WO2009074957A1

WO2009074957A1 - A method of treating keratinous fibers, comprising exposing them to short-duration light pulses

Info

Publication number: WO2009074957A1
Application number: PCT/IB2008/055191
Authority: WO
Inventors: Henri Samain
Original assignee: L'oreal
Priority date: 2007-12-10
Filing date: 2008-12-10
Publication date: 2009-06-18
Also published as: FR2924597A1; FR2924597B1; US20110017227A1; WO2009080988A3; EP2229216A2; WO2009080988A2

Abstract

The present invention relates to a method of cosmetically treating keratinous fibersmade of hair, comprising subjecting the fibers to light pulses that are emitted by a treatment apparatus and that are of duration less than or equal to 5×10 -12 s.

Description

A METHOD OF TREATING KERATINOUS FIBERS, COMPRISING EXPOSING THEM TO SHORT-DURATION LIGHT PULSES

The present invention relates to methods of treating human or animal keratinous fibers, by exposing them to short-duration light pulses, for example a head of hair.

It is known that hair can be bleached lastingly by exposing it to short-duration light pulses having relatively large peak power.

Publication EP 0 685 220 discloses a method of bleaching hair by irradiation with a neodymium-doped yttrium aluminum garnet (YAG) laser, it being possible for the duration of the pulses to lie in the range 10 nanoseconds (ns) to 100 ns, for example.

Publications EP 0 682 937, EP 0 685 180, and US 2007/0167936 disclose other methods and apparatus for treating keratinous fibers using lasers.

Choosing the irradiation parameters is critical because, outside the required conditions in terms of pulse duration and peak power, the bleaching of the melanin of the hair might no longer take place or the hair overheats and is damaged to the point of being burnt .

The range over which the lasers used in the above publications are effective in bleaching is not very wide, and there therefore exists a non-negligible risk of going outside that range.

Certain flash-pumped lasers give pulses ranging from about ten picoseconds (ps) to a few tens of ns . Those lasers deliver very high excitation energy but they require relatively low firing rates, lying approximately in the range one hertz (Hz) to a few tens of Hz.

Certain diode-pumped lasers of the "Q-switched" type have pulse durations ranging from 100 ps to about 1 microsecond (μs) . Diode-pumping procures pulse energy that is lower than the pulse energy procured in flash- pumped mode, but it makes it possible to achieve higher rates. As a result, each pulse can treat only a relatively small surface area, but it is possible to compensate for that drawback by sweeping the surface to be treated, such sweeping being made possible by the higher rate. There exists a need for further improving methods of treating keratinous fibers with light, and, for example, for further reducing the risk of going outside the effectiveness range.

An object of the invention, in one of its aspects, is to satisfy that need, and it achieves this object by means of a method of treating keratinous fibers, comprising the step consisting in subjecting the fibers to light pulses emitted by treatment apparatus, in particular light pulses that are visible, infrared, or ultraviolet light pulses, of duration less than or equal to 5 x ICT¹² seconds (s) , or better still less than or equal to 2 x 10^~12 s. Said treatment apparatus advantageously comprises a laser.

For example, the treatment is a treatment for bleaching hair, it being possible for the hair to have its natural color or to be colored artificially, the bleaching being performed with a view to the hair being dyed so as to be colored differently or with a view to it returning to its natural color. The treatment of the invention can also be used to treat hair for effects other than bleaching, e.g. for transforming the keratin (rearranging or transforming proteins, at the primary, secondary, or tertiary level) , with effects, for example, on shape, softness, and/or sheen.

It is possible to focus the light onto the surface of a hair, in order to obtain very high local energy, with spatial resolution that can be very fine, e.g. of the order of one micrometer. The result of these impacts is that the keratin is transformed only at the location where the impact takes place. If the light is focused onto the surface of each individual hair, it is possible to modify the surface without damaging or transforming the core of each hair or each hair as a whole. This can make it possible to plane the surface so as to gain softness or sheen, or it can make it possible to generate roughness or patterns.

By focusing the light from the laser in the form of a multitude of tiny points (of size of the order of one micrometer, for example) , it is possible to obtain an effect of a change in the feel or in the styling properties, e.g. propensity to curl or to untangle, stiffness, etc.

By focusing onto the inside of each hair, it is possible to heat the keratin locally and to modify it without modifying or degrading the surface. This can make it possible to melt the keratin locally in order to gain strength or rigidity, or in order to repair damaged fibers .

The treatment may be performed in such a manner as to increase the porosity of the fibers. This can be advantageous, especially for natural hair, because certain fibers are difficult to permeate for exogenous compounds such as dyes, for example.

Exposure to laser radiation may be used to modify proteins and to cauterize the hair, hair points, split ends, or indeed hair ends.

The invention may also be implemented for cutting into the hair.

The treatment may concern at least one lock of hair, e.g. at least ten locks of hair, each lock of hair being, for example, at least 10 centimeters (cm) in length and at least 0.5 cm in width, or the treatment may concern the entire head of hair or more local zones thereof.

The keratinous fibers treated may be dry or otherwise, e.g. damp or wet.

The treatment may also concern eyelashes, eyebrows, or facial or body hair. The term "visible light" is used to mean that the spectrum of the light received by the keratinous fibers contains at least one wavelength in the range 380 nm to 750 nm. The pulses received by the keratinous fibers may have at least one dominant wavelength in any one of the ranges 1000 nm to 1600 nm, 700 nm to 900 nm, 350 nm to 450 nm, and 500 nm to 800 nm.

The term "duration" of a pulse is used to designate the time α for which the light power reaching the keratinous fibers is greater than or equal to one half of its peak power P_c, as shown in Figure 1.

The number of light pulses to which the same region of keratinous fibers may be exposed can depend on the energy density (energy per unit area) of the radiation that reaches the keratinous fibers, on the color thereof, and on the treatment to be performed, e.g. on the degree of bleaching that is desired.

Treatment of the keratinous fibers by local exposure to a plurality of successive pulses can be advantageous because it makes it possible, in particular, to achieve bleaching treatment that is more progressive, and it can further reduce the risk of damaging the keratinous fibers . Spraying a cooling gas flow onto the keratinous fibers may be unnecessary.

The duration of a pulse may lie in the range 10^~15 s to 5000 x 10^~15 s, or better still 10^~15 s to 1000 x 10^~15 s, or even better still 10 x 10^~15 s (10 femtoseconds) to 800 x 10^~15 s (800 femtoseconds), with a frequency that is, for example, greater than or equal to 100 Hz, better still greater than or equal to 1 kilohertz (kHz) , and even better still 1 megahertz (MHz) .

The pulses may be emitted at a frequency that depends, for example, on the laser used and on the speed at which the keratinous fibers are swept, if they are swept at all. Light pulses of short duration may be obtained, for example, by using a broadband laser associated with mode- locking apparatus, capable of locking a large number of modes of the cavity of the laser with good phase stability, e.g. a laser whose amplifier material is titanium-sapphire, or an erbium-doped or ytterbium-doped material, in fiber or crystal form.

The light received by the keratinous fibers is advantageously non-monochromatic, the spectral width of the pulses received by the keratinous fibers being, for example, greater than or equal to 200 nm. Under certain circumstances, the bandwidth may be even broader, and may, for example, extend from the infrared to the ultraviolet (UV) . A relatively broad spectrum may be useful for reinforcing the effectiveness of the method, when the compounds that it is desired to reach in and/or on the keratinous fibers have relatively broad absorption bands, which is true, for example, for melanin, and can be true for other colorants previously applied to the keratinous fibers .

The treatment apparatus may further comprise nonlinear optical apparatus associated with the laser in order to broaden the emission spectrum of the radiation emitted by the laser. As mentioned above, a relatively broad spectrum can improve effectiveness, in particular on melanin. In an implementation of the invention, the spectrum received by the keratinous fibers may thus be broadened to the extent of ranging from the ultraviolet to the infrared, and of generating a light that appears white .

A relatively broad spectrum can also be advantageous in that it makes it possible to treat dyed hair, containing melanin and at least one other colorant, because those compounds can then be reached simultaneously. The non-linear optical apparatus may, for example, comprise a photonic-crystal optical fiber.

The treatment apparatus may further comprise a frequency doubling unit associated with the laser, in particular when said laser emits in the infrared.

Where applicable, the treatment apparatus may be wavelength-tunable .

The light emitted by the treatment apparatus may be centered on a wavelength lying in the range 400 nm to 440 nm, within which melanin absorbs particularly well.

The laser from which the pulses are generated may be a titanium-sapphire laser and may advantageously be associated with a frequency doubling unit, thereby making it possible to obtain pulses centered around 400 nm. The treatment apparatus may thus further comprise collimation apparatus for collimating the light beam emitted by the laser, thereby making it possible to use a laser that is less powerful and thus less costly, while achieving an energy level that is sufficient to destroy selectively the melanin or any other compound, or to obtain the desired reaction.

Where applicable, the collimation apparatus may be adjustable, in order to enable the energy density reaching the keratinous fibers to be adjusted, this adjustment being performed, for example, as a function of the initial color of the keratinous fibers to be treated or of the desired degree of bleaching. The collimation apparatus may be adjustable manually or automatically.

The treatment apparatus may thus further comprise a lens associated with the laser, e.g. a lens having a numerical aperture lying in the range 0.1 to 1. Lenses having such numerical apertures are, for example, known from certain kinds of recent optical storage disk reader equipment . It is possible to use a laser whose mean electrical power lies in the range 0.001 watts (W) to 50 W, for example. Given the rapidity of each pulse, the lasers useful to the invention may deliver peak power in range 100 megawatts (MW) to 100 gigawatts (GW) .

The pulses useful to the invention have, for example, energy density of the order of one joule per square centimeter (J/cm²) . Depending on the efficiencies, on the pulse durations, and on the hair, said energy density may vary in the range 0.01 J/cm² to 10 J/cm², for example .

Low power can facilitate implementing treatment apparatus that operates with an independent energy source, such as batteries, rechargeable or otherwise.

The target surface illuminated by a pulse may have its largest dimension greater than or equal to 0.1 micrometers (μm) and/or less than or equal to 100,000 μm.

The keratinous fibers and the treatment apparatus may be caused to move relative to each other during the treatment .

The keratinous fibers may be treated in a single pass or in a plurality of passes.

The method of the invention may further comprise applying a composition to the keratinous fibers prior to exposure to the light pulses, e.g. a composition comprising: a) at least one oxidizing or reducing agent; these compounds are not necessarily involved in the laser impact process but they can serve to supplement the bleaching by attacking artificial colorants specifically, for example; b) at least one colorant; said at least one colorant can be applied at the same time as the laser impact or immediately therebefore or thereafter, which makes it possible to save time in the overall treatment; for example, a colorant is applied at substantially the same time as the exposure to the laser radiation is performed; as a result, the hair comes out dyed and the melanin comes out bleached; therefore, the coloring is particularly visible.

In another of its aspects, the invention also provides apparatus for treating keratinous fibers, which apparatus comprises:

^• a light source arranged to emit light pulses of duration less than or equal to 2 x 10^~12 s; and

^• a system making it possible to direct the pulses towards the keratinous fibers to be treated. This system may, for example, include a handheld instrument .

The source may comprise a laser, in particular a "femto" laser emitting light pulses of duration of the order of magnitude of in the range 1 femtosecond to 10 picoseconds.

An advantage related to using a femto laser for treating the keratinous fibers is that, by means of its small geometrical extent (product of the area multiplied by the emission solid angle) it is possible to collimate the beam onto a very small area. This makes it possible to concentrate the energy onto very small zones and thus to use a laser having relatively low mean power and/or having relatively low energy per pulse, resulting in advantages in terms of price, consumption, and compactness.

It is possible to compensate for this low energy by extensive sweeping of the surface of the lock of hair, which is possible because femto lasers make it possible to achieve rates as high as one GHz in certain configurations, without losing the quality and the duration of the pulses. Crystal-based femto lasers are well suited to such high rates.

By way of example, the laser used in the treatment apparatus is a laser having a cavity formed by two mirrors situated on either side of a broadband amplifier material, in particular titanium-sapphire or ytterbium, and mode-locking apparatus. The pumping light may be generated by at least one flash lamp or by at least one diode .

The laser may further comprise a cavity formed by a fiber of an amplifier material, e.g. titanium-sapphire or ytterbium, a coupler for injecting the pumping light, a coupler for extracting the laser pulses, and mode-locking apparatus. The pumping light is advantageously generated by at least one diode, but, in a variant, said light is generated by a flash lamp or by a laser. The treatment apparatus may further comprise nonlinear optical apparatus receiving light from the laser, and comprising, for example, a photonic-crystal fiber.

The treatment apparatus may further comprise a frequency doubling unit receiving the light emitted by the laser.

The treatment apparatus may be arranged to determine at least one of the following: the number of pulses that should reach the zone to be treated; the frequency of the pulses; and the energy density per pulse; as a function of the initial color of the keratinous fibers to be treated. Thus, the darker the hair, the higher the number of pulses and/or the energy density per pulse can be.

The treatment apparatus may also be arranged to determine, automatically, at least one of the following: the number of pulses; the frequency of the pulses; and the energy density per pulse; as a function of the desired post-treatment color. Thus, the lower the degree of bleaching, the lower the energy density can be. The treatment apparatus may further comprise color analysis apparatus for assisting the bleaching treatment. By way of example, said color analysis apparatus may be used to determine the color of the keratinous fibers prior to treatment, for example, in order to determine the number of light pulses necessary for achieving the desired bleaching of a given zone of the keratinous fibers. The lighter the fibers, the higher said number of pulses can be.

The color analysis apparatus may also serve to determine the moment at which a predetermined degree of bleaching is achieved. After each pulse, the fibers are a little more bleached, so that, by analyzing the color of the fibers during the treatment, it is possible to detect the moment at which the desired color is achieved. The color analysis apparatus for analyzing the color of the keratinous fibers can thus be useful for preventing further exposure to the light pulses of those keratinous fibers for which the color analysis apparatus indicates that they have already been sufficiently bleached. By way of example, the color analysis apparatus may, for example, comprise a color camera or any other suitable detector.

The shape of the light spot reaching the keratinous fibers when a light pulse is emitted may be circular or polygonal, e.g. substantially square or rectangular, or of some other shape. A polygonal shape can be advantageous for enabling a zone that is to be treated to be swept completely, by juxtaposition of the light spots. At least two different zones to be treated of the keratinous fibers may be exposed successively to the light pulses in various manners.

By way of example, the light pulses may be emitted by a treatment head that is moved relative to the keratinous fibers on going over from treating a first zone to treating a second zone. It is then possible to trigger emission of the light pulses as a function of the movement of the treatment head relative to the keratinous fibers, in order, for example, to prevent the same region of keratinous fibers from receiving more than a predefined number of pulses, each time the treatment head passes in amongst the keratinous fibers to be bleached. The treatment head may be moved relative to the keratinous fibers manually, the treatment head belonging to a handheld instrument. In a variant, the treatment head may be moved relative to the fibers in automated manner.

By way of example, the treatment apparatus may further comprise at least one actuator, e.g. a robot, making it possible to move the treatment head relative to the keratinous fibers. The laser may be secured rigidly to the treatment head or it need not be secured rigidly thereto. In particular, the laser may be connected optically to the treatment head via a flexible cord. Said flexible cord may comprise at least one optical fiber. Regardless of whether the treatment head is stationary or otherwise during the time taken for treating a given zone, it is possible to cause the direction in which the light pulses are emitted relative to the keratinous fibers to vary. By modifying over time the orientation of the beam directed towards the keratinous fibers, such a sweeping movement may optionally be combined with a movement of the treatment head relative to the keratinous fibers, along said fibers. The sweeping may also take place, without necessarily modifying the orientation of the light beam directed towards the keratinous fibers, e.g. by using a ribbon cable of juxtaposed optical fibers that are illuminated sequentially. Regardless of the manner in which the sweeping is obtained and by way of example, said sweeping may take place in a first direction and the movement of the treatment head relative to the keratinous fibers may take place in a second direction that is substantially perpendicular to the first direction. The speed of sweeping in the first direction may depend on the speed of sweeping in the second direction, and vice versa. It is possible to treat at least two different regions of the keratinous fibers differently.

The bleaching may thus take place in non-uniform manner over the keratinous fibers, in order to create effects. For example, the bleaching may take place in discrete regions, which may be disposed as matrix dots, for example. It is thus possible to expose the keratinous fibers selectively in order to achieve a dot- matrix pattern. The bleaching may take place in a checkerboard pattern or in other patterns. It is also possible to interpose a mask in the path of the light, making it possible to form a pattern having a predetermined outline on the keratinous fibers.

The keratinous fibers may be coated with a composition forming a screen to the light pulses at the locations that it is not desired to treat, e.g. a composition comprising one or more inorganic materials, such as pigments, aluminas, silicas, nitrides, carbides, carbonates, and compounds based on titanium or on silicon. One or more organic or mixed organic and inorganic materials such as polymers, gels, or fluids, may optionally contain pigments.

Such a composition may be cold (of temperature at least 5°C below ambient temperature) or very cold (of temperature at least 20⁰C below ambient temperature) .

The scalp and/or the skin may also be coated with a screen-forming composition, e.g. a composition comprising at least one of the above-listed compounds.

The keratinous fibers may also be coated with compositions facilitating the treatment, e.g. a gel reducing losses by reflection of the light at the fiber/air interface. For example, the composition may extend continuously between the optical medium of the treatment apparatus, through which medium the light pulses propagate, and the keratinous fibers.

Such a treatment-facilitating composition may be deposited on the hair in such a manner as to cause the path of the light to be made more rectilinear. Preferably, this composition is of refractive index that is, if possible, close to the refractive index of the hair. It is also preferable for the composition to gum the hair and to form a surface that is smoother than the hair itself.

The treatment-facilitating composition may comprise a gel, e.g. carbomer, a guar gum, or an inorganic or organic liquid, e.g. a silicone, a vegetable oil, or paraffin oil, etc.

It is also possible to achieve a desired degree of bleaching by treating the keratinous fibers partially only, in such a manner as to cause the regions having the different degrees of bleaching to be juxtaposed. These regions that have different colors at the microscopic scale can, when observed from a certain distance, no longer be discernable individually with the naked eye, and, by color mixing, generate an intermediate color. It is possible to achieve bleaching that is graduated over a head of hair, e.g. by modifying the spatial frequency and/or the size of the regions bleached by exposure to the light pulses.

Once the bleaching has been performed, it is then possible, where applicable, to perform coloring of the keratinous fibers.

When treating a head of hair, after a lock of hair has been bleached, it is possible to maintain said lock of hair isolated from the remainder of the head of hair while the lock of hair is being colored. The treatment apparatus may further comprise detection apparatus making it possible to check whether keratinous fibers are present facing the treatment head, and may be arranged to prevent light pulses from being emitted in the absence of keratinous fibers. The treatment apparatus may be arranged so as to form a screen to light outside a treatment space, and may further comprise means making it possible to prevent light from leaking beyond the treatment space. Said means may, for example, be constituted by a flexible gasket, by a row of bristles, or by a baffle.

The treatment apparatus may further comprise, e.g. at the handheld instrument, two portions mounted to move relative to each other, e.g. in the form of prongs, arranged to close onto the keratinous fibers. The treatment space is defined between these moving portions, which are, for example, hinged together. The treatment apparatus may be arranged to detect closure of the treatment space and to authorize emission of the light pulses only if this condition is satisfied. The treatment apparatus further comprises, for example, a switch actuated on closure of the treatment space. The treatment apparatus may further comprise pieces in relief, e.g. teeth, arranged to emit the light towards the keratinous fibers. The light can exit between the teeth.

The treatment apparatus may be arranged to detect relative movement between the keratinous fibers and the treatment head, and to allow emission of the pulses only in the event of movement, in order to avoid burning or excessively bleaching the hair in the absence of movement . The treatment head may further comprise an applicator member suitable for applying a substance to the keratinous fibers, e.g. to a lock of hair. This applicator member comprises, for example, an inking pad. The treatment head may be arranged so that the applicator member applies the above-mentioned substance after the keratinous fibers have been exposed to the light pulses. The substance may be a hair coloring substance or a care product.

The treatment head may further comprise means for combing a lock of hair before and/or after said lock of hair is inserted into the treatment head. The invention can be better understood on reading the following detailed description of non-limiting implementations thereof, and on examining the accompanying drawings, in which: • Figure 1, described above, diagrammatically shows how the power of a pulse received by the keratinous fibers varies as a function of time;

^• Figure 2 is a diagrammatic and fragmentary view of treatment apparatus of the invention; • Figure 3 is a diagrammatic and fragmentary view showing the use of the treatment apparatus of Figure 2;

^• Figures 4 and 5 are diagrammatic and fragmentary views respectively in longitudinal section and in cross- section on V-V, showing the treatment head of the apparatus of Figure 2;

^• Figure 6 shows how a lock of hair is swept;

^• Figures 7 to 9 are diagrammatic and fragmentary views of variants of processing heads of the invention; and • Figures 10 to 12 are diagrammatic and fragmentary cross-sectional views of other variants of treatment heads of the invention.

The treatment apparatus 1 for treating keratinous fibers that is shown in Figure 2 comprises a base station 2 and a handheld instrument 3 connected to the base station .

The handheld instrument 3 is arranged to receive a lock M of hair to be treated and to expose the hair to the light pulses in a treatment space, as shown in Figure 3.

The base station 2 can comprise all or some of the means necessary for generating the light pulses for treating the keratinous fibers, and, in particular, can comprise a pulse light source such as a laser. The handheld instrument 3 can be connected to the base station via at least one flexible cord 4 making it possible to convey the light pulses towards the keratinous fibers, said at least one flexible cord comprising, for example, one or more optical fibers.

In a variant, the light pulses are emitted from the handheld instrument 3, the base station 2 comprising, for example, an electrical power supply and a system for controlling operation of the handheld instrument 3.

In another variant, the base station 2 does not exist, and the treatment apparatus is entirely incorporated into the handheld instrument 3. The treatment apparatus 1 can also be implemented without a handheld instrument 3, it being, for example, in the form of a booth inside which the user is placed, the irradiation of the hair taking place remotely, it being possible for the hair to have been previously prepared for the treatment, e.g. by being placed on a suitable support or backing.

The handheld instrument 3 can, as shown, further comprise a handle 6 and a push-button 7 making it possible to trigger emission of the light pulses. The handheld instrument 3 incorporates a treatment head that can comprise an optical deflector making it possible to deflect the light that it receives in order to sweep at least one fraction of the zone to be treated. Said optical deflector can comprise a moving mirror, in particular an oscillating mirror.

The flexible cord 4 can further comprise one or more electrical cables making it possible to exchange information between the handheld instrument 3 and the base station 2. The flexible cord 4 can further comprise a cable making it possible to convey to the base station 2 a signal representative of a pressure on the button 7.

The treatment apparatus can further comprise collimation apparatus (or "focusing" apparatus) placed in the path of the light between the light source and the keratinous fibers to be treated, in order, for example, to increase the energy density of the light beam directed onto the keratinous fibers and/or to make it possible to adjust the energy density per unit area.

Such collimation apparatus is, for example, incorporated into the handheld instrument, and can, for example, be situated upstream from the optical deflector. The collimation apparatus comprises, for example, a convergent lens, e.g. of numerical aperture lying in the range 0.1 to 1, but, without going beyond the ambit of the present invention, the collimation apparatus can be otherwise and comprise one or more convergent, divergent, or other lenses.

The treatment apparatus 1 can further comprise computer means 13, a screen 14, and a keyboard 15, as shown in Figure 2. The keyboard 15 can, for example, make it possible to input the initial color of the fibers, the desired degree of bleaching, or the desired final color after bleaching, but other acquisition means can be used, e.g. a scanner 16 or a camera. The computer means 13 can comprise a microcomputer or other computer or electronic means .

The computer means 13 can be arranged to act on the emission of the light pulses, in particular on the triggering, the frequency, and/or the power thereof, and on the optical deflector, if it is present, in particular on the angular positioning thereof, on the focusing apparatus, if it is present, and to process information coming from the handheld instrument, such information coming, for example, from the button 7, from a camera, if one is present, disposed in the handheld instrument, or relating to other sensors incorporated into said handheld instrument, e.g. so as to detect movement of the hair relative to the handheld instrument 3.

The computer means 13 can be programmed to determine automatically at least one of following: the number of pulses; the frequency of the pulses; and the energy density per pulse; as a function, for example, of the final color of the fibers after bleaching and/or of the initial color of the fibers.

The screen 14 can make it possible to view, prior to treatment, the head of hair that is to be obtained after treatment, e.g. in the form of a two-dimensional (2D) or three-dimensional (3D) image.

The computer means 13 can also make it possible to select an image of a desired head of hair and to determine the treatment to be performed on the head of hair in order to obtain a head of hair as in the selected image, in particular when the treatment involves forming a pattern on the head of hair.

The selected pattern can be selected from a library of images stored in a memory, or it can be read from a photograph, e.g. by means of the scanner 16. It is thus possible, for example, to acquire an image, e.g. a logo, by using the scanner 16, and to draw said logo on the head of hair by selectively bleaching said head of hair.

In the example shown, the computer means 13 are external to the base station 2, but they can also be incorporated at least partially into the base station or into the handheld instrument in variants that are not shown .

The laser of the treatment apparatus makes it possible to generate light pulses of very short duration, in particular less than 5 x 10^~12 s.

In an implementation of the invention, the laser used is an optical fiber laser such as, for example, the laser sold by the German company Toptica Photonics AG under the reference "FFS (FemtoFiber Scientific) ultrafast erbium fiber laser system", comprising an oscillator "FFS. bu Base Unit", an amplifier "FFS. sys", a tunable second harmonic generation (frequency doubling) unit "FFS.tshg", and a continuous light generator "FFS.cont".

In this example, it is possible to place a collimator at the beam outlet so as to obtain zones having a diameter of about 2 μm on the hair. Prior to collimation, the beam can be sent to an optical deflector, the sweeping speed being 100 Hz for example.

Such a laser is capable of emitting at a rate of 100 MHz, each pulse being of duration of about 100 femtoseconds, and the spectral coverage of the apparatus extends approximately from 525 nm to 700 nm. Such a range does not correspond to the spectral range of the light exiting from the laser itself, but rather it corresponds to the range of the light exiting from the apparatus, it being understood that it is the module (s) disposed after the laser (dispersion, compression, and doubling modules) that result in this range. The treatment apparatus using said laser makes it possible to treat dark locks of hair in one second by 100,000,000 points having a diameter of 2 μm, i.e. about 400 square millimeters (mm²) .

In another implementation of the invention, the laser used is a laser sold under the reference "Femtoregen IC 1035-1000 FS HE Reg Amp" by the Austrian company High Q Laser. At the outlet of such an ytterbium crystal laser, it is possible to dispose a frequency doubling unit, an optical deflector, and a collimator, until zones having a diameter of 100 μm per pulse are obtained. The laser is capable of emitting at a frequency of 1 kHz, each pulse being of duration of about 400 femtoseconds and having a dominant wavelength of about 515 nm.

The treatment apparatus comprising such a laser makes it possible to treat dark locks of hair in one second by 1,000 points having a diameter of 100 μm, i.e. about 10 mm².

Another example of a laser having very short pulses is proposed by Amplitude System, a company located in Pessac, France, under the reference "Laser t-pulse 200" and makes it possible to sweep at a frequency of 100 Hz over an angular range of ±10°. In another example, the laser used is a laser sold by the French company Thales Laser and known under the name "BRIGHT ULTRAFAST KHZ SERIES". That laser emits pulses of duration of about 120 femtoseconds, with energy per pulse of about 1.5 millijoules (mJ) , at the rate in range 1 pulse per second to 5000 pulses per second. The light is centered around 780 nm. A frequency doubling module (Thales Laser module) is added to the laser, thereby making it possible, when said module is connected, to achieve a frequency centered around 390 nm.

The apparatus further comprises a lens making it possible to act, by focusing, to adjust the energy density, and the size of the spot.

A second filter optical apparatus makes it possible to adjust the energy density without modifying the size of the spot.

Hair is irradiated with this apparatus and it is possible, depending on the use, to obtain bleaching of zones of hair, or effects of modification of the keratin with small melted points in the surfaces of the hairs.

The handheld instrument 3 can be in various configurations making it possible to expose keratinous fibers to the treatment light.

The handheld instrument 3 can further comprise any means for receiving and guiding hair, e.g. as can be seen in Figure 2, a groove 10 formed between a top branch 12 and a bottom branch 13, defining the treatment space.

The branches 12 and 13 can be stationary relative to each other or, in a variant, they can be arranged in such a manner as to move apart in the manner of pliers, for example, in order to make it easier for the keratinous fibers that are to be treated to be put in place between them.

Closure of the branches can be detected in order to prevent pulses from being emitted in the event that the branches are not closed. Screen-forming means can be disposed between the branches on either side of the treatment space, in order to prevent light leaks, e.g. a flexible gasket, a row of bristles, or a baffle. At lest one of the branches, e.g. the bottom branch, can, in its face facing the other branch, be provided with an outlet window 14 making it possible for the light to reach the fibers to be treated, as shown in Figures 4 and 5. One or more mirrors 15 or other light-guide means can be disposed inside the handheld instrument 3, so as to steer the light pulses appropriately towards the outlet window 14.

The handheld instrument 3 can be provided with a single outlet window 14 in one of the branches only, the other branch then constituting a screen making it possible to absorb the residual light passing through the lock of hair M.

In a variant, the handheld instrument 3 can be provided with means for exposing at least two opposite faces of the lock of hair M simultaneously to the light pulses .

For this purpose, the handheld instrument 3 can be provided with a second outlet window in the top branch, facing the bottom branch, and with means making it possible to subdivide the laser radiation into two beams, so that the light pulses are emitted from each branch towards the keratinous fibers. Said means can, for example, comprise at least one semi-reflective surface or a plurality of optical fibers.

Where applicable, each branch is fed alternately with the light to be projected onto the fibers. In order to feed the branches alternately, the above-mentioned optical deflector can, for example, deflect the light alternatively towards one branch and then towards the other branch, or alternately towards respective ones of two optical fibers conveying the light to the outlet windows .

The sweeping of the keratinous fibers with the light beam coming from the treatment head takes place, for example, in the direction Di perpendicular to the direction D₂ in which the handheld instrument is moved relative to the lock of hair M, as shown in Figure 6. As a function of the ratio between the sweeping frequency and the emission frequency at which the light pulses are emitted by the laser, the same region of the keratinous fibers can be exposed successively to more than one light pulse during a sweeping cycle.

The number of pulses to which the same region is exposed can be determined as a function of the energy density, or vice versa, by using, for example, relationships involving the emission frequency at which the light pulses are emitted by the laser.

The bleaching of the keratinous fibers can be uniform or otherwise. For example, the treatment device can be arranged so that light pulses reach only certain zones of the keratinous fibers at each sweeping cycle, so as to bleach differently at least two keratinous fibers that are situated in said zones. For example, it is possible to lighten only certain regions of the keratinous fibers so as to obtain an intermediate tone between the initial color of the lock of hair and white.

It is also possible to achieve bleaching that is graduated over the head of hair.

In order to obtain bleaching that is graduated along the lock of hair, it is possible, for example, to increase the energy density per unit area received by the keratinous fibers while the treatment head is being moved therealong, e.g. by acting on the frequency of the pulses . It is also possible to effect a plurality of passes and to cause the number of passes to depend on the position on the head of hair.

It is also possible to cause the speed with which the handheld instrument 3 is moved relative to the keratinous fibers to vary, it being possible for a movement at a slow speed to make it possible to expose the keratinous fibers to energy that is higher than at a fast speed. It is also possible to cause the dimensions of bleached regions alternating with non-bleached regions to vary.

Figure 7 diagrammatically shows a variant of handheld instrument 3 that is provided with a groove for receiving fibers to be treated that is formed on a single branch.

In this example, the handheld instrument 3 is not provided with a screen making it possible to absorb the residual light passing through the lock of hair M. In the example of Figure 2, the handheld instrument 3 is moved manually relative to the hair, but, without going beyond the ambit of the present invention, it is possible for the treatment head to be moved relative to the keratinous fibers in automated manner. By way of example, Figure 8 shows, very diagrammatically, a treatment head connected to an actuator 20 making it possible to move it relative to the hair .

The treatment apparatus can further comprise combing means for combing the lock of hair M before and/or after exposure to the treatment light, it being possible for said combing means to comprise pieces in relief that are transparent to the treatment light.

The handheld instrument can, in particular, further comprise one or more teeth 24 or other pieces in relief placed before and/or after the treatment space, as shown diagrammatically in Figure 10. It is possible to cause the pulses to be emitted as a function of the movement of the treatment head relative to the hair.

The handheld instrument 3 can further comprise means making it possible to determine the speed of movement of the lock of hair M exposed to the light pulses relative to the treatment head. Said means can comprise at least one rotary member that is mounted to turn under the effect of the lock of hair M moving in the treatment head in order to enable the treatment apparatus to compute the power and/or the number and/or the frequency of the light pulses automatically as a function of said speed of movement, and/or to synchronize the triggering of the pulses with the movement of the lock of hair M. By way of example, Figure 11 shows a treatment head having two opposite rollers 30 that are mounted to turn in contact with the lock of hair M inserted between them.

The rotation of the rollers 30 is measured, and the treatment apparatus can further comprise computer means adapted to act on the emission of the light pulses as a function of said rotation.

The treatment apparatus can further comprise means for not subjecting the same region of the fibers twice to more than a predefined number of pulses when the handheld instrument 3 is stationary relative to the keratinous fibers, in order not to damage said fibers.

The treatment apparatus 1 can, to this end, further comprise at least one apparatus for measuring the color of the fibers. In the example shown in Figure 12, the color of the keratinous fibers is determined in real time or almost in real time by using a camera 40 received in the treatment head, and that is shown very diagrammatically . Naturally, without going beyond the ambit of the present invention, it is possible for said camera 40 to be replaced by any other suitable color detector. The image generated by the camera 40 is, for example analyzed in order to determine the degree of bleaching of the keratinous fibers. Once the desired degree of bleaching is achieved, the light pulses are no longer emitted.

The camera 40 can also serve to verify the presence of a lock of hair M to be treated or to determine the speed of movement of the keratinous fibers relative to the treatment head, by analyzing the speed of movement of the boundary between the bleached regions and the non- bleached regions, relative to the treatment head.

The treatment apparatus can be arranged in a manner such as to dye the hair while the lock of hair M is moving . For this purpose, the handheld instrument 3 can further comprise an applicator member 50 comprising, for example, an inking pad making it possible to deposit a colorant substance on the lock of hair M, as shown in Figure 9. Said inking pad is carried by a support that does not hinder the lock of hair M in its passing between the branches 12 and 13.

A substance other than a colorant substance can be applied upstream of the treatment space, e.g. a substance making it easier for the hair to slide. A substance insensitive to the wavelength of the light received by the keratinous fibers or, conversely, activated by said light can also be applied to the fibers prior to the bleaching treatment, e.g. in order to facilitate said treatment, or in order to obtain a particular coloring. Variant implementations (not shown) of the invention can combine characteristics coming from the various implementations that are described above.

In other aspects, the invention also relates to the use of light pulses emitted by a laser for performing certain treatment on keratinous fibers, the pulses emitted by the laser being as defined above or having other time or spectrum characteristics, the pulses being sufficiently short and intense to procure the desired result .

In said other aspects:

^• the keratinous fibers can be subjected to pulses focused onto the cores of the fibers;

^• the keratinous fibers can be subjected to the pulses in order to modify their porosity and/or their mechanical properties, in particular their styling properties; • the keratinous fibers can be subjected to the pulses in order to modify their sheen, e.g. in order to smooth their surfaces;

^• the keratinous fibers can be subjected to the pulses in order to repair damaged fibers; • the keratinous fibers can be subjected to the pulses in order to modify their feel; or

^• the keratinous fibers can be subjected to the pulses in order to cauterize them, in particular in order to cauterize their points, split-ends, or the extremities of split ends.

The expression "comprising a" should be understood to mean "comprising at least one" unless otherwise specified.

Claims

1. A method of cosmetically treating keratinous fibers made of hair, comprising subjecting the fibers to light pulses that are emitted by a treatment apparatus and that are of duration less than or equal to 5 x ICT¹² s.

2. A method according to claim 1, the duration lying in the range 10^"15 s to 1000 x 10^"15 s.

3. A method according to any preceding claim, the duration lying in the range 10 x 10^~15 s to 800 x 10^~15 s.

4. A method according to any preceding claim, the spectral width of the emitted pulses being greater than or equal to 1 nm.

5. A method according to any preceding claim, the pulses having at least one dominant wavelength in any one of the ranges 1000 nm to 1600 nm, 700 nm to 900 nm, 350 nm to 450 nm, and 500 nm to 800 nm.

6. A method according to any preceding claim, the treatment apparatus (1) comprising a laser.

7. A method according to the preceding claim, the treatment apparatus further comprising a non-linear optical apparatus associated with the laser in order to broaden the emission spectrum of the radiation emitted by the laser.

8. A method according to claim 7, the non-linear optical apparatus comprising a photonic-crystal optical fiber.

9. A method according to any one of claims 6 to 8, the treatment apparatus further comprising a frequency doubling unit associated with the laser.

10. A method according to any one of claims 6 to 9, the light emitted by the laser being centered on a wavelength situated in the range 400 nm to 440 nm.

11. A method according to any one of claims 6 to 10, the laser being a titanium-sapphire laser.

12. A method according to any one of claims 6 to 11, the treatment apparatus further comprising a lens associated with the laser.

13. A method according to the preceding claim, the lens having a numerical aperture lying in the range 0.1 to 1.

14. A method according to any preceding claim, the peak power of each pulse being greater than or equal to 0.001 watts (W) .

15. A method according to any preceding claim, the pulses being emitted at a frequency greater than or equal to

1 MHz.

16. A method according to any preceding claim, the surface illuminated by each pulse having its largest dimension greater than or equal to 0.1 μm.

17. A method according to any preceding claim, the surface illuminated by each pulse having its largest dimension less than or equal to 100,000 μm.

18. A method according to any preceding claim, in which the keratinous fibers and the treatment apparatus are caused to move relative to each other.

19. A method according to claim 18, the keratinous fibers being treated in a single pass.

20. A method according to claim 18, the keratinous fibers being treated in a plurality of passes.

21. A method according to any preceding claim, the keratinous fibers being subjected to the pulses in order to bleach them.

22. A method according to any one of claims 1 to 21, the keratinous fibers being subjected to pulses that are focused onto their surfaces.

23. A method according to any one of claims 1 to 21, the keratinous fibers being subjected to pulses that are focused onto the cores of the fibers.

24. A method according to any one of claims 1 to 20, the keratinous fibers being subjected to the pulses in order to modify their porosity.

25. A method according to any one of claims 1 to 20, the keratinous fibers being subjected to the pulses in order to modify their mechanical properties, in particular the styling properties.

26. A method according to any one of claims 1 to 20, the keratinous fibers being subjected to the pulses in order to modify their sheen.

27. A method according to any one of claims 1 to 20, the keratinous fibers being subjected to the pulses in order to smooth their surfaces.

28. A method according to any one of claims 1 to 20, the keratinous fibers being subjected to the pulses in order to repair damaged fibers.

29. A method according to any one of claims 1 to 20, the keratinous fibers being subjected to the pulses in order to modify their feel.

30. A method according to any one of claims 1 to 20, the keratinous fibers being subjected to the pulses in order to cauterize them, in particular in order to cauterize their points, split-ends, or the extremities of split ends .

31. A method according to any one of claims 1 to 30, further comprising applying a composition to the keratinous fibers before they are exposed to the light pulses .

32. A method according to any one of claims 1 to 30, further comprising applying a composition to the keratinous fibers while they are being exposed to the light pulses.

33. A method according to any one of claims 1 to 30, further comprising applying a composition to the keratinous fibers after they have been exposed to the light pulses.

34. A method according to claims 31 to 33, the composition comprising at least one compound inducing bleaching of hair, in particular an oxidizing or reducing agent .

35. A method according to claims 31 to 33, the composition comprising at least one compound inducing coloring of the hair.

36. Apparatus for treating keratinous fibers, which apparatus comprises: ^• a source (2) arranged to emit light pulses of duration less than or equal to 5 x 10^~12 s; and

^• a system (3, 4) making it possible to direct the pulses towards the keratinous fibers to be treated.

37. Apparatus according to claim 36, the source (2) comprising a laser.

38. Apparatus according to claim 37, the laser having a cavity formed by two mirrors, a broadband amplifier material disposed in the cavity, and mode-locking apparatus .

39. Apparatus according to claim 37, the laser having a cavity formed by a fiber of an amplifier material, a coupler for injecting the pumping light, a coupler for extracting the laser pulses, and mode-locking apparatus.

40. Apparatus according to any one of claims 37 to 39, further comprising non-linear optical apparatus receiving the light from the laser.

41. Apparatus according to claim 40, the non-linear optical apparatus comprising a photonic-crystal fiber.

42. Apparatus according to any one of claims 36 to 41, further comprising a frequency doubling unit receiving the light emitted by the laser.

43. Apparatus according to any one of claims 36 to 42, further comprising at least one composition to be applied to the keratinous fibers.