Vickers, Inc.

Leslie E Lawson

Peter Edward Watts

John Sleeman Rogers

Michael Ingham

Frank E Smith

Changes occurring in the electrical conductivity of liquids used to process image-wise exposed radiation-sensitive devices are used as a measure of the deterioration in effectiveness of the liquids. This deterioration is compensated for by varying the processing conditions, such as temperature, time, scrubbing action and processing liquid composition, in accordance with the change in conductivity.

Method and apparatus for controlling the processing of radiation

A concentrate for dilution with water to obtain a fountain solution for lithographic printing comprises a lithographic desensitizing material dissolved in a vehicle liquid comprising an organic solvent liquid optionally in admixture with water. Preferred desensitizing materials are organo substituted ammonium salts of desensitizing acids and a preferred organic solvent liquid is isopropyl alcohol. The fountain solution obtained on dilution of the concentrate may be used with printing machines having integrated damping/inking equipment.

Lithographic fountain concentrates containing a desensitizing material

During the processing of an image-wise exposed radiation sensitive device, such as a radiation sensitive plate for lithographic printing plate production, by contacting the device with developer liquid, a temperature sensitive member is immersed in the developer liquid. The member produces an output signal in dependence on the temperature of the developer liquid. This signal is used to control the degree to which the device is processed in a manner dependent on the temperature of the developer liquid for example by controlling the residence time of the device in the developer liquid, by controlling the degree to which the developer liquid is agitated in contact with the device, or by controlling the degree to which the device is subjected to an overall exposure to radiation prior to or during contact with the developer liquid.

Processing of radiation sensitive devices

A positive working radiation sensitive plate is image-wise exposed, developed and desensitized, and dried. Thereafter an oleophilic composition including a solvent capable of softening the image is applied to the plate and the plate is then washed to remove the oleophilic composition from the non-image areas. The image accepts ink readily even when the image-wise exposure is effected using a continuous tone original in the absence of a half-tone screen.

Treating developed lithoplate with oleophilic composition

A composition for improving the ink receptivity of lithographic printing images comprises an organic solvent liquid capable of softening the surface of the printing image and a film forming alkali-resistant oleophilic material such as a liquid hydrocarbon solution of a normally solid hydrocarbon or fat. The composition is for use in the case where the printing image is formed by alkaline development of an image-wise exposed radiation sensitive coating such as a phenol formaldehyde resin in admixture with a sensitiser. The composition may be applied before exposure to form an alkali resistant oleophilic layer on the radiation sensitive coating or it may be applied after image-wise exposure but before alkali development.

Lithographic plate ink receptivity improving composition and method

The amount of water present on a lithographic printing plate during printing is determined by measuring the amount of water present on a surface which is other than that of the printing plate but which carries an amount of water related to the amount of water present on the printing plate. The surface upon which the measurement is made may be the surface of a control pad mounted on the printing roller in the gap between opposite ends of the printing plate, the surface of one of the rollers of the damp train applying water to the printing plate, or the surface of an auxiliary roller contacting one of the rollers of the damp train applying water to the printing plate. The amount of water subsequently applied to the printing plate may be regulated in dependence upon the amount of water determined as being already present on the printing plate.

Printing plate water sensing means and method

A desensitizing composition comprises an aqueous solution comprising (i) a polymer containing structural units derived from acrylamide and from 1% by weight to 25% by weight of structural units containing carboxyl groups and (ii) desensitizing acidic material in an amount such that the pH of the solution is less than 5.5. The carboxyl group containing structural units may be derived from acrylic acid and/or an acrylic acid salt and the desensitizing acidic material may be phosphoric acid. The composition may be used as a substitute for gum arabic solution in lithographic plate making processes and lithographic printing processes.

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Surbiton, United Kingdom

Leslie E Lawson