WO2024245842A1

WO2024245842A1 - Process for shaping the hair using uv-visible radiation

Info

Publication number: WO2024245842A1
Application number: PCT/EP2024/064043
Authority: WO
Inventors: Floriane SLEZARSKI; Sophie FRECHIN; Gabin Vic; Alexandre HEBBRECHT
Original assignee: LOreal SA
Current assignee: LOreal SA
Priority date: 2023-06-01
Filing date: 2024-05-22
Publication date: 2024-12-05
Anticipated expiration: 2025-12-01
Also published as: FR3149173A1; CN121218903A; FR3149173B1

Abstract

The present invention relates to a process for shaping keratin fibres, notably the hair, comprising steps with the aim of subjecting a tensioned lock of hair to illumination: exposing said keratin fibres to light radiation having an emission maximum in a wavelength range of between 280 nm and 650 nm, the process being characterized in that the keratin fibres to be treated receive an irradiance of greater than or equal to 1 W/cm² and less than or equal to 50 W/cm2.

Description

Process for shaping the hair using UV-visible radiation

The present invention relates to a process for shaping keratin fibres using UV-visible light radiation. The process relates in particular to shaping human keratin fibres, and chiefly the hair. More particularly, the shaping process is a process for straightening.

There are numerous techniques for shaping the hair.

One of the most common consists in using heated straightening tongs (generally referred to as “straighteners” or “straightening iron”). The general design of such appliances is well known. These tongs make it possible to straighten hair fibres at high temperature (between 180 to 230°C) without excessively pulling on the hair fibres, unlike blow drying. However, in order to obtain a good straightened appearance, it is necessary to carry out several passes of the tongs, which considerably extends the treatment time.

Furthermore, the repeated application of the flat straightening irons can sometimes cause damage to the hair fibres due to the operating temperature of the straightening iron.

Straightening irons also enable shaping of the curl type, by winding the treated lock of hair around one or both arms of the iron.

In order to facilitate and improve the shaping which can be obtained with these appliances, it is known to combine them with diffusion of steam onto the hair (see for example EP2236053B1).

“Permanent” chemical processes are also known for long-lasting shaping, comprising the application of a reducing composition which is able to cause the disulfide bonds present in the keratin fibre to break. This method then involves, preferably after rinsing the hair, a second step that consists in reconstituting the disulfide bonds by applying an oxidizing composition known as a fixer to the hair. The hair may, prior to the application of the reducing composition, be tensioned using suitable devices such as curlers, or be straightened. The reconstitution of the disulfide bonds makes it possible to maintain the head of hair in the desired shape.

A second method involves a step of lanthionization using a composition comprising a base belonging to the family of hydroxides which is able to convert the disulfide bridges into monosulfide bridges. This type of treatment is mainly used for shaping naturally kinky hair.

In order to obtain satisfactory performance in terms of durability of shaping, the compositions used in these chemical treatments may comprise relatively high concentrations of chemical active agents (for example reducing agents or hydroxide compounds). Thus, thioglycolic acid may, for example, be used in certain compositions, at mass concentrations of between 6% and 11%, and sodium hydroxide at 2%. Products comprising thioglycolic acid have an unpleasant odour, which may be present during the application and may also persist on the hair once the treatment has been performed. In addition, the treatments described above may lead to irreversible damage to the hair caused by changes in the intrinsic properties of the hair fibre. These treatments may also irritate the scalp due to their relatively high concentration of chemical active agents. It is moreover known practice to supply heat during the treatment in order to activate the processes. The heating step is generally carried out at a temperature of between 80 and 120°C and for a duration of approximately 20 to 30 minutes. This heating step is therefore liable to cause even greater damage to the hair.

The heating energy can be supplied by different means, and for example by exposing the hair to infrared radiation (see for example FR2941600A1) or else microwave radiation (see for example WO2013183021A1).

Among the sources of energy used in the context of hair treatments, exposure to UV radiation is also known.

Thus, document US56053180A describes hairstyling appliances, such as combs, curling tongs and hairbrushes equipped with UV diodes. The UV radiation is intended for cleaning and disinfection and is not intended to contribute to the actual hair treatment. The power of the radiation is not described; however, in the context of disinfection applications, it is considered that exposure to UVC at a power of less than 100 mJ/cm² is more than enough to destroy the vast majority of bacteria.

Document DE102005059936A describes a process for treating the hair, comprising the shaping thereof and the application of a reducing composition (opening of disulfide bonds) before exposing the hair treated in this way to UV radiation. After exposure, an oxidizing composition (re-forming of disulfide bonds) is then applied in order to fix the head of hair. It is simply indicated that the UV light assists in the phenomenon of reducing disulfide bonds, and makes it possible to reduce the treatment time compared to a “conventional” permanent-waving process.

Exposure to UV is also used in other hair treatment processes, such as notably described in documents US5246019A, WO2015165949, WO2020234311 and WO2007048473, which target the bleaching and/or dyeing of the hair, and WO2017108767, WO2007048472A1 which target the application of photopolymerizable care compositions.

Given the limitations mentioned previously, there is always a need to improve processes for shaping keratin fibres such as the hair, in particular human hair.

To this end, the subject of the present invention is a process for shaping keratin fibres, in particular human keratin fibres, notably the hair, comprising the steps with the aim of:

- applying a mechanical tension to the keratin fibres to be treated,

- exposing said keratin fibres to light radiation having an emission maximum in a wavelength range of between 280 nm and 650 nm,

the process being characterized in that the keratin fibres to be treated receive an irradiance of greater than or equal to 1 W/cm² and less than or equal to 50 W/cm².

Thus, unlike the processes presented above which employ very low-power UV exposure to assist the action of customary reducing formulas and unlike the processes which on the other hand require high-power UV exposure (crosslinking, bleaching), it has been discovered that exposure to light radiation in the UV-visible range of moderate power made it possible to obtain shaping of keratin fibres. Such power is low enough to limit the potentially negative effects of the radiation on the hair (lightening, damage), and high enough to no longer require high concentrations of disulfide bond-reducing products.

It is known from the article Direct Ultraviolet Laser-Induced Reduction of Disulfide Bonds in Insulin and Vasopressin, ACS Omega 2020, 5, 7962−7968 , that it is possible to reduce disulfide bonds in insulin and vasopressin using UV laser radiation. However, this document does not mention the possibility of obtaining such a reduction in keratin fibres in order to shape said fibres. Moreover, it is difficult to envisage using such powerful laser radiation for shaping a head of hair.

The illumination power employed in the process which is the subject of the present application can be obtained by using LEDs, in particular UV LEDs.

Without wishing to be bound by a particular theory, although the targeted radiation power does not a priori make it possible to cause a change in disulfide bridges, the applicant believes that the shaping, and notably the straightening, can be explained at least in part by electron transitions in the melanin of the hair, due to the absorption of the electromagnetic wave. Heat is then released from the core of the strand of hair towards the outside thereof. This heat is internal to the strand of hair, and this no longer represents the traditional picture of a straightening iron of the type which uses thermal conduction from plates towards the inside of the strand of hair.

The heat generated makes it possible to act on hydrogen bonds, which are heavily present in the keratin of the hair, which bonds also make a significant contribution to the staying power and shape of the hair.

It should also be noted that, unlike shaping processes using infrared radiation, the use of UV-visible radiation makes it possible to obtain an effect even on light-coloured hair, since the melanin present is sufficient to absorb a suitable amount of radiation to generate sufficient heat. Thus, while the present process can be carried out on all hair types, it is particularly suitable to “light-coloured” hair having a tone depth of higher than 6 (dark blonde) and notably of higher than 8 (light blonde).

Preferentially, the keratin fibres to be treated receive an irradiance of greater than or equal to 2 W/cm², better still 4 W/cm², even better still 6 W/cm².

Preferentially, the keratin fibres to be treated receive an irradiance of less than or equal to 25 W/cm², better still 12 W/cm², even better still 8 W/cm².

The best results were obtained for irradiance values of between 6 and 8 W/cm².

The process which is the subject of the present application can be carried out with different types of tools and notably using a tongs-type tool such as described in the abovementioned application WO2020234311A1.

Advantageously, the irradiance step is the main source of heat, better still the only source of heat, and the process is carried out without any additional source of heat. In particular, the process is carried out without a step of heating by thermal conduction (heated plates) and/or without heating by additional radiation (microwave or infrared radiation, for example), and/or without heating by convection (hot air blowing, for example).

Preferentially, the keratin fibres to be treated are moved in front of an optical illumination window so as to be subjected to a total fluence of greater than or equal to 10 J/cm² and less than or equal to 100 J/cm² per pass. Of course, the keratin fibres can also be held stationary relative to the UV light source and placed in an illumination chamber. Nevertheless, moving the fibres relative to the light sources enables better control of their exposure and makes it possible to ensure that each fibre portion receives substantially the same treatment. This also makes it possible to use more ergonomic and compact appliances for carrying out the process.

The keratin fibres are preferably moved in front of the light sources at a relative speed of less than or equal to 10 cm/second, preferably less than 2 cm/second. Preferentially, the speed of movement is greater than or equal to 0.5 cm/second.

According to a first variant embodiment, the process comprises a single step of exposure to light radiation.

According to a second, preferred, embodiment, the process comprises a plurality of steps of exposure to light radiation, the steps being repeated in succession. The exposure step can be repeated twice to 10 times, better still twice to 5 times. The number of passages makes it possible to increase the total fluence received by the fibres, while making it possible to maintain a relatively small illumination window in a compact appliance.

Preferably, the wavelength of the emission maximum of the light radiation is greater than or equal to 315 nm, better still greater than or equal to 350 nm, or even greater than or equal to 370 nm.

More preferably, the wavelength of the emission maximum of the light radiation is less than or equal to 650 nm, better still less than or equal to 500 nm, or even less than or equal to 460 nm.

Advantageously, the wavelength of the emission maximum of the ultraviolet radiation is between 370 and 460 nm.

Preferentially, the keratin fibres to be treated are mechanically tensioned with a force of greater than or equal to 0.1 N, preferably greater than or equal to 1 N, better still greater than or equal to 15 N.

More preferentially, the keratin fibres to be treated are mechanically tensioned with a force of less than or equal to 1000 N, preferably less than or equal to 30 N, better still less than or equal to 20 N.

Advantageously, the keratin fibres to be treated are mechanically tensioned with a force of between 1 and 30 N, better still between 15 and 20 N.

According to a first embodiment, the treatment process is a straightening process and the keratin fibres to be treated are tensioned in a substantially rectilinear manner. The tensioning can be carried out notably using a comb, preferably a comb detachably or non-detachably integrated into a treatment appliance comprising sources of illumination which are suitable for carrying out the process. Additionally or alternatively, the keratin fibres may be mechanically tensioned by being gripped between treatment plates of the appliance. To this end, the treatment appliance comprising suitable sources of illumination may be in the form of an iron comprising two arms which are articulated relative to one another and which are able to adopt a spaced-apart configuration that enables the insertion of a lock of keratin fibres to be treated, and a closed configuration for gripping said keratin fibres to be treated. For a more detailed description of the type of appliance which may be used, reference may be made to application WO2020208077.

According to a second embodiment, the treatment process is a curling process and the keratin fibres to be treated are tensioned and wound. The keratin fibres to be treated can notably be wound onto curler-type accessories.

Alternatively, they can also be wound around the arms of a tongs-type appliance as mentioned previously, as can be achieved with the arms of a straightening iron.

Highly advantageously, the process is carried out in the absence of any composition, and in particular of any composition which is able to reduce disulfide bonds in the keratin fibres to be treated. If a composition is applied beforehand to the keratin fibres to be treated, said composition comprises less than 6% by mass of ingredients which are able to reduce disulfide bonds, and notably less than 6% of thiol compounds such as thioglycolic acid. Preferably, said composition comprises less than 1% by mass of ingredients which are able to reduce disulfide bonds; better still, it does not contain such ingredients.

Preferably, said composition also comprises less than 1% by mass of alkaline agents of the hydroxide/sodium hydroxide type; better still, it does not comprise such agents.

According to a first variant embodiment, the process is carried out on keratin fibres to be treated which have been moistened beforehand with an aqueous composition, the aqueous composition comprising substantially only water.

Preferentially, the process is carried out on keratin fibres which have not been moistened beforehand (“dry” hair, i.e. hair which is substantially at equilibrium with the ambient humidity, or even which is slight dehydrated, and more particularly which has either not been washed in water for at least two hours prior to carrying out the process, or which has been dried using a hairdryer).

Additionally advantageously, the process does not comprise a step of applying an oxidizing composition which is able to restore disulfide bonds.

Thus, preferentially, the compositions of the invention optionally used before (at most 2 hours before, better still at most 12 hours before) and/or during and/or after (at most 2 hours after, better still at most 12 hours after) the step of UV illumination do not contain any agents chosen from oxidizing agents, reducing agents, hydroxide-type alkaline agents or colorants.

The illumination step can be followed, within a short period, by additional treatment steps. These steps can in particular be steps of applying cosmetic compositions and/or of drying. This additional treatment step can take place in a time interval of less than a week, preferably less than 48 h, better still less than 24 h. Unlike some treatments, such as hair dyeing which it is not recommended to perform before at least 72 h, or even a week, after a permanent-wave, the present shaping process can be virtually immediately followed by such a treatment without an additional treatment other than optional rinsing or washing (preferably without an intermediate washing or rinsing step).

Likewise, the process can be carried out on keratin fibres which have previously been subjected to a bleaching and/or dyeing process less than 2 hours beforehand.

Further aims, features and advantages of the invention will become apparent from reading the following description, which is given only by way of non-limiting example and with reference to the appended drawings, in which:

is a photograph of a lock of hair before treatment by a process which is the subject of the present application.

is a photograph of the lock of hair from after treatment by the process which is the subject of the present application.

, , present results obtained for another reference lock.

and present results obtained for a reference lock which has previously been subjected to a bleaching process.

, , show results obtained on the lock from which has been subjected to a dyeing step following the bleaching step.

and show results obtained for a reference lock which has been subjected to double bleaching.

shows a 2.7 g lock of Caucasian hair having a length of 27 cm before treatment according to the process which is the subject of the present application. The lock of hair is wavy. The keratin fibres forming the lock are subjected to mechanical tensioning which tends to keep them rectilinear (straight), and are subjected to a step of UV illumination having an emission maximum of between 385 nm and 405 nm, such that the fibres receive an illumination power of 6 watts per cm2.

To this end, the lock of hair is moved relative to an illumination device at a speed of approximately 1 cm per second for a 2 cm optical window. The lock is exposed to the light for 2 seconds per centimetre. The fluence value is therefore substantially 12 J per cm2 per passage.

The total illumination power is obtained by subjecting the lock to a plurality of passes (4 passes) through the illumination device, such that the total fluence received by the lock is substantially equal to 48 J/cm2.

shows the lock of hair after treatment.

It was observed that four passes made it possible to obtain a substantially equivalent degree of straightening on the lock to that which can be obtained with a straightening iron set to 210°C. However, the straightened lock is less compact and retains a greater mid-length width.

It should be noted that the present straightening process also has less staying power and some reformation of curls is observed even after washing/shampooing. The staying power in an atmosphere having 80% relative humidity is also lower than straightening carried out with a straightening iron set to 210°C. However, in light of the disadvantages mentioned above regarding alternative shaping methods, this straightening process constitutes a particularly beneficial solution.

The following figures show results for other locks with other parameters. Parameters which are not specified are identical to those of the previous example.

shows another reference lock of slightly wavy Caucasian hair (curliness level equal to 4) before treatment. The lock has a tone depth assessed to be 4 (chestnut brown).

shows the straightening obtained after illuminating the lock from at a wavelength of 385 nm and an illumination power of 10 watts per cm2. The speed of movement is 2.7 cm per second and 4 passes of the lock in front of the sources of illumination are carried out.

shows the straightening obtained after illuminating the lock from at a wavelength of 385 nm and an illumination power of 16 watts per cm2. The speed of movement is 5.4 cm per second and 5 passes of the lock in front of the sources of illumination are carried out.

shows a reference lock of Caucasian hair having a curliness level equal to 4 and an initial tone depth equal to 4. The reference lock was also subjected to a bleaching treatment using the powdered product L'OREAL PROFESSIONNEL BLOND STUDIO 9.

shows the straightening obtained after illuminating the bleached lock from at a wavelength of 385 nm and an illumination power of 8 watts per cm2. The speed of movement is 1.3 cm per second and 4 passes of the lock in front of the sources of illumination are carried out.

Figures 8 to 10 show the straightenings obtained after illuminating the bleached lock from at a wavelength of 385 nm and an illumination power of 6 watts per cm2. The speed of movement is 1.3 cm per second and 4 passes of the lock in front of the sources of illumination are carried out. Before carrying out the process, the bleached locks were subjected to an additional dyeing step using a L'OREAL PROFESSIONNEL MAJIREL product. More specifically, the lock from was dyed using the product MAJIREL 4; the lock from was dyed using the product MAJIREL 6.66, and the lock from was dyed using the product MAJIREL 7.43.

shows a reference lock of Caucasian hair having a curliness level equal to 4 and an initial tone depth equal to 4. The reference lock was also subjected to a double bleaching treatment using the powdered product L'OREAL PROFESSIONNEL BLOND STUDIO 9.

Claims

Process for shaping keratin fibres, in particular human keratin fibres, notably the hair, comprising the steps with the aim of:
- applying a mechanical tension to the keratin fibres to be treated,
- exposing said keratin fibres to light radiation having an emission maximum in a wavelength range of between 280 nm and 650 nm,
the process being characterized in that the keratin fibres to be treated receive an irradiance of greater than or equal to 1 W/cm² and less than or equal to 50 W/cm² and in that the keratin fibres to be treated are moved in front of an optical illumination window so as to be subjected to a total fluence of greater than or equal to 10 J/cm² and less than or equal to 100 J/cm² per pass.
Process according to Claim 1, characterized in that the keratin fibres to be treated receive an irradiance of greater than or equal to 6 W/cm².
Process according to either one of Claims 1 and 2, characterized in that the keratin fibres to be treated receive an irradiance of less than or equal to 8 W/cm².
Process according to any one of Claims 1 to 3, characterized in that the process comprises a single step of exposure to light radiation.
Process according to any one of Claims 1 to 3, characterized in that the process comprises a plurality of steps of exposure to light radiation, the steps being repeated in succession.
Process according to any one of Claims 1 to 3, characterized in that the wavelength of the emission maximum of the light radiation is greater than or equal to 315 nm, better still greater than or equal to 350 nm, or even greater than or equal to 370 nm.
Process according to any one of Claims 1 to 6, characterized in that the wavelength of the emission maximum of the light radiation is less than or equal to 500 nm, or even less than or equal to 460 nm.
Process according to any one of Claims 1 to 7, characterized in that the keratin fibres to be treated are mechanically tensioned with a force of greater than or equal to 0.1 N, preferably greater than or equal to 1 N, better still greater than or equal to 15 N.
Process according to any one of Claims 1 to 8, characterized in that the keratin fibres to be treated are mechanically tensioned with a force of less than or equal to 1000 N, preferably less than or equal to 30 N, better still less than or equal to 20 N.
Process according to any one of Claims 1 to 9, characterized in that the keratin fibres to be treated are tensioned in a substantially rectilinear manner.
Process according to any one of Claims 1 to 9, characterized in that the keratin fibres to be treated are tensioned and wound.
Process according to any one of the preceding claims, characterized in that the process is carried out in the absence of any composition which is able to reduce disulfide bonds in the keratin fibres to be treated.
Process according to any one of Claims 1 to 12, characterized in that the process is carried out on keratin fibres to be treated which have been moistened beforehand with an aqueous composition; the aqueous composition is water.
Process according to any one of Claims 1 to 12, characterized in that the process is carried out on keratin fibres which have not been moistened beforehand.
Process according to any one of Claims 1 to 14, characterized in that it does not comprise a step of applying an oxidizing composition which is able to restore disulfide bonds.