Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
P~ior method~ and ~pparatus for making color
copies o~ color origin~ls by electrostatic technlques has
involved the steps of optically projectin~ color resolved
images of the original onto a single charged eIectrophotvgxaphic
me~ber or a plurality o~ charged eIectrophotographic
~embers, one for each color resolved lmage to form
corre~pondin~ latent eIectrostatic images, developins each
l~tent electrostatic image with its proper color and then
fixing each image in superimposed relationships~ The
images projected onto the electrophoto~raphic members were
obtained by projecting an image o~ the original thereon
through a plurality o colox separation filters, one for
each color to be reproduced. Depending on the system
employed, the final composite image has been either formed
directly on a single electrophotographic member or
txansferred from one or more electrophotographic members to
a sheet of carrier m~terial, such as plain paper. Although
m~ny di~ferent types o electrostatic systems which have been
proposed or constructed, these systems have proven to be
generally unsatisfactory. Some of the reasons are that
the resultin~ apparatus has been too large in size, co~plex
in construction, expensive to build and operate, unreliable
and/or not capable o producing images having quality or
resolution compatible with copies made by photographic
and/or lithographic techniques. In addition, these
systems have not included the capability for making changes
in the color, size or hue o~ the final copy, if such changes
are either desired or required except by very difficult
or expensive means involving changes in the process.
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~ n electrophotographic Eilm now is avallable
which has ~ualities and properties which make it far
superior to any other known eIectrophotographic film.
The said electrophoto~ra,phic film features a photoconductive
coating tha~ is wholly inorganic, mi~rocrystalline,
eIectrically anisotropic in nature, which does not have
reciprocity or intexmit-tency effects, operates at low
Yoltages~ has ~ery high sensitivity and can produce toned
images of exceptionall~ high ~ualit~ from either analog
; 10 or digital information. This electrophotographic film is
well suited for use in making high resolution color
copies o~ color originals by electrostatic techniques/ and,
in faGt, ha~ properties which enable'it to be used for this
purpose in a manner that hitherto has not been achievable
with other types of electrophotographic me~bers.
8ecause of the high speed of response of said
co~ting (capable of being exposed in nanoseconds), the
~pparatus can comprise a high-speed machine~
Among the su~gestions made in the prior art,
the following are believed pertinent to the field of the
invention.
U.S. Patent to Lushex 3,399,611
'' Smith 3,690,756
Nagamatsu et al 3,832,170
Katayama et al 4,095,879
Watanabe et al 4,120,577
Barasch 4,124,286
No inference should be drawn that the above
represents a comprehen5ive investigation of the prior art;
that ~ny or all are pe~tinent to the invention; that the
apparatus therein is analogous to the inventionj that the
invention hexein is the equivalent of any disclosed therein.
5 ~ ~
Accordingly~ the .inYention concerns a me-thod
and apparatus ma~ing of color copies of a
color original by forming color resolved latent
electrostatic images of the original on a rotatiny
electrophotoyrcphic member, developing each latent
electrostatic image so formed with color
corresponding developing material and then
transferring each developed image to a sheet
of carrier material in superimposed and registered
relationship. The latent electrostatic images
are formed on the electrophotographic member
~y means of a laser system whose output beam is
modulated with digital information corresponding
to each one of the color resolved images~ and
developed with colored developing material from
individual developing units.
Each color image is formed, deyeloped
and transferred during one revolution of the
electrophotographic member so that there are
as many revolutions as colors; also there are as
many transfers-to the same sheet of carrier
material as coloxs bein~ printed on that
sheet.
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The preferred embodiments of this inventi.On
now will be described, by way of example, with reference
to the drawin~s accompanying this speci~ication in which:'
The sole figure is a fragmentar,y view
partially in perspective and partially in block diagram
form of an apparatus for making color pr,ints of color
originals accoxding to this invention, it being
understood that some of the de-tails are more'or less
symbolic or dia~rammatic.
Reerring now to the drawing, there'is
shown an embodiment of an electxophoto~raphic co~yin~
app~ratus constructed according to this invention and
' identified by reference numeral ll.
~n oxiginal to be copied is deposited on
a 1at bed scanner 13 where its imagery is rapidly
scanned and converted into three or four color separation
digital information, Flat bed scanner 13 may include a
white light source, an optical scanning unit, xed, green
.
- and blue filter units for orming the three colo~
separations ~nd an ~nalog to digital converter for ~
converting the analog information into digital dat~. The
- three or four color separations may be formed
- simultaneously by airectins images of the original through
all three filters at the same time. A special filter
or scanner system may be used for black pigment.
The dig.ital data so obtained is fed into
a computer 15 where it is stored, either permanently or
temporarily, and further processed. The further ~rocessing
includes convertin~ the red, ~reen, blue and black digital
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dat~ respecti~el~ t~ c~an, ma~enta, yellow and black ~alues.
The furthe.r processin~ ma~ also include such operations ~s
linear scaling, croppin~, density shi.fting, ~all~a
modiication, color balancin~, color reversal, c~ptioning
and the like.
~ graphic display terminal 17 which is connected
to compute~ 15 enables the imayes stored in the computer to
be monitored at any time~
~ laser system 19 for writing images using the
digital da~a is also connected to computer 15. Laser
system 19 may comprise a scanning prism/ a laser and an
- ~cousto-optical modulator for modulating the output beam
of the laser in accordance ~ith digital information~
Laser system 19 is arran~ed to scan over a particular
an~le. Instead of a single laser, laser s~stem 19 may
include a pluralit~ o~ lasers, each arranged to sc~n
a portion ofthat particular angle.
There is an electrophotographic member in the
form o~ a rotar~ electrophotographic arum 21 mounted on
an axle 23 ~hich is jouxnalled ~or rotation on a support
frame 25 ~n the direction shown by the arrows~ The suppo
frame 25 is broken aw~y and bearings, journals and bracXets
are not illustrated in order to simplif~ the view Drum 21
is driven by a motor 27 whose output shaft is mechanically
coupled as indicated at 22 to axle 23. The peripheral
sur~ace of drum 21 comprises a photoconductive coaking on
a conductive substrate~ The conductive substrate may
either be a sleeve mounted on drum 21 or an inte~ral part
of drum 21. Thus, it ~ay comprise a ~e~al substrate with
the photoconductive coatin~ on its surface o.r an insulative
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sheet material having an ohmic layer hetween the sheet
material and the photoconductive coating. In either
event, the metal substate or ohmic layer is required to
be connected electrically into a charging circui-t comprising
a corona voltage source. The photoconductive coating is
one in which latent electrostatic images can be formed by
laser writing at very high speed and then developed to
provide prints having high quality and high resolution.
An example of such a coating is the coating described in
U.S. Patent 4,025,339.
Positioned around the path of travel of the
peripheral surface of drum 21 and in the following order
are a charging station 31, an exposure s-tation 33, a
developing station 35, a transfer station 37 and an
ultrasonic or other type of cleaning station 39. As can
be seen, developing station 35 is located just below
drum 21.
At charging station 31 there is a charging
device ~1 for applying a uniform electrostatic charge
to the photoconductive surface of drum 21. Charging
device may comprise one or a series of corona wires
eonneeted to a switehable eoronalvoltage souree 42 by
a suitable eonnection 40. The wire or wires (not shown)
of the deviee 41 may be reeiproeated and/or rotated to
produce uniform charge.
As the portion of surface charged at charging
station 31 passes through the exposure sta-tion 33, a
latent electrostatic image corresponding to one of the
four color image components of the original (i.e., cyan,
~ ,, . . ~,
m~enta, yellow or black) is "wri-tten" on the sur~ace
by the laser beams 20 ~rom the laser system l9~ (The
beam or beams are illustrated only in symbolic fashion
in the view.)
As the l~tent eIectrostatic image is moved .
. through the .developin~ station-35, it is developed with
its corxesponding colored developing material (toner) from
a ~eveloping device 43~
Developing device 43 includes four indi~idual
developing units 45, 47, 4g and 51 mounted in a row on
a frame 53. Each developin~ unit includes a weIl having
~ quantity of di~ferent colored li~uid toner developing
material and a ton~r applicator ro:Ller partially immersed in
its well. The color of the liquid toner in each well
corxesponds to one of the four colors of the color resolved
image components of the original. Thus~ the colors of
the toners in the ~oux wells are respectively cyan,
- magentaj yellow and black~
Frame 53 is mounted on a rigid subcarriage 54
which is guided on tracks 55 for stepwise m~vement
tangential to the drum 21 in which movement it will
carry the developing units 45, 47, 49 and 51 seriatim
to the developing station 35. The frame 53 and subcarriage
54 are dri~en by a screw and nut arrangement in which
there is a programmed stepping motor 57 whose sha:~t is
coupled to the screw 59 wh.ich engages a suitable nut
mounted to the subcarriage 54. The nut could comprise a
threaded bracket 61 dependent from the subcarriage 5~.
The ~otor 57 may be mounted upon and the screw shaft 5
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journalled in a block .62 that is connec-ted with the
support 25. Its electrical connections ~re not shown
in the dra~in~ .
The developing units ~5, 47, ~9 and 51 are
~rranged on the carria~e 53 in the ordex in whi~h it
is desired to trans~er -the four developed images onto
the receptor at the transfer s~-ation 37. Thus, if the
. de~eloped images are transferred in the order ~an,' magenta,
~ello~ and black, these will be the tone~ colors in the
~ells of the developing units 45~ 47, 49 and 51,
respeotively, assuming that the operatin~ stroke'of
the subcarriage 54 is to the left. (See double-headed
arro~ which indicates directions of moyement o~
.~ ' c~rriaga 53-54).
: In operation/ when a mu:Lticolor image is to
- be xeproduced, the appar~tus is synchronized and
programmed so that thè carriage 53 steps to the'left
bringing the toner applicatox roller of the developing
unit 45 into engagement with the bottom surface o~ the
,electrophotographic drum 21 a short time before arrival
of the leading edge of the first latent image'which was
.applied at the e,xposure station 33~ This gives ~he
applicator roller of the unit 45 suf~icient time'to
com~ence picking up the colored toner from its well to
provide good development.. Alternatively, the applicator
rollers may be continuously rotating slowly to keep the
toner flowing on the roller surfaces. Suitable friction
drive means capable of bein~ overridden may be used ~o
rotate the applicator rollers,
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The carriage 53 m~intains the applicator roller
of deyel~pin~ unit 45 in en~agement with the dr~m 21 during
a dwell pexiod until the complete applied laten't 'image
of th~t particular color o~ the unit 45 has been toned,
The'drum rotation causes ox accompanies rotatlon of the
applicator roller~ 'In the blank area between latent images
for ~ ~r~ction of a revolu-tion of the dr~um 21, the'
carriage 53 is stepped once more to the left as viewed
. in the.'figure, now bring.ing the applicator roller
.l0 . of the second developing unit 47 into engagement with the
bottom surface of the drum 21~ The applicator roller o~
developing unit 45 is now idle, having moved t~ the left .
' of the developing station~ This developin~ unit ~7 will be
applying the magenta toner from its well to the drum 21
.
: 15 at the developing station to.tone the second latent image
applied by the laser s~stem l9. It remains in pOSition
for the same duration o~.dwell as before.
' ' '. . , The first to~ed im,age of c~an is carried on the
drum 21'around to'the.transfer station 37 where it is
transferred to the receptor sheet S carried on the transfex
roller 65. An~ toner remaining on the surface'o~. drum 21 .
is cleaned of~ at station 39 by a cleanin~ device'67, such
- as a vacuum manifold or an ultrasonic apparatus so that
the photoconductive coating on the drum 21 is ready ~or
the following image to be pxoduced auring the next
revolution~ Thus, when the carriage 53 and subcarriage 54
are moved one step to the leXt to bring the appIica-tor
roller o~ the develop.ing unit 47 into engagement with the
botto}n of the roller 21, the~e may still be ~ ~ortion of
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the pxeYious toned image rotating towara the -transfer
station 37 on the le~t side o~ the roller 21, and the
nex-t follo~iny image may al.xeady be partially ~pplied
in latent ~oxm on the x~ght side of the drum 21 and be
moving toward the developing station 35.
~ n this ~anner, th.e carxi~ge 53 steps to the
left and dwells once fox each revolution o~ the drum 21
. until it has carried all ~our of the developing st~tions
45,~47, 49 and 51 into en~agement with the drum 21 and
four developed ima~es have been transfer~ed to the
.
paper me~ber S.
This could be consi.dered one complete or
overall cycle made up of foux step and dwell cycles because
a complete multicolored image has been made. One revolution
of the transfer roller 65 may be used to remove the
receptor member S while the drum 21 rotates free o~ any
de~eloping unit~ In this period of time, the motor 57 may
b~ programmed to reverse the screw 59 to return the
subaarriage 54 to its home position on the right as shown
in the views. This need not be done by stepping.
Preferably, contact and/or transfer of toner be-~ween the
applicator rollers o~ the developing units 45, 47, 49 and
,
51 and the drum 21 is avoided duriny this return stroke~
For example, the entire carriage 53 could be mounted on
springs which in turn are seated on the subcarriaye S4
which is directly movea by the screw 59. A simple cam,
relay, le~er or the like can pull the carriage 53 slightly
downw~rd ~o~rd the subcarri.age 55 and hold same while
the subcarriaye 55 is mo~ing toward the right back to its
ho~e position, releasin~ same therea~ter.
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~ ltern~ti~ely, the drum 21 and transfer
rolle~ 65 can be moved slightly upward during the return
movement~
Another alternative would be to permi-t contac-t
S of applicator xollers with the drum 21 during the xeturn
movement and provide me~ns such as 63 to clean the drum 21
of any toner which may be -transferred onto the blank part
of the drum 21 durin~ this movement.
: Another alternative, but one which is not as
pre$erred, is .to reverse the order of transfer of colored
. images on alternate sheets vf paper S. Thus, the laser
system 19 would be commanded by the computer 15 to
reverse the order of writing the colored images and the
. . latent images would be developed in the order 51~49, 47
; 15 a~d 45 on the re.turn stroke of the subcarriage 54 and carriage
- 53 from left to right, step b~ step
Xn~any event~ the ~arious components are
re~uired to be synchronized in movement and in operation
: so that when a particular color image is written ~y the
laser s~s-tem 19 onto the drum 21, it will reach the
.
developing station.35 at the time that the applicator
roller o~ the developing unit of th~t same color is engaged
against the bottom suxface of the drum 21- Thus each latent
electrostatic image is developed with its proper colored
toner and in the proper order.
After the latent electrostatic image is
developed at the developing station, excess to~er is removed
~rom the surface of drum 21 as the developed image i5 moved
to the transfer station 37 bya vacuu~ knife 63 located
along the path of travel be-tween these two stations. ~t
1~7512
the transfer st~tion 37~ the developed ~nage i~
transferred t~ a sheet of ca,rrier material S, SUCh as
plain p~per deri~ed ~rom a supply of such sheets indicated
at 64v
- 5 Loc~ted at tr~nsfer s-tation 37 is the transfer
- roller 65 which is mounted for rotation in the directi,on
shown b~ the arrows ~nd driven in any suitable manner at
the same'linear surface rate of speed as drum 21. ~ sheek~
. of carrier materi~l S is fed through guides 67 by a feed
mechRnis~ whose vacuum cups are shown ~t 68 ana brought
. into contact ~rith transfer roller 65. By an~ means known
in the art~ such ~s electrostatic attraction, sheet S is
wrapped around and held securel~ on the peripheral surface'
of transfer roller'65 as transfer roller 65 is rotated,
After each developed image has been transferred
.: to the receptor or sheet S which is enwrapped around the
transfer roller 651. the surface of the drum 21 moves in a
clockwise direction throuyh'the area w~ich is'designated
the cleaning ~tation 39. At this station, excess toner which
ma~ have remained upon the surface'of the drum 21 af-ter
tr~nsfer is removed by the cleaning device 67 which, as
mentioned abo~e, can be in the form of a ~acuum manifold
or ultrasonic app~ratus that removes and/or ~issipates
the remaining toner.
The charging, image forming, developing,
txansferring ana cleaning steps are repeated for each one
of the color resolved images, If there are three, the
total number of imayes transferred to -the receptor sheet
is three; if there are four color images, the total number
of imayes transferred is foux. These i.ma,~es are required
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7 'j ~ 2
to be in per~ect recJistration which is ~ simple' matter
to be'achieved with the apparatus of the invention. The
color mixin~ to'achieve the reproduction through 'the
~se of toners of different basic colors such'as cyan,
magenta, ~ellow and black must consider their
transparency and perhaps other characteristics which, of
course, are known to those skilled in this art. Obviously,
-the toner character must be taken into consideration to
achieve the most realistic results.
As the final composite color ima~e of the '
individual co:lor images is being formed on the receptor
sheet through a series of seriatim transfers of the multiple
different colors making up the final color image, the
rollers 21 and 65 are rotating together at the 5ame speed.
These rollers are identical in diameter; hence, the number
of revolutions of each in order ~o pxoduce 5 single
composite color image on the receptor S is equal and
consists of the nu~ber of colors making up the final
composite color image. Normall~, this is four, and the
receptor sheet S is held in place on the peripher~ of the
rollex while this is taking place.
When the composite ima~e has been comple-ted and
all of the colors makirlg same up have been transferred to
the sheet S, the image is a series of, for example, four
toned but unfixed images plaCed on top of one another
At this point in the operation of the machine, either before
the sheet S is released from the transfer roller 65 or
immediately thereaEter, the toned composite color image
is fixed to the sheet by passing same past a fixing
device 69. ~his ma~ be a heatex or other suitable fixing
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means. For example~ instead of or in addition to applyiny
heat, the device 69 ~lay ~oll or spray a protective overcoat
or resinous glaze onto the completed composi-te'ima~e. There
are ~any different forms oE material which a.re transparent
and rel~tively abrasion-resistant and which are used in
protecting inked or toned imac~es that can be applied~
Preferably, a glossy or glazed finish is desired to give
the resulting image some dep~h'of appearance~ The
comple-t'ed sheet S is carried to the left in the view and
deposited in ~n output tra~ 73.
After ~he de~eloping .device 43 has been moved back
to the xight to its "home" position which is -that illustrated
in the view, thQ apP~ratus 11 has completed its o~erall -'
cycle and is read~ for making another composite'copy, with
the same informa-tion derived from the computex store or
dif~erent information carried in said store.
Additional toner for the de~eloping-uni~s may
be stored in reservoirs 75, 77, 79 and 81 mountea on the
botto~ of frame 25 which may be provided with pumps and
flexible connections to enable transfer to the respective
wells of the develop~ngunits~
Although the invention has been described with
' re~erence to making color copies of color originals, it can
be appreciated that:the apparatus can also be usedr if
desired, to make black and white copies ~rom black and
white original.s or to make black and white copies o~ color
~riginals.
In the operation of the apparatus 11, the
programming of the functions of the various co~ponents can
be achieved by suitable programmin~ means such as banks
~ 1~ 6 ~
or relays, shafts, cams a~d the like. Pre~erably, the
operation is pro~rammed by the computer with suitable
control and/or enablin~ signals bein~ tran5mitted on the
lines 100 to the several mokors, drive means, etc , of
the apparatus.
Achieving reyistration of the superimposed
images on the paper member S is a matter of care~ul
construction and synchronization of the moving parts of
the apparatus 11 but adjustments are easible either by
manually operated mechanical means, automatic sensing
devices, laser pattern adjustment and/or a combination
~hereof.
Reference in the claims to a "cycle" is generally
intended to mean a revolution o~ the drum 21 and transfer
roller 65 during which one color irnpression is produced
and transferred. For a four~color complete composite,
it takes four such ''cycles", the overall process or overall
cycle being complete after the sheet S has been released,
its composite imaye ~ixed and/or overcoated, deposited
in its output tra~, the developin~ device moved ba~k to
"home" position and the apparatus made ready for the next
series of cycles or revolutions to begin.
.
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