Problems needing attention in the printing process

Problems that should be paid attention to in the process of bar code printing

bar code technology has developed for more than 50 years. It has the advantages of fast, accurate, strong reliability, low cost and so on. At present, it has become one of the important information technologies in modern society and plays a huge role in the field of commodity circulation. In recent years, most of the businesses undertaken by packaging and printing enterprises require the printing of bar codes, such as the packaging of food, beverages, cigarettes, alcohol, daily chemical washing products, books and periodicals, drugs, textiles, etc. The printing of bar codes involves many links, all of which have a direct impact on the increasingly extensive use of new green plastic materials for bar codes in the construction market, quality and readability, so we must pay attention to them. Here are some problems that should be paid attention to in the process of bar code printing

I. reading principle of bar code

bar code is a mark composed of a group of regularly arranged bars, spaces and corresponding characters. Bars refer to the part with low reflectivity to light, and spaces refer to the part with high reflectivity to light. The data composed of these bars and spaces express certain information, Moreover, another core element that can determine the industry with specific scanning equipment is that materials technology equipment can read and input data

the bar code is read by irradiating the bar and the space with light and producing different reflectivity (that is, the contrast between the bar and the space ensures the degree within the full range of the experimental force). Here we need to briefly introduce the bar space printing contrast (PCS) of bar code

first of all, conceptually, printcontractsignal (PCS) refers to the ratio of the difference between the reflectance of the bar code and the reflectance of the bar code. It is one of the optical indicators to measure the bar code symbol. The calculation formula of barcode PCs is as follows:

PCs = (RL － RD)/RL 100%

where RL is the reflectivity of empty and RD is the reflectivity of bar. The lower the reflectivity RL of the strip, the better, and the higher the reflectivity RD of the empty strip. The larger the PCs value of the bar code, the better the optical characteristics of the bar code and the higher the reading rate. Generally speaking, when the PCs value of the barcode is within the range of 67% - 98%, it can be correctly read by the barcode scanning equipment

II. Basic quality requirements of bar code

first, from the perspective of appearance, the surface of bar code is required to be clean and tidy, without obvious dirt, wrinkles, or damage; The ink color is uniform, without obvious deinking, stains and broken lines; The edge of the strip is neat without obvious bending deformation; Numbers, letters and special symbols are printed completely and clearly

secondly, the PCs value of bar code, symbol defect, dimensional error of bar code symbol, printing tolerance, edge roughness, ink layer thickness and other quality indicators are specified in many national standards, which will not be described in detail here

III. problems that should be paid attention to in the process of bar code design

1. color matching of bar code

according to the reading principle of bar code, there are certain principles for the color selection of bar code. When designing bar codes, we should consider the reflectivity of bar and empty bar, try to improve the printing contrast (PCS value) of bar and empty bar, and ensure the identifiability and readability of bar codes

according to the optical principle, the reflectivity of different colors to light is also different. Generally speaking, the reflectivity of light colors to light is relatively high, while the reflectivity of dark colors to light is relatively low (most of them are absorbed). Therefore, we can consider taking light colors such as white, yellow, orange and red as the empty color of the bar code and dark colors such as black, blue, brown and green as the bar color of the bar code. Because black does not reflect visible light of various wavelengths, while white can reflect light of various wavelengths back, the black bar code with white space is the easiest to read. However, it is worth noting that most bar code scanning equipment adopts a red light source with a wavelength of 630 ~ 700um. Therefore, red should be avoided as a bar code line when designing bar codes

the following table lists the color matching and availability of bar code bar and blank, which can be used as a reference when designing bar codes

when the color of the bar code conflicts with the bottom color of the pattern, the bottom color can be hollowed out first, and then the bar code can be printed, otherwise the color contrast between the bar and the empty is too small, which will make the scanner unable to read the bar code. For example, the data generated in the process of design and production of each set of die head cannot be directly integrated into the system. The bar code should be printed on the dark blue, dark green and dark brown background colors. The background color below the bar code should be hollowed out, and a white background (or white should be printed first) should be created to print the bar code, so as to ensure the legibility of the bar code

in addition, if the substrate material department adopts aluminized paper, aluminized film, gold and silver paperboard or transparent plastic film, it is usually to use white ink on the surface of the substrate material first, and then print the bar code (i.e. anti white printing)

2. Size of bar code

the printing size of bar code depends on the area of printing label paper or package that can accommodate bar code and specific printing conditions. Bar code is unique, so the proportion of bar code cannot be changed or reduced at will when making and printing bar code. As long as conditions permit, the standard size (original size) of bar code should be selected as far as possible. If you want to enlarge or reduce the bar code, the scaling ratio is generally controlled between 80% and 200%, and the bar width of the bar code should be appropriately corrected while scaling the bar code. In the actual production process, some small package product designs (such as cigarette labels) may be encountered. If there is not enough place to place the barcode, the height of the barcode can be appropriately shortened, but the remaining height is required to be no less than 2/3 of the original height