IPC分类号：
B44C1/17 | B41M3/12 | B32B3/00 | C09J7/02
国民经济行业分类号：
C2438 | C2436 | C2435 | C2434 | C2433 | C2432 | C2431 | C3076 | C3075 | C2439
当前申请(专利权)人：
REED, KENNETH JAMES
原始申请(专利权)人：
REED, KENNETH JAMES
当前申请(专利权)人地址：
London, GB2
发明人：
REED, KENNETH J. | LYTHGOE, ALAN L.
代理机构：
JACKSON, WILLIAM E.
摘要：
A dry release transfer is disclosed in which a releasable layer is adhered to a carrier sheet and a stress-resisting transferable design layer is printed on the releasable layer. The releasable layer is normally pre-stressed so that when an external force is applied to the carrier sheet , e.g. by rubbing with a stylus, this force is transmitted to the releasable layer. Since the releasable layer cannot yield to the applied force by stretching, because it is held by the stress-resisting layer, the adhesive bond between the releasable layer and the carrier sheet is weakened or is ruptured or partial or complete cohesive failure occurs within the releasable layer, thereby facilitating transfer of the design layer. A method of producing such transfers is also disclosed.
技术问题语段：
Two types of dry transfers having different transfer mechanisms have been previously described in British Pat. Nos. 959,670 and 1,491,678 but several major problems exist with such dry transfers.|In general print quality is limited and is inadequate for important applications such as preparation of original artwork.|All the transfer mechanisms hitherto known do not give adequate control of transfer properties and frequently lead to failure to transfer or accidental or unwanted transfer.|Furthermore the exclusive use of pressure sensitive adhesives in prior art dry transfers has restricted their field of use.|Consequently the stressing of the releasable layer leads to partial or complete cohesive failure of the releasable layer or weakening or rupture of the adhesive bond between the design and the carrier.|A direct tensile force, peeling force, shearing or twisting force applied to the carrier sheet will cause stress-failure of the release layer.|Stress-failure of the release layer by an external force requires that the transferable layer possesses sufficient stress-resisting properties so that the force applied to the carrier sheet is transmitted to the intervening release layer to cause cohesive or adhesive stress-failure or by a combination of these.|The stress-resisting properties of the transferable layer should not be obtained by means of rigidity causing brittleness.|Carrier sheets with the release layer have little or no air permeability and the drying of conventional inks which rely partly on substrate absorption is very slow.|High release coatings have even worse printability and ink-pick than inherently high release carrier sheets, such as polyethylene, and moreover any adhesive layer which overlaps the transferable layer will also be transferred and contaminate the receiving surface with a sticky layer outside the design.|Adhesive-failure of the release layer is generally obtained when the release layer is based as a polymer which has been physically, chemically or thermally stressed.|The interaction normally causes swelling of the release layer and the swollen material is of much lower tensile strength and readily shows cohesive failure.|The process of swelling also causes stressing of the adhesive bonds of the release layer to the carrier sheet and can lead to a permanent reduction of adhesion even if the liquid component is volatile and eventually evaporates.|This can lead to a permanent reduction of adhesion and it can also cause cohesive-failure since the action of any liquid swelling component is intensified at elevated temperatures.|Plastics and transparentised cellulosic materials are well known to have very poor printability compared with normal printing papers particularly when printed by lithography and this is evident as weak and non-uniform print solids and repellency spots in fine line detail and half-tones.|This poor printability is a result of low and uneven wet ink transfer due to zero absorbency of the substrate and to poor wetting of the plastic by the ink.|In fact it is disadvantageous to have a very low reduced releasable layer adhesion with a high tack adhesive because such adhesives must be protected with a silicone coated protective paper in storage and removal of such paper applies a peel bond of several grams per centimeter and this would cause unwanted transfer onto the protective paper if the reduced layer adhesion were too low.
技术功效语段：
Such pre-stressing substantially reduces the level of the external force required to cause physical release of the transferable layer. Such transfer sheets can be prepared with accurately predetermined release characteristics including release by a small applied external force.
权利要求：
We claim:
1. A dry release transfer sheet which comprises a carrier sheet, a releasable layer adhered thereto and a stress-resisting transferable design layer printed on said releasable layer, said releasable layer having low cohesive strength and low tensile strength compared with the transferable layer and providing a surface capable of being wetted with an ink in printing said design layer and said design layer having an elongation at break which is at least 0.5% and a thickness which is at least 3 times the thickness of the releasable layer, whereby application of an external force to the carrier sheet in the region of the design layer causes stressing of the releasable layer and cohesive failure within the releasable layer thus physically releasing the design layer from the carrier sheet and enabling subsequent transfer of the design layer with an underlying portion of releasable layer.
2. A transfer sheet according to claim 1 in which the transferable design layer has a Young's Modulus which is substantially greater than that of the releasable layer.
3. A transfer sheet according to claim 1 in which the transferable design layer is a multi-layer film comprising at least one coloured ink and a clear or coloured layer of substantial film strength, the latter layer providing the major stress-resisting properties of the transferable design layer.
4. A transfer sheet according to claim 1 which includes an adhesive layer superposed on said transferable design layer, either in register therewith or overlapping onto the releasable layer.
5. A transfer sheet according to claim 1 in which the transferable design layer is 5 to 50 .mu.m thick.
6. A transfer sheet according to claim 1 in which the releasable layer is 0.1 to 1 .mu.m thick.
7. A transfer sheet according to claim 6 in which the releasable layer comprises a material having low cohesive strength selected from waxes, soaps, surfactants, and low molecular weight polymers having low tensile strength and mixtures thereof.
8. A transfer sheet according to claim 1 in which the transferable design layer comprises a photopolymerised ink film.
9. A transfer sheet according to claim 8 in which the photopolymerised ink film is produced by photopolymerisation of an ethylenically unsaturated monomer or prepolymer composition containing a photoinitiator.
10. A transfer sheet according to claim 9 in which the unsaturated monomer or prepolymer contains acryloyl or methacryloyl groups.
11. A transfer sheet according to claim 10 in which the monomer or prepolymer is capable of cross-linking on photpolymerisation.
12. A transfer sheet according to claim 10 in which the prepolymer is an acrylated or methacrylated urethane prepolymer.
13. A transfer sheet according to claim 12 in which the urethane prepolymer contains 2 to 6 acryloyl groups per molecule.
14. A dry release transfer sheet which comprises a carrier sheet, a releasable layer adhered thereto and a stress-resisting transferable design layer printed on said releasable layer, said releasable layer having low cohesive strength and low tensile strength compared with the transferable layer and providing a surface capable of being wetted with an ink in printing said design layer and said design layer comprising a cross-linked photopolymerised ink film having an elongation at break which is at least 0.5% and a thickness which is at least 3 times the thickness of the releasable layer, whereby application of an external force to the carrier sheet in the region of the design layer causes stressing of the releasable layer and cohesive failure within the releasable layer thus physically releasing the design layer from the carrier sheet and enabling subsequent transfer of the design layer with the whole or part of its underlying portion of releasable layer.
15. A dry release transfer which comprises a carrier sheet, a thin releasable layer adhered thereto and a stress-resisting transferable design layer printed on said releasable layer, said transferable design layer having an elongation at break which is at least 0.5% and a thickness which is at least 3 times the thickness of the releasable layer, said releasable layer comprising a wax containing composition and having low cohesive strength and low tensile strength compared with the transferable layer, whereby application of an external force to the carrier sheet in the region of the design layer causes weakening or rupture of the adhesive bond between the design layer and the carrier sheet accompanied by partial or complete cohesive failure within the releasable layer thus physically releasing the design layer from the carrier sheet and enabling subsequent transfer of the design layer with an underlying portion of the releasable layer.
16. A transfer sheet according to claim 15 in which the releasable layer is chemically pre-stressed by interaction with a liquid component of the transferable layer or of a superposed adhesive layer.
17. A transfer sheet according to claim 15, in which the design layer is physically prestressed by shrinkage of the transferable design layer.
18. A transfer sheet according to claim 17 in which shrinkage of the design layer arises by evaporation of a solvent or polymerisation.
19. A transfer sheet according to claim 15 in which the design layer is a photopolymerised ink composition.
20. A transfer sheet according to claim 19 in which the design layer is cross-linked polymerised ink.
21. A transfer sheet according to claim 15 in which the releasable layer includes an anti-static agent.
22. A transfer sheet according to claim 21 in which the anti-static agent is selected from quaternary ammonium compounds and polyoxyethylene derivatives.