Factors affecting fastness to adhesion as follows:

1. The influence of ink resin system
Resin is an important part of the ink, its important role is first as a carrier of pigment, powder pigments, fillers and other solid substances mixed together, by making the ink on the substrate drying, consolidation film, resin system is one of the key components affecting the ink on the substrate adhesion fastness.

For plastic packaging and printing of BOPP, PET, NY, etc are the main types of backing material, base material of different molecular structure is different also, in order to obtain good ink adhesion fastness, printing ink resins with the base material has good affinity, general printing production process of polypropylene (PP) film using chlorinated polypropylene resin type of ink, printing of polyester (PET) Film will use polyurethane ink, although now with the development of ink technology, suitable for BOPP, PET, NY and other substrates of universal ink has begun to use, but in actual use still need to effectively identify the type of ink, misuse of ink or ink from different manufacturers will cause poor quality accidents of ink adhesion fastness.

2. Influence of pigment dispersion
Paint as a carrier of the ink color, mostly small molecule organic matter or inorganic matter, not directly with printed substrate to form effective adhesion, therefore can only put the pigment shattered into small, uniform particles, evenly distributed to the resin, resin on the surface of pigment wetting and package, so as to get a stable suspension system; The dispersion of pigments, in addition to directly affect the ink itself viscosity, gloss, stability, fineness, coloring power and covering power, ink adhesion also has a great impact. Good dispersion system, as well as to achieve the best pigment fineness also make the package more resin for small pigment particles in good condition, after fixation into a film in the plastic substrate surface, forming uniform package resin film pigment particles, increase the resin with plastic film on the surface of the contact area, to improve fastness.

3. Influence of solvent
Solvent-based inks are mostly used in plastic gravure printing. As an essential organic solvent in the ink system, it also has a great impact on the fastness of ink to adhesion on the surface of plastic substrate.

1) The solvent volatilization of printing ink affects the fastness of printing ink
Production needs to adapt ink to printing, printing ink resin's ability to release organic solvent and solvent volatilization speed directly affect the ink attachment fastness, volatile solvent good its solvent release better than the volatile solvent with a slower, but the high proportion of high volatile solvent will lead to ink surface drying too quickly, and the inner solvent release impeded, dry incomplete, in actual life In the process of production, it is necessary to add an appropriate amount of slow drying solvent or medium slow drying solvent to make the solvent volatilization gradient moderate and improve the solvent release ability.

2) ink solvent in the true solvent and false solvent ratio will also affect the ink fastness to adhesion
Although the false solvent can not actually dissolve the resin, but its coordination with the true solvent can make the polarity of the mixed solvent system adjustable in a large range, so as to adapt to the polarity of the ink resin itself, to achieve the best solubility. In the solvent system with suitable polarity, the resin molecules have a microcosmic stretch state, which is conducive to the dispersion and wetting of pigment grinding process, and the formation of uniform wrapped state. But if false solvent to join imbalance, can make the resin system stability, the micro resin molecules become curled up, and even multiple resin molecules intertwined together by false solvent packages, not well in the process of dispersion and pigment particles to form a good wetting, affect the ink on the surface of solid substrates with the uniformity of film, adhesion

3) swelling effect to improve ink adhesion
Solvent - based inks in the presence of organic solvents, ink and plastic substrate contact on the surface of the plastic substrate interaction, that is, swelling. Swelling effect makes the surface of the plastic substrate coarser, forming a small "pit", ink film with its physical anchor cooperation, can play an important role in improving the fastness to adhesion.

4. Influence of substrate surface properties
Commonly used plastic packaging printing base material BOPP, PET, etc., the general base material on the surface is smooth, after processing and molding without surface treatment, basic cannot be directly used for printing, even the polar materials such as PET can not completely meet the use, so need to the base material surface corona treatment, after corona treatment, let the film surface is more reactive, Film is more easily infiltrated by most inks and solvents, improving ink fastness to adhesion.