Another problem is that the printing needs to transfer ink to the substrate with a certain pressure. In order to make the corrugated paper surface completely printable relative to the corrugation trough, the printing pressure must be higher than the printing pressure required for the smooth surface material, which inevitably generates a greater pressure at the crest of the micro-corrugated cardboard. , resulting in a decrease in the strength of the fine corrugated cardboard.
In order to solve the above problems, a special rubber blanket was developed. The elasticity of the blanket was smooth. Therefore, even if a large amount of pressure is applied during printing, the pressure at the crest of the paperboard will not be greatly increased. This avoids the damage of the fine corrugated cardboard and ensures that the overprinting accuracy and the fine corrugated cardboard stacking are smooth. The emergence of such blankets has greatly promoted the development of direct offset printing of fine corrugated board.
One of the most important conditions for the direct offset printing of fine corrugated board is to optimize the ink so that the effect of the washboard is minimized. The development of the blanket is mainly for the printing of fine corrugated cardboard, compensating the change in the printing pressure between the back and the groove of the fine corrugated cardboard by its high compressibility. However, the remaining pressure difference can still cause the ridges and recesses to expand and ink overprint to varying degrees. This needs to be compensated by the ink during the printing of fine corrugated cardboard. Print tests show that optimizing the ink significantly reduces the washboard effect. It prints in a wider color gamut and has been shown to be best suited for the printing of fine corrugated cardboard.
The successful application of the direct printing of micro-corrugated board technology by the offset press has made corrugated box packaging and printing enter a new stage of development. Due to the high quality and low cost of direct offset printing on micro-corrugated cardboard, the printing and packaging industry can no longer ignore this technology.
The design concept and market demand for displaying products and promoting products through storage and transportation packaging also promoted the rise of direct-printing micro-corrugated cardboard technology by offset presses, and also established new printing quality standards for corrugated paper box packaging. Of course, this does not mean that only offset printing will have the future of direct printing of fine corrugated cardboard. Thick cardboard boxes are still printed mainly by flexo printing. Many long-lasting cardboard boxes will still use flexo printing because of their relatively simple shapes and design patterns. Similarly, high-quality corrugated cartons will also be offset-printed and then processed. Despite all kinds of restrictions, direct-printing micro-corrugated cardboard offset printing currently occupies a certain market share and will continue to grow.
IV. Indirect offset printing of fine corrugated cardboard
The indirect printing method of the fine corrugated cardboard is to print the cardboard surface paper first, and then paste the printed tissue paper to the corrugated paper. Offset printing uses conventional PS plates. Since the resolution of PS plates is relatively high, very fine printing patterns can be printed. At present, most of the high-grade corrugated boxes used in sales packaging in China are offset printing. In the corrugated box production process, offset printing is a kind of pre-printing method. That is, the first paper is printed on the front and then on the fine corrugated cardboard. It is not much different from the ordinary offset printing process, and it is not considered in this case. Only Simple analysis of its main features. Offset printing corrugated boxes have the following characteristics:
â– Easy plate making, regular plate making for PS plate.
â– Can finish the surface, such as laminating, polishing and so on.
â– High printing costs.
â– It is not suitable to use paperboard linkage production line. It is only suitable for single-faced corrugating machine and the production efficiency is low.
â– Limited format, generally smaller than flexo print carton format.
â– The printing products are very fine, and the number of screens can reach 150-200 lines/inch. The printing quality is relatively stable.
â– Due to more post-processes, the strength of the board is reduced.
â– The ink generally contains benzene, which has some pollution.
Direct printing on micro-corrugated cardboard, due to the effect of printing pressure, the strength of the carton will certainly decline, which is a major drawback of direct printing of micro-corrugated cardboard. The effect of printing on the strength of micro-corrugated board is mainly reflected in the printed area and the printed position. In general, as the printing area increases, the board strength decreases proportionately. The total printing is reduced by about 40%; transverse belt printing is reduced by about 35% at the center width of 50mm; about 30% at the width of the lower edge of 50mm; and the width of printing is reduced by about 30% at the upper and lower sides by 50mm; on the side and end of the carton. The central part is reduced by about 5% in vertical printing of 50mm.
With the continuous development of printing technology and process, the printing of fine corrugated cardboard will further develop. There will be more competition between several printing methods of micro-corrugated cardboard, and this competition will also promote the development of micro-corrugated cardboard printing. Several printing methods of micro-corrugated cardboard will occupy a certain market with its own characteristics. (Text / Song Weiwei)
China Senbo Industry Co.,ltd , https://www.yylpaper.com