Liquid developing material applicator

An apparatus for developing an electrostatic latent image with liquid developing material. The apparatus includes a liquid developing material applicator, wherein a single piece housing fabricated from a non-conductive material is provided for defining an elongated aperture adapted for transporting liquid developing material into contact with the image on the surface of a photoreceptive member, the housing further including a planar surface adjacent the elongated aperture for providing a liquid developing material application region in which the liquid developing material can flow freely in contact with the photoreceptive member. A developing roll situated adjacent to and downstream from the liquid developing material is also provided for for attracting the liquid developing material to image areas of the electrostatic latent image.

This invention relates generally to an electrostatographic printing 
machine, and more particularly concerns an apparatus for applying a liquid 
developer material to a latent image bearing surface such as a 
photoreceptive member in a xerographic copying or printing machine. 
Generally, the process of electrostatographic copying is initiated by 
exposing a light image of an original document to a substantially 
uniformly charged photoreceptive member. Exposing the charged 
photoreceptive member to a light image discharges the photoconductive 
surface thereof in areas corresponding to non-image areas in the original 
input document while maintaining the charge in image areas, resulting in 
the creation of an electrostatic latent image of the original document on 
the photoreceptive member. This latent image is subsequently developed 
into a visible image by a process in which developer material is deposited 
onto the surface of the photoreceptive member. Typically, this developer 
material comprises carrier granules having toner particles adhering 
triboelectrically thereto, wherein the toner particles are 
electrostatically attracted from the carrier granules to the latent image 
for forming a powder toner image on the photoreceptive member. 
Alternatively, liquid developer materials comprising a liquid carrier 
material having toner particles dispersed therein have been utilized, 
wherein the liquid developer material is applied to the latent image with 
the toner particles being attracted toward the image areas to form a 
liquid image. Regardless of the type of developer material employed, the 
toner particles of the developed image are subsequently transferred from 
the photoreceptive member to a copy sheet, either directly or by way of an 
intermediate transfer member. Once on the copy sheet, the image may be 
permanently affixed to provide a "hard copy" reproduction of the original 
document or file. In a final step, the photoreceptive member is cleaned to 
remove any charge and/or residual developing material from the 
photoconductive surface in preparation for subsequent imaging cycles. 
The above described electrostatographic reproduction process is well known 
and is useful for light lens copying from an original, as well as for 
printing applications involving electronically generated or stored 
originals. Analogous processes also exist in other printing applications 
such as, for example, digital laser printing where a latent image is 
formed on the photoconductive surface via a modulated laser beam, or 
ionographic printing and reproduction where charge is deposited on a 
charge retentive surface in response to electronically generated or stored 
images. Some of these printing processes develop toner on the dis-charged 
area, known as DAD, or "write black" systems, in contradistinction to the 
light lens generated image systems which develop toner on the charged 
areas, knows as CAD, or "write white" systems. The subject invention 
applies to both such systems. 
The use of liquid developer materials in imaging processes is well known. 
Likewise, the art of developing electrostatographic latent images formed 
on a photoconductive surface with liquid developer materials is also well 
known. Indeed, various types of liquid developing material development 
systems have heretofore been disclosed. 
Liquid developers have many advantages, and often produce images of higher 
quality than images formed with dry toners. For example, images developed 
with liquid developers can be made to adhere to paper without a fixing or 
fusing step, thereby eliminating a requirement to include a resin in the 
liquid developer for fusing purposes. In addition, the toner particles can 
be made to be very small without resulting in problems often associated 
with small particle powder toners, such as airborne contamination which 
can adversely affect machine reliability and can create potential health 
hazards. Development with liquid developers in full color imaging 
processes also has many advantages, including, among others, production of 
a texturally attractive output document due to minimal multilayer toner 
height build-up (whereas full color images developed with dry toners often 
exhibit substantial height build-up of the image in regions where color 
areas overlap). In addition, full color imaging with liquid developers is 
economically attractive, particularly if surplus liquid carrier containing 
the toner particles can be economically recovered without cross 
contamination of colorants. Further, full color prints made with liquid 
developers can be processed to a substantially uniform finish, whereas 
uniformity of finish is difficult to achieve with powder toners due to 
variations in the toner pile height as well as a need for thermal fusion, 
among other factors. 
Although specific liquid development systems may vary, one well known type 
of system includes a roll member adapted to transport liquid developer 
material into a position proximate to the photoconductive surface such 
that the electrostatic latent image recorded thereon can attract the 
liquid developer material in image configuration. In such systems, the 
roll member is typically partly submerged in a sump of liquid developer 
material with the roll member being rotated at a sufficiently high 
velocity so as to transport the liquid developer to the surface of the 
photoreceptor in the form of a thin toner film formed along the surface of 
the roll member. In addition, an electrical field is generally induced 
across a gap between the photoconductive surface and the roll member by 
applying an electrical bias to the roll member for maintaining a toning 
meniscus across the gap to provide a desired density of toner particles 
entrained in the liquid developer and to reduce undesirable background 
staining of the photoreceptor as it passes the developer apparatus. 
Generally, in the field of electrostatographic printing and copying, 
development of a latent image takes place at high speeds, which requires 
that a large amount of uniformly characteristic liquid developer material 
be supplied to the photoconductive surface as uniformly as possible to 
produce a high quality image without any variations in the development 
thereof. However, in the roll development system of the type described 
hereinabove, it has been found that it may be difficult to uniformly apply 
the liquid developer material to the entire surface of the developing roll 
member. Furthermore, since the amount of liquid developer applied to the 
photoconductive surface is limited to the amount of developing material 
applied to the surface of the developing roll member, it is typically 
difficult to apply a relatively large amount of developer material to the 
latent image. As a result, alternative systems have also been disclosed in 
the art, wherein the liquid developing material developer material is 
brought into contact with the latent image on the photoreceptor by means 
of a fountain-type apparatus, in which a flow of liquid developer material 
is pumped into a gap between a development electrode and the 
photoconductive surface for developing the latent image thereon. While 
this approach permits the application of large amounts of liquid developer 
to the latent image as compared to other methods, these fountain-type 
devices are generally very complex structures made up of numerous 
cooperative and interactive elements. In addition, the development 
electrode utilized in these devices is generally a fixed conductive 
electrode which can become coated with charged toner particles that tend 
to suppress any development field generated thereby. 
Thus, some problems and inadequacies remain with respect to known apparatus 
used for liquid developing material development in the field 
electrostatographic printing. The following disclosures may be relevant to 
some aspects of the present invention: 
U.S. Pat. No. 4,044,718 
Patentee: Blake et. al. 
Issued: Aug. 30, 1977 
U.S. Pat. No. 4,289,092 
Patentee: McChesney et. al. 
Issued: Sep. 15, 1981 
U.S. Pat. No. 4,398,818 
Patentee: Jeromin et. al. 
Issued: Aug. 16, 1983 
U.S. Pat. No. 4,827,309 
Patentee: Kato 
Issued: May 2, 1989 
U.S. Pat. No. 4,883,018 
Patentee: Sagiv 
Issued: Nov. 28, 1989 
U.S. Pat. No. 5,300,990 
Patentee: Thompson 
Issued: Apr. 5, 1994 
The relevant portions of the foregoing patents may be briefly summarized as 
follows: 
U.S. Pat. No. 4,044,718 discloses a fountain for moving liquid toner into 
engagement with a receptor for developing an electrostatic image into a 
visible image. The fountain incorporates an electrode positioned at the 
bottom of a liquid toner pool formed by electrical insulating end, side, 
and bottom members. 
U.S. Pat. No. 4,289,092 discloses a liquid development fountain having 
plural spaced slots in its upper surface against which a record baring 
material is passed and through which developer is moved in a sinuous path 
to repetitively contact the record member through the slots. 
U.S. Pat. No. 4,398,818 discloses a liquid toner fountain for the 
development of electrostatic images including multiple distribution plates 
with lateral liquid distribution for producing smooth streamline flow, a 
slotted metalized plastic electrode, and a funnel shaped understructure 
which drains access toner liquid into a sump to recover developer and 
prevent evaporation. The apparatus provides a laminar liquid flow in a gap 
between a charge bearing surface and a development electrode to prevent 
disturbance of already deposited toner and also provides an even flow rate 
along the length of the fountain for avoiding density radiance due to 
uneven flow rates. The developer fluid in the gap is maintained free of 
debris by draining off all fluid into the sump. 
U.S. Pat. No. 4,827,309 discloses a liquid developing apparatus with a 
plurality of fountains and discharge slits arranged alternately in 
parallel to each other and extending laterally. Each fountain slit is 
coupled to a cylindrical developer guide having a hollow pipe member 
including supply openings inserted therein for producing liquid developer 
jets which move upward to the latent image carrier through the fountain 
slits and are subsequently discharged through discharge slits located on 
either sides of the fountain slits. 
U.S. Pat. No. 4,883,018 discloses a liquid developing material development 
system, wherein a liquid developer material is pumped partially upward 
from a lowermost region of a development zone toward an uppermost region 
thereof, thereby forming a pressure barrier which prevents the escape of 
liquid developer material from the lowermost region of the development 
zone. A ceiling roller prevents the escape of liquid developer material 
from the uppermost region of the development zone. 
U.S. Pat. No. 5,300,990 discloses a liquid electrophotographic printer 
developer for a laser printer, including a bath of liquid toner, a charged 
reverse direction developer roller, and in relatively close spaced 
relationship from it, a same direction rigidizing/squeegee roller charged 
to about the same potential as the developer roller. A common wiping means 
is provided for cleaning both the developer and the rigidizing/scweegy 
rollers and directing access toner into a recycle system. In a preferred 
embodiment, a series of developer systems with different colored toners 
are employed to create a multicolor image on a copy sheet. 
In accordance with one aspect of the present invention, there is provided a 
liquid developing material applicator, comprising a single piece housing 
fabricated from a non-conductive material, wherein the housing defines an 
elongated aperture adapted for transporting liquid developing material 
into contact with an image bearing surface. The housing further includes a 
planar surface adjacent the elongated aperture for providing a liquid 
developing material application region in which the liquid developing 
material can flow freely with the imaging member. A drainage channel is 
also provided for allowing excess liquid developing material to flow away 
from the liquid developing material application region. 
In accordance with another aspect of the present invention, an apparatus 
for developing an electrostatic latent image on an imaging member with a 
liquid developing material is provided, the apparatus comprising: a liquid 
developing material applicator, including a single piece housing 
fabricated from a non-conductive material, the housing defining an 
elongated aperture adapted for transporting liquid developing material 
into contact with the imaging member, the housing further including a 
planar surface adjacent the elongated aperture for providing a liquid 
developing material application region in which the liquid developing 
material can flow freely with the imaging member; and a 
developing/metering roll situated adjacent the liquid developing material 
applicator and downstream therefrom relative to a path of travel of the 
imaging member. 
In accordance with another aspect of the present invention, a liquid ink 
type electrostatographic printing machine is provided, including an 
apparatus for developing an electrostatic latent image on a photoreceptive 
member with a liquid developing material, comprising: a liquid developing 
material applicator, including a single piece housing fabricated from a 
non-conductive material, the housing defining an elongated aperture 
adapted for transporting liquid developing material into contact with the 
photoreceptive member, the housing further including a planar surface 
adjacent the elongated aperture for providing a liquid developing material 
application region in which the liquid developing material can flow freely 
in contact with the photoreceptive member; and a developing roll situated 
adjacent the liquid developing material applicator and downstream 
therefrom relative to a path of travel of the photoreceptive member.

For a general understanding of the features of the present invention, 
reference is made to the drawings, wherein like reference numerals have 
been used throughout to designate identical elements. FIG. 3 is a 
schematic elevational view illustrating a full-color liquid developing 
material based electrostatographic printing machine incorporating the 
features of the present invention. Inasmuch as the art of 
electrostatographic printing is well known, the various processing 
stations employed in the printing machine of FIG. 3 will be described 
briefly with reference thereto. It will become apparent from the following 
discussion that the apparatus of the present invention may be equally well 
suited for use in a wide variety of printing machines and is not 
necessarily limited in its application to the particular 
electrostatographic described herein. While the present invention will 
hereinafter be described in connection with a preferred embodiment 
thereof, it will be understood that the description of the invention is 
not intended to limit the invention to this preferred embodiment. On the 
contrary, the description is intended to cover all alternatives, 
modifications, and equivalents as may be included within the spirit and 
scope of the invention as defined by the appended claims. 
Turning now to FIG. 3, a photoreceptive member 100 is rotated along a 
curvilinear path defined by rollers 98 and 99. The photoreceptor 100 
preferably includes a continuous multilayered belt including a substrate, 
a conductive layer, an optional adhesive layer, an optional hole blocking 
layer, a charge generating layer, a charge transport layer, and, in some 
embodiments, an anti-curl backing layer. Initially, belt 100 is charged to 
a uniform potential at a charging station by charging unit 101a, which 
typically includes a corona generating device capable of spraying ions 
onto the surface of the photoreceptive member 100 to produce a relatively 
high, substantially uniform charge thereon. 
After a uniform charge is placed on the surface of the photoreceptive 
member 100, the electrostatographic printing process proceeds by either 
inputting a computer generated color image into an image processing unit 
44 or, for example, by placing a color input document 10 to be copied on 
the surface of a transparent imaging platen 112. A scanning assembly 
preferably comprising a high powered light source 13, mirrors 14a, 14b and 
14c, a series of lenses (not shown), a dichloric prism 15 and a plurality 
of charge-coupled devices (CCDs) 117 operating in association with one 
another is provided, whereby light from the light source 13 is directed 
onto the input document 10 with the light reflected from the color 
document 10 being transmitted to the CCDs 117. The reflected light is 
separated into the three primary colors by the dichroic prism 15 such that 
each CCD 117 provides an analog output voltage which is proportional to 
the intensity of the incident light of each of the primary colors. 
Thereafter, the analog signal from each CCD 117 is converted into a 
digital signal corresponding individual picture elements or so-called 
pixels making up the original input document. These digital signals, which 
represent the blue, green, and red density signals, are input into the 
image processing unit 44 where they are converted into individual bitmaps 
representing the color components of each pixel (yellow (Y), cyan (C), 
magenta (M), and black (Bk)), the receptive values of exposure for each 
pixel, and the color separation therebetween. The image processing unit 44 
can store bitmap information for subsequent images or can operate in a 
real time mode. The image processing unit 44 may also contain a shading 
correction unit, an undercolor removal unit (UCR), a masking unit, a 
dithering unit, a gray level processing unit, and other imaging processing 
sub-systems known in the art. 
The digital output signals generated by the image processing unit 44 
described hereinabove are transmitted to a series of individual raster 
output scanners (ROSs) 20a, 20b, 20c and 20d for writing complementary 
color image bitmap information onto the charged photoreceptive belt 100 by 
selectively erasing charges thereon. Each ROS writes the image information 
in a pixel by pixel manner. It will be recognized that the present 
description is directed toward a Recharge, Expose, and Develop (READ) 
process, wherein the charged photoconductive surface of photoreceptive 
member 100 is serially exposed to record a series of latent images thereon 
corresponding to the substractive color of one of the colors of the 
appropriately colored toner particles at a corresponding development 
station. Thus, the photoconductive surface is continuously recharged and 
re-exposed to record latent images thereon corresponding to the 
subtractive primary of another color of the original. This latent image is 
therefore serially developed with appropriately colored toner particles 
until all the different color toner layers are deposited in superimposed 
registration with one another on the photoconductive surface. It should be 
noted that either discharged area development (DAD) discharged portions 
are developed, or charged area development (CAD), wherein charged areas 
are developed can be employed, as will be described. 
As previously noted, the present invention is directed to the apparatus 
which is utilized for carrying out the development process utilizing 
liquid developer materials, such apparatus being depicted schematically at 
reference numerals 103a, 103b, 103c and 103d. Each developer unit 
transports a different color liquid developer material into contact with 
the electrostatic latent image so as to develop the latent image with 
pigmented toner particles to create a visible image. By way of example, 
developer unit 103a transports cyan colored liquid developer material, 
developer unit 103b transports magenta colored liquid developer material, 
developer unit 103c transports yellow colored liquid developer material, 
and developer unit 103d transports black colored liquid developer 
material. Each different color developer material comprises pigmented 
toner particles disseminated through a liquid carrier, wherein the toner 
particles are charged to a polarity opposite in polarity to the charged 
latent image on the photoconductive surface such that the toner particles 
pass by electrophoresis to the electrostatic latent image to create a 
visible developed image thereof. Each of the developer units 103a, 103b, 
103c and 103d are substantially identical to one another and will be 
described hereinafter in greater detail with reference to FIGS. 1 and 2. 
Generally, the liquid carrier medium is present in a large amount in the 
developer composition, and constitutes that percentage by weight of the 
developer not accounted for by the other components. The liquid medium is 
usually present in an amount of from about 80 to about 98 percent by 
weight, although this amount may vary from this range provided that the 
objectives of the present invention are achieved. By way of example, the 
liquid carrier medium may be selected from a wide variety of materials, 
including, but not limited to, any of several hydrocarbon liquids 
conventionally employed for liquid development processes, including 
hydrocarbons, such as high purityalkanes having from about 6 to about 14 
carbon atoms, such as Norpar.RTM. 12, Norpar.RTM. 13, and Norpar.RTM.15, 
and including isoparaffinic hydrocarbons such as Isopar.RTM. G, H, L, and 
M, available from Exxon Corporation. Other examples of materials suitable 
for use as a liquid carrier include AmscO.RTM. 460 Solvent, Amsco.RTM. 
OMS, available from American Mineral Spirits Company, Soltrol.RTM., 
available from Phillips Petroleum Company, Pagasol.RTM., available from 
Mobil Oil Corporation, Shellsol.RTM., available from Shell Oil Company, 
and the like. Isoparaffinic hydrocarbons provide a preferred liquid media, 
since they are colorless, environmentally safe, and possess a sufficiently 
high vapor pressure so that a thin film of the liquid evaporates from the 
contacting surface within seconds at ambient temperatures. 
The toner particles can be any pigmented particle compatible with the 
liquid carrier medium, such as those contained in the developers disclosed 
in, for example, U.S. Pat. Nos. 3,729,419; 3,841,893; 3,968,044; 
4,476,210; 4,707,429; 4,762,764; 4,794,651; and U.S. application Ser. No. 
08/268,608 the disclosures of each of which are totally incorporated 
herein by reference. The toner particles should have an average particle 
diameter from about 0.2 to about 10 microns, and preferably from about 0.5 
to about 2 microns. The toner particles may be present in amounts of from 
about 1 to about 10 percent by weight, and preferably from about 1 to 
about 4 percent by weight of the developer composition. The toner 
particles can consist solely of pigment particles, or may comprise a resin 
and a pigment; a resin and a dye; or a resin, a pigment, and a dye. 
Suitable resins include poly(ethyl acrylate-co-vinyl pyrrolidone), 
poly(N-vinyl-2-pyrrolidone), and the like. Suitable dyes include Orasol 
Blue 2GLN, Red G, Yellow 2GLN, Blue GN, Blue BLN, Black CN, Brown CR, all 
available from Ciba-Geigy, Inc., Mississauga, Ontario, Morfast Blue 100, 
Red 101, Red 104, Yellow 102, Black 101, Black 108, all available from 
Morton Chemical Company, Ajax, Ontario, Bismark Brown R (Aldrich), Neolan 
Blue (Ciba-Geigy), Savinyl Yellow RLS, Black RLS, Red 3GLS, Pink GBLS, and 
the like, all available from Sandoz Company, Mississauga, Ontario, among 
other manufacturers. Dyes generally are present in an amount of from about 
5 to about 30 percent by weight of the toner particle, although other 
amounts may be present provided that the objectives of the present 
invention are achieved. Suitable pigment materials include carbon blacks 
such as Microlith.RTM. CT, available from BASF, Printex.RTM. 140 V, 
available from Degussa, Raven.RTM. 5250 and Raven.RTM. 5720, available 
from Columbian Chemicals Company. Pigment materials may be colored, and 
may include magenta pigments such as Hostaperm Pink E (American Hoechst 
Corporation) and Lithol Scarlet (BASF), yellow pigments such as Diarylide 
Yellow (Dominion Color Company), cyan pigments such as Sudan Blue OS 
(BASF), and the like. Generally, any pigment material is suitable provided 
that it consists of small particles and that combine well with any 
polymeric material also included in the developer composition. Pigment 
particles are generally present in amounts of from about 5 to about 40 
percent by weight of the toner particles, and preferably from about 10 to 
about 30 percent by weight. 
In addition to the liquid carrier vehicle and toner particles which 
typically make up the liquid developer materials suitable for the present 
invention, a charge control additive sometimes referred to as a charge 
director may also be included for facilitating and maintaining a uniform 
charge on toner particles by imparting an electrical charge of selected 
polarity (positive or negative) to the toner particles. Examples of 
suitable charge control agents include lecithin, available from Fisher 
Inc.; OLOA 1200, a polyisobutylene succinimide, available from Chevron 
Chemical Company; basic barium petronate, available from Witco Inc.; 
zirconlure octoate, available from Nuodex; as well as various forms of 
aluminum stearate; salts of calcium, manganese, magnesium and zinc; 
heptanoic acid; salts of barium, aluminum, cobalt, manganese, zinc, 
cerium, and zirconlure octoates and the like. The charge control additive 
may be present in an amount of from about 0.01 to about 3 percent by 
weight, and preferably from about 0.02 to about 0.05 percent by weight of 
the developer composition. 
After image development, the liquid image on the photoconductor may be 
conditioned to compress the image and remove some of the liquid carrier 
therefrom, as shown, for example, by U.S. Pat. No. 4,286,039, among 
various other patents. An exemplary apparatus for image conditioning is 
shown at reference numeral 21a, 21b, 21c and 21d, each comprising a 
roller, similar to roller 18a which may include a porous body and a 
perforated skin covering. The roller 18a is typically biased to a 
potential having a polarity which inhibits the departure of toner 
particles from the image on the photoreceptor 100 while compacting the 
toner particles of the image onto the surface of the photoreceptive 
member. In this exemplary image conditioning system, a vacuum source (not 
shown)is also provided and coupled to the interior of the roller for 
creating an airflow through the porous roller body to draw liquid from the 
surface of the photoreceptor, thereby increasing the percentage of toner 
solids in the developed image. In operation, roller 18a rotates against 
the liquid image on belt 100 such that the porous body of roller 18 a 
absorbs excess liquid from the surface of the image through the pores and 
perforations of the roller skin covering. The vacuum source, typically 
located along one end of a central cavity, draws liquid through the roller 
skin to a central cavity for depositing the liquid in a receptacle or some 
other location which permits either disposal or recirculation of the 
liquid carrier. The porous roller 18a is thus continuously discharged of 
excess liquid to provide continuous removal of liquid from the image on 
belt 100. It will be recognized by one of skill in the art that the vacuum 
assisted liquid absorbing roller described hereinabove may also find 
useful application in an embodiment in which the image conditioning system 
is provided in the form of a belt, whereby excess liquid carrier is 
absorbed through an absorbent foam layer in the belt, as described in U.S. 
Pat. Nos. 4,299,902 and 4,258,115. 
After image conditioning of the first developed image, the image on belt 
100 is advanced to a lamp 34a where any residual charge left on the 
photoreceptive surface is extinguished by flooding the photoconductive 
surface with light from lamp 34a. Thereafter, imaging and development are 
repeated for subsequent color separations by first recharging and 
reexposing the belt 100, whereby color image bitmap information is 
superimposed over the previous developed latent image. Preferably, for 
each subsequent exposure an adaptive exposure processor is employed that 
modulates the exposure level of the raster output scanner (ROS) for a 
given pixel as a function of the toner previously developed at the pixel 
site, thereby allowing toner layers to be made independent of each other, 
as described in U.S. application Ser. No 07/927,751. The reexposed image 
is next advanced through a development station and subsequently through an 
image conditioning station and each step is repeated as previously 
described to create a multi layer image made up of black, yellow, magenta, 
and cyan toner particles as provided via each developing station 103a, 
103b, 103c and 103d. It should be evident to one skilled in the art that 
the color of toner at each development station could be in a different 
arrangement. 
After the multi layer image is created on the photoreceptive member, it is 
advanced to an intermediate transfer station where charging device 111 
generates a charge for electrostatically transferring the image from the 
photoconductive belt 100 to an intermediate transfer member 110. The 
intermediate member 110 may be in the form of either a rigid roll or an 
endless belt, as shown in FIG. 3, having a path defined by a plurality of 
rollers in contact with the inner surface thereof. The intermediate member 
preferably comprises a multi layer structure comprising a substrate layer 
having a thickness greater than 0.1 mm and a resistivity of about 10.sup.6 
ohm-cm and insulating top layer having a thickness less than 10 micron, a 
dielectric constant of approximately 10, and a resistivity of about 
10.sup.13 oh-mcm. The top layer also has an adhesive release surface. It 
is also preferred that both layers have a similar hardness of less than 
about 60 durometer. Preferably, both layers are composed of Viton.TM. (a 
fluoroelastomer of vinylidene fluoride and hexafluoropropylene) which can 
be laminated together. The intermediate transfer member is typically 
dimensionally stable in nature for providing uniform image deposition 
which results in a controlled image transfer gap and better image 
registration. 
The multi layer image on the intermediate transfer member 110 may be image 
conditioned in a manner similar to the image conditioning described 
hereinabove with respect to the developed image on the photoconductive 
belt 100 by means of a roller 120 which conditions the image by reducing 
fluid content while inhibiting the departure of toner particles from the 
image as well as compacting the toner image. Preferably, roller 120 
conditions the multi layer image so that the image has a toner composition 
of more than 50 percent solids. In addition, the multi layer image present 
on the surface of the intermediate member may be transformed into a 
tackified or molten state by heat, as may be provided by a heating element 
32. More specifically, heating element 32 heats both the external wall of 
the intermediate member and generally maintains the outer wall of member 
110 at a temperature sufficient to cause the toner particles present on 
the surface to melt, due to the mass and thermal conductivity of the 
intermediate member. The toner particles on the surface maintain the 
position in which they were deposited on the outer surface of member 110, 
so as not to a alter the image pattern which they represent while 
softening and coalescing due to the application of heat from the exterior 
of member 110. Thereafter, the intermediate transfer member continues to 
advance in the direction of arrow 22 to a transfix nip 34 where the 
tackified toner particle image is transferred, and bonded, to a recording 
sheet 26 with limited wicking thereby. At the transfix nip 34, the toner 
particles are forced into contact with the surface of recording sheet 26 
by a normal force applied through backup pressure roll 36. Some of the 
advantages provided by the use of an intermediate transfer member include 
reduced heating of the recording sheet as a result of the toner or marking 
particles being pre-melted on the intermediate, as well as the elimination 
of an electrostatic transfer device for transferring charged particles to 
a recording sheet. 
After the developed image is transferred to intermediate member 110, 
residual liquid developer material may remain on the photoconductive 
surface of belt 100. A cleaning station 31 is therefore provided, 
including a roller formed of any appropriate synthetic resin which may be 
driven in a direction opposite to the direction of movement of belt 100, 
to scrub the photoconductive surface clean. It will be understood, 
however, that a number of photoconductor cleaning devices exist in the 
art, any of which would be suitable for use with the present invention. In 
addition, any residual charge left on the photoconductive surface may be 
extinguished by flooding the photoconductive surface with light from lamp 
34d in preparation for a subsequent successive imaging cycle. In this way, 
successive electrostatic latent images may be developed. 
The foregoing discussion provides a general description of the operation of 
a liquid developing material based electrostatographic printing machine 
incorporating the development apparatus of the present invention therein. 
The detailed structure of the development apparatus will be described 
hereinafter with reference to FIGS. 1 and 2. It will be understood that 
the development system of the present invention may be utilized in a 
multicolor electrophotographic printing machine or, in a monocolor 
printing machine. The developed image may be transferred directly to the 
copy sheet or, as described, to an intermediate member prior to transfer 
to the copy sheet. Multicolor printing machines may use this type of 
development unit where successive latent images are developed to form a 
composite multicolor toner image which is subsequently transferred to a 
copy sheet or, in lieu thereof, single color liquid images may be 
transferred in superimposed registration with one another directly to the 
copy sheet. 
Referring now to FIGS. 1 and 2, a developer unit 103 including an 
developing material applicator 113 in accordance with the present 
invention will be described with an understanding that the developer units 
103a, 103b, 103c and 103d shown and described in the apparatus of FIG. 3 
are substantially identical thereto. In general, the only distinction 
between developer units is the color of the liquid developer material 
being used. As depicted in FIG. 1, the developer unit 103 includes an 
developing material applicator 113 and a metering roll 123 situated 
adjacent to one another and in close proximity to the surface of 
photoreceptive belt 100. 
The liquid developing material applicator 113 of the present invention 
includes a housing 115 having a substantially planar surface 116 
positioned opposite belt 100 and adjacent thereto. The housing 115 is of a 
single piece construction fabricated from a suitable nonconductive 
material such as a polycarbonate or other reinforced polymer based 
material, whereby fabrication and manufacturing can be accommodated by 
nonheavyduty machining or via plastic extrusion. The housing 115 also 
includes an elongated aperture 117 situated along a central portion of the 
planar surface and extending along a longitudinal axis of the housing so 
as to be oriented substantially transverse to the belt 100 along the 
direction of travel thereof, as indicated by arrow 26. The aperture 117 
provides a path of travel for liquid developer material being transported 
therethrough and also defining a liquid developing material application 
region in which the liquid developing material can flow freely for 
contacting the liquid developer material with the surface of the 
photoreceptor belt 100. Coupled to the elongated aperture 117 are inlet 
ports 118, located at opposite ends of the elongated aperture 117. Liquid 
developer material is pumped through the inlet ports 118 and into the 
elongated aperture 117 such that the liquid developer material flows out 
of the elongated aperture 117 into contact with the surface of 
photoreceptor belt 100. An overflow drainage channel 119 partially 
surrounds the aperture 117 for collecting excess developer material which 
may not be transferred over to the photoreceptor surface. The overflow 
channel is connected to an outlet port 120 for removal of excess or 
extraneous liquid developer material and, preferably, for directing this 
excess material to a sump whereat the liquid developer material can be 
collected and recycled for subsequent use. 
Slightly downstream of and adjacent to the developing material applicator 
113, in the direction of movement of the photoreceptor surface 100, is an 
electrically biased developer roller 123, the peripheral surface thereof 
being situated in close proximity to the under surface of the 
photoreceptor 100. Preferably, the peripheral surface of the developer 
roller 123 is within about 50 to 75 microns (0.002 to 0.003 inches) from 
the surface of the photoreceptor 100. The developer 123 rotates in a 
direction opposite the movement of the photoconductor surface so as to 
provide a substantial shear force which is exerted on the toner and 
carrier liquid film in the area of the nip between the developer roller 
and the photoreceptor, for minimizing the thickness of the film of the 
developer liquid on the surface of the photoreceptor. This shear force 
removes a predetermined amount of the liquid developer material from the 
surface of the photoreceptor and transports the excess developer material 
in the direction of the developing material applicator. The excess 
developer material eventually falls away from the rotating metering roll 
for collection in the sump, as previously described. A DC power supply 125 
is also provided for maintaining an electrical bias is maintained on the 
metering roll at a selected polarity such that image areas of the 
electrostatic latent image on the photoconductive surface attract toner 
for providing a developed latent image. This electrophoretic development 
process minimizes the existence of toner particles in background regions 
and maximizes toner deposition in image areas on the photoreceptor. 
In operation, liquid developing material is pumped through inlet ports 118 
into the elongated aperture 117. The developer material flows in the 
direction of the photoreceptor, filling the gap between the photoreceptor 
100 and the planar surface 116 of liquid developing material applicator 
113. As the belt 100 moves in the direction of arrow 26, a portion of the 
liquid developer material moves therewith in the direction of the metering 
roll 123. The metering roll is biased via the DC power supply 125, causing 
toner particles in the developer material to be attracted to the 
electrostatic latent image on the photoreceptor. The developing roller 123 
also meters a predetermined amount of liquid developer material adhering 
to the photoconductive surface of belt 100 and acts as a seal for 
transporting the extraneous liquid developer material away from the 
photoreceptor. 
In review, the liquid developing material applicator of the present 
invention combines a liquid developing material applicator with an 
electrically biased developing roll for providing uniform development of a 
latent electrostatic image on a photoreceptor. The liquid developing 
material applicator comprises a single piece body fabricated from a 
suitable nonconductive material and includes an elongated aperture for 
allowing developer material to be contacted with the latent image on the 
photoreceptor. Thereafter, a biased developing roller causes the 
developing material to be attracted to image areas on the photoreceptor 
while also providing a shear force for simultaneously removing excess 
liquid from the surface of the photoconductor. 
It is, therefore, apparent that there has been provided, in accordance with 
the present invention, an apparatus for developing an electrostatic latent 
image with liquid developing material. This apparatus fully satisfies the 
aspects of the invention hereinbefore set forth. While this invention has 
been described in conjunction with specific embodiments thereof, it is 
evident that many alternatives, modifications and variations will be 
apparent to those skilled in the art. Accordingly, it is intended to 
embrace all such alternatives, modifications, and variations as fall 
within the spirit and broad scope of the appended claims.