TFT-LCD Detailed process

Working principle of TFT-LCD liquid crystal display

In thin film transistor liquid crystal display (TFT-LCD), the function of TFT is a switch tube. TFT is commonly used in three terminal devices. A semiconductor layer is formed on a glass substrate, and a source electrode and a drain electrode are connected at both ends. And through the gate insulating film opposite the semiconductor, the voltage applied to the gate to control the source and drain of the current.

For the display screen, each pixel can be viewed as a liquid crystal between the pixel electrode and the common electrode. What is more important is that it can be viewed as a capacitor from the point of view of electricity. The equivalent circuit is shown in figure 1. To j row I column pixel P (I, J) charge, it is necessary to turn on the switch T (I, J) on the signal line D (I) to apply the target voltage. When the pixel electrode is fully charged, even if the switch is off, the charge in the capacitor is preserved. The function of the data (column) driver is to apply the target voltage to the signal line, and the gate (line) driver acts as the switch on and off. Because the voltage added on the liquid crystal layer can be stored, the liquid crystal layer can work stably. This display voltage can also be re written in a short period of time through the TFT, therefore, even for high definition LCD, can also meet the image quality requirements.

The key to display the image is also the molecular orientation of the liquid crystal under the electric field. Through the alignment of the inside of the substrate, the liquid crystal molecules are arranged to produce the desired deformation to realize different display modes. Under the action of the electric field, the liquid crystal molecule has a change of orientation, and the intensity of the incident light changes through the liquid crystal layer by the cooperation of the polarizer. In order to achieve image display.

Simple matrix thin film transistor liquid crystal display with passive TN-LCD and STN-LCD is different, it has a thin film transistor in each pixel of the liquid crystal display (TFT), which can effectively overcome the crosstalk non gating, which can display static characteristics and scanning line LCD screen is independent of the number, thus greatly improving the image quality. The switching unit (i.e. TFT) characteristics, it is necessary to meet the low on state resistance, closed state resistance is very large this requirement.

The color display of thin film transistor liquid crystal display is realized by adding a layer of color filter on the front panel of the display. It requires the production of red, green, blue and black matrix for each pixel.

The main advantages of TFT-LCD LCD

With the maturity of TFT technology in the early 90s, the development of color LCD flat panel display, less than 10 years, the rapid growth of TFT-LCD into the mainstream display, which has its advantages are inseparable. Main features are:

(1) good use characteristics

The application of low voltage, low driving voltage, solid use safety and reliability is improved; flat, and thin, save a lot of raw materials and the use of space; low power consumption, the power consumption is about CRT display 1/10, left and right one percent reflective TFT-LCD even only CRT, save a lot of energy and TFT-LCD products; specification, size series, variety, flexible and easy to use, maintenance, update, easy to upgrade, long service life and many other features. Display range from 1 inches to 40 inches display all application range and large projection plane is full size display terminal; display quality from the most simple monochromatic character graphics to high resolution, high color fidelity, high brightness, high contrast, high response speed of the video display of various specifications; display has a direct type of projection type, perspective, also reflection type.

(2) good environmental protection

No radiation, no flicker, no harm to the health of users. In particular, the emergence of TFT-LCD electronic books, will bring the human paperless office, paperless printing era, lead to human learning, communication and record of civilization revolution.

(3) wide scope of application

It can be used normally in the temperature range from -20 DEG C to +50 DEG C, and the working temperature of TFT-LCD can be reduced to 80 degrees below zero. The utility model not only can be used as a mobile terminal display, but also can be used as a large screen projection tv.

(4) a high degree of automation in manufacturing technology

Large scale industrial production characteristics. TFT-LCD industry mature technology, large-scale production of finished product rate of 90% or more.

(5) TFT-LCD is easy to integrate and update

It is the perfect combination of large scale semiconductor integrated circuit technology and light source technology. At present, there are amorphous, polycrystalline and monocrystalline silicon TFT-LCD, there will be other materials in the future TFT, both the glass substrate and plastic substrate.