Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/004—Photosensitive materials
  • G03F7/06—Silver salts
  • G03F7/07—Silver salts used for diffusion transfer
• • 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
• • 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
  • B41N3/04—Graining or abrasion by mechanical means

Definitions

• the invention relates to a process for the production of base material for offset printing plates, in which an aluminum strip, in particular a pure aluminum strip, is provided with a defined surface roughness at least on one surface side and then with an aluminum oxide layer, and the use of such a base material in the production of offset printing plates by the silver salt diffusion process.
• the latent negative image of the printed image to be produced is first produced on a photo paper by appropriate exposure.
• the photo paper (negative paper) thus exposed is now passed together with the plate base material through a basic developer-fixing salt solution, so that a thin layer of liquid is retained between the exposed silver salt layer of the photo paper and the offset printing plate surface to be produced.
• the silver salt dissociated by the exposure is reduced to silver in the photo paper.
• the unexposed portions of the silver salt are detached from the fixing component of the solution (for example, sodium riothothiosulfate) with formation of a complex and onto the offset printing plates base material, where - due to the different position of aluminum and silver in the voltage series - the silver of the detached silver salt complex is reflected in the form of a positive image on the surface of the offset printing plate base material.
• the offset printing plate produced in this way is now treated on its printing surface with a weak organic acid and finally dried.
• the printing plate is first moistened with water, the water not being accepted by the areas of the printing plate surface covered with silver and a water film being formed only in the silver-free surface areas. Then the oily printing ink is applied, which in turn is only accepted by the areas of the printing plate surface covered with silver.
• This color image is then transferred to the print carrier via an intermediate carrier using the known offset printing principle, e.g. onto the paper to be printed.
• the defined surface roughness of the offset printing plate has i.a. the purpose of ensuring the so-called water flow of the surface to the required extent, i.e. to cause a water film which is as uniform as possible to form on the silver-free areas when the printing plate surface is moistened.
• the quality of the offset printing plates produced in this way is determined on the one hand by the quality of the print quality achieved but on the other hand also by the plate service life, that is to say by the number of prints to be made with an offset printing plate.
• the surface roughness mentioned can be indicated by the mean roughness value R a and the average roughness depth R z , measured in each case parallel and perpendicular to the longitudinal direction of the aluminum strip.
• the measuring sections for these roughness depth measurements have lengths of 4 mm and are each divided into five evaluation areas of 0.8 mm.
• the mean roughness value R a is understood to mean the arithmetic mean of the absolute amounts of all distances of the recorded roughness profile from the center line of this roughness profile within the measuring section.
• the roughness depth is understood to be the distance perpendicular to this center line between the highest and the lowest point of the roughness profile within an evaluation area.
• the average roughness depth R z is the mean value of the roughness depths determined from these five evaluation areas of a measuring section.
• the surface roughness is produced, for example, by brushing, after which the surface aluminum oxide slide is formed without any special measures due to the action of atmospheric oxygen.
• the surface roughness measured perpendicular to the length of the strip, has a mean roughness value R a of 0.47 ⁇ m and an average roughness depth R z of 4.31 pm, and, measured parallel to the length of the strip, has a center roughness value R a of 0, 73 ⁇ m and an average roughness of 3.82 ⁇ m.
• the service life of the offset printing plates made from such a known base material corresponds to approximately 10,000 proofs with moderate print quality. Presentation of the invention
• the invention is based on the object of specifying a method for producing a base material for offset printing plates, in which an aluminum strip, in particular a pure aluminum strip, is provided on a surface side with a defined surface roughness and then with an aluminum oxide layer, and wherein the base material produced by the method according to the invention is at its Use according to the invention in the production of offset printing plates by the silver salt diffusion process leads to offset printing plates which ensure high printing quality and relatively long service lives.
• Roll is produced with a defined surface structure and the oxide layer is then produced by galvanic anodization. This impression of the surface roughness can advantageously be carried out with the aid of a roller when the aluminum strip is rolled out to its final thickness.
• the anodization process is carried out in such a way that the rollers used for embossing have such a surface structure that the aluminum oxide layer applied by the galvanic anodization has a basis weight of 0.2 to 2.0 g / m 2 in the base material for offset printing plates produced according to the invention , before geous but from 1.0 to 1.5 g / m 2 measured according to DIN 50944 and that the surface roughness of the finished base material roughness values from 0.05 to 1.0 pm and average roughness depths from 0.4 to 10.0 microns having.
• Offset printing plates produced with such a base material according to the silver salt diffusion process have a service life of approximately 20,000 to 40,000 proofs.
• the surface roughness on the finished base material - measured perpendicular to the lengthwise strip length - mean roughness values of 0.15 to 0.50 pm and mean roughness depths of 1.0 to 3.0 ⁇ m, and - measured parallel to the lengthwise strip length - mean roughness values of 0 , 05 to 0.30 ⁇ m and average roughness depths of 0.4 to 2.5 pm.
• the invention further relates to the use of the base material according to the invention in the production of offset printing plates by the silver salt diffusion process.
• an aluminum roughing strip of Al 99.0 quality in accordance with DIN 1712, a width of 1100 mm and a thickness of 0.6 mm is soft-annealed at 550 ° C. for 8 hours and then in roll stands whose rolls have a rough-ground surface three successive roll passes rolled to 0.1 mm.
• This aluminum strip is then subjected to DC anodization in a strip anodizing plant with an electrolyte consisting of 20% sulfuric acid with a Strosi density of approximately 2 A / dm 2 .
• the anodization is carried out in such a way that the weight per unit area of the aluminum oxide layer produced by the direct current anodization according to DIN 50944 is approximately 0.8 g / m 2 , which corresponds to an aluminum oxide layer thickness of approximately 0.25 ⁇ m.
• the surface roughness of the offset printing plate base material produced in this way then has, for example, measured perpendicular to the belt stretch, a mean roughness value R a of 0.29 ⁇ m and an average roughness depth R z of 2.07 ⁇ m, and, measured parallel to the longitudinal length of the strip, a mean roughness value R a of 0.15 ⁇ m and an average roughness R z of 0.88 ⁇ m.
• the service life of the offset printing plates made from this base material using the silver salt diffusion process is surprisingly long and corresponds to around 25,000 proofs with very good print quality.
• the same soft-annealed aluminum roughing strip with a thickness of 0.6 mm is used as described in the first method variant.
• This roughing strip is then pre-rolled in thicknesses of 0.3 or 0.15 mm in two pass passes on roll stands, the rolls of which have a rough-ground surface, and is then milled in a roll, of which at least one of the two rolls has a surface structure generated by sandblasting onto the Rolled out to a final thickness of 0.1 mm.
• the subsequent galvanic anodization is then carried out analogously to the first method variant and is carried out in such a way that the weight per unit area of the aluminum oxide layer produced is approximately 1.2 g / m 2 , which corresponds to an aluminum oxide layer thickness of approximately 0.4 ⁇ m.
• the surface roughness of the base material produced in this way has, for example, measured perpendicular to the lengthwise strip length, a mean roughness value R a of 0.6 ⁇ m and a mean roughness depth R z of 3.4 ⁇ m, and, measured parallel to the lengthwise strip length, a mean roughness value R a of 0. 6 um and an average roughness depth R z of 3.6 ⁇ m.
• the service life of the offset printing plates made from this basic material corresponds to approximately 30,000 proofs.
• the process according to the invention for the production of base material which is used for the production of offset printing plates using the silver salt diffusion process, is relatively inexpensive and leads to offset printing plates which are relatively long with good print quality

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Printing Plates And Materials Therefor (AREA)

Applications Claiming Priority (2)

Publications (1)

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• 1980
  • 1980-03-11 AT AT0133280A patent/AT375880B/de active
  • 1980-05-29 BE BE6/47174A patent/BE883547A/fr not_active IP Right Cessation
  • 1980-06-06 NL NL8003326A patent/NL8003326A/nl not_active Application Discontinuation
• 1981
  • 1981-03-10 IT IT20247/81A patent/IT1168081B/it active
  • 1981-03-11 WO PCT/AT1981/000004 patent/WO1981002547A1/de not_active Application Discontinuation
  • 1981-03-11 JP JP56500891A patent/JPS57500329A/ja active Pending
  • 1981-03-11 EP EP81900668A patent/EP0048721A1/de not_active Withdrawn
  • 1981-03-11 BR BR8107432A patent/BR8107432A/pt unknown

Non-Patent Citations (1)

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