Analysis of Printability and Application of Ink and Wash in Corrugated Box

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. Ink printing technology is one of the key factors. It is very important to understand the relevant characteristics of ink and the application of ink printing.

The relationship between the physical characteristics of an ink painting and the suitability of printing ink in application

1. Color: The ultimate goal of printing is to achieve color reproduction.

n Color intensity: The main factor that affects the 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.

The three properties of n colors 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. It is the degree of reaction color close to natural color light.

n Main factors affecting color

Because of the appearance of color, there are phenomena of transmissivity, reaction rate, and foreign matter (that is, under the condition of the same light source, the two colors are very matched and not matched 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.

n 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. The general standard light source is D65 and D50, because it has the same characteristics of red, green and blue energy in the visible spectrum (360-750 nm), making it easy 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, the actual color test still has an error of 10% to 20%. For the LCH system, the purity of the color that can be measured is only 5% to 10%. If the ΔE is measured, the error is only about 3%. Therefore, as long as there is a complete inspection system, high-quality colors can be measured.

2, viscosity: the size of the cohesion of ink, ink is one of the main indicators.

Determination of viscosity:

The viscosity measurement tool is the viscosity ring and stopwatch. The detection method is to use a viscosity cup with a specified capacity and a hole diameter, and fill the viscosity cup with the time required for the ink flowing out of the ink detection until it breaks (calculated using a stopwatch). Because the specifications of viscosity cups currently used are not the same and there are many types, the results measured by different specifications of viscosity cups are not the same. At present, most of the viscosity cups for water-based inks use Japan's RIGOSHA4#CUP and domestic coated No. 4 cups.

Water ink viscosity control range

n The viscosity of the ink used in the actual printing is between 15 seconds 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 tends to graze the printed product to produce burrs; if the viscosity is too small, it will affect the ability of the carrier to drive the color material, and the phenomenon of watermark leakage or insufficient color strength may be caused in the field printing.

n It is better to use ink viscosity between 8 seconds and 15 seconds (RIGOSHA4#CUP) for network cable and small print. The viscosity range of the ink has good fluidity and strong reproduction performance for the dot. The printed product is clear and structured. Small deformation, difficult to dirty version sticky.

n Multi-color printing products should meet the premise of overprinting, and reasonably arrange the printing color sequence. It controls the machine 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 directly affects the quality of the printed matter. However, due to the different printing conditions. The requirements for upper machine viscosity are not the same. In order to more accurately control the ink machine's viscosity, 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 for the optimal range of values ​​for printing.

3, drying is also one of the more important indicators of ink, because the speed of drying and viscosity can be directly reflected in the quality of printing.

n 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.

n 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, the problem can be based on the level of PH value, add appropriate amount of quick-drying agent adjustment or use faster printing ink.

PH value

The water-based ink contains a certain amount of amine solvent for controlling and improving the stability of the ink. Therefore, the PH value is one of the important indicators to ensure the ink compatibility. The pH value of the ink factory is generally controlled between 8.2?.2(25°C). When used according to actual needs, such as the substrate or the temperature is controlled to be between 8.0?.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 hours). A suitable amount of PH stabilizer is added to adjust it to ensure the stable printability of the ink.

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