Table Of ContentSpringer Series in Electrophysics
Volume 14
Springer Series in Electrophysics
Volume I Structural Pattern Recognition By T. Pavlidis
Volume 2 Noise in Physical Systems Editor: D. Wolf
Volume 3 The Boundary-Layer Method in Diffraction Problems
By V. M. Babic. N. Y. Kirpicnikova
Volume 4 Cavitation and Inhomogeneities in Underwater Acoustics
Editor: W. Lauterborn
Volume 5 Very Large Scale Integration (VLSI)
Fundamentals and Applications Editor: D. F. Barbe 2nd Edition
Volume 6 ~arametric Electronics An Introduction
By K.-H. L6cherer, C. D. Brandt
Volume 7 Insulating Films on Semiconductors Editors: M. Schulz, G. Pensl
Volume 8 Fundamentals of Ocean Acoustics
By L. Brekhovskikh, Yu. Lysanov
Volume 9 Principles of Plasma Electrodynamics
By A. F. Alexandrov. L. S. Bogdankevich, A. A. Rukhadze
Volume 10 Ion Implantation Techniques Editors: H. Ryssel, H. Glawischnig
Volume II Ion Implantation: Equipment and Techniques
Editors: H. Ryssel. H. Glawischnig
Volume 12 VLSI Technology
Fundamentals and Applications Editor: Y. Tarui
Volume 13 Physics of Highly Charged Ions
By R. K. J anev, L. P. Presnyakov, V. P. Shevelko
Volume 14 Electrophotography and Development Physics
By L. B. Schein 2nd Edition
Volume 15 Relativity and Engineering By J. Van Bladel
Volume 16 Electromagnetic Induction Phenomena By D. Schieber
Volume 17 Concert Hall Acoustics By Y. Ando
Volume 18 Planar Circuits for Microwaves and Lightwaves By T. Okoshi
Volume 19 Physics of Shock Waves in Gases and Plasmas
By M. A. Liberman. A. L. Velikovich
Volume 20 Kinetic Theory of Particles and Photons By J. Oxcnius
Volume 21 Picosecond Electronics and Optoelectronics
Editors: G.A. MOUTOU, D.M. Bloom, C.-H. Lee
This series has been renamed
Springer Series in Electronics and Photonics starting with Volume 22.
Volumes 22-31 are listed at the end of the book.
L.B. Schein
Electrophotography
and
Development Physics
Second Edition
With 208 Figures
Springer -Verlag
Berlin Heidelberg New York
London Paris Tokyo
Hong Kong Barcelona
Budapest
Dr. Lawrence B. Schein
IBM Research Division, Almaden Research Center, 650 Harry Road,
San Jose, CA 95120, USA
ISBN-13: 978-3-540-55858-3 e-ISBN-13: 978-3-642-77744-8
00 1: 10.1007/978-3-642-77744-8
library of Congress Cataloging·in-Publication Data. Schein. L. B. (Lawrence B.), 1944-Electrophotography
and development phy.ics! L. B. Schein. - 2nd cd. p. cm. - (Springer ~ries in electrophysics ; v. 14) Includes
bibliographical references and index. ISBN 3-54ll-55g58-6 (Berlin: alk. paper). - ISBN 0-387·55858-6 (New
York: alk. paper) I. Xerography-Developing and developert. L Title. II. Series. TRH145.S34 1992 686.4'4-
dc20 92-29462
Thi~ work is ~ubject to copyright. All righlS are re~rved, whether the whole or pari of the material is concerned,
specifically the rightS of translation, reprinting, reu~ of illumations, r«itation, broadcasting, reproduction on
microfilm or in any other way, and storage in data banks. Duplication of this publication Or parts thereof isper·
mitted only under the provisions of the German Copyright Law of September 9, 1965, in its current vertion, and
permission for use must always be obtained from Springer·Verlag. Violations are liable for prosecution under
the German Copyright Law.
C Springer-Verlag Berlin Heidelberg 1988, 1992
The use of general descriplive names, regiSlered names, trademarks, elC. in this publication does not imply, even
in the absence of a specific stalemenl. thaI such names are eumpt from Ihe relevant protective laws and regula
tions and therefore free for general use.
54/3140-543210-Printed on acid-free paper
Dedicated to my parents
BERNARD AND SYLVIA SCHEIN
Preface to the Second Edition
During the last four years, since this book was first published, the field of
electrophotography has experienced some astonishing changes. Most obvious
is the emergence of high quality color copying and printing. Successful im
plementation of color electrophotography required the solution of many tech
nical problems, some of which necessitated the invention of new development
systems. In addition, major advances in our understanding of the technology
have occurred. Background development was identified in the first edition as
one of the major unsolved problems in electrophotography; significant
progress has been made (Sect. 12-6.6). The effective dielectric constant
problem has been solved, with experiments and theory in agreement (Sect.
12-6.2.2), and a major advance in our understanding of insulator, i.e. toner,
charging has occurred with the identification of an experiment that can dis
tinguish between the low and high density limits of the surface state theory
(Sect. 12-4.3).
In order to bring these new results to the attention of the electropho
tographic community, it was decided to update the 1988 version of this book.
To make it as easy as possible for the reader to identify and learn the new re
sults, this second edition is organized as follows. Chapter 11 is devoted to
color electrophotography. Chapter 12 updates Chaps. 1-10. Each section in
Chap. 12 is identical in subject to the earlier section indicated by the number
following 12- and assumes knowledge of the earlier section.
The author would like to acknowledge the IBM Corporation for encour
aging and supporting the writing of this second edition and the many people
who have assisted in bringing out this book, including Sheila Hill and Pam Hale
of the Publication Department at the IBM Almaden Research Center,
Deborah Hollis of Springer-Verlag, who has patiently edited all twelve chap
ters, Lynn Ritter of Dataquest, who kindly supplied the market information,
and Robert Durbeck, Peter Castle, Barry Schechtman, and Connie Schein,
who critically reviewed Chaps. 11 and 12 before publication.
San Jose, California L. B. Schein
March,1992
VII
Preface to the First Edition
Electrophotography (also called xerography), the technology inside the famil
iar copier, has become increasingly important to modern society. Since the
first automatic electrophotographic copiers were introduced in 1959, they
have become indispensable to the modern office and now constitute a multi
billion dollar industry involving many of the world's largest corporations. By
the 1990s, it is expected that electrophotography will be one of the most pre
valent printer technologies. This will occur because of the growing need for
printers that are quiet, that can produce multiple fonts, and that can print
graphics and images. Electrophotographic printers satisfy these requirements
and have demonstrated economic and technical viability over an enormous
speed range, from 6 to 220 pages per minute, with output quality that ap
proaches offset printing.
Organizations contemplating designing a new electrophotographic copier
or printer need to deal with two sets of issues. First, for each of the six process
steps in electrophotography there are several different technologies that must
be evaluated and chosen. For example, there are three development technol
ogies (two component, monocomponent and liquid); cleaning can be done
with a blade or brush; and the photoconductor can be inorganic or organic:,
either of which can be configured in the form of a belt or a drum. Second,
once a technology for each step is chosen, it must be optimized and integrated
with the other process steps. This optimization and integration is facilitated
by a firm scientific understanding of the technologies being considered. Un
fortunately, certain key technologies in electrophotography are not well un
derstood, even after years of industrial practice.
Perhaps the most crucial technologies which are not well understood are
those used in the development step, because this step most directly determines
the quality of the images. It is in this step that the "blackness" of the lines and
solid areas, the cleanliness of the nonimaged areas, the uniformity of solid
areas, and the ratio of the "blackness" of lines to solid areas are determined.
Those who used Xerox copiers during the 1960s will remember that they
would only reproduce the edges of solid areas (Fig. 3.1), a copy quality defect
attributable to characteristics of the open cascade development system
(Chap. 5). The generally perceived high copy quality of the Eastman Kodak
line of copiers introduced in 1976 resulted directly from the introduction of a
new development system, conductive magnetic brush development (Chap. 7).
IX
There are several reasons why aspects of the development system are not
well understood. First are the scientific reasons. It is known that the proper
toner charge is important to good development (toner is the black plastic
powder that ends up on the paper); yet our understanding of toner charging,
and more generally insulator charging, can be characterized as pre-scientific,
with most knowledge being empirical. While our knowledge of the physics of
solid area and character development is becoming relatively firm, our under
standing of the causes of background development (the black spots on copies
due to toner developing onto the white or nonimaged areas) is lacking because
not enough attention has been given to this problem.
Second, there have been several recent inventions that are opening up the
possibility of further improvements in the development step and which chal
lenge electrophotographic scientists to understand and improve. In 1980,
Canon introduced the first monocomponent development system based on
magnetic, insulating toner (Sect. 9.5) which was an important factor making
it possible for Canon to manufacture and sell the first electrophotographic
copier for under $1000. Only a few years ago, in 1985, Ricoh and Toshiba
both announced new monocomponent development systems based on non
magnetic, insulating toner (Sect. 9.6). Also, new tools for measuring toner
charge distributions are becoming available which will help characterize and
design new toner systems (Sect. 4.4.4). And there has been a virtual explo
sion in the patent literature on charge control agents, which are toner additives
that assist in controlling the toner charge (Sect. 4.4.3).
The primary purpose of this book is to discuss critically the physics of all
known electrophotographic development technologies and their associated
toner charging mechanisms. To assist the reader who may be new to electro
photography, a tutorial is presented in which the technical history and market
of electrophotography are examined (Chap. 1), followed by a discussion of the
physics within each of the six electrophotographic process steps (Chap. 2). In
selecting the literature to review for this book the following choices were
made. I have attempted to reference completely the scientific literature on
development physics up to October 1987. In the two chapters on toner
charging (Chaps. 4 and 8) the physics of static electricity is thoroughly dis
cussed and related to our understanding of toner charging. Patents are only
referenced if they contain important physics unavailable elsewhere. Materials
and engineering problems are not discussed because they are beyond the scope
of a single book. In the tutorial on electrophotography (Chap. 2), papers and
review articles have been selected that will allow the interested reader to find
the appropriate literature.
The author would like to acknowledge his management, Don Burland and
Bob Durbeck, and the IBM Corporation for allowing and encouraging the
writing of this book. The stimulation of my many colleagues at the IBM
Almaden Research Center and in Joe Woods's Technology Laboratory at the
IBM Boulder facility are also appreciated. Others at IBM whom I would like
x
to acknowledge include Hans Coufal, who initially suggested that a new book
on electrophotography would be useful, Lorraine Rodriquez's Publications
Department staff, especially Linda Perez, and Villa Ma's library staff, espe
cially Beverly Clarke.
I have been working on many aspects of electrophotography since Sep
tember 1983 at IBM and 1970-1975 at the Xerox Corporation. I would like
also to acknowledge Mike Shahin at Xerox who suggested I look into the
"new" magnetic brush development system, and Mike's and Mark Tabak's
continual support during the years it took to sort out the physics of the
insulative magnetic brush development system.
Writing a book is a strain on any family. I appreciate the support and
understanding of my wife Connie and children, Daniel and Benjamin, during
those many weekends and evenings when I was unavailable to them.
The author would also like to acknowledge the people who have critically
reviewed chapters in this book prior to publication, including Bob Durbeck,
Don Burland, Hans Coufal, Bruce Terris, Peter Castle, Joe Abbott,
K Jenkins, Gene Bishop, Campbell Scott, Vlad Novotny, Connie Schein,
Lynn Ritter, John Bickmore and Bill Greason.
Finally, I would like to acknowledge my many colleagues over the years,
who are too numerous to mention; their comments and criticisms have helped
shape my thinking and the field. This book is in fact the sum total of the
thinking of all of the people who have shared with me the fun and excitement
of working on electrophotographic development physics.
San Jose, California L. B. Schein
October, 1987
XI
Contents
1. Introduction .... 1
1.1 Technical History 3
1.2 Copier Market 14
1.3 Printer Market 17
1.4 Alternative Powder Marking Technologies 20
1.4.1 Magnetography 22
1.4.2 Ionography ...... . 24
2. The Electrophotographic Process 26
2.1 The Six Steps of Electrophotography 26
2.1.1 Charge 27
2.1.2 Expose 29
2.1.3 Develop 32
2.1.4 Transfer 36
2.1.5 Fuse 38
2.1.6 Clean 38
2.2 Implementation-Interactions 39
2.3 Subsystem Choices 42
2.3.1 Photoreceptor ,. 42
2.3.2 Charge 44
2.3.3 Light Source 44
2.3.4 Develop 46
2.3.5 Transfer 47
2.3.6 Fuse .. 47
2.3.7 Clean 49
3. The Development Step 50
3.1 Challenges 50
3.2 Focus .... 53
3.3 Descriptions 57
4. Toner Charging for Two Component Development Systems 63
4.1 Metal-Metal Contact Charging 64
4.2 Metal-Insulator Contact Charging . . . . . 65
4.2.1 Controversies ......... . 66
4.2.2 Experimental and Theoretical Difficulties 69
XIII
