Chromogenic compounds of the formula ##STR1## wherein each of Y.sub.1 and Y.sub.2 independently represents an amino-substituted phenyl radical of the formula ##STR2## a 3-indolyl radical of the formula ##STR3## or a 3-carbazolyl radical of the formula ##STR4## and Q represents alkyl of 1 to 12 carbon atoms or unsubstituted or substituted aryl or aralkyl, while each of X.sub.1 and X.sub.2 independently represents hydrogen, alkyl containing not more than 12 carbon atoms which is unsubstituted or substituted by halogen, hydroxyl, cyano or lower alkoxy, or represents cycloalkyl, phenyl, benzyl, or phenyl or benzyl which is substituted by halogen, lower alkyl or lower alkoxy, or X.sub.1 and X.sub.2 together with the nitrogen atom to which they are attached represent a 5- or 6-membered heterocyclic radical, X.sub.3 represents hydrogen, halogen, nitro, lower alkyl or lower alkoxy, each of R and Z.sub.1 independently represents hydrogen, alkyl containing not more than 12 carbon atoms which is unsubstituted or substituted by halogen, hydroxyl, cyano or lower alkoxy, or represents alkenyl containing not more than 12 carbon atoms, acyl of 1 to 12 carbon atoms, phenyl, benzyl, or phenyl or benzyl which is substituted by halogen, lower alkyl, lower alkoxy or nitro, and Z.sub.2 represents hydrogen, lower alkyl or phenyl, and the rings A, B and D, each independently of the other, can be unsubstituted or substituted by cyano, nitro, halogen, lower alkyl, lower alkoxy or lower alkoxycarbonyl, and the ring D can also contain an unsubstituted or substituted phenyl radical or a fused benzene ring. These compounds are particularly suitable for use as color formers in pressure-sensitive or heat-sensitive recording materials.

The present invention relates to chromogenic propenylenesulfone compounds, 
a process for their manufacture and their use as colour formers in 
pressure-sensitive or heat-sensitive recording material. 
The novel chromogenic sulfone compounds have the general formula 
##STR5## 
wherein each of Y.sub.1 and Y.sub.2 independently represents an 
amino-substituted phenyl radical of the formula 
##STR6## 
a 3-indolyl radical of the formula 
##STR7## 
a 3-carbazolyl radical of the formula 
##STR8## 
and Q represents alkyl of 1 to 12 carbon atoms or unsubstituted or 
substituted aryl or aralkyl, whilst each of X.sub.1 and X.sub.2 
independently represents hydrogen, alkyl containing not more than 12 
carbon atoms which is unsubstituted or substituted by halogen, hydroxyl, 
cyano or lower alkoxy, or represents cycloalkyl, phenyl, benzyl, or phenyl 
or benzyl which is substituted by halogen, lower alkyl or lower alkoxy, or 
X.sub.1 and X.sub.2 together with the nitrogen atom to which they are 
attached represent a 5- or 6-membered heterocyclic radical, X.sub.3 
represents hydrogen, halogen, nitro, lower alkyl or lower alkoxy, each of 
R and Z.sub.1 independently represents hydrogen, alkyl containing not more 
than 12 carbon atoms which is unsubstituted or substituted by halogen, 
hydroxyl, cyano or lower alkoxy, or represents alkenyl containing not more 
than 12 carbon atoms, acyl of 1 to 12 carbon atoms, phenyl, benzyl, or 
phenyl or benzyl which is substituted by halogen, lower alkyl, lower 
alkoxy or nitro, and Z.sub.2 represents hydrogen, lower alkyl or phenyl, 
and the rings A, B and D, each independently of the other, can be 
unsubstituted or substituted by cyano, nitro, halogen, lower alkyl, lower 
alkoxy or lower alkoxycarbonyl, and the ring D can also contain an 
unsubstituted or substituted phenyl radical or a fused benzene ring. 
Preferred propenylenesulfone compounds of the formula (1) are those in 
which Y.sub.1 and Y.sub.2 are amino-substituted phenyl radicals of the 
formula (1a) or 3-carbazolyl radicals of the formula (1c). 
In the definition of the radicals of the sulfone compounds, lower alkyl and 
lower alkoxy usually denote those groups or group components which contain 
1 to 5, in particular 1 to 3, carbon atoms. Lower alkyl is e.g. methyl, 
ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, or amyl, and 
lower alkoxy is e.g. methoxy, ethoxy or isopropoxy. 
The term "aryl" denotes preferably phenyl. Acyl is in particular formyl, 
lower alkylcarbonyl, for example acetyl or propionyl, or benzoyl. Further 
acyl radicals are lower alkylsulfonyl, for example methylsulfonyl or 
ethylsulfonyl, and phenylsulfonyl. Phenyl, benzoyl and phenylsulfonyl can 
be substituted e.g. by halogen, methyl, methoxy or ethoxy. 
The radicals Y.sub.1 and Y.sub.2 can be different. For example, Y.sub.1 is 
a radical of the formula (1a) and Y.sub.2 is a radical of the formula (1a) 
which is different from Y.sub.1 or is a 3-indolyl radical of the formula 
(1b) or a 3-carbazolyl radical of the formula (1c). Preferably, however, 
Y.sub.1 and Y.sub.2 are identical radicals. Q is preferably an 
unsubstituted or substituted aryl radical. 
Alkyl radicals represented by R, X.sub.1, X.sub.2 and Z.sub.1 can be 
straight chain or branched. Examples of such alkyl radicals are: methyl, 
ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, n-hexyl, n-octyl or 
n-dodecyl. 
Substituted alkyl radicals represented by R, X.sub.1, X.sub.2 and Z.sub.1 
are in particular cyanoalkyl, haloalkyl, hydroxyalkyl, alkoxyalkyl, each 
containing a total of 2 to 4 carbon atoms, for example .beta.-cyanoethyl, 
.beta.-chloroethyl, .beta.-hydroxyethyl, .beta.-methoxyethyl or 
.beta.-ethoxyethyl. 
Cycloalkyl represented by X.sub.1 and X.sub.2 is for example cyclopentyl or 
preferably cyclohexyl. 
Preferred substituents in the benzyl and phenyl moiety of the X, Z.sub.1 
and R radicals are e.g. halogen atoms, or methyl or methoxy groups. 
Examples of such araliphatic and aromatic radicals are: p-methylbenzyl, o- 
or p-chlorobenzyl, o- or p-tolyl, xylyl, o-, m- or p-chlorophenyl or o- or 
p-methoxyphenyl. 
A heterocyclic radical represented by X.sub.1 and X.sub.2 together with the 
nitrogen atom to which they are attached is e.g. pyrrolidino, piperidino, 
pipecolino, morpholino, thiomorpholino or piperazino. 
Alkenyl represented by R and Z.sub.1 is e.g. allyl, 2-methallyl, 
2-ethallyl, 2-butenyl or octenyl. 
An acyl radical within the definition of R and Z.sub.1 is in particular 
formyl, lower alkylcarbonyl, for example acetyl or propionyl, or also 
benzoyl. Benzoyl can be substituted in the benzene ring by halogen, methyl 
or methoxy. 
Each of X.sub.1, X.sub.2 and Z independently represents preferably lower 
alkyl or benzyl, whilst Z.sub.2 preferably represents methyl or phenyl. 
Advantageously, X.sub.1 and X.sub.2 can also represent phenyl, lower 
alkylphenyl or lower alkoxyphenyl. X.sub.3 preferably represents hydrogen, 
methyl, methoxy or chlorine. R is preferably alkyl of 1 to 8 carbon atoms 
or benzyl and, in particular, ethyl, n-butyl or n-octyl. 
As alkyl, Q can have the same meanings as those assigned to the X, Z and R 
radicals. As aralkyl, Q is preferably benzyl or phenylethyl. 
An aryl radical represented by Q can be phenyl, diphenyl or naphthyl. These 
aromatic carbocyclic groups, and especially phenyl, can contain halogen, 
cyano, nitro, lower alkyl, lower alkoxy, methylenedioxy or acyl of 1 to 8 
carbon atoms. Particularly preferred acyl radicals are alkanoyl radicals 
of 2 to 4 carbon atoms, such as acetyl or propionyl. 
As an aryl radical, Q is preferably phenyl or phenyl which is substituted 
by halogen, methoxy or methyl. Examples of these aryl radicals are: 
phenyl, o-, m- or p-methylphenyl, o-, m- or p-methoxyphenyl, o-, m- or 
p-chlorophenyl, o-, m- or p-bromophenyl or o-, m- or p-fluorophenyl, 
3,4-dimethoxyphenyl, 3,4-dichlorophenyl, and naphthyl. 
The rings A, B and D are preferably not further substituted. If they do 
contain substituents, each independently of the other is further 
substituted in particular by halogen, lower alkyl or lower alkoxy, e.g. by 
chlorine, methyl or methoxy. Advantageously, each benzene ring can contain 
1 or 2 substituents. The substituents of the rings A and D are preferably 
in the para-position to the nitrogen atom. The ring D can also contain one 
or two fused benzene nuclei, which thus complete e.g. a 
1,2-benzocarbazole, 3,4-benzocarbazole or 1,2,3,4-dibenzocarbazole ring. 
Chromogenic propenylenesulfone compounds having an interesting utility are 
those of the formula 
##STR9## 
wherein each of Y.sub.3 and Y.sub.4 independently represents an 
amino-substituted phenyl radical of the formula 
##STR10## 
a 3-indolyl radical of the formula 
##STR11## 
or a 3-carbazolyl radical of the formula 
##STR12## 
and Q.sub.1 represents alkyl of 1 to 12 carbon atoms, preferably lower 
alkyl, or an unsubstituted or substituted aryl radical, whilst each of 
X.sub.4 and X.sub.5 independently represents lower alkyl, phenyl, lower 
alkylphenyl, lower alkoxyphenyl or benzyl, and X.sub.4 also represents 
hydrogen, or X.sub.4 and X.sub.5 together with the nitrogen atom to which 
they are attached represent pyrrolidino, piperidino or morpholino, X.sub.6 
represents hydrogen, halogen, lower alkyl or lower alkoxy, each of R.sub.1 
and Z.sub.3 independently represents alkyl of not more than 12 carbon 
atoms which is unsubstituted or substituted by halogen, cyano or lower 
alkoxy, or represents lower alkylcarbonyl, phenyl, or benzyl which is 
unsubstituted or substituted by halogen, lower alkyl or lower alkoxy, and 
Z.sub.3 also represents hydrogen and Z.sub.4 represents hydrogen, methyl 
or phenyl, and the rings A.sub.1, B.sub.1 and D.sub.1, each independently 
of the other, can be unsubstituted or substituted by cyano, halogen, lower 
alkyl or lower alkoxy and the ring D.sub.1 can also contain one or two 
fused benzene nuclei. 
Preferred sulfone compounds of the formula (2) are those in which Y.sub.3 
and Y.sub.4 are amino-substituted phenyl radicals of the formula (2a) or 
3-carbazolyl radicals of the formula (2c). Q.sub.1 preferably represents 
phenyl or phenyl which is substituted by halogen, methyl or methoxy. 
Particularly interesting sulfone compounds are those of the formulae 
##STR13## 
wherein X.sub.7 represents lower alkyl, phenyl, lower alkylphenyl, lower 
alkoxyphenyl or benzyl, X.sub.8 represents hydrogen, lower alkyl or 
benzyl, X.sub.9 represents hydrogen, methyl, methoxy or ethoxy, T 
represents hydrogen, halogen, methyl or methoxy, Z.sub.4 represents 
hydrogen, methyl or phenyl, Z.sub.5 represents hydrogen, acetyl, alkyl of 
1 to 8 carbon atoms, benzyl or phenyl, W represents halogen, methoxy or 
methyl or, in particular, hydrogen, and R.sub.2 represents alkyl of 1 to 8 
carbon atoms or benzyl. 
Preferred sulfone compounds are those of the formula (5) and, in 
particular, of the formula (3). 
Halogen in connection with the substituents in the formulae (1) to (5) is 
e.g. fluorine, bromine or, preferably, chlorine. 
The propenylenesulfone compounds of the formulae (1A) and (1B) are obtained 
by reacting a vinylene carbenium salt of the formula 
EQU [Y'--CH.dbd.CH--CH--Y"].sup..sym. An.sup..crclbar. ( 6) 
or the carbinol base thereof of the formula 
##STR14## 
with a sulfinic acid of the formula 
EQU Q--SO.sub.2 H (8) 
or a salt thereof, in which formulae (6) to (8) one of Y' and Y" has the 
meaning of Y.sub.1 and the other has the meaning of Y.sub.2, and 
An.sup..crclbar. is the anion of an inorganic or organic acid and Y.sub.1, 
Y.sub.2 and Q are as defined above. 
Suitable anions An.sup..crclbar. are both anions of inorganic acids, e.g. 
the chloride, bromide, fluoride, sulfate, phosphate or perchlorate ion, 
and of organic acids, e.g. the acetate ion, or of aromatic or aliphatic 
sulfonic acids, such as the benzenesulfonate, p-toluenesulfonate, 
methanesulfonate or ethanesulfonate ion, and also anions of acid alkyl 
esters of inorganic acids, e.g. the methosulfate or ethosulfate ion. 
Salts of the sulfinic acid of the formula (8) are e.g. the alkali metal, 
alkaline earth metal, ammonium or amine salts. 
It is advantageous to carry out the reaction in a polar organic solvent, 
especially in a lower aliphatic alcohol, for example methanol, ethanol or 
isopropanol; an ethylene glycol monoalkyl ether, such as ethylene glycol 
monomethyl or monoethyl ether; or in a cyclic ether, for example 
tetrahydrofurane or dioxane and preferably in the presence of an acid 
catalyst. Examples of suitable acid catalysts are lower aliphatic 
carboxylic acids, such as formic acid or acetic acid, and inorganic acids, 
such as hydrochloric acid, sulfuric acid, phosphoric acid or perchloric 
acid. 
The reaction can be carried out at a temperature from 10.degree. to 
100.degree. C., preferably from 40.degree. to 80.degree. C. The reaction 
time depends on the temperature and is ordinarily from 5 minutes to 2 
hours. 
The vinylene carbenium salts of the formula (6) can be obtained according 
to the method of H. Schmidt and R. Wizinger, Annalen der Chemie, Vol. 623, 
pp. 204 to 216. 
A preferred process for obtaining the carbenium salts of the formula (6) 
comprises reacting, in acid medium, a compound of the formula 
EQU Y'--CH.dbd.CH--E (9) 
with an aldehyde of the formula 
EQU Y"--CHO (10) 
wherein E represents hydrogen or carboxyl and Y' and Y" have the given 
meanings. When E is carboxyl, a decarboxylation is simultaneously 
effected. 
The carbenium salt of the formula (6) is isolated by methods commonly known 
and employed in the art, e.g. by pouring the reaction mixture into water, 
whereupon the respective salt precipitates readily, in accordance with the 
choice of the anion An.sup..crclbar.. The precipitate is collected by 
filtration, washed and dried. The aqueous solution can also be made 
alkaline, whereupon the carbinol base of the formula (7) precipitates. 
A further mode of obtaining the vinylene carbenium salts of the formula (6) 
consists in reacting an aldehyde of the formula 
EQU Y'--CHO (11) 
with the acetyl compound of the formula 
EQU Y"--COCH.sub.3 ( 12) 
and reducing the reaction product of the formula 
EQU Y'--CH.dbd.CH--CO--Y" (13) 
to the carbenium salt of the formula (6), wherein Y' and Y" have the given 
meanings. The reaction of the aldehyde of the formula (11) with the acetyl 
compound of the formula (12) can be carried out at a temperature from 
10.degree. to 150.degree. C. The reaction medium can be water or a polar 
organic solvent, preferably a lower aliphatic alcohol. It is advantageous 
to add an acid condensation agent, e.g. a lower aliphatic carboxylic acid, 
or a basic condensation agent, preferably a tertiary amine, for example 
pyridine, triethylamine or triethanolamine, or an alkali metal hydroxide, 
e.g. sodium hydroxide or potassium hydroxide. The reduction is 
advantageously carried out in an ether, such as diethyl ether, 
tetrahydrofurane or dioxane, in the temperature range from 20.degree. to 
120.degree. C., preferably at the boiling temperature of the solvent. 
Suitable reducing agents are e.g. metal hydrides, such as lithium 
aluminium hydride or sodium borohydride. 
The propenylenesulfone compounds of the formulae (1) to (5) are normally 
colourless or faintly coloured. When these colour formers are brought into 
contact with an acid developer, e.g. an electron acceptor, then, depending 
on the meaning of Y.sub.1 and Y.sub.2, they produce intense red, violet, 
blue and green shades of excellent lightfastness. They are therefore also 
very useful when mixed with one or more other known colour formers, for 
example 3,3-(bis-aminophenyl)-phthalides, 3,3-(bis-indolyl)-phthalides, 
3-aminofluoranes, 2,6-diaminofluoranes or spiropyranes, to produce blue, 
navy blue, grey or black colourations. 
The propenylenesulfone compounds of the formulae (1) to (5) exhibit both on 
clay and on phenolic substrates an improved colour intensity and 
lightfastness. They are suitable in particular as rapidly developing 
colour formers for use in a pressure-sensitive recording material, which 
can also be a copying material. 
A pressure-sensitive material consists for example of at least one pair of 
sheets, which contain at least one colour former of the formulae (1) to 
(5) dissolved in an organic solvent, and a solid electron acceptor as 
developer. The colour former effects a coloured marking at those points 
where it comes into contact with the electron acceptor. 
Typical examples of such developers are attapulgite clay, bentonite, 
acid-activated bentonite, halloysite, montmorillonite, silica, alumina, 
aluminium sulfate, aluminium phosphate, zinc chloride, kaolin or any clay 
or acidic organic compound, for example unsubstituted or ring-substituted 
phenols, salicylic acid or salicylates and their metal salts, or an acidic 
polymer material, for example a phenolic polymer, an alkylphenolacetylene 
resin, a maleic acid/colophonium resin or a partially or completely 
hydrolysed polymer of maleic acid and styrene, ethylene or vinyl methyl 
ether, or carboxypolymethylene. Mixtures of these polymeric compounds can 
also be used. Preferred developers are attapulgite clay, acid-activated 
bentonite, zinc salicylates or the condensation products of p-substituted 
phenols with formaldehyde. These latter can also contain zinc. These 
electron acceptors are preferably applied in the form of a layer to the 
face of the receiver sheet. 
In order to prevent the colour formers contained in the pressure-sensitive 
recording material from becoming active prematurely, they are usually 
separated from the electron acceptor. This can advantageously be 
accomplished by incorporating the colour formers in foamlike, sponge-like 
or honeycomb-like structures. Preferably, the colour formers are enclosed 
in microcapsules, which as a rule can be ruptured by pressure. 
When the capsules are ruptured by pressure, for example with a pencil, and 
the colour former solution is transferred in this manner to an adjacent 
sheet which is coated with an electron acceptor, a coloured area is 
produced. This colour results from the dye which is formed and which is 
absorbed in the visible range of the electromagnetic spectrum. 
The colour formers are encapsulated preferably in the form of solutions in 
organic solvents. Examples of suitable solvents are preferably 
non-volatile solvents, for example a polyhalogenated paraffin, such as 
chloroparaffin, or a polyhalogenated diphenyl, such as trichlorodiphenyl, 
and also tricresyl phosphate, di-n-butyl phthalate, dioctyl phthalate, 
trichlorobenzene, trichloroethyl phosphate, an aromatic ether, such as 
benzylphenyl ether, a hydrocarbon oil, such as paraffin, an alkylated 
derivative of diphenyl, napthalene or triphenyl, terphenyl, dibenzyl 
toluene, partially hydrogenated terphenyl, or other chlorinated or 
hydrogenated, condensed aromatic hydrocarbons. 
Mixtures of different solvents are often used in order to obtain an optimum 
solubility for the colour formation, a rapid and intense colouration, and 
a viscosity which is advantageous for the microencapsulation. 
The capsule walls can be formed evenly around the droplets of the colour 
former solution by coacervation; and the encapsulating material can 
consist of gelatin and gum arabic, as described e.g. in U.S. Pat. No. 
2,800,457. The capsules can also be formed preferably from an aminoplast 
or a modified aminoplast by polycondensation, as described in British 
patent specification Nos. 989,264; 1,156,725; 1,301,052 and 1,355,124. 
Also suitable are microcapsules which are formed by interfacial 
polymerisation, e.g. capsules formed from polyester, polycarbonate, 
polysulfonamide, polysulfonate, but in particular from polyamide or 
polyurethane. 
The microcapsules containing the colour formers of formula (1) can be used 
for the manufacture of a wide variety of known kinds of pressure-sensitive 
copying material. The various systems differ substantially from one 
another in the arrangement of the capsules, the colour reactants and the 
support. 
A preferred arrangement is that in which the encapsulated colour former is 
in the form of a layer on the back of a transfer sheet and the electron 
acceptor is in the form of a layer on the face of a receiver sheet. 
However, the components can also be used in the paper pulp. 
Another arrangement of the constituents is that wherein the microcapsules 
which contain the colour former, and the developer, are in or on the same 
sheet, in the form of one or more individual sheets, or are present in the 
paper pulp. 
Such pressure-sensitive copying materials are described, for example, in 
U.S. Pat. Nos. 2,730,457; 2,932,582; 3,418,250; 3,427,180 and 3,516,846. 
Further systems are described in British patent specification Nos. 
1,042,596; 1,042,597; 1,042,598; 1,042,599 and 1,053,935. Microcapsules 
which contain the colour formers of formula (1) are suitable for each of 
these systems and for other pressure-sensitive systems. 
The capsules are preferably secured to the support by means of a suitable 
adhesive. Since paper is the preferred support, these adhesives are 
principally papercoating agents, for example gum arabic, polyvinyl 
alcohol, hydroxymethyl cellulose, casein, methyl cellulose or dextrin. 
The paper employed comprises not only normal paper made from cellulose 
fibres, but also paper in which the cellulose fibres are replaced 
(partially or completely) by synthetic polymer fibres. 
The sulfone compounds of the formulae (1) to (5) can also be used as colour 
formers in a thermoreactive recording material. This recording material 
contains normally at least one carrier, one colour former, one solid 
electron acceptor and, if appropriate, also a binder. Thermoreactive 
recording systems comprise, for example, heat-sensitive recording and 
copying materials and papers. These systems are used, for example, for 
recording information, e.g. in electronic computers, teleprinters or 
telewriters, or in recording and measuring instruments. The image (mark) 
formation can also be effected manually with a heated pen. Laser beams can 
also be used to produce heat-induced marks. The thermoreactive recording 
material can be so composed that the colour former is dispersed or 
dissolved in one binder layer and the developer is dissolved or dispersed 
in the binder in a second layer. A second possibility consists in 
dispersing both the colour former and the developer in one layer. By means 
of heat the binder is softened at specific areas and the colour former 
comes into contact with the electron acceptor at those points where heat 
is applied and the desired colour develops at once. 
Suitable developers are the same electron acceptors as are used in 
pressure-sensitive papers. Examples of developers are the clays and 
phenolic resins already mentioned, or phenolic compounds, for example 
4-tertbutylphenol, 4-phenylphenol, 4-hydroxydiphenyl ether, 
.alpha.-naphthol, .beta.-naphthol, 4-hydroxymethylbenzoate, 
4-hydroxyacetophenone, 2,2'-dihydroxydiphenyl, 4,4-isopropylidenediphenol, 
4,4'-isopropylidene-bis-(2-methylphenol), 4,4'-bis-(hydroxyphenyl)valeric 
acid, hydroquinone, pyrogallol, phloroglucinol, p-, m- and 
o-hydroxybenzoic acid, gallic acid, 1-hydroxy-2-naphthoic acid, as well as 
boric acid and organic, preferably aliphatic, dicarboxylic acids, for 
example tartaric acid, oxalic acid, maleic acid, citric acid, citraconic 
acid and succinic acid. 
Fusible, film-forming binders are preferably used for the manufacture of 
the thermoreactive recording material. These binders are normally 
water-soluble, whereas the propenylenesulfone compounds and the developers 
are insoluble in water. The binder should be able to disperse and fix the 
colour former and the developer at room temperature. 
By applying heat the binder softens or melts, so that the colour former 
comes into contact with the developer and a colour is able to form. 
Examples of binders which are soluble, or at least swellable, in water are 
e.g. hydrophilic polymers, for example polyvinyl alcohol, polyacrylic 
acid, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, 
polyacrylamide, polyvinyl pyrrolidone, gelatin and starch. 
If the colour former and the developer are in two separate layers, it is 
possible to use water-insoluble binders, i.e. binders which are soluble in 
non-polar or only weakly polar solvents, for example natural rubber, 
synthetic rubber, chlorinated rubber, alkyd resins, polystyrene, 
styrene/butadiene copolymers, polymethylmethacrylates, ethyl cellulose, 
nitrocellulose and polyvinyl carbazole. The preferred arrangement, 
however, is that in which the colour former and the developer are 
contained in one layer in a water-soluble binder. 
The thermoreactive coatings can contain further ingredients. To improve the 
degree of whiteness, to facilitate the printing of papers, and to prevent 
the heated pen from sticking, the coatings can contain e.g. talc, 
TiO.sub.2, ZnO, CaCO.sub.3, clay or also organic pigments, for example 
urea/formaldehyde polymers. In order to effect the colour formation only 
within a limited temperature range, it is possible to add substances such 
as urea, thiourea, acetamide, acetanilide, stearic amide, phthalic 
anhydride, phthalic nitrile or other appropriate fusible products which 
induce the simultaneous melting of the colour former and developer. 
Thermographic recording materials preferably contain waxes.

In the following Examples, which further illustrate the present invention, 
the percentages are by weight unless otherwise indicated. 
EXAMPLE 1 
A mixture of 3.8 g of a vinylene carbenium salt of the formula 
##STR15## 
[obtained by the method of H. Schmidt and R. Wizinger, Annalen der Chemie 
623, 204 (1959)], 4 g of sodium p-toluenesulfinate and 1 ml of glacial 
acetic acid in 50 ml of methanol is refluxed for 10 minutes. The 
precipitate obtained after cooling is collected by filtration and washed 
with methanol, affording 3.5 g of a compound of the formula 
##STR16## 
A sample of this substance recrystallised from toluene melts at 
172.degree.-174.degree. C. with decomposition. 
When applied to a paper coated with acid-activated bentonite, a solution of 
the compound of the formula (22) in toluene produces immediately an 
intense blue, lightfast colour with .mu. max at 700 nm. 
The colour formers of the formula 
##STR17## 
listed in the following tables are obtained in the same manner as 
described in Example 1. 
TABLE 
______________________________________ 
Shade on 
Ex- acid-activated 
ample Y T bentonite 
______________________________________ 
##STR18## H blue 
3 
##STR19## H blue 
4 
##STR20## H blue 
5 
##STR21## H blue 
6 
##STR22## Cl blue 
7 
##STR23## CH.sub.3 
blue 
8 
##STR24## H blue 
9 
##STR25## H blue 
10 
##STR26## CH.sub.3 
blue 
11 
##STR27## CH.sub.3 
blue 
12 
##STR28## H red 
______________________________________ 
EXAMPLE 13 
Production of a Pressure-Sensitive Copying Paper 
A solution of 3 g of the propenylenesulfone compound of the formula (22) in 
97 g of partially hydrogenated terphenyl is emulsified in a solution of 12 
g of pigskin gelatin in 88 g of water of 50.degree. C. A solution of 12 g 
of gum arabic in 88 g of 50.degree. C. is then added, followed by the 
addition of 200 ml of water of 50.degree. C. The resulting emulsion is 
poured into 600 g of ice water, whereupon the coacervation is effected. A 
sheet of paper is coated with the resulting suspension of microcapsules 
and dried. A second sheet of paper is coated with acid-activated 
bentonite. The first sheet and the sheet of paper coated with 
acid-activated bentonite are laid on top of each other with the coated 
sides face to face. 
Pressure is exerted on the first sheet by writing by hand or typewriter and 
an intense blue copy of excellent lightfastness develops on the sheet 
which is coated with clay. 
Corresponding intense and lightfast blue and red copies are also obtained 
by using each of the other colour formers of the formula (23) indicated in 
Examples 2 to 12 of the table. 
EXAMPLE 14 
In a ball mill, 32 g of bis-(4-hydroxyphenyl)-dimethylmethane (Bis-phenol 
A), 3.8 g of the distearylamide of ethylene diamine, 39 g of kaolin, 20 g 
of an 88% hydrolysed polyvinyl alcohol and 500 ml of water are ground to a 
particle size of about 5.mu.. In a second ball mill, 6 g of the compound 
of the formula (22), 3 g of a 88% hydrolysed polyvinyl alcohol and 60 ml 
of water are ground to a particle size of about 3.mu.. 
Both dispersions are mixed and applied to paper to a dry coating weight of 
5.5 g/m.sup.2. An intense blue colour of excellent lightfastness is 
produced by contacting the paper with a heated ball-point pen. 
Intense and lightfast blue and red shades can also be obtained by using 
each of the other colour formers of Examples 2 to 12 of the table.