physical features
When it is turned on after being electrified, the arrangement becomes orderly and light can easily pass through; When there is no electricity, the arrangement is chaotic, which hinders the passage of light. Let the liquid crystal block or let the light pass like a gate. Technically, a liquid crystal panel consists of two pieces of quite exquisite sodium-free glass materials, called substrates, with a layer of liquid crystal sandwiched between them. When the light beam passes through this layer of liquid crystal, the liquid crystal itself will stand in rows or distort irregularly, thus blocking or making the light beam pass smoothly. Most liquid crystals belong to organic compounds and consist of long rod-like molecules. In the natural state, the long axes of these rod-like molecules are roughly parallel. Pour the liquid crystal into a machined groove plane, and the liquid crystal molecules will be arranged along the groove, so if those grooves are very parallel, the molecules are also completely parallel. Liquid crystal is an intermediate substance between crystalline state and liquid state. It has some characteristics of both liquid and crystal, showing some unique properties.
Edit this paragraph classification
Nematic phase, for example: ammonium oleate CH3(CH2)7CH=CH(CH2)7COONH4 smectic phase, for example: azoxyanisole: CH3OC6H4(NO). =NC6H4OCH3 cholesteric, for example: cholesteryl benzoate: C6H5COOC27H45 discotic thermotropic liquid crystal (thermotropic LC) Recursive liquid crystal (recentrant LC) nematic phase: nematic phase.
[2] Nematic phase is the simplest liquid crystal phase, and the rod-like molecules of this kind of liquid crystal are only arranged at equal intervals. But their centers of gravity are disordered and flow under the action of external force, so they are easy to orient along the flow direction and cross each other. Therefore, this type of liquid crystal has considerable fluidity. Nematic liquid crystals can be divided into uniaxial nematic liquid crystals and biaxial nematic liquid crystals. Smectic phase: smectic phase
[3] The smectic structure is the closest to the crystalline structure of all liquid crystals. In this liquid crystal, rod-like molecules are arranged in a layered structure based on the strong interaction provided by functional groups perpendicular to the long axis of the molecules, and the long axis of the molecules is perpendicular to the plane of the lamellae. In the layers, the molecular arrangement keeps a lot of two-dimensional solid order, but these layers are not strictly rigid. Molecules can move in this layer, but not between layers. Therefore, the flexible two-dimensional molecular sheets can slide each other, but the flow perpendicular to the layer direction is very difficult. For this reason, smectic liquid crystals are usually very viscous in all directions. Cholesteric phase: cholesteric phase
In this kind of liquid crystal, long molecules are flat, and they are uniformly arranged in the layer through the interaction of end groups, but their long axes are on the plane of the lamellae, and the molecules in the layer are similar to nematic. However, the orientation of the long axis of molecules between two adjacent layers turns to a certain angle in turn and accumulates layer by layer to form a spiral structure due to the action of optically active groups protruding from the lamellar plane.
Lyotropic liquid crystal
Lyotropic liquid crystal is a liquid crystal formed by two or more components, one of which is water or other polar solvents. This is a liquid crystal substance formed by dissolving a solute in a solvent. A typical solute is composed of amphiphilic molecules, one end of which is hydrophilic and the other end is hydrophobic. Such as sodium dodecyl sulfonate or sodium fatty acid soap. Its solvent is water. When these solutes are dissolved in water, different nuclear phases and lamellae will be formed at different concentrations due to the hydrophilic and hydrophobic groups of amphiphilic molecules. The core phase is spherical or cylindrical. The layered phase is composed of layered arrangement similar to smectic phase. The long rod-like solute molecules in lyotropic liquid crystals are generally much larger than those in thermotropic liquid crystals, and the molecular axis ratio is about 15. The most common are soapy water, washing powder solution, surfactant solution and so on. The interaction between solutes is secondary. The ordered arrangement of molecules will inevitably bring some crystal characteristics to this solution. Such as optical anisotropy, electrical anisotropy and even affinity anisotropy. For example, the rainbow on the surface of soap bubbles and the washing effect are the embodiment of this anisotropy. Lyotropic liquid crystal is different from thermotropic liquid crystal. They exist widely in nature and biology, and are unconsciously applied in all fields of human life. Such as soap and detergent. Biophysics, biochemistry, bionics and other fields have attracted much attention. This is because many biomembranes and organisms in the life process, such as nerves, blood, biomembranes and other life phenomena, such as metabolism, digestion and absorption, perception and information transmission, are related to the substances and properties of lyotropic liquid crystals. Therefore, in the fields of bioengineering, life, medical treatment, artificial life and so on, the research of lyotropic liquid crystal science has attracted much attention.
Edit the usage of this paragraph.
The liquid crystal should be fully stirred before use. The liquid crystal containing the solid chiral agent should be heated to 60 degrees Celsius, and then quickly cooled to room temperature and fully stirred. In addition, it should not be left for too long during use. Especially low threshold voltage liquid crystal, because low threshold voltage liquid crystal has liquid crystal display screen.
Because of these different characteristics, we should pay attention to the following aspects when using these liquid crystals: the liquid crystals should be fully stirred before use, and the prepared liquid crystals should be put into production immediately, and the standing storage time should be shortened as much as possible to avoid chromatographic phenomena. The prepared LCD should be stored in a cool cover and used up within one shift (eight hours) as far as possible. Unused liquid crystals need to be recycled and stirred before retesting. Generally speaking, as time goes on, the driving voltage will increase. After the liquid crystal is taken out of the original bottle, the original bottle should be sealed in time to reduce the exposure time to air, which will increase the leakage current of the liquid crystal. From PI curing to liquid crystal filling, it is best to fill the empty LCD box with low threshold voltage, and the production time is less than 24 hours. Generally, the filling speed is slow when filling liquid. Low threshold voltage liquid crystal must be covered with a suitable hood when sealing, and it should be as far away from the ultraviolet light source as possible during the whole liquid crystal filling period except the curing period of sealant. Otherwise, the wrong direction and the increase of threshold voltage will appear near the ultraviolet light. Liquid crystal is an organic polymer, which is easily soluble in various solvents or reacts with other chemicals. Liquid crystal itself is also a good solvent, so it should be as far away from other chemicals as possible during use and storage. 1922, Frenchman G. Friedel carefully analyzed the liquid crystals known at that time and divided them into nematic, smectic and cholesteric types. The source of the name, the first two are taken from Greek linear and clear LCD screens respectively.
Detergent (soap); The names of cholesterol types are of historical significance. For example, according to modern classification, they belong to chiral type. In fact, Fried disagreed with the word liquid crystal. He thought "mesophase" was the most appropriate expression. Discotic liquid crystals discovered only in 1970' s are nematic or columnar systems composed of highly symmetric undisturbed molecules. In addition to the classification of types, liquid crystals can be divided into thermotropic liquid crystals and lyotropic liquid crystals due to different conditions (conditions). Thermotropic liquid crystals are formed by heating and adding solvents respectively. An example of lyotropic liquid crystal formation is soapy water. At high concentration, soap molecules are layered and water molecules are between them. The concentration is slightly lower, and the combination is different. In fact, a substance can have multiple liquid crystal phases. It was also found that after heating the mixture of two kinds of liquid crystals to obtain isotropic liquid, and then cooling, it can be observed that the secondary is nematic and nematic liquid crystals. This phase change substance is called near phase change liquid crystal. Molecular structure of liquid crystal. The stable liquid crystal phase is van der Waals force between molecules. Because of the high molecular density, repulsive anisotropy has a great influence, but attraction is the power to maintain high density and make the collective reach the liquid crystal state. It is very important to balance exclusion and attraction. Another example is that when molecules have polar groups, dipole interaction becomes an important attraction.
The purpose of editing this paragraph
One of the results of liquid crystal molecular arrangement is selective light scattering. Because this arrangement will be affected by external forces, liquid crystal materials have great potential in manufacturing devices. Chiral nematic liquid crystals between two glass plates can form different textures after a certain procedure. Steroid liquid crystal selectively reflects light due to its spiral structure. The simplest thermometer (common thermometer in fish tanks) is made by using circular polarization in white light and according to the principle of color change. In medical treatment, skin cancer and breast cancer can also be detected by applying steroid liquid crystal to suspicious parts and then comparing with normal skin color (because cancer cells metabolize faster than ordinary cells, the temperature will be higher than ordinary cells). Electric field and magnetic field have great influence on liquid crystal, and the dielectric behavior of nematic liquid crystal phase is the basis of various photoelectric applications (displays made of liquid crystal materials with external electric field have developed rapidly since 1970' s). Because they have many advantages, such as small size, low power consumption, low working voltage and easy design of multi-color panels. However, because it is not a light-emitting display, the clarity, viewing angle and environmental temperature limit in the dark are not ideal. In any case, TV and computer screens are made of liquid crystal, which is very beneficial. In the past, the large screen was subject to the demand of high voltage, and the volume and weight of the transformer were indescribable. In fact, color projection electric system can also use chiral nematic liquid crystal to make polarizer, filter and photoelectric regulator.
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model
There is a close relationship between LCD and LCD, and many factors such as the output, advantages and disadvantages of LCD are related to LCD itself.
Quality, price and market trends. Among them, the LCD panel is related to the response time, color, viewing angle, contrast and other parameters that players value most. From the LCD panel, we can see the performance and quality of this LCD. Kobayashi is looking for information about LCD panels on the Internet. As long as it is aimed at the current mainstream LCD panel, let everyone have a bottom in mind when purchasing LCD monitors.
VA type
VA LCD panel is widely used in current display products, especially in high-end products. Its most obvious technical features are 16.7M color (8bit panel) and large viewing angle. At present, VA LCD panels are divided into MVA and PVA.
MVA type
Multi-domain vertical alignment is a multi-quadrant vertical alignment technology. It uses protrusions to make the liquid crystal stand at a certain angle instead of the traditional vertical. When the voltage is applied to make the liquid crystal molecules become horizontal to let the backlight pass through, the speed is faster, which can greatly shorten the display time, and because the protrusions change the orientation of the liquid crystal molecules, the viewing angle is wider. The viewing angle can be increased to more than 160 degrees, and the reaction time can be shortened to less than 20 ms
Polyvinyl alcohol type
It is a panel type introduced by Samsung, and it is an image vertical adjustment technology. This technology directly changes the structure of the liquid crystal cell, greatly improves the display efficiency, and obtains better brightness output and contrast than MVA. In addition, on the basis of these two types, two improved panels, S-PVA and P-MVA, have been developed. In terms of technical development, the viewing angle can reach 170 degrees, the response time can be controlled within 20ms (accelerated to 8ms GTG through Overdrive), and the contrast can easily exceed the high level of 700: 1. Most products of Samsung's own brand are PVA LCD panels.
IPS type
IPS LCD panel has the advantages of large viewing angle, delicate color and so on, and looks transparent, which is also a way to identify IPS LCD panel. Many Philips LCD monitors use IPS panels. S-IPS is the second generation IPS technology, which introduces some new technologies to improve the gray inversion phenomenon of IPS mode at some specific angles. Independent panel manufacturers of LG and Philips are also LCD panels featuring ips technology.
TN type
This type of LCD panel is used in entry-level and mid-range products, which is affordable and low-priced. Many manufacturers choose this panel. Technically, compared with the first two types of LCD panels, the technical performance is slightly inferior. The gorgeous color of 16.7M can't be displayed, but it can only reach the color of 16.7M (6bit panel), but the response time can be easily improved. The viewing angle is also limited, and the viewing angle will not exceed 160 degrees. At present, TN liquid crystal panels are mostly used for products with response time less than 8ms in the market.
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brief introduction
LCD(Liquid Crystal Display (LCD) is an ultra-thin flat panel display device, which is composed of a certain number of color or black and white pixels and placed in front of a light source or a reflector. Liquid crystal displays are favored by engineers because of their low power consumption, and are suitable for electronic devices that use batteries. Each pixel consists of the following parts: a row of liquid crystal molecules suspended between two transparent electrodes (indium tin oxide), and two polarization filters with perpendicular polarization directions. If there is no liquid crystal between the electrodes, the light passing through one filter will be blocked by the other filter, and the polarization direction of the light passing through one filter will be rotated by the liquid crystal, so that it can pass through the other filter. Liquid crystal molecules themselves are charged. If a small amount of charge is added to the transparent electrode of each pixel or sub-pixel, the liquid crystal molecules will be rotated by electrostatic force, and the passing light will also rotate and change a certain angle, so that it can pass through the polarizing filter. Before the charge is applied to the transparent electrode, the liquid crystal molecules are in an unconstrained state, and the charge on the molecules makes these molecules form a spiral or ring (crystal shape). In some liquid crystal displays, the chemical surface of the electrode can be used as a seed, so the molecules crystallize at a desired angle. The light passing through one filter rotates after passing through the liquid chip, so that the light can pass through another polarizer, and a small part of the light can be absorbed by the polarizer, but other devices are transparent. After the charge is applied to the transparent electrode, the liquid crystal molecules will be arranged along 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 dispersed, the polarization direction of the transmitted light will be completely perpendicular to the second polarizer, so it will be completely blocked by the light. At this time, the pixel will not emit light. By controlling the rotation direction of the liquid crystal in each pixel, we can control the light that illuminates the pixel more or less. Many liquid crystals will turn black under the action of alternating current, destroying the spiral effect of liquid crystals, and when the current is turned off, the liquid crystals will become bright or transparent. In order to save electricity, LCD adopts multiplexing mode. In the multiplexing mode, the electrodes at one end are connected in groups, each group of electrodes is connected to a power supply, and the electrodes at the other end are also connected in groups, and each group is connected to the other end of the power supply. The grouping design ensures that each pixel is controlled by an independent power supply, and the electronic equipment or the software driving the electronic equipment controls the display of pixels by controlling the on-off sequence of the power supply. The indicators for testing LCD display include the following important aspects: display size, response time (synchronization rate), array type (active and passive), viewing angle, supported colors, brightness and contrast, resolution and screen aspect ratio, and input interfaces (such as visual interface and video display array).
brief history
The first operable LCD was based on dynamic scattering mode (DSM), and George? The team led by Hailmann developed this kind of LCD. Hailmann founded Optel Company, which developed a series of liquid crystal displays based on this technology. 1970 12, the rotational nematic field effect of liquid crystal is registered as a patent by Santer and Hoffman-lerouke Central Laboratory in Herfrich, Switzerland. 1969, James? Ferguson discovered the rotational nematic field effect of liquid crystal in Ohio University, and registered the same patent in the United States in February 197 1. 197 1 year, his company (ILIXCO) produced the first LCD based on this feature, which quickly replaced the DSM LCD with poor performance.
Display principle
Using the basic characteristics of liquid crystal to realize display. Natural light is "filtered" into linearly polarized light after passing through a polarizer. Because the twisted pitch of liquid crystal molecules in the box is much larger than the wavelength of visible light, when linearly polarized light with the same or orthogonal arrangement direction of liquid crystal molecules along the surface of the alignment film is incident, its polarization direction will be twisted by 90 degrees after passing through the whole liquid crystal layer and will be emitted from the other side, and the orthogonal polarizer plays the role of light transmission. If a certain voltage is applied to the liquid crystal cell, the long axis of the liquid crystal begins to tilt along the electric field direction. When the voltage reaches about 2 times of the threshold voltage, the liquid crystal molecules between the two electrodes in the liquid crystal cell are all rearranged along the electric field direction except the liquid crystal molecules on the electrode surface. At this time, the function of 90 optical rotation disappears, and the optical rotation between the vibrating plates of orthogonal plates is lost, which makes the device unable to transmit light. If a parallel polarizer is used, the opposite is true. In this way, the liquid crystal box is powered on or off, so that the light changes its transmission shielding state, thus realizing display. When the upper polarizer and the lower polarizer are orthogonal or parallel, the display displays a normally white or normally black mode.
Transmission and reflection display
LCD can be displayed by transmission or reflection, depending on the position of its light source. The transmissive LCD is illuminated by a light source behind the screen, while the viewing is on the other side (front) of the screen. This type of LCD is mainly used in applications requiring high brightness display, such as computer monitors, PDA's and mobile phones. The power consumption of lighting equipment used to illuminate LCD is often higher than that of LCD itself. Reflective liquid crystal displays, commonly used in electronic clocks and computers, sometimes reflect external light back to illuminate the screen through the scattering reflective surface on the back. The contrast of this liquid crystal is very high, because the light has to pass through the liquid crystal twice, so it has to be cut twice. Not using lighting equipment significantly reduces power consumption, so the life of equipment using batteries is longer. Small reflective liquid crystal displays are often used in pocket calculators because of their low power consumption and sufficient power supply from photovoltaic cells. Transflective LCD can be used as transmissive and reflective. When the external light is sufficient, the LCD works as a reflection type, and when the external light is insufficient, it can work as a transmission type.
color display
In color LCD, each pixel is divided into three units, or sub-pixels, and additional color filters are marked with red, green and blue respectively. The three sub-pixels can be controlled independently, and the corresponding pixels produce thousands or even millions of colors. Old cathode ray tubes used the same method to display colors. According to needs, the color components are arranged according to different pixel geometric principles.
Common LCD dot spacing
Common liquid crystal display point distance table: 12. 1 inch (800× 600)-0.308mm12.1inch (1024× 768)-0.240mm/kloc. -0.279 mm 14. 1 inch (1400× 1050)-0.204 mm 15 inch (1 024× 768)-0.20. 5 inch (65438-0.242 mm 19 inch widescreen (1440×900)-0.283 mm 19 inch widescreen (1680×1050)-0. Inch (1200×600-0. 156 mm 20.8 inch (2048×1536)-0.207mm21.3 inch (1600×/kloc) Kloc-0/ mm 22-inch widescreen (1600×600 displays suitable for Internet access and word processing include 15 inch, 19 inch, 19 inch widescreen, 22 inch widescreen and 26 inch widescreen. Their point spacing is large, and the text display size is appropriate.
Advantages of editing this LCD screen
1. Compared with the traditional CRT, the biggest advantages of LCD are power consumption and volume. For the traditional 17 inch CRT, its power consumption is almost above 80W, while the power consumption of 17 inch LCD is mostly around 40W. In this way, LCD has obvious advantages in energy saving. 2. Compared with the traditional CRT, liquid crystal also shows some performance in environmental protection. This is because there is no high-voltage component like CRT in LCD, so the X-rays caused by high voltage will not exceed the standard, so its radiation index is generally lower than CRT. 3. Because CRT displays control the electron beam through the electromagnetic field generated by the deflection coil, and because the electron beam cannot be positioned absolutely on the screen, CRT displays often have different degrees of geometric distortion and linear distortion. The liquid crystal display (LCD) will not have any geometric distortion and linear distortion due to principle problems, which is also a big advantage.
Edit the solution of this LCD screen.
The first trick: check whether the graphics card is overclocked. If the graphics card is used excessively, irregular and intermittent horizontal stripes will appear. At this time, the overclocking amplitude should be appropriately reduced. Pay attention to reduce the frequency of video memory first. The second measure: check whether the connection between the monitor and the graphics card is loose. Poor contact can lead to "disorder" and "spots" on the screen, which is the most common phenomenon. The third measure: check whether the resolution or refresh rate of the display is set too high. The resolution of LCD is generally lower than that of CRT. If it exceeds the optimal resolution recommended by the manufacturer, screen diffusion may occur. The fourth measure: check the quality of the graphics card. If there is a problem with the screen display after replacing the graphics card, and the first and second measures don't work, you should check whether the anti-electromagnetic interference and electromagnetic shielding quality of the graphics card are qualified. The specific method is to install some components (such as hard disk) that may cause electromagnetic interference as far away from the graphics card as possible, and then see if the screen disappears. If it is determined that the electromagnetic shielding function of the graphics card is not enough, the graphics card should be replaced or a self-made shielding cover should be made. Fifth measure: If the above five measures can't solve the problem, it may be the quality problem of the monitor. At this time, please change other monitors for testing. The sixth measure: check whether an incompatible graphics card driver is installed. This situation is generally easy to be ignored, because the update speed of graphics card drivers is getting faster and faster (especially NVIDIA graphics cards), and some users can't wait to install the latest version of drivers. In fact, some of the latest drivers are either beta versions or optimized versions of a particular graphics card or game, and the use of such drivers may sometimes lead to a screen. Therefore, it is recommended that you try to use drivers certified by Microsoft, and it is best to use drivers provided by graphics card manufacturers.