GB1578662A

GB1578662A - Photosensitive compositions

Info

Publication number: GB1578662A
Application number: GB424177A
Authority: GB
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1976-02-02
Filing date: 1977-02-02
Publication date: 1980-11-05
Also published as: ES455588A1; FR2339881A1; DE2704368A1; NL185872B; JPS5942684B2; JPS52112681A; NL7701089A; DE2704368C2; FI770367A; FR2339881B1; AU513012B2; NL185872C; BR7700555A; IT1076960B; AU2187177A

Description

(54) PHOTOSENSITIVE COMPOSITIONS (71) We, EASTMAN KODAK COMPANY, a Company organized under the laws of the State of New Jersey, United States of America of 343 State Street, -Rochester, New York 14650, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to the photosensitization of radiation-sensitive materials and particularly to the photosensitization of radiation-sensitive unsaturated materials such as unsaturated vesiculators which release a gas upon exposure to radiation, unsaturated monomers and photocross-linkable unsaturated polymers, and azides such as photocross-linkable polymeric azides used in photomechanical resists and lithographic plates.

It is known in the photographic art to reproduce images by processes which involve imagewise exposure of a radiation-sensitive material to modify the physical characteristics of the material in the areas of the layer which have been exposed.

Among the radiation-sensitive materials which have been used in such processes are photohardenable materials such as polymers which are rendered insoluble or hardened on exposure to actinic radiation. The resulting difference in physical properties between exposed and unexposed areas can be employed to prepare images by such procedures as application of mechanical pressure, application of heat or treatment with solvents. Thus, the layer can be treated with a solvent for the unhardened material which is a non-solvent for the hardened polymer, thereby removing unhardened material leaving an image of hardened polymer.

Alternatively, the layer can be heated to a temperature which is between the tackifying point of the material in unexposed areas of the layer and material in exposed areas of the layer so that the lower melting material can be toned with a coloured powder or transferred to a receiving surface. Such processes have been employed to prepare lithographic printing plates, stencils, photoresists, and similar photographic and photomechanical images. However, the speed of photopolymerizable material is often relatively slow and it is desirable to increase the speed of the photopolymerization reaction. As a result, many compounds have been proposed in the past as sensitizers. For example, 2 - benzoylmethylene - 1 methyl - p - naphtholthiazoline (BNTZ), disclosed in U.S. Patent 2,732,301 is useful as a sensitizer for contact printing materials.

The preparation of BNTZ requires an involved synthesis so that it has been desirable to provide new sensitizers that have speeds comparable to BNTZ and which may be easier to synthesize.

We have now discovered new sensitizers for photosensitive materials, including unsaturated monomers, unsaturated polymers, vesiculators, and azides.

In accordance with the invention there is provided a photosensitive composition comprising an unsaturated radiation-sensitive material or a photopolymerizable azide material which material contains, as a sensitizer, a 3substituted coumarin compound having an absorptive maximum of from 250 to 550 nm.

Preferably, the sensitizer has the formula

wherein Q is -CN or --ZZ-R' in which R' is a substituted or un-substituted alkyl group or an alkoxy group having from 1 to 10 carbon atoms, a substituted or unsubstituted aryl group or an aryloxy group having from 6 to 12 carbon atoms or a substituted or unsubstituted heterocyclic group having from 5 to 15 nuclear carbon and hetero atoms, and Z is a carbonyl group, a sulphonyl group, a sulphinyl group or an arylenedicarbonyl group; R2, R3, R4 and R5 each independently is hydrogen, an alkoxy group having from 1 to 6 carbon atoms, an alkyleneoxy group having from 1 to 6 carbon atoms, an alkylthio group having from 1 to 6 carbon atoms, a dialkylamino group in which each alkyl moiety has from 1 to 4 carbon atoms, hydroxy, halogen, nitro or a 5- or 6-membered heterocyclic group, or two or three of R2, R3, R4 and R5 together with the nuclear carbon atoms to which they are attached form a fused ring or fused ring system, each ring being a 5- or 6-membered ring; and R6 is hydrogen, an alkyl group having from 1 to 4 carbon atoms or an aryl group having from 6 to 12 carbon atoms.

R' may be an alkyl group having 1--10 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 and cyclohexyl; a substituted alkyl group; an aryl group such as phenyl; a substituted aryl group with substituents such as nitro, alkoxy, halogen, carboalkoxy, alkyl, aryl, carboxy, hydroxy, amino and substituted amino such as dialkylamino and trialkylammonium; an alkoxy group such as methoxy, ethoxy and butoxy; or an aryloxy group such as phenoxy.

R' may be a 3-coumarinyl group having the formula

or a pyridinium group having the formula

wherein R2, R3, R4, R5 and R6 are as defined above; Ra is an alkyl group having from 1 to 4 carbon atoms such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, n-butyl, and sec-butyl; and Xs is an anion such as FSO3e, BF4s, p-toluene sulphonate and halide e.g. Cle, Bre and If3.

R' may be a heterocyclic group such as nicotinyl, nicotinium, furyl, 2benzofuranyl, 2-thiazolyl and 2-thienyl.

Examples of heterocyclic groups from which R2, R3, R4 and R5 may be chosen include pyrrolidino, morpholino, piperidino and pyridinium.

The 3-substituted coumarin sensitizers may be used alone or in combination with one or more additional sensitizers including coumarin sensitizers.

In accordance with another aspect of the invention there is provided a photographic element comprising a support having thereon a photosensitive composition of the invention.

In a particularly useful embodiment there is provided a presensitized lithographic printing plate which comprises a support having a surface coated with a layer of a photosensitive composition comprising an unsaturated, photocross-linkable polymer and a 3-substituted coumarin compound having an absorptive maximum of from 250 to 550 nm. The surface of the support may be hydrophilic.

A lithographic printing plate can be made from the presensitized plate by imagewise exposing the plate to actinic radiation whereby the polymer in the exposed areas is cross-linked and thereafter removing the polymer composition from the unexposed areas without removing it from the exposed areas e.g. by dissolving the composition in a solvent in which the cross-linked polymer is insoluble.

In another particularly useful embodiment there is provided a vesicular material which comprises a support coated with a layer of a heat-deformable, gasimpermeable polymeric binder containing an unsaturated vesiculating agent and a 3-substituted coumarin compound having an absorptive maximum of from 250 to 550 nm.

A vesicular image can be formed from the vesicular material by imagewise exposing the material to actinic radiation and heating the material sufficiently to allow the gas liberated by the vesiculating agent to expand within the polymeric binder.

Typical coumarins which are useful in the invention are for example: 3 - benzoyl - 5,7 - dimethoxycoumarin 3 - benzoyl - 7 - methoxycoumarin 3 - benzoyl - 6 - methoxycoumarin 3 - benzoyl - 8 - ethoxycoumarin 7 - methoxy - 3 - (p - nitrobenzoyl)coumarin 3 - benzoylcoumarin 3 - (p - nitrobenzoyl)coumarin 3 - benzoylbenzo[flcoumarin 3,3' - carbonylbis(7 - methoxycoumarin) 3 - acetyl - 7 - methoxycoumarin 3 - benzoyl - 6 - bromocoumarin 3,3' - carbonylbiscoumarin 3 - benzoyl - 7 - dimethylaminocoumarin 3,3' - carbonylbis(7 - diethylaminocoumarin) 3 - carboxycoumarin 3 - carboxy - 7 - methoxycoumarin 3 - ethoxycarbonyl - 6 - methoxycoumarin 3 - ethoxycarbonyl - 7 - methoxycoumarin 3 - acetylbenzo[f]coumarin 3 - acetyl - 7 - methoxycoumarin 3 - (I - 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[f]coumarin 3 - (4 - ethoxycinnamoyl) - 7 - methoxycoumarin 3 - (4 - dimethylaminocinnamoyl)coumarin 3 - (4 - - diphenylaminocinnamoyl)coumarin 3 - [(3 - methylbenzothiazol - 2 - ylidene)acetyl]coumarin 3 - [(I - methylnaphtho[l,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 - phenylsulphonylcoumarin 7 - methoxy - 3 - phenylsulphinylcoumarin 1,4 - bis(7 - diethylamino - 3 - coumarylcarbonyl)benzene 7 - diethylamino - 5',7' - dimethoxy - 3,3' - carbonylbiscoumarin 7 - dimethylamino - 3 - thenoyl coumarin 7 - diethylamino - 3 - furoyl coumarin 7 - diethylamino - 3 - thenoyl coumarin 3 - benzoyl - 7 - (I - pyrrolidinyl)coumarin 5,7,6' - trimethoxy - 3,3' - carbonylbiscoumarin 5,5,7' - trimethoxy - 3,3' - carbonylbiscoumarin 7 - diethylamino - 6' - methoxy - 3,3' - carbonylbiscoumarin 3 - nicotinoyl - 7 - methoxycoumarin 3 - (2 - benzofuranylcarbonyl) - 7 - methoxycoumarin 3 - (7 - methoxy - 3 - coumarinoyl) - 1 - methylpyridinium fluorosulphate 3 - (5,7 - diethoxy - 3 - coumarinoyl) - 1 - methylpyridinium fluoroborate N -(7 - methoxy - 3 - coumarinoylmethyl)pyridinium bromide 9- (7 - diethylamino - 3 - coumarinoyl)- 1,2,4,5 - tetrahydro 3H,6H,IOH[l]benzopyrano[9,9a,1 - gh]quinolazine - 10 - one

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. PandyaAgr. Univ.

J. Research 4, 345 (1955) C. A. 52, 7307b. Bis compounds are described in L. L.

Woods and M. Fooladi J. Chem. Eng. Data 12, 624 (1967).

Illustrative preparations are as follows: Preparation I Preparation of 3 - benzoyl - 5,7 - dimethoxycoumarin.

A mixture of 18.2 g of 4,6 - dimethoxysalicylaldehyde, 20.0 g ethyl benzoylacetate, 20 ml acetonitrile and 30 drops piperidine was heated gently on a hot plate for 45 minutes. After cooling the product was collected and recrystallized twice from acetonitrile and once from benzene containing a small amount of acetonitrile. The product has a melting point of 178"C--179"C.

Analysis: Calc.: C, 69.7; H, 4.5 Found: C, 69.7; H, 4.5 Preparation 2 Preparation of 3 - acetyl - 7 - methoxycoumarin.

A mixture of 15.2 g of 2 - hydroxy - 4 - methoxybenzaldehyde and 13.5 g ethyl acetoacetate was warmed on a hot plate until solution was attained. Thirty drops of piperidine were added and the reaction mixture continued to be heated gently.

After several minutes the reaction mixture solidified. After cooling, the product was recrystallized from a mixture of alcohol and acetonitrile. The yield was 20 g.

Analysis: Calc.: C, 66.1; H, 4.6 Found: C, 65.7; H, 4.7 Preparation 3 Preparation of 3 - (4 - ethoxycinnamoyl) - 7 - methoxycoumarin.

A suspension of 2.18 g 3 - acetyl - 7 - methoxycoumarin and 1.65 g pethoxybenzaldehyde in 100 ml alcohol was heated under reflux on a steam bath.

Acetonitrile was added until solution was attained. Fifty drops of piperidine were added and the reaction mixture heated under reflux for 90 minutes. An additional fifty drops of piperidine were added and the solution was heated under reflux another hour. The product separated upon cooling and was washed with alcohol before being recrystallized from a mixture of alcohol and acetonitrile.

Analysis: Calc.: C, 72.0; H, 5.2 Found: C, 71.6; H, 5.4 Preparation 4 Preparation of 3,3' - carbonylbis(7 - diethylaminocoumarin).

4-diethylamino salicylaldehyde (1) Phosphoryl chloride (61.2 g, 0.40 mole) is added dropwise with stirring and cooling to 90 g dimethylformamide. The temperature is maintained at 250C by means of an ice bath as 60.4 g (0.36 mole) m-diethylaminophenol is added in small portions. The reaction mixture is stirred at room temperature for 1/2 hour, then heated on a steam bath for 1/2 hour. (2) After cooling to room temperature, the reaction mixture is poured into 1200 ml 1 molar sodium acetate and stirred for 1 hour. The solution is diluted to 2000 ml and stirred an additional 2 hours before collecting the product, 4-diethylaminosalicylaldehyde, as brown crystals, in a yield of 21.0 g. Occasionally the product remains a tar. The tar is taken up in acetic acid and twice the volume of water added to precipitate the product as a brown crystalline material.

3,3' - carbonylbis(7 - diethylaminocoumarin) (3) A mixture of 52.5 g (0.27 mole) 4 - diethylaminosalicylaldehyde, 22.5 g (0.13 mole) dimethyl - 1,3 - acetonedicarboxylate, 500 ml 95 percent by volume ethyl alcohol and 30 ml piperidine is heated under reflux on a steam bath for 3 hours. After cooling, the solid is collected, washed with a small amount of ethyl alcohol, and recrystallized twice from a mixture of ethyl alcohol and acetonitrile.

The yield was 38.0 g and the product had a melting point of 213"C.

Preparation 5 Preparation of methyl 7 - diethylamino - 3 - coumarinoylacetate.

A solution of 1.93 g 4 - diethylaminosalicylaldehyde and 1.80 g dimethyl 1,3 - acetone dicarboxylate in 10 ml. alcohol containing 10 drops piperidene was heated under reflux on a steam bath for 2 hours. After chilling in the freezer, the product was collected and recrystallized from a mixture of alcohol and acetonitrile.

The yield was 2.6 g (82 /").

Preparation 6 Preparation of 7 - diethylamino - 5',7' - dimethoxy - 3,3' carbonvlbiscoumarin.

a mixture of 1.75 g methyl 7 - diethylamino - 3 - coumarinoylacetate and 1.1 g 4,6 - dimethoxysalicylaldehyde in 25 ml acetonitrile was heated until the reagents were dissolved. One and a half millilitres piperidine were added and the reaction mixture heated under reflux on a steam bath for 2 hours. After chilling in a freezer, the product was collected and recrystallized from a mixture of acetonitrile and pyridine. The yield was 1.15 g. (46 / > ).

In order to use the sensitizers of the invention in an aqueous system or in an aqueous processable photoreactive polymer system, it is advantageous to incorporate in the sensitizer molecule a solubilizing group which does not substantially affect their ability to function as sensitizers. However, some shift in the absorption range may occur. Particularly useful groups include sulphonate groups and onium groups, including cyclo-onium salt groups, e.g. pyridinium and oxonium groups.

Some of these compounds retain sufficient solubility in conventional organic coating solvents to allow them to be used in systems which require coating from organic solvents but are intended for processing with water.

The preferred compounds are of the formula:

in which the values for R2, R3, R4, R5, Ra, Ra and Xe are as defined above.

Preparation 7 Preparation of 3 - nicotinoyl - 7 - methoxy coumarin.

A mixture of 0.65 g ethyl nicotinoylacetate, 0.5 g 2-hydroxyanisaldehyde and 10 ml alcohol was heated on a steam bath until solution was attained. Five drops of piperidine were added and heated was continued. After several minutes the reaction mixture solidified. An additional 10 ml of alcohol were added and the reaction mixture heated another 15 minutes. After cooling, the solid was collected and recrystallized twice from a mixture of alcohol and acetonitrile.

Preparation of 3 -(7 - methoxy - 3 - coumarinoyl) - 1 - methyl pyridinium fluorosulphate.

Two millilitres of methylfluorosulphonate was added to a stirred solution of 1.5 g 3 - nicotinoyl - 7 - methoxycoumarin in 120 ml dichloromethane.

The solution was stirred for 1/2 hour and a solid product was collected which was recrystallized from alcohol to provide yellow needles in a yield of 1.5 g.

Calc: C, 51.6; H, 3.6; N, 3.5; S, 8.1 Found: C, 51.5; H, 3.6; N, 3.6; S, 8.5 Preparation 8 Preparation of 3 - (5,7 - diethoxy - 3 - coumarinoyl) - 1 - methylpyridinium fluoroborate.

One-half millilitre of methyl fluorosulphonate was added to a stirred solution of 0.5 g, 5,7 - diethoxy - 3 - nicotinoyl coumarin in 20 ml dichloromethane. The dichloromethane was evaporated, the residue dissolved in alcohol and 50 percent fluoroboric acid was added dropwise until precipitation was complete. After chilling, the product was collected and recrystallized from alcohol.

Calc: C, 54.4; H, 4.6; N, 3.2 Found: C, 54.5; H, 4.8; N, 3.3 The materials whose light-sensitivity is improved by the sensitizers of this invention are simple and polymeric compounds having a light-sensitive group selected from azide (-N3), and unsaturated groups e.g., olefinic

groups.

Many of these materials are photopolymerizable or photohardenable. These terms "photopolymerizable" and "photohardenable" as used herein refer to systems in which the molecular weight of at least one component of the photosensitive layer is increased by exposure to actinic radiation sufficiently to result in a change in the solubility or the rheological and thermal behavior of the exposed areas.

Among suitable photopolymerizable or photohardenable systems are: (1) those in which a photopolymerizable monomer is present alone or in combination with a compatible binder, or (2) those in which the photohardenable group, within or attached to a polymer backbone, becomes activated on exposure to light and may then cross-link by reacting with a similar group or other reactive sites on adjacent polymer chains. Where the monomer or photohardenable group is capable of addition polymerization, e.g., a vinyl monomer, the photopolymerized chain length may involve addition of many similar units initiated by a single photochemical act.

Where only dimerization of similar compounds is involved, e.g., cinnamoyl compounds, the average molecular weight of the photosensitive constituent can be at best only doubled by a single photochemical act.

The photopolymerizable layer can be composed of any addition-polymerizable monomer (vis., ethylenically unsaturated monomer) and coumarin sensitizer in admixture with one or more other similar monomers. The photopolymerizable layer can also contain added preformed compatible condensation or addition polymers as well as immiscible polymeric or non-polymeric organic or inorganic fillers or reinforcing agents, which are essentially transparent, e.g., the organophilic silicas, bentonites, silica and powdered glass, having a particle size less than 0.4x 10-3 inch (10 microns) and in amounts varying with the desired properties of the photopolymerizable layer. The preferred monomers are the ethylenically unsaturated, addition-polymerizable monomers, particularly those wherein the said ethylenic linkages are terminal, i.e., those monomers having the characteristic CH2=C < group, i.e., the vinyl monomers. Because of the greater speed with which such compositions polymerize to rigid materials, it is preferred that the photopolymerizable layer contain appreciable proportions of ethylenically unsaturated polymerizable materials containing a plurality of the polymerizable linkages per molecule.

Exemplary photopolymerizable monomers also include acrylic monomers, particularly bis-, tris-, etc. acrylates and methacrylates.

The photopolymerizable layer may be composed of a polymerizable monomer and a polymerizable polymer in admixture with the coumarin sensitizer. Where a photopolymerizable molecule has more than one reactive site, a cross-linked network can be produced.

A typical cross-linkable photopolymer is disclosed in U.S. Patent 1,965,710 which describes a resist image formed from a layer of cinnamal ketone containing another resinous material which, after exposure under a design, may be selectively dissolved in the unexposed area whereby the area of the support thus bared may be etched. U.S. Patents 2,610,120; 2,690,966; 2,670,285; 2,670,286; and 2,670,287 respectively disclose light-sensitive photomechanical resist compositions containing polymeric materials containing combined polymeric units having R CH=CH-CO-groups wherein R is an aryl group such as a phenyl and mnitrophenyl sensitized with nitro, triphenylmethane, anthrone, quinone and ketone compounds.

Exemplary photo-cross-linkable polymers include cinnamylideneacetate esters of poly(vinyl alcohol), cinnamic acid esters of poly(vinyl alcohol), cinnamic acid esters of cellulose, cinnamic acid esters of hydroxyalkylcellulose, cinnamoylated polystyrene, cinnamyl vinyl ketone polymers and unsaturated polyesters.

Other photopolymerizable materials which may be sensitized with the coumarins, as disclosed herein, are disclosed in U.S. Patent 3,779,989. These are light-sensitive polymers which contain a diarylcyclopropene substituent, such as a diarylcyclopropenium ion or a diarylcyclopropenyl group, directly attached to a phenyl group which in turn is attached to a polymer backbone. These polymers are useful in preparing photomechanical images and for other purposes. Another class of light-sensitive polymers are disclosed in U.S. Patent 3,782,938. These lightsensitive polymers have appended to a polymer backbone a light-sensitive unsaturated cyclic group which is a 3- to 6-membered carbocyclic or monocyclic heterocyclic ring containing an ethylenic double bond or a 5- to 6-membered ethylenically unsaturated carbocyclic or heterocyclic ring free of exocyclic double bonds and fused to an aromatic ring of the benzene series.

Additional light-sensitive polymers which can be sensitized with the coumarins are also disclosed in U.S. Patent 3,030,208. These light-sensitive compounds are soluble polycondensation products predominately linked through ester bonds and having

groups bonded to aromatic nuclei.

Still other photopolymerizable materials are disclosed in U.S. Patent 3,929,489.

In a particularly useful embodiment of the invention the photopolymerizable material has incorporated into the polymer molecule disulphonamido units having a valence of at least one and having the structural formula:

wherein (a) R is hydrogen or an alkali metal, (b) X and Y are the same or different arylene radicals of 6 to 12 carbons, said radicals being unsubstituted or substituted with chlorine atoms, and (c) A and B are the same or different and are selected from -H, -COOR",

wherein R" is -H, an alkyl group of from 1 to 8 carbon atoms, or an aryl group of from 6 to 14 carbon atoms; R, is hydrogen or an alkyl group of from 1 to 8 carbon atoms and R2 is hydrogen, or an alkyl group of from 1 to 8 carbon atoms; and wherein at least one of A and B is a

group.

Examples of suitable disulphonamido units are described in U.S. Patent No.

3,546,180.

Exemplary azides which can be sensitized by the compounds of the invention include the poly(vinyl azidobenzoates) and poly(vinyl azidophthalates) of U.S.

Patents 2,948,610; 3,002,003; and 3,096,311.

The azide polymers can be represented by various formulas. The polymers contain recurring polymeric units which can be represented simply as

in which U represents the recurring atoms of the polymer chain proper and Z is a linkage joining the azide group to the recurring atoms of the polymer chain, for example, the atoms and groups: -CH2-, -CO-, phenylene, -C6H4-CH2- O-CO-, -C6H4-CO-O-, -C6H4-O-, -C6H3(COOH)-CO-O-, and -C6H4-O-C2H4-O-. In copolymers, additional polymeric units U1, U2 etc., differing from U are present and the copolymers can therefore be represented as

Polymers may also be used which contain recurring units of the structure

in which the Z's are the same or different linkages such as mentioned above as may be present, for example, in aryl azide derivatives of hydrolyzed cellulose esters in which case two or more azide groups can be adjoined to a single recurring polymeric unit of the cellulosic chain. Similarly, more than one azide group can be attached to Z as in the case of a diazidophenyl group.

The inherently light-sensitive alkali soluble azide polymers particularly efficacious for use contain recurring units of the formula

in which R is a bivalent aromatic radical of the benzene series whose free valences do not necessarily belong to the aromatic nucleus, for example, phenylene, -C6H4-CH2-CO, -C6H4-CO(:, -C6H4-, C6H3(COOH9CO 0- and -C6H4-O-C2H4-O-. In some cases the acid group of the inherently light-sensitive alkali soluble azide polymer, such as a carboxyl group, is not attached to the recurring polymeric unit containing the azide group, but may be present on some other recurring unit of the polymer, for example, as in the case of the maleic acid azidostyrene copolymer described hereinafter. In the vinyl azidophthalate copolymers described hereinafter, the carboxyl group is attached directly to the aromatic nucleus bearing the azide group.

Useful light-sensitive film-forming azidostyrene homopolymers contain the following recurring structural unit:

or copolymers of said azidostyrene consist of the following recurring structural units in random combination:

wherein the ratio of II(a) units to II(b) units in each resin molecule can vary from 1:19 to 19:1, i.e. II(b) are present from 5 to 95 mole percent, and wherein m represents in each instance 1 or 2, n represents 0, 1 or 2, X represents a chlorine atom, an alkyl group containing from 1 to 4 carbon atoms, e.g. methyl, ethyl, propyl or butyl, an alkoxy group containing from 1 to 4 carbon atoms, e.g. methoxy, ethoxy, propoxy or butoxy, or a nitro group, and R represents a unit such as ethylene, isobutylene, a 1,3-butadiene, styrene or a substituted styrene, an a,- unsaturated mono- or di-carboxylic acid unit such as acrylic acid, an a-alkylacrylic acid, maleic acid, citraconic acid or itaconic acid, or an anhydride, alkyl ester, imide, N-alkyl imide, nitrile, amide or N-alkyl or N,N-dialkyl substituted amide of these acids, fumaric or mesaconic acid or an alkyl ester thereof, a nitrile, an amide or N-alkyl or N,N-dialkyl substituted amide, a vinyl alkyl ketone such as vinyl methyl ketone a vinyl halide such as vinyl chloride, a vinylidene halide such as vinylidene chloride, and wherein in each instance in the above the alkyl and alkoxy groups contain from 1 to 4 carbon atoms.

Unsaturated radiation-decomposable vesiculating agents capable of generating a gas upon imagewise exposure which can be sensitized by coumarins include the vesiculating agents described in U.S. Patent No. 4,128,422.

These vesiculating agents release a gas upon exposure to light. When incorporated in a heat-deformable, relatively gas impermeable film coating, exposed to actinic radiation, and heated, the gas is released upon exposure and allowed to expand on heating because of the softened matrix which is deformed by gas expansion. Upon cooling, the exposed areas are permanently deformed and opaque to the transmission of light, thus images can be viewed by projection if coated on a transparent support. If coated on an opaque substrate, the image appears white, when viewed by reflected light.

Preferred radiation-decomposable vesiculating agents are cyclopropenones having the formula

wherein R' and R2 are the same or different, and are each a substituted or unsubstituted aryl radical containing from 6 to 10 carbon atoms in the aromatic ring, or an aralkenyl radical having 6 to 10 carbon atoms in the aryl portion such as, for example, phenyl or naphthyl, and 1 to 5 carbon atoms in the alkenyl portion such as, for example, 2,2-diphenylvinyl, 2-phenylvinyl or 2-naphthylvinyl.

The substituents of each of the substituted aryl radicals are one or more of 1) an alkyl or alkoxy radical containing from 1 to 5 carbon atoms; 2) a nitro radical; 3) an aryloxy radical containing from 6 to 10 carbon atoms; and 4) a polymer to which the aryl radical is attached as a dependent moiety, the polymer having at least one repeating unit with the formula -(-R3-)- wherein R3 is a lower alkylene r platinum; synthetic resins and polymeric materials such as poly(alkyl acrylates), e.g. poly(methyl methacrylate), polyester film base - e.g. poly(ethylene terephthalate), poly(vinyl acetals), polyamides -- e.g. nylon and cellulose ester film base - e.g. cellulose nitrate, cellulose acetate, cellulose ester with a hydrolyzed surface, cellulose acetate propionate and cellulose acetate butyrate.

The optimum coating thickness of the radiation-sensitive layer will depend upon such factors as the use to which the coating will be put, the particular radiation-sensitive polymer employed, and the nature of other components which may be present in the coating. Typical coating thicknesses can be from 0.05 to 10.0 microns or greater, with thicknesses of from 0.1 to 2.5 microns being preferred for lithographic printing plate applications.

Generally, the sensitizers of the invention are employed at a concentration of 3x106 to 6xl0-4 moles of sensitizer per gram of polymer or 0.1 to 20 percent by weight of the light-sensitive material, preferably I to 11 percent.

The results recorded in the examples that follow were obtained with the general procedure described below.

In each Example 1--11, 6x10-5 mole of sensitizer is dissolved in 10 ml of a 2 percent solution of the light-sensitive polymer in cyclohexanone. Five millilitres of this solution is spin-coated on aluminium. Identical, freshly prepared coatings using equimolar amounts of 2 - benzoylmethylene - 1 - methyl - p - naphthothiazoline are used as a control.

Strips of the dried coatings are exposed through a 0.15 O.D. incremented step wedge and developed by dissolving away the non-cross-linked polymer in a tray of 1 ,2-dichloroethane.

Light sources which may be used include broad spectrum light sources, filtered or unfiltered, including Xenon or carbon arcs, narrow spectrum sources such as mercury lamps and lasers which emit within low (uv) to medium (visible light) wavelengths.

Three different light sources are used in the following examples: A. Ozamatic source - a commercial unit which uses a full spectrum, high pressure mercury lamp.

B. 366 nm - The wavelength of the mercury line isolated by filtration of a high pressure mercury lamp.

C. 3500 A - A laboratory built exposure device containing an arrangement of Rayonet photochemical reactor lamps whose emission maximum is at 350 nm.

D. 405 nm - The wavelength of the mercury line isolated by filtration of a high pressure mercury lamp.

E. 436 nm-The wavelength of the mercury line isolated by filtration of a high pressure mercury lamp.

The light-sensitive polymer used in all of the samples in Examples 1--4 was poly(vinyl cinnamate). In Example 5, the polymer was poly(vinyl acetate-covinylazidobenzoate). In Examples 6-9 and 11, the polymer was a modified poly(vinyl alcohol) consisting of 20 percent free hydroxyl groups, 12 percent acetate groups, 37 percent 2,3 - diphenylcyclopropenecarboxylate groups, and 31 percent benzoate groups.

In Example 10, the polymer was poly(vinylacetate-co-vinylbenzoate-co-vinyl cinnamylideneacetate), (mole ratio 12:38:50).

The following examples are included for a further understanding of the invention: Example 1 - Ligt Source: A Sensitizer Relative Speed 2 - benzoylmethylene - 1 - methyl - - naphthothiazoline (BNTZ) (control) 3 - benzoyl - 5,7 - dimethoxycoumarin 1 3 - benzoyl - 7 - methoxycoumarin 1 3 - benzoyl - 6 - methoxycoumarin 0.5 3 - benzoyl - 8 - ethoxycoumarin 0.25 3 - benzoylcoumarin 0.17 3 - (p - nitrobenzoyl)coumarin 0.25 5,7,7' - trimethoxy - 3,3' - carbonylbis - coumarin 1.75 3,3' - carbonylbis(5,7 - dimethoxycoumarin) 1.75 In this and the remaining examples, the respective light-sensitive polymer sensitized with 2 - benzoylmethylene - 1 - methyl - /3 - naphthothiazoline served as the control. For comparative purposes, this combination is assigned a relative speed of one. It is 350 to 500 times faster than unsensitized poly(vinyl cinnamate).

Example 2 - Light Source: C Sensitizer Relative Speed 2 - benzoylmethylene - 1 - methyl - - naphthothiazoline (control) 1 3 - benzoyl - 5,7 - dimethoxycoumarin 2 Example 3 - Light Source: A Sensitizer Relative Speed 2 - benzoylmethylene - 1 - methyl - - naphthothiazoline (control) 3 - benzoylbenzo[f]coumarin 0.6 3,3' - carbonylbis(7 - methoxycoumarin) 1.2 3 - cyano - 7 - methoxycoumarin 0.1 3,3' - carbonylbis(6 - methoxycoumarin) 0.8 Example 4 - Light Source: B Sensitizer Relative Speed 2 - benzoylmethylene - I - methyl - - naphthothiazoline (control) 3 - benzoylbenzo[f]coumarin 2 Example 5 - Light Source: A Sensitizer Relative Speed none (control) (1) 5,7,7' - Trimethoxy - 3,3' - carbonylbiscoumarin 40* 3,3' - Carbonylbis(7 - diethylaminocoumarin) 10* *This corresponds to a speed 4 times faster than that of poly(vinyl cinnamate) sensitized with BNTZ.

Example 6 - Light Source: C Sensitizer Relative Speed 2 - benzoylmethylene - 1 - methyl - - naphthothiazoline (control) 3 - benzoyl - 5,7 - dimethoxycoumarin 2 3 - benzoyl - 7 - methoxycoumarin 2 3 - acetyl - 7 - methoxycoumarin 1.4 3 - benzoyl - 7 - methoxycoumarin 2 3 - acetyl - 7 - methoxycoumarin 2 3 - benzoyl - 6 - bromocoumarin 0.7 3,3' - carbonylbiscoumarin 1.2 Example 7 - Light Source: A Sensitizer Relative Speed 2 - benzoylmethylene - 1 - methyl - - naphthothiazoline (control) 1 5,7,7' - Trimethoxy - 3,3' - carbonylbiscoumarin 1.75 3,3' - Carbonylbis(5,7 - dimethoxycoumarin) 1.7 7 - (I - Pyrrolidinyl) - 3 - thenoylcoumarin 1.4 Example 8 Light Relative Speed Source (BNTZ=1) 3-benzoyl-7-dimethylamino- A 0.8 coumarin 3-benzoyl-7-dimethylamino- D 0.7 coumarin 3-benzoyl-7-dimethylamino- B 0.5 coumarin 7-diethylamino-4-methylcoumarin* A 0.2 *This sample is for comparison -- it is not a sensitizer of this invention.

Example 9 Light Relative Speed Source (BNTZ=1) 3,3'-carbonylbis(7-diethyl- A 1.0 aminocoumarin) E 2.0 D 0.7 B 1.0 Example 10 Light Relative Speed Source (BNTZ=1) 3,3'-carbonylbis(7-diethyl- A 1.2 aminocoumarin) E 2.5 Example 11 Light Relative Speed Sensitizer Source (BNTZ=I) 3-(4-ethoxycinnamoyl)-7-methoxycoumarin A 0.33 B 0.5 3-[(3-methylbenzothiazol-2-ylidene)- A 0.025 acetyl]coumarin B 0.025 3-(1 -adamantoyl)-7-methoxycoumarin A 0.2 B 1.0 3,3'-carbonylbis(7-acetoxycoumarin) A 0.4 B 2 7-methoxy-3-phenylsulphonylcoumarin A 0.25 l,4-bis(7-diethylamino-3-coumarylcar- A 0.22 bonyl)benzene 7-methoxy-3-(p-nitrobenzoyl)coumarin A 0.30 3-nicotinoyl-7-methoxycoumarin A 2.1 3(2-benzofuranylcarbonyl)-7-methoxy- A 0.9 coumarin Example 12 3,3' - Carbonylbis(7 - diethylaminocoumarin (4x 10-5 mole) is dissolved in 10 ml of a 2.1 /" dichloroethane solution of a light sensitive polymer, poly(l,4 cyclohexylenebis(oxyethylene)l,4 - phenylenediacrylate).

5 millilitres of this solution is spin-coated on aluminium.

A second coating was prepared identical to the first but containing 4x10-5 mole 3 - benzoyl - 7 - methoxy coumarin instead of 3,3' - carbonylbis(7 diethylaminocoumarin).

A third coating was prepared identical to the first but containing 6x 10-5 mole of 2 - benzoylmethylene - 1 - methyl - p - naphthothiazoline instead of 3,3' carbonylbis(7 - diethylaminocoumarin).

The coatings were exposed in the usual manner but developed by swab develoment for 15 second with a developer similar to that described in Example 3 of U.S. Patent 3,707,373 and rinsed with water. Standard inking techniques may be used for better visibility of the image.

Light Source: A Sensitizer Relative Speed 2 - benzoylmethylene - 1 - methyl - - naphthothiazoline 1.0 3,3' - carbonylbis(7 - diethylaminocoumarin) 1.8 3 - benzoyl - 7 - methoxycoumarin 1.0 Example 13 Utility in a vesicular imaging system.

A dope comprising 0.75 g polymeric polysulphonamide binder .20 g 2 - (4 - methoxyphenyl) - 3 - phenylcyclopropenone 3.08 g acetone 3.08 g 2-methoxyethanol is coated at a 4x10-3 inch (10 microns) wet thickness on subbed poly(ethylene terephthalate) at a coating block temperature of 27"C. After normal drying at 49"C, the coating is "flash dried" for 10 seconds at 650C.

A second coating, identical to the first, is prepared except that 14 mg BNTZ is added to the dope.

A third coating, identical to the first, is prepared except that 15 mg 3 benzoyl - 7 - methoxycoumarin is added to the dope.

The coatings are exposed for identical times through a 0.15 density step tablet to a 400 watt mercury arc lamp and developed for 1 second at 1500C.

The H & D curve is plotted and the relative speeds are calculated from the differences in the log exposure at an optical density of 1.

Coating Relative Speed Unsensitized coating 1 BNTZ sensitized coating 2 3 - Benzoyl - 7 - methoxycoumarin sensitized coating 1.6 Example 14 - A Comparative Example 3,3' - Carbonylbis(7 - diethylaminocoumarin) was compared to 7 dimethylamino - 4- methylcoumarin in a photopolymerizable coating, as described in Example 10 of U.K. Patent No. 1,463,816.

A dope comprising: a. 10 ml of a 10% dichloromethane solution of the following polymer:

Inherent viscosity 0.21 in cyclohexanone, polystyrene equivalent molecular weight of the polymer, about 25,000 to 30,000.

b. 0.5 ml of a 10% dichloroethane solution of benzene chromium tricarbonyl, c. 0.15 g. of a plasticizer of the following structure:

d. 10 ml of dichloroethane, e. .040 g 7 - dimethylamino - 4 - methylcoumarin, was whirl-coated on grained anodized aluminium. The dried coating was overcoated with an aqueous 10% solution of a 2% succinoylated poly(vinyl alcohol) as described in Belgian Patent No. 843,755.

A second coating was prepared identical to the first with the exception that 3,3' - carbonylbis(7 - diethylaminocoumarin) was used in place of the 7 dimethylamino - 4 - methylcoumarin.

Both coatings were exposed for 1 minute to a 1000 watt Xenon wedge spectrograph.

The coatings were then heated for 7 seconds at 1240C on a hot block.

The exposed coatings were swab-developed with an alkaline ethanolic aqueous developer. The images were hand inked.

The coating containing 7 - dimethylamino ;4 - methylcoumarin showed no increase in speed and no increase in spectral sensitivity range beyond that of a typical unsensitized coating.

The coating containing 3,3'- carbonylbis(4- diethylaminocoumarin) extended the spectral sensitivity range from 430 nm to 540 nm thereby improving the overall speed of the coating by rendering it sensitive to visible light.

Example 15 A coating identical to the second coating of Example 14 was whirler coated on grained phosphoric acid anodized aluminium and overcoated as in Example 14.

The dried coating was laser exposed at 488 nm and required 2x 104 ergs/cm2. It was heated and processed as in Example 14. The image was hand inked.

A coating identical to the first coating of Example 14 failed to produce an image when laser exposed at 488 nm.

Example 16 A solution 1 g of 2 - hydroxy - 3 - methacryloyloxypropyl - 4 methacryloyloxybenzoate having the formula:

1 g of poly(methyl methacrylate-co-ethyl acrylate-co-methacrylic acid) (weight ratio 51.6:34.4:14), and 0.1 g of 3 - benzoyl - 7 - methoxycoumarin in 5 ml of methyl ethyl ketone was coated on copper clad epoxy fiberglass printed circuit board at a wet thickness of 0.008 in. (20 microns) at 430C, air dried 5 minutes and baked at 80--900C for 5 minutes. The cooled element was exposed in a Colight M99 Printer for 2 minutes under a 0.15 O.D. incremented step wedge and developed by spraying with aqueous 4% sodium carbonate solution for 1 minute and rinsing with tap water for 1 minute to produce a resist image. Three steps developed. When a sensitizer mixture of 0.1 g benzophenone and 0. I g Michler's ketone was used in place of the coumarin compound, six steps developed. A control with no sensitizer did not produce any developed steps.

These results illustrate the capability of coumarin sensitizers of the invention to sensitize photopolymerizable compositions.

Example 17 The following coating compositions were prepared: 6x10-5 mole coumarin sensitizer.

10 ml of 2% by weight solution in 4-butyrolactone:ethoxyethyl acetate (1:3 by weight) of the polymer used in Example 11.

Five millilitres of this solution was spin-coated on aluminium.

An identical, freshly prepared coating using an equimolar amount df BNTZ was used as a control.

Strips of the dried coatings were exposed to a high pressure mercury lamp through a 0.15 O.D. incremented step wedge and developed by swabbing with Kodak Polymatic LN Developer. The developed strips were inked for better visibility of the images.

The following results were obtained: Sensitizer Relative Speed BNTZ 1

Example 18 The following coating compositions were prepared: 6x10-5 mole coumarin sensitizer.

10 ml of 2% by weight solution in cyclohexanone of the polymer used in Example 11.

The solution was coated, exposed and compared to a control coating as in Example 17 with the following results: Sensitizer Relative Speed BNTZ

Example 19 A dope comprised of 1 g of a light-sensitive polymer of the following structure

and 0.01 g of a sensitizer of the following structure

in 18 ml dichloroethane and 2 ml dimethyl formamide was spin coated at 150 rpm on a subbed aluminium plate. A portion of the plate was exposed for 4 minutes through a Kodak T-14 control scale on an "Xposer I" (Colight, Inc.). The exposed plate was developed by swabbing with MX854-3 developer (a polymatic LN type developer) and inked. The speed is 0.7 of the speed of a comparative plate containing BNTZ as a sensitizer.

A second portion of the plate was exposed in the same manner and developed using 90 percent water, 5 percent methanol and 5 percent ammonium hydroxide.

Example 20 The following samples (A-H) were prepared by whirl coating cyclohexanone solutions containing 2% of the polymer used in Example 11 and the sensitizers 3,3' - carbonylbis(7 - diethylaminocoumarin) and/or 3 - benzoyl - 7 methoxycoumarin at the concentration of 3 or 6x10-3M on subbed aluminium.

Sample Concentration of the sensitizer (in 10-3M) in the coating solution

A 6 B 3 C 6 D 3 E 6 6 F 6 3 G* 3 6 H 3 3 *A similar coating containing Michler's ketone instead of 3 - benzoyl - 7 methoxycoumarin also increased the response of the plate in the 350370 nm range as compared to that of (B).

The samples were exposed to an unfiltered Hg-high pressure lamp through step tablets. The wedge diagrams were obtained using a Xenon arc. LN developer was used to develop the exposed plates.

Sample B, which has a lower concentration of 3,3' - carbonylbis(7 diethylaminocoumarin), was almost twice as fast as A. The coatings C and D showed similar response. Of the mixed-sensitized coatings (E-H) sample G showed the highest response at 350370 nm and at 488 nm. The speed of sample G at 488 nm was equal to that of B and at 350370 nm, it showed a speed similar to that of C. Using the Hg-high pressure lamp exposure the mixed sensitized sample (G) was the highest in speed. It showed a speed 1.25 times that of B.

WHAT WE CLAIM IS: 1. A photosensitive composition comprising an unsaturated radiation-sensitive material or a photopolymerizable azide material which material contains, as a sensitizer, a 3-substituted coumarin compound having an absorptive maximum of from 250 to 550 nm.

2. A composition as claimed in Claim 1, wherein the unsaturated light-sensitive material comprises an ethylenically unsaturated monomer.

3. A composition as claimed in Claim -2, wherein the monomer is a vinyl monomer.

4. A composition as claimed in any one of the preceding claims, wherein the unsaturated light-sensitive material comprises an unsaturated polymer.

5. A composition as claimed in Claim 4, wherein the unsaturated polymer is an unsaturated polyester.

6. A composition as claimed in Claim 4, wherein the unsaturated polymer is a cinnamylideneacetate ester of poly(vinyl alcohol), a cinnamic acid ester of poly(vinyl alcohol), a cinnamic acid ester of cellulose, a cinnamic acid ester of a hydroxyalkylcellulose, a cinnamoylated polystyrene or a cinnamyl vinyl ketone polymer.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. in 18 ml dichloroethane and 2 ml dimethyl formamide was spin coated at 150 rpm on a subbed aluminium plate. A portion of the plate was exposed for 4 minutes through a Kodak T-14 control scale on an "Xposer I" (Colight, Inc.). The exposed plate was developed by swabbing with MX854-3 developer (a polymatic LN type developer) and inked. The speed is 0.7 of the speed of a comparative plate containing BNTZ as a sensitizer. A second portion of the plate was exposed in the same manner and developed using 90 percent water, 5 percent methanol and 5 percent ammonium hydroxide. Example 20 The following samples (A-H) were prepared by whirl coating cyclohexanone solutions containing 2% of the polymer used in Example 11 and the sensitizers 3,3' - carbonylbis(7 - diethylaminocoumarin) and/or 3 - benzoyl - 7 methoxycoumarin at the concentration of 3 or 6x10-3M on subbed aluminium. Sample Concentration of the sensitizer (in 10-3M) in the coating solution A 6 B 3 C 6 D 3 E 6 6 F 6 3 G* 3 6 H 3 3 *A similar coating containing Michler's ketone instead of 3 - benzoyl - 7 methoxycoumarin also increased the response of the plate in the 350370 nm range as compared to that of (B). The samples were exposed to an unfiltered Hg-high pressure lamp through step tablets. The wedge diagrams were obtained using a Xenon arc. LN developer was used to develop the exposed plates. Sample B, which has a lower concentration of 3,3' - carbonylbis(7 diethylaminocoumarin), was almost twice as fast as A. The coatings C and D showed similar response. Of the mixed-sensitized coatings (E-H) sample G showed the highest response at 350370 nm and at 488 nm. The speed of sample G at 488 nm was equal to that of B and at 350370 nm, it showed a speed similar to that of C. Using the Hg-high pressure lamp exposure the mixed sensitized sample (G) was the highest in speed. It showed a speed 1.25 times that of B. WHAT WE CLAIM IS:

1. A photosensitive composition comprising an unsaturated radiation-sensitive material or a photopolymerizable azide material which material contains, as a sensitizer, a 3-substituted coumarin compound having an absorptive maximum of from 250 to 550 nm.

7. A composition as claimed in Claim 4, wherein the unsaturated polymer

comprises units having a valence of at least one and having the structural formula:

wherein (a) R is hydrogen or an alkali metal, (b) each of X and Y, independently is an arylene group having from 6 to 12 carbon atoms, the arylene group being unsubstituted or substituted with chlorine, and (c) each of A and B, independently, is -H, -COOR",

wherein R" is hydrogen, an alkyl group having from 1 to 8 carbon atoms or an aryl group having from 6 to 14 carbon atoms; R1 is hydrogen or an alkyl group having from 1 to 8 carbon atoms; and R2 iS hydrogen or an alkyl group having from 1 to 8 carbon atoms; and wherein at least one of A and B is a

group.

8. A composition as claimed in Claim 1, wherein the unsaturated light-sensitive material is an unsaturated vesiculating agent.

9. A composition as claimed in Claim 8, wherein the unsaturated vesiculating agent is a cyclopropenone having the formula:

wherein R' and R2 are the same or different, and are each an aralkenyl radical having from 6 to 10 carbon atoms in the aryl portion and from 1 to 5 carbon atoms in the alkenyl portion, an unsubstituted aryl radical having from 6 to 10 carbon atoms in the aromatic ring, or a substituted aryl radical having from 6 to 10 carbon atoms in the aromatic ring in which the substituents are one or more of a. an alkyl or alkoxy radical having from 1 to 5 carbon atoms; b. a nitro radical; c. an aryloxy radical having from 6 to 10 carbon atoms; and d. a polymer to which the aryl radical is attached as a dependent moiety, the polymer having at least one repeating unit of the formula -(-R3-)- wherein R3 is a lower alkylene radical having from 1 to 5 carbon atoms.

10. A composition as claimed in Claim 8 or Claim 9, wherein the vesiculating agent is contained in a polymeric binder.

11. A composition as claimed in Claim 1, wherein the photopolymerizable azide material is a homopolymer or copolymer containing a recurring structural unit of the formula:

wherein X represents a chlorine atom, an alkyl group having from I to 4 carbon atoms, an alkoxy group having from 1 to 4 carbon atoms or a nitro group, n represents 0, 1 or 2 and m represents 1 or 2, the structural unit being present in an amount of from 5 to 95 mole percent when the azide material is a copolymer.

12. A composition as claimed in any one of the preceding claims, wherein the material contains from 0.1 to 20 percent by weight of the sensitizer.

13. A composition as claimed in any one of the preceding claims, wherein the sensitizer has the formula:

wherein Q is -CN or -Z-R1 in which R1 is a substituted or unsubstituted alkyl group or an alkoxy group having from 1 to 10 carbon atoms, a substituted or unsubstituted aryl group or an aryloxy group having from 6 to 12 carbon atoms or a substituted or unsubstituted heterocyclic group having from 5 to 15 nuclear carbon and hetero atoms, and Z is a carbonyl group, a sulphonyl group, a sulphinyl group or an arylenedicarbonyl group; R2, R3, R4 and R5 each independently is hydrogen, an alkoxy group having from 1 to 6 carbon atoms an alkyleneoxy group having from 1 to 6 carbon atoms, an alkylthio group having from 1 to 6 carbon atoms, a dialkylamino group in which each alkyl moiety has from 1 to 4 carbon atoms, hydroxy, halogen, nitro or a 5- or 6-membered heterocyclic group, or two or three of R2, R3, R4 and R5 together with the nuclear carbon atoms to which they are attached form a fused ring or fused ring system, each ring being a 5- or 6-membered ring; and R6 is hydrogen, an alkyl group having from 1 to 4 carbon atoms or an aryl group having from 6 to 12 carbon atoms.

14. A composition as claimed in Claim 13, wherein the sensitizer has the formula shown in which R2, R3, R4 and R5 each independently is hydrogen, an alkoxy group having from 1 to 6 carbon atoms, a dialkylamino group in which each alkyl moiety has from I to 4 carbon atoms, halogen, nitro or a 5- or 6-membered heterocyclic group.

15. A composition as claimed in Claim 13, wherein the sensitizer has the formula shown in which R1 comprises a 3-coumarinyl group having the formula:

or a pyridinium group having the formula:

R2, R3, R4 and R5 each independently is hydrogen, an alkoxy group having from 1 to 6 carbon atoms, an alkyleneoxy group having from 1 to 6 carbon atoms, an alkylthio group having from 1 to 6 carbon atoms, a dialkylamino group in which each alkyl moiety has from 1 to 4 carbon atoms, hydroxy, halogen, nitro or a 5- or 6-membered heterocyclic group, or two or three of R2, R3, R4 and R5 together with the nuclear carbon atoms to which they are attached form a fused ring or fused ring system, each ring being a 5- or 6-membered ring; and R6 is hydrogen, an alkyl group having from 1 to 4 carbon atoms or an aryl group having from 6 to 12 carbon atoms; R8 is an alkyl group having from I to 4 carbon atoms; and Xe is an anion.

16. A composition as claimed in Claim 14, wherein the sensitizer has the formula shown in which the heterocyclic group is a 3-coumarinyl group having the formula:

wherein R2, R3, R4 and R5 each independently is hydrogen, an alkoxy group having from 1 to 6 carbon atoms, a dialkylamino group in which each alkyl moiety has from 1 to 4 carbon atoms, halogen, nitro or a 5- or 6-membered heterocyclic group.

17. A composition as claimed in any one of Claims 1 to 12, wherein the 3substituted coumarin compound is 3 - benzoyl - 7 - dimethylaminocoumarin.

18. A composition as claimed in any one of Claims 1 to 12, wherein the 3substituted coumarin compound is 3,3' - carbonylbis(7 - diethylaminocoumarin).

19. A composition as claimed in any one of Claims 1 to 12, wherein the 3substituted coumarin compound is 3 - benzoylbenzo[f]coumarin.

20. A composition as claimed in any one of Claims 1 to 12, wherein the 3substituted coumarin compound is 3 - benzoyl - 5,7 - dimethoxycoumarin.

21. A composition as claimed in any one of Claims 1 to 12, wherein the 3substituted coumarin compound is 3 - benzoyl - 7 - methoxycoumarin.

22. A composition as claimed in any one of Claims 1 to 12, 14 and 16 to 21, wherein the material contains from 1 to 11 percent by weight of the sensitizer.

23. A composition as claimed in Claim 13 or 15, wherein the material contains from 1 to 11 percent by weight of the sensitizer.

24. A composition as claimed in any one of Claims 1 to 12, 14 and 16 to 22 containing one or more additional sensitizers.

25. A composition as claimed in any one of Claims 13, 15 and 23 containing the 3-substituted coumarin compound and one or more additional sensitizers.

26. A composition as claimed in any one of Claims 1 to 12 containing as sensitizers 3,3' - carbonylbis(7 - diethylaminocoumarin) and 3 - benzoyl - 7 methoxycoumarin.

27. A composition as claimed in any one of Claims 1 to 12 containing, as sensitizers, 3,3' - carbonylbis(7 - diethylaminocoumarin) and Michler's ketone.

28. A composition as claimed in Claim 1 substantially as hereinbefore described in any one of the embodiments described in any one of Examples 1 to 15.

29. A composition as claimed in Claim 1 substantially as hereinbefore described in any one of the embodiments described in any one of Examples 16 to 20.

30. A photographic element comprising a support having thereon a photosensitive composition as claimed in any one of Claims 1 to 12, 14, 16 to 21 and 28.

31. A photographic element comprising a support having thereon a photosensitive composition as claimed in any one of Claims 22, 24, 26, 27 and 29.

32. A photographic element comprising a support having thereon a photosensitive composition as claimed in any one of Claims 13, 15, 23 and 25.

33. A presensitized lithographic printing plate which comprises a support having a surface coated with a layer of a photosensitive composition comprising an unsaturated photo-cross-linkable polymer and a 3-substituted coumarin compound having an absorption maximum of from 250 to 550 nm.

34. A presensitized plate as claimed in Claim 33, wherein the surface of the support is hydrophilic.

35. A presensitized plate as claimed in Claim 33 or 34, wherein the layer of the photosensitive composition has a thickness of from 0.1 to 2.5 microns.

36. A presensitized plate as claimed in any one of Claims 33 to 35, wherein the support is aluminium.

37. A presensitized plate as claimed in Claim 36, wherein the support is anodized aluminium.

38. A presensitized plate as claimed in Claim 33 substantially as hereinbefore described in any one of the Examples.

39. A method of making a lithographic printing plate which method comprises imagewise exposing a presensitized plate as claimed in any one of Claims 33 to 38 to actinic radiation whereby the polymer in the exposed areas is cross-linked and thereafter removing the polymer composition from the unexposed areas without removing it from the exposed areas.

40. A method as claimed in Claim 39, wherein the actinic radiation is provided by a laser.

41. A method of making a lithographic printing plate as claimed in Claim 39 substantially as hereinbefore described in any one of the Examples.

42. A vesicular material which comprises a support coated with a layer af a heat-deformable, gas-impermeable polymeric binder containing an unsaturated vesiculating agent and a 3-substituted coumarin compound having an absorptive maximum of from 250 to 550 nm.

43. A vesicular material as claimed in Claim 42 substantially as hereinbefore described in Example 13.

44. A method of forming a vesicular image which method comprises imagewise exposing a vesicular material as claimed in Claim 42 or 43 to actinic radiation and heating the material sufficiently to allow the gas liberated by the vesiculating agent to expand within the polymeric binder.

45. A method of forming a vesicular image as claimed in Claim 44 substantially as hereinbefore described in Example 13.