Developer for liquid toner imager

An imaging system including a movable electrostatic imaging surface, apparatus for providing an electrostatic image on the electrostatic image surface and a development electrode having a developer surface with contiguous portions in spaced relationship with the electrostatic imaging surface to form a development region. The system includes apparatus for moving the developer surface such that the contiguous portions of the developer surface sequentially enter the region at an entrance and leaves the development region at an exit, apparatus for moving the electrostatic imaging surface so that it enters the development region at the exit and leaves the region at the entrance and apparatus for providing a liquid developer of a selectable color to the development region at the exit. The system also includes apparatus for transferring the developed image to a substrate.

FIELD OF THE INVENTION 
The present invention relates generally to multicolor imaging. 
BACKGROUND OF THE INVENTION 
Proposals for various types of multicolor imaging apparatus and techniques 
appear in the patent literature. There is described in Japanese Patent 
document 58002863 to Kawamura an image recording device for use in a color 
printer which include nozzle heads which spray liquid coloring toner onto 
electrostatic latent images on the side of a photosensitive drum and thus 
develop images thereon. A single nozzle is provided for each color and the 
nozzles reciprocate along a nozzle guide. Alternating current apparatus is 
disposed between the nozzle and the drum in order to spread out the 
impingement area of the toner on the drum. 
U.S. Pat. NO. 4,690,539 describes transfer apparatus in which a plurality 
of liquid images are transferred from a photoconductive member to a copy 
sheet. The liquid images, which include a liquid carrier having toner 
particles dispersed therein, are attracted from the photoconductive member 
to an intermediate web. A substantial amount of the liquid carrier is 
removed from the intermediate web and the toner particles are secured 
thereon. Thereafter, another liquid image having toner particles of a 
different color from the toner particles of the first liquid image is 
attracted to the intermediate member. Once again the liquid carrier 
material is removed from the web and the toner particles of the second 
liquid image are secured thereon. Thereafter, all of the toner particles 
are transferred from the intermediate member to the copy sheet, in image 
configuration. 
U.S. Pat. No. 3,900,003 describes a liquid developing device for use in 
multicolor electrophotographic copying machines, having a plurality of 
feed pipes for supplying different liquid color developers to a developing 
station, which feed pipes are connected to a common developer supply pipe. 
Valves are provided in the feed pipes wherein each of the valves are 
actuated by an electrical signal to supply only one selected liquid color 
developer to the developing station at a time. The liquid developing 
device is also provided with a belt for removing residual liquid developer 
remaining on an image bearing member after development and with a 
plurality of blades for scraping and collecting the thus removed liquid 
developer, which are selected and actuated in correspondence with a 
selected color. 
U.S. Pat. No. 4,504,138 describes a method and apparatus for developing 
electrostatic latent images formed on a photoconductor surface comprising 
the steps of applying a thin viscous layer of electrically charged toner 
particles to an applicator roller preferably by electrically assisted 
separation thereof from a liquid toner suspension. A restricted passage is 
defined between the applicator roller and the photoconductor surface 
approximately the thickness of the viscous layer and the toner particles 
are transferred from the applicator roller to the photoconductor surface 
due to their preferential adherence to the photoconductor surface under 
the dominant influence of the electric field of the electrostatic latent 
image carried by the photoconductive surface. 
U.S. Pat. No. 4,400,079 describes a developing system for an 
electrophotographic copier in which a roller having a conductive outer 
surface is disposed adjacent to the imaging surface to form a gap. The 
roller is driven at a peripheral linear velocity substantially greater 
than the velocity of movement of the imaging surface and is supplied with 
liquid developer at a location spaced from the gap to cause the roller to 
inject the developer into the gap. The roller is coupled to a source of 
electrical potential. 
U.S. Pat. No. 4,342,823 describes a perforate development electrode and a 
method for developing electrostatic images directly on a final image 
bearing sheet, formed of electrophotographic material coated onto a 
substrate, by means of a perforate development electrode and liquid toner, 
without immersing the material in a bath of toner. The method comprises 
spraying liquid toner against pressure reducing means adjacent to the 
electrode to reduce and make uniform the pressure of the flowing liquid 
toner and flowing the liquid toner uniformly over and through the 
perforate development electrode and over the image side of the sheet 
without contacting the side opposite the image side with the toner. 
U.S. Pat. No. 4,233,385 describes a method of liquid development of charge 
images formed on a surface of a tape-like record carrier, for example by 
an electrostatic printer. The record carrier is simultaneously sprayed 
with developer liquid in two flows which are directed towards each other. 
As a result two separate, uniform and oppositely directed flow zones 
meeting at one common turbulent flow zone are obtained. Both during 
pre-development and final development the charge images are brought into 
contact with a large quantity of fresh developer liquid. 
U.S. Pat. No. 4,073,266 describes apparatus for developing a latent 
electrostatic image on an electrophotographic copying material by means of 
a toner dispersion. An infeed roller applies the toner dispersion to the 
copying material and downstream thereof, a distribution roller acts on the 
surface of the copying material. Squeegee rollers downstream of the 
distribution roller effect removal of unused toner. Toner which adheres to 
the distribution roller during application of voltage thereto is sprayed 
off and recovered for recycling, the spraying agent being toner 
dispersion. 
U.S. Pat. No. 3,405,683 describes apparatus for the development of latent 
electrostatic images on an electrophotographic material with a liquid 
developer which includes means to feed the electrophotographic material 
through a pair of rotatable nip rolls and nozzle means adapted to 
simultaneously spray the electrostatic image and the nip roll which 
contacts the latent image. 
SUMMARY OF THE INVENTION 
It is a particular feature of the present invention that a highly 
efficient, simple and relatively low cost "instant" color change 
multicolor electrostatic imaging system is provided. 
There is thus provided in a preferred embodiment of the invention a 
multicolor electrostatic imaging system including a movable electrostatic 
imaging surface, apparatus for providing an electrostatic image on the 
electrostatic image surface, a development electrode having a developer 
surface including contiguous portions and being in spaced relationship 
with the electrostatic imaging surface to form a development region and 
apparatus for moving the developer surface such that the contiguous 
portions of the developer surface sequentially enter the region at an 
entrance and exit the region at an exit, apparatus for providing a liquid 
developer of a selectable color to the development region at the exit, and 
apparatus for transferring the developed image to a substrate. 
In a preferred embodiment of the invention the apparatus for providing a 
liquid developer includes multicolor spray apparatus having a multiplicity 
of spray outlets including a plurality of spray outlets, sequentially 
distributed among the multiplicity of spray outlets, for supplying liquid 
developer of each of a plurality of colors. 
In a preferred embodiment of the invention the apparatus for providing a 
liquid developer supplies the liquid developer to the developer surface 
after it exits from the development region. Alternatively in a preferred 
embodiment of the invention the apparatus for providing a liquid developer 
supplies the liquid developer directly to the electrostatic imaging 
surface. 
The imaging system includes, in a preferred embodiment of the invention, 
apparatus for moving the electrostatic imaging surface so that it enters 
the development region at the exit and leaves the region at the entrance. 
Additionally in a preferred embodiment of the invention the apparatus for 
providing a liquid developer supplies the liquid developer to the imaging 
surface before it enters the development region. 
In a preferred embodiment of the invention the electrostatic imaging 
surface is cylindrical and the system also includes apparatus for moving 
the imaging surface with a velocity having a direction opposite of that of 
the developer surface at the development region. 
There is further provided an imaging system including an imaging surface, 
apparatus for forming multiple electrostatic latent images sequentially on 
the imaging surface, development apparatus for sequentially developing the 
multiple electrostatic images with separate liquid developers, the 
development means including: a development electrode having a developer 
surface comprising contiguous portions and which is closely spaced from 
the electrostatic imaging surface to form a development region, apparatus 
for moving the developer surface such that the contiguous portions of the 
developer surface sequentially enter the region at an entrance and leave 
the region at an exit, apparatus means for sequentially supplying the 
separate liquid developers to the developing region to separately develop 
each of the multiple images and separate apparatus for removing residual 
amounts of each of the separate residual developers remaining on the 
surface of the development electrode after it exits the development 
region. 
In a preferred embodiment of the invention the imaging apparatus also 
includes apparatus for reusing the residual developer after its removal 
from the development electrode. 
In a preferred embodiment of the invention the separate means for removing 
includes a plurality of single color cleaning assemblies, each 
corresponding to a given one of a plurality of colors. The separate 
apparatus for removing includes in a preferred embodiment of the 
invention, a final cleaning assembly, downstream of the plurality of 
cleaning assemblies. 
In a preferred embodiment of the invention the imaging system also includes 
single color toner receiving apparatus associated with at least one of the 
single color cleaning assemblies. In a preferred embodiment of the imaging 
system also includes apparatus communicating with the single color toner 
receiving apparatus for recycling single color toner to the apparatus for 
sequentially supplying. In a preferred embodiment of the invention, the 
single color cleaning assemblies include apparatus for selectably engaging 
the developing electrode. The cleaning assemblies include scraper blade 
means in a preferred embodiment of the invention. 
In a preferred embodiment of the invention the apparatus for removing 
residual developer includes at least one resilient blade in contact with 
the development electrode. 
There is further provided, in a preferred embodiment of the invention, 
imaging apparatus including an imaging surface, apparatus for forming an 
electrostatic latent image on the imaging surface and development 
apparatus for sequentially developing the electrostatic images with a 
liquid developer, the development means including: a development electrode 
having a developer surface comprising contiguous portions and which is 
closely spaced from the electrostatic imaging surface to form a 
development region, apparatus for moving the developer surface such that 
the contiguous portions of the developer surface sequentially enter the 
region at an entrance and leave the region at an exit and apparatus for 
providing the liquid developer to the development region to separately 
develop the images, wherein the liquid developer is in a turbulent state 
at the development region. 
In a preferred embodiment of the invention the apparatus for providing the 
liquid developer supplies the liquid developer to the development region 
at the exit. In a preferred embodiment of the invention the liquid 
developer is sprayed on the developer surface after it exits the 
development region. 
In a preferred embodiment of the invention the imaging surface includes 
contiguous portions which subsequently enter the development region at the 
exit and leave the development region at the entrance and wherein the 
means for providing the liquid developer includes spraying the liquid 
developer on the imaging surface before it enters the development region.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
Reference is now made to FIG. 1 which illustrates a multicolor 
electrostatic imaging system constructed and operative in accordance with 
a preferred embodiment of the present invention. As seen in FIG. 1 there 
is provided an image bearing surface typically embodied in a rotating 
photoconductive drum 10. Operatively associated with photoconductive drum 
10 is photoconductor charging apparatus 11 and imaging apparatus 12, for 
providing a desired latent image on drum 10. The latent image normally 
comprises image areas at a first electrical potential and background areas 
at another electrical potential. 
Also associated with photoconductive drum 10 are a multicolor liquid 
developer spray assembly 14, a developing assembly 16, an excess liquid 
removal assembly 18, an intermediate transfer member 20 and a cleaning 
station 22. 
The developing assembly 16 preferably comprises a developer roller 17 
spaced from the photoconductive drum 10 and typically rotating in the same 
sense as drum 10, as indicated by arrows 19. This rotation provides for 
the surface of drum 10 and roller 17 to have opposite velocities in their 
region of propinquity. 
Photoconductive drum 10, photoconductor charging apparatus 11 and imaging 
apparatus 12 may be any suitable drum, charging apparatus and imaging 
apparatus such as are well known in the art. Developing assembly 16 is of 
particular construction several embodiments of which are described in 
detail hereinbelow. 
Excess liquid removal assembly 18 typically comprises a biased squeegee 
roller preferably formed of resilient conductive polymeric material, and 
is charged to a potential of several hundred to a few thousand volts with 
the same sign as the sign of the charge on the toner particles. 
Intermediate transfer member 20 may be any suitable intermediate transfer 
member such as those described in U.S. patent application Ser. No. 306,062 
filed Feb. 6, 1989, the disclosure of which is incorporated herein by 
reference, and is arranged for electrostatic transfer of the image from 
the image bearing surface. Intermediate transfer member 20 is associated 
with a pressure roller 24 for transfer of the image onto a further 
substrate 25, such as paper, preferably by heat and pressure. A fuser 26 
may be associated with the substrate 25, for fixing the image thereon, if 
required. Cleaning station 22 may be any suitable cleaning station, such 
as that described in U.S. Pat. No. 4,439,035, the disclosure of which is 
hereby incorporated herein by reference. 
In accordance with a preferred embodiment of the invention, after 
developing each image in a given color, the single color image is 
transferred to intermediate transfer member 20. Subsequent images in 
different colors are sequentially transferred onto intermediate transfer 
member 20. When all of the desired images have been transferred thereto, 
the complete multi-color image is transferred from transfer member 20 to 
substrate 25. Pressure roller 24 therefore only produces operative 
engagement between intermediate transfer member 20 and substrate 25 when 
transfer of the composite image to substrate 25 takes place. 
Alternatively, each single color image is transferred to the paper after 
its formation. In this case the paper is fed through the machine once for 
each color or is held on a platen and contacted with the intermediate 
transfer member during image transfer. Alternatively, the intermediate 
transfer member is omitted and the developed single color images are 
transferred sequentially directly from drum 10 to substrate 25. 
According to a preferred embodiment of the invention, excess liquid 
containing toner particles of various colors is collected from cleaning 
station 22, excess liquid removal assembly 18 and developer assembly 16 
and supplied to a separator 30 which is operative to separate relatively 
clean carrier liquid from the various colored toner particles. The 
separator may typically be of the type described in U.S. patent 
application Ser. No. 319,124, filed Mar. 6, 1989, the disclosure of which 
is hereby incorporated herein by reference. Clean carrier liquid is 
supplied from separator 30 to a carrier liquid reservoir 32, which also 
may receive additional supplies of carrier liquid, as necessary. Carrier 
liquid from reservoir 32 is supplied to cleaning station 22. 
Reference is now made additionally to FIG. 2, which is a pictorial 
illustration of part of the apparatus of FIG. 1, not including 
photoconductive drum 10, intermediate transfer member 20, roller 24, 
substrate 25 and fuser 26. It is seen in FIGS. 1 and 2 that multicolor 
toner spray assembly 14 receives separate supplies of colored toner from 
four different reservoirs 40, 42, 44 and 46, typically containing the 
colors Yellow, Magenta, Cyan and Black respectively. Pumps 48, 50, 52 and 
54 may be provided along respective supply conduits 56, 58, 60 and 62 for 
providing a desired amount of pressure to feed the colored toner to 
multicolor spray assembly 14. 
Associated with each of reservoirs 40, 42, 44 and 46 are typically provided 
containers of charge director and concentrated toner material, indicated 
respectively by reference numerals 64 and 66 as well as a supply of 
carrier liquid, indicated generally by reference numeral 67. 
Each of the reservoirs 40, 42, 44 and 46 also typically receives an input 
of recycled toner of a corresponding color from developer assembly 16, 
which will be described hereinbelow in greater detail. 
Reference is now made to FIG. 3 which illustrates one embodiment of a 
multicolor toner spray assembly indicated by reference number 69. In the 
embodiment of FIG. 3 it is seen that there is provided a linear array of 
spray outlets 70, each of which communicates with one of the four conduits 
56, 58, 60 and 62. The spray outlets are preferably interdigitated such 
that every fourth outlet is of the same color and that every group of four 
adjacent outlets includes outlets of four different colors. The spacing of 
the spray outlets and their periodicity is selected to enable 
substantially complete coverage of the photoconductor to be realized for 
each given color separately. 
Preferably the center to center spacing of the outlets is as small as 
possible. In the embodiment of FIG. 3, the center to center spacing of 
outlets 70 is typically 2 mm. The nozzle openings of the outlets are 
restricted to provide a desired flow configuration and preferably have a 
generally rectangular cross section. In any event, the amount of toner 
that is applied to the drum in accordance with the present invention is 
sufficient to provide a layer of toner of thickness at least sufficient to 
substantially fill the gap between drum 10 and developer roller 17. 
It is a characteristic of preferred embodiments of the invention that 
developer roller 17 is a reverse roller, that is, the surfaces of 
developer roller 17 and drum 10 move in opposite directions at the 
development region. In the present invention the flow of liquid developer 
is high enough so that there is a substantial amount of liquid developer 
at the point of propinquity of drum 10 and roller 17 such that the toner 
is in a turbulent rather than laminar state. For reasons which are not 
clearly understood, this turbulent flow has resulted in excellent images. 
It is also believed that this turbulence allows for relatively high 
spacings between the spray outlets without substantial deterioration of 
image quality. 
Reference is now made to FIGS. 4A and 4B and FIGS. 5A-5E, which together 
illustrate a preferred embodiment of the spray assembly indicated by 
reference number 81, which is composed of a predetermined sequence of 
modular elements 72, 74, 76, and 78 arranged in a stack. 
Disposed in sealing engagement between each of the adjacent modular 
elements illustrated in FIGS. 5A-5D is a spacer element 84 (FIG. 5E), 
typically much thinner than the remaining modular elements, which seals 
the various spray outlets from each other and prevents color 
contamination. 
It may be appreciated from a consideration of FIGS. 5A-5E, that each of the 
modular elements illustrated therein defines a part of four conduits 
corresponding to conduits 56, 58, 60 and 62 as well as two apertures 80 
and 82 for accommodating connection and tightening bolts (not shown) which 
hold spray assembly 81 together. 
Additionally each modular element has formed at one end a slit 86 which 
together with adjacent spacer elements 84 forms a rectangular spray outlet 
90 each communicating via a respective channel 88 to respective conduits 
56, 58, 60 and 62. 
It may be appreciated that the modular element 72 illustrated in FIG. 5A 
corresponds to a spray outlet communicating with conduit 62, while the 
modular element 74 illustrated in FIG. 5B corresponds to a spray outlet 
communicating with conduit 60. The modular element 76 illustrated in FIG. 
5C corresponds to a spray outlet communicating with conduit 58, while the 
modular element 78 illustrated in FIG. 5D corresponds to a spray outlet 
communicating with conduit 56. 
Modular elements 72, 74, 76 and 78 are each typically of thickness 1 mm. 
This thickness defines one generally rectangular dimension of each spray 
outlet, whose other dimension, the width of slit 86, is normally selected 
to provide a desired application of toner to the drum 10 as described 
hereinabove. Spacer elements 84 typically have a thickness of 0.1 mm. Slit 
width is typically 0.6 mm. 
It is a particular feature of the embodiment of FIGS. 4A-5E that relatively 
small spatial separations between adjacent spray outlets may be realized. 
For the typical dimensions mentioned above, the center to center spacing 
between adjacent outlets for the same color is 4.4 mm, while in the 
embodiment of FIG. 3, the corresponding spacing is 8 mm. 
Reference is now made to FIG. 7 and FIGS. 8A-8D, which together illustrate 
a preferred alternative embodiment of a multicolor spray assembly which is 
indicated by reference number 15, similar to the embodiment illustrated in 
FIGS. 4A-4B and FIGS. 5A-5E and indicated by reference number 14. The 
major differences between the two embodiments are in the shape of the 
spray outlets and in the resultant change in the distance between the 
modular elements. 
In the embodiment of FIGS. 4A and 4B, the spray outlet is rectangular and 
formed by the upper and lower walls of slit 86 and spacer elements 84 
adjoining the modular element. The spray outlets for the embodiment of 
FIGS. 7 and 8A-8D is formed of a tubular extension 108 at the end of each 
modular element 110, 112, 114 and 116. 
Modular elements 110, 112, 114 and 116 are each typically of thickness 2 
mm. Tubular extensions 108 have a typical inner diameter of 1 mm and a 
typical outer diameter of 1.5 mm. Thus the spray outlet center to center 
spacing for this embodiment is typically 2.1 mm, compared to 1.1 mm for 
the embodiment of FIG. 4A and 4B, and the spacing between sprays of the 
same color is about 8.4 mm instead of 4.4 mm for the embodiment of FIGS. 
4A and 4B. 
The outer surfaces of tubular extensions 108 are tapered at their exit ends 
in order to reduce the wall thickness at the output face of the extensions 
to a minimum. It is believed that this reduction reduces dripping of the 
liquid developer. 
Reference is now made to FIG. 6 which illustrates a developer assembly 90 
constructed and operative in accordance with a preferred embodiment of the 
invention. The developer assembly comprises developer roller 17 which 
operatively engages photoconductor drum 10 in spaced relationship 
therewith and, due to its rotation in the same sense as photoconductor 
drum 10, acts as a metering device. Developer roller 17 is typically 
maintained at +200 Volts when the voltage of the image areas of the 
photoconductor 10 is approximately +1000 Volts and the voltage on the 
background areas of the photoconductor 10 is approximately +100 Volts. The 
above voltages are suitable for the use of negatively charged toner and a 
selenium coated photoconductor drum. If it is desired to use a positively 
charged toner or another type of photoconductor material, correspondingly 
different voltages will be appropriate. This embodiment utilizes 
multicolor spray assembly 14, illustrated in FIGS. 4A-4B and 5A-5E and the 
spray is directed toward the under surface of photoconducting drum 10. 
FIG. 9 illustrates a different preferred embodiment of the invention with a 
developer assembly 91, similar to that of FIG. 6, but utilizing spray 
assembly 15 of FIG. 7. Here the spray is directed to the upper surface of 
developer roller 17. It should be noted that the rotation of developer 
roller 17 is such as to carry the developer liquid away from a development 
region 93. Nevertheless the multicolor spray assembly produces a 
sufficient amount of force to assure that there is a supply of liquid 
developer at the development region as will be illustrated with the aid of 
FIG. 10. 
In FIG. 10 photoconductive drum 10 is shown in phantom and liquid developer 
sprayed from the tubular extension is seen to form in its absence a thick 
accumulation of developer. It is now understood that the net effect of the 
spray, and the movement of developer roller 17 and photoconducting drum 10 
is to form development region 93 filled with developer at the point of 
propinquity of drum 10 and roller 17 and to the left of that point. The 
amount of developer in that region and its extent is easily changed by 
varying the rotation speeds of drum 10 and roller 17 and the amount of 
liquid developer supplied. 
Very little liquid carries through to the right of the development region 
due to the metering effect of developer roller 17. It is also clearly 
understood that for this embodiment as well as for the others disclosed 
herein, there is substantial turbulence of the liquid developer in the 
development region. 
For both the embodiments of FIG. 6 and FIG. 9 it is seen that the toner at 
the developer interface is removed from the development region quickly 
after the flow is interrupted. This allows for almost instant change of 
developer color at development region 93. 
A preferred type of toner for use with the present invention is that 
described in Example 1 of U.S. Pat. No. 4,794,651, the teachings of which 
are incorporated herein by reference. Other toners may alternatively be 
employed. For colored liquid developers, carbon black is replaced by color 
pigments as is well known in the art. 
Operatively associated with developer roller 17 are a plurality of color 
specific toner cleaning assemblies 92, each of which is selectably brought 
into operative association with developer roller 17 only when toner of a 
color corresponding thereto is supplied to development region 93 by spray 
assembly 14. 
Each of cleaning assemblies 92 comprises a blade member 94 including a 
preferably resilient main portion 96 and side wiping portions 98 arranged 
to engage the two edges of the roller developer surface. Blade member 94 
is mounted on a linkage 100 which is selectably positioned by a 
conventional actuator 102. Associated with each of the cleaning assemblies 
92 is a toner collection member 104 which serves to collect the toner 
removed by the cleaning assembly 92 from the developing electrode and thus 
to prevent contamination by mixing of the various colors. 
As noted above, the toner collected by collection members 104 is recycled 
to the corresponding toner reservoirs. A final toner collection member 106 
always engages the developer roller 17. The toner collected thereby is 
supplied to separator 30 (FIG. 1). Alternatively the toner collected by 
collection member 106 may be supplied directly to the black (K) toner 
reservoir 46. 
An alternative preferred embodiment of the invention is shown in FIGS. 
11-14. FIG. 11 shows a general cross-sectional schematic view of the 
system. The liquid handling is similar to that of the previous embodiments 
with the changes therefrom mainly in the development and image transfer 
regions. These changes are shown more clearly in FIG. 12 which is an 
enlarged view of the relevant portion of FIG. 11. In FIGS. 11 and 12 
functionally unchanged elements are referenced with the same reference 
numbers as used in earlier drawings illustrating the other embodiments of 
the invention. 
In the embodiment of FIGS. 11 and 12 developer roller 17 is approximately 
at 7:30 o'clock in relation to drum 10 and a multicolor spray assembly 120 
is at approximately 10 o'clock. Cleaning station 22 utilizes a wetted 
sponge roller 118 followed by a resilient blade 119. 
Multicolor spray assembly 120 comprises a linear spray assembly for each of 
the colors. Unlike the embodiments of spray assembly 14, spray outlets 121 
do not form a linear array for all of the colors, but rather each linear 
color array is displaced from its neighbors both axially and in the 
process direction. This arrangement is shown most clearly in FIGS. 13 and 
14. 
Spray outlets 121 spray downward onto a downward moving portion of 
photoconductive drum 10 and are formed with a bend which changes the 
direction of flow from generally upward at the connection to supply 
conduit manifolds 124, 126, 128 and 130 respectively to an downward angle 
at the exits from spray outlets 121. This change in direction has been 
found to reduce dripping from the exits of the spray outlets when the 
color is changed, which is important to reduce the time required between 
color changes. Supply conduit manifolds 124, 126, 128 and 130 are 
continuations of supply conduits 56, 58, 60 and 62 and are fed with liquid 
toner preferably from both ends. 
In a preferred embodiment of the invention the supply conduits are fed by 
elastic tubing in order to allow for faster cut-off of the flow. 
In the embodiment of the invention shown in FIGS. 11 and 12, substrate 25 
is held on a backing roller 125. The apparatus can operate in two ways. In 
both cases the individual color images are formed and sequentially 
developed on drum 10 and sequentially transferred to intermediate transfer 
member 20. In the first preferred embodiment of the invention the images 
are all transferred to intermediate transfer member 20 in registration and 
then the complete multicolor image is transferred as a whole to substrate 
25. In the second preferred embodiment the single color images are 
transferred individually to substrate 25 without being assembled as a 
group on intermediate transfer member 20. 
It is understood that in some preferred embodiments of the present 
invention the multicolor spray assemblies spray onto a downward facing 
portion of photoconductor drum 10. The spray may be upward or with an 
upward directional component, as shown in FIG. 1. For other embodiments of 
the invention the spray direction may be horizontal or alternatively the 
spray direction may have a downward component or it may be directed at 
developer roller 17. It is a further feature of a preferred embodiment of 
the invention that the multicolor spray assembly is operative to provide a 
plurality of jets of toner whose cross sectional extent upon impingement 
with the drum does not significantly exceed the cross sectional of the 
opening of each spray nozzle. 
It is a further characteristic of the illustrated preferred embodiments of 
the invention that developer roller is a reverse roller and that the 
liquid developer is supplied to a development region comprising the side 
of the region of propinquity between roller 17 and drum 10 at which roller 
17 leaves that region. This has a number of effects. Firstly, if 
sufficient liquid developer is supplied, the liquid developer is in a 
turbulent state which is believed to reduce the close spacing requirement 
for the spray nozzles. 
Development takes place in this development region and the developer roller 
17 carries excess carrier liquid away from the development region for 
reuse. Additionally, roller developer 17 also acts as a metering roller, 
so that the amount of liquid remaining on the background areas of the 
image on drum 10 when it leaves the development area is reduced and 
loosely adhering toner on the image which tends to reduce image quality is 
removed and carried away by development roller 17. 
While the invention has been described utilizing a roller developer, it is 
understood that the invention can be practiced utilizing a belt developer. 
It will be appreciated by persons skilled in the art that the present 
invention is not limited by what has been particularly shown and described 
hereinabove. Rather the scope of the present invention is defined only by 
the claims which follow: