Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
  • B41M5/36—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using a polymeric layer, which may be particulate and which is deformed or structurally changed with modification of its' properties, e.g. of its' optical hydrophobic-hydrophilic, solubility or permeability properties
  • B41M5/368—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using a polymeric layer, which may be particulate and which is deformed or structurally changed with modification of its' properties, e.g. of its' optical hydrophobic-hydrophilic, solubility or permeability properties involving the creation of a soluble/insoluble or hydrophilic/hydrophobic permeability pattern; Peel development
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
  • B41C1/00—Forme preparation
  • B41C1/10—Forme preparation for lithographic printing; Master sheets for transferring a lithographic image to the forme
  • B41C1/1008—Forme preparation for lithographic printing; Master sheets for transferring a lithographic image to the forme by removal or destruction of lithographic material on the lithographic support, e.g. by laser or spark ablation; by the use of materials rendered soluble or insoluble by heat exposure, e.g. by heat produced from a light to heat transforming system; by on-the-press exposure or on-the-press development, e.g. by the fountain of photolithographic materials
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
  • B41C2210/00—Preparation or type or constituents of the imaging layers, in relation to lithographic printing forme preparation
  • B41C2210/02—Positive working, i.e. the exposed (imaged) areas are removed
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
  • B41C2210/00—Preparation or type or constituents of the imaging layers, in relation to lithographic printing forme preparation
  • B41C2210/06—Developable by an alkaline solution
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
  • B41C2210/00—Preparation or type or constituents of the imaging layers, in relation to lithographic printing forme preparation
  • B41C2210/22—Preparation or type or constituents of the imaging layers, in relation to lithographic printing forme preparation characterised by organic non-macromolecular additives, e.g. dyes, UV-absorbers, plasticisers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
  • B41C2210/00—Preparation or type or constituents of the imaging layers, in relation to lithographic printing forme preparation
  • B41C2210/24—Preparation or type or constituents of the imaging layers, in relation to lithographic printing forme preparation characterised by a macromolecular compound or binder obtained by reactions involving carbon-to-carbon unsaturated bonds, e.g. acrylics, vinyl polymers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
  • B41C2210/00—Preparation or type or constituents of the imaging layers, in relation to lithographic printing forme preparation
  • B41C2210/26—Preparation or type or constituents of the imaging layers, in relation to lithographic printing forme preparation characterised by a macromolecular compound or binder obtained by reactions not involving carbon-to-carbon unsaturated bonds
  • B41C2210/262—Phenolic condensation polymers, e.g. novolacs, resols

Definitions

• the present invention relates to heat-sensitive positive working elements, in particular heat-sensitive printing plate precursors whose heat-sensitive coating comprises a phenolic resin whose solubility in alkaline developers has been reversibly reduced by the use of a second polymer; the invention furthermore relates to a process for their production as well as to a process for imaging such elements.
• the technical field of lithographic printing is based on the immiscibility of oil and water, wherein the oily material or the printing ink is preferably accepted by the image area, and the water or fountain solution is preferably accepted by the non-image area.
• the background or non-image area accepts the water and repels the printing ink
• the image area accepts the printing ink and repels the water.
• the printing ink in the image area is then transferred to the surface of a material such as paper, fabric and the like, on which the image is to be formed.
• the printing ink is first transferred to an intermediate material, referred to as blanket, which then in turn transfers the printing ink onto the surface of the material on which the image is to be formed; this technique is referred to as offset lithography.
• a frequently used type of lithographic printing plate precursor (in this context the term printing plate precursor refers to a coated printing plate prior to exposure and developing) comprises a photosensitive coating applied onto a substrate on aluminum basis.
• the coating can react to radiation such that the exposed portion becomes so soluble that it is removed during the developing process.
• Such a plate is referred to as positive working.
• a plate is referred to as negative working if the exposed portion of the coating is hardened by the radiation.
• the remaining image area accepts printing ink, i.e. is oleophilic
• the non-image area (background) accepts water, i.e. is hydrophilic. The differentiation between image and non-image areas takes place during exposure.
• a film containing the information to be transferred is attached to the plate precursor under vacuum in order to guarantee good contact.
• the plate is then exposed by means of a radiation source.
• the plate can also be exposed digitally without a film, e.g. with a UV laser.
• a positive plate the area on the film corresponding to the image on the plate is so opaque that the light does not reach the plate, while the area on the film corresponding to the non-image area is clear and allows light to permeate the coating, whose solubility increases.
• a negative plate the opposite takes place: The area on the film corresponding to the image on the plate is clear, while the non-image area is opaque.
• the coating beneath the clear film area is hardened due to the incident light, while the area not affected by the light is removed during developing.
• the light-hardened surface of a negative working plate is therefore oleophilic and accepts printing ink, while the non-image area that used to be coated with the coating removed by the developer is desensitized and therefore hydrophilic.
• US-A-4,708,925 One example of a positive working, direct laser-addressable printing plate precursor is described in US-A-4,708,925.
• the patent describes a lithographic printing plate precursor whose imaging layer comprises a phenolic resin and a radiation-sensitive onium salt. As described in the patent, the interaction between the phenolic resin and the onium salt results in an alkali solvent resistance of the composition, which restores the alkali solubility by photolytic decomposition of the onium salt.
• the printing form precursor can be used as a precursor of a positive working printing form or as a precursor of a negative printing form, if additional process steps are added between exposure and developing, as described in detail in British patent no. 2,082,339.
• the printing form precursors described in US-A-4,708,925 are UV-sensitive and can additionally be sensitized to visible and IR radiation.
• EP-A-0 823 327 describes IR-sensitive printing plate precursors whose radiation-sensitive coating comprises, in addition to an IR absorber and a polymer such as for example novolak, a substance that decreases the solubility of the composition in an alkaline developer.
• a polymer such as for example novolak
• sulfonic acid esters, phosphoric acid esters, aromatic carboxylic acid esters, carboxylic acid anhydrides, aromatic ketones and aldehydes, aromatic amines and aromatic ethers are mentioned as such "insolubilizers”.
• These printing plate precursors show a high degree of IR sensitivity and do not require additional process steps between exposure and developing; moreover, they can be handled under normal lighting conditions (daylight with a certain portion of UV radiation), i.e. no yellow light is necessary.
• the resistance of the developed printing plates to printing chamber chemicals is not completely satisfactory.
• WO 99/21725 discloses IR-sensitive positive working printing plate precursors whose heat-sensitive layer comprises a substance that improves the resistance of the non-heated areas to an attack by the alkaline developer; this substance is selected from compounds with polyalkylene oxide units, siloxanes, as well as esters, ethers and amides of multivalent alcohols. These printing plate precursors as well are characterized by a high degree of IR sensitivity and can be used under normal daylight conditions. An improved resistance to printing chamber chemicals would be desirable in this case, too. For applications involving higher numbers of copies, a baking step is recommended.
• EP-A-1 101 607 describes IR-sensitive elements whose IR-sensitive coatings additionally comprise a carboxylic acid derivative of a cellulose polymer.
• a carboxylic acid derivative of a cellulose polymer By using this acidic cellulose polymer, the resistance of the coating to organic solvents, which are e.g. used in some printing inks, fountain solutions and washing solutions, could be improved, which allows higher number of prints in the case of printing plates.
• carboxyl-group containing polymers of the methacrylic/acrylic acid type, copolymers of maleic acid, an acidic polyester, an acidic colophonium derivative as well as polyvinyl acetals with the following structural unit were tested as well
• the solvent resistance could not be improved with such polymers.
• the acidic cellulose polymer there is still a demand for coatings with superior resistance to pressroom chemicals, in particular in the field of lithographic printing plate precursors; the use of the acidic cellulose polymer resulted for example in a deterioration of the alkaline developer resistance.
• WO 99/01795 describes heat-sensitive coatings which use polymers with specific functional groups Q as insolubilizers for novolaks, said polymers preferably do not comprise diazide groups or acid or acid-forming groups.
• the heat-sensitive coating comprises nitrogen-containing compounds as insolubilizers for novolak wherein at least one nitrogen atom is quaternized and forms part of a heterocyclic ring; examples include e.g. quinolinium compounds, benzothiazolium compounds and pyridinium compounds, and in particular cationic trimethylmethane dyes such as Victoria Blue (C I Basic Blue 7), crystal violet (C I Basic Violet 3) and ethyl violet (C I Basic Violet 4).
• nitrogen-containing compounds as insolubilizers for novolak wherein at least one nitrogen atom is quaternized and forms part of a heterocyclic ring
• examples include e.g. quinolinium compounds, benzothiazolium compounds and pyridinium compounds, and in particular cationic trimethylmethane dyes such as Victoria Blue (C I Basic Blue 7), crystal violet (C I Basic Violet 3) and ethyl violet (C I Basic Violet 4).
• WO 98/42507 and EP-A 0 823 327 describe xanthone, flavanone, flavone, 2,3-diphenyl-1-indenone, pyrone, thiopyrone and 1'-(2'-acetonaphthonyl)benzoate as insolubilizers for novolaks.
• the first object is surprisingly achieved by an element comprising:
• the inventive process for imaging these elements comprises the following steps:
• the heat-sensitive elements according to the present invention can e.g. be printing plate precursors (in particular precursors of lithographic printing plates), printed circuit boards for integrated circuits or photomasks.
• a dimensionally stable plate or foil-shaped material is preferably used as a substrate in the production of printing plate precursors.
• a material is used as dimensionally stable plate or foil-shaped material that has already been used as a substrate for printing matters.
• substrates include paper, paper coated with plastic materials (such as polyethylene, polypropylene, polystyrene), a metal plate or foil, such as e.g. aluminum (including aluminum alloys), zinc and copper plates, plastic films made e.g.
• an aluminum plate or foil is especially preferred since it shows a remarkable degree of dimensional stability, is inexpensive and furthermore exhibits excellent adhesion to the coating.
• a composite film can be used wherein an aluminum foil has been laminated onto a polyethylene terephthalate film.
• a metal substrate in particular an aluminum substrate, is preferably subjected to a surface treatment, for example graining by brushing in a dry state or brushing with abrasive suspensions, or electrochemical graining, e.g. by means of a hydrochloric acid electrolyte, and optionally anodizing.
• a surface treatment for example graining by brushing in a dry state or brushing with abrasive suspensions, or electrochemical graining, e.g. by means of a hydrochloric acid electrolyte, and optionally anodizing.
• the metal substrate can be subjected to an aftertreatment with an aqueous solution of e.g. sodium silicate, calcium zirconium fluoride, polyvinylphosphonic acid or phosphoric acid.
• an aqueous solution e.g. sodium silicate, calcium zirconium fluoride, polyvinylphosphonic acid or phosphoric acid.
• substrate also encompasses an optionally pretreated substrate exhibiting, for example, a hydrophilizing layer on its surface.
• the heat-sensitive coating comprises at least one polymer that reduces the aqueous alkaline developer solubility of a phenolic resin, whereby this reduction in solubility is reversed by the application of heat.
• this polymer is briefly referred to as “insolubilizer” or “inhibitor polymer”.
• the inhibitor polymer is selected from:
• the inhibitor polymer (i) can be depicted as follows:
• the polymer chain can comprise further substituents, such as e.g. C 1 -C 4 alkyl groups, OH, and
• it is a polyolefin skeleton, which in addition to the (hetero)cyclic moiety comprises and optionally OH as substituents.
• the symbol represents a saturated cyclic or heterocyclic moiety, wherein the heteroatom - if present - is selected from N, O and S (preferably N). In the case of a heterocyclic moiety, 2 heteroatoms can be present as well.
• the (hetero)cyclic moiety can comprise 4 to 8 (especially preferred 5 to 7) ring atoms. It is preferably a heterocyclic moiety wherein one of the ring atoms is a nitrogen atom; it is especially preferred that the nitrogen atom is adjacent to the carbonyl function.
• Especially preferred inhibitor polymers (i) comprise a lactam substituent and are represented by formula (II): wherein n is 3, 4 or 5, preferably 3.
• polyvinylpyrrolidone as well as copolymers derived from vinylpyrrolidone and vinylacetate are especially preferred; in the case of the copolymers, the amount of parts derived from vinylacetate is preferably 10-85 mole-% and the amount of parts derived from vinylpyrrolidone is preferably 15-90 mole-%.
• the inhibitor polymer (ii) can be depicted as follows:
• the polymer chain can comprise further substituents, such as e.g. C 1 -C 4 alkyl groups, OH, and
• it is a skeleton without any additional substituents or with as further substituent.
• the symbol represents an unsaturated heterocyclic moiety, wherein further heteroatoms selected from N, O and S (preferably N) can be present in the ring in addition to the nitrogen atom shown above, which is bonded to the two adjacent carbon atoms via a single bond and a double bond, and furthermore comprises a free electron pair.
• the heterocyclic moiety can comprise 4 to 8 (especially preferred 5 to 7) ring atoms.
• the heterocyclic moiety comprises another nitrogen atom which is bonded to the two adjacent carbon atoms via a single bond.
• Especially preferred inhibitor polymers (ii) are represented by formula (IV): wherein further double bonds can be present in addition to the double bond shown in formula (IV); means that the nitrogen atom depicted in the formula is bonded to the carbon atom directly or via a spacer, resulting in a mono- or polyunsaturated heterocyclic moiety as defined above.
• polyvinyl imidazole is especially preferred.
• a copolymer (iii) is used as inhibitor polymer, which comprises both the side chain shown in formula (I) (preferably formula (II)) and the side chain shown in formula (III) (preferably formula (IV)).
• Such a copolymer can be depicted as follows:
• Formula (V) is to be understood such that both block copolymers and copolymers with (statistically or regularly) alternating functional side chains are to be encompassed.
• formula (VI) represents a preferred copolymer.
• the total amount of the inhibitor polymer(s) in the heat-sensitive coating is preferably 0.1 to 60 wt.-%, more preferred 10 to 40 wt.-% and especially preferred 10 to 20 wt.-%, based on the dry layer weight.
• the inhibitor polymer is not particularly restricted.
• the molecular weight is preferably in the range of 10,000 to 500,000.
• Novolak resins a polyvinylphenol polymer, a vinylphenol/hydrocarbylacrylate copolymer, a pyrogallol/acetone polymer or mixtures thereof can for example be used as phenolic resins in the present invention.
• Novolak resins are preferably used in the present invention, i.e. condensation products of suitable phenols, e.g. phenol itself, C-alkyl-substituted phenols (including cresols, xylenols, p-tert-butylphenol, p-phenylphenol and nonylphenols), and of diphenols (e.g.
• the total amount of the phenolic resin(s) in the heat-sensitive coating is preferably larger than the amount of inhibitor polymer.
• the amount of novolak resin is preferably at least 40 wt.-%, more preferred at least 50 wt.-%, still more preferred at least 70 wt.-% and especially preferred at least 80 wt.-%.
• the amount does not exceed 95 wt.-%, preferably 85 wt.-%.
• Imaging of the heat-sensitive elements can be carried out either by direct application of heat or by IR radiation, which is absorbed and converted into heat by photothermal conversion material (in the following also simply referred to as IR absorber).
• IR radiation which is absorbed and converted into heat by photothermal conversion material (in the following also simply referred to as IR absorber).
• the chemical structure of the IR absorber is not particularly restricted, as long as it is capable of converting the radiation it absorbed into heat. It is preferred that the IR absorber show essential absorption in the range of 650 to 1,300 nm, preferably 750 to 1,120 nm, and it preferably shows an absorption maximum in that range. It is furthermore preferred that the IR absorber does not or not essentially absorb radiation in the UV range of 300 to 420 nm.
• the absorbers are for example selected from carbon black, phthalocyanine pigments/dyes and pigments/dyes of the squarylium, croconate, merocyanine, cyanine, indolizine, pyrylium or metaldithiolin classes, especially preferred from the cyanine class.
• the compounds mentioned in Table 1 of US-A-6,326,122 for example are suitable IR absorbers. Further examples can be found in US-B-6,410,207 and EP-A-1 176 007.
• an IR absorber is present in the heat-sensitive coating, it is preferably present in an amount of at least 0.1 wt.-%, based on the dry layer weight, more preferred at least 1 wt.-%, still more preferred at least 2 wt.-%. Usually, the amount of IR absorber does not exceed 25 wt.-%, more preferred 20 wt.-% and most preferred 15 wt.-%. A single IR absorber or a mixture of two or more can be present; in the latter case, the amounts given refer to the total amount of all IR absorbers.
• the radiation-sensitive coating of the present invention can comprise dyes or pigments for coloring the layer.
• colorants include e.g. phthalocyanine pigments, azo pigments, carbon black and titanium dioxide, ethyl violet, crystal violet, azo dyes, anthraquinone dyes and cyanine dyes.
• the amount of colorant is preferably 0 to 20 wt.-%, based on the dry layer weight, especially preferred 0.5 to 10 wt.-%.
• the inventive radiation-sensitive coating can additionally comprise further additives such as plasticizers or inorganic fillers.
• plasticizers include e.g. dibutyl phthalate, dioctyl phthalate, didodecyl phthalate, dibutyl sebacate, triacetyl glycerin and triaryl phosphates.
• the amount of plasticizer is not particularly restricted, however, it is preferably 0 to 10 wt.-%, based on the dry layer weight, especially preferred 0.25 to 5 wt.-%.
• Developing aids such as e.g. polyvinyl phenols, tetrahydrophthalic acid or anhydride, pyromellitic acid etc. should be mentioned as another optional component.
• Their amount is not particularly restricted, however, it is preferably 0 to 20 wt.-%, based on the dry layer weight, especially preferred 0.5 to 10 wt.-%.
• the radiation-sensitive coating can comprise surfactants (e.g. anionic, cationic or neutral tensides or mixtures thereof).
• Suitable surfactants include siloxane-containing polymers, fluorine-containing polymers and polymers with ethylene oxide and/or propylene oxide groups. They are preferably present in an amount of 0 to 10 wt.-%, based on the dry layer weight, especially preferred 0.2 to 5 wt.-%.
• the heat-sensitive layer is produced by applying a solution of all components onto an optionally pretreated substrate and drying. All solvents and solvent mixtures can be used in which the phenolic resin and the inhibitor polymer are both soluble. If the phenolic resin and the inhibitor polymer have very different solubility characteristics, a solvent mixture of 2 or more components is usually required, with one component commonly being water. In particular in the case of inhibitor polymers (i) and in particular those of formula (II), a mixture of water, tetrahydrofuran (THF), optionally propylene glycol monomethylether (PGME) and optionally methyl lactate (ML) has proven to be convenient.
• THF tetrahydrofuran
• PGME propylene glycol monomethylether
• ML optionally methyl lactate
• the water content in such a solvent mixture is preferably 0.5 to 20 vol.-%, based on the entire solvent mixture, especially preferred 5 to 15 vol.-%.
• the amount of PGME is preferably 0 to 30 vol.-%, especially preferred 10 to 20 vol.-%.
• the amount of THF is preferably 30 to 90 vol.-%, especially preferred 50 to 75 vol.-%, and the amount of ML is preferably 0 to 30 vol.-%, especially preferred 10 to 20 vol.-%.
• the following rule of thumb applies: The more novolak is used, the less water is used; the more inhibitor polymer is used, the more water is used.
• the coating can be carried out by means of common coating processes, e.g. coating by means of doctor blades, spin coating, coating with a slot coater etc.
• the dry layer weight of the heat-sensitive layer in lithographic printing plate precursors is preferably 0.5 to 4.0 g/m 2 , especially preferred 1 to 2 g/m 2 .
• Imaging can be carried out by the application of direct heat or by means of IR radiation. If IR radiation is used, e.g. in the form of IR lasers or IR laser diodes that emit in the range of 750 to 1,120 nm, the heat-sensitive coating should contain an IR absorber. All image-setters with IR lasers known to the person skilled in the art can be used.
• the image-wise exposed/heated elements such as e.g. printing plate precursors, are developed with an aqueous alkaline developer which usually has a pH value in the range of 10 to 14.
• aqueous alkaline developer which usually has a pH value in the range of 10 to 14.
• Commercially available developers can be used for this purpose.
• Developed printing plates can furthermore be subjected to a "baking" step in order to increase the abrasion resistance of the printing areas; however, this is not necessarily required for the printing plates according to the present invention since due to their excellent solvent resistance, high numbers of copies can be printed without any loss in quality.
• the printing plates according to the present invention are characterized by an excellent chemical resistance to organic solvents e.g. contained in fountain solutions, washing solutions and some printing inks (e.g. petrol ethers, glycols and glycol ethers, as well as straight-chain, branched and cyclic alkanols), while their developability and IR sensitivity are maintained at a high level.
• organic solvents e.g. contained in fountain solutions, washing solutions and some printing inks (e.g. petrol ethers, glycols and glycol ethers, as well as straight-chain, branched and cyclic alkanols)
• some printing inks e.g. petrol ethers, glycols and glycol ethers, as well as straight-chain, branched and cyclic alkanols
• the heat-sensitive elements of the present invention are not sensitive to visible light and the UV portion of daylight under common processing conditions for printing plates so that they can be processed under white light, i.e. do not require yellow light conditions.
• a solution (9 wt.-%) was prepared by dissolving 79 wt.-% PD 140 A (m/p-cresol novolak, available from Borden Chemicals), 20 wt.-% PVP/VA-W 635 (vinylpyrrolidone/vinylacetate copolymer; aqueous solution; 60% polyvinylpyrrolidone, 40% vinylacetate; 50% solids content) and 1 wt.-% Trump dye (IR dye absorbing at 830 nm) in a solvent mixture of acetone, methyl lactate, THF, propylene glycol methylether (PGME) and water (weight ratio: 37:10:37:10:6).
• PD 140 A m/p-cresol novolak, available from Borden Chemicals
• PVP/VA-W 635 vinylpyrrolidone/vinylacetate copolymer
• aqueous solution 60% polyvinylpyrrolidone, 40% vinylacetate; 50% solids content
• This solution was applied onto a substrate by means of a wire-wound blade, resulting in a dry layer weight of 1.5 g/m 2 .
• the substrate was an electrochemically grained and anodized aluminum plate sealed with polyvinylphosphonic acid. The coating was dried at 100°C for 10 minutes.
• the plate was exposed in a Creo Trendsetter image-setter (830 nm) with 400 mJ/cm 2 in a checkerboard pattern with different point sizes, developed at 25°C with the developer 9005, commercially available from Kodak Polychrome Graphics, rinsed, gummed with a gumming solution 850 S, available from Kodak Polychrome Graphics, which had been diluted with water in a ratio of 1:1, and dried.
• the plate showed a good image with a high resolution, i.e. the checkerboard pattern of 1 x 1 pixels (10 ⁇ m) was visible.
• Another printing plate was prepared by carrying out exposure, developing and gumming as described above, however, a solid area and a digital gray scale of FOGRA and GATF as well as different screen values with 80 lines/cm were used for exposure and the printing plate was used on a MAN-Roland 200 printing press. 10% isopropanol to which 4% Combifix (fountain solution additive, available from Hostmann-Steinberg) had been added was used as fountain solution; Hartmann Schwarz Offset S 8900 Cora was used as printing ink. The number of copies yielded by the non-conditioned plate was 65,000; the ElectraExcel plate (same substrate and conditioned for 3 days at 55°C) only yielded 50,000 copies.
• Example 1 a 9 wt.-% solution was prepared by dissolving 38.5 wt.-% 6564 LB (phenol/m-cresol novolak from Bakelite), 38.5 wt.-% PD 140 A, 20 wt.-% PVP/VA, 1 wt.-% Trump dye and 2 wt.-% crystal violet in a solvent mixture of 31 % methyl lactate, 56% THF and 13% water.
• the resistance to "washing agents” also increased in combination with a higher content of PVP.
• PVP/VA-357 (30% PVP, 70% VA) was used, a first attack by the washing agent was observed after 1 minute, while such an attack was only observed after 4 minutes when PVP/VA-535 (50% PVP, 50% VA) was used.
• a coating solution was prepared by dissolving the following solids:
• the plate was exposed in a Creo Trendsetter image-setter with 400 mJ/cm 2 in a checkerboard pattern with different point sizes and developed at 20°C for 30 seconds with the developer Goldstar from KPG.
• the plate showed a good image with a high resolution.
• the above-mentioned comparison plate yielded no image.

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