From the moment of production, paper as a printing substrate is exposed to the process of natural ageing regardless of the type of cellulose fibres in its composition. Accordingly, the prints ...produced by the various printing techniques are also exposed to several factors that impair the quality of the print i.e. its colour over time. Therefore, it is very important to properly select the printing substrate for achieving a high quality of graphic products. For that purpose, three types of papers with hemp fibres were used as printing substrates which were printed with laboratory hand-operated instrument Esiproof using flexographic cyan (C), magenta (M), yellow (Y) and black (K) water-based inks. Prints were artificially aged in SunTEST XLS+ test chamber according to standard ASTM D 6789-02 for 48 and 96 hours. Based on changes in the reflectance spectra of each printed ink after exposure to electromagnetic radiation it was noticed how composition of printing substrate strongly influence on colour stability of prints due time. An increase of exposure time to electromagnetic radiation leads to a decrease in the value of the reflectance of the printing substrate and cyan, magenta and yellow prints. It was confirmed how electromagnetic radiation have the greatest impact on the reflectance of yellow print, while the black one is the most stabile regardless of the substrate it was printed on.
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One of the greatest simplifications of the transfer equation is where all incident and scattered light is assumed to be perfectly diffuse, only two opposite directions of light transport are ...considered, and the light intensity is assumed to vary along one axis only. Such two-flux approximations have been presented by many authors, starting with a paper by Schuster 1. One of the most famous two-flux approximations is the approximation presented by Kubelka and Munk 2 in 1931 and further developed by Kubelka 3,4. Kubelka and Munk gave a comprehensive formulation and a treatment with a clear aim towards practical methods of measurement. It was quickly adapted for use by the papermaking industry 5-8 and has now been in widespread use for decades in the measurement and prediction of colour, brightness and opacity of paper sheets. Most of the information reported here is taken from the references cited at the end of the article which should be consulted for a more in-depth study.Original Abstract: Jedno od najvecih pojednostavnjenja jednadzbe transfera pretpostavlja: upadno i rasprseno zracenje je savrseno difuzno, promatraju se samo dva suprotna smjera prijenosa svjetlosti, i intenzitet svjetlosti se mijenja samo duz jedne osi. Takvu aproksimaciju dva smjera prijenosa svjetlosti zapoceo je Schuster 1, a nastavili su Kubelka i Munk 2 1931. a model je dalje usavrsio Kubelka 3-4. Kubelka i Munk su dali sazeti oblik i pristup s jasnim ciljem ka prakticnim metodama mjerenja. Ta metoda je bila brzo prihvacena u papirnoj industriji 5-8 i danas ima siroku primjenu u mjerenju i procjeni obojenja, svjetline i opaciteta pri proizvodnji papira. Vecina informacija u ovom clanku preuzeta je iz referenca ciji se popis nalazi na kraju clanka i koje je potrebno konzultirati za detaljniju analizu.
This paper describes the improved removal of impurities (coating, ink/toner) from offset prints produced by digital printing of two-side coated paper. The substrates were printed by conventional and ...digital offset processes. Based on image analysis results it was established that deinking flotation is an inefficient method for ink particle removal from digital offset printed paper, but it is efficient for ink removal from conventional offset printed paper. On the other hand, pre-treatment with hydrogen peroxide solution gives better results for ink particle removal from digital offset prints than from conventional offset prints. Optimal parameters for hydrogen peroxide pre-treatment for both offset prints were chosen based on unprinted substrate mass loss results in the preliminary investigation. These results showed that hydrogen peroxide pre-treatment is more successful at removal of impurities in comparison with flotation deinking without pre-treatment.
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This research observes changes in the properties of commercially available hemp office papers exposed to photo-oxidation for artificial aging. In order to accelerate the changes that naturally occur ...in paper, photo-oxidation was performed using a Xenon light source. The electromagnetic radiation was administered in doses of 550?W/m2 over 24 hours with a temperature of 60°C. Three types of hemp office papers that differ in chemical composition and manufacturing process were used as samples. The strength properties (tensile index, elongation at break, tear index), surface properties (Bendtsen roughness, Bekk smoothness), pH of paper extracts, and optical properties were observed. The listed properties of artificially aged samples were compared to those of unaged commercial paper samples. The results show that, after only 24 hours, accelerated aging with a Xenon arc lamp affects all observed paper properties. For all analyzed office papers, the values of the tensile index, Bekk smoothness, and pH of paper extracts decreased, while the values of elongation break, tear index, and Bendtsen roughness increased due accelerated aging. Regarding the CIE L*a*b* color space value, lightness (L*) generally decreased after the aging treatment, and all paper samples became less reddish (a* decreased) and more yellow (b* increased). The obtained results of this research reveal that pulp with hemp fibers can produce higher-quality office paper that is more stable against light and temperature influences than those made with post-consumer fibers. However, to increase the durability of manufactured paper, hemp fibers must be bleached.
Kubelka-Munk theory was quickly adapted for use by the papermaking industry and has now been in widespread use for decades in the measurement and prediction of colour, brightness and opacity of paper ...sheets. Though it remains the most used in practice, it has some disadvantages and the second part of the article will cover a system that is less applicable to the theory itself (an ink-dyed sheet of paper or strongly absorbing media) as well as numerical methods (simulations of individual photon paths) which are used to improve the results obtained by the K-M theory. The most commonly used are Monte Carlo simulation model, GRACE and DORT. Most of the information reported here is taken from the references cited at the end of the article which should be consulted for a more in-depth study.Original Abstract: Kubelka i Munk dali su sazeti oblik i pristup s jasnim ciljem ka prakticnim metodama mjerenja. Njihova metoda je bila brzo prihvacena u papirnoj industriji i danas ima siroku primjenu u mjerenju i procjeni obojenja, svjetline i opaciteta pri proizvodnji papira. Unatoc tome navedena metoda posjeduje neke nedostatke i drugi dio clanka ce pokriti sustave na koje se ne moze tako kvalitetno primijeniti (otisnuti i reciklirani papir). Takoder ce biti rijeci i o numerickim modelima (simulacije putanja pojedinacnih fotona) koji se koriste kao nadopuna rezultatima dobivenima K-M metodom. Najcesce koristeni su Monte Carlo simulacijski modeli, GRACE i DORT. Vecina informacija u ovom clanku preuzeta je iz referenca ciji se popis nalazi na kraju clanka i koje je potrebno konzultirati za detaljniju analizu.
Jedno od najvećih pojednostavnjenja jednadžbe transfera pretpostavlja: upadno i raspršeno zračenje je savršeno difuzno, promatraju se samo dva suprotna smjera prijenosa svjetlosti, i intenzitet ...svjetlosti se mijenja samo duž jedne osi. Takvu aprokimaciju dva smjera prijenosa svjetlosi započeo je Schuster 1, a nastavili su Kubelka i Munk 2 1931. a model je dalje usavršio Kubelka 3-4. Kubelka i Munk su dali sažeti oblik i pristup s jasnim ciljem ka praktičnim metodama mjerenja. Ta metoda je bila brzo prihvaćena u papirnoj industriji 5-8 i danas ima široku piimjenu u mjerenju i procjeni obojenja, svjetline i opaciteta pri proizvodnji papira. Većina informacija u ovom članku preuzeta je iz referenca čiji se popis nalazi na kraju članka i koje je potrebno konzultirati za detaljniju analizu.
Kubelka i Munk dali su sažeti oblik i pristup s jasnim ciljem ka praktičnim metodama mjerenja. Njihova metoda je bila brzo prihvaćena u papirnoj industriji i danas ima široku primjenu u mjerenju i ...procjeni obojenja, svjetline i opaciteta pri proizvodnji papira. Unatoč tome navedena metoda posjeduje neke nedostatke i drugi dio članka će pokriti sustave na koje se ne može tako kvalitetno primijeniti (otisnuti i reciklirani papir). Također će biti riječi i o numeričkim modelima (simulacije putanja pojedinačnih fotona) koji se koriste kao nadopuna rezultatima dobivenima K-M metodom. Najčešće korišteni su Monte Carlo simulacijski modeli, GRACE i DORT. Većina informacija u ovom članku preuzeta je iz referenca čiji se popis nalazi na kraju članka i koje je potrebno konzultirati za detaljniju analizu.
Rad daje pregled postojećih tehnoloških rješenja elektroničkog papira i pregled njegove komercijalne upotrebe. Pregled najčešćih tehnoloških rješenja daje uvid u osnovne principe koje koristi svaka ...od spomenutih tehnologija. U zaključku rada daje se nekoliko mogućih smjerova daljnjeg razvoja tehnologije elektroničkog papira, ovisno o do sada istraženim mogućnostima i zahtjevima te o razvoju tržišta.
This study focuses on the research of changes in the optical characteristics of selected
offset inks (Yellow, Red 032, Process Blue and Black) printed as a part of Pantone
colour book. These changes ...that occur as a result of natural and accelerated ageing
(caused by thermal and UV/VIS radiation) were observed through reflectance
spectra in the visible region. A Pantone colour book is a system for identifying,
matching and controlling ink colours in the graphic industry. This colour book
is the international reference for accurate colour communication. The durability
of colours and its unchanged quality play an important role in ensuring accurate
colour communication and control. In order to examine optical modifications, the
samples were exposed to elevated temperatures and UV/VIS lamp radiation. The
FTIR spectroscopy was additionally used for the characterization of printed inks
before and after ageing.
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