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
1999-07-12
2001-04-03
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...
C503S202000, C503S212000
Reexamination Certificate
active
06211115
ABSTRACT:
FIELD OF THE INVENTION
The present invention concerns black and white substantially light-insensitive thermographic recording materials containing a substantially light-insensitive organic silver salt and a novel reducing agent.
BACKGROUND OF THE INVENTION
Thermal imaging or thermography is a recording process wherein images are generated by the use of thermal energy. Most of the “direct” thermographic recording materials are of the chemical type in which upon heating an irreversible chemical reaction takes place and a coloured image is produced.
EP-A 248 405 discloses a thermal recording material with a colour-developing layer, which contains an electron acceptor and an electron donor in addition to the usual additives, characterized in that the electron acceptor is a metallic double salt of a long-chain fatty acid with 16 to 35 carbon atoms and the electron donor is a polyhydric aromatic compound of formula (I):
wherein R is an alkyl group with 18 to 35 carbon atoms,
wherein R
1
is a C
18
- to C
35
-alkyl group, n is an integer of 2 or 3, —X— is —CH
2
—, —CO
2
—, —CO—, —O—, —CONH—, —CO(R′)N— (wherein R′ is a C
18
- to C
35
-group), —SO
2
—, —SO
3
— or —SO
2
NH—. Example 4 concerns a thermosensitive recording material with a colour-developing layer containing silver aluminium double salt of octadecyl 2,3,4-trihydroxybenzoate.
EP-A 599 580 discloses a thermal recording sheet comprising, in order: (a) a substrate; (b) an intermediate layer which comprises a pigment having an oil absorption according to Japanese Industrial Standard (JIS) K501 of 100 mL/100 g or less; and (c) a thermal color developing layer which comprises a leuco dye type chromogenic component consisting of a leuco dye and an organic color developer and a metal chelate type chromogenic component consisting of an electron acceptor and an electron donor, wherein: the organic color developer is at least one of compounds of formula (I) and formula (II):
wherein R is propyl, isopropyl, or butyl;
the electron acceptor is a metal double salt of a fatty acid having 16 to 35 carbon atoms; and the electron donor is a polyhydric aromatic compound of formula (III), which is the same as formula (I) of EP-A 248 405.
JP 09142029 discloses a recording layer containing at least one kind of aminobenzene sulfonamide derivative shown by formula I, at least one kind of multi-value phenolic compound, shown by formula II [same formula as formula I of EP-A 248 405 wherein X═—CH
2
—, —CO
2
—, —CO—, —O—, —CONH—, —CON(R′)—] and a high class aliphatic metallic salt, is formed on the supporting body of a heat sensitive recording body.
The thermosensitivity of organic silver salt/reducing agent systems is dependent upon the choice of reducing agent. However, increased thermosensitivity is generally associated with poorer image gradation i.e. dependence of image density upon applied thermal energy, reduced stability and poorer image colour. There is therefore a need for reducing agents which increase the thermosensitivity of organic silver salt/reducing agent systems without substantially affecting the gradation, stability and image colour of prints made therewith.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to provide thermographic recording materials with increased thermosensitivity without significantly affecting the gradation, stability and image colour of prints made therewith.
Further objects and advantages of the invention will become apparent from the description hereinafter.
SUMMARY OF THE INVENTION
Surprisingly it has been found that prints of thermographic recording materials containing novel 3,4-dihydroxyphenyl compounds exhibit increased thermosensitivity without significantly affecting the gradation, stability and image colour of prints made therewith. In fact there is even a marginal improvement in image colour.
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 containing a substantially light-insensitive organic silver salt, 1,2-dihydroxyphenyl-compound in thermal working relationship therewith and a binder, wherein the 1,2-dihydroxyphenyl-compound is represented by formula (I):
where n is 0 or 1; R is —(C═O)R
1
, —(C═O)NR
1
R
2
, —CN, —SO
3
R
2
, SO
2
R
2
, —SOR
2
, —SO
2
NR
2
R
3
or —PO
3
R
2
R
3
; R
1
is H or an alkyl group with 12 or less carbon atoms; and R
1
and R
3
are independently H or an alkyl or an aryl group; and R
1
and R
2
can together provide the atoms to close a carbocyclic or heterocyclic ring; and R
2
and R
3
can together represent the atoms to close a carbocyclic or heterocyclic ring.
A recording process is also provided comprising the steps of: (i) providing the above-described substantially light-insensitive black and white monosheet thermographic recording material; (ii) bringing an outermost layer of the recording material into proximity with a heat source; (iii) applying heat from a heat source image-wise to the recording material while maintaining proximity to the heat source to produce an image; and (iv) removing the recording material from the heat source.
Preferred embodiments of the present invention are disclosed in the detailed description of the invention.
DETAILED DESCRIPTION OF THE INVENTION
According to a preferred embodiment of the recording process according to the present invention the heat source is a thermal head.
Organic reducing agents
The organic reducing agent used in the thermographic recording materials of the present invention is a 2,3,4-trihydroxyphenyl-compound represented by formula (I). The alkyl group with 12 or less carbon atoms of R
1
may also be a substituted alkyl group with 12 or less carbon atoms. The alkyl or aryl groups of R
2
or R
3
may also be substituted. In a preferred embodiment the —(CH═CH)
n
R group has a Hammett substituent constant &sgr;
p
greater than 0.25. Hammett substituent constants are, for example, listed on pages 28 and 29 of Advances in Linear Free Energy Relationships, edited by N. B. Chapman and J. Shorter and published by Plenum Press, London in 1972. Particularly preferred —(CH═CH)
n
R groups are formyl, oxo-alkyl, oxo-aryl, cyano, carbamido, diphenoxyphosphoryl, alkylsulfinyl, alkylsulfonyl and sulfonylamino groups.
Preferred reducing agents for use in the present invention are selected from the group consisting of: consisting of: 2,3,4-trihydroxy-acetophenone, 2,3,4-trihydroxy-propionophenone, 2,3,4-trihydroxybenzaldehyde and 2,3,4-trihydroxybenzonitrile.
Compounds according to formula(I) are long known, the synthesis of a wide range of 2,3,4-trihydroxy-phenyl-oxo-derivatives, for example being described in Beilsteins Handbuch der Organischen Chemie, Vierte Auflage, Achter Band, Springer Verlag, Berlin (1925): p. 388, 393, 398, 399, 400, 417, 684 and 685. 2,3,4-trihydroxy-benzaldehyde, 2′,3′,4′-trihydroxyacetophenone, 2,3,4-trihydroxybenzophenone are all commercially available from Aldrich and can be used to produce other derivatives such as 2,3,4-trihydroxybenzonitrile by methods known to synthetic chemists.
Auxiliary reducing agents
The reducing agents used in accordance with the present invention being considered as primary or main reducing agents may be used in conjunction with so-called auxiliary reducing agents. Such auxiliary reducing agents are e.g. hydroquinone or catechol substituted with strongly electron-withdrawing groups such as sulfonic acid groups; hydrazides such as disclosed in EP-A 762 196, sulfonyl hydrazide reducing agents such as disclosed in U.S. Pat. No. 5,464,738; trityl hydrazides and formyl-phenyl-hydrazides such as disclosed in U.S. Pat. No. 5,496,695; trityl hydrazides and formyl-phenyl-hydrazides with diverse auxiliary reducing agents such as disclosed in U.S. Pat. No. 5,545,505, U.S. Pat. No. 5,545,507 and U.S. Pat. No. 5,558,983; acrylonitrile compounds as disclosed in U.S. Pat. No. 5,545,515 and U.S. Pat. No. 5,635,339; 2-substituted malondialdehyde compou
Horsten Bart
Loccufier Johan
Slabbinck Peter
AGFA-GEVAERT
Baker & Botts L.L.P.
Hess Bruce H.
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