In order to better stimulate the consumer's vision and stimulate their desire to buy, many manufacturers now prefer to use a large area of ​​color to carry out product packaging design, especially in domestic tobacco and wine packaging design is more like the application of a large area of ​​red Yellow block or gold silver block. In order to achieve the customer's expectations for product packaging, packaging and printing manufacturers need to pay close attention to the practical application of spot colors in the production process, so as to avoid the product does not achieve the desired effect of the customer, resulting in customer complaints, complaints and even returns compensation.
In packaging printing, two color printing processes are generally used, one is normal four-color printing, that is, using medium yellow, magenta (or magenta), sky blue and black ink overprinting to reproduce color originals; the other is spot color printing Only original colors other than four colors are used to copy originals. When printing a large area of ​​background color, spot color printing is more commonly used. If the product manuscript contains many pictures of different colors, it needs to be scanned and separated by an electronic color separation machine or a color desktop system, and then produced by a normal four-color printing process. If the product manuscript is composed of uniform color patches of different colors or regular gradient patches and texts, spot colors may sometimes be used for printing in consideration of improving print quality and reducing the number of overprints.
The inks that are prepared by spot color printing are obtained according to the principle of subtractive colorants, and their color has lower transparency and higher saturation. Ink-colored, spot-colored blocks are usually printed in the field and the amount of ink is appropriately increased. When the thickness of the ink layer on the layout is large, the sensitivity of the change in the thickness of the ink layer to the color change is reduced, so it is easier to obtain a uniform and thick ink printing effect. Due to the uneven technical level of the current paper manufacturers, the color of the same specification paper surface will appear more or less deviation, or partial green, or yellowish, this gives packaging and printing manufacturers control the color band of the product. It's trouble. If you can reasonably and properly use the opacity of spot color patches, you can solve the above problems well.
The use of four-color printing results in the combined effect of subtractive color absorption and additive color mixing of the dots, and the color block has a higher brightness and lower saturation. For light-colored color blocks, a four-color printing process is used. Due to the low coverage of the ink by the ink, the ink has a lack of thickness. Because of the network point of view, it will inevitably make people feel the presence of patterns. In addition, the four-color printing process overprinted out of the color block is composed of a certain percentage of dots, when printing dots, the ink layer thickness must be strictly controlled, easily due to changes in the thickness of the ink layer and changes in the printing process conditions cause color intensity changes, Changes in the degree of dot enlargement have led to a change in color and uneven ink. If the color of the color block cannot be overprinted with a multi-color machine at one time, color shift may easily occur due to the uneasy control of the color of the semi-finished product. If sky blue and magenta are overprinted into purple, if the sky blue ink is large, it will be blue, if the magenta ink is large, it will be reddish. At this time, it may be possible to change the superimposed color blocks to a special purple version. Although there is one more printing plate, the printing preparation time is shortened, the printing speed is improved, the hue control is stable, the production efficiency is improved, and the waste products are also reduced. The production cost is also reduced. Of course, this phenomenon should be taken into account when planning the process.
In the printing of a large area of ​​light-colored uniform color blocks, usually used in the original ink to add a diluting agent to match the spot color ink, and then field printing, so that the ink layer is thicker, easier to get uniform color, thick effect. If a four-color printing process is used, low-level flat-screen dots must be used, but low-level flat-screen dots are likely to be small due to slight sand grains or slight exhaustion during printing. all. When printing, it is easy to supply too much water due to the layout, paper powder piled up on the printing plate and blanket, paper smoothness is low and other reasons cause the poor transfer of ink in the small network, resulting in the lighter ink and uneven ink, resulting in batch color, so that Increased scrap.
For a dark, large-area color patch, a four-color printing process may be required to be formed by superimposing high-number dots of several colors. The ink layer is too thick and back rubbing occurs. With the spot color printing process, only one color is printed, and the back stain is not likely to occur. With the four-color printing process, some parts of the graphic text may be synthesized by several colors, while the spot color printing technology is used, and the corresponding parts only print one color to avoid overprinting errors.
The above is the use of spot color inks formulated with three primary colors. In fact, in the packaging and printing, in addition to the three primary color inks, there is a kind of ink that people like to use - metal ink. Due to its special metallic luster, metallic inks have been widely used in packaging and printing, especially in tobacco and wine packaging printing. The merchandise package printed with metallic ink looks elegant and can improve the grade of the product. However, since the adhesion of metal ink itself is not strong, in actual printing, the difficulty is also greater than the ordinary spot color ink.
There are two kinds of common metallic inks, namely gold ink and silver ink. Gold ink is made of copper-zinc alloy powder and gold oil. The content of copper and zinc in gold powder is different, and the color of gold ink is also different. The zinc content is low, the gold ink is reddish; the zinc content is high, and the gold ink color is partial green. At present, gold powder (ink) sold in the market is divided into red gold powder (ink), green gold powder (ink), and green gold powder (ink). The silver ink is made of silver aluminum powder and silver adjustment oil. Different silver powder particles have different metallic luster, coarse silver particles and strong metallic luster. Appropriate addition of some bright yellow, bright oil, red dry oil, dibutyl ester and other auxiliary agents in the gold and silver ink can enhance the affinity, viscosity, and fluidity of the gold and silver ink, so that the adhesion performance of the gold and silver ink is obtained. Improve and improve the print transfer performance of gold and silver ink.
In the printing of gold and silver ink, there are generally two ways, one is to first print and then print gold and silver ink, that is, use strong hiding power, and ink color similar to the gold (silver) ink base color. The ink is printed with pale yellow ink, clear yellow ink, or fake gold ink to create a background color. In order to increase the metallic luster, about 10% of gold ink may be added in an appropriate amount. Yinyin ink generally uses fake silver ink to make the background color. Fake silver ink can be diluted by whitening agent, white ink, black ink, detackifier, No. 6 varnish, and white dry oil. The printing ink of silver ink is better than gold ink, and it can basically meet the requirements of general package printing with only one printing. If you encounter a large area of ​​silver packaging products or the use of paper is poor, you need to take two prints to be able to show a good silver luster. This kind of method has higher requirements for the technical level of the printing operator and is more difficult. The other is to hollow out the position of the gold and silver inks on the other color plates. The gold and silver inks are directly printed on the paper. This method is well-understood for general printer operators. Moreover, if the colors used in the product are four colors of gold and silver, it is possible to use a four-color offset press to print all the colors including gold and silver ink at one time, thereby saving time and shortening the construction period. However, during prepress planning, care should be taken not to allow gold and silver blocks and other color blocks to be overprinted, and 0.1 to 0.2 mm trapping should be provided. Another thing to note is that after printing gold and silver ink, do not rush to dry because the drying speed of gold and silver ink is slower than that of ordinary ink. Do not add more dry oil, otherwise the gold and silver ink particles will become thicker, and the ink roller Increased ink deposits will cause the prints to stick.
In short, spot color printing is a flexible and complex color printing process that should be used properly and reasonably. In the actual production process of printing and packaging, spot colors are sometimes used singly, but in many cases two or three colors in a normal four color are used in combination with one or two spot colors. Whether or not to use spot colors depends on whether it is conducive to reducing the rate of rejects and improving product quality. Is it beneficial to save time, shorten the construction period, and increase production efficiency? Is it not conducive to reducing production costs and increasing corporate income? This requires the process and technical personnel of the packaging and printing manufacturer to comprehensively consider the technical level of the factory, the skills of the operators, and the use of machinery and equipment during the process planning so as to formulate a reasonable production process.