Liquid crystal is a high-tech material with special physical, chemical and optical properties. Since the 20th century, thin display technology has been widely used.
Familiar with the state of matter (called phase) gas, liquid and solid liquid crystal (liquid crystal for short) liquid crystal phase should have special shape combination. Now the definition of liquid crystal with crystal optical properties is relaxed, including a certain temperature range. The compound composed of organic compound carbon has the same practical value as the electromagnetic field sensor with special optical properties combined with the force between two kinds of liquid crystals.
1888 Ollie's name is Leontzlko family, a strange organic compound. When solid crystals with two melting points are heated at 145℃, the liquid will be turbid. When the pure substance is melted but transparent, continue to heat to 175℃. German physicist Li Man is in the middle zone. This turbid liquid is called Crystal Ratio, which is like a horse and a mule. It is called a mule in the field of machinery. Liquid crystal has been found, and its use is known.
Liquid crystal display material is used to display numbers on the display panel of electric meter calculator. The original liquid photoelectric display materials used the electro-optical effect of liquid crystal to convert characters, images and other signals. The arrangement order of liquid crystals is clear and transparent. When the DC electric field is applied to disturb the arrangement, the liquid crystals become transparent, and the color is deepened to display digital images.
The electro-optic effect of liquid crystal refers to the light phenomenon modulated by electric field, such as interference, scattering, diffraction, optical rotation, absorption and so on.
Some polymer solutions of organic compounds at constant temperature or concentration have both liquid fluidity and crystal anisotropy. The photoelectric effect of liquid crystal is controlled by temperature conditions. Liquid crystals are called thermotropic liquid crystals. Lyotropic liquid crystal is controlled by low temperature liquid crystal similar to liquid crystal, which is used to display concentration conditions.
According to the color-changing characteristics of liquid crystal, liquid crystal can change from red to green with the change of temperature, and blue represents an experimental temperature. When the liquid crystal meets hydrogen chloride and hydrocyanic acid, the liquid crystal sheet in the chemical plant hangs on the wall, and a small amount of toxic gas escapes from the liquid crystal to remind it of discoloration, so as to quickly check and repair the leakage.
The types of liquid crystals are classified according to the characteristics of liquid crystal bridge bond rings. At present, there are 654.38+00,000 kinds of liquid crystal materials. Liquid crystal display materials such as biphenyl liquid crystal, phenyl naphthene liquid crystal and ester liquid crystal have obvious advantages: low driving voltage, low power consumption, high reliability, information display, color display, flicker, physical hazards, automatic production process, low cost, easy to carry, etc. Due to some advantages, the TV range of computer terminal is made of liquid crystal material.
[Edit this paragraph]
Liquid crystal history
Crystal liquid crystal-liquid crystal 1850 Prussian doctor Rudolf? Rudolf virchow et al. found that the nerve fiber extract contains seed-seeking substances 1877 German physicist Otto? Otto lehmann observed and solved the phenomenon of liquid crystallization with polarizing microscope.
Ollie Brad, botanist Frederick? Friedrich Reinitzer heated cholesterol benzoate to study the role of cholesterol in plants. On June 18833 and June 14, the thermal melting of cholesteryl benzoate was observed. When it melts at 145.5℃, it produces bright turbidity. When the temperature rises to 178.5℃, the luster disappears. When the clarified liquid cools slightly, turbidity reappears.
Lenin confirmed this discovery many times. German physicist Lehman was asked to build a heating function microscope to discuss the crystallization process of liquid crystal cooling. The further study of Lenin's composite instrument began with all the work of Lehman. The original soft crystal of this substance was renamed as crystallization fluid. The name of Fliessende kristalle is exact, which is different from that of liquid crystal. Lenizen is known as the father of liquid crystal.
Identification of liquid crystals by L. gattermann and A Ristschke's oxygen azo ether Lehman: G. tammann, a famous scientist in the 20th century, observed the phenomenon of ultrafine crystal suspension; W. Nernst realized that D. Vorlander was a mixer of tautomers of liquid crystal compounds, and he tried to predict which compounds could present liquid crystals by gathering experience.
Physical characteristics of liquid crystal
Power on, turn on the light, arrange and change the order, so that light can pass easily; In short, the liquid crystal panel is composed of two delicate sodium glass materials, called the substrate, and the liquid crystal beam passes through each layer. The liquid crystal itself stands upright or twists in a regular way to block or make the light beam pass smoothly. Liquid crystals are all organic compounds, and some rod-shaped shafts make parallel liquid crystals pour into the machined groove plane. The liquid crystals are arranged along the grooves, but they are all completely parallel, if not parallel.
[Edit this paragraph]
liquid crystal
Nematic phase
Smectic phase
cholesteric phase
Discoid
Thermotropic liquid crystal
Reproducing liquid crystal
[Edit this paragraph]
Liquid crystal use
Liquid crystals should be filled and stirred before being poured. Liquid crystal containing solid chiral agent should be heated to 60 degrees Celsius, then quickly cooled to room temperature, filled and stirred, and allowed to stand during use. Because liquid crystals with low threshold voltage have some similar characteristics, some liquid crystals should pay attention to:
Liquid crystal should be filled and stirred before use, and the liquid crystal should be put into production immediately, and the static storage room should be shortened as much as possible to avoid chromatographic phenomena.
The prepared liquid crystal should be covered and stored in a cool place, and as far as possible, it needs to be stirred, retested and reused after class (8) is used up, and it will increase with the increase of intermittent driving voltage.
The original bottle of LCD should be taken from the original bottle and sealed with light shielding to reduce the leakage current of LCD when exposed to air.
Low threshold voltage liquid crystal display chip empty box PI solid baking liquid crystal filling process chamber 24 empty box filling operation adopts a relatively low filling speed.
The liquid crystal seal with low threshold voltage must be covered with a suitable hood. In the whole liquid crystal filling process, except for the curing period of the sealant, it should be as far away from the ultraviolet light source as possible, otherwise it will approach the phenomenon that the threshold voltage of ultraviolet light rises in the wrong direction.
High substances in liquid crystal machines are easily dissolved in various solvents or react with their chemicals. The storage process of liquid crystal itself should be as far away from its chemicals as possible.
1922 g friedel carefully analyzed three kinds of known liquid crystals: nematic, smectic and cholesteric. The first two names are taken from the Greek linear detergent (soap); Historical significance of naming cholesterol Modern category belongs to chiral category. In fact, Freud's liquid crystal words also agree that "mesophase" is an appropriate expression.
It was only in the 1970 generation that discotic liquid crystals were found to have high symmetry, and the conditions (conditions) for producing liquid crystals were the same as those for thermotropic liquid crystals (lyotropic liquid crystals) except for the types of nematic or columnar systems, which were produced by heating and adding solvent-like liquid crystals.
An example of lyotropic liquid crystal is soap water with high concentration, which is contracted in a layered group with slightly lower water concentration.
In fact, this substance has a liquid crystal phase. It is found that the mixture of two kinds of liquid crystals is heated by isotropic liquid, and then cooled, and nematic and layered liquid crystal phase change substances are observed, which are called recentrant LC liquid crystal structure.
Stable liquid crystal interface, where the Kawara Tsutomu aggregation density is high, and the repulsive anisotropy has greater attraction, and then the high density is maintained, so that the collective reaches the liquid crystal state and the auditory attraction is balanced, and the dipole interaction of ten important polar groups is important.
[Edit this paragraph]
Liquid crystal application
The liquid crystal arrangement shows a selective light scattering arrangement influenced by external forces. The potential range of liquid crystal material manufacturing equipment is between two glass plates. Chiral nematic liquid crystals have the same texture after a certain program treatment.
Steroid liquid crystal spiral structure light selective reflection uses white circular polarization to make thermometer simply according to the principle of color change (see thermometer in fish tank). Medical skin cancer and breast cancer detection suspected parts coated with steroid liquid crystal and skin color ratio (cancer cells metabolize faster than ordinary cells, and the temperature is higher than ordinary cells)
Electric field and magnetic field liquid crystal have great influence on the phase dielectric of nematic liquid crystal, which is the basis of various photoelectric applications. As the super display of 1970 generation, the applied electric field made of liquid crystal material has many advantages, such as fast volume, low power consumption, low working voltage and easy color screen design. The clarity of luminous display in the dark and the temperature limit of viewing angle environment are ideal. On the TV computer screen, the manufacture of ten-type screen made of liquid crystal material is subject to high voltage demand. It goes without saying that the size and weight of transformer are actually limited. colour
[Edit this paragraph]
liquid crystal panel
Liquid crystal panel is closely related to LCD. The output, advantages and disadvantages of LCD panels are related to the quality and price of LCD itself. The LCD panel is related to the player's attention to response time, color, viewing angle, contrast and other parameters. Look at the performance and quality of LCD panel. Lin He. Com should refer to the current mainstream LCD panels and let the family buy LCD bottoms.
VA-type: VA-type LCD panels are widely used in display products at present. High-end products 16.7M color (8-8bit panel) have obvious technical features. At present, there are two types of VA panels: MVA and polyvinyl alcohol.
MVA type: multi-domain vertical alignment technology uses protrusions to make the liquid crystal static, instead of the traditional vertical deviation to a certain angle; The applied voltage changes the level of liquid crystal, thus shortening the general principle of backlight faster and bigger. Changing the arrangement of liquid crystals broadens the viewing angle, which can be increased to 160 degrees and the reaction time can be shortened to less than 20 ms
PVA type: Samsung push panel type, which is an image vertical adjustment technology. This technology directly changes the structure of the liquid crystal cell to improve the display efficiency, which is superior to MVA brightness transmittance. Except for the improved S-PVAP-MVA, the technological development of the two panel types tends to reach the viewing angle of 170 degrees, the response time is controlled within 20ms (accelerated to 8ms GTG by Overdrive), and the ratio easily exceeds 700: 1. Some products of Samsung's own brand are high.
IPS type: IPS LCD panel has the advantages of visual angle and delicate color. Identifying IPS LCD panel Philips is more transparent. Less liquid crystal displays use IPS panel S-IPS, and the second generation IPS technology introduces some new technologies to improve the gray inversion phenomenon at some specific angles in IPS mode. LG Philips independent panel manufacturer ips technology features push LCD panel.
TN type: This type of LCD panel is applied to entry-level products with affordable prices, and the technology selected by many manufacturers is slightly inferior to the first two types of LCD panels in technical performance. It can display 16.7m bright color and 16.7m color (6bit panel). It is easy to improve the viewing angle, and the viewing angle is limited above 160 degrees. At present, all products with 8ms response on the market adopt TN LCD panel.
[Edit this paragraph]
liquid-crystal display
Liquid crystal display or ultra-thin display device of liquid crystal display panel is placed in front of light source or reflector by a certain number of color or black-and-white pixel groups. Liquid crystal display is favored by engineers because of its low power consumption, and it is suitable for electrical equipment using batteries.
Each pixel consists of several parts: liquid crystal suspended between two transparent electrodes (indium tin oxide) has two mutually perpendicular polarization directions; Liquid crystal light does not pass between electrodes, and its filter will inevitably prevent the polarization of light passing through the filter from rotating to liquid crystal.
The liquid crystal itself is charged, and a small amount of charge is added to each pixel or pixel transparent electrode to make the electrostatic force of the liquid crystal rotate, so that light can pass through the polarizing filter at the same angle as the rotation.
Before the charge is added to the transparent electrode, the liquid crystal is in a constrained state. The charge causes some groups of spiral or annular (crystalline) LCD polarizing substances to crystallize at a desired angle as seeds. The light passing through the filter passes through the polarization line of the liquid chip and rotates, so that the light can pass through another polarizer and be absorbed by the optical polarizer. The rest of the equipment is transparent.
The liquid crystal with charge and transparent electrode is arranged along the electric field, which limits the polarization of the transmitted light to the rotating pseudo liquid crystal, and the pseudo liquid crystal completely scatters the transmitted light, and its polarization to the second polarizer is completely perpendicular to the light, completely blocking the pixel from emitting light. Control the rotation of the liquid crystal of each pixel to control me to illuminate the pixel with less light.
Let the liquid crystal alternating current turn black. Alternating current destroys the spiral effect of liquid crystal. Turn off the current. The LCD becomes bright or transparent.
The power-saving LCD adopts multiplexing mode, and each group of electrodes is connected to the power supply, and the other group of electrodes is connected to each connected power supply. The design of the other group ensures that each pixel is controlled by an independent power supply, controlling the on/off sequence of the power supply, thus controlling the pixel display.
There are several important aspects in checking LCD display indicators: display reaction time (synchronization rate), array type (color brightness ratio supported by main viewing angle), screen aspect ratio and input interface (such as visual interface video display array).
brief history
The first LCD operation was based on dynamic scattering mode (DSM), and George? Hailmann led the team to develop LCD and founded Optel Company to develop a series of LCD 197065438+ February liquid crystal rotating nematic field effects. The registered patent of Fairy Techl Fauchhoffman-Le Rocco Yang Laboratory in Switzerland is 1969 James? Ferguson discovered the nematic field effect of liquid crystal rotation in Ohio University, and registered the same patent in February 19765438+ 197 1 Company (ILIXCO) produced the first LCD with poor performance based on different characteristics.
Display principle
Using the basic properties of liquid crystal, the self-light is filtered by polarizer. Since the twisted pitch of the liquid crystal cell is much higher than that of the liquid crystal arrangement on the surface of the alignment film along which light waves are seen, the polarized light is twisted by 90 degrees with respect to the whole liquid crystal layer, and the other side of the polarizer plays a role in transmitting light. A constant voltage is applied to the liquid crystal cell. The tilt voltage along the liquid crystal axis of the electric field is about twice the threshold voltage. Except for the liquid crystal on the electrode surface, the liquid crystal between the two electrodes in the liquid crystal box changes along the electric field and is rearranged at 90 degrees. The optical activity disappears, and the optical activity between alternating vibrating plates makes the device transparent. Instead, a parallel polarizer is used.
By turning on or off the liquid crystal cell, the light can change its transmission shielding state to realize the white or black mode in the alternating or parallel direction of the display polarizer.
Transmission and reflection display
LCD transmissive display and reflective display depend on the position where the light source is placed. When the transmissive LCD is illuminated by the backlight of the screen, the other side (front) of the screen needs high brightness display. For example, the power consumption of computer monitors and PDA mobile phones used to illuminate LCD lighting equipment is often higher than that of LCD itself.
Both electric clocks and computers (weather) have reflective liquid crystal displays. Various types of LCDs illuminate the screen by scattering light reflected from the outside of the reflective surface from the surface. The heavier light should be reduced by two liquid crystals. After using lighting equipment, the power consumption is obviously reduced. Battery devices last longer. The power consumption of reflective liquid crystal is not low. As for photovoltaic cells, they are enough to power pocket calculators.
The transflective LCD is used as both transmissive and reflective, and uses external light. LCD plays a reflective role, and external light can be used as transmitted light.
color display
A color LCD has three cells per pixel or an additional filter per pixel, and the red, green and blue pixels are controlled independently, which can produce millions or even millions of colors. CRT adopts the same display color, and the color components are arranged according to the geometric principle of the same pixel as required.
See LCD point distance.
See LCD point distance table:
12. 1 inch (800× 600)-0.308mm.
12. 1 inch (1024× 768)-0.240mm.
14. 1 inch (1024×768)-0.279 mm.
14. 1 inch (1400× 1050)-0.204 mm.
15 inch (1024× 768)-0.297mm.
15 inch (1400×1050)-0.218mm.
15 inch (1600×1200)-0.190mm
16 inch (1280× 1024)-0.248 mm.
17 inch (1280× 1024)-0.264 mm.
17 inch widescreen (1280× 768)-0.2895mm.
17.4 inch (1280× 1024)-0.27 mm.
18 inch (1280×1024)-0.285438+0mm.
19 inch (1280× 1024)-0.294 mm.
19 inch (1600× 1200)-0.242 mm.
19 inch widescreen (1440× 900)-0.283mm.
19 inch widescreen (1680×1050)-0.243mm.
20-inch widescreen (1680×1050)-0.258mm.
20. 1 inch (1200×1024)-0.312mm.
20. 1 inch (1600×1200)-0.255mm.
20. 1 inch (2560× 2048)-0.156mm
20.8 inches (2048×1536)-0.207mm.
2 1.3 inch (1600× 1200)-0.27 mm.
2 1.3 inch (2048× 1536)-0.2 1 mm
22-inch widescreen (1600× 1024)-0.294 mm
22.2 inches (3840×2400)-0. 1245 mm
23-inch widescreen (1920×1200)-0.258mm.
23. 1 inch (1600× 1200)-0.294 mm.
24-inch widescreen (1920×1200)-0.27mm.
26-inch widescreen (1920×1200)-0.287mm.
Light 20-inch flat LCD 17 inch, 23-inch widescreen LCD and 24-inch widescreen LCD are basically text defects. Dot spacing including 15 inch, 19 inch, 19 inch widescreen, 22 inch widescreen and 26 inch widescreen is more suitable than text display.
[Edit this paragraph]
Advantages of LCD screen
The radiation of LCD screen is less, ignoring the radiation of several watt bulbs.