Analysis of the Main Factors Influencing the Quality of Ink and Wash Color Printing(I)

In terms of printing chromatics, the color printing process is essentially a process of "decomposition" to "synthesizing" colors, and our colors have become darker and darker during the more than 20 years of ink-to-print printing. And discoloration and water insolence or dullness are undesirable to us. However, we have the responsibility to pay attention to this focus of many years in manufacturing and use, and to enumerate some of the points in the packaging printing industry for pure technical communication, and strive to reach the ink and wash The quality of other inks.

First, the theoretical analysis of the ink transfer failure

Water-based inks, especially water-washable inks, have different pH values ​​in their structure. The price of ink is forced to use inorganic pigments in competition with the market. As a result, color inks become unstable - darker and darker. Fading and discoloration (gloss) have become one of the focuses of joint research by domestic and foreign counterparts.
We know that the chemical stability of color ink is related to the chemical nature of the colorant used in the ink system. Inorganic pigments are generally more active than organic compounds. This is because inorganic compounds are soluble in water and are easily ionized into ions. The reaction between ions can be completed instantaneously, while the organic compound pigments are the opposite. Therefore, it is said that it is suitable for washing in ink and water, and it is also relatively less polluted with respect to the environment, but its chemical stability is poor, for example, when organic chromium yellow is easily changed to red after encountering alkali.

Another focus is that we tend to emphasize the use of contrasting colors to enhance the visual stimuli - sharp and striking personality after juxtaposition. The use of color-contradictory colors to juxtapose them together, with an uncoordinated approach to deepen consumers' impressions of package printing and decorating. However, I do not know that when organic and inorganic inks are used in the three-primary system, when the contrast color (area, brightness, and saturation) changes, the intensity of contrast will also change. When it comes to acid and alkali, it will often appear transient. To reconcile, with the passage of time, juxtaposition of color ink will be dark to dark or light, achromatic, and dull. Whether it is the organic pigments in the ink system that cause the organic pigments to darken or darken the color hue, or the inorganic pigments in the ink system encounter the alkali, the color hue becomes deep and dark until it fades, which is also unavoidable - brightness (brightness )reduce. This kind of physical or chemical change is not often called the hue deviation accident caused by the unequal quantity or purity of the three primary colors and the gray balance. It is mostly due to the fact that the ink is mixed with a few metal oxides that are both sexes. Strong alkalis become acidic and darken; in the case of strong acids, they are alkaline faded and extinct. Although the eye fatigue caused by glossiness is reduced, the efficiency of reading increases, but it is often difficult to achieve a bright appearance of the packaging and decoration of trademarks and product samples due to the deviation of gloss. This subjective or objective assessment of the quality of water-based color inks is often Based on similar products. But only one point is the same - pH.

When we were exploring water-based color inks around pH, when we consulted Alanius, Browns, Laurel, Louis, and other authoritative theoretical theories about acid and alkali, especially when it comes down to this phenomenon : In the aqueous solution can not only ionize to produce hydroxide (OH) but also ionized to produce hydrogen ion (H+) will happen, two kinds of metals in contact with each other, interdiffusion to the inside and so on. It will be understood that due to the above reasons, increasing the amount of alkali causes the ink system, especially the alkaline printing ink film, to be in an unstable state after being printed on the substrate (the remaining trace amount of alkali is temporarily blocked, and once contacted with water, the ink film It will be destroyed, and under the action of external force, the ink dripped from the sphere into an irregular mixture, and then the dry ink film formed on the surface will be rough and dull.

Although there are few thixotropy systems and osmotic condensation systems in the breakdown of ink and wash, it is worthwhile to analyze this issue gradually. The above difference is nothing more than: the former is at a certain speed, the shear force decreases with time, the latter is the contrary, the grasp is not good, not the color hue is difficult to stabilize, is to bring endless printing problems. For many years, when we were thixotropy, we often neglected the indirect thixotropy. The simplest difference is that the oscillating ink system becomes a gel under the external rhythm of vibration, and its rhythm and vibration can be gently. Beat, there is a regular Akira 虬谑 虬谑 虬谑 虬谑 虬谑 龋 筒 筒 筒 筒 筒 斐 斐 斐 斐 斐 斐 斐 斐 斐 斐 斐 斐 斐 斐 斐 斐 斐 斐 斐 赡幔蹦 搴 搴 搴 搴 搴 搴 搴 搴 搴 搴 搴 搴 % % % % % %2%, and particles For symmetry, the formation of a gel is completely a result of the alignment of the particles.

From a microscopic point of view, we are observing another type of ink thixotropy, which is the cause of the malfunction. The feature of the swellable ink system is that when the excision is removed, the viscosity of the ink system is immediately "thinned." The swellable ink system suspension is highly concentrated and low in nature. General solids content up to 40%, good wetting properties. If we increase temperature or increase the pH, the concentration decreases and the viscosity increases, or if some of the water is added in an appropriate amount, it does not resemble a condensable ink. When the external force is removed, the system will remain in a solid state (this phenomenon Although it is rare, once it does occur, it is really a headache.) At least for a while, it is in a solidified state and then thinned. However, ink is completely resistant to water and discoloration can no longer be avoided.

In solving the above two kinds of condensing failures, especially the rare oscillating ink system, we have solved practical problems, especially in terms of difficulty, which is more important than the oscillating ink system, and it is difficult to know how many times it is. . We know that the recovery of thixotropic structures from structural to non-structural, or from the deconstruction of structures to the recovery of structures is the process of isothermal and reversible transformation. The second is that this repeated transformation of the architecture is related to time, that is, the destruction and formation of the structure is a function of time. At the same time, the mechanical strength of the structure also varies with time. The deformation of the ink system produced by the shear force of this object (if the f/D ratio is temporarily reduced, the system has thixotropy), can be seen as the “gel-sol” of the water-based color ink system at a constant temperature. The performance of the mutual conversion process. The viscosity of a large-scale ink under the external force stirred, the state of its destruction was destroyed, with time, with the increase of time, with the decline of the ambient temperature, the state of its condensation gradually increased, until the restoration of the original state.

It is known that adding a certain amount of macromolecule compounds or associative colloids to a hydrosol can significantly increase the stability of the sol to electrolytes before the 1980s and call it a "protective effect," and since the 1980s it has been called " Space stability." Regardless of how it is called, the use of animal glue in the ink system for thousands of years will enable carbon black to be stably suspended in water. Although no thixotropy is required for rotary ink (flexible letterpress printing ink or gravure printing ink), in order to stabilize the ink, the stability during storage is often achieved by the method of using the emulsion and the solution binder, but this method of ink manufacturing Although the method is more scientific than a single resin solution and can prevent precipitation or delamination of the ink in storage printing, it will inevitably lead to different degrees of thixotropy. In severe cases, the ink is not easy to pour out of the ink tank. After stirring, the effect is slight. The normal fluidity of the transfer of the printing ink will affect the ink transfer in the ink fountain and the pump tube and even block the pipeline and transfer the ink. In a word, scientific pH control always affects thixotropy, especially the graphic effect of ink packaging printing.