A letter from the Editor
The second issue of the journal in 2019 is, somewhat unexpectedly and with some delay, published as a regular issue, again. Unfortunately, a special thematic edition will be released later this year. This time, three papers have been published to cover research and new achievements in a wide field.
The first original scientific paper deals with the problem of achieving good print quality, with special attention on the print register with modern roll-to-roll inkjet presses. These machines are already well-established in the market, and the author presents the mathematical model for the correction of the register, which is required to be performed due to the influence of the ink on the substrate and the deformations that occur during the printing process.
The second paper summarizes the study of the possibility of using sensitive dyes in a two-dimensional code for the production of smart packaging. The use of thermochromic, hydrochromic and photochromic dyes as sensors for irreversible detection of the exposure of the packaging to high temperatures, humidity and light are discussed. The starting points for further research on the use of modern inkjet printing techniques and new sensitive dyes are also given.
The third paper is devoted to image analysis and digital image processing, with an emphasis on edge detection in a computer-modulated 3D color image with established algorithms and the use of corresponding software, compared to the visual perception of observers. The topic will be interesting primarily for experts in the field of 3D modeling and printing.
In Topicalities the editor Markéta Držková (firstname.lastname@example.org) summed up the news regarding Drupa 2020, which will be held in June next year, where we can again expect to see breakthrough achievements and future printing technologies. Furthermore, you will find short project presentatitons from our research areas under Horizon 2020, achievements of the European Federation for Print and Digital Communication Intergraf, and two highlights in the printing of conductive lines and graphene-based printed electronics.
Among the novelties of the library, an overview of new issues in the field of history of the press, classical photographs, materials, nanoparticles, and printed electronics is presented.
Three doctoral theses are also introduced. Martin Schmid successfully defended the thesis in the field of cognitive process control in the printing industry at the Technical University of Munich. The author has shown that, in the field of conventional technologies, by means of appropriate methods, it is possible to achieve substantially increased efficiency in material utilization and in the production management. The other presented thesis was defended by Colleen Erin Robertson at the University of North Carolina. She compared print vs. digital technology for students with low incidence disability and found the advantages or greater relevance of both print and digital technologies in different areas of teaching and learning. Jari Keskinen successfully defended the thesis on supercapacitors on flexible substrates at the Tampere University of Technology. Using roll-to-roll printing technology, he produced and demonstrated the use of supercapacitors on cardboard and polyethylene terephthalate substrate.
Among the announced events in the near future, I would highlight the 46th International iarigai Conference: Advances in Printing and Media Technology, which will be held in September in Stuttgart, however, many other international organizations and institutions also offer conferences, workshops, summer schools and other opportunities for presenting achievements, discussions and acquiring new knowledge.
I would expect that the upcoming iarigai Conference in Stuttgart will also be a milestone for the Journal of Print and Media Technology Research. For more than a year there have been discussions and coordination on the optimization of publishing activities of two major international organizations – the International Association of Research Organizations for Information, Media and Graphic Arts Industries and the International Circle of Educational Institutes for Graphic Arts Technology and Management.
Both associations also publish scientific Journals, and both have also recognized the importance of publishing quality scientific papers in indexed Journals, that are highly ranked at international level. Up to now, co-operation and pooling of power in the publication of a joint Journal has already been agreed, with only a few details left to coordinate. Changes of the Editorial Board, the Scientific Advisory Board, and in the areas covered by the Journal will be revealed shortly. I am convinced that the Journal will become even more relevant to you as an interesting source of scientific papers, topicalities and also as a publication in which you would like to publish the results of your research work.
Ljubljana, July 2019
A model for the prediction of print quality of a roll-to-roll inkjet press
Heidelberger Druckmaschinen AG, Gutenbergring, 69168 Wiesloch, Germany
In this paper, a simulation model for the web dynamics of a digital label printing machine is presented and an exemplary application from practice is shown to verify the model. The basis is an extended modeling of the web dynamics including thermal effects in order to calculate the dynamic behavior of the continuous web. It is shown how thermal excitation can be used to measure the transfer function of the web dynamics and the influence of web tension control systems. Furthermore, a post-processing algorithm is presented which links the output data of the web dynamics simulation with the behavior of the inkjet printing data path and thus simulates digital inkjet printing. The results can be used to explain both registration errors from color to color as well as color density fluctuations within a raster image printed by a single color. As a practical example, a digital inkjet printing machine is considered in the following, in which a periodic variation in the color impression of a raster or solid surface can be recognized in the printed image. The fluctuation period corresponds to one revolution of the rotary encoder, which serves as a trigger signal for the inkjet printheads. With the help of the simulation model for the web dynamics and the presented post-processing algorithm, the origin of the error can be understood. Measurement and simulation are compared to verify the model. If the amplitude and the phase angle of the encoder error are measured, the print quality can be ensured by compensating the error within the inkjet printing data path. This is shown both in the simulation and on the basis of measured data.
Keywords: web dynamics, register, thermal effects, digital printing, transfer function
JPMTR 122 | 1904 Original scientific paper
Smart packaging by the application of sensitive dyes
Mustafa Bilgin and Johannes Backhaus
E-mails: email@example.com; firstname.lastname@example.org
Bergische Universität Wuppertal, Rainer-Gruenter-Straße 21, 42119 Wuppertal, Germany
Smart packages can communicate with their users or other clients via the Internet of Things. By means of sensitive dyes implemented in an intelligent code, the code is able to report the history of critical environmental influences on the package and accordingly on the packed goods during the entire transport path. So all steps from manufacturing to delivery can be traced without any energy supply. Moreover, these intelligent codes are composed of different sensitive dyes in the form of dots. Each smart dot can change its colour from an inactive state into active states, in the form of colour gradations. Thus, a critical value of colour gradation can be defined as limitations that set the sensitive dot’s state from inactive  to active . Hence, static consumer or product information and dynamic information about environmental influences – e.g. water/moisture, temperature, UV-light, pressure, acids, etc., can be stored in one entire code. The use of various sensitive dyes also adds a significant anti-counterfeiting feature and a chemical fingerprint. The intelligent code can be cost-efficiently printed as a printable sensor. Furthermore, the intelligent code can be read and analysed by usual smart devices, e.g. smartphone, tablet, etc. – linked to a specific web server where the code can be compared with its original state, to indicate critical deviations. The foreground of this paper is the application of sensitive dyes (sensitive dyes are as well named as smart materials) in order to get information for comprehensive research. First, the printability of the sensitive dyes is examined as well as their reaction process and behaviour depending on technical parameters, e.g. viscosity. Second, their reaction processes and reaction times in dependence on different layer thicknesses based on various polyester screens and the remissions of the printed samples are analysed. Third, the characteristic wavelength changing of the sensitive dyes is shown, which will allow further investigations by a smartphone.
Keywords: smart materials, intelligent code, thermochromism, hydrochromism, photochromism
JPMTR 123 | 1901 Research paper
The evaluation of rendered color shading using edge detection method
Dejana Javoršek, Nika Bratuž and Helena Gabrijelčič Tomc
DDepartment of Textiles, Graphic Arts and Design, Faculty of Natural Sciences and Engineering, University of Ljubljana, Snežniška 5, 1000 Ljubljana, Slovenia
Color reproduction in 3D computer-generated scenes is affected by scene setting, object and camera properties, illumination and rendering technique. Regardless of controllable conditions in a computer-generated environment, the achievement of colorimetric accuracy is complex, it depends the most on hue, saturation, and lightness of the virtual object’s color and has to be considered from different perspectives. Visual perception of object color and shading is also influenced by object form, usually defined by contours. The aim of this research was to introduce edge detection method for evaluation of rendered color shading and to define how participants perceptually match color shaded renderings with predefined and proposed edge detection representations. The testing objects were color renderings of shaded objects whose colors were defined with tiff textures in the test chamber consisting of four lights, camera, and an object with shadows. In the experimental part, different edge detection methods and color channel models were used on selected colors of color renderings. It was confirmed that color, light intensity and background influence the frequency of detected edge pixels. Moreover, it was established that visual evaluation is also affected by color, background and light intensity. When the results of the frequency of detected edges and visual evaluation were compared, it was demonstrated that edge detection can be a suitable supportive method for evaluation of rendered color shading.
Keywords: color rendering, scene settings, photometric lights, standard lights, visual perception
JPMTR 124 | 1902 Research paper