Elaborate: the relationship between ink density and printing quality
The so-called ink concentration is the coloring power of the ink, which is a common name that reflects the dispersion of the ink and the pigment content in the ink. In other words, the higher the degree of pigment dispersion, the higher the ink concentration; the higher the pigment content in the ink, the greater its concentration. In addition to the pigment determines the ink concentration, the binder, filler and additives, etc., also affect the ink concentration to a certain extent. The production process shows that the ink concentration is one of the important indicators that affect the printing quality. Therefore, correctly understanding and understanding several factors related to the ink concentration is of great significance for the production process control of the printing process and improving the printing quality of the product. .
Ink is a hydrophobic colloid. It is a homogeneous mixture of pigments, binders, fillers and additives. Pigments are coloring substances that play a role in color development in inks. It is a colored substance that is insoluble in water and insoluble in the binder, but can be uniformly dispersed in the binder. It is a powdery solid. The pigment content in the ink determines the durability and concentration of the ink, and also affects the drying performance of the ink. As the main material for color development, pigments have a decisive influence on the quality and suitability of ink. Therefore, for printing, only the pigment particles are fine, the oil absorption is large, the specific gravity is small, the hiding power is small, the coloring power is strong, the stability is good, the color is less, the color is bright, and it has heat resistance, light resistance, acid and alkali resistance, etc. Only with good performance can the ink color of the printed product get a better quality effect. According to the properties and chemical composition of pigments, pigments are divided into inorganic pigments and organic pigments. Inorganic pigments include various metal oxides, chromates, carbonates, sulfates, and sulfides, such as aluminum powder, copper powder, carbon black, zinc white, and titanium white, etc., all belong to the category of inorganic pigments. Inorganic pigments have good light resistance and heat resistance, and have a large specific gravity and strong hiding power, but they are not suitable for multi-color, high-speed printing requirements. Commonly used organic pigments include chromogenic pigments and lake pigments. Chromogenic pigments mainly include: phthalocyanine pigments, nitroso pigments, azo pigments and reduced pigments. Lake pigments include: basic dye lakes, azo lake pigments and acid dye lakes. Most organic pigments have good coloring power, small particles, light specific gravity, soft texture, bright color and high concentration. They are the main raw materials for color inks. The binder is also the main component of the ink. It is the raw material that makes the ink a fluid and has a certain viscosity. It serves to mix and connect solid particles such as powdered pigments, and transfer and adhere the pigments that are stuck together. At the same time, it has a certain glossiness on the printed matter. Its color, tensile force, viscosity, water resistance, and dryness are important factors that affect the performance of the ink. Its dosage is also an important condition for changing the fluidity and concentration of the ink. The filler is a fine, white powdery solid substance, so it can be uniformly and well dispersed in the binder. Such as potassium sulfate, magnesium carbonate, calcium carbonate and aluminum hydroxide are all fillers, they play a role in adjusting the ink's ink properties, consistency and concentration in the ink. After the pigments, binders and fillers in the ink are processed into finished inks with a certain amount of proportion, often due to different printing conditions, the original ink's thinness, density and dryness may not be able to adapt to various conditions. Generally, it needs to be adjusted by using some auxiliary agents, such as anti-sticking agent, detackifying agent, dry oil, gloss paste and gloss oil, etc. After these additives are added to the ink, the concentration of the ink will also be changed.
The density of the ink is large, and the consistency is also large. Therefore, the size of the ink concentration determines the depth of the ink hue. When the ink concentration is large, the printing hue is darker; otherwise, the printing hue is lighter. The ink with higher density consumes relatively less ink and the ink color quality is better. On the contrary, the ink with lower density uses more ink during printing and the ink color is relatively light. The density of the ink is particularly prominent when printing large-area plate products. It can be seen that the ink concentration directly affects the printing quality of the product. Therefore, when printing thin screen or thin line products, it is generally necessary to use high density ink to print, and the product that prints the solid surface is suitable to use a slightly lower concentration Ink to print. Due to the "thixotropic" side of the ink, when the printing environment temperature is high, the machine speed is fast, the ink becomes thinner due to heat, and its concentration decreases. This requires that the ink with a higher concentration be used for printing, which can better ensure the ink color of the product. quality. On the contrary, the ink with a lower density can be used for printing.
If the ink with low density is used to print the background color or multi-color printing plate, it is necessary to increase the amount of ink on the layout to obtain the required printing hue, but it is easy to cause the product to suffer from disadvantages. Based on this situation, the inks used in color printing products are generally adjusted to a deeper hue, and the density is also adjusted to a larger value, the printing effect is better, and it is conducive to the anti-sticking of printed products. In addition, when printing a large-area solid plate, line plate or anilox plate, the printing speed should be adjusted a little slower to reduce the friction coefficient and heat during the printing process, to prevent the ink from becoming thin and flowing because the temperature rises too quickly The increase of the property causes the decrease of the concentration, and the disadvantage of the lightening of the printing ink appears.
Process practice and analysis show that the original ink's concentration is unchanged when it is not used. However, in the process of use, as the consistency and fluidity change, the concentration also changes. Changes in conditions such as printing speed, temperature, and amount of fountain solution will affect the ink concentration. If the water content of the printing plate is too large during the printing process, the ink concentration will also be diluted, making the printed ink appear pale. It can be seen that the ink concentration is a variable factor that affects the ink color quality of the product. Therefore, it is very important to correctly understand and understand certain conditions related to the ink concentration and take corresponding technical measures for printing, which is very important for ensuring the quality of the printing ink color.
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