GB2104089A - Aminofluoran derivatives and recording materials containing them - Google Patents

Abstract

A 2-amino-6-diarylaminofluoran derivative is of the general formula: <IMAGE> where Ar and Ar' are each a C6-20 aryl group, which may have alkyl or alkoxy substituents, or a C4-36 heterocyclic residue, or they together complete a heterocyclic nucleus; R1 and R2 each are H, C1-20 alkyl, C5-7 cycloalkyl, C7-18 aralkyl, C6-20 optionally substituted aryl, or heterocyclic; R3 is H, halogen, C1-5 alkyl or alkoxy, C1-20 alkylamino, C2-40 dialkylamino, C2-20 acylamino, NO2 or NH2; R4 is H, halogen or C1-5 alkyl or alkoxy; and rings A and B may bear other substituents, e.g. alkyl, alkoxy or halogen. 23 specific compounds are shown. Condensation synthesis is from a p- aminophenol and benzoylbenzoic acid or a fluoran and alkylating or arylating agent. The compounds are used in color forming recording materials, especially microencapsulated in pressure-sensitive material or in a binder in heat-sensitive material. A black or greenish black dye is formed upon contact with an electron- accepting substance such as a clay, organic acid or metal salt thereof.

Description

SPECIFICATION Amino-fluoran derivatives and recording materials containing them The present invention relates to novel fluoran derivatives and recording materials containing the fluoran derivative as a dye precursor.

The fluoran compounds of the present invention are particularly useful as dye precursors employed in recording materials, especially a pressure-sensitive recording sheet, a heat-sensitive recording sheet or an energizable heat-sensitive recording sheet, and also employable in a lightsensitive recording sheet, an ultrasonic wave recording sheet, an electron beam recording sheet, an electrostatic recording sheet, a presensitized printing plate, a textile printing material, a typewriter ribbon, an ink for a ball point pen, a crayon and the like.

Hitherto, fluoran compounds have been employed as dye precursors for recording materials.

However, many suffer from the defects that they are unstable in the atmosphere and that dyes produced therefrom have poor light fastness and poor moisture resistance.

Therefore, an object of the present invention is to provide a novel fluoran derivative which has excellent properties in particular as dye precursors for recording materials.

The above-described object of the present invention is attained with fluoran derivatives which have an amino group at the 2-position of their fluoran skeleton and an diarylamino group at the 6position of their fluoran skeleton.

The fluoran derivatives of the present invention are colorless or slightly colored powders which are stable in the atmosphere, form a black color instantaneously when brought into intimate contact with a conventional electron-accepting substance, such as activated clay, a phenol-formaldehyde resin, or bisphenol A, and do not undergo deterioration in their color-forming abilities such as coloration or decomposition on storage. Consequently, they are excellent for use as dye precursors in recording materials.

Preferred fluoran derivatives of the present invention are represented by the following general formula (I);

wherein Ar and Ar', which may be the same or different, each represents an aryl group (C6 to C20) or a heterocyclic residue (C4 to C36), and they link with each other to form a heterocyclic ring.

Substituents R1 and R2 in general formula (I) may be the same or different and they each represents a hydrogen atom, an alkyl group (C, to C20), a cycloalkyl group (C5 to C7), an aralkyl group (C7 to C18), an aryl group (C6 to C20) or a heterocyclic residue; further, they may link with each other to form a heterocyclic ring (C4 to C6).

Substituent R3 in general formula (I) represents a hydrogen atom, an alkyl group (C1 to C5), an alkoxy group (Ct to C6), a halogen atom (e.g. Cl, Br), a nitro group, an amino group, an alkylamino group (C1 to C20), a dialkylamino group (C2 to C40) or an acylamino group (C2 to C20); substituent R4 represents a hydrogen atom, an alkyl group (C, to C5), an alkoxy group (C1 to C5) or a halogen atom (e.g., Cl, Br).

Benzene rings A and B in the above-described general formula (I) may also have substituents.

An aryl group represented by Ar or Ar' in the above-described general formula (I) may have substituents; examples of such substituents include alkyl groups (C1 to C14), alkoxy groups (C1 to C14) and halogen atoms (e.g., Cl, Br). Of such alkyl and alkoxy groups, those which have 10 or less carbon atoms are preferable. Specific examples of the preferred aryl groups represented by Ar or Ar' include a phenyl group, alkyl (C1 to C10) substituted phenyl groups, alkoxy (C1 to C10) substituted phenyl groups, halogen (e.g., Cl) substituted phenyl groups, a naphthyl group, alkyl (C1 to C10) substituted naphthyl groups, halogen (e.g., Cl) substituted naphthyl groups and alkoxy (C1 to C10) substituted naphthyl groups.

Specific examples of a heterocyclic residue represented by Ar or Ar' in the above-described general formula (I) include a furyl group, pyrrolyl groups, thienyl groups, indolyl groups, carbazolyl groups, phenoxazinyl groups, phenothiazinyl groups and phenazinyl groups which are represented by the following formulae, respectively;

wherein R and R' each represents a hydrogen atom or an alkyl group (C, to C12).

Examples of heterocyclic nuclei formed by connecting Ar to Ar' include a carbazole, phenoxazine, phenothiazine or phenazine nucleus, represented by the following formulae, respectively;

wherein R represents an alkyl group (C, to C,2).

An alkyl group, a cycloalkyl group, an aralkyl group and an aryl group represented by R1 or R2 in general formula (I), each may have substituents. Specific examples of such a substituent include alkyl groups (C1 to C20), alkoxy groups (C, to C20), a cyano group, a nitro group, halogen atoms (e.g., Cl, etc.), alkoxycarbonyl groups (C2 to C20), aryloxycarbonyl groups (C7 to C20), alkylcarbonyloxy groups (C2 to C20), arylcarbonyloxy groups (C7 to C20), alkylsulfonyloxy groups (C, to C20), arylsulfonyloxy groups (C6 to C20), carbamoyl groups, sulfamoyl group, alkylamino groups (C, to C12), dialkylamino groups (C2 to C24), acylamino group (C2 to C20), alkylsulfonylamino groups (C, to C20), arylsulfonylamino groups (C6 to C20), alkylsulfonyl groups (C1 to C20), arylsulfonyl groups (C6 to C20), alkylcarbonyl groups (C2 to C20), arylcarbonyl groups (C7 to C20) and so on.These substituents may further have substituents.

Specific examples of preferred substituents represented by R, or R2 include a hydrogen atom, alkyl groups having 1 2 or less carbon atoms, alkoxy substituted alkyl groups, halogen (e.g., Cl) substituted alkyl groups, aralkyl groups (C7 to C,2), cycloalkyl groups (C5 to C7), a phenyl group, alkyl (C, to C,2) substituted phenyl groups, alkoxy (C, to C,2) substituted phenyl groups, halogen (e.g., Cl) substituted phenyl groups, cyano substituted phenyl groups, N,N-dialkylcarbamoyl (C3 to C2,) substituted phenyl groups, N,N-dialkylsulfamoyl (C2 to C20) substituted phenyl groups, dialkylamino (C2 to C20) substituted phenyl groups, acylamino (C2 to C,g) substituted phenyl groups and arylsulfonylamino (C, to C16) substituted phenyl groups.

Preferred examples of substituents represented by R3 or R4 in the above-described general formula (I) include alkyl groups having 4 or less carbon atoms, alkoxy groups having 4 or less carbon atoms and halogen atoms.

Benzene ring A and benzene ring B in general formula (I) may have substituents. Examples of such substituents includes alkyl groups, alkoxy groups, halogen atoms (e.g., Cl, etc.), a nitro group, an amino group, alkylamino groups (C, to C4), dialkylamino groups (C2 to C8) and acylamino groups (C2 to C5). Of these substituents, alkyl groups having 4 or less carbon atoms, alkoxy groups having 4 or less carbon atoms and halogen atoms are more preferred.

In the above-described fluoran derivatives in the present invention, the fluoran derivatives having the following general formula (II) are more preferred (wherein Ar and Ar' are each optionally substituted phenyl and R3 is a hydrogen atom):

wherein substituents R, and R2, which may be the same or different, each represents a hydrogen atom, an alkyl group (C1 to C16), an aralkyl group.(C7 to C16) or a group represented by

wherein R is hydrogen atom, alkyl group (C1 to C4), alkoxy group (C1 to C4), Cl, Br, CN or a dialkylsulfamoyl group and I represents an integer of 1 to 5, substituent R4 represents H, -CH3 or halogen, substituents R5 and R6, which may be the same or different, each represents an alkyl group (C to C4) or an alkoxy group (Ca to C4), and m and n each represents 0 or an integer of 1 to 5.

The fluoran derivatives to which the present invention relates are novel compounds, and are generally obtained as colorless or light colored crystals. However, they turn rapidly greenish black to black when brought into contact with an electron-accepting substance. The produced dye is remarkably stable compared with dyes produced from conventional color forming agents, and hardly undergoes discoloration and fading even when irradiated with light, heated or moistened for long time periods.

Therefore, they are of great advantage, in particular from the viewpoint of long term storage of recorded material. In addition, they are excellent in stability previous to color formation and do not undergo deterioration and coloration and retain sufficient color forming ability upon long-range storage. Thus, the fluoran derivatives of the present invention possess almost ideal properties as color former employed in recording materials such as pressure-sensitive copying paper, heat-sensitive copying paper and the like.

Specific examples of fluoran derivatives of the present invention are named below.

(1) 2-Octylamino-6-diphenylaminofluoran, (2) 2-Octylamino-6-(N-phenyl-N-p-tolyl)aminofl uoran, (3) 2-Octylamino-6-(N-p-tolyl-N-p-anisyl)aminofluoran, (4) 2-Dibenzyíamino-6-(N-p-tolyl-N-p-anisyl)aminofluoran, (5) 2-Dibenzylamino-6-(N-phenyl-N-p-tolyl)aminofluoran, (6) 2-Anilino-3-methyl-6-diphenylaminofluora (7) 3-Anilino-3-methyl-6-(N-phenyl-N-p-anisyl)aminofluoran, (8) 2-Anilino-3-methyl-6-(N-phenyl-N-p-tolyl)aminofluoran, (9) 2-Anilino-3-methyl-6-di-p-tolylaminofluoran, (1 0) 2-Anilino-3-methyl-6-di-p-anisylaminofluoran, (11) 2-Butyl-3-chloro-6-(N-phenyl-N-p-tolyl)aminofluoran, (1 2) 2-Butyl-3-chloro-6-(N-phenyl-N-p-anisyl)aminofluoran, (1 3) 2-Anilino-3-chloro-6-(N-phenyl-N-p-tolyl)aminofluoran, (14) 2-Anilino-3-chíoro-6-(N-phenyl-N-p-anisyl)aminofluoran, (1 5) 2-o-Chloroanilino-6-(N-phenyl-N-p-anisyl)aminofluoran, (1 6) 2-o-Chloroanilino-6-di-p-anisylaminofluoran, (17) 2-Anilino-6-diphenylaminofluoran, (1 8) 2-p-Chloroanilino-6-(N-phenyl-N-p-tolyl)aminofluoran, (1 9) 2-p-tolylamino-6-(N-phenyl-N-p-tolyl)aminofluoran, (20) 2-o-Anisylamino-6-(N-phenyl-N-p-tolyl)aminofluoran, (21) 2-(N-p-bromophenyl)anilino-6-(N-phenyl-N-p-tolyl)aminofluoran, (22) 2-i N-p-(N,N-dibutylsu lfamoyl)phenyl )anilino-6-(N-phenyl-N-p-tolyl)aminofluoran, (23) 2-(N-p-cyanophenyl)anilino-6-(N-phenyl-N-p-anisyl)aminofluoran.

The structures of these compounds are given in Table 1.

Table 1 General Formula

Compound Ar N- R R -N R1 No. Ar'/ 3 R4 2 (1) S N H H -NHC8H17 , (2) N- H H -NHC8H17 CH3 0 (3) N- H H -NHC8H17 CH3O (4) < N- H H -N(CH2 e 32 CH30 ss CH3O (5) N- H H -N(CH2 O )2 CH3

Compound Ar R3 R4 -N R1 No. Ar' R3 No. Ar'R2 (6) N- H CH3 (7) CH3 -NH (7) N- H CH3 -NH CH30 (8) N- H CH3 -NH CH N 3 CH3 CH3 ss N- H CH3 -NH CH3 CH3 < (10) N- H CH3 -NH CH30 (11) N- H Ct -NHC4Hg d CH3

Compound Ar'\N~ Ar R4 N / No. N Ar'R2 Ar' H CL -NHCqH9 (12) N- H Ct -NHC4Hg CH30 ss H N- H Ct -NH d CH3' (14) N- H Ct -NH CH3O H N- H H -NH d ca/ (16) CH30 t N- H H -NH 9 C}i3o (17) N- H H -NH '

Ar Compound R -N Ar R ompound.N' R3 R4 No. ~Ar\Rz Q, T (18) N- H H -NHCt CH3 (19) N- H H -NH ss H3 CH3 (20) N- H H -NH (zo) CH3 (21) N- H H \0\ CH3 CH3 (22) -H H \0 CH3 (23) N- H H CH30 MN Processes for synthesizing the fluoran derivatives of the present invention are illustrated below.

The fluoran derivatives of the present invention can be synthesized using the process represented by reaction scheme A or B, Ar, Ar' and R, to R4 have the same meanings as above.

wherein R represents H, -CH3,

-S02CH3,

etc.

Scheme B

wherein R' represents H or R1, X represents a halogen atom (e.g., Cl, Br, I) or a sulfonyloxy group of the formula -0S02R8, and P5 represents an alkyl group (C, to C8) or an aryl group (C6 to C,2).

Scheme A involves the reaction of a benzoylbenzoic acid derivative with a p-aminophenol derivative in the presence of an acid catalyst.

As examples of useful acid catalysts which may be employed in such a reaction, mention may be made of Lewis acids such as zinc chloride, aluminium chloride, magnesium chloride and the like; and BrMnsted acids such as sulfuric acid, p-toluenesuifonic acid, methanesulfonic acid and the like.

Scheme B involves the reaction of a fluoran derivative with an alkylating agent or an arylating agent in the presence of a catalyst. Useful catalysts include metallic copper powder, copper compounds such as cuprous iodide, cupric iodide and the like; nickel compounds; and cobalt compounds. Of these catalysts, metallic copper powder made of fine particles is particularly favourable.

Specific examples of synthesizing the fluoran derivatives of the present invention are given below.

Unless otherwise indicated in the following examples, all pressures were atmospheric and all temperatures were room temperature.

SYNTHESIS EXAMPLE 1 Synthesis of 2-Dibenzylamino-6-(N-phenyl-N-p-tolyl)aminofluoran (5) 6.3 g (0.013 mole) of 2-amino-6-(n-phenyl-N-p-tolyl)-aminofluoran, 6.4 g (0.05 mole) of benzyl chloride, 1 g of copper powder, 7.5 g of potassium carbonate and 1 2 ml of dimethylformamide were mixed and refluxed with stirring for 5 hours. After cooling, the reaction mixture was poured into water, and extracted with ethyl acetate.

The solvent was removed from the extract by evaporation, and the residue was purified by being passed through a column of silica gel. Thus, 3.5 g of 2-dibenzylamino-6-(N-phenyl-N-ptolyl)aminofluoran was obtained.

SYNTHESIS EXAMPLE 2 Synthesis of 2-Anilino-3-methyl-6-(N-phenyl-N-p-tolyl)a minofluoran (8) A mixture of 6.0 g (0.015 mole) of 2-f2-hydroxy-4-(N-phenyl-N-p-tolyl)aminojbenzoylbenzoic acid, 3.0 g (0.015 mole) of 3-methyl-4-anilinophenol and 18 ml of concentrated 96% sulfuric acid was stirred for 10 hours at a temperature of 400 C. The reaction mixture was poured into ice water, neutralized with sodium hydroxide, and extracted with ethyl acetate. After removal of the solvent from the extract by evaporation, the residue was purified by being passed through a column of silica gel.

Thus, 2.3 g of 2-anilino-3-methyl-6-(N-phenyl-N-p-tolyl)aminofluoran was obtained.

SYNTHESIS EXAMPLE 3 Synthesis of 2-(N-p-cyanophenyl)anilino-6-(N-phenyl-N-p-anisyl)aminofluororan (23) A mixture of 4.0 g (0.01 mole of 2-j2-hydrnxy-4-(N-phenyl-N-p-anisyl)amino)benzoylbenzoic acid, 2.6 g (0.01 mole) of 4-hydroxy-4'-cyanotriphenylamine, 4 ml of concentrated 96% sulfuric acid and 4 ml of 20% fuming sulfuric acid was stirred for 1 5 hours at a temperature of 300C to 40cm. The reaction mixture was poured into ice water, neutralized with sodium hydroxide, and extracted with toluene. After removing the solvent from the extract by evaporation, the residue was purified by being passed through a column of silica gel. Thus, 3.4 g of 2-(N-p-cyanophenyl)anilino-6-(N-p-anisyl)aminofluoran was obtained.

Representative fluoran derivatives of the present invention and the color hues developed on activated clay are shown in Table 2.

TABLE 2 Compound No. Hue on Activated Clay (1) Greenish-black (7) Black (9) Black (11) Greenish-black (14) Black (15) Black ,per8) Greenish-black (20) Black (22) Black (23) Black Processes for preparing recording materials utilizing dye precursors to which the present invention relates are described below.

Pressure-sensitive copying paper in which the dye precursors of the present invention can be employed may take various forms, as described in previous patents, for example, U.S. Patents 2,505,470; 2,505,471; 2,505,489; 2,548,366; 2,712,507; 2,730,456; 2,730,457 and 3,418,250.

The dye precursors are dissolved in a solvent (e.g., synthetic oils such as alkylated naphthalenes, alkylated diphenyls, alkylated diphenylmethanes, alkylated terphenyls; vegetable oils such as cotton oil, castor oil; animal oils; mineral oils; or mixtures thereof) individually, as a mixture thereof or together with conventional dye precursors, and the resulting solution is dispersed into a binder or microencapsulated using a conventional process and then coated on a support such as paper, a plastic sheet, a resin-coated paper or the like.

A suitable amount of the dye precursor varies with the thickness(es) of the coated layer(s), the form of the pressure-sensitive copying paper, the process for encapsulating the dye precursor(s) and other conditions and such is selected depending upon these factors; however, the amount can be easily determined by one skilled in this art using conventional procedures. For encapsulating the dye precursor in microcapsules, conventional processes based on coacervation of a hydrophilic colloid, as described in U.S. Patents 2,800,457 and 2,800,458; interfacial polymerization, as described in British Patents 867,797; 950,443 and 1,091,076; and the like can be employed.

In addition, a heat-sensitive copying paper in which a dye precursor of the present invention is employed is generally prepared in the following manner.

A dye precursor, an electron-accepting substance and a heat-fusible substance (used in the case that the dye precursor or electron-accepting susbtance is not molten at the desired temperatures) are ground to a fine size and mixed with a solution of a binder dissolved or dispersed in a solvent or dispersion medium, respectively. The thus prepared composition is coated on a support such as paper, a plastic sheet, a resin-coated paper, etc., and dried at 500C. For the preparation of a mixed solution, all of the components may be simultaneously mixed and ground or the components may be combined in various groups, ground and dispersed separately and then mixed with one another.

Also, the above-described coating composition may be incorporated into a paper support during its manufacture.

In addition, an opacity-providing agent may be admixed at the time of mixing.

With respect to the amounts of the ingredients constituting the heat-sensitive recording paper, the amount of dye precursor is 1 to 2 parts by weight, the amount of electron-accepting substance is 1 to 6 parts by weight, the amount of heat-fusible substance is O to 30 parts by weight, the amount of binder is 1 to 1 5 parts by weight and the amount of dispersion medium (or solvent) is 20 to 300 parts by weight.

As the dye precursor there may be employed one or more of the fluoran derivatives of the present invention, or a mixture of one or more of the fluoran derivatives of the present invention with other known color forming agent (color former) as are used in conventional pressure-sensitive copying papers, such as 3,3-bis-(p-dimethylmainophenyl)-6-dimethylaminophthalide, known as Crystal Violet lactone ("Crystal" is a registered Trade Mark), or known fluoran derivatives.

As an electron-accepting substance to react with the recording material, there may be employed a clay (e.g., activated clay, acid clay or attapulgite), an organic acid (e.g., salicyclic acid, tannic acid, gallic acid), a metal salt thereof (e.g., a polyvalent metal salt of an aromatic carboxylic acid) preferably a zinc salt, a phenolic compound, an acidic polymer such as a phenol-formaldehyde resin, phenol resin or bisphenol A. Of these, organic acids or metal salts thereof are most preferred.

A dispersion medium (or solvent) must only slightly dissolve the dye precursors and the electronaccepting substances, or undesired coloration takes place. Accordingly, water is most preferred for use as a dispersion medium (or solvent), though hydrocarbons such as hexane, ligroin or petroleum ether may be used.

The binders which may be used in the present invention are conventional and include styrenebutadiene copolymers, alkyd resins, polybutylmethacrylate, vinyl chloride-vinyl acetate copolymers, styrene-maleic an hydroxide copolymers, synthetic rubbers, gum arabic, polyvinyl alcohol, hydroxyethyi cellulose and the like.

Taking into account correlation with the dispersing media (solvents), water-soluble binders such as gum arabic, polyvinyl alcohol, hydroxymethyl cellulose and the like are especially preferred among the above binders.

Specific examples of heat-fusible substances which may be used in the present invention includestearic acid amide, erucic acid amide, oleic acid amide, ethylenebisstearamide, benzoin, acnaphthol, p- naphthol, p-t-butylphenol, p-phenylphenyl, 4,4'-cyclohexylidenediphenol, 4,4'-isopropylidenediphenol, phthalic anhydride, maleic anhydride, stearic acid, erucic acid, palmitic acid, p-hydroxybenzoic acid methyl ester, phthalic acid diphenyl ester, triphenylphosphate, p-hydroxydiphenyl ether, 2,2-bisI4-(P- hydroxyethoxy)phenyl Ipropane, p-bis(ss-hydroxyethoxy)benzene and the like. Preferred examples of the heat-fusible substances are those having a melting point of 50 to 2000C, more preferably 70 to 1 500C.

These substances are colorless or light colored solids at ordinary room temperature but melt sharply at temperatures suitable for copying, that is, in the vicinity of 500C to 1 800C, and in the molten state dissolve therein at least either the dye precursor or the electron-accepting substances, desirably both.

Preparation of an energizable heat-sensitive recording paper using the dye precursors of the present invention may be carried out in a manner as described in Japanese Patent Applications (OPI) 11344/74 and 48930/75 (The term "OPI" as used herein refers to a "published unexamined Japanese patent application"). That is, a conductive substance, the dye precursor and an electron accepting substance are dispersed with a binder into a dispersion medium which at most only slightly dissolves the dye precursor and the electron accepting substance, such as water, and the resulting dispersion is coated on a support such as paper. Alternatively, a conductive substance is applied to a support to form a conductive layer and a dispersion obtained by dispersing the dye precursor and an electron accepting substance in water together with a binder is coated thereon.In addition, where both the dye precursor and the electron-accepting substance are not molten at the desired temperatures (generally 700C to 1200 C), a heat-fusible substance which melts within the desired temperature range and dissolves therein at least the dye precursor or the electron accepting substance is added, whereby the sensitivity to Joule's heat generated by passage of electricity is controiled.

As for the electron-accepting substances and the heat fusible substances, the same substances as described for the preparation of a heat-sensitive recording paper, respectively, can be employed also in the energizable heat-sensitive recording paper.

A light-sensitive recording sheet per the present invention can be prepared in the same manner as described in Japanese Patent Publications 24188/63, 10550/70, 13258/70, 204/74, 6212/74 and 28449/74; Japanese Patent Applications (OPI) 31615/72,32532/73, 9227/74, 135617/74, 80120/75, 8731 7/75 and 126228/75, except that the diarylaminofluoran derivative of the present invention is employed instead of dye precursors such as the lactone, lactam, spiropyran, carbinol, ethylene, leuco Aura mine or oxazine compounds disclosed therein.

Other recording materials can also be prepared using the diarylaminofluoran derivatives of the present invention instead of conventional dye precursors.

EXAMPLE 1 One part by weight of dye precursor Compound (8) in Table 1 was dissolved in 30 parts by weight of a mixed alkylated (principally diisopropyl) naphthalene. The solution was emulsified by being added with vigorous stirring to 50 parts by weight of water in which 6 parts by weight of gelatin and 4 parts by weight of gum arabic had been dissolved to produce oil droplets having a diameter of 1 y to 10,u. 250 parts by weight of water was further added. Acetic acid was added to the resulting emulsion till the pH of the emulsion became about 4, whereupon, coacervation took place to result in the formation of capsule walls of gelatin and gum arabic around the oil droplets. Formaline was added thereto and then the pH of the emulsion was raised to 9 with NaOH to harden the walls.

The thus obtained microcapsule dispersion was coated on paper and dried at 500C. This coated paper was superposed in face-to-face with a sheet of paper coated with a clay (e.g., activated clay, acid clay, attapulgite), a phenol resin, 4,4'-isopropylidenediphenol, zinc 3,5-bis(a-methylbenzyl)salicylate, zinc paratoluenesulfonate of 2,2'-methylenebisphenol and pressure or impact applied. A black image was obtained in a moment. The image obtained had high density and exhibited excellent light fastness and heat resistance.

EXAMPLE 2 Microcapsule-coated paper was prepared in the same manner as in Example 1 except that Compound (19) in Table 1 was used as the dye precursor instead of the dye precursor in Example 1.

This paper formed color rapidly with high density. Characters developed on this pressure-sensitive copying paper had excellent light resistance and heat resistance.

EXAMPLE 3 30 parts by weight of dye precursor Compound (17) in Table 1, 150 parts by weight of a 10% aqueous solution of polyvinyl alcohol (a polymerization degree of 1 700 and a sapdnffication degree of 98%) and 70 parts by weight of water were mixed and ground for 2 hours to prepare a dispersion. The particle size after grinding was about 5 microns. (Component A) Separately, 30 parts by weight of bisphenol A (4,4'-isopropylidenediphenol), 30 parts by weight of acetoanilide, 150 parts by weight of a 10% aqueous solution of polyvinyl alcohol (a polymerization degree of 1 700 and a saponification degree of 98%) and 55 parts by weight of water were mixed and ground for 2 hours to prepare a second dispersion. The particle size of insoluble materials after grinding was about 5 microns. (Component B) Next, 5 parts by weight of component A and 40 parts by weight of component B were mixed, coated on paper and dried at 500C to prepare heat-sensitive recording paper.

The thus prepared heat-sensitive recording paper formed a black color on the application of heat with a hot pen or the like. Also, heat was applied to this heat-sensitive recording paper on which an original was superposed using a heat-sensitive copying machine to produce a black copy. The resulting color image was stable to light and its hue and density were not changed by irradiation for one hour with an ultraviolet lamp.

Claims (14)

1. A fluoran derivative which has an amino group at the 2-position of its fluoran skeleton and a diarylamino group at the 6-position of its fluoran skeleton.

2. A fluoran derivative as claimed in Claim 1, which is represented by the following general formula:

wherein Ar and Ar' each represents an optionally substituted aryl group having 6 to 20 carbon atoms or heterocyclic residue having 4 to 36 carbon atoms, or Ar and Ar' together represent the atoms required to complete a heterocyclic nucleus; R1 and R2 each represents a hydrogen atom, a C1--20 alkyl group, a C5-7 cycloalkyl group, a C7--18 aralkyl group, a C6--20 optionally substituted aryl group or a heterocyclic residue; or R1 and R2 together represent the atoms required to complete a heterocyclic ring; R3 represents a hydrogen or halogen atom, a Cl-S alkyl group, a Cl-S alkoxy group, a nitro group, an amino group, a C1--20 alkylamino group, a C2-40 dialkylamino group or a C2-20 acylamino group; R4 represents a hydrogen or halogen atom, a Cl-S alkyl group or Cl-S alkoxy group; and the benzene rings marked A and B may also have other substituents.

3. A fluoran derivative as claimed in Claim 2, wherein R3 and/or R4 represents an alkyl or alkoxy group having up to 4 carbon atoms.

4. A fluoran derivative as claimed in Claim 2 or 3, wherein the benzene ring A and/or B bears as susbXituent one or more alkyl, alkoxy, Cl-4 alkylamino, C2-8 dialkylamino, C2-5 acylamino, nitro or amino group or a halogen atom.

5. A fluoran derivative as claimed in Claim 1, 2, 3 or 4, wherein Ar or Ar' represents a furyl, pyrrolyl, thienyl, indolyl, carbazolyl, phenoxazinyl, phenothiazinyl or phenazinyl group.

6. A fluoran derivative as claimed in Claim 1, 2, 3 or 4, wherein Ar or Ar' together complete a carbazole, phenoxazine, phenothiazine or phenazine nucleus.

7. A fluoran derivative as claimed in any of Claims 1 to 4, which is represented by the general formula:

wherein R1 and R2 each represents a hydrogen atom, a C1--18 alkyl group, a C7-1 6 aralkyl group or a phenyl group optionally substituted by a C1 .4 alkyl or alkoxy group or a dialkylsulfamoyl or cyano group or a chlorine or bromine atom; R4 represents a hydrogen or halogen atom or methyl group; R5 and R8 each represents a Cl-4 alkyl or alkoxy group; and m and n each represents 0 or an integer of 1 to 5.

8. Any of the fluoran compounds (1) to (23) shown hereinbefore.

9. A method of synthesising a fluoran derivative as claimed in any preceding claim, which comprises reacting benzylbenzoic acid derivative with a p-aminophenol derivative as shown in Scheme A hereinbefore.

10. A method of synthesising a fluoran derivative as claimed in any of Claims 1 to 8, which comprises reacting a fluoran derivative with an alkylating or arylating agent as shown in Scheme B hereinbefore.

11. A method of synthesis as claimed in Claim 9 or 10, substantially as hereinbefore described in Synthesis Examples 1,2 or 3.

12. A recording material which contains a fluoran derivative as claimed in any of Claims 1 to 8 or made by the method of Claim 9, 10 or 11.

1 3. A pressure-sensitive material as claimed in Claim 12, which includes a layer of microcapsules containing a solution of the fluoran derivative.

14. A heat-sensitive recording material as claimed in Claim 12, which includes a layer of the fluoran derivative, a binder and optionally a heat-fusible substance.

1 5. A pressure-sensitive or heat-sensitive material as claimed in Claim 13 or 14, substantially as hereinbefore described in Example 1,2 or 3.

1 6. A method of forming a black or greenish black image, which comprises bringing the fluoran derivative in a material as claimed in Claim 12, 13, 14 or 1 5 into contact with an electron-accepting substance.

1 7. A material bearing an image formed by the method of Claim 1 6.