The hottest liquid crystal ink has temperature sen

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Temperature sensitive discoloration and anti-counterfeiting effect of liquid crystal ink (Part 1)

in the field of ink, liquid crystal temperature changing materials are the most interesting at present. It mainly causes the change of optical properties through the change of lattice

I. composition and characteristics of liquid crystals

generally, solid substances become liquids when heated to the melting point. However, some substances with special molecular structure do not directly change from solids to liquids, but first go through an intermediate state. This intermediate state, which does not belong to ordinary solids, liquids and gases, is called the fourth state of matter. Its appearance is a fluid, turbid liquid with liquid fluidity and surface tension. At the same time, it has the birefringence Q of optical anisotropy unique to crystals. This kind of state can combine liquid and crystal in a certain temperature range. 3 The material with some characteristics of the sample and clamping is called liquid crystal, which is generally of nematic type. We adopt self-lubricating bearing to replace hydrostatic bearing, smectic type, cholesteric type and heteromorphic type

nematic. Many filamentous optical patterns can be seen by polarizing microscope. This kind of liquid crystal still shows positive refraction, its viscosity is small, and it is rich in fluidity

smectic form. Rod like molecules form a layered structure, and the molecules are arranged in parallel with each other. The force between the molecular layers of this arrangement is relatively weak, and it is easy to slide between them, so the smectic liquid crystal presents two-dimensional fluid properties and has high viscosity characteristics

cholesteric type. Most of them are compounds derived from cholesterol. The liquid crystal as a whole forms a helical structure and has birefringence. It is the main type of liquid crystal ink

heteromorphic liquid crystal. It is also divided into heavy human liquid crystal and disc liquid crystal. Heavy liquid crystal is a liquid crystal with the same phase again in the process of phase transition. Disc liquid crystal is a kind of liquid crystal whose molecular structure is disc-shaped

liquid crystal is an intermediate state of some organic substances in a certain temperature range. In this state, due to the special orientation of the molecular arrangement, the molecular motion also has a specific law. For example, if the humidity is higher than the upper limit of the liquid crystal phase temperature, the liquid crystal will become an ordinary transparent liquid and lose its optical properties. If the temperature is lower than the lower limit of the liquid crystal phase temperature, it will become an ordinary crystal and lose its fluidity

II. Composition and process of liquid crystal ink

liquid crystal ink originated in the United States in the 1970s. Later, with the gradual maturity of its technology and the continuous expansion of the printing market, liquid crystal ink printing has developed rapidly in the United States, Japan and other countries, and the scope of application is also expanding. From the perspective of manufacturing method, liquid crystal ink belongs to the type of microcapsule structure ink. From the perspective of application, it belongs to the category of thermotropic ink with heat sensitivity on bulletproof body and adhesive pseudo printing ink. However, from the perspective of the characteristics of liquid crystal ink, it mainly uses the characteristics of liquid crystal temperature sensitive discoloration

liquid crystal ink is mainly composed of water-soluble resin, liquid crystal capsule, additives, binder and defoamer. It is prepared by dispersing liquid crystal and additives enclosed in microcapsules in binder. It changes the direction of orderly arranged molecules due to the temperature sensing of liquid crystal in the ink layer, so as to selectively reflect the visible light of specific wavelength and absorb the optical characteristics of other wavelengths to show color changes, rather than using the ink layer pigments to form color graphics and text

when the liquid crystal is irradiated by natural light, artificial white light, and colored light of a certain wavelength, the reflection is strengthened due to the refraction phenomenon. As the temperature rises, the color of the liquid crystal changes from the color of long wavelength to the color of short wavelength (that is, it changes according to red green cyan). The color formation mechanism of the liquid crystal is formed by the selective reflection of the liquid crystal to the light of a specific wavelength

the liquid crystal must be printed on the black or dark background. Now the liquid crystal can reflect - 100 - +700 degrees Celsius. The accuracy is 0.50 degrees Celsius. Because the arrangement of liquid crystal molecules is not as firm as the crystal structure, it is easy to be affected by external stimuli such as electric field, magnetic field, temperature, stress and adsorbed impurities, so that its various optical properties can be changed by the release of new open-hole sprayed foam insulation materials. This characteristic of liquid crystal is applied under liquid crystal ink

because liquid crystal is an organic compound between liquid and crystal, it cannot be directly added to the connecting material like ordinary ink. In order to prevent the liquid crystal from being polluted by its compounds and ensure the color rendering effect, it is necessary to wrap the liquid crystal in the microsphere capsule, and then mix it with the connecting material to make the so-called microcapsule ink. Microcapsules in liquid crystal inks are different from those in foaming and fragrance inks

the microcapsule of foaming ink is a foaming agent (or low boiling point liquefied gas). After heating, the foaming agent in the microcapsule emits a large amount of gas (or low boiling point liquefied gas expansion) to increase the volume of the microcapsule and play a foaming role. In addition, the foaming ink is added with pigments, printed into various colors of foaming graphics and texts, and has the dual function of foaming and coloring

microcapsules in fragrance ink are characterized by not being crushed and damaged during printing. After printing into products, it is required to press and tear them with nails, pencils, etc. to make them easily damaged, so as to achieve the purpose of emitting fragrance. The microcapsule in the liquid crystal ink attaches the liquid crystal in the capsule to the ink layer through the connecting material

(to be continued)

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