Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
`" 1153236
--1--
LONG-RUNNING WATER DEVELOPABLE
PRINTING PLATES AND COMPOSI~IONS
Background of the Invention
Planographic printing plates function by
5 providing dif~erential ink adsorptivity between exposed
and non-exposed areas after development. This is
ordinarily effected by coating a hydrophilic substrate
(e.g., an oligomeric diazonium resin coated aluminum
sheet) with a photocurable composition. `When the photo-
10 curable composition is exposed to light, it hardens. Thesubsequent application of an appropriate solvent washes
away unhardened, non-light exposed areas without removing
the photocured areas on the substrate. The hardened areas
will accept ink while the washed away areas with the hydro-
15 philic background areas will repell ink. This wouldtherefore provide a good planographic printing plate.
The expense, inconvenience, and even the
possibility of fire hazards in having to store developing
solutions have been recently overcome by the development
20 of a truly pure water developable lithographic printing
plate as described in copending Canadian Patent Applica-
tion Serial No. 346,444, filed 26 February, 1980. This
technology is a substantial advance in the art, but does
have its limitations, particularly in the running life of
; 25 the printing p~ate.
It is one aspect of the present invention to
improve the press life of water developable printing
plates.
:
Summary of the Invention
The present invention relates to water
developable printing plate compositions and printing
plates which have a longer press life than previous water
developable plates and compositions. It has been found
that the use of high amounts of oligomeric ethylenically
35 unsaturated components, wbile maintaining no more than a
j .
1153Z3~i
maximum ratio of low molecular weight ethylenically
unsaturated materials to film forming resins, enables the
use of lower amounts of water-softenable binder ~aterials
which provides a water developable printing plate with
longer press life capabilities.
The compositions useful according to the present
invention comprise a homogeneous mixture of:
A. 0.9 to less than lO percent by weight of a
water softenable polymeric binder,
B. 30 to 70 percent by weight of at least
diethylenically unsaturated polymericable
materials of which at least 50 percent by
weight of these materials have more than two
ethylenically unsaturated groups and a
molecular weight greater than 500,
C. 0.01 to 10 percent by weight of a free
radical photo-initiator system,
D. lO to 40 percent by weight of an organic
solvent soluble film forming binder, and
E. preferably 1 to 20% by weight of an
oligomeric, photosensitive, organic solvent
soluble diazonium resin,
wherein the ratio of at least diethylenically unsaturated
monomers having a molecular weight of less than or equal
to 500 to the total amount of film forming binders (A plus
D) is less than l/0.6.
Detailed Description of the Invention
As noted above, there are at least five
different components in the present invention, the water
softenable binder, the organic solvent soluble film
forming binder, the ethylenically unsaturated materials,
the photoinitiator system, and the solvent soluble
oligomeric diazonium resin. Each of these materials will
be described in their turn.
~ / ~
, . . . . .
~lS3Z36
--3--
The Oligomeric Diazonium Re
The photoreactive solvent soluble oligomeric
resin component which is optionally, but preferably used
iR the present invention is a diazo resin. These resins
must be organic solvent soluble, but may also be somewhat
water soluble and are known in the art as represented by
U.S. Patent Nos. 4,104,072; 3,933,499; 3,837,858; and
3,899,332. Examples of diazos useful in forming such
resins, which resins are generally known in the art, are:
4-diazo-diphenylamine,
1-diazo-4-N,N-dimethylamino-benzene,
l-diazo-4-N,N-diethylamino-benzene,
l-diazo-4-N-ethyl-N-hydroxyethylamino-benzene,
l-diazo-4-N-methyl-N-hydroxyethylamino-benzene,
1-diazo-2,5-diethoxy-4-benzoylamino-benzene,
l-diazo-4-N-benzylamino-benzene,
l-diazo-4-N,N-dimethylamino-benzene
l-diazo-4-morpholino-benzene,
l-diazo-2,5-dimethoxy-4-p-tolylmercaptobenzene,
1-diazo-2-ethoxy-4-N,N-dimethylaminobenzene,
p-diazo-dimethyl aniline,
l-diazo-2,5-dibutoxy-4-morpholino-benzene,
l-diazo-2,5-diethoxy-4-morpholino-benzene,
l-diazo-2,5-dimethoxy-4-morpholino-benzene,
1-diazo-2,5-diethoxy-4-morpholino-benzene,
l-diazo~2,5-diethoxy-4-p-tolylmercapto-benzene,
l-diazo-3-ethoxy-4-N-methyl-N-benzylamino-benzene,
l-diazo-3-chloro-4-N,N-diethylamino-benzene,
l-diazo-3-methyl-4-pyrrolidino-benzene,
l-diazo-2-chloro-4-N,N-dimethylamino-5-methoxy-ben2ene,
and
l-diazo-3-methoxy-4-pyrrolidino benzene.
These diazos are organic solvent soluble when an
appropriate anion is selected, for example from amongst
those known in the art, such as tetrafluoroborate,
~iS3Z36
triisopropylonapthalene sul~onate, p-toluene sulfonate,
lauryl sulfate, hexafluorophosphate, 2-naphthalene
sulfonate, etc. These resins, as noted in the list above,
are organic solvent soluble, light-sensitive, negative
working aromatic diazo resins. The diazo resins are
generally useful as 1-20% by weight of active ingredients
in the printing composition. Preferably they are present
as 3-8% by weight of the composition. The preparation of
these resins is generally described in U.S. Patent No.
2,714,066. It must be noted that the diazo resins used in
the practice of the present invention is not synonymous
with or inclusive of diazonium salts as known in the art.
Diazo resins have more than one diazonium group in the
molecule. Diazo resins comprise a number of salts, at
least two, covalently bonded together. For example, a
useful diazo resin can be represented by the formula
1-- ~ --N2 ~n r ~ 3
wherein n is about 4 or 5.
It is interesting to note that polymerization does
not necessarily occur through generation of a Lewis acid
from the anion. The anion shown above does not form or
generate a Lewis acid when the diazo resin is photo-
initiated. Lewis acids may be generated in other diazo
resins, but non-Lewis acid generating resins are useful in
the present invention.
_e Organic Solvent Soluble Resin
3a The binder resin component, which is an organic
solvent soluble film forming resin, is generally known in
the art. It is preferably selected from epoxy resins,
polyesters, polyallyl orthophthalate prepolymers,
pollyallyl isophthalate prepolymers, polyvinyl formals,
liS3236
--5--
polyurethanes, polyvinyl butyrals, polyoxyethylene oxides,
polyvinyl hydrogen phthalates, polyacrylates,
polymethacrylates, cellulose acetate esters, and polyvinyl
chlorides. Some of these resins are disclosed as useful
in plate compositions in U.S. Patent Nos. 4,104,072;
3,899,332; 3,837,858; and 3,933,499. These binder resins
may or may not enter into the polymerization which occurs
upon exposure to radiation. Prepolymers or fully
polymerized materials may be useful as long as they are
capable of orming a film with sufficient structural
integrity to be self-supporting. These resins are
generally useful as 10-40% by weight of the printing
composition, excluding solvents and other non-functional
additives. Preferably 15-35% by weight solid ingredients
are binder resin. A minimum molecular weight of at least
1,000, preferably 2000, and most preferably 3500 is
desired. There is no required upper limit for the
molecular weight. Molecular weights of 2,000,000 or
3,000,000 are known in the art and are useful. The use of
binders having a molecular weight less than 200,000 and
preferably less than 100,000 appears to make the
compositions more readily developable. It is preferred
that these resins be more oleophilic than hydrophilic.
When the binder resin is selected so that it is a
prepolymer capable of independently crosslinking or
polymerizing upon heating (which can be readily determined
outside of the compositions of the present invention), the
plate on which the composition is coated can be
post-heated (i.e., after development) to control the dot
size of the image on the plate and also to strengthen the
integrity of the image. This would improve press life.
Because the dots are given more structural integrity by
post-heating, underexposure during imaging may be used to
produce dots with fine resolution. These dots would
ordinarily be removed in development or on the press, but
post-heating with these particular types of binder resins
would make the dots secure to the printing plate. This is
llS3236
--6--
believed to be unique in negative acting water developable
plates. It is preferred that such crosslinking or
polymerizable can be initiated at a temperature of at
least 100C. Higher polymerization temperatures are also
advantageous. Examples of this class of binder are
polyallyl isophthalate and polyallylorthophthalate
prepolymers such as
O C H2
,~C-O-CH2-CH-CH2 0
. I ~ CH- CH2- 0- C
C O-CI~2-C~ H2 \13--C-o-C~2-CIi=C}~2¦
'. _ 10
The Ethylenically Unsaturated Materials
The polyfunctional unsaturated monomer or
oligomer component useful in the present invention is a
free radical polymerizable polyethylenically unsaturated
compound. These compounds may be true monomers or dimers,
trimers, oligomers, or polymers having at least 2,
preferably 2 to 12, and most preferably 2 to 5
ethylenically unsaturated groups such as acrylate,
methacrylate, vinyl, acrylamide and allyl. Preferred are
compounds having multiple acrylate and methacrylate groups
such as acrylic and methacrylic esters of polyols.
Examples of these materials are trimethylolpropane
triacrylate, pentaerythritol tetraacrylate, pentacry-
thritol triacrylate, ethylene glycol diacrylate, ethylene
glycol dimethaorylate, pentaerythritol tetramethacrylate,
diallyl phthalate, diallyl adipate, diallyl succinate,
etc. Suitable ethyleneically unsaturated, free-radical
initiated, chain-propagating addition polymerizable
compounds include alkylene or polyalkylene glycol
diacrylates, e.g., diethylene glycol diacrylate, glycerol
diacrylate, glycerol triacrylate, l,3-propanediol
dimethacrylate, 1,2,4-butanetriol trimethacrylate,
.
,
llS3236
1,4-cyclohexanediol diacrylate, sorbitol hexaacrylate; bis[l-(3-acryloxy-2-
hydroxy)]p-ethoxy-phenyl-dimethylmethane, tris-hydroxethylisocyanurate trimeth-
acrylate, the bis-acrylates and bis-methacrylates of polyethylene glycols of
molecular weight 200-500 and the like; unsaturated amides, c.g., methylene bis-
acrylamide, methylene bis-methacrylamide, 1,6-hexamethylene bisacrylamide, diethy-
lene triamine trisacrylamide, B-methacrylaminoethyl methacrylate; vinyl esters
such as divinyl succinate, divinyl adipate, and divinyl phthalate. Mixtures of
these esters may also be used as well as mixtures of these compounds with alkyl
esters of acrylic acid and methacrylic acid including such esters as methyl
acrylate, methyl methacrylate, ethyl acrylate, isopropyl methacrylate, n-hexl
acrylate, stearyl acrylate, allyacrylate, styrene, diallyl phthalate and the
like. These compounds are generally known in the art, as, for example, in British
Patent No. 1,482,953 and United States Patent Nos. 3,954,475 and 3,905,815. The
polyfunctional unsaturated materials are generally useful as 30-70% by weight of
active ingredients in the printing composition. Preferably they are present as
40-60% by weight of the composition.
The oligomeric materials having molecular weights in excess of 500 are,
by themselves, well known in the art. They may have essentially linear backbones
which are terminated by a multiplicity of ethylenically unsaturated-groups such
as those disclosed in United States Patent No. 4,316,949, filed 14 December, 1979
or they may be highly branched with ethylenically unsaturated groups randomly
pendant from the backbone, as dlsclosed in United States Patent No. 4,228,232,
(which issued to patent from the continuation-in-part of United States Serial No.
15,586, filed 27 February, 1979). Other examples are included in United States
Patents 3,700,643; 4,065,587i and 4,153,778. Many other highly polymerizable
oligomers are known in the art. The ethylenically unsaturated materials dis-
closed in Canadian Serial No. 352,477, filed May 22, 1980 and United States
Patent No. 4,316,949 are preferred.
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llS3Z36
--8--
The Free-Radical Photoinitiator System
_ _
The free-radical photoinitiator systems of the
present invention are generally known. They are compounds
which absorb radiation, generally actinic radiation, and
are activated to become agents which abstract hydrogens
from hydrogen donors. There may also be or may need to be
sensitizers present to enable the compounds to be
photoactivated. Examples of these materials are the
benzoins, acetophenones, naphthoquinones and benzophenones
(as disclosed in British Patent No. 1,4~2,953), vinyl
substituted halomethyl-s-tr~azine compounds (as disclosed
in U.S. Patent No. 3,954,475), and aromatic onium
compounds (as disclosed in U.S. Patents Nos. 4,058,400;
4,058,401). Other desirable photoinitiator systems are
generally known in the prior art such as in U.S. Patent
Nos. 3,775,113; 3,887,450; 3,895,949; and 4,043,819. The
photoinitiator systems are generally useful as 0.01-10% by
weight of active ingredients in the printing composition.
Preferably they are present as 1-6% by weight of the
composition. When needed, spectral sensitizers are
usually included at a level of about 10 to 70~ by weight
of the photoinitiator.
The ~ater Softenable Binder
_
The water-softenable polymer of this invention
is a water soluble or at least water softenable polymer
which is also soluble in organic solvent systems. By
water softenable it is meant that the ~oung's modulus of
the polymer decrea~es in the presence of water. Thi~
modulus can be measured on commercially available
equipment such as the "Rheovibron"*model D-DV-II-C
manufactured by Toyo Baldwin Co., ~td. A polymer which
formed a molecular suspension in water would be one
example of a non-soluble (in water) polymer that was water
softenable. Another exàmple of a water softenable polymer
is a polymer in which a portion of the bonds within or
without (e.g., hydrogen bondings) the polymers are broken
* Trade Mark
r~
llS;~236
in the presence of water. Specific examples of these
polymers include polyvinyl pyrrolidone, partially
hydrolyzed polyvinyl acetate, poly(vinylpyrrolidone/vinyl
acetate copolymer), hydroxyalkyl cellulose resins (e.g.,
hydroxypropyl cellulose), alkyl vinyl ethers
maleicanlydride copolymers, and organic solvent soluble
polyvinyl alcohol derivatives or copolymers. These
materials are generally well known in the art. British
Patent No. 1,482,953 discloses the use of photopolymeric
compositions suitable for the preparation of relief plates
developable with water which contain amino-substituted
hydroxyalkyl cellulose resins which would also be useful
and are a species of hydroxyalkyl cellulose resins. The
term water-softenable as used in the practice of the
present invention includes water soluble resins unless
otherwise stated. The water- softenable resins are
generally useful as 0.9-10% by weight of solid ingredients
in the printing composition. Preferably they are present
as 5-10% by weight of the composition.
The su~strates of the present invention may be
any substrate, including metal, polymer and paper
surfaces. Cnly when the coated article is to be used as a
lithographic printing plate must the substrates be
hydrophilic on their surfaces. The substrate for a
printing plate may be any material which may be coated on
at least one surface thereof to provide this hydrophilic
property. The substrates normally used for lithographic
plates, such as those of U.S. Patent Nos. 556,3807
2,100,063t 2,251,181; 3,181,461; 2,373,357; and 4,116,695
30 are useful in the practice of the present invention.
Preferred are polymeric or metal substrates. Particularly
desirable are aluminum and zinc substrates. Most
preferred are aluminum substrates which have a permanent
hydrophilic coating reacted onto the surface thereof by
35 reaction of an aqueous solution of a soluble silicate as
in U.S. Patent No. 2,714,066. This form of aluminum or
zinc substrate is referred to as smooth, grained, or
~iS3236
--10--
grained and anodized. A variety of alloys may be used
with the aluminum, as is known in the prior art such as
U.S. Patent No. 4,116,695. When the term aluminum
substrate or aluminum plate is used in the art, it is
understood that the material is predominantly but not
necessarily exclusively aluminum.
over this substrate is usually applied another
coating which comprises a water-soluble light-sensitive
diazo resin which may be the same as some of those
described above as part of the photoreactive composition.
These resins are well known in the art and are also
disclosed in U.S. Patent Nos. 2,714,066 and 3,905,815.
In a preferred practice of the present
invention, a sixth component may be added or a particular
organic solvent soluble resin selected. This component is
an oleophilic polymer which is added to the composition to
improve its ink receptivity. As the printing plates
operate to provide an image by having areas of ink
receptivity (oleophilic areas) and non-ink receptivity
(oleophobic areas) in a subtractive development process,
enhanced ink reception in the imaged areas where the
composition is retained on the plate is desirable. Some
of the binder resins listed above ~re also oleophilic, and
resins in that list which are oleophilic may be added to
the composition so that more than one organic solvent
soluble resin is present. The oleophilic resin need not
be a film forming resin, as structural integrity is
provided by other components, but it i9 preferred that the
oleophilic re~in i9 a film forming polymer. Any
compatible ~ilm forming oleophilic resin i9 useful, and
cellulose acetate esters such as cellulose acetate
butyrate and cellulose acetate propionate have been found
to be particularly desirable. This ingredient shows
useful effects in weight percentages of from O.S to 40% of
the composition (the maximum is where it also constitutes
the binder resin).
.
liS323t~
--11--
There are numerous other additives which may be
desirably added to these compositions. It is generally
desirable to have a solvent system in the compositions
when they are applied to the substrate. These solvents of
course tend to evaporate out of the composition after it
has been coated out. These solvent systems may comprise
one or more solvents to keep all of the ingredients
compatable. The solvents are usually organic polar
solvents but some minor amount (e.g., up to about 25% by
weight) of non-polar solvents may be included.
Particularly desirable solvents include methylethyl ketone
(and other ketones such as cyclohexanone and acetone),
amides tsuch as dimethyl- formamide), chlorinated
hydrocarbons (such as ethylene dichloride),
2-nitropropane, diacetone alcohol, and short chain (e.g.,
1 to 5 carbons) aliphatic alcohols. Many of these
materials are disclosed in British Patent No. 1,447,142.
These are the types of organic solvents from amongst which
all materials previously referred to as organic solvent
soluble can find a solvent system of one or more solvents.
Dyes or pigments may also be used in the
printing compositions. Acutance dyes would also be useful
in compositions of the present invention. Many of these
materials are disclosed in British Patent No. 1,~47,142
for printing compositions.
For the purpose of inhibiting premature polymeri-
zation and reducing any polymerization in non-imaged areas
from scattered light, the incorporation of stabilizer~
such as phenothiazine and phenolic stabilizers may be
useful. These materials are well known in the art and are
exemplified by di-t-butyl-p-cresol, hydroquinone, quinone,
hydroquinone monomethyl ether, amyl quinone, n-butyl
phenol etc. These stabilizers are usually present in
amounts from 0.0002 to 1 percent by weight of the solids
in the composition.
The compositions may also contain inert
particulate filler which is transmissive or transparent to
11S3236
actinic light. The particles may also be so small as to
not interrupt light transmission. Organophilic silicas,
bentonites and powdered glass are examples of these
materials. All should be smaller than 10 microns,
preferably smaller than 1 micron, and most preferably
smaller than 0.1 microns.
Flow control agents, viscosity modifiers, and
surfactants may also be useful in the present
compositions.
The following examples will further enable an
understanding of the present invention. All percentages
are by weight unless otherwise stated. All plates were
treated with commercially available diazo desensitizing
compositions after development.
Example l
A homogeneous mixture comprising 9.8 by weight
of polyvinylpyrolidone, 10% by weight of the polyalkyl
phthalate prepolymer described above by structural
formula, 5% cellulose acetate butyrate, 6% of the
fluoroborate salt of the condensation product of
paraformaldehyde a p-diazo diphenylamine, 12% of a
dispersion (50/50 weight percent) of a red pigment in a
copolymer ~86/14) of vinyl chloride and vinyl acetate, 2%
of 2-(p-methoxystyryl)-4,6-bis-(tri-chloromethyl)-s-
Z5 triazine, and 55.2% by weight of a mixture of polyethylen-
ically unsaturated materials comprising 70~ by welght of
an oligomer (OL-I) of the formula:
llS3Z;~6
--13--
CH2=CH--O-C--CH2
Il I ~C~
CH =CH-O-C-CH -C-CH2-0-~H-CH2-N N
CH2=CH--O--C--CH2 OH C--C--CH3
O O CH3
CH2-C-O-CHZCH2
ll
2 CH O CH2--C--CH2--C--O--CH=CH
OH CH --C--O--CH=CH2
2 il
and 30 percent pentaerythritol tetraacrylate. This was
brought to a solution in a blend of 60% ethyleneglycol
15 monomethyl ether, 27% dimethyl formamide, and 13% methyl
ethyl ketone and coated onto anodized, silicated aluminum
which had been squeeze roll coated with a water soluble,
light sensitive p-diazodiphenylamine-formaldehyde resin
from a 2 . 5% aqueous solution. The plate was air dried at
20 about 80C.
The dried plate was exposed to a carbon arc
source of ultraviolet radiation for 100 seconds at 1.37
meters. The exposed sheet was developed with tap water
with a few seaonds o$ gentle scrubbing with a soft cloth.
25 The plate was then treated with a commercially available
aqueous desensitizing and gumming ~olution, then buf~ed
dry and mounted on a llthographic printing press. In an
accelerated abrasion press test condition, the plate ran
for about 10,000 impressions without loss of detail. The
30 plates faithfully reproduced 150 line screens cantaining
3% high light dots and 97% shadows.
.
,
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~53236
Examples 2-6
These examples show that press life is highly dependent upon maintain-
ing less than 10 percent by weight of water softenable binder.
The following materials were used in preparing the compositions used
in these examples.
Polyvinyl Pyrrolidone (PVP)
2,6-bis-trichloromethyl-4-p-methoxystyryl-s-triazine (TMT)
Oligomer of Example 1 (OL-I)
Oligomer of Example 1 of United States Patent No. 4,316,949 (OL-II)
Pentaerythritol Triacrylate (PETA)
Cellulose Acetate Butyrate (CAB)
Diallyl Phthalate Resin of Example 1 ~DPR)
Diazonium Resin of Example 1 (DZR)
Perylene Red Pigment dispersion (50/50) in Vinyl Acetate/Vinyl Chloride
(86/14) Copolymer (PRAC)
All compositions contained 450 ppm of phenothiazine based on the combined weight
of ethylenically unsaturated materials.
These compositions were dissolved in the solvent mixture of Example 1
as 10% solids and coated at 250 mg/ft2 on an aluminum substrate, dried, exposed,
developed, desensitized, and placed on press as in Example 1. The number of
prints under accelerated abrasion press test conditions was recorded. The
results are shown in Table 1,
- 14 -
.
.
.
`~ :
1153236
-15-
Table 1
Example 2 3 4 5 b
PVP 4.82 9.65 14.47 19.31 24.15
TMT 1.93 1.93 1.93 1.93 1.93
CAB 2.90 2.90 2.90 2.90 2~90
DPR 14.47 14.47 14.47 14.47 14.47
OLrI 16.90 15.20 13.52 11.82 10.13
OLrII 23.64 21.96 20.27 18.58 16.88
PETA 17.38 15.93 14.48 13.03 11.58
DZR 5.80 5.80 5.80 5.80 5.80
PRAC 12.16 12.16 12.16 12.16 12.16
rmpressions
(X1000) 16 11 7 7 6
As can be seen from these Examples, the press life falls
15 off rather significantly with more than 10% by weiqht of
water-softenable binder.
Examples 7 and 8
A comparison was made between a plate having
only low molecular weight ethylenically unsaturated
20 materials and one having a high proportion of oligomeric
ethylenically unsaturated materials. Amongst additional
materials in the composition were the triacrylate of
trihydroxy ethyl isocyanurate (TTEI) and an insert
polyurethane binder (PUB).
:
,' '
.
, ' ~ ' ' :
.
liS3236
-16-
Table 2
Example 7 8
PVP 19.88 9.84
TMT 1.99 1.97
CAB 0.99 0.98
DPR 23.86 9.84
TTCI 29.82
PETA ----- 17.72
OL-II ----- 41.34
PRAC 12.52 12.40
DZR 5.96 5.91
PU~ 4.98 ----
These compositions were dissolved as 10% solids
in the solvent mixture of Example 1, coated at 250 mg/ft2,
dried, exposed, developed and placed on press as in
Example 1. Under accelerated abrasion press test
conditions the first plate broke down at 3500 impressions
while the second plate broke down after 7000 impressions.
These examples show the improved press life available from
practice of the present invention as compared to the
technology of Canadian Serial No. 346,444 filed 26
February 1980.
.
ExampIes 9, 10 and 11
~: The following compositions were prepared for
evaluation.
.
1153236
-17-
Table 3
Example 9 10 11
PVP 4.92 5.00 0.96
TMT 1.97 2.00 1.91
CAB 0.98 3.00 2.87
DPR 24.61 6.00 14.34
OL-I 34.45 21.00 18.40
OL-II --- 28.00 25.10
PETA 14.76 21~00 19.54
DZR 5.91 4.00 5.74
PRAC 12.40 10.00 12.04
These compositions were dissolved, coated,
dried, exposed, developed, desensitized and mounted on
press as in Example 1. All plates provided at least 7,000
impressions before being damaged~
15One other aspect of the present invention is the
fact that the coatings of the present invention, in spite
of the high concentration of ethylenically unsaturated
materials, are non-tacky compositions with as high a level
of monomeric unsaturated materials as are allowable in the
20: practice of the present invention are usually so tacky
~ that the composition could be pulled off the substrate
:~ ~from contact with another }ayer. This did not occur in
~ any of the above examples.
: :
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