On the Adjustment of Ink Printing Suitability (Part Two)

2.2 Ink Tone Precautions

2.2.1 The standard light source should be selected for colorimetric comparison. Generally, with the naked eye color comparison, fluorescent lamps are mostly used to cover the 40W fluorescent lamp and observed under 10cm, or light from the northern half of the day can be used. This natural light The CIE specifies a C light source that is close to 6500K.

2.2.2 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 corrugated paint whiteboard paper are not the same.

2.2.3 should pay attention to the main color palette, red blue (purple), yellow (golden red), yellow blue (soft yellow), red (orange), blue reddish (purple) , green, the main color is often referred to as the color head, the composition is very small, but the impact of the results of the ink tone is serious, the color of the head is also involved in the subtractive mixing, such as blue and yellow ink and red head blue The reduced green brightness resulting from the mixing 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.

2.2.4 should pay attention to color brightness and saturation adjustment techniques, color brightness and saturation adjustment is through the correct use of achromatic ink (ie, white and black ink) to achieve, the color ink into white ink can be Increase the brightness, adjust the black ink to reduce the brightness and make it dark, and the white ink in the color ink can make the saturation decrease and fade.

2.2.5 Scratch color comparison must wait until the ink film has dried completely.

2.2.6 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 flexographic printing is 20 Micron below.

3 Ink and Moisture Mixing - Modulation

3.1 Suitability of printing operations.

The applicability of ink and wash is mainly determined by the rheological behavior of ink and wash. The operational compatibility of ink and wash is to adjust the rheological properties of the ink, so that the ink in the printing transfer process has the rheological behavior in line with the printing conditions to ensure the smooth operation of the printing operation.

3.1.1 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 process of using ink, if the viscosity is too large, it can be brewed with 5% to 15% of the mixed solvent. This solvent is composed of water and ethanol in a ratio of 7:3. Do not use excessive tap water to adjust the adjustment. Otherwise, it is likely to cause poor dryness; if the viscosity is too small, it can be reconstituted with new ink of the same kind with the same kind of high viscosity.

3.1.2 Viscosity and its deployment.

Viscosity is a property index that characterizes ink resistance to ink film separation during transfer. The ink is thin and low-viscosity, and stickiness is usually not taken seriously. In fact, stickiness may also cause poor printability and further affect the printing quality. When the viscosity is too large, corrugated paper may appear to pull paper and block. Edition, uneven print, dry after light and other failures, this phenomenon in the acrylic 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.

3.1.3 Liquidity and its 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. In case of liquidity, if the ink flow is too large, there will be defects such as extended pattern, unclear gradation, lack of ink, and unclear color. This failure can be adjusted during the design of ink and ink by changing the formula. To adjust or replace the ink, if the fluidity is too small, poor ink transfer, uneven ink distribution, and inconsistent ink color (before deep or light before or after dark) can occur. This phenomenon can be achieved by reconstituting thinner materials (water-based binders). : Ethanol: Water = 2:3:5) Adjusted.

3.1.4 Foam and Elimination Ink is low viscosity, thin, and liquid. In the printing process, ink pumps are used to recycle ink. Air is inevitably mixed into the flowing ink. Bubbles may form due to the large surface tension of the ink. (Liquid air). Blistering affects the normal operation of the ink printing job, and in severe cases it will make the printing job impossible. The method for eliminating foam is to add a defoamer with a formula content of 0.3% to 0.5% on the one hand, such as tributyl phosphate, 080, etc., commonly used for ink and wash; on the other hand, it is necessary to minimize the chances of contact between ink and air, such as guarantees. When the ink supply is continuous, reduce the circulation amount of the ink pump as much as possible, and use a non-leaking ink-absorbing tube and ensure that the ink tube mouth is deeper than the liquid surface of the ink fountain 30 cm.

3.1.5 Stability and Formulation The stability of ink is the continuous and uniform performance of the ink during storage or use. Since ink is a thin, low-viscosity liquid, the phenomenon of gradation of pigments and binders tends to occur. The stability of the ink is deteriorated, resulting in thinning and thickening in the storage container. Without stirring, the ink is uneven in 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.

3.2 Deployment of Print Quality Adaptability

The print quality adaptability of ink and wash refers to the dryness that the ink displays 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.

3.2.1 Dryness. The drying of the 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 (2 l°C). Excessive dryness will cause the ink to dry on the printer during the transfer process, followed by blocking, non-imprinting, or imprinting defects; drying too slow will result in quit printing, stickiness, dot expansion, and layer failure. Clear, superimposed adhesion problems such as adhesion. 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 slow down. The correct method should be to dilute with a mixed solvent of water and ethanol. If the dryness is too fast, the proportion of water may be increased. If the dryness is too slow, the proportion of water may be reduced.

3.2.2 Adhesion. The adhesion of the ink is the property that the dried printing film adheres to the surface of the printing object. The adhesion of the ink is mainly affected by the performance and amount of the binder resin used, and the use shows that the high acid rosin synthetic resin ink has poorer adhesion than the acrylic resin ink, and the surface structure of the printing object also affects the adhesion, and the surface has a rough yellow plate. The poor adsorption of paper and ink film is easy to discolor, resulting in poor adsorption mainly due to the molecular weight of the resin used in the ink, insufficient amount of resin, too much filler, excessive ink dilution, and loose paper surface structure. Adsorption can be improved by changing the type of resin, in the application can be added to the new same type of linking material, especially in the field dilution is the best way to use compound materials and composite solvent compound method is more appropriate.

3.2.3 resistance. The resistance of ink is mainly refers to the printing film of water, organic solvents, acid and alkali solution of durable color retention properties. The durability of the ink is affected by the structure, molecular weight and amount of the ink resin. Durability can be improved to a certain extent by changing the structure of the formulation, but at present, measures such as sizing (moisture-proof oil) or surface coating after printing can achieve satisfactory results.

Source: PACK.CN