Electrophoretic migration imaging process

In general, materials having the structure ##STR1## WHEREIN N EQUALS 1 OR 2; PA1 A represents phenylene, naphthylene, anthracenyl, anthracenediyl, and dibenzothien-diyl; PA1 R.sub.1 and R.sub.2, which may be the same or different when taken alone represent hydrogen, cyano, alkylcarbonyl and arylcarbamoyl, arylcarbonyl, cyanoaryl; PA1 R.sub.1 and R.sub.2, when taken together, represent sufficient atoms to form substituted and unsubstituted radicals selected from the group consisting of furanylidene, fluorenylidene, pyrimidinylidene, thiazolidinylidene, pyrrolinyl, and indenyl, isoxazolinylidene, pyrazolinylidene and indanylidene, wherein said substituents are selected from the group consisting of hydrogen, cyano, aryl, oxo, thioxo, nitro, alkyl, nitroaryl, carbamoyl and cyanoalkyl; and PA1 Alkyl represents an alkyl group having from one to six carbon atoms; aryl represents an aromatic nucleus selected from the group consisting of benzene, naphthalene or anthracene, are useful in electrophoretic migration imaging processes.

FIELD OF THE INVENTION 
This invention relates to electrophoretic migration imaging processes and, 
in particular, to the use of certain novel photosensitive pigment 
materials in such processes. 
BACKGROUND OF THE INVENTION 
In the past, there has been extensive description in the patent and other 
technical literature of electrophoretic migration imaging processes. For 
example, a description of such processes may be found in U.S. Pat. No. 
2,758,939 by Sugerman issued Aug. 14, 1956; U.S. Pat. Nos. 2,940,847, 
3,100,426, 3,140,175 and 3,143,508, all by Kaprelian; 3,384,565, 3,384,488 
and 3,615,558, all by Tulagin et al; 3,384,566 by Clark; and 3,383,993 by 
Yeh. In addition to the foregoing patent literature directed to 
conventional photoelectrophoretic migration imaging processes, another 
type of electrophoretic migration imaging process which advantageously 
provides for image reversal is described in Groner, U.S. Pat. No. 
3,976,485 issued Aug. 24, 1976. This latter process has been termed 
photoimmobilized electrophoretic recording or PIER. 
In general, each of the foregoing electrophoretic migration imaging 
processes typically employs a layer of electrostatic charge-bearing 
photoconductive particles, i.e., electrically photosensitive particles, 
positioned between two spaced electrodes, one of which may be transparent. 
To achieve image formation in these processes, the charge-bearing 
photosensitive particles positioned between the two spaced electrodes, as 
described above, are subjected to the influence of an electric field and 
exposed to activating radiation. As a result, the charge-bearing 
electrically photosensitive particles are caused to migrate 
electrophoretically to the surface of one or the other of the spaced 
electrodes, and one obtains an image pattern on the surface of these 
electrodes. Typically, a negative image is formed on one electrode, and a 
positive image is formed on the opposite electrode. Image discrimination 
occurs in the various electrophoretic migration imaging processes as a 
result of a net change in charge polarity of either the exposed 
electrically photosensitive particles (in the case of conventional 
electrophoretic migration imaging) or the unexposed electrically 
photosensitive particles (in the case of the electrophoretic migration 
imaging process described in the above-noted Groner patent application) so 
that the image formed on one electrode surface is composed ideally for 
electrically photosensitive particles of one charge polarity, either 
netative or positive polarity, and the image formed on the opposite 
polarity electrode surface is composed ideally of electrically 
photosensitive particles having the opposite charge polarity, either 
positive or negative. 
In any case, regardless of the particular electrophoretic migration imaging 
process employed, it is apparent that an essential component of any such 
process is the electrically photosensitive particles. And, of course, to 
obtain an easy-to-read, visible image it is important that these 
electrically photosensitive particles be colored, as well as electrically 
photosensitive. Accordingly, as is apparent from the technical literature 
regarding electrophoretic migration imaging processes, work has been 
carried on in the past and is continuing to find particles which possess 
both useful levels of electrical photosensitivity and which exhibit good 
colorant properties. Thus, for example, various types of electrically 
photosensitive materials are disclosed for use in electrophoretic 
migration imaging processes, for example, in U.S. Pat. Nos. 2,758,939 by 
Sugarman, 2,940,847 by Kaprelian, and 3,384,488 and 3,615,558 by Tulagin 
et al., noted hereinabove. 
In large part, the art, to date, has generally selected useful electrically 
photosensitive or photoconductive pigment materials for electrophoretic 
migration imaging from known classes of photoconductive materials which 
may be employed in conventional photoconductive materials which may be 
employed in conventional photoconductive elements, e.g., photoconductive 
plates, drums, or webs used in electrophotographic office-copier devices. 
For example, both Sugarman and Kaprelian in the above-referenced patents 
state that electrically photosensitive materials useful in electrophoretic 
migration imaging processes may be selected from known classes of 
photoconductive materials. And, the phthalocyanine pigments described as a 
useful electrically photosensitive material for electrophoretic imaging 
processes in U.S. Pat. No. 3,615,558 by Tulagin et al. have long been 
known to exhibit useful photoconductive properties. 
SUMMARY OF THE INVENTION 
In accord with the present invention, a group of materials has been 
discovered which are useful in electrophoretic migration imaging 
processes. With one exception, these materials are novel over the prior 
art known to applicants. None have been previously identified as 
photoconductors. Said materials have the following structure: 
##STR2## 
wherein 
n equals 1 or 2; 
A represents phenylene, naphthylene, anthracenyl, anthracenediyl, and 
dibenzothien-diyl 
R.sub.1 and R.sub.2, which may be the same or different when taken alone 
represent hydrogen, cyano, alkylsulfonyl, alkylcarbonyl and arylcarbamoyl, 
cyanoaryl, arylcarbonyl, and hydrogen; 
R.sub.1 and R.sub.2, when taken together, represent sufficient atoms to 
form substituted and unsubstituted radicals selected from the group 
consisting of furanylidene, fluorenylidene, pyrimidinylidene, 
thiazolidinylidene, pyrrolinyl, and indenyl, isoxazolinylidene, 
pyrazolinylidene, indanylidene and dithiolyl, wherein said substituents 
are selected from the group consisting of hydrogen, cyano, aryl, oxo, 
thiooxo, nitro, alkyl, nitroaryl, carbamoyl, and cyanoalkyl, except that 
when: 
(A) A represents anthracene nucleus and 
(i) R.sub.1 and R.sub.2 when taken together represent 
1,3,5-trihydro-2,4,6-trioxo-pyrimidin-5-ylidene; 
3-cyano-4-phenyl-2-oxo-pyrrolin-5-ylidene; or 3-carboxy-inden-1-ylidene; 
or 
(ii) taken alone R.sub.1 represents cyano and R.sub.2 represents methyl 
sulfonyl ethoxycarbonyl or phenylcarbamoyl; and 
(iii) either R.sub.1 or R.sub.2 is alkylcarbonyl or phenylcarbonyl then n 
represents 2 or 
(B) A represents phenylene and R.sub.1 and R.sub.2 taken together represent 
4,5-dicyano-1,3-dithiol-2-ylidene; then n represents 2; or 
(C) R.sup.1 is hydrogen, R.sup.2 must be other than hydrogen. 
Aryl, as a suffix or prefix, is defined herein to mean an aromatic nucleus 
such as benzene, naphthalene and anthracene. Functional equivalents of 
both A above and Aryl may be used and both A and Aryl can have 
non-interfering substituents. Alkyl, as a prefix or suffix, is defined 
herein to mean alkyl radicals having from 1 to about 6 carbon atoms. 
When used in an electrophoretic migration imaging process, charge-bearing, 
electrically photosensitive particles formulated from the materials of the 
present invention are positioned between two spaced electrodes; preferably 
these particles are contained in an electrically insulating carrier such 
as an electrically insulating liquid or an electrically insulating, 
liquefiable matrix material, e.g., a thixotropic or a heat- and/or 
solvent-softenable material, which is positioned between the spaced 
electrodes. While so positioned between the spaced electrodes, the 
photosensitive particles are subjected to an electric field and exposed to 
a pattern of activating radiation. As a consequence, the charge-bearing, 
electrically photosensitive particles undergo a radiation-induced 
variation in their charge polarity and migrate to one or the other of the 
electrode surfaces to form on at least one of these electrodes an image 
pattern representing a positive-sense or negative-sense image of the 
original radiation exposure pattern.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In accordance with one embodiment of the present invention there is 
provided a group of novel colorant materials which are useful in 
electrophoretic migration imaging processes. These materials have the 
formula: 
##STR3## 
wherein 
n equals 1 or 2; 
A represents phenylene, naphthylene, anthracenyl, anthracenediyl and 
dibenzothien-diyl; 
R.sub.1 and R.sub.2, which may be the same or different when taken alone 
represent hydrogen, cyano, and cyanoaryl, arylcarbonyl, hydrogen; 
R.sub.1 and R.sub.2, when taken together, represent sufficient atoms to 
form substituted and unsubstituted radicals selected from the group 
consisting of furyanylidene, fluorenylidene, pyrimidinylidene, 
thiazolidinylidene, pyrrolinyl, and indenyl, isoxazolinylidene, 
pyrazolinylidene, indanylidene and dithiolyl, wherein said substituents 
are selected from the group consisting of hydrogen, cyano, aryl, oxo, 
thiooxo, nitro, alkyl, nitroaryl, carbamoyl, and cyanoalkyl, except that 
when: 
(A) A represents an anthracene nucleus and 
(i) R.sub.1 and R.sub.2 when taken together represent 
1,3,5-trihydro-2,4,6-trioxo-pyrimidin-5-ylidene; 
3-cyano-4-phenyl-2-oxo-pyrrolin-5-ylidene; or 3-carboxy-inden-1-ylidene; 
or 
(ii) taken alone R.sub.1 represents cyano and R.sub.2 represents methyl 
sulfonyl, phenylcarbamoyl or ethoxycarbonyl; or 
(iii) either R.sub.1 or R.sub.1 is alkylcarbonyl or phenylcarbonyl then n 
represents 2 or 
(iv) both R.sub.1 and R.sub.2 represent cyano, then n represents 1 or 
(B) A represents a phenylene nucleus and R.sub.1 and R.sub.2 taken together 
represent 4,5-dicyano-1,3-dithiol-2-ylidene then n represents 2 or 
(C) R.sub.1 is hydrogen, R.sub.2 must be other than hydrogen. 
In accordance with another embodiment of the present invention, there is 
provided an electrophoretic migration imaging process which comprises 
subjecting an electrically photosensitive colorant material positioned 
between two electrodes to an applied electric field and exposing said 
material to an image pattern of radiation to which the material is 
photosensitive, thereby obtaining image formation on at least one of said 
electrodes, the improvement which comprises using as at least a portion of 
said material an electrically photosensitive colorant material according 
to Formula I. 
In accordance with another embodiment of the present invention there is 
provided a group of materials which are especially useful in 
electrophoretic migration imaging processes. Such especially useful 
materials have a structure according to general Formula I wherein 
n is 2; 
A represents naphthylene, anthracenediyl or benzothiophen-diyl; 
R.sub.1 and R.sub.2, are both cyano or when taken together provide 
sufficient atoms to form a substituted or unsubstituted furanylidene 
radical and said substituents are selected from the group consisting of 
cyano, phenyl, nitrophenyl and oxo. 
In addition to the useful levels of electrophotosensitivity exhibited by 
the materials of Formula I above in electrophoretic migration imaging 
processes, the materials of Formula I generally exhibit certain other 
properties whicn make these materials quite useful in electrophoretic 
migration imaging processes. The materials of Formula I are typically 
highly colored materials, generally exhibiting an absorption maximum to 
visible light at a wavelength greater than 410 nm, preferably in the 420 
to 600 nm region of the visible spectrum. 
In general, the photosensitive materials of Formula I above which have, to 
date, been found most useful in the present invention because of their 
high degree of photosensitivity tend to exhibit a maximum absorption 
wavelength, .lambda.max, within the range of from about 420 to about 600 
nm. A variety of different materials within the class defined by Formula I 
has been tested and found to exhibit useful levels of electrical 
photosensitivity in electrophoretic migration imaging processes. A partial 
listing of representative such materials is included herein in Table I. 
TABLE I 
__________________________________________________________________________ 
Material: 
__________________________________________________________________________ 
5,5'-(9,10-anthracenediyldimethyllidyne)bis[3-cyano-4- 
phenyl-(5H)-furan-2-one] 
##STR4## 
5,5'-(9,10-anthracenediyldimethylidyne)bis[3,4- 
di-(p-nitrophenyl)-(5H)-furan-2-one] 
##STR5## 
9,10-bis(dicyanoethenyl)anthracene 
##STR6## 
9-(9-anthracenylmethylidyne)-2,7-dinitrofluorene 
##STR7## 
5-(9-anthracenylmethylidyne)-1,3,5-trihydro-pyrimidine- 
2,4,6-trione 
##STR8## 
5,5'-(9,10-anthracenediyldimethylidyne)bis(1,3-diethyl- 
1,3,5-trihydro-pyrimidine-2,4,6-trione) 
##STR9## 
5-(9-anthracenylmethylidyne)-1,3-diethyl-1,3,5- 
trihydro-pyrimidine-2,4,6-trione 
##STR10## 
5-(9-anthracenylmethylidyne)-1,3-diethyl-2-thioxo- 
1,3,5-trihydro-pyrimidine-4,6-dione 
##STR11## 
2,2'-(9,10-anthracenediyldimethylidyne)bis(indan-1,3- 
dione) 
##STR12## 
10. 
9-dicyanoethenyl anthracene 
##STR13## 
5,5'-(9,10-anthracenediyldimethylidyne)bis(N-ethyl- 
2-thioxo-thiazolidin-4-one) 
##STR14## 
5,5-(9,10-anthracenediyldimethylidyne)bis(3-carbamoyl- 
4-phenyl-furan-2-one) 
##STR15## 
5-(9-anthracenylmethylidyne)-3-cyano-4-phenyl- 
furan-5-one 
##STR16## 
4,4'-(9,10-anthracenediyldimethylidyne)bis(3-phenyl- 
isoxazolin-5-one) 
##STR17## 
4-(9-anthracenylmethylidyne)-3-phenyl-isoxazolin-5-one 
##STR18## 
5,5'-(9,10-anthracenediyldimethylidyne)bis(2-thioxo- 
thiazolidin-4-one) 
##STR19## 
4,4'-(1,4-phenylenedimethylidyne)bis(3-carbamoyl- 
1-phenyl pyrazolin-5-one) 
##STR20## 
1,1'-(1,4-phenylenedimethylidyne)bis(3-carboxy-indene) 
##STR21## 
2,6-bis(dicyanoethenyl)naphthalene 
##STR22## 
20. 
5,5'-2,6-naphthalenediyldmethylidyne)bis(3-cyano- 
4-phenyl-furan-2-one) 
##STR23## 
2,6-bis[.beta.-cyano-.beta.-(p-cyanophenyl)ethenyl]naphthalene 
##STR24## 
5,5'-(dibenzothien-2,8-diyldimethylidyne)bis(3-cyano- 
4-phenyl-furan-2-one) 
##STR25## 
5,5'-(dibenzothien-2,8-diyldimethylidyne)bis[3,4- 
di(p-nitrophenyl)-furan-2-one] 
##STR26## 
5,5'-(dibenzothien-2,8-diyldimethylidyne)bis(3-carbamoyl- 
4-phenyl-furan-2-one) 
##STR27## 
__________________________________________________________________________ 
the materials described by general Formula I are prepared by the same 
general procedures. Illustrative of such procedures is the preparation of 
5,5'-(9,10-anthracenediyldimethylidyne)bis[3,4-di(p-nitrophenyl)-furan-2-o 
ne] as follows. 
A solution of 1.17 g (5.0 m mole) of 9,10-anthracenedicarboxaldehyde, 3.26 
g (10.0 m mole) of 3,4-di-p-nitrophenyl-2(5H)furanone, 0.5 ml of 
piperidine and 0.5 ml of acetic acid in 100 ml of toluene was refluxed 
with stirring for two hours with about 0.2 ml of water azeotropically 
collected in a Dean Stark trap. A bright red solid separated at reflux, 
the mixture was cooled and the solid collected to give 3.9 g of the 
material having a m.p. greater than 400.degree. C. 
Calcd for C.sub.48 H.sub.26 N.sub.4 O.sub.12 (850.8): C, 67.7; H, 3.09; N, 
6.59. Found: C, 67.1; H, 3.1; N, 6.3. 
As indicated hereinabove, the electrically photosensitive material 
described herein is useful in the preparation of the electrically 
photosensitive imaging particles used in electrophoretic migration imaging 
processes. In general, electrically photosensitive particles useful in 
such processes have an average particle size within the range of from 
about 0.01 micron to about 20 microns, preferably from about 0.01 to about 
5 microns. Typically, these particles are composed of one or more colorant 
materials such as the colorant materials described in the present 
invention. However, these electrically photosensitive particles may also 
contain various nonphotosensitive materials such as electrically 
insulating polymers, charge control agents, various organic and inorganic 
fillers, as well as various additional dyes or pigment materials to change 
or enhance various colorant and physical properties of the electrically 
photosensitive particle. In addition, such electrically photosensitive 
particles may contain other photosensitive materials such as various 
sensitizing dyes and/or chemical sensitizers to alter or enhance their 
response characteristics to activating radiation. 
When used in an electrophoretic migration imaging process in accord with 
the present invention, the electrically photosensitive materials described 
by Formula I hereinabove, are typically positioned in particulate form, 
between two or more spaced electrodes, one or both of which typically 
being transparent to radiation to which the electrically photosensitive 
material is light-sensitive, i.e., activating radiation. Although the 
electrically photosensitive material, in particulate form, may be 
dispersed simply as a dry powder between two spaced electrodes and then 
subjected to a typical electrophoretic migration imaging operation such as 
that described in U.S. Pat. No. 2,758,939 by Sugarman, it is more typical 
to disperse the electrically photosensitive particulate material in an 
electrically insulating carrier, such as an electrically insulating 
liquid, or an electrically insulating, liquefiable matrix material, such 
as a heat- and/or solvent-softenable polymeric material or a thixotropic 
polymeric material. Typically, when one employs such a dispersion of 
electrically photosensitive particulate material and electrically 
insulating carrier material between the spaced electrodes of an 
electrophoretic migration imaging system, it is conventional to employ 
from about 0.05 part to about 2.0 parts of electrically photosensitive 
particulate material for each 10 parts by weight of electrically 
insulating carrier material. 
As indicated above, when the electrically photosensitive particles used in 
the present invention are dispersed in an electrically insulating carrier 
material, such carrier material may assume a variety of physical forms and 
may be selected from a variety of different materials. For example, the 
carrier material may be a matrix of an electrically insulating, normally 
solid polymeric material capable of being softened or liquefied upon 
application of heat, solvent, and/or pressure so that the electrically 
photosensitive particulate material dispersed therein can migrate through 
the matrix. In another, more typical embodiment of the invention, the 
carrier material can comprise an electrically insulating liquid such as 
decane, paraffin, Sohio Odorless Solvent 3440 (a kerosene fraction 
marketed by the Standard Oil Company, Ohio), various isoparaffinic 
hydrocarbon liquids such as those sold under the trademark Isopar G by 
Exxon Corporation and having a boiling point in the range of 145.degree. 
C. to 186.degree. C., various halogenated hydrocarbons such as carbon 
tetrachloride, trichloromonofluoromethane, and the like, various alkylated 
aromatic hydrocarbon liquids such as the alkylated benzenes, for example, 
xylenes, and other alkylated aromatic hydrocarbons such as are described 
in U.S. Pat. No. 2,899,335. An example of one such useful alkylated 
aromatic hydrocarbon liquid which is commercially available is Solvesso 
100 made by Exxon Corporation. Solvesso 100 has a boiling point in the 
range of about 157.degree. C. to about 177.degree. C. and is composed of 9 
percent dialkyl benzenes, 37 percent trialkyl benzenes, and 4 percent 
aliphatics. Typically, whether solid or liquid at normal room 
temperatures, i.e., about 22.degree. C., the electrically insulating 
carrier material used in the present invention is a material having a 
resistivity greater than about 10.sup.9 ohm-cm, preferably greater than 
about 10.sup.12 ohm-cm. When the electrically photosensitive particles 
formed from the materials of the present invention are incorporated in a 
carrier material, such as one of the above-described electrically 
insulating liquids, various other addenda may also be incorporated in the 
resultant imaging suspension. For example, various charge control agents 
may be incorporated in such a suspension to improve the uniformity of 
charge polarity of the electrically photosensitive particles dispersed in 
the liquid suspension. Such charge control agents are well known in the 
field of liquid electrographic developer compositions where they are 
employed for purposes substantially similar to that described herein. 
Thus, extensive discussion of the materials herein is deemed unnecessary. 
These materials are typically polymeric materials incorporated by 
admixture thereof into the liquid carrier vehicle of the suspension. In 
addition to, and possibly related to, the aforementioned enhancement of 
uniform charge polarity, it has been found that the charge control agents 
often provide more stable suspensions, i.e., suspensions which exhibit 
substantially less settling out of the dispersed photosensitive particles. 
In addition to the foregoing charge control agent materials, various 
polymeric binder materials such as various natural, semi-synthetic or 
synthetic resins, may be dispersed or dissolved in the electrically 
insulating carrier to serve as a fixing material for the final 
photosensitive particle image formed on one of the spaced electrodes used 
in electrophoretic migration imaging systems. Here again, the use of such 
fixing addenda is conventional and well known in the closely related art 
of liquid electrographic developer compositions so that extended 
discussion thereof is unnecessary herein. 
The process of the present invention will be described in more detail with 
reference to the accompanying drawing, FIG. 1, which illustrates a typical 
apparatus which employs the electrophoretic migration imaging process of 
the invention. 
FIG. 1 shows a transparent electrode 1 supported by two rubber drive 
rollers 10 capable of imparting a translating motion to electrode 1 in the 
direction of the arrow. Electrode 1 may be composed of a layer of 
optically transparent material, such as glass or an electrically 
insulating, transparent polymeric support such as poly(ethylene 
terephthalate), covered with a thin, optically transparent, conductive 
layer such as tin oxide, indium oxide, nickel, and the like. Optionally, 
depending upon the particular type of electrophoretic migration imaging 
process desired, the surface of electrode 1 may bear a "dark charge 
exchange" material, such as a solid solution of an electrically insulating 
polymer and 2,4,7-trinitro-9-fluorenone as described by Groner in U.S. 
Pat. No. 3,976,485 issued Aug. 24, 1976. 
Spaced opposite electrode 1 and in pressure contact therewith is a second 
electrode 5, an idler roller which serves as a counter electrode to 
electrode 1 for producing the electric field used in the electrophoretic 
migration imaging process. Typically, electrode 5 has on the surface 
thereof a thin, electrically insulating layer 6. Electrode 5 is connected 
to one side of the power source 15 by switch 7. The opposite side of the 
power source 15 is connected to electrode 1 so that as an exposure takes 
place, switch 7 is closed and an electric field is applied to the 
electrically photosensitive particulate material 4 which is positioned 
between electrodes 1 and 5. Typically electrically photosensitive 
particulate material 4 is dispersed in an electrically insulating carrier 
material such as described hereinabove. 
The electrically photosensitive particulate material 4 may be positioned 
between electrodes 1 and 5 by applying material 4 to either or both of the 
surfaces of electrodes 1 and 5 prior to the imaging process or by 
injecting electrically photosensitive imaging material 4 between 
electrodes 1 and 5 during the electrophoretic migration imaging process. 
As shown in FIG. 1, exposure of electrically photosensitive particulate 
material 4 takes place by use of an exposure system consisting of light 
source 8, an original image 11 to be reproduced, such as a photographic 
transparency, a lens system 12, and any necessary or desirable radiation 
filters 13, such as color filters, whereby electrically photosensitive 
material 4 is irradiated with a pattern of activating radiation 
corresponding to original image 11. Although the electrophoretic migration 
imaging system represented in FIG. 1 shows electrode 1 to be transparent 
to activating radiation from light source 8, it is possible to irradiate 
electrically photosensitive particulate material 4 in the nip 21 between 
electrodes 1 and 5 without either of electrodes 1 or 5 being transparent. 
In such a system, although not shown in FIG. 1, the exposure source 8 and 
lens system 12 is arranged so that image material 4 is exposed in the nip 
or gap 21 between electrodes 1 and 5. 
As shown in FIG. 1, electrode 5 is a roller electrode having a conductive 
core 14 connected to power source 15. The core is in turn covered with a 
layer of insulating material 6, for example, baryta paper. Insulating 
material 6 serves to prevent or at least substantially reduce the 
capability of electrically photosensitive particulate material 4 to 
undergo a radiation induced charge alteration upon interaction with 
electrode 5. Hence, the term "blocking electrode" may be used, as is 
conventional in the art of electrophoretic migration imaging, to refer to 
electrode 5. 
Although electrode 5 is shown as a roller electrode and electrode 1 is 
shown as essentially a translatable, flat plate electrode in FIG. 1, 
either or both of these electrodes may assume a variety of different 
shapes such as a web electrode, rotating drum electrode, plate electrode, 
and the like as is well known in the field of electrophoretic migration 
imaging. In general, during a typical electrophoretic migration imaging 
process wherein electrically photosensitive material 4 is dispersed in an 
electrically insulating, liquid carrier, electrodes 1 and 5 are spaced 
such that they are in pressure contact or very close to one another during 
the electrophoretic migration imaging process, e.g., less than 50 microns 
apart. However, where electrically photosensitive particulate material 4 
is dispersed simply in an air gap between electrodes 1 and 5 or in a 
carrier such as a layer of heat-softenable or other liquefiable material 
coated as a separate layer on electrode 1 and/or 5, these electrodes may 
be spaced more than 50 microns apart during the imaging process. 
The strength of the electric field imposed between electrodes 1 and 5 
during the electrophoretic migration imaging process of the present 
invention may vary considerably; however, it has generally been found that 
optimum image density and resolution are obtained by increasing the field 
strength to as high a level as possible without causing electrical 
breakdown of the carrier medium in the electrode gap. For example, when 
electrically insulating liquids such as isoparaffinic hydrocarbons are 
used as the carrier in the imaging apparatus of FIG. 1, the applied 
voltage across electrodes 1 and 5 typically is within the range of from 
about 100 volts to about 4 kilovolts or higher. 
As explained hereinabove, image formation occurs in electrophoretic 
migration imaging processes as the result of the combined action of 
activating radiation and electric field on the electrically photosensitive 
particulate material 4 disposed between electrodes 1 and 5 in the attached 
drawing. Typically, for best results, field application and exposure to 
activating radiation occur concurrently. However, as would be expected, by 
appropriate selection of various process parameters such as field 
strength, activating radiation intensity, incorporation of suitable light 
sensitive addenda in or together with the electrically photosensitive 
particles formed from the material of Formula I, e.g., by incorporation of 
a persistent photoconductive material, and the like, it is possible to 
alter the timing of the exposure and field application events so that one 
may use sequential exposure and field application events rather than 
concurrent field application and exposure events. 
When disposed between imaging electrodes 1 and 5 of FIG. 1, electrically 
photosensitive particulate material 4 exhibits an electrostatic charge 
polarity, either as a result of triboelectric interaction of the particles 
or as a result of the particles interacting with the carrier material in 
which they are dispersed, for example, an electrically insulating liquid, 
such as occurs in conventional liquid electrographic developing 
compositions composed of toner particles which acquire a charge upon being 
dispersed in an electrically insulating carrier liquid. 
Image discrimination occurs in the electrophoretic migration imaging 
process of the present invention as a result of the combined application 
of electric field and activating radiation on the electrically 
photosensitive particulate material dispersed between electrodes 1 and 5 
of the apparatus shown in FIG. 1. That is, in a typical imaging operation, 
upon application of an electric field between electrodes 1 and 5, the 
particles 4 of charge-bearing, electrically photosensitive material are 
attracted in the dark to either electrodes 1 or 5, depending upon which of 
these electrodes has a polarity opposite to that of the original charge 
polarity acquired by the electrically photosensitive particles. And, upon 
exposing particles 4 to activating electromagnetic radiation, it is 
theorized that there occurs neutralization or reversal of the charge 
polarity associated with either the exposed or unexposed particles. In 
typical electrophoretic migration imaging systems wherein electrode 1 
bears a conductive surface, the exposed, electrically photosensitive 
particles 4, upon coming into electrical contact with such conductive 
surface, undergo an alteration (usually a reversal) of their original 
charge polarity as a result of the combined application of electric field 
and activating radiation. Alternatively, in the case of photoimmobilized 
electrophoretic recording (PIER), wherein the surface of electrode 1 bears 
a dark charge exchange material as described by Groner in aforementioned 
U.S. Pat. No. 3,976,485, one obtains reversal of the charge polarity of 
the unexposed particles, while maintaining the original charge polarity of 
the exposed electrically photosensitive particles, as these particles come 
into electrical contact with the dark charge exchange surface of electrode 
1. In any case, upon the application of electric field and activating 
radiation to electrically photosensitive particulate material 4 disposed 
between electrodes 1 and 5 of the apparatus shown in FIG. 1, one can 
effectively obtain image discrimination so that an image pattern is formed 
by the electrically photosensitive particles which corresponds to the 
original pattern of activating radiation. Typically, using the apparatus 
shown in FIG. 1, one obtains a visible image on the surface of electrode 1 
and a complementary image pattern on the surface of electrode 5. 
Subsequent to the application of the electric field and exposure to 
activating radiation, the images which are formed on the surface of 
electrodes 1 and/or 5 of the apparatus shown in FIG. 1 may be temporarily 
or permanently fixed to these electrodes or may be transferred to a final 
image receiving element. Fixing of the final particle image can be 
effected by various techniques, for example, by applying a resinous 
coating over the surface of the image bearing substrate. For example, if 
electrically photosensitive particles 4 are dispersed in a liquid carrier 
between electrodes 1 and 5, one may fix the image or images formed on the 
surface of electrodes 1 and/or 5 by incorporating a polymeric binder 
material in the carrier liquid. Many such binders (which are well known 
for use in liquid electrophotographic liquid developers) are known to 
acquire a charge polarity upon being admixed in a carrier liquid and 
therefore will, themselves, electrophoretically migrate to the surface of 
one or the other of the electrodes. Alternatively, a coating of a resinous 
binder (which has been admixed in the carrier liquid), may be formed on 
the surfaces of electrodes 1 and/or 199 5 upon evaporation of the liquid 
carrier. 
The electrically photosensitive colorant material of Formula I may be used 
to form monochrome images, or the material may be admixed with other 
electrically photosensitive material of proper color and photosensitivity 
and used to form polychrome images. Said electrically photosensitive 
colorant material of the present invention also may be used as a 
sensitizer for other electrophotosensitive material in the formation of 
monochrome images. When admixed with other electrically photosensitive 
materials, selectively the photosensitive material of the present 
invention may act as a sensitizer and/or as an electrically photosensitive 
particle. Many of the electrically photosensitive colorant materials 
having Formula I have especially useful hues which make them particularly 
suited for use in polychrome imaging processes which employ a mixture of 
two or more differently colored electrically photosensitive particles. 
When such a mixture of multicolored electrically photosensitive particles 
is formed, for example, in an electrically insulating carrier liquid, this 
liquid mixture of particulate material exhibits a black coloration. 
Preferably, the specific cyan, magenta, and yellow particles selected for 
use in such a polychrome imaging process are chosen so that their spectral 
response curves do not appreciably overlap whereby color separation and 
subtractive multicolor image reproduction can be achieved. 
The following examples illustrate the utility of the Formula I materials in 
electrophoretic migration imaging processes. 
EXAMPLES 
Imaging Apparatus 
An imaging apparatus was used in each of the succeeding examples to carry 
out the electrophoretic migration imaging process described herein, 
including the photoimmobilized electrophoretic recording (PIER) process 
described by Groner in U.S. Pat. No. 3,976,485 and photoelectrophoresis 
(PEP). This apparatus was a device of the type illustrated in FIG. 1. In 
this apparatus, a translating film based having a conductive coating 
served as electrode 1 and was in pressure contact with a 10 centimeter 
diameter aluminum roller 14 covered with dielectric paper coated with 
poly(vinyl butyral) resin which served as electrode 5. Plate 1 was 
supported by two 2.8 cm. diameter rubber drive rollers 10 positioned 
beneath film plate 1 such that a 2.5 cm. opening, symmetric with the axis 
of the aluminum roller 14, existed to allow exposure of electrically 
photosensitive particles 4 to activating radiation. The original 
transparency 11 to be reproduced was taped to the back side of film plate 
1. 
The original transparency to be reproduced consisted of adjacent strips of 
clear, red, green and blue filters. The light source consisted of a Kodak 
Carousel Projector 860H with a 300 watt ELH Lamp and a 6.8 cm. f/3.5 lens. 
The light was modulated with a Kodak No. 5 eleven step 0.3 neutral density 
step tablet. The residence time in the action of 0.25 cm and a translation 
velocity of 25 cm/second (for PIER: 0.25 cm and a translational velocity 
of 1 inch/second) zone was 10 milliseconds (PIER 100 milliseconds). 
Exposure expressed as the log of the light intensity (Log I) in the nip 
was as follows: 
______________________________________ 
Log I 
erg/cm.sup.2 /sec. 
Filters 
PEP PIER 
______________________________________ 
*WO Clear 4.70 4.46 
*W29 Red 4.09 3.84 
*W99 Green 3.24 3.00 
*W47B Blue 3.04 2.76 
______________________________________ 
*WRATTEN FILTER NUMBERS 
The voltage between the electrode 5 and film plate 1 was about 2 kv. Film 
plate 1 was negative polarity in the case where electrically 
photosensitive particulate material 4 carried a positive electrostatic 
charge, and film plate 1 was positive in the case where electrically 
photosensitive electrostatically charged particles were negatively 
charged. The translational speed of film plate 1 was about 25 cm. per 
second. In the following examples, image formation occurs on the surfaces 
of film plate 1 and electrode 5 after simultaneous application of light 
exposure and electric field to electrically photosensitive material 
evaluated for use as electrically photosensitive particulate material 4 
was admixed with a liquid carrier as described below to form a liquid 
imaging dispersion which was placed in nip 21 between the electrodes 1 and 
5. If the material being evaluated for use as material 4 possessed a 
useful level of electrical photosensitivity in an electrophoretic, 
suspension one obtained a negative-appearing image reproduction of 
original 11 on electrode 5 and a complementary image on electrode 1. When 
the above described apparatus was used to form images according to the 
aforementioned photoimmobilized electrophoretic recording process (PIER) 
described in U.S. Pat. No. 3,976,485, electrode 1 was overcoated with a 6 
micron thick dark charge exchange layer consisting of 38% 
2,4,7-trinitro-9-fluorenone in Lexan 145 polycarbonate. The speed of 
electrode 1 in this case was about 2.5 cm/second. 
IMAGING DISPERSION PREATION 
Imaging dispersions were prepared to evaluate each of the material in Table 
I. The dispersions were prepared by first making a stock solution of the 
following components. The stock solution was prepared simply by combining 
the components: 
______________________________________ 
PEP PIER 
______________________________________ 
Isopar G 2.2 g Isopar G 2.5 g 
Solvesso 100 Piccotex 100 
2.5 g 
(Exxon Corp.) 1.3 g 
Piccotex 100 
(Penn. Industrial 
Chem. Corp.) 1.4 g 
*PVT 0.1 g 
______________________________________ 
*PVT is poly(vinyltoluene-co-laurylmethacrylate-co-lithium 
methacrylate-co-methacrylic acid) 56/40/3.6/0.4 
A 5 g. aliquot of the stock solution was combined in a closed container 
with 0.045 g. of the Table I material to be tested and 12 g. of Pioneer 
440 stainless steel balls. The preparation was then milled for three hours 
on a paint shaker. 
EXAMPLES 1-3 
Materials 1, 2 and 3 from Table 1 were evaluated in a photoelectrophoretic 
(PEP) and in the PIER process. In each case images were obtained which 
exhibited that materials 1, 2 and 3 possessed useful levels, 
electrophotosensitivity. Dmax and Dmin data are presented in tables II-IV. 
The relative sensitivity measurements reported in Example 1 are relative 
reciprocal electrical sensitivity measurements. The relative reciprocal 
electrical sensitivity measures the speed of a given material relative to 
other material typically within the same test group of elements. The 
relative reciprocal sensitivity values are not absolute sensitivity 
values. However, relative reciprocal sensitivity values are related to 
absolute sensitivity values. The relative reciprocal electrical 
sensitivity is a dimensionless number and is obtained simply by 
arbitrarily assigning a value, Ro, to one particular reciprocal absolute 
sensitivity of one particular photoconductive control element. The 
relative reciprocal sensitivity Rn, of any other photoconductive element, 
n, relative to this value, Ro, may then be calculated as follows: 
EQU Rn= (a.sub.n) (Ro/Ao) value 
wherein An is the absolute reciprocal electrical sensitivity in (cm.sup.2 
/ergs) of n, Ro is the sensitivity vlue arbitrarily assigned to the 
control element, and Ao is the absolute reciprocal electrical sensitivity 
measured in (cm.sup.2 /ergs) of the control element. 
TABLE II 
__________________________________________________________________________ 
Example 1 
Material 1 from Table I 
CHARGE EXCHANGE RELATIVE SENSITIVITY 
DISPERSION 
ELECTRODES .DELTA.D = 0.1 
.DELTA.D = (D.sub.MAX - D.sub.MIN)/2 
__________________________________________________________________________ 
PEP 0.1 OD Cermet 
CLEAR 
1.00* 0.74 
(Cr . SiO) RED -- -- 
Evaporated on 
GREEN 
-- -- 
polyethylene tere- 
BLUE -- -- 
phthalate 
PEP 0.1 OD Cermet 
CLEAR 
3.63 1.04 
(Cr . SiO) RED -- -- 
Evaporated on 
GREEN 
7.07 2.40 
polyethylene tere- 
BLUE -- -- 
phthalate 
PEP PIER CLEAR 
2.14 0.98 
RED -- -- 
GREEN 
2.51 -- 
BLUE -- -- 
PEP PIER CLEAR 
9.53 1.70 
RED -- -- 
GREEN 
19.23 4.07 
BLUE -- -- 
PEP 0.4 OD CLEAR 
1.23 0.73 
Nickelized RED -- -- 
polyethylene tere- 
GREEN 
1.35 -- 
phthalate BLUE -- -- 
PIER PIER CLEAR 
-- -- 
RED -- -- 
GREEN 
-- -- 
BLUE -- -- 
__________________________________________________________________________ 
*Arbitrarily assigned a relative value of 1.00. 
TABLE III 
______________________________________ 
Example 2 
Material 2 from Table I 
CHARGE EXCHANGE 
DISPERSION ELECTRODES D.sub.MAX 
D.sub.MIN 
______________________________________ 
PEP 0.1 OD Cermet 0.61 0.37 
(Cr . SiO) 
Evaporated on polyethylene 
terephthalate 
PEP 0.4 OD Nickelized 0.58 0.24 
polyethylene terephthalate 
PEP PIER 0.74 0.26 
PIER PIER 0.40 0.15 
______________________________________ 
TABLE IV 
______________________________________ 
Example 3 
Material 3 from Table I 
CHARGE EXCHANGE 
DISPERSION ELECTRODES D.sub.MAX 
D.sub.MIN 
______________________________________ 
PEP 0.1 OD Cermet 0.43 0.22 
(Cr . SiO) 
Evaporated on polyethylene 
terephthalate 
PEP 0.4 OD Nickelized 0.44 0.24 
polyethylene terephthalate 
PEP PIER 0.40 0.20 
PIER PIER 0.26 0.18 
______________________________________ 
In the following Examples 4 through 25, image quality was determined 
visually with regard to Dmax, Dmin., speed and color saturation. Most of 
the materials were tested in both the PIER and PEP processes of migration 
imaging. In the case of PIER, the conductive layer and dark charge 
exchange layer are the same as previously described. In the case of PEP, 
the conductive layer consists of Cermet (Cr.SiO) coated on an estar film 
base. The results are described in Table V. In each case, the charge 
exchange electrode was negatively charged. 
TABLE V 
______________________________________ 
PEP PIER 
EXAMPLE TABLE I IMAGE IMAGE 
NUMBER MATERIAL n QUALITY QUALITY 
______________________________________ 
4 1 2 Excellent Very Good 
5 2 2 Very Good Very Good 
6 3 2 Very Good Very Good 
7 4 1 Poor Fair 
8 5 1 No Image Poor 
9 6 2 Poor Poor 
10 8 1 Poor No Image 
11 10 2 Fair Fair 
12 12 2 Poor Fair 
13 13 2 Fair Fair 
14 14 1 Poor Fair 
15 15 2 Fair Good 
16 16 1 No Image Poor 
17 17 2 No Image Poor 
18 18 2 Poor Poor 
19 19 2 No Image Poor 
20 20 2 Very Good Very Good 
21 21 2 Fair Fair 
22 22 2 No Image Fair 
23 23 2 Very Good -- 
24 24 2 Good -- 
25 25 2 Very Weak -- 
______________________________________ 
The invention has been described in detail with particular reference to 
certain preferred embodiments thereof, but it will be understood that 
variations and modifications can be effected within the spirit and scope 
of the invention.