Bar code is also called line code and bar code, it is a general product packaging label, can be said to be the product's ID card. It can reflect a lot of information through it, and plays an important role in the production, sales, storage, inspection and communication of commodities. Bar codes are widely used in products such as trademarks, packaging, books and periodicals, and become a link for communication. In addition, it is of great significance to understand and master some knowledge of barcode printing and use, and to improve the printing quality of barcode. ?
1. Barcode structure and reading principle
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A bar code is a symbol composed of a set of parallel lines of different widths, black and white, and a combination of specific formats and spacings. It is usually printed on commodities or printed products. It can replace various text information and can be read at any time by a photoelectric readout device. data. The EAN barcode system consists of the barcode symbol itself, the barcode reading device, the interface, and the computer, and completes the input and output of commodity information. There are two types of barcode reading symbols. The barcode symbols are rectangular line graphics. The information reading of the optical scanner is mainly to read and recognize these barcode symbols. Numeric symbols are numbers and letters outside the line, including 0-9 digits, A-Z letters, which can be directly recognized by the naked eye, generally 8 to 16 digits, different code systems, and different digits. The arrangement, width and number of barcode lines are stipulated by each user, and determine the meaning of the code. Generally, there are marks for the first reading and the last reading at both ends, and some are also printed with numbers under the line, which can be directly recognized or interpreted by an optical text reader, so that they can also perform commodity counting, statistics and management. ?
What is the reading performance of the bar code system, that is to say whether the bar code system can be used normally, mainly depends on the reading ability of the system and the printing quality of the bar code. Barcode as a kind of coding information, it is a specific language for communication between human and computer. The black and white line symbol in the bar code, the thick black line is regarded as 1 in the computer, the thin black line represents 0, through the logic conversion, it can be expressed as Arabic numbers and arrays from 0 to 9, so there must be a reading device It can be read only when used together. The reading system mainly includes a scanner and a decoder. The scanner is a component that directly contacts the barcode to read the signal. It consists of a light emitter, a photodetector, and an optical lens. It can read the information abbreviated by the barcode at a very fast speed. When scanning, when the light beam emitted from the light emitter shines on the bar code, the photodetector responds according to the light intensity of the light beam reflected from the bar code. When the scanning light spot sweeps onto the white paper surface or is between two black lines When there is a blank space, the reflected light is strong, and the detector outputs a large current; when scanning into a black line, the reflected light is weak, and the detector outputs a small current, and responds differently according to the length of the black line. The change of light and dark changes into current signals of different sizes, which are amplified and sent to the decoder. Translate the signal into data through the decoder, perform local inspection and display, and connect with the keyboard and send it to the electronic computer for data processing. Therefore, the printing quality of the barcode is related to whether it can be read normally. The ink color is uniform and consistent, the layout is not dirty and not blurred, and the lines are clear and unbroken, which is the basic quality requirement for bar code printing.
Second, the printing method of the bar code and the problems that should be paid attention to?
There are two ways to print bar codes. One is the use of printing equipment for batch printing and copying, which belongs to commercial bar code label production. This method generally imprints the bar code and the pattern together. Second, it is controlled by the computer and prints barcode labels and barcode files in a timely manner. The former is suitable for bar codes with a large number, fixed specifications, and the same content. It is designed and printed at the same time as the outer packaging graphics. The latter can be controlled by the computer, real-time printing as required, with greater flexibility. Barcode printing equipment includes inkjet printers, thermal printers, thermal transfer printers, impact dot matrix printers, and laser printers. In order to ensure that the printed barcode meets the specifications, the plate-making process should be considered according to the printing process and the characteristics of the substrate. For example, in the flexographic printing process, appropriate reduction in line width may be considered during plate making to compensate for the widening deviation in printing. For printing heat shrinkable packaging materials, the position of the barcode after the film shrinks should be considered, and the vertical and horizontal shrinkage multiples should be calculated in advance in order to adjust it during plate making. ?
In order to facilitate the normal reading when using, pay attention to the color matching of the barcode. For the barcode reading system, the scanner light source is generally a red light source with a wavelength of 630-700nm, so the red light effect of the ink color should be considered. The incident light of the scanner irradiates the bar code surface of different materials and colors, and the reflection effect is also different. Black ink can completely absorb red light, and the reflectivity of printed products to incident light is generally below 3%, so most bar codes are designed to be printed with black ink. White ink is completely reflective of red light, and the reflectivity of its printed matter to incident light is close to 100%, so it is the most ideal blank color. For the above reasons, most barcodes on printed products are printed on white paper. However, some packaging products, from the decorative effect, also choose other color combinations, so you should pay attention to the color matching. Generally, the colors with high reflectivity to red light include yellow, orange, red, and light brown. And black, green, purple, cyan, etc., have lower reflectivity to red light. Reasonable design of bar code printing color should fully consider the factors such as the reflectivity of the color to red light. Transparent film packaging is not suitable for direct printing of bar codes. It should be printed with white ink or yellow, orange and red as the substrate, and then printed with dark bar codes, such as black, dark green, dark blue, etc., so that it is easy to read and use. ?
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