The best printing quality is affected by the color

2022-10-15
  • Detail

Printing quality is affected by color matching in pad printing technology

in pad printing technology, the correct restoration of color plays an important role in printing quality. In color matching, color matching related to color measurement equipment is an objective scientific problem, which can be expressed by data; The problem of color matching unrelated to equipment is subjective, which is limited by the level of artistic cultivation and observation that won them the Nobel Prize. In order to meet the needs of customers, both the influence of objective data and the required artistic effect should be considered when printing

the observation target, the observation light source or light and the observer (human vision or a certain color measurement equipment) are the three elements necessary to form a specific color. None of them is indispensable. The observer's ability to feel color is limited by many factors, and almost all variables are included in the three elements of observation color, which affect the matching ability of color, The change of any one of these variables will have an effect on the image color after the transfer. The influence of these variables will be introduced below

influence of printing materials

a certain color required by customers usually comes from a color matching (color matching) system such as Pantone or a standard color sample. For the influence of substrate, the following four aspects are mainly considered:

(1) the influence of substrate color and surface characteristics of substrate material or medium

(2) the printing method required to achieve a certain hiding power

(3) the additive of ink The influence of diluents and catalysts

(4) produce printers that adapt to a certain color standard. In recent years, with the continuous development of XPS industry (offset printing, silk screen printing or pad printing)

substrate color and surface characteristics

the surface color of printing materials is an important factor affecting the color restoration of images obtained by pad printing technology. When observing the printing color, the color seen is formed by the light reflected from the surface of the substrate and the overprint layer of the printing ink into the eyes of people. Due to the thick ink layer accumulated on the substrate in pad printing, light usually passes through the ink layer to the substrate, and then reflects on the surface of the substrate, and then passes through the ink layer again and reflects to human eyes. The amount of light reflected on the substrate of the printing material is related to the color of the material itself, especially the color of the substrate itself is darker, and the influence is more obvious when observing the lighter tone printed on it

the surface characteristics of printing materials, such as smoothness or flatness and porosity, also play an important role in the color reproduction effect. Observing the same color printed on two media with the same color but different flatness, the visual effect is different: the color printed on a smooth substrate looks brighter and higher; The same color printed on porous rough surfaces such as fabrics appears gray. This is due to the difference in the reflected light of the two hostages. When the light shines on the smooth and flat medium surface, most of the light is reflected at the same angle. However, if we buy an electronic tensile testing machine with poor quality for the reason of price, most of the reflected light enters the human eye; On the contrary, rough and porous surfaces reflect light from different angles, and much less light enters the human eye

therefore, the closer the color matching between the printing and the substrate, the better the pad printing effect will be obtained: a certain color can be reproduced on the coated or non coated colored paper medium, while it has poor reproducibility on the darker plastic medium. In addition, for a specific printing method, one or more layers of white ink should be preprinted as the base color, otherwise a better matching effect will not be obtained. For example, for transparent bright pigments, in order to avoid losing their characteristics, a layer of white ink is preprinted before printing any color

printing times

as mentioned above, we can see the color of the substrate itself while observing the color of the print. In order to reduce the influence of the substrate, the selected ink should be as opaque as possible. In pad printing, the thickness of the printing ink layer after drying is about 20% of the corrosion depth of the printing plate. If the etching depth is 0.001 inch, the film thickness after drying is between 0.0002 inch and 0.00025 inch, which is much thinner than silk screen printing. Therefore, too thin film is enough to cover up the influence of the color of the substrate. One of the solutions is to reduce the etching depth, but when the depth exceeds 0.0015 inch, the effective transmission of ink is greatly reduced, and the image becomes blurred and begins to blur. Therefore, we can only take another method, that is, to increase the number of printing. In pad printing, this process is called double printing or multiple printing

adopting multiple printing will undoubtedly prolong the production time. Therefore, before adopting multiple printing, it is necessary to determine whether it can obtain the required productivity. Even if a single printing does not achieve the ideal color matching, it is not necessary to adopt multiple printing at the expense of production time, which can be achieved by reducing the amount of diluent in the ink or stinging pigments. In addition, before using multiple printing, it should also be determined whether to maintain good detail clarity of the image without deformation or bending in the printing process with the increase of printing times

ink additive

the additive components in the ink components will also affect the color of the ink. Diluents, catalysts and flow agents are generally colorless, which will lead to the decline of the covering power of the ink. For example, adding a catalyst (such as hardener) in the proportion of 2:1 to the ink will reduce the coverage by 50%, which is almost as obvious as the difference between single printing and multiple printing. Therefore, it is very important for those who implement the natural color to know the required additives and the specific proportion when adding them, so as to complete the correct addition before color presentation

production of color samples

standard color samples are the guarantee for correct printing. Because the thickness of the ink film obtained by each printing method is different, the color samples, whether obtained by silk screen printing or offset printing, must be corrected during use. The color samples used for reference in pad printing also need to be corrected

observe the environment

light is generated by electromagnetic radiation, so light comes from the expression of part of the electromagnetic spectrum. The spectral range that can be observed by the human eye is called the primary light, from red light in a longer wavelength band to blue light in a shorter wavelength band. Since the light color seen by the human eye is only light of a specific wavelength within the visible light wave range, the light conditions in the observation environment have a great impact on the observation results. If the color to be matched is observed in the daytime, and the color matching is obtained under the condition of fluorescent lamp, then this kind of matching is not really accurate

in addition, the environment of observation target turnover also affects the color of observation image. For example, the color perception obtained by observing the same image under a darker background is different from that under a brighter background. It is more important to let the intelligent machine operate when showing the samples to customers for comments. We should try our best to ensure that the customer's observation conditions are consistent with the environmental conditions for establishing the ink process during printing, or change the lighting conditions during production to be consistent with the customer's observation conditions

observer

can be a human observer or some kind of color measurement equipment (such as spectrophotometer). No observer can observe the same image in the same way. Human vision can distinguish 10 million colors, and an individual's psychological state affects his or her feelings about colors. When a person is in a healthy state, the observed color is different from the color feeling he gets when he is tired, sick or depressed; The feelings of adults are different from those of children. Moreover, a specific group of people are less sensitive to color changes within a certain wavelength range, and some are even color blind patients. Therefore, judging the correctness of a color should be based on the visual characteristics of multiple people

color measurement equipment, such as spectrophotometer, is expressed in the form of a set of color stimulus matching in a simulated three-dimensional color model, also known as color space, by measuring the reflected light from the object. In the process of measurement, each kind of equipment completes the color measurement of color samples after correction under certain given conditions. These given conditions include lighting conditions or light source type, observation angle, whether to consider the influence of gloss, etc

the results measured by different devices under the same environmental conditions will have the same color matching performance in the color space. But in fact, there are differences between different equipment, and the results are also different. Even the same equipment itself, without changing any conditions, the two consecutive measurement results may be different. In most cases, these subtle differences will not have much impact on the results, but for different equipment under different conditions or the specified color tolerance is too small, there will be problems. Although the printing department and the customer may use the same equipment, we cannot guarantee that these equipment will observe the color and complete the measurement in the same way after correction, so there are often differences. For example, the person who specifies or sets the color takes the gloss factor into account when measuring the color sample, while the printer observes the color matching, and does not consider the gloss factor when measuring the color sample. Then, although the matching result observed by the naked eye is acceptable. Therefore, when matching the color within a specific tolerance range generated by the computer, it is very important to ensure that the measuring equipment and the equipment used in setting the color are observed in the same environment

color measurement plays a very important role in color matching. The measurement results can produce a lot of useful information, which can directly show the position of the matched color in the color space, and provide help for reliable matching. However, in other cases, although the matching effect is good from the measurement results, it is not ideal from the visual effect or artistic effect. This is because human vision still plays a major role in the evaluation of color matching, so we should not only consider the role of measurement tools in color matching, but also consider the impact of subjective perception of human vision

Copyright © 2011 JIN SHI