Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Patent
1999-06-22
2000-08-29
Chapman, Mark
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
430137, G03G 900
Patent
active
061106321
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns improvements in printing, more especially it concerns improvements in transfer or direct printing of ceramic colours onto substrates.
It is well established to screen print inks or suspensions of ceramic colours onto water-slide paper in order to form decals. Such decals are used for the decoration of ware such as table china and porcelain, for domestic or hotel/restaurant use, tiles, giftware and promotional ware, earthenware objects, glass and glass ceramics and vitreous enamelled metals by well established procedures including wetting the decal to release the printed pattern. positioning the decal on the ware and then firing the combination to produce a durable decoration on the surface of the ware. This technology can be used for highly decorative colour prints yielding high value decorated objects. However, the screen printing process requires the preparation of a separate screen for each colour, extended drying times for the inks used and may create environmental problems arising from the solvents released from the inks during drying, and possible dimensional changes to the paper substrate.
It has been proposed, almost from the introduction of electrostatic photocopiers, to use photocopying onto conventional water-slide paper in order to produce decals in a rapid manner and without the use of solvent-based inks. We mention the following published patent specifications as examples of these prior proposals: GB 2151189. GB 2238985, DF 4041358. DE 3917156 and EP 647885.
Other proposals have been identified recently, namely JP08-119668 (Konica), JP08-11496 (Brother) and EP 751434 (Ricoh). These proposals are from photocopier manufacturers and, in our view, fail to teach decals that can be fired onto ware with reliable colour, gloss and density.
It has been proposed to incorporate coloured pigments in toner particles for two-part developers (see Xerox Corporation EP 22638), but no guidance is given regarding pigment content except for carbon black, for which 10% is quoted. We believe that state-of-the-art colour photocopier toners exclusively use organic pigments or dyes in concentrations below 10% by weight. eg 3 to 5 wt %. Where inorganic pigments have been used, eg black magnetic toner particles, we believe that quantities of from 20 wt % up to 60 wt % may be used.
The prior proposals to print decals have not, however, been adopted commercially, despite the apparent desirable characteristics of a photocopying-based process. We believe that certain of the problems found in such prior proposals have been either difficulty in depositing adequate colour density or, where a thick deposit of toner has been deposited, difficulty in applying the decal because of brittleness, reticulation of the covercoat, and in firing the decal without bubbling and distortion caused by the organic material in the toner. Our own tests have shown that the use of a photocopying process is far from straightforward, and that there remains a need for a commercially acceptable ceramic printing process based on electrostatic or electrophotographic printing.
It must be understood that conventional photocopying or laser printing processes and equipment are intended to produce a permanent print on paper, for which fixing the toner onto the paper by heat fusion and, usually, pressure, forms an essential part. For decal manufacture, the pigment or toner deposit may be regarded as temporary, and a covercoat provides integrity.
The terms "electrostatic printing" as used hereinafter, is intended to cover the broadest possible scope, including charged area development, discharged area development or development by charging an insulating surface, including electrography or ionography.
The present invention now provides electrophotographic printing toner particles comprising 71 to 90 wt % of inorganic ceramic colour and 29 to 10 wt % of an organic polymeric material.
The invention further provides a two-part developer for electrostatic printing comprising 2 to 22%, suitably 2 to 20 wt %, preferably 2 to 18 wt % mor
REFERENCES:
patent: 4623602 (1986-11-01), Bakker et al.
patent: 5948471 (1999-09-01), Zimmer
Dunford Dominic Manton
Eadon Desmond Gerard
Evans Iona Gwawr
Hogan Geraldine Bridget Martina
Holloway Joanne Margaret
Chapman Mark
Cookson Matthey Ceramics PLC
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