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
2001-11-06
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
06313065
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to improved substantially light-insensitive black and white monosheet thermographic recording materials.
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 thermography a visible image pattern is formed by image-wise heating of a recording material containing matter that by chemical or physical process changes colour or optical density. Most of the “direct” thermographic recording materials are of the chemical type. On heating to a certain conversion temperature, an irreversible chemical reaction takes place and a coloured image is produced.
U.S. Pat. No. 3,846,136 discloses that the thermosensitive or other hardenable layers in thermographic materials can be hardened with organic or inorganic hardening agents such as aldehydes and blocked aldehydes, ketones, carboxylic and carbonic acid derivatives, sulfonate esters, sulfonyl halides and vinyl sulfonyl ethers, active halogen compounds, epoxy compounds, aziridines, active olefins, isocyanates, carbodiimides, mixed function hardeners and polymeric hardeners such as oxidized polysaccharides like dialdehyde starch and oxy-guargum and the like. However, this disclosure is merely an invitation to experiment, because almost all hardening agents known for gelatino silver halide emulsion photographic-sensitive materials processed by wet treatment are enumerated and there is no example using them.
WO 95/12495 (=U.S. Pat. No. 5,710,095) discloses a method of recording an image by image-wise heating a recording material, the recording material comprising on the same side of a support, called the heat sensitive side, (1) one or more layers comprising an imaging composition essentially consisting of (i) a substantially light-insensitive organic silver salt being in thermal working relationship with (ii) a reducing agent, and (2) at the same side covering the imaging composition a protective layer, characterized in that the image-wise heating proceeds with a thermal head contacting the heat-sensitive side and through the protective layer mainly comprising a cured polymer or cured polymer composition. In a preferred embodiment thereof, the protective layer contains hydrophilic polymers having active hydrogen atoms at least part of which has reacted with hardening agents selected from the group consisting of polyisocyanates, polyepoxides, aldehydes and hydrolysed tetraalkyl orthosilicates.
U.S. Pat. No. 5,468,603 discloses a thermographic emulsion layer containing an organic silver salt, a polyisocyanate, a binder, e.g. BUTVAR™ B-79, and a large selection of reducing agents, with a sterically hindered bisphenols being preferred, provided with a protective layer comprising a polymeric fluorinated surfactant. DESMODUR™ 3300 is disclosed in U.S. Pat. No. 5,468,603 for photothermographic emulsion layers.
U.S. Pat. No. 5,468,228 discloses a thermographic emulsion layer containing an organic silver salt, a binder, e.g. BUTVAR™ B-79, a substituted propene compound and a large selection of reducing agents, with a sterically hindered bisphenosl being preferred. DESMODUR™ 3300 is disclosed in U.S. Pat. No. 5,468,228 for photothermographic emulsion layers.
In coating thermographic materials from solvents with protective layers it is desirable for economic and logistical reasons to coat the organic silver salt-containing layer simultaneously with a protective layer. This requires hardening of both layers to prevent significant interfacial mixing thereof. However, the use of such hardeners was found to affect significantly the image gradation of the resulting materials.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to provide a substantially light-insensitive black and white thermographic recording material with a hardened thermosensitive element.
It is therefore another object of the present invention to provide a substantially light-insensitive black and white thermographic recording materials which upon printing exhibits an image gradation which is not significantly affected by the thermosensitive element being hardened.
Further objects and advantages of the invention will become apparent from the description hereinafter.
SUMMARY OF THE INVENTION
Surprisingly it has been found that this adverse effect on image gradation upon hardening the thermosensitive element could be avoided by the use of 1,2-dihydroxy-benzene derivatives as reducing agents in combination with specific polyisocyanates as hardeners, the gradation of substantially light-insensitive black and white monosheet thermographic recording materials based on substantially light-insensitive organic silver salts and reducing agents therefor being substantially unaffected by the hardening process.
The above-mentioned objects are realized by a substantially light-insensitive black and white monosheet thermographic recording material comprising a support and a thermosensitive element provided with a protective layer, the thermosensitive element containing a substantially light-insensitive organic silver salt, a 1,2-dihydroxy-benzene derivative in thermal working relationship therewith and a first polymer having active hydrogen atoms at least part of which has reacted with a first polyisocyanate selected from the group consisting of: hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanat, naphthylene diisocyanate and triphenylmethane-p,p′,p″-trityl triisocyanate; and the protective layer being exclusive of fluorine-containing compounds.
A recording process is further provided according to the present invention comprising the steps of: (i) bringing an outermost layer of the above-mentioned thermographic recording material in proximity with a heat source; and (ii) applying heat from the heat source imagewise to the recording material while maintaining proximity to the heat source to produce an image; and (iii) removing the recording material from the heat source.
Preferred embodiments of the invention are disclosed in the dependent claims.
DETAILED DESCRIPTION OF THE INVENTION
In a preferred embodiment of the recording process, according to the present invention, the heat source is a thermal head with a thin film thermal head being particularly preferred.
Definitions
By substantially light-insensitive is meant not intentionally light sensitive.
By substantially solvent-free aqueous medium is meant that solvent, if present, is present in amounts below 10% by volume of the aqueous medium. 1,2-dihydroxy-benzene derivatives are compounds having a benzene ring substituted with two hydroxy groups ortho to one another.
By a polymer having active hydrogen atoms is meant a polymer having substituents with hydrogen atoms which readily react such as hydroxy groups, thiol groups, carboxy groups, —N—H groups, amino groups, amido groups etc.
By polyisocyanate is meant a compound having at least two isocyanate groups which may or may not be blocked with groups which are readily displaced during a hardening process, wherein the polyisocyanate reacts with the active hydrogen atoms of a polymer having active hydrogen atoms.
The term fluorine-containing compounds includes all compounds containing fluorine and all compounds with fluorine-containing compounds as impurities and includes polymeric fluorinated surfactants such as disclosed in U.S. Pat. No. 5,468,603. U.S. Pat. No. 5,468,603 discloses a polymeric fluorinated surfactant containing at least three different groups within the polymer chain derived from reactive monomers, the monomers comprising: (a) a fluorinated, ethylenically unsaturated monomer; (b) a hydroxyl-containing, ethylenically unsaturated monomer; and (c) a polar, ethylenically unsaturated monomer; which is produced by addition copolymerization.
Reducing Agents
Suitable organic reducing agents according to the present invention are 1,2-dihydroxybenzene derivatives, such as catechol; 3-(3,4-dihydroxyphenyl) propionic acid; 3,4-dihydroxybenzoic acid and its esters; gallic
Horsten Bartholomeus Cyriel
Jansen Guy Denis
Slabbinck Peter
AGFA-GEVAERT
Hess Bruce H.
Leydig , Voit & Mayer, Ltd.
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