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 ink color is often referred to as ink. 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 objects, and print applications, the problem of incompatible ink and ink properties and printing operations and printing quality is more prominent in the practical use of water-based inks. The principles and methods of sexual deployment 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. The water-based ink belongs to Newtonian fluid system, with low viscosity and good fluidity. The viscosity is 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 parses the original and determines that the primary color ink coloration 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 first be analyzed, and the color of the original is decomposed into the three primary colors of the color material, that is, the color of the original. Which of the three primary colors of the colorants are subtracted and mixed to make judgments. 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 adjustment, scraping color comparison According to the original color analysis results, formulate the ideal tricolor ink (base ink). Accurately weigh the appropriate amount of base ink (eg 10g), pick up each base ink with a dipstick 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, the main color is compared with the color of the original, so the repeated and detailed work of coloring, scraping, and color comparison is performed until the color is adjusted. It 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 for colorimetric comparison. Generally, fluorescent light is used for most of the eye color comparisons. It is covered with two 40W fluorescent lamps and observed at about 10CM, or it can use light from the northern half of the day. This natural light is regulated by the CIE. The C light source is close. The color temperature is 6500K.
B. Scratch paper should use the same paper as the printing object as much as possible. For example, the brightness, hue, and saturation of the same ink on the corrugated yellow board paper and the corrugated paint whiteboard paper are not the same.
When C is color-shifted, pay attention to the dominant color. Red is bluish (purple), yellowish (gold-red), yellow is bluish (bright yellow), reddish (orange), blue is reddish (purple), and Green, the dominant color is usually called the color head, which is the basis of the composition, but it has a serious impact on the results of the ink tone matching, and the color caster also participates in the subtractive mixing, such as the blue-headed yellow ink mixed with the red-headed blue. The lowering of the green luminance with a dirty color is caused by 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 the achromatic ink that is white ink and black ink, the color ink to adjust the white ink can increase the brightness, Adjusting the black ink will reduce the brightness and make it dark, and the white ink in the color ink will reduce the saturation and lighten it.
E color comparison must wait until the ink film has dried completely.
The basic 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 flexographic printing is required to be 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 blending viscosity are the main performance indicators that characterize the suitability of 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 process of using ink, if the viscosity is too large, 5%~15% of the mixed solvent can be used for reconstitution. This solvent is composed of water, ethanol, and erythritol. It should not be washed with excessive tap water. 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 blending viscosity are the performance indicators for resisting the ink film separation during the transfer process. 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 fluidity and blending fluidity are the comprehensive characterizations associated with ink viscosity, viscosity, and consistency, which are influenced by factors such as the characteristics of the waterborne binder, the structure of the pigmented filler, 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 light before or after dark) phenomenon, this phenomenon can be through the thinning material (water Binder: Ethanol: Water = 2..3..5) Adjusted.
D foam and its elimination of water-based ink is low viscosity, thin, and liquid. In the printing process, ink pumps are used to recycle ink, and air is inevitably mixed into the flowing ink. Because the surface tension of the ink is relatively large, the liquid air is formed. Bubbles. Blistering affects the normal operation of the ink printing job, and in severe cases it will make the printing job impossible. The method of eliminating foam is to add a defoamer with a formula content of 0.3%~0.5% on the one hand, such as tributyl phosphate and 080, which are commonly used for ink and water; on the other hand, the chances of contact between the ink and air are reduced as much as possible. Under continuous conditions, reduce the circulation amount of the ink pump as much as possible, use a non-leaking ink-absorbing tube and ensure that the ink tube mouth penetrates 30CM below the liquid surface of the ink tank.
E. Stability and Formulation The stability of water-based ink refers to the continuous and uniform performance of the ink during storage or use. Because water-based ink is a thin, low-viscosity liquid, the phenomena of gradation of pigments and binders tends to occur. The stability of the ink becomes worse, and it becomes thinner and thicker 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, lightness, 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.
The drying of the A drying water-based ink is mainly caused by the volatilization of the water composite solvent, the decomposition and coagulation of the resin ammonium salt, and drying. 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 (21°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 In the ink design should control the resin reasonable acid value, choose a reasonable combination of volatile solvent system and the ratio, the ink can not be used in the ink dilution excess, in particular, can not add an excessive amount of water, due to the latent heat of evaporation of water If the water is too large, the dryness of the ink will be slow, and it should be diluted with a mixed solvent of water and ethanol. The amount of dry and excessive water can be large, and the amount of dry and slow water should be small.
The adhesion property of the B-adhesive aqueous ink refers to the property that the dried printing film adheres to and adheres to the surface of the printing object. The adhesion of water-based ink is mainly affected by the properties and amount of all the resins of the binder. The use shows that the high acid rosin addition resin ink has poorer adhesion than the acrylic resin ink, and the surface structure of the printed object also affects the adhesion, and the surface has a rough yellow plate. The poor adsorption of the paper film is easy to discolor, resulting in poor absorption mainly due to the low molecular weight of the resin used for the ink, insufficient amount of the resin, too much filler, excessive dilution of the ink, and soft surface structure of the paper. Improvement of adsorption can be achieved by replacing new resin varieties, adding new similar materials in the application, especially on site
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