The introduction of thixotropic screen printing inks has improved the printing speed and screen printing accuracy of commercial ceramic decorative products, while also reducing waste. In the market competition, ink manufacturers develop their thixotropic screen printing inks (which are both thermoplastic and cold printing) to ensure their technological leadership. The thixotropic screen printing ink developed can be used for ceramic tiles, tableware, glass, and enamel products. Recently, a series of low-melting thermoplastic inks have been developed to reach the peak of research. Source: Jingdezhen Sanlei Porcelain Chemical Co., Ltd.
The ink itself is composed of organic-containing binders and inorganic pigments dispersed therein. Inorganic pigments are in turn composed of a metal oxide and a transparent flux (glass frit).
The mature technology for the production of pigments is to ball mill the water together with the frit and plastic so that the average particle size of 90% is below a few microns. After drying, the pigment is then crushed through a fine screen. Although processed pigments can produce high-quality inks, today's trend is to use finer screens, so the pigment must be finer.
The difficulty is that the color intensity of the pigment may be reduced after the pigment has been ground to the desired fineness. In order to overcome this problem, a new pigment milling technique has been developed that is currently used in the production of inks.
Thixotropy inks have rheological properties similar to those of cold screen printing inks or thermoplastic screen printing inks. These properties have the following advantages in printing.
1. Reduce scrap
It is possible that any downtime may occur due to mechanical or operational personnel during any printing process. With traditional inks, rebooting can often result in dirty prints or other defects. Since thixotropic screen printing inks have good rheological properties, the use of such inks helps to solve the above problems. When the blade scrapes the ink, the fluidity of the ink increases, so that the ink is uniformly deposited on the print. After the printing is completed, the fluidity of the ink is lowered, thereby preventing the ink from overflowing on the screen. It should be noted that the thixotropy screen printing ink after the squeegee has enough fluidity to meet the requirements of continuous high speed printing. At the same time, thixotropic screen printing inks are also suitable for semi-automatic screen printing machines with slower printing speeds.
2. Improve printing accuracy
Fine-grained pigments are formulated with thixotropy binders for use in higher mesh screens. Although the amount of pigment permeation is reduced, color tone screen printing can be performed directly on tiles and plates. Thicker ink films can be printed with thixotropic screen printing inks. The use of inks of any conventional linking material, when passing through a coarser screen, results in a decrease in the sharpness of the image due to the ink being deposited too thick. With thixotropic inks, however, the screen will not be filled with ink, and the image will not be distorted by the paste. Thixotropic inks can print both color blocks and fine screen prints. This thixotropic screen printing ink screen printing directly on the substrate can produce the effect of analog ink jet printing. When printing high-precision multi-color images, the use of thixotropic screen printing ink directly printed on the object, the ink layer can maintain a certain thickness without affecting the fine level of the image.
The initial appearance of cold thixotropic screen printing inks has higher viscosities, which allows printers to reduce the viscosity of the ink, but this is not often required. If necessary, use the following method: Add a small amount of diluent to the ink, and keep stirring it until the diluent is evenly dispersed in the ink. It should be noted that the viscosity of the thixotropic ink will decrease after stirring. Therefore, care must be taken not to make the ink too thin. Never add thinner to the ink on the screen.
Thermoplastic enamel inks are formulated with very fine sheet-like enamel pigments. The thin-sheet structure allows the temperature of the preheated pigment to fall. It also helps to avoid burning enamel paint in the initial melting stage. Thermoplastic enamel inks may also use suitable diluents, and are generally used when it is desired to reduce the viscosity of the ink, but at normal room temperature.