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All you need to know about TFT displays

Known for their resilience and versatility, TFT displays have revolutionised how information can be presented and managed across multiple industries. TFT stands for thin film transistor, and in displays, this refers to an active-matrix LCDs (liquid crystal displays). They are being used more frequently in new applications and designs, as they enable a better visual presentation and user experience. In comparison to standard passive matrix LCDs, a TFT provides very sharp images with shortened response times. Plus, TFTs consume less power than other display types, making them energy efficient.


How do TFTs work?

In short, TFTs are flat panel displays which use thin film transistors to control the individual pixel's brightness and colours. The structure of the display is sandwich-like, with the TFT layer in the middle. At the base, there is a backlight which is the light source, this is then followed by the TFT layer which controls the light flow through the display, and a colour filter dictates the colour. Finally, a top layer of glass houses the visible screen. Touch panels can then also be added on top of this to increase capabilities in certain applications.


The TFT acts as switches that pass the correct voltage onto the relevant liquid crystals to dictate whether these pixels are lit (on) or dark (off). The TFT are the active elements within the display. The electrical charge received by the liquid crystal pixels causes them to alter their molecular structure, allowing the varying colour wavelengths of the backlight to ‘pass-through’.

The TFT layer of the display is arranged in a matrix. The characteristics of the pixels within this are determined by the underlying density (resolution) of the colour matrix and TFT layout. The more pixels the higher detail is available. Each pixel within the TFT is paired with a transistor. Each transistor contains a capacitor, which allows each individual sub-pixel to retain its charge, rather than needing a new electrical charge to be sent each time it needs to be changed. This technology enables a display that operates using minimal energy, without running out of operation. A TFT is in constant flux and refreshes rapidly depending upon the incoming signal from the control device.


What are the applications and benefits?

TFTs are very versatile and resilient and, therefore have a vast number of applications. These displays are designed to withstand physical shock and vibration, as well as to be protected against environmental elements such as water and dust exposure. In the most physically demanding applications, they can also be housed in robust enclosures to enhance their durability even more.

Most commonly you will find TFTs in mobile devices, computer screens and some TV’s. But due to their high readability performance, they are suited to outdoor use as well as indoor. The high levels of brightness and contrast mean that they can still be readable even in direct sunlight. For outdoor applications where visibility is paramount, particularly in emergencies, this is ideal. An operator can easily monitor a system's status with clarity through a TFT.

TFTs are also known for having a wide temperature range, which increases their functionality in diverse climates. They are engineered to function in temperatures from the bitter cold (-30?)?to the scorching hot (+85?).

All these factors contribute to the impressive longevity of TFTs. They have long lifetimes which for users means minimal maintenance is required, as well as reduced need for replacement and repair costs. This adds to their popularity in remote applications and hard-to-reach installations.


What are the limitations?

 

  • Due to their design and more advanced technology, TFTs are currently more expensive than standard monochrome displays, and even some OLED displays.
  • Although TFTs do provide an overall good contrast, the contrast ratio is still slightly limited. They often struggle to display deep blacks and bright whites simultaneously.
  • Unlike other display technologies like OLED, TFT screens cannot emit their own light, they do still require a backlight to generate the display imagery.
  • Similarly with viewing angles, although TFTs have much better viewing angles than standard LCDs, when viewing from extreme angles this is still limited, and the image quality can appear degraded. If working in an application where viewing angle is key, IPS options could be considered, as these typically offer 85 degrees viewing from all angles.
  • TFTs are susceptible to image retention, which can eventually cause ghost images to appear on the display screen.

 

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