Gold and Silver Ink and Printing Technology Points (I)

With the development of society, the improvement of living standards and the rapid progress of today's printing technology, the artistic effects of packaging, decoration, and color layout are increasing. It is not just to print gold and silver on cigarette packs or wine labels, but gold or silver ink will also be printed on the covers or texts of some high-end publications and exquisite albums to increase product quality. The gold and silver inks can exhibit metallic luster, giving people a solemn, luxurious, colorful and magnificent appearance. Their products are imprinted with delicate textures, strong hiding power, and floating sensations. They have excellent visual effects. They are high-grade packaging products and commercial products. The first choice for color rendering and embellishment when printing publications.

First, the composition of gold and silver ink

Like other inks, gold and silver inks are mainly composed of pigments and linking materials. Gold inks are made of gold powder and gold transfer oil. Silver inks are made of aluminum powder and silver regulating oil.

The pigment is a coloring substance in the ink, which gives the ink a certain color. The pigments in the gold and silver inks are ground from metal powder (ie, gold powder and silver powder). The pigment in gold ink is gold powder, which is actually a copper-zinc alloy powder (mainly copper) with a particle size of 50 μm to 100 μm. The content of zinc in the gold powder is generally between 8% and 30%. Different zinc content, gold ink will have a different color. Gold ink with zinc content between 8% and 12% has a reddish color and is customarily referred to as red gold. Gold ink with a zinc content between 20% and 30% has a partial blue color. Gold; between the red gold and the green gold is called the red gold. Silver powder is actually aluminum powder and is composed of 65% aluminum flake and 35% volatile hydrocarbon solvents. Aluminum pigments have a small specific gravity and are easy to float in liquids. Silver powder has a difference in particle size, so the resulting metallic luster is also different. The coarse particles of silver reflect the luster more strongly, while the fine particles of silver reflect the luster more weakly. Silver ink used for printing generally uses aluminum powder having a particle diameter of 64 μm to 128 μm.

The binder is a liquid component in the ink, which is a carrier of the pigment so that powdery pigment particles can be uniformly dispersed therein. At the same time, it also acts as a binder, allowing the pigment to eventually adhere to the surface of the substrate material. The binder material largely determines the viscosity, viscosity, fluidity, adhesion and drying performance of the ink. Therefore, the quality of the binder material directly affects the performance of the ink. The link material used in gold and silver ink is a special type of varnish, which is generally called gold transfer oil or silver regulating oil. The main components are oil, resin, organic solvent and other materials. Gold and silver inks have the following performance requirements: 1 Must have sufficient viscosity to combine well with gold powder or silver powder. 2 The transparency must be high, and it cannot influence the hue of gold and silver ink. 3 The acidity of the transfer oil or silver oil is low, otherwise it will react with the powder or silver powder. 4 The transfer oil or silver adjustment oil should have quick-drying property and fast fixing property to prevent the back of the gold ink or silver ink from appearing dirty.

Gold and silver inks are often supplemented with auxiliary materials such as plasticizers, antioxidants, and desiccants to improve the printability of inks.

Second, the characteristics of gold and silver ink

1. Fineness of the ink The finer 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 cells on the plate cylinder during the gravure printing process, thereby causing blockages and decreasing the ink transfer rate. When offset printing is also easy to accumulate on the ink roller, plate and blanket, resulting in printing plate resistance to printing force, blanket damage and other failures. Therefore, when deploying gold and silver inks, it is necessary to choose gold powder and silver powder with high fineness and good floatability as far as possible so as to facilitate uniform deployment and obtain a good print.

2. Luster of ink The luster 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 gloss of the ink is poor. However, with the increase of metal pigment particles, the printability of gold and silver inks will also decrease, the transfer performance is relatively poor, and paste plates are liable to occur. Therefore, the grain size of gold powder and silver powder should be balanced.

3. Heat resistance Compared with the pigments in other inks, gold powder and silver powder in gold and silver inks have the characteristics of high conductivity and high thermal conductivity. Gold ink is poor in heat resistance and easily discolored when exposed to heat. Therefore, high temperature and heat accumulation should be avoided during use. Silver ink has good light and heat reflection properties, good heat resistance, and is not susceptible to discoloration under high temperature conditions.

4. Chemical properties The chemical properties of gold ink are not stable enough. Chemical contact with acids, alkalis and sulfides will occur in varying degrees of chemical changes, which will greatly reduce its metallic luster and cause blackness. Second, gold ink It is also easy to cause a chemical reaction with air and water vapor to cause discoloration. Therefore, be sure to tightly seal the container when storing the golden ink. The chemical properties of silver ink are relatively stable, but the silver ink is not acid-resistant and easily reacts with acidic substances, thus reducing the metallic luster of the print. Therefore, a neutral auxiliary agent should be used to adjust the ink during the printing process.

5. The weight of the ink The common ink is generally made of organic pigments and binders, but the gold and silver inks are composed of denser copper powder and silver powder, and the linking material is used to ensure the stability of the ink and the gold and silver powder. Dispersion to avoid powder particle deposition and stencil printing. The better the suspension, the better the gold or silver powder, the better the metallic luster of gold and silver ink. In addition, the adhesion of gold and silver inks is poor, and they must strictly comply with the process requirements when they are used, otherwise it is difficult to obtain satisfactory gold and silver ink printing products.

Third, the deployment of gold and silver ink and color change

Generally, boxed inks can be used. If the amount is large, gold and silver inks can be prepared for cost saving. The use of gold or silver powder 30% to 50%, gold or silver oil transfer 70% to 50%, the two can be fully mixed to obtain gold and silver ink, add some auxiliary materials can adjust its printability.

When using gold powder, you should choose gold powder with high fineness and low buoyancy, which is good for evenness when printing and solvent, and get better imprinting. In the deployment of gold ink, the dilute consistency of gold ink shall be determined according to the printing suitability of the substrate and the change of the climate season, and different auxiliary agents shall be applied to enhance the affinity, adhesion and fluidity of the gold ink so that the gold ink may be used. The adsorption performance is improved, thereby improving the transferability of the gold ink. The use of silver powder is generally 400-1000 mesh silver powder. Silver ink formulated with 1000-mesh silver powder has relatively poor metallic luster. The 400-mesh silver powder blended with silver ink has a better metallic luster and is suitable for large areas. Printed product. However, the silver powder is not acid-resistant. When it encounters acidic substances, it will cause a chemical reaction to reduce the metallic luster. Therefore, neutral auxiliary materials must be used for preparation of ink and printing.

When replacing the ink, in order to ensure the ink is pure, it is necessary to clean the ink roller before replacing the gold ink, clean it with some yellow ink, and then clean it again; when printing the silver ink, apply some white ink and clean the ink roller again to prevent color deviation. . After the ink roller is completely dry, it can be printed under the ink so as to avoid ink failure.

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