The influence of printed ink
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The effect on the ink color of the printed product
Plate printing is a widely used production process. How to improve the quality and production efficiency of color prints is worthy of analysis and discussion.
The visual effect of printed ink color is one of the important factors to measure the quality of printed matter. There are several cases that directly affect the ink color of printed products.
(-) The effect of the thickness and viscosity of the printed ink layer on the ink color of the print
Moderate printing ink layer is an important measure to ensure the quality of printed ink and prevent the printed matter from sticking. If the ink layer is thicker, the viscosity tends to increase, and the paper is easily generated, which affects the uniformity of the ink color of the printed product. If the printing ink layer is thin and the ink viscosity is insufficient, the printed ink color is weak, and the printed product visual effect is also It is bad. As the printing machine rotates for a longer time or the printing speed increases, the friction coefficient increases and the ink temperature gradually increases. As a result, the ink becomes thinner and its viscosity decreases accordingly. Therefore, these conditions must be considered when adjusting the ink to ensure a relatively balanced printing ink color for the batch products. However, in the actual production process, the decrease of the viscosity of the ink is inevitable. In the early stage of printing, the ink color of the printed product is relatively thick, and it becomes lighter in the future. The rotation angle of the transfer iron roller can be appropriately adjusted to increase the supply. The amount of ink keeps the front and back of the ink color consistent. In addition, in order to prevent the viscosity variation of the ink from being too strong and affecting the balance of the ink color of the printing, the contact between each rubber roller and the iron roller should not be too tight, and the colloid should not be too hard, so as to minimize the frictional heat and keep the ink proper. concentration.
(2) The influence of printing pressure on the color of printed products
Printing pressure is one of the important conditions for the transfer of the imprint. Since the surface of the printing plate is not absolutely flat, the surface of the paper is inevitably subject to fine irregularities and uneven thickness. If the printing pressure is insufficient or uneven, the printing on the printing surface Ink will inevitably appear uneven. Therefore, the ideal printing process is based on the "three flats" (ie, the plate surface is flat compared with the inking roller and the liner to obtain good contact conditions), and the thinner ink layer passes the balanced printing pressure. To achieve a more uniform ink color on the print. If the printing pressure is insufficient or uneven, the liner and the printing plate surface have poor contact conditions. By increasing the amount of ink, the visual effect of the ink color of the layout can be satisfied, but this not only increases the consumption of the ink, but also easily occurs. It is not advisable that the printed matter is dirty.
(3) The influence of rubber roller quality on printed products and ink color
As far as the embossing and printing process is concerned, whether the printed product can obtain the desired ink color has a close relationship with the quality of the rubber roller. The equipment for printing color prints has five or six or even more than three types of ink transfer rollers, ink distribution rollers and ink rollers. Among them, the ink transfer roller and the ink roller have a great influence on the ink color. The quality of the rubber roller is mainly manifested in the aspects of elasticity, viscosity, center of gravity and surface finish, and the viscosity which mainly affects the color of the ink is viscosity. In the printing process, the rubber roller only maintains a certain viscosity to ensure uniformity of the amount of ink applied to the printing plate per printing cycle. However, in the actual production process, the viscosity of the rubber roller is not stable. First, due to the increase of paper dust in the ink, the viscosity of the colloid is affected. Secondly, the tackifier (ie, glycerin) on the surface of the gel increases with temperature and the use time. When it is extended and lost, the viscosity of the surface of the rubber roller is gradually reduced, and the ink absorption performance is correspondingly decreased, thereby affecting the balance of the ink color of the printed product. Therefore, the printing plate products should use a more stable polyurethane rubber roller. If printing bulk products, the rubber rollers should be cleaned at the right time.
(4) The influence of the difference in the cleanliness of the paper on the ink color of the printed product
In fact, the relationship between paper and ink is complicated. If you only consider the color of a book, you should note that the smoothness of the surface of the paper has a certain relationship with the color of the ink. If the pressure of each plate is consistent, the smoothness of the surface of the paper is inversely proportional to the amount of ink consumed, and the amount of ink absorbed by the smoother is small, and conversely, the amount of ink absorbed is large. Therefore, if there is a difference in the smoothness of the front and back of the paper, the method of increasing the amount of ink and pressure should be taken as appropriate to make appropriate adjustments. It is customary to print the glossy surface first, and the pressure and ink supply amount are appropriately increased when the rough surface is printed, so that the positive and negative ink colors all have an ideal visual effect. Practice has shown that the effect of using the above method is much better than simply increasing the amount of ink, and the printing quality is better.
(5) The effect of light changes on the color of printed products
The light sources that usually identify the ink color of the print are three types of daylight, fluorescent light, and electric light. The three light sources have different illumination conditions, and the color of the emitted light is different. The gaze is pure white light, the fluorescent lamp is blue in the white, and the electric light is reddish and slightly yellowish. Although the daylight and fluorescent light sources are somewhat similar, the difference between the two should be considered when identifying higher quality products. The effect of light on the identification of ink is not only related to the light source, but also to the intensity of the light and the angle of illumination. Under the same light source, the intensity of the reflected light on the sample is mainly determined by the distance between the sample and the light source, and the near is strong and the weak is weak. The correct angle of illumination should be that the angle of incidence is equal to the angle of reflection. Light irradiation on the proofs inevitably has partial refraction, but it does not have much influence on the identification of ink. When distinguishing the ink color of the printing, whether it is day or night, the intensity of the light source and the irradiation angle should be the same to prevent the color shift or the ink color from being mutated before and after the ink adjustment error.
(6) Imprinting is not allowed to affect the color of the ink
For products with dot color, whether the overprint of each color plate is accurate will have a great impact on the printing hue. The accurate hue effect of overprinting is also good, and the hue of printed products with inaccurate overprinting will be deviated. This is due to the difference in position printed by the dots of each color, which inevitably produces a visual chromatic aberration. Therefore, for printing reticulated color products, overprinting must be precise to ensure that the printing hue meets the process requirements. In order to prevent misalignment caused by paper stretching and variation, the color deviation caused by the overprinting, for the high quality requirements of the dot color forming products, multicolor machine should be used to complete the color printing at one time to improve the quality of overprinting. In addition, the paper should be hanged to reduce the variation of the printed sheets during the printing process.