Note: Descriptions are shown in the official language in which they were submitted.
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LITHOGRAPHIC PRINTING SYSTEM
WITH REUSABLE SUPPORT SURFACES
AND LITHOGRAPHIC CONSTRUCTIONS
FOR USE THEREWITH
BACKGROUND OF THE INVENTION
Field of the Invention
s The present invention relates to digital printing
apparatus and methods, and more particularly to lithographic
printing plate constructions that may be imaged on- or off-
press using digitally controlled laser output.
Description of the Related Art.
In offset lithography, an image is present on a plate or
mat as a pattern of ink-accepting (oleophilic) and ink-
repellent (oleophobic) surface areas. Ink is retained on the
oleophilic regions and rejected where the plate is oleophobic.
~s In a dry printing system, the plate is simply inked and the
image transferred onto a recording material; the plate first
makes contact with a compliant: intermediate surface called a
blanket cylinder which, in turn, applies the image to the paper
or other recording medium. In typical sheet-fed press systems,
zo the recording medium is pinned to an impression cylinder, which
brings it into contact with the blanket cylinder.
In a wet lithographic system, the non-image areas are
hydrophilic, and the necessary ink-repellency is provided by an
initial application of a dampening (or "fountain") solution to
is the plate prior to or in conjunction. with inking. The ink-
repellent fountain solution prevents ink from adhering to the
non-image areas, but does not affect the oleophilic character
of the image areas.
Both dry and wet lithographic printing plates generally
so comprise a printing surface disposed on some form of support,
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which may or may not contribute to the pattern of ink
receptivity and rejection. For example, as disclosed in
U.S. Patent No. 5,339,737, laser-imageable lithographic
printing constructions may include a first, topmost layer
chosen for its affinity for (or repulsion of) ink or an ink-
abhesive fluid; an imaging layer, which ablates in response
to imaging (e. g., infrared, or "IR") radiation, thereunder;
and beneath the imaging layer, a strong, durable substrate
characterized by an affinity for (or repulsion of) ink or an
ink-abhesive fluid opposite to that of the first layer.
Ablation of the imaging layer weakens the topmost layer as
well. By disrupting its anchorage to an underlying layer,
the topmost layer is rendered easily removable in a post-
imaging cleaning step, creating an image spot having an
affinity for ink or an ink-abhesive fluid differing from
that of the unexposed first layer. In this type of
construction, as with many traditional photoex:posure-type
designs, the substrate is a heavy polymeric film that
accepts ink and confers needed strength and durability to
the construction. The price of these qualities, however, is
material cost and the manufacturing capacity for handling
such films.
U.S. Patents 5,783,364 and 5,807,658 disclose wet
and dry lithographic printing members that include metallic
inorganic layers. These layers exhibit both hydrophilicity
and substantial durability at very thin application levels,
and ablatively absorb imaging radiation, thereby
facilitating direct imaging without chemical development.
They can also be used to form optical interference
structures which, in addition to providing color, likewise
absorb imaging radiation and ablate in response to imaging
pulses. Wet lithographic printing members based on this
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concept may include a protective layer that provides
protection against handling and environmental damage,
extends plate shelf life, and entrains debris generated by
ablation. The layer washes away during the printing make
s ready process, effectively cleaning the plate and
disappearing without the need for a separate removal
process. Once again, however, these printing members
contemplate heavy polymeric substrates.
Some applications require greater dimensional
stability than can be conferred by a plastic film. One such
application involves special types of web presses, typically
used by publishers of newspapers, that do not provide
clamping mechanisms to retain printing plates against the
plate cylinders. Instead, the leading and trailing edges of
each the plate are crimped and inserted into a slot on the
corresponding cylinder, so the plate is held against the
surface of the cylinder by the mechanical flexion of the
bent edges. Film or plastic materials cannot .readily
provide the necessary shape retention and physical strength
to accommodate use in such presses. For example, while it
may be possible to produce relatively permanent bends in a
polyester substrate using heat-set equipment, such an
approach may prove cumbersome and costly. For these
applications, the plastic film substrate is typically
laminated to a heavy-duty metal support as described, e.g.,
in U.S. Patent No. 5,188,032.
Metal sheets may also be employed directly as
substrates, as is typically done with large-sized plates.
The dimensional stability of plastic- or film-based plates
tends to decrease with size unless the thickness of the
substrate is increased; however, depending on the size of
74611-38(S)
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3a
the plate, the amount of thickening necessary to retain
acceptable rigidity can render the plate unwieldy,
uneconomical or both. By contrast, metal substrates can
provide high degrees of structural integrity at relatively
modest thicknesses.
Metal supports or substrates are, of course, more
expensive than their plastic counterparts, and require
specialized, heavy-duty processing equipment. Although
substantially intact after even long print runs, they are
part
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of the plate structure, integrally bound to the remaining
plate layers, and therefore cannot be reused.
DESCRIPTION OF THE INVENTION
Brief Summary of the Invention
In one aspect of the invention, there is provided
a removable printing member adapted for use on a support
member, the printing member comprising: a. a printing
structure for accepting a lithographic printing pattern, the
printing structure comprising a topmost layer and a
bottommost polymeric layer; and b. on an exposed side of the
bottommost layer of the printing structure, a layer of
adhesive for adhering the printing member to the support
member, the adhesive layer formed of a material
characterized by an adhesion strength sufficiently strong to
prevent relative movement between the support member and
printing member during printing, and sufficiently weak to
permit the printing structure to be peelable from the
support member without heating, the adhesive not exhibiting
substantial adhesion to the topmost layer so that the
printing structure, when rolled with the adhesive against
the topmost layer, is free to unroll.
In a second aspect of the invention, there is
provided a method of printing comprising the steps of: a.
providing a printing member in rolled form, the member
comprising a printing structure for accepting a lithographic
printing pattern the printing structure having (i) a topmost
layer, (ii) a bottommost polymeric layer, and (iii) on an
exposed side of the bottommost layer, a layer of adhesive
for adhesive for adhering the printing structure to a
support, the adhesive layer formed of a material
characterized by an adhesion strength sufficiently strong to
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prevent relative movement between the support and printing
structure during printing, and sufficiently weak to permit
the printing structure to be peelable from the support
without heating, the adhesive not exhibiting substantial
adhesion to the topmost layer so that the printing
structure, when rolled with the adhesive against the topmost
layer, is free to unroll; b. providing a support for bearing
the printing member; c. unrolling a segment of the printing
member from the roll and adhering the segment to the
support; d. printing by applying ink to a sheet and
transferring the ink, in an imagewise pattern, to a
recording medium; and e. following the printing step,
peeling the printing member from the support without
substantially heating the adhesive.
In a third aspect of the invention, there is
provided a printing system comprising: a. a plate cylinder;
b. a supply of lithographic printing material in rolled form,
the printing material comprising an adhesive for affixation
to the plate cylinder; c. an applicator for unrolling a
segment of the printing material and applying it to the plate
cylinder; d. a lithographic imaging system for impressing an
image onto the applied printing material; and e. a removal
apparatus for removing the applied printing material
following use so as to facilitate application of a new
segment of the printing material onto the plate cylinder.
In accordance with the present invention,
provision is made for re-use of the plate substrate or
support, which may be a metal sheet affixable (e.g., by
crimping or using clamps) to a plate cylinder, or may
instead be the permanent surface of such a cylinder. In
this way, the traditional "plate" is replaced with a thin,
easily manufactured printing member, which is separated from
the support following its use. In one approach, the
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printing member has a printing structure for accepting a
lithographic printing pattern, and beneath the printing
structure, a layer of adhesive. When the printing member is
applied to the metal surface of a plate cylinder or other
support, the adhesive holds the printing member against the
support with enough strength to prevent relative movement
therebetween during printing; in this way, registration
among printing members associated with separate printing
stations (which sequentially encounter the recording medium
to which ink is applied) remains intact. When the printing
job is done, the printing member is peeled from the support
and recycled or discarded. In other words, notwithstanding
the strength of the adhesive in maintaining registration, it
does not prevent the printing member from being peeled from
the support, preferably without substantial residue thereon.
It should be emphasized that the printing member
may be in the traditional form of a cut sheet, or may
instead be provided in some other form, e.g., as a roll that
is applied to the support in sections. For example, such a
roll might be contained within the interior of the cylinder
and wound in increments around the exterior surface as print
jobs are completed; see, e.g., U.S. Patent No. 5,355,795.
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In another embodiment, the adhesive is heat-responsive,
losing adhesion with increasing temperature. The adhesive-
backed member is applied to the support (and, if necessary,
heated and then cooled to cause adhesion), whereupon printing
s may be carried out in the usual fashion. To facilitate removal
of the member, the support is heated. Preferably, the surface
of the support and the printing-member layer bearing the
adhesive are chosen such that, upon heating, the adhesive is
better retained by the member so as to minimize residue on the
io support.
In a third embodiment, the printing member is held onto
the exterior surface of a porous cylindrical support (e.g., the
plate cylinder of a lithographic printing press) by negative
pressure; that.is, a vacuum applied to the interior of the
~s cylinder is communicated through radial pores, thereby
retaining the member (generally in the form of a sheet) against
the exterior cylinder surface. Because the members used in
connection with this embodiment of the invention are typically
quite thin (e.g., on the order of 0.001-0.002 inch), it is
Zo necessary to utilize a cylinder configuration specifically
adapted to avoid deforming the retained member; for example,
conventional vacuum plate-retention systems typically have
widely spaced, relatively large-diameter air passages that
would create depressions on the printing-member surface,
zs resulting in uneven printing. The present invention therefore
makes use of cylinders having continuous, uniform distributions
of small-diameter pores contiguous over the surface of the
cylinder (or at least that portion of the cylinder underlying
the image portion of the member), thereby creating a highly
so uniform retention force and avoiding pressure concentrations
that might cause surface depressions. Following printing,
positive pressure may be used to facilitate removal of the used
printing member.
The invention further comprises on-press systems for
ss continuous, automatic application, imaging, and removal of
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lithographic material in accordance with the present invention.
Brief Description of the Drawings
The foregoing discussion will be understood more readily
s from the following detailed description of the invention, when
taken in conjunction with the accompanying drawings, in which:
FIG. 1 is an exploded isometric view of a representative
embodiment of the invention, showing the manner in which a
printing member is mounted to a cylindrical support either
directly or by means of a metal carrier, which is itself
clamped to the cylinder;
FIG. 2 is an end view of a lithographic printing structure
having an adhesive layer, and a carrier and cylinder
assembly to which the printing structure is adhered in
accordance with the invention;
FIGS. 3-6 are sectional views of rolled printing
constructions in accordance with the present invention;
FIG. 7 schematically illustrates an apparatus for applying
the constructions shown in FIGS. 3-6 to metal substrates;
zo FIG. 8 schematically illustrates an on-press application,
imaging and removal system for adhesive-based embodiments;
FIG. 9 is an isometric view of a porous cylinder to which
a printing structure may be attached by means of negative
pressure;
25 FIG. 10 is a sectional end view of a cylinder adapted for
negative-pressure plate attachment and which contains
internal supply and uptake rollers;
FIG. 11 is a partially cutaway isometric view of a vacuum
manifold tube; and
3o FIG. 12 is an end view of a cylinder utilizing the tube
shown in FIG. 11 and adapted for negative-pressure plate
attachment.
The drawings and components shown therein are not
necessarily to scale.
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.7
Detailed Description of the Preferred Embodiments
The printing members utilized in connection with
the present invention may take many forms, and. are not
restricted in terms of type or construction. For example,
suitable members range from traditional photoexposure
constructions to members imaged, ablatively or otherwise, by
laser or spark discharge. Suitable members imaged by laser
discharge are disclosed, for example, in U.S. Patent Nos.
5,339,737 and 5,379,698. Representative constructions
include three-layer members having an oleophobic (for dry
printing) or hydrophilic (for wet printing) surface layer; a
thin-metal or polymeric imaging layer, which ablates in
response to laser imaging pulses, thereunder; and a non-
a:blative, oleophilic (ink-accepting) substrate beneath the
imaging layer. Two-layer members utilize oleo:phobic or
hydrophilic surface layers ablatable by laser discharge, and
oleophilic substrates thereunder that do not ablate.
In another preferred approach, the member
comprises a surface layer based on certain metallic
materials, and an oleophilic .Layer thereunder. The metallic
materials are both hydrophilic: and durable, making them
desirable for wet-plate constructions, In one version, the
material is a very thin (50-500 A, with 300 A preferred for
titanium) layer of a metal that may or may not develop a
native oxide surface 12s upon exposure to air. This layer
ablates in response to IR radiation, and an image is imposed
onto the member through patterned exposure to the output of
one or more lasers (as disclosed, for example, in U.S.
Patent No. 5,385,092. The me~..al is preferably at least one
d-block (transition) metal, aluminum, indium or tin; in the
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7a
case of a mixture, the metals are present as an alloy or an
intermetallic. The oleophilic layer can also be treated in
various ways to improve adhesion to the metal layer. For
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example, plasma treatment of a film surface with a working gas
that includes oxygen (e.g., an argon/oxygen mix) results in the
addition of oxygen to the film surface, improving adhesion by
rendering that surface reactive with the metals) of layer 12.
s Oxygen is not, however, necessary to successful plasma
treatment. Other suitable working gases include pure argon,
pure nitrogen, and argon/nitrogen mixtures. See, e.Q., Bernier
et al., ACS Symposium Series 440, Metallization of Polymers, p.
147 (1990).
Alternatively, the member may contain a metallic
inorganic layer above the metal layer. The inorganic layer may
comprise a compound of at least one metal with at least one
non-metal, or a mixture of such compounds. Along with the
underlying metal layer, the inorganic layer ablatively absorbs
imaging radiation, and consequently is applied at a thickness
of only 100-2000 ~. The metal component of the inorganic layer
may be a d-block (transition) metal, an f-block (lanthanide)
metal, aluminum, indium or tin, or a mixture of any of the
foregoing (an alloy or, in cases in which a more definite
zo composition exists, an intermetallic). Preferred metals
include titanium, zirconium, vanadium, niobium, tantalum,
molybdenum and tungsten. The non-metal component may be one or
more of the p-block elements boron, carbon, nitrogen, oxygen
and silicon. A metal/non-metal compound in accordance herewith
25 may or may not have a definite stoichiometry, and may in some
cases (e. g., A1-Si compounds) be an alloy. Preferred
metal/non-metal combinations include TiN, TiON, TiOX (where 0.9
< x < 2.0), TiAlN, TiAICN, TiC and TiCN.
In wet-plate embodiments where the metallic or metallic
3o inorganic layer represents the uppermost surface layer, the
member may also include a protective layer applied thereover.
This layer preferably comprises a polyalkyl ether compound with
a molecular weight that depends on the mode of application and
the conditions of plate fabrication. For example, when applied
35 as a liquid, the polyalkyl ether compound may have a relatively
1 4 611- 3 8 ( S ) CA 02231011 2002-08-02
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substantial average molecular weight (1.e., at. least 600) if
the plate undergoes heating during fabrication or
experiences heat during storage or shipping; otherwise,
lower molecular weights are acceptable. A coating liquid
should also exhibit sufficient viscosity t.0 facilitate even
coating at application weights appropriate to the material
to be coated.
A preferred formulation for aqueous coating
comprises 80 wt% polyethylene glycol (PEG) with an average
molecular weight of about 8000 combined. with 20 wt%
hydroxypropyl cellulose to serve as a thickener. A
formulation according to this specification was prepared by
combining 4.4 parts by weight ("pbw") of Fluracol 8000TM
(supplied by BASF, Mt. Olive, NJ) with 1.1 pbw of Klucel GTM
or 99-G "FF" grade hydroxypropyl cellulose (supplied by the
Aqualon division of Hercules Inc., Wilmington, DE). The
ingredients were blended together as dry powders and the
mixture slowly added to 28 pbw of water at 50-55°C with
rapid agitation, allowing the powders to be wetted between
additions. The mixture was stirred for 20-30 min. while
maintaining the temperature between 50-55°C, thereby wetting
the Klucel particles and dissolving the Pluracol, At this
point 66.5 pbw of cold water (ca. 5-10°C) was added all at
once, bringing the mixture temperature close to or below
room temperature. Stirring was continued .for 1-2 hours
until solution was complete. The fluid viscosity was
measured at about 100 cp.
Qther materials and formulations can be used to
advantage. For example, the ~aolyalkyl ether c<~n be replaced
with a polyhydroxyl compound, a polycarboxirlic acid, a
polysulfonamide or a polysulfonic acid or mixtures thereof.
Gum arabic or the gumming agents found :in c~omme~rcial plate
74611-38 (S) cA o223ioii 2oo2-os-o2
IO
finishers and fountain solutions can also be used to provide
the protective layer. The TRUE BLUETM plate cleaning
material and the YARN TOTALTM fountain solution supplied by
Varn Products Company, Oakland, NJ are also suitable for
this purpose, as are the FPC product from the Printing
Products Division of Hoescht Celanese, Somerville, NJ, the
G-7A-"V"-COMB fountain solution supplied by Rosos Chemical
Co., Lake Bluff, IL, the VANISH'rM plate cleaner and scratch
remover marketed by Allied Photo Offset Supply Corp.,
Hollywood, FL, and the POLY-PLATETM plate-cleaning solution
also sold by Allied. Still. another useful finishing
material is polyvinyl alcohol, applied as a very thin layer.
The protective layer is preferably applied at a
minimal thickness consistent with its roles, namely,
providing protection against handling and environmental
damage, extending plate shelf life by shielding the plate
from airborne contaminants, and entraining debris produced
by imaging. The thinner the protective layer can be made,
the more quickly it will wash off during press make-ready,
the shorter will be the roll-up time, and the :less the layer
will affect the imaging sensitivity of the plate.
In preferred constructions of the present
invention, the member includes a substrate lays=r that is
thinner than conventional substrates. For example, it is
possible to utilize polyester film, a typical :ink-receptive
material used in lithographic plate constructions, in
thicknesses of 0.001 to 0.002 inch. Of course, larger and
smaller gauges may be appropriate to different applications;
for example, stronger polymeric materials may be used at
smaller thicknesses.
74 611- 3 8 ( S ) cA o223ioii 2oo2-os-o2
10a
Refer to FIG. l, which il.lust.rates the basic
approach of the invention to adhesive affixation of a thin
printing member to a reusable surface. A printing member
100, which includes an adhesive backing 102, is applied
either directly to the exterior surface 104 of a cylindrical
support (e. g., a stainless-steel or aluminum plate cylinder)
106, or instead to a surface 108 of a metal (e. g.,
stainless-steel) carrier 110 that itse~.f attaches to the
cylinder 106. For example, the carrier 110 may have a pair
of marginal tabs (one of which is
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shown at 112) that are received by slots in cylinder 106, or by
conventional clamps located within a cylinder void segment 115.
This is shown more clearly in FIG. 2, which also
illustrates the characteristics of member 100 in greater
s detail. The marginal tabs of carrier 110 are received in a
pair of clamps 120a, 120b. The member 100 comprises a printing
structure, indicated generically at 122, and an adhesive layer
124. The printing structure 122 may comprise a plurality of
cooperative layers which, in response to actinic radiation or
imaging (e. g., IR) laser pulses -- and, if necessary,
subsequent processing -- assume an imagewise pattern of regions
exhibiting differential affinities for ink and/or fountain
solution. Typically, as shown in FIG. 1, the printing area 130
of the member 100 -- that is, the portion of the member surface
~s that actually receives the imagewise pattern -- is a subregion
of the overall member surface.
In first and second embadiments, shown generally in FIG.
2, the printing member 100 comprises a printing structure 122
for accepting a lithographic printing pattern, and beneath the
zo printing structure, a layer 124 of adhesive. In the first
embodiment, member 100 may be applied to the metal surface of a
plate cylinder or other support. The adhesive layer 124 is
pressure sensitive, and holds the printing member against
carrier 110 (or the surface of cylinder 106) with enough
zs strength to prevent relative movement therebetween during
printing. The adhesive is nonetheless weak enough to permit
member 100 to be peeled from carrier 110 when the printing job
is done, preferably without leaving any substantial residue.
Useful adhesives also resist the action of the chemical
3o reagents (such as fountain solution, plate cleaners and/or ink
solvents) typically encountered during printing.
Suitable adhesives for this purpose include acrylic
materials, such as those formulated for repeated applications
and removals. Since the surface area of member 100 is so
ss large, bulk relative movement will be substantially prevented
74611-38 (S) CA 02231011 2002-08-02
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by even moderate forces of adhesion. In one exemplary
version of this embodiment, the 4560 double--coated polyester
film tape supplied by Internaa~ional Tape Co., Windham, NH
was applied to the back (palyester) surface of a wet
lithographic printing plate (with the ~>ermanent-bonding
surface of the tape against the polyester layer), and the
composite construction applied to a plate cylinder in a
four-color lithographic pri.ntinc~ press; printing with the
plate was found not to disrupt registration. The low-tack
side of the 4560TM product (which contacts the carrier or
plate cylinder) is an acrylic adhesive having an adhesion
value of 16 oz./in. width and a tack value of 4.0". In
commercial practice, however, it is generally ;preferable to
apply the adhesive as a single coat beneath the bottom layer
of printing structure 122; the member, as supplied, has a
backing liner beneath adhesive layer 124, and 'which the user
removes just prior to application. Nonetheless, use of a
double-sided material is not without benefit; :because of the
thickness of the tape (approximately 0.004 inc:h), the plate
to which the 4560 product had been applied - - a Ti/TiN
p:Late in accordance with U.S. 5,'783,364 - - was found to
exhibit good scratch resistanc~.e. Accordingly, it is
possible to use the adhesive as a deformable layer to
prevent scratches in accordance with U.S. Patent No.
5,704,291,
Successful results were also achieved using the
550TM double-coated polyester film tape supplied by
International Tape Co., applied to the :bac:l~ surface of a wet
printing plate. The low-tack side of this product has an
adhesion value of 10 oz/in. width and a tack value of 4.0"
74611-38 (S) cA o223ioii 2oo2-os-o2
12a
The chemical resistance of this version, however, may be
inadequate for long runs.
In a second embodiment, adhesive layer 124 is a
heat-responsive material. When applied (either directly or
following a heating and cooling Cycle),. the adhesive retains
member 100 against: carrier 110 (or the exterior surface of
CA 02231011 1998-03-04
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cylinder 106) with sufficient strength to prevent relative
movement therebetween during printing, but releases upon
heating of the surface to which it is applied. Accordingly,
cylinder 106 has associated therewith a selectably actuable
s heating unit 135, which heats the exterior surface of the
cylinder (and, by conduction, carrier 110 if used) or other
plate-bearing device to a sufficient temperature to allow
convenient removal of member 100. Preferably, the adhesive is
formulated (and/or the bottom surface of printing structure 122
is treated) such that the adhesive preferentially adheres to
printing structure 122 rather than to carrier.110 or to the
surface of cylinder 106.
The heat-responsive adhesive 124 may be a polyurethane, a
polyamide (or copolyamide), an ethylene vinyl acetate, a
polysilane (which may be applied, for example, by plasma
activation of a polyester surface prior to depositing
hexamethyldisiloxane), or any other heat-responsive material
that loses internal cohesion at convenient operating
temperatures ranging from, for example, 200-350 °F. To
2o encourage the adhesive to remain primarily on printing
structure 122 during removal thereof, the bottom surface of
printing structure 122 may be treated. Typically, treatment
involves roughening the surface, increasing adhesion thereto
through creation of a three-dimensional topology. In one
zs approach, the bottom layer of printing structure 122 is
polymeric (e. g., polyester), and the bottom surface is treated
by plasma discharge. Of course, other forms of roughening
(e. g., by mechanical means) may be better suited to other
materials or in different applications, and the skilled
3o practitioner can readily identify the most appropriate
technique without undue experimentation. Alternatively, a
"tie" coat, which exhibits an affinity for the heat-responsive
adhesive, is applied to the bottom surface of printing
structure 122, and the adhesive is applied to the tie coat.
CA 02231011 1998-03-04
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Titanium metallization provides an advantageous tie coat for a
variety of adhesive materials.
For this embodiment, it is especially preferred to
utilize a polished or unpolished stainless-steel carrier 110
s (or cylinder 106) so as to minimize affinity for the heated
adhesive. However, as another alternative (or in addition to
treatment of printing structure 122), cylinder 106 or carrier
110 may be treated to encourage release. For example, a plasma
may be applied to the metal surface to remove oils, after which
the surface is coated with a fluoropolymer or silane by plasma
deposit (e. g., through plasma activation of decomposable
siloxanes such as hexamethyldisiloxane).
Printing structures in accordance with the first and
second embodiments may be designed for manufacture and use in
~s roll form. FIGS. 3-6 illustrate, in greater detail, suitable
constructions that lend themselves to this type of arrangement.
FIG. 3 shows two adjacent spiral winds 150, 152 of a dry
printing structure utilizing a surface that also serves as a
release layer. The printing structure shown at 150, 152
zo comprises an ink-abhesive silicone or fluoropolymer first layer
160; an imaging layer 162 (e. g., a thin metal such as titanium
applied at 200 A or less, in accordance with the '698 patent,
or a polymeric layer as described in the '737 patent) that
ablates in response to imaging radiation; and an ink-receptive
zs base 164, which may be, for example, polyester film having a
thickness of 0.001 inch or less. A pressure-sensitive adhesive
layer 166 underlies base 164. Adhesive layer 166 does not
adhere to layer 160, which thereby provides a release surface
that enables layers 160-166 to be continuously unrolled. Once
so again, adhesive layer 166 can be designed to provide cushioning
in accordance with the '335 application.
FIG. 4 shows two adjacent spiral winds 180, 182 of a wet
printing structure utilizing the approach of the '267
application. The printing structure comprises a hydrophilic
ss barrier layer 190, which itself preferably comprises at least
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one compound selected from the group consisting of polyalkyl
ethers, polyhydroxyl compounds, polycarboxyl acids,
polysulfonamides and polysulfonic acids; a refractory
hydrophilic layer 192 that comprises a compound of at least one
s metal with at least one non-metal, the at least one non-metal
being selected from the group consisting of boron, carbon,
nitrogen, silicon and oxygen (e.g., titanium nitride, or
titanium nitride over titanium), and which ablates in response
to .imaging radiation; and an ink-receptive base 194, which may
be, for example, polyester film having a thickness of 0.001
inch or less. A hot-melt adhesive layer 196 underlies base
194. The adhesive exhibits no substantial tack until it is
heated, and therefore does not adhere to layer 190 at room
temperature; once again, the lack of adhesion permits layers
~s 190-196 to be continuously withdrawn from the roll.
The absence of tack is not absolute, however, and most
hot-melt adhesives can be expected to leave some minor residue
on layer 190. But this layer is expressly formulated to wash
away during the printing make-ready process, effectively
zo cleaning the plate and disappearing, along with the entrained
adhesive residue.
FIG. 5 shows an alternative to the embodiment of FIG. 4,
which includes a release liner 198. This liner facilitates the
use of virtually any adhesive desired in the adhesive layer
is 200. Liner 198 may be, for example, a polyester coated with
silicone on the side in contact with adhesive layer 200; the
uncoated side, rolled into contact with layer 190, will not
adhere to that layer. Alternatively, liner 198 may be any
other inert material that interacts neither with adhesive layer
so 200 nor protective layer 190. It should be noted that
protective layer 190 is optional in this construction and can,
if desired, by omitted.
Although this approach requires removal of the release
liner prior to lamination (or other attachment) to a metal
ss support, the approach is highly general, and may be applied to
CA 02231011 1998-03-04
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a variety of different types of printing constructions. For
example, it is possible to apply layers 198, 200 to a wet-plate
construction in accordance with the '737 patent; such a
construction may include a polyvinyl alcohol or other
s hydrophilic, polymeric material as a surface layer; an imaging
layer (e. g., a thin metal or polymeric layer as described
above) that ablates in response to imaging radiation; and an
ink-receptive (e.g., polyester base). The adhesive layer 200
is permanently applied to the underside of the polyester layer
(although removable from the support to which the construction
is applied, as described hereinabove), and release liner 198
underlies the adhesive layer 200.
Refer now to FIG. 6, which shows one wind of a rollable
printing construction that also utilizes a release material,
but which unrolls with the adhesive layer exposed. The
illustrated construction includes a protective hydrophilic
layer 190 and a refractory hydrophilic layer 192, and includes
a temporary support 210 on which the other layers are built up.
Support 210 may be an inexpensive paper sheet or a polymeric
zo mat.erial, and desirably may also be recycled. A release layer
212a, 212b may be applied to each side of support 210. The
function of layer 212a is to prevent adhesion to an adhesive
layer 214, and layer 212a may therefore be omitted depending on
the nature of support 210 (or if a layer 214 is a hot-melt
z5 adhesive). The function of layer 212b is to allow support 210
to be stripped from layer 190 following application of the
construction to a support. In one approach, layer 212b is a
silicone release layer formulated for controlled release.
Alternatively, layer 212b may be a heat-activated substance,
so such as a wax; the carnauba wax coatings used in hot-stamping
foil applications, for example, represent suitable materials.
Although solid at room temperature, the wax liquefies when
heated, facilitating removal of support 210. Because layer 190
is hydrophilic, it is desirable that release layer 212b exhibit
ss some hydrophilicity as well. Indeed, if the wax is
CA 02231011 1998-03-04
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sufficiently hydrophilic, it may serve, as a single layer, the
functions of both layer 212b and 190.
Support 210 serves as a manufacturing substrate for the
construction. Protective layer 190, refractory hydrophilic
s layer 192, base 194 and adhesive layer 214 are sequentially
deposited or coated onto layer 212b (or directly onto support
210). In use, adhesive layer 214 is (removably) applied to a
metal support, and support 210 stripped away from the
construction to permit printing. Any residue of layer 212b is
entrained within protective layer 190 and washed away during
print make-ready.
FIG. 7 illustrates an apparatus, indicated generally at
250, that can be used to apply plate material in roll form to
metal sheets 255 that serve as re-usable supports. A
continuous processing path through which sheets 255
successively pass includes an entry 257, a surface-preparation
chamber 260, the atmosphere of which is controlled by a source
of clean air 262, an application chamber 265, and an exit 267.
As sheets pass through preparation chamber 260, they first
2o encounter a surface-processing unit 270. This device may
provide for removal of surface debris and/or corona treatment.
In addition, unit 270 may sense the presence on sheets 255 of
ali:eady-used printing constructions, deploying a knife or blade
(and, depending on the type of adhesive used, activating a heat
is lamp as well) to peel the used material off. _
A pair of drive rollers 272 form a nip that feeds sheets
255 to application chamber 265. Located in chamber 265 is a
cassette or roll 275 of adhesive-backed plate material in
accordance with the present invention. The plate material 275
so feeds into the nip of a pair of application rollers 280 (which
may be heated if hot-melt adhesive is used). Rollers 280 apply
plate material 275 to sheets 255, and the material 275 is cut
to length by a blade 285. The finished plates leave apparatus
250 through exit 267.
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A roll of adhesive material can also be applied directly
and automatically to the plate cylinder of a print station
within a printing press, as shown in FIG. 8, rather than to an
intE~rmediate carrier as discussed above. The press components
s include a plate cylinder 300, a blanket cylinder 302 in rolling
contact with the plate cylinder 300, and an inking system 305.
System 305 transfers ink onto an imaged plate adhered to plate
cylinder 300; in a dry system, ink is transferred directly to
the plate, whereas in a wet configuration, inking system 305
includes means for applying fountain solution to the plate
prior to inking. Blanket cylinder 302 receives ink in the
imagewise pattern of the plate, and transfers this pattern to a
recording medium (not shown).
Plate material 306 is applied to cylinder 300 by an
~s app:licator 308, which includes a roll 310 of plate material
306. If the plate material 306 does not include a release
liner (as in FIGS. 2-4), it is drawn off supply roll 310 and
applied directly to the surface of cylinder 300 by a
retractable tensioning and application roller 312. When the
Zo entire surface of cylinder 300 has been covered, a blade (not
shown) is drawn axially across plate material 306 and the
resulting edge pressed against cylinder 300 by roller 312.
Preferably, the leading and trailing edges of the applied
material do not overlap; instead, applicator 308 cuts the plate
zs material 306 to retain a small circumferential gap (exposing
the surface of cylinder 300) between edges.
If plate material 306 does include a release liner 315
(as in FIG. 5), a takeup roller 318 rotates to remove liner 315
from plate material 306 as it is dispensed. In operation, the
so leading edge of release liner 315 is initially affixed to
tak.eup roller 318, and the rotation rate of roller 315 adjusts
so that the amount of release liner 315 taken up matches the
amount of plate material 306 dispensed.
After application of plate material 306 to cylinder 300
ss is complete, an imaging system 320 applies a lithographic image
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to the plate. Preferably, the, imaging system is a laser-
ablation apparatus as described, for example, in the '092
patent. Ink is applied to the imaged plate as discussed above,
and following use of the plate, it is stripped from cylinder
s 300 by a removal apparatus 322. Removal apparatus 322 may
include a retractable blade 325 which, when extended, is biased
so as to skim along the surface of plate material 306 and
engage the leading edge, lifting the material from cylinder 300
such that continued rotation thereof strips the complete length
of material. The system may also include a cylinder cleaner
325 that engages cylinder 300 after plate material has been
stripped off, removing residual adhesive from the cylinder
surface. Suitable cleaning devices are conventional in the art
and typically include rotating brushes, foam rollers or the
~s like, and may employ a cleaning liquid or solvent.
Alternatively or in addition, a heater 135 (see FIG. 1)
may be associated with cylinder 300 to accommodate hot-melt
adhesive plate materials. The heater is activated following
imaging and use of the applied plate-material segment, allowing
zo removal apparatus 322 to conveniently strip the material.
In a third embodiment of the present invention, the
printing structure itself is directly attached to a porous
cylinder by means of negative pressure. A suitable
configuration is shown in FIG. 9. The illustrated cylinder 400
zs hay; a continuous, uniform distribution of small-diameter pores .
contiguous over its surface 402 (or at least that portion of
surface 402 underlying the image portion of a member applied
thereto). The body of cylinder 400 is sealed and a vacuum pump
404, which may be located within cylinder 400 or externally
so (but in sealed fluid communication with the interior of
cylinder 400), evacuates air from the cylinder interior to
crE:ate a negative pressure that holds a printing structure
wrapped around surface 402 with sufficient force to prevent its
circumferential movement; pump 404 may also operate in reverse
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to assist initial positioning of the printing structure and its
removal following use.
The cylinder 400 may be any type of structure having the
requisite porosity and resistance to deformation. The optimal
s size of the pores and their density for a particular
application are determined by the thickness and rigidity of the
printing structure that is applied thereto, as well as by the
need for sufficient air transfer to produce an adequate
negative pressure. Generally, the pores are less than 1 mm in
diameter, and may be substantially smaller than this. For
example, tubular materials furnished by Mott Metallurgical
Corp. have uniformly distributed pores whose average size may
be on the order of 1 micron or less. The Membralox Division of
US Filter Corp. offers multichannel ceramic membranes, and
Rhone-Poulenc offers ceramic and silicon-carbide membrane
elements. Pall Filter Corp. sells ceramic, silicon carbide,
and porous metal sheet and tubular constructions similar to
those of the other manufacturers. Sintered metals with
variable pore sizes are also widely available. Any of these
zo may be used directly, or as outer layers around a metal mesh
skeleton (or conventionally perforated tube) for support.
In use, the printing member (actually, printing structure
122.) is wrapped around the surface 402 of cylinder 400, and
vacuum pump 404 is activated until a vacuum corresponding to
is sufficient retention strength is achieved. Preferably, vacuum
pump 404 is equipped with suitable feedback circuitry that
automatically terminates pumping when a user-selectable
retention strength is reached, reactivating pump 404 only as
necessary to maintain this level. Following printing, the
3o interior of cylinder 400 is vented (or vacuum pump 404 run in
reverse), facilitating ready removal of the printing structure.
It should be stressed that printing structure 122 may be
wrapped around the entire circumference of cylinder 400 to
create a seamless or near-seamless printing member.
74611-38 (S) cA o223ioii 2oo2-os-o2
21
FIG. 10 illustrates a version of the cylinder
shown in FIG. 9 that has been configured for internal
storage and dispensing of plate material. The cylinder 450,
shown sectionally in the figure, includes first and second
side plates; the inner face of the side plate visible in the
figure is indicated at 452. The body of the cylinder
defines an annular chamber 454x, which does not form a
complete circle but is instead arcuate in cross-sectian;
chamber 455 is closed at opposite ends to form a space or
gap 460. The outer edge 462 of chamber 45r~ is porous as
described above; the side edges 465, 467 and the inner edge
4'70 are completely nonporous. A conduit 475 mans along
inner plate face 452. Conduit 475 is in fluid communication
at one end with the interior of chamber 455 and at the other
end with a rotary vacuum union, not shown, on the outer face
of the illustrated side ;plate. This rotary union couples
conduit 475 with vacuum pump 404 (FIG. 9).
Situated within the interior of cylinder 450 are a
plate-material supply spool 480 and a takeup spool 482.
These are configured, in accordance with conventional means
(see, e.g., U.S. Patent Nos. 5,355,795, 5,657,692 and
5,.727,749, to facilitate withdrawal and uptake of a
sufficient amount of a plate material 485 to cover the
exterior surface 462 of cylinder 450. Thus, during
operation, plate material frorr~ supply ~spoo~ 480 emerges from
gap 460, passing over edge 467 of chamber 455 and wrapping
around exterior surface 462, then re-entering cylinder 450
over opposed edge 465 onto uptake spoo:l_ 482. ~lacuum pump
404 is activated to draw plate material 48~ tightly against
surface 462 (obviating the need for mechanical tensioning
74 611- 3 8 ( S ) cA o223ioii 2oo2-os-o2
21a
mechanisms to keep the plate material from slipping). lnlhen
a given segment of plate material has been imaged and fully
used, chamber 455 is vented. or, preferably, vacuum pump 404
is run in reverse, allowing material to pass easily over
surface 462. Rollers 480, 482 are advanced so that a fresh
segment of plate material
CA 02231011 1998-03-04
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485 is brought over surface 462, reading for imaging and use.
Imaging is accomplished using an imaging system as shown in
FIG. 8, and once again, plate material 485 receives ink from an
inking system and transfers it, in accordance with the image
s thereon, onto a blanket cylinder.
An alternative design, providing for complete
circ:umferential coverage without a gap or void, is shown in
FIGa. 11 and 12. This design may be used with a more
traditional mandrel arrangement. The illustrated embodiment
includes a tubular vacuum manifold 500 as shown in FIG. 11.
The manifold comprises a steel or other metal body with a
circ:umferentially spaced-apart series of axial grooves or
channels 502 cut into the interior surface 504. Channels 502
intrude only partially into the annular thickness of manifold
~s 500,, and extend fully to each end of the manifold 500. A
series of apertures 506, distributed along the axial lengths of
channels 502, pass entirely through manifold 500, fully
spanning the thickness between the recessed surface of the
channels 502 and the outer surface 510 of manifold 500.
2o Accordingly, the exterior of manifold 500 is in fluid
communication, by means of apertures 506, with channels 502.
Apertures 506 need not be particularly small; for example, they
may be several millimeters in diameter.
With reference to FIG. 12, manifold 500 is in firm,
2s airtight contact with a conventional press mandrel 515, which
it completely surrounds. A porous cylindrical member 400 as
discussed above concentrically surrounds tubular manifold 500.
Finally, a printing structure 122 is wrapped around the
exterior surface of cylinder 400. The edges of printing
so structure 122 can butt against each other firmly, effectively
joining to create only an insigificant seam 520.
At one axial end of the structure shown in FIG. 12,
manifold 500 terminates in a plate cover (not shown), which
seals the ends of channels 502. At the opposite end, a
ss toroidal chamber (also not shown) forms a plenum over the open
CA 02231011 1998-03-04
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ends of channels 502. A rotary vacuum union is in fluid
communication with the chamber, coupling channels 502 with a
vacuum pump as discussed above. Activation of the vacuum pump
draws air through channels 502 and apertures 506, creating
s negative pressure against plate structure 122. But because of
the presence of porous cylinder 400, plate structure 122 is not
sucked into the large-diameter apertures 506. Although the
vacuum is not uniform around cylinder 400 -- being locally
concentrated, instead, at the apertures 506 -- the apertures
are themselves evenly distributed around the surface 510 of
manifold 500, so the draw on plate structure 122 is symmetric.
It will therefore be seen that the foregoing represents
an improvement to lithographic printing systems in providing
reusable application surfaces. The terms and expressions
~s employed herein are used as terms of description and not of
limitation, and there is no intention, in the use of such terms
and expressions, of excluding any equivalents of the features
she>wn and described or portions thereof, but it is recognized
that various modifications are possible within the scope of the
zo invention claimed.
