Selected publications

KLANJŠEK GUNDE, Marta, AHTIK, Jure, GOLOB, Gorazd, OPARA KRAŠOVEC, Urša. Color rendering properties of light continuously modulated by an electrochromic switchable device. Color res. appl.. [Print ed.], 2009, vol. 34, no. 4, pp. 321–329.

Abstract: Every chromogenic switchable window gives rise to considerable change of spectral power distribution of the light crossing trough. The filtered light continuously changes during charging/discharging of the device, seen as its coloration/discoloration. As this process occurs continuously, it causes continuous Change of colors on an illuminated multicolored scene. The ability of an electrochromic (EC) switchable unit to modulate daylight and different artificial lights passing through it is studied here. The color rendering properties such a variable light are evaluated. The range of the effect and its consequences on the color of a scene can be adequately described by the change in chroma and hue angle during the modulation of light. These effects were evaluated by different light sources shining through the same EC unit.

Selected publications

ČERNIČ, Marjeta, BRAČKO, Sabina. Influence of paper on colorimetric properties of an ink jet print. J. imaging sci. technol., Jan./Feb. 2007, vol. 51, no. 1, pp. 53–60.

Abstract: Paper for ink jet printing has to obtain optimal printing runnability, printability, and printing quality. Therefore, it must have some specific properties that ensure optimal drying time, mechanical stability of a print, and its light and water resistance. The paper surface should enable the printing ink to be dried as fast as possible. The aim of the applied research was to determine how an ink jet color print on paper changes with time immediately after printing, and how long it takes for the colour print to stabilize. Color differences Delta E-ab were measured that appeared on print after a certain amount of time with regards to values attained immediately after printing. The influence of paper on colorimetric properties and optical density of a print was analysed by measuring some structural, surface, and sorption properties. The values attained show that the paper surface should enable wetting and ink penetration in paper structure. The biggest changes in colorimetric properties of print became visible during 1 h after printing; however, color print finally stabilizes only after 96 h. Research results confirmed the importance of paper sorption properties for obtaining high-quality ink jet color prints.

BRAČKO, Sabina, ŠOLAR, Alenka, FORTE-TAVČER, Petra, SIMONČIČ, Barbara. Colour constancy of vat prints on cotton fabrics. Color. technol., 2009, vol. 125, no. 4, pp. 222–227.

Abstract: Colour constancy of prints with vat dyes on cotton fabrics was investigated by computing the CMCCON02 colour inconstancy index with the key element CAT02 for chromatic adaptation transform. The results show that the highest changes in colour appearance can be expected when the average daylight is replaced with fluorescent light. If D65 daylight is replaced with some other type of daylight, such as D50 or D55, only minor colour deviations occur which do not substantially change the colour appearance of the prints. The analysis of the influence of the lightness and chromaticity of prints shows that the chromaticity of the samples significantly affects their colour constancy. The change of appearance of the prints with lower chroma because of changed illumination conditions is less probable. The influence of a dye blend composition was also investigated. On average, multi-coloured dye blends have proved to be more colour constant.

BOGATAJ, Urška, MUCK, Tadeja, BRAČKO, Sabina, LOZO, Branka. Readability of processed digitally printed two-dimensional codes. J. imaging sci. technol., May/Jun. 2010, vol. 54, no. 3, pp. 030502/1–030502/6.

Abstract: Despite the evident success of conventional one-dimensional (1D) bar codes and their role in automatic product identification, logistics, supply, and retail, these 1D technologies can encode only a limited amount of data and are susceptible to damage and obscuration. On the other hand, two-dimensional (2D) codes which began appearing in the 1980s are becoming more and more popular because of their ability to encode a large amount of data in a small area. They can also be read even if they are partially damaged or erased. Because of their advantages in comparison to linear bar codes and their increasingly frequent use the authors analyzed two 2D codes (DATA MATRIX code and OR code). The purpose of our research was to determine the lowest raster tone value for each printing color and each printing technique which would enable the 2D code reading with two different readers. For testing the readability of codes, lightfastness, accelerated aging, and water resistance were used. Codes were created and printed in four process inks (cyan, magenta, yellow and black), each of them in the following raster tone values: 15%, 20%, 25%, 30%, 50%, and 100%. Samples were printed using three different digital printing technologies (ink jet, laser, and magnetography). After printing, the samples were illuminated by Xe light, exposed to accelerated aging (at 80 C and 65% relative humidity) for six days, and immersed in water to determine their water resistance. All printed samples, before and after illumination and accelerated aging, were read with laser and charge coupled device based readers, and the lowest raster tone value of the code for each printing technique and each printing ink was determined.

MOŽINA, Klementina, MEDVED, Tanja, RAT, Blaž, BRAČKO, Sabina. Influence of light on typographic and colorimetric properties of ink jet prints. J. imaging sci. technol., Nov./Dec. 2010, vol. 54, no. 6, pp. 060403/1–060403/8.

Abstract: The purpose of this study is to examine the influence of light on the changes in typographic and colorimetric properties of ink jet prints in order to establish an appropriate typeface style and type size for business correspondence to ensure information permanence. The prints were made with six ink jet printers from different manufacturers on four different office papers. Four different, widely used typefaces (one old-style, one transitional, and two sans-serif) in five different sizes (6, 8, 10, 12, and 16 pt) were tested. The resistance of printed business correspondence to light was evaluated according to the ISO 12040 standard. The color differences were determined spectrophotometrically. The differences in typographic tonal density and wicking of typefaces were measured with image analysis. After the exposure to light, the biggest difference in typographic tonal density was observed at type sizes 6 and 8 pt, and at one of the sans-serif typefaces.

DEBELJAK, Mirica, BRAČKO, Sabina, HLADNIK, Aleš, GREGOR-SVETEC, Diana. Comparison of ultraviolet inkjet printing on different synthetic fibrous papers. Tappi j., May 2010, pp. 17–25.

Abstract: We investigated the printability of fibrous synthetic papers with ultraviolet (UV) inkjet technology. Cyan, magenta, yellow, and black (CMYK) color fields were printed on two types of fibrous synthetic papers using two different wide-format UV inkjet printers. Spectrophotometric and densitometric measurements were performed on CMYK color fields with different ink coverages, along with a microscopic analysis of unprinted paper, black prints with 100% ink coverage, and a print mottle of magenta and black prints. Colorimetry and optical densities of the CMYK prints were qualitatively and quantitatively compared. Color deviations in CMYK prints were affected by paper type and were dependent on the UV inkjet printer used.

BRAČKO, Sabina, RIJAVEC, Tatjana, BIZJAK, Grega, GORENŠEK, Marija. Impregnation dyeing of cotton/polyester spun yarn mixture with photoluminescent pigments = Pamuk/poliester iplik karißiminin parlayan pigmentler ile emdirme yöntemine göre boyanmasi. Tekstil ve konfeksiyon dergisi, 2011, vol. 21, no. 1, pp. 58–64.

Abstract: The research focuses on the technologically plain and inexpensive procedure of impregnation dyeing of spun yarn with photoluminescent pigment Special lux TPLL-9E Yellow-Green (Special Chem, Italy). The pigment concentration was 50 and 150 g of pigment per kilogram of yam and two binding agents were used, i.e. Elastil Transparent FG (Minerva, Italy) and Padding Binder FM/N (Minerva, Italy), as well as a mixture of both. The impregnated coating was conducted on yarns with linear density Nm 125/1 and Nm 20/1, where the mixture ratio of cotton/polyester was 50/50 and 67/33. The luminance measurements were made on the unwashed, once washed and five times washed yams. In some cases, a high luminance level of yarns up to 500 mcd/m2 was measured, which decreased only slightly after one wash, and after five washes, it dropped to 230 mcd/m2. In accordance with the expectations, the luminescence decreased exponentially with time; however, the yams could still be noticed in the darkness even after 12 hours.

Selected publications

BOGATAJ, Urška, MUCK, Tadeja, BRAČKO, Sabina, LOZO, Branka. Readability of processed digitally printed two-dimensional codes. J. imaging sci. technol., May/Jun. 2010, vol. 54, no. 3, pp. 030502/1–030502/6.

Abstract: Despite the evident success of conventional one-dimensional (1D) bar codes and their role in automatic product identification, logistics, supply, and retail, these 1D technologies can encode only a limited amount of data and are susceptible to damage and obscuration. On the other hand, two-dimensional (2D) codes which began appearing in the 1980s are becoming more and more popular because of their ability to encode a large amount of data in a small area. They can also be read even if they are partially damaged or erased. Because of their advantages in comparison to linear bar codes and their increasingly frequent use the authors analyzed two 2D codes (DATA MATRIX code and OR code). The purpose of our research was to determine the lowest raster tone value for each printing color and each printing technique which would enable the 2D code reading with two different readers. For testing the readability of codes, lightfastness, accelerated aging, and water resistance were used. Codes were created and printed in four process inks (cyan, magenta, yellow and black), each of them in the following raster tone values: 15%, 20%, 25%, 30%, 50%, and 100%. Samples were printed using three different digital printing technologies (ink jet, laser, and magnetography). After printing, the samples were illuminated by Xe light, exposed to accelerated aging (at 80 C and 65% relative humidity) for six days, and immersed in water to determine their water resistance. All printed samples, before and after illumination and accelerated aging, were read with laser and charge coupled device based readers, and the lowest raster tone value of the code for each printing technique and each printing ink was determined.

Selected publications

KLANJŠEK GUNDE, Marta, AHTIK, Jure, GOLOB, Gorazd, OPARA KRAŠOVEC, Urša. Color rendering properties of light continuously modulated by an electrochromic switchable device. Color res. appl.. [Print ed.], 2009, vol. 34, no. 4, pp. 321–329.

Abstract: Every chromogenic switchable window gives rise to considerable change of spectral power distribution of the light crossing trough. The filtered light continuously changes during charging/discharging of the device, seen as its coloration/discoloration. As this process occurs continuously, it causes continuous Change of colors on an illuminated multicolored scene. The ability of an electrochromic (EC) switchable unit to modulate daylight and different artificial lights passing through it is studied here. The color rendering properties such a variable light are evaluated. The range of the effect and its consequences on the color of a scene can be adequately described by the change in chroma and hue angle during the modulation of light. These effects were evaluated by different light sources shining through the same EC unit.

Selected publications

GREGOR-SVETEC, Diana. High modulus polypropylene fibers. 2, Influence of fiber preparation upon structure and morphology. J. appl. polym. sci., 2006, vol. 100, no. 2, pp. 1067–1082.

Abstract: The influence of drawing on the limiting draw ratio upon formation of the morphological structure of fibers spun fro, binary polypropylene (PP) blends was studied. Fibers were Spun from a fiber-grade CR-polymer and from the blends of a fiber-grade CR-polymer with a molding-grade polymer in the composition range of 10-50 wt % added. As-spun fibers were immediately moderately and additionally highly drawn at the temperature of 145 degrees C. The structure and morphology of these fibers were investigated by small-angle X-ray scattering, wide-angle X-ray scattering, differential scanning calorimetry, scanning electron microscopy, density, birefringence, and sound velocity measurements. It was shown that continuously moderately drawn fibers are suitable precursors for the production of high tenacity PP fibers of very high modulus, because of so called oriented "smectic" structure present in these fibers. With drawing at elevated temperature, the initial metastable structure of low crystallinity was disrupted and a c-axis orientation of monoclinic crystalline modification was developed. Hot drawing increased the size of crystallites and crystallinity degree, the orientation of crystalline domains, and average orientation of the macromolecular chains and resulted in extensive fibrillation and void formation. It was found that the blend composition has some influence on the structure of discontinuously highly drawn fibers. With increasing the content of the molding-grade polymer in the blend, the size of crystalline and amorphous domains, density and crystallinity, as well as amorphous orientation decreased. Relationship has been established between the mechanical properties, crystallinity, and orientation of PP fibers. It was confirmed that by blending the fiber-grade CR-polymer by a small percentage of the molding-grade polymer, maximization of elastic modulus is achieved, mainly because of higher orientation of amorphous domains.

VRABIČ, Urška, JESIH, Adolf, GREGOR-SVETEC, Diana. Physical and absorptive changes in plasma treated viscose fibres. Fibres Text. East. Eur., 2007, vol. 15, no. 5/6 (64/65), pp. 124–126.

Abstract: Chemical modification of the fibres was successful in improving their different properties, but there are environmental concerns related to the disposal of chemicals after treatment. Taking into account the advantages related to the technology of plasma treatment and the differentiated changes of the fibre matter processed is plasma treatment, increasingly replacing chemical applications in finishing and pre-treatment of textiles products. For industrial uses, regenerated cellulose fibres are used to replace traditional materials, for example, nonwovens, like hygiene and medical products. The most important characteristics for hygiene and medical products are absorption ability and capability of water retention. The main aspect of our research was to analyse the physical and absorptive characteristics of viscose fibres, treated with plasma. The study revealed that plasma surface treatment modifies the absorptive structure, tensile and other physical properties of viscose fibres.

GREGOR-SVETEC, Diana. Melt spinning of plastic-grade polypropylene. Acta chim. slov.. [Tiskana izd.], 2009, vol. 56, no. 4, pp. 959–966.

Abstract: The goals of our research were to optimize the melt spinning of filaments spun from plastic-grade polypropylene polymer and to compare the structural characteristics of as-spun filaments obtained from plastic- and fiber-grade polymers. The melt spinning of polypropylene filaments was carried out on an Extrusion Systems Ltd. laboratory spin-draw device. The spinning process was optimized in order to avoid the onset of spinline instabilities and spinline diameter fluctuations and was carried out as gravitational spinning with no-take-up application. From measurement of the average molecular weight and molecular weight distribution, some degradation of molecules and narrowing of molecular weight distribution in both types of as-spun filaments was determined. At both tested as-spun filaments, produced by rapid cooling of an extruded jet, only the spherulitic structure composed of alpha-monoclinic crystals was established. In comparison to the filaments spun from the fiber-grade polymer, filaments spun from the plastic-grade polymer had higher density, melting enthalpy, and higher crystallinity, resulting in higher tenacity of these filaments.

SFILIGOJ-SMOLE, Majda, ŽUPERL, Kristina, STANA-KLEINSCHEK, Karin, KUREČIČ, Manja, BELE, Marjan, GREGOR-SVETEC, Diana, RIBITSCH, Volker. Electrokinetic properties of polypropylene-layered silicate nanocomposite fibers. J. appl. polym. sci., 2009, vol. 113, no. 2, pp. 1276–1281.

Abstract: Nanocomposite fibers based on polypropylene (PP) polymer were prepared with different content of nanofiller. Filaments were spun from an isotactic iPP homopolymer. Montmorillonite modified by N,N-dimethyl-N,N dioctadecylammonium cations was used for preparation of PP nanocomposite fibers. A PP grafted with acrylic acid was added as a coupling agent. Nanocomposite fibers were characterized, i.e., the surface morphology of PP nanocomposite fibers was observed and surface properties were defined by electrokinetic properties determination by zeta potential measurements. For particle distribution observation the plasma etching was involved as a method for sample preparation. The addition of nanoparticles has an impact on ZP value of nanofilled fibers, however, isoelectric point IEP is not significantly influenced by different concentrations of nanofiller.

DEBELJAK, Mirica, MUCK, Tadeja, GREGOR-SVETEC, Diana. Evaluation of printability on synthetic papers printed by UV ink jet. Nordic Pulp and Paper Research Journal, 2009, vol. 24, no. 3, pp. 313–318.

Abstract: The aim of this research was to investigate the quality of UV prints on various synthetic papers. Prints with the CMYK color fields on three types of synthetic papers (Neobond, Pretex, and Yupo) were made using an UV Ink Jet printer. On the unprinted synthetic papers, roughness and surface tension were measured. Densitometric measurements on the CMYK color fields of 20%, 40%, 60%, 80%, and 100% raster tone value and image analysis of the black (K) color at 20% raster tone value were also performed. The analysis revealed some deviations in the optical density of prints and raster tone value between papers. The optimal print was obtained on the synthetic paper Pretex, where the dot gain was low and the circularity of the printed dots was almost ideal. The prints on the synthetic paper Yupo were the most uniform while those on the synthetic paper Neobond were more uneven. The roughness of paper was also found to have a significant influence on the print quality while the surface tension of paper at the UV ink-jet printing process has less impact.

GREGOR-SVETEC, Diana, TIŠLER KORLJAN, Barbara, LESKOVŠEK, Mirjam, SLUGA, Franci. Monofilaments produced by blending virgin with recycled polypropylene = Ham ve geri dönüşüm polipropilen polimerlerinin karişimindan elde edilen monofilamentler. Tekstil ve konfeksiyon dergisi, 2009, vol. 19, no. 3, pp. 181–188.

Abstract: Our research addresses the use of 100% recycled polypropylene from separately collected packaging waste in Slovenia for the manufacture of monofilaments. The goal of this research was to optimise the melt spinning of monofilaments and to compare the properties of monofilaments obtained from the virgin polymer and from blends of virgin and recycled polymer. Monofilaments were Spun from the pure virgin polymer, from a blend of 85% virgin and 15% recycled polymer, and from 50% virgin and 50%, recycled polymer. It was established that the addition of the recycled polymer to the virgin polymer lowered the crystallinity and average molecular orientation of as-spun monofilaments, which influenced the tensile properties of the monofilaments. Because of the poor miscibility of the virgin with the recycled polypropylene. which also contained some fractions of polyethylene. the as-spun monofilaments were porous, brittle and rigid, and had a high tendency to break.

GREGOR-SVETEC, Diana. Influence of layer composition on properties of recycled boards. Cellul. Chem. Technol., 2010, vol. 44, no. 10, pp. 505–512.

Abstract: In the present study, three types of recycled boards with different top layer composition have been analysed. The quality of coated boards with different fibrous composition has been evaluated by determining their structural, mechanical, optical and surface properties. The slight increase in virgin fibre content in the top layer, from 10 to 20%, has been found to improve the surface, the optical and mechanical properties of coated recycled boards. A greater influence on the mechanical properties is exerted by the addition of a higher percentage of chemical pulp in the top layer of the three-layered structure of recycled boards, rather than by the addition of a forth layer from recovered paper and board. Additionally, the investigation aimed at determining the viscoelastic properties of the boards and assessing the influence of a 90% relative humidity on their tensile properties. Besides lowering tensile strength, humidity has even a more significant influence on the viscoelastic properties. Of the coated recycled boards under study, the influence of humidity has been found as less pronounced in the boards containing higher amounts of chemical pulp in the top layer.

DEBELJAK, Mirica, GREGOR-SVETEC, Diana. Optical and color stability of aged speciality papers and ultraviolet cured ink jet prints. J. imaging sci. technol., Nov./Dec. 2010, vol. 54, no. 6, pp. 060402/1–060402/9.

Abstract: The present study deals with the optical and color stability of aged specialty papers and ultraviolet cured (UV) ink jet prints. As paper substrates, a fiber synthetic paper and two types of lignin-free papers with included security elements were used. Prints of CMYK color fields using UV Curable Inks were made using a UV ink jet printer, Oce Arizona 250 (R) GT. Samples of papers and UV ink jet prints were artificially aged using standard techniques of accelerated aging, such as moist heat (80 degrees C and 65% RH), dry heat (105 degrees C) and treatment with the a xenon arc lamp (35 degrees C CT, 50 degrees C BST, 35% RH). Aging was performed for periods of 1, 2, 3, 6, and 12 days. In this study, optical properties of untreated and treated paper substrates such as the whiteness and yellowness index and color differences between untreated and treated UV ink jet prints were followed. The tested paper substrates behaved differently. The fiber synthetic paper was more stable than both lignin-free cellulose papers. Some color differences during accelerated aging were observed in prints. The effect depends on the particular ink and type of accelerated aging. On average, dry heat treatment and treatment with the xenon arc lamp showed greater impact on CMYK prints than moist heat treatment. The most stable among the prints was the black ink.

DEBELJAK, Mirica, BRAČKO, Sabina, HLADNIK, Aleš, GREGOR-SVETEC, Diana. Comparison of ultraviolet inkjet printing on different synthetic fibrous papers. Tappi j., May 2010, pp. 17–25.

Abstract: We investigated the printability of fibrous synthetic papers with ultraviolet (UV) inkjet technology. Cyan, magenta, yellow, and black (CMYK) color fields were printed on two types of fibrous synthetic papers using two different wide-format UV inkjet printers. Spectrophotometric and densitometric measurements were performed on CMYK color fields with different ink coverages, along with a microscopic analysis of unprinted paper, black prints with 100% ink coverage, and a print mottle of magenta and black prints. Colorimetry and optical densities of the CMYK prints were qualitatively and quantitatively compared. Color deviations in CMYK prints were affected by paper type and were dependent on the UV inkjet printer used.

GREGOR-SVETEC, Diana, SFILIGOJ-SMOLE, Majda. Homogenity of poly(propylene) and poly(ethylene terephthalate) fibers. Tex. res. j., 2010, vol. 80, no. 15, pp. 1569–1580.

Abstract: Diffuse small-angle X-ray scattering is caused by inhomogeneity in the electron density distribution of a material and is often attributed to the existence of microvoids in polymers. The content, dimensions and relative surfaces of the microvoid system can be determined thereby. The dimensions of the coherently scattering domains and the sizes of the inhomogeneities are related by the form, or shape factor (f). Changes in this factor highlight structural changes in polymer fibers caused by different treatments. In the present paper the microvoid system of differently treated poly(ethylene terephthalate) (PET) and poly(propylene) (PP) fibers were studied after subjugation to different treatments. PP fibers were spun from two different polymers and drawn at different temperatures, whereas PET fibers were treated in different media. The form factors found for PET and PP fibers were rather high. For PP fibers, drawn at different temperatures and draw ratios, the form factors were between 2 and 5. Untreated PET samples had form factors of about 6. A supercritical fluid treatment could increase the form factor up to 8. Conventional water dyeing and hot air treatments caused considerable changes in the microvoid system and increased the form factor to values even larger than 8.

DEMŠAR, Andrej, ŽNIDARČIČ, Dragan, GREGOR-SVETEC, Diana. Impact of UV radiation on the physical properties of polypropylene floating row covers. Afr. j. biotechnol., 2011, vol. 10, no. 41, pp. 7998–8006.

Abstract: In the intensive horticulture, various ways of protected area are used for the growth of seedlings and the cultivation of vegetables in all seasons. The easiest and the cheapest form of protected area is agrotextile, which can be laid directly over vegetable crops (row cover). Agrotextiles are nonwovens which are manufactured from textile fibres which are usually of chemical origin. Textiles, used as agrotextiles require suitable tensile strength and good permeability characteristics with no significant deterioration under the influence of weather changes and UV radiation. Properties of agrotextiles depend on the fibres made of and on the type and conditions of production. The purpose of this study was to analyse the influence of simulated sun light radiation (xenon lamp) on physical properties of polypropylene (PP) nonwoven material, which is used for the production of agrotextiles. The research showed that the properties of row cover change when radiated with UV light. Tensile, tearing and bursting properties worsen after radiation and air permeability and water vapour show little increase. The changes in the properties are a consequence of changes in fibres, molecular and supermolecular structure which is exhibited in changed fibres and consequently also nonwoven properties.

GRILJ, Silva, MUCK, Tadeja, HLADNIK, Aleš, GREGOR-SVETEC, Diana. Recycled papers in everyday office use. Nordic Pulp and Paper Research Journal, 2011, vol. 26, no. 3, pp. 349–355.

Abstract: The use of recycled papers is becoming more and more important because of mostly ecological and economical reasons. The scarcity of native pulpwood resources is also a reason in some parts of the world. Recycled papers are relatively widely used, although not so much for everyday office purposes. The main goal of this research was to determine whether 100% recycled papers can replace papers made of virgin fibres for the purpose of electrophotographic printing in everyday office use. The print quality of both paper types was determined using recycled papers and papers made of virgin fibres as printing substrates. On the prints, the edge sharpness, print micro-nonuniformity, colour gamut and halftone values were determined. The results obtained for print quality on the recycled papers were very promising. Prints on the recycled papers achieved similar, in some cases identical, results as prints on papers made of virgin fibres.

Selected publications

GRILJ, Silva, MUCK, Tadeja, HLADNIK, Aleš, GREGOR-SVETEC, Diana. Recycled papers in everyday office use. Nordic Pulp and Paper Research Journal, 2011, vol. 26, no. 3, pp. 349–355.

Abstract: The use of recycled papers is becoming more and more important because of mostly ecological and economical reasons. The scarcity of native pulpwood resources is also a reason in some parts of the world. Recycled papers are relatively widely used, although not so much for everyday office purposes. The main goal of this research was to determine whether 100% recycled papers can replace papers made of virgin fibres for the purpose of electrophotographic printing in everyday office use. The print quality of both paper types was determined using recycled papers and papers made of virgin fibres as printing substrates. On the prints, the edge sharpness, print micro-nonuniformity, colour gamut and halftone values were determined. The results obtained for print quality on the recycled papers were very promising. Prints on the recycled papers achieved similar, in some cases identical, results as prints on papers made of virgin fibres.

Selected publications

VESEL, Alenka, MOZETIČ, Miran, HLADNIK, Aleš, DOLENC, Jožica, ZULE, Janja, MILOŠEVIĆ, Slobodan, KRSTULOVIĆ, Nikša, KLANJŠEK GUNDE, Marta, HAUPTMAN, Nina. Modification of ink-jet paper by oxygen-plasma treatment. J. phys., D, Appl. phys., 2007, vol. 40, pp. 3689–2696.

Abstract: A study on oxygen-plasma treatment of ink-jet paper is presented. Paper was exposed to a weakly ionized, highly dissociated oxygen plasma with an electron temperature of 5 eV, a positive-ion density of 8 x 10(15) m(-3) and a density of neutral oxygen atoms of 5 x 10(21) m(-3). Optical emission spectroscopy (OES) was applied as a method for detection of the reaction products during the plasma treatment of the paper. OES spectra between 250 and 1000 nm were measured continuously during the plasma treatment. The wettability of the samples before and after the plasma treatment was determined by measuring the contact angle of a water drop. The appearance of the surface-functional groups was determined by using high-resolution x-ray photoelectron spectroscopy (XPS), while changes in the surface morphology were monitored with scanning electron microscopy (SEM). Already after 1 s of the plasma treatment the surface, which was originally hydrophobic, changed to hydrophilic, as indicated by a high absorption rate of a water drop into the paper. The OES showed a rapid increase of the CO and OH bands for the first few seconds of the plasma treatment, followed by a slow decrease during the next 40 s. The intensity of the O atom line showed reversed behaviour. The XPS analyses showed a gradual increase of oxygen-rich functional groups on the surface, while SEM analyses did not show significant modification of the morphology during the first 10 s of the plasma treatment. The results were explained by degradation of the alkyl ketene dimer sizing agent during the first few seconds of the oxygen-plasma treatment.

HLADNIK, Aleš, ČERNIČ, Marjeta, BUKOŠEK, Vili. Role of paper coating pigments and additives in darkfastness of ink jet prints. J. imaging sci. technol., Jan./Feb. 2008, vol. 52, no. 1, pp. 010507/1–010507/7.

Abstract: The article discusses changes that occur when paper samples printed with an office ink jet printer HP 5550 are exposed to elevated temperature and relative humidity without the presence of light for a prolonged time period according to accelerated artificial aging standard EN ISO 5630-3. The effects of paper coating pigment type (pyrogenic silica, precipitated and ground calcium carbonate) and the amounts of binder and dye fixative on print quality and darkfastness are examined. Results show that both color chroma and print density of prints made with the dye-based inks-cyan, magenta and yellow-on calcium carbonate coatings are higher compared to coatings where silica is used. The opposite is true for the black pigment-based ink where silica clearly outperforms calcium carbonate coating pigments. Accelerated artificial aging deteriorates color vividness much more severely with ground CaCO(3) than with precipitated CaCO(3) coatings, while prints on silica coatings exhibit the highest darkfastness.

ČRNE-HLADNIK, Helena, PEKLAJ, Cirila, KOŠMELJ, Katarina, HLADNIK, Aleš, JAVORNIK, Branka. Assessment of Slovene secondary school students’ attitudes to biotechnology interms of usefulness, moral acceptability and risk perception. Public underst. sci., 2009, vol. 18, no. 6, pp. 747–758.

Abstract: Quantitative and qualitative studies among 469 high school students of average age 17 years were conducted. The students' attitudes to four practical applications of biotechnology were examined: genetically modified plants (Bt corn), genetically modified animals (salmon), and hemophilia germ line and somatic gene therapy. Each of the four applications was examined from three different viewpoints: usefulness, moral acceptability and risk perception. Bt corn production proved to be the most acceptable in terms of both usefulness and risk perception. Values for genetically modified salmon and germ line gene therapy were comparable, but much lower than those for the other two applications; this was true for both usefulness and moral acceptability. In addition, students found genetically modified salmon to be ethically much less acceptable than Bt corn. Significant gender differences were observed in the case of germ line gene therapy and genetically modified salmon.

ZUPIN, Živa, DIMITROVSKI, Krste, HLADNIK, Aleš. Evaluation of influence of densities and weaves on physical and mechanical properties of “squared” cotton woven fabrics = [Procjena utjecaja gustoće i veza na fizikalno-mehanička svojstva kvadratičnih uzoraka pamučnih tkanina = Beurteilung des Einflusses der Dichte und der Bindung auf physikalisch-mechanische Eigenschaften quadratischer Baumwollgewebe-Muster]. Tekstil, 2009, vol. 58, no. 7, pp. 309–320.

Abstract: In order to evaluate the influence of densities and weaves on mechanical properties of squared cotton woven fabrics and to estimate the damages of yarns which occur during the weaving process, as well as to predict the values of breaking force and breaking elongation, 23 samples of fabrics were woven. All sample were designed and produced in an original way under the same production conditions. The simplest method for calculating tensile characteristics of fabrics based on the conditions of measurement, number of threads in fabrics, and breaking force and elongation of individual threads was used. A very good correlation between the theoretically calculated and the measured red values of breaking force was found. The prediction of breaking elongation of a fabric depends highly, on the chosen density as well as on the selected weave. The correlation between the predicted and measured values is substantially lower, however, similar to the case of breaking force, it call be described with a linear relationship. The measurement results were evaluated with the modern statistical methods ANOVA and PCA. The statistical findings confirmed conclusions based oil classical analyses of measured results. Moreover, the interaction between the influential parameters (ANOVA) and correlations among individual physical and mechanical properties of fabrics were identified and visualized (PCA).

ILEC, Eva, SIMONČIČ, Barbara, HLADNIK, Aleš. Evaluation of surfactant detergency using statistical analysis. Tex. res. j., 2009, vol. 79, no. 4, pp. 318–325.

Abstract: In this article the use of statistical analysis to determine the efficiency of surfactants as washing agents is presented. Two types of surfactants of different ion activities, three different types of fabrics, and four different types of soil tea, coffee, red wine, and charcoal - were used for this research. The application of soil to fabric samples was carried out with the pad-dry method. The washing of all the soiled samples was carried out in a Launder-Ometer using the standard method at two temperatures, 40 and 60 degrees C. A colorimetric evaluation according to a CIELAB system was used for all the samples, where the Delta E* values between the washed and unwashed samples, as well as between the washed and unsoiled samples, represent the criteria for the soil removal efficiency. A multi-factorial analysis of variance was used to explain the effects of the surfactant ionic activity, the fabric type, and the soil type on the efficiency of the surfactants as detergents. The results revealed that the efficiency of both studied anionic and non-ionic surfactants are similar when removing the tea, coffee, or wine soils, but when removing the charcoal soil the non-ionic surfactant proved to be more efficient. The surfactant detergency was not significantly improved when the temperature was increased from 40 to 60 degrees C.

JAVORŠEK, Dejana, JAVORŠEK, Andrej, HLADNIK, Aleš. Comparison of chromatic adaptation transforms used in textile printing sample preparation. Color. technol., 2010, vol. 126, no. 5, pp. 275–281.

Abstract: As image-capturing devices, such as scanners or digital cameras, normally describe data in RGB colour space, it is impossible to get a complete raw spectral description of a sample's colour. Device characterisation enables conversion of RGB values to corresponding XYZ tristimulus values of a sample. For transformation of tristimulus values from one illuminant to another, chromatic adaptation transforms should be used. Within our research, chromatic adaptation transforms were implemented in the field of digital textile printing of textile substrate with reactive dyes. Five chromatic adaptation transforms were investigated and their performance was assessed with cluster analysis. Results showed that the lowest mean colour differences were generated with the D50-D65 illuminant pair, followed by D50-A and D65-A. The same performance ranking of different chromatic adaptation transforms was obtained for both D50-A and D65-A illuminant pairs. The Bradford method showed the best results irrespective of the examined illuminant pair combination.

DEBELJAK, Mirica, BRAČKO, Sabina, HLADNIK, Aleš, GREGOR-SVETEC, Diana. Comparison of ultraviolet inkjet printing on different synthetic fibrous papers. Tappi j., May 2010, pp. 17–25.

Abstract: We investigated the printability of fibrous synthetic papers with ultraviolet (UV) inkjet technology. Cyan, magenta, yellow, and black (CMYK) color fields were printed on two types of fibrous synthetic papers using two different wide-format UV inkjet printers. Spectrophotometric and densitometric measurements were performed on CMYK color fields with different ink coverages, along with a microscopic analysis of unprinted paper, black prints with 100% ink coverage, and a print mottle of magenta and black prints. Colorimetry and optical densities of the CMYK prints were qualitatively and quantitatively compared. Color deviations in CMYK prints were affected by paper type and were dependent on the UV inkjet printer used.

PAVKO-ČUDEN, Alenka, ANGELOVA, Yordanka, HLADNIK, Aleš. Analysis of loop length basic weft knitted structures with elastane = [Analiza duljine očice temeljnih kulirnih pletiva s elastanom = Analyse der Maschenlänge der Kulierware mit Elasthan]. Tekstil, 2010, vol. 59, no. 11, pp. 492–507.

Abstract: Knitting with elastane core-spun yarns results in a compact, or very compact structure because of the yarn extension in the knitting zone, fabric relaxation in unloaded state after relaxation and yarn compression within the knitted structure. This results in knitted loop geometry changes and hence results in changes of knitted fabric structural parameters. The purpose of the investigation was to evaluate the most frequently applied loop models for the loop length calculations. As anticipated, the structures made from conventional yarns without elastane show the best agreement with the studied geometrical loop models. Structures made from the elastane core-spun yarns do not correspond to geometrical loop models for individual structures. The investigated loop models cannot be generally applied, when designing both conventional and elasticised knitted fabrics in various structures. The research objective was also to define new loop models based on multiple linear regression.

HLADNIK, Aleš, LAZAR, Mihael. Paper and board surface roughness characterization using laser profilometry and gray level cooccurrence matrix. Nordic Pulp and Paper Research Journal, 2011, vol. 26, no. 1, pp. 99–105.

Abstract: Image texture analysis tool gray level cooccurrence matrix was implemented to assess surface topography of eight commercial paper and board samples varying considerably in roughness. Height data for individual specimens were acquired by confocal laser profilometer. Strong linear relationship was found between the texture measures "Correlation" and "Energy" derived from gray level cooccurrence matrix on one hand and ISO topography descriptors Rq and Ra on the other. Correlation of these data to those obtained with a conventional roughness method Bendtsen was only a rough one. The applied technique can also be used for determination of paper formation and quantification of print mottling.

GRILJ, Silva, MUCK, Tadeja, HLADNIK, Aleš, GREGOR-SVETEC, Diana. Recycled papers in everyday office use. Nordic Pulp and Paper Research Journal, 2011, vol. 26, no. 3, pp. 349–355.

Abstract: The use of recycled papers is becoming more and more important because of mostly ecological and economical reasons. The scarcity of native pulpwood resources is also a reason in some parts of the world. Recycled papers are relatively widely used, although not so much for everyday office purposes. The main goal of this research was to determine whether 100% recycled papers can replace papers made of virgin fibres for the purpose of electrophotographic printing in everyday office use. The print quality of both paper types was determined using recycled papers and papers made of virgin fibres as printing substrates. On the prints, the edge sharpness, print micro-nonuniformity, colour gamut and halftone values were determined. The results obtained for print quality on the recycled papers were very promising. Prints on the recycled papers achieved similar, in some cases identical, results as prints on papers made of virgin fibres.

Selected publications

ĐORĐEVIĆ, Dejana, CERKOVNIK, Janez, GORENŠEK, Marija. The comparasion of the kinetics of hydrolysis of some reactive dyes before and after purification. Fibres Text. East. Eur., 2006, vol. 14, no. 2 (56), pp. 85–88.

Abstract: A dimethylformamide-tetrachloroethylene (DMF/TCE) solvent-nonsolvent mixture was used for the purification of monochloro-s-triazine, monofluoro-s-triazine and bis (monofluoro-s-triazine) reactive dyes. The question is important for dye-house practice in the textile industry, when using reactive dyes for dyeing cotton fabrics and expecting good dye stability after washing. Dye purity was tested by sodium analysis on the basis of the results of the inductively coupled plasma/atomic emission spectroscopy (ICP AES method). The stability of commercial and purified dyes in solutions of pH 7 and pH 12 at 20 °C (60 °C) was investigated by the HPLC method. The pseudo-first-order rate law was used to calculate the rate constants of hydrolysis of dyes in alkaline media. Neutral solutions of all dyes examined at 20 °C remained unchanged after 24 hours. No apparent difference was found between the rates of hydrolysis of all the commercial and purified reactive dyes studied.

GREGOR-SVETEC, Diana, ĐORĐEVIĆ, Dejana. Samokopirni papirji. Del 2, Vrednotenje nanosa mikrokapsul s pomočjo slikovne analize. Papir (Ljublj.), 2007, vol. 35, no. 2, pp. 27–[29]. [COBISS.SI-ID 1944944]

Abstract: With the image analysis the visual assessment of uniformity of microcapsules coating and the surface coverage is numerical upgraded. The values that can be obtained from the image analysis are the average size of macromolecules, surface of macromolecules, number of macromolecules and the surface coverage. At analysed carbonless copy papers some differences in these values have been determined; CB copy papers of different producers differ in the surface of microcapsules and surface coverage up to 30 % and CFB copy papers over 50 %. Between sensitivity and durability of copies, surface and size of microcapsules and the surface coverage some correlation exists.

ĐORĐEVIĆ, Dejana, MUCK, Tadeja. Obstojnost UV ink jet odtisov na različnih materialih. Papir (Ljublj.), 2008, vol. 36, no. 1, pp. 26–[30]. [COBISS.SI-ID 2030704]

Abstract: Nowadays, the printing speed has become more important and deadlines of final prints are shortening. The UV curing technology with UV inks enable us immediate use of prints or print finishing. The UV drying process based on radical polymerization dries prints in a moment. Certainly all parameters of the drying process have to be suitable. This article presents the preliminary research on the field of UV ink jet printing. Three very different materials were printed and used to test the limits of applied UV ink-jet technology. Final print quality was determinate by evaluating of light-fastness and mechanical stability of prints. The adhesiveness of ink depending on used printing material was also determined. Beside mechanical stability we used optical and scanning electron microscopy. We found out that microscopic methods are very useful for determining the ink adhesiveness on the surface of the printing materials.

ĐORĐEVIĆ, Dejana, HLADNIK, Aleš, JAVORŠEK, Andrej. Performance of five chromatic adaptation transforms using large number of color patches. Acta graph., 2009, vol. 20, no 1/4, pp. 9–19, illustr. [COBISS.SI-ID 2454128]

Abstract: Input devices in general use light sources with different color temperatures. As a consequence, in color acquisition, display and rendering processes a number of chromatic adaptations transforms (CATs) are being used. In our study, color transformations between three illuminant source pairs (D50-A, D50-D65 and D65-A) were investigated using five CATs (Bradford, von Kries, XYZ Scaling, CMCCAT97 and CMCCAT00). Research was made on 8190 color patches that were printed with inkjet printer. Results showed that color differences obtained with the Bradford method were the lowest regardless of the implemented illuminant source pair. The same ranking of CATs was observed in all combinations of illuminant source pairs, however the smallest color differences were generated with D50-D65 CATs and the biggest with D65-A models.

MUCK, Tadeja, ĐORĐEVIĆ, Dejana, KREFT, Marko. Use of confocal microscopy as a nondestructive method in the study of ink jet dot formation. J. imaging sci. technol., July/Aug. 2009, vol. 53, no. 4, pp. 040201/1–040201/6, illustr. [COBISS.SI-ID 2219888]

Abstract: The dot formation of the printing ink on the substrate is the final and the most important phase in the printing process. The drying mechanism and ink distribution on the printing surface depend on ink characteristics as well as on many other factors, for example surface energy, roughness, sizing and porosity. Suitable dot gain and high circularity (near 1) of printed dots predict the final print quality. High deviation from ideal circularity could cause undesired printing phenomena like wicking and bleeding. The aim of the study is to determine the ink dot formation with three different microscopic methods, optical microscopy (OM), scanning electron microscopy (SEM) and confocal laser microscopy (CLSM). The main goal of our research was to evaluate the applicability of CLSM as a nondestructive method for three-dimensional visualization in the analysis of ink dot formation on UV Ink-Jet (IJ) prints. To validate the feasibility of such means in a 3D context, the obtained images are compared to those obtained by traditional two-dimensional (2D) imaging system such as OM and SEM. We show that CLSM produces replica of the cross-sectioned dot profile as seen in SEM. This means that CLSM technique can be used to rapidly assess the dot profile without physical sectioning.

ĐORĐEVIĆ, Dejana, JAVORŠEK, Andrej, HLADNIK, Aleš. Comparison of chromatic adaptation transforms used in textile printing sample preparation. Color. technol., 2010, vol. 126, no. 5, pp. 275–281. [COBISS.SI-ID 2429552]

Abstract: As image-capturing devices, such as scanners or digital cameras, normally describe data in RGB colour space, it is impossible to get a complete raw spectral description of a sample’s colour. Device characterisation enables conversion of RGB values to corresponding XYZ tristimulus values of a sample. For transformation of tristimulus values from one illuminant to another, chromatic adaptation transforms should be used. Within our research, chromatic adaptation transforms were implemented in the field of digital textile printing of textile substrate with reactive dyes. Five chromatic adaptation transforms were investigated and their performance was assessed with cluster analysis. Results showed that the lowest mean colour differences were generated with the D50-D65 illuminant pair, followed by D50-A and D65-A. The same performance ranking of different chromatic adaptation transforms was obtained for both D50-A and D65-A illuminant pairs. The Bradford method showed the best results irrespective of the examined illuminant pair combination.

JAVORŠEK, Dejana, JAVORŠEK, Andrej. Colour management in digital textile printing. Color. technol., 2011, vol. 127, no. 4, pp. 235–239. [COBISS.SI-ID 2603376]

Abstract: On the basis of simulated prints, a customer can decide on the colour appropriateness for a selected pattern. This article presents the possibilities and correct procedure for colour management application in the field of digital printing onto a textile substrate. The aim of the research was to establish whether long-term and expensive pre- and after-treatments can be avoided with the help of an appropriate development of printer profiles. The latter would be conducted through a print simulation on paper printed with a Canon laser or ink-jet printer. The results have confirmed that a print simulation on paper can be conducted with both printers, while a Canon ink-jet printer offers better results. In addition, by calculating the colour inconstancy index CMCCON02, the illuminant influence on the colour change of substrates under five different illuminations was determined. The results showed that simulated colours should be compared with original colours under daylight illuminants (D50, D55 and D75), while indoor illuminants A and F2 are not appropriate for a comparison, especially in the case of simulation with a Canon ink-jet printer (CMCCON02 index >5).

Selected publications

KLANČNIK, Maja. Dyeability of new polyesters. Color. technol., 2006, vol. 122, no. 6, pp. 334–337.

Abstract: The popularity of comfortable stretch garments led to the rediscovery of polybutyleneterephthalate and to the development of a new inherently elastic bicomponent polyethyleneterephthalate-polytrimethyleneterephthalate fibre. The aim of this study was a comparison of the dyeability of these new elastic polyesters and a regular polyethyleneterephthalate fibre in an exhaust dyeing procedure as a function of temperature in the range 100-130 degrees C. Dyeing was evaluated in terms of colour strength, colour characteristics and fastness properties.

KLANČNIK, Maja. Kinetics of hydrolysis of halogeno-s-triazine reactive dyes as a function of temperature. Chem. biochem. eng. q., 2008, vol. 22, no. 1, pp. 81–88.

Abstract: The kinetics of alkaline hydrolysis of azo reactive dyes: monofunctional with one monohalogeno-s-triazine reactive group and bifunctional with two identical monohalogeno-s-triazine reactive groups was studied in the temperature range from 50 degrees C to 80 degrees C by means of high performance liquid chromatography. From the determined pseudo-first order hydrolysis rate coefficients, the chemical reactivity of particular dyes and their sensitivity to temperature changes according to the Arrhenius equation were evaluated. The hydrolysis rate coefficient of monofunctional dyes is more temperature dependent than that of homobifunctional dyes. Reactive dyes with a less reactive monochloro-s-triazine group are more sensitive to temperature variations than reactive dyes with a more reactive monofluoro-s-triazine group. Among the studied dyes, the bis(monofluorotriazine) form of the homobifunctional dye exhibits the lowest sensitivity to temperature variations.

Selected publications

HLADNIK, Aleš, LAZAR, Mihael. Paper and board surface roughness characterization using laser profilometry and gray level cooccurrence matrix. Nordic Pulp and Paper Research Journal, 2011, vol. 26, no. 1, pp. 99–105.

Abstract: Image texture analysis tool gray level cooccurrence matrix was implemented to assess surface topography of eight commercial paper and board samples varying considerably in roughness. Height data for individual specimens were acquired by confocal laser profilometer. Strong linear relationship was found between the texture measures "Correlation" and "Energy" derived from gray level cooccurrence matrix on one hand and ISO topography descriptors Rq and Ra on the other. Correlation of these data to those obtained with a conventional roughness method Bendtsen was only a rough one. The applied technique can also be used for determination of paper formation and quantification of print mottling.

Selected publications

MOŽINA, Klementina, ČERNIČ, Marjeta, BEŠKOVNIK, Barbara, BRAČKO, Sabina. Light fastness of ink jet colour prints. Professional papermaking, 2006, no. 1, pp. 72–77.

Abstract: The purpose of the study was to examine the influence of light on the overall change in optical properties of ink jet papers and colorimetric properties of colour prints. Colour prints were applied on three different, randomly selected papers. The prints differed in color and intensity of its application. The experimental part of the study consisted of two parts. In the first part, light fastness of colour prints and papers was evaluated according to the ISO 12040 standard (Xenotest). In the second part, the prints were exposed to three different illuminants, i.e. D65, A, and F11. The differences in colour, brightness, chorma, hue and total difference were determined spectrophotometrically. The results showed that daylight (xenon) caused the biggest changes in colour of the ink jet color prints. It has been found that the degree and speed of fading depend on the colour of prints and the intensity of its application. The results have also shown that the light fastness of prints highly depends on the paper optical characteristics, too.

MOŽINA, Klementina, ČERNIČ, Marjeta, DEMŠAR, Andrej. Non-destructive methods for chemical, optical, colorimetric and typographic characterisation of a reprint. J. cult. herit., 2007, [No.] 8, pp. 339–349.

Abstract: The quality of production (e.g. paper, typesetting, reproduction of illustrations, printing and bookbinding) of a book (reprint) is very important. The quality of a 1978 reprint of a book from 1921 was studied using standard and non-destructive testing methods such as microscopic and spectroscopic techniques. Chemical, physical and colorimetric properties of the papers, colour differences of the prints and typographic tonal density were analysed. Results showed that the reprint is not an identical copy of the original. Some of the differences in the reprint compared with the original (e.g. typographic tonal density) could easily have been avoided while others (e.g. structural and optical properties of paper, colour prints) are unavoidable, mainly because of the influence of internal and external factors on ageing. Ageing influences the properties of paper and colour print: optical and colour properties deteriorate and colour fades. It is concluded that precise and systematic evaluation of the properties of an old book should be carried out before a reprint is prepared. The results of the research, using non-destructive methods such as microscopy, spectroscopy and image analysis, are useful for characterising the properties of paper and printing ink, typography and reproduction of illustrations.

MOŽINA, Klementina, MEDVED, Tanja, RAT, Blaž, BRAČKO, Sabina. Influence of light on typographic and colorimetric properties of ink jet prints. J. imaging sci. technol., Nov./Dec. 2010, vol. 54, no. 6, pp. 060403/1–060403/8.

Abstract: The purpose of this study is to examine the influence of light on the changes in typographic and colorimetric properties of ink jet prints in order to establish an appropriate typeface style and type size for business correspondence to ensure information permanence. The prints were made with six ink jet printers from different manufacturers on four different office papers. Four different, widely used typefaces (one old-style, one transitional, and two sans-serif) in five different sizes (6, 8, 10, 12, and 16 pt) were tested. The resistance of printed business correspondence to light was evaluated according to the ISO 12040 standard. The color differences were determined spectrophotometrically. The differences in typographic tonal density and wicking of typefaces were measured with image analysis. After the exposure to light, the biggest difference in typographic tonal density was observed at type sizes 6 and 8 pt, and at one of the sans-serif typefaces.

Selected publications

LOZO, Branka, VYÖRYKKÄ, Jouko, VUORINEN, Tapani, MUCK, Tadeja. Nondestructive microscopic and spectroscopic methods for depth profiling of ink jet prints. J. imaging sci. technol., jul./avg. 2006, vol. 50, no. 4, pp. 333–340.

Abstract: The binding process of printing inks on the printing substrate is one of the final phases in the creative chain of a new product formation-the print. It is not only the expected mechanism of ink drying that influences the ink distribution on the substrate surface, but also the properties of the substrate itself. Many factors, like hydrophobicity, roughness, and porosity influence the ink distribution on both coated and uncoated papers. The aim of this study was to evaluate the applicability of several nondestructive methods in the analysis of vertical and radial ink distribution on diverse ink jet prints. What are the limits and the extent of confocal Raman, ultraviolet (UV) Raman, CLSM and Fourier-transform infrared (FTIR) PAS in the analysis of ink jet ink distribution in the z direction of the print? In the experiment, both dye- and pigment-based ink jet inks were printed on different types of coated and uncoated papers. The results show a correlation between the confocal Raman and CLSM methods for depth profiling. UV Raman proved useful in the surface analysis of prints while FTIR PAS was useful for measurements at low depth in the z direction. The applied microscopic and spectroscopic methods provide a precise distinction between the upper homogeneous and the inside nonhomogeneous ink layers. Sporadic streams of deeply penetrated ink jet ink were also detected.

LOZO, Branka, STANIĆ, Maja, JAMNICKI, Sonja, MAHOVIĆ POLJAČEK, Maja, MUCK, Tadeja. Three-dimensional ink jet prints - impact of infiltrants. J. imaging sci. technol., Sep./Oct. 2008, vol. 52, no. 5, pp. 051004/1–051004/8.

Abstract: Among various rapid prototyping methods, some are based on a conventional ink jet printing process. The three-dimensional (3D) printing process discussed uses powder material as a substrate and liquid binder as an ink. Three-dimensional prints are usually finished by an infiltrant agent prior to the final use. Epoxy resin, cyanoacrylate, and a polyurethane-based agent are regularly used. The impact of infiltrant type on the selected mechanical properties and surface appearance of 3D inkjet prints was the focus of the study. The type of infiltrant agent used greatly contributes to the discussed final properties of the prints. As a case study. the application of 3D printing in conventional printing technology was studied. The 3D prints can be used as a negative matrix for conventional photopolymer flexographic printing plate production. It is important that the applied infiltrant does not influence the 3D print dimensions, as well as provide the optimum combination of mechanical and surface properties.

MAUKO, Alenka, MUCK, Tadeja, MLADENOVIČ, Ana. 3D visualization and quantification of bowing marble microstructure. Constr. build. mater.. [Print ed.], jun. 2009, vol. 23, iss. 6, pp. 2380–2385.

Abstract: Confocal laser scanning microscopy (CLSM) is a method for the three-dimensional visualization of the structure of various types of materials, and can be applied in all cases where the investigated material has sufficient transparency. It is widely used in medicine and biology to determine the characteristics of cells and molecules. In the case of opaque materials such as stone, CLSM can be used with relative ease to visualize directly the 3D microstructure of the stone, by filling the voids with fluorescent-dyed resin. This method represents an important improvement over the conventional method, which consists of the application of stereological tools to predict, from 2D images, the main 3D characteristics of the microstructure of stone samples, for example their porosity. This paper is concerned with qualitative and quantitative characterization of the microstructure of bowing marble by means of CLSM microscopy, using an innovative technique of sample preparation and an upgraded macro for conventional image analysis (IA) software. (C) 2008 Elsevier Ltd. All rights reserved.

MUCK, Tadeja, JAVORŠEK, Dejana, KREFT, Marko. Use of confocal microscopy as a nondestructive method in the study of ink jet dot formation. J. imaging sci. technol., July/Aug. 2009, vol. 53, no. 4, pp. 040201/1–040201/6.

Abstract: The formation of the printing ink dot on the substrate is the final and the most critical phase in the printing process. The ink distribution on the printing surface and the drying mechanism depend on ink characteristics as well as on many other factors, for example, surface energy, roughness, sizing, and porosity. Suitable dot gain and high circularity (near unity) of printed dots predict the final print quality. High deviation from ideal circularity could cause undesired phenomena like wicking and bleeding. The aim of the present study is to determine ink dot formation by three different microscopic methods, optical microscopy (OM), scanning electron microscopy (SEM), and confocal laser scanning microscopy (CLSM). The main goal of the authors research was to evaluate the applicability of CLSM as a nondestructive method for three-dimensional visualization in the analysis of ink dot formation on UV ink jet prints. To validate the feasibility of such means in a three-dimensional context, the images obtained are compared to those obtained by traditional two-dimensional imaging systems such as OM and SEM. The authors show that the CLSM produces a replica of the cross-sectioned dot profile as seen in SEM. This means that the CLSM technique can be used to rapidly assess the dot profile without physical sectioning.

MAUKO, Alenka, MUCK, Tadeja, MIRTIČ, Breda, MLADENOVIČ, Ana, KREFT, Marko. Use of confocal laser scanning microscopy (CLSM) for the characterization of porosity in marble. Mater. charact.. [Print ed.], 2009, no. 7, vol. 60, pp. 603–609.

Abstract: Confocal microscopy offers several advantages over conventional light optical microscopy, including the ability to control depth of field, elimination or reduction of background information away from the focal plane and the capability to collect serial optical sections and three dimensional imaging from thick specimens. Although the technique is widely used in many scientific fields, especially in biology and medicine, the use of confocal laser scanning microscopy is relatively unknown in the field of building materials. In the following article, an example of application of this technique to geomaterials is given, together with a description of sample preparation and a practical example of investigation of the porosity of bowing marbles.

DEBELJAK, Mirica, MUCK, Tadeja, GREGOR-SVETEC, Diana. Evaluation of printability on synthetic papers printed by UV ink jet. Nordic Pulp and Paper Research Journal, 2009, vol. 24, no. 3, pp. 313–318.

Abstract: The aim of this research was to investigate the quality of UV prints on various synthetic papers. Prints with the CMYK color fields on three types of synthetic papers (Neobond, Pretex, and Yupo) were made using an UV Ink Jet printer. On the unprinted synthetic papers, roughness and surface tension were measured. Densitometric measurements on the CMYK color fields of 20%, 40%, 60%, 80%, and 100% raster tone value and image analysis of the black (K) color at 20% raster tone value were also performed. The analysis revealed some deviations in the optical density of prints and raster tone value between papers. The optimal print was obtained on the synthetic paper Pretex, where the dot gain was low and the circularity of the printed dots was almost ideal. The prints on the synthetic paper Yupo were the most uniform while those on the synthetic paper Neobond were more uneven. The roughness of paper was also found to have a significant influence on the print quality while the surface tension of paper at the UV ink-jet printing process has less impact.

BARBARIĆ-MIKOČEVIĆ, Željka, DŽIMBEG - MALČIĆ, Vesna, MUCK, Tadeja. Digital suplicator prints recycling possibilities. Appita j., Jan/Mar 2010, vol. 63, no. 1, pp. 45–52.

Abstract: In this work the recycling of paper printed by a digital duplicator using both chemical deinking flotation and washing was examined. In addition to fatty alcohol ethoxylate, a commonly used surfactant in the paper recycling, two other surfactants, sodium laurylethersulphate and cocamiclopropyl betaine were studied. To evaluate the efficiency of these chemicals, an image analysis of handsheets, as well as an evaluation of their optical characteristics, was carried out. The laboratory handsheets from the treatment with fatty alcohol ethoxylate possessed the highest reflectance; but this treatment showed lower flotation efficiency. Washing process conditions including surfactant concentration, disintegration temperature and disintegration and homogenization time were then varied. The results of spectrophotometric measurements of reflectance values in the visible spectrum of electromagnetic radiation showed that the best flotation efficiency was achieved by increasing the quantity of surfactant, decreasing the disintegration temperature and increasing the disintegration and homogenization time. Under these processing conditions, values of absorption coefficient were lower, the number of specks decreased.

BOGATAJ, Urška, MUCK, Tadeja, BRAČKO, Sabina, LOZO, Branka. Readability of processed digitally printed two-dimensional codes. J. imaging sci. technol., May/Jun. 2010, vol. 54, no. 3, pp. 030502/1–030502/6.

Abstract: Despite the evident success of conventional one-dimensional (1D) bar codes and their role in automatic product identification, logistics, supply, and retail, these 1D technologies can encode only a limited amount of data and are susceptible to damage and obscuration. On the other hand, two-dimensional (2D) codes which began appearing in the 1980s are becoming more and more popular because of their ability to encode a large amount of data in a small area. They can also be read even if they are partially damaged or erased. Because of their advantages in comparison to linear bar codes and their increasingly frequent use the authors analyzed two 2D codes (DATA MATRIX code and OR code). The purpose of our research was to determine the lowest raster tone value for each printing color and each printing technique which would enable the 2D code reading with two different readers. For testing the readability of codes, lightfastness, accelerated aging, and water resistance were used. Codes were created and printed in four process inks (cyan, magenta, yellow and black), each of them in the following raster tone values: 15%, 20%, 25%, 30%, 50%, and 100%. Samples were printed using three different digital printing technologies (ink jet, laser, and magnetography). After printing, the samples were illuminated by Xe light, exposed to accelerated aging (at 80 C and 65% relative humidity) for six days, and immersed in water to determine their water resistance. All printed samples, before and after illumination and accelerated aging, were read with laser and charge coupled device based readers, and the lowest raster tone value of the code for each printing technique and each printing ink was determined.

STAREŠINIČ, Marica, MUCK, Tadeja, STANIĆ, Maja, KLANJŠEK GUNDE, Marta. Development of image analysis procedures for evaluation of printed electronicsquality = Razvoj metod slikovne analize za oceno tiskovne prehodnosti tiskane elektronike. Inf. MIDEM, 2011, vol. 41, no. 1, pp. 12–17.

Abstract: The procedures described in this work show the feasibility of the first stage of standardized methods for evaluation of printability of printed electronics. 

Printed electronics are electronically functional devices printed onto media like paper, plastic, flexible materials, textiles etc. One of the main goals of printed electronics is simply that electronic components could be printed with mass printing technologies, enabling fast production speed and cheaper products. A new area of applied research is focusing on providing several methods for quality evaluation of printed components to perform fast on-line characterisation. Within present research we study the potential to develop a system for detection of printing defects and imperfections such as substrate non-uniformity and poor surface ink coverage during in-line (in-situ) production of printed electronics. The possibilities for fast and relevant in-line control of printed electronic devices are introduced and applied on printed antenna samples applied for RFID (Radio Frequency Identification) tags. For evaluation and the prospects of development of procedures for in-line control, image analysis is used with applying ImageJ software. Each separate layer (surface of printing material and conductive printed ink) was captured by CCD camera, stereo microscope and scanning electron microscope. Further, it was evaluated by ImageJ software. For automatic and relevant evaluation different routines were used, developed, modified or upgraded; 1) macro for printing surface coating non-uniformity, 2) macro for evaluation of percentage of coverage of conductive ink on the printed substrate and 3) procedure including 3D visualization plug-in to evaluate ink layer thickness in all three (x, y, z) dimensions. The first routine presented here gives the information about the homogeneity or potential defects of printing material surface (with or without pre-coating). The non-uniformity of surface coatings and functional layers is an important property of printed electronics as it is directly related to the electrical properties and therefore to the performance of printed electronic. Other two routines give relevant information about percentage of coverage and thickness of printed functional ink layer. That tells us whether printed electronic element is OK or destruct. This way a reliable procedure was obtained for quick on-line (in situ) testing of printed electronics. These results present the first stage of our research, which is focused on to set up the steps and possibilities for using presented in-line control methods for evaluation of printed electronic devices. The presented procedures could in future be applied for in-line control at printing speeds.

GRILJ, Silva, MUCK, Tadeja, HLADNIK, Aleš, GREGOR-SVETEC, Diana. Recycled papers in everyday office use. Nordic Pulp and Paper Research Journal, 2011, vol. 26, no. 3, pp. 349–355.

Abstract: The use of recycled papers is becoming more and more important because of mostly. ecological and economical reasons. The scarcity of native pulpwood resources is also a reason in some parts of the world. Recycled papers are relatively widely used, although not so much for everyday office purposes. The main goal of this research was to determine whether 100% recycled papers can replace papers made of virgin fibres for the purpose of electrophotographic printing in everyday office use. The print quality of both paper types was determined using recycled papers and papers made of virgin fibres as printing substrates. On the prints, the edge sharpness, print micro-nonuniformity, colour gamut and halftone values were determined. The results obtained for print quality on the recycled papers were very promising. Prints on the recycled papers achieved similar, in some cases identical, results as prints on papers made of virgin fibres.

Selected publications

MOŽINA, Klementina, MEDVED, Tanja, RAT, Blaž, BRAČKO, Sabina. Influence of light on typographic and colorimetric properties of ink jet prints. J. imaging sci. technol., Nov./Dec. 2010, vol. 54, no. 6, pp. 060403/1–060403/8.

Abstract: The purpose of this study is to examine the influence of light on the changes in typographic and colorimetric properties of ink jet prints in order to establish an appropriate typeface style and type size for business correspondence to ensure information permanence. The prints were made with six ink jet printers from different manufacturers on four different office papers. Four different, widely used typefaces (one old-style, one transitional, and two sans-serif) in five different sizes (6, 8, 10, 12, and 16 pt) were tested. The resistance of printed business correspondence to light was evaluated according to the ISO 12040 standard. The color differences were determined spectrophotometrically. The differences in typographic tonal density and wicking of typefaces were measured with image analysis. After the exposure to light, the biggest difference in typographic tonal density was observed at type sizes 6 and 8 pt, and at one of the sans-serif typefaces.

Selected publications

STAREŠINIČ, Marica, BOH, Bojana. Patent informatics : the issue of relevance in full-text patent document searches. Online inf. rev. (Print), 2009, vol. 33, no. 1, pp. 157–172.

Abstract: Purpose-The purpose of this paper is to discuss the issue of relevance in full-text patent document searches from the viewpoint of end-users in science and technology. It aims to present three cases of patent document analysis for relevance, with an additional case of improved search profile with increased relevance, and to summarise the findings in the form of instructions for users. Design/methodology/approach-Two methodological approaches were used for the analysis of patent documents: value-added processing of the bibliographic part of patent documents for the identification of trends; and structuring of data into systems for the determination of patent relevance. Overall, four sets of full-text patent documents were analysed, covering the topics of: microencapsulated phase change materials; digital photography and image sensors; patient document processing; and patent analysis. Findings-Value-added analysis of the bibliographic parts of patent documents is a quick and useful option for the recognition of research trends. However, where non-relevant patent documents are present in a data set, automatic bibliographic analysis may lead to conclusions that are mathematically and statistically correct, but that are not reliable or may even be incorrect for the user's research. Non-adequate terminology is one of the main obstacles to relevant patent searches, especially if well-defined keywords are non-existent, as with cases of newly emerging and fast developing scientific and technological fields. Originality/value-Based on the bibliographic and content analyses of patent documents, the paper provides instructions for users in the form of ten general rules for increasing the relevance of full-text patent document searches.

ŠUMIGA, Boštjan, KNEZ, Emil, VRTAČNIK, Margareta, FERK SAVEC, Vesna, STAREŠINIČ, Marica, BOH, Bojana. Production of melamine-formaldehyde PCM microcapsules with ammonia scavenger used for residual formaldehyde reduction. Acta chim. slov.. [Tiskana izd.], 2011, vol. 58, no. 1, pp. 14–25.

Abstract: Paraffinic phase change materials (PCM) were microencapsulated by in situ polymerization of melamine-formaldehyde prepolymers. Partly methylated trimethylolmelamine was used as an aminoaldehyde prepolymer for the microcapsule wall, a styrene-maleic acid anhydride copolymer as an emulsifier and modifying agent, and ammonia as a scavenger for reducing residual formaldehyde. For the determination of residual formaldehyde in a ppm concentration range, EDANA and malachite green analytical methods were studied, and the EDANA 210.1-99 was applied for the determination of residual formaldehyde in 25 samples of microcapsules, produced in a 200-L reactor. A linear correlation was observed between the added ammonia scavenger concentration and the reduction of residual formaldehyde concentration. Compared with 0.45% (4500 ppm) formaldehyde in a non-treated microcapsule suspension, with ammonia scavenger concentrations 0.80, 0.90 and 1.35%, the concentration of residual formaldehyde dropped to 0.27, 0.20 and 0.09% (i.e. 2700, 2000 and 900 ppm), respectively. Morphological characterisation of microcapsules by SEM and microcapsule wall permeability measurements by gravimetry / mass loss at an elevated temperature (135 degrees C) suggested that ammonia positively contributed to the wall elasticity / durability, while microcapsules with no ammonia scavenger added tended to have more brittle walls, and were more prone to cracking.

STAREŠINIČ, Marica, MUCK, Tadeja, STANIĆ, Maja, KLANJŠEK GUNDE, Marta. Development of image analysis procedures for evaluation of printed electronicsquality = Razvoj metod slikovne analize za oceno tiskovne prehodnosti tiskane elektronike. Inf. MIDEM, 2011, vol. 41, no. 1, pp. 12–17.

Abstract: The procedures described in this work show the feasibility of the first stage of standardized methods for evaluation of printability of printed electronics. Printed electronics are electronically functional devices printed onto media like paper, plastic, flexible materials, textiles etc. One of the main goals of printed electronics is simply that electronic components could be printed with mass printing technologies, enabling fast production speed and cheaper products. A new area of applied research is focusing on providing several methods for quality evaluation of printed components to perform fast on-line characterisation. Within present research we study the potential to develop a system for detection of printing defects and imperfections such as substrate non-uniformity and poor surface ink coverage during in-line (in-situ) production of printed electronics. The possibilities for fast and relevant in-line control of printed electronic devices are introduced and applied on printed antenna samples applied for RFID (Radio Frequency Identification) tags. For evaluation and the prospects of development of procedures for in-line control, image analysis is used with applying ImageJ software. Each separate layer (surface of printing material and conductive printed ink) was captured by CCD camera, stereo microscope and scanning electron microscope. Further, it was evaluated by ImageJ software. For automatic and relevant evaluation different routines were used, developed, modified or upgraded; 1) macro for printing surface coating non-uniformity, 2) macro for evaluation of percentage of coverage of conductive ink on the printed substrate and 3) procedure including 3D visualization plug-in to evaluate ink layer thickness in all three (x, y, z) dimensions. The first routine presented here gives the information about the homogeneity or potential defects of printing material surface (with or without pre-coating). The non-uniformity of surface coatings and functional layers is an important property of printed electronics as it is directly related to the electrical properties and therefore to the performance of printed electronic. Other two routines give relevant information about percentage of coverage and thickness of printed functional ink layer. That tells us whether printed electronic element is OK or destruct. This way a reliable procedure was obtained for quick on-line (in situ) testing of printed electronics. These results present the first stage of our research, which is focused on to set up the steps and possibilities for using presented in-line control methods for evaluation of printed electronic devices. The presented procedures could in future be applied for in-line control at printing speeds.

Selected publications

GORENŠEK, Marija, SLUGA, Franci, URBAS, Raša. Improving the ultraviolet protection factor of cotton fabric. AATCC review, Feb. 2007, vol. 7, no. 2, pp. 44–48.

Abstract: The effects of cover factor, reactive dyes in pale and deep hues, double layers of fabric, and ultraviolet (UV) absorption on the UV Protection Factor (UPF) of a lightweight, bleached cotton fabric were investigated. UV transmission and reflectance were measured and the UV absorbency of the dyes was calculated. The undyed fabric provided low protection against UV rays in single and double layers. Application of monofluoro-s-triazine reactive dyes (particularly the deep red dye) increased the UPF. The effect of the UV absorber was most pronounced on the blank-dyed fabric. A double-layer of fabric with the blank-dyed fabric facing the source of UV radiation and the dyed layer facing the skin exhibits very good to excellent UPF.

GABRIJELČIČ, Helena, URBAS, Raša, SLUGA, Franci, DIMITROVSKI, Krste. Influence of fabric constructional parameters and thread colour on UV radiation protection. Fibres Text. East. Eur., 2009, vol. 17, no. 1 (72), pp. 46–54.

Abstract: The purpose of the research presented was to analyse the influence of the fabric surface cover factor and fabric colour values on the degree of UV ray transmittance and the UV protective factor (UPF). The research was carried out on lightweight coloured fabrics woven in sateen weave with different densities of warp and weft threads and with a different colours in the weft. Measurements of the UPF were performed using the "in vitro" method in the range of UVA and UVB ray wavelengths, from 280 to 400 nm. The results of the research confirm the importance of the fabric surface openness for the UV protective factor and expose the influence of the fabric face and reverse sides as well as of colour values L*, C*(ab), h(ab) of warp and weft threads on the UPF in sufficiently closed woven constructions. Namely, constructions with less than the 5% surface openness offer excellent protection (UPF above 50), whereas constructions with less than 10% surface openness offer good to very good protection (a UPF above 20). At covet-age higher than 95%, the fabrics analysed could be generally divided into three groups with respect to the effectiveness of their UV protection: fabrics of darker colours (black, blue) with extremely high UPF values, fabrics of chromatic lighter colours (yellow, red, green) with UPF values half of those of darker colours in general, and white fabrics (bleached) in which the desired UPF values are not reached regardless of the degree of the cover factor.

DIMITROVSKI, Krste, SLUGA, Franci, URBAS, Raša. Evaluation of the structure of monofilament PET woven fabrics and their protection properties. Tex. res. j., 2010, vol. 80, no. 11, pp. [1027]–1037.

Abstract: The importance of protection against ultraviolet radiation (UV) is increasing daily. The dependence of the UV protection level on different clothes is determined by the shape and design of fabrics, and especially by their construction parameters. The fabric structure represents an important factor which is in most cases the only condition for good protection. Other possibilities to ensure good or even excellent protection, mainly by finishing treatments, can be efficient only if the fabric structure is closed enough. To determine the key parameters which contribute to the closeness of the structure and offer suitable UV protection, an analysis of monofilament woven fabric structure was made. Monofilament fabric samples used in the production of high-module screen-printing meshes, which are characterized by the excellent dimension stability of the structure, the properties of which change with varying diameters of the monofilaments and the fabric density, were chosen for this research. A broad spectrum of similar but structurally different fabrics assures referential samples are available for the evaluation of UV protection properties. In all the samples tested, the parameters of transmission and reflection were measured. Moreover, the values of absorption and the ultraviolet protection factor (UPF) were calculated. The values calculated on the basis of a determined mathematical model matched well with the measured values and they can together represent the basis for successful planning of fabrics with suitable UV protection properties.

URBAS, Raša, KOSTAJNŠEK, Klara, DIMITROVSKI, Krste. Impact of structure and yarn colour on UV properties and air permeability of multilayer cotton woven fabrics. Tex. res. j., 2011, vol. 81, no. 18, 10 pp.

Abstract: The aim of our work was to establish whether very good to excellent UV (ultraviolet) protective properties of fabrics can be obtained through a suitable fabric construction and yarn colour, at the same time ensuring suitable air permeability. For this purpose, six different fabric structures divided into three groups were employed. The samples were made in blue and red combinations of weft with different sequences and proportions between the upper and lower weave threads. A comparison of different fabric structures and colours was attempted to enable the impact assessment of the mentioned parameters on both, UV protective properties and air permeability of fabrics. The analysis comprised the investigation of physical and permeability properties, as well as the colour measurements on twelve different cotton fabrics. The research indicated excellent UV protection (> 60) in all samples. UV protection depended on their construction and in a sufficiently closed structure, also on the colour of the used yarn. There was no significant difference between the samples in blue and red. In addition to excellent UV protection, four samples (one double-weft and three double fabrics) also demonstrated very high air permeability, which was 3–5 times higher than in the one-layer sample, which demonstrated the best UV protective properties. The research has shown that fabrics with a very high ultraviolet protection factor (UPF) value and good air permeability can be made by using a suitable construction and yarn colours that sufficiently absorb UV light, the latter being particularly important for light summer cotton clothes.

Selected publications

VRABIČ, Urška, JESIH, Adolf, GREGOR-SVETEC, Diana. Physical and absorptive changes in plasma treated viscose fibres. Fibres Text. East. Eur., 2007, vol. 15, no. 5/6 (64/65), pp. 124–126.

Abstract: Chemical modification of the fibres was successful in improving their different properties, but there are environmental concerns related to the disposal of chemicals after treatment. Taking into account the advantages related to the technology of plasma treatment and the differentiated changes of the fibre matter processed is plasma treatment, increasingly replacing chemical applications in finishing and pre-treatment of textiles products. For industrial uses, regenerated cellulose fibres are used to replace traditional materials, for example, nonwovens, like hygiene and medical products. The most important characteristics for hygiene and medical products are absorption ability and capability of water retention. The main aspect of our research was to analyse the physical and absorptive characteristics of viscose fibres, treated with plasma. The study revealed that plasma surface treatment modifies the absorptive structure, tensile and other physical properties of viscose fibres.