Bar codes are also called line codes and bar codes. It is a commonly used product packaging label and can be said to be the identity of a product. Through it can reflect a lot of information, so that it plays an important role in the production, sales, storage and inspection and exchange of goods. Bar codes are widely used in trademarks, packaging, books, and other products to become a link for communication. Therefore, understanding and mastering the bar code printing, using a number of process technologies, and improving the bar code printing quality are of great significance.
Bar code structure and reading principle
The bar code is a set of symbols with different widths and widths, black and white parallel lines combined with a specific format and spacing, usually printed on the goods or printed matter, can replace a variety of text information, and can read through the photoelectric reading device, read at any time Take data. The EAN bar code system consists of barcode symbols themselves, bar code reading, interfaces, and computers to complete the input and output of commodity information. There are two types of symbols for bar code reading. Bar code symbols are rectangular line patterns. The information reading system of an optical scanner mainly reads and recognizes these bar code symbols. The digital 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 from 8 to 16 digits. The code system has different 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 two ends of the reading end-reading, and some still have numbers printed under the lines, which can be directly identified or read by an optical reader, and thus can also count, count, and manage commodities.
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 that people communicate with the computer. Black and white thickness and white line symbol in bar code, thick black line as 1 in the computer, fine black lines represent 0, through logic conversion, can be expressed as 0-9 Arabic numerals and arrays, therefore, 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 when the scanning light spot sweeps onto the white paper surface or between the two black lines. In the 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, the detector outputs a small current, and according to the width or width of the black line, the response is made with different lengths of time. The change of the bar code's light and dark turns into a small, different current signal, which is amplified and sent to the coder. The decoder translates the signal into data, performs local inspection and display, and connects with the keyboard and sends it to the computer for data processing. How the bar code print quality relates to the ability to read the problem properly. Therefore, the ink is uniform, the layout is not dirty, the lines are clear without breaking, and it is the basic quality requirement for bar code printing.
Barcode printing and its problems
There are two kinds of bar code printing methods, one is the use of printing equipment for bulk printing and copying, is a commercial bar code label production, this way generally bar code and graphics together imposition and printing. The other is controlled by a computer and prints bar code labels and bar code files in due course. 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 design 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 is appropriately reduced in making a plate to compensate for the deviation caused by the distortion in printing. For the printing of heat-shrinkable packaging materials, 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 layout can be adjusted according to the shrinkage factor at the time of plate making.
In order to facilitate the normal reading during use, attention should be paid to the selection of barcode printing ink. Bar code reading system, set the scanner light source is generally a red light source with a wavelength of 630 ~ 700mm, 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 resulting reflection effects are also different. Black ink can be completely absorbed by red light. The reflectance of incident light on printed materials is generally below 3%. Therefore, most bar codes are designed to use black ink colors for printing. The white ink is totally reflective to red light, and its reflectance to 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 directly on white paper.
However, some packaging products, from the design and process effects, also have the option to use other colors for printing, so pay attention to match the nature of the color. In general, red, yellow, orange, red, light brown, and the like have high reflectance of red light, while green, black, violet, and cyan 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 or orange red as the substrate. Then, dark bar codes, such as black, dark green, and dark blue, should be printed so that they can be easily read and used. .