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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to recording materials, particularly thermographic
and photothermographic image-recording materials employing certain di- and
triarylmethane dye precursor compounds and to a method of forming color
employing the dye precursor compounds.
2. Background Art
Various dry image-recording materials that can be processed by a dry method
only, that is, without the use of any treatment with liquids have been
proposed. Among such image-recording materials are the thermographic and
photothermographic materials of the silver salt type which employ moderate
heating to develop a visible image and which comprise an
oxidation-reduction image-forming combination comprising a
non-photosensitive organic silver salt oxidizing agent such as the silver
salt of a long chain fatty acid and a reducing agent for silver ions,
typically, an organic reducing agent. In addition to the above, the
photothermographic materials also include a photosensitive compound such
as a light-sensitive silver halide or a photosensitive compound-forming
component such as a component capable of forming a light-sensitive silver
halide. The latter materials are often referred to as heat developable
photographic materials and require an imagewise exposure to light to form
a latent image prior to the heat development step.
The addition of dye-forming compounds to materials of the silver salt type
for providing a color image or a color enhanced image also has been
proposed. Usually color formation is achieved by color coupling to form a
dye image, for example, by including a color-forming coupler and using a
p-phenylenediamine, sulfonamidophenol or other color-developing agent as
the organic reducing agent or by oxidation of a leuco dye to its colored
form, for example, by employing a readily oxidizable indoaniline or
phenolic leuco dye as the organic reducing agent. These and other means
for generating dye images in silver salt materials have been described by
J. W. Carpenter and P. W. Lauf in their review of "Photothermographic
Silver Halide Systems", Research Disclosure, No. 17029, June, 1978. The
formation of multicolor images using at least 2 or 3 color image-forming
layers also has been disclosed in U.S. Pat. Nos. 4,021,240, 4,452,883 and
4,460,681.
Other dry image-recording materials for producing color images from
colorless precursor(s) also have been proposed. One system commonly
employed for pressure-sensitive and heat-sensitive recording materials to
produce dye images comprises a two-component system utilizing a coloration
reaction between a colorless dye precursor (color former) and an acidic
material (color developer). Among the colorless dye precursors used as the
color former are triarylmethane compounds including bridged triarylmethane
compounds possessing a lactone, lactam or other ring-closing moiety, for
example, 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (Crystal
Violet Lactone), 3-piperidino-6-methyl-7-anilinofluoran and Rhodamine B
anilinolactam. The acidic material used as the color developer is usually
a phenol derivative or an aromatic carboxylic acid derivative, for
example, p-tert-butylphenol, 2,2-bis(p-hydroxyphenyl) propane,
o-hydroxy-naphthoic acid, p-hydroxybenzoic acid,
3,5-di-tert-butylsalicylic acid and so forth.
In these two-component systems, the color former and the color developer
can be carried on the same or on separate supports. Where the two
components are coated on the same side of a common support, a binder or
some other means such as encapsulation is employed for physically
separating the color former and color developer to prevent premature
mixing and coloration. Images are formed by the imagewise application of
pressure, heat, electricity or other stimulus to effect contact between
the two components to bring about the coloration reaction. Depending upon
the dye precursor used as the color former, the coloration reaction
brought about by contacting the two components may comprise dissociation,
or it may comprise ring-opening in those compounds containing a cyclic
ring-closing moiety as part of their structure. For example, color formers
such as the aforementioned triarylmethane compounds possessing a lactone
or lactam moiety ring-closed on the methane carbon atom become ring-opened
and colored by an ionization or hydrogen-bonding reaction when contacted
with the acidic material. Such imaging systems for pressure-sensitive,
heat-sensitive and electrothermic recording materials are described in
U.S. Pat. Nos. 3,924,027, 4,502,067, 4,133,933 and in U.S. Pat. No.
4,132,436.
Although 3,3-disubstituted thiophthalides and dithiophthalides have been
disclosed previously, none of the triarylmethane compounds described are
dye precursors, i.e., color formers, since they do not exhibit the
color-forming properties of dyes. In particular, R. Meyer, Ber. 33, pp.
2570-2576 and R. Meyer and J. Szanecki, ibid, pp. 2577-2583 disclose the
synthesis of 3.3-dithiotluorane, dithiophenylphthalide
(3,3-diphenylthiophthalide) and dithiodichlorofluorane by fusing the
corresponding phthalides with phosphorus pentasulfide. The
3.3-dithiofluorane and the dithiodiphenylphthalide lack the auxochromic
substituents necessary to complete the auxochromophoric system of a
triarylmethane dye. The dithiodichlorofluorane also does not exhibit the
properties of a dye, presumably because the chloro groups are not
providing an auxochromic effect.
I. P. Soloveichik, et al., Zhurnal Organicheskoi Khimii, Vol. 10, No. 3,
pp. 615-618, March, 1974 disclose the preparation of
3,3-diphenylthiophthalide by reacting the 3,3-diphenyldithiophthalide of
Meyer and Szanecki with mercuric acetate and also by reacting
o-benzoylbenzoic acid and phosphorus pentasulfide followed by phenylation
with the Friedel-Crafts reaction as previously described by I. O'Brochta,
et al., J. Am. Chem. Soc., 61, 2762 (1959). U.S. Pat. No. 2,097,435
discloses a synthesis for thiophthalides including
3,3-diphenylthiophthalide by reacting the corresponding phthalide with
sodium hydrosulfide under anhydrous conditions in the absence of air or
oxygen. Like the 3,3-diphenyldithiophthalide discussed above,
3,3-diphenylthiophthalide is not a dye precursor since the 3,3-phenyl
moieties lack an auxochromic substituent to impart dye properties.
As discussed in Gilman, Henry, Organic Chemistry, An Advanced Treatise,
Vol. III, John Wiley & Sons, New York, 1953, pp. 247-55, a chromophore
called a chromogene may be colored but does not yet represent a dye. To
achieve this a further introduction of salt-forming groups, "auxochromes",
into the molecule is required. The function of chromophore and auxochrome
groups according to modern theory is necessary for modifying the molecule
so as to introduce the possibility of resonance and thus color.
SUMMARY OF THE INVENTION
The present invention is concerned with novel imaging systems useful for
heat-sensitive, light-sensitive, pressure-sensitive and other
image-recording materials for producing dye images that employ di- and
triarylmethane dye precursor compounds possessing certain S-containing
ring-closing moieties, namely, a thiolactone, dithiolactone or thioether
moiety. When contacted with a Lewis acid material capable of opening the
thiolactone, dithiolactone or thioether moiety, the compound is rendered
colored, i.e., converted to its chromophore color which is a function of
the auxochromophoric system of the di- or triarylmethane dye. Indeed, the
ability of these dye precursor compounds to form a colored dye almost
instantaneously when contacted with Ag+ renders these compounds eminently
suitable for use as color formers in reactions employing silver salts
including imaging systems employing inorganic silver salts, such as,
silver halides and particularly imaging systems employing organic silver
salts, such as silver behenate. In systems of the latter type, color
formation is particularly efficient since it is effected by a phase
change, i.e., effected by melting of the organic silver salt to provide
the Ag+ necessary for coloration rather than requiring a change of state.
Besides their ability to readily form color with Lewis acids and especially
with Ag+, these dye precursor compounds possess other properties that
compare favorably with color formers previously used in heat-, light- and
pressure-sensitive recording materials. They are substantially colorless
at the concentrations used in the image-recording layers and are
relatively free from decomposition or coloration due to heat, light,
humidity, etc. during storage, that is, prior to contacting with the Lewis
acid. They provide a wide range of colors as may be desired not only for
monochromes and bichromes but for full color images, and the color images
formed exhibit reasonable resistance to heat, light and humidity.
Moreover, when they are employed in imaging systems which use heat to form
or develop color, color formation may be readily achieved at only
moderately elevated temperatures.
It is, therefore, one object of the present invention to provide a method
of forming color employing certain di- and triarylmethane dye precursor
compounds.
It is another object of the present invention to provide novel recording
materials employing said compounds.
Other objects of the invention will in part be obvious and will in part
appear hereinafter.
The invention accordingly comprises the method involving the several steps
and the relation and order of one or more of such steps with respect to
each of the others, and the products and compositions possessing the
features, properties and the relation of elements which are exemplified in
the following detailed disclosure, and the scope of the application of
which will be indicated in the claims.
For a fuller understanding of the nature and objects of the invention,
reference should be had to the following detailed description.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
As noted above, the present invention is concerned with novel recording
materials employing color-forming di- and triarylmethane compounds
possessing certain S-containing ring-closing moieties and with color
formation employing these compounds. Specifically, the method of forming
color according to the present invention comprises contacting (a) 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 or thioether
moiety and (b) a Lewis acid material capable of opening the thiolactone,
dithiolactone or thioether moiety whereby said compound is rendered
colored, i.e., converted to its chromophore color which is a function of
the auxochromophoric system of the triarylmethane dye.
The Lewis acid material may be an organic or inorganic electron pair
acceptor, and such materials suitable for a given thiolactone,
dithiolactone or thioether dye precursor may be determined empirically. In
this regard, it will be understood that the thiolactone, dithiolactone and
thioether dye precursors do not react with all Lewis acids but that each
thiolactone, dithiolactone and thioether reacts with at least one Lewis
acid. Where both sulfur and oxygen are present in the ring-closed moiety
as in the thiolactones, Lewis acid materials such as boron trifluoride
etherate and aluminum chloride may be employed, but preferably, the Lewis
acid material selected for both the thiolactones and dithiolactones and
for the thioethers has a strong preference for coordinating with sulfur
such as the metal ions classified as "soft acids" by Pearson, Ralph G.,
Hard and Soft Acids and Bases, Chem. Brit., 1967, 3, (3), p. 103.
Preferably, the metal ion is that of a heavy metal, such as silver, gold,
mercury and palladium. Silver is particularly preferred because of its
exceptional ability for complexing with the thiolactone, dithiolactone and
thioether moieties.
Contacting the dye precursor and Lewis acid material may be achieved in any
suitable and convenient manner as desired for a given color-forming
application, for example, by admixing solutions of the two components or
by applying the Lewis acid material in liquid, gaseous, melted or other
fluid form to the dye precursor coated on or absorbed into a substrate.
Also, color formation may be effected imagewise. As an illustration, the
dye precursor may be disposed in a layer and a solution of the Lewis acid
material applied imagewise by coating through a stencil, spraying in an
imagewise pattern, etc. or a Lewis acid material such as Ag+ may be
provided imagewise as a function of processing a selectively exposed
photosensitive silver halide layer adjacent the dye precursor layer by
applying an aqueous processing composition.
Rather than applying a solution, the Lewis acid material and dye precursor
may be used in "dry" systems. They may be used as solids or one or both
may be encapsulated and contained in a single sheet in the same or
different layers or contained in separate superposed sheets, and color
formation brought about in an imagewise fashion by the imagewise
application of heat, pressure or other stimulus necessary to effect
imagewise contact between the two components. In systems employing two
sheets, the dye precursor may be coated in a binder on one sheet and the
Lewis acid material coated in a binder on the other and heat applied
imagewise to the superposed sheets to effect melting and contact of the
two components, or a sheet coated with a layer of dye precursor
encapsulated in oil may be superposed with the second sheet coated with
Lewis acid material, and pressure applied imagewise to the superposed
sheets to rupture the capsule walls and effect contact between the two
components.
In a preferred embodiment, the two components are contained in the same
sheet, that is, a single support carries the dye precursor and the Lewis
acid material. The Lewis acid material preferably is a silver salt. In a
particularly preferred embodiment, a thermographic image-recording
material for producing dye images is provided which comprises a support
carrying a di- or triarylmethane thiolactone, dithiolactone or thioether
dye precursor, an organic silver salt and optionally, a heat-fusible
organic acidic material. For photothermographic use, the image-recording
material additionally includes in catalytic association with the organic
silver salt, a photosensitive silver halide or a photosensitive silver
halide-forming component and a reducing agent. Preferably, the dye
precursor is a triarylmethane thiolactone, particularly, a thiophthalide
and the organic silver salt is silver behenate.
Novel di- and triarylmethane dye precursors particularly useful in the
imaging systems in accordance with this invention are disclosed and
claimed in the copending application of P. F. King Ser. No. 935,533 filed
Dec. 5, 1986, now abandoned which is a continuation-in-part of application
Ser. No. 809,157 filed Dec. 16, 1985.
The novel di- and triarylmethane dye precursors useful in the present
invention may be represented by the formula
##STR1##
wherein X is
##STR2##
ring B represents a substituted or unsubstituted carbocyclic aryl ring,
e.g., of the benzene or naphthalene series or a heterocyclic aryl ring,
e.g., pyridine or pyrimidine; and Z and Z' taken individually represent
the moieties, to complete the auxochromophoric system of a diarylmethane
or a triarylmethane dye when said S-containing ring is open and Z and Z'
when taken together represent the bridged moieties to complete the
auxochromophoric system of a bridged triarylmethane dye when said
S-containing ring is open. In a preferred embodiment, B represents a
substituted or unsubstituted benzene ring and Z and Z' taken individually
represent the aryl moieties, the same or different, to complete the
auxochromophoric system of a triarylmethane dye when said S-containing
ring is open and Z and Z' when taken together represent the bridged aryl
moieties to complete the auxochromophoric system of a briged
triarylmethane dye when said S-containing ring is open. Usually, at least
one of Z and Z' whether taken individually or together possesses as an
auxochromic substituent, a nitrogen, oxygen or sulfur atom or a group of
atoms containing nitrogen, oxygen or sulfur. Preferably, X is
##STR3##
In the triarylmethane compounds represented in formula I above, the aryl
moieties Z and Z', when taken individually, may be the same or different
and typically represent heterocyclic aryl groups containing nitrogen,
oxygen or sulfur as the heterocyclic atom, particularly N-heterocyclic
aryl groups such as julolidin-3-yl, indol-3-yl, pyrr-2-yl, carbazol-3-yl,
and indolin-5-yl wherein the N atom of the indolyl, pyrryl, carbazolyl and
indolinyl groups may be substituted with hydrogen or alkyl having 1 to 6
carbon atoms, or the aryl moieties Z and Z' typically may be carbocyclic
aryl, particularly phenyl or naphthyl groups which include an
appropriately positioned auxochromic substituent, i.e., an atom or group
that produces an auxochromic effect, which substituent is usually
positioned para to the meso carbon atom. Typically, Z and Z' when taken
together represent aryl groups bridged by a heteroatom, such as, oxygen,
sulfur or nitrogen to form, for example, 4H-chromeno [2,3-C] pyrazole and
particularly represent carbocyclic aryl groups, such as, phenyl groups
bridged with a heteroatom, preferably oxygen, sulfur or nitrogen
substituted with hydrogen or an alkyl group having 1 to 6 carbon atoms to
provide a xanthene, thioxanthene or an acridine dye, which dyes possess an
auxochromic substituent(s) para to the meso carbon atom, i.e., in the
3-position or in the 3,6-positions or meta and para to the meso carbon
atom, i.e., in the 3,7-positions.
In the diarylmethane compounds, one of Z and Z' may be heterocyclic aryl or
carbocyclic aryl as discussed, above and the other of Z and Z' may be, for
example, phenoxy, thiophenoxy, alkoxy containing 1 to 20 carbon atoms,
alkylthio containing 1 to 20 carbon atoms, -N,N-(disubstituted)amino
wherein each said substituent may be alkyl containing 1 to 20 carbon
atoms, carbocyclic aryl containing 6 to 12 carbon atoms, aralkyl
containing 7 to 15 carbon atoms particularly phenyl- and
naphthyl-substituted alkyl or alkaryl containing 7 to 15 carbon atoms
particularly alkyl-substituted phenyl and naphthyl. Representative alkyl
groups include methyl, butyl, hexyl and octadecyl and representative aryl
groups include phenyl and naphthyl. Representative alkaryl groups include
p-octylphenyl, o-methylnaphthyl and p-hexylphenyl, and representative
aralkyl groups include phenethyl, benzyl and naphthylmethyl.
Examples of useful auxochromic substituents include --OR.sub.1 wherein
R.sub.1 is hydrogen, alkyl usually having 1 to 6 carbon atoms, aralkyl
usually having 7 to 15 carbon atoms, alkaryl usually having 7 to 15 carbon
atoms or carbocyclic aryl usually having 6 to 12 carbon atoms; --SR.sub.2
wherein R.sub.2 has the same meaning given for R.sub.1 ; --NR.sub.3
R.sub.4 wherein R.sub.3 and R.sub.4 each represent hydrogen, alkyl usually
having 1 to 6 carbon atoms, .beta.-substituted ethyl, cycloalkyl usually
having 5 to 7 carbon atoms, aralkyl usually having 7 to 15 carbon atoms,
alkaryl usually having 7 to 15 carbon atoms or
##STR4##
wherein R.sub.5 and R.sub.6 each are hydrogen, alkyl usually having 1 to 6
carbon atoms, halo such as chloro, bromo, fluoro and iodo, nitro, cyano,
alkoxycarbonyl wherein said alkoxy has 1 to 6 carbon atoms, sulfonamido
(--NHSO.sub.2 R.sub.0), sulfamoyl (--SO.sub.2 NHR.sub.0), sulfonyl
(--SO.sub.2 R.sub.0), acyl (--COR.sub.0) or carbamyl (--CONR.sub.0)
wherein R.sub.0 usually is alkyl having 1 to 20 carbon atoms, benzyl or
phenyl and R.sub.3 and R.sub.4 taken together represent the atoms
necessary to complete a heterocyclic ring usually piperidino, pyrrolidino,
N-methylpiperidino, morpholino or
##STR5##
wherein q is an integer 2 to 5 and R.sub.7 has the same meaning as
R.sub.5,
##STR6##
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