FR2719472A1 - Cosmetic decolourisation of hair by laser irradiation - Google Patents

Abstract

An improved process for the cosmetic decolorisation of hair comprises decolourising hair by irradiation with a laser beam.

Description

 The invention relates to a method for performing a cosmetic treatment on discolored hair. It has indeed been discovered that the results of cosmetic treatments on bleached hair were significantly improved when said treatment is carried out on bleached hair by irradiation with a laser beam.

 It is known that, in order to bleach or lighten the hair, a chemical treatment is conventionally carried out using an oxidizing agent, such as hydrogen peroxide or persalts, which destroys at least a portion of the natural coloring products and / or artificial present in the hair.

 The conventional method of chemical bleaching of the hair requires the use of relatively powerful and / or concen- trating oxidizing agents, which have the effect of degrading not only the coloring substances, but also the keratin fiber of the hair. As a result, the hair thus discolored is fragile and must then be treated with care.

 For these reasons, it is difficult or sometimes impossible to obtain good results with cosmetic treatments applied to chemically bleached hair.

For example, it is possible to apply to such hair permanent deformation treatments used for natural hair, because these treatments consist in applying to the hair reducing agents, at relatively high pH, then an oxidizing agent, which have clearly aggressive effects on the keratin fiber of the hair. In fact,
The application of a conventional permanent deformation treatment on chemically discolored hair causes irreversible damage and even breakage of the hair.

 This explains why experienced hairdressers do not agree to carry out a permanent deformation operation immediately or shortly after chemical bleaching. To perform a perm on hair thus weakened, they use compositions for permanent "low", that is to say significantly less dosed reducing agent and / or having a pH close to neutrality. Under these conditions, the degradations of the hair are more limited However, the hair thus treated have a zigzag curl unattractive. The loops obtained do not have the elasticity of those obtained by permanent deformation of the natural hair. In addition, when the hair has been heavily discolored, it is possible that the perm does not induce any crimp. It is recalled here that the operation of permanent hair deformation is commonly called "permanent", and that the hair having undergone such an operation are said to be "permed".

 Moreover, it is known that a large proportion of people want to obtain a so-called "hair", that is to say a hair that is not completely discolored, but in which only certain locks of hair are discolored. This is a so-called "wicking" operation. The case of the hair is very delicate, because then we find on the same hair with natural hair and very discolored hair. Natural hair needs, to curl, a product of permanent "strong", while to limit the problems of degradation, it should be applied on the discolored hair a product of permanent "weak" Such a procedure not being practically usable, these difficulties are generally solved by coating the faded locks with a protective substance, then a fairly strong permanent composition is applied to the whole of the hair. With this technique, the natural hair is fairly well permed, but the discolored locks are generally quite damaged and have unsightly curls. In addition, this technique is time consuming because it requires to coat with the protective product each faded strand. The final result is quite unsatisfactory because some locks (natural locks) curl well while other locks (faded locks) curl little.

 In fact, in the case of virtually all cosmetic treatments applied to discolored hair, there are difficulties of implementation or disappointing results.

 We know for example that some people want to get not faded locks but colored locks with a shade different from that of the rest of the hair. For this, it is first necessary to discolor said locks, then to apply on the hair a coloring agent. It is found that on the discolored locks, the hue is not stable. Moreover, with oxidation dyes which only develop a coloration in the presence of an oxidizing agent, the previously discolored locks are more damaged because they are more sensitive to the inevitably degrading effect of oxidation dye treatments. In addition, some dyes hardly color previously discolored hair. In addition, the streaks discolored and then dyed have dyestuff problems. Indeed, by washing with a shampoo, they tend to fade quickly.

 The application of hair conditioning agents to discolored hair also leads to disappointing results, as these hair are easily entangled and the application of conditioning agents, such as detanglers or foams to rinse, do not prevent the breakage of discolored hair, during disentangling because of their fragility.

 Similarly, after the application of certain hair lacquers, discolored hair associated with hair not discolored by lacquer grains may be torn off during combing.

 Similar problems can be encountered after applying styling lotions. In addition, the discolored hair is softer than natural hair, it follows that the hairstyle does not have a homogeneous appearance, even after application of a hairspray or styling lotion, especially when the hair is bad.

 Moreover, the application of shampoos that contain detergents is less well tolerated by the keratin fibers of discolored hair, in particular in the case of frequent shampoos. So we see that virtually all cosmetic treatments applied to discolored hair pose difficult problems or sometimes impossible to solve.

 The invention overcomes these various disadvantages through the discovery that it is possible to discolor the hair by irradiation with laser radiation, and without altering the mechanical and physicochemical properties of the hair.

 The invention therefore makes it possible to apply, with good results, and without taking special precautions, the various usual cosmetic treatments, including those just mentioned. These improved results are obtained by applying said treatments to bleached hair not chemically but by irradiation using a laser beam, under particular conditions which make it possible, on all types of hair, to be naturally colored or artificially, a discoloration of intensity easily controllable, without significant degradation of the keratinous fiber, and with a reasonable duration of treatment.

This bleaching process is particularly well suited to obtaining a hair hair. In addition, the hair thus discolored, having retained the mechanical and physico-chemical properties they had before discoloration, can be submitted without delay to other cosmetic treatments, without the need to use protective substances, and improved results are obtained for all the usual cosmetic treatments.

 The theoretical possibility of bleaching hair with laser radiation has been mentioned in Tech. News, Laser Focus, Vol.19, No. 9, p.26, September 1983. In addition, in US Pat. No. 4,492,341, there is described an experimental device for studying the destruction of melanin in human hair. using laser radiation. In fact, this US patent discloses neither a method nor a device for practically applying laser irradiation to hair discoloration.

 It has now been discovered that it is possible to bleach locks of hair, regardless of their original color (natural or artificial), without degradation of the keratinous fiber, by successively subjecting portions of locks of hair to be treated to a irradiation by a laser beam provided to choose a power of the laser radiation adapted to the type of hair to be discolored.

 Studies on isolated hair of various origins (European, Japanese, Mexican and Scandinavian natural hair) made it possible to study the light power necessary to obtain a good hair discoloration without degradation of the keratin fiber, with a single laser pulse (single shot ). It has been found that very dark hair (Japanese and Mexican) does not discolor sufficiently deep or burst under irradiation when the power per unit area is further increased for a given pulse duration. By using a peak power less than the highest peak power which, in one-shot shooting, for the pulse duration used and for the type of hair studied, does not cause the keratin fiber to burst, then successive shots, in sequence, on the same area of the treated isolated hair. It has been found that isolated hair, even very dark hair of the Japanese or Mexican type, can be discolored without damage, thereby lowering the peak power and making several successive passes over a treated area, thereby allowing the hair to be discolored first. superficial layers, then the deeper layers and finally the hair can be discolored completely.

 Similar studies made on strands of hair have shown that it is possible to discolor the hair arranged in locks, provided to select a laser power laser adapted to the type of hair treated. This power must be sufficient to degrade or destroy melanin, but must not exceed a certain threshold. It has been found that the darker the natural color of the hair, the lower the threshold.

So we arrive at this surprising result that the more difficult the hair to discolor, the more the power of the laser radiation must be moderate.

 As will be apparent to those skilled in the art, it is actually the energy provided to the melanin grains over a sufficiently short period of time which must be sufficient to degrade or destroy the melanin. It is therefore in reality the density of energy supplied per unit area, in a sufficiently short time, which must reach a sufficiently high threshold for the hair to be discolored. In the present application, when we speak of "power" or "peak power", it must be understood that it is a simplification of language, because it is in fact the energy supplied during each pulse. which is important, and therefore the duration of the pulse, which must be no more than a microsecond (approximate duration of melanin relaxation time) in the case of natural hair discoloration, must be taken into account.

 It has also been discovered that artificially colored hair can be discolored similarly, as long as it is performed, as for undyed hair, by adapting the power of the laser radiation to the natural color of the hair. It is only after doing this preliminary step. corresponding to the degradation of melanin, that one can undertake the actual decolorization, corresponding to the degradation of the artificial dye. Indeed, the degradation of artificial dyes requires higher energies than the degradation of melanin, so that if one sought to directly degrade said dyes, the hair would be destroyed by bursting of the keratinous fiber, as in the reported experiments above.

 We also know that some older people have a "white" hair that is in fact an unattractive yellowish tint. The process of fading by laser irradiation makes it possible to transform this yellowish coloration into pure white.

 The subject of the invention is therefore an improved process for performing a cosmetic treatment on bleached hair, characterized in that said treatment is carried out on bleached hair by irradiation with the aid of laser radiation.

The subject of the invention is in particular a cosmetic treatment method as defined above in which the hair to which the treatment is applied has been bleached by a process in which at least part of the wick or part of the wick is at least partially discolored. hair by irradiation of said wick or portion of wick using a laser beam of sufficient power to discolor the hair, this fading process comprising the following steps s
an area of said portion of wick is treated by irradiation with the aid of a laser beam emitted in the form of pulses to at least partially bleach the hair of said zone, by degradation of the melanin of the hair,
if necessary, by relative displacement of said wick with respect to said laser beam, one or more other zones are successively treated in a similar manner so as to treat all of said wick portion,
the previous treatments are optionally repeated until the desired degree of discoloration for said wick or part of wick is obtained,
- Operation is carried out with laser radiation of sufficient power to provide, by pulse, an energy density of 0.1 to 1.2 J / cm 2 at 532 nm, said selected energy density not being greater than a threshold beyond which the keratin fiber of the hair is damaged, said threshold being all the lower as the natural color of the hair to be treated is darker.

 It is known that a laser essentially consists of an active medium that is amplified by a pumping mechanism that selectively supplies energy to the atoms, said active medium being enclosed in a resonant cavity. The active medium is then capable of emitting a light beam, substantially monochromatic, polarized and coherent. Because of this coherence, a laser beam concentrates a much higher energy than that of a radiation emitted by a conventional light source.

 Some lasers, especially those with a solid active medium, are able to emit laser radiation in the form of very short pulses (generally between the femtosecond and the microsecond). The concentration of energy over such short time intervals confers on the laser pulse a power, called peak power, considerable. In the method of the invention, lasers are preferably used for producing controlled pulses. For example, ruby lasers or lasers whose active medium contains rare earth ions or actinides, for example a neodymium laser, may be used. The realization of such lasers is well known. The active ions can be inserted in a crystalline matrix such as yttrium-aluminum garnet (abbreviated to YAG), or in an amorphous matrix such as a glass. The frequency of recurrence of the pulses is adjusted by means of a flashlight lamp. The available energy can be adjusted using conventional systems, including polarizers.

 Preferably, lasers emitting in the near ultraviolet, in the visible or in the near infrared, for example at wavelengths of 300 to 1100 nm are used. For example, a YAc-neodymium laser emitting at 1.06 KLm may be used, optionally with a frequency multiplier which makes it possible, for example, to obtain a wavelength emission of 532 nm (double frequency) or of 355 nm (triple frequency). ).

The determination of the peak power-pulse duration torque (for example the peak power of the laser beam for a given pulse duration) can be easily determined taking into account the conditions concerning the energy density per pulse, depending on the natural hair color, even if it is dyed hair. More precisely, it is desirable not to exceed a maximum energy density per pulse which is of the order of:
- 0.35 J / cm2 for dark brown hair (Japanese or Mexican type),
- 0.4 J / cm2 for dark brown hair,
- 0,5 J / cm2 for light brown hair,
- 0.7 J / cm2 for dark blond hair,
- 1.2 J / cm2 for light blonde hair.

The various energy density data provided above have been established for 532 nm wavelength radiation. When the wavelength used is different, an X nm correction factor should be applied
532 as discussed in more detail in the experimental section below.

Moreover, it is recalled that the different shades of hair can be defined objectively by the luminance (L), according to the colorimetric coordinate system clE- (L ~ a, b). In the present application, the hair colors mentioned correspond to the luminance ranges mentioned below.

<tb><SEP> Type <SEP> of <SEP> hair <SEP> L
<tb> Japanese <SEP> or <SEP> Mexican <SEP> Lower <SEP> to <SEP> 18
<tb><SEP> chestnut <SEP> dark <SEP> 18-20
<tb><SEP> brown <SEP> clear <SEP> 22-24
<tb><SEP> blond <SEP> dark <SEP> 28-35
<tb><SEP> blond <SEP> clear <SEP> 45-52
<Tb>
The process described above, which corresponds to at least partial decolorization by degradation of the melanin of the hair, must be carried out in all cases, even if the dyed hair is treated with a coloring agent, and in the latter case, the bleaching process comprises an additional step of irradiating hair, similar to that described above, but by laser radiation providing a higher energy density, sufficient to destroy or degrade the agent dye; this energy density is in particular at least 0.8 J / cm 2. It is generally less than 2 J / cm 2 at 532 nm.

 In order to carry out the preliminary stage of melanin degradation, it is sufficient to know the natural color of the dyed hair to be treated, and then irradiation conditions that are suitable for the hair having this natural color are applied, said conditions having been determined. previously, once and for all, by simple routine experiments.

 The duration of the pulses can range, for example, from 10 picoseconds to 100 nanoseconds.

 The laser bleaching process obviously requires discolouring the hair by locks, by successively irradiating areas of said wick. Generally, the irradiation surface may vary in the range of 0.1-2 cm 2.

 This method is therefore particularly well suited to obtaining hair hair. To successively treat the zones to be discolored by relative displacement of a wick with respect to the laser beam, it is possible to move the wick relative to the apparatus used for the treatment, or vice versa, and / or to vary periodically the direction of the wick. laser beam so as to perform successive scans of the treated area. This periodic variation of the direction of the laser beam can be obtained for example by means of an oscillating mirror.

 It has been found that when fading is done by laser shots in sequence, the hair tends to heat up locally. In order for this local heating to be not harmful to the hair, it is necessary to limit the frequency of recurrence of the pulses, and / or to make sufficient relative movements of the lock of hair treated with respect to the laser beam so as to avoid cumulative heating up, after which we can return to a previously treated area, having had time to cool sufficiently, to complete the treatment, and so on. Another solution to avoid local heating of the hair is to cool the hair in the treated area. The hair can be cooled in the treated zone in particular by circulation of a fluid. The simplest solution is to create a gaseous flow bathing the hair in the treated zone, for example by suctioning the air or by blowing a gas, possibly previously cooled, such as air, nitrogen, helium, carbon dioxide, etc. It is of course possible to use a gas charged with water vapor or charged with liquid particles (aerosol), for example droplets of water.

 In practice, it is easy to determine a suitable frequency of recurrence of the pulses and / or an appropriate speed of movement of the lock of hair relative to the laser beam, by simple routine experiments, said suitable frequency and / or said appropriate speed being those for which we do not observe harmful heating of the hair. For example, a pulse recurrence frequency of 5 to 50 Hz may be chosen. The method of periodically varying the direction of the laser beam, as indicated above, is also one of the means of combating the local heating of the hair. In the case where one applies hair cooling measures, it is possible to operate with recurrence frequencies pulses greater than those just indicated. The frequency of the pulses, in this case, can range, for example, up to 1000 Hz, in particular from 10 to 100 Hz approximately. The capacity of the cooling system to evacuate the heat produced, so as to avoid the thermal degradation of the hair, must obviously be adapted to the choice of the frequency of the pulses, which itself, determines the duration of the treatment.

 Treated hair can be dry or wet.

 In order to be able to discolor the lock of hair treated in good conditions, it is preferable to dispose this lock in the form of a sheet of hair, and it is then possible to discolor the hair of the treated area by irradiating at least one of the faces of said hair. tablecloth. Preferably, the thickness of the sheet of hair corresponds to the thickness of about 3 to 20 superimposed hair.

According to a particular embodiment, the fading step of the laser bleaching process is characterized by the fact:
- That one operates with a treatment device comprising a receptacle for the lock of hair to be treated, the surface of said receptacle having an orifice for the output of said laser beam,
applying, over at least a part of their length, the hair of said wick spread out in a sheet on the surface of said receptacle, so that an area to be treated is opposite said orifice,
- that the irradiation of said zone is carried out,
and that, by relative displacements of said wick relative to the laser beam, the other zones to be treated are successively irradiated. Devices for such an implementation will be described hereinafter. With these devices, the relative displacements of the wick relative to the laser beam can be obtained by relative movements of the wick relative to said receptacle and / or by periodic variations in the direction of the laser beam, as indicated above.

 One of the advantages of discolouring hair by laser beam irradiation is that it is possible to continuously control the discoloration produced and to stop the treatment to the degree of discoloration chosen.

 As indicated above, the main advantage of laser discoloration is that the hair is not degraded and retain the mechanical and physicochemical properties it had before treatment. This is a considerable advantage since it can be performed on the hair so discolored other treatments with a degrading effect, without necessarily observing a minimum period between the two operations and without taking special precautions. Thus it is possible to permeate the discolored hair by irradiation with a laser beam either immediately or shortly after fading. It is not necessary to take special measures to protect discolored locks before applying the permanent composition. It is possible, and even desirable, to use normal-strength perming compositions for natural hair, which makes it possible to obtain good results both for the discolored locks and for the rest of the hair.

 The invention therefore makes it possible in particular to implement a method for permitting discolored hair, characterized in that the permanent deformation treatment of the hair, according to the known methods, is carried out on hair discolored by irradiation with a laser beam. .

To carry out the hair bleaching step defined above, it is possible to use a device which comprises:
a body provided with a receptacle, said receptacle being intended to serve as a housing, on at least a part of the length of the hair, for a strand of hair to be treated spread out in a sheet,
means for conveying a laser beam so as to irradiate at least one zone of a lock of hair disposed in said receptacle,
and, if necessary, means for cooling said hair in the zone or zones of irradiation.

In particular embodiments, this device may also have the following characteristics, taken separately or, where appropriate, in combination:
said receptacle comprises a groove with a wide bottom, making it possible to spread said sheet on said bottom;
said groove may be associated with a releasable part of cooperating shape capable of insertion into said groove by providing, between said part and the bottom of the groove, a space constituting a housing for said sheet; said piece is for example releasable by actuating a lever for introducing the wick to be treated in the receptacle or remove it; the bottom of said groove and / or a face of said piece facing said bottom may comprise an orifice for the output of a laser beam to the area to be irradiated; likewise, the bottom of said groove or a face of said piece facing said bottom may comprise an orifice for the creation of a gas flow (by suction or by blowing);
- In another embodiment, said receptacle comprises a slot-shaped groove opening on the surface of said body and having a depth sufficient to allow the insertion of said web over its entire width; similarly to that mentioned above for the first embodiment, at least one of the facing faces of said thin slot may include an orifice for the output of a laser beam; and at least one of the facing faces of said thin slot may include an orifice for the creation of a gas flow.

 It should be noted finally that the laser channel and the duct for creating a gas flow can be confused.

 Of course, the receptacle must be a confined space sealed to light to prevent the laser radiation can cause damage to the user or his customers.

 The present invention also relates to the use of hair bleaching with laser radiation to improve the cosmetic treatment processes performed on bleached hair.

 By the method which has just been described in detail, it is possible to perform on the hair thus discolored and in good conditions various cosmetic treatments necessary for the care of the hair. These treatments include the performance of a permanent deformation, a color, a shampoo, or the application of a lacquer, a conditioning composition, a setting lotion, etc.

 The technical processes of cosmetic treatments whose results can be improved by the method of the invention are known per se. The following is an illustration of the case of permanent hair deformation.

The stage of permanent deformation of the hair which has been discolored by the process indicated above can be carried out according to the usual methods, which is not possible.
FIG. 5 represents a schematic sectional view of a second embodiment of the device, with a receptacle in the form of a thin slot,
FIG. 6 is a vertical longitudinal sectional view of the device of FIG. 5,
and FIG. 7 schematizes the mode of use of the device of FIG. 5.

 It can be seen in FIG. 1 that the device comprises an elongated hollow body (1) whose front end (la) of reduced section has a receptacle in the form of a flat bottom groove (2). A conduit (3) for the laser beam emerges in the bottom of the groove (2) after bending back with the aid of the mirror (4), and forms an outlet window (3a) on the surface of the wall (2) . The dashed lines (3b) schematize the propagation of the laser beam inside the body (1) or can represent a waveguide.

 A cooperating piece (5) movable about the axis (6) is held engaged in the receptacle by means of return means such as a tension spring (not shown) and is releasable by actuation of the lever (7) which is provided with the piece (5) at its rear end.

A flexible tube (8) is connected to a source of compressed air (not shown) and opens into the face (9), facing the bottom of the groove, of the part (5), through an orifice (8a). The rear part of the body (1) serves as a grip handle of the device by the manipulator. To bleach the hair, it releases the piece (5) to be able to arrange the lock of hair (10), divided into a sheet as shown in Figure 4, then let the piece (5) re-engage in the groove. The wick is thus disposed in the space between the faces (2) and (9), the laser transmitter (not shown) is actuated as well as the cooling system and the device is moved relative to the wick (or vice -versa) to decolorize successively all the wick or part of the wick to be treated. It is preferable to carry out displacements which are not too slow, for example of the order of 0.1-5 centimeters per second, and to operate by successive passages, which makes it possible very easily to control the evolution of discoloration, in good safety conditions. But it is also possible, with efficient cooling, to use lower movement speeds, or discontinuous displacements.

 The body of the device can be made of any suitable material, for example light metal such as aluminum or plastic. The pipe (8) is a conventional flexible pipe. It can be connected to a suction system instead of the source of compressed air.

 The device shown in Figures 5 and 6 comprises an elongated body (11) of which only the front portion has been shown, the rear portion not shown forming a handle. We see that the end of the body (11) separates into two branches (11a) and (i lb) separated by a slot whose facing faces (12) and (13) constitute a housing for a lock of hair (14). ) as in the first embodiment, a laser channel (15) opens on the face (13) of the slot after returning by the mirror (16), and a channel (17) connected to a source of compressed air emerges on the surface of the wall (12) at (17a).

 This device is used in a similar manner to the previous one. The controllers for the laser beam and the cooling circuit, which can be coupled, can be installed on the device or in a separate control unit which can be optionally actuated by the foot. It is also possible to provide power control devices. laser, depending on the color of the wick to be treated, this slaving can be performed automatically after reading the color by a suitable detector.

 The following examples illustrate the invention.

EXAMPLE 1
We take four strands of natural European hair of 0.25 g having a length of 20 cm. The wick n01 is subjected to three fading treatments (Formula No. 01) of 30 minutes.

Formula No. 1 60 g of the following formula: - Nonylphenol oxyethylenated (4 EO) 25 g - Nonylphenol oxyethylenated (9 EO) 20 g - Lauryl acid oxyethylenated (2 EO) 7g - Oleic acid 30 g - Propylene glycol 12 g - 1- hydroxy4 phenylaminoanthraquinone 0.05 g - Ammonia (20%) 7g - demineralised water qs 100 g mixed with 50 g of the following powder - sodium persulfate 30 g - potassium persulfate 25 g - anhydrous sodium silicate 3g - colloidal silica 0 4 g - ammonium chloride 12 g - 1-hydroxy-4-phenylamino anthraquinone 0.3 g and mixed in addition with 120 ml of the following solution - hydrogen peroxide 30 volumes 100 g - phosphoric acid qs pH 3
The wick No. 2 undergoes discoloration by laser irradiation according to the invention using the apparatus of the type shown in Figure I The source of laser radiation is a laser Suielite Continum; wavelength: 532 nm; firing frequency: 1 Hz; beam diameter: 5 mm; duration of the pulse: 4 ns.

 Both wicks have equivalent lightening. (It is to obtain a discoloration of the wick n "1 equivalent to that of wick nO 2 that it was necessary to treat three times the wick nO 1).

 The two wicks are wound, and a third undoloured on 9 mm diameter rolls, then the first permanent lotion (Formula No. 2) is applied for 15 minutes. Rinse, apply the second permanent lotion (Formula 3). Let sit for 5 minutes then rinse.

Formula 2: - Thioglycolic acid 10 g - Ammonia qs pH 9 - Demineralised water qs 100 g
Formula 3: - Oxygenated water qs 8 volumes - Citric acid qs pH 3 - Demineralised water qs 100 g
His wick No. 4, having undergone no treatment, serves as a control.

 The four locks are washed and compared.

curling
The locks 2 and 3 have good crimps. The first wick is practically not curly. The four wet and combed locks were suspended from one end. After a few minutes, the locks 2 and 3 have a curly appearance. The curls are tonics. The lower end of the hair has gone back up. The first wick does not go up. After a few minutes, measure the height of the locks (distance from the root to the tip without stretching the wick).

Wicks: height of the dry wick 1. Chemical discoloration then permanent 30 cm 2. Laser discoloration then permanent 22 cm 3. Permanent 22 cm 4. Natural 31 cm
The wicks nO 2, 3 and 4 have a pleasant and healthy touch. Wick # 1 has an abnormal, slippery or "softened" feel.

EXAMPLE 2
We perform a wicking on a hair of European person. For this purpose, about 50 locks of 0.5 g are disengaged and treated by the bleaching process according to the invention.

 Once the hair rinsed, the hair is wrapped on hair curlers 9 mm in diameter and is carried a strong permanent (lotion 2 and lotion 3, see Example 5). We remove the curlers and rinse. It is found that the hair is curled homogeneously. The discolored locks are just as curly as the natural locks. The touch of the whole hair is good.

EXAMPLE 3
It is performed on a hair of a European person a wicking on many small locks, called "scan". For this purpose, about 150 strands of 0.15 g which are treated by the fading process according to the invention are disengaged by means of a comb.

 Once the hair is rinsed, we dry the hair.

 Two weeks later, all the hair is rolled on hair curlers 9 mm in diameter and a strong permanent (lotion 2 and lotion 3 of Example 5). We remove the curlers and rinse. It is found that the hair is curled homogeneously.

The discolored locks are just as curly as the natural locks. The touch of the whole hair is good.

EXAMPLE 4
We take two strands of natural European hair brown and a lock of natural European hair 70% gray. The first is subjected to three bleaching treatments (formula nl) of 30 minutes using hydrogen peroxide, persalts and ammonia.

 The second wick undergoes discoloration by laser irradiation according to the invention.

 The first two wicks have equivalent lightenings.

The three locks are dyed with a coloring using a weight-for-weight mixture of formulas n04 and 5
Formula 4 - Para-phenylene diamine 0.1 g - Metahydroxyphenol 0.3 g - Metahydroxyphenol 0.1 g - Metaaminophenol 0.1 g - Ortho methyl meta N hydroxyethyl phenol 0.2 g - Ammonia (20%) 10 g - Alcohol ethyl 10 g - demineralised water qs 100 g
Formula n05 - Hydrogen peroxide 20 volumes 100 g - Phosphoric acid qs pH 2.5
It is observed that the first strand is very strongly dyed. The shade is a coppery-gold. The next two are moderately dyed and although the wick treated by the laser irradiation and then by the dye is a little darker than the natural wick treated by the dyeing, the shades are very close (chestnut-copper).

 In addition, when shampooing (6 shampoos) the three locks, we see that the shades of locks 2 and 3 hold very well. Conversely, the shade of the first wick is faded to give a yellow tint.

EXAMPLE 5
We take two strands of natural European hair brown and a lock of natural European hair 70% gray. The first is subjected to three bleaching treatments (formula n01) of 30 minutes using hydrogen peroxide, persalts and ammonia.

 The second wick undergoes discoloration by laser irradiation according to the invention.

 The first two wicks have equivalent lightenings.

 The three locks are placed under styling rollers.

 The three locks are treated with a lacquer employing a mixture of anionic polymer (formula No. 6).

Formula n06 - "Gantrez" neutralized to 100% by
aminomethyl propanol 5g - ethyl alcohol qs 100 g, the formula being pressurized with dimethyl ether (30 g per 100 g of formula).

 We see that the wicks 2 and 3 are softer and easier to unravel than the first.

EXAMPLE 6
We take two strands of natural European hair brown and a lock of natural European hair 70% gray. The first is subjected to three bleaching treatments (formula n01) of 30 minutes using hydrogen peroxide, persalts and ammonia.

 The second wick undergoes discoloration by laser irradiation according to the invention.

 The first two wicks have equivalent lightenings.

 The three locks undergo a treatment of 8 shampoos (formula n07) (0.5 g of shampoo per gram of hair).

Formula n07 - Sodium lauryl ether sulphate (2.2 EO) 15 g MA - Laurylbetaine 2.5 g - Demineralised water qs 100 g
It can be seen that the locks 2 and 3 are softer and easier to tear than the first one.

Claims (17)

 1. Improved process for the cosmetic treatment of bleached hair, characterized by the fact that said treatment is applied to faded hair by irradiation with the aid of laser radiation.  2. Method according to the preceding claim, characterized in that said cosmetic treatment is chosen from at least one of the following treatments: permanent deformation operation, dyeing, shampooing or application of a conditioning composition, lotion of styling or lacquer.  3. Method according to claim 1 or 2, wherein the hair has been bleached at least partially by irradiation of a wick or portion of wick using a laser beam of sufficient power to bleach hair.  4. Method according to claim 3, wherein, to carry out the discoloration  an area of said portion of wick is treated by irradiation with the aid of a laser beam emitted in the form of pulses to at least partially bleach the hair of said zone, by degradation of the melanin of the hair,  if necessary, by relative displacement of said wick with respect to said laser beam, one or more other zones are successively treated in a similar manner so as to treat all of said wick portion,  the previous treatments are optionally repeated until the desired degree of discoloration for said wick or part of wick is obtained,  - Operation is carried out with laser radiation of sufficient power to provide, by pulse, an energy density of 0.1 to 1.2 J / cm 2 at 532 nm, said chosen energy density not being greater than a threshold beyond which the keratin fiber of the hair is damaged, said threshold being all the lower as the natural color of the hair to be treated is darker.  5. Method according to claim 4, characterized in that one operates so as not to exceed a maximum energy density per pulse which is of the order of:  - 0.35 J / cm2 for Japanese type hair,  - 0.4 J / cm2 for dark brown hair,  - 0,5 J / cm2 for light brown hair,  - 0.7 J / cm2 for dark blond hair,  - 1.2 J / cm 2 for light blond hair, the energy density values being given here for a wavelength radiation of 532 nm, and to be multiplied by a correction factor equal to  532 when the radiation used has a wavelength x (expressed in nanometers) other than 532 nm.  6. Method according to the preceding claim, characterized in that one operates in such a way as to obtain an energy density (in joules / cm 2), per pulse, of  0.2-0.35 for Japanese type hair,  - 0.2-0.4 for dark brown hair,  - 0.15-0.5 for light brown hair,  - 0.15-0.7 for dark blond hair,  - 0.1-1.2 for light blond hair, the energy density values being given here for 532 nm wavelength radiation, and to be multiplied by a correction factor equal to x  532 when the radiation used has a wavelength λ (expressed in nanometers) other than 532 nm.  7. Method according to any one of the preceding claims, characterized in that in addition, during the fading step, when the hair to be treated are dyed with a coloring agent, a step is carried out additional hair irradiation, analogous to that described in any preceding claim, but with a higher energy density sufficient to destroy or degrade the coloring agent.  8. Method according to claim 7, characterized in that said higher energy density is at least 0.8 J / cm 2 per pulse at 532 nm.  9. Method according to any one of claims 3 to 8, characterized in that, during the bleaching, to avoid harmful local heating for the hair, the frequency of the pulses is limited and / or relative displacements are carried out. sufficient of the wick to be treated with respect to the laser beam, and / or the hair is cooled in the treated zone.  10. Method according to any one of claims 3 to 9, characterized in that, during the fading step, the wick is arranged beforehand so as to form a sheet of hair, and that the hair is discolored of the treated area by irradiating at least one of the faces of said web.  11. Method according to any one of claims 3 to 10, characterized in that, during the fading step  - It operates with a treatment device comprising a receptacle for the lock of hair to be treated, the surface of said receptacle having an orifice for the output of said laser beam,  at least a portion of their length is applied to the hair of said wick lying flat on the surface of said receptacle, so that an area to be treated is opposite said orifice,  the irradiation of said zone is carried out,  and by relative displacements of said wick relative to the laser beam, the other zones to be treated are successively irradiated.  12. The method of claim 11, characterized in that said relative movements comprise relative movements of said wick relative to said receptacle.  13. Method according to any one of claims 9 and 10, characterized in that said relative displacements are obtained by varying the direction of the laser beam so as to perform scans of the area to be treated.  14. Method according to any one of claims 9 to 13, characterized in that the hair is cooled by circulation of a fluid.  15. The method of claim 14, characterized in that the hair is cooled by creating a gas flow in the treated area.  16. Use of hair bleaching with laser radiation to improve cosmetic treatment processes performed on bleached hair.  17. Use according to the preceding claim, characterized in that said discoloration is carried out according to the method of any one of claims 4 to 15.