The role of water-based ink in corrugated box printing

The relationship between the physical properties of ink and the printability of ink in application

Color: The ultimate purpose of printing is to achieve color reproduction

Color strength: The main factor affecting color strength in printing is the thickness of the ink transferred to the printing plate through the ink transfer device, that is, the amount of ink transferred

The three attributes of color are hue, lightness, and purity Paint Online at coatingol.

Hue: It reflects the inherent color appearance of color and is the main difference between color and color

Brightness: It reflects the lightness and darkness of the color

The main factors affecting color;

Because of the appearance of color, there are transmittance, reflectivity and isomorphism (that is, under the condition of a same light source, two colors match very well, but do not match under another light source)

The surface state of the substrate has an impact on the color development of the ink

Problems such as the thickness and color density of the ink layer will cause changes in the color depth

Determination of color

Light (light) source: because there is light, there is color, and the wavelength of light is different.

Computer detection system, because different colors have their own wavelengths, the computer detects the color according to the wavelength it feels.

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, but the purity of the color cannot be measured.
LCH system, the color purity that can be measured has an error of only 5-10%, and the error of △E is only about 3%
.
Therefore, as long as there is a complete inspection system, high-quality color can be measured
.

Viscosity: The size of ink cohesion is one of the main indicators of ink
.

Determination of viscosity:

Tools for viscosity measurement are viscosity rings and stopwatches
.
The detection method is to use a viscosity cup with a specified capacity and leak hole diameter, and fill the viscosity cup with ink to detect the time required for the outflow of ink until it breaks (calculated with a stopwatch)
.

Because the currently used viscosity cups have different specifications and many types, the measured results of different specifications of viscosity cups are different
.

The control range of water-based ink viscosity

Generally, the viscosity of ink used in solid printing is between 15 and 25 seconds.
The ink in this viscosity range has good advection and good adaptability to solid printing
.
If the viscosity is too high, the ink is easy to be dirty, and the printed product will have burrs; if the viscosity is too small, it will affect the ability of the carrier to drive the pigment, and there will be water marks leaking white or insufficient color strength in solid printing
.

It is better to use ink viscosity between 8-15 seconds for screen line and small print printing.
The ink in this viscosity range has good fluidity and strong reproducibility of dots.
The printed product has clear dots, distinct layers, small deformation, and is not easy to be dirty.
sticky version
.

Multi-color printing products should meet the premise of overprinting without leakage, and reasonably arrange the printing color sequence
.
Control the viscosity of the machine before and after the color sequence and the drying time of the ink layer to ensure that the ink color printed in 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
.
But due to different printing conditions
.

The requirements for the viscosity of the ink on the machine are also different.
In order to control the viscosity of the ink on the machine more accurately, the viscosity of the ink should be checked regularly during the printing process
.
Combine the effects of printed products with different viscosities, record the optimal value, and keep printing with the viscosity within this optimal value range
.

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

Drying principle

The drying of general ink includes three methods: volatilization, absorption and reactive curing
.
Operators must understand the drying principle of ink in detail, so as to adjust the drying time of ink reasonably according to different products or substrates
.

drying speed

If the drying is too fast, the ink layer is easy to crust, and the ink is easy to dry and adhere to the printing plate, causing the dirty plate to stick to the plate, the printing is not full and the dots are unclear, and the printed matter is fluffed.
Drying agent adjustment; if drying is too slow, it is easy to cause adhesion, which will make the printed matter dirty and even affect the overlapping printing
.

This problem can be adjusted by adding an appropriate amount of quick-drying agent according to the pH value, or using faster-drying ink for printing
.
pH value: It is one of the important indicators to ensure the adaptability of ink wash
.

The water-based ink contains a certain amount of amine solvent, which is used to control and improve the stability of the water-based ink
.
The pH value of ink is generally controlled between 8.
2 and 9.
2 (25°C)
.

When used, it should be controlled between 8.
0 and 9.
5 according to actual needs, such as the difference in substrate or temperature
.
The tools for measuring pH are pH meters and thermometers
.

Due to the volatilization of the amine solution in the ink and the influence of 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 2-4 hours).
detection
.
An appropriate amount of pH stabilizer is added to adjust it to ensure the stable printability of the ink
.

Other Factors Affecting Ink Printing

All links in printing are interrelated.
Under the condition that the various indicators of the ink itself are normal, there may be other factors that affect the ink and cause various printing quality problems
.
Listed below are several major factors that affect ink painting
.

Substrate (cardboard)

printing plate

Anilox roll

printing speed

printing pressure

Weather changes (temperature and humidity)

The temperature is most sensitive to the viscosity and drying speed of the ink
.

In summary, in the production process, the printing factory should combine its own equipment conditions and a full understanding of other printing factors such as ink and water, and cooperate with each other to achieve the best printing quality
.