Response time definition and meaning

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 > Response time definition and meaning

The tft lcd displays images by controlling the rotation of the liquid crystal through TFT. The commonly used liquid crystal material for display devices is nematic liquid crystal. Its molecules are rod-shaped, with the long axis of the molecule generally pointing in one direction. Liquid crystal has uniaxial crystal properties optically, and the optical axis direction is along the long axis direction. Electrically, it has dielectric anisotropy, that is, the long axis and short axis directions show different electrical properties. This is the fundamental reason why liquid crystal molecules can rotate in an electric field. When no voltage is applied, the liquid crystal molecules of each pixel are arranged neatly. After the voltage is applied, the rod-shaped liquid crystal molecules begin to rotate. When the voltage is removed, the liquid crystal molecules return to their original state by relying on the weak force between the molecules, and the liquid crystal continues to rotate. and complete the display of the screen during the process of returning to the original position.

Types of response times

The response time is divided into two test methods: the response time from black screen to white screen and the response time from grayscale screen to grayscale screen. Usually, the measurement method of response time from black screen to white screen is used.

The response time definition from grayscale picture to grayscale picture:

The display screen displays 8 levels of gray scale in sequence, namely L0, L36, L73, L109, L146, L82, L219, and L255, and records the time required to convert between gray scale images.

Gray to Gray response time

The response time definition from black screen to white screen:

The time it takes for the display to go from 10% brightness to 90% brightness and from 90% brightness to 10% brightness is the response time from black to white.

Black to white response time

What factors affect response time?

The response time of the liquid crystal display is related to the viscosity system and elastic coefficient of the liquid crystal material, the thickness of the liquid crystal cell and the applied driving voltage.

The viscosity coefficient and elastic coefficient of liquid crystal

The viscosity coefficient and elastic coefficient of liquid crystal are related to the general type and ratio of liquid crystal. The viscosity coefficient of positive liquid crystal is higher and the elastic coefficient is small, while the opposite is true for positive liquid crystal. Usually the viscosity coefficient is small, the elastic coefficient is large, and the response speed is fast.

liquid crystal driving voltage

The driving voltage of liquid crystal is related to the type of liquid crystal. The driving voltage of positive liquid crystal is generally ±3.2V, and the driving voltage of negative liquid crystal is generally 5V. Using a larger driving voltage will cause the liquid crystal to rotate excessively and reduce the transmittance.

the thickness of the lcd cell

Reducing the thickness of the liquid crystal layer can improve the response time of the TFT display, because the rotation of the liquid crystal controls the display of the picture. The fewer liquid crystals involved in the rotation, the shorter the time required. However, the thickness of the liquid crystal layer cannot be reduced arbitrarily and must be within a smaller range, because the thickness of the liquid crystal layer will affect the final picture color of the TFT display. A thicker layer will turn the white screen yellow, and a thinner layer will turn the white screen blue.

What kind of tft display should I choose?

The black-to-white response time of a TN-type display is 20ms, and the black-to-white response time of an IPS-type display is 30ms. However, it should be noted that these data are measured at 25°C. , because the liquid crystal will gradually transform from liquid crystal state to solid state, the viscosity coefficient will increase, the response time will be reduced a lot, and the picture conversion will be slow. Therefore, if you have a relatively high demand for response time, choose the type of monitor and install it appropriately. temperature to use it.

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