Corrugated board barcode printing process introduction

Due to the rapid development of computer technology, bar codes, which are the darlings of the information age, show a broader prospect. China joined the International EAN Coding Association in 1991 and in the same year promulgated the national standard for barcodes.

Bar codes are usually printed by a computer or printed by different printing methods. As far as the carton industry is concerned, since hand-engraved rubber plates could not replicate bar codes in the past, users often printed bar code labels through other printing methods, and then put them on cartons for circulation. Now, due to the adoption of corrugated board production lines, water-based printing slotting machines and flexible photosensitive resin plates, the problem of flatness of corrugated paperboard, problems of printing plates, and printing machinery are basically solved, and the necessary prerequisite for the direct printing of bar codes on corrugated cardboard is initially established. .

However, feedback from many provinces and cities indicates that most manufacturers' attempts have not achieved the intended purpose. Mainly in the verification of the bar code printed on the corrugated board, the computer misread (Misread) or read (Nonread). This has caused many industry leaders, business leaders, and printers to attach great importance to it.

In fact, barcodes are a very rigorous system. It is not easy to understand it completely. Of course, as a printer, as long as you have some basic knowledge in this area, and reasonable process arrangements. For the flexible printing of corrugated board, a more reasonable process is: bar code original film→plate making→printing proofing→verification→batch printing.

Original film

The original film (negative film) of the barcode is recommended to be provided by the barcode center to ensure sufficient accuracy. The carton industry generally prints an EAN code, which is a kind of multivariate code. If possible, the bar code can be appropriately enlarged in a range of no more than two times to reduce the difficulty of plate making and printing, and the bar code printing quality can be guaranteed.

Plate making

With high-quality original film, the production of flexible photosensitive plates is not complicated. The film's film surface and the flexible plate should be closely exposed. Before each exposure, the UV film should be cleaned. The ratio of the drug solution should meet the specific gravity requirements. When it is too thick, the fresh drug solution should be replaced. There are many plate types that can be used. For printers who are involved in flexographic printing, DO-PONT Cyrel TDR155 and TDR250 are recommended. For smaller bar codes, DuPont "Silicon" UXL67 or UXL90 can be used for padding. The DuPont plate is recommended because, from the published patent specifications, DuPont's formulas are unique. The most notable feature is that when the plate comes in contact with the liquid, the strength of the DuPont plate decreases slightly, while the strength of the plates of other brands decreases, and it is easy to wash out the graphic. If expensive imported plate-making equipment is used, the choice of plates can be appropriately relaxed.

print

There are many problems in printing. First, because the corrugated board itself is not as smooth as offset paper, the second is the use of dark brown cardboard, kraft paper, third, the domestic water-based ink on the senior sizing paper, poor adhesion fastness, of course, printing technology, The quality of the printers themselves needs to be improved.

Barcode printing thickness difference should be controlled within 0.1mm (refer to the blank, blank area and bar printing thickness difference). Since the water-based printing machine uses an anilox roller transfer ink technology, it can meet the above requirements. Corrugated cardboard face paper should use thicker smooth paper. To prevent collapse deformation. Printing barcodes on corrugated cardboard with dark brown cardboard and kraft paper is difficult to read no matter what color is used. Because the bar code's optical properties such as reflectivity, reflection density, PCS value are regulated. The empty color is too dark and close to the stripe, which will reduce the PCS value and make the barcode difficult to read. In general, the bar color should be dark, and the empty color should be light, avoiding red stripes. Because the bar code scanner light source is generally a helium-neon laser, a semiconductor laser, or an LED, a red light source with a wavelength between 630 and 780 mm. Red light has the highest reflectance and is white. Therefore, printing barcodes with red stripes is not readable and should be noticed.

The safest color for barcodes is black and white. Therefore, it is preferable to use whiteboard as the panel, and the black color is used to satisfy the optical characteristics of the barcode. If you have to print the bar code on brown cardboard, there is no good way. Only print the white bar on the bar code position and then print the black bar color. Direct bar code printing on corrugated board sets new requirements for aqueous inks. In the case of composite printing by a high-speed aqueous printing press, quick-drying performance is required, and in addition, it is necessary to solve the problem of poor adhesion when printed on advanced sizing paper or coated paper. Such problems should be kept in close contact with the ink supplier and the manufacturer, and they should be solved by adjusting the resins and additives.

It is worth mentioning that the flexographic printing due to the softness of the plate may cause deformation under pressure, resulting in widening of the bar code black bars, and because the bar code direction is at a zero degree with the plate cylinder axial direction, the white part of the bar code bar It will be widened, so bar code centers have to narrow the bar codes when making bar code films, which is different from other printing methods. How much is it appropriate to narrow (reduce)? The usual calculation formula is: Percentage reduction (BWR) = K÷R × 100%. In the formula, R refers to the final copy length of the printed product, and the K value is a constant proportion of the composition, which is determined by the thickness of the printing plate.

The different K constants of different thicknesses of the plate: In practice, the height of the graphic relief, the orientation of the printing plate, and the size of the printing pressure have a certain influence on the BWR.

The experimental method is also a common method of flexo printing. That is, a precise scale photo negative film, a flexible version of the system, adjust the pressure after the paste, and then try to print. Then accurately measure and compare the negative and the print, and then calculate the amount of negative reduction. In the whole process of printing barcodes, the original film is provided and the small batch proofing is verified. The help provided by the barcode center is indispensable, and the cartons manufacturing plant must do a good job at the same time. It is not advisable for cartons to make their own films. Although some manufacturers may have Barco, ArtPro, CoreDRAW, and other software to “generate” barcodes, they often lack hardware devices such as power extensions, laser imagesetters, and bar code verification. With the usual printing, scanning, multiple films, there will be errors in the camera, it is best to use the bar code center, because people are professional. Compared with other printing methods, we should understand that printing bar codes directly on corrugated cardboard is a new process. There are many factors that are constrained, such as changes in the softness of plates, rough paper, the state of corrugated cardboard, and the change in printing pressure. And so on, the stability of printing quality is poor, and quality management work is also difficult. However, this is an unavoidable issue for carton manufacturers.

As long as we dare to innovate and dare to accept challenges while holding a rigorous scientific attitude and patience to conduct experiments, the bar code printing quality will gradually stabilize.



Source: China Packaging Li Huanzhang