Printing ink related knowledge training

One of the lithographic inks. It is a general term for metallic inks such as sheet metal (tinplate) printed on offset offset printing presses and wet offset printing, and on processing steel sheets and aluminum sheets.

Printing ink has inner coating and outer coating. External coatings can be divided into printing white ink and roller coating white ink, color ink, varnish and so on.

The main characteristics of the printing ink is the adhesion of the metal sheet, resistance to cooking, baking and baking, solvent resistance, light resistance and good processing (molding, punching, seams, etc.). Dry forms are baking and UV curing. The resin binders and pigments used in printing inks are strictly selected and specially processed to meet the requirements of the printing process and food hygiene requirements.

Iron printing ink is widely used in the printing of food, beverage cans, thermos shells, toys, cosmetics boxes, etc.

Iron printing inks are thermosetting inks that require high temperature drying. The particularity of Indian iron determines the factors that affect the color change of the ink. The following are the main factors affecting the ink color change in tinplate printing:

one. Influencing factors during deployment

1. Inaccurate weighing or uneven mixing during deployment

Ink preparation is to weigh the corresponding amount of the components of the original ink according to the ink ratio, and then put together and stir evenly. At present, electronic scales are commonly used for weighing. When an operator weighs the original ink, the ink color may be inaccurate during printing due to inaccurate weighing or uneven stirring during dispensing, especially when light ink is dispensed. For example, pink, light green, light blue and so on. Light-colored inks are generally prepared by adding a large amount of white ink or diluting agent to the original ink of the corresponding hue, wherein the proportion of the original ink is small, but the color rendering effect in the spot ink is very obvious. If the original ink weight is slightly inaccurate, the hue of the spot ink will be greatly affected.

2. When producing standard color drafts (proofs), the proportion of small batches of spot color inks is inaccurate

In printing iron, the standard color draft used to guide printing is made by proofing. The spot color ink used in the proofing is the small batch of ink dispensed by the operator. After the sample draft is completed, the customer's signature confirmation will become the standard color draft for guiding the printing. Once the customer sign and confirm, the proportion of the spot color ink on the standard color draft shall be based on the proportion when the small batch of ink is prepared at the time of proofing. If the proportion of the ink in the low-volume production is not accurate, the color difference when printing the large-volume ink will be very large, and this difference is especially reflected in the spot ink with a large difference in the ratio of the original ink of each component. For example, yellow: magenta = 100:1, yellow: magenta: cyan = 100:8:0.3, etc. If one or 0.3 of the ink is weighed, the weight is slightly inaccurate. There will be a big change in color.

3. Excessive amount of dilution oil (dipping oil)

Imprinted ink has the characteristics of resistance to mechanical processing, and its performance is characterized by higher viscosity and less fluidity, which is very unfavorable for the transfer of ink during printing. In order to improve the printability, an appropriate amount (less than 5%) of diluent is often added to reduce the ink stickiness while increasing the fluidity. However, the amount of diluent added can not be too much, because after tinplate printing is completed, it should be baked in a 150°C-180°C oven for 10-15 minutes. During the baking process, the thinner and the ink are dried together. If the diluent is added in excessive quantity, the ink is too thin, and the dots will be made ridiculous after baking, and the actual color will be changed accordingly, resulting in a difference between the actual color of printing and the standard color draft.