Record receiver having plural interactive leaves or a colorless – Having plural interactive leaves
Patent
1995-03-22
1997-08-19
Hess, Bruce H.
Record receiver having plural interactive leaves or a colorless
Having plural interactive leaves
428195, 428500, 428913, 428914, B41M 5035, B41M 538
Patent
active
056588461
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a thermal transfer printing (TTP) dye sheet, in particular to a dye sheet having an improved dye binder.
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 thereby to form an image on the receiver sheet. In such a process, the dye sheet and receiver sheet are placed in intimate contact, the thermal stimuli are applied to the dye sheet to cause dye transfer 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. The thermal stimuli may be provided by a programmable print head which is in contact with the dye sheet or by for example, a laser in a light-induced thermal transfer process (LITT).
Dye-sheets conventionally comprise a substrate having on one surface thereof a dye coat which typically comprises a thermally transferable dye dispersed or dissolved in a binder. Dye-sheets may also comprise a back coat to impart desirable properties for example, good handling and thermal characteristics to the dye sheet. Further, a primer or subbing layer may be employed between the substrate and the dye coat and/or the substrate and the back coat for example to improve the adhesion of the coat to the substrate.
Many materials have been suggested for use as the binder including, cellulosic polymers as disclosed in J03264393, polyvinylbutyral as disclosed in EP-A-141678, epoxy resins and phenolic resins. J59199295 discloses an ink composition for sublimation dye transfer consisting of cellulose acetate, polystyrene, a disperse dye, silica and methylethyl ketone.
During the TTP process, application of a thermal stimulus to an area of the dye coat of the dye sheet heats that area of the sheet to a temperature typically in excess of 100.degree. C. as a result of which the dye in that area of the dye sheet is transferred to the receiver sheet. On removal of the thermal stimulus the temperature of the heated area then decreases to the ambient operating temperature in the process.
However, once the thermal stimulus is removed and the temperature of the heated area of the the dye sheet is decreasing, there may be still be sufficient heat to cause unwanted, uncontrolled residual transfer of dye to the receiver sheet which may cause a reduction in image quality. This effect is known as low temperature thermal transfer.
We have now found that by employing a dye sheet binder comprising a polymer having a monomeric unit of an optionally substituted styrene provided that where unsubstituted styrene is present in the polymer then the polymer is a copolymer problems due to low temperature thermal transfer may be reduced or avoided and other significant advantages may also be secured.
Accordingly, a first aspect of the invention provides a thermal transfer printing dye sheet which comprises a substrate having on one side, a dye coat comprising a binder and a thermally transferable dye wherein the binder comprises a mixture of a polymer having, as at least 10% of the monomeric units of the polymer, a monomeric unit of formula (I); cyano group or an ester group of formula --CO.sub.2 Z wherein Z is an optionally substituted C.sub.1 to C.sub.6 hydrocarbyl group with the proviso that where Y is an unsubstituted phenyl group the second polymer also has a substituted styrene and/or a non-styrene monomeric unit.
Dye-sheets according to the present invention have been found to exhibit a particularly advantageous combination of characteristics. In particular, good resistance to low temperature thermal transfer may be achieved which provides for improved image quality and images may be produced which have excellent optical density.
Also, we have found that when the dye sheet is to be used to produce multi-colour images by using a dye sheet comprising a plurality of panels of different uniform colours, usually magenta, yellow and cyan, improved colour balance between the dyes by ma
REFERENCES:
Database WPI Week Week 8607, Derwent Publications Ltd., London, GB; AN 86-046114 & JP A 61 000 692 (Oike Kogyo KK) 6 Jan. 1986.
Hess Bruce H.
Imperial Chemical Industries plc
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