Liquid immersion development machine having a development system adapted to compensate for copy paper roughness

A development system for developing a latent image so as to compensate for differences in the surface roughness of different types of copy papers receiving the developed image. The development system includes a development unit for each color of toner particles being used within the machine for latent image development. Each development unit has a first developer material supply source, and a second developer material supply source, containing respectively a first developer material and a second developer material of a same color. In order to more fully correct for hue and density differences in images of the same color developed and transferred onto rough versus smooth surface type copy papers, the first developer material importantly contains a higher level of pigmentation than the second developer material.

BACKGROUND 
This invention relates generally to electrostatographic reproduction 
machines, and more particularly to a liquid immersion reproduction machine 
having a development system adapted to compensate for differences in 
surface roughness of different types of copy paper. 
In electrophotographic printing, a charged photoconductive member is 
exposed to a light image of an original document. The irradiated areas of 
the photoconductive surface are charged to record an electrostatic latent 
image thereon corresponding to the informational area contained within the 
original document. Generally, the electrostatic latent image is developed 
by bringing a developer mixture into contact therewith. A dry developer 
mixture usually comprises carrier granules having toner particles adhering 
triboelectrically thereto. Toner particles are attracted from the carder 
granules to the latent image forming a toner powder image thereon. 
Alternatively, a liquid developer material or materials of different colors 
may be employed in what is referred to as a Liquid Immersion Development 
(LID) electrophotographic reproduction machine for developing the latent 
image. Liquid development is frequently carded out with a rotating 
developer roller immersed or partially immersed in a liquid developer 
material or developer bath with a stationary electrode being employed to 
create the necessary electrostatic field between the developer roller and 
the photoconductive surface. However, liquid development as disclosed, for 
example, in U.S. Pat. No. 5,355,201 can also be carried out with an 
applicator head or lip supplying liquid developer material from a supply 
source directly to a latent image on the photoconductive surface to 
develop the latent image. 
As disclosed for example in U.S. Pat. No. 5,378,574 liquid developer 
materials typically each include a colorless liquid carrier having 
dispersed therein, charged solid toner particles at a desired 
concentration level, and dye or pigment particles loaded at a desired 
level by bonding them to the toner particles forming charged pigmented 
toner particles. Typically to develop with such liquid developer material, 
it is brought into contact with an electrostatic latent image so that the 
charged pigmented toner particles, along with some of the liquid carrier, 
are attracted by the latent image, thus developing the image. After such 
image development on the photoconductive surface, the image is conditioned 
to remove excess liquid carrier therefrom, and is subsequently transferred 
to a copy sheet for fusing to form a finished hard copy. 
The quality of the finished hard copy depends in great part on the 
selections and effectiveness of development parameters, such as a toner 
concentration level, a toner pigmentation level, and a charge level In a 
LID reproduction machine, the practice for example is to set and control 
at a single desired point or level, the toner concentration in each 
developer material, for each color of toner particles being used for image 
development. In order to have uniform looking quality toner images, the 
toner particles at such a desired concentration level usually a/so have 
only one desired level of pigmentation. 
Unfortunately, it has been found, particularly in multicolor LID 
reproduction machines, that the use of the same developer materials each 
having one toner concentration level, and one pigmentation level for 
developing images to be transferred onto copy papers having different 
surface roughnesses, ordinarily results in undesirable color shifts in 
some transferred images. In other words, it has been found that when 
transferring images developed with developer materials of the same color 
onto both smooth surface and rough surface papers, the apparent hue and 
density of the image will change on relatively rough surface papers due to 
loss of gloss on such papers. 
While this effect can be compensated for to some extent by doubling or 
tripling the developed mass on the rough paper, simply increasing the mass 
will instead tend to cause a loss of latitude in the development, in image 
conditioning, and in transfer and transfuse subsystems. It was 
additionally found that merely increasing the toner concentration, and 
thus merely increasing the developed mass per unit image area, does not 
sufficiently prevent detectable hue and density differences between 
conventionally developed images transferred to rough surface type copy 
papers. 
There is therefore a need for a LID reproduction machine having a 
development system adapted to develop images so as to compensate for 
differences in the surface roughness of different types of copy paper. 
SUMMARY OF THE INVENTION 
Pursuant to an aspect of the present invention, there is provided a liquid 
immersion development reproduction machine including an image bearing 
member having a photoconductive imaging surface; latent imaging devices 
for recording an electrostatic latent image on the imaging surface; an 
electronic control subsystem for controlling elements and process of the 
machine; copy sheet supply units for holding and selectively supplying 
different types of copy sheets each type having a different surface 
roughness; and a development system for developing the latent image so as 
to compensate in such development for differences in the surface roughness 
of the different types of copy papers receiving the developed image. The 
development system includes a development unit for each color of toner 
particles being used within the machine for latent image development. Each 
development unit has a first, and at least a second, developer material 
supply source containing respectively a first developer material and a 
second developer material of a same color. In order to more fully correct 
for hue and density differences in images of the same color developed and 
transferred onto rough versus smooth surface type copy papers, the first 
developer material importantly contains a higher level of pigmentation 
than the second developer material.

DESCRIPTION OF THE INVENTION 
For a general understanding of the features of the present invention, 
reference is made to the drawings. In the drawings, like reference 
numerals have been used throughout to designate identical elements. FIG. 1 
is a schematic elevational view illustrating an electrophotographic LID 
reproduction machine 8 incorporating the features of the present invention 
therein. 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 LID reproduction machines and is not necessarily limited 
in its application to the particular embodiment. 
Referring now to FIG. 1, the electrophotographic LID reproduction machine 8 
employs a photoconductive member 10 shown as a drum mounted rotatably 
within the machine. A photoconductive surface 12 is mounted on the 
exterior circumferential surface of drum 10 and entrained thereabout. A 
series of processing stations are positioned about drum 10 such that as 
drum 10 rotates in the direction of arrow 14, it passes sequentially 
therethrough. Drum 10 is driven at a predetermined speed relative to the 
other machine operating mechanisms by a drive motor. Timing detectors 
sense the rotation of drum 10 and communicate with an electronic control 
subsystem (ESS) 15 of the machine, so as to synchronize and control the 
various aspects and operations of the machine with the rotation of drum 
10. In this manner, the proper sequence of events is produced at the 
respective processing stations. 
As illustrated, drum 10 initially rotates with its photoconductive surface 
12 through charging station AA. At charging station AA, a corona 
generating device, indicated generally by the reference numeral 16, sprays 
ions onto photoconductive surface 12 producing a relatively high, 
substantially uniform charge thereon. Next, the charged photoconductive 
surface is rotated on drum 10 to exposure station BB. At exposure station 
BB, a light image of an original document is projected onto the charged 
portion of the photoconductive surface 12. 
Exposure station BB, for example, includes a moving lens system, generally 
designated by the reference numeral 18. An original document 20 is 
positioned face down on a generally planar, substantially transparent 
patent 22. 
In operation, a filter is employed in association with lens 18 so that a 
selected color is transmitted onto photoconductive surface 12 to 
selectively discharge portions thereof. For example, a red filter is 
employed to discharge selected areas with the charged areas being 
developed with the subtractive primary of red, i.e. cyan colored liquid 
developer material. 
Lamps 24 are adapted to move in a timed relationship with lenses 18 to scan 
successive incremental areas of original document 20. In this manner, a 
flowing light image of original document 20 is projected onto the charged 
portion of photoconductive surface 12. This selectively dissipates the 
charge on photoconductive surface 12 to record an electrostatic latent 
image thereon corresponding to the informational areas in original 
document 20. Selected optical filters (not shown) having colors 
complimentary to the color of the respective liquid developer materials 
are interposed into the light path to optically filter the light image. 
While a light lens system has heretofore been described, one skilled in the 
art will appreciate that other techniques may be used, such as a raster 
output scanner employing a modulated laser beam to discharge selected 
areas of the photoconductive surface to record the electrostatic latent 
image thereon. 
After exposure, drum 10 rotates the electrostatic latent image recorded on 
photoconductive surface 12 to a development system station CC including 
developer units in accordance with the present invention. As shown, 
development system station CC includes a plurality of development or 
developer units in accordance with the present invention, generally 
indicated by the reference numerals 26, 28, 30 and 32. Each of the 
developer units 26, 28, 30 and 32 is suitable for developing a latent 
image on the imaging surface so as to compensate for differences in the 
surface roughness of the different types of copy papers receiving the 
developed image. Except for the fact that each contains a different color 
of developer materials, the developer units 26, 28, 30 and 32 are 
substantially identical to one another. Accordingly, a detailed 
description of one, e.g. unit 26, will suffice for a similar description 
of each of the others. 
Liquid developer materials suitable for the color machine 8 generally 
comprise a liquid vehicle, toner particles, and a charge control additive. 
The liquid medium may be any of several hydrocarbon liquids conventionally 
employed for liquid development processes, including hydrocarbons, such as 
high purity alkanes having from about 6 to about 14 carbon atoms, such as 
Norpar.RTM. 12, Norpar.RTM. 13, and Norpar.RTM. 15, available from Exxon 
Corporation, and including isoparaffinic hydrocarbons such as Isopar.RTM. 
G, H, L, and M, available from Exxon Corporation, 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 are 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. 
Generally, the liquid 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. 
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, may 
be present in amounts of from about 1 to about 10, and preferably from 
about 2 to about 4 percent by weight of the developer composition. Such 
toner particles can be any colored particle compatible with the liquid 
medium or carrier. For example, 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, all available from Sandoz Company, Mississauga, 
Ontario, and the like. 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. 
Suitable pigmentation or 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 it combines 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 accordance with the present invention, (to be described below) a first 
developer material "Da" of any one color will advantageously be made to 
have a pigmentation level of about 18% by weight of the toner particles 
for developing images to be transferred onto relatively rough surface type 
copy paper. A second developer material "Db" of the same color is made to 
have a significantly lower level of pigmentation, e.g. 10% by weight of 
the toner particles, and is provided at the same developer unit for 
developing images to be transferred onto relatively smooth surface type 
copy papers. 
Examples of suitable charge control agents include lecithin (Fisher Inc.); 
OLOA 1200, a polyisobutylene succinimide available from Chevron Chemical 
Company; basic barium petronate (Witco Inc.); zirconlure octoate (Nuodex); 
aluminum stearate; salts of calcium, manganese, magnesium and zinc; 
heptanoic acid; salts of barium, aluminum, cobalt, manganese, zinc, 
cerium, and zirconium octoates; salts of barium, aluminum, zinc, copper, 
lead, and iron with stearic acid; 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. 
Referring now to FIGS. 1 and 2, each development unit, e.g. 26, has a first 
developer material supply source 26A, and at least a second developer 
material supply source 26B, containing respectively a first developer 
material Da, and a second developer material Db, of a same color. As such, 
the first and second sources 26A, 26B each supply one color, e.g. cyan 
developer materials, and 28A, 28B a second color, 30A, 30B a third color, 
and 32A, 32B a fourth color. 
Importantly in accordance with the present invention, in each developer 
unit 26, 28, 30, 32, the first developer material Da of each color 
importantly is made to contain a higher level of pigmentation than the 
second developer material Db of that color. This is in order to more fully 
correct for hue and density differences in toner images of the same color 
that are transferred onto a sheet 34 comprising relatively rough versus 
relatively smooth surface type copy papers 34A, 34B. For example, the 
pigmentation level of each first developer material Da at each developer 
unit is preferably 18% (by weight of the toner particles), while that of 
the second developer material Db at that developer unit is significantly 
less at about 10% (by weight of the toner particles). 
As further illustrated in FIGS. 1 and 2, each developer unit, e.g. 26 
includes a common developer material applicator assembly 48 that is 
connected to the first and to the second supply sources, e.g. 26A, 26B, of 
each developer unit 26, 28, 30, 32. The developer material applicator 
assembly 48 of each developer unit, includes an applicator tip 58. Each 
applicator assembly 48 includes a first member 50 and a second member 52 
that define a channel 56 for extruding developer material to the 
application tip 58 thereof. It also includes a control means 60 and a 
gating device 62 that are connected to the ESS control subsystem 15, for 
selectively extruding a layer of either the first developer material Da, 
or the second developer material Db of the particular color of the 
developer unit onto the electrostatic latent image being developed. 
Accordingly, the electronic control subsystem 15 is programmed to select 
for any given color, the first higher pigmentation developer material Da 
from the first supply source 26A, 28A, 30A, 32A when the copy paper 
supplied is a relatively rough surface type copy paper. It is also 
programmed to select for any given color, the second relatively lower 
pigmentation developer material Db from the second supply source 26B, 28B, 
30B, 32B when the copy paper supplied is a relatively smooth surface type 
copy. 
Referring now to FIG. 2, a voltage source 66 is provided for electrically 
biasing liquid applicator 48 of each developer unit to a suitable 
magnitude and polarity so as to ensure that the electrostatic latent image 
recorded on the surface 12 attracts the liquid developer material Da, Db 
thereto. 
By way of example, when the sheet supply source selected is 33A (containing 
the first type of copy sheets 34A each having a relatively rough image 
receiving surface), developer unit 26 will be controlled to extrude cyan 
colored first developer material Da from the first source 26A, and 
developer unit 28 similarly will extrude magenta colored developer 
material of the first type thereof Da, from its first source 28A. 
Similarly, developer unit 30 will extrude yellow colored developer 
material from its first source 30A, and developer unit 32 will extrude 
black colored developer material from its first source 32A. 
When the sheet supply source selected is 33B containing the second type of 
copy sheets 34B each having a relatively smooth image receiving surface, 
developer units 26, 28, 30 and 32 (under the control of the ESS 15) will 
each extrude the second developer material Db of their respective colors 
from their respective second supply sources 26B, 28B, 30B, and 32B in 
accordance with present invention. 
Referring again to FIG. 1, each liquid toner image formed on the imaging 
surface 12 in accordance with the present invention, may be transferred 
after its respective cycle, to a suitable selected copy sheet 34A, or 34B 
selectively fed from copy sheet supplies 33A or 33B as shown. 
Alternatively, successive liquid images may be developed in superimposed 
registration with one another on the surface 12, thus forming a composite 
multicolor liquid image, then followed by such transfer. For example, copy 
sheet type 34A has a relatively rough image receiving surface, and copy 
sheet type 34B has a relatively smooth image receiving surface. In either 
case, the toner image is transferred as such at a transfer station DD. 
In accordance with the present invention, the composite multicolor liquid 
toner image will be transferred to a copy sheet 34A, or 34B depending on 
whether the type of developer material used was a high pigmentation 
material Da, or a low pigmentation material Db. As also shown, prior to 
such transferring of the multicolor liquid toner image to a copy sheet 
34A, or 34B, the image is contacted and conditioned by a conditioning 
roller 36. 
At the transfer station DD, a transfer roller 38 is provided and maintained 
at a suitable voltage and temperature, for assisting in an electrostatic 
transfer of the image from photoconductive surface 12 to copy sheet 34A, 
or 34B. Preferably, transfer roller 38 applies pressure and is 
electrically biased to ensure the transfer of the composite multicolor 
liquid image to sheet 34A, 34B. 
After the composite multicolor liquid toner image has been transferred to a 
selected copy sheet 34A, or 34B, the copy sheet advances on conveyor 40 
through fusing station EE. Fusing station EE includes a radiant heater 42 
which radiates sufficient heat energy to permanently fuse the toner to 
copy sheet 34A, 34B in image configuration. Conveyor belt 40 advances the 
copy sheet in the direction of arrow 44, through radiant fuser 42 to catch 
tray 46. When copy sheet 34A, 34B is located in catch tray 46, it may be 
readily removed therefrom by the machine operator. 
With continued reference to FIG. 1, invariably, some residual liquid 
developer material remains adhering to photoconductive surface 12 of drum 
10 after the transfer thereof to copy sheet 34A, 34B. This material is 
removed from photoconductive surface 12 at cleaning station FF. Cleaning 
station FF, for example, includes a flexible resilient blade 68. This 
blade has the free end portion thereof in contact with photoconductive 
surface 12 to remove any material adhering thereto. Thereafter, lamp 70 is 
energized to discharge any residual charge on photoconductive surface 12 
preparatory for the next successive imaging cycle. In this way, successive 
electrostatic latent images may be developed. 
The development system of the present invention may be utilized in a 
multicolor electrophotographic LID reproduction machine or, in a monocolor 
printing machine. The developed image may be transferred directly to a 
copy sheet or to an intermediate member prior to transfer to the copy 
sheet. Multicolor LID reproduction 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 
In recapitulation, each developer unit 26, 28, 30, 32 of the development 
system of the present invention has a first developer material supply 
source 26A, 28A, 30A, 32A, and a second developer material supply source 
26B, 28B, 30B, 32B containing respectively a first developer material Da, 
and a second developer material Db of a same color. In order to more fully 
correct for hue and density differences in images of the same color 
developed and transferred onto rough versus smooth surface type copy 
papers, the first developer material Da importantly contains a higher 
level of pigmentation than does the second developer material Db. 
The problem of color shifts when developing and transferring liquid toner 
images onto both smooth surface and rough surface copy papers is addressed 
by connecting a liquid developer materials applicator assembly 48 for a 
given color of developer material to two or more sumps, where each sump 
contains the same color of developer material but at different pigment 
loadings in the toner. When developing and transferring liquid toner 
images onto smooth surface papers, each applicator is advantageously 
switched to a sump containing developer material of the color having a 
relatively lower pigment loading. On the other hand, for images to be 
transferred to relatively rough surface papers, sumps containing developer 
materials having relatively higher pigment loadings will be selected so as 
to compensate for the effects of otherwise apparent lower gloss on such 
rough surface papers. The pigment or hue used in each sump can also be 
varied slightly from one pigment loading to the next so as to provide 
additional compensation for such effects of paper roughness. 
It has been found that the major part of the hue and density correction in 
toner developed images transferred onto copy sheets can be accomplished by 
adjusting the pigmentation (both loading and pigments) of the toners used 
for images to be transferred to each paper type. To do so, each color 
developer material is provided in two or more pigmentation levels in 
separate sumps which are selectable for connection to an applicator, 
depending on the paper type selected. The need for flushing each 
applicator between developer material sump changes will be minimal because 
the developer materials being supplied through each applicator are the 
same color or are very close in color. 
It is, therefore, apparent that there has been provided, in accordance with 
the present invention, an apparatus for developing an electrostatic latent 
image with a first liquid developer material of a first color having a 
first level of pigmentation, or with a second developer material of the 
same first color having a second and significantly lower level of 
pigmentation, depending on whether the copy sheet to receive the developed 
image is a rough surface type or a smooth surface type paper. This 
apparatus thus fully satisfies the aims and advantages 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.