Analysis of the situation affecting the printing quality of gold and silver ink

Gold and silver inks are colored by copper, zinc, and aluminum metal powders. The granular metal powders are the main components of inks. Therefore, the adhesion, viscosity, and fluidity of gold and silver inks are inferior to those of ordinary inks. Inconsistent ink, blotting, stencil, color fade, etc. Therefore, the correct analysis of the factors that affect the printing quality of gold and silver ink, the use of appropriate technical measures for the control of the gatekeeper, to avoid the blindness of the operation and process, improve the printing quality of gold and silver ink is of great significance.

1 lack of metallic luster

In general, the chemical properties of gold and silver powders in gold and silver ink are not stable. When acid, alkali, sulfide gas or water vapor is encountered, a certain degree of chemical change will occur, and the printing ink will lack a metallic luster. Among them, the color shift of golden ink is changed from golden yellow to reddish brown, and then turns blackish. In addition, the gold powder is easily converted to copper carbonate under the conditions of relatively concentrated carbon dioxide gas and high humidity, and the gold ink on the printed product gradually becomes dark. After the silver ink is discolored, it appears grayish.

In order to prevent the occurrence of the above situation, gold powder and silver powder used in the deployment of gold and silver ink should avoid heat, moisture and contact with acid-alkali substances during use and storage. Unused gold and silver powder should be sealed to ensure their quality. stable. In addition, if the gold and silver ink deployment is too much, the use of time is too long, the printer speed is too fast, the number of the use of the rubber roller is too many, the contact pressure between the ink roller is too large, etc., are easy to make the ink oxidation and black. If the pH value of the paper is in a slightly acidic state, for example, offset paper, whiteboard paper, and paperboard are generally of the acid-acid nature, chemical reactions easily occur after printing, and the gold and silver ink layers on the paper surface lose their metallic luster.

In order to reduce or prevent the occurrence of printing defects, the gold and silver inks should be used with adjustments. Normally, it is advisable to continuously print for three to four hours at a time. The speed of the printer is controlled between 2500 and 3000 sheets per hour. The ink roller is best. Use two, and the glue should be soft; the level and position of the ink roller should be adjusted well so as not to increase the frictional heat due to the excessive contact pressure and cause black oxidation of the ink; gold and silver ink printing paper to use coated paper, glass card Paper and other surface smooth paper is good.

2 Gold and silver ink on the printed product 1) Uneven lining If the liner is soft or left with foreign matter, it is impossible to maintain the ink and paper surface on each particle of the printing plate during the printing process. Full contact, so local printing layout is inevitable. In addition, printing plates with different web sizes will produce a certain degree of unevenness in the lining. Therefore, the lining of the printed silver ink should use a neutral, hard-type lining, and the lining of the uneven lining should be used. Replace it to improve the ink color quality.

2) The rubber roller is too hard, the colloid is broken or the rubber roller is too hard to make the ink transfer uneven; if the rubber roller is not round or the surface of the roller is damaged, it will certainly produce uneven ink transfer and make the printing ink layer thickness difference. Therefore, the printing roller of gold and silver ink, the colloid should be soft, colloidal to be intact and have a more accurate center of the circle, which is also an important condition for achieving a uniform and full ink printing ink.

3) The gold and silver inks are too thin. If the proportion of gold, silver powder and gold oil is improperly proportioned, when the amount of gold oil is too much, the liquidity of the gold and silver ink will be too large, and the viscosity will be poor, and the printing process will be poor. Ink and cloth will be thin, so the saturation of coloring is poor, and the print will look a bit bloated.

4) Version is not firm, printing pressure is not uniform, and gold and silver inks are printed using a letterpress process. If a rubber sheet is used as the plate base, the plywood has poor firmness, large deformation coefficient under pressure, and poor flatness, resulting in printing. The pressure is not uniform, so that the printing ink layer is inevitably easy to bloom. Therefore, the printing of gold and silver ink layout should adopt good flatness, high hardness, solid metal plate support, such as magnetic metal plate tray, aluminum plate tray, can better improve the quality of printing ink color.

5) The surface roughness of the paper The brightness of the ink layer has a great relationship with the glossiness of the paper surface. If the paper surface is rough and the gloss is poor, the gold and silver ink will soon be absorbed by the fibrous tissue of the paper. Then the brightness of the printing ink layer is poor, such as the use of offset paper, letterpress paper and white cardboard printing gold and silver ink, the color rendering effect is inevitably not ideal. Therefore, in order to ensure the printing quality of gold and silver inks, gold and silver inks should be printed with paper glossy paper such as glass cards or coated papers.

3 gold and silver layout imprint roughening and hair paste 1) Improper ink transfer The ink's fluidity determines the ink transfer effect and print quality. If the gold and silver inks are too thin or too thick, the blots on the edge of the layout or reversed white when inked are liable to accumulate ink and become thicker or appear ill-printed. Then, to what extent is the viscosity of printing gold and silver inks appropriate? This is hard to say, nor can it be standardized with a uniform standard. Because the printer structure and performance are different and the printing environment temperature conditions are different, the printing ink concentration requirements will be different. In general, when the printer has many ink rollers, high speed, and high printing temperature, the gold and silver inks are properly regulated so that the ink is relatively thin after being heated, and it just meets the printing requirements. If the ink is adjusted to the desired viscosity for printing, the ink will be easily diffusing when the ink is heated and thinned during printing.

2) Ink is too large When printing gold and silver ink, if the ink volume is too large, the ink layer on each ink roller is too thick. After being applied to the printing plate, the graphic plate surface will retain too much ink, so the pressure During the printing process, the excess ink is bound to be pushed onto the edge of the layout and the imprinting of the imprints. Therefore, printing gold and silver ink should control the amount of ink.

3) The lining of the loose packing is not tightened, and the edge of the printing plate will appear as a raised print. Therefore, a good lining process technique should be used.

4) Printing pressure is heavier If the pad plate is uneven, or the bottom plate is not square enough so that the plate is bowed or the pressure of the pad is too heavy, it may cause the printed graphic to be paste and thick, and the pad printing process is good. Technical relations, printing plate should be flat, solid, high and low.

4 Undercoat crystallization

1) When the base color ink layer is over-printed and the base color ink is dried, if the dry oil amount is too much, the ink layer on the print product will dry too fast, so that the gold and silver ink will not adhere when the ink is superimposed. Therefore, the amount of dry oil should be moderate.

2) The undercoat ink layer is printed thick. The ink layer is thick. The ink layer of the print product has high brightness and good visual effects. However, if the printing ink layer is too thick and the crystal surface is formed after the conjunctiva is formed, it is difficult for the gold and silver inks to be overprinted, and it is easy to pull the ink layer off after printing. Therefore, the thickness of the undercoat ink layer should be controlled. In general, the overprinted undercoat ink layer should be appropriately thinned, and even the undercoat ink should be relatively deepened to make the printing ink layer thinner.

3) Overprinting time interval is too long. If the printed sheet is printed after the background color is printed, if the ink is too dry, the ink layer will be too dry and overprinted. Even if it can be overprinted, the ink color will be generated. In order to prevent such situations from happening, the base ink is dried after printing to 89%, and the effect will be relatively better.

After the crystallization of the underlying color ink layer, remedial measures should be taken to ensure product quality. According to the experience of production practice, we can use cloth to wipe the background color ink layer and destroy the crystalline film to enhance the adhesion of gold and silver ink. Secondly, we can add alkaline liquid or 389 resin oil and industrial soap flakes to gold and silver ink. Third, the pressure on the printing of gold and silver ink is appropriately increased so that the gold and silver ink adheres firmly to the background ink.

Source: "Printing World" Author: Tanghui Yu