EP1641619A1 - Imageable element comprising sulfated polymers - Google Patents

Abstract

Sulfated polymers, imageable elements containing these polymers, and methods for preparing images useful as lithographic printing plates from these imageable elements are disclosed. The elements can be thermally imaged and developed in water or in fountain solution so that an alkaline developer is not required. They can be imaged and developed on press using fountain solution so that it is unnecessary to mount them in a separate exposure device.

Description

TITLE IMAGEABLE ELEMENT COMPRISING SULFATED POLYMERS Field of the Invention The invention relates to sulfated polymers. In particular, this invention relates to sulfated polymers and their use in lithographic printing plate precursors. Background of the Invention In conventional or "wet" lithographic printing, ink receptive regions, known as image areas, are generated on a hydrophilic surface. When the surface is moistened with water and ink is applied, the hydrophilic regions retain the water and repel the ink, and the ink receptive regions accept the ink and repel the water. The ink is transferred to the surface of a material upon which the image is to be reproduced. Typically, the ink is first transferred to an intermediate blanket, which in turn transfers the ink to the surface of the material upon which the image is to be reproduced. Imageable elements useful as lithographic printing plate precursors typically comprise an imageable layer applied over the hydrophilic surface of a substrate. The imageable layer includes one or more radiation-sensitive components, which may be dispersed in a suitable binder. Alternatively, the radiation-sensitive component can also be the binder material. Following imaging, either the imaged regions or the unimaged regions of the imageable layer are removed by a suitable developer, revealing the underlying hydrophilic surface of the substrate. If the imaged regions are removed, the precursor is positive working. Conversely, if the unimaged regions are removed, the precursor is negative working. In each instance, the regions of the imageable layer (i.e., the image areas) that remain are ink-receptive, and the regions of the hydrophilic surface revealed by the developing process accept water and aqueous solutions, typically a fountain solution, and repel ink. Conventional imaging of the imageable element with ultraviolet and/or visible radiation was carried out through a mask, which has clear and opaque regions. Imaging takes place in the regions under the clear regions of the mask but does not occur in the regions under the opaque regions. However, direct digital imaging, which obviates the need for imaging through a mask, is becoming increasingly important in the printing industry. Imageable elements for the preparation of lithographic printing plates have been developed for use with infrared lasers. Thermally imageable, elements are disclosed, for example, in Shimazu, U.S. Pat. No. 6,294,311 , U.S. Pat. No. 6,352,812, and U.S. Pat. No. 6,593,055; Patel, U.S. Pat. No. 6,352,811 ; Savariar-Hauck, U.S. Pat. No. 6,358,669, U.S. Pat. No. 6,528,228; West, U.S. Pat. No. 6,090,532; Parsons, U.S. Pat. No. 6,280,899; McCullough, U.S. Pat. Pub. No. 2002/0136961; and W099/21715; Haley, U.S. Pat. No. 5,372,907; Nguyen, U.S. Pat. No. 5,919,601 ; Kobayashi, U.S. Pat. No. 5,965,319; Busman, U.S. Pat. No. 5,763,134; and WO 00/17711. Imaged imageable elements typically require processing in a developer to convert them to lithographic printing plates. Developers are typically aqueous alkaline solutions, which may also contain substantial amounts of organic solvents. Because of their high pH and the presence of organic solvents, disposal of substantial quantities of developer is expensive and can cause environmental problems. Processing of the imaged imageable element in a developer also introduces additional costs in, for example, the cost of the developer, the cost of the processing equipment, and the cost of operating the process. On-press developable lithographic printing plate precursors can be directly mounted on a press after imaging and developed with ink and/or by fountain solution during the initial press operation. These precursors do not require a separate development step before mounting on press. On press imaging, in which the precursor is both imaged and developed on press, eliminates mounting the precursor in a separate imaging device. Thus, a need exists for imageable elements useful as lithographic printing plate precursors that can be developed in water and/or in fountain solution. Preferably, development can be carried out on press to avoid a separate development step. Summary of the Invention The invention is an imageable element useful as a printing plate precursor. The element comprises an imageable layer over a substrate; in which the imageable layer comprises: a photothermal conversion material, and a sulfated polymer comprising sulfate groups and a polymer backbone. The sulfate groups may be attached to aromatic groups and/or alkyl groups and/or to groups that are part of the polymer backbone and/or groups that are pendent to the polymer backbone. In one aspect, the sulfated polymer is a sulfated phenolic resin. The phenolic group may be either pendent to the polymer backbone, part of the polymer backbone, or both. In another aspect, the sulfate groups of the sulfated polymer are attached to alkyl groups that are pendent to the polymer backbone, attached to the polymer backbone, or both. The imageable elements do not require development in a conventional developer that has a high pH and/or contains an organic solvent. They can be developed with water or on-press using fountains solution and/or ink as the developer. Detailed Description of the Invention Unless the context indicates otherwise, in the specification and claims, the terms sulfated polymer, infrared absorber, photothermal conversion material, surfactant, coating solvent, and similar terms also include mixtures of such materials. Thermal imaging refers to imaging with a hot body, such as a thermal head, or with infrared radiation. Unless otherwise specified, all percentages are percentages by weight. The imageable elements comprise an imageable layer, which comprises a sulfated polymer and a photothermal conversion material. Sulfation refers to the process of introducing sulfate ester groups into a polymer or into a monomer that will be converted to a polymer. Typically, sulfation involves conversion a hydroxyl group to a sulfate group, such as by methods discussed below. Sulfate group refers to the sulfate ester group, which may be in acid form (-OS0₃H) and/or in salt form (-OSO₃ ^" X⁺). Sulfated polymer and sulfated resin refers to a polymer that contains sulfate groups, typically one in which the hydroxyl groups for at least some of the repeating units of the polymer have been converted to sulfate groups (sulfate ester groups). The sulfate groups that are attached either to aryl groups (i.e., to form sulfated phenolic hydroxyl groups) or to alkyl groups (i.e., to form sulfated aliphatic hydroxyl groups). If the sulfate groups are attached to alkyl groups (for example, aliphatic hydroxyl groups that are converted to sulfate groups), the alkyl groups may be either part of the main chain of the polymer (polymer backbone) or pendent to the main chain of the polymer. If the sulfate groups are attached to aryl groups (for example, phenolic groups are converted to sulfate groups), the aryl groups may be either part of the main chain of the polymer (polymer backbone) or pendent to the main chain of the polymer. The repeating units of the polymer that comprise the sulfate groups can be randomly interspersed among the repeating units of the polymer, or can be distributed in a more orderly fashion, such as in a segmented polymer or a block copolymer. The sulfate groups may be in the acid form (-OS0₃H), in the salt form with a counterion X⁺ (-OSO₃ ^" X⁺), or both. Useful counterions (X⁺) include sodium; potassium; ammonium; substituted ammonium, preferably containing one to twelve carbon atoms, such as methyl ammonium, dimethyl ammonium, trimethyl ammonium, tetramethyl ammonium, ethyl ammonium, diethyl ammonium, triethyl ammonium, tetraethyl ammonium, methyldiethyl ammonium, dimethylethyl ammonium, 2-hydroxyethyl ammonium, di-(2-hydroxyethyl) ammonium, tri-(2-hydroxyethyl) ammonium, 2-hydroxyethyl-dimethyl ammonium; n-propyl ammonium, di-(n-propyl) ammonium, tri-(n-propyl) ammonium, tri-(n- propyl) methyl ammonium and tetra-(n-propyl) ammonium; pyridinium; iodonium; sulfonium; and diazonium. The sulfated polymer may be prepared by sulfation of a precursor polymer. The precursor polymer has hydroxyl groups that can be converted to sulfate groups. It can be prepared by homopolymerization of a monomer having either a hydroxyl group or a group, such as acetate, that can be converted to a hydroxyl group after polymerization, or by copolymerization of such a monomer with other monomers. Examples of such monomers include:

in which R is hydrogen or an alkyl group, typically methyl; and R' is a COR group, i.e., OR' is an ester group, typically acetate. When the precursor polymer is prepared by copolymerizing the precursor monomer with one or more other polymerizable monomers, any other polymerizable monomer or monomers may be used to form the copolymer, - provided the resulting sulfated polymer is still operative in the invention. Typical other polymerizable monomers include, for example, acrylic acid; acrylic acid esters such as methyl acrylate, ethyl acrylate, propyl acrylate, and butyl acrylate; methacrylic acid; methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, and butyl methacrylate; methacrylamides and acrylamides, such as methacrylamide, acrylamide, and the acrylamide and methacrylamide of p-aminobenzoic acid; methacrylonitrile; acrylonitrile; maleic acid; maleic anhydride; maleate esters; maleic acid amides; maleic acid imides, such as N-phenylmaleimide, N-cyclohexylmaleimide, and N-benzylmaleimide; itaconic acid; itaconic anhydride; itaconic acid esters; itaconic acid amides; itaconic acid imides, crotonic acid, crotonic anhydride, crotonic acid esters, crotonic acid amides; crotonic acid imides, fumaric acid, fumaric acid esters, fumaric acid amides, alpha, beta-unsaturated lactones, alpha, beta-unsaturated lactams, alpha, beta-unsaturated hydrocarbons; vinyl esters, such as vinyl acetate; alpha, beta-unsaturated ketones, such as methyl vinyl ketone; and styrene and substituted styrenes. When a vinyl ester, such as vinyl acetate, is used, the ester groups in the resulting polymer or copolymer may be converted to hydroxyl groups by hydrolysis. The resulting hydroxyl groups will be attached to the main chain of the polymer rather than to pendent groups. Preferably, when the precursor polymer is a copolymer, at least 30 mol% of recurring units that comprise the polymer comprise a hydroxyl group that may be converted to a sulfate group or a group, such as acetate, that can be converted to a hydroxyl that can be converted to a sulfate group. In the sulfated polymer, at least 30 mol% of recurring units that comprise the polymer comprise either the hydroxyl group or the sulfate group. The precursor polymers can be prepared by methods, such as free radical polymerization, which are well known to those skilled in the art and which are described, for example, in Chapters 20 and 21 , of Macromolecules, Vol. 2, 2nd Ed., H.G. Elias, Plenum, New York, 1984. Useful free radical initiators are peroxides such as benzoyl peroxide, hydroperoxides such as cumyl hydroperoxide and azo compounds such as 2,2'-azobisisobutyronitrile (AIBN). Suitable solvents include liquids that are inert to the reactants and which will not otherwise adversely affect the reaction. Typical solvents include, for example, esters such as ethyl acetate and butyl acetate; ketones such as methyl ethyl ketone, methyl isobutyl ketone, methyl propyl ketone, and acetone; alcohols such as methanol, ethanol, isopropyl alcohol, and butanol; ethers such as dioxane and tetrahydrofuran, and mixtures thereof. Methods for sulfating organic compounds are described, for example, in

Jacobson, U.S. Patent 6,448,435, and in Sulfation and Sulfation Processes, N.C. Foster (The Chemithon Corporation, 1997). Methods for sulfating hydroxyl- containing polymers are described in Schweiger, U.S. Pat. No. 4,177,345; Tyler, U.S. Pat. No. 4,318,815; and Myers, U.S. Pat. No. 5,750,656. The sulfated polymer may be prepared by, for example, reaction of a hydroxyl containing polymer resin with a sulfating agent in an organic solvent to convert hydroxyl groups to sulfate groups. Typical sulfating agents include, for example, sulfur trioxide (S0₃); chlorosulfonic acid (CIS0₃H); sulfamic acid (H2NSO3H); the sulfur trioxide-pyridine complex; sulfur trioxide trialkylamine complexes, such as the sulfur trioxide-trimethylamine complex and the sulfur trioxide-thethylamine complex; sulfur trioxide/triarylamine complexes; and the sulfur trioxide/N,N-dimethyIformamide complex. In the reaction of a sulfating agent with a polymer to yield a sulfated polymer, the reaction may be controlled so that fewer than all the hydroxy groups of the polymer are sulfated. One particularly useful way of controlling the number of hydroxy groups that are replaced is limit the amount of sulfating agent used in the reaction. Other conventional methods may be suitable for preparing the sulfated polymer. For example, a sulfated polymer may be prepared by homopolymerization or by copolymerization using a sulfated monomer, using for example, the methods described above, or by sulfating a polymer that comprises protecting groups at some sites normally occupied by hydroxy groups. Degree of sulfation, a measure of the number of repeating units that comprise sulfate groups, is defined as the ratio of the number of units in the polymer that comprise sulfate groups to the total number of units in the polymer that comprise hydroxyl groups. For example, a degree of sulfation of 0.25 indicates that 25% of the hydroxyl groups of the polymer are sulfated, that is, at least 25% of the total number of hydroxyl groups and sulfate groups in the polymer are sulfate groups. Typically, the degree of sulfation is 0.25 or greater, preferably about 0.3 or greater, and more preferably about 0.5 or greater, that is, at least 50% of the total number of hydroxyl groups and sulfate groups in the polymer are sulfate groups. Sulfated polymers in salt form (i.e., comprising predominantly -SO₃ ^" X⁺ groups) may be more suitable than sulfated polymers in acid form (i.e., comprising predominantly -OSO₃H groups), for use in the imageable elements. A phenolic resin is a polymeric material having a structure including hydroxy-substituted aromatic rings (phenolic groups) as part of the polymer backbone, pendent to the polymer backbone, or both. Phenolic resins have a multiplicity of phenolic hydroxyl groups, either on the polymer backbone or on pendent groups. Novolac resins, resol resins, acrylic resins that contain pendent phenol groups, and polyvinyl phenol resins are preferred phenolic resins. Phenolic resins in which the phenolic group is part of the polymer backbone are generally made by a condensation reaction between a substituted or unsubstituted phenol and an aldehyde or ketone. Depending on the preparation route for the condensation reaction, a range of phenolic resins with varying structures and properties can be formed. The type of catalyst and the molar ratio of the reactants used in the preparation of phenolic resins determine the molecular structure, and therefore the physical properties of the resin. Novolac resins are commercially available and are well known to those skilled in the art. They are typically prepared by the condensation reaction of a phenol, such as phenol, m-cresol, o-cresol, p-cresol, etc, with an aldehyde, such as formaldehyde, paraformaldehyde, acetaldehyde, etc. or a ketone, such as acetone, in the presence of an acid catalyst. Typical novolac resins include, for example, phenol-formaldehyde resins, cresol-formaldehyde resins, phenol- cresol-formaldehyde resins, p-f-butylphenol-formaldehyde resins, and pyrogallol- acetone resins. Particularly useful novolac resins are prepared by reacting m- resol, mixtures of m-cresol and p-cresol, or phenol with formaldehyde using conventional conditions typically in a molar ratio of between about 2:1 and 1:1 , phenol to aldehyde or ketone, preferably between about 2:1 to about 5:4. Novolac resins are well-known and are described, for example, in Kubo, U.S. Pat. No. 4,308,368; Nishioka, U.S. Pat. No. 4,845,008; Hirai, U.S. Pat. No. 5,437,952; DeBoer, U.S. Pat. No. 5,491 ,046; Mizutani, U.S. Pat. No. 5,143,816; and Engebrecht , GB 1 ,546,633. Resole resins are obtained by reaction of phenolic compounds with aldehydes, but under different reaction conditions than those that produce novolac resins. Resole resins are obtained by the alkaline-catalyzed reaction between a phenolic reactant and an aldehyde reactant. A molar ratio of less than one mole phenol reactant per mole of aldehyde reactant must be used in the preparation of a resole resin. A molar ratio of less than 1 :1 to about 1 :3 is generally used to prepare resole resins. Resole resins derived from formaldehyde contain reactive methylol (-CH₂OH) groups. In some embodiments, the sulfated phenolic resin is characterized by an average molecular weight of about 1 kDa to about 500 kDa. One sulfated phenolic resin includes repeating units represented by structures A and B:

B in which R-i, R₂, R₃, and R are each independently hydrogen, alkyl, alkenyl, alkynyl, aryl, alkaryl, or aralkyl; and X^® is a positively charged counterion. For this sulfated phenolic resin, m, the degree of sulfation, is defined as the ratio of the number of B units (i.e., sulfated phenolic units) to the sum of the number of A units plus the number of B units (i.e., total number of phenolic-type units). "Alkyl" refers to linear or branched saturated hydrocarbon substituents having one to about twenty carbon atoms or, preferably, one to about twelve carbon atoms. Examples of such substituents include methyl, ethyl, n-propyl, isopropyl, n-butyl, /so-butyl, sec-butyl, -erf-butyl, pentyl, /so-amyl, and hexyl. Alkyl substituents may be substituted with one or more substituents, such as alkoxy, hydroxyl, amino, halo, nitro, acyl, cyano, carboxy, or thioalkyl, for example. Alkenyl and alkynyl indicate linear or branched unsaturated hydrocarbon substituents having one to about twenty carbon atoms or, preferably, one to about twelve carbon atoms. Alkenyl substituents comprise a double bond in the carbon chain and alkynyl substituents comprise a triple bond. Alkenyl and alkynyl substituents may also be substituted at a substitutable position with one or more substituents, such as alkoxy, hydroxyl, amino, halo, nitro, acyl, cyano, carboxy, or thioalkyl, for example. Aryl refers to a carbocyclic aromatic system containing one, two or three rings wherein such rings may be attached together in a pendent manner or may be fused, such as phenyl, naphthyl, tetrahydronaphthyl, indane and biphenyl. Aryl substituents may also be substituted with one or more substituents, such as alkyl, haloalkyl, alkoxy, hydroxyl, amino, halo, nitro, alkylamino, acyl, cyano, carboxy, thioalkyl, alkoxycarbonyl, for example. An aryl substituent comprising an alkyl substituent at a substitutable position is referred to herein as alkaryl, such as benzyl, diphenylmethyl, triphenylmethyl, phenylethyl, and diphenylethyl. In one embodiment, Rι, R₃, and R₄ are hydrogen and R₂ is methyl (i.e., the polymer is a cresol/formaldehyde novolac resin). In another embodiment, m is in the range from about 0.25 (i.e., 1 B unit to 3 A units) to about 1.0 (i.e., all B units). In other embodiments, m is greater than about 0.5. Another sulfated phenolic resin is a polymer including repeating units represented by the structures A and B, with R_{1 f} R₂, R₃, and R and m as defined above, and with X^® representing a positive ion selected from the group consisting of lithium ion, potassium ion, and sodium ion. Another sulfated phenolic resin is a polymer including repeating units represented by the structures A and B, with R-i, R₂, R₃, and R₄ and m as defined above, and with X^® representing a positive ion selected from the group consisting of ammonium, alkylammonium, aryl ammonium, cyclic ammonium, pyrrolidinium, pyridinium, diazonium, sulfonium, and iodonium. The diazoniums, sulfoniums, and iodoniums disclosed in Newman, U.S. Pat. No. 4,708,925; and Oohashi, U.S. Published Application 2002/0068241 may also be used. In particular, the counterion X^® may be ammonium. In some embodiments, the sulfated phenolic resin is water-soluble to a significant degree. For example, one gram of a water-soluble sulfated phenolic resin may be dissolved in about 100 ml of water or less at room temperature. More preferably, at least about 3 to about 15 grams or more of a water-soluble sulfated phenolic resin may readily be dissolved in 100 ml water at room temperature. For some water-soluble sulfated phenolic resins of the invention, the degree of sulfation may be about 0.25 or greater, preferably about 0.3 or greater, and most preferably about 0.5 or greater. An aqueous solution of a sulfated phenolic resin should be maintained at a neutral to basic pH. If the pH of an aqueous solution of a sulfated phenolic resin is less than 5, especially less than 4, the sulfated phenolic resin is not stable in solution and may decompose or form a precipitate. For a discussion on the pH-dependence of the solubility of phenolic resins, see Flanagin, Macromolecules 32, 5337 (1999). The pH of the solution may be adjusted by conventional means, including adding a suitable quantity of acid, base, or buffer. In some embodiments of a thermally sensitive composition, the sulfated phenolic resin accounts for at least about 50% by weight of the thermally sensitive composition. In other embodiments, the sulfated phenolic resin may account for at least 70%, at least 80%, at least 90%, or at least 95% of the thermally sensitive composition, by weight. A thermally sensitive composition comprising the sulfated phenolic resin may include components such as a binder or a radiation-absorbing component. Many binders are known in the art of thermally sensitive or photosensitive compositions. Polymeric binders are preferred. A water-soluble binder, for example, may used. Suitable water-soluble binders include, for example, polyvinyl pyrrolidone, polyvinyl alcohol, polyacrylamide, polyacrylic acid, polyvinylimidazole, polyethyleneimine, poly(ethyloxazoline), gelatin, starches, dextrin, amylogen, gum arabic, agar, algin, carrageenan, fucoidan, laminaran, corn hull gum, gum ghatti, karaya gum, locust bean gum, pectin, guar gum, hydroxypropylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose, and carboxymethylcellulose. Binders that are not water-soluble are also suitable. Some suitable water- insoluble binders include polyvinyl pyrrolidone/vinyl acetate copolymers and polyvinyl pyrrolidone/vinyl caprolactam copolymers, for example. Where the thermally sensitive composition comprises a binder, the binder comprises not more than about 30% by weight of the thermally sensitive composition, preferably not more than about 20%, more preferably not more than about 10%, and most preferably not more than about 5%, by weight. The imageable layer comprises an infrared absorber, known as a photothermal conversion material. Photothermal conversion materials absorb radiation and convert it to heat. Although a photothermal conversion material is not necessary for imaging with a hot body, imageable elements that contain a photothermal conversion material may also be imaged with a hot body, such as a thermal head or an array of thermal heads. The photothermal conversion material may be any material that can absorb radiation and convert it to heat. Suitable materials include, for example, dyes and pigments. Suitable pigments include, for example, carbon black, Heliogen Green, Nigrosine Base, iron (III) oxide, manganese oxide, Prussian Blue, and Paris blue. Because of its low cost and wide absorption bands that allow it to be used with imaging devices having a wide range of peak emission wavelengths, one useful pigment is carbon black. The size of the pigment particles should not be more than the thickness of the layer that contains the pigment. Preferably, the size of the particles will be half the thickness of the layer or less. The photothermal conversion material may be a dye with the appropriate absorption spectrum. Dyes, especially dyes with a high extinction coefficient in the range of 750 nm to 1200 nm, are preferred. Examples of suitable dyes include dyes of the following classes: methine, polymethine, cyanine, arylmethine, hemicyanine, streptocyanine, squarylium, pyrylium, oxonol, naphthoquinone, anthraquinone, porphyrin, azo, croconium, triarylamine, thiazolium, indolium, oxazolium, indocyanine, indotricarbocyanine, oxatricarbocyanine, phthalocyanine, thiocyanine, thiatricarbocyanine, merocyanine, cryptocyanine, naphthalocyanine, polyaniline, polythiophene, chalcogenopyryloarylidene and bis(chalcogenopyrylo)polymethine, polypyrrole, oxyindolizine, pyrazoline azo, and oxazine classes. Absorbing dyes are disclosed in numerous publications, for example, Nagasaka, EP 0,823,327; DeBoer, U.S. Pat. No. 4,973,572; Jandrue, U.S. Pat. No. 5,244,771 ; and Chapman, U.S. Pat. No. 5,401 ,618. Examples of useful absorbing dyes include: ADS-830A and ADS-1064 (American Dye Source, Montreal, Canada), EC2117 (FEW, Wolfen, Germany), Cyasorb IR 99 and Cyasorb IR 165 (Glendale Protective Technology), Epolite IV-62B and Epolite 111-178 (Epoline), PINA-780 (Allied Signal), Spectral R 830A and Spectral R 840A (Spectra Colors), and IR Dye A, whose structure is shown below:

IR Dye A When the imageable element is to be developed with water or fountain solution, infrared absorbing compounds that are soluble in water are preferred. Water soluble N-alkyl sulfate infrared absorbing cyanine compounds of Structure I may be used in the imageable layer.

I in which: R is hydrogen, or R is one or more alkyl, substituted or unsubstituted aralkyl, alkoxy, carboxyl, nitro, cyano, trifluoromethyl, acyl, alkyl sulfonyl, aryl sulfonyl, or halogen groups, or R is the atoms necessary to form a substituted or unsubstituted benzo group; A is (CH₂)_n; where n is 1-5; preferably 2-4; Y is O, S, NR', or C(R')₂, where R' is hydrogen or alkyl; preferably methyl; Z is hydrogen, halogen, alkyl, substituted or unsubstituted aralkyl; substituted or unsubstituted aroxyl, substituted or unsubstituted thioaroxyl, or substituted or unsubstituted diphenylamino; m is zero or one; and X is a cation, preferably sodium, potassium, lithium, ammonium, or substituted ammonium. Y is preferably S or C(CH₃)2. The preparation of these infrared absorbing compounds described in U.S. Patent Application 10/736,364, filed December 15, 2003. The triethyl ammonium salts, for example, may be prepared by following procedure:

The amount of infrared absorber is generally sufficient to provide an optical density of at least 0.05, and preferably, an optical density of from about 0.5 to at least about 2 to 3 at the imaging wavelength in the imageable layer. As is well known to those skilled in the art, the amount of compound required to produce a particular optical density can be determined from the thickness of the layer in which it is present and the extinction coefficient of the infrared absorber at the wavelength used for imaging using Beer's law. The photothermal conversion material typically comprises about 0.1 to 25% by weight of the imageable layer, based on the total weight of the imageable layer. When the photothermal conversion material is a pigment, it preferably comprises about 10% to about 20% by weight, of the imageable layer. When the photothermal conversion material is a dye, the infrared absorber typically comprises about 2% to about 15% by weight of the imageable layer. The imageable layer may also comprise other ingredients such as dyes and surfactants that are conventional ingredients of imageable compositions and imageable layers. Surfactants may be present in the imageable layer, as, for example, coating aids. A dye may be present to aid in the visual inspection of the imaged and/or developed element. Printout dyes distinguish the imaged regions from the unimaged regions during processing. Contrast dyes distinguish the unimaged regions from the imaged regions in the developed imageable element. Preferably, these dyes do not absorb the imaging radiation. Other conventional ingredients include, for example, dispersing agents, biocides, plasticizers, viscosity modifiers or rheology modifiers, defoamers, preservatives, antioxidants, and combinations thereof. Additional binders, for example water soluble binders such as polyvinyl pyrrolidone may also be present. The substrate comprises a support, which may be any material conventionally used to prepare imageable elements useful as lithographic printing plates. The support is preferably strong, stable and flexible. It should resist dimensional change under conditions of use so that color records will register in a full-color image. Typically, it can be any self-supporting material, including, for example, polymeric films such as polyethylene terephthalate film, ceramics, metals, or stiff papers, or a lamination of any of these materials. Metal supports include aluminum, zinc, titanium, and alloys thereof. Typically, polymeric films contain a sub-coating on one or both surfaces to modify the surface characteristics to enhance the hydrophilicity of the surface, to improve adhesion to subsequent layers, to improve planarity of paper substrates, and the like. The nature of this layer or layers depends upon the substrate and the composition of subsequent layers. Examples of subbing layer materials are adhesion-promoting materials, such as alkoxysilanes, aminopropyltriethoxy- silane, glycidoxypropyltriethoxysilane and epoxy functional polymers, as well as conventional subbing materials used on polyester bases in photographic films. The surface of an aluminum support may be treated by techniques known in the art, including physical graining, electrochemical graining, chemical graining, and anodizing. The substrate should be of sufficient thickness to sustain the wear from printing and be thin enough to wrap around a cylinder in a printing press, typically about 100 μm to about 600 μm. Typically, the substrate comprises an interlayer between the aluminum support and the imageable layer. The interlayer may be formed by treatment of the aluminum support with, for example, silicate, dextrine, hexafluorosilicic acid, phosphate/fluoride, polyvinyl phosphonic acid (PVPA), vinyl phosphonic acid copolymers, or a water-soluble diazo resin. The backside of the support (i.e., the side opposite the imageable layer) may be coated with an antistatic agent and/or a slipping layer or matte layer to improve handling and "feel" of the imageable element. The imageable element may be prepared by applying the imageable layer over the hydrophilic surface of the substrate using conventional techniques. The imageable layer may be applied by any conventional method, such as coating or lamination. Typically the ingredients of the imageable layer are dispersed or dissolved in a suitable coating solvent, such as water or a mixture of water and an organic solvent such as methanol, ethanol, /so-propyl alcohol, and/or acetone, and the resulting mixture coated by conventional methods, such as spin coating, bar coating, gravure coating, die coating, slot coating, or roller coating. After coating, the layer is dried to remove the coating solvent. The resulting element may be air dried at ambient temperature or at an elevated temperature, such as at about 65°C for about 20 seconds in an oven. Alternatively, the resulting imageable element may be dried by blowing warm air over the element. The coating weight for the imageable layer is typically about 0.5 g/m² to about 2.5 g/m², preferably about 1 g/m² to about 1.5 g/m². The element may be thermally imaged with a laser or an array of lasers emitting modulated near infrared or infrared radiation in a wavelength region that is absorbed by the imageable element. Infrared radiation, especially infrared radiation in the range of about 800 nm to about 1200 nm, is typically used for imaging. Imaging is conveniently carried out with a laser emitting at about 830 nm, about 1056 nm, or about 1064 nm. Suitable commercially available imaging devices include image setters such as the CREO® Trendsetter (Creo, Burnaby, British Columbia, Canada), the Screen PlateRite model 4300, model 8600, and model 8800 (Screen, Rolling Meadows, Chicago, Illinois, USA), and the Gerber Crescent 42T (Gerber). Alternatively, the imageable element may be thermally imaged using a hot body, such as a conventional apparatus containing a thermal printing head. A suitable apparatus includes at least one thermal head but would usually include a thermal head array, such as a TDK Model No. LV5416 used in thermal fax machines and sublimation printers, the GS618-400 thermal plotter (Oyo Instruments, Houston, TX, USA), or the Model VP-3500 thermal printer (Seikosha America, Mahwah, NJ, USA). Imaging produces an imaged element, which comprises a latent image of imaged regions and complementary unimaged regions. Development of the maged element to form a printing plate, or printing form, converts the latent mage to an image by removing the imaged regions, revealing the hydrophilic surface of the underlying substrate. The imaged element is washed with an aqueous liquid, such as water or fountain solution, either on press or in a conventional rinse/gum apparatus. This process removes the imaged regions, but does not remove the complementary unimaged regions. The imaged imageable element may be developed in water. Although distilled or deionized water may be used, the imaged element typically can be developed in tap water. Although development with tap water will typically be carried out in a separate processor, rather than on press, it is not necessary to prepare and dispose of expensive, high pH developers when water is used. In addition, only a simple processor is necessary so expensive processors are not required to develop the imaged imageable element in water. Alternatively, the imaged imageable element can be directly mounted on press after imaging and developed with fountain solution during the initial prints. No separate development step is needed before mounting on press. This eliminates the separate development step along with both the processor and developer, thus simplifying the printing process and reducing the amount of expensive equipment required. The imaged imageable element is mounted on the plate cylinder of a lithographic press and developed with fountain solution by rotating the press cylinders and contacting the element with fountain solution. Numerous aqueous fountain solutions are known to those skilled in the art. Fountain solutions are disclosed, for example, in Matsumoto, U.S. Pat. No. 5,720,800; Archer, U.S. Pat. No. 5,523,194; Chase, U.S. Pat. No. 5,279,648; Bondurant, U.S. Pat. Nos. 5,268,025, 5,336,302, and 5,382,298; Egberg, U.S. Pat. No. 4,865,646; and Daugherty, U.S. Pat. No. 4,604,952. Typical ingredients of aqueous fountain solutions, in addition to water, typically deionized water, include pH buffering systems, such as phosphate and citrate buffers; desensitizing agents, such as dextrin, gum arabic, and sodium carboxymethylcellulose; surfactants and wetting agents, such as aryl and alkyl sulfonates, polyethylene oxides, polypropylene oxides, and polyethylene oxide derivatives of alcohols and phenols; humectants, such as glycerin and sorbitol; low boiling solvents such as ethanol and 2-propanol; sequestrants, such as borax, sodium hexametaphosphate, and salts of ethylenediamine tetraacetic acid; biocides, such as isothiazolinone derivatives; and antifoaming agents. Typical pH ranges for fountain solutions are: about 3.7 to about 6.7 for sheet fed presses, and about 7.0 to about 9.6 for web presses. In conventional wet press lithographic printing, fountain solution and then ink are applied to the printing plate. For presses with integrated inking/dampening system, the ink and fountain solution are emulsified by various press rollers before being transferred to the plate as emulsion of ink and fountain solution. However, in this invention, the ink and fountain solution may be applied in any combination or sequence, as needed for the plate. For on-press imaging, the imageable element is imaged while mounted on a lithographic printing press cylinder, and the imaged imageable element is developed on press with fountain solution during the initial press operation. This is especially suitable for computer-to-press application in which the imageable element (or elements, for multiple color presses) is directly imaged on the plate cylinder according to computer generated digital imaging information and, with minimum or no treatment, directly prints out regular printed sheets. On-press imaging may be carried out on, for example, a Quickmaster Dl 46-4 press (Heidelberger Druckmaschinen, Heidelberg, Germany). INDUSTRIAL APPLICABILITY The imageable elements of the invention can be developed with water or on-press using fountain solution as the developer thus avoiding the costs associated with the use of aqueous alkaline developers. Once the imageable element has been imaged and developed to form a lithographic printing plate, printing can then be carried out by applying a fountain solution and then lithographic ink to the image on its surface. The fountain solution is taken up by the unimaged regions, i.e., the surface of the hydrophilic substrate revealed by the imaging and development process, and the ink is taken up by the imaged regions, i.e., the regions not removed by the development process. The ink is then transferred to a suitable receiving material (such as cloth, paper, metal, glass or plastic) either directly or indirectly using an offset printing blanket to provide a desired impression of the image thereon. The advantageous properties of this invention can be observed by reference to the following examples, which illustrate but do not limit the invention. EXAMPLES In the Examples, "coating solution" refers to the mixture of solvent or solvents and additives coated, even though some of the additives may be in suspension rather than in solution, and "total solids" refers to the total amount of nonvolatile material in the coating solution even though some of the additives may be nonvolatile liquids at ambient temperature. Except where indicated, the indicated percentages are percentages by weight based on the total solids in the coating solution. Glossary

AP resin Acetone-pyrogallol phenolic resin (Clariant, Brignais, France)

DMF N,N-dimethylformamide Fisher's base 1 ,3,3-trimethyl-2-methyleneindoline; CAS# 118-12-7 (TCI America, Portland, OR, USA))

Intermediate A 2-chloro-1-formyl-3-hydroxymethylenecyclohexene Intermediate B 2,3,3-trimethyl-(3-sulfapropyl)indolenium, inner salt IR Dye A 2-[2-[2-chloro-3-[[1 ,3-dihydro-1 ,1-dimethyl-3-(3-suIfopropyl)- 2H-benz[e]indol-2-ylidene]ethylidene]-1 -cyclohexen-1 - yl]ethenyl]-1 , 1 -dimethyl-3-(3-sulfopropyl)-1 H- benz[e]indolium inner salt (Eastman Kodak, Rochester, NY, USA) IR Dye B 2-[2-[2-chloro-3-[[1 ,3-dihydro-3,3-dimethyl-1-(3-sulfapropyl)- 2H-indol-2-ylidene]ethylidene]-1 -cyclohexen-1 -yl]ethenyl]- 3,3-dimethyl-1-(3-sulfapropyl)-3H-lndolium, inner salt, compound with N,N-diethyl-1-ethylamine (1 :1) IR Dye C 2-[2-[2-chloro-3-[[1 ,3-dihydro-3,3-dimethyl-1-(3-sulfapropyl)- 2H-indol-2-ylidene]ethylidene]-1 -cyclohexen-1 -yljethenyl]- 3,3-dimethyl-1-(3-sulfapropyl)-3H-lndolium, inner salt, compound with sodium (1 :1) IR Dye D See structure below

IR Dye E 4-[5-(4,6,6-tricyano-5-(4-carboxyphenyl)-2,4- hexadienylidene)-2-(4,6,6-tricyano-5-(4-carboxyphenyl)- 1 ,3,5-hexatrienyl)-1 -cyclopenten-1 -yl]-1 -piperazinecarboxylic acid, ethyl ester, compound with N,N-diethylethanamine (1 :3) IR Dye F See structure below IR Dye G 2-[2-[2-chloro-3-[[1 ,3-dihydro-1 ,1-dimethyl-3-(3-sulfopropyl)- 2H-benz[e]indol-2-ylidene]ethylidene]-1 -cyclohexen-1 - yl]ethenyl]-1 ,1-dimethyl-3-(3-sulfopropyl)-1 H- benz[e]indolium inner salt. IR Dye H Infrared-absorbing dye (Siber Hegner North America, Baltimore, MD, USA, catalog number SH820WS)

LB-6564 Phenol/cresol novolac resin (Bakelite AG, Southampton, UK) LODYNE® 103A Fluorosurfactant (Ciba Specialty Chemicals, Tarrytown, New York, USA) LODYNE® S-228M Anionic surfactant, blend of fluoro and silicone surfactants (Ciba Specialty Chemicals, Tarrytown, NY, USA) m-TMI 3-lsopropenyl-alpha, alpha-dimethylbenzyl isocyanate

N-13 Novolac resin; 100% m-cresol; MW 13,000 (Eastman Kodak Rochester, NY, USA) Polyacrylamide Polyacrylamide (m.w. ~10 kDa) (Sigma-Aldrich, Milwaukee, Wl, USA) Poly(acryIic acid) Poly(acrylic acid) (m.w. ~2 kDa) (Sigma-Aldrich, Milwaukee, Wl, USA) Poly(vinyl alcohol) 88% Polyvinyl alcohol (m.w. -13 kDa to -23 kDa) (Sigma- Aldrich, Milwaukee, Wl, USA)

Poly(vinyl alcohol) 75% Polyvinyl alcohol (m.w. -9 kDa to -10 kDa) (Sigma- Aldrich, Milwaukee, Wl, USA)

PP-1 Poly(4-hydroxystryene), MW = 23,000 (Hoechst) PP-2 60:40 Poly(styrene-co-allyl alcohol), MW = 2,200 (Aldrich, Milwaukee, Wl, USA)

PP-3 Copolymer, see structure below (Kokusan Chemical, Tokyo, Japan)

PP-4 Copolymer, see structure below (Kodak Polychrome Graphics, Gumna, Japan)

PP-9 Poly(2-hydroxyethyl methacrylate), MW = 300,000 (Scientific Polymer Products, Ontario, NY, USA)

PP-10 Poly(2-hydroxypropyl methacrylate), MW = 300,000 (Scientific Polymer Products, Ontario, NY, USA) PVP K15 Polyvinyl pyrrolidone (m.w. -6 kDa to -15 kDa), supplied as a pale yellow aqueous solution having about 30% solids (ISP Technologies, Wayne, NJ, USA)

PVP K30 Polyvinyl pyrrolidone (m.w. -40 kDa to -80 kDa), supplied as a solid (ISP Technologies, Wayne, NJ, USA) PVP K60 Polyvinyl pyrrolidone (m.w. -240 kDa to -450 kDa), supplied as a yellow aqueous solution having about 49% solids (ISP Technologies, Wayne, NJ, USA)

PVP K90 Polyvinyl pyrrolidone (m.w. -900 kDa to -1500 kDa), supplied as a yellow aqueous solution having 21.6% solids (ISP Technologies, Wayne, NJ, USA)

Pyridine - Sulfating agent (Aldrich, Milwaukee, Wl, USA) S0 complex

Substrate A 0.3 mm thick aluminum sheet which had been electrograined, anodized and treated with a solution of poly(vinylphosphonic) acid

Substrate B Electrochemically grained and anodized aluminum substrate, post-treated with poly(vinylphosphonic acid) (PVPA)

THF Tetrahydrofuran VAZO®-64 Azobisisobutyronitrile (DuPont, Wilmington, Delaware, USA)

IR Dye D

IR Dye E

IR Dye F

IR Dye G

General Procedures for the Synthesis of Sulfated Polymers 1. Synthesis of sulfated polymers that contain the ammonium ion This example describes a general procedure for the synthesis of sulfated polymers that contain the ammonium ion (Sulfated polymers 1A, 2A, 3A, 4A, 5A, 6A, 7A, 8A, 9A and 10A). 5.0-10.0 g of precursor polymer, 2.0-8.0 g of pyridine-S0₃ complex, and 25-100 g of pyridine was added to a 250 ml flask equipped with magnetic stirring bar, and the reaction mixture stirred at room temperature for 18 hours. The solvent was decanted from the reaction mixture, and the viscous residue was stirred with 2-10 ml of 30% aqueous ammonium hydroxide for 30 minutes. The polymer was precipitated in 600-1 ,000 ml of 2-propanol, tetrahydrofuran, acetone, or diethylether and filtered off. The resulting polymer was dissolved in 20-100 g of water, and the solution stored for further use. 2. Synthesis of sulfated polymers that contain the pyridinium ion This example describes a general procedure for the synthesis of sulfated polymers that contain the pyridinium ion (Sulfated polymers 3B, 4B, 5B and 8B). 5.0-10.0 g of precursor polymer, 2.0-8.0 g of pyridine-S03 complex, and 25-100 g of pyridine was added to a 250 ml flask equipped with magnetic stirring bar, and the reaction mixture stirred at room temperature for 18 hours. The solvent was decanted from the reaction mixture, and the viscous residue was precipitated in 600-1 ,000 ml of 2-propanol, tetrahydrofuran, acetone, or diethylether and filtered off. The resulting polymer was dissolved in 20-100 g of water or water/alcohol, and the solution stored for further use. 3. Synthesis of sulfated polymers that contain the tetramethylammonium ion This example describes a general procedure for the synthesis of sulfated polymers that contain the tetramethylammonium ion (e.g., 3C, 4C, and 5C). In a 250 ml flask equipped with magnetic stirring bar, 5.0-10.0 g of precursor polymer, 2.0-8.0 g of pyridine-S0₃ complex (Aldrich, Milwaukee, Wl, USA), and 25-100 g of pyridine was added, and the mixture was stirred at room temperature for 18 hours. The solvent was decanted from the reaction mixture, and the product stirred with 2-10 ml of 25% tetramethylammonium hydroxide for 30 minutes. The reaction mixture was then precipitated in 600-1 ,000 ml of 2- propanol or tetrahydrofuran, and the resulting polymer was then dissolved in 20- 100 g of water (or water/alcohol) for further use. Alternatively, sulfamic acid may be used as the sulfating agent for these polymers. 4. Synthesis of sulfated polymers that contain the sodium ion This example describes a general procedure the synthesis of sulfated polymers that contain the sodium ion (e.g., 6B and 7B). In a 250 ml flask equipped with magnetic stirring bar, 5.0-10.0 g of precursor polymer, 2.0- 8.0 g of pyridine-S0₃ complex), and 25-100 g of pyridine was added, and the mixture was stirred at room temperature for 18 hours. After decant solvent the polymer was stirred with 10-20 ml of 10% sodium hydroxide for 30 min. The reaction mixture was then precipitated in 600-1 ,000 ml of isopropyl alcohol or tetrahydrofuran, and the resulting polymer was then dissolved in 20-100 g of water (or water/alcohol) for further use. Example 1 This example illustrates the synthesis of precursor polymer 5 (PP-5).

PP-5

600 g of 2-methoxyethanol, 49.9 g of hydroxyethylmethacrylate, 32.8 g of styrene, 7.5 g of butylmethacrylate, 7.7 g of methacrylic acid, 1.96 g of VAZO®- 64, and 0.245 g of dodecylmercaptan were charged in to four necked 2 L flask equipped with a heating mantle, temperature controller, mechanical stirrer, condenser, nitrogen inlet and dropping funnel. The reaction mixture was heated to 80°C under nitrogen. A mixture of 149.6 g of hydroxyethylmethacrylate, 98.3 g of styrene, 22.4 g of butylmethacrylate, 23.0 g of methacrylicacid, 3.90 g of VAZO®-64, and 0.73 g of dodecylmercaptan was added over a period of 2 hours, followed by additional 0.98g of VAZO®64. After the reaction mixture was heated at 80°C for an additional 2h, an additional 0.98 g of VAZOΘ-64 was added. The reaction mixture was heated for an additional 4 h and allowed to cool to room temperature. Polymer conversion was >98%. The viscosity was 550cps at 40%n on-volatiles. The acid number was 50.0. The polymer was precipitated in water/ice mixture by using air driven mixer at 4000 rpm. The product was filtered off and dried at about 49°C (120°F) over night in an oven. Example 2 This example illustrates the synthesis of precursor polymer 6 (PP-6). PP-6

Synthesis of Monomer 1 : 50.23 g of m-TMI was charged in to four necked 500ml flask, equipped with a heating mantle, temperature controller, mechanical stirrer, condenser, and nitrogen inlet. The reaction mixture was heated to 30°C under a nitrogen atmosphere. Then a mixture of 234.2 g of dimethylacetamide and 27.82 g of p-aminophenol was added at 30°C. Two hours later the temperature was raised slowly to 40°C. The progress of the reaction was monitored by disappearance of the NCO absorption at 2275 cm^"1.

m-TMI p-Amino phenol

Synthesis of precursor polymer 6: 210.0 g of Dimethylacetamide, 120 g of Monomer 1 (25% non-volatiles), 48.87 g of N-phenylmaleimide, and 21.0 g of methacrylamide were charged in to four necked 500 ml flask. The reaction mixture was heated at 60°C. Nitrogen was passed through the reaction mixture for one hour after which a nitrogen atmosphere was maintained over the reaction mixture during the rest of the reaction. 0.135 g of VAZO®-64 was added, and the reaction mixture was maintained at 58 to 60°C for 22 hours. The conversion to polymer at this stage was approximately 94% based on percent nonvolatiles. An additional 0.3 g of VAZO®-64 was added and temperature was raised to 80°C. The polymer conversion was remained the same after several hours. The viscosity was 50 cps at 25% non-volatiles. The polymer was precipitated in water/ice mixture by using air driven mixer at 4000 rpm. The product was filtered off and dried at about 49°C (120°F) overnight in an oven. Example 3 This example illustrates the synthesis of precursor polymer 7 (PP-7).

PP-7

300.0 g of Dimethylacetamide, 30.0 g of hydroxyethyl methacrylate, 48.87 g of N-phenylmaleimide, and 21.0 g of methacrylamide were charged in to four necked 1 L flask equipped with a heating mantle, temperature controller, mechanical stirrer, condenser, and nitrogen inlet. The reaction mixture was heated at 60°C. Nitrogen was passed through the reaction mixture for one hour after which a nitrogen atmosphere was maintained over the reaction mixture during the rest of the reaction. 0.135 g of VAZO®-64 was added, and the reaction mixture was maintained at 58 to 60°C for 22 hours. The conversion to polymer at this stage was approximately 80% based on percent nonvolatiles. An additional 0.3g of VAZO® 64 was added and temperature was raised to 80°C for an additional two hours. The polymer conversion was >98% and viscosity was 275 cps at 25% non-volatile. The polymer was precipitated in water/ice mixture by using air driven mixer at 4000 rpm. The product was filtered off and dried at about 49°C (120°F) overnight in an oven. Example 4 This example illustrates the synthesis of precursor polymer 8 (PP-8). PP-8 The procedure of Example 3 was repeated, except that 50.0 g of hydroxyethyl methacrylate, 35.0 g of N-phenylmaleimide and 15.0 g of methacrylamide were used. Example 5 This example illustrates preparation of 2-chloro-1-formyl-3- hydroxymethylenecyclohexene (Intermediate A).

80 ml of DMF was placed in a 500 ml round bottom flask equipped with a magnetic stirrer, a nitrogen gas inlet, a condenser, a thermometer and a pressure-equalizing additional funnel. The flask was cooled in an ice-water bath and 74 ml of phosphorous oxychloride was slowly added to the DMF while the reaction temperature was maintained between 10 and 15°C for one hour. Upon the completion of the addition, the reaction mixture was allowed to warm to room temperature for 30 minutes. A mixture of 20 g of cyclohexanone and 100 ml of DMF was slowly added o the flask the reaction temperature was maintained between 40 and 50°C. The mixture was heated at 55°C for 3 hours in a water bath, and was then slowly poured into a mixture of 600 g of ice and 400 g of water. After the reaction mixture was stirred for about 15 h, the precipitate was filtered and washed with water until a neutral filtrate was obtained. The resulting yellow solid was collected and dried at ambient temperature in dark overnight. The yield was 26 g. Example 6 Preparation of 2,3,3-trimethyl-(3-sulfapropyl)indolenium, inner salt (Intermediate B).

16 g of 2,3,3-trimethylindolenine (TCI America) was mixed with 15 g of 1 ,3-propanediol cyclic sulfate (Aldrich) in 200-ml of toluene in a 500-ml flask equipped with condenser and stirring bar. The mixture was heated at 100°C in an oil bath for 14 hours. After the reaction mixture was cooled to room temperature, the toluene was decanted, and the orange solid residual was stirred with 500-ml of acetone for 3 h. The suspension was filtered and washed with 3x30ml of acetone. The product was dried in ambient temperature. Yield: 16.6 g. Proton NMR (in DMSO-d₆): 51.53 (6H, s), 2.20 (2H, pentet), 2.85 (3H, s), 3.88 (2H, t), 4.56 (2H, t) and 7.50 -8.00 (4H, m). Example 7 Synthesis of 2-[2-[2-chloro-3-[[1 ,3-dihydro-3,3-dimethyl-1 -(3-sulfapropyl)- 2H-indol-2-ylidene]ethylidene]-1 -cyclohexen-1 -yl]ethenyl]-3,3-dimethyl-1 -(3- sulfapropyl)-3H-lndolium, inner salt, compd. with N,N-diethyl-1-ethylamine (1 :1) [Dye B]

0.3 g of triethylamine and 0.2 g of acetic anhydride were dissolved in 5 g of DMF. 0.59 g of intermediate B and 0.18 g of intermediate A were added to the DMF solution. The mixture was stirred at room temperature for 1 h and the color turned into dark green. Another portion of 0.3 g of triethylamine and 0.2 g of acetic anhydride was added and the reaction mixture was stirred overnight. After the reaction mixture was cooled to 0-5°C in a water-ice bath, the resulting precipitate was filtered off, washed with 30 ml of ethyl acetate, and dried in a vacuum. Yield: 0.40 g. Proton NMR (in DMSO-d₆): δ 1.16 (9H, t), 1.68 (12H, s), 1.83 (2H, m),

2.02 (4H, m), 2.74 (4H, m), 3.10 (6H, m), 3.87 (4H, t), 4.26 (4H, t), 6.41 (2H, d), 7.2-7.8 (8H, m), 8.26 (2H, d) and 8.85 (1 H, br). Example 8 Synthesis of 2-[2-[2-chloro-3-[[1 ,3-dihydro-3,3-dimethyl-1-(3-sulfapropyl)- 2H-indol-2-ylidene]ethylidene]-1 -cyclohexen-1 -yl]ethenyl]-3,3-dimethyl-1 -(3- sulfapropyl)-3H-lndolium, inner salt, compd. with sodium (1 :1 ) [Dye C]

© Na

2.0 g of dye formed in Example 3 was stirred with 20-ml water, 30 ml methanol and 1 g of sodium acetate for 1 h. The solid was filtered off, washed with 10 ml of water followed by 10 ml of methanol, and dried at room temperature overnight. Yield: 1.8 g. Proton NMR (in DMSO-d₆): δ 1.69 (12H, s), 1.84 (2H, m), 2.03 (4H, m), 2.75 (4H, m), 3.89 (4H, t), 4.27 (4H, t), 6.42 (2H, d), 7.2-7.8 (8H, m) and 8.28 (2H, d). Example 9 This Example illustrates evaluation of the sulfated polymers in imageable elements. Following the general procedures for the preparation of sulfated polymers, the following sulfated polymers were prepared.

© Θ © © 2A:X = NH₄ A:X =NH₄

© © 3A:X = NH₄ © 3B : X = Pyridinium © 3C:X = Tetramethyl ammonmm

© © 4A:X = NH₄ © 4B : X = Pyridinium © 4C : X = Tetramethyl ammonium

® ® 5A:X = NH₄ ® 5B : X = Pyridinium ® 5C : X = Tetramethyl ammonium

6A:X ⁺ = NH₄ ⁺ ® © 6B:X = Na

7A: x^@- © = NH, © 7B:X = Sodium

© © 8A:X = NH₄ © 8B:X = Pyridinium © © 9A : X = NH₄ 10A :-? - NH® The coating solutions for the imageable layers were prepared as shown in

Table 1. In addition to the ingredients listed, sample contained a trace (<0.01%) of LODYNE® S-228M. With the exception of 9-3, 9-4, 9-5, and 9-8, each coating solution was coated onto an electrochemically grained, anodized and post- treated with polyvinylphosphoric acid (PVPA) aluminum substrate using a wire wound bar. The resulting imageable element, consisting of the imageable layer on the substrate, was dried in a Ranar conveyor oven at about 76°C for about one minute. 9-3, 9-4, 9-5, and 9-8 were each coated from a sample coater, a slot coating device, and the resulting imageable element dried on a rotating drum. The dry coating weight of the imageable layers was between 0.5 - 2.0 g/m². Each of the imageable elements was placed on a CREO® Trendsetter 3244x image setter (CreoScitex, Burnaby, British Columbia, Canada), and imaged with a 830 nm laser at a power of 12 W and a range of drum speeds from 210 to 50 rpm (imaging energies of 130 to 550 mJ/cm²). Each imaged imageable element was developed in tap water or fountain solutions to remove the non-imaged regions.

Table 1

The minimum exposure energies to achieve good images varied from 160 to 550 mJ/cm² for Examples 9-1 to 9-16. No images were observed for Examples 9-2 and 9-17. Very weak images were formed in Examples 9-18, 9-19 and 9-20, but the imaged regions would not accept ink. Example 10 This example illustrates the preparation of sulfated novolac resins. Novolac A - An aqueous solution of a sulfated novolac resin prepared by the following method. LB 6564 (6 g, 0.05 mol) was dissolved in dimethylformamide (20 g). S0 -pyridine complex (4 g, 0.025 mol) and pyridine (2 g, 0.025 mol) was added, and the mixture was stirred at room temperature overnight. 5 mL of 30% ammonium hydroxide was added, which caused an exothermic reaction and clouding of the solution. The resulting solution was stirred for 30 min. 100 ml tetrahydrofuran was added, and a precipitate formed.

The precipitate mixture was stirred for 30 sec and then allowed to sit for 10 min.

The tetrahydrofuran solvent was decanted off, and 10 ml acetone was added to wash the precipitate. The acetone was decanted off, and the precipitate was dried with flowing nitrogen. The solid precipitate was dissolved in water to make a 15 wt% solution. The aqueous solution of sulfated novolac resin was maintained at a pH of about 7. In experiments similar to those described herein, if the pH was greater than about 8, or especially greater than about 9, the imageable layer containing the sulfated novolac was observed to dissolve away during water development, regardless of exposure energy. Although a latent image could be seen in the imaged imageable layer, both imaged and unimaged regions of the imageable layer washed away. On the other hand, if the pH of the novolac solution was less than 5, or especially less than 4, the sulfated novolac resin was apparently not stable in solution and decomposed or formed a precipitate. Using this method, theoretically 100% of the available hydroxyl groups on the phenolic resin starting material were converted to -OSθ3^"(NH4)⁺. Novolac B - An aqueous solution (15 wt%) of a sulfated novolac resin prepared using the method for Novolac A, except that only 1.5 g (0.009 mol)

SO₃-pyridine complex was used. Theoretically 37.5% of the available hydroxyl groups on the phenolic resin starting material were converted to -OSO₃ NH₄)^"1". Novolac C - An aqueous solution (15 wt%) of a sulfated novolac resin prepared using the method for Novolac A, except that only 2.0 g (0.013 mol)

S0₃-pyridine complex was used. Theoretically 50% of the available hydroxyl groups on the phenolic resin starting material were converted to -OSθ₃ ^"(NH₄)⁺. Novolac D - An aqueous solution (15 wt%) of a sulfated novolac resin prepared using the method for Novolac A, except that 5 ml of 30% potassium hydroxide solution was used in place of ammonium hydroxide. Theoretically

100% of the available hydroxyl groups on the phenolic resin starting material were converted to -OS0₃ ^"K⁺. Novolac X - An aqueous solution (16.7 wt%) of a sulfated novolac resin prepared using the method for Novolac A, except that LB 6564 was replaced with N-13 resin, and 3.0 g (0.019 mol) SO₃-pyridine complex was used. Using this method, theoretically 75% of the available hydroxyl groups on the phenolic resin starting material were converted to -OSO3~(NH₄)⁺. Novolac Y - An aqueous solution (16.5 wt.-%) of a sulfated novolac resin prepared using the method for novolac A, except that LB 6564 resin was replaced with N-13 resin. Theoretically 100% of the available hydroxyl groups on the phenolic resin starting material were converted to -OS0₃ ^"(NH₄)⁺. Example 11 This example illustrates the preparation of sulfated novolac resins. Example 11A This example illustrates preparation of a sulfated phenolic resin with an ammonium counterion. In a 250 ml flask equipped with magnetic stirring bar, 10.0 g of N-13, 8.0 g of pyridine-S0₃ complex, and 50 g of pyridine were mixed, and the mixture was stirred at room temperature for 18 hours. The solvent was then decanted from the reaction mixture. The product was stirred with 10 ml of 30% aqueous ammonium hydroxide for 30 minutes. The resulting sulfated phenolic resin was precipitated in 600 ml of /so-propyl alcohol. The precipitate was then dissolved in 100 g of water to yield a 17 wt% aqueous solution. The sulfated phenolic resin in aqueous solution was maintained at a pH of about 7 or above. The sulfated resin is stable in neutral or basic conditions, but will decompose when exposed to acidic conditions. Based on the quantity of reagents used, the theoretical degree of sulfation

(i.e., assuming 100% substitution) was about 0.60. The sulfur content of the precipitate was about 7.8% by weight, which suggested a degree of sulfation of about 0.40. This result may indicate either that the reaction was slightly incomplete, or that the pyridine-S0₃ complex had partially decomposed prior to the sulfation reaction. Example 11 B This example illustrates preparation of a sulfated phenolic resin with pyridinium counterion. In a 250-mL flask equipped with magnetic stirring bar, 10.0 g of N-13, 8.0 g of pyridine-SO₃ complex, and 50 g of pyridine were mixed, and the mixture was stirred at room temperature for 18 hours. Solvent was then decanted from the reaction. The resulting polymer was then washed three times with 50 ml of iso propyl alcohol and then dissolved in 85 g of water to form a 26.7 wt% aqueous solution. The sulfated phenolic resin in aqueous solution was maintained at a pH of about 7 or above. Example 11C This example illustrates preparation of a sulfated phenolic resin with ammonium counterion. 50.0 g of pyridine-S0₃ complex was added into a solution containing 36.0 g of LB 6564 phenolic resin and 120 g of DMF. The solution was stirred at room temperature for about 20 hours. 60 ml of 28% aqueous ammonium hydroxide solution was added and the mixture was stirred for another two hours. Then 135 ml of methanol was added, and the mixture stirred for an additional two hours. The resulting cloudy suspension was filtered and the sulfated phenolic resin was precipitated by adding 1.5 L of acetone into the filtrate while stirring. After the acetone was decanted and the remaining precipitate dried with a stream of nitrogen gas, the precipitate was dissolved in 100 ml of water to form a 24.3 wt% aqueous solution. The sulfated phenolic resin in aqueous solution was maintained at a pH of about 7 or above. Example 11 D This example illustrates preparation of a sulfated phenolic resin with ammonium counterion. 25.0 g of pyridine-S0₃ complex was added into a solution containing 18.0 g of N-15 and 60 g of DMF. The solution was stirred at room temperature for about 20 hr. 30 ml of 28% aqueous ammonium hydroxide solution was then added and the mixture was stirred for another two hours. Then 70 ml of methanol was added, and the mixture was stirred for an additional two hours. The resulting cloudy suspension was filtered and the sulfated phenolic resin was precipitated by adding 800 ml of acetone into the filtrate while stirring. After the acetone was decanted and the precipitate dried in a stream of nitrogen gas, the precipitate was dissolved in 150 ml of water to form a 12.8 wt% aqueous solution. The sulfated phenolic resin in aqueous solution was maintained at a pH of about 7 or above. Example 11 E This example illustrates preparation of a sulfated phenolic resin with ammonium counterion. In a 250-mL flask equipped with magnetic stirring bar, 5.0 g of AP resin, 4.0 g of pyridine-SO3 complex, and 40 g of pyridine were mixed, and the mixture was stirred at room temperature for 18 hr. The solvent was then decanted from the reaction. The reaction product was stirred with 5 ml of 30% aqueous ammonium hydroxide for 0.5 hr. The resulting sulfated phenolic resin was precipitated in 350 ml of THF. The precipitate was then dissolved in 30 g of water to yield a 21 wt% aqueous solution. Example 12 This example illustrates the preparation and imaging of imageable elements containing sulfated novolac resins. Example 12A A coating solution was prepared by combining 9.8 g of a 17 wt% aqueous solution of the sulfated phenolic resin from Example 11 A, 40 g of water, 0.4 g of IR Dye G, and 0.1 g of 10% LODYNE® 103A. Substrate B was mounted on a hot rotating drum and contacted with the coating solution, which was delivered to the substrate by a pump. The coated substrate was dried by blowing hot air about 65.5°C onto the imageable layer for about 2 min. Dry coating weight of the imageable layer was about 0.86 g/m². The resulting imageable element was imaged on a CREO® Trendsetter with 830 nm infrared laser radiation at a power of 12 W and a range of drum speeds from 210 to 50 rpm (corresponding to imaging energies of 130 to 540 mJ/cm²). The imaged imageable element was developed in tap water to remove the unexposed regions of the imageable layer. The resolution of the resulting image appeared to be at least 2 to 98% at 175 lines per inch, and the minimum exposure energy to achieve a good image was about 250 mJ/cm². A second imageable element was imaged at 250 mJ/cm² and then mounted directly on an A.B. Dick 9870 Duplicator Press (A.B. Dick, Niles, IL, USA). The press was charged with Van Son Rubber Base black Ink (Van Son Ink, Mineola, NY, USA). The aqueous fountain solution contained about 23.5 ml/L (3 oz per gallon) Varn Litho Etch142W (Varn International, Addison, IL, USA), and about 23.5 ml/L (3 oz per gallon) Varn PAR (alcohol substitute) in water. The imaged imageable element was developed in fountain solution to yield a printable lithographic printing plate. A printing plate that printed at least 250 copies of good prints was produced. Example 12B A coating solution was prepared by combining 9.8 g of a 17 wt% aqueous solution of the sulfated phenolic resin prepared in Example 11 A, 35 g of water, 5 g of /so-propyl alcohol, 0.4 g of IR Dye E, and 0.1 g of 10% LODYNE® 103A. The coating solution was coated onto Substrate B as in Example 12A. Dry coating weight of the imageable layer was about 0.86 g/m². The resulting imageable element was imaged at 250 mJ/cm² as in Example 12A, mounted directly on an A.B. Dick Press, and developed in fountain solution. The developed plate printed at least 250 copies of good quality prints. Example 12C A coating solution was prepared by combining 2.5 g of a 26.7 wt% aqueous solution of the sulfated phenolic resin prepared in Example 11B, 7.5 g of water, 0.075 g of IR Dye G, and 0.02 g of 10% LODYNE® 103A was coated onto Substrate B with a wire-wound bar. The resulting imageable element was dried at 100°C in a Ranar conveyor oven (Ranar Mfg. Co. Inc., El Segundo, California) for about 1 min. The dry coating weight of the imageable layer was about 1.0 g/m². The resulting imageable element was imaged as in Example 12A at a power of 12 W and a range of drum speeds from 210 to 50 rpm (corresponding to exposure energies ranging from 130 to 550 mJ/cm²) and developed as in Example 12A. The minimum imaging energy to achieve a good image was about 200 mJ/cm² Example 12D A coating solution was prepared by combining 13.5 g of

24.3 wt% aqueous solution of the sulfated phenolic resin prepared in Example 11C, 37.5 g of water, 0.25 g of IR Dye G, and 0.1 g of 10% LODYNE® 103A and coated onto Substrate B as described in Example 12A. The dry coating weight of the imageable layer was about 0.86 g/m². The resulting imageable element was imaged at a power of 12 W and a range of drum speeds from 250 to 60 rpm (corresponding to exposure energies ranging from 110 to 500 mJ/cm² as described in Example 12A). The resulting imaged imageable element was preheated in a Heavy Duty Oven (Wisconsin Oven Corp., East Troy, Wisconsin) at about 133°C (272°F) for about 2 min and was developed in tap water as in Example 12A. The resolution of the resulting image appeared to be at least 2 to 98% at 175 lines per inch, and the minimum exposure energy to achieve a good image was about 150 mJ/cm². In a second experiment, the imaged imageable element was developed in tap water without preheating. The minimum exposure energy to obtain a good image without preheating was about 550 mJ/cm². Example 12E A coating solution was prepared by combining 3.3 g of 12.8 wt% aqueous solution of the sulfated phenolic resin prepared in Example 11 D, 6.7 g of water, 0.075 g of IR Dye G, and 0.02 g of 10% LODYNE® 103A and coated onto Substrate B as described in Example 12C. The dry coating weight of the imageable layer was about 1.0 g/m². The resulting imageable element was imaged as in Example 12A at a power of 12 W and a range of drum speeds from 210 to 50 rpm (corresponding to exposure energies ranging from 130 to 550 mJ/cm²), preheated at about 143°C (290°F), and developed in tap water as in Example 12D. The minimum imaging energy to achieve a good image was about 160 mJ/cm². In a second experiment, the imaged imageable element was developed in tap water without preheating. The minimum exposure energy to obtain a good image without preheating was about 550 mJ/cm². Example 12F A coating solution was prepared by combining 2.86 g of 21 wt% aqueous solution of the sulfated resin prepared in Example 1 E, 7.2 g of water, 0.05 g of IR Dye G, and 0.01 g of 10% LODYNE® 103A and coated onto Substrate B as described in Example 12C. The dry coating weight of the imageable layer was about 0.8 g/m². The resulting imageable element was imaged as in Example 12A at a power of 12 W and a range of drum speeds from 250 to 60 rpm (corresponding to exposure energies ranging from 110 to 500 mJ/cm²) and developed as in Example 12A. The resolution of the resulting image appeared to be at least 5 to 97% at 175 lines per inch, and the minimum exposure energy to achieve a good image was about 400 mJ/cm². Example 13 Example 13A and 13B Coating solutions were prepared as Table 2. A sufficient quantity of water was used to give a dry coating weight of about 1.5 g/m². Each coating solution was coated onto Substrate B with a wire-wound bar. The dry coating weight of the imageable layer was about 1.5 g/m². Table 2

After the resulting imageable elements were aged for 48 hr at room temperature, they were imaged with the CREO® Trendsetter with 830 nm infrared laser radiation, using an internal test pattern (15.5 W laser power; drum speed of 117, 100, 87, 77, and 70 rpm, corresponding to imaging energies of 300, 350, 400, 450 and 500 mJ/cm²). Latent images were observed. The imaged imageable elements were drenched in cold tap water for 20 sec, rubbed with a wet cotton pad for a further 10 sec, and dried. The unexposed regions of the imageable layer were removed, revealing the hydrophilic aluminum substrate. The optimum exposure energy for both compositions 13A and 13B was 400 mJ/cm². The resolution at 400 mJ/cm² was at least 2 to 98% at 150 lines per inch. The printing plate of Example 13A was inked by hand using a wet rag with printing ink applied. The ink preferentially stuck to the green coating of the plate. Water was retained on the aluminum substrate. Example 13A was repeated twice, except that the imaged imageable element was dried for 1 min and for 3 min in the oven. In each case, the results were the same as those for Example 13A. Example 13A was repeated twice more, except that the time between coating and imaging was 24 hr and 72 hr, respectively. The imageable element aged for 72 hr produced the same result as above. The imageable element aged for only 24 hr did not achieve 2 to 98% resolution at 400 mJ/cm² imaging energy. Most of the imaged regions of the imageable layer were removed by the tap water. Example 13C This Comparative Example demonstrates that a water- soluble binder having low molecular weight may not provide sufficient resistance to water or a liquid developer to make a useful imageable layer. An aqueous coating solution was prepared according to Table 3. Sufficient of water was used to give a dry coating weight for the imageable layer of about 1.5 g/m². Table 3

A substrate was coated as in Example 13A and the resulting imageable element consisting of the imageable layer over the substrate dried at 100°C for 10 min in the oven, to yield a printing plate precursor. After the precursor aged at room temperature for 48 hours, it was imaged as in Example 13A. A latent image was observed. On developing with water, both the imaged and unimaged regions of the imageable layer were removed. Example 13D The procedure of Example 13C was repeated, except that the ingredients listed in Table 4 were used to prepare the aqueous coating solution. A sufficient quantity of water was used to give a coating weight of about 1.5 g/m² for the imageable layer. Table 4

Following aging and imaging as in Example 13A, a latent image was observed. When the imaged precursor was drenched in cold tap water for 20 sec, rubbed with a wet cotton pad for a further 10 sec, and dried, an image was developed. The optimum exposure energy was 450 mJ/cm². Examples 13E to 13H The procedure of Example 13A was repeated, except that the ingredients listed in Table 5 were used to prepare the aqueous coating solution. A sufficient quantity of water was used to give a coating weight of about 1.5 g/m² for the imageable layer. Table 5

Following aging and imaging as in Example 13A, latent images were observed. When the imaged precursor was drenched in cold tap water for 20 sec, rubbed with a wet cotton pad for a further 10 sec, and dried, an image was developed. The optimum exposure energy was 450 mJ/cm². When the imaged precursors were developed as in Example 13A, the unexposed regions of the imageable layers were removed, revealing the hydrophilic aluminum substrate. For Examples 13F and 13H, the optimum exposure energy was 450 mJ/cm². For examples 13E and 13G, the optimum exposure energy was 500 mJ/cm². Examples 13E to 13H were repeated, except that period between coating and imaging was 96 hrs. After imaging and developing, the results were the same. Examples 131 to 13K The procedure of Example 13A was repeated, except that the ingredients listed in Table 6 were used to prepare the aqueous coating solutions. A sufficient quantity of water was used to give a coating weight of about 1.5 g/m² for the imageable layer. Table 6

Following aging and imaging as in Example 13A, a latent images were observed. When the imaged precursors were developed as in Example 13A, images were formed. The optimum exposure energy was 550 mJ/cm² for each example. Examples 13L and 13M. Comparative Example 13N, and Examples 130 and 13Q The procedure of Example 13A was repeated, except that the ingredients listed in Table 7 were used to prepare the aqueous coating solutions. A sufficient quantity of water was used to give a coating weight of about 1.5 g/m² for the imageable layer. Table 7

Following aging and imaging as in Example 13A, latent images were observed. When the imaged precursors were developed as in Example 13A, images were formed. For Examples 13L and 13P, the optimum exposure energy was 400 mJ/cm². For Examples 13M and 13Q, the optimum exposure energy was 450 mJ/cm². For Example 130 the optimum exposure energy was 350 mJ/cm². Comparative Example 13N, no optimum exposure was found, and the imaged precursor did not develop completely in water. Example 14 This example illustrates preparation of printing plate precursors and imaged printing plates having imageable layers comprising water-soluble binders. Examples 14A to 14E The procedure of Example 13A was repeated, except that the ingredients listed in Table 8 were used to prepare the aqueous coating solutions. A sufficient quantity of water was used to give a coating weight of about 1.5 g/m² for the imageable layer. Table 8

Following aging and imaging as in Example 13A, latent images were observed. When each imaged precursor was drenched in cold tap water for 20 sec, rubbed with a wet cotton pad for a further 10 sec, and dried, an image was developed. The optimum exposure energy was 450 mJ/cm². For Example 4A, the optimum exposure energy was 300 mJ/cm². For Examples 4B and 4C, the optimum exposure energy was 350 mJ/cm². For Example 4D, the optimum exposure energy was 400 mJ/cm². For Example 4E, the optimum exposure energy was 450 mJ/cm². Examples 14F to 14H. Comparative Example I, and Examples 14J and 14L The procedure of Example 13A was repeated, except that the ingredients listed in Table 9 were used to prepare the aqueous coating solutions. A sufficient quantity of water was used to give a coating weight of about 1.5 g/m² for the imageable layer. Table 9

Examples 14F, 14G, 14J, 14K and 14L were aged for 48 hours and the printing plate precursors were imaged as described for Example 13A. Latent images were observed. When each imaged precursor was drenched in cold tap water for 20 sec, rubbed with a wet cotton pad for a further 10 sec, and dried, an image was developed. For Example 14F, the optimum exposure energy was 500 mJ/cm². For Examples 14G and 14L, the optimum exposure energy was 300 mJ/cm². For Examples 14J and 14K, the optimum exposure energy was 350 mJ/cm². Example 14H and Comparative Example 141 were not aged prior to imaging. The printing plate precursors were imaged as described for Example 13A. Latent images were observed. When each imaged precursor was drenched in cold tap water for 20 sec, rubbed with a wet cotton pad for a further 10 sec, and dried, an image was developed. The printing plate formed in Example 14H was mounted on the A.B. Dick Press. It printed at least 250 good-quality impressions. The printing plate formed in Comparative Example 141 was mounted on the A.B. Dick Press. When ink and fountain solution were applied to the plate surface, the image dissolved away in the fountain solution, leaving no image from which an impression could be made. Examples 14M to 14Q The procedure of Example 13A was repeated, except that the ingredients listed in Table 10 were used to prepare the aqueous coating solutions. A sufficient quantity of water was used to give a coating weight of about 1.5 g/m² for the imageable layer. Table 10

Following aging and imaging as in Example 13A, latent images were observed. When each imaged precursor was drenched in cold tap water for 20 sec, rubbed with a wet cotton pad for a further 10 sec, and dried, an image was developed. For Examples 1.4M and 14N, the optimum exposure energy was 250 mJ/cm². For Examples 140 and 14P, the optimum exposure energy was 400 mJ/cm². For Example 14Q, the optimum exposure energy was 300 mJ/cm². Examples 14R and 14S The procedure of Example 13A was repeated, except that the ingredients listed in Table 11 were used to prepare the aqueous coating solutions. A sufficient quantity of water was used to give a coating weight of about 1.5 g/m² for the imageable layer. Table 11

Following aging and imaging as in Example 13A, latent images were observed. When each imaged precursor was drenched in cold tap water for 20 sec, rubbed with a wet cotton pad for a further 10 sec, and dried, an image was developed. For Example 14R, the optimum exposure energy was 350 mJ/cm². For Comparative Example 14S, no optimum exposure was found, and the imaged precursor did not develop completely in water. Examples 14T to 14W The procedure of Example 13A was repeated, except that the ingredients listed in Table 12 were used to prepare the aqueous coating solutions. A sufficient quantity of water was used to give a coating weight of about 1.5 g/m² for the imageable layer. Table 12

Following aging and imaging as in Example 13A, latent images were observed. When each imaged precursor was drenched in cold tap water for 20 sec, rubbed with a wet cotton pad for a further 10 sec, and dried, an image was developed. For each of Examples 4T to 4W, optimum exposure energy was 400 mJ/cm². Having described the invention, we now claim the following and their equivalents.

Claims

What is claimed is: 1. An imageable element comprising an imageable layer over a substrate; in which the imageable layer comprises a photothermal conversion material, and a sulfated polymer comprising sulfate groups. 2. The element of claim 1 in which the sulfate groups are attached to aryl groups. 3. The element of claim 2 in which the sulfated polymer is a sulfated novolac resin. 4. The element of claim 1 in which the sulfate groups are attached to alkyl groups. 5. The imageable element of claim 1 in which the sulfated polymer is: 1 ) a sulfated co-polymer of methyl methacrylate, acrylonitrile, methacrylamide, and CH₂=C(CH₃)-C0₂-(CH₂)₂-NH-CO-NH-p-C₆H₄-OH; 2) a sulfated co-polymer of acrylonitrile, methacrylamide, N- phenylmaleimide, CH₂=C(CH₃)-CO-NH-p-C₆H₄-CO₂H, and CH₂=C(CH₃)-Cθ₂-(CH₂)₂-NH-CO-NH-p-C₆H₄-OH; or 3) a sulfated co-polymer of butyl methacrylate, styrene, hydroxyethyl methacrylate, and methacrylic acid. 6. The imageable element of any preceding claim in which the sulfated polymer comprises hydroxyl groups and the sulfate groups, and at least 50% of the sum of the hydroxyl groups and the sulfate groups are sulfate groups. 7. The imageable element of any preceding claim in which at least 30 mol% of recurring units that comprise the polymer comprise either the hydroxyl group or the sulfate group. 8. A method for forming an image, the method comprising the steps of: thermally imaging the imageable element of any of claims 1 to 7 and forming an imaged imageable element comprising imaged and complementary unimaged regions in the imageable layer; and developing the imaged imageable element with either an aqueous liquid or a fountain solution and removing the imaged regions to form the image. 9. The method of claim 8 in which development is carried out on press. 10. The method of claim 9 in which imaging is carried out on press.