Note: Descriptions are shown in the official language in which they were submitted.
o
This invention relates generally to printing and
more particularly it pertains to a method for preparing
dry lithograph plates.
Offset printing has traditionally been performed
with greasy ink and water repellent. The developed out
image on the lithograph plate consisted of bare metallic
background and pigmented printing positions.
In the printing press the plate was exposed to
both a water fountain and ink fountain with the desired
effect that wet metallic background repelled the ink
while the pigmented area attracted it~
This practice is satisfactory as long as a
careful balance of ink and water is maintained, and
further that no interruptions are incurred where the
plate may dry and become oxidized.
An object of an aspect of this invention is to
provide a lit~ograph plate which when exposed and
developed presents an ink repellant image background in
the dry state.
An object of an aspect of this invention is to
provide new materials and methods for lithography which
require no water fountain.
An obejct of an aspect of the invention is to
proviee a photo-lithographic plate which prints a
sharper impression for a greater number of copies and
will resist the corrosive affects of the atmosphere
both in the press and in storage.
Various aspects of the invention are as followso
--1--
~ O
A dry planographic printing plate comprising a base layer,
and at least two additional layers disposed in superimposed
relation to each other and both overlying said base layer, one
of said additional layers being a layer of silicone rubber
material and another of said additional layers being capable of
being removed in selected areas so as to define the boundaries
of an image to be printed from said plate, said silicone rubber
material being adapted in the absence of dampening to pr~vide
an ink repellent background for said image.
A dry planographic printing plate comprising a base layer
and at least two additional layers disposed in superimposed
relatlon to each other and both overlying said base layer, one
o said additional layers being a layer of silicone rubber
material, and another of said additional layers being light
sensitive and capable of being removed in selected areas so as
to define the boundaries of an image to be pxinted from said
plate, said silicone rubber material being adapted in the
absence of dampening to provide an ink repellent background for
said image.
: 20
A dry planographic printing plate comprising a base layer,
a layer of silicone rubber material overlying said base layer,
and a continuous chemically etchable metallic layer mounted on
the outside surface of.the silicone rubber layer and capable of
~ being etched away in selected areas so as to define the
- 25 boundaries of an image to be printed from said plate, said
silicone rubber material being adapted in the absence of
dampening to provide an ink repellent background fox said
image.
-la-
.
.
7(3
A dry planographic master to be sensitized, imaged and
developed in accordance with known methods wherein said master
is comprised of a flexible substrate capable of being rolled
and mounted on an offset lithographic press, a layer of
5 silicone rubber bonded ~o at least one surface of the flexible
substrate and a chemically etchable metallic foil mounted on
the expos.ed surface of the silicone rubber layer in the area to
be imaged.
An imaged dry p~anographic printing plate, which accepts
10 ink in the image area and prints therefrom, and repels ink in
- the non-image area, comprising a base layer, an ink-receptive
image area, and a silicone rubber materi~al overlying said base
layer and providing the ink repellent non-image area.
A process for printing planographically in the absence of
dampening with an imaged dry planographic printing plate which
accepts ink in the image area and prints therefrom and which
repels ink in the non-image area, which process comprises
rolling the surface of the imaged dry planographic prinking
plate with ink in the absence of dampening, whereby the ink is
contacted with the image and the non-image areas of the plate,
the ink being repelled in the non-image area by a silicone
rubber material and the ink being accepted in the image area,
and thereafter transferring ink accepted in the image area to
an ink-receptive surface.
Other objects and attendant advantages of this
invention will become more readily apparent and understood
from the following detailed specification and single sheet
of accompanying drawings in which:
-lb-
Figs, 1, 2, 3, and 4 are much enlarg~d Cros~-sections
of a novel photo-lithograph plate in the respective or~er of
preparation for a representative plate according to this inven-
tion;
Fig. 5 schematically depicts the burn or formation of
the image on a-photo-lithograph plate such as that of Fiy. A;
Figs. 6 and 7 are much enlarged cross sections of
exposed plates depicting the subsequent steps of development
and etching respectively; and
Fig, 8 is a somewhat schematic depiction of the
printing press arrangement using the-plates of this invention.
Referring now to the details of the invention there
is first provided a lithograph plate base indicated by
reference numeral 10. This base 10 may be of any material
such as metal, plastic, or paper which is capable of being
rolled and mounted on a standard offset lithograph press.
The base 10 is then given a coat 12 of offset ink
repellent material such as silicone rubber solution on one
face as shown in Fig. 2. The preferred method of coating
is to first clean or etGh the base and then roll or
squeegee thereon a solution hereafter called Formula X,
comprising any of the above in paste form dissolved in
two parts by weight of ~ola-tile solvent film cleaner. The
former rubher constituent is made by the Dow Corning Corp.
and also by the General Electric Company. The solvent is
manufactured by the P, & J0 Corporation. The solvent is
P & J Cleaner and its chemical name trichloroethane,
A thin to~ping web 14 which may be of metal is
applied on the still tacky surface of the silicone rubber
coat 12 and rolled flat so as to adhere well and be
perfectly smooth as shown in Fig, 3.
~2-
After allowing this assembl~ to dry, it is given a
coating 16 of the usual photo sensitizing ammonium dichromate
solution as shown in Fig. 4 to resuli in a sensitive photo~
lithograph plate 18.
The plate 18 is mounted in contact with a photo-
transparency T and exposed to strong light from an arc lamp L
as shown in Fig. 5. This causes the coating 16 to harden in
the exposed areas. When rub-developed with the usual developing
solutions as shown in Fig. 6, the soft background of coating 16
washes away down to the topping web l4 while the image areas
remain.
An etch of acid or solvent suited for material of the
web 14 is then performed removing the web 14 at the exposed
background areas only as shown in Fig. 7. This exposes the
silicone rubber coat 12 as a bac~ground image and this portion
even when dry is repellent to offset ink unlike bare metal,
while the remaining raised print areas are receptive thereto.
~ or this reason the thus prepared exposed, and
developed lithogxaph plate 20 may be installed as shown in Fig.
8 on an offset pre~s P and used without a water fountain.
The unique nature of the coat 12 in repellin~ ink,
- water, and the like can be utilized in various other offset,
gravure and letter press plates other than the above described
laminated dry surface plate. Typical procedures (not illustrated~
will now be discussed.
For preparation o~ positive lithograph or offset
plates, a presensitized plate is rolled or squeegeed with ihe
Formula X to deposit an overall coat of silicone rubber. After
a half hour drying period, it is exposed to a light image in the
_3_
7~
usual manner for about 1 and 1/2 minutes and developed out with
a zylene, ethylene glycol and P. & J. ~ilm cleaner solution
made up in the respective proportions o~ l/Z r 1/8 and 1/2 ~z.
The plate is ~hen flooded with light in the presence
of heat for 3 minutes. The plate is then ready for the press
or it may first be etched, copperized or filled with a filler
as desired.
For preparation of negative lithograph or offset plates,
a presensitized plate is e~posed, lacquered, washed and dried
in the normal ~anner but not gummed up.
~ ext the plate is recoated with sensitizing material
and Formula X is applied and allowed to dry a half houx for
the silicone rubber to form a coat overall. The plate is then
fl~oded with light for 3 minutes in the presence of heat.
Finally the plate is developed out using the zyleneJ
ethylene glycol ~nd P. & J~ film ~leaner solution as I~lentioned
above.
Okviously, many other modifications and variations of
the present invention are possible in light of the above teachings~
It is~ therefore, to ba understood that within the scope of the
appended claims the invention may be practiced otherwise than
as specifically describedO
-
--4--
SUPPLEMEN~ARY DISCLOSURE
This supplementary disclosure is directed to supplementary
features of the planographic plate, the method of producing th~
same and the planographic printing method employing the same
which is disclosed in the principal disclosure.
Various aspects of the invention set out in this Supple-
mentary Disclosure are as follows:
A planographic plate comprising, on a flexible substrate,
a continuous silicone rubber containing layer, and overlying
0 said silicone rubber containing layer a layer of a
photo-responsive diazo compound which, upon exposure to light,
is oleophilic and ink receptive when dry.
~ .
A proces~ of dry planographic ~rinting which comprises
providing a flexible planographic plate comprised of a flexible
15 substrate and a silicone rubber containing layer having a
surface energy which is so low that the silicone rubber surface
will not remove conventional lithographic printing ink from an
inking roller passed thereover, subjecting said plate to an
imaging treatment whereby at selected areas thereof an ink
20 receptive image is formed, attaching the imaged plate to the
plate cylinder of a printing press, and without wetting the
unimaged areas of the plate, repeatedly (1) rolling the surface
of the imaged plate with an ink roller to ink the imaged areas
and (2) printing from the ink image on to a receiving surface.
The process of producing a dry planographic plate which
comprises coating at least on~ surface of a flexible substrate
having sufficient strength to withstand the stresses normally
produced by the lithographic process with a silicone rubber
containing material which upon curing gives a surface having
low enough surface energy that the silicone rubber containing
material will not remove conventional lithographic ink from
rotating inking rollers, and thereafter curing said silicone
rubber containing material.
~; -5-
The new planographlc plate of this supplementar~
disclosure comprises a sheet of flexible substrate sufficient-
ly strong to withstand the stresses normally employed in a
lithographic printing process~ said substrate having coated
on at least one surface thereof a layer of silicone rubber
having a surface energy low enough that the silicone rubber
will not remove conventional lithographic printing ink from
an inking roller of a printing press.
The term silicone rubber as employed in the present
specification and claims represents a diorganopolysiloxane
composition which upon curing to a solid elastic state
provides a surface having a surface energy low enough that
it will not remove conventional lithographic printing lnk
from an inking roller. Representative silicone rubbers to
be employed in the present invention result from the curing
of a diorganopolysiloxane selected drom the yroup consist-
ing of:
(a) linear diorganopolysiloxanes having terminal
silicon-bonded acyloxy groups;
(b) linear diorganopolysiloxanes having terminal
reactive end-blocking groups and a metal salt
of carboxylic acid; and
(c) linear -~luid diorganopolysiloxanes having
terminal silicon-bonded hydroxy groups, a
metal salt of an organic carboxylic acid and
a member of the group consisting of an alkyl
silicate or methyl hydrogen polysiloxanes.
-5a-
.
, ~
~6~07~)
1 The term diorganopolysiloxane as employed herein represent~
disubsti~uted polysiloxanes wherein the substituents are mono-
valent aliphatic or cyanoalkyl groups having rom l to 4 carbon
atoms, inclusive. Representative aliphatic and cyanoalkyl groups
include methyll ethyl, propyl, butyl, vinyl, allyl, beta-cyanoethyl,
beta-cyanopropyl and halo alkyl groups such as 3,3,3-trifluoro-
propyl and chloromethyl. Representative organic carboxylic acida
include tin naphthenate, tin octoate, lead octoate, tin oleate,
iron stearate, tin butyrate, dibutyl tin dilaura~e, dibutyl tin
diacetate, zinc naphthenate, lead 2-ethylhexoate and the like with
the tin and zinc salts generally being preferred. The term
reactive end groups as employed in the present invention designates
acetoxy, hydroxy and oxime groups.
The diorganopolysiloxane compositions employed to pro-
duce the solid but elastic sillcone rubber films of the present
invention are conveniently applied to at least one surface of the
flexible substrate in the form of an aqueous emulsion or acqueous
or solvent dispersion. The diorganopolysilox~ne compositions are
applied to the substrate by means o a blade coater, Mayer bar~
reverse roll coater, knife or by other commonly employed coating
techniques. The surface to be coated should be clean and preferably
dry when the diorganopolysiloxane composition is applied. The
silicone rubber film can be of any desired thickness as long as
the film is coherent, continuous and securely bonded ~o the
substrate. It has been found convenient to apply the diorgano-
polysiloxane composition in an amount sufficien~ to provide a
coating of silicone rubber having a thickness of from 0.02 to 0.2
mils. Films thicker than 0.2 mils can be employed; however, they
are generally not deemed to be necessary.
Following the application of the diorganopolysiloxane
- 6 -
1 composition to the surface of ~he subs~rate, the diorganopoly-
siloxane composition must be allowed to cure to produce the solid
but elastic silicone rubber. Most of the diorganopolysiloxane
compositions of the present invention cure at room temperature.
The curing generally takes place within minutes to 24 hours.
However~ the curing time will vary according to thickness of the
film, humidity and temperature. While most of the diorganopoly-
siloxanes cure at room temperatures and, therefore, do not require
additional heating, the coated plate can be keated to decrease
the cure time if desired. When employing a diorganopolysiloxane
composition comprising a fluid diorganopolysiloxane having terminal
silicone bonded hydroxy groups, a metal salt of a carboxylic acid
and a methylhydrogen polysiloxane, heat curing is recommended,
temperatures of from 90 to 500~F are operable and temperatures
between 90- and 160~F are preferred. Curing is obtained by hea~ing
the fil~ to be cured for a period of from about 10 seconds to
about 3 minutes or more. The cured solid but elastic silicone rub-
- ber films of the present invention have a free surface energy (Ts)
of 25 or less ergs/cm. . The use of silicone rubbers havi~g a
- ~ 20 surface energy above about ~ ergs/cm.2 resul~s in background areas
which remove ink from a rotating ink roller and thereby cause back-
ground inking and toning.
The flexible substrate employed in the present invention
should be sufficiently flexible that it can be mounted on a lltho-
graphic press and strong enough that it can withstand the s~resses
normally produced by the lithographic process. Representative
substrates include coated papers, metals or plastics such as poly-
(ethylene-glycol terephthalate). While aluminum appears to be the
preferred metal aubstrate on the basis of cost, handling properties,
and the like, sheets of lithographic zinc, foils of copper, steel
- 7 ~
` ~L6~7V
1 and copper surfaces all can be employed as the flexible subs~rate
in the present invention.
, Any grade of paper can be employed as the substrate in
the present invention provided that it has the s~rength to with-
stand the stresses normally employed in the lithographic process.
Such papers are well known in the art and generally range from 70
to 250 pounds per ream. The diorganopolysiloxane compositions
employed to produce the solid but elas~ic silicone rubber coating
can be applied directly to the surface of the paper. However, such
10 application often requires the use of relatively large amount of
diorganopolysiloxane compositions and the use of such large
amounts is generally not economically desirable. Therefore, in a
convenient pro~edure~ the surface of the paper plate is precoated
prior to the application of the diorganopolysiloxane composition.
The precoat serves to "hold out" the aqueous emulsion or organic
solvent carrier employed in the application of the diorganopoly-
siloxane compositipn. Coatings which provide the deqired carrier
"hold out" and are useful in the present invention include poly-
vinyl alcohol, casein, starch9 carboxylated starch, hydroxy-
20 ethylated starch, alpha protein, styrene butadiene based coatings,
acrylic copolymer coatings, vinyl acetates, fluorocarbons and the
like. Such coatings may contain fillers, pigments, antlfoam
agents, spreading agents and other additives commonly employed in
` ~ paper coating compositions. A coated paper substrate designed to
give 15,000 or more copies is easily provided by a paper base
made from moderately beaten che~mical wood pulp fibers and weighing
from 80-90 pounds per ream of 500 sheets (25 x 38 inches in size).
A specific example of a suitable paper is one weighing 87 pounds
per ream made from a furnish containing beaten wood pulp fibers of
30 coniferousand deciduous trees, a small portion of clay filler~
3D ~
6~7~
1 rosin size and alum. The paper is then coated on one or both sides
with about 10 pounds per ream dry weight o clay and casein in a
5:1 ratio. '~he sheet is then dried and calendered.
Figures 9, 10, 11, 12, 13aand 13b are enlarged cross-
sections of plates having an ink repellent silicone rubber back-
ground.
The new planographic plate of the supplementary disclosure
as depicted by Figure 9 is comprised of a flexible substrate 1-05
having at least one surface thereof continuously coated with a fil~
106 of solid but elastic ink-repellent silicone rubber. Following
the curing of the diorganopolysiloxane to obtain the solid but
elastic silicone rubber layer, the plate is ready to be imaged. A
short run imaged plate is produced by passing the plate through a
xerographic electrophotographic copier. In this process, a powder
image previously electrostatically formed on a selenium-plated
drum is transferred by contact to the plate. The plate and image
are then heated to~cause the powder particles to fuse to each
other and to the surface of the plate. The i~aged plate produced
in this manner is mounted on a printing press, inked and used to
produce clean copies having no ink in the background areas. This
method of imaging the plate is useful for producing copies of
line copy and the like.
A pre-sensitized plate as illustrated by Figure lO is
prepared by applying to the cured solid but elastic surface of the
silicone rubber film 106 one of the water soluble photo-responsive
diazo compounds employed in conventional diazo-sensitized litho-
graphic plates. The dried powdered photo-responsive diazo compound
is rubbed over and onto the surface of the silicone rubber to pro-
duce a photo-responsive diazo layer 113 which adheres to the surface
of the silicone rubber. The excess diazo not adhering to the
_ 9 _
,~
6~iQ~
1 surface is removed by light brushing~ air knife or the like. The
sensitized plate thus prepared is exposed through a negative
transparency 114 to radiation having a wave length of the proper
magnitude to initiate the photo-response of the diazo layer.
Cenerally, actinic radiation will be suffi~ient to initlate ~he
photo-responsive reaction. However, radiation having a wave length
outside of the range of actinic radiation may be employed when
necessary. During the radiation procedure, those areas of the
plate exposed to radiation become insoluble and oleophilic forming
an image area 115 which adheres to the silicone rubber layer 116.
Following the radizton or exposure procedure, the surface of the
plate is washed with water to remove the unexposed water soluble
diazo compound leaving bared surfacesll6 of ink repelling silicone
rubber as the background. The washed plate is then dried and
mounted on a printing press. The rota~ing ink roIlers of the press
are applied to the sur~ace of the plate inking the oleophilic
image areas but leaving the unimaged silicone rubber background
areas clear.
In another embodiment of the present invention as
illustrated by Figure 11, the ink repellent silicone rubber i8
applied to the surface of a conventional pre-sensitized litho-
- graphic plate to provide in the non-imaged areas a silicone rubber
surface which will not remove ink from ink rollers and, therefore,
does not require wétting with a fountain solution. This embodiment
results in the formation of a long run pre-sensitized plate that
can be imaged by exposure through a posi~ive transparency and can
be made as follows. A flexible substrate such as an aluminum-base
diazo-sensitized plate as disclosed in the Case and Jewett U.S.
Patent No. 2,714,066 or a pàper-base sensi~ized plate as disclosed
in the Brinnick et al UJS. Patent No~ 2,778,735 is prepared.
-- 10 --
6~f~J
t The diazo sensi~ized pla~e comprised o~ a subs~ra~e 120 and a
diazo coating 121 is then coated with a layer 122 of silicone
rubber as hereln defined. The silicone rubber i8 applied by
conventional coating methods, and if desired, can be further
squeegeedor wiped down with a soft cloth to leave a film which
after hardening may be as thin as 0.05 mils or even 0.02 mils.
A thicker film, for example from 0.05 to 0.2 mils, can be left
if desired. A very thin film may harden sufficiently in about
half an hour, especially if the atmosphere is rather humid. But
ordinarily, especially for thicker films, it is preferred to let
the film age for about 24 hours before developing an i~age formed
thereo~. A latent image itself can be for~ed in the film any
time after the film has become reasonably firm by exposure of the
plate through a positive transparency 123. This exposure insolub_
ilizes the underlying diazo compound in the exposed areas 124,
that is the background or non-image area, but leaves the diazo
compound unchanged and still soluble in the image area 126.
The latent image so formed can then be developed at once, or if
desired the development can be postponed for 24 hours or longerO
Development is readily accomplished merely by swabb~ing the surface
with a cotton pad wet with water containing a small amount of a
wetting agen~ such as sodium lauryl sulfonate~ alkyl phenyl ethers,
polyethylene glycol, trimethyl nonyl ether of prupylene
alkylene glycol ethers and the like. The swabbing does not affect
the background area 124 where the exposed diazo compound apparently
acts to bond the sil$cone rubber to the underlying base; but in the
imaged areas 126 the silicone rubber and the- underlying still
soluble diazo compound are removed by the swabbing, laying bare
the surface of the original substrate. In those cases where the
si-licone rubber layer is unusually thick or has been aged for a
D
6V7(~
t considerable period, the swabbing liquid may be a m~x~ure o~ equal
parts of trichlo~oethane (sold a~ P & J cleaner) and xylene and
about 1/4 part of ethylene glycol. The bared surface of the
substrate in the image area 126 accepts ink from the rotating
anking rollers and prints it either directly upon paper or upon
an offset blanket which will transfer the print to paper. Normally
the substrate image, when dry, will accept either oil-base ink or
aqueous-base ink, depending upon which is applied first. In
most cases~ the layer of silicone rubber will be ~in enough
that the recesses left by its removal in the image area are so
shallow that the plate can be considered to be a planographic
plate. Of course, thicker layers of silicone rubber can be used,
`~ and in such cases the image areas 126 may be too deep to be inked
by the usual inking roller. Deep image recesses may be filled
with ink-receptive matter to make the image flush with the plate
surface. For use when printing with greasy lithographic ink is
contemplated the recess filler used should be oleophilic, e.g.,
a viscous polyvinyl acetate emulsion, asphaltum, lacquers or the
like. When use of aqueous ink is contemplated, the recess
filler should be hydrophilic, for example, a mixture of zinc-
carboxymethylcellulose and clay, or the li~e.
In a still further embodiment of the present inven ion,
- - as illustrated by Figure 12, a long las~ing plate tha~ can be
. given a laten~ image by exposure through a negative transparency
is made as follows. A flexible metal substrate 130 such as
aluminum or zinc is coated with from 1 to 50 grams per square
meter of diorganopolysiloxane composition to form silicone layer
131. Immediately after applying the diorganopolysiloxane layer 131
and while the layer is still tacky, a sheet of soft chemically
; etchable me~allic foil 133 ls pressed into intima~e contact with
- 12 -
~. , ` ,' .
~L6~V
1 the liquid layer. Representative chemically ethable metallic
foils include ~inc, copper and alu~lnum. The sandwich so formed
is allowed to age for from 12 to 96 hours to permit the silicone
rubber to cure or become solid, and to form an adhesive bond with
the metallic foil 133. Thereafter, the exposed surface of the
foil 133 is cleaned by brief immersion in a standard etching
solution, washed and dried. Next the clean and dry surface is given
a photopolymerizable photo-resist layer 134 and exposed through
a negative transparency 136. The exposure hardens and insolubilizPs
the photopolymerizable material in the exposed areas 138 to form
a latent image. Thereafter, the surface s swabbed with a photo-
resist developer which removes all the unexposed photopolyermizabl
material in area 140 and leaves the underlying foil 133 bare, but
does not remove the photopolymerized layer in the image area 138.
Then the surface is again immersed in the same etching solution
in which the foil 133 had previously been cleaned and allowed to
remain there until all of the foil 133, except that covered by
the photopolymer image, has been disso~ved down to the underlying
silicone rubber background 131. The plate is then thoroughly
washed and dried. This plate, after the background had been etched
away, has an image area of metal, still covered by ~he photopolymer
resist, raised slightly above the silicone background, and so is
not, strictly speaking, a planographic plate. However, the plate
can be used in the same way, and on the same printing press, as
the other plates having si~icone rubber background areas as
described above. In such use the rotating inking rollers and
offset blanket will come in contact with the sillcone rubber
background. The sillcDne rubber background remalns free of
ink as in the previously discussed cases and doesnot print on
the offset blanket or paper.
- 13 -
D
7 [)
~ nother embodimen-t o~ the present invention as illustrated
by Figures 13, 14 is prepared as follows- a silicated aluminum plate
50 is sensitized with a conventional diazo compou~d, exposed and
developed by swabbi~g with an aqueous emulsion of lacquer which
removes unreacted diazo and leaves a layer of lacquer 51 on the
exposed image area 52. ~fter washing, the entire surface of the
plate is again swabbed with aqueous solution of a photo-responsive
diazo compound such as the formaldehyde condensate of a paradiazo-
diphenyl amine salt or the like to form the layer 53. The plate
is then allowed to dry, and thereafter coated with a layer of sili-
cone rubber 54. The silicone layer is cured and the en-tire plate
exposed to radiation of sufficient wave length to initiate the
photo-responsive reaction o~ the diazo compound. By this -treatment
the diazo compound is insolubilized and its adherence to the
silicone rubber layer is improved, and likewise the silicone
rubber layer itself is further cured. ~ext, the plate is swabbed
vigorously with a mixture of e~ual parts of l,l,l-trichloroethane
and xylene and 1/4 part of ethylene glycol which penetra~es through
the silicone layer 54 and loosens the lacquer layer 51 covering
the image area 52. The lacquer and overlying silicone rubber
come away from the image leaving the imaged area 52 slightly
recessed. The plate thus prepared can be used in this condition
or the recessed areas can be filled with oleophilic material such
as viscous polyvinyl acetate emulsion. In the la-tter case the
resulting plate has a level surface, with imaged areas of
oleophilic polyvinyl acetate and ink-repellent background areas of
a silicone rubber.
By way of amplifying the description of Figures 13 and
14, the silicated aluminum plate 50 is sensitized, exposed and
~ - 1~
6'6'~
developed. During development of this plate by use o~ the aqueou~
-- lacquer emulsion, the unexposed and soluble diazo in the non-
image areas is removed leaving the insoluble exposad diazo image
layer 5~ coated with the layer of lacquer 51. The exposed and
developed plate comprised of the substrate 50, the insoluble diazo
image 52 and the lacquer layer 51 is then coated with an aqueous
solution of photosensitive diazo material to produce the
anchoring diazo layer 53. The plate is then allowed to dry and
a layer of silicone rubber 54 is applied over the unexposed
anchoring diazo layer 53. After the silicone layer is allowed to
cure the entire plate depicted by Figure 13 is exposed to actinic
radiation which insolubilizes the entire anchoring diazo layer 53.
The exposed plate is then swabbed with a mixture of trichloroethane,
xylene and ethylene glycol. This mixture penetrates the silicone
layer 54 and the anchoring diazo layer 53 and dissolves the
lacquer layer 51 causing the lacquer and anchoring diazo and
silicone layers immediately above the image to come free leaving
; a plate shown in Figure 14 consisting of a substrate 50, an
insoluble diazo image area 52 and e~posed anchor diazo layer 55
covered by the silicone rubber layer 54. The relative thic~nesses
of the various layers are not accurately depicted by the drawings.
The second exposure of the entire plate causes the anchor diazo
layer to become insolubilized and to bond the silicone to the
non-image areas of the plate. The lacquer layer prevents the
anchoring diazo layer from bonding securely to the diazo image
area and -thereby allows the silicone and anchoring diazo layer
to be removed by the trichloroethane containing mixture.
Other plates can be made by coating a metal or paper
plate with layer of silicone rubber, curing the silicone rubber
at room temperature for several hours, and then using an engraver's
14a -
1 tool to cut a pattern ~hrough the silicone to the un(lerl~ln~ ~ase,
The pattern is then ink-receptive, but the silicone layer is not.
Tl1is plate thus prepared can then be employed on a press or the
pattern can be ~illed with an oleophilic substance before the
plate is so employed.
EXAMPLE l
A paper plate is prepared from paper stock which is
- composed of about equal amounts of long fibers and short fibers and
contains from ~ to 8 percent mineral filler. The paper stock is
` 10 sized with rosin and alum and weighs-about 52 pounds per ream
~500 sheets - 25" x.38"). One side of the paper is base-coated
with lO pounds per ream dry weight of a coating comprised of clay
(lOO parts), casein (20 parts) and dimethylol urea (2 par~s) and
is then dried and calendered. The paper plate is then revers-
roll coated with 2 pounds dry weight per ream of a xylene disper-
sion of a diorganopolysiloxane composition comprised of a
dimethylpolysiloxane, methylhydrogensiloxane and ~inc octoate,
and the resulting layer of diorganopolysilo~ane is dried and cured
for 40 seconds at 500F. The silicone rubber coated plate is then
fed through a Xerox~ 91~ copy machine, (an ofice si~e seleniu~
drum copies). As a result of this procedure, a powder image
previously elec~rostatically formed on a selenium-plated drum i8
transferred to the plate. ~l'hiE~ image is then heated to cause
powder particles to fuse to each other and to the surface of the
plate, The plate thus prepared is then mounted on a rotary offset
duplicator (Addressograph-Multigraph Corporation, Multilith*
No. 1250, an office size offset duplicating machine,) from which
the molleton rollers (water fountain rollers3 have been removed.
The plate is merely clamped to the plate cylinder and while dry is
inked with regular lithographic ink (Addressograph-Multigraph ink
No. Ml* 3~, a linseed oil based medium tack test ink) by the inking
roller and the ima~e is printed on the off~let blanket ~rom which
it was transferred to a paper sheet. Fifty copies having
~r~ -15 -
~ *Indicates a Trade Mark
1 clean un-inked background areas are produced from this plate.
EXAMPLE 2
A paper substrate as prepared in ~xample 1 is air ~ni~e
coated with 3 pounds per ream dry welght of a diorganopolysiloxane
composition composed of dimethylpolysiloxane ha~ing silicon-bonded
hydroxy groups, methylhydrogen polysiloxanes and dibutyl tin laurate,
The diorganopolysiloxane composition is dispersed in toluene ln an
amount sufficient to provide a dispersion having about 10 percent by
weight of solids. The coating layer is cured at 300~F for about 5
minutes. This plate is then sensitized by rubbing the silicone rub-
ber surface with a cotton pledget filled with powdered double
chloride of zinc and the para-formaldehyde condensate of diazotized
para-aminodiphenyl amine. Excess diazo powder is then carefully
wiped off. The sensitized plate thus prepared is then exposed
through a negative transparency to a 35 amp. double carbon arc at a
distance of 36 inches for one minutes. The partially exposed plate
is then washed or developed with water to remove the diazo compound
from the unexposed areas. The plate thus prepared was completely
dried and clamped to the plate cylinder of a rotary offRet dupli-
cator as described in Example 1 and the plate inked and employed toproduce over 50 copies. The copies thus produced were clean with
no toning or inking in the bac~ground areas.
E~AMPLE 3
An aluminum based diazo sensi~itzed plate is prepared by
coating an aluminum plate with an aqueous solution of sodium sili-
cate and thereafter coating the silicated surface with an aqueous 1
percent solution of the double salt of ~inc and condensa~e of para-
formaldehyde and para-dia~o-diphenyl amine as described in United
States Patent No. 2,714,066. After the diazo coating has dried, a
layer of the diorganopolysiloxane composition is applied by Mayer bar
coater. The diorganopolysiloxane composition com~ises dimethyl-
- 16 -
v
1 polysiloxane gums, silane oxime and titanium dioxide. '~'he ~rface
bearing the dior~anopolysiloxane coating i~ wiped down ~/ith ~ 80ft
cloth to leave a film which has a thickness o 0.05 mils after
curing for about 12 hours at room temperature. The plate thus
prepared is exposed through a positive transparency for 60 seconds
- to a 35 ampere double arc at~a distance of 36 inches. Following
the exposure, the surface of the exposed plate is swabbed with a
water solution containing a small amount of ~astman Kodak's FOTOFLO*,~
a wetting agent, currently used in the lithographic trade of unknoT~n
~0 compositions. This water removes the silicone layer and soluble
diazo compound rom the unimaged areas, laying bare the surface of
the original substrate in these areas. Thereafter, the plate is
dried~ mounted on a rotary press as described in Example 1, inked
and employed to produce lOOO clean copies.
EXAMPLE 4
A S mil sheet of aluminum foil having a surface roughened
by sand blasting is coated with a 0.2 mil layer of a diorganopoly-
siloxane comprised of hydroxyl end-blocked dimethylpolysiloxane
and vinyltriacetoxy silane, said composition on curing forming an
acetoxy end-blocked vinyl substituted dimethylpolysiloxane silicone
rubber~ Immediately thereafter while the diorganopolysiloxane
layer is still llquid, a 3 mil sheet of soft copper foil is pressed
i~to intimate contact with the aforesaid layer. The sandwich so
formed is allowed to age for 72 hours. Following the aging period,
the exposed surface of the copper is cleaned by immersing for two
minutes in a standard etching solution consistlng of the following:
lOO milliliters of calcium chloride solution
of 40-41 F Baume,
380 grams of ~inc chloride,
285 milliliters of ferric chloride solution
of 50-41 F Baume, and
~Indicates a Trade Mark
- 17 -
1 14 milliliters o~ 38 percent hydrochloric acid.
Following the etching procedure; the copper surface is immediately
washed and dried, The dry copper surface is then given a photo-
resist layer of a photopolymerizable material containing a poly-
vinyl cinnamate polymers. The photo-resist layer is dried and the
surface exposed through a negative transparency to the light
from a 35 ampere double arc at a distance of 36 inches for three
minutes. Following the exposure period, the surface of the pla~e
is swabbed with developer which removes all of the unexposed
1p photopolymerizable material and leaves the underlying copper bare
but does not remove the photopolymerized layer in the image area.
The surface of the plate is then immersed in the same etching
solution in which the copper was previously cleaned and allowed
to remain there until all the copper except that covered by
the photopolymer image has been dissolved. The plate is then
washed and driedO The plate thus prepared is then mounted on a
rotary press as described in Example 1, coated with ink and used
to print 10,000 copies.
EXAMPLE 5
A sand blasted aluminum plate is treated with sodium
silicate, washed and dried, and thereafter sensitized by swabbing
with an aqueous 2 percent solution of a zinc salt of the con-
densate of para-formaldehyde and para-diazodiphenyl amineO
-~ ~ Following the coating procedure the plate is dried and the dried
plate ~exposed through a negative transparency for 60 seconds to
a 35 ampere double arc at a distance o 36 inches. The image
so formed is developed by swabbing the surface of the pla~e with
`~ an emulsified colored nitrocellulose lacquer in an aqueous solution- of gum arabic. This procedure removes the diazo compound from the
unexposed or background area but does not remove the exposed
.
- 18~--
13 ' ' '
~6~
l image. In addition, the emulsion breaks su~icientl~J ~o permit
- the lacquer to adhere to and coat the surface of the image. ~he
plate is then uashed with water to remove all traces of the gum
arabic from the surface of the plate without removing the lacquer
from the image area. ~ollowing the removal of the gum arabic,
the pla~e is again swabbed all over with an aqueous solu~ion of
theformaldehyde condensate of a para-diazodiphenyl amine salt and
then allowed to dry. The dried plate is ~hen roller coated wi~h
a diorganopolysiloxane composition comprises of an acetoxy end-
blocked dimethylpolysiloxane and dibutyl tin diacetate in an amount
sufficient ot provide about 35 grams per square meter of the
diorganopolysiloxane composition. This layer is allowed to
aircure for 30 minutes and then it is exposed over its entire
surface to radiation from a 35 ampere double arc lamp at a distance
of 24 inches for 3 minutes. By this treatment the diazo compound
is insolubilized and its adherence to the silicone layer improved,
and likewise the silicone layer itself is further cured~ Next,
the plate is rubbed with a mixture` of equal parts of 1,1,1-
trichloroethane and xylene and 1/4 part of ethylene glycolO Thia
liquid penetrates through the silicone layer and loos~ens the
lacquer layer covering the image and the rubbing removes the
loosened silicone rubber leaving the image area slightly recessed.
Thé depressions thus formed are filled with polyvinyl acetate
emulsion and allowed to dry. The resulting plate has a level
surface, with image areas of oleophilic polyvinyl acetate and
ink repellent background areas of silicone rubberO The plate thus
prepared is mounted on a lithographic press as described in Example
l and used to print 1500 copies.
The various diorganopolysiloxane compositions employed
in the present invention are known in ~ha art and are prepared in
- 19 -
D
.
f~
1 accordance with known methods. Represèn~a~ive acetoxy end-blocked
diorganopolysiloxanes to be employed in the present inventlon,
such as the dimethylpolysiloxanes, vinyl substitu~ed dimethyl-
polysiloxanes, alkyl substituted dimethylpolysiloxanes, cyanoalkyl
Subs~ituted dimethlypolysiloxanes and 3,3,3-trifluoropropyl and
other haloalkyl substituted dimethylpolysiloxanes, are prepared
in accordance with methods known to the skilled in the art as
illustrated by ~he teachings of United States Patent Nos.
3,035,016 and 3,077,465. Representative diorganopolysiloxane
compositions comprised of dimethylpolysiloxanes having terminal
silicon-bonded hydroxy groups, methyl hydrogen polysiloxane and
dibutyl tin 'dilaurate or dibutyl tin diacetate are also well known
in the art and are produced in accordance with known methods. A
representative method of production is taught in United States
Patent No. 2,985,545. Similarly, the diorganopolysiloxane com-
positions comprised of diorganopolysiloxanes having terminal
sllicon-bonded hydroxy groups, an alkyl silicate and a metallic
salt of an organic carboxylic acid are known in the art and are
produced by known methods such as the procedures taught by United
States Patent No. 2,843,555.
The photo-responsive diazo compounds to be employed in
the present invention are well known in the art. Representative
diazo compounds are described in United States Patent Nos.
2,714,066 and 2,778,735, and include 4-(N-benzyl-N-ethyl)-amino-
aniline, 4-(N-2,6-dichloro-benzyl)-amino-aniline, 4-(N-cyciohexyl~-
amino-aniline, 4-amino-2,5,4'-tribromo diphenylamine, 4-amino-2',
4',6'-trichloro-diphenylamine, 4-amino-2-[N-~2 9 5-diethoxy-phenyl)-
sulfamido]-diphenylamine, 4-amino-3,6-dimethoxy-diphenylamine-2'-
carboxylic acid, l-amin~-2,5-di-n-propoxy-4'-me~hyl-diphenylsulfide,
N-(2,6-dichlorobenzyl)-3-amino-carbazol, 4-N-2,3,4,6-tetrachloro-
benzyl)-amino-aniline, 4-(N-2,6-dichloro-benzyl-N-ethyl)-amino-2,5-
- 20 ~
~ , ' ` ,
1 diethoxy-anilin~ and 4-amino-2,5,4'-triethoxy-diphenylether and
their aldehyde condensates and the sulfonates of both.
The term conventional lithographic ink as employed in
the present invention refers to the inks commonly employed by
tpose skilled in the art and may be generally de~ined as being
hlghly pigmented varnishes of hèa~bodied linseèd oil or ~he
equivalen~ and giving inkometer values from about 12-20 when
measured at 90F and 40b r.p.m. Thie inkometer values are standard
test values and the test is fully set for~h in United States
Patent No. 2,101,322.
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