Hair dyeing method

Abstract

The present invention relates to a cosmetic hair dyeing method comprising the steps of: (a) applying to at least one strand of hair an aqueous dye composition comprising at least one oxidation dye or dyes and one or more nitrogen-based alkaline agents; and (b) exposing the hair impregnated with the dyeing composition to microwave radiation.

Description

[Technical Field]

[0001] The present invention relates to a method for dyeing hair. [Background technology]

[0002] Prior art Numerous techniques for dyeing hair are already available, using different types of dye compositions.

[0003] Additionally, the use of microwave radiation in the field of surface repair to increase the action of cleaning agents is known. In particular, WO 98 / 03621, WO 98 / 03622, WO 98 / 03623, WO 99 / 25802, and WO 99 / 37745 describe hard surface treatments in which exposure to microwave radiation is combined with cleaning agents containing bleach.

[0004] In the field of hair shaping, German Patent Application Publication No. 3148538, US Patent Application Publication No. 2006 / 0108358, US Patent Application Publication No. 2010 / 0006116 or US Patent Application Publication No. 2007 / 056860 disclose the use of microwave radiation directly on the hair.

[0005] US Patent Application Publication No. 2006 / 042649 and US Patent No. 6,079,422 describe heated curlers that can be placed in a microwave oven before use to curl hair. In these documents, there is an aspect of heat generation by the microwaves used, but these microwaves do not come into direct contact with the hair.

[0006] WO 2013 / 183021 discloses a method for the treatment of keratinous fibers, which method comprises the application of a molding composition followed by the application of mechanical tension and then exposure to microwave radiation.

[0007] WO 2011 / 141882 and FR 3062786 describe methods for treating hair by placing it under mechanical tension and exposing it to microwave radiation.

[0008] WO 2013 / 125052 describes a method for coloring hair using synthetic direct dyes and heating of keratin fibers.

[0009] WO 2019 / 122850 discloses a method for dyeing hair using a dyeing composition and simultaneous treatment with radio frequency radiation having a frequency between 1 MHz and 300 MHz.

[0010] Shaping the hair and dyeing the same hair usually require two different operations, which, on the one hand, result in long accumulated immobility times and, on the other hand, make immediate successive application unsuitable due to the risk of alteration of the shade obtained in the hair, as well as a significantly increased risk of damage to the keratin fibers. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] International Publication No. 98 / 03621 [Patent Document 2] International Publication No. 98 / 03622 [Patent Document 3] International Publication No. 98 / 03623 [Patent Document 4] International Publication No. 99 / 25802 [Patent Document 5] International Publication No. 99 / 37745 [Patent Document 6] DE 3148538 A1 [Patent Document 7] US Patent Application Publication No. 2006 / 0108358 [Patent Document 8] US Patent Application Publication No. 2010 / 0006116 [Patent Document 9] US Patent Application Publication No. 2007 / 056860 [Patent Document 10] US Patent Application Publication No. 2006 / 042649 [Patent Document 11] U.S. Patent No. 6,079,422 [Patent Document 12] International Publication No. 2013 / 183021 [Patent Document 13] International Publication No. 2011 / 141882 [Patent Document 14] French Patent Application Publication No. 3062786 [Patent Document 15] International Publication No. 2013 / 125052 [Patent Document 16] International Publication No. 2019 / 122850 Summary of the Invention [Problem to be solved by the invention]

[0012] Consequently, in light of these documents, there remains a need to improve hair dyeing methods by preserving the hair fiber as much as possible while increasing effectiveness, and to provide a method for simultaneously dyeing and shaping hair. [Means for solving the problem]

[0013] Dyeing method The present invention aims to meet this need and provides at least (a) applying to at least one strand of hair an aqueous dye composition comprising one or more oxidation dyes and one or more nitrogen-based alkaline agents; (b) exposing the hair impregnated with the dyeing composition to microwave radiation. The present invention relates to a cosmetic hair dyeing method, comprising the steps of:

[0014] The method according to the invention makes it possible to obtain an improved hair dyeing process thanks to the three-part combination of oxidative dyes, nitrogen-based alkaline agents, and microwave radiation. The use of microwave radiation results in the excitation of targeted molecules while the dyeing composition is still present on the hair, allowing for shorter exposure times for comparable results.

[0015] It is also possible to reduce the concentration of oxidation dye and / or nitrogen-based alkaline agent used to achieve a given level of coloration.

[0016] In particular, the good coverage of grey hair, good durability and low selectivity result in very good dyeing results, while causing limited damage to the hair.

[0017] The use of microwave radiation makes it possible to accelerate the dyeing reaction and therefore reduce the resting time required for the composition.

[0018] The durability and uniformity results obtained from the method according to the invention are very good, the hair experiences less damage and the risk of irritation is limited.

[0019] Depending on the duration of exposure to microwave radiation, different results are obtained, particularly depending on the base color of the hair strand.

[0020] The duration of exposure to microwave radiation may range from 1 second to 30 minutes, even better from 1 second to 10 minutes, even better from 1 second to 5 minutes, and very preferentially from 1 second to 3 minutes.

[0021] The method according to the invention may further comprise a hair shaping step (d) comprising the application of mechanical tension to said strand of hair, in particular via a device for the application of mechanical tension having a receiving surface intended to receive the strand of hair, in particular a step of winding the strand of hair with curlers.

[0022] The method according to the invention can therefore contribute in parallel to the degree of shaping of the hair and also offers the possibility of carrying out the dyeing and shaping process simultaneously in a long-lasting, fast and satisfactory manner: the curls are well defined, sufficiently durable and damage is limited.

[0023] In this alternative, the shaping step (d) can be carried out before the step (a) of applying the composition, or between step (a) and step (b) of exposing to microwave radiation.

[0024] The method according to the invention may optionally further comprise one or more pretreatment steps carried out before steps (a) and (b) and / or before or after step (d).

[0025] The method according to the invention may optionally further comprise one or more post-treatment steps carried out after step (b) and / or after step (c).

[0026] These further pre-treatment or post-treatment steps may include the application of one or more further compositions other than those present in step (a), which may or may not be applied immediately after microwave treatment.

[0027] When the shaping step (d) is carried out, the method according to the invention may comprise a step (e) of applying a hair shaping composition comprising either one or more film-forming fixing polymers, also called fixing polymers, or one or more agents that break the disulfide bridges of keratin, such as thiol-containing reducing agents. Preferably, the method according to the invention does not comprise such a step (e).

[0028] The method according to the present invention may further comprise a step (c) of rinsing the hair one or more times after any of steps (a), (b) and (d), preferably a single rinsing step carried out after step (b) of exposing to microwave radiation.

[0029] composition The dyeing composition preferably comprises at least 5% by weight of water at room temperature (25° C.) and atmospheric pressure (760 mm of mercury).

[0030] The dyeing composition is in particular a composition (a1) comprising one or more oxidation dyes and one or more nitrogen-based alkaline agents. * ), and in particular aqueous compositions (a1) comprising at least one oxidizing agent ** The aqueous composition (a1) can be obtained from a mixture of several compositions, which is a mixture of the aqueous composition (a1). ** ) itself can result from the mixing of two or more compositions, the mixing of the compositions being preferably carried out at the time of use of the dyeing composition.

[0031] Preferably, the dyeing composition (a1) comprises at least one oxidizing agent.

[0032] Preferably, composition (a1) comprises hydrogen peroxide, which may be derived from an anhydrous hydrogen peroxide precursor, such as urea peroxide, which is then added to composition (a1). * ) or directly in composition (a1). More preferentially, hydrogen peroxide is present in composition (a1). ** ) in the form of an aqueous solution of hydrogen peroxide.

[0033] In an alternative form, composition (a1) does not comprise an oxidizing agent. In this alternative form, the method according to the invention advantageously comprises, after step (b), a step (f) of applying an oxidizing composition, said oxidizing composition then preferably containing hydrogen peroxide in an aqueous medium.

[0034] Preferably, the dye composition (a1) has a pH greater than 7, in particular in the range from 7.1 to 13, even better from 7.5 to 12, and even better still from 8 to 11.

[0035] One or more nitrogen-based alkaline agents are contained in the composition (a1).

[0036] An agent is considered alkaline when, when introduced into water at room temperature and atmospheric pressure, it results in a pH greater than 7 at a concentration of 1% by weight.

[0037] The nitrogenous alkaline agent contained in the dye composition (a1) is preferably selected from ammonia and alkanolamines, in particular monoethanolamine.

[0038] In the dyeing composition (a1), the concentration of the nitrogenous alkaline agent may vary from 0.01% to 20% by weight, better still from 0.1% to 15% by weight, and even better still from 0.5% to 10% by weight, relative to the total weight of the composition.

[0039] Preferably, the dye composition (a1) comprises one or more oxidation bases preferentially chosen from para-phenylenediamines, para-aminophenols, and heterocyclic bases, such as pyrazoles.

[0040] Even more preferentially, the dyeing composition (a1) comprises one or more couplers preferably chosen from meta-diphenols, meta-aminophenols, meta-phenylenediamines, or heterocyclic couplers, such as indoles.

[0041] In the dye composition (a1), the concentration of the oxidation dyes may vary from 0.001% to 20% by weight, better still from 0.01% to 15% by weight, and even better still from 0.1% to 10% by weight, relative to the total weight of the composition.

[0042] The cosmetic composition used in the method according to the invention may also comprise at least one compound selected from solvents, silicone or non-silicone fatty substances, silicone or non-silicone anionic, cationic, non-ionic or amphoteric surfactants, polymers, in particular anionic, cationic, non-ionic or amphoteric treating or thickening polymers, antidandruff agents or agents effective against hair loss.

[0043] microwave radiation The term "microwave" should be understood to mean electromagnetic radiation with a frequency in the range of 500 MHz to 300 GHz.

[0044] Preferably, the frequency of the microwave radiation used in the method of the invention is in the range from 500 MHz to 300 GHz, even better from 500 MHz to 10 GHz, even better from 900 MHz to 5 GHz, and very preferentially from 2 GHz to 3 GHz.

[0045] The microwave power used during step (b) may be in the range of up to 500W, preferably 10-300W, even better 100-250W, even better still 10-50W.

[0046] Preferably, the surface power density of the hair induced by the microwave radiation is less than 0.1 W / cm 2 ~100W / cm 2 The range can be:

[0047] The exposure to microwave radiation may be carried out by means of a microwave-emitting antenna, said antenna and at least a part of the bunch to be treated being inserted in a preferably microwave-tight enclosure.

[0048] Optionally, at least during step (b), the housing contains the hair to be treated, which is impregnated with the dye composition. The term "containing hair" should be understood to mean containing the hair over a given width over its entire length or part thereof. The housing may, for example, cover the hair over a length of 5 cm or more. Thus, hair of at least 5 cm in length can be treated in the housing at one time.

[0049] The enclosure may be defined at least in part by a case having a housing configured to receive at least a portion of the hair to be treated and optionally a hair shaping tool, and by a cover rotatable relative to the case between an open position and a closed position providing access to the housing, the microwave emitting antenna being located within the housing.

[0050] In the alternative, the housing is in the form of a helmet.

[0051] The housing may be stationary relative to the hair being treated during microwave emission, or may be movable relative to the hair, allowing longer hairs to be treated.

[0052] The housing may comprise at least one seal of an electrically conductive material, which may be, for example, elastically deformable and capable of blocking the microwaves used in step (b) while allowing hair to exit the housing. The seal may comprise a foam loaded with electrically conductive particles, a brush formed of electrically conductive bristles, or a comb with metal teeth.

[0053] If the housing is in the form of a helmet, it may have an electromagnetic shield through which the treated hair can pass. Such a shield makes it possible to protect the user's head from the emitted microwaves while treating the user's hair. The electromagnetic shield may be formed, for example, by a metal grid or mesh.

[0054] assembly According to another of its aspects, another subject of the invention is an assembly for dyeing hair, comprising at least one dyeing composition comprising one or more oxidative dyes and one or more nitrogen-based alkaline agents, and a device suitable for exposing the hair to microwave radiation as defined above.

[0055] The device may comprise a microwave-emitting antenna, the antenna and at least a part of the bunch to be treated being inserted into a microwave-tight enclosure, in particular as described above.

[0056] The microwaves can be generated internally in the device suitable for exposing the hair to microwave radiation, or externally by a microwave generator, for example a solid state generator, such as a magnetron.

[0057] In the alternative, the oscillator is located inside the housing.

[0058] The microwave emission can be achieved by a non-linear antenna, for example an antenna of helical type.

[0059] The antenna may be formed of a sufficiently rigid wire, for example with a diameter in the range of 1-3 mm, so that no support rods are required for maintenance or rotation. Alternatively, the antenna comprises a flexible wire or a conductive track arranged on a support structure, in particular a helical support structure. This support structure may be made of any insulating material, preferably PTFE or glass.

[0060] If the antenna is helical, it preferably has a fixed helical pitch, for example in the range of 4 to 5 mm. The radius of the helix is ​​preferably constant, for example in the range of 4 to 10 mm. The diameter of the antenna is, for example, 8 to 10 mm.

[0061] The axial extension of the antenna may vary from 50 to 80 mm, and even better from 65 to 75 mm.

[0062] The antenna may in particular be arranged in a tube closed at one end, which may be made of PTFE or another insulating material.

[0063] The antenna may also be embedded in an insulating material, preferably a flexible insulating material, especially silicone.

[0064] Said device suitable for exposing hair to microwave radiation may comprise a hair shaping tool, in particular a tool for applying mechanical tension, in particular a curler. The term "curler" denotes a tool that makes it possible to wind the hair around the longitudinal axis of the device according to a defined diameter, thereby creating a mechanical tension according to the diameter. The diameter of said curler may depend on the desired curling effect.

[0065] The curler may have teeth at the ends of branches that laterally delimit the hair-receiving surface, said teeth of the curler being advantageously arranged around the antenna.

[0066] The shaping tool may optionally be configured to lay the treated hair flat during exposure to microwaves.

[0067] Removal of mechanical tension on said tresses of hair is preferably carried out after step (b) of exposing to microwave radiation.

[0068] The device may comprise a housing capable of receiving a shaping tool, said housing may be coated with a conductive foam arranged to extend into the hair exit slot, whereby the deformability of the foam at the slot makes it possible to obtain a good tightness of the closure.

[0069] Optionally, the moulding tool and the antenna form an integral assembly that is installed in the housing.

[0070] The moulding tool may be made of PTFE or other insulating material, especially a thermoplastic insulating material.

[0071] The device used to carry out the method according to the invention may be equipped with, for example, an acoustic and / or optical warning system to warn the user of microwave leakage outside the enclosure and / or excessive temperatures inside the enclosure.

[0072] The device advantageously comprises a safety system which prevents microwave emission if the enclosure is not closed and / or in the event of abnormal operation, for example microwave leakage and / or excessive temperature.

[0073] The device may be configured to control the duration of microwave emission so that the treatment does not reach a duration that is prone to damage the hair.

[0074] The method according to the invention may comprise, before step (b), a step of detecting closure of the housing, for example a switch that is activated when the housing is closed.

[0075] Initiation of microwave radiation may depend on detection of closure of the enclosure. After initiation of microwave radiation, continued microwave emission may depend on no microwave leakage being detected, particularly by a microwave-sensitive sensor located outside the enclosure.

[0076] The method according to the invention may further comprise, before step (b), a step of detecting the position of the hair intended to be treated. This detection step can be carried out, for example, by an optical sensor and / or a mechanical detector. Optionally, the detection can be carried out indirectly by detecting the position of a shaping tool.

[0077] The method according to the invention may, for example, comprise a step of measuring the temperature to which the treated hair is subjected during step (b). This step of measuring the temperature may be carried out by means of a thermometer, without contact with the hair.

[0078] The device may comprise a microwave generator and also a shaping tool in one and the same handpiece. The term "handpiece" refers to the part that the user operates with one hand while treating the hair.

[0079] The device may be equipped with sensors that sense individual hair characteristics, such as color, mechanical strength, surface condition, or humidity, and the device can control at least one parameter of the treatment, such as microwave energy, solvent temperature, duration of treatment, and / or applied mechanical stress, accordingly depending on the characteristics thus detected.

[0080] The features given above for the method apply to the assembly and vice versa.

[0081] A better understanding of the invention will be obtained from reading the following description and examining the accompanying drawings, which are presented merely as an indication and without limiting the invention in any way. [Brief explanation of the drawings]

[0082] [Figure 1] 1 illustrates the various steps of an example hair dyeing method according to the present invention. [Figure 2] 1 shows a schematic partial view of an example of a device suitable for carrying out the method according to the invention; [Figure 3] 1 shows a handpiece of an example of a device suitable for carrying out a method according to the invention in an open position. [Figure 4] FIG. 4 shows the handpiece of FIG. 3 in a closed position. [Figure 5] FIG. 10 shows the shaping tool once removed from the handpiece of an alternative form of device suitable for carrying out the method according to the invention. [Figure 6] 6 is a cross-sectional side view of a device suitable for carrying out the method according to the invention, comprising the molding tool of FIG. 5, with the housing closed. DETAILED DESCRIPTION OF THE INVENTION

[0083] The various steps or stages of an example of a hair dyeing method according to the present invention are shown in FIG. 1 and are described in detail below.

[0084] In this example, during step 11, an aqueous dye composition (a1) comprising one or more oxidation dyes and one or more nitrogenous alkaline agents is applied to at least one strand of hair.

[0085] In step 12, the hair contacted with the dyeing composition is exposed to microwave radiation having a frequency of 500 MHz or higher, preferably in the range of 900 MHz to 5 GHz. The duration of exposure to microwave radiation is preferably in the range of 1 second to 3 minutes. The surface power density of the hair induced by the microwave radiation is 0.1 W / cm. 2~100W / cm 2 The range can be:

[0086] The method according to the invention further comprises, in the example described, one or more hair rinsing steps 13, preferably a single hair rinsing step 13, carried out after the step 12 of exposing to microwave radiation.

[0087] The method according to the invention may further comprise a hair shaping step 14, in particular a step of winding the hair strand with curlers, comprising the application of mechanical tension to said at least one strand of hair via a device for the application of mechanical tension having a receiving surface intended to receive said strand of hair. This shaping step 14 is carried out before step 11 of applying the dye composition or between steps 11 and 12.

[0088] The method according to the invention may further comprise one or more pre-treatment steps 15 carried out before steps 11 and 12, for example comprising the application of one or more further compositions other than those used during step 11.

[0089] For example, one or more post-treatment steps 16, including the application of one or more additional compositions other than those used in step 11, may be performed after step 12 and / or after step 13.

[0090] Preferably, as in the described example, the dyeing composition (a1) comprises hydrogen peroxide. The dyeing composition may be a mixture of several compositions, and in the considered example, a composition (a1) comprising one or more oxidation dyes and one or more nitrogen-based alkaline agents. * ), and the aqueous composition (a1) containing hydrogen peroxide ** The dyeing composition (a1) is a mixture of the oxidation dye and the nitrogen-based alkaline agent, and the concentrations thereof, which are mixed at the time of use.

[0091] A device 100 suitable for carrying out the method according to the invention is shown in Figure 2, comprising a handpiece 3 connected by a flexible waveguide 2 to a base unit 1 comprising a microwave generator. The handpiece 3 is envisaged to be operated by a user to be placed close to a person's head, as illustrated, for treating at least one strand of hair H. The handpiece 3 can be made in various ways and defines a microwave-tight treatment enclosure 4.

[0092] In the example shown in Figure 3, the handpiece 3 comprises a case 10 defining a housing 6, onto which a cover 11 is connected by a shaft 12. The handpiece is shown in a closed state in Figure 4. The flexible waveguide 2 is only partially shown in Figures 3 onwards.

[0093] The case 10 carries an antenna 30 which, in the illustrated example, is helically shaped with a longitudinal axis 7 .

[0094] In the example considered, the antenna 30 is constructed from a helical metal wire and placed in a tube 32 of insulating material, for example silicone or PTFE.

[0095] The antenna 30 is supported at one axial end of the case 10 by an end plate 14 of the semi-annular outline case 10 .

[0096] The cover 11 has a similar end plate 15 on the opposite side to close the opening 5 in the housing 6 , by which a molding tool can be introduced into the handpiece 3 .

[0097] The inner surface of the housing 6 is defined by an electrically conductive coating 7 that makes it possible to reflect microwaves and makes the enclosure 4 gastight against microwaves. This coating 7 can be made of conductive foam, for example of semi-cylindrical shape, for the cover and case in the form of a disk on the end plate 15 and a ring on the end plate 14.

[0098] The case 10 and cover 11 define a hair exit slot 19 located at the bottom of the recess 18 opposite the hinge axis 12.

[0099] The coating 7 preferably protrudes into the slot 19, as can be seen in Figure 6, to provide good tightness of the closure despite the passage of hair. The edge of the coating therefore extends slightly beyond the edge of the cover body 17 and the edge of the case that closes the slot 19.

[0100] The handpiece 3 is provided with a member (not shown) for locking the cover in the closed position and also with an opening detector.

[0101] A temperature detector may be present within the housing 4, for example on the inner surface of the housing 4, to measure the temperature of the hair strand being treated, and may enable the microwave emission to be shut off or adjusted, for example by a control system having a microprocessor, if a temperature above a predetermined threshold is detected.

[0102] In a particular embodiment, the case 10 defines a housing 6 which receives a molding tool consisting, in the example considered, of a curler 20 shown in Figure 5. The insertion of the antenna inside the curler 20 is facilitated by the presence of a tube 32 shown in Figure 3 in which the wires of the antenna 30 are placed.

[0103] The curler 20 comprises several branches 21 which define a surface for receiving the hair H, which has a width L measured along the longitudinal axis X of the curler 20 .

[0104] In this example, axis X is parallel to the axis of rotation of cover 11 and coincides with longitudinal axis 7 of antenna 30 .

[0105] In the example considered, the curler 20 comprises four branches 21 which are slightly curved towards the axis X and pass the smallest distance to the axis X approximately in the middle of their length.

[0106] The branches 21 may have ribs 23 oriented perpendicular to the axis X, preferably spanning the entire width L in the most uniform manner possible, to help keep the tufts spread across the branches 21 .

[0107] The branches 21 connect at both ends to annular portions 25 .

[0108] The curler 20 has teeth 26 at the ends of the branches 21 which laterally delimit the hair receiving surface.

[0109] The curler 20 can be made of any insulating material, preferably PTFE.

[0110] The curler 20 preferably has a rotationally symmetrical shape about a median plane of symmetry perpendicular to the axis X.

[0111] As illustrated in FIG. 6, in order to keep the curler in the center of the housing 6, the curler 20 is provided with studs 27 with enlarged heads, which are connected at their bases to corresponding annular portions 25 and supported on the coating 7.

[0112] The studs 27 are, for example, positioned between the teeth 26 as illustrated.

[0113] The width W of the hair exit slot 19 is slightly greater than L, and the length of the housing 6 is substantially equal to the length of the curler 20, so that the curler is fixed with a small amount of play in both the axial and radial directions of the housing 6.

[0114] To use the handpiece 3, a strand of hair impregnated with the dyeing composition is wound onto the curlers 20, which are then placed inside the case 10 by moving them laterally relative to the case 10 and introducing them through the opening 5. The cover 11 is then closed again and the hair emerges through the slot 19. Once the exposure to microwaves has been carried out, the strand of hair is removed by performing the operation in reverse.

[0115] Example Examples of results obtained by the method according to the invention are summarized in Table 1 below.

[0116] In this example, the dyeing test was carried out on Caucasian type hair with a color depth level equal to 6 (DL6) and hair containing 90% natural white hair (NW90).

[0117] The composition used in this example is a composition (a1) containing one or more oxidation dyes and one or more nitrogen-based alkaline agents. * ), and an aqueous composition (a1) comprising at least one oxidizing agent. ** ), the mixing of the compositions being carried out at the time of use of the dyeing composition (in a 1:1 ratio, preparing 10 g of the mixture per gram of hair). More specifically, the compositions used are commercially available Majirel brand oxidation dyeing products combined with 20 volumes of L'Oreal Professionnel brand oxidizing agent. References 6.66, 7.3, and 5 were used, corresponding to Intense Red, Golden Blonde, and Light Cashew, respectively. In addition to the oxidation base and coupler, these Majirel dyeing products contain nitrogen-based alkaline agents, such as ethanolamine and ammonia (ammonium hydroxide). For example, in reference 6.66, the concentration of ethanolamine is equal to 0.63%.

[0118] The dye composition (a1) was applied with a brush to both sides of the hair tresses and the tresses thus impregnated were subsequently exposed to microwave radiation at a power of 30 W for 3 minutes.

[0119] The colorimetric parameters observed are ΔE, which corresponds to the visual variation of two given colors before and after treatment according to the method of the present invention, comparable to the increase in color tint, and to a measure of the variation in chromaticity before and after treatment according to the present invention.

[0120] The results obtained using the method according to the invention were compared with those obtained using a prior art dyeing method in which microwave radiation is not used and the hair impregnated with the dyeing composition is left to stand at room temperature (AT) for 30 minutes.

[0121] [Table 1]

[0122] Compared to the prior art method, the observed colorimetric parameters remained comparable, while the processing time required for the method according to the invention was reduced by a factor of 10.

[0123] Many modifications can be made to the methods and devices as described without departing from the scope of the invention.

[0124] The present invention is not limited to any particular type of forming tool or any particular type of microwave emitting antenna. [Explanation of symbols]

[0125] 1 base unit 2 Flexible waveguide 3 Handpieces 4. Housing, processing housing 5 Opening 6. Housing 7. Coating 10 cases 11 Cover 12 Hinge shaft, shaft 14, 15 End plates 17 End of cover body 18 Recess 19 slots, exit slots 20 curlers 21 Branch 23 Ribs 25 Annular section 26 teeth 27 studs 30 Antenna 32 tubes 100 devices

Claims

1. at least (a) applying to at least one strand of hair an aqueous dye composition (a1) comprising one or more oxidation dyes and one or more nitrogen-based alkaline agents; (b) exposing the hair impregnated with the dyeing composition to microwave radiation. A cosmetic hair dyeing method comprising the steps of:

2. 2. The method according to claim 1, wherein the frequency of the microwave radiation used in the method of the invention is in the range from 500 MHz to 300 GHz, even better from 500 MHz to 10 GHz, even better from 900 MHz to 5 GHz, and very preferentially from 2 GHz to 3 GHz.

3. 3. The method according to claim 1 or 2, further comprising a hair shaping step (d) comprising the application of mechanical tension to said at least one strand of hair, in particular via a device for the application of mechanical tension having a receiving surface intended to receive said strand of hair, in particular a step of winding the strand of hair with curlers, wherein the shaping step (d) is preferably carried out before step (a) of applying the composition or between step (a) and step (b) of exposing to microwave radiation.

4. The dye composition (a1) is in particular a composition (a1) comprising one or more oxidation dyes and one or more nitrogen-based alkaline agents. * ), and in particular aqueous compositions (a1) comprising at least one oxidizing agent ** 4. The method according to claim 1, wherein the dye composition is obtained from a mixture of several compositions, the mixture being a mixture of:

5. 5. The method according to claim 1, wherein the dyeing composition (a1) comprises at least one oxidizing agent.

6. The dyeing composition (a1) is in particular a composition (a1 ** 6. The method of claim 5, wherein the hydrogen peroxide is in the form of an aqueous hydrogen peroxide solution present in a

7. 7. The method according to claim 1, wherein the dyeing composition (a1) has a pH greater than 7, in particular in the range from 7.1 to 13, even better from 7.5 to 12, and even better from 8 to 11.

8. 8. The method according to claim 1, wherein the nitrogenous alkaline agent contained in the dye composition (a1) is selected from ammonia and alkanolamines, in particular monoethanolamine.

9. 9. The method according to claim 1, wherein in the dyeing composition (a1) the concentration of the nitrogenous alkaline agent ranges from 0.01% to 20% by weight, better still from 0.1% to 15% by weight, and even better still from 0.5% to 10% by weight, relative to the total weight of the composition.

10. 10. The method according to claim 1, wherein the dyeing composition (a1) comprises one or more couplers, preferably selected from meta-diphenols, meta-aminophenols, meta-phenylenediamines, or heterocyclic couplers, such as indoles.

11. 11. The method according to claim 1, wherein in the dye composition (a1) the concentration of oxidation dye(s) ranges from 0.001% to 20% by weight, better still from 0.01% to 15% by weight, and even better still from 0.1% to 10% by weight, relative to the total weight of the composition.

12. 12. The method according to any one of claims 1 to 11, wherein the exposure to microwave radiation is carried out by means of a microwave-emitting antenna, said antenna and at least a part of the bunch to be treated being inserted in a microwave-tight enclosure.

13. The surface power density of hair induced by microwave radiation is 0.1 W / cm 2 ~100W / cm 2 13. The method according to any one of claims 1 to 12, wherein the range is

14. 14. The method according to any one of claims 1 to 13, wherein the duration of exposure to microwave radiation ranges from 1 second to 30 minutes, even better from 1 second to 10 minutes, even better still from 1 second to 5 minutes, and very preferentially from 1 second to 3 minutes.

15. Assembly for dyeing hair, comprising at least one dyeing composition comprising one or more oxidative dyes and one or more nitrogen-based alkaline agents, and a device suitable for exposing the hair to microwave radiation having a frequency in the range from 500 MHz to 300 GHz, even better from 500 MHz to 10 GHz, even better from 900 MHz to 5 GHz, and very preferentially from 2 GHz to 3 GHz.

16. 16. An assembly according to claim 15, wherein the device comprises a microwave-emitting antenna (30), said antenna and at least a part of the bunch to be treated being inserted into a microwave-tight enclosure (4).

17. Assembly according to claim 15 or 16, wherein the device comprises a hair shaping tool, in particular a tool for mechanical application of tension, in particular a curler.

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