Synthesis of photoreactive polymeric binders

A photoreactive binder that may be used to enhance photospeed in either conventional plates or on-press developable lithographic printing plates. Briefly, a polymer of m-isopropenyl-.alpha.,.alpha.-dimethylbenzyl isocyanate is derivatized for vinyl group reactivity by reacting the isocyanate groups thereof with hydroxyalkyl acrylate. The resulting photopolymeric binder provides significantly higher photospeed than the non-reactive binder currently utilized in the production of conventional printing plates. The resulting lithographic printing plate also shows better durability (as manifested by longer run-length) and is more easily developed by the microencapsulated developers utilized in the present invention. As to the preparation of the photoreactive binders, the application discloses a method of copolymerizing m-isopropenyl-.alpha.,.alpha.-dimethylbenzyl isocyanate (m-TMI) through complexation with an electron-deficient monomer such as maleic anhydride to accelerate free radical copolymerization with other monomers, and thus, provides greater monomer-to-polymer conversion. Use of the resulting product in the photoresist of a lithographic printing plate improves its adhesion to an underlying substrate.

FIELD OF THE INVENTION 
In general, the several composition and method manifestations of the 
present invention relate to photoreactive polymeric binders, and more 
particularly, to photoreactive polymeric binders capable of being readily 
and functionally incorporated into planographic photoresists to improve 
durability while concurrently maintaining and/or enhancing 
photosensitivity. 
CROSS-REFERENCE TO RELATED APPLICATIONS 
U.S. patent application Ser. No. 08/146,710, filed on Nov. 1, 1993 by L. C. 
Wan, A. C. Giudice, J. M. Hardin, C. M. Cheng, and R. C. Liang, commonly 
assigned, and tifled "On-Press Developable Lithographic Printing Plates", 
describes a lithographic printing plate for use on a printing press, with 
minimal or no additional processing after exposure to actinic radiation. 
The plate comprises a printing plate substrate, a polymeric resist layer 
capable of imagewise photodegradation or photohardening, and a plurality 
of microencapsulated developers capable of blanket-wise promoting the 
washing out of either exposed or unexposed areas of the polymeric resist. 
The microencapsulated developers may be integrated into the polymeric 
resist layer, or may form a separate layer deposited atop the polymeric 
resist layer, or may be coated onto a separate substrate capable of being 
brought into face-to-face contact with the resist layer. 
U.S. patent application Ser. No. 08/147,044, filed Nov. 1, 1993 by F. R. 
Kearney, J. M. Hardin, M. J. Fitzgerald, and R. C. Liang, commonly 
assigned, and titled "Lithographic Printing Plates with Plasticized 
Photoresists", discloses the use of plasticizers, surfactants, and lithium 
salts as development aids for negative-working, on-press developable 
lithographic printing plates. Briefly, plasticizers, which are dispersible 
or soluble in press fountain solutions and soluble in acrylic monomers and 
oligomers, are incorporated into a photoresist. Such plasticizers make the 
photoresist more permeable to fountain solution prior to crosslinking, 
while being easily extracted with ink and fountain solution after 
crosslinking. The surfactants facilitate the dispersion of hydrophobic 
imaging compositions in the fountain solution and reduce scumming. 
Further, lithium salts may also be incorporated into the photoresist to 
disrupt hydrogen bonding of, for example, urethane acrylate polymers which 
tend to associate by hydrogen bonding, thus enhancing developability. 
U.S. patent Ser. No. 08/146,479, filed Nov. 1, 1993 by L. C. Wan, A. C. 
Giudice, W. C. Schwarzel, C. M. Cheng, and R. C. Liang, commonly assigned, 
and titled "Lithographic Printing Plates with Dispersed Rubber Additives", 
describes the use of rubbers and surfactants to enhance the durability of 
on-press developable printing plates. The rubbers are preferably 
incorporated into a photoresist as discrete rubber particles. To ensure a 
uniform and stable dispersion, the rubber components are suspended in the 
photoresist preferably by means of surfactants having HLBs approximately 
between 7.0 and 18.0. 
The disclosures of the aforementioned copending applications are hereby 
incorporated by reference. 
BACKGROUND OF THE INVENTION AND DESCRIPTION OF THE PRIOR ART 
At the present time, virtually all printed copy is produced through the use 
of three basic types of printing plates. One type is a relief plate which 
prints from a raised surface. Another type is an intaglio plate which 
prints from a depressed surface. The third type is the lithographic plate 
which prints from a substantially fiat surface which is neither 
appreciably raised above nor appreciably depressed below the adjacent and 
surrounding non-printing areas. Printing is occasioned by an ink's 
respective affinity and/or aversion to areas of different chemical 
properties. Lithographic printing plates are commonly processed to have 
water-repellent (hydrophobic), oil-receptive (oleophilic) image areas and 
water-receptive (hydrophilic) non-image areas. 
Prior to processing for use, conventional lithographic plates will 
typically have a hydrophobic, photoreactive polymeric layer (i.e. 
photoresist) coated or otherwise deposited atop a hydrophilic substrate. 
In preparing a conventional lithographic plate for use on a printing press, 
the plate is first exposed to actinic radiation. Specific chemical 
reactions are caused to occur in the plate's photoresist by exposure to 
actinic radiation. Such photoinduced chemical reactions may either reduce 
or enhance the solubility of the photoresist, depending on whether the 
resist is negative-working or positive- working. In negative-working 
plates, exposure to actinic radiation will generally cause a "hardening" 
of the photoresist. In positive-working plates, exposure to actinic 
radiation will generally cause a "softening" or "solubilization" of the 
photoresist. 
After photoexposure, a wet development step is normally conducted. The 
objective of such wet development is to provide preferential solvation of 
the areas of the photoresist which have undergone photoinduced chemical 
change. Solvation under conventional development techniques will typically 
involve treating the exposed plate with organic solvents in a developing 
bath. For negative-working resists, the solvent will swell and dissolve 
the unexposed portions of the resist. The solvent should not swell the 
exposed portions or distortion of the developed image may result. For 
positive-working resists, the response of the unexposed and exposed 
coatings are reversed, but the same general principles apply. 
As a result of the preferential solvation and washing away of portions of 
the photoresist, corresponding portions of the underlying hydrophilic 
substrate are uncovered. For negative-working plates, the aforementioned 
hydrophobic image areas correspond to the portions of the photoresist 
remaining after solvation and washing. The aforementioned hydrophilic 
non-image areas correspond to uncovered portions of the substrate. The 
image and non-image areas thus differentiated, the processed plate may 
then be mounted onto a printing press and run. 
Encumbered by required wet development, the processing of conventional 
lithographic plates prior to their use on a printing press is time and 
labor consuming and involves the use of substantial quantities of organic 
chemicals. It will be appreciated that there is considerable 
attractiveness for innovations that would satisfactorily eliminate or 
reduce conventional lithography's long-felt dependency upon the conduct of 
wet development and thereby permit the use of lithographic plates on a 
printing press immediately after exposure without required intermediary 
processing. 
In the past, dry-developable lithographic printing plates have been 
suggested which enable the wet processing steps of lithographic printing 
plates after exposure to be omitted and printing to be conducted by 
directly mounting the exposed plates on a printing press. Among printing 
plates that may be characterized as "on-press" developable (or related 
thereto) are: e.g., U.S. Pat. No. 4,273,851, issued to Muzyczko et al. on 
Jun. 16, 1981; U.S. Pat. No. 4,879,201, issued to Hasegawa on Nov. 7, 
1989; U.S. Pat. No. 4,916,041, issued to Hasegawa et al. on Apr. 10, 1990; 
U.S. Pat. No. 4,999,273, issued to Hasegawa on Mar. 12, 1991; and U.S. 
Pat. No. 5,258,263, issued to Z. K. Cheema, A. C. Giudice, E. L. Langlais, 
and C. F. St. Jacques on Nov. 2, 1993. 
Despite the methodologies and approaches embodied in the aforementioned 
patents, there is a continuing need for a lithographic printing plate that 
can be readily developed on a printing press and that produces a plate 
having durable image areas needed for good run length. Difficulty in the 
realization simultaneously of both "on press developability" and 
"durability" is believed to originate from an apparent contradiction 
between photoresist removability ("developability") on the one hand and 
"durability" on the other: To make a photoresist more durable was to make 
the photoresist less developable. 
The present invention seeks to more closely align the competing goals of 
"durability" and "developability" by utilizing photoreactive, polymeric 
binders capable of effectively functioning as both a matrix and as a 
photoreactive component. 
In conventional lithographic printing plates, polymeric binders are 
incorporated into the photoresist to provide film forming properties 
during coating and to act as the physical backbone or matrix for the 
resulting photopolymerized structure resulting from exposure. Since 
conventional wet development techniques are oftentimes based upon the use 
of strong solvents, tough and comparatively durable polymeric binders may 
be utilized. The dictates of more narrowly defined parameters for "on 
press developability", govern latitude in choice of photoresist 
components, in general, and effectively preclude the use of tough and 
durable binders or other components that may not be removable under the 
conditions of a lithographic printing operation. 
By way of illustration, in the U.S. patent application Ser. No. 08/146,710 
cross-referenced above and entitled "On-Press Developable Lithographic 
Printing Plates", on-press development is effectuated by the use of 
high-boiling point, low-vapor pressure developers. These comparatively 
weak developers solubilize portions of the photoresist such that they may 
be easily washed away "on-press" by fountain and ink solutions. In this, 
and like systems, binders that are less durable but more easily dispersed 
in the fountain and ink solutions are favored. However, with such binders, 
durability is compromised. 
In order to compensate for the losses in durability, a photoresist may be 
designed thicker and with a larger proportion of binder to prevent 
tackiness. An increase in binder, however, would normally be balanced by a 
proportionate decrease in photopolymerizable monomers; a concomitant loss 
of photosensitivity would be expected. It has been found that a printing 
plate that can be developed effectively "on-press" and which provides 
image areas of good durability can be realized by utilizing in a 
photoresist layer thereof a polymeric binder having both structural and 
photoreactive capabilities. While developed in the context of "on-press" 
developable printing plates, several diverse applications of the inventive 
photoreactive polymeric binder are envisioned and enabled by the present 
disclosure. 
SUMMARY OF THE INVENTION 
The present invention provides a photoreactive polymeric binder that may be 
used to improve durability while maintaining and/or enhancing the 
photosensitivity of a lithographic printing plate. Briefly, in one 
embodiment, a photoreactive binder is provided comprising a derivatized 
copolymer of m-isopropenyl-.alpha.,.alpha.-dimethylbenzyl isocyanate 
(m-TMI) and an ethylenically unsaturated comonomer. In a method aspect, 
m-TMI is copolymerized with an ethylenically unsaturated monomer and 
subsequently derivatized for vinyl group reactivity by reacting the 
isocyanate groups thereof with a hydroxyalkyl acrylate. The resulting 
photopolymeric binder provides significantly higher photospeed than the 
non-reactive binder currently utilized in the production of conventional 
printing plates. The resulting lithographic printing plate also shows 
better durability (as manifested by longer run-length) and is more easily 
developed by high-boiling point, low-vapor pressure developers. As to the 
preferred preparation of preferred photoreactive binders, the application 
describes a method of copolymerizing 
m-isopropenyl-.alpha.,.alpha.-dimethylbenzyl isocyanate (m-TMI) through 
complexation with an electron-deficient monomer such as maleic anhydride 
to accelerate free-radical copolymerization with other monomers, thus 
providing greater monomer to polymer conversion, and higher molecular 
weight particularly for polymers containing a high degree of m-TMI 
substitution. Use of the resulting product in the photoresist of a 
lithographic printing plate improves its adhesion to an underlying 
substrate, and thus enhances durability. 
In this light, it is an objective of the present invention to provide a 
photoreactive polymeric binder which may be incorporated into a 
photopolymerizable, photocrosslinkable or otherwise photorearrangeable 
composition to effectuate both higher photosensitivity and greater 
durability. 
It is another object of the present invention to provide a high speed, 
non-tacky lithographic printing plate that may be utilized effectively 
with a microencapsulated developer system. 
It is another object of the present invention to provide an efficient and 
effective process for producing durable and photosensitive photoresists. 
It is another objective of the present invention to provide a photoreactive 
polymeric binder comprising a derivatized copolymer of 
m-isopropenyl-.alpha.,.alpha.-dimethylbenzyl isocyanate and an 
ethylenically unsaturated comonomer. 
It is another objective of the present invention to provide a method of 
synthesizing a photoreactive polymeric binder by copolymerizing 
m-isopropenyl-.alpha.,.alpha.-dimethylbenzyl isocyanate with an 
ethylenically unsaturated comonomer, and derivatizing the isocyanate 
groups thereof with a hydroxyalkyl acrylate or hydroxyalkyl methacrylate. 
It is another objective of the present invention to provide a photoreactive 
polymeric binder comprised of a derivatized copolymer of 
m-isopropenyl-.alpha.,.alpha.-dimethylbenzyl isocyanate, ethylenically 
unsaturated comonomers, and maleic anhydride. 
It is another object of the present invention to provide a method of 
synthesizing a photoreactive polymeric binder by utilizing maleic 
anhydride as a "matchmaker" to give higher monomer-to-polymer conversion, 
higher molecular weight binder and potential pendant carboxylic acids for 
improved adhesion and/or developability. 
DETAILED DESCRIPTION OF THE INVENTION 
Throughout this disclosure the term "on-press" is used to describe both 
development and printing plates, (e.g., "on-press development", 
"developing on-press" and "on-press developable lithographic printing 
plates"). As used herein, the modifier "on-press" will be defined as 
indicating an ability to develop a useful imagewise distribution of 
oleophilic and hydrophobic polymeric areas on a printing press after 
imagewise exposure, without resort to wet development steps or like 
intermediary processing. "On-press" techniques should be contrasted with 
other so-called "dry development" techniques: e.g., dry collotype and 
laser ablation techniques, wherein oleophilic and hydrophobic image areas 
are formed at exposure; and peel-apart and thermal transfer techniques, 
wherein oleophilic and hydrophilic image areas are formed after a laminar 
separation. 
In embodiments most closely related to the field of lithography, the 
present invention provides a photoresist system which is comprised of at 
least a photosensitive polymerizable monomer and a photoreactive polymeric 
binder. As formulated, the photoresist system may be prepared as a coating 
which may be deposited on a suitable lithographic printing plate 
substrate. Upon photoexposure, exposed regions of the printing plate's 
photoresist coating are hardened by the effects of homopolymerization of 
the polymerizable monomer and by graft polymerization or cross linking 
involving the photoreactive polymeric binder. The resulting printing plate 
may be developed through conventional methods or through the innovative 
processes described briefly below and more fully in the cross-referenced 
applications. 
According to one embodiment of the invention, a photoreactive binder 
comprises a copolymer of repeating units of a derivatized 
m-isopropenyl-.alpha.,.alpha.-dimethyl isocyanate (m-TMI) and repeating 
units from an ethylenically unsaturated copolymerizable monomer, the 
polymer having the having the following chemical structure, CS(I): 
##STR1## 
wherein --M-- represents polymerized unit of ethylenically unsaturated 
monomers; n is an integer from 1 to 18, preferably from 2 to 6; by weight, 
y is approximately 70 to 95%, preferably 80 to 90%, and, z is from 
approximately 5 to 30%, preferably greater than 10%; R.sub.1 is H, or an 
alkyl group, such as a methyl group. 
Ethylenically unsaturated monomers that may be used with the present 
invention may be selected by one skilled in the an in view of the present 
disclosure. Typically, the ethylenically unsaturated monomers will have 
the formula H.sub.2 C.dbd.CR.sub.4 R.sub.5, wherein R.sub.4 and R.sub.5 
are each H, Cl, an alkyl group, such as a methyl group, --CO.sub.2 
CH.sub.3, --CO.sub.2 CH.sub.2 CH.sub.3, --CO.sub.2 Bu, --CO.sub.2 C.sub.8 
H.sub.17, --CO.sub.2 C.sub.12 H.sub.25, --CO.sub.2 Ph, --CO.sub.2 CH.sub.2 
CH.sub.2 N(CH.sub.3).sub.2, --Ph, --CN, --C.sub.6 H.sub.4 CH.sub.2 Cl, 
--C.sub.6 H.sub.4 N, --F, --COOH, --SO.sub.3 H, or their salts. 
Ethylenically unsaturated monomers substituted for added functionality are 
also contemplated. 
The photoreactive copolymer of chemical structure (I) is obtained by 
copolymerizing an m-isopropenyl-.alpha.,.alpha.-dimethyl isocyanate 
monomer with copolymerizable ethylenically unsaturated monomers (M', 
below) and derivatizing the pendant isocyanates of the intermediate 
copolymer with a hydroxyalkyl acrylate or methacrylate, such as 
4-hydroxybutyl acrylate. This process is illustrated by the following 
Synthesis Scheme, SS (I): 
##STR2## 
Radical copolymerization, step 1 in Synthesis Scheme (I), is performed, for 
example, in either the presence of a thermal initiator such as 
2,2'-azobis-(2-methylpropionitrile), AIBN, in methyl ethyl ketone, MEK, at 
70.degree. C., or t-butyl peroxybenzoate, t-BPB, in refluxing toluene. 
Reference may be made to the examples, infra, for representative 
illustration. Other suitable polymerization initiators are known in the 
art and can be used in the practice of the present invention. 
Derivatization, step 2 in Synthesis Scheme (I), is done in the presence 
initially of radical inhibitors such as 2,6-di-t-butyl-4-methylphenol 
(BHT) and air, then catalysts for the urethane reaction such as dibutyl 
tin dilaurate (DBTDL), triethylamine, and esters of p-dimethylaminobenzoic 
acid. Reference may be made to the examples, infra, for representative 
illustration. 
It is noted that while 4-hydroxybutyl acrylate (HBA) is the preferred 
compound for derivatization, other hydroxyalkyl acrylates and 
methacrylates as well as other vinyl substituted compounds may be used. 
Examples of such compounds are 2-hydroxyethyl acrylate, 2-hydroxyethyl 
methacrylate, 2-hydroxpropyl acrylate, 4-hydroxybutyl vinyl ether, allyl 
alcohol. 
The subject of matter represented by Synthesis Scheme (I) and chemical 
structure (I) are encompassed in U.S. patent application Ser. No. 
08/147,045. 
According to a second and preferred embodiment of the invention, maleic 
anhydride is utilized (as a "matchmaker") to increase the 
"monomer-to-polymer" conversion rate of a radical copolymerization step 
set forth in, for example, step 1 of Synthesis Scheme (I). In this regard, 
it will be appreciated that maleic anhydride has an electron poor double 
bond that may form a charge transfer complex with electron-donor monomers 
such as styrene, .alpha.-methylstyrene, vinyl ethers and vinylcarbazole, 
forming alternate copolymers. The donor-acceptor monomers can then 
copolymerize with a third "neutral" monomer such as methyl methacrylate or 
2-chloroethyl methacrylate. With regard to its use in accelerating m-TMI 
copolymerization, maleic anhydride (functioning as an acceptor) may 
complex with m-TMI (functioning as a donor), and thereby accelerate 
free-radical copolymerizations with other ethylenically unsaturated 
comonomers. Maleic anhydride molecules which are not complexed with m-TMI, 
may still react favorably with m-TMI radicals and result in maleic 
anhydride radicals which in turn react favorably with acrylate or 
methacrylate monomers. Electron deficient monomers such as maleic 
anhydride significantly accelerate the rate and conversion, as well as 
increase molecular weight as compared to the copolymerization of m-TMI and 
the ethylenically unsaturated comonomers alone, particularly when the 
concentration of m-TMI is high in the monomer composition. Aside from 
maleic anhydride, other useful electron deficient monomers include maleate 
esters (e.g., diethyl maleate, dibutyl maleate), fumarate esters, and 
fumaronitrile. In certain equivalent embodiments, maleic anhydride may be 
replaced (completely or in part) with, for example, n-butyl maleimide. 
Regardless, maleic anhydride is preferred. 
In contrast to the polymeric binders of the first embodiment, i.e. chemical 
structure (I), the photoreactive polymeric binder synthesized through the 
maleic anhydride accelerated copolymerization are comprised of polymers 
having the following generic chemical structure, CS (II): 
##STR3## 
wherein --M--, R.sub.1, n, y and z in chemical structure (II) are as 
described for chemical structure (I); the sum of v and x are from greater 
than 0 to approximately 10%, and R.sub.2 and R.sub.3 are H, alkyl or aryl 
group, and more preferably --(CH.sub.2).sub.n O.sub.2 CCH.dbd.CH.sub.2. In 
a presently preferred embodiment, the sum of v and x is approximately 5% 
by weight; z is approximately 12% by weight; and y is approximately 86% by 
weight. 
The photoreactive polymeric binders of chemical structure (II) are obtained 
by initially copolymerizing m-TMI with maleic anhydride and other 
ethylenically unsaturated monomers, such as methyl methacrylate and butyl 
methacrylate. The introduction of maleic anhydride results in higher 
conversion of higher molecular weight compounds. The compounds are then 
derivatized with a hydroxyalkyl acrylate, such as 4-hydroxybutyl acrylate. 
The process is illustrated by the synthesis scheme, SS (II): 
##STR4## 
As with Synthesis Scheme (I), the radical copolymerization step, step 1 of 
Synthesis Scheme (II), can be performed, for example, in the presence of 
AIBN in either MEK at 70.degree. C. or t-BPB in refluxing toluene. 
Reference may be made to the examples, infra, for representative 
illustration. Other suitable polymerization initiators are known in the 
art and can be used in the practice of the present invention. 
The protocol for the derivatization step, step 2 of Synthesis Scheme (II), 
is the same as the derivatization step for Synthesis Scheme (I). It is 
noted however that upon derivatization, some of the maleic anhydride units 
are typically hydrolyzed with provision of carboxylic acid groups pendant 
from the polymer. These pendant groups promote better adhesion to the 
printing plate substrate. Such enhanced adhesion helps to prevent the 
photoresist from being undercut from an underlying substrate by fountain 
solution and thus contributes to greater durability. 
It will be appreciated, that in the photoresist system of the present 
invention, photohardening of the photoresist layer is effected by 
reactions involving both the photoreactive binder and the principal 
photoactive component of the photoresist composition, for example, a 
photopolymerizable, photocrosslinkable or photorearrangeable compound, 
typically a photopolymerizable ethylenically unsaturated monomer. The 
principal photoactive component may include, any variety of compounds, 
mixtures, or mixtures of reaction compounds or materials capable of being 
physically altered by photoexposure or of promoting physical alteration 
(e.g., hardening) of the properties of the layer in areas of 
photoexposure. Compounds and materials suitable for this purpose include 
monomeric and oligomeric photopolymerizable compounds which undergo 
free-radical or cation-initiated addition polymerization. A large number 
of useful compounds is available, generally characterized by a plurality 
of terminal ethylenic groups. 
Especially preferred for promoting photohardening of polymeric resist layer 
is a polymerizable monomer which forms a macromolecular or polymeric 
material upon photoexposure, preferably a photopolymerizable ethylenically 
unsaturated monomer having at least one terminal ethylenic group capable 
of forming a high polymer by free-radical initiated or cation-initiated 
chain-propagated addition polymerization. Examples of such unsaturated 
compounds include acrylates, acrylamides, methacrylates, methacrylamides, 
allyl compounds, vinyl ethers, vinyl esters, N-vinyl compounds, styrene, 
crotonates and the like. Polymerization can be effected by using a 
photoinitiator, such as a free-radical generating, addition 
polymerization-initiating system activatable by actinic radiation. Such 
initiating systems are known and examples thereof are described below. 
Preferred polymerizable monomers are the polyfunctional acrylate monomers, 
such as the acrylate and methacrylate esters of ethylene glycol, 
trimethylolpropane and pentaerythritol. These can be polymerized in 
exposed regions of a polymeric photoresist in the presence of a 
photoinitiator. Suitable photoinitiators include the derivatives of 
acetophenone (such as 2,2-dimethoxy-2-phenylacetophenone), benzophenone, 
benzil, ketocoumarin (such as 3-benzoyl-7-methoxy coumarin), xanthone, 
thioxanthone, benzoin or an alkyl-substituted anthraquinone, diaryl 
iodonium salt, triaryl sulfonium salts, azobisisobutyronitrile and 
azo-bis-4-cyano-pentoic acid, although others can be employed. 
The practical concentration of the monomer or monomers employed is about 
7.5%-70% by weight based on the total solids of the composition, and 
preferably between 15-40%. 
The photoresist systems of the present invention can be suitably coated 
into a layer which, upon photoexposure, undergoes hardening as the result 
of polymerization of the polymerizable monomer and grafting of the monomer 
onto the photoreactive polymeric binder and cross-linking reactions 
involving the photoreactive polymeric binder. If desired, other 
crosslinking agents, such as bis-azides and polythiols, can be included to 
promote crosslinking of polymerizable monomer or the binder. 
If desired, preformed polymers having pendant pyridium ylide groups, which 
groups, upon photoexposure, undergo ring expansion (photorearrangement) to 
a diazepine group with accompanying insolubilization can also be blended 
with the photoreactive polymer of this invention. Examples of polymers 
having such pyridium ylide groups are set forth in U.S. Pat. No. 
4,670,528, issued to L. D. Taylor and M. K. Haubs on Jun. 2, 1987. 
To prepare a lithographic plate according to an embodiment of the present 
invention, the photoresist system is deposited as layer onto a substrate. 
Certain factors are considered in determining the appropriate materials 
for the substrate. Such factors vary with the particular lithographic 
needs of individual projects and are believed to be within the grasp of 
one skilled in the pertinent art. Regardless, for most lithographic needs 
envisioned, suitable substrates will generally include those to which the 
polymeric resist layer can be adhered adequately, prior to photoexposure, 
and to which photoexposed printing (image) areas are adhered after 
photoexposure. Other pertinent considerations may be extrapolated on the 
basis of the present disclosure. 
In practice, substrate materials for use in the manufacture of printing 
plates will oftentimes be subjected to one or more treatments in order to 
improve adhesion of the photoresist, or to increase the hydrophilic 
properties of the substrate material, and/or to improve the developability 
of the photoresist, as is described in U.S. Pat. No. 4,492,616 (issued 
Jan. 8, 1985 to E. Pliefke, et al.). Thus, the substrates will typically 
be treated (for example, with polyvinylphosphonic acid or silicate or by 
anodization, or by corona discharge or plasma treatment, or by roughening 
or graining treatment) to promote desired adhesion of the polymeric 
photoresist. 
Especially preferred substrates are the metallic substrates of aluminum, 
zinc, steel or copper. These include the known bi-metal and tri-metal 
plates such as aluminum plates having a copper or chromium layer; copper 
plates having a chromium layer; steel plates having copper or chromium 
layers; and aluminum alloy plates having a cladding of pure aluminum. 
Other preferred substrates are silicone rubbers and metallized plastic 
sheets such as poly(ethylene terephthalate). 
Preferred plates are the grained, anodized aluminum plates, where the 
surface of the plate is roughened mechanically or chemically (e.g., 
electrochemically) or by a combination of roughening treatments. Anodized 
plates can be used to provide an oxide surface. Still more preferred 
plates are anodized aluminum plates which, for example, have been treated 
with polyvinylphosphonic acid or otherwise provided with a resinous or 
polymeric hydrophilic layer. 
Examples of printing plate substrate materials which can be used in the 
production of printing plates of the invention, and methods of graining 
and hydrophilizing such substrates are described, for example, in U.S. 
Pat. No. 4,153,461 (issued May 8, 1979 to G. Berghauser, et al.); the 
aforementioned U.S. Pat. No. 4,492,616 issued to E. Pliefke, et al.; U.S. 
Pat. No. 4,618,405 (issued Oct. 21, 1986 to D. Mohr, et al.); U.S. Pat. 
No. 4,619,742 (issued Oct. 28, 1986 to E. Pliefke); and U.S. Pat. No. 
4,661,219 (issued Apr. 28, 1987 to E. Pliefke). 
It is common practice in preparing photoresist compositions to employ 
photosensitizers, coinitiators, and activators. Photosensitizers and 
coinitiators are relied upon to capture photons of exposing radiation. 
They may absorb light of different wavelengths from the principal 
photoinitiator. The activator in contrast is not relied upon to respond 
directly to exposing radiation, but rather adjacent activator and 
photosensitizer molecules react, following excitation of the latter by 
photon capture, causing release of a free radical which in turn induces 
immobilization addition reactions at sites of ethylenic unsaturation. 
Photoexposure of the printing plates can be accomplished according to the 
requirements dictated by the particular composition of the polymeric 
photoresist and the thickness thereof. In general, actinic irradiation 
from conventional sources can be used for photoexposure, for example, 
relatively long wavelength ultraviolet irradiation or visible irradiation. 
UV sources will be especially preferred and include carbon arc lamps, "D" 
bulbs, Xenon lamps and high pressure mercury lamps. 
The thickness of the photoresist can vary with the particular requirements. 
In general, it should be of sufficient thickness to provide a durable 
photohardened printing surface. Thickness should be controlled, however, 
such that it can be exposed within exposure-time requirements and should 
not be applied at a thickness that hampers ready removal of the layer in 
non-exposed areas by developers. When utilizing an anodized, gained 
aluminum substrate, good results are obtained by using a polymeric 
photoresist having a thickness in the range of from about 0.2 microns to 
about 3 microns above the microstructure of the grains, preferably about 
0.2 to 0.6 microns "above the grain". 
A polymeric photoresist can be provided with colorants, e.g., tint dyes, to 
provide a desired and predetermined visual appearance. Especially 
preferred will be a colorant, or a precursor of a species, respectively, 
capable either of being rendered colorless, or being provided with 
coloration by the irradiation of the plate-making photoexposure step. Such 
dye or dye-precursor compounds and the light absorption differences 
promoted by the photoexposure allow the platemaker to distinguish readily 
the exposed from the non-exposed regions of the plate in advance of 
mounting and running the photoexposed plate on a printing press. 
In addition, the operability of the polymeric photoresist may be improved 
by the addition of other components or additives. For example, the 
polymeric photoresist can contain plasticizers, hardeners, or other agents 
to improve coatability. If desired, macromolecular organic binders which 
are non-photoreactive and typically employed in the production of 
photoresist compositions can be employed to advantage. The polymeric 
photoresist may also contain antioxidant materials to prevent undesired 
(premature) polymerization and examples include derivatives of 
hydroquinone; methoxy hydroquinone; 2,6-di-(t-butyl)-4-methylphenol; 
2,2'-methylene-bis-(4-methyl-6-t-butylphenol); tetrakis 
{methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate} methane; 
diesters of thiodipropionic acid, triarylphosphite. While the use of such 
additives is unnecessary for the operability of the present invention, 
incorporation of such additives may dramatically enhance performance. 
The plasticizers, contrast dyes, imaging dyes and other additives may be 
microencapsulated and incorporated into the photoresist itself or a 
separate layer facially positioned or positionable atop the photoresist. 
Inclusion in the microcapsules would provides a wider latitude in the 
selection of such additives, since neither the solubility of the additives 
in the photopolymerizable compositions nor the inhibition or retardation 
effect of some additives on polymerization would be an issue in such a 
system. 
For wet development, a diluted alkaline solution optionally containing up 
to 10% by volume of organic solvents may be used. Examples of useful 
alkaline compounds include inorganic compounds such as sodium hydroxide, 
potassium hydroxide, lithium hydroxide, sodium benzoate, sodium silicate 
and sodium bicarbonate; and organic compounds such as ammonia, 
monoethanolamine, diethanolamine and triethanoloamine. Water-soluble 
organic solvents useful as developers include isopropyl alcohol, benzyl 
alcohol, ethyl cellosolve, butyl cellosolve, diacetone alcohol and the 
like. Depending on particular needs, the developing solution may contain 
surfactants, dyes, salts for inhibiting the swelling of the photoresist, 
or salts for corroding the metal substrate. 
As another means of development, it is noted that the present invention is 
especially well suited for several on-press development systems. For 
example, good results have been accomplished using the photoreactive 
polymeric binders of the present invention in a photoresist that is in 
contact or brought into contact with the microencapsulated developer 
systems described in U.S. patent application Ser. No. 08/146,710, 
cross-referenced above. The photoresist also incorporated a plasticizing 
system and a dispersed, particulate rubber system, as described in the 
above cross-referenced U.S. patent applications Ser. Nos. 08/147,044 and 
08/146,479, respectively. See, Example 6, infra, for a representative 
example.

The present invention will now be described in further detail by the 
following non-limiting examples of several of its embodiments. Unless 
otherwise indicated, all parts, percents, ratios and the like are by 
weight. 
EXAMPLES 
Preparation of Photopolymer 1 
In a 500 ml, three-necked, round bottom flask fitted with a 250 ml addition 
funnel with a dry N.sub.2 inlet, a Claisen adapter bearing a septum, and a 
condenser with an exit to a gas bubbler, toluene (30 g) was sparged for 5 
minutes with N.sub.2. In the addition funnel, a solution of 
m-isopropenyl-.alpha.,.alpha.-dimethyl isocyanate (13.5 g), methyl 
methacrylate (41.0 g), butyl methacrylate (45.5 g), toluene (50 g), and 
t-butyl peroxybenzoate (0.2 g) was sparged for 15 minutes with N.sub.2. 
The stirred toluene was brought to reflux in a 120.degree. C. bath and the 
contents of the addition funnel were added over 2 hours. After refluxing 
an additional 6 hours, a 5% solution of BHT in toluene (10 g) was added. 
Dry air was then introduced and heating discontinued. After 15 minutes, 
4-hydroxybutyl acrylate (11.62 g), triethylamine (2 g of a 10% solution) 
and dibutyl tin dilaurate (2 g of a 10% solution) were added and the 
solution is heated at 80.degree. C. for 21 hours. Methanol (10 g) was 
subsequently added and after heating for 0.5 hrs, 187.4 g of reaction 
solution was poured into a brown polyethylene bottle. 
A 100 g portion of the reaction solution, diluted with methyl ethyl ketone 
(50 g) was mixed into stirred hexanes (3 L) giving a soft amber 
precipitate (.about.75 g). The amber precipitate was dissolved in acetone 
(150 g) and reprecipitated over 2 hours in stirred methanol (3 L). A 
stringy, white precipitant was collected by vacuum filtration, rinsed with 
methanol (2.times.100 ml), broken into small pieces and air dried 
overnight. 31.1 g of white precipitant was retrieved (31.1 g, 53% yield). 
GPC: Mw 116,221: Mn 58,875; DSC: Tg 72.degree. C. 
Preparation of Photopolymer 2 
By the procedure described for the preparation of Photopolymer 1, 
m-isopropenyl-.alpha.,.alpha.-dimethyl isocyanate (13.5 g), methyl 
methacrylate (63 g), butyl methacrylate (23.5 g), toluene (50 g) and 
t-butyl peroxybenzoate (0.2 g) were used in polymerization, followed by 
the derivatization with 4-hydroxybutyl acrylate (11.6 g) to give 27.4 g of 
solid (47.0%). GPC: Mw 113,099; Mn 55,775; DSC: Tg 90.degree. C. 
Preparation of Photopolymer 3 
Photopolymer 3 was prepared in the same manner as Photopolymer 2, except 1 
g of maleic anhydride was used to replace 1 g of the methyl methacrylate 
in the monomer feed, giving 36.55 g of solid (74.4%). GPC: Mw 140,765; Mn 
52,768; DSC: Tg 87.degree. C. 
Preparation of Photopolymer 4 
Photopolymer 4 was prepared in the same manner as Photopolymer 2, except 15 
g of m-isopropenyl-.alpha.,.alpha.-dimethyl isocyanate, 61.5 g of methyl 
methacrylate, 23.5 g of butyl methacrylate and 1.25 g of t-butyl 
peroxybenzoate were used in the monomer feed, giving a 65.5% yield. GPC: 
Mw 33750; Mn 11400; DSC: Tg 72.degree. C. 
Preparation of Photopolymer 5 
Photopolymer 5 was prepared in the same manner as Photopolymer 4, except 
1.25 g of methyl methacrylate were substituted with 1.25 g of maleic 
anhydride, giving a 77% yield. GPC: Mw 54625, Mn 15636; DSC: Tg 82.degree. 
C. 
Preparation of Photopolymer 6 
By the procedure described for Photopolymer 1, 
m-isopropenyl-.alpha.,.alpha.-dimethyl isocyanate (13.5 g), methyl 
methacrylate (62 g), butyl methacrylate (23.5 g), toluene (50 g) and 
t-butyl peroxybenzoate (0.5 g) were used in the polymerization. In the 
subsequent derivatization, 4-hydroxybutyl acrylate (8.7 g), triethylamine 
(2 g of a 10% soln.) and dibutyl tin dilaurate (10 g of a 10% soln.) were 
utilized and the solution heated at 80.degree. C. for 21 hours. Methanol 
(20 g) was added. After heating 0.5 hours, an amber solution was obtained 
(198.73 g, 43.4% solids, 78% yield). GPC: Mw 86,000; Mn 37,000; DSC: Tg 
76.7.degree. C. This solution was used directly in formulating a 
photoresist layer. 
Preparation of Photopolymer 7 
Preparation of Photopolymer 7 was the same as Photopolymer 6, except 1 g of 
maleic anhydride replaced 1 g of the methyl methacrylate in the monomer 
feed, giving an amber solution (191.73 g, 49.93% solids, 87% yield). GPC: 
Mw 145,000; Mn 36,000; DSC: Tg 88.4.degree. C. This solution was used 
directly in formulating a photoresist layer. 
The efficacy of the maleic anhydride acceleration mechanism used in the 
preparation of Photopolymers 3, 5, and 7 will be evident from the results 
summarized in Table 1, below. 
TABLE 1 
__________________________________________________________________________ 
Maleic Anhydride as the 
"Match Maker" For TMI/Acrylate Copolymerization 
Photo- Photo- Photo- 
Photo- 
polymer 3 
Photo- 
polymer 5 
Photo- 
polymer 7 
polymer 2 
w/MA polymer 4 
w/MA polymer 6 
w/MA 
__________________________________________________________________________ 
Wt % m-TMI 
13.5 13.5 15 15 13.5 13.5 
Wt % MMA 
63 62 61.5 60.25 63.0 62 
Wt % BMA 
23.5 23.5 23.5 23.5 23.5 23.5 
Wt % MA 
0 1 0 1.25 0.0 1.0 
% Initiator 
0.2 0.2 1.25 1.25 0.5 0.5 
Mw 113099 
140765 
33750 54625 86000 145000 
Mn 55775 52768 11400 15636 37000 36000 
% Yield 
47 74 65.5 77 78 87 
__________________________________________________________________________ 
As shown in Table 1, the use of 1% maleic anhydride in the synthesis of 
Photopolymers 3 and 7 gave lower residual monomer and higher weight 
average molecular weight than the corresponding Photopolymers 2 and 6. 
Likewise the use of 1.25% maleic anhydride in the synthesis of 
Photopolymer 5 shows a higher conversion and molecular weight than the 
corresponding Photopolymer 4 synthesized without maleic anhydride. 
Preparation of Photopolymer 8 
In a 2 L, three-necked, round bottom flask fitted with a mechanical 
stirrer; dry N.sub.2 inlet; fluid metering pump delivery tube; and Claisen 
adapter bearing a thermometer and a condenser with an exit to a gas 
bubbler, toluene (140 g) was sparged for 5 minutes with N.sub.2. In an 
addition pump reservoir, a solution of 
m-isopropenyl-.alpha.,.alpha.-dimethyl isocyanate (44.3 g), maleic 
anhydride (8.87 g), methyl methacrylate (285.9 g), butyl methacrylate 
(104.16 g), toluene (191.69 g) and t-butyl peroxybenzoate (1.55 g) was 
sparged for 15 minutes with N.sub.2. 
The initial charge was stirred (150 rpm) and brought to reflux in a 
120.degree. C. bath, whereupon a solution of t-butyl peroxybenzoate (0.66 
g) in toluene (10 g) was injected, and the contents of the feed reservoir 
were metered out for a period of 6 hours. After heating an additional 2 
hours, a 10% solution of ethyl 4-N,N-dimethylaminobenzoate (EPD) in 
toluene (23.05 g) was added under dry N.sub.2 and heating discontinued. 
After 30 minutes, 4-hydroxybutyl acrylate (40.01 g), BHT (44.33 g of a 5% 
solution), DBTDL (44.33 g of a 10% solution) and dry air were introduced, 
and the solution heated at 80.degree. C. for 16 hours. Methanol (50 g) was 
added, and after heating for 0.5 hours, 957.3 g of a reaction solution was 
obtained (40.2% solids, theory: 50%), giving a 78% yield. GPC: Mw 107,000; 
Mn 35,000; DSC: Tg 90.4.degree. C. This solution was used directly in 
formulating a photoresist layer. 
Preparation of Photopolymer 9 
By the procedure described for the preparation of Photopolymer 8, 
m-isopropenyl-.alpha.,.alpha.-dimethylbenzyl isocyanate (44.3 g), maleic 
anhydride (11.08 g), methyl methacrylate (283.68 g), butyl methacrylate 
(104.16 g), toluene (346.72 g) and t-butyl peroxybenzoate (4.42 g) were 
used in the polymerization, followed by derivatization with 4-hydroxybutyl 
acrylate (30.16 g). 935.8 g of solution was obtained (51.82% solids; 
theory 986.03 g, 49.4%), constituting a 99.6% yield. GPC: Mw 127,029; Mn 
22,500; DSC: Tg 75.degree. C. 
Preparation of Photopolymer Rx-2 
In the manner of the procedures described for the preparation of 
Photopolymers 1 to 9, Photopolymer Rx-2 is prepared in accordance with the 
following tabulated protocol. 
______________________________________ 
STEPS: mole 
Components % wt wt (g) % 
______________________________________ 
INITIAL CHARGE: 
Maleic Anhydride 8.5 0.75 0.11 
m-TMI 17.5 1.552 0.10 
Methyl Methacrylate 56 4.96 0.65 
Butyl Methacrylate 18 1.596 0.15 
Toluene -- 32 -- 
ADDITION I (Under Dry Nitrogen): 
t-Butyl Peroxybenzoate 
-- 0.396 -- 
Toluene -- 2 -- 
ADDITION II (Under Dry Nitrogen): 
Maleic Anhydride 8.5 6.78 0.10 
m-TMI 17.5 13.962 0.10 
Methyl Methacrylate 56 44.67 0.65 
Butyl Methacrylate 18 14.361 0.15 
Toluene -- 35.344 -- 
t-butyl Peroxybenzoate 
-- 0.93 -- 
QUENCH I (Under Dry Nitrogen): 
Ethyl 4-N,N-Dimethylaminobenzoate, 
-- 4.61 -- 
10% 
DERIVATIZATION (Under Dry Air): 
4-Hydroxybutyl Acrylate 
-- 10.56 0.10 
Dibutyl Tin Dilaurate, 10% 
-- 8.866 -- 
2,6-Di-t-Butyl-4-methylphenol, 5% 
-- 8.866 -- 
QUENCH II 
Methanol -- 10 -- 
______________________________________ 
02.203 g of solution was obtained (50.60% solids). GPC: Mw 100,300; Mn 
17,959; DSC: Tg 88.7.degree. C. (onset), 96.6.degree. C. (midpoint); 
m-TMI-HBA Pendant Vinyl: 9.5 mole %. 
Example 1 
An aluminum substrate was electrochemically grained and anodized to give a 
porous aluminum oxide surface. This surface was then treated with a 
polymeric acid to produce an aluminum plate which was suitable for 
lithographic printing. A solution was then prepared based on the 
formulation in Table 2. 
TABLE 2 
______________________________________ 
Component % Solids 
______________________________________ 
Photopolymer 1 56.35 
Hexafunctional Urethane Acrylate (Ebecryl 8301 from 
10.70 
Radcure) 
Defunctional Urethane Acrylate (PU788 from Morton) 
2.88 
Trimethylolpropane triacrylate 
4.76 
Cab-o-Sil M5 Silica 1.00 
Hycar Rubber (1300 .times. 33 from B. F. Goodrich) 
4.00 
3-benzoyl-7-methoxycoumarin 1.40 
4-(4-methylphenylthio)phenyl!-phenylmethanone 
1.80 
2,2'-bis(o-chlorophenyl)-4,4',5,5'-tetraphenyl-1,2- 
3.50 
biimidazole 
Diphenyl Phosphate 2.25 
4,4'-methylenebis-(2,6-diisopropyl-N,N-dimethylaniline) 
2.25 
Pluronic L43 (from BASF) 2.50 
Triethylene Glycol Diacetate 
3.00 
Lithium Chloride 0.62 
Leuco Crystal Violet 3.00 
2,6-di-(t-butyl)-4-methylphenol 
0.14 
Ciba-Geigy Irganox 1035 0.10 
______________________________________ 
A 7% solution of the formulation in MEK/Toluene was spin coated onto a 
plate at a spin rate of 200 rpm. 
The coated plate was then exposed to actinic radiation from a standard 
mercury halide lamp, which had an emission peak in the ultraviolet range 
at 364 nm. The plate was then exposed through an UGRA target mask to 
produce a test image. The plate was then developed with a mixture of 55% 
ethyl acetate and 45% isopropanol, washed with 60% ethyl acetate and 40% 
isopropanol, and dried in a 70.degree. C. oven for 10 minutes. The 
developed plate was subsequently gummed with a protective finisher, and 
stored under ambient conditions. 
The plate was then placed on a Komori printing press and run in standard 
operation. The plate was run continuously for more than 50,000 good 
impressions. 
Example 2 (Comparative) 
A formulation identical to that in table 2 was coated on an aluminum 
substrate in the same manner as in Example 1, except that 19.6% 
poly(methyl methacrylate), i.e. Acryloid Resin A-11 from Rohm & Haas, and 
36.75% of a 50/50 copolymer of ethyl methacrylate and methyl acrylate, 
i.e. Acryloid Resin B-72 from Rohm & Haas, were substituted for 
Photopolymer 1. When this plate was exposed and developed under conditions 
identical to those of the previous example, the photoresist degraded to a 
state of practical uselessness before the completion of 1000 impressions. 
Example 3 
Photopolymer 2 (0% maleic anhydride) and Photopolymer 3 (1% maleic 
anhydride) were tested using the same aluminum substrate and formulation 
set forth in Example 1, except for a lower binder to monomer ratio. Their 
compositions are shown in Table 3. 
TABLE 3 
______________________________________ 
Component Plate 3A Plate 3B 
______________________________________ 
Photopolymer 2 (0% maleic anhydride) 
40.25 -- 
Photopolymer 3 (1% maleic anhydride) 
-- 40.25 
Hexafunctional Urethane Acrylate (Ebecryl 
18.1 18.1 
8301 from Radcure) 
Difunctional Urethane Acrylate (PU788 
5.40 5.40 
from Morton) 
Trimethylolpropane triacrylate 
8.93 8.93 
Cab-o-Sil M5 Silica 1.00 1.00 
Hycar Rubber (1300 .times. 33 from B. F. 
4.00 4.00 
Goodrich) 
3-benzoyl-7-methoxycoumarin 
1.40 1.40 
4-(4-methylphenylthio)phenyl!- 
1.80 1.80 
phenylmethanone 
2,2'bis(o-chlorophenyl)-4,4',5,5'-tetraphenyl- 
3.50 3.50 
1,2-biimidazole 
Diphenyl Phosphate 2.25 2.25 
4,4'-methylenebis-(2,6-diisopropyl-N,N- 
2.25 2.25 
dimethylaniline) 
Pluronic L43 (from BASF) 
2.50 2.50 
Triethylene Glycol Diacetate 
3.00 3.00 
Lithium Chloride 0.62 0.62 
Leuco Crystal Violet 3.00 3.00 
2,6-di-(t-butyl)-4-methylphenol 
0.14 0.14 
Irganox 1035 (from Ciba-Geigy) 
0.10 0.10 
______________________________________ 
Both plates were exposed through an UGRA target mask and a step wedge (3 
step/stop), developed by solvents and gummed as described in Example 1. 
Both plates could be run for more than 50,000 good impressions. However, 
Photopolymer 3 (1% maleic anhydride) showed roughly a 25% faster 
photospeed than Photopolymer 2 (0% maleic anhydride). 
Example 4 
Photopolymers 6 (0% maleic anhydride) and Photopolymer 7 (1% maleic 
anhydride) were tested using the same aluminum substrate and formulation 
set forth in Example 1, except for a lower binder to monomer ratio. Their 
compositions are shown in Table 4: 
TABLE 4 
______________________________________ 
Component Plate 4A Plate 4B 
______________________________________ 
Photopolymer 6 (0% maleic anhydride) 
49.00 -- 
Photopolymer 7 (1% maleic anhydride) 
-- 49.00 
Hexafunctional Urethane Acrylate (Ebecryl 
15.57 15.57 
8301 from Radcure) 
Difunctional Urethane Acrylate (PU788 
4.19 4.19 
from Morton) 
Trimethylolpropane triacrylate 
6.92 6.92 
Cab-o-Sil M5 Silica 1.00 1.00 
Hycar Rubber (1300 .times. 33 from B. F. 
4.00 4.00 
Goodrich) 
3-benzoyl-7-methoxycoumarin 
1.40 1.40 
4-(4-methylphenylthio)phenyl!- 
1.80 1.80 
phenylmethanone 
2,2'-bis(o-chlorophenyl)4,4',5,5'-tetraphenyl- 
3.50 3.50 
1,2-biimidazole 
Diphenyl Phosphate 2.25 2.25 
4,4'-methylenebis-(2,6-diisopropyl-N,N- 
2.25 2.25 
dimethylaniline) 
Pluronic L43 (from BASF) 
2.50 2.50 
Triethylene Glycol Diacetate 
3.00 3.00 
Lithium Chloride 0.62 0.62 
Leuco Crystal Violet 3.00 3.00 
2,6-di-(t-butyl)-4-methylphenol 
0.14 0.14 
Ciba-Geigy Irganox 1035 
0.10 0.10 
______________________________________ 
After exposure at 2.5, 5, 7.5, 10 and 40 LU, solvent development, and 
gumming as in Example 1, the plates were run on a Multigraphics Form Press 
for 50,000 impressions. Plate 4B (Photopolymer 7) showed an initial 
maximum step Dmax of 3 (7.5 LU), dropping back to 2 and remaining steady 
for the run. At 5 LU, 2% highlight dot decreased to 3% by 15,000 
impressions, where it remained through the run. In contrast, Plate 4A 
(Photopolymer 6) required 10 LU for an initial step Dmax of 3 which 
dropped to 1 by 25,000 impressions. At 7.5 LU, the step Dmax was 2 and 
dropped to 1 and highlight dot was 3% dropped to 5% by 50,000 impressions. 
Again, the performance of the photopolymer containing 1% maleic anhydride 
was superior to the photopolymer containing no maleic anhydride. 
Example 5 
Photopolymer 8 (2% maleic anhydride) was tested using the same aluminum 
substrate and formulation set forth in Example 1, except for a lower 
binder to monomer ratio. The composition is shown in Table 5: 
TABLE 5 
______________________________________ 
Component % Solids 
______________________________________ 
Photopolymer 8 (2% maleic anhydride) 
49.00 
Hexafunctional Urethane Acrylate (Ebecryl 8301 from 
15.57 
Radcure) 
Defunctional Urethane Acrylate (PU788 from Morton) 
4.19 
Trimethylolpropane triacrylate 
6.92 
Cab-o-Sil M5 Silica 1.00 
Hycar Rubber (1300 .times. 33 from B. F. Goodrich) 
4.00 
3-benzoyl-7-methoxycoumarin 1.40 
4-(4-methylphenylthio)phenyl!-phenylmethanone 
1.80 
2,2'-bis(o-chlorophenyl)-4,4',5,5'-tetraphenyl-1,2- 
3.50 
biimidazole 
Diphenyl Phosphate 2.25 
4,4'-methylenebis-(2,6-diisopropyl-N,N-dimethylaniline) 
2.25 
Pluronic L43 (from BASF) 2.50 
Triethylene Glycol Diacetate 
3.00 
Lithium Chloride 0.62 
Leuco Crystal Violet 3.00 
2,6-di-(t-butyl)-4-methylphenol 
0.14 
Irganox 1035 (from Ciba-Geigy) 
0.10 
______________________________________ 
After exposure at 2.5, 5, 7.5, 10 and 20 LU, solvent development and 
gumming as in Example 1, the plate was run on a Komori printing press for 
100,000 impressions. At 10 LU, initial 2% highlight dot coverage on paper 
remained above 100,000 impressions. At 7.5 LU, 2% highlight dot dropped to 
3% by 60,000 impressions, where it remained through the run. 
Example 6 
A photoresist solution with 7% of solid was made according to the 
formulation set forth below. The photoresist solution contained a 
photoreactive polymeric binder prepared in accordance with the present 
invention: 
______________________________________ 
Component % (w/w) 
______________________________________ 
Photoreactive Acrylic Binder* 
51.75 
Ebecryl 8301 oligomer (from Radcure) 
17.42 
Trimethylolpropane triacrylate 
4.68 
Polyurethane PU788 (from Morton) 
7.74 
Acrylated Nitrile Butadiene (Hycar 1300 .times. 33, 
4.00 
Goodrich) 
3-benzoyl-7-methoxy coumarin** 
1.40 
4-benzoyl-4-methyl diphenyl sulfide** 
1.80 
2-phenyl-4,6-bis-(trichloromethyl-5-triazine)** 
2.21 
Triethylene glycol diacetate 
3.50 
Leuco Crystal Violet Dye 2.77 
2,6-di-tert-butyl-4-methyl phenol (BHT)*** 
0.13 
Irganox 1035 (from Ciba-Geigy) 
0.10 
Pluronic L43 Surfactant (from BASF) 
2.50 
______________________________________ 
Notes: 
*The photoreactive binder contained methyl methacrylate, butyl 
methacrylate, maleic anhydride, and an mTMI adduct with hydroxybutyl 
acrylate; 
**Radical initiator, 
***Antioxidant 
The photoresist composition was coated onto an anodized aluminum plate by 
continuous roll coating, exposed to actinic radiation, then on-press 
developed. On-press development of the photoresist was effectuated by the 
agency of high-boiling, low-vapor pressure developers liberated from 
ruptured microcapsules coated atop the photoresist. 
The microcapsules were prepared by first dissolving 8.0 g HEC 330 PA (from 
Hercules), 3.9 g Versa TL 502 (from National Starch), 0.06 g Aerosol OT 
(from Fisher) in 425 g H.sub.2 O. A mixture of 21.5 g gamma nonalactone, 
89.5 g dibutyl phthalate, and 11.1 g Desmodur N-100 (from Miles) was then 
dispersed into the aqueous phase at 1500 rpm for 10 minutes. To encourage 
the formation of prewall, a small amount of dibutyl tin dilaurate (0.12 g) 
was added into the oleophilic phase. 1.4 g of triethylene tetramine was 
added and allowed to react for 2 hours at room temperature. 41.1 g of a 
melamine-formaldehyde prepolymer (CYMEL 385, from American Cyanamid) was 
added and the pH adjusted to between 5 and 5.5 with 1N sulfuric acid. The 
reaction was continued at 65.degree. C. for one hour. 10.0 gs of urea were 
added to react for one hour to quench all residual formaldehyde and/or 
melamine-formaldehyde condensate in the mixture. Sodium Chloride (18.3 g) 
was added and the pH was brought to 9 and the reaction allowed to continue 
for 30 minutes, then slowly cooled to 25.degree. C. The microcapsules were 
washed extensively with deionized water in a centrifuge. 
A microcapsule-containing coating solution was subsequently prepared 
utilizing 9.45 g microcapsules (at 39.7% w/v), 0.47 g Silica 2040 (at 40% 
w/v), 1.13 g PVA 205 (at 10% w/v), 2.24 g Pluronic L43 surfactant (at 5% 
w/v); Tx100 surfactant (at 10% w/v), 0.06 g LiCl (at 2% w/v) and 11.47 g 
H.sub.2 O. 
The microcapsule-containing coating solution was coated atop the 
photoresist. After exposing the plate to 40 UV light units, the plate was 
run through a pressure roller then mounted and ran on a Multigraphics 1250 
lithographic printing press. The plate on-press developed within 20 
impressions.