EP0899093A2 - Method and coating agent for electrocoagulation printing - Google Patents
Method and coating agent for electrocoagulation printing Download PDFInfo
- Publication number
- EP0899093A2 EP0899093A2 EP98116206A EP98116206A EP0899093A2 EP 0899093 A2 EP0899093 A2 EP 0899093A2 EP 98116206 A EP98116206 A EP 98116206A EP 98116206 A EP98116206 A EP 98116206A EP 0899093 A2 EP0899093 A2 EP 0899093A2
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- Prior art keywords
- positive electrode
- coating agent
- ink
- coating
- coagulated ink
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
- B41C1/00—Forme preparation
- B41C1/10—Forme preparation for lithographic printing; Master sheets for transferring a lithographic image to the forme
- B41C1/105—Forme preparation for lithographic printing; Master sheets for transferring a lithographic image to the forme by electrocoagulation, by electro-adhesion or by electro-releasing of material, e.g. a liquid from a gel
Definitions
- steps (b), (c) and (d-1) of the above electrocoagulation printing method are repeated several times to define a corresponding number of printing stages arranged at predetermined locations along the aforesaid path and each using a coloring agent of different color, and to thereby produce several differently colored images of coagulated ink which are transferred at the respective transfer positions onto the substrate in superimposed relation to provide a polychromic image.
- the coating agent of the present invention which is produced by the aforementioned method is preferably a liquid under the usual operating condition, or more specifically, at the temperature range of from about 20 to about 60°C.
- a coating agent having a form other than a liquid For example, when the coating agent of the present invention is a solid, a means is required to heat a means of applying the coating agent and/or the positive electrode surface.
- the viscosity of the coating agent is preferably from about 100 to about 100,000 cps, or more preferably, from about 1,000 to about 30,000 cps at 30°C.
- the viscosity of the coating agent can be appropriately controlled by changing the types and amount of the aforementioned silicon oxide and oily substance.
- a coating agent with high viscosity can be obtained by using either an oil-soluble thickener produced by modifying dextrin or an oil-soluble resin such as ethyl cellulose.
- step (c) of the above electrocoagulation printing method is carried out by:
- any remaining non-coagulated ink is advantageously removed from the positive electrode surface, for example, the step (c) (iv) is carried out by scraping the surface with a soft rubber squeegee 11, as shown in Fig. 2, so as to fully uncover the coagulated ink.
- the non-coagulated ink thus removed is collected and recirculated back to the aforesaid ink discharge unit.
- the belt 17 with the coagulated ink retaining surface 171 thereof imprinted with the polychromic images 200 is guided so as to travel along a path extending in a plane intersecting the longitudinal axis of the positive electrode 3 at right angles, thereby exposing the coagulated ink retaining surface to permit contacting thereof by the web S.
- the belt is preferably guided so as to travel along a horizontal path with the coagulated ink retaining surface facing downwardly, the support roller and pressure roller having rotation axes disposed in a plane extending perpendicular to the horizontal path.
- a coating agent comprising 25.0% by weight of SILYSIA 530 (BET surface area: 500 m 2 /g) manufactured by Fuji Silysia Chemical Ltd. as the silicon oxide and 75.0% by weight of oleic acid as the oily substance was produced.
- the viscosity of the coating agent was 3000 cps (30°C). Printing was performed in the same condition and method as in Example 1 except that the above coating agent was used.
- Crater-like pitting with a diameter of from about 1 to about 2 mm was observed on the surface of the positive electrode after the printing was completed. Image density of the portion corresponding to the pitting on the surface of the positive electrode was reduced, providing printing matter with uneven density.
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- Chemical & Material Sciences (AREA)
- Dispersion Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Inks, Pencil-Leads, Or Crayons (AREA)
- Printing Methods (AREA)
- Duplication Or Marking (AREA)
- Ink Jet Recording Methods And Recording Media Thereof (AREA)
- Printing Plates And Materials Therefor (AREA)
Abstract
An improved electrocoagulation printing method
comprises the steps of a) providing a positive electrode having
a passivated surface moving at substantially constant speed
along a predetermined path; b) coating the positive electrode
surface with a coating agent containing silicon oxide and an
oily substance to form on the surface micro-droplets of the
coating agent; c) forming on the positive electrode surface
having micro-droplets thereon a plurality of dots of coagulated
ink representative of a desired image, by electrocoagulation
of an electrolytically coagulable printing ink comprising an
electrolytically coagulable polymer, a liquid medium, a
soluble electrolyte and a coloring agent; and d-1) bringing
a substrate into contact with the positive electrode surface
to cause transfer of the dots of coagulated ink from the positive
electrode surface onto the substrate and thereby imprint the
substrate with the image.
The method prevents anode abrasion and pitting during
electrocoagulation printing.
Description
The present invention pertains to improvements in the
field of electrocoagulation printing. More particularly, the
invention relates to a method of preventing anode abrasion and
pitting during electrocoagulation printing.
In US Patent No. 4,895,629 of January 23, 1990, the
inventor of the present application 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
coagulated ink representative of an image are produced. These
dots of coagulated ink are thereafter contacted with a substrate
such as paper to cause transfer of the coagulated ink onto the
substrate and thereby imprint the substrate with the image.
As explained in this patent, the positive electrode is coated
with an oily substance prior to electrical energization of the
negative electrodes in order to weaken the adherence of the
dots of coagulated ink to the positive electrode. In addition,
by using an olefinic substance as the oily substance, 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.
The electrocoagulation printing ink which is injected
into the gap defined between the positive and negative
electrodes consists essentially of a solution or a dispersion
comprising an electrolytically coagulable polymer, a liquid
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 ink, any remaining non-coagulated ink 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 coagulated ink which is thereafter
transferred onto the substrate. The surface of the positive
electrode is thereafter cleaned by means of a plurality of
rotating brushes and a cleaning liquid to remove any residual
coagulated ink adhered to the surface of the positive electrode.
When a polychromic image is desired, the negative and
positive electrodes, the positive electrode coating device,
ink injector, rubber squeegee and positive electrode cleaning
device 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 ink 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 adapted to bring the substrate into contact with
the dots of coagulated ink 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.
The inventor has observed that the metal oxide used in
combination with the olefinic substance for coating the
positive electrode causes abrasion and pitting of the positive
electrode so that it is necessary to regrind the surface of
such an electrode after every forty hours of printing. This
of course requires shutdown of the printing apparatus and
removal of the electrode. Where a positive electrode made of
stainless steel or aluminum is utilized, Fe3+ or Al3+ ions are
released from the surface of the electrode as a result of the
abrasion and pitting thereof. As explained in the inventor's
copending US application No. 08/376,245, these ions crosslink
the electrolytically coagulable polymer contained in the ink,
resulting in a viscosity increase leading to an ultimate
gelation of the ink.
It is therefore an object of the present invention to
overcome the above drawbacks and to provide a method of
preventing anode abrasion and pitting during
electrocoagulation printing.
In accordance with the present invention, there is thus
provided an electrocoagulation printing method comprising the
steps of:
It has surprisingly been found, according to the
invention, that by using the coating agent containing silicon
oxide and an oily substance, one eliminates the abrasion and
pitting of the positive electrode, without substantially
affecting passivation, so that the requirement to regrind the
surface of the positive electrode is significantly reduced.
Moreover, since there is no longer any release of contaminant
ions from the surface of the positive electrode due to abrasion
and pitting thereof, the ink is stable and does not undergo
an undesirable increase in viscosity during electrocoagulation
printing. Thus, there is no longer any need to utilize two
separate inks, that is, a starting ink and a replenishing ink
having different concentrations of sequestering agent, as
proposed in the aforementioned US application No. 08/376,245,
and one may use only the starting ink which contains a
sequestering agent for complexing other contaminant ions.
Where a polychromic image is desired, steps (b), (c) and
(d-1) of the above electrocoagulation printing method are
repeated several times to define a corresponding number of
printing stages arranged at predetermined locations along the
aforesaid path and each using a coloring agent of different
color, and to thereby produce several differently colored
images of coagulated ink which are transferred at the respective
transfer positions onto the substrate in superimposed relation
to provide a polychromic image. It is also possible to repeat
several times steps (a) through (d-1) to define a corresponding
number of printing stages arranged in tandem relation and each
using a coloring agent of different color, and to thereby
produce several differently colored images of coagulated ink
which are transferred at respective transfer positions onto
the substrate in superimposed relation to provide a polychromic
image, the substrate being in the form of a continuous web which
is passed through the respective transfer positions for being
imprinted with the colored images at the printing stages.
Alternatively, the printing stages defined by repeating
several times steps (a) through (d-1) can be arranged around
a single roller adapted to bring the substrate into contact
with the dots of coagulated ink of each printing stage and the
substrate which is in the form of a continuous web is partially
wrapped around the roller and passed through the respective
transfer positions for being imprinted with the colored images
at the printing stages. The last two arrangements are described
in the inventor's US Patent No. 4,895,629.
When a polychromic image of high definition is desired,
it is preferable to bring an endless non-extendible belt moving
at substantially the same speed as the positive electrode and
having on one side thereof a coagulated ink retaining surface
adapted to releasably retain dots of coagulated ink to cause
transfer of the differently colored images at the respective
transfer positions onto the coagulated ink retaining surface
of such a belt in superimposed relation to provide a polychromic
image, and thereafter bring the substrate into contact with
the coagulated ink retaining surface of the belt to cause
transfer of the polychromic image from the coagulated ink
retaining surface onto the substrate and to thereby imprint
the substrate with the polychromic image.
As explained in a copending US patent application in the
name of the inventor, filed concurrently with the present
application, by utilizing an endless non-extendible belt
having a coagulated ink retaining surface such as a porous
surface on which dots of coagulated ink can be transferred and
by moving such a belt from one printing unit to another, so
that the coagulated ink retaining surface of the belt contacts
the coagulated ink in sequence, it is possible to prevent the
paper web from being displaced between the positive electrode
and the pressure rollers in a direction parallel to the
longitudinal axis of the positive electrode, and to
significantly improve the registration of the differently
colored images upon their transfer onto the coagulated ink
retaining surface of the belt, thereby providing a polychromic
image of high definition which can thereafter be transferred
onto the paper web or other substrate and in which the
differently colored images are perfectly superimposed. For
example, use can be made of a belt comprising a plastic material
having a porous coating of silica.
Accordingly, the present invention also provides, in
another aspect thereof, a multicolor electrocoagulation
printing method comprising the steps of:
The invention provides a coating agent to be used in
coating a positive electrode surface in advance of forming on
the positive electrode surface a plurality of dots of coagulated
ink by electrocoagulation of an electrolytically coagulable
printing ink, the coating agent containing silicon oxide and
an oily substance. The silicon oxide may be silicon dioxide.
The oily substance may be an olefinic compound, such as
unsaturated fatty acid selected from the group consisting of
arachidonic acid, linoleic acid, linolenic acid, oleic acid
and palmitoleic acid.
The coating agent according to this invention contains
silicon oxide and an oily substance. The silicon oxide can be
silicon dioxide (silica). The use of hydrophilic silicon
dioxide may be preferable. Still more, it is preferable for
the silicon dioxide to have a BET surface area of from about
100 to about 600 m2/g. For example, a product sold by Degussa
AG under the trade name of FK500LS having a BET surface area
of about 450 m2/g can preferably be used. The silicon dioxide
is preferably used in an amount of from about 2 to about 40%
by weight, or more preferably, in an amount of from about 5
to about 30% by weight, based on the total weight of the coating
agent.
The oily substance can be fatty acids, higher alcohols,
ester compounds of fatty acids. Preferably the oily substance
is a non-volatile compound. A coating agent containing a
volatile oily substance tends to change in the composition
thereof as the printing time passes. Any such oily substance
can be used singly or in combination.
Examples of fatty acids include unsaturated fatty acids
such as arachidonic acid, linoleic acid, linolenic acid, oleic
acid, palmitoleic acid and myristoleic acid, and saturated
fatty acids such as caprylic acid, pelargonicacid, capricacid,
lauric acid, isostearic acid, myristic acid and stearic acid.
Examples of higher alcohols include octyl alcohol, decyl
alcohol, lauryl alcohol, myristyl alcohol, oleyl alcohol,
isostearyl alcohol, 2-hexadecyl alcohol and 2-octyldodecyl
alcohol. Given as examples of the ester compounds of fatty
acids are unsaturated or saturated monoesters, diesters and
triesters.
Examples of monoesters include: monoesters of
unsaturated fatty acids such as methyl oleate, ethyl oleate,
propyl oleate, butyl oleate, isobutyl oleate, octyl oleate,
isooctyl oleate, lauryl oleate, oleyl oleate, 2-ethylhexyl
oleate, methyl linoleate, methyl linolenate and methyl
ricinoleate; monoesters of saturated fatty acids such as methyl
caprylate, methyl caproate, methyl enanthate, methyl
pelargonate, methyl caprate, methyl undecanoate, methyl
laurate, methyl tridecanoate, methyl myristate, methyl
pentadecanoate, cetyl 2-ethylhexanoate, isopropyl myristate,
octyldodecyl myristate, 2-ethylhexyl stearate and isononyl
isononanate. Monoesters derived from natural fats and oils are
also used to reduce the production cost. Examples of such a
monoester include palm kernel oil methyl ester, coconut oil
methyl ester, palm oil methyl ester, beef tallow fatty acid
methyl ester, rapeseed oil methyl ester and rapeseed butyl ester.
Examples of diesters include dibutoxyethyl sebacate and
neopentyl glycol dicaprate. Examples of triesters include:
triesters of unsaturated vegetable oils such as corn oil,
linseed oil, olive oil, peanut oil, bean oil, sunflower oil,
safflower oil, palm oil, palm kernel oil, coconut oil and castor
oil; triglycerides of unsaturated fatty acids such as oleic
acid, linoleic acid and linolenc acid; triglycerides of
saturated fatty acids such as seridocaprylic acid, capric acid
and myristic acid.
The use of olefinic substances containing at least one
double bond is preferable, then 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. Particularly, unsaturated fatty acid selected
from the group consisting of arachidonic acid, linoleic acid,
linolenic acid, oleic acid and palmitoleic acid can be
preferably used.
A coating agent containing silicon dioxide as silicon
oxide and unsaturated fatty acid as an oily substance is
preferably used. A preferred coating agent contains form about
5 to about 10% by weight of silicon dioxide and from about 90
to about 95% by weight of unsaturated fatty acid, or more
preferably, about 7.5% by weight of silicon dioxide and about
92.5% by weight of unsaturated fatty acid so as to achieve the
desired action of the coating agent while keeping suitable
viscosity thereof.
The coating agent of the present invention may further
contain a nonionic surfactant having a chain of polyethylene
oxide (CH2CH2O), which has an effect on softening of the dots
of coagulated ink, to weaken the adhesion of the dots of
coagulated ink to the positive electrode. The types and amount
of the surfactant are preferably determined so as to impart
an appropriate hardness to the dots of coagulated ink.
Specifically, the amount of the surfactant is preferably from
about 5 to about 50% by weight, or more preferably, from about
10 to about 40% weight. Examples of the surfactants include
polyoxyethylene lauryl ether, polyoxyethylene oleyl ether,
polyoxyethylene octylphenyl ether, polyoxyethylene
nonylphenyl ether, polyoxyethylene sorbitanoleic acid ester,
polyoxyethylene tetraoleic acid sorbitol and polyoxyethylene
polydimethylsiloxane. The coating agent may also contain
unsaturated vegetable wax such as carnauba wax to adjust the
viscosity as well as to increase the lubricating property of
the coating agent.
The coating agent of the present invention can be produced
only by mixing with stirring using a mixer or by using a
dispersing machine to micronize silicon oxide further. As a
dispersing machine, generally used one such as roller mill,
ball mill, pebble mill, attritor, or sand mill may be adopted.
A coating agent containing silicon dioxide with a desired
particle size distribution can be produced by appropriately
controlling the dispersing condition, for example, a size of
milling media used in a dispersing machine, packing density
of the milling media, dispersion treating time and discharge
rate. Unexpected bulky particles mixed in the coating agent
of the present invention may prevent the electrocoagulation
of printing ink comprising an electrolytically coagulable
polymer, thereby to lower the image quality. It is therefore
desirable to remove the bulky particles and the like by
filtration or the like. As a filter, a gravitational, vacuum,
pressure or centrifugal filter, or any conventionally known
apparatus may be used.
The coating agent of the present invention which is
produced by the aforementioned method is preferably a liquid
under the usual operating condition, or more specifically, at
the temperature range of from about 20 to about 60°C. There
is a tendency to accompany difficulty in coating uniformly the
positive electrode surface with a coating agent having a form
other than a liquid. For example, when the coating agent of
the present invention is a solid, a means is required to heat
a means of applying the coating agent and/or the positive
electrode surface. The viscosity of the coating agent is
preferably from about 100 to about 100,000 cps, or more
preferably, from about 1,000 to about 30,000 cps at 30°C. The
viscosity of the coating agent can be appropriately controlled
by changing the types and amount of the aforementioned silicon
oxide and oily substance. In addition, a coating agent with
high viscosity can be obtained by using either an oil-soluble
thickener produced by modifying dextrin or an oil-soluble resin
such as ethyl cellulose.
An electrolytically coagulable printing ink according
to this invention contains at least an electrolytically
coagulable polymer, a liquid medium, a soluble electrolyte and
a coloring agent. As an electrolytically coagulable polymer,
use can be made of a linear high molecular weight compound,
that is , a polymer having a weight average molecular weight
between about 10,000 and about 1,000,000, preferably between
about 100,000 and about 600,000.
Moreover, the electrolytically coagulable polymer
suitably contains a reaction site which includes a functional
group selected from the group consisting of an amino group,
an amide group and a carboxyl group. The reaction site makes
a chemical bond with the multivalent metallic ion produced from
the positive electrode, especially a trivalent ion such as
ferric ion and aluminum ion, to thereby cause an
electrocoagulation of the ink.
Examples of suitable polymers include natural polymers
such as albumin, gelatin, casein and agar, and synthetic
polymers such as polyacrylic acid and polyacrylamide. A
particularly preferred polymer is an anionic copolymer of
acrylamide and acrylic acid having a weight average molecular
weight of about 250,000 and sold by Cyanamid Inc. under the
trade mark ACCOSTRENGTH 86.
The polymer used can be in a liquid form either solution
or dispersion which includes colloid, etc. The polymer can
preferably be used in an amount of from about 6.5 to about 12%
by weight, or more preferably, in an amount of from about 7
to about 10% by weight, based on the total weight of the ink,
so as to provide suitable tone of dots of coagulated ink while
keeping suitable viscosity of the coating agent. Water can
preferably be used as a liquid medium for dispersing or
dissolving the polymer to provide the desired electrolytically
coagulable printing ink.
Preferred soluble electrolytes include alkali metal
halides such as lithium chloride, sodium chloride and potassium
chloride, and alkaline earth metal halides such as calcium
chloride. Potassium chloride is particularly preferred. The
soluble electrolyte can preferably be used in an amount of from
about 4.5 to about 10% by weight based on the total weight of
the ink, when operating at a temperature ranging from about
35 to about 60°C.
The coloring agent can be a dye or a pigment. Examples
of suitable dyes are water soluble dyes, include indigo dye,
azo dye, anthraquinone dye, fluoran dye, dioxazine dye, oxazine
dye and phthalocyanine dye. Examples of suitable pigments
include organic pigments such as azo pigment, phthalocyanine
pigment, quinacridone pigment, anthraquinone pigment,
dioxazine pigment, thioindigo pigment, perynone pigment,
perylene pigment, isoindolinon pigment and azomethine pigment,
and inorganic pigments such as carbon black. A dispersing
agent may be added for uniformly dispersing the pigment into
the ink. Preferred dispersing agents include an anionic
dispersing agent; a metal salt of naphtalenesulfonic acid-formaldehyde
condensation product. The pigment can preferably
be used in an amount of from about 6.5 to about 15% by weight,
and the dispersing agent in an amount of from about 0.1 to about
6.0% by weight, based on the total weight of the ink.
The positive electrode used can be in the form of a moving
endless belt as described in the inventor's US Patent No.
4,661,222, or in the form of a revolving cylinder as described
in the aforementioned US Patent Nos. 4,895,629 and 5,538,601,
the teachings of which are incorporated herein by reference.
Referring now to Fig. 1, there is illustrated an
embodiment of an electrocoagulation printing apparatus for
carrying out the method of the present invention. This
apparatus 1 comprises a positive electrode 3 made of stainless
steel, a plurality of negative electrodes 5 having a diameter
of 50 µm and spaced from the positive electrode 3 by a constant
predetermined gap, a coating unit 7 for coating the positive
electrode surface with a coating agent to form micro-droplets
thereof on the positive electrode surface, an ink discharge
unit 9 for supplying electrocoagulation printing ink to the
positive electrode 3, a removing unit 11 using a soft
polyurethane squeegee for removing non-coagulated ink from the
positive electrode surface, a transferring unit 13 using a
pressure roller formed of polyurethane for transferring the
dots of coagulated ink onto the substrate from the positive
electrode surface, and a cleaning unit 15 for cleaning the
positive electrode surface by jetting a cleaning liquid
thereagainst. As shown in Fig. 1, when using a positive
electrode in the form of the revolving cylindrical positive
electrode, the printing steps (b), (c) and (d-1) are arranged
around the positive cylindrical electrode. Figure 2 shows an
enlarged schematic illustration of a printing unit of an
electrocoagulation printing apparatus, explaining the method
of the steps of the present invention, in which parts similar
to those previously described with reference to Fig. 1 are
denoted by the same reference numerals.
Preferably, the positive electrode surface and the ink
are maintained at a temperature of about 35-60°C, or more
preferably about 40°C, to increase electric conductivity of the
ink in step (c) and a release of metal ions from the positive
electrode surface into ink, thereby the metal ions are released
in a quantity sufficient to increase optical density of the
coagulated ink, and a coagulation efficiency in step (c) is
increased.
The coating agent of the invention is advantageously
applied onto the positive electrode surface by providing a
distribution roller extending parallel to the positive
cylindrical electrode and having a peripheral coating
comprising an oxide ceramic material, applying the coating
agent onto the ceramic coating to form on a surface thereof
a film of the coating agent uniformly covering the surface of
the ceramic coating, the film of coating agent breaking down
into micro-droplets having substantially uniform size and
distribution, and transferring the micro-droplets from the
ceramic coating onto the positive electrode surface. As
explained in inventor's US Patent No. 5,449,392 of September
12, 1995, the teaching of which is incorporated herein by
reference, 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 coating agent
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 generally have
a size ranging from about 1 to about 5 µ. A particularly
preferred oxide ceramic material forming the aforesaid ceramic
coating comprises a fused mixture of alumina and titania. Such
a mixture can comprise form about 60 to about 90% by weight
of alumina and from about 10 to 40% by weight of titania.
According to a preferred embodiment of the invention,
as shown in Fig. 2, the coating agent is applied onto the ceramic
coating by disposing an applicator roller 73 parallel to the
distribution roller 71 and in pressure contact engagement
therewith to form a first nip 72, and rotating the applicator
roller 73 and the distribution roller 71 in register while
feeding the coating agent into the first nip 72 by using a ink
feeding device 77, whereby the coating agent upon passing
through the first nip 72 forms a film uniformly covering the
surface of the ceramic coating. The micro-droplets are
advantageously transferred from the distribution roller 71 to
the positive electrode 3 by disposing a transfer roller 75
parallel to the distribution roller 71 and in contact engagement
therewith to form a second nip 74, positioning the transfer
roller 75 in pressure contact engagement with the positive
electrode 3 to form a third nip 76, and rotating the transfer
roller 75 and the positive electrode 3 in register for
transferring the micro-droplets from the distribution roller
71 to the transfer roller 75 at the second nip 74 and thereafter
transferring the micro-droplets from the transfer roller 75
to the positive electrode 3 at the third nip 76. Such an
arrangement of rollers is described in the aforementioned US
Patent No. 5,449,392.
Preferably, the applicator roller and the transfer roller
are each provided with a peripheral covering of a resilient
material which is resistant to attack by the coating agent,
such as a synthetic rubber material. For example, use can be
made of a polyurethane having a Shore A hardness of from about
50 to about 70 in the case of the applicator roller, or a Shore
A hardness of from about 60 to about 80 in the case of the transfer
roller.
When use is made of a positive electrode of cylindrical
configuration rotating at substantially constant speed about
its central longitudinal axis, step (c) of the above
electrocoagulation printing method is carried out by:
As explained in US Patent No. 4,895,629, spacing of the
negative electrodes from one another by a distance which is
equal to or greater than the electrode gap prevents the negative
electrodes from undergoing edge corrosion. On the other hand,
coating of the positive electrode with the coating agent of
this invention prior to electrical energization of the negative
electrodes weakens the adherence of the dots of coagulated ink
to the positive electrode and also prevents an uncontrolled
corrosion and pitting of the positive electrode.
Examples of suitable metals from which the positive and
negative electrodes can be made are stainless steel, platinum,
chromium, nickel and aluminum. The positive electrode is
preferably made of stainless steel, tin or aluminum so that
upon electrical energization of the negative electrodes,
dissolution of the passive oxide film on such an electrode
generates metallic ions, especially multivalent ions, which
then initiate coagulation of the ink. Particularly, trivalent
ions such as ferric ion and aluminum ion are suitable for causing
coagulation of the ink.
The gap which is defined between the positive and negative
electrodes can range from about 50 µm to about 100 µm, the
smaller the electrode gap the sharper are the dots of coagulated
ink produced. Where the electrode gap is of the order of 50
µm, the negative electrodes are preferably spaced from one
another by a distance of about 75 µm.
The positive electrode surface coated with the coating
agent is preferable polished to increase the adherence of the
micro-droplets onto the positive electrode surface, prior to
step (c) (ii). For example, as shown in Fig. 2, use can be made
of a rotating brush 8 provided with a plurality of radially
extending bristles 81 made of horsehair and having extremities
contacting the surface of the positive electrode 3. The
friction caused by the bristles 81 contacting the surface of
the positive electrode 3 upon rotation of the brush 8 has been
found to increase the adherence of the micro-droplets onto the
positive electrode surface.
The step (c) (ii) of the above electrocoagulation
printing method is advantageously carried out by continuously
discharging the ink onto the positive electrode surface 3 from
an ink discharge unit 9 disposed adjacent the electrode gap
6 and allowing the ink to flow along the positive electrode
surface, the ink being thus carried by the positive electrode
3 upon rotation thereof to the electrode gap 6 to fill same.
After coagulation of the ink, any remaining non-coagulated
ink is advantageously removed from the positive
electrode surface, for example, the step (c) (iv) is carried
out by scraping the surface with a soft rubber squeegee 11,
as shown in Fig. 2, so as to fully uncover the coagulated ink.
Preferably, the non-coagulated ink thus removed is collected
and recirculated back to the aforesaid ink discharge unit.
The optical density of the dots of coagulated ink may
be varied by varying the voltage and/or pulse duration of the
pulse-modulated signals applied to the negative electrodes.
According to a preferred embodiment, as shown in Fig.
2, step (d-1) is preferably carried out by providing at each
transfer position a pressure roller 13 extending parallel to
the positive cylindrical electrode 3 and pressed thereagainst
to form a nip 14 and permit the pressure roller 13 to be driven
by the positive electrode 3 upon rotation thereof, and passing
the substrate S through the nip 14. Preferably, the pressure
roller is provided with a peripheral covering of a synthetic
rubber material such as a polyurethane having a Shore A hardness
of about 95. A polyurethane covering with such a hardness has
been found to further improve transfer of the coagulated ink
from the positive electrode surface onto the substrate. The
pressure exerted between the positive electrode and the
pressure roller preferably ranges from about 50 to about 100
kg/cm2.
After step (d-1), the positive electrode surface is
generally cleaned to remove therefrom any remaining coagulated
ink. According to a preferred embodiment, as shown in Fig. 2,
the positive electrode is rotatable in a predetermined
direction and any remaining coagulated ink is removed from the
positive electrode surface by providing an elongated rotatable
brush 151 extending parallel to the longitudinal axis of the
positive electrode 3, the brush being provided with a plurality
of radially extending bristles 152 made of horsehair and having
extremities contacting the positive electrode surface,
rotating the brush 151 in a direction opposite to the direction
of rotation of the positive electrode 3 so as to cause the
bristles 152 to frictionally engage the positive electrode
surface, and directing jets of cleaning liquid produced by high
pressure injectors 153 under pressure against the positive
electrode surface. In such an embodiment, the positive
electrode surface and the ink are preferably maintained at a
temperature of about 35-60°C by heating the cleaning liquid to
thereby heat the positive electrode surface upon contacting
same and applying the ink on the heated electrode surface to
cause a transfer of heat therefrom to the ink.
Figure 3 shows a schematic illustration of a multicolor
electrocoagulation printing apparatus for carrying out the
method of the present invention. This apparatus 2 comprises
a central positive electrode 3 in the form of a revolving
cylinder and four identical printing units 20 (20A, 20B, 20C,
20D) arranged around the positive cylindrical electrode 3,
wherein the first printing unit 20A is adopted to print in yellow
color, the second printing unit 20B in magenta color, the third
printing unit 20C in cyan color and the forth printing unit
20D in black color, respectively.
In a particularly preferred embodiment, there are at
least two printing stages each including one such pressure
roller 131 and wherein the pressure rollers are arranged in
pairs with the pressure rollers of each pair being diametrically
opposed to one another. The provision of two pairs of
diametrically opposed pressure rollers arranged around the
positive cylindrical electrode 3 prevents such an electrode
from flexing since the forces exerted by the pressure rollers
of each pair cancel each other out.
An endless non-extendible belt 17 moving at substantially
the same speed as the positive electrode 3 has on one side
thereof a coagulated ink retaining surface 171 and is brought
into contact with the positive electrode surface 3 by the
pressure rollers 131 to cause transfer of the dots of coagulated
ink from the positive electrode surface onto the coagulated
ink retaining surface 171.
Preferably, the dots of the electrocoagulation printing
ink representative of the polychromic image are moistened
between the aforementioned steps (e) and (f) so that the
polychromic image is substantially completely transferred onto
the substrate. As shown in Fig. 3, use can be made of a
moistening unit 19 comprising a plurality of spray nozzles 191.
According to another preferred embodiment, the substrate
is in the form of a continuous web and step (f) is carried out
by providing a support roller 135 and a pressure roller (not
shown) extending parallel to the support roller 135 and pressed
thereagainst to form a nip through which the belt 17 is passed,
the support roller 135 and pressure roller being driven by the
belt 17 upon movement thereof. The web S is guided by a pair
of guide rollers 137 so as to pass through the nip between the
pressure roller and the coagulated ink retaining surface 171
of the belt 17, for being imprinted with the polychromic images
200 which are transferred from the surface 171 onto the web
S. Preferably, the belt 17 with the coagulated ink retaining
surface 171 thereof imprinted with the polychromic images 200
is guided so as to travel along a path extending in a plane
intersecting the longitudinal axis of the positive electrode
3 at right angles, thereby exposing the coagulated ink retaining
surface to permit contacting thereof by the web S. Where the
longitudinal axis of the positive electrode extends vertically,
the belt is preferably guided so as to travel along a horizontal
path with the coagulated ink retaining surface facing
downwardly, the support roller and pressure roller having
rotation axes disposed in a plane extending perpendicular to
the horizontal path. Such an arrangement is described in the
aforementioned US application filed concurrently with the
present application, the teaching of which is incorporated
herein by reference.
After step (f), the coagulated ink retaining surface of
the belt is generally cleaned to remove therefrom any remaining
coagulated ink. According to a preferred embodiment, as shown
in Fig. 3, any remaining coagulated ink is removed from the
coagulated ink retaining surface 171 of the belt 17 by providing
at least one elongated rotatable brush 211 disposed on the one
side of the belt 17 and at least one support roller 213 extending
parallel to the brush 211 and disposed on the opposite side
of the belt 17, the brush 211 and support roller 213 having
rotation axes disposed in a plane extending perpendicular to
the belt 17, the brush 211 being provided with a plurality of
radially extending bristles 212 made of horsehair and having
extremities contacting the coagulated ink retaining surface,
rotating the brush 211 in a direction opposite to the direction
of movement of the belt 17 so as to cause the bristles 212 to
frictionally engage the coagulated ink retaining surface while
supporting the belt 17 with the support roller 213, directing
jets of cleaning liquid under pressure against the coagulated
ink retaining surface 171 by using at least one high pressure
injector 215, and removing the cleaning liquid with any
dislodged coagulated ink from the coagulated ink retaining
surface 171.
The present invention will be explained in more detail
with reference to the following examples which are not intended
to be limiting of the present invention insofar as it may be
made without departing from the spirit of the invention.
A coating agent comprising 7.5% by weight of Silica FK
500LS (BET surface area: 450 m2/g) manufactured by Degussa AG
as the silicon oxide and 92.5% by weight of oleic acid as the
oily substance was produced. The viscosity of the coating
agent was 3000 cps (30°C).
The electrocoagulation printing ink was manufactured
from the following raw materials:
| - Carbon black pigment (Carbon black Monarch 120: Cabot Corporation) | 8.8% by weight |
| - Aqueous anionic dispersant solution (effective component: 42% by weight) (Closperse 2500: Boehem Filatex Canada Inc.) | 0.75% by weight |
| - Anionic acrylamide polymer (Accostrength 86: Mitsui Cytec, Ltd.) | 8.8% by weight |
| - Potassium chloride (soluble electrolyte) | 8.8% by weight |
| - EDTA disodium dihydrate (metal ion chelating agent) | 0.03% by weight |
| - Water (liquid medium) | 72.82% by weight |
| Total | 100% by weight |
The coating agent was used in an electrocoagulation
printing apparatus of the type described in U.S. Patent No.
4,895,629. The electrocoagulation printing ink and a cleaning
liquid used for cleaning the positive electrode were heated
to 40°C, thereby to maintain the ink and the positive electrode
surface at 40°C. Printing was intermittently carried out for
about 40 hours. When the level of the electrocoagulation
printing ink in the ink discharge unit dropped, the ink was
added to keep a solution level constant. After about 40 hours
of the printing, conditions of the positive electrode surface
and of a resulting printed matter were inspected by eyes.
As a result, no significant abrasion or pitting was
observed on the surface of the positive electrode after about
40 hours since the start of the printing. The resulting printed
matter had excellent quality without uneven density.
A coating agent comprising 7.5% by weight of Silica FK
500LS mentioned above as the silicon oxide and 92.5% by weight
of isostearic acid as the oily substance was produced. The
viscosity of the coating agent was 3000 cps (30°C). Printing
was performed in the same condition and method as in Example
1 except that the above coating agent was used.
Substantially the same results as in Example 1 were
obtained.
A coating agent comprising 7.5% by weight of Silica FK
500LS mentioned above as the silicon oxide and 92.5% by weight
of methyl oleate as the oily substance was produced. The
viscosity of the coating agent was 3000 cps (30°C). Printing
was performed in the same condition and method as in Example
1 except that the above coating agent was used.
Substantially the same results as in Example 1 were
obtained.
A coating agent comprising 25.0% by weight of SILYSIA
530 (BET surface area: 500 m2/g) manufactured by Fuji Silysia
Chemical Ltd. as the silicon oxide and 75.0% by weight of oleic
acid as the oily substance was produced. The viscosity of the
coating agent was 3000 cps (30°C). Printing was performed in
the same condition and method as in Example 1 except that the
above coating agent was used.
Substantially the same results as in Example 1 were
obtained.
A coating agent comprising 7.5% by weight of AEROSIL R972
(BET surface area: 110 m2/g) manufactured by Degussa AG as the
silicon oxide and 92.5% by weight of oleic acid as the oily
substance was produced. The viscosity of the coating agent was
500 cps (30°C). Printing was performed in the same condition
and method as in Example 1 except that the above coating agent
was used.
Substantially the same results as in Example 1 were
obtained.
A coating agent comprising 7.5% by weight of Silica FK
500LS mentioned above as the silicon oxide, 65% by weight of
oleic acid as the oily substance, and further 26% by weight
of polyoxyethylenetetraoleic acid sorbitol (the number of
ethylene oxide addition mols: 30, HLB: 10.5), and 1.5% by weight
of ethyl cellulose having a molecular weight of 80,000 was
produced. The viscosity of the coating agent was 6000 cps
(30°C). Printing was performed in the same condition and method
as in Example 1 except that the above coating agent was used.
Substantially the same results as in Example 1 were
obtained.
A coating agent comprising 50% by weight of dichromium
trioxide and 50% by weight of oleic acid was produced. The
viscosity of the coating agent was 750 cps (30°C). Printing
was performed in the same condition and method as in Example
1 except that the above coating agent was used.
Crater-like pitting with a diameter of from about 1 to
about 2 mm was observed on the surface of the positive electrode
after the printing was completed. Image density of the portion
corresponding to the pitting on the surface of the positive
electrode was reduced, providing printing matter with uneven
density.
Claims (11)
- An electrocoagulation printing method comprising the steps of:a) providing a positive electrode having a passivated surface moving at substantially constant speed along a predetermined path;b) coating the positive electrode surface with a coating agent containing silicon oxide and an oily substance to form on the surface micro-droplets of the coating agent;c) forming on the positive electrode surface having micro-droplets thereon a plurality of dots of coagulated ink representative of a desired image, by electrocoagulation of an electrolytically coagulable printing ink comprising an electrolytically coagulable polymer, a liquid medium, a soluble electrolyte and a coloring agent; andd-1) bringing a substrate into contact with the positive electrode surface to cause transfer of the dots of coagulated ink from the positive electrode surface onto the substrate and thereby imprint the substrate with the image.
- A method as claimed in claim 1, wherein steps (b), (c) and (d-1) are repeated several times to define a corresponding number of printing stages arranged at predetermined locations along the path and each using a coloring agent of different color, and to thereby produce several differently colored images of coagulated ink which are transferred at respective transfer positions onto the substrate in superimposed relation to provide a polychromic image.
- A method as claimed in claim 1, wherein steps (a), (b) (c) and (d-1) are repeated several times to define a corresponding number of printing stages each using a coloring agent of different color and to thereby produce several differently colored images of coagulated ink which are transferred at respective transfer positions onto the substrate in superimposed relation to provide a polychromic image.
- An electrocoagulation printing method comprising the steps of:a) providing a positive electrode having a passivated surface moving at substantially constant speed along a predetermined path;b) coating the positive electrode surface with a coating agent containing silicon oxide and an oily substance to form on the surface micro-droplets of the coating agent;c) forming on the positive electrode surface having micro-droplets thereon a plurality of dots of coagulated ink representative of a desired image, by electrocoagulation of an electrolytically coagulable printing ink comprising an electrolytically coagulable polymer, a liquid medium, a soluble electrolyte and a coloring agent;d-2) bringing an endless non-extendible belt moving at substantially the same speed as the positive electrode and having on one side thereof a coagulated ink retaining surface adapted to releasably retain dots of electrocoagulated ink, into contact with the positive electrode surface to cause transfer of the dots of coagulated ink from the positive electrode surface onto the coagulated ink retaining surface of the belt and to thereby imprint the coagulated ink retaining surface with the image;e) repeating steps (b), (c) and (d-2) several times to define a corresponding number of printing stages arranged at predetermined locations along the path and each using a coloring agent of different color, and to thereby produce several differently colored images of coagulated ink which are transferred at respective transfer positions onto the coagulated ink retaining surface in superimposed relation to provide a polychromic image; andf) bringing a substrate into contact with the coagulated ink retaining surface of the belt to cause transfer of the polychromic image from the coagulated ink retaining surface onto the substrate and to thereby imprint the substrate with the polychromic image.
- A method as claimed in claims 1 to 4, wherein step (b) is carried out by providing a distribution roller extending parallel to the positive electrode and having a peripheral coating comprising an oxide ceramic material, applying the coating agent onto the ceramic coating to form on a surface thereof a film of the coating agent uniformly covering the surface of the ceramic coating, the film of the coating agent breaking down into micro-droplets having substantially uniform size and distribution, and transferring the micro-droplets from the ceramic coating onto the positive electrode surface.
- A method as claimed in claims 1 to 5, wherein the silicon oxide in the coating agent is silicon dioxide which is present in the coating agent in an amount of from 2 to 40% by weight, based on the total weight of the coating agent.
- A coating agent to be used in coating a positive electrode surface in advance of forming on the positive electrode surface a plurality of dots of coagulated ink by electrocoagulation of an electrolytically coagulable printing ink, the coating agent containing silicon oxide and an oily substance.
- A coating agent as claimed in claim 8, wherein the silicon oxide is silicon dioxide.
- A coating agent as claimed in claim 8, wherein the silicon dioxide is present in the coating agent in an amount of from 2 to 40% by weight, based on the total weight of the coating agent.
- A coating agent as claimed in claim 8 or 9, wherein the silicon dioxide has a BET surface area of from 100 to 600 m2/g.
- A coating agent as claimed in claims 7 to 10, wherein the oily substance is an olefinic compound which is unsaturated fatty acid selected from the group consisting of arachidonic acid, linoleicacid, linolenic acid, oleic acid and palmitoleic acid.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2214606 CA2214606C (en) | 1997-08-29 | 1997-08-29 | Method of preventing anode abrasion during electrocoagulation printing |
| CA2214606 | 1997-08-29 |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| EP0899093A2 true EP0899093A2 (en) | 1999-03-03 |
| EP0899093A3 EP0899093A3 (en) | 1999-04-28 |
| EP0899093B1 EP0899093B1 (en) | 2002-03-13 |
Family
ID=4161397
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP98116206A Expired - Lifetime EP0899093B1 (en) | 1997-08-29 | 1998-08-27 | Method and coating agent for electrocoagulation printing |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0899093B1 (en) |
| JP (1) | JPH11138984A (en) |
| CA (1) | CA2214606C (en) |
| DE (1) | DE69804175T2 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1036653A2 (en) * | 1999-03-18 | 2000-09-20 | Toyo Ink Manufacturing Co., Ltd. | Electrocoagulation printing ink and its use |
| US6859542B2 (en) | 2001-05-31 | 2005-02-22 | Sonion Lyngby A/S | Method of providing a hydrophobic layer and a condenser microphone having such a layer |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1153993A4 (en) * | 1999-11-18 | 2003-02-26 | Toyo Ink Mfg Co | Electrocoagulation printing ink and its use |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5538601A (en) * | 1995-09-14 | 1996-07-23 | Elcorsy Inc. | Electrocoagulation printing and apparatus |
-
1997
- 1997-08-29 CA CA 2214606 patent/CA2214606C/en not_active Expired - Fee Related
-
1998
- 1998-08-27 DE DE1998604175 patent/DE69804175T2/en not_active Expired - Fee Related
- 1998-08-27 EP EP98116206A patent/EP0899093B1/en not_active Expired - Lifetime
- 1998-08-28 JP JP24360798A patent/JPH11138984A/en active Pending
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5538601A (en) * | 1995-09-14 | 1996-07-23 | Elcorsy Inc. | Electrocoagulation printing and apparatus |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1036653A2 (en) * | 1999-03-18 | 2000-09-20 | Toyo Ink Manufacturing Co., Ltd. | Electrocoagulation printing ink and its use |
| EP1036653A3 (en) * | 1999-03-18 | 2001-03-07 | Toyo Ink Manufacturing Co., Ltd. | Electrocoagulation printing ink and its use |
| US6406606B1 (en) | 1999-03-18 | 2002-06-18 | Toyo Ink Mfg. Co., Ltd. | Electrocoagulation printing ink and method |
| EP1247646A3 (en) * | 1999-03-18 | 2003-07-02 | Toyo Ink Manufacturing Co., Ltd. | Electrocoagulation printing ink and its use |
| US6859542B2 (en) | 2001-05-31 | 2005-02-22 | Sonion Lyngby A/S | Method of providing a hydrophobic layer and a condenser microphone having such a layer |
| USRE40781E1 (en) | 2001-05-31 | 2009-06-23 | Pulse Mems Aps | Method of providing a hydrophobic layer and condenser microphone having such a layer |
Also Published As
| Publication number | Publication date |
|---|---|
| CA2214606C (en) | 2002-11-19 |
| CA2214606A1 (en) | 1999-02-28 |
| DE69804175T2 (en) | 2002-09-26 |
| EP0899093B1 (en) | 2002-03-13 |
| DE69804175D1 (en) | 2002-04-18 |
| EP0899093A3 (en) | 1999-04-28 |
| JPH11138984A (en) | 1999-05-25 |
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