Physical Properties
When energized conducts, the arrangement becomes orderly, allowing light to pass through easily; when not energized, the arrangement is chaotic, preventing light from passing through. Allowing liquid crystals to block or let light through like a gate. In technical simplicity, LCD panels contain two pieces of fairly delicate sodium-free glass material called Substrates with a layer of liquid crystal sandwiched between them. When a beam of light passes through this layer of liquid crystals, the liquid crystals themselves stand in a row or twist in an irregular pattern, thus blocking or allowing the beam of light to pass through smoothly. Most liquid crystals are organic complexes, consisting of long, rod-shaped molecules. In their natural state, the long axes of these rod-shaped molecules are roughly parallel. When liquid crystals are poured into a well-machined grooved plane, the liquid crystal molecules follow the grooves, so that if the grooves are perfectly parallel, the molecules are also perfectly parallel. Liquid crystal is an intermediate substance between the crystalline state and the liquid state. It combines some of the characteristics of both liquids and crystals and exhibits some unique properties.
Edited classification
Nematic phase (nematic) e.g.: ammonium oleate CH3(CH2)7CH=CH(CH2)7COONH4 Near-crystalline phase (smectic) e.g.: p-oxoazoanisole: CH3OC6H4(NO)=NC6H4OCH3 Cholesteric phase (cholesteric) e.g.: Cholesteryl benzoate: C6H5COOC27H45 Discoid (discotic) Thermotropic liquid crystals (thermotropic LC) Reproducible liquid crystals (reproducrant LC) Toward the columnar phase: Toward the columnar phase
[2] Toward the columnar phase is the simplest phase of liquid crystals, and the rods of such liquid crystals are simply arranged equally between each other. However, their centers of gravity are arranged in a disordered manner, and when flow occurs under the action of an external force, they can easily be oriented in the direction of flow and traverse each other. Therefore, this type of liquid crystal has considerable mobility. Nematic phase liquid crystals are further divided into uniaxial nematic phase liquid crystals and biaxial nematic phase liquid crystals. Near-crystalline phase: Near-crystalline phase
[3] The near-crystalline structure is the class of all liquid crystals having the closest crystalline structure. In this type of liquid crystals, the rod-like molecules are arranged equally with each other in a lamellar structure relying on strong interactions perpendicular to the direction of the long axis of the molecules provided by the functional groups contained therein, and the long axis of the molecules is perpendicular to the plane of the lamellae. In the layer, the molecular arrangement maintains a large number of two to the solid order, but these laminae are not strictly rigid, the molecules can be active within the layer, but can not come and go between the layers, as a result of this type of flexible two-dimensional molecules can be sliding between each other, and perpendicular to the direction of the laminae flow just to be difficult. As a result, near-crystalline liquid crystals are generally very viscous in all directions. Cholesteric phase: Cholesteric phase
In this type of liquid crystal, long molecules are flat, relying on the interaction of the end groups, each other equally arranged in layers, but their long axis is in the plane of the lamellae, molecules within the layer and to the column type is similar to the adjacent two layers, the molecular orientation of the long axis, due to the role of the optically active groups sticking out of the plane of the lamellae, the order of the rules of the twisted at a certain angle, the layers add up to form a helical structure. The formation of helical surface structure.
Solvatized liquid crystals
Solvatized liquid crystals are liquid crystals formed from two or more components, one of which is water or another polar solvent. This is a liquid crystalline state formed by dissolving a solute in a solvent. Typically the solute portion is composed of an amphiphilic molecule having a hydrophilic group at one end and a hydrophobic group at the other end. Examples include alkali metal fatty salts such as sodium dodecyl sulfate or fatty acid sodium soap. Its solvent is water, when these solutes are dissolved in water, in different concentrations, due to the role of amphiphilic molecules hydrophilic, hydrophobic group will form different core phase (middle) and layer phase (lamella), the core phase is spherical or columnar. The core phase is spherical or columnar, while the lamella phase consists of a layer arrangement similar to that of the near-crystalline phase. The long, rod-shaped solute molecules in solvated liquid crystals are generally much larger than the long, rod-shaped molecules that make up thermotropic liquid crystals, with molecular axis ratios around 15. The most common are soapy water, laundry detergent solutions, and surfactant solutions. Solute-solute interactions are of secondary importance. Due to the ordered arrangement of molecules necessarily give this solution some kind of crystalline properties. Examples are optical anisotropy, electrical anisotropy, to affinity anisotropy. For example, the rainbow on the surface of a soap bubble and the washing action is a manifestation of this anisotropy. Solvation-induced liquid crystals are different from thermo-induced liquid crystals. They exist widely in nature, in living organisms, and are used unknowingly in various fields of human life. For example, soap detergents, etc. Biophysics, biochemistry, biomimicry fields are y concerned. This is because many biofilms, organisms, such as nerves, blood, biofilms and other life substances and life processes such as metabolism, digestion and absorption, perception, information transfer and other life phenomena are related to solvated liquid crystalline state substances and properties. Therefore, in the field of bioengineering, life, healthcare and artificial life research, the research of solvatochromic liquid crystal science has attracted much attention.
Edit paragraph use
Liquid crystal should be fully stirred before use before infusion and use, add solid chiral agent liquid crystal, to be heated to 60 degrees Celsius, and then quickly cooled to room temperature and fully stirred. And in the process of use can not be static time is too long. Especially low threshold voltage liquid crystal, because of the low threshold voltage liquid crystal with liquid crystal display
Have these different characteristics, so in the use of these liquid crystals should pay attention to the following aspects: Liquid crystal in the use of the full stirring, the deployment of the liquid crystal should be put into production immediately, as far as possible to shorten the time of storage, to avoid the phenomenon of chromatography. Blended liquid crystals should be covered with a blackout deposit, and try to use up in a shift (eight hours), the liquid crystals need to be recycled and stirred to re-test the voltage and then use. Generally with the extension of time, the driving voltage will increase. Liquid crystal from the original bottle after taking, the original bottle should be promptly capped and kept in the shade, to reduce the time of open exposure to the air in general exposure to the air for too long, will increase the leakage current of liquid crystal. Filling low threshold voltage LCD chip empty box is best from the PI solid baking to filling liquid crystal process, flow storage production time within twenty-four hours of the empty box, filling liquid operation generally use a relatively low filling speed. Low threshold voltage liquid crystal in the sealing must be covered with a suitable shade, and in the entire filling liquid crystal period in addition to the sealing adhesive curing period, to try to stay away from ultraviolet light sources. Otherwise, misdirection and increased threshold voltage will occur close to the UV light. Liquid crystal is an organic polymer substance, it is easy to dissolve in various solvents or react with other chemicals, liquid crystal itself is also a good solvent, so try to stay away from other chemicals in the use and storage process. In 1922, the Frenchman Friedel (G. Friedel) carefully analyzed the liquid crystals known at that time, and divided them into three categories: nematic (nematic), laminar (smectic), cholesteric (cholesteric). The source of the name, the first two were taken from the Greek linear and clear Liquid Crystal Display
Cleaner (soap); cholesteric type of the name has a historical significance, such as the modern classification, they belong to the hand to column type. In fact, Fried disagreed with the term liquid crystal, believing that 'intermediate phase' was the most appropriate expression. Discotic liquid crystals, discovered in the 1970s, are columnar or columnar systems composed of overlapping protomolecules with high symmetry. In addition to the classification of types, liquid crystals are classified into thermotropic LC and lypotropic LC due to the different conditions (conditions) under which they are generated, which are caused by heating, addition of solvents to form liquid crystals, and formation of liquid crystals in the thermal phase, which leads to the generation of liquid crystal phases, respectively. An example of lyotropic liquid crystal generation is soap water. At high concentrations, soap molecules are layered, with water molecules between the layers. When the concentration is a little lower, the combination is different. In fact, a substance can have multiple liquid crystal phases. It has also been found that the two liquid crystal mixtures heated to obtain isotropic liquid and then cooled, you can observe the next to the column type, lamellar liquid crystals. This phase change of the substance, known as the reproducible liquid crystal (recentrant LC). Liquid crystal molecular structure. Stabilized liquid crystal phase is the van der Fahrenheit force between molecules. Because of the high density of molecular aggregation, repulsive anisotropy has a greater impact, but the attractive force is to maintain the high density, so that the collective to achieve the liquid crystal state of the force, the repulsive force and attractive force is very important to check and balance each other. Another example is that when the molecule has a polar group, the dipole interaction becomes an important attractive force.
Edit Usage
One of the consequences of the arrangement of liquid crystal molecules is that they exhibit selective light scattering. Because the arrangement can be affected by external forces, liquid crystal materials have a high potential for fabricating devices. Chiral nematic liquid crystals, which range between two glass plates, can form different textures after certain procedures. Steroidal liquid crystals, which selectively reflect light due to their helical structure, utilize circularly polarized light in white light, the simplest of which is a thermometer made on the color-changing principle (the thermometer often seen in fish tanks). In medicine, the detection of skin and breast cancer can also be done by applying steroid liquid crystals to the suspected area, and then comparing the color with that of normal skin (because the metabolism of cancer cells is faster than that of normal cells, the temperature will be higher than that of normal cells). Electric and magnetic fields have a tremendous influence on liquid crystals, and the dielectric behavior of nematic liquid crystal phases is the basis for various optoelectronic applications (the use of liquid crystal materials to create displays with an applied electric field has been developing rapidly since the 1970s. This is because they have many advantages such as small volume, low power consumption, low operating voltage, and easy design of multi-color surface panels. However, because they are not light-emitting displays, their clarity in the dark, viewing angle and ambient temperature limitations are not ideal. In any case, the screens of TVs and computers are manufactured with liquid crystal material, which is very favorable. Large screens were constrained in the past by the need for high voltages, and the size and weight of the transformers were unspeakable. In fact, the color projection system can also use chiral nematic liquid crystals to manufacture such as polarizing plates, filters, and photoelectric regulators.
Edit LCD panel
Model
LCD panel and LCD monitor have a fairly close relationship, LCD panel production, superiority, and many other factors are linked to the LCD monitor itself LCD
quality, price, and market direction. Among them, the LCD panel is related to the player's most important response time, color, viewing angle, contrast ratio and other parameters. From the LCD panel can tell how this LCD monitor performance, quality? Xiaolin on the Internet to find the LCD panel information, as long as it is for the current mainstream LCD panel, so that we have a bottom in the heart when buying LCD monitors.
VA-type
VA-type LCD panels in the current monitor products are more widely used, used in high-end products, 16.7M color (8bit panel) and a large viewing angle is its most obvious technical characteristics, the current VA-type panels are divided into two kinds: MVA, PVA.
MVA-type
The full name ( Multi-domain Vertical Alignment), is a multi-quadrant vertical alignment technology. It is the use of protrusions so that when the liquid crystal is stationary is not the traditional upright, but biased to a certain angle stationary; when the voltage is applied to the liquid crystal molecules to change into a horizontal in order to allow the backlight to pass through the faster, so that you can significantly shorten the display time, but also because of the protrusions to change the orientation of the liquid crystal molecules, so that the field of view of a wider angle. The increase in viewing angle is up to 160 degrees or more, and the response time is reduced to less than 20ms.
PVA type
Samsung launched a panel type, is a kind of image vertical adjustment technology, the technology directly change the structure of the liquid crystal unit, so that the display performance is greatly improved can be better than MVA brightness output and contrast ratio. In addition, on the basis of these two types and extend the improved S-PVA and P-MVA two types of panels, in the development of technology tends to be more up, the viewing angle of up to 170 degrees, the response time is controlled within 20 milliseconds (Overdrive acceleration to achieve 8ms GTG), and the contrast can easily exceed the high level of 700:1, Samsung's own brand of the majority of the product for the PVA LCD panels.
IPS type
IPS type LCD panel has a large viewing angle, color fine and other advantages, looks more transparent, which is also a way to identify the IPS type LCD panel, PHILIPS a lot of LCD monitors use IPS type panel. S-IPS, on the other hand, is the second generation of IPS technology, which in turn introduces some new technologies to improve the phenomenon of gray-scale reversal of the IPS model at some specific angles. LG and Philips autonomous panel makers also introduced LCD panels with IPS as a technical feature.
TN type
This type of LCD panel is used in entry-level and mid-range products, affordable and inexpensive, and is chosen by many manufacturers. Technically, compared with the first two types of LCD panels in the technical performance is slightly inferior, it can not show 16.7M brilliant colors, can only reach 16.7M colors (6bit panel) but the response time is easy to improve. Viewing angle is also subject to certain restrictions, the viewing angle will not exceed 160 degrees. Now on the market in general within 8ms response time of the products are mostly used in the TN LCD panel.
Editorial section of the liquid crystal display
Introduction
Liquid crystal display, or LCD (Liquid Crystal Display), for the plane of the ultra-thin display device, it consists of a certain number of color or black and white pixels, placed in front of the light source or reflective surface. Liquid crystal displays are favored by engineers because of their low power consumption, and are suitable for battery-operated electronic devices. Each pixel consists of the following parts: an array of liquid crystal molecules suspended between two transparent electrodes (indium tin oxide), and two polarizing filters whose polarization directions are perpendicular to each other. Without the liquid crystals between the electrodes, light passing through one of the filters would inevitably be blocked by the other, and the direction of polarization of the light passing through one of the filters is rotated by the liquid crystals to enable it to pass through the other one. The liquid crystal molecules themselves carry an electric charge, and by adding a small amount of charge to the transparent electrodes of each pixel or sub-pixel, the molecules of the liquid crystals will be rotated by electrostatic force, and the light passing through will be rotated at the same time, changing a certain angle, so as to be able to pass through the polarization filters. Before the charge is applied to the transparent electrodes, the liquid crystal molecules are in an unconstrained state, and the charge on the molecules causes these molecules to form a helix or ring (crystalline) shape. In some LCDs, the chemical surfaces of the electrodes act as crystalline seeds for the crystals so that the molecules crystallize at the desired angle, and the light rays that pass through one filter rotate in a polarized line of defense after they pass through the liquid chip, thus allowing the light rays to pass through the other polarizer. A small portion of the light is absorbed by the polarizer, but the rest of the device is transparent. After adding charge to the transparent electrode, the liquid crystal molecules will be arranged in the direction of the electric field, thus limiting the rotation of the polarization direction of the transmitted light, if the liquid crystal molecules are completely broken up, the direction of polarization of the light passing through the liquid crystal will be completely perpendicular to the second polarizer, and thus be completely blocked by the light, at this time, the pixel does not emit light, by controlling the direction of the rotation of the liquid crystals in each pixel, we can control the amount of light that illuminates the pixel, as much or as little as we want. It can be more or less. Many LCDs turn black under the action of alternating current, which destroys the spiral effect of liquid crystals, and turn off the current, the LCD will become bright or transparent. To save power, LCD displays are multiplexed. In multiplexing mode, the electrodes at one end are connected together in groups, with each group connected to a power supply, and the electrodes at the other end are also connected together in groups, with each group connected to the other end of the power supply. The grouping design ensures that each pixel is controlled by a separate power supply, and that the electronic device or the software that drives the electronic device controls the display of the pixel by controlling the power supply's on/off sequence. The electronics or software driving the electronics controls the display of the pixels by controlling the power on/off sequence. The metrics used to test LCD monitors include the following important aspects: display size, response time (sync rate), array type (active and passive), viewing angle, supported colors, brightness and contrast, resolution and screen aspect ratio, and input interfaces (e.g., visual interfaces and video display arrays).
Brief History
The first operational LCDs were based on Dynamic Scattering Mode (DSM), which was developed by a group led by George Heilman of RCA. The LCD was developed by a team led by George Heilmann of RCA, who founded Optech, a company that developed a series of LCDs based on this technology. In December 1970, the rotating nematic field effect of liquid crystals was patented in Switzerland by the Central Laboratory of Sente and Helfrich Hoffmann-Lerocke. In 1969, James K. Furgeson's patent was registered at the Ohio State University in the United States. In 1969, James Ferguson discovered the rotating nematic field effect of liquid crystals at Kent State University (Ohio University) and registered the same patent in February 1971 in the U.S. In 1971, his company (ILIXCO) produced the first LCD based on this characteristic, which soon replaced the poor performance of the DSM-type LCDs.
The display is realized by utilizing the basic properties of liquid crystals. Natural light after a polarizer "filter" for linearly polarized light, because the liquid crystal molecules in the box distortion pitch is much larger than the wavelength of visible light, so when the liquid crystal molecules along the surface of the orientation of the film is aligned with the same direction or orthogonal to the linear polarization of the incident light, the direction of its polarization in the entire liquid crystal layer will be twisted 90 ° by the other side of the shot, the orthogonal polarizer plays a role in transmittance, orthogonal polarization of the liquid crystal layer. The orthogonal polarizer plays the role of light transmission; if a certain value of voltage is applied to the liquid crystal box, the long axis of the liquid crystal begins to tilt along the direction of the electric field, when the voltage reaches about 2 times the threshold voltage, in addition to the electrode surface of the liquid crystal molecules, all the liquid crystal molecules between the two electrodes in the liquid crystal box become rearranged along the direction of the electric field, at which time the function of 90 ° spinning disappears, and the spinning effect is lost between the orthogonal sheet oscillator, so that the device Can not transmit light. If the use of parallel polarizers is the opposite. It is this way to use the liquid crystal box to energize or de-energize the method to make the light to change the state of light transmission and blocking, so as to realize the display. When the upper and lower polarizers are oriented orthogonally or parallel to each other, the display appears in constant white or constant black mode.
Transmissive and reflective displays
LCDs can be either transmissive or reflective, depending on where the light source is placed. Transmissive LCDs are illuminated by a light source behind the screen, while viewing is on the other side (front) of the screen. This type of LCD is mostly used in applications that require high brightness displays, such as computer monitors, PDAs, and cell phones. The power consumption of the lighting equipment used to illuminate the LCD is often higher than that of the LCD itself. Reflective LCDs, commonly found in electronic clocks and computers, (sometimes) illuminate the screen by reflecting light back from the outside by a reflective surface that scatters behind it. This type of LCD has a higher contrast ratio because the light is cut twice as it passes through the liquid crystal twice. The power consumption is significantly reduced by not using an illuminator, so the battery life of devices that use batteries is longer. Because a small reflective LCD consumes so little power that a photocell is enough to power it, it is often used in pocket-sized calculators. Semi-permeable reflective LCDs can be used as either transmissive or reflective. When there is a lot of external light, the LCD works as a reflective type, and when there is not enough external light, it works as a transmissive type.
Color display
In a color LCD, each pixel is divided into three cells, or subpixels, with additional filters marking red, green and blue. The three subpixels can be controlled independently, and the corresponding pixels produce thousands or even millions of colors. Older CRTs used the same method to display colors. The color components are arranged according to different pixel geometries as needed.
Common LCD dot pitch
Common LCD dot pitch table: 12.1-inch (800×600) - 0.308 mm 12.1-inch (1024×768) - 0.240 mm 14.1-inch (1024×768) - 0.279 mm 14.1-inch (1400×1050) - 0.204 mm 15-inch (1024×768) - 0.297 mm 15-inch (1400×1050) - 0.218 mm 15-inch (1600×1200) - 0.190 mm 16-inch (1280×1024) - 0.248 mm 17-inch (1280×1024) - 0.264 mm 17-inch widescreen (1280×768) - 0.2895 mm 17-inch widescreen (1280×768) - 0.264 mm 768) - 0.2895 mm 17.4-inch (1280×1024) - 0.27 mm 18-inch (1280×1024) - 0.281 mm 19-inch (1280×1024) - 0.294 mm 19-inch (1600×1200) - 0.242 mm 19-inch widescreen (1440×900) - 0.283 mm 19-inch widescreen (1680×1050) - 0.243 mm 20-inch widescreen (1680×1050) - 0.258 mm 20.1-inch (1200×1024) - 0.312 mm 20.1-inch (1600×1200) - 0.255 mm 20.1-inch (2560×2048) - 0.156 mm 20.8-inch (2048×1536) - 0.156 mm 20.8-inch (2048×1536) - 0.156 mm 20.8-inch (2048×1536) - 0.156 mm inch (2048×1536) - 0.207 mm 21.3-inch (1600×1200) - 0.27 mm 21.3-inch (2048×1536) - 0.21 mm 22-inch widescreen (1600×1024) - 0.294 mm 22.2-inch (3840×2400) - 0.1245 mm 23-inch widescreen ( 1920×1200) - 0.258 mm 23.1-inch (1600×1200) - 0.294 mm 24-inch widescreen (1920×1200) - 0.27 mm 26-inch widescreen (1920×1200) - 0.287 mm Not only 20-inch widescreen LCDs, but also 17-inch, 23-inch widescreen, and 24-inch widescreen LCDs basically have the text too small. Suitable monitors for internet surfing and word processing include the five sizes of 15", 19", 19" widescreen, 22" widescreen and 26" widescreen, all of which have a larger dot pitch and the right size text display.
Edit the advantages of LCD screen
1. LCD monitors and traditional CRT compared to the biggest advantage is still in the power consumption and volume, for the traditional 17-inch CRT, its power consumption is almost always in the 80W or more, and 17-inch LCD power consumption of most of the 40W up and down, so that counting, LCD in the energy-saving can be said to be a clear advantage. 2. Compared with the traditional CRT liquid crystal in the performance of environmental protection performance, this is because the liquid crystal display does not exist inside the high-pressure components like CRT, so it does not appear due to the high pressure caused by x-rays exceeded the standard situation, so its radiation indicators are generally lower than the CRT. 3. As the CRT display is to rely on the electromagnetic field generated by the deflection coil to control the electron beam, and because the electron beam on the screen can not be absolutely localized, so the CRT display will often have varying degrees of geometric distortion, linear distortion. And liquid crystal display because of its principle does not appear any geometric distortion, linear distortion, which is also a major advantage.
Edit this section of the solution to the LCD screen screen
The first move: check whether the graphics card is overclocked. If the graphics card is overclocked and used, irregular, intermittent horizontal lines will generally appear. At this point, the overclocking amplitude should be reduced appropriately. Note that the first to reduce the video memory frequency. The second move: check whether the monitor and graphics card wires are loose. Poor contact will lead to the emergence of "stray waves", "stray dots" like a splash screen is the most common phenomenon. The third move: check whether the monitor resolution or refresh rate is set too high. LCD monitor resolution is generally lower than the CRT monitor, if more than the best resolution recommended by the manufacturer, the phenomenon of splash screen may occur. The fourth move: check the quality of the graphics card. If the replacement of the graphics card after the problem of screen, and in the use of the first two strokes failed to work, it should check the card's anti-electromagnetic interference and electromagnetic shielding quality is not over the top. Specific approach is: some of the components that may produce electromagnetic interference as far away from the installation of the card (such as hard disk), and then see if the screen disappears. If it is determined that the electromagnetic shielding function of the graphics card is not pass, it should replace the graphics card, or homemade shielding cover. The fifth move: If you use the above five strokes, still can not solve the problem, it may be the quality of the monitor. At this time, please replace the other monitor for testing. The sixth trick: check whether the installation of incompatible graphics card drivers. This situation is generally easy to be ignored, because the graphics card driver update speed is getting faster and faster (especially NVIDIA graphics cards), some users are always eager to install the latest version of the driver. In fact, some of the latest drivers are either beta versions or versions optimized for a specific graphics card or game, and using these drivers may sometimes lead to splash screens. Therefore, it is recommended that you try to use Microsoft-certified drivers, preferably those provided by the graphics card manufacturer.