What Are The Specific Requirements for Titanium Dioxide for Ink?

1. Effect on ink whiteness

(1) The impact of impurities in titanium dioxide on the whiteness of ink. The ink made of titanium dioxide with good whiteness is durable and does not turn yellow, and can keep the color of the printed matter bright and vivid in various environments. Generally speaking, if trace amounts of iron, chromium, cobalt, copper and other impurities are mixed into titanium dioxide, the prepared ink will produce color casts and reduce the whiteness. This is caused by the impurity ions in titanium dioxide, especially metal ions, which distort the crystal structure of titanium dioxide and lose its symmetry. Rutile titanium dioxide is more sensitive to impurities. For example, when the content of iron oxide in rutile titanium dioxide is greater than 0.003%, it will show color, and when its content in anatase titanium dioxide is greater than 0.009%, it will show color. 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. If titanium dioxide with edges on the particle surface is used, the reflection of light will be greatly weakened and the whiteness of the ink will be reduced. The size of titanium dioxide particles should be controlled at 0.2~0.4μm, which is equivalent to about 1/2 of the wavelength of visible light, in order to obtain high scattering ability and make its color appear whiter. When the particle size is less than 0.1 μm, the crystal is transparent. If the particle size exceeds 0.5 μm, the light scattering ability of the pigment will be reduced and the whiteness of the ink will be affected. For this reason, titanium dioxide particles are required to have appropriate size and uniform distribution to show good whiteness. Practice has proven that rutile titanium dioxide has better hiding power than anatase titanium dioxide, so it is more widely used in ink production.

2. Effect on ink hiding power

(1) The refractive index of the titanium dioxide crystal itself will directly affect the hiding power of the ink. During the gravure composite film ink printing process, in order to obtain brightly colored and beautiful prints, white ink must be used as a base, and then color printing is performed. This requires titanium dioxide to have good tinting and hiding power, otherwise the effect will be poor. Generally, the refractive index of titanium dioxide is the best among white pigments. When preparing white ink, titanium dioxide with a high refractive index should be used to enhance the hiding power of the white ink.

(2) The influence of titanium dioxide particle size, particle structure and dispersion on the hiding power of white ink. Generally, in the range 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. Since titanium dioxide itself has an obvious crystal structure, its refractive index is larger than that of the developer. The greater the difference in the refractive index between the two, the stronger the hiding power of the titanium dioxide used. Practice has proven that rutile titanium dioxide has better hiding power than anatase titanium dioxide, so it is more widely used in ink manufacturing.

3. Effect on the tinting strength of ink

The tinting power of titanium dioxide depends on the ability of titanium dioxide to scatter visible light, and it has a direct impact on the tinting power of the ink. The greater the scattering coefficient, the stronger the tinting power; the higher the refractive index of titanium dioxide, the stronger the tinting power. Titanium dioxide has the highest refractive index among white pigments, and the refractive index of rutile titanium dioxide is higher than that of anatase titanium dioxide. Therefore, when choosing titanium dioxide, you must choose titanium dioxide with strong scattering ability and high refractive index.

4. Impact on dispersion performance

Whether the shape and light reflection of titanium dioxide particles are uniform directly affects the dispersion performance of titanium dioxide. If the surface of the titanium dioxide particles is smooth and the reflection is uniform, the dispersion will be good, and the prepared white ink will have better gloss and whiteness; on the contrary, if the particle surface is rough and the diffuse reflection will increase, the gloss will be greatly reduced and the dispersion will be poor. , directly affects the whiteness and transfer performance of white ink. For this reason, titanium dioxide must be processed before it can be used.

In addition, there are the following factors that affect ink:

1. Good light and weather resistance: If the printed matter is placed outdoors for a long time, it is necessary to ensure that the titanium dioxide has good light and weather resistance, otherwise the ink will turn yellow and powder.

2. Good heat resistance: For baking iron printing ink, the baking temperature during the printing process reaches about 180°, which takes up to 2 hours. Such printing conditions require that the titanium dioxide in the ink has excellent heat resistance, otherwise the white ink will turn yellow and lose its luster at high temperatures, and even the printed matter will be scrapped.

3. Oil absorption: With the improvement of printing speed and technology, inks with lower viscosity are needed, and the oil absorption of titanium dioxide has become the key. Try to reduce the oil absorption amount while keeping the color density unchanged, which will help to prepare the ink with higher viscosity.