Abstract:
A method of preparing a lithographic printing plate in which no pre-heat step is used comprising the steps of:—providing a lithographic printing plate precursor comprising a support and a photopolymerizable image-recording layer, the image-recording layer comprising a monomer and a binder;—image-wise exposing the precursor in an exposure unit;—off press developing the exposed precursor with an aqueous solution in a processing unit; characterized in that the ratio of the total amount of monomer to the total amount of binder is at least 1 and the time lapse between exposing an image-area of the precursor and contacting the image-area with the aqueous solution is at least 1 minute.
Abstract:
A method of making a lithographic printing plate includes the steps of: a) providing a lithographic printing plate precursor including (i) a support having a hydrophilic surface or which is provided with a hydrophilic layer, (ii) a coating on the support including a photopolymerizable layer, and, optionally, an intermediate layer between the photopolymerizable layer and the support, wherein the photopolymerizable layer includes a polymerizable compound and a polymerization initiator, b) image-wise exposing the coating in a plate setter, c) optionally, heating the precursor in a pre-heating unit, d) developing the precursor off-press in a gumming unit by treating the coating of the precursor with a gum solution, thereby removing the non-exposed areas of the photopolymerizable layer from the support, wherein the photopolymerizable layer further includes a polymer containing an acid group and a basic nitrogen-containing compound capable of neutralizing the acid group, or wherein the photopolymerizable layer further includes a polymer containing an acid group which is neutralized by a basic nitrogen-containing compound.
Abstract:
A method for making a lithographic printing plate precursor is disclosed comprising the steps of a. providing a lithographic printing plate precursor including a support having a hydrophilic surface or which is provided with a hydrophilic layer, a photopolymerizable coating comprising a photopolymerizable composition, and an overcoat layer comprising a water soluble low molecular weight acid, wherein said overcoat layer has a surface pH-value ranging between 1 to 6; b. image-wise exposing the precursor; c. optionally heating the exposed precursor; d. processing the obtained precursor by applying a gum solution and optionally brushing the precursor, and/or by mounting the precursor on a plate cylinder of a lithographic printing press and rotating the plate cylinder while feeding dampening liquid and/or ink to the coating. The printing plate obtained after imaging and processing in an off-press configuration with a gum solution or in an on-press configuration with fountain solution and ink shows an improved roll-up performance in the start-up of a printing process on a printing press.
Abstract:
A method of making a lithographic printing plate includes the steps of: a) providing a lithographic printing plate precursor including (i) a support having a hydrophilic surface or which is provided with a hydrophilic layer, (ii) a coating on the support, including a photopolymerizable layer and, optionally, an intermediate layer between the photopolymerizable layer and the support, wherein the photopolymerizable layer includes a polymerizable compound, a polymerization initiator and a binder, b) image-wise exposing the coating in a plate setter, c) optionally, heating the precursor in a pre-heating unit, d) treating the precursor in a gumming station, including a first and at least a second gumming unit, wherein the precursor is consecutively developed in the first and the second gumming unit with a gum solution, thereby removing non-exposed areas of the photopolymerizable layer from the support and gumming the plate in a single step.
Abstract:
A heat-sensitive positive-working lithographic printing plate precursor includes a support having a hydrophilic surface or which is provided with a hydrophilic layer, a heat-sensitive coating including an IR absorbing agent, a phenolic resins and a first polymer, wherein the first polymer is an alkaline soluble polymer including a monomeric unit having a structure according to Formula I or Formula II, wherein at least one of the aromatic groups Ar1 and Ar2 is an optionally substituted heteroaromatic group;
Abstract:
A method for making a lithographic printing plate includes the steps of providing a heat-sensitive lithographic printing plate precursor including on a support having a hydrophilic surface or which is provided with a hydrophilic layer, a heat-sensitive coating; image-wise exposing the precursor with IR-radiation or heat; and developing the image-wise exposed precursor with an alkaline developing solution, wherein an anti-sludge agent is present in the precursor or in the developing solution or in the precursor and the developing solution, and wherein the anti-sludge agent is a 5-membered heteroaromatic compound, including a —NH— group wherein the hydrogen is capable of being deprotonated in the alkaline developing solution, selected from the group consisting of an optionally substituted benztriazole, 1,2,3-triazole, tetrazole, or indazole compound. According to the above method, the formation of sludge is inhibited or reduced.
Abstract:
A method is disclosed for accurate reproduction of high-quality halftone images comprising microdots by means of lithographic plate materials which comprise a heat-sensitive positive-working coating that requires wet processing. Such microdots have a dot size ≦25 μm and may be obtained by stochastic screening or by amplitude-modulated screening at a ruling of not less than 150 lpi. It has been established that the “physical right exposure energy density” (physical REED) lies in the range from CP to 1.5*CP, wherein the physical REED is defined as the energy density at which the physical area on the plate, occupied by a microdot corresponding to a 50% halftone in the image data, coincides with the 50% target value; and wherein CP is the clearing point of the plate which is defined as the minimum energy density that is required to obtain, after processing, a dissolution of 95% of the coating. An accurate reproduction of microdots can therefore be achieved by exposing the material with light having an energy density in the range from CP to 1.5*CP. Loss of microdots by overexposure is thereby avoided.
Abstract:
A polymer for a heat-sensitive lithographic printing plate precursor is disclosed wherein the polymer comprises a phenolic monomeric unit of which the phenyl group is substituted by a group A characterised in that the group A comprises an imide or thioimide group and wherein the modification of the polymer increases the chemical resistance of the coating of the printing plate precursor.
Abstract:
The invention relates to a method of making a lithographic printing plate comprising the steps of providing a photopolymer printing plate precursor that is photopolymerizable upon absorption of light in the wavelength range from 300 to 700 nm, exposing said printing plate precursor with light in the range from 300 to 700 nm and processing said exposed precursor with an aqueous alkaline developer, characterized in that the alkaline developer comprises a polyethyleneoxide/polypropyleneoxide surfactant having a specific composition. The method leads to less depositions in the developing apparatus and on the processed printing plates and the developer used has an increased sedimentation stability.
Abstract:
A positive working printing plate precursor is disclosed which comprises a hydrophilic support and a coating provided thereon which comprises in the order given a first layer containing an oleophilic resin soluble in an aqueous alkaline developer and a second layer comprising a water repellent-compound. Furthermore, the coating comprises an infrared absorbing dye containing a perfluoroalkyl group providing a printing plate precursor with high sensitivity.