Bar codes are also called line codes and barcodes. It is a general merchandise packaging label and can be said to be the identity of a product. Through it can reflect a lot of information, played an important role in the production of goods, sales, storage and inspection and communication information. Bar codes are widely used in trademarks, packaging, books, and other products to become a link for communication. In addition, it is of great significance to understand and master some knowledge of bar code printing and use and improve the printing quality of bar codes. 
First, the structure of the bar code and reading principle
æ¡å½¢ç Bar code is a set of symbols with different width and width, black and white parallel lines in accordance with a specific format and spacing, usually printed on goods or printed matter, can replace various text information, and can be read at any time through a photoelectric reading device. Take data. The EAN barcode system consists of a bar code symbol itself, a barcode reading device, an interface, and a computer, which completes the input and output of commodity information. There are two kinds of barcode reading symbols, bar code symbol for the rectangular line graphics, optical scanners to read the main information is to read and identify these bar code symbols. Digital symbols are numbers and letters outside the line, including 0 to 9 digits, A to Z letters, which can be directly recognized by the naked eye, generally from 8 bits to 16 bits, with different code systems and different numbers of digits. The arrangement, width, and number of lines of the bar code are stipulated by each manufacturer and determine the meaning of the code. Generally, there are marks at the beginning and end of reading on both ends, and some are printed on the underside of the line, which can be directly identified or interpreted by an optical character reader, and thus can also count, count, and manage products.
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The reading performance of the barcode system, that is to say whether the barcode system can be used normally depends on the reading ability of the system and the printing quality of the barcode. Bar code, as a kind of coded information, is a specific language for people and computers to communicate with each other. Black and white line thickness in the bar code symbol, thick black lines in the computer as 1, thin black lines 0, through the logic conversion, can be expressed as 0-9 Arabic numerals and arrays, so there must be a reading device Use it together to read. The reading system mainly includes a scanner and a decoder. The scanner is a part that directly contacts the bar code reading signal. It consists of a light emitter, a photo detector, and an optical lens. It can read the information abbreviated by the bar code at an extremely fast speed. During scanning, when the light beam emitted from the light emitter shines on the bar code, the photo detector responds according to the light intensity of the light beam reflected from the bar code, and scans the light spot to the white paper surface or the two black lines. When there is a gap between the two, the reflected light is strong and the detector outputs a large current; when scanning into a black line, the reflected light is weak, the detector outputs a small current, and according to the width of the black line, a response of different lengths of time is made, along with the bar code The light and dark changes into current signals of different sizes, which are amplified and sent to the decoder. The signal is translated into data by the decoder, local inspection and display, and connected to the keyboard and sent to the computer for data processing. Therefore, the bar code printing quality is related to the ability to read normally. The ink is uniform and uniform, the layout is not dirty, the lines are clear without breaking, and it is the basic quality requirement for bar code printing.
Second, the bar code printing and should pay attention to the problem
There are two kinds of bar code printing methods. First, the use of printing equipment for bulk printing and copying, is a commercial bar code label production, this way generally bar code and pattern together imposition printing. The second is computer-controlled printing of bar code labels and bar code files. The former applies to a large number of barcodes with the same specifications and the same content, and is designed and printed at the same time as the packaging graphic. The latter can be controlled by computers, real-time printing as required, with greater flexibility. Bar code printing devices include inkjet printers, thermal printers, thermal transfer printers, impact dot matrix printers, and laser printers. In order to ensure that the printed bar code 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, it is considered that the line width can be appropriately reduced when making a plate, so as to compensate for the expanded deviation in printing. For the printed heat-shrinkable packaging material, the position of the barcode after shrinking the film should be considered, and the vertical and horizontal shrinkage factors should be calculated in advance so that the adjustment can be made during the plate making.

In order to facilitate normal reading, attention should be paid to the color matching of barcodes. Bar code reading system, set the scanner light source is generally a red light source with a wavelength of 630 ~ 700nm, it should consider the red effect of ink. The scanner's incident light shines on the surface of the bar code of different materials and colors, and the reflected effect is also different. Black ink is completely absorbed by red light, and the reflectance of incident light on printed materials is generally below 3%. Therefore, most bar codes are designed to be printed with black ink. The white ink is completely reflective to red light, and its reflectance of incident light is close to 100%. Therefore, it is the ideal blank color. For the above reasons, most of the bar codes on printed products are printed on white paper. However, some packaging products, starting from the decorative effect, there are other colors to choose, so you should pay attention to match the nature of the color. Usually, red, yellow, orange, red, and brown are the colors with high red reflectivity. The black, green, purple, and cyan colors have low reflectance to red light. Reasonably designing the bar code printing color should fully consider the factors such as the reflectivity of the red light. Transparent film packaging is not suitable for direct printing of bar codes. It should be printed with white ink or yellow, orange red as the substrate, and then printed with a dark bar code, such as black, dark green, dark blue, etc., which is easy to read and use. 
First, the structure of the bar code and reading principle
æ¡å½¢ç Bar code is a set of symbols with different width and width, black and white parallel lines in accordance with a specific format and spacing, usually printed on goods or printed matter, can replace various text information, and can be read at any time through a photoelectric reading device. Take data. The EAN barcode system consists of a bar code symbol itself, a barcode reading device, an interface, and a computer, which completes the input and output of commodity information. There are two kinds of barcode reading symbols, bar code symbol for the rectangular line graphics, optical scanners to read the main information is to read and identify these bar code symbols. Digital symbols are numbers and letters outside the line, including 0 to 9 digits, A to Z letters, which can be directly recognized by the naked eye, generally from 8 bits to 16 bits, with different code systems and different numbers of digits. The arrangement, width, and number of lines of the bar code are stipulated by each manufacturer and determine the meaning of the code. Generally, there are marks at the beginning and end of reading on both ends, and some are printed on the underside of the line, which can be directly identified or interpreted by an optical character reader, and thus can also count, count, and manage products.

The reading performance of the barcode system, that is to say whether the barcode system can be used normally depends on the reading ability of the system and the printing quality of the barcode. Bar code, as a kind of coded information, is a specific language for people and computers to communicate with each other. Black and white line thickness in the bar code symbol, thick black lines in the computer as 1, thin black lines 0, through the logic conversion, can be expressed as 0-9 Arabic numerals and arrays, so there must be a reading device Use it together to read. The reading system mainly includes a scanner and a decoder. The scanner is a part that directly contacts the bar code reading signal. It consists of a light emitter, a photo detector, and an optical lens. It can read the information abbreviated by the bar code at an extremely fast speed. During scanning, when the light beam emitted from the light emitter shines on the bar code, the photo detector responds according to the light intensity of the light beam reflected from the bar code, and scans the light spot to the white paper surface or the two black lines. When there is a gap between the two, the reflected light is strong and the detector outputs a large current; when scanning into a black line, the reflected light is weak, the detector outputs a small current, and according to the width of the black line, a response of different lengths of time is made, along with the bar code The light and dark changes into current signals of different sizes, which are amplified and sent to the decoder. The signal is translated into data by the decoder, local inspection and display, and connected to the keyboard and sent to the computer for data processing. Therefore, the bar code printing quality is related to the ability to read normally. The ink is uniform and uniform, the layout is not dirty, the lines are clear without breaking, and it is the basic quality requirement for bar code printing.
Second, the bar code printing and should pay attention to the problem
There are two kinds of bar code printing methods. First, the use of printing equipment for bulk printing and copying, is a commercial bar code label production, this way generally bar code and pattern together imposition printing. The second is computer-controlled printing of bar code labels and bar code files. The former applies to a large number of barcodes with the same specifications and the same content, and is designed and printed at the same time as the packaging graphic. The latter can be controlled by computers, real-time printing as required, with greater flexibility. Bar code printing devices include inkjet printers, thermal printers, thermal transfer printers, impact dot matrix printers, and laser printers. In order to ensure that the printed bar code 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, it is considered that the line width can be appropriately reduced when making a plate, so as to compensate for the expanded deviation in printing. For the printed heat-shrinkable packaging material, the position of the barcode after shrinking the film should be considered, and the vertical and horizontal shrinkage factors should be calculated in advance so that the adjustment can be made during the plate making.

In order to facilitate normal reading, attention should be paid to the color matching of barcodes. Bar code reading system, set the scanner light source is generally a red light source with a wavelength of 630 ~ 700nm, it should consider the red effect of ink. The scanner's incident light shines on the surface of the bar code of different materials and colors, and the reflected effect is also different. Black ink is completely absorbed by red light, and the reflectance of incident light on printed materials is generally below 3%. Therefore, most bar codes are designed to be printed with black ink. The white ink is completely reflective to red light, and its reflectance of incident light is close to 100%. Therefore, it is the ideal blank color. For the above reasons, most of the bar codes on printed products are printed on white paper. However, some packaging products, starting from the decorative effect, there are other colors to choose, so you should pay attention to match the nature of the color. Usually, red, yellow, orange, red, and brown are the colors with high red reflectivity. The black, green, purple, and cyan colors have low reflectance to red light. Reasonably designing the bar code printing color should fully consider the factors such as the reflectivity of the red light. Transparent film packaging is not suitable for direct printing of bar codes. It should be printed with white ink or yellow, orange red as the substrate, and then printed with a dark bar code, such as black, dark green, dark blue, etc., which is easy to read and use. 
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