Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D11/00—Inks
  • C09D11/02—Printing inks
  • C09D11/10—Printing inks based on artificial resins
  • C09D11/101—Inks specially adapted for printing processes involving curing by wave energy or particle radiation, e.g. with UV-curing following the printing

Definitions

• This invention relates to printing and in particular to screen printing (commonly known as silk screen printing).
• silk screen printing commonly known as silk screen printing
• the silk screen printing process involves the use of a screen of silk, polyester, nylon, metal gauze or any other suitable mesh-like or perforated material.
• silk screen printing will be used herein and it will be appreciated that no restriction to "silk” material is thereby intended.
• the printing inks required for screen printing are quite different from those to be used for other forms of printing.
• the screen printing inks being generally used at present are organic solvent-based and usually contain ethyl or nitro cellulose resins. They are dried in warm air tunnels by driving off the organic solvents, and are thus potentially hazardous to the printing operatives.
• Another problem which arises with such organic solvent-based screen printing inks relates to solvent loss from the ink on the printing screen whereby the ink increases in viscosity and after a certain period of time will not properly pass through the open areas of the printing mesh. This "drying in” results in loss of printed image and is described as screen stability, i.e. inks with poor screen stability "dry in” rapidly.
• Posters printed with offset litho inks have less tendency to curl when they dry out compared to those produced with screen printing inks.
• the screen printing process achieves its high quality print appearance by a much higher ink deposit, the curl problem is pronounced with screen printing inks. Therefore the adhesives used with screen printed posters need to have better adhesion properties to prevent overlap curl.
• a printing ink for silk screen printing characterised in that the screen printing ink is a water-based ink that is at least partially curable by irradiation and comprises an emulsion of a resin dispersed in water.
• UV radiation refers to eloctro-magnetic radiations having wavelengths shorter than those of the visible spectrum, and the term thus includes UV (ultra-violet) and electron beam radiations.
• the emulsion has said resin wholly (or at least substantially) in dispersed phase and wholly (or at least substantially) insoluble in the water, the water being the continuous phase of the emulsion.
• said resin comprises 30% to 60% ( preferably 50% ) of the emulsion.
• said resin comprises an unsaturated acrylate resin, e.g. polyester acrylate resin. It is envisaged that an epoxy acrylate resin and/or a urethane acrylate resin might additionally or alternatively be employed.
• the water-based screen printing ink has a composition which comprises one or more photoinitiators and is at least partially curable by irradiation comprising electromagnetic radiations in the ultra-violet light waveband.
• the screen printing ink may be at least partially curable by irradiation with an electron beam.
• photoinitiator(s) may be omitted from the printing ink composition.
• the water-based printing ink composition is subjected to heat or to thermal radiation, e.g. is subjected to electromagnetic radiations in the infra-red light waveband, prior to curing.
• the following relates to the production of individual silk screen printed sheets and their treatment for application onto hoarding sites in accord with embodiments of the present invention.
• the embodiments are concerned with the usual combinations of multiple sheet posters (e.g. "16 sheet”, “48 sheet” or “96 sheet” posters) for pasting up onto large hoardings.
• the screen printing method used in these embodiments may be for the production of four colour halftone prints as well as continuous line and tone colour prints.
• the screen printing ink in each of these embodiments comprises an emulsion of a resin dispersed in water, i.e. is water miscible, and dries by exposure to Ultra Violet radiation.
• the emulsion has said resin wholly (or at least substantially) in dispersed phase and wholly (or at least substantially) insoluble in the water, the water being the continuous phase of the emulsion.
• the screen printing ink contains water and is water thinnable to a considerable extent, but the water is to be regarded as a carrier or diluent (rendering the ink aqueously reducible in viscosity) rather than as a solvent.
• the water-based screen ink contains at least 40% water.
• the printing ink comoosition comprises: an Ultra Violet curing resin emulsified with water, e.g. an equal part of water; a photoinitiator and an aqueous pigment dispersion.
• water e.g. an equal part of water
• a photoinitiator e.g. an aqueous pigment dispersion
• the water is the continuous phase and the resin (amounting to 50% of the emulsion) is the dispersed phase.
• Example 1 A composition as formulated in Example 1 was printed through a screen made from 165 threads per cm polyester mesh halfcalendered. The calendered side was positioned face down towards the substrate, ie. M.G. (machine glazed) poster paper. The stencil was made from direct emulsion using a half-tone positive. The print was producer, on an S.P.S. cylinder action screen printing press. The ink was dried through a two lamp S.P.S. U.V. dryer (rated at 300 watt per inch). The resultant dried print was a good half tone image of high definition.
• Example 2 A composition as formulated in Example 2 was printed and dried in the same manner as for Example 1. The resultant dried print was a good half tone image of high definition.
• Photoinitiator Quantacure* ITX ( 7) 3.0
• a composition formulated as in Example 3 was printed and dried in the same manner as for Example 1.
• the resultant dried print was a good half tone image of high definition.
• Example 4 A specific formulation of this fourth embodiment is provided in Example 4.
• a fifth embodiment was devised in which the ethoxy propanol was replaced by a mixture of Abater and an acrylic monomer - Tripropylene glycol diacrylate (T.P.G.D.A.) - for maintaining the appropriate dispersion of the resin solids.
• T.P.G.D.A. acrylic monomer - Tripropylene glycol diacrylate
• Example 5 A composition formulated as in Example 5 was printed and dried in the same manner as for Example 1. The resultant dried print was a good half tone image of high definition.
• Laromer* PE 55W is a 50% emulsion of a polyester acrylate in water obtainable from B.A.S.F.
• Darocur* 1173 is a Hydroxy-2-methyl-1-propan-1-one obtainable from E. Merck
• Aquadisperse* Phthalo Blue GB EP is an aqueous dispersion of pigment Blue 15 obtainable from TennantK.V.K.
• n-vinyl pyrrolidone is a UV reactive solvent obtainable from B.A.S.F.
• Omyalite* 95T is a calcium carbonate extender obtainable from Croxton & Garry.
• Irgacure* 651 is Benzil Dimethyl Ketal obtainable from Ciba Geigy.
• Quantacure* ITX is isopropylthioxanthon e obtainable from Ward Blenkinsop.
• Curlout* Plus is a modified acrylic solution polymer obtainable front American Carbonyl Inc.
• Alcoprint* PTF is an acrylic copolymer in mineral oil thickner obtainable from Allied Colloids.
• Alcoprint* PHL is a humectant and surfactant blend obtainable from Allied Colloids.
• Alcoprint* PSJ is a silicone emulsion softner/lubricant obtainable from Allied Colloids.
• T.P.G.D.A. is a Tripropylene Glycol Diacrylate obtainable from Degussa.

Landscapes

• Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Wood Science & Technology (AREA)
• Organic Chemistry (AREA)
• Inks, Pencil-Leads, Or Crayons (AREA)
• Photosensitive Polymer And Photoresist Processing (AREA)

Applications Claiming Priority (6)

Publications (1)

Family

ID=27263113

Family Applications (1)

Country Status (8)

Families Citing this family (11)

Family Cites Families (8)

• 1987
  • 1987-07-30 EP EP19870904912 patent/EP0296176A1/en not_active Withdrawn
  • 1987-07-30 WO PCT/GB1987/000540 patent/WO1988000961A1/en not_active Application Discontinuation
  • 1987-07-30 ES ES8702246A patent/ES2004959A6/es not_active Expired
  • 1987-07-30 AU AU77802/87A patent/AU608532B2/en not_active Ceased
  • 1987-07-30 GR GR871218A patent/GR871218B/el unknown
  • 1987-07-30 JP JP50453887A patent/JPH01503391A/ja active Pending
• 1988
  • 1988-03-28 DK DK169388A patent/DK169388A/da not_active IP Right Cessation
• 1989
  • 1989-01-27 FI FI890430A patent/FI890430A0/fi not_active IP Right Cessation

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events