Label-printing process for substantially light-insensitive...

Details Label-printing process for substantially light-insensitive... Label-printing process for substantially light-insensitive...

1999-11-30

2001-06-12

Hilten, John S. (Department: 2854)

Typewriting machines

Sheet or web

For feeding web record-medium

C503S207000

Reexamination Certificate

active

06244766

ABSTRACT:

DESCRIPTION
1. Field of the Invention
The present invention concerns a label-printing process using substantially light-insensitive elongated imaging materials.
2. Background of the Invention
Thermal imaging or thermography is a recording process wherein images are generated by the use of thermal energy. In direct thermal printing a visible image pattern is produced by image-wise heating of a recording material e.g. image signals can be converted into electric pulses and then via a driver circuit selectively transferred to a thermal printhead, which consists of microscopic heat resistor elements, thereby converting the electrical energy into heat via the Joule effect. This heat brings about image formation in the thermographic material.
Label-printing by means of thermography is known with tapes on the basis of monosheet materials such as colourless or light coloured dye precursor leuco-dye systems, as disclosed in U.S. Pat. No. 4,370,370, EP-A 479 578 and EP-A 754 564, diazo systems, as disclosed in JP 60-01077A, or two-sheet thermal dye transfer systems, such as disclosed in EP-A 656 264 and U.S. Pat. No. 4,943,555. EP-A 754 564 also discloses applied energy per unit area in different printing tests in the invention examples in the ranges of 20-140 mJ/mm
2
, 80-140 mJ/mm
2
, 30-50 mJ/mm
2
, 80-100 mJ/mm
2
, 30-35 mJ/mm
2
and 20-200 mJ/mm
2
; as well as specific energies of 30 mJ/mm
2
, 40 mJ/mm
2
, 80 mJ/mm
2
and 90 mJ/mm
2
.
EP 736 799A discloses a recording material comprising a support having provided thereon at least a recording layer comprising (a) a heat-responsive microcapsule having encapsulated therein an organic silver salt; (b) a developer for the organic silver salt and (c) a water-soluble binder. A heat recording energy per unit area of 60 mJ/mm
2
is disclosed in the invention examples.
Printing apparatuses for the production of labels using tape are disclosed in EP-A-322 918, EP-A-322 919 and EP-A-0267 890. These printers each include a printing device having a cassette bay for receiving a cassette or tape holding case. In EP-A-0267 890, the tape holding case houses an ink ribbon and a substrate tape, the latter comprising an upper imaging layer secured to a backing layer by adhesive. In EP-A-322 918 and EP-A-322 919, the tape holding case houses an ink ribbon, a transparent imaging tape and a double-sided adhesive tape which is secured at one of its adhesive coated sides to the image tape after printing and which has a backing layer peelable from its other adhesive coated side. With both these apparatus, the image transfer medium (ink ribbon) and an imaging tape (substrate) are in the same cassette.
EP 622 217 discloses a method for making an image by means of a direct thermal imaging element, comprising on a support a thermosensitive layer containing an organic silver salt and a reducing agent, the imaging element being imagewise heated by means of a thermal head having energizable heating elements, characterised in that the activation of the heating elements is executed line by line with a line-duty-cycle &Dgr; representing the ratio of activation time to total line time, according to the equation
P≦P
max
=3.3 W/mm
2
+(9.5 W/mm
2
×&Dgr;)
where P
max
is the maximal value over all heating elements of the time averaged power density P (expressed in W/mm
2
) dissipated by a heating element during a line time.
Labels produced with monosheet direct thermal materials based on leuco-dyes have a well-known propensity to fade when exposed to light and thermal dye transfer systems are expensive to assemble and produce waste due to the disposal of the donor lint resulting in ecological objections.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to provide a label-printing process for producing labels from monosheet imaging tape which do not fade.
It is therefore a further object of the present invention to provide a label-printing process for printing labels from monosheet imaging tape which have excellent light stability and image tone.
Further objects and advantages of the invention will become apparent from the description hereinafter.
SUMMARY OF THE INVENTION
It has been surprisingly found that labels produced using monosheet substantially light-insensitive transparent imaging materials based on organic silver salts do not fade and have excellent light stability and image tone. It has also been surprisingly found that the image density is primarily dependent upon the heating energy used to produce a dot, for which the term “dot energy” will be used, regardless of how the heating power is supplied.
The above-mentioned objects are realised by a label-printing process for obtaining a desired optical density and a desired colour tone with a substantially light-insensitive elongated imaging material comprising:
selecting an elongated imaging material, the selected elongated imaging material having a support and a thermosensitive element;
supplying image data to a processing unit of a thermal printer including a printhead having energizable heating elements arranged in a column C;
converting the image data which are not zero into at least one activation pulse per pixel to be printed;
energising the heating elements printing-line by printing-line adjacent to the selected elongated imaging material thereby producing an image;
transporting the selected thermographic sheet material past and adjacent to the printhead in a transport direction with a transport system;
forming an image dot with a heat energy of 50 to 200 mJ/mm
2
of heating element surface area;
wherein the thermosensitive element contains a substantially light-insensitive organic silver salt, a reducing agent therefor in thermal working relationship therewith and a binder; and the thermosensitive element excludes a colourless or light coloured dye precursor and also excludes an encapsulated organic silver salt in a heat-responsive microcapsule.
An apparatus for the printing of labels is also provided according to the present invention comprising:
a selector of a substantially light-insensitive elongated imaging material, the selected elongated imaging material having a support and a thermosensitive element;
a source of image data to a processing unit of a thermal printer including a printhead having energizable heating elements arranged in a column C;
a converter of the image data which are not zero into at least one activation pulse per pixel to be printed;
an energizer of the heating elements printing-line by printing-line adjacent to the selected substantially light-insensitive elongated imaging material thereby producing an image;
a transport system to transport the imaging material past and adjacent to the printhead in a transport direction with said transport system;
an image dot former with a heat energy of 50 to 200 mJ/mm
2
of heating element surface area;
wherein the thermosensitive element contains a substantially light-insensitive organic silver salt, a reducing agent therefor in thermal working relationship therewith and a binder; and the thermosensitive element excludes a colourless or light coloured dye precursor and also excludes an encapsulated organic silver salt in a heat-responsive microcapsule. With the substantially light-insensitive elongated imaging material, a desirable colour tone is a neutral tone as defined by CIELAB a* and b*-values and a desirable optical density, D
vis
is above 1.2 and even more desirably above 1.5.
Preferred embodiments of the present invention are disclosed in the detailed description of the invention.


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patent: 5216438 (1993-06-01), Nakao et al.
patent: 5411929 (1995-05-01), Ford et al.
patent: 5489567 (1996-02-01), Koshizuka et al.
patent: 5525571 (1996-06-01), Hosoi
patent: 5633670 (1997-05-01), Kwak
patent: 5765954 (1998-06-01), Nunokawa et al.
patent: 5826994 (1998-10-01), Palmer
patent: 6028029 (2000-02-01), Takeuchi
patent: 0479578 (1992-04-01), None
patent: 0622217 (1994-11-01), None
patent: 0687572 (1995-12-01), None
patent: 0736799 (1996-10-01)

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