CA1053956A - Photopolymer process - Google Patents

Abstract

Abstract of the Disclosure The invention concerns a process for making photographic images. The process involves the photooxygenation of a film of a photooxidizable composition containing certain essential compo-nents to form peroxides in the exposed areas of the film, and de-composition of the peroxides to form a crosslinked polymer in the exposed areas. Essential to the composition are an ethylenically unsaturated component capable of forming a crosslinked polymer, and an oxidizable component containing allylic hydrogens.

Description

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This invention relates to photooxidizable compositions and to photooxidizable elements, for example, printing plates embodying a layer of such compositions. More particularly, the invention relates to a process for making lithographic plates.
Other methods for producing printing plates from polymeric mate-rials involve the exposure of a film of a light-sensitive polymer to actinic light which causes the exposed areas of their surfacas to cross-link and form solvent-insoluble compounds. The films are then developed by removal of the unexposed partsofapolymer coating with a solvent. For instance, United States patent 3,556,792 discloses the use of solvent-soluble polymers contain-ing substituted allyl groups which may be used for making prillting plates.
Such methods are less subject to the adverse influence of oxygen but the re-sulting plates are not entirely satisfactory for use as lithographic plates.
Compositions capable of being converted under th~ influence of actinic radiation to rigid, insoluble, tough structures have become increasing-ly important in the preparation of printing elements. One of the fundamental patents relating to such compositions is United States 2,760,~63 to Plambeck.
In the process of the Plambeck pa~ent, printing elements are produced directly by exposing to actinic light~ through an image bearing process transparency, a layer of an essentially transparent composition containing an addition poly-merizable, ethylenically unsaturated monomer and an addition polymerization initiator activatable by actinic radiation. The layer of polymerizable com-position is supported on a suitable support, and exposure of the composition is continued until substantial polymeri~ation of the composition has occurred in the exposed areas with substantially no polymerization occurring in the nonexposed areas. The unchanged material in ~he latter areas then is removed, as by treatment with a suitable solvent in which the polymerized composition in the exposed areas is insoluble. In the case of printing plates, this results ln a raised relief image which corresponds to the transparent image of the transparency and which is suitable for use in letterpress and dry off-set work.
While extremely useful in the preparation of relief printing ele-ments~ lithographic printing elements and images from dry transfer processes,

- 2 - ~ ~

the photopolymer compositions of the types disclosed by the Plambeclc patent become less sensitive to actinic radiation due to the diffusion of oxygen from the air into the photopolymer layer. The oxygen acts to :inhibit the desired polymerization and cross-linking reactions. There are means of remo~-ing or preventing oxygen from saturating or desensitizing the photopolymer layer. One way is to store or treat the element in an essentially oxygen-free atmosphere of an inert gas such as carbon d.io~ide. This technique gives satisfactory results but requires special equipment and is time consuming.
It also is known to add certain metal compounds such as tin salts~ which are soluble in the photopolymer composition but which are non-reacti~e with the addition polymerization initiator. While a number of these compounds sub-stantially reduce the influence of oxygen and improve the photographic speed of the photopolymer element, their utilization has not been entirely satis-factory.
; According to one aspect of the invention, there is provided aprocess for making a photographic ~nage which comprises exposing selected areas of a sensitized photooxidizable composition in film form to light having a wave length of from about 3,900 to about 127000 Angstroms in the presence of oxygen to form peroxides in said areas, and decomposing said peroxides to form free radic~ls which effect polymerization or cross-linking of the compo-sition in the exposed areas of the film~ said sensitized photooxidizable composition comprising a mixture of a photooxygenation sensitizer with a photooxidizable composition comprising as essential components 1) at least 5%
by weight7 based on the total weight of the photooxidi able composition of a polymerizable ethylenically unsatur~ted component selected from ethylenically u~saturated monomers, ethylenically unsaturated polymers and mixtures thereof;
capable of fo~ming a high polymer by additio~ polymeri~ation or of forming a cross-linked composition and 2) an oxidi~able component diffe:rent from the said polymerizable ethylenically unsaturated component7 which oxidizable . ~ 3

3~
component contributes to the composition at least 1.0 x 10 moles per looocc of the composition of olefinic unsaturation of the type i~ which there is no more than one hydrogen atom on each of the double bond carbons and in which there is at least one allylic hydrogen on at least one of the carb~ns adja-cent to the double bond carbons, which allylic hydrogen is not on a bridge-head carbon.
According to a further aspect of the invention there is provided a photosensitive film comprising a sensiti~ed photooxidizable composition comprisi~g a mixture o~ a photooxygenation sensiti~er with a photooxidazable composition comprising as essential components 1) at least 5~o.by ~eight, based on the total weight of the photooxidizable composition, of a polymeriz-able ethylenically unsaturated component selected from ethylenically unsatur-ated monomers, ethylenically unsaturated polymers arld mixtures thereof~ cap-able of forming a high polymer by addition polymerization or a cross-linked composition and 2) an oxidi~able component different from the said polymeriz-able ethylenically unsaturated cornponent, which oxidizable component contrib-utes to the composition at least 1.0 x 10 moles per lOOOcc of the composi-tion of olefinic unsaturation of the type in which there is no more than one hydrogen atom on each of the double bond carbons and in which there is at least one allylic hydrogen on at least one of the carbons adjacent to the double bond carbons~ which allylic hydrogen is not on a bridge~head carbon.
The process of this invention is applicable to the preparation of relief printing plates~ but is particularly useful i~ the preparation of lithographic printing plates and photoresists.
The photoo~idizable compositions of the process of this invention deposited as a film on a support, are selectively exposed to light and polymerized and/or cross-linked in the exposed '~' , - 3a -5~
areasO The unexposed areas of the film then are removed by use of a suitable solvent for the photooxidizable composition or by other means such as use of an air knife exposing the substrate. The photooxidi~able compositions of the process of this invention may be used to prepare negativa or positive working lithographic plates. In preparing a negative working plate, the photooxidi 2-able compositions of the process of this invention are deposited as a film on a metal backing support, are selectively exposed to light and polymerized and/or crosslinked in the exposed areas.
The unexposed areas of the film are removed, exposing a hydro-philic metal substrate. If the high polymer formed in the ex-posed areas of the film is oleophilic, it accepts greasy inX, wher~as the metal surface corresponding to the unexposed areas of the film, being hydrophilic, accepts water and rejects the greasy ink. In preparing a positive working plate, the photooxidizable compositions are hydrophilic and are deposited as a film on an ; oleophilic backing sheet. Selective exposure to light polymerizes and/or crosslinks the exposed areas and the unexposed areas are then removed.~ Since the crosslinked polymer f~und in the exposed areas of the film is hydrophilic, it accepks water and rejects greasy ink, whereas the oleophilic backing corresponding to the unexposed area of the film accepts the greasy ink.
The process is believed to involve the formation of per-oxides (peroxides or hydroperoxides) and their decomposition to generate free radicals which effect polymerization and crosslink~
ing or crosslinking alone of the photooxidizable compositionsO
The initial raaction involves the phokosensitiæed oxidation of an allylic hydrogen~containing component of the composition, result-ing in ~he formation of peroxide ~roups on and in the ilm o said compo~ition. The peroxides formed in the light-struck areas of the film then are decomposed~ eithar concurrently with or subse-quent to their formation, by the action of héat~ or a metal cata-lyst or a reducin~ agent to provide the frae radicals necessary for the polymeri~ation and/or crosslinking raactions.

The process of this invention is ~d~antageous in tha-t it is possible to utilize low light levels. Also, the process is not inhibited by oxygen during the exposure step. Furthermore, low levels of visible light are operative, thus making it possible to prepare printing plates by projection of a photographic trans-parency.
The process is also applicable to the preparation of lithographic camera plates. In this procedure, the copy is ex posed to light, the light being absorbed in the dark areas of the copy and reflected by the light areas. The reflected light is passed through a lens system and projected on the surface of the photooxidizable composition.
The process of this invention is illustrated more specif-ically by the following examples. In all the examples, the solu-tion preparation, film coatiny and subsequent operations were carried out in the dark under safe lights.
E~ample 1 This example illustrates the insolubilization of a film of hydroxypropyl cellulose containing pentaerythritol triacrylate and the reaction product of Bisphenol A and 1,2,4-trimethyl-4-chlorocarbonylcyclohexene, ~ , as the photooxidizable material.
Vanadium oxyacetylacetonate was employed as the catalyst.
CH

~C~o_ C~
~ CH3 0 CH3 0 ~3 ., .

Bisphenol~A, 4 4 g (~.019 mol), and triethylamine, 3~9 ~ g. tO~038 mol), were dissolved in 40 ml. of anhydrous diethyl 1 ether under a nitro~en atmosphere. A solution of 7.2 g. (0.038 mol) of 1,2,4-trimethyl 4-chlorocarbonylcyclohexene (pr~pared by the Diels~Alder reaction o 2,3-dimethyl-1,3-butadiene! and meth-acrylyl chloride) in 10 ml. of anhydrous diethyl ether was added dropwise at ambient temperature to the Bisphenol A solution, and .

53~S6 the resulting mixture was stirred for two days under nitrogen.
The reaction mixture was transferred to a separatory funnel and extracted successively with 5% hydrochloric acid, water, and sat-urated a~ueous sodium chloride. The ether layer was dried over anhydrous magnesium sulfate, filtered, and the ether removed under vacuum to give a viscous liquid. The product was purified by col-umn chromatography on silica gel and 7.8 g. (76%) of a white solid, m~p. 54-56C., was isolated. NMR, IR, and mass spectral analyses were consistent with the assigned structure.
A sheet of 14 x 14 cm. grained aluTninum (Lith-Kem-~o Division of Lith-Kem Corporation, Lynbrook, N.Y.) was pretreated to improve adhesion by coating with a five percent by volume solu-tion of y-methacryloxypropyltrimethoxy silane (Union Carbide, A-174 Silane) in methanol. The coating was applied with a whirl coater (Tasope'Face Up Whirler, Tasope'Co., Aurora, Missouri) and heated for two minutes under the whirler's infrared lamps.
A photooxidizable composition was prepared as follows:

Grams hydroxypropyl cellulose (Klucel GF, Hercules Incorporated) 0.100 pentaerythritol triacrylate 0.075 ~ 0.023 ~;
rose bengal 0.0043 solvent - 11 ml. of anhydrous ethanol;
the solution was filtered before coating.
The solution was coated on the pretreated ~rained alum-inum sheet using the Tasope~whirler at maximum speed. The-dried 1 30 film thickness was about three-microns. The dried film was cov~
ered wlth a Stau~fer 21 Step Sensitivit~ Guide (#AT 20 x 0.15) and exposed for five minutes from a distance of 60 cm. to a 375 ....... ...
watt Sylvania R32 photoflood lamp. Following exposure, the step yuide was removed and the film was degassed by severa:L evacuation nitrogen flush cycles. The film was then covered with a I ~ fr~

~a~5;~6 similarly degassed solution of vanadium oxyacetylacetonate in benzene (0.10 gm./100 ml.) under a nitrogen atmosphere. After 30 minutes, the film was removed from the catalyst solution and etched in water. The unexposed areas of the film were removed, exposing the aluminum, whereas the exposed areas were insolu-bilizedO

This example illustrates the use of sulfur dioxide asthe peroxide reducing agent for the photooxidizable composition described in Example 1.
Film preparation, exposure, and ~ilm degassing were car-ried out as described in Example 1. The film was then contacted with a gaseous mixture of sulfur dioxide (two and one-half percent by volume) and nitrogen for 30 minutes. The ~ilm was etched in water and exhibited insolubiliæation through step ~16 Example 3 This example illustrates the lnsolubilization of a film of hydroxypropyl cellulose containing N,N'-methylene-bisacrylamide and the compound shown in formula 1 , as the photooxidiæable mate-rial. Vanadium oxyacetylacetonate was employed as the catalyst~
A photooxidizable composition was prepared as follows:
Grams hydroxypropyl cellulose (Klucel GF~ Hercules I~lcorporated) 0O479 N,N'-methylene,bisacrylamide 0.096 1 0.112 .~ ~
rose bengal, added in two ml.
of water 0.0138 solvent - 16 ml. of methyl cellosolve, the solution was filtered before coatiny.
The solution was coated on pretreated grainecl aluminum ~Example 1) using the whirl coater to obtain a dried film thick-ness of about five microns. The dried film was exposed by pro-jection through a set of Kodak Wratten Gelatin Filters described ' - below:

t~

Si3Y1~6 Step No Filter 'Den's'i't~

2 0.3

4 ~09 1.2 1.5 8 2.0 ' 9 2.3 2.6 A Bell ~ Howell 16 mm. movie projector was used to expose the film from a distance of 3~4 meters. The exposure time was three ~' minutes.
The film was degassed and treated with vanadium oxy- ' acetylacetonate in benzene as described in Example 1. The film ' was washed with water in a commercial etching unit for two minutes. ~' A sharp image of the step wedge was produced, with insolubilization '~
visible through step #5.
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. .
This example illustrates the insolubilization of a film of pentaerythritol triacrylate and diethyl 1,2-dimethylcyclohexene-trans-4,5-dicarboxylate~ ~ , as the photooxidizable material.
Vanadium oxyacetylacetonate was employed as the catalyst.
o CH ~ C-OE t CH3 ~ OE t .

A ~hotooxidizable composition was prepared as follows:

., .

~ . ".

i3~S~
Grams pentaerythritol triacrylate 8.34 zinc tetraphenylporphin, in 0.055 1.4 ml. of chloroform 2 (prepared by the Diels-Alder 0.45 ~ reaction of ethyl fumarate and 2,3-dimethyl-1,3-butadiene) The solution was coated on a glass plate using a five mil doctor blade and exposed by projection through the Kodak Wratten Filter wedge described in Example 3~ A 375 watt Sylvania R32 photoflood lamp was employed from a distance of 1 4 metersO
The exposure time was 10 minutes.
Following exposure, the plate was stored in a nitrogen atmosphere for 30 minutes and then sprayed with a degassed, 0~1%
solution of vanadium oxyacetylacetonate in methanol. After 10 minutes, the plate was etched in acetone 7 this resulting in a yood image of the step wedge and visible insolubilization through step ~9.
~
This example illustrates the insolubilization of a film of a composition containing an unsaturated polyester, diallyl adipate, cobalt naphthenate, and a modified, unsaturated poly-ester as the photooxidizable material.
The photooxidizable material was prepared by the Diels-Alder reaction of a fumarate polyester (Atlac 382E~, molecular weiyht 3,000, Atlas Chemical Industries; based on bisphenol A and propylene oxide) with 2,3-dimethyl 1,3 butadiene (DMB). Twenty-five ~rams Atlac 382E (0 059 mol. unsaturation) and 9. 7a g. of DMB (0.118 mol., 100% exce~s), were dissolved in 25.0 g. of re-agent ~rade toluene in a ~OOOO ml. polymerization bottle. The i reaction was run under air. To prevent crosslinking o~ the poly ester, about 1% hydroquinone was added as an inhibitor The re-action mixture was heated at 100Co for 24 hours (Analysis for unreacted DMB by ~as-liquid chromato~raphy indicated the reaction was complete after 22.5 hrs.). The polymer was precipitated by q _, S3~5~
pouring the reaction mixture into about 800.0 ml. of rapidly stirring hexane. The solvent was decanted and the gummy polymer was redissolved in benzene, filtered through glass wool, repre-cipitated by pourlng into hexane, and dried. A study of the product, and of Atlac 382E and hydrogenated Atlac 382E, by nuclear magnetic resonance indicated the polyester was modified 100 4% with DMB~ The polymer contains units of the following structure:

~1H-C~2-O~)-C-~-O-C~2-C~I-O-C7H-C3 C~ f ~2 /c=c CH3 C~13 A photooxidizable composition was prepared as follows:
rams Atlac 382E 0 75 DMB-Atlac 382E 0.25 diallyl adipate 0.10 cobalt naphth~enate (Tenneco, 0.033 Nuodex,~6% Co) methylene blue, in 1.6 ml. of 2.2 x 10-4 chloroform ~-The solution was coated on grained aluminum using a 10 mil doctor blade. The dried film was covered with a photographic negativa and exposed for 15 minutes from a distance of 30 cm. to a 375 watt Sylvania R32 photoflood lamp. During exposure the film was cooled by an air blower. Following exposure, the film was heated under nitrogen at 80C. for 30 minutes and then etched in tetrahydrofuran (T~) for about one minuteO A relie~ image of the negative remained in the exposed areas of the film.
Exam~le 6 This example illus~rates the insolubilization of a film of an unsaturated polyester containillg pentaerythritol triacrylate ~s`~
and a modified, unsaturated polyester as the photooxidizable mate rial. Vanadium oxyacetylacetonate was employed as the catalyst.
A photooxidizable composition was prepared as follows:
Grams Atlac 382E 0.75 DM~-Atlac 382E ~prepared as in 0.75 Example 5) pentaerythritol triacrylate 0.50 zinc tetraphenylporphin 0.20 solvent - 18 ml. of benzene The solution was coated on grained aluminum using the whirl coater at maximum speed. The film was allowed to air dry for 30 minutes, and then was exposed as described in Example 3 for 10 minutes. The film was placed under nitrogen for 90 minutes The plate was carefully brushed with a degassed solution of 0.05 g. of vanadium oxyacetylacetonate in 25 ml. of methanol and al~
lowed to stand under nitrogen for 15 minutes. The plate was re-moved and dipped in a 50-50 hexane-benzene solution. The unex-posed areas dissolved away exposing the aluminum and leaving un-dissolved polymer throuyh step ~10.
E ~
This example illustrates the insolubilization of a film of a composition containing a chain extended, unsaturated poly-ester, modified to be photooxidizable, and diallyl adipate and vanadium oxyacetylacetonate.
A fumarate polyester ~Atlac 382E, molecular weight 3,000, Atlas Chemical Industries: based on bisphenol~A and propylene ox-ide) was chain extended with toluene diisocyanate and partially modified in a Diels-Alder reaction with 2,3-dimethyl-1,3~
butadiene ~DMB~.
Atlac 382E, 25 g~, was dissolved in 100 ml. of benzene and about 25 ml. of benzene was distilled off under a nitrogen atmosphere. Toluene diisocyanate, 1.16 g. ~6.67x10-3 mol), and five microliters of a 10~ solution of stannous octoat:e in hexane , ~ 11 -.. . . . , .. ,,.. , . ; - . ~ ~ - . :. -~43 5~Sq;i was added to the Atlac solution, and the reaction mixture was refluxed overnight. The polymer was precipitated by pouring the viscous solution into one liter of hexane. The polymer was iso-lated, redissolved in benzene/ filtered through glass wool, re-precipitated from one liter of hexane, and dried at 50C under pump vacuum overnight~ A 1% solution of the chain extended poly-mer in benzene had a specific viscosity of 0.30 at 25C., com-pared to 0.13 for Atlac 382E.
The chain extended Atlac 382E was partially modified in a Diels-Alder reaction with 2,3-dimethyl-1,3-butadiene (DMB).
The chain extended Atlac, 25 g. (0.059 mol unsaturation), DMB, 0.92 g. (0.011 mol), and 0.025 g. of copper powder were added to a polymerization bottle with 90 ml. o reagent grade toluene.
The bottle was capped under air and heated at 80C. overnight.
The copper was removed and the modified polymer precipitated by filtering the solution into one liker o~ hexane. The polymer was isolated, redissolved in benzene, reprecipitated from one liter of hexane, and dried at ambient temperature under pump vacuum overnight. NMR examination of the polymer indicated 10-20~ mod-ification by DMB This polymer will be referred to as chain ex-tended, DMB-Atlac 382E.
A photooxidizable composition was prepared as follows:
Grams chain extended, DMB-Atlac 382E 1.00 diallyl adipate 0.10 vanadium oxyacetylacetonate, 0.OlG
in 0.7 ml. of methylene chloride and 1.~ ml. o ` acetone rose bengal, in 0O2 ml. of 20/80 6 x 10-4 (vol./vol.) methanol/acetone acetone - 0.5 ml.
The solu~ion was coated on vinyltriethoxysilane-primed gxained aluminum using a 10 mil doctor blade. The driecl film was exposed as described in Example 5, placed in a vacuum at: 80C.

l for 30 minutes, and etched in T~F. The unexposed areas dissolved~ -:.

~3~3i5i~
exposing the aluminum and leaving an excellen-t reproduction of the negative.
Another photooxidizable composition was p.repared as followso - Grams chain ex~ended, DMB-Atlac 382E ~.00 diallyl adipate 0.20 vanadium oxyacetylacetonate, in 0~04 ml. of methylene chloride 0.0021 me~hylene blue, in 0.3 ml. of methylene chloride 3.1 x 10-4 solvent - seven ml of methylene chloride The solution was coated on vinyltriethoxysilane--primed grained aluminum to give a dried film thickness of 20 m.ils. The film was exposed as described in Example 5 with air blower cool-ing, heated in air at 80C. for 30 minutes, and etched by lightly brushing the film in acetone. A relief image of the negative re-mained in the exposed areas of the film.
Example 8 1 20 This example illustrates the insolubilization of a film ; of a composition containing a chain extended, unsaturated poly-ester, modified to be photooxidizable, and diallyl adipate and cobalt naphthenate.
A photooxidizable composition was prepared as follows:
~rams chain extended, DMB-Atlac 382E lo 00 (described in Example 7) - diallyl adipake 0.10 cobalt naphthenate (Tenneco, Nuodex, 6% Co) - 0.033 methylene blue, in 1~6 ml. of chloroform 2.2 x 10 ~ ilm preparation and exposure were as described in Example 5. The film was etched in THF and, ùpon drying, a sharp image of the negative remained.
Examp~e 9 This example illustrates the insolubilization of a ilm :

~53~5~
of an unsaturated polyester containing co~alt naphthenate and a modified, unsaturated polyester as the photooxidizable material The example was carried out in a manner identical to that of Example 5, except the diallyl adipate of Example 5 was excluded from the composition. After etching, an image of the negative was visible.

~ . ..
This example illustrates the insolubilization of a film of natural rubber containing pentaerythritol triacrylate and ferric acetylacetonate. The natural rubber serves as the photooxidizable material.
A photooxidizable composition was prepared as follows:
Grams pale crepe natural rubber 0.535 (precipitated once from methanol) pentaerythritol triacxylate 0.054 ferric acetylacetonate ) in 1.3 ml. 2.7 x 10 4 ) of benzoin ) chloroform 1~6 x 10-3 zinc tetraphenylporphin 0.88 solvent - 20 ml. of benzene The solution was coated on primed grained aluminum (Example 1) using the whirl coater to obtain a dried film thick-ness of about two microns. The film was exposed with air blower cooling for 10 minutes, as described in Example 1. Immediately following ~xposure, the sample was placed in a nitrogen atmosphere for 45 minutes and then etched in benzene. The exposed areas were insolubili~ed through step #5.
Example 11 This example illustrates the insolubilization of a film of ethylene-propylene-ethylidenenorbornene terpolymer rubber ~EPsyn 40 A EPDM~ Copolymer Rubber and Chemical Corp.~ 5 8 x ' 10 4 mol un.saturation~gm., Mooney viscosity of 40 ~ML-B' @
2~0F~) con-taining pentaerythritol triacrylate and ferric acetyl-acetonate, The EPDM rubber serves as the photooxidi~able material.

- lg -. " .. . ..

A photooxidizable composition was prepared as follows:
Grams EPsyn 40-A EPDM 0.375 (precipitated once from methanol) pentaerythritol triacrylate 0.038 ferric acetylacetonate ) in 0.9 ml~ 1.9 x 10-4 ) of benzoin ) chloroform 1.1 x 10-3 zinc -tetraphenylporphin 0.050 solvent - 11 ml. of benzene The solution was coated on primed grained aluminum (Example 1) using the whirl coater to obtain a dried film thick-ness of about four microns. The film was exposed with air blower cooling as described in Example 1, and subsequently treated as described in Example 10. The unexposed areas were removed, bar-ing the aluminum, while the exposed areas were insolubilized -through step #11.
Exam~le 12 This example illustrates the ins~lubilization of a film of poly(N,N-dimethylacrylamide) containing N,N'-methylene-bis-acrylamide and diethyl 1,2-dimethylcyclohexene-trans-4,5-di-carboxylate, 2 , as the photooxidi2able material, the insolubilized film having the ability to reject ink.
A solution of 36.0 g. of hydroxypropyl cellulose ~Klucel~
L, Hercules Incorporated) 5.4 g. of dimethylol urea, ancl 0.27 g.
of ~toluenesulfonic acid in 972 ml. of water was used to whirl-coat six mil grained aluminum plates. The coated plates were cured for 15 minutes at 125~C. A solution of ~he following composition was prepared and whirl-coated on one o~ the coated plates:
poly~N,N-dimethylacrylamide) 1.0 g.
(intrinsic viscosity, 2.34 in water at 25C~) N;N'-methylene-bisacrylamide 0.5 g.
Diethyl 1,2 dimethylcyclohexene- 0.18 g.
trans-4,5-dicarboxyla*e ~ f ~ J~ m~/~
.

~s~
zlnc tetraphenylporphin OrO74 g~
- ethanol 10 ml.
chloroform 10 ml.
The plate was allowed to dry for one hour, and was exposed for 10 minutes as described in Example 3. The plate was placed under nitrogen for two hours and sprayed with a degassed solution of 0.2% (wt/vol) vanadium oxyacetylacetonate in methanol. After standing under nitrogen for 10 minutes, the plate was removed and washed wi-th tap water. The (poly)N,N-dimethylacrylamide layer remaineA in the exposed areas through step ~6, but it dissolved off the rest of the plate, exposing the hydroxypropyl cellulose sublayer~ The plate was wiped with Rosos offset ~ountain solution (3 ozO/gal ) and coated with Lith-Kem-Ko rub-up ink. The ink was rejected in the insolubili2ed areas and was accepted in the back-ground areas.
The photooxidizable compositions used i.n the process of this invention must contain an oxidizable component which will contribute to the composition at least 1.0 x 10 3 moles per 1000 cc. of the composition, and preferably at least 1.0 x 1~-2 moles per 1000 cc. of the composition, of olefinic unsaturation of the type in which there is no more than one hydrogen atom on each of the double bond carbons and in which there is at least one allylic hydrogen on at least one of the carbons adjacent to the ~ouble bond carbons~ which allylic hydrogen is not on a bridge-head carbon~ Such unsaturation can be termed photooxidizable un-saturation, and an example of this type of unsaturation is illus~
trated by the structural unit -C=f-CH, in which R i5 hydrogen or R
Cl-C6 alkyl~
In general, suitable photooxidizable unsaturation, wheth-er in a polymer or a low molecular weight compound, will be thatprovidiny olefinic units corresponding to those of the general formula Rl-C = f~R3 wherein the Rl~ R2, R3 and R4 subct:ituents ~r~ ~c ~ 7~
.i .

be hydrogen, an alkyl group containing one to twenty carbon atoms, an aryl group or a substituted aryl group. Furthermore, Rl and R2~ R3 and R4~ Rl and R3 and R2 and R4 may be combined in the form o~ an alicyclic or heterocyclic r;nga However, one of the R~s must contain the -CH group in order that at least one allylic hydrogen atom is present, and the carbon in this group can not be a bridgehead carbon. Also, at any one time, when any of the R~s is hydrogen, there can be no more than one hydrogen on each of the double bond carbons~
1~ When the R~s are alkyl, they may be straight chain alkyl, such as methyll ethylj n-propyl, n-butyl, n-amyl, n hexyl, or octadecyl. Moreover one of them may be a branched chain alkyl, such as isopropyl, isobutyl, t-butyl and isoamyl, as long as none of the remaining R~s is branched. Also, one of the R's may be an unsaturated alkyl group containing a carbon-carbon double bond in conjugation wlth the ole~inic double bond. When the R's are aryl, khere normally will be no more than two of them which are aryl and they ordinarily will be singly substituted on the double bond carbons The aryl substituents, such as phenyl and naphthyl, also : O
may themselves be substituted with -R', -OR', NHC-OR~, -Cl, -Br and ~F substituents, wherein R9 is an alkyl group containing one to six carbon atoms, or is aryl~ such as phenyl~ Furthermore, if only on~ of the R's is aryl, then the aryl group may contain a O O O O
-CN, -C-R~, -C-ORY, -OC-R' or -OC-NHR~ substituent~ These same , , o substituents, ~lus the -NHC-ORI, -Cl, -Br and -~ substltuents listed earlier, also may occur elsewhere in the polymer molecule provided they are separated from the olefinic unsaturation in the polymer by at least one carbon atom, and preferably by two or more carbon atoms~
, The desired photooxidizable unsaturation may be present in the composition in the form of mono-, or polyfunctional (di-or greater) unsaturated materials. Representative examples of '~

' : .
- . ,, . ~ : - :

- sunsaturated photooxidizable materials include trimethyleth-ylene, tetramethylethylene, 1~2~dimethycyclohexene, diethyl 1,2-dimethyleyclohexene-4~5-dicarboxylate, X-ethylidene-norbornane, 2-methylnorbornene~ 2-3~dime~hyl-norbornene, cyclopentene, 1~
methyl-cyelopentene, 1,2-dimethyl-cyclopent~ne, ~ trimethyl styrene, indene~ alXyl-sub~tituted indenes and alkyl-substitu~ed furansO
A representative example of diunsaturated photooxidizable material is the reaction product of bisphenol A and 1~2,4-trime~hyl-4-chlorocarbonylcyclohexene~ 1 Representative examples of poly-unsaturated photooxidi2ab1e materials i~clude the EPDM rubbers, natural rubber, the ho~opolymers and copolymers of butadiene, isoprene, 2~3-dimethyl-1,2-butadiene and 1,3~pentadiene, and the copolymers of these dienes with vinyl monomers such as acrylic and methacrylic ac.ids, their esters and amides, styrene, vinyl pyri-dine, vinyl ethers, sulfides, esters, ketones and halides, vinyl-idene halides and allyl ethers and esters. Polyunsaturated photooxidizable materials may additio~ally contain certain other ~ypes of unsaturation, for example fumarate or maleate unsatura-tion, or the type represented by the characteristic CH2=C~ group, : ~hen the photooxidizable unsaturation is not already present in a polymer structure, it may be introduced into a base polymexO Exemplary of such base polymars are unsaturated poly~
esters, into which the desired unsaturation may be introduced through utilization of the Diels-Alder reaction~ Also~ since esteriication reactions may be used to introduce the oleinic u~saturation into pol~mers containing hyaroxyl groups, th~ base polymers may include`polymers such as poly(vinyl alcoholj and poly(vinyl acetate) which has ~een partly hyd~olyzed; partly or comple~ely hydrolyzed copolymers of vi~yl acetate with o~her vinyl nomers such as vinyl chloride; cellulose and cellulo~e esters;
starch; cellulose which has been partly or completely reacted wi~h an:alkylene oxideO such as eth~lene oxide ox propylene ox-., .
ide, for example, hydro~yethyl cellulose or hydroxypropy:l - ~8 -' .
. ., ~l~53'~i6 c~: ulose; phenoxy resîns and other resins prepared by condensing a polyhydroxy compound with epichlorohydrin; polymers or copoly~-mers of hydroxyalkyl acrylates or methacrylates; polymers ox co-polymers of hydroxyalkyl vinyl sulfides; and polymèrs or copoly-mers of hydroxyalkyl acrylamides~
The reactant ut.ilized to introduce the photooxidizable olefinic unsaturation lnto the base polymer must provide allylic hydrogen to the produet polymer, that is, the latter must contain at least one hydrogen on at least one of the carbons adjacent to the double bond carbons, which allylic hydrogen is not on a bridge-head carbon~ Furthermore~ it is necessary in the product polymer that there ~e no more than one hydrogen atom on each of the double bond carbons~ The choice of reactant will depend upon khe reac-tion involved in preparing the product polymer.. Thus, 1,3-buta-diene, isoprene and 2,3-dimethyl-1,3-butadiene preferably are used in a Diels-Alder reaction~ as with an unsaturated-polyesterO
However, the use of cyclopentadiene in this reaction will not pro-vide products useful in the proces~ of this invention, since such products have the all~lic hydrogens attached to bridgehead carbonsc 2Q In an addition polymerization xeaction, a reactant such as 5-ethylidene-2-norbornene is used to obtain the desired unsaturation~
In an esterification reaction, the acid, acid halide, acid anhy~
dride or ester reactant will contain the desired unsaturation some where in the moleculeO Thus, depending upon the reaction involved, suitable reactants are exemplified by those which provide olefinic units such as those e~isting in butene-2, trimethylethyle~e, tetramethylethylene-1,2-dimethyl cyclohexene, 2-ethylidenenorbor~
nane, ~-methyl-2~norbornene~ 2,3-dimethyl-2~norbornene, cyclo-~ pente~e, l-methylcyclopente~e, 1~2-dimethylcyclopentene, ~
; 30 ~rimethyl styrene, inde~e and alkyl ~ubsti~tuted indenes, and alkyl substituted furans.
Also essential to the compositions used in the process o~ this inv~ntion is an ethylenically unsaturated compo~ent capable of forming a crosslinked pol~e~. This componerlt shouId comprise .
-- 1 9 ~
~ :~

~53~S~
- QT least 5~ of the photooxidizable compositionO This component ma~ be either mon~meric or polymeric~ ~nd mixtures of monomers and of polymers and of monomers with polymers may be used. The preferred monomers are those having termina:L ethylenic unsatura tion of the C~2=C~ type. When using a monoethylenically unsat~
urated monomer it is necessary to have a polymeric component or a polyfunctional monomeric component also presentO Such a poly-meric component is prefexably an unsaturate~ polymer which will copolymerize with the monomer to form a crosslinked polymer Rep-resentative of the monoethylenically unsaturated monomer~; are acrylic and methacrylic acidsl their esters with Cl C~0 monohydric alcohols, for example, methyl acrylateO ethyl acrylate, n-butyl acrylate, methyl methacrylate and isopropyl methacrylate, and their esters with other alcohols, for example, hydroxyethyl ac-rylate~ hydroxyethyl methacrylate, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate and 2-chloroethyl acrylate, acrylamide, methacrylamide~ N-vinylpyrrolidone, ac.rylonitrile ; and methacrylonitrile; vin~l esters such as vinyl acetate, vinyl trimethylacetate, vinyl propionate and vinyl benzoate; viny-l eth-ers and sulfides such as methyl vinyl ether and methyl vinyl sul fide; vinyl ketones such as methyl vinyl ketone; vinyl halid~s and vinylidene halides such as vinyl chloride and vinylidene chlorlde; allyl ethers such as allyl phenyl ether and allyl iso amyl ether: allyl esters such as al-lyl acetate, allyl butyrate and ~llyl benzoate, and vinyl aromatics such as styrene and ~-m~th~ls tyrene O
In addition to or in place of the above monomers, whichara all monoethylenically unsaturated, it is advantageous to utilize in the photooxidizable composition, as all or part of the ethylenically unsaturated component, monomers which are poly-ethylenically unsaturated~ since such monomers ordinarily provide a more tightly cro~slinked system~ These crosslinking monomers - have their unsaturation in ~he form of at least two ~5~
o o CH~-C-C- or CH2=f-CH~ O~-C~
. R R
groupsc wherein R is hydrogen or a Cl-C3 alkyl yroupO One useful monomer is 1,3~5-triacryloylhexahydro-1~3,5-triazine. This com~
pound and related compounds such as the corresponding metha-cryloyl drivative have the structural formula CH / \ CH2 C~2=f ~\ / ~c_f--c~ I

wherein R is hydrogen or a Cl-C3 alkyl groupO
~ ther suitahle monomers may be defined by the struc-tural formula CH2--~C ~ C ~ X ~ A - X - C f=CH2 II
. R R
; wherein R again is ~ydrogen or a Cl-C3 alkyl group, both X~s are either -N~- or -O and A is alkylene9 s~bstituted alkylen~ or alkyl~ne oxy alkylenec Exemplary of th~ latter are those com-pounds ~a~ing the formula CH~ C C/ NH~ CH20CH~- NHC/ C = C~2 III
R R
A preferred monomer havins this formula is NjN' oxydimethylene bis~acrylamide)u When X in formula II above again is ~NH ~ bu-t A is alkylene ox substituted alkylene~ ~his is descriptive of another pre~erred monomer~ N~v methylene-bis(acrylamide)O Thi~ compound ~:
is one member of ~he most preferred group of monomers for use in : the process of this inventlon, which monomers are rep:eesented by ~ompound~ havi~g the ~orm~la -.

'' ." .

o ~ 3 ~6 /o CH2 C C ~ N~ ~ (CHR')n- NH--C - C==~H2 IV
R
wherein ~ is hydrogen or a Cl-C3 alkyl group, Rl is hydrogen~ a Cl-C3 alkyl ~roup or phenyl~ n i~ 1 tG 6 and the total number of carbon atoms in -(C~R~)n~ is no more than 10.
Representative of compounds of fonnula IV above are N~N'-methylene~bis(acrylamide)~ N,N9-methylene b:is(methacrylamide) f ~,N'-methylene~bi~ ethylacrylamide), N~N' methylene~bis(a-propylacryl-amide)~ N,NI-ethylene bis(acrylamide), N,NI~ethylene~bis(methacryl-amide), NcN~-(1,6~hexamethylene)-bis(acryl~ide)~ N,N'-(1,6-hexa-methylene)~bis(methacrylamide) 9 N~NI-ethylidene bis(acrylamide), N,N'-ethylidene~bis~methacrylamide~ N,N'-benzylidene bis( acry l -amide), N,N~-butylidene bis(methacrylamide) and NjNI~propylldene~
bis(acrylamide)O These compounds may be prepared by conventional reactions well known in the art, for example, in UOSo 2,475,846 (to American Cyanamid) f 194go ; Also use~ul monomers are those wherein X in formula II
above is -0-~ When A is alkylene or substituted alkylene, the compounds are di~, tri a~d tetra-acrylates of certain polyhydr alcohols. These ac~ylates may be illustrated by the general a ~ormula CH2 `C~C--O ~ (C:R"R~9 ~ n~0~C--CYCH2 V
R R
wherein R is hydrogen or a Cl-C3 alkyl group, Rll is hydrogen, a Cl C3 alkyl group, -CH20H or -CH20C - cc CH~ R~" is hydrogenJ
R ~o a Cl~C3 alkyl group f CH20H or - CH~OC - C ~ CH2, n is 1 to 6 and the total number of carbon a~om~ in -(C~ is no mo~e than eleven~ Representative of ~hese compounds are ethylene gly-col diacrylate, ethylene glycol dimethacrylat~, ethy:Lene glycol d1(~-ethylacrylate)~ ethylene glycol di(~-propylacrylate), 1,3-propylene glycol diacrylate~ 1,4-butylene ~ly~ol diacrylate, 1 f 5-pentane diol dimeth~crylate, glycerol diacryl~*e, glycerol 22 =;~ .

1 ~

3~S16 Triacrylate, trimethylolpropane triacrylate, trimethylolpropane t_ ethacrylate, pentaerythr.itol diacrylate, pentaerythritol tri-acrylate, pentaerythritol tetramethacrylate and pentaerythritol tetraacrylate~ .
Closely related to the preceding acrylates are those which are derived from di ~ tri- and tetra ethylene glyGol and di- and tri-propylene glycol. These compounds are those of formula II wherein X is ~O- and A is alkylene oxy alkylene, ar,d they may be more specifically illustrat~d by the formula CH2= f C - O ~ ~CHRI'9'CH2O)n C - C= CH~ ~I
R
wherein R is hydrogen or a Cl-C3 alkyl group, R"" is hydrogen or methyl, n is 2 to 4 when R"" is hydro~en and is 2 to 3 when R""
is methylc Representative of these compounds are diethylene glycol diacrylate, diethylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, tetraethylene glycol diacrylate, tetraet~ylene glycol dimethacrylate~ di-propylene glycol diacrylate~ dipropylene glycol dimethacrylate, tripropylane glycol diacrylate and tripropylene glycol dimeth-acrylatee Representative o~ those monomers which are allyl esters are triallyl cyanurate, diallyl ph~halate, diallyl maleate, di~
allyl fumarate, triallyl trimesate~ diallyl adipate and diallyl succinate Most o~ these monomers are characterized by the struc~
tural formula ,~,0 ,~,0 CH2==C ~C~ O~C --¦B)n C ~ O-~CH~ C--C~ VII
R R
: wherein R is hydrogen or a Cl C3 alkyl group D B is vinylene or an arylene~ alkylene or substituted alkylene group, and n i5 zero or lo Representative arylene groups are phenylene and naphthylene~
: Exemplary alkylene yroups are methylene and ethyl~ne t and the total number of carbon a~oms in ~h~ alkylene or substituted alkylene groups is no more than 8~ Other useful.Qrosslinking ~3 ~

;. :
-- ~ r , ~53~5~i mers include divinylbenzene, divinylacetylene, diisopropenyl-biphenyl and crotyl methacrylate The amount o crosslinking monomer may be widely variedO
As already mentionedS the crosslinking monomer can constitute all of the ethylenically unsaturated component capable of forming a crosslinked polymer, and preferably will amount to at least about five percent by weight of said ethylenically unsaturated cGmpon ent Also useful as crosslinking agents are polymer3 contain ing a pluxality of addition polymerizable unsaturated linkages~
Representative of such polymers are the ethyl~nically un~at~rated addition polymerizable polyesters derived from unsaturated diols or unsaturated dibasic carboxylic acidsc Typical polyesters are those derived from maleic or fumaric acid and diols such as ethylene glycol, propylene glycol, trimethylene glycol and di~
ethylene glycol~ These unsaturated polymers may be used alone or in combination with a crosslinking monomerD .
The photooxidi7.ab1e compositivns also may conkain ~ sat-urated polymer component as a viscosity regulatlng agent ~xem-plary o~ such polymers are cellulose esters such as celluloseacetate, cellulose acetate succinate and cellulsse ace~ate bu~y-rate; cellulose ethers such as methyl cellul~se, ethyl cellulese, benzyl cellulose; hydroxyethyl cellulose and hydroxypropyl cel~u lose; poly~vinyl alcohol); poly(vinyl alcohol) esters such as poly(vinyl acetate) and copolymers of vinyl acetate with other vinyl monomers such as vinyl chloride, methyl acrylate and me~hyl methacrylate; poly(vi~yl chloride); vinylidene chloride copclymers : such a~ poly~vinylidene chloride-acrylonitrile)~ poly~vinylldene chloride-methyl acrylate) and poly(vinylidene chloride~vinyi acetake); polyacrylates and polyacrylate esters such as poly-; ~methyl methacrylate~ and poly~ethyl methacrylate): poly~ethylene oxids~; poly(vinyl acetals) such as poly(vinyl butyral) and ~oly-~vinyl formal) arld polystyrerl . The saturated polymer compcnent may constitute from about five to about 90~ by weight of th~

: - 24 ; ; .

;¦Lo53~pr6 photooxidizable composition~
The sensitizers used in the process of this invention are generally well known and are characterized as being useul in photosensitized oxidations~ Thu~, they a.re photooxygenation sPnsitizers. Among the bes~ sensitizers are those which absorb visible light, in the range of about ~900 to about 7700 Angstroms, namely, fluorescein derivatives, xanthene dyes, porphyrins and porphins, polycyclic aromatic hydrocarbons and phthalocyanl^les.
The preferred sensitizers are methylene blule and zinc tetraphenyl~
porphinO Additional useful sensitizers are~ erythrosin B; rose bengal; eosin Y; crystal violet; methylene green, safrin blu1sh, l,l-diethyl 1,2~2~-cyanine iodide: 1-ethyl-2~3~ ethylnaph~ho-[1~2d]-thiazolin-2-ylidene-2 methylpropenyl]-naphthol-~1,2al-thiazoliwm bxomide; pinacyanol chloxide; ethyl red; l,ll--diethyl- -2,2'-dicarbocyanine iodide; 3,3' diethyloxycarbocyanine iodide, 3,3'-diethyl-thiazolino carbocyanine iodide; fluorescein; methylene violet; methylene blue oleate; methylene blue dodecyl ben~e~e sul-~onate; copper phthalocyanine; pentacene; naphthacene, copper tet~
raphenylpor~hin; tin tetraphenylporphin acridine orange; methyl--ene violet~ Bernthsen; hemin; chlorophyll; prophyrazines, oct~
phenylporphins; benzoporphins; hypericin; 3,4-benzpyrene, acri dine rubrene 4,4~-bis~dimethylamino) benzophenone; fluor~ e anthraquinone; and phenanthrenequinoneO
The amount o~ sensitizer is not critical, but the b~st results are obtained when the concentration is adjusted so ~hat 50 to 90~ or mor~ of ~he incident light is absorbed at the w~v~
length corresponding to the abso.rption maximum of the par~icular qensitizer employedO The sensitizer may be ineorporated into ~he photooxidizable composition when ~e ccmposi~.ion is being f~med or it may be diffused into the film of the co~mposition with a sui~- :
able solvent. The oxygen required for the reaction nor]mally is obtained rom the air preserlt O However ~ an atmo~phere of pu~e oxygen may be provided ~ if desiredO
After the peroxides have been formed in the exposed ~as - 2S ~

~ i3~
01~ the film, they are decomposed to provide the free radicals ne~led for the polymerization and/or crosslinking reactionO ~he decomposition reactlon is preerably carried out catalytically using, for example~ a metal redox catalyst~ The ca~alyst may be added to the photooxidiza~le composition prior to film prepara-tion, in which instance peroxide decomposition proceeds concur-,~
rently with peroxide formation~ The catalyst also may be addedsubsequent to film exposureO This may be accomplished by any of sev~ral means~ for example, by spraying~ brush coating or contac~
ting the film with a solution of ~he catalyst in a solvent which is capable of swelling the film.
The preferred catalysts are salts or complexes of metals, preferably transition metals; capable of existing in more than one valence state. Vanadium oxyacetylacetonate, vanadium oxysulfate, ferric acetylacetonate-benzoin, manganese octoate, lead naphthen ate and cobaltic acetylacetonate are among the preferred catalysts.
Other effective catalysts include titanyl acetylacetonate~ cobalt-ous naphthenate, cobaltous 2-ethylhexanoate0 cobaltous stearate, . cobaltic stearateg cobaltous acetylacetonate~ manganous stearate~
manganic stearate, manganous acetylacetonate, manganic acatyl ac~tonate, manganese naphthenate, ~irconium acetylacetonate, vanadyl naphthenate, ferrous sul~ate, ferrous pyropho~phate~ fer~
rous sulfide, the ferrous complex of ethylenedinitrilotetraacetic acid, ferrous o-phenanthroline, ferrous ferroc~anide, ~errous acetylacetonate and the corresponding ni~kel, copper~ mercury and chromium compoundsO No~metallic reducing agents which can be used to carry out decomposition of the hydroperoxides include poly ~mines such as diethylenetriami~e, triethylenetetraamine, tetra~
ethylen~pentamine~ monoamines, sodium hyposulfite and sulfur di-oxideD The decomposition reaction can also be initiated therm~ally.
The photooxidizable compositio~ also may cvntain up to about 50% by weight o an inert particula~e iller which is essen-tially transparent to the radiation used~ Repr~sentativ~s of such .
~ 26 ~ 395i~
ers are the organophilic silicas, the bentonites, silica and powdered glass, all having a particle size less than 0.4 mil in their maximum dimensionO Particles of 0.1 micron or less in size are preferredO Such fillers can impart desirable pxoperties to the photooxidizable compositions For example, use of submicron silica affords a printing plate with a harder and more durable imageO
In the preparation of some of the photooxidiæable compo-~itions used in the process of this invention, it may be desirable to have present a small amount of a p~enolic antioxidant to act as an inhibitor for premature thermal polymerization during pro-cessing or storage of the cornpositions~ Such antioxidants are well known in the art and they are exemplified by hydroquinone, di-t-butyl-p-aresol, hydroquinone monomethylether, pyrogallol, quinone, t-butyl-catechol, hydroquinone monobenzylether, methyl hydroquinone, amyl quinone, amyloxy hydro~uinone, n~butyl phenol phenol and hydroquinone monopropyl ether The phenolic anti-oxidant may be used in an amount within the range of from about OoOOl to about 2% by weight, preferably about 1% by welght, based on the ethylenically unsaturated component of the photooxidizable composition.
l'he photooxidizable compo~itions of the process of thi5 invention may be cast from solution onto a suitable support.
Ordinarily, the support member o~ a lithographic plate is metal- :
surfaced or composed of entire sheets of metalO Metals such as aluminum, zinc, chromium~ tin, magnesium and steel may be use~c Aluminum and zinc are preferred~ In ~he case of metallic surfaces, : oxides may be presen~; either throngh exposure to air or through :
~pecial treatmentO For examples in th~ case of a7uminumO the sur-30 fa~e may~ i desired, be chemically or electrolytically anodi2ed. `-In the case of a positive working li~hographic plat~ it may be ne~essary to coat th~ metal ~upport with a durable, oleophilic polymer coating before applying the p~otooxidizable composition~
In casting the photooxidizable compositi-oD onto the suppc,rt, a ~;i39~6 ~ol~tion of the components in a suitable solvent may be used, and conventional coating techniques may be employedO Alternatively, those photooxidizable compositions o the process of this inven-tion which are thermoplastic may be thexmoformed in plastic fab ricatiQn equipment onto a metal substrate.
When the photooxidizable elements prepared as described above are subjected to the process of this invention, the pho~o-~ oxidizable composition becomes crosslinked in the exposed areas, : whereas the composition in the unexposed areas remains soluble-Subsequent removal of the soluble material, as by washing of ~he plate, leaves an image of the negative or positive used in th~
process. The solvent used in washing the plate will vary accord ing to the solubill~y of the photooxidizable compos.ition~ Re-moval of the soluble material from the unexposed areas may ; frequently be accelerated by brushing or scrubbingc In large scale work, application of the solvent will advantageously be carried out by means of jets or sprays, The printing surfaces made in accordance with this in-vention are particularly applicable in lithographyO ~owever, they also are useful in classes of printing wherein the ink is carried by the raised portion of the relief, such as in dry o~f-set print-ing and ordinary letterpress printing~ Furthermore; the photo-oxidizable compositions of this invention may be used as photo-resists over an etchable metal. In this instance, a thin layer of the composition will become insolubilized in irrad.iated areas and protect the metal beneath from etching, as in a photoengraving process.

~: 23 -

Claims (19)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for making a photographic image which comprises exposing selected areas of a sensitized photooxidizable composition in film form to light having a wave length of from about 3,900 to about 12,000 Angstroms in the presence of oxygen to form peroxides in said areas and decomposing said peroxides to form free radicals which effect polymerization or cross-linking of the composition in the exposed areas of the film, said sensitized photo-oxidizable composition comprising a mixture of a photooxygenation sensitizer with a photooxidizable composition comprising as essential components 1) at least 5% by weight, based on the total weight of the photooxidizable composi-tion of a polymerizable ethylenically unsaturated component selected from ethylenically unsaturated monomers, ethylenically unsaturated polymers and mixtures thereof; capable of forming a high polymer by addition polymerization or of forming a cross-linked composition and 2) an oxidizable component different from the said polymerizable ethylenically unsaturated component, which oxidizable component contributes to the composition at least 1.0 x 10-3 moles per 1000cc of the composition of olefinic unsaturation of the type in which there is no more than one hydrogen atom on each. of the double bond car-bons and in which there is at least one allylic hydrogen on at least one of the carbons adjacent to the duuble bond carbons, which allylic hydrogen is not on a bridge-head carbon.

2. The process of Claim l wherein component 1) is an ethylenically un-saturated monomer.

3. The process of Claim 2 wherein the ethylenically unsaturated monomer is one having its unsaturation in the form of at least two or groups wherein R is hydrogen or a C1-C3 alkyl group.

4. The process of Claim 1 wherein component 1) is an ethylenically unsaturated polymer.

5. The process of Claim 1 wherein component 2) is a compound con-taining olefinic units corresponding to those of the formula wherein R1, R2, R3 and R4 may be hydrogen, an alkyl group containing one to twenty carbon atoms, an aryl group or a substituted aryl group, and wherein R1 and R2, R3 and R4, R1 and R3 and R2 and R4 may be combined in the form of an alicyclic or heterocyclic ring.

6. The process of Claim 5 wherein component 2) is a polymer.

7. The process of Claim 1 wherein the film also contains a saturated polymer.

8. The process of Claim 1 wherein the light has a wave length of from about 3900 to about 7700 Angstroms.

9. The process of Claim 1 wherein the peroxides are decomposed by the action of heat.

10. The process of Claim 1 wherein the peroxides are decomposed by the action of a reducing agent.

11. The process of Claim 1 wherein the peroxides are decomposed by the action of a metal catalyst.

12. The process of Claim 11 wherein the metal catalyst is a transi-tion metal catalyst.

13. The process of Claim 1 wherein the film includes methylene blue as a photooxygenation sensitizer.

14. The process of Claim 1 wherein the film includes zinc tetraphenyl-porphin as a photooxygenation sensitizer.

15. A printing element prepared according to the process of Claim 1.

16. The printing element of Claim 15 wherein the element is a litho-graphic plate.

17. The printing element of Claim 15 wherein the element is a relief printing plate.

18. The printing element of Claim 15 wherein the element is a photo-resist.

19. A photosensitive film comprising a sensitized photooxidizable composition comprising a mixture of a photooxygenation sensitizer with a photooxidizable composition comprising as essential components 1) at least 5% by weight, based on the total weight of the photooxidizable composition, of a polymerizable ethylenically unsaturated component selected from ethyleni-cally unsaturated monomers, ethylenically unsaturated polymers and mixtures thereof, capable of forming a high polymer by addition polymerization or a cross-linked composition and 2) an oxidizable component different from the said polymerizable ethylenically unsaturated component, which oxidizable com-ponent contributes to the composition at least 1.0 x 10-3 moles per 1000cc of the composition of olefinic unsaturation of the type in which there is no more than one hydrogen atom on each of the double bond carbons and in which there is at least one allylic hydrogen on at least one of the carbons adja-cent to the double bond carbons, which allylic hydrogen is not on a bridge-head carbon.