First, the theoretical analysis of the ink transfer failure
Water-based inks, especially water-washable inks, differ in their structure by the rise in pH; the price of ink is forced to use inorganic pigments in competition with the market, resulting in instability of the color ink - darkening, darkening 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 - distinctive and eye-catching 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, faded and dull.
Whether it is the organic pigments in the ink system that cause the organic pigments to darken or darken the color, or the inorganic pigments in the ink system encounter an alkali, the color hue becomes deep and dark until it fades, which is unavoidable—that is, brightness (brightness). )reduce. This physical or chemical change is not the same as the often-known hues of the three primary colors, which are not equal or the balance of the ash and the gray balance. Mostly because 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 is reduced due to glossiness, the reading efficiency is increased, but it is often difficult to achieve the bright appearance of the packaging and decoration of trademarks and product samples due to the deviation of gloss. When assessing the quality of water-based color inks, it is often based on similar products. . But only one point is the same - PH value.
In the exploration of water-based color inks around pH, we reviewed the authoritative theoretical arguments of Alanius, Browns, Laurel, and Lewis on the acid-base aspect, and concluded that this phenomenon is: The ability of ionization to generate hydroxide (OH-) and the generation of hydrogen ions (H+) can generate two kinds of metals that contact each other and diffuse into one another. 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 the thixotropy system and the oscillating system are rarely found in the breakdown of ink and wash, it is worthwhile to analyze this issue step by step. 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 discussed thixotropy, the indirect thixotropy was often overlooked. The simplest method of identification is that the oscillating ink system is gelled under external rhythmic vibrations. The rhythmic vibration can be Tap gently, with regular circular motion or pendulum agitating, that is, if there is no external action, it will not cause the ink to form condensation. When the solid content reaches about 1%-2% and the particle is not symmetrical, it forms a coagulation. The glue is the result of the alignment of the particles.
From the microscopic structure point of view, we observe another type of ink thixotropy, which is the cause of the failure. The feature of the swellable ink system is that when the excision is cancelled, the viscosity of the ink system is immediately “thinned.†The swellable ink system Suspensions are highly concentrated and low viscous.
Analysis of the Main Factors Affecting the Quality of Ink Printing
September 19 10:04:05, 2019
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