Pressure-Sensitive or Heat-Sensitive Recording Material

The present invention relates to a pressure-sensitive or heat-sensitive recording material which contains in its colour reactant system, as developer for the colour former, at least one compound of the formula ##STR3## wherein X is the direct bond or ##STR4## each of R.sub.1, R.sub.2 and R.sub.3 independently is hydrogen or unsubstituted or substituted alkyl, aryl or aralkyl, or R.sub.1 and R.sub.3, together with the nitrogen atom to which they are attached, are a 5- or 6-membered heterocyclic radical, Q is carbon or an unsubstituted or substituted hydrocarbon radical, Y is halogen, and m is 1 to 3.

Preferred compounds of the formula (1) are those wherein Y is chlorine. Q is preferably carbon and the preferred value of m is 3.

Alkyl radicals R have advantageously 1 to 12 carbon atoms and can be straight chain or branched. Examples of such radicals are: methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, n-hexyl, n-octyl or n-dodecyl. Substituted alkyl radicals R are in particular: cyanoalkyl, haloalkyl, alkoxyalkyl or carbalkoxyalkyl, each containing a total of 2 to 5 carbon atoms. Examples of such substituted alkyl radicals are: .beta.-cyanoethyl, .beta.-chloroethyl, .beta.-methoxyethyl, .beta.-ethoxyethyl, carbomethoxymethyl or .beta.-carboethoxyethyl.

Arylkyl radicals R are usually phenethyl or, in particular, benzyl, whilst aryl is preferably naphthyl, diphenyl and, most preferably, phenyl. The aralkyl and aryl radicals can be substituted by halogen, nitro, lower alkyl, lower alkoxy, lower alkylcarbonyl or lower alkoxycarbonyl groups.

Preferred substituents of aralkyl and aryl radicals R are e.g. halogen, nitro, methyl, methoxy, ethoxy, carbomethoxy, carboethoxy or acetyl. Examples of such araliphatic and aromatic radicals are: methylbenzyl, chlorobenzyl, nitrophenyl, tolyl, xylyl, chlorophenyl, methoxyphenyl, carbomethoxyphenyl or acetophenyl.

A heterocyclic radical represented by R.sub.1 and R.sub.3, together with the nitrogen atom to which they are attached, is preferably saturated and is e.g. pyrrolidino, piperidino, pipecolino, morpholino, thiomorpholino or piperazino.

Q can be an aliphatic, cycloaliphatic, aliphaticaromatic or aromatic hydrocarbon radical which is unsubstituted or substituted. An aliphatic radical Q is in particular a C.sub.1 -C.sub.6 alkylene radical, preferably a C.sub.1 -C.sub.4 alkylene radical, which can be straight chain or branched and substituted by halogen, carboxyl, --SO.sub.3 H, phenyl or halophenyl. A cycloaliphatic radical Q is in particular the cyclohexylene group. As an aromatic radical, Q is preferably diphenylene or, most preferably, phenylene which can be substituted by halogen, carboxyl, --SO.sub.3 H, lower alkyl or lower alkoxy.

Within the scope of the definition of the above radicals, lower alkyl and lower alkyl usually denote those groups or group constituents which contain 1 to 5, especially 1 to 3, carbon atoms, e.g. methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl or amyl, and methoxy, ethoxy or isopropoxy.

Throughout this specification, halogen as substituent of compounds of the formula (1) is e.g. fluorine, bromine or, preferably, chlorine.

In formula (1), the grouping ##STR5## is preferably ##STR6## and especially ##STR7## .

Important colour developers of the formula (1) to be used in the practice of this invention have the formula ##STR8## wherein X.sub.1 is the direct bond or ##STR9## each of R.sub.4, R.sub.5 and R.sub.6 independently is alkyl of at most 12 carbon atoms which is unsubstituted or substituted by halogen, cyano or lower alkoxy, or is benzyl, phenyl or naphthyl, or benzyl or phenyl each of which is substituted by halogen, lower alkyl or lower alkoxy, and R.sub.5 and R.sub.6 are also hydrogen, or R.sub.4 and R.sub.6, together with the nitrogen atom to which they are attached, are a saturated 5- or 6-membered heterocyclic radical, Q.sub.1 is carbon, alkylene of 1 to 6 carbon atoms or phenylene, Hal is halogen and m is 1 to 3. The preferred identity of Q.sub.1 is carbon and m is accordingly 3.

Preferred substituents in the benzyl and phenyl moiety of radicals R.sub.4, R.sub.5 and R.sub.6 are e.g. halogen, methyl or methoxy. Each benzene ring can contain 1 to 3 substituents. The preferred identity of R.sub.5, and especially of R.sub.6, is hydrogen.

Particularly interesting colour developers are those of the formula ##STR10## wherein X.sub.2 is the direct bond or ##STR11## each of R.sub.7, R.sub.8 and R.sub.9 independently is lower alkyl, phenyl, benzyl or naphthyl, or phenyl or benzyl each of which is substituted by halogen, methyl or methoxy, and R.sub.8 and R.sub.9 are also hydrogen, and Hal is halogen, especially chlorine.

Preferred colour formers are those of the formula ##STR12## wherein R.sub.10 is lower alkyl, benzyl, phenyl, or phenyl which is substituted by halogen, methyl or methoxy, and X.sub.3 is the direct bond or preferably --NH--.

The compounds of the formula (1) employed in the practice of this invention as colour developers or electron acceptors for colour formers are products which are obtained e.g. by reaction of 1 mole of a compound of the formula ##STR13## with an aldehyde of the formula

or the hydrate thereof, in which formulae (5) and (6) above R.sub.1, R.sub.2, X, Y, Q and m have the given meanings.

Compounds of the formulae (1) to (5) and pertinent preparatory methods are described e.g. in Chemical Abstracts, Vol. 69, 1968, 18741b, and Journal of General Chemistry of the USSR 46, 1792-1795 (1976).

Examples of starting compounds of the formula (5) are: methylthiourea, ethylthiourea, phenylthiourea, tolylthiourea, N,N-dimethylthiourea, N,N-diethylthiourea, N,N-diphenylthiourea, 2-naphthylthiourea, thioacetamide, thiopropionamide or thiobenzamide.

Examples of starting aldehydes of the formula (6) are: chloroacetaldehyde, bromoacetaldehyde, fluoroacetaldehyde, trichloroacetaldehyde, tribromoacetaldehyde, trifluoroacetaldehyde, tribromopropionaldehyde, .alpha.-chlorocrotonaldehyde, trichlorobutyraldehyde, 2,3-dibromo-3,3-dichloropropional, 2,2,3-trichloropentanal, trichlorobenzaldehyde, 2,3-dichloro-3-phenylpropionaldehyde, 2,2,3-trichloro-3-phenylpropionaldehyde, 2-chloro-2,3-dibromo-3-phenylpropionaldehyde and 2,2,3-trichloro-3-(3'-chlorophenyl)-propionaldehyde.

The compounds of the formulae (1) to (4) are virtually colourless and odourless and are very reactive with the conventional colour formers, so that spontaneous, permanent and non-fading recordings or copies are obtained.

The colour formers suitable for the recording or copying material employed in this invention are known colourless or faintly coloured substances which, when brought into contact with the compounds of the formulae (1) to (4), become coloured or change colour. It is possible to use colour formers or mixtures thereof which belong e.g. to the classes of the phthalides, fluoranes, benzofluoranes, spiropyranes, azomethines, leuco-auramines, triarylmethane-leuco dyes, phenoxazines, phenothiazines, and of the chromeno or chromano colour formers. Examples of such suitable colour formers are: crystal violet lactone (Registered Trademark), 3,3-(bisaminophenyl)-phthalides, 3,3-(bis-substituted indolyl)-phthalides, 3-(aminophenyl)-3-indolyl-phthalides, 6-dialkylamino-2-n-octylaminofluoranes, 6-dialkylamino-2-arylaminofluoranes, 6-dialkylamino-3-methyl-2-arylaminofluoranes, 6-dialkylamino-2- or -3-lower alkylfluoranes, 6-dialkylamino-2-dibenzylaminofluoranes, bis-(aminophenyl)-furyl-, -phenyl- or -carbazolylmethanes, or benzoyl-leucomethylene blue.

The compounds of the formulae (1) to (4) are suitable for use as colour developers in a pressure-sensitive, or especially heat-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 dissolved in an organic solvent, and a developer of the formulae (1) to (4). The colour former effects a coloured marking at those points where it comes into contact with the developer.

The developers of the formulae (1) to (4) can be used by themselves, in admixture with each other, or in admixture with known developers. These developers are preferably applied in the form of a layer to the face of the receiver sheet.

Typical examples of known 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, for example a phenolic polymer, an alkylphenolacetylene resin, a maleic acid/rosin resin, or a partially or completely hydrolysed polymer of maleic acid and styrene, ethylene or vinyl methyl ether, or carboxypolymethylene.

In order to prevent the colour formers contained in the pressure-sensitive recording material from becoming active prematurely, they are usually separated from the developer. This can advantageously be accomplished by incorporating the colour formers in foam-like, sponge-like or honeycomb-like structures. Preferably, the colour formers are enclosed in microcapsules, which usually 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 the developer of the formula (1), 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-butylphthalate, an aromatic ether such as benzylphenyl ether, a hydrocarbon oil such as paraffin or kerosene, an alkylated derivative of diphenyl, naphthalene or triphenyl, dibenzyl toluene, terphenyl, partially hydrogenated terphenyl, a benzylated xylene, 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 specifications 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 can be used for the production 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, i.e. the developers, 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 developer 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 components 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.

The capsules are preferably secured to the support by means of a suitable adhesive. As paper is the preferred support, these adhesives are principally paper-coating agents, for example gum arabic, polyvinyl alcohol, hydroxymethyl cellulose, casein, methyl cellulose, dextrin, starch or polymer lattices.

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 compounds of the formulae (1) to (4) are preferably employed as developers in a thermoreactive recording material. This recording material usually contains at least one carrier, one colour former, one solid developer and, optionally, also a binder. Thermoreactive recording systems comprise, for example, heat-sensitive recording and copying materials and papers. These systems are used e.g. for recording information, for example 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 composed such 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. Another 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 developer at those points where heat is applied and the desired colour develops at once. The developers of the formulae (1) to (4) can be used by themselves, in admixture with each other, or in admixture with other known developers.

For this purpose it is known to employ the same developers as are used in pressure-sensitive papers, and also phenolic compounds, e.g. 4-tert-butylphenol, 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 production of the thermoreactive recording material. These binders are normally water-soluble, whereas the colour formers 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.

The action of heat softens or melts the binder, so that the colour former comes in 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 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, inert clays 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.

A solution of 3 g of crystal violet lactone 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 water of 50.degree. C. is then added, followed by the addition of 200 ml of water of 50.degree. C. The resultant emulsion is poured into 600 g of icewater and cooled, whereupon coacervation is effected. A sheet of paper is coated with the suspension of microcapsules and dried. A second sheet of paper is coated with a compound of the formula ##STR14## (m.p. 104.degree. C.). The first sheet and the sheet of paper coated with the compound of the formula (11) 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 develops on the sheet coated with the developer.

In a ball mill, 32 g of a compound of the formula ##STR15## (m.p. 119.degree. C.), 3.8 g of the distearylamide of ethylenediamine, 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 2-phenylamino-3-methyl-6-diethylamino-fluorane, 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 black colour of excellent lightfastness is produced by contacting the paper with a heated ball-point pen. The developers of the formula (13) listed in the following table can also be used in the same way as described in Examples 1 and 2.