Metrology for Printing and Graphic Arts Substrates

Summary

This program aims to develop the metrology to enable quantitative understanding of, and the development of standards, in quality and reliability controls in manufacturing of graphic arts substrates, such as cellulosic paper based on digital, automated processes. This project describes the efforts to be performed at NIST, in joint research with the United States Government Publishing Office (GPO). 

Description

Paper is a complex, heterogeneous, multi-phased material. While there is a significant body of work related to the dielectric properties of cellulose, comparatively fewer studies have been done on printing and writing grades of paper.  In our previous work, we have been able to differentiate between papers of containing a variety of wood and non-wood fiber species via resonant cavity dielectric spectroscopy as well as several other attributes, including recycled fiber content.

Through those investigations we have determined that while dielectric properties largely depend upon the anisotropy and the fiber species content of the sheet, the presence of additives, such as inorganic fillers (ash content), organic colorants and optical brightening agents (OBAs), and the percentage of recycled fiber, also affect the observed dielectric loss of a sample.  In this effort, we will probe the underlying mechanisms that drive these variables to influence dielectric and optical behavior of printing substrates.

Our competencies include, but not limited to, spectroscopy (optical, microwave, and X-ray micro-diffraction, etc.), electrochemistry, as well as semiconductor process integration knowledge.

The projects within this program include the characterization and understanding of the nature / composition of graphic arts substrates (e.g., paper) and their application packaging. The developed metrology and documentary standards we develop will aid advanced manufacturing, document security and commercialization of advanced complex integrated systems. Towards this end, the following are some of the current projects within the program:

1. Paper Aging:
   • UV / Photo aging via heat and UV light exposure in accelerated fade testing chamber: We have previously collected dielectric loss data on papers of recycled and virgin fiber content artificially aged in an accelerated fade testing chamber using UV light (340 nm) at an irradiance of 0.72 W/m² with an elevated temperature (50°C).
   •  Natural aging: Evaluating previously collected dielectric loss data on bond papers of varying cotton content with known years of manufacture over a 40-year period.
   • Nuclear and related radiation aging (in progress): 
     • Radiation sources ⁶⁰Co (g-cell radiation) ⁹⁰Sr, ⁸⁵Kr (β-radiation sources).  
     • Vary radiation dose to determine accelerated paper aging threshold.
     • Examine radiation accelerated aging on cotton bond papers (25%, 50%, and 100% cotton) 
     • Compare watermarked and non-watermarked areas
2. Characterize the impact of aging by-products in paper on dielectric loss:
   Titrate standard Whatman filter paper (pure cellulose) with known paper aging end products (e.g., furaldehyde) to quantify the impact on dielectric loss
3. Methods development and characterization: 
   Use ionic liquids to separate the cellulose from all the additives in the paper. 
   Perform the following spectroscopic studies on the pure cellulose:
   • Chiral dichroism method development and characterization 
   • UV-Vis-NIR reflectance
   • Microwave cavity dielectric measurements

Project time lines and deliverables

FY2019 Q4

• Compare recycled vs. virgin office copier papers

FY2020 Q1:  

• Experimental set up and calibration (in progress)
• Demonstration and go / no-go testing (in progress)
• Initial radiation work (in progress)

FY2020 Q2:  

• Study bond papers of varying cotton content
• Compare watermarks and other surface modifications

FY2020 Q3:  

• Study secure printing substrates, i.e., papers with the inclusion of synthetic polymer components (fibers, ribbons, planchettes, etc.)

Major Accomplishments

2019

• Successfully determined the recycled fiber content of commercial office copier papers using broadband dielectric / resonant cavity spectroscopy.
• Demonstrated real-time monitoring of cellulosic paper aging using broadband dielectric / resonant cavity spectroscopy.
• Demonstrated the feasibility of using broadband RF monitoring to understand the elementary events that occur in the early stages paper aging

 
2018

• Demonstrated Broadband Dielectric Spectroscopic Studies of Biological Material Evolution and in Paper