Tyre comprising a sidewall with at least one high-contrast sidewall element

Abstract

The present invention relates to a vehicle tyre (1), the tyre comprising at least one sidewall (2) with at least one high-contrast sidewall element (3) consisting of a texture comprising projections (4, 5) that are raised with respect to a sidewall surface (21) in contact with the surrounding air and / or cavities (6) that are recessed with respect to the sidewall surface (21). The invention discloses a rubber composition of the sidewall (2) that exhibits a good trade-off between tear strength and rolling resistance. According to the invention, the weight ratio of the reinforcing filler content to the plasticiser content is at most 4.50, the sum of the reinforcing filler content and the crumb rubber content is at least 30 phr and at most 70 phr, and the weight ratio of the crumb rubber content to the reinforcing filler content is at least 0.20 and at most 2.50.

Description

Tire comprising a sidewall with at least one high contrast sidewall element

[0001] The present invention relates to a tire for a vehicle, comprising a sidewall with at least one high contrast sidewall element.

[0002] A tire comprises two sidewalls, a sidewall being the portion of the tire connecting one end of the tread, intended to come into contact with the ground, to a bead, intended to be mounted on a rim.

[0003] In the following, the external surface of a sidewall, in contact with atmospheric air, is referred to, more simply, as the "sidewall surface". A sidewall surface generally comprises at least one graphic element and / or, possibly, an aesthetic element. A graphic element, usually called marking and comprising letters, numbers or symbols, is generally intended to communicate technical, commercial or legal information.

[0004] By definition, a high-contrast sidewall element refers to a sidewall surface element consisting of a specific texture different from that of the sidewall surface, which is most often smooth. This texture gives said high-contrast sidewall element a darker appearance than that of any portion of sidewall surface adjacent to said high-contrast sidewall element, such that this high-contrast sidewall element can be visually distinguished from any portion of adjacent sidewall surface. A high-contrast sidewall element may have as its object either a graphic element or an aesthetic element, or a portion of sidewall surface surrounding said graphic or aesthetic element, which makes said graphic or aesthetic element particularly visible on the sidewall surface.

[0005] Thus, whether for the enhancement of graphic elements or aesthetic elements of the sidewall surface, there is a constant concern among tire designers to produce sidewall elements with high contrast.

[0006] It is known to produce the texture of these high-contrast sidewall elements either by means of protrusions in relief relative to the sidewall surface, or by means of cavities in relief relative to the sidewall surface, or by means of a combination of protrusions and cavities. This texture is made of a rubbery material, also called a rubber composition or elastomeric composition, identical to that of the portion sidewall in contact with atmospheric air, since this texture comes from the material of the sidewall.

[0007] High contrast flanking elements formed by a texture comprising strand-like or blade-like protrusions have been described in WO 2007045425 A1, WO 2011036061 A1 and WO 2014202731 A1. High contrast flanking elements formed by a texture comprising cavities recessed relative to the flanking surface have been described in WO 2014040967 A1.

[0008] The texture of a high-contrast sidewall element is most often produced by molding during the curing of the tire. The corresponding mold element, intended to produce the texture of the high-contrast sidewall element, is produced, by way of non-exhaustive examples, by machining or by laser engraving. The texture of a high-contrast sidewall element can also be produced directly on the sidewall surface of the tire after curing, for example by laser engraving. The texture is therefore made of the same material as that of the rest of the sidewall.

[0009] The texture of the high-contrast sidewall elements, comprising protrusions in the form of strands or blades, makes it possible to absorb a large portion of the incident light rays, after one or more successive reflections on the walls of the protrusions. This makes it possible to give the texture a blacker appearance and, consequently, to improve its contrast and therefore its visibility compared to any adjacent portion of the sidewall surface. Furthermore, this particular texture makes it possible to obtain a pleasant touch on the sidewall surface, of the "velvet" type. Finally, the texture used has a water-repellent and slightly hydrophobic effect. In a particular embodiment, the texture can be positioned on a surface set back from the sidewall surface, such that it is embedded in the sidewall, which has the advantage of protecting it, for example, against wear caused by scraping the sidewall surface against a pavement.

[0010] Similarly, the texture of the high-contrast flank elements, comprising cavities recessed relative to the flank surface, makes it possible to absorb a large part of the incident light rays, after one or more successive reflections on the walls of the cavities. This specific texture has the advantage of being set back relative to the flank surface, which makes it possible to ensure the durability of said texture by protecting it against wear caused by scraping the sidewall surface against a pavement. It also has the advantage of not disturbing the aerodynamic flow of air, near the sidewall surface, when the tire is rolling.

[0011] It has been observed, on the sidewall surfaces of tires comprising high-contrast sidewall elements, that the visual appearance of the texture of said high-contrast sidewall elements changes over time, which may in particular result from the appearance of cracks or micro-cracks, linked both to the conditions of use of the tire and the aging of the material.

[0012] It is therefore necessary, in order to obtain a sidewall element with high contrast that lasts throughout the life of the tire, to be able to reduce these cracks, or at least delay their appearance, but with a limited impact on the hysteresis of the sidewall material, and therefore on the rolling resistance of the tire. It is in fact known that the resistance to cracking (or tearability) and the hysteresis of a rubber composition are linked.

[0013] Increasing the durability of a high-contrast sidewall element is indeed an important commercial issue for a tire manufacturer. For example, when a user replaces only the tires fitted to the front of their vehicle, they may notice a significant difference between the visual appearance of a high-contrast sidewall element observed on new tires fitted to the front of the vehicle and that observed on used tires fitted to the rear of the vehicle. This difference in visual appearance between the front and rear tires may be deemed unacceptable by the user, especially when their vehicle is a sports or prestige vehicle.

[0014] The inventors therefore set themselves the objective, for a tire comprising a sidewall with at least one high-contrast sidewall element, of increasing the durability of the visual appearance of said high-contrast sidewall element, using a rubber composition adapted to the sidewall, in particular near the sidewall surface, presenting a satisfactory compromise between tear resistance and hysteresis.

[0015] This objective was achieved by a tire for a vehicle, comprising a sidewall with at least one high-contrast sidewall element: - the high-contrast sidewall element consisting of a texture comprising protuberances, in relief relative to a sidewall surface, in contact with the air atmospheric, and / or cavities, hollow relative to the flank surface, -the sidewall comprising a rubber composition based on an elastomer matrix, at least one reinforcing filler, at least one crosslinking system, at least one plasticizing agent and at least one rubber crumb, - the weight ratio between the rate of reinforcing filler, expressed in pce, and the rate of plasticizing agent, expressed in pce, being at most equal to 4.50, - the sum of the rate of reinforcing filler, expressed in pce, and the rate of rubber crumb, expressed in pce, being at least equal to 30 pce and at most equal to 70 pce, - and the weight ratio between the rate of rubber crumb, expressed in pce, and the rate of reinforcing filler, expressed in pce, being at least equal to 0.20 and at most equal to 2.50.

[0016] According to the invention, the high-contrast sidewall element is constituted by a texture comprising protuberances, in relief relative to a sidewall surface, in contact with atmospheric air, and / or cavities, hollow relative to the sidewall surface.

[0017] Also according to the invention, the sidewall comprises a rubber composition based on an elastomer matrix, at least one reinforcing filler, at least one crosslinking system, at least one plasticizing agent, and at least one rubber crumb.

[0018] The expression "rubber composition based on" means a rubber composition comprising the mixture and / or the in situ reaction product of the different constituents used, some of these constituents being able to react and / or being intended to react with each other, at least partially, during the different phases of manufacture of the rubber composition, the rubber composition thus being able to be in a totally or partially crosslinked state or in a non-crosslinked state.

[0019] A rubber composition comprises at least one and often several elastomers, in particular several diene elastomers. This mixture of elastomers, in particular diene elastomers, is called an elastomer matrix. Preferably, the elastomer matrix comprises at least two different diene elastomers.

[0020] The term "elastomer" means a polymer, i.e., a homopolymer or copolymer, with elastic properties obtained after crosslinking. The term rubber is a common synonym for elastomer.

[0021] By "diene elastomer" or indistinctly "diene rubber", whether natural or synthetic, we mean an elastomer consisting at least in part of diene monomer units (monomers carrying two carbon-carbon double bonds, conjugated or not). Diene elastomers are non-thermoplastic.

[0022] Diene elastomers can be classified into two categories: "essentially unsaturated" diene elastomers and "essentially saturated" diene elastomers. An "essentially unsaturated" diene elastomer is a diene elastomer derived at least in part from conjugated diene monomers, having a content of units or motifs of diene origin (conjugated dienes) that is greater than 15% (mol %). Thus, diene elastomers such as butyl rubbers or copolymers of dienes and alpha-olefins such as EPDM do not fall within the previous definition and can be described as "essentially saturated" diene elastomers (low or very low content of motifs of diene origin, always less than 15%).

[0023] The term diene elastomer capable of being used in the rubber compositions in accordance with the invention is understood in particular to mean: a) Any homopolymer of a diene monomer, conjugated or not, having from 4 to 18 carbon atoms; b) Any copolymer of a diene, conjugated or not, having from 4 to 18 carbon atoms and at least one other monomer; the other being able to be ethylene, an olefin or a diene, conjugated or not.

[0024] Suitable conjugated dienes are conjugated dienes having 4 to 12 carbon atoms, in particular 1,3-dienes, such as 1,3-butadiene and isoprene.

[0025] Suitable non-conjugated dienes are non-conjugated dienes with 6 to 12 carbon atoms, such as 1,4-hexadiene, ethylidene norbornene, dicyclopentadiene.

[0026] Suitable olefins are vinylaromatic compounds having 8 to 20 carbon atoms and aliphatic α-monoolefins having 3 to 12 carbon atoms.

[0027] Suitable vinyl aromatic compounds are, for example, styrene, ortho-, meta-, para-methyl styrene, the commercial mixture "vinyl-toluene", para-terti obuty 1 styrene.

[0028] Suitable aliphatic α-monoolefins are, in particular, acy clic aliphatic α-monoolefins having from 3 to 18 carbon atoms.

[0029] More specifically, the diene elastomer is: (has 1 ) Any homopolymer of a conjugated diene monomer, in particular any homopolymer obtained by polymerization of a conjugated diene monomer having from 4 to 12 carbon atoms; (b 1) Any copolymer obtained by copolymerization of one or more conjugated dienes with each other or with one or more vinylaromatic compounds having from 8 to 20 carbon atoms; (c') Any copolymer obtained by copolymerization of one or more dienes, conjugated or not, with ethylene, an α-monoolefin or their mixture, such as, for example, elastomers obtained from ethylene, propylene with a non-conjugated diene monomer of the aforementioned type.

[0030] A reinforcing filler, intended to reinforce a rubber composition, may be an organic filler such as carbon black, or an inorganic filler such as silica or alumina in combination with a coupling agent between the inorganic filler and the diene elastomer, or a mixture of these types of fillers.

[0031] The crosslinking system may be any type of system known to those skilled in the art in the field of tire rubber compositions. It may in particular be based on sulfur, and / or peroxide and / or bismaleimides. Preferably, the crosslinking system is based on sulfur: this is then referred to as a vulcanization system. The sulfur may be provided in any form, in particular in the form of molecular sulfur, or a sulfur-donating agent. At least one vulcanization accelerator is also preferably present, and, optionally, also preferably, various known vulcanization activators may be used such as zinc oxide, stearic acid or an equivalent compound such as stearic acid salts and transition metal salts, guanidine derivatives (in particular diphenylguanidine), or even known vulcanization retarders.Any compound capable of acting as an accelerator for the vulcanization of diene elastomers in the presence of sulfur may be used as an accelerator, in particular accelerators of the thiazole type and their derivatives, accelerators of the sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea and xanthate types.

[0032] A plasticizing agent is a common processing agent, known to those skilled in the art and usually used in rubber compositions. A plasticizing agent may be selected from the group consisting of plasticizing oils, plasticizing resins with a high glass transition temperature Tg, and combinations thereof.

[0033] Any extender oil, whether aromatic or non-aromatic and known for its plasticizing properties with respect to elastomers, can be used. At room temperature (23°C), these oils, more or less viscous, are liquids (that is to say, as a reminder, substances having the capacity to eventually take the shape of their container), in contrast in particular to high Tg hydrocarbon resins which are by nature solid at room temperature. The plasticizing oil generally has a glass transition temperature Tg, lower than -20°C, preferably lower than -40°C. The glass transition temperature Tg of the plasticizing oil is measured according to the ASTM D3418 (2008) standard.

[0034] By definition, a high Tg hydrocarbon resin, typically at least equal to 30°C, is solid at room temperature and pressure (23°C, 1 atm), while a plasticizing oil is liquid at room temperature and a low Tg hydrocarbon resin is viscous at room temperature. Hydrocarbon resins, also called hydrocarbon plasticizing resins, are polymers well known to those skilled in the art, essentially based on carbon and hydrogen but which may contain other types of atoms, for example oxygen, which can be used in particular as plasticizing agents or tackifying agents in polymer matrices. They are by nature at least partially miscible (i.e., compatible) at the rates used with the polymer compositions for which they are intended, so as to act as true diluting agents.As is known, these hydrocarbon resins can also be referred to as thermoplastic resins in that they soften upon heating and can thus be molded. The glass transition temperature Tg of the plasticizing resin is measured according to ASTM D3418 (2008).

[0035] A rubber composition, particularly in contact with atmospheric air, such as a rubber composition for a tire sidewall, may also contain anti-ozone waxes, such as, for example, paraffin waxes, microcrystalline waxes or mixtures of paraffin and microcrystalline waxes.

[0036] These waxes consist of a mixture of linear alkanes and non-linear alkanes (isoalkanes, cycloalkanes, branched alkanes) derived from petroleum refining or the catalytic hydrogenation of carbon monoxide (Fisher Tropsch process) mainly comprising chains of at least 20 carbon atoms. The determination of the distribution of the alkane is carried out by gas chromatography coupled with a flame ionization detector ("GC-FID"). The chromatogram is analyzed according to the EWF ("European Wax Federation") method.

[0037] All known anti-ozone waxes can be used, including natural waxes such as candelilla wax or carnauba wax. These waxes can also be used for cutting.

[0038] Commercially available anti-ozone waxes include, for example, "Varazon 4959", "Varazon 6500" and "Varazon 6810" from Sasol, "Ozoace 0355" from Nippon Seiro, "Negozone 9343" from H&R and "H3841" from Yanggu Huatai.

[0039] In the invention, the rubber composition comprises, in addition to the elastomer matrix, a rubber powder (also called "crumb rubber" in English) which is in the form of granules, possibly put in the form of a rubber plate, and which is a recycling product.

[0040] Most often, these rubber powders come from grinding or micronizing vulcanized rubber compounds already used for a first application, for example, in a tire, shoe soles, or seals. They are therefore a product of recycling these materials.

[0041] As is known, rubber crumb can be obtained more particularly by reducing used tires into granules from which reinforcing materials such as steel or textile fibers have been removed.

[0042] Rubber crumb can be prepared by cryogenic grinding of used tires, for example according to the process described in document US 7,445,170, comprising successive and independent steps of granulation, separation of metal and textile reinforcements, cooling and micronization in order to obtain a rough distribution of micron particles of vulcanized mixture (also called microparticles). This micronization can be carried out using an impact crusher of conical shape as described in document US 7,861,958. The cryogenized input enters the mill (for example, CUM150 mills from Netzsch or CW250 from Alpine can be used), then is transferred by gravity to a rotor rotating at high speed. The cryogenized input is thus projected onto the walls of the rotor chamber multiple times leading to its micronization. The particles can then pass through a series of two vibrating screens of the same size in order to separate the last elements not made of vulcanized mixture. A gross distribution of micron particles of vulcanized mixture is obtained. By "microparticles" is meant particles which have a size, namely their diameter, in the case of spherical particles, or their largest dimension, in the case of anisometric particles, of a few tens or hundreds of microns.The size of the microparticles can be determined by techniques known to those skilled in the art, such as, for example, microscopy. Rubber crumb is commercially available from suppliers such as, for example, Lehigh Technology.

[0043] Rubber crumbs can be simple ground or micronized rubber, without any further treatment. However, it is also known that rubber crumbs can undergo treatment to modify them. This treatment can consist of a chemical modification of functionalization or devulcanization. It can also be a thermomechanical, thermochemical, or biological treatment.

[0044] According to a first essential characteristic of the invention, the weight ratio between the level of reinforcing filler, expressed in pce, and the level of plasticizing agent, expressed in pce, is at most equal to 4.50.

[0045] According to a second essential characteristic of the invention, the sum of the reinforcing filler rate, expressed in pce, and the rubber crumb rate, expressed in pce, is at least equal to 30 pce and at most equal to 70 pce.

[0046] According to a third essential characteristic of the invention, the weight ratio between the rate of rubber crumb, expressed in pce, and the rate of reinforcing filler, expressed in pce, is at least equal to 0.20 and at most equal to 2.50.

[0047] The rates of the various constituents are expressed in "pce". The unit "pce" or "parts per hundred of elastomer" represents the part by mass per hundred parts by mass of elastomer or rubber. In English, this unit translates to "phr" ("parts per hundred of rubber"). Elastomers in rubber crumb are excluded from the reference elastomer mass.

[0048] The combination of these essential characteristics of the rubber composition gives the sidewall, and in particular any high contrast sidewall element, satisfactory tear resistance, combined with low hysteresis contributing to low rolling resistance of the tire.

[0049] Advantageously, the weight ratio between the level of reinforcing filler, expressed in pce, and the level of plasticizing agent, expressed in pce, is at least equal to 1.50, preferably at least equal to 2.00 and at most equal to 4.00, and more preferably at least equal to 2.00 and at most equal to 3.50.

[0050] Also advantageously the sum of the rate of reinforcing filler, expressed in pce, and the rate of rubber crumb, expressed in pce, is at least equal to 35 pce and at most equal to 65 pce, preferably at least equal to 35 pce and at most equal to 63 pce, and more preferably at least equal to 40 pce and at most equal to 63 pce.

[0051] Advantageously, the weight ratio between the rate of rubber powder, expressed in pce, and the rate of reinforcing filler, expressed in pce, is at least equal to 0.25 and at most equal to 1.50.

[0052] Preferably, the rate of reinforcing filler is at least equal to 5 pce and at most equal to 70 pce, preferably at least equal to 5 pce and at most equal to 60 pce, more preferably at least equal to 5 pce and at most equal to 55 pce, even more preferably at least equal to 10 pce and at most equal to 50 pce, and even more preferably at least equal to 20 pce and at most equal to 45 pce.

[0053] More preferably, the reinforcing filler mainly comprises carbon black.

[0054] When reference is made to a “majority” compound, this means, within the meaning of the present invention, that this compound is the majority among the compounds of the same type in the composition, that is to say that it is the one which represents the largest quantity by weight among the compounds of the same type, and preferably more than 50% by weight, more preferably more than 75% by weight. Thus, a “majority” filler is one which represents the greatest weight among the fillers in the composition.

[0055] Preferably the level of plasticizing agent is at least equal to 2 pce and at most equal to 28 pce, preferably at least equal to 7 pce and at most equal to 24 pce, and more preferably at least equal to 10 pce and at most equal to 20 pce.

[0056] More preferably, the at least one plasticizing agent is chosen from the group consisting of plasticizing oils, high Tg plasticizing resins, and combinations thereof.

[0057] Even more preferably, the plasticizing agent is a plasticizing oil selected from the group consisting of naphthenic oils, paraffinic oils, naphthenic oils, DAE oils, polyolefin oils, MES oils, TDAE oils, RAE oils, TRAE oils, SRAE oils, mineral oils, vegetable oils, ether plasticizers, ester plasticizers, phosphate plasticizers, sulfonate plasticizers and mixtures of these oils, more preferably is an oil selected from the group consisting of MES oils, TDAE oils, RAE oils, TRAE oils, SRAE oils, mineral oils, vegetable oils and mixtures of these plasticizing oils.

[0058] Preferably, the elastomer matrix comprises at least one isoprene elastomer and at least one butadiene elastomer.

[0059] By "isoprenic elastomer" is meant, in a known manner, a homopolymer or a copolymer of isoprene. In other words, an isoprene elastomer can be chosen from the group consisting of natural rubber (NR), synthetic polyisoprenes (IR), the various isoprene copolymers and the mixtures of these elastomers. Among the isoprene copolymers, mention will be made in particular of isobutene-isoprene (butyl rubber - IIR), isoprene-styrene (SIR), isoprene-butadiene (BIR) or isoprene-butadiene-styrene (SBIR) copolymers. Preferably, the isoprene elastomer can be chosen from the group consisting of natural rubber, synthetic cis-1,4 polyisoprenes, and their combinations. More preferably still, isoprene telastomer is chosen from the group consisting of natural rubber, synthetic polyisoprenes having a rate (mol%) of cis-1,4 bonds greater than 90% (more preferably still greater than 98%), and the combination of these elastomers.

[0060] By "butadiene elastomer" is meant, in a known manner, a homopolymer or a copolymer of butadiene. In other words, a butadiene elastomer can be chosen from the group consisting of polybutadienes (BR), the various copolymers of butadiene and the mixtures of these elastomers. Among the copolymers of butadiene, mention will be made in particular of butadiene-styrene (SBR) or ethylene-butadiene (EBR) copolymers. Preferably, the butadiene elastomer can be a cis-1,4 polybutadiene; in particular a polybutadiene having a rate (mol%) of cis-1,4 bonds greater than 90%, more preferably still greater than 96%.

[0061] More preferably, the elastomer matrix comprises at least one isoprene elastomer at a rate at least equal to 20 pce and at most equal to 80 pce, preferably at least equal to 30 pce and at most equal to 70 pce, more preferably at least equal to 35 pce and at most equal to 65 pce, and at least one butadiene elastomer at a rate at least equal to 20 pce and at most equal to 80 pce, preferably at least equal to 30 pce and at most equal to 70 pce, more preferably at least equal to 35 pce and at most equal to 65 pce.

[0062] Preferably, the rubber powder content is at least equal to 2 pce and at most equal to 35 pce, preferably at least equal to 5 pce and at most equal to 33 pce, more preferably at least equal to 6 pce and at most equal to 32 pce, even more preferably at least equal to 7 pce and at most equal to 31 pce, and even more preferably at least equal to 8 pce and at most equal to 30 pce.

[0063] It should be noted that, for the purposes of the present invention, rubber crumb is not considered to be a reinforcing filler. Consequently, the level of rubber crumb is not included in the level of reinforcing filler.

[0064] Advantageously, the rubber crumb has a microparticle size distribution such that it comprises less than 1% by mass of particles not retained through a 600 μm sieve and less than 10% by mass of microparticles not retained through a 105 μm sieve, relative to the total mass of the rubber crumb microparticles. Preferably, the rubber crumb has a microparticle size distribution such that it comprises less than 1% by mass of microparticles not retained through a 600 µm sieve and less than 10% by mass of microparticles not retained through a 177 µm sieve, based on the total mass of rubber crumb microparticles. The distribution of rubber crumb microparticles is determined according to ASTM D5644-01 (2013).

[0065] To obtain such a rubber crumb having such distributions, an additional sieving step according to a size criterion was carried out. The sieving can be carried out by different technologies (vibration, centrifugation, suction) known to those skilled in the art. Preferably, this sieving step is carried out using a series of sieves stacked in order of size (sieves with calibrated mesh sizes such as the commercial products of the Gericke company, for example). Thus, the largest particles are retained on the sieve while the smallest pass to the lower stage on the next sieve. Those skilled in the art will understand that the distributions considered subsequently can be composed of all the particles passing a given sieve or all the particles retained between 2 stages.

[0066] Preferably, the rubber crumb has a microparticle size distribution such that it comprises less than 1% by mass of microparticles not retained through a 250 μm sieve and less than 10% by mass of microparticles not retained through a 177 μm sieve, relative to the total mass of the rubber crumb microparticles.

[0067] Advantageously, the rubber crumb is a rubber crumb that has not undergone any modification by a treatment chosen from the group consisting of thermal, mechanical, biological and chemical treatments and their combinations.

[0068] The rubber composition previously described, with all its embodiments, is, in particular, the constituent material of the high-contrast sidewall element, integral with the sidewall and consisting of a texture comprising protuberances, in relief relative to a sidewall surface, in contact with atmospheric air, and / or cavities, hollow relative to the sidewall surface.

[0069] According to a first embodiment of texture, the high contrast flank element is constituted by a texture comprising protuberances, in relief relative to a flank surface, having an average height at least equal to 0.2 mm and at most equal to 0.8 mm, preferably at least equal to 0.25 mm and at most equal to 0.5 mm.

[0070] Average height means the arithmetic mean of the heights of all the protrusions. If the average height is less than 0.2 mm, the texture is likely to disappear quickly under the effect of repeated scraping of the sidewall surface against pavements. If the average height is greater than 0.8 mm, the time taken to produce the mold part, intended to mold the protrusions, becomes prohibitive with regard to the desired contrast effect.

[0071] According to a first embodiment of the protuberances, the high-contrast flank element is constituted by a texture comprising protuberances in the form of strands, distributed according to a surface density at least equal to 5 strands / mm 2 and at most equal to 100 strands / mm 2 , preferably at least equal to 8 strands / mm 2 and at most equal to 50 strands / mm 2 , and even more preferably at least equal to 11 strands / mm 2 and at most equal to 30 strands / mm 2.

[0072] A texture comprising at least 5 strands / mm 2 has a homogeneous visual appearance, because below this, the human eye perceives separate strands. In a texture comprising a large number of strands, typically beyond 100 strands / mm 2 , the strands necessarily have a small diameter, which makes the texture less resistant to tearing, for example, in the case of repeated scraping of the sidewall surface against sidewalks.

[0073] Advantageously, the high-contrast flank element is constituted by a texture comprising protuberances in the form of strands having an average diameter at least equal to 0.03 mm and at most equal to 0.5 mm.

[0074] By average diameter, we mean the arithmetic mean of the diameters of a given strand, measured over the entire height of the strand. This average diameter is not necessarily constant from one strand to another. Such a strand texture, produced by molding, is less sensitive to strands being torn off during demolding, which would then remain stuck in the mold, which would require specific cleaning of the latter. In addition, these strands being torn off would degrade the visual uniformity of the high-contrast element.

[0075] According to a preferred variant of the first embodiment of the protuberances, the high-contrast flank element is constituted by a texture comprising strand-like protrusions having a diameter that decreases from a strand base, interfacing with the flank surface, and a free strand top.

[0076] Such a strand texture, produced by molding, is less sensitive to strands being torn off during demolding, which would then remain stuck in the mold, requiring specific cleaning of the latter. In addition, these strands being torn off would degrade the visual uniformity of the high-contrast element.

[0077] According to a second embodiment of the protuberances, the high-contrast flank element is constituted by a texture comprising blade-shaped protuberances distributed at a pitch at least equal to 0.1 mm and at most equal to 0.5 mm, preferably at least equal to 0.15 mm and at most equal to 0.3 mm.

[0078] Blades are protrusions that are easier to mold because their shape facilitates the flow of the elastomeric material and therefore their molding. If the pitch between the blades is less than 0.1 mm, the blades are too brittle. If the pitch between the blades is greater than 0.5 mm, the human eye perceives separate blades.

[0079] Advantageously, the high-contrast flank element is constituted by a texture comprising blade-shaped protuberances having an average width at least equal to 0.03 mm and at most equal to 0.5 mm.

[0080] Average width means the arithmetic mean of the widths of a given blade, measured over the entire height of the blade. This average width is not necessarily constant from one blade to another.

[0081] According to a preferred variant of the second embodiment of the protrusions, the high contrast flank element is constituted by a texture comprising blade-shaped protrusions having a width which decreases from a blade base, interfacing with the flank surface, and a free blade top.

[0082] According to a second texture embodiment, the high-contrast flank element is constituted by a texture comprising cavities, hollow relative to a flank surface, having an average depth at least equal to 0.2 mm and at most equal to 0.7 mm, preferably at least equal to 0.25 mm and at most equal to 0.4 mm.

[0083] Average depth is the arithmetic mean of the depths of all the cavities. This method of producing texture, even if it can be achieved by molding, is particularly suitable for production by laser ablation of the material, or laser engraving, on the baked tire.

[0084] Advantageously, the high-contrast flank element is constituted by a texture comprising cavities whose openings on the flank surface are distributed according to a surface density at least equal to 5 openings s / mm 2 and at most equal to 100 openings / mm 2, preferably at least equal to 8 aperture s / mm 2 and at most equal to 50 openings / mm 2 , and preferably at least equal to 11 openings / mm 2 and at most equal to 30 openings / mm 2 .

[0085] A texture comprising at least 5 openings / mm 2 has a homogeneous visual appearance, because below this, the human eye perceives separate openings. A texture comprising more than 100 openings / mm 2 behaves like an almost smooth surface that directly reflects light, which is not the desired effect.

[0086] Advantageously, the high-contrast flank element is constituted by a texture comprising cavities whose openings on the flank surface have an average diameter at least equal to 0.03 mm and at most equal to 0.5 mm.

[0087] By average diameter is meant an arithmetic mean of the diameters, not necessarily identical, of the openings on the flank surface.

[0088] The contrast between a high-contrast flank element and a portion of flank surface adjacent to said high-contrast flank element is due to a difference in brightness between the two areas. An adjacent surface portion, which may be smooth or have a different texture, has a higher brightness than the texture of said high-contrast flank element, i.e. it appears visually lighter.

[0089] Brightness can be quantified by luminous luminance, expressed in candela / m 2, which measures the luminous flux coming from an illuminated surface that is reflected in the observer's eye. But the relationship between luminous luminance and the visual perception of brightness is not linear and is complex. This is why, on a practical level, the International Commission on Illumination (CIE) has defined the brightness L*, a parameter that characterizes the capacity of a surface to reflect light, from the luminous luminance of light produced by a primary or secondary source, expressed in candelas per square meter (cd / m 2 ), relative to the luminous luminance of white taken as a reference. Thus, in the following, the luminosity L* is expressed according to a scale ranging from 0 to 100 in accordance with the L*a*b* colorimetric model adopted in 1976 by the International Commission on Illumination. The value 100 represents white or total reflection and the value 0 represents black or total absorption.

[0090] To calculate the difference between a first brightness L*1 of the texture of the high-contrast flank element and a second brightness L*2 of an adjacent flank surface portion, the first brightness L*1 and the second brightness L*2 must be measured respectively using a spectro-colorimeter, for example a KONICA-MINOLTA CM 700D spectro-colorimeter. To measure the first brightness L*1 of the texture, the spectro-colorimeter is positioned on the texture and this measurement is carried out with the SCI mode (Specular Reflection Included Mode) set at an angle of 8° and with a light setting of type D65 (setting defined according to CIE). Similarly, to measure the second brightness L*2 of an adjacent flank surface portion, the spectro-colorimeter is positioned on said flank surface portion.In order to improve the determination of this second brightness L*2, it is possible to carry out a plurality of brightness measurements on several adjacent portions of flank surface, then to deduce an associated average brightness.

[0091] Advantageously, the texture of the high-contrast flank element has a first brightness L*1 at least equal to 1 and at most equal to 15, preferably at least equal to 4 and at most equal to 13.

[0092] The lower the brightness of the high-contrast sidewall element in the new condition of the tire, the greater the contrast for a given brightness of an adjacent sidewall surface portion, and the more significant this contrast will remain over time on the aged tire. Indeed, over time, this first brightness L* 1 of the texture of the high-contrast sidewall element tends to increase due, for example, to dust, dirt, or aging of the material. Furthermore, in this brightness range, there is good contrast with any adjacent sidewall surface portion, which, in conventional tire designs, has a brightness most often between between 24 and 28. It should be noted that a texture with a first brightness L*l, typically at least equal to 9, is easier to achieve, but the contrast is low.

[0093] Also advantageously any portion of flank surface adjacent to the high contrast flank element has a second brightness L*2 at least equal to L*l+5, preferably at least equal to L*l+10 and even more preferably at least equal to L*l+12.

[0094] The greater the difference in brightness, the greater the contrast. The greater the difference in brightness on the new tire, the more significant it will remain over time on the older tire.

[0095] Advantageously, any portion of flank surface adjacent to the high-contrast flank element has a second brightness L*2 at least equal to 18, preferably at least equal to 22.

[0096] The rubber composition described within the scope of the present invention is illustrated by the following non-limiting examples.

[0097] In order to confirm the properties of the rubber composition of the present invention, eleven rubber compositions (C1, C2, C3, C4, C5 and C6: examples according to the invention, T1: reference, and T2, T3, T4 and T5: comparative examples) were used. Each of the formulations of the rubber compositions is presented in Table 1 with the amounts of the various ingredients expressed in phr.

[0098] Each rubber composition was produced as follows: the reinforcing filler, the elastomer matrix, the rubber crumb, the plasticizing agent and the various other ingredients such as the anti-ozone wax, with the exception of the vulcanization system, were successively introduced into an internal mixer having an initial tank temperature equal to 60°C, the internal “Banbury” type mixer being filled to approximately 70% of its volume. The thermomechanical work (non-productive phase) was then carried out in a single step lasting from 3 minutes to 4 minutes, until a maximum “drop” temperature of 165°C was reached. The mixture thus obtained was recovered and cooled, then the vulcanizing agent (sulfur) and the vulcanization accelerator (N-cyclohexyl-2-benzothiazolesulfenamide) of the crosslinking system were incorporated on an external mixer (homo-finisher) at a temperature of 30°C, the everything being mixed (productive phase) for a period of more than 5 minutes and less than 12 minutes.

[0099] The rubber compositions thus obtained were then calendered into sheets for the measurement of their tear resistance and rolling resistance properties according to the protocols below.

[0100] Regarding the tear test, the measurement of tear resistance is carried out as follows. At 100°C, the force required to achieve rupture (FRD, in Mpa (in N / mm)) is determined and, at 100°C, the strain at rupture (DRD, in %) is measured. To do this, a test piece measuring 10 x 145 x 2.5 mm is used, notched in the center of its length by 3 notches to a depth of 3 mm, to cause the specimen to rupture. This allows the energy required to cause rupture (fracture energy) of the specimen to be determined, which is the product of the FRD and DRD. The force required to achieve rupture and the strain at rupture are measured on a specimen stretched at 375 mm / min to cause the specimen to rupture.

[0101] The tear performance results are expressed in base 100, with the value 100 being assigned to the tear energy of the reference rubber composition (Tl). The values ​​of energy at break, in base 100, of the tested rubber compositions are presented in Table 2. The higher the value, i.e. the greater the deviation of energy at break from the reference, the higher the tear resistance, in relative value, i.e. the higher the tear performance.

[0102] To measure the hysteresis of a rubber compound, an essential parameter with respect to rolling resistance, it is necessary to measure the dynamic properties of the rubber compound. Dynamic properties, such as the dynamic shear modulus (or dynamic modulus) G', the viscous shear modulus G”, the loss factor tan ô, and the complex dynamic modulus G*, are obtained from measurements carried out on a viscoanalyzer (Metravib VA4000) with glued specimens of vulcanized rubber compounds. The specimens used are described in ASTM D 5992-96 (the version published in September 2006 but initially approved in 1996 is used) in Figure X2.1 (specimens circular). The diameter “d” of each test piece is 10 mm (the circular section is thus 78.5 mm 2), the thickness “L” of each specimen is 2 mm, giving a “d / L” ratio of 5 (as opposed to the ISO 2856 standard, mentioned in paragraph X2.4 of the ASTM standard, which recommends a d / L value of 2).

[0103] The response of a specimen of vulcanized rubber composition, subjected to a sinusoidal stress in alternating simple shear, at a frequency of 10 Hz, at a temperature of 23 ° C, is recorded. A strain amplitude sweep is carried out from 0.1% to 50% (peak to peak on the forward cycle, i.e. 12 measurement points), then from 50% to 0.1% (peak to peak on the return cycle, i.e. 11 measurement points). After each data acquisition, the dynamic shear elastic modulus (G') and the viscous shear modulus (G") on the return cycle, as well as the loss factor (tan ô), which corresponds to the ratio G" / G', were calculated. Similarly, the complex modulus (G*) is defined as the absolute value of the complex sum of the elastic modulus (G) and the viscous modulus (G"): G* = (G2 +G"2) 0 ' 5 .

[0104] Each value of tan ô at 10 Hz and 23°C is representative of the hysteresis of the corresponding rubber composition, therefore of the contribution of the rubber composition to the rolling resistance of a tire.

[0105] The hysteresis performance results are expressed in base 100, with the value 100 being assigned to the reference rubber composition (Tl). The hysteresis performance results of the examples (C1, C2, C3, C4, C5 and C6) according to the invention and of the comparative examples (T2, T3, T4 and T5) are shown in Table 2. The values ​​indicated correspond to the ratio between the loss factor of the reference composition Tl and that of the rubber composition X: tan δ (Tl, 10 Hz, 23°C) / tan δ (X, 10 Hz, 23°C) x 100, where X represents one of the rubber compositions C1, C2, C3, C4, C5, C6, T2, T3, T4 and T5. The higher the value, the lower the loss factor of the rubber composition, relative to that of the reference, the better the hysteresis performance, therefore the lower the contribution of the rubber composition to the rolling resistance, and therefore the rolling resistance.

[0106] The formulations of the various rubber compositions are shown in Table 1 below, with all quantities expressed in pce: [Table 1] (1) Isoprenic elastomer: natural rubber; (2) Butadiene elastomer: cis-1,4 polybutadiene synthesized with a neodymium catalyst having a cis-1,4 bonding rate of at least 98 mol%; (3) Carbon black of grade ASTM N550 according to ASTM D1765-14 having an STSA measured according to ASTM D6556-10 equal to 39 m 2 / g, a COAN index measured according to ASTM D3493-16 equal to 85 ml / 100g; (4) Rubber crumb obtained by recycling (micronization of used tires), and marketed by Lehigh Technology, the percentage of rubber crumb microparticles retained by a 250 μm sieve of which is less than 1% by weight, measured according to standard ASTM D5644-01 (2013), and the percentage of rubber crumb particles, retained by a 177 μm sieve, of which is less than 10% by weight, relative to the total weight of the rubber crumb particles, the rubber crumb being unmodified; (5) Anti-ozone wax marketed by Sasol under the commercial reference “Varazon 4959”; (6) TDAE oil marketed by H&R under the commercial reference “VivaTec 500”; (7) Mixture of 2 antioxidants: ((N-(l,3-dimethylbutyl)-N-phenyl-para-phenylenediamine marketed by Flexsys under the reference “Santoflex 6-PPD” and 2,2,4-trimethyl-l,2-dihydroquinolone marketed by Lanxess; (8) Stearic acid marketed by Uniquema under the reference “Pristerene 4931”; (9) Zinc oxide: commercial quality, marketed by Umicore; (10) N-dicyclohexyl-2-benzothiazolesulfenamide marketed by Flexsys under the reference “Santocure CBS”. A / C weight ratio: ratio between the rate of reinforcing filler, expressed in pce, and the rate of the plasticizing agent, expressed in pce; Sum A + B: sum of the reinforcing filler rate, expressed in pce, and the rubber crumb rate, expressed in pce; B / A weight ratio: ratio between the rubber crumb rate, expressed in pce, and the reinforcing filler rate expressed in pce.

[0107] The results of the respective performances in tearability and hysteresis are presented in Table 2 below: [Table 2]

[0108] The results in Table 2 show that the rubber compositions according to the invention (C1 to C6) have both the best tear and hysteresis performances compared to the reference rubber composition T1 and compared to the comparative rubber compositions (T2 to T5).

[0109] In conclusion, the rubber composition according to the invention makes it possible to obtain a sidewall presenting a good compromise of performance properties in terms of tearability and hysteresis, which makes it possible to have a marking with high contrast which is durable over time, throughout the life of the tire.

[0110] The characteristics of the texture constituting a high-contrast sidewall element according to the invention are illustrated by schematic figures 1 to 5, not shown to scale: -Figure 1: Perspective view of a portion of a tire including a sidewall with high-contrast elements, -Figure 2: Half meridian section of a tire including a sidewall with a high-contrast element, -Figure 3: Texture of a high-contrast element including shaped protrusions of strands, according to a first variant of the first preferred embodiment of the texture, -Figure 4: Texture of a high-contrast element comprising blade-shaped protuberances, according to a second variant of the first preferred embodiment of the texture, -Figure 5: Texture of a high-contrast element comprising cavities, according to the second preferred embodiment of the texture.

[0111] Figure 1 is a perspective view of a portion of tire 1 comprising a sidewall 2 with high-contrast elements 3. Among the high-contrast elements 3 are represented two graphic elements 31, intended to communicate technical, commercial or legal information, and an aesthetic element 32.

[0112] Figure 2 is a half-meridian section of a tire 1 comprising a sidewall 2 with a high-contrast element 3 consisting of a texture comprising protuberances 3, in relief relative to the surface of the sidewall 21. The protuberances 4 have the shape of strands as shown in Figure 3.

[0113] Figure 3 is a texture of a high-contrast element 3 comprising strand-shaped protrusions 4, according to a first variant of the first preferred embodiment of the texture. The strand-shaped protrusions 4, in relief relative to a flank surface, have an average height FL at least equal to 0.2 mm and at most equal to 0.8 mm, preferably at least equal to 0.25 mm and at most equal to 0.5 mm. By average height, we mean the arithmetic mean of the heights of all the protrusions. The strand-shaped protrusions 4, spaced apart by an average pitch P4, are distributed according to a surface density at least equal to 5 strands / mm 2and at most equal to 100 strands / mm2, preferably at least equal to 8 strands / mm2 and at most equal to 50 strands / mm2, and more preferably at least equal to 11 strands / mm2 and at most equal to 30 strands / mm2. The strand-shaped protrusions 4, having a diameter varying over the entire height of the strand, have an average diameter D4 at least equal to 0.03 mm and at most equal to 0.5 mm. In the embodiment shown, the strand-shaped protrusions 4 have a diameter which decreases from a strand base, in interface with the flank surface, and a free strand top.

[0114] Figure 4 is a texture of a high-contrast element 3 comprising blade-shaped protrusions 5, according to a second variant of the first preferred embodiment of the texture. The blade-shaped protrusions 5, in relief relative to a flank surface, have an average height LL at least equal to 0.2 mm and at most equal to 0.8 mm, preferably at least equal to 0.25 mm and at most equal to 0.5 mm. By average height is meant the arithmetic mean of the heights of all the protrusions. The blade-shaped protrusions 5 are distributed according to a pitch P5 at least equal to 0.1 mm and at most equal to 0.4 mm, preferably at least equal to 0.15 mm and at most equal to 0.3 mm. The blade-shaped protrusions 5, having a width varying over the entire height of the blade, have an average width D5 at least equal to 0.03 mm and at most equal to 0.5 mm.In the embodiment shown, the blade-like protrusions 5 have a width that decreases from a blade base, interfacing with the flank surface, and a free blade apex.

[0115] Figure 5 is a texture of a high-contrast element 3 comprising cavities 6, according to the second preferred embodiment of the texture. The cavities 6, recessed relative to a flank surface, have an average depth He at least equal to 0.2 mm and at most equal to 0.8 mm, preferably at least equal to 0.25 mm and at most equal to 0.5 mm. By average depth, we mean the arithmetic mean of the depths of all the cavities. A cavity 6 is constituted by a cavity interior 62, formed in the thickness of the flank, and an opening 61, opening into the surface of the flank. The openings 61 on the flank surface, spaced apart by a pitch PÔ, are distributed according to a surface density at least equal to 5 openings s / mm 2and at most equal to 100 openings / mm 2 , preferably at least equal to 8 openings / mm 2 and at most equal to 50 openings / mm 2 , and preferably at least equal to 11 openings / mm 2 and at most equal to 30 openings / mm 2 . The openings 61 on the flank surface have an average diameter of at least 0.03 mm and at most 0.5 mm. By average diameter is meant an arithmetic mean of the diameters, not necessarily identical, of the openings on the flank surface.

Claims

Claims 1. Tire (1) for a vehicle, comprising a sidewall (2) with at least one high-contrast sidewall element (3): -the high-contrast sidewall element (3) being constituted by a texture comprising protuberances (4, 5), in relief relative to a sidewall surface (21), in contact with atmospheric air, and / or cavities (6), hollow relative to the sidewall surface (21), -the sidewall (2) comprising a rubber composition based on an elastomer matrix, at least one reinforcing filler, at least one crosslinking system, at least one plasticizing agent and at least one rubber crumb, characterized in that the weight ratio between the reinforcing filler content, expressed in pce, and the plasticizing agent content, expressed in pce, is at most equal to 4.50, in that the sum of the reinforcing filler content, expressed in pce, and the rubber crumb content, expressed in pce, is at least equal to 30 pce and at most equal to 70 pce, and in that the weight ratio between the rubber crumb content, expressed in pce, and the reinforcing filler content, expressed in pce, is at least equal to 0.20 and at most equal to 2.

50.

2. Tire (1) according to claim 1, in which the weight ratio between the level of reinforcing filler, expressed in pce, and the level of plasticizing agent, expressed in pce, is at least equal to 1.50, preferably at least equal to 2.00 and at most equal to 4.00, and more preferably at least equal to 2.00 and at most equal to 3.

50.

3. Tire (1) according to one of claims 1 or 2, in which the sum of the reinforcing filler content, expressed in pce, and the rubber crumb content, expressed in pce, is at least equal to 35 pce and at most equal to 65 pce, preferably at least equal to 35 pce and at most equal to 63 pce, and more preferably at least equal to 40 pce and at most equal to 63 pce.

4. Tire (1) according to any one of claims 1 to 3, in which the weight ratio between the rate of rubber crumb, expressed in pce, and the rate of reinforcing filler, expressed in pce, is at least equal to 0.25 and at most equal to 1.

50.

5. Tire (1) according to any one of claims 1 to 4, in which the reinforcing filler rate is at least equal to 5 pce and at most equal to 70 pce, preferably at least equal to 5 pce and at most equal to 60 pce, more preferably at least equal to 5 pce and at most equal to 55 pce, even more preferably at least equal to 10 pce and at most equal to 50 pce, and even more preferably at least equal to 20 pce and at most equal to 45 pce.

6. Tire (1) according to any one of claims 1 to 5, in which the reinforcing filler mainly comprises carbon black.

7. Tire (1) according to any one of claims 1 to 6, in which the level of plasticizing agent is at least equal to 2 pce and at most equal to 28 pce, preferably at least equal to 7 pce and at most equal to 24 pce, and more preferably at least equal to 10 pce and at most equal to 20 pce.

8. Tire (1) according to any one of claims 1 to 7, wherein the at least one plasticizing agent is chosen from the group consisting of plasticizing oils, high Tg plasticizing resins, and combinations thereof.

9. Tire according to any one of claims 1 to 8, in which the rubber crumb content is at least equal to 2 pce and at most equal to 35 pce, preferably at least equal to 5 pce and at most equal to 33 pce, more preferably at least equal to 6 pce and at most equal to 32 pce, even more preferably at least equal to 7 pce and at most equal to 31 pce, and even more preferably at least equal to 8 pce and at most equal to 30 pce.

10. A tire according to any one of claims 1 to 9, wherein the rubber crumb has a microparticle size distribution such that it comprises less than 1% by mass of microparticles not retained through a 250 µm sieve and less than 10% by mass of microparticles not retained through a 177 µm sieve, relative to the total mass of the rubber crumb microparticles.

11. Tire (1) according to any one of claims 1 to 10, in which the high-contrast sidewall element (3) is constituted by a texture comprising protuberances (4, 5), in relief relative to a sidewall surface (21), having an average height (H4, H5) at least equal to 0.2 mm and at most equal to 0.8 mm, preferably at least equal to 0.25 mm and at most equal to 0.5 mm.

12. Tire (1) according to claim 11, in which the high-contrast sidewall element (3) is constituted by a texture comprising strand-shaped protuberances (4), distributed according to a surface density at least equal to 5 strands / mm 2 and at most equal to 100 strands / mm 2 , preferably at least equal to 8 strands / mm 2 and at most equal to 50 strands / mm 2 , and even more preferably at least equal to 11 strands / mm 2 and at most equal to 30 strands / mm 2 .

13. Tire (1) according to one of claims 11 or 12, in which the high-contrast sidewall element (3) consists of a texture comprising strand-shaped protuberances (4) having an average diameter (D4) at least equal to 0.03 mm and at most equal to 0.5 mm.

14. A tire (1) according to any one of claims 11 to 13, wherein the high contrast sidewall element (3) is constituted by a texture comprising strand-shaped protrusions (4) having a diameter which decreases from a strand base, interfacing with the sidewall surface (21), and a free strand top.

15. Tire (1) according to claim 11, in which the high-contrast sidewall element (3) is constituted by a texture comprising blade-shaped protuberances (5) distributed at a pitch (P5) at least equal to 0.1 mm and at most equal to 0.4 mm, preferably at least equal to 0.15 mm and at most equal to 0.3 mm.

16. Tire (1) according to claim 15, wherein the high-contrast sidewall element (3) is constituted by a texture comprising blade-shaped protrusions (5) having an average width (D5) at least equal to 0.03 mm and at most equal to 0.5 mm.

17. Tire (1) according to one of claims 15 or 16, in which the high-contrast sidewall element (3) consists of a texture comprising protuberances in the form of blades (5) having a width which decreases from a blade base, interfacing with the flank surface (21), and a free blade apex.

18. Tire (1) according to any one of claims 1 to 10, in which the high-contrast sidewall element (3) is constituted by a texture comprising cavities (6), hollow relative to a sidewall surface (21), having an average depth (He) at least equal to 0.2 mm and at most equal to 0.7 mm, preferably at least equal to 0.25 mm and at most equal to 0.4 mm.

19. Tire (1) according to claim 18, in which the high-contrast sidewall element (3) is constituted by a texture comprising cavities (6) whose openings (61) on the sidewall surface (21) are distributed according to a surface density at least equal to 5 openings / mm 2 and at most equal to 100 openings / mm 2 , preferably at least equal to 8 openings / mm 2 and at most equal to 50 openings / mm 2 , and preferably at least equal to 11 openings / mm 2 and at most equal to 30 openings / mm 2 .

20. Tire (1) according to one of claims 18 or 19, in which the high-contrast sidewall element (3) is constituted by a texture comprising cavities (6) whose openings (61) on the sidewall surface (21) have an average diameter (De) at least equal to 0.03 mm and at most equal to 0.5 mm.

21. Tire (1) according to any one of claims 1 to 20, wherein the texture of the high-contrast sidewall element (3) has a first brightness L*1 at least equal to 1 and at most equal to 15, preferably at least equal to 4 and at most equal to 13.

22. Tire (1) according to any one of claims 1 to 21, wherein any portion of sidewall surface (21) adjacent to the high contrast sidewall element (3) has a second brightness L*2 at least equal to L* 1+5, preferably at least equal to L*l+10 and even more preferably at least equal to L*l+12.

23. Tire (1) according to any one of claims 1 to 22, wherein any portion of sidewall surface (21) adjacent to the high contrast sidewall element (3) has a second brightness L*2 at least equal to 18, preferably at least equal to 22.

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