Modification of a single-solvent-based gravure ink for enhance wettability and substrate adhesion

In this research, the effect of solvent types and pigment types on C-type ester-based gravure inks were studied. Three of the widely used solvent types and two of the pigment types were used in this study. The characteristics of the modified inks were investigated by measuring the most important physical properties of the inks: (i) surface energy, (ii) contact angle, (iii) viscosity and (iv) substrate adhesion. The experiment results showed that the ink properties changed significantly depending on the solvent type, while pigment type variation had a negligible effect on the ink properties. From this experiment, the most improved properties were obtained in the ethyl-acetate-based ink. In order to further improve the ink properties without suppressing the advantage of this solvent type, small amounts of various aqueous additives and surfactants were added to find suitable formulations. From this stage of study, three ink formulations with suitable printability and wetting properties were achieved. These formulations were C-type ethyl-acetate-based ink with one of the following surfactants; 0.8 percent of Zonyl FS-300, 0.1 percent of Zonyl FSJ, and 12 percent of hexane. The wetting and print performance characteristics of these formulations were tested by practically using them in the pilot press trials. The results from pilot press trials indicated that the new ink formulations with low concentration aqueous surfactants may be used to minimize printing problems such as pinholing and fish-eye effect. However, even the best performance formulation was found to have quite high temperature sensitivity and surface tension higher than the theoretical upper surface tension limit. These, unfortunately, lead to poor printing quality. Therefore, further study is needed to find a better ink formulation with superior properties that will overcome print quality difficulties and completely solve the printing problems

Determining the effect of printing ink sequence for process colors on color gamut and print quality in flexography

The effect of printing ink sequence for process colors on color gamut and image quality was studied, to determine if there was an optimum printing ink sequence for flexographic printing. The results of using four process color inks (Cyan, Magenta, Yellow, and Black) in various sequences in flexography were analyzed in this research. White oriented polypropylene (OPP) film was printed with UV inks on a Mark Andy LP3000 flexo press. The sequences were analyzed based on differences in the color gamut, their volume, ability of the sequence to reproduce better-looking images, and rendering of maximum ink coverage. The results suggest there was no one particular sequence that was proved to be optimum. Among the five sequences (YMCK, MYCK, CMYK, KYMC, and KCMY) tested, only one (KCMY) printed well without producing any moiré-like pattern. The other four sequences (CMYK, YMCK, MYCK, and KYMC) did produce a moiré-like pattern in the heavy ink coverage or shadow regions of the print. However, the sequences showing the moiré-like pattern exhibited bigger color gamuts compared to the one that does not produce a moiré-like pattern. The actual cause for the moiré-like pattern formations is unknown. It may not be due to faulty screen angles. Instead it is suspected that it is related to the wetability of the CMY inks underneath the Black. Further research is needed to find the real reason for the formations of these moiré-like patterns. Thus, it will be difficult to have one optimum ink sequence for flexography, as one sequence may be preferable for obtaining a bigger gamut for a given hue angle, while some other sequence may produce better-looking images without any moiré-like printing artifacts appearing in the prints. If the image to be printed has more colors (requiring a bigger gamut) and limited or no shadow regions, it is recommended to print in the order of CMYK. If the image to be printed has more shadow regions, and less colors (can be printed with a smaller gamut), it is suggested to print with the KCMY sequence

A Study of the Lightfastness of High-Chroma Water-Based Flexographic Printing Inks

The study of new material for package printing is critical because packaging is not only about visual aesthetics, but also function. Technologies such as High-chroma ink that aid expanded gamut printing can be especially useful in package printing. The thesis experiment examined the lightfastness characteristics of High-chroma water-based flexographic printing inks sets within the context of package printing applicability. Using conventional water-based flexographic printing inks as a standard, the study examined whether High-chroma inks exhibit different lightfastness characteristics. First, the researcher chose yellow and magenta process color water-based flexographic inks because of the traditional process colors, they are the least stable in terms of lightfastness characteristics. The tested yellow and magenta each have two types of lightfastness specifications which are described as fair and excellent. The inks were produced by a K-proofer to simulate the ink’s solid and tint surfaces on package printing. Next, a Q-sun xenon test chamber was used to simulate environmental lighting conditions using a procedure described by ASTM International Standard Practice for Evaluating the Relative D3424-11 Method 3. After each time exposure duration, a spectrodensitometer was used to collect the density and colorimetric (L*a*b*) values of the standard ink set and High-chroma ink set. Lastly, the values were used to calculate ∆D and ∆E00 for analysis. The total experiment duration was 230 hours. The results showed that there are no significant lightfastness characteristic differences between standard and High-chroma inks. The most significant difference result obtained was in the comparison of the magenta ink in fair lightfastness standard, in which the High-chroma ink exhibited better lightfastness characteristic colorimetric values than the standard ink. The results of comparing yellow and magenta inks showed that magenta had a better lightfastness characteristic densitometric and colorimetric attributes than yellow ink. Each tested ink color exhibited unique characteristics that need to be tested and examined before implementation to fit specifics package printing requirement

A study of producing smoother gradients in the flexographic process on oriented polypropylene with UV ink by varying screening techniques, gradient lengths and the surrounding

Printers find that producing smooth gradients in the highlight area is a great challenge for flexographic printing. Screening technology vendors claim that hybrid screening technologies produce smoother gradients and enhance reproducible dots in the highlight areas. This study was designed to investigate if hybrid screening technologies can achieve better gradient results than other screening technologies—conventional screening and FM screening—with the flexographic process. A single test form was printed on oriented polypropylene with UV ink, as these are common materials used in flexible packaging. The first objective was to see how different pressure settings impact tone reproduction of each screening technique. There were three pressure settings—kiss impression, moderate pressure and high pressure. Tone reproduction curves of all three screening techniques were evaluated to see the change due to the different pressure settings. The results show that FM screening had a high sensitivity to change in pressure, while AM and hybrid screenings were more forgiving to variations in pressure settings. In the highlight areas, hybrid screening is the least sensitive to changes in pressure. The second objective was to study whether smoother gradients can be produced by altering three variables: screening techniques, gradient lengths and the impact of the surrounding. These variables were used to create a gradient matrix. Printed sheets from different points in the press run were collected for data analysis. There were two types of data analysis, measurement based evaluation and visual evaluation. Because of difficulty in the methodology for analyzing the measured data, the conclusions were then based on the results from the visual evaluation. There are three aspects to the problems with gradient smoothness: highlight breaking in AM screening, graininess of FM screening, and a disjunction at the transition point of hybrid screening. When minimum dot size, transition point, and transfer curve are set correctly, hybrid screening would be the best selection to use with the flexographic process. The surrounding, or solid frames around the gradients, did not truly enhance gradient smoothness at kiss impression

Test Targets 7.0: A Collaborative effort exploring the use of scientific methods for color imaging and process control

Test Targets is a culmination of teaching and learning that reflects quality and analytic aspects of printing systems and their optimization. The creation of the Test Targets publication is a total experience that reflects the innovation, problem solving, and teamwork of the diverse team of faculty, staff, students, and professionals responsible for its contents and production

Европейский и национальный контексты в научных исследованиях - 2021 : Технология

В настоящем электронном сборнике «Европейский и национальный контексты в научных исследованиях. Технология» представлены работы молодых ученых по геодезии и картографии, химической технологии и машиностроению, информационным технологиям, строительству и радиотехнике. Предназначены для работников образования, науки и производства. Будут полезны студентам, магистрантам и аспирантам университетов.=In this Electronic collected materials “European and national dimension in research. Technology” works in the fields of geodesy, chemical technology, mechanical engineering, information technology, civil engineering, and radio-engineering are presented. It is intended for trainers, researchers and professionals. It can be useful for university graduate and post-graduate students

Experimental and theoretical study of the color changes in OPP-based printing substrate on the gravure printing

In this study, the color change performances of the prints that are made with gravure printing technique on OPP-based printing substrate used in food packaging are studied experimentally and modeled analytically using artificial neural networks. In this printing technique using solvent ink, small variations in the printing conditions and ink viscosity significantly affect the colors obtained as a result of the printing as the printing surface is not absorbent. In the test print made, samples were taken at certain intervals and color changes were determined with spectrophotometer measurements from test charts. The analytical relation giving the color changes based on the parameters they are linked to was obtained via artificial neural networks. Thus, the color deviations during normal production process shall be determined to ensure that necessary precautions are taken