LIGHT-SENSITIVE COMPOSITION

Abstract: A light-sensitive composition comprises a diazo resin, a polymeric binder, and at least one compound having at least one structural unit selected from the group consisting of ureido bond, thioureido bond, urethane bond and thiourethane bond. The light-­ sensitive composition can suitably be used for preparing a presensitized plate for use in making lithographic printing plates and is excellent in developability with an aqueous alkaline developer.

Description: The present invention relates to a negative working light-sensitive composition suitable for preparing a presensitized plate for use in making lithographic printing plates, which is excellent in developability with an aqueous alkali developer. Most of the materials which are used as light-sensitive substances for negative working presensitized plate for use in making lithographic printing plates (hereinafter referred to as "PS plate(s)") are diazonium compounds and most commonly used are diazo resins such as a condensate of p-diazodiphenylamine and formaldehyde. Compositions for the light-sensitive layer of PS plates in which a diazo resin is used can be divided into two groups, one of which simply comprises diazo resins, in other words those free of binders as disclosed in U.S. Patent No. 2,714,066; and the other of which comprises a mixture of a diazo resin and a binder as disclosed in U.S. Patent 4,275,138[Japanese Patent Un-examined Publication (hereunder referred to as J.P. KOKAI) No. 50-30604]. However, most of the recent light-sensitive compositions for PS plates in which diazonium compounds are used comprise a diazonium compound and a polymer serving as a binder to achieve high printing durability. As such a light-sensitive layer, there have been known so-called alkali-developable ones whose unexposed areas are removed or developed with an aqueous alkaline developer; and so-called solvent developable ones whose unexposed areas are removed with an organic solvent type developer as disclosed in U.S. Patent 4,275,138[Japenese Patent Publication for Opposition Purpose (hereinafter referred to as "J.P. KOKOKU") No. 52-7364]. However, the alkali developable ones have lately become major interest from the viewpoint of safety in work operations and health of operators. Examples of binders useful in such an alkaline developable light-sensitive layer include polymers obtained by copolymerizing 2-hydroxyethyl(meth)acrylate and a carboxyl group containing monomer such as methacrylic acid as disclosed in the aforesaid U.S.Patent 4,275,138(J.P. KOKOKU No. 52-7364); polymers obtained by copolymerizing a monomer having aromatic hydroxyl group(s) and a carboxyl group containing monomer such as methacrylic acid as disclosed in J.P. KOKOKU No. 57-43890; polymers obtained by reacting residual hydroxyl groups of polyvinyl acetal resin with an acid anhydride and then reacting a part of the resultant carboxylic acid with a halogen compound having hydroxyl or cyano group(s) as described in U.S. Patent 4,741,985(J.P. KOKAI No. 61-128123); polymers prepared by reacting sulfonyl isocyanate with a polymer having free OH group(s) as described in U.S. Patent 3,732,105(J.P. KOKAI No. 47-9902); and polyurethane resins carrying substituents having acidic hydrogen atom(s) as described in DE 3716607A[Japanese Patent Application Serial (hereinafter referred to as "J.P.A.") No. 62-121666]. However, further improvements in the developability of these light-sensitive layers conventionally proposed are required. DE-A-3319991 and EP-A-00899507 disclose light-sensitive compositions comprising a diazo resin, a polyurethane resin and a compound having an ureido bond. US-A-3867147 discloses a light-sensitive composition comprising a diazo resin and a polyurethane. It is the object of the present invention to provide a light-sensitive composition excellent in developability with an aqueous alkaline developer. According to the present invention, there is provided a light-sensitive composition which comprises a diazo resin, a polyurethane resin as a polymeric binder and at least one non-polymeric compound having at least one structural unit selected from the group consisting of a thioureido bond (=N-CS-N=), an urethane bond (=N-CO-O-) and a thiourethane bond (=N-CS-O-) (hereinafter referred to as "compound(s)" of the present invention). Specific examples of the compounds of the present invention include those represented by the following general formulas (1) to (3). (R₁)(R₂)N-CS-N(R₃)(R₄) (1) (R₁)(R₂)N-CO-O-R₃ (2) (R₁)(R₂)N-CS-O-R₃ (3) In the foregoing formulas (1) to (3), R₁ to R₄ may be the same or different and each represents a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted acyl group or a substituted or unsubstituted amino group or may be bonded together to form a ring structure. More specifically, R₁ to R₄ each represents a methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, 2-ethylhexyl, nonyl, decyl, lauryl, stearyl, behenyl, cyclopentyl, cyclohexyl, 2-hydroxyethyl, 2-hydroxypropyl, 3-hydroxypropyl, 2-methoxyethyl, 2-ethoxyethyl, 3-methoxypropyl, 3-ethoxypropyl, 2,3-dichloropropyl, 2,3-dibromopropyl, -CH₂COOH, -CH(COOH)-CH₂-COOH, -CH₂CH₂COOH, -CH₂CH₂SO₃Na, -CH₂CH₂SO₃H, phenyl, naphthyl, tolyl, xylyl, fluorophenyl, chlorophenyl, bromophenyl, ethylphenyl, propylphenyl, hydroxyphenyl, methoxyphenyl, ethoxyphenyl, -Phe-SO₃Na, -Phe-SO₃K, -Phe-NHNHCHO (wherein "Phe" means a phenylene group), benzyl, methylbenzyl, dimethylbenzyl, ethylbenzyl, propylbenzyl, fluorobenzyl, chlorobenzyl, bromobenzyl, hydroxybenzyl, methoxybenzyl, ethoxybenzyl, vinyl, propenyl, butenyl allyl, -CO-CH₃. -CO-C₂H₅, - CO-OH, -CO-OCH₃, -CO-OC₂H₅, -CO-NH₂, -CO-COOH, -CO-CH₂COOH, -NH₂, -NHCH₃, N(CH₃)₂, -NH-Ph and -N(Ph)₂ wherein "Ph" means a phenyl group). The following compound may be encompassed with in the scope of this invention: The compound of the present invention also include the following compounds which comprise two structural units in a molecule: R₁OCONH(CH₂)₆NHCOOR₂ , wherein R and R₂ have the same meanings as defined above. The molecular weight of the compound of the present invention is preferably less than 20,000. It is molecular weight is excessively large, the effect of improving the developability becomes low. More preferably, it is less than 5,000 and most preferably less than 1,000. The amount of the compound of the present invention in the light-sensitive composition ranges from 1 to 25 wt%, preferably 2 to 20 wt% and more preferably 3 to 15 wt% based on the amount of the polymeric binder. If it is less than 1 wt%, the developability improving effect is sufficient, while if it is more than 25 wt%, the printing durability of the resulting lithographic printing plate is impaired. The light-sensitive diazo resins used in the present invention are diazo resins such as cordensates of aromatic diazonium salts and active carbonyl group containing compounds, for instance, formaldehyde and particularly those soluble in organic solvents are preferably used in the invention. Examples of such diazo resins are inorganic salts of organic solvent-soluble diazo resins which are reaction products of a condensate of p-diazodiphenylamine and formaldehyde or acetaldehyde with hexafluorophosphate or tetrafluoroborate; organic salts of organic solvent-soluble diazo resins which are reaction products of the foregoing condensate and sulfonates such as p-toluene sulfonic acid or salts thereof, propyl naphthalene sulfonic acid or salts thereof, butyl naphthalene sulfonic acid or salts thereof, dodecylbenzene sulfonic acid or salts thereof, 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid or salts thereof, dioctylnaphthalene sulfonic acid or salts thereof or a mixture thereof, as described in J.P. KOKOKU No. 47-1167. In addition to the foregoing examples, a product obtained by condensing 3-methoxy-4-diazodiphenylamine and 4,4′-bis-methoxy-methyl-diphenyl ether and then converting it to a mesitylene sulfonate as disclosed in Can. Patent 1,172,492 (J.P. KOKAI No. 58-27141) is also suitably employed in the invention. As polymeric binders polyurethane resins as disclosed in BP 2185120(J.P. KOKAI Nos. 62-123452 and 62-123453) and DE 3716607A(J.P.A. No. 62-12166) are preferred. They can extremely improve the developability enhancing effect of the compounds of the present invention and thus they are the preferred polymeric binders to the combined with the light-sensitive diazo resin. The amounts of these light-sensitive diazo resins and the polymeric binder in the light-sensitive composition of the invention suitably range from 3 to 40% by weight for the former and from 97 to 60% by weight for the latter bases on the total weight of these two components. The sensitivity thereof becomes higher as the content of the diazo resin decreases, but if it is less than 3% by weight, photohardening of the binder becomes insufficient and thus the resulting photohardened film gets swollen with a developer during the developing process, which possibly makes the film fragile. On the contrary, if the amount thereof is more than 40% by weight, the sensitivity of the light-sensitive layer obtained is lowered and the composition cannot be practivally used. Therefore, the preferred amount of the diazo resin ranges from 5 to 30% by weight and that of the polymeric binder ranges from 95 to 70% by weight. The light-sensitive composition of the present invention may further comprise a variety of additives. For instance, there may be added, to the composition, alkyl ethers such as ethyl cellulose and methyl cellulose for improving the coating properties of the composition; surfactants such as fluoro-surfactants; plasticizers such as tricresyl phosphate, dimethyl phthalate, dibutyl phthalate, trioctyl phosphate, tributyl phosphate, tributyl citrate, polyethylene glycol and polypropylene glycol, for imparting flexibility and wear resistance to the resulting film; coloring substances for making the image portions visible after development, such as acridine dyes, cyanine dyes, styryl dyes, triphenylmethane dyes or pigments such asphthalocyanine; or common stabilizers for the diazo resins such as phosphoric acid, phosphorous acid, pyrophosphoric acid, oxalic acid, boric acid, p-toluenesulfonic acid, benzenesulfonic acid, p-hydroxybenzenesulfonic acid, 2-methoxy-4-hydroxy-5-benzoyl-benzenesulfonic acid, malic acid, tartaric acid, dipicolinic acid, polyacrylic acid and copolymers thereof, polyvinyl phosphonic acid and copolymers thereof, polyvinyl sulfonic acid and copolymers thereof, 5-nitronaphthalene-1-phosphonic acid, 4-chlorophenoxymethyl phosphonic acid, sodium phenyl-methyl-pyrazolone sulfonate, 2-phosphonobutane tricarboxylic acid-1.2.4, 1-phosphonoethane tricarboxylic acid-1.2.2, 1-hydroxyethane-1,1-diphosphonic acid. The amount of these additives to be added to the composition may vary depending on the kind of the composition and the purpose of the additives, but it generally ranges from 0.5 to 30% by weight on the basis of the total solid content of the light-sensitive layer. The light-sensitive composition of this invention is dissolved in a proper organic solvent and is then applied to the surface of a substrate having a hydrophilic surface in an amount ranging from 0.5 to 5 g/m² which is expressed in the amount weighed after drying to obtain a PS plate. Upon coating the same, the concentration of the composition in an organic solvent preferably ranges from 1 to 50% by weight. Examples of organic solvents include methyl cellosolve, ethyl cellosolve, 1-methoxy-2-propanol, methyl cellosolve acetate, acetone methyl ethyl ketone, methanol, dimethylfomamide,dimethylsulfoxide, ethylene dichloride, cyclohexanone, dioxane and tetrahydrofuran. In addition to these solvents, mixed solvents thereof as well as these solvents and mixtures thereof containing a small amount of solvents such as water and toluene which do not dissolve the diazo resins and polymeric binders may also suitably be used. After applying the light-sensitive composition dissolved in such a solvent to the substrate, the layer applied is preferably dried at a temperature ranging from 50 to 120 °C . The drying is carried out first at a rather low temperature and then at an elevated temperature. Alternatively, the coated layer may be directly dried at an elevated temperature by appropriately selecting the solvent and the concentration. The PS plate composed of a substrate having a hydrophilic surface provided thereon with a light-sensitive layer applied is imagewise exposed to light and is then developed with a developer comprised of a weak alkaline water to form relief images negative with respect to the original. Light sources suitable for exposing the PS plate include, for instance, a carbon arc lamp, a mercury lamp, a xenon lamp, a metal halide lamp, a strobo, ultraviolet rays and laser rays. Examples of developers used for developing the PS plates having a layer of the composition of the present invention include weak alkaline aqueous solutions such as those composed of water, an organic solvent having a solubility in water of not more than 10% by weight at ordinary temperature (e.g., benzyl alcohol and ethylene glycol monophenyl ether), an alkaline agent (e.g., triethanolamine and monoethanolamine), an anionic surfactant (e.g., aromatic sulfonic acid salts, dialkylsulfosuccinic acid salts, alkylnaphthalene sulfonic acid salts, surfactants represented by the following general formulas: and branched alkylsulfuric acid ester salts), and those composed of water, optionally contamination inhibiting agents (e.g., sodium sulfite and sodium salt of sulfopyrazolone) and agents for softening hard water (e.g., tetrasodium ethylenediaminetetraacetate and a compound represented by the formula: (CH₂COONa)₃). As substrate having a hydrophilic surface to which the composition of the present invention is applied, particularly preferred are aluminium plates subjected to a hydrophilization treatment. The surface of the aluminium plates is preferably grained by wire brush graining, brush graining in which the surface is grained with a nylon brush while pouring a slurry of abrasive particles thereon, ball graining, chemical graining, electrolytic graining or combined graining comprised of a combination of these graining techniques and then optionally anodized by passing an electric current (D.C. or A.C.) in an electrolyte composed of sulfuric acid, phosphoric acid, oxalic acid, boric acid, chromic acid, sulfamic acid or a mixture thereof to form a strong passive film on the surface. The hydrophilization of the surface of the aluminum plate can be achieved by the formation of such a passive film, but particularly preferred are those further subjected to the following treatment: a silicate (sodium silicate or potassium silicate) treatment as disclosed in U.S. Patent Nos. 2,714,066 and 3,181,461; a treatment with a fluorozirconate as disclosed in U.S. Patent No. 2,946,638; a phosphomolybdate treatment as disclosed in U.S. Patent No. 3,201,247; a polyacrylic acid treatment as disclosed in German Patent No. 1,091,433; a polyvinyl sulfonic acid treatment as disclosed in German Patent No. 1,134,093 and U.K. Patent No. 1,230,447; a phosphonic acid treatment as disclosed in J.P. KOKOKU No. 44-6409; a phytic acid treatment as disclosed in U.S. Patent No. 3,307,951; a combined treatment with a hydrophilic organic polymeric compound and a bivalent metal as disclosed in J.P. KOKAI Nos. 58-16893 and 58-18291; and a hydrophilization by application of an underlying coating of a water soluble polymer having a sufficient acid group(s). Example of such hydrophilization treatments include a silicate electrodeposition technique as disclosed in U.S. Patent No. 3,658,662. The light-sensitive composition of the present invention is superior in developability with an aqueous alkaline developer or shows a very short developing time and, therefore, can suitably be used for preparing PS plates. The present invention will hereinafter be explained in more detail with reference to the following working Examples and further the effects practically achived by the present invention will also be discussed in detail in comparison with the following Comparative Examples. Examples 1 to 15 and Comparative Example 1 The surface of an aluminum plate of 0.3 mm thickness was grained with a nylon brush and an aqueous suspension of 400 mesh pumice stone and was sufficiently washed with water. The plate was then immersed in 10% aqueous solution of sodium hydroxide at 70°C for 60 for etching, followed by washing it with running water, neutralizing and washing with a 20% nitric acid solution, and then electrolytically graining the plate by the electrochemical graining method as disclosed in J.P. KOKAI No. 53-67507, in other words electrolytically graining the plate in 1% aqueous nitric acid solution utilizing an alternating waved current of V A = 12.7 V and V C = 9.1 V so that the quantity of electricity at the anode time was 160 cb/dm². Subsequently, the aluminum plate was immersed in 30% aqueous sulfuric acid solution at 55°C for 2 min to desmut the plate and was anodized in a 7% sulfuric acid aqueous solution till the thickness of the resultant anodized film was 2.0 g/m². Thereafter, the plate was immersed in a 3% aqueous solution of sodium silicate maintained at 70°C for 1 min, then washed with water and dried. A solution of a light-sensitive composition having the following composition was applied to the surface of the aluminum plate thus prepared with a whirler and then dried at 80°C for 2 min. The amount of the composition coated was 1.5 g/m² (weighed after drying). Solution of the Light-sensitive Composition In the composition , the polymer (a) was a polyurethane resin having carboxyl groups and hydroxyl groups prepared according to preparation Example 9 of J.P. KOKAI No. 62-123453. Likewise, a comparative PS plate was produced in the same manner as mentioned above except for using the light-sensitive composition free of the compound of the present invention (Comparative Example). A developer obtained by diluting the aqueous alkaline developer DN-3C (available from Fuji Photo Film Co., Ltd.: dilution = 1 : 2) was dropped on the surface of these PS plates, the surface thereof was rubbed with a sponge after a constant time period while washing with water to estimate the time required for completely developing the PS plates (devoloping time). The results observed are summarized in Table I given below. The results listed in Table I indicate that the PS plate in which the compound of the present invention was used can be developed with an aqueous alkaline developer within a short period of time and that they are excellent in developability. Examples 16 and 17 and Comparative Example 2 A solution of the light-sensitive composition having the following composition was applied to the surface of an aluminium plate treated as in Example 1 with a whirler and was dried at 100°C for 2 min. The coated amount of the composition was 2,4 g/m² weighed after drying. Composition of the Solution In this connection, the polymer (b) was a copolymer of 2-hydroxyethyl methacrylate/acrylonitrile/ methyl methacrylate/ methacrylic acid (molar ratio of copolymerization = 35/35/25/5) having an average molecular weight of 12,000. Likewise, a comparative PS plate was prepared in the same manner as mentioned above except that the compound of the present invention was not used (Comparative Example 2). The developing time of these PS plates was determined in the same manner as in Example 1 to 15. The results observed are listed in Table II given below. As seen from the results shown in Table II, the PS plates in which the compound of the present invention was used can be developed with an aqueous alkaline developer within a very short period of time and they are excellent in developability.

Claims: A light-sensitive composition which comprises a diazo resin, a polyurethane resin as a polymeric binder, and at least one non-polymeric compound having at least one structural unit selected from the group consisting of a thioureido bond, an urethane bond and a thiourethane bond. The light-sensitive composition of claim 1 wherein the compound is at least one member selected from the group consisting of those represented by the following general formulas (1) to (3): N(R₁)-CS-N(R₃)(R₄) N(R₁)(R₂)-CO-0-R₃ N(R₁)(R₂)-CS-0-R₃ wherein R₁ to R₄ may be the same or different and each represents a hydrogen atom, a substituted or unsubstituted alkyl, a substituted or unsubstituted aryl, a substituted or unsubstituted aralkyl, a substituted or unsubstituted alkenyl, a substituted or unsubstituted acyl or a substituted or unsubstituted amino group or may be bonded together to form a ring structure. The light-sensitive composition of claim 2 wherein R₁ to R₄ each represents a group selected from the group consisting of methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, 2 -ethylhexyl, nonyl, decyl, lauryl, stearyl, behenyl, cyclopentyl, cyclohexyl, 2-hydroxyethyl, 2-hydroxypropyl, 3 -hydroxypropyl, 2-methoxyethyl, 2-ethoxyethyl, 3 -methoxypropyl, 3-ethoxypropyl, 2, 3-dichloropropyl, 2, 3-dibromopropyl, -CH₂COOH, -CH(COOH)-CH₂-COOH, -CH₂CH₂COOH, -CH₂CH₂SO₃Na, -CH₂CH₂SO₃K, phenyl, naphthyl, tolyl, xylyl, fluorophenyl, chlorophenyl, bromophenyl, ethylphenyl, propylphenyl, hydroxyphenyl, methoxyphenyl, ethoxyphenyl, -Phe-S0₃Na, -Phe-SO₃K, -Phe-NHNHCHO (Phe means a phenylene group), benzyl, methylbenzyl, dimethylbenzyl, ethylbenzyl, propylbenzyl, fluorobenzyl, chlorobenzyl, bromobenzyl, hydroxybenzyl, methoxybenzyl, ethoxybenzyl, vinyl, propenyl, butenyl, allyl, -CO-CH₃, -CO-C₂H₅, -CO-OH, -CO-OCH₃, -CO-OC₂ H5, -CO-NH₂, -CO-COOH, -CO-CH₂ COOH, -NH₂, -NHCH₃, -N(CH₃)₂, -NH-Ph and -N(Ph)₂ (Ph means a phenyl group). The light-sensitive composition of claim 1 wherein the compound is at least one member selected from the group consisting of those represented by the following formulas: R₁OCONH(CH₂)₆NHCOOR₂ , and wherein R₁ and R₂ have the same meanings as defined above. The light-sensitive composition of claim 1 wherein the molecular weight of the compound is less than 20,000. The light-sensitive composition of claim 5 wherein the molecular weight of the compound is less than 5,000. The light-sensitive composition of claim 1 wherein the amount of the compound added to the composition ranges from 1 to 25% by weight on the basis of the weight of the polymeric binder. The light-sensitive composition of claim 7 wherein the amount of the compound in the composition ranges from 2 to 20% by weight on the basis of the weight of the polymeric binder. The light-sensitive composition of claim 7 wherein the amount of the diazo resin ranges from 3 to 40% by weight and that of the polymeric binder ranges from 97 to 60% by weight on the basis of the total weight of these two components. The light-sensitive composition of claim 7 wherein the amount of the diazo resin ranges from 5 to 30% by weight and that of the polymeric binder ranges from 95 to 70% by weight on the basis of the total weight of these two components. The light-sensitive composition of claim 1 wherein it further comprises at least one additive selected from the group consisting of alkyl ethers, surfactants, plasticizers, dyes or pigments and stabilizers for the diazo resin. The light-sensitive composition of claim 11 wherein the amount of the additive ranges from 0.5 to 30% by weight on the basis of the total solid content of the composition. The light-sensitive composition of claim 1 wherein the polyurethane resin has a carboxyl group. The light-sensitive composition of claim 13 wherein the polyurethane resin has additionally a carbon-carbon unsaturated bond.

Inventors: SEKIYA, TOSHIYUKI
Applicants: FUJI PHOTO FILM CO., LTD.
Application year: 1989
Main classification: G03F7
IPC codes: G03F7