TFT displays are considered part of our daily lives. A lot of applications use displays and we all come across multiple displays daily, without paying much attention to them.
Televisions, computer screens, tablets, notebooks, cell phones. Nowadays all these products are equipped with a TFT display. Not even mentioning industrial, medical, marine and automotive applications. Displays make our lives easier and are offered in a wide variety of forms. Due to the great supply of displays, it is not always easy to determine which display is suitable for your project.
We'd like to focus on passive and active displays to clarify the difference:
TFT displays are revolutionary in the color display industry. These active matrix displays are widely used in various applications, so continue reading to find out everything there is on TFT displays.
What is a TFT display?
LCD vs. TFT Display
The terms LCD display and TFT display (or active matrix display) are often used interchangeably. But what's the difference?
An LCD (Liquid Crystal Display) is a flat display with a low power consumption. Liquid crystals are embedded between two layers of polarizing material. Behind the layers, a backlight is placed. By regulating the voltage between the glass plates, the crystals will rotate and the light transmittance can be adjusted. Displaying an image on the LCD.
A TFT display (Thin-Film Transistor) uses thin film transistor technology. Adding this layer to an LCD will provide a better and sharper image. Therefore, a TFT display (or active matrix display) is actually an improved version of an LCD display.
How does a TFT Display or Active Matrix Display work?
The difference between TFT displays and LCD displays is now clear, but how does TFT technology work? TFT stands for Thin Film Transistor. For each RGB sub pixel there is a transistor integrated into the glass. These sub pixels can therefore be individually controlled and turned on and off. This allows development and production of vibrant color images, with high resolutions. In addition, the response time of a TFT is faster, making it interesting for many manufacturers.
A TFT is made by combining a thin film of a semi-conductive active layer with a layer that acts as an electrical insulator. They are laid on a supported under layer together with metal contacts.
An LCD pixel is then actively controlled by one to four transistors. By adjusting the voltage, the transistors turn the pixels on and off easily. Red, green and blue color filters are placed on the inside of the top glass to show the color information. The intensity of light transmission is controlled by color filters. As a result, millions of colors can be displayed on one screen.
The embedded TFT layer on the screen reduces crosstalk between pixels. Crosstalk occurs when a signal sent to a pixel, also affects the pixel next to it. This makes TFT display technology the technology that offers the best resolution and image quality. TFT’s are therefore more expensive than regular LCD’s.
TFT displays have become todays standard in producing LCD monitors.
TFT Display Technologies
TN, MVA & IPS
A TFT display is actually a custom LCD display. TFT technology ultimately ensures that a displayed image is sharper, brighter and more beautiful than a normal LCD. But there are also differences within TFT display technology itself. There are technologies that provide a sharper image, better viewing angle or a faster display.
TN, MVA and IPS are TFTdisplay technologies that all offer advantages over the others. Depending on the application, one of these technologies will probably fit your application.
TN (Twisted Nematic)
An LCD includes, among other things, liquid crystals. These crystals can be controlled in several ways. Also the structure and the way crystals transmit light, can be influenced. The oldest technology used for this, is the TN technology. TN stands for Twisted Nematic, this technology uses liquid crystals that can twist the polarization of light.
Behind the screen, a polarizing layer causes the light of the backlight to be polarized in one direction. If no voltage is applied to the cells, a TN TFT display will light up. And the crystals are automatically rotated 90 degrees. As a result, the polarization of the incoming light changes 90 degrees. By placing an electrical voltage on the cells, the crystals return to their right position. The polarization remains untouched and retains direction of polarization, provided behind the scenes. A second polarization filter for the crystals causes the non-twisted light to be blocked and the pixels remain black.
If the pixels of a TN display are active, the image will remain dark. Only when the pixels are off, the screen will light up. The TN technology has a fast response time and is therefore ideally suited for fast moving images like movies. One drawback is that the viewing angles of a TN display are limited. In addition, there is a relatively large color gradient when viewing the screen from the side. This occurs because the twisted crystals do not block the same amount of light from every angle.
In particular gamers use TFT displays with TN technology. They especially value the fast response time of a TN display. Since they are often sitting right in front of the screen, the somewhat smaller viewing angle is no problem for gamers.
Benefits of the TN technology:
- Fast response time
- Low cost price
MVA (Multiple-domain Vertical Alignment)
MVA stands for Multiple-domain Vertical Aligment and is the improved version of VA technology. This technology is the same as the TN technology we’ve discussed earlier.
With MVA technology, the crystals are vertically oriented, just like the TN technology. Because the crystals are always parallel to each other and do not interfere, the MVA technology also has similarities with IPS (see below).
Since TN and IPS technology are combined in the MVA technology, MVA TFT displays switch relatively quickly. TN (or VA) crystals are always active or non-active. With the MVA technology, the crystals can also be slightly active or non-active. This makes the contrast of the display better. In addition, the viewing angles are larger and there is a nicer transition in the crystals and thus colors.
Samsung has produced its own MVA based technology called PVA (Pattern Vertical Alignment). PVA allows excellent color reproduction and a wide color range. It also offers fantastic response times and has viewing angles that approach the great viewing angles of IPS.
MVA technology benefits:
- High contrast
- Beautiful color display
- Viewing angles greater than TN technology's
IPS (In Plane Switching)
IPS is a TFT display technology and stands for In-Plane Switching. IPS is a variant of an LCD and is used in phones, laptops, tablets, televisions or computer displays.
The base of IPS is similar to TN and MVA. A display has pixels. Each pixel of a display consists of three subpixels. The subpixels are red, green and blue. In an LCD, the pixels are turned on and off by liquid crystals. A transistor in the pixels determines how much color is transmitted from each pixel. This way, millions of colors can be combined.
With IPS, each pixel has a transistor, but each subpixel also has a transistor. This gives IPS a very precise control of the pixels. The special alignment of the pixels also contributes to precise control of the display.
IPS displays are mainly used in the graphics industry, because of their great viewing angles. Its high color brightness makes IPS perfect for the demands of the graphic industry.
IPS was originally developed by LG. Several other brands also developed their own IPS technologies. Among others, Samsung (PLS), AUO (AHVA) and BOE/Hydis (AFFS) have designed IPS solutions for their own TFT lines.
IPS technology benefits:
- Wide viewing angles
- Colors look the same from every angle
- You can see subtle color differences due to the high contrast
- Color proof
Buying a TFT Display?
Consider these 10 Tips
Custom or Standard
Standard, partially custom, or custom made, we can provide it all.
Keep in mind a minimum order quantity is often required for a custom TFT display solution.
Will the TFT displays be used indoors or outdoors? For each location, other specifications are important. Consult your product specialist to check which solution fits best.
There are many different display sizes. Do you need small, medium or large displays? It's important to know exactly which dimensions are needed for your application.
Most displays have a standard resolution at which the images are the sharpest. If desired this resolution can be scaled.
What resolution do you need?
Brightness & Backlight
Clarity of a display depends on its resolution and backlight. Ambient light also affects the clarity and readability. More information about backlights?
There are several types of interfaces available. Standard interfaces, TTL or LVDS. Together with our customers, we check what best suits the application. Information about cables can be found here.
Contrast & Viewing angle
Depending on the application, you can determine which level of contrast you need and which viewing angles are important for the application.
Where the display is used is important for the temperature determination. For example, a display used in a cooling cell must be able to cope with severe cold.
A TFT display has an edge around the active area. In this area no image is showed. So it's important to determine the size of the active area in advance.
Do you need the same display for the next few years. Or do you need the display once for a large production? The availability is different for each display. Our product specialist is happy to tell you more about it.
TFT Display Specifications
Size, resolution & temperature
TFT displays are available in a lot of different, standard sizes. If you are looking for displays with a custom size, we can help you. We supply TFT displays in small, medium and large sizes.
The resolution of a display describes the number of pixels in a display. The higher the resolution of a screen, the more pixels it has.
In general, the higher the resolution, the sharper the display image. For TFT screens there is a basic resolution, but this can be adjusted. Our product specialists can help you decide which resolution best suits your application.
Want to know more about resolutions? Contact us, we'd be happy to help!
Frequently requested resolutions:
Small TFT displays:
- 320 x 240 : Small industrial
- 640 x 480 : Small industrial
- 800 x 480 : Small industrial widescreen
- 1024 x 600: Small industrial widescreen
Medium TFT displays:
- 800 x 600 : Medium industrial
- 1024 x 768 : Medium industrial
- 1280 x 1024 : Medium industrial
- 1366 x 768 : Medium widescreen
Large TFT displays:
- 1920 x 1080 : Large widescreen
TFT displays can have either of three temperature ranges:
- Consumer: 0 tot +50 °C
- Industrial: -20 tot +70 °C
- Automotive: -30 tot +85 °C
The surrounding area of the display (environment) and the application itself are determining for the needed temperature range of the display. Temperature has a big impact on the life cycle of the TFT display. We can advise you on the right temperature range for your application.
Why choose a TFT display?
Due to the complex lithography processes, the price of a TFT display is higher than the price of passive LCD displays.
But TFT’s or active matrix displays offer significant benefits:
- TFT displays respond quickly and are therefore suitable for displaying video images
- High color saturations and contrasts result in good image quality
- More colors can be generated than with passive displays, thanks to the interface
- High energy efficiency
- TFT displays are not sensitive to burn-ins
Also in comparison with AMOLED’s, TFT’s have a number of advantages:
- TFT’s have a longer lifetime
- TFT displays cost less
- TFT’s have better availability
- TFT displays are a good fit for the industrial market
QUESTIONS OR ADVICE?
Talk to a product specialist
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