Color printing is essentially a process of "decomposing" to "compositing" colors. In the process of ink manufacturing to printing, color darkening, darkening, fading, and lack of water resistance or dullness have always been the key to color printing quality. Where In this regard, I would like to point out some technical exchanges with the packaging and printing community and strive to make the inks reach the high quality of their quality.

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, the color ink becomes unstable and becomes darker. Darkness, fade and extinction (gloss) has become one of the focuses of joint research by domestic and foreign counterparts.

We know that the chemical stability of color inks is related to the chemical nature of the pigments used in the ink system. General inorganic compound pigments are more active than organic compounds because inorganic compounds are soluble in water and can be easily ionized into ions. The reaction between ions can be completed instantaneously, while the organic compound pigments are reversed. Therefore, it is applicable to ink and wash, it is easy to wash, and it is also less polluting to the environment, but its chemical stability is poor. For example, when organic chromium yellow is easily met with alkali, it becomes red easily. (Dissecting the real purpose of mainstream funds and discovering the best opportunities for profit!)

Another focus is that we often emphasize the use of contrasting colors to enhance the distinctive and eye-catching personality after visual stimulation. Using colors that are mutually contradictory in color, they are juxtaposed to create a deeper impression on consumers' impressions of packaging 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. See Table 1 for details.

Whether the organic pigments in the ink-and-wash system encounter acid, which causes the hue of the color to darken or darken, or after the inorganic pigments in the ink system meet the alkali, the hue of the ink becomes dark and fades until it fades. )reduce. This kind of physical or chemical change is not the accidental hue deviation caused by the unequal amount or purity of the three primary colors and the gray balance. Most of them are caused by the presence of a few metal oxides that are bisexual in the ink. Alkali is acidic and darkens and darkens; when acid is alkaline, it fades and fades. 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 The same kind of product is the basis, but only one point is the same - the PH value. See Table 2 for details.

Red + yellow red tends to purple yellow tends to green red + green red tends to orange blue tends to green yellow + blue yellow tends orange blue tends to purple red + green red more red green more vivid
Blue + Orange Blue Blue Orange More Bright
Yellow + Purple Yellow Yellow Purple
Red + orange red tends orange orange tends yellow red + purple red tends orange violet tends blue yellow + green yellow tends orange green tends blue yellow + orange tends green orange tends yellow blue + green blue tends to purple green tendencies Reddish blue + violet blue tends to cyan tends to red orange + green orange tends to red green tends to green orange + purple orange tends to yellow violet tends to blue green + purple green tends to yellowish violet tends to red orange + yellow orange red Orange tends to red yellow orange tends to yellow yellow green + blue green yellow green tends to yellow blue green tends to blue red violet + blue purple red violet tends to red blue violet tends to blue black + red black has green taste red bright and tends Orange black + yellow black purple yellow yellow black + blue black orange blue blue black orange black orange blue black and orange flavor and tend to yellow black + green black red purple clear + red and white green Redness tends to red gray + yellow and white purple yellow tends to yellow brown + There have White Orange poured supervisor inch monitor with partners + Orange White Blue White Orange flavor tends orange gray + Green White Green White taste tends red green-gray white yellow white + purple purple taste tends Zi Hui

When we explore water-based color inks around the pH value and consult the authoritative acid-base theory of Achem Niuus, Browns, Laurel, and Lewis, we can find that only hydrogen ions can be produced by ionization in aqueous solutions. Roots (OH-) can ionize to produce hydrogen ions (H+), and two kinds of metals that come into contact with each other can be generated and diffuse into each other. It is because of the above reason that increasing the amount of alkali causes the ink system, especially the alkaline printing ink film, to be in an unstable state on the substrate (the remaining trace amount of alkali is temporarily blocked, and once the film is contacted with water, the ink film will be Destruction), and under the action of external forces, the liquid droplets of the ink from the spherical to irregular mixture of a dry ink film formed after the surface is rough and matt.

In terms of the failure of ink and wash, thixotropy and segregation systems rarely occur. Here, you may wish to analyze this issue step by step. The difference between the above is nothing more than: The former is at a certain speed, the shear force decreases with time, and the latter is the opposite. It is not easy to grasp, not the color hue, which is difficult to stabilize, and that is to bring endless problems to printing. For many years, when we focused on thixotropy, indirect thixotropy was often overlooked. The simplest difference is that the oscillating ink system is gelled under external rhythmic vibrations. Its rhythmic vibrations can be tapping, regular circle movements or pendulum agitation. The external role cannot cause the ink to form condensation. When the solid content is about 1-2%, and the particles are not symmetrical, the formation of the gel is completely the result of the orientation of the particles.

From the perspective of microstructure, another type of swellable ink system that causes ink thixotropic breakdown is characterized by: when the external cut is removed, the viscosity of the ink system immediately “leans”. The swellable ink system suspension is highly concentrated and low viscous. General solids content up to 40%, good wetting properties. If we reduce the concentration when the temperature rises or the PH value increases, the viscosity increases, or the appropriate amount of water is added, it will not be like a condensable ink. When the excisional force is removed, the system will remain in a solidified state (though this phenomenon is rare, once it is indeed a very headache), at least for a period of time is the solidification state, and then thinning. However, ink is completely resistant to water, and fade has been unavoidable.

In view of the above two kinds of condensing failures, especially for the rare oscillating ink system, it is more important than the oscillating ink system in solving difficulties, and it is more difficult. We know that the recovery of thixotropic structures from structure to structure, or from the disintegration of structures to the recovery of structures is the process of isothermal reversible transformation. This repeated transformation of the structure 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. Viscosity of larger ink under external agitation, its state of condensation has been destroyed, with time, with the increase of time and the decline of the ambient temperature, its condensation state gradually increased until the restoration of the original state.

We know that the addition of a certain amount of macromolecule compounds or associative colloids to hydrosols can significantly increase the stability of sol to electrolytes before the 1980s and call them “protective effects.” "Space stability" enables carbon black to be stably suspended in water. Although there is no thixotropy for the requirements of rotary ink (flexible letterpress ink or gravure printing ink), in order to stabilize the ink, the emulsion and the solution binder are often used to achieve stability during storage. Although this method of producing ink is scientific than a single resin solution and can prevent precipitation or delamination of ink in storage printing, it will inevitably lead to different degrees of thixotropy. In severe cases, the ink will not easily pour out of the ink tank. Affect the normal flow of printing ink transfer, while the