LCD ink introduction (on)

First, the characteristics and composition of liquid crystal ink

1, the characteristics of liquid crystal micro-capsule ink

Liquid crystal inks are prepared by dispersing liquid crystals, additives and the like enclosed in microcapsules in a binder. The liquid crystal ink does not constitute a color image with a pigment. It is a kind of liquid crystal that causes changes in the alignment molecule direction caused by the temperature of the liquid crystal in the ink layer, thereby selectively reflecting visible light of a specific wavelength and absorbing optical properties of other wavelengths of light. A special ink that exhibits color changes. 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 from red to green to cyan) . Now the liquid crystal can reflect -100 ~ 700 °C, the accuracy is 0.50 °C. Since the molecular arrangement of the liquid crystal is not as strong as the crystal structure, it is easily influenced by external stimuli such as an electric field, a magnetic field, a temperature, a stress, and an adsorption impurity to cause various optical properties to change. Liquid crystal inks use this characteristic of liquid crystals.

Since the liquid crystal is an organic compound between the liquid and the crystal, it cannot be directly added to the binder like a normal ink. In order to prevent the liquid crystal from being contaminated by other substances and ensure the color rendering effect, it is necessary to enclose the liquid crystal in the microcapsules and then mix with the connecting material to make the microcapsule ink. However, the microcapsules in the liquid crystal ink are different from the microcapsules in the foaming ink and the fragrance ink. Microcapsules in foamed inks and fragrance inks do not require breakage during application, but under certain conditions after printing, the heartwood in the microcapsules is “shelled” and released. However, the microcapsules in the liquid crystal ink are used to fix the liquid crystals in the capsules in the ink layer through the connecting material, and the microcapsules are required to not only pass through the printing plate smoothly, but also must have permanent sturdiness. In addition, the liquid crystal ink does not need to process any material and is a kind of transparent “clean ink”. Liquid crystal microencapsulation has the following advantages:

(1) Prevent the pollution of the liquid crystal itself

(2) Extended service life for long-term preservation

(3) Improve printability

The amount of liquid crystal added to the ink was 40% of the total ink, and the diameter of the microcapsules was between 10 and 30 μm.

2, the main components of liquid crystal ink

The liquid crystal ink is mainly composed of a water-soluble resin, a liquid crystal capsule, an additive, a binder, and a defoamer. Its main components are as follows:

(1) Liquid Crystals Due to the different chemical compositions and structures of various liquid crystals, optical coloration effects are also different. In use, according to the color rendering effect, the concentrated liquid crystals are often mixed in proportions. Commonly used are cholesteryl n-butyrate, cholesteryl oleate, cholesteryl linoleate, cholesteryl benzoate, and cholesteryl cinnamyl. Acid esters, cholesteryl ethyl carbonate, cholesteryl oleate esters, and the like.

(2) Capsule wall The capsule wall is composed of gelatin, gum arabic, formaldehyde, acetic acid, sodium hydroxide and the like.

Gelatin is a water-soluble animal glue that absorbs and swells in water. When heated to 35°C, it becomes a colorless, transparent solution that solidifies after cooling. Gelatin has a strong protective effect on other colloids. The aqueous gelatin solution has an isoelectric point of pH=4.7. Hardening reaction occurs between gelatin and formaldehyde to produce a gelatin polymer of methanol. The polymer is very hard and never softens. These properties are extremely important for controlling the temperature, pH value, degree of hardening of glue liquid in the process of making liquid crystal microcapsules.

Gum arabic is a water-soluble vegetable gum, and 5% or less of a dilute aqueous solution can form a physical adsorption film. In the preparation of liquid crystal microcapsules, it plays a role of dispersion coating liquid crystal.

Formaldehyde reacts with gelatin particles to form a permanently hardened polymer that forms the hard shell of the microsphere capsule.

Acetic acid is used to adjust the pH and control the isoelectric point of the gelatin solution.

Sodium hydroxide is also used to adjust the pH, while also playing a role in hardening the microcapsule shell walls.

(3) Binder The binder is a water-based resin, commonly used water-soluble polyvinyl alcohol, water-sol resin. Polyvinyl alcohol binder has the characteristics of transparency and good gloss. In order to improve its adhesion, polyvinyl alcohol with a degree of polymerization of 2000 or more is generally used. Polyvinyl alcohol has poor durability, low mechanical strength, and is particularly resistant to water and moisture. Therefore, it is protected by a layer of acrylic varnish after printing.

The water-soluble resin is an acrylic copolymer and has good durability and mechanical strength.

Liquid crystal inks are prepared by dispersing liquid crystals, additives and the like enclosed in microcapsules in a binder.

Second, the main market of LCD ink printing

Liquid crystal ink is a kind of new ink with great vitality. It has a wide range of applications. In terms of its functions, it is mainly used in the two major directions of temperature display and color change.

1, the temperature display

Mainly thermometers, thermometers, automatic temperature recorders, testing machinery and testing equipment and other substrates with temperature display requirements. At present, foreign countries also use liquid crystal printing tape as a one-time body temperature tester.

2, hair color changes

Advertising, trademark labels, arts and crafts, medals, jewelry and other accessories and security printing products.

If the calendar used in printing the picture will change with the seasons temperature showed different effects, the picture throughout the year at different temperatures changes different colors; if printed children's book, pointing touch can change the picture with the children color; and printed trademark, wrapping paper, posted on a number of products sensitive to heat, according to the change of color patterns, understand the quality of interior trim changes, such as brightly colored candy wrappers on the screen becomes dark, you should eat the candy as soon as possible out, or you need to melt. Pattern printed on the container of the liquid crystal, the temperature within the vessel may be displayed items in the valuable, sensitive to heat, cold bulky items, maintaining the temperature of the liquid crystal can be used as a printed card tips. As for the use of liquid crystal ink as a forgery-proof ink, the main use is the use of its liquid crystal thermochromic characteristics, and now plays a large role in the field of anti-counterfeiting packaging and decoration, and its anti-counterfeiting effect is also ideal.