FIELD OF THE INVENTION
[0001] The present invention pertains to improvements in the field of electrocoagulation
printing. More particularly, the invention relates to an electrocoagulation printing
method and apparatus which prevent formation of undesirable background on electrocoagulation
printed images.
BACKGROUND OF THE INVENTION
[0002] In U.S. Patent No. 4,895,629 of January 23, 1990, Applicant has described a high-speed
electrocoagulation printing method and apparatus in which use is made of a positive
electrode in the form of a revolving cylinder having a passivated surface onto which
dots of colored, coagulated colloid representative of an image are produced. These
dots of colored, coagulated colloid are thereafter contacted with a substrate such
as paper to cause transfer of the colored, coagulated colloid onto the substrate and
thereby imprint the substrate with the image. As explained in this U.S patent, the
positive electrode is coated with an olefinic substance, or a dispersion containing
an olefinic substance and a metal oxide prior to electrical energization of the negative
electrodes in order to weaken the adherence of the dots of coagulated colloid to the
positive electrode and also to prevent an uncontrolled corrosion of the positive electrode.
In addition, gas generated as a result of electrolysis upon energizing the negative
electrodes is consumed by reaction with the olefinic substance so that there is no
gas accumulation between the negative and positive electrodes.
[0003] The electrocoagulation printing ink which is injected into the gap defined between
the positive and negative electrodes consists essentially of a liquid colloidal dispersion
containing an electrolytically coagulable colloid, a dispersing medium, a soluble
electrolyte and a coloring agent. Where the coloring agent used is a pigment, a dispersing
agent is added for uniformly dispersing the pigment into the ink. After coagulation
of the colloid, any remaining non-coagulated colloid is removed from the surface of
the positive electrode, for example, by scraping the surface with a soft rubber squeegee,
so as to fully uncover the colored, coagulated colloid which is thereafter transferred
onto the substrate.
[0004] When a polychromic image is desired, the negative and positive electrodes, the positive
electrode coating device, ink injector and soft rubber squeegee are arranged to define
a printing unit and several printing units each using a coloring agent of different
color are disposed in tandem relation to produce several differently colored images
of coagulated colloid which are transferred at respective transfer stations onto the
substrate in superimposed relation to provide the desired polychromic image. Alternatively,
the printing units can be arranged around a single roller (a pressure roller) adapted
to bring the substrate into contact with the dots of colored, coagulated colloid produced
by each printing unit, and the substrate which is in the form of a continuous web
is partially wrapped around the roller and passed through the respective transfer
stations for being imprinted with the differently colored images in superimposed relation.
[0005] The present inventors have observed that the rubber squeegee which is used for removing
non-coagulated colloid from the surface of the positive electrode leaves on the surface
coagulated colloid (some of coagulated dots scraped by the soft rubber squeegee) and
non-coagulated colloid (non-coagulated ink left after having been scraped by the soft
rubber squeegee) which is transferred with the colored, coagulated colloid onto the
substrate during contact with same. The above-described coagulated colloid and non-coagulated
colloid create on a non-image portion an undesirable background (so-called fogging).
Further, when black (K), cyan (C), magenta (M), and yellow (Y) coloring agents are
used to provide a polychromic image and these images are transferred onto the substrate
in superimposed relation, mixing of colors caused by fogging of several colors adversely
affects color saturation.
DISCLOSURE OF THE INVENTION
[0006] It is therefore an object of the present invention to overcome the above drawbacks
and to provide method and apparatus of preventing formation of undesirable background
on electrocoagulation printed images.
[0007] According to the present invention there is provided an electrocoagulation printing
method comprising the steps of: (a) providing a positive electrode made of an electrolytically
inert metal and having a continuous passivated surface as a positive electrode active
surface moving along a predetermined path; (b) forming or said positive electrode
active surface a plurality of dots of coagulated ink representative of a desired image
by electrocoagulation of electrocoagulation printing ink; (c) bringing a substrate
into contact with said dots of coagulated ink to cause transfer of the dots of coagulated
ink from said positive electrode active surface onto the substrate, characterised
by between steps (b) and (c); (d) applying a first oily substance onto said positive
electrode active surface to mix the first oily substance with fogging ink in a non-image
portion; (e) removing the fogging ink mixed with the first oily substance from said
positive electrode active surface without altering said dots of coagulated ink.
[0008] In the specification given herein, "fogging ink" means coagulated ink and non-coagulated
ink which are left on a non-image portion. According to the present invention, step
(d) is carried out by applying on the positive electrode active surface a first oily
substance to dislodge fogging ink mixed with the first oily substance from the positive
electrode active surface without altering the dots of coagulated ink. Accordingly,
the fogging ink can be removed from a non-image portion of the positive electrode
active surface in such a state that unaltered dots of coagulated ink are left on the
positive electrode active surface. Since the fogging ink does not remain on the non-image
portion, formation of undesirable background (so-called fogging) on a printed image
can be prevented.
[0009] According to the present invention there is further provided an electrocoagulation
printing apparatus, comprising: a positive electrode made of an electrolytically inert
metal and having a continuous passiavated surface as a positive electrode active surface
moving along a predetermined path; an ink feeding part which supplies electrocoagulation
printing ink onto said positive electrode active surface; a negative electrode for
reproducing on said positive electrode active surface dots of coagulated ink by electrocoagulation;
and a transfer part which brings a substrate into contact with the dots of coagulated
ink to cause transfer of the dots of coagulated ink from said positive electrode active
surface to said substrate; characterised by a fogging ink removing portion which supplies
a first oily substance onto said positive electrode active surface and removes fogging
ink mixed with the first oily substance from said positive electrode active surface
without altering said dots of coagulated ink.
[0010] According to the present invention there is further provided an electrocoagulation
printing system comprising: at least one positive electrode made of an electrolytically
inert metal and having a continuous passivated surface as a positive electrode active
surface moving along a predetermined path; a plurality of ink feeding parts which
supply electrocoagulation printing ink onto said positive electrode active surface;
a plurality of negative electrodes for reproducing on said positive electrode active
surface dots of coagulated ink by electrocoagulation; and a plurality of transfer
parts which bring a substrate into contact with the dots of coagulated ink to cause
transfer of the dots of coagulated ink from said positive electrode active surface
to said substrate; characterised by a plurality of fogging ink removing portions which
supply a first oily substance onto said positive electrode active surface and remove
fogging ink mixed with the first oily substance from said positive electrode active
surface without altering said dots of coagulated ink.
[0011] An electrocoagulating printing method, apparatus and system, all embodying the present
invention, will now be described, by way of example, with reference to the accompanying
diagrammatic drawings, in which:
Fig. 1 is an outside perspective view of an electrocoagulation printing apparatus
to which the present invention is applied;
Fig. 2 is a cross-sectional view taken along the lines 2-2 in Fig. 1;
Fig. 3(A) is a diagram showing the state of the surface of a revolving cylinder at
position (a) shown in Fig. 2; Fig. 3(B) is a diagram showing the state of the surface
of the revolving cylinder at position (b) shown in Fig. 2; Fig. 3(C) is a diagram
showing the state of the surface of the revolving cylinder at position (c) shown in
Fig. 2; Fig. 3(D) is a diagram showing the state of the surface of the revolving cylinder
at position (d) shown in Fig. 2; Fig. 3(E) is a diagram showing the state of the surface
of the revolving cylinder at position (e) shown in Fig. 2; and Fig. 3(F) is a diagram
showing the state of the surface of the revolving cylinder at position (f) shown in
Fig. 2;
Fig. 4 is an outside perspective view of a printing system when polychromic printing
is effected with the electrocoagulation printing apparatus being disposed in tandem
relation.
Fig. 5 is an outside perspective view of a printing system when polychromic printing
is effected by a single revolving cylinder.
Fig. 6 is a block diagram of a controller of the electrocoagulation printing apparatus.
Fig. 7 is a flowchart which schematically shows an electrocoagulation printing method
to which the present invention is applied.
DESCRIPTION OF THE PREFERRED EMBODIMENTS FOR IMPLEMENTING THE INVENTION
[0012] First, the structure of an electrocoagulation printing apparatus to which the present
invention is applied will be described with reference to Figs. 1, 2, and 6.
[0013] As shown in Figs. 1 and 2, an electrocoagulation printing apparatus 10 to which the
present invention is applied includes a columnar revolving cylinder 12 serving as
a positive electrode at the central portion thereof. The revolving cylinder 12 is
axially supported in a vertical direction (i.e., a longitudinal direction) thereof
so as to be rotatable around a revolving cylinder shaft 12A in a predetermined direction
(i.e., the direction indicated by arrow A in Figs 1 and 2). The revolving cylinder
shaft 12A is connected to a motor 162 (see Fig. 6) via a gear or the like (not shown)
and the revolving cylinder 12 is rotated in the direction indicated by arrow A by
driving force of the motor 162.
[0014] The surface 12B of the revolving cylinder 12 which is defining a positive electrode
active surface is made of an electrolytically inert metal such as stainless steel
or aluminum, and tin. chromium, nickel, and the like can also be used therefor. Further,
the surface 12B is a passivated surface and a passivated layer is formed thereon.
[0015] An oiler 14 serving as a positive electrode coating part for coating a second oily
substance on the surface 12B of a positive electrode is arranged around the revolving
cylinder 12. The oiler 14 is constructed such that an applicator roller 16, a first
distribution roller 22, a first transfer roller 18, a second distribution roller 24,
and a second transfer roller 20 are each axially supported parallel to the revolving
cylinder shaft 12A (in the longitudinal direction thereof) and are disposed in pressure
contact with one another. The second transfer roller 20 is provided to contact the
surface 12B at a predetermined pressure. These rollers 20, 24, 18, 22, and 16 have
a driving section, which is independent of that of the revolving cylinder 12 and formed
by a motor, a gear, and the like (which are all not shown). Preferably, the applicator
roller 16, the first transfer roller 18, and the second transfer roller 20 are each
provided with a peripheral covering of a resilient material which is resistant to
deterioration caused by the olefinic substance, such as a synthetic rubber material.
For example, a polyurethane having a Shore A hardness of about 50 to about 70 is used
in the case of the applicator roller 16 and a polyurethane having a Shore A hardness
of about 60 to about 80 is used in the case of the first and second transfer rollers
18 and 20. Meanwhile, the oiler 14 includes a second oily substance feeding portion
(not shown) for supplying a second oily substance onto the applicator roller 16.
[0016] A printing head 30 serving as negative electrodes is provided at the downstream side
of the oiler 14 in the direction indicated by arrow A in Fig. 1, a predetermined distance
apart from the surface 12B of the positive electrode (i.e., at a gap between the surface
12B and the printing head 30) and parallel to the revolving cylinder shaft 12A (i.e.,
in the longitudinal direction of the revolving cylinder shaft 12A). The printing head
30 is provided with a large number of negative electrodes (i.e., pin electrodes),
not shown, of which tip ends are perpendicularly directed toward the surface 12B so
as to obtain a resolution of at least 200dpi. It is suitable that a gap defined between
the pin electrodes (not shown) and the surface 12B is set in the range from about
30 µm to about 100 µm. The smaller the gap the sharper are the dots of coagulated
ink produced. It is preferable that at least tip end portion of the pin electrodes
is made of electrolytically inert metal such as stainless steel, platinum, chromium,
nickel and aluminum. The printing head 30 is connected to a print head control part
164 (see Fig. 6) and the gradation of dots corresponding to the pin electrodes, not
shown (which is the gradation of 256 in the present embodiment) is controlled by applied
voltage and/or applying time.
[0017] An inker 32 serving as an ink feeding part for supplying predetermined ink 110 (see
Fig. 3(B)) to the surface 12B of the positive electrode is disposed at the upstream
side of the printing head 30 in the direction indicated by arrow A in Fig. 1 and at
the downstream side of the oiler 14 in the vicinity of the printing head 30 (see Fig.
2). The inker (ink supply port) 32 is disposed in the vicinity of the upper portion
of the surface 12B by a predetermined distance apart from the surface 12B so that
the ink flows downward on the surface 12B due to its gravity.
[0018] A first squeegee 34 for removing the ink 110 from the surface 12B of the positive
electrode and an oil cascade unit 40 serving as a fogging ink removing part are disposed
at the downstream side of the printing head 30 in the direction indicated by arrow
A in Fig. 1. The oil cascade unit 40 is provided with an oily substance supply port
38 for supplying a first oily substance 140 (see Fig. 3(E)), and a second squeegee
36 for removing a fogging ink 130 (see Fig. 3(D)) mixed with the first oily substance
140, which the oily substance supply port 38 and the second squeegee 36 will be described
later. The first squeegee 34 and the second squeegee 36 are each made from soft rubber
having a wedge-shaped (acute-angled triangular) cross sectional configuration and
extending along the direction parallel to the revolving cylinder 12 (i.e., the longitudinal
direction of the cylinder 12). Respective acute angle portions of the squeegees 34,
36 are brought into slide-contact with the surface 12B. The oily substance supply
port 38 is, in the same manner as the inker 32, disposed in the vicinity of the upper
portion of the surface 12B by a predetermined distance apart the surface 12B so that
the first oily substance 140 flows downward on the surface 12B due to its gravity,
The basic structure of the oil cascade unit 40 is as shown in Fig. 1, but the oil
cascade unit 40 is shown as a black box in Fig. 2.
[0019] A pressure roller 70 forming a part of a transfer part is disposed at the downstream
side of the oil cascade unit 40 in the direction indicated by arrow A in Fig. 1 and
at the upstream side of the oiler 14 in such a manner as to pressure contact with
the surface 12B of the positive electrode and to be axially supported parallel to
the revolving cylinder shaft 12A (i.e., in the longitudinal direction of the revolving
cylinder 12). Accordingly, when the revolving cylinder rotates in the direction indicated
by arrow A, the pressure roller 70 is rotated in the direction indicated by arrow
B in Fig. 1.
[0020] A substrate 80 is nipped between the surface 12B of the positive electrode and the
pressure roller 70. For this reason, the substrate 80 is provided to move in the direction
indicated by arrow C in Fig. 1. The electrocoagulation printing apparatus 10 includes
a take-up part 172 (see Fig. 6) controlled by a take-up control part 170 at the side
where the substrate 80 is wound.
[0021] A collected-ink receiver 42 is disposed below the first squeegee 34 so as to receive
ink collected by the first squeegee 34. The collected-ink receiver 42 is connected
to an ink reservoir 48 via a pipe 56. The ink reservoir 48 is provided with a filter
part (not shown) for removing refuse or the like mixed with the collected ink. The
ink reservoir 48 is connected to a pump 50 by a pipe 58. The pump 50 allows ink in
the ink reservoir 48 to be continuously supplied for the inker 32 by a pipe 60. The
pump 50 is connected to a pump control part 168 (see Fig. 6).
[0022] A mixture receiver 44 is disposed below the second squeegee 36 so as to receive a
mixture of the fogging ink 130 and the first oily substance 140 collected by the second
squeegee 36. The mixture receiver 44 is connected by a pipe 52 to a separator 46 which
separates the fogging ink 130 and the first oily substance 140 from each other and
the separator 46 is connected by a pipe 54 to the oily substance supply port 38. The
mixture receiver 44, the pipe 52, the separator 46, and the pipe 54 form circulation
means. The first oily substance 140 is separated from the fogging ink 130 by the separator
46 in such a manner as to admix water with the first oily substance and the mixture
to form an aqueous phase containing the removed fogging ink and an oily phase containing
the first oily substance, separate the oily phase from the aqueous phase (for example,
by decantation or centrifugation), filter the separated oily phase to remove therefrom
suspended solids and recover the filtered oily phase for circulation back to the oily
substance supply port 38. Diatomaceous earth or the like can be used for filtering
the oily phase. Accordingly, the separator 46 includes a built-in power source (for
example, a motor and a pump), not shown, and the power source is controlled by a separator
control portion 166 (see Fig. 5).
[0023] As shown in Fig. 6, the electrocoagulation printing apparatus 10 includes a controller
150 for controlling the entire apparatus. Connected to the controller 150 are an operation
control part 152 for controlling an operating part 154 such as a keyboard, a mouse,
and the like, a display control part 156 for controlling a display part 158 such as
a display, a motor driver 160, a print head control part 164, a separator control
part 166, a pump control part 168, a paper-feeding control part 178, a take-up control
part 170, and an oiler control part 174.
[0024] Next, an operation of the electrocoagulation printing apparatus 10 according to the
present invention will be described with reference to Figs. 3 and 7.
[0025] When a predetermined power switch (not shown) of the controller 150 is turned on
by an operator, the electrocoagulation printing apparatus 10 is actuated. The display
part 158 allows display of predetermined information, and when the operator effects
a predetermined operation to the operating part 154, the revolving cylinder 12 starts
rotating.
[0026] In the electrocoagulation printing apparatus 10, first, step S10 in Fig. 7 allows
formation of micro-droplets of the second oily substance on the surface of a positive
electrode. Namely, the second oily substance is applied onto the surface 12B of the
positive electrode by the oiler 14. Examples of suitable second oily substance which
may be used to coat the surface of the positive electrode include unsaturated compounds,
particularly, unsaturated fatty acids such as arachidonic acid, linoleic acid, linolenic
acid, oleic acid, palmitoleic acid and myristoleic acid, and unsaturated vegetable
oils such as corn oil, linseed oil, olive oil, peanut oil, soybean oil and sunflower
oil. Further, a mixture of two or more kinds of unsaturated compounds may also be
used as the second oily substance. The second oily substance is advantageously applied
onto the surface 12B of the positive electrode in the form of an oily dispersion containing
the metal oxide as dispersoid. Examples of suitable metal oxides include aluminum
oxide, ceric oxide, chromium oxide, cupric oxide, magnesium oxide, manganese oxide,
titanium dioxide and zinc oxide, and chromium oxide is the preferred metal oxide.
Depending on the type of metal oxide used, the amount of metal oxide may range from
about 10 to about 60% by weight, based on the total weight of the dispersion. Preferably,
the second oily substance and the metal oxide are present in the dispersion in substantially
equal amounts. A particularly preferred dispersion contains about 50% by weight of
oleic acid or linoleic acid and about 50% by weight of chromium oxide.
[0027] The second oily substance is applied onto the surface 12B of the positive electrode
by the oiler 14 equipped with a distribution roller extending parallel to the revolving
cylinder 12 and having a peripheral coating comprising an oxide ceramic material.
The second oily substance is applied onto the ceramic coating to form a film of the
second oily substance uniformly covering the surface of the ceramic coating, the film
of the second oily substance breaks down into micro-droplets having substantially
uniform size and distribution, and the micro-droplets are transferred from the ceramic
coating onto the surface 12B of the positive electrode via a transfer roll. As explained
in U.S. Patent No. 5,449,392 of September 12, 1995, the use of a distribution roller
having a ceramic coating comprising an oxide ceramic material enables one to form
on a surface of such a coating a film of the second oily substance which uniformly
covers the surface of the ceramic coating and thereafter breaks down into micro-droplets
having substantially uniform size and distribution. The micro-droplets formed on the
surface of the ceramic coating and transferred onto the positive electrode surface
12B generally have a size ranging from about 1 to about 5 µm.
[0028] A particularly preferred oxide ceramic material forming the aforesaid ceramic coating
comprises a fused mixture of alumina and titania. Such a mixture may comprise about
60 to about 90 weight % of alumina and about 10 to about 40 weight % of titania.
[0029] In some instances, depending on the type of second oily substance used, Applicant
has noted that the film of second oily substance only partially breaks down on the
surface of the ceramic coating into the desired micro-droplets. Thus, in order to
ensure that the film of second oily substance substantially completely breaks down
on the ceramic coating into micro-droplets having substantially uniform size and distribution,
first and second distribution rollers 22, 24 are provided each extending parallel
to the revolving cylinder 12 and having a peripheral coating comprising an oxide ceramic
material.
[0030] The second oily substance is applied onto the ceramic coating of the first distribution
roller 22 by disposing the applicator roller 16 parallel to the first distribution
roller 22 and in pressure contact engagement therewith to form a first nip, and rotating
the applicator roller 16 and the first distribution roller 22 in register while feeding
the second oily substance into the first nip, whereby the second oily substance forms
the film uniformly covering the surface of the ceramic coating when passing through
the first nip.
[0031] In the oiler 14, at least partially broken film of the second oily substance is transferred
from the first distribution roller 22 to the second distribution roller 24 and the
micro-droplets are transferred from the second distribution roller 24 to the positive
electrode surface 12B. Namely, the first transfer roller 18 is disposed between the
first distribution roller 22 and the second distribution roller 24 in parallel relation
thereto, and the first transfer roller 18 is disposed in pressure contact engagement
with the first distribution roller 22 to form a second nip. Further, the first transfer
roller 18 is disposed in pressure contact engagement with the second distribution
roller 24 to form a third nip. The first distribution roller 22 and the first transfer
roller 18 are rotated in register so that the at least partially broken film is transferred
from the first distribution roller 22 to the first transfer roller 18 at the second
nip, and the second transfer roller 20 is disposed parallel to the second distribution
roller 24 and in pressure contact engagement therewith to form a fourth nip. The second
transfer roller 20 is disposed in pressure contact engagement with the positive electrode
surface 12B to form a fifth nip. The second distribution roller 24, the second transfer
roller 20, and the surface 12B are rotated in register in order that the at least
partially broken film is transferred from the first transfer roller 18 to the second
distribution roller 24 at the third nip, then, the micro-droplets are transferred
from the second distribution roller 24 to the second transfer roller 20 at the fourth
nip, and thereafter, the micro-droplets are transferred from the second transfer roller
20 to the positive electrode surface 12B at the fifth nip. Such an arrangement of
rollers is described in the aforementioned U.S. Patent Application No. 08/527,866
filed on September 14, 1995.
[0032] As described above, in the oiler 14, the second oily substance is applied onto the
ceramic coating of the first distribution roller 22, to form the film of the second
oily substance for uniformly covering the surface of the ceramic coating on the surface
thereof, the film of the second oily substance is at least partially broken down into
micro-droplets having substantially uniform size and distribution, the at least partially
broken film is transferred from the first distribution roller 22 to the second distribution
roller 24, the film is substantially completely broken down into desired micro-droplets
having substantially uniform size and distribution on the ceramic coating of the second
distribution roller 24, and the micro-droplets are transferred from the ceramic coating
of the second distribution roller 24 to the positive electrode surface 12B via a transfer
roll. It is desired that the ceramic coatings of the first distribution roller 22
and the second distribution roller 24 comprise the same oxide ceramic material.
[0033] As shown in Fig. 3(A), the micro-droplets of the second oily substance 100 transferred
onto the positive electrode surface 12B by the second transfer roller 20 of the oiler
14 have substantially uniform distribution on the surface 12B.
[0034] Next, in step S20 in Fig. 7, ink is filled into a gap between the positive electrode
surface and pin electrodes. Namely, ink is continuously supplied from the inker 32
to the positive electrode surface 12B. The ink is allowed to flow downward along the
surface 12B, and is conveyed to the gap due to rotation of the surface 12B in the
direction indicated by arrow A in Figs. 1 and 2 to fill the gap. Any remaining ink
flowing downward from the surface 12B is collected in the collected-ink receiver 42
and the collected ink is circulated back to the inker 32 via the ink reservoir 48,
the pump 50 and the pipes 56, 58, and 60.
[0035] As shown in Fig. 3(B), the ink layer is formed to cover the micro-droplets of the
second oily substance 100 on the positive electrode surface 12B.
[0036] The colloid generally used in an electrocoagulation printing ink is a linear colloid
of high molecular weight, that is, one having a molecular weight comprised between
about 10,000 and about 1,000,000, preferably between 100,000 and 600,000. Examples
of suitable colloids include natural polymers such as albumin, gelatin, casein and
agar, and synthetic polymers such as polyacrylic acid, polyacrylamide and polyvinyl
alcohol. A particularly preferred colloid is an anionic copolymer of acrylamide and
acrylic acid having a molecular weight of about 250,000 and sold by Cyanamid Inc.
under the trade mark ACCOSTRENGTH 86. The colloid is preferably used in an amount
of about 6.5 to about 12% by weight, and more preferably in an amount of about 7%
by weight, based on the total weight of the electrocoagulation printing ink. Water
is preferably used as the medium for dispersing the colloid to provide the desired
electrocoagulation printing ink.
[0037] The ink also contains a soluble electrolyte and a coloring agent. Preferred electrolytes
include halides, for example, alkali metal halides such as lithium chloride, sodium
chloride and potassium chloride, alkaline earth metal halides such as calcium chloride,
metal halides such as nickel chloride, copper chloride and manganese chloride, and
ammonium chloride. The electrolyte is preferably used in an amount of about 6.5 to
about 9% by weight, based on the total weight of the ink. The coloring agent can be
a dye or a pigment. Examples of suitable dyes which may be used to color the colloid
are the water soluble dyes available from HOECHST such as Duasyn Acid Black for coloring
in black and Duasyn Acid Blue for coloring in cyan, or those available from RIEDEL-DEHAEN
such as Anti-Halo Dye Blue T. Pina for coloring in cyan, Anti-Halo Dye AC Magenta
Extra V01 Pina for coloring in magenta and Anti-Halo Dye Oxonol Yellow N. Pina for
coloring in yellow. When using a pigment as a coloring agent, use can be made of the
pigments which are available from CABOT CORP. such as Carbon Black Monarch ® 120 for
coloring in black, or those available from HOECHST such as Hostaperm Blue B2G or B3G
for coloring in cyan. Permanent Rubine F6B or L6B for coloring in magenta and Permanent
Yellow DGR or DHG for coloring in yellow. A dispersing agent is added for uniformly
dispersing the pigment into the ink. Examples of suitable dispersing agents include
the non-ionic dispersing agent sold by ICI Canada Inc. under the trade mark SOLSPERSE
27000. The pigment is preferably used in an amount of about 6.5 to about 12% by weight,
and the dispersing agent in an amount of about 0.4 to about 6% by weight, based on
the total weight of the ink.
[0038] Subsequently, in step S30 in Fig. 7, when pin electrodes selected correspondingly
to an image are electrically energized, dots corresponding to the image are formed
on the surface of a positive electrode. Namely, when the pin electrodes (not shown)
of the printing head 30 corresponding to image dots are electrically energized, activation
of the passive layer on the surface 12B of the positive electrode corresponding to
the electrically energized pin electrodes generates multivalent at least trivalent
ions which then initiate coagulation of the colloid to form the dots 120. This state
is shown in Fig. 3(C).
[0039] When the spacing of the pin electrodes is set at a distance which is equal to or
greater than the gap between the positive electrode surface 12B and the pin electrodes,
it is possible to prevent the pin electrodes from undergoing edge corrosion. When
the gap and the diameter of the pin electrode is of the order of 50 µm the pin electrodes
are preferably spaced from one another by a distance of about 75 µm (see U.S. Patent
No. 4,895,629). On the other hand, when the surface 12B is coated with the second
oily substance prior to electrical energization of the pin electrodes, the adherence
of the dots of coagulated ink to the surface 12B is weakened and an uncontrolled corrosion
of the surface 12B is prevented. In addition, gas generated as a result of electrolysis
upon energizing the negative and positive electrodes is consumed by reaction with
the unsaturated compound. Accordingly, when the unsaturated compound is used as the
second oily substance, no gas is accumulated between the pin electrodes and the surface
12B.
[0040] Next, in step S40 in Fig. 7, the non-coagulated ink not associated with the dots
and the micro-droplets of the second oily substance are scraped from the positive
electrode surface. Namely, after formation of the dots 120, the most part of the non-coagulated
ink 110 is removed from the surface 12B by scraping the surface 12B with the first
squeegee 34 and the dots 120 of coagulated ink are brought into a sufficiently uncovered
state. At this time, the unscraped non-coagulated ink 110 and a portion of dots of
the coagulated ink scraped by the squeegee remain, as the fogging ink 130, on the
surface 12B. This state is shown in Fig. 3(D). Meanwhile, the non-coagulated ink 110
removed by the first squeegee 34 is collected to be circulated as described above.
[0041] In step S50 in Fig. 7, the first oily substance is applied onto the surface of the
positive electrode. Namely, the first oily substance 140 is continuously supplied
onto the surface 12B of the positive electrode from the oily substance supply port
38. The first oily substance 140 may be of the same type as or the different type
from the second oily substance. In the present embodiment, from an economical standpoint,
oleic acid which is the same as that used for the second oily substance is used for
the first oily substance. Fig. 3(E) shows the state in which the first oily substance
is supplied onto the surface 12B.
[0042] In step S60 in Fig. 7, the fogging ink mixed with the first oily substance is removed
from the surface of the positive electrode without altering the dots. Namely, the
fogging ink 130 is removed by applying the first oily substance 140 onto the surface
12B of the positive electrode to cause the fogging ink 130 to be mixed with the first
oily substance 140 and by scraping the mixture from the surface 12B by the second
squeegee 36. This state is shown in Fig. 3(F).
[0043] The mixture of the fogging ink 130 and the first oily substance 140 removed from
the surface 12B of the positive electrode is collected, the first oily substance 140
is separated from the collected mixture, and the separated first oily substance 140
is circulated back to the oily substance supply port 38.
[0044] Finally, in step S70 in Fig. 7, the dots are transferred from the positive electrode
surface to a substrate such as a printing paper and an electrocoagulation printed
image is formed on the substrate.
[0045] As described above, the present embodiment is constructed such that, after the dots
120 of coagulated ink are appeared by removing the non-coagulated ink 110, the first
oily substance 140 is applied onto the surface 12B, and the fogging ink 130 mixed
with the first oily substance 140 can be removed from the surface 12B without altering
the dots 120 of coagulated ink. For this reason, formation of undesirable background
(so-called fogging) on a primed image is prevented.
[0046] Meanwhile, in the present embodiment, the revolving cylinder 12 is used as the positive
electrode, but a moving endless belt as disclosed in U.S. Patent No. 4,661,222 may
also be used.
[0047] Further, in a preferred embodiment, the oiler 14 includes two transfer rollers and
two distribution rollers. However, the present invention can be achieved even when
only each one of transfer roller and distribution roller is provided.
[0048] Moreover, in a preferred embodiment, transfer of the dots formed on the positive
electrode surface to the substrate is effected in such a manner that the positive
electrode surface is directly brought into pressure contact with the substrate by
a pressure roller. However, the dots formed on the positive electrode surface may
also be transferred finally to the final substrate via an intermediate transfer member.
[0049] Next, a polychromic image printing system to which the present invention is applied
will be described.
[0050] First, a printing system in which the above-described electrocoagulation printing
system 10 is disposed in tandem relation will be described with reference to Fig.
4. In Fig. 4, the same components as those shown in Figs. 1, 2, and 6 will be denoted
by the same reference numerals, and a description thereof will be omitted. Further,
in Fig. 4, any one of the electrocoagulation printing apparatuses 10 corresponding
to four colors of Y, M, C, and K is not shown.
[0051] The above printing system includes four electrocoagulation printing apparatuses 10
used for full color printing. Four colors of ink of Y, M, C, and K are respectively
used in the electrocoagulation printing apparatuses 10. A color separated image corresponding
to each of the colors is transferred to the substrate 80, and finally, a polychromic
image is printed thereon.
[0052] This printing system includes substrate conveying rollers 92, 94, and the like, which
are supported parallel to the revolving cylinder shafts 12A. These conveying rollers
are each provided to properly hold a state in which the substrate is nipped by the
positive electrode surface 12B and the pressure roller 70.
[0053] Further, connected to the controller 150 are control parts 152, 156, 160, 164, 166,
168, and 174 of these electrocoagulation printing apparatuses 10. The controller 150
controls each electrocoagulation printing apparatus 10 at a predetermined timing.
Meanwhile, this printing system has a single paper-feeding control part 178 and the
take-up control part 170.
[0054] This printing system prevents formation of fogging which is caused by transfer of
fogging ink of each color onto the substrate 80, and therefore, polychromic image
printing can be effected in which deterioration of color saturation caused by mixture
of colors is improved.
[0055] Next, a printing system similar to that disclosed in U.S. Patent No. 5,538,601 will
be described. The printing system disclosed therein is, as shown in Fig. 5, constructed
in such a manner that printing stations 88 corresponding to the four colors and formed
from the parts of the electrocoagulation printing apparatus 10 excepting a revolving
cylinder 12' are disposed around the single revolving cylinder 12' of the electrocoagulation
printing apparatus 10. In Fig. 5, the same components as those shown in Figs. 1, 2,
4, and 6 are denoted by the same reference numerals, and a description thereof will
be omitted. Further, in this figure, any one of the four printing stations 88 of Y,
M, C, and K is not shown.
[0056] The above printing system has a single revolving cylinder 12, single paper-feeding
control part 178, and single take-up control part 170. The substrate 80 is fed by
a roller (not shown) in the direction indicated by arrow D in Fig. 5 and is sequentially
conveyed in the directions indicated by arrows E, F, G, H, and I.
[0057] According to this printing system, in the same way as the printing system shown in
Fig. 4, formation of fogging due to the transfer of fogging ink of each color onto
the substrate 80 is not caused, and therefore, the polychromic image printing can
be effected in which deterioration of color saturation caused by mixture of colors
is improved, and a compact-type printing system can be provided.
[0058] Meanwhile, even in each of the above-described polychromic printing systems, a moving
endless belt may be used as a positive electrode in the same way as in a monochromatic
printing apparatus.
[0059] Further, in each of the above-described polychromic printing systems, the same type
of ink (for example, the same color ink) may also be used repeatedly in each of the
printing apparatuses or in each of the printing stations.
1. An electrocoagulation printing method comprising the steps of:
(a) providing a positive electrode (12) made of an electrolytically inert metal and
having a continuous passivated surface as a positive electrode active surface (12B)
moving along a predetermined path;
(b) forming on said positive electrode active surface (12B) a plurality of dots of
coagulated ink representative of a desired image by electrocoagulation of electrocoagulation
printing ink (110);
(c) bringing a substrate (80) into contact with said dots of coagulated ink to cause
transfer of the dots of coagulated ink from said positive electrode active surface
(12B) onto the substrate (80), characterised by between steps (b) and (c);
(d) applying a first oily substance (140) onto said positive electrode active surface
(12B) to mix the first oily substance (140) with fogging ink (130) in a non-image
portion;
(e) removing the fogging ink (130) mixed with the first oily substance (140) from
said non-image portion of said positive electrode active surface (12B) without altering
said dots of coagulated ink.
2. An electrocoagulation printing method to which the electrocoagulation printing method
according to Claim 1 is applied,
wherein a plurality of printing stages is defined which is arranged at predetermined
locations along said path and each use different electrocoagulation printing ink (110),
steps (b), (d), (e) and (c) are repeated several times, thereby several images are
reproduced at respective transfer part on said substrate (80).
3. An electrocoagulation printing method according to Claim 1 or to Claim 2, characterised in that said first oily substance (140) is selected from the group consisting of unsaturated
fatty acids and unsaturated vegetable oils.
4. An electrocoagulation printing method according to Claim 1 or to Claim 2,
characterised in that said step (b) includes the steps of:
(i) providing a plurality of electrolytically inert negative electrodes electrically
insulated from one another and arranged in rectilinear alignment to define a series
of corresponding negative electrode active surfaces disposed in a plane parallel to
the longitudinal axis of said positive electrode (12) and spaced from the positive
electrode active surface (12B) by a constant predetermined gap, said negative electrodes
being spaced from one another by a distance at least equal to said electrode gap;
(ii) coating the positive electrode active surface (12B) with a second oily substance
to form on said surface (12B) micro-droplets of the second oily substance;
(iii) filing said electrode gap with said electrocoagulation printing ink (110);
(iv) electrically energizing selected ones of said negative electrodes to cause selectively
coagulation of the electrocoagulation printing ink (110) and adherence of coagulated
ink onto the positive electrode active surface (12B) coated with the second oily substance
opposite the electrode active surfaces of said energized negative electrodes while
said positive electrode (12) is rotating, thereby forming dots of said coagulated
ink; and
(v) removing any remaining non-coagulated ink from said positive electrode active
surface (12B).
5. An electrocoagulation printing method according to Claim 4, characterised in that said step (b) (ii) includes the steps of: providing first and second distribution
rollers (22, 24) extending parallel to said positive electrode (12) and each having
a peripheral coating comprising an oxide ceramic material; applying said second oily
substance onto the ceramic coating of said first distribution roller (22) to form
on the surface thereof a film of said second oily substance uniformly covering the
surface of said ceramic coating, said film of second oily substance at least partially
breaking down into micro-droplets having substantially uniform size and distribution;
transferring the at least partially broken film from said first distribution roller
(22) to said second distribution roller (24) so as to cause said film to substantially
completely break on the ceramic coating of said second distribution roller (24) into
said micro-droplets having substantially uniform size and distribution; and transferring
said micro-droplets from the ceramic coating of said second distribution roller (24)
onto said positive electrode active surface (12B).
6. An electrocoagulation printing method according to any one of Claims 1, 2 and 4, characterised in that a mixture of fogging ink removed from said positive electrode active surface (12B)
and the first oily substance (140) is collected, the first oily substance (140) is
separated from the collected mixture, and the separated first oily substance (140)
is applied again onto said positive electrode active surface (12B).
7. An electrocoagulation printing method according to Claim 6, characterised in that said first oily substance (140) is separated from said mixture by admixing water
with said mixture to form an aqueous phase containing said removed fogging ink (130)
and an oily phase containing said first oily substance (140), separating said oily
phase from said aqueous phase, filtering the separated oily phase to remove therefrom
suspended solids, and recovering the filtered oily phase for reapplication onto said
positive electrode active surface (12B).
8. An electrocoagulation printing apparatus (10), comprising:
a positive electrode (12) made of an electrolytically inert metal and having a continuous
passiavated surface as a positive electrode active surface (12B) moving along a predetermined
path;
an ink feeding part (32) which supplies electrocoagulation printing ink (110) onto
said positive electrode active surface (12B) ;
a negative electrode for reproducing on said positive electrode active surface (12B)
dots of coagulated ink by electrocoagulation; and
a transfer part (70) which brings a substrate (80) into contact with the dots of coagulated
ink to cause transfer of the dots of coagulated ink from said positive electrode active
surface (12B) to said substrate (80); characterised by
a fogging ink removing portion (40) which supplies a first oily substance (140) onto
said a non-image portion of said positive electrode active surface (12B) and removes
fogging ink (130) mixed with the first oily substance (140) from said non-image portion
of said positive electrode active surface (12B) without altering said dots of coagulated
ink.
9. An electrocoagulation printing apparatus (10) according to Claim 8, characterised by a coating part (14) for coating the positive electrode active surface (12B) with
a second oily substance.
10. An electrocoagulation printing apparatus (10) according to Claim 8, characterised by circulation means (44, 46, 52, 54) in which a mixture of fogging ink (130) removed
from said positive electrode active surface (12B) and the first oily substance (140)
is collected, the first oily substance (140) is separated from the collected mixture,
and the separated first oily substance (140) is applied again onto said positive electrode
active surface (12B).
11. An electrocoagulation printing system comprising:
at least one positive electrode (12, 12') made of an electrolytically inert metal
and having a continuous passivated surface as a positive electrode active surface
(12B) moving along a predetermined path;
a plurality of ink feeding parts (32) which supply electrocoagulation printing ink
(110) onto said positive electrode active surface (12B) ;
a plurality of negative electrodes for reproducing on said positive electrode active
surface (12B) dots of coagulated ink by electrocoagulation; and
a plurality of transfer parts (70) which bring a substrate (80) into contact with
the dots of coagulated ink to cause transfer of the dots of coagulated ink from said
positive electrode active surface (12B) to said substrate (80);
characterised by a plurality of fogging ink removing portions which supply a first oily substance
(140) onto a non-image portion of said said positive electrode active surface (12B)
and remove fogging ink (130) mixed with the first oily substance (140) from said non-image
portion of said positive electrode active surface (12B) without altering said dots
of coagulated ink.
12. An electrocoagulation printing system according to Claim 11, comprising a plurality
of printing stations (10), characterised in that each of said printing stations (10) has the positive electrode (12), one of said
plurality of ink feeding parts (32), one of said plurality of negative electrodes,
one of said plurality of fogging ink removing portions (40) and one of said plurality
of transfer parts (70).
13. An electrocoagulation printing system according to Claim 11, comprising the positive
electrode (12'), and a plurality of printing stations (88), characterised in that each printing station (88) has one of said plurality of ink feeding parts (32), one
of said plurality of negative electrodes, one of said plurality of fogging ink removing
portions (40), and one of said plurality of transfer parts (70), and further characterised in that said plurality of printing stations (88) are disposed along the path of the positive
electrode (12').
14. An electrocoagulation printing system according to any of Claims 11 to 13, characterised by a coating part (14) for coating the positive electrode active surface (12B) with
a second oily substance.
1. Ein Verfahren zum Drucken mittels elektrischer Koagulation mit den folgenden Schritten:
(a) Bilden einer positiven Elektrode (12) aus einem elektrolytisch inerten Metall
und mit einer kontinuierlichen, passivierten Oberfläche als aktive Fläche einer positiven
Oberfläche (12B), die sich entlang eines vorgegebenen Wegs bewegt;
(b) Bilden einer Vielzahl von Punkten aus einem koagulierten Farbstoff, die das gewünschte
Bild wiedergeben, durch Elektrokoagulation einer elektrisch zu koagulierenden Druckfarbe
(110);
(c) In Kontakt Bringen eines Substrats (80) mit den Punkten koagulierten Farbstoffs
zur Verursachung eines Transfers der Punkte des koagulierten Farbstoffs von der aktiven
Oberfläche der positiven Elektrode (12B) auf das Substrat (80),
gekennzeichnet durch zwischen den Schritten (b) und (c):
(d) Aufbringen einer ersten öligen Substanz (140) auf die aktive Oberfläche (12B)
der positiven Elektrode zum Vermischen der ersten öligen Substanz (140) mit Schleierfarbe
(130) in einem Nicht-Bildbereich;
(e) Entfernen des Schleierfarbstoffs (13), der mit der ersten öligen Substanz vermischt
ist, von dem Nicht-Bildbereich der aktiven Oberfläche (12B) ohne Beeinträchtigen der
Punkte des koagulierten Farbstoffs.
2. Ein Verfahren zum Drucken mittels elektrischer Koagulation, bei dem das Elektrokoagulationsverfahren
nach Anspruch 1 angewendet wird, wobei
eine Mehrzahl von Druckstufen definiert werden, die an vorbestimmten Orten entlang
des Weges angeordnet sind und die jeweils eine andere Elektrokoagulations-Druckfarbe
(110) verwenden, und die Schritte (b), (d), (e) und (c) mehrmals wiederholt werden,
wodurch mehrere Bilder an dem jeweiligen Transferteil auf dem Substrat reproduziert
werden.
3. Ein Verfahren zum Drucken mittels elektrischer Koagulation nach Anspruch 1 oder Anspruch
2, dadurch gekennzeichnet, dass die erste ölige Substanz (140) aus der Gruppe bestehend aus ungesättigten Fettsäuren
und ungesättigten pflanzlichen Ölen gewählt ist.
4. Ein Verfahren zum Drucken mittels elektrischer Koagulation nach Anspruch 1 oder Anspruch
2,
dadurch gekennzeichnet, dass der Schritt (b) die folgenden Schritte aufweist:
(i) Vorsehen einer Mehrzahl von elektrolytisch inerten negativen Elektroden, die voneinander
elektrisch isoliert und in geradliniger Ausrichtung angeordnet sind, um eine Reihe
von entsprechenden aktiven Flächen negativer Elektroden zu bilden, die in einer Ebene
parallel zu der Längsachse der positiven Elektrode (12) und mit einem konstanten vorgegebenen
Spalt von der aktiven Fläche (12B) der positiven Elektrode beabstandet angeordnet
sind, wobei die negativen Elektroden voneinander um eine Strecke beabstandet sind,
die wenigstens dem Elektrodenabstand gleich ist;
(ii) Beschichten der aktiven Fläche (12B) der positiven Elektrode mit einer zweiten
öligen Substanz zur Bildung von Mikro-Tröpfchen der zweiten öligen Substanz auf der
Oberfläche (12B);
(iii) Füllen des Elektrodenspalts mit der Elektrokoagulationsdruckfarbe (110);
(iv) elektrisches Beaufschlagen ausgewählter der negativen Elektroden zum Bewirken
einer selektiven Koagulation der Elektrokoagulationsfarbe (110) und Anhaften der koagulierten
Druckfarbe auf die aktive Oberfläche (12B) der positiven Elektrode, die mit der zweiten
öligen Substanz beschichtet ist, gegenüberliegend zu de aktiven Elektrodenflächen
der elektrisch beaufschlagten negativen Elektroden während die positive Elektrode
(13) gedreht wird, wodurch sich Punkte der koagulierten Druckfarbe bilden; und
(v) Entfernen aller verbleibender nicht-koagulierter Druckfarbe von der aktiven Fläche
(12B) der positiven Elektrode.
5. Ein Verfahren zum Drucken mittels elektrischer Koagulation nach Anspruch 4,
dadurch gekennzeichnet, dass Schritt (b) (ii) die folgenden Schritte aufweist:
Vorsehen erster und zweiter Distributionswalzen (22, 24), die sich parallel zu der
positiven Elektrode (12) erstrecken und jeweils eine Außenbeschichtung bestehend aus
einem Keramikoxidmaterial haben;
Aufbringen einer öligen Substanz auf die keramische Beschichtung der ersten Distributionswalze
(22) zum Bilden eines Films der zweiten öligen Substanz, der die Fläche der keramischen
Beschichtung gleichförmig belegt, wobei der aus der zweiten öligen Substanz bestehende
Film wenigstens teilweise in Mikro-Tröpfchen mit einer im wesentlichen gleichmäßigen
Größe und Verteilung zerfällt;
Transferieren des wenigstens teilweise zerfallenen Films von der ersten Distributionswalze
(22) auf die zweite Distributionswalze (24), um ein vollständiges Zerfallen des Films
auf der keramischen Beschichtung der zweiten Distributionswalze (24) in die Mikro-Tröpfchen
mit im wesentlichen gleichförmiger Größe und Verteilung zu bewirken; und
Transferieren der Mikro-Tröpfchen von der keramischen Beschichtung der zweiten Distributionswalze
(24) auf die aktive Fläche (12B) der positiven Elektrode.
6. Ein Verfahren zum Drucken mittels elektrischer Koagulation nach einem der Ansprüche
1, 2 oder 4, dadurch gekennzeichnet, dass eine Mischung von Schleierfarbe, die von der aktiven Fläche (12B) der positiven Elektrode
entfernt ist, und der ersten öligen Substanz (140) gesammelt wird, die erste ölige
Substanz (140) von der gesammelten Mischung getrennt wird und die abgetrennte ölige
Substanz wieder auf die aktive Fläche (12B) der positiven Elektrode aufgebracht wird.
7. Ein Verfahren zum Drucken mittels elektrischer Koagulation nach Anspruch 6, dadurch gekennzeichnet, dass die erste ölige Substanz (140) von der Mischung durch Zugeben von Wasser zu der Mischung
zur Bildung einer wässrigen Phase, die die entfernte Schleierfarbe (130) enthält und
eine ölige Phase, die die erste ölige Substanz (140) enthält, Trennen der öligen Phase
von der wässrigen Phase, Filtern der abgetrennten öligen Phase zum Entfernen der suspendierten
Festteile und Rückgewinnen der gefilterten öligen Phase zur erneuten Aufbringung auf
die aktive Fläche (12B) der positiven Elektrode (12B).
8. Eine Vorrichtung (10) zum Drucken mittels elektrischer Koagulation, mit:
einer positiven Elektrode (12), die aus einem elektrolytisch inerten Metall gefertigt
ist und eine kontinuierliche, passivierte Fläche als aktive Fläche (12B) der positiven
Elektrode hat und sich entlang eines vorgegebenen Wegs bewegt,
einem Farbzufuhrteil (32), das Elektrokoagulationsdruckfarbe (110) auf die aktive
Fläche (12B) der positiven Elektrode aufbringt,
einer negative Elektrode zum Reproduzieren von Punkten der Koagulationsfarbe auf der
aktiven Fläche (12b) der positiven Elektrode durch Elektrokoagulation, und
einem Transferteil (70), das ein Substrat (80) in Berührung mit den Punkten koagulierter
Druckfarbe bringt, um einen Transfer der Punkte koagulierter Farbe von der aktiven
Fläche (12B) der positiven Elektrode auf das Substrat (80) zu bewirken,
gekennzeichnet durch
einen Schleierfarbenentfernungsabschnitt (40), der eine erste ölige Substanz (140)
auf den Nicht-Bildbereich der aktiven Fläche (12B) der positiven Elektrode aufbringt
und mit der erst öligen Substanz vermischte Schleierfarbe (130) von dem Nicht-Bildbereich
der aktiven Fläche (12B) entfernt, ohne die Punkte der koagulierten Farbe zu beeinflussen.
9. Eine Vorrichtung (10) zum Drucken mittels elektrischer Koagulation nach Anspruch 8,
gekennzeichnet durch einen Beschichtungsteil (14) zum Beschichten der aktiven Fläche (12B) der positiven
Elektrode mit einer zweiten öligen Substanz.
10. Eine Vorrichtung (10) zum Drucken mittels elektrischer Koagulation nach Anspruch 8,
gekennzeichnet durch Zirkulationsmittel (44, 46, 52, 54), in denen ein Gemisch aus der Schleierfarbe (130),
die von der aktiven Fläche (12B) der positiven Elektrode entfernt worden ist, und
der ersten öligen Substanz (140) gesammelt wird, die erste ölige Substanz (140) aus
dem gesammelten Gemisch abgetrennt wird und die abgetrennte erste ölige Substanz (140)
wieder auf die aktive Fläche (12B) der positiven Elektrode aufgebracht wird.
11. Ein System zum Drucken mittels elektrischer Koagulation, mit:
wenigstens einer positiven Elektrode (12, 12'), die aus einem elektrolytisch inerten
Metall gefertigt ist und eine kontinuierliche, passivierte Fläche als aktive Fläche
(12B) der positiven Elektrode hat und sich entlang eines vorgegebenen Wegs bewegt,
einer Mehrzahl von Farbzufuhrteilen(32), die Elektrokoagulationsdruckfarbe (110) auf
die aktive Fläche (12B) der positiven Elektrode aufbringen,
einer Mehrzahl von negativen Elektroden zum Reproduzieren von Punkten der Koagulationsfarbe
auf der aktiven Fläche (12b) der positiven Elektrode durch Elektrokoagulation, und
einer Mehrzahl von Transferteilen (70), die ein Substrat (80) in Berührung mit den
Punkten koagulierter Druckfarbe bringen, um einen Transfer der Punkte koagulierter
Farbe von der aktiven Fläche (12B) der positiven Elektrode auf das Substrat (80) zu
bewirken,
gekennzeichnet durch
eine Mehrzahl von Schleierfarbenentfernungsabschnitten, die eine erste ölige Substanz
(140) auf den Nicht-Bildbereich der aktiven Fläche (12B) der positiven Elektrode aufbringen
und mit der ersten öligen Substanz vermischte Schleierfarbe (130) von dem Nicht-Bildbereich
der aktiven Fläche (12B) entfernen, ohne die Punkte der koagulierten Farbe zu beeinflussen.
12. System zum Drucken mittels elektrischer Koagulation nach Anspruch 11 mit einer Mehrzahl
von Druckstationen, dadurch gekennzeichnet, dass jede Druckstation (10) die positive Elektrode (12), eine aus der Mehrzahl der Farbzufuhrteile
(32), eine aus der Mehrzahl von negativen Elektroden, eine aus der Mehrzahl von Schleierfarbenentfernungsabschnitten
(40) und eine aus der Mehrzahl von Transferteilen (70) aufweist.
13. System zum Drucken mittels elektrischer Koagulation nach Anspruch 11 mit der positiven
Elektrode (12'), und einer Mehrzahl von Druckstationen (88), dadurch gekennzeichnet, dass jede der Druckstationen (88) eine aus der Mehrzahl der Farbzufuhrteile (32), eine
aus der Mehrzahl von negativen Elektroden, eine aus der Mehrzahl von Schleierfarbenentfernungsabschnitten
(40) und eine aus der Mehrzahl von Transferteilen (70) aufweist und weiter dadurch gekennzeichnet, dass die Mehrzahl von Druckstationen (88) entlang des Weges der positiven Elektrode (12')
angeordnet sind.
14. System zum Drucken mittels elektrischer Koagulation nach einem der Ansprüche 11 bis
13, gekennzeichnet durch einen Beschichtungsteil (14) zum Beschichten der aktiven Fläche (12B) der positiven
Elektrode mit einer zweiten öligen Substanz.
1. Procédé d'impression par électrocoagulation, comprenant les étapes consistant à :
(a) prévoir une électrode positive (12) formée d'un métal inerte du point de vue électrolytique
et possédant une surface continue passivée en tant que surface active (12B) de l'électrode
positive se déplaçant le long d'un trajet prédéterminé,
(b) former sur ladite surface active (12B) de l'électrode positive une pluralité de
points d'encre coagulée représentatifs d'une image désirée par électrocoagulation
de l'encre d'impression par électrocoagulation (110);
(c) placer un substrat (80) en contact avec lesdits points d'encre coagulée pour provoquer
le transfert des points d'encre coagulée depuis la.surface active (12B) de l'électrode
positive sur le substrat (80),
caractérisé en ce qu'entre les étapes (b) et (c):
(d) on applique une première substance huileuse (140) sur ladite surface active (12B)
de l'électrode positive pour mélanger la première substance huileuse (140) à une encre
de voilement (130) dans une partie ne correspondant pas à l'image;
(e) on retirer l'encre de voilement (130) mélangée à la première substance huileuse
(140), de ladite partie ne correspondant pas à l'image de ladite surface active (12B)
de l'électrode positive sans modification desdits points d'encre coagulée.
2. Procédé d'impression par électrocoagulation, pour lequel on applique le procédé d'impression
par coagulation selon la revendication 1, selon lequel
on définit une pluralité d'étages d'impression, qui sont disposés en des emplacements
prédéterminés le long dudit trajet, et lors de chaque utilisation d'une encre différente
d'impression par électrocoagulation (110), on répète à plusieurs reprises les étapes
(b), (d), (e) et (c), ce qui a pour effet que plusieurs images sont reproduites dans
la partie de transfert respective sur ledit substrat (80).
3. Procédé d'impression par électrocoagulation selon la revendication 1 ou la revendication
2, caractérisé en ce que ladite première substance huileuse (140) est choisie dans le groupe comprenant des
acides gras insaturés et des huiles végétales insaturées.
4. Procédé d'impression par électrocoagulation selon la revendication 1 ou la revendication
2,
caractérisé en ce que ladite étape (b) inclut les étapes consistant à :
(i) prévoir une pluralité d'électrodes négatives inertes du point de vue électrolytique,
qui sont isolées électriquement les unes des autres et sont disposées selon un alignement
rectiligne pour définir une série de surfaces actives d'électrodes négatives correspondantes
disposées dans un plan parallèle à l'axe longitudinal de ladite électrode positive
(12) et en étant séparées de la surface active (12B) de l'électrode positive par un
intervalle prédéterminé constant, lesdites électrodes négatives étant séparées les
unes des autres par une distance au moins égale audit intervalle entre électrodes;
(ii) recouvrir une surface active (12B) de l'électrode positive par une seconde substance
huileuse pour former des micro-gouttelettes de la seconde substance huileuse sur ladite
surface (12B);
(iii) remplir ledit intervalle entre électrodes avec ladite encre d'impression par
coagulation (110);
(iv) activer électriquement des électrodes sélectionnées parmi lesdites électrodes
négatives pour provoquer une coagulation sélective de l'encre d'impression par électrocoagulation
(110) et l'adhérence de l'encre coagulée sur la surface active (12B) de l'électrode
positive recouverte par la seconde substance huileuse à l'opposé des surfaces actives
desdites électrodes négatives excitées, alors que ladite électrode positive (12) tourne,
ce qui conduit à la formation de points de ladite encre coagulée; et
(v) éliminer toute huile non coagulée restante de ladite surface active (12B) de l'électrode
positive.
5. Procédé d'impression par électrocoagulation selon la revendication 4, caractérisé en ce que ladite étape (b) (ii) inclut les étapes consistant à : prévoir des premier et second
rouleaux de distribution (22,24) qui s'étendent parallèlement à ladite électrode positive
(12) et comprennent chacun un revêtement périphérique comprenant un matériau céramique
à base d'oxyde; appliquer ladite seconde substance huileuse au revêtement céramique
dudit premier rouleau de distribution (22) pour former sur la surface de ce rouleau
un film de ladite seconde substance huileuse recouvrant uniformément la surface dudit
revêtement céramique, ledit film de la seconde substance huileuse se divisant partiellement
en micro-gouttelettes possédant une taille et une distribution essentiellement uniformes;
transférer le au moins un film divisé partiellement depuis ledit premier rouleau de
distribution (22) audit second rouleau de distribution (24) de manière à amener ledit
film à se diviser essentiellement complètement sur le revêtement céramique dudit second
rouleau de distribution (24) pour former lesdites micro-gouttelettes ayant une taille
et une distribution essentiellement uniformes; et transférer lesdites micro-gouttelettes
depuis le revêtement céramique dudit second rouleau de distribution (24) à ladite
surface active (12B) de l'électrode positive.
6. Procédé d'impression par électrocoagulation selon l'une quelconque des revendications
1, 2 et 4, caractérisé en ce qu'un mélange de l'encre de voilement retirée de ladite surface active (12B) de l'électrode
positive et de ladite première substance huileuse (140) est collecté, la première
substance huileuse (140) est séparée du mélange collecté, et la première substance
huileuse séparée (140) est appliquée à nouveau sur ladite surface active (12B) de
l'électrode positive.
7. Procédé d'impression par électrocoagulation selon la revendication 6, caractérisé en ce que ladite première substance huileuse (140) est séparée dudit mélange, par addition
d'eau audit mélange pour former une phase aqueuse contenant ladite encre de voilement
retirée (130) et une phase huileuse contenant ladite première substance huileuse (140),
avec séparation de ladite phase huileuse par rapport à la phase aqueuse, filtrage
de la phase huileuse séparée pour en éliminer des substances solides en suspension,
et récupération de la phase huileuse filtrée pour sa réapplication sur ladite surface
active (12B) de l'électrode positive.
8. Dispositif d'impression par électrocoagulation (8), comprenant :
une électrode positive (12) formée d'un métal inerte du point de vue électrolytique
et possédant une surface continue passivée en tant que surface active (12B) de l'électrode
positive, se déplaçant le long d'un trajet prédéterminé;
une partie d'amenée d'encre (32) qui envoie de l'encre d'impression par électrocoagulation
(110) à ladite surface active (12B) de l'électrode positive;
une électrode négative pour reproduire, sur ladite surface active (12B) de l'électrode
positive, des points d'encre coagulée par électrocoagulation; et
une partie de transfert (70) qui place un substrat (80) en contact avec les points
d'encre coagulée pour provoquer le transfert des points d'encre coagulée depuis ladite
surface active (12B) de l'électrode positive audit substrat (80) ;
caractérisé par
une partie (40) de réception de l'encre de voilement, qui envoie une première substance
huileuse (140) à ladite partie ne correspondant pas à l'image de ladite surface active
(12B) de l'électrode positive et retire l'encre de voilement (103) mélangée à la première
substance lumineuse (140) à partir de ladite partie ne correspondant pas à l'image
de ladite surface active (12B) de l'électrode positive, sans modification desdits
points d'encre coagulée.
9. Dispositif d'impression par électrocoagulation (10) selon la revendication 8, caractérisé par une partie de revêtement (14) servant à recouvrir la surface active (12B) de l'électrode
positive avec une seconde substance huileuse.
10. Dispositif d'impression par électrocoagulation (10) selon la revendication 8, caractérisé par des moyens de circulation (44,46,52,54), dans lesquels un mélange de l'encre de voilement
(130) retirée de ladite surface active (12B) de l'électrode positive et de la première
substance huileuse (140) est collecté, la première substance huileuse (140) est séparée
du mélange collecté, et la première substance huileuse séparée (140) est à nouveau
appliquée à ladite surface active (12B) de l'électrode positive.
11. Système d'impression par électrocoagulation comprenant :
au moins une électrode positive (12,12') formée d'un métal inerte du point de vue
électrolytique et possédant une surface continue passivée en tant que surface active
(12B) de l'électrode positive, se déplaçant le long d'un trajet prédéterminé;
une pluralité de parties d'amenée d'encre (32) qui envoient une encre d'impression
par électrocoagulation (110) à ladite surface active (12B) de l'électrode positive;
une pluralité d'électrodes négatives pour reproduire, sur ladite surface active (12B)
de l'électrode positive, des points d'encre coagulée par électrocoagulation; et
une pluralité de parties de transfert (70), qui placent un substrat (80) en contact
avec les points d'encre coagulée de manière à provoquer le transfert des points d'encre
coagulée depuis ladite surface active (12B) de l'électrode positive audit substrat
(80);
caractérisé par une pluralité de parties de retrait de l'encre de voilement, qui délivrent une première
substance huileuse (140) sur une partie ne correspondant pas à l'image de ladite surface
active (12B) de l'électrode positive et retirent l'encre de voilement (33) mélangée
à la première substance huileuse (140), de ladite partie ne correspondant pas à l'image
de ladite surface active (12B) de l'électrode positive, sans modification desdits
points d'encre coagulée.
12. Système d'impression par électrocoagulation selon la revendication 11, comprenant
une pluralité de postes d'impression (10), caractérisé en ce que chacun desdits postes d'impression (10) possède l'électrode positive (12), l'une
de ladite pluralité de parties d'amenée d'encre (32), l'une de ladite pluralité d'électrodes
négatives, l'une de ladite pluralité de parties (40) d'élimination de l'encre de voilement
et l'une de ladite pluralité de parties de transfert (70).
13. Système d'impression par électrocoagulation selon la revendication 11, comprenant
une électrode positive (12') et une pluralité de postes d'impression (88), caractérisé en ce que chaque poste d'impression (88) comporte l'une de ladite pluralité de parties d'amenée
d'encre (32), l'une de ladite pluralité d'électrodes négatives, l'une de ladite pluralité
de parties (40) de retrait de l'encre de voilement, et l'une de ladite pluralité de
parties de transfert (70), et caractérisé en outre en ce que ladite pluralité de postes d'impression (88) sont disposés le long du trajet de l'électrode
positive (12').
14. Système d'impression par électrocoagulation selon l'une quelconque des revendications
1 à 13, caractérisé par une partie de revêtement (14) servant à recouvrir la surface active (12B) de l'électrode
positive au moyen d'une seconde substance huileuse.