LCD ink introduction (below)

Third, liquid crystal ink screen printing

Liquid-crystal ink printing refers to printing with inks doped with liquid crystals, so that the printed products have a reversible reaction or an irreversible reaction. The key to liquid crystal printing technology is the ability to display brightly colored liquid crystals at different temperatures, and the color gamut needs to be a series. The production of liquid crystal microcapsules is also critical. Microcapsules are required to be small and uniform, and the walls of the capsules are transparent and thin. , Incorporation of ink, requiring solvent-resistant, stable, reliable, long life; printing process must also ensure that the liquid crystal microcapsules are not crush; the surface covered with protective film.

1, plate making

(1) Nylon mesh or polyester mesh is generally available. If the ink load is large, stainless steel mesh plate can be used.

(2) The number of screen meshes is preferably 100-175 mesh, and is selected according to the requirements of the ink microcapsule diameter and ink layer thickness. Since the screen liquid crystal microcapsule ink is water-soluble, the photosensitive resist which has strong water resistance should be used when making the plate.

2, printing LCD ink printing should pay attention to the following points:

(1) When printing, care should be taken to ensure that the printing plate is filled with enough ink at a time and the ink is uniform. It is best not to fill ink in the middle to prevent foaming.

(2) Since the microcapsule ink tends to clog the screen plate, when the screen is blocked or foamed during printing, the machine must 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 substrate is insufficient, which will affect the color effect. If the pressure is too high, the liquid crystal capsule will be broken.

(4) In order to make the color of the printing part obvious, the black color or dark color should be used for the printing background. The background color can be water-soluble ink, and it can also be printed with organic solvent ink. Must be fully dried after printing, ink film should not remain organic solvents, otherwise it will respond to the liquid crystal, affect the color effect.

(5) During the printing process, it is necessary to pay attention to the smoothness and smoothness of the ink layer, and the thickness of the ink layer is controlled at 15 to 35 μm. Uneven or too thin ink layer will reduce the effect of ink color. The printing process should be used to thicken the ink layer, such as the use of a softer scraper, a slightly smaller angle of the scraper, a slightly larger net distance, and an increase in ink. Viscosity and so on.

(6) Printing color sequence arrangement. Can choose black (or dark color) ink to print the background color, and then use liquid crystal ink to print the desired pattern; also can use the liquid crystal ink to fill the base first, and then use the water-soluble black (or dark color) ink to print the desired negative graphic pattern. cover.

3, post-press processing

(1) The drying method of printed matter is preferably natural drying, and it can also be dried with hot air at about 40°C.

(2) Do not press the printed matter when it is stacked. After drying, try not to pile too much overlap, and when breaking, do not apply excessive partial pressure, so as to avoid liquid crystal microcapsules being crushed.

(3) When using a liquid crystal ink, the color temperature range and the durability of the liquid crystal should be determined according to the purpose of 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.

Source: 21st Century Fine Chemicals Network