Application of Gravure Gold and Silver Ink and Points for Attention

With the development of society and the improvement of living standards, people are increasingly demanding the packaging of goods. Often, fine ink products such as cigarette packets and wine labels are printed with gold or silver ink. Gold and silver inks can exhibit metallic luster, giving people a solemn, luxurious, splendid and colorful feeling that cannot be represented by spectral colors. Therefore, gold and silver inks have been widely used in packaging and decoration printing. The use of gold and silver inks on commodity packaging and trademark labels can not only embellish and contrast other colors, but also improve product documentation as a whole. , How to improve the quality of silver ink printing, its importance is self-evident.
1. The composition of gold and silver ink is the same as other inks. Gold and silver inks are mainly composed of pigments and linking materials. Simply put, gold ink is made up of gold powder and gold transfer oil. Silver ink is Made of aluminum powder and silver adjustment oil.
1. pigment. We know that pigments are colorants in inks. They give inks a certain color. Pigments in gold and silver inks are made by grinding metal powders, mainly gold powder and silver powder.
The pigment in gold ink is gold powder, which is actually a powder made of copper and zinc alloy. The content of zinc in gold powder is generally about 8% to 30%, and the zinc content is between 8% and 12%. The color of gold ink is reddish, and it is customarily called red gold. The color of gold ink with a zinc content of between 20% and 30% is partial blue. It is generally called green gold, and is between red gold and green gold. Green gold. In gravure printing, the golden ink used in the deployment of gold ink is generally used for the 800-point gold powder, and the surface of the gold powder particles are mostly coated with a surfactant, and can be better combined with the resin binder.
Silver powder is actually aluminum powder and is composed of 65% aluminum flakes and 35% volatile hydrocarbon solvents. Aluminum pigments have a small specific gravity and are easy to float in liquids. What is used in the gravure silver ink is the floating silver powder that has floating ability in the link material. The silver ink generally uses silver powder of 400 to 1000 meshes. If silver ink is printed on a large area, a lower mesh silver powder, such as 400 mesh silver powder, can be used to modulate the silver ink. After printing, the metal ink has a high gloss.
2. Link material. The binder is a liquid component in the ink. On the one hand, it is the carrier of the pigment, so that the powdered pigment particles can be uniformly dispersed therein. On the other hand, it is also used as a binder so that the pigment can be finally fixed. Substrate material surface. The binder material largely determines the viscosity, viscosity, flowability and drying performance of the ink. Therefore, the quality of the binder material directly affects the performance of the ink.
The linking material used in gold and silver inks is a special varnish, which is generally called gold transfer oil or silver regulating oil. The main components are oil, resin, and organic solvent auxiliary materials. The linking material of gravure gold and silver ink should meet the following conditions: It must have enough viscosity to combine well with gold powder or silver powder. Transparency must be high and it must not affect the hue of gold and silver ink. The acidity of the gold transfer oil or silver regulating oil is low, otherwise the gold powder or the silver powder may react chemically. The transfer oil or silver transfer oil should also have fast-drying properties and quick fixability to prevent back-scratching of gold or silver ink prints.
Second, the characteristics of gold and silver ink The fineness of the ink. The better the fineness of the ink, the better the dispersibility of the pigment particles. Compared with the pigments in other inks, the pigment particles of the gold and silver inks are coarser, and it is easy to block the printing cylinders during the gravure printing process. Caverns, resulting in blockages and reduced ink transfer rates. Therefore, when deploying gold and silver inks, it is necessary to select gold powder and silver powder with high fineness and good floatability so as to facilitate uniform deployment and get a good print.
2. The gloss of the ink. The glossiness of gold and silver inks is largely related to the particle size of gold powder or silver powder. In general, the larger the particles, the better the gloss of the ink; conversely, the smaller the particles, the less the gloss of the ink. However, it is worth noting that with the increase of metal pigment particles, the printability of gold and silver inks will also decrease, the transfer performance will be relatively poor, and printing defects such as stencil printing will easily occur.
3. Heat resistance. Compared with the pigments in other inks, the gold powder and the silver powder in the gold and silver ink have the characteristics of high conductivity and high thermal conductivity, and the golden ink has poor heat resistance and is easily discolored when exposed to heat. Therefore, high temperature and heat accumulation should be avoided during use. The silver ink has good light and heat reflection properties, good heat resistance, and is not susceptible to discoloration under high temperature conditions.
4. Chemical instability. Silver ink chemical properties are relatively stable, but the silver ink is not acid-resistant, and can easily react with acidic substances, thus reducing the metallic luster of the imprint. Therefore, neutral auxiliary materials should be used for printing in the printing process. This should be paid special attention. . The chemical nature of gold ink is not stable enough. It will cause chemical changes in different degrees when it comes in contact with acids, alkalis, and sulfides. It will reduce its metallic luster and gold ink will appear black. Second, gold ink is also very easy. Discoloration occurs due to chemical reaction with air and water vapor. Therefore, be sure to seal the container tightly when storing the gold ink.
Third, the design process should pay attention to some issues According to the type of substrate materials and printing processes, rational design layout, both to do a nice appearance, but also fully consider the characteristics of gold and silver ink and printing process, try to happen printing malfunction.
1. In general, gold and silver inks are mainly applied in the field parts or color patches, and it is better not to design them into gold or silver for very small texts of Yin, Yang and levels.
2. When printing gold and silver ink on paper, the background ink is usually laid first. For example, when printing silver ink, first lay a light layer of white ink, and then print the silver ink. This can not only improve the gloss of the silver ink layer, but also Strengthen the silver ink adhesion on paper.
3. If the substrate material is aluminum foil or vacuum aluminized paper, transparent yellow can be printed on it to achieve the golden effect; in the composite film printing process of plastic film, the transparent yellow is printed on the OPP plastic film and then the aluminum foil is compounded. It can also achieve a golden effect, which can not only save expensive metallic ink, but also achieve the desired effect.
4. In the process of plate design, the order arrangement of gold and silver inks should be taken into consideration to ensure the metallic color.
5. If it is a printed product, after printing gold ink and silver ink, UV coating or water-based coating should also be considered, or the print should be coated to prevent oxidation or discoloration of the gold ink.
Fourth, the printing process should pay attention to the problems affect the quality of gravure printing products, there are many factors, such as the type of substrate material, the characteristics of the printing press, ink characteristics and environmental temperature and humidity. Therefore, in the gravure printing process must be strictly related to technology, margin, silver ink printing quality.
1. Reasonable choice of substrate materials. The properties of the substrate materials must be compatible with the printing process characteristics of gold and silver inks. Only by selecting the appropriate substrate materials can the printing effect and metallic luster of gold and silver be highlighted. It is required that the physical and chemical indicators of the whiteness, uniformity, smoothness, surface strength, and flatness of the substrate materials be good, the stretching rate is small, and the ink absorption is moderate. If the flatness of the substrate material is not good, the stretchability is large, and the solidity is poor, and it is difficult to maintain a constant printing pressure, it is easy to produce the disadvantages of uneven printing pressure, poor adhesion of the inked ink layer, and ink quality. Therefore, if gold and silver inks are to be printed on paper, substrate materials such as coated paper, glass cardboard, and whiteboard paper can be selected, and the metallic luster of gold and silver inks can be highlighted. If the substrate material is a plastic film, the plastic film must be pre-treated between printing, such as corona treatment, to improve the printability of the plastic film and the adhesion of gold and silver ink.
2. Gold, silver ink printability control. The control of the performance of gold and silver ink includes the following aspects: the viscosity of the ink. Viscosity is the most important control pointer in ink applications. It directly affects the transfer performance of inks and the quality of prints. Too low a viscosity can easily cause the ink to spread. Conversely, if the viscosity is too high, the transfer performance of the ink is relatively poor, and a large area is prone to appear. Some inaccurate ink lines, thin lines and other defects. When large areas of gold and silver ink are printed, the viscosity of the ink can be adjusted slightly lower to ensure that the ink layer after printing is uniform; when printing gold and silver ink on lines with smaller areas, the viscosity of the ink should be slightly higher. Dryness of ink. The drying speed of the ink should be appropriate, the drying speed of the ink is too fast, and the dry plate is liable to occur, which affects the transfer of the ink. However, the drying speed of the ink cannot be too slow, or else the back stain of the printed matter may occur. The general principle of selecting the ink drying speed is that under the existing conditions of the printing machine, the ink should be able to be fully dried before the next printing group and before rewinding or stacking, but it cannot be dried on the printing plate. During the printing process, appropriate amounts of slow-drying solvents or fast-drying solvents can be added to the gold and silver inks to adjust the drying speed of the gold and silver inks.
In addition, the use of gold and silver ink should also follow the principle of follow-up with the printing, the amount of ink each deployment should not be too much, to avoid the excessive deployment of ink to make the powder in the air exposure time is too long, and the oxygen of the air The water vapor undergoes a chemical reaction and loses its golden luster.
3. Press control. Printing pressure. The appropriate printing pressure should be set according to factors such as the printing method, ink performance, and the ink absorption properties of the substrate material. The printing pressure is too large, the ink spreads, the graphic is easily thickened and widened, and even the stencil is printed; the printing pressure is too small, Insufficient ink may cause inaccurate graphics. In the printing process of gold and silver ink, if it is a large-area solid color patch, the printing pressure can be appropriately increased to make the ink layer even and thick; if it is a small line or text, the printing pressure should be reduced appropriately , Avoid imprint expansion, paste version and other ills. Tension control. The tension should be adjusted according to the type of substrate material and its stretching rate. For example, the stretching rate of PE film is relatively large, and the tension value should be small; and for paper or plastic films with low elasticity such as PET, OPP, the tension can be appropriately large. some. In addition, the winding tension should not be too large to prevent back sticking. Printing speed. When printing gold ink, the speed of the printing machine cannot be too fast. Otherwise, the heat generated due to friction will continue to accumulate, which will easily cause oxidation and darkening of the gold ink. This will not only affect the gloss of the gold ink, but may also cause the stencil. . Drying capacity. The temperature of the drying oven should not be too high, otherwise it will easily cause the shrinkage of the substrate material, especially the PE film. Therefore, when setting the temperature of the drying oven, factors such as the printing speed, the printing tension, the type of substrate material, and the size of the printing pattern must be taken into consideration.
In addition, the printing roller of gold and silver ink should be cleaned in time after printing so as to prevent the dry knot from being formed in the net of the roller and cause the clogging of the cell.
4. Environmental temperature and humidity control. If the humidity is too high, the content of water vapor in the air is high, which easily discolors the gold ink, and also affects the moisture content of the paper substrate material, resulting in dimensional deformation, resulting in failures such as overprinting. If the humidity is too low and the air is too dry, static electricity can easily occur. Therefore, the temperature and humidity in the printing room should be kept constant. In general, the relative humidity is controlled between 55% and 60%, and the temperature is controlled between 20 and 28°C.
Fifth, plastic printing gold, silver when the common fault 1. The back of the print is dirty. Causes: The drying speed of the ink is too slow to completely dry; the printing speed is too fast; the winding tension is too large or the printing stack is too high; the operating environment temperature is too high; the drying ability of the printing press is low. Solution: Add quick-drying solvent, or change the formulation of gold and silver oil; reduce the printing speed; reduce the winding tension or stacking height of printing products; reduce the operating environment temperature; increase the air volume and far-infrared light intensity.
2. Paste version. Reason: Ink drying is too fast, it has dried in the plate cavity before being transferred to the substrate material; ink particles are too thick; printing plate is not cleaned in time, leaving the residual ink in the mesh cavity, resulting in the network point Blockage; Ink mixed with dust, sand and other impurities. Solution: Slow down the drying speed of the ink; replace the ink; clean the printing plate at any time; filter the ink and cap the ink tank; meanwhile, keep the environmental sanitation of the production workshop.
3. The ink layer has poor fastness, and gold and silver inks are easy to fall off. Reasons: Gold â–¡ Silver Powder and Gold â–¡ Silver Oil