Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
This invention reLates to p~otopolymerizable systems
which include photopolymerizable compositions that are
liyht-sensitive latexes which form water developabLe printing
plates when coated on suitable backing members. Selected
image areas can be insolubilized and crosslinked by exposure
to actinic radiation and the composition in the non-radiated
non-image areas can be washed away with water to provide the
desired planographic image.
Emulsion photopolymerizabLe syste-ns are taught in
U.S. Patents 4,186,069; 4,224,398; and 4,288,520. In these
systems, the photo~polymerizable coating is an emulsion mix-ture
of a polymer component having water insoluble poLymer
particulates within an aqueous suspension medium, toget~er
with a water solubLe or water dispersiblè light-sensitive
component including a polymer having at least two moieties per
moLecule. Such polymers are sensitive to actinic radiation,
and by generating a free radical or other crossLinking species
form a matrix of crosslinked polymer which encapsulate or
entrap therein and disperse therethrough the water insoluble
polymer. Prior ~o curing this system is a three-phase
emulsion including the water insoluble polymer particulates
within the aqueous suspension medium with which is
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also mixed the light-sensitive polymer. ~Yhen the coating
composition is applied to a suitable backing member~. the
aqueous suspension is substantiall~ removed to realize a
two-phase mixture of the polymer particulates and light-
sensltive polymer.
It has long been known to use water insoluble po~y-
mers in producing light-sensitive coatings for use on sub-
strates such as planographic printing plates in which the
polymers are incorporated as part of a solvent system layer
which uses organic materials and which must be driven off
from the platel, a requirement which is time and energy con-
suming, wasteful of solvents and possibly-hazardous to the
operator and the environment.
Vse o~ watex soluble sys*ems generally avoids the
disadvantages of the organic base systems~ but they are not
particularly long lasting because the pol~mers are water
soluble and are therefore sub3ect to erosion of the image
area when in use and/or through`the action of atmospheric
moisture. The emulsion systems of the aforementioned pat-
ents provide an improved stability with respect to otherwater based systemsl, but they are still characteried b~ a
shelf-life which is less than optimum, especially under high
humidity conditions. Additionally~, the imag~s provi~ed by
such emulsion systems often inclucle spots which ar~ commer-
cially unacceptable.
It is therefore ~he object of the pr~sen~ inventionto provide a photopolymerizable system and a water develop-
able printin~ plate based on such a system which exhibits
improved propertiesl, particularly with respect to shelf-life
under high hl-midity conditions. This and other oh~iects of
the invention will become apparent to those skill~d in this
art from the following detailed description.
This inventioh relates to photopolymerizable compo-
sitions a~d printing plates therefrom~, and more particularly
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to light-sensitive latex coating comp~sitions which comprise
a water soluble diazo polymer reaction product o~ ~ diazo~ryl-
amine and an aldehyde and an aqueous cationic or nonionic dis-
persion of water insoluble polymer, This systern preferably
contains a water miscible or~anic solvent which improves the
shelf-life of the composition~ espec-lall~ under high humidity
conditions.
The light-sensitive coating composition of the
present invention is an emulsion mixture of a cationic or
nonionic polar emulsion component having water insoluble
polyrner particulates wlthin an àqueous suspension medium
to~ether with a wa$er soluble or water dispersible component
which is a diazo polymer reaction product ot a diazoarylamine
lS and an aldehyde. The water-insoluble po~ymer emulsion compo-
nent and the light-sensitive component are generally present
in quantities of the same order o~ magnitude but can vary
from a weight percent ratio o~ about 25:1 to 1:25, prefer-
ably abou~ 5:1 to 1:5,
The water soluble diazo pol~mer used in the present
invention are prepared by the well known condensa*ion reac-
tion of a diazoaryl amine such a p-diazodiphenylamine and an
aldehyde such as formaldehyde or paraformaldehyde which
results in the formation of an oligomer or low molecular
weight polymer. Many such diazo polymers are~commercially
available and typical examples include Diazo-8000 sold by
Polychrorne CorporatioD of Yonkers~, New Yorkl, which is a zinc
chloride salt of th~ reactlon product of para-diazodiphenyl-
amine with paraformaldehyde~, and Diazo Resin No. 4 of Fair-
mount Chemicals~, which is a reactlon product of para-diphenyl-
amine diazonium chloride with ~ormaldehyde. Salts of the
reaction product of p-diazodiphenylamine with paraformalde-
hyde are especially preferred. Zinc chloride, phosphate~.
sulfate salts and the like can be utilized; the zinc chloride
salts being preferred,
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The a~ueous dispersion of the water insoluble poly-
mer o~ the present invention is cationic or nonionic ei-ther
as a result of the use of an emulsifier or br having the
cationic or nonionic group linked to the polymer. The water
insoluble polymer is preferably a solid particulate having
a size in the range of about 100 Angstroms to 10 microns in
diameter. In general, any polymer which carries a cationic
or nonionic group or which can be formulated into an emul-
sion using a cationic or nonionic emulsifier can be employecl
in the present invention~ Suitable polymers include the
homopolymers and copolymers of styrene, ethyl acrylate,
butyl acrylate, ethyl methacrylate, butyl methacrylate,
vinyl acetate~ vinyl chloride, vinylidene chloride, buta-
diene, methylstyrene, vinyl toluene, dimethylaminoethyl
acrylate, æcrylic acid, methacrylic acid, isoprene, chloro-
prene, maleic anhydride, ethylene glycol acrylates such as
polyethylene glycol acrylate, halogenated vinyl aromatics
such as chlorostyrene and bromostyrene, methylvinyl ether,
vinyl pyrrolidone, polyurethane and the like,
Among the cationic and nonionic emulsifiers which
can be used in the present invention are: ammonium salts o
substituted amines containing alkyl and/or aryl groups at-
tached to the nitrogen, alkyl or aryl sulfonium salts, alkyl
and alkyl-aryl polyethers, cationic or nonionic ~luorosur~ac-
tants and polyoles.
Various cationic ancl nonionic emulsions are commer-
cially available and can be used in the practi~ce o~ the
present invention. For example, Witcobond ~Y-212~ a cation-
omeric polyurethane emulsion sold by Witco can be used in
the presènt invention. Such emulsions are carried by U.S.
Patents 3,873,484 and 4,160,065.
~ A typical nonionic
emulsion is Vondic 1310~ sold by Dainippon Inc., which is
available as a polyurethane emulsion~ -
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Wh~n it is desired to enhance the sensitivity of
the light-sensitive diazo polymer, known sensitizers can ~e
included in the composition. For example, the composition
can contain Michler's ketone/ benzoin, benzoin methyl ether
and other well known sensitizers which may be water solu-
bilized as required by the use of amines amine saltsl, ~ua-
ternary amines, or polyalkoxy groups.
The light-sensitive composition of the present in-
vention generally contains stabilizers which are derivatives
of pyridine-N-oxide or other quaternized ammonium compounds,
Typical examples include nicotinamide-N-oxide~, pyridine-N-
oxide, quinoline-N-o~ide, 4-nitroquinoline-N-oxide, tetra-
methyl ammonium chloride, dimethyldiallyl ammoniurn chloride~
These stabilizers are present at a weight percent ratio range
of from about 1:50 to 2:1, preferably 1:10 to 1~ ela*ive
to said light-sensitive diazo polymers.
The compositions of the present invention can also
include antihalation agents~7 dyes, pigments~ -Eillerst plasti-
cizers~, e~tenders, crosslinked particles and other materials
for aiding in maintaining or modifging the YiScosity ~ plas-
- - ticity and/or stability of the compositions. It will bP
appreciated that any dyes should be water soluble cationic
or nonionic dyes although anionic dyes having at mos~ one
anionic group can also be used.
It has been found that the inclusion of a ~ater
miscible organic solvent in the aqueous dispe~sion o~ the
water insoluble polymer improves the shelE-life of the com-
position especially under high humidi~y conditions. Typica-
organic solvents which can be used include methanol, ethanol~,
acetone~, dimethylformamide~, methylcellosolve~, acetonitrile,
dioxane, propanol, etc. The water miscible or~anic solvent
will generally be about 0.1 - 75 weight percent~, pre-Eerably
about 1 to 40 weight percent~. based on the weight of the
total solvent system.
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The photosensitive compositions o~ the present
invention can be applied to any conventional substrate such
as aluminum, copper~, 7,illCI, magnesium~, steel or plastic~, in
any convenient ~ashion such as spray, roll or dip methods.
After coating, the aqueous phase is evapora-ted or dried -to
remove the water or water and miscible organic solvent at
low or elevated temperatures with or without i~position o~ a
vacuum to leave the water insoluble emulsion and light-sensi-~
tive polymer together with a small amount of residual water
or water and miscible organic solvent on the substrate.
Areas o~ the composition which are exposed to actinic radi-
ation harden and become hydrophobi~, while the portions
which are not so exposed remain ~ater receptive and can be
remcved by simple water developmentO
In order to further illustrate the invention~ vari-
ous examples are set forth below. Throughout these examplesl,
as well as throughout this speci~ication and claimst, all
parts and percentages are by weight and all temperatures in
degrees Centrigrade unless otherwise specified.
Example I
A photopolymerizable composition was prepared by
mixing 5.37 percent of a cationomeric polyurethane emulsion
~Witcobond W-~12) and 0.6~ percent o- a water soluble diazo-
polymer which was the zinc chloride salt of a reaction pro-
duct of para-diazodiphenylamine and paraformaldehyde. The
composition additionally contained 0,1~ perce~t zinc chloride~,
0.48 percent tris~2-chloroethyl)phosphate~, 0.16 percent
nicotinamide-N-oxide~, 0.032 percent methyl green~, 76.6 per-
cent ~Yater and 16.5 percent dimethyl~ormamide. The photo-
sensitive composition was coated on a grained anodized and
silicated sheet o~ aluminum and allowed to dry. The plate
- was thereafter exposed to ultraviolet radiation~ developed
with tap water and gummed in the conventional fashion~ The
resul-tin~g lithographic plate was found to produce 30,000
good ~uality copies. A sample of the thusly produced plate
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with a coating weight of 0.75g/~ was subjected to acceler-
ated shelf-life tes~ing under high humidity conditions by
exposure to 90 percent humidity at 38C. :Eor 120h. The
plate showed quite satisfactory properties in exposure speed~r
adhesion and development. Another sample subjec~ed to ac-
celerated shelf-life testing at 60~C. and low humidity ~or
120h. also performed satisfactorily.
Example II
The substrate used in the previous example was
coated with an emulsion containing 4.09 percent oE a non-
ionic polyurethane emulsion (Vondic 1310F~YDainippon Inc.)
and 0~66 percent of ~he same diazopolymer used in Example I.
The composition additionally contained 0.16 percent zinc
chloride, 0.49~ tris(2-chloroethyl)-phos~hate~, 0.16 percent
nicotinamide-N-ogid~e, 0.25P Surfynol S~(Air Produc-ts Inc.)
0.04 percent Zonyl~FSC (du Pont)l, 77.8 percent water and
1~.4 percent 2-methoxyethanol(methylcellosolve). The compo-
sition was subjected ~o the same accelerated shelf li~e as
in Example I without any negative ef~ects.
~arious changes and modi-Eications can be made in
the process and products oE this învention without departing
from the spirit and scope thereoE. The various embodi~ents
which have been disclosed herein were ~or the purpose of
~urther illustrating the inventionl, hut were not intended to
limit it.
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