There are two ways to print bar code. One is to use printing equipment for batch printing and copying, which belongs to commercial bar code label production. In this way, bar code and pattern are generally printed together. The second is to print bar code label and bar code file timely under the control of computer. The former is suitable for the design and printing of barcode with large quantity, fixed specifications and the same content at the same time as the graphic of outer package. The latter can be controlled by computer to realize instant printing according to requirements, with strong flexibility. Barcode printing equipment includes inkjet printer, thermal printer, thermal transfer printer, impact dot matrix printer and laser printer. In order to ensure that the bar code after printing meets the specification requirements, plate making process should be considered according to the characteristics of printing process and substrate. For example, flexographic printing process, in plate making can consider appropriate reduction of line width, in order to make up for the printing deviation. For printing heat shrinkable packaging materials, it is necessary to consider the position of the bar code after the film shrinks, and calculate the longitudinal and transverse shrinkage ratio in advance, so as to adjust it during plate making.
In order to make it easy to read, we should pay attention to the color matching of bar code. In the bar code reading system, the scanner light source is generally a red light source with wavelength of 630-700nm, so the red light effect of ink color should be considered. When the incident light of the scanner irradiates the bar code surface of different materials and colors, the reflection effect is also different. Black ink can completely absorb red light, and the reflectivity of the printed matter to the incident light is generally below 3%. Therefore, most bar codes are designed to be printed with black ink. And white ink for red light is completely reflective, its print reflectivity of incident light is close to 100%, so it is the most ideal blank color. Based on the above reasons, most of the barcodes on printed products are printed on white paper. But some packaging products, starting from the decorative effect, also choose other colors, so we should pay attention to match according to the nature of color. Generally, the colors with high red reflectance are yellow, orange, red, light brown, etc. Black, green, purple, cyan and so on have low reflectance to red light. In order to design the printing color of bar code reasonably, we should fully consider the red light reflectance and other factors. Transparent film packaging is not suitable for direct printing bar code, should be printed with white ink or yellow, orange red as the substrate, and then printed with dark bar code, such as black, dark green, dark blue, etc., so that it is easy to read and use.