Note: Descriptions are shown in the official language in which they were submitted.
3~3
B~C~GROU~ID
This invention relates to lithograplli.c printing plates
with visible images and to a process for making such plates.
Lithographic printing techniques, using, for example,
anodized and silicated aluminur,l base plates such as described
in Fromsonlpatent llo. 3,1gl,461 issued May 4, 1965, have come
into widespread use in the printing industry and especially in
offset printing and direct lithographic printing by newspapers
using converted letterpress printing presses.
A conventional negative working lithographic printing,
plate of this type has a coating of a light sensitive sub-
stance that is adherent to ~.he aluminum base slleet for ex-
posure. If the light sensitive coating is applied to the base
sheet by the manufac~u~er, the sheet is reEerre(l to as a
"presensitized plate". If the light sensi.tive substance is
applied to the base by the lithograpl~e]^ or trade pla~e mclker,
the plate is referred to as a "w.ipe-on plate". Depending on
the nature of the photosensitive coatin~, employed, a coated
plate may be utilized to reproduce directly the i~age to whicl
it is exposed, in which case it is termed a positive-acting
plate, or to produce an image cor.~plementary to the one to
which it is exposed, in whicll case it is termed a ne~ative
acting plate. In either case, the image area of the developed
plate is oleophilic and the non-image area is hydrophilic. ! ''
In the case of negative worl~ing pla~e, the surface
is coated witll an aqueous solution of a col~ventional diazo
resin. The plate is dried and exposed ~hrougll a negative.
3~3
The exposed image areas become water insoluble and the un-
exposed non-image areas remain water soluble. The plate is
conventionally developed with a lithographic lacquer which
consists of a two-phase system, one phase containing an
oleophilic resin in a solvent and the other phase a
hydrophilic gum. Upon application, the oleophilic resin
adheres to and makes visible the exposed insoluble areas,
while the hydrophilic phase dissolves away the unexposed
soluble non-image or background areas. In this way, the
visible image is made oleophilic or ink receptive and the
background is made hydrophilic or ink repellent.
In the present invention we provide a lithographic
substrate and plate that produces a visible image upon
development without relying on a component of the developer
to become adhered to the image area.
SUMMARY
The present invention provides an aluminum litho-
graphic substrate which has been treated to render the sur-
face hydrophilic and negatively charged and thereafter
ionically colored with a cationic dye.
The invention further provides an aluminum printing
plate the surface of which has been treated to render it
hydrophilic and negatively charged and then coated simultan-
eously or sequentially with a light sensitive, cationic,
3~3
positiv~ly cl~r~c~ ~ia~oniull m~l~c~ l(l(l (ILiol~ Iy~. .L`h~
coate~ surface is capa~l~ of l~avi.n~ its solul~ility altercd
upon exposure ~o ac~inic li~llt all~l tl-lere~lf~:er cl~velope~ to
produce a visible, dyed imay~ l a l~y~rol?l~ilic ~.lck~,round free
of the cliazoniuM material an~ dye.
This invention :Eurther ~r~vi(~ (lye(l~noclize~l
aluminum article. Normally, ~Ino~ize~ ~lull~ um is dyed using
anionic and non-ionic dyes. U~ to llow, c.ltionic dycs
could not be used ~ecause tl)e surf,~ce o~ ~no~li..(~d a].~minu
is ei.~her neutral or acicl. It ha~ lloW l~C~ liscovere~l tllat
anodized aluminum can be effectively ~y~ ~r coLor~ witll a
cationic dye by first treatinl~ thc ~nodi.7,~ lluminulll to render
the surface ~hereof anionic. This makes i~ not~ po~sible to
color code products and ~rovi(l~ ~ visibl~ i.mage 011
lithograpllic pla~e withoul: i tl~ erEc~ WiL~ cl~veLo
proce~s or alterin~ ~he litho~ ic prop~ ies oF ~I pl.lt~.
It has been proposed to use an anionic dye on an anodized
. aluminum substrate for lithographic purposes (U.S. Patent Number 3 280 734).
However, this was not commercially successful because the dye remained
in the background after developing which caused scumming and toning
during pr;nting.
The present invention employs a cationic dye for anodized
aluminum which is ionically removed from the background during develop-
ment of the plate,while the color remains permanently in the image area
after exposure and development, without undergoing any change during
either process. This results in a visible image, with the substrate
ionically colored in the image area, and a suitable lithographic
background (hydrophylic and oleophobic) which has been ionically
c e red of the cat;onic dye.
~ 4
5~30~
DESCRIPTION
Cationic dyes used in the invention can be ap~lied
to the negatively charged substrate or incorporated in the
light sensitive material to provide a visible image on the
plate. Suitable dyes include basic cationic dyes such as
Victoria Green, Rhodamine B, Rhodamine 5GLD, crystal violet,
extra pure APN, Paper Blue R and the like. -
Cationic light sensitive materials that can be usedin the invention are diazonium materials having reactive sites
capable of being chemically altered by light or chemically
reacted with an anionic material. For example, 4-diazo
diphenylamine condensed with a carbonyl compound such as
formaldehyde has the needed multiplicity of reactive sites
each having the desired dual functionality. Preferred are
water soluble diazonium compounds but water insoluble compounds
can also be used. Suitable diazonium compounds are described
in U . S . 3,849,392 to Steppan and U.S. 3,311,065 to Steppan.
Suitable anionic materials are water soluble and
include the alkali metal salts of alkylaryl sulfonates havin~
l-~o 20 carbon atoms in the alkyl portion and 6 to 14 carbon
atoms in~the aryl portion, alkali me-tal salts of alkyl
sulfonates having 12 to 20 carbon atoms and ammonium and
alkali metal salts o~ sul-Eated higher fatty alcohols having 10
to 20 carbon a~oms. ~nionic materials are dissolved in an
ionizing reaction medium (usually water)~and the concentration
of the anionic material is sufficient to couple with the light
sensitive material and to dissolve the coupled reaction product
from tl-e unexposed areas.
Specific examples of anionic surEàctants are given
herein together witll a test to detennine suitability.
3~
The aluminum substrate is treated to render the
surface hydrophilic and anionically charged. The preferred
lithographic substrate is anodized aluminum which may be
pretreated before anodizing to roughen or grain the surface,
for example using mechanical, chemical or electrochemical
techniques as are well known in the art and it may be
post-treated after anodizing. It is preferred to impart
hydrophilicity and a negative charge by silicating as des-
cribed in Fromson U.S. patent No. 3,181,461.
After treatment with the anionic materialS the
image can be reinforced with an oleophilic W curable
material which can be coated on and then cured.
Suitable W curable materials are commercially
available from a number of sources in the form of W curable
in~s, coatings, oligomers and monomers. Such commercially
available materials can be obtained from the following
companies: Inmont Corporation, Sinclair & Valentine,
Celanese Chemical Company, 3-M Company, Desoto Chemical
Company, Paulimer Industries, Shell Chemical, Mobile Chemical,
W.R. ~race, Design Coat Company, and Ware Chemical Corpora-
tion.
W curable materials including monomers and oligomers
are described in the following patents:
U.S. 3,297,745 1967
U~S. 3,380,381 1968
U.S. 3,673,140 1972
U.S. 3,770,643 1972
U.S. 3,712,871 1973
U.S. 3,804,736 1974
There are also materials that will cure upon exposure
to other sources of radiation, for example an electron beam.
~ 5~3~
These curable materials can be used in special applications in
place of the W material and are commercially available.
Electron beam curable compositions are described in U.S. patents
3,5~6,526-30, 1971.
Producing a visible image by chemical amplification
after exposure to actinic radiation makes it possible to sub-
stantially reduce exposure times normally re~luired with
diazonium compounds. This can be expressed er,~pirically as
simply the amount of actlnic light necessary to produce an
image capable of running on a lithograpllic press. Chemical
amplification makes it possible to reduce the amount of light
needed to attain this by a factor of from 2 ko 10 or more.
This means that a diazo sensitized plate that normally re~uired
1 or ~ minutes to image can be imaged in a matter of seconds.
The amount of diazo on the plate can also be reduced.
The amount of light necessary to produce an image
capable o~ running on a lithographic press can also be
expressed in terms of millijoules per square centiMeter. The
amount of actinic light can be from less than abou~ 100 to as
little as 5 millijoules/cm2 at UV wave lengths of 300-400
namometers. This ~eans that plates can be exposed with 10W
power lasers s-uch as àre marketed by EOCOM Inc. and developed
to produce a visible image.
~ fter treatment witll the preferred anionic material,
the developed amplified image can be blanket exposed to
actinic light to photo react any remaining light sensitive
sites in tlle image area. Thls includes coupled dia~oniutn and
anionic materials which remain light sensitive after coupling.
A test to determine whe~her a particular anionic
material is suitable is as ~ollows:
A 5~/~ aqueous solution of ti~e anionic material
is prepared. An aluminurn lithograpl~ic plate grained, anodized,
and silicated is coated with a 1% solution of a li~ht sensitive
diazo condensation product (such as Eairmont 's Chemical Diazo
~4). The coated plate is exposed to a Stouffer Gral~hic Arts
Guide for a relatively short period of time -- 5 to 10 secon(ls.
The exposed plate is immersed in the 5% solution of anionic
material for 10 seconds. The plate is then rinse~ and
lacquered with a standard l:ithographic lac~luer (such as
Fairmont ' s Dlack Lacquer) . Another plate, iderltically pre-
pared and exposec~, is treated with the Black Lacquer only.
This is the control. The two plates are compared. If the
anionic rnaterial is effective, the post-treated plate will
show significant difference in ligllt sensitivity versus the
con tro l .
The effectiveness of certain anionlc materials can
be enhanced by either a pH adjustment and/or the use of a
co-solvent. The optimum pll for most anionic materials
useful i.n this invention is in the range of F~H 2-1~). Suitable
co-solvents are alcohols such as ethanol, butanol and the like ¦
an~l glycols.
~ lany different salts of anionic materials are suit-
able; -tllese include sodium, llthiurn, ammonium, or triethanol
amine sal ts and tlle like . Exarnples of suitabl e anionic
surfactants (and their commercial sources) are as follows: ` !
1. Sodium lauryl sulfate (Proctor & Gamble, Equex S.
E(luex SP; Alcolac, Inc. Sipex SB).
2. Ammonium lauryl sulfate (Alcolac, Inc.,
Sipon L-22).
.' . I .
'~ 5~30~
3. Sodium la~lryl etl~er sul~a~e (Alcolac, Inc,,
Sipon ~S).
~. Sodium ~odecy] ~enzene sulEollate (~lcolac,
Il~c. Siponate DS-XO).
5. Ammonium lauryl ether sulfollate (Alcolac, Inc.
Sipon EA).
6. Triethanolamlne lauryl sulEate (~lcolac, Inc.
Sipon LT-6).
7. Sodium al]cyl sulfate (Alcolac, Inc., Sipex OL.S).
. Sodium stearate (~mery Incls.).
9. Sodium palmitate (Emery Inds.).
10. Sodium oleate (~latlerson~ Coleman & Bel]).
11. Dioctyl sodium sulfosuccinate (Cyanamicr,
Aerosol OT).
12. Tetrasodium N-Cl, 2 dicarboxyetllyl 1) - N -
octadecyl sul~osuccinate (~yallalnld, ~erosol 22).
13. Sodium Xylelle sul~otlate (Wl~co Cllemical,
UItra SXS).
14. Sodium toluene sul~onate (W:itco Cllemical,
Ultra STS),
15. Sodium Gumene sulfonate (Witco Chemical,
Ultra SCS hydrotrope).
16. Sodium dihexyl sulfosuccinate (Cyanami~e
Aerosol AY-65)
17. Sodium diamyl sulfosuccillate (Cyanami~e Aerosol
AY-G5).
l~. Atlionic phos~hate surEactallt (Rollm ~ llaas Co ,
Tri~on QS-30).
19. Sodium al~ylaryl polyetller su]:~atc (Rollm &
llaas Co., Trlton ~-30 COllC. ) .
3~
20. l'llospilate surfactallt, l~otassiunl salt (l~ohr,l &
llaas Co., Triton ~1-66).
. 21. Sodiurn alkylaryl polyetller sulforlate (Rohm &
llaas Co., Triton X-200).
Sodium lauryl sulfate is preEer~-ed ~ecause of its
availa~ilitv and cost.
~XAM ~ 1 (control)
~ , , :
A 1',' solution of tlle formaldellyde condensation product
o~ a diphenylamine - 4 - diazonium zinc chloride double salt .¦ ..
(Fairmont Diazo l'esin ~y4) is prepared in water. The solution
is placed in a t~o roll coating machine. A brushecl ~rained,
anoclized and silicated plate, 10 x 16 ~ 0.1~ no-Coil Delta :
Plate) is coated ace down ~llrougll tlle machine. The coated
plate is dried and placed in a I~u ~rc Plate ~1akel- exposure .
unit, 24 inches ~rom tlle source (4 Icw lam~ tou.E:Eer Grapllic
Arts Step scale is step exposed on the plate for the i.oll.owin~
times: 1 second, 5 seconds, lO seconds, 15 seconds, 30 seconds,
and 60 seconcls. The exposed plate is then developed with
~airmont's black lacquer for ~ipe-on plates. Aiter clevelopment,¦
rinsing, ancl dryin~ the solid step exposure level is read Eor
each exposure time: 1 second - no image, 5 seconcls - no image, ¦
10 seconds - a ghost image, lS seconds - a solid 1, 30 seconds -
a solid 3, and ~0 seconds - a solid 5 --- normcll for thi.s type
of p~ate system.
. ~
EX~ 2 ~ 3~3
A brush grained, anodized silicated aluminum plate
(Alloy 1100) is immersed in a dye bath of a 1,' so1ution of a
basic (cationic) dye such as DuPont's Victoria Green Liquid,
Rhodamine B Liquid, Rhodamine 5 GLD, crystal violet extra
pure APN or Paper Blue R Liquid. The dyecl plate is then coated
as in Example 1. The coated plate is tllen exposed in a ~ k~ i
~u Arc flip top exposure unit for 5 seconds to a newspaper
page negative. The exposed, dyed plate is immersed in a 5C/o
solution of sodium lauryl sulfate. Immediately upon removal
from the batll a strong visible image is seen on the plateO
E~U~ J
A brushed grained, silicatecl, ancl anodized plate
(Ano-Coil's Delta Plate) is coated with a 1% cliazo coating
(Fairmont P~esin #4) containing l/2% Victoria Green Liquicl dye
(DuPont). The plate is dryed and exposed for 5 seconds on a
Nu Arc as in Example 7. The plate is ~leveloped in a 5%
solution of amtnonium lauryl sulfate. Upon application oE the
developer with a sponge, a visible image becornes im~ediately
apparent.
. . ' ' ' I
Lxam!~le 4
~ lithographic plate (Ano-Coil's Delta plate) is dyed
in a 1% solution of VicT oria Green Liquid. The plate is
coated with a 1% solution of ~airmont diazo resin ~4 exposed
to a newspaper negative for 10 seconds and immersed in a 5%
solution o:E sodium lauryl sulfate. Immediately an image becomes
visible. The plate is rinsed in tap water and dryed. The
plate is placed on a Goss Metro rress and 50,000 good images
are obtained.
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303
E,~ PLE 5
. . ._ _
A plate is prepared as in Example 2 but a~ter devel-
opment it is rubbed with a UV curable emulsion (~xample 6)
rinsed, dryed, and re-exposed tI~rougll a P~G UV processor at
25 ft./minute. The plate is placed on a Goss ~etro newspaper
press and 250,000 impressions are obtained.
~ '
~Xl~IPL~, 6
A brush grai.ned, anodized, silicated, aluminum plate
is coated wit'n a l~o solution of water soluble poly~unctional
diazo resin (Fairmont's diazo resin #~? containing l/2%
Victoria Green liquid dye as in Example 2 and dryed. The sensi-l
tized plate is then placed in an Eocom Laserite Platemaker
and scanned witIl an ion argon laser. A scanni.n~ time of 1 ~l
rminute is necessary to scan a pla~e approximately 23 x 1~. The
approximate laser powe~ at the plate surface is 8 m;j/cm2.
A~ter scannin~, the plate is developed wi.tb a 5% solution of
sodium lauryl sulfate as in ~xample 2 to produce a strong
quality visible image.
: . I
E~MPL~ 7
. .
A plate was coated, laser exposed and developed as
in ~xample 5 using 10 mj/cm2 laser power. Tllis tiné after
.dev~lopment, the plate was rubbed with tlle following UV
curable emulsion: , I
(A) 30 grms Inmont UV Blue Inl~ ¦
. 12.5 cc Span ~0 (I.C.I.)
120 mls Cellosolve Acetate
(~) 250 mils 8 ~e Gum Arabic
12.5 grms Pluronic .~38 (BASF)
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Mix by adding ~B) to (A) ~hile stirring. The emulsion
can be applied with sponge, cloth, or brush. After treatment
with the W emulsion the plate is re-exposed in a high inten-
sity W processor such as a PPG Industries, Model PC2502A at
25 ft~minute. A tough and abrasion resistant visible image
is produced.
EXAMP~E 8
~ plate as described in Example 8 was dyed with a cationic
water soluble dye, 1% Victoria Green (DuPont)~ The plate was
coated with a 1% solution of diazo resin and dried. This
plate was laser exposed as in Example 5 with laser power of
4 mj/cm
After exposure to the laser, the plate is developed by
hand with sodium lauryl sulfate (5% solution). The thus
treated plate is then lacquered with a black lacquer from
Western Litho Company (Jet Black). A dense black image results.
EXAMPLE 9
An aluminum sheet (Alloy 1100) ;s degreased using a
commercially formulated de~reasing compound such as Aldet
(Wyandotte Chemical Company). The plate is degreased at 180
to 1~35F for 30 seconds at a concentration o~ 6 to 8 ounces/
gallon. Next the plate is rinced and anodized for 50 AMP -
minutes using sulfuric acid (280 grams/liter at 90F), rinsed
and silicated with sodium silicate (3%), rinsed and finally
dyed with a cationic dye such as Rodamine 5 GLD (DuPont) at 4
grams/liter. The dyed sheet is rinsed in tap water for
several minutes and then dried. A brightly colored aluminum
sheet results- The dye can be easily discharged using an
anionic surfactant (5%) such as sodium lauryl sulfate.
EXAMPLE 10
An aluminum sheet is degreased, rinsed and silicated as in
Example 9 but not anodized- The anionically charged surface isthen
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5~3~
., '.
dyed with a cationic dye such as Dupont's Paper Blue R Liquid 5 cc/liter
at room temperature for one minute. A b1ue sheet results. The dye is
resistant to rinse water but is easily discharged by immersion in a 5%
solution of sodium lauryl sulfate. ~ -
EXAMPLE 11
:---- !
A sheet of aluminum is degreased and anodized as In Example
9 but not silicated and a second sheet is degreased, anodized, and sili-
cated as in Example 9. Both sheets are then immersed for 30 seconds in a
1% solution of copper BF, an anionic dye, tSandoz) at 160 F and a pH
of 5.5. The first sheet which is not silicated and therefore cationically
charged takes the dye readily. The second sheet which is silicated will
not dye. The first sheet is immersed in 5% anionic surfactant to see if
the dye can be removed. It will not discharge w;th this treatment.
. , I
--1 4--
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