GB1575584A

GB1575584A - Photosensitive compositions

Info

Publication number: GB1575584A
Application number: GB250877A
Authority: GB
Original assignee: Asahi Chemical Industry Co Ltd; Asahi Kasei Kogyo KK
Current assignee: Asahi Kasei Corp; Asahi Chemical Industry Co Ltd
Priority date: 1976-01-24
Filing date: 1977-01-21
Publication date: 1980-09-24
Also published as: JPS5290304A; DE2702708B2; JPS5534930B2; DE2702708A1

Description

(54) PHOTOSENSITIVE COMPOSITIONS (71) We, ASAHI KASEI KOGYO KABUSHIKI KAISHA, a corporation organised under the laws of Japan of 25-1 Dojima-hamadori l-chome, Kita-ku, Osaka, Japan, 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 novel photosenstive compositions. More particularly, it is concerned with photosensitive compositions which are photopolymerizable by the action of actinic light and which are useful in the preparation of relief images, especially relief printing plates for flexographic printing having a superior resistance to solvent-type flexographic inks and superior mechanical properties.

Many prior art references teach various photosensitive compositions useful in the preparation of relief printing plates. The flexographic printing plates obtained from the unsaturated polyester type photosensitive compositions disclosed in, for example, Japanese Patent No. 542,045 have an insufficient resistance to solvent. type flexographic inks containing organic solvents including lower alkyl alcohols such as methyl alcohol, ethyl alcohol and isopropyl alcohol; esters such as ethyl acetate and n-butyl acetate; and ketones such as acetone and methylethyl ketone.

Japanese Patent as Laid Open No. 37521/1972 describes photosensitive compositions containing a specific block copolymer as a binder and the relief printing plates obtained therefrom having a good resistance to alcohol-based, solvent-type flexographic inks. However, these compositions suffer from economic disadvantages in features of their use such as the thickness of the flexographic printing plates, usually from 0.4 mm. to 10 mm; and the printing machines employed. The flexographic printing plates obtained from the photosensitive compositions containing a polyester-polyether block polymer described in British Patent No. 1,425,274 have improved mechanical properties and printing durability but their resistance to solvent-type flexographic inks is not sufficient.

According to this invention, there is provided a liquid photosensitive composition comprising: (I) 100 parts by weight of a prepolymer having terminal ethylenically unsaturated groups and a number average molecular weight of about 2,000 to 30,000 whose main segment is (i) a residue of a hydrogenated 1;2-polybutadiene having an average of about 1.2 to 2.0 terminal hydroxy groups per molecule and a degree of hydrogenation of pendent vinyl groups of the 1,2-addition units of about 50 to 100 percent; (ii) a residue of a chain-extended hydrogenated 1,2-polybutadiene having 2 to 20 urethane bonds obtained by reaction between the hydrogenated 1,2polybutadiene (i) and a diisocyanate; (iii) a residue of a hydrogenated 1,2polybutadiene having terminal carboxyl groups obtained by reaction between the hydrogenated 1,2-polybutadiene (i) and a dicarboxylic acid; or (iv) a residue of a chain-extended hydrogenated 1,2-polybutadiene having terminal carboxyl groups obtained by reaction between a chain-extended hydrogenated 1,2-polybutadiene having terminal hydroxy groups and 2 to 20 urethane bonds prepared by reaction between the hydrogenated 1,2-polybutadiene (i) and a diisocyanate, and a dicarboxylic acid, (II) about 5 to 100 parts by weight of at least one polymerizable ethylenically unsaturated monomeric compound, (III) a photopolymerization initiator in an amount of from about 0.001 to 10 weight percent of the total weight of the prepolymer (I) and the polymerizable ethylenically unsaturated monomeric compound (II), and (IV) a thermal polymerisation inhibitor in an amount of from about 0.001 to 2.0 weight percent of the total weight of the prepolymer (I) and the polymerizable ethylenically unsaturated monomeric compound (II).

The photosensitive compositions according to this invention are liquid and have a suitable viscosity from the view point of processability.

The hydrogenated 1 ,2-polybutadienes which may be employed in the preparation of the prepolymers of this invention are 1,2-polybutadienes in which at least about 50 percent of pendent vinyl groups of the 1,2-addition units are hydrogenated and poly-l-butenes. The hydrogenation ratio greatly affects the mechanical properties of the photopolymerized articles. When a hydrogenated 1,2polybutadiene having a hydrogenation ratio of less than 50 percent is employed, the rubber elasticity of the flexographic printing plates obtained therefrom is reduced and the hardness becomes higher and accordingly a good printing quality cannot be produced.

Also, the hydrogenated 1 ,2-polybutadienes according to this invention have at least 1.2, and preferably 1.5 to 2.0, terminal hydroxy groups as an average per molecule. When the average number of terminal hydroxy groups per molecule is below 1.2, flexographic printing plates having a sufficient mechanical strength cannot be obtained. On the other hand, when the average number of terminal hydroxy groups per molecule increases to 2, the elongation and especially the mechanical strength are further improved.

The hydrogenated 1,2-polybutadienes according to this invention may contain from 0 to about 20 percent of 1,4-addition units.

These hydrogenated 1,2-polybutadienes having at least about 1.2 terminal hydroxy groups may be commericially available polybutadienes or produced by conventional methods. For example, one method comprises subjecting butadiene to anion polymerization, adding ethylene oxide to the terminals of the resulting polybutadiene to give terminal hydroxy groups and subsequently hydrogenating the pendent vinyl groups of the 1,2-addition units. Another method comprises polymerizing butadiene using a metal salt such as NaPdCl4, KPdCl4, NH4PdCl4 or PdBr2 as a polymerization initiator, introducing tydroxy groups onto the terminals of the resulting polybutadiene and hydrogenating the vinyl groups of the 1,2addition units. A further method comprises subjecting l-butene to radical polymerization using a peroxide or azo compound having a hydroxy group such as tert-butyl-P-hydroxyethyl peroxide or 4,4'-azo-bis-4-cyano-n-amyl alcohol to produce poly-l-butenes having terminal hydroxy groups.

The prepolymers having terminal polymerizable ethylenically unsaturated groups which may be employed in this invention include the following five types of prepolymers: The prepolymers (I) may be prepared by effecting a reaction between the hydrogenated 1,2-polybutadienes having terminal hydroxy groups and (a) a carboxylic acid or dicarboxylic acid having 3 to 5 carbon atoms and one ethylenically unsaturated group, or its anhydride or chloride, or the dicarboxylic acid monoester of a lower alkyl alcohol having 1 to 3 carbon atoms.

Exemplary carboxylic acids, dicarboxylic acids, anhydrides, chlorides and monoesters (a) include acrylic acid, methacrylic acid, acrylic anhydride, methacrylic anhydride, acrylic chloride, methacrylic chloride, itaconic anhydride, the monomethyl, monoethyl, mono-n-propyl or monoisopropyl ester of itaconic acid, or the monomethyl, monoethyl, mono-n-propyl or monoisopropyl ester of maleic or fumaric acid.

For this reaction, any conventional method may be employed. For example, the reaction may be carried out in the presence or absence of an esterification catalyst such as p-toluenesulfonic acid or sulfuric acid, and a thermal polymerization inhibitor such as hydroquinone at a temperature of from about 60"C to 1800C in a nitrogen atmosphere.

The prepolymers (II) of this invention may be prepared by effecting a reaction between a chain-extended hydrogenated 1,2-polybutadiene whose terminals are hydroxy groups and (a) a carboxylic acid having 3 to 5 carbon atoms and one ethylenically unsaturated group as employed in the preparation of the prepolymers (I) by any conventional method as in the preparation of the prepolymer (I).

The prepolymers (III) of this invention may be prepared by effecting by conventional methods a reaction between a chain-extended hydrogenated 1,2polybutadiene whose terminals are isocyanates and (b) an alcohol having one to three ethylenically unsaturated groups. For example, the reaction may be carried out at a temperature of from about 50"C to 1200C under a dry air atmosphere in the presence or the absence of a catalyst such as dibutyltin dilaurate, and preferably in the presence of a thermal polymerization inhibitor such as hydroquinone.

Exemplary alcohols (b) include: (i) a compound consisting of

wherein: Rl represents a hydrogen atom or the methyl group, and R2 represents the oxycyclohexylene group, theCH2C(CH3)2CH2Ogroup, the -CH2C(CH2Br)2CH2O- group, an oxyalkylene group of the formula

wherein: R3 represents a hydrogen atom, methyl, monochloromethyl or monobromomethyl; and p represents an integer of 1 to 20 or the -(CH2)qO group wherein q represents an integer of 5 to 20, or (ii) trimethylolpropane diacrylate or dimethacrylate, trimethylolethane diacrylate or dimethyacrylate, glycerine diacrylate or dimethacrylate or pentaerythritol triacrylate or trimethacrylate, or (iii) allyl alcohol, 2-bromoallyl alcohol, 2-chloroallyl alcohol, glycerol diallyether, trimethylolpropane diallylether or allyl vinyl carbinol.

Examples of suitable compounds (i) include 2-hydroxyethyl acrylate or methacrylate, 2-hydroxypropyl acrylate or methacrylate, 3-bromo-2hydroxypropyl acrylate or methacrylate, 3-chloro-2-hydroxypropyl acrylate or methacrylate, 4-hydroxy-n-butyl acrylate or methacrylate, neopentyl glycol monoacrylate or monomethacrylate, dibromoneopentyl glycol monoacrylate or monomethacrylate, 1,6-hexanediol monoacrylate or monomethacrylate, 1,8octanediol monoacrylate or monomethacrylate, 1,9-nonanediol monoacrylate or monomethacrylate, 1,10-decanediol monoacrylate or monomethacrylate, 1,12dodecanediol monoacrylate or monomethacrylate, 1,18-octadecanediol monoacrylate or monomethacrylate, diethylene glycol monoacrylate or monomethacrylate, dipropylene glycol monoacrylate or monomethacrylate, dibutylene glycol monoacrylate or methacrylate, tetraethylene glycol monoacrylate or methacrylate, monoacrylates or methacrylates of polyoxyethylene diols having a number average molecular weight of about 200 to 900, monoacrylates or monomethacrylates of polyoxypropylene diols having a number average molecular weight of about 200 to 1,200, monoacrylates or monomethacrylates of polyoxybutylene diols having a number average molecular weight of about 200 to 1,500, and compounds of the formula:

The prepolymers (IV) may be prepared by effecting a reaction between a hydrogenated 1 ,2-polybutadiene having terminal carboxyl groups obtained by reaction between (i) a hydrogenated 1,2-polybutadiene having terminal hydroxy groups and (ii) a dicarboxylic acid, and (c) a compound having one ethylenically unsaturated group and one oxirane ring.

Exemplary dicarboxylic acids include oxalic acid, malonic acid, succinic acid, succinic anhydride, glutaric acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, cyclopentane 1,3-dicarboxylic acid, cyclohexane 3,6-dicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid and phthalic anhydride.

Exemplary compounds (c) include glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, glycidyl a-ethyl crotonyl glycidyl ether, glycidyl crotonate, monomethyl or monoethyl itaconate monoglycidyl ester and monomethyl or monoethyl fumarate monoglycidyl ester.

For these two reactions, any conventional method may be employed. For example, the esterification may be carried out in the same manner as in the preparation of the prepolymers (I). The reaction with the compound may be carried out at a temperature of from 600C to 1800C in the presence of an epoxy ring opening catalyst such as trimethylbenzyl ammonium hydroxide and a thermal polymerization inhibitor such as hydroquinone under a dry air atmosphere.

The prepolymers (V) may be,prepared by effecting a reaction between a chainextended hydrogenated 1,2-polybutadiene having terminal carboxyl groups obtained by reaction between (i) a chain-extended hydrogenated 1,2-polybutadiene having terminal hydroxy groups and (ii) a dicarboxylic acid as employed in the preparation of the prepolymers (IV), and (c) a compound having one ethylenically unsaturated group and one oxirane ring as employed in the preparation of the prepolymers (IV), by any conventional method as in the preparation of the prepolymer (IV).

The chain-extended hydrogenated 1,2-polybutadienes which are employed in the preparation of the prepolymers (II), (III) and (V) are prepared by reacting a hydrogenated 1,2-polybutadiene with a diisocyanate at a temperature of, generally about 400C to 1200C., and preferably about 50"C. to 1000C. in an inert gas atmosphere such as nitrogen gas in the presence or the absence of a catalyst and in a mole ratio of OH/NCO < 1 or OH/NCO > 1. The catalyst may be, for example, a tertiary amine such as N,N-dimethylbenzylamine, N,N-dimethyllauryl amine or triethylene diamine (diazobicyclooctane), or an organo-heavy-metal compound soluble in the reaction system such as ferrous acetoacetate, dibutyltin dilaurate, dibutyltin di-2-hexoate, stannous oleate or stannous octoate.

When the chain-extending reaction is effected in a mole ratio of OH/NCO < 1, the terminals of the chain-extended hydrogenated 1,2-polybutadienes are isocyanate groups. On the other hand, when the chain-extending reaction is effected in a mole ratio of OH/NCO > 1, the terminals of the chain-extended hydrogenated 1,2-polybutadienes are hydroxy groups.

Exemplary diisocyanates which may be employed in the preparation of the chain-extended hydrogenated 1 ,2-polybutadienes include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hydrogenated 2,4-tolylene diisocyanate, hydrogenated 2,6-tolylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 1,3-dimethylphenyl-2,4-diisocyanate, 1,3-dimethylphenyl-4,6diisocyanate, 1 ,4-dimethyl phenyl-2,5-diisocyanate, 1-chlorophenyl-2,4- diisocyanate, 4,4'-diphenyl diisocyanate, 3,3'-dimethyl-4,4'-diphenyl diisocyanate, 2,4'-diphenyl diisocyanate, 3, 3'-dimethoxy-4,4'-diphenylmethane diisocyanate, 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, l,4-naphthylene diisocyanate, 1,5-naphthylene diisocyanate, 2,6naphthylene diisocyanate, 2,7-naphthylene diisocyanate, p-xylylene diisocyanate m-xylylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,7-heptamethylene diisocyanate, 1,8-octamethylene diisocyanate, 1 ,9-nonamethylene diisocyanate, 1,10decamethylene diisocyanate, 2,2,4-trimethyl-1,5-pentamethylene diisocyanate, 2,2'-dimethyl- 1 ,5-pentamethylene diisocyanate, 3-methoxy- 1 ,6-hexamethylene diisocyanate, 3-butoxy- 1 ,6-hexamethylene diisocyanate, w,w'-dipropylether diisocyanate, 1,4-cyclohexyl diisocyanate, 1,3-cyclohexyl diisocyanate and mixtures of these diisocyanates.

The number average molecular weight of the prepolymer and the total number of urethane bonds which are present in the chain-extended hydrogenated 1,2butadiene affect the properties of photopolymerized articles. According to this invention, the number average molecular weight of the prepolymer is in the range of from about 2,000 to 30,000, and preferably 2,500 to 25,000. When the number average molecular weight is below 2,000, among mechanical properties the rubber elasticity especially of the photopolymerized articles is poor for flexographic printing plates. On the other hand, when the number average molecular weight is above 30,000, the rubber elasticity is superior but the viscosity of the photosensitive composition containing such a prepolymer remarkably increases, and as a result the workability such as the processability and the developability of photosensitive compositions are very much diminished. As the total number of urethane bonds increases, the rubber elasticity of the photopolymerized articles is improved but the solvent resistance tends to diminish. Thus, the total number of the urethane bonds according to this invention is in the range of from 2 to 20 in order to produce flexographic printing plates having a good balance between rubber elasticity and solvent resistance.

Thus, the number average molecular weight of the hydrogenated 1,2polybutadienes which may be employed in this invention is in the range of from about 1,800 to 29,800, and, when chain-extended hydrogenated 1,2-polybutadienes are prepared, the range of the number average molecular weights of the hydrogenated 1,2-polybutadienes is from about 500 to 5,000 and preferably from about 1,000 to 4,000.

Examples of suitable polymerizable, ethylenically unsaturated monomeric compounds include: (I) Compounds of the formula

wherein: R1 represents hydrogen or methyl R5 represents an alkyl group having 1 to 20 carbon atoms, cyclohexyl, an alkoxyalkyl group having at most 15 carbon atoms, a cyanoalkyl group having at most 8 carbon atoms, a tertiary amino alkyl group having at most 18 carbon atoms, a hydrogen atom, an oxyalkylene group of the formula:

wherein: R3 represents a hydrogen atom, methyl, monochloromethyl or monobromemethyl, p represents an integer of 1 to 20, the HCH2)qOH group, wherein q is an integer of 5 to 20, the -CH2C(CH3)2CH2OH group or the -CH2C(CH2B r)2CH2OH group; (2) Compounds of the formula:

wherein: R' represents hydrogen or methyl, R6 and R7 each represent a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, cyclohexyl or benzyl, or R6 is hydrogen and R7 is -R8-OH, where R8 is an alkylene group having 1 to 12 carbon atoms; (3) Compounds of the formula:

wherein: R1 represents a hydrogen or methyl , is an integer of 2 to 4, R9 represents a radical of a polyol having , terminal hydroxy groups and a number average molecular weight of at most 1,000; (4) Compounds of the formula:

wherein: R' and R" each represent hydrogen or methyl, and R'O represents an alkylene group having 1 to 6 carbon atoms; (5) Compounds of the formula:

wherein: R' represents hydrogen or methyl, R12 represents hydrogen, methyl, monochloromethyl or monobromomethyl; (6) Aromatic compounds having at least one CH2=C group and one benzene nucleus; (7) Heterocyclic compounds having one ethylenically unsaturated group; and (8) Other ethylenically unsaturated monomeric compounds.

Exemplary compounds (1) include methyl acrylate or methacrylate, ethyl acrylate or methacrylate, isopropyl acrylate or methacrylate, n-butyl acrylate or methacrylate, n-pentyl acrylate or methacrylate, neopentyl acrylate or methacrylate, dibromoneopentyl acrylate or methacrylate, n-hexyl acrylate or methacrylate, n-octyl acrylate or methacrylate, n-decyl acrylate or methacrylate, isodecyl acrylate or methacrylate, lauryl acrylate or methacrylate, stearyl acrylate or methacrylate, 2-ethylhexyl acrylate or methacrylate, cyclohexyl acrylate or methacrylate, methoxymethyl acrylate or methacrylate, ethoxybutyl acrylate or methacrvlate, 2-methoxypropyl acrylate or methacrylate, n-butoxymethyl acrylate or methacrylate; cyanomethyl acrylate or methacrylate, cyanobutyl acrylate or methacrylate; (N,N-dimethylamino)-methyl acrylate or methacrylate, 2-(N,Ndimethylamino)-ethyl acrylate or methacrylate, 2-(N,N-diethylamino)-ethyl acrylate or methacrylate, 2-(N,N-dibenzylamino)-ethyl acrylate or methacrylate, 2 (N,N-diethylamino)-propyl acrylate or methacrylate; acrylic acid, methacrylic acid, and the same compounds (i) as described above.

Exemplary compounds (2) include acrylamide, methacrylamide, N,N-dimethyl acrylamide or methacrylamide, N,N-diethyl acrylamide or methacrylamide, N,Ndiisopropyl acrylamide or methacrylamide, N,N-dodecyl acrylamide or methacrylamide, N-isopropyl acrylamide or methacrylamide N-cyclohexyl acrylamide or methacrylamide, N-benzyl acrylamide or methacrylamide, Nmethylol acrylamide or methacrylamide, 2-hydroxyethyl acrylamide or methacrylamide, 2-hydroxypropyl acrylamide or methacrylamide, 4-hydroxy-nbutyl acrylamide or methacrylamide and the products obtained by ester-amide exchange reaction between methyl acrylate or methacrylate and an amino-alcohol having at most 12 carbon atoms.

Exemplary compounds (3) include ethyleneglycol di-acrylate or -methacrylate, diethyleneglycol di-acrylate or -methacrylate, triethyleneglycol di-acrylate or -methacrylate, tetraethyleneglycol di-acrylate or -methacrylate, polyethyleneglycol (number average molecular weight: 200 to 1,000) di-acrylate or -methacrylate, propyleneglycol di-acrylate or -methacrylate, dipropylene-glycol di-acrylate or methacrylate, polypropyleneglycol (number average molecular weight: 100 to 1,000) di-acrylate or -methacrylate, butyleneglycol di-acrylate or -methacrylate, trimethylolethane tri-acrylate or -methacrylate, trimethylolpropane tri-acrylate or methacrylate, pentaerythritol tetra-acrylate or -methacrylate, neopentyl glycol diacrylate or -methacrylate, dibromoneopentyl glycol di-acrylate or -methacrylate, 1,8-octanediol di-acrylate or -methacrylate, 1,9-nonanediol di-acrylate or -methacrylate, 1,10-decanediol di-acrylate or -methacrylate, 1,1 2-dodecanediol diacrylate or -methacrylate and 1,18-octadecanediol di-acrylate or -methacrylate, etc.

Exemplary compounds (4) include N,N'-methylene-bisacrylamide, N,N'methylenebis-methacrylamide, N,N'-trimethylenebisacrylamide, N,N'trimethylenebismethacrylamide, N,N'-hexamethylenebisacrylamide and N,N'hexamethylenebismethacrylamide.

Exemplary compounds (5) include 2-acid phosphoxyethyl acrylate or methacrylate, 3-chloro-2-acid phosphoxypropyl acrylate or methacrylate and 3bromo-2-acid phosphoxypropyl acrylate or methacrylate.

Exemplary compounds (6) include styrene, alphamethylstyrene, alphachlorostyrene, p-tert-butylstyrene, p-sec-butylstyrene, aminostyrene, methoxystyrene, vinyltoluene, vinylbenzoic acid, vinylphenol, allylbenzene, allyltoluene, monoallylphthalate, diallylphthalate and divinylbenzene.

Exemplary compounds (7) include N-vinylcarbazole, N-vinylpyrrolidone, 2vinylpyridine, 4-vinylpyridine, vinylquinoline, 2-vinylimidazole, 4-vinylimidazole, 5-vinylimidazole, 2-vinylbenzimidazole, N-vinyltetrazole, 2-vinylpyrazine, 2vinylthiazole, N-vinyloxazolidone, 2-vinylbenzoxazole, 2-vinylfuran, 2isopropenylfuran and 2-vinylthiophene.

Exemplary compounds (8) include vinyl acetate, vinyl propionate, vinyl laurate, methylvinyl benzoate, beta-hydroxyethyl vinyl benzoate, vinyl succinate, vinyl adipate, divinylphthalate, divinylterephthalate, diphenylpropane derivatives such as 2,2' - bis - (4 - methacryloxydiethoxyphenyl) - propane, 2,2' - bis - (4 acryloxydiethoxyphenyl) - propane, 2,2' - bis - (4 - methacryloxyethoxyphenyl) propane and 2,2' - bis - (4 - acryloxyethoxyphenyl) - propane; acrylonitrile; oligoesters having terminal ethylenically unsaturated groups and a number average molecular weight of at most about 1,000 obtained by reacting ethylene glycol, propylene glycol, polyoxyethylene diol having a number average molecular weight of at most about 400 or polyoxypropylene diol having a number average molecular weight of at most about 400 or a mixture thereof with a dicarboxylic acid or its mixture as described in the preparation of the prepolymer (IV), and subsequently reacting the resulting oligoester with a carboxylic acid or dicarboxylic acid as described in the preparation of the prepolymer (I), and the same alcohols (ii) as described above.

Of these compounds, a compound of the formula:

wherein t is an integer of 8 to 20 is especially effective for improving the solvent resistance of photopolymerized articles.

The amount and kind of the polymerizable ethylenically unsaturated monomeric compounds are suitably chosen depending upon the properties of photopolymerized articles in accordance with their use and the processability of the photosensitive compositions containing such monomeric compounds.

Typically, the amount is in the range of from about 5 to 100 parts by weight, and preferably 20 to 70 parts by weight based on 100 parts by weight of the prepolymer.

It is necessary that the reaction of photosensitive compositions should be initiated only by the action of actinic light and that they should be thermally stable.

Therefore, preferably, polymerization initiators are thermally inactive below 40"C and initiate photopolymerization upon irradiation with actinic light.

Exemplary photopolymerization initiators include benzoins such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin n-propyl ether, benzoin isopropyl ether, benzoin n-butyl ether, benzoin isobutyl ether, benzoin sec-butyl ether, benzoin n-amyl ether, benzoin isoamyl ether, alpha-methylbenzoin, alphaethylbenzoin, alphamethyl benzoin methyl ether, alpha-phenylbenzoin, alphaallylbenzoin; anthraquinones such as anthraquinone, chloroanthraquinone, methylanthraquinone, ethylanthraquinone, tertiary butyl-anthraquinone; diketones such as benzil, diacetyl; phenones such as acetophenone, benzophenone, omega-bromoacetophenone; 2-naphthalene sulfonyl chloride; disulfides such as diphenyl disulfide, tetraethylthiuram disulfide; dyes such as Eosine G (C.I. 45380) and Thionine (C.I. 52025); and the like.

These photopolymerization initiators are typically used in an amount of from about 0.001 to 10 weight percent, and preferably from about 0.01 to 5 weight percent of the total weight of the prepolymer and the polymerizable, ethylenically unsaturated monomeric compound.

Known stabilizers (i.e. thermal polymerisation inhibitors) are employed for the purpose of maintaining storage stability (shelf like) of the photosensitive compositions. Such stabilizers may be added when the components of a photosensitive composition are admixed or may be added to each component separately prior to admixing of the components.

Exemplary stabilizers include hydroquinone, monotert-butyl hydroquinone, 2,5-di-tert-butyl hydroquinone, catechol, tert-butyl catechol, 2,6-di-tert-butyl cresol, benzoquinone, 2,5-diphenyl-p-benzoquinone, p-methoxyphenol, picric acid and di-p-fluorophenylamine.

These stabilizers are added only for preventing thermal polymerization without the actinic radiation set forth above without restraining the photopolymerization reaction. Consequently, the amount of the stabilizers may be from about 0.001 to 2.0 percent by weight, and preferably from about 0.005 to 1.0 percent by weight of the total weight of the prepolymer and the polymerizable, ethylenically unsaturated monomeric compound.

Furthermore, various compounds may be incorporated into the photosensitive compositions in order to adjust the viscosity of the photosensitive composition, the mechanical properties and the solvent resistance after photopolymerization in an amount of from about 0.01 to 100 parts by weight based on 100 parts by weight of the photosensitive composition. These compounds include, for example, dioctylphthalate, butylphthalyl butylene glycolate, polyester type plasticizers, epoxy type plasticizers, various phosphates and polyethers such as polypropylene glycol, process oil, liquid paraffin, liquid rubber such as butyl rubber, butadiene rubber, SBR and NBR, depolymerized natural rubber, unsaturated polyester, alkyd resin and unsaturated polyurethane.

The photosensitive compositions of this invention are photopolymerized by actinic radiation having wavelengths of from 2,000 to 8,000 Angstroms. Practical sources of such actinic radiation include carbon arc lamps, super high pressure mercury lamps, high pressure mercury lamps, low pressure mercury lamps, xenon lamps, ultra-violet fluorescent lamps and sunlight.

When the photosensitive compositions of this invention are exposed to actinic light through a process transparency, e.g., a negative or positive films, the areas corresponding to the transparent image portions are photopolymerized in from about 10 seconds to 60 minutes and the non-image areas, i.e., the unexposed areas, remain substantially unphotopolymerized. These non-exposed areas may be washed away with a solvent liquid such as water, an aqueous solution, an aqueous surfactant solution hydrogenation ratio of 950/, ("GI 2000" trade mark, made by Nippon Soda K.K.) were reacted with 22.2 g. of a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate in a weight ratio of 3 to 2 at 600 C. for 3 hours under a nitrogen atmosphere with stirring. Then, to the resulting polymer having terminal isocyanates, there was added a mixture of 12 g. of 2-hydroxyethyl methacrylate, 0.3 g. of hydroquinone and 0.6 g. of dibutyltin dilaurate and the resulting mixture was subjected to reaction at 800 C. for 2 hours to give a prepolymer having a number average molecular weight of about 7,300.

Synthesis 2 320 g. of hydrogenated 1,2-polybutadiene having 1.5 terminal hydroxy groups on average per molecule, a number average molecular weight of 3,200 and a hydrogenation ratio of 91 /n ("GI 3000" trade mark, made by Nippon Soda K.K.) were reacted with 15.1 g. of hexamethylene diisocyanate at 600C. for 4 hours under a nitrogen atmosphere with stirring. Then, to the resulting polymer having terminal isocyanates, there was added a mixture of 7 g. of 2-hydroxypropyl acrylate, 0.3 g. of hydroquinone and 0.6 g. of dibutyltin dilaurate, and the resulting mixture was subjected to reaction at 800 C. for 3 hours to give a prepolymer having a number average molecular weight of about 20,500.

Synthesis 3 In a one litre Parr reactor there was charged 165 ml. of dioxane; 56 g. of 1butene were then introduced therein and polymerization was carried out in the presence of t-butyl-p-hydroxyethyl peroxide at 1200C. for 3 hours. Then resulting polymer was precipitated in methanol, separated and further dissolved in n-hexane, precipitated in methanol and separated to give a poly-1-butene having 1.8 terminal hydroxy groups on average per molecule and a number average molecular weight of about 4,000.

200 g. of this poly-l-butene were reacted with 41.7 g. of a mixture of 2,4tolylene diisocyanate and 2,6-tolylene diisocyanate in a weight ratio of 3 to 2 at 600 C. for 2 hours under a nitrogen atmosphere with stirring. Then, to the resulting polymer having terminal isocyanates there was added a mixture of 46 g. of 2hydroxypropyl methacrylate, 0.1 g. of hydroquinone and 0.05 g. of dibutyltin dilaurate, and the resulting mixture was subjected to reaction at 800 C. for 4 hours to give a prepolymer having a number average molecular weight of about 8,300.

Synthesis 4 215 g. of poly-l-butene having 1.9 terminal hydroxy groups on average per molecule and a number average molecular weight of about 4,300 obtained in the same manner as in Synthesis 3 were mixed with 14.4 g. of diphenylmethane diisocyanate, and the mixture was subjected to reaction at 700 C. for 3 hours under a nitrogen atmosphere with stirring. Then, to the resulting polymer having terminal isocyanate groups there were added 7 g. of 6-hydroxyethyl methacrylate, 0.1 g. of hydroquinone and 0.6 g. of dibutyltin dilaurate, and the resulting mixture was subjected to reaction at 800 C. for 3 hours to give a prepolymer having a number average molecular weight of about 23,000.

Synthesis 5 300 g. of poly-l-butene having 1.8 terminal hydroxy groups on average per molecule and a number average molecular weight of about 1,500 obtained in the same manner as in Synthesis 3 were mixed with 64.8 g. of a mixture of hydrogenated 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate in a weight ratio of 3 to 2, and 0.3 g. of dibutyltin dilaurate was added thereto. The resulting mixture was subjected to reaction at 800 C. for 3 hours under a nitrogen atmosphere with stirring. Then, to the resulting polymer having terminal isocyanate groups, there were added 77.7 g. of 2-hydroxypropyl methacrylate and 0.08 g. of hydroquinone, and the mixture was subjected to reaction at 800 C. for 2 hours to give a prepolymer having a number average molecular weight of about 2,100.

Synthesis 6 220 g. of hydrogenated 1,2-polybutadiene having 1.6 terminal hydroxy groups on average per molecule, a number average molecular weight of 2,200 and a hydrogenated ratio of 97% ("HPBG 2000" trade mark, made by Shin Nippon Rika K.K.), 13.8 g. of methacrylic acid, 0.05 g. of hydroquinone and 0.1 g. of ptoluenesulfonic acid were charged into a one liter flask and stirred. The reaction was carried out at about 800 C. under reduced pressure by introducing dry air into the flask. When the acid value became almost zero, the contents of the flask were taken out from the flask to give about 230 g. of a prepolymer having a number average molecular weight of about 2,300.

Synthesis 7 (A) Preparation of 1,2-polybutadiene Having Terminal Hydroxy Groups In a 1.5 liter flask there were charged 100 g. of tetrahydrofuran and 200 mg. of o-terphenyl, and the mixture was stirred and the air in the flask was replaced with nitrogen gas. Then, a sodium dispersion having an average particle diameter of 8.9 microns obtained by mixing purified kerosene as a dispersing agent, linoleic acid dimer as a dispersion stabilizer and sodium in a concentration of 50% by weight at 110"C. for 30 minutes at a speed of 10,000 r.p.m. was added thereto in an amount of 2 g. based on the sodium content. The dark reddish brown solution thus formed was cooled to -500C. and 2.7 g. of butadiene was introduced over a period of 4 hours to give a dark green solution of butadiene dimer dianion. Then, the temperature of this solution was adjusted to --300C. and 500 g. of butadiene were introduced to give a dark green viscous solution. An excess amount of ethylene oxide was introduced into the resulting solution in 2 minutes while maintaining the reaction temperature of -30"C. to give a polymer having terminal hydroxy groups. After removal of the solvent by distillation under reduced pressure there were obtained 490 g. of 1,2-polybutadiene having 1.7 terminal hydroxy groups on average per molecule and a number average molecular weight of about 27,000.

MnxOHV Average number of terminal hydroxy groups per molecule = 56.1x103 where in=number average molecular weight OHV=hydroxy group value (KOH mg./g.) (B) Hydrogenation of 1,2-polybutadiene Having Terminal Hydroxy Groups 80 parts by weight of 1,2-polybutadiene having terminal hydroxy groups and 20 parts by weight of anhydrous tetrahydrofuran were thoroughly mixed, and one percent by weight, based on the weight of the 1,2-polybutadiene, of stabilized nickel ("Stabilized Nickel N 103", made by Nikki Kagaku K.K.) was added thereto.

Hydrogen was introduced under a pressure of 50 to 60 Kg./cm2. at 1600C. for 4 to 8 hours while restoring the pressure of hydrogen to 50 to 60 Kg./cm2. whenever the pressure decreased to 10 kg./cm2. The hydrogenation was terminated when the decreasing ratio of hydrogen pressure became less than 1 Kg./cm2./30 minutes, and the reaction mixture was cooled to room temperature and tetrahydrofuran was added thereto to yield a 20% polymer solution. Active clay was added to the resulting solution, the mixture was subjected to filtration and the filtrate was distilled firstly at 80 C, under atmospheric pressure and secondly at 120 C. under reduced pressure to give hydrogenated 1,2-polybutadiene having terminal hydroxy groups.

Iodine value of hydrogenated polymer Hydrogenation ratio=# 1- #x100 Iodine value of unhydrogenated polymer Using this hydrogenation method, the 1,2-polybutadiene having terminal hydroxy groups obtained in (A) was hydrogenated to give hydrogenated 1,2polybutadiene having a hydrogenation ratio of 95%.

270 g. of this hydrogenated 1,2-polybutadiene were thoroughly mixed with 1.2 g. of itaconic anhydride, 0.02 g. of p-toluenesulfonic acid and 0.2 g. of hydroquinone, and the mixture thus obtained was subjected to reaction at 130 C. for 3 hours and subsequently at 150 C. for 10 hours with stirring to give a polymer.

Synthesis 8 320 g. of hydrogenated 1,2-polybutadiene having 1.5 terminal hydroxy groups on average per molecule, a number average molecular weight of about 3,200 and a hydrogenated ratio of 91% obtained by hydrogenating 1,2-polybutadiene having 1.5 terminal hydroxy groups on average per molecule and a number average molecular weight of 3,000 ("PBG 3000" trade mark, made by Nippon Soda K.K.) in the same manner as in Synthesis 7(B) were mixed with 8.7 g. of a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate in a weight ratio of 3 to 2, and the resulting mixture was subjected to reaction at 600 C. for 4 hours under a nitrogen atmosphere with stirring to give a prepolymer having terminal hydroxy groups and a number average molecular weight of about 20,000.

200 g. of the resulting polymer were thoroughly mixed with 1.2 g. of itaconic anhydride, 0.02 g. of p-toluenesulfonic acid and 0.2 g. of hydroquinone and the resulting mixture was subjected to reaction at 1300C. for 3 hours and at 1500C. for 10 hours with stirring to give a prepolymer.

Synthesis 9 220 g. of hydrogenated 1,2-polybutadiene having 1.7 terminal hydroxy groups on average per molecule, a number average molecular weight of about 2,200 and a hydrogenation ratio of 95% obtained by hydrogenating 1,2-polybutadiene having 1.7 terminal hydroxy groups on average per molecule and a number average molecular weight of 2,000 ("PBG 2000" trade mark, made by Nippon Soda K.K.) in the same manner as in Synthesis 7(B) were mixed with 22.6 g. of m-phenylene diisocyanate, and the resulting mixture was subjected to reaction at 600 C. for 3 hours under a nitrogen atmosphere with stirring to give 242.6 g. of a polymer having terminal isocyanate groups and a number average molecular weight of about 7,000.

The resulting polymer was further reacted with 12 g. of 2-hydroxyethyl methacrylate in the presence of 0.3 g. of hydroquinone and 0.6 g. of dibutyltin dilaurate at 800 C. for 2 hours to give a prepolymer having a number average molecular weight of about 7,300.

Synthesis 10 (Comparative) 300 g. of 1,2-polybutadiene having 1.6 terminal hydroxy groups on average per molecule and a number average molecular weight of 3,000 ("PBG 3000" trade mark, made by Nippon Soda K.K.) were mixed with 20.9 g. of a mixture of 2,4tolylene diisocyanate and 2,6-tolylene diisocyanate in a weight ratio of 3 to 2, and the resulting mixture was subjected to reaction at 600 C. for 3 hours under a nitrogen atmosphere with stirring. To the resulting polymer having terminal isocyanate groups there was added a mixture of 98 g. of 2-hydroxyethyl methacrylate, 0.3 g. of hydroquinone and 0.6 g. of dibutyltin dilaurate, and the resulting mixture was subjected to reaction at 800 C. for 4 hours to give a prepolymer having a number average molecular weight of about 6,800.

Synthesis 11 220 g. of hydrogenated 1 ,2-polybutadiene having 1.7 terminal hydroxy groups on average per molecule, a number average molecular weight of about 2,200 and a hydrogenation ratio of 43% obtained by hydrogenating 1 ,2-polybutadiene having 1.7 terminal hydroxy groups on average per molecule and a number average molecular weight of 2,000 ("PBG 2000" trade mark, made by Nippon Soda K.K.) in the same manner as in Synthesis 7(B) were mixed with 22.2 g. of a mixture of 2,4tolylene diisocyanate in a weight ratio of 3 to 2, and the resulting mixture was subjected to reaction at 600 C. for 4 hours under a nitrogen atmosphere with stirring to give 242.2 g. of a polymer having terminal isocyanate groups and a number average molecular weight of about 7,000. The resulting polymer was further reacted with 12 g. of 2-hydroxyethyl methacrylate in the presence of 0.3 g. of hydroquinone and 0.6 g. of dibutyltin dilaurate at 800 C. for 2 hours to give a prepolymer having a number average molecular weight of about 7,200.

Synthesis 12 (Comparative) 130 g. of hydrogenated 1 ,2-polybutadiene having 1.9 terminal hydroxy groups on average per molecule, a number average molecular weight of about 1,300 and a hydrogenation ratio of 98% obtained by hydrogenating 1 ,2-polybutadiene having 1.9 terminal hydroxy groups on average per molecule and a number average molecular weight of 1,300 ("PBG 1000" trade mark, made by Nippon Soda K.K.) in the same manner as in Synthesis 7(B) were mixed with 35 g. of a mixture of 2,4tolylene diisocyanate and 2,6-tolylene diisocyanate in a weight ratio of 3 to 2, and the resulting mixture was subjected to reaction at 600 C. for 2 hours under a nitrogen atmosphere with stirring to give 265 g. of a prepolymer having terminal isocyanate groups and a number average molecular weight of about 1,600, The resulting polymer was further reacted with 70 g. of 2-hydroxyethyl methacrylate in the presence of 0.3 g. of hydroquinone and 0.6 g. of dibutyltin dilaurate at 800 C. for 3 hours to give 335 g. of a prepolymer having a number average molecular weight of about 1,900.

Synthesis 13 220 g. of the same hydrogenated 1,2-polybutadiene as in Synthesis 9 were mixed with 22.2 g. of a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate in a weight ratio of 3 to 2, and the resulting mixture was subjected to reaction at 600 C. for 3 hours under a nitrogen atmosphere with stirring to give 242.2 g. of a polymer having terminal isocyanate groups and a number average molecular weight of about 7,000. The resulting polymer was further reacted with 12 g. of 2-hydroxyethyl methacrylate in the presence of 0.3 g. of hydroquinone and 0.6 g. of dibutyltin dilaurate at 800 C. for 2 hours to give a prepolymer having a number average molecular weight of about 7,300.

Synthesis 14 220 g. of the same hydrogenated 1,2-polybutadiene was in Synthesis 9 were mixed with 37.6 g. of 3,3'-dimethyldiphenylmethane diisocyanate, and the resulting mixture was subjected to reaction at 600 C. for 5 hours under a nitrogen atmosphere with stirring to give 257.6 g. of a polymer having terminal isocyanate groups and a number average molecular weight of about 10,000. The resulting polymer was further reacted with 12 g. of 2-hydroxyethyl methacrylate in the presence of 0.3 g. of hydroquinone and 0.6 g. of dibutyltin dilaurate at 800 C. for 2 hours to give a prepolymer having a number average molecular weight of about 10,200.

Synthesis 15 320 g. of the same hydrogenated 1,2-polybutadiene as in Synthesis 8 were mixed with 15.1 g. of hexamethylene diisocyanate, and the mixture was subjected to reaction at 600 C. for 4 hours under a nitrogen atmosphere with stirring to give 335.1 g. of a polymer having terminal isocyanate groups and a number average molecular weight of about 17,000. The resulting polymer was further reacted with 7 g. of 2-hydroxypropyl acrylate in the presence of 0.3 g. of hydroquinone and 0.6 g. of dibutyltin dilaurate at 800 C. for 3 hours to give a prepolymer having a number average molecular weight of about 17,600.

Synthesis 16 (Comparative) 320 g. of the same hydrogenated 1,2-polybutadiene as in Synthesis 8 were mixed with 14.4 g. of a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate in a weight ratio of 3 to 2, and the resulting mixture was subjected to reaction at 600 C. for 6 hours under a nitrogen atmosphere with stirring to give 334.4 g. of a polymer having terminal isocyanate groups and a number average molecular weight of about 34,000. The resulting polymer was further reacted with 4 g. of 2-hydroxypropyl acrylate in the presence of 0.3 g. of hydroquinone and 0.6 g. of dibutyltin dilaurate at 800 C. for 3 hours to give a prepolymer having a number average molecular weight of about 34,400.

Synthesis 17 The same procedure as in Synthesis 7(A) was repeated except that 800 g. of butadiene were employed instead of 500 g. of butadiene, and there were obtained 770 g. of 1,2-polybutadiene having 1.5 terminal hydroxy groups on average per molecule and a number average molecular weight of about 43,000.

This I ,2-polybutadiene was hydrogenated in the same manner as in Synthesis 7(B) to give hydrogenated 1,2-polybutadiene having a hydrogenation ratio of 95%.

430 g. of this hydrogenated 1,2-polybutadiene were thoroughly mixed with 1.2 g. of itaconic anhydride, 0.02 g. of dibutyltin dilaurate and 0.2 g. of hydroquinone, and the resulting mixture was subjected to reaction at 1300C. for 3 hours and subsequently at 1500C. for 10 hours with stirring to give a prepolymer.

Synthesis 18 (Comparative) 320 g. of the same hydrogenated 1 ,2-polybutadiene as in Synthesis 8 were mixed with 263 g. of hydrogenated 1,2-polybutadiene having a number average molecular weight of about 3,000 and a hydrogenation ratio of 91% obtained by hydrogenating, 1,2-polybutadiene having no terminal hydroxy groups ("PB .3000" trade mark, made by Nippon Soda K.K.) in the same manner as in Example 7(B) to give 583 g. of hydrogenated 1,2-polybutadiene having 0.8 terminal hydroxy group on average per molecule. The resulting hydrogenated 1,2-polybutadiene were mixed with 15.1 g. of hexamethylene diisocyanate, and the mixture was subjected to reaction at 600 C. for 4 hours under a nitrogen atmosphere with stirring to give 598 g. of a polymer having terminal isocyanate groups and a number average molecular weight of about 12,500. The resulting polymer was further reacted with 7 g. of 2-hydroxypropyl acrylate in the presence of 0.3 g. of hydroquinone and 0.6 g. of dibutyltin dilaurate at 800 C. for 3 hours to give a prepolymer having a number average molecular weight of 12,700.

Synthesis 19 290 g. of hydrogenated 1,2-polybutadiene having 1.5 terminal hydroxy groups on average per molecule, a number average molecular weight of 2,900 and a hydrogenation ratio of 95% ("HPBG 3000" trade mark, made by Shin Nippon Rika K.K.) were reacted with 15 g. of succinic anhydride at 1000C. under reduced pressure, and the reaction was continued until the acid value became constant at about 27.6 to give a hydrogenated 1 ,2-polybutadiene having terminal carboxyl groups. 152 g. of the resulting hydrogenated 1,2-polybutadiene were reacted with 10.7 g. of glycidyl methacrylate in the presence of 1 g. of trimethylbenzyl ammonium hydroxide at 800 C. until the acid value became almost zero and there was obtained a prepolymer having a number average molecular weight of about 3,250.

Synthesis 20 190 g. of hydrogenated 1,2-polybutadiene having 1.8 terminal hydroxy groups on average per molecule, a number average molecular weight of 1,900 and a hydrogenation ratio of 97% ("HPBG 2000" trade mark, made by Shin Nippon Rika K.K.) were reacted with 13 g. of a mixture of 2,4-tolylene diisocyanate and 2,6tolylene diisocyanate in a weight ratio of 3 to 2 at 700 C. under a nitrogen atmosphere with stirring until the specific absorptions due to the isocyanate group on an infra red chart disappeared. Then, the reaction solution was cooled to room temperature and 4.5 g. of phthalic anhydride were added thereto and the temperature of the mixture was raised to 1000 C. to carry out the reaction.

Subsequently, to the resulting reaction solution there were added 3.5 g. of allyl glycidyl ether, 1 g. of trimethylbenzyl ammonium hydroxide and 0.2 g. of hydroquinone, and the mixture was subjected to reaction at 1200C. to give a prepolymer having a number average molecular weight of about 12,000.

The invention is illustrated by the following examples.

EXAMPLE 1 Preparation of Photopolymerized Articles 100 g. of the prepolymer in Synthesis 1, a variety of ethylenically unsaturated compounds set forth in Table 1, hydroquinone and a photopolymerization initiator set forth in Table 1 were thoroughly mixed to give uniform photosensitive compositions.

On a transparent glass sheet, 5 mm. in thickness, there was placed a spacer, 1 mm. in thickness and then each of the photosensitive compositions was charged thereto, and then a transparent glass sheet, 5 mm. in thickness, was placed on the spacer. The resulting assembly was exposed for 20 minutes to a 300 W. highpressure mercury lamp set at a distance of 35 cm. from one side of the glass sheets and subsequently the two glass sheets were removed. The properties of the photopolymerized article were measured and the results are shown in Table 1 below.

Preparation of Flexographic Printing Plate and Printing Using the Prepared Plate On a transparent glass sheet, 10 mm. in thickness, there was placed a negative film and the negative film was covered with a polyester film, 9 microns in thickness, and a spacer, 2 mm. in thickness, was placed thereon. Then, each of the same photosensitive compositions was charged thereto and a polyester film, 100 microns in thickness, was laminated to the layer of the photosensitive composition and a transparent glass sheet, 5 mm. in thickness, was placed thereon. The resulting assembly was exposed to a 500 W. high-pressure mercury lamp set at a distance of about 30 cm. from each of the glass sheets at room temperature, first from the upper glass sheet for about 1 minute, and second from the glass sheet of the negative film side for 5 minutes. After exposure, the two glass sheets and the polyester film covering the negative film were removed and the photopolymerized layer on the polyester base film was washed with a 2% aqueous surfactant solution ("Lipponox" trade mark, non-ion type,

made by Lion Fat & Oil Co., Ltd.) and dried to produce a printing plate for flexographic printing having a relief height of 0.8 mm. and a resolution of 133 lines per inch. Using this printing plate, a rotary printing was run on polyester film and high-density polyethylene film, respectively with an alcoholic flexographic ink comprising 93% by weight of isopropyl alcohol and 7% by weight of toluene. At least 500,000 clear and precise prints were obtained without any damage of the relief image and without any enlargement of letters. Furthermore, the same procedure of preparing flexographic printing plates using the same photosensitive compositions as described above was repeated except that the thickness of the printing plate was changed to 3 mm. and the relief height was changed to 1.0 mm.

Using each of the printing plates a paperback printing was run with an alcoholic flexographic ink containing about 10 percent by weight of ethyl acetate, and at least 500,000 clear and precise prints were obtained without observing any damage to the relief image and any enlargement of letters and fine lines.

EXAMPLE 2 Each of the photosensitive compositions set forth in Table 2 was photopolymerized in the same manner as in Example 1 to give photopolymerized articles. The properties of the articles are shown in Table 2 below. Also using the same photosensitive compositions, flexographic printing plates were prepared and rotary printings and paperback printings were run using the resulting printing plates in the same manner as in Example 1 to give at least 500,000 clear and precise prints without observing any deformation of the relief image and any enlargement of letters.

EXAMPLE 3 100 g of each of the prepolymers obtained in Syntheses 7 to 9, 37 g. of lauryl methacrylate, 8 g. of 1,3-butyleneglycol dimethacrylate, 5 g. of polypropyleneglycol dimethacrylate having a number average molecular weight of 676, 0.225 g. of hydroquinone and 4.5 g. of benzoin n-butyl ether were thoroughly mixed to give uniform photosensitive compositions. Each of the resulting photosensitive compositions was photopolymerized in the same manner as in Example I to give photopolymerized articles. The properties of the articles are shown in Table 3 below.

EXAMPLE 4 (Comparative) 100 g. of each of the prepolymers obtained in Syntheses 10 and 11, 30 g. of lauryl methacrylate, 20 g. of polypropyleneglycol dimethacrylate having a number average molecular weight of 676, 0.15 g. of hydroquinone and 3 g. of benzoin methyl ether were thoroughly mixed to give uniform photosensitive compositions.

Each of the resulting photosensitive compositions was photopolymerized in the same manner as in Example I to give photopolymerized articles. The properties of the articles are shown in Table 4 below. Also using the same photosensitive compositions, flexographic printing plates were prepared and rotary printings were run using the resulting printing plates in the same manner as in Example 1. The results are shown in Table 4 below, together with the results of Example 1, Run No.

1.

EXAMPLE 5 100 g. of each of the prepolymers obtained in Syntheses 12 to 17, 30 g. of lauryl methacrylate, 8 g. of 1,3-butylene glycol dimethacrylate, 5 g. of polypropyleneglycol dimethacrylate having a number average molecular weight of 676, 0.2 g. of hydroquinone and 4.0 g. of benzoin methyl ether were thoroughly mixed to give uniform photosensitive compositions. Each of the resulting photosensitive compositions was . photopolymerized in the same manner as in Example 1 to give photopolymerized articles. The properties of the articles are shown in Table 5 below. Also using the same photosensitive compositions, flexographic printing plates were prepared and rotary printings were run using the resulting printing plates in the same manner as in Example 1. The results are shown in Table 5.

EXAMPLE 6 100 g. of each of the prepolymers obtained in Syntheses 18, 2 and 1, 30 g. of lauryl methacrylate, 8 g. of 1,3-butylene glycol dimethacrylate, 5 g. of polypropyleneglycol dimethacrylate having a number average molecular weight of 676, 0.27 g. of hydroquinone and 4.3 g. of benzoin methyl ether were thoroughly mixed to give uniform photosensitive compositions. Each of the resulting photosensitive compositions was photopolymerized in the same manner as in Example 1 to give.photopolymerized articles. The properties of the articles are shown in Table 6. Also using the same photosensitive compositions, flexographic printing plates were prepared and rotary printings were run using the resulting printing plates in the same manner as in Example 1. The results are shown in Table 6 below.

EXAMPLE 7 100 g. of the prepolymer obtained in Synthesis 1, 8 g. of 1,3-butyleneglycol dimethacrylate, 5 g. of polypropyleneglycol dimethacrylate having a number average molecular weight of 676, 30 g. of another polymerizable, ethylenically unsaturated monomer set forth in Table 7 below, 0.15 g. of hydroquinone and 3 g. of benzoin methyl ether were thoroughly mixed to give uniform photosensitive compositions. Each of the resulting photosensitive compositions was photopolymerized in the same manner as in Example 1 to give photopolymerized articles. The properties of the articles are shown in Table 7 below.

EXAMPLE 8 100 g. of the prepolymer obtained in Synthesis 1, 30 g. of lauryl methacrylate, 5 g. of polypropyleneglycol dimethacrylate having a number average molecular weight of 676, 8 g. of another ethylenically unsaturated monomer set forth in Table 8 below, 0.15 g. of hydroquinone and 3 g. of benzoin methyl ether were thoroughly mixed to give uniform photosensitive compositions. Each of the resulting photosensitive compositions was photopolymerized in the same manner as in Example 1 to give photopolymerized articles. The properties of the articles are shown in Table 8.

EXAMPLE 9 100 g. of the prepolymer obtained in Synthesis 19, 40 g. of lauryl methacrylate, 10 g. of 1,3-butylene glycol dimethacrylate, 20 g. of 2,2'-bis-(4methacryloxyethoxyphenyl)-propane, 0.1 g. of hydroquinone and 3 g. of benzoin isobutyl ether were thoroughly mixed to give a uniform photosensitive composition. The resulting photosensitive composition was photopolymerized in the same manner as in Example 1 to give a photopolymerized EXAMPLE 10 100 g. of the prepolymer obtained in Synthesis 20, 20 g. of lauryl methacrylate, 10 g. of stearyl methacrylate, 5 g. of N-vinylcarbazole, 15 g. of 2,2' - bis - (4 methacryloxydiethoxyphenyl) - propane, 0.15 g. of hydroquinone and 2.5 g. of benzoin isopropyl ether were thoroughly mixed to give a uniform photosensitive composition. The resulting photosensitive composition was photopolymerized in the same manner as in Example 1 to give a photopolymerized article. The properties of the article are as follows: Shore hardness A 50 Tensile strength 65 Kg./cm2.

Elongation 150% Swellability 9% (Isopropyl alcohol) EXAMPLE 11 (Comparative) 600 g. of 1 4-polybutadiene having 2.0 terminal hydroxy groups on average per molecule and a number average molecular weight of 3,000 ("R-45M", trade mark, made by Arco Corp.) were mixed with 42 g. of a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate in a weight ratio of 3 to 2, and the resulting mixture was subjected to reaction at 400 C. for 2 hours under a nitrogen atmosphere with stirring. Then, to the resulting polymer having terminal isocyanate groups there were added simultaneously 20 g. of 2-hydroxyethyl methacrylate, 0.3 g. of hydroquinone and 0.2 g. of dibutyltin dilaurate, and the resulting mixture was subjected to reaction at 850C. for 4 hours to give a prepolymer having a number average molecular weight of about 16,300.

100 g. of this prepolymer, 20 g. of n-decyl methacrylate, 3 g. of benzoin npropyl ether and 0.15 g. of hydroquinone were thoroughly mixed to give a uniform photosensitive composition. The resulting photosensitive composition was photopolymerized in the same manner as in Example I to give a photopolymerized article. The properties of the article are as follows: Shore hardness A 76 Tensile strength 72 Kg./cm2.

Elongation 61% Swellability 18% (Isopropyl alcohol) Also using the same photosensitive composition, a flexographic printing plate was prepared in the same manner as in Example 1 and a paperback printing was run using this printing plate with an alcoholic flexographic ink. Enlargement of letters was observed soon after the printing was initiated, and around about 2,000 prints part of the relief image of the printing plate was broken off due to a lowering in mechanical strength caused by swelling.

EXAMPLE 12 (Comparative) 320 g. of butadiene-acrylonitrile copolymer having 1.8 terminal carboxyl groups on average per molecule and a number average molecular weight of 3,200 ("Hycar CTBN" trade mark, made by B. F. Goodrich Co.) 56 g. - of glycidyl methacrylate, 1.4 g. of trimethylbenzyl ammonium hydroxide and 0.3 g. of hydroquinone were mixed, and the resulting mixture was subjected to reaction at 80"C. for 8 hours with stirring to give a prepolymer. 100 g. of this prepolymer, 30 g. of lauryl methacrylate, 20 g. of diethyleneglycol dimethacrylate, 3 g. of benzoin methyl ether and 0.15 g. of hydroquinone were thoroughly mixed to give a uniform photosensitive composition. The resulting photosensitive composition was photopolymerized in the same manner as in Example 1 to give a Photopolemerized article. The properties of the article are as follows: Shore hardness A 55 Tensile strength 15 Kg./cm2.

Elongation 100% Swellability Isopropyl alcohol 20% Ethyl acetate 121% Also using the same photosensitive composition, a flexographic printing plate was prepared in the same manner as in Example 1. The mechanical strength of the resulting plate was poor and the printing durability was lower than that of Example 1, Run No. 1. Also this printing plate was not suitable for a printing using a solventtype flexographic printing ink as in Example 11.

In the following tables which set out the results of the test on the photopolymerized articles of Examples 1 to 8 as well as in Examples 9 to 12, the properties were measured as follows: Tensile strength: JIS K6301.3 Elongation: JIS K6301.3 Shore hardness A: Durometer Type A Measuring temperature: 200C Sample: 1 mm. (thick)x10 mm. (broad)xlO mm. (long) Five of the same samples were superimposed and subjected to measurement.

Swellability%: Increase in weight (%) after immersing the photopolymerized articles in isopropyl alcohol or ethyl acetate at 200C for 24 hours.

TABLE 1 Properties of photopolymerized article Inhibitor Swellability Polymerizable ethylenically (Hydro- Photo- Shore Tensile (Isopropyl Run unsaturated compound quinone) initiator hardness strength Elongation alcohol) No. (g.) (g.) (g.) A (Kg./cm2.) (%) (%) 1 Lauryl methacrylate 30 0.15 Benzoin polypropyleneglycol di- isoamyl 56 55 150 5 methacrylate (Mn=676) 20 ether 3 2 Lauryl methacrylate 37 0.24 Benzoin polypropyleneglycol di- n-butyl 50 55 130 3 methacrylate (M=676) 5 ether 1,3-Butyleneglycol di- 4.8 methacrylate 8 Naphthene process oil 10 3 Lauryl methacrylate 30 0.24 Benzoin 54 58 212 8 Trimethylolethane tri- n-butyl methacrylate 5 ether 2,2'-Bis(4-methacryloxy 4.8 diethoxyphenyl)propane 15 4 n-Decyl methacrylate 40 0.23 Benzoin 56 60 120 4 1,9-Nonanediol di- n-butyl methacrylate 10 ether 4.5 5 Polypropyleneglycol mono- 40 0.25 Benzoin 65 68 140 6 methacrylate (Mn=380) n-butyl Trimethylolpropane tri- ether methacrylate 10 4.5 TABLE 2 Prepolymer Photosensitive composition Properties of photopolymerized article (100 g.) Inhibitor Swellability Syn- Polymerizable ethylenically Hydro- Photo Shore Tensile (Isopropyl thesis unsaturated monomer quinone) tiator hardness strength Elongation alcohol) No. (g.) (g.) (g.) A (Kg./cm2.) (%) (%) 2 Stearyl methacrylate 30 0.15 Benzoin 50 60 140 4 Neopentylglycol di- methyl methacrylate 20 ether 3 3 n-Nonyl methacrylate 30 0.15 Benzoin 60 70 150 8 Stearyl methacrylate 10 n-butyl 1,3-Butyleneglycol di- ether methacrylate 10 3 4 Lauryl methacrylate 30 0.15 Benzoin 48 60 150 2 Polypropyleneglycol isopropyl dimethacrylate (Mn=676) 20 ether 3 5 n-Octyl methacrylate 50 0.155 Benzoin 55 62 120 6 Trimethylolpropane n-butyl trimethacrylate 5 ether 3.1 6 Lauryl methacrylate 30 0.15 Benzoin 58 50 140 8 Polypropyleneglycol sec-butyl dimethacrylate(Mn=676) 10 ether 2,2'-Bis(4-methacryloxy- 3 ethoxyphenyl)propane 10 TABLE 3 Properties of polymerized article Swellability Shore Tensile (Isopropyl Run hardness strength Elongation alcohol) No. Prepolymer A (Kg/cm2.) (%) (%) 1 Synthesis 7 42 50 150 3 2 Synthesis 8 45 58 160 5 3 Synthesis 9 52 57 135 4 TABLE 4 Properties of Photopolymerized Article Prepolymer Swellability Durability of hydrogenation Shore Tensile Isopropyl Ethyl printing plate Run ratio Photo- hardness strength Elongation alcohol acetate (number of prints) No. (%) initiator A (Kg./cm2.) (%) (%) (%) 100,000 200,000 500,000 1 Synthesis 10 Benzoin 85 58 53 6 30 C (Comparative) Methyl0 ether 2 Synthesis 11 Benzoin 78 53 60 8 28 C (Comparative) methyl43 ether Example 1 Synthesis 1 Benzoin 56 55 150 5 23 A 95 isoamyl Run No. 1 ether A: At least 500,000 clear and precise prints were obtained without any damage of the relief image.

C: Before obtaining 100,000 prints parts of the relief image were broken off due to lowness in elongation and highness in hardness.

TABLE 5 Properties of Photopolymerized Article Swellability Durability of Shore Tensile Isopropyl Ethyl printing plate Run hardness strength Elongation alcohol acetate (number of prints) No. Prepolymer(Mn) A (Kg./cm2.) (%) (%) (%) 100,000 200,000 500,000 1 Synthesis 12 about 75 110 90 6 65 B (Comparative) 1,900 2 Synthesis 13 about 50 55 130 3 36 A 7,300 3 Synthesis 14 about 55 60 180 3 35 A 10,200 4 Synthesis 15 about 46 65 205 5 30 A 17,600 5 Synthesis 16 about 42 62 210 4 25 - - (Comparative) 34,400 6 Synthesis 12 about 38 40 180 3 18 - - (Comparative) 43,300 A: The same as defined in Table 4.

B: Before obtaining 200,000 prints parts of the relief image were broken off.

-: The viscosity of the photosensitive composition was too high to produce a printing plate in the same method as in Example 1.

TABLE 6 Properties of Photopolymerized Article Swellability Durability of Prepolymer Shore Tensile Isopropyl Ethyl printing plate Run (Average number of hardness strength Elongation alcohol acetate (number of prints) No. terminal hydroxy group) A (Kg./cm2.) (%) (%) (%) 100,000 200,000 500,000 1 Synthesis 18 45 32 100 12 52 B (Comparative) 0.8 2 Synthesis 2 52 64 130 4 25 A 1.5 3 Synthesis 1 54 60 140 5 23 A 1.7 A: The same as defined in Table 4.

B: The same as defined in Table 5.

TABLE 7 Properties of Photopolymerized Article Swellability Another Shore Tensile (Isopropyl Run polymerizable ethylenically hardness strength Elongation alcohol) No. unsaturated monomer A (Kg/cm2.) (%) (%) 2-Ethylhexyl methacrylate 57 60 140 4 2 Stearyl methacrylate 50 54 170 4 3 1,8-Octanediol monomethacrylate 59 64 120 6 4 1,18-Octadecanediol monomethacrylate 53 58 163 5 TABLE 8 Properties of Photopolymerized Articlc Another Swellability polymerizable ethylenically Shore Tensile (Isopropyl Run unsaturated monomer hardness strength Elongation alcohol) No. (g.) A (Kg./cm2.) (%) (%) 2,2'-Bis(4-methacryloxy- 52 60 160 2 diethoxyphenyl)-propane 60 73 130 3 2 N-Vinylcarbazole 3 Oligoester having terminal 50 60 170 4 ethylenically unsaturated groups* * Obtained by reacting a 1:1 weight mixture of ethyleneglycol and propyleneglycol with a 4:1 weight mixture of adipic acid and isophthalic acid in a weight ratio of 11 to 10 and subsequently esterifying the resulting oligoester with methacrylic acid.

Claims

WHAT WE CLAIM IS:

1. A liquid photosensitive composition comprising: (I) 100 parts by weight of a prepolymer having terminal ethylenically unsaturated groups and a number average molecular weight of about 2,000 to 30,000 whose main segment is (i) a residue of a hydrogenated 1,2-polybutadiene having about 1.2 to 2.0 terminal hydroxyl groups on average per molecule and a degree of hydrogenation of pendent vinyl groups of the 1,2-addition units of about 50 to 100 percent, (ii) a residue of a chain-extended, hydrogenated 1,2polybutadiene having 2 to 20 urethane bonds obtained by reaction between the hydrogenated 1 ,2-polybutadiene (i) and a diisocyanate, (iii) a residue of a hydrogenated 1,2-polybutadiene having terminal carboxyl groups obtained by reaction between the hydrogenated 1,2-polybutadiene (i) and a dicarboxylic acid, or (iv) a residue of a chain-extended, hydrogenated 1,2-polybutadiene having terminal carboxyl groups obtained by reaction between a chain-extended hydrogenated 1,2-polybutadiene having terminal hydroxy groups and 2 to 20 urethane bonds having been prepared by reaction between the hydrogenated 1,2- polybutadiene (i) and a diisocyanate, and a dicarboxylic acid, (II) about 5 to 100 parts by weight of at least one polymerizable ethylenically unsaturated monomeric compound, (III) a photopolymerization initiator in an amount of from about 0.001 to 10 weight percent of the total weight of the prepolymer (I) and the polymerizable ethylenically unsaturated monomeric compound (II), and (IV) a thermal polymerisation inhibitor in an amount of from about 0.001 to 2.0 weight percent of the total weight of the prepolymer (I) and the polymerizable ethylenically unsaturated monomeric compound (II).

2. A photosensitive composition as claimed in claim 1, wherein the terminal ethylenically unsaturated group is a residue of a carboxylic acid or dicarboxylic acid having three to five carbon atoms and one ethylenically unsaturated group, its anhydride, its chloride or the dicarboxylic acid monoester of a lower alkyl alcohol having one to three carbon atoms.

3. A photosensitive composition as claimed in claim 2, wherein the carboxylic acid is methacrylic acid.

4. A photosensitive composition as claimed in claim 2, wherein the anhydride is itaconic anhydride.

5. A photosensitive composition as claimed in claim 1, wherein the terminal ethylenically unsaturated group is a residue ofcan alcohol having one to three ethylenically unsaturated groups and consisting of: (i) a compound of the formula

wherein: R1 represents a hydrogen atom or methyl group, R2 represents the oxycyclohexylene group, -CH2C(CH3)2CH2O- group, -CH2C(CH2Br)2CH2O- group, an oxyalkylene group of the formula

or -(CH2)4-O-] C- wherein: R3 represents a hydrogen atom, methyl, monochloromethyl or monobromomethyl group; p represents an integer of 1 to 20 or a CH2)qO group wherein q represents an integer of 5 to 20; (ii) trimethylolpropane di-acrylate or -methacrylate, trimethylolethane diacrylate or -methacrylate, glycerine di-acrylate or -methacrylate or pentaerythritol tri-acrylate or -methacrylate, or (iii) allyl alcohol, 2-bromoallyl alcohol, 2-chloroallyl alcohol, glycerol diallyether, trimethylolpropane diallylether or allyl vinyl carbinol.

6. A photosensitive composition as claimed in claim 5, wherein the compound (i) consists of 2-hydroxyethyl acrylate or methacrylate, 2-hydroxypropyl acrylate or methacrylate, 3-bromo-2-hydroxylpropyl acrylate or methacrylate, 3-chloro-2hydroxypropyl acrylate or methacrylate 4-hydroxy-n-butyl acrylate or methacrylate, neopentyl glycol monoacrylate or monomethacrylate- dibromoneopentyl glycol monoacrylate or monomethacrylate, 1,6-hexanediol monoacrylate or monomethacrylate, 1,8-octanediol monoacrylate or monomethacrylate, 1,9-nonanediol monoacrylate or monomethacrylate, 1, 10-decanediol monoacrylate or monomethacrylate, 1,12-dodecanediol monoacrylate or monomethacrylate, 1,18-octadecanediol monoacrylate or monomethacrylate, diethylene glycol monomethacrylate, dipropylene glycol monoacrylate or monomethacrylate, dibutylene glycol monoacrylate or methacrylate, tetraethylene glycol monoacrylate or methacrylate, monoacrylates or methacrylates of polyoxyethylene diols having a number average molecular weight of from about 200 to 900, a monoacrylate or monomethacrylate of a polyoxypropylene diol having a number average molecular weight of about 300 to 1,200 or a monoacrylate or monomethacrylate of a polyoxybutylene diol having a number average molecular weight of from about 200 to 1,500, or a compound of the formula:

7. A photosensitive composition as claimed in claim 6, wherein the compound (i) is 2-hydroxyethyl methacrylate.

8. A photosensitive composition as claimed in claim 6, wherein the compound (i) is 2-hydroxypropyl acrylate.

9. A photosensitive composition as claimed in claim 6, wherein the compound (i) is 2-hydroxypropyl methacrylate.

10. A photosensitive composition as claimed in claim 1, wherein the terminal ethylenically unsaturated group is a residue of a compound having one ethylenically unsaturated group and one oxirane ring.

11. A photosensitive composition as claimed in claim 10, wherein the compound having one ethylenically, unsaturated group and one oxirane ring consists of glycidyl acrylate, glycidyl methacrylate, glycidyl a-ethyl acrylate or allyl glycidyl ether.

12. A photosensitive composition as claimed in claim 1, wherein the hydrogenated 1,2-polybutadiene has 1.5 to 2.0 terminal hydroxyl groups on average per molecule.

13. A photosensitive composition as claimed in claim 1, wherein the hydrogenated 1,2-polybutadiene contains from 0 to about 20 percent. of 1,4addition units.

14. A photosensitive composition as claimed in claim 1, wherein the hydrogenated 1,2-polybutadiene is poly-l-butene having from about 1.2 to 2 terminal hydroxy groups on average per molecule.

15. A photosensitive composition as claimed in claim 1, wherein the diisocyanate consists of 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, hydrogenated 2,4-tolylene diisocyanate, hydrogenated 2,6-tolylene diisocyanate, a mixture of hydrogenated 2,4-tolylene diisocyanate and hydrogenated 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hydrogenated 4,4'diphenylmethane diisocyanate, m-xylylene diisocyanate, 1,6-hexamethylene diisocyanate, m-phenylene diisocyanate or 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate.

16. A photosensitive composition as claimed in claim 1, wherein the dicarboxylic acid consists of oxalic acid, malonic acid, succinic acid, succinic anhydride, glutaric acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, cyclopentane 1,3-dicarboxylic acid, cyclohexane 3,6-dicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid or phthalic anhydride.

17. A photosensitive composition as claimed in claim 1, wherein the prepolymer is a polymer obtained by reaction between (1) methacrylic acid or itaconic anhydride and (2) a hydrogenated 1 ,2-polybutadiene having from about 1.2 to 2.0 terminal hydroxy groups on average per molecule and a hydrogenation ratio of pendent vinyl groups of the 1,2-addition units of 50 to 100 percent or a poly-lbutene having about 1.2 to 2.0 terminal hydroxy groups on average per molecule.

18. A photosensitive composition as claimed in claim 1, wherein the prepolymer is a polymer obtained by reaction between (1) methacrylic acid or itaconic anhydride and (2) a chain-extended hydrogenated 1 ,2-polybutadiene having terminal hydroxy groups and 2 to 20 urethane bonds or a chain-extended poly-l-butene having terminal hydroxy groups and 2 to 20 urethane bonds having been prepared by reaction between (i) a hydrogenated 1,2-polybutadiene having about 1.2 to 2.0 terminal hydroxy groups on average per molecule and a hydrogenation ratio of pendent vinyl groups of the 1,2-addition units of from about 50 to 100 percent of a poly-l-butene having about 1.2 to 2.0 terminal hydroxy groups on average per molecule, and (ii) a diisocyanate consisting of 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, hydrogenated 2,4-tolylene diisocyanate, hydrogenated 2,6-tolylene diisocyanate, a mixture of hydrogenated 2,4-tolylene diisocyanate and hydrogenated 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hydrogenated 4,4'-diphenylmethane diisocyanate, m-xylylene diisocyanate, 1,6hexamethylene diisocyanate, )n-phenylene diisocyanate or 3,3'-dimethyl-4,4'diphenylmethane diisocyanate.

19. A photosensitive composition as claimed in claim 1, wherein the prepolymer is a polymer obtained by reaction between (1) an alcohol having one ethylenically unsaturated group consisting of 2-hydroxyethyl methacrylate, 2hydroxypropyl acrylate, 2-hydroxypropyl methacrylate and 6-hydroxyhexyl methacrylate and (2) a chain-extended, hydrogenated 1 ,2-polybutadiene having terminal isocyanates and 2 to 20 urethane bonds or a chain-extended poly-l-butene having terminal isocyanates and 2 to 20 urethane bonds having been prepared by reaction between (i) a hydrogenated 1 ,2-polybutadiene having about 1.2 to 2.0 terminal hydroxy groups on average per molecule and a hydrogenation ratio of pendent vinyl groups of the 1,2-addition units of about 50 to 100 percent or a poly l-butene having about 1.2 to 2.0 terminal hydroxy groups on average per molecule and (ii) a diisocyanate consisting of 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, hydrogenated 2,4-tolylene diisocyanate, hydrogenated 2,6-tolylene diisocyanate, a mixture of hydrogenated 2,4-tolylene diisocyanate and hydrogenated 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hydrogenated 4,4'diphenylmethane diisocyanate, m-xylylene diisocyanate, 1,6-hexamethylene diisocyanate, m-phenylene diisocyanate or 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate.

20. A photosensitive composition as claimed in claim 1, wherein the prepolymer is a polymer obtained by reaction between (1) glycidyl methacrylate or allyl glycidyl ether and (2) a hydrogenated 1,2-polybutadiene having terminal carboxyl groups or a poly-l-butene having terminal carboxyl groups having been prepared by reaction between (i) a hydrogenated 1 ,2-polybutadiene having about 1.2 to 2.0 terminal hydroxy groups on average per molecule and a hydrogenation ratio of pendent vinyl groups of the 1,2-addition units of about 50 to 100 percent, or a poly-l-butene having about 1.2 to 2.0 terminal hydroxyl groups on average per molecule and (ii) succinic anhydride or phthalic anhydride.

21. A photosensitive composition as claimed in claim 1, wherein the prepolymer is a polymer obtained by reaction between (1) glycidyl methacrylate or allyl glycidyl ether and (2) a chain-extended hydrogenated 1,2-polybutadiene having terminal carboxyl groups or a chain-extended poly- 1 -butene having terminal carboxyl groups obtained by reaction between (i) a chain-extended 1,2polybutadiene having terminal hydroxy groups and 2 to 20 urethane bonds or a chain-extended poly-l-butene having terminal hydroxy groups and 2 to 20 urethane bonds having been prepared by reaction between a hydrogenated 1,2polybutadiene having about 1.2 to 2.0 terminal hydroxy groups on average per molecule and a hydrogenation ratio of pendent vinyl groups of the 1,2-addition units of about 50 to 100 percent, or a poly-l-butene having about 1.2 to 2.0 terminal hydroxy groups on average per molecule and a diisocyanate consisting of 2,4tolylene diisocyanate, 2,6-tolylene diisocyanate, a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, hydrogenated 2,4-tolylene diisocyanate, hydrogenated 2,6-tolylene diisocyanate, a mixture of hydrogenated 2,4-tolylene diisocyanate and hydrogenated 2,6-tolylene diisocyanate, 4,4'diphenylmethane diisocyanate, hydrogenated 4,4'-diphenylmethane diisocyanate, m-xylylene diisocyanate, 1,6-hexamethylene diisocyanate, m-phenylene diisocyanate and 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate and (ii) succinic anhydride or phthalic anhydride.

22. A photosensitive composition as claimed in claim 1, wherein the polymerizable ethylenically unsaturated monomeric compound is a compound of the formula:

wherein: Rl represents hydrogen or methyl, R5 represents an alkyl group having 1 to 20 carbon atoms, cyclohexyl, an alkoxyalkyl group having at the most 15 carbon atoms, a cyanoalkyl group having at the most 8 carbon atoms, a tertiary aminoalkyl group having at the most 18 carbon atoms, a hydrogen atom, an oxyalkylene group bf the formula:

or -[CH2)4-O&num; pH wherein: R3 represents a hydrogen atom, methyl, monochloromethyl or monobromomethyl, p represents an integer of 1 to 20, the {CH2)qOH group wherein: q is an integer of 5 to 20, the -CH2C(CH3)2CH2OH group or the CH2C(CH2Br)2CH2OH group.

23. A photosensitive composition as claimed in claim 13, wherein the polymerizable, ethylenically unsaturated monomeric compound is a compound of the formula:

wherein: t is an integer of 8 to 20.

24. A photosensitive composition as claimed in claim 1, wherein the polymerizable ethylenically unsaturated monomeric compound is a compound of the formula:

wherein: R1 represents a hydrogen atom or methyl group, g is an integer of 2 to 4, and R9 represents a radical of a polyol having g terminal hydroxy groups and a number average molecular weight or at most 1,000.

25. A photosensitive composition as claimed in claim 1, wherein the polymerizable ethylenically unsaturated monomeric compound consists of 2,2' bis - (4 - methacryloxydiethoxyphenyl - propane, 2,2' - bis - (4 acryloxydiethoxyphenyl) - propane, 2,2' - bis - (4 - methacryloxyethoxphenyl) propane or 2,2' - bis(4 - acryloxyethoxyphenyl) - propane.

26. A photosensitive composition as claimed in claim 1, substantially as herein described with reference to any of the specific Examples 1 to 10.