EP0517960B1 - Korrekturflüssigkeit für eine lithographische Diazo-Druckform - Google Patents

Korrekturflüssigkeit für eine lithographische Diazo-Druckform Download PDF

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Publication number
EP0517960B1
EP0517960B1 EP91201424A EP91201424A EP0517960B1 EP 0517960 B1 EP0517960 B1 EP 0517960B1 EP 91201424 A EP91201424 A EP 91201424A EP 91201424 A EP91201424 A EP 91201424A EP 0517960 B1 EP0517960 B1 EP 0517960B1
Authority
EP
European Patent Office
Prior art keywords
correction fluid
lithographic printing
diazo
printing plate
water
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 - Lifetime
Application number
EP91201424A
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English (en)
French (fr)
Other versions
EP0517960A1 (de
Inventor
Triphon Vermeersch Joan
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.)
Agfa Gevaert NV
Original Assignee
Agfa Gevaert NV
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.)
Filing date
Publication date
Application filed by Agfa Gevaert NV filed Critical Agfa Gevaert NV
Priority to DE1991613031 priority Critical patent/DE69113031T2/de
Priority to EP91201424A priority patent/EP0517960B1/de
Priority to JP4160391A priority patent/JPH05216246A/ja
Publication of EP0517960A1 publication Critical patent/EP0517960A1/de
Application granted granted Critical
Publication of EP0517960B1 publication Critical patent/EP0517960B1/de
Anticipated expiration legal-status Critical
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Classifications

    • 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
    • B41N3/08—Damping; Neutralising or similar differentiation treatments for lithographic printing formes; Gumming or finishing solutions, fountain solutions, correction or deletion fluids, or on-press development

Definitions

  • the present invention relates to a correction fluid for correcting a diazo-based lithographic printing plate and a method for correcting a diazo-based lithographic printing plate having a polyester film support coated with a hydrophillic layer comprising polyvinyl alcohol hardened with a tetraalkylorthosilicate.
  • Lithography is the process of printing from specially prepared surfaces, some areas of which are capable of accepting lithographic ink, whereas other areas, when moistened with water, will not accept the ink.
  • the areas which accept ink form the printing image areas and the ink-rejecting areas form the background areas.
  • a photographic material is made image-wise receptive to oily or greasy inks in the photo-exposed (negative-working) or in the non-exposed areas (positive-working) on a hydrophillic background.
  • lithographic printing plates also called surface litho plates or planographic printing plates
  • a support that has affinity to water or obtains such affinity by chemical treatment is coated with a thin layer of a photosensitive composition.
  • Coatings for that purpose include light-sensitive polymer layers containing diazo compounds, dichromate-sensitized hydrophillic colloids and a large variety of synthetic photopolymers.
  • a generally used negative-working diazo-sensitized system is based on the capability of diazo compounds to harden a polymer when exposed to ultraviolet and blue radiation.
  • Diazo compounds which have been used for the preparation of lithographic printing plates based on their hardening properties are e.g. diazonium salts whose photolysis products can harden polymers (natural colloids or synthetic resins) directly and diazonium polymers.
  • diazonium salts whose photolysis products can harden polymers (natural colloids or synthetic resins) directly and diazonium polymers.
  • polymers containing diazonium groups have a large structure they may remain water soluble owing to the presence of the ionic diazonium groups. When these groups are destroyed by exposure to light an insoluble resin is formed.
  • the diazo resin or diazonium salt will be dissolved and removed by a suitable solvent, e.g. water, in the non-exposed or insufficient exposed parts of the lithographic printing plate precursor.
  • a suitable solvent e.g. water
  • the hydrophillic or oleophobic surface of the plate will thus be in the non-exposed or insufficient exposed parts while the oleophillic diazo resin will remain in the exposed parts.
  • supports can be used for the manufacturing of a diazo-sensitized lithographic printing plate.
  • Common supports are metal supports like Al or Zn.
  • a typical hydrophillic layer in these systems is a layer containing polyvinyl alcohol and hydrolysed tetraethyl orthosilicate and preferably also silicium dioxide and/or titanium dioxide as described in e.g. GB-P-1419512, FR-P-2300354, US-P-3971660 and 4284705.
  • the imaged lithographic printing plate is corrected. i.e. some of the imaged areas are selectively deleted before mounting it on an offset press for example for correcting misspellings, punctuation errors etc.. Deletion of parts of the imaged areas can be accomplished by applying a hydrophillic coating over the imaged areas thus rendering them hydrophillic. However this method has the disadvantage that the applied hydrophillic coating vanishes during printing.
  • Another method for deleting parts of an image on a lithographic printing plate is the etching or removal of image areas. The latter method is commonly employed for correcting diazo-based lithographic printing plates having a metal support.
  • the correction fluid used in accordance with this method mostly comprises fluorine containing compounds. See for example US-P-3.248.332, FR-A-2027332 and the Japanese unexamined patent applications laid open to public numbers 172147/61, 211041/61 198157/61 and 27190/62.
  • the correction fluid for correcting diazo-based lithographic printing plates having a metal support are not suited for correcting diazo-based lithographic printing plate having a polyester film support coated with a hydrophillic layer as described above because the hydrophillic layer is strongly attacked by the correction fluid so that the hydrophobic polyester film base is exposed.
  • a correction fluid comprising a mixture of water and a water miscible organic solvent and an inorganic fluoride in a concentration from 0.5% by weight to 4% by weight, the inorganic fluoride being potassium hydrogendifluoride or ammonium fluoride.
  • Diazo-based lithographic printing plates having a polyester film support coated with a hydrophillic layer comprising polyvinyl alcohol hardened with a tetraalkyl orthosilicate are disclosed in FR-P-2300354, US-P-3971660, US-P-4284705 and EP-A-0450199 (prior art under Art. 54(3)(4)). It has been found that these lithographic printing plates can be corrected without severely damaging the hydrophillic layer by using a correction fluid comprising an inorganic fluoride dissolved in a mixture of water and a water miscible organic solvent.
  • the hydrophillic layer is dramatically damaged while a concentration smaller than 0.5% by weight does not yield a sufficient rapid correction of the image.
  • the content of inorganic fluoride is between 1% by weight and 3% by weight.
  • Inorganic fluorides suitable for use in accordance with the present invention are e.g. alkali metal fluorides, alkaline-earth metal fluorides, ammonium fluoride etc.
  • Preferably used are potassium hydrogendifluoride or ammonium fluoride.
  • Suitable water miscible organic solvents for use in accordance with the present invention are e.g. ethylene glycol diacetate, diethylene glycol dimethyl ether, diethylene glycol dimethyl ether, lactone, N-vinyl pyrrolidone, dimethylformamide, methylglycol, 2-methoxy-propan-1-ol, 1-methoxy-propan-2-ol, 2-ethoxy-ethanol or mixtures thereof. Methylglycol is preferred for ecological reasons.
  • the ratio by volume of water miscible organic solvent to water is preferably from 9:1 to 1:1. Too large an amount of water affects the hydrophillic layer while too small an amount does not allow sufficient fluoride to be dissolved and does not yield a sufficiently rapid correction of the image areas.
  • the most preferred range of ratios of water miscible organic solvent to water is from 5:1 to 2:1.
  • the pH of the correction fluid is preferably between 4 and 8 and most preferably around 7. When the pH of the correction is too low the correction fluid appears to be too aggressive so that the hydrophillic layer of the lithographic printing plate is damaged.
  • the correction fluid is preferably bufferred around the desired pH. Suitable buffers for use in accordance with the present invention are e.g. phosphate buffers, citrate buffers, acetate buffers etc. Citrate buffers are preferably used.
  • the correction fluid in accordance with the present invention may also comprise thickening agents e.g. carboxy methylcellulose, hydroxypropyl cellulose, high molecular weight compounds e.g. a vinyl acetate maleic acid anhydride copolymer, polyacrylamides etc..
  • thickening agents e.g. carboxy methylcellulose, hydroxypropyl cellulose, high molecular weight compounds e.g. a vinyl acetate maleic acid anhydride copolymer, polyacrylamides etc.
  • a diazo-based lithographic printing plate as disclosed in EP-A-0450199 or US-P-3971660 is information-wise exposed and subsequently developed as disclosed in these applications.
  • the obtained imaged lithographic printing plate is subsequently corrected in the image areas using a correction fluid as described above.
  • the correction fluid may be applied e.g. by wiping the image areas with a cloth wetted with the correction fluid.
  • the correction fluid may be present in a correction stylus to be used for correcting the image on the lithographic printing plate. After a short reaction time, i.e. from 1 second to 1 minute depending upon the strength of the particular composition of the correction fluid and the condition of the plate surface, the surface is wiped clean and the diazo compound thereby removed.
  • a lithographic printing plate was prepared as described in EP-A-0450199. Part of the image was removed by applying with a brush a correction fluid containing 2% ammoniumfluoride dissolved in a mixture of water and methylglycol in a ratio by volume of 1 part of water to 3 parts of methylglycol. The pH of the correction fluid was 7.
  • the correction fluid was left on the image part to be removed for 10 to 30s and was then removed together with the image part by a wet cotton pad. No severe damage of the hydrophillic layer of the plate and no ink acceptance was noticed on the image parts removed during printing.

Landscapes

  • Photosensitive Polymer And Photoresist Processing (AREA)
  • Printing Plates And Materials Therefor (AREA)

Claims (7)

  1. Korrekturflüssigkeit zur Korrektur einer lithographischen Druckform, bestehend aus einer Mischung aus Wasser und einem mit Wasser mischbaren organischen Lösungsmittel und einem anorganischen Fluorid in einer Konzentration von 0,5 Gew.-% bis 4 Gew.-%, wobei es sich bei dem anorganischen Fluorid um Kalium bifluorid oder Ammoniumfluorid handelt.
  2. Korrekturflüssigkeit nach Anspruch 1, wobei es sich bei dem mit Wasser mischbaren organischen Lösungsmittel um Dimethylformamid, Methylglykol, 2-Methoxypropan-1-ol, 1-Methoxypropan-2-ol oder 2-Ethoxyethanol oder eine Mischung daraus handelt.
  3. Korrekturflüssigkeit nach Anspruch 1 oder 2, wobei das Volumenverhältnis des mit Wasser mischbaren Lösungsmittels zu Wasser 9:1 bis 1:1 beträgt.
  4. Korrekturflüssigkeit nach den vorhergehenden Ansprüchen, wobei die Konzentration an anorganischem Fluorid zwischen 1 Gew.-% und 3 Gew.-% liegt.
  5. Korrekturflüssigkeit nach den vorhergehenden Ansprüchen, wobei der pH-Wert der Korrekturflüssigkeit zwischen 4 und 8 liegt.
  6. Verfahren zur Korrektur einer lithographischen Diazo-Druckform mit einem Polyesterfolienträger, der mit einer hydrophilen, Polyvinylalkohol umfassenden und mit einem Orthokieselsäuretetraalkylester gehärteten hydrophilen Schicht beschichtet ist, unter Verwendung einer Korrekturflüssigkeit, bestehend aus einer Mischung aus Wasser und einem mit Wasser mischbaren organischen Lösungsmittel und einem anorganischen Fluorid in einer Konzentration von 0,5 Gew.-% bis 4 Gew.-%.
  7. Verfahren nach Anspruch 6, wobei es sich bei dem anorganischen Fluorid um Kalium bifluorid oder Ammoniumfluorid handelt.
EP91201424A 1991-06-10 1991-06-10 Korrekturflüssigkeit für eine lithographische Diazo-Druckform Expired - Lifetime EP0517960B1 (de)

Priority Applications (3)

Application Number Priority Date Filing Date Title
DE1991613031 DE69113031T2 (de) 1991-06-10 1991-06-10 Korrekturflüssigkeit für eine lithographische Diazo-Druckform.
EP91201424A EP0517960B1 (de) 1991-06-10 1991-06-10 Korrekturflüssigkeit für eine lithographische Diazo-Druckform
JP4160391A JPH05216246A (ja) 1991-06-10 1992-05-26 ジアゾベース平版印刷版用修正液

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP91201424A EP0517960B1 (de) 1991-06-10 1991-06-10 Korrekturflüssigkeit für eine lithographische Diazo-Druckform

Publications (2)

Publication Number Publication Date
EP0517960A1 EP0517960A1 (de) 1992-12-16
EP0517960B1 true EP0517960B1 (de) 1995-09-13

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP91201424A Expired - Lifetime EP0517960B1 (de) 1991-06-10 1991-06-10 Korrekturflüssigkeit für eine lithographische Diazo-Druckform

Country Status (3)

Country Link
EP (1) EP0517960B1 (de)
JP (1) JPH05216246A (de)
DE (1) DE69113031T2 (de)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB9710552D0 (en) 1997-05-23 1997-07-16 Horsell Graphic Ind Ltd Planographic printing
ATE333378T1 (de) * 2002-04-25 2006-08-15 Fuji Photo Film Co Ltd Korrekturflüssigkeit für lithographische druckplatten

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL6918761A (de) * 1968-12-30 1970-07-02
FR2098542A5 (en) * 1970-07-20 1972-03-10 Perraguin Gerard Plates for offset reprodn - correction using a universal solvent mixt

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
Collins: Concise English Dictionary, 3rd ed. p.490 *

Also Published As

Publication number Publication date
EP0517960A1 (de) 1992-12-16
DE69113031T2 (de) 1996-04-04
DE69113031D1 (de) 1995-10-19
JPH05216246A (ja) 1993-08-27

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