THERMAL WATERLESS LITHOGRAPHIC PRINTING PLATE

Abstract: A waterless or driographic printing plate which can be thermally imaged by an infrared laser is composed of a substrate; a thermal imaging layer containing a photothermal conversion material, such as an infrared absorbing material, and a thermoplastic polyurethane with pendent allyl groups; and a cross-linked silicone polymer top layer. It was discovered that when the imaging layer contains an allyl functional polyurethane mixed with an infrared absorbing dye or pigment, the polymeric layer will have enhanced solubility in certain solvents when exposed to infrared radiation. In addition, the polymeric layer continues to exhibit excellent adhesion to the silicone in unexposed areas so that the infrared absorbing layer can endure development with a suitable organic solvent, or a solvent mixture. Mild brushing or rubbing with the developing solvent readily removes laser-struck portions of the infrared imaging layer while unexposed areas remain firmly intact.

Description: FOR THE PURPOSES OF INFORMATION ONLY Codes used to identify States party to the PCT on the front pages of pamphlets publishing international applications under the PCT. AL Albania ES Spain LS Lesotho SI Slovenia AM Armenia FI Finland LT Lithuania SK Slovakia AT Austria FR France LU Luxembourg SN Senegal AU Australia GA Gabon LV Latvia sz Swaziland AZ Azerbaijan GB United Kingdom MC Monaco TD Chad BA Bosnia and Herzegovina GE Georgia MD Republic of Moldova TG Togo BB Barbados GH Ghana MG Madagascar TJ Tajikistan BE Belgium GN Guinea MK The former Yugoslav TM Turkmenistan BF Burkina Faso GR Greece Republic of Macedonia TR Turkey BG Bulgaria HU Hungary ML Mali TT Trinidad and Tobago BJ Benin IE Ireland MN Mongolia UA Ukraine BR Brazil IL Israel MR Mauritania UG Uganda BY Belarus IS Iceland MW Malawi US United States of America CA Canada IT Italy MX Mexico UZ Uzbekistan CF Central African Republic JP Japan NE Niger VN Viet Nam CG Congo KE Kenya NL Netherlands YU Yugoslavia CH Switzerland KG Kyrgyzstan NO Norway zw Zimbabwe CI Cδte d'lvoire KP Democratic People's NZ New Zealand CM Cameroon Republic of Korea PL Poland CN China KR Republic of Korea PT Portugal cu Cuba KZ Kazakstan RO Romania cz Czech Republic LC Saint Lucia RU Russian Federation DE Germany LI Liechtenstein SD Sudan DK Denmark LK Sri Lanka SE Sweden EE Estonia LR Liberia SG Singapore opaque top layer However, masked printing plates are costly to manufacturing and require more complicated processing such as flood exposing and the removal of the mask U S Patent 5,339,737 teaches physically transforming an infra-red-absorbing layer by laser ablation using high doses of laser energy in order to remove the overlying silicone layer However, this process is relatively time consuming In order to circumvent the problem, U S Patent 5,353,705 describes adding an ablatable, but non- infrared absorbing, layer, below the infrared absorbing layer Another approach, taught in U S Patent 5,379,698, involves using a metallic or metal oxide thin film as the imaging layer Yet another approach is taught in U S Patent 5,487,338 and involves using an infrared reflective layer situated below the infrared absorbing layer All of the above approaches, however, introduce additional cost to the manufactuπng of CTP waterless printing plates In addition, the debris produced during imaging of these printing plates generally requires an additional step and/or complicated devices to clean the plate subsequent to imaging Despite the improvements made in the manufacture of CTP waterless printing plates, there continues to be a need for a more cost effective and efficient manufacture of high performance CTP waterless printing plates SUMMARY OF THE INVENTION The present invention is a waterless printing plate imageable with minimal infrared energy that can be imaged free of debris In particular, the present invention is a dry planographic printing plate precursor element comprising, A) a substrate, B) a composite layer structure having an inner surface contiguous to the substrate and an outer surface, the composite layer structure comprising (a) a first layer applied to a surface of the substrate, the first layer consisting essentially of at least one photothermal conversion material and a thermoplastic polyurethane containing allyl groups, and (b) a silicone layer compπsed of a cross-linked silicone polymer An added embodiment of this invention is a method for forming a planographic printing plate comprising the steps, in the order given I) providing the planographic printing plate precursor element of this invention described supra, II) imagewise exposing the composite layer structure to thermal energy to provide exposed portions and complimentary unexposed portions in the composite layer structure, wherein the exposed portions are selectively permeable to a developer liquid, and III) applying the developer liquid to the composite layer structure to remove the exposed portions to produce an imaged planographic printing plate having uncovered ink receptive areas and complimentary ink repellent areas of the silicone layer In a preferred embodiment of this invention the thermoplastic polyurethane containing allyl groups contains pendent allyl groups and is prepared by reacting a dnsocyanate and a diol material containing at least one allyl functional diol, and the photothermal conversion material is an infrared absorbing mateπal DETAILED DESCRIPTION OF THE INVENTION This invention relates to an imaging element which can be imaged with thermal energy More particularly, this invention relates to dry, thermal lithographic printing plates, which can be imaged by thermal energy typically by imagewise exposure with an infrared emitting laser, a laser emitting in the visible, or the like A key aspect of the present invention lies in the discovery that when the imaging layer of the plate contains an allyl functional polyurethane mixed with an infrared absorbing dye or pigment, the polymeric layer will have enhanced solubility in certain solvents when exposed to infrared radiation In addition, the polymeric layer will continue to exhibit excellent adhesion to the silicone in the unexposed areas The infrared absorbing (thermal) layer of the present invention can therefore endure development with a suitable organic solvent, or a solvent mixture Mild brushing or rubbing with the developing solvent will readily remove the laser-struck portion of the infrared sensitive layer while the unexposed area remains firmly intact Plate Construction The plate construction of the present invention includes a composite layer structure supported by a substrate The composite layer structure includes a silicone top layer overlying a first layer, hereinafter identified as a "thermal" layer having an inner surface contiguous to the substrate Optionally, the construction may also include (a) a protection layer atop the silicone layer, (b) an adhesion promotion layer between silicone and the thermal layer, and (c) a pπmer layer between the thermal layer and substrate Thermal Layer The thermal layer is composed of a unique composition which consists essentially of at least one photothermal conversion material and an allyl functional polyurethane Thus, two essential components of the thermal layer are (i) an allyl functional polyurethane, and (n) an photothermal conversion mateπal As used herein the term "allyl functional polyurethane" is intended to mean a thermoplastic polyurethane containing allyl groups which may be either pendent or terminal allyl groups As used herein the "photothermal conversion material" is a component which absorbs incident radiation and converts the radiation to thermal energy Typically, the photothermal conversion material is an "infrared absorbing" compound Optional ancillary ingredients such as non-absorbing colorants, print-out dyes, surfactants, and acid or base generators may also be added to the thermal layer for cosmetic reasons, quality control and/or to facilitate image inspections before or after development The thermal layer hereinafter will be described as an "infrared absorbing layer" having an infrared absorbing composition with at least one "infrared absorbing material", but is not intended to be limited thereby The allyl functional polyurethane may be prepared, for example, by reacting a dnsocyanate with an allyl functional diol Mixtures of different dnsocyanates and of different diols may be used to prepare the polyurethane with the proviso that at least one of the diols must contain at least one allyl group Useful allyl functional diols have the general formula HOCR 1 2 -CR 2 (OH)-CR 3 2 -O-CR 4 2 -CR 5 =CR 6 2 where R 1 - R 6 are individually selected from hydrogen or alkyl groups Preferably, all R groups are hydrogen Commercially available diols having an allyl groups include 3- allyloxy-1 ,2-propanedιol and tπmethylolpropane allyl ether Other diols having an allyl ester group include allyl 4,4-bιs-(hydroxyethyloxyphenyl)-pentanoate and allyl 2,2- bιs(hydroxymethyl)propanoate These allyl functional diols may be used alone or in combination, or further in combination with a diol not containing the allyl functionality Examples of useful diols, not containing the allyl functionality, include ethylene glycol, polyethylene glycol, propylene glycol, polypropylene gylcol, neopentyl glycol, butanediol, and 2,2-bιs(hydroxymethyl) propionic acid In making the allyl functional polyurethane both aromatic and aliphatic dnsocyanates may be reacted with the diol or diol mixture Examples of aromatic dnsocyanates include 2,4-toluene dnsocyanate, 2,6-toluene dnsocyanate, p-xylene dnsocyanate, m-xylene dnsocyanate, tetramethylxylene dnsocyanate, 4,4'- diphenylmethane dnsocyanate, 1 ,5-naphthaleπe dnsocyanate, 3,3'-dιmethylbιphenyl- 4 4'-dιιsocyanate and the like Examples of aliphatic dnsocyanates are hexamethylene dnsocyanate, tπmethylhexamethylene dnsocyanate, isophorone dnsocyanate, 4-4'- methylenebis (cyclohexyl isocyanate), methylcyclohexane-2,4-(or 2,6)-dιιsocyanate, 1 ,4- bιs(ιsocyanatomethyl) cyclohexaπe and the like The allyl functional polyurethane also may be prepared by reacting a dnsocyanate with a COOH functional diol such as dimethylol propionic acid, and then converting the COOH groups on the resulting polyurethane into allyl ester groups The other essential ingredient of the infrared absorbing layer is the infrared absorber which is selected from either a dye or pigment A primary factor in selecting the infrared absorber is its extinction coefficient which measures the efficiency of the dye or pigment in absorbing infrared radiation in accordance with Beer's Law Useful infrared absorbing compounds typically have a maximum absorption wavelength (λ max ) in some part of the electromagnetic spectrum greater than about 750 nm, that is in the infrared region and near infrared region of the spectrum More particularly, they must have high absorptivity in a part of the wavelength region from about 780 nm to about 1300 nm and typically from about 800 nm to about 1100 nm Thus the extinction coefficient must have a sufficient value to efficiently absorb the infrared radiation exposure usually having wavelengths from 780 nm to 1300 nm The infrared absorbing compounds can be dyes or pigments, and a wide range of compounds are well known in the art Classes of materials that are useful include, but are not limited to, tπarylamine, thiazolium, indolium, oxazolium, polyaniline, polypyrrole, polythiophene, squaπlium, croconate, cyanine, phthalocyanme, merocyanine, chalcogenopyryloarylidine, bιs(chalcogenopyryrlo)polymethιne, oxyindohzine, qumoid, indolizme, pyrylium, and thiolene metal complexes (e g metal dithiolene) dyes and pigments Other useful classes include thiazine, azulenium and xanthene dyes and dark inorganic pigments Examples of infrared absorbing dyes useful in the present invention include, Cyasorb IR 99 and Cyasorb IR 165 (both available from Glendale Protective Technology), Epolite IV-62B and Epolite 111-178 (both available from the Epoline Corporation), PINA-780 (available from the Allied Signal Corporation), SpectraIR 830A and SpectraIR 840A (both available from Spectra Colors Corporation) Examples of infrared absorbing pigments are Projet 900, Projet 860 and Projet 830 (all available from the Zeneca Corporation) Carbon black pigments may also be used Carbon black pigments are particularly advantageous due to their wide absorption bands since such carbon black- based plates can be used with multiple infrared imaging devices having a wide range of peak emission wavelengths Other ingredients that optionally may be present in the infrared absorbing layer include dyes and acid or base generators for visible image readout Suitable dyes of this type include Solvent biue 35, Victoπa pure blue BO, 4-(phenylazo) diphenyiamme, ethyl orange Pergascnpt Red I-6B (available from the Ciba-Geigy Corporation), and the like Suitable acid generators include lodomum and sulfonium salts Silicone Layer The silicone layer used in the present invention may be a crosslinked polydiorganosiloxane comprising the following repeating units. R -Si-O- R wherein each R is independently selected form a monovalent alkyl, aryl or alkenyl group, or a combination thereof R may contain functional substituent groups such as hydroxyl, halogen, ammo, alkoxy, aryloxy, (meth)acryloxy, and thiol Preferably the R group is methyl which should be in the majority when a mixture of R groups is used The silicone layer may optionally contain pigments and fillers such as silica, calcium carbonate, and titanium oxide Adhesion promoters may also be added to the coating to improve silicone layer formation. Polydiorganosiloxane networks may be formed, for example, by known crosshnking reactions such as the condensation of a silanol and acyloxy or alkoxy silanes, the addition of hydrosilane to alkenyl groups, and the photo-initiated polymerization of (meth)acrylate or epoxy groups; however, preferred are the condensation and addition methods. For the condensation crosshnking method, a silanol terminated diorganosiloxane polymer, for example, may be reacted with polyacyloxy or polyalkoxy silane crosslinkers in the presence of a suitable catalyst This reaction may be accelerated both by heat and moisture For a better pot life during manufacturing, a silicone network may be formed via the self condensation between polydiorganosiloxane with tπaikoxysilyl groups on both ends as is descπbed in European Patent Application EP0763780A2. Catalysts suitable for this condensation are organic carboxylic acid salts of tin, zinc and other multivalent metals that are well known in the art Adhesion promoters may also be included in this type of silicone coating formulation Preferred adhesion promoters are aminosilanes, such as represented by the general formula where R is unsubstituted or monosubstituted amino-alkyl, R' and R" are each alkyl or aryl, m is 1 or 2 and n is 0 or 1 , m+n being equal to 1 or 2 Specific examples of such aminosilanes are γ-aminopropyltπethoxy silane and γ-[N-(2-amιnoethyl)-amιno]propyl tπmethoxy silane Polydiorganosiloxanes cross nked via addition reaction between hydrosilane and alkenyl groups may be prepared, for example, from a vinyl functional polydiorganosiloxane and methyl hydrosiloxane homopolymer or copolymer in the presence of a suitable catalyst The alkenyl groups in the siloxane polymer may be randomly distπbuted along the polymeric chain, or located at the chain ends The addition catalysts may be selected from known ones, however, preferred are elemental platinum, platinum chloride, chloroplatinic acid and platinum coordinated with olefins To improve pot-life, volatile inhibitors such as ketones, alcohols and alkynes may be used Particularly preferred are alkynes such as those disclosed in US Patent No 4,184,006 Specific examples of such alkynes are 2-methyl-3-butyne-2-ol, ethynylcyclohexanol, 2- butyne, 2-methyl-but-1-en-3-yne, and phenyl acetylene Organic solvents may be used to facilitate film formation of the silicone layer Suitable solvents include aliphatic and aromatic hydrocarbons, ketones, and esters Specific examples of useful solvents are hexane, heptane, toluene, xylene, 2-butanone, and amyl acetate The amount of solvents used primarily depends upon molecular weights of silicone starting mateπals, coating thickness and the coating application technique Coating methods for applying silicone coatings are known in the art Preferred coating methods for use in this invention include whirl coating, wire-wound bar coating, direct gravure coating, gravure-offset coating, liquid curtain coating, slit- extrusion coating, meniscus coating and the like The coating weight of the silicone layer may be in the range between about 0 2 to about 10 g/m 2 , and preferably in the range between about 1 0 to about 3 0 g/m 2 Substrate Substrates which may be used in the planographic plate of this invention may be any sheet material conventionally used to prepare lithographic printing plates Suitable substrates include metals such as aluminum sheets, paper, paper coated on one or both sides with an α-olefin polymer such as polyethylene, films such as cellulose acetate film, polyvinyl acetal film, polystyrene film polypropylene film, polyester film such as polyethylene terephthalate film, polyamide film, polyimide film, nitrocellulose film, polycarbonate film, polyvinylchioπde film, composite films such as polyester, polypropylene or polystyrene film coated with polyethylene film, metalized paper or films, metal/paper laminates, and the like Such substrates may contain an antihalation compound or sub coatings A preferred substrate is an aluminum sheet The surface of the aluminum sheet may be treated by metal finishing techniques known in the art including brush roughening, electrochemical roughening, chemical roughening, anodizing, and silicate sealing and the like If the surface is roughened, the average roughness Ra is preferably in the range from 0 1 to 0 8 μm, and more preferably in the range from 0 1 to 0 4 μm The preferred thickness of the aluminum sheet is in the range from about 0 005 inch to about 0 020 inch The surface of plastic films may be treated using the surface treatment techniques known in the art to improve adhesion between the substrate and organic coatings Optional Layers The planographic printing plate of this invention may contain one or more ancillary layers to improve interlayer adhesion, to reduce halation effects, to improve pnnting surface characteristics, and the like Optional layers that may be added to modify the essential plate construction include a protective layer laminated on top of silicone layer, an adhesion promotion layer between silicone and the infrared absorbing layer, and a primer layer between the radiation sensitive layer and the substrate An optional pπmer layer may be inserted between the infrared absorbing layer and substrate to, for example, prevent heat loss, especially when the substrate is a metal sheet, regulate ink receptivity, serve as a dye acceptor, if the developed plate needs to be dyed for visual image contrast enhancement, act as an adhesion promoter The pπmer layer may be a thermoplastic coating, provided the coating is not soluble in the solvents employed to make the infrared absorbing layer Examples of thermoset coatings include polyester-melamine coatings, acrylic melamine coatings, epoxy coatings, and polyisocyanate coatings An example of a thermoplastic coating is polyvinyl alcohol When cured by ultraviolet radiation, the primer layer may be prepared from free radical polymeπzable coatings, cationic crosslinkable coatings catalyzed by photo generated acid, and diazo resin with suitable binders An optional adhesion promotion layer may be inserted between the silicone top layer and the infrared absorbing layer preferred are aminosilanes of the general formula where R is unsubstituted or mono-substituted amino-alkyl, R' and R" are each alkyl or aryl, m is 1 or 2 and n is 0 or 1 , m+n being equal to 1 or 2 Specific examples of such aminosilanes are γ-aminopropyltπethoxy silane and v-[N-(2-amιnoethyl)amιno]propyl tπmethoxy silane An optional protective layer may be laminated on top of silicone layer to protect the silicone surface during storage and handling Typically the protective layer is a thin polymeric film including polyesters such as polyethylene terephthalate, polyolefins such as polyethylene and polypropylene, and the like The protective layer is designed to be easily removed without damaging the silicone layer surface either prior to or duπng processing Plate Imaging and Processing The waterless plate of the present invention is imaged by the method comprising the following steps First a waterless plate precursor as described above is provided which is composed of, a substrate and a composite layer structure The composite layer structure is further composed of a first thermal layer, e g an infrared absorbing layer, applied to a surface of the substrate and a silicone layer The first thermal layer contains as essential components, a thermoplastic polyurethane containing pendent allyl groups and typically at least one photothermal conversion material, e g an infrared absorbing material The silicone layer is comprised of a crosslinked silicone polymer Next the composite layer structure is imagewise exposed to thermal energy to provide exposed portions and complimentary unexposed portions in the composite layer structure As a result of the imaging exposure, the exposed portions become selectively permeable to a developer liquid Finally, the developer liquid is applied to the composite layer structure to remove the exposed portions to produce an imaged planographic printing plate having uncovered ink receptive areas and complimentary ink repellent areas of the silicone layer In a preferred embodiment of this invention, the photothermal conversion material is an infrared absorbing compound and imaging exposure is earned out with an infrared emitting laser The waterless plate of this invention and its methods of preparation have already been descπbed above This waterless plate may be imaged with a laser or an array of lasers emitting infrared radiation in a wavelength region that closely matches the absorption spectrum of the infrared absorbing layer Suitable commercially available imaging devices include image setters such as a Creo Trendsetter (available from the CREO Corporation, Bπtish Columbia Canada) and a Gerber Crescent 42T (available from the Gerber Corporation) Although the infrared absorbing layer of the composite layer structure is typically exposed through the silicone layer, the infrared absorbing layer may also be imaged through the substrate in those instances when the substrate is composed of a material which is transparent to infrared radiation, e g , polyethylene terephthalate When the silicone surface of the planographic printing plate is protected by a protective layer which is transparent to infrared radiation, the protective layer may remain in place during imaging exposure, or it may be removed In either event, the protective layer typically is removed pπor to development Following the imaging step, the plate is then developed with a developer liquid When portions of the composite layer structure are exposed to infrared radiation, the exposed thermal layer portions therein selectively have enhanced solubility or dispersibi ty in a developer liquid The developer liquid may be any liquid or solution which can both penetrate the silicone layer and selectively dissolve or disperse the reaction products without substantially affecting the unexposed areas of the infrared absorbing layer Preferred developer solutions are those that contain polypropylene glycol ethers A more preferred developer solution is tπpropyiene glycol n-butyl ether The developer liquid may be diluted with a non-developing liquid As used herein, the term non-developing liquid is intended to mean any liquid which does not penetrate the silicone layer and/or does not selectively dissolve or disperse the exposed areas Non- developing liquids include liquids such as polypropylene glycol and aliphatic hydrocarbon solvents Specific aliphatic hydrocarbon solvents are heptane and isoPar seπes solvents from Exxon Chemical Company Typically the developer liquid is applied to the imaged waterless plate by rubbing or wiping the silicone layer with an applicator containing the developer liquid in the development operation the developer liquid penetrates the silicone layer and dissolves or disperses the imaged areas of the infrared absorbing layer and the wiping action physically removes the solubilized areas along with overlying areas of the silicone layer Alternatively the imaged waterless plate may be brushed with the developer liquid or the developer liquid may be applied to the plate by spraying the silicone layer with sufficient force to remove the solubilized areas In either instance a developed printing plate is produced which has uncovered areas which are ink receptive and complimentary areas of the silicone layer, not exposed to infrared radiation, which effectively are ink repellent The developer liquid may be applied at room temperature or at elevated temperatures over the range from about 25°C to about 50°C Preferably, the developer is applied at a temperature between about 35°C to about 40°C After development is complete, the developer liquid remaining on the plate typically is removed with a non-developing cleaning liquid to avoid damage to the silicone layer in the non-exposed areas Suitable cleaning liquids include aqueous surfactant solutions, polypropylene glycols and aliphatic hydrocarbon solvents The waterless laser-imageable printing plate of the present invention will now be illustrated by the following examples, but is not intended to be limited thereby Example 1 Preparation of Polyurethane Solution (I) 98 2 g (0 393 mol) 4,4'-dιphenylmethane dnsocyanate was dispersed in 350 g dry 2-butanone at room temperature (ca 25°C) until a uniform milky dispersion was obtained Then 51 8 g (0 393 mol) 3-allyloxypropane-1 ,2-dιol was added to the flask at a rate such that the temperature of the mixture was maintained below 40°C The mixture was stirred without external heating for two additional hours Then 3 g 5% dibutyl tin dilaurate solution in dry 2-butanone was added also at a rate such that temperature of the mixture was maintained below 40°C The mixture was stirred without external heating for two additional hours Finally, the reaction was driven to completion at 60°C Completion of the reaction was indicated by the disappearance of NCO absorption bands in the infrared spectra After filtration, the product solution contained 30% polyurethane resin and was slightly hazy Example 2 Preparation of Polyurethane Solution (II) 98 0 g (0 392 mol) 4,4'-dιphenylmethane dnsocyanate was dissolved in 250 g dry 2-butanone at 60°C Then a solution containing 34 1 g (0 258 mol) 3-allyloxypropane- ,2-dιol, 17 9 g (0 134 mol) 2,2-bιs(hydroxymethyl) propionic acid in 50 g 2-butanone and 50 gram N,N'-dιmethylformamιde premixed with 3 g 5% dibutyl tin dilaurate solution in dry 2-butanone was dropwise added to the flask at a rate such that the temperature of the mixture was maintained below 65°C The mixture was stirred at 60°C until the completion of the reaction as indicated by the disappearance of NCO absorption bands in the infrared spectra The product solution containing 30% polyurethane resin was filtered through filter paper before use Example 3 Preparation of Polyurethane Solution (III) 40 0 g (0 16 mol) 4,4'-dιphenylmethane dnsocyanate and 27 8 g (0 16 mol) of toluene 2,4-dιιsocyanate were dissolved in 239 g dry 2-butanone at 60°C Then a solution containing 43 1 g (0 32 mol) 3-allyloxypropane-1 ,2-dιol in 20 g of 2-butanone premixed with 1 3 g 5% dibutyl tin dilaurate solution in dry 2-butanone was dropwise added to the flask at a rate such that the temperature rise due to the exotherm of the reaction was controlled below 5 degree, viz the temperature of the mixture was maintained below 65°C The mixture was stirred at 60°C until the completion of the reaction as indicated by the disappearance of NCO absorption bands in the infrared spectra The product solution containing 30% polyurethane resin was filtered through filter paper before use Example 4 Preparation of Polyurethane Solution (IV) 98 0 g (0 392 mol) 4,4'-dιphenylmethane dnsocyanate was dissolved in 250 g dry 1 ,4-dιoxane at room temperature Then a solution containing 52 5 g (0 134 mol) 2,2- bιs(hydroxymethyl) propionic acid in 100 g 1 ,4-dιoxane premixed with 3 g 5% dibutyl tin dilaurate solution in dry 2-butanone was dropwise added to the flask at a rate such that the temperature of the mixture was maintained below 35°C The mixture was stirred without external heating for two additional hours Finally, the reaction was driven to completion at 60°C Completion of the reaction was indicated by the disappearance of NCO absorption bands in the infrared spectra The product solution contained 30% polyurethane resin Example 5 To an aluminum sheet prepared using brush roughening, anodic oxidation and silicate treatments was applied the following solution on a whirl coater spinning at 80 rpm. Component Parts by weight Polyurethane Solution (I) (Example 1) 10 00 SpectraIR 830A 1 0 34 Solvent Blue 35 2 0 07 2-butanone 80 00 1 SpectraIR 830A is an infrared absorbing dye available from Spectra Colors Corporation 2 Solvent Blue 35 is a dye available from Spectra Colors Corporation After drying at 110°C for 2 minutes, a silicone coating was applied by a whirl coater also spinning at 80 rpm The silicone coating was made up of the following Component Parts by weight PS 225 3 2 0 SL 6020 4 0 2 SL 6040 5 0 06 PC 075 b 0 06 IsoPar E 7 70 0 3 PS225 is a silicone gum with randomly distributed vinyl groups along a polydimethyl siloxane main chain from United Chemical 4 SL6020 is a hydromethyl siloxane polymer, a product of GE Silicones 5 SL6040 is a volatile inhibitor product of GE Silicones 6 PC075 is a platinum complex from United Chemicals 7 IsoPar E is an isoparafin solvent from Exxon Chemical The silicone coating was cured at 125°C for 2 minutes The resulting plate was then imaged by a Creo Trendsetter at 120 mJ/cm 2 (laser power 8 5 W/cm 2 , drum speed 155 rpm) The laser image was barely visible The imaged plate was rubbed with a soft pad soaked with tπpropylene glycol n-butyl ether (Dowanol TPNB, available from Dow Chemical Company) until the silicone layer and the polyurethane layer in the laser struck area were completely removed The developed plate was immediately washed with a surfactant solution containing 5 wt % Pelex NBL (sodium n-butyl naphthalene sulfonate from High Point Chemical Corporation) The plate was tested on an R & P H-125 sheet- fed press with Sun Chemical Dπlith ink "H" cyan (available from Sun Chemical Corporation) in the absence of fountain solution in the dampening system More than 20,000 good quality impressions were obtained Example 6 Example 5 was repeated with the exception that polyurethane solution II (Example 2) was used in place of the polyurethane solution I The resulting plate was then imaged by a Creo Trendsetter at 200 mJ/cm 2 (laser power 8 5 W/cm 2 , drum speed 93 1 rpm) The laser image was slightly visible The imaged plate was rubbed with a soft pad soaked with tπpropylene glycol n-butyl ether (Dowanol TPNB) until the silicone layer and the polyurethane layer in the laser struck area was completely removed The developed plate was immediately washed with a surfactant solution containing 5 wt % Pelex NBL (sodium n-butyl naphthalene sulfonate, available from High Point Chemical Corporation) The plate contained high resolution images with exposed aluminum oxide as the ink-receptive image area surrounded by a durable silicone surface as the ink- repelhng non-image area Example 7 Example 5 was repeated except that Epolite 111-178 (available from Epoline Corporation) was substituted for SpectraIR 830A used in Example 5 and Solvent Blue 35 was omitted The resulting plate was then imaged by a Gerber Crescent 42T at 220 mJ/cm 2 The laser image was barely visible, but was developed fully when the plate was rubbed with a soft pad soaked with Dowanol TPNB The developed plate was immediately washed with a surfactant solution containing 5 wt % Pelex NBL (sodium n- butyl naphthalene sulfonate) The plate contained high resolution images with exposed aluminum oxide as the ink-receptive image area surrounded by a durable silicone surface as the ink-repelling non-image area Example 8 Example 5 was repeated except that the following silicone coating was used Component Parts by weight PS 445 8 2 0 SL 6020 0 2 SL 6040 0 06 PC 075 0 06 IsoPar E 70 0 8 PS445 is a vinyl terminated polydimethylsiloxane from United Chemical The silicone coating was cured at 125°C for 2 minutes The resulting plate was then imaged by a Creo Trendsetter at 200 mJ/cm 2 (laser power 8 5W/cm 2 , drum speed, 93 1 rpm) The laser image was slightly visible The imaged plate was rubbed with a soft pad soaked with tπpropylene glycol n-butyl ether (Dowanol TPNB) until the silicone layer and the polyurethane layer in the laser struck area was completely removed The developed plate was immediately washed with a surfactant solution containing 5 % Pelex NBL (sodium n-butyl naphthalene sulfonate) The plate contained high resolution images with exposed aluminum oxide as the ink-receptive image area surrounded by a durable silicone surface as the ink-repelling non-image area Example 9 To an aluminum sheet prepared using brush roughening, anodic oxidation and silicate treatments was applied the following solution on a whirl coater spinning at 80 rpm Component Parts by weight Polyurethane Solution (I) (Example 1) 10 00 SpectraIR 830A 0 34 2-butanone 80 00 After drying at 110°C for 2 minutes, the IR absorbing layer was first coated with 0 50% 3-amιnopropyl tπethoxy silane in isoPar E on a whirl coater spinning at 80 rpm, and then coated using the same coating technique with the following silicone solution Component Parts by weight PS 345 5 9 5 0 Ethyl tπacetoxy silane 0 25 Dibutyl tin diacetate, 4 wt % in isoPar E 0 25 IsoPar E 95 0 9 PS 345 5 is a silanol terminated polydimethyl siloxane available from United Chemicals The silicone coating was cured at 125°C for 4 minutes The resulting plate was then imaged by a Creo Trendsetter at 200 mJ/cm 2 (laser power 8 5 W/cm 2 , drum speed 93 1 rpm) The laser image was slightly visible The imaged plate was rubbed with a soft pad soaked with tπpropylene glycol n-butyl ether (Dowanol TPNB) until the silicone layer and the polyurethane layer in the laser struck area were completely removed, whereas the rest of the silicone coating remained intact The developed plate was immediately washed with a surfactant solution containing 5 wt % Pelex NBL (sodium n- butyl naphthalene sulfonate) The plate contained high resolution images with exposed aluminum oxide as the ink-receptive image area surrounded by a durable silicone surface as the ink-repelling non-image area Example 10 Example 5 was repeated with the exception that Polyurethane Solution III (Example 3) was used in place of the Polyurethane Solution I The resulting plate was then imaged by a Creo Trendsetter at 200 mJ/cm 2 (laser power 8 5 W/cm 2 , drum speed 93 1 rpm) The laser image was slightly visible The imaged plate was rubbed with a soft pad soaked with tπpropylene glycol n-butyl ether (Dowanol TPNB) until the siiicone layer and the polyurethane layer in the laser struck area were completely removed The developed plate was immediately washed with a surfactant solution containing 5 wt % Pelex NBL (sodium n-butyl naphthalene sulfonate) The plate contained high resolution images with exposed aluminum oxide as the ink-receptive image area surrounded by a durable silicone surface as the ink-repelling non-image area Example 11 Preparation of Polyurethane Powder (V) 51 g N-methyl pyrrolidone and 204 g dry acetone was mixed in a 500 ml flask fitted with a mechanical stirrer and a nitrogen purge 63 7 g (0 250 mol) 4,4'- diphenylmethane dnsocyanate was added and the mixture was heated to 60°C The solution became clear at 50°C At 60°C 45/7 g (0 263 mol) tπmethylol-propane allyl ether was added over a period of one hour After two and one half hours, 0 55 g of 5% solution of dibutyl tin dilaurate in dry 2-butanone was added After an additional one and one half hours, the reaction mixture was cooled to room temperature and poured into 5 kg ice/water mixture (1 3 by weight) The precipitated polyurethane was collected and dπed at room temperature to produce Polyurethane Powder (V) Example 12 Example 5 was repeated with the exception that 3 0 g dry Polyurethane Powder V (Example 1 ) was used in place of the Polyurethane Solution I The resulting plate was then imaged by a Creo Trendsetter at 200 mJ/cm 2 (laser power 8 5 W/cm 2 drum speed 93 1 rpm) The laser image was slightly visible The imaged plate was rubbed with a soft pad soaked with tπpropylene glycol n-butyl ether (Dowanol TPNB) until the silicone layer and the polyurethane layer in the laser struck area were completely removed The developed plate was immediately washed with a surfactant solution containing 5 wt % Pelex NBL (sodium n-butyl naphthalene sulfonate, available from High Point Chemical Corporation) The plate contained high resolution images with exposed aluminum oxide as the ink-receptive image area surrounded by a durable silicone surface as the ink-repelling non-image area Examples 13-16 The waterless plate of Example 5 was imaged by a Creo Trendsetter at 200 mJ/cm 2 (laser power 8 5 W/cm 2 , drum speed 93 1 rpm) and then developed with the developers shown in the table below EX DEVELOPER 13 200 g polypropylene glycol 10 (mol wt 725) and 100 g Surfadone LP 300 11 14 200 g isoPar V 12 and 100 g Surfadone LP 300 11 15 400 g polypropylene glycol 10 (mol Wt 725) and 100 g ethanol 16 tπpropylene glycol methyl ether (Dowanol TPM, available from Dow Chemical) 10 The polypropylene glycol is available from Aldπch Chemical 11 Surfadone LP 300 is N-dodecyl pyrrolidone, available from International Specialty Products 12 IsoPar V is an isoparafin solvent from Exxon Chemical Company The developed plates were immediately washed with a surfactant solution containing 5 wt % Pelex NBL (sodium n-butyl naphthalene sulfonate) These plates contained high resolution images with exposed aluminum oxide as the ink-receptive image area surrounded by a durable silicone surface as the ink-repelling non-image area Examples 17 - 20 (COMPARATIVE) To demonstrate the importance of selecting a suitable developer, the waterless plate of Example 5 was imaged by a Creo Trendsetter at 200 mJ/cm 2 (laser power 85 , drum speed 93 1 rpm) and then developed with the following comparative developers shown in the table below EX DEVELOPER RESULTS 17 PE 400 imaged area developed, (polyethylene glycol but silicone in non- from Union Carbide) image area was damaged 18 polypropylene silicone and IR glycol (mol wt 725) absorbing layers remained attached to substrate in the laser struck area 19 ethanol silicone and IR absorbing layers were washed away in the laser struck and non-struck areas 20 200 g polypropylene imaged area developed glycol (mol Wt 725) but silicone in non- and 100 g 2-methoxy image area was damaged propanol EXAMPLES 21-26 (COMPARATIVE) Example 5 was repeated with the exception that Polyurethane Solution IV was used in place of the Polyurethane Solution I The resulting plate was then imaged by a Creo Trendsetter at 200 mJ/cm 2 (laser power 85 , drum speed 93 1 rpm) The silicone coating in the laser struck area became less glossy The table below summanzes the results EX DEVELOPER RESULTS 21 Dowanol TPNB Silicone and IR absorbing layers remained attached to substrate in the laser struck area Excessive rubbing resulted in damage of silicone coating in laser non-struck area 22 Dowanol TPM Silicone and IR absorbing layers remained attached to substrate in the laser struck area 23 ethanol Silicone and IR absorbing layers were washed away in the laser struck and non- struck areas 24 200 g The IR-absorbing layer in polypropylene laser struck or non-struck glycol (mol Wt areas remained undissolved, 725) and 100 g silicone removed slightly Surfadone LP 300 faster in the laser struck area than in non-struck area 25 200 g isoPar V The IR-absorbing layer in and 100 g laser struck or non-struck Surfadone LP 300 areas remained undissolved, silicone removed in the laser struck area, but silicone in non-struck area was partially damaged 26 400 g The IR-absorbing layer in polypropylene laser struck or non-struck glycol (mol wt areas remained undissolved, 725) and 100 g silicone removed slightly ethanol faster in the laser non- struck area than in struck area Example 27 Example 5 was repeated except that the silicone and underlying layer in the laser struck areas were removed using a Toray Model TWL 860KII processor (available from Toray Industries, Inc ) which was modified by filling the soak section and brush section with tπpropylene glycol n-butyl ether, and the dye section with 1wt % aqueous solution of Plex NBL In this processor, the laser imaged printing plate travels through the soak section, then the brush section, and finally through the dye section When the soak temperature was set at 38°C, the brush temperature at 32°C and the plate traveled at 2 ft/mm, a high quality printing plate was obtained where 2%-98% half tone dots at 150 lines per inch were resolved Those skilled in the art having the benefit of the teachings of the present invention as hereinabove set forth, can effect numerous modifications thereto These modifications are to be construed as being encompassed within the scope of the present invention as set forth in the appended claims

Claims: What is claimed is 1 A dry planographic printing plate precursor element compπsing A) a substrate, B) a composite layer structure having an inner surface contiguous to the substrate and an outer surface, the composite layer structure compπsing (a) a first layer applied to a surface of the substrate, the first layer consisting essentially of at least one photothermal conversion material and a thermoplastic polyurethane containing allyl groups, and (b) a silicone layer comprised of a crosshnked silicone polymer 2 The element of claim 1 wherein the thermoplastic polyurethane contains pendent allyl groups and is prepared by reacting a dnsocyanate and a diol matenal containing at least one allyl functional diol 3 The element of claim 2 wherein the dnsocyanate is an aryl dnsocyanate 4 The element of claim 3 wherein the aryl dnsocyanate is one or more compounds selected from the group consisting of 2,4-toluene dnsocyanate, 2,6-toluene dnsocyanate, p-xylene dnsocyanate, m-xylene dnsocyanate, tetramethyl-xylene dnsocyanate, 4,4'-dιphenylmethane dnsocyanate, 1 ,5-naphthalene dnsocyanate, and 3,3'-dιmethylbιphenyl-4,4'-dιιsocyanate 5 The element of claim 3 wherein the aryl dnsocyanate is 4,4'- diphenyl- methane dnsocyanate 6 The element of claim 2 wherein the dnsocyanate is an alkyl dnsocyanate 7 The element of claim 6 wherein the alkyl dnsocyanate is one or more compounds selected from the group consisting of hexamethylene dnsocyanate, tπmethylhexamethylene dnsocyanate, isophorone dnsocyanate, 4-4'- methyienebιs(cyclohexyl isocyanate), methylcyclohexane-2,4-dιιsocyanate, methylcyclohexane-2,6-dιιsocyanate, and 1 ,3-bιs(ιsocyanatomethyl) cyclohexane 8 The element of claim 2 wherein 70% or more of the diol material is the allyl functional diol 9 The element of claim 2 wherein the allyl functional diol is represented by the following formula HOCR 1 2 -CR 2 (OH) -CR 3 2 -O- CR 2 -CR 5 =CR 6 2 wherein R 1 , R 2 , R 3 , R 4 , R 5 , and R 6 are each individually a hydrogen atom or an alkyl group containing 1 to 4 carbon atoms 10 The element of claim 2 wherein the allyl functional diol is 3-allyloxypropane- 1 ,2-dιol, tπmethylolpropane allyl ether, or a combination thereof 11 The element of claim 2 wherein the allyl functional diol is allyl 4,4-bιs- (hydroxyethyloxyphenyl)pentanoate, allyl 2,2-bιs(hydroxymethyl)propanoate, or a combination thereof 12 The element of claim 2 wherein the diol material contains one or more non- allyl functional diol compounds 13 The element of claim 1 wherein the photothermal conversion material is an infrared absorbing material 14 The element of claim 13 wherein the infrared absorbing mateπal is a dye, a pigment or a combination thereof having an absorption band in the region between 700 nm and 1400 nm 15 The element of claims 13 wherein the infrared absorbing material is a dye or pigment of the type selected from the group consisting of tπarylamine, thiazolium, indolium, oxazolium, polyaniiine, polypyrrole, polythiophene, thiolene metal complexes, squaπlium, croconate, cyanine, phthalocyanine, merocyanine, chalcogenopyryloarylidine, bιs(chalcogenopyrylo)polymethιne, oxindolizine, quinoid, indolizine, pyrylium, thiazine, azulenium, xanthene, carbon black, and and dark inorganic pigments 16 The element of claim 1 wherein the crosslinked silicone polymer is the reaction product of a vinyl functional polysiloxane copolymer and a polymer or copolymer of methyl hydrosiioxane 17 The element of claim 1 wherein the substrate is an aluminum sheet 18 The element of claim 1 wherein a primer layer is between the substrate and the composite layer structure 19 The element of claim 1 wherein an adhesion promotion layer is between the first layer and the silicone layer 20 The element of claim 1 wherein a removable protective layer is laminated to the silicone layer 21 A method for forming a planographic printing plate comprising the steps, in the order given I) providing the planographic printing plate precursor element of any one of claims 1 through 20, II) imagewise exposing the composite layer structure to thermal energy to provide exposed portions and complimentary unexposed portions in the composite layer structure, wherein the exposed portions are selectively permeable to a developer liquid, and III) applying the developer liquid to the composite layer structure to remove the exposed portions to produce an imaged planographic printing plate having uncovered ink receptive areas and complimentary ink repellent areas of the silicone layer 22 The method of claim 21 , wherein the photothermal conversion mateπal is an infrared absorbing compound, and wherein the imagewise exposing is carried out with an infrared emitting laser 23 The method of claim 21 , wherein a removable protective layer is laminated to the silicone layer and wherein the removable protective layer is removed from the silicone layer before (III) applying the developer liquid to the planographic printing plate 24 The method of claim 21 , wherein the developer liquid comprises a propyleneglycol ether 25 The method of claim 24, wherein the propyleneglycol ether is tπpropyleneglycol-n-butyl ether 26 The method of claim 24, wherein the developer liquid is diluted with a non- developing liquid 27 The method of claim 26, wherein the non-developer liquid is polypropylene glycol, aliphatic hydrocarbon solvents, or a combination thereof 28 The method of claim 21 , wherein the developer liquid is applied to the composite layer structure by wiping or rubbing the silicone layer with an applicator containing the developer liquid 29 The method of claim 21 , wherein the developer liquid is applied to the composite layer structure by soaking in the developer liquid and then wiping or rubbing the silicone layer with an applicator containing a developer liquid 30 The method of claim 21 , wherein the developer liquid is applied to the composite layer structure at a temperature between about 25°C to about 50°C 31 The method of claim 21 , wherein the developer liquid is applied to the composite layer structure at a temperature between about 35°C to about 40°C 32 The method of claim 21 , wherein after step (III) the imaged planographic printing plate is cleaned by applying a non-developing cleaning liquid to the uncovered ink receptive areas and complimentary ink repellent areas 33 The method of claim 32, wherein the non-developing cleaning liquid is an aqueous surfactant solution, a polypropylene glycol, or a hydrocarbon solvent

Inventors: DO THI NGUYEN, GOODMAN RICHARD M, HUANG JIANBING, PAPPAS S PETER, DO, THI, NGUYEN, GOODMAN, RICHARD, M., HUANG, JIANBING, PAPPAS, S., PETER
Applicants: KODAK POLYCHROME GRAPHICS
Application year: 1998
Main classification: B41N1
IPC codes: B41C1, B41N1, G03F7