scholarly journals Back-trap mottle: A review of mechanisms and possible solutions

BioResources ◽  
2021 ◽  
Vol 16 (3) ◽  
pp. 6426-6447
Author(s):  
Hak Lae Lee ◽  
Hye Jung Youn ◽  
Ming He ◽  
Jiachuan Chen
Keyword(s):  
Coating Layer ◽  
Offset Printing ◽  
Coating Structure ◽  
Paper Substrate ◽  
Coated Paper ◽  
Printing Process ◽  
Coated Papers ◽  
Coating Uniformity ◽  
Color Density

Print mottle is a serious and common uneven printing defect that occurs when printing coated paper by the offset multicolor printing process. It is characterized by a non-uniform appearance in terms of brightness, gloss, or color density that appears mostly in solid printed areas. Back-trap print mottle and water-interference print mottle occur when the quality of the paper substrate, especially the coating layer quality, is not satisfactory. To cope with this quality problem of coated papers, the understanding of the offset printing process, the requirements of coated-paper quality, and the reasons for this problem should be addressed. In this review, the basic process of offset printing and the mechanisms of print mottles were explored, the importance of coating uniformity in both the coating structure and process was reviewed, and the approaches to cope with print mottle were introduced.

Evaluation of cut quality of woodfree coated papers

TAPPI Journal ◽  
2013 ◽  
Vol 12 (9) ◽  
pp. 9-15
Author(s):  
BENOÎT DUFOUR, ◽  
WOLFGANG BAUER ◽  
JEAN-FRANCIS BLOCH
Keyword(s):  
Coating Layer ◽  
The State ◽  
Point Of View ◽  
Test Method ◽  
Offset Printing ◽  
Paper Properties ◽  
Coated Papers ◽  
Cut Quality ◽  
Printing Papers

Dusting and blanket pollution are of particular interest in offset printing. Papers must be free of dust and loose particles to drastically reduce the wash interval of the blankets. Those particles are mainly generated during converting operations, such as sheeting. Considering the end-customer point of view, the visual aspect of the cut appears to be very important. To study in detail the influence of the sheeting parameters and paper properties on cut quality, a new test method to quantify the cut quality of woodfree coated papers has been developed. In particular, this method takes into consideration the state of the coating layer near the cutting edges.

Analysis on Ink Layer Rub Resistance for Coated Paper Prints

2011 ◽  
Vol 380 ◽  
pp. 173-178
Author(s):  
Wen Hua Zhou ◽  
Bei Hai He ◽  
Chun Xiu Zhang ◽  
Yue Han
Keyword(s):  
Loss Rate ◽  
Fine Particles ◽  
Coating Layer ◽  
Color Difference ◽  
Coated Paper ◽  
Coated Papers ◽  
Color Density ◽  
Viscosity Reducer ◽  
The Impact ◽  
Print Color

Having been coated, the surface unevenness and pores on paper were covered by a coating layer composed of fine particles and binders, which can absorb ink well, thereby a good uniformity and smoothness of paper could be obtained, consequently, the reproducing capability for printing dot and good whiteness, gloss and opacity can be improved. In theory, the ink rub resistance for coated paper print is mainly affected by the ink absorbance property of paper, printing conditions, ink components, rub medium and so on. In this study, seven different kinds of coated papers, the viscosities of the inks were adjusted with a viscosity adjusting agent, and then the prints were prepared by proofing with the ink with different viscosities. After drying, the prints were used for rub testing. The impact of the basic properties of coated paper and the content of reducer in inks on rub resistance were discussed on the basis of a comparative analysis of the experimental data. Printing color density loss rate and print color difference were exploited in this paper to characterize the ink rub resistance for coated paper prints. In this study, it was found that ink rub resistance was mainly influenced by ink absorbency and smoothness of the paper. Under the similar conditions, the color density of coated paper print decreases with the rub strength increasing, color difference increased gradually, but not linearly. With the increase of ink viscosity reducer content, printing density loss rates as well as color difference changed, but not be linearly.

scholarly journals Assessment of Mini-Tablets Coating Uniformity as a Function of Fluid Bed Coater Inlet Conditions

Pharmaceutics ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 746
Author(s):  
Magdalena Turk ◽  
Rok Šibanc ◽  
Rok Dreu ◽  
Maja Frankiewicz ◽  
Małgorzata Sznitowska
Keyword(s):  
Coating Layer ◽  
Spectrophotometric Analysis ◽  
Material Distribution ◽  
Spray Chamber ◽  
Colorimetric Analysis ◽  
Swirl Generator ◽  
Coating Uniformity ◽  
Fluid Bed ◽  
Inlet Conditions

This study concerned the quality of mini-tablets’ coating uniformity obtained by either the bottom spray chamber with a classical Wurster distributor (CW) or a swirl distributor (SW). Mini-tablets with a diameter of 2.0, 2.5, and 3.0 mm were coated with hypromellose using two different inlet air distributors as well as inlet airflow rates (130 and 156 m3/h). Tartrazine was used as a colorant in the coating layer and the coating uniformity was assessed by spectrophotometric analysis of solutions obtained after disintegration of the mini-tablets (n = 100). Higher uniformity of coating material distribution among the mini-tablets was observed in the case of SW distributor, even for the biggest mini-tablets (d = 3.0 mm), with an RSD no larger than 5.0%. Additionally, coating thickness was evaluated by colorimetric analysis (n = 1000), using a scanner method, and expressed as a hue value. A high correlation (R = 0.993) between inter-tablet variability of hue and UV-Vis results was obtained. Mini-tablets were successfully coated in a fluid bed system using both a classical Wurster distributor as well as a swirl generator. However, regardless of the mini-tablets’ diameter, better film uniformity was achieved in the case of a distributor with a swirl generator.

scholarly journals A Study on the Assessment of Quality of Printed Sheets in Offset Sheet-Fed Printing 

2021 ◽  
Vol 31 (1) ◽  
pp. 41-45
Keyword(s):  
Quality Management ◽  
Total Quality Management ◽  
Quality Parameters ◽  
Low Density ◽  
Total Quality ◽  
Offset Printing ◽  
Pareto Chart ◽  
Printing Process ◽  
Ishikawa Diagram

The quality parameters of printed sheets should be controlled constantly during the sheet-fed offset printing process. This allows the detection of any problems in the initial stages of the printing process. The final control of the quality of printing sheets will eliminate error products before delivering to the costumers. The results of this control should be analyzed continuously. The total quality management (TQM) is an effective method in controlling, doing statistics, and assessing the errors in the offset printing process. Simultaneously, this method delivers the main errors frequently occurred in the printing process. This paper presents the possibility of using some tools of the TQM method such as Pareto chart, Ishikawa diagram, and 5xWhy to analyze and assess the quality of printing sheets in sheet-fed offset printing. The studied results show that the two main errors of the printed sheets are hickeys (occupied 29 %) and low density (occupied 17%). Moreover, the causes of hickey error are analyzed and shown in this paper.

scholarly journals Preventive maintenance features specific to offset printing machines

2021 ◽  
Vol 343 ◽  
pp. 08012
Author(s):  
Emilia Bălan ◽  
Liviu Berculescu ◽  
Răzvan-George Răcheru ◽  
Dorin Vasile Piţigoi ◽  
Lucia Adăscăliţa
Keyword(s):  
Preventive Maintenance ◽  
Offset Printing ◽  
Printing Process ◽  
Machine Performance ◽  
Continuous Quality ◽  
Study Results ◽  
Maintenance Activities ◽  
Printing Processes

In the printing industry, where production never stops, it is very important to continuously maintain machine performance. If a machine breaks down, the production will stop and it will disturb the production process. Therefore, the maintenance system must be managed efficiently to solve those problems. The paper presents the study results on continuous quality improvement of offset printing using preventive maintenance features. Offset printing is a process that involves a multitude of variables, independent and interdependent factors. The offset printing process was analyzed and the factors that have a significant influence on the quality of the process and the products made were identified. The defects that may occur during the printing process and the causes thereof have also been identified and the types of non-conformities of the end products were estabilished. The experimental method was used. The case study was conducted on Manroland 508. For the planning of preventive maintenance activities, the duration of the maintenance works necessary to ensure the proper functioning of the offset printing machines was established. Finally, maintenance activities that would guarantee and continuously improve the quality of the printing processes and the printed products were issued.

Paper-Based Plasmonic Surface for Chemical Biosensing by the Attenuated Total Reflection Method

MRS Advances ◽  
2017 ◽  
Vol 2 (42) ◽  
pp. 2303-2308 ◽  
Author(s):  
Nobuko Fukuda ◽  
Srimongkon Tithimanan ◽  
Hirobumi Ushijima ◽  
Noritaka Yamamoto
Keyword(s):  
Protein Detection ◽  
Gold Surface ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Reflection Method ◽  
Paper Substrate ◽  
Coated Paper ◽  
Coated Papers ◽  
Atomic Force ◽  
Si Wafer

ABSTRACTWe demonstrate the detection of an increase in refractive index and/or thickness by specific adsorption of proteins on a plasmonic surface on a paper substrate in the Otto configuration. Propagating surface plasmon resonance is observed on a gold surface deposited onto polymer-coated papers through angular scans of reflectivity in the Otto configuration under attenuated total reflection conditions. According to a surface analysis with atomic force microscope, the gold surface roughness on a polyvinyl chloride (PVC)-coated paper is comparable to that of a Si wafer, leading to the achievement of protein detection. On the other hand, the propagating length of the surface plasmons is shorter than that on the Si wafer. According to an observation of the gold surface with scanning electron microscope, the gold grain size on the PVC-coated paper is smaller than that on the Si wafer. Thus, many boundaries cause a reduction in the propagating length on the PVC-coated paper.

scholarly journals The Change of Printouts' Quality Depending on Pressure of a Blanket Cylinder Against an Impression Cylinder and a Plate Cylinder in Offset Machine

2014 ◽  
Vol 8 (1) ◽  
pp. 9-15 ◽  
Author(s):  
Agnieszka Jurkiewicz ◽  
Yuriy Pyr'yev
Keyword(s):  
Optical Density ◽  
Research Method ◽  
Quality Parameters ◽  
Offset Printing ◽  
Coated Paper ◽  
Machine Manufacturer ◽  
Uncoated Paper ◽  
Two Parameters ◽  
Optimal Settings

Abstract According to lots of books, the pressure in offset printing affects the optical density and the quality of printouts. One of the quality parameters is a tone value increase. An advantage of our research method is obtaining printing effects for different pressures on one printout, thus meaning for identical printing conditions. We obtained the same printing conditions through using different amounts of underlay sheets fixed to the blanket cylinder, under a blanket. The pressure was increased from optimal settings - in accordance with the machine manufacturer’s recommendation. The test printouts were printed using Adast Dominant 515, on a coated and an uncoated paper. The optical density value was measured on the tone value scale from 10% to 100% stepping regularly by 10%. For this scale the tone value increase was computed. The research shows that for both types of paper the optical density and the tone value increase changes not very much above the optimal pressure recommended by the machine manufacturer. A difference in the optical density and in the tone value increase is bigger for coated paper than for uncoated paper. Changes in these two parameters are negligible in places where used form 0 to 4 underlay sheets and are quite significant in the place where 5 underlay sheets were.

scholarly journals OPTIMIZING THE ROLE OF INKING UNIT IN OFFSET PRINTING MACHINE

KREATOR ◽  
2021 ◽  
Vol 2 (2) ◽  
Author(s):  
Juliandri . ◽  
Anton Hadiwijaya ◽  
Yessy Yerta Situngkir
Keyword(s):  
Offset Printing ◽  
Printing Process ◽  
Maintenance Schedule ◽  
Potential Problems ◽  
Routine Procedures ◽  
Printing Machine ◽  
Standard Operations

In-depth observations have been made on the printing process using the Heidelberg Speedmaster CD 102 machine. In this process, the ink unit becomes the biggest concern because of its role in the quality of the printout. Observations are made directly in the field on routine procedures carried out and discuss events in the field to identify problems and determine actions. The results of the study indicate that there are several things that must be improved related to the routine maintenance schedule, the technical setup of the inking unit and identification of potential problems as a reference for improving standard operations in the field.Keywords—Inking unit, offset printing machine, speedmaster machine

The influence of coating composition on the structural and functional properties of coated paper for packaging applications

2020 ◽  
Vol 35 (3) ◽  
pp. 408-418
Author(s):  
Petronela Nechita
Keyword(s):  
Functional Properties ◽  
Coating Layer ◽  
Binder Content ◽  
Structure And Properties ◽  
Coated Paper ◽  
Coated Papers ◽  
Structural And Functional Properties ◽  
Coating Composition ◽  
Pigment Type ◽  
Coated Surfaces

AbstractThe work presented in this paper is focussed on study of structure and properties of coating layers based on natural pigments (ground calcium carbonate and clay) and butadiene acrylonitrile latex as binder in correlation with functional properties of the final coated paper. It is quantified the influence of binder content and pigment type on the structural and liquids penetration properties of coating layer. The obtained results confirm that by increasing of binder content in the coating formulations a reduced efficiency of light-scattering and increased roughness for coated surfaces is obtained. At the high binder amounts (over 15 pph), the coating layer porosity is reduced and as result a lower liquids penetration in the coated papers is obtained.

scholarly journals The Influence of Drying Conditions of Clay-Based Polymer Coatings on Coated Paper Properties

Coatings ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 12
Author(s):  
Petronela Nechita
Keyword(s):  
Coating Layer ◽  
Polymer Coatings ◽  
Structure And Properties ◽  
Coated Paper ◽  
Paper Properties ◽  
Coated Papers ◽  
Polymer Binders ◽  
Surface Optical ◽  
Coating Color ◽  
Drying Conditions

Coatings based on pigment and polymer binders are applied on paper surfaces to improve their surface, optical, and printing properties. Besides the coating composition, the structure and properties of the coated papers are influenced by the coating layer consolidation upon drying. In this study, the influence of drying conditions on the structure and properties of coating layers based on natural pigments (clay) and polymer binders (butadiene acrylonitrile latex) has been analyzed. Using a laboratory rod Mayer device, the coatings were applied as thin layer (about 15–16 g/m2) on the paper surface and samples of coated paper were dried at 20 and 105 °C temperatures. The optical, structural, and water absorption properties of the coating layer were evaluated by the measurement of gloss, opacity, void fraction, light scattering, and contact angle. The obtained results highlighted that both the drying temperature and latex content in the coating color have a synergic effect on the coated paper quality.

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