Effect of paper and printing press variables on the rates of adhesion failure in the linting of offset printing

Lint problems occur when loosely bonded particles detach from the surface of uncoated paper and accumulate on the printing blanket. We investigated the effect of paper and the printing press variables of printing tone and ink tack on linting using a lint camera system and also by stopping the press repeatedly to wash the lint samples off the blanket. Lint particles were classified into small particles (with area 0–8000?μm²) and large particles (with area above 8000?μm²). There have been many contradictory reports about the most important paper and printing variables affecting linting because many previous researchers have not adequately addressed that linting is a dynamic process, which involves two adhesion failures and separations, driven by the splitting of the viscous ink film. The first failure is for the removal of lint particles from the paper surface to the blanket, while the second failure is for the separation of the lint particles from the blanket. The key finding of this study is that these two rates of adhesion failure are generally correlated. That is, a higher rate of lint particle separation from the paper surface is associated with a higher rate of separation from the blanket. This finding held for varying the grade of paper, the ink viscosity and the printing tone, and for small and large particles. Previous contradictory results from linting studies are because lint has only been measured after completing a printing trial, with no means of examining the two underlying adhesion failure processes.     

Physical properties of (La,Sr)Ti(O,N)3 thin films grown by pulsed laser deposition

Thin films of La_xSr_1−xTiO_3+x/2 (x = 0, 0.25, 0.5, 0.75, 1) were grown by laser ablation on two different kinds of substrates (SrTiO₃ (STO) and MgO) and were subsequently ammonolysed to yield the corresponding oxynitrides La_xSr_1−xTi(O,N)₃. For both substrates all films were found to grow epitaxially to the (1 0 0) direction of the cubic perovskite structure, except for x = 0.5 that grew parallel to the (1 1 0) direction. For some of the films TiN was detected as impurity phase. Scanning electron microscopy revealed that the films are dense and homogeneous with thicknesses around 350 nm. Atomic force microscopy showed that the surface roughness of the films varied between 4.2 and 14.1 nm. The employed substrate had a strong influence on the electrical properties. Films grown on STO exhibited a metallic behaviour, in contrast to the films grown on MgO, which were insulating.     

Investigation of lint particle adhesion in offset printing using Weibull statistics

Linting is one of the biggest concerns for the newspaper printing industry. In the offset printing process, lint particles from the paper are removed from the paper surface under the force of the tacky ink, adhere to the printing blanket and disrupt the transfer of ink, causing deterioration in image quality and affecting the pressroom productivity. This paper deals with the bond strength of the lint particles released from the paper substrate and printing blanket surface. The strength distribution of lint particles was characterised in order to study the dynamics of linting. The dynamics was modelled using a system with two first-order rate equations. Weibull statistics were used to describe the particle size distribution of the lint collected after the sheet-fed printing trials. In this investigation, the lint samples were collected by washing the lint from the printing blanket, filtering and performing image analysis to measure the particles. In order to analyse the data, the lint particle size was set as an independent variable. The number of small particles removed is as expected much higher than the number of larger particles. When the ink tack is increased and thus also the force working on the lint particles, then the relative increase in large particles is higher than the number of small particles. The removal rate of particles from the printing blanket is independent of particle size indicating that both the adhesion force between particles and blanket and the removal force due to ink tack is proportional to the particle area.