The application of gold and silver ink in the most

With the development of society and the improvement of living standards, people have higher and higher requirements for commodity packaging. Gold ink or silver ink is often printed on some fine products, such as cigarette bags 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 ink have been widely used in packaging and decoration printing. The proper use of gold and silver ink on commodity packaging and trademark labels can not only embellish and foil other colors, but also improve the grade of products as a whole. How to improve the quality of silver ink printing is of self-evident importance

I. composition of gold and silver ink

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

1. pigment. We know that pigment is the colorant in ink, which gives ink a certain color. The pigment in gold and silver ink is made of metal powder, mainly gold powder and silver powder

the pigment in gold ink is gold powder, which is actually a powder made of copper and zinc alloys. The zinc content in gold powder is generally about 8% ~ 30%. Among them, the gold ink with zinc content of 8% ~ 12% is red, which is customarily called red gold, while the gold ink with zinc content of 20% ~ 30% is blue, which is generally 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 wrapped 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. What is used in gravure silver ink is floating silver powder with floating ability in binder. Silver ink generally adopts 400 ~ 1000 mesh silver powder. If silver ink is printed on a large area, silver powder with a lower mesh number can be used, such as 400 mesh silver powder to prepare silver ink, which has a high metallic luster after printing

2. Binder. Binder is a liquid component in ink. On the one hand, it is the carrier of pigment, so that powdered pigment particles can be evenly dispersed in it. On the other hand, it also acts as an adhesive, so that the pigment can finally be fixed on the surface of substrate materials. 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, which is generally called gold blending oil or silver blending oil. Its main components are oil, resin and organic solvent auxiliary materials. The binder of gravure gold and silver ink should meet the following conditions: ① it must have enough viscosity to combine well with gold powder or silver powder. ② Transparency must be high and cannot affect the hue of gold and silver ink. ③ The acidity of gold blending oil or silver blending oil should be low, otherwise the gold powder or silver powder will have a chemical reaction. ④ Gold blending oil or silver blending oil should also have fast drying and fast fixation to prevent gold ink or silver ink printing from sticking on the back

II. Characteristics of gold and silver ink

1. Fineness of ink. The better the fineness of the ink, the better the dispersion of the pigment particles. Compared with the pigments in other inks, the pigment particles of gold and silver inks are thicker, which is easy to block the holes on the plate cylinder in the gravure printing process, resulting in blocking the plate and reducing the transfer rate of the ink. Therefore, when mixing gold and silver inks, we should choose gold and silver powders with high fineness and good floatability, so as to facilitate the mixing evenly and get a good impression

2. Gloss of ink. To a large extent, the gloss of gold and silver ink is related to the particle size of gold powder or silver powder. Generally speaking, the larger the particle, 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 heat conductivity. The heat resistance of gold ink is poor, and it 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 silver ink are relatively stable, but silver ink is not acid resistant, and it is easy to react with acidic substances, so that the metallic luster of the imprint is reduced. Therefore, neutral auxiliary materials should be used to adjust ink in the printing process, which should be paid special attention to. The chemical properties of gold ink are not stable enough, and chemical changes will occur in varying degrees in contact with acid, alkali and sulfide, which will greatly reduce its metallic luster, and the gold ink will appear black; Secondly, gold ink is also easy to react with air and water vapor to cause discoloration. Therefore, when storing gold ink, you must seal and cover the container tightly

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, and try to have printing failures

1. Generally speaking, gold and silver inks are mainly used on the field parts or color blocks, and it is best 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 bottom color 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, transparent yellow is printed on OPP plastic film and then aluminum foil is compounded. The ink layer of printed matter 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 arrangement of gold and silver inks should be considered to ensure the metal color

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

IV. problems that should be paid attention to 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 gravure printing process, 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 be compatible with 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, uniformity, smoothness, surface strength, flatness and other physical and chemical indicators of the substrate material are good, the expansion rate is small, and the ink absorption is moderate. If the flatness of the substrate material is not good, the flexibility is large, and the firmness is poor, it is difficult to maintain a constant printing pressure, and it is easy to produce uneven printing pressure, weak 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, such as corona treatment, in order to improve the printability of the plastic film and the adhesion of gold and silver ink before replacing the oil printing with suitable viscosity

2. Control of printing suitability of gold and silver inks. The control of gold and silver ink performance mainly includes the following aspects: ① ink viscosity. Viscosity is the most important control index in the application of ink, which 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, which is prone to uneven inking and fine line fracture in a large area of the field. When printing gold and silver ink in a large area, the viscosity of the ink can be adjusted slightly lower to ensure the uniformity of the ink layer after printing; When gold and silver inks are printed on lines with small area, 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, but 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 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 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 situation to adjust the drying speed of the gold and silver inks

Jinan new era Gold Testing Instrument Co., Ltd. has studied various materials

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 expose gold powder to the air for too long, and lose its golden luster due to chemical reaction with oxygen and water vapor in the air

3. Control of printing machine. ① Printing pressure. The appropriate printing pressure should be set according to the printing method, ink performance and ink absorption performance of the substrate material. If the printing pressure is too high, the ink will spread out, and the graphics and texts will become thicker and wider, or even paste the plate; The printing pressure is too small, and the ink transmission is insufficient, and the graphics and texts may be inked unevenly. In the process of gold and silver ink printing, if it is a large area of field color blocks, 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 bad disadvantages such as blotting, paste and so on. 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 the back from sticking dirty. 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, which will easily 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 the drying oven should not be too high