Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
  • G03C3/00—Packages of films for inserting into cameras, e.g. roll-films, film-packs; Wrapping materials for light-sensitive plates, films or papers, e.g. materials characterised by the use of special dyes, printing inks, adhesives
• • 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
  • B41N6/00—Mounting boards; Sleeves Make-ready devices, e.g. underlays, overlays; Attaching by chemical means, e.g. vulcanising

Definitions

• the present invention relates to a method for obtaining a good shelf life of heat sensitive elements, developable by an aqueous solution.
• the present invention especially relates to the use of interleaves in the packaging of said heat sensitive elements.
• 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 imagewise receptive to oily or greasy ink in the photo-exposed (negative working) or in the non-exposed areas (positive working) on a hydrophilic background.
• lithographic 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 hydrophilic colloids and a large variety of synthetic photopolymers. Particularly diazo-sensitized systems are widely used.
• the exposed image areas become insoluble and the unexposed areas remain soluble.
• the plate is then developed with a suitable liquid to remove the diazonium salt or diazo resin in the unexposed areas.
• thermoplastic polymer particles By image-wise exposure to an infrared laser, the thermoplastic polymer particles are image-wise coagulated thereby rendering the surface of the imaging element at these areas ink acceptant without any further development.
• a disadvantage of this method is that the printing plate obtained is easily damaged since the non-printing areas may become ink accepting when some pressure is applied thereto. Moreover, under critical conditions, the lithographic performance of such a printing plate may be poor and accordingly such printing plate has little lithographic printing latitude.
• EP-A- 800 928 discloses a heat sensitive imaging element comprising on a hydrophilic surface of a lithographic base an image forming layer comprising hydrophobic thermoplastic polymer particles dispersed in a water insoluble alkali soluble or swellable resin and a compound capable of converting light into heat, said compound being present in said image forming layer or a layer adjacent thereto, wherein said alkali swellable or soluble resin comprises phenolic hydroxy groups and/or carboxyl groups.
• said alkali swellable or soluble resin comprises phenolic hydroxy groups and/or carboxyl groups.
• Analogous imaging elements comprising on a hydrophilic surface of a lithographic base an image forming layer comprising hydrophobic thermoplastic polymer particles dispersed in a water or alkali soluble or swellable resin and a compound capable of converting light into heat, said compound being present in said image forming layer or a layer adjacent thereto are disclosed in e.g.
• poly(meth)acrylate latices are used as thermoplastic polymer particles and no specific hydrophilic resin is mentioned
• carbon black or an IR-dye are mentioned as the compound capable of converting light into heat.
• IR-dyes In order to prepare an imaging element as described above, that is processable on the press, preferably IR-dyes should be used. Carbon black causes indeed a soiling on the press when removing the unexposed areas.
• the heat sensitive coating contains a certain amount of water during the drying process and further during the preservation. If this water becomes already active during the preservation of the material this will result in a deteriorating of the properties of the material. Therefore these materials should be dried and packed at a very dry condition. This is impossible in practice. The drying of production rooms is very expensive and ask a lot of effort to guarantee the stability in function of the time. Furtheron there originates problems of dust attraction and electrostatic problems.
• shelf life of a material is determined by subjecting the material during a short time to a certain temperature to make it possible to make predictions on a long term.
• a standard test packing the material moistureproof at a temperature treatment of 50°C.
• a good shelf life is defined when the material endures a period of 3 days without considerable deterioration of the product properties.
• a method to obtain a good shelf life of a heat sensitive imaging element developable by an aqueous solution by introducing a moisture regulating member in a packaging of said elements whereby the amount of water in the imaging element is reduced to a level corresponding to an equilibrium moisture content below 65.5 % R.H. at 50°C.
• a moisture accepting sheet is used in the packaging of said material.
• said sheet material is paper or paperlike material which can be coated. Suitable paper is e.g.H + E 36 g, H + E 40 g, Intermills 60 g.
• Other suitable sheet material is plastic or coated plastic.
• the sheet material can also be from inorganic nature, glass or ceramic.
• the absorbing element is a backing coating on the imaging element.
• the pile of heat sensitive elements with intermediate sheets is preferably packed in a polyethylene-aluminum-paper laminate with the paper side being the outside of the packaging material.
• a preferred imaging element comprises on a lithographic base with a hydrophilic surface an image forming layer including thermoplastic particles of a homopolymer or a copolymer of styrene and a hydrophilic polymer containing carboxyl groups, wherein said imaging element further contains an anionic IR-cyanine dye being present in said image forming layer or a layer adjacent thereto,
• Such heat sensitive imaging elements are described with their exposure and development in EP-A- 98 200 187 .
• the lithographic base is preferably an anodized roughned aluminum support but a flexible support coated with a hydrophilic hardened layer can also be used.
• the imaging element can after exposure to an IR-laser be developed by rinsing the element with an aqueous solution.
• the exposed imaging element is mounted directly on the press.
• a 0.30 mm thick aluminum foil was degreased by immersing the foil in an aqueous solution containing 5 g/l of sodium hydroxide at 50°C and rinsed with demineralized water.
• the foil was then electrochemically grained using an alternating current in an aqueous solution containing 4 g/l of hydrochloric acid, 4 g/l of hydroboric acid and 5 g/l of aluminum ions at a temperature of 35°C and a current density of 1200 A/m 2 to form a surface topography with an average center-line roughness Ra of 1.1 ⁇ m.
• the aluminum foil was then etched with an aqueous solution containing 300 g/l of sulfuric acid at 60°C for 180 seconds and rinsed with demineralized water at 25°C for 30 seconds.
• the foil was subsequently subjected to anodic oxidation in an aqueous solution containing 200 g/l of sulfuric acid at a temperature of 45°C, a voltage of about 10 V and a current density of 150 A/m 2 for about 300 seconds to form an anodic oxidation film of 3.00 g/m 2 of Al 2 O 3 then washed with demineralized water, posttreated with a solution containing polyvinylphosphonic acid and subsequently with a solution containing aluminum trichloride, rinsed with demineralized water at 20°C during 120 seconds and dried.
• lithographic base On above mentioned lithographic base, was coated a layer from an 2.61% wt solution in water, with a wet coating thickness of 30 ⁇ m.
• the resulting layer contained 75% W/W of polystyrene latex, 10 % of a heat absorbing compound, presented in formula (I), 15% W/W of Glascol E15, additionally 6 mg/m 2 of a fluorosurfactant was added.
• This layer was dried on a temperature of 60°C for at least 42 seconds.
• Glascol E15 is a polyacrylic acid, commercial available at N.V. Allied Colloids Belgium.
• the heat absorbing compound is represented by formula I.
• the imaging element was conditioned at 15% RH at 22°C during at least 12 h. Then a pile of 20 plates was put together in a moisture proof package consisting of a polyethylene - aluminium - paper laminate. The outside of the packaging material was the paper side. Also the packaging material was preconditioned during at least 24 h at the same environmental condition.
• Both the imaging element and an interleave paper of 36 g/m 2 was conditioned at 22°C/30% RH during at least 12h. Then a pile of 20 plates was put together with between each plate a preconditioned interleave paper in a moisture proof package consisting of a polyethylene - aluminium - paper laminate. The outside of the packaging material was the paper side. Also the packaging material was preconditioned during at least 24 h at the same environmental condition.
• the used interleave paper is commercial available at Hoffmann und Engelmann, Neustadt - Wein No, Germany.
• Both the imaging element and an interleave paper of 36 g/m 2 was conditioned at 22°C/40% RH during at least 12h. Then a pile of 20 plates was put together with between each plate a preconditioned interleave paper in a moisture proof package as described in former examples.
• the used interleave paper is commercial available at Hoffmann und Engelmann, Neustadt - Wein No, Germany.
• Both the imaging element and an interleave paper of 36 g/m 2 was conditioned at 22°C/45% RH during at least 12h. Then a pile of 20 plates was put together with between each plate a preconditioned interleave paper in a moisture proof package consisting as described above.
• the used interleave paper is commercial available at Hoffmann und Engelmann, Neustadt - Wein No, Germany.
• the imaging element was conditioned at 22°C/60% RH during at least 12h.
• the interleave paper was preconditioned at 40% RH at 22°C during at least 12h. Then a pile of 20 plates was put together with between each plate a preconditioned interleave paper in a moisture proof package as described above. This stapling of the materials was carried out as fast as possible, trying to limit the moisture exchange with the environment.
• the packaging material was preconditioned during at least 24 h at 60% RH at 22 °C.
• the used interleave paper is commercial available at Hoffmann und Engelmann, Neustadt - Wein No, Germany.
• the moisture content of both the imaging element and absorbing material is determined.
• the used type of instrument is a SGA100 model, commercially available at VTI Corporation, Florida.
• a strip of the testing material was placed in the balans and dried at 50°C-1%RH till equilibrium. Then the humidity was increased in steps of 10% RH untill state of equilibrium before setting the next step. The increase in weight was registrated.
• the data are graphically presented as amount of water per unit of area and in the zone 30-60 RH, the absorption seems to be very linear. Following equation can be presented for both the imaging element and the absorbing material:
• Imaging element Absorbing element d L 0.785 g/m 2 36.0 g/m 2 22 °C a L 0.3949 10-3 0.7333 10-3 b L 5.4777 10-3 20.5111 10-3 50 °C a L 0.3439 10-3 0.8583 10-3 b L -7.5159 10-3 1.3083 10-3
• [ MC ] 22 [( aIL ⁇ RHIL + bIL ) ⁇ dIL ] + [( aIM ⁇ RHIM + bIM ) ⁇ dIM ]
• the above mentioned packages were placed for different times both at 50°C and as a reference on 22°C. After determined times the above mentioned materials were imaged on a Creo 3244TTM external drum platesetter at 2400 dpi at 150 rpm with a power setting of 15,5 Watt. The imaged plates were printed on a GTO46 printing machine with a K+E 800 Skinnex ink and fountain Rotamatic. The prints were inspected concerning image quality and quotated. The staining behaviour of the different materials is evaluated. This material property is concerned as the most critical parameter in respect to shelf life.

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• Engineering & Computer Science (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Printing Plates And Materials Therefor (AREA)
• Photosensitive Polymer And Photoresist Processing (AREA)
• Materials For Photolithography (AREA)

Priority Applications (3)

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Cited By (2)

Citations (4)

• 1999
  • 1999-08-13 EP EP19990202645 patent/EP1076013B1/fr not_active Expired - Lifetime
  • 1999-08-13 DE DE69930460T patent/DE69930460T2/de not_active Expired - Lifetime
• 2000
  • 2000-08-03 JP JP2000235692A patent/JP2001092148A/ja active Pending

Patent Citations (4)

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