CA1099849A - Acid-resistant copolymer and photographic element incorporating same - Google Patents

Abstract

Abstract A photocrosslinkable polymer and imaging element containing said polymer are described wherein acid resistance is achieved by vinyl ester recurring units. A process for etching an element so prepared features exposure, development, and etching in an acid bath.

Description

-~;3~8~9 BACKGROUND OF THE INVENTION

1) Fleld of the Invention The invention relates to a light~sensi-tive, film-forming polymer use~ul in making a photographic element, having increased resistance to acids.

2) State of the Prior Art Photoresist polymers have been developed containing poly(vinyl cinnamate). An early resist lacquer comprising the homopolymer derived by esterifying poly(vinyl alcohol) with cinnamoyl chloride in pyridine is disclosed in U.S. Patent No. 2,610,120 and U.S. Patent No. 2,690,966.
The resist polymer has been modified by coesterifying the poly(vinyl alcohol) with other acid compounds, such as dibasic or monobasic phenyl acid salts, as descri-bed, for example, in U.S. Patent No. 2,861,058 and U.S. Patent No.

3,560,465, respectively, in addition to a cinnamoyl chloride~. Further~ the cinnamate moiety has been modified by providing for certain substituents on the phenyl radical~
as in the aforesaid Patent No~ 2,861,058. A photoresist is further taught in U.S. Patent No. 3,696,o72 wherein the vinyl cinnamate polymer is further modified by a second ethylenical]y unsaturated group in conjugation with the unsaturated sites of the cinnamate moiety.
Publications relating to the general background of --photo-sensitive polymers include U.S. Paten-t No. 3,821,167;

Defensive Publication T-900,009; U.S. Patent No. 2,725,372;
British Patent Speciflcation No. 1,353,506, East German Pa-tent No. 5g,237; and Canadian Patent No. 986,778.

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All of the afore-described pho~oresists provide resistance to acid etches to varying degrees, depending largely on the corrosiveness of the acid used. Because of new high speed etching techniques for materials such as magnesium, photoresists having increased resistance to acids are needed. What is desired then is polymers having increased resistance, when photocrosslinked, to particularly corrosive etches, such as hot nitric acid, so that deep etching can be achieved more quickly without sacrificing image quality.

SU~ARY OF THE INVENTION
The invention concerns a light-sensitive polymer, a photographic element prepared therefrom, and an etching process, the polymer having resistance to corrosive acid etches such as hot nitric acid.
In one aspect the invention features a polymer comprising from about 30 to about 97 mole percent of recurring units having the general structure:

~CH? - CHt O - C = O
CH
GH

and from about 3 to about 70 mole percent of recurring uni-ts having the general structure:

~g~84~

tCH2 ~ CHt o k~= .
~H

~ ~~n where n is O or 1.
In another aspect, this invention features a polymer comprising the repeating uni-ts Rl tCH2 - IHt ~ CH = CH - C = O

wherein Rl is hydrogen or a lower alkyl or alkoxy radical containing from 1 to 5 carbon atoms.
In yet another aspect, this invention features a light-sensitive film-~orming polymer comprising from about 30 to about 97 mole percent of recurring units having the general structure CH2 - IH t O - C = O

wherein R is hydrogen, a lower alkyl radical containing from 1 to 5 carbon atoms, a halogen radical, or a nitro radical in the meta or ortho posi-tions; and from about 3 to about 70 mole percent of recurring units having -the general structure R
CH2 - IH t ~ CH = CH ~ C = O

wherein n = 1 or 0, and Rl is hydrogen or a lower alkyl or alkoxy radical containing from 1 to 5 carbon atoms.
In still another aspect, the invention ~eatures a photographic element comprising any of these polymers on a suitable support.
The process of the invention, to prepare an etched element, comprises the steps of imagewise exposing to activating radiation an element comprising a support, coated on the support~ a light-sensitive film-~orming polymer comprising from about 30 to about 97 mole percent of recurring units having the general structure tCH2 - fH ~
o f=o C~ .
IIH

_~2 ., .. , .... .. - , .

~6~9~

and ~rom about 3 to about 70 mole percent of recurring units having the general structure tCH2 - CHt C = O
CH
~ .

where n is O or 1 and Rl and R2 are as de~ined above, and a thiazoline sensitizer in admixture with said polymer, removing the unexposed portions of said polymer ;:.
by washing the element in a developer solution;
and subjecting the element to an acid bath for a time and at a temperature sufficient~to etch the portions of the support not coated wi-th the polymer.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
As described in the afore-discussed prior art, useful.photoresists have been provided in the past by esteri-fying poly(vinyl alcohol) with at least a cinnamoyl acid chloride. It has been discovered that a photosensitive copolymer having enhanced acid resistance~ particularly use~ul in photoresist applications, is achieved by co-esteri-~ying at least a portion o~ poly(v:inyl alcohol) with a naphthoyl acid chloride or a 3-(naphthyl) acryloyl chloride, as well as with a cinnamoyl chloride, to provide a copolymer ~6--containing as dependent moieties both a einnamate eross-linking moiety, and a naphthoate or 3-(naphthyl)aerylate .moiety.
More speci~ically, useful light-sensitive film-forming polymers, in accordance with the invention, comprise those containing from about 30 to about 97 mole pereent of reeurring units (I) and (II) having the general structure (I) ~ CH2 - CHt----.
O-CI = O
ICH
dH

.

and from about 3 to about.70 mole pereent of reeurring units having the general strueture (II) ~ CH2 - CH ~

C = O
CH
Il .
n C~

where n ls O or 1. It has been found that if the naphthoate reeurring unit exeeeds 70 mole pereent o~ the eopolymer, the .

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crosslinkability of the cinnamate becomes significantly impaired.
In addition, it is contemplated that full equivalents of the afore~described copolymers, for this invention, are those wherein the recurring units are those having the formulas (I') ~CH2 ~ C~t O - C = O
C~l ~ ~ ~ R3 wherein R3 is a lower alkyl radical preferably containing from 1 to 5 carbon atoms, such as methyl, ethyl~ propyl, etc.;
a halogen radical, for example, chloride, bromide and the like, or a nitro radical in a position other than the para position, and (II') ~ ~ CH2 - ~H

CH - C~I~n ICl O

with n having the value noted above, wherein R4 is a ; lower alkyl or alkoxy radical preferably containing from 1 to 5 carbon atoms, for example, methyl, ethyl, propyl, methoxy, ethoxy, propoxy, and the like. It is further contemplated that the copolymer of the in~ention can contain other vinyl ester repeating units, such as the additional repeating unit ... . . .

.

` ~J95~4~1 ~ CH2 - ~H ~
= O

~1 the mole percent of such benzoate recurring unit being no -mor,e than about 10~. Such additional repeating units can be produced by adding the proper mole ratio of benzoyl chloride to poly(vinyl alcohol), following the procedures hereinafter discussed.
Still another contemplated equivalent is a homopolymer of repeating unit (II) above~;with n = 1.
, Such polymers will produce, upon exposure to light rich in W, and development, a crosslinked copolymer reslstant to hot concéntrated nitric acid for a,time period sufficient to provide a "deep etch" of the support . .. .. . . . ., .. ~ . ........ ~ ............. ..... . .. . . .
underlying what was the nonexposed areas of the-polymer.
"Deep etch" as used herein, means an etch sufficient to remove at least 370 microns of the support. Removal of as .
much as 1000 microns is common. The actual time period ~or such acid e-tch ~ill of course vary, depending upon the , .. .
material comprislng the support.
The above-described copolymers can be prepared b~ , the~sequentiaI addition~ in either order, of a naphthoyl acid halide or a 3-(naphthy1)acryloyl acid halide and cinnamoyl acid halide to a suspension of poly(vinyl alcohol) (hereinafter?
PVA) in a /ertiar~ amine sol.ent sucb as pyridine, to _ g_ ' :

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esterify the alcohol groups. The mole ratio of added reactants is adjusted to achieve the desired mole percent of the copolymer recurring units. The sequence of addition of the acid chlorides can be modified even to the extent of adding them altogether or adding first a portion of the first acid chloride~ all of the second, and then the remainder of the first. Except as noted above with regard to the sequence of addition, the conditions of the reactionsg such as temperatures and times3 can be those of the art, such as those disclosed in the aforesaid U.S. Patent No.
3,560,465. In addition, the following preparations are set forth as nonlimiting examples:

Pieparation No. 1 of Poly[vinyl cinnamate-co-vinyl a-naphthoate]
50:50 A pyridine (300 ml) suspension of 13.7 g "Elvanol 71-30-M" PVA [a medium molecular weight poly(vinyl alcohol)g 100% hydrolyzed, manufactured by DuPont] was stirred at 60C
for 16 hours to swell the polymer. The suspension was cooled to 50C and 28.5 g a-naphthoyl chloride was added. After stirring 6 hours at 50~C 25 g of cinnamoyl chloride was added. Warming was continued for another 16 hours after which the solution was cooled. The reaction mixture was precipitated into water and the resultant fiberous polymer washed thoroughly with water and dried to give 41.8 g of polymer. The product was readily soluble in solvents such as cyclohexanone and 1,2-dichloroe~hane.

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Preparation No. 2 of Poly[vinyl cinnamate-co-vinyl ~-naphthoate]
80:20 A poly(vinyl alcohol) obtained under the trademark "Elvanol 71-30-M", from American Hoechst, (4.4 g) was suspended in 150 ml of pyridine at 60C for 16 hours~ The suspension was cooled to 50C and 3.8 g of ~-naphthoyl chloride was added. Stirring at 50C continued for 6 hours after which 12.4 g o~ cinnamoyl chloride was added. The reaction mixture was warmed at 50C for 16 hours, then cooled and filtered. The polymer solution was precipitated into water and ~horoughly washed with water. After drying, 13.4 g of polymer was obtained.

Preparation ~o. 3 of Poly~vinyl cinnamate-co-vinyl a-naphthoate-co-vinyl acetate] 44:44:12 A medi~m molecular weight poly(vinyl alcohol), 88~
hydrolized, (4.9 g), obtained under the trademark "~inol 523"
from Air Products, was suspended in 150 ml of pyridine at 60C fo~r 16 hours. The suspension was cooled to 50C and 8.4 g of a-naphthoyl chloride was added. After additional warming for 6 hours, 7.3 g of cinnamoyl chloride was added and `the reaction mixture warmed for 16 hours. The cool solution ~as filtered and precipitated into water. The resulting fiberous product was dried, giving 9.8 g of product.

Preparation No. 4 of Poly[vinyl cinnamate-co-~inyl 3-(a-naphthyl)acrylate~(50:50) "Elvanol 71-30 M" (4.4 gm) was suspended in 150 ml o~ pyridine at 60C for 16 hours. me suspension was cooled to 50C and 8.4 g of cinnamoyl chloride was added. The reaction ~ixture was stirred at 50C for 6 hours after which 10.9 g o~ 3~ naphthyl)acryloyl chloride was added. The reaction .

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mix-ture was then stirred at 50C' for 12 hours followed by hours at 75C. The amber, viscous solution was cooled and filtered. The resulting dope was then precipitated into vigorously stirred water. The resulting polymer was collected and blended with water in a high speed Waring blender. The polymer, consisting of small granules, was dried at 50 for 1~ days in an air oven to a final weight of 14.2 g.

It is common for poly(vinyl alcohol) to be acetylated to a certain degree, so that the final copolymers described above may have up to as much as 25 mole percent acetate groups, without adversely affecting the copolymer photo-resist properties. For example, as noted in Preparation No. 3 above, the "~inol 523" poly(vinyl alcohol) has a theoretical acetate content of 10 to 15~ Small amounts of free hydroxyls may also be present.
Because of the aforesaid properties, the above-described polymer can be conveniently utilized as a photoresist or as a coating for a lithographic plate, and in such cases, will preferably further include a sensitizer and a pigment in admixture with the copolymer, and a support on which the copolymer and its addenda are coated. Where used as a lithographic coating, the polymer can further include a print-out dye former and accelerator incorporated in and intermixed with the polymer.

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Suitable sensitizers for the copolymer include anthrones, such as l-carbethoxy 2-keto-3-methyl-2-azabenzanthrone, benzanthrone and those anthrones disclosed in U.S. Patent No. 2,670,285; nitro sensitizers such as those disclosed in U.S. Patent No.
2,610,120; triphenylmethanes such as those disclosed in U.S.
Patent No. 2,690,966; quinones such as those disclosed in U.S. Patent No. 2,670,286; cyanine dye sensitizers, naphthone sensitizers such as 6-methoxybeta-2-furyl-2-acrylonaphthone, pyrylium or thiapyrylium salts, such as 2,6-bis(p-ethoxyphenyl)-4-(p-n-amyloxyphenyl)-thiapyrylium perchlorate and 1,3,5-triphenylpyrylium fluoroborate; furanone; anthraquinones such as 2-chloroanth:raquinone., thiazoles such as 2-benzoyl-carbethoxymethylene-l-methyl-betanaphthothiazole and methyl 2-(N-methylbenzothiazolylidene) dithioacetate; methyl 3-methyl-2-benzo~hiazolidene dithioacetate; thiazolines such as 3-ethyl-2-benzoylmethylenenaphthol[1~2-d]-thiazoline, benzothiazoline, 2-[bis(2-furoyl)methylene]-1-methyl naphtho[l,2-d]thiazoline, (2-benzoylmethylene)-1-methyl-beta-naphthothiazoline; 1,2-dihydro~l-ethyl-2-phenacylidene-20 naphthol[l,2-d]-thiazole; naphthothiazoline; quinolizones;
` Michler's ketone; and Michler's thioketone as well as other sensitizers, such as those disclosed in French Patent Nos.
1,23~,262, 1,089,290 and 1,086,257 and U.S. Patent Nos.
2,732,301; 2,670,285 and 2,732,301; and nitro aromatics such as nitroacenaphthalene.
The crosslinkable copolymers o~ this invention, such as those incorpo:rating one or more of the cinnamate repeating units, are directly responsive to actinic ra~iation.
The sensitizers noted above enhance this responsiveness and in some instances appear to extend the wavelength of response of the copolymer.
It is further contemplated that the crosslinkable copolymers of this invention need not be directly cross-linked in response to exposure to actinic radiation.
Certain radiation responsive sensitizers should act as crosslinking agents, such as ketone-type and azide-type sensitizers. Typical aryl ketone sensitizers of this class in-clude such compounds as benz(a)-anthracene-7,12-dione and 4,4'-bis-(dimethylamino)-benzophenone. Other advantageous ketone-type sensitizers are, for example, 4,4'-tetraethyldiamino-diphenyl ketone, dibenzalacetone and 4,4'-bis(dimethylamino)-benzophenone imide, as well as additional sensitizers of the type described in U.S. Patent No. 2,670,287.
Another class o~ sensitizers for the photocross-linkable polymers of the invention are coumarins which have an absorptive maximum between about 250 to about'550 nm~
These coumarins preferably have the formula:

R5 R7 ~

~$ R8 wherein Q is -CN or -Z-R10 in which Z is a linking group selected ~rom carbonyl, sul~onyl, sulfinyl or arylenedicarborlyl ~14-~9~

RlO is alkyl having l-lO carbon atoms such as, for example, methyl, ethyl, propyl, isopropyl, tert. butyl, isobutyl~
butyl, amyl, hexyl, heptyl, octyl, nonyl, decyl, including cycloalkyl such as cyclopentyl, cyclohexyl, etc., substituted alkyl, etc.; aryl such as phenyl, substituted aryl with sub-stituents such as nitro, alkoxy, halogen, carboalkoxy, alkyl, aryl, carboxy, hydroxy, amino, substitu~ed amino such as dialkylamino, trialkylammoniumg etc.,; alkoxy such as methoxy, ethoxy, butoxy etc.; aryloxy such as phenoxyl etc.; a heterocyclic group having about 5 to 15 nuclear carbon and hetero atoms such as pyridyl and pyridinium having the formula:

Rll X

in which Rll is alkyl having 1-4 carbon atoms including methyl, ethyl, propyl, isopropyl, butyl, n-butyl, isobutyl, sec -butyl, etc.; and ~3 is an anion including FSo3~3, ~FL~3, p-toluene sul~onate, halogen, e.g. Cl~, Br~, I~ etc., nicotinyl, nicotinium, furylg 2-benzo~uranyl, 2-thiazolyl, 2-thienyl, etc., or a 3-coumarinyl having the ~ormula:

~

;~ ~ O ~o and wherein R5~ R6, R7 and R8 each independently is hydrogen, alkoxy having 1-6 carbon atoms, dialkylamino ~ith each alkyl of the dialkylamino group having 1-~ carbon atoms, halogen, nitro, or a 5- or 6-membered heterocyclic group such as pyrrolidino, morpholino, piperidino, pyridinium, etc.; and R9 is hydrogen, alkyl having 1-4 carbon atoms or aryl of 6-12 carbon atoms; it being noted that two or three of ~ - R8 and the nuclear carbon atoms to ~hich they are attached can together form a fused ring or fused ring system, each ring being a 5- or 6-membered ring.
Typical courmarins which are use~ul herein are ~or example:
3-benzoyl-5,7-dimethoxycoumarin 3,benzoyl-7-methoxycoumarin 3-benzoyl-6-methoxycoumarin 3-benzoyl-8-e-thoxycoumarin 7-methoxy-3-(p-nitrobenzoyl)coumarin 3-benzoylcoumarin 3-(p-nitrobenzoyl)coumarin 3-benzoylbenzo[f]coumarin 3,3'-carbonylbis(7-methoxycoumarin) 3-acetyl-7-methoxycoumarin 3-benzoyl-6-bromocoumarin 3,3'-carbonylbiscoumarin 3~benzoyl-7-dimethylaminocoumarin 3,3'-carbonylbis(7-diethylami:nocoumarin) 3-carboxycoumarin 3-carboxy-7-methoxycoumarin 3-ethoxycarbonyl-~-methoxycoumarin 30- 3-ethoxycarbonyl-7-methoxycoumarin 3-acetylbenzo[f]coumarin ... .

3-acetyl-7-methoxycoumarin 3~ adamantoyl)-7-methoxycoumarin 3-benzoyl 7-hydroxycoumarin 3-benzoyl-6-nitrocoumarin 3-benzoyl-7-acetoxycoumarin 3-benzoyl-7-diethylaminocoumarin 7-dimethylamino-3-(4-iodobenzoyl)coumarin 7-diethylamino-3-(4-iodobenzoyl)coumarin 7-methoxy-3~(4-methoxybenzoyl)coumarin 3-(4-nitrobenzoyl)benzo[~]coumarin 3-(4-ethoxycirmamoyl)-7-methoxycoumarin 3-(4-dimethylaminocinnamoyl)coumarin 3-(4-diphenylaminocinnamoyl)coumarin 3-[(3-methylbenzothiazol-2-ylidene)acetyl]coumarin 3-[(1-methylnaphtho[1,2-d]thiazol-2-ylidene)-acetyl]coumarin 3,3'-carbonylbis(6-methoxycoumarin) 3,3~-carbonylbis(7-acetoxycoumarin) 3,3'-carbonylbis(7-dimethylaminocoumarin) 3-cyano-6-methoxycoumarin 3-cyano-7-methoxycoumarin 7~methoxy~3~phenylsulfonylcoumarin 7-methoxy-3-phenylsul~inylcoumarin 1,4-bis(7-diethylamino-3-coumarylcarbonyl)benzene 7-diethylamino~5',7'-dimethoxy~3,3'~carbonyl-- biscoumarin 7-dirnethylami.no-3-thenoyl coumarin 7~diethylamino-3-furoyl coumarin 7~diethylamino-3-thenoyl coumarin 3-benzoyl-7-(1-pyrrolidinyl)coumarin

5,7,6~~trimethoxy-3~3~~carbonylbiscoumarin 5,5,7'-trimetho~y-3,3'~carbonylbiscoumarin 7-diethylamino~6'~methoxy-3,3'-carbonylbiscoumarin , ~)9S~8~
3-nicotinoyl-7-methoxycoumarin 3-(2-benzofuranylcarbonyl)-7-methoxycoumarin 3-(7-methoxy-3-coumarinoyl)-1-methylpyridinium fluorosulfate 3-(5,7-diethoxy-3-coumarinoyl)-1-methylpyridinium fluoroborate N-(7-methoxy-3-coumarinoylmethyl)pyridinium ~romide 9-(7-diethylamino-3-coumarinoyl)-1,2,4,5-tetra-hydro-3H, 6H, lOH [1] benzopyrano[9, 9a, l-gh]-quinolazine-10-one, i.e., N(C2H5)2 ' Preparations of organocarbonyl coumarins are found in Chemical Reviews, 36 1, (1945), S. M. Sethna and N. H. Shah; R. K. Pandya and K. C. Pandya Agr. Uni~t. J~
Research 4, 345 (1955) C. A. 52, 7307b. Bis compounds are described in L. L. Woods and M. Fooladi J. Chem. Eng Data 2, 624 (1967).
The sensitizer can be present in the coating composition in any desired concentration effective to stimulate crosslinking in response to radiation or can be omitted entirely where the crosslinkable polymer is itself radiation-sensitive. It is generally preferred to incorporate the sensltizer in a concen-tration of from 0.01 to 20 percent by~weight based on the weight of the crosslinking polymer.
Pigments for the copolymer, usually selected to aid in visually comparing the developed image areas with the nonimage areas,~ include the following: Victoria Blue (Color Index Pigment Blue I), Palomar Blue (Color Index Pigment ; Blue 15), Monastral Blue BF (Color Index Pigment Blue 15 (74160)), and ~atchung Red B (Color Index Pigment Red 48).

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Suitable support materials ~or the copolymers o~
the invention can be chosen from among a ~ariety of materials which do not directly chemically react with the coating composition. The particular material chosen will depend upon the end photographic use. Such support materials include ~iber base materials such as paper, polye-thylene-coated paper, polypropylene-coated paper, parchment, cloth, etc.; sheets and ~oils o~ such me-tals as aluminum, copper, magnesium, zinc, etc.; glass and glass coated with such metals as chromium, chromium alloys, steel, silver, gold, platinum3 etc.~ synthetic resin and polymeric materials such as poly(alkyl acrylates), e.g., poly(me-thyl methacrylate), polyester film base--e.g., poly(ethylene terephthalate), poly(vinyl acetals), polyamides--e.g., nylon and cellulose ester ~ilm base--e.g., cellulose nitrate, cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate and the like.~
Of these, particularly useful support materials for photoresist etching include magnesium and copper. Speci~ic support materials which are useful in ~orming print ng - plates, particularly lithographic printing plates, include supports such as zinc, anodized aluminum, grained aluminum, copper and specially prepared metal and paper supports;
superficially hydrolyzed cellulose ester rilms; and polymeric supports such as polyole~ins, polyesters, polyamide, etc.
For lithographic uses, the supports can be preliminary coated~-i.e.; be~ore receipt o~ the radiation-` sensitive coating--with known subbing layers such as -19- ..

. ., copolymers o~ vinylidene chloride and acrylic monomers--e.g., acrylonitrile, methyl acrylate, etc. and unsaturated dicarboxylic acids such as itaconic acid, etc.; carboxymethyl cellulose; gelatin; polyacrylamide; and similar polymer materials. The support can also carry a filter or anti-halation layer compound of a dyed polymer layer which absorbs the exposing radiation after it passes through the radiation-sensitive layer, thus eliminating unwanted reflection from the support .
The coating compositions also can include a variety of other photographic addenda utilized for their known purpose, such as agents to modify the flexibility of the coating, agents to modify its surface characteristics, agentS to modify the adhesivity of the coating to the support, antioxidants, preservatives, and phenolic resinsj such as thermoplastic "Novalac" resins or solvent-soluble resole resins incorporated in the composition to improve the resistance of the polymer composition to etchants when it is used as a photoresist.
Coating compositions containing the light-sensitive polymers of this invention can be prepared by dispersing or dissolving the polymer in any suitable solvent or com-bination of solvents used in the art to prepare polymer dopes. Solvents that can be used to advantage include ketones such as 2-butanone, ~-methyl-2-pentanone, cyclo~
hexanone, 4-butyrolactone, 2,L~-pentandione, 2,5-hexandione, etc.; esters such as 2-ethoxyethyl acetate, 2-methoxyethyl acetate, n~butyl acetate, etc.; chlorinated solvents such as .
~ .

' ' chloroform, dichloroethane, trichloroethane, tetrachloro-ethane~ etc.; as well as dimethylformamide and dimethyl-sul~o~ide; and mixtures of these solvents. Typically -the light-sensitive copolymer is employed in the coating composition in the range from about 1 to 30 percent by weight. Preferably the copolymer comprises 5 to 20 percent by weight o~ the composition in a solvent such as listed above.
As used herein, "coating" refers to any application o~ a làyer of the copolymer, with its addenda, to a support, such as by con~entional coating techniques, lamination of preformed layers, or by any other means of strata formation.
Using such conven-tional coating techniques~ the composition can be sprayed, brushed, applied by a roller or immersion coaterg flowed over the surface, picked up by immersion, impregnated or spread by other means Elements thus formed are dried at room temperature, under ~acuum or at ele~ated temperature.
Typical coating thicknesses can be from about 0.05 to 10.0 microns or greater, and will ~ary depending upon the photographic use. For photoresist use, the coating is preferably from 1 to about 5 microns thick, and thicknesses of from 0.1 to 2.5 microns are preferred for lithographic plate applica-tions.
Photomechanical images can be prepared with photo-sensitive elements of the invention by imagewise exposing the element to a light source to harden or insolubilize the polymer in exposed areas. Suitable light sources which can be employed in exposing the elements include sources rich '"~.

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: in visible radiation and sources rich in ultraviolet radiation, such as carbon arc lamps, mercury vapor lamps, ~luorescent lamps, tungsten lamps3 photoflood lamps, and the like.
The exposed element can be developed with a solvent for the unexposed, uncrosslinked polymer which is a non-solvent ~or the exposed hardened polymer. Such solvents can be selected from the solvents listed above as suitable coating solvents as well as others well known in the art. Such deveIopment is conventional, so that ~urther details are unnecessary.
When the developed element is used in acid etching, a 1 to 5 minute treatment in an acid such as hot 20~ nitric acid, depending on the depth of etching required, at a temperature of from 100 to 150~, produces excellent relief images signi~icantly ~ree from acid at-tack in the raised por-tions protected by the copolymer. _ _ _ _ Examples The following nonexhaustive examples are further illustrative o~ the invention:

Example 1 A coating composition was prepared as follows:
10.O g the copolymer of Preparation No. 1 5.0 g 4-butyrolactone 35.0 g 2-ethoxyethyl acetate 100.0 mg hydroquinone (a thermal st&bilizer) 200.0 mg 2~[bis(2-furoyl)methylene]-1-methylnaphtho[l,2-d]thiazoline .. _ . . . . . .. . .. .... .... .

~ -22-- . : ' . :

~9~g~4~
, , The photoresist was stirred for 24 hours and filtered through a 2-4 micron pore size filter disk. To 30 g of the filtered composition was added 2.0 g of the following pigment formulation:
Monastral Blue BF 15.68%
a C8F17 fltlorocarbon sulfate, anionic 0.32%
surfactant, believed to be a potassium salt, obtainable under the trademark "FC-98" from 3M Corp.
2-Ethoxyethyl acetate 84.0 This composltion was roller coated on Dowetch Deadline PRC magnesium plate via a Gyrex Micro-9 roller coater using a roller with a pressure setting of 2.5 pounds and an interference setting of 35. Double passing the plate through the rollers with a 30-second dwell yielded a dry resist coating of 3.25 microns. The plates were prebaked for 10 minutes at 80C and exposed to a 200-watt mercury-vapor lamp in an "Exposure I" light unit manufactured by Coli~ht, Inc.
Minneapolls, Minnesota for one minute through a KODAK T-14 step-wedge. The exposed portion yielded insoluble resist (under the 9th step (1.2 density)) after 30 second spray development in a hot trichloroeth~lene. The imaged ma~nesium plate was then .
etched with 20% nitric acid in a spray etcher obtained under the trademark "D~narnil" from Western Technology Inc.~ for 2 minutes at 120F. m e nitric acid etchant was prepared as `
follows-Etchant Formula~

6000 mil Distilled water ~ 400 mil Hunt Auto Express Etching Additive 30 Manufact~red b~v Hunt Chemical Corporation 1600 ml Concentrated nitric acid ,.
~ ~ -23-~. ~
. ~"~ ~ .

~ .. . ~, .- .... .. . .. . . . .. , .. " .. .. ~ , 99~

The nitric acid consumed during etching was replaced by the addition of 6 ml o~ concentrated nitric acid ~or each gram o~ magnesium reacted.
The resist coating yielded excellent protection for the magnesium. No sign o~ resist chipping, blistering or pinholing was observed after etching -to a depth of 625 microns.

Example ?
A coating COmpQsitiOn was prepared as ~ollows:
2.0 g Copolymer of Preparation No. 2 `
3.6 g 4-Butyrolactone 11.0 g 2-Ethoxyethyl acetate 20.0 mg Hydroquinone 40.0 g 2-(Benzoylmethylene)-l-methyl-naphtho[1,2-d]-thiazoline The above materials were mixed 24 hours and filtered through a 2-4 micron pore size disk ~ilter.
The filtered composition was whirl coated at 115 rpm yielding 3.75 micron dry coatings on PRC magnesium. The plates were exposed for 2 minutes to a step 8 and processed as in Example 1, yielding excellent etched images.

Example 3 A resist compo~sition was prepared as follows: `
2.0 g ~opolymer of preparation No. 4 4.0 g 4-butyrolactone 12.0 g 2-ethoxyethyl acetate 20.0 mg hydroquinone 40.0 mg 3,3'-ca~bonylbis (7-diethylaminocoumarin) .

-24_ - ` . . ~:
.

~9~B4~

A plate was prepared as in Exarnple 1, was exposed for 30 seconds to the 8th step on a lL~ stepwedgeg and was processed as in Example 1. Although the quality of the coating was initially less than that of Example 1, ~he resist image withstood the nitric acid etchant equally as well as the resist of Example 1.

Comparative Examples The ~ollowing examples, submitted by way of comparison, indicate the superiority o~ the acid resistance of the copolymers of the invention.

Comparative Example No. 1 A coating was prepared as in Example 1, except that an equivalent amount o~ Kodak "Photo Resist Type 4,"
; a homopolymer of poly(vinyl cinnamate), was used in place o~ the copolymer. After exposure, development, and etching as in Example 1, the "protected" areas were found to be chipped, blistered and pinholea.

.
Comparative Example No. 2 ; A coating was prepared as in Example lg except that an equivalent amount of a copolymer comprising 50 mole percent benzoate in place of the 50 mole percent a~naphthoate was used, to show the importance of the presence o~ the added aromatic carbon atoms. The photoresist containing the benzoate was evaluated as described ~or Example 1, and it was ~ound that the exposed "protective" coating sloughed o~f aur1ng the acid etch, permltting etching o~ the exposed areas. Thus, the benzoate copolymer did not give the excellent acid resistance available with the naphthoate copolymer. __ __ _ `

3~34~
-The invention has been described in detail with particular reference to certain preferred embodlments thereo~ but it will be understood that variations and modi~ications can be e~fected within the spirit and scope of the invention.

... . -. .
.. - . . . . ,, ,: , :,.

Claims (10)

What is claimed is:

1. A light-sensitive film-forming polymer comprising from about 30 to about 97 mole percent of recurring units having the general structure and from about 3 to about 70 mole percent of recurring units having the general structure:
where n is 0 or 1.

2. A polymer of claim 1 containing from 3 to 70 mole percent of recurring units having the general structure where n = 0, or 1.

3. A polymer of claim 1 containing from 3 to 70 mole percent of recurring units having the general structure:

wherein = 0, or 1.

4. A photographic element comprising a support having thereon the polymer of claim 1.

5. An element as defined in claim 4, and further including a thiazoline sensitizer in admixture with said polymer.

6. An element as defined in claim 5, and further including a pigment in admixture with said polymer.

7. A lithographic plate comprising a support, and coated on the support, a light-sensitive film-forming polymer comprising from about 30 to about 97 mole percent of recurring units having the general structure and from about 3 to about 70 mole percent of recurring units having the general structure where n is 0 or 1, and a thiazoline sensitizer in admixture with said polymer..ang.

8. A process for preparing an etched photographic element, comprising the steps of imagewise exposing to activating radiation an element comprising a support, a light-sensitive film-forming polymer on the support comprising from about 30 to about 97 mole percent of recurring units having the general structure and from about 3 to about 70 mole percent of recurring units having the general structure where n is 0 or 1, R1 is hydrogen, alkyl containing from 1 to 5 carbon atoms, halogen or nitro in the meta or ortho positions; and R2 is hydrogen or alkyl or alkoxy containing from 1 to 5 carbon atoms;
and a thiazoline sensitizer in admixture with said polymer;

removing the unexposed portions of said polymer by washing the element in a developer solution, and subjecting the element to an acid bath for a time and at a temperature sufficient to etch the portions of the support not coated with the polymer.

9. A light-sensitive film-forming polymer comprising from about 30 to about 97 mole percent of recurring units having the general structure wherein R1 is hydrogen, alkyl containing from 1 to 5 carbon atoms, halogen, or nitro in the meta or ortho positions;
and from about 3 to about 70 mole percent of recurring units having the general structure wherein n = 1 or 0, and R2 is hydrogen or alkyl or alkoxy containing from 1 to 5 carbon atoms.

10. A photographic element comprising a support having thereon the polymer of claim 9.