Record receiver having plural interactive leaves or a colorless – Having plural interactive leaves
Patent
1996-10-08
1998-07-28
Hess, Bruce H.
Record receiver having plural interactive leaves or a colorless
Having plural interactive leaves
428195, 428480, 428500, 428502, 428522, 428913, 428914, B41M 5035, B41M 538
Patent
active
057862974
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a thermal transfer printing (TTP) receiver sheet.
Thermal transfer printing is a printing process in which a dye is caused, by thermal stimuli, to transfer from a dye sheet to a receiver sheet. In such processes, the dye sheet and receiver sheet are placed in intimate contact, the thermal stimuli are applied to the dye sheet and the dye sheet and receiver sheet are then separated. By applying the thermal stimuli to pre-determined areas in the dye-sheet, the dye is selectively transferred to the receiver to form the desired image.
Receiver sheets conventionally comprise a substrate with a dye-receiving polar surface on one side, into which a dye is thermally transferable and retainable. Where the substrate is itself polar and capable of receiving a dye, the dye may be transferred directly to a surface of the substrate. However receiver sheets typically comprise a substrate supporting a receiver layer specifically tailored to receive the dye. However, such systems have the problem that the high temperatures (250.degree.-350.degree. C.) involved in the dye transfer, can cause the dye sheet and the receiver sheet to melt bond together preventing clean separation and in extreme cases preventing any separation.
It is known that this problem can be overcome by incorporating release agents such as silicone and fluorine containing compounds, for example fluoro surfactants, in the receiver sheet.
However, as disclosed in EP 424037, the use of such conventional materials leads to bleeding (pressure transfer) of the dye from the dye sheet to the receiver sheet, ie the dye can migrate as soon as the dye sheet and the receiver sheet are brought together.
There is also a tendency for the amount of release agent to be reduced by transfer to the dye sheet such that in multicolour printing there is insufficient remaining in the final print operation to prevent bonding. Any increase in the amount of release agent to counteract this effect would of course increase dye bleeding.
EP 424037 suggests that the problem may be overcome by using release agents capable of forming a cross-linked structure and points out that conventionally used fluoro surfactants totally lack the ability to cross-link and that the release agents must contain either an unsaturated functional group (eg vinyl) or at least two separate functional groups for sufficient cross-linking to take place.
Unfortunately, such cross-linking affects the "writability" of the surface, that is to say the acceptance by the surface of the various inks used in common writing implements, in particular aqueous based inks which are being increasingly used for environmental reasons. Writability is particularly important in the medical field where notes may need to be written on a patient's records.
Whilst the receiver sheets disclosed in EP 424037 may have improved properties in terms of release and dye bleeding, there is also the disadvantage that the release agents suggested are not readily available; indeed no specific example of a cross-linkable fluoro compound is given.
It is an object of this invention to provide a receiver sheet which has appropriate release properties, is capable of accepting ink, particularly aqueous based inks, from common writing implements, which does not suffer from pressure transfer of dye and which can use materials which are readily available commercially.
According to one aspect of the invention, there is provided a receiver sheet for diffusion transfer printing comprising a substrate having thereon a dye receiver layer comprising a dye receptive polymer and the reaction product of a first compound having at least two reactive functional groups and a second, fluorine containing, compound having a single reactive functional group.
The reaction product has reduced mobility and hence reduces transfer to the dye sheet during printing without producing a cross-linked surface which would prevent penetration of ink and reduce writability.
The first compound may be an amine resin, preferably a melamine resin such as hexamethox
REFERENCES:
patent: 5290750 (1994-03-01), Kushi et al.
Hess Bruce H.
Imperial Chemical Industries plc
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