MOLPRINT

1. MOLPRINT MOLECULAR UNDERSTANDING OF PRINTABILITY Jarl B. Rosenholm, Åbo Akademi University (coordinator) Martti Toivakka, Åbo Akademi University Kai-Erik Peiponen, University of Joensuu Jussi Timonen, University of Jyväskylä (University of Oulu) Matti Murtomaa, University of Turku Heidi Fagerholm, Top Analytica, Turku

2. MOLPRINT INDUSTRIAL PROJECT PARTNERS M-real Oyj StoraEnso Oyj Omya Oy Ciba Specialty (Raisio) Chemicals Oy Hansaprint Oy KSV Instruments Oy

3. MOLPRINT New printing tech-niques require a range of coated and noncoated paper qualities. Advanced inks are pigment based, solvent based or water based, which should set fast without mottling

4. MOLPRINT WHY The diverging requirements set by new printing techniques has made the traditional specification standards used by paper manufacturers (Bendtsen, PPS, Cobb, HST) unsatisfactory, which is considered to be the greatest obstacle for a fast development of this industry. HOW Paper qualities aimed for different printing techniques are characterised thoroughly with physico-chemical and structural means in two- and three-dimensions, in order to establish new common standards for the printers and for the paper makers.

5. MOLPRINT The research has to account for all the process stages Digital or Ink-Jet printing PRINTING METHOD A CALENDERING / SURFACE SIZING / COATING BASE PAPER / SC / COATED PAPER / PACKAGES CALENDERING / SURFACE SIZING / COATING Offset or flexo printing PRINTING METHOD B

6. MOLPRINT WHAT will be done • Chemical and physical surface and bulk properties • Surface (2D) and cross-sectional (3D) structure • 2D- and 3D- transport and setting of printing ink • Optical properties related to visual response • Heat transport and electric/hydrostatic conductivity

7. MOLPRINT WHO is doing

8. MOLPRINT Pigment Coated Papers Laboratory of Paper Coating and Converting, Åbo Akademi University To understand the interactions that occur in various printing processes between printing liquids (inks, emulsified inks, foun-tain solutions) and pigment coated papers Through use of both experiments and mathematical modeling, the project strives to identify those chemical and morphological properties of inks and coated paper surface that control the printability and quality of coated paper products

9. MOLPRINT • HOW it will be done • Influence of ink constituents and paper surface characteristics on the ink tack development, ink setting and ink adhesion are investigated • Ink constituents are separated chromatographically • The “microstructure” and chemistry in commercial inks is analyzed and consequences for the printability and print quality is evaluated • Properties ink/fountain solution emulsions are measured

10. MOLPRINT EXPERIMENTAL PROCEDURES Hg-porosimetry Thin-layer wicking (TLW) Thin-layer chromatography (TLC, into latex) Tack, gloss, print density etc. Flexo Heat/coldset offset Rotogravure

11. MOLPRINT • MODELING: Current models ignore chemistry! Develop 2D surface and 3D bulk model of coating structure, including heterogeneity caused by chemistry • Clarify the influence of nonuniformities on dominant mechanisms that control printability and print quality

12. MOLPRINT • Ink and Solvent Interaction and their Transport during Printing • Department of Physical Chemistry, Åbo Akademi University • Relate the surface energy and structure with the dynamic 2D-spreading and setting of inks on pigment coated papers • Investigate the simultaneous fast 2D- and 3D-penetration of model solutions into the bulk paper structure (ink-jet printing). • A mathematical model is developed: • which describes the liquid transport and ink setting processes • serves as a new specification for printers and paper makers

13. MOLPRINT HOW it will be done The surface energy and spreading is measured as wetting () The surface structure and interaction energy with AFM The setting speed, e.g. with D-QCM The penetration is investigated as 2D-3D-liquid flow The amount of liquid absorbed is evaluated from volumetric and/or geometric considerations The binding of ink is characterized spectrometrically

14. MOLPRINT

15. -1 0 1 1 0 cos * -1 cos  MOLPRINT

16. MOLPRINT Interfacial structures – Process aspect Top Analytica, Ltd Characterize the physical surface and cross-sectional structure of paper and coating layers – molecular structure Identify the surface chemical structure of paper and coating layers – macroscopic properties The relationship between these properties –how should “printability” be defined Identify the most suitable analytical techniques for studying of the above mentioned relationships

17. MOLPRINT • HOW it will be done • The paper manufacturing is investigated step-by-step, from the base paper to the printed product as case studies, including: • Base paper structure  Structure after calendering  •  Structure after surface sizing/coating  Printabilty • In between these steps; surface properties, interaction between process chemicals and pigments and the interaction between the ink and the surface is analyzed

18. 290 285 280 Binding Energy (eV) MOLPRINT EXPERIMENTAL PROCEDURES TOF-SIMS < 2 nm ESCA 2 - 5 nm Na+ Mg + K (SEM)-EDX ~ mm 100 mm

19. MOLPRINT EXPERIMENTAL PROCEDURES Blue = CaCO3 Green = Kaolin Red / Brown = C, O 200 m

20. MOLPRINT Optical measurement of print quality Department of Physics, University of Joensuu Unfortunately, the variation of gloss deteriorates the print quality. The gloss depends on various paper and printing variables such as the micro-roughness and texture of paper, absorption of ink and spectro-scopic properties of the ink. There are conventional glossmeters that give information on relativelylarge area and provide a number, which is related to the average gloss of a surface. Unfortunately, such devices are not sensitive to detect gloss in normal direction which is the usual geometry for visual evaluation namely that of reading news papers or magazines.

21. MOLPRINT • HOW is it done We have developed a novelglossmeter that is based on detection of local gloss variation by a diffractive element based glossmeter (DOG). It is free of the problems related to the conventional glossmeters (see. Kari Myller ” A glossmeter based on a diffractive optical element”, University of Joensuu, Department of Physics, Dissertations 42 (2004)). This device is sensitive to small gloss variation of planar and curved surfaces. Furthermore, it can be utilized for detection of average gloss from a macroscopic surface. The setup of DOG is shown in figure

22. MOLPRINT • HOW it will be done • The key point of the DOG is the diffractive optical element (DOE), which is a computer-generated hologram and fabricated using modern electron beam lithography. DOE is exploited as an analyser of the amplitude and phase of the reflected light field from the print. It provides, e.g.: • Information on the quality of the print itself such as gloss variation. • Information on anisotropy of the surface morphology on print area. • Thus, it is an useful device for quality inspection of prints

23. MOLPRINT Effect of nip pressure and calandering on the surface morphology and bulk structure of paper Department of Physics, University of Jyväskylä • Understand morphological changes induced in the structure of paper by nip pressure and calandering. • To relate these morphological changes to printing quality

24. MOLPRINT • HOW it will be done X-ray Microtomography (XMT) Department of Physics, University of Jyväskylä resolution ~ 0.9 m complete 3-D internal structure Optical coherence tomography (OCT) Optoelectronics and Measurement Techniques Laboratory, University of Oulu resolution ~ 10 m penetration depth ~ 40 m

25. microfocus X-ray tube X-ray CCD camera object manipulator sample Computer 3D image MOLPRINT X-ray Microtomography (XMT) Uses X-rays to produce 2D shadowgrams from multiple angles Reconstructs 3D images from shadow-grams Nondestructive – no sample preparation needed Sample sizes from 2mm-68 mm with respective voxel sizes 0.9-20 m

26. MOLPRINT Structure of paper with a coating layer using XMT Penetration of coating layer in base paper The numerical characteristics of the internal structure (morphology and composition) from the 3D-volume

27. MOLPRINT Optical coherence tomography (OCT), Optoelectronics and Measurement Techniques Laboratory, University of Oulu

28. MOLPRINT Heat transport and electrical conduction Laboratory of Industrial Physics, University of Turku • Electrostatics play an important role in, for example: • xerography, gravure printing, laser and ink jet printing • further handling of printouts • future products & processes (intelligent papers and packages, ...) • Thermo-analytical properties: • heat conduction in paper and polymers • high printing speed -> small melting time

29. MOLPRINT • HOW it will be done • Development of new electrostatic methods for studying: • electrical conduction and charge decay • charging properties of papers and polymers • effects of moisture, morphology, composition etc. on the electrostatic properties • Development of new thermo-analytical methods • heat conduction in polymers and papers with different composition & morphology

30. MOLPRINT Effect of surface coverage of a glass pipe by small particles on the triboelectrification of magnesium stearate doped glucose powder

31. MOLPRINT Thank you for your attention!