Tso-Pei Hsieh

Abstract

Ink tack is a term used by printers to describe the force required to split an ink film. Such film splitting is influenced by rheological and adhesive properties as well as the internal cohesion of ink. Furthermore, the concept of ink tack in printing is associated with the forces or energy developed in the splitting of ink film at the exit of a printing nip. Stefan studied the forces required to split a thin film. He found that the force required to split a thin film is inversely proportional to the cube of the thickness of that film. This association between the film thickness and film splitting force has been questioned in the literature and by this study. In printing, the practical condition related to ink film splitting forces might be revealed by measurement on the Inkometer ( Inkometer response), paper picking, and ink trapping. This study used these responses. The purpose of this study was to investigate the relationship (not mathematical) between ink film thickness (0.6 to 5.4 pm) that should include the film thicknesses found on presses. Experiment one was accomplished on the Inkometer with the two black vegetable-oil-based inks to obtain the Inkometer response under the proposed three way factorial experimental design ( inks, ink film thicknesses, and time.) Experiment two made use of the IGT Printability Tester with the same inks, the IGT oil, and one of the paper samples to find the critical picking velocity under the proposed two way factorial experimental design ( fluids, ink film thicknesses.) Experiment three was accomplished with the IGT Printability Tester, the same inks, and two substrates including a second paper sample and a plastic film. The response is gravimetric trapping under the proposed three way factorial experimental design ( inks, substrates, and ink film thicknesses.) Inkometer response, picking velocity, and gravimetric trapping are not direct measurements of film splitting force. They are related to film splitting force. The greater the Inkometer response, the more tacky the ink. The higher the picking velocity the lower the splitting force. With increased gravimetric trapping of the second-down inks, the more tacky the first-down inks. The data was analyzed by ANOVA at a level of significance equal to 0.05 ( two-sided ) to test the null hypotheses. The null hypotheses are the following: Hq^: There is no significant effect due to vegetable-oil-based ink film thickness on ink tack as measured by an Inkometer. Hq2: There is no significant effect due to film thickness of vegetable-oilbased fluid on picking velocity under the proposed experimental design on the IGT Printability Tester. H.Q3: There is no significant effect due to the first down vegetable-oil-based ink film thickness on ink trapping capability under the proposed experimental design on the IGT Printability Tester. An overview of the results show that the ink film thickness could affect the Inkometer response and gravimetric trapping, and the oil-based fluids' film thicknesses could affect the picking velocity within the film thicknesses range of 0.6 to 5.4 pm. The graph of data, regression analysis, and R2 are prepared for predicting and evaluating the specific tendency of the measurements ( Inkometer response, picking velocity, and gravimetric trapping ) when ink film thicknesses change. They also show the tendency of change of the splitting forces at the different film thicknesses. The other general results on the basis of the graphs, regression analysis, and Rz show that the Inkometer response increases when ink film thicknesses increased from 0.6 to 5.4 pm with both of the inks and at each time interval. Picking velocity decreased when the ink film thicknesses increased up to about 3.0 pm and then increases with increased ink film thickness from around 3.0 pm to 5.4 pm at each the ink level. The gravimetric trapping on both the paper and plastic substrates and with both inks decrease with the ink film thickness increased from 0.6 to 5.4 pm. There is no consistent agreement with the equation proposed by Stefan.

Library of Congress Subject Headings

Printing-ink

Publication Date

4-1-1993

Document Type

Thesis

Department, Program, or Center

School of Print Media (CIAS)

Advisor

Daniels, Chester

Comments

Note: imported from RIT’s Digital Media Library running on DSpace to RIT Scholar Works. Physical copy available through RIT's The Wallace Library at: Z247 .H754 1993

Campus

RIT – Main Campus

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