EP0007233A1 - 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
EP0007233A1
EP0007233A1 EP79301377A EP79301377A EP0007233A1 EP 0007233 A1 EP0007233 A1 EP 0007233A1 EP 79301377 A EP79301377 A EP 79301377A EP 79301377 A EP79301377 A EP 79301377A EP 0007233 A1 EP0007233 A1 EP 0007233A1
Authority
EP
European Patent Office
Prior art keywords
bath
aluminium
anodising
printing plate
lithographic printing
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.)
Granted
Application number
EP79301377A
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German (de)
French (fr)
Other versions
EP0007233B1 (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
Priority date (The priority date 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 date listed.)
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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
Publication of EP0007233A1 publication Critical patent/EP0007233A1/en
Application granted granted Critical
Publication of EP0007233B1 publication Critical patent/EP0007233B1/en
Expired legal-status Critical Current

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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 p resensitised 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 sane 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.
  • 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 process of treating aluminium comprising anodising it in a bath containing sulphate ions is characterised by first immersing it in a bath containing phosphate ions.
  • Immersion may be 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.
  • 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 phosphate treatment may be by a simple immersion process, or the aluminium surface may be subjected to anodising treatment in the phosphate bath asrwell as in the sulphate bath.
  • the phosphate bath should serve also as a "liquid junction" cell for introducing anodising current into the web without the use of contact rolls or the like; in this case the aluminium will be electrolytically etched in the phosphate bath.
  • 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 of 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 lighographic printing plates.
  • the anodic coating is thin compared with conventional coatings, and penetration of dye into the coating is not significant.

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 sane 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.
  • 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 process of treating aluminium comprising anodising it in a bath containing sulphate ions is characterised by first immersing it in a bath containing phosphate ions.
  • Immersion may be 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.
  • Subject to suitable choice of its composition (its pH especially) the phosphate treatment may be by a simple immersion process, or the aluminium surface may be subjected to anodising treatment in the phosphate bath asrwell as in the sulphate bath. When the aluminium is a foil in continuous web form, however, we prefer that the phosphate bath should serve also as a "liquid junction" cell for introducing anodising current into the web without the use of contact rolls or the like; in this case the aluminium will be electrolytically etched in the phosphate bath.
    • 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 of 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 lighographic printing plates. The anodic coating is thin compared with conventional coatings, and penetration of dye into the coating is not significant.

Claims (6)

1. A method of treating aluminium comprising anodising it in a bath containing sulphate ions characterised by first immersing it in a bath containing phosphate ions.
2. A method in accordance with Claim 1 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.
3. A method of making a presensitised lithographic printing plate comprising anodising aluminium sheet or foil subsequently applying a lithographic photosensitive coating to it, characterised in that the sheet or foil is anodised by the method claimed in Claim 1 or Claim 2..
4. Aluminium treated by the method claimed in Claim 1.
5. Aluminium foil treated by the method claimed in Claim 2.
6. A presensitised lithographic printing plate made by the method claimed in Claim 3.
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
GB2970578 1978-07-13
GB7829705 1978-07-13

Publications (2)

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

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

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4396470A (en) * 1980-10-23 1983-08-02 Vickers P.L.C. Lithographic printing plates
EP0121880A1 (en) * 1983-04-07 1984-10-17 Hoechst Aktiengesellschaft Two-step process for the production of anodically oxidized flat materials of aluminium, and their use in the preparation of offset printing plates
US4554216A (en) * 1982-02-23 1985-11-19 Hoechst Aktiengesellschaft Process for manufacturing support materials for offset printing plates
US4554057A (en) * 1982-02-23 1985-11-19 Hoechst Aktiengesellschaft Process for manufacturing support materials for 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
US4606975A (en) * 1983-08-03 1986-08-19 Hoechst Aktiengesellschaft Process for the two-stage anodic oxidation of aluminum bases for offset printing plates and product thereof
EP1642745A3 (en) * 2004-10-04 2006-05-24 Konica Minolta Medical & Graphic, Inc. Aluminum support for planographic printing plate, its manufacturing process, and planographic printing plate material

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3834998A (en) * 1971-10-21 1974-09-10 Fuji Photo Film Co Ltd Method of producing aluminum planographic printing plates
US3929591A (en) * 1974-08-26 1975-12-30 Polychrome Corp Novel lithographic plate and method
DE2557222A1 (en) * 1974-10-02 1977-06-30 Polychrome Corp METHOD OF MANUFACTURING AN ALUMINUM CARRIER SHEET FOR PRINTING PLATES

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3834998A (en) * 1971-10-21 1974-09-10 Fuji Photo Film Co Ltd Method of producing aluminum planographic printing plates
US3929591A (en) * 1974-08-26 1975-12-30 Polychrome Corp Novel lithographic plate and method
DE2557222A1 (en) * 1974-10-02 1977-06-30 Polychrome Corp METHOD OF MANUFACTURING AN ALUMINUM CARRIER SHEET FOR PRINTING PLATES

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4396470A (en) * 1980-10-23 1983-08-02 Vickers P.L.C. Lithographic printing plates
US4554216A (en) * 1982-02-23 1985-11-19 Hoechst Aktiengesellschaft Process for manufacturing support materials for offset printing plates
US4554057A (en) * 1982-02-23 1985-11-19 Hoechst Aktiengesellschaft Process for manufacturing support materials for offset printing plates
EP0121880A1 (en) * 1983-04-07 1984-10-17 Hoechst Aktiengesellschaft Two-step process for the production of anodically oxidized flat materials of aluminium, and their use in the preparation of offset printing plates
JPS59193298A (en) * 1983-04-07 1984-11-01 ヘキスト・アクチエンゲゼルシヤフト Manufacture of plate-like, sheet-like or strip-like materialfrom aluminum or aluminum alloy
US4566952A (en) * 1983-04-07 1986-01-28 Hoechst Aktiengesellschaft Two-stage process for the production of anodically oxidized aluminum planar materials and use of these materials in manufacturing offset-printing plates
JPH0437159B2 (en) * 1983-04-07 1992-06-18 Hoechst Ag
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
US4606975A (en) * 1983-08-03 1986-08-19 Hoechst Aktiengesellschaft Process for the two-stage anodic oxidation of aluminum bases for offset printing plates and product thereof
EP1642745A3 (en) * 2004-10-04 2006-05-24 Konica Minolta Medical & Graphic, Inc. Aluminum support for planographic printing plate, its manufacturing process, and planographic printing plate material

Also Published As

Publication number Publication date
EP0007233B1 (en) 1982-04-28
DE2962623D1 (en) 1982-06-09
ATE926T1 (en) 1982-05-15

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