Tyre comprising sidewall having at least one high-contrast sidewall element

Abstract

The invention relates to a tyre (1) for a vehicle, said tyre comprising at least one sidewall (2) having at least one high-contrast sidewall element (3), said high-contrast sidewall element (3) being made up of a texture such that the high-contrast sidewall element (3) has a high-contrast profile. The texture comprises protrusions (4, 5) protruding relative to the sidewall surface (21) and / or cavities (6) recessed relative to the sidewall surface (21) in contact with ambient air. A rubber composition of a sidewall (2) that exhibits a good compromise between blooming reduction and ozone erosion resistance is disclosed. According to the invention, the elastomer matrix comprises an isoprene elastomer in a content of at least 35 phr and at most 65 phr and a butadiene elastomer in a content of at least 35 phr and at most 65 phr, the reinforcing filler content is at least 5 phr and at most 70 phr, the anti-ozone wax content is at least 1.2 phr and at most 2.8 phr, and the particulate rubber content is at least 2 phr and at most 30 phr.

Description

Technical Field

[0001] The present invention relates to a tire for a vehicle, the tire comprising a sidewall having at least one high-contrast sidewall element. Background Technology

[0002] A tire consists of two sidewalls, which are the parts of the tire that connect the end of the tread (which is designed to contact the ground) to the bead (which is designed to be mounted on the rim).

[0003] In the following text, the outer surface of the tire sidewall that comes into contact with atmospheric air is more simply referred to as the "sidewall surface". The sidewall surface typically includes at least one graphic element and / or optional aesthetic elements. The graphic element (which is often referred to as a mark and includes letters, numbers, or symbols) is usually designed to convey technical, commercial, or legal information.

[0004] By definition, a high-contrast sidewall element refers to a sidewall surface element composed of a specific texture that differs from the texture of the sidewall surface (which is most typically smooth). This texture makes the high-contrast sidewall element appear darker than any adjacent portion of the sidewall surface, making it visually distinguishable from any other adjacent sidewall surface portion. The body of the high-contrast sidewall element can be a graphic or aesthetic element, or a portion of the sidewall surface surrounding the graphic or aesthetic element, thereby making the graphic or aesthetic element particularly visible on the sidewall surface.

[0005] Therefore, tire designers have always focused on producing high-contrast sidewall elements, whether for enhancing the graphic or aesthetic aspects of the sidewall surface.

[0006] The texture of these high-contrast sidewall elements is known to be produced by protrusions that project relative to the sidewall surface, or cavities that are recessed relative to the sidewall surface, or a combination of protrusions and cavities. This texture is made of the same rubber material (also called a rubber composition or elastomer composition) as the sidewall portion that is in contact with atmospheric air, because this texture is integral with the sidewall.

[0007] High-contrast sidewall elements comprising textures including protrusions in the form of blades or flakes have been described in documents WO 2007045425 A1, WO 2011036061 A1 and WO 2014202731 A1. High-contrast sidewall elements comprising textures including cavities recessed relative to the sidewall surface have been described in document WO 2014040967 A1.

[0008] The texture of high-contrast sidewall elements is most typically produced by molding during the tire curing process. As a non-limiting example, the molded elements (designed to produce the texture of high-contrast sidewall elements) are produced by machining or laser etching. The texture of high-contrast sidewall elements can also be produced, for example, directly on the sidewall surface of the cured tire by laser etching. Thus, the texture is composed of the same material as the rest of the sidewall.

[0009] The texture of high-contrast sidewall elements, including protrusions in the form of blades or slats, absorbs most of the incident light after one or more consecutive reflections on the walls of the protrusions. This allows the texture to appear darker, thus increasing its contrast and consequently its visibility relative to any adjacent portion of the sidewall surface. Furthermore, this special texture provides a comfortable feel on a "velvet" type sidewall surface. Finally, the texture used has water-repellent and slightly hydrophobic properties. In certain embodiments, the texture can be located on a surface recessed relative to the sidewall surface, such that it is embedded in the sidewall, which has the advantage of protecting it from wear caused by scratches from the sidewall surface to the road surface.

[0010] Similarly, the texture of high-contrast sidewall elements, including cavities recessed relative to the sidewall surface, can absorb most of the incident light after one or more consecutive reflections on the walls of the cavities. This particular texture, recessed relative to the sidewall surface, has the advantage of ensuring its durability by protecting it from wear caused by scratches from the sidewall surface to the road surface. It also has the advantage of not interfering with the aerodynamic flow of air near the sidewall surface when the tire is rolling.

[0011] It has been found that on tire sidewall surfaces including high-contrast sidewall elements, the contrast between the high-contrast sidewall elements and any adjacent sidewall surface portions varies over time.

[0012] Changes in contrast over time lead to changes in texture and the visual appearance of the tire sidewall surface.

[0013] Changes in texture may result from dirt accumulation, at least partial wear, or aging of the materials that make up the texture.

[0014] Changes in the visual appearance of the tire sidewall surface typically result in at least a localized change in its color (blue staining, turning dark brown, white spots), a change in its brightness (a duller appearance), or the appearance of surface scratches or cracks.

[0015] More comprehensively, the aging of the tire sidewall surface is related to the elastomeric properties of its materials. Conventional rubber compositions, in a known manner, contain natural or synthetic diene elastomers with carbon-carbon double bonds in their molecular chains. These double bonds are chemically more reactive than carbon-carbon single bonds, and therefore can deteriorate more or less rapidly after prolonged exposure to the atmosphere due to known mechanisms of oxidation and ozone decomposition. The effects of ozone promote the formation of cracks on the tire sidewall surface. These deterioration mechanisms are further accelerated by the effects of heat (thermal oxidation) or light (photo-oxidation).

[0016] To combat the chemical degradation of rubber compositions due to ozone, it is known to use anti-ozone agents, such as anti-ozone waxes. These anti-ozone waxes provide protection under static conditions by forming a protective surface coating. However, these anti-ozone waxes are characterized by their ability to migrate to the sidewall surface and crystallize, which alters the visual appearance of the sidewall surface by producing a speckled appearance, a dark gray appearance, or a lighter color. This phenomenon is known as blooming. This phenomenon also results in uneven coloring and dulls the sidewall surface, which is initially dark and glossy.

[0017] Therefore, uneven color on the sidewall surface reduces the contrast effect of high-contrast elements and impairs the visual and aesthetic appearance of the sidewall.

[0018] In order to achieve a durable high-contrast sidewall element throughout the tire's lifespan, it is necessary to reduce or eliminate the degradation of the tire sidewall surface's color and / or gloss, while also ensuring its good resistance to ozone erosion (which causes cracks on the sidewall surface).

[0019] In fact, extending the lifespan of contrast is a significant business factor for tire manufacturers. Therefore, for example, when a user replaces only the tires mounted on the front of their vehicle, they might notice a significant difference in contrast observed on a brand-new tire mounted on the front of the vehicle compared to the contrast observed on a worn tire mounted on the rear. This difference in contrast between front and rear tires might be considered unacceptable by the user, especially if their vehicle is a sports car or luxury car. Summary of the Invention

[0020] For a tire including a sidewall with at least one high-contrast sidewall element, the inventors aim to improve the durability of the contrast between the high-contrast sidewall element and adjacent sidewall surface portions over a period of time through a suitable rubber composition of the sidewall (particularly near the sidewall surface).

[0021] This objective has been achieved through tires for vehicles, the tires including a sidewall having at least one high-contrast sidewall element: - The high-contrast sidewall element is composed of a texture that includes protrusions that are in contact with atmospheric air and / or cavities that are recessed relative to the sidewall surface. - The sidewall contains a rubber composition based on an elastomer matrix, at least one reinforcing filler, at least one crosslinking system, at least one plasticizer, at least one anti-ozone wax, and at least one granular rubber; - The elastomer matrix comprises an isoprene elastomer in a content of at least 35 phr and at most 65 phr and a butadiene elastomer in a content of at least 35 phr and at most 65 phr; - The content of reinforcing filler is at least 5 phr and at most 70 phr; - The content of anti-ozone wax is at least 1.2 phr and at most 2.8 phr; - And the content of granular rubber is at least 2 phr and at most 30 phr.

[0022] According to the present invention, the high-contrast sidewall element is composed of a texture that includes protrusions that are in contact with atmospheric air and protrude relative to the sidewall surface and / or cavities that are recessed relative to the sidewall surface.

[0023] According to the present 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 plasticizer, at least one anti-ozone wax, and at least one granular rubber.

[0024] The statement "rubber composition based on" means that the rubber composition contains reaction mixtures and / or in-situ reaction products of different components used, some of which are capable and / or designed to react with each other at least partially at different stages of the production of the rubber composition, so that the rubber composition can be in a fully or partially crosslinked state, or in a non-crosslinked state.

[0025] The rubber composition contains at least one elastomer, and typically contains multiple elastomers, particularly multiple diene elastomers. The mixture of elastomers (especially diene elastomers) is referred to as the elastomer matrix. Preferably, the elastomer matrix contains at least two different diene elastomers.

[0026] "Elastomer" refers to a polymer (i.e., a homopolymer or copolymer) that possesses elastic properties acquired after cross-linking. The term rubber is a common synonym for elastomer.

[0027] "Diene elastomer" or equivalent "diene rubber" (whether natural or synthetic) refers to an elastomer that is at least partially composed of diene monomer units (monomers with two conjugated or non-conjugated carbon-carbon double bonds). Diene elastomers are non-thermoplastic.

[0028] Diene elastomers can be classified into two categories: "substantially unsaturated" diene elastomers and "substantially saturated" diene elastomers. "Substantially unsaturated" diene elastomers are diene elastomers obtained by having at least a portion of a diene source (conjugated diene) mode or unit content greater than 15% (mol%) of a conjugated diene monomer. Therefore, EPDM-type copolymers such as butyl rubber or diene and α-olefin are not included in the foregoing definition and can be specifically classified as "substantially saturated" diene elastomers (low or very low diene source mode content, always less than 15%).

[0029] Specifically, the diene elastomer that can be used in the rubber composition according to the present invention means: a) Any homopolymer of conjugated or non-conjugated diene monomers having 4 to 18 carbon atoms; b) Any copolymer of a conjugated or non-conjugated diene having 4 to 18 carbon atoms with at least one other monomer; the other monomer may be ethylene, olefin or conjugated or non-conjugated diene.

[0030] Suitable conjugated dienes are those having 4 to 12 carbon atoms, especially 1,3-dienes, such as 1,3-butadiene and isoprene.

[0031] Suitable nonconjugated dienes are those with 6 to 12 carbon atoms, such as 1,4-hexadiene, ethylidene norbornene, or dicyclopentadiene.

[0032] Suitable olefins are vinyl aromatic compounds having 8 to 20 carbon atoms and α-aliphatic monoolefins having 3 to 12 carbon atoms.

[0033] Suitable vinyl aromatic compounds include, for example, styrene, (o-, m-, p-)methylstyrene, commercial "vinyl toluene" mixtures, and p-tert-butylstyrene.

[0034] Suitable α-aliphatic monoolefins are particularly α-acyclic aliphatic monoolefins having 3 to 18 carbon atoms.

[0035] More specifically, the diene elastomer is: (a') Any homopolymer of a conjugated diene monomer, especially any homopolymer obtained by polymerization of a conjugated diene monomer having 4 to 12 carbon atoms; (b') Any copolymer obtained by copolymerizing one or more conjugated dienes with each other or by copolymerizing one or more conjugated dienes with one or more vinyl aromatic compounds having 8 to 20 carbon atoms; (c') Any copolymer obtained by copolymerization of one or more dienes (whether conjugated or non-conjugated) with ethylene, α-monoolefins or mixtures thereof, for example, an elastomer obtained from ethylene, propylene and non-conjugated diene monomers of the type described above.

[0036] The reinforcing filler (which is designed to reinforce the rubber composition) can be an organic filler (e.g., carbon black) or an inorganic filler (e.g., silica or alumina combined with a binder between the inorganic filler and the diene elastomer) or a mixture of these types of fillers.

[0037] The crosslinking system can be any type of system known to those skilled in the art of tire rubber compositions. In particular, it can be based on sulfur and / or peroxides and / or bismaleimides. Preferably, the crosslinking system is based on sulfur: then it is referred to as a curing system. Sulfur can be added in any form (particularly molecular sulfur or sulfur donors). It is also preferred that at least one curing accelerator is present, and optionally, and preferably, various known curing activators or known curing retarders can be used, such as zinc oxide, stearic acid or equivalent compounds (e.g., stearates and transition metal salts), guanidine derivatives (particularly diphenylguanidine). As an accelerator, any compound that can act as a curing accelerator for diene elastomers in the presence of sulfur can be used, particularly thiazole-type accelerators and their derivatives, such as sulfenamides, thiurams, dithiocarbamates, dithiophosphates, thioureas, and xanthate-type accelerators.

[0038] Plasticizers are commonly known and used in rubber compositions by those skilled in the art. Plasticizers may be selected from plasticizing oils, high glass transition temperature (Tg) plasticizing resins, and combinations thereof.

[0039] Any additive oil known to have plasticizing properties relative to the elastomer (whether aromatic or non-aromatic) can be used. At ambient temperature (23°C), these oils (more or less viscous) are liquids (as a reminder, substances that ultimately take on their container shape), which is particularly different from high-Tg hydrocarbon resins (which are essentially solids at ambient temperature). The glass transition temperature (Tg) of plasticizing oils is typically below -20°C, preferably below -40°C. The glass transition temperature (Tg) of plasticizing oils is measured according to standard ASTM D3418 (2008).

[0040] By definition, high Tg hydrocarbon resins (typically at least 30°C) are solid at ambient temperature and pressure (23°C, 1 atm), while plasticizing oils are liquid at ambient temperature, and low Tg hydrocarbon resins are viscous at ambient temperature. Hydrocarbon resins (also known as hydrocarbon plasticizers) are polymers well-known to those skilled in the art, primarily based on carbon and hydrogen, but capable of containing other types of atoms (e.g., oxygen), and can be used particularly as plasticizers or thickeners in polymer matrices. They are inherently at least partially miscible (i.e., compatible) with the contents used in the polymer compositions in which they are employed, for example, acting as true diluents. In a known manner, these hydrocarbon resins can also be classified as thermoplastic resins because they soften upon heating and are therefore moldable. The glass transition temperature (Tg) of plasticizers is measured according to standard ASTM D3418 (2008).

[0041] The anti-ozone waxes involved can be, for example, paraffin wax, microcrystalline wax, or a mixture of paraffin wax and microcrystalline wax. They consist of a mixture of linear and nonlinear alkanes (isoalkanes, cycloalkanes, branched alkanes) obtained from petroleum refineries or catalytic hydrogenation of carbon monoxide (Fisher Tropsch process), and mainly contain chains with at least 20 carbon atoms.

[0042] The alkane distribution was determined by gas chromatography with a flame ionization detector (“GPC-FID”). Chromatography was performed according to the EWF (“European Wax Federation”) method.

[0043] All known anti-ozone waxes (including natural waxes) can be used, such as candelilla wax or carnauba wax. Furthermore, these waxes can be used in blend form.

[0044] Anti-ozone waxes are commercially available, such as Sasol's "Varazon 4959", "Varazon 6500" and "Varazon 6810", Nippon Seiro's "Ozoace 0355", H&R's "Negozone 9343" and Yanggu Huatai's "H3841".

[0045] Granular rubber is in the form of granules and can optionally be made into rubber sheets.

[0046] Typically, this granular rubber is obtained by grinding or micronizing cured rubber compounds that have already been used in their initial applications (such as tires, shoe soles, and seals). Therefore, it is a product of the recycling of these materials.

[0047] In a known manner, granular rubber can be obtained more specifically by reducing waste tires (from which reinforcing materials such as steel or fabric fibers have been removed) into granules.

[0048] Granulated rubber can be prepared by cryogenic crushing of waste tires, for example, according to the method described in document US 7445170, which includes successive and independent steps of granulation, separation of metal and fabric reinforcements, cooling, and micronization, thereby obtaining a coarse distribution of fine particles (also called microparticles) of the cured mixture. This micronization can be carried out using an impact mill with a conical shape, such as that described in document US 7861958. The cryogenic feed material enters the mill (e.g., a CUM150 mill manufactured by Netzsch or a CW250 manufactured by Alpine can be used), and is then transferred by gravity to a high-speed rotating rotor. Thus, the cryogenic feed material is repeatedly impacted against the walls of the rotor chamber, resulting in its micronization. The particles can then be separated from the final components not made from the cured mixture by passing through a series of two vibrating screens of the same size. A coarse distribution of fine particles of the cured mixture is obtained. "Microparticles" refers to particles with a size (i.e., its diameter in the case of spherical particles, or its maximum size in the case of unequal-axis particles) of tens or hundreds of micrometers. The size of the particles can be determined using techniques known to those skilled in the art, such as microscopy. Granular rubber is commercially available from suppliers such as Lehigh Technology.

[0049] Granular rubber can be simple rubber fragments or microparticles without further processing. However, it is also known that granular rubber can be processed to modify it. Such processing can include chemical modification such as functionalization or desulfurization. It can also be thermo-mechanical treatment, thermo-chemical treatment, or biological treatment.

[0050] According to the present invention, the elastomer matrix comprises an isoprene elastomer in a content of at least 35 phr and at most 65 phr and a butadiene elastomer in a content of at least 35 phr and at most 65 phr.

[0051] In a known manner, "isoprene elastomer" refers to a homopolymer or copolymer of isoprene. In other words, isoprene elastomers can be selected from natural rubber (NR), synthetic polyisoprene (IR), various isoprene copolymers, and mixtures of these elastomers. Isoprene copolymers particularly include isobutylene-isoprene (butyl rubber-IIR) copolymers, isoprene-styrene (SIR) copolymers, isoprene-butadiene (BIR) copolymers, or isoprene-butadiene-styrene (SBIR) copolymers. Preferably, isoprene elastomers can be selected from natural rubber, synthetic cis-1,4-polyisoprene, and combinations thereof. Even more preferably, isoprene elastomers are selected from natural rubber, synthetic polyisoprene with a cis-1,4 bond content (mol%) greater than 90% (more preferably greater than 98%), and combinations of these elastomers.

[0052] In a known manner, "butadiene elastomer" refers to a homopolymer or copolymer of butadiene. In other words, a butadiene elastomer can be selected from polybutadiene (BR), various butadiene copolymers, and mixtures of these elastomers. Among butadiene copolymers, butadiene-styrene (SBR) copolymers or ethylene-butadiene (EBR) copolymers will be specifically mentioned. Preferably, the butadiene elastomer can be cis-1,4-polybutadiene; particularly, the content (mol%) of cis-1,4 bonds is greater than 90%, and more preferably greater than 96% of the polybutadiene.

[0053] The unit "pce" or "parts per 100 parts of elastomer" indicates a percentage by mass of the elastomer or rubber. In English, this unit is expressed as "phr" ("parts per 100 parts of rubber"). The elastomer in granular rubber is not included in the mass of the elastomer being discussed.

[0054] According to the present invention, the content of reinforcing filler is at least 5 phr and at most 70 phr.

[0055] According to the present invention, the content of the anti-ozone wax is at least 1.2 phr and at most 2.8 phr.

[0056] According to the present invention, the granular rubber content is at least 2 phr and at most 30 phr.

[0057] The inventors have discovered that, for an elastomer matrix having the aforementioned contents of isoprene elastomer and butadiene elastomer, a combination of the aforementioned contents of reinforcing filler, anti-ozone wax and granular rubber can achieve a satisfactory compromise between reduced blooming and sidewall resistance to ozone.

[0058] Advantageously, the content of the anti-ozone wax is at least 1.4 phr and at most 2.6 phr, preferably at least 1.6 phr and at most 2.4 phr.

[0059] Advantageously, the content of granular rubber is at least 5 phr and at most 20 phr, preferably at least 5.5 phr and at most 19.5 phr, more preferably at least 6 phr and at most 19 phr, and even more preferably at least 6 phr and at most 18 phr.

[0060] It should be noted that, according to the present invention, granular rubber is not considered a reinforcing filler. Therefore, the content of granular rubber is not included in the content of reinforcing fillers.

[0061] Advantageously, relative to the total mass of the granular rubber particles, the particle size distribution of the granular rubber comprises less than 1% by mass of particles not retained by a 600 µm sieve and less than 10% by mass of particles not retained by a 105 µm sieve. Preferably, relative to the total mass of the granular rubber particles, the particle size distribution of the granular rubber comprises less than 1% by mass of particles not retained by a 600 µm sieve and less than 10% by mass of particles not retained by a 149 µm sieve. More preferably, relative to the total mass of the granular rubber particles, the particle size distribution of the granular rubber comprises less than 1% by mass of particles not retained by a 600 µm sieve and less than 10% by mass of particles not retained by a 177 µm sieve. Even more preferably, relative to the total mass of the granular rubber particles, the particle size distribution of the granular rubber comprises less than 1% by mass of particles not retained by a 400 µm sieve and less than 10% by mass of particles not retained by a 177 µm sieve. The distribution of granular rubber microparticles was determined according to standard ASTM D5644-01 (2013).

[0062] To obtain granular rubber with this distribution, an additional sieving step is performed according to size criteria. Sieving can be carried out using various techniques known to those skilled in the art (vibration, centrifugation, suction). Preferably, this sieving step is performed using a series of sieves stacked in size order (e.g., sieves with calibrated mesh sizes, such as commercial products from Gerricke). Thus, larger particles are trapped by the sieves, while smaller particles pass to lower grades to reach the next sieve. Those skilled in the art will understand that the distribution considered below can consist of all particles that pass through a given sieve, or of all particles trapped between two grades.

[0063] Furthermore, granular rubber is granular rubber that has not been modified by any treatment selected from heat treatment, mechanical treatment, biological treatment and chemical treatment and combinations thereof.

[0064] Furthermore, the ratio between the content of granular rubber (in phr) and the content of anti-ozone wax (in phr) is at least 5.50 and at most 17.00, preferably at least 6.00 and at most 17.00, more preferably at least 6.50 and at most 12.50.

[0065] Preferably, the content of reinforcing filler is at least 10 phr and at most 60 phr, more preferably at least 15 phr and at most 55 phr, more preferably at least 15 phr and at most 50 phr, and even more preferably at least 15 phr and at most 45 phr.

[0066] Advantageously, the total content of reinforcing filler and granular rubber is at least 30 phr and at most 65 phr, preferably at least 30 phr and at most 60 phr, more preferably at least 35 phr and at most 50 phr.

[0067] Preferably, the reinforcing filler mainly comprises carbon black.

[0068] When referring to a “major” compound, within the meaning of this invention, it means that the compound is dominant among compounds of the same type in the composition, that is, the compound that accounts for the largest amount by weight among compounds of the same type, and preferably greater than 50% by weight, more preferably greater than 75% by weight. Therefore, a “major” filler is the filler that accounts for the largest weight among the fillers in the composition.

[0069] Advantageously, the ratio between the content of reinforcing filler (in phr) and the content of plasticizer (in phr) is at least 1.00 and at most 5.00, preferably at least 1.50 and at most 4.50, more preferably at least 2.00 and at most 4.00, and even more preferably at least 2.00 and at most 3.50.

[0070] When the plasticizer is a mixture of hydrocarbon resin and oil, in order to calculate the above ratio, the plasticizer content is the sum of the hydrocarbon resin content (in phr) and the oil content (in phr).

[0071] Advantageously, at least one plasticizer in the rubber composition is selected from plasticizing oils, high glass transition temperature (Tg) plasticizing resins, and combinations thereof.

[0072] The aforementioned rubber composition (and all embodiments thereof) is particularly the constituent material of a high-contrast sidewall element, which is integral with the sidewall and is composed of a texture comprising protrusions that are in contact with atmospheric air and / or cavities that are recessed relative to the sidewall surface.

[0073] According to a first embodiment of the texture, the high-contrast sidewall element is composed of a texture that includes protrusions that project relative to the sidewall surface, the average height of which is at least 0.2 mm and at most 0.8 mm, preferably at least 0.25 mm and at most 0.5 mm.

[0074] Average height refers to the arithmetic mean of the heights of all protrusions. If the average height is less than 0.2 mm, the texture will easily disappear quickly under repeated scraping of the road surface by the tire sidewall. If the average height is greater than 0.8 mm, the production time of the molded parts designed for the molded protrusions becomes prohibitive relative to the desired contrast effect.

[0075] According to a first embodiment of the protrusion, the high-contrast sidewall element is formed by a texture comprising leaf-shaped protrusions, the protrusions being based on at least 5 blades / mm. 2 And at most 100 blades / mm 2 Preferably, at least 8 blades / mm 2 And at most 50 blades / mm 2 Even more preferred is at least 11 blades / mm 2 And at most 30 blades / mm 2 Surface density distribution.

[0076] Includes at least 5 blades / mm 2 The texture has a uniform visual appearance because below this level, the human eye perceives individual blades. This is especially true when there are a large number of blades (typically greater than 100 blades / mm). 2 In the texture of a tire, the blades must have a small diameter, which makes the texture less tear-resistant, for example, when the tire sidewall is repeatedly scraped against the road surface.

[0077] Advantageously, the high-contrast sidewall element is formed by a texture that includes leaf-shaped protrusions with an average diameter of at least 0.03 mm and at most 0.5 mm.

[0078] "Average diameter" refers to the arithmetic mean of the diameters of a given blade measured over its overall height. This average diameter is not necessarily constant from one blade to another. This type of texture (with blades provided by molding) is less sensitive to tearing of the blades when removed from the mold, where they will remain embedded and require specific cleaning. Furthermore, such tearing of the blades will impair the visual uniformity of high-contrast elements.

[0079] According to a preferred variant of the first embodiment of the protrusion, the high-contrast sidewall element is formed by a texture that includes protrusions in the form of blades having a diameter that decreases from the base of the blade (which engages with the sidewall surface) and free blade apex.

[0080] This type of texture (with blades provided by molding) is less sensitive to tearing of the blades when removed from the mold, as these blades will remain embedded in the mold and therefore require specific cleaning. Furthermore, such tearing of the blades will impair the visual uniformity of high-contrast elements.

[0081] According to a second embodiment of the protrusion, the high-contrast sidewall element is formed by a texture comprising protrusions in the form of sheet-like structures, the protrusions being distributed at a spacing of at least 0.1 mm and at most 0.5 mm, preferably at least 0.15 mm and at most 0.3 mm.

[0082] Thin sheets are easier to mold because their shape facilitates the flow of the elastomeric material and thus aids in its molding. If the spacing between the sheets is less than 0.1 mm, the sheets are too fragile. If the spacing between the sheets is greater than 0.5 mm, the individual sheets will be perceptible to the human eye.

[0083] Advantageously, the high-contrast sidewall element is formed by a texture that includes protrusions in the form of thin sheets, the average width of which is at least 0.03 mm and at most 0.5 mm.

[0084] "Average width" refers to the arithmetic mean of the widths of a given sheet measured over its entire height. This average width is not necessarily constant from one sheet to another.

[0085] According to a preferred variant of the second embodiment of the protrusion, the high-contrast sidewall element is composed of a texture that includes protrusions in the form of sheet-like structures having a width that decreases from the base of the sheet (which is attached to the sidewall surface) and free sheet apexes.

[0086] According to the second texture embodiment, the high-contrast sidewall element is composed of a texture comprising cavities recessed relative to the sidewall surface, the average depth of which is at least 0.2 mm and at most 0.7 mm, preferably at least 0.25 mm and at most 0.4 mm.

[0087] "Average depth" refers to the arithmetic mean of the depths of all cavities. Although the texture of this implementation can be produced by molding, it is particularly well-suited for production by laser ablation or laser etching of the material on a cured tire.

[0088] Advantageously, the high-contrast sidewall element is formed by a texture comprising cavities, the openings of which on the sidewall surface are at least 5 openings / mm. 2 And at most 100 openings / mm 2 Preferably, there are at least 8 openings / mm. 2 And at most 50 openings / mm 2 Even more preferred is at least 11 openings / mm 2 And at most 30 openings / mm 2 Surface density distribution.

[0089] Includes at least 5 openings / mm 2 The texture has a uniform visual appearance because below this level, the human eye perceives individual openings. This includes more than 100 openings / mm. 2 The texture becomes an almost smooth surface that directly reflects light, which is not the desired effect.

[0090] Furthermore, the high-contrast sidewall element is formed by a texture including cavities, the average diameter of the openings of the cavities on the sidewall surface being at least 0.03 mm and at most 0.5 mm.

[0091] The average diameter refers to the arithmetic mean of the diameters of the openings on the sidewall surface (which are not necessarily the same).

[0092] The contrast between the high-contrast sidewall element and the adjacent sidewall surface portion is due to the brightness difference between the two areas. The adjacent surface portion (which may be smooth or may have different textures) is brighter than the texture of the high-contrast sidewall element, meaning it appears brighter visually.

[0093] Brightness can be measured by luminance (in cd / m²). 2 Luminance (L*) is quantified by its representation, measuring the stream of light emitted from an illuminated surface and reflected into the observer's eye. However, the ratio between luminance and visual perception of brightness is not linear but complex. Therefore, the International Commission on Illumination (CIE) defines luminance L* from a practical perspective as a parameter that characterizes the ability of a surface to reflect light (in candela per square meter, cd / m²) based on the brightness of light produced from a primary or secondary light source and relative to white luminance as a reference. 2 (This is a simplified representation). Therefore, in the following text, luminance L* is represented in levels from 0 to 100 according to the L*a*b* color model adopted by the International Commission on Illumination in 1976. A value of 100 represents white or total reflection, and a value of 0 represents black or total absorption.

[0094] To calculate the difference between the first luminance L*1 of the texture of a high-contrast sidewall element and the second luminance L*2 of the surface portion of an adjacent sidewall, the first luminance L*1 and the second luminance L*2 need to be measured separately using a spectrophotometer (e.g., a KONICA-MINOLTA CM 700D spectrophotometer). To measure the first luminance L*1 of the texture, the spectrophotometer is placed on the texture and parameterized at an 8° angle using SCI (including specular reflection) and the measurement is performed using a D65 type light adjustment (adjustment as defined by CIE). Similarly, to measure the second luminance L*2 of the surface portion of an adjacent sidewall, the spectrophotometer is placed on the sidewall surface portion. To improve the determination of the second luminance L*2, multiple luminance measurements can be performed on multiple adjacent sidewall surface portions, and the associated average luminance can then be inferred from them.

[0095] Advantageously, the first brightness L*1 of the texture of the high-contrast sidewall element is at least 1 and at most 15, preferably at least 4 and at most 13.

[0096] The lower the brightness of the high-contrast sidewall elements in a brand-new tire, the greater the contrast for a given brightness of adjacent sidewall surface portions, and this contrast is maintained more significantly over time in aged tires. In fact, the initial brightness L*1 of the texture of the high-contrast sidewall elements tends to increase over time, for example, due to dust, dirt, and material aging. Furthermore, within this brightness range, there is good contrast with any adjacent sidewall surface portion (which in conventional tire designs typically has a brightness between 24 and 28). It should be noted that textures with a first brightness L*1 (which is typically at least 9) are easier to manufacture but have lower contrast.

[0097] Furthermore, the second brightness L*2 of any sidewall surface portion adjacent to the high-contrast sidewall element is at least L*1+5, preferably at least L*1+10, and even more preferably at least L*1+12.

[0098] The greater the difference in brightness, the greater the contrast. The greater the difference in brightness on brand new tires, the more significant the difference in brightness will be on aging tires over a period of time.

[0099] Furthermore, any portion of the sidewall surface adjacent to the high-contrast sidewall element has a second brightness L*2, which is at least 18, preferably at least 22.

[0100] The rubber compositions described in the context of this invention are illustrated by the following non-limiting examples.

[0101] To confirm the properties of the rubber compositions according to the invention, ten rubber compositions were used (C1, C2, C3, C4, and C5: embodiments according to the invention; T1 and T3: references; T2, T4, and T5: comparative examples). Each formulation of the rubber compositions is shown in Tables 1 and 3, where the amounts of various components are expressed in phr.

[0102] Each rubber composition is produced as follows: reinforcing fillers, elastomer matrix, anti-ozone wax, granular rubber (if present), plasticizer, and various other components besides the curing system are continuously introduced into a closed mixer with an initial tank temperature of 60°C; the "Banbury" type closed mixer is filled to approximately 70% of its volume. A thermomechanical process (non-production stage) is then performed in a single step for approximately 3 to 4 minutes until the maximum "discharge" temperature of 165°C is reached. The resulting mixture is recovered and cooled, and then the curing agent (sulfur) and curing activator (N-cyclohexyl-2-benzothiazole sulfenamide) of the crosslinking system are introduced into an open mixer (homogenizer) at 30°C, where all materials are mixed (production stage) for a time greater than 5 minutes and less than 12 minutes.

[0103] The resulting rubber compositions are then calendered into sheets to measure their ozone resistance properties and blooming according to the following scheme.

[0104] Ozone resistance was measured according to the method described below. After curing at 150°C for 40 min in a bell compressor, followed by cooling to ambient temperature (23°C) for one day, and then drying in air at 77°C for 28 days, ten specimens of each elastomer composition to be tested were placed on a trapezoid with a 10% elongation gradient at different elongations ranging from 10% to 100%. The “B15” specimens were obtained from MFTR (known as Monsanto) sheets, with two beads at the ends used to hold the specimen. The specimens, designated “B15”, had the following dimensions: 78.5 mm * 15 mm * 1.5 mm. After exposure to 38°C and 50 ppm (parts per billion) of ozone for 192 hours, the changes in the number and depth of cracks on each facet were recorded. The subjective rating ranged from 0 to 5 (0: no cracks; 1 to 4: increasingly larger and deeper cracks present; 5: specimen fractured). The average score of all deformations was used as the classification criterion. The lower the average value, the better the ozone resistance.

[0105] Table 2 shows the difference between the average score of all deformations for each sample (T2 and C1 to C3) and the reference (T1).

[0106] Similarly, Table 4 shows the difference between the average score of all deformations for each sample (T4, T5, C4, and C5) and the reference (T3).

[0107] Negative values ​​in Tables 2 and 4 indicate improved ozone resistance compared to reference T1 in Table 2 and reference T3 in Table 4.

[0108] The "blooming" performance was measured as follows. After cutting the sheet of the cured rubber composition, 2.5 mm thick samples were dried in air at 70°C for 12 h. They were then dried in air at 40°C for 4 weeks. After being removed from the oven and exposed to ambient temperature (23°C) for 15 min, mechanical stimulation was applied to exhibit blooming of the wax. In this case, mechanical stimulation included scraping the sample with a metal blade. The degree of blooming (white surface) was then evaluated by a subjective rating value representing the final appearance of the sample. The subjective rating values ​​obtained for each sample range from 0 to 3 and correspond to the "blooming score". These values ​​(ranging from 0 to 3) correspond to the following appearance of the sample: 0 - No frosting. The scratched surface remains black.

[0109] 1- Slight frost.

[0110] 2- Moderate frost.

[0111] 3- Completely frosted. The scraped surface is white.

[0112] The lower the rating (i.e., the lower the frosting level), the better the frosting performance.

[0113] Table 2 shows the difference in frosting values ​​between each sample (T2 and C1 to C3) and the reference (T1). Similarly, Table 4 shows the difference in frosting values ​​between each sample (T4, T5, C4, and C5) and the reference (T3). Negative values ​​in Tables 2 and 4 indicate improvements in frosting performance compared to each reference (T1, T3), respectively.

[0114] In the example of Test 1, a reference rubber composition (T1) (excluding granular rubber) and rubber compositions of the sidewalls of compositions T2 (comparison) and C1 to C3 (according to the present invention) were compared as defined in Table 1 below: [Table 1] (1) Natural rubber; (2) Cis-1,4 polybutadiene with a cis-1,4 bond content of at least 98 mol% synthesized using a neodymium catalyst; (3) According to standard ASTM D1765-14, ASTM N550 grade carbon black has an STSA of 39 m as measured according to standard ASTM D6556-10. 2 / g, and the COAN index measured according to standard ASTM D3493-16 is equal to 85 ml / 100g; (4) Granulated rubber obtained by recycling (tire micronization) Lehigh Technology, wherein the percentage of granulated rubber particles retained by a 400 µm sieve relative to the total weight of granulated rubber particles is less than 1% by weight relative to the total weight of granulated rubber particles, as measured by standard ASTM D5644-01 (2013), and the percentage of granulated rubber particles retained by a 250 µm sieve is less than 12% by weight, and the granulated rubber is unmodified; (5) Granulated rubber obtained by recycling (tire micronization) Lehigh Technology, wherein the percentage of granulated rubber particles retained by a 250 µm sieve relative to the total weight of granulated rubber particles is less than 1% by weight relative to the total weight of granulated rubber particles, as measured by standard ASTM D5644-01 (2013), and the percentage of granulated rubber particles retained by a 177 µm sieve is less than 10% by weight, and the granulated rubber is unmodified; (6) Granulated rubber obtained by recycling (tire micronization) Lehigh Technology, wherein the percentage of granulated rubber particles retained by a 600 µm sieve relative to the total weight of granulated rubber particles is less than 1% by weight relative to the total weight of granulated rubber particles, as measured by standard ASTM D5644-01 (2013), and the percentage of granulated rubber particles retained by a 400 µm sieve is less than 12% by weight, and the granulated rubber is unmodified; (7) Anti-ozone wax sold by Sasol under the trade name "Varazon 4959"; (8) TDAE oil sold by H&R under the trade name "VivaTec 500"; (9) C5 plasticized hydrocarbon resin sold by Exxon under the trade name “Escorez 1102”; (10) A mixture of the following two antioxidants: N-(1,3-dimethylbutyl)-N-phenyl-p-phenylenediamine sold by Flexsys under the designation “Santoflex 6-PPD” and 2,2,4-trimethyl-1,2-dihydroquinone sold by Lanxess; (11) Stearic acid sold by Uniquema under the designation "Pristerene 4931"; (12) Zinc oxide: Product quality, sold by Umicore; (13) N-dicyclohexyl-2-benzothiazole sulfenamide sold by Flexsys under the designation “Santocure CBS”.

[0115] The obtained performance is shown in Table 2 below: [Table 2] The results in Table 2 show that, relative to the reference rubber composition (T1) and the rubber composition of the comparative example (T2), only the rubber compositions C1, C2 and C3 according to the present invention have better blooming properties and better ozone resistance properties.

[0116] In the example of Test 2, a comparison was made between a reference rubber composition (T3) (excluding granular rubber) as defined in Table 3 below, and (comparative) compositions T4 and T5 with rubber compositions of C4 to C5 (according to the present invention) for the tire sidewall: [Table 3] The ingredients in Table 3 are the same as those listed in Table 1.

[0117] The obtained performance is shown in Table 4 below: [Table 4] The results in Table 4 also show that, compared with the reference elastomer composition (T3) and the comparative rubber compositions (T4 and T5), the embodiments (C4 and C5) according to the present invention have both better blooming properties and better ozone resistance properties.

[0118] In summary, the rubber composition according to the invention enables the production of a sidewall with a good trade-off between frosting and ozone resistance properties, which results in durable, high-contrast sidewall elements throughout the tire's life. Attached Figure Description

[0119] Indicative Figures 1 to 5 The features of the texture constituting the high-contrast sidewall element according to the present invention are described. Figures 1 to 5 Not drawn to scale: - Figure 1 : A three-dimensional view of a portion of a tire, including the sidewall with high-contrast elements; - Figure 2 : The meridional half-section of a tire, including the sidewall with high-contrast elements; - Figure 3 The texture of a high-contrast element including a leaf-shaped protrusion, according to a first variant of the first preferred embodiment of the texture; - Figure 4 A texture comprising a high-contrast element in the form of a sheet, according to a second variant of a first preferred embodiment of the texture; - Figure 5A texture comprising a high-contrast element with a cavity, according to a second preferred embodiment of the texture. Detailed Implementation

[0120] Figure 1 This is a perspective view of a portion of a tire 1, including a sidewall 2 with high-contrast elements 3. The high-contrast elements 3 shown include two graphic elements 31 (designed to convey technical, commercial, or legal information) and an aesthetic element 32.

[0121] Figure 2 The high-contrast element 3 is defined as a meridional half-section of a tire 1 including a sidewall 2 with a high-contrast element 3, the high-contrast element 3 being formed by a texture including a protrusion 4 protruding from the surface of the sidewall 21. Figure 3 The blade shape shown.

[0122] Figure 3 The texture of the high-contrast element 3, including blade-shaped protrusions 4, is a first variant of the first preferred embodiment of the texture. The average height H4 of the blade-shaped protrusions 4 protruding relative to the sidewall surface is at least 0.2 mm and at most 0.8 mm, preferably at least 0.25 mm and at most 0.5 mm. The average height means the arithmetic mean of the heights of all protrusions. The blade-shaped protrusions 4, separated by an average spacing P4, are arranged according to at least 5 blades / mm. 2 And at most 100 blades / mm 2 Preferably, at least 8 blades / mm 2 And at most 50 blades / mm 2 More preferably, at least 11 blades / mm 2 And at most 30 blades / mm 2 The surface density distribution. The average diameter D4 of the blade-shaped protrusion 4, whose diameter varies along the overall height of the blade, is at least 0.03 mm and at most 0.5 mm. In the illustrated embodiment, the blade-shaped protrusion 4 has a diameter that decreases from the blade base (which engages with the sidewall surface) and a free blade apex.

[0123] Figure 4The texture of the high-contrast element 3, comprising sheet-like protrusions 5, is a second variant of the first preferred embodiment of the texture. The average height H5 of the sheet-like protrusions 5 protruding relative to the sidewall surface is at least 0.2 mm and at most 0.8 mm, preferably at least 0.25 mm and at most 0.5 mm. The average height means the arithmetic mean of the heights of all protrusions. The sheet-like protrusions 5 are distributed according to a spacing P5 of at least 0.1 mm and at most 0.4 mm, preferably at least 0.15 mm and at most 0.3 mm. The average width D5 of the sheet-like protrusions 5, whose width varies along the overall height of the sheet, is at least 0.03 mm and at most 0.5 mm. In the illustrated embodiment, the sheet-like protrusions 5 have a width decreasing from the base of the sheet (where it engages with the sidewall surface) and a free sheet apex.

[0124] Figure 5 The texture of the high-contrast element 3, including cavity 6, is based on a second preferred embodiment of the texture. The average depth H6 of the cavity 6 recessed from the sidewall surface is at least 0.2 mm and at most 0.8 mm, preferably at least 0.25 mm and at most 0.5 mm. "Average depth" means the arithmetic mean of the depths of all cavities. The cavity 6 is composed of a cavity interior 62 formed in the thickness of the sidewall and an opening 61 leading to the sidewall surface. The openings 61 in the sidewall surface, separated by a spacing P6, are based on at least 5 openings / mm. 2 And at most 100 openings / mm 2 Preferably, there are at least 8 openings / mm 2 And at most 50 openings / mm 2 Even more preferably, at least 11 openings / mm 2 And at most 30 openings / mm 2 Surface density distribution. The average diameter D6 of the openings 61 on the sidewall surface is at least 0.03 mm and at most 0.5 mm. The average diameter refers to the arithmetic mean of the diameters of the openings on the sidewall surface (which are not necessarily the same).

Claims

1. Tyre (1) for vehicle, said tyre (1) comprising a sidewall (2) having at least one high-contrast sidewall element (3): - said high-contrast sidewall element (3) is constituted by a texture comprising projections (4, 5) projecting with respect to the sidewall surface (21) and / or cavities (6) recessed with respect to the sidewall surface (21) in contact with atmospheric air; - said sidewall (2) comprises a rubber composition based on an elastomeric matrix, at least one reinforcing filler, at least one crosslinking system, at least one plasticizer, at least one anti- ozone wax and at least one particulate rubber; characterized in that said elastomeric matrix comprises isoprene elastomer in an amount of at least 35 phr and at most 65 phr and butadiene elastomer in an amount of at least 35 phr and at most 65 phr, said reinforcing filler is in an amount of at least 5 phr and at most 70 phr, said anti- ozone wax is in an amount of at least 1.2 phr and at most 2.8 phr and said particulate rubber is in an amount of at least 2 phr and at most 30 phr.

2. Tyre (1) according to claim 1, wherein, said anti- ozone wax is in an amount of at least 1.4 phr and at most 2.6 phr, preferably at least 1.6 phr and at most 2.4 phr.

3. Tyre (1) according to claim 1 or 2, wherein, said particulate rubber is in an amount of at least 5 phr and at most 20 phr, preferably at least 5.5 phr and at most 19.5 phr, more preferably at least 6 phr and at most 19 phr, still more preferably at least 6 phr and at most 18 phr.

4. Tyre (1) according to any one of claims 1 to 3, wherein, the ratio between the amount of said particulate rubber expressed in phr and the amount of said anti- ozone wax expressed in phr is at least 5.50 and at most 17.00, preferably at least 6.00 and at most 17.00, more preferably at least 6.50 and at most 12.

50.

5. Tyre (1) according to any one of claims 1 to 4, wherein, said reinforcing filler is in an amount of at least 10 phr and at most 60 phr, preferably at least 15 phr and at most 55 phr, more preferably at least 15 phr and at most 50 phr, still more preferably at least 15 phr and at most 45 phr.

6. Tyre (1) according to any one of claims 1 to 5, wherein, the sum of the amount of said reinforcing filler and the amount of said particulate rubber is at least 30 phr and at most 65 phr, preferably at least 30 phr and at most 60 phr, more preferably at least 35 phr and at most 50 phr.

7. A tyre (1) according to any one of claims 1 to 6, wherein, said reinforcing filler mainly comprises carbon black.

8. Tyre (1) according to any one of claims 1 to 7, wherein, the ratio between the amount of said reinforcing filler expressed in phr and the amount of said plasticizer expressed in phr is at least 1.00 and at most 5.00, preferably at least 1.50 and at most 4.50, more preferably at least 2.00 and at most 4.00, even more preferably at least 2.00 and at most 3.

50.

9. Tyre (1) according to any one of claims 1 to 8, wherein, said high-contrast sidewall element (3) is constituted by a texture comprising projections (4, 5) projecting with respect to the sidewall surface (21), said projections (4, 5) having an average height (H4, H5) of at least 0.2 mm and at most 0.8 mm, preferably at least 0.25 mm and at most 0.5 mm.

10. Tyre (1) according to claim 9, wherein, Said high-contrast sidewall element (3) is composed of a texture comprising protrusions (4) in the form of leaves, said protrusions (4) having a surface density distribution of at least 5 leaves / mm 2 and at most 100 leaves / mm 2 , preferably at least 8 leaves / mm 2 and at most 50 leaves / mm 2 , even more preferably at least 11 leaves / mm 2 and at most 30 leaves / mm 2 .

11. Tyre (1) according to either of Claims 9 or 10, wherein, The high-contrast sidewall element (3) is composed of a texture comprising protrusions (4) in the form of leaves, the protrusions (4) having an average diameter (D4) of at least 0.03 mm and at most 0.5 mm.

12. Tyre (1) according to any one of claims 9 to 11, wherein, The high-contrast sidewall element (3) is composed of a texture comprising protrusions (4) in the form of leaves, the protrusions (4) having an average diameter (D4) of at least 0.03 mm and at most 0.5 mm.

13. Tyre (1) according to claim 9, wherein, The high-contrast sidewall element (3) is composed of a texture comprising protrusions (5) in the form of flakes, the protrusions (5) being distributed according to a pitch (P5) of at least 0.1 mm and at most 0.4 mm, preferably at least 0.15 mm and at most 0.3 mm.

14. Tyre (1) according to claim 9 or 13, wherein, The high-contrast sidewall element (3) is composed of a texture comprising protrusions (5) in the form of flakes, the protrusions (5) having an average width (D5) of at least equal to 0.03 mm and at most equal to 0.5 mm.

15. A tyre (1) according to any one of claims 9 or 13 or 14, wherein, The high-contrast sidewall element (3) is composed of a texture comprising protrusions (5) in the form of flakes, the protrusions (5) having an average width (D5) of at least equal to 0.03 mm and at most equal to 0.5 mm.

16. A tyre (1) according to any one of claims 1 to 8, wherein, The high-contrast sidewall element (3) is composed of a texture comprising cavities (6) recessed with respect to the sidewall surface (21), the cavities (6) having an average depth (H6) of at least 0.2 mm and at most 0.7 mm, preferably at least 0.25 mm and at most 0.4 mm.

17. Tyre (1) according to claim 16, wherein, Said high-contrast sidewall element (3) is composed of a texture comprising cavities (6) with a surface density distribution of at least 5 openings / mm 2 and at most 100 openings / mm 2 , preferably at least 8 openings / mm 2 and at most 50 openings / mm 2 , even more preferably at least 11 openings / mm 2 and at most 30 openings / mm 2 of the sidewall surface (21).

18. Tyre (1) according to either of Claims 16 or 17, wherein, The high-contrast sidewall element (3) is composed of a texture comprising cavities (6), the cavities (6) having an average diameter (D6) of at least 0.03 mm and at most 0.5 mm of the opening (61) on the sidewall surface (21).

19. Tyre (1) according to any one of claims 1 to 18, wherein, The first luminance L*1 of the texture of the high-contrast sidewall element (3) is at least 1 and at most 15, preferably at least 4 and at most 13.

20. A tyre (1) according to any one of claims 1 to 19, wherein, The portion of any sidewall surface (21) adjacent to the high-contrast sidewall element (3) has a second luminance L*2, the second luminance L*2 being at least L*1 + 5, preferably at least L*1 + 10, even more preferably at least L*1 + 12.

21. Tyre (1) according to any one of claims 1 to 20, wherein, The portion of any sidewall surface (21) adjacent to the high-contrast sidewall element (3) has a second luminance L*2, the second luminance L*2 being at least 18, preferably at least 22.

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