Although there are many display panel technologies available today, the TFT LCD It remains one of the most widely used displays. It's also the basis for many other variants, so it's interesting to understand how this type of display technology works and what it is.
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What is a TFT LCD screen?
An TFT LCD screen Thin Film Transistor (Liquid Crystal Display) is a display technology that is becoming increasingly popular today, from small displays on all types of devices to large television screens.
The TFT type transistor is a type of semiconductor that is used to improve efficiency, reduce cost and provide a more compact size compared to CRTsTFT LCD displays are active matrix displays that control pixels individually, although the lighting is done collectively.
TFT LCD structure
The TFT LCD screen is built with three fundamental layersThese layers are sandwiched between glass substrates and another layer with an RGB (Red Green Blue) color filter. The layer between the two glass layers is liquid crystal.
La TFT glass substrate layer It is the deepest or backmost layer of a device's circuit board. It is made of amorphous silicon, a type of silicon with a non-crystalline structure. This way, by controlling the applied voltage, the colors displayed at each pixel can be controlled.
The outer sides of the glass substrates have filter layers called polarizersThese filters allow only certain light beams to pass through if they are polarized in a specific way. If not polarized correctly, the light doesn't pass through the polarizer, creating an opaque LCD screen.
Between the two layers of substrate are liquid crystalsTogether, liquid crystal molecules can behave like a liquid in terms of motion, but maintain their structure as a solid crystal. There are a variety of chemical formulas available for use in this layer. Typically, liquid crystals are aligned to position the molecules in a certain way to induce specific light-passing behaviors through the polarization of light waves. To do this, a magnetic or electric field must be used.
As you well know, transistors follow the same operating principle as FETs or field-effect transistors. For this reason, conduction through them can be controlled by applying a signal or voltage to the gate. When a signal is applied to the gate to flow current between the drain and source, the current will flow to a subpixel, allowing light to pass through.
This is how a TFT LCD screen works. Of course, as you well know, there are then variants, such as LED screens, LEDs with IPS panel, VA panel, or TN, among other variants that are currently flourishing to try to alleviate the disadvantages of these panels and provide them with interesting improvements, while maintaining reasonable prices as this is a mature and economical technology.
Architecture of a TFT pixel
Finally, I would like to add that within a TFT LCD screen, each pixel can be characterized by its three sub pixelsThese three subpixels create the RGB color of that overall pixel—red, green, or blue, or a combination of these primary colors to generate the other colors and shades. When all the colors are displayed simultaneously, they correspond to white light. Filters and polarization achieve different brightness levels depending on the alignment of the liquid crystal.
These subpixels act as capacitors or storage units within a device, each with its own independent structural and functional layers, as described above. Thus, when the graphics processor sends the information for a frame, it can be displayed by controlling all the elements of the screen as intended.