liquid crystal (LC) is a polymer material, and it has been widely used in light and thin display technology since the middle of the 2th century because of its special physical, chemical and optical characteristics.
People are familiar with the state of matter (also known as phase) as gas, liquid and solid, but unfamiliar with plasma and Liquid Crystal (LC). Liquid crystal phases can only be produced if they have molecular combinations with special shapes. They can flow and have the optical properties of crystallization. The definition of liquid crystal has now been relaxed to include substances that can be liquid crystal phase in a certain temperature range and normal crystallization at a lower temperature. The composition of liquid crystal is an organic compound, that is, a compound centered on carbon. Liquid crystals with two substances at the same time are combined by intermolecular forces. Their special optical properties and sensitivity to electromagnetic fields are of great practical value.
In p>1888, an Austrian scientist named Leinitzel synthesized a strange organic compound with two melting points. When its solid crystal is heated to 145℃, it melts into a liquid, but it is turbid, while all pure substances are transparent when melted. If heated to 175℃, it seems to melt again and become a clear and transparent liquid. Later, the German physicist Liemann called the turbid liquid in the "middle zone" crystal. It is like a mule that is neither like a horse nor a donkey, so some people call it a mule in the organic world. Since the discovery of liquid crystal, people didn't know its purpose. It was not until 1968 that people used it as a material in the electronic industry.
The most common use of liquid crystal display materials is the display board of electronic watches and calculators. Why do they display numbers? It turns out that this liquid photoelectric display material uses the electro-optical effect of liquid crystal to convert electrical signals into visible signals such as characters and images. Under normal circumstances, the molecular arrangement of liquid crystal is very orderly and appears clear and transparent. Once the DC electric field is applied, the molecular arrangement is disrupted, and some liquid crystals become opaque and the color is deepened, so that numbers and images can be displayed.
the electro-optic effect of liquid crystal refers to its interference, scattering, diffraction, optical rotation, absorption and other optical phenomena modulated by electric field.
some organic compounds and polymers have both liquid fluidity and crystal anisotropy in a certain temperature or concentration solution, which is called liquid crystal. Liquid crystal whose photoelectric effect is controlled by temperature conditions is called thermotropic liquid crystal; Lyotropic liquid crystals are controlled by concentration conditions. Liquid crystals for display are generally low molecular thermotropic liquid crystals.
according to the color change of liquid crystal, people use it to indicate temperature and alarm toxic gas. For example, liquid crystal can change its color from red to green and blue with the change of temperature. This can indicate the temperature in an experiment. Liquid crystal will change color when it meets toxic gases such as hydrogen chloride and hydrocyanic acid. In chemical plants, people hang liquid crystal tablets on the wall. Once a trace of toxic gas escapes and the liquid crystal changes color, people are reminded to check and fill the leak quickly.
there are many kinds of liquid crystals, which are usually classified according to the characteristics of central bridge bonds and rings of liquid crystals. At present, more than 1, kinds of liquid crystal materials have been synthesized, among which there are thousands of commonly used liquid crystal display materials, mainly biphenyl liquid crystal, phenylcyclohexane liquid crystal and ester liquid crystal. Liquid crystal display materials have obvious advantages: low driving voltage, small power consumption, high reliability, large display information, color display, no flicker, no harm to human body, automatic production process, low cost, can be made into various specifications and types of liquid crystal displays, and is convenient to carry. Due to these advantages. Computer terminals and televisions made of liquid crystal materials can greatly reduce the size. Liquid crystal display technology has a profound impact on the structure of display imaging products, and promoted the development of microelectronics and photoelectric information technology. Crystalline liquid-liquid crystal as early as 185, Prussian doctor Rudolf? 6? Virchow and others found that the extract of nerve fibers contained an unusual substance. In 1877, the German physicist Otto? 6? Otto Lehmann observed the phenomenon of liquid crystallization for the first time with a polarizing microscope, but he didn't know the cause of this phenomenon.
Friedrich, a plant physiologist at the German University in Prague, Austria? 6? 4 Friedrich Reinitzer studied the role of cholesterol in plants by heating Cholesteryl Benzoate, and observed the abnormal behavior of cholesteryl benzoate during hot melting on March 14th, 1883. It melts at 145.5℃ and produces a turbid substance with luster. When the temperature rises to 178.5℃, the luster disappears and the liquid is transparent. The clarified liquid cooled slightly, and the turbidity reappeared, showing blue instantly, and the color was blue-purple just before the crystallization began.
After repeatedly confirming his findings, Lenizer asked the German physicist Lehman for advice. At that time, Lehman built a microscope with heating function to discuss the process of cooling and crystallization of liquid crystal, and later it was equipped with a polarizer, which was the most instrument for in-depth study of Lenezer's compounds. Since then, Lehman's energy has been completely focused on this kind of substance. At first, he called it a soft crystal, and then renamed it a crystalline fluid. Finally, he was convinced that polarized light was unique to crystals, and the name of Fliessende kristalle was correct. The name is only one step away from the liquid crystal (fluent ge crystal). Lenizer and Lehman were later known as the fathers of liquid crystals.
oxygen azo ethers synthesized by L. gattermann and A Ristschke were also identified as liquid crystals by Lehman. However, in the 2th century, famous scientists such as G. tammann thought that Lehman's observation was only the phenomenon that extremely fine crystals were suspended in liquid to form colloid. W. Nernst thinks that liquid crystal is only a mixture of tautomers of compounds. However, the chemist D. Vorlander's efforts enabled him to predict what kind of compounds are most likely to exhibit liquid crystal characteristics through aggregation experience, and then synthesize them to obtain these compounds, so the theory was proved.
Physical characteristics of liquid crystal
When it is energized, it conducts, and the arrangement becomes orderly, making it easy for light to pass through; When there is no electricity, the arrangement is chaotic, preventing light from passing through. Let the liquid crystal block or let the light pass through like a gate. Technically speaking, the liquid crystal panel contains 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 twist irregularly, thus blocking or making the light beam pass smoothly. Most liquid crystals belong to organic compounds, which are composed of long rod-shaped molecules. In the natural state, the long axes of these rod-like molecules are roughly parallel. Pour the liquid crystal into a well-processed grooved plane, and the liquid crystal molecules will be arranged along the grooves, so if those grooves are very parallel, the molecules are also completely parallel.