Flexo Printing Research Articles

Elimination of the Solid Graininess Issue with Different Micro-Pattern Structures at Flexo Printing

Flexo printing is a relief printing system, and ink transfers on the solid areas are not transferring well during the printing. That is why graininess is increasing and pinholes are occurring on the solid areas. This is a well-known issue in the flexo printing system. Micro-patterns usually eliminate these pinholes. Using correct micro-patterns allows homogeneous ink laydown and increases solid ink density. Micro-pattern holes behave like gravure cylinders on plate surfaces, and this makes for better ink transfer to the substrate. In this study, a more successful micro-pattern structure than the ones currently used was found by examining the solid ink density (SID) values and ink laydown obtained from the structure by producing eight different micro-pattern structures of 1000 LPI and 1500 LPI (line per inch) pattern screen frequencies with the same polymer structure and type. Densitometric values of solid prints made with the developed micro-patterns were measured. By eliminating the pinholes formed in solid prints and at the screen dot shapes, the ink is distributed more homogeneously without graininess. It has been determined that this results in a more stable measurement of ink density and eliminates the measurement of excess ink and low density.

Flexo-printed polymer waveguides for integration in electro-optical circuit boards

Electro-optical circuit boards (EOCBs) offer great potential for short-ranged data transmission in highly electro-magnetic inflicted environments. Finding a cost-efficient way to manufacture EOCB only using additive printing processes could establish, increase, and secure data transmission in PCB systems. Flexo printing is an efficient manufacturing process that combines high contour resolution and layout flexibility to create optical waveguides. Previous research has shown that printing waveguides on a polymethylmethacrylate substrate can enable optical data transmission for up to 20 cm. However, a thermo-resistant polyimide (PI) substrate is needed to integrate printed waveguides into PCB. Since PI does not meet optical demands, waveguide cores must be separated by printed optical cladding. This research aims to investigate the additive printing process, which stacks various polymers to achieve waveguides that are ready for integration. Further, the integration in PCB is validated according to functional testing of the optical structures. An entire manufacturing process for printed EOCB is presented, which enables the investigation of optical coupling processes in upcoming research.

The Influence of Anilox Roller Lines on the Ink Impression on Different Polymer Substrates in Flexo Printing

The Influence of Anilox Roller Lines on the Ink Impression on Different Polymer Substrates in Flexo Printing

Study of color reproduction features at “Nargus” LLC

The features of color recreation were studied at “Nagrus” LLC. For this, the quality control process at the enterprise and the statistics of rejects and the reasons for their occurrence were analyzed; the features of the use of inks in the process of flexo printing were considered and the stages of ink preparation for printing were described. The main factors that affect the quality of products at the stage of prepress and during the process of manufacturing flexo plates were also found.
 The process of preparing pantone colors for printing a run was analyzed; a table of dependence of pantone deviations on various materials was created; a technique has been developed to increase the speed of paint selection and recommendations regarding its application. Factors that have the greatest influence on the quality of a flexographic plate during its manufacture were found, and a technique for the optimal choice of plates for non-absorbent materials was developed.

Mechanical and barrier properties of flexible packaging materials after the flexo printing process

The Journal of the National Science Foundation of Sri Lanka publishes the results of research in all aspects of Science and Technology. The journal also has a website at http://www.nsf.gov.lk/. 2021 Impact Factor: 0.682The JNSF provides immediate open access to its content on the principle that making research freely available to the public supports a greater global exchange of knowledge.

Use and analysis of UV varnish printed braille information on commercial packaging products

This paper investigates the possibility of reproducing Braille by UV ink-jet printing on self-adhesive labels, previously printed by flexo printing technology. The aim was to determine whether it is possible to reproduce Braille, the degree of quality of created Braille dots (cells), the legibility of Braille text, and how many layers of varnish are necessary for quality reproduction. The Braille letter was applied to the previously printed label (design) using 8, 10, 12, 14 and 16 layers of varnish. It has been found that it is possible to reproduce a quality and legible Braille. With the increase in the number of layers, the assessment of legibility and quality of reproduction by the respondents also increased. Samples reproduced with 12 layers of varnish received a very good grade of legibility and good grade for quality of Braille. Samples reproduced with 8 and 10 layers received bad grades for legibility, and even worse for quality, while samples with a higher number of layers of varnish, 14 and 16, received even better grades. The threshold for quality reproduction would therefore be the use of 12 layers of varnish, where a good ratio of workmanship and economy is obtained.

Investigation of the Effect of Different Screening Methods on Print Quality in Digital Printing System

Digital printing is the process of printing the designs and photos prepared in computer environment with advanced printing technologies on different materials in a high quality and fast way. The digital printing system, which is increasing its effectiveness today, has taken great steps with technology since the first years of its existence and has started to have a voice in the sector for the last ten years. The digital printing, which is an alternative to the offset printing system in making design a product, exhibits significant improvements in terms of production efficiency, cost and quality. Offset has become competitive with flexo printing with the developing color efficiency in digital printing machines. High quality and different applications can be made with digital printing machines. In order to achieve this (screening) process, it is necessary to know the boundaries of the color universe that can be seen or produced by the devices and machines used in the system. In this study, the difference between colors and color consistency and basic measurements such as color values, dot gain were evaluated by changing the selection of screen methods used in digital printing. The differences caused by the screening structure variable have been shown with graphics and tables, then suggestions have been made. It has been determined that the change in the screening structures in digital printing creates differences in dot swelling, density and color.

Printability of paper and paperboard surface treatment with gum rosin and derivatives

PurposeThis study aims to provide control of liquids, especially against water-based ink on the paper and paperboard surface with natural substances, in also practical and greenway.Design/methodology/approachThe paper surface was treated with natural rosin and its derivatives to obtain a hydrophobic effect and to improve printing properties. The oleoresin samples collected from Pinus nigra Arnold and Pinus pinaster Aiton trees in the controlled area and turpentine content removed was by hydrodistillation. The gum rosin (GR), fortified 10% with maleic anhydride (MGR) and esterified with 10% pentaerythritol (PMGR) samples solved in a simply alcohol and sprayed the base paper surface directly with a spray gun. Base paper samples were paperboard, bleached paper and test liner paper. Then, flexo printing was applied and printability properties were measured.FindingsThe treatment weights of these paper samples were 1.8 ± 0.5, 1.3 ± 0.5 and 0.7 ± 0.2 g/m2, respectively, compared to the base paper. Greater Cobb60 results were obtained from modified rosin samples than unmodified gum rosin-sized paperboards and the PMGR surface treatment reduces Cobb60 values by 20% and MGR treatment reduces 15% comparing to the base sheet. Then, the printing procedure was applied to the surface of the treated materials using a flexo printing system. As a result of the treatment better print density, chroma and print lightness value consumed a less hydrophobic agent and controlling water-based flexo ink on the base paper surface.Originality/valueThe unique aspect of this work was improving the hydrophobicity of the paper surfaces was achieved by spraying with natural rosin and derivatives.

Study on the Reduction Treatment of ink Sludge in Flexo Printing

The paper studied about the characteristics of ink sludge of flexo printing and analyzed the possibility different reduction treatment and disposal. Industrial analysis and elemental analysis to confirm the elemental content, TGA and DTG were used to analyze the weight loss and heat absorption and desorption behavior of dry sludge at different temperature. GC-MS and XRF analysis was applied to analysis the composition and content of the compounds. Three kinds treatment for for ink sludge based on different needs.

Enhancing Printing Resolution on Hydrophobic Polymer Surfaces Using Patterned Coatings of Cellulose Nanocrystals.

High-resolution inkjet printing of a hydrophobic polymer surface (polystyrene, PS) was accomplished using a patterned coating of cellulose nanocrystals (CNCs) that prevents the ink from bleeding. A periodically crack-free, wrinkled (wavelength of around 850 nm) stamp was prepared by surface oxidation of an uniaxially stretched poly(dimethylsiloxane) elastomeric substrate and was used as a template to transfer aligned patterns of cellulose nanocrystals (CNCs) onto PS surfaces by wet stamping. The morphology of the aligned CNC coatings on PS was then compared with randomly deposited CNCs on PS using atomic force microscopy. The wettability of the CNCs and polymer surfaces with water and ink was measured and analyzed in the context of inkjet printing. This biomaterial coating technique enables high-resolution printing of modern water-based inks onto hydrophobic surfaces for applications in renewable packaging and printing of biomolecules for high throughput diagnostics. Further, with suitable modifications, the technology is scalable to roll-to-roll manufacturing for industrial flexo printing.

Scaling Behavior of Pattern Formation in the Flexographic Ink Splitting Process

We considered pattern formation, i.e. viscous fingering, in the ink splitting process between an elastic flexographic printing plate and the substrate. We observed an unexpected scaling behavior of the emerging pattern length scale (i.e., finger width) as a function of printing velocity, fluid viscosity, surface tension, and plate elasticity coefficients. Scaling exponents depended on the ratio of the capillary number of the fluid flow, and the elastocapillary number defined by plate elasticity and surface tension. The exponents significantly differed from rigid printing plates, which depend on the capillary number only. A dynamic model is proposed to predict the scaling exponents. The results indicate that flexo printing corresponded to a self-regulating dynamical equilibrium of viscous, capillary, and elastic forces. We argue that these forces stabilize the process conditions in a flexo printing unit over a wide range of printing velocities, ink viscosities, and mechanical process settings.

Estimation Of Screen Density According To Different Screening Methods With Artificial Neural Network Method In Flexo Printing System

Choice of dot shape is the most important factors that affect the printing quality in the flexographic printing system. The aim of the operations performed by the machine operator during the printing process (densitometric measurements, ink settings, etc.) is to achieve the same quality from the first printing to last printing. This study attempts to estimate screen density values obtained from the same polymer structure (DFR), 175 Lpi screening and 10 different screen structures using the Artificial Neural Networks method (ANN). Data necessary for calculations were obtained from real values as a result of experimental studies. The correlation coefficient of the data obtained from the model created with ANN for screen density values was found to be 98,902% and this value was found to be consistent with scientific values. According to the results, the neural network model used in flexographic printing systems of different screening methods predictable effect on the printing result.

Dijital Termal Flekso Baskı Kalıbı Hazırlama Parametrelerinin, Kalıp Üzerindeki Nokta Yapısına Etkisinin İncelenmesi

Flexo printing is defined as an elevated printing technique that uses flexible plates and liquid ink enabling rotary printing. Flexo printing is the most common printing technique used primarily in the packaging and labels industry. Besides production efficiency and printing quality, its most important attributes aim to ensure quality, cost-effectiveness and fast plate-making. There are some troubles about productivity and quality during the development of the plate. During the thermal developing process of digital plates, developing parameters determine the image properties on the plate. In this study; exposure parameters of the flexographic digital plate making are accepted constant parameters and parameters of the developing process accepted variable parameters. In order to systematic analysis of the developing parameters, MiniTAB test design software was used. The output of the test design software were entered the developing machine and plates made by the different temperature, pressure, speed and revision thermally. Developed plates were analysed by dot measure device, hardness measure device and microscope. As a result of study; the effects of thermal plate preparation parameters on the plate’s dot structure were determined.

Spot-color matching system of flexo printing based on radius basis function neural network

Spot-color matching system of flexo printing based on radius basis function neural network

Statistical analysis of printing elementsreproduction on thermally developed CTP flexo printing plates

This study presents statistical evaluation of the dot area and line width on thermally developed CtP flexo printingplates using image analysis software PerfectEye v4.03. The aim of the study was to determine whether the dot area and line width when different processing parameters are applied (different main exposure time and different numberof rotations of developing drum during developing process) were statistically different from each other or not. Im-age analysis of dots and lines were performed with a VipTronic Vipdens measuring device using CCD camera and a PerfectEye image analysis software. The shape data, dot area and line width were compared by applying one way ANOVA (analysis of variance) method followed by post hoc Tukey’s test using the software SPSS (Statistical Pack-age for Social Science) and independent sample T-test with a 0.05 significance level. Statistical analysis revealedthat the difference between the dot area and line width for different processing conditions are significant with a 95% confidence level.

Development of printable bioactive paper containing laccase

Compatibility of Trametes versicolor and Trametes hirsuta laccases was studied with polymers used for flexographic inks. The aim was to produce bioactive paper with ability to change color. Optimum pH for the stability of Trametes versicolor and Trametes hirsuta laccases was determined during storage at room temperature for 60 days. The optimum pH for the stability of both laccases was 8–9. The stabilization effect of flexo printing inks on the enzymes was tested in liquid form and when coated on paper. Sulfo polyester resin HZ1100D stabilized the two laccases both in solution and on paper. For example, Trametes versicolor laccase remained stable for at least 8 weeks when coated with HZ1100D polymer. Furthermore, the adsorption of the flexo inks to cellulose was studied with quartz crystal microbalance with dissipation monitoring (QCM-D). It was observed that HZ1100D also adsorbs well on cellulose over a wide pH range. The results suggested that laccases are well suited to bioactive paper applications. Large scale manufacturing of bioactive paper products by flexo printing would be possible because of the compatibility of laccases with flexo inks.

Design of roll-to-roll printing equipment with multiple printing methods for multi-layer printing

In this paper, a novel design concept for roll-to-roll printing equipment used for manufacturing printed electronic devices by multi-layer printing is presented. The roll-to-roll printing system mainly consists of printing units for patterning the circuits, tension control components such as feeders, dancers, load cells, register measurement and control units, and the drying units. It has three printing units which allow switching among the gravure, gravure-offset, and flexo printing methods by changing the web path and the placements of the cylinders. Therefore, depending on the application devices and the corresponding inks used, each printing unit can be easily adjusted to the required printing method. The appropriate printing method can be chosen depending on the desired printing properties such as thickness, roughness, and printing quality. To provide an example of the application of the designed printing equipment, we present the results of printing tests showing the variations in the printing properties of the ink for different printing methods.

A New Black Water Based Ink Prepared by Chinese Traditional Materials for Screen Printing Ancient Books

Ink is one of “the four treasures in the study”. Inks prepared by the traditional materials is usually in the form of Chinese ink and ink stick, which are unsuitable for the modern printing technology such as screen printing, offset print, gravure or flexo printing. On the other hand, modern commodity printing inks most prepared by modern chemical pigments and chemical reagents, which would emit a certain amount of pollutants. Reproduction of Chinese ancient books, if printed by using modern commodity printing inks, would lost their lasting ancient charm such as antique, quaint, hoary, vintage, archaic, etc. In the present research, a new black water based ink is prepared by Chinese traditional materials such as, Chinese wood oil soot, bone glue, borneol, musk, pepper, etc. not including any modern chemical reagents which could cause pollution of the environment. The viscosity, fineness and rheology property of the ink were characterized. As an application example, the ink is used to duplicate the Tripitaka book sample by screen printing on Xuan papers. The original is the Tripitaka printed in the Ming Dynasty and from the temple of Wutaishan, Shanxi Province, China. The Reproduce is lasting ancient charm and durable.

Study on the Adjustment to the Pressure of Flexible Printing on the Board

During the flexo printing process of corrugated flexible resin version, precise pressure control is the key technical indicators of ink transfer, printing graphic reproduction as well as reducing the the loss of physical properties of corrugated board. The gaps △L between the printing roller and the impression cylinder were adjusted by the worm in this paper, different printing pressures are produced in the printing process, the impact of pressure change on flexo printing quality was described quantitatively. The results showed that: 7.5mm thick corrugated board used AB-type hardness of 36 Shore A, when a thickness of 3.94mm DuPont flexible resin was printed, the optimal pressure gap △L was 10.9mm, the flexible resin version of the real size was 3.73mm, and the thickness of corrugated board was 7.17mm, the board thickness was 7.30mm after decompression, the thickness of corrugated board after the printing was compressed by 2.7%. The result of this paper offers a certain theoretical reference and practical guidance to improve the quality of flexo and the production of high quality corrugated board.

Printing of Polymer Microcapsules for Enzyme Immobilization on Paper Substrate

Poly(ethyleneimine) (PEI) microcapsules containing laccase from Trametes hirsuta (ThL) and Trametes versicolor (TvL) were printed onto paper substrate by three different methods: screen printing, rod coating, and flexo printing. Microcapsules were fabricated via interfacial polycondensation of PEI with the cross-linker sebacoyl chloride, incorporated into an ink, and printed or coated on the paper substrate. The same ink components were used for three printing methods, and it was found that laccase microcapsules were compatible with the ink. Enzymatic activity of microencapsulated TvL was maintained constant in polymer-based ink for at least eight weeks. Thick layers with high enzymatic activity were obtained when laccase-containing microcapsules were screen printed on paper substrate. Flexo printed bioactive paper showed very low activity, since by using this printing method the paper surface was not fully covered by enzyme microcapsules. Finally, screen printing provided a bioactive paper with high water-resistance and the highest enzyme lifetime.