EP0007233B1 - A method of treating aluminium foil or a lithographic printing plate support and products so obtained - Google Patents

A method of treating aluminium foil or a lithographic printing plate support and products so obtained Download PDF

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Publication number
EP0007233B1
EP0007233B1 EP79301377A EP79301377A EP0007233B1 EP 0007233 B1 EP0007233 B1 EP 0007233B1 EP 79301377 A EP79301377 A EP 79301377A EP 79301377 A EP79301377 A EP 79301377A EP 0007233 B1 EP0007233 B1 EP 0007233B1
Authority
EP
European Patent Office
Prior art keywords
bath
aluminium foil
printing plate
anodising
aluminium
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP79301377A
Other languages
German (de)
French (fr)
Other versions
EP0007233A1 (en
Inventor
Alan Thomas
David Philip Rowlands
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Balfour Beatty PLC
Original Assignee
BICC PLC
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Publication date
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Application filed by BICC PLC filed Critical BICC PLC
Priority to AT79301377T priority Critical patent/ATE926T1/en
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Classifications

    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02—Anodisation
    • C25D11/04—Anodisation of aluminium or alloys based thereon
    • C25D11/16—Pretreatment, e.g. desmutting
    • 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
    • B41N3/00—Preparing for use and conserving printing surfaces
    • B41N3/03—Chemical or electrical pretreatment
    • B41N3/034—Chemical or electrical pretreatment characterised by the electrochemical treatment of the aluminum support, e.g. anodisation, electro-graining; Sealing of the anodised layer; Treatment of the anodic layer with inorganic compounds; Colouring of the anodic layer

Definitions

  • This invention relates to the treatment of aluminium (including its alloys); especially aluminium foil in continuous web form. Primarily, but not exclusively, it is concerned with the pre-treatment of aluminium that is subsequently to be coated with photosensitive material to make a presensitised lithographic printing plate.
  • Aluminium for this purpose is almost always anodised, generally using a bath based on sulphuric acid, though phosphoric acid is used by at least one manufacturer.
  • Sulphuric acid gives a hard, adherent and abrasion-resistant coating, but there are problems in getting satisfactory adhesion of some attractive sensitive coatings (for example polyvinyl cinnamate among negative-working coatings and orthoquinone diazide sulphonate-based resists amongst positive-working coatings).
  • Phosphoric acid anodising gives much better adhesion with these and some other coatings, but the anodic coating is much softer and tends to abrade away during printing to an extent that may limit the number of copies that can be taken off the plate.
  • DE-A 2557222 illustrates the use of an auxiliary electrolytic cell as a mere means for introducing current into a web of aluminium foil for the purpose of anodising it
  • US-A 3929591 describes a process in which, prior to being anodised, an aluminium foil is etched in an entirely separate A.C. anodising process.
  • the invention is based in part on the realisation that anodic oxidation takes place at the surface of the metal, not of the coating, and that it will not of itself destroy the existing exposed surface of the coating.
  • a method of treating aluminium comprising passing the web through a first bath containing phosphate ions and afterwards through an anodising bath containing sulphate ions is characterised by passing current between an anode immersed in the first bath and a cathode immersed in the anodising bath.
  • the web may be passed through the baths by dipping or, with some advantages, by spraying or flooding the surface of the aluminium.
  • the phosphate ions are preferably orthophosphate ions, but more complex phosphates can be used.
  • the phosphate and sulphate ions may be the only anions present to any substantial extent in the respective baths, but the presence of other anions that are inert or that modify, rather than radically alter, the effect of the treatment may be present. In particular the presence of minor amounts of sulphate in the phosphate bath and/or of phosphate in the sulphate bath is not excluded.
  • the associated cations should be wholly or mainly hydrogen ions, but neutral or alkaline salt solutions may be suitable in some cases.
  • the accompanying drawing shows the distinctive part of apparatus in which a web of aluminium foil 1 is passed, on the run, through a first bath 2 containing 45% aqueous orthophosphoric acid and, with or without intermediate washing (not shown), through a second bath 3 containing 15% sulphuric acid.
  • Current is supplied from a conventional power pack and flows between an inert anode 4 immersed in the first bath and an inert cathode 5 immersed in the second bath via both the electrolytes and the part 6 to the aluminium web extending between the two baths.
  • the bath temperatures are both around 20°C
  • the applied potential is about 16.5 V
  • the mean current density at each of the immersed length of the foil is about 200 Am-2.
  • the line speed is such that the dwell time in each bath is approximately four minutes.
  • the anodised web After washing and drying the anodised web is coated with a proprietary positive-working lithographic resist comprising a resin sensitised with the 2,4 dihydroxybenzophenone ester of 1, 2, 5 diazo naphthol sulphonic acid and coloured with a blue dye to yield presensitised plates with excellent adhesion and press life compared with the best current commercial anodised- aluminium presensitised lithographic printing plates.
  • the anodic coating is thin compared with conventional coatings, and penetration of dye into the coating is not significant.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Printing Plates And Materials Therefor (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)
  • Chemical Treatment Of Metals (AREA)

Abstract

Aluminium (1) is immersed in a bath (2) containing phosphate ions before anodising in a bath (3) containing sulphate ions. When the substrate is aluminium foil in web form, preferably the phosphate bath serves as a liquid junction cell by which the anodising current is introduced into the web. Aluminium foil or sheet so processed is especially suitable as a base for a presensitised lithographic printing plate.

Description

  • This invention relates to the treatment of aluminium (including its alloys); especially aluminium foil in continuous web form. Primarily, but not exclusively, it is concerned with the pre-treatment of aluminium that is subsequently to be coated with photosensitive material to make a presensitised lithographic printing plate.
  • Aluminium for this purpose is almost always anodised, generally using a bath based on sulphuric acid, though phosphoric acid is used by at least one manufacturer. Sulphuric acid gives a hard, adherent and abrasion-resistant coating, but there are problems in getting satisfactory adhesion of some attractive sensitive coatings (for example polyvinyl cinnamate among negative-working coatings and orthoquinone diazide sulphonate-based resists amongst positive-working coatings). Phosphoric acid anodising gives much better adhesion with these and some other coatings, but the anodic coating is much softer and tends to abrade away during printing to an extent that may limit the number of copies that can be taken off the plate.
  • In some cases aluminium that has been anodised in sulphuric acid has been treated subsequently with phosphoric acid, and this has been found to give a useful improvement in adhesion while retaining part of the advantages of the use of sulphuric acid for anodising, but this presents obvious difficulties in control of the operation.
  • DE-A 2557222 illustrates the use of an auxiliary electrolytic cell as a mere means for introducing current into a web of aluminium foil for the purpose of anodising it, and US-A 3929591 describes a process in which, prior to being anodised, an aluminium foil is etched in an entirely separate A.C. anodising process.
  • The invention is based in part on the realisation that anodic oxidation takes place at the surface of the metal, not of the coating, and that it will not of itself destroy the existing exposed surface of the coating.
  • In accordance with the invention, a method of treating aluminium comprising passing the web through a first bath containing phosphate ions and afterwards through an anodising bath containing sulphate ions is characterised by passing current between an anode immersed in the first bath and a cathode immersed in the anodising bath.
  • The web may be passed through the baths by dipping or, with some advantages, by spraying or flooding the surface of the aluminium.
  • The phosphate ions are preferably orthophosphate ions, but more complex phosphates can be used.
  • The phosphate and sulphate ions may be the only anions present to any substantial extent in the respective baths, but the presence of other anions that are inert or that modify, rather than radically alter, the effect of the treatment may be present. In particular the presence of minor amounts of sulphate in the phosphate bath and/or of phosphate in the sulphate bath is not excluded. We prefer that the associated cations should be wholly or mainly hydrogen ions, but neutral or alkaline salt solutions may be suitable in some cases.
    • Example
  • The accompanying drawing shows the distinctive part of apparatus in which a web of aluminium foil 1 is passed, on the run, through a first bath 2 containing 45% aqueous orthophosphoric acid and, with or without intermediate washing (not shown), through a second bath 3 containing 15% sulphuric acid. Current is supplied from a conventional power pack and flows between an inert anode 4 immersed in the first bath and an inert cathode 5 immersed in the second bath via both the electrolytes and the part 6 to the aluminium web extending between the two baths. Under typical conditions the bath temperatures are both around 20°C, the applied potential is about 16.5 V and the mean current density at each of the immersed length of the foil is about 200 Am-2. The line speed is such that the dwell time in each bath is approximately four minutes.
  • After washing and drying the anodised web is coated with a proprietary positive-working lithographic resist comprising a resin sensitised with the 2,4 dihydroxybenzophenone ester of 1, 2, 5 diazo naphthol sulphonic acid and coloured with a blue dye to yield presensitised plates with excellent adhesion and press life compared with the best current commercial anodised- aluminium presensitised lithographic printing plates. The anodic coating is thin compared with conventional coatings, and penetration of dye into the coating is not significant.

Claims (4)

1. A method of treating aluminium foil in web form comprising passing the web through a first bath containing phosphate ions and afterwards through an anodising bath containing sulphate ions characterised by passing current between an anode immersed in the first bath and a cathode immersed in the anodising bath.
2. A method of making a presensitised lithographic printing plate comprising anodising aluminium sheet or foil and subsequently applying a lithographic photosensitive coating to it, characterised in that the sheet or foil is treated by the method claimed in Claim 1.
3. Aluminium foil treated by the method claimed in Claim 1.
4. A presensitised lithographic or printing plate made by the method claimed in Claim 2.
EP79301377A 1978-07-13 1979-07-12 A method of treating aluminium foil or a lithographic printing plate support and products so obtained Expired EP0007233B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT79301377T ATE926T1 (en) 1978-07-13 1979-07-12 PROCESSES FOR THE TREATMENT OF ALUMINUM FOILS OR PLANTOGRAPHS AND THE PRODUCTS OBTAINED IN THE WAY.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB7829705 1978-07-13
GB2970578 1978-07-13

Publications (2)

Publication Number Publication Date
EP0007233A1 EP0007233A1 (en) 1980-01-23
EP0007233B1 true EP0007233B1 (en) 1982-04-28

Family

ID=10498399

Family Applications (1)

Application Number Title Priority Date Filing Date
EP79301377A Expired EP0007233B1 (en) 1978-07-13 1979-07-12 A method of treating aluminium foil or a lithographic printing plate support and products so obtained

Country Status (3)

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EP (1) EP0007233B1 (en)
AT (1) ATE926T1 (en)
DE (1) DE2962623D1 (en)

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2088901B (en) * 1980-10-23 1983-12-07 Vickers Ltd Anodised aluminium sheet for lithographic printing plate production
DE3206469A1 (en) * 1982-02-23 1983-09-01 Hoechst Ag, 6230 Frankfurt METHOD FOR THE PRODUCTION OF CARRIER MATERIALS FOR OFFSET PRINTING PLATES
DE3206470A1 (en) * 1982-02-23 1983-09-01 Hoechst Ag, 6230 Frankfurt METHOD FOR THE PRODUCTION OF CARRIER MATERIALS FOR OFFSET PRINTING PLATES
DE3312497A1 (en) * 1983-04-07 1984-10-11 Hoechst Ag, 6230 Frankfurt TWO-STAGE METHOD FOR THE PRODUCTION OF ANODICALLY OXIDIZED FLAT MATERIALS FROM ALUMINUM AND THE USE THEREOF IN THE PRODUCTION OF OFFSET PRINTING PLATES
US4605480A (en) * 1983-06-13 1986-08-12 Hoechst Aktiengesellschaft Device for continuously anodically oxidizing aluminum strips on one surface thereof and use of these aluminum strips in the production of offset printing plates
DE3328048A1 (en) * 1983-08-03 1985-02-21 Hoechst Ag, 6230 Frankfurt METHOD FOR THE TWO-STAGE ANODIC OXIDATION OF CARRIER MATERIALS MADE OF ALUMINUM FOR OFFSET PRINTING PLATES
JP2006103087A (en) * 2004-10-04 2006-04-20 Konica Minolta Medical & Graphic Inc Aluminum support for lithographic printing plate, its manufacturing method, lithographic printing plate material and image forming method

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5133444B2 (en) * 1971-10-21 1976-09-20
US3929591A (en) * 1974-08-26 1975-12-30 Polychrome Corp Novel lithographic plate and method
US3935080A (en) * 1974-10-02 1976-01-27 Polychrome Corporation Method of producing an aluminum base sheet for a printing plate

Also Published As

Publication number Publication date
EP0007233A1 (en) 1980-01-23
DE2962623D1 (en) 1982-06-09
ATE926T1 (en) 1982-05-15

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