Five rigid indexes of quality of high-quality domestic offset printing ink

Color density

Color density is the saturation of color. Nowadays, newspapers are no longer the same as black and white, and they have been replaced by graphic illustrations. Therefore, users have higher requirements for the color density of offset printing inks for newspaper printing. Advertisements, pictures, and topics on color newspapers are more eye-catching, so the color density of the ink needs to be relatively increased. However, the color density of many newspaper inks is not ideal now. In order to ensure the printing density, printing companies have to increase the amount of ink, or increase the percentage of dots, but the result of this will inevitably result in piles of ink and increase the amount of ink used. Increasing the amount of ink will also cause the dots to be connected. The normal dot offset increase should be controlled below 25%. If the ink is large, it will cause the loss of gradation and excessive increase of dots, especially the pictures, and the consequences of the increase of dots are more obvious. In addition, the serious problem that occurred in the past few years is the lack of black ink color saturation. It still exists today, but it is no longer a big problem. The reason for the low black ink color density is that the printing factory used black ink with low price and slightly lower quality in order to reduce costs during ordinary text printing. It is precisely because of this demand that naturally some ink factories produce this kind of inferior ink, which affects the overall quality of the ink.

The reasons why domestic inks are not ideal in terms of color density are as follows: First, most ink factories currently do not produce their own pigments, but purchase domestic pigments for grinding. There is still a gap in quality between domestic pigments and imported pigments; Cost saving, using less pigments, resulting in insufficient color saturation of the ink; the key point is that even if the quality and amount of pigments pass, the national standard stipulates that the particle size of the ink should not be greater than 15μm, the finer the grinding, The more vivid the color of the ink. If the pigment processing technology is not good enough, such as grinding particle size is not suitable, the color density of the ink will also be affected. Of course, the level and color of the printed matter are not only related to the ink, but also related to the process conditions such as plate making, printing equipment, and water-ink balance. The quality of the ink is also a prerequisite and guarantee for the improvement of the printing quality.

Overprintability

Newspaper printing has two main requirements for offset ink color registration, one is color sequence, and the other is the gradual change of ink viscosity. At present, the standard color sequence of newspaper printing in the world is cyan-magenta-yellow-black, and its viscosity should be gradually reduced, otherwise the ink will pull back. Now some large ink factories have noticed that the viscosity value of the ink is opened according to the printing color sequence, and they often communicate with the ink supplier to adjust the ink's ink properties in time.

Dryness

The drying speed of the ink usually affects the printing quality, and at the same time it will cause a lot of printing failures, such as causing the back of the printed matter to be dirty, and even causing the web printing to fail to proceed normally. Users generally report that the dryness of domestic inks has a great influence on the quality of printing. Due to the incomplete drying of inks, printing defects and waste products appear. Drying is greatly affected by seasons and climate.

Printability

In modern printing, there are more types of substrates, more types of auxiliary consumables, and the performance difference is also larger. Therefore, the requirements for ink are also more complicated. In general, the company attaches great importance to the printability of inks. In order to ensure the on-press printing suitability of inks and the adaptability of inks to various consumables and substrates, they often keep in touch with several fixed ink suppliers to set their own special requirements. Tell the ink supplier. For example, when printing copperplate paper with ordinary offset ink, the graphics printed on the copperplate paper have bright colors and good gloss; while printing light coated paper with the same ink, the through-printing phenomenon is more serious and the glossiness decreases, but the market seems There is no printing ink specifically suitable for light-coated paper, so it is hoped that ink factories can develop corresponding inks according to different printing materials, especially new materials commonly used now, such as light-coated paper.

In addition, the equipment of the newspaper printing plant is different, and the selected inks are also different.

The printing press is a method of feeding ink, and the performance requirements of the ink are relatively high. At present, the performance of domestic printing inks, such as rheology and viscosity, can not fully meet the requirements. The printing equipment in the ink-out mode also has the problems of scumming and smearing, and the newspapers have relatively high requirements for pictures and headlines. Therefore, the ink factory needs to adjust the relevant performance of the ink according to the actual situation. It can be seen that the printability of offset printing ink needs to be further adjusted. If each user puts forward special requirements, the ink factory may not be able to cope with it.

stability

For printing plants, the stability of ink is also related to print quality. Some companies have used some foreign brand inks produced in China. Although the ink formula is the same as imported products, due to the gap between the production conditions and management level of domestic ink factories and the original ink production factories, the performance of the same brand and model of ink difference. If the same red ink is used and the ink is adjusted in the same proportion, there is obvious color difference.

There is still a big gap between the domestic ink and imported ink in terms of ink coloring, environmental protection and drying speed, and the domestic ink has poor fluidity and high viscosity, and sometimes it is necessary to add an adhesive. The printing plant hopes that the viscosity of the ink can be improved and gradually replace imported high-end, high-priced ink. Newspaper printing requires high viscosity and low viscosity inks with good transfer performance in terms of printing effect, especially the high-speed printing machine has higher requirements for the drying of ink.

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