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
• • 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 a composition sensitive to IR radiation and to heat, and a lithographic plate coated with this composition.
• composition sensitive to IR radiation and to heat which is useful for the production of a lithographic plate of the positive type.
• It also relates to a composition sensitive to laser radiation which is useful for the production of a lithographic plate of the positive type.
• the technique of printing by means of lithographic plates is based on differential partition between fatty substances and water.
• the fatty substance or ink is retained preferentially by the image area and the water is preferentially retained by the non-image area.
• the non-image area retains the water and repels the ink, while the image area accepts the ink and repels the water.
• the ink on the image area is transferred onto the surface of a material on which it is desired to reproduce the image, such as, for example, paper, textile and the like.
• the lithographic plates used in printing processes are formed from an aluminium support covered with a composition sensitive to light (photosensitive).
• a composition sensitive to light photosensitive
• the printing process is termed "positive”.
• the portion exposed to heat or to radiation of appropriate wavelength becomes insoluble in an alkaline developing bath, the printing process is termed "negative”.
• the remaining, image area is lipophilic and hence accepts the ink, while the non-image area is hydrophilic and accepts the water.
• composition sensitive to radiation emitted by a laser could impart greater reliability to the system.
• compositions comprising a polymeric binder and a solubility inhibitor have been investigated.
• a solubility inhibitor has the ability to render the polymeric binder insoluble in a suitable alkaline developing bath as long as it has not been exposed to a sufficient quantity of heat and of then rendering it soluble in the said developing bath after such exposure to heat.
• many of the compositions described until now also comprise a so-called IR absorber, usually consisting of a compound capable of absorbing IR radiation and of transforming part of the radiation absorbed into heat, giving it up to the immediately surrounding environment.
• the present invention aims to provide a composition sensitive to heat and a lithographic plate of the positive type coated with the said composition wherein the solubility inhibitor is a hydroxylated acrylic polymer, a hydroxylated acrylic copolymer or a derivative thereof.
• the present invention also aims to provide a composition sensitive to IR radiation and a lithographic plate of the positive type coated with the said composition wherein the solubility inhibitor is a hydroxylated acrylic polymer, a hydroxylated acrylic copolymer or a derivative thereof.
• the present invention also aims to provide a composition sensitive to laser radiation and a lithographic plate of the positive type coated with the said composition wherein the solubility inhibitor is a hydroxylated acrylic polymer, a hydroxylated acrylic copolymer or a derivative thereof.
• lithographic plate means a support covered with a coating which, after being suitably exposed and developed, is used, as a planographic matrix, in printing processes wherein there is differential partition between fatty substances and water.
• Typical examples of support materials are constituted by plates of aluminium, zinc, copper, polyester and paper covered with a polymer.
• the support is a sheet of grained aluminium, oxidized and suitably treated to receive the photosensitive composition.
• positive type means that the portion of the photosensitive coating exposed to the radiation or to heat becomes soluble in such a way that it can be removed during the process of development of the plate.
• the development process is performed in alkalis having a conductivity of from 75 to 110 mS.
• polymeric binder means a polymer soluble in alkali, such as for example a novolac resin, a resol resin, a vinylphenolic resin, derivatives thereof or mixtures thereof.
• the thus obtained compound is variously modified such as, for example, by reaction with amides.
• heat-sensitive composition means a composition which includes a polymeric binder and has the property of being insoluble in an alkaline developing bath as long as it has not been exposed to a sufficient quantity of heat and of then being soluble in the said bath after such exposure to heat.
• solubility inhibitor means a compound capable of rendering a heat-sensitive composition that contains it insoluble in a suitable alkaline developing bath as long as the said composition has not been exposed to a sufficient quantity of heat and/or laser radiation and of then rendering it soluble in the said developing bath after such exposure to heat and/or laser radiation.
• hydroxyl number means the number of milligrams of KOH equivalent to the hydroxyl content of 1 gram of the compound under test. The determination is made by acetylating the compound under test with acetic anhydride in pyridine, hydrolysing with water the excess acetic anhydride that has not reacted and titrating the free acetic acid with KOH (phenolphthalein indicator).
• acidity number means the number of milligrams of KOH necessary to neutralize the free acid present in 1 gram of the compound under test.
• IR absorber means a compound capable of absorbing IR radiation and of transforming part of the absorbed radiation into heat and giving it up to the immediately surrounding environment.
• an absorber is soluble in water, ketones, glycols, glycolethers, alcohols, esters and mixtures thereof.
• absorbers are the commercial products KF 646, KF 645, KF810, KF 1003, KF 1002, IR HBB 812 and KF 818 from the company Riedel-de Haen/Allied/Signal (Seelze, Germany), the commercial product ADS 830A and ADS 1060A, ADS793EI, ADS798MI, ADS798MP, ADS800AT, ADS805PI, ADS805PP, ADS805PA, ADS805PF, ADS812MI, ADS815EI, ADS818HI, ADS818HT, ADS822MT, ADS838MT, ADS840MT, ADS845BI, ADS905AM,ADS956BGI, ADS1040P, ADS1054P, ADS1050P, ADS1120P from the firm American Dye Source (Varennes, Quebec, Canada), the commercial products YKR - 3070, YKR - 3082, D99-029
• a particularly interesting family of absorbers is that characterized by the following structural formula: wherein X, Y, R, R' and R'' can take many meanings. Typical examples of these meanings are: simple or condensed heterocyclic ring for X, simple or fused heterocyclic ring for Z and Y together with the carbon atom to which they are bound, hydrogen, C 1-3 alkyl, SO 3 - or COO - for R and R' independently of one another and H or Cl for R''.
• heterocyclic rings are:
• absorbers are:
• IR radiation means radiation of a wavelength of from of from 780 to 1400 nm.
• a typical example of a device used to generate IR radiation is a laser diode which emits at ca. 830 nm.
• laser radiation means radiation of a wavelength of from 600 to 1400 nm.
• Absorber capable of absorbing radiation having a wavelenght of from 600 to 780 nm are well known in the art.
• Typical examples of such absorbers are the commercial products ADS640PP, AD640HI, ADS640HI, ADS675MT, ADS680BP, ADS740PP, ADS745HT, ADS760MP, ADS775MI, ADS775MP, ADS775HI, ADS775PI, ADS775PP, ADS780MT and ADS780BP from the firm American Dye Source (Varennes, Quebec, Canada).
• nominal wavelength means a wavelength of from 805 to 830 nm.
• die means a coloured compound or preparation capable of dyeing the photosensitive composition in order to reveal the image after the exposure to light and/or after development.
• Typical examples of dyes are BasonylTM blue 636 (Colour Index 42595) from the firm Basf (Germany), Sudan Yellow 150 (Colour Index 11021) from the firm Basf (Germany), Solvent Green 3 (Colour Index 61565), Solvent Blue 59 (Colour Index 61552), Solvent Blue 35 (Colour Index 61554) or mixtures thereof.
• triazine intends to mean the entire family of the substituted trichloromethyl-s-triazines of known type.
• additive means a compound used to improve or confer a desired property on the photosensitive composition such as for example an enhancer developing agent, a pigment, a plasticizer capable of rendering the emulsion less resistant to heat and hence more sensitive, without however having an insolubilizing function, or an agent capable of modifying the surface and/or interfacial tension and thus improving the spreadability characteristics on the support and the covering power of the heat-sensitive composition.
• Typical examples of pigments are: HeliogenTM Blue L 6700 F (PB 15:6 colour index 74160), HeliogenTM Blue L 6875 F (PB 15:2 colour index 74160) from the firm Basf (Germany), and from the WaxolineTM series: BLUE AP FW (colour index SB 36 PART 2 61551), VIOLET A FW (colour index SV 13 PART 2 60725), GREEN G FW (colour index SB 3 PART 2 61565) from the firm Avecia Limited (ex Zeneca Ltd.) or mixtures thereof.
• agents capable of modifying the surface and/or interfacial tension are the copolymers dimethylpolysiloxane-modified polyethers, mixtures of high-boiling aromatic solvents, ketones and esters and fluorinated surfactants.
• Typical examples of such agents are the commercial products BYK 300, 302 and 341, BYKETOLTM OK from the firm BYK Mallinckrodt and FC 430 and FC 431 from the firm 3M.
• the present invention relates to a heat-sensitive composition of the positive type comprising a polymeric binder and a solubility inhibitor, characterized in that the said solubility inhibitor is a hydroxylated acrylic polymer, a hydroxylated acrylic copolymer or a derivative thereof wherein some hydroxyl groups have been esterified with a carboxylic acid or a reactive derivative thereof.
• the present invention also relates to a lithographic plate of the positive type coated with a heat-sensitive composition comprising a polymeric binder and a solubility inhibitor, characterized in that the said solubility inhibitor is a hydroxylated acrylic polymer, a hydroxylated acrylic copolymer or a derivative thereof wherein some hydroxyl groups have been esterified with a carboxylic acid or a reactive derivative thereof.
• a solubility inhibitor is a hydroxylated acrylic polymer, a hydroxylated acrylic copolymer or a derivative thereof wherein some hydroxyl groups have been esterified with a carboxylic acid or a reactive derivative thereof.
• the present invention relates to a laser sensitive composition of the positive type comprising a polymeric binder and a solubility inhibitor, characterized in that the said solubility inhibitor is a hydroxylated acrylic polymer, a hydroxylated acrylic copolymer or a derivative thereof wherein some hydroxyl groups have been esterified with a carboxylic acid or a reactive derivative thereof.
• the present invention also relates to a lithographic plate of the positive type coated with a laser composition comprising a polymeric binder and a solubility inhibitor, characterized in that the said solubility inhibitor is a hydroxylated acrylic polymer, a hydroxylated acrylic copolymer or a derivative thereof wherein some hydroxyl groups have been esterified with a carboxylic acid or a reactive derivative thereof.
• the said hydroxylated acrylic copolymer has a hydroxyl number of from 40 to 200, preferably from 100 to 170.
• the said hydroxylated acrylic copolymer has a mean ponderal molecular weight (MW) of from 3000 to 30,000 atomic mass units (a.m.u.) and, preferably, from 6000 to 20,000 a.m.u. and has a polydispersity index (MW/Mn) of from 1.5 to 6.
• MW mean ponderal molecular weight
• a.m.u. atomic mass units
• MW/Mn polydispersity index
• Suitable hydroxylated acrylic copolymers are the MacrynalTM resins from Hoechst, such as, for example, MacrynalTM SM 510 N (hydroxyl number: 135-155), SM 513, (hydroxyl number: 110-130), SM 515 (hydroxyl number: 145-160) and SM 516 (hydroxyl number: 130-150).
• Suitable carboxylic acids are the aliphatic and aromatic mono-and polycarboxylic acids.
• the acid is a bicarboxylic acid selected from the group comprising maleic, fumaric, malonic and phthalic acid.
• Typical examples of reactive derivatives of aliphatic carboxylic acids are those selected from the group comprising chloride and anhydride.
• the hydroxylated polymer according to the present invention is modified by partial esterification with maleic anhydride.
• the said partial esterification is performed using from 10 to 90% of the stoichiometric quantity of the reactive aliphatic carboxylic acid derivative required to esterify all the hydroxyl groups of the hydroxylated polymer. More preferably from 20 to 60%, still more preferably from 20 to 30%.
• esterification reaction of some hydroxyl groups of a hydroxylated polymer with an aliphatic carboxylic acid or a reactive derivative thereof is readily performed by standard techniques well known to the specialist in the field.
• the said polymeric binder comprises a novolac resin having a mean ponderal molecular weight of from 2000 to 14,000.
• the said polymeric binder consists of a mixture of two or more novolacs.
• a first novolac has a mean ponderal molecular weight of from 3000 to 5000 and a second novolac has a mean ponderal molecular weight of from 6000 to 10,000.
• the composition also comprises an IR absorber capable of absorbing IR radiation of from 780 to 1400 nm, preferably from 780 to 1100 nm, and of converting it into heat.
• an IR absorber capable of absorbing IR radiation of from 780 to 1400 nm, preferably from 780 to 1100 nm, and of converting it into heat.
• composition of the present invention can also comprise a dye.
• the said dye is Basonyl blue 636 (Colour Index 42595) and is present in quantities sufficient only to dye the composition.
• the composition of the present invention can also comprise a plasticizer, a triazine and other additives of a standard nature.
• the plasticizer has the purpose of modifying the toughness and the hardness of the said composition by varying its sensitivity to heat without appreciably affecting its sensitivity to the developers.
• composition of the present invention can also contain solubility inhibitors belonging to other classes such as, for example, organometallic compounds and organic salts of metals which are the subject of another patent application, which is included here by reference, filed on the same date by the Applicant.
• solubility inhibitors belonging to other classes such as, for example, organometallic compounds and organic salts of metals which are the subject of another patent application, which is included here by reference, filed on the same date by the Applicant.
• the said compositions are organic derivatives of titanium.
• a typical example of such compounds is triethanolaminated titanium isopropoxide, also known as TyzorTM TE.
• the MacrynalTM SM 510 N having an OH number of ca. 160, and the hydroquinone was placed in 50 l a top-loading glass reactor, equipped with a mechanical stirrer of 0.45-0.5 kW power with rotating teflon paddle, a 3 litre dropping funnel and a reflux condenser.
• This reactor was also equipped with a heating mantle with double thermocouple control: one placed at the base of the reactor and the other at the top of the heating mantle.
• the maleic anhydride was dissolved separately in half of the volume of butyl acetate with heating (50°C) and stirring, prolonged contact with the air being avoided so as to avoid the moisture contained therein transforming the anhydride to the acid.
• the container that had contained the maleic anhydride solution was washed with a portion of the remaining butyl acetate.
• the temperature of the first resistor was reset to 88°C and that of the second resistor to 90°C.
• the reaction mixture was allowed to react for 5 hours at 90°C. Then the heating resistors were switched off and the reaction mixture was allowed to cool with stirring.
• the product thus obtained could be used as such to prepare the heat-sensitive composition of the present invention and was mainly composed of the desired esterification product (50-60% w/w) and of butyl acetate (40-50% w/w).
• the desired esterification product had the following characteristics: Acidity No. 75 ⁇ 10 mg KOH/g Viscosity (with cup No.3) 200 ''
• composition No. 1 Component % (w/w) % (w/w) % (w/w) R7100 46.9 53.9 60.9 PN 320 20.1 23.1 26.1 MacrynalTM SM 510 N 30 20 10 "Z” 3 3 3 Composition No. 4 5 6 Component % (w/w) % (w/w) % (w/w) R7100 46.9 53.9 60.9 PN 320 20.1 23.1 26.1 Polymer of Example 1 30 20 10 "Z” 3 3 3 Composition No.
• compositions of the previous Example 2 were spread on an aluminium support which had previously been treated by standard techniques.
• the plate thus coated was dried in a forced circulation oven such as the PID system M80-VF from the firm MPM Instruments s.r.l. (of Bernareggio, Milan, Italy) at 90°C for 8 minutes.
• the weight of the photosensitive coating is 1.6-2.2 g/cm 2 .
• a 2 x 30 cm strip of plate was immersed in successive "steps" of 4 cm/10 sec in a graduated cylinder containing the 10% sodium metasilicate pentahydrate solution at the temperature of 24°C.
• the values indicate the first step visible independently of the thickness of the remaining coating; the value 1 is equivalent to a time of 10 seconds and the value 6 is equivalent to a time of 60 seconds.
• the resistance of the composition to the solution used is highest for the value 6 and lowest or zero resistance for the value 1.
• a 2 x 30 cm strip of plate was immersed in successive "steps" of 4 cm/10 sec in a graduated cylinder containing a solution of LAP98 at the temperature of 24°C.
• the LAP98 had the following composition: water (85% w/w), sodium metasilicate pentahydrate (13% w/w), surfactants (0.5% w/w) and other additives (1.5% w/w).
• the values indicate the first step visible independently of the thickness of the remaining coating; the value 1 is equivalent to a time of 10 seconds and the value 6 is equivalent to a time of 60 seconds.
• the resistance of the composition to the solution used is highest for the value 6 and lowest or zero resistance for the value 1.
• a 2 x 30 cm strip of plate was immersed in successive "steps" of 4 cm/10 sec in a graduated cylinder containing a 40% aqueous solution of isopropyl alcohol at a temperature of 24°C.
• the values indicate the first step visible independently of the thickness of the remaining coating; the value 1 is equivalent to a time of 1 minute and the value 6 is equivalent to a time of 6 minutes.
• the resistance of the composition to the solution used is highest for the value 6 and lowest or zero resistance for the value 1.
• the exposed plates were immediately developed in a tray using, as reference, LAP98 from the firm Lastra S.p.A. as developer at a temperature of from 24 to 25°C for 45 seconds of immersion time with stirring plus 15 seconds of wiping with a cotton pad.
• cleaningness of the base is used to mean that the developer has removed the composition from the regions that have been exposed to laser radiations.

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• Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Thermal Sciences (AREA)
• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Photosensitive Polymer And Photoresist Processing (AREA)
• Materials For Photolithography (AREA)

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Citations (7)

• 2000
  • 2000-07-24 EP EP20000202653 patent/EP1072404B1/fr not_active Expired - Lifetime

Patent Citations (7)

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