How to Control the Consistency of A5 Self Adhesive Labels Printing Colors

How to Control the Consistency of A5 Self Adhesive Labels Printing Colors

In the daily production process, how to maintain the consistency of label printing color has always been a difficult problem for production operators. Many label printing companies have been complained or even returned by customers because of the color difference of label products. So, how to control the consistency of product color in the label production process? The author will discuss with you from the following aspects.

(1) Establish a reasonable color management system

We know that it is impossible to completely avoid chromatic aberration in printed matter. The key to the problem is how to control chromatic aberration within a reasonable range. Then, the first step for label printing enterprises to control the color consistency of label products is to establish a sound and reasonable color management system, so that operators can understand the scope of qualified products. Specifically, there are the following points.

1. Clarify the upper and lower limits of product color

When we produce a label product for the first time, we should formulate the upper limit, standard and lower limit of the color of the label product, which will be designated as "proof sheet" after confirmation by the customer. In the future production, based on the standard color of the proof sheet, it is strictly stipulated that the color fluctuation cannot exceed the upper and lower limits. In this way, while ensuring the color consistency of the label product, it can also give the production personnel a reasonable color fluctuation range, and also make the product The color standard is more operational.

2. Improve the system of signature, inspection and random inspection of the first and last parts

If you want to further ensure the implementation of the color standard, the inspection items of the color of the label products should be added to the sample signature system of the first and last parts of the label products, so that the production management personnel can control the color difference of the label products, and the unsuitable label products will not be passed the inspection. . At the same time, patrol inspection and random inspection are strengthened to ensure that label products exceeding the reasonable range of color difference can be found and processed in time during the production process of label product printing.

(2) Printing standard light source is very important

According to the author's understanding, many label printing companies do not use standard lighting sources for printing, which poses a hidden danger to the color consistency control of label products. Many label printing companies use lighting sources to see colors that are very different from those seen in daylight during the night shift, resulting in differences in printed colors. Therefore, it is recommended that the majority of label printing enterprises must use the printing standard lighting source for lighting, and the qualified enterprises also need to be equipped with a standard light source box, so that employees can compare the color of label products under the standard light source. This can effectively avoid the problem of color difference of printed products caused by non-standard lighting sources.

(3) Ink problems will cause color difference

The author has also encountered such a situation: after the label product is placed at the customer's place for a period of time, the color of the ink gradually changes (mainly fading), but the same phenomenon did not occur in the previous batches of products. This is generally caused by the use of expired ink. The shelf life of ordinary UV ink is usually one year, and the use of expired ink is prone to fading of label products. Therefore, label printing companies must pay attention to the use of inks produced by regular manufacturers when using UV inks. At the same time, they should pay attention to the shelf life of the inks and update the inventory in time to avoid using expired inks. In addition, pay attention to the amount of ink additives used in the printing production process. If the ink additives are used in excess, the color of the ink after printing may also change. Therefore, when using various ink additives, it is best to communicate with the ink supplier first, and then determine the correct ratio range of the additives.

(4) Color consistency of spot color ink

In the production process of label printing, it is often necessary to prepare spot color inks, and many label printing companies are far from the color of the samples when preparing spot color inks. The main reason for this situation is that the ink ratio is not correct. Spot color inks are prepared from a variety of primary color inks, and most UV inks are Pantone (PANTONE) color systems, so when we formulate spot color inks, we often formulate according to the ratio given on the Pantone color card. However, it should be pointed out here that the ink ratio on the Pantone color chart is not necessarily completely accurate, and there are often small differences. At this time, there are certain requirements for the experience of the printing staff, because the sensitivity of the printing staff to the ink color is very important. Printing staff should learn more and practice more, and accumulate experience in this area in order to achieve the level of proficiency. What I want to remind everyone here is that not all inks are based on the Pantone color system. When encountering non-Pantone color inks, the ratio on the Pantone color card cannot be used, otherwise it will be difficult to formulate the required s color.

In addition, many label printing companies are currently equipped with electronic scales to ensure the accuracy of the ink ratio. This behavior is worth promoting. Standardization is one of the important measures for the progress of industrial production. For the spot color ink prepared for the first time, the operator should record its ink ratio on the process card, so as to provide a data basis for the next preparation of the spot color ink, and at the same time, it can also ensure that different shifts and different operators can prepare the spot color ink. Color consistency.

(5) Prepress plate making and color consistency

Many label printing companies have encountered such a situation: the color of the label products printed by themselves when chasing samples is far from the color of the samples provided by customers. Most of these problems are caused by the unequal dot density and size on the printing plate and the dot density and size on the sample. In this case, I recommend the following steps to improve. First of all, it is very important to measure the number of screen lines of the sample with a special screen ruler to confirm that the number of screen lines of the printing plate is consistent with the number of screen lines of the sample. Secondly, observe through a magnifying glass whether the dot size of each color printing plate is consistent with the dot size of the corresponding color of the sample. If it is inconsistent, it needs to be adjusted to the same or approximate size. It should be noted here that because the dots after printing will expand, the dot size set during plate making is slightly smaller than the dots on the sample. Finally, observe whether the hue of the printing ink is consistent with the color of the sample ink. Under normal circumstances, if the above three items can be achieved, the color of the printed label product is basically the same as that of the customer's sample, and the difference will not be too large.

(6) Anilox roller parameters in flexo printing are related to color consistency

When many label printing companies use flexo printing equipment to print labels, this situation has occurred: when chasing the color of the sample provided by the customer, it cannot reach the same or close to the color of the sample. Its size and density are very close to customer samples, and the hue of the ink used is similar. So what is the cause of the chromatic aberration?

The color of flexo label products is not only affected by the ink hue, dot size and density, but also by the number of mesh lines and the depth of the mesh of the anilox roller. In general, the ratio of the number of screen lines of the anilox roll to the number of screen lines of the printing plate is 3:1 or 4:1. Therefore, when using flexo printing equipment to print label products, in order to keep the color close to the sample, in addition to paying attention to the size and density of the dots in the plate making process as much as possible to be consistent with the sample, also pay attention to the number of screen lines of the anilox roller and the depth of the cells. , by adjusting these parameters to achieve the effect that the color of the label product is close to that of the sample. Of course, flexo printing also has unique advantages in color consistency control, that is, its short ink path and metered ink feeding method. Once these parameters are determined, the color of the same label for each batch produced in the future will be basically the same.

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