First, the composition and process of LCD ink
Liquid crystal ink originated in the United States in the 1970s. Later, as its technology matured and the printing market continued to expand, liquid crystal ink printing was rapidly developed in the United States, Japan, and other countries, and its application range was also expanding. The liquid crystal ink is a microcapsule structure ink type in terms of production methods. From the application point of view, it belongs to the category of temperature-sensitive thermochromic inks for anti-counterfeit printing inks, but in terms of the characteristics of liquid crystal inks, it mainly uses the characteristics of temperature-sensitive discoloration of liquid crystals. .
The liquid crystal ink is mainly composed of a water-soluble resin, a liquid crystal capsule, an auxiliary agent, a binder, and a defoamer. The liquid crystal ink is prepared by dispersing liquid crystals, additives and the like enclosed in the microcapsules in a binder. It is caused by the temperature change of the liquid crystal in the ink layer, which causes the change of the molecular orientation of the ordered array, so that the optical characteristic that selectively reflects light of a specific wavelength exhibits color change instead of forming a color image with the ink layer pigment.
When the liquid crystal is irradiated with natural light, artificial white light, and color light of a certain wavelength, reflection is strengthened due to the refraction phenomenon, and as the temperature rises, the color changes from a long wavelength to a short wavelength (i.e., changes in red-green-cyan), The color forming mechanism of the liquid crystal is due to the liquid crystal selectively reflecting light of a specific wavelength.
Liquid crystals must be printed on black and dark backgrounds. Ready-to-use liquid crystals can reflect -100 to +700 degrees Celsius. The accuracy is 0.50 degrees Celsius. Since the arrangement of liquid crystal molecules is not as strong as the crystal structure, it is easily affected by external stimuli such as electric field, magnetic field, temperature, stress, and adsorption impurities, causing various optical properties to change. Liquid crystal inks have applications in liquid crystals. This feature.
Since the liquid crystal is an organic compound between the liquid and the crystal, it cannot be directly added to the connecting material like ordinary ink. In order to prevent the liquid crystal from being contaminated by its compound, in order to ensure the color rendering effect, it is necessary to enclose the liquid crystal in microsphere capsules, and then mix with the connecting material to make a so-called microcapsule type ink. The microcapsules in the liquid crystal ink are different from the microcapsules in the foaming and aroma inks.
The microcapsules of the foaming ink are foaming agents (or low-boiling liquefied gases). Upon heating, the foaming agent in the microcapsules emits a large amount of gas (or low-boiling liquefied gas expander) to increase the volume of the microcapsules from foaming. effect. In addition, pigments are added to the foaming ink, printed into various colored foaming graphics, and have dual functions of foaming coloration.
The characteristics of microcapsules in scented inks are that they are not crushed and damaged during printing, but they are required to be easily broken by pressing and tearing with nails, pencils, etc. after printing into finished products, so as to achieve the purpose of emitting fragrance. The microcapsules in the liquid crystal ink attach the liquid crystal in the capsule to the ink layer through the connecting material.
Second, the liquid crystal ink printing technology requirements
Liquid crystal inks can be screen or gravure, but silk screens are better. The key to liquid crystal printing technology is the ability to display brightly colored liquid crystals at different temperatures, and to make a series of color temperature values. The liquid crystal microcapsules have to be small and uniform, the capsule wall is transparent and thin, and the ink is incorporated, and the solvent resistance is required to be stable, reliable, and long-lived; the liquid crystal microcapsules are also not to be crushed during the printing process, and the surface is covered with a protective film.
1. Platemaking The screen mesh number should be 100-175 mesh, and it should be selected according to the requirements of ink microcapsule diameter and ink layer thickness. Since the screen liquid crystal microcapsule ink is water-soluble. Therefore, the use of strong water resistance photoresist should be used for plate making.
2, printing LCD ink printing should pay attention to the following points:
(1) The plate should be filled with enough ink at a time and the ink should be uniform. It is best not to fill the ink in the middle to prevent foaming.
(2) When plugging and blistering are found during printing, the machine should be shut down immediately and thoroughly cleaned with alcohol water.
(3) The printing pressure should be moderate. The pressure is low, and the amount of ink on the printing substrate is insufficient; if the pressure is too high, the liquid crystal capsule will be broken and the color effect will be affected.
(4) In order to make the color of the printing part obvious, the black color or dark tone should be used for the printing background. The bottom layer can use water-soluble ink, and organic solvent ink can also be used. Printing methods available screen printing, offset printing, gravure. When organic solvent inks are used, they must be fully dried after printing. The organic solvent should not remain in the ink film. Otherwise, they will react with the liquid crystal and affect the color effect.
(5) It should be noted that the ink layer should be smooth and clean, and the thickness of the ink layer should be controlled to 15 to 35 μm to improve the color effect.
(6) Printing color sequence arrangement. Can use black (or dark color) ink to print the background color first, and then use liquid crystal ink to print the desired pattern; you can also use the liquid crystal ink to fill the bottom first, and then use the water-soluble black (or dark color) ink to print the required dark picture pattern to cover .
3, post-press treatment (1) The best drying method is natural drying, can also be used about 40 degrees Celsius heat seal drying, do not speed up. Heated rapidly and dried rapidly.
(2) Do not press the printed matter when it is stacked. After drying, try not to pile too much overlap, when breaking, etc. should not be too large partial pressure, in order to avoid liquid crystal microcapsules are pressure sensitive.
(3) When using liquid crystal inks, the temperature range of the discoloration should be determined according to the purpose of use and the durability of the liquid crystal should be considered according to the use. In order to improve the surface wear resistance, temperature resistance, gas barrier and maintain its gloss, the surface can be coated with varnish or protective film.
Third, the anti-counterfeiting function of liquid crystal ink
Liquid crystal ink is a kind of new ink material with great vitality and yet to be developed. The range of its printing applications is very wide, and in terms of its function, it is mainly used in the two major directions of temperature display and hair color change.
Temperature display: As long as it is a thermometer, body temperature, temperature recorder, testing machinery and testing equipment, such as temperature display requirements of the substrate. At present, foreign countries also use liquid crystal printing tape as a one-time body temperature tester.
Hair color changes: advertising, trademark labels, arts and crafts, medals, jewelry and other accessories and security printing products. If used for printing calendar pictures, it will show different colors as the temperature of the four seasons changes.
If printed into a children's album, the color of the screen can be changed with the child's pointing and touching; printed trademarks, wrapping paper, etc., are affixed to some products that are afraid of heat, and the changes in the color of the pattern can be used to understand the quality changes of the contents, such as candy packaging. If the bright picture on the paper is grayed out, you should eat the candy as soon as possible, or you must dissolve it. A liquid crystal pattern is printed on the container to display the humidity of the contents of the container. On large items such as precious, heat-resisting and cold, the liquid crystal printing can be used as a reminder card for preserving the temperature.
As for the use of liquid crystal ink as a forgery-proof ink, the main use is the use of the characteristic of temperature-sensitive discoloration of liquid crystals, and now it has also played a significant role in the field of anti-counterfeiting packaging and decoration, and its anti-counterfeiting effect is also ideal.
Liquid crystal ink originated in the United States in the 1970s. Later, as its technology matured and the printing market continued to expand, liquid crystal ink printing was rapidly developed in the United States, Japan, and other countries, and its application range was also expanding. The liquid crystal ink is a microcapsule structure ink type in terms of production methods. From the application point of view, it belongs to the category of temperature-sensitive thermochromic inks for anti-counterfeit printing inks, but in terms of the characteristics of liquid crystal inks, it mainly uses the characteristics of temperature-sensitive discoloration of liquid crystals. .
The liquid crystal ink is mainly composed of a water-soluble resin, a liquid crystal capsule, an auxiliary agent, a binder, and a defoamer. The liquid crystal ink is prepared by dispersing liquid crystals, additives and the like enclosed in the microcapsules in a binder. It is caused by the temperature change of the liquid crystal in the ink layer, which causes the change of the molecular orientation of the ordered array, so that the optical characteristic that selectively reflects light of a specific wavelength exhibits color change instead of forming a color image with the ink layer pigment.
When the liquid crystal is irradiated with natural light, artificial white light, and color light of a certain wavelength, reflection is strengthened due to the refraction phenomenon, and as the temperature rises, the color changes from a long wavelength to a short wavelength (i.e., changes in red-green-cyan), The color forming mechanism of the liquid crystal is due to the liquid crystal selectively reflecting light of a specific wavelength.
Liquid crystals must be printed on black and dark backgrounds. Ready-to-use liquid crystals can reflect -100 to +700 degrees Celsius. The accuracy is 0.50 degrees Celsius. Since the arrangement of liquid crystal molecules is not as strong as the crystal structure, it is easily affected by external stimuli such as electric field, magnetic field, temperature, stress, and adsorption impurities, causing various optical properties to change. Liquid crystal inks have applications in liquid crystals. This feature.
Since the liquid crystal is an organic compound between the liquid and the crystal, it cannot be directly added to the connecting material like ordinary ink. In order to prevent the liquid crystal from being contaminated by its compound, in order to ensure the color rendering effect, it is necessary to enclose the liquid crystal in microsphere capsules, and then mix with the connecting material to make a so-called microcapsule type ink. The microcapsules in the liquid crystal ink are different from the microcapsules in the foaming and aroma inks.
The microcapsules of the foaming ink are foaming agents (or low-boiling liquefied gases). Upon heating, the foaming agent in the microcapsules emits a large amount of gas (or low-boiling liquefied gas expander) to increase the volume of the microcapsules from foaming. effect. In addition, pigments are added to the foaming ink, printed into various colored foaming graphics, and have dual functions of foaming coloration.
The characteristics of microcapsules in scented inks are that they are not crushed and damaged during printing, but they are required to be easily broken by pressing and tearing with nails, pencils, etc. after printing into finished products, so as to achieve the purpose of emitting fragrance. The microcapsules in the liquid crystal ink attach the liquid crystal in the capsule to the ink layer through the connecting material.
Second, the liquid crystal ink printing technology requirements
Liquid crystal inks can be screen or gravure, but silk screens are better. The key to liquid crystal printing technology is the ability to display brightly colored liquid crystals at different temperatures, and to make a series of color temperature values. The liquid crystal microcapsules have to be small and uniform, the capsule wall is transparent and thin, and the ink is incorporated, and the solvent resistance is required to be stable, reliable, and long-lived; the liquid crystal microcapsules are also not to be crushed during the printing process, and the surface is covered with a protective film.
1. Platemaking The screen mesh number should be 100-175 mesh, and it should be selected according to the requirements of ink microcapsule diameter and ink layer thickness. Since the screen liquid crystal microcapsule ink is water-soluble. Therefore, the use of strong water resistance photoresist should be used for plate making.
2, printing LCD ink printing should pay attention to the following points:
(1) The plate should be filled with enough ink at a time and the ink should be uniform. It is best not to fill the ink in the middle to prevent foaming.
(2) When plugging and blistering are found during printing, the machine should be shut down immediately and thoroughly cleaned with alcohol water.
(3) The printing pressure should be moderate. The pressure is low, and the amount of ink on the printing substrate is insufficient; if the pressure is too high, the liquid crystal capsule will be broken and the color effect will be affected.
(4) In order to make the color of the printing part obvious, the black color or dark tone should be used for the printing background. The bottom layer can use water-soluble ink, and organic solvent ink can also be used. Printing methods available screen printing, offset printing, gravure. When organic solvent inks are used, they must be fully dried after printing. The organic solvent should not remain in the ink film. Otherwise, they will react with the liquid crystal and affect the color effect.
(5) It should be noted that the ink layer should be smooth and clean, and the thickness of the ink layer should be controlled to 15 to 35 μm to improve the color effect.
(6) Printing color sequence arrangement. Can use black (or dark color) ink to print the background color first, and then use liquid crystal ink to print the desired pattern; you can also use the liquid crystal ink to fill the bottom first, and then use the water-soluble black (or dark color) ink to print the required dark picture pattern to cover .
3, post-press treatment (1) The best drying method is natural drying, can also be used about 40 degrees Celsius heat seal drying, do not speed up. Heated rapidly and dried rapidly.
(2) Do not press the printed matter when it is stacked. After drying, try not to pile too much overlap, when breaking, etc. should not be too large partial pressure, in order to avoid liquid crystal microcapsules are pressure sensitive.
(3) When using liquid crystal inks, the temperature range of the discoloration should be determined according to the purpose of use and the durability of the liquid crystal should be considered according to the use. In order to improve the surface wear resistance, temperature resistance, gas barrier and maintain its gloss, the surface can be coated with varnish or protective film.
Third, the anti-counterfeiting function of liquid crystal ink
Liquid crystal ink is a kind of new ink material with great vitality and yet to be developed. The range of its printing applications is very wide, and in terms of its function, it is mainly used in the two major directions of temperature display and hair color change.
Temperature display: As long as it is a thermometer, body temperature, temperature recorder, testing machinery and testing equipment, such as temperature display requirements of the substrate. At present, foreign countries also use liquid crystal printing tape as a one-time body temperature tester.
Hair color changes: advertising, trademark labels, arts and crafts, medals, jewelry and other accessories and security printing products. If used for printing calendar pictures, it will show different colors as the temperature of the four seasons changes.
If printed into a children's album, the color of the screen can be changed with the child's pointing and touching; printed trademarks, wrapping paper, etc., are affixed to some products that are afraid of heat, and the changes in the color of the pattern can be used to understand the quality changes of the contents, such as candy packaging. If the bright picture on the paper is grayed out, you should eat the candy as soon as possible, or you must dissolve it. A liquid crystal pattern is printed on the container to display the humidity of the contents of the container. On large items such as precious, heat-resisting and cold, the liquid crystal printing can be used as a reminder card for preserving the temperature.
As for the use of liquid crystal ink as a forgery-proof ink, the main use is the use of the characteristic of temperature-sensitive discoloration of liquid crystals, and now it has also played a significant role in the field of anti-counterfeiting packaging and decoration, and its anti-counterfeiting effect is also ideal.
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