Dye diffusion thermal transfer printing

Details Dye diffusion thermal transfer printing Dye diffusion thermal transfer printing

1996-06-03

1999-06-29

Tran, Huan

Incremental printing of symbolic information

Thermal marking apparatus or processes

347213, B41J 3114, B41J 3116

Patent

active

059175303

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to dye diffusion thermal transfer printing, which should be taken to cover sublimation transfer printing, and relates particularly to the efficient use of dye in such printing, the term "dye" being taken to cover dyes, inks and other soluble colorants.
2. Description of the Prior Art
In diffusion thermal transfer printing, heat is applied to selected pixel areas of a dye donor sheet or ribbon by a suitable heat source, such as a series of resistive heating wires or a scanning laser beam. This heating causes diffusion of dye in the selected areas, and transfer of the dye to form printed pixels on an adjacent receiver sheet or ribbon.
The transfer may also be by sublimation, wherein the heating of the donor sheet causes the dye to enter the vapour phase. The dye then crosses an air gap and condenses onto the surface of the receiver sheet from where it may then diffuse inwards.
After printing, the dye sheet or ribbon is left with a number of dye depleted pixel areas where the dye has transferred to the receiver. The dye sheet or ribbon cannot therefore be reused, and must be discarded after a single print from the sheet or after the end of the ribbon is reached. This is wasteful, as much dye still remains on the dye sheet or ribbon in the regions which were not printed from.


SUMMARY OF THE INVENTION

The present invention aims to provide a system which is less wasteful of dye, and, from a first aspect, provides a dye diffusion thermal transfer printing system comprising dye donor means carrying an amount of thermally diffusible dye, receiver means for receiving dye from the donor means, and means for heating selected regions of the donor means to cause dye in those regions to transfer to the receiver means, wherein means are provided for replenishing, with thermally diffusable dye, regions of the donor means which have become depleted of dye through printing.
From a second aspect, the invention provides a method of dye diffusion thermal transfer printing in which selected regions of a dye donor means are heated to cause dye in those regions to transfer to a receiver means, wherein regions of the donor means which have become depleted in dye through printing are replenished with thermally diffusable dye.
The replenishment of the dye depleted regions allows the donor means to be used repeatedly, so that it need not be discarded after merely a single print run or at the ribbon end. Therefore, at least some of the dye remaining in the unprinted regions of the donor means is not lost, and may be used during further print operations. Moreover, savings are also provided because the dye donor means itself is re-used. For example, a dye ribbon may typically comprise a substrate for supporting a dye layer, a dye binder within which dye is dispersed to form a dye layer, and a laser light absorbing material either as a separate layer or dispersed with the dye, and, by the present invention, all of these materials are able to be re-used.
In a preferred form, the depleted regions are supplied with dye from other regions of the donor means. In this case, means may be provided for supplying heat to the donor means after printing to cause dye from undepleted regions of the donor means to diffuse into the depleted regions. This replenishment heating means may heat the donor means in any suitable manner. It need not be of as high an intensity as the print heating means and, indeed, it is preferable for the replenishment heating means to operate at a low power level to provide a more even dispersion of dye.
In this preferred self-reservoir form, the donor means may comprise a dye ribbon or sheet having a supporting substrate with a dye layer thereon which is thicker than is standard to enable sufficient dye to be held within the layer to replenish the dye transfer regions over a plurality of print cycles. The dye diffuses from the body of the layer to replenish the dye depleted surface regions. In this embodiment, the replenishment heat may be

REFERENCES:
patent: 4462035 (1984-07-01), Koto

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