Title: Stabilizers for use in substantially light-insensitive thermographic recording materials
Abstract: A substantially light-insensitive black and white monosheet thermographic recording material comprising a support and a thermosensitive element, the thermosensitive element containing a substantially light-insensitive organic silver salt, an organic reducing agent therefor in thermal working relationship therewith, a binder and at least one stabilizer selected from the group consisting of 1-phenyl-5-mercaptotetrazole compounds in which the phenyl group is substituted with a substituent containing an optionally substituted aryl group; and ##STR1##
Patent Number: 6,908,731 Issued on 06/21/2005 to Geuens, et al.
| Inventors:
|
Geuens; Ingrid (Emblem, BE);
Uyttendaele; Carlo (Mortsel, BE);
Hoogmartens; Ivan (Wilrijk, BE);
Loccufier; Johan (Zwijnaarde, BE)
|
| Assignee:
|
Agfa-Gevaert (Mortsel, BE)
|
| Appl. No.:
|
712189 |
| Filed:
|
November 13, 2003 |
Foreign Application Priority Data
| Current U.S. Class: |
430/618; 430/611; 430/620; 430/964; 430/965 |
| Intern'l Class: |
G03C 001/34; G03C001/49.4 |
| Field of Search: |
430/611,618,620,964,965
|
References Cited [Referenced By]
U.S. Patent Documents
| 4201582 | May., 1980 | White.
| |
| 5686228 | Nov., 1997 | Murray et al.
| |
| 5922529 | Jul., 1999 | Tsuzuki et al.
| |
| 5958668 | Sep., 1999 | Matsumoto et al.
| |
| 6348308 | Feb., 2002 | Loccufier et al.
| |
| 2001/0038977 | Nov., 2001 | Katoh.
| |
| 2002/0155401 | Oct., 2002 | Yamaguchi.
| |
| Foreign Patent Documents |
| 0 218 385 | Apr., 1987 | EP.
| |
| 0 256 820 | Feb., 1988 | EP.
| |
| 0 295 507 | Dec., 1988 | EP.
| |
| 0 713 133 | May., 1996 | EP.
| |
| 0 807 850 | Nov., 1997 | EP.
| |
| 0 838 722 | Apr., 1998 | EP.
| |
| 0 897 130 | Feb., 1999 | EP.
| |
| 0 901 040 | Mar., 1999 | EP.
| |
| 0 933 672 | Aug., 1999 | EP.
| |
| 1 079 269 | Feb., 2001 | EP.
| |
| 1 164 421 | Dec., 2001 | EP.
| |
| WO 94/1636/1 | Jul., 1994 | WO.
| |
| WO 96/1021/3 | Apr., 1996 | WO.
| |
| WO 01/9694/4 | Dec., 2001 | WO.
| |
Other References
Search Report for EP 02 10 2586 (Feb. 27, 2003).
|
Primary Examiner: Schilling; Richard L.
Attorney, Agent or Firm: Leydig, Voit & Mayer, Ltd.
Parent Case Text
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS
This application claims the benefit of U.S. Provisional Application No. 60/429,284
filed Nov. 26, 2002, which is incorporated by reference. In addition, this application
claims the benefit of European Application No. 02102586.1 filed Nov. 14, 2002,
which is also incorporated by reference.
Claims
1. A substantially light-insensitive black and white monosheet thermographic
recording material comprising a support and a thermosensitive element, said thermosensitive
element containing a substantially light-insensitive organic silver salt, an organic
reducing agent therefor in thermal working relationship therewith, a binder and
at least one stabilizer selected from the group consisting of 1-phenyl-5-mercaptotetrazole
compounds in which said phenyl group is substituted with a substituent containing
an optionally substituted aryl group; and
##STR44##
2. Substantially light-insensitive black and white monosheet thermographic recording
material according to claim 1, wherein said substituent for said phenyl group is
selected from the group consisting of -NHCO-phenyl, -NHCO-(1-naphthyl), -NHCO-(2-naphthyl),
-NHCONH-phenyl, -NHSO
2-phenyl, -NHSO
2-(1-naphthyl), -NHSO
2-(2-naphthyl),
-SO
2NH-phenyl, -CONH-phenyl, -CONH-(1-naphthyl), -CONH -(2-naphthyl),
-NHCO-(2-thienyl) and -NHCONHCO-phenyl groups.
3. Substantially light-insensitive black and white monosheet thermographic recording
material according to claim 1, wherein said optional substituent for said aryl
group is selected from the group consisting of halogen atoms, ester groups, -OCOO-alkyl
groups, -NHCOO-alkyl groups, -NHOC-alkyl groups, -CONH-alkyl groups, -S-alkyl groups
and mercapto, alkyl, alkoxy, nitrile, acyl and nitro groups.
4. Substantially light-insensitive black and white monosheet thermographic recording
material according to claim 1, wherein said 1-phenyl-5-mercaptotetrazole compound
in which said phenyl group is substituted with a substituent containing an optionally
substituted aryl group is represented by formula (I):
##STR45##
wherein R
1 is -NH-(C═O)-Ar, -NH-(C═O)-NH-Ar, -NH-(C═O)-O-Ar,
-O-(C═O)-NH -Ar, -(C═O)-NH-Ar, -NH-SO
2-Ar, -O-(C═O)-Ar,
-O-(C═O)-O-Ar, -(C═O)-Ar, -(C═O)-O-Ar, -SO
2-Ar,
-SO
2-NH-Ar, or -Ar; and Ar is an optionally substituted aryl or heteroaryl group.
5. Substantially light-insensitive black and white monosheet thermographic recording
material according to claim 1, wherein said 1-phenyl-5-mercaptotetrazole compound
in which said phenyl group is substituted with a substituent containing an optionally
substituted aryl group is represented by formula (II):
##STR46##
wherein R
2 is -NH-(C═O)-Ar, -NH-(C═O)-NH-Ar, -NH-(C═O)-O-Ar,
-O-(C═O)-NH-Ar, -(C═O)-NH-Ar, -NH-SO
2-Ar, -O-(C═O)-Ar,
-O-(C═O)-O-Ar, -(C═O)-Ar, -(C═O)-O-Ar, -SO
2-Ar,
-SO
2-NH-Ar, or -Ar; and Ar is an optionally substituted aryl or heteroaryl group.
6. Substantially light-insensitive black and white monosheet thermographic recording
material according to claim 4, wherein said aryl or heteroaryl group is substituted.
7. Substantially light-insensitive black and white monosheet thermographic recording
material according to claim 1, wherein said at least stabilizer is selected from
the group consisting of:
##STR47##
##STR48##
##STR49##
8. Substantially light-insensitive black and white monosheet thermographic recording
material according to claim 1, wherein said thermosensitive element further comprises
an optionally substituted benzotriazole.
9. Substantially light-insensitive black and white monosheet thermographic recording
material according to claim 5, wherein said aryl or heteroaryl group is substituted.
Description
FIELD OF THE INVENTION
The present invention concerns stabilizers for use in substantially light-insensitive
thermographic recording materials.
BACKGROUND OF THE INVENTION
Thermography is an image-forming process including a heating step and
hence includes photothermography in which the image-forming process includes image-wise
exposure and direct thermal processes in which the image-forming process includes
an image-wise heating step. In direct thermal printing a visible image pattern
is produced by image-wise heating of a recording material.
EP-A 0 218 385 discloses a thermally developable light-sensitive material which
has at least one light-sensitive silver halide containing layer on a support and
which further contains a compound represented by the general formula (I):
wherein X is the residue of the development restrainer; J is a divalent linkage;
F is an immobilizing group that is capable of reducing the diffusibility of the
compound of formula (I) or a silver salt or silver complex thereof during thermal
development; m is 0 or 1; and n is an integer of 1 to 3. EP-A 0 218 385 discloses
the following 1-phenyl-5-mercaptotetrazole compounds in which the phenyl group
is substituted with a substituent containing an optionally substituted aryl group:
##STR2##
EP-A 0 256 820 discloses a thermal developing light-sensitive material comprising
a support and, provided thereon, photographic structural layers comprising at least
one layer containing light-sensitive-silver halide, said photographic structural
layer comprising a compound represented (1): Formula (1) X
1-L
1-A
wherein X
1 represents a residual group of a photographic restrainer,
L
1 is a mere bonding hand or a divalent group and A is selected from
the group consisting of a hydrogen atom, an amino group, a hydroxyl group, a carboxyl
group or a salt thereof, a sulfo group or a salt thereof and a sulfin group or
a salt thereof, and a compound represented by general formula (2): Formula (2) X
2-L
2-B
wherein X
2 represents a residual group of a photographic restrainer,
L
2 is a divalent group and B is a ballast group. EP-A 0 256 820 discloses
the following 1-phenyl-5-mercaptotetrazole compounds in which the phenyl group
is substituted with a substituent containing an optionally substituted aryl group:
##STR3##
EP-A 0 295 507 discloses a process for the production of colour images by the
photographic dye diffusion process in which a first light-sensitive sheet material
is imagewise exposed, at least one of said first light-sensitive sheet material
and a second light-insensitive sheet material is moistened with an aqueous liquid
and the two sheet materials are together heated to 50° C. to 100° C.
with their coated surfaces in contact and then separated, said first sheet material
containing, on a layer support, at least one light-sensitive silver halide emulsion
layer and at least one non-diffusible colour providing compound which is capable
of being decomposed imagewise in the process of development to release a diffusible
dye and said second sheet material containing a salt of a strong organic base and
a weak acid, wherein said first sheet material contains a combination of compounds
corresponding to the following formulae I and II:
##STR4##
wherein R
1 denotes hydrogen, alkyl with up to 6 carbon atoms,
halogen, hydroxy, alkoxy or substituents which together form a condensed benzene
ring, and
##STR5##
wherein R
2 denotes a group which can be split off in the process
of development of the material and R
3 denotes hydrogen, halogen, alkyl
with up to 4 carbon atoms, alkoxy, carboxy, carbalkoxy, carbonamido or sulphonamido.
EP-A 0 295 507 also discloses the following 1-phenyl-5-mercaptotetrazole compounds
in which the phenyl group is substituted with a substituent:
##STR6##
EP-A 0 838 722 discloses a photothermographic material comprising (a) a reducible
silver source, (b) a photocatalyst, (c) a reducing agent, (d) a binder, and (e)
at least one compound of the following general formula (I): X-L
1-D wherein
D is an electron donative group of atoms, with the proviso that where D is a hydrazino
group which is not a part of a semicarbazido group, no oxo group is substituted
to the carbon atom which is directly attached to a nitrogen atom of the hydrazine,
X ia a group capable of promoting adsorption to silver halide, and L
1
is a valence bond or a linking group. EP-A 0 838 722 discloses the following 1-phenyl-5-mercaptotetrazole
compounds in which the phenyl group is substituted with a substituent containing
an optionally substituted aryl group:
##STR7##
EP-A 0 218 385, EP-A 0 256 820, EP-A 0 295 507 and EP-A 0 838 722 all disclose
the use of 1-phenyl-5-mercaptotetrazole compounds in which the phenyl group is
substituted with a substituent containing an optionally substituted aryl group.
However, the technology of substantially light-insensitive thermographic materials
containing substantially light-insensitive organic silver salts is substantially
different from that of photothermographic materials containing substantially light-insensitive
organic silver salts, despite the fact that in both cases the image results from
the reduction of organic silver salts. However, this a superficial similarity masking
the fact that the realization of the species which catalyze this reduction is completely
different, being image-wise exposure of photosensitive silver halide-containing
photo-addressable thermally developable elements in the case of photothermographic
recording materials and image-wise heating of thermosensitive elements which do
not contain photosensitive silver halide in the case of thermographic recording
materials. This difference in technology is further underlined by the nature of
the ingredients used in the two types of materials, the most significant difference
being the absence of photosensitive silver halide and spectral sensitizing agents
in substantially light-insensitive thermographic recording materials, but also
reflected in the different reducing agents used, stronger reducing agents being
used in substantially light-insensitive thermographic recording materials, the
different stabilizers, the different toning agents etc. Furthermore, the thermal
development processes themselves are significantly different in that the whole
material is heated at temperatures of less than 150° C. for periods of seconds
(e.g. 10s) in the case of photothermographic recording materials, whereas in the
case of substantially light-insensitive thermographic recording materials the materials
are image-wise heated at much higher temperatures for periods of ms (e.g. 10-20
ms). Moreover, thermal development in substantially light-insensitive thermographic
recording materials involves the liquid crystalline phases of the organic silver
salts, whereas this is not the case in the thermal development step in the case
of photothermographic recording materials even when using the same organic silver
salts. Realization of a neutral image tone is a major problem in the case of substantially
light-insensitive thermographic recording materials due to the very short heating
times, whereas it is much less of a problem in photothermographic recording materials
due to the much longer heating times.
EP-A 0 713 133 discloses a thermal imaging system consisting of (i) a donor
element comprising on a support a donor layer containing a binder and a thermotransferable
reducing agent capable of reducing a silver source to metallic silver and (ii)
a receiving element comprising on a support a receiving layer comprising a silver
source, capable of being reduced by means of heat in the presence of a reducing
agent, a binder and a stabiliser selected from the group consisting of benzotriazoles,
heterocyclic mercaptanes, sulphinic acids, 1,3,4-triazo-indinolines, 1,3-dinitroaryl
compounds, 1,2,3-triazoles, phthalic acids and phthalic acid derivatives. EP-A
0 713 133 discloses that preferred heterocyclic mercaptanes are mercaptotetrazoles
corresponding to the following general formula (C):
##STR8##
and discloses the following 1-phenyl-5-mercapto-tetrazole compounds:
##STR9##
EP-A 0 901 040 discloses a substantially light-insensitive monosheet recording
material comprising a support and a thermosensitive element containing a substantially
light-insensitive organic silver salt, an organic reducing agent therefor in thermal
working relationship therewith and a binder, characterized in that said thermosensitive
element further contains an unsaturated carbocyclic or heterocyclic stabilizer
compound substituted with a -SA group where A is hydrogen, a counterion to compensate
the negative charge of the thiolate group or a group forming a symmetrical or an
asymmetrical disulfide and said recording material is capable of producing prints
with a numerical gradation value defined as the quotient of the fraction (2.5-0.1)/(E
2.5-E0.1)
greater than 2.3, where E
2.5 is the energy in Joule applied in a dot
area of 87 μm×87 μm of the imaging layer that produces an optical
density value of 2.5, and E
0.1, is the energy in Joule applied in a
dot area of the imaging layer material that produces an optical density value of
0.1. EP-A 0 901 040 discloses the following 1-phenyl-5-mercapto-tetrazole compounds:
##STR10##
WO 94/16361 discloses a multilayer heat-sensitive material which comprises: a
color-forming layer comprising: a color-forming amount of finely divided, solid
colorless noble metal or iron salt of an organic acid distributed in a carrier
composition; a color-developing amount of a cyclic or aromatic organic reducing
agent, which at thermal copy and printing temperatures is capable of a color-forming
reaction with the noble metal or iron salt; and an image-toning agent; characterized
in that (a) the carrier composition comprises a substantially water-soluble polymeric
carrier and a dispersing agent for the noble metal or iron salt and (b) the material
comprises a protective overcoating layer for the color-forming layer. Furthermore,
WO 94/16361 discloses that suitable antifoggants are well-known photographic anti-foggants
such as mercaptobenzotriazole, chromate, oxalate, citrate, carbonate, benzotriazole
(BZT), 5-methylbenzotriazole, 5,6-dimethylbenzotriazole, 5-bromobenzotriazole,
5-chlorobenzotriazole, 5-nitro-benzotriazole, 4-nitro-6-chlorobenzotriazole, 5-nitro-6-chlorobenzotriazole,
4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene, benzimidazole, 2-methylbenzimidazole,
5-nitrobenzimidazole, 1-phenyl-5-mercaptotetrazole, 2-mercaptobenzimidazole, 2-mercaptobenzothiazole,
2-mercaptobenzoxazole, 2-mercaptothiazoline, 2-mercapto-4-methyl-6,6′-dimethylpyrimidine,
1-ethyl-2-mercapto-5-amino-1,3,4-triazole, 1-ethyl-5-mercapto-1,2,3,4-tetrazole,
2,5-dimercapto-1,3,4-thiodiazole, 2-mercapto-5-aminothiodiazole, dimethyldithiocarbamate,
and diethyldithiocarbamate.
WO 96/10213 discloses a thermographic imaging element comprising a substrate
having
coated on at least one surface thereof a thermographic imaging system comprising
at least one layer comprising light-insensitive organic silver salt; reducing agent
for silver ion; binder; toner; and a dye which absorbs radiation in the wavelength
range of 750-1100 nm, wherein said at least one layer comprising said light-insensitive
organic silver salt forms an image density greater than about 1.0 when exposed
to 0.10-2.0 joules/cm
2 of said radiation in 0.20 to 200 microseconds.
WO 96/10213 does not disclose a stabilizer against the influence of light, but
mentions the optional incorporation of benzotriazole in the thermographic imaging
element, but only exemplifies the incorporation of benzotriazole.
Substantially light-insensitive thermographic recording materials contain
the imaging-forming components both before and after image formation and unwanted
image-forming must be hindered both during storage prior to printing and in prints
exposed to light on light-boxes e.g. during examination by radiologists. Furthermore,
such stabilization must take place without adverse effects upon the image quality
particularly the image tone. Thermographic printers are being introduced with ever
higher throughputs, which require thermographic recording materials able to provide
stabilization without an adverse effect on the image quality at such faster throughputs.
There is therefore a need for stabilizers which fulfil these requirements.
ASPECTS OF THE INVENTION
It is therefore an aspect of the present invention to provide stabilizers for
use in substantially light-insensitive thermographic recording materials suitable
for use in high throughput thermographic printers without adverse effect on the
image tone.
Further aspects and advantages of the invention will become apparent from
the description hereinafter.
SUMMARY OF THE INVENTION
It has been surprisingly found that specific types of 5-mercapto-tetrazole compounds
provide effective stabilization in substantially light-insensitive thermographic
recording materials suitable for use in high throughput thermographic printers
without an adverse effect on the image tone as characterized by CIELAB a* and b*
values. The L*, a* and b* CIELAB-values were determined by spectrophotometric measurements
according to ASTM Norm E179-90 in a R(45/0) geometry with evaluation according
to ASTM Norm E308-90.
Aspects of the present invention are realized with a substantially light-insensitive
black and white monosheet thermographic recording material comprises a support
and a thermosensitive element, the thermosensitive element containing a substantially
light-insensitive organic silver salt, an organic reducing agent therefor in thermal
working relationship therewith, a binder and at least one stabilizer selected from
the group consisting of 1-phenyl-5-mercaptotetrazole compounds in which the phenyl
group is substituted with a substituent containing an optionally substituted aryl
group; and
##STR11##
Preferred embodiments of the present invention are disclosed in the detailed
description of the invention.
DETAILED DESCRIPTION OF THE INVENTION
Definitions
The term alkyl means all variants possible for each number of carbon atoms in
the alkyl group i.e. for three carbon atoms: n-propyl and isopropyl; for four carbon
atoms: n-butyl, isobutyl and tertiary-butyl; for five carbon atoms: n-pentyl, 1,1-dimethylpropyl,
2,2-dimethylpropyl and 2-methyl-butyl etc.
The term acyl group as used in disclosing the present invention eans -(C═O)
-aryl and -(C═O) -alkyl groups.
The L*, a* and b* CIELAB-values are defined in ASTM Norm E179-90 in a R(45/0)
geometry with evaluation according to ASTM Norm E308-90.
Substantially light-insensitive means not intentionally light sensitive.
Heating in association with the expression a substantially water-free condition
as used herein, means heating at a temperature of 80 to 250° C. The term "substantially
water-free condition" as used herein means that the reaction system is approximately
in equilibrium with water in the air, and water for inducing or promoting the reaction
is not particularly or positively supplied from the exterior to the element. Such
a condition is described in T. H. James, "The Theory of the Photographic Process",
Fourth Edition, Macmillan 1977, page 374.
Thermosensitive Element
The term thermosensitive element as used herein is that element which contains
all the ingredients which contribute to image formation. According to the present
invention, the thermosensitive element contains one or more substantially light-insensitive
organic silver salts, one or more reducing agents therefor in thermal working relationship
therewith and a binder. The element may comprise a layer system in which the above-mentioned
ingredients may be dispersed in different layers, with the proviso that the substantially
light-insensitive organic silver salts are in reactive association with the reducing
agents i.e. during the thermal development process the reducing agent must be present
in such a way that it is able to diffuse to the particles of substantially light-insensitive
organic silver salt so that reduction to silver can occur. Such materials include
the possibility of one or more substantially light-insensitive organic silver salts
and/or one of more organic reducing agents therefor being encapsulated in heat-responsive
microcapsules, such as disclosed in EP-A 0 736 799 herein incorporated by reference.
1-phenyl-5-mercaptotetrazole Compounds
The substantially light-insensitive thermographic recording material of the present
invention can contain at least one 1-phenyl-5-mercaptotetrazole compound in which
the phenyl group is substituted with a substituent containing an optionally substituted
aryl group. Preferred substituents for the phenyl group include -NHCO-phenyl, -NHCO-(1-naphthyl),
-NHCO-(2-naphthyl), -NHCONH-phenyl, -NHSO
2-phenyl, -NHSO
2-(1-naphthyl),
-NHSO
2-(2-naphthyl), -SO
2NH-phenyl, -CONH-phenyl, -CONH-(1-naphthyl),
-CONH-(2-naphthyl), -NHCO-(2-thienyl) and -NHCONHCO-phenyl groups. Preferred substituents
for the aryl group are selected from the group consisting of halogen atoms, ester
groups, -OCOO-alkyl groups, -NHCOO-alkyl groups, -NHOC-alkyl groups, -CONH-alkyl
groups, -S-alkyl groups and mercapto, alkyl, alkoxy, nitrile, acyl and nitro groups.
According to a first embodiment of the substantially light-insensitive
black and white monosheet thermographic recording material, according to the present
invention, the 1-phenyl-5-mercaptotetrazole compound in which the phenyl group
is substituted with a substituent containing an optionally substituted aryl group
is represented by formula (I):
##STR12##
wherein R
1 is -NH-(C═O)-Ar, -NH-(C═O)-NH-Ar, -NH-(C═O)-O-Ar,
-O-(C═O)-NH-Ar, -(C═O)-NH-Ar, -NH-SO
2-Ar, -O-(C═O)-Ar,
-O-(C═O)-O-Ar, -(C═O)-Ar, -(C═O)-O-Ar, -SO
2-Ar,
-SO
2-NH-Ar, or -Ar; and Ar is an optionally substituted aryl or heteroaryl
group. Preferred substitutents for the aryl and heteroaryl groups include halogen
atoms, ester groups, -OCOO-alkyl groups, -NHCOO-alkyl groups, -NHOC-alkyl groups,
-CONH-alkyl groups, -S-alkyl groups and mercapto, alkyl, alkoxy, nitrile, acyl
and nitro groups.
According to a second embodiment of the substantially light-insensitive
black and white monosheet thermographic recording material, according to the present
invention, the 1-phenyl-5-mercaptotetrazole compound in which the phenyl group
is substituted with a substituent containing an optionally substituted aryl group
is represented by formula (II):
##STR13##
wherein R
2 is -NH-(C═O)-Ar, -NH-(C═O)-NH-Ar, -NH-(C═O)-O-Ar,
-O-(C═O)-NH -Ar, -(C═O)-NH-Ar, -NH-SO
2-Ar, -O-(C═O)-Ar,
-O-(C═O)-O-Ar, -(C═O)-Ar, -(C═O)-O-Ar, -SO
2-Ar,
-SO
2-NH-Ar, or -Ar; and Ar is an optionally substituted aryl or heteroaryl
group. Preferred substitutents for the aryl and heteroaryl groups include halogen
atoms, ester groups, -OCOO-alkyl groups, -NHCOO-alkyl groups, -NHOC-alkyl groups,
-CONH-alkyl groups, -S-alkyl groups and mercapto, alkyl, alkoxy, nitrile, acyl
and nitro groups.
According to a third embodiment of the substantially light-insensitive
black and white monosheet thermographic recording material, according to the present
invention the at least one stabilizer is selected from the group consisting of:
##STR14##
##STR15##
##STR16##
1-phenyl-5-mercaptotetrazole compounds in which the
phenyl group is substituted with a substituent containing an optionally substituted
aryl group and
##STR17##
according to the present invention, can be prepared from readily available
starting materials using standard organic chemistry techniques known to one skilled
in the art and available in such reference books such as Houben-Weyl.
Suitable 1-phenyl-5-mercaptotetrazole (PMT) compounds in which the phenyl
group is substituted with a substituent containing an optionally substituted aryl
group, according to the present invention, include:
| PMT-1 |
##STR18##
|
1-(3′-benzoyl-amino- phenyl)-5-mercapto- tetrazole |
| PMT-2 |
##STR19##
|
1-[3′-(2-naphthoyl-amino)- phenyl]-5-mercapto- tetrazole |
| PMT-3 |
##STR20##
|
1-[4′-(benzoyl-amino)- phenyl]-5-mercapto- tetrazole |
| PMT-4 |
##STR21##
|
1-[3′-(p-nitro-benzoyl- amino)-phenyl]-5-mercapto- tetrazole |
| PMT-5 |
##STR22##
|
1-[3′-(p-chloro-benzoyl- amino)-phenyl]-5-mercapto- tetrazole |
| PMT-6 |
##STR23##
|
1-[3′-(p-methoxy-benzoyl- amino)-phenyl]-5-mercapto- tetrazole |
| PMT-7 |
##STR24##
|
1-[3′-(m-methyl-benzoyl- amino)-phenyl]-5-mercapto- tetrazole |
| PMT-8 |
##STR25##
|
1-[3′-(p-methyl-benzoyl- amino)-phenyl]-5-mercapto- tetrazole |
| PMT-9 |
##STR26##
|
| PMT-10 |
##STR27##
|
| PMT-11 |
##STR28##
|
| PMT-12 |
##STR29##
|
| PMT-13 |
##STR30##
|
| PMT-14 |
##STR31##
|
| PMT-15 |
##STR32##
|
Organic Silver Salt
According to a fourth embodiment of the substantially light-insensitive
black and white monosheet thermographic recording material of the present invention,
the organic silver salts are not double organic salts containing a silver cation
associated with a second cation e.g. magnesium or iron ions.
According to a fifth embodiment of the substantially light-insensitive
black and white monosheet thermographic recording material of the present invention,
at least one of the organic silver salts is a substantially light-insensitive silver
salt of an organic carboxylic acid.
According to a sixth embodiment of the substantially light-insensitive
black and white monosheet thermographic recording material of the present invention,
at least one of the organic silver salts is a substantially light-insensitive silver
salt of an aliphatic carboxylic acids known as a fatty acid, wherein the aliphatic
carbon chain has preferably at least 12 C-atoms, e.g. silver laurate, silver palmitate,
silver stearate, silver hydroxystearate, silver oleate and silver behenate, which
silver salts are also called "silver soaps". Other silver salts of an organic carboxylic
acid as described in GB-P 1,439,478, e.g. silver benzoate, may likewise be used
to produce a thermally developable silver image. Combinations of different silver
salt of an organic carboxylic acids may also be used in the present invention,
as disclosed in EP-A 964 300.
Organic silver salts may be dispersed by standard dispersion techniques.
Ball mills, bead mills, microfluidizers, ultrasonic apparatuses, rotor stator mixers
etc. have been found to be useful in this regard. Mixtures of organic silver salt
dispersions produced by different techniques may also be used to obtain the desired
thermographic properties e.g. of coarser and more finely ground dispersions of
organic silver salts.
Reducing Agents
According to an seventh embodiment of the black and white thermographic
recording material, according to the present invention, the reducing agent is an
organic compound containing at least one active hydrogen atom linked to O, N or
C, such as is the case with, aromatic di- and tri-hydroxy compounds. 1,2-dihydroxybenzene
derivatives, such as catechol, 3-(3,4-dihydroxyphenyl) propionic acid, 1,2-dihydroxybenzoic
acid, gallic acid and esters e.g. methyl gallate, ethyl gallate, propyl gallate,
tannic acid, and 3,4-dihydroxy-benzoic acid esters are preferred, with those described
in EP-A 0 692 733 and EP-A 0 903 625 being particularly preferred.
Combinations of reducing agents may also be used that on heating become
reactive partners in the reduction of the one or more substantially light-insensitive
organic silver salt. For example, combinations of sterically hindered phenols with
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 as disclosed in U.S. Pat. Nos. 5,545,505, 5,545,507 and 5,558,983;
acrylonitrile compounds as disclosed in U.S. Pat. Nos. 5,545,515 and 5,635,339;
and 2-substituted malonodialdehyde compounds as disclosed in U.S. Pat. No. 5,654,130.
Binder of the Thermosensitive Element
The film-forming binder of the thermosensitive element may be all kinds of natural,
modified natural or synthetic resins or mixtures of such resins, in which the at
least one organic silver salt can be dispersed homogeneously either in aqueous
or solvent media: e.g. cellulose derivatives, starch ethers, galactomannan, polymers
derived from α,β-ethylenically unsaturated compounds such as polyvinyl
chloride, after-chlorinated polyvinyl chloride, copolymers of vinyl chloride and
vinylidene chloride, copolymers of vinyl chloride and vinyl acetate, polyvinyl
acetate and partially hydrolyzed polyvinyl acetate, polyvinyl alcohol, polyvinyl
acetals that are made from polyvinyl alcohol as starting material in which only
a part of the repeating vinyl alcohol units may have reacted with an aldehyde,
preferably polyvinyl butyral, copolymers of acrylonitrile and acrylamide, polyacrylates,
polymethacrylates, polystyrene and polyethylene or mixtures thereof.
Suitable water-soluble film-forming binders for use in thermographic recording
materials according to the present invention are: polyvinyl alcohol, polyacrylamide,
polymethacrylamide, polyacrylic acid, polymethacrylic acid, polyvinylpyrrolidone,
polyethyleneglycol, proteinaceous binders, polysaccharides and water-soluble cellulose
derivatives. A preferred water-soluble binder for use in the thermographic recording
materials of the present invention is gelatine.
The binder to organic silver salt weight ratio is preferably in the range of
0.2 to 7, and the thickness of the thermosensitive element is preferably in the
range of 5 to 50 μm. Binders are preferred which do not contain additives,
such as certain antioxidants (e.g. 2,6-di-tert-butyl-4-methylphenol), or impurities
which adversely affect the thermographic properties of the thermographic recording
materials in which they are used.
Toning Agent
According to an eighth embodiment of the black and white monosheet thermographic
recording material, according to the present invention, the thermosensitive element
contains a toning agent, which enables a neutral black image tone to be obtained
in the higher densities and neutral grey in the lower densities.
According to a ninth embodiment of the black and white monosheet thermographic
recording material, according to the present invention, the thermosensitive element
further contains a toning agent selected from the group consisting of phthalimides,
phthalazinones, benzoxazine diones and naphthoxazine diones e.g. phthalimides and
phthalazinones within the scope of the general formulae described in U.S. Pat.
No. 4,082,901; the toning agents described in U.S. Pat. Nos. 3,074,809, 3,446,648
and 3,844,797; and the heterocyclic toner compounds of the benzoxazine dione or
naphthoxazine dione type as disclosed in GB 1,439,478, U.S. Pat. Nos. 3,951,660
and 5,599,647, herein incorporated by reference.
According to a tenth embodiment of the substantially light-insensitive
black and white monosheet thermographic recording material, according to the present
invention, the substantially light-insensitive thermographic material contains
a thermosensitive element, the thermosensitive element containing one or more toning
agents selected from the group consisting of phthalazinone, benzo[e][1,3]oxazine-2,4-dione,
7-methyl-benzo[e][1,3]oxazine-2,4-dione, 7-methoxy-benzo[e][1,3]oxazine-2,4-dione
and 7-(ethylcarbonato)-benzo[e][1,3]oxazine-2,4-dione.
Auxiliary Antifoggants
According to an eleventh embodiment of the black and white monosheet thermographic
recording material, according to the present invention, the thermographic recording
material further contains an auxiliary antifoggant to obtain improved shelf-life
and reduced fogging.
According to a twelfth embodiment of the black and white monosheet thermographic
recording material, according to the present invention, the thermographic recording
material further contains an antifoggant selected from the group consisting of
benzotriazole, substituted benzotriazoles and aromatic polycarboxylic acid such
as ortho-phthalic acid, 3-nitro-phthalic acid, tetrachlorophthalic acid, mellitic
acid, pyromellitic acid and trimellitic acid and anhydrides thereof.
According to a thirteenth embodiment of the black and white monosheet thermographic
recording material, according to the present invention, the thermosensitive element
further contains an optionally substituted benzotriazole.
Polycarboxylic Acids and Anhydrides Thereof
According to a fourteenth embodiment of the black and white monosheet thermographic
recording material, according to the present invention, the thermosensitive element
further contains at least one polycarboxylic acid and/or anhydride thereof in a
molar percentage of at least 15 with respect to all the organic silver salt(s)
present and in thermal working relationship therewith. The polycarboxylic acid
may be aliphatic (saturated as well as unsaturated aliphatic and also cycloaliphatic)
or an aromatic polycarboxylic acid, may be substituted and may be used in anhydride
form or partially esterified on the condition that at least two free carboxylic
acids remain or are available in the heat recording step.
Surfactants and Dispersants
Surfactants and dispersants aid the dispersion of ingredients which are
insoluble in the particular dispersion medium. The substantially light-insensitive
thermographic material used in the present invention may contain one or more surfactants,
which may be anionic, non-ionic or cationic surfactants and/or one or more dispersants.
Suitable dispersants are natural polymeric substances, synthetic polymeric substances
and finely divided powders, e.g. finely divided non-metallic inorganic powders
such as silica.
Support
According to a fifteenth embodiment of the substantially light-insensitive
black and white monosheet thermographic recording material, according to the present
invention, the support is transparent or translucent. It is preferably a thin flexible
carrier made transparent resin film, e.g. made of a cellulose ester, e.g. cellulose
triacetate, polypropylene, polycarbonate or polyester, e.g. polyethylene terephthalate.
The support may be in sheet, ribbon or web form and subbed if needs be to improve
the adherence to the thereon coated thermosensitive element. The support may be
dyed or pigmented to provide a transparent coloured background for the image.
Protective Layer
According to a sixteenth embodiment of the substantially light-insensitive
black and white monosheet thermographic recording material, according to the present
invention, the thermosensitive element is provided with a protective layer. In
general this protects the thermosensitive element from atmospheric humidity and
from surface damage by scratching etc. and prevents direct contact of printheads
or heat sources with the recording layers. Protective layers for thermosensitive
elements which come into contact with and have to be transported past a heat source
under pressure, have to exhibit resistance to local deformation and good slipping
characteristics during transport past the heat source during heating. A slipping
layer, being the outermost layer, may comprise a dissolved lubricating material
and/or particulate material, e.g. talc particles, optionally protruding from the
outermost layer. Examples of suitable lubricating materials are a surface active
agent, a liquid lubricant, a solid lubricant or mixtures thereof, with or without
a polymeric binder.
Coating Techniques
The coating of any layer of the substantially light-insensitive thermographic
material used in the present invention may proceed by any coating technique e.g.
such as described in Modern Coating and Drying Technology, edited by Edward D.
Cohen and Edgar B. Gutoff, (1992) VCH Publishers Inc., 220 East 23rd Street, Suite
909 New York, N.Y. 10010, USA. Coating may proceed from aqueous or solvent media
with overcoating of dried, partially dried or undried layers.
Thermographic Processing
Thermographic imaging is carried out by the image-wise application
of heat either in analogue fashion by direct exposure through an image or by reflection
from an image, or in digital fashion pixel by pixel either by using an infra-red
heat source, for example with a Nd-YAG laser or other infra-red laser, with a substantially
light-insensitive thermographic material preferably containing an infra-red absorbing
compound, or by direct thermal imaging with a thermal head.
In thermal printing image signals are converted into electric pulses and then
through a driver circuit selectively transferred to a thermal printhead. The thermal
printhead consists of microscopic heat resistor elements, which convert the electrical
energy into heat via Joule effect. The operating temperature of common thermal
printheads is in the range of 300 to 400° C. and the heating time per picture
element (pixel) may be less than 1.0 ms, the pressure contact of the thermal printhead
with the recording material being e.g. 200-1000 g/linear cm, i.e. with a contact
zone (nip) of 200 to 300 μm a pressure of 5000 to 50,000 g/cm
2,
to ensure a good transfer of heat.
In order to avoid direct contact of the thermal printing heads with the outermost
layer on the same side of the support as the thermosensitive element when this
outermost layer is not a protective layer, the image-wise heating of the recording
material with the thermal printing heads may proceed,through a contacting but removable
resin sheet or web wherefrom during the heating no transfer of recording material
can take place.
Activation of the heating elements can be power-modulated or pulse-length
modulated at constant power. EP-A 654 355 discloses a method for making an image
by image-wise heating by means of a thermal head having energizable heating elements,
wherein the activation of the heating elements is executed duty cycled pulsewise.
EP-A 622 217 discloses a method for making an image using a direct thermal imaging
element producing improvements in continuous tone reproduction.
Image-wise heating of the recording material can also be carried out using
an electrically resistive ribbon incorporated into the material. Image- or pattern-wise
heating of the recording material may also proceed by means of pixel-wise modulated ultra-sound.
Industrial Application
Thermographic imaging can be used for the production of reflection
type prints and transparencies, in particular for use in the medical diagnostic
field in which black-imaged transparencies are widely used in inspection techniques
operating with a light box.
The invention is illustrated hereinafter by way of comparative examples and invention
examples. The percentages and ratios given in these examples are by weight unless
otherwise indicated.
Subbing Layers on the Emulsion Side of the Support
Subbing layer Nr. 01 has the composition:
| copolymer of 88% vinylidene chloride, 10% methyl |
79.1 |
mg/m2 |
| acrylate and 2% itaconic acid |
| Kieselsol ® 100F, a colloidal silica from BAYER |
18.6 |
mg/m2 |
| Mersolat ® H, a surfactant from BAYER |
0.4 |
mg/m2 |
| Ultravon ® W, a surfactant from CIBA-GEIGY |
1.9 |
mg/m2 |
Subbing layer Nr. 02 has the composition:
| copolymer of 88% vinylidene chloride, 10% methyl |
151 |
mg/m2 |
| acrylate and 2% itaconic acid |
| Kieselsol ® 100F, a colloidal silica from BAYER |
35 |
mg/m2 |
| Mersolat ® H, a surfactant from BAYER |
0.75 |
mg/m2 |
Ingredients in the Thermosensitive Element in Addition to the Above-mentioned Ingredients
| BL5HP = |
S-LEC BLSHP, a polyvinyl butyral from SEKISUI; |
| Oil = |
BAYSILON, a silicone oil from BAYER; |
| VL = |
DESMODUR VL, a 4,4′-diisocyanatodiphenylmethane |
| |
from BAYER; |
| Reducing agents: |
| R01 = |
3,4-dihydroxybenzonitrile; |
| R02 = |
3,4-dihydroxybenzophenone; |
| Toning agent: |
| T01 = |
7-(ethylcarbonato)-benzo[e][1,3]oxazine-2,4-dione; |
| T02 = |
7-methyl-benzo[e][1,3]oxazine-2,4-dione; |
| Stabilizers: |
| S01 = |
glutaric acid |
| S02 = |
tetrachlorophthalic acid anhydride |
| S03 = |
benzotriazole |
| S04 = |
##STR33##
|
| PMT-C1 = |
1-phenyl-5-mercapto-tetrazole |
| PMT-C2 = |
##STR34##
|
| PMT-C3 = |
##STR35##
|
| PMT-C4 = |
##STR36##
|
| PMT-C5 = |
##STR37##
|
| PMT-C6 = |
##STR38##
|
| PMT-C7 = |
##STR39##
|
| PMT-C8 = |
##STR40##
|
| PMT-C9 = |
##STR41##
|
| PMT-C10 = |
##STR42##
|
| PMT-C11 = |
##STR43##
|
Ingredients in the Protective Layer
| ERCOL ™ 48 20 = |
a polyvinylalcohol from ACETEX |
| |
EUROPE; |
| LEVASIL ™ VP AC 4055 = |
a 15% aqueous dispersion of colloidal |
| |
silica with acid groups predominantly |
| |
neutralized with sodium ions and a |
| |
specific surface are of 500 m2/g, from |
| |
BAYER AG has been converted into |
| |
the ammonium salt; |
| ULTRAVON ™ W = |
75-85% concentrate of a sodium |
| |
arylsulfonate from Ciba Geigy |
| |
converted into acid form by passing |
| |
through an ion exchange column; |
| SYLOID ™ 72 = |
a silica from Grace; |
| SERVOXYL ™ VPDZ 3/100 = |
a mono [isotridecyl polyglycolether (3 |
| |
EO)] phosphate, from SERVO |
| |
DELDEN B.V.; |
| SERVOXYL ™ VPAZ 100 = |
a mixture of monolauryl and dilauryl |
| |
phosphate, from SERVO DELDEN |
| |
B.V.; |
| MICROACE TALC P3 = |
an Indian talc from NIPPON TALC; |
| RILANIT ™ GMS = |
a glycerine monotallow acid ester, from |
| |
HENKEL AG |
| TMOS = |
tetramethylorthosilicate hydrolyzed in |
| |
the presence of methanesulfonic acid. |
COMPARATIVE EXAMPLES 1 TO 3
The substantially light-insensitive thermographic materials of COMPARATIVE EXAMPLES
1 to 3 were prepared by coating a dispersion with the following ingredients in
2-butanone onto a 175 μm thick blue-pigmented polyethylene terephthalate
support with CIELAB a*- and b*-values of -;9.5 and -;17.9 respectively subbed on
the emulsion-coated side with subbing layer 01 giving layers after drying at 50°
C. for 1 h in a drying cupboard with the compositions given in Table 1.
| TABLE 1 |
| |
stabilizer |
|
|
R01 |
R02 |
T01 |
T02 |
S01 |
S02 |
|
|
| Comparative |
|
conc. |
AgBeh |
BL5HP |
mol % |
mol % |
mol % |
mol % |
mol % |
mol % |
VL |
Oil |
| example |
|
mol % |
coverage |
[g/ |
vs |
vs |
vs |
vs |
vs |
vs |
[g/ |
[g/ |
| nr. |
type |
vs AgB |
[g/m2] |
m2] |
AgB |
AgB |
AgB |
AgB |
AgB |
AgB |
m2] |
m2] |
| 1 |
S03 |
10 |
3.89 |
15.12 |
50 |
30 |
5 |
10 |
22 |
5 |
0.17 |
0.035 |
| 2 |
PMT- |
10 |
3.89 |
15.12 |
50 |
30 |
5 |
10 |
22 |
5 |
0.17 |
0.035 |
| |
C1 |
| 3 |
PMT- |
10 |
3.89 |
15.12 |
50 |
30 |
5 |
10 |
22 |
5 |
0.17 |
0.035 |
| |
C2 |
The thermosensitive elements were then coated with an aqueous composition with
the following ingredients, which was adjusted to a pH of 3.8 with 1N nitric acid,
to a wet layer thickness of 85 μm and then dried at 50° C. for 15 minutes
to produce a protective layer PRO-L with the composition:
