Describe the preparation of water-based ink printability

The so-called ink printability means that the ink is transferred to the surface of the printing object under a certain printing pressure at a certain printing speed with a certain printing speed. After the printing film is dried, it is fixed on the surface of the printing object to express the desired printing effect. performance. It can be seen that the printing suitability of the ink includes both the suitability of the printing operation and the suitability of the printing quality. The suitability of the printing operation of the ink involves the ink being adapted to the corresponding type, machine speed, press pressure and printing object, so as to ensure that the ink can From the packaging container - ink fountain - ink roller - printing plate - the smooth transfer of printing objects; ink printing quality adaptability refers to the fixation, drying speed, color and filming of the ink film transferred to the surface of the printing object. After the gloss, fastness, resistance and other guarantee print quality.

The aspect of the color effect expressed by the ink is generally called the ink color, and other aspects other than the ink color that are related to the printability of the ink are called ink properties. The ink printing suitability is mainly to solve the optimal matching between ink and ink and printing effect. Due to the particularities of ink structure and printing plate type, printing object, and use of printing crystals, the problem of incompatible ink and ink properties and printing jobs and printing quality is more prominent in the practical use of water-based inks. Adaptability principles and methods are discussed.

First, the structure and properties of water-based ink

Water-based inks consist of water composite binders, pigments, fillers and additives. It has the following properties:

1. Water-based inks are alkaline composite systems with a pH of 7-9.

2. Water-based ink belongs to Newtonian fluid system, viscosity bottom, good fluidity, use viscosity of about 30 seconds (paint No. 4 cup).

3. Water-based inks are soluble in water before they dry, and they dry out and turn into water-insoluble blots.

4. Water-based inks are a combination of infiltration, volatilization, and chemical conversion.

5. Due to the absence of VOC, water-based inks determine the environmental protection of these inks.

6. Water-based inks are suitable for flexographic printing and are mainly used for the printing of packaging and decorating products, such as kraft paper bags and corrugated cardboard boxes. They can also be used for gravure printing, such as candy paper printing.

Second, the deployment of water-based ink color - adjust the ink color

Color is the most intuitive evaluation indicator of printing quality. This indicator is determined by the color properties of the ink. If the water-based ink is used for solid printing at the flexographic printing plate, the ink color distribution is one of the key factors for the success or failure of the printing. The ink color mixing is discussed below.

1. Ink color matching method

The key to the success or failure of ink hue is to master the correct method. The hue of ink and wash can be based on the following methods:

A, parse the original, determine the primary color

Ink-toning is performed on the color sample of the original. In order to reduce the blindness of the color-matching, the color of the original must be analyzed first, and the color of the original is decomposed into the three primary colors of the color material, that is, which color materials are used for the color of the original. The primary colors are judged by subtractive mixing. At present, the analytical manuscript is mainly a combination of instrument colorimetry and human eye colorimetry. The instrument colorimetry is the use of spectrophotometer, densitometer, electronic color separation instrument to measure the optical density or tristimulus value of the original color. The quantified data representing the color is obtained; human eye colorimetry is a qualitative range of the three colors required to form the original color based on the original color in combination with experience. Because the color measurement of the instrument is more complicated, and the color is not a pure physical phenomenon after all, but a comprehensive reflection of physical and human visual physiology and psychology, that is, the final effect of printing color depends on the human visual psychology experience, so in the actual ink tone distribution Visual alignment is more straightforward and convenient, and instrument colorimetry is only used for standard analysis of colors.

B, base ink hand adjustment, scraping color comparison

According to the results of the original color analysis, the ideal tricolor ink (base ink) is formulated. Accurately weigh the required amount of base ink (eg 10g), pick up each base ink with a dip knife and mix it evenly on the glass plate, visually measure the color of the ink and the original, and measure the edge adjustment. When the transferred ink color is similar to the original color , It is desirable to adjust the ink on the scratch paper for scratching. If the ink is printed at the end of the ink, it is mainly compared with the color of the original color and the color of the original. After repeated coloring, scraping, and color comparison, the detailed and meticulous work is performed. The color is exactly the same as the face of the original. Then, the amount of the base ink remaining is accurately weighed, and the remaining amount of the base ink is subtracted from the initial amount of the base ink that is called. This difference can be initially used as the amount of base ink required for preparing the original color, and finally, The base ink is weighed in this amount for deployment, scraping, and color matching, and the ink color of the adjusted ink matches the original color.

2. Ink tone with precautions

In order to quickly and accurately formulate the ink color of ink, you should also pay attention to the following matters:

A, standard light source should be selected when colorimetric, usually with the naked eye color comparison, most of the use of fluorescent lamps, 40W fluorescent lamp two cover, observed in about 10CM, or can also use the light of the second half of the day, this natural light and CIE regulations The C light source is close, the color temperature is 6500K.

B, scraping paper as much as possible using the same paper and printing objects, such as the same ink on the corrugated yellow cardboard and corrugated paint white paper color, the brightness, hue and saturation are not the same.

C, coloring should pay attention to the main color, red and blue (purple), yellow (golden red), yellow blue (soft yellow), red (orange), blue reddish (purple), Greenish, the dominant color is often called the color head, which occupies a very small proportion, but it has a serious effect on the results of the ink tone matching, and the color caster also participates in the subtractive mixing, such as the mixing of blue-headed yellow ink and red-headed blue. The resulting reduction in the green brightness with a dirty color is due to the black component of the blue ink being mixed with the equivalent yellow and blue components to produce a black component.

D, color adjustment should pay attention to the color brightness and saturation adjustment techniques, color brightness and saturation adjustment is through the correct use of achromatic ink that is white ink and black ink, the color ink to adjust the white ink can increase the brightness , Adjust the black ink to reduce the brightness and make it dark. In the color ink, white ink can be used to reduce the saturation and lighten it.

E, color comparison must be waited until the ink film is completely dry.

F. The base ink used for toning must be dispersed to the standard fineness. If the pigment and filler particles in the ink are too large, the saturation and brightness of the ink will be weakened. Generally, the fineness of the ink used in the flexo plate is less than 20 μm. .

Third, the deployment of water-based ink and ink - ink transfer

1. Adaptability of print jobs

The operational suitability of water-based inks refers to the adaptability exhibited by a series of transfer processes of ink fountains, ink pumps, ink rollers, and printing plates under certain printing pressure conditions. It is mainly determined by the rheological behavior of ink and wash. The operational compatibility of the water-based ink is to adjust the rheological properties of the ink, so that the ink in the printing transfer process has the rheological behavior compatible with the printing conditions to ensure the smooth operation of the printing operation.

A, viscosity and its deployment

Viscosity is the main performance index that characterizes the suitability of ink printing operations. The viscosity of ink is lower than other inks. Too much or too little ink viscosity is not conducive to the print job, and even affect the quality of the print. Viscosity over the General Assembly caused the ink in the transmission process, poor transmission of ink, bad transfer, print bite, paste, orange peel and other faults; viscosity is too low will cause ink stability is poor, easy to bubble in the process of transmission, Prints are prone to defects such as pinholes, hair voids, halos, water lines, powders, and ash. In the use of ink, if the viscosity is too large, 5% to 15% of the mixed solvent can be used for reconstitution. The solvent is composed of water:ethanol=7:3. Do not use excessive tap water when adjusting. Otherwise, Poor dryness may result; if the viscosity is too small, new inks of the same kind with the same kind of viscosity may be used for reconstitution.

B, viscosity and its deployment

Viscosity is a property index that characterizes ink resistance to ink film separation during transfer. Water-based inks are thin and low-viscosity, and stickiness is usually not taken seriously. In fact, sticky discomfort can also cause poor printability, further affecting the printing quality. When the viscosity is too large, corrugated paper may be pulled to print paper. Blocking of the plate, uneven printing, and lack of light after the failure, this phenomenon in the acrylic water-based ink when the molecular weight of acrylic resin is too large when the performance is obvious, the solution is to use an appropriate aqueous retting agent.

C, liquidity and deployment

Fluidity is a comprehensive characterization associated with the viscosity, viscosity, and consistency of inks, and is influenced by the characteristics of the water-based binder, the structure of the pigment, and the solid content of the ink composition. Water-based ink If the flowability is too large, the appearance of pattern expansion, unclear gradation, lack of ink, and unclear color, etc., this failure can be adjusted by changing the formula in the ink design, and it can be adjusted to the new liquidity in the use of ink and wash. Ink adjustment or ink replacement If the fluidity is too small, poor ink transfer, uneven ink distribution, and inconsistent ink color (pre-deep or dark before or after dark) can occur. Material: Ethanol: Water = 2:3:5) Adjusted.

D. Foam and its elimination of water-based inks are low-viscosity, thin, and liquid-like. In the printing process, ink pumps are used to recycle ink. Air is inevitably mixed with the flow of ink. Because the surface tension of the ink is relatively large, the liquid is formed. Pack of air bubbles. Blistering affects the normal operation of the ink printing job, and in severe cases it will make the printing job impossible. The foam elimination method is to add an anti-foaming agent with a formula content of 0.3% to 0.5% on the one hand, such as tributyl phosphate, 080, which is commonly used for ink and wash; on the other hand, the chances of contact between ink and air are reduced as much as possible. When the ink supply is continuous, reduce the circulation amount of the ink pump as much as possible, use a non-leaking ink suction tube and ensure that the ink tube mouth is deeper than the liquid surface of the ink fountain at 30CM.

E. Stability and Formulation The stability of water-based ink refers to the continuous homogeneity of the ink during storage or use. Because water-based ink is a thin, low-viscosity liquid, the phenomenon of gradation between pigment and filler is often observed. The stability of the ink is degraded, dilute and thick in the storage container, and the ink is uneven before and after the printing process. This may be due to unreasonable formulation, poor viscosity of the binder, excessive pigment content, poor dispersion, and excessive solvent. If so, this can be solved by adjusting the formulation; or it can be diluted during use. Overcompensate the balance of the ink, so that you can add new ink to the ink fountain to adjust. In fact, even a well-designed ink will have different levels of delamination during storage, which is usually eliminated by short-time stirring.

2. Adaptability of print quality

The print quality adaptability of water-based ink refers to the dryness of the ink after it is transferred from the printing plate to the surface of the printing object to form the printing film, and the comprehensive properties of the color, brightness, abrasion resistance, abrasion resistance, and water resistance and durability exhibited by the dried printing film. . The formulation of color has been discussed in the ink tone allocation, and the other aspects of the printing ink quality are discussed here.

A, drying

The drying of water-based inks is mainly dried by the volatilization of the water-composite solvent, decomposition and coagulation of the ammonium salt of the resin. The ideal drying should be dry on the machine. After printing, the drying speed is generally controlled within the range of 20 mm/15 seconds to 25 mm/15 seconds (2 l°C). Excessive dryness will cause the ink to dry on the printer during the transfer process, causing blockages, non-imprinting, or imprinting defects. Drying too slowly will cause post-printing, blotting, dot extension, and unclear gradation. Overlay adhesion and other printing failures. Dryness should be controlled in the ink design reasonable acid resin price, choose a reasonable combination of volatile solvent system and the ratio, the ink can not be used in excess when the ink is diluted, in particular, can not add an excessive amount of water, due to water