There are many factors that affect the printing quality of corrugated boxes, such as printing equipment, printing plates, printing substrates, printing pressure, and printing suitability of water-based inks. As one of the key factors, ink-and-ink printing technology is very important for how to grasp the relevant characteristics of ink and ink and the application skills of ink printing. Reprinted from: Ke Yin Network
The relationship between the physical characteristics of ink and ink and the suitability of printing ink in application
Color: The ultimate goal of printing is to achieve color reproduction.
â– Color Intensity: The main factor affecting color intensity in printing is the thickness of the ink transferred to the printing plate by the ink transfer device, that is, the amount of ink transferred.
â– The three properties of color are hue, brightness, and purity, respectively.
Hue: It is the inherent color appearance of the reaction color, which is the main difference between color and color.
Brightness: It reflects the degree of color shade. Purity: Saturation, the degree to which the reaction color is close to natural color.
â– The main factors affecting the color;
Because of the appearance of color, there are phenomena of transmission, reflectance, and foreign matter (that is, under the condition of the same light source, the two colors match very well, while they do not match under the other light source). The color may be affected by different variables of the observation conditions (such as the viewing angle, the degree of illumination, the opacity of the glossy ink, and overprinting, etc.).
The surface state of the substrate affects the color development of the ink. Such as finish, ink absorption, surface color and so on.
Problems such as the thickness and color density of the ink layer can cause changes in shades of color. The drying time of the ink layer has an effect on the observation and measurement of the color. Because the surface of the ink layer is different from the reflective transmission and the light absorption and drying after the ink is dried. Dark inks are darker in color and lighter inks are lighter in color, which is the changing pattern of wet ink and dry ink.
â– Determination of color
Light (light) source: Because there is light only, the wavelength of light is different, even if the same color reflects the color under the effect of different light, there is a difference, so when detecting the color, it is best to use a standard color light source. General standard light sources include D65 and D50, which have the same characteristics of red, green, and blue energy in the visible spectrum (360 to 750 nm), making it easier to observe slight differences in color. Therefore, it is important to use a standard light source if the requirements for color are strict.
Computer detection system, because different colors have their own wavelength, the computer is based on the perceived wavelength to determine the color, the general computer film is CIEL.AB system (L represents the brightness of the color white to black range that is light and dark degree. A refers to The range of red to green in color. B refers to the range of blue to yellow in color). According to the LAB value of the measured color, only the hue and brightness of the color can be measured, and the purity of the color cannot be measured (the three attributes of the aforementioned color). Therefore, an error of 10 to 20% is still present in the actual color test if LCH is added. System, the purity of the color can be measured is only 5 to 10% error, measured â–³ E, the error is only about 3%. Therefore, as long as there is a complete inspection system, high-quality colors can be measured.
Viscosity: The size of ink cohesion is one of the main indicators of ink.
Viscosity measurement:
Viscosity measurement tools are viscosity rings and stopwatches. The test method is to use the viscosity cup with the specified capacity and the hole diameter to fill the viscous cup with the time needed by the ink to detect the ink flowing out until it is broken (calculated by the stopwatch). Because the specifications of viscosity cups currently used are not the same and there are many types, the results of different viscosity cups are not the same. At present, most of the measuring viscosity cups for water-based ink use Japan's RIGOSHA4#CUP and domestic coated No. 4 cups.
Water-based ink viscosity control range
â– In general, the viscosity of ink used in the field printing is between 15 and 25 seconds (RIGOSHA4#CUP) seconds. The viscosity of the ink in this viscosity range is good, and the printing adaptability in the field is good. If the viscosity is too high, the ink is easily dirty, so that the printed product has burrs; if the viscosity is too small, it affects the ability of the carrier to drive the color material, and there are phenomena such as missing water marks or insufficient color strength in the field printing.
â– It is better to use ink viscosity between 8 to 15 seconds (RlGOSHA4#CUP) for screen and small print. The viscosity range of the ink is good, and the dot reproduction performance is strong. The printed product is clear, structured, and distorted. Small, difficult to dirty version sticky.
â– Multi-color printing products should satisfy the premise of overprinting and reasonably arrange printing color sequences. It controls the viscosity of the color sequence and the drying time of the ink layer to ensure that the ink of the latter color can cover the previous color.
As mentioned above, the size of the viscosity can directly affect the quality of the printed matter. However, due to the different printing conditions. The requirements for the viscosity of the machine are not the same. In order to more accurately control the viscosity of the ink on the machine, the viscosity of the ink should be checked regularly during the printing process. Combine the effects of the products printed with different viscosities, record the best values, and maintain the viscosities at the optimal value range for printing. Drying is also one of the more important indicators of ink and wash, because the speed of drying and viscosity can be directly reflected in the quality of printing.
â– Drying principle
The drying of general inks includes three ways of volatilization, absorption, and reactive curing. The operator must understand the drying principle of the ink in detail in order to rationally adjust the drying time of the ink according to the different products or substrates.
â– Drying speed
The drying is too fast, the ink layer is easy to crust, the ink is easy to attach to the printing plate, causing the dirty plate to stick to the plate, the printing is not full and the dots are not clear, the printed material has burrs and other phenomena, and this problem can be added slowly in the ink. Dry agent adjustment; drying too slowly, prone to adhesion, so that dirty printed flowers, or even affect the color printing. This problem can be adjusted according to the pH value, adding appropriate amount of quick-drying agent or using a faster drying ink printing. pH: It is one of the important indicators to ensure the compatibility of ink and ink.
The water-based ink contains a certain amount of amine solvent for controlling and improving the stability of the ink. The ink factory pH is generally controlled between 8.2 and 9.2 (25°C). When used according to actual needs, such as the substrate or the temperature is controlled to between 8.0 to 9.5. The pH measurement tool is a pH meter and a thermometer. Due to the volatilization of the amine solution in the ink and the acidity and alkalinity of the substrate, the pH value will change during the printing process. It is recommended that the operator should check the pH value of the ink regularly (preferably within 2 to 4 hours). . A suitable amount of pH stabilizer is added to adjust it to ensure stable printability of the ink.
Other factors that affect ink printing
Each link in the printing process is related to each other. Under the condition that the control of ink and ink itself is normal, there may be other factors affecting the ink and ink and various printing quality problems may arise. Here are some of the more important factors affecting the ink.
Substrate (Cardboard)
â– Absorption of the cardboard is poor, which can easily cause the printing ink layer to dry badly.
â– The water resistance of the paperboard is too strong, which can easily cause poor ink transfer. â– The surface of the paperboard is poor in smoothness, and it is easy to make the printing ink level not level well. Leakage, poor overprinting, and dot expansion are common. Such phenomena;
â– The difference between the surface color and the pH of the paperboard will make the printed colors different.
The number of plates in the printing plate and the number of lines in the anilox roller are the main factors that determine the ink loading and the precision of the printed matter. The combination of the two is unsatisfactory, which can result in different ink supply volumes, making it difficult for print to be expected. Effect â– Bad printing plate material is prone to print graphic paste, printing pattern is not clear around the problem, even worse, the plate is easy to aging, deformation and loss of print recovery.
â– poor design of the printing plate pattern, will make the multi-color overprinted prints, the overall graphic layering sense is insufficient, overprinting is unclear, such as poor stacking phenomenon.
Anilox roller
The mesh number of the anilox roller and whether or not it has a scraper largely determine the ink loading and precision of the ink. If the usage time of the anilox roller is too long or the maintenance and cleaning are not clean, it is easy to cause clogging of the mesh, scratches on the surface, wear and the like. The resulting color inconsistencies in the print, the printed article has articles or can not reach the expected ink layer and color intensity and other issues.
Printing speed
Different printing speeds also have a certain influence on printed products. Mainly in the easy dirty version, overprinting is not allowed, the printing of dry goods affected by the color and the depth of the problem. The speed of the machine differs from the requirements for the printability of the ink.
â– When the speed is faster, the viscosity of the ink needs to be lower, and the drying is faster;
â– When the speed is slow, the viscosity of the ink is required to be slightly higher and the drying is slightly slower.
Printing pressure
The adjustment of printing pressure is very important.
â– Pressure is too large. Printing and graphics will be deformed due to pressure, which will easily cause dirty plate stencil, causing problems such as burrs and ghosting around the prints. â– The pressure is too small. The printing is easy to appear false, the pattern is missing or not Ink phenomenon.
Changes in the weather (temperature and humidity temperature are most sensitive to the viscosity and drying speed of the ink.
â– When the temperature is too high, the moisture of the ink in the printing process evaporates too quickly, the ink dries quickly, and the ink viscosity rises significantly:
â– When the temperature is low, the ink in the printing process evaporates slowly and slowly.
Humidity also has a great influence on the drying speed of the ink, which is mainly reflected in the drying time of the print.
The effect of temperature and humidity on the ink will also cause print quality problems. The optimum temperature and humidity for ink printing is preferably controlled at 15 to 25°C (relative humidity 60 to 80%). At the same time, the operating personnel should make appropriate adjustments to the printability of ink and wash according to changes in temperature and changes in the temperature and humidity of the actual printing shop.
In summary, during the production process, the printing factory should combine its own equipment conditions and other ink printing and other printing factors to fully understand and cooperate with each other in order to achieve the best printing quality.
Application of Water-based Ink in Corrugated Box Printing