Who can tell me the principle and structure of LCD display?
Author:Mao Jiangfeng Time:2021-07-21 11:21 Browse(807)
Working principle of LCD
The working principle of LCD.
we have known for a long time that substances can be divided into three types: solid state, liquid state and gas state.
although the arrangement of liquid molecular center of mass does not have any regularity.

Who can tell me the principle and structure of LCD display?

however, if these molecules are long (or flat), the liquid molecular center of mass can be divided into three types, Their molecular orientation may be regular.
so we can subdivide the liquid into many types.
the liquid with irregular molecular orientation is directly called liquid.
the liquid with directional molecules is called "liquid crystal", also referred to as "liquid crystal" Calculators are all liquid crystal products.
liquid crystal was discovered in 1888 by reinitzer, an Austrian botanist. It is an organic compound with regular molecular arrangement between solid and liquid.
generally, the most commonly used liquid crystal type is nematic liquid crystal.
the molecular shape is slender rod shape, with length and width of about 1nm ~ 10nm. Under the action of different electric current and electric field, the liquid crystal is a kind of liquid crystal, The liquid crystal molecules will rotate 90 degrees regularly, resulting in the difference of light transmittance, so as to produce the difference of light and dark when the power is on / off. According to this principle, each pixel can be controlled to form the required image.
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1. Working principle of passive matrix LCD.
TN-LCD The display principle between STN-LCD and dstn-lcd is basically the same.
the difference is that there are some differences in the twist angle of liquid crystal molecules.
take a typical TN-LCD as an example.
to introduce its structure and working principle.
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in the TN-LCD panel with a thickness of less than 1cm,
it is usually composed of two large glass substrates, with color filters inside A splint made of a matching membrane, etc,The color filter is composed of red, green and blue colors.
it is regularly made on a large glass substrate.
each pixel is composed of three color units (or sub-pixel).
suppose there is a panel with a resolution of 1280 × 1024.
then it actually has 3840 × There are 1024 transistors and sub-pixel.
the upper left corner (gray rectangle) of each sub-pixel is an opaque thin film transistor.
the color filter can produce RGB primary colors.
each interlayer contains the grooves formed on the electrode and alignment film.
the upper and lower interlayer are filled with multi-layer liquid crystal molecules (the liquid crystal space is less than 5 cm) × On the other hand,
between the different layers, the long axis of the liquid crystal molecules is continuously twisted by 90 degrees along the parallel plane of the polarizing plate.
among them,
the orientation of the long axis of the two layers of liquid crystal molecules adjacent to the polarizing plate, The liquid crystal molecules near the upper interlayer are arranged in the direction of the upper groove.
while the liquid crystal molecules in the lower interlayer are arranged in the direction of the lower groove.
finally, they are packaged into a liquid crystal cell.
the liquid crystal cells are connected with the driving IC, the driving IC, the driving IC, the driving IC, the driving IC, the driving IC, and the driving IC The control IC is connected with the printed circuit board.
under normal circumstances, when the light irradiates from the top to the bottom.
generally, only one angle of light can pass through, which is led into the groove of the upper interlayer through the upper polarizing plate, and then goes out from the lower polarizing plate through the channel of twisted arrangement of liquid crystal molecules, A complete path of light penetration is formed.
and two polarizing plates are attached to the interlayer of the LCD.
in addition, two polarizing plates are attached to the interlayer of the LCDThe arrangement and transmission angle of the two polarizing plates are the same as the groove arrangement of the upper and lower interlayer.
when a certain voltage is applied to the liquid crystal layer.
due to the influence of the external voltage, the liquid crystal will change its initial state and no longer arrange in the normal way, So the light passing through the liquid crystal will be absorbed by the second layer polarizer, and the whole structure will be opaque.
as a result, black appears on the display screen.
when the liquid crystal layer does not apply any voltage.
the liquid crystal is in its initial state, and the direction of the incident light will be twisted by 90 degrees, so that the incident light of the backlight can pass through the whole structure, Results white appears on the display screen.
in order to make every independent pixel on the panel produce the color you want.
multiple cold cathode lamps must be used as the backlight of the display.
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2. The working principle of active matrix LCD.
the structure of TFT-LCD is basically the same as that of TN-LCD.
only the electrodes on the interlayer of TN-LCD are used The working principle of TFT-LCD is different from that of TN-LCD in many ways.
the imaging principle of TFT-LCD is "back transparent" mode.
when the light source irradiates,
the light first penetrates upward through the lower polarizing plate, Liquid crystal molecules are used to conduct light.
because the electrodes of the upper and lower interlayer are changed into FET electrode and common electrode.
when the FET electrode is turned on, the arrangement state of liquid crystal molecules will also change, and the display purpose can be achieved by shading and transmitting light.
but the difference is.
because the FET transistor has capacitive effect, it can maintain the potential state,The previously transparent liquid crystal molecules will remain in this state until the next time the FET electrode is electrified to change its arrangement.
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LCD is the abbreviation of liquid crystal display.
liquid crystal display is a kind of digital display technology. The LCD used in this paper is a layered structure composed of different parts.
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this paper introduces the structure of liquid crystal display      The LCD is composed of two glass plates with a thickness of about 1 mm, in which liquid crystal material is contained      5 of μ Because the liquid crystal material itself does not emit light.
so in the.
     There are light tubes on both sides of the display screen as light sources.
while there are light tubes on the back of the LCD screen      A backlight plate (or even light plate) and a reflective film.
the backlight plate is made of fluorescent materials.
the backlight plate is made of fluorescent materials      It can emit light.
its main function is to provide a uniform background light source.
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     The light from the backlight enters the packet after passing through the first layer of polarization filter      The liquid crystal layer contains thousands of liquid crystal droplets.
all the droplets in the liquid crystal layer are contained in the liquid crystal layer      In a small cell structure.
one or more cells make up one cell on the screen.
     The pixel is a transparent electrode between the glass plate and the liquid crystal material.
the electrode is divided into rows.
     And column.
at the intersection of row and column, the rotation of liquid crystal can be changed by changing the voltage.
at the intersection of row and column, the rotation of liquid crystal can be changed by changing the voltage      Light state.
the effect of liquid crystal materials is similar to that of small light valves.
in liquid crystal materials.
the effect of liquid crystal materials is similar to that of small light valves      The control circuit and the drive circuit are located around the materialWhen the electrode in the LCD produces      When the electric field is generated.
the liquid crystal molecules will be distorted, and the light passing through them will be distorted.
when the electric field is generated      Regular refraction is carried out.
and then it is filtered on the screen through the second filter layer.
the second filter layer      Display.
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is displayed
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