PROCESS FOR TREATING KERATIN FIBERS USING A HALOCHROMIC TRIARYLMETHANE DIRECT DYE, AN ALKALINE REVEALER AND THEN AN ACIDIC ERASER

Abstract

The present invention relates to a process for treating keratin fibers, especially human keratin fibers such as the hair, using i) at least one triarylmethane or sulfonophthalein direct dye of formula (I) or (I) as defined below, ii) an alkaline revealer, iii) an eraser at acidic pH. A subject of the invention is also a composition comprising at least one triarylmethane direct dye of formula (I) or (I) as defined below and at least one thickener and/or at least one hydrotropic solvent, and a multi-compartment kit comprising i), ii) and iii) in three separate compartments. The present invention makes it possible in particular to obtain keratin fiber coloring with intense and persistent tints which can be modified, erased and reformed several times without any loss of color.

Claims

1.-23. (canceled)

24. A method for treating keratin fibers, wherein the method comprises: i) applying to the keratin fibers a composition (A) comprising at least one compound chosen from compounds of formula (I) or (I), mineral or organic base salts thereof, optical isomers thereof, geometrical isomers thereof, or tautomeric isomers thereof, or solvates thereof: ##STR00028## wherein in formulae (I) and (I): R is chosen from a hydrogen atom, a halogen atom, a (C.sub.1-C.sub.6)alkyl a group, or a (C.sub.1-C.sub.6)alkoxy group; R is chosen from a hydrogen atom, a (C.sub.1-C.sub.6)alkyl group, or a benzyl group; R is chosen from a hydrogen atom, a (C.sub.1-C.sub.6)alkyl group, or a (C.sub.1-C.sub.6)alkoxy group; R is chosen from a hydrogen atom, a halogen atom, or a group chosen from hydroxyl, (C.sub.1-C.sub.4)alkyl, (C.sub.1-C.sub.6)alkoxy, or carboxyl groups; X is chosen from a heteroatom; and M is chosen from a hydrogen atom, an alkali metal, an alkaline-earth metal, or an ammonium group; ii) applying to the keratin fibers a composition (B) having a basic pH to switch on a change of a color of the keratin fibers; and iii) applying to the keratin fibers a composition (C) having an acidic pH to switch off the change of the color of the keratin fibers; wherein: when the composition (A) comprises at least one compound chosen from compounds of formula (I), the applying the composition (A) is followed by ii) applying the composition (B), and the applying the composition (B) is followed by iii) applying of the composition (C); when the first composition (A) comprises at least on compound chosen from compounds of formula (I), the applying the composition (A) is followed by iii) applying the composition (C), and the applying the composition (C) is followed by ii) the applying the composition (B); and wherein steps ii) and iii) are optionally repeated several times.

25. The method of claim 24, wherein the at least one compound chosen from compound of formula (I) or (I) is a dye with a color change zone at a pH ranging from 4.5 to 8.

26. The method of claim 24, wherein the at least one compound of formula (I) or (I) is chosen from compounds of formula (Ia), (Ia), (Ib), (Ib), (Ic), (Ic), (Ie), (Ie), (If), or (If), or the alkali metal or alaline-earth metal salts thereof: ##STR00029## ##STR00030## ##STR00031## ##STR00032## ##STR00033## wherein in formula (Ia), Hal and Hal, which may be identical or different, are chosen from halogen atoms; wherein in formula (Ia): Hal and Hal, which may be identical or different, are chosen from halogen atoms; and M is chosen from a hydrogen atom, an alkali metal, an alkaline-earth metal, or an ammonium group; wherein in formula (Ib): Hal and Hal, which may be identical or different, are chosen halogen atoms; and ALK is chosen from a (C1-C6)alkyl group; wherein in formula (Ib): Hal and Hal, which may be identical or different, are chosen from halogen atoms; ALK is chosen from a (C1-C6)alkyl group; and M is chosen from a hydrogen atom, an alkali metal, an alkaline-earth metal, or an ammonium group; wherein in formula (Ic): Hal and Hal, which may be identical or different, are chosen from halogen atoms; ALK is chosen from a (C1-C6)alkyl group; and ALK is chosen from (C.sub.1-C.sub.6)alkyl group; wherein in formula (Ic): Hal and Hal, which may be identical or different, are chosen from halogen atoms; ALK is chosen from a (C1-C6)alkyl group; ALK is chosen from (C1-C6)alkyl group; and M is chosen from a hydrogen atom, an alkali metal, an alkaline-earth metal, or an ammonium group; wherein in formula (Id): Hal and Hal, which may be identical or different, are chosen from halogen atoms; and ALK is chosen from a (C.sub.1-C.sub.6)alkyl group; wherein in formula (Id): Hal and Hal, which may be identical or different, are chosen from halogen atoms; ALK is chosen from a (C1-C6)alkyl group; and M is chosen from a hydrogen atom, an alkali metal, an alkaline-earth metal, or an ammonium group; wherein in formula (Ie): M is chosen from a hydrogen atom, an alkali metal, an alkaline-earth metal, or an ammonium group; and wherein in formula (If): M is chosen from a hydrogen atom, an alkali metal, an alkaline-earth metal, or an ammonium group.

27. The method of claim 24, wherein the at least one compound of formula (I) or (I) is chosen from compounds of formula (1), (1), (2), (2), (3), (3), (4), (4), (5), (5), (6), or (6) below: ##STR00034## ##STR00035## ##STR00036## ##STR00037## wherein in formulae (1), (2), (3), (4), (5), and (6), M is chosen from a hydrogen atom, an alkali metal, an alkaline-earth metal, or an ammonium group.

28. The method of claim 24, wherein the at least one compounds of formula (I) or (I) is present in an amount ranging from 0.001% to 10% by weight, relative to the total weight of composition (A).

29. The method of claim 24, wherein the composition (A) further comprises at least one additional halochromic dye other than the at least one compound of formula (I) or (I), and the at least one additional halchromic dye is chosen from compounds of formulae (II) or (II), mineral or organic base salts thereof, optical isomers thereof, geometrical isomers thereof, tautomeric isomers thereof, or solvates thereof: ##STR00038## wherein in formulae (II) and (II): R is chosen from a hydrogen atom, a halogen atom, or a group chosen from i) (C.sub.1-C.sub.6)alkyl which is optionally substituted, with at least one halogen atom, ii) optionally substituted (C.sub.1-C.sub.6)alkoxy, iii) R.sub.aC(X), iv) R.sub.aC(X)X, v) R.sub.aXC(X), or vi) iso(thio)cyanate, with R.sub.a being chosen from a hydrogen atom, a heterocyclic group, a (C.sub.1-C.sub.4)alkyl group optionally substituted with at least one halogen atom, or at least one carboxyl groups; R is chosen from i) a hydrogen atom, ii) a halogen atom or iii) a group chosen from (C.sub.1-C.sub.6)alkyl which is optionally substituted with at least one group chosen from: a) hydroxyl, b) (di)(C.sub.1-C.sub.4)(alkyl)amino, c) (di)carboxy(C.sub.1-C.sub.4)alkylamino, or iv) (C.sub.1-C.sub.6)alkoxy; X is chosen from a heteroatom; and M is chosen from a hydrogen atom, an alkali metal or alkaline-earth metal, an ammonium group, or a (C.sub.1-C.sub.6)alkyl(thio)carbonyl group; and M is chosen from a hydrogen atom, an alkali metal, an alkaline-earth metal, or an ammonium group.

30. The method of claim 24, wherein the composition (A) further comprises at least one additional halochromic dye chosen from compounds of formula (IIa), (IIa), (IIb), (IIb), (IIc), (IIc), (IId), (IId), (IIe), (IIe), (IIf), or (IIf): ##STR00039## wherein in formula (IIa): Hal and Hal, which may be identical or different, are chosen from halogen atoms; X is chosen from a heteroatom; and M is chosen from a hydrogen atom, an alkali metal or alkaline-earth metal, an ammonium group, or a (C.sub.1-C.sub.6)alkyl(thio)carbonyl group; ##STR00040## wherein in formula (IIa): Hal and Hal, which may be identical or different, are chosen from halogen atoms; X is chosen from a heteroatom; M is chosen from a hydrogen atom, an alkali metal or alkaline-earth metal, an ammonium group, or a (C1-C6)alkyl(thio)carbonyl group; and M is chosen from a hydrogen atom, an alkali metal, an alkaline-earth metal, or an ammonium group; ##STR00041## wherein in formula (IIb): Hal, Hal, and Hal, which may be identical or different, are chosen from halogen atoms; X is a heteroatom; and M is chosen from a hydrogen atom, an alkali metal or alkaline-earth metal, an ammonium group, or a (C1-C6)alkyl(thio)carbonyl group; ##STR00042## wherein in formula (IIb): Hal, Hal, and Hal, which may be identical or different, are chosen from halogen atoms; X is a heteroatom; M is chosen from a hydrogen atom, an alkali metal or alkaline-earth metal, an ammonium group, or a (C1-C6)alkyl(thio)carbonyl group; and M is chosen from a hydrogen atom, an alkali metal, an alkaline-earth metal, or an ammonium group; ##STR00043## wherein in formula (IIc): Hal is a halogen atom; X is a heteroatom; and M is chosen from a hydrogen atom, an alkali metal or alkaline-earth metal, an ammonium group, or a (C1-C6)alkyl(thio)carbonyl group; ##STR00044## wherein in formula (IIc): Hal is a halogen atom; X is a heteroatom; M is chosen from a hydrogen atom, an alkali metal or alkaline-earth metal, an ammonium group, or a (C1-C6)alkyl(thio)carbonyl group; and M is chosen from a hydrogen atom, an alkali metal, an alkaline-earth metal, or an ammonium group; ##STR00045## wherein in formula (lid): X is a heteroatom; and M is chosen from a hydrogen atom, an alkali metal or alkaline-earth metal, an ammonium group, or a (C1-C6)alkyl(thio)carbonyl group; ##STR00046## wherein in formula (IId): X is a heteroatom; M is chosen from a hydrogen atom, an alkali metal or alkaline-earth metal, an ammonium group, or a (C1-C6)alkyl(thio)carbonyl group; and M is chosen from a hydrogen atom, an alkali metal, an alkaline-earth metal, or an ammonium group; ##STR00047## wherein in formula (IIe): R.sub.b is chosen from i) optionally substituted (C.sub.1-C.sub.4)alkyl, ii) isothiocyanate, iii) R.sub.aOC(O) or iv) R.sub.aC(O)N(R), wherein R.sub.a is chosen from a hydrogen atom, a heterocyclic group, a (C.sub.1-C.sub.4)alkyl group, or at least one carboxyl groups optionally substituted with at least one halogen atom; X is a heteroatom; p is an integer between 1 and 5; and; and M is chosen from a hydrogen atom, an alkali metal or alkaline-earth metal, an ammonium group, or a (C1-C6)alkyl(thio)carbonyl group; ##STR00048## wherein in formula (IIe): R.sub.b is chosen from i) optionally substituted (C.sub.1-C.sub.4)alkyl, ii) isothiocyanate, iii) R.sub.aOC(O), or iv) R.sub.aC(O)N(R) with R.sub.a chosen from a hydrogen atom, a heterocyclic group, a (C.sub.1-C.sub.4)alkyl group, or at least one carboxyl groups optionally substituted with at least one halogen atom; X is a heteroatom; p is an integer between 1 and 5; and; M is chosen from a hydrogen atom, an alkali metal or alkaline-earth metal, an ammonium group, or a (C1-C6)alkyl(thio)carbonyl group; and M is chosen from a hydrogen atom, an alkali metal, an alkaline-earth metal, or an ammonium group; ##STR00049## wherein in formula (IIf): ALK is an (C.sub.1-C.sub.4)alkylene group; Z is chosen from a group NR.sub.cR.sub.d, wherein Rc and Rd, which may be identical or different, are chosen from a hydrogen atom or a (C.sub.1-C.sub.4)alkyl group optionally substituted with at least one carboxyl group; X is a heteroatom; and M is chosen from a hydrogen atom, an alkali metal or alkaline-earth metal, an ammonium group, or a (C1-C6)alkyl(thio)carbonyl group; ##STR00050## wherein in formula (IIf): ALK is a (C.sub.1-C.sub.4)alkylene group; Z is chosen from a group NR.sub.cR.sub.d, wherein Rc and Rd, which may be identical or different, are chosen from a hydrogen atom or a (C.sub.1-C.sub.4)alkyl group optionally substituted with at least one carboxyl group; X is a heteroatom; M is chosen from a hydrogen atom, an alkali metal or alkaline-earth metal, an ammonium group, or a (C1-C6)alkyl(thio)carbonyl group; and M is chosen from a hydrogen atom, an alkali metal, an alkaline-earth metal, or an ammonium group.

31. The method of claim 29, wherein the at least one additional halochromic dye is chosen from compounds of formula 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, or 6: ##STR00051## ##STR00052## ##STR00053## wherein in formulae 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, and 6, M is chosen from a hydrogen atom, an alkali metal or alkaline-earth metal, an ammonium group, or a (C1-C6)alkyl(thio)carbonyl group; and M is chosen from a hydrogen atom, an alkali metal, an alkaline-earth metal, or an ammonium group.

32. The method of claim 29, wherein, the at least one halochromic dye other than the at least one compound of formula (I) or (I) is present in an amount ranging from 0.001% to 10% by weight, relative to the total weight of the composition (A).

33. The method of claim 24, wherein the composition (B) has a pH ranging from 7.5 to 12.5.

34. The method of claim 24, wherein the composition (B) comprises at least one mineral or organic alkaline agent chosen from: a) aqueous ammonia, b) alkanolamines, c) oxyethylenated and/or oxypropylenated (C.sub.1-C.sub.6)alkylenediamines, d) mineral or organic hydroxides, e) basic amino acids, f) alkali metal or alkaline-earth metal silicates or metasilicates, g) carbonates and bicarbonates, or h) compounds of formula (III) below: ##STR00054## wherein in formula (III), W is a divalent C.sub.1-C.sub.6 alkylene radical optionally substituted with a hydroxyl group or a C.sub.1-C.sub.6 alkyl radical; R.sub.x, R.sub.y, R.sub.z and R.sub.t, which may be identical or different, are chosen from a hydrogen atom, or a C.sub.1-C.sub.6 alkyl group, a C.sub.1-C.sub.6 hydroxyalkyl group, or a C.sub.1-C.sub.6 aminoalkyl group.

35. The method of claim 24, wherein the composition (C) has a pH ranging from 0.5 to 6.

36. The method of claim 24, wherein the composition (C) comprises at least one organic or mineral acid chosen from i) hydrochloric acid HCl, ii) hydrobromic acid HBr, iii) sulfuric acid H.sub.2SO.sub.4, iv) phosphoric or orthophosphoric acid H.sub.3PO.sub.4, v) (C.sub.1-C.sub.6)alkylsulfonic acids (Alk-S(O).sub.2OH); vi) arylsulfonic acids (ArS(O).sub.2OH); vii) carboxylic acids; viii) sulfonic acids; ix) (C.sub.1-C.sub.6)alkoxysulfinic acids (Alk-OS(O)OH); x) aryloxysulfinic acids; xi) triflic acid CF.sub.3SO.sub.3H; or xii) tetrafluoroboric acid HBF.sub.4.

37. The method of claim 24, wherein the composition (A) further comprises at least one hydrotropic solvent comprising at least one liquid organic compound with a Hansen solubility parameter H of greater than 0 and less than 16 MPa.sup.1/2.

38. The method of claim 24, wherein the composition (A) comprises at least one hydrotropic solvent chosen from: alcohol ethers; aliphatic esters of C.sub.1-C.sub.4 carboxylic acids and of C.sub.3-C.sub.10 monoalcohols or polyhydroxylated alcohols, interrupted with at least one non-adjacent ether function; aromatic ethers; (C.sub.6-C.sub.10)aryl(C.sub.1-C.sub.6)alkyl ethers of a C.sub.1-C.sub.6 alkyl optionally bearing a hydroxyl group; alkanols bearing an aryl substituent; lactones of formula (iii), or mixtures thereof: ##STR00055## wherein in formula (iii), R is chosen from a hydrogen, a linear or branched C.sub.1-C.sub.8 alkyl, or a linear or branched C.sub.1-C.sub.4 hydroxyalkyl; n has the value of 1, 2 or 3; or sulfones.

39. The method of claim 38, wherein the alkanols bearing an aryl substituent comprise a C.sub.6-C.sub.10 aryl part and a C.sub.1-C.sub.4 alkyl part, wherein the alkyl part is terminated or interrupted with a heteroatom or a hydroxyl group; and wherein the sulfones comprise at least one 5- to 7-membered cyclic sulfone optionally substituted with at least one (C.sub.1-C.sub.4)alkyl group, or mixtures thereof.

40. The method of claim 37, wherein the composition (A) further comprises at least one additional organic solvent other than the hydrotropic solvents, wherein the additional solvent is chosen from C.sub.1-C.sub.4 lower alkanols, polyols, or polyol ethers.

41. The method of claim 24 further comprising: after applying the composition (A) and before applying the composition (B) and/or the composition (C), drying the keratin fibers.

42. A composition (A.sub.1) comprising: at least one dyeing compound chosen from compounds of formula (I) or (I), mineral or organic base salts thereof, optical isomers thereof, geometrical isomers thereof, tautomeric isomers thereof, or solvates thereof: ##STR00056## optionally at least one additional dye other than the at least one dyeing compound of formula (I) or (I), wherein the additional dye is chosen from compounds of formula (II) or (II), mineral or organic base salts thereof, optical isomers thereof, geometrical isomers thereof, tautomeric isomers thereof, or solvates thereof: ##STR00057## at least one hydrotropic solvent comprising at least one liquid organic compound with a Hansen solubility parameter H of greater than 0 and less than 16 MPa.sup.1/2, and optionally, at least one additional solvent other than the hydrotropic solvent chosen from C.sub.1-C.sub.4 lower alkanols, polyols, or polyol ethers; and/or at least one thickener; wherein in formulae (I) and (I): R is chosen from a hydrogen atom, a halogen atom, a (C.sub.1-C.sub.6)alkyl group, or a (C.sub.1-C.sub.6)alkoxy group; R is chosen from a hydrogen atom, a (C.sub.1-C.sub.6)alkyl group, or a benzyl group; R is chosen from a hydrogen atom, a (C1-C6)alkyl group, or a (C1-C6)alkoxy group; R is chosen from a hydrogen atom, a halogen atom, or a group chosen from hydroxyl, (C1-C4)alkyl, (C1-C6)alkoxy, or carboxyl groups; X is a heteroatom; and M is chosen from a hydrogen atom, an alkali metal, an alkaline-earth metal, or an ammonium group; wherein in formulae (II) and (II): R is chosen from a hydrogen atom, a halogen atom, or a group chosen from i) (C1-C6)alkyl which is optionally substituted, with at least one halogen atom, ii) optionally substituted (C1-C6)alkoxy, iii) RaC(X), iv) RaC(X)X, v) RaXC(X), or vi) iso(thio)cyanate, wherein Ra is chosen from a hydrogen atom, a heterocyclic group, a (C1-C4)alkyl group optionally substituted with at least one halogen atom, or at least one carboxyl group; R is chosen from i) a hydrogen atom, ii) a halogen atom, or iii) a group chosen from (C1-C6)alkyl, which is optionally substituted with at least one group chosen from: a) hydroxyl, b) (di)(C1-C4)(alkyl)amino, c) (di)carboxy(C1-C4)alkylamino, or iv) (C1-C6)alkoxy; X is a heteroatom; M is chosen from a hydrogen atom, an alkali metal or alkaline-earth metal, an ammonium group, or a (C1-C6)alkyl(thio)carbonyl group; and M is chosen from a hydrogen atom, an alkali metal, an alkaline-earth metal, or an ammonium group.

43. A multi-compartment device comprising: i) a first compartment comprising a composition (A) comprising at least one dyeing compound chosen from compounds of formula (I) or (I), mineral or organic base salts thereof, optical isomers thereof, geometrical isomers thereof, or tautomeric isomers thereof, or solvates thereof: ##STR00058## ii) a second compartment comprising a composition (B) at a basic pH comprising at least one mineral or organic alkaline agent; and iii) a third compartment containing a composition (C) at an acidic pH comprising at least one organic or mineral acid; wherein in formulae (I) and (I): R is chosen from a hydrogen atom, a halogen atom, a (C.sub.1-C.sub.6)alkyl group, or a (C.sub.1-C.sub.6)alkoxy group; R is chosen from a hydrogen atom, a (C.sub.1-C.sub.6)alkyl group, or a benzyl group; R is chosen from a hydrogen atom, a (C1-C6)alkyl group, or a (C1-C6)alkoxy group; R is chosen from a hydrogen atom, a halogen atom, or a group chosen from hydroxyl, (C1-C4)alkyl, (C1-C6)alkoxy, or carboxyl groups; X is a heteroatom; and M is chosen from a hydrogen atom, an alkali metal, an alkaline-earth metal, or an ammonium group.

Description

EXAMPLES

Example 1

[0337] The following compositions were prepared; the amounts are given in g per 100 g of composition: [0338] Composition (A) comprising the compounds of formula (I) of the invention and comparative composition (A) comprising the triarylmethane dye outside the invention; the amounts are given in g per 100 g of composition

TABLE-US-00001 Composition (A) Comparative Ingredients invention composition (A) Ethanol 15 15 Hydroxyethylcellulose (HEC- 1.5 1.5 Natrosol 250 HHR) Benzyl alcohol 5 5 Phenoxyethanol 1 1 Caprylyl glycol 1 1 Sodium salt of Chlorophenol Red (1) 0.5 Disodium salt of Erioglaucine 0.5 Water qs 100 qs 100 [0339] Switch-on revealing composition (B) at basic pH

TABLE-US-00002 Ingredients Amount Monoethanolamine (MEA) 5 Water qs 100

[0340] pH of the composition 11.40.5 [0341] Switch-off erasing composition (C) at acidic pH:

TABLE-US-00003 Ingredients Amount Phosphoric acid 5 Water qs 100

[0342] pH of the composition 1.40.5

[0343] Each of the compositions (A) according to the invention and comparative compositions (A) are applied to locks according to the same protocol, namely: [0344] a lock of natural hair containing 90% white hairs (tone depth TD9) [0345] then left to stand on the lock for 30 minutes at 31 C. [0346] then rinsing with water, then drying

[0347] Once the keratin fibers have been dried, the switch treatment is applied. [0348] To obtain switching on, composition (B) is applied to each lock by spraying. [0349] To obtain switching off, composition (C) is applied to each lock by spraying.

Colorimetric Results:

[0350] The color of the locks was evaluated in the CIE L* a* b* system, using a ColorShot MultiSpectral colorimeter (illuminant D65, angle 10). In this L* a* b* system, the three parameters respectively denote the intensity of the color (L*), the green/red color axis (a*) and the blue/yellow color axis (b*). The lower the value of L*, the more intense the color.

Color Build-Up:

[0351] The colorimetric measurements were taken just after applying composition (A) or (A), and then after each of the switch treatments.

[0352] The variation in coloring between the locks of untreated hair and of treated hair is defined by (E*) according to the following equation:

E*={square root over ((L*L.sub.0*).sup.2+(a*a.sub.0*).sup.2+(b*b.sub.0*).sup.2)}

[0353] In this equation, L*, a* and b* represent the values measured on locks of hair after treatment and L.sub.0*, a.sub.0* and b.sub.0* represent the values measured on locks of hair before treatment. The higher the value of E*, the greater the color build-up.

[0354] The variation in coloring between the locks of hair treated and revealed (switched on) with composition (B) and erased (switched off) with composition (C) is defined by (E*.sub.ON-OFF) according to the following equation:

[00001]$.Math..Math.E_{\mathrm{ON}-\mathrm{OFF}}^{*}=\sqrt{{\left(L_{\mathrm{OFF}}^{*}-L_{\mathrm{ON}}^{*}\right)}^2+{\left(a_{\mathrm{OFF}}^{*}-a_{\mathrm{ON}}^{*}\right)}^2+{\left(b_{\mathrm{OFF}}^{*}-b_{\mathrm{ON}}^{*}\right)}^2}$

[0355] In this equation, L*.sub.ON, a*.sub.ON and b*.sub.ON represent the values measured on locks of hair after treatment with composition (A) or (A) and then application of the revealing composition (B) and L*.sub.OFF, a*.sub.OFF and b*.sub.OFF represent the values measured on locks of hair after treatment with composition (A) or (A), then application of the revealing composition (B) and then application of the erasing composition (C). The higher the value of E*.sub.ON-OFF, the greater the variation in color between the application of the revealer and of the eraser.

TABLE-US-00004 E switch on vs. E vs SWITCH Name Treatment L* a* b* C reference OFF Composition Spontaneous 36.4 5.5 16.4 17.4 18.8 (A) of the result* invention Composition SWITCH ON 30.8 9.8 3.3 10.4 31.1 35.8 (A) of the invention Composition SWITCH 46.5 18.4 34.4 39.0 13.9 (A) of the OFF invention Comparative Spontaneous 44.1 15.2 9.6 18.0 30.4 Composition result* (A) Comparative SWITCH ON 44.4 13.6 11.1 17.6 28.2 1.8 Composition (A) Comparative SWITCH 46.1 13.2 11.4 17.5 27.3 Composition OFF (A)

[0356] It is seen from the results in the above table that after composition (A) of the invention has been applied before the switch treatment, the composition of the invention makes it possible to obtain significantly more intense coloring than that of the comparative composition (36.4 versus 44.1). On applying the revealer (composition B) to the keratin fibers treated with composition (A) of the invention, the color becomes much more intense (30.8 versus 36.4), whereas for the fibers treated with the comparative composition (A), the intensity virtually does not change (44.4 versus 44.1). Next, on applying the erasing composition (C) to the keratin fibers treated with composition (A) of the invention, the color lightens very significantly (L*.sub.ON-OFF=46.5-30.8=15.7), whereas for the fibers treated with the comparative composition, the lightening is very weak (L*.sub.ON-OFF=46.1-44.4=1.7).

[0357] Moreover, as regards the color build-up, a very large amplitude was measured for the colors obtained via the process of the invention, namely after applying composition (A), the E* of color build-up is E*=18.8, after application of the revealing composition (B), E*=31.1; and after application of the erasing composition (C), E=13.9. In addition, the value of E*.sub.ON-OFF for the process of the invention is E*.sub.ON-OFF=35.8. For the comparative process, the values obtained are, respectively, after applying composition (A), E*=30.4, after applying composition (B), E*=28.2 and after applying composition (C), E*=27.3 with a value for E*.sub.ON-OFF=1.8.

[0358] It is thus seen that the switch on-switch off revealed-erased coloring amplitude is much larger via the process of the invention compared with that of the comparative process.

[0359] In addition, the process according to the invention allows successive appearance(s)/disappearance(s) of color within a few seconds, generally on applying the revealing composition, without the need to use a hairdryer. Numerous ON/OFF cycles may be performed in sequence, and very good persistence of the order of 5 to 8 shampoo washes was observed. Moreover, the integrity and feel of the hair are respected.

[0360] Other dyes according to the invention were evaluated as regards the intensity and the variation E*.sub.ON-OFF on light-colored hair and on dark hair.

[0361] Results on light-colored hair (tone depth=10):

TABLE-US-00005 Compound Treatment Shade L* a* b* E*.sub.ON-OFF Chlorophenol Red OFF Yellow 61.5 24.7 58.7 86.6 (1) ON Violet 32.7 25.9 23.0 Bromocresol Purple OFF Yellow 66.7 17.9 63.2 95.7 (2) ON Blue 31.6 13.8 25.7 Bromocresol Purple Na Salt, OFF Yellow 66.1 15.0 62.1 89.8 (2) ON Blue 31.2 10.8 20.5 Bromothymol Blue Na Salt, OFF Yellow 66.5 20.1 59.4 84.1 (3) ON Blue 36.3 10.4 12.9 Bromocresol Green OFF Yellow 53.8 16.2 40.5 60.5 (4) ON Blue 35.7 12.5 9.6 Phenol Red OFF Yellow 64.4 32.6 54.8 61.5 (5) ON Red 36.6 36.1 0.0

[0362] It is seen from the above table that the process of the invention using the compounds of formula (I) or (I) makes it possible to obtain significantly stronger intensities (L* significantly smaller between the colors after application of the revealer (switch on) than after application of the erasing composition (switch off)). Furthermore, the color variations E*.sub.ON-OFF between the switch-off treatment and the switch-on treatment are very high (>60). This tendency was observed even after several switch-off-switch-on cycles.

[0363] Results on dark hair (TD=4):

TABLE-US-00006 E switch Treatment on vs. on dark E vs SWITCH Name hair TD4 L* a* b* C reference OFF Chlorophenol ON 23.7 3.6 6.1 7.1 31.1 4.8 Red (1) Chlorophenol OFF 21.7 3.2 1.8 3.7 13.9 Red (1) Bromocresol ON 24.3 3.2 6.2 7.0 24.3 5.1 Purple Na Salt (2) Bromocresol OFF 21.5 2.0 2.2 3.0 21.5 Purple Na Salt (2) Bromocresol ON 24.0 2.7 5.3 6.0 24.0 4.1 Green (4) Bromocresol OFF 21.8 0.5 2.8 2.8 21.8 Green (4)

TABLE-US-00007 Compound Treatment Shade Chlorophenol Red (1) OFF Yellow ON Violet Bromocresol Purple Na Salt (2) OFF Yellow ON Blue Bromocresol Green (4) OFF Yellow ON Blue

[0364] It is seen from the above table that the process of the invention using the compounds of formula (I) or (I) makes it possible to obtain significantly stronger intensities and chromaticity observable even on dark hair (L* and C* significantly smaller between the colors after application of the revealer (switch on) than after application of the erasing composition (switch off)).

Example 2: Comparative Study (Vs. FR 1 441 822)

[0365] The following compositions were prepared:

TABLE-US-00008 Composition Composition (A.sub.2) P Ingredients Invention Comparative Bromothymol Blue Na Salt (3) 1.55 10.sup.3 mol Alizarin red 1.55 10.sup.3 mol EtOH/Water 50/50 wt qs 100 g qs 100 g [0366] Switch-on revealing composition (B.sub.1) at basic pH

TABLE-US-00009 Ingredients Amount Monoethanolamine (MEA) 5 g Water qs 100 g

[0367] pH of the composition 11.40.5 [0368] Switch-off erasing composition (C.sub.1) at acidic pH:

TABLE-US-00010 Ingredients Amount Phosphoric acid 5 g Water qs 100 g

[0369] pH of the composition 1.30.5

[0370] Each of the compositions (A.sub.2) and (P) are applied to locks (1.5 g of composition/g of hair) according to the same protocol, namely: [0371] a lock of natural hair containing 90% white hairs [0372] then left to stand on the lock for 30 minutes at 31 C. [0373] then rinsing with water, then drying

[0374] Once the keratin fibers have been dried, the switch treatment is applied. [0375] To obtain switching on, composition (B.sub.1) is applied to each lock by spraying. [0376] To obtain switching off, composition (C.sub.1) is applied to each lock by spraying.

Colorimetric Results:

[0377] The color of the locks was evaluated in the CIE L* a* b* system, using a Konica-Minolta 3600d colorimeter (illuminant D65, angle 10).

[0378] The variation in coloring between the locks of hair treated and revealed (switched on) with composition (B.sub.1) and erased (switched off) with composition (C.sub.1) is defined by E*.sub.ON-OFF as in example 1.

[0379] The higher the value of E*.sub.ON-OFF, the greater the variation in color between the application of the revealer and of the eraser.

TABLE-US-00011 Nom L* a* b* E*.sub.ON-OFF A.sub.2 SWITCH OFF 62.6 3.9 29.1 32.6 (Invention) Acidic pH SWITCH ON 52.1 10.6 1.8 Basic pH P SWITCH OFF 60.8 6.8 21.2 18 (Comparative) Acidic pH SWITCH ON 51.2 10.4 6.4 Basic pH

[0380] It is thus seen that the switch on-switch off revealed-erased colouring amplitude is much larger via the process of the invention compared with that of the comparative process.