Record receiver having plural interactive leaves or a colorless – Having a colorless color-former – developer therefor – or... – Method of use – kit – or combined with marking instrument or...
Reexamination Certificate
1999-11-30
2002-06-11
Hess, Bruce H. (Department: 1774)
Record receiver having plural interactive leaves or a colorless
Having a colorless color-former, developer therefor, or...
Method of use, kit, or combined with marking instrument or...
C503S200000, C503S202000, C503S212000, C503S226000
Reexamination Certificate
active
06403527
ABSTRACT:
FIELD OF THE INVENTION
The present invention concerns the use of substantially light-insensitive mono sheet direct thermal imaging materials for producing labels.
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 print head, 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 mono sheet 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.
WO 87/03541A discloses a recording material which comprises (a) at least one di- or triarylmethane dye precursor compound possessing within its di- or triarylmethane structure an aryl group substituted in the ortho position to the meso carbon atom with an S-containing moiety ring-closed on the meso carbon atom selected from a thiolactone, dithiolactone and thioether moiety and (b) a Lewis acid material capable of opening said S-containing moiety whereby said compound is rendered colourless, which Lewis acid material can be an organic silver salt. U.S. Pat. No. 5,750,464 and U.S. Pat. No. 5,411,929A disclose refinements of the concept of WO 87/03541A in which the organic silver salt opens the S-containing moiety rendering said compound containing the S-containing moiety colourless.
U.S. Pat. No. 3,708,378 provides a single integral imaging sheet that in a single rapid operation may be converted to a label carrying the desired retro-reflective informative symbols. It discloses a light-stable heat-sensitive imaging sheet on which retro-reflective images may be rapidly defined comprising (1) a support layer, (2) a uniform continuous mono layer of retro-reflective elements disposed on one side of the support layer, and (3) an imaging layer disposed over the retro-reflective elements comprising, in uniform distribution throughout the layer, a light-stable heat-sensitive material that is rapidly chemically modified as to its light-transmitting properties by exposure to heat, the imaging layer being selected from the group consisting of (1) normally transparent light-stable layers that are adapted to be converted to transparent when exposed to heat and (2) normally opaque light-stable layers that are adapted to be converted to transparent when exposed to heat, whereby light beamed against the sheet will be retro-reflected only by retro-reflective elements exposed through the transparent areas. Examples 1 and 2 both disclose a silver behenate-based imaging layer using methyl gallate as a reducing agent therefore.
U.S. Pat. No. 3,708,378 contains no teaching about the use of organic silver salt-based materials for conventional labelling applications. The patent literature over thermographic materials for labelling applications in the intervening twenty-eight years has exclusively concerned other imaging systems mono sheet materials such as the above-mentioned leuco-dye systems.
Labels produced with mono sheet thermographic materials based on leuco-dyes have a well-known propensity to fade when exposed to light, the thermographic materials disclosed in U.S. Pat. No. 5,750,464, U.S. Pat. No. 5,411,929A and WO 87/03541A concern colour removal rather than colour formation, 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 mono sheet direct thermal imaging materials for labelling applications which do not fade.
It is therefore a further object of the present invention to provide substantially light-insensitive mono sheet direct thermal imaging materials for labelling applications with 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 substantially light-insensitive mono sheet direct thermal imaging materials based on organic silver salts do not fade and have excellent light stability and image tone.
The above-mentioned objects are realized by a process for using a substantially light-insensitive mono sheet direct thermal imaging material for producing a non-retro-reflective readable object attachable to a second object for information purposes, the mono sheet direct thermal imaging material including a support, a thermosensitive element and an attaching layer, wherein the thermosensitive element contains a substantially light-insensitive organic silver salt, a reducing agent therefore in thermal working relationship therewith, a binder and does not contain a di- or triarylmethane dye precursor compound possessing within its di- or triarylmethane structure an aryl group substituted in the ortho position to the meso carbon atom with an S-containing moiety ring-closed on the meso carbon atom selected from a thiolactone, dithiolactone and thioether moiety.
Preferred embodiments of the present invention are disclosed in the detailed description of the invention.
DETAILED DESCRIPTION OF THE INVENTION
Definitions
A label according to the present invention is a non-retro-reflective readable object attachable to a second object for information purposes.
A direct thermal imaging material is a material in which coloration is obtained in areas of the material to which heat is supplied either directly by an external heat source or indirectly by heat produced upon absorption of infra-red radiation in these areas of the material.
Transparent means capable of transmitting visible light without appreciable scattering.
By substantially light-insensitive is meant not intentionally light sensitive.
The descriptor aqueous in the term aqueous medium for the purposes of the present invention includes mixtures of water-miscible organic solvents such as alcohols e.g. methanol, ethanol, 2-propanol, butanol, iso-amyl alcohol etc.; glycols e.g. ethylene glycol; glycerine; N-methyl pyrrolidone; methoxypropanol; and ketones e.g. 2-propanone and 2-butanone etc. with water in which water constitutes more than 50% by weight of the aqueous medium with 65% by weight of the aqueous medium being preferred and 80% by weight of the aqueous being particularly preferred.
The encapsulated organic silver salt in a heat-responsive microcapsule disclosed in EP 736 799A whose use in the thermosensitive element of the present invention is preferably excluded has a wall which isolates the substances incorporated therein from the exterior at room temperature, but becomes permeable without being destroyed when pressure is applied or when heated. The microcapsule can be prepared by any of interfacial polymerization, internal polymerization and external polymerization.
Interfacial polymerization comprises emulsifying a core substance comprising an organic silver salt that has been dissolved or dispersed in an organic solvent in an aqueous solution having a water-soluble polymer therein and then forming a polymer wall around the emulsified oil droplets of the core substance.
A leuco-dye is a colourless or weakly coloured compound derived from a dye. Colourless or light coloured dye precursor leuco-dye systems whose use in the thermosensitive element of the present invention is excluded include leuco triarylmethane, indolyl phthalide, diphenylmethane, 2-anilinofluoran, 7-anilinofluoran, xanthene and spiro compounds such as disclosed in EP-A 754 564.
By the term “heat so
Horsten Bartholomeus Cyriel
Jansen Guy Denis
Agfa-Gevaert
Hess Bruce H.
Leydig , Voit & Mayer, Ltd.
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