EP2259766A2

EP2259766A2 - Composition for dyeing keratin fibres comprising at least one direct dye comprising a disulphide/protected-thiol function and at least one siliceous compound comprising a thiol function and method using the composition

Info

Publication number: EP2259766A2
Application number: EP09716887A
Authority: EP
Inventors: Alain Lagrange
Original assignee: LOreal SA
Current assignee: LOreal SA
Priority date: 2008-02-29
Filing date: 2009-02-16
Publication date: 2010-12-15
Also published as: FR2928087A1; WO2009109457A2; WO2009109457A3; FR2928087B1

Abstract

The invention relates to a composition comprising i) one or more direct dye(s) comprising a disulphide function or functions or comprising a protected-thiol function or functions, and ii) one or more siliceous compounds comprising a thiol function or functions, used for dyeing keratin fibres, in particular human keratin fibres such as the hair. It also relates to the method of dyeing keratin fibres using said composition and to the use of direct dyes comprising a disulphide or protected-thiol function associated with the siliceous compounds comprising thiol functions, in the dyeing and lightening of keratin fibres. This composition allows new systems for very powerful, homogeneous hair dyeing, which are fast with respect to external agents and which do not impair the cosmetic properties of keratin fibres.

Description

COMPOSITION FOR DYEING KERATIN FIBRES COMPRISING AT

LEAST ONE DIRECT DYE COMPRISING A DISULPHIDE/PROTECTED-

THIOL FUNCTION AND AT LEAST ONE SILICEOUS COMPOUND

COMPRISING A THIOL FUNCTION AND METHOD USING THE COMPOSITION

The subject of the invention is a composition comprising at least one direct dye comprising a disulphide or protected-thiol function and at least one siliceous compound comprising a thiol function, used for dyeing keratin fibres, in particular human keratin fibres such as the hair. A subject of the invention is also the method for dyeing keratin fibres using said composition and the use of direct dyes comprising a disulphide function associated with the siliceous compound comprising a thiol function in the dyeing and lightening of keratin fibres.

It is known practice to dye keratin fibres by direct dyeing or semi-permanent dyeing. Direct dyeing or semi-permanent dyeing comprises providing the colour through a coloured molecule which is adsorbed at the surface of the hair or penetrates into the hair. Thus, the method conventionally used in direct dyeing comprises applying, to the keratin fibres, direct dyes which are coloured or colouring molecules having an affinity for the fibres, leaving the fibres in contact with the colouring molecules and then rinsing the fibres. Generally, this technology produces chromatic colourings.

For several years, scientific research has been carried out in order to modify the colour of keratin materials, especially of keratin fibres, and in particular for masking white fibres, modifying the colour of the fibres permanently or fleetingly, and satisfying new desires and needs in terms of colours and durability. In application EP 1 647 580 or WO 2005/097051, a direct dye comprising a disulphide function capable of grafting to the hair covalently, by means of a reducing treatment, has been proposed. These direct dyes are more resistant, on the keratin fibres, to shampooing. The reducing agents described in these documents are reducing agents that are small in size and have a low molecular molar mass, such as thioglycolic acid, thiolactic acid and their associated salts, cysteine, and borohydrides, and have a tendency to migrate inside the fibre, thereby impairing the integrity of this fibre and result in it becoming brittle. Furthermore, the prior art reducing agents have the drawback of generating unpleasant odours.

The objective of the present invention is to provide new hair dyeing systems for obtaining colourings which are virtually odourless, homogeneous, very intense and fast with respect to external agents, and which do not impair the cosmetic properties of keratin fibres.

Another objective of the invention is to provide dyeing systems for obtaining colourings that are visible on dark hair and lightening effects on naturally or artificially dark keratin fibres without degradation of the fibre.

Another object of the invention is to make it possible to efface the colouring on light hair or on dark hair at the moment this is desired, while at the same time limiting the detrimental effects thereof on the quality of the fibre.

These objectives are achieved with the present invention, the subject of which is a dye composition comprising, in a suitable cosmetic medium, i) one or more dyes chosen from direct dyes comprising a disulphide function or functions, or comprising a protected-thiol function or functions, and ii) one or more siliceous compound (s) comprising a thiol function or functions.

A subject of the invention is also a method for dyeing keratin fibres, in particular human keratin fibres, such as the hair, comprising applying, to the fibres, the dye composition mentioned above.

Another subject of the invention is the use, for dyeing keratin fibres, in particular the hair, of one or more direct dye(s) comprising a disulphide function or functions, or comprising a protected-thiol function or functions, and of one or more siliceous compound (s) comprising a thiol function or functions.

The composition according to the invention makes it possible in particular to powerfully and homogeneously dye human keratin fibres such as the hair, while at the same time observing the integrity of the fibres. Without being held by any theory, we think that the siliceous compounds comprising a thiol function that are of use in the present invention can reduce the cysteine molecules present at the surface of the hairs, thus allowing the appearance of thiol functions at the surface of the hair and then the covalent bonding of the direct dyes comprising a disulphide, thiol or protected-thiol function, directly to the hair, while at the same time avoiding penetrating into the hairs. These siliceous compounds can themselves bind to the cysteine-unit-rich proteins of the surface of the hairs and establish other bonds with the dyes comprising disulphide, thiol or protected-thiol units, through "sulphur-sulphur" bond exchanges. Where appropriate, the establishment of asymmetric disulphide bonds between the surface of the hair, the polymers and the colouring chromophores derived from the dyes of the invention can be aided by an oxidizing agent which bonds together two thiol functions belonging to two different species.

The siliceous compounds comprising a thiol function or functions thus perform a mordanting role for the surface bonding of the disulphide or thiol or protected-thiol dyes. Unexpectedly, keratin fibre degradation is very limited.

The colourings obtained are aesthetic, very intense and very fast with respect to common attacks such as sunlight, perspiration or sebum, and to other hair treatments such as successive shampooing operations, while at the same time being kind to the keratin fibres. The intensity obtained is particularly notable. The same is true with regard to the homogeneity of the colour.

Another advantage of the invention concerns the effacing of the colouring, as desired, which is made possible with a minimum detrimental effect on the quality of the keratin fibre.

For the purpose of the present invention, and unless otherwise indicated: - a "direct dye comprising a disulphide function or functions" is a direct dye comprising one or more chromophores which absorb (s) light in the visible spectrum, and comprising one or more disulphide bonds: -S-S- between two carbon atoms, directly or indirectly linked to the chromophore (s) of the dye. Preferably, a single disulphide bond is indirectly linked to the chromophore (s) ; the -S-S- bond being capable of being reduced in a cosmetically acceptable medium; when the direct dye contains several chromophores, the chromophores may be identical or different; ■ a "direct dye comprising a protected-thiol function" is a direct dye comprising a chromophore, and comprising one or more protected- thiol functions -SY' where Y' is a protective group known to those skilled in the art, for instance those described in the books "Protective Groups in Organic Synthesis", T. W. Greene, John Willey & Sons ed., NY, 1981, pp. 193-217; "Protecting Groups" , P. Kocienski, Thieme, 3rd ed., 2005, chap. 5; and Ullmann' s Encyclopedia, "Peptide Synthesis" , p. 4-5, 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 10.1002/14356007. al9 157;

■ a "chromophore" is a radical derived from a dye, i.e. a radical derived from a molecule which absorbs light in the visible range of radiation visually and physiologically perceptible by humans, i.e. at an absorption wavelength λ_abs of between 400 and 800 nm, limits included; the chromophore may be fluorescent, i.e. it is capable of absorbing in the UV or visible radiation range at a wavelength λ_abs of between 250 and 800 nm and capable of re-emitting in the visible range at an emission wavelength λ_em of between 400 and 800 nm;

■ the disulphide dyes according to the invention contain one or more chromophores, and these disulphide dyes are capable of absorbing light at a wavelength λ_abs in particular between 400 and 700 nm, limits included;

■ the "fluorescent" disulphide dyes according to the invention are dyes containing at least one fluorescent chromophore, and these disulphide dyes are capable of absorbing in the visible range at a wavelength λ_abs of particularly between 400 and 800 nm and of re-emitting in the visible range at a wavelength λ_em that is higher than that absorbed, of between 400 and 800 nm. The difference between the absorption wavelength and the emission wavelength, also known as Stoke' s shift, is between 1 nm and 100 nm. More preferably, the fluorescents dyes are dyes capable of absorbing at a wavelength λ_abs of between 420 nm and 550 nm and of re-emitting in the visible range at a wavelength λ_em of between 470 and 600 nm;

■ the chromophores are said to be "different" when they differ by virtue of their chemical structure, and may be chromophores derived from different families or from the same family provided that they have different chemical structures: for example, the chromophores may be chosen from the family of azo dyes, but differ by virtue of the chemical structure of the radicals of which they are formed or by virtue of the respective position of these radicals;

■ an "alkylene chain" represents a C1-C20 divalent chain; particularly C₁-C₆, more particularly C1-C2 when the chain is linear; optionally substituted with one or more groups, which may be identical or different, chosen from hydroxyl, (C1-C2) alkoxy,

(poly) hydroxy (C₂-C₄) alkoxy, (di) (Ci-C₂) (alkyl) - amino, R^a-Z^a-C(Z^b)- and R^a-Z^a-S(O)_t- with Z^a and Z^b, which may be identical or different, representing an oxygen or sulphur atom or an NR^a' group, R^a representing an alkali metal, a hydrogen atom or an alkyl group or else being absent if another part of the cationic molecule, and R^a' representing a hydrogen atom or an alkyl group, and t is 1 or 2;

■ a "C1-C30 divalent, saturated or unsaturated, optionally substituted hydrocarbon-based chain", represents a hydrocarbon-based chain, particularly a Ci-Cs hydrocarbon-based chain, comprising optionally one or more double bonds π, which are conjugated or nonconjugated, particularly the hydrocarbon-based chain is saturated; said chain is optionally substituted by one or more, identical or different, groups chosen from hydroxyl, (Ci-C₂) alkoxy, (poly) hydroxy (C₂-C₄) - alkoxy, (di) (Ci-C₂) (alkyl) amino, R^a-Z^a-C(Z^b)- and R^a-Z^a-S(O)_t- with Z^a and Z^b, which may be identical or different, representing an oxygen or sulphur atom or an NR^a' group, R^a representing an alkali metal, a hydrogen atom or an alkyl group or else being absent if another part of the cationic molecule, and R^a' representing a hydrogen atom or an alkyl group, and t is 1 or 2; the "aryl" or "heteroaryl" radicals or the aryl or heteroaryl part of a radical can be substituted with at least one substituent borne by a carbon atom, chosen from: - a C1-C16, preferably Ci-Cs, alkyl radical optionally substituted with one or more radicals chosen from the radicals: hydroxyl, C1-C2 alkoxy, (poly) hydroxy (C2-C4) alkoxy, acylamino, amino substituted with two Ci-C₄ alkyl radicals, which may be identical or different, optionally bearing at least one hydroxyl group, or it being possible for the two radicals to form, with the nitrogen atom to which they are attached, a saturated or unsaturated, optionally substituted heterocycle comprising from 5 to 7 ring members, preferably 5 or 6 ring members, optionally comprising another heteroatom identical to or different from nitrogen; - a halogen atom;

- a hydroxyl group;

- a C1-C2 alkoxy radical;

- a (poly) hydroxy (C2-C4) alkoxy radical;

- an amino radical; - a 5- or 6-membered heterocycloalkyl radical;

- a 5- or 6-membered heteroaryl radical which is optionally cationic, preferably imidazolium, and optionally substituted with a (C1-C4) alkyl radical, preferably methyl; - an amino radical substituted with one or two C₁-C₆ alkyl radicals, which may be identical or different, optionally bearing at least: i) one hydroxyl group, ii) one amino group optionally substituted with one or two optionally substituted C1-C3 alkyl radicals, it being possible for said alkyl radicals to form, with the nitrogen atom to which they are attached, a saturated or unsaturated, optionally substituted heterocycle comprising from 5 to 7 ring members, optionally comprising at least one other heteroatom identical to or different from nitrogen, iii) one quaternary ammonium group -N⁺R'R"R"', M^" for which R' , R" and R'", which may be identical or different, represent a hydrogen atom or a C1-C4 alkyl group; and M^~ represents the counterion of the corresponding organic or inorganic acid or halide, iv) or a 5- or 6-membered heteroaryl radical which is optionally cationic, preferably imidazolium, and optionally substituted with a (C1-C4) alkyl radical, preferably methyl; an acylamino radical (-NR-COR' ) in which the R radical is a hydrogen atom or a C1-C4 alkyl radical optionally bearing at least one hydroxyl group, and the R' radical is a C1-C2 alkyl radical; a carbamoyl radical

((R)₂N-CO-) in which the R radicals, which may or may not be identical, represent a hydrogen atom, or a Ci-C₄ alkyl radical optionally bearing at least one hydroxyl group; an alkylsulphonylamino radical (R' SO₂-

NR-) in which the R radical represents a hydrogen atom, or a Ci-C₄ alkyl radical optionally bearing at least one hydroxyl group, and the R' radical represents a Ci-C₄ alkyl radical or a phenyl radical; an aminosulphonyl radical ((R)₂N-SO₂-) in which the R radicals, which may or may not be identical, represent a hydrogen atom or a Ci-C₄ alkyl radical optionally bearing at least one hydroxyl group; a carboxylic radical in acid or salified form (preferably, with an alkali metal or an ammonium, substituted or unsubstituted) ;

- a cyano group;

- a nitro or nitroso group;

- a polyhaloalkyl group, preferably trifluoro- methyl; the cyclic or heterocyclic part of a nonaromatic radical may be substituted with at least one substituent chosen from the groups:

- hydroxyl, - Ci -C₄ al koxy, (po l y) hydroxy ( C₂ -C₄ ) al koxy,

- Ci-C₄ alkyl,

- alkylcarbonylamino (RCO-NR'-) in which the R' radical is a hydrogen atom, or a Ci-C₄ alkyl radical optionally bearing at least one hydroxyl group, and the R radical is a C1-C2 alkyl radical or an amino radical which is optionally substituted with one or two identical or different Ci-C₄ alkyl groups, themselves optionally bearing at least one other hydroxyl group, it being possible for said alkyl radicals to form, with the nitrogen atom to which they are attached, a saturated or unsaturated, optionally substituted heterocycle comprising from 5 to 7 ring members, optionally comprising at least one other heteroatom atom identical to or different from nitrogen;

- alkylcarbonyloxy (RCO-O-) in which the R radical is a Ci-C₄ alkyl radical or an amino group which is optionally substituted with one or two identical or different Ci-C₄ alkyl groups, themselves optionally bearing at least one hydroxyl group, it being possible for said alkyl radicals to form, with the nitrogen atom to which they are attached, a saturated or unsaturated, optionally substituted heterocycle comprising from 5 to 7 ring members, optionally comprising at least one other heteroatom identical to or different from nitrogen;

- alkoxycarbonyl (RG-CO-) in which the R radical is a C1-C4 alkoxy radical, and G is an oxygen atom, or an amino group that is optionally substituted with a Ci-C₄ alkyl group, itself optionally bearing at least one hydroxyl group, it being possible for said alkyl radical to form, with the nitrogen atom to which it is attached, a saturated or unsaturated, optionally substituted heterocycle comprising from 5 to 7 ring members, optionally comprising at least one other heteroatom identical to or different from nitrogen; " a cyclic or heterocyclic radical, or a nonaromatic part of an aryl or heteroaryl radical, may also be substituted with one or more oxo groups;

■ a hydrocarbon-based chain is unsaturated when it comprises one or more double bonds and/or one or more triple bonds;

■ an "aryl" radical represents a condensed or noncondensed, monocyclic or polycyclic carbon- based group containing from 6 to 22 carbon atoms, and at least one ring of which is aromatic; preferably, the aryl radical is a phenyl, biphenyl, naphthyl, indenyl, anthracenyl or tetra- hydronaphthyl ;

■ a "heteroaryl radical" represents a condensed or noncondensed, optionally cationic, monocyclic or polycyclic group comprising from 5 to 22 ring members, and from 1 to 6 heteroatoms chosen from nitrogen, oxygen, sulphur and selenium atoms, and at least one ring of which is aromatic; preferably, a heteroaryl radical is chosen from acridinyl, benzimidazolyl, benzobistriazolyl, benzopyrazolyl, benzopyridazinyl, benzoquinolyl, benzothiazolyl, benzotriazolyl, benzoxazolyl, pyridinyl, tetrazolyl, dihydrothiazolyl, imidazopyridinyl, imidazolyl, indolyl, isoquinolyl, naphthaimidazolyl, naphthooxazolyl, naphthopyrazolyl, oxadiazolyl, oxazolyl, oxazolopyridyl, phenazinyl, phenooxazolyl, pyrazinyl, pyrazolyl, pyrilyl, pyrazoyltriazyl, pyridyl, pyridinoimidazolyl, pyrrolyl, quinolyl, tetrazolyl, thiadiazolyl, thiazolyl, thiazolopyridinyl, thiazoylimidazolyl, thiopyrylyl, triazolyl and xanthylyl and the ammonium salt thereof; - a "cyclic radical" is a condensed or noncondensed, monocyclic or polycyclic, nonaromatic cycloalkyl radical containing from 5 to 22 carbon atoms, which may comprise one or more unsaturations;

■ a "heterocyclic radical" is a radical which may contain one or two unsaturations but which is nonaromatic, monocyclic or polycyclic and condensed or noncondensed, containing from 5 to 22 ring members, and comprising from 1 to 6 hetero- atoms chosen from nitrogen, oxygen, sulphur and selenium atoms;

■ a "heterocycloalkyl radical" is a saturated heterocyclic radical;

^■ an "alkyl radical" is a linear or branched, C1-C20, preferably Ci-Cs, hydrocarbon-based radical; ■ an "alkenylene radical" is an alkyl radical as defined above, which may contain from 1 to 4 conjugated or unconjugated double bonds -C=C-; in particular, the alkenylene group contains 1 or 2 unsaturation (s) ; ■ the expression "optionally substituted" attributed to the alkyl radical implies that said alkyl radical may be substituted with one or more radicals chosen from the radicals i) hydroxyl, ii) C1-C4 alkoxy, iii) acylamino, iv) amino which is optionally substituted with one or two Ci-C₄ alkyl radicals, which may be identical or different, it being possible for said alkyl radicals to form, with the nitrogen atom which bears them, a heterocycle comprising from 5 to 7 ring members, optionally comprising another heteroatom identical to or different from nitrogen; v) or a quaternary ammonium group -N⁺R' R"R'", M^" for which R' , R" and R'", which may be identical or different, represent a hydrogen atom, or a Ci-C₄ alkyl group, or else -N⁺R'R"R'" forms a heteroaryl such as imidazolium optionally substituted with a Ci-C₄ alkyl group, and M^~ represents the counterion of the corresponding organic or inorganic acid or halide;

■ an "alkoxy radical" is an alkyl-oxy radical for which the alkyl radical is a linear or branched, C1-C16, preferably Ci-Cs, hydrocarbon-based radical;

■ when the alkoxy group is optionally substituted, this implies that the alkyl group is optionally substituted as defined above;

■ the "tone height" is the unit known to hairstyling professionals, and published in the book "Science des traitements capillaries" [the Science of hair treatments] by Charles ZVIAK 1988, published by Masson, p. 215 and 278; the tone heights extend from 1 (black) to 10 (light blond) , one unit corresponding to one tone; the higher the number, the lighter the shade; " a "dark" keratin fibre is a keratin fibre which has a luminescence L* expressed as a number in the C. I. E. L*a*b* system, of less than or equal to 45, and preferably less than or equal to 40, given, moreover, that L* = 0 is equivalent to black and L* = 100 to white;

■ "naturally or artificially dark" hair is hair of which the tone height is less than or equal to 6

(dark blond) and preferably less than or equal to 4 (chestnut brown) . Artificially coloured hair is hair of which the colour has been modified by a dyeing treatment, for example dyeing with direct dyes or oxidation dyes.

1.1. Direct dyes comprising a disulphide function, of the invention :

According to one embodiment of the invention, the direct dyes comprising a protected-thiol or disulphide function are chosen from the dyes of formula (I) :

the organic or inorganic acid salts thereof, the optical and geometric isomers thereof and the solvates thereof such as hydrates, in which formula (I) :

• U represents a radical chosen from: ii) -S- Cat - (X' )_P' - D; and iii) -Y;

• A and A' , which may be identical or different, represent a radical containing one or more cationic or noncationic, fluorescent or nonfluorescent chromophore (s) ;

• Y represents a thiol-function-protecting group;

• X and X' , which may be identical or different, represent a linear or branched, saturated or unsaturated, C1-C30 divalent hydrocarbon-based chain, optionally interrupted and/or optionally terminated at one or two of its ends with one or more divalent groups or combinations thereof chosen from:

-N(R)-, -N⁺(R) (R)-, -O-, -S-, -CO- and -SO2- with R, which may be identical or different, chosen from a hydrogen and a C₁-C₄ alkyl, hydroxyalkyl or aminoalkyl radi cal ;

■ a condensed or noncondensed, saturated or unsaturated, aromatic or nonaromatic (hetero) cyclic radical optionally comprising one or more heteroatoms, which may be identical or different, and optionally substituted;

• p and p' , which may be identical or different, are 0 or 1; • C_sat and C'_sat, which may be identical or different, represent a linear or branched, optionally substituted, optionally cyclic Ci-Cis alkylene chain;

• D corresponds to a radical chosen from hydroxyl, hydroxyalkyl, alkoxy, carboxylic, carboxylate, amino, alkylamino and dialkyl- amino radicals.

One particular embodiment of the invention concerns the dye compositions comprising, as dye comprising a disulphide function, a dye of formula (I) as defined above.

Another particular embodiment of the invention focuses on the dye compositions comprising one or more fluorescent dye(s) comprising a disulphide or protected-thiol function or functions with a view to dyeing and/or lightening dark keratin fibres. More particularly, the fluorescent dye(s) comprise (s) a disulphide function or functions.

1.1.1. Y:

In accordance with one particular embodiment of the invention, in the abovementioned formula (I) , Y is a protective group known to those skilled in the art, for instance those described in the books "Protective Groups in Organic Synthesis" , T. W. Greene, John Willey & Sons ed., NY, 1981, pp. 193-217; "Protecting Groups", P. Kocienski, Thieme, 3rd ed., 2005, chap. 5, and Ullmann' s Encyclopedia, "Peptide Synthesis" , p. 4-5, 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 10.1002/14356007. al9 157.

In particular, when Y represents a thiol-function- protecting group, the latter is chosen from the following radicals:

^■ (C₁-C₄) alkylcarbonyl; ■ (C₁-C₄) alkylthiocarbonyl;

^■ (C₁-C₄) alkoxycarbonyl;

^■ (C₁-C₄) alkoxythiocarbonyl;

^■ (C₁-C₄) alkylthio-thiocarbonyl;

^■ (di) (C₁-C₄) (alkyl) aminocarbonyl; ■ (di) (C₁-C₄) (alkyl) aminothiocarbonyl;

^■ arylcarbonyl such as phenylcarbonyl;

^■ aryloxycarbonyl;

^■ aryl (C₁-C₄) alkoxycarbonyl;

^■ (di) (C₁-C₄) (alkyl) aminocarbonyl, such as dimethylaminocarbonyl ;

^■ (C₁-C₄) (alkyl) arylaminocarbonyl;

^■ carboxy;

^■ SC>₃ ^~; M⁺ with M⁺ representing an alkali metal such as sodium or potassium, or else a counterion of the cationic chromophore A and

M⁺ are absent;

^■ optionally substituted aryl, such as phenyl, dibenzosuberyl or 1, 3, 5-cycloheptatrienyl;

^■ optionally substituted heteroaryl; including, in particular, the cationic or noncationic heteroaryls comprising from 1 to 4 heteroatoms, below: i) 5-, 6- or 7-membered monocyclic heteroaryls, such as furanyl or furyl, pyrrolyl or pyrryl, thiophenyl or thienyl, pyrazolyl, oxazolyl, oxazolium, isoxazolyl, isoxazolium, thiazolyl, thiazolium, isothiazolyl, isothiazolium, 1, 2, 4-triazolyl, 1,2,4-tri- azolium, 1, 2, 3-triazolyl, 1, 2, 3-triazolium, 1, 2, 4-oxazolyl, 1, 2, 4-oxazolium, 1, 2, 4-thia- diazolyl, 1, 2, 4-thiadiazolium, pyrylium, thiopyridyl, pyridinium, pyrimidinyl, pyrimidinium, pyrazinyl, pyrazinium, pyridazinyl, pyridazinium, triazinyl, triazinium, tetrazinyl, tetrazinium, azepine, azepinium, oxazepinyl, oxazepinium, thiepinyl, thiepinium, imidazolyl, imidazolium; ii) 8- to 11-membered bicyclic heteroaryls, such as indolyl, indolinium, benzoimidazolyl, benzoimidazolium, benzoxazolyl, benz- oxazolium, dihydrobenzoxazolinyl, benzothia- zolyl, benzothiazolium, pyridoimidazolyl, pyridoimidazolium, thienocycloheptadienyl, these monocyclic or bicyclic groups being optionally substituted with one or more groups such as (C₁-C₄) alkyl, for instance methyl, or polyhalo (C₁-C₄) alkyl, for instance trifluoromethyl ; iii) or tricyclic heteroaryl ABC below: in which the two rings A and C optionally comprise a heteroatom, and the ring B is a 5-, 6- or 7-membered, particularly

6-membered, ring and contains at least one heteroatom, such as pyperidyl or pyranyl;

optionally substituted, optionally cationic heterocycloalkyl; the heterocycloalkyl group represents in particular a saturated or partially saturated, 5-, 6- or 7-membered monocyclic group comprising from 1 to 4 heteroatoms chosen from oxygen, sulphur and nitrogen, such as di/tetrahydrofuranyl, di/tetrahydrothiophenyl, di/tetrahydro- pyrrolyl, di/tetrahydropyranyl, di/tetra/ hexahydrothiopyranyl, dihydropyridyl, piperazinyl, piperidinyl, tetramethyl- piperidinyl, morpholinyl, di/tetra/hexa- hydroazepinyl or di/tetrahydropyrimidinyl, these groups being optionally substituted with one or more groups such as (C₁-C₄) alkyl, oxo or thioxo; or the heterocycle represents the following group:

in which R'^c, R'^d, R'^e, R'^f, R'^g and R'^h, which may be identical or different, represent a hydrogen atom or a (C₁-C₄) alkyl group, or else two groups R' ^g with R'^h, and/or R' ^e with R'^f, form an oxo or thioxo group, or else R' ^g with R'^e together form a cycloalkyl; and v represents an integer between 1 and 3, limits included; preferably, R' ^c to R'^h represent a hydrogen atom; and An'"^~ represents a counterion;

-C(NR'^cR'^d)=N⁺R'^eR'^f; An'"^" with R'^c, R'^d, R' ^e and R'^f, which may be identical or different, representing a hydrogen atom or a (C₁-C₄) alkyl group; preferably, R' ^c to R' ^f represent a hydrogen atom; and An'"^~ represents a counterion;

-C (NR'^cR'^d)=NR'^e; with R'^c, R'^d and R'^e being as defined above; optionally substituted (di) aryl (C₁-C₄) alkyl, such as 9-anthracenylmethyl, phenylmethyl or diphenylmethyl, optionally substituted with one or more groups in particular chosen from (C₁-C₄) alkyl, (C₁-C₄) alkoxy such as methoxy, hydroxyl, alkylcarbonyl, and (di) (C₁-C₄)- (alkyl) amino such as dimethylamino;

■ optionally substituted (di) heteroaryl (C₁-C₄) - alkyl; the heteroaryl group is in particular cationic or noncationic, and monocyclic, comprising 5 or 6 ring members and from 1 to

4 heteroatoms chosen from nitrogen, oxygen and sulphur, such as the groups pyrrolyl, furanyl, thiophenyl, pyridyl, pyridyl N-oxide, such as 4-pyridyl or 2-pyridyl N-oxide, pyrylium, pyridinium or triazinyl, optionally substituted with one or more groups such as alkyl, in particular methyl; advantageously, the (di) heteroaryl (C₁-C₄) alkyl is (di) heteroarylmethyl or (di) heteroaryl- ethyl;

CR¹R²R³ with R¹, R² and R³, which may be identical or different, representing a halogen atom or a group chosen from:

- (C₁-C₄) alkyl; - (C₁-C₄) alkoxy;

- optionally substituted aryl, such as phenyl optionally substituted with one or more groups such as (C₁-C₄) alkyl, (C₁-C₄) alkoxy or hydroxyl ; - optionally substituted heteroaryl, such as thiophenyl, furanyl, pyrrolyl, pyranyl or pyridyl, optionally substituted with a (C₁-C₄) alkyl group;

- P (Z¹) R' ¹R' ²R'³ with R'¹ and R'², which may be identical or different, representing a hydroxyl, (C₁-C₄) alkoxy or alkyl group, R'³ representing a hydroxyl or (C₁-C₄) alkoxy group, and Z¹ representing an oxygen or sulphur atom; - a sterically hindered cyclic radical; and

■ optionally substituted alkoxyalkyl, such as methoxymethyl (MOM) , ethoxyethyl (EOM) and isobutoxymethyl . According to one particular embodiment, the protected-thiol fluorescent dyes of formula (I) comprise a group Y which is a i) cationic, aromatic, 5- or 6-membered monocyclic heteroaryl group comprising from 1 to 4 heteroatoms chosen from oxygen, sulphur and nitrogen, such as oxazolium, isoxazolium, thiazolium, isothiazolium, 1, 2, 4-triazolium, 1, 2, 3-triazolium, 1 , 2 , 4-oxazolium, 1, 2, 4-thiadiazolium, pyrylium, pyridinium, pyrimidinium, pyrazinyl, pyrazinium, pyridazinium, triazinium, tetrazinium, oxazepinium, thiepinyl, thiepinium or imidazolium; ii) cationic, 8- to 11-membered bicyclic heteroaryl group, such as indolinium, benzoimidazolium, benzoxazolium or benzothiazolium, these monocyclic or bicyclic heteroaryl groups being optionally substituted with one or more groups such as alkyl, for instance methyl, or polyhalo (C₁-C₄) alkyl, for instance trifluoromethyl; iii) or heterocyclic group below:

in which R' ^c and R' ^d, which may be identical or different, represent a hydrogen atom or a (C₁-C₄) alkyl group; preferably, R' ^c to R'^d represent a (C₁-C₄) alkyl group such as methyl; and An'"^~ represents a counterion .

In particular, Y represents a group chosen from oxazolium, isoxazolium, thiazolium, isothiazolium, 1 , 2 , 4-triazolium, 1, 2, 3-triazolium, 1, 2, 4-oxazolium, 1, 2, 4-thiadiazolium, pyrylium, pyridinium, pyrimidinium, pyrazinium, pyridazinium, triazinium, imidazolium, benzoimidazolium, benzoxazolium and benzothiazolium, these groups being optionally substituted with one or more (C₁-C₄) alkyl groups, in particular methyl.

In particular, Y represents a protective group such as :

> (C₁-C₄) alkylcarbonyl, for instance methyl- carbonyl or ethylcarbonyl;

> arylcarbonyl, for instance phenylcarbonyl;

> (C₁-C₄) alkoxycarbonyl;

> aryloxycarbonyl;

> aryl (C₁-C₄) alkoxycarbonyl;

> (di) (C₁-C₄) (alkyl) aminocarbonyl, for instance dimethylaminocarbonyl;

> (C₁-C₄) (alkyl) arylaminocarbonyl;

> optionally substituted aryl such as phenyl;

> 5- or 6-membered monocyclic heteroaryl, such as imidazolyl or pyridyl;

> 5- or 6-membered cationic monocyclic heteroaryl, such as pyrylium, pyridinium, pyrimidinium, pyrazinium, pyridazinium, triazinium or imidazolium; these groups being optionally substituted with one or more identical or different (C₁-C₄) alkyl groups, such as methyl;

> 8- to 11-membered cationic bicyclic heteroaryl, such as benzoimidazolium or benzoxazolium; these groups being optionally substituted with one or more identical or different (C₁-C₄) alkyl groups, such as methyl;

> cationic heterocycle of formula below:

> -C (NH₂) =N⁺H₂; An'"^";

> -C(NH₂)=NH; > Sθ3-, M⁺ with M⁺ representing an alkali metal such as sodium or potassium.

1.1.2. C_sat and C_sat:

As indicated above, in the formulae (I) , C_sat and C _sat, independently of one another, represent a linear or branched, optionally substituted, optionally cyclic C₁-C₁₈ alkylene chain.

By way of substituent, mention may be made of amino, (C₁-C₄) alkylamino or (C₁-C₄) dialkylamino groups or the group R^a-Z^a-C(Z^b)- (in which Z^a and Z^b, which may be identical or different, represent an oxygen or sulphur atom or an NR^a' group, and R^a' represents an alkali metal, a hydrogen atom or a Ci-C₄ alkyl group, and R^a' represents a hydrogen atom or a Ci-C₄ alkyl group) preferably present on the carbon in the beta- or gamma-position with respect to the sulphur atoms.

Preferably, in the case of the formulae (I) , C_sat and C sat represent a - (CH₂) k~ chain with k being an integer between 1 and 8, limits included.

1.1.3. X and X' :

In accordance with one particular embodiment of the invention, in the abovementioned formulae (I) , when p is equal to 1, X and X' , which may be identical or different, represent the following sequence:

-(T)t-(Z)_z-(T')f-

said sequence being linked in the formulae (I) symmetrically as follows:

- C_sat (or C _Sat) - (T) _t- (Z) z- (A or A'); in which

T and T' , which may be identical or different, represent one or more radicals or combinations thereof chosen from: -0-; -S-; -N(R)-; -N⁺(R) (R⁰)-; -SO-; -SO₂-; -CO-; with R and R°, which may be identical or different, representing a hydrogen atom, or a Ci-C₄ alkyl, Ci-C₄ hydroxyalkyl or aryl (C₁-C₄) alkyl radical; and a cationic or noncationic, preferably monocyclic, heterocycloalkyl or heteroaryl radical, preferably containing two heteroatoms (more preferably, two nitrogen atoms) and preferably comprising from 5 to 7 ring members, more preferably imidazolium; the indices t and t' , which may be identical or different, are 0 or 1; Z represents:

■ - (CH₂) in- with m being an integer between 1 and 8; ■ - (CH₂CH₂O) _q- or - (OCH₂CH₂) _q- in which q is an integer between 1 and 5, limits included;

■ an aryl, alkylaryl or arylalkyl radical of which the alkyl radical is Ci-C₄ and the aryl radical is preferably Ce, being optionally substituted with at least one SO3M group with

M representing a hydrogen atom, an alkali metal or an ammonium group substituted with one or more identical or different, linear or branched, Ci-Cis alkyl radicals, optionally bearing at least one hydroxyl; z is 0 or 1.

Moreover, according to one particular embodiment of the invention, Z represents:

where M represents a hydrogen atom, an alkali metal or an ammonium group or an ammonium group substituted with one or more identical or different, linear or branched, C1-C10 alkyl radicals optionally bearing at least one hydroxyl, and 0-4 represents an integer between 0 and 4, limits included.

1.1.4. A and A' :

The radicals A and/or A' of the formulae (I) may contain one or more chromophores, which may be identical or different.

By way of chromophores A and/or A' that are of use in the present invention, mention may be made of radicals derived from acridine, acridone, anthranthrone, anthrapyrimidine, anthraquinone, azine, azo, azomethine, benzanthrone, benzimidazole, benzimidazolone, benzindole, benzoxazole, benzopyran, benzothiazole, benzoquinone, bisazine, bisisoindoline, carboxanilide, coumarin, cyanin (such as azacarbo- cyanin, diazacarbocyanin, diazahemicyanin, hemicyanin or tetraazacarbocyanin) , diazine, diketopyrrolopyrrole, dioxazine, diphenylamine, diphenylmethane, dithiazine, flavonoid, such as flavanthrone and flavone, fluorindine, formazan, hydrazone, in particular arylhydrazone, hydroxy ketone, indamine, indanthrone, indigoid and pseudoindigoid, indophenol, indoaniline, isoindoline, isoindolinone, isoviolanthrone, lactone, methine, naphthalimide, naphthanilide, naphtholactam, naphthoquinone, nitro, in particular nitro (hetero) - aromatic, oxadiazole, oxazine, perilone, perinone, perylene, phenazine, phenothiazine, phthalocyanin, polyene/carotenoid, porphyrin, pyranthrone, pyrazolanthrone, pyrazolone, pyrimidinoanthrone, pyronine, quinacridone, quinoline, quinophthalone, squarane, stilbene, tetrazolium, thiazine, thioindigo, thiopyronine, triarylmethane and xanthene dyes.

By way of fluorescent chromophores A and/or A' that are of use in the present invention, mention may be made of the radicals derived from acridine, acridone, benzanthrone, benzimidazole, benzimidazolone, benzindole, benzoxazole, benzopyran, benzothiazole, coumarin, difluoro-{2- [ (2iϊ-pyrrol-2-ylidene-kN) methyl] - lH-pyrrolato-kN}boron (BODIPY®) , diketopyrrolopyrrole, fluorindin, (poly) methine (in particular cyanin and styryl/hemicyanin) , naphthalimide, naphthanilide, naphthylamine (for instance dansyl) , oxadiazole, oxazine, perilone, perinone, perylene, polyene/carotenoid, squarane, stilbene and xanthene dyes .

Mention may also be made of the fluorescent dyes A and/or A' described in documents EP 1133975, WO 03/029359, EP 860636, WO 95/01772, WO 95/15144 and EP 714954 and those listed in the encyclopaedia "The chemistry of synthetic dye" by K. Venkataraman, 1952, Academic press vol. 1 to 7, in the encyclopaedia "Kirk Othmer" "Chemical technology", chapter "dyes and Dye intermediate", 1993, Wiley and sons, and in various chapters of the encyclopaedia " ULLMANN 's ENCYCLOPEDIA of Industrial chemistry" 7th edition, Wiley and sons, in The Handbook — A Guide to Fluorescent Probes and Labeling Technologies , 10th Ed Molecular Probes/ Invitrogen - Oregon 2005, distributed via the Internet or in the previous printed editions.

Among the nitro chromophores A and/or A' that can be used according to the invention, mention may, in a nonlimiting manner, be made of the radicals derived from the following dyes: - 1 , 4-diamino-2-nitrobenzene

- l-amino-2-nitro-4-β-hydroxyethylaminobenzene

- l-amino-2-nitro-4-bis (β-hydroxyethyl) aminobenzene

- 1, 4-Bis (β-hydroxyethylamino) -2-nitrobenzene

- l-β-hydroxyethylamino-2-nitro-4-bis- (β-hydroxyethyl- amino) benzene

- 1 -β-hydroxyethylamino-2 -nitro-4 -aminobenzene

- l-β-hydroxyethylamino-2-nitro-4- (ethyl) (β-hydroxyethyl) aminobenzene

- 1 -amino-3-methyl-4 -β-hydroxyethylamino-6-nitrobenzene - l-amino-2-nitro-4-β-hydroxyethylamino-5-chlorobenzene

- 1 , 2-Diamino-4-nitrobenzene

- 1 -amino-2 -β-hydroxyethy1amino-5-nitrobenzene

- 1, 2-Bis (β-hydroxyethylamino) -4-nitrobenzene - l-amino-2-tris (hydroxymethyl) -methylamino-5-nitro- benzene

- 1 -Hydroxy-2 -amino-5-nitrobenzene

- 1 -Hydroxy-2 -amino-4 -nitrobenzene

- l-Hydroxy-3-nitro-4-aminobenzene - l-Hydroxy-2-amino-4 , 6-dinitrobenzene

- 1 -β-hydroxyethyloxy-2 -β-hydroxyethylamino-5-nitrobenzene

- 1 -Methoxy-2 -β-hydroxyethylamino-5-nitrobenzene

- 1 -β-hydroxyethyloxy-3-methylamino-4 -nitrobenzene - l-β,γ-dihydroxypropyloxy-3-methylamino-4-nitrobenzene

- 1 -β-hydroxyethylamino-4 -β, γ-dihydroxypropyloxy-2- nitrobenzene

- 1-β, γ-dihydroxypropylamino-4-trifluoromethyl-2 -nitrobenzene - l-β-hydroxyethylamino-4-trifluoromethyl-2-nitro- benzene

- 1 -β-hydroxyethylamino-3-methyl-2 -nitrobenzene

- 1-β-aminoethy1amino-5-methoxy-2 -nitrobenzene

- l-Hydroxy-2-chloro-6-ethylamino-4 -nitrobenzene - l-Hydroxy-2-chloro-6-amino-4-nitrobenzene

- l-Hydroxy-6-bis- (β-hydroxyethyl) amino-3-nitrobenzene

- 1 -β-hydroxyethylamino-2 -nitrobenzene

- l-Hydroxy-4-β-hydroxyethylamino-3-nitrobenzene .

Among the azo chromophores A and/or A' that can be used according to the invention, mention may be made of the radicals derived from the cationic azo dyes described in patent applications WO 95/15144, WO 95/01772 and EP 714954.

Among the azo chromophores, mention may also be made of those described in the Colour Index International 3rd edition, and in particular the following compounds: - Disperse Red 17

- Acid Yellow 9

- Acid Black 1

- Basic Red 22 - Basic Red 76

- Basic Yellow 57

- Basic Brown 16

- Acid Yellow 36

- Acid Orange 7 - Acid Red 33

- Acid Red 35

- Basic Brown 17

- Acid Yellow 23

- Acid Orange 24 - Disperse Black 9.

Mention may also be made of 1- (4' -aminodi- phenylazo) -2-methyl-4-bis (β-hydroxyethyl) aminobenzene and 4-hydroxy-3- (2-methoxyphenylazo) -1-naphthalene- sulphonic acid.

Among the quinone chromophores A and/or A' , those mentioned in the abovementioned Colour Index

International are suitable, and among these, mention may be made, inter alia, of the radicals derived from the following dyes:

- Disperse Red 15

- Solvent Violet 13

- Acid Violet 43 - Disperse Violet 1

- Disperse Violet 4

- Disperse Blue 1

- Disperse Violet 8

- Disperse Blue 3 - Disperse Red 11

- Acid Blue 62

- Disperse Blue 7

- Basic Blue 22

- Disperse Violet 15 - Basic Blue 99 and also the following compounds:

- l-N-methylmorpholiniumpropylamino-4-hydroxy- anthraquinone

- l-Aminopropylamino-4-methylaminoanthraquinone - 1-Aminopropylaminoanthraquinone

- 5-β-hydroxyethyl-l , 4-diaminoanthraquinone

- 2-Aminoethylaminoanthraquinone

- 1,4-Bis(β, γ-dihydroxypropylamino) anthraquinone .

Among the azine chromophores A and/or A' , those listed in the Colour Index International are suitable, and for example the radicals derived from the following dyes :

- Basic Blue 17 - Basic Red 2.

Among the triarylmethane chromophores A and/or A' that can be used according to the invention, mention may be made, in addition to those listed in the Colour Index, of the radicals derived from the following dyes:

- Basic Green 1

- Acid Blue 9

- Basic Violet 3

- Basic Violet 14 - Basic Blue 7

- Acid Violet 49

- Basic Blue 26

- Acid Blue 7.

Among the indoamine chromophores A and/or A' that can be used according to the invention, mention may be made of the radicals derived from the following dyes:

- 2-β-hydroxyethylamino-5- [bis (β-4' -hydroxyethyl) - amino] anilino-1, 4-benzoquinone - 2-β-hydroxyethylamino-5- (2' -methoxy-4' -amino) anilino- 1, 4-benzoquinone

- 3-N-(2'-Chloro-4' -hydroxy) phenylacetylamino-6- methoxy-1, 4-benzoquinoneimine

- 3-N-(3'-Chloro-4' -methylamino) phenylureido-6-methyl- 1, 4-benzoquinoneimine

- 3- [ 4 ' -N- (Ethylcarbamylmethyl) amino] phenylureido-6- methyl-1, 4-benzoquinoneimine .

Mention may also be made of the chromophores described in documents US 5 888 252, EP 1133975, WO 03/029359, EP 860636, WO 95/01772, WO 95/15144 and EP 714954. Mention may also be made of those listed in the encyclopaedia "The chemistry of synthetic dye" by K. VENKATARAMAN, 1952, Academic press vol. 1 to 7, in the encyclopaedia "Kirk Othmer" "Chemical technology", chapter "dyes and Dye intermediate", 1993, Wiley and sons, and in various chapters of the encyclopaedia "ULLMANN' s ENCYCLOPEDIA of Industrial chemistry" 7th edition, Wiley and sons.

Preferably the chromophores A and/or A' are chosen from those derived from dyes of azo, anthraquinone and hydrazone type.

Preferably, the fluorescent chromophores A and/or A' are chosen from those derived from dyes of coumarin, (poly) methine (in particular cyanin and styryl/ hemicyanin) and naphthalimide type.

According to one variant, A and/or A' of the formulae (I) contain at least one cationic radical borne by or included in at least one of the chromophores .

Preferably, the cationic radical is a quaternary ammonium.

These cationic radicals are, for example, an alkylammonium, acridinium, benzimidazolium, benzobistriazolium, benzopyrazolium, benzopyridazinium, benzoquinolium, benzothiazolium, benzotriazolium, benzoxazolium, bipyridinium, bistetrazolium, dihydrothiazolium, imidazopyridinium, imidazolium, indolium, isoquinolium, naphthoimidazolium, naphthooxazolium, naphthopyrazolium, oxadiazolium, oxazolium, oxazolopyridinium, oxonium, phenazinium, phenooxazolium, pyrazinium, pyrazolium, pyrazoyltriazolium, pyridinium, pyridinoimidazolium, pyrrolium, pyrylium, quinolium, tetrazolium, thiadiazolium, thiazolium, thiazolopyridinium, thiazoylimidazolium, thiopyrylium, triazolium or xanthylium radical.

Examples of cationic chromophores that are of use in the present invention have been mentioned above. Other examples are given in patent applications WO 95/01772, WO 95/15144, EP 714954, EP 318294 and WO 03/029359.

According to one particular embodiment, the radicals A, A' in the formulae (I) or (II) comprise at least one cationic azo chromophore described, for example, in EP 850636, FR 2788433, EP 920856, WO 9948465, FR 2757385, EP 850637, EP 918053, WO 9744004, FR 2570946, FR 2285851, DE 2538363, FR 2189006, FR 1560664, FR 1540423, FR 1567219, FR 1516943, FR 1221122, DE 4220388, DE 4137005, WO 0166646, US 5708151, WO 9501772, WO 515144, GB 1195386, US 3524842, US 5879413, EP 1062940, EP 1133976, GB 738585, DE 2527638, FR 2275462, GB 1974- 27645, Acta Histochem. (1978) , 61(1) , 48-52; Tsitologiya (1968) , 10(3) , 403-5; Zh. Obshch. Khim. (1970) , 40(1) , 195-202 ; Ann. Chim. (Rome) (1975) , 65(5-6) , 305-14; Journal of the Chinese Chemical Society (Taipei) (1998) , 45(1) , 209-211; Rev. Roum. Chim. (1988) , 33(4) , 377-83; Text. Res. J. (1984) , 54(2) , 105-7; Chim. Ind. (Milan) (1974) , 56(9) , 600-3; Khim. Tekhnol. (1979) , 22(5) , 548-53; Ger. Monatsh. Chem. (1975) , 106(3) , 643-8; MRL Bull. Res. Dev. (1992) , 6(2) , 21-7; Lihua Jianyan, Huaxue Fence (1993) , 29(4) , 233-4; Dyes Pigm. (1992) , 19(1) , 69-79; Dyes Pigm. (1989) , 11(3) , 163-72. By way of example of dyes comprising a disulphide function or functions, mention may be made of the following dyes:

with M representing: a hydrogen atom, an alkali metal or an ammonium group or an ammonium group substituted with one or more identical or different, linear or branched, Ci-Cio alkyl radicals optionally bearing at least one hydroxyl .

These particular compounds, independently of any choice of free or salified form, and also the method for preparing them, are known in the art.

By way of particular examples, mention may also be made of the following compounds, which are novel and the preparation of which is described in the present invention

M having the same meaning as previously.

According to another variant of the invention, the direct dye comprising a disulphide function is a cationic dye comprising at least one quaternary ammonium radical and such that, in formula (I) with p and p' equal to 1; A and/or A' , which may be identical or different, more preferably identical, represent W-N=N-Ar- or Ar-N=N-W-, with W representing a condensed or noncondensed heteroaryl, comprising a quaternary ammonium, optionally substituted preferably with one or more alkyl groups; Ar represents a 5- or 6-membered

(hetero)aryl radical of phenyl type or a (hetero) aromatic bicycle of naphthyl, benzopyrydyl, indolinyl or benzoindolinyl type, optionally substituted with one or more halogen atoms, preferably chlorine or fluorine; with one or more alkyl groups, preferably Ci-C₄ alkyl groups; with one or more hydroxyl groups; with one or more alkoxy groups; with one or more hydroxyalkyl groups; with one or more amino or (di) alkylamino groups, preferably with the alkyl part being Ci-C₄.

According to one variant, p=l, z=t'=O, t=l and T represents -N(R)-, preferably in the para-position on Ar relative to the azo function.

In particular in one variant, p=l, z=t'=O, t=l and T represents -N(R)-, preferably in the para-position on Ar relative to the azo function, and T' represents an -N(R)- or -N⁺(R) (R⁰)- group or an imidazolium.

According to another particular embodiment of the invention, the disulphide dye is a cationic fluorescent dye comprising at least one fluorescent chromophore and one quaternary ammonium radical as defined in formula (I) with p and p' equal to 1:

A and/or A' , which may be identical or different, more preferably identical, represent W-C (R⁰) =C (R^d) -Ar- or -W-C (R⁰) =C (R^d) -Ar, with W representing a heterocycle or a heteroaryl, comprising a quaternary ammonium; Ar represents a 5- or 6-membered (hetero)aryl radical of phenyl or pyridium type, or a (hetero) aromatic bicycle of naphthyl, benzopyridinium, indolinyl or benzo- indolinyl type, optionally substituted with one or more halogen atoms, preferably chlorine or fluorine; with one or more alkyl groups, preferably Ci-C₄ alkyl groups; with one or more hydroxyl groups; with one or more alkoxy groups; with one or more hydroxyalkyl groups; with one or more amino or (di) alkylamino groups, preferably with the alkyl part being Ci-C₄; with one or more acylamino groups; with one or more 5- or 6-membered heterocycloalkyl or heteroaryl groups, preferably chosen from pyrrolidinyl, piperazinyl, piperidinyl and imidazolinyl; R° and R^d, which may be identical or different, represent a hydrogen atom or a Ci-C₄ alkyl group.

According to another variant, the disulphide dye is a cationic fluorescent dye comprising at least one quaternary ammonium radical and such that, in formula (I) with p and p' equal to 1, A and/or A' represent a naphthalimidyl radical of formula:

with representing the bond with the group X or X', C_sat or C'_sat in which R^e, R^f, R^g and R^h, which may be identical or different, represent a hydrogen atom or an optionally substituted C₁-C₆ alkyl group.

According to one embodiment of the invention, p=l, z=t'=0, t=l and T represents -N(R)-, preferably in the para-position on Ar relative to the olefin function -C(R^c)=C(R^d) -.

In particular in one variant, p=l, z=t'=0, t=l and T represents -N(R)-, preferably in the para-position on Ar relative to the olefin function -C (R⁰) =C (R^d) -, and T' represents an -N (R) - or -N_τ+ (R) (R ) - group or an imidazolium.

Preferably, W is an imidazolium, pyridinium, benzimidazolium, pyrazolium, benzothiazolium or quinolinium, optionally substituted with one or more Ci-C₄ alkyl radicals which may be identical or different.

By way of example of dyes of the invention, mention may be made of the disulphide dyes chosen from formulae (III) to (XVI) below:

in which formulae (III) to (XVI) :

• G and G' , which may be identical or different, represent an -NR_cR_d group, an -NR'_cR'_d group or a C₁-C₆ alkoxy group which is optionally substituted, preferably unsubstituted; preferably, G and G' represent an -NR_cR_d group and an -NR'_cR'_d group, respectively;

• R¹, R², R³ and R⁴, which may be identical or different, represent a hydrogen atom or an alkyl Ci-C₆ alkyl group;

• R_a and R' _a, which may be identical or different, represent an aryl (C₁-C₄) alkyl group or a Ci-C₆ alkyl group optionally substituted with a hydroxyl group or an amino, Ci-C₄ alkylamino or Ci-C₄ dialkylamino group, it being possible for said alkyl radicals to form, with the nitrogen atom which bears them, a heterocyle comprising from 5 to 7 ring members, optionally comprising another heteroatom identical to or different from nitrogen; preferably, R_a and R' _a represent a C1-C3 alkyl group optionally substituted with a hydroxyl group, or a benzyl group;

• R_b and R'_b, which may be identical or different, represent a hydrogen atom, or an aryl (C₁-C₄) alkyl group or a Ci-C₆ alkyl group which is optionally substituted; preferably, R_b and R'_b represent a hydrogen atom or a C₁-C₃ alkyl or benzyl group;

• R₀, R' _c, R_d and R'_d, which may be identical or different, represent a hydrogen atom, an aryl (C₁-C₄) alkyl group, a Ci-C₆ alkoxy group or a Ci-C₆ alkyl group which is optionally substituted; R₀, R' _c, R_d and R'_d preferably represent a hydrogen atom, a hydroxyl group, a C1-C3 alkoxy group, an amino group, a C1-C3 (di) alkylamino group, or a C₁-C₃ alkyl group which is optionally substituted with i) a hydroxyl group, ii) an amino group, iii) a C1-C3 (di) alkylamino group, or iv) a quaternary ammonium group (R") (R'") (R"")N -; or else two adjacent radicals R_c and R_d, R' ₀ and R'_d/ borne by the same nitrogen atom, together form a heterocyclic or heteroaryl group; preferably, the heterocycle or the heteroaryl is monocyclic and comprises between 5 and 7 ring members; more preferably, the groups are chosen from imidazolyl and pyrrolidinyl;

• R_e and R'_e, which may be identical or different, represent a linear or branched, optionally unsaturated, divalent, C₁-C₆ alkylenyl hydrocarbon- based chain;

• Rf and R' _f , which may be identical or different, represent a quaternary ammonium group

(R") (R'") (R"")N⁺- where R", R'" and R"", which may be identical or different, represent a hydrogen atom or a Ci-C₄ alkyl group, or else

(R") (R'") (R"")N⁺- represents an optionally substituted cationic heteroaryl group, preferably an imidazolinium group optionally substituted with a C1-C3 alkyl group;

• R_g, R'_g, R"_g, R'"g, R_h, R'h, R"h and R"'_h, which may be identical or different, represent a hydrogen atom, a halogen atom, an amino, Ci-C₄ alkylamino, Ci-C₄ dialkylamino, cyano, carboxyl, hydroxyl or trifluoromethyl group, an acylamino, Ci-C₄ alkoxy, (poly) hydroxy (C2-C4) alkoxy, alkylcarbonyloxy, alkoxycarbonyl or alkylcarbonylamino radical, an acylamino, carbamoyl or alkylsulphonylamino radical, an aminosulphonyl radical, or a C1-C16 alkyl radical optionally substituted with a group chosen from C1-C12 alkoxy, hydroxyl, cyano, carboxyl, amino, Ci-C₄ alkylamino and Ci-C₄ dialkylamino, or else the two alkyl radicals borne by the nitrogen atom of the amino group form a heterocycle comprising from 5 to 7 ring members and optionally comprising another heteroatom identical to or different from that of the nitrogen atom; preferably, R_g, R'_g, R"_g, R'"_g, Rh, R'h, R"h and R'"h represent a hydrogen atom, a halogen atom or a C1-C3 alkyl group;

• or else two groups R_g and R'_g; R"_g and R'''_g; R_h, and R'h/ R"h and R'"h, borne by two adjacent carbon atoms, together form a benzo or indeno ring or a fused heterocycloalkyl or fused heteroaryl group; the benzo, indeno, heterocycloalkyl or heteroaryl ring being optionally substituted with a halogen atom, an amino, Ci-C₄ alkylamino, Ci-C₄ dialkyl- amino, nitro, cyano, carboxyl, hydroxyl or trifluoromethyl group, an acylamino, Ci-C₄ alkoxy, (poly) hydroxy (C₂-C₄) alkoxy, alkylcarbonyloxy, alkoxycarbonyl or alkylcarbonylamino radical, an acylamino, carbamoyl or alkylsulphonylamino radical, an aminosulphonyl radical, or a Ci-Ci₆ alkyl radical optionally substituted with: a group chosen from Ci-Ci₂ alkoxy, hydroxyl, cyano, carboxyl, amino, Ci-C₄ alkylamino and Ci-C₄ dialkylamino, or else the two alkyl radicals borne by the nitrogen atom of the amino group form a heterocycle comprising from 5 to 7 ring members and optionally comprising another heteroatom identical to or different from that of the nitrogen atom; preferably, R_g and R'_g; R"_g and R'"_g together form a benzo group;

• or else, when G represents -NR_cR_d and G' represents -NR'_cR'_d, two groups R_c and R'_g; R' _c and R"_g; R_d and R_g; R' _d and R'"_g together form a saturated heteroaryl or heterocycle optionally substituted with one or more Ci-C₆ alkyl groups, preferably a heterocycle containing one or two heteroatoms chosen from nitrogen and oxygen and comprising between 5 and 7 ring members; more preferably, the heterocycle is chosen from morpholinyl, piperazinyl, piperidinyl and pyrrolidinyl groups;

• R₁, R'_x, R"χ and R"'_ir which may be identical or different, represent a hydrogen atom or a Ci-C₄ alkyl group; • Ri, R₂, R₃, R₄, R'i, R'₂, R' ₃ and R'₄, which may be identical or different, represent a hydrogen atom or a Ci-C₄ alkyl, Ci-Ci₂ alkoxy, hydroxyl, cyano, carboxyl, amino, Ci-C₄ alkylamino or Ci-C₄ dialkylamino group, it being possible for said alkyl radicals to form, with the nitrogen atom which bears them, a heterocycle comprising from 5 to 7 ring members, optionally comprising another heteroatom identical to or different from nitrogen; preferably, Ri, R₂, R₃, R₄, R'i, R'₂, R' ₃ and R' ₄ are hydrogen atoms or an amino group; more preferably, R₁, R₂, R₃, R₄, R'i, R' ₂, R' 3 and R' ₄ represent a hydrogen atom;

• T_a and T_b, which may be identical or different, represent i) either a covalent σ bond, ii) or one or more radicals or combinations thereof chosen from -SO₂-, -0-, -S-, -N(R)-, -N⁺(R) (R⁰)- and -CO-, with R and R°, which may be identical or different, representing a hydrogen atom, a Ci-C₄ alkyl or Ci-C₄ hydroxyalkyl radical, or an aryl- (C₁-C₄) alkyl; preferably, T_a is identical to T₁₃ and they represent a covalent σ bond or a group chosen from -N(R)-, -C(O)-N(R)-, -N(R)-C(O)-, -O-C(O)-, -C(O)-O- and -N⁺(R) (R⁰)-, with R and R°, which may be identical or different, representing a hydrogen atom or a Ci-C₄ alkyl group; more preferably, T_a and T_b represent a σ bond; iii) or a cationic or noncationic, preferably monocyclic, preferably identical heterocycloalkyl or heteroaryl radical, preferably containing two heteroatoms (more preferably two nitrogen atoms) and preferably comprising from 5 to 7 ring members, such as imidazolium;

• , which may be identical or different, represent an optionally substituted heterocyclic group; preferably, the heterocycles are identical, monocyclic and saturated, and comprise in total two nitrogen atoms and from 5 to 8 ring members;

• represent an aryl or heteroaryl group fused to the imidazolium or phenyl ring; or else is absent from the imidazolium or phenyl ring; preferably, when the ring is present, the ring is a benzo; • m, m' , n and n' , which may be identical or different, represent an integer between 0 and 6, limits included, with m+n, m'+n' , which may be identical or different, representing an integer between 1 and 10, limits included; preferably, m+n=m'+n' = an integer between 2 and 4, limits included; more preferably, m+n=m'+n' = an integer equal to 2;

M' representing an anionic counterion derived from a salt of an organic or inorganic acid, or of an organic or inorganic base, providing the electroneutrality of the molecule.

By way of example of the disulphide direct dyes of the invention, mention is made of those having the following chemical structures:

2M¹

10

2M' with M' and An representing an anionic counterion.

Among the protected-thiol dyes of formula (I) with U representing Y, where Y is a protective group, the compounds having the following formulae may in particular be selected:

with An^" and M' , which may be identical or different, preferably identical, representing anionic counterions. More particularly, the anionic counterion is chosen from halides such as chloride or bromide, and mesylate.

The dye composition that is of use in the invention contains, in a suitable cosmetic medium, an amount of dye(s) comprising a thiol, disulphide or protected-thiol function or functions as defined above of generally between 0.001% and 30% relative to the total weight of the composition. Preferably, this amount is between 0.01% and 5% by weight relative to the total weight of the composition. By way of example, the dye(s) is (are) present in an amount of between 0.01% and 2%.

It being understood that, in the medium, the interaction between siliceous compound (s) comprising a thiol function or functions according to the invention and the disulphide or protected-thiol dye(s) can generate the dye(s) by reductive cleavage of the disulphide function (s) -S-S- to -SH.

Preferably, the direct dye according to the invention is a dye comprising a disulphide function or functions .

1.5 The cosmetically acceptable salt of an organic or inorganic acid and counterion of the dyes of the invention :

- a "salt of an organic or inorganic acid" is more particularly chosen from a salt derived i) from hydrochloric acid HCl, ii) from hydrobromic acid HBr, iϋ) from sulphuric acid H₂SO₄, iv) from alkyl- sulphonic acids: AIk-S(O)₂OH, such as methylsulphonic acid and ethylsulphonic acid; v) from arylsulphonic acids: Ar-S(O)₂OH, such as benzenesulphonic acid and toluenesulphonic acid; vi) from citric acid; vii) from succinic acid; viii) from tartaric acid; ix) from lactic acid; x) from alkoxysulphinic acids: AIk-O-S(O)OH, such as methoxysulphinic acid and ethoxysulphinic acid; xi) from aryloxysulphinic acids, such as tolueneoxysulphinic acid and phenoxysulphinic acid; xii) from phosphoric acid H₃PO₄; xiii) from acetic acid CHsC(O)OH; xiv) from triflic acid CF3SO3H, and xv) from tetrafluoroboric acid HBF₄;

- an "anionic counterion" is an anion or an anionic group associated with the cationic charge of the dye; more particularly, the anionic counterion is chosen from i) halides such as chloride or bromide; ii) nitrates; iii) sulphonates, among which are C₁-C₆ alkyl sulphonates: AIk-S (O) 2θ^~, such as methyl sulphonate or mesylate and ethyl sulphonate; iv) arylsulphonates : Ar-S(O)2θ^~, such as benzene- sulphonate and toluenesulphonate or tosylate; v) citrate; vi) succinate; vii) tartrate; viii) lactate; ix) alkyl sulphates: AIk-O-S(O)O^", such as methyl sulphate and ethyl sulphate; x) aryl sulphates: Ar-O-S(O)O^'' such as benzene sulphate and toluene sulphate; xi) alkoxy sulphates: AIk-O-S (0) 2θ^~, such as methoxy sulphate and ethoxy sulphate; xii) aryloxysulphates : Ar-O-S (0) 2θ^~, xiii) phosphate; xiv) acetate; xv) triflate; and xvi) borates such as tetrafluoroborate .

Moreover, the addition salts that can be used in the context of the invention are in particular chosen from addition salts with a cosmetically acceptable base, such as alkali metal hydroxides, for instance sodium hydroxide or potassium hydroxide, aqueous ammonia, amines or alkanolamines .

2. Siliceous compound comprising a thiol function :

The siliceous compound comprising a thiol function is an organic compound comprising one or more silicon atoms and one or more "free" thiol functions SH.

The siliceous compound according to the invention may be nonpolymeric siliceous compounds comprising a thiol function or functions or siliceous oligomers comprising a thiol function or functions, linear siliceous polymers comprising a thiol function or functions such as α, ω-SH, nonlinear siliceous polymers comprising a thiol function or functions, including branched polymers comprising a thiol function or functions, hyperbranched polymers comprising a thiol function or functions, siliceous dendrimers comprising a thiol function or functions and crosslinked siliceous polymers comprising a thiol function or functions.

Furthermore, these compounds have in particular a molecular molar mass (MM) of greater than or equal to 200, and preferably ranging from 200 to 1000.

One particular embodiment of the invention concerns nonpolymeric siliceous compounds comprising a thiol function or functions.

More particularly, the siliceous compounds comprising a thiol function or functions according to the invention contain from 1 to 15 silicon atom(s) per molecule, and preferably 1 silicon atom per molecule.

The siliceous compounds comprising a thiol function or functions according to the invention contain in particular 1 to 12 -SH thiol group (s) per molecule, and preferably 1 to 2 -SH groups per molecule .

By way of example of siliceous compounds comprising a thiol function or functions according to the invention, mention may be made of the siliceous compounds belonging to formulae (A) , (B) , (C) and (D) below:

in which formula (A) :

> Ri, R2 and R3, which may be identical or different, represent: i) a hydrogen atom, or a group chosen from ϋ ) hydroxyl, (C1-C20) alkyl, iv ) (C1-C20) alkenylene, v ) (C1-C20) alkoxy, vi ) (C3-C9) cycloalkyloxy, vi i ) optionally substituted aryl such as phenyl or naphthyl, vi i i ] aryloxy such as phenoxy, ix ) cycloalkyl such as cyclopentyl or cyclohexyl, cycloalkyloxy such as cyclopentyloxy or cyclohexyloxy,

Xi. (C₁-C₆) alkylcarbonyloxy or (Ci-C₆) alkyl- C(O)-O-,

XlIj G- (C1-C20) alkyl, or xiii] G- (C1-C20) alkoxy with G representing a hydroxyl, (Ci-C₆) alkoxy, or thiol SH group; or else

> two substituents Ri and R2, Ri and R3, R2 and R3 form, together with the silicon atom which bears them, an optionally substituted, monocyclic heterocycle comprising from 4 to 8 ring members, and bearing, in particular in the α-position with respect to the silicon, 1 or 2 heteroatoms, preferably oxygen, said heterocycle being more particularly optionally substituted with a

(C1-C4) alkyl group;

> or three substituents Ri, R2 and R3 form, together with the silicon atom which bears them, a fused bicyclic, optionally substituted, heterocycle comprising from 4 to 8 ring members, and bearing, particularly in the α-position with respect to the silicon, 1, 2 or 3 heteroatoms, preferably oxygen, said heterocycle being more particularly optionally substituted with a (C₁-C₄) alkyl group;

> X represents: i) a σ bond, 11. a heteroatom such as oxygen or an NR group with R representing a hydrogen atom or a (C₁-C₄) alkyl group, or else

X forms, with one of the substituents Ri, R2 or R₃ and the silicon atom which bears it, a heterocycle, particularly comprising 4-7 ring members, more particularly saturated and comprising 5 ring members, optionally substituted in particular with a carboxyl group;

> ALK represents a C1-C20 alkylene chain,

- which is optionally interrupted and/or terminated, in the α-position with respect to X, when X is other than a bond or a heteroatom, with: i) a heteroatom such as oxygen or sulphur; ii) a group chosen from -C(O)-, -N(R)-,

-N(R)-C(O)-, -C(O)-N(R)-, -N(R)-C(O)-N(R')",

-0-C(O)- and -C(O)-O- with R and R', which may be identical or different, representing a hydrogen atom or a (C₁-C₄) alkyl group; or iii) a monocyclic heterocycle comprising from 1 to

3 heteroatoms chosen from oxygen, sulphur or nitrogen, optionally substituted and comprising from 5 to 7 ring members, such as piperazine or piperidine; and

- which is optionally substituted, in particular with one or more -SH or aryl groups, such as phenyl, or with an amino acid such as phenylalanine;

which formula (B) :

> p, q, r, s, t and u are 0 or 1 ;

> x is an integer between 1 and 20, limits included, in particular between 1 and 10;

> m is an integer between 1 and 4, limits included, and n is an integer between 1 and 3;

> R'i, R' 2, R' 3, R' 4 and R'₅, which may be identical or different, represent: i) the same groups as Ri, R2 and R3 as defined above, ii) or a trisubstituted siloxane group R_aR_bR_cSi-O- with R_a, R_b and R_c, which may be identical or different, representing the same groups as Ri, R2 and R3 as defined above, iii) or a group R' _aR' _bR' _cSi-O-Si (R' _d) (R' _e) -ALK"-, with ALK" being as defined for ALK above, and R'_a, R'_b, R'_c, R'_d and R'_e, which may be identical or different, representing:

- a hydrogen atom,

- a hydroxyl group, - a (C₁-C₄) alkoxy group,

- a (C₁-C₄)alkyl group, or

- a group R"_aR"_bR"_cSi-O-, with R"_a, R"_b and R"_c, which may be identical or different, representing a hydrogen atom or a (C₁-C₄)alkyl group;

> ALK and ALK' , which may be identical or different, represent a group as defined for ALK above;

> X and X' , which may be identical or different, represent : i ) a σ bond, ii ) a heteroatom such as oxygen, or an NR group with R representing a hydrogen atom or a (C₁-C₄) alkyl group;

in particular, in formula (B) :

- X does not represent a bond when s is zero,

- when m is 1, then p, q and r are 1, - when m is 2, then p is 0, and q and r are 1,

- when m is 3, then p and q are 0 and r is 1,

- when m is 4, then p, q and r are 0,

- when n is 1, then t and u are 1,

- when n is 2, then t is 1 and u is 0, and - when n is 3, then t and q are 0,

in which formulae (C) and (D) :

^ X, X' and X", which may be identical or different, preferably identical, represent the same atoms or groups as X or X' defined above; in particular, X, X' and X" are identical, and more particularly X, X' and X" represent an oxygen atom;

> R'i to R' ₄, and R"i to R"₄, which may be identical or different, are as R' i to R' ₄ defined above, more particularly, R' to R' and R' to R"₄, represent a (C₁-C₄) alkyl, (C₁-C₄) alkoxy, (C₅-C₇)- cycloalkyl, (C₅-C₇) cycloalkyloxy, HS- (C1-C20) alkyl or HS- (C1-C20) alkoxy group, an aryl group such as phenyl, an aryloxy group such as phenoxy, or a group R_aR_bR_cSi-O- with R_a, R_b and R₀, which may be identical or different, representing a hydrogen atom or a (C₁-C₄) alkyl group;

it being understood that, in formulae (C) and (D) , at least one SH function is on one of the groups R' 1 to R'₄, and R"i to R"₄.

Preferably, the siliceous compounds comprising a thiol function or functions according to the invention are those of formula (A) .

By way of siliceous compounds comprising a thiol function or functions that can be used according to the invention, mention may be made of the following compounds :

Preferably, the siliceous compounds comprising a thiol function or functions according to the invention is 1-propanethiol, 3- (triethoxysilyl) - .

The concentration of siliceous compounds comprising a thiol function or functions is between 0.001% and 40% of the composition, preferably between 0.1% and 15%, preferably between 0.4% and 10%, this percentage being expressed as weight per weight. 3 . The medi um :

The medium suitable for dyeing, also called dyeing support, is a cosmetic medium generally constituted of water or of a mixture of water and one or more organic solvent (s) or of a mixture of organic solvents.

The term "organic solvent" is intended to mean an organic substance capable of dissolving another substance without chemically modifying it.

3.1 The organic solvents :

By way of organic solvent, mention may, for example, be made of Ci-C₄ lower alkanols, such as ethanol and isopropanol; polyols and polyol ethers, such as 2-butoxyethanol, propylene glycol, propylene glycol monomethyl ether, diethylene glycol monoethyl ether and diethylene glycol monomethyl ether, and also aromatic alcohols such as benzyl alcohol or phenoxy- ethanol, and mixtures thereof.

The solvents are preferably present in proportions of preferably between 1% and 40% by weight approximately, relative to the total weight of the dye composition, and even more preferably between 5% and

30% by weight approximately.

3.2 The adjuvants:

The dye composition in accordance with the invention may also contain various adjuvants conventionally used in compositions for dyeing the hair, such as anionic, cationic, nonionic, amphoteric or zwitterionic surfactants, or mixtures thereof, anionic, cationic, nonionic, amphoteric or zwitterionic non-thiolated and siliceous polymers or blends thereof, inorganic or organic thickeners, and in particular anionic, cationic, nonionic and amphoteric polymeric associative thickeners, antioxidants, penetrating agents, sequestering agents, fragrances, buffers, dispersing agents, conditioning agents such as, for example, volatile or non-volatile and modified or non- modified silicones, film-forming agents, ceramides, preservatives or opacifiers.

The above adjuvants are in general present in an amount of between, for each of them, 0.01% and 20% by weight relative to the weight of the composition.

Of course, those skilled in the art will take care to select this or these possible additional compound (s) in such a way that the advantageous properties intrinsically associated with the dye composition in accordance with the invention are not, or are not substantially, impaired by the addition (s) envisaged.

3.3 The additional dyes:

The dye composition may, in addition, contain one or more additional direct dyes other than the disulphide or protected-thiol direct dyes. These direct dyes are, for example, chosen from those conventionally used in direct dyeing, and among which mention may be made of all aromatic and/or nonaromatic dyes commonly used, such as neutral, acidic or cationic nitrobenzene direct dyes, neutral, acidic or cationic azo direct dyes, natural direct dyes, neutral, acidic or cationic quinone, and in particular anthraquinone, direct dyes, azine, triarylmethane and indoamine direct dyes, methines, styryls, porphyrins, metalloporphyrins, phthalocyanins, methine cyanins, and fluorescent dyes.

Among the natural direct dyes, mention may be made of lawsone, juglone, alizarine, purpurin, carminic acid, kermesic acid, purpurogallin, proto- catechaldehyde, indigo, isatin, curcumin, spinulosine, apigenidin and orceins. Use may also be made of extracts or decoctions containing these natural dyes, and in particular henna-based poultices or extracts.

According to the invention, the additional direct dye(s) used according to the invention preferably represent (s) from 0.001% to 10% by weight, approximately, of the total weight of the dye composition, and even more preferably from 0.05% to 5% by weight approximately.

The dye composition may also contain one or more oxidation bases and/or one or more couplers conventionally used for dyeing keratin fibres.

Among the oxidation bases, mention may be made of para-phenylenediamines, bisphenylalkylenediamines, para-aminophenols, bis-para-aminophenols, ortho-amino- phenols and heterocyclic bases, and addition salts thereof.

Among these couplers, mention may in particular be made of meta-phenylenediamines, meta-aminophenols, meta-diphenols, naphthalene couplers and heterocyclic couplers, and addition salts thereof.

The coupler (s) is (are) each generally present in an amount of between 0.001% and 10% by weight of the total weight of the dye composition, preferably between 0.005% and 6%.

The oxidation base(s) present in the dye composition is (are) in general (each) present in an amount of between 0.001% and 10% by weight of the total weight of the dye composition, preferably between

0.005% and 6% by weight.

In general, the addition salts of the oxidation bases and of the couplers that can be used in the context of the invention are in particular chosen from the addition salts with an acid, such as hydrochlorides, hydrobromides, sulphates, citrates, succinates, tartrates, lactates, tosylates, benzene- sulphonates, phosphates and acetates, and the addition salts with a base, such as alkali metal hydroxides, for instance sodium hydroxide or potassium hydroxide, aqueous ammonia, amines or alkanolamines .

According to one particular embodiment, the composition of the present invention contains at least one oxidation base and, optionally, at least one coupler, as defined above.

The compositions may also comprise one or more oxidant (s) .

The oxidant may be chosen, for example, from hydrogen peroxide, urea peroxide, alkali metal bromates such as sodium bromate, persalts such as perborates and persulphates, and enzymes such as peroxidises and two- electron or four-electron oxidoreductases such as uricases, and 4-electron oxidases such as laccases. The use of hydrogen peroxide is particularly preferred.

The content of oxidant is in general between 1% and 40% by weight, relative to the weight of the composition, preferably between 1% and 20% by weight, relative to the weight of the composition.

3.4 The pH:

The pH of the dye composition comprising the dye(s) is generally between 2 and 12 approximately, and preferably between 3 and 11 approximately. It can be adjusted to the desired value by means of acidifying or basifying agents customarily used in the dyeing of keratin fibres, or else using conventional buffer systems . The pH of the composition according to the invention is preferably between 6 and 9.

Among the acidifying agents, mention may be made, by way of example, of inorganic or organic acids such as hydrochloric acid, orthophosphoric acid, sulphuric acid, carboxylic acids such as acetic acid, tartaric acid, citric acid or lactic acid, and sulphonic acids.

Among the basifying agents, mention may be made, by way of example, of aqueous ammonia, alkali metal carbonates, alkanolamines such as mono-, di- and triethanolamines, and also derivatives thereof, sodium hydroxide, potassium hydroxide, and the compounds of formula (α) below:

in which W_a is a propylene residue optionally substituted with a hydroxyl group or a Ci-C₄ alkyl radical; R_ai, R_a2, R_a3 and R_a4, which may be identical or different, represent a hydrogen atom, a Ci-C₄ alkyl radical or a Ci-C₄ hydroxyalkyl radical.

According to one particular embodiment of the invention, the dye composition contains alkaline agents including at least monoethanolamine .

3.5 Forms of the composition:

The dye composition may be in various galenical forms, such as in the form of a liquid, lotion, cream or gel, or in any other form suitable for dyeing keratin fibres. It may also be packaged under pressure in an aerosol bottle in the presence of a propellant and may form a foam. 4 The dyeing method

A subject of the invention is also a method of direct dyeing which comprises the application to keratin materials, in particular keratin fibres such as dark hair, of a dye composition containing one or more direct dye(s) comprising a disulphide function or functions and one or more siliceous compound (s) comprising a protected-thiol function or functions. After a leave-in time, the keratin fibres are rinsed, allowing coloured fibres to appear.

According to one particular embodiment, in the method of the invention, the leave-in time after application of the composition containing one or more direct dye(s) comprising a disulphide function or functions and one or more siliceous compound (s) comprising a thiol function or functions is fixed for between 5 minutes and 1 hour, preferably between 15 minutes and 1 hour.

This composition may be obtained by extemporaneously mixing at least two compositions, one of which comprises one or more disulphide or thiol dye(s) comprising a protected-thiol function or functions, and the other of which comprises one or more siliceous compound (s) comprising a protected-thiol function or functions.

According to one variant, the dyeing method according to the invention comprises applying, with or without intermediate rinsing, to keratin materials, in particular keratin fibres such as dark hair, i) a dye composition comprising, in a cosmetic medium, one or more disulphide or protected-thiol dye(s) , in particular disulphide or protected-thiol fluorescent dye(s) , and ii) a composition comprising one or more siliceous compound (s) comprising a thiol function or functions. The application may be carried out in any order. Preferably, the composition with the siliceous thiol is applied as a post-treatment.

The duration of the post-treatment with a siliceous compound comprising a protected-thiol function or functions may be short, for example from 1 second to 30 minutes, preferably from 1 minute to 15 minutes.

When a dye comprising a protected-thiol function or functions of formula (I) comprises a group Y protecting the thiol function, the method of the invention may be preceded by a deprotection step aimed at restoring the SH function in situ.

By way of example, it is possible to deprotect the S-Y function of the dyes of the invention with protective group Y by adjusting the pH as follows:

The deprotection step may also be carried out during a step of pretreatment of the hair, for instance a reducing pretreatment of the hair. A treatment with an oxidant may optionally be combined as a post-treatment. Any type of oxidant that is conventional in the field may be used. Thus, it may be chosen from hydrogen peroxide, urea peroxide, alkali metal bromates, persalts such as perborates and persulphates, and also enzymes, among which mention may be made of peroxidases, 2-electron oxidoreductases, such as uricases, and 4-electron oxygenases such as laccases. The use of hydrogen peroxide is particularly preferred. The duration of the optional post-treatment with an oxidant is between 1 second and 40 minutes, preferably between 1 and 10 minutes.

The application of the dye composition according to the invention is generally carried out at ambient temperature. It may, however, be carried out at temperatures ranging from 20 to 80⁰C, preferably between 20 and 60⁰C.

The composition may be applied to dry hair, or the application may be preceded by wetting of the hair.

A subject of the invention is also a multicompartment dyeing device or dyeing "kit" in which a first compartment contains a dye composition comprising one or more disulphide or protected-thiol dye(s) , and a second compartment contains one or more siliceous compound (s) comprising a thiol function or functions. Said device may contain a third compartment comprising one or more oxidant (s) .

The examples which follow serve to illustrate the invention without, however, being limiting in nature.

The disulphide direct dyes that are of use in the present invention are known compounds and can be prepared according to methods known to those skilled in the art, in particular using the methods described in application EP 1 647 580. DYEING EXAMPLE

Example 1 : Synthesis of 2, 2' -{disulphanediylbis- [ethane-2, l-diylimino-4 , 1-phenylenediazene- 2, 1-diyl] }bis (1, 3-dimethyl-lH-imidazol-3- ium) dichloride [1]

Synthes i s scheme

The cystamine base (552.2 mg; 3.62 mmol) obtained from cystamine dihydrochloride by addition of sodium hydroxide and extraction with ethyl acetate, is solubilized in 2 ml of pentanol. 2- [ (4-Methoxy- phenyl) diazenyl] -1, 3-dimethyl-lH-imidazol-3-ium chloride (2.42 mg; 9.1 mmol) , in suspension in 80 ml of dichloromethane, is added. The mixture is brought to 50⁰C and stirred for 1 hour. It is concentrated under vacuum (elimination of dichloromethane) , 20 ml of water are added, and the reaction mixture is kept at 50⁰C for a further hour. It is then cooled and poured into 50 ml of pentanol; a red precipitate appears, which is filtered off and washed with acetone and then dried under vacuum. 1.1 g of dark red powder in accordance with the above structure are thus obtained. The dye compositions were prepared with the ingredient contents given in the table below:

Procedure

Application to locks of hair comprising 90% natural white (NW) or permanent-waved white (PW) hairs.

Compositions 1 and 2 are applied to the NW or PW hair, followed by a leave-in time of 25 minutes at ambient temperature (22.6°C) . The locks are then rinsed and then dried.

Colorimetric results

The colour of the locks after dyeing was evaluated in the L*a*b* system by means of a MINOLTA® CM2600D spectrophotometer .

In the L*a*b* system, the three parameters denote, respectively, the intensity (L*) , the shade (a*) and the saturation (b*) . According to this system, the higher the value of L, the lighter or more relatively unintense the colour. Conversely, the lower the value of L, the stronger or more highly intense the colour. a* and b* indicate two colour axes, indicates the green/red colour axis and b* the blue/yellow colour axis .

The variation in colour between natural and permanent- waved hair was measured by ΔE according to the above equation on the basis of the values of L_o*ao*bo* of the natural locks after treatment (dying with composition 1 or 2) and of the values of L*a*b* of the permanent- waved locks after treatment (dyeing with composition 1 or 2) .

The higher the value of ΔE, the greater the difference in colour between natural hair and permanent-waved hair, and in the present case, the poorer the homogeneity of the colour.

The results are given in the tables below:

It appears, on the basis of the dyeing results of Tables 1 and 2, that the composition according to the invention produces more intense shades, this being the case on the NW or PW locks (L* lower with the composition of the invention versus the comparative) . Furthermore, the colourings obtained using the composition and the method according to the invention are less selective versus the comparative (i.e. more homogeneous with composition 1 ΔE_composition i = 1.44 versus ΔE_composition 2 = 3.58) .

Claims

1. Dye composition comprising, in a suitable cosmetic medium, i) one or more dyes chosen from direct dyes comprising a disulphide function or functions, or comprising a protected-thiol function or functions, and ii) one or more siliceous compound (s) comprising a thiol function or functions.

2. Composition according to the preceding claim, in which the dye(s) is (are) of formula (I) :

• U represents a radical chosen from: i) -S- C',at - (X' )p_' - A'; ii) -S- Cat - (X' )_P' - D; and iϋ) -Y;

• Y represents a thiol-function-protecting group;

-N(R)-, -N⁺(R) (R)-, -O-, -S-, -CO- and -SO2- with R, which may be identical or different, chosen from a hydrogen and a Ci-C₄ alkyl, hydroxyalkyl or aminoalkyl radical;

• p and p' , which may be identical or different, are 0 or 1;

• C_sat and C _sat, which may be identical or different, represent a linear or branched, optionally substituted, optionally cyclic Ci-Cis alkylene chain; • D corresponds to a radical chosen from hydroxyl, hydroxyalkyl, alkoxy, carboxylic, carboxylate, amino, alkylamino and dialkyl- amino radicals.

3. Composition according to the preceding claim, in which Y represents a group chosen from:

^■ (C₁-C₄) alkylcarbonyl;

^■ (C₁-C₄) alkylthiocarbonyl;

^■ (C₁-C₄) alkoxycarbonyl; ■ (C₁-C₄) alkoxythiocarbonyl;

^■ (C₁-C₄) alkylthio-thiocarbonyl;

^■ (di) (C₁-C₄) (alkyl) aminocarbonyl;

^■ (di) (C₁-C₄) (alkyl) aminothiocarbonyl;

^■ arylcarbonyl; ■ aryloxycarbonyl;

^■ aryl (C₁-C₄) alkoxycarbonyl;

^■ (di) (C₁-C₄) (alkyl) aminocarbonyl;

^■ (C₁-C₄) (alkyl) arylaminocarbonyl;

^■ carboxyl; ■ SC>₃ ^~; M⁺ with M⁺ representing an alkali metal, or else a counterion of the cationic chromophore A and M⁺ are absent;

^■ aryl;

^■ optionally substituted heteroaryl; optionally substituted, optionally cationic heterocycloalkyl; or the heterocycle represents the following group:

in which R'^c, R'^d, R'^e, R'^f, R'^g and R'^h, which may be identical or different, represent a hydrogen atom or a (C₁-C₄) alkyl group, or else two groups R' ^g with R'^h, and/or R' ^e with R'^f, form an oxo or thioxo group, or else R' ^g with R'^e together form a cycloalkyl; and v represents an integer between 1 and 3, limits included; ■ -C(NR'^cR'^d)=N⁺R'^eR'^f; An'"^" with R'^c, R'^d, R' ^e and R'^f, which may be identical or different, representing a hydrogen atom or a (C₁-C₄) alkyl group; -C(NR'^cR'^d)=NR'^e; with R'^c, R'^d and R'^e being as defined above;

^■ optionally substituted (di) aryl (C₁-C₄) alkyl;

^■ optionally substituted (di) heteroaryl (C₁-C₄) - alkyl;

^■ CR¹R²R³ with R¹, R² and R³, which may be identical or different, representing a halogen atom or a group chosen from:

- (C₁-C₄) alkyl;

- (C₁-C₄) alkoxy;

- optionally substituted aryl; - optionally substituted heteroaryl;

- P (Z¹) R' ¹R' ²R'³ with R'¹ and R'², which may be identical or different, representing a hydroxyl, (C₁-C₄) alkoxy or alkyl group, R'³ representing a hydroxyl or (C₁-C₄) alkoxy group, and Z¹ representing an oxygen or sulphur atom;

^■ a sterically hindered cyclic group; and

^■ optionally substituted alkoxyalkyl.

4. Composition according to Claim 2 or 3, in which C_sat and C g_at represent a - (CH₂) _k~chain with k being an integer between 1 and 8, limits included.

5. Composition according to any one of Claims 2 to 4, in which p is equal to 1, X and X' , which may be identical or different, represent the following sequence :

-(T)t-(Z)_z-(T')f- said sequence being linked in the formulae (I) of (II) symmetrically as follows:

- C_sat (or C _Sat) - (T) _t- (Z) _z- (A or A'); in which T and T' , which may be identical or different, represent one or more radicals or combinations thereof chosen from: -O-; -S-; -N(R)-; -N⁺(R) (R⁰)-; -SO-; -SO₂-; and -CO-; with R and R°, which may be identical or different, representing a hydrogen atom, or a Ci-C₄ alkyl, Ci-C₄ hydroxyalkyl or aryl (C₁-C₄) alkyl radical; and a cationic or noncationic, preferably monocyclic, heterocycloalkyl or heteroaryl radical, preferably containing two heteroatoms; t and t' , which may be identical or different, are 0 or

1;

Z represents:

■ - (CH₂) _m- with m being an integer between 1 and 8;

■ - (CH₂CH₂O) _q- or - (OCH₂CH₂) _q- in which q is an integer between 1 and 15;

■ an aryl, alkylaryl or arylalkyl radical of which the alkyl radical is Ci-C₄ and the aryl radical is preferably Ce, being optionally substituted with at least one SO3M group with M representing a hydrogen atom, an alkali metal or an ammonium group substituted with one or more identical or different, linear or branched, Ci-Cis alkyl radicals, optionally bearing at least one hydroxyl; z is 0 or 1.

6. Composition according to any one of the preceding claims, in which the direct dye comprising a disulphide function is chosen from the dyes of formulae (III) to

which formulae (III) to (XVI) :

• R¹, R², R³ and R⁴, which may be identical or different, represent a hydrogen atom or an alkyl C₁-C₆ alkyl group; • R_a and R' _a, which may be identical or different, represent an aryl (C₁-C₄) alkyl group or a C₁-C₆ alkyl group optionally substituted with a hydroxyl group or an amino, Ci-C₄ alkylamino or Ci-C₄ dialkylamino group, it being possible for said alkyl radicals to form, with the nitrogen atom which bears them, a heterocycle comprising from 5 to 7 ring members, optionally comprising another heteroatom identical to or different from nitrogen; preferably, R_a and R' _a represent a C1-C3 alkyl group optionally substituted with a hydroxyl group, or a benzyl group;

• R_b and R'_b, which may be identical or different, represent a hydrogen atom, or an aryl (C₁-C₄) alkyl group or a C₁-C₆ alkyl group which is optionally substituted; preferably, R_b and R'_b represent a hydrogen atom or a C₁-C₃ alkyl or benzyl group;

• R₀, R' _c, R_d and R'_d/ which may be identical or different, represent a hydrogen atom, an aryl (C₁-C₄) alkyl group, a C₁-C₆ alkoxy group or a C₁-C₆ alkyl group which is optionally substituted; R₀, R' _c, R_d and R'_d preferably represent a hydrogen atom, a hydroxyl group, a C1-C3 alkoxy group, an amino group, a Ci-C₃ (di) alkylamino group, or a C₁-C₃ alkyl group which is optionally substituted with i) a hydroxyl group, ii) an amino group, iii) a C1-C3 (di) alkylamino group, or iv) a quaternary ammonium group (R") (R'") (R"")N -; or else two adjacent radicals R_c and R_d, R' ₀ and R'_d/ borne by the same nitrogen atom, together form a heterocyclic or heteroaryl group; preferably, the heterocycle or the heteroaryl is monocyclic and comprises between 5 and 7 ring members; more preferably, the groups are chosen from imidazolyl and pyrrolidinyl; • R_e and R'_e/ which may be identical or different, represent a linear or branched, optionally unsaturated, divalent, C₁-C₆ alkylenyl hydrocarbon- based chain;

• R_f and R' _f , which may be identical or different, represent a quaternary ammonium group

(R") (R'") (R"")N⁺- represents an optionally substituted cationic heteroaryl group, preferably an imidazolinium group optionally substituted with a Ci-C₃ alkyl group;

• Rg, R'g, R"_g, R'"g, R_h , R'h, R"h and R'"_h, which may be identical or different, represent a hydrogen atom, a halogen atom, an amino, C1-C4 alkylamino, C1-C4 dialkylamino, cyano, carboxyl, hydroxyl or trifluoromethyl group, an acylamino, C1-C4 alkoxy, (poly) hydroxy (C2-C4) alkoxy, alkylcarbonyloxy, alkoxycarbonyl or alkylcarbonylamino radical, an acylamino, carbamoyl or alkylsulphonylamino radical, an aminosulphonyl radical, or a C1-C16 alkyl radical optionally substituted with a group chosen from C1-C12 alkoxy, hydroxyl, cyano, carboxyl, amino, Ci-C₄ alkylamino and Ci-C₄ dialkylamino, or else the two alkyl radicals borne by the nitrogen atom of the amino group form a heterocycle comprising from 5 to 7 ring members and optionally comprising another heteroatom identical to or different from that of the nitrogen atom; preferably, R_g, R'_g, R"_g, R'"_g, Rh, R'h, R"h and R'"h represent a hydrogen atom, a halogen atom or a C1-C3 alkyl group;

• or else two groups R_g and R'_g; R"_g and R'''_g; R_h, and R'h; R"h and R'"h, borne by two adjacent carbon atoms, together form a benzo or indeno ring or a fused heterocycloalkyl or fused heteroaryl group; the benzo, indeno, heterocycloalkyl or heteroaryl ring being optionally substituted with a halogen atom, an amino, Ci-C₄ alkylamino, Ci-C₄ dialkylamino, nitro, cyano, carboxyl, hydroxyl or trifluoromethyl group, an acylamino, Ci-C₄ alkoxy, (poly) hydroxy (C2-C4) alkoxy, alkylcarbonyloxy, alkoxycarbonyl or alkylcarbonylamino radical, an acylamino, carbamoyl or alkylsulphonylamino radical, an aminosulphonyl radical, or a C1-C16 alkyl radical optionally substituted with: a group chosen from C1-C12 alkoxy, hydroxyl, cyano, carboxyl, amino, Ci-C₄ alkylamino and Ci-C₄ dialkylamino, or else the two alkyl radicals borne by the nitrogen atom of the amino group form a heterocycle comprising from 5 to 7 ring members and optionally comprising another heteroatom identical to or different from that of the nitrogen atom; preferably, R_g and R'_g; R"_g and R'"_g together form a benzo group;

• or else, when G represents -NR_cR_d and G' represents -NR'_cR'_d, two groups R₀ and R'_g; R' _c and R"_g; R_d and R_g; R' _d and R'"_g together form a saturated heteroaryl or heterocycle optionally substituted with one or more C₁-C₆ alkyl groups, preferably a heterocycle containing one or two heteroatoms chosen from nitrogen and oxygen and comprising between 5 and 7 ring members; more preferably, the heterocycle is chosen from morpholinyl, piperazinyl, piperidinyl and pyrrolidinyl groups;

• R₁, R'_x, R"i and R'"_x, which may be identical or different, represent a hydrogen atom or a Ci-C₄ alkyl group;

• R₁, R₂, R₃, R₄, R'i, R' ₂, R' 3 and R'₄, which may be identical or different, represent a hydrogen atom or a Ci-C₄ alkyl, Ci-Ci₂ alkoxy, hydroxyl, cyano, carboxyl, amino, Ci-C₄ alkylamino or Ci-C₄ dialkylamino group, it being possible for said alkyl radicals to form, with the nitrogen atom which bears them, a heterocycle comprising from 5 to 7 ring members, optionally comprising another heteroatom identical to or different from nitrogen; preferably, Ri, R₂, R₃, R₄, R'i, R'₂, R' ₃ and R' ₄ are hydrogen atoms or an amino group; more preferably, Ri, R₂, R₃, R₄, R'i, R'₂, R' ₃ and R' ₄ represent a hydrogen atom;

• T_a and T_b, which may be identical or different, represent i) either a covalent σ bond, ii) or one or more radicals or combinations thereof chosen from -SO₂-, -O-, -S-, -N(R)-, -N⁺(R) (R⁰)- and -CO-, with R and R°, which may be identical or different, representing a hydrogen atom, a Ci-C₄ alkyl or Ci-C₄ hydroxyalkyl radical, or an aryl- (C₁-C₄) alkyl; preferably, T_a is identical to T_b and they represent a covalent σ bond or a group chosen from -N(R)-, -C(O)-N(R)-, -N(R)-C(O)-, -O-C(O)-, -C(O)-O- and -N⁺(R) (R⁰)-, with R and R°, which may be identical or different, representing a hydrogen atom or a Ci-C₄ alkyl group; more preferably, T_a and T_b represent a σ bond; iii) or a cationic or noncationic, preferably monocyclic, preferably identical heterocycloalkyl or heteroaryl radical, preferably containing two heteroatoms (more preferably two nitrogen atoms) and preferably comprising from 5 to 7 ring members, such as imidazolium; )

• , which may be identical or different, represent an optionally substituted heterocyclic group; preferably, the heterocycles are identical, monocyclic and saturated, and comprise in total two nitrogen atoms and from 5 to 8 ring members; represents an aryl or heteroaryl group fused to the imidazolium or phenyl ring; or else is absent from the imidazolium or phenyl ring; • m, m' , n and n' , which may be identical or different, represent an integer between 0 and 6, limits included, with m+n, m'+n' , which may be identical or different, representing an integer between 1 and 10, limits included; preferably, m+n=m'+n' = an integer between 2 and 4, limits included; more preferably, m+n=m'+n' = an integer equal to 2; M' representing a counterion or an organic or inorganic acid salt.

7. Composition according to any one of the preceding claims, in which the direct dye comprising a disulphide function is chosen from:

with An , M' , which may be identical or different, representing anionic counterions.

8. Composition according to any one of the preceding claims, in which the direct dye comprising a protected- thiol function is chosen from:

ArV

9. Composition according to any one of the preceding claims, in which the siliceous compound comprising a thiol function has a molecular molar mass of greater than or equal to 200, and in particular between 200 and 1000.

10. Composition according to any one of the preceding claims, in which the siliceous compound comprising a thiol function or functions is chosen from those of formulae (A) , (B) , (C) and (D) below:

in which formula (A) :

> Ri, R₂ and R3, which may be identical or different, represent : i) a hydrogen atom, or a group chosen from ii) hydroxyl, iii) (C₁-C₂₀) alkyl, iv) (C1-C20) alkenylene, v) (C1-C20) alkoxy, vi) (C3-C9) cycloalkyloxy, vii) optionally substituted aryl, viii) aryloxy, ix) cycloalkyl, x) cycloalkyloxy, xi) (C₁-C₆) alkylcarbonyloxy or (C₁-C₆) alkyl-

C(O)-O-, xii) G- (Ci-C₂₀)alkyl, or xiii) G- (C1-C20) alkoxy with G representing a hydroxyl, (C₁-C₆) alkoxy, or thiol SH group; or else

> two substituents R₁ and R₂, Ri and R₃, R₂ and R₃ form, together with the silicon atom which bears them, an optionally substituted, monocyclic heterocycle comprising from 4 to 8 ring members, and bearing 1 or 2 heteroatoms;

> or three substituents Ri, R₂ and R₃ form, together with the silicon atom which bears them, a fused, bicyclic, optionally substituted heterocycle comprising from 4 to 8 ring members and bearing 1, 2 or 3 heteroatoms;

> X represents: i) a σ bond, ii) a heteroatom or an NR group with R representing a hydrogen atom or a (C₁-C₄) alkyl group, or else iϋ) X forms, with one of the substituents Ri, R₂ or R₃ and the silicon atom which bears it, a heterocycle;

> ALK represents a Ci-C₂O alkylene chain, - which is optionally interrupted and/or terminated in the α-position with respect to X, when X is different from a bond or a heteroatom, with: i) a heteroatom; ii) a group chosen from -C(O)-, -N(R)-, -N(R)-C(O)-, -C(O)-N(R)-, -N(R)-C(O)-N(R')", -0-C(O)- and -C(O)-O- with R and R', which may be identical or different, representing a hydrogen atom or a (C₁-C₄) alkyl group; or iii) a monocyclic heterocycle comprising from 1 to 3 heteroatoms chosen from oxygen, sulphur and nitrogen, optionally substituted and comprising from 5 to 7 ring members; and - which is optionally substituted;

(B)

which formula (B) :

> p, q, r, s, t and u are 0 or 1;

> x is an integer between 1 and 20, limits included; ^ m is an integer between 1 and 4, limits included, and n is an integer between 1 and 3;

> R'i, R' 2, R' 3, R' 4 and R' 5, which may be identical or different, represent: i) the same groups as Ri, R₂ and R₃ as defined above, ii) or a trisubstituted siloxane group R_aR_bR_cSi-O- with R_a, R_b and R_c, which may be identical or different, representing the same groups as Ri, R2 and R3 as defined above, iii) or a group R' _aR' _bR' _cSi-O-Si (R' _d) (R' _e) -ALK"-, with ALK" being as defined for ALK above, and R'_a, R'_b, R'_c, R'_d and R'_e, which may be identical or different, representing:

• a hydrogen atom,

• a hydroxyl group, • a (C₁-C₄) alkoxy group,

• a (C₁-C₄) alkyl group, or

• a group R"_aR"_bR"_cSi-O-, with R"_a, R"_b and R"_c, which may be identical or different, representing a hydrogen atom or a (C₁-C₄) alkyl group;

> X and X' , which may be identical or different, represent : i) a σ bond, ii) a heteroatom such as oxygen or an NR group with R representing a hydrogen atom or a (C₁-C₄) alkyl group;

in which formulae (C) and (D) :

> X, X' and X", which may be identical or different, represent the same atoms or groups as X or X' defined above;

> R' i to R' ₄, and R"i to R"₄, which may be identical or different, are as R' i to R' ₄ defined above, it being understood that, in formulae (C) and (D) , at least one SH function is on one of the groups R' i to R'₄, and R"i to R"₄.

11. Composition according to any one of Claims 1 to 10, in which the siliceous compound comprising a thiol function is chosen from the following compounds:

12. Composition according to any one of Claims 1 to 10, in which the siliceous compound comprising a thiol function is (3-mercaptopropyl) triethoxysilane .

13. Method of dyeing keratin fibres which comprises applying, to the fibres, a dye composition as defined in any one of the preceding claims.

14. Method of dyeing keratin fibres which comprises, in a first step, applying, to the fibres, a dye composition comprising one or more dye(s) comprising a disulphide function or functions or comprising a protected-thiol function or functions as defined in any one of Claims 1 to 8, and then, in a second step, applying one or more siliceous compound (s) comprising a thiol function or functions as defined in any one of Claims 1 and 9 to 12.

15. Dyeing method according to Claim 13 or 14, in which the keratin fibres are dark and have a tone height of less than 6, preferably less than or equal to 4.

16. Use of one or more direct dye(s) comprising a disulphide function or functions and of one or more siliceous compound (s) comprising a thiol function or functions, for dyeing keratin fibres.

17. Use according to the preceding claim, for lightening dark keratin fibres having a tone height of less than 6, preferably less than or equal to 4, of one or more direct dye(s) comprising a disulphide function or functions or comprising a protected-thiol function or functions and one or more siliceous compound (s) comprising a thiol function or functions.