• Categories:Applications
• Author:
• Origin:
• Time of issue:2023-06-21
• Views:0

(Summary description)1. Influence on ink whiteness

 

(1) The effect of impurities in titanium dioxide on the whiteness of ink. The ink made of titanium dioxide with good whiteness is durable and does not yellow, which can keep the color of the print bright and bright in various environments. Generally speaking, if there are trace amounts of iron, chromium, cobalt, copper and other impurities mixed into titanium dioxide, the prepared ink will produce color cast and reduce whiteness. This is caused by the impurity ions in titanium dioxide, especially metal ions, which distort the crystal structure of titanium dioxide and lose symmetry. Rutile titanium dioxide is more sensitive to impurities, such as iron oxide in rutile titanium dioxide content greater than 0.003% will show color, and its content in anatase titanium dioxide greater than 0.009% will produce color reaction. Therefore, it is very important to choose fine, impurity-free titanium dioxide.

(2) The influence of the shape, size and distribution of titanium dioxide particles on whiteness. High-quality titanium dioxide particles have a smooth shape and no edges, and if the use of titanium dioxide with angular edges on the surface of the particles, it will greatly weaken the reflection of light and reduce the whiteness of the ink. The size of titanium dioxide particles should be controlled at 0.2~0.4μm, that is, equivalent to about 1/2 of the wavelength of visible light, so that high scattering ability can be obtained and its color appears whiter. When the particle size is less than 0.1 μm, the crystal is transparent, if the particle size exceeds 0.5 μm, it will reduce the scattering ability of the pigment to light and affect the whiteness of the ink. For this reason, the particle size of titanium dioxide is required to be suitable and evenly distributed to show good whiteness. Practice has proved that rutile titanium dioxide has better hiding power than anatase titanium dioxide, so it is more widely used in ink production.

 

2. The effect on the ink hiding power

(1) The refractive index of titanium dioxide crystals will directly affect the size of ink hiding power. In the process of gravure composite film ink printing, in order to make the print get a bright and beautiful effect, it is necessary to use white ink as a base, and then color printing. This requires titanium dioxide to have good coloring power and hiding power, otherwise the effect will be poor. Generally, the refractive index of titanium dioxide is the best in white pigments, and when preparing white ink, more titanium dioxide with high refractive index should be selected to enhance the hiding power of white ink.

 

(2) The effect of particle size, particle structure and dispersion of titanium dioxide on the hiding power of white ink. Generally, in the range of greater than 1/2 of the wavelength of visible light, the smaller the particle size, the smoother the particle surface, the better the dispersion of titanium dioxide in the resin binder, and the stronger its hiding power. Because titanium dioxide itself has an obvious crystal structure, its refractive index is larger than that of the color spreading agent, and the greater the difference in refractive index between the two, the stronger the hiding power of the titanium dioxide used. Practice has confirmed that rutile titanium dioxide has better hiding power than anatase titanium dioxide, so it is more widely used in ink manufacturing.