——How the water-based ink adapts to the high-quality carton printing contrasts the successful experience and development trend of the direct-printing corrugated carton produced by the foreign water-based ink flexo printing. The corrugated paper box in China will also increase the multifunctionality of the transport and marketing packaging from a single transport packaging function. The direction of quality development. The good news is that high-quality carton flexo printing technology featuring fine dot overprinting and color gradation printing has been developed under the cooperation of various technologies such as color separation and plate making, water-based ink, and high-precision printing machinery and supporting consumables. The emergence of strong printing plants has greatly enhanced the competitiveness of the carton industry, and has made it possible for some imported high-precision three-color and four-color printing machines to play their due role. In this high-precision dot overprinting and color lithography printing, the water-based ink must not only stably and accurately reproduce the gradient distribution (gradation design), proper color density, and gray balance of each color plate, but also must have It can adapt to the comprehensive printing adaptability of overprinting.
First, the characteristics of several stages of corrugated box printing At present, there are still some corrugated papers are still made of lithographic offset paper sheet to the carton method, but this kind of carton is more precise than the picture printing (but more low-coated coated paper, more In addition to the appearance of tile scars, the production efficiency, production cost, carton strength, and specifications suitable for printing have lagged far behind the production method of water-based ink flexo-printing cartons. With the continuous improvement of flexographic technology and the constant change of market demand, the different quality requirements for packaging materials can also be compared and analyzed from the aspect of printing level, which can be roughly divided into the following four printing forms:
(1) Solid-color printing, mostly based on text and simple solid graphics, requires only a single color ink, a wide range of viscosity, and can be used for continuous printing over a long period of time. The resulting hue and color concentration fluctuations are not easily noticeable. The requirements are not high;
(2) The combination of monochrome solid and grid dot pattern printing must take into account whether the designed grid points will be pasted or blocked under certain printing pressure. The range of the upper machine viscosity of the water-based ink becomes narrower, and at the same time, it is necessary to take into consideration the requirement that the concentration of the ground is appropriate and the grid point is clear;
(3) Monochrome printing of dot patterns requires that the water-based ink have the appropriate concentration gradient and sufficient contrast, the upper machine viscosity is very low, and the range of change is very narrow, generally they are spot-color inks;
(4) Color gradation printing, the three-primary water-based inks with relatively fixed performance parameters such as hue and concentration directly carry out color-overprinting of dots, delicate change of dot-levels, and strong color reduction ability. If a smooth, dense high-quality white paperboard can be selected, Printing can realistically reproduce the effect of a manuscript at a specified number of lines, like offset lithography.
The above four printing forms will appear in the same printed product in combination with each Other in practical applications. In order to improve the operability of the printing job, it is required to scientifically and reasonably distribute the color separation of each pattern and require plate making, and it is also required that the performance of the water-based ink be easily adjusted and controlled within a certain allowable range.
The establishment and application of three-primary water-based inks for color lithography printing includes the technical requirements necessary for these four types of printing modalities and represents the technical level of high-quality flexographic printing of corrugated boxes.
Second, on the three primary colors of water-based ink The so-called three primary colors, generally refers to the natural light by the subtractive method decomposition of yellow (Y), magenta (M) and sky blue (C) three colors. The three-color ink and other components are mixed to obtain black (K). Therefore, lithographic offset printing is generally referred to as four-color printing together with black printing. Unlike lithographic offset printing, flexographic printing has not yet established a unified primary color ink standard. In particular, corrugated paper is characterized by its extremely strong permeability and absorbency, and the paper changes greatly. To establish the three primary colors of water-based ink on these papers, more difficulties need to be overcome: (1) Strong absorption leads to ink flow Sex is not easy to maintain, and the color density of the imprinting is easy to change;
(2) The change of corrugated paper quality is large, and the difference in the color of water-based inks on different papers is large;
(3) The enlargement of outlets is particularly serious. Under the same conditions, there are obviously different outlet expansion rates depending on the printing pressure and the design of the plate-making outlets.
(4) The ink with overlapping dots needs a certain degree of transparency, and it is difficult to reconcile with the high hiding power that conventional aqueous ink should have.
(5) With the difference in paper quality and the quality of the water-based ink series, the machine parameters such as the order of the printing color need to be re-explored. In spite of this, for the time being, the use of paper-related SWOP reference management has been temporarily adopted in the world. Some well-known laser color separation printing companies in China have taken the lead in establishing the color separation method for the three primary colors of corrugated paper flexo printing in practice, and cooperated with printing plants and ink factories to expand the network, overlay printing, and color control. Can make effective exploration and adjustment, printing out very characteristic products.
Summarizing the practical experience we have obtained, we believe that the three primary colors of water-based inks can be used not only for the printing of three colors, but also for the printing of common indicators. The three primary colors (black, if necessary) must be applied as a whole. The dryness and stickiness requirements of each color have appropriate differences. The balance of transparency and hiding power must be balanced, as well as the leveling and printing color sequence. All of them need to be considered in an integrated manner. It is also emphasized that the amount of ink and the viscosity of the machine must be maintained in the printing process. Good stability. Therefore, a set of three-color water-based inks suitable for corrugated paper printing should have at least the following characteristics:
(1) The hue and color density of the printing ink of the ink should be as consistent as possible with the requirement for the color separation of the plate making. The “primary colors†obtained under different color separation conditions will be very different. Once they are established, the requirements for the water-based ink index, color separation platemaking conditions, and paper quality will remain relatively unchanged.
(2) The imprinting is smooth, smooth, and has good leveling. It can highlight the change of the tone of the gradation version, so that the physical patterns, landscapes, and figures are better represented in the relatively loose and rough resistance. (3) Color hue, color density, and viscosity have high stability. In the effective control of the upper machine viscosity range, select the appropriate number of lines of the anilox roller, control the amount of ink, in the pressure stable, overprinted under precise conditions, to obtain a stable print density and dot definition. That is, each batch of ink is required to have good stability, and it is also required to maintain the storage stability of each color ink and the stability over time on the upper printing machine under printing conditions of low viscosity and relatively high color density.
Third, the establishment and application of the three primary colors of water-based ink It can be said that under the condition that the standard is difficult to establish, the printing factory can only cooperate with the color separation plate-making company and the ink manufacturer from the actual conditions of its own to establish the reproduction of three primary colors, hue, and plate-making outlets. The relationship between sex and printing pressure and precision. Of course, the conditional carton printing plant will directly conduct color separation and plate making according to the actual situation and experience according to their own originals, and let the ink manufacturer produce special “three primary colors†water-based inks that match the separation conditions. As long as they can meet the needs of users, the tri-color prints under this special condition will have a considerable competitive advantage.
Improving the fineness of the pattern, designing the artistic layout into gradational dots, and printing images in the living room on a corrugated box with a hierarchical version of a dot is a major sign of the progress of the water-based flexographic printing technology. It not only improves the marketing competitiveness of products, but also greatly promotes the cooperation and development of related industries. It is believed that this will surely become the development trend of the industry.
The printing and production of high-quality cartons certainly require high-quality color separation and platemaking technology, high-quality water-based inks, and skilled printing operation techniques and high-precision multi-color printing units as the basis, but I also recommend that carton printing plants should be able to gradually Emphasis on continuously improving the printing skills in practice, pay attention to the accumulation of technology and personnel training. For example, from the beginning of the printing of finely-designed dot patterns, it is necessary to make specific practice in grasping the printing conditions with clear dots, balanced color density, smooth ink transfer, and less printing defects. Such as: 1 rational design of the density version of the dot density and expansion rate; 2 learn to choose more comprehensive performance, easy to adapt to a wide range of printing conditions of water-based ink; 3 training skilled operators, so that they have more opportunities to directly understand the printing process The mutual restriction between printing plates, ink, machinery, printing materials and all kinds of supporting materials; 4 establish a reasonable and economic concept of cost, a reasonable combination of the various cost elements, the correct choice.
As an integrated ink manufacturer, Hanghua Ink Chemicals Co., Ltd. has also been developing water-based inks that can meet various printing requirements in the past ten years with the continuous development of flexographic technology, and has accumulated considerable practical experience and dedication. Improve and perfect the application performance of each series of water-based inks, which can meet the needs of current field printing, dot printing and color gradation printing.
IV. Product Description of Hanghua Ink Hanghua Ink Chemical Co., Ltd. started as early as 1993, timely digested the formula technology imported from Japan, and directly selected the high-quality acrylic copolymer resin from an internationally renowned resin company, and extensively screened domestic and foreign companies. A large number of pigments, according to the actual conditions of domestic flexographic printing, printing, and printing and machinery, continue to optimize the formula, specifically established for the WBI BF series water-based ink system for corrugated paperboard, cardboard, kraft paper flexographic printing (Other WFT, etc. The series is applied to the water-based inks for high-end printing of narrow-width flexo printers and various types of water-based coatings. The specifically designed low viscosity, high color density aqueous inks are particularly suitable for high quality carton printing and exhibit the following features:
(1) Bright color, smooth print, high gloss, suitable for a wide range of paper quality. Among them, the three primary colors of ink are very suitable for printing with color gradation printing, and can restore the original effect quite realistically;
(2) Carefully selected pigments and dispersion systems with good stability, maintaining good hue stability, and maintaining good stability and good leveling even when printed at a relatively low viscosity;
(3) Excellent viscosity stability, showing excellent flow performance, generally directly on the machine, suitable for printing at various speeds, such as setting to a very low viscosity to achieve a printing speed of 300 sheets per minute and printing for a long time Can still maintain good stability.
(4) Good re-dissolution performance, smooth ink-discharging process, manifested as failures such as blocking and stenciling;
(5) Comprehensively balance the friction resistance and water resistance performance, and can also adjust and improve the friction resistance as needed, and make it have the same (heap height) anti-skid performance;
(6) It has good drying properties, strong penetrating power, and it is not prone to back side sticking. Moreover, the difference in dryness of the three primary colors and various colors of inks can be adjusted and controlled within a certain range, which can meet the strict requirements of color overlay printing.
(7) Extremely low VOC content, which can be directly diluted with water, meeting the requirements for non-toxic and non-heavy metal ions in food packaging. V. Concluding remarks The rapid development of water-based ink technology, color separation plate-making technology and the organic combination of high-precision, high-efficiency flexographic printing machines have enabled the water-based flexo printing of corrugated cartons directly. High-quality print quality is an important part of high-quality corrugated cartons. A wide range of water-based inks with good performance, good performance, and stable quality can make carton factories more able to improve the competitiveness of their products. (Hanghua Ink Chemical Co., Ltd. Gong Zhangshui Xie Jiayi)