Discussion on Printing Quality of Gold and Silver Ink

The formation of gold and silver ink color is developed by copper, zinc, aluminum metal powder, which is the main body of the ink. Because of their granular properties, the gold and silver inks have better adhesion, viscosity, and fluidity than ordinary inks. If the printability cannot be grasped, it is easy to produce unfavorable conditions such as dull color, uneven ink, crystallization of the print, stencil, and discoloration.

One, gold, silver ink dull, lack of metallic luster

The chemical properties of gold and silver powders in gold and silver inks are generally not stable enough. When acid, alkali, water vapor, sulfide gas, and carbonic acid gas are encountered, a certain degree of chemical change will occur and the printing ink will lack a metallic luster. . The metal's color change pattern changes from golden yellow to reddish brown, which in turn turns blackish. Because the red copper oxide can be generated when the copper is oxidized, it becomes black copper oxide after further oxidation. 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 discoloration of the silver ink, it was slightly grayish and lacked a silver metallic texture. In order to prevent the occurrence of the above-mentioned unfavorable conditions, gold powder and silver powder for gold and silver inks shall be prepared. During use and storage, heat, moisture and contact with acid-alkali substances shall be avoided. Unfinished gold and silver powders shall be sealed to ensure their quality. The stability is a condition. In addition, if the amount of gold and silver ink is too much, the use of time is too long, the speed of the printer is too fast, the number of branches using the rubber roller is too much, and the contact pressure between the ink rollers is too high, the ink is easily oxidized and blackened and darkened. The pH value of the paper is in a slightly acidic state. For example, offset paper, white paper, and paperboard generally have the characteristic of being acid-saturated. After the printing, the chemical reaction easily occurs and the gold and silver ink layers on the paper lose their metallic luster and brightness. In order to reduce or prevent the occurrence of printing defects, the gold and silver inks should be used with adjustments. Generally, it is appropriate to print three or four hours at a time. The speed of the printer is controlled at 2500 to 3,000 sheets per hour; two ink rollers are used. The glue should be softer, and the height should be aligned with the front and back (that is, in contact with the iron roller) so that the contact pressure is too heavy to aggravate the frictional heat and the black oxidation becomes dark. Gold and silver ink printing papers are preferably made of glossy paper, such as coated paper and glass cards, and have a strong sense of metallic ink.

Second, the printed gold, silver ink color, color saturation is not good

1. Padded or rugged

If the liner is soft, the printing pressure will inevitably be impregnable. Therefore, it is impossible to maintain a full and appropriate contact condition between the ink and the paper surface of each dot of the printing plate in the printing process. It is inevitable that the partial printing plate will be emitted. In addition, the lining has been used for a long time, because the paper surface foreign materials such as sand, paper crushed, pulp agglomerates, printing plates of different web sizes (press type) will make the lining produce a certain degree of uneven shape, which is also the imprinted hair The source of flowers, so the printing of gold and silver ink pad lining should use a neutral hard pad, the use of deformation of uneven padding should be replaced to improve the ink color quality.

2. The roller is too hard and not sticky or broken

If the rubber roller is too hard, the adhesiveness is poor and it is easy to make the ink transfer uneven. The lack of a good center of the rubber roller and the damage of the colloidal surface will inevitably lead to uneven ink transfer and the difference in thickness of the printing ink layer. Therefore, the printing roller of gold and silver ink should be soft and the colloid should be intact. With a more accurate center of the circle, the entire surface of the roller is evenly distributed. This is also an important condition for achieving a uniform and full ink color of the gold and silver inks.

3. The gold and silver inks are too thin, and the ink color is caused by poor fluidity and viscosity.

If the proportion of gold, silver powder and gold oil blending is improper; that is, when the amount of gold oil is too much, the liquidity of the gold and silver ink is too large, and the viscosity is also poor, and the ink and ink in the printing process will be biased. Thin, so the color saturation is poor, the imprinting appears to have some flowers. Therefore, the thickness of gold and silver inks should be appropriate to ensure the quality of ink printing.

4. The underlay is not solid and the printing pressure is not uniform, causing the gold and silver layers to bloom.

If gold and silver inks are printed using a letterpress process, if plywood is used as a plate support, the plywood has poor firmness, large compression deformation coefficient, and poor flatness. When printing gold and silver ink layouts, printing pressure variation tends to occur. To make the printing pressure uneven or insufficient, so that the printing ink layer is inevitably easy to bloom. Therefore, the printing of gold and silver ink layout should adopt a good flatness, hardness, solid strong metal tray, such as magnetic metal plate tray, aluminum tray, can better improve the printing ink quality.

5. Large gaps in paper fibers, rough surfaces, high ink absorption, resulting in gold and silver ink

The brightness of the printed ink layer has a great influence on 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 ink is printed. Bad, such as the use of offset paper, letterpress paper and white cardboard printing gold and silver ink, the color effect is necessarily not ideal. Therefore, in order to ensure the printing quality of gold and silver inks, it is better to print gold and silver inks with good paper glossiness, such as glass or coated paper, and the printing process is better.

Third, the gold and silver plate surface roughening and paste the reasons

1. Improper ink transfer

How the ink flow 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 the negative image may become thicker or appear ill-printed. So, to what extent is the consistency and viscosity of printed gold and silver inks appropriate? This is hard to say, nor can it be standardized with a uniform standard. Because of the different performance of printers and the different printing environment temperatures, there are differences in the printing ink concentration requirements. In general, the printer has many ink rollers, fast speeds, and high printing temperatures. The gold and silver inks are thickened appropriately so that the ink will be relatively thin after being exposed to heat, which is exactly in line with the printing requirements. If the ink is adjusted to the fluidity required for printing at once, the ink in the printing becomes too dilute after the printing, and the printing easily expands.

2. Too much ink

When printing gold and silver inks, if the ink volume is too large, the ink layer on each ink roller is too thick, and after being applied to the printing platen, due to the excessive amount of ink in the graphic layout, then, during the printing process, excess The ink is bound to be squeezed to the edge of the layout, so that the imprinting of hair. Therefore, the printing of gold and silver ink should control the appropriate amount of ink to ensure print quality.

3. Packed with loose pine

When the overwrapping lining repeatedly pad or pad sticker piece does not adhere to the trailing part and flutter, and the lining is not tightened and packaged, the raised edge of the printing plate will appear after the printing, so the good lining technology should be shut off.

4. Printing pressure is heavy

When the pad is not flat, the bottom plate is not square enough to make the plate bow or plate pressure is too heavy, it will also cause the printed text to become paste, thick, this should be a good pad technology, the printing plate should be pad Flat, solid, high and low pads are suitable.

Fourth, the underlying ink layer crystallization so that gold, silver ink is not attached

1. Crystallization due to overdrying of the undercoat ink layer

When printing background ink, if the amount of dry oil is too much, the drying speed of the ink layer on the print will be too fast. After the ink layer is conjunctated, a layer of crystallized film will be produced, so that the gold and silver inks will not be overprinted. Therefore, the amount of dry oil should be moderate.

2. Crystallization due to over-printing of the undercoat ink layer

The printing ink layer is thick, the brightness of the printed ink layer is high, and the visual effect is better. However, if the printing ink layer is too thick and the crystal surface is formed after the conjunctiva is formed, the gold and silver ink will be difficult to print. After printing, it is easy to pull off the ink layer. Therefore, the thickness of the undercoat ink layer should be controlled. Generally speaking, The overprinted ink layer should be printed thin enough, and even the dark ink of the background color can be adjusted darker to make the printing ink thinner. It can also meet the quality requirements.

3. Crystallization of ink layer due to too long stacking time interval

Background printed sheets, if placed too long, the ink layer is too dry, will also make gold and silver ink overprint can not be attached, overprinting ink hair, in order to prevent such occurrences, background ink printing and drying to eight 90% can be overprinted.

After the crystallization of the underlying color ink layer, remedial measures should be taken to ensure product quality. The cloth can be used to wipe the underlying ink layer and destroy the crystalline film to enhance the gold and silver ink adhesion ability. Second, add alkaline liquid or 389 resin oil processing industrial soap tablets in gold and silver ink. Thirdly, the pressure on the printing of gold and silver inks should be appropriately increased so that the gold and silver inks will adhere firmly to the background ink.