We live in a colorful world. The sky, grassland, ocean and grassland have their own colors. In printing production, color is not only an element of design, but also an important standard for product acceptance. Even if the customer reluctantly accepts a print with poor color quality, it may not be patronized next time. Many products are due to the problem of color quality control is not good, so the loss of important customers. It can be seen that mastering the law of color presentation and controlling the color quality are the technologies that must be mastered in production and production. Only having advanced equipment without good technological cooperation will inevitably lead to elimination in the fierce industry competition. The function of color quality control is the core of printing quality control. In the whole production management of printing enterprises, color management is in the central position. With the development of economy and the improvement of material and cultural living standards, customers' requirements for printing quality are also increasing. In the face of increasingly fierce competition among enterprises in the industry, printing enterprises must constantly improve product quality and improve the quality of gradation and color reproduction of printed matter. In order to control the product image quality, the key is to control the color. In the printing process, we must take effective methods to control the parameters to ensure the repeatability and quality stability of the product reproduction. 2 color quality requirements of printing products Color quality control is a management process that covers a wide range of aspects, including manuscript, pre press design, plate making, plate printing, proofing, printing and so on. It includes pre press color management and color and tone control in the printing process. From the perspective of printing image reproduction technology, the quality of a printed product mainly has four requirements (image quality characteristic parameters) In addition, it can also be used to analyze the failure patterns such as tone and color reproduction, image resolution, moire and surface characteristics. For color dot printing, it is required that step harmony and color reproduction should be faithful to the original, without color deviation, uniform ink color, good luster, no deformation of dot, accurate overprint, no double image, transparent printing, all kinds of bars, sticky dirt on the back and mechanical traces. There are many factors affecting the gradient and color reproduction of printing images, such as: ink film thickness, dot enlargement, printing color sequence and overprint, ink hue and field density, ink temperature and viscosity, water supply (water ink balance), paper properties, plate depth, printing pressure, etc. This paper mainly from the ink balance in the printing process to analyze the influence of printing color gradient, color reproduction quality control methods. [next] 3 the influence of water and ink balance on color analysis offset printing uses the principle of water and oil to print. The quality of printed matter is directly affected by the ink balance control. Ink control is not only static, but also dynamic throughout the production process. Sometimes, when the same product is produced by the same equipment, in several batches or by different machines at the same time, the color difference often occurs. Even if the parameters of the equipment are adjusted correctly, the ink color will be inconsistent after entering the batch production. At this time, it is particularly important to control the ink balance. In the actual printing, many operators do not pay enough attention to the balance of ink and water until the ink is seriously emulsified after printing for a period of time, resulting in ink roller deinking, printing sticky dirty, dull color, white image, paper moisture deformation before they realize the need to control the ink balance. 1) Ink is relatively insoluble ink and water is not absolutely insoluble. In the actual production process, there is pressure between the water roller and the water roller and the plate cylinder. The ink and water will be fused together after the extrusion of the cots and cots, so that the ink emulsion, so the ink balance is relative. It is impossible to keep a strict demarcation line between water and oil in the transfer process of ink. Some additives in the binder of offset resin ink have hydrophilicity, and some additives have hydrophilicity and lipophilicity at the same time, so emulsion of ink is inevitable. There are two kinds of emulsification state of ink: when the water is large, the formation of "oil in water", when the water small ink is large, the formation of "oil in water". Once the ink is emulsified, its hue, brightness and saturation will be damaged due to the infiltration of water molecules. In such an ink condition, the product printed will inevitably have the problem of hue offset. As the saturation of the ink decreases, the ink volume will have to be increased during printing, which will lead to the increase of field density value.Generally, water emulsion ink, ink light, small water will make the blank part of the page will adhere to the ink, resulting in dirt. Therefore, the key to offset printing is to control the ink balance. 2) The influence of ink and water imbalance on printing color quality Under the mechanical pressure between the ink roller and the printing plate and the rolling effect between the ink rollers, the ink containing small water droplets is easy to cause the dot and paste, not smooth, the level is not clear, the color of the picture and text is dark, the brightness is reduced, the ink color is light, the water mark is produced in the field part, sometimes too much water will be thrown on the printed matter, which will cause the paper adhesion and damage the image and text quality. ② When the water roller and the surface of the ink roller accumulate excessive water and ink, there will be an axial strip of obvious shallow marks on the plate layout and printed parts, resulting in "water bar" and "ink bar". Too much moisture on the page will be transferred to the paper after the printing plate and blanket transfer, causing the paper to be uneven, warped and even curled, which will affect the next color overprint and back printing. It is easy to cause one-sided four-color overprint or the positive and negative overprint is not correct. When the positive and negative overprint sheets flow into the binding process, the binding folding, page matching and binding quality will be affected It's a big impact. ③ Ink emulsification when the ink on the ink roller is emulsified, the nature and structure of the ink will be changed and destroyed. The ink roller is easy to throw ink, splash on the equipment and printed matter, resulting in flying ink spots. The emulsified ink layer on the printed matter will prolong the oxidation and conjunctiva time of the ink, slow down the drying speed, cause the ink to be sticky and dirty on the back, and make the printing image appear false and white, resulting in color distortion. ④ The water is too small. When the water is too small, first of all, there will be ink stains in the blank part of the printed matter, the text and lines appear rough edges, and the printing plate starts to get dirty. As time goes on, the ink gradually blocks the non inked part, and "paste version" will appear. The small amount of page water reflected in the printed matter is more intuitive than the general layout, as long as timely sampling and careful inspection is easy to correct and avoid. [next] 4 how to do a good job in the daily operation of ink and water balance can be well controlled in the production. It is necessary to control the ink emulsification in the minimum range to ensure the clear layers and bright colors of the printed matter, which is the reflection of the operator's ability to grasp the ink balance and the comprehensive ability of the operation skills. 1) Reasonably adjust the pressure between the water transfer roller and the plate water roller, between the ink roller and the printing plate cylinder, and between the ink rollers. When adjusting the pressure, it is necessary to achieve the "three levelings" (the mutual pressure between the water roller, the ink roller and the roller), the "three constant" (the printing pressure, speed and pH value should be constant), and the correct mastery of the "three diligence" (looking at the sample sheet, cleaning rubber, mixing ink bucket) is the prerequisite to ensure the balance of ink and water. When replacing the new water glue velvet cover, the force should be even, the surface should be flat and the tension should be consistent. 2) The ink in the ink holder can not be adjusted too thin. Too thin ink, liquidity, viscosity reduction, water resistance performance decline, easy to produce emulsion. The amount of toner oil should be controlled within 10%, offset paper printing can be slightly higher. Dry oil is both a drier and an emulsifier, and excessive use will cause ink emulsification or glue burning. Generally, the amount of red dry oil should be controlled at 1%, and the white dry oil should be controlled within 0.5%. 3) When the operator wants to pre adjust and print new products according to the graphic area of the page, it should be noted that the pre inking amount of the page should not be too large after the version is changed, otherwise, the water volume will be increased when starting the machine, which is easy to cause large amount of water and ink. In the process of printing and registration and color proofreading of the page, it is necessary to repeatedly start and stop the machine. At this time, the ink control is a difficult point. We should attach great importance to it, and the ink control after normal printing is relatively easy. Pre opening water consumption should also be controlled, not too large, otherwise it will lead to large water and small ink, resulting in ink transfer system deinking, ink emulsification speed up. In the normal printing process, try to use a small amount of water under the premise of ensuring the normal water supply and the layout is not dirty. 4) Keep the machine running at a constant speed to avoid the change of water and ink volume caused by the change of machine speed, which is easy to cause the imbalance between ink and water, and make the ink color of printed matter inconsistent. [next] 5) reasonable control of the amount of fountain solution is an important condition for ink and water balance. According to the color requirements of different sheets, the ink amount of each color group and the proportion of fountain solution dosage can be determined. In the fountain solution, the original solution is controlled at about 5%, and the amount of wetting powder is controlled at about 4%. The pH value of fountain solution should be set between 5 and 6. If the pH value is too low, the acid is strong. The blank part of the printing plate will be deeply corroded, and coarse sand holes will appear, which is not easy to form a strong hydrophilic layer. As a result, the blank part will appear oil in water phenomenon due to the existence of more moistening solution, which will cause the printing plate dirty, weaken the printing plate resistance rate, and cause the screen point damage and "plate dropping". The ink contains acid water droplets, which will cause pigment decomposition, ink pulverization, color dimming, saturation reduction, and the speed of ink layer oxidation conjunctiva. If the pH value is too high, it will dissolve the diazo compounds in the graphics and text parts, resulting in incomplete graphics and texts, which will also damage the printing plate and reduce the printing resistance.The acidity and alkalinity of paper will also affect the pH control of fountain solution. In general, alkaline fountain solution is used for printing acid paper and acid fountain solution is used for alkaline paper to make it relatively comprehensive and neutral as far as possible. The amount of alcohol added in fountain solution should be controlled at about 15%. The appropriate concentration of alcohol in the fountain solution can form a water film on the surface of the water transfer roller, and the water transmission is uniform, which helps the fountain solution fully spread on the printing plate surface. Therefore, the amount of water can greatly reduce and reduce the ink emulsification, making the printing ink bright and easy to dry. If the alcohol concentration is not enough, the fountain solution on the surface of the water transfer roller is transmitted in a linear manner, which is easy to cause uneven water transmission and ink drawing 。 Excessive alcohol will cause waste and increase printing costs. The water temperature of alcohol moistening system should be controlled at about 8 ℃ to avoid the heat generated by the high-speed running of ink roller, which will reduce the water content of the plate and increase the water volume of the plate, which will cause oil emulsification. 6) The printing workshop with ideal production environment control should keep constant temperature and humidity, keep doors and windows as few as possible and avoid wind. The temperature should be controlled between 22 ℃ and 25 ℃, and the relative humidity should be kept between 55% and 65%. This is conducive to reducing the plate surface temperature, reducing alcohol volatilization and the amount of fountain solution, which is conducive to the control of ink and water balance. When the temperature is higher than 25 ℃, the water in the page is easy to evaporate and the page is easy to get dirty. When the relative humidity is higher than 65%, it is easy to cause ink emulsification, reduce the paper surface strength, and slow down the ink layer drying, which is lower than 45%. The paper is easy to carry static electricity, which increases the printing difficulty and affects the print quality. [next] 5 manifestation and identification of ink and water imbalance. For research or experimental products, colorimeter, densitometer and other equipment can be used to monitor the whole process of printing. After printing a few sheets, use the instrument to measure, find the place to be adjusted, adjust, print again, and then adjust But for the production of some enterprises, due to the limitations of production cycle and production process control, there is a certain gap between the actual control method of color in large-scale production and the method used in research work. Moreover, due to the tight time and heavy task in the production process, it is impossible to accurately measure with densitometer every time. Generally, only the sample sheet can be measured After the press is finished, it is up to the captain to adjust, and frequently adjust the printing pressure, lining or stop frequently, which has a great impact on the production efficiency of printing. Therefore, the captain is required to have a strong control over color and equipment, so as to ensure both production efficiency and product quality in the printing process. In the production process of printing, color realization is not independent, but integrated into the equipment and operation method, closely linked with the equipment, operation method and production process, and highly unified. After the production printing sample is determined, in order to ensure the accuracy and consistency of printing color and make the product bright, saturated and without color difference, the operator should listen to, look at and sample more in the production process, so as to find out the problems affecting the product quality. For example, during the operation of the machine, if the captain can hear the sound of "silk" coming from the ink roller and check the printing sheet at this time and find that the imprint is dim and dull, then the captain should judge that it is the imbalance of ink and water and the serious emulsification of ink. Sometimes the ink color on the printed matter is light, which does not mean that the ink color can be saturated immediately by increasing the amount of ink. If it is found that after increasing the amount of ink, the ink color is not deepened in time, it may be determined that it is caused by excessive water, and the ink balance needs to be adjusted. And if the just printed product ink color dark, soft paper, in the inspection of the printing plate, there is a plate surface brightness, also shows that the water is too large. Misregistration, overprint failure, paper surface scuffing or peeling these quality problems are very common in printing, sometimes paper problems, sometimes printing machine failure, but if the paper quality and equipment faults are eliminated, there are still these problems, then it can be judged that the ink is large. In the printing process, the operator should not only ensure the normal operation of the equipment and the continuous quality sampling of the product, but also check the ink supply and water supply system of the equipment. When there are water droplets in the ink hopper, it is necessary to consider that the water volume is too large, because the excessive water will be transferred to the ink hopper through the ink roller, forming small water droplets. In the same way, if the rubber cleaning, found that the blanket drag tip and the printing plate appear water droplets, you can also determine the layout of water is too large. Too much water in the paper delivery part of the performance is uneven, paper curl. [next]In order to obtain high-quality printing products, it is very important to master the water supply of printing plate. Therefore, it is very important to control the water balance and standardize the operation. The amount of water in the page is closely related to the transfer of ink, the accuracy of overprint, the emulsification and drying of ink, the printing plate resistance and imprinting gloss. The water supply of printing plate should be determined according to the actual printing conditions. However, due to too many variable factors, it is necessary to pay close attention to the change of water volume in the printing process and adjust the water supply of printing plate in time. In short, according to the principle of ink and water balance, the water supply plate, control in the blank part of the plate began to dirty minimum. Today, with the continuous development of printing technology, the continuous pursuit of high-quality and high-quality printing products in the market makes printing enterprises pay more attention to improving the quality of product colors and the accuracy and delicacy of colors. In order to obtain ideal printing materials, printing operators and quality management links should carefully monitor and control In order to ensure the color stability, reduce the reject rate, improve the quality of printed products, and prolong the service life of printing equipment and save the printing consumables, this paper analyzes the factors influencing the printing process, such as ink balance, printing pressure, registration and drying speed, etc Printing enterprises, has a good practical significance.
Dongguan Beite packaging materials Co., Ltd. - located in Dongguan City, the world's manufacturing city, is a subsidiary of Beite packaging (China) Co., Ltd., with a plant area of 6000 square meters. It is a flexible packaging enterprise integrating R & D, production and sales. It has a complete set of domestic advanced production equipment, a scientific and humanized management system and a group of experienced technical personnel For backing, to provide customers with quality products and first-class service.
The company produces composite bags, roll film, fruit bags, aluminum foil bags, suction mouth bags, self-supporting bags, zipper bags, anti-static bags, special-shaped bags, etc., which are suitable for the internal and external packaging of food, daily chemicals, electronics, toys, medicine, cosmetics, industrial products and other industries.
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