In our daily life, bags must be used frequently. When we go to the supermarket to buy something, we usually use composite soft bags. Sometimes I don't know what to buy. I may see that the package is good. So there are all kinds of colorful bags. Uniform ink color, bright and pure color are the basic requirements of packaging product quality, and printing color difference is a common problem of printing product quality. In the end, how to produce color difference in printing, specific analysis, in order to suit the case.

1、 Printing color difference caused by pressure discomfort
The ideal printing process is based on the "three levels", so that a thin ink layer can balance the printing pressure to obtain a more uniform ink color. When the printing pressure is insufficient or uneven, and there is poor contact between the liner and the plate surface, it is necessary to increase the amount of ink input to meet the visual effect of page inking. However, this will not only increase the consumption of ink, but also easily lead to color difference and sticky quality problems.
2、 Printing color difference caused by poor ink roller
There are three kinds of rollers on the ink transfer roller, which have a greater impact on the ink transfer roller and ink roller. The elasticity, viscosity, centrality, hardness and surface finish of the ink roller largely determine the ink quality. If there are some problems such as poor elasticity, insufficient viscosity, eccentric roller body, super hard colloid and poor colloid finish, uneven or unstable ink brushing will be easily caused in printing process, resulting in inconsistent ink color of each printing sheet.
3、 Printing color difference caused by poor ink feeding device
When the centrality of the iron roller is poor or there is wear and deformation, the steel plate of the ink holder also suffers from wear and deformation, and the mechanism controlling the rotation of the ink holder roller has defects, which makes the ink output unstable in the printing process, and also causes the color difference of printing. In addition, attention should be paid to the reasonable ink feeding device. There are two ways to adjust the ink in the ink hopper, one is to adjust the gap between the ink hopper steel sheet and the ink (ink feeding) iron roller; the other is to adjust the rotation radian of the ink transfer iron roller.
4、 Printing color difference caused by poor fountain
If the lithography process is not suitable to run the plate, it is also prone to color difference. In addition, if the water roll sleeve aging or adsorption ink, impurities, will affect the water roller water absorption and the uniform transmission of fountain solution. Moreover, if the water bucket device leakage phenomenon, it will also affect the uniform transmission of moisture in the printing plate. The existence of these undesirable conditions will destroy the uniform and stable transfer of printing ink, and make the ink color difference.
5、 Printing color difference caused by poor ink
Printing ink layer thickness and viscosity is not suitable, easy to produce color difference. In printing, only with moderate and uniform ink layer can the ink quality of the printed matter be guaranteed and the printing smudging fault can be effectively prevented.
6、 Color difference caused by poor substrate material
In the daily printing process, we can find that the substrate material difference is also one of the causes of printing color difference, such as the substrate gloss and hue difference, will produce printing color difference problem. Taking embossed aluminized paper as an example, the color difference of aluminized paper surface will result in inconsistent color development effect.
7、 Printing color difference caused by poor machine
Sharp tools make good work. To maintain the good performance of the machine is a reliable guarantee to improve the quality of printing ink. However, if there are bad conditions in the machine, it is easy to cause the color difference problem. Therefore, usually should pay attention to do a good job in the maintenance of equipment, to pay attention to the lubrication of key parts of the machine.
8、 Color difference caused by poor printing plate
The printing plate is one of the basic elements of image and text reproduction quality. In the printing process, the printing plate must be kept stable without deformation and abrasion, so as to ensure the stability of ink transmission. In the process of printing, if the dot layout is distorted due to paste or abrasion, and the lines are worn and enlarged, the ink color of the printed matter will inevitably be deviated due to the change of the amount of ink absorbed by the page.
9、 Different light source characteristics and different viewing angles on the color difference of printed matter
Generally, the light source for identifying ink color of printed matter mainly includes sunlight (natural light), fluorescent lamp and incandescent lamp. If the sunlight is alcohol white, the color of the light emitted is relatively accurate. The light of fluorescent lamp is blue in white, similar to sunlight. But the incandescent lamp's light has the partial yellow color in the red, therefore, it is difficult to accurately identify the color. Although sunlight and fluorescent lamp are similar, the difference between them should be considered when identifying high quality color products.