Barcode performance and use of commodity printing and packaging 2

(3) Requirements for substrates. In terms of optical characteristics, in order to ensure that the scanning light source is incident at 45° and 15°, it is required that the substrate have good light dispersion characteristics. In respect of materials, paper substrates generally have white blanks on the paper itself, and have certain requirements for the whiteness, opacity and gloss of the paper.

The whiteness requirement is to make the paper surface have a better reflective ability; the requirement of opacity is to prevent the incident light from passing through the back of the paper and reduce the light signal, resulting in a decrease in reflectivity; a lower gloss is required to reduce the incident light. Specular reflection effect. For transparent or translucent printing carriers, the same color as the contents (especially the liquid content) of the package should be disabled as the stripe color to prevent the color of the contents from deepening the space color, making the empty color closer to the stripe, and lowering the PCS value.

This problem is often overlooked in practical applications. For example, a white open space, dark blue or dark green bar code is printed on a transparent package of blue or green liquid, and the blue and green contents make the white space pale blue or light green; on black The barcode of the white open space and the black bar is printed on the transparent packaging of the watermelon seeds, and the black content will make the white open space grayish. At this time, the concentration of the white-base printing ink should be deepened so that the color of the contents will not be revealed from the base color, or the color matching may be changed to avoid the occurrence of the above phenomenon.

When there is a conflict between the color of the packaging and decorating design and the color of the bar code design, the bar code design shall prevail and the color of the packaging and decorating design shall be modified. When the carrier leaks light through the color, the following measures should be taken: open up a color with the same space color, large enough, the ink is strong enough to print the bar code; if the bar code is printed on the plastic film seal and the back part of the decoration, should be sealed An opaque interlayer is sandwiched between the two layers to ensure that the color of the backside decoration does not affect the bar code PCS value.

When aluminum foil or other reflective material is used as a carrier, the color of the body can be roughened or the base color of white, yellow and orange red can be blank, and the bar code can be printed in black, dark blue, dark green, or dark brown; the body of the reflective material can also be used. For bar color, printing bar codes with white, yellow, orange, and red blank colors is called reverse printing.

The principle of reverse printing is still based on this color design that satisfies the required reflectance, reflectivity, and PCS values ​​of the bars and spaces. For the dimensional stability requirements of the printing materials, materials with good weather resistance, dimensional stability after stress, good colorability, moderate ink expansion, low permeability, moderate smoothness and smoothness should be selected.

Coated paper, offset paper, whiteboard paper in paper, biaxially oriented polypropylene film in plastic, aluminum foil in metal, and tinplate are good substrates for bar code marking. The corrugated paperboards used in large packagings may not be directly used as substrates, except for large-scale EAN, UPC, and ITF codes because the surface is not sufficiently smooth and the ink permeability is not uniform, which may cause large printing errors. Instead, it uses adhesive printing labels. Non-polar group polypropylene films with poor tinting strength and braids with poor dimensional stability cannot be used as substrates for bar code marks.

(4) The requirements for the ink. In ink color matching, ink color shift should be considered. The color shift of the ink has a great influence on the accuracy of the bar code. In theory, as long as the use of ink in accordance with the color matching can meet the requirements of the bar code, but due to defects in the printing ink impure defects, color cast phenomenon occurs, such as the blue ink due to the wrong absorption of red light, will cause red light The reflectance increases, reducing the PCS value of the barcode. Therefore, the color of the ink should be strictly controlled so that the density of the ink is uniform, the saturation of the hue is high, and the purity is high. It is preferable to determine whether the reflectance of a particular ink under red light meets the requirements before printing a magnetic barcode.

Reflectiveness and gloss of metallic inks (such as gold) can cause specular reflections and cannot be used for bar code printing. Since bar code printing is field printing, the reflection density that can be achieved by printing is related to the optical characteristics of the ink and the ink layer thickness. In the printing process, the reflection density of the printing ink increases with the increase of the ink thickness, and when the ink thickness reaches a certain value The density is saturated, so pay special attention to the ink concentration and ink layer thickness. Different printing processes, the ink layer thickness is quite different, offset is 2 ~ 4μm, embossing 8μm, flexo 10μm, gravure 12μm, screen printing can reach 30μm.

According to the test, the reflective density of printed matter obtained from the above printing types can reach 0.3 or more, and black, cyan, blue, and green colors can absorb all the red light. Therefore, the bar code stripe colors and reflections are printed using the above-mentioned printing methods. The rate can meet the requirements. Barcode printing ink viscosity should not be too large, and in the printing should pay attention to the amount of ink and printing pressure.

The amount of ink supply is large, the substrate cannot be completely absorbed in a short time, and it will spread on the surface of the substrate to reduce the precision; the ink supply is small, the lines are not full or even broken, etc.; the printing pressure is too high, the ink shear stress When it is enlarged, the fluidity also becomes larger. On the other hand, the ink spreads. On the other hand, the printing area between the plate cylinder and the impression cylinder becomes wider, and the bar code symbol width becomes wider. These will affect the accuracy of bar code printing, so according to different printing methods, different ink rheology and ink absorption properties of substrates, adjust the control of ink supply, printing pressure, printing speed and other factors. (Finish)