The bar code is from the United States. T. Woodland first presented in 1949. In recent years, with the continuous popularization of computer applications, the application of barcode has been greatly developed. The bar code can indicate the country of manufacture, manufacturer, product name, date of manufacture, book classification number, mail start and end location, type, date, etc. of the product, and is therefore available in many areas such as commodity distribution, library management, postal and telecommunications management, and banking systems. A wide range of applications. Bar code is a certain length, width and width of the line and the number of symbols, it is a use of ordinary printing methods printed through the photoelectric scanning reading device read computer graphics language. Bar code is a kind of data input technology and automatic identification technology researched and developed in recent decades. It can reflect many kinds of information such as the category of the product, the manufacturer, weight, amount, date of manufacture, and circulation time.
Barcodes are one-dimensional and two-dimensional. Bar code code system more, such as one-dimensional bar code UPC code, EAN code, 39 code, ISBN code. The two-dimensional bar code is developed for the one-dimensional bar code's small capacity of information and the ability to reduce the bar code area and improve resistance to contamination. It differs from the one-dimensional bar code in that text data can also be bar coded, and its data can be applied not only In English, numbers, Chinese characters, symbols, fonts and even blanks can also be handled, information storage up to 1100 numbers (one-dimensional bar code only 15 numbers). In addition, two-dimensional bar code can also use encryption technology, so that the anti-counterfeiting performance of goods is greatly improved.
In addition to conventional barcodes, there are some new types of barcodes, such as:
(1) Invisible bar code. There are three types of invisible barcodes: overlaid invisible barcodes, photochemically processed invisible barcodes, and invisible ink printed invisible barcodes.
(2) Watermark magnetic code. The watermark magnetic code is a binary interval created by the computer after the wet magnetic coating is produced. It is retained in the magnetic oxide after drying, resulting in a unique unchangeable 12-digit number, plus a special magnetic head. Watermark magnetic verification track for reading. The watermark magnetic code can be combined with the hologram to form a holographic magnetic stripe anti-counterfeiting technology, so as to form a better anti-counterfeiting effect.
(3) Metal barcodes. Compared with ordinary bar code, it has the characteristics of no fear of stains on the surface, strong anti-aging ability, and can also be made into invisible bar codes. There are also new two-dimensional metal bar codes.
Barcodes can be printed in various ways such as lithography, letterpress, gravure, screen printing, and non-printing (inkjet). No matter which method is used for printing, the printing quality is required to be good. To sum up, there are mainly the following aspects:
(1) To ensure correct scanning and reading, the printed bar code shall be neat and legible, and there shall be no obvious defects (defects). There shall be no extraneous black spots (blotches) in the space. Usually the maximum diameter of the defect and stain shall be ≤ the narrowest bar code. 0.4 times the nominal.
(2) Controlling the size error of the barcode is to improve the read-first rate of the reading apparatus and reduce the decoding error rate. This will not only improve the quality requirements for plate making, printing or printing, but also increase the tolerance requirements for reading devices.
(3) In order to read reliably, there should be obvious contrast signals between bars and spaces in the bar code after printing. The greater the contrast signal of the bar code, the better the reading performance.
(4) Printing tolerance must be strictly controlled when printing, otherwise it will affect the reading effect.
(5) There is a certain requirement for the edge roughness of the bar code. When the roughness is too large, it cannot be read.
(6) The thickness of bar and empty ink layer in the barcode should generally be controlled within 0.1mm. Otherwise, the correctness of the reading will be affected because the bar and space are on different scanning planes.
Barcode printing quality requirements
Bar code quality directly affects the use of bar codes. Bar codes that fail to meet quality requirements will not only improve management efficiency, but will cause confusion. Although the bar code quality has been improved to some extent in recent years, examples of goods being rejected by supermarkets due to poor bar code quality have also occurred from time to time. Therefore, improving the bar code quality is very important for both manufacturers and sellers.
Bar code printing looks very simple, it does not have complicated patterns and beautiful soft tones, so some companies use their printing requirements is relatively simple, it is not true, because the bar code's empty combination contains specific information, and by the specific reading equipment Reading, therefore, there are strict rules on bar code printing accuracy, color matching, and printing position. details as follows:
1. Empty color match.
When you match the colors, you must ensure that the contrast of the empty colors is large enough. The color of the bar may be: dark blue, dark green, dark brown, black, and the empty colors may be red, orange, yellow, white, of which the black and white are the best, and the true colors of the metal materials (such as gold and silver) are not suitable Or empty color.
2. Printing position
According to different packaging forms, the position of the product bar code should be selected to meet the scanning requirements of the scanning equipment. It should be noted that the bar code should be at least 5 mm away from the edge, overlap, wrinkle, or corner of the package to prevent the bar code from being worn, obscured, or deformed with the package, causing problems during scanning. Such as a company's dried bean curd, its packaging bag barcode identification can not read the real thing in the bag can be read, but the bag is loaded with the real thing, after vacuum packaging, the bar code due to improper position caused wrinkled deformation and can not read . Therefore, the company should judge the bar code printing position based on the actual sales status of the goods.
3. Bar code size
According to the size of the outer package of the product and the area allowed for printing, the bar code amplification factor is selected in the range of 0.8-2.00 times the standard bar code size. (The standard bar code refers to a bar code with a magnification factor of 1.00 and a size of 37.29*26.26 mm).
4. Bar code stripe height
The height of the bar code cannot be shortened in principle. If the position of the bar code must be shortened, the bar code technician should be consulted.
5. Bar code left and right blank area
When scanning the barcode, the scanner must have a low-level reset signal of a certain width to determine the start and end of the scanned barcode. Therefore, left and right blank areas must be sized according to the four corner marks of the film, otherwise the barcode will be difficult or even impossible to be Reading.
6. Printing materials
When printing bar code symbols on transparent materials (such as plastics, glass, etc.), the color of the bar cannot be printed but the background color (empty color) is not printed. Otherwise, the scanner will not be able to read the empty reflection signal. Therefore, the bar code printed on the transparent material must first be preprinted with the background color.
7. Ink requirements
The color matching of the ink should fully consider the color cast of the ink, and the color cast of the ink has a great influence on the accuracy of the barcode. Theoretically speaking, as long as the ink is used according to the color matching ratio, the bar code printing requirement can be satisfied. However, due to the defects of the printing ink in the coloring phase, the color cast occurs. Therefore, the color of the ink should be accurately controlled so that the ink density is uniform, the hue is saturated, and the purity is high. It is preferable to determine whether the reflectance of a certain ink under red light meets the requirements before printing the barcode. The reflective and glossy properties of gold ink can cause specular reflection effects that affect scanner readability and cannot be used to print bar codes. In addition, the concentration of ink and the thickness of the ink layer should also be suitable for bar code printing requirements. Since the bar code printing is a solid printing, the reflection density that the printing can achieve is related to the optical characteristics of the ink and the ink layer thickness. During the printing process, the printed reflection density increases with the increase of the thickness of the ink. When the thickness of the ink reaches a certain value, the density reaches saturation. General ink saturation density requirements: black ink 1.8 ~ 2.0; cyan ink 1.45 ~ 1.70; magenta ink 1.25 ~ 1.50; yellow ink 0.90 ~ 1.05; other special The color ink is 0.8 or more. Due to the difference in the printing process, the thickness of the printed ink layer is also different, generally offset printing is 2 ~ 4μm; embossing printing is 8μm; flexographic printing is 10μm; gravure printing is 12μm; screen printing is 30μm.
8. Substrate requirements
Since the scanning light source is incident at a 45° angle and the collection angle of the reflected light is 15° when the barcode is read, when the reflected light exceeds a range of 15°, the reflected light signal cannot be collected, which is equivalent to a black effect. Therefore, in order to satisfy the bar code scanning feature, substrates are required to have good light scattering properties without specular reflection. Therefore, the white quality, opacity, and gloss of the paper have a certain influence on the reading of the bar code. In addition, consideration should also be given to the selection of materials with good weather resistance, dimensional stability after stress, good colorability, low ink permeability, moderate smoothness, and smoothness.