Classifications

• • 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
  • B41C1/1016—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 characterised by structural details, e.g. protective layers, backcoat layers or several imaging layers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41N—PRINTING PLATES OR FOILS; MATERIALS FOR SURFACES USED IN PRINTING MACHINES FOR PRINTING, INKING, DAMPING, OR THE LIKE; PREPARING SUCH SURFACES FOR USE AND CONSERVING THEM
  • B41N1/00—Printing plates or foils; Materials therefor
  • B41N1/12—Printing plates or foils; Materials therefor non-metallic other than stone, e.g. printing plates or foils comprising inorganic materials in an organic matrix
  • B41N1/14—Lithographic printing foils
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/004—Photosensitive materials
  • G03F7/09—Photosensitive materials characterised by structural details, e.g. supports, auxiliary layers
  • G03F7/11—Photosensitive materials characterised by structural details, e.g. supports, auxiliary layers having cover layers or intermediate layers, e.g. subbing layers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
  • B41C2201/00—Location, type or constituents of the non-imaging layers in lithographic printing formes
  • B41C2201/02—Cover layers; Protective layers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
  • B41C2201/00—Location, type or constituents of the non-imaging layers in lithographic printing formes
  • B41C2201/12—Location, type or constituents of the non-imaging layers in lithographic printing formes characterised by non-macromolecular organic compounds
• • 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
  • B41C2210/04—Negative working, i.e. the non-exposed (non-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
  • B41C2210/08—Developable by water or the fountain 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

Definitions

• the invention relates to a novel lithographic printing plate precursor.
• Lithographic printing typically involves the use of a so-called printing master such as a printing plate which is mounted on a cylinder of a rotary printing press.
• the master carries a lithographic image on its surface and a print is obtained by applying ink to said image and then transferring the ink from the master onto a receiver material, which is typically paper.
• ink as well as an aqueous fountain solution also called dampening liquid
• dampening liquid are supplied to the lithographic image which consists of oleophilic (or hydrophobic, i.e. ink-accepting, water-repelling) areas as well as hydrophilic (or oleophobic, i.e. water-accepting, ink-repelling) areas.
• driographic printing the lithographic image consists of ink-accepting and ink-abhesive (ink-repelling) areas and during driographic printing, only ink is supplied to the master.
• Lithographic printing masters are generally obtained by the image-wise exposure and processing of a radiation sensitive layer on a lithographic support. Imaging and processing renders the so-called lithographic printing plate precursor into a printing plate or master. Image-wise exposure of the radiation sensitive coating to heat or light, typically by means of a digitally modulated exposure device such as a laser, triggers a physical and/or chemical process, such as ablation, polymerization, insolubilization by cross-linking of a polymer or by particle coagulation of a thermoplastic polymer latex, solubilization by the destruction of intermolecular interactions or by increasing the penetrability of a development barrier layer.
• a digitally modulated exposure device such as a laser
• the most popular lithographic plate precursors require wet processing since the exposure produces a difference in solubility or difference in rate of dissolution in a developer between the exposed and the non-exposed areas of the coating.
• positive working lithographic plate precursors the exposed areas of the coating dissolve in the developer while the non-exposed areas remain resistant to the developer.
• negative working lithographic plate precursors the non-exposed areas of the coating dissolve in the developer while the exposed areas remain resistant to the developer.
• lithographic plate precursors contain a hydrophobic coating on a hydrophilic support, so that the areas which remain resistant to the developer define the ink-accepting, hence printing areas of the plate while the hydrophilic support is revealed by the dissolution of the coating in the developer at the non-printing areas.
• Photopolymer printing plates rely on a working-mechanism whereby the coating—which typically includes free radically polymerisable compounds—hardens upon exposure. “Hardens” means that the coating becomes insoluble or non-dispersible in the developing solution and may be achieved through polymerization and/or crosslinking of the photosensitive coating upon exposure to light and/or heat.
• Photopolymer plate precursors can be sensitized to blue, green or red light i.e. wavelengths ranging between 450 and 750 nm, to violet light i.e. wavelengths ranging between 300 and 450 nm or to infrared light i.e. wavelengths ranging between 750 and 1500 nm.
• the exposure step is followed by a heating step to enhance or to speed-up the polymerization and/or crosslinking reaction.
• a toplayer or protective overcoat layer over the imageable layer is required to act as an oxygen barrier to provide the desired sensitivity to the plate.
• a toplayer typically includes water-soluble or water-swellable polymers such as for example polyvinylalcohol. Besides acting as barrier for oxygen, the toplayer should best be easily removable during processing and be sufficiently transparent for actinic radiation, e.g. from 300 to 450 nm or from 450 to 750 nm or from 750 to 1500 nm.
• the classical workflow of photopolymer plates involves first an exposure step of the photopolymer printing plate precursor in a violet or infrared platesetter, followed by an optional pre-heat step, a wash step of the protective overcoat layer, an alkaline developing step, and a rinse and gum step.
• pre-heat step and/or wash step are eliminated and where the processing and gumming step are carried out in one single step or where processing is carried out with a neutral gum and then gummed in a second step.
• on-press processing wherein the plate is mounted on the press and the coating layer is developed by interaction with the fountain and/or ink that are supplied to the plate during the press run, has become very popular.
• the non-image areas are removed from the support and thereby define the non-printing areas of the plate.
• the lithographic printing plate precursors In order to be able to evaluate the lithographic printing plates for image quality, such as for example image resolution and detail rendering (usually measured with an optical densitometer) before mounting them on the press, the lithographic printing plate precursors often contain a colorant such as a dye or a pigment in the coating. Such colorants provide, after processing, a contrast between the image areas containing the colorant and the hydrophilic support where the coating has been removed which enables the end-user to evaluate the image quality and/or to establish whether or not the precursor has been exposed to light.
• a colorant such as a dye or a pigment in the coating.
• Such colorants provide, after processing, a contrast between the image areas containing the colorant and the hydrophilic support where the coating has been removed which enables the end-user to evaluate the image quality and/or to establish whether or not the precursor has been exposed to light.
• a high contrast between the image and the hydrophilic support is required in order to obtain a good image registration (alignment) of the different printing plates in multi-colour printing in order to ensure image sharpness (resolution) and a correct rendering of the colours in the images present.
• a print-out image is also known for heat-sensitive photopolymer lithographic printing plates.
• Such plates are usually image-wise exposed by an IR laser and often comprise, beside an IR dye as a light-to-heat conversion compound, also a dye which absorbs in the visible light wavelength range and changes colour upon heating.
• This colour change can be obtained for example with a heat-decomposable dye which bleaches upon heating such as disclosed in EP 897 134, EP 925 916, WO 96/35143, EP 1 300 241.
• this heat-induced colour change can be the result of a shift of the absorption maximum of a visible dye as disclosed in EP 1 502 736 and EP 419 095.
• the leuco dye technology involves a switch between two chemical forms whereby one is colourless. If the colour switch is caused by for example pH or temperature, the transformation is reversible. Irreversible switches are typically based on redox reactions.
• contrast-providing colorants obtained from leuco dyes that become coloured in the presence of a thermal acid generator is described for example, in U.S. Pat. Nos. 7,402,374; 7,425,406 and 7,462,440.
• the colouring of the printing areas is initiated by image-wise exposure whereby the image areas are visualized before performing development of the plate precursor.
• image-wise exposure whereby the image areas are visualized before performing development of the plate precursor.
• EP 2 297 611 discloses an imaging element comprising a topcoat layer disposed on a photopolymerisable imageable layer comprising a water-soluble polymer binder and a composition that is capable of changing colour upon exposure to infrared radiation which comprises an acid-generating compound, an infrared radiation absorbing compound and optionally one or more compounds that generate a colour in the presence of the acid.
• Thermochromic dye technology involves the design of an IR dye containing a thermocleavable group whereby a colour shift is obtained upon exposure with heat and/or light.
• This technology offers lithographic contrast which is enhanced by increasing either the thermochromic dye concentration or the exposure energy.
• this technology is especially suitable for thermofuse plates—i.e. plates including an image-recording layer that works by heat-induced particle coalescence of a thermoplastic polymer latex,—and does not work well in the photosensitive layer of photopolymer based printing plates. Indeed, only an acceptable contrast in such printing plates is feasible when exposed by very high laser energy and/or when a substantially high concentration of the thermochromic dye is incorporated in the coating.
• the printing plate material of the present invention has the specific feature that it contains a two layer coating of which the toplayer includes an infrared absorbing compound capable of forming a coloured compound—whereby a print-out image is formed—upon exposure to IR light and/or heat.
• a coloured compound is a compound which is visible for the human eye, typically the portion of the electromagnetic spectrum that is visible to the human eye are wavelengths from about 390 to 700 nm.
• efficient plate detection by punch bender and/or registration systems is possible, the need for an additional ink jet print system to inkjet plate information after imaging and/or for a laborous precontrole of the plate by means of for example an acidic gum, is not needed anymore.
• the development is preferably carried out by treating the precursor with a gum solution, however more preferably 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 precursor.
• the lithographic printing plate precursor according to the present invention is negative-working, i.e. after exposure and development the non-exposed areas of the coating are removed from the support and define hydrophilic (non-printing) areas, whereas the exposed coating is not removed from the support and defines oleophilic (printing) areas.
• the hydrophilic areas are defined by the support which has a hydrophilic surface or is provided with a hydrophilic layer.
• the hydrophobic areas are defined by the coating, hardened upon exposing, optionally followed by a heating step. Areas having hydrophilic properties means areas having a higher affinity for an aqueous solution than for an oleophilic ink; areas having hydrophobic properties means areas having a higher affinity for an oleophilic ink than for an aqueous solution.
• Hardened means that the coating becomes insoluble or non-dispersible for the developing solution and may be achieved through polymerization and/or crosslinking of the photosensitive coating, optionally followed by a heating step to enhance or to speed-up the polymerization and/or crosslinking reaction.
• this optional heating step hereinafter also referred to as “pre-heat”, the plate precursor is heated, preferably at a temperature of about 80° C. to 150° C. and preferably during a dwell time of about 5 seconds to 1 minute.
• the coating contains a toplayer and at least one layer including a photopolymerisable composition, said layer is also referred to as the “photopolymerisable layer”.
• the toplayer is provided on top of the photopolymerisable layer.
• the coating may further include other layers such as for example an intermediate layer, located between the support and the photopolymerisable layer and/or between the top layer and the photopolymerisable layer, an adhesion improving layer and/or other layers.
• the coating of the printing plate precursor is preferably capable of being developed on-press with dampening liquid and/or ink.
• the printing plate of the present invention is characterized in that it can be exposed at a low energy density, i.e. below 190 mJ/m 2 ; preferably between 70 and 190 mJ/m 2 ; more preferably between 75 and 150 mJ/m 2 and most preferably between 80 and 120 mJ/m 2 .
• the coating includes a toplayer or protective overcoat layer which preferably acts as an oxygen barrier layer.
• a toplayer or protective overcoat layer which preferably acts as an oxygen barrier layer.
• Low molecular weight substances present in the air may deteriorate or even inhibit image formation and therefore a toplayer is applied to the coating.
• a toplayer should preferably be easily removable during development, adhere sufficiently to the photopolymerisable layer or optional other layers of the coating and should preferably not inhibit the transmission of light during exposure.
• the toplayer is provided on top of the photopolymerisable layer.
• the toplayer includes an infrared absorbing compound which is capable of forming a coloured compound—whereby a print-out image is formed—upon exposure to infrared light and/or heat.
• the infrared absorbing compound is preferably an infrared absorbing dye, also referred to as IR dye.
• the colour-forming IR dye is also referred to herein as thermochromic infrared absorbing dye or thermochromic IR dye.
• the thermochromic IR dye has a main absorption in the infrared wavelength range of the electromagnetic spectrum—i.e. a wavelength range between about 750 and 1500 nm—and does preferably not have a substantial light absorption in the visible wavelength range of the electromagnetic spectrum—i.e.
• thermochromic compound preferably a dye
• the thermochromic compound includes at least one thermocleavable group which is transformed by a chemical reaction, induced by exposure to IR radiation or heat, into a group which is a stronger electron-donor.
• the exposed thermochromic dye absorbs substantially more light in the visible wavelength range of the electromagnetic spectrum, or in other words, the thermochromic IR dye undergoes a hypsochromic shift whereby a visible image is formed, also referred to as print-out image.
• print-out image also referred to as print-out image. The formation of this print-out image is clearly different from a process of the prior art where a compound changes from an essentially colourless compound into a pale-coloured to coloured compound.
• thermochromic dyes of the present invention typically change absorption from the UV wavelength range of the electromagnetic spectrum to the visible wavelength range of the electromagnetic spectrum, i.e. these compounds typically have a batochromic shift.
• the contrast of the print-out image obtained by such a process is much weaker compared to the colour forming process described above of the thermochromic dyes of the present invention.
• the contrast of the print-out image may be defined as the difference between the optical density at the exposed area and the optical density at the non-exposed area, and is preferably as high as possible. This enables the end-user to establish immediately whether or not the precursor has already been exposed and processed, to distinguish the different color selections and to inspect the quality of the image on the plate precursor.
• the contrast of the print-out image preferably increases with increasing optical density in the exposed areas and can be measured in reflectance using an optical densitometer, equipped with several filters (e.g. cyan, magenta, yellow).
• the concentration of the thermochromic IR dyes with respect to the total dry weight of the coating may be from 0.1% wt to 20.0% wt, more preferably from 0.5% wt to 15.0% wt, most preferred from 1.0% wt to 10.0% wt.
• thermochromic IR dye is preferably represented by Formulae I, II or III:
• Ar 1 , Ar 2 and Ar 3 independently represent an optionally substituted aromatic hydrocarbon group or an aromatic hydrocarbon group with an annulated benzene ring which is optionally substituted,
• W 1 and W 2 independently represent a sulphur atom, an oxygen atom, NR′′ wherein R′′ represents an optionally substituted alkyl group, NH, or a —CM 10 M 11 group wherein M 10 and M 11 are independently an optionally substituted aliphatic hydrocarbon group or an optionally substituted (hetero)aryl group, or wherein M 10 and M 11 together comprise the necessary atoms to form a cyclic structure, preferably a 5- or 6-membered ring;
• M 1 and M 2 independently represent hydrogen, an optionally substituted aliphatic hydrocarbon group or together comprise the necessary atoms to form an optionally substituted cyclic structure, preferably M 1 and M 2 together comprise the necessary atoms to form an optionally substituted cyclic structure which may comprise an optionally substituted annulated benzene ring, preferably a 5- or 6-membered ring, more preferably a 5-membered ring, most preferably a 5-membered ring having a cyclic structure of 5 carbon atoms;
• M 3 and M 4 independently represent an optionally substituted aliphatic hydrocarbon group
• M 5 , M 6 , M 7 and M 8 , M 16 and M 17 independently represent hydrogen, a halogen or an optionally substituted aliphatic hydrocarbon group,
• a 1 to A 8 independently represent hydrogen, a halogen atom, an optionally substituted aliphatic hydrocarbon group or an optionally substituted (hetero)aryl group, or wherein each of A 1 and A 2 , A 3 and A 4 , A 5 and A 6 , or, A 7 and A 8 , together comprise the necessary atoms to form a cyclic structure, preferably 5- or 6-membered ring;
• M 12 and M 13 and M 14 and M 15 independently represent an optionally substituted aliphatic hydrocarbon group or an optionally substituted (hetero)aryl group, or wherein, two of said M 14 , M 15 , A 5 or A 7 together comprise the necessary atoms to form at least one cyclic structure, preferably 5- or 6-membered ring; two of said M 12 , M 13 , A 2 or A 4 together comprise the necessary atoms to form at least one cyclic structure preferably 5- or 6-membered ring;
• M 9 is a group which is transformed by a chemical reaction, induced by exposure to IR radiation or heat, into a group which is a stronger electron-donor than said M 9 ; and said transformation provides an increase of the integrated light absorption of said dye between 350 and 700 nm;
• thermochromic IR dye can be a neutral, an anionic or a cationic dye depending on the type of the substituting groups and the number of each of the substituting groups.
• the dye of formula I, II or III comprises at least one anionic or acid group such as —CO 2 H, —CONHSO 2 R h , —SO 2 NHCOR i , —SO 2 NHSO 2 R i , —PO 3 H 2 , —OPO 3 H 2 , —OSO 3 H, —S—SO 3 H or —SO 3 H groups or their corresponding salts, wherein R h , R i and R j are independently an aryl or an alkyl group, preferably a methyl group, and wherein the salts are preferably alkali metal salts or ammonium salts, including mono- or di- or tri- or tetra-alkyl ammonium salts.
• anionic or acid groups may be present on the aromatic hydrocarbon group or the annulated benzene ring of Ar 1 , Ar 2 or Ar 3 , or on the aliphatic hydrocarbon group of M 3 , M 4 or M 12 to M 15 , or on the (hetero)aryl group of M 12 to M 15 .
• Other substituting groups can be selected from a halogen atom, a cyano group, a sulphone group, a carbonyl group or a carboxylic ester group.
• At least one of M 3 , M 4 or M 12 to M 15 is terminally substituted with at least one of these groups, more preferably with —CO 2 H, —CONHSO 2 —Me, —SO 2 NHCO-Me, —SO 2 NHSO 2 —Me, —PO 3 H 2 or —SO 3 H groups or their corresponding salt, wherein Me represents a methyl group.
• thermochromic IR dye represented by Formulae I, II or III above includes M 9 represented by one of the following groups:
• a, b, c and d independently are 0 or 1;
• R 17 represents hydrogen, an optionally substituted aliphatic hydrocarbon group or an optionally substituted (hetero)aryl group, or wherein R 17 and R 5 or R 17 and R 11 together comprise the necessary atoms to form a cyclic structure;
• R 4 represents —OR 10 , —NR 13 R 14 or —CF 3 ;
• R 10 represents an optionally substituted (hetero)aryl group or an optionally branched aliphatic hydrocarbon group
• R 13 and R 14 independently represent hydrogen, an optionally substituted aliphatic hydrocarbon group or an optionally substituted (hetero)aryl group, or wherein R 13 and R 14 together comprise the necessary atoms to form a cyclic structure;
• R 6 represents an optionally substituted aliphatic hydrocarbon group or an optionally substituted (hetero)aryl group, —OR 10 , —NR 13 R 14 or —CF 3 ;
• R 5 represents hydrogen, an optionally substituted aliphatic hydrocarbon group, a SO 3 - group, a —COOR 18 group or an optionally substituted (hetero)aryl group, or wherein R 5 together with at least one of R 10 , R 13 and R 14 comprise the necessary atoms to form a cyclic structure;
• R11, R 15 and R 16 independently represent hydrogen, an optionally substituted aliphatic hydrocarbon group or an optionally substituted (hetero)aryl group, or wherein R 15 and R 16 together comprise the necessary atoms to form a cyclic structure;
• R 12 represents an optionally substituted aliphatic hydrocarbon group or an optionally substituted (hetero)aryl group
• R 7 and R 9 independently represent hydrogen or an optionally substituted aliphatic hydrocarbon group
• R 8 represents —COO— or —COOR 8′ wherein R 8 ′ represents hydrogen, an alkali metal cation, an ammonium ion or a mono-, di-, tri- or tetra-alkyl ammonium ion;
• R18 represents an optionally substituted (hetero)aryl group or an alpha-branched aliphatic hydrocarbon group.
• thermochromic IR dyes used in the present invention are described in EP 1 910 082 pages 4 to 8, IRD-001 to IRD-101, and incorporated herein by reference.
• thermochromic IR dye is represented by Formula IV
• Ar 1 , Ar 2 , W 1 , W 2 and M 1 to M 9 are as defined above.
• thermochromic IR dye is represented by Formula IV wherein
• Ar 1 and Ar 2 independently represent an optionally substituted aryl group
• W 1 and W 2 represent —C(CH 3 ) 2 ;
• M 1 and M 2 together comprise the necessary atoms to form an optionally substituted 5-membered ring which may comprise an optionally substituted annulated benzene ring;
• M 3 and M 4 independently represent an optionally substituted aliphatic hydrocarbon group
• M 5 , M 6 , M 7 and M 8 represent hydrogen
• R 4 , R 5 , R 6 , R 11 , R 12 , R 15 , and R 16 are as defined above;
• the IR dye comprises at least one anionic group or an acid group, such as —CO 2 H, —CONHSO 2 R h , —SO 2 NHCOR i , —SO 2 NHSO 2 R j ,—PO 3 H 2 , —OPO 3 H 2 , —OSO 3 H, —SO 3 H or —S—SO 3 H groups or their corresponding salts, wherein R h , R i and R j are independently an aryl or an alkyl group. More preferably, at least one of the aliphatic hydrocarbon groups of M 3 or M 4 is terminally substituted with at least one of said anionic groups or acid groups.
• Ar 1 and Ar 2 independently represent an optionally substituted aryl group
• W 1 and W 2 represent —C(CH 3 ) 2 ;
• M 1 and M 2 together comprise the necessary atoms to form an optionally substituted 5-membered ring which may comprise an optionally substituted annulated benzene ring;
• M 3 and M 4 independently represent an optionally substituted aliphatic hydrocarbon group
• M 5 , M 6 , M 7 and M 8 represent hydrogen
• R 4 is —OR 10 , wherein R 10 is an optionally branched aliphatic hydrocarbon group
• R 5 represents hydrogen, an optionally substituted aliphatic hydrocarbon group or an optionally substituted (hetero)aryl group,
• R 6 represents an optionally substituted aliphatic hydrocarbon group or an optionally substituted (hetero)aryl group
• the IR dye comprises at least one anionic group or an acid group, such as —CO 2 H, —CONHSO 2 R h , —SO 2 NHCOR i , —SO 2 NHSO 2 R i , —PO 3 H 2 , —OPO 3 H 2 , —OSO 3 H, —SO 3 H or —S—SO 3 H groups or their corresponding salts, wherein R h , R i and R j are independently an aryl or an alkyl group. More preferably, at least one of the aliphatic hydrocarbon groups of M 3 or M 4 is terminally substituted with at least one of said anionic groups or acid groups.
• the salts are preferably alkali metal salts or ammonium salts, including mono- or di- or tri- or tetra-alkyl ammonium salts.
• the optional counter ions in order to obtain an electrically neutral compound may be selected from for example a halogen, a sulphonate, a perfluorosulphonate, a tosylate, a tetrafluoroborate, a hexafluorophosphate, an arylborate, an arylsulphonate; or a cation such as alkali metal salts or ammonium salts, including mono- or di- or tri- or tetra-alkyl ammonium salts.
• thermochromic IR dye Especially preferred thermochromic IR dye are presented by one of the following formulae V to XII:
• M + Li + , Na + , K + , NH 4 + , R′R′′R′′′NH + wherein R′, R′′, R′′′ independently represent hydrogen, an optional substituted alkyl or aryl group;
• thermochromic IR dyes mentioned above may also be coupled to each other or to other IR dyes as to form IR dye dimers or oligomers.
• thermochromic IR dyes may also be formed by ionic interactions. Dimers, consisting of two different IR dyes, may be formed for example by an interaction between a cationic and an anionic IR dye, as described in e.g. WO/2004069938 and EP 1 466 728. IR dyes may also be ionically bond to a polymer as e.g. described in EP 1 582 346 wherein IR dyes, comprising two to four sulphonate groups are ionically bonded to a polymer comprising covalently attached ammonium, phosphonium, and sulphonium groups.
• Supra-molecular complexes comprising two or more thermochromic R dyes, may also be formed by hydrogen bonding or dipole-dipole interaction.
• the colour difference between the exposed and non-exposed areas of the coating calculated from the L*a*b* values of the image areas (exposed areas) of the coating and the L*a*b* values of non-image areas (non-exposed areas) of the coating is denoted as ⁇ E.
• a print-out image is formed characterised by a CIE 1976 colour difference ⁇ E of at least 2, more preferably at least 2,5 and most preferably at least 3.
• a CIE 1976 colour difference ⁇ E of at least 2 is obtained at very low exposure energies, for example below 150 mJ/m 2 .
• ⁇ E is the CIE 1976 colour distance Delta E that is defined by the pair wise Euclidean distance of the CIE L*a*b* colour coordinates.
• CIE L*a*b* colour coordinates are obtained from reflection measurement in 45/0 geometry (non-polarized), using CIE 2° observer and D50 as illuminant. More details are described in CIE S 014-4/E: 2007 Colourimetry—Part 4: CIE 1976 L*a*b* Colour Spaces and CIE publications and CIE S 014-1/E:2006, CIE Standard Colourimetric Observers.
• the CIE 1976 colour system is described in e.g. “Colorimetry, CIE 116-1995: Industrial Colour Difference Evaluation”, or in “Measuring Colour” by R. W. G. Hunt, second edition, edited in 1992 by Ellis Horwood Limited, England.
• the toplayer may further include a binder.
• Preferred binders which can be used in the toplayer are polyvinyl alcohol.
• the polyvinylalcohol has preferably a hydrolysis degree ranging between 74 mol % and 99 mol %, more preferably between 80-98%.
• the weight average molecular weight of the polyvinylalcohol can be measured by the viscosity of an aqueous solution, 4% by weight, at 20° C. as defined in DIN 53 015, and this viscosity number ranges preferably between 2 and 26, more preferably between 2 and 15, most preferably between 2 and 10.
• the overcoat layer may optionally include other ingredients such as inorganic or organic acids, matting agents, surfactants, (organic) waxes or wetting agents as disclosed in EP 2 916 171 and are incorporated herein by reference.
• the coating thickness of the toplayer is between 0.10 and 1.75 g/m 2 , preferably between 0.20 and 1.3 g/m 2 , more preferably between 0.25 and 1.0 g/m 2 and most preferably between 0.30 and 0.8 g/m 2 .
• the toplayer has a coating thickness between 0.25 and 1.75 g/m 2 and comprises a polyvinylalcohol having a hydrolysis degree ranging between 74 mol % and 99 mol % and a viscosity number as defined above ranging between 3 and 26.
• the hydrophilic polymers in the protective overcoat layer may result in a problematic viscosity increase of press chemicals such as for example fountain solution and/or developer solution. Therefore, the thickness of the protective overcoat layer should preferably not be too high e.g. above the ranges as given above.
• the coating of the present invention further includes at least one borate compound.
• the borate compound is preferably present in photopolymerisable layer.
• the borate compound present in the coating refers to a chemical compound including a borate anion and preferably a cation as counterion.
• the borate anion is a tetrahedral boron anion.
• the borate compound is preferably represented by the following Formula A:
• R b 1 , R b 2 , R b 3 and R b 4 are independently an optionally substituted aliphatic hydrocarbon group, an optionally substituted aryl or heteroaryl group; alternatively, two or more of R b 1 , R b 2 , R b 3 and R b 4 can be joined together to form a heterocyclic ring with the boron atom, such a ring may include up to seven carbon, nitrogen, oxygen and/or nitrogen atoms; and M + is an alkali metal cation such as e.g. Li + , Na + , K + or an optional substituted onium ion.
• R b 1 , R b 2 , R b 3 and R b 4 are independently an optionally substituted aryl or heteroaryl group. More preferably, R b 1 , R b 2 , R b 3 and R b 4 are independently an optionally substituted aryl group.
• the borate compound includes at least one optionally substituted phenyl group, more preferably at least two optionally substituted phenyl groups, even more preferably at least three optionally substituted phenyl groups and most preferably four optionally substituted phenyl groups.
• Examples of the optionally substituted onium ion include pyridinium, ammonium, iodonium or sulfonium.
• Examples of a pyridinium ion include N-alkyl-3-pyridinium group, an N-benzyl-3-pyridinium group, an N-(alkoxy polyalkyleneoxy alkyl)-3-pyridinium group, an N-alkoxycarbonylmethyl-3-pyridinium group, an N-alkyl -4pyridinium group, an N-benzyl-4-pyridinium group, an N-(alkoxy polyalkyleneoxy alkyl)-4-pyridinium group, an N-alkoxycarbonylmethyl-4-pyridinium group, N-alkyl-3,5-dimethyl-4-pyridinium, N-alkyl-3-pyridinium group or N-alkyl-4-pyridinium, an N-methyl-3-pyridinium, an N-octyl-3pyridinium, an N-methyl-4-pyridinium, or an N-octyl-4-pyridinium is particularly preferred, and an No
• the optional substituted onium ion is preferably an ammonium ion represented by Formula B:
• R n 1 ,R n 2 and R n 3 are independently an optionally substituted aliphatic hydrocarbon group, an optionally substituted aryl or heteroaryl group or a halogen atom.
• the optional substituted onium ion is most preferably a iodonium ion; more preferably an optionally substituted dipenyl iodonium salt.
• Diphenyl iodonium salts substituted with electron-donating groups, for example, alkyl groups or alkoxyl groups, and asymmetric diphenyl iodonium salts are particularly preferred.
• the borate anion present in the photopolymerisable layer originates from the counterion of the photoinitiator (as described below).
• borate compounds including a iodonium ion include 4-hexyloxyphenyl-2,4-diethoxyphenyl iodonium tetrafluoroborate, 4-octyloxyphenyl phenyliodonium tetraphenylborate, [4-[(2-hydroxytetradecyl) -oxy ]phenyl]phenyliodonium tetraphenylborate, bis(4-t-butylphenyl)iodonium tetraphenylborate, 4- methylphenyl-4′-hexylphenyliodonium tetraphenylborate ⁇ 4-methylphenyl-4′-cyclohexylphenyliodonium tetraphenylborate, bis(t-butylphenyl)iodonium tetrakis(pentafluorophenyl)borate, 4-hexylphenyl-phenyl-
• Preferred compounds include bis(4-t-butylphenyl)iodonium tetraphenylborate, 4-methylphenyl-4′-hexyiphenyliodonium tetraphenylborate, 2- methyl-4-t-butylphenyl-4′-methylphenyliodonium tetraphenylborate, and 4- methylphenyl-4′-cyclohexylphenyliodonium tetraphenylborate.
• M + is an alkali metal cation such as e.g. Li + , Na + , K + , or an optional substituted ammonium ion according to Formula B or an optionally substituted diphenyl iodonium ion. More preferably, M + is preferably an alkali metal cation such as e.g. Li + , Na + , K + or an optionally substituted diphenyl iodonium ion; most preferably an optionally substituted diphenyl iodonium ion.
• the phenyl groups of the iodonium ion are preferably substituted with a group including at least six carbon atoms.
• the borate compound is preferably present in an amount comprised between 0.05 and 30% by weight, more preferably between 0.1 and 25% by weight, and most preferably from 0.5 and 15% by weight relative to the components of the photopolymerisable layer.
• An aliphatic hydrocarbon group preferably represents an alkyl, cycloalkyl, alkenyl, cyclo alkenyl, allyl, or alkynyl group; suitable groups thereof are described below.
• An aromatic hydrocarbon group preferably represents a hetero(aryl) group; suitable hetero(aryl) groups—i.e. suitable aryl or heteroaryl groups—are described below.
• alkyl herein means all variants possible for each number of carbon atoms in the alkyl group i.e. methyl, ethyl, for three carbon atoms: n-propyl and isopropyl; for four carbon atoms: n-butyl, isobutyl and tertiary-butyl; for five carbon atoms: n-pentyl, 1,1-dimethyl-propyl, 2,2-dimethylpropyl and 2-methyl-butyl, etc.
• alkyl groups are methyl, ethyl, n-propyl, isopropyl, n-butyl, 1-isobutyl, 2-isobutyl and tertiary-butyl, n-pentyl, n-hexyl, chloromethyl, trichloromethyl, iso-propyl, iso-butyl, iso-pentyl, neo-pentyl, 1-methylbutyl and iso-hexyl, 1,1-dimethyl-propyl, 2,2-dimethylpropyl and 2-methyl-butyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and methylcyclohexyl groups.
• the alkyl group is a C 1 to C6-alkyl group.
• a suitable alkenyl group is preferably a C 2 to C6-alkenyl group such as an ethenyl, n-propenyl, n-butenyl, n-pentenyl, n-hexenyl, iso-propenyl, iso-butenyl, iso-pentenyl, neo-pentenyl, 1-methylbutenyl, iso-hexenyl, cyclopentenyl, cyclohexenyl and methylcyclohexenyl group.
• a suitable alkynyl group is preferably a C 2 to C 6 -alkynyl group; a suitable aralkyl group is preferably a phenyl group or naphthyl group including one, two, three or more C 1 to C6-alkyl groups; a suitable alkaryl group is preferably a C 1 to C 6 -alkyl group including an aryl group, preferably a phenyl group or naphthyl group.
• a cyclic group or cyclic structure includes at least one ring structure and may be a monocyclic- or polycyclic group, meaning one or more rings fused together.
• Suitable aryl groups may be represented by for example an optionally substituted phenyl, benzyl, tolyl or an ortho- meta- or para-xylyl group, an optionally substituted naphtyl, anthracenyl, phenanthrenyl, and/or combinations thereof.
• the heteroaryl group is preferably a monocyclic or polycyclic aromatic ring comprising carbon atoms and one or more heteroatoms in the ring structure, preferably, 1 to 4 heteroatoms, independently selected from nitrogen, oxygen, selenium and sulphur.
• Preferred examples thereof include an optionally substituted furyl, pyridinyl, pyrimidyl, pyrazoyl, imidazoyl, oxazoyl, isoxazoyl, thienyl, tetrazoyl, thiazoyl, (1,2,3)triazoyl, (1,2,4)triazoyl, thiadiazoyl, thiofenyl group and/or combinations thereof.
• a cyclic group or cyclic structure includes at least one ring structure and may be a monocyclic- or polycyclic group, meaning one or more rings fused together.
• Halogens are selected from fluorine, chlorine, bromine or iodine.
• substituted in e.g. substituted alkyl group means that the alkyl group may be substituted by other atoms than the atoms normally present in such a group, i.e. carbon and hydrogen.
• a substituted alkyl group may include a halogen atom or a thiol group.
• An unsubstituted alkyl group contains only carbon and hydrogen atoms.
• the optional substituents on the alkyl, cycloalkyl, alkenyl, cycloalkenyl, alkynyl, aralkyl, alkaryl, aryl and heteroaryl group are preferably selected from —Cl, —Br, —I, —OH, —SH, —CN, —NO 2 , an alkyl group such as a methyl or ethyl group, an alkoxy group such as a methoxy or an ethoxy group, an aryloxy group, a carboxylic acid group or an alkyl ester thereof, a sulphonic acid group or an alkyl ester thereof, a phosphonic acid group or an alkyl ester thereof, a phosphoric acid group or an an ester such as an alkyl ester such as methyl ester or ethyl ester, a thioalkyl group, a thioaryl group, thioheteroaryl, —SH,
• the lithographic printing plate used in the present invention comprises a support which has a hydrophilic surface or which is provided with a hydrophilic layer.
• the support is preferably a grained and anodized aluminium support, well known in the art. Suitable supports are for example disclosed in EP 1 843 203 (paragraphs [0066] to [0075]).
• the surface roughness, obtained after the graining step, is often expressed as arithmetical mean center-line roughness Ra (ISO 4287/1 or DIN 4762) and may vary between 0.05 and 1.5 ⁇ m.
• the aluminum substrate of the current invention has preferably an Ra value between 0.1 and 1.4 ⁇ m, more preferably between 0.3 and 1.0 ⁇ m and most preferably between 0.4 and 0.9 ⁇ m.
• the lower limit of the Ra value is preferably about 0.1 ⁇ m. More details concerning the preferred Ra values of the surface of the grained and anodized aluminum support are described in EP 1 356 926.
• an Al 2 O 3 layer is formed and the anodic weight (g/m 2 Al 2 O 3 formed on the aluminum surface) varies between 1 and 8 g/m 2 .
• the anodic weight is preferably >2.0 g/m 2 , more preferably 2.5 g/m 2 and most preferably ⁇ 3.0 g/m 2
• the grained and anodized aluminium support may be subjected to so-called post-anodic treatments, for example a treatment with polyvinylphosphonic acid or derivatives thereof, a treatment with polyacrylic acid or derivatives thereof, a treatment with potassium fluorozirconate or a phosphate, a treatment with an alkali metal silicate, or combinations thereof.
• post-anodic treatments for example a treatment with polyvinylphosphonic acid or derivatives thereof, a treatment with polyacrylic acid or derivatives thereof, a treatment with potassium fluorozirconate or a phosphate, a treatment with an alkali metal silicate, or combinations thereof.
• Enlargement or sealing of micropores of the amodized aluminum as disclosed in JP2001-253181A or JP2001-322365A may be performed.
• the support may be treated with an adhesion promoting compound such as those described in EP 1 788 434 in [0010] and in WO 2013/182328.
• a plastic support for example a polyester support, provided with one or more hydrophilic layers as disclosed in for example EP 1 025 992 may also be used.
• the coating has at least one layer including a photopolymerisable composition, said layer is also referred to as the “photopolymerisable layer”.
• the coating may include an intermediate layer, located between the support and the photopolymerisable layer.
• the photopolymerisable layer includes at least one polymerisable compound, an initiator and optionally a binder.
• the photopolymerisable layer has a coating thickness preferably ranging between 0.2 and 5.0 g/m 2 , more preferably between 0.4 and 3.0 g/m 2 , most preferably between 0.6 and 2.2 g/m 2 .
• the polymerisable compound is a polymerisable monomer or oligomer including at least one terminal ethylenic unsaturated group, hereinafter also referred to as “free-radical polymerisable monomer”.
• the polymerisation involves the linking together of the free-radical polymerisable monomers.
• Suitable free-radical polymerisable monomers include, for example, multifunctional (meth)acrylate monomers (such as (meth)acrylate esters of ethylene glycol, trimethyloipropane, pentaerythritol, ethylene glycol, ethoxylated trimethyloipropane, urethane (meth)acrylate) and oligomeric amine di(meth)acrylates.
• the (meth)acrylic monomers may also have other ethylenically unsaturated groups or epoxide groups in addition to the (meth)acrylate group.
• the (meth)acrylate monomers may also contain an acidic (such as a carboxylic acid or phosphoric acid) or basic (such as an amine) functionality.
• Suitable free-radical polymerisable monomers are disclosed in [0042] and [0050] of EP 2 916 171 and are incorporated herein by reference.
• suitable examples of initiators include onium salts, carbon-halogen bond-containing compounds such as [1,3,5] triazines having trihalomethyl groups, organic peroxides, aromatic ketones, thio compounds, azo based polymerization initiators, azide compounds, ketooxime esters, hexaarylbisimidazoles, metallocenes, active ester compounds, borates and quinonediazides.
• onium salts, especially iodonium and/or sulfonium salts are preferable in view of storage stability.
• More specific suitable free-radical initiators include, for example, the derivatives of acetophenone (such as 2,2-dimethoxy-2-phenylacetophenone, and 2-methyl-l-[4-(methylthio) phenyll-2-morpholino propan-l-one); benzophenone; benzil; ketocoumarin (such as 3-benzoyl-7-methoxy coumarin and 7-methoxy coumarin); xanthone; thioxanthone; benzoin or an alkyl-substituted anthraquinone; onium salts (such as diaryliodonium hexafluoroantimonate, diaryliodonium triflate, (4-(2-hydroxytetradecyl -oxy)-phenyl) phenyliodonium hexafluoroantimonate, triarylsulfonium hexafluorophosphate, triarylsulfonium p-toluenesul
• borate salts such as tetrabutylammonium triphenyl(n-butyl)borate, tetraethylammonium triphenyl(n-butyl)borate, diphenyliodonium tetraphenylborate, diphenyliodonium tetraphenylborate wherein the phenyl groups of the iodonium salt are substituted with a group including at least six carbon atoms, and triphenylsulfonium triphenyl(n-butyl)borate, and borate salts as described in U.S. Pat. Nos.
• haloalkyl substituted s-triazines such as 2,4-bis(trichloromethyl)-6-(p-methoxy -styryl)-s-triazine, 2,4-bis(trichloromethyl)-6-(4-methoxy-naphth-l-yl) -s-triazine, 2,4-bis(trichloromethyl)-6-piperonyl-s- triazine, and 2,4-bis(trichloromethyl) -6-[(4 -ethoxy-ethylenoxy)-phen-1-yl]-s-triazine, and s-triazines as described in U.S.
• Optionally substituted trihaloalkyl sulfones wherein halo independently represents bromo, chloro or iodo and sulfone is a chemical compound containing a sulfonyl functional group attached to two carbon atoms, are particularly preferred initiators. Tribromomethyl phenyl sulfones are most preferred initiators. More details concerning this initiator can be found in unpublished copending application EP 18163285.2 paragraphs [0029] to [0040].
• the amount of the initiator typically ranges from 0.1 to 30% by weight, preferably from 0.5 to 15% by weight, most preferably from 2 to 10% by weight relative to the total dry weight of the components of the photopolymerisable composition.
• a very high sensitivity can be obtained by the combination of an optical brightener as sensitizer and a polymerisation initiator.
• the photopolymerisable layer may also comprise a co-initiator.
• a co-initiator is used in combination with a free radical initiator.
• Suitable co-initiators for use in the photopolymer coating are disclosed in U.S. Pat. Nos. 6,410,205; 5,049,479; EP 1 079 276, EP 1 369 232, EP 1 369 231, EP 1 341 040, US 2003/0124460, EP 1 241 002, EP 1 288 720 and in the reference book including the cited refences: Chemistry & Technology UV & EB formulation for coatings, inks & paints—Volume 3—Photoinitiators for Free Radical and Cationic Polymerisation by K.K.
• a very high sensitivity can be obtained by including a sensitizer such as for example an optical brightener in the coating.
• a sensitizer such as for example an optical brightener in the coating.
• optical brighteners as sensitizers are described in WO 2005/109103 page 24, line 20 to page 39.
• Useful sensitizers can be selected from the sensitizing dyes disclosed in U.S. Pat. Nos. 6,410,205; 5,049,479; EP 1 079 276, EP1 369 232, EP 1 369 231, EP 1 341 040, US 2003/0124460, EP 1 241 002 and EP 1 288 720.
• co-initiators may be present in the photopolymerizable layer to further increase the sensitivity.
• Preferred co-initiators are sulfur-compounds, especially thiols like e.g. 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, 2-mercapto-benzimidazole, 4-methyl-3-propyl-1,2,4-triazoline-5-thione, 4-methyl-3-n-heptyl -1,2,4-triazoline-5-thione, 4-phenyl-3-n-heptyl-1,2,4-triazoline-5-thione, 4-phenyl-3,5-dimercapto-1,2,4-triazole, 4-n-decyl-3,5-dimercapto-1,2,4-triazole, 5-phenyl-2-mercapto-1,3,4-oxadiazole, 5-methylthio-1,3,4-thiadiazoline -2-thione, 5-hexylthi
• polythioles as disclosed in WO 2006/048443 and WO 2006/048445. These polythiols may be used in combination with the above described thiols, e.g. 2-mercaptobenzothiazole.
• the photopolymerizable layer may optionally include infrared light absorbing dyes as sensitizers absorbing light between 750 nm and 1300 nm, preferably between 780 nm and 1200 nm, more preferably between 800 nm and 1100 nm.
• sensitizers are heptamethinecyanine dyes disclosed in EP 1 359 008 paragraph [0030] to [0032].
• the photopolymerizable layer preferably includes a binder.
• the binder can be selected from a wide series of organic polymers. Compositions of different binders can also be used. Useful binders are described in for example EP 1 043 627 in paragraph [0013]. Also particulate shaped polymers including homopolymers or copolymers prepared from monomers such as ethylene, styrene, vinyl chloride, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, acrylonitrile, vinyl carbazole, acrylate or methacrylate, or mixtures thereof.
• Thermally reactive polymer fine particles including a thermally reactive group such as an ethylenically unsaturated group, a cationic polymerizable group, an isocyanate group, an epoxy group, a vinyloxy group, and a functional group having an active hydrogen atom, a carboxy group, a hydroxy group, an amino group or an acid anhydride.
• a thermally reactive group such as an ethylenically unsaturated group, a cationic polymerizable group, an isocyanate group, an epoxy group, a vinyloxy group, and a functional group having an active hydrogen atom, a carboxy group, a hydroxy group, an amino group or an acid anhydride.
• the average particle diameter of the polymer fine particle is preferably 0.01 mm to 3.0 mm.
• Particulate polymers in the form of microcapsules, microgels or reactive microgels are suitable as disclosed in EP 1 132 200; EP 1 724 112; US 2004/106060.
• the photopolymerisable layer may also comprise particles which increase the resistance of the coating against manual or mechanical damage.
• the particles may be inorganic particles, organic particles or fillers such as described in for example U.S. Pat. No. 7,108,956. More details of suitable spacer particles described in EP 2 916 171 [0053] to [0056] are incorporated herein by reference.
• the photopolymerizable layer may also comprise an inhibitor.
• Particular inhibitors for use in the photopolymer coating are disclosed in U.S. Pat. No. 6,410,205, EP 1 288 720 and EP 1 749 240.
• the photopolymerizable layer may further comprise an adhesion promoting compound.
• the adhesion promoting compound is a compound capable of interacting with the support, preferably a compound having an addition-polymerizable ethylenically unsaturated bond and a functional group capable of interacting with the support.
• interacting each type of physical and/or chemical reaction or process whereby, between the functional group and the support, a bond is formed which can be a covalent bond, an ionic bond, a complex bond, a coordinate bond or a hydrogen-bond, and which can be formed by an adsorption process, a chemical reaction, an acid-base reaction, a complex-forming reaction or a reaction of a chelating group or a ligand.
• the adhesion promoting compounds described in EP 2 916 171 [0058] are incorporated herein by reference.
• surfactants may be added into the photopolymerisable layer to allow or enhance the developability of the precursor; especially developing with a gum solution.
• Both polymeric and small molecule surfactants for example nonionic surfactants are preferred. More details are described in EP 2 916 171 [0059] and are incorporated herein by reference.
• the lithographic printing plate precursor according to the present invention can be prepared by (i) applying on a support the coating as described above and (ii) drying the precursor.
• the printing plate precursor is preferably image-wise exposed by a laser emitting IR light.
• the image-wise exposing step is carried out off-press in a platesetter, i.e. an exposure apparatus suitable for image-wise exposing the precursor with a laser such as a laser diode, emitting around 830 nm or a Nd YAG laser emitting around 1060 nm, or by a conventional exposure in contact with a mask.
• the precursor is image-wise exposed by a laser emitting IR light.
• the precursor may be pre-heated in a preheating unit, preferably at a temperature of about 80° C. to 150° C. and preferably during a dwell time of about 5 seconds to 1 minute.
• This preheating unit may comprise a heating element, preferably an IR-lamp, an UV-lamp, heated air or a heated roll.
• a preheat step can be used for printing plate precursors comprising a photopolymerisable composition to enhance or to speed-up the polymerization and/or crosslinking reaction.
• the plate precursor may be processed (developed).
• a pre-rinse step might be carried out especially for the negative-working lithographic printing precursors having a protective oxygen barrier or topcoat.
• This pre-rinse step can be carried out in a stand-alone apparatus or by manually rinsing the imaged precursor with water or the pre-rinse step can be carried out in a washing unit that is integrated in a processor used for developing the imaged precursor.
• the washing liquid is preferably water, more preferably tap water. More details concerning the wash step are described in EP 1 788 434 in [0026].
• the non-exposed areas of the image-recording layer are at least partially removed without essentially removing the exposed areas.
• the processing liquid also referred to as developer
• the processing liquid can be applied to the plate e.g. by rubbing with an impregnated pad, by dipping, immersing, coating, spincoating, spraying, pouring-on, either by hand or in an automatic processing apparatus.
• the treatment with a processing liquid may be combined with mechanical rubbing, e.g. by a rotating brush.
• any water-soluble protective layer present is preferably also removed.
• the development is preferably carried out at temperatures between 20 and 40° C. in automated processing units.
• the processing step as described above is replaced by an on-press processing whereby the imaged precursor is mounted on a press and processed on-press by rotating said plate cylinder while feeding dampening liquid and/or ink to the coating of the precursor to remove the unexposed areas from the support.
• dampening liquid is supplied to the plate during start-up of the press and after a number of revolutions of the plate cylinder also the ink supply is switched on.
• supply of dampening liquid and ink is started simultaneously, or only ink can be supplied during a number of revolutions before switching on the supply of dampening liquid.
• the processing step may also be performed by combining embodiments described above, e.g. combining development with a processing liquid with development on-press by applying ink and/or fountain.
• the processing liquid may be an alkaline developer or solvent-based developer.
• Suitable alkaline developers have been described in US2005/0162505.
• An alkaline developer is an aqueous solution which has a pH of at least 11, more typically at least 12, preferably from 12 to 14.
• Alkaline developers typically contain alkaline agents to obtain high pH values can be inorganic or organic alkaline agents.
• the developers can comprise anionic, non-ionic and amphoteric surfactants (up to 3% on the total composition weight); biocides (antimicrobial and/or antifungal agents), antifoaming agents or chelating agents (such as alkali gluconates), and thickening agents (water soluble or water dispersible polyhydroxy compounds such as glycerine or polyethylene glycol).
• the processing liquid is a gum solution whereby during the development step the non-exposed areas of the photopolymerisable layer are removed from the support and the plate is gummed in a single step.
• the development with a gum solution has the additional benefit that, due to the remaining gum on the plate in the non-exposed areas, an additional gumming step is not required to protect the surface of the support in the non-printing areas.
• the precursor is processed and gummed in one single step which involves a less complex developing apparatus than a developing apparatus comprising a developer tank, a rinsing section and a gumming section.
• the gumming section may comprise at least one gumming unit or may comprise two or more gumming units.
• These gumming units may have the configuration of a cascade system, i.e. the gum solution, used in the second gumming unit and present in the second tank, overflows from the second tank to the first tank when gum replenishing solution is added in the second gumming unit or when the gum solution in the second gumming unit is used once-only, i.e. only starting gum solution is used to develop the precursor in this second gumming unit by preferably a spraying or jetting technique. More details concerning such gum development is described in EP1 788 444.
• a gum solution is typically an aqueous liquid which comprises one or more surface protective compounds that are capable of protecting the lithographic image of a printing plate against contamination, e.g. by oxidation, fingerprints, fats, oils or dust, or damaging, e.g. by scratches during handling of the plate.
• Suitable examples of such surface protective compounds are film-forming hydrophilic polymers or surfactants.
• the layer that remains on the plate after treatment with the gum solution preferably comprises between 0.005 and 20 g/m 2 of the surface protective compound, more preferably between 0.010 and 10 g/m 2 , most preferably between 0.020 and 5 g/m 2 . More details concerning the surface protective compounds in the gum solution can be found in WO 2007/057348 page 9 line 3 to page 11 line 6.
• the gum solution preferably has a pH value between 3 and 11, more preferably between 4 and 10, even more preferably between 5 and 9, and most preferably between 6 and 8.
• a suitable gum solution is described in for example EP 1 342 568 in [0008] to [0022] and WO2005/111727.
• the gum solution may further comprise an inorganic salt, an anionic surfactant, a wetting agent, a chelate compound, an antiseptic compound, an anti-foaming compound and/or an ink receptivity agent and/or combinations thereof. More details about these additional ingredients are described in WO 2007/057348 page 11 line 22 to page 14 line 19.
• the plate may be dried in a drying unit.
• the plate is dried by heating the plate in the drying unit which may contain at least one heating element selected from an IR-lamp, an UV-lamp, a heated metal roller or heated air.
• the plate After drying the plate can optionally be heated in a baking unit. More details concerning the heating in a baking unit can be found in WO 2007/057348 page 44 line 26 to page 45 line 20.
• the printing plate thus obtained can be used for conventional, so-called wet offset printing, in which ink and an aqueous dampening liquid is supplied to the plate.
• Another suitable printing method uses a so-called single-fluid ink without a dampening liquid.
• Suitable single-fluid inks have been described in U.S. Pat. Nos. 4,045,232; 4,981,517 and 6,140,392.
• the single-fluid ink comprises an ink phase, also called the hydrophobic or oleophilic phase, and a polyol phase as described in WO 00/32705.
• a 0.3 mm thick aluminium foil was degreased by spraying with an aqueous solution containing 26 g/I NaOH at 65° C. for 2 seconds and rinsed with demineralised water for 1.5 seconds.
• the foil was then electrochemically grained during 10 seconds using an alternating current in an aqueous solution containing 15 g/l HCl, 15 g/l SO42- ions and 5 g/l Al3+ ions at a temperature of 37° C. and a current density of about 100 A/dm2.
• the aluminium foil was then desmutted by etching with an aqueous solution containing 5.5 g/l of NaOH at 36° C. for 2 seconds and rinsed with demineralised water for 2 seconds.
• the foil was subsequently subjected to anodic oxidation during 15 seconds in an aqueous solution containing 145 g/l of sulfuric acid at a temperature of 50° C. and a current density of 17 A/dm2, then washed with demineralised water for 11 seconds and dried at 120° C. for 5 seconds.
• the support thus obtained was characterized by a surface roughness Ra of 0.35-0.4 ⁇ m (measured with interferometer NT1100) and had an oxide weight of 3.0 g/m 2 .
• the photosensitive composition PL-01 as defined in Table 1 was coated onto the above described support S-01.
• the components were dissolved in a mixture of 35% by volume of MEK and 65% by volume of Dowanol PM (1-methoxy-2-propanol, commercially available from DOW CHEMICAL Company).
• the coating solution was applied at a wet coating thickness of 30 ⁇ m and then dried at 120° C. for 1 minute in a circulation oven.
• FST 510 is a reaction product from 1 mole of 2,2,4-trimethylhexamethylenediisocyanate and 2 moles of hydroxyethyl-methacrylate commercially available from AZ Electronics as a 82 wt.
• CN 104 is an epoxy acrylate oligomer commercially available from Arkema; 3) Initiator-01 is bis(4-tert-butylphenyl)-iodonium tetraphenyl borate 4) S2025 is an infrared absorbing dye commercially available from FEW Chemicals 5) S-LEC BX35-Z, a polyvinylbutyral commercially available from Sekisui; 6) Tegoglide 410 is a surfactant commercially available from Evonik Tego Chemie GmbH; 7) Sipomer PAM 100 is a methacrylate phosphonic ester commercially available from Rhodia; 8) Albritect CP 30, is a copolymer of vinylphosphonic acid and acrylic acid commercially available as a 20 wt. % aqueous dispersion from Rhodia.
• Inventive printing plate precursors PPP-01 to PPP-08 having a coating thickness of respectively 1.225; 1.245; 1.285; 1.985; 0.512 and 0.552 g/m 2 were obtained and comparative printing plate precursors PPP-09 to PPP-11 having a coating thickness of respectively 1.205; 0.510 and 0.522 g/m 2 were obtained.
• composition of the inventive protective overcoat layers (g/m 2 ) Ingredients OC-01 OC-02 OC-03 OC-04 OC-05 OC-06 OC-07 OC-08 g/m 2 Inv Inv Inv Inv Inv Inv Inv Inv Inv Inv Mowiol4-88 0.736 0.736 0.736 0.450 0.450 0.450 0.450 (1) Mowiol8-88 0.226 0.226 0.226 0.226 — — — (1) Luviskol K30 0.231 0.231 0.231 0.231 — — — — (2) IR-01 (3) 0.020 0.040 0.080 0.150 0.020 0.050 — — IR-02 (3) — — — — — — — 0.050 0.090 Lutensol A8 0.012 0.012 0.012 0.012 0.012 0.012 0.012 0.012 0.012 0.012 0.012 0.012 0.012 0.012 0.012 0.012
• composition of the comparative protectiveovercoat layers Ingredients OC-09 OC-10 OC-11 g/m 2 reference comparative comparative Mowiol4-88 (1) 0.736 0.410 0.410 Mowiol8-88 (1) 0.226 — — Luviskol K30 (2) 0.231 — — IR-03 (3) — 0.020 0.020 Black XV (4) — — 0.020 Omnicat 250 (5) — 0.060 0.060 utensol A8 (6) 0.012 0.012 0.012 (1) (2) and (6) see Table 2 3)
• IR-03 is an infrared absorbing dye commercially available from FEW chemicals having the following formula: 4) Black XV is 6-diethylamino-3-methyl-2-(2,4-xylidino) fluoran, a leuco dye commercially available from Mitsui; 5) Acid generator is (4-methylphenyl)[4-(2-methylpropyl)phenyl]-hexafluorophosphate commercial
• the printing plate precursors PPP-01 to PPP-11 were imaged at 2400 dpi with a High Power Creo 40W TE38 thermal platesetterTM (200 Ipi Agfa Balanced Screening (ABS)), commercially available from Kodak and equipped with a 830 nm IR laser diode, at energy densities between 50 and 200 mJ/cm 2 . Printing plates PP-01 to PP-11 were obtained.
• the total colour difference ⁇ E is a single value that takes into account the difference between the L, a* and b* values of the image areas and the non-image areas:
• ⁇ E ⁇ square root over ( ⁇ L 2 + ⁇ a 2 + ⁇ b 2 ) ⁇
• a total colour difference ⁇ E above or equal to 2 is defined as a clear print out image.
• a total colour difference ⁇ E below 2 is defined as an unsufficient print out image.
• the photopolymerisable layer PL-02 as defined in Table 8 was coated onto the above described support S-01 (see Example 1).
• the components were dissolved in a mixture of 35% by volume of MEK and 65% by volume of Dowanol PM (1-methoxy-2-propanol, commercially available from DOW CHEMICAL Company).
• the coating solution was applied at a wet coating thickness of 30 ⁇ m and then dried at 120° C. for 1 minute in a circulation oven.
• composition of the photosensitive layer (g/m 2 ) Ingredients g/m 2 PL-02 FST 510 (1) 0.250 CN 104 (2) 0.250 Initiator-02 (3) 0.060 S0094 (4) 0.020 Ruco coat EC4811 (5) 0.250 Tegoglide 410 (6) 0.0015 Sipomer PAM 100 (7) 0.130 Albritect CP 30 (8) 0.024 1)
• FST 510 is a reaction product from 1 mole of 2,2,4-trimethylhexamethylenediisocyanate and 2 moles of hydroxyethyl-methacrylate commercially available from AZ Electronics as a 82 wt.
• S0094 is an infrared absorbing dye commercially available from FEW Chemicals having the following structure: 5) Ruco coat EC4811 is a polyether polyurethane commercially available from Rudolf Chemistry 6) Tegoglide 410 is a surfactant commercially available from Evonik Tego Chemie GmbH; 7) Sipomer PAM 100 is a methacrylate phosphonic ester commercially available from Rhodia; 8) Albritect CP 30, is a copolymer of vinylphosphonic acid and acrylic acid commercially available as a 20 wt. % aqueous dispersion from Rhodia.
• composition of the protective layer (g/m 2 ) Ingredients OC-12 g/m 2 comp Mowiol 4-88 (1) 0.785 Mowiol 8-88 (1) 0.343 Mowiol 6-98 (1) 0.685 IR-02(2) 0.158 Acticide LA1206 (3) 0.012 Metolat FC 355 (4) 0.018 Lutensol A8 (5) 0.0015 1) Mowiol 4-88 TM, Mowiol 8-88 TM are partially hydrolyzed polyvinylalcohols and Mowiol 6-98 TM is a fully hydrolysed polyvinylalcohol commercially available from Kuraray; 2) IR-02 is an infrared absorbing dye having the following formula: 3) Acticide LA1206 is a biocide, commercially available from Thor. 4) Metolat FC 355 is an ethoxylated ethylenediamine, commercially available from Munzing Chemie. 5) Lutensol A8 TM is a surface active agent, commercially available
• the printing plate precursor PPP-12 was imaged at 2400 dpi with a High Power Creo 40W TE38 thermal platesetterTM (200 Ipi Agfa Balanced Screening (ABS)), commercially available from Kodak and equipped with a 830 nm IR laser diode, at energy densities between 80 and 300 mJ/cm 2 .
• Printing plate PP-12 was obtained.
• a total colour difference ⁇ E above or equal to 2 is defined as a clear print out image.
• a total colour difference ⁇ E below 2 is defined as an unsufficient print out image.
• the comparative samples clearly demonstrate that the formation of a printout image is suppressed when the total dry weight of the protective topcoat containing the thermochromic dye is too high, i.e. 2 g/m 2 : At a significantly elevated dye concentration (157 mg/m 2 ), the printout image at exposure energies of 90 to 150 mJ/cm 2 remains very weak.
• the photosensitive compositions as defined in Table 11 were coated onto the above described support S-01.
• the components were dissolved in a mixture of 35% by volume of MEK and 65% by volume of Dowanol PM (1-methoxy -2-propanol, commercially available from DOW CHEMICAL Company).
• the coating solution was applied at a wet coating thickness of 30 ⁇ m and then dried at 120° C. for 1 minute in a circulation oven.
• composition of the photosensitive layer Ingredients g/m 2 PL-03 PL-04 PL-05 FST 510 (1) 0.250 0.250 0.250 CN 104 (2) 0.250 0.250 0.250 Initiator-01 (4) 0.045 0.045 0.045 S2539 (5) 0.020 0.020 0.020 Ruco coat EC4811 (6) 0.250 0.250 0.250 Tegoglide 410 (9) 0.0015 0.0015 0.0015 Sipomer PAM 100 (10) 0.130 0.130 0.130 Albritect CP 30 (11) 0.024 0.024 0.024 Black XV (12) — 0.020 — IR-01 (13) — — 0.020 1) FST 510 is a reaction product from 1 mole of 2,2,4-trimethylhexamethylenediisocyanate and 2 moles of hydroxyethyl-methacrylate commercially available from AZ Electronics as a 82 wt.
• CN 104 is an epoxy acrylate oligomer commercially available from Arkema; 3) SR494 is an ethoxylated pentaerythritol tetraacrylate commercially available from Arkema; 4) Initiator-01 is bis(4-tert-butylphenyl)-iodonium tetraphenyl borate 5) S2539 is an infrared absorbing dye commercially available from FEW Chemicals having the following structure: 6) Ruco coat EC4811 is a polyether polyurethane commercially available from Rudolf Chemistry 7) S-LEC BX35-Z, S-LEC BL1 and S-LEC BL10 are polyvinylbutyral resins commercially available from Sekisui; 8) Gohsefimer LL-02 is a polyvinyl alcohol having a low hydrolysis degree commercially available from Nippon Goshei; 9) Tegoglide 410
• Black XV is 6-diethylamino-3-methyl-2-(2,4-xylidino) fluoran, a leuco dye commercially available from Mitsui 13
• IR-01 is an infrared absorbing dye having the following formula:
• composition of the protective layers OC-13 and OC-14 Ingredients OC-13 OC-14 g/m 2 inventive reference Mowiol 4-88 (1) 0.30 0.30 Mowiol 4-98 (1) 0.18 0.18 IR-01 (2) 0.05 — Lutensol A8 (3) 0.01 0.01 1) Mowiol 4-88 TM and Mowiol 4-98 TM are partially hydrolyzed polyvinylalcohols commercially available from Kuraray; 2) IR-01 is an infrared absorbing dye having the following formula: 3) Lutensol A8 TM is a surface active agent commercially available from BASF.
• the printing plate precursors PPP-13 to PPP-15 were imaged at 2400 dpi with a High Power Creo 40W TE38 thermal platesetterTM (200 Ipi Agfa Balanced Screening (ABS)), commercially available from Kodak and equipped with a 830 nm IR laser diode, at energy densities between 50 and 200 mJ/cm2. Printing plates PP-13 to PP-15 were obtained.
• a High Power Creo 40W TE38 thermal platesetterTM 200 Ipi Agfa Balanced Screening (ABS)
• ABS Balanced Screening
• a total colour difference ⁇ E above or equal to 2 is defined as a clear print out image.
• a total colour difference ⁇ E below 2 is defined as an unsufficient print out image.
• the stability of the print-out image was evaluated by determining the total colour difference ⁇ E before and after exposing a printing plate to regular white office light (800 lux). As a reference, the total colour difference ⁇ E was also determined of a printing plate which was stored in a bag protected from external light.
• the total colour difference ⁇ E of the printing plates was measured immediately after the exposure step (see below). Subsequently, the printing plates were exposed to regular white office light (800 lux) as well as stored in a bag protected from external light for one hour. The ⁇ E was re-measured after one hour and the obtained results are summarized in Table 14 below.
• the total colour difference ⁇ E was measured immediately after exposure to regular white office light (800 lux) and after a time period of one hour.
• the total colour difference ⁇ E of the printing plates was measured immediately after the exposure step. Subsequently, the printing plates were exposed to regular white office light (800 lux) as well as stored in a bag protected from external light for one hour. The ⁇ E was re-measured after one hour and the obtained results are summarized in Table 14.
• the print-out image of the comparative printing plate PP-14 is weak and fades away after storage of one hour.
• the total colour difference ⁇ E is low and decreases further after storage in a bag and/or after exposure to regular white office light (800 lux).

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