engleski

Non-destructive methods in the Study of IJ Ink - Substrate Interaction

Quality of ink-jet prints significantly depends on the interaction between the printing substrate and IJ ink. The penetration of printing ink should be low in order to retain high optical colour density (1, 2). The surface of the paper also plays an important role ; it should have controlled absorption capacity for printing inks, should not dust, and should have suitable level of smoothness as well as other properties necessary for good operability and printability (3, 4). The aim of this study was to investigate the radial and vertical distribution of Ink-Jet printing ink on and below the surface of different types of papers as well as to determine the influence of the paper surface on the print quality. To achieve this aim the following methods were used: Penetration - Dynamics Analyser – PDA is an analytical instrument designed for investigation of penetration dynamics of liquids into solid samples, such as papers. The analytical technique employed is based on recording the change of intensity of ultrasonic signals transmitted by solid samples while one of their sides is in contact with a liquid (sample is immersed into the water bath). Slit-Scanning Densitometer is used in qualitative and quantitative evaluation of thin layer chromatograms. It was used for investigation of both, radial and vertical distribution of different spots of printing ink by measurements in reflection mode (for the wavelengths of 580 nm). We used Ink Jet printer Canon BJC 8500, printing resolution 600 dpi and the colour intensity 100%. Confocal Laser Scanning Microscopy – CLSM is presented as non-conventional method for non-destructive study of interaction of Ink-Jet inks and printing substrate. It was used for investigation of tree-dimensional structure of paper, pore volumen (5, 6) and for evaluation of ink penetration in z-direction (7). For observation and measurement with Confocal laser microscopy we used the spots of printing ink, with scann area 460 µ m × 460 µ m, air objective with numerical aperture 0, 6, laser beam wavelength of 458 nm and resolution in z-direction 2, 7 µ m. The vertical distribution was made by observing the border of the ink spot with CLSM and subsequently by using the software for cutting the slices in z-direction. The number of slices needed from the most fluorescent to not visible part of the dot was calculated. Photoacoustics and photoacoustic spectroscopy are methods for studiing the optical and thermal properties of the printed area at different depths beneath the sample surface. Also the physical principles of indirect photo acoustics effect and its applications in the field of graphic arts were explained. These are the non-destructive methods, too. Cross section analysis of prints was made by microtome (slice thickness 30 µ m) and than studied with Optical Microscopy - OM. This destructive method enables an detailed access to the undersurface migration of the printing ink through the inside layers of the printing substrate. We wanted to qualify the importance of the informations achived by these measurement techniques. The limits of each method are especially important in the study of ink – paper interactions as well as the influence of the substrate on the print quality. This is the reason why we studied Ink-Jet prints printed od several completely different types of paper: Z - Zweckform Photo Paper is recommended for IJ prints, one side coated, high glossy, (130 g/m2, 170 μ m), K – Carton board is one side coated multilayered white board, (300 g/m2, 430 μ m), I - ICP Permanent Paper made at the Pulp & Paper Institute in Ljubljana, which corresponds to standard – ISO 9706 and is no surface treatment, (70 g/m2, 110 μ m), T – Three-ply Tissue Paper with a low percentage of secondary fibres, (60 g/m2, 185 μ m). A hudge range of quatity characteristics of papers was meant to define the limits of each of the measuring method. We expact that the application of non-destructive methods in the study of Ink-Jet prints will be informing enough in comparison with the destructive motheds. Confocal laser scanning microscopy and Photoacoustic spectroscopy might give us a very detailed view to the penetration process in the z- direction. The data presented in this paper make part of a larger experiment of the stabiliy of Ink-Jet prints. The part of the study regarding the abrasive resistence of the prints (before and after the accelerated aging) has allready been presented and the paper is to be printed.

Ink Jet prints; PDA; Slit-scanning densitometer; CLSM; Photoacoustic spectroscopy

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