The application of the hottest gold silver ink and

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With the development of society and the improvement of living standards, people have higher and higher requirements for commodity packaging. Gold or silver ink is often printed on some fine products such as cigarette packets and wine labels. Gold ink and silver ink can show the luster of metal, giving people a solemn, luxurious, magnificent and dazzling feeling, which can not be expressed by spectral color. Therefore, gold and silver inks have been widely used in packaging, decoration and printing. The proper use of gold and silver inks in commodity packaging and trademark labels can not only embellish and foil other colors, but also improve the quality of products as a whole. How to improve the quality of silver ink printing is self-evident

I. composition of gold and silver inks

like other inks, gold and silver inks are mainly composed of pigments and binders. In short, gold inks are made of gold powder and gold blending oil, and silver inks are made of aluminum powder and silver blending oil

1. Pigment

as we know, pigment is the colorant in ink, which endows the ink with a certain color. The pigment in gold and silver ink is made of metal powder, mainly gold powder and silver powder

the pigment in the gold ink is gold powder, which is actually a powder made of copper and zinc alloys. The zinc content in the gold powder is generally about 8%~30%. Among them, the gold ink with zinc content between 8%~12% is red, which is traditionally called red gold, while the gold ink with zinc content between 20%~30% is blue. First, the sample can be installed first, which is called green gold, and the gold between red gold and green gold is called green red gold. In gravure printing, 800 mesh gold powder is generally used to prepare gold ink, and the surface of gold powder particles is mostly coated with surfactant, which can be better combined with resin binder

silver powder is actually aluminum powder, which is composed of 65% flake aluminum powder and 35% volatile hydrocarbon solvents. Aluminum pigment has a small specific gravity and is easy to float in the liquid. Gravure silver ink is a kind of floating silver powder with floating ability in the binder. Silver ink generally uses 400~1000 mesh silver powder. If silver ink is printed on a large area, silver powder with a lower mesh number can be used. For example, 400 mesh silver powder and silver ink have high metallic luster after printing

2. Binder

binder is the liquid component in the ink. On the one hand, it is the carrier of pigment, so that the powdered pigment particles can be evenly dispersed in the flame retardancy of the material. On the other hand, it also acts as an adhesive, so that the pigment can finally be fixed on the surface of the substrate material. Binder largely determines the viscosity, viscosity, fluidity and drying performance of ink. Therefore, the quality of binder directly affects the performance of ink

the binder used in gold and silver inks is a special ink blending oil, generally called gold blending oil or silver blending oil. Its main components are oil, resin and organic solvent auxiliary materials. The bonding materials for gravure gold and silver inks shall meet the following conditions: ① there must be enough adhesion level transfer degree to combine well with gold or silver powder. ② Transparency must be high and cannot affect the hue of gold and silver ink. ③ The acidity of the gold or silver blending oil should be low, otherwise the gold or silver powder will have a chemical reaction. ④ The gold transfer oil or silver transfer oil should also have fast drying and fast fixation, so as to prevent the back of gold ink or silver ink printing from sticking

II. Characteristics of gold silver ink

1 Ink fineness

the better the ink fineness, the better the dispersion of pigment particles. Compared with the pigments in other inks, the pigment particles of gold and silver inks are thicker. It is easy to block the holes on the plate cylinder in the gravure printing process, resulting in plate blocking and a decrease in the ink transfer rate. Therefore, gold and silver powders with high fineness and good floatability should be selected when preparing gold and silver inks to facilitate uniform preparation and good imprinting

2. Gloss of ink

the gloss of gold and silver ink is largely related to the particle size of gold or silver powder. Generally speaking, the larger the particle size, the better the gloss of ink; On the contrary, the smaller the particle, the worse 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 decline, and the transfer performance is relatively poor, which is prone to printing failures such as paste

3. Heat resistance

compared with the pigments in other inks, the gold powder and silver powder in gold and silver ink have the characteristics of high conductivity and thermal conductivity. The gold ink has poor heat resistance and is easy to change color in case of heat. Therefore, high temperature and heat accumulation should be avoided during use; Silver ink has good light and heat reflection performance, good heat resistance, and is not easy to change color under high temperature conditions

4. Unstable chemical properties

the chemical properties of the silver ink are relatively stable, but the silver ink is not acid resistant and is easy to react with acidic substances, so that the metal luster of the imprint is reduced. Therefore, neutral auxiliary materials should be used to adjust the ink during the printing process, which should be paid special attention. The chemical properties of gold ink are not stable enough, and the contact with acid, alkali and sulfide will cause chemical changes to varying degrees, which will greatly reduce its metallic luster, and the gold ink will appear black; Secondly, the gold ink is easy to change color due to chemical reaction with air and water vapor. Therefore, the container must be tightly sealed when storing the gold ink

III. some problems that should be paid attention to in the design process

according to the type of substrate material and printing process, the layout should be designed reasonably, which should not only be beautiful and generous, but also take full account of the characteristics of gold and silver ink and printing process, so as to avoid printing failures as much as possible

1. Generally speaking, gold and silver inks are mainly used on the field parts or color blocks, and it is better not to design gold or silver for very small Yin, Yang and level transitions

2. When printing gold and silver ink on paper, it is usually necessary to lay the background ink first. For example, when printing silver ink, lay a layer of light white ink first, and then print silver ink. This can not only improve the gloss of silver ink layer, but also strengthen the adhesion of silver ink on paper

3. If the substrate material is aluminum foil or vacuum aluminized paper, printing transparent yellow on it can achieve the golden effect; In the plastic film composite internal printing process, the transparent yellow is printed on the OPP plastic film and then the aluminum foil is compounded. The printing ink layer can also achieve the golden effect, which can not only save expensive metal ink, but also achieve the desired effect

4. In the process of plate making design, the color sequence of gold and silver ink should be considered to ensure the metal color

5. For surface printing products, after printing gold ink and silver ink, UV glazing or water-based glazing should also be considered, or the printed matter should be coated to prevent oxidation discoloration or falling off of gold ink

IV. problems needing attention in the printing process

there are many factors that affect the quality of gravure printing products, such as the type of substrate material, the characteristics of printing machine, the characteristics of ink, environmental temperature and humidity, etc. Therefore, in the process of gravure printing, we must strictly control the process technology and the printing quality of margin and silver ink

1. Reasonable selection of substrate materials

the performance of substrate materials must adapt to the printing process characteristics of gold and silver inks. Only selecting appropriate substrate materials can highlight the printing effect and metallic luster of gold and silver. It is required that the whiteness, evenness, smoothness, surface strength, flatness and other physical and chemical indicators of the substrate materials are good, the expansion rate is small, and the ink absorption is moderate. If the flatness of the substrate material is not good, the elasticity is large, and the firmness is poor, it is difficult to maintain a constant printing pressure, and it is easy to suffer from uneven printing pressure, poor adhesion of the imprinted ink layer, and ink quality problems. Therefore, if you want to print gold and silver ink on paper, you can choose coated paper, glass paperboard, whiteboard and other substrate materials, which can well highlight the metallic luster of gold and silver ink. If the substrate material is plastic film, the plastic film must be pretreated before printing, such as corona treatment, to improve the printability of the plastic film and the adhesion of gold and silver ink

2. The control of printing suitability of gold and silver inks the control of the performance of gold and silver inks mainly includes the following aspects: ① the viscosity of ink. Viscosity is the most important control index in ink application. It directly affects the transfer performance of ink and the quality of printed matter. Too low viscosity is easy to cause ink spreading; On the contrary, if the viscosity is too high, the transfer performance of the ink is relatively poor, and it is easy to suffer from uneven inking and broken thin lines in a large area of the field. When printing gold and silver ink in large area, the viscosity of the ink can be adjusted slightly lower to ensure that the ink layer is uniform after printing; When gold and silver inks are printed on smaller lines, the viscosity of the ink should be slightly higher. ② Dryness of ink. The drying speed of the ink should be appropriate. If the drying speed of the ink is too fast, it is easy to dry the plate and affect the transfer of the ink. However, the drying speed of the ink should not be too slow, otherwise the back of the printed matter will be sticky and dirty. The general principle for selecting the ink drying speed is that under the existing conditions of the printing machine, the ink should be fully dried before the next printing color deck and before rewinding or stacking, but it cannot be dried on the printing plate. During the printing process, an appropriate amount of slow drying solvent or fast drying solvent can be added to the gold and silver inks according to the specific conditions to adjust the drying speed of the gold and silver inks

in addition, the use of gold and silver inks should also follow the principle of printing with adjustment. The amount of ink allocated each time should not be too much, so as to avoid excessive ink allocation, which will cause the gold powder to be exposed to the air for too long, and the gold luster will be lost due to the chemical reaction with the oxygen and steam in the air

3. Control of printing press

① printing pressure. The appropriate printing pressure should be set according to the printing mode, ink performance and ink absorption performance of the substrate material. If the printing pressure is too high, the ink will spread out, and the text will become thicker and wider, or even paste the plate; The printing pressure is too low, the ink transfer is insufficient, and the graphics and text may be inked unevenly. In the process of gold and silver ink printing, if it is a large area of field color block, the printing pressure can be appropriately increased to make the ink layer uniform and thick; If it is a small line or text, the printing pressure should be appropriately reduced to avoid the generation of bad defects such as enlarged imprint and pasted version. ② Tension control. The tension should be adjusted according to the type of substrate material and its expansion rate. For example, the expansion rate of PE film is relatively large, and the tension value should be smaller; For paper, pet, OPP and other plastic films with small expansion rate, the tension can be appropriately larger. In addition, the winding tension should not be too large to prevent back sticking. ③ Printing speed. When printing gold ink, the speed of the printing machine should not be too fast. Otherwise, the heat generated by friction will continue to accumulate, and it is easy to oxidize and blacken the gold ink, which will not only affect the gloss of the gold ink, but also cause paste. ④ Drying capacity. The temperature of drying oven should not be too high, otherwise it is easy to cause shrinkage deformation of substrate materials, especially PE film. Therefore, when setting the temperature of the drying oven, it is necessary to comprehensively consider the printing speed, printing tension, types of substrate materials and printing drawings

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