD). This kind of display uses environmental light, ambient light to reflect, and produce some colors. The colors are not perfect, not perfectly clear, but this technology is becoming increasingly popular because it allows to have color displays in battery powered applications. For example, a smartwatch would be a case for that technology, or an electrical bike or scooter, where we can not only have a standard monochrome LCD display but also a TFT LCD color display without the backlight; we can see the image even in

strong sunlight and not need backlight at all. So, this kind of TFL LCD display technology is getting more and more popular when we have outdoor LCD displays and need a low power consumption.

On the picture above, we have some examples of how transmissive and reflective LCD displays work in the sunlight. If we have a simple image, like a black and white pattern, then on a transmissive LCD display, even with 1000 candela brightness, the image probably will be lower quality than for a reflective LCD display; if we have sunlight, we have very strong light reflections on the surface of the screen. We have talked about contrast in more detail in the lecture Sunlight Readable Displays. So, reflective LCD displays are a better solution for outdoor applications than transmissive LCD displays, where you need a really strong backlight, 1000 candela or more, to be really seen outdoors.

To show you how the backlight of LCD displays is built, we took the picture above. You can see the edge backlight there, where we have LEDs here on the small PCB on the edge, and we have a diffuser that distributes the light to the whole surface of LCD screen.

In addition to the backlight, we have something that is called a frontlight. It is similar to backlight, it also uses the LEDs to put the light into it, but the frontlight needs to be transparent as we have the display behind. On the example on the picture above we can see an e-paper display. The e-paper display is also a TFT display variation, but it is not LCD (liquid crystal), it is a different technology, but the back of the display is the same and it is reflective. The example you see is the Kindle 4 eBook reader. It uses an e-paper display and a frontlight as well, so you can read eBooks even during the night.

In conclusion, the type of panel to be used is determined by the purpose of the monitor. In photography, graphics design, video and picture edits, where the displayed colors, as well as the viewing angle and contrast, are of great importance, the IPS should be considered. If the refresh rate, price and the reaction time is needed more than the other characteristics, the TN panel should be considered.

For our PresentationPoint users and digital signage in general, we can transform this recommendation as follows. For advertising and public information screens e.g. in hotels: use an IPS panel. In areas where the graphics qualities are not that important, use a TN panel. Think here about information screens in factories.

So, why would anyone ever buy a TN panel? For starters, they’re cheap. They don’t cost a lot to produce, so they’re often used in the most budget-friendly options. If you don’t value color reproduction or need excellent viewing angles, a TN panel might be fine for your office or study.

TN panels also have the lowest input lag—typically around one millisecond. They can also handle high refresh rates of up to 240 Hz. This makes them an attractive option for competitive multiplayer games—especially eSports, where every split-second counts.

IPS technology was developed to improve upon the limitations of TN panels—most notably, the poor color reproduction and limited viewing angles. As a result, IPS panels are much better than TNs in both of these areas.

In particular, IPS panels have vastly superior viewing angles than TNs. This means you can view IPS panels from extreme angles and still get accurate color reproduction. Unlike TNs, you’ll notice very little shift in color when you view one from a less-than-ideal perspective.

IPS panels are also known for their relatively good black reproduction, which helps eliminate the “washed out” look you get with TN panels. However, IPS panels fall short of the excellent contrast ratios you’ll find on VAs.

While high refresh rates were typically reserved for TNs, more manufacturers are producing IPS panels with refresh rates of 240 Hz. For example, the 27-inch 1080p ASUS VG279QM uses an IPS panel and supports 280 Hz.

Previously, TNs exhibited less input lag than any other panel, but IPS technology has finally caught up. In June 2019, LG announced its new Nano IPS UltraGear monitors with a response time of one millisecond.

Despite the gap being closed, you’ll still pay more for an IPS panel with such a low response time than you would for a TN with similar specs. If you’re on a budget, expect a response time of around four milliseconds for a good IPS monitor.

One last thing to be aware of with IPS panels is a phenomenon called “IPS glow.” It’s when you see the display’s backlight shining through it at more extreme viewing angles. It’s not a huge problem unless you view the panel from the side, but it’s something to keep in mind.

VA panels are something of a compromise between TN and IPS. They offer the best contrast ratios, which is why TV manufacturers use them extensively. While an IPS monitor typically has a contrast ratio of 1000:1, it’s not unusual to see 3000:1 or 6000:1 in a comparable VA panel.

In terms of viewing angles, VAs can’t quite match the performance of IPS panels. Screen brightness, in particular, can vary based on the angle from which you’re viewing, but you won’t get the “IPS glow.”

VAs have slower response times than TNs and the newer Nano IPS panels with their one-millisecond response rates. You can find VA monitors with high refresh rates (240 Hz), but the latency can result in more ghosting and motion blur. For this reason, competitive gamers should avoid VA.

Compared to TNs, VA panels do offer much better color reproduction and typically hit the full sRGB spectrum, even on lower-end models. If you’re willing to spend a bit more, Samsung’s Quantum Dot SVA panels can hit 125 percent sRGB coverage.

When compared to CRT monitors, all LCD panels suffer from some form of latency issue. This was a real problem when TN panels first appeared, and it’s plagued IPS and VA monitors for years. But technology has moved on, and while many of these issues have been improved, they haven’t been eliminated entirely.

Office or study use: Your budget should be your primary concern here. VA is the do-it-all panel, with superior viewing angles to TN, but either would do the trick. You can save some money because you don’t need high refresh rates or ultra-low latency. They’re still nice, though. You’ll see a noticeable difference in smoothness just when moving the Windows cursor on a monitor with a 144 versus 60 Hz refresh rate.

Photo and video editors/Digital artists: IPS panels are still generally favored for their ability to display a wide gamut of colors. It’s not unusual to find VA panels that also cover a wide gamut (125 percent sRGB, and over 90 percent DCI-P3), but they tend to exhibit more motion blur during fast-paced action than IPS panels. If you’re serious about color accuracy, you’ll need to properly calibrate your monitor.

Programmers who mount monitors vertically: You might think TN panels are great for programmers, but that’s not necessarily the case. TN panels have particularly bad viewing angles on the vertical axis. If you mount your monitor in portrait mode (as many programmers and mobile developers do), you’ll get the worst possible viewing angles from a TN panel. For the best possible viewing angles in this scenario, invest in an IPS display.

Competitive online gamers: There’s no question TN panels are still favored in the eSports world. Even the cheapest models have fast response times and support for high refresh rates. For 1080p gaming, a 24-inch will do just fine, or you could opt for a 1440p, 27-inch model without breaking the bank. You might want to go for an IPS panel as more low-latency models hit the market, but expect to pay more.

Non-competitive, high-end PC gamers: For a rich, immersive image that pops, a VA panel will provide a higher contrast ratio than IPS or TN. For deep blacks and a sharp, contrasting image, VA is the winner. If you’re okay with sacrificing some contrast, you can go the IPS route. However, we’d recommend avoiding TN altogether unless you play competitively.

If you can, check out the monitor you’re interested in in-person before you buy it. You can perform some simple ghosting and motion blur tests by grabbing a window with the mouse and moving it rapidly around the screen. You can also test the brightness, watch some videos, and play with the onscreen display to get a feel for it.

We’ll get to how the technology works below, but what you probably want to know off the bat is which technology is right for you. Here we’ll break down the main characteristics of each type: IPS, VA and TN.

Both IPS and VA have two main advantages over TN panels. The first is that they offer much better viewing angles. In other words, you can view both VA and IPS panels from far shallower angles and still be able to see what’s on-screen without much, or any, colour degradation. This is quite a big deal.

VA panels don’t tend to be quite as good as IPS, and as a result there can be a somewhat noticeable variation in brightness when viewed from different angles. ButIPS suffers from what’s known as ‘IPS glow’. This is where the backlight of the LCD shines through when the display is viewed from a certain angle.

You shouldn’t normally notice this unless viewing from an extreme angle, but it can sometimes be seen in the corners of large displays, particularly if they’re not manufactured to a high standard. Some users are particularly bothered by this; for most it’s all but unnoticeable in general use.

As for other differences, IPS tends to have a faster response time than VA since its crystals don’t have to tip over and then twist as they do with VA (see below). You can get fast-refreshing gaming monitors that use VA, but they offer a poor experience due to the slow pixel response time. IPS is slower than TN, but can be fast enough for responsive gaming.

Meanwhile, VA’s last hurrah is contrast. Since its resting state blocks light, its black level is the lowest of all LCDs, yet it can still produce bright colours when needed. A typical IPS or TN panel will have a contrast of 1000:1 or lower. VA panels can double that. This is the reason VA tends to be the best choice for TVs, where a deep black level is important for enjoying movies.

As for TN, it isn’t all bad news – it has a couple of key advantages. The first is that it’s easier to produce so can be used to make cheaper monitors.

If you’re after a monitor that offers great image quality for day-to-day work and image editing, but aren’t particularly bothered about super-competitive gaming, then go for an IPS screen. They deliver the best all-round experience for work and play, and you can still get gaming IPS monitors that refresh at over 100Hz, making them nearly as good as the best TN gaming screens.

However, if gaming is your be-all and end-all then TN is the way to go. Not only are they the most responsive – with the latest displays having refresh rates of 240Hz – but they also tend to be relatively affordable.

These fundamentals apply to all the different types of LCD available to buy. However, in order to improve certain characteristics of the displays, different types of LCD have been developed that tweak the way in which the liquid crystal, polarising filters and the electrodes are arranged and controlled.

The original and most basic version of a modern LCD is TN, or twisted nematic. This has the polarisers arranged at ninety degrees to one another, so that – normally – no light passes through them. However, the resting state of the crystal has the molecules arranged in a helix, which twists the polarisation of the light as it passes through, in turn allowing it to pass through the second filter.

When a voltage is applied to the liquid crystal the molecules point directly towards the viewer, so no longer twisting the light, resulting in it being blocked by the second polarising filter. TN works well enough, but famously suffers from poor viewing angles (see above), which is why alternative models were developed.

The most famous of these is IPS, or in-plane switching. Here the polarising filters are in the same orientation so that light is blocked when the crystal is in its resting twisted state, rather than allowed to pass through as it would in TN. Then, when activated, the crystals line up in the same direction as the polarising filters and parallel to their surface: for instance, when switched they’re in-plane.

There are several variations on IPS, such as S-IPS and H-IPS, that use slightly different pixel structures and layouts, and have optimisations for faster response times – most displays that are referred to as IPS are in fact S-IPS panels – but the fundamentals are the same.

The other most common variant is Vertical Alignment (VA). Here the crystals are arranged perpendicular to the polarisers, which are again orientated at right-angles as they are with TN. As such, in its resting state a VA panel blocks light as the light isn’t being twisted. When a voltage is applied the crystals tip to a more horizontal position and twist, allowing light to pass through.

A thin-film-transistor liquid-crystal display (TFT LCD) is a variant of a liquid-crystal display that uses thin-film-transistor technologyactive matrix LCD, in contrast to passive matrix LCDs or simple, direct-driven (i.e. with segments directly connected to electronics outside the LCD) LCDs with a few segments.

In February 1957, John Wallmark of RCA filed a patent for a thin film MOSFET. Paul K. Weimer, also of RCA implemented Wallmark"s ideas and developed the thin-film transistor (TFT) in 1962, a type of MOSFET distinct from the standard bulk MOSFET. It was made with thin films of cadmium selenide and cadmium sulfide. The idea of a TFT-based liquid-crystal display (LCD) was conceived by Bernard Lechner of RCA Laboratories in 1968. In 1971, Lechner, F. J. Marlowe, E. O. Nester and J. Tults demonstrated a 2-by-18 matrix display driven by a hybrid circuit using the dynamic scattering mode of LCDs.T. Peter Brody, J. A. Asars and G. D. Dixon at Westinghouse Research Laboratories developed a CdSe (cadmium selenide) TFT, which they used to demonstrate the first CdSe thin-film-transistor liquid-crystal display (TFT LCD).active-matrix liquid-crystal display (AM LCD) using CdSe TFTs in 1974, and then Brody coined the term "active matrix" in 1975.high-resolution and high-quality electronic visual display devices use TFT-based active matrix displays.

The liquid crystal displays used in calculators and other devices with similarly simple displays have direct-driven image elements, and therefore a voltage can be easily applied across just one segment of these types of displays without interfering with the other segments. This would be impractical for a large display, because it would have a large number of (color) picture elements (pixels), and thus it would require millions of connections, both top and bottom for each one of the three colors (red, green and blue) of every pixel. To avoid this issue, the pixels are addressed in rows and columns, reducing the connection count from millions down to thousands. The column and row wires attach to transistor switches, one for each pixel. The one-way current passing characteristic of the transistor prevents the charge that is being applied to each pixel from being drained between refreshes to a display"s image. Each pixel is a small capacitor with a layer of insulating liquid crystal sandwiched between transparent conductive ITO layers.

The circuit layout process of a TFT-LCD is very similar to that of semiconductor products. However, rather than fabricating the transistors from silicon, that is formed into a crystalline silicon wafer, they are made from a thin film of amorphous silicon that is deposited on a glass panel. The silicon layer for TFT-LCDs is typically deposited using the PECVD process.

Polycrystalline silicon is sometimes used in displays requiring higher TFT performance. Examples include small high-resolution displays such as those found in projectors or viewfinders. Amorphous silicon-based TFTs are by far the most common, due to their lower production cost, whereas polycrystalline silicon TFTs are more costly and much more difficult to produce.

The twisted nematic display is one of the oldest and frequently cheapest kind of LCD display technologies available. TN displays benefit from fast pixel response times and less smearing than other LCD display technology, but suffer from poor color reproduction and limited viewing angles, especially in the vertical direction. Colors will shift, potentially to the point of completely inverting, when viewed at an angle that is not perpendicular to the display. Modern, high end consumer products have developed methods to overcome the technology"s shortcomings, such as RTC (Response Time Compensation / Overdrive) technologies. Modern TN displays can look significantly better than older TN displays from decades earlier, but overall TN has inferior viewing angles and poor color in comparison to other technology.

Most TN panels can represent colors using only six bits per RGB channel, or 18 bit in total, and are unable to display the 16.7 million color shades (24-bit truecolor) that are available using 24-bit color. Instead, these panels display interpolated 24-bit color using a dithering method that combines adjacent pixels to simulate the desired shade. They can also use a form of temporal dithering called Frame Rate Control (FRC), which cycles between different shades with each new frame to simulate an intermediate shade. Such 18 bit panels with dithering are sometimes advertised as having "16.2 million colors". These color simulation methods are noticeable to many people and highly bothersome to some.gamut (often referred to as a percentage of the NTSC 1953 color gamut) are also due to backlighting technology. It is not uncommon for older displays to range from 10% to 26% of the NTSC color gamut, whereas other kind of displays, utilizing more complicated CCFL or LED phosphor formulations or RGB LED backlights, may extend past 100% of the NTSC color gamut, a difference quite perceivable by the human eye.

In-plane switching was developed by Hitachi Ltd. in 1996 to improve on the poor viewing angle and the poor color reproduction of TN panels at that time.

In 2004, Hydis Technologies Co., Ltd licensed its AFFS patent to Japan"s Hitachi Displays. Hitachi is using AFFS to manufacture high end panels in their product line. In 2006, Hydis also licensed its AFFS to Sanyo Epson Imaging Devices Corporation.

It achieved pixel response which was fast for its time, wide viewing angles, and high contrast at the cost of brightness and color reproduction.Response Time Compensation) technologies.

Less expensive PVA panels often use dithering and FRC, whereas super-PVA (S-PVA) panels all use at least 8 bits per color component and do not use color simulation methods.BRAVIA LCD TVs offer 10-bit and xvYCC color support, for example, the Bravia X4500 series. S-PVA also offers fast response times using modern RTC technologies.

A technology developed by Samsung is Super PLS, which bears similarities to IPS panels, has wider viewing angles, better image quality, increased brightness, and lower production costs. PLS technology debuted in the PC display market with the release of the Samsung S27A850 and S24A850 monitors in September 2011.

TFT dual-transistor pixel or cell technology is a reflective-display technology for use in very-low-power-consumption applications such as electronic shelf labels (ESL), digital watches, or metering. DTP involves adding a secondary transistor gate in the single TFT cell to maintain the display of a pixel during a period of 1s without loss of image or without degrading the TFT transistors over time. By slowing the refresh rate of the standard frequency from 60 Hz to 1 Hz, DTP claims to increase the power efficiency by multiple orders of magnitude.

Due to the very high cost of building TFT factories, there are few major OEM panel vendors for large display panels. The glass panel suppliers are as follows:

External consumer display devices like a TFT LCD feature one or more analog VGA, DVI, HDMI, or DisplayPort interface, with many featuring a selection of these interfaces. Inside external display devices there is a controller board that will convert the video signal using color mapping and image scaling usually employing the discrete cosine transform (DCT) in order to convert any video source like CVBS, VGA, DVI, HDMI, etc. into digital RGB at the native resolution of the display panel. In a laptop the graphics chip will directly produce a signal suitable for connection to the built-in TFT display. A control mechanism for the backlight is usually included on the same controller board.

The low level interface of STN, DSTN, or TFT display panels use either single ended TTL 5 V signal for older displays or TTL 3.3 V for slightly newer displays that transmits the pixel clock, horizontal sync, vertical sync, digital red, digital green, digital blue in parallel. Some models (for example the AT070TN92) also feature input/display enable, horizontal scan direction and vertical scan direction signals.

New and large (>15") TFT displays often use LVDS signaling that transmits the same contents as the parallel interface (Hsync, Vsync, RGB) but will put control and RGB bits into a number of serial transmission lines synchronized to a clock whose rate is equal to the pixel rate. LVDS transmits seven bits per clock per data line, with six bits being data and one bit used to signal if the other six bits need to be inverted in order to maintain DC balance. Low-cost TFT displays often have three data lines and therefore only directly support 18 bits per pixel. Upscale displays have four or five data lines to support 24 bits per pixel (truecolor) or 30 bits per pixel respectively. Panel manufacturers are slowly replacing LVDS with Internal DisplayPort and Embedded DisplayPort, which allow sixfold reduction of the number of differential pairs.

The bare display panel will only accept a digital video signal at the resolution determined by the panel pixel matrix designed at manufacture. Some screen panels will ignore the LSB bits of the color information to present a consistent interface (8 bit -> 6 bit/color x3).

With analogue signals like VGA, the display controller also needs to perform a high speed analog to digital conversion. With digital input signals like DVI or HDMI some simple reordering of the bits is needed before feeding it to the rescaler if the input resolution doesn"t match the display panel resolution.

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Kim, Sae-Bom; Kim, Woong-Ki; Chounlamany, Vanseng; Seo, Jaehwan; Yoo, Jisu; Jo, Hun-Je; Jung, Jinho (15 August 2012). "Identification of multi-level toxicity of liquid crystal display wastewater toward Daphnia magna and Moina macrocopa". Journal of Hazardous Materials. Seoul, Korea; Laos, Lao. 227–228: 327–333. doi:10.1016/j.jhazmat.2012.05.059. PMID 22677053.

Again, IPS is the clear winner here. The vertical viewing angles are very similar to the horizontal ones on both IPS and VA panels. Unfortunately, this is one area where TN panels are usually much, much worse. TN monitors degrade rapidly from below, and colors actually inverse - resulting in a negative image that can be distracting. For this reason, if you decide to buy a TN monitor, look for one with an excellent height adjustment, or consider buying a VESA mounting arm, as you should mount TN monitors at eye level. Even when mounted properly, larger TN displays can appear non-uniform at the edges.

There"s usually not much difference between VA and IPS panels in terms of gray uniformity. It"s rare for monitors to have uniformity issues, and even on monitors that perform worse than average, it"s usually not noticeable with regular content. TN monitors tend to perform a bit worse than usual, though, and the top half of the screen is almost always darker than the rest, but that"s an artifact of the bad vertical viewing angles.

Black uniformity tends to vary significantly, even between individual units of the same model, and there"s no single panel type that performs the best. It"s rare for monitors to have good black uniformity, and almost every monitor we"ve tested has some noticeable cloudiness or backlight bleed. IPS and TN panels can look slightly worse due to their low contrast ratios, as the screen can take on more of a bluish tint when displaying dark scenes. Like with contrast, black uniformity issues usually aren"t very noticeable unless you"re looking at dark content and you"re in a dark room. If you only use your monitor in a bright environment, generally speaking, you don"t need to worry about black u