Vpliv optičnih lastnosti papirja v odvisnosti od gramature na upodobitev barv pri tisku

Završnik, Jerca (author), Javoršek, Dejana (mentor), Možina, Klemen (co-mentor)

Papir je ploščat, higroskopičen, anizotropičen, dvostran, viskoelastičen in nehomogen material, s katerim se srečujemo na vsakodnevni ravni. Njegova uporabnost je največkrat odvisna od gramature. Ta mu daje in omogoča različne fizikalno-mehanske lastnosti, ki vplivajo tudi na optične lastnosti. Glavni cilj diplomske naloge je bil, poudariti pomen lastnosti papirja v odvisnosti od gramature na upodobitev barv pri laserskem tisku. Eksperimentalni del je bil zasnovan na preizkušanju osmih vzorcev papirja z gramaturami 90, 100, 120, 140, 160, 200, 300 in 350 g/m2 ter z referenčnim vzorcem pisarniškega papirja gramature 80 g/m2. Meritve so bile razdeljene na dva dela, in sicer: meritve optičnih in površinskih lastnosti papirja ter spektrofotometrične meritve barvnih odtisov na vzorcih. Za ugotavljanje vpliva gramature na optične lastnosti papirja je bilo potrebno izračunati ISO belino, stopnjo beline po CIE enačbi ter neprosojnost, izmeriti zrcalni sijaj in hrapavost ter določiti razporeditev vlaken v vzorcih. V drugem delu pa so bile opravljene še meritve na natisnjenih barvnih tablicah in izračunane barvne razlike med odtisi na papirjih različnih gramatur v primerjavi z referenčnim vzorcem papirja. Rezultati so pokazali, da je vpliv gramature pri nekaterih lastnostih večji kot pri drugih, vendar obstaja povezava tako z optičnimi kot tudi s površinskimi lastnostmi papirja. Ta je najbolj očitna pri vrednotenju ISO beline, zrcalnega sijaja in neprosojnosti. Naštete lastnosti so zaznavno vplivale tudi na upodobitev barv na odtisnjenih barvnih tablicah, pri katerih so bile ponekod razlike v barvah vidne že s prostim očesom. Grafični prikazi razlik barvnih vrednosti so pokazali naraščanje razlik skupaj z gramaturo. Upodobitve z največjimi barvnimi razlikami pa so pri barvah s prisotnimi toni oranžne, rjave, vijolične in črne barve. Predvideva se, da je na razlike pri papirjih z višjo gramaturo vplivala tudi višja temperatura utrjevanja tonerja, ki se uporablja pri laserskem tisku. Ob upoštevanju navedenih ugotovitev bi bili pri vsakodnevnem tisku omogočeni kakovostnejši in ponovljivi odtisi tudi v maloformatnem laserskem tisku z nizkimi nakladami.

• Language: Slovenian
• Keywords: papir, gramatura, optične lastnosti, barvne razlike, elektrofotografija
• Work type: Bachelor thesis/paper
• Organization: NTF - Faculty of Natural Sciences and Engineering
• Year: 2018
• PID: 20.500.12556/RUL-102704
• Publication date in RUL: 07.09.2018

Secondary language

• Language: English
• Title: The Influence of the Optical Properties of Paper in regard to Grammage on Colour Reproduction

Abstract

Paper is a flat, hygroscopic, anizotropic, double-sided, viscoelastic, and non homogenous material, which is used on a daily basis. Its usability most often depends on grammage, which provides and enables different physical-mechanical properties that affect some of the optical properties, as well. The main purpose of this diploma thesis was to emphasise the the meaning of the paper properties in regard to grammage on the colour reproduction in laser printing and thus achieve a better print repeatability. The empirical part was based on the testing of eight paper samples; their grammages were 90, 100, 120, 140, 160, 200, 300, and 350 g/m2. The applied reference paper was office paper with the grammage of 80 g/m2. The measurements were divided into two parts – the measurements of optical and surface properties, and the spectrophotometric measurements. To determine the inflluence of grammage on the paper properties, ISO brightness, CIE whiteness, and opacity, had to be calculated. Additionally, the specular reflection and roughness had to be measured, and the fiber distribution in samples had to be determined. Then, measurements on colour reference charts had to be taken and colour differences calculated among the prints on different paper in regard to the reference sample. The results showed that the effect of grammage is greater in some properties than others, and that there is a link with both the optical and the surface properties of the paper. The link is most obvious in the measuring and calculating of the ISO brightness, the specular reflection, and opacity. The mentioned properties also affected the colour reproduction on the printed charts, in which some of the differences could be seen optically. The colour value graphs showed the colour difference rising along with the grammage, especially in the colour tones of orange, brown, purple, and black. We predict that the higher temperatures of toner fixing had a bigger effect in paper of higher grammage. A more quality and repeatable prints could be enabled in small-format laser print with small circulations by observing these findings in everyday print.

• Keywords: paper, grammage, optical properties, color differences, electrophotography