PROCESS FOR DYEING KERATIN FIBRES USING AT LEAST ONE PARTICULAR 2-AZO(BENZ)IMIDAZOLIUM DYE AND AT LEAST ONE FLUORESCENT DYE

Abstract

The present invention relates to a process for dyeing keratin fibres, in particular human keratin fibres such as the hair, using one or more particular 2-azo(benz)imidazolium dyes and one or more fluorescent dyes. The present invention also relates to a cosmetic composition comprising the dyes defined above, and also to a multi-compartment device containing said dyes. The present invention also relates to the use of said dyes for dyeing light keratin fibres, especially human keratin fibres such as the hair, in chestnut-brown, dark chestnut-brown, brown, brown with a glint, or even black, without using an additional dye other than those defined above.

Claims

1. Process for dyeing keratin fibres, in particular human keratin fibres such as the hair, comprising the application to said keratin fibres of the following ingredients: (a) one or more 2-azo(benz)imidazolium dyes chosen from the compounds of formula (I) below, the optical isomers thereof, the geometrical isomers thereof, the tautomers thereof, the organic or mineral, acid or base salts thereof, the solvates thereof such as hydrates, and mixtures thereof, ##STR00044## in which formula (I): R, which may be identical or different, represent an optionally substituted linear or branched C.sub.1 to C.sub.6 alkyl radical, n denotes an integer equal to 0, 1 or 2, when n is equal to 2, the two radicals R may form, with the carbon atoms to which they are attached, an optionally substituted, saturated or unsaturated 6-membered ring, preferably benzo, R.sub.1 and R.sub.2, which may be identical or different, represent an optionally substituted, saturated or unsaturated, linear or branched C.sub.1 to C.sub.6 alkyl radical; R.sub.3, which may be identical or different, represent: a C.sub.1 or C.sub.2 alkyl radical, preferably a methyl radical, a hydroxyl radical, a nitro radical (NO.sub.2), an amino radical (NH.sub.2), a halogen atom, preferably a chlorine atom, a linear or branched C.sub.1 to C.sub.6, preferably C.sub.1 to C.sub.4 and more preferentially C.sub.1 to C.sub.2 alkoxy radical, such as a methoxy radical, or alternatively, when R.sub.3 is borne by the carbon atom located ortho to R.sub.4, R.sub.3 may form with R.sub.4 a saturated or unsaturated, 5- or 6-membered, optionally substituted and preferably unsubstituted heterocycle, which may contain one or two non-adjacent heteroatoms such as oxygen and/or nitrogen, m denotes an integer ranging from 0 to 4, when m is equal to 2, 3 or 4, two adjacent radicals R.sub.3 may form, with the carbon atoms to which they are attached, a 6-membered aromatic ring, preferably benzo, optionally substituted with one or more hydroxyl or amino groups, R.sub.4 represents: a hydrogen atom, a linear or branched C.sub.1 to C.sub.6, preferably C.sub.1 to C.sub.4 and more preferentially C.sub.1 to C.sub.2 alkoxy radical, such as a methoxy radical, or a radical NR.sub.5R.sub.6 in which R.sub.5 and R.sub.6, which may be identical or different, represent, independently of each other: a hydrogen atom, a linear or branched C.sub.1 to C.sub.6 alkyl radical, optionally substituted with one or more hydroxyl groups or a (di)(C.sub.1-C.sub.6)alkylamino group, a phenyl optionally substituted with one or more radicals chosen from the following radicals: i) amino, ii) (di)(hydroxy)(C.sub.1-C.sub.6)alkylamino, iii) C.sub.1 to C.sub.6 alkoxy, iv) (C.sub.1-C.sub.6)acylamino optionally substituted with a carboxyl radical, v) carboxyl and vi) aromatic or non-aromatic, saturated or unsaturated, 5- or 6-membered heterocycles, optionally substituted with one or more radicals, which may be identical or different, chosen from C.sub.1 to C.sub.6 alkyl radicals, optionally substituted phenyls, and C.sub.1 to C.sub.6 alkyl carboxylate radicals, R.sub.5 and R.sub.6 may form, with the nitrogen atom that bears them, a saturated or unsaturated, 4- to 8-membered heterocycle, or alternatively, when two radicals R.sub.3 are borne on carbons located ortho to R.sub.4, each of the two R.sub.3 may form, respectively, with R.sub.5 or R.sub.6 a 6-membered ring; preferably, the phenyl group substituted with R.sub.3 and R.sub.4 represents a julolidine group, or a radical of formula (II) ##STR00045## in which: m has the same meaning as previously, R.sub.3, which may be identical or different, represent: a chlorine atom, a C.sub.1 to C.sub.3 alkyl radical, an amino radical, or a radical OR.sub.7, with R.sub.7 representing a hydrogen atom or a C.sub.1 or C.sub.2 alkyl radical, when m is equal to 2, 3 or 4, two adjacent radicals R.sub.3 may form, with the carbon atoms to which they are attached, a 6-membered aromatic ring, preferably benzo, optionally substituted with one or more groups chosen from hydroxyl and amino groups, R.sub.4 represents: a hydrogen atom, a hydroxyl radical, a linear or branched C.sub.1 to C.sub.4 and preferably C.sub.1 to C.sub.2 alkoxy radical, such as a methoxy or ethoxy radical, a radical NR.sub.5R.sub.6 in which R.sub.5 and R.sub.6, which may be identical or different, represent, independently of each other, a linear or branched C.sub.1 to C.sub.6, preferably C.sub.1 to C.sub.4 and more preferentially C.sub.1 to C.sub.2 alkyl radical, optionally substituted with one or more hydroxyl groups, or when two radicals R.sub.3 are borne on carbons located ortho to R.sub.4, each of the two R.sub.3 may form, respectively, with R.sub.5 or R.sub.6 a 6-membered ring; preferably, the phenyl group substituted with R.sub.3 and R.sub.4 represents a julolidine group, and Y.sup. represents an anionic counterion or a mixture of organic or inorganic anions which ensure the electrical neutrality of the compounds of formula (I); and (b) one or more fluorescent dyes; said fluorescent dyes being direct dyes chosen from cyanin dyes, styryl/hemicyanin dyes, naphthalimide dyes, and mixtures thereof; it being understood that the 2-azo(benz)imidazolium dye(s) (a) and the fluorescent dye(s) (b) are applied to said keratin fibres together or sequentially.

2. Process according to claim 1, characterized in that the 2-azo(benz)imidazolium dye(s) chosen from the compounds of formula (I) are dyes which absorb light in the blue-violet range, preferably in the blue range.

3. Process according to claim 1, characterized in that n is equal to 0 or 2.

4. Process according to claim 1, characterized in that n is equal to 2, and the two radicals R form, with the carbon atoms to which they are attached, an optionally substituted, saturated or unsaturated, 6-membered ring, preferably an optionally substituted, unsaturated 6-membered ring such as benzo, and more preferentially an unsubstituted, unsaturated 6-membered ring such as unsubstituted benzo.

5. Process according to claim 1, characterized in that R.sub.1 and R.sub.2 are identical and represent an unsubstituted C.sub.1 to C.sub.2 alkyl radical, and more preferentially a methyl radical.

6. Process according to claim 1, characterized in that: R.sub.4 represents a radical NR.sub.5R.sub.6 in which R.sub.5 and R.sub.6, which may be identical or different, represent: a hydrogen atom, a linear or branched C.sub.1 to C.sub.6, preferably C.sub.1 to C.sub.4 and more preferentially C.sub.1 to C.sub.2 alkyl radical, optionally substituted with a hydroxyl group or a (di)(C.sub.1-C.sub.6)alkylamino group, and preferably (di)(C.sub.1-C.sub.2)alkylamino, a phenyl radical optionally substituted with one or more radicals, in particular in the ortho and/or para position, chosen from: amino radicals, (di)(hydroxy)(C.sub.1-C.sub.6)alkylamino, preferably (di)(hydroxy)(C.sub.1-C.sub.4)alkylamino and more preferentially (di)(hydroxy)(C.sub.1-C.sub.2)alkylamino radicals, such as a (di)hydroxyethylamino or (di)ethylamino radical, C.sub.1 to C.sub.6, preferably C.sub.1 to C.sub.4 and more preferentially C.sub.1 to C.sub.2 alkoxy radicals, such as a methoxy radical, or alternatively, R.sub.5 and R.sub.6 form, together with the nitrogen atom that bears them, a saturated or unsaturated, 4- to 8-membered and preferably 5- to 6-membered heterocycle, and more preferentially a saturated 5-membered ring, such as a piperidine ring, more preferentially, R.sub.4 represents a radical NR.sub.5R.sub.6, in which R.sub.5 and R.sub.6, which may be identical or different, represent: i) a hydrogen atom, ii) a (C.sub.1-C.sub.4)alkyl radical, iii) a phenyl radical which is substituted, in particular in the para position, with a group chosen from amino and (di)(C.sub.1-C.sub.4)alkylamino, or R.sub.5 and R.sub.6 form, together with the nitrogen atom that bears them, a saturated, 4- to 8-membered and preferably 5- to 6-membered heterocycle, and even more preferentially a saturated 5-membered ring, such as piperidino.

7. Process according to claim 1, characterized in that: R.sub.3, which may be identical or different, represent, independently of each other: a hydrogen atom, a methyl radical, a hydroxyl radical, a nitro radical, an amino radical, a chlorine atom, a linear or branched C.sub.1 to C.sub.4 and preferably C.sub.1 to C.sub.2 alkoxy radical, and more preferentially a methoxy radical, or alternatively, when R.sub.3 is borne by the carbon located ortho to R.sub.4, R.sub.3 may form with R.sub.4 a saturated or unsaturated, 5- or 6-membered, optionally substituted and preferably unsubstituted heterocycle, and when m is equal to 2, 3 or 4, two adjacent radicals R.sub.3 may form, together with the carbon atoms to which they are attached, an unsubstituted 6-membered aromatic ring, preferably benzo.

8. Process according to claim 1, characterized in that m is 0.

9. Process according to claim 1, in which the 2-azo(benz)imidazolium dye(s) (a) are chosen from the following compounds, the optical isomers thereof, the geometrical isomers thereof, the tautomers thereof, the organic or mineral, acid or base salts thereof, the solvates thereof such as hydrates, and mixtures thereof: ##STR00046## ##STR00047## ##STR00048## ##STR00049## ##STR00050## ##STR00051## ##STR00052## Y.sup. being as defined in claim 1, and preferably, the 2-azo(benz)imidazolium dyes (a) are chosen from compounds (2), (4) and (9).

10. Process according to claim 1, characterized in that the fluorescent dye(s) (b) are direct and cationic and are chosen from styryl or hemicyanin cationic dyes.

11. Process according to claim 1, characterized in that the fluorescent dye(s) (b) are dyes which absorb light in the yellow, orange and red range, preferably in the absorption wavelength .sub.abs between 400 nm and 500 nm inclusive.

12. Process according to claim 1, characterized in that the fluorescent dye(s) (b) are dyes which bear at least one cationic chromophore chosen from formulae (III), (IV), (IIIa) and (IVa) below:
W+[C(R.sup.c)C(R.sup.d)].sub.mAr(*)Q.sup.(III)
Ar[C(R.sup.d)C(R.sup.c)].sub.mW.sup.+(*)Q.sup.(IV), in which formulae (III) and (IV): W.sup.+ represents a cationic heteroaryl group, in particular comprising a quaternary ammonium optionally substituted with one or more (C.sub.1-C.sub.8)alkyl groups optionally substituted in particular with one or more hydroxyl groups; W.sup.+ represents a divalent heteroaryl radical as defined for W.sup.+; Ar represents an aryl group such as phenyl or naphthyl, optionally substituted preferably with i) one or more halogen atoms such as chlorine or fluorine; ii) one or more (C.sub.1-C.sub.8)alkyl and preferably C.sub.1-C.sub.4 alkyl groups such as methyl; iii) one or more hydroxyl groups; iv) one or more (C.sub.1-C.sub.8)alkoxy groups such as methoxy; v) one or more hydroxy(C.sub.1-C.sub.8)alkyl groups such as hydroxyethyl, vi) one or more amino or (di)(C.sub.1-C.sub.8)alkylamino groups, preferably with the C.sub.1-C.sub.4 alkyl part optionally substituted with one or more hydroxyl groups, such as (di)hydroxyethylamino, vii) with one or more acylamino groups; viii) one or more heterocycloalkyl groups such as piperazinyl, piperidyl or 5- or 6-membered heteroaryl such as pyrrolidinyl, pyridyl and imidazolinyl; Ar is a divalent aryl radical as defined for Ar; m represents an integer between 1 and 4 inclusive, in particular, m is 1 or 2; better still 1; R.sup.c and R.sup.d which may be identical or different, represent a hydrogen atom or optionally a substituted (C.sub.1-C.sub.8)alkyl and preferably C.sub.1-C.sub.4 alkyl group, or alternatively R.sup.c is contiguous with W or W and/or R.sup.d is contiguous with Ar or Ar and form, with the atoms that bear them, a (hetero)cycloalkyl; in particular, R is contiguous with W.sup.+ or W.sup.+ and forms a (hetero)cycloalkyl such as cyclohexyl; Q.sup. is an organic or mineral anionic counterion; (*) represents the part of the fluorescent chromophore that is bonded to the rest of the dye; preferably, W.sup.+ or W.sup.+ is an imidazolium, pyridinium, benzimidazolium, pyrazolium, benzothiazolium or quinolinium radical optionally substituted with one or more identical or different C.sub.1-C.sub.4 alkyl radicals; preferably, the fluorescent chromophore(s) are chosen from those with m=1, Ar representing a phenyl group substituted para to the styryl group C(R.sup.d)C(R.sup.c).sup. with a (di)(hydroxy)(C.sub.1-C.sub.6)(alkyl)amino group such as dihydroxy(C.sub.1-C.sub.4)alkylamino, and W.sup.+ representing an imidazolium or pyridinium group, preferably ortho- or para-pyridinium; ##STR00053## where --|-- represents the bond with the dye in which formulae (IIIa) and (IVa) R.sup.e, R.sup.f, R.sup.g and R.sup.h, which may be identical or different, represent a hydrogen atom or a (C.sub.1-C.sub.6)alkyl group which is optionally substituted, preferentially with a di(C.sub.1-C.sub.6)alkylamino or tri(C.sub.1-C.sub.6)alkylammonium group such as trimethylammonium.

13. Process according to claim 1, characterized in that the fluorescent dye(s) (b) are chosen from the dyes of formulae (V), (VI) and (VII) and also organic or mineral, acid or base salts thereof, optical, geometric and tautomeric isomers thereof, and solvates thereof such as hydrates: ##STR00054## in which formulae (V), (VI) and (VII): R.sub.1 and R.sub.2, which may be identical or different, represent a hydrogen atom or a C.sub.1-C.sub.6 alkyl group; preferentially a hydrogen atom; G.sub.1 represents a hydrogen atom or a group chosen from NH.sub.2 and OH; R.sub.a, R.sub.a, R.sub.a, R.sub.a, R.sub.b, R.sub.b, R.sub.b and R.sub.b, which may be identical or different, represent a) a hydrogen atom, b) a halogen atom, a group from among: c) amino, d) (C.sub.1-C.sub.4)alkylamino, e) (C.sub.1-C.sub.4)dialkylamino, f) cyano, g) carboxyl C(O)OH or carboxylate C(O)O.sup., Q.sup.+, h) hydroxyl OH or alkoxide O.sup.Q.sup.+, i) (poly)halo(C.sub.1-C.sub.6)alkyl such as trifluoromethyl, j) acylamino, k) (C.sub.1-C.sub.6)alkoxy, l) (C.sub.1-C.sub.6)alkylthio, m) (poly)hydroxy(C.sub.2-C.sub.4)alkoxy, n) (C.sub.1-C.sub.6)alkylcarbonyloxy, o) (C.sub.1-C.sub.6)alkoxycarbonyl, p) (C.sub.1-C.sub.6)alkylcarbonylamino, q) acylamino, r) carbamoyl, s) (C.sub.1-C.sub.6)alkylsulfonylamino, t) aminosulfonyl, u) SO.sub.3H or sulfonate SO.sub.3.sup., Q.sup.+ or v) (C.sub.1-C.sub.6)alkyl optionally substituted with a group chosen from (C.sub.1-C.sub.6)alkoxy, hydroxyl, cyano, carboxyl, amino, (di)(C.sub.1-C.sub.4)alkylamino, or alternatively the two alkyl radicals borne by the nitrogen atom of the amino group form a 5- to 7-membered heterocycle optionally comprising another nitrogen or non-nitrogen heteroatom; in particular, R.sub.a, R.sub.a, R.sub.a, R.sub.a, R.sub.b, R.sub.b, R.sub.b and R.sub.b represent a hydrogen or halogen atom or a (C.sub.1-C.sub.4)alkyl group, preferably a hydrogen atom; or alternatively two groups R.sub.a and R.sub.a; R.sub.b and R.sub.b borne by two adjacent carbon atoms together form a benzo or indeno ring, a fused heterocycloalkyl or fused heteroaryl group; the benzo, indeno, heterocycloalkyl or heteroaryl ring being optionally substituted with a halogen atom, an amino, (C.sub.1-C.sub.4)alkylamino, (C.sub.1-C.sub.4)dialkylamino, nitro, cyano, carboxyl, hydroxyl or trifluoromethyl group, an acylamino, (C.sub.1-C.sub.4)alkoxy (poly)hydroxy(C.sub.1-C.sub.4)alkoxy, (C.sub.1-C.sub.4)alkylcarbonyloxy, (C.sub.1-C.sub.4)alkoxycarbonyl or (C.sub.1-C.sub.4)alkylcarbonylamino radical, an acylamino, carbamoyl or alkoxyalkylsulfonylamino radical, an aminosulfonyl radical, or a (C.sub.1-C.sub.6)alkyl radical optionally substituted with: a group chosen from (C.sub.1-C.sub.6)alkoxy, hydroxyl, cyano, carboxyl, amino, (C.sub.1-C.sub.4)alkylamino and (C.sub.1-C.sub.4)dialkylamino, or alternatively the two alkyl radicals borne by the nitrogen atom of the amino group form a 5- to 7-membered heterocycle optionally comprising another nitrogen or non-nitrogen heteroatom; preferentially, R.sub.a and R.sub.a together form a benzo group; or alternatively, two groups R.sub.i and R.sub.a; and/or a group R.sub.i and R.sub.a together form a fused (hetero)cycloalkyl, preferentially cycloalkyl such as cyclohexyl; R.sub.g represents a hydrogen atom, a (hetero)aryl(C.sub.1-C.sub.4)alkyl group or a (C.sub.1-C.sub.6)alkyl group that is optionally substituted; preferentially, R.sub.b represents a hydrogen atom or a (C.sub.1-C.sub.3)alkyl or benzyl group; R.sub.e represents a covalent bond, a linear or branched, optionally substituted (C.sub.1-C.sub.8)alkylene or (C.sub.2-C.sub.8)alkenylene hydrocarbon-based chain, preferably R.sub.e represents an unsubstituted (C.sub.1-C.sub.6)alkylene; R.sub.f represents a hydrogen atom, a (C.sub.1-C.sub.4)alkoxy group, an amino group R.sub.3R.sub.4N, a quaternary ammonium group M, R.sub.3R.sub.4R.sub.5N.sup.+ in which R.sub.3, R.sub.4 and R.sub.5, which may be identical or different, represent a (C.sub.1-C.sub.4)alkyl group or R.sub.3R.sub.4N represents an optionally substituted heteroaryl group, preferentially an optionally substituted imidazolyl group, or alternatively M, R.sub.3R.sub.4R.sub.5N.sup.+ represents an optionally substituted cationic heteroaryl group, preferentially an imidazolinium group optionally substituted with a (C.sub.1-C.sub.3)alkyl group; G represents i) a group NR.sub.cR.sub.d, ii) OR with R representing a) a hydrogen atom, b) an optionally substituted, preferentially unsubstituted (C.sub.1-C.sub.6)alkyl group, c) an optionally substituted (hetero)aryl group, d) an optionally substituted (hetero)aryl(C.sub.1-C.sub.6)alkyl group such as benzyl, e) optionally substituted (hetero)cycloalkyl, f) optionally substituted (hetero)cycloalkyl(C.sub.1-C.sub.6)alkyl; according to a particular embodiment, G represents a group NR.sub.cR.sub.d, according to another particular embodiment, G represents a (C.sub.1-C.sub.6)alkoxy group; or alternatively when G represents NR.sub.cR.sub.d, two groups R.sub.e and R.sub.a and/or R.sup.d and R.sub.a together form a saturated heteroaryl or heterocycle, optionally substituted with one or more (C.sub.1-C.sub.6)alkyl groups, preferentially a 5- to 7-membered heterocycle containing one or two heteroatoms chosen from nitrogen and oxygen; more preferentially, the heterocycle is chosen from morpholinyl, piperazinyl, piperidyl and pyrrolidinyl groups; R.sub.c and R.sub.d, which may be identical or different, represent a hydrogen atom or a group from among: a) optionally substituted (hetero)aryl such as phenyl, b) optionally substituted (hetero)aryl(C.sub.1-C.sub.4)alkyl, c) optionally substituted (hetero)cycloalkyl, d) optionally substituted (hetero)cycloalkyl(C.sub.1-C.sub.4)alkyl, f) (C.sub.2-C.sub.5)alkyl or g) (C.sub.1-C.sub.8)alkyl which is optionally substituted, preferably optionally substituted with a hydroxyl, carboxyl, carboxylate, sulfate or sulfonate group; or alternatively two adjacent radicals R.sub.c and R.sub.d borne by the same nitrogen atom together form an optionally substituted heterocyclic or optionally substituted heteroaryl group; R.sub.i and R.sub.I, which may be identical or different, represent a hydrogen atom or a (C.sub.1-C.sub.4)alkyl group; ##STR00055## represents a (hetero)aryl group fused to the phenyl ring; or alternatively is absent from the phenyl; preferentially, when the ring is present, the ring is a benzo; m represents an integer between 1 and 18 inclusive, particularly an integer between 1 and 14 inclusive; preferentially an integer between 2 and 10 inclusive; more preferentially an integer between 3 and 8; more particularly an integer between 4 and 6; M represents an anionic counterion, derived from a salt of an organic or mineral acid, or from an organic or mineral base that ensures the electrical neutrality of the dye; Q.sup.+ represents a cationic counterion, derived from a salt of an organic or mineral acid, or from an organic or mineral base that ensures the electrical neutrality of the dye such as alkali metal, alkaline-earth metal or ammonium; it being understood that when the dye comprises a carboxylate, sulfonate or alkoxide group, then M and Q.sup.+ may be absent to ensure the electrical neutrality of said dye.

14. Process according to claim 1, characterized in that the fluorescent dye(s) (b) are chosen from the styryl dyes of formula (VIII) below, and also organic or mineral, acid or base salts thereof, optical, geometric and tautomeric isomers thereof, and solvates thereof such as hydrates: ##STR00056## in which formula (VIII) G, G.sub.1, R.sub.a, R.sub.a, R.sub.a, R.sub.b, R.sub.b, R.sub.b, R.sub.i, R.sub.i, R.sub.1, R.sub.2 and m are: R.sub.1 and R.sub.2, which may be identical or different, represent a hydrogen atom or a C.sub.1-C.sub.6 alkyl group; preferentially a hydrogen atom; G.sub.1 represents a hydrogen atom or a group chosen from NH.sub.2 and OH; R.sub.a, R.sub.a, R.sub.a, R.sub.a, R.sub.b, R.sub.b, R.sub.b and R.sub.b, which may be identical or different, represent a) a hydrogen atom, b) a halogen atom, a group from among: c) amino, d) (C.sub.1-C.sub.4)alkylamino, e) (C.sub.1-C.sub.4)dialkylamino, f) cyano, g) carboxyl C(O)OH or carboxylate C(O)O.sup., Q.sup.+, h) hydroxyl OH or alkoxide O.sup.Q.sup.+, i) (poly)halo(C.sub.1-C.sub.6)alkyl such as trifluoromethyl, j) acylamino, k) (C.sub.1-C.sub.6)alkoxy, l) (C.sub.1-C.sub.6)alkylthio, m) (poly)hydroxy(C.sub.2-C.sub.4)alkoxy, n) (C.sub.1-C.sub.6)alkylcarbonyloxy, o) (C.sub.1-C.sub.6)alkoxycarbonyl, p) (C.sub.1-C.sub.6)alkylcarbonylamino, q) acylamino, r) carbamoyl, s) (C.sub.1-C.sub.6)alkylsulfonylamino, t) aminosulfonyl, u) SO.sub.3H or sulfonate SO.sub.3.sup., Q.sup.+ or v) (C.sub.1-C.sub.6)alkyl optionally substituted with a group chosen from (C.sub.1-C.sub.6)alkoxy, hydroxyl, cyano, carboxyl, amino, (di)(C.sub.1-C.sub.4)alkylamino, or alternatively the two alkyl radicals borne by the nitrogen atom of the amino group form a 5- to 7-membered heterocycle optionally comprising another nitrogen or non-nitrogen heteroatom; in particular, R.sub.a, R.sub.a, R.sub.a, R.sub.a, R.sub.b, R.sub.b, R.sub.b and R.sub.b represent a hydrogen or halogen atom or a (C.sub.1-C.sub.4)alkyl group, preferably a hydrogen atom; or alternatively two groups R.sub.a and R.sub.a; R.sub.b and R.sub.b borne by two adjacent carbon atoms together form a benzo or indeno ring, a fused heterocycloalkyl or fused heteroaryl group; the benzo, indeno, heterocycloalkyl or heteroaryl ring being optionally substituted with a halogen atom, an amino, (C.sub.1-C.sub.4)alkylamino, (C.sub.1-C.sub.4)dialkylamino, nitro, cyano, carboxyl, hydroxyl or trifluoromethyl group, an acylamino, (C.sub.1-C.sub.4)alkoxy (poly)hydroxy(C.sub.1-C.sub.4)alkoxy, (C.sub.1-C.sub.4)alkylcarbonyloxy, (C.sub.1-C.sub.4)alkoxycarbonyl or (C.sub.1-C.sub.4)alkylcarbonylamino radical, an acylamino, carbamoyl or alkoxyalkylsulfonylamino radical, an aminosulfonyl radical, or a (C.sub.1-C.sub.6)alkyl radical optionally substituted with: a group chosen from (C.sub.1-C.sub.6)alkoxy, hydroxyl, cyano, carboxyl, amino, (C.sub.1-C.sub.4)alkylamino and (C.sub.1-C.sub.4)dialkylamino, or alternatively the two alkyl radicals borne by the nitrogen atom of the amino group form a 5- to 7-membered heterocycle optionally comprising another nitrogen or non-nitrogen heteroatom; preferentially, R.sub.a and R.sub.a together form a benzo group; or alternatively, two groups R.sub.i and R.sub.a; and/or a group R.sub.i and R.sub.a together form a fused (hetero)cycloalkyl, preferentially cycloalkyl such as cyclohexyl; R.sub.g represents a hydrogen atom, a (hetero)aryl(C.sub.1-C.sub.4)alkyl group or a (C.sub.1-C.sub.6)alkyl group that is optionally substituted; preferentially, R.sub.b represents a hydrogen atom or a (C.sub.1-C.sub.3)alkyl or benzyl group; R.sub.e represents a covalent bond, a linear or branched, optionally substituted (C.sub.1-C.sub.8)alkylene or (C.sub.2-C.sub.8)alkenylene hydrocarbon-based chain, preferably R.sub.e represents an unsubstituted (C.sub.1-C.sub.6)alkylene; R.sub.f represents a hydrogen atom, a (C.sub.1-C.sub.4)alkoxy group, an amino group R.sub.3R.sub.4N, a quaternary ammonium group M, R.sub.3R.sub.4R.sub.5N.sup.+ in which R.sub.3, R.sub.4 and R.sub.5, which may be identical or different, represent a (C.sub.1-C.sub.4)alkyl group or R.sub.3R.sub.4N represents an optionally substituted heteroaryl group, preferentially an optionally substituted imidazolyl group, or alternatively M, R.sub.3R.sub.4R.sub.5N.sup.+ represents an optionally substituted cationic heteroaryl group, preferentially an imidazolinium group optionally substituted with a (C.sub.1-C.sub.3)alkyl group; G represents i) a group NR.sub.cR.sub.d, ii) OR with R representing a) a hydrogen atom, b) an optionally substituted, preferentially unsubstituted (C.sub.1-C.sub.6)alkyl group, c) an optionally substituted (hetero)aryl group, d) an optionally substituted (hetero)aryl(C.sub.1-C.sub.6)alkyl group such as benzyl, e) optionally substituted (hetero)cycloalkyl, f) optionally substituted (hetero)cycloalkyl(C.sub.1-C.sub.6)alkyl; according to a particular embodiment, G represents a group NR.sub.cR.sub.d, according to another particular embodiment, G represents a (C.sub.1-C.sub.6)alkoxy group; or alternatively when G represents NR.sub.cR.sub.d, two groups R.sub.c and R.sub.a and/or R.sub.d and R.sub.a together form a saturated heteroaryl or heterocycle, optionally substituted with one or more (C.sub.1-C.sub.6)alkyl groups, preferentially a 5- to 7-membered heterocycle containing one or two heteroatoms chosen from nitrogen and oxygen; more preferentially, the heterocycle is chosen from morpholinyl, piperazinyl, piperidyl and pyrrolidinyl groups; R.sub.i and R.sub.I, which may be identical or different, represent a hydrogen atom or a (C.sub.1-C.sub.4)alkyl group; m represents an integer between 1 and 18 inclusive, particularly an integer between 1 and 14 inclusive; preferentially an integer between 2 and 10 inclusive; more preferentially an integer between 3 and 8; more particularly an integer between 4 and 6; preferably: R.sub.1 and R.sub.2, which may be identical or different, represent a hydrogen atom; R.sub.i and R.sub.i, which may be identical or different, represent a hydrogen atom or a (C.sub.1-C.sub.4)alkyl group, preferably hydrogen; R.sub.a, R.sub.a and R.sub.a, which may be identical or different, represent a hydrogen atom, a halogen atom such as fluorine, or an OH, O.sup.Q.sup.+, (C.sub.1-C.sub.6)alkoxy, nitro, or cyano group, with Q.sup.+ as defined as a cationic counterion, derived from a salt of an organic or mineral acid, or from an organic or mineral base that ensures the electrical neutrality of the dye such as alkali metal, alkaline-earth metal or ammonium; R.sub.b, R.sub.b and R.sub.b, which may be identical or different, represent a hydrogen atom or a (C.sub.1-C.sub.6)alkyl group; or alternatively two contiguous radicals R.sub.b and R.sub.b form, together with the carbon atoms that bear them, a benzo group that is condensed or fused to the pyridinium group, said benzo group possibly being substituted; preferably, said benzo group is unsubstituted; G represents a group NR.sub.cR.sub.d or (C.sub.1-C.sub.6)alkoxy group which is optionally substituted, preferentially unsubstituted; according to a particular embodiment, G represents a group NR.sub.cR.sub.d, according to another particular embodiment, G represents a (C.sub.1-C.sub.6)alkoxy group; R.sub.i and R.sub.I, which may be identical or different, represent a hydrogen atom or a (C.sub.1-C.sub.4)alkyl group; ##STR00057## represents an aryl or heteroaryl group fused to the phenyl ring; or alternatively is absent from the phenyl ring; preferentially, when the ring is present, the ring is a benzo; m represents an integer between 1 and 18 inclusive; particularly an integer between 2 and 16 inclusive; preferentially an integer between 3 and 10; more preferentially an integer between 4 and 6; R.sub.c and R.sup.d, which may be identical or different, represent a hydrogen atom, a (C.sub.2-C.sub.4)alkyl group or a substituted (C.sub.1-C.sub.8)alkyl group, preferably (C.sub.2-C.sub.4)alkyl substituted in particular with one or more groups chosen from i) cyano, ii) (C.sub.1-C.sub.3)alkoxy, iii) hydroxyl and iv) (C.sub.1-C.sub.3)alkylcarbonyl, preferably with one or more hydroxyl groups; and M representing an anionic counterion, derived from a salt of an organic or mineral acid, or from an organic or mineral base that ensures the electrical neutrality of the dye; it being understood that when the dye comprises an alkoxide group, then M and Q.sup.+ may be absent to ensure the electrical neutrality of said dye.

15. Process according to claim 1, characterized in that the fluorescent dye(s) (b) are chosen from the styryl dyes of formula (IX) below, and also organic or mineral, acid or base salts thereof, optical, geometric and tautomeric isomers thereof, and solvates thereof such as hydrates: ##STR00058## in which formula (IX) G, G.sub.1, R.sub.a, R.sub.a, R.sub.b, R.sub.b and m are: G.sub.1 represents a hydrogen atom or a group chosen from NH.sub.2 and OH; R.sub.a, R.sub.a, R.sub.b, and R.sub.b, which may be identical or different, represent a) a hydrogen atom, b) a halogen atom, a group from among: c) amino, d) (C.sub.1-C.sub.4)alkylamino, e) (C.sub.1-C.sub.4)dialkylamino, f) cyano, g) carboxyl C(O)OH or carboxylate C(O)O.sup., Q.sup.+, h) hydroxyl OH or alkoxide O.sup.Q.sup.+, i) (poly)halo(C.sub.1-C.sub.6)alkyl such as trifluoromethyl, j) acylamino, k) (C.sub.1-C.sub.6)alkoxy, l) (C.sub.1-C.sub.6)alkylthio, m) (poly)hydroxy(C.sub.2-C.sub.4)alkoxy, n) (C.sub.1-C.sub.6)alkylcarbonyloxy, o) (C.sub.1-C.sub.6)alkoxycarbonyl, p) (C.sub.1-C.sub.6)alkylcarbonylamino, q) acylamino, r) carbamoyl, s) (C.sub.1-C.sub.6)alkylsulfonylamino, t) aminosulfonyl, u) SO.sub.3H or sulfonate SO.sub.3.sup., Q.sup.+ or v) (C.sub.1-C.sub.6)alkyl optionally substituted with a group chosen from (C.sub.1-C.sub.6)alkoxy, hydroxyl, cyano, carboxyl, amino, (di)(C.sub.1-C.sub.4)alkylamino, or alternatively the two alkyl radicals borne by the nitrogen atom of the amino group form a 5- to 7-membered heterocycle optionally comprising another nitrogen or non-nitrogen heteroatom; in particular, R.sub.a, R.sub.a, R.sub.b, and R.sub.b, represent a hydrogen or halogen atom or a (C.sub.1-C.sub.4)alkyl group, preferably a hydrogen atom; or alternatively two groups R.sub.a and R.sub.a; R.sub.b and R.sub.b borne by two adjacent carbon atoms together form a benzo or indeno ring, a fused heterocycloalkyl or fused heteroaryl group; the benzo, indeno, heterocycloalkyl or heteroaryl ring being optionally substituted with a halogen atom, an amino, (C.sub.1-C.sub.4)alkylamino, (C.sub.1-C.sub.4)dialkylamino, nitro, cyano, carboxyl, hydroxyl or trifluoromethyl group, an acylamino, (C.sub.1-C.sub.4)alkoxy (poly)hydroxy(C.sub.1-C.sub.4)alkoxy, (C.sub.1-C.sub.4)alkylcarbonyloxy, (C.sub.1-C.sub.4)alkoxycarbonyl or (C.sub.1-C.sub.4)alkylcarbonylamino radical, an acylamino, carbamoyl or alkoxyalkylsulfonylamino radical, an aminosulfonyl radical, or a (C.sub.1-C.sub.6)alkyl radical optionally substituted with: a group chosen from (C.sub.1-C.sub.6)alkoxy, hydroxyl, cyano, carboxyl, amino, (C.sub.1-C.sub.4)alkylamino and (C.sub.1-C.sub.4)dialkylamino, or alternatively the two alkyl radicals borne by the nitrogen atom of the amino group form a 5- to 7-membered heterocycle optionally comprising another nitrogen or non-nitrogen heteroatom; preferentially, R.sub.a and R.sub.a together form a benzo group; or alternatively, two groups R.sub.i and R.sub.a; and/or a group R.sub.i and R.sub.a together form a fused (hetero)cycloalkyl, preferentially cycloalkyl such as cyclohexyl; R.sub.g represents a hydrogen atom, a (hetero)aryl(C.sub.1-C.sub.4)alkyl group or a (C.sub.1-C.sub.6)alkyl group that is optionally substituted; preferentially, R.sub.b represents a hydrogen atom or a (C.sub.1-C.sub.3)alkyl or benzyl group; R.sub.e represents a covalent bond, a linear or branched, optionally substituted (C.sub.1-C.sub.8)alkylene or (C.sub.2-C.sub.8)alkenylene hydrocarbon-based chain, preferably R.sub.e represents an unsubstituted (C.sub.1-C.sub.6)alkylene; G represents i) a group NR.sub.cR.sub.d, ii) OR with R representing a) a hydrogen atom, b) an optionally substituted, preferentially unsubstituted (C.sub.1-C.sub.6)alkyl group, c) an optionally substituted (hetero)aryl group, d) an optionally substituted (hetero)aryl(C.sub.1-C.sub.6)alkyl group such as benzyl, e) optionally substituted (hetero)cycloalkyl, f) optionally substituted (hetero)cycloalkyl(C.sub.1-C.sub.6)alkyl; according to a particular embodiment, G represents a group NR.sub.cR.sub.d, according to another particular embodiment, G represents a (C.sub.1-C.sub.6)alkoxy group; or alternatively when G represents NR.sub.cR.sub.d, two groups R.sub.c and R.sub.a and/or R.sub.d and R.sub.a together form a saturated heteroaryl or heterocycle, optionally substituted with one or more (C.sub.1-C.sub.6)alkyl groups, preferentially a 5- to 7-membered heterocycle containing one or two heteroatoms chosen from nitrogen and oxygen; more preferentially, the heterocycle is chosen from morpholinyl, piperazinyl, piperidyl and pyrrolidinyl groups; m represents an integer between 1 and 18 inclusive, particularly an integer between 1 and 14 inclusive; preferentially an integer between 2 and 10 inclusive; more preferentially an integer between 3 and 8; more particularly an integer between 4 and 6.

16. Process according to claim 1, characterized in that the fluorescent dye(s) (b) are chosen from the styryl dyes of formulae (X), (XI), (XII) and (XIII) below, and also organic or mineral, acid or base salts thereof, optical, geometric and tautomeric isomers thereof, and solvates thereof such as hydrates: ##STR00059## in which formulae (X), (XI), (XII) and (XIII): R.sup.1, R.sup.2, R.sup.3 and R.sup.4, which may be identical or different, represent a hydrogen atom or a (C.sub.1-C.sub.6)alkyl group; preferably, R.sup.2 and R.sup.3 represent a hydrogen atom and R.sup.1 and R.sup.4, which may be identical or different, represent a hydrogen atom or a (C.sub.1-C.sub.4)alkyl group; R.sup.5, R.sup.6, R.sup.7, R.sup.8 and R.sup.9, which may be identical or different, represent i) a hydrogen atom or ii) a halogen atom such as Cl, Br or F, iii) a group OR in which R represents a hydrogen atom or Q.sup.+, wherein Q.sup.+ represents a cationic counterion, derived from a salt of an organic or mineral acid, or from an organic or mineral base that ensures the electrical neutrality of the dye such as alkali metal, alkaline-earth metal or ammonium, or a (C.sub.1-C.sub.3)alkyl group, a group from among iv) aryl such as benzene, v) aryl(C.sub.1-C.sub.3)alkyl such as benzyl, vi) cyano, vii) nitro, viii) (C.sub.1-C.sub.3)alkylthio, ix) amino NR.sup.10R.sup.11 with R.sup.10 and R.sup.11, which may be identical or different, representing a) a hydrogen atom, b) a (C.sub.2-C.sub.4)alkyl group or c) a substituted (C.sub.1-C.sub.8)alkyl group, preferably (C.sub.2-C.sub.4)alkyl optionally substituted with one or more groups chosen from: cyano, (C.sub.1-C.sub.3)alkoxy, hydroxyl, and (C.sub.1-C.sub.3)alkylcarbonyl; in particular, R.sup.10 and R.sup.11, which may be identical or different, represent a hydrogen atom or a (C.sub.1-C.sub.6)alkyl group substituted with one or more hydroxyl, cyano or (C.sub.1-C.sub.3)alkylcarbonyl groups such as hydroxyethyl; m represents an integer between 1 and 18 inclusive; particularly an integer between 2 and 16 inclusive; preferentially an integer between 3 and 10; more preferentially an integer between 4 and 6; M represents an anionic counterion derived from a salt of an organic or mineral acid, or from an organic or mineral base that ensures the electrical neutrality of the dye; it being understood that when the dye comprises an alkoxide group, then M and Q.sup.+ may be absent to ensure the electrical neutrality of said dye.

17. Process according to claim 1, characterized in that the fluorescent dye(s) (b) of the invention are chosen from those of formulae (XIV) and (XV) below: ##STR00060## in which formulae (XIV) and (XV): R.sup.5 and R.sup.8, which may be identical or different, represent a hydrogen atom or a (C.sub.1-C.sub.4)alkoxy group such as methoxy, preferably, R.sup.5 and R.sup.8 represent a hydrogen atom; R.sup.7 represents a (C.sub.1-C.sub.4)alkoxy group or NR.sup.10R.sup.11 with R.sup.10 and R.sup.11, which may be identical or different, representing a) a hydrogen atom, or b) a (C.sub.1-C.sub.8)alkyl group optionally substituted with one or more groups chosen from i) hydroxyl, ii) RZC(X)Y with X, Y and Z representing an oxygen or sulfur atom or N(R), or alternatively X and/or Z represent a bond, R and R, which may be identical or different, represent a hydrogen atom or a (C.sub.1-C.sub.6)alkyl group, preferably, X represents an oxygen atom, iii) sulfonic SO.sub.3H, iv) sulfonate SO.sub.3.sup., Q.sup.+, v) carboxylate C(O)O.sup., Q.sup.+ with Q.sup.+ representing a cationic counterion such as an alkali metal or alkaline-earth metal; in particular, R.sup.7 represents a group NR.sup.10R.sup.11 with R.sup.10 and R.sup.11, which may be identical or different, representing a) a hydrogen atom, or b) a (C.sub.1-C.sub.6)alkyl group optionally substituted with one or more groups chosen from i) hydroxyl, ii) carboxyl, iii) carboxylate, iv) sulfonic, and v) sulfonate, more particularly chosen from identical or different groups representing a) a hydrogen atom, or b) a (C.sub.1-C.sub.6)alkyl group optionally substituted with one or more groups chosen from i) hydroxyl, ii) carboxyl, and iii) carboxylate; m represents an integer between 1 and 18 inclusive; particularly an integer between 1 and 6 inclusive; preferentially an integer between 1 and 4; more preferentially an integer between 1 and 2; and M represents an anionic counterion, derived from a salt of an organic or mineral acid, or from an organic or mineral base that ensures the electrical neutrality of the dye; it being understood that when the dye comprises an alkoxide group, then M and Q.sup.+ may be absent to ensure the electrical neutrality of said dye.

18. Process according to claim 16, characterized in that the fluorescent dye(s) (b) are chosen from: the fluorescent dyes of formula (X) with: and also the organic or mineral, acid or base salts thereof, the optical isomers, geometrical isomers and tautomers thereof, and the solvates thereof such as hydrates; the fluorescent dyes of formula (XI) with: and also the organic or mineral, acid or base salts thereof, the geometrical isomers and tautomers thereof, and the solvates thereof such as hydrates; the fluorescent dyes of formulae (X) and (XI): ##STR00061## with M as defined in the preceding claim; and and and and also the organic or mineral, acid or base salts thereof, the geometrical isomers and tautomers thereof, and the solvates thereof such as hydrates; the fluorescent dyes of formula (XII) with: and also the organic or mineral, acid or base salts thereof, the optical isomers, geometrical isomers and tautomers thereof, and the solvates thereof such as hydrates; the fluorescent dyes of formula (XIII) with: and also the organic or mineral, acid or base salts thereof, the geometrical isomers and tautomers thereof, and the solvates thereof such as hydrates; and the fluorescent dyes of formulae (XII) and (XIII) below: ##STR00062## with: and and and also the organic or mineral, acid or base salts thereof, the geometrical isomers and tautomers thereof, and the solvates thereof such as hydrates; and preferably, the fluorescent dye(s) (b) are chosen from the following compounds: ##STR00063## and also the organic or mineral, acid or base salts thereof, the geometrical isomers and tautomers thereof, and the solvates thereof such as hydrates; with M and Q.sup.+ as defined in the preceding claim.

19. Process according to claim 1, characterized in that it also comprises the application to said keratin fibres of one or more reducing agents, preferably chosen from i) the reducing agents of formula (XVI) below, and also the addition salts thereof, and mixtures thereof:
H(X).sub.q(R.sub.10).sub.t(XVI) in which formula (XVI): X represents P, S or SO.sub.2, q represents an integer equal to 0 or 1, t represents an integer equal to 1 or 2, and R represents a linear or branched, saturated or unsaturated C.sub.1 to C.sub.20 alkyl radical, optionally interrupted with a heteroatom, and/or optionally substituted with one or more radicals chosen from hydroxyl, halo, amine, carboxyl, ((C.sub.1-C.sub.30)alkoxy)carbonyl, amido, ((C.sub.1-C.sub.30)alkyl)aminocarbonyl, ((C.sub.1-C.sub.30)acyl)amino, mono- or dialkylamino, and mono- or dihydroxylamino radicals; ii) thioglycolic acid, iii) thiolactic acid, iv) glyceryl monothioglycolate, v) cysteamine, vi) N-acetylcysteamine, vii) N-propionylcysteamine, viii) cysteine, ix) N-acetylcysteine, x) thiomalic acid, xi) pantetheine, xii) 2,3-dimercaptosuccinic acid, xiii) N-(mercaptoalkyl)--hydroxyalkylamides, xiv) N-mono- or N,N-dialkylmercapto-4-butyramides, xv) aminomercaptoalkylamides, xvi) N-(mercaptoalkyl)succinamic acid derivatives, xvii) N-(mercaptoalkyl)succinimide derivatives, xviii) alkylamino mercaptoalkylamides, xix) the azeotropic mixture of 2-hydroxypropyl thioglyconate and of (2-hydroxy-1-methyl)ethyl thioglycolate, xx) mercaptoalkylaminoamides, xxi) N-mercaptoalkylalkanediamides xxii) formamidinesulfinic acid derivatives, addition salts thereof, and mixtures thereof.

20. Process according to claim 1, not using any reducing agent.

21. Process according to claim 1, characterized in that the 2-azo(benz)imidazolium dye(s) (a) and the fluorescent dye(s) (b), are applied together to said keratin fibres; preferably, the process comprises a step of applying to said keratin fibres a cosmetic composition which comprises a) one or more 2-azo(benz)imidazolium dyes (a) chosen from the compounds of formula (I), and also the optical isomers thereof, the geometrical isomers thereof, the tautomers thereof, the organic or mineral, acid or base salts thereof, the solvates thereof such as hydrates, and mixtures thereof, and one or more fluorescent dyes (b).

22. Process according to claim 1, characterized in that it comprises at least the following two successive steps: a first step of applying to said keratin fibres a cosmetic composition comprising one or more fluorescent dyes (b), followed by, a second step of applying to said fibres a cosmetic composition comprising one or more 2-azo(benz)imidazolium dyes (a) chosen from the compounds of formula (I), and also the optical isomers thereof, the geometrical isomers thereof, the tautomers thereof, the organic or mineral, acid or base salts thereof, the solvates thereof such as hydrates, and mixtures thereof.

23. Process according to claim 1, characterized in that it comprises at least the following two successive steps: a first step of applying to said keratin fibres a cosmetic composition comprising one or more 2-azo(benz)imidazolium dyes (a) chosen from the compounds of formula (I), and also the optical isomers thereof, the geometrical isomers thereof, the tautomers thereof, the organic or mineral, acid or base salts thereof, the solvates thereof such as hydrates, and mixtures thereof, followed by a second step of applying to said fibres a cosmetic composition comprising one or more fluorescent dyes (b).

24. Process according to claim 22, which comprises at least two successive steps in which the pH of the cosmetic composition(s) is between 6 and 11 inclusive, particularly between 7 and 10, more particularly between 7.5 and 9.5, such as between 9 and 9.5.

25. Cosmetic composition comprising one or more 2-azo(benz)imidazolium dyes (a) chosen from the compounds of formula (I), and also the optical isomers thereof, the geometrical isomers thereof, the tautomers thereof, the organic or mineral, acid or base salts thereof, the solvates thereof such as hydrates, and mixtures thereof, and one or more fluorescent dyes (b), said composition optionally having a pH between 6 and 11 inclusive, particularly between 7 and 10 and more particularly between 7.5 and 9.5, such as between 9 and 9.5.

26. Multi-compartment device comprising a first compartment containing one or more 2-azo(benz)imidazolium dyes (a) chosen from the compounds of formula (I), and also the optical isomers thereof, the geometrical isomers thereof, the tautomers thereof, the organic or mineral, acid or base salts thereof, the solvates thereof such as hydrates, and mixtures thereof, and a second compartment containing one or more fluorescent dyes (b).

27. Use of one or more fluorescent dye(s) (b), combined with one or more 2-azo(benz)imidazolium dye(s) (a) chosen from the compounds of formula (I), and also the optical isomers thereof, the geometrical isomers thereof, the tautomers thereof, the organic or mineral, acid or base salts thereof, the solvates thereof such as hydrates, and mixtures thereof, for the dyeing of light keratin fibres, especially human keratin fibres such as the hair, in chestnut-brown, dark chestnut-brown, brown, brown with a glint or even black, without using an additional dye other than (a) or (b).

Description

EXAMPLES

[0396] In the examples that follow, all the amounts are given as weight percentages relative to the total weight of the composition, unless otherwise indicated.

[0397] The synthesis of the 2-azo(benz)imidazolium dyes is known to those skilled in the art. By way of example, the synthesis of the dyes of structure (2a) or (9a) is described in the Ciba Specialty Chemicals Holding Inc. patents WO2004/100912 A2, 2004; The synthesis of compounds (4a), (13a) and (37a) is performed using the methods described, for example, in Russian Journal of Organic Chemistry, 1996, vol. 32, #12, pages 1799-1802; Journal of the Indian Chemical Society, 1968, vol. 45, #5 pages 425-432; L'Oral CH560539DE2227214, 1972.

I. Example 1: Sequential Application of 2-azo(benzo)imidazolium Dye of Formula (I) Followed by Fluorescent Dye

a) Preparation of the Compositions

[0398] Composition (A1), comprising a 2-azo(benzo)imidazolium dye of formula (I) according to the invention, was prepared from the ingredients whose contents are mentioned in the table below.

TABLE-US-00009 Composition A1 [00033] 5 10.sup.3 mol Aqueous ammonia pH = 9-9.5 Water qs 100 Colour in solution Violet-blue

[0399] Composition (B1), comprising a fluorescent dye, was prepared from the ingredients whose contents are mentioned in the table below.

TABLE-US-00010 Compo- sition B1 [00034] 5 10.sup.3 mol Aqueous ammonia pH = 9-9.5 Water qs 100 Colour in Red- solution orange

b) Procedure

[0400] Composition (A1) obtained above was applied to 0.5 g locks of hair containing 90% white hairs, in a bath ratio equal to 2.

[0401] After a leave-on time of 30 minutes at room temperature, the locks of hair were rinsed with water, washed with shampoo and dried under a hood for 5 minutes.

[0402] Composition (B1), obtained above, was then applied to each of the locks of hair, in a bath ratio equal to 2.

[0403] After a leave-on time of 20 minutes at room temperature, the locks of hair were rinsed with water, washed with shampoo and dried under a hood for 5 minutes.

[0404] The colour of the locks was evaluated visually.

c) Results

[0405] The results of the colouring on the locks of hair containing 90% white hairs are given in the table below.

TABLE-US-00011 Locks dyed with A1 + B1 Colour after dyeing Dark prune

[0406] The results obtained above show that the sequential application of a 2-azo(benzo)imidazolium dye of formula (I) according to the present invention and of a fluorescent dye makes it possible to obtain very intense and chromatic colours.

[0407] These results also show that the process according to the invention, using only two particular direct dyes, a 2-azo(benzo)imidazolium dye of formula (I) combined with a fluorescent dye, makes it possible to obtain dark colours.

II. Example 2: Sequential Application of Fluorescent Dye Followed by 2-azo(benzo)imidazolium Dye of Formula (I)

a) Compositions

[0408] Compositions (A1) and (B1) were prepared from the ingredients mentioned in Example 1.

b) Procedure

[0409] Composition (B1) obtained above was applied to 0.5 g locks of hair containing 90% white hairs, in a bath ratio equal to 2.

[0410] After a leave-on time of 20 minutes at room temperature, the locks of hair were rinsed with water, washed with shampoo and dried under a hood for 5 minutes.

[0411] Next, composition (A1) obtained above was then applied to each of the locks of hair, in a bath ratio equal to 2.

[0412] After a leave-on time of 30 minutes at room temperature, the locks of hair were rinsed with water, washed with shampoo and dried under a hood for 5 minutes.

[0413] The colour of the locks was evaluated visually.

c) Results

[0414] The results of the colouring on the locks of hair containing 90% white hairs are given in the table below.

TABLE-US-00012 Locks dyed with B1 + A1 Colour after dyeing Black

[0415] The results obtained above show that the sequential application of a fluorescent dye and of a 2-azo(benzo)imidazolium dye of formula (I) according to the present invention makes it possible to obtain very intense and chromatic colours.

[0416] These results also show that the process according to the invention, using only two particular direct dyes, a 2-azo(benzo)imidazolium dye of formula (I) combined with a fluorescent dye, makes it possible to obtain black colours.

III. Example of Combined Application

a) Compositions

[0417] Compositions (C1) to (C3) were prepared from the ingredients whose contents are mentioned in the table below.

TABLE-US-00013 Cl C2 C3 [00035] 5 10.sup.3 mol [00036] 5 10.sup.3 mol [00037] 5 10.sup.3 mol [00038] 5 10.sup.3 mol 5 10.sup.3 mol [00039] 5 10.sup.3 mol Aqueous ammonia pH = 9-9.5 pH = 9-9.5 pH = 9-9.5 Water qs 100 qs 100 qs 100

b) Procedure

[0418] Each of the compositions (C1) to (C3) obtained above was applied to 0.5 g locks of hair containing 90% white hairs, in a bath ratio equal to 2.

[0419] After a leave-on time of 45 minutes at room temperature, the locks of hair were rinsed with water, washed with shampoo and dried under a hood for 5 minutes.

[0420] The colour of the locks was evaluated visually.

c) Results

[0421] The results of the colouring on the locks of hair containing 90% white hairs are given in the table below.

TABLE-US-00014 Locks dyed Locks dyed Locks dyed with C1 with C2 with C3 Colour after dyeing Black with a Black with Warm violet-blue a violet brown glint glint

[0422] The results obtained above show that the process according to the invention makes it possible to obtain very intense and chromatic colours.

[0423] These results also show that the combination of only two particular direct dyes, i.e. a 2-azo(benzo)imidazolium dye of formula (I) combined with a fluorescent dye, makes it possible to obtain brown or black colours.

IV. Comparative Example of a Combined Application

a) Preparation of the Compositions

[0424] Compositions (A2) and (A3), comprising a 2-azo(benzo)imidazolium dye of formula (I) according to the invention, were prepared from the ingredients whose contents are mentioned in the table below.

TABLE-US-00015 Composition A2 Composition A3 [00040] 5 10.sup.3 mol [00041] 5 10.sup.3 mol Aqueous ammonia pH = 9.1 pH = 9.1 Water qs 100 qs 100

[0425] Compositions (B2) and (B3), comprising a fluorescent dye, were prepared from the ingredients whose contents are mentioned in the table below.

TABLE-US-00016 Composition B2 Composition B3 [00042] 5 10.sup.3 mol [00043] 5 10.sup.3 mol Aqueous ammonia pH = 9.1 pH = 9.1 Water qs 100 qs 100

b) Procedure

[0426] The compositions (A2), (A3), (B2) and (B3) thus obtained were then applied by means of a brush at an amount of 2 g of composition on 1 g locks.

[0427] After a leave-on time of 30 minutes, the locks of hair were wrung dry with a paper and rinsed with water. The locks were then washed with a shampoo (0.4 g of shampoo per 1 g of hair) and left to dry.

c) Results

[0428] The colour of the locks thus obtained was evaluated in the CIE L*a*b* system, using a Minolta Spectrophotometer CM2600D colorimeter.

[0429] In this system, L* represents the intensity of the colour, a* indicates the green/red colour axis and b* the blue/yellow colour axis.

[0430] The lower the value of L, the darker or more intense the colour. The higher the value of a*, the redder the shade, and the higher the value of b*, the yellower the shade.

[0431] The table below represents the colouring intensity values obtained:

TABLE-US-00017 Composition Colour L*(D65) a*(D65) b*(D65) Control lock 90% white 57.81 2.56 17.27 hair A2 Light blue 32.16 0.84 7.32 A3 Orange 39.88 37.97 30.67 B2 Light green 47.44 39.91 41.98 blue B3 orange 41.42 15.09 4.61

d) Procedure for a Combined Application

[0432] Compositions (A2), (A3), (B2) and (B3) obtained above were mixed so as to obtain the following mixtures:

[0433] A2+B2 in a 1/1 ratio, and

[0434] A3+B3 in a 1/1 ratio.

[0435] The compositions (A2+B2) and (A3+B3) thus obtained were then applied by means of a brush at an amount of 2 g of composition on 1 g locks.

[0436] After a leave-on time of 30 minutes, the locks of hair were wrung dry with a paper and rinsed with water. The locks were then washed with a shampoo (0.4 g of shampoo per 1 g of hair) and left to dry.

[0437] The colour of the locks thus obtained was evaluated in the CIE L*a*b* system, using a Minolta Spectrophotometer CM2600D colorimeter.

[0438] In this system, L* represents the intensity of the colour, a* indicates the green/red colour axis and b* the blue/yellow colour axis.

[0439] The lower the value of L, the darker or more intense the colour. The higher the value of a*, the redder the shade, and the higher the value of b*, the yellower the shade.

[0440] The chromaticity of the colour obtained is measured by (C*) which corresponds to the following equation:

C*={square root over ((a*).sup.2+(b*).sup.2)}

[0441] The greater the C* value, the more the colour of the locks is chromatic.

e) Results

[0442] The results are given in the table below.

TABLE-US-00018 Composition Colour C* A2 + B2 Mahogany brown 14.43 A3 + B3 Purple brown 10.05

[0443] The results obtained above show that the simultaneous application of a 2-azo(benzo)imidazolium dye of formula (I) according to the present invention and of a fluorescent dye, chosen from cyanin, styryl/hemicyanin, and naphthalimide dyes (A2+B2), provides more chromatic colorations than a comparative process, comprising the simultaneous application of a 2-azo(benzo)imidazolium dye and a fluorescent dye different from the fluorescent dyes used in the present invention (A3+B3).

V. First Comparative Example of a Sequential Application

a) Compositions

[0444] Compositions (A2), (A3), (B2) and (B3) were prepared from the ingredients mentioned in Example 4.

b) Procedure for a Combined Application

[0445] Composition (A2) obtained above was applied by means of a brush at an amount of 2 g of composition on a 1 g lock of hair containing 90% white hairs.

[0446] After a leave-on time of 30 minutes, the lock of hair was wrung dry with a paper and rinsed with water.

[0447] Next, composition (B2) obtained above was then applied to the lock of hair, by means of a brush at an amount of 2 g of composition per 1 g of lock.

[0448] After a leave-on time of 30 minutes, the lock of hair was wrung dry with a paper and rinsed with water. The lock was then washed with a shampoo (0.4 g of shampoo per 1 g of hair) and left to dry.

[0449] The same protocol was repeated with compositions (A3) and (B3). In other words, composition (A3) obtained above was applied by means of a brush at an amount of 2 g of composition on a 1 g lock of hair containing 90% white hairs.

[0450] After a leave-on time of 30 minutes, the lock of hair was wrung dry with a paper and rinsed with water.

[0451] Next, composition (B3) obtained above was then applied to the lock of hair, by means of a brush at an amount of 2 g of composition per 1 g of lock.

[0452] After a leave-on time of 30 minutes, the lock of hair was wrung dry with a paper and rinsed with water. The lock was then washed with a shampoo (0.4 g of shampoo per 1 g of hair) and left to dry.

[0453] The colour of the locks thus obtained was evaluated in the CIE L*a*b* system, using a Minolta Spectrophotometer CM2600D colorimeter.

[0454] In this system, L* represents the intensity of the colour, a* indicates the green/red colour axis and b* the blue/yellow colour axis.

[0455] The lower the value of L, the darker or more intense the colour. The higher the value of a*, the redder the shade, and the higher the value of b*, the yellower the shade.

[0456] The variation in the colouration of the locks before and after dyeing is measured by (E*) which corresponds to the colour uptake according to the following equation:

E*=(L*L.sub.o).sup.2+(a*a.sub.o).sup.2+(b*-b.sub.o*).sup.2

[0457] In this equation, L*, a* and b* represent the values measured after dyeing with (A2, then B2) or (A3, then B3), and L.sub.0*, a.sub.0* and b.sub.0* represent the values measured before dyeing, corresponding to an untreated control lock (100% white hair).

[0458] The greater the E* value, the greater the difference in colour of the lock before and after dyeing, which shows good colour uptake.

c) Results

[0459] The results are given in the table below.

TABLE-US-00019 L* Process Colour (D65) E* A2, then B2 Mahogany brown 21.43 39.00 A3, then B3 Red mahogany 26.14 34.08

[0460] The results obtained above show that the sequential application of a 2-azo(benzo)imidazolium dye of formula (I) according to the present invention and of a fluorescent dye, chosen from cyanin, styryl/hemicyanin, and naphthalimide dyes (A2, then B2), results in better dyeing properties, in particular in terms of colour uptake and intensity, than a comparative process (A3, then B3), wherein a fluorescent dye, different from the fluorescent dyes used in the present invention, is applied after a 2-azo(benzo)imidazolium dye.

VI. Second Comparative Example of a Sequential Application

a) Compositions

[0461] Compositions (A2), (A3), (B2) and (B3) were prepared from the ingredients mentioned in Example 4.

b) Procedure for a Combined Application

[0462] Composition (B2) obtained above was applied by means of a brush at an amount of 2 g of composition on a 1 g lock of hair containing 90% white hairs.

[0463] After a leave-on time of 30 minutes, the lock of hair was wrung dry with a paper and rinsed with water.

[0464] Next, composition (A2) obtained above was then applied to the lock of hair, by means of a brush at an amount of 2 g of composition per 1 g of lock.

[0465] After a leave-on time of 30 minutes, the lock of hair was wrung dry with a paper and rinsed with water. The lock was then washed with a shampoo (0.4 g of shampoo per 1 g of hair) and left to dry.

[0466] The same protocol was repeated with compositions (B3) and (A3). In other words, composition (B3) obtained above was applied by means of a brush at an amount of 2 g of composition on a 1 g lock of hair containing 90% white hairs.

[0467] After a leave-on time of 30 minutes, the lock of hair was wrung dry with a paper and rinsed with water.

[0468] Next, composition (A3) obtained above was then applied to the lock of hair, by means of a brush at an amount of 2 g of composition per 1 g of lock.

[0469] After a leave-on time of 30 minutes, the lock of hair was wrung dry with a paper and rinsed with water. The lock was then washed with a shampoo (0.4 g of shampoo per 1 g of hair) and left to dry.

[0470] The colour of the locks thus obtained was evaluated in the CIE L*a*b* system, using a Minolta Spectrophotometer CM2600D colorimeter.

[0471] In this system, L* represents the intensity of the colour, a* indicates the green/red colour axis and b* the blue/yellow colour axis.

[0472] The lower the value of L, the darker or more intense the colour. The higher the value of a*, the redder the shade, and the higher the value of b*, the yellower the shade.

[0473] The variation in the colouration of the locks before and after dyeing is measured by (E*) which corresponds to the colour uptake according to the following equation:

E*=(L*L.sub.o).sup.2+(a*a.sub.o).sup.2+(b*b.sub.o).sup.2

[0474] In this equation, L*, a* and b* represent the values measured after dyeing with (A2, then B2) or (A3, then B3), and L.sub.0*, a.sub.0* and b.sub.0* represent the values measured before dyeing, corresponding to an untreated control lock (100% white hair).

[0475] The greater the E* value, the greater the difference in colour of the lock before and after dyeing, which shows good colour uptake.

[0476] The chromaticity of the colour obtained is measured by (C*) which corresponds to the following equation:

C*={square root over ((a*).sup.2+(b*).sup.2)}

[0477] The greater the C* value, the more the colour of the locks is chromatic.

c) Results

[0478] The results are given in the table below.

TABLE-US-00020 L* Process Colour (D65) E* C* B2, then A2 Mahogany brown 24.68 36.05 12.61 B3, then A3 purple brown 28.36 33.20 10.71

[0479] The results obtained above show that the sequential application of a fluorescent dye, chosen from cyanin, styryl/hemicyanin, and naphthalimide dyes and of a 2-azo(benzo)imidazolium dye of formula (I) according to the present invention (B2, then A2), results in better dyeing properties, in particular in terms of chromaticity, colour uptake and intensity, than a comparative process (B3, then A3), wherein a fluorescent dye, different from the fluorescent dyes used in the present invention, is applied before a 2-azo(benzo)imidazolium dye.