Sastav razvijača u funkciji kvalitete tiskovne forme za plošni tisak

master's thesis

• Author: Natalija Pintar
• Mentor: Sanja Mahović Poljaček (mentor)
• Committee member: Sanja Mahović Poljaček (član povjerenstva)
• Granter: University of Zagreb; Faculty of Graphic Arts; Zagreb
• Defense date and country: 2009-9-00, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Graphic Technology

Abstract

Tiskovna forma za plošni tisak ima ravnu površinu, a razlika između slobodnih i tiskovnih

površina postiže se fi zikalno-kemijskim svojstvima. Tiskovne površine su oleofi lne (hidrofobne)

i zato na sebe u procesu otiskivanja adsorbiraju masno tiskarsko bojilo, a slobodne

površine su hidrofi lne pa u procesu otiskivanja adsorbiraju otopinu za vlaženje.

Konvencionalan način izrade tiskovne forme većinom se sastoji od slijedećih koraka: procesa

osvjetljavanja fotoaktivnog sloja kroz kopirni predložak, razvijanja u otopini razvijača

i ispiranja tiskovne forme. Za ova istraživanja korištene su konvencionalne tiskovne forme

oslojene pozitivskim diazo kopirnim slojem koji je nakon osvjetljavanja topiv u lužnatoj otopini.

Uzorci su osvjetljeni i razvijeni u jednakim vremenskim intervalima, ali su kao razvijači

korištene otopine s različitom molarnom koncentracijom lužine. Kao razvijač je korištena

otopina dobivena otapanjem kristala KOH različitih molarnih koncentracija: 0,2 moldm-3, 0,4

moldm-3, 0,5 moldm-3, 0,6 moldm-3, 0,8 moldm-3, 1 moldm-3 i 1,5 moldm-3 . Karakterizacija

izrađenih uzoraka tiskovnih formi provedena je mjerenjem rastertonskih vrijednosti na

tiskovnim površinama i određivanjem kuta močenja na slobodnim površinama otopinom za

vlaženje.

Rezultati dobiveni ovim istraživanjem ukazali su da molarna koncentracija lužine u otopini

razvijača ima značajan utjecaj na karakteristike slobodnih i tiskovnih površina. Previsoka

molarna koncentracija lužine u razvijaču uzrokuje otapanje kompletnog fotoaktivnog sloja

čineći tiskovnu formu neupotrebljivom za daljnju eksploataciju. Istovremeno previsoka

koncentracije lužine u razvijaču uzrokuje i smanjenje adsorpcijske sposobnosti slobodnih

površina. Nasuprot previsokoj molarnoj koncentraciji, preniska molarna koncentracija

ne ukloni sasvim fotoaktivni sloj sa slobodnih površina čime je onemogućeno potrebno

prihvaćanje otopine za vlaženje.

Dobiveni rezultati ukazuju na potrebu praćenja sastava razvijača kod determiniranja procesa

razvijanja tiskovnih formi te korištenje optimalnih uvjeta obrade za postizanje najviše

kvalitete tiskovne forme.

Abstract (english)

The printing and nonprinting surfaces on a lithography printing plate are in the same level

and the difference between them is achieved through opposite physical-chemical properties.

The printing surfaces are oleophilic (hydrophobic) and in the printing process they attract

oily based printing ink and the nonprinting surfaces are hydrophilic which enables them to

adsorb fountain solution in the printing process.

The conventional printing plate making process consists mainly of following major processes:

exposure of the photoactive coating through fi lm, developing process in developing solution

and washing out. Diazo positive printing plates were used in this research. The diazo positive

photoactive coating becomes soluble in alkaline solution by exposure. Samples prepared for

this research are all exposed and developed in the same time but are developed in solution

with different molar concentration of potassium alkali. Molar concentrations used were 0,2

moldm-3, 0,4 moldm-3, 0,5 moldm-3, 0,6 moldm-3, 0,8 moldm-3, 1 moldm-3 i 1,5 moldm-3.

Characterization of printing and nonprinting areas of the printing plate was made on prepared

samples. The measurements of the coverage values of printing areas and of the contact

angle between nonprinting areas and fountain solution were performed.

The results obtained by this research have showed that molar concentration of alkali in

a developing solution has signifi cant infl uence on characteristics of printing as well as

nonprinting areas. If the molar concentration of alkali in solution is to high, dissolving of

whole photoactive coating will occur which makes printing plate useless for exploitation.

The nonprinting areas are also damaged when developing in solution with high molar

concentration alkali solution. When the molar concentration of alkali in solution is to low

some parts of photoactive coating remains on nonprinting areas which disables adsorption

of the fountain solution on those areas.

Obtained results indicate that it is essential to monitor chemical composition of developing

solution to determine parameters of the developing process. To obtain best possible printing

plate quality one must keep results of this research in mind and use optimal process

requirements.

• Keywords: plošni tisak; tiskovna forma; razvijanje; molarna koncentracija; kontaktni kut; rastertonska vrijednost
• Keywords (english): lithography; printing plate; developing process; molar concentration; contact angle; coverage value
• Language: croatian
• URN:NBN: urn:nbn:hr:216:975772
• Study programme: Title: Graphic technology; specializations in: Graphic technology, Design of graphic products; Course: Graphic technology; Study programme type: university; Study level: graduate; Academic / professional title: sveučilišni/a magistar/magistra inženjer/inženjerka grafičke tehnologije (sveučilišni/a magistar/magistra inženjer/inženjerka grafičke tehnologije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Closed access
• Created on: 2024-04-17 10:13:04